JP2010019555A - Gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas sensor maintaining performance stably for a long period, and having a stable characteristic, a high manufacturing yield, and high response speed. <P>SOLUTION: This gas sensor is equipped with a p-type domain 6 provided from the surface to the inside of an n-type SiC substrate 1, a catalyst 3 arranged on the surface of the p-type domain, a p-side electrode 11 positioned on the catalyst 3, a source electrode 21 and a drain electrode 22, an n-type channel for connecting a source to a drain in contact with the p-type domain in the substrate, and an n-side electrode 12 positioned on the rear surface of an n-type domain of a semiconductor substrate. In the gas sensor, a voltage is applied between the n-side electrode and the p-side electrode with the catalyst 3 interposed therebetween, and a reverse bias voltage is applied to a p-n junction 15. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a gas sensor, and more specifically to a gas sensor with excellent durability that is attached to an exhaust path of an automobile or the like.

  In the automobile field, a highly reliable and highly sensitive gas sensor is required to improve the accuracy of engine control for exhaust gas regulation and fuel efficiency improvement and to grasp the gas components inside and outside the vehicle interior. Oxygen sensors using stabilized zirconia, which is used as an air-fuel ratio sensor for automobiles, and electric resistance gas sensors using metal oxide semiconductors, which are widely used, are excellent in reliability, but have low sensitivity and response speed It has a problem. On the other hand, as a gas sensor having both sensitivity and response speed, a MOSFET sensor in which a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is combined with an oxide semiconductor or the like is known (Non-Patent Document 1). As this MOSFET type sensor, a sensor combining an ion conductive oxyacid salt and a MOSFET has also been proposed (Patent Document 1).

M.Ali, et.al., "SiC-based FET for detection of NOxand O2 using InSnOx as a gate material", Sensors and Actuators B 122 (2007) 182-186 Japanese Patent Laid-Open No. 2001-281213

  In the above-described MOSFET type gas sensor, since the channel for controlling the electron flow is located on the surface of the semiconductor substrate, it is easily exposed to a high-temperature ambient gas. Therefore, there is a problem in ensuring long-term reliability. In addition, the semiconductor surface such as SiC tends to vary in the interface order density, and the sensor characteristics become unstable, resulting in a decrease in manufacturing yield. Further, since the channel is located on the semiconductor surface, it has a disadvantage that the response speed becomes slow due to the influence of the interface state. Therefore, an object of the present invention is to provide a gas sensor that maintains its performance stably for a long period of time, stabilizes its characteristics, suppresses a decrease in manufacturing yield, and has a high response speed.

  The gas sensor of the present invention is electrically connected to the first conductive type semiconductor substrate, the second conductive type region provided from the surface of the first conductive type semiconductor substrate to the inside, and the surface of the second conductive type region. A gas sensitive layer, a second conductive side electrode located on and electrically connected to the gas sensitive layer, and a source electrode and a drain electrode provided on the surface so as to sandwich the second conductive type region, Electrically connecting the first conductivity type passage in contact with the second conductive side region in the semiconductor substrate and connecting the source electrode and the drain electrode, and the front or back surface in communication with the first conductivity type passage. And a connected first conductive side electrode. Then, a voltage is applied between the first conductive side electrode and the second conductive side electrode through the gas sensitive layer, and a reverse bias voltage is applied to the pn junction between the second conductive side region and the first conductive type passage. Is applied.

  In the above structure, the first conductivity type passage (channel) is located inside the semiconductor substrate ahead of the second conductivity type region, and a pn junction is formed at the interface between the second conductivity type region and the channel. A voltage is applied between the first conductive side electrode and the second conductive side electrode, and a reverse bias voltage is always applied to the pn junction. When gas adsorption occurs in the gas sensitive layer, the electric resistance fluctuates, so that the reverse bias voltage to the pn junction that is constantly applied fluctuates, and the overhang of the depletion layer changes to change the channel cross section. For this reason, the change in gas adsorption amount changes the ease with which carriers pass through the channel, and appears as a change in the current value between the source and drain electrodes. Thereby, the gas adsorption amount can be detected with high response speed and high sensitivity. Further, since the channel is located inside the semiconductor substrate, it is not exposed to gas and long-term reliability is not deteriorated. Since the channel is not affected by the interface state, the characteristics are stable and the manufacturing yield does not decrease. In the case of the above structure, the carrier flows in the direction along the plate surface of the channel on the semiconductor substrate.

  According to another gas sensor of the present invention, a first conductivity type semiconductor substrate, a source electrode located on the front surface of the semiconductor substrate, a drain electrode located on the back surface, and a first electrode that communicates the source electrode and the drain electrode. A conductive type passage is provided so as to surround the second conductive type region exposed on the front surface or the back surface, a gas sensitive layer electrically connected to the exposed second conductive type region, and a gas sensitive layer on the gas sensitive layer A second conductive side electrode positioned and electrically connected; and a first conductive side electrode electrically connected to a front surface or a back surface communicating with the first conductive type passage. Then, a reverse bias voltage is applied to the pn junction around the passage in the first conductive side region by applying a voltage between the first conductive side electrode and the second conductive side electrode through the gas sensitive layer. It is characterized by.

  According to the above structure, the channel (passage) is formed along the direction penetrating the semiconductor substrate. The depletion layer protruding from the pn junction surrounding the channel changes in size depending on the amount of gas adsorbed in the gas sensitive layer, and appears as a change in the current flowing between the source / drain electrodes. For this reason, even in this structure, the response speed is high and the sensitivity is sufficiently high. Further, since the channel is provided inside the semiconductor substrate so as to penetrate the semiconductor substrate, it is not exposed to gas and long-term reliability can be ensured. Further, since the channel is not affected by the interface state, the characteristics are stable and the manufacturing yield does not decrease. In this case, the carrier flows through the channel in the direction perpendicular to the plate surface of the semiconductor substrate.

  The gas sensitive layer can be either an oxide semiconductor, an ion conductive oxyacid salt, or a combination of a solid electrolyte and an ion conductive oxyacid salt. As a result, a gas sensor with high sensitivity and high response speed can be provided.

  A sensitizer can be included in the sensitive layer to increase sensitivity. As a result, the gas selectivity can be improved and the concentration can be accurately detected even if the gas has a very low concentration. The sensitizer is determined according to the type of the detection gas and the sensitive layer, and will be described in detail later.

  The gas sensitive layer can be porous. Thereby, the gas-sensitive layer located under the second conductive side electrode can have a gas adsorption portion having a sufficient surface area.

  In the gas sensor of the present invention, since the channel is not exposed to the gas, the performance is stably maintained for a long period of time, and the performance is not affected by the interface order, so that the characteristics are stable and the production yield is not lowered, and the response speed is high.

(Embodiment 1)
FIG. 1 is a diagram showing a gas sensor 10 according to Embodiment 1 of the present invention. In this gas sensor 10, a catalyst layer 3 whose electric resistance changes when gas molecules are adsorbed is provided on the surface side of an n-type SiC substrate 1, and a p-type region 6 is formed thereunder. In this embodiment, the oxide semiconductor catalyst 3 is used for the gas sensitive layer. A pn junction 15 is formed between the tip in the depth direction of the p-type region 6 and the n-type SiC substrate. Under this (inside the SiC substrate), an n-type channel 5 is formed. A p-type region 6 is also provided on the back side of the channel 5 so as to sandwich the n-type channel 5 from above and below. The following portions are formed from the back surface to the front surface of SiC substrate 1 in the region of n-type channel 5.
(Back surface p-side electrode 11b / p-type region 6 / n-type channel 5 / p-type region 6 / catalyst layer 3 / front surface p-side electrode 11a)
Both the front surface p-side electrode 11a and the rear surface p-side electrode 11b are connected to the negative electrode of the constant voltage power source 9 and have the same potential. The positive electrode of the constant voltage power source is connected to the n-type region of the n-type SiC substrate. Therefore, a reverse bias voltage is applied to the pn junction 15 formed between the two p-type regions 6 and the n-type region. In the above n-type SiC substrate, the n-type carrier concentration in the n-type region is such that the depletion layer overhang due to application of the reverse bias voltage is increased toward the channel 5 side. It is desirable to be smaller. Therefore, the n-type SiC substrate is preferably the n ^- SiC substrate 1. Further, although depending on the temperature range to be used, in the following description, the case where the semiconductor substrate is a SiC substrate will be described, but other semiconductor substrates such as a silicon substrate may be used.

A source electrode 21 and a drain electrode 22 are provided on the surface side of SiC substrate 1 so as to sandwich p-type region 6. From the drain electrode 22 at the potential V _D , the current _ID flows constantly to the source electrode 21 through the n-type channel 5. The carrier of the current _ID is an electron, and the electron flows from the source electrode 21 side of the ground potential through the n-type channel 5 to the drain electrode 22 side of the potential V _D , so that the current _ID flows from the drain to the source. Will flow.

The catalyst layer 3 on the surface side is formed of WO ₃ or the like of an oxide semiconductor, and the electric resistance changes when the gas to be detected is adsorbed. As the catalyst layer 3, a gas having high gas selectivity is used in accordance with the detection target gas. In order to increase the gas selectivity of the catalyst 3, it is usually performed to add a sensitizer corresponding to the catalyst 3 and the detection target gas. Table 1 shows the gas to be detected and a catalyst (sensitive agent) 3 having selectivity for the gas. Moreover, about the catalyst 3 in which addition of a sensitizer is normally performed, a sensitizer is also shown. In the embodiment of the present invention, at least the detection target gas, the catalyst 3, and the sensitizer shown in Table 1 are used. Other catalysts 3 and sensitizers may be used with other gases as detection targets.

When gas molecules are adsorbed on the catalyst layer 3 and the electric resistance changes, the voltage applied to the pn junction on the surface side of the n-type channel 5 changes. FIG. 2 is an enlarged view of the channel 5 portion. As described above, since the reverse bias voltage is applied to the pn junction 15 on the front surface side and the back surface side of the channel 5, the depletion layers K _a and K _b project to the n-type region. For this reason, the flow of electrons is limited to the n-type region between them by the depletion layers K _a and K _b . Among these, the depletion layer _Kb formed on the back surface side is directly connected to the negative electrode of the constant voltage power source without interposing the catalyst layer, and maintains a constant size regardless of the presence or absence of gas adsorption. To do. In contrast, the depletion layer K _a of the surface side, depending on the amount of gas adsorption, the reverse bias voltage applied to the pn junction 15 is changed in accordance with the gas adsorption amount, its size is changed . For this reason, the cross-sectional area of the n-type channel 5 changes according to the gas adsorption amount, and the ease of passing electrons changes, and as a result, the current _ID changes. The gas adsorption amount can be known from the change in the current _ID . The gas adsorption amount of the detection target is proportional to the gas concentration of the detection target in the atmosphere when the gas concentration in the atmosphere is low. Therefore, as shown in FIG. 3, the gas concentration of the detection target can be known from the change of the current _ID .

  The catalyst layer 3 may be formed on the p-type region 6 by pressure-bonding the powder paste, or may be screen-printed with the powder paste. Alternatively, vapor deposition may be performed by a sputtering method or a vapor phase method such as a CVD (Chemical Vapor Deposition) method. Moreover, it can also vapor-deposit by the vacuum evaporation method suitable for mass production. The manufacture of the p-type region 6, the n-side electrode 12, and the p-side electrode 11 can be easily performed using a normal semiconductor processing apparatus and processing method.

  As shown in FIG. 1, channel 5 is not exposed on the front and back surfaces of SiC substrate 1, and is located closer to the thickness center side of SiC substrate 1 than p-type region 6. For this reason, reliability can be maintained in the long term. In addition, since it is not affected by variations in the interface state density on the surface, the sensor characteristics are stable, and a reduction in manufacturing yield can be prevented. Moreover, since it is not influenced by the interface state of the surface, a high response speed can be obtained.

(Modification of the first embodiment of the present invention)
FIG. 4 is a diagram showing a modification of the gas sensor 10 according to Embodiment 1 of the present invention. The p-side electrode 11b on the back surface side is connected to the p-type region 6 with the catalyst layer 3 interposed, similarly to the front surface side. This point is different from the gas sensor 10 shown in FIG. Also on the back surface side, since the p-side electrode 11b is connected to the p-type region 6 with the catalyst layer 3 interposed, the size of the depletion layer Kb formed in the pn junction 15 located on the back surface side of the channel 5 is It changes depending on the amount of gas adsorption in the catalyst layer 3 on the back side.

In Figure 2, the depletion layer K _b is fixed, the cross-sectional area of the channel 5 was dependent only on the depletion layer K _a surface side. However, since the depletion layers K _a and K _b are both affected by the amount of gas adsorption and change in size due to the above deformation, it is possible to double the variation in the cross-sectional area of the channel 5 due to gas adsorption. Therefore, the sensitivity can be doubled. Further, the advantages of the above-described first embodiment can be directly enjoyed in this modified example. That is, channel 5 is not exposed on the front and back surfaces of SiC substrate 1 and is located near the thickness center of the SiC substrate. For this reason, reliability can be maintained in the long term. In addition, since it is not affected by variations in the interface state density on the surface, the sensor characteristics are stable, and a reduction in manufacturing yield can be prevented. Moreover, since it is not influenced by the interface state of the surface, a high response speed can be obtained.

(Embodiment 2)
FIG. 5 is a diagram showing the gas sensor 10 according to Embodiment 2 of the present invention. This gas sensor 10 is different from the first embodiment in that an ion conductive oxyacid salt 33 is used for the sensitive layer. The ion conductive oxyacid salt 33 generates an electrochemical dissociation equilibrium of the oxyacid salt in accordance with a change in the partial pressure of the gas to be detected, thereby causing an electromotive force change. For this reason, when the negative electrode of the constant voltage power source is connected to the p-type region 6 on the surface side with the ion conductive oxyacid salt 33 interposed, the reverse bias voltage applied to the pn junction 15 changes. Therefore, as described above, after changing the cross-sectional area of the channel 5 the size of the depletion layer K _a is changed, resulting in a change in the drain current I _D. As a result, the concentration of the target gas can be detected by the change in the drain current _ID . In the first embodiment, a change in electrical resistance is caused by the adsorption of the target gas, thereby causing a change in channel cross-sectional area. On the other hand, in the present embodiment, an electrochemical dissociation equilibrium of the ion conductive oxyacid salt 33 occurs according to the change in the gas partial pressure, and an electromotive force is generated in the ion conductive oxyacid salt 33. The reverse bias voltage applied to the pn junction 15 changes. This utilizes the change in the cross-sectional area of the channel 5 due to the change in the extent of the depletion layer overhang. Therefore, since the part other than the sensitive layer being the ion conductive oxyacid salt 33 is the same as that of the first embodiment, the description is concentrated on the ion conductive oxyacid salt and the other parts are omitted.

1. Gas to be detected The gas to be detected is mainly carbon dioxide (CO ₂ ), nitric oxide (NO), nitrogen dioxide (NO ₂ ), etc., but other gases can be used without problems. . For example, sulfur monoxide (SO), sulfur dioxide (SO ₂ ), and the like are possible.
2. Ion conductive oxyacid salt The ion conductive oxyacid salt is, of course, a specific compound depending on the gas to be detected.

(1) In the case of nitric oxide (NO) and nitrogen dioxide (NO ₂ ) Metal nitrite and / or metal nitrate may be used as the ion conductive oxyacid salt. And it is preferable to include platinum (Pt) particles as a sensitizer in order to increase sensitivity.
Examples of the metal nitrite include lithium nitrite (LiNO ₂ ), sodium nitrite (NaNO ₂ ), potassium nitrite (KNO ₂ ), rubidium nitrite (RbNO ₂ ), cesium nitrite (CsNO ₂ ), and barium nitrite. (Ba (NO ₂ ) ₂ ), strontium nitrite (Sr (NO ₂ ) ₂ ), and the like. It is good to comprise from 1 type, or 2 or more types of these.
Examples of the metal nitrate include lithium nitrate (LiNO ₃ ), sodium nitrate (NaNO ₃ ), potassium nitrate (KNO ₃ ), rubidium nitrate (RbNO ₂ ), magnesium nitrate (Mg (NO ₃ ) ₂ ), calcium nitrate ( Ca (NO ₃ ) ₂ ), strontium nitrate (Sr (NO ₃ ) ₂ ), barium nitrate (Ba (NO ₃ ) ₂ ), scandium nitrate (Sc (NO ₃ ) ₃ ), cerium nitrate (Ce (NO ₃ ) ₃ ), Zirconium nitrate (Zr (NO ₃ ) ₄ ), iron nitrate (Fe (NO ₃ ) ₂ , Fe (NO ₃ ) ₃ ), copper nitrate (Cu (NO ₃ ) ₂ ), cobalt nitrate (Co (NO ₃ )) ₂ ), tin nitrate (Sn (NO ₃ ) ₄ ), indium nitrate (In (NO ₃ ) ₃ ), nickel nitrate (Ni (NO ₃ ) ₂ ), lead nitrate ( Pb (NO ₃ ) ₂ ), bismuth nitrate (Bi (NO ₃ ) ₃ ), and rare earth nitrates may be used alone or in combination.

(2) Carbon dioxide (CO ₂ )
As the ion conductive oxyacid salt, a metal carbonate and / or a metal hydrogen carbonate is used.
Examples of the metal carbonate include lithium carbonate (Li ₂ CO ₃ ), sodium carbonate (Na ₂ CO ₃ ), potassium carbonate (K ₂ CO ₃ ), rubidium carbonate (Rb ₂ CO ₃ ), and cesium carbonate (Cs ₂ CO). ₃ ), magnesium carbonate (Mg (CO ₃ ) ₂ ), calcium carbonate (CaCO ₃ ), strontium carbonate (SrCO ₃ ), barium carbonate (BaCO ₃ ), iron carbonate (FeCO ₃ ), copper carbonate (Cu ₂ CO ₃ ) , nickel carbonate (NiCO _3), lead carbonate (PbCO _3), manganese carbonate (MnCO _3), cadmium carbonate (CdCO _3), silver carbonate _(Ag 2 _CO 3), of cobalt carbonate (CoCO ₃₎ and rare earth nitrates, one Or it is good to comprise from 2 or more types.
As the metal carbon hydrogen salt may, for example, sodium bicarbonate (NaHCO _3), potassium bicarbonate (KHCO _3), bicarbonate rubidium (RbHCO _3), to consist of one or two or more of cesium hydrogencarbonate (CsHCO ₃₎ Is good.

3. Arrangement of ion conductive oxyacid salt The ion conductive oxyacid salt 33 can be arranged by pressure bonding a powder paste. Further, the powder paste may be arranged by screen printing. Furthermore, you may join a powder paste by heat-melting crimping | compression-bonding. Further, the thin film may be formed by a sputtering method or a CVD method. You may vapor-deposit by a vacuum evaporation method.

  The ion conductive oxyacid salt 33 can improve the gas selectivity of the detection target. Further, it is the same as in the first embodiment in that the channel 5 is formed near the thickness center of the semiconductor substrate. For this reason, reliability can be maintained in the long term. In addition, since it is not affected by variations in the interface state density on the surface, the sensor characteristics are stable, and a reduction in manufacturing yield can be prevented. Moreover, since it is not influenced by the interface state of the surface, a high response speed can be obtained.

(Modification of Embodiment 2 of the present invention)
FIG. 6 is an enlarged view of a portion of the sensitive layer of the gas sensor 10 in a modification of the second embodiment of the present invention. Other portions are the same as those of the gas sensor 10 shown in FIG. The gas sensor 10 of the modification shown in FIG. 6 is different from the contents of the sensitive layer of the gas sensor shown in FIG. 5 in that (ion conductive oxyacid salt 33 / solid electrolyte 34) is used for the sensitive layer. That is, the solid electrolyte 34 is disposed in contact with the p-type region 6 on the surface side of the channel 5, and the ion conductive oxyacid salt 33 is disposed thereon.

  The advantage of combining the solid electrolyte 34 and the ion conductive oxyacid salt 33 is that a lower concentration target gas can be detected. The reason is considered to be that an ion bridge is formed between the ion conductive oxyacid salt 33 and the solid electrolyte 34 by the solid electrolyte 34 and a large chemical potential is formed. The structure in which the channel 5 is formed near the thickness center of the semiconductor substrate 1 is unchanged. For this reason, reliability can be maintained in the long term. In addition, since it is not affected by variations in the interface state density on the surface, the sensor characteristics are stable, and a reduction in manufacturing yield can be prevented. Moreover, since it is not influenced by the interface state of the surface, a high response speed can be obtained.

(Embodiment 3)
FIG. 7 is a diagram showing the gas sensor 10 according to Embodiment 3 of the present invention. In the present embodiment, the sensitive layer is not particularly new compared to the above-described one. In the case of the gas sensor 10 shown in FIG. 7, the catalyst 3 is used. Instead of the catalyst 3, an ion conductive oxyacid salt 33 or (ion conductive oxyacid salt 33 / solid electrolyte 34) may be used. A feature of the present embodiment is that the current ID flows along the thickness direction of the semiconductor substrate 1. In the gas sensor 10 shown in FIG. 7, the channel 5 is provided so as to penetrate the semiconductor substrate 1. In order to change the cross-sectional area of the channel 5, a reverse bias voltage is applied to the pn junction 15.

  P-side electrodes 11 a and 11 b are connected to the p-type region 6 positioned so as to surround the n-type channel 5 with the catalyst layer 3 interposed therebetween. In FIG. 7, two p-type regions 6 facing each other are provided for a semiconductor substrate having a rectangular planar shape, and one p-side electrode is provided in each of the two p-type regions. The remaining n-type region including the channel 5 is connected to the n-side electrode 12a on the front surface and the n-side electrode 12b on the back surface. Therefore, a voltage (reverse bias voltage with respect to the pn junction 15) is applied from the constant voltage power supply 9 with the catalyst 3 interposed between the n-side electrodes 12a and 12b and the p-side electrodes 11a and 11b.

The source electrode 21 is connected to the n-type region on the front surface side, and the drain electrode 22 is connected to the n-type region on the back surface side, and is connected by the channel 5. The channel 5, current flows through _{I D} by the drain voltage _{V D.} However, as shown in FIG. 8, when the gas is adsorbed on the catalyst 3, the current _ID changes due to the change in the size of the depletion layers K _a and K _b as described above. Thereby, the concentration of the gas in the atmosphere can be detected by the change of the current _ID .

  The gas sensor 10 shown in FIG. 7 can be easily manufactured using a normal semiconductor processing apparatus and processing method. In addition, two n-side electrodes 12a and 12b are provided in total, one on each of the front and back surfaces, but only one in total may be provided on the front or back surface. Further, the p-side electrodes 11a and 11b may be one in total. This is because the depletion layer can change the cross-sectional area of the channel 5 even if only one side is generated, and the amount of gas adsorption can be detected.

Since the channel 5 is formed so as to penetrate in the thickness direction of the semiconductor substrate 1, the structure in which the main part of the channel is formed near the center of the semiconductor substrate is unchanged. For this reason, reliability can be maintained in the long term. In addition, since it is not affected by variations in the interface state density on the surface, the sensor characteristics are stable, and a reduction in manufacturing yield can be prevented. Moreover, since it is not influenced by the interface state of the surface, a high response speed can be obtained. Furthermore, since the thickness of the semiconductor substrate 1 is about 4 μm, the response speed of gas detection can be made larger than when the current _ID flows along the plate surface of the semiconductor substrate.

  Although the embodiments of the present invention have been described above, the embodiments of the present invention disclosed above are merely examples, and the scope of the present invention is not limited to these embodiments. The scope of the present invention is indicated by the description of the scope of claims, and further includes meanings equivalent to the description of the scope of claims and all modifications within the scope.

  According to the present invention, it is possible to obtain a gas sensor whose performance is stably maintained for a long period of time, whose characteristics are stable, and whose response speed is large, and by using a semiconductor such as SiC having high heat resistance, exhaust gas regulation is achieved. It is expected to contribute to improved fuel economy.

It is a figure for demonstrating the gas sensor in Embodiment 1 of this invention. It is a figure which shows the depletion layer in the channel of the gas sensor shown in FIG. It is a figure which shows the change of electric current ID according to a gas concentration change. It is a figure which shows the gas sensor of the modification in Embodiment 1 of this invention. It is a figure which shows the gas sensor in Embodiment 2 of this invention. It is the elements on larger scale of the gas sensor of the modification in Embodiment 2 of this invention. It is a figure which shows the gas sensor in Embodiment 3 of this invention. It is an enlarged view of the channel of the gas sensor of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate (SiC substrate), 3 Gas sensitive layer (Catalyst (oxide semiconductor)), 5 n-type channel, 6 p-type area | region, 9 Constant voltage power supply (battery), 10 Gas sensor, 11a, 11b p side electrode, 12 , 12a, 12b n-side electrode, 15 pn junction, 21 source electrode, 22 drain electrode, 31 ammeter, 33 gas sensitive layer (ion conductive oxyacid salt), 34 solid electrolyte, D drain electrode, _ID drain current, K _a , K _b depletion layer, S source electrode, V _D drain voltage.

Claims (5)

A first conductivity type semiconductor substrate;
A second conductivity type region provided from the surface to the inside of the first conductivity type semiconductor substrate;
A gas sensitive layer electrically connected to the surface of the second conductivity type region;
A second conductive side electrode located on and electrically connected to the gas sensitive layer;
A source electrode and a drain electrode provided on the surface so as to sandwich the second conductivity type region;
A first conductivity type path in contact with the second conductive side region in the semiconductor substrate and connecting the source electrode and the drain electrode;
A first conductive side electrode electrically connected to a front surface or a back surface communicating with the first conductivity type passage;
A voltage is applied between the first conductive side electrode and the second conductive side electrode through the gas sensitive layer, and a reverse bias is applied to the pn junction between the second conductive side region and the first conductive type passage. A gas sensor, wherein a voltage is applied. A first conductivity type semiconductor substrate;
A source electrode located on the front surface and a drain electrode located on the back surface of the semiconductor substrate;
A second conductivity type region which is provided so as to surround the first conductivity type passage connecting the source electrode and the drain electrode, and is exposed on the front surface or the back surface;
A gas sensitive layer electrically connected to the exposed second conductivity type region;
A second conductive side electrode located on and electrically connected to the gas sensitive layer;
A first conductive side electrode electrically connected to a front surface or a back surface communicating with the first conductivity type passage;
A voltage is applied between the first conductive side electrode and the second conductive side electrode with the gas sensitive layer interposed, and a reverse bias voltage is applied to the pn junction around the passage of the first conductive side region. A gas sensor.   3. The gas sensitive layer according to claim 1, wherein the gas sensitive layer is any one of an oxide semiconductor, an ion conductive oxyacid salt, or a combination of a solid electrolyte and an ion conductive oxyacid salt. The gas sensor described.   The gas sensor according to any one of claims 1 to 3, wherein the sensitive layer includes a sensitizer in order to increase sensitivity. The gas sensor according to claim 1, wherein the sensitive layer is porous.

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