JP2014032078A - Infrared radiation element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an infrared radiation element capable of efficiently applying infrared radiation.SOLUTION: An infrared radiation element 1 comprises: a substrate 2; a thin film 3 formed over one surface of the substrate 2; a through hole 2a which goes through in a thickness direction of the substrate 2; a lattice-like first infrared radiation 4a formed at the opposite side of the substrate 2 in the thin film 3. The infrared radiation element 1 also comprises: plural pads 9 which are electrically connected to the first infrared radiation layer 4a; and a second infrared radiation layer 4b which is disposed separated away from the radiation layer 4a in an opening 4aa of the first infrared radiation layer 4a and which has the infrared radiation ratio higher than that of the thin film 3.

Description

  The present invention relates to an infrared radiation element.

  2. Description of the Related Art Conventionally, an infrared emitting element manufactured using a manufacturing technology of MEMS (micro electro mechanical systems) has been researched and developed. This type of infrared radiation element can be used as an infrared source (infrared light source) such as a gas sensor or an optical analyzer.

  As this type of infrared radiation element, for example, a radiation source having the configuration shown in FIGS. 3 and 4 is known (Patent Document 1).

  The radiation source includes a substrate 13, a first insulating layer 22 formed on the substrate 13, a radiation surface layer 11 formed on the first insulation layer 22, and a second surface formed on the radiation surface layer 11. An insulating layer 24 and a plurality of extremely thin incandescent filaments 10 formed on the second insulating layer 24 are provided. In addition, the radiation source is formed so as to cover each incandescent filament 10, a third insulating layer 26 that protects each incandescent filament 10, and both ends of each incandescent filament 10 through openings formed in the third insulating layer 26. A pair of metal pads 15 and 15 connected to each other is provided. The second insulating layer 24 is provided to electrically insulate the radiating surface layer 11 from the incandescent filament 10. Further, in Patent Document 1, the incandescent filament 10 is formed by other elements (first insulating layer 22, radiation surface layer 11, second insulating layer 24, third insulating layer 26) having a multilayer structure as a uniform flat plate. It is written that it is surrounded. Patent Document 1 describes that the purpose of providing the first insulating layer 22 and the third insulating layer 26 is to protect the incandescent filament 10 and the radiating surface layer 11 from oxidation.

  An opening 14 is formed in the substrate 13 corresponding to the radiation surface layer 11. Patent Document 1 describes an aqueous potassium hydroxide (KOH) solution, an ethylenediamine aqueous solution to which a small amount of pyrocatechol is added, and tetramethylammonium hydroxide (TMAH) as an etching solution that can be used to form the opening 14. Yes.

  The substrate 13 is formed of a (100) -oriented silicon chip. The first insulating layer 22 is made of a silicon nitride layer having a thickness of 200 nm. The radiation surface layer 11 is made of a polysilicon film having a thickness of about 1 μm and doped with boron, phosphorus or arsenic. The second insulating layer 24 is made of a silicon nitride layer having a thickness of about 50 nm. The incandescent filament 10 is made of a tungsten layer having a thickness of about 400 nm. The third insulating layer 26 is made of a silicon nitride layer having a thickness of about 200 nm. The metal pad 15 is made of, for example, aluminum, and forms ohmic contact with the incandescent filament 10 through an opening formed in the third insulating layer 26.

In the radiation source, the radiation surface layer 11 has an area of 1 mm ² . Regarding the dimensions of the incandescent filament 10, for example, the thickness is 0.1-1 μm, the width is 2-10 μm, and the interval is 20-50 μm.

  Although the incandescent filament 10 is heated by the current flowing through the incandescent filament 10, the incandescent filament 10 is used exclusively for heating the radiating surface layer 11, and the radiating surface layer 11 is the main heat radiating source. Behave as.

JP-A-9-184757

  By the way, as an infrared radiation element, an element capable of emitting infrared radiation with higher efficiency is often desired from the viewpoint of reducing power consumption.

  However, the radiation source described above uses the incandescent filament 10 exclusively for heating the radiation surface layer 11, and the radiation surface layer 11 behaves as the main heat radiation source, and the second insulating layer 24 and the radiation surface layer 11. Due to the respective heat capacities, it is difficult to emit infrared rays with high efficiency.

  This invention is made | formed in view of the said reason, The objective is to provide the infrared rays radiating element which can radiate | emit infrared rays with higher efficiency.

  The infrared radiation element of the present invention is provided on the opposite side of the substrate, the thin film portion provided on one surface side of the substrate, the through-hole penetrating in the thickness direction of the substrate, and the substrate side in the thin film portion. A grid-shaped first infrared radiation layer, a plurality of pads electrically connected to the first infrared radiation layer, and an opening of the first infrared radiation layer spaced apart from the first infrared radiation layer And a second infrared radiation layer having an infrared emissivity higher than that of the thin film portion.

  In this infrared radiation element, it is preferable that the first infrared radiation layer and the second infrared radiation layer are formed of the same material and have the same thickness.

  In this infrared radiating element, it is preferable that the first infrared radiating layer has a size of the opening portion that decreases from the peripheral portion toward the central portion.

  The infrared radiation element preferably includes a third infrared radiation layer that is disposed outside the first infrared radiation layer and spaced apart from the first infrared radiation layer and has a higher infrared emissivity than the thin film portion.

  In the infrared radiation element of the present invention, infrared radiation can be emitted with higher efficiency.

(A) is a schematic plan view of the infrared radiation element of embodiment, (b) is A-A 'schematic sectional drawing of (a), (c) is B-B' schematic sectional drawing of (a). It is principal process sectional drawing for demonstrating the manufacturing method of the infrared rays radiating element of embodiment. It is a top view of the radiation source of a prior art example. It is A-A 'sectional drawing of the radiation source of FIG.

  Below, the infrared radiation element 1 of this embodiment is demonstrated based on FIG.

  The infrared radiation element 1 includes a substrate 2, a thin film portion 3 provided on one surface side of the substrate 2, a through hole 2a penetrating in the thickness direction of the substrate 2, and a side opposite to the substrate 2 side in the thin film portion 3. And a grid-shaped first infrared radiation layer 4a. In short, in the infrared radiation element 1, the substrate 2 is formed with a through hole 2a that exposes the surface of the thin film portion 3 opposite to the first infrared radiation layer 4a side. The infrared radiation element 1 emits infrared rays from the first infrared radiation layer 4a by energization to the first infrared radiation layer 4a.

  In addition, the infrared radiation element 1 is disposed away from the first infrared radiation layer 4a at the two pads 9 electrically connected to the first infrared radiation layer 4a and the opening 4aa of the first infrared radiation layer 4a. And a second infrared radiation layer 4b having a higher infrared emissivity than the thin film portion 3. In addition, the infrared radiation element 1 includes a third infrared radiation layer 4 c that is disposed outside the first infrared radiation layer 4 a and is separated from the first infrared radiation layer 4 a and has a higher infrared emissivity than the thin film portion 3.

  Further, the infrared radiation element 1 includes a pair of electrodes 7 formed so as to be in contact with the peripheral portion of the first infrared radiation layer 4a on the one surface side of the substrate 2, and a wiring is connected to each of the electrodes 7. The above-described pad 9 is electrically connected through 8.

  The infrared radiation element 1 includes a protective layer 5 that covers the first infrared radiation layer 4a, the second infrared radiation layer 4b, and the third infrared radiation layer 4c on the opposite side of the thin film portion 3 from the substrate 2 side. The protective layer 5 is formed of a material that is transparent to infrared rays emitted from the first infrared radiation layer 4a, the second infrared radiation layer 4b, and the third infrared radiation layer 4c. In FIG. 1A, the protective layer 5 is not shown.

  In the infrared radiation element 1, the first infrared radiation layer 4a generates heat by energizing the first infrared radiation layer 4a. Thereby, as for the infrared radiation element 1, the temperature of the 1st infrared radiation layer 4a rises, and the temperature of the 2nd infrared radiation layer 4b and the 3rd infrared radiation layer 4c also rises. Therefore, the infrared radiation element 1 emits not only infrared rays from the first infrared radiation layer 4a but also infrared rays from the second infrared radiation layer 4b and the third infrared radiation layer 4c.

  Hereinafter, each component of the infrared radiation element 1 will be described in detail.

  The substrate 2 is formed of a single crystal silicon substrate having a (100) plane on the one surface. However, the substrate 2 is not limited thereto, and may be formed of a single crystal silicon substrate having a (110) plane. The substrate 2 is not limited to a single crystal silicon substrate, but may be a polycrystalline silicon substrate or other than a silicon substrate. The material of the substrate 2 is preferably a material having a higher thermal conductivity and a larger heat capacity than the material of the thin film portion 3.

  The outer peripheral shape of the substrate 2 is rectangular. Although the external size of the board | substrate 2 is not specifically limited, For example, it is preferable to set to 10 mm □ or less (10 mm × 10 mm or less). Moreover, the board | substrate 2 makes the opening shape of the through-hole 2a rectangular. The through-hole 2a of the substrate 2 is formed in a shape in which the opening area on the other surface side is larger than that on the one surface side. Here, the through hole 2 a of the substrate 2 is formed in a shape in which the opening area gradually increases as the distance from the thin film portion 3 increases. The through hole 2 a of the substrate 2 is formed by etching the substrate 2. In the case where a single crystal silicon substrate having one (100) surface is employed as the substrate 2, the through hole 2a of the substrate 2 is formed by, for example, anisotropic etching using an alkaline solution as an etching solution. be able to. The opening shape of the through hole 2a of the substrate 2 is not particularly limited. Therefore, the method for forming the through hole 2a of the substrate 2 is not limited to anisotropic etching using an alkaline solution as an etching solution, but employs dry etching using, for example, an inductively coupled plasma type dry etching apparatus. You can also. In addition, in the infrared emitting element 1, when the mask layer when forming the through hole 2 a is made of an inorganic material during manufacturing, the mask layer may remain on the other surface side of the substrate 2. As the mask layer, for example, a laminated film of a silicon oxide film and a silicon nitride film can be employed.

  In the thin film portion 3, the portion of the substrate 1 that covers the through hole 2a on the one surface side constitutes a diaphragm portion 3D, and the portion of the substrate 2 that is formed on the peripheral portion of the through hole 2a on the one surface side of the substrate 1, A support portion 3S that supports the diaphragm portion 3D is configured.

The thin film portion 3 includes a silicon oxide film 31 on the substrate 2 side and a silicon nitride film 32 laminated on the opposite side of the silicon oxide film 31 from the substrate 2 side. The thin film portion 3 is not limited to the laminated film of the silicon oxide film 31 and the silicon nitride film 32. For example, the thin film portion 3 may have a single layer structure of the silicon oxide film 31 or the silicon nitride film 32, or other than SiO ₂ and Si ₃ N ₄ A single layer structure made of an electrically insulating material or a laminated structure of two or more layers may be used.

  The thin film portion 3 also has a function as an etching stopper layer when the substrate 2 is etched from the other surface side of the substrate 2 to form the through hole 2a when the infrared radiation element 1 is manufactured.

  The 1st infrared radiation layer 4a, the 2nd infrared radiation layer 4b, and the 3rd infrared radiation layer 4c reduce the emissivity of infrared rays by impedance mismatch with the gas (for example, air, nitrogen gas, etc.) which the protective layer 5 contacts. The sheet resistance is set so as to suppress it.

  The first infrared radiation layer 4a has a lattice shape in plan view. The outer size of the first infrared radiation layer 4a is preferably set smaller than the planar size of the surface facing the through hole 2a in the thin film portion 3. That is, it is preferable to set the first infrared radiation layer 4a to be smaller than the planar size of the diaphragm portion 3D described above. Here, the planar size of the diaphragm portion 3D is not particularly limited, but is preferably set to 5 mm □ or less, for example.

  The outer size of the first infrared radiation layer 4a is preferably set so that the outer size of the region excluding the contact regions where the electrodes 7 overlap each other is 3 mm □ or less.

The material of the first infrared radiation layer 4a is tantalum nitride. That is, the first infrared radiation layer 4a is made of a tantalum nitride layer. The material of the first infrared radiation layer 4a is not limited to tantalum nitride, and for example, titanium nitride, nickel chromium, tungsten, titanium, thorium, platinum, zirconium, chromium, vanadium, rhodium, hafnium, ruthenium, boron, iridium, niobium, Molybdenum, tantalum, osmium, rhenium, nickel, holmium, cobalt, erbium, yttrium, iron, scandium, thulium, palladium, lutetium, or the like may be employed. Further, as the material of the first infrared radiation layer 4a, conductive polysilicon may be adopted. That is, the first infrared radiation layer 4a may be composed of a conductive polysilicon layer. For the first infrared radiation layer 4a, it is preferable to employ a tantalum nitride layer or a conductive polysilicon layer from the viewpoint of chemical stability at high temperatures and ease of design of sheet resistance. The tantalum nitride layer can change the sheet resistance by changing its composition. The conductive polysilicon layer can change the sheet resistance by changing the impurity concentration and the like. The conductive polysilicon layer can be composed of an n-type polysilicon layer or a p-type polysilicon layer doped with an n-type impurity or a p-type impurity at a high concentration. In the case where the conductive polysilicon layer is an n-type polysilicon layer and phosphorus is used as the n-type impurity, the impurity concentration is, for example, in the range of about 1 × 10 ¹⁸ cm ^{−3 to} 5 × 10 ²⁰ cm ^−3. What is necessary is just to set suitably. Further, when the conductive polysilicon layer is a p-type polysilicon layer and boron is used as the p-type impurity, the impurity concentration is in the range of about 1 × 10 ¹⁸ cm ⁻³ to 1 × 10 ²⁰ cm ^−3. What is necessary is just to set suitably.

  When the above-mentioned gas is air, tantalum nitride is employed as the material of the first infrared radiation layer 4a, and the first infrared radiation layer 4a is heated to a desired use temperature of, for example, 500 ° C. The sheet resistance at which the infrared emissivity from the first infrared emitting layer 4a is maximized is 189 Ω / □ (189 Ω / sq.), And the maximum emissivity is 50%. That is, if the sheet resistance of the first infrared radiation layer 4a is 189 Ω / □, the infrared radiation element 1 can maximize the infrared emissivity by impedance matching with air. Therefore, in order to suppress the decrease in emissivity and ensure emissivity of, for example, 40% or more, the sheet resistance of the first infrared radiation layer 4a may be set in the range of 73 to 493Ω / □. If the sheet resistance at which the emissivity is maximized at a desired use temperature is called a prescribed sheet resistance, the sheet resistance of the first infrared radiation layer 4a at the desired use temperature is a prescribed sheet resistance of ± 10%. It is more preferable to set the range.

  The infrared peak wavelength λ emitted from the first infrared radiation layer 4a in the infrared radiation element 1 depends on the temperature of the first infrared radiation layer 4a. Here, if the absolute temperature of the first infrared radiation layer 4a is T [K] and the peak wavelength is λ [μm], these satisfy the relationship of λ = 2898 / T. That is, the relationship between the absolute temperature T of the first infrared radiation layer 4a and the peak wavelength λ of the infrared radiation emitted from the first infrared radiation layer 4a satisfies the Vienna displacement law. Therefore, in the infrared radiation element 1, the first infrared radiation layer 4a constitutes a black body.

The infrared radiation element 1 can change Joule heat generated in the first infrared radiation layer 4a by adjusting input power applied between the pair of pads 9 and 9 from an external power source (not shown), for example. The temperature of the infrared radiation layer 4a can be changed. Therefore, the infrared radiation element 1 can change the temperature of the first infrared radiation element 4a in accordance with the input power to the first infrared radiation layer 4a. In addition, the infrared radiation element 1 can change the peak wavelength λ of infrared radiation emitted from the first infrared radiation layer 4a by changing the temperature of the first infrared radiation layer 4a. For this reason, the infrared radiation element 1 can be used as a high-power infrared light source in a wide infrared wavelength range. For example, when the infrared radiation element 1 is used as an infrared light source of a gas sensor, it is preferable that the peak wavelength λ of infrared radiation emitted from the first infrared radiation layer 4a is about 4 μm. The temperature may be about 800K. Here, in the infrared radiation element 1, the first infrared radiation layer 4a forms a black body as described above. Thus, the infrared radiation element 1, the total energy E is assumed to be approximately proportional to T ⁴ the unit area of the first infrared radiation layer 4a is radiated per unit time (i.e., Stefan - satisfy the Boltzmann's Law Guessed) The infrared radiation element 1 can increase the amount of infrared radiation as the temperature of the first infrared radiation layer 4a is increased.

  The first infrared radiation layer 4a is formed on the surface of the thin film portion 3 opposite to the substrate 2 side. The first infrared radiation layer 4a has a lattice shape in plan view as described above. In the first infrared radiation layer 4a, the size of each opening 4aa may be the same, but it is preferable that the size of the opening 4aa decreases as it approaches the center from the periphery as shown in FIG. That is, in the first infrared radiation layer 4a, it is preferable that the size of the opening 4aa close to the center is smaller than that of the opening 4aa in the periphery. Thereby, the infrared radiation element 1 can achieve a uniform temperature distribution of the first infrared radiation layer 4a, and can suppress the variation of the infrared wavelength depending on the position of the first infrared radiation layer 4a. Become.

  The second infrared radiation layer 4b is formed on the surface of the thin film portion 3 opposite to the substrate 2 side. Therefore, the second infrared radiation layer 4b and the first infrared radiation layer 4a are formed on the same plane.

  The planar shape of the second infrared radiation layer 4b is a rectangular shape (in the illustrated example, a square shape) that is slightly smaller than the opening 4aa of the lattice-shaped first infrared radiation layer 4a. In the infrared radiation element 1, it is preferable that the second infrared radiation layer 4b is disposed inside all the openings 4aa in the first infrared radiation layer 4a from the viewpoint of radiating infrared rays with higher efficiency.

  Although the material similar to the 1st infrared radiation layer 4a can be employ | adopted for the material of the 2nd infrared radiation layer 4b, it is preferable to employ | adopt the same material as the 1st infrared radiation layer 4a. The thickness of the second infrared radiation layer 4b is preferably the same as the thickness of the first infrared radiation layer 4a. The infrared radiation element 1 includes the first infrared radiation layer 4a and the second infrared radiation layer 4b formed of the same material and having the same thickness. The layer 4b can be formed at the same time, and the cost can be reduced.

  The second infrared radiation layer 4b preferably has a larger planar size as long as it does not contact the inner surface of the opening 4aa in the first infrared radiation layer 4a. Thereby, the temperature of the 2nd infrared radiation layer 4b becomes closer to the temperature of the 1st infrared radiation layer 4a, and it becomes possible to radiate infrared rays more efficiently.

  The third infrared radiation layer 4c is formed on the surface of the thin film portion 3 opposite to the substrate 2 side. Therefore, the 3rd infrared radiation layer 4c, the 2nd infrared radiation layer 4b, and the 1st infrared radiation layer 4a are formed on the same plane.

  Two third infrared radiation layers 4c are provided, and each planar shape is C-shaped. In the infrared radiation element 1, the two infrared radiation layers 4c are arranged so that the two third infrared radiation layers 4c surround the first infrared radiation layer 4a. Although the 3rd infrared radiation layer 4c is formed ranging over the diaphragm part 3D and the support part 3S of the thin film part 3, what is necessary is just to be formed at least on the diaphragm part 3D.

  Although the material similar to the 1st infrared radiation layer 4a can be employ | adopted for the material of the 3rd infrared radiation layer 4c, it is preferable to employ | adopt the same material as the 1st infrared radiation layer 4a. The thickness of the third infrared radiation layer 4c is preferably the same as the thickness of the first infrared radiation layer 4a.

  The infrared radiation element 1 includes the first infrared radiation layer 4a and the third infrared radiation layer 4c formed of the same material and having the same thickness. The layer 4c can be formed at the same time, and the cost can be reduced.

  The infrared radiation element 1 includes the first infrared radiation layer 4a, the second infrared radiation layer 4b, and the third infrared radiation layer 4c formed of the same material and having the same thickness. The layer 4a, the second infrared radiation layer 4b, and the third infrared radiation layer 4c can be formed at the same time, and the cost can be reduced.

  The protective layer 5 is composed of a silicon nitride film. The protective layer 5 is not limited to a silicon nitride film, and may be formed of, for example, a silicon oxide film, or may have a stacked structure of a silicon oxide film and a silicon nitride film. The protective layer 5 preferably has a high transmittance with respect to infrared rays of a desired wavelength or wavelength range emitted from the first infrared radiation layer 4a when the first infrared radiation layer 4a is energized, but the transmittance is 100%. Is not a requirement.

  The infrared radiation element 1 is a thin film in consideration of the stress balance of the sandwich structure composed of the thin film portion 3, the first infrared radiation layer 4a, the second infrared radiation layer 4b, the third infrared radiation layer 4c, and the protective layer 5. It is preferable to set the material and thickness of each of the portion 3 and the protective layer 5. Thereby, the infrared radiation element 1 can improve the stress balance of the above-described sandwich structure, and can further suppress the warpage and breakage of the sandwich structure, thereby further improving the mechanical strength. Can be achieved.

  The thicknesses of the first infrared radiation layer 4a, the second infrared radiation layer 4b, and the third infrared radiation layer 4c are reduced in the heat capacity of the first infrared radiation layer 4a, the second infrared radiation layer 4b, and the third infrared radiation layer 4c. From the viewpoint of achieving this, the thickness is preferably 0.2 μm or less.

  The total thickness of the thickness of the thin film portion 3, the thickness of the first infrared radiation layer 4a, and the thickness of the protective layer 5 reduces the heat capacity of the laminated structure of the thin film portion 3, the first infrared radiation layer 4a, and the protective layer 5. From the viewpoint of achieving this, for example, it is preferably set in the range of about 0.1 μm to 1 μm, and more preferably 0.7 μm or less. For example, the infrared radiation element 1 is configured such that the thickness of the silicon oxide film 31 of the thin film portion 3 is 160 nm, the thickness of the silicon nitride film 32 of the thin film portion 3 is 160 nm, and the thickness of the protective layer 5 is 100 nm. What is necessary is just to set the thickness of the infrared radiation layer 4a suitably. These numerical values are examples and are not particularly limited.

  The pair of electrodes 7 are formed on the one surface side of the substrate 2 so as to be in contact with the peripheral portion of the first infrared radiation layer 4a (the left and right end portions in FIG. 1A). Each electrode 7 is formed on the first infrared radiation layer 4a through a contact hole 5a formed in the protective layer 5, and is electrically connected to the first infrared radiation layer 4a. Here, each electrode 7 is in ohmic contact with the first infrared radiation layer 4a.

  As a material of each electrode 7, Al-Si which is a kind of aluminum alloy is adopted. The material of each electrode 7 is not particularly limited, and for example, Al—Cu, Al or the like may be adopted. Moreover, each electrode 7 should just be a material in which the part which contact | connects the 1st infrared radiation layer 4a at least can make ohmic contact with the 1st infrared radiation layer 4a, and not only a single layer structure but a multilayer structure may be sufficient as it. For example, each electrode 7 has a three-layer structure in which a first layer, a second layer, and a third layer are laminated in order from the first infrared radiation layer 4a side, and the first layer material in contact with the first infrared radiation layer 4a. May be a refractory metal (such as Cr), the second layer material may be Ni, and the third layer material may be Au. In the infrared radiating element 1, the temperature of the first infrared radiating layer 4 a is limited by the material of each pad 9 as long as at least a portion in contact with the first infrared radiating layer 4 a is formed of a refractory metal in each pad 9. It is possible to raise without any loss.

  Each wiring 8 and each pad 9 are preferably made of the same material as each electrode 7 and set to the same layer structure and the same thickness. Thereby, the infrared radiation element 1 can form each wiring 8 and each pad 9 simultaneously with each electrode 7. The thickness of the pad 9 is preferably set in the range of about 0.5 to 2 μm.

  The number of pads 9 is not limited to two and may be plural. For example, two pads 9 may be connected to each electrode 7. In short, the number of the pads 9 is not particularly limited in the infrared radiation element 1 as long as the first infrared radiation layer 4a can be energized to cause the first infrared radiation layer 4a to generate heat.

  Moreover, the infrared radiation element 1 should just be equipped with at least the 1st infrared radiation layer 4a and the 2nd infrared radiation layer 4b as an infrared radiation layer, and the structure which is not equipped with the 3rd infrared radiation layer 4c may be sufficient.

  Below, the manufacturing method of the infrared radiation element 1 is demonstrated based on FIG.

  In manufacturing the infrared radiation element 1, first, a substrate 2 made of a single crystal silicon substrate or the like whose one surface is a (100) plane is prepared (see FIG. 2A).

  After the substrate 2 is prepared, the first step of forming the thin film portion 3 on the one surface side of the substrate 2 is performed to obtain the structure shown in FIG. As a method for forming the silicon oxide film 31 in the thin film portion 3, for example, a thin film forming technique such as a thermal oxidation method or a CVD (Chemical Vapor Deposition) method can be adopted, and a thermal oxidation method is preferable. Moreover, as a method for forming the silicon nitride film of the thin film portion 3, a thin film forming technique such as a CVD method can be used, and a LPCVD (Low Pressure Chemical Vapor Deposition) method is preferable.

  After the first step, the second step of forming the first infrared radiation layer 4a, the second infrared radiation layer 4b, and the third infrared radiation layer 4c on the thin film portion 3 is performed, as shown in FIG. Get the structure. As a method for forming the first infrared radiation layer 4a, the second infrared radiation layer 4b, and the third infrared radiation layer 4c, for example, a thin film formation technique such as a sputtering method, a vapor deposition method, or a CVD method, and a photolithography technique and an etching technique are used. Can be used.

  After the second step, a third step for forming the protective layer 5 is performed, followed by a fourth step for forming the contact hole 5a, and then each electrode 7, each wiring 8, and each pad 9 are formed. By performing the fifth step, the structure shown in FIG. As a method for forming the protective layer 5 in the third step, for example, a thin film forming technique such as a CVD method and a processing technique using a photolithography technique and an etching technique can be used. As a CVD method for forming the protective layer 5, a plasma CVD method is preferable. In forming the contact hole 5a in the fourth step, a photolithography technique and an etching technique may be used. Etching in the fourth step may be wet etching or dry etching. In forming each electrode 7, each wiring 8, and each pad 9 in the fifth step, for example, a thin film forming technique such as a sputtering method, a vapor deposition method and a CVD method, and a processing technique using a photolithography technique and an etching technique are used. Can be used. Etching in the fifth step may be wet etching or dry etching.

  After the fifth step, the infrared radiation element 1 having the structure shown in FIG. 2E is obtained by performing the sixth step of forming the diaphragm portion 3D by forming the through hole 2a in the substrate 2. In forming the through hole 2a, for example, the substrate 2 is etched from the other surface side using a laminated film (not shown) of the silicon oxide film and the silicon nitride film on the other surface side of the substrate 2 as a mask layer. May be formed. In forming the mask layer, for example, first, a silicon oxide film serving as a base of the mask layer is formed on the other surface side of the substrate 2 simultaneously with the formation of the silicon oxide film 31 of the thin film portion 3, and the silicon of the thin film portion 3 is formed. A silicon nitride film is formed on the other surface side of the substrate 2 simultaneously with the formation of the nitride film 32. The patterning of the laminated film of the silicon oxide film and the silicon nitride film that is the basis of the mask layer may be performed using a photolithography technique and an etching technique. The etching of the substrate 2 employs anisotropic etching using an alkaline solution, but is not limited thereto, and can be formed by etching using, for example, an inductively coupled plasma type dry etching apparatus. Here, in the manufacturing method of the infrared radiation element 1 of the present embodiment, it is possible to increase the accuracy of the thickness of the thin film portion 3 by using the thin film portion 3 as an etching stopper layer when forming the through hole 2a. In addition, it is possible to prevent a part of the substrate 2 or residue from remaining on the through hole 2a side in the thin film portion 3. Moreover, in the manufacturing method of the infrared radiation element 1 of this embodiment, it becomes possible to increase the accuracy of the thickness of the thin film portion 3 by using the thin film portion 3 as an etching stopper layer when forming the through hole 2a. It is possible to suppress variations in mechanical strength of the thin film portion 3 and variations in heat capacity of the diaphragm portion 3D for each infrared radiation element 1.

  In the manufacture of the infrared radiation element 1 described above, the process until the formation of the through hole 2a is completed at the wafer level, and after forming the through hole 2a, the individual infrared radiation elements 1 may be separated. That is, in manufacturing the infrared radiation element 1, for example, a silicon wafer as a base of the substrate 2 is prepared, and a plurality of infrared detection elements 1 are formed on the silicon wafer according to the above-described manufacturing method. What is necessary is just to isolate | separate to the detection element 1. FIG.

  As can be seen from the method for manufacturing the infrared radiating element 1 described above, the infrared radiating element 1 can be manufactured using MEMS manufacturing technology.

  The infrared radiation element 1 of the present embodiment described above includes a substrate 2, a thin film portion 3 provided on one surface side of the substrate 2, a through hole 2 a penetrating in the thickness direction of the substrate 2, and the thin film portion 3. A grid-like first infrared radiation layer 4a provided on the side opposite to the substrate 2 side is provided. The infrared radiation element 1 is disposed away from the first infrared radiation layer 4a at the plurality of pads 9 electrically connected to the first infrared radiation layer 4a and the opening 4aa of the first infrared radiation layer 4a. And a second infrared radiation layer 4b having a higher infrared emissivity than the thin film portion 3. Thereby, the infrared radiation element 1 emits infrared rays from the first infrared radiation layer 4a and the second infrared radiation layer 4b by energizing the first infrared radiation layer 4a to generate heat. Here, in the infrared radiation element 1, since the first infrared radiation layer 4a is formed in a lattice shape, it becomes possible to reduce the heat capacity of the first infrared radiation layer 4a, the temperature is likely to rise, Since the second infrared radiation layer 4b is disposed in the opening 4aa of the first infrared radiation layer 4a, the temperature difference between the second infrared radiation layer 4b and the first infrared radiation layer 4b can be reduced. Therefore, the infrared radiation element 1 can emit infrared rays with higher efficiency. The infrared radiation element 1 reduces the heat capacity of the laminated structure on the one surface side of the substrate 2, thereby responding to the temperature change of the first infrared radiation layer 4 a with respect to the voltage waveform applied between the pair of pads 9, 9. It becomes possible to increase the speed, and the temperature of the first infrared radiation layer 4a is likely to rise, and it becomes possible to increase the output and the response speed.

  In addition, the infrared radiation element 1 includes a third infrared radiation layer 4 c that is disposed outside the first infrared radiation layer 4 a and is separated from the first infrared radiation layer 4 a and has a higher infrared emissivity than the thin film portion 3. Thereby, the infrared radiation element 1 can emit infrared rays with higher efficiency.

  In addition, the infrared radiation element 1 suppresses a decrease in infrared emissivity due to impedance mismatch with the gas in contact with the protective layer 5 with respect to the first infrared radiation layer 4a, the second infrared radiation layer 4b, and the third infrared radiation layer 4c. The sheet resistance is set so as to. Therefore, the infrared radiation element 1 can suppress a decrease in the emissivity of the first infrared radiation layer 4a, the second infrared radiation layer 4b, and the third infrared radiation layer 4c. Therefore, the infrared radiation element 1 of the present embodiment can reduce power consumption.

  In the infrared radiation element 1, the substrate 2 is formed from a single crystal silicon substrate, and the thin film portion 3 is composed of a silicon oxide film 31 and a silicon nitride film 32. As a result, the infrared radiation element 1 has a larger heat capacity and thermal conductivity of the substrate 2 than the thin film portion 3, and the substrate 2 has a function as a heat sink. It is possible to improve the stability of infrared radiation characteristics.

  In the infrared radiation element 1, the first infrared radiation layer 4a, the second infrared radiation layer 4b, the third infrared radiation layer 4c, the electrode 7, the wiring 8 and the pad 9 are arranged in a direction in which the pair of electrodes 7 and 7 are arranged in plan view. It is preferable that the orthogonal infrared radiation elements 1 are arranged in line symmetry with the center line as the axis of symmetry. Thereby, the infrared radiation element 1 can further improve the mechanical strength, and can suppress in-plane variation of the temperature of the first infrared radiation layer 4a.

  The infrared radiation element 1 is not limited to an infrared light source (infrared light source) for a gas sensor, but is used for an infrared light source for flame detection, an infrared light source for infrared light communication, an infrared light source for spectroscopic analysis, and the like. Is possible.

DESCRIPTION OF SYMBOLS 1 Infrared radiation element 2 Board | substrate 2a Through-hole 3 Thin film part 4a 1st infrared radiation layer 4aa Opening part 4b 2nd infrared radiation layer 4c 3rd infrared radiation layer 9 Pad

Claims (4)

  A substrate, a thin film portion provided on one surface side of the substrate, a through-hole penetrating in the thickness direction of the substrate, and a lattice-shaped first infrared ray provided on the opposite side of the thin film portion from the substrate side A radiation layer; a plurality of pads electrically connected to the first infrared radiation layer; and an opening of the first infrared radiation layer that is spaced apart from the first infrared radiation layer and is more infrared than the thin film portion. An infrared radiation element comprising: a second infrared radiation layer having a high emissivity.   The infrared radiation element according to claim 1, wherein the first infrared radiation layer and the second infrared radiation layer are formed of the same material and have the same thickness.   3. The infrared radiation element according to claim 1, wherein the first infrared radiation layer has a size of the opening that decreases from the periphery toward the center. 4.   4. The apparatus according to claim 1, further comprising a third infrared radiation layer that is disposed outside the first infrared radiation layer and spaced apart from the first infrared radiation layer and has a higher infrared emissivity than the thin film portion. The infrared radiation element according to item 1.

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