JP6730280B2 - Limiting current type gas sensor - Google Patents

Description

The present embodiment relates to a limiting current type gas sensor.

Conventionally, resistance change type, capacitance change type, zirconia (ZrO ₂ ) solid electrolyte type, and the like are known as humidity sensors that detect the concentration of water vapor in the gas to be measured.

The resistance variable type using a polymer film has an advantage that it is inexpensive and can be easily made into a device. On the other hand, the measurement accuracy in the low humidity region is low and the temperature dependence is large. Further, there is a disadvantage that elution due to dew condensation causes element deterioration and destruction.

The capacitance change type has the advantages of good linearity, measurable in the whole range of relative humidity, and low temperature dependence. On the other hand, there is a disadvantage that water other than pure water (tap water, etc.) and organic solvents have a great influence. Further, while the capacitance at a humidity of 0% RH is several hundred pF, the capacitance change at a change of 1% RH is 1 pF or less, and periodic calibration is required for accurate humidity measurement. It is an effective device when you do not require the accuracy of humidity measurement in a general office environment, but it is an atmosphere with high accuracy humidity measurement, condensation, and gas exposure (weather observation applications and bathrooms), 100°C. Use in the above-mentioned high temperature atmosphere is unexpected. To improve durability, it is necessary to develop a new polymer material. While future R&D is expected, new material development requires time and cost.

Humidity sensors using zirconia solid electrolytes are commercially available for measuring humidity at high temperatures. Oxygen sensors using a zirconia solid electrolyte are used for improving the combustion efficiency of automobiles and reducing NO _x , and have a proven track record in durability as materials. However, since zirconia is used after being raised to several hundred degrees Celsius, the power consumption is as high as 100 W, and handling of high-temperature objects is difficult, so the market is limited to some industrial applications.

Therefore, in recent years, the zirconia thin film limiting current type has attracted attention. This type of limiting current type oxygen sensor has the advantages of high reliability and good linearity.

U.S. Pat. No. 4,487,680 Japanese Unexamined Patent Publication No. 5-312772 JP, 2009-75011, A JP 2006-17429 A JP, 2014-196995, A

Hideaki Takahashi, Keiichi Saji, Haruyoshi Kondo, "Thin film limiting current type oxygen sensor" Toyota Central Research Laboratory R&D Review Vol. 27 No. 2 (1992.6) M. Asheghi and K.E.Goodson, “THERMAL CONDUCTIVITY MODEL FOR NEARLY PURE AND DOPED THIN SILICON LAYERS AT HIGH TEMPERATURES”, Proceedings of IMECE'03, 2003 ASME International Mechanical Engineering Congress Washington,D.C., November 15-21, 2003

However, in the limiting current type gas sensor including the limiting current type of zirconia thin film, improvement and stabilization of sensor characteristics are required. Further, in the limiting current type gas sensor including the limiting current type of zirconia thin film, further improvement in response speed is required.

The present embodiment provides a limiting current type gas sensor capable of improving the sensor characteristics and further stabilizing the sensor characteristics.

Further, the present embodiment provides a limiting current type gas sensor capable of improving the response speed.

According to one aspect of the present embodiment, the substrate, the heater disposed on the substrate via the first insulating layer, and the heater disposed on the heater via the second insulating layer, take in the gas to be measured. A gas introduction path, a lower electrode arranged on the gas introduction path, a solid electrolyte layer arranged on the lower electrode, and an upper electrode arranged on a surface of the solid electrolyte layer facing the lower electrode. If, on the substrate, and a said cavity portion which is substantially larger than the heater, the gas introduction path, the limiting current type gas sensor that consists of a porous membrane is provided. Alternatively, a limiting current type gas sensor is provided in which the gas introduction path is a gas diffusion path having a hollow microchannel. Alternatively, the lower electrode is provided with a limiting current type gas sensor configured by a porous Pt/Ti film.

According to another aspect of the present embodiment, a substrate, a heater arranged on the substrate via a first insulating layer, and a gas intake unit arranged on the heater via a second insulating layer. A lower electrode arranged on the gas intake part, a solid electrolyte layer arranged on the lower electrode, and an upper electrode arranged on a surface of the solid electrolyte layer facing the lower electrode. The substrate includes a cavity formed substantially larger than the heater, the gas intake portion includes a gas introduction path for introducing a measurement gas, and a columnar portion disposed on the gas introduction path. consists, the columnar portion, a limiting current type gas sensor that consists by columnar membranes with the orthogonal direction of the gas diaphragm structure is provided. Alternatively, the limiting current type gas sensor is provided in which the columnar portion is composed of a porous film having a gas diffusion structure in the in-plane direction. Alternatively, there is provided a limiting current type gas sensor in which the gas introduction path is a gas diffusion path provided with a microchannel having a porous membrane or a hollow structure. Alternatively, there is provided a limiting current type gas sensor in which the lower electrode is a porous electrode, and the porous electrode is a laminated film of a porous oxide film and a Pt/Ti film or a porous Pt/Ti film. Alternatively, there is provided a limiting current type gas sensor in which the lower electrode is a columnar electrode, and the columnar electrode is a laminated film of a columnar oxide film and a Pt/Ti film or a columnar Pt/Ti film.

According to one aspect of this embodiment, a substrate, a porous electrode formed using a porous material on the substrate, and a solid electrolyte material formed on an upper surface portion of the porous electrode. Solid electrolyte layer, a particle mixed layer formed at the interface between the solid electrolyte layer and the porous electrode, particles of the porous material and particles of the solid electrolyte material are mixed, and the solid electrolyte layer There is provided a limiting current type gas sensor including at least a dense electrode arranged on a surface facing the particle mixing layer.

According to one aspect of the present embodiment, the substrate, the porous electrode arranged in the region of the sensor portion on the substrate via the insulating layer, and the solid electrolyte layer arranged on the upper surface of the porous electrode. And an upper electrode disposed on the surface of the solid electrolyte layer facing the porous electrode, and a gas diffusion path having a predetermined aspect ratio and introducing a gas to be measured toward the sensor portion. A limiting current type gas sensor is provided.

According to another aspect of the present embodiment, a step of forming a heater on a substrate with a first insulating layer interposed therebetween, and a gas collecting step for arranging a heater on the heater with a second insulating layer interposed therebetween to take in a gas to be measured. A step of forming a gas introduction path having an inlet, a step of forming a lower electrode on the gas introduction path, a step of forming a solid electrolyte layer on the lower electrode, and the lower part on the solid electrolyte layer. A method of manufacturing a limiting current type gas sensor is provided, which includes a step of forming an upper electrode on a surface facing an electrode, and a step of forming a cavity portion substantially larger than the heater on the substrate.

According to another aspect of the present embodiment, a step of forming a heater on a substrate via a first insulating layer, a step of forming a lower electrode on the heater via a second insulating layer, and a step of forming the lower electrode A step of forming a solid electrolyte layer on the electrode, a step of forming an upper electrode on the surface of the solid electrolyte layer, the surface facing the lower electrode, and the heater is disposed on the heater via the second insulating layer, A method of manufacturing a limiting current type gas sensor is provided, which includes a step of forming a gas introduction path for introducing a gas to be measured and a step of forming a cavity portion substantially larger than the heater in the substrate.

According to another aspect of the present embodiment, a step of forming a porous electrode using a porous material on a substrate, and particles of the porous material and a solid electrolyte on at least a part of the porous electrode. A step of forming a particle mixed layer in which particles of the material are mixed, a step of forming a solid electrolyte layer using the solid electrolyte material on the porous electrode so as to cover at least the particle mixed layer, and the solid electrolyte And a step of forming a dense electrode on at least a surface facing the particle mixing layer, including a top surface portion of the layer.

According to another aspect of the present embodiment, a step of forming a porous electrode in the area of the sensor portion on the substrate via an insulating layer, and a step of forming a solid electrolyte layer on the upper surface of the porous electrode. A step of forming an upper electrode on a surface of the solid electrolyte layer facing the porous electrode, and an upper layer portion of the insulating layer having a predetermined aspect ratio and directing a gas to be measured toward the sensor portion. And a process of forming a gas diffusion path to be introduced as a limiting current type gas sensor.

According to another aspect of the present embodiment, a step of forming a porous electrode in the area of the sensor portion on the substrate via an insulating layer, and a step of forming a solid electrolyte layer on the upper surface of the porous electrode. A step of forming an upper electrode on a surface of the solid electrolyte layer facing the porous electrode, and a gas diffusion path having a predetermined aspect ratio and introducing a gas to be measured toward the sensor portion. And forming a lid surrounding the region of the sensor portion and mounting the lid on the substrate, a method for manufacturing a limiting current type gas sensor is provided.

According to another aspect of the present embodiment, there is provided a sensor network system including any of the limiting current type gas sensors described above.

According to the present embodiment, it is possible to provide a limiting current type gas sensor that can improve the sensor characteristics and further stabilize the sensor characteristics.

Further, according to the present embodiment, it is possible to provide a limiting current type gas sensor capable of improving the response speed.

(A) The typical plane pattern block diagram of the limiting current type gas sensor which concerns on 1st Embodiment, (b) The schematic cross-section figure of the limiting current type gas sensor which follows the IA-IA line of FIG. 1(a). It is a figure which shows an example of the formation method of the porous electrode applied to the limiting current type gas sensor which concerns on 1st Embodiment, Comprising: (a) The typical cross-section figure which shows the film-forming process of a porous formation film, (b). ) A schematic cross-sectional structure diagram showing the etching process of the porous film, and (c) a schematic cross-sectional structure diagram showing the formation process of the Pt/Ti laminated film. The figure which shows typically the temperature characteristic of the limiting current type gas sensor which applied the porous oxide film which concerns on 1st Embodiment. The figure which shows roughly about the temperature characteristic of the limiting current type gas sensor which applied the porous oxide film which concerns on 1st Embodiment. (A) A schematic plan view of the wafer applied to manufacture of the limiting current type gas sensor according to the first embodiment, (b) A schematic cross-sectional structural view of the wafer along the line IA0-IA0 of FIG. 5(a). .. FIG. 6A is a schematic plan view showing one step of the method of manufacturing the limiting current type gas sensor according to the first embodiment, and FIG. 6B is a schematic sectional structural view taken along the line IA1-IA1 of FIG. (A) A schematic plan view showing one step of a method of manufacturing the limiting current type gas sensor according to the first embodiment, (b) a schematic cross-sectional structural view taken along the line IA2-IA2 of FIG. 7(a). FIG. 8A is a schematic plan view showing one step of the method of manufacturing the limiting current type gas sensor according to the first embodiment, and FIG. 8B is a schematic sectional structural view taken along the line IA3-IA3 of FIG. FIG. 9A is a schematic plan view showing one step of the method of manufacturing the limiting current type gas sensor according to the first embodiment, and FIG. 9B is a schematic sectional structural view taken along the line IA4-IA4 of FIG. 9A. FIG. 10A is a schematic plan view showing one step of the method of manufacturing the limiting current type gas sensor according to the first embodiment, and FIG. 10B is a schematic sectional structural view taken along the line IA5-IA5 of FIG. FIG. 11A is a schematic plan view showing one step of the method of manufacturing the limiting current type gas sensor according to the first embodiment, and FIG. 11B is a schematic sectional structural view taken along the line IA6-IA6 of FIG. FIG. 12A is a schematic plan view showing one step of the method of manufacturing the limiting current type gas sensor according to the first embodiment, and FIG. 12B is a schematic sectional structural view taken along the line IA7-IA7 of FIG. 13A is a schematic plan view showing one step of the method of manufacturing the limiting current type gas sensor according to the first embodiment, and FIG. 13B is a schematic sectional structural view taken along the line IA8-IA8 of FIG. (A) The typical top view which shows 1 process of the manufacturing method of the limiting current type gas sensor which concerns on 1st Embodiment, (b) The typical cross-section figure which follows the IA9-IA9 line of FIG. 14 (a). 15A is a schematic plan view showing one step of the method of manufacturing the limiting current type gas sensor according to the first embodiment, and FIG. 15B is a schematic sectional structural view taken along the line IA10-IA10 of FIG. 16A is a schematic plan view showing one step of the method of manufacturing the limiting current type gas sensor according to the first embodiment, and FIG. 16B is a schematic sectional structural view taken along the line IA11-IA11 of FIG. 17A is a schematic plan view showing one step of the method of manufacturing the limiting current type gas sensor according to the first embodiment, and FIG. 17B is a schematic sectional structural view taken along the line IA12-IA12 of FIG. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to a first modification of the first embodiment, (b) a schematic diagram of the limiting current type gas sensor along the line IB-IB in FIG. 18( a ). Sectional structure diagram. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to a second modification of the first embodiment, (b) a schematic diagram of the limiting current type gas sensor along the IC-IC line in FIG. 19( a ). Sectional structure diagram. FIG. 20A is a diagram showing an example of a method for forming the low-concentration doped polysilicon layer shown in FIG. 19, and is a schematic cross-sectional structure diagram showing a forming step of the polysilicon layer, and a schematic showing an impurity implanting step. Cross-sectional structure diagram, (c) a schematic cross-sectional structure diagram showing the patterning step. It is a figure which shows the structural example of the low concentration doped polysilicon layer shown in FIG. 19, (a) 1st schematic cross-section structural drawing, (b) 2nd schematic cross-sectional structural drawing, (c) 3rd FIG. 6D is a schematic cross-sectional structure diagram, FIG. 4D is a fourth schematic cross-sectional structure diagram, and FIG. It is a figure which shows the structural example of the low concentration doped polysilicon layer shown in FIG. 19, (a) 6th schematic sectional structural drawing, (b) 7th schematic sectional structural drawing, (c) 8th. FIG. 9 is a schematic cross-sectional structure diagram of FIG. 9, (d) a ninth schematic cross-sectional structure diagram, and (e) a tenth schematic cross-sectional structure diagram. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to a third modification of the first embodiment, (b) a schematic diagram of the limiting current type gas sensor along the ID-ID line in FIG. 23( a ). Sectional structure diagram. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to a fourth modification of the first embodiment, (b) a schematic diagram of the limiting current type gas sensor along the line IE-IE in FIG. 24( a ). Sectional structure diagram. Regarding the in-plane temperature distribution, (a) a schematic bird's-eye view configuration diagram showing a result when a simulation is performed using the limiting current type gas sensor shown in FIG. 24, (b) using a limiting current type gas sensor according to a comparative example. FIG. 3 is a schematic bird's-eye view configuration diagram showing a result when a simulation is performed. FIG. 6 is a schematic characteristic diagram showing the relationship between the impurity concentrations of B, As, and P and the thermal conductivity in the lightly doped polysilicon layer. Concerning the in-plane temperature distribution, the results of a simulation using the limiting current type gas sensor shown in FIG. 24 are compared with the results of a simulation using the limiting current type gas sensor according to the comparative example. FIG. FIG. 25 is a schematic characteristic diagram showing the relationship between the thickness of the lightly doped polysilicon layer and the in-plane temperature distribution of the limiting current type gas sensor shown in FIG. 24. (A) A schematic cross-sectional structure diagram showing a sensor portion of the limiting-current type gas sensor according to the first embodiment, and (b) a schematic cross-sectional structure showing a sensor portion of the limiting-current type gas sensor according to the second embodiment. FIG. 6C is a schematic cross-sectional structure diagram showing the sensor portion of the limiting current type gas sensor according to the third embodiment, and FIG. 6D is a schematic sectional view showing the sensor portion of the limiting current type gas sensor according to the fourth embodiment. Sectional structural drawing, (e) Schematic sectional structural view showing the sensor part of the limiting current type gas sensor according to the fifth embodiment, (f) showing the sensor part of the limiting current type gas sensor according to the sixth embodiment. FIG. (A) The typical plane pattern block diagram of the limiting current type gas sensor which concerns on 2nd Embodiment, (b) The schematic cross-section figure of the limiting current type gas sensor which follows the IIA-IIA line of FIG. 30(a). (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to a first modified example of the second embodiment, (b) a schematic diagram of the limiting current type gas sensor along the line IIB-IIB in FIG. 31( a ). Sectional structure diagram. (A) A schematic plane pattern configuration diagram of a limiting current type gas sensor according to a second modification of the second embodiment, (b) a schematic diagram of the limiting current type gas sensor along the line IIC-IIC in FIG. 32( a ). Sectional structure diagram. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to a third modification of the second embodiment, (b) a schematic diagram of the limiting current type gas sensor along the IID-IID line in FIG. 33( a ). Sectional structure diagram. 34A is a schematic plan pattern configuration diagram of the limiting current type gas sensor according to the third embodiment, and FIG. 34B is a schematic cross-sectional structural diagram of the limiting current type gas sensor along the line IIIA-IIIA in FIG. (A) A schematic plan view showing one step of a method of manufacturing the limiting current type gas sensor according to the third embodiment, (b) a schematic cross-sectional structural view taken along the line IIIA1-IIIA1 of FIG. 35(a). (A) A schematic plan view showing one step of the method of manufacturing the limiting current type gas sensor according to the third embodiment, (b) a schematic cross-sectional structural view taken along the line IIIA2-IIIA2 of FIG. 36(a). (A) The schematic plan view which shows 1 process of the manufacturing method of the limiting current type gas sensor which concerns on 3rd Embodiment, (b) The schematic cross-section figure which follows the IIIA3-IIIA3 line of FIG. 37 (a). 38A is a schematic plan view showing one step of the method of manufacturing the limiting current type gas sensor according to the third embodiment, and FIG. 38B is a schematic sectional structural view taken along line IIIA4-IIIA4 of FIG. 38A. (A) A schematic plan view showing one step of the method of manufacturing the limiting current type gas sensor according to the third embodiment, (b) a schematic cross-sectional structural view taken along the line IIIA5-IIIA5 of FIG. 39(a). (A) A schematic plan view showing one step of the method of manufacturing the limiting current type gas sensor according to the third embodiment, (b) a schematic cross-sectional structural view taken along the line IIIA6-IIIA6 of FIG. 40(a). 41A is a schematic plan view showing one step of the method of manufacturing the limiting current type gas sensor according to the third embodiment, and FIG. 41B is a schematic sectional structural view taken along the line IIIA7-IIIA7 in FIG. 41A. (A) A schematic plan view showing one step of the method of manufacturing the limiting current type gas sensor according to the third embodiment, (b) A schematic cross-sectional structural view taken along the line IIIA8-IIIA8 of FIG. 42(a). (A) A schematic plan view showing one step of a method of manufacturing the limiting current type gas sensor according to the third embodiment, (b) a schematic cross-sectional structural view taken along the line IIIA9-IIIA9 of FIG. 43(a). (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to a first modified example of the third embodiment, (b) a schematic diagram of the limiting current type gas sensor along the line IIIB-IIIB in FIG. 44( a ). Sectional structure diagram. (A) A schematic plane pattern configuration diagram of a limiting current type gas sensor according to a second modification of the third embodiment, (b) a schematic diagram of the limiting current type gas sensor along the line IIIC-IIIC in FIG. 45(a). Sectional structure diagram. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to a third modification of the third embodiment, (b) a schematic diagram of the limiting current type gas sensor along the line IIID-IIID in FIG. 46(a). Sectional structure diagram. (A) A schematic plane pattern configuration diagram of a limiting current type gas sensor according to a fourth modification of the third embodiment, (b) a schematic diagram of the limiting current type gas sensor along the line IIIE-IIIE in FIG. 47(a). Sectional structure diagram. (A) A schematic plane pattern configuration diagram of a limiting current type gas sensor according to a fifth modified example of the third embodiment, (b) a schematic diagram of the limiting current type gas sensor along the line IIIF-IIIF in FIG. 48( a ). Sectional structure diagram. (A) The schematic plane pattern block diagram of the limiting current type gas sensor which concerns on 4th Embodiment, (b) The schematic cross-section figure of the limiting current type gas sensor which follows the IVA-IVA line of FIG. 49(a). (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to a first modification of the fourth embodiment, (b) a schematic diagram of the limiting current type gas sensor along the line IVB-IVB in FIG. 50( a ). Sectional structure diagram. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to a second modification of the fourth embodiment, (b) a schematic diagram of the limiting current type gas sensor along the line IVC-IVC in FIG. 51( a ). Sectional structure diagram. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to a third modification of the fourth embodiment, (b) a schematic diagram of the limiting current type gas sensor along the line IVD-IVD in FIG. 52( a ). Sectional structure diagram. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to a fourth modification of the fourth embodiment, (b) a schematic diagram of the limiting current type gas sensor along the IVE-IVE line in FIG. 53( a ). Sectional structure diagram. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to a fifth modification of the fourth embodiment, (b) a schematic diagram of the limiting current type gas sensor along the IVF-IVF line in FIG. 54(a). Sectional structure diagram. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to a sixth modified example of the fourth embodiment, (b) a schematic diagram of the limiting current type gas sensor along the IVG-IVG line in FIG. 55(a). Sectional structure diagram. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to a seventh modified example of the fourth embodiment, (b) a schematic diagram of the limiting current type gas sensor along the IVH-IVH line of FIG. 56( a ). Sectional structure diagram. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to a first example of the fifth embodiment, (b) a schematic diagram of the limiting current type gas sensor along the line VA1-VA1 of FIG. 57(a) Sectional structure diagram. (A) A schematic plane pattern configuration diagram showing another configuration of the limiting current type gas sensor shown in FIG. 57, (b) a schematic cross-sectional structural diagram of the limiting current type gas sensor taken along the line VA2-VA2 of FIG. 58(a) .. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to a first modification of the first example of the fifth embodiment, (b) a limiting current type along the line VB1-VB1 in FIG. 59(a). The schematic cross-section figure of a gas sensor. (A) A schematic plane pattern configuration diagram showing another configuration of the limiting current type gas sensor shown in FIG. 59, (b) a schematic cross-sectional structural diagram of the limiting current type gas sensor along the line VB2-VB2 of FIG. 60(a) .. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to Modification 2 of the first example of the fifth embodiment, (b) a limiting current type along the line VC1-VC1 of FIG. 61(a). The schematic cross-section figure of a gas sensor. (A) A schematic plan pattern configuration diagram showing another configuration of the limiting current type gas sensor shown in FIG. 61, (b) a schematic cross-sectional structural diagram of the limiting current type gas sensor along the line VC2-VC2 of FIG. 62(a) .. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to Modification 3 of the first example of the fifth embodiment, (b) a limiting current type along the line VD1-VD1 in FIG. 63(a). The schematic cross-section figure of a gas sensor. (A) A schematic plane pattern configuration diagram showing another configuration of the limiting current type gas sensor shown in FIG. 63, (b) A schematic cross-sectional structural diagram of the limiting current type gas sensor taken along line VD2-VD2 of FIG. 64(a) .. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to a second example of the fifth embodiment, (b) a schematic diagram of the limiting current type gas sensor along the line VE1-VE1 of FIG. Sectional structure diagram. (A) A schematic plane pattern configuration diagram showing another configuration of the limiting current type gas sensor shown in FIG. 65, (b) a schematic cross-sectional structural diagram of the limiting current type gas sensor taken along the line VE2-VE2 of FIG. 66(a) .. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to a modification 1 of the second example of the fifth embodiment, (b) a limiting current type along the line VF1-VF1 of FIG. 67(a). The schematic cross-section figure of a gas sensor. (A) A schematic plane pattern configuration diagram showing another configuration of the limiting current type gas sensor shown in FIG. 67, (b) a schematic cross-sectional structural diagram of the limiting current type gas sensor taken along the line VF2-VF2 of FIG. 68(a) .. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to Modification 2 of the second example of the fifth embodiment, (b) a limiting current type along the line VG1-VG1 in FIG. 69(a). The schematic cross-section figure of a gas sensor. (A) A schematic plan pattern configuration diagram showing another configuration of the limiting current type gas sensor shown in FIG. 69, (b) a schematic sectional structure diagram of the limiting current type gas sensor along the line VG2-VG2 in FIG. 70(a) .. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to Modification 3 of the second example of the fifth embodiment, (b) a limiting current type along the line VH1-VH1 of FIG. 71(a). The schematic cross-section figure of a gas sensor. (A) A schematic plane pattern configuration diagram showing another configuration of the limiting current type gas sensor shown in FIG. 71, (b) A schematic cross-sectional structural diagram of the limiting current type gas sensor along the line VH2-VH2 in FIG. 72(a) .. (A) A schematic plane pattern configuration diagram of a limiting current type gas sensor according to a third example of the fifth embodiment, (b) a schematic diagram of the limiting current type gas sensor along the line VJ1-VJ1 in FIG. 73(a) Sectional structure diagram. (A) A schematic plane pattern configuration diagram showing another configuration of the limiting current type gas sensor shown in FIG. 73, (b) A schematic cross-sectional structural diagram of the limiting current type gas sensor taken along the line VJ2-VJ2 of FIG. 74(a) .. (A) A schematic plane pattern configuration diagram of a limiting-current type gas sensor according to Modification 1 of the third example of the fifth embodiment, (b) a limiting-current type along the line VK1-VK1 of FIG. 75(a). The schematic cross-section figure of a gas sensor. (A) A schematic plane pattern configuration diagram showing another configuration of the limiting current type gas sensor shown in FIG. 75, (b) a schematic cross-sectional structural diagram of the limiting current type gas sensor along the line VK2-VK2 of FIG. 76(a) .. (A) A schematic plane pattern configuration diagram of a limiting-current type gas sensor according to Modification 2 of the third example of the fifth embodiment, (b) a limiting-current type along the line VL1-VL1 in FIG. 77(a). The schematic cross-section figure of a gas sensor. (A) A schematic plan pattern configuration diagram showing another configuration of the limiting current type gas sensor shown in FIG. 77, (b) a schematic cross-sectional structural diagram of the limiting current type gas sensor taken along the line VL2-VL2 of FIG. 78(a) .. (A) A schematic plane pattern configuration diagram of a limiting current type gas sensor according to Modification 3 of the third example of the fifth embodiment, (b) a limiting current type along the VM1-VM1 line of FIG. 79(a). The schematic cross-section figure of a gas sensor. (A) A schematic plane pattern configuration diagram showing another configuration of the limiting current type gas sensor shown in FIG. 79, (b) a schematic cross-sectional structural diagram of the limiting current type gas sensor along the VM2-VM2 line of FIG. 80(a) .. (A) A schematic plan pattern configuration diagram of the limiting current type gas sensor according to the first example of the sixth embodiment, (b) a schematic diagram of the limiting current type gas sensor along the VIA1-VIA1 line in FIG. 81(a) Sectional structure diagram. (A) A schematic plane pattern configuration diagram showing another configuration of the limiting current type gas sensor shown in FIG. 81, (b) a schematic cross-sectional structural diagram of the limiting current type gas sensor taken along the line VIA2-VIA2 of FIG. 82(a) .. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to Modification 1 of the first example of the sixth embodiment, (b) a limiting current type along line VIB1-VIB1 of FIG. 83(a). The schematic cross-section figure of a gas sensor. (A) A schematic plane pattern configuration diagram showing another configuration of the limiting current type gas sensor shown in FIG. 83, (b) a schematic cross-sectional structural diagram of the limiting current type gas sensor taken along line VIB2-VIB2 of FIG. 84(a) .. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to Modification 2 of the first example of the sixth embodiment, (b) a limiting current type along the line VIC1-VIC1 of FIG. 85(a). The schematic cross-section figure of a gas sensor. (A) A schematic plane pattern configuration diagram showing another configuration of the limiting current type gas sensor shown in FIG. 85, (b) A schematic cross-sectional structural diagram of the limiting current type gas sensor taken along line VIC2-VIC2 of FIG. 86(a) .. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to Modification 3 of the first example of the sixth embodiment, (b) a limiting current type along the line VID1-VID1 in FIG. 87(a). The schematic cross-section figure of a gas sensor. (A) A schematic plane pattern configuration diagram showing another configuration of the limiting current type gas sensor shown in FIG. 87, (b) a schematic cross-sectional structural diagram of the limiting current type gas sensor along the line VID2-VID2 of FIG. 88(a) .. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to a second example of the sixth embodiment, (b) a schematic diagram of the limiting current type gas sensor along the VIE1-VIE1 line in FIG. 89(a) Sectional structure diagram. (A) A schematic plane pattern configuration diagram showing another configuration of the limiting current type gas sensor shown in FIG. 89, (b) a schematic cross-sectional structural diagram of the limiting current type gas sensor taken along line VIE2-VIE2 of FIG. 90(a) .. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to a modification 1 of the second example of the sixth embodiment, (b) a limiting current type along the line VIF1-VIF1 in FIG. 91(a). The schematic cross-section figure of a gas sensor. (A) A schematic plan pattern configuration diagram showing another configuration of the limiting current type gas sensor shown in FIG. 91, (b) a schematic cross-sectional structural diagram of the limiting current type gas sensor taken along the line VIF2-VIF2 of FIG. 92(a) .. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to Modification 2 of the second example of the sixth embodiment, (b) a limiting current type along the line VIG1-VIG1 in FIG. 93(a). The schematic cross-section figure of a gas sensor. (A) A schematic plan pattern configuration diagram showing another configuration of the limiting current type gas sensor shown in FIG. 93, (b) a schematic cross-sectional structural diagram of the limiting current type gas sensor taken along the line VIG2-VIG2 of FIG. 94(a) .. (A) A schematic plane pattern configuration diagram of a limiting current type gas sensor according to Modification 3 of the second example of the sixth embodiment, (b) a limiting current type along the line VIH1-VIH1 of FIG. 95(a). The schematic cross-section figure of a gas sensor. (A) A schematic plane pattern configuration diagram showing another configuration of the limiting current type gas sensor shown in FIG. 95, (b) a schematic cross-sectional structural diagram of the limiting current type gas sensor taken along line VIH2-VIH2 of FIG. 96(a) .. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to a third example of the sixth embodiment, (b) a schematic diagram of the limiting current type gas sensor along the line VIJ1-VIJ1 in FIG. 97(a) Sectional structure diagram. (A) A schematic plane pattern configuration diagram showing another configuration of the limiting current type gas sensor shown in FIG. 97, (b) a schematic cross-sectional structural diagram of the limiting current type gas sensor taken along line VIJ2-VIJ2 of FIG. 98(a) .. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to Modification 1 of the third example of the sixth embodiment, (b) a limiting current type along the line VIK1-VIK1 of FIG. 99(a). The schematic cross-section figure of a gas sensor. (A) A schematic plane pattern configuration diagram showing another configuration of the limiting current type gas sensor shown in FIG. 99, (b) a schematic cross-sectional structural diagram of the limiting current type gas sensor taken along line VIK2-VIK2 of FIG. 100(a) .. (A) A schematic plane pattern configuration diagram of a limiting current type gas sensor according to Modification 2 of the third example of the sixth embodiment, (b) a limiting current type along the line VIL1-VIL1 of FIG. 101(a). The schematic cross-section figure of a gas sensor. (A) A schematic plane pattern configuration diagram showing another configuration of the limiting current type gas sensor shown in FIG. 101, (b) A schematic cross-sectional structural diagram of the limiting current type gas sensor taken along the line VIL2-VIL2 of FIG. 102(a) .. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to Modification 3 of the third example of the sixth embodiment, (b) a limiting current type along the line VIM1-VIM1 of FIG. 103(a). The schematic cross-section figure of a gas sensor. (A) A schematic plane pattern configuration diagram showing another configuration of the limiting current type gas sensor shown in FIG. 103, (b) a schematic cross-sectional structural diagram of the limiting current type gas sensor along the line VIM2-VIM2 of FIG. 104(a) .. The flowchart figure which shows the operation|movement which detects gas concentration using the limiting current type gas sensor which concerns on this Embodiment. The schematic diagram which shows the relationship between YSZ temperature and time in gas concentration detection operation|movement in the limiting current type gas sensor which concerns on this Embodiment. FIG. 3 is a schematic cross-sectional structure diagram illustrating the operating principle of the limiting current type gas sensor according to the present embodiment. 3 is an energy diagram illustrating hopping conduction of oxygen ions (O ²⁻ ) in the limiting current type gas sensor according to the present embodiment. FIG. 3 is a schematic explanatory diagram of current-voltage characteristics in the limiting current type gas sensor according to the present embodiment. In the limiting current type gas sensor according to the present embodiment, a schematic cross-sectional view for explaining ionic conduction. The typical bird's-eye view composition (perspective view) showing the lid of the package which stores the limiting current type gas sensor concerning this embodiment. The typical bird's-eye view composition (perspective view) showing the body of the package which stores the limiting current type gas sensor concerning this embodiment. The schematic block block diagram which shows the limiting current type gas sensor which concerns on this Embodiment. The typical block block diagram of the sensor package which mounts the limiting current type gas sensor which concerns on this Embodiment. The typical block block diagram of the sensor network to which the limiting current type gas sensor which concerns on this Embodiment is applied. 116A is a schematic plan pattern configuration diagram of the limiting current type gas sensor according to the seventh embodiment, and FIG. 116B is a schematic sectional structural diagram of the limiting current type gas sensor along the line IA-IA in FIG. 116A. The typical cross section structure figure showing the important section of the limiting current type gas sensor concerning a 7th embodiment. In the limiting current type gas sensor according to the seventh embodiment, (a) a schematic cross-sectional structure diagram for explaining the basic structure of the Pt+YSZ particle mixed layer, (b) for explaining the basic structure of the Pt+YSZ particle mixed layer. 3C is another schematic cross-sectional structure diagram, and (c) is another schematic cross-sectional structure diagram shown for explaining the basic structure of the Pt+YSZ particle mixed layer. In order to explain the basic characteristics of the Pt+YSZ particle mixed layer in the limiting current type gas sensor according to the seventh embodiment, (a) a schematic view showing an example in which a Pt+YSZ particle mixed layer is present, b) A schematic view showing, as an example, a case where a Pt+YSZ particle mixed layer does not exist for comparison. FIG. 13 is a schematic diagram showing the case where a Pt+YSZ particle mixed layer is present and the case where no Pt+YSZ particle mixed layer is present in order to explain the basic characteristics of the Pt+YSZ particle mixed layer in the limiting current type gas sensor according to the seventh embodiment. (A) A schematic plan view showing one step (1) of the method of manufacturing the limiting current type gas sensor according to the seventh embodiment, (b) a schematic cross section taken along line IB-IB in FIG. 121(a) Structural drawing. (A) A schematic plan view showing one step (No. 2) of the method of manufacturing the limiting current type gas sensor according to the seventh embodiment, (b) a schematic cross section taken along the line IC-IC of FIG. 122(a) Structural drawing. (A) A schematic plan view showing one step (No. 3) of the method of manufacturing the limiting current type gas sensor according to the seventh embodiment, (b) a schematic cross section taken along the line ID-ID of FIG. 123(a) Structural drawing. (A) A schematic plan view showing one step (4) of the method of manufacturing the limiting current type gas sensor according to the seventh embodiment, (b) a schematic cross section taken along the line IE-IE of FIG. 124(a). Structural drawing. (A) A schematic plan view showing one step (No. 5) of the method of manufacturing the limiting current type gas sensor according to the seventh embodiment, (b) a schematic cross section taken along the line IF-IF of FIG. 125(a). Structural drawing. (A) A schematic plan view showing a step (No. 6) of the method of manufacturing the limiting current type gas sensor according to the seventh embodiment, (b) a schematic cross section taken along line IG-IG of FIG. 126(a) Structural drawing. (A) A schematic plan view showing one step (No. 7) of the method of manufacturing the limiting current type gas sensor according to the seventh embodiment, (b) a schematic cross section taken along line IH-IH of FIG. 127(a). Structural drawing. (A) A schematic plan view showing one step (8) of the method of manufacturing the limiting current type gas sensor according to the seventh embodiment, (b) a schematic cross section taken along line IJ-IJ of FIG. 128(a) Structural drawing. The typical plane pattern block diagram of the limiting current type gas sensor which concerns on 8th Embodiment. The schematic plane pattern block diagram which expanded the sensor part of the limiting current type gas sensor which concerns on 8th Embodiment. FIG. 130 is a schematic cross-sectional structure diagram taken along the line IIA-IIA in FIG. 130. (A) A schematic plan view showing one step (1) of the method of manufacturing the limiting current type gas sensor according to the eighth embodiment, (b) a schematic cross section taken along line IIB-IIB of FIG. 132(a) Structural drawing. (A) A schematic plan view showing one step (2) of the method of manufacturing the limiting current type gas sensor according to the eighth embodiment, (b) a schematic cross section taken along line IIC-IIC of FIG. 133(a). Structural drawing. (A) A schematic plan view showing one step (3) of the method of manufacturing the limiting current type gas sensor according to the eighth embodiment, (b) a schematic cross section taken along the line IID-IID of FIG. 134(a) Structural drawing. (A) A schematic plan view showing one step (No. 4) of the method of manufacturing the limiting current type gas sensor according to the eighth embodiment, (b) a schematic cross section taken along line IIE-IIE of FIG. 135(a) Structural drawing. (A) A schematic plan view showing one step (No. 5) of the method of manufacturing the limiting current type gas sensor according to the eighth embodiment, (b) a schematic cross section taken along line IIF-IIF of FIG. 136(a) Structural drawing. (A) A schematic plan view showing one step (6) of the method of manufacturing the limiting current type gas sensor according to the eighth embodiment, (b) a schematic cross section taken along line IIG-IIG of FIG. 137(a). Structural drawing. (A) A schematic plan view showing one step (7) of the method of manufacturing a limiting current type gas sensor according to the eighth embodiment, (b) a schematic cross section taken along line IIH-IIH of FIG. 138(a). Structural drawing. 138 shows one step (No. 8) of the method of manufacturing the limiting current type gas sensor according to the eighth embodiment, and is a schematic cross-sectional structure view taken along the line IIH-IIH in FIG. 138(a). The typical plane pattern block diagram of the limiting current type gas sensor which concerns on 9th Embodiment. The schematic plan view which shows 1 process (the 1) of the manufacturing method of the limiting current type gas sensor which concerns on 9th Embodiment. The schematic plan view which shows 1 process (the 2) of the manufacturing method of the limiting current type gas sensor which concerns on 9th Embodiment. The schematic plan view which shows 1 process (3) of the manufacturing method of the limiting current type gas sensor which concerns on 9th Embodiment. The schematic plan view which shows 1 process (the 4) of the manufacturing method of the limiting current type gas sensor which concerns on 9th Embodiment. The schematic plan view which shows 1 process (the 5) of the manufacturing method of the limiting current type gas sensor which concerns on 9th Embodiment. The schematic plan view which shows 1 process (the 6) of the manufacturing method of the limiting current type gas sensor which concerns on 9th Embodiment. (A) A schematic cross-sectional structure diagram showing one step (beam structure forming step) of the method of manufacturing the limiting current type gas sensor according to the present embodiment, (b) of the method of manufacturing the limiting current type gas sensor according to the present embodiment The schematic cross-section figure which shows 1 process (another beam structure formation process). (A) Layout diagram (top view) of the beam structure of the limiting current type gas sensor according to the present embodiment, (b) A schematic cross-sectional structure diagram taken along the line IIIA-IIIA in FIG. 148(a). (A) The typical plane pattern block diagram of the limiting current type gas sensor which concerns on 10th Embodiment, (b) The schematic cross-section figure of the limiting current type gas sensor which follows the IA-IA line of FIG. 149 (a). (A) A schematic plan view showing one step (1) of the method of manufacturing a limiting current type gas sensor according to the tenth embodiment, (b) a schematic cross section taken along the line IB-IB of FIG. 150(a) Structural drawing. (A) A schematic plan view showing one step (No. 2) of the method of manufacturing the limiting current type gas sensor according to the tenth embodiment, (b) a schematic cross section taken along the line IC-IC in FIG. 151(a) Structural drawing. (A) A schematic plan view showing one step (No. 3) of the method of manufacturing the limiting current type gas sensor according to the tenth embodiment, (b) a schematic cross section taken along the line ID-ID of FIG. 152(a) Structural drawing. (A) A schematic plan view showing one step (No. 4) of the method of manufacturing the limiting current type gas sensor according to the tenth embodiment, (b) a schematic cross section taken along the line IE-IE of FIG. 153(a). Structural drawing. (A) A schematic plan view showing one step (5) of the method of manufacturing the limiting current type gas sensor according to the tenth embodiment, (b) a schematic cross section taken along the line IF-IF of FIG. 154(a) Structural drawing. (A) A schematic plan view showing one step (6) of the method of manufacturing the limiting current type gas sensor according to the tenth embodiment, (b) a schematic cross section taken along the line IG-IG of FIG. 155(a) Structural drawing. (A) A schematic plan view showing one step (7) of the method of manufacturing the limiting current type gas sensor according to the tenth embodiment, (b) a schematic cross section taken along line IH-IH of FIG. 156(a) Structural drawing. (A) A schematic plan view showing one step (8) of the method of manufacturing the limiting current type gas sensor according to the tenth embodiment, (b) a schematic cross section taken along line IJ-IJ of FIG. 157(a) Structural drawing. (A) A schematic plan view showing one step (9) of the method of manufacturing the limiting current type gas sensor according to the tenth embodiment, (b) a schematic cross section taken along line IK-IK of FIG. 158(a) Structural drawing. (A) A schematic plan view showing one step (10) of the method of manufacturing a limiting current type gas sensor according to the tenth embodiment, (b) a schematic cross section taken along the line IL-IL of FIG. 159(a) Structural drawing. (A) A schematic plan view showing one step (11) of the method of manufacturing a limiting current type gas sensor according to the tenth embodiment, (b) a schematic cross section taken along line IM-IM of FIG. 160(a) Structural drawing. (A) A schematic plan view showing one step (12) of the method of manufacturing the limiting current type gas sensor according to the tenth embodiment, (b) a schematic cross section taken along the line IN-IN of FIG. 161(a) Structural drawing. (A) The typical plane pattern block diagram of the limiting current type gas sensor which concerns on 11th Embodiment, (b) The typical cross-section structural drawing of the limiting current type gas sensor which follows the IIA-IIA line of FIG. 162 (a). (A) A schematic plan view showing one step (1) of the method of manufacturing a limiting current type gas sensor according to the eleventh embodiment, (b) a schematic cross section taken along line IIB-IIB of FIG. 163(a). Structural drawing. (A) A schematic plan view showing one step (No. 2) of the method of manufacturing the limiting current type gas sensor according to the eleventh embodiment, (b) a schematic cross section taken along line IIC-IIC of FIG. 164(a). Structural drawing. (A) A schematic plan view showing one step (No. 3) of the method of manufacturing the limiting current type gas sensor according to the eleventh embodiment, (b) a schematic cross section taken along the line IID-IID of FIG. 165(a) Structural drawing. (A) A schematic plan view showing one step (No. 4) of the method of manufacturing the limiting current type gas sensor according to the eleventh embodiment, (b) a schematic cross section taken along line IIE-IIE of FIG. 166(a). Structural drawing. (A) A schematic plan view showing one step (No. 5) of the method of manufacturing the limiting current type gas sensor according to the eleventh embodiment, (b) a schematic cross section taken along the line IIF-IIF of FIG. 167(a). Structural drawing. (A) A schematic plan view showing a step (6) of the method of manufacturing the limiting current type gas sensor according to the eleventh embodiment, (b) a schematic cross section taken along line IIG-IIG of FIG. 168(a). Structural drawing. (A) A schematic plan view showing one step (7) of the method of manufacturing the limiting current type gas sensor according to the eleventh embodiment, (b) a schematic cross section taken along line IIH-IIH of FIG. 169(a). Structural drawing. (A) A schematic plan view showing one step (8) of the method of manufacturing the limiting current type gas sensor according to the eleventh embodiment, (b) a schematic cross section taken along line IIJ-IIJ of FIG. 170(a) Structural drawing. (A) A schematic plan view showing one step (9) of the method of manufacturing the limiting current type gas sensor according to the eleventh embodiment, (b) a schematic cross section taken along line IIK-IIK of FIG. 171(a) Structural drawing. (A) A schematic plan view showing one step (10) of the method of manufacturing the limiting current type gas sensor according to the eleventh embodiment, (b) a schematic cross section taken along the line IIL-IIL of FIG. 172(a). Structural drawing. (A) A schematic plan view showing one step (11) of the method of manufacturing the limiting current type gas sensor according to the eleventh embodiment, (b) a schematic cross section taken along line IIM-IIM of FIG. 173(a). Structural drawing. (A) The typical plane pattern block diagram of the limiting current type gas sensor which concerns on 12th Embodiment, (b) The typical cross-section structural drawing of the limiting current type gas sensor which follows the IIIA-IIIA line of FIG. 174 (a). (A) A schematic plan view showing one step (No. 1) of the method of manufacturing the limiting current type gas sensor according to the twelfth embodiment, (b) a schematic cross section taken along line IIIB-IIIB of FIG. 175(a) Structural drawing. (A) A schematic plan view showing one step (No. 2) of the method of manufacturing the limiting current type gas sensor according to the twelfth embodiment, (b) a schematic cross section taken along line IIIC-IIIC of FIG. 176(a) Structural drawing. (A) A schematic plan view showing one step (No. 3) of the method of manufacturing the limiting current type gas sensor according to the twelfth embodiment, (b) a schematic cross section taken along line IIID-IIID of FIG. 177(a). Structural drawing. (A) A schematic plan view showing one step (No. 4) of the method of manufacturing the limiting current type gas sensor according to the twelfth embodiment, (b) a schematic cross section taken along line IIIE-IIIE in FIG. 178(a) Structural drawing. (A) A schematic plan view showing one step (5) of the method of manufacturing the limiting current type gas sensor according to the twelfth embodiment, (b) a schematic cross section taken along line IIIF-IIIF in FIG. 179(a) Structural drawing. (A) A schematic plan view showing one step (6) of the method of manufacturing the limiting current type gas sensor according to the twelfth embodiment, (b) a schematic cross section taken along line IIIG-IIIG in FIG. 180(a) Structural drawing. (A) A schematic plan view showing one step (7) of the method of manufacturing a limiting current type gas sensor according to the twelfth embodiment, (b) a schematic cross section taken along line IIIH-IIIH of FIG. 181(a) Structural drawing. (A) A schematic plan view showing one step (8) of the method of manufacturing the limiting current type gas sensor according to the twelfth embodiment, (b) a schematic cross section taken along line IIIJ-IIIJ of FIG. 182(a) Structural drawing. (A) A schematic plan view showing one step (9) of the method of manufacturing the limiting current type gas sensor according to the twelfth embodiment, (b) a schematic cross section taken along line IIIK-IIIK of FIG. 183(a) Structural drawing. (A) A schematic plan view showing one step (10) of the method of manufacturing the limiting current type gas sensor according to the twelfth embodiment, (b) a schematic cross section taken along line IIIL-IIIL of FIG. 184(a) Structural drawing. (A) A schematic plan view showing one step (11) of the method of manufacturing a limiting current type gas sensor according to the twelfth embodiment, (b) a schematic cross section taken along line IIIM-IIIM of FIG. 185(a) Structural drawing. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to a first modified example of the twelfth embodiment, (b) a schematic diagram of the limiting current type gas sensor along the IVA-IVA line in FIG. 186(a). Sectional structure diagram. (A) A schematic plan view showing one step (1) of the method of manufacturing the lid in the limiting current type gas sensor according to the first modification of the twelfth embodiment, (b) the IVB of FIG. 187(a). -A schematic cross-sectional structural view taken along the line IVB. (A) A schematic plan view showing one step (No. 2) of the method of manufacturing the lid in the limiting current type gas sensor according to the first modification of the twelfth embodiment, (b) the IVC of FIG. 188(a). -A schematic cross-sectional structural view taken along the line IVC. (A) A schematic plan view showing one step (3) of the method of manufacturing the lid in the limiting current type gas sensor according to the first modification of the twelfth embodiment, (b) the IVD of FIG. 189(a). -A schematic cross-sectional structural view taken along the line IVD. (A) A schematic plan view showing one step (part 4) of the method of manufacturing the lid body in the limiting current type gas sensor according to the first modification of the twelfth embodiment, (b) the IVE of FIG. 190(a). -A schematic cross-sectional structure diagram along the IVE line. (A) A schematic plan view showing a step (5) of the method of manufacturing the lid body in the limiting current type gas sensor according to the first modification of the twelfth embodiment, (b) the IVF of FIG. 191(a). -A schematic cross-sectional structural view taken along the line IVF. (A) A schematic plan view showing one step (6) of the method of manufacturing the lid in the limiting current type gas sensor according to the first modified example of the twelfth embodiment, (b) the IVG of FIG. 192(a). -A schematic cross-sectional structural view taken along the line IVG. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to a second modification of the twelfth embodiment, (b) a schematic diagram of the limiting current type gas sensor along the line VA-VA in FIG. 193(a). Sectional structure diagram. (A) A schematic plan pattern configuration diagram of a limiting current type gas sensor according to a third modified example of the twelfth embodiment, (b) a schematic diagram of the limiting current type gas sensor along the VIA-VIA line in FIG. 194(a). Sectional structure diagram.

Next, embodiments will be described with reference to the drawings. In the description of the drawings, the same or similar parts are designated by the same or similar reference numerals. However, it should be noted that the drawings are schematic and the relationship between the thickness and the plane dimension, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, the specific thickness and dimensions should be determined in consideration of the following description. Further, it is needless to say that the drawings include portions in which dimensional relationships and ratios are different from each other.

Further, the embodiments described below exemplify devices and methods for embodying the technical idea, and do not specify the material, shape, structure, arrangement, etc. of component parts to the following. .. Various modifications can be added to the respective embodiments within the scope of the claims.

In the following description of the first to twelfth embodiments, in the description of the first to sixth embodiments, the direction from the lower electrode 28D side to the upper electrode 28U side in each drawing is shown for convenience. Is defined as upward (upward), and vice versa is defined as downward (downward). Similarly, in the description of the seventh to twelfth embodiments, for convenience, the direction from the porous electrode 5D side to the dense electrode 5U side in each drawing is defined as the upper side and the opposite direction is defined as the lower side.

Further, the vertical direction means a substantially vertical direction in a plan view with respect to the plane pattern of the limiting current type gas sensor. Further, the in-plane direction means substantially the same plane direction as the plane pattern of the limiting current type gas sensor.

(First to sixth embodiments)
This embodiment is roughly classified into, for example, first to sixth embodiments according to the structure of the sensor portion SP of the limiting current gas sensor.

The sensor portion SP of the limiting current type gas sensor according to the first embodiment is, as schematically shown in FIG. 29A, a porous oxide film (a porous film) serving as a gas introduction path for taking in the gas to be measured GS. ) 51, a lower electrode 28D disposed on the porous oxide film 51, a solid electrolyte layer 30 disposed so as to cover the porous oxide film 51 and the lower electrode 28D, and a solid electrolyte layer 30 facing the lower electrode 28D. And an upper electrode 28U disposed in the.

As schematically shown in FIG. 29B, the sensor portion SP of the limiting current type gas sensor according to the second embodiment has a porous Pt film (porous film) serving as a gas introduction path for taking in the gas GS to be measured. ) 61, the lower electrode 28D arranged on the porous Pt film 61, the solid electrolyte layer 30 arranged so as to cover the porous Pt film 61 and the lower electrode 28D, and the solid electrolyte layer 30 facing the lower electrode 28D. And an upper electrode 28U disposed in the.

The sensor portion SP of the limiting current type gas sensor according to the third embodiment is arranged on a gas diffusion path MP which is a gas introduction path for taking in the measured gas GS, as schematically shown in FIG. 29(c). Lower electrode 28D, a solid electrolyte layer 30 arranged so as to cover lower electrode 28D, and an upper electrode 28U arranged on solid electrolyte layer 30 facing lower electrode 28D.

The sensor portion SP of the limiting current type gas sensor according to the fourth embodiment is arranged on a gas diffusion path MP which is a gas introduction path for taking in the gas GS to be measured, as schematically shown in FIG. 29(d). Porous oxide film (porous film) 71, a lower electrode 28D arranged on the porous oxide film 71, a solid electrolyte layer 30 arranged so as to cover the porous oxide film 71 and the lower electrode 28D, and a lower electrode 28D, and the upper electrode 28U arranged on the solid electrolyte layer 30 facing 28D.

The sensor portion SP of the limiting current type gas sensor according to the fifth embodiment has a gas introduction path (not shown) for taking in the gas GS to be measured and a gas introduction path, as schematically shown in FIG. 29(e). The gas intake part 303 including the columnar film (columnar part) arranged, the lower electrode 28D arranged on the gas intake part 303, and the gas intake part 303 and the lower electrode 28D were arranged so as to be covered. The solid electrolyte layer 30 and the upper electrode 28U arranged on the solid electrolyte layer 30 facing the lower electrode 28D are provided.

The sensor portion SP of the limiting current type gas sensor according to the sixth embodiment is, as schematically shown in FIG. 29(f), on a gas introduction path (not shown) for taking in the measured gas GS and on the gas introduction path. A gas intake part 305 composed of an arranged porous film (columnar part), a lower electrode 28D arranged on the gas intake part 305, and a gas intake part 305 and a lower electrode 28D are arranged so as to be covered. The solid electrolyte layer 30 and the upper electrode 28U arranged on the solid electrolyte layer 30 facing the lower electrode 28D.

Hereinafter, an application example to the limiting current type gas sensor according to each embodiment will be described more specifically.

(First embodiment)
(Schematic configuration)
The schematic plane pattern configuration of the limiting current type gas sensor 1A according to the first embodiment is represented as shown in FIG. 1A, and the schematic diagram of the gas sensor 1A along the line IA-IA in FIG. The cross-sectional structure is represented as shown in FIG.

First, the outline of the configuration will be described. A limiting current type gas sensor 1A according to the first embodiment has a MEMS (Micro Electro Mechanical Systems) beam structure as shown in FIGS. 1(a) and 1(b). The micro heater MH, the sensor portion SP, the heater connecting portions 21 and 22, the terminal electrode connecting portions 23 and 24, the opening portion 45, and the like, which are provided on the provided substrate (for example, Si) 12, are provided.

The sensor portion SP includes a porous oxide film (porous film) 51 arranged via a SiN film 201 on a substrate 12 corresponding to an active region (described later), and a lower electrode arranged on the porous oxide film 51. 28D, a solid electrolyte layer 30 arranged so as to cover the porous oxide film 51 and the lower electrode 28D, and an upper electrode (for example, a Pt film) 28U arranged on the solid electrolyte layer 30 facing the lower electrode 28D. Prepare The porous oxide film 51 functions as a gas introduction path and has a gas intake port 51G.

The lower electrode 28D can be formed by a Pt/Ti electrode, which is a laminated film of a Pt film and a Ti film, with a thickness of, for example, about 100 nm. The Ti film is used to make the bond with the porous oxide film 51 dense and to strengthen it.

The solid electrolyte layer 30 can be formed of a YSZ film having a thickness of about 1 μm. This is because if it is thin, the upper and lower electrodes 28U and 28D are electrically connected. For example, the solid electrolyte layer 30 is arranged so as to cover the periphery of the lower electrode 28D and prevents conduction between the upper and lower electrodes 28U and 28D.

In plan view, since the active region of the substrate 12 has a rectangular shape, the porous oxide film 51, the lower electrode 28D, the solid electrolyte layer 30, and the upper electrode 28U of the sensor portion SP are all rectangular. May be included, or other shapes may be used. Further, it is desirable that the porous oxide film 51, the lower electrode 28D, the solid electrolyte layer 30, and the upper electrode 28U that form the sensor portion SP are arranged at the center of the sensor surface without eccentricity, but on the microheater MH. If so, they may be arranged in an eccentric state.

In a plan view, the heater connection portions 21 and 22 are arranged so as to face each other in the lateral direction in the drawing (in-plane direction along the cross section of FIG. 1B) with the sensor portion SP as the center. The heater connecting portion 21 has a connecting pad 211, a wiring portion 212, and a terminal portion 213, and the heater connecting portion 22 has a connecting pad 221, a wiring portion 222, and a terminal portion 223. The terminal electrode connecting portions 23 and 24 are arranged so as to be orthogonal to the heater connecting portions 21 and 22 with the sensor portion SP as a center and to face each other in the vertical direction in the drawing. The terminal electrode connection part 23 has a connection pad (detection terminal) 231 and a wiring part 232, and the terminal electrode connection part 24 has a connection pad (detection terminal) 241 and a wiring part 242.

The heater connecting portions 21 and 22 and the terminal electrode connecting portions 23 and 24 are provided on the SiN film 201, and are formed by, for example, a laminated film (Pt/Ti laminated film) of a Ti film having a thickness of 20 nm and a Pt film having a thickness of 100 nm. can do.

The terminal portions 213 and 223 of the heater connection portions 21 and 22 are connected to the micro-heater MH, and the wiring portion 232 of the terminal electrode connection portion 23 extends in the direction of the sensor portion SP to extend the extension end 28D1 of the lower electrode 28D. The wiring portion 242 of the terminal electrode connecting portion 24 is connected to the extending end 28U1 of the upper electrode 28U by extending in the direction of the sensor portion SP.

Here, the connection pads 231 and 241 of the terminal electrode connection portions 23 and 24 are connected to a detection circuit that detects a predetermined gas concentration in the measured gas by a limiting current method. As will be described later in detail, as shown in FIG. 106, the detection circuit 107 is limited by supplying the detection voltage V to the upper electrode 105U and the porous electrode (porous electrode) 105D of the solid electrolyte layer 106. The oxygen concentration can be detected based on the electric current. Further, the detection circuit 107 can detect the water vapor concentration based on the limiting current.

The terminal portions 213 and 223 of the heater connection portions 21 and 22 are covered with the SiN film 26 arranged so as to surround the outer peripheral portion of the sensor portion SP in a plan view. The SiO ₂ film 25 is embedded between the SiN film 26 and the terminal portions 213 and 223.

The opening 45 is outside the SiN film 26 in plan view, and the active region and the non-active region (corresponding to each corner of the substrate 12 excluding the heater connecting portions 21 and 22 and the terminal electrode connecting portions 23 and 24 ( Each of them is arranged in an L-shape at the boundary with (described later). The opening 45 is opened at the time of forming the cavity C of the boat-shaped structure, and may have a shape other than the L-shape, such as a straight shape (I-shape). good.

The microheater MH is provided between the first and second insulating layers (eg, SiO ₂ film) 181 and 182 that form the insulating layer 18. The microheater MH is, for example, a polysilicon layer (polysilicon heater) having a thickness of 0.2 μm, and has a high concentration of B (boron) that is a p-type impurity (for example, 4×10 ¹⁹ cm 2) by an ion implantation method. ^-3 ) to have a resistance value of about 300Ω. The thermal conductivity of the micro heater MH is desirably about 80 W/mK, for example.

In the limiting current type gas sensor 1A according to the first embodiment, the microheater MH is arranged, for example, in a rectangular shape below the solid electrolyte layer 30, and has a larger area than the solid electrolyte layer 30. It is desirable to be formed.

Here, the micro-heater MH is for heating the solid electrolyte layer 30, and, for example, the terminal portions 213 and 223 formed in the openings 37 opened in the second insulating layer 201 and the second insulating film 182. From the above, a predetermined voltage applied to the connecting pads 211 and 221 is supplied via the wiring portions 212 and 222.

The microheater MH is not limited to being arranged between the first and second insulating layers 181 and 182 on the substrate 12, but may be arranged below the substrate 12 or embedded inside the substrate 12. It may be. Alternatively, a structure in which a laminated film (not shown) of a SiO ₂ film/SiN film including a micro heater MH made of polysilicon may be formed on the surface of the substrate 12.

The micro heater MH can also be formed by a Pt heater or the like formed by printing.

Although it depends on the size (scale) of the gas sensor 1A, not only the micro heater MH but also a nano size heater can be applied as long as it has a larger area than the sensor portion SP.

In the cross-sectional structure of FIG. 1B with the sensor portion SP facing upward, a boat-shaped cavity C connected to the opening 45 is formed in the substrate 12 below the microheater MH. An insulating layer 16 made of a SiON film is provided at an interface between the cavity C and the first insulating layer 181 corresponding to the cavity C, and an interface between the substrate 12 and the first insulating layer 181 corresponding to an inactive region of the substrate 12 is provided. An insulating layer 16 and an insulating layer 14 made of a SiO ₂ film are provided on the substrate.

The substrate 12 having the MEMS beam structure has a thickness of, for example, about 10 μm and is formed such that the cavity C is substantially larger than the micro heater MH to prevent heat from escaping from the membrane. ing. The planar shape of the cavity C is not particularly limited, but it is desirable to form a rectangular shape like the sensor portion SP and the micro heater MH.

Note that the MEMS beam structure may be formed to have an open type structure (see FIG. 18) in which the substrate 12 is arranged so as to surround the sensor portion SP in plan view. Further, the cavity portion C may have a structure formed by bonding the substrates 12 together. Therefore, the substrate 12 is not limited to Si, but epoxy resin, ceramics, or the like can be used.

That is, the limiting current type gas sensor 1A according to the first embodiment includes the substrate 12, the heater MH arranged on the substrate 12 via the first insulating layer 181, and the second insulating layer 182 on the heater MH. A gas introduction path 51 that is arranged via the gas introduction path 51 to take in the gas to be measured, a lower electrode 28D arranged on the gas introduction path 51, a solid electrolyte layer 30 arranged on the lower electrode 28D, and a solid electrolyte layer 30 on the solid electrolyte layer 30. The upper electrode 28U is disposed on the surface facing the lower electrode 28D, and the cavity 12 is formed on the substrate 12 so as to be substantially larger than the heater MH.

In short, the limiting current type gas sensor 1A according to the first embodiment has a substrate 12 having a MEMS beam structure in which the cavity C has a boat-shaped structure, as shown in FIGS. 1(a) and 1(b). Then, along with the heating of the micro heater MH, the gas to be measured (for example, O ₂ gas) is introduced into the solid electrolyte layer 30 of the sensor portion SP via the gas intake port 51G of the porous oxide film 51. Is configured. That is, the gas to be measured is taken into the porous oxide film 51 from the gas intake port 51G, introduced into the solid electrolyte layer 30 through the lower electrode 28D, and then diffused into the solid electrolyte layer 30 by heating. It The introduction of the gas to be measured into the solid electrolyte layer 30 may be accompanied by a suction operation.

As described above, the limiting current type gas sensor 1A according to the first embodiment is accompanied by the heating of the micro-heater MH, but by using the beam structure (boat structure) having the MEMS structure as a basic structure, the sensor portion SP The heat capacity of the sensor is reduced to improve the sensor sensitivity.

The gas inlet 51G can be integrally formed of the same material as the porous oxide film 51 so as to extend in the direction along the terminal electrode connecting portion 23 in a plan view, and its volume and thickness, Alternatively, it is possible to change the intake amount of the gas to be measured by adjusting the width and the like. The gas intake port 51G can be formed separately from the porous oxide film 51, and in a plan view, other than the direction along the terminal electrode connecting portion 23, for example, the direction along the terminal electrode connecting portion 23 or You may arrange|position so that it may extend in the direction which follows the heater connection parts 21*22.

Further, in the limiting current type gas sensor 1A shown in FIG. 1A, the heater connecting portions 21 and 22 are arranged in the horizontal direction, and the terminal electrode connecting portion 23 is arranged at the lower end side in the vertical direction so as to be orthogonal to this. Although the terminal electrode connecting portions 24 are respectively arranged on the upper end side in the vertical direction, the positions of the terminal electrode connecting portions 23 and 24 can be exchanged, and the positions of the heater connecting portions 21 and 22 can be exchanged.

Next, an example of a method of forming a porous electrode will be described.

The method of forming the porous electrode is expressed as shown in FIGS. 2(a) to 2(c). The porous electrode is composed of, for example, a porous oxide film 51 which is a nano-sized porous film, and a lower electrode 28D which is a Pt/Ti laminated film (Pt/Ti electrode) formed on the porous oxide film 51. To be done.

To form the porous electrode, as shown in FIG. 2A, for example, a YSZ containing 70 vol% to 50 vol% YSZ particles 511 and 30 vol% to 50 vol% SiO ₂ 512 is formed on the substrate 120 by a sputtering method. A SiO ₂ film (porous film) 510 is formed.

Next, as shown in FIG. 2B, for example, by hydrofluoric acid (HF) etching treatment, only the SiO ₂ 512 in the YSZ-SiO ₂ film 510 is removed, and the porous oxide film 51 in which only the YSZ particles 511 remain is removed. Form.

After that, as shown in FIG. 2C, a Pt/Ti laminated film is formed on the YSZ particles 511 in the porous oxide film 51 by, for example, a sputtering method to include the porous oxide film 51 and the lower electrode 28D. Forming a porous electrode.

The porous oxide film 51 can be easily formed by sputtering the YSZ-SiO ₂ film 510 that is an oxide and performing an etching process. In particular, it has high thermal stability, can form holes with a diameter of about 10 nm, and is excellent in gas throttle performance.

Note that the step of forming the porous oxide film 51 is not limited to the above example, and for example, a sol-coated porous formation film containing Al ₂ O ₃ or SiO ₂ or YSZ and spin-coated is baked. It can also be formed by

The porous oxide film 51 is, for example, a porous film (Al ₂ O ₃ —SiO ₂ film) containing 70 vol% Al ₂ O ₃ and 30 vol% SiO ₂ , or 70 vol% YSZ and 30 vol% Al _2. O ₃ and also by the porous formed film (YSZ-Al ₂ O ₃ film) to HF etching process comprising, it can be formed similarly.

The porous electrode may be a porous Pt film or a porous Pt/Ti film.

Here, the temperature characteristics of the porous film will be described.

In the case of a nano-sized porous film, the current value is proportional to the temperature T to the -a power (current value ∝T ^-a ). The a value can be adjusted by the porous film structure. That is, the smaller the pores of the porous film, the larger the value a.

Since the porous oxide film 51 is formed of a porous film having such temperature characteristics, it has temperature dependency and the current value decreases as the temperature rises. That is, as shown in FIG. 3, in the porous oxide film 51, as the temperature increases, the distance Lnm (for example, 100 nm) between the central portions of the holes hardly changes, but the distance between both ends changes from HW to HS. .. When the distance between both ends becomes narrow (HW>HS), the flow rate of the gas passing therethrough is limited and decreases, and as a result, the current value decreases (current value ∝gas flow rate).

The relationship between the temperature T and the saturation current Isat in the porous oxide film 51 is expressed as shown in FIG. When the temperature T is T1° C. (for example, 400° C.), T2° C. (for example, 450° C.), T3° C. (for example, 500° C.), and T4° C. (for example, 700° C.) Comparing with, the saturation current Isat decreases as the temperature T increases.

On the other hand, when the micro flow path is used as a gas introduction path, in Knudsen diffusion, the current value is proportional to the temperature T to the power of 0.5 (current value ∝ T ^0.5 ), and in normal diffusion, the current value is Is proportional to the temperature T to the power of 0.75 (current value ∝T ^0.75 ). That is, in the case of the micro flow path, the flow rate of the passing gas increases as the temperature becomes higher, and the current value accordingly increases.

Therefore, in the limiting current type gas sensor 1A according to the first embodiment which employs the porous oxide film 51, the sensor characteristics can be improved by reducing the heat capacity by the cavity portion C.

(Production method)
Next, a method of manufacturing the limiting current type gas sensor 1A according to the first embodiment shown in FIGS. 1A and 1B will be described.

Prior to the description of the manufacturing method, first, a wafer 100 applied to manufacture the limiting current type gas sensor 1A according to the first embodiment will be briefly described.

A schematic plane configuration of the wafer 100 applied to manufacture the limiting current type gas sensor 1A according to the first embodiment is represented as shown in FIG. 5A, and the IA0-IA0 line of FIG. A schematic cross-sectional structure of the wafer 100 along is shown in FIG. 5B.

As shown in FIGS. 5A and 5B, the wafer 100 has a plurality of element regions 104 defined by the element isolation regions 102, and the element isolation regions 102 are formed at the end of the manufacturing process of the gas sensor 1A. It is diced along. As a result, the wafer 100 is divided for each gas sensor 1A.

In FIG. 5B, WC1 indicates the width in the cross-sectional direction of the formation area CA of the cavity portion C, WS1 indicates the width in the cross-sectional direction of the formation area SA of the sensor portion SP, and AA1 indicates the active area. A cross-sectional width of AA is shown, and CA1 is a cross-sectional width of the element region 104. A portion of the element region 104 excluding the active region AA becomes a non-active region.

In the description of the manufacturing method, Si is silicon as a semiconductor material, Pt is platinum as a porous material, Ti is titanium as an electrode material, and YSZ is solid. Yttria-Stabilized Zirconia as an electrolyte material.

Here, in the method of manufacturing the limiting current type gas sensor 1A according to the first embodiment, the step of forming the heater MH on the substrate 12 via the first insulating layer 181 and the second insulating layer 182 on the heater MH. Forming a gas introduction path 51 having a gas intake port 51G for taking in the gas to be measured, a step of forming a lower electrode 28D on the gas introduction path 51, and a solid state on the lower electrode 28D. The step of forming the electrolyte layer 30, the step of forming the upper electrode 28U on the surface of the solid electrolyte layer 30 facing the lower electrode 28D, and the formation of the cavity portion C substantially larger than the heater MH on the substrate 12. And a step of performing.

That is, a method of manufacturing the limiting current type gas sensor 1A according to the first embodiment shown in FIGS. 1A and 1B is shown in FIGS.

Originally, a plurality of gas sensors are manufactured collectively on the wafer 100, but for convenience of description, here, a case where the limiting current type gas sensor 1A is formed on the substrate 12 will be described.

(A) First, as shown in FIGS. 6A and 6B, for example, the element isolation regions 102 formed in a lattice shape along the dicing line on the surface of the Si wafer 100 having a thickness of 10 μm. The insulating film is removed to form a surface 12a corresponding to the active area AA and a surface 12b corresponding to the other non-active area on the substrate 12. The insulating film in the element isolation region 102 is removed by, for example, selective etching using a LOCOS (Local Oxidation of Silicon) technique. Due to the shape of the element isolation region 102, the upper surface of the substrate 12 has a shape in which the inclined surface 12c is provided in the peripheral portion between the surface 12a corresponding to the active area AA and the surface 12b corresponding to the inactive area.

(B) Next, as shown in FIGS. 7(a) and 7(b), after forming a SiO ₂ film of about 0.5 μm thickness on the upper surface of the substrate 12 by a CVD (Chemical Vapor Deposition) method or the like, By selectively etching and removing the SiO ₂ film on the surface 12c and the surface 12a corresponding to the active area AA, the insulating layer 14 made of the SiO ₂ film is formed only on the surface 12b corresponding to the non-active area. Form.

Then, the insulating layer 16 made of a SiON film having a thickness of about 0.5 μm is uniformly formed on the upper surface of the substrate 12 by a plasma CVD (P-CVD) method or the like.

The insulating layer 14 may be formed by leaving a part of the insulating film in the element isolation region 102.

(C) Next, as shown in FIGS. 8A and 8B, a first insulating layer 181 made of a SiO ₂ film having a thickness of about 0.5 μm is formed on the insulating layer 16 by a CVD method or the like. After that, a polysilicon layer having a thickness of about 0.2 μm is further formed on the upper surface by a low pressure CVD method or the like, and the polysilicon layer is patterned by etching or the like to form a micro heater MH having a tapered portion Ht. Form.

The micro-heater MH is formed on the surface 12a corresponding to the active area AA, for example, in a size of about 300 μm square. Further, the microheater MH has a resistance value of 300Ω because B is implanted at a high concentration by an ion implantation (I/I) method.

(D) Next, as shown in FIGS. 9A and 9B, a SiON film (second insulating layer) 182 having a thickness of about 0.5 μm is formed on the entire surface by P-CVD or the like.

(E) Next, as shown in FIGS. 10A and 10B, after forming a SiN film 201 having a thickness of about 0.5 μm on the entire surface by a P-CVD method or the like, the SiN film 201 and the For selectively etching the second insulating layer 182 to form the terminal portions 213 and 223 of the heater connection portions 21 and 22 connected to the micro heater MH, for example, near the end portion of the surface 12a corresponding to the active area AA. The opening 37 is opened.

(F) Next, as shown in FIGS. 11A and 11B, the Pt/Ti laminated film is deposited by sputtering or the like so as to have a thickness of about 0.5 μm, and the Pt/Ti laminated film is deposited. The film is patterned by etching to form the connecting pads 211 and 221, the heater connecting portions 21 and 22, the wiring portions 212 and 222, and the terminal portions 213 and 223.

At the same time, the Pt/Ti laminated film is patterned by etching to form the connecting pads 231 and 241 and the wiring portions 232 and 241 of the terminal electrode connecting portions 23 and 24 in the direction orthogonal to the heater connecting portions 21 and 22.

(G) Next, as shown in FIGS. 12A and 12B, after the SiO ₂ film 25 and the SiN film 26 are formed by the CVD method or the like so as to fill the inside of the opening 37. For example, the SiO ₂ film 25 and the SiN film 26 are selectively etched and patterned so as to surround the sensor portion SP.

(H) Next, as shown in FIGS. 13A and 13B, a porous oxide film 51 and a gas inlet 51G for taking in the gas to be measured are formed by sputtering and etching.

(I) Next, as shown in FIGS. 14A and 14B, a lower electrode 28D made of a Pt/Ti laminated film having a thickness of about 100 nm is formed on the porous oxide film 51 by a sputtering method or the like, and The extension end 28D1 of the lower electrode 28D is connected to the wiring portion 232 of the terminal electrode connecting portion 23.

(J) Then, as shown in FIGS. 15(a) and 15(b), a solid electrolyte layer 30 made of a YSZ film is sputtered to a thickness of about 1 μm so as to cover the porous oxide film 51 and the lower electrode 28D. Formed with a thickness of. The solid electrolyte layer 30 entirely covers the periphery of the porous oxide film 51 and the lower electrode 28D except for the extending end 28a of the lower electrode 28D.

(K) Next, as shown in FIGS. 16A and 16B, as the upper electrode 28U, a Pt film having a thickness of about 100 nm is formed on the surface of the solid electrolyte layer 30 facing the lower electrode 28D by the sputtering method. The extending end 28U1 of the upper electrode 28U is connected to the wiring portion 232 of the terminal electrode connecting portion 24.

(L) Next, as shown in FIGS. 17A and 17B, as a MEMS beam structure, a protective SiO ₂ film having an opening 431 for forming the cavity C of the boat-shaped structure (etching) is formed. A mask 43 is formed on the entire surface (deposition+patterning). Then, using the protective SiO ₂ film 43 as a mask, the substrate 12 of the surface 12a corresponding to the active area AA is selectively deep-etched to form a substrate 12 of the MEMS beam structure connected to the opening 45, which is about 400 μm square. The cavity C having the boat-shaped structure is formed.

Finally, by removing the protective SiO ₂ film 43 by etching, the limiting current type gas sensor 1A according to the first embodiment having the configuration shown in FIGS. 1A and 1B is obtained. To be

As described above, in the above-described limiting current type gas sensor 1A, the cavity portion C is formed so as to be substantially larger than the micro-heater MH, so that the heat capacity is reduced and the heating by the micro-heater MH is performed around the sensor. It is possible to easily suppress the unnecessary expansion.

In particular, since the porous oxide film 51 has high thermal stability, it has high gas throttling performance. Moreover, the amount of gas to be measured can be easily controlled only by adjusting the size of the gas intake port 51G, and the limiting current type gas sensor 1A having excellent sensor characteristics can be obtained.

Further, since the porous oxide film 51 is adopted, the gas diffusion path MP is not required, so that the manufacturing is easy and no special equipment such as a high pressure sputtering apparatus is required, so that the manufacturing cost can be reduced. ..

Therefore, according to the limiting current type gas sensor according to the first embodiment, the sensor characteristics can be easily improved, and the manufacturing is easy and the manufacturing cost can be reduced.

(First Modification of First Embodiment)
The schematic plane pattern configuration of the limiting current type gas sensor 1B according to the first modified example of the first embodiment is represented as shown in FIG. 18(a), and is along the line IB-IB in FIG. 18(a). , A schematic cross-sectional structure of the gas sensor 1B formed in the MEMS beam structure is shown in FIG. 18(b).

That is, the limiting current type gas sensor 1B according to the first modified example of the first embodiment has a cavity portion having an open structure in which the substrate 12 is arranged so as to surround the sensor portion SP in a plan view as a MEMS beam structure. It may be formed to have C. The cavity C of the open type structure can be easily formed by, for example, forming the cavity C of the boat type structure and then deeply etching the substrate 12 from the back surface side.

The other configurations are basically the same as those of the limiting current type gas sensor 1A, and thus the duplicate description will be omitted.

With such a configuration, the limiting-current type gas sensor 1B having excellent sensor characteristics can be obtained as in the limiting-current type gas sensor 1A described above.

(Second Modification of First Embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 1C according to the second modified example of the first embodiment is represented as shown in FIG. 19(a), and is along the IC-IC line in FIG. 19(a). , A schematic cross-sectional structure of the gas sensor 1C formed in the MEMS beam structure is shown in FIG. 19(b).

That is, the limiting current type gas sensor 1C according to the second modified example of the first embodiment is configured to increase the thermal conductivity inside the in-plane membrane so as to make the temperature uniform.

More specifically, for example, in the limiting current type gas sensor 1A including the cavity portion C having the boat structure shown in FIGS. 1A and 1B, the thermal conductivity is high below the micro heater MH. An undoped or low-doped polysilicon layer (for example, 140 W/mK) 300 is inserted in the limiting current type gas sensor 1C according to the second modification of the first embodiment.

In the limiting current type gas sensor 1C according to the second modified example of the first embodiment, the low-concentration doped polysilicon layer 300 has a low impurity ion such as B, As (arsenic) or P (phosphorus) in the polysilicon layer. It is formed by doping or undoping to a concentration (for example, 10 ¹⁸ /cm ³ or less).

Here, an example of a method of forming the lightly doped polysilicon layer 300 will be described with reference to FIGS. The formation of the low-concentration doped polysilicon layer 300 illustrated is, for example, substantially in accordance with the steps shown in FIGS. 8A and 8B.

First, as shown in FIG. 20A, a polysilicon layer 301 having a thickness of about 0.6 μm is formed on the upper surface of the first insulating layer 181, for example, by the low pressure CVD method.

Next, as shown in FIG. 20B, by controlling the acceleration energy and the dose amount when implanting B, for example, a low concentration layer LC having a thickness of 0.4 μm is formed on the lower side of the polysilicon layer 301. A high concentration layer HC having a thickness of 0.2 μm is formed on the upper layer side.

Then, as shown in FIG. 20C, the polysilicon layer 301 is patterned by etching or the like to form a micro heater MH made of a high concentration layer HC having a heating area L1 and a low concentration of the same size as the heating area L1. A lightly doped polysilicon layer 300 of layer LC is formed. By changing the etching conditions, it is possible to form only the outer peripheral portion of the microheater MH into a tapered shape.

The lightly doped polysilicon layer 300 may be formed in various sizes and shapes as shown in FIGS. 21(a) to 21(e) and 22(a) to 22(e). it can.

For example, as shown in FIG. 21A, the lightly doped polysilicon layer 300 may have the same size as the micro-heater MH, and the outer peripheral portion thereof may be formed in a tapered shape, or FIG. As shown in, each outer peripheral portion may be formed in a vertical shape.

The lightly doped polysilicon layer 300 may be formed larger than the micro heater MH as shown in FIG. 21C, or smaller than the micro heater MH as shown in FIG. 21D. You may form.

Further, the low-concentration doped polysilicon layer 300 may be formed in such a shape that the micro-heater MH is embedded in the surface so that the respective upper surfaces are flush with each other, as shown in FIG. As shown in 22(a), the micro heater MH may be formed so as to be housed inside.

The lightly doped polysilicon layer 300 may be formed so that a part of the microheater MH housed inside is exposed as shown in FIG. 22B, or as shown in FIG. 22C. As described above, the entire micro-heater MH housed inside may be exposed.

Further, the low-concentration doped polysilicon layer 300 may be formed so as to be stacked on the upper and lower surfaces of the micro heater MH as shown in FIG. 22(d), or as shown in FIG. 22(e). It may be formed so as to embed the lower half of the heater MH.

The low-concentration doped polysilicon layer 300 is formed to have a thickness of, for example, about 0.6 μm so that the thermal conductivity thereof is 6.25 times that in the case where the low-concentration doped polysilicon layer 300 is not provided. it can.

With such a configuration, since the low-concentration doped polysilicon layer 300 has a high resistance, the limiting current type gas sensor 1C having a better temperature characteristic and an excellent sensor characteristic without affecting the heater characteristic of the micro-heater MH. Can be

(Third Modification of First Embodiment)
The schematic plane pattern configuration of the limiting current type gas sensor 1D according to the third modified example of the first embodiment is represented as shown in FIG. 23(a), and is along the ID-ID line of FIG. 23(a). , A schematic cross-sectional structure of the gas sensor 1D formed in the MEMS beam structure is shown in FIG. 23(b).

That is, in the structure of the limiting current type gas sensor 1B including the cavity C of the open type structure shown in FIGS. 18A and 18B, a low concentration doped poly having a high thermal conductivity is provided below the micro heater MH. The silicon layer 300 is inserted in the limiting current type gas sensor 1D according to the third modification of the first embodiment.

Also with such a configuration, it is possible to increase the thermal conductivity inside the in-plane membrane and to make the temperature uniform, so that the limiting current type gas sensor 1D has better temperature characteristics and excellent sensor characteristics. be able to.

(Fourth Modification of First Embodiment)
The schematic plane pattern configuration of the limiting current type gas sensor 1E according to the fourth modified example of the first embodiment is represented as shown in FIG. 24(a), and is along the line IE-IE in FIG. 24(a). The schematic cross-sectional structure of the gas sensor 1E formed in the MEMS beam structure is shown in FIG.

The limiting current type gas sensor 1E according to the fourth modified example of the first embodiment corresponds to each corner of the substrate 12 in plan view, as shown in FIGS. 24(a) and 24(b). The opening 45 to be arranged has an I shape. The openings 45 are arranged so that their respective longitudinal directions are along the respective sides of the substrate 12, and their respective lateral directions are also arranged along one of the two sides in contact with the respective sides of the substrate 12. To be done. Then, the gas sensor 1E has porous oxidation on the frame portion 121 defined by the opening 45 on the substrate 12, and the central portion 33 supported by the arm portion 31 between the openings 45 with respect to the frame portion 121. The sensor portion SP including the film 51, the lower electrode 28D, the solid electrolyte layer 30, and the upper electrode 28U, the SiN film 26, and the like are arranged.

Further, in the gas sensor 1E, the micro heater MH and the lightly doped polysilicon layer 300 are provided inside the in-plane membrane. Further, the substrate 12 having the MEMS beam structure has an open structure in which the cavity portion C is formed corresponding to the in-plane membrane.

The central portion 33 and the arm portion 31 are respectively provided along the longitudinal direction of the opening 45 in a plan view, and one end of each side of the central portion 33 is supported by the arm portion 31. Therefore, the connection portion of the arm portion 31 with the frame portion 121 and the connection portion with the central portion 33 can be connected more firmly against deformation due to stress.

Here, a micro-heater (4×10 ¹⁹ cm ⁻³ ) MH composed of a high-concentration layer HC having a thickness of 0.2 μm and a low-concentration doped polysilicon layer (1×10 ¹⁸ cm composed of a low-concentration layer LC having a thickness of 0.4 μm). ^-3 or less) 300 and the temperature uniformity of the limiting current type gas sensor 1E will be described with respect to the result of simulation.

The simulation result of the limiting current type gas sensor 1E is shown as shown in FIG. 25(a), and for comparison, the limit of the comparative example including only the micro heater MH made of the high concentration layer HC of 0.2 μm thickness. The simulation result of the current type gas sensor 1F is expressed as shown in FIG. However, the simplification of the actual gas sensors 1E and 1F was used for the simulation.

As is clear from FIGS. 25A and 25B, the provision of the low-concentration doped polysilicon layer 300 allows the limiting current type gas sensor 1E to have a more uniform temperature distribution in the surface than the limiting current type gas sensor 1F. I was able to improve my sex.

FIG. 26 shows the relationship between the impurity concentrations of B, As, and P in the lightly doped polysilicon layer 300 and the thermal conductivity.

As shown in FIG. 26, in the case of any impurity, for example, by suppressing (or undoping) the doping concentration to 10 ¹⁸ /cm ³ or less, a low-concentration doped poly with a thermal conductivity of about 140 W/mK is used. The silicon layer 300 can be formed.

FIG. 27 shows the temperature distribution in the plane of the limiting current type gas sensor 1E and the temperature distribution in the plane of the limiting current type gas sensor 1F for comparison.

FIG. 28 shows the relationship between the thickness of the low-concentration layer LC used for forming the low-concentration doped polysilicon layer 300 and the in-plane temperature distribution.

As apparent from FIGS. 27 and 28, when the thickness of the low-concentration doped polysilicon layer 300 provided in the limiting current type gas sensor 1F is set to, for example, about 0.4 μm, the in-plane temperature distribution is set to about 7%. It has been found that it can be improved over the limiting current type gas sensor 1F.

(Second embodiment)
(Schematic configuration)
A schematic plane pattern configuration of the limiting current type gas sensor 2A according to the second embodiment is represented as shown in FIG. 30(a), and has a MEMS beam structure along the line IIA-IIA in FIG. 30(a). A schematic cross-sectional structure of the gas sensor 2A provided is shown in FIG. 30(b). The limiting current type gas sensor 2A according to the second embodiment is configured such that the porous oxide film 51 of the limiting current type gas sensor 1A described above is changed to a porous Pt film (porous film) 61. Since the other configurations are basically the same, redundant description will be omitted as much as possible, and the configuration of a characteristic part will be described in more detail.

That is, as shown in FIGS. 30(a) and 30(b), the limiting current type gas sensor 2A according to the second embodiment has a MEMS beam structure substrate (for example, Si having a cavity C having a ship structure). ) 12, a porous Pt film 61 as a gas introduction path arranged in the active region AA on the substrate 12, a lower electrode (Pt/Ti laminated film) 28D arranged on the porous Pt film 61, and a porous Pt. A solid electrolyte layer (YSZ film) 30 arranged so as to cover the membrane 61 and the lower electrode 28D, and an upper electrode (for example, Pt film) 28U arranged on the solid electrolyte layer 30 facing the lower electrode 28D. ..

In addition, as shown in FIGS. 30A and 30B, the limiting current type gas sensor 2A includes first and second insulating layers (eg, SiO ₂ films) 181, 182 on a rectangular substrate 12. The insulating layer 18 made of, and accompanying the heating of the micro heater MH, the gas to be measured (for example, O ₂ gas) is passed through the gas inlet 61G of the porous Pt film 61 arranged on the SiN film 201. Is introduced into the solid electrolyte layer 30 of the sensor portion SP. That is, the gas to be measured is taken into the porous Pt film 61 through the gas intake port 61G, which replaces the porous oxide film 51, is introduced into the solid electrolyte layer 30 through the lower electrode 28D, and is then solidified by heating. It is diffused in the electrolyte layer 30. The introduction of the gas to be measured into the solid electrolyte layer 30 may be accompanied by a suction operation.

The gas inlet 61G can be integrally formed of the same material as the porous Pt film 61 so as to extend in the direction along the terminal electrode connecting portion 23 in a plan view, and its volume and thickness, Alternatively, it is possible to change the intake amount of the gas to be measured by adjusting the width and the like. The gas inlet 61G can be formed separately from the porous Pt film 61, and in plan view, other than the direction along the terminal electrode connecting portion 23, for example, the direction along the terminal electrode connecting portion 23 or You may arrange|position so that it may extend in the direction which follows the heater connection parts 21*22.

In plan view, the porous Pt film 61, the lower electrode 28D, the solid electrolyte layer 30, and the upper electrode 28U of the sensor portion SP are preferably arranged at the center of the sensor surface without any eccentricity. If it is above, it may be arranged in an eccentric state.

The porous Pt film 61 may be formed by sputtering and etching instead of the process of forming the porous oxide film 51 when manufacturing the limiting current type gas sensor 1A described above.

As described above, also in the case of the limiting current type gas sensor 2A to which the porous Pt film 61 is applied, as in the case of the limiting current type gas sensor 1A described above, the cavity portion C is substantially larger than the micro heater MH. By forming it in the above manner, it is possible to reduce the heat capacity and to easily prevent the heating by the micro heater MH from being unnecessarily spread to the periphery of the sensor.

In particular, since the porous Pt film 61 has high thermal stability, it has high gas squeezing performance. In addition, the amount of gas to be measured can be easily controlled only by adjusting the size of the gas inlet 61G, and the limiting current type gas sensor 2A having excellent sensor characteristics can be obtained.

Further, since the porous Pt film 61 is adopted, the gas diffusion path MP is not required, so that the manufacturing is easy.

Particularly, in the limiting current type gas sensor 2A, since the porous Pt film 61 can also be used as the lower electrode 28D, the Pt/Ti laminated film can be omitted.

Therefore, according to the limiting current type gas sensor according to the second embodiment, the sensor characteristics can be easily improved, and furthermore, the gas sensor can be easily manufactured.

(First Modification of Second Embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 2B according to the first modified example of the second embodiment is expressed as shown in FIG. 31(a), and is along the line IIB-IIB in FIG. 31(a). , A schematic cross-sectional structure of the gas sensor 2B formed in the MEMS beam structure is shown in FIG. 31(b).

That is, the limiting current type gas sensor 2B according to the first modified example of the second embodiment has a cavity portion having an open structure in which the substrate 12 is arranged so as to surround the sensor portion SP in plan view as a MEMS beam structure. It may be formed to have C. The cavity C of the open type structure can be easily formed by, for example, forming the cavity C of the boat type structure and then deeply etching the substrate 12 from the back surface side.

The other configurations are basically the same as those of the limiting current type gas sensor 2A, and thus the duplicate description will be omitted.

Even with such a configuration, the limiting current type gas sensor 2B capable of easily improving the sensor characteristics can be obtained as in the limiting current type gas sensor 2A described above.

(Second Modification of Second Embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 2C according to the second modified example of the second embodiment is represented as shown in FIG. 32(a), and is along the line IIC-IIC in FIG. 32(a). , A schematic cross-sectional structure of the gas sensor 2C formed in the MEMS beam structure is shown in FIG. 32(b).

That is, the limiting current type gas sensor 2C according to the second modified example of the second embodiment is configured to increase the thermal conductivity inside the in-plane membrane so as to make the temperature uniform.

More specifically, for example, in the limiting-current type gas sensor 2A including the cavity C having the boat-shaped structure shown in FIGS. 30A and 30B, the thermal conductivity is high below the micro heater MH. The low-concentration doped polysilicon layer (for example, about 140 W/mK) 300 is inserted in the limiting current type gas sensor 2C according to the second modification of the second embodiment.

According to such a configuration, it is possible to obtain the limiting current type gas sensor 2C having better temperature characteristics and excellent sensor characteristics.

(Third Modification of Second Embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 2D according to the third modified example of the second embodiment is expressed as shown in FIG. 33(a), and is along the IID-IID line of FIG. 33(a). A schematic cross-sectional structure of the gas sensor 2D formed in the MEMS beam structure is shown in FIG. 33(b).

That is, in the structure of the limiting current type gas sensor 2B including the cavity C of the open type structure shown in FIGS. 31A and 31B, a low concentration doped poly having a high thermal conductivity is provided below the micro heater MH. The silicon layer 300 is inserted in the limiting current type gas sensor 2D according to the third modification of the second embodiment.

With such a configuration as well, it is possible to obtain the limiting current type gas sensor 2D having better temperature characteristics and excellent sensor characteristics.

(Third Embodiment)
(Schematic configuration)
A schematic plane pattern configuration of the limiting current type gas sensor 3A according to the third embodiment is represented as shown in FIG. 34(a), and has a MEMS beam structure along the line IIIA-IIIA in FIG. 34(a). A schematic cross-sectional structure of the gas sensor 3A provided is shown in FIG. 34(b). The limiting current type gas sensor 3A according to the third embodiment is different from the limiting current type gas sensor according to the above-described first and second embodiments in the configuration of the gas diffusion path, and other configurations. Are basically the same.

First, the outline of the configuration will be described. The limiting current type gas sensor 3A according to the third embodiment is a sensor on a substrate (for example, Si) 12 as shown in FIGS. 34(a) and 34(b). On the surface, SiN films (third/fourth insulating films) 201/202 forming the SiN layer 20, sensor portion SP, gas intake port (opening) 47 of gas diffusion path (gas introduction path) MP, SiN film 26, the heater connection portions 21 and 22, the terminal electrode connection portions 23 and 24, the opening portion 45, and the like.

The sensor portion SP covers the gas diffusion path MP arranged in the active region near the center of the substrate 12, the lower electrode (porous Pt/Ti film) 28D that is a porous electrode, and the lower electrode 28D in plan view. The solid electrolyte layer (YSZ film) 30 thus arranged and the upper electrode (for example, Pt film) 28U arranged on the solid electrolyte layer 30 facing the lower electrode 28D are provided. The substrate 12 (active region), the lower electrode 28D, the solid electrolyte layer 30, and the upper electrode 28U may all have a rectangular shape or any other shape.

The gas diffusion path MP is arranged below the lower electrode 28D via the SiN film 202. The gas intake port 47 of the gas diffusion path MP is, in plan view, the SiN film 26 in the active region corresponding to one direction of the sensor portion SP (for example, the left end side in the direction along the cross section of FIG. 34B). It is placed in the vicinity. The SiN film 26 is an outer peripheral portion of the sensor portion SP, and is arranged so as to surround the sensor portion SP in a rectangular frame shape while maintaining a predetermined distance from the sensor portion SP.

Outside the SiN film 26 and between the active region and the non-active region on the substrate 12, four openings 45 are arranged in an L shape so as to correspond to the respective corners. The opening 45 is formed when the cavity C having a boat-shaped structure is formed. The opening 45 may have a shape other than the L-shape, such as a straight shape (I-shape).

Further, at the edge portion (peripheral end portion of the sensor surface) on the substrate 12 further outside the opening portion 45, for connecting the heater connection portions 21 and 22 so as to correspond to each opening portion 45 in plan view. The pads 211 and 221 and the connecting pads 231 and 241 of the terminal electrode connecting portions 23 and 24 are arranged. The connecting pads 211 and 221 are connected to the terminal portions 213 and 223 immediately below the SiN film 26 via the wiring portions 212 and 222 that are drawn out toward the sensor portion SP, respectively. The connecting pad 231 is connected to the extending end 28D1 of the lower electrode 28D of the sensor portion SP via the wiring portion 232 extended toward the sensor portion SP, and the connecting pad 241 is connected to the sensor portion SP. It is connected to the extending end 28U1 of the upper electrode 28U of the sensor portion SP via the wiring portion 242 drawn out in the direction.

On the other hand, a micro-heater MH having a larger area than that of the sensor portion SP is provided between the first and second insulating layers (e.g., SiO ₂ film) 181 and 182 forming the insulating layer 18 corresponding to the lower portion of the sensor portion SP. In addition, a cavity portion (boat-shaped structure) C of the substrate 12 having the MEMS beam structure is formed below the micro heater MH so as to have a larger area.

Described more specifically below, the limiting-current type gas sensor 3A according to the third embodiment includes first and second limiting current sensors on the substrate 12, as shown in FIGS. 34(a) and 34(b). A gas diffusion path MP having a micro heater MH arranged between the insulating layers 181 and 182 and having a hollow structure between the upper second insulating layer 182 and the lower electrode 28D in the sensor portion SP. The gas to be measured (for example, O ₂ gas) is introduced into the solid electrolyte layer 30 via the. That is, the gas to be measured is taken into the gas diffusion path MP immediately below the SiN film 202 from the gas intake port 47 along with the heating of the micro heater MH, passes through the gas flow path (micro flow path) 42, and passes through the gas. After being introduced into the solid electrolyte layer 30 from the lower electrode 28D of the introduction port (opening) 41, it is diffused in the solid electrolyte layer 30. The introduction of the gas to be measured into the solid electrolyte layer 30 may be accompanied by a suction operation.

The lower electrode 28D and the solid electrolyte layer 30 have one side wall portion of the gas diffusion path MP on the side facing the gas intake port 47 (for example, the right end side in the direction along the cross section of FIG. 34B). It is arranged so as to cover the part.

The lower electrode 28D is formed of a porous Pt/Ti film, which is a laminated film of a porous Pt film and a Ti film, with a thickness of, for example, about 100 nm. The Ti film is used to make the bond between the porous Pt film and the underlying SiN film 202 denser and stronger.

Here, the lower electrode 28D is arranged such that a part of the lower electrode 28D protrudes into the flow path 42 from the portion that becomes the gas introduction port 41 of the gas diffusion path MP. It has a fine gas introduction passage formed in (not shown).

For example, in the limiting current type gas sensor 3A according to the third embodiment, the lower electrode 28D itself is formed in a nanostructure. That is, Pt mixed with carbon nanotubes (CNT) may be sintered, and finally, CNT may be burned off to form a metal particle sintered layer (dense Pt) in which a fine gas introduction path is formed as the lower electrode 28D. Carbon nanoparticles may be applied instead of CNTs.

The fine gas introduction path in the lower electrode 28D can be formed by, for example, a heat treatment process of nanowires, nanotubes, nanoparticles, etc. having a nanometer scale contained in the metal particle sintered layer, or an etching treatment process combined with the heat treatment process. Is. Nanowires, nanotubes, and nanoparticles can be formed of, for example, carbon (C), zinc oxide (ZnO), or the like.

That is, the metal particle sintered layer in the lower electrode 28D and the fine gas introduction path formed in the metal particle sintered layer will not be described in detail here, but the metal particle sintered layer includes nanowires. May be. The nanowire may include CNT or ZnO. The metal particle sintered layer is provided with carbon nanotubes or carbon nanoparticles, and the fine gas introduction path is formed by burning the carbon nanotubes or carbon nanoparticles by burning the metal particle sintered layer in the atmosphere. It may be done. The metal particle sintered layer may be provided with ZnO, and the fine gas introduction path may be formed by etching ZnO by wet etching after burning the metal particle sintered layer in the atmosphere.

Furthermore, the metal particles of the metal particle sintered layer may include any one of Pt, Ag, Pd, Au, and Ru. Further, the metal particle sintered layer may include nanowires that are confined in the metal particle sintered layer and are not burned by burning in the atmosphere. The nanowires or nanoparticles have a diameter of about 0.1 μm or less. The length of the nanowire is, for example, about 10 μm or less. The advantage of using the nanowires is that the gas permeation amount can be controlled by the shape (diameter, length) of the nanowires, and the gas permeation amount can be controlled by the ratio of the nanowires.

As described above, in the limiting current type gas sensor 3A according to the third embodiment, the gas permeation amount can be controlled by the shape of the fine gas introduction passage of the lower electrode 28D. Further, in the limiting current type gas sensor 3A according to the third embodiment, the gas permeation amount can be controlled by the content ratio of the fine gas introduction passage of the lower electrode 28D.

The solid electrolyte layer 30 is formed of a YSZ film having a thickness of about 1 μm. This is because if it is thin, the upper and lower electrodes 28U and 28D are electrically connected. For example, the solid electrolyte layer 30 is arranged so as to cover the periphery of the lower electrode 28D and prevents conduction between the upper and lower electrodes 28U and 28D.

The gas diffusion path MP controls the flow rate of the gas to be measured according to the ratio of the channel length of the micro channel 42 from the gas intake port 47 that takes in the gas to be measured to the gas inlet 41 and the channel cross-sectional area. It is possible. For example, the width (W)=30 μm, depth (D)=0.1 μm, length (L) of the gas diffusion path MP is set so that “flow path length/cross-sectional area=100 μm ⁻¹ (aspect ratio)”. )=300 μm, the aspect ratio becomes “3” or more and the limiting current characteristic becomes good.

The gas diffusion path MP may be arranged in a state of being eccentric with respect to the center of the sensor surface, and it is preferable that the gas introduction port 41 is arranged near the center of the substrate 12 in plan view. On the other hand, the lower electrode 28D, the solid electrolyte layer 30, and the upper electrode 28U may be stacked on the gas introduction port 41 with the gas introduction port 41 as the center. That is, the gas diffusion path MP, the lower electrode 28D, the solid electrolyte layer 30, and the upper electrode 28U that form the sensor portion SP are eccentric to the center of the sensor surface in different directions on the micro heater MH. It may be arranged in a state.

The limiting current type gas sensor 3A according to the third embodiment can control the flow rate of the gas to be measured according to the aspect ratio of the gas diffusion path MP, and can improve the sensor characteristics by increasing the aspect ratio, The sensor characteristics can be more stabilized by increasing the accuracy of forming the diffusion path MP.

The substrate 12 having the MEMS beam structure has a thickness of, for example, about 10 μm and is formed such that the cavity C is substantially larger than the micro heater MH to prevent heat from escaping from the membrane. ing.

The MEMS beam structure may be formed to have an open structure (see FIG. 44) in which the substrate 12 is arranged so as to surround the sensor portion SP in plan view. Further, the cavity portion C may have a structure formed by bonding the substrates 12 together.

As described above, the limiting current type gas sensor 3A according to the third embodiment uses the beam structure (boat type structure) having the MEMS structure as a basic structure to reduce the heat capacity of the sensor portion SP and reduce the sensor sensitivity. We are trying to improve.

In short, the limiting current type gas sensor 3A according to the third embodiment includes the substrate 12, the heater MH arranged on the substrate 12 via the first insulating layer 181, and the second insulating layer 182 on the heater MH. A gas introduction path MP, which is disposed via the gas introduction path MP, a lower electrode 28D arranged on the gas introduction path MP, a solid electrolyte layer 30 arranged on the lower electrode 28D, and a solid electrolyte layer 30 The upper electrode 28U is disposed on the surface facing the lower electrode 28D, and the cavity 12 is formed on the substrate 12 so as to be substantially larger than the heater MH.

In the limiting current type gas sensor 3A according to the third embodiment, the micro heater MH is not limited to being arranged between the first and second insulating layers 181 and 182 on the substrate 12 which is the sensor portion SP. It may be arranged under the substrate 12, or may be embedded inside the substrate 12. Alternatively, a laminated film (not shown) of a SiO ₂ film/SiN film including a micro heater MH made of polysilicon may be formed on the surface of the substrate 12.

(Production method)
The method of manufacturing the limiting current type gas sensor 3A according to the third embodiment includes the step of forming the heater MH on the substrate 12 via the first insulating layer 181 and the second insulating layer 182 on the heater MH. A step of forming the lower electrode 28D, a step of forming the solid electrolyte layer 30 on the lower electrode 28D, a step of forming the upper electrode 28U on the surface of the solid electrolyte layer 30 facing the lower electrode 28D, and a heater MH A step of forming a gas introduction path MP, which is disposed above the second insulation layer 182 and introduces a gas to be measured, and a step of forming a cavity portion C substantially larger than the heater MH in the substrate 12. Have.

A method for manufacturing the limiting current type gas sensor 3A according to the third embodiment shown in FIGS. 34(a) and 34(b) is represented as shown in FIGS. The steps shown in FIGS. 10A and 10B until the SiN film 201 having a thickness of about 0.5 μm is formed by the P-CVD method or the like are the limiting current according to the first embodiment. Since it is similar to the case of the gas sensor 1A, the subsequent steps will be described.

(A) As shown in FIGS. 35(a) and 35(b), for example, after forming the SiN film 201 on the second insulating layer 182, further forming a flow path for forming the gas diffusion path MP. The layer 35 is formed in advance (deposition+patterning).

The flow path forming layer 35 is formed using a film forming member having a different etching selection ratio from the SiN films 201 and 202, for example, a polysilicon film. The flow path forming layer 35 has a length (L) of 300 μm and a width (W) such that the aspect ratio of the gas diffusion path MP is, for example, “flow path length/flow path cross-sectional area=100 μm ⁻¹ ”. Is 30 μm and the thickness (depth (D)) is 0.1 μm.

Here, the predetermined aspect ratio of the gas diffusion path MP can be easily increased by increasing the flow path length of the gas diffusion path MP or decreasing the cross-sectional area (flow path cross-sectional area) of the gas diffusion path MP. The sensor characteristics can be improved by increasing the aspect ratio of the gas diffusion path MP.

(B) Next, as shown in FIGS. 36(a) and 36(b), SiN having a thickness of about 0.5 μm, which has a different etching selection ratio from the flow path forming layer 35 on the entire surface by P-CVD or the like. After forming the film 202, the SiN films 201 and 202 and the second insulating layer 182 are further selectively etched to form the terminal portions 213 and 223 of the heater connection portions 21 and 22 connected to the micro heater MH. The opening 37 is formed.

(C) Next, as shown in FIGS. 37(a) and 37(b), the Pt/Ti laminated film is deposited by sputtering or the like so as to have a thickness of about 0.5 μm, and the Pt/Ti laminated film is deposited. The film is patterned by etching to form the connecting pads 211 and 221, the heater connecting portions 21 and 22, the wiring portions 212 and 222, and the terminal portions 213 and 223.

At the same time, the Pt/Ti laminated film is patterned by etching to form the connecting pads 231 and 241 and the wiring portions 232 and 241 of the terminal electrode connecting portions 23 and 24 in the direction orthogonal to the heater connecting portions 21 and 22.

In this way, the heater connection portions 21 and 22 and the terminal electrode connection portions 23 and 24 are arranged so as to be orthogonal to each other.

(D) Next, as shown in FIGS. 38(a) and 38(b), after the SiO ₂ film 25 and the SiN film 26 are formed by the CVD method or the like so as to fill the opening 37, For example, the SiO ₂ film 25 and the SiN film 26 are selectively etched and patterned so as to surround the sensor portion SP.

Simultaneously with or before or after the patterning of the SiO ₂ film 25 and the SiN film 26, the SiN film 202 on the flow path forming layer 35 is selectively etched and removed so that the flow path forming layer 35 is exposed. An opening serving as an inlet 41 for the measured gas is formed.

(E) Next, as shown in FIGS. 39(a) and 39(b), a lower electrode 28D made of a porous Pt/Ti film having a thickness of about 100 nm is formed by a sputtering method or the like, and the lower electrode 28D is extended. The end 28D1 is connected to the wiring portion 232 of the terminal electrode connecting portion 23.

(F) Next, as shown in FIGS. 40A and 40B, a solid electrolyte layer 30 made of a YSZ film is formed with a thickness of about 1 μm by a sputtering method so as to cover the lower electrode 28D. To do. The solid electrolyte layer 30 entirely covers the periphery of the lower electrode 28D except the extending end 28D1 of the lower electrode 28D.

(G) Next, as shown in FIGS. 41(a) and 41(b), a Pt film having a thickness of about 100 nm is formed as the upper electrode 28U on the surface facing the lower electrode 28D on the solid electrolyte layer 30 by the sputtering method. The extending end 28U1 of the upper electrode 28U is connected to the wiring portion 242 of the terminal electrode connecting portion 24.

(H) Next, as shown in FIGS. 42A and 42B, as a MEMS beam structure, a protective SiO ₂ film (etching) having an opening 431 for forming the cavity C of the boat-shaped structure is formed. A mask 43 is formed on the entire surface (deposition+patterning).

(I) Next, as shown in FIGS. 43A and 43B, the substrate 12 is selectively deep-etched by using the protective SiO ₂ film 43 as a mask to form an opening 45, and A cavity portion C having a boat-shaped structure is formed as the substrate 12 having the MEMS beam structure.

Although it depends on the size of the limiting current type gas sensor 3A according to the third embodiment, the cavity C is preferably about 400 μm square so as to be substantially larger than the micro heater MH.

In addition, after removing the protective SiO ₂ film 43 by etching, the SiN film 202 on the flow channel forming layer 35 is further selectively removed by etching to remove the gas of the measurement target gas so that the flow channel forming layer 35 is exposed. An opening to be the intake port 47 is formed.

(J) After that, for example, the polysilicon film forming the flow path forming layer 35 for forming the gas diffusion path MP is selectively removed by wet etching, thereby forming the gas diffusion paths MP shown in FIGS. The limiting current type gas sensor 3A according to the third embodiment having the configuration shown in b) is obtained.

The step of forming the gas diffusion path MP may be performed before the step of forming the cavity portion C, or may be performed simultaneously with the step of forming the cavity portion C.

As described above, by forming the cavity C so as to be substantially larger than the micro heater MH, the heat capacity is reduced and the heating by the micro heater MH is easily suppressed from being unnecessarily spread to the periphery of the sensor. it can.

Further, the aspect ratio of the gas diffusion path MP can be easily increased by increasing the flow path length of the micro flow path 42 of the gas diffusion path MP or decreasing the cross-sectional area.

In particular, since the porous Pt/Ti film forming the lower electrode 28D has high thermal stability, it has high gas throttling performance.

Therefore, according to the limiting current type gas sensor according to the third embodiment, it is possible to easily improve the sensor characteristics and further stabilize the sensor characteristics.

(First Modification of Third Embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 3B according to the first modified example of the third embodiment is represented as shown in FIG. 44(a), and is along the line IIIB-IIIB in FIG. 44(a). A schematic cross-sectional structure of the gas sensor 3B formed in the MEMS beam structure is shown in FIG. 44(b).

That is, the limiting current type gas sensor 3B according to the first modified example of the third embodiment has, as a MEMS beam structure, an open type cavity portion in which the substrate 12 is arranged so as to surround the sensor portion SP in a plan view. It may be formed to have C. The cavity C of the open type structure can be easily formed by, for example, forming the cavity C of the boat type structure and then deeply etching the substrate 12 from the back surface side.

The other configurations are basically the same as those of the limiting current type gas sensor 3A, and thus the duplicate description will be omitted.

With such a configuration, similarly to the limiting current type gas sensor 3A described above, the sensor characteristics can be easily improved, and the limiting current type gas sensor 3B can be further stabilized. ..

(Second Modification of Third Embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 3C according to the second modified example of the third embodiment is represented as shown in FIG. 45(a), and is along the line IIIC-IIIC in FIG. 45(a). A schematic cross-sectional structure of the gas sensor 3C formed in the MEMS beam structure is shown in FIG. 45(b).

That is, the limiting current type gas sensor 3C according to the second modified example of the third embodiment is configured to increase the thermal conductivity inside the in-plane membrane so as to make the temperature uniform.

More specifically, for example, in the limiting current type gas sensor 3A including the cavity C having the boat-shaped structure shown in FIGS. 34(a) and 34(b), the thermal conductivity is high below the micro heater MH. The low-concentration doped polysilicon layer (for example, 140 W/mK) 300 is inserted in the limiting current type gas sensor 3C according to the second modified example of the third embodiment.

According to such a configuration, it is possible to obtain the limiting current type gas sensor 3C that has better temperature characteristics, can easily improve the sensor characteristics, and can further stabilize the sensor characteristics.

(Third Modification of Third Embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 3D according to the third modified example of the third embodiment is represented as shown in FIG. 46(a), and is along the line IIID-IIID of FIG. 46(a). A schematic cross-sectional structure of the gas sensor 3D formed in the MEMS beam structure is shown in FIG. 46(b).

That is, in the structure of the limiting current type gas sensor 3B including the cavity C of the open type structure shown in FIGS. The silicon layer 300 is inserted in the limiting current type gas sensor 3D according to the third modified example of the third embodiment.

With such a configuration, it is possible to obtain the limiting current type gas sensor 3D which has better temperature characteristics, can easily improve the sensor characteristics, and can further stabilize the sensor characteristics.

(Fourth Modification of Third Embodiment)
The schematic plane pattern configuration of the limiting current type gas sensor 3E according to the fourth modification of the third embodiment is represented as shown in FIG. 47(a), and is along the line IIIE-IIIE in FIG. 47(a). , A schematic cross-sectional structure of the sensor 3E in which the MEMS beam structure is formed in a boat-shaped structure is shown in FIG. 47(b).

That is, in the limiting current type gas sensor 3E according to the fourth modification of the third embodiment, as shown in FIGS. 47(a) and 47(b), in a plan view, for example, the gas diffusion path of the sensor portion SP. The MP has two openings (a plurality of gas inlets) 471 and 472.

In the case of the limiting current type gas sensor 3E, by using the two openings 471 and 472 in the step of forming the gas diffusion path MP, for example, the polysilicon film forming the flow path forming layer 35 is efficiently wet-etched. It is possible.

Therefore, according to the limiting current type gas sensor according to the fourth modified example of the third embodiment, it is possible to easily improve the sensor characteristics, and further, it is possible to more easily form the gas diffusion path. Become.

In the structure of the limiting current type gas sensor 3E, it is easy to insert the low-concentration doped polysilicon layer 300 having a high thermal conductivity below the micro heater MH or to form the MEMS beam structure in an open structure. ..

(Fifth Modification of Third Embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 3F according to the fifth modified example of the third embodiment is represented as shown in FIG. 48(a), and is along the line IIIF-IIIF in FIG. 48(a). , A schematic cross-sectional structure of the gas sensor 3F in which the MEMS beam structure is formed in a boat structure is shown in FIG. 48(b).

That is, in the limiting current type gas sensor 3F according to the fifth modified example of the third embodiment, as shown in FIGS. 48(a) and 48(b), a plurality of openings 471. One of the parts 472 (for example, the gas inlet 472) is closed by a lid member 49 such as a glass frit, a SiN film, or a SiO ₂ film after the gas diffusion path MP is formed.

Also in the case of this limiting current type gas sensor 3F, the gas diffusion path MP can be easily formed by using the two gas intake ports 471 and 472 in the step of forming the gas diffusion path MP.

Moreover, by closing either of the gas intake ports 471 and 472 with the lid member 49 after the gas diffusion path MP is formed, it is possible to suppress an excessive increase in the introduction amount of the gas to be measured.

Therefore, according to the limiting current type gas sensor of the fifth modified example of the third embodiment, the sensor characteristics can be easily improved, and further, the gas diffusion path can be formed more easily and the gas introduction It is possible to solve the problem that the gas throttling performance deteriorates as the amount increases.

In the structure of the limiting current type gas sensor 3F, it is easy to insert the low-concentration doped polysilicon layer 300 having a high thermal conductivity below the micro heater MH or to form the MEMS beam structure in an open structure. ..

(Fourth Embodiment)
(Schematic configuration)
A schematic plane pattern configuration of the limiting current type gas sensor 4A according to the fourth embodiment is represented as shown in FIG. 49(a), and has a MEMS beam structure along the line IVA-IVA of FIG. 49(a). The schematic cross-sectional structure of the gas sensor 4A provided is shown in FIG. 49(b). In the limiting current type gas sensor 4A according to the fourth embodiment, a porous oxide film 71 is further arranged under the lower electrode 28D of the limiting current type gas sensor 3A described above. Since the configuration is basically the same, redundant description will be omitted as much as possible, and the configuration of a characteristic part will be described in more detail.

The limiting current type gas sensor 4A according to the fourth embodiment, as shown in FIGS. 49(a) and 49(b), is a gas introduction path arranged in the active region on the substrate 12 as a sensor portion SP. Of the gas diffusion path MP, the porous oxide film (porous film) 71, the lower electrode (Pt/Ti laminated film) 28D arranged on the porous oxide film 71, the porous oxide film 71 and the lower electrode 28D. The solid electrolyte layer (YSZ film) 30 arranged as described above and the upper electrode (for example, Pt film) 28U arranged on the solid electrolyte layer 30 facing the lower electrode 28D are provided.

That is, in the limiting current type gas sensor 4A, the gas to be measured (for example, O ₂ gas) is taken into the sensor portion SP from the gas diffusion path MP having a hollow structure as the micro heater MH is heated. After being introduced into the solid electrolyte layer 30 through the porous oxide film 71 of the gas introduction port 41 and the lower electrode 28D, it is diffused into the solid electrolyte layer 30. The introduction of the gas to be measured into the solid electrolyte layer 30 may be accompanied by a suction operation.

The porous oxide film 71 may be formed by forming the porous oxide film 71 by sputtering and etching in a step prior to the step of forming the lower electrode 28D when manufacturing the limiting current type gas sensor 3A described above.

As described above, also in the case of the limiting current type gas sensor 4A to which the porous oxide film 71 is added, the cavity portion C is substantially larger than the micro heater MH as in the case of the limiting current type gas sensor 3A described above. By forming it in the above manner, it is possible to reduce the heat capacity and to easily prevent the heating by the micro heater MH from unnecessarily spreading to the periphery of the sensor.

In particular, since the porous oxide film 71 has high thermal stability, it is possible to obtain the limiting current type gas sensor 4A having high gas throttle performance and excellent sensor characteristics.

Moreover, the aspect ratio of the gas diffusion path MP can be easily increased by increasing the flow path length of the micro flow path 42 of the gas diffusion path MP or by reducing the cross-sectional area. Can be offset.

Therefore, according to the limiting current type gas sensor of the fourth embodiment, the sensor characteristics can be easily improved, and the sensor characteristics can be further stabilized.

(First Modification of Fourth Embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 4B according to the first modified example of the fourth embodiment is represented as shown in FIG. 50(a), and is along the line IVB-IVB in FIG. 50(a). A schematic cross-sectional structure of the gas sensor 4B formed in the MEMS beam structure is shown in FIG. 50(b).

That is, the limiting current type gas sensor 4B according to the first modified example of the fourth embodiment has a cavity portion having an open structure in which the substrate 12 is arranged so as to surround the sensor portion SP in plan view as a MEMS beam structure. It may be formed to have C. The cavity C of the open type structure can be easily formed by, for example, forming the cavity C of the boat type structure and then deeply etching the substrate 12 from the back surface side.

The other configurations are basically the same as those of the limiting current type gas sensor 4A, and thus the duplicate description will be omitted.

With such a configuration, similarly to the limiting current type gas sensor 4A described above, the sensor characteristics can be easily improved, and the limiting current type gas sensor 4B can be further stabilized. ..

(Second Modification of Fourth Embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 4C according to the second modified example of the fourth embodiment is represented as shown in FIG. 51(a), and is along the line IVC-IVC in FIG. 51(a). , A schematic sectional structure of the gas sensor 4C formed in the MEMS beam structure is shown in FIG. 51(b).

That is, the limiting current type gas sensor 4C according to the second modified example of the fourth embodiment is configured to increase the thermal conductivity inside the in-plane membrane so as to make the temperature uniform.

More specifically, for example, in the limiting current type gas sensor 4A including the cavity portion C having the boat structure shown in FIGS. 49A and 49B, the thermal conductivity is high below the micro heater MH. The low-concentration polysilicon layer (for example, 140 W/mK) 300 is inserted in the limiting current type gas sensor 4C according to the second modification of the fourth embodiment.

With such a configuration, similarly to the limiting current type gas sensor 4A described above, it is possible to easily improve the sensor characteristics and to provide the limiting current type gas sensor 4C that can further stabilize the sensor characteristics. ..

(Third Modification of Fourth Embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 4D according to the third modified example of the fourth embodiment is represented as shown in FIG. 52(a), and is along the line IVD-IVD in FIG. 52(a). , A schematic sectional structure of the gas sensor 4D formed in the MEMS beam structure is shown in FIG. 52(b).

That is, in the structure of the limiting current type gas sensor 4B including the cavity C of the open type structure shown in FIGS. 50A and 50B, a low concentration doped poly having a high thermal conductivity is provided below the micro heater MH. The silicon layer 300 is inserted in the limiting current type gas sensor 4D according to the third modification of the fourth embodiment.

With such a configuration, similarly to the limiting current type gas sensor 4B described above, the sensor characteristics can be easily improved, and the limiting current type gas sensor 4D can be further stabilized. ..

(Fourth Modification of Fourth Embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 4E according to the fourth modified example of the fourth embodiment is represented as shown in FIG. 53(a), and is along the line IVE-IVE of FIG. 53(a). , A schematic cross-sectional structure of the gas sensor 4E formed in the MEMS beam structure is shown in FIG. 53(b).

That is, in the limiting current type gas sensor 4E according to the fourth modified example of the fourth embodiment, a low concentration doped polysilicon layer (for example, 140 W/mK) 300 having a high thermal conductivity is inserted below the micro heater MH. An example in which the low-concentration doped polysilicon layer 300 is formed to be larger than the micro heater MH by increasing the thermal conductivity inside the in-plane membrane so as to make the temperature uniform. Is.

Other than that, the configuration is basically the same as that of the limiting current type gas sensor 4C, and a duplicate description will be omitted.

(Fifth Modification of Fourth Embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 4F according to the fifth modified example of the fourth embodiment is represented as shown in FIG. 54(a), and is along the IVF-IVF line in FIG. 54(a). A schematic cross-sectional structure of the gas sensor 4F formed in the MEMS beam structure is shown in FIG. 54(b).

That is, in the limiting current type gas sensor 4F according to the fifth modified example of the fourth embodiment, a low-concentration doped polysilicon layer (for example, 140 W/mK) 300 having high thermal conductivity is inserted below the micro heater MH. An example in which the low-concentration doped polysilicon layer 300 is formed to be larger than the micro heater MH by increasing the thermal conductivity inside the in-plane membrane so as to make the temperature uniform. Is. Since the thermal conductivity only inside the membrane is increased and the heat that propagates the beam and escapes does not change, the power consumption does not increase unlike the case where silicon is on the entire surface.

The other configurations are basically the same as those of the limiting current type gas sensor 4D, and duplicated description will be omitted.

(Sixth Modification of Fourth Embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 4G according to the sixth modified example of the fourth embodiment is represented as shown in FIG. 55(a), and is along the line IVG-IVG in FIG. 55(a). , A schematic cross-sectional structure of the gas sensor 4G in which the MEMS beam structure is formed into a boat-shaped structure is shown in FIG. 55(b).

That is, as shown in FIGS. 55(a) and 55(b), the limiting current type gas sensor 4G according to the sixth modified example of the fourth embodiment has, for example, a left end side of the sensor portion SP in plan view. On the right end side, openings (gas inlets) 471 and 472 of the gas diffusion path MP are provided.

In the case of this limiting current type gas sensor 4G, by using the two openings 471 and 472 in the step of forming the gas diffusion path MP, for example, the polysilicon film forming the flow path forming layer 35 is efficiently wet-etched. It is possible.

Therefore, according to the limiting current type gas sensor according to the sixth modified example of the fourth embodiment, it is possible to easily improve the sensor characteristics, and it is possible to more easily form the gas diffusion path. Become.

In the structure of the limiting current type gas sensor 4G, it is easy to insert the low-concentration doped polysilicon layer 300 having high thermal conductivity below the micro-heater MH or to form the MEMS beam structure in an open structure. ..

(Seventh Modification of Fourth Embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 4H according to the seventh modified example of the fourth embodiment is represented as shown in FIG. 56(a), and is along the line IVH-IVH in FIG. 56(a). , A schematic cross-sectional structure of the gas sensor 4H in which the MEMS beam structure is formed in a boat-shaped structure is shown in FIG. 56(b).

That is, in the limiting current type gas sensor 4H according to the seventh modified example of the fourth embodiment, as shown in FIGS. 56(a) and 56(b), a plurality of openings 471. One of the parts 472 (for example, the gas intake port 472) is closed by a lid member 49 such as a glass frit, a SiN film or a SiO ₂ film after the gas diffusion path MP is formed.

Also in the case of this limiting current type gas sensor 4H, the gas diffusion path MP can be easily formed by using the two gas intake ports 471 and 472 in the step of forming the gas diffusion path MP.

Moreover, by closing one of the gas intake ports 471 and 472 with the lid member 49 after the gas diffusion path MP is formed, it is possible to prevent the introduction amount of the gas to be measured from increasing excessively.

Therefore, according to the limiting current type gas sensor according to the seventh modified example of the fourth embodiment, it is possible to easily improve the sensor characteristics, moreover, the gas diffusion path can be formed more easily, and the gas introduction It is possible to solve the problem that the gas throttling performance deteriorates as the amount increases.

In the structure of the limiting current type gas sensor 4H, it is easy to insert the low-concentration doped polysilicon layer 300 having a high thermal conductivity below the micro heater MH or to form the MEMS beam structure in an open structure. ..

(Fifth Embodiment)
(Schematic configuration)
In the fifth embodiment, as schematically shown in FIG. 29(e), the gas intake portion 303 is provided in the sensor portion SP of the limiting current gas sensor, so that the porous film described above is provided. The temperature dependence of is improved.

In short, the limiting current type gas sensor according to the fifth embodiment includes the substrate 12, the heater MH disposed on the substrate 12 via the first insulating layer 181, and the heater MH via the second insulating layer 182. And the lower electrode 28D disposed on the gas inlet 303, the solid electrolyte layer 30 disposed on the lower electrode 28D, and the lower electrode 28D disposed on the solid electrolyte layer 30. The upper electrode 28U disposed on the surface facing the substrate and the cavity C formed on the substrate 12 to be substantially larger than the heater MH. And a columnar film (columnar portion) arranged on the gas introduction path and provided with a gas throttling structure in the perpendicular direction.

(First Example of Fifth Embodiment)
As a first example of the fifth embodiment, first, a case will be described in which the gas intake part 303 of the sensor portion SP is configured by the gas diffusion path MP1 serving as a gas introduction path and the columnar films 53 and 57.

Here, the gas diffusion path MP1 has an in-plane gas throttle structure, and the columnar films 53 and 57 have a perpendicular gas throttle structure.

The schematic plane pattern configuration of the limiting current type gas sensor 5A1 according to the first example of the fifth embodiment is represented as shown in FIG. 57(a), and is along the line VA1-VA1 of FIG. 57(a). , A schematic cross-sectional structure of the gas sensor 5A1 formed in the MEMS beam structure is shown in FIG. 57(b).

That is, as shown in FIGS. 57(a) and 57(b), the sensor portion SP of the limiting current type gas sensor 5A1 according to the first example of the fifth embodiment has a gas diffusion path (having a hollow structure ( Gas introduction path) MP1, columnar oxide film (columnar film) 53 arranged on gas diffusion path MP1, porous oxide film 51 arranged to cover columnar oxide film 53, and arranged on porous oxide film 51 The lower electrode (Pt/Ti laminated film) 28D thus formed, the solid electrolyte layer 30 arranged so as to cover the porous oxide film 51 and the lower electrode 28D, and the solid electrolyte layer 30 opposed to the lower electrode 28D. And an upper electrode 28U.

In the case of the limiting current type gas sensor 5A1 according to the first example of the fifth embodiment, the porous oxide film 51 and the lower electrode 28D constitute a porous electrode, and the gas diffusion path MP1 and the columnar oxide film 53 serve as a gas collector. The inserting unit 303 is configured.

The other configurations are basically the same as those of the limiting current type gas sensor 1A and the like, and thus duplicated description will be omitted.

Note that, as in the limiting current type gas sensor 5A1 shown in FIG. 57(b), the cavity portion C of the substrate 12 having the MEMS beam structure is not limited to the boat type structure, and the limits shown in FIGS. 58(a) and 58(b) are not limited. The cavity C having an open structure such as the current gas sensor 5A2 may be used.

(Modification 1 of the first example of the fifth embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 5B1 according to the first modification of the first example of the fifth embodiment is represented as shown in FIG. 59(a), and VB1- of FIG. 59(a). A schematic cross-sectional structure of the gas sensor 5B1 formed in the MEMS beam structure along the line VB1 is represented as shown in FIG. 59(b).

That is, the sensor portion SP of the limiting current type gas sensor 5B1 according to the first modification of the first example of the fifth embodiment has a hollow structure as shown in FIGS. 59(a) and 59(b). Gas diffusion path (gas introduction path) MP1, columnar oxide film (columnar film) 53 arranged on the gas diffusion path MP1, and lower electrode (porous Pt/Ti film) arranged so as to cover the columnar oxide film 53. 28DA, a solid electrolyte layer 30 arranged so as to cover the lower electrode 28DA, and an upper electrode 28U arranged on the solid electrolyte layer 30 facing the lower electrode 28DA.

In the case of the limiting current type gas sensor 5B1 according to the modified example 1 of the first example of the fifth embodiment, the lower electrode 28DA constitutes a porous electrode, and the gas diffusion path MP1 and the columnar oxide film 53 form the gas intake portion. 303 is configured.

The other configurations are basically the same as those of the limiting current type gas sensor 1A and the like, and thus duplicated description will be omitted.

Note that, as in the limiting current type gas sensor 5B1 shown in FIG. 59(b), the cavity portion C of the substrate 12 having the MEMS beam structure is not limited to the boat-shaped structure, and the limits shown in FIGS. 60(a) and 60(b) are provided. The cavity C having an open structure such as the current gas sensor 5B2 may be used.

(Modification 2 of the first example of the fifth embodiment)
A schematic plane pattern configuration of a limiting current type gas sensor 5C1 according to Modification 2 of the first example of the fifth embodiment is represented as shown in FIG. 61(a), and VC1- of FIG. 61(a). A schematic cross-sectional structure of the gas sensor 5C1 formed in the MEMS beam structure along the line VC1 is represented as shown in FIG. 61(b).

That is, the sensor portion SP of the limiting current type gas sensor 5C1 according to the modified example 2 of the first example of the fifth embodiment has a hollow structure as shown in FIGS. 61(a) and 61(b). A gas diffusion path (gas introduction path) MP1, a columnar Pt/Ti film (columnar film) 57 arranged on the gas diffusion path MP1, and a porous oxide film 51 arranged so as to cover the columnar Pt/Ti film 57. , A lower electrode (Pt/Ti laminated film) 28D arranged on the porous oxide film 51, a solid electrolyte layer 30 arranged so as to cover the porous oxide film 51 and the lower electrode 28D, and a solid facing the lower electrode 28D. And an upper electrode 28U disposed on the electrolyte layer 30.

In the case of the limiting current type gas sensor 5C1 according to the modification 2 of the first example of the fifth embodiment, the porous electrode is constituted by the porous oxide film 51 and the lower electrode 28D, and the gas diffusion path MP1 and the columnar Pt/Ti. The membrane 57 and the gas intake portion 303 are configured.

The other configurations are basically the same as those of the limiting current type gas sensor 1A and the like, and thus duplicated description will be omitted.

Note that, as in the limiting current type gas sensor 5C1 shown in FIG. 61(b), the cavity C of the substrate 12 having the MEMS beam structure is not limited to the boat-shaped structure, and the limit shown in FIGS. 62(a) and 62(b). The cavity C having an open structure such as the current gas sensor 5C2 may be used.

(Modification 3 of the first example of the fifth embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 5D1 according to the modified example 3 of the first example of the fifth embodiment is represented as shown in FIG. 63(a), and VD1- of FIG. 63(a). A schematic cross-sectional structure of the gas sensor 5D1 formed in the MEMS beam structure along the line VD1 is represented as shown in FIG. 63(b).

That is, the sensor portion SP of the limiting current type gas sensor 5D1 according to the modified example 3 of the first example of the fifth embodiment has a hollow structure as shown in FIGS. 63(a) and 63(b). Gas diffusion path (gas introduction path) MP1, columnar Pt/Ti film (columnar film) 57 arranged on the gas diffusion path MP1, and lower electrode (porous Pt) arranged so as to cover the columnar Pt/Ti film 57. /Ti film) 28DA, a solid electrolyte layer 30 arranged so as to cover the lower electrode 28DA, and an upper electrode 28U arranged on the solid electrolyte layer 30 facing the lower electrode 28DA.

In the case of the limiting current type gas sensor 5D1 according to the modification 3 of the first example of the fifth embodiment, the lower electrode 28DA constitutes a porous electrode, and the gas diffusion path MP1 and the columnar Pt/Ti film 57 serve as a gas collector. The inserting unit 303 is configured.

The other configurations are basically the same as those of the limiting current type gas sensor 1A and the like, and thus duplicated description will be omitted.

Note that, as in the limiting current type gas sensor 5D1 shown in FIG. 63(b), the cavity portion C of the substrate 12 having the MEMS beam structure is not limited to the boat-shaped structure, and the limits shown in FIGS. 64(a) and 64(b) are provided. The cavity C having an open structure such as the current gas sensor 5D2 may be used.

(Second Example of Fifth Embodiment)
As a second example of the fifth embodiment, first, a case will be described in which the gas intake portion 303 of the sensor portion SP is composed of the porous oxide film 51 serving as a gas introduction path and the columnar films 53 and 57.

Here, the porous oxide film 51 has an in-plane gas constriction structure, and the columnar films 53 and 57 have a perpendicular gas constriction structure.

A schematic plane pattern configuration of the limiting current type gas sensor 5E1 according to the second example of the fifth embodiment is represented as shown in FIG. 65(a), and is along the line VE1-VE1 of FIG. 65(a). , A schematic sectional structure of the gas sensor 5E1 formed in the MEMS beam structure is shown in FIG. 65(b).

That is, the sensor portion SP of the limiting current type gas sensor 5E1 according to the second example of the fifth embodiment is, as shown in FIG. 65(a) and FIG. 65(b), the first portion serving as a gas introduction path. The porous oxide film 51A, the columnar oxide film (columnar film) 53 arranged on the first porous oxide film 51A, the second porous oxide film 51B arranged so as to cover the columnar oxide film 53, and the second Of the lower electrode (Pt/Ti laminated film) 28D arranged on the porous oxide film 51B, the solid electrolyte layer 30 arranged so as to cover the second porous oxide film 51B and the lower electrode 28D, and the lower electrode 28D. And an upper electrode 28U disposed on the opposing solid electrolyte layer 30.

In the case of the limiting current type gas sensor 5E1 according to the second example of the fifth embodiment, the porous electrode is constituted by the second porous oxide film 51B and the lower electrode 28D, and the first porous oxide film 51A and the columnar oxide film 51A. The gas intake part 303 is constituted by the film 53.

The other configurations are basically the same as those of the limiting current type gas sensor 1A and the like, and thus duplicated description will be omitted.

Note that, as in the limiting current type gas sensor 5E1 shown in FIG. 65(b), the cavity portion C of the substrate 12 having the MEMS beam structure is not limited to the boat-shaped structure, and the limit shown in FIGS. 66(a) and 66(b). The cavity C having an open structure such as the current gas sensor 5E2 may be used.

(Modification 1 of the second example of the fifth embodiment)
The schematic planar pattern configuration of the limiting current type gas sensor 5F1 according to the first modification of the second example of the fifth embodiment is represented as shown in FIG. 67(a), and VF1- of FIG. 67(a). A schematic cross-sectional structure of the gas sensor 5F1 formed in the MEMS beam structure along the line VF1 is shown in FIG. 67(b).

That is, the sensor portion SP of the limiting current type gas sensor 5F1 according to the modified example 1 of the second example of the fifth embodiment is provided with a gas introduction path as shown in FIGS. 67(a) and 67(b). A porous oxide film 51, a columnar oxide film (columnar film) 53 arranged on the porous oxide film 51, a lower electrode (porous Pt/Ti film) 28DA arranged so as to cover the columnar oxide film 53, and a lower part. The solid electrolyte layer 30 is arranged so as to cover the electrode 28DA, and the upper electrode 28U is arranged on the solid electrolyte layer 30 facing the lower electrode 28DA.

In the case of the limiting current type gas sensor 5F1 according to the first modification of the second example of the fifth embodiment, the lower electrode 28DA constitutes a porous electrode, and the porous oxide film 51 and the columnar oxide film 53 form a gas intake portion. 303 is configured.

The other configurations are basically the same as those of the limiting current type gas sensor 1A and the like, and thus duplicated description will be omitted.

Note that, as in the limiting current type gas sensor 5F1 shown in FIG. 67(b), the cavity portion C of the substrate 12 having the MEMS beam structure is not limited to the boat type structure, and the limits shown in FIGS. 68(a) and 68(b) are provided. The cavity C having an open structure such as the current gas sensor 5F2 may be used.

(Modification 2 of the second example of the fifth embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 5G1 according to the second modification of the second example of the fifth embodiment is represented as shown in FIG. 69(a), and VG1- of FIG. 69(a). A schematic cross-sectional structure of the gas sensor 5G1 formed in the MEMS beam structure along the line VG1 is shown in FIG. 69(b).

That is, the sensor portion SP of the limiting current type gas sensor 5G1 according to the modified example 2 of the second example of the fifth embodiment is provided with a gas introduction path as shown in FIGS. 69(a) and 69(b). Of the first porous oxide film 51A, the columnar Pt/Ti film (columnar film) 57 arranged on the first porous oxide film 51A, and the second Pt/Ti film 57 arranged so as to cover the columnar Pt/Ti film 57. Porous oxide film 51B, lower electrode (Pt/Ti laminated film) 28D arranged on second porous oxide film 51B, and solid electrolyte arranged so as to cover second porous oxide film 51B and lower electrode 28D. The layer 30 and the upper electrode 28U disposed on the solid electrolyte layer 30 facing the lower electrode 28D are provided.

In the case of the limiting current type gas sensor 5G1 according to the modified example 2 of the second example of the fifth embodiment, the porous electrode is constituted by the second porous oxide film 51B and the lower electrode 28D, and the first porous oxide film. 51A and the columnar Pt/Ti film 57 constitute a gas intake part 303.

The other configurations are basically the same as those of the limiting current type gas sensor 1A and the like, and thus duplicated description will be omitted.

Note that, as in the limiting current type gas sensor 5G1 shown in FIG. 69(b), the cavity portion C of the substrate 12 having the MEMS beam structure is not limited to the boat type structure, and the limits shown in FIGS. 70(a) and 70(b) are not limited. The cavity C having an open structure such as the current gas sensor 5G2 may be used.

(Modification 3 of the second example of the fifth embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 5H1 according to the modified example 3 of the second example of the fifth embodiment is represented as shown in FIG. 71(a), and VH1- of FIG. 71(a). A schematic cross-sectional structure of the gas sensor 5H1 formed in the MEMS beam structure along the line VH1 is represented as shown in FIG. 71(b).

That is, the sensor portion SP of the limiting current type gas sensor 5H1 according to the modified example 3 of the second example of the fifth embodiment is provided with a gas introduction path as shown in FIGS. 71(a) and 71(b). Porous oxide film 51, a columnar Pt/Ti film (columnar film) 57 arranged on the porous oxide film 51, and a lower electrode (porous Pt/Ti film) arranged so as to cover the columnar Pt/Ti film 57. 28DA, a solid electrolyte layer 30 arranged so as to cover the lower electrode 28DA, and an upper electrode 28U arranged on the solid electrolyte layer 30 facing the lower electrode 28DA.

In the limiting current type gas sensor 5H1 according to the modified example 3 of the second example of the fifth embodiment, the lower electrode 28DA constitutes a porous electrode, and the porous oxide film 51 and the columnar Pt/Ti film 57 serve as a gas collector. The inserting unit 303 is configured.

The other configurations are basically the same as those of the limiting current type gas sensor 1A and the like, and thus duplicated description will be omitted.

Note that, as in the limiting current type gas sensor 5H1 shown in FIG. 71(b), the cavity portion C of the substrate 12 having the MEMS beam structure is not limited to the boat type structure, and the limits shown in FIGS. 72(a) and 72(b) are not limited. The cavity C having an open structure such as the current gas sensor 5H2 may be used.

(Third Example of Fifth Embodiment)
As a third example of the fifth embodiment, first, a case will be described in which the gas intake portion 303 of the sensor portion SP is composed of the porous Pt film 61 serving as a gas introduction path and the columnar films 53 and 57.

Here, the porous Pt film 61 has an in-plane gas constriction structure, and the columnar films 53 and 57 have a perpendicular gas constriction structure.

A schematic plane pattern configuration of the limiting current type gas sensor 5J1 according to the third example of the fifth embodiment is represented as shown in FIG. 73(a), and is along the line VJ1-VJ1 in FIG. 73(a). , A schematic cross-sectional structure of the gas sensor 5J1 formed in the MEMS beam structure is shown in FIG. 73(b).

That is, as shown in FIGS. 73(a) and 73(b), the sensor portion SP of the limiting current type gas sensor 5J1 according to the third example of the fifth embodiment has a porous Pt film as a gas introduction path. 61, a columnar oxide film (columnar film) 53 arranged on the porous Pt film 61, a porous oxide film 51 arranged so as to cover the columnar oxide film 53, and a lower electrode arranged on the porous oxide film 51. (Pt/Ti laminated film) 28D, a solid electrolyte layer 30 arranged so as to cover the porous oxide film 51 and the lower electrode 28D, and an upper electrode 28U arranged on the solid electrolyte layer 30 facing the lower electrode 28D. Equipped with.

In the case of the limiting current type gas sensor 5J1 according to the third example of the fifth embodiment, the porous oxide film 51 and the lower electrode 28D constitute a porous electrode, and the porous Pt film 61 and the columnar oxide film 53 serve as a gas collector. The inserting unit 303 is configured.

The other configurations are basically the same as those of the limiting current type gas sensor 1A and the like, and thus duplicated description will be omitted.

Note that, as in the limiting current type gas sensor 5J1 shown in FIG. 73(b), the cavity portion C of the substrate 12 having the MEMS beam structure is not limited to the boat type structure, and the limits shown in FIGS. 74(a) and 74(b) are not limited. The cavity portion C having an open structure such as the current type gas sensor 5J2 may be used.

(Modification 1 of Example 3 of the fifth embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 5K1 according to the first modification of the third example of the fifth embodiment is represented as shown in FIG. 75(a), and VK1- of FIG. 75(a). A schematic cross-sectional structure of the gas sensor 5K1 formed in the MEMS beam structure along the line VK1 is represented as shown in FIG. 75(b).

That is, the sensor portion SP of the limiting current type gas sensor 5K1 according to the modified example 1 of the third example of the fifth embodiment is provided with a gas introduction path as shown in FIGS. 75(a) and 75(b). A porous Pt film 61, a columnar oxide film (columnar film) 53 arranged on the porous Pt film 61, a lower electrode (porous Pt/Ti film) 28DA arranged so as to cover the columnar oxide film 53, and a lower part. The solid electrolyte layer 30 is arranged so as to cover the electrode 28DA, and the upper electrode 28U is arranged on the solid electrolyte layer 30 facing the lower electrode 28DA.

In the case of the limiting current type gas sensor 5K1 according to the first modification of the third example of the fifth embodiment, the lower electrode 28DA constitutes a porous electrode, and the porous Pt film 61 and the columnar oxide film 53 form a gas intake portion. 303 is configured.

The porous Pt film 61 is adjusted so that the Pt particle diameter φ is larger than the Pt particle diameter φ of the lower electrode 28DA.

The other configurations are basically the same as those of the limiting current type gas sensor 1A and the like, and thus duplicated description will be omitted.

Note that, as in the limiting current type gas sensor 5K1 shown in FIG. 75(b), the cavity portion C of the substrate 12 having the MEMS beam structure is not limited to the boat-shaped structure, and the limits shown in FIGS. 76(a) and 76(b) are not limited thereto. The cavity C having an open structure such as the current gas sensor 5K2 may be used.

(Modification 2 of the third example of the fifth embodiment)
The schematic planar pattern configuration of the limiting current type gas sensor 5L1 according to the second modification of the third example of the fifth embodiment is represented as shown in FIG. 77(a), and VL1- of FIG. 77(a). A schematic cross-sectional structure of the gas sensor 5L1 formed in the MEMS beam structure along the line VL1 is represented as shown in FIG. 77(b).

That is, the sensor portion SP of the limiting current type gas sensor 5L1 according to the modified example 2 of the third example of the fifth embodiment, as shown in FIGS. 77(a) and 77(b), has a gas introduction path. Porous Pt film 61, columnar Pt/Ti film (columnar film) 57 arranged on the porous Pt film 61, porous oxide film 51 arranged so as to cover the columnar Pt/Ti film 57, and porous oxide film 51 on the lower electrode (Pt/Ti laminated film) 28D, the solid electrolyte layer 30 arranged so as to cover the porous oxide film 51 and the lower electrode 28D, and on the solid electrolyte layer 30 facing the lower electrode 28D. And an upper electrode 28U disposed in the.

In the case of the limiting current type gas sensor 5L1 according to the modified example 2 of the third example of the fifth embodiment, the porous oxide film 51 and the lower electrode 28D constitute a porous electrode, and the porous Pt film 61 and the columnar Pt/Ti. The membrane 57 and the gas intake portion 303 are configured.

The other configurations are basically the same as those of the limiting current type gas sensor 1A and the like, and thus duplicated description will be omitted.

Note that, as in the limiting current type gas sensor 5L1 shown in FIG. 77(b), the cavity portion C of the substrate 12 having the MEMS beam structure is not limited to the boat type structure, and the limit shown in FIGS. 78(a) and 78(b) is not limited. The cavity C having an open structure such as the current type gas sensor 5L2 may be used.

(Modification 3 of the third example of the fifth embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 5M1 according to Modification 3 of the third example of the fifth embodiment is represented as shown in FIG. 79(a), and VM1- of FIG. 79(a). A schematic cross-sectional structure of the gas sensor 5M1 formed in the MEMS beam structure along the VM1 line is represented as shown in FIG. 79(b).

That is, the sensor portion SP of the limiting current type gas sensor 5M1 according to the modified example 3 of the third example of the fifth embodiment is provided with a gas introduction path as shown in FIGS. 79(a) and 79(b). Porous Pt film 61, a columnar Pt/Ti film (columnar film) 57 arranged on the porous Pt film 61, and a lower electrode (porous Pt/Ti film) arranged so as to cover the columnar Pt/Ti film 57. 28DA, a solid electrolyte layer 30 arranged so as to cover the lower electrode 28DA, and an upper electrode 28U arranged on the solid electrolyte layer 30 facing the lower electrode 28DA.

In the case of the limiting current type gas sensor 5M1 according to the modification 3 of the third example of the fifth embodiment, the lower electrode 28DA constitutes a porous electrode, and the porous Pt film 61 and the columnar Pt/Ti film 57 serve as a gas collector. The inserting unit 303 is configured.

The porous Pt film 61 is adjusted so that the Pt particle diameter φ is larger than the Pt particle diameter φ of the lower electrode 28DA.

The other configurations are basically the same as those of the limiting current type gas sensor 1A and the like, and thus duplicated description will be omitted.

Note that, as in the limiting current type gas sensor 5M1 shown in FIG. 79(b), the cavity portion C of the substrate 12 having the MEMS beam structure is not limited to the boat-shaped structure, and the limits shown in FIGS. 80(a) and 80(b) are provided. The cavity C having an open structure such as the current gas sensor 5M2 may be used.

With any of the configurations, the temperature dependence of the porous film can be easily improved, and the limiting current type gas sensor capable of further stabilizing the sensor characteristics can be obtained.

In either case, it is also possible to insert the low-concentration doped polysilicon layer 300 having high thermal conductivity below the micro heater MH.

Further, instead of the porous Pt film 61, a porous Pt/Ti film may be applied.

(Sixth Embodiment)
(Schematic configuration)
In the sixth embodiment, as schematically shown in FIG. 29(f), the gas intake portion 305 is provided in the sensor portion SP of the limiting current type gas sensor, so that the porous film described above is provided. The temperature dependence of is improved.

In short, the limiting current type gas sensor according to the sixth embodiment includes the substrate 12, the heater MH arranged on the substrate 12 via the first insulating layer 181, and the heater MH via the second insulating layer 182. The gas intake part 305 arranged as a lower electrode, the lower electrode 28D arranged on the gas intake part 305, the solid electrolyte layer 30 arranged on the lower electrode 28D, and the lower electrode 28D on the solid electrolyte layer 30. An upper electrode 28U disposed on a surface facing the substrate, and a cavity C formed on the substrate 12 to be substantially larger than the heater MH. The gas intake portion 305 is a gas introduction path for introducing a measurement gas. And a porous membrane (columnar portion) arranged on the gas introduction path and having a gas diffusion structure in the in-plane direction.

(First Example of Sixth Embodiment)
As a first example of the sixth embodiment, first, a case will be described in which the gas intake portion 305 of the sensor portion SP is configured by the gas diffusion passage MP1 serving as a gas introduction passage and the porous membranes 51 and 61. ..

Here, the gas diffusion path MP1 has an in-plane gas throttle structure, and the porous membranes 51 and 61 have an in-plane gas diffusion structure.

A schematic plane pattern configuration of the limiting current type gas sensor 6A1 according to the first example of the sixth embodiment is represented as shown in FIG. 81(a), and is taken along line VIA1-VIA1 of FIG. 81(a). , A schematic cross-sectional structure of the gas sensor 6A1 formed in the MEMS beam structure is shown in FIG. 81(b).

That is, as shown in FIGS. 81(a) and 81(b), the sensor portion SP of the limiting current type gas sensor 6A1 according to the first example of the sixth embodiment has a gas diffusion path (having a hollow structure). Gas introduction path) MP1, a porous oxide film (porous film) 51 arranged on the gas diffusion path MP1, a columnar oxide film 53 arranged so as to cover the porous oxide film 51, and a columnar oxide film 53 on the columnar oxide film 53. The lower electrode (Pt/Ti laminated film) 28D arranged, the solid electrolyte layer 30 arranged so as to cover the columnar oxide film 53 and the lower electrode 28D, and the solid electrolyte layer 30 opposed to the lower electrode 28D. And an upper electrode 28U.

In the case of the limiting current type gas sensor 6A1 according to the first example of the sixth embodiment, the columnar electrode is constituted by the columnar oxide film 53 and the lower electrode 28D, and the gas diffusion path MP1 and the porous oxide film 51 are used for gas extraction. The inserting unit 305 is configured.

Here, the columnar electrode has a gas throttle structure in the direction perpendicular to the surface.

The other configurations are basically the same as those of the limiting current type gas sensor 1A and the like, and thus duplicated description will be omitted.

Note that, as in the limiting current type gas sensor 6A1 shown in FIG. 81(b), the cavity portion C of the substrate 12 having the MEMS beam structure is not limited to the boat type structure, and the limit shown in FIGS. 82(a) and 82(b) is not limited. The cavity C having an open structure such as the current type gas sensor 6A2 may be used.

(Modification 1 of the first example of the sixth embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 6B1 according to the first modification of the first example of the sixth embodiment is represented as shown in FIG. 83(a), and VIB1- of FIG. 83(a). A schematic cross-sectional structure of the gas sensor 6B1 formed in the MEMS beam structure along the line VIB1 is represented as shown in FIG. 83(b).

That is, the sensor portion SP of the limiting current type gas sensor 6B1 according to the first modification of the first example of the sixth embodiment has a hollow structure as shown in FIGS. 83(a) and 83(b). Gas diffusion path (gas introduction path) MP1, porous oxide film (porous film) 51 arranged on gas diffusion path MP1, and lower electrode (columnar Pt/Ti film) arranged so as to cover porous oxide film 51. ) 28DB, a solid electrolyte layer 30 arranged so as to cover the lower electrode 28DB, and an upper electrode 28U arranged on the solid electrolyte layer 30 facing the lower electrode 28DB.

In the case of the limiting current type gas sensor 6B1 according to the modified example 1 of the first example of the sixth embodiment, the lower electrode 28DB constitutes a columnar electrode, and the gas diffusion path MP1 and the porous oxide film 51 form the gas intake portion. 305 is configured.

The other configurations are basically the same as those of the limiting current type gas sensor 1A and the like, and thus duplicated description is omitted.

Note that, as in the limiting current type gas sensor 6B1 shown in FIG. 83(b), the cavity portion C of the substrate 12 having the MEMS beam structure is not limited to the boat type structure, and the limit shown in FIGS. 84(a) and 84(b) is not limited. The cavity C having an open structure such as the current gas sensor 6B2 may be used.

(Modification 2 of the first example of the sixth embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 6C1 according to the second modification of the first example of the sixth embodiment is represented as shown in FIG. 85(a), and VIC1- of FIG. 85(a). A schematic cross-sectional structure of the gas sensor 6C1 formed in the MEMS beam structure along the line VIC1 is represented as shown in FIG. 85(b).

That is, the sensor portion SP of the limiting current type gas sensor 6C1 according to the modified example 2 of the first example of the sixth embodiment has a hollow structure as shown in FIGS. 85(a) and 85(b). A gas diffusion path (gas introduction path) MP1, a porous Pt film (porous film) 61 arranged on the gas diffusion path MP1, a columnar oxide film 53 arranged so as to cover the porous Pt film 61, and a columnar oxidation. A lower electrode (Pt/Ti laminated film) 28D arranged on the film 53, a solid electrolyte layer 30 arranged so as to cover the columnar oxide film 53 and the lower electrode 28D, and a solid electrolyte layer 30 facing the lower electrode 28D. And an upper electrode 28U disposed above.

In the case of the limiting current type gas sensor 6C1 according to the modified example 2 of the first example of the sixth embodiment, the columnar electrode is constituted by the columnar oxide film 53 and the lower electrode 28D, and the gas diffusion path MP1 and the porous Pt film 61. And form a gas intake unit 305.

The other configurations are basically the same as those of the limiting current type gas sensor 1A and the like, and thus duplicated description will be omitted.

Note that, as in the limiting current type gas sensor 6C1 shown in FIG. 85(b), the cavity portion C of the substrate 12 having the MEMS beam structure is not limited to the boat-shaped structure, and the limit shown in FIGS. 86(a) and 86(b). The cavity C having an open structure such as the current gas sensor 6C2 may be used.

(Modification 3 of the first example of the sixth embodiment)
A schematic plane pattern configuration of a limiting current type gas sensor 6D1 according to Modification 3 of the first example of the sixth embodiment is represented as shown in FIG. 87(a), and VID1- of FIG. 87(a). A schematic cross-sectional structure of the gas sensor 6D1 formed in the MEMS beam structure along the line VID1 is represented as shown in FIG. 87(b).

That is, the sensor portion SP of the limiting current type gas sensor 6D1 according to the modification 3 of the first example of the sixth embodiment has a hollow structure as shown in FIGS. 87(a) and 87(b). Gas diffusion path (gas introduction path) MP1, porous Pt film (porous film) 61 arranged on the gas diffusion path MP1, and lower electrode (columnar Pt/Ti film) arranged so as to cover the porous Pt film 61. ) 28DB, a solid electrolyte layer 30 arranged so as to cover the lower electrode 28DB, and an upper electrode 28U arranged on the solid electrolyte layer 30 facing the lower electrode 28DB.

In the case of the limiting current type gas sensor 6D1 according to the modified example 3 of the first example of the sixth embodiment, the lower electrode 28DB forms a columnar electrode, and the gas diffusion path MP1 and the porous Pt film 61 form the gas intake part. 305 is configured.

The other configurations are basically the same as those of the limiting current type gas sensor 1A and the like, and thus duplicated description will be omitted.

Note that, as in the limiting current type gas sensor 6D1 shown in FIG. 87(b), the cavity portion C of the substrate 12 having the MEMS beam structure is not limited to the boat-shaped structure, and the limit shown in FIGS. 88(a) and 88(b). The cavity C having an open structure such as the current type gas sensor 6D2 may be used.

(Second Example of Sixth Embodiment)
As a second example of the sixth embodiment, first, a case will be described in which the gas intake portion 305 of the sensor portion SP is composed of the porous oxide film 51 serving as a gas introduction path and the porous films 51 and 61. ..

Here, the porous films 51 and 61 are provided with an in-plane gas throttle structure.

The schematic plane pattern configuration of the limiting current type gas sensor 6E1 according to the second example of the sixth embodiment is represented as shown in FIG. 89(a), and is along the VIE1-VIE1 line in FIG. 89(a). , A schematic cross-sectional structure of the gas sensor 6E1 formed in the MEMS beam structure is shown in FIG. 89(b).

That is, the sensor portion SP of the limiting current type gas sensor 6E1 according to the second example of the sixth embodiment, as shown in FIGS. 89(a) and 89(b), serves as a gas introduction path. Porous oxide film 51A, second porous oxide film (porous film) 51B arranged on first porous oxide film 51A, and columnar oxide film 53 arranged so as to cover second porous oxide film 51B. A lower electrode (Pt/Ti laminated film) 28D arranged on the columnar oxide film 53, a solid electrolyte layer 30 arranged so as to cover the columnar oxide film 53 and the lower electrode 28D, and the lower electrode 28D. And an upper electrode 28U disposed on the solid electrolyte layer 30.

In the case of the limiting current type gas sensor 6E1 according to the second example of the sixth embodiment, the columnar electrode is constituted by the columnar oxide film 53 and the lower electrode 28D, and the first porous oxide film 51A and the second porous oxide film are formed. The gas intake part 305 is constituted by the film 51B.

The other configurations are basically the same as those of the limiting current type gas sensor 1A and the like, and thus duplicated description will be omitted.

Note that, as in the limiting current type gas sensor 6E1 shown in FIG. 89(b), the cavity portion C of the substrate 12 having the MEMS beam structure is not limited to the boat-shaped structure, and the limits shown in FIGS. 90(a) and 90(b) are not limited. The cavity C having an open structure such as the current gas sensor 6E2 may be used.

(Modification 1 of the second example of the sixth embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 6F1 according to the modified example 1 of the second example of the sixth embodiment is represented as shown in FIG. 91(a), and VIF1- of FIG. 91(a). A schematic cross-sectional structure of the gas sensor 6F1 formed in the MEMS beam structure along the VIF1 line is shown in FIG. 91(b).

That is, the sensor portion SP of the limiting current type gas sensor 6F1 according to the first modification of the second example of the sixth embodiment is provided with a gas introduction path as shown in FIGS. 91(a) and 91(b). Is formed so as to cover the first porous oxide film 51A, the second porous oxide film 51B arranged on the first porous oxide film 51A, and the second porous oxide film 51B. A lower electrode (columnar Pt/Ti film) 28DB, a solid electrolyte layer 30 arranged so as to cover the lower electrode 28DB, and an upper electrode 28U arranged on the solid electrolyte layer 30 facing the lower electrode 28DB.

In the case of the limiting current type gas sensor 6F1 according to the modification 1 of the second example of the sixth embodiment, the lower electrode 28DB constitutes a columnar electrode, and the first porous oxide film 51A and the second porous oxide film 51B. And form a gas intake unit 305.

The other configurations are basically the same as those of the limiting current type gas sensor 1A and the like, and thus duplicated description will be omitted.

As in the limiting current type gas sensor 6F1 shown in FIG. 91(b), the cavity portion C of the substrate 12 having the MEMS beam structure is not limited to the boat-shaped structure, and the limit shown in FIG. 92(a) and FIG. 92(b). The cavity C having an open structure such as the current gas sensor 6F2 may be used.

(Modification 2 of the second example of the sixth embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 6G1 according to the second modification of the second example of the sixth embodiment is represented as shown in FIG. 93(a), and VIG1- of FIG. 93(a). A schematic cross-sectional structure of the gas sensor 6G1 formed in the MEMS beam structure along the line VIG1 is represented as shown in FIG. 93(b).

That is, the sensor portion SP of the limiting current type gas sensor 6G1 according to the modified example 2 of the second example of the sixth embodiment is provided with a gas introduction path as shown in FIGS. 93(a) and 93(b). On the columnar oxide film 51, the porous Pt film (porous film) 61 arranged on the porous oxide film 51, the columnar oxide film 53 arranged so as to cover the porous Pt film 61, and the columnar oxide film 53. The lower electrode (Pt/Ti laminated film) 28D arranged, the solid electrolyte layer 30 arranged so as to cover the columnar oxide film 53 and the lower electrode 28D, and the solid electrolyte layer 30 opposed to the lower electrode 28D. And an upper electrode 28U.

In the case of the limiting current type gas sensor 6G1 according to the modification 2 of the second example of the sixth embodiment, the columnar electrode is constituted by the columnar oxide film 53 and the lower electrode 28D, and the porous oxide film 51 and the porous Pt film 61. And form a gas intake unit 305.

The other configurations are basically the same as those of the limiting current type gas sensor 1A and the like, and thus duplicated description will be omitted.

Note that, as in the limiting current type gas sensor 6G1 shown in FIG. 93(b), the cavity portion C of the substrate 12 having the MEMS beam structure is not limited to the boat-shaped structure, and the limit shown in FIGS. 94(a) and 94(b). The cavity C having an open structure such as the current gas sensor 6G2 may be used.

(Modification 3 of the second example of the sixth embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 6H1 according to the modified example 3 of the second example of the sixth embodiment is represented as shown in FIG. 95(a), and VIH1- of FIG. 95(a). A schematic cross-sectional structure of the gas sensor 6H1 formed in the MEMS beam structure along the line VIH1 is represented as shown in FIG. 95(b).

That is, the sensor portion SP of the limiting current type gas sensor 6H1 according to the modified example 3 of the second example of the sixth embodiment, as shown in FIGS. 95(a) and 95(b), is provided with a gas introduction path. A porous oxide film 51, a porous Pt film (porous film) 61 arranged on the porous oxide film 51, a lower electrode (columnar Pt/Ti film) 28DB arranged so as to cover the porous Pt film 61, The solid electrolyte layer 30 is arranged so as to cover the lower electrode 28DB, and the upper electrode 28U is arranged on the solid electrolyte layer 30 facing the lower electrode 28DB.

In the case of the limiting current type gas sensor 6H1 according to the modified example 3 of the second example of the sixth embodiment, the columnar electrode is constituted by the lower electrode 28DB, and the gas intake portion is constituted by the porous oxide film 51 and the porous Pt film 61. 305 is configured.

The other configurations are basically the same as those of the limiting current type gas sensor 1A and the like, and thus duplicated description will be omitted.

Note that, as in the limiting current type gas sensor 6H1 shown in FIG. 95(b), the cavity portion C of the substrate 12 having the MEMS beam structure is not limited to the boat-shaped structure, and the limit shown in FIG. 96(a) and FIG. 96(b). The cavity C having an open structure such as the current gas sensor 6H2 may be used.

(Third Example of Sixth Embodiment)
As a third example of the sixth embodiment, first, a case will be described in which the gas intake portion 305 of the sensor portion SP is composed of a porous Pt film 61 serving as a gas introduction path and porous films 51, 61. ..

Here, the porous films 51 and 61 have a gas diffusion structure in the in-plane direction.

A schematic plane pattern configuration of the limiting current type gas sensor 6J1 according to the third example of the sixth embodiment is expressed as shown in FIG. 97(a), and is along the line VIJ1-VIJ1 in FIG. 97(a). , A schematic cross-sectional structure of the gas sensor 6J1 formed in the MEMS beam structure is shown in FIG. 97(b).

That is, the sensor portion SP of the limiting current type gas sensor 6J1 according to the third example of the sixth embodiment is, as shown in FIGS. 97(a) and 97(b), a porous Pt film serving as a gas introduction path. 61, a porous oxide film (porous film) 51 arranged on the porous Pt film 61, a columnar oxide film 53 arranged so as to cover the porous oxide film 51, and a lower portion arranged on the columnar oxide film 53. Electrode (Pt/Ti laminated film) 28D, solid electrolyte layer 30 arranged so as to cover columnar oxide film 53 and lower electrode 28D, and upper electrode 28U arranged on solid electrolyte layer 30 facing lower electrode 28D. With.

In the case of the limiting current type gas sensor 6J1 according to the third example of the sixth embodiment, the columnar electrode is constituted by the columnar oxide film 53 and the lower electrode 28D, and the gas extraction is performed by the porous Pt film 61 and the porous oxide film 51. The inserting unit 305 is configured.

The other configurations are basically the same as those of the limiting current type gas sensor 1A and the like, and thus duplicated description will be omitted.

Note that, as in the limiting current type gas sensor 6J1 shown in FIG. 97(b), the cavity portion C of the substrate 12 having the MEMS beam structure is not limited to the boat-shaped structure, and the limit shown in FIGS. 98(a) and 98(b) is not limited. The cavity C having an open structure such as the current gas sensor 6J2 may be used.

(Modification 1 of Example 3 of the sixth embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 6K1 according to the first modification of the third example of the sixth embodiment is represented as shown in FIG. 99(a), and VIK1- of FIG. 99(a). A schematic cross-sectional structure of the gas sensor 6K1 formed in the MEMS beam structure along the line VIK1 is represented as shown in FIG. 99(b).

That is, the sensor portion SP of the limiting current type gas sensor 6K1 according to the first modification of the third example of the sixth embodiment has a gas introduction path as shown in FIGS. 99(a) and 99(b). A porous Pt film 61, a porous oxide film (porous film) 51 arranged on the porous Pt film 61, a lower electrode (columnar Pt/Ti film) 28DB arranged so as to cover the porous oxide film 51, The solid electrolyte layer 30 is arranged so as to cover the lower electrode 28DB, and the upper electrode 28U is arranged on the solid electrolyte layer 30 facing the lower electrode 28DB.

In the case of the limiting current type gas sensor 6K1 according to the modified example 1 of the third example of the sixth embodiment, the lower electrode 28DB constitutes a columnar electrode, and the porous Pt film 61 and the porous oxide film 51 form a gas intake portion. 305 is configured.

The other configurations are basically the same as those of the limiting current type gas sensor 1A and the like, and thus duplicated description is omitted.

Note that, as in the limiting current type gas sensor 6K1 shown in FIG. 99(b), the cavity portion C of the substrate 12 having the MEMS beam structure is not limited to the boat type structure, and the limits shown in FIGS. 100(a) and 100(b) The cavity C having an open structure such as the current type gas sensor 6K2 may be used.

(Modification 2 of the third example of the sixth embodiment)
A schematic plane pattern configuration of the limiting current type gas sensor 6L1 according to the second modification of the third example of the sixth embodiment is represented as shown in FIG. 101(a), and VIL1- in FIG. 101(a). A schematic cross-sectional structure of the gas sensor 6L1 formed in the MEMS beam structure along the line VIL1 is represented as shown in FIG. 101(b).

That is, the sensor portion SP of the limiting current type gas sensor 6L1 according to the second modification of the third example of the sixth embodiment has a gas introduction path as shown in FIGS. 101(a) and 101(b). Is formed so as to cover the first porous Pt film 61A, the second porous Pt film (porous film) 61B arranged on the first porous Pt film 61A, and the second porous Pt film 61B. The columnar oxide film 53, the lower electrode (Pt/Ti laminated film) 28D arranged on the columnar oxide film 53, the solid electrolyte layer 30 arranged so as to cover the columnar oxide film 53 and the lower electrode 28D, and the lower electrode. 28D, and the upper electrode 28U arranged on the solid electrolyte layer 30 facing 28D.

In the case of the limiting current type gas sensor 6L1 according to the second modification of the third example of the sixth embodiment, the columnar electrode is constituted by the columnar oxide film 53 and the lower electrode 28D, and the first porous Pt film 61A and the first porous Pt film 61A are provided. The second porous Pt film 61B constitutes the gas intake part 305.

The other configurations are basically the same as those of the limiting current type gas sensor 1A and the like, and thus duplicated description will be omitted.

Note that, as in the limiting current type gas sensor 6L1 shown in FIG. 101(b), the cavity portion C of the substrate 12 having the MEMS beam structure is not limited to the boat type structure, and the limits shown in FIGS. 102(a) and 102(b) The cavity C having an open structure such as the current type gas sensor 6L2 may be used.

(Modification 3 of Example 3 of the sixth embodiment)
A schematic plane pattern configuration of a limiting current type gas sensor 6M1 according to Modification 3 of Example 3 of the sixth embodiment is represented as shown in FIG. 103(a), and VIM1- of FIG. 103(a). A schematic cross-sectional structure of the gas sensor 6M1 formed in the MEMS beam structure along the line VIM1 is represented as shown in FIG. 103(b).

That is, the sensor portion SP of the limiting current type gas sensor 6M1 according to the modified example 3 of the third example of the sixth embodiment is provided with a gas introduction path as shown in FIGS. 103(a) and 103(b). Is formed so as to cover the first porous Pt film 61A, the second porous Pt film (porous film) 61B arranged on the first porous Pt film 61A, and the second porous Pt film 61B. A lower electrode (columnar Pt/Ti film) 28DB, a solid electrolyte layer 30 arranged so as to cover the lower electrode 28DB, and an upper electrode 28U arranged on the solid electrolyte layer 30 facing the lower electrode 28DB.

In the case of the limiting current type gas sensor 6M1 according to the modified example 3 of the third example of the sixth embodiment, the lower electrode 28DB constitutes a columnar electrode, and the first porous Pt film 61A and the second porous Pt film 61B. And form a gas intake unit 305.

The other configurations are basically the same as those of the limiting current type gas sensor 1A and the like, and thus duplicated description will be omitted.

Note that, as in the limiting current type gas sensor 6M1 shown in FIG. 103(b), the cavity portion C of the substrate 12 having the MEMS beam structure is not limited to the boat-shaped structure, and the limit shown in FIGS. 104(a) and 104(b). The cavity C having an open structure such as the current type gas sensor 6M2 may be used.

With any of the configurations, the temperature dependence of the porous film can be easily improved, and the limiting current type gas sensor capable of further stabilizing the sensor characteristics can be obtained.

In either case, it is also possible to insert the low-concentration doped polysilicon layer 300 having high thermal conductivity below the micro heater MH.

Further, instead of the porous Pt films 61, 61A, 61B, a porous Pt/Ti film may be applied.

(Operating principle)
Here, the operating principle of the limiting current type gas sensor will be briefly described.
-Operation to detect gas concentration-
First, when the zirconia solid electrolyte is heated to several hundred degrees and a voltage is applied to the zirconia solid electrolyte, oxygen ions ionized at the catalyst electrode are conducted from one side of the solid electrolyte to the other side. At this time, if the amount of oxygen gas sucked into the electrolyte is limited by utilizing small pores or porosity, a saturation phenomenon will occur in which the current becomes a constant value even if the voltage is increased. This current is called the limiting current and is proportional to the ambient oxygen concentration. Therefore, if a constant voltage is applied, the oxygen concentration can be detected from the flowing current value. It is also possible to detect the concentration of water vapor by the same principle by switching the applied voltage.

A flowchart showing the operation of detecting the gas concentration by the limiting current type gas sensor is expressed as shown in FIG. Further, in the limiting current type gas sensor, the relationship between the YSZ temperature and time in the gas concentration detecting operation is schematically shown in FIG. 106, and the schematic cross-sectional structure for explaining the operation principle is as shown in FIG. 107. Represented by

In FIG. 107, the solid electrolyte layer 106 is aged by the microheater MH to several hundred degrees Celsius, for example, about 500 degrees Celsius, and a voltage V is applied between the upper electrode (cathode) 105U and the porous electrode (anode) 105D to generate a current. When I is flown, oxygen ions (O ²⁻ ) are injected into the solid electrolyte layer 106 at the upper electrode 105U by an electrochemical reaction of O ₂ +4e ⁻ ⇔2O ²⁻ .

On the other hand, the porous electrode _{^{105D, 2O 2- ⇔O 2 + 4e}} - release of the oxygen gas (O ₂ gas) generated by the reaction.

Oxygen ions (O ²⁻ ) are propagated in the solid electrolyte layer 106 based on hopping conduction. Here, an energy diagram for explaining hopping conduction of oxygen ions (O ²⁻ ) is schematically represented as shown in FIG. When the electric field Ex is applied to the solid electrolyte layer 106, the effect causes the bottom of the conductor to be tilted by −eEx. Since the height of the conduction barrier of oxygen ions (O ²⁻ ) is reduced by that amount, hopping conduction of oxygen ions (O ²⁻ ) is performed together with thermal excitation.

When the amount of oxygen gas sucked into the solid electrolyte layer 106 is limited, a saturation phenomenon in which the current becomes a constant value appears even when the voltage is increased. In the limiting current type gas sensor, the limiting current in the current-voltage characteristic is schematically represented as shown in FIG. That is, in FIG. 109, the current appearing in the period T ₂ represents the limiting current I _O for oxygen gas, and the current appearing in the period T ₃ represents the limiting current I _W for water vapor.

Since the limiting currents I _O and I _W are proportional to the ambient oxygen concentration and water vapor concentration, the values of the limiting currents I _O and I _W and the oxygen concentration and water vapor concentration values are associated in advance and registered in the detection circuit 107. I'll do it. In this way, by measuring the values of the limiting currents I _O and I _W , it is possible to detect the oxygen concentration and water vapor concentration corresponding thereto.

Also, by switching the voltage applied between the upper electrode 105U and the porous electrode 105D, not only the oxygen concentration but also the water vapor concentration can be detected.

The operation of detecting the gas concentration using the limiting current type gas sensor will be described with reference to FIGS. 105 and 106.

In FIG. 106, T _on corresponds to the heater on period and T _off corresponds to the heater _off period. Heating power supplied to the heater on time T _on is, for example, about 5 mW.

(A) First, a micro heater is used to heat the sensor from room temperature to a measurement temperature (for example, 500° C.) (FIG. 105: step S1→S2: NO→S1→... ). As shown in FIG. 106, for example, the YSZ temperature T rises from 0° C. to about 500° C. during the time t=0 to t=0.1 seconds.

(B) When the measured temperature is reached (FIG. 105: step S2: YES), a certain time is waited until it stabilizes (FIG. 105: step S3). As shown in FIG. 106, for example, the YSZ temperature T is maintained at about 500° C. during the waiting period T _W of time t=0.1 seconds to t=0.3 seconds.

(C) Next, a voltage is applied between the upper electrode 105U and the porous electrode 105D (FIG. 105: step S4). As shown in FIG. 106, for example, the YSZ temperature T is maintained at about 500° C. during the measurement period T _M of time t=0.3 seconds to t=0.5 seconds.

(D) Next, the value of the limiting current is measured, and the gas concentration corresponding to the limiting current is detected (FIG. 105: step S5).

(E) Next, the micro heater is turned off to cool the sensor. As shown in FIG. 106, for example, the YSZ temperature T is cooled from about 500° C. to room temperature from time t=0.5 seconds.

In the temperature cycle described above, for example, heating, standby, measurement, and cooling may be repeated about once per minute.

(Electrochemical reaction)
In a limiting current type gas sensor, a schematic sectional structure for explaining ionic conduction is represented as shown in FIG.

An electrochemical reaction in the limiting current type gas sensor will be described with reference to FIGS. 109 and 110.

(A) When the solid electrolyte layer 106 is aged by a micro heater to, for example, about 500° C., and a voltage V is applied between the cathode 105U and the anode 105D to flow a current I, the current I flows in a period T ₁ in FIG. Increases and reaches the limiting current I _O.

In the period T ₁ of FIG. 109, the oxygen ion O ²⁻ diffuses in the solid electrolyte layer 106 due to the electrochemical reaction of O ₂ +4e ⁻ ⇔2O ²⁻ . At this time, the flow amount of the oxygen gas O ₂ is larger than the amount of diffusion of the oxygen ions O ²⁻ .

(B) During the period T ₂ of FIG. 109 in which the limiting current I _O is held, the electrolysis reaction of oxygen gas molecules is performed, and as shown in FIG. 110, at the interface between the cathode 105U and the solid electrolyte layer 106, Oxygen ions O ^{2 −} are injected into the solid electrolyte layer 106 by the electrochemical reaction of O ₂ +4e ⁻ ⇔ 2O ^{2 −} .

On the other hand, in the interface between the anode 105D and the solid electrolyte layer _{^{106, 2O 2- ⇔O 2 + 4e}} - by the reaction, the release of oxygen gas O ₂ is produced.

(C) When the temperature T of the solid electrolyte layer 106 is maintained at, for example, about 500° C. and the voltage V is further increased, the current I increases and reaches the limiting current I _W in the period T ₃ in FIG. 109.

(D) During the period T ₃ in FIG. 109 in which the limiting current I _W is held, the electrolysis reaction of the adsorbed oxygen gas O _{ad and} the electrolysis reaction of water vapor (H ₂ O) are performed.

Here, as shown in FIG. 110, at the interface between the cathode 105U and the solid electrolyte layer 106, oxygen ions O ²⁻ are injected into the solid electrolyte layer 106 due to the electrochemical reaction of O ₂ +4e ⁻ ⇔2O ^2−. .. Further, hydrogen is released due to the electrochemical reaction of H ₂ O+2e ⁻ ⇔H ₂ +O ^{2 −} . That is, the water vapor (H ₂ O) is electrolyzed, and the oxygen ions O ²⁻ move inside the solid electrolyte layer 106 by hopping conduction.

On the other hand, in the interface between the anode 105D and the solid electrolyte layer 106, the electrolysis of adsorbed oxygen gas ^{_{O ad, 2O 2- ⇔O 2 +}} 4e - release of the oxygen gas O ₂ is generated by the reaction. Similarly, due to the electrolysis of water vapor (H ₂ O), oxygen gas O ₂ is released by the reaction of 2O ^2- ↔O ₂ +4e ⁻ .

(E) When the temperature T of the solid electrolyte layer 106 is maintained at, for example, about 500° C. and the voltage V is further increased, the current I increases, and the electrolysis reaction of the adsorbed oxygen gas O _ad during the period T ₄ in FIG. And the electrolysis reaction of water vapor (H ₂ O). Further, the electrolysis of the solid electrolyte layer 106 starts.

Here, as shown in FIG. 110, at the interface between the cathode 105U and the solid electrolyte layer 106, oxygen ions O ²⁻ are injected into the solid electrolyte layer 106 due to the electrochemical reaction of O ₂ +4e ⁻ ⇔2O ^2−. .. In addition, hydrogen is released due to the electrochemical reaction of H ₂ O+2e ⁻ ⇔H ₂ +O ^{2 −} . That is, the water vapor (H ₂ O) is electrolyzed, and the oxygen ions O ²⁻ move within the solid electrolyte layer 106 by hopping conduction.

On the other hand, in the interface between the anode 105D and the solid electrolyte layer 106, the electrolysis of adsorbed oxygen gas ^{_{O ad, 2O 2- ⇔O 2 +}} 4e - release of the oxygen gas O ₂ is generated by the reaction. Similarly, due to the electrolysis of water vapor (H ₂ O), oxygen gas O ₂ is released by the reaction of 2O ^2- ↔O ₂ +4e ⁻ .

Further, by the electrolysis of the solid electrolyte layer 106, the oxygen vacancy concentration is also in equilibrium with the atmospheric oxygen partial pressure based on the following formula O _O ^x ⇔ 1/2·O ₂ (g)+V _O ^.. +2e′. Dependent. This equation shows that the electronic conductivity depends on the oxygen partial pressure in equilibrium with the solid, and at high temperatures, the entropy of the product system is larger, so at high temperatures the reaction is biased to the right, so it also depends on temperature. ..

(package)
A schematic bird's-eye view configuration showing the lid 131 of the package accommodating the limiting-current type gas sensor according to each embodiment is represented as shown in FIG. As shown in FIG. 111, the package lid 131 has a large number of through holes 132 through which gas can pass but foreign matter cannot pass. For the package lid 131, a metal mesh, a metal with small holes, a porous ceramic, or the like can be applied.

A schematic bird's-eye view configuration showing the main body 141 of the package accommodating the limiting current type gas sensor according to each embodiment is represented as shown in FIG. 112. As shown in FIG. 112, a package main body 141 accommodates a chip 142 of a limiting current type gas sensor having a plurality of terminals and is electrically connected by a plurality of bonding wires 143. A lid 131 is put on the upper part of the package body 141 and mounted on a printed circuit board or the like by soldering.

(Example of sensor node configuration using energy harvester power supply)
As shown in FIG. 113, the limiting current type gas sensor (sensor node) according to each embodiment includes sensors 151, a wireless module 152, a microcomputer 153, an energy harvester power supply 154, and a storage element 155.

The configuration of the sensors 151 is as described in each embodiment.

The wireless module 152 is a module including an RF circuit that transmits and receives wireless signals.

The microcomputer 153 has a management function of the energy harvester power supply 154, and inputs the power from the energy harvester power supply 154 to the sensors 151. At this time, the microcomputer 153 may input power based on a heater power profile that saves power consumption of the sensors 151.

For example, the first power, which is a relatively large power, may be input for the first period T1, and then the second power, which is a relatively small power, may be input for the second period T2. Further, the data may be read in the second period T2, and after the second period T2 has passed, the power supply may be stopped only in the third period T3.

The energy harvester power supply 154 obtains electric power by collecting energy such as sunlight, illumination light, vibration generated by a machine, and heat.

Power storage element 155 is, for example, a lithium-ion power storage element capable of storing electric power.

The operation of such a sensor node will be described below.

First, as shown by (1) in FIG. 113, electric power from the energy harvester power supply 154 is supplied to the microcomputer 153. As a result, the microcomputer 153 boosts the voltage from the energy harvester power supply 154, as indicated by (2) in FIG. 113.

Next, as shown in (3) of FIG. 113, after reading the voltage of the storage element 155, as shown in (4) and (5) of FIG. 113, power supply to the storage element 155, Electric power is drawn from the storage element 155.

Next, as shown in (6) in FIG. 113, power is supplied to the sensors 151 based on the heater power profile, and as shown in (7) in FIG. 113, the sensor resistance value, the Pt resistance value, etc. Read the data.

Next, as shown by (8) in FIG. 113, power is supplied to the wireless module 152, and as shown by (9) in FIG. 113, data such as the sensor resistance value and the Pt resistance value is transferred to the wireless module 152. Send to.

Finally, as indicated by (10) in FIG. 113, the wireless module 152 wirelessly transmits data such as the sensor resistance value and the Pt resistance value.

(Sensor package: Block structure)
A schematic block configuration of the sensor package 96 including the limiting current type gas sensor according to each embodiment is represented as shown in FIG.

As shown in FIG. 114, the sensor package 96 equipped with the limiting current type gas sensor according to each embodiment has a thermistor section 90 for a temperature sensor, a YSZ sensor section 92 for a humidity/oxygen sensor, and a thermistor section 90. An AD/DA conversion unit 94 that receives analog information SA ₂ ·SA ₁ from the YSZ sensor unit 92 and also supplies control signals S2 ·S1 to the thermistor unit 90 ·YSZ sensor unit 92, and digital input/output from the outside And signals DI and DO.

As the thermistor section 90, for example, an NTC thermistor, a PTC thermistor, a ceramic PTC, a polymer PTC, a CTR thermistor or the like can be applied.

The limiting current type gas sensor according to each embodiment can be applied to the YSZ sensor unit 92. In the YSZ sensor unit 92, absolute humidity (Absolute Humidity) and relative humidity (RH: Relative Humidity) can be measured, but since the temperature becomes a reference when detecting relative humidity (RH), the thermistor unit 90 is used. The detected temperature information is needed.

(Sensor network)
A schematic block configuration of a sensor network system to which the limiting current gas sensor according to each embodiment is applied is represented as shown in FIG.

As shown in FIG. 115, the sensor network is a network in which many sensors are connected to each other. Already, new approaches using sensor networks have started in various fields such as factories, medical/healthcare, transportation, construction, agriculture, and environmental management.

In these fields, it is desired to use a sensor having high durability and high response speed, and therefore it is desirable to apply the limiting current type gas sensor according to each embodiment as, for example, a humidity sensor. Since such a humidity sensor uses zirconia, it has excellent durability. Therefore, it is possible to provide a highly reliable sensor network.

(Seventh to ninth embodiments)
(Seventh embodiment)
(Schematic configuration)
A schematic plane pattern configuration of the sensor portion of the limiting current type gas sensor 1A according to the seventh embodiment is represented as shown in FIG. 116(a), and the MEMS along the line IA-IA in FIG. 116(a) is shown. (Micro Electro Mechanical Systems) The schematic cross-sectional structure of the sensor portion formed in the beam structure is shown in FIG. 116(b).

That is, the limiting current type gas sensor 1A according to the seventh embodiment, as shown in FIGS. 116(a) and 116(b), corresponds to the substrate 12 having the MEMS beam structure and the sensor portion in the central portion, respectively. So that the porous electrode (Ti/Pt electrode) 5D arranged on the substrate 12, the Pt+YSZ mixed particle film (particle mixed layer) 11 and the Pt+YSZ mixed particle film 11 formed on the porous electrode 5D are surrounded. A solid electrolyte layer (YSZ thin film) 4 disposed on the solid electrolyte layer 4 and a dense electrode (Pt electrode) 5U disposed substantially vertically to the substrate 12 on the solid electrolyte layer 4 facing the porous electrode 5D. Equipped with.

In addition, Pt is platinum (Platinum) as a porous material, Ti is titanium (Titanium) as an electrode material, and YSZ is yttrium-stabilized zirconia (Yttria-Stabilized Zirconia) as a solid electrolyte material. is there.

In addition, as shown in FIGS. 116(a) and 116(b), this limiting current type gas sensor 1A has a porous electrode 5D, a Pt+YSZ mixed particle film 11, a solid electrolyte layer 4, and a dense electrode in at least the sensor portion. A porous membrane (porous layer) 13 arranged so as to cover 5U is provided. The porous film 13 is formed of, for example, Al ₂ O ₃ —SiO _{2 so} as to have a thickness of about 5 μm.

Further, the limiting current type gas sensor 1A according to the present embodiment has the insulating layer 3 as shown in FIGS. 116(a) and 116(b), and the openings 3b and 3b patterned in the insulating layer 3 are provided. In, the extended end side of the porous electrode 5D is connected to one detection terminal 2b, and the extended end (second dense electrode portion) side of the dense electrode 5U is connected to the other detection terminal 2b. The insulating layer 3 is, for example, a SiON film (silicon vaginated film) having a thickness of 1 μm.

The detection terminals 2b and 2b are polysilicon layers having a thickness of about 400 nm and are formed by ion implantation at a higher concentration than that of the microheater 2 described later.

Here, the dense electrode 5U has a surface of the solid electrolyte layer 4 facing the Pt+YSZ mixed grain film 11 in the sensor portion as a first dense electrode portion, and partially includes a part of the first dense electrode portion, The extended portion extending from a part of the first dense electrode portion is used as a second dense electrode portion, the first dense electrode portion is made of Pt (first electrode material), and the second dense electrode portion is made of Ti. It may be formed of a laminated film of (second electrode material)/Pt.

The porous electrode 5D is formed of a laminated film of Ti/Pt with a thickness of, for example, about 0.1 μm or more. This is because if it is thin, Pt aggregates and becomes insulating. In addition, it is also possible to use porous Pt having a pore diameter of about several μm to form the porous electrode 5D.

The solid electrolyte layer 4 is formed of YSZ having a thickness of about 0.3 μm or more. This is because if it is thin, the upper and lower electrodes 5D and 5U are electrically connected. For example, the solid electrolyte layer 4 is arranged so as to cover the outer peripheral portion of the Pt+YSZ mixed particle film 11 and the end portion of the porous electrode 5D on the side where the Pt+YSZ mixed particle film 11 is formed. It is possible to prevent electrical conduction between the upper and lower electrodes 5D and 5U including the above.

The Pt+YSZ mixed grain film 11 is arranged at the interface between the solid electrolyte layer 4 and the porous electrode 5D, and has a thickness of, for example, about 10 nm to 1000 nm. In the Pt+YSZ mixed grain film 11, Pt particles and YSZ particles are mixed while maintaining the shape of the particles, so that, for example, oxygen at the time of detecting the gas concentration at the sensor portion between the solid electrolyte layer 4 and the porous electrode 5D. It is possible to improve the response speed of (O) (details will be described later).

The substrate 12 having the MEMS beam structure is arranged so as to surround the sensor portion in a plan view, and is formed of, for example, a SiON film having a thickness of about 2 μm.

Here, the dense electrode 5U is disposed in contact with the surface of the solid electrolyte layer 4 facing the porous electrode 5D and the Pt+YSZ mixed grain film 11, and is formed in a metal particle sintered layer and a metal particle sintered layer (not shown). And a fine gas introduction path (not shown).

For example, in the limiting current type gas sensor 1A according to the present embodiment, the electrodes 5D and 5U themselves are formed in a nanostructure. That is, the metal particle sintered layer (dense Pt) in which Pt mixed with carbon nanotubes (CNT) is sintered, and finally CNT is burnt off to form a fine gas introduction path may be applied as the dense electrode 5U. Carbon nanoparticles may be applied instead of CNTs.

The dense electrode 5U made of dense Pt has a thickness of, for example, about 0.1 μm or more. This is because if it is too thin, Pt aggregates and insulates.

The fine gas introduction path in the dense electrode 5U can be formed by, for example, a heat treatment process of nanowires, nanotubes, nanoparticles, etc. having a nanometer scale contained in the metal particle sintered layer, or an etching treatment process combined with the heat treatment process. Is. Nanowires, nanotubes, and nanoparticles can be formed of, for example, carbon (C), zinc oxide (ZnO), or the like.

That is, the detailed description of the metal particle sintered layer and the fine gas introduction path formed in the metal particle sintered layer in the dense electrode 5U will be omitted here, but the metal particle sintered layer includes nanowires. May be. The nanowire may include CNT or ZnO. Further, the metal particle sintered layer is provided with carbon nanotubes or carbon nanoparticles, and the fine gas introduction path is formed by the combustion of the metal particle sintered layer in the atmosphere, whereby the carbon nanotubes or carbon nanoparticles are burned. It may be formed. The metal particle sintered layer may be provided with ZnO, and the fine gas introduction path may be formed by etching ZnO by wet etching after burning the metal particle sintered layer in the atmosphere.

Furthermore, the metal particles of the metal particle sintered layer may include any one of Pt, Ag, Pd, Au, and Ru. Further, the metal particle sintered layer may include nanowires that are confined in the metal particle sintered layer and are not burned by burning in the atmosphere. The nanowires or nanoparticles have a diameter of about 0.1 μm or less. The length of the nanowire is, for example, about 10 μm or less. The advantage of using the nanowires is that the gas permeation amount can be controlled by the shape (diameter, length) of the nanowires, and the gas permeation amount can be controlled by the ratio of the nanowires.

As described above, the limiting current type gas sensor 1A according to the present embodiment can control the gas permeation amount by the shape of the fine gas introduction path of the dense electrode 5U.

Further, the limiting current type gas sensor 1A according to the present embodiment can control the gas permeation amount by the content ratio of the fine gas introduction passage of the dense electrode 5U.

On the other hand, as shown in FIGS. 116A and 116B, the limiting current type gas sensor 1A according to the present embodiment has an insulating layer (for example, 1 μm thick) arranged on the substrate 12 having the MEMS beam structure. A SiON film) 1a is further provided, and a micro-heater 2 for heating is embedded in the same layer as the detection terminals 2b and 2b at least between the insulating layer 1a and the insulating layer 3 in the sensor portion. The microheater 2 is a polysilicon layer (polysilicon heater) having a thickness of about 400 nm, and has a resistance value of about 300Ω by ion implantation. The microheater 2 heats the solid electrolyte layer 4 by applying a predetermined voltage between the heater electrode portions (Ti/Pt laminated film) 9 9 connected to the electrode layers 2 a 2 a. The micro heater 2 can also be formed by a Pt heater or the like formed by printing.

The limiting-current type gas sensor 1A according to the present embodiment has a double-supported beam-structured MEMS element structure as a basic structure to reduce the heat capacity of the sensor portion and improve the sensor sensitivity.

In the limiting current type gas sensor 1A according to the present embodiment, the micro-heater 2 is limited to the case where the micro-heater 2 is arranged between the substrate 12 and the porous electrode 5D, which are the upper part of the substrate 12, with the insulating layers 1a and 3 interposed therebetween. Alternatively, it may be arranged on the lower surface of the insulating layer 1a facing the surface on which the porous electrode 5D is formed, or on the lower portion of the substrate 12. Further, the micro heater 2 may be embedded inside the substrate 12. Alternatively, the substrate 12 may have a structure in which a laminated film 103 of a silicon oxide film/silicon nitride film including a micro-heater 2 formed of polysilicon is formed (see, for example, FIG. 148).

In the limiting current type gas sensor 1A according to the present embodiment, as shown in FIGS. 116(a) and 116(b), for example, the detection voltage supplied to the dense electrode 5U and the porous electrode 5D is detected. By applying between the terminals 2b and 2b, the detection circuit 107 for detecting a predetermined gas concentration in the gas to be measured by the limiting current method is connected.

The detection circuit 107 can detect the oxygen concentration based on the limiting current. Further, the detection circuit 107 can detect the water vapor concentration based on the limiting current.

The detection terminals 2b and 2b and the heater electrode portions 9 and 9 are arranged such that their extending directions are substantially orthogonal to each other.

According to the limiting current type gas sensor 1A according to the present embodiment, the Pt+YSZ mixed grain film 11 is arranged between the porous electrode 5D and the solid electrolyte layer 4, so that oxygen at the time of detecting the gas concentration in the sensor portion is detected. It is possible to improve the response speed of oxygen in the gas (O ₂ ).

(Basic structure)
A basic cross-sectional structure of a main part of the limiting current type gas sensor 1A according to the seventh embodiment is represented as shown in FIG. 117.

That is, as shown in FIG. 117, the basic configuration of the sensor portion of the limiting current type gas sensor 1A according to the present embodiment is formed using a silicon substrate 12 and a laminated film of Pt and Ti on the silicon substrate 12. A Ti/Pt electrode 5D, a YSZ thin film 4 formed by using YSZ on the upper surface of the Ti/Pt electrode 5D, and a Pt+YSZ mixed film provided at the interface between the YSZ thin film 4 and the Ti/Pt electrode 5D. A grain film (grain mixed layer) 11 and a Pt electrode 5U disposed on at least the surface of the YSZ thin film 4 facing the Pt+YSZ mixed grain film 11 are provided.

Further, as a basic configuration of the sensor portion of the limiting current type gas sensor 1A according to the present embodiment, as shown in FIG. 117, at least the surface of the Pt electrode 5U facing the YSZ thin film 4 and the Pt+YSZ mixed grain film 11 is covered. The Al ₂ O ₃ —SiO ₂ film 13 thus arranged may be provided.

A basic schematic cross-sectional structure of the Pt+YSZ mixed grain film 11 and a schematic cross-sectional structure showing a part of the Pt+YSZ mixed grain film 11 (circled in the figure) in an enlarged manner are shown in FIG. Represented as shown.

As shown in FIG. 118(a), the Pt+YSZ mixed grain film 11 mainly exists while the Pt maintains the shape of the particles (Pt region) 11a and the YSZ mainly maintains the shape of the particles. The layer (YSZ region) 11b to be formed is mixed in a nested state, and the Pt particles and the YSZ particles are adjacent to each other at the boundary portion where the layers 11a and 11b are in contact with each other.

Ideally, as shown in FIG. 118(b), the Pt particles of the layer 11a and the YSZ particles of the layer 11b are more mixed with each other, and the mixed area is further improved, so that the YSZ thin film 4 and Ti/ The Pt electrode 5D is laminated. As shown in FIG. 118(c), the layer 11b has a structure in which a tip portion protruding toward the layer 11a is folded back, a structure in which a part of the protruding layer 11b is branched in a branch shape, or the like. Is also good.

In short, the Pt+YSZ mixed grain film 11 is formed by laminating the layers 11a and 11b between the YSZ thin film 4 and the Ti/Pt electrode 5D, and the layers 11a and 11b are mixed. By increasing the area, more accurate sensing becomes possible.

Further, the nesting state can be formed not only by stacking the layers 11a and 11b but also by annealing the stacked YSZ thin film 4 and the Ti/Pt electrode 5D.

To further explain, the basic function of the Pt+YSZ mixed grain film 11 having the above-described structure is expressed as shown in FIG. 119(a). For comparison, FIG. 119(b) schematically shows a case where Pt particles and YSZ particles do not exist in a state of being adjacent to each other.

As shown in FIG. 119(a), when the Pt particle and the YSZ particle are adjacent to each other, the moving distance LC of oxygen (O) moving between the Pt particle and the YSZ particle is as shown in FIG. As shown in, when the Pt particles and the YSZ particles are not adjacent to each other, the distance is shorter than the moving distance LN of oxygen (O) moving between the Pt particles and the YSZ particles.

That is, in the case of the Pt+YSZ mixed grain film 11 in which the Pt particles and the YSZ particles are present adjacent to each other, the increase in the Pt particles in contact with the YSZ particles makes it possible to shorten the transfer time of oxygen (O). More accurate sensing can be realized.

FIG. 120 shows the time (Time) when the measurement temperature of the micro-heater 2 is 550° C. in order to explain the basic characteristics of the Pt+YSZ mixed grain film 11 in the limiting current type gas sensor 1A according to the seventh embodiment. And the current value (current value I/It ₌₃₆₀₀ after 1 hour) flowing between the anode (A)/cathode (K) are shown in comparison.

As is clear from FIG. 120, the current value converges to “1” in the case where the Pt+YSZ mixed grain film 11 is provided (W11), as compared with the case where the Pt+YSZ mixed grain film 11 is not provided (WO11). It is possible to shorten the time until it is done.

Therefore, according to the limiting current type gas sensor 1A according to the present embodiment, since the Pt+YSZ mixed grain film 11 is provided, the oxygen concentration during the gas concentration detection at the sensor portion between the solid electrolyte layer 4 and the porous electrode 5D is detected. The response speed can be improved, and the response speed of the limiting current type gas sensor 1A can be improved.

(Production method)
The method of manufacturing the limiting current type gas sensor 1A according to the seventh embodiment includes a step of forming a Ti/Pt electrode 5D using a laminated film of Pt and Ti on the silicon substrate 12 corresponding to the sensor portion, and a Ti/Pt electrode 5D. A step of forming a Pt+YSZ mixed particle film (particle mixed layer) 11 in which Pt particles and YSZ particles are mixed on at least the sensor portion on the Pt electrode 5D, and Ti/Pt so as to cover at least the Pt+YSZ mixed particle film 11. The method includes a step of forming the YSZ thin film 4 on the electrode 5D, and a step of forming the Pt electrode 5U on at least the surface facing the Pt+YSZ mixed grain film 11 including the upper surface portion of the YSZ thin film 4.

More specifically, the method of manufacturing the limiting current type gas sensor 1A according to the seventh embodiment shown in FIGS. 116(a) and 116(b) is represented as shown in FIGS.

(A) First, as shown in FIGS. 121(a) and 121(b), a silicon substrate 12 having a thickness of about 10 μm is prepared, and about 1 μm is formed on the upper surface of the silicon substrate 12 by a plasma CVD (P-CVD) method. A thick SiON film 1a is formed.

(B) Next, as shown in FIGS. 122(a) and 122(b), a polysilicon layer having a thickness of about 400 nm is formed on the SiON film 1a, and the polysilicon layer is patterned by etching or the like. Then, the detection terminals 2b and 2b, the micro-heater 2 and the electrode layers 2a and 2a connected to the micro-heater 2 are formed in directions orthogonal to each other. Further, by the ion implantation method, the micro heater 2 is set so that the resistance value between the electrode layers 2a and 2a is 300Ω, and the detection terminals 2b and 2b and the electrode layers 2a and 2a have a higher concentration than the micro heater 2. Is formed.

(C) Next, as shown in FIGS. 123A and 123B, a SiON film 3 having a thickness of about 1 μm is formed on the entire surface by P-CVD. Then, the SiON film 3 is patterned to form openings 3a and 3b, and a part of the electrode layers 2a and 2a connected to the detection terminals 2b and 2b and the microheater 2 are selectively exposed.

(D) Next, as shown in FIGS. 124(a) and 124(b), a Ti/Pt electrode 5D and a heater electrode portion 9 having a thickness of 500 nm are formed by a sputtering method or the like, and Ti extending from the sensor portion is formed. The extended end of the /Pt electrode 5D is located on one of the detection terminals 2b exposed in the opening 3b of the SiON film 3, and the heater electrode section 9 is located on the electrode layers 2a and 2a exposed in the opening 3a of the SiON film 3. , Connect each.

(E) Next, as shown in FIGS. 125(a) and 125(b), a YSZ film having a thickness of 2 nm and a Pt film having a thickness of 2 nm are formed by a sputtering method and then annealed at 1000° C. Then, the Pt+YSZ mixed grain film 11 is formed on the Ti/Pt electrode 5D in the sensor portion.

The Pt+YSZ mixed grain film 11 can also be formed by performing a printing and sintering process using a mixed paste of YSZ particles and Pt particles.

(F) Next, as shown in FIGS. 126A and 126B, the YSZ thin film 4 is formed to a thickness of 0.5 μm by the lift-off process, and the Ti/Pt electrode 5D of the sensor portion is formed by the YSZ thin film 4. And the periphery of the Pt+YSZ mixed grain film 11 is covered.

(G) Next, as shown in FIGS. 127(a) and 127(b), as the dense electrode 5U, the surface of the YSZ thin film 4 facing the Pt+YSZ mixed grain film 11 in the sensor portion by the sputtering method (the first fine density). After the Pt film 5Pt is formed on the electrode portion), the extended end (second dense layer) including a part of the Pt film 5Pt and connected to the other detection terminal 2b exposed in the opening 3b of the SiON film 3 is formed. The electrode portion) is formed of a Ti/Pt laminated film 5Ti. The dense electrode 5U is formed so that the film thickness of the Pt film 5Pt and the Ti/Pt laminated film 5Ti is about 100 nm.

The dense electrode 5U may be formed by forming the Pt film 5Pt after forming the Ti/Pt laminated film 5Ti.

(H) Next, as shown in FIGS. 128(a) and 128(b), the silicon substrate 12 corresponding to the sensor portion is selectively etched to form a cavity C (Cavity: Cavity) is formed. The cavity C is preferably about 300 μm×300 μm, though it depends on the size of the limiting current type gas sensor 1A according to the present embodiment.

(I) After that, a porous film (for example, an Al ₂ O ₃ —SiO ₂ film) 13 having a thickness of about 5 μm is formed by printing so as to cover the sensor portion, and thereby, FIGS. The limiting current type gas sensor 1A according to the seventh embodiment having the configuration shown in (b) is completed.

As described above, according to the limiting current type gas sensor 1A according to the seventh embodiment, the response speed at the time of gas concentration detection can be improved by disposing the Pt+YSZ mixed grain film 11.

(Eighth Embodiment)
(Schematic configuration)
The schematic plane pattern configuration of the limiting current type gas sensor 1A according to the eighth embodiment is shown in FIG. 129, and the enlarged schematic plane pattern configuration of the main part is shown in FIG. The schematic cross-sectional structure of the sensor portion formed in the MEMS (Micro Electro Mechanical Systems) beam structure along the line IIA-IIA in FIG. 130 is shown in FIG. 131.

That is, as shown in FIGS. 129 to 131, the limiting current type gas sensor 1A according to the eighth embodiment includes a substrate 12 having a MEMS beam structure, a porous electrode 5D arranged on the substrate 12, and a porous electrode. The Pt+YSZ mixed particle film (particle mixed layer) 11 formed on the electrode 5D, the solid electrolyte layer 4 disposed on the porous electrode 5D on which the Pt+YSZ mixed particle film 11 is formed, and the porous electrode 5D are opposed to each other. On the solid electrolyte layer 4, a metal particle sintered layer (not shown) and a fine gas introduction path (not shown) formed in the metal particle sintered layer are arranged substantially vertically to the substrate 12. And a dense electrode 5U.

Further, this limiting current type gas sensor 1A has an insulating film 8 arranged on a porous electrode 5D via a Pt+YSZ mixed grain film 11 as shown in FIG. 131, and an opening patterned in this insulating film 8 is provided. The solid electrolyte layer 4 is arranged on the Pt+YSZ mixed grain film 11 of the portion 7 and on the insulating film 8 surrounding the opening 7.

Further, the limiting current type gas sensor 1A may include the insulating layer 3 arranged on the substrate 12, and the porous electrode 5D may be arranged on the insulating layer 3, as shown in FIG. 131.

The porous electrode 5D is made of a porous material, that is, porous Pt having a pore diameter of about several μm, and has, for example, a thickness of about 1 μm or more, and prevents Pt from aggregating and insulating. The porous electrode 5D can also be formed by a Ti/Pt laminated film.

The solid electrolyte layer 4 is formed of YSZ (Yttria-Stabilized Zirconia) having a thickness of about 4 μm or more, which is a solid electrolyte material. This is because if it is thin, the upper and lower electrodes 5D and 5U are electrically connected.

The substrate 12 having the MEMS beam structure is formed of, for example, a silicon substrate having a thickness of about 10 μm.

In the limiting current type gas sensor 1A according to the eighth embodiment, the electrodes 5D and 5U themselves are formed in a nanostructure. That is, Pt mixed with carbon nanotubes (CNT) is sintered, and finally CNT is burnt off to apply a metal particle sintered layer (dense Pt) in which a fine gas introduction path is formed as the dense electrode 5U. Carbon nanoparticles may be applied instead of CNTs.

The dense electrode 5U made of dense Pt has a thickness of, for example, about 1 μm or more. This is because if it is too thin, Pt aggregates and insulates.

In the limiting current type gas sensor 1A according to the eighth embodiment, since the oxygen gas uptake can be controlled by the dense electrode 5U, a favorable limiting current characteristic is obtained, and a limiting current type gas sensor with improved detection sensitivity is provided. Can be provided.

Here, the metal particle sintered layer serving as the dense electrode 5U includes CNTs or carbon nanoparticles, and the fine gas introduction path burns the CNTs or carbon nanoparticles by burning the metal particle sintered layer in the atmosphere. It may be formed by

Further, the metal particle sintered layer is provided with zinc oxide (ZnO), and the fine gas introduction path is formed by etching ZnO by wet etching after burning the metal particle sintered layer in the atmosphere. Is also good.

The limiting current type gas sensor 1A according to the eighth embodiment can control the gas permeation amount by the shape of the fine gas introduction passage.

Further, the limiting current type gas sensor 1A according to the eighth embodiment can control the gas permeation amount based on the content ratio of the fine gas introduction passage.

The metal particles of the metal particle sintered layer may include any one of Pt, Ag, Pd, Au, and Ru.

The limiting current type gas sensor 1A according to the eighth embodiment, as shown in FIG. 129, applies a voltage between the dense electrode 5U and the porous electrode 5D to thereby obtain a predetermined gas concentration in the measured gas. A detection circuit 107 is provided to detect the voltage by the limiting current method. Here, the detection circuit 107 can detect the oxygen concentration based on the limiting current. Further, the detection circuit 107 can detect the water vapor concentration based on the limiting current.

Moreover, according to the limiting current type gas sensor 1A according to the present embodiment, by providing the Pt+YSZ mixed grain film 11, it is possible to improve the response speed of oxygen at the time of gas concentration detection. The response speed of can be improved.

Note that, as shown in FIGS. 129 to 131, the limiting current type gas sensor 1A according to the present embodiment includes the first stress relaxation low thermal expansion film 6 (5U) disposed on the dense electrode 5U, and Pt+YSZ mixed particles. Second stress relaxation low thermal expansion film 6 (5D) arranged on the porous electrode 5D on which the membrane 11 is formed, and third stress relaxation low thermal expansion film 6 (4) arranged on the solid electrolyte layer 4. And may be provided.

In addition, as shown in FIGS. 129 to 131, the limiting current type gas sensor 1A according to the present embodiment has the first stress relaxation low thermal expansion film 6 (5U) and the third stress relaxation low thermal expansion film in plan view. 6(4) and the first warpage suppressing porous insulating film 10 (5U) disposed on the dense electrode 5U and the second stress relaxation low thermal expansion film 6 (5D) in plan view. The second warpage suppressing porous insulating film 10 (5D) disposed on the porous electrode 5D via the Pt+YSZ mixed grain film 11 so as to extend between the third stress relaxation low thermal expansion film 6(4). And may be provided.

As shown in FIGS. 129 to 131, the limiting current type gas sensor 1A according to the eighth embodiment has, as a basic structure, a MEMS element structure having a cantilever structure. Although a detailed structure will be described later, a sensor portion is arranged in the central portion, and a porous electrode 5D and a dense electrode 5U connected to the sensor portion are arranged in the beam portion of the both-end supported beam structure, and the porous electrode 5D. A detection circuit 107 is connected between the dense electrodes 5U.

The micro-heater 2 for heating is embedded in the central sensor part, and the heat capacity of the central sensor part is reduced and the sensor sensitivity of the central part is reduced by using the double-supported beam structure MEMS element structure as a basic structure. We are trying to improve.

In the limiting current type gas sensor 1A according to the eighth embodiment, the substrate 12 includes the micro heater 2 as shown in FIG. The micro-heater 2 may be arranged above the substrate 12 or below the substrate 12. Further, the micro heater 2 may be embedded inside the substrate 12, as shown in FIG. The micro heater 2 can be formed of, for example, a Pt heater formed by printing or a polysilicon heater. In addition, a laminated film 103 of a silicon oxide film/silicon nitride film including the micro-heater 2 formed of polysilicon may be formed on the surface of the substrate 12 (see, for example, FIG. 148).

The porous electrode 5D and the dense electrode 5U can be formed of porous Pt electrodes. The porous Pt electrode can be formed by printing, vapor deposition, or sputtering. The thickness of the porous electrode 5D and the dense electrode 5U is, for example, about 0.1 μm to 10 μm.

Insulating film 8 is _{Al 2 O 3, Al 2 O} 3 -SiO 2, YSZ-SiO 2, or can be formed with either YSZ-Al ₂ O _3. The insulating film 8 can be formed by a printing process or a sputtering process. The thickness of the insulating film 8 is, for example, about 1.0 μm to 10 μm.

The solid electrolyte layer 4, YSZ, can be formed in at least one of stabilized zirconia included (YSZ) film of YSZ-SiO ₂ or YSZ-Al ₂ O _3,. The solid electrolyte layer 4 can be formed by a printing process or a sputtering process. The thickness of the solid electrolyte layer 4 is, for example, about 0.1 μm to 10 μm.

The film density of the stress relaxation low thermal expansion film 6 can be adjusted by the amount of gas to be detected. The stress relaxation low thermal expansion film 6 can be formed of either a dense film, a porous film, or a composite film of a dense film and a porous film.

Further, the stress relaxation low thermal expansion film 6 may be formed of a material containing at least one of SiO ₂ , Al ₂ O ₃ , YSZ, and mullite. The stress relaxation low thermal expansion film 6 can be formed by a printing process or a sputtering process. The thickness of the stress relieving low thermal expansion film 6 is, for example, about 1.0 μm to 5.0 μm.

The warp suppressing porous insulating film 10 may be made of a material containing at least one of SiO ₂ , Al ₂ O ₃ , YSZ, and mullite. The warp suppressing porous insulating film 10 can be formed by a printing process or a sputtering process. The thickness of the warp suppressing porous insulating film 10 is, for example, about 1.0 μm to 5.0 μm.

Moreover, in the limiting current type gas sensor 1A according to the eighth embodiment, the substrate 12 may have a MEMS beam structure. The substrate 12 can be formed of a silicon substrate having a thickness of 10 μm or less, preferably 2 μm or less. If the MEMS is applied, the thickness of the substrate 12 can be set to 2 μm or less, so that the heat capacity becomes small and the power consumption in the microheater 2 can be reduced.

In addition, as shown in FIGS. 129 to 131, the limiting current type gas sensor 1A according to the eighth embodiment is formed as a cantilevered beam structure on a cavity C (cavity) formed in the substrate 12. Has been done. The beam structure is a beam structure formed by MEMS and having a thickness of 10 μm or less, preferably 2 μm or less.

The insulating layer 3 can be formed of a porous film containing any one of Al ₂ O ₃ , Al ₂ O ₃ —SiO ₂ , YSZ-SiO ₂ , and YSZ-Al ₂ O ₃ . The insulating layer 3 functions as a gas intake film and can be formed by a printing process or a sputtering process. Here, the thickness of the insulating layer 3 is, for example, about 0 to 10 μm. The insulating layer 3 does not necessarily have to be provided. In that case, the porous electrode 5D, which can be formed of a porous Pt electrode, can be used as the gas intake film.

Such a limiting current type gas sensor 1A may be manufactured by a method other than the MEMS. The thickness of the silicon substrate 12 in this case is, for example, about 600 μm.

(Production method)
As shown in FIGS. 132 to 136, the method of manufacturing the limiting current type gas sensor 1A according to the eighth embodiment includes a step of forming a porous electrode (porous Pt) 5D on the substrate 12 and a porous electrode 5D. A step of forming a Pt+YSZ mixed particle film (particle mixed layer) 11 on which Pt particles and YSZ particles are mixed, and a step of forming an insulating film 8 on the porous electrode 5D on which the Pt+YSZ mixed particle film 11 is formed, A step of patterning the insulating film 8 to form the opening 7, and a step of forming the solid electrolyte layer (YSZ thin film) 4 on the Pt+YSZ mixed grain film 11 of the opening 7 and on the insulating film 8 surrounding the opening 7. And a step of forming a dense electrode (Pt electrode) 5U substantially vertically with respect to the substrate 12 on the solid electrolyte layer 4 facing the porous electrode 5D.

Although not shown, the dense electrode 5U includes a metal particle sintered layer and a fine gas introduction path formed in the metal particle sintered layer.

The Pt+YSZ mixed grain film 11 may be selectively formed, for example, only on at least a part of the porous electrode 5D corresponding to the opening 7.

In addition, as shown in FIG. 137, the manufacturing method of the limiting current type gas sensor 1A according to the eighth embodiment is such that the first stress relaxation low thermal expansion film 6 (5U) is formed on the dense electrode 5U, and the Pt+YSZ mixed film is formed. The second low stress thermal expansion film 6 (5D) for stress relaxation is formed on the porous electrode 5D on which the granular film 11 is formed, and the third low thermal expansion film 6 (4) for stress relaxation is formed on the solid electrolyte layer 4. Have steps.

In addition, as shown in FIG. 138, in the method of manufacturing the limiting current type gas sensor 1A according to the eighth embodiment, the first stress relaxation low thermal expansion film 6 (5U) and the third stress relaxation low heat are viewed in a plan view. The step of forming the first warp suppressing porous insulating film 10 (5U) on the dense electrode 5U across the expansion film 6(4) and the second stress relaxation low thermal expansion film 6 in plan view. The second warp suppressing porous insulating film 10 (5D) is formed on the porous electrode 5D on which the Pt+YSZ mixed grain film 11 is formed so as to extend between (5D) and the third stress relaxation low thermal expansion film 6(4). ) Is formed.

In addition, as shown in FIG. 139, in the method of manufacturing the limiting current type gas sensor 1A according to the eighth embodiment, the substrate 12 is etched in the direction of the arrow shown in FIG. Forming the beam structure.

The method of manufacturing the limiting current type gas sensor 1A according to the eighth embodiment may include a step of forming the micro heater 2 on the upper portion of the substrate 12 or the lower portion of the substrate 12.

Further, the method of manufacturing the limiting current type gas sensor 1A according to the eighth embodiment may include a step of forming the micro heater 2 embedded inside the substrate 12.

Further, the method of manufacturing the limiting current type gas sensor 1A according to the eighth embodiment includes a step of forming the insulating layer 3 on the substrate 12, and the porous electrode 5D may be formed on the insulating layer 3. ..

In addition, in the method of manufacturing the limiting current type gas sensor 1A according to the eighth embodiment, the microheater 2, the insulating layer 3, the porous electrode 5D, the dense electrode 5U, the insulating film 8, the solid electrolyte layer 4, and the stress relaxation low heat. The expansion film 6 (6(4).6(5U).6(5D)), the warp suppressing porous insulating film 10 (10(5U).10(5D)), and the Pt+YSZ mixed particle film 11 are formed by a printing process. Can be formed by.

Next, a method of manufacturing the limiting current type gas sensor 1A according to the eighth embodiment will be described with reference to FIGS. 132 to 139.

(A) First, as shown in FIGS. 132(a) and 132(b), the insulating layer 3 is formed on the substrate 12 in which the micro heater 2 is embedded. Here, since the insulating layer 3 is a porous film, it serves as a passage for gas. The formation of the insulating layer 3 may be omitted.

(B) Next, as shown in FIGS. 133A and 133B, the porous electrode 5D is formed on the insulating layer 3 and the substrate 12. Since the porous electrode 5D is formed of, for example, a porous Pt electrode, gas may pass through the porous Pt electrode.

Further, after forming the porous electrode 5D, for example, the Pt+YSZ mixed grain film 11 is formed on the upper surface thereof. For the Pt+YSZ mixed grain film 11, for example, after forming a laminated film of a YSZ film having a thickness of 2 nm and a Pt film having a thickness of 2 nm by a sputtering method, annealing treatment is performed at 1000° C. It can be formed by using a printing and sintering process.

(C) Next, as shown in FIGS. 134(a) and 134(b), after forming the insulating film 8 on the porous electrode 5D on which the Pt+YSZ mixed grain film 11 is formed, the insulating film 8 is patterned. Then, the opening 7 is formed.

Here, when the Pt+YSZ mixed particle film 11 is formed on a part of the upper surface of the porous electrode 5D, the insulating film 8 is formed to stabilize the zirconia (solid electrolyte layer 4)/porous Pt electrode (porous By stabilizing the contact area between the electrodes 5D), contact between the end surface of the stabilized zirconia (solid electrolyte layer 4) and the porous Pt electrode (porous electrode 5D) is eliminated, and the porous Pt electrode (porous electrode 5D) is formed. ) And the Pt electrode (dense electrode 5U), the current leak component can be removed.

(D) Next, as shown in FIGS. 135(a) and 135(b), the solid electrolyte layer 4 is formed on the Pt+YSZ mixed grain film 11 in the opening 7 and on the insulating film 8 surrounding the opening 7. .. The solid electrolyte layer 4 is formed of YSZ here, for example.

(E) Next, as shown in FIGS. 136(a) and 136(b), the dense electrode is formed on the solid electrolyte layer 4 so as to face the porous electrode 5D and substantially vertically with respect to the substrate 12. Form 5U. As shown in FIG. 136(a), the dense electrode 5U is also formed by extending on the insulating film 8, the insulating layer 3, and the substrate 12. The dense electrode 5U is formed of, for example, a porous Pt electrode.

(F) Next, as shown in FIGS. 137(a) and 137(b), the first stress relaxation low thermal expansion film 6 (5U) is formed on the dense electrode 5U, and the Pt+YSZ mixed grain film 11 is formed. The second stress relaxation low thermal expansion film 6 (5D) is formed on the formed porous electrode 5D, and the third stress relaxation low thermal expansion film 6 (4) is formed on the solid electrolyte layer 4. The film density of the stress relaxation low thermal expansion film 6 can be adjusted by the amount of gas to be detected.

The stress relaxation low thermal expansion film 6 can be formed of either a dense film, a porous film, or a composite film of a dense film and a porous film. The stress relaxation low thermal expansion film 6 is formed of a material containing at least one of SiO ₂ , Al ₂ O ₃ , YSZ, and mullite.

The stress relaxation low thermal expansion film 6 can be formed by a printing process or a sputtering process. The stress relaxation low thermal expansion film 6 is an insulating film having a low coefficient of thermal expansion, and by forming the stress relaxation low thermal expansion film 6, the stress at the time of heating can be relaxed.

(G) Next, as shown in FIGS. 138(a) and 138(b), between the first stress relaxation low thermal expansion film 6 (5U) and the third stress relaxation low thermal expansion film 6(4). The first warp suppressing porous insulating film 10 (5U) is formed over the dense electrode 5U, and the second stress relaxing low thermal expansion film 6 (5D) and the third stress relaxing low thermal expansion film 6 ( 4) The second warpage suppressing porous insulating film 10 (5D) is formed on the porous electrode 5D so as to extend over the gap 4). The warp suppressing porous insulating film 10 is formed of a material containing at least one kind of SiO ₂ , Al ₂ O ₃ , YSZ, and mullite.

The warp suppressing porous insulating film 10 can be formed by a printing process or a sputtering process. By forming the warp suppressing porous insulating film 10, the warp of the beam structure during heating can be reduced and the durability can be improved.

(H) Next, as shown in FIG. 139, the substrate 12 is etched from the back surface in the direction of the arrow shown. As a result, as shown in FIGS. 129 to 131, a beam structure having both ends is formed on the cavity C formed in the substrate 12. By forming the beam structure in this manner, the heat capacity of the sensor portion can be reduced and the heat conduction can be reduced. As a result, low power consumption during heating can be achieved.

As described above, also in the limiting current type gas sensor 1A according to the eighth embodiment, the Pt+YSZ mixed grain film 11 is arranged similarly to the seventh embodiment, so that the response speed at the time of gas concentration detection can be improved. Can be improved.

(Ninth Embodiment)
(Schematic configuration)
A schematic plane pattern configuration of the limiting current type gas sensor 1A according to the ninth embodiment is represented as shown in FIG. In the eighth embodiment shown in FIG. 129, an example in which the porous electrode 5D and the porous electrode 5U are arranged only on one arm of the two arms on one side of the four arms of the double-supported beam structure showed that.

On the other hand, in the ninth embodiment, as shown in FIG. 140, the porous electrodes 5D ₁ and 5D ₂ are provided on both arms of two arms on one side among the four arms of the double-supported beam structure.・Dense electrodes 5U ₁ and 5U ₂ are arranged. Moreover, the porous electrodes 5D ₁ and 5D ₂ are electrically connected to each other. Similarly, the dense electrodes 5U ₁ and 5U ₂ are also electrically connected to each other.

As shown in FIG. 140, the limiting current type gas sensor 1A according to the ninth embodiment includes a substrate 12, porous electrodes 5D ₁ and 5D ₂ arranged on the substrate 12, and at least a porous electrode of a sensor portion. Pt+YSZ mixed grain film (particle mixed layer) 11 formed on 5D, insulating film 8 (not shown) arranged on porous electrode 5D on which Pt+YSZ mixed grain film 11 is formed, and patterning on insulating film 8 Solid electrolyte layer 4 arranged on the Pt+YSZ mixed grain film 11 of the formed opening 7 (not shown) and on the insulating film 8 surrounding the opening 7, and the solid electrolyte layer facing the porous electrodes 5D ₁ and 5D _2. 4, and dense electrodes 5U ₁ and 5U ₂ arranged substantially in the vertical direction with respect to the substrate 12 and provided with a metal particle sintered layer and a fine gas introduction path formed in the metal particle sintered layer.

In addition, as shown in FIG. 140, the limiting current type gas sensor 1A according to the ninth embodiment is configured by applying a voltage between the dense electrodes 5U ₁ and 5U ₂ and the porous electrodes 5D ₁ and 5D _2. A detection circuit 107 for detecting a predetermined gas concentration in the gas to be measured by a limiting current method is provided. Here, the detection circuit 107 can detect the oxygen concentration based on the limiting current. Further, the detection circuit 107 can detect the water vapor concentration based on the limiting current.

Moreover, according to the limiting current type gas sensor 1A according to the ninth embodiment, by providing the Pt+YSZ mixed grain film 11, it is possible to improve the oxygen response speed at the time of detecting the gas concentration, and the limiting current type gas sensor 1A. The response speed as 1A can be improved.

The limiting current type gas sensor 1A according to the ninth embodiment, as shown in FIG. 140, has a first stress relaxation low thermal expansion film 6 (5U ₁ ), which is disposed on the dense electrodes 5U ₁ and 5U _2. 6 (5U ₂ ), the second low thermal expansion film for stress relaxation 6 (5D ₁ ), 6 (5D ₂ ) arranged on the porous electrodes 5D ₁ , 5D ₂ and the solid electrolyte layer 4 It may be provided with the third stress relaxation low thermal expansion film 6(4).

Also, limiting current type gas sensor 1A according to the ninth embodiment, as shown in FIG. 140, in a plan view, the first stress relieving for a low thermal expansion layer _{6 (5U 1) · 6 (} 5U 2) and the third The first warpage suppressing porous insulating films 10 (5U ₁ ), 10 (5U ₂ ) disposed on the dense electrodes 5U ₁ , 5U ₂ so as to straddle the stress relaxation low thermal expansion film 6 (4) and In plan view, the porous electrode 5D ₁ · spans between the second stress relaxation low thermal expansion films 6 (5D ₁ )· 6 (5D ₂ ) and the third stress relaxation low thermal expansion film 6 (4 ). 5D for arranged second warp suppressing over ₂ porous insulating film _{10 (5D 1) · 10 (} 5D 2) and may include a.

Alternatively, the insulating layer 3 may be provided on the substrate 12, and the porous electrodes 5D ₁ and 5D ₂ may be provided on the insulating layer 3.

The other structure is the same as that of the eighth embodiment.

(Production method)
As shown in FIGS. 141 to 144, the manufacturing method of the limiting current type gas sensor 1A according to the ninth embodiment is a step of forming the porous electrodes 5D, 5D ₁ , 5D ₂ on the substrate 12 (FIG. 141). A step of forming the Pt+YSZ mixed particle film 11 on the porous electrode 5D, a step of forming the insulating film 8 on the porous electrode 5D on which the Pt+YSZ mixed particle film 11 is formed, and a step of patterning the insulating film 8. The step of forming the opening 7 (FIG. 142), the step of forming the solid electrolyte layer 4 on the Pt+YSZ mixed grain film 11 of the opening 7 and the insulating film 8 surrounding the opening 7 (FIG. 143), and the porous On the solid electrolyte layer 4 facing the electrode 5D, the dense electrodes 5U and 5U each including a metal particle sintered layer and a fine gas introduction path formed in the metal particle sintered layer in a substantially vertical direction with respect to the substrate 12. _And the step of forming 1.5U ₂ (FIG. 144).

In addition, as shown in FIG. 145, the manufacturing method of the limiting current type gas sensor 1A according to the ninth embodiment is, as shown in FIG. 145, on the dense electrodes 5U ₁ and 5U ₂ the first stress relaxation low thermal expansion film 6 (5U ₁ ). 6 (5U ₂₎ to form a porous electrode 5D ₁ · 5D on ₂ second stress relieving for a low thermal expansion layer _{6 (5D 1) · 6 (} 5D 2) is formed, third on the solid electrolyte layer 4 There is a step of forming a low thermal expansion film 6 (4) for stress relaxation.

In addition, as shown in FIG. 146, the manufacturing method of the limiting current type gas sensor 1A according to the ninth embodiment, as shown in FIG. 146, shows the first stress relaxation low thermal expansion films 6 (5U ₁ ) and 6 (5U ₂ ). When the third stress across between the relaxation for low thermal expansion layer 6 (4), a dense electrode 5U ₁ · 5U for the first warp suppressing over ₂ porous insulating film _{10 (10 (5U 1) ·} 10 (5U2) ) Is formed, and in a plan view, it extends over between the second stress relaxation low thermal expansion films 6 (5D ₁ ), 6 (5D ₂ ) and the third stress relaxation low thermal expansion film 6 (4), And a step of forming the second warp suppressing porous insulating film 10 (10(5D ₁ )·10(5D ₂ )) on the porous electrodes 5D ₁ ·5D ₂ .

In addition, as shown in FIG. 140, in the method of manufacturing the limiting current type gas sensor 1A according to the ninth embodiment, as shown in FIG. 140, the substrate 12 is etched, and the beam structure having both ends is provided on the cavity C formed in the substrate 12. To form.

Further, the manufacturing method of the limiting current type gas sensor 1A according to the ninth embodiment has a step of forming the insulating layer 3 on the substrate 12 and a porous electrode on the insulating layer 3 as shown in FIG. 5D, 5D ₁ and 5D ₂ may be formed.

In the ninth embodiment, as shown in FIG. 140, of the four arms of the double-supported beam structure, the two porous electrodes 5D ₁ ·5D ₂ ·dense electrode 5U are formed on both arms of two arms on one side. _Since only the structure in which 1.5U ₂ is arranged is different from that of the eighth embodiment (see, for example, FIG. 129), most of the detailed manufacturing process of each part is the same as that of the eighth embodiment.

As described above, also in the limiting current type gas sensor 1A according to the ninth embodiment, the Pt+YSZ mixed grain film 11 is arranged as in the seventh and eighth embodiments, so that the gas concentration detection The response speed can be improved.

Hereinafter, the outline of the limiting current type gas sensor 1A will be further described.

(Beam structure)
A schematic cross-sectional structure showing one step (beam structure forming step) of the method of manufacturing the limiting current type gas sensor 1A according to the seventh to ninth embodiments is represented as shown in FIG. One step of the method of manufacturing the limiting current type gas sensor 1A according to the seventh to ninth embodiments (another beam structure forming step) is represented as shown in FIG. 147(b).

In particular, in the structures of the eighth and ninth embodiments, in the beam structure having the MEMS structure, as shown in FIG. 147(a), the open structure in which the cavity C is formed in the open structure at the bottom of the substrate 12. In addition, as shown in FIG. 147(b), a ship-shaped structure in which the cavity C is formed inside the substrate 12 is possible. In either case, for example, anisotropic etching of a silicon substrate or the like can be applied.

In each of the structures shown in FIGS. 147(a) and 147(b), a micro-heater is formed on a part of the thinned substrate 12, but the illustration is omitted here. Further, the device heating unit 200 represents the vertical sensor structure of the limiting current type gas sensor 1A.

That is, the layout diagram (top view) of the beam structure of the limiting current type gas sensor 1A according to the eighth and ninth embodiments is represented as shown in FIG. 148(a), and is indicated by IIIA in FIG. 148(a). A schematic cross-sectional structure taken along the line -IIIA is shown in FIG. 148(b).

In the case of this structural example, a silicon substrate having a (100) plane is used as the substrate 12, and the bottom surface of the device heating unit 200 is a (100) plane and the side surface is a (111) plane by anisotropic etching. A cavity C is formed.

On the surface of the substrate 12, a laminated film 103 of silicon oxide film/silicon nitride film including a micro-heater made of polysilicon is formed. The area of the device heating unit 200 is, for example, about 0.1 mm ² .

In the structural example shown in FIGS. 148(a) and 148(b), the laminated film 103 including the micro-heater is formed on the bottom of the device heating unit 200 of the vertical sensor structure, and the substrate 12 is removed. There is. That is, as in this structural example, in the limiting current type gas sensor 1A according to the eighth and ninth embodiments, the thinned substrate 12 is removed and only the laminated film 103 including the micro heater is formed. It may be formed.

(Micro heater)
In the limiting current type gas sensor 1A according to the eighth and ninth embodiments, the micro heater 2 can be formed by the following process flow.

First, a PSG (Phosphorus Silicon Glass) film having a thickness of 3 μm is formed on the silicon substrate 12, a SiN film is formed on the PSG film, and then the SiN film is patterned (removal of the SiN film is performed at a high concentration portion).

Next, a polysilicon layer is formed, and P (phosphorus) is diffused into the polysilicon layer by, for example, heat treatment at about 1000° C. to form a heavily doped polysilicon layer. The portion with the SiN film becomes a lightly doped polysilicon layer.

Further, a vertical sensor structure is formed and PSG etching is performed with BHF (5:1) to form a beam structure.

As described above, in the limiting current type gas sensor 1A according to the eighth and ninth embodiments, the micro-heater 2 having the beam structure can be easily formed on the cavity C.

In the limiting current type gas sensor 1A according to the eighth and ninth embodiments, the microheater 2 arranged in the laminated film 103 portion of FIGS. 148(a) and 148(b) has the following process flow. It may be formed by.

First, a laminated film 103, which is a multilayer insulating film of SiO ₂ /SiN/SiO ₂ , is formed on a Si (100) substrate 12, and a Pt heater (micro heater 2) is formed thereon.

Next, the device heating unit 200 is formed on the micro heater 2.

Further, the cavity C is formed by anisotropically etching the silicon substrate 12 using a TMAH solution.

As described above, the micro-heater 2 having the beam structure can be easily formed on the cavity C by such a process.

Regarding the operating principle, in the limiting current type gas sensors according to the seventh to ninth embodiments, as described above, the operation of detecting the gas concentration is the limiting current type gas sensors according to the first to sixth embodiments. Since it is substantially the same as the case, detailed description is omitted.

Further, the description of the electrochemical reaction is substantially the same as that of the limiting current type gas sensors according to the first to sixth embodiments, as described above, and thus detailed description thereof will be omitted.

Further, as to the package, as described above, it is substantially the same as the case of the limiting current type gas sensor according to the first to sixth embodiments, and therefore detailed description thereof will be omitted.

Further, the configuration example of the sensor node using the energy harvester power supply is substantially the same as that of the limiting current type gas sensor according to the above-described first to sixth embodiments, and therefore detailed description thereof will be omitted.

Further, in the limiting current type gas sensor according to the seventh to ninth embodiments, the schematic block configuration of the sensor package is substantially the same as that of the limiting current type gas sensor according to the above-described first to sixth embodiments. Since it is similar to the above, detailed description will be omitted.

Furthermore, the schematic block configuration of the sensor network system to which the limiting current type gas sensor according to the seventh to ninth embodiments is applied is the same as that of the limiting current type gas sensor according to the above-described first to sixth embodiments. Since they are substantially the same, detailed description will be omitted here.

(10th to 12th embodiments)
(Tenth Embodiment)
(Schematic configuration)
A schematic plane pattern configuration of the limiting current type gas sensor 1A according to the tenth embodiment is represented as shown in FIG. 149(a), and is a MEMS (Micro Electro Micro Electrode) along a line IA-IA in FIG. 149(a). A schematic cross-sectional structure of the sensor 1A formed in a beam structure is shown in FIG. 149(b).

That is, the limiting current type gas sensor 1A according to the tenth embodiment corresponds to the substrate 12 having the MEMS beam structure and the sensor portion in the central portion, respectively, as shown in FIGS. 149(a) and 149(b). A porous electrode (porous Pt electrode) 5D arranged on the substrate 12, a solid electrolyte layer (YSZ film) 4 arranged so as to cover the porous electrode 5D, and a solid electrolyte facing the porous electrode 5D. On the layer 4, a dense electrode (porous Pt electrode) 5U arranged substantially in the vertical direction with respect to the substrate 12 is provided.

Further, the limiting current type gas sensor 1A has an insulating layer 3 on almost the entire surface thereof, and a gas to be measured (a gas to be measured) is provided via a gas diffusion path 15 formed in an upper layer portion of the insulating layer 3 with a predetermined aspect ratio. For example, O ₂ gas) is introduced toward the sensor portion.

In short, the limiting current type gas sensor 1A according to the tenth embodiment includes the substrate 12, the porous electrode 5D arranged in the region of the sensor portion on the substrate 12 via the insulating layer 3, and the porous electrode 5D. The solid electrolyte layer 4 arranged on the upper surface part, the dense electrode 5U arranged on the surface of the solid electrolyte layer 4 facing the porous electrode 5D, and a predetermined aspect ratio, and a gas to be measured is used as a sensor part. And a gas diffusion path 15 that is introduced toward.

The gas diffusion path 15 includes a gas intake port 15b for taking in the measurement gas, a gas introduction port 15c for introducing the measurement gas, and a gas flow path (micro flow path) connecting the gas introduction port 15c and the gas intake port 15b. 15a, the flow rate of the gas to be measured can be controlled according to the aspect ratio (ratio between the channel length of the microchannel and the channel cross-sectional area).

Actually, in the limiting current type gas sensor 1A according to the tenth embodiment, the gas diffusion path 15 has an aspect ratio of, for example, "flow channel length/cross-sectional area=100 μm ^-1 (predetermined aspect ratio)". In addition, the gas flow path 15a is formed with a width (W)=30 μm, a depth (D)=0.1 μm, and a length (L)=300 μm (the aspect ratio is 3 or more, and the limiting current characteristic is good). Become).

That is, in the limiting current type gas sensor 1A according to the tenth embodiment, the flow rate of the gas to be measured can be controlled according to the aspect ratio of the gas passage 15a, and the sensor characteristic can be improved by increasing the aspect ratio. By increasing the accuracy of forming the gas diffusion path 15, the sensor characteristics can be further stabilized.

The gas inlet 15b of the gas diffusion path 15 is provided in an open state corresponding to the region of the non-sensor portion on the upper layer side of the insulating layer 3, and the gas inlet 15c is the upper layer of the insulating layer 3. The gas flow path 15a is provided in an open state corresponding to the area of the sensor portion on the side of the portion, and the gas flow path 15a is formed substantially horizontally in the upper layer portion of the insulating layer 3.

In addition, the limiting current type gas sensor 1A according to the tenth embodiment is configured such that the heater electrode portions (Pt/Ti laminated film) 9a and 9a embedded in the openings 3a and 3a patterned in the insulating layer 3 are provided. A predetermined voltage for heating the solid electrolyte layer 4 is applied to the micro-heater 2 connected to the electrode layers 2a and 2a.

In addition, the limiting current type gas sensor 1A according to the tenth embodiment is insulated from the one and the other detection terminals 9b and 9b in which, for example, a Pt/Ti laminated film is embedded in the openings 3b and 3b in the insulating layer 3. The openings 3c and 3c in the layer 3 are further provided with one and the other connection terminals 9c and 9c in which, for example, a Pt/Ti laminated film is embedded. One and the other detection terminals 9b and 9b and the one and the other connection terminals 9c and 9c are connected via the electrode layers 2a and 2a and the same electrode layers 2b and 2b, respectively.

A detection circuit 107 for detecting a predetermined gas concentration in the measured gas by a limiting current method is connected to the one and the other detection terminals 9b and 9b. Further, the extension end of the porous electrode 5D is provided at the one connection terminal 9c connected to the one detection terminal 9b, and the extension end of the dense electrode 5U is provided at the other connection terminal 9c connected to the other detection terminal 9b. , Each connected.

In addition, Pt is platinum (Platinum) as a porous material, Ti is titanium (Titanium) as an electrode material, and YSZ is yttrium-stabilized zirconia (Yttria-Stabilized Zirconia) as a solid electrolyte material. is there.

Here, the insulating layer 3 is formed of, for example, a SiON film (silicon vaginated film) with a thickness of 1.0 μm or more.

The electrode layers 2a, 2a and the electrode layers 2b, 2b are polysilicon layers having a thickness of about 0.3 μm, and are formed in a higher concentration than the micro heater 2 by ion implantation.

The heater electrode portions 9a and 9a, the detection terminals 9b and 9b, and the connection terminals 9c and 9c are formed of, for example, a laminated film of a Ti film having a thickness of 20 nm and a Pt film having a thickness of 100 nm.

The porous electrode 5D is formed of a porous Pt film with a thickness of, for example, about 100 nm. It is also possible to use a Ti/Pt laminated film having a pore diameter of about several μm for forming the porous electrode 5D.

The solid electrolyte layer 4 is formed of a YSZ film having a thickness of about 1 μm. This is because if it is thin, the upper and lower electrodes 5D and 5U are electrically connected. For example, the solid electrolyte layer 4 is arranged so as to cover the periphery of the porous electrode 5D, and conduction between the upper and lower electrodes 5D and 5U is prevented.

The substrate 12 having the MEMS beam structure has an open structure that is arranged so as to surround the sensor portion in a plan view, and is formed of, for example, a silicon substrate having a thickness of about 10 μm.

Here, the porous electrode 5D is arranged on the surface of the gas diffusion path 15 that faces the gas introduction port 15c, and a fine gas introduction path (not shown) formed in the metal particle sintered layer and the metal particle sintered layer described later. Have).

For example, in the limiting current type gas sensor 1A according to the tenth embodiment, the electrodes 5D and 5U themselves are formed in a nanostructure. That is, Pt mixed with carbon nanotubes (CNT) may be sintered, and finally the CNT may be burnt off to form a fine gas introduction path to form a metal particle sintered layer (dense Pt) as the porous electrode 5D. .. Carbon nanoparticles may be applied instead of CNTs.

The fine gas introduction path in the porous electrode 5D is formed by, for example, a heat treatment process of nanowires, nanotubes, nanoparticles, etc. having a nanometer scale contained in the metal particle sintered layer, or an etching treatment process combined with the heat treatment process. It is possible. Nanowires, nanotubes, and nanoparticles can be formed of, for example, carbon (C), zinc oxide (ZnO), or the like.

That is, a detailed description of the metal particle sintered layer and the fine gas introduction path formed in the metal particle sintered layer in the porous electrode 5D will be omitted here, but the metal particle sintered layer includes nanowires. It may be. The nanowire may include CNT or ZnO. Further, the metal particle sintered layer is provided with carbon nanotubes or carbon nanoparticles, and the fine gas introduction path is formed by the combustion of the metal particle sintered layer in the atmosphere, whereby the carbon nanotubes or carbon nanoparticles are burned. It may be formed. The metal particle sintered layer may be provided with ZnO, and the fine gas introduction path may be formed by etching ZnO by wet etching after burning the metal particle sintered layer in the atmosphere.

Furthermore, the metal particles of the metal particle sintered layer may include any one of Pt, Ag, Pd, Au, and Ru. Further, the metal particle sintered layer may include nanowires that are confined in the metal particle sintered layer and are not burned by burning in the atmosphere. The nanowires or nanoparticles have a diameter of about 0.1 μm or less. The length of the nanowire is, for example, about 10 μm or less. The advantage of using the nanowires is that the gas permeation amount can be controlled by the shape (diameter, length) of the nanowires, and the gas permeation amount can be controlled by the ratio of the nanowires.

As described above, in the limiting current type gas sensor 1A according to the tenth embodiment, the gas permeation amount can be controlled by the shape of the fine gas introduction passage of the porous electrode 5D. Further, the limiting current type gas sensor 1A according to the tenth embodiment can control the gas permeation amount by the content ratio of the fine gas introduction passage of the porous electrode 5D.

On the other hand, in the limiting current type gas sensor 1A according to the tenth embodiment, as shown in FIGS. 149(a) and 149(b), an insulating layer (for example, 0 .5 μm thick SiON film) 1a is further provided, and a micro-heater 2 for heating is embedded in the same layer as the electrode layers 2a and 2a at least between the insulating layer 1a and the insulating layer 3 in the sensor portion. .. The microheater 2 is a polysilicon layer (polysilicon heater) having a thickness of about 0.3 μm, and has a resistance value of about 300Ω by ion implantation.

The microheater 2 heats the solid electrolyte layer 4 by applying a predetermined voltage between the heater electrode portions 9a and 9a. The micro heater 2 can also be formed by a Pt heater or the like formed by printing.

The limiting current type gas sensor 1A according to the tenth embodiment has a beam structure (open type structure) having a MEMS structure as a basic structure to reduce the heat capacity of the sensor portion and improve the sensor sensitivity. ..

In the limiting current type gas sensor 1A according to the tenth embodiment, the microheater 2 is arranged between the substrate 12 which is a sensor portion and the porous electrode 5D with the insulating layers 1a and 3 interposed therebetween. Not limited to this, it may be disposed on the lower surface of the insulating layer 1a facing the surface on which the porous electrode 5D is formed, or on the lower portion of the substrate 12. Further, the micro heater 2 may be embedded inside the substrate 12. Alternatively, it may be configured such that a laminated film (not shown) of a silicon oxide film/silicon nitride film including the micro-heater 2 formed of polysilicon is formed on the surface of the substrate 12.

In the limiting current type gas sensor 1A according to the tenth embodiment, as shown in FIGS. 149(a) and 149(b), for example, a detection voltage supplied to the dense electrode 5U and the porous electrode 5D. Is applied between the detection terminals 9b and 9b to connect the detection circuit 107 for detecting a predetermined gas concentration in the gas to be measured by the limiting current method.

The detection circuit 107 can detect the oxygen concentration based on the limiting current. Further, the detection circuit 107 can detect the water vapor concentration based on the limiting current.

The heater electrode portions 9a, 9a and the detection terminals 9b, 9b are arranged so that their directions are substantially orthogonal to each other.

According to the limiting current type gas sensor 1A of the tenth embodiment, the aspect ratio of the gas diffusion path 15 can be increased, so that the sensor characteristics can be easily improved.

(Production method)
The method of manufacturing the limiting current type gas sensor 1A according to the tenth embodiment includes a step of forming the porous electrode 5D in a region corresponding to the sensor portion on the substrate 12 via the insulating layer 3 and a step of forming the porous electrode 5D. A step of forming the solid electrolyte layer 4 on the upper surface, a step of forming the dense electrode 5U on the surface of the solid electrolyte layer 4 facing the porous electrode 5D, and a predetermined aspect ratio, And forming a gas diffusion path 15 introduced toward the sensor portion in the upper layer portion of the insulating layer 3.

More specifically, a method of manufacturing the limiting current type gas sensor 1A according to the tenth embodiment shown in FIGS. 149(a) and 149(b) is represented as shown in FIGS. 150 to 161. Here, a gas flow having a width (W)=30 μm, a depth (D)=0.1 μm, and a length (L)=300 μm so that the aspect ratio of the gas flow path 15a is 100 (predetermined aspect ratio). The case of forming the path 15a will be described.

(A) First, as shown in FIGS. 150(a) and 150(b), a substrate 12 made of silicon having a thickness of about 10 μm is prepared, and an upper surface of the substrate 12 is subjected to a plasma CVD (P-CVD) method. An insulating layer 1a made of a SiON film having a thickness of 0.5 μm is formed.

(B) Next, as shown in FIGS. 151(a) and 151(b), a polysilicon layer having a thickness of about 0.3 μm is formed on the insulating layer 1a, and the polysilicon layer is etched or the like. By patterning, the micro-heater 2 and the electrode layers 2a, 2a and the electrode layers 2b, 2b connected to the micro-heater 2 are formed. The electrode layers 2a, 2a and the electrode layers 2b, 2b are formed at positions orthogonal to each other. The micro heater 2 is formed so that the width between the electrode layers 2a and 2a is about 300 μm.

The concentration of the micro heater 2 is set by the ion implantation method so that the resistance value between the electrode layers 2a and 2a is 300Ω, and the electrode layers 2a and 2a and the electrode layers 2b and 2b are higher than the micro heater 2. It is formed (implanted) to a concentration.

(C) Next, as shown in FIG. 152 (a) and FIG. 152 (b), SiON film (first insulating film) of about 0.5μm thick by P-CVD method on the entire surface to form a _{3 1.}

(D) Next, as shown in FIG. 153 (a) and FIG. 153 (b), a portion for forming a gas diffusion path 15 in the upper surface of the SiON film _{3 1,} the flow path forming for forming a gas flow path 15a The film 19a is formed (deposition+patterning).

Flow channel forming film 19a is etching selectivity is different from the film forming member is formed using, for example, a polysilicon film and the SiON film 3 ₁ which constitutes the insulating layer 3. Further, the flow path forming film 19a and the gas introduction port 15b and the gas introduction so that the aspect ratio of the gas flow path 15a is, for example, “flow path length/flow path cross-sectional area=100 (predetermined aspect ratio)”. The length (L) including the opening 15c is 400 μm, the width (W) is 30 μm, and the thickness (depth (D)) is 0.1 μm.

Here, the predetermined aspect ratio of the gas diffusion path 15 can be easily increased by increasing the flow path length of the gas flow path 15a or decreasing the cross-sectional area (flow path cross-sectional area) of the gas flow path 15a. The sensor characteristics can be improved by increasing the aspect ratio of the gas diffusion path 15.

(E) Next, as shown in FIGS. 154(a) and 154(b), an intake port forming film for forming the gas intake port 15b so as to overlap with one end side of the flow channel forming film 19a. 19b is deposited to a thickness of about 0.5 μm, and an introduction port forming film 19c for forming the gas introduction port 15c is formed to a thickness of about 0.5 μm so as to overlap the other end side of the flow path forming film 19a. Depot to the thickness of. Inlet formed film 19b and the introduction port forming layer 19c are both etching selectivity is different from the film forming member is formed using, for example, a polysilicon film and the SiON film 3 ₁ which constitutes the insulating layer 3.

That is, the intake port forming film 19b and the introducing port forming film 19c are formed in a circular shape having a diameter of, for example, about 50 μm and are formed so as to overlap with both ends of the flow path forming film 19a, respectively, so that the length (L) is It is possible to form the gas flow path 15a of 300 μm.

The formation of the flow path forming film 19a, the intake port forming film 19b, and the introduction port forming film 19c for forming these gas diffusion paths 15 is performed before forming the porous electrode 5D.

(F) Next, as shown in FIGS. 155(a) and 155(b), the polysilicon film is etched so that it has the same height as the upper surfaces of the intake port forming film 19b and the inlet port forming film 19c. film forming member selected ratios are different, for example, a SiON film (second insulating film) _{3 2} by embedding the upper passage-forming layer 19a.

That, SiON film _{3 2} constituting the insulating layer 3 is entirely depot so as to have a thickness of about 0.6μm by P-CVD method.

(G) Next, as shown in FIGS. 156(a) and 156(b), the insulating layer 3 is selectively removed, and the openings 3a and 3a connected to the electrode layers 2a and 2a and the electrode layers 2b and 2b. The openings 3b and 3b and the openings 3c and 3c connected to the.

(H) Next, as shown in FIGS. 157(a) and 157(b), the insides of the openings 3a and 3a, the openings 3b and 3b, and the openings 3c and 3c are formed by, for example, a Pt/Ti laminated film. Buried, heater electrode portions 9a, 9a, detection terminals 9b, 9b, and connection terminals 9c, 9c made of a laminated film of a Ti film and a Pt film are formed.

As the heater electrode portions 9a and 9a, the detection terminals 9b and 9b, and the connection terminals 9c and 9c, for example, a Ti film having a thickness of 20 nm is formed along the side wall and the bottom portion, and a part of the Ti film is formed on the insulating layer 3. In addition, a Pt film having a thickness of 100 nm may be embedded inside so as to cover the protrusion and the insulating layer 3.

(I) Next, as shown in FIGS. 158(a) and 158(b), a porous electrode 5D made of a porous Pt film having a thickness of about 100 nm is formed with a width of about 200 μm (along the gas diffusion path 15) by a sputtering method or the like. (The length in the direction), the upper surface of the introduction port forming film 19c exposed on the surface of the insulating layer 3 is closed, and the extended end of the porous electrode 5D extending from the sensor portion is connected to one connection terminal 9c.

(J) Next, as shown in FIGS. 159(a) and 159(b), a solid electrolyte layer 4 made of a YSZ film is formed to a thickness of about 1 μm by a sputtering method. By forming the solid electrolyte layer 4 to have a width (length in the direction along the gas diffusion path 15) of about 250 μm, for example, the extension end side of the porous electrode 5D connected to one connection terminal 9c of the sensor portion. The periphery of the porous electrode 5D except for is covered.

(K) Next, as shown in FIGS. 160(a) and 160(b), as the dense electrode 5U, a thickness of about 100 nm is formed on the surface of the solid electrolyte layer 4 facing the porous electrode 5D in the sensor portion by the sputtering method. The porous Pt film is formed, and the extended end of the porous Pt film extending from the sensor portion is connected to the other connection terminal 9c.

(L) Next, as shown in FIGS. 161(a) and 161(b), the substrate 12 corresponding to the sensor portion is selectively deep-etched to remove the substrate 12 having the MEMS beam structure from the cavity C (Cavity: (Cavity) is formed into an open structure having an open structure. As the cavity C, depending on the size of the limiting current type gas sensor 1A according to the tenth embodiment, the length in the direction orthogonal to the gas diffusion path 15×the length in the direction along the gas diffusion path 15 is 500 μm. ×400 μm is preferable.

(M) After that, the polysilicon films forming the flow channel forming film 19a, the intake port forming film 19b, and the inlet port forming film 19c for forming the gas diffusion path 15 are selectively etched by, for example, wet etching. By removing, the limiting current type gas sensor 1A according to the tenth embodiment having the configuration shown in FIGS. 149(a) and 149(b) is obtained.

As described above, according to the limiting current type gas sensor 1A according to the tenth embodiment, the flow path length of the gas flow path 15a is lengthened or the cross-sectional area (flow path cross-sectional area) of the gas flow path 15a is reduced. By doing so, the aspect ratio of the gas diffusion path 15 can be easily increased, so that the sensor characteristics can be easily improved.

Moreover, according to the limiting current type gas sensor 1A according to the tenth embodiment, the gas diffusion path 15 having a large aspect ratio can be formed accurately (precision), so that the sensor characteristics can be further stabilized.

Although the gas inlet port 15c is arranged substantially in the center of the sensor part, the gas inlet port 15b can be freely arranged anywhere in the non-sensor part, and the desired flow can be obtained. It is easy to form the gas flow path 15a having a path length.

(Eleventh Embodiment)
(Schematic configuration)
A schematic planar pattern configuration of the limiting current type gas sensor 2A according to the eleventh embodiment is represented as shown in FIG. 162(a), and is a MEMS (Micro Electro Micro Electrode) along a line IIA-IIA in FIG. 162(a). A schematic cross-sectional structure of the sensor 2A formed in the mechanical system) beam structure is represented as shown in FIG. 162(b).

As shown in FIGS. 162(a) and 162(b), in the limiting current type gas sensor 2A according to the eleventh embodiment, the substrate 12 of the MEMS beam structure is the limit according to the tenth embodiment described above. Different from that of the current type gas sensor 1A, the other structure is the same, and thus the duplicated description is omitted as much as possible, and the manufacturing method will be described in more detail.

That is, in the limiting current type gas sensor 2A according to the eleventh embodiment, as shown in FIGS. 162(a) and 162(b), the substrate 12 having the MEMS beam structure in which the cavity C has the boat shape, and the central portion. Corresponding to the respective sensor portions of, the porous electrode (porous Pt electrode) 5D arranged on the substrate 12, the solid electrolyte layer (YSZ film) 4 arranged so as to cover the porous electrode 5D, and the porous electrode. On the solid electrolyte layer 4 facing the electrode 5D, a dense electrode (porous Pt electrode) 5U arranged substantially in the vertical direction with respect to the substrate 12 is provided.

Further, the limiting current type gas sensor 2A has an insulating layer 3 on almost the entire surface thereof, and a gas to be measured (through a gas diffusion path 15 formed in the upper layer portion of the insulating layer 3 with a predetermined aspect ratio). For example, O ₂ gas) is introduced toward the sensor portion.

Also with the limiting current type gas sensor 2A according to the eleventh embodiment, since the aspect ratio of the gas diffusion path 15 can be increased, the sensor characteristics can be easily improved, and the gas diffusion path 15 can be accurately formed. The sensor characteristics can be made more stable.

(Production method)
A method of manufacturing the limiting current type gas sensor 2A according to the eleventh embodiment is represented as shown in FIGS. 163 to 173.

(A) First, as shown in FIGS. 163(a) and 163(b), a silicon substrate 12 having a thickness of about 10 μm is prepared, and the upper surface of the substrate 12 is formed in accordance with the region where the cavity C of the boat-shaped structure is formed. For example, the polysilicon film 1b having a different etching selection ratio from the substrate 12 is deposited so as to have a thickness of about 0.1 μm.

Then, a P-CVD method is used to deposit, for example, a SiON film having an etching selection ratio different from that of the polysilicon film 1b to form an insulating layer 1a having a thickness of about 0.5 μm on the upper surface of the substrate 12.

(B) Next, as shown in FIGS. 164(a) and 164(b), a polysilicon layer having a thickness of about 0.3 μm is formed on the insulating layer 1a, and the polysilicon layer is etched or the like. By patterning, the micro heater 2 and the electrode layers 2a and 2a connected to the micro heater 2 and the electrode layers 2b and 2b are formed. The electrode layers 2a, 2a and the electrode layers 2b, 2b are formed at positions orthogonal to each other.

The concentration of the micro heater 2 is set by the ion implantation method so that the resistance value between the electrode layers 2a and 2a is 300Ω, and the electrode layers 2a and 2a and the electrode layers 2b and 2b are higher than the micro heater 2. It is formed (implanted) to a concentration.

(C) Next, as shown in FIG. 165 (a) and FIG. 165 (b), SiON film (first insulating film) of about 0.5μm thick by P-CVD method on the entire surface to form a _{3 1.}

(D) Next, as shown in FIG. 166 (a) and FIG. 166 (b), a portion for forming a gas diffusion path 15 in the upper surface of the SiON film _{3 1,} the flow path forming for forming a gas flow path 15a The film 19a is formed (deposition+patterning).

Flow channel forming film 19a is etching selectivity is formed by using the film forming member, such as a different polysilicon film and the SiON film 3 _1. The length of the flow channel forming film 19a includes the gas intake port 15b and the gas inlet port 15c so that the aspect ratio is “flow channel length/flow channel cross-sectional area=100 (predetermined aspect ratio)”. (L) is 400 μm, width (W) is 30 μm, and thickness (depth (D)) is 0.1 μm.

Here, the predetermined aspect ratio of the gas diffusion path 15 can be easily increased by increasing the flow path length of the gas flow path 15a or decreasing the cross-sectional area (flow path cross-sectional area) of the gas flow path 15a. The sensor characteristics can be improved by increasing the aspect ratio of the gas diffusion path 15.

(E) Next, as shown in FIGS. 167(a) and 167(b), a circular gas intake port 15b having a diameter of, for example, about 50 μm is formed so as to overlap with one end side of the flow path forming film 19a. The intake gas forming film 19b for forming is deposited so as to have a thickness of about 0.5 μm, and is formed into a circular gas having a diameter of, for example, about 50 μm so as to overlap with the other end side of the flow path forming film 19a. The introduction port forming film 19c for forming the introduction port 15c is deposited so as to have a thickness of about 0.5 μm. Inlet formed film 19b and the introduction port forming layer 19c are both etching selectivity is different from the film forming member is formed using, for example, a polysilicon film and the SiON film 3 ₁ which constitutes the insulating layer 3.

As in the case of the limiting current type gas sensor 1A according to the tenth embodiment described above, a flow path forming film 19a for forming the gas diffusion path 15 having the gas flow path 15a having a length (L) of 300 μm. The formation of the inlet port forming film 19b and the inlet port forming film 19c is performed before forming the porous electrode 5D.

(F) Next, as shown in FIGS. 168(a) and 168(b), a poly-silicon film is formed by P-CVD so as to have the same height as the upper surfaces of the inlet port forming film 19b and the inlet port forming film 19c. silicon film as an etching selection ratio is different film forming member, fully and depot, for example, a SiON film (second insulating film) 3 ₂ a thickness of about 0.6 .mu.m, embedding the upper flow channel forming film 19a.

(G) Next, as shown in FIGS. 169(a) and 169(b), the insulating layer 3 is selectively removed, and the openings 3a and 3a connected to the electrode layers 2a and 2a and the electrode layers 2b and 2b. The openings 3b and 3b and the openings 3c and 3c connected to the.

Further, the insulating layer 3 is selectively removed, and about four openings 17 having a depth reaching the polysilicon film 1b are formed. The openings 17 are preferably formed, for example, nearer to the four corners of the polysilicon film 1b in order to efficiently perform the wet etching described later.

(H) Next, as shown in FIGS. 170(a) and 170(b), the insides of the openings 3a and 3a, the openings 3b and 3b, and the openings 3c and 3c are formed by, for example, a Pt/Ti laminated film. The heater electrode portions 9a and 9a, the detection terminals 9b and 9b, and the connection terminals 9c and 9c, which are embedded, are formed of a laminated film of a Ti film having a thickness of 20 nm and a Pt film having a thickness of 100 nm.

(I) Next, as shown in FIGS. 171(a) and 171(b), a porous electrode 5D made of a porous Pt film having a thickness of about 100 nm is formed by a sputtering method or the like and exposed on the surface of the insulating layer 3. The upper surface of the introduction port forming film 19c is closed and the extended end of the porous electrode 5D extending from the sensor portion is connected to one of the connection terminals 9c.

(J) Next, as shown in FIGS. 172(a) and 172(b), a solid electrolyte layer 4 made of a YSZ film is formed to a thickness of about 1 μm by a sputtering method, and one connection terminal 9c of the sensor portion is formed. The periphery of the porous electrode 5D is covered, except for the extended end side of the porous electrode 5D connected to.

(K) Next, as shown in FIGS. 173(a) and 173(b), as the dense electrode 5U, a thickness of about 100 nm is formed on the surface of the solid electrolyte layer 4 facing the porous electrode 5D in the sensor portion by the sputtering method. The porous Pt film is formed, and the extended end of the porous Pt film extending from the sensor portion is connected to the other connection terminal 9c.

(L) After this, for example, by wet etching, the polysilicon films forming the flow path forming film 19a, the intake port forming film 19b, and the introducing port forming film 19c for forming the gas diffusion path 15 are selectively formed. The polysilicon film 1b and the underlying substrate 12 are selectively removed via the opening 17 to have the structure shown in FIGS. 162(a) and 162(b). The limiting current type gas sensor 2A according to the eleventh embodiment is obtained.

That is, the limiting current type gas sensor 2A according to the eleventh embodiment includes the gas diffusion path 15 having a predetermined aspect ratio and introducing the gas to be measured toward the sensor portion in the upper layer portion of the insulating layer 3. At the same time, as the substrate 12 having the MEMS beam structure, a cavity C (cavity) is formed on the substrate 12 corresponding to the sensor portion in a boat shape.

As described above, also with the limiting current type gas sensor 2A according to the eleventh embodiment, the flow path length of the gas flow path 15a is lengthened or the cross-sectional area (flow path cross-sectional area) of the gas flow path 15a is reduced. As a result, the aspect ratio of the gas diffusion path 15 can be easily increased, so that the sensor characteristics can be easily improved.

Moreover, according to the limiting current type gas sensor 2A of the eleventh embodiment, the gas diffusion path 15 having a large aspect ratio can be accurately formed, so that the sensor characteristics can be further stabilized.

Although the gas inlet port 15c is arranged substantially in the center of the sensor part, the gas inlet port 15b can be freely arranged anywhere in the non-sensor part, and the desired flow can be obtained. It is easy to form the gas flow path 15a having a path length.

(Twelfth Embodiment)
(Schematic configuration)
A schematic planar pattern configuration of the limiting current type gas sensor 3A according to the twelfth embodiment is represented as shown in FIG. 174(a), and is a MEMS (Micro Electro Micro Electrode) along a line IIIA-IIIA in FIG. 174(a). A schematic cross-sectional structure of the sensor 3A formed in the mechanical system) beam structure is shown in FIG. 174(b). Here again, redundant description will be omitted as much as possible, and characteristic portions will be described in more detail.

That is, as shown in FIGS. 174(a) and 174(b), the limiting current type gas sensor 3A according to the twelfth embodiment corresponds to the substrate 12 of the MEMS beam structure and the central sensor portion, respectively. A porous electrode (porous Pt electrode) 5D arranged on the substrate 12, a solid electrolyte layer (YSZ film) 4 arranged so as to cover the porous electrode 5D, and a solid electrolyte facing the porous electrode 5D. On the layer 4, a dense electrode (porous Pt electrode) 5U arranged substantially in the vertical direction with respect to the substrate 12 and a lid 110 provided on the substrate 12 so as to surround the region of the sensor portion are provided.

Further, the limiting current type gas sensor 3A introduces a gas to be measured (for example, O ₂ gas) toward the sensor portion via a gas diffusion path 115 formed in the lid 110 with a predetermined aspect ratio. Is configured to.

In addition, in the case of this limiting current type gas sensor 3A, since the gas to be measured introduced into the sensor portion is provided with the lid 110, the gas to be measured is introduced through the gas outlet passage 40 provided in the insulating layers 1a and 3 on the substrate 12 side. To the cavity C side.

In short, the limiting current type gas sensor 3A according to the twelfth embodiment includes the substrate 12, the porous electrode 5D arranged in the region of the sensor portion on the substrate 12 via the insulating layer 3, and the porous electrode 5D. The solid electrolyte layer 4 arranged on the upper surface portion, the dense electrode 5U arranged on the surface of the solid electrolyte layer 4 facing the porous electrode 5D, and a predetermined aspect ratio. And a gas diffusion path 115 that is introduced to the lid 110. The gas diffusion path 115 is formed in the lid 110 that is further provided.

The gas diffusion path 115 includes a gas inlet 115b for taking in the gas to be measured, a gas inlet 115c for introducing the gas to be measured, and a gas passage (micro passage) connecting the gas inlet 115c and the gas inlet 115b. 115a, the flow rate of the gas to be measured can be controlled according to the aspect ratio (ratio between the flow channel length of the micro flow channel and the flow channel cross-sectional area).

The lid 110 is formed so as to expose the heater electrode portions 9a, 9a and the detection terminals 9b, 9b on the insulating layer 3, and is a space area (cavity) provided corresponding to the area of the sensor portion. It has CAa.

In the gas diffusion path 115, the gas inlet 115c is provided in the ceiling portion of the space area CAa in the lid 110, and the gas inlet 115b is provided in the area of the non-sensor portion of the upper surface of the lid 110. There is. Then, a space between the gas intake port 115b and the gas introduction port 115c is provided, for example, through a plurality of linear gas flow paths 115a (115a _-1 115a _-2 115a _-3 ) which are included in a U shape. It is connected almost horizontally.

Actually, in the limiting current type gas sensor 3A according to the twelfth embodiment, the aspect ratio of the gas diffusion path 115 is set to be, for example, “flow channel length/flow channel cross-sectional area=100 (predetermined aspect ratio)”. Further, the gas flow paths 115a (115a _-1 115a _-2 115a _-3 ) are formed with a width (W)=30 μm, a depth (D)=0.1 μm, and a length (L)=300 μm.

The gas lead-out path 40 has an opening structure that is opened to the insulating layer 3, the micro-heater 2 and the insulating layer 1a in the substantially central portion of the sensor portion at a depth reaching the cavity C of the substrate 12 having the MEMS beam structure. For example, it is composed of a large-diameter first opening 40a and a small-diameter second opening 40b.

The limiting current type gas sensor 3A according to the twelfth embodiment includes a gas diffusion passage 115 formed in a lid 110 mounted on the substrate 12 of the MEMS beam structure by bonding and having a predetermined aspect ratio. By increasing the aspect ratio of the gas diffusion path 115, the sensor characteristics can be easily improved, and the gas diffusion path 115 can be accurately formed, so that the sensor characteristics can be made more stable. You can

(Production method)
The method of manufacturing the limiting current type gas sensor 3A according to the twelfth embodiment includes a step of forming a porous electrode 5D in a region on the substrate 12 corresponding to the sensor portion via the insulating layer 3, and a step of forming the porous electrode 5D. A step of forming the solid electrolyte layer 4 on the upper surface, a step of forming the dense electrode 5U on the surface of the solid electrolyte layer 4 facing the porous electrode 5D, and a predetermined aspect ratio, The method further includes a step of providing a gas diffusion path 115 introduced toward the sensor portion, separately forming a lid 110 surrounding the area of the sensor portion, and adhering it to the upper layer portion of the insulating layer 3.

First, in the method of manufacturing the limiting current type gas sensor 3A according to the twelfth embodiment shown in FIGS. 174(a) and 174(b), the manufacturing method of the sensor portion is shown in FIGS. 175 to 185.

(A) As shown in FIGS. 175(a) and 175(b), a substrate 12 made of silicon and having a thickness of about 10 μm is prepared, and the upper surface of the substrate 12 is subjected to a plasma CVD (P-CVD) method to a thickness of about 0. An insulating layer 1a made of a SiON film having a thickness of 5 μm is formed.

(B) Next, as shown in FIGS. 176(a) and 176(b), a polysilicon layer having a thickness of about 0.3 μm is formed on the insulating layer 1a, and the polysilicon layer is etched or the like. By patterning, the micro heater 2 and the electrode layers 2a and 2a connected to the micro heater 2 and the electrode layers 2b and 2b are formed. The electrode layers 2a, 2a and the electrode layers 2b, 2b are formed at positions orthogonal to each other. The micro heater 2 is formed so that the width between the electrode layers 2a and 2a is about 300 μm.

The concentration of the micro heater 2 is set by the ion implantation method so that the resistance value between the electrode layers 2a and 2a is 300Ω, and the electrode layers 2a and 2a and the electrode layers 2b and 2b are higher than the micro heater 2. It is formed (implanted) to a concentration.

Further, a circular opening 40A having a diameter of about 50 μm is formed at a depth reaching the insulating layer 1a in the micro-heater 2 at, for example, a substantially central portion of the sensor portion.

(C) Then, as shown in FIGS. 177(a) and 177(b), an insulating layer 3 made of a SiON film having a thickness of about 0.5 μm is uniformly formed on the entire surface by an P-CVD method, and an opening is formed. The insulating layer 3 is embedded in the insulating layer 1a in the portion 40A, and a recessed portion which will be the first opening portion 40a of the gas lead-out path 40 is formed on the upper surface thereof. The depth of the first opening 40a is about 0.3 μm depending on the thickness of the polysilicon layer (microheater 2).

(D) Next, as shown in FIGS. 178(a) and 178(b), the insulating layer 3 buried in the bottom surface of the first opening 40a and the insulating layer 1a below it are removed by etching. A circular opening having a diameter of, for example, about 30 μm, which will be the second opening 40 b of the gas outlet 40, is formed with a depth reaching the substrate 12. The depth of the second opening 40b is about 1 μm depending on the thickness of the insulating layers 1a and 3.

(E) Next, as shown in FIGS. 179(a) and 179(b), the etching selection ratio between the first opening 40a and the second opening 40b is lower than that of the insulating layers 1a and 3. It is filled with a polysilicon film 27 having a different thickness, for example, about 1.3 μm.

(F) Next, as shown in FIGS. 180(a) and 180(b), the insulating layer 3 is selectively removed, and the openings 3a and 3a connected to the electrode layers 2a and 2a and the electrode layers 2b and 2b. The openings 3b and 3b and the openings 3c and 3c connected to the.

(G) Next, as shown in FIGS. 181(a) and 181(b), the insides of the openings 3a and 3a, the openings 3b and 3b, and the openings 3c and 3c are formed by, for example, a Pt/Ti laminated film. Buried, heater electrode portions 9a, 9a, detection terminals 9b, 9b, and connection terminals 9c, 9c made of a laminated film of a Ti film and a Pt film are formed.

As the heater electrode portions 9a and 9a, the detection terminals 9b and 9b, and the connection terminals 9c and 9c, for example, a Ti film having a thickness of 20 nm is formed along the side wall and the bottom portion, and a part of the Ti film is formed on the insulating layer 3. In addition, a Pt film having a thickness of 100 nm may be embedded inside so as to cover the protrusion and the insulating layer 3.

(H) Next, as shown in FIGS. 182(a) and 182(b), a porous electrode 5D made of a porous Pt film having a thickness of about 100 nm is formed by a sputtering method or the like, and is exposed on the surface of the insulating layer 3. The upper surface of the polysilicon film 27 is closed, and the extended end of the porous electrode 5D extending from the sensor portion is connected to one connection terminal 9c.

(I) Next, as shown in FIGS. 183(a) and 183(b), a solid electrolyte layer 4 made of a YSZ film is formed to a thickness of about 1 μm by a sputtering method, and one connection terminal 9c of the sensor portion is formed. The periphery of the porous electrode 5D is covered, except for the extended end side of the porous electrode 5D connected to.

(J) Next, as shown in FIGS. 184(a) and 184(b), as a dense electrode 5U, a thickness of about 100 nm is formed on the surface of the solid electrolyte layer 4 facing the porous electrode 5D in the sensor portion by the sputtering method. The porous Pt film is formed, and the extended end of the porous Pt film extending from the sensor portion is connected to the other connection terminal 9c.

(K) Next, as shown in FIGS. 185(a) and 185(b), the substrate 12 corresponding to the sensor portion is selectively deep-etched to remove the substrate 12 having the MEMS beam structure from the cavity C (Cavity: (Cavity) is formed into an open structure having an open structure.

(L) Next, the polysilicon film 27 embedded in the first opening 40a and the second opening 40b is selectively removed by, for example, wet etching to form the gas outlet 20.

(M) Thereafter, as will be described later, a separately formed lid 110 is attached to the insulating layer 3 by using an adhesive or the like, whereby the configuration shown in FIGS. 174(a) and 174(b) is obtained. The limiting current type gas sensor 3A according to the twelfth embodiment having the above is obtained.

(First Modification of Twelfth Embodiment)
(Schematic configuration)
A schematic plane pattern configuration of the limiting current type gas sensor 4A according to the first modified example of the twelfth embodiment is represented as shown in FIG. 186(a), and is along the line IVA-IVA of FIG. 186(a). , A schematic cross-sectional structure of the sensor 4A formed in the MEMS (Micro Electro Mechanical Systems) beam structure is shown in FIG. 186(b).

That is, as shown in FIGS. 186(a) and 186(b), the limiting current type gas sensor 4A according to the first modified example of the twelfth embodiment includes a substrate 12 having a MEMS beam structure and a sensor in the central portion. A porous electrode (porous Pt electrode) 5D arranged on the substrate 12, a solid electrolyte layer (YSZ film) 4 arranged so as to cover the porous electrode 5D, and a porous electrode 5D corresponding to the respective portions. On the solid electrolyte layer 4 facing the substrate 12, a dense electrode (porous Pt electrode) 5U arranged substantially in the vertical direction with respect to the substrate 12, and a lid 112 provided on the substrate 12 so as to surround the region of the sensor portion. With.

Further, the limiting current type gas sensor 4A introduces a gas to be measured (for example, O ₂ gas) toward the sensor portion via a gas diffusion path 116 formed in the lid 112 with a predetermined aspect ratio. Is configured to.

In short, the limiting current type gas sensor 4A according to the first modified example of the twelfth embodiment includes a substrate 12, a porous electrode 5D arranged in the area of the sensor portion on the substrate 12 via an insulating layer 3, and The solid electrolyte layer 4 arranged on the upper surface of the porous electrode 5D, and the dense electrode 5U arranged on the surface of the solid electrolyte layer 4 facing the porous electrode 5D have a predetermined aspect ratio, The gas diffusion path 116 for introducing the measurement gas toward the sensor portion is provided, and the gas diffusion path 116 is formed in the lid 112 that is further provided.

In the case of the limiting current type gas sensor 4A according to the first modification of the twelfth embodiment, the gas diffusion path 116 provided in the lid 112 introduces the gas to be measured 116a into which the gas to be measured is introduced. And a gas flow channel (micro flow channel) 116c that connects the gas introduction port 116b and the gas intake port 116a, and has an aspect ratio (of the flow channel length of the micro flow channel and the flow channel cross-sectional area). It is possible to control the flow rate of the measured gas according to the ratio).

Further, in the gas diffusion path 116, the gas introduction port 116b is provided in the ceiling portion of the space region CAa in the lid 112, and the gas intake port 116a is provided in the region of the non-sensor portion of the upper surface of the lid 112. Has been. The gas inlet 116a and the gas inlet 116b are connected in a substantially horizontal direction via, for example, one linear gas flow passage 116c.

Since other configurations are the same as those of the limiting current type gas sensor 3A according to the twelfth embodiment described above, duplicate description will be omitted as much as possible, and a manufacturing method thereof will be described using the lid 112 as an example.

(Production method)
In the limiting current type gas sensor 4A according to the first modified example of the twelfth embodiment, the method for manufacturing the lid 112 is represented as shown in FIGS. 187 to 192.

(A) First, as shown in FIGS. 187(a) and 187(b), a substrate (first lid member) 112a made of silicon having a thickness of about 10 μm is prepared, and the gas diffusion path 116 on the surface side thereof is formed. A flow path forming film 112b for forming the gas flow path 116c is formed (deposited+patterned) on the portion to be formed.

For example, one end of the flow path forming film 112b corresponds to the region of the non-sensor portion, and the other end corresponds to the substantially central portion of the sensor portion.

The flow channel forming film 112b is formed by using a film forming member having a different etching selection ratio from Si forming the substrate 112a, for example, a silicon oxide (SiO ₂ ) film. Further, the flow channel forming film 112b and the gas introduction port 116a and the gas introduction port are configured such that the aspect ratio of the gas flow channel 116c is, for example, “flow channel length/flow channel cross-sectional area=100 (predetermined aspect ratio)”. Not including the opening 116b, the length (L) is 300 μm, the width (W) is 30 μm, and the thickness (depth (D)) is 0.1 μm.

Here, the predetermined aspect ratio of the gas diffusion path 116 can be easily increased by increasing the flow path length of the gas flow path 116c or decreasing the cross-sectional area (flow path cross-sectional area) of the gas flow path 116c. The sensor characteristics can be improved by increasing the aspect ratio of the gas diffusion path 116.

(B) Next, as shown in FIGS. 188(a) and 188(b), a film forming member having a different etching selection ratio from the SiO ₂ film, for example, a polysilicon film (second lid member) 112c is formed on the entire surface. Deposition is performed and the flow path forming film 112b is embedded.

(C) Next, as shown in FIGS. 189(a) and 189(b), the polysilicon film 112c is selectively removed by etching, and one end side of the flow path forming film 112b is opened to form a gas diffusion path. The gas inlet 116a of 116 is formed.

(D) Next, as shown in FIGS. 190(a) and 190(b), the back surface (lower part) side of the substrate 112a is selectively etched to form a space area CAa for housing the sensor portion.

(E) Next, as shown in FIGS. 191(a) and 191(b), the back surface side of the substrate 112a is further selectively removed by etching, and the other end side of the flow path forming film 112b is opened, The gas inlet 116b of the gas diffusion path 116 is formed in the ceiling portion of the space area CAa.

Here, the gas intake port 116a and the gas introduction port 116b are, for example, circular with a diameter of about 50 μm, and are formed on both ends of the flow channel forming film 112b so that the flow channel length of the gas flow channel 116c is 300 μm. To be done.

(F) Next, as shown in FIGS. 192(a) and 192(b), the SiO ₂ film forming the flow path forming film 112b is selectively removed by HF (hydrofluoric acid) etching to remove gas. By forming the gas flow passage 116c connected to the port 116a and the gas introduction port 116b, the lid 112 of the limiting current type gas sensor 4A according to the first modified example of the twelfth embodiment is obtained.

(G) After that, the formed lid body 112 is attached onto the insulating layer 3 by using an adhesive or the like, so that the twelfth embodiment has the configuration shown in FIGS. 186(a) and 186(b). The limiting current type gas sensor 4A according to the first modified example of the embodiment is obtained.

As described above, also with the limiting current type gas sensor 4A according to the first modified example of the twelfth embodiment, the flow channel length of the gas flow channel 116c is lengthened, or the cross-sectional area of the gas flow channel 116c (flow channel disconnection) By reducing the area, it is possible to easily increase the aspect ratio of the gas diffusion path 116, so that the sensor characteristics can be easily improved.

Moreover, according to the limiting current type gas sensor 4A according to the first modified example of the twelfth embodiment, the gas diffusion path 116 having a large aspect ratio can be accurately formed, so that the sensor characteristics can be more stabilized.

(Second Modification of Twelfth Embodiment)
(Schematic configuration)
A schematic plane pattern configuration of the limiting current type gas sensor 5A according to the second modification of the twelfth embodiment is represented as shown in FIG. 193(a), and is along the line VA-VA in FIG. 193(a). , A schematic cross-sectional structure of a sensor 5A formed in a MEMS (Micro Electro Mechanical Systems) beam structure is shown in FIG. 193(b).

That is, as shown in FIGS. 193(a) and 193(b), the limiting current type gas sensor 5A according to the second modified example of the twelfth embodiment includes the substrate 12 having the MEMS beam structure and the sensor in the central portion. A porous electrode (porous Pt electrode) 5D arranged on the substrate 12, a solid electrolyte layer (YSZ film) 4 arranged so as to cover the porous electrode 5D, and a porous electrode 5D corresponding to the respective portions. On the solid electrolyte layer 4 facing to the substrate 12, a dense electrode (porous Pt electrode) 5U arranged substantially vertically with respect to the substrate 12, and a lid 113 provided on the substrate 12 so as to surround the region of the sensor portion. With.

Further, this limiting current type gas sensor 5A introduces a gas to be measured (for example, O ₂ gas) toward the sensor portion via a gas diffusion path 117 formed in the lid 113 with a predetermined aspect ratio. Is configured to.

In short, the limiting current type gas sensor 5A according to the second modified example of the twelfth embodiment includes a substrate 12, a porous electrode 5D arranged in the area of the sensor portion on the substrate 12 via an insulating layer 3, The solid electrolyte layer 4 arranged on the upper surface of the porous electrode 5D, and the dense electrode 5U arranged on the surface of the solid electrolyte layer 4 facing the porous electrode 5D have a predetermined aspect ratio, A gas diffusion path 117 for introducing the measurement gas toward the sensor portion is provided, and the gas diffusion path 117 is formed in the lid 113 further provided.

In the case of the limiting current type gas sensor 5A according to the second modified example of the twelfth embodiment, the gas diffusion path 117 provided in the lid 113 introduces the gas to be measured 117a into which the gas to be measured is introduced. And a gas flow channel (micro flow channel) 117c that connects the gas introduction port 117b and the gas intake port 117a, and has an aspect ratio (of the flow channel length of the micro flow channel and the flow channel cross-sectional area). It is possible to control the flow rate of the measured gas according to the ratio).

Further, the gas diffusion path 117 is provided, for example, in a substantially vertical direction at a ceiling portion of the space area CAa in the lid 113 at a substantially central portion of the sensor portion, and a space between the gas intake port 117a and the gas introduction port 117b is provided. They are connected in a straight line via a gas flow path 117c. The aspect ratio of the gas diffusion path 117 can be easily controlled by, for example, adjusting the diameter of the gas flow path 117c (the diameter of the flow path forming film) and the flow path length (the thickness of the polysilicon film).

Also with the limiting current type gas sensor 5A according to the second modified example of the twelfth embodiment, the flow path length of the gas flow path 117c is lengthened or the cross-sectional area (flow path cross-sectional area) of the gas flow path 117c is reduced. As a result, the aspect ratio of the gas diffusion path 117 can be easily increased, so that the sensor characteristics can be easily improved.

Moreover, according to the limiting current type gas sensor 5A according to the second modification of the twelfth embodiment, the gas diffusion path 117 having a large aspect ratio can be accurately formed, so that the sensor characteristics can be more stabilized.

(Third Modification of Twelfth Embodiment)
(Schematic configuration)
A schematic plane pattern configuration of the limiting current type gas sensor 6A according to the third modified example of the twelfth embodiment is represented as shown in FIG. 194(a), and is along the VIA-VIA line in FIG. 194(a). , A schematic cross-sectional structure of the sensor 6A formed in the MEMS (Micro Electro Mechanical Systems) beam structure is shown in FIG. 194(b).

That is, as shown in FIGS. 194(a) and 194(b), the limiting current type gas sensor 6A according to the third modified example of the twelfth embodiment includes a substrate 12 having a MEMS beam structure and a sensor in the central portion. A porous electrode (porous Pt electrode) 5D arranged on the substrate 12, a solid electrolyte layer (YSZ film) 4 arranged so as to cover the porous electrode 5D, and a porous electrode 5D corresponding to the respective portions. On the solid electrolyte layer 4 facing each other, a dense electrode (porous Pt electrode) 5U arranged substantially vertically with respect to the substrate 12, and a lid 114 provided on the substrate 12 so as to surround a region of the sensor portion. With.

Further, this limiting current type gas sensor 6A introduces a gas to be measured (for example, O ₂ gas) toward the sensor portion via a gas diffusion path 118 formed in the lid 114 with a predetermined aspect ratio. Is configured to.

In short, the limiting current type gas sensor 6A according to the third modified example of the twelfth embodiment includes a substrate 12, a porous electrode 5D arranged in the area of the sensor portion on the substrate 12 via an insulating layer 3, and The solid electrolyte layer 4 arranged on the upper surface of the porous electrode 5D, and the dense electrode 5U arranged on the surface of the solid electrolyte layer 4 facing the porous electrode 5D have a predetermined aspect ratio, A gas diffusion path 118 for introducing the measurement gas toward the sensor portion is provided, and the gas diffusion path 118 is formed in the lid 114 further provided.

In the case of the limiting current type gas sensor 6A according to the third modified example of the twelfth embodiment, the gas diffusion passage 118 provided in the lid 114 introduces the gas to be measured 118a into which the gas to be measured is introduced. And a gas channel (microchannel) 118c that connects the gas inlet 118b and the gas inlet 118a, and has an aspect ratio (of the channel length of the microchannel and the channel cross-sectional area). It is possible to control the flow rate of the measured gas according to the ratio).

Further, in the gas diffusion path 118, the gas introduction port 118 b is provided in the ceiling portion of the space area CAa in the lid 114, and the gas intake port 118 a is provided in the side surface portion of the lid 114. The gas intake port 118a and the gas introduction port 118b are connected in a substantially horizontal direction via, for example, one linear gas passage 118c.

Also by the limiting current type gas sensor 6A according to the third modified example of the twelfth embodiment, the flow path length of the gas flow path 118c is lengthened or the cross-sectional area (flow path cross-sectional area) of the gas flow path 118c is reduced. As a result, the aspect ratio of the gas diffusion path 118 can be easily increased, so that the sensor characteristics can be easily improved.

Moreover, according to the limiting current type gas sensor 6A according to the third modification of the twelfth embodiment, the gas diffusion path 118 having a large aspect ratio can be accurately formed, so that the sensor characteristics can be more stabilized.

The gas diffusion path 118 can also be formed so as to be drawn out in any of the oblique directions corresponding to the four corners of the lid 114.

In addition, the method of manufacturing the limiting current type gas sensors 1A to 6A according to the tenth to twelfth embodiments may include a step of forming the micro-heater 2 on the upper portion of the substrate 12 or the lower portion of the substrate 12.

Moreover, the manufacturing method of the limiting current type gas sensors 1A to 6A according to the tenth to twelfth embodiments may include a step of forming the micro heater 2 embedded inside the substrate 12.

Moreover, in the manufacturing method of the limiting current type gas sensors 1A to 6A according to the tenth to twelfth embodiments, the microheater 2, the insulating layer 3, the porous electrode 5D, the dense electrode 5U, and the solid electrolyte layer 4 are printed. Can be formed by.

Regarding the operation principle, in the limiting current type gas sensors according to the tenth to twelfth embodiments, as described above, the operation of detecting the gas concentration is the limiting current type gas sensors according to the first to sixth embodiments. Since it is substantially the same as the case, detailed description is omitted.

Further, the description of the electrochemical reaction is substantially the same as that of the limiting current type gas sensors according to the first to sixth embodiments, as described above, and thus detailed description thereof will be omitted.

Further, as to the package, as described above, it is substantially the same as the case of the limiting current type gas sensor according to the first to sixth embodiments, and therefore detailed description thereof will be omitted.

Further, the configuration example of the sensor node using the energy harvester power supply is substantially the same as that of the limiting current type gas sensor according to the above-described first to sixth embodiments, and therefore detailed description thereof will be omitted.

Further, in the limiting current type gas sensor according to the tenth to twelfth embodiments, the schematic block configuration of the sensor package is substantially the same as that of the limiting current type gas sensor according to the first to sixth embodiments described above. Since it is similar to the above, detailed description will be omitted.

Furthermore, the schematic block configuration of the sensor network system to which the limiting current type gas sensor according to the tenth to twelfth embodiments is applied is the same as that of the limiting current type gas sensor according to the above-described first to sixth embodiments. Since they are substantially the same, detailed description will be omitted here.

As described above, according to the present embodiment, it is possible to provide the limiting current type gas sensor that can improve the sensor characteristics and further stabilize the sensor characteristics.

Further, according to the present embodiment, it is possible to provide a limiting current type gas sensor capable of improving the response speed.

Further, according to the present embodiment, it is possible to easily and precisely form a gas diffusion path having a large aspect ratio by utilizing the etching selection ratio, and as a result, the sensor characteristics can be improved and the sensor It is possible to provide a limiting current type gas sensor that can further stabilize the characteristics.

[Other Embodiments]
As described above, although some embodiments are described, it should not be understood that the descriptions and drawings forming a part of the disclosure are exemplifications, and limit each embodiment. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

As described above, each embodiment includes various aspects not described here. For example, the concentration of carbon dioxide can be detected by replacing zirconia with another material or combining some materials.

The limiting current type gas sensor of the present embodiment can be applied to an oxygen sensor and a humidity sensor. Further, such a sensor can be applied to exhaust gas of automobiles and sensor networks.

1A, 1B, 1C, 1D, 1E, 2A, 2B, 2C, 2D, 3A, 3B, 3C, 3D, 3E, 3F, 4A, 4B, 4C, 4D, 4E, 4F, 4G, 4H, 5A, 5A1, 5A2, 5B1, 5B2, 5C1, 5C2, 5D1, 5D2, 5E1, 5E2, 5F1, 5F2, 5G1, 5G2, 5H1, 5H2, 5J1, 5J2, 5K1, 5K2, 5L1, 5L2, 5M1, 5M2, 6A, 6A1, 6A2, 6B1, 6B2, 6C1, 6C2, 6D1, 6D2, 6E1, 6E2, 6F1, 6F2, 6G1, 6G2, 6H1, 6H2, 6J1, 6J2, 6K1, 6K2, 6L1, 6L2, 6M1, 6M2... (Sensor node)
1a, 3, 14, 16, 18... Insulating layers 1b, 27... Polysilicon film 2, MH... Micro heater 2a... Electrode layer 2b... Detection terminal (electrode layer)
3 ₁ ... SiON film (first insulating film)
3 ₂ ... SiON film (second insulating film)
3a, 3b, 3c, 7, 17, 37, 45... Openings 4, 30, 106... Solid electrolyte layer (YSZ, YSZ thin film)
5D, 5D ₁ , 5D ₂ , 105D... Porous electrode (Ti/Pt electrode, porous Pt, anode)
5U, 5U ₁ , 5U ₂ ... Dense electrode (Pt electrode, porous Pt, cathode)
5Pt... Pt film 5Ti... Ti/Pt laminated film 6, 6(4), 6(5U), 6(5D), 6(5U ₁ ), 6(5U ₂ ), 6(5D ₁ ), 6(5D ₂ )... Low thermal expansion film 8 for stress relaxation... Insulating films 9 and 9a... Electrode portion 9b for heater... Detection terminal 9c... Connection terminal 10, 10 (5U), 10(5D), 10(5U ₁ ), 10(5U ₂ ) 10(5D ₁ ), 10(5D ₂ )... Warp suppressing porous insulating film 11... Pt+YSZ mixed particle film (particle mixed layer)
11a... Layer (Pt region)
11b... Layer (YSZ region)
12, 120... Substrate (silicon substrate)
13... Porous film (porous layer, Al ₂ O ₃ —SiO ₂ film, porous film)
15, 115, 116, 117, 118, MP, MP1... Gas diffusion paths 15a, 42, 115a, 115a- ₁ , 115a- ₂ , 115a- ₃ , 116c, 117c, 118c... Gas flow paths (micro flow paths)
15b, 47, 51G, 61G, 115b, 116a, 117a, 118a, 471, 472... Gas inlet 15c, 41, 115c, 116b, 117b, 118b... Gas inlet 19a... Flow path forming film 19b... Inlet forming film 19c ... inlet formed film 20,201,202 ... SiN layer 21, 22 ... heater connection portion 23, 24 ... terminal electrode connecting portion 25,512 ... SiO ₂ film 26 ... SiN film 28D, 28DA, 28DB ... lower electrode 28D1... Lower electrode extension ends 28U, 105U... Upper electrode 28U1... Upper electrode extension end 35... Flow path forming layer 40... Gas outlet 40a... First opening 40b... Second opening 40A... Opening Hole 43... Protective SiO ₂ film 49... Lid members 51, 71... Porous oxide film 53... Columnar oxide film 57... Columnar Pt/Ti film 61... Porous Pt film 90... Thermistor section 92... YSZ sensor section (limit current formula) Gas sensor)
94... AD/DA converter 96... Sensor package 100... Wafer 102... Element isolation region 103... Laminated film 104... Element region 107... Detection circuits 110, 112, 113, 114... Lid 112a... Substrate (first lid member)
112b... Flow path forming film (SiO ₂ film)
112c... Polysilicon film (second lid member)
131... Package lid 132... Through hole 141... Package body 142... Limiting current type gas sensor chip 143... Bonding wire 151... Sensors 152... Wireless module 153... Microcomputer 154... Energy harvester power supply 155... Storage elements 181, 182... first and second insulating layers 200 ... device heating unit 300 ... lightly doped polysilicon layer 301 ... polysilicon layer 303, 305 ... gas intake portion 510 ... YSZ-SiO ₂ film 511 ... YSZ particles AA ... active region C ... Cavity part, cavity CAa... Space area GS... Measured gas SP... Sensor part

Claims (24)

Board,
A heater disposed on the substrate via a first insulating layer,
A gas introduction path which is arranged on the heater via a second insulating layer and takes in a gas to be measured;
A lower electrode arranged on the gas introduction path,
A solid electrolyte layer disposed on the lower electrode,
An upper electrode disposed on a surface of the solid electrolyte layer facing the lower electrode,
The substrate includes a cavity portion formed substantially larger than the heater ,
The gas introduction path, the limiting current type gas sensor, wherein Rukoto constituted by a porous membrane. Board,
A heater disposed on the substrate via a first insulating layer,
A gas introduction path which is arranged on the heater via a second insulating layer and takes in a gas to be measured;
A lower electrode arranged on the gas introduction path,
A solid electrolyte layer disposed on the lower electrode,
An upper electrode disposed on a surface of the solid electrolyte layer facing the lower electrode,
A cavity portion formed on the substrate substantially larger than the heater;
Equipped with
The limiting current type gas sensor, wherein the gas introduction path is a gas diffusion path having a hollow micro flow path. The limiting current type gas sensor according to claim 2, wherein the gas diffusion path includes a gas intake port that takes in the gas to be measured. The limiting current type gas sensor according to claim 2, wherein the gas diffusion path includes a plurality of gas inlets for taking in the gas to be measured. The limiting current type gas sensor according to claim 4, wherein any one of the plurality of gas intake ports is closed. Board,
A heater disposed on the substrate via a first insulating layer,
A gas intake portion arranged on the heater via a second insulating layer;
A lower electrode disposed on the gas intake section,
A solid electrolyte layer disposed on the lower electrode,
An upper electrode disposed on a surface of the solid electrolyte layer facing the lower electrode,
A cavity portion formed on the substrate substantially larger than the heater;
Equipped with
The gas intake section,
A gas introduction path for taking in the measured gas,
A columnar portion arranged on the gas introduction path,
Consists of
The limiting column type gas sensor, wherein the columnar portion is composed of a columnar film having a gas constriction structure in a direction perpendicular to the surface. Board,
A heater disposed on the substrate via a first insulating layer,
A gas intake portion arranged on the heater via a second insulating layer;
A lower electrode disposed on the gas intake section,
A solid electrolyte layer disposed on the lower electrode,
An upper electrode disposed on a surface of the solid electrolyte layer facing the lower electrode,
A cavity portion formed on the substrate substantially larger than the heater;
Equipped with
The gas intake section,
A gas introduction path for taking in the measured gas,
A columnar portion arranged on the gas introduction path,
Consists of
The limiting column type gas sensor, wherein the columnar portion is composed of a porous film having an in-plane gas diffusion structure. 8. The limiting current type gas sensor according to claim 1, wherein the heater further comprises an undoped or lightly doped polysilicon layer. The substrate includes a beam structure having a MEMS structure,
9. The limiting current type gas sensor according to claim 1, wherein the beam structure is a boat type structure in which the cavity portion is formed in a boat type on the substrate. The substrate includes a beam structure having a MEMS structure,
9. The limiting current type gas sensor according to claim 1, wherein the beam structure is an open type structure in which the cavity is formed in the substrate in an open type. 11. A detection circuit for detecting a predetermined gas concentration in the gas to be measured by a limiting current method by applying a voltage between the upper electrode and the lower electrode, further comprising: The limiting current type gas sensor according to any one of 1. The limiting current type gas sensor according to claim 11, wherein the detection circuit detects the oxygen concentration based on the limiting current. The limiting current type gas sensor according to claim 11, wherein the detection circuit detects the water vapor concentration based on the limiting current. The limiting current type gas sensor according to claim 1, wherein the lower electrode is formed of a Pt/Ti film. Board,
A heater disposed on the substrate via a first insulating layer,
A gas introduction path which is arranged on the heater via a second insulating layer and takes in a gas to be measured;
A lower electrode arranged on the gas introduction path,
A solid electrolyte layer disposed on the lower electrode,
An upper electrode disposed on a surface of the solid electrolyte layer facing the lower electrode,
A cavity portion formed on the substrate substantially larger than the heater;
Equipped with
The limiting current type gas sensor, wherein the lower electrode is composed of a porous Pt/Ti film. The limiting current type gas sensor according to claim 2, wherein the lower electrode is composed of a porous Pt/Ti film. The porous film may be YSZ or Al. ₂ O ₃ The limiting current type gas sensor according to claim 1, which is a porous oxide film containing a. The limiting current type gas sensor according to claim 1, wherein the porous film is a porous Pt film or a porous Pt/Ti film. The limiting current type gas sensor according to claim 2, wherein a porous oxide film is further disposed on the gas diffusion path. Board,
A heater disposed on the substrate via a first insulating layer,
A gas intake portion arranged on the heater via a second insulating layer;
A lower electrode disposed on the gas intake section,
A solid electrolyte layer disposed on the lower electrode,
An upper electrode disposed on a surface of the solid electrolyte layer facing the lower electrode,
A cavity portion formed on the substrate substantially larger than the heater;
Equipped with
The gas intake section,
A gas introduction path for taking in the measured gas,
A columnar portion arranged on the gas introduction path,
Consists of
The limiting current type gas sensor, wherein the gas introduction path is a gas diffusion path provided with a microchannel having a porous membrane or a hollow structure. The limiting current type gas sensor according to claim 6, wherein the columnar film is formed of a columnar oxide film or a columnar Pt/Ti film. Board,
A heater disposed on the substrate via a first insulating layer,
A gas intake portion arranged on the heater via a second insulating layer;
A lower electrode disposed on the gas intake section,
A solid electrolyte layer disposed on the lower electrode,
An upper electrode disposed on a surface of the solid electrolyte layer facing the lower electrode,
A cavity portion formed on the substrate substantially larger than the heater;
Equipped with
The gas intake section,
A gas introduction path for taking in the measured gas,
A columnar portion arranged on the gas introduction path,
Consists of
The lower electrode is a porous electrode,
The limiting current type gas sensor, wherein the porous electrode is composed of a laminated film of a porous oxide film and a Pt/Ti film or a porous Pt/Ti film. The limiting current type gas sensor according to claim 7, wherein the porous film is composed of a porous oxide film or a porous Pt film. Board,
A heater disposed on the substrate via a first insulating layer,
A gas intake portion arranged on the heater via a second insulating layer;
A lower electrode disposed on the gas intake section,
A solid electrolyte layer disposed on the lower electrode,
An upper electrode disposed on a surface of the solid electrolyte layer facing the lower electrode,
A cavity portion formed on the substrate substantially larger than the heater;
Equipped with
The gas intake section,
A gas introduction path for taking in the measured gas,
A columnar portion arranged on the gas introduction path,
Consists of
The lower electrode is a columnar electrode,
The limiting electrode type gas sensor, wherein the columnar electrode is composed of a laminated film of a columnar oxide film and a Pt/Ti film or a columnar Pt/Ti film.