JP2001281213A - Gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an NO2 gas sensor, NO gas sensor, and CO2 gas sensor which are compact, capable of obtaining sufficient sensitivity and responsivity, high in selectivity, and superior in stability. SOLUTION: The gas sensors are each formed by forming FET using a semiconductor substrate, a gate-control-type p-n junction diode, or the gate area of a Schottky diode or a conductive oxyacid salt and collector or a solid electrolyte, conductive oxyacid salt, and collector on a rectification barrier electrode. The gas sensors each contain platinum particles in the surfaces of metal nitrite and metal nitrate. The gas sensors are each used for measuring the concentration of NO2 gas, concentration of NO gas, and concentration of CO2 gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device for measuring a concentration of nitrogen oxide gas or a concentration of carbon dioxide gas in an atmosphere, which is incorporated in an environmental measuring equipment, an air ventilation equipment, an air cleaning equipment or the like. Gas sensor element.

[0002]

2. Description of the Related Art In recent years, there has been an increasing interest in environmental problems such as the air environment and living environment, and sensors for measuring the concentration of nitrogen dioxide, nitric oxide gas or carbon dioxide gas released into the atmosphere have been developed. Attention has been paid. As these sensors, those using a system such as a chemiluminescence system, an infrared absorption system, and an ultraviolet absorption system are known. However, these sensors have not come into widespread use because of their large size and high cost. Although a constant potential electrolytic method and a semiconductor method using a change in electric resistance of a metal oxide have been proposed, it is difficult to measure the concentration of only nitrogen dioxide, nitric oxide gas or carbon dioxide gas.

[0003] Some sensors using a solid electrolyte have been proposed as small and inexpensive sensors. However, a gas sensor using a solid electrolyte requires a detection electrode and a counter electrode or a reference electrode in order to use an electromotive force or a current as a detection signal, and the counter electrode or the reference electrode often uses water vapor in the air atmosphere or a gas not intended for detection. It is known to change chemically. Attempts have also been made to contact the counter electrode or reference electrode side with a certain reference gas in order to eliminate such effects, but there is a problem in miniaturizing the sensor element.

On the other hand, as a sensor that does not use a counter electrode or a reference electrode, a sensor element in which a noble metal or metal oxide is bonded as a gas detection material to a gate region of a field effect transistor (FET) or a Schottky diode has been proposed. ing. Specifically, for example, Lundstrom et al. (Appl. Phy
s. Lett., 26 (1975) p55, Surface Science, 64 (1977) p
498) and Dobos et al. (Anal. Chem. Sym., 17 (1983) p464)
Uses palladium which is a noble metal as a gate electrode,
We have proposed FET sensors that detect hydrogen gas and carbon monoxide gas. Fukuda et al. Have proposed an FET sensor that detects carbon monoxide gas using tin oxide, which is a metal oxide, as a gate electrode (Digest of Techni).
cal Paper of Transducers '99, vol.1 (1999) p656).
Furthermore, Nakagomi et al. (Digest of Technical Paper of Tr
ansducers '99, vol.1 (1999) p942) and Spetz et al. (Digest
of Technical Paper of Transducers '99, vol.1 (199
9) p946) uses a silicon carbide semiconductor substrate that operates at a relatively high temperature to perform selective gas detection, and joins platinum, which is a noble metal, to the gate electrode, and detects a Schottky diode that detects carbon monoxide. A gas sensor is proposed.

[0005] However, in a gas sensor of an FET or a Schottky diode using a noble metal or metal oxide for the detection electrode, gas adsorption and reaction occur on the surface of the noble metal or metal oxide, and if the gas is easily adsorbed, it is not known. It has the characteristic of also detecting gas. That is, since a noble metal or metal oxide is used for the gate electrode, there is a limit on the detection target gas. Therefore, there has not been reported a gas sensor that selectively detects nitrogen dioxide gas, nitric oxide gas, and carbon dioxide gas using an FET or a Schottky diode.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention, small and sufficient sensitivity and responsiveness is obtained a high selectivity, the oxygen-containing gas ₂ such as excellent NO _X and CO to the stability sensor It is to provide.

[0007]

The present inventors have SUMMARY OF THE INVENTION may, FET having such characteristics, the gate control type pn junction diode NO _X and CO ₂ which or with Schottky diodes,
As a result of repeated studies to develop such a gas sensor, the following present invention has been proposed.

(1) A gas sensor wherein an ion-conductive oxyacid salt and a current collector are formed in a gate region of a field effect transistor having a source region, a drain region, and a gate region formed in a semiconductor substrate. (2) A gas sensor in which a solid electrolyte is further formed in the gate region. (3) A gas sensor in which an ion-conductive oxyacid salt and a current collector are formed in a gate region of a gate control type pn junction diode in which a p-type region, an n-type region, and a gate region are formed in a semiconductor substrate. (4) A gas sensor in which a solid electrolyte is further formed in the gate region. (5) A gas sensor in which an ion-conductive oxyacid salt and a current collector are formed on a rectifying barrier electrode of a Schottky diode having a rectifying barrier electrode formed on a semiconductor substrate. (6) A gas sensor in which a solid electrolyte is further formed on the rectifying barrier electrode. (7) The gas sensor wherein the oxyacid salt contains a metal nitrite and / or a metal nitrate. (8) A gas sensor wherein the metal nitrite contains at least one of lithium nitrite, sodium nitrite, potassium nitrite, rubidium nitrite, cesium nitrite, barium nitrite, and strontium nitrite. (9) The metal nitrate is lithium nitrate, sodium nitrate, potassium nitrate, rubidium nitrate, magnesium nitrate, calcium nitrate, strontium nitrate, barium nitrate, scandium nitrate, cerium nitrate, zirconium nitrate, iron nitrate, copper nitrate, cobalt nitrate, nitric acid A gas sensor containing at least one of tin, indium nitrate, nickel nitrate, lead nitrate, bismuth nitrate and rare earth nitrate. (10) The gas sensor wherein the oxyacid salt contains a metal carbonate and / or a metal bicarbonate. (11) The metal carbonate is lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate,
A gas sensor containing at least one of magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, iron carbonate, copper carbonate, lead carbonate, nickel carbonate, manganese carbonate, cadmium carbonate, silver carbonate, cobalt carbonate, and rare earth carbonate. (12) The metal bicarbonate is sodium bicarbonate,
A gas sensor containing at least one of potassium hydrogen carbonate, rubidium hydrogen carbonate, and cesium hydrogen carbonate. (13) the solid electrolyte is a sodium ion conductor;
A gas sensor comprising at least one of a lithium ion conductor, a potassium ion conductor, a proton conductor, an oxide ion conductor, and a fluorine ion conductor. (14) The surface of the metal nitrite and the metal nitrate is
Gas sensor containing platinum particles. Here, silicon or silicon carbide is used for the semiconductor substrate,
Since silicon is a standard material and easy to handle, and silicon carbide can operate at high temperatures, it can also be used in high-temperature-acting ion-conductive oxyacid salts.

[0009]

[Action] The present invention describes a case of using as a NO _X gas sensor. The NO _X sensor, FE using a semiconductor substrate
T, forming a current collector with a conductive metal nitrite and / or metal nitrate for improving selectivity to interfering gas in a gate region or a rectifying barrier electrode of a gate controlled pn junction diode or a Schottky diode. , Or FET using a semiconductor substrate, gate controlled pn
The formation of a current collector with a solid electrolyte and a conductive metal nitrite and / or metal nitrate to improve the sensitivity to low-concentration gases in the gate region or rectifying barrier electrode of a junction diode or Schottky diode Become. The nitrogen dioxide gas sensor of the present invention shows high selectivity and sensitivity to nitrogen dioxide gas, but further oxidizes nitrogen monoxide to nitrogen dioxide by the surface of metal nitrite and metal nitrate containing platinum particles. And good sensitivity can be obtained with respect to the total amount of nitrogen dioxide gas and nitric oxide gas.

A case where the present invention is used as a CO ₂ gas sensor will be described. This CO ₂ sensor is an FE using a semiconductor substrate.
T, forming a current collector with a conductive metal carbonate and / or a metal bicarbonate which enhances selectivity to an interfering gas in a gate region or a rectifying barrier electrode of a gate control type pn junction diode or a Schottky diode. Or FET using a semiconductor substrate, gate control type p
Forming a current collector with a solid electrolyte and a conductive metal carbonate and / or a metal bicarbonate to improve the sensitivity to low concentration gas in the gate region or the rectifying barrier electrode of the n-junction diode or Schottky diode It consists of doing.

The operation of the ion-conductive oxyacid salt formed on the gate region or the rectifying barrier electrode will be described. A dissociation equilibrium occurs, and the resulting electromotive force change is reflected in the output characteristics of the FET, the gate control type pn junction diode, or the Schottky diode, and thereby the gas concentration of the detection target is measured. That is, metal nitrite and metal nitrate have a dissociation equilibrium with nitrogen dioxide, and carbonate and metal bicarbonate have a dissociation equilibrium with carbon dioxide, thereby improving selectivity.

In the above description, only the detection of CO _{2 and} the detection of NO _X have been described, but the present invention is not limited to this. That is, in the present invention, the chemical equilibrium of a gas such as NO _X or CO ₂ between the surrounding atmosphere and the ion-conductive oxyacid salt is used, and this effect is transmitted to a gate region, a rectifying barrier, and the like of the semiconductor substrate. To detect gas. Therefore, for example, it is conceivable to detect SO _X using sulfates such as lithium sulfate, sodium sulfate, and calcium sulfate as ion-conductive oxyacid salts.

Next, the solid electrolyte formed on the gate region or the rectifying barrier electrode is at least one of a sodium ion conductor, a lithium ion conductor, a proton conductor, an oxide ion conductor and a fluorine ion conductor. Preferably, the solid electrolyte is provided between the gate region or the rectifying barrier electrode and the ion-conductive oxyacid salt. This makes it possible to detect a lower concentration of gas. This is because a solid electrolyte is inserted between the gate region or rectifying barrier electrode and the ionic conductive oxyacid salt to form an ionic bridge between the oxyacid salt and the solid electrolyte, resulting in a large electrochemical potential. it is conceivable that. However, without ionic conductive oxyacid salt,
Even if a solid electrolyte and a current collector were provided, gas sensitivity could not be obtained.

The current collector formed in the gate region or the rectifying barrier electrode controls the voltage of the oxyacid salt, and the stability is improved by applying the voltage.

[0015]

Since the gas sensor of the present invention does not require a counter electrode or a reference electrode, it is less likely to be chemically affected by water vapor in the atmosphere or a gas not intended for detection.
In addition, the electromotive force based on the dissociation equilibrium of metal oxyacid salts to nitrogen dioxide, nitric oxide or carbon dioxide, etc.
It is obtained as output characteristics of a gate control type pn junction diode or a Schottky diode, and the selectivity is improved. Therefore, the technical significance of the present invention is that in any environment, nitrogen dioxide gas, nitric oxide gas, carbon dioxide gas, or the like can be measured reliably over a long period of time and quickly. large.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The gas sensor according to the embodiment has good selectivity to an interfering gas in a gate region or a rectifying barrier electrode of an FET using a semiconductor substrate, a gate control type pn junction diode, or a Schottky diode. Forming a current collector with ionic conductive oxyacid salt, or increasing the sensitivity to low-concentration gas in the gate region or rectifying barrier electrode of a FET using a semiconductor substrate, a gate-controlled pn junction diode, or a Schottky diode. And forming a current collector with the solid electrolyte, the ionic conductive oxyacid salt, and the solid electrolyte.

<FET Using Silicon Semiconductor Substrate> In the gas sensor of the embodiment, an FET using a silicon semiconductor substrate is used. A known method can be applied as a method for manufacturing the FET. That is, after an oxide film is formed on the surface of the p-type silicon semiconductor based on the thermal oxidation method, a mask layer for forming an element isolation region is formed based on a lithography technique and a dry etching technique. Next, an n-type region is formed in the p-type silicon substrate by an ion implantation method, and is used as an element isolation region. At this time, the mask layer functions as a stopper layer. Then, the mask layer is removed by wet etching, and an oxide film is formed again based on a thermal oxidation method. Based on this, a mask layer for forming a p-type region is formed based on a lithography technique and a dry etching technique. Thereafter, a p-type region of a low concentration impurity region is formed by ion implantation, and the mask layer is removed by wet etching. Next, an oxide film is formed based on a thermal oxidation method to form source / drain regions. Then, based on the lithography technology and the dry etching technology, a mask layer for an n-type source / drain region is formed, and an n-type region of a high-concentration impurity region is formed by ion implantation, followed by a chemical vapor deposition (CVD) method. To form a contact hole for source / drain electrodes based on a lithography technique and a dry etching technique, and form an ohmic electrode by vapor deposition. Further, in order to obtain environmental resistance of the device itself, silicon nitride is deposited on the entire surface of the device by a CVD method. Further, tantalum oxide may be deposited by a CVD method in order to further increase the insulating property of the gate region. An oxyacid salt or a solid electrolyte and an oxyacid salt are stacked on the gate region, and a current collector is bonded to the upper portion or a part thereof. Note that the dimensions of the source region, the drain region, the gate region, the current collector, and the like can be arbitrarily determined depending on the optimum current to be measured.

<Gate control type p using silicon semiconductor substrate
n-junction diode> In the gas sensor of the embodiment, a gate control type pn-junction diode using a silicon semiconductor substrate is used. A known method can be applied as a method of manufacturing the gate control type pn junction diode. That is, after forming an oxide film on the surface of the p-type silicon semiconductor based on the thermal oxidation method, based on the lithography technology and the dry etching technology,
A mask layer for forming an element isolation region is formed. Next, an n-type region is formed in the p-type silicon substrate by an ion implantation method, and is used as an element isolation region. At this time, the mask layer functions as a stopper layer. Then, the mask layer is removed by wet etching, and an oxide film is formed again based on a thermal oxidation method. Based on this, a mask layer for forming a p-type region is formed based on a lithography technique and a dry etching technique. Thereafter, a p-type region of a low concentration impurity region is formed by ion implantation, and the mask layer is removed by wet etching. Next, an oxide film is formed based on a thermal oxidation method in order to form an n-type region. Then, based on the lithography technique and the dry etching technique, a mask layer for an n-type region is formed, an n-type region of a high concentration impurity region is formed by ion implantation, and the mask layer is removed by wet etching. Then, to form ohmic electrodes in p and n type regions, CVD
A silicon dioxide layer is deposited by a method, a contact hole for an electrode is formed based on a lithography technique and a dry etching technique, and an ohmic electrode is formed by vapor deposition. Further, in order to obtain environmental resistance of the device itself, silicon nitride is deposited on the entire surface of the device by a CVD method. In addition, tantalum oxide is used to further improve the insulation of the gate region.
It may be deposited by a CVD method. An oxyacid salt or a solid electrolyte and an oxyacid salt are laminated on the upper part of the pn junction region, and a current collector is joined to the upper part or a part thereof. The p-type region,
The dimensions of the n-type region, the current collector, and the like can be arbitrarily determined according to the optimum current to be measured.

<Schottky Diode Using Silicon Semiconductor Substrate> In the gas sensor of the embodiment, a Schottky diode using a silicon semiconductor substrate is used. A well-known method can be applied as a method of manufacturing the Schottky diode. That is, after cleaning the n-type silicon semiconductor with hydrofluoric acid and removing the oxide film, a rectifying barrier electrode (Schottky electrode) is deposited by depositing a metal such as Pt or Au having a large work function.
Form as An ohmic electrode (back surface electrode) is formed on the back surface opposite to the Schottky electrode. Further, an oxyacid salt or a solid electrolyte and an oxyacid salt are laminated on the Schottky electrode, and a current collector is bonded to an upper part or a part thereof. The dimensions of the Schottky electrode and the like can be arbitrarily determined according to the optimum current to be measured.

<Schottky Diode Using Silicon Carbide Semiconductor Substrate> In the gas sensor of the embodiment, a Schottky diode using a silicon carbide semiconductor substrate is used. A well-known method can be applied as a method of manufacturing the Schottky diode. That is, after cleaning the n-type silicon carbide semiconductor substrate with hydrofluoric acid and removing the oxide film, platinum having a large work function,
A metal such as gold is formed as a Schottky electrode by vapor deposition. An ohmic electrode (back surface electrode) is formed on the back surface opposite to the Schottky electrode. Further, an oxyacid salt or a solid electrolyte and an oxyacid salt are laminated on the Schottky electrode, and a current collector is bonded to an upper part or a part thereof. The dimensions of the Schottky electrode and the like can be arbitrarily determined according to the optimum current to be measured.

<Ion-Conducting Oxygenate> In the gas sensor of the embodiment, when nitrogen dioxide gas or nitric oxide gas is to be detected, metal nitrite and / or metal nitrate is added to the ion-conductive oxyacid salt. When a carbon dioxide gas is to be detected, a metal carbonate and / or a metal bicarbonate is used as the oxyacid salt.

Examples of the metal nitrite include lithium nitrite (LiNO2), sodium nitrite (NaNO2), potassium nitrite (KNO2), rubidium nitrite (RbNO2), cesium nitrite (CsNO2), and barium nitrite (Ba (NO2) 2) and strontium nitrite (Sr (NO2) 2), and it is preferable to contain one or more of these. These may deviate somewhat from the stoichiometric composition. Further, it may contain water of crystallization.

Examples of metal nitrates include lithium nitrate (LiNO3), sodium nitrate (NaNO3), potassium nitrate (KNO3), rubidium nitrate (RbNO3), magnesium nitrate (Mg (NO3) 2), and calcium nitrate (Ca (NO3) 2), strontium nitrate (Sr (NO3) 2), barium nitrate (Ba (NO3)
2), scandium nitrate (Sc (NO3) 3), cerium nitrate (C
e (NO3) 3), zirconium nitrate (Zr (NO3) 4), iron nitrate (F
e (NO3) 2, Fe (NO3) 3), copper nitrate (Cu (NO3) 2), cobalt nitrate (Co (NO3) 2), tin nitrate (Sn (NO3) 4), indium nitrate (In (NO3) 3), preferably contains at least one of nickel nitrate (Ni (NO3) 2), lead nitrate (Pb (NO3) 2), bismuth nitrate (Bi (NO3) 3) and rare earth nitrate.
These may deviate somewhat from the stoichiometric composition. Further, it may contain water of crystallization.

Further, the surface of the metal nitrite and the metal nitrate may contain platinum particles.

Examples of the metal carbonate include, for example, lithium carbonate (Li2CO3), sodium carbonate (Na2CO3), potassium carbonate (K2CO3), rubidium carbonate (Rb2CO3), cesium carbonate (Cs2CO3), magnesium carbonate (MgCO3), and calcium carbonate (MgCO3). CaCO3), strontium carbonate (SrCO3), barium carbonate (BaCO3), iron carbonate (FeCO3), copper carbonate (Cu2CO
3) contains at least one of lead carbonate (PbCO3), nickel carbonate (NiCO3), manganese carbonate (MnCO3), cadmium carbonate (CdCO3), silver carbonate (Ag2CO3), cobalt carbonate (CoCO3) and rare earth carbonate Is preferred. These may deviate somewhat from the stoichiometric composition. Also,
It may contain water of crystallization.

The metal bicarbonate preferably contains, for example, at least one of sodium bicarbonate (NaHCO3), potassium bicarbonate (KHCO3), rubidium bicarbonate (RbHCO3) and cesium bicarbonate (CsHCO3). . These may deviate somewhat from the stoichiometric composition. Further, it may contain water of crystallization.

The ion-conductive oxyacid salt used in the gas sensor of the embodiment is bonded to a gate region, a rectifying barrier electrode, or a solid electrolyte by pressure bonding of a powder paste, screen printing of the powder paste, heat fusion bonding, or the like. Each joining method is not particularly limited as long as it has a holding force.

<Solid Electrolyte> In the gas sensor of the embodiment, a solid made of at least one of a sodium ion conductor, a lithium ion conductor, a potassium ion conductor, a proton conductor, an oxide ion conductor and a fluorine ion conductor is used. Use electrolyte. As a sodium ion conductor,
Na-β '' alumina, Na-β alumina, Na1 + xZr2SixP3-xO
12 (NASICON, where 0 ≦ x ≦ 3); Li-β alumina, Li14Zn (CeO4), Li5AlO4, Li4S
iO4, Li4GeO4, Li3VO4, Li2MoO4, Li4ZrO4, as potassium ion conductors, K-β alumina, K2MgTi7O16, as proton conductors, Sb2O5 / 5H2O, HUO2PO4 / 4H2O, H3
(PMo12O40) ・ 29H2O, SrCe1-xYbxO3 (0 ≦ x ≦ 1), as oxide ion conductors, ZrO2-CaO, ZrO2-Y2O3, ZrO
2-MgO, CeO2-CaO, CeO2-La2O3, CeO2-Gd2O3, Bi2O3-Y2O
3, Bi2O3-WO3, as fluoride ion conductor, LaF3, Pb
F2, CaF2, TlSn2F5 and the like. These are bonded to the gate region or the rectifying barrier electrode in the form of a film, but their dimensions are not particularly limited as long as they are conductive and have a holding power. They may also deviate somewhat from the stoichiometric composition. Particularly, NASICON, which can be formed into a film at a low temperature, is preferable.

<Current Collector> In the gas sensor of the embodiment, a current collector is used as the detection electrode. The metal used for the current collector may be any one or more of gold, platinum, palladium, silver, copper, aluminum, nickel, iridium and the like. In particular,
Gold, platinum, and mixtures and alloys thereof are preferred because of their excellent corrosion resistance. The current collector is a wire, mesh,
Pressed or screen printed powder pastes are preferred. These are not particularly limited in size as long as they have a holding force.

<Structure of Sensor> FIGS. 1, 2, 3, 4, 5, 6, 7, and 8 show examples of the structure of the gas sensor of the embodiment. FIG. 1 shows a field effect transistor in which a source region 3, a source electrode 4, a drain region 5, a drain electrode 6, and a gate region 7 (gate insulating film) are formed on a silicon semiconductor substrate 2. Oxyacid salt 8 and current collector 9
Is provided as a gas sensor.

FIG. 2 shows a source region 3 in a silicon semiconductor substrate 2.
A field-effect transistor in which a source electrode 4, a drain region 5, a drain electrode 6, and a gate region 7 are formed, and a solid electrolyte 10, an ionic conductive oxyacid salt 8, and a current collector 9 are provided above the gate region 7. The gas sensor 1 is used.

In the gas sensor shown in FIGS. 1 and 2, lead wires are drawn out from the source electrode 4, the drain electrode 6, and the current collector 9, respectively, so that the DC power supply 11 or the DC ammeter 12
It is connected to the. The dimensions of the gas sensor of FIGS. 1 and 2 are not particularly limited, but usually the gate width is 10 to 1000.
μm, the gate length is about 20-5000 μm, the area of the ionic conductive oxyacid salt is about the same as the gate area, the thickness of the ionic conductive oxyacid salt is about 10-3000 μm, and the area of the solid electrolyte is the same as the gate area. The thickness of the solid electrolyte is about 10 to 2000 μm.

The gas sensor of the embodiment shown in FIGS. 1 and 2 applies a DC voltage between the source electrode 4 and the drain electrode 6 and a DC voltage between the source electrode 4 and the current collector 9, respectively. A DC current flowing between the drain and the drain electrode 6 is detected as a sensor signal. At this time, nitrogen dioxide gas, nitric oxide gas, or carbon dioxide gas, which is the gas to be detected, is guided onto the ionic conductive oxyacid salt.

FIG. 3 shows that the p-type regions 13 and p
A gate-controlled pn junction diode formed with a mold electrode 14, an n-type region 15, an n-type electrode 16, and a gate region 7, provided with an ion-conductive oxyacid salt 8 and a current collector 9 above the gate region 7, The gas sensor 1 is used.

FIG. 4 shows that the p-type regions 13 and p
A gate-controlled pn junction diode formed with a type electrode 14, an n-type region 15, an n-type electrode 16, and a gate region 7, and a solid electrolyte 10, an ion-conductive oxyacid salt 8, a current collector 9 are provided, and the gas sensor 1 is provided.

In the gas sensor of FIGS. 3 and 4, the p-type electrode 14,
Lead wires are respectively drawn from the n-type electrode 16 and the current collector 9 and connected to the DC power supply 11 or the DC ammeter 12. Although the dimensions of the gas sensor in FIGS. 3 and 4 are not particularly limited, usually, the gate width is about 10 to 1000 μm, the gate length is about 20 to 5000 μm, the area of the ion conductive oxyacid salt is about the same as the gate region, The thickness of the oxyacid salt is about 10 to 3000 μm, the area of the solid electrolyte is about the same as the gate area, and the thickness of the solid electrolyte is 10
２０００2000 μm.

The gas sensor of the embodiment shown in FIGS.
DC voltage is applied between the p-type electrode 14 and the n-type electrode 16.
Alternatively, a DC voltage is applied between the n-type electrode 16 and the current collector 9 to detect a DC current flowing between the p-type electrode 14 and the n-type electrode 16 as a sensor signal. At this time, nitrogen dioxide gas, nitric oxide gas, or carbon dioxide gas, which is the gas to be detected, is guided onto the ionic conductive oxyacid salt.

FIG. 5 shows a rectifying barrier electrode 1 on a silicon semiconductor substrate 2.
7 is a Schottky diode on which an ionic conductive oxyacid salt 8 and a current collector 9 are provided above a rectifying barrier electrode 17.
The back surface electrode 18 is provided on the side opposite to the rectifying barrier electrode to form the gas sensor 1.

FIG. 6 shows a rectifying barrier electrode 1 on a silicon semiconductor substrate 2.
A solid electrolyte 10, an ion-conductive oxyacid salt 8, and a current collector 9 on the rectification barrier electrode 17, and a back electrode 1 on the side opposite to the rectification barrier electrode.
8 is provided as the gas sensor 1.

FIG. 7 shows a Schottky diode in which a rectifying barrier electrode 17 is formed on a silicon carbide semiconductor substrate 19. Ion conductive oxyacid salt 8 and current collector 9 are provided above rectifying barrier electrode 17.
The back surface electrode 18 is provided on the side opposite to the rectifying barrier electrode to form the gas sensor 1.

FIG. 8 shows a Schottky diode in which a rectifying barrier electrode 17 is formed on a silicon carbide semiconductor substrate 19. The solid electrolyte 10, the ion-conductive oxyacid salt 8, and the current collector 9 are rectified on the rectifying barrier electrode 17. A back electrode 18 is provided on the side opposite to the barrier electrode, and serves as a gas sensor 1.

In the gas sensors of FIGS. 5, 6, 7 and 8, the rectification
The barrier electrode 17, the current collector 9, and the rear surface electrode 18
The lead wire is pulled out and the DC power supply 11 or DC power supply
It is connected to a flow meter 12. 5, 6, 7 and 8
The size of the sensor is not particularly limited, but usually a rectifying barrier
The area of the electrode 17 is 100 μm 2 to 30 mm ²Degree, ion
The area of the conductive oxyacid salt is about the same as the area of the rectifying barrier electrode 17.
The thickness of the ion conductive oxyacid salt is 10-3000 μm
The area of the solid electrolyte is the same as the area of the rectifying barrier electrode 17.
And the thickness of the solid electrolyte is about 10 to 2000 μm.
You.

The gas sensor of the embodiment shown in FIGS. 5, 6, 7 and 8 applies a DC voltage between the rectifying barrier electrode 17 and the back electrode 18 and a DC voltage between the rectifying barrier electrode 17 and the current collector 9, respectively. The applied DC current flowing between the rectifying barrier electrode 17 and the back surface electrode 18 is detected as a sensor signal. At this time, nitrogen dioxide gas, nitric oxide gas, or carbon dioxide gas, which is the gas to be detected, is guided onto the ionic conductive oxyacid salt.

The optimum operating temperature of the gas sensor of the embodiment varies depending on the material constituting the sensor element and the type of coexisting gas, but the temperature range in which metal nitrite, metal nitrate, metal carbonate and metal bicarbonate are not decomposed, That is, -50 to 500
° C, preferably -50 to 2 when using a silicon semiconductor.
50 ° C., 100 to 400 when using a silicon carbide semiconductor
It is in the range of ° C.

[0045] The gas sensor of the embodiment has good responsiveness, from 1 second to
A response is obtained in 5 minutes, preferably 1 second to 3 minutes.

[0046]

EXAMPLES The present invention will be described in detail with reference to the following examples, but the present invention is not limited to these examples.

<Embodiment 1> Gate area 100 × 300 μm 2
The ionic conductive oxyacid salt (film thickness: 1 mm) shown in Table 1 was provided to the FET having a temperature of 50 to 200 ° C (here, 150 ° C).
In the above, the gas sensor produced was inserted into a measuring cell in which test gases of various concentrations were circulated in dry air, and 3 V was applied between the source and drain electrodes, and the source and gate electrodes (current collector 9)
A current (ID) flowing between the source and drain electrodes when a voltage of 0.5 to 1.0 V (0.5 V in this case) was applied between the electrodes was measured. Fig. 9 shows the results of a nitrogen dioxide gas sensor using sodium nitrite as the ion-conductive oxyacid salt, and the results of a nitric oxide gas sensor using sodium nitrate as the ion-conductive oxyacid salt and platinum particles dispersed on the surface. Fig. 10 shows the results of a carbon dioxide gas sensor using NASICON as the solid electrolyte and a 1: 2 complex salt (molar ratio) of sodium carbonate and barium carbonate as the ion-conductive oxyacid salt. FIG. 12 shows the results of a carbon dioxide gas sensor using sodium hydrogen carbonate as the oxyacid salt, and FIG. 13 shows the changes over time in the sensor sensitivity. Here, the thickness of the solid electrolyte was 100 μm.

In dry air, nitrogen dioxide gas concentration 0.5 ppm
When the test gas is passed, the concentration of nitric oxide gas is 1pp
When the test gas of m is circulated, the carbon dioxide gas concentration is 1
The response speed and sensitivity of each sensor were examined when a test gas of 000 ppm was passed. Further, in the case of a nitrogen dioxide gas sensor and a nitric oxide gas sensor,
000 ppm carbon dioxide gas, relative humidity 80% (30 ° C)
Water vapor, 100 ppm carbon monoxide gas, in the case of a carbon dioxide gas sensor, 80% relative humidity (30 ° C.) water vapor,
A response was confirmed by flowing a mixed gas of 5 ppm nitric oxide gas and 5 ppm nitrogen dioxide gas and 100 ppm carbon monoxide gas, and the selectivity was examined. Table 1 shows the results.

[0049]

[Table 1] No. Test gas Conductive oxyacid salt Collector Response speed Sensitivity Selectivity 1 NO2 LiNO2 Au ◎ ◎ ◎ 2 NO2 NaNO2 Au ◎ ◎ ◎ 3 NO2 KNO2 Au ◎ ◎ ◎ 4 NO2 RbNO2 Au ○ ○ ○ 5 NO2 CsNO2 Au ○ ○ ○ 6 NO2 Ba (NO2) 2 Au ○ ◎ ○ 7 NO2 Sr (NO2) 2 Au ○ ◎ ○ 8 NO2 NASICON -NaNO2 Au ◎ ◎ ◎ 9 NO LiNO3 + Pt Au ◎ ◎ ◎ 10 NO NaNO3 + Pt Au ◎ ◎ ◎ 11 NO KNO3 + Pt Au ◎ ◎ ◎ 12 NO RbNO3 + Pt Au ○ ○ ○ 13 NO Mg (NO3) 2 + Pt Au ○ ◎ ○ 14 NO Ca (NO3) 2 + Pt Au ○ ◎ ○ 15 NO Sr (NO3) 2 + Pt Au ○ ◎ ○ 16 NO Ba (NO3) 2 + Pt Au ◎ ○ 17 17 NO Sc (NO3) 3 + Pt Au ○ 18 18 NO Ce (NO3) 3 + Pt Au ○ ○ 19 NO Zr (NO3) 4 + Pt Au ○ 20 NO Fe (NO3) 2 + Pt Au ○ ○ ○ 21 NO Fe (NO3) 3 + Pt Au ○ ○ ○ 22 NO Cu (NO3) 2 + Pt Au ○ ○ ○ 23 NO Co (NO3) 2 + Pt Au ○ ○ ○ 24 NO Sn (NO3) 4 + Pt Au ○ ○ ○ 25 NO In (NO3) 3 + Pt Au ◎ ◎ ◎ 26 NO Ni (NO3) 2 + Pt Au ○ ○ ○ 27 NO Pb (NO3) 2 + Pt Au ○ ○ ○ 28 NO Bi (NO3) 3 + Pt Au ○ ○ ○ 29 NO La (NO3) 3 + Pt Au ○ ○ ○ 30 NO Pr (NO3) 3 + Pt Au ○ ○ ○ 31 NO NASICON- NaNO3-Pt Au ◎ ◎ ◎ 32 CO2 Li2CO3 Au ◎ ◎ ◎ 33 CO2 Na2CO3 Au ◎ ◎ ◎ 34 CO2 K2CO3 Au ◎ ◎ ◎ 35 CO2 Rb2CO3 Au ○ ○ ○ 36 CO2 Cs2 CO3 Au ○ ○ ○ 37 CO2 MgCO3 Au ○ ○ ○ 38 CO2 CaCO3 Au ◎ ◎ ◎ 39 CO2 SrCO3 Au ◎ ◎ ◎ 40 CO2 BaCO3 Au ◎ ◎ ◎ 41 CO2 FeCO3 Au ○ ○ ○ 42 CO2 Cu2 CO3 Au ○ ○ ○ 43 CO2 PbCO3 Au ○ ○ ○ 44 CO2 NiCO3 Au ○ ◎ ○ 45 CO2 MnCO3 Au ○ ○ ○ 46 CO2 CdCO3 Au ○ ○ ○ 47 CO2 Ag2CO3 Au ○ ○ ○ 48 CO2 CoCO3 Au ○ ◎ ○ 49 CO2 La2 (CO3) 3 Au ○ ○ ○ 50 CO2 Ce2 (CO3) 3 Au ○ ○ ○ 51 CO2 NASICON -Li2CO3-BaCO3 Au ◎ ◎ ◎ 52 CO2 NaHCO3 Au ◎ ◎ ◎ 53 CO2 KHCO3 Au ◎ ◎ ○ 54 CO2 RbHCO3 Au ○ ○ ○ 55 CO2 CsHCO3 Au ○ ○ ○ 56 CO2 NASICON-NaHCO3 Au ◎ ◎ ◎ 57 NO2 None Pt × × 59 NO2 None Au × × 60 NO None Pt × × 61 NO None Au × × 62 CO2 None Pt × × 63 CO2 None Au × ×

[0050] The response speed is the time required for the current to reach 90% of the current value when the response becomes constant after the introduction of the test gas. Evaluation: A: Within 1 minute O: Over 1 minute and within 3 minutes Δ: Over 3 minutes and within 5 minutes ×: Over 5 minutes

The sensor sensitivity is obtained by dividing the absolute value of the difference between the current value before the introduction of the test gas and the current value after the introduction by the current value before the introduction.
It is a value (% unit) multiplied by 00. Evaluation: ◎: 5% or more ：: 2% or more and less than 5% Δ: 0.5% or more and less than 2% ×: Less than 0.5%

The selectivity is a property that is not affected by a coexisting gas other than the test gas. Evaluation: ：: Not affected by all coexisting gases ○: Not affected by two types of coexisting gases △: Not affected by one type of coexisting gases ×: Affected by all coexisting gases It was assumed.

<Embodiment 2> Gate area 100 × 300 μm 2
The solid electrolyte shown in Table 1 (film thickness 100 μm)
m) and ionic conductive oxyacid salt (film thickness 1 mm)
The prepared gas sensor was inserted into a measurement cell in which test gases of various concentrations were circulated in dry air at a temperature of 200 ° C. (here, 150 ° C.), and evaluation was performed in the same manner as in Example 1.
Table 1 shows the results.

In Example 1, the nitrogen dioxide gas sensor using lithium nitrite, sodium nitrite, and potassium nitrite as the ion conductive oxyacid salts showed equivalent results.

Further, nitrogen dioxide gas sensors using rubidium nitrite, cesium nitrite, barium nitrite, and strontium nitrite as the ion conductive oxyacid salts also showed the same results.

In Example 1, lithium nitrate, sodium nitrate, potassium nitrate, and indium nitrate were used as the ion-conductive oxyacid salts, respectively, and the nitric oxide gas sensor containing Pt on the surface showed equivalent results.

Further, a nitric oxide gas sensor containing Pt on the surface using another nitrate as the ion-conductive oxyacid salt showed the same result.

In Example 1, carbon dioxide gas sensors using lithium carbonate, sodium carbonate, potassium carbonate, calcium carbonate, strontium carbonate, barium carbonate, and sodium hydrogen carbonate as the ion-conductive oxyacid salts showed equivalent results.

A carbon dioxide gas sensor using another carbonate or bicarbonate as the ion-conductive oxyacid salt also showed equivalent results.

[0060] In Example 2, NASICON was used as the solid electrolyte.
Nitrogen dioxide gas sensor using sodium nitrite as ionic conductive oxyacid salt, NASICON as solid electrolyte Nitric oxide gas sensor containing platinum on the surface using sodium nitrate as ionic conductive oxyacid salt, NASICON as solid electrolyte The carbon dioxide gas sensor using lithium carbonate and barium carbonate as the ion conductive oxyacid salt, and the carbon dioxide gas sensor using NASICON as the solid electrolyte and sodium hydrogen carbonate as the ion conductive oxy acid salt showed good results.

<Comparative Example 1> Gate region 100 × 300 μm 2
A gold electrode or a platinum electrode is provided on an FET having
The prepared gas sensor was inserted into a measurement cell in which test gases of various concentrations were circulated in dry air at ℃, and evaluation was performed in the same manner as in Examples 1 and 2. Table 1 (No. 5)
7 to 63).

[0062] The gas sensor of the embodiment is different from that of the comparative example.
Excellent in response speed, sensitivity, and selectivity.

Example 3 A gate-controlled pn junction diode having a gate width of 100 μm and a gate length of 3000 μm was provided with an ion-conductive oxyacid salt (film thickness: 1 mm) as shown in Table 2 at 150 ° C. in dry air. Insert the prepared gas sensor into the measurement cell in which various concentrations of the test gas are passed, and apply 5 V between the p-type electrode and the n-type electrode and apply 1.0 V between the n-type and the gate electrode (current collector 9). The current (I) flowing between the p-type electrode and the n-type electrode at this time was measured. This gas sensor was evaluated in the same manner as in Example 1. Table 2 shows the results.

Example 4 A solid electrolyte (film thickness 100 μm) and an ion conductive oxyacid salt (film thickness 1 mm) shown in Table 2 were applied to a gate control type pn junction diode having a gate width of 100 μm and a gate length of 3000 μm. The gas sensor manufactured was inserted into a measurement cell provided with test gases of various concentrations in dry air at 150 ° C., and evaluation was performed in the same manner as in Example 3. Table 2 shows the results.

[0065]

[Table 2] No. Test gas Conductive oxyacid salt Collector Response speed Sensitivity Selectivity 64 NO2 LiNO2 Au ◎ ◎ ◎ 65 NO2 NaNO2 Au ◎ ◎ ◎ 66 NO2 KNO2 Au ◎ ◎ ◎ 67 NO2 RbNO2 Au ○ ○ ○ 68 NO2 CsNO2 Au ○ ○ ○ 69 NO2 Ba (NO2) 2 Au ○ ○ ○ 70 NO2 Sr (NO2) 2 Au ○ ○ ○ 71 NO2 NASICON -NaNO2 Au ◎ ◎ ◎ 72 NO LiNO3 + Pt Au ◎ ◎ ◎ 73 NO NaNO3 + Pt Au ◎ ◎ ◎ 74 NO KNO3 + Pt Au ◎ ◎ ◎ 75 NO RbNO3 + Pt Au ○ ○ ○ 76 NO Mg (NO3) 2 + Pt Au ○ ○ ○ 77 NO Ca (NO3) 2 + Pt Au ○ ○ ○ 78 NO Sr (NO3) 2 + Pt Au ○ ○ ○ 79 NO Ba (NO3) 2 + Pt Au ○ 80 80 NO Sc (NO3) 3 + Pt Au ○ ○ 81 NO Ce (NO3) 3 + Pt Au ○ 82 82 NO Zr (NO3) 4 + Pt Au ○ ○ 83 NO Fe (NO3) 2+ t Au ○ ○ ○ 84 NO Fe (NO3) 3 + Pt Au ○ ○ ○ 85 NO Cu (NO3) 2 + Pt Au ○ ○ ○ 86 NO Co (NO3) 2 + Pt Au ○ ○ ○ 87 NO Sn (NO3) 4 + Pt Au ○ ○ ○ 88 NO In (NO3) 3 + Pt Au ◎ ◎ ◎ 89 NO Ni (NO3) 2 + Pt Au ○ ○ ○ 90 NO Pb (NO3) 2 + Pt Au ○ ○ 91 NO Bi (NO3) 3 + Pt Au ○ ○ ○ 92 NO La (NO3) 3 + Pt Au ○ ○ ○ 93 NO Pr (NO3) 3 + Pt Au ○ ○ ○ 94 NO NASICON -NaNO3-Pt Au ◎ ◎ ◎ 95 CO2 Li2CO3 Au ◎ ◎ ◎ 96 CO2 Na2CO3 Au ◎ ◎ ◎ 97 CO2 K2CO3 Au ◎ ◎ ◎ 98 CO2 Rb2CO3 Au ○ ○ ○ 99 CO2 Cs2CO3 Au ○ ○ ○ 100 CO2 MgCO3 Au ○ ○ ○ 101 CO2 CaCO3 Au ◎ ◎ ◎ 102 CO2 SrCO3 Au ◎ ◎ ◎ 103 CO2 BaCO3 Au ◎ ◎ ◎ 104 CO2 FeCO3 Au ○ ○ ○ 105 CO2 Cu2CO3 Au ○ ○ ○ 106 CO2 PbCO3 Au ○ ○ ○ 107 CO2 NiCO3 Au ○ ○ ○ 108 CO2 MnCO3 Au ○ ○ ○ 109 CO2 CdCO3 Au ○ ○ ○ 110 CO2 Ag2CO3 Au ○ ○ ○ 111 CO2 CoCO3 Au ○ ○ ○ 112 CO2 La2 (CO3) 3 Au ○ ○ ○ 113 CO2 Ce2 (CO3) 3 Au ○ ○ ○ 114 CO2 NASICON -Li2CO3-BaCO3 Au ◎ ◎ ◎ 115 CO2 NaHCO3 Au ◎ ◎ ◎ 116 CO2 KHCO3 Au ○ ○ ○ 117 CO2 RbHCO3 Au ○ ○ ○ 118 CO2 CsHCO3 Au ○ ○ ○ 119 CO2 NASICON − NaHCO3 Au ◎ ◎ ◎ 120 NO2 None Pt × × 121 NO2 None Au × × 123 NO None Pt × × 124 NO None Au × × 125 CO2 None Pt × × 126 CO2 None Au × ×

In Example 3, nitrogen dioxide gas sensors using lithium nitrite, sodium nitrite, and potassium nitrite as the ion-conductive oxyacid salts showed equivalent results.

Further, nitrogen dioxide gas sensors using rubidium nitrite, cesium nitrite, barium nitrite, and strontium nitrite as the ion conductive oxyacid salts also showed similar results.

[0068] In Example 3, lithium nitrate, sodium nitrate, potassium nitrate, and indium nitrate were used as the ion-conductive oxyacid salts, respectively, and the nitric oxide gas sensor containing Pt on the surface showed equivalent results.

Further, a nitric oxide gas sensor containing platinum on the surface using another nitrate as the ion-conductive oxyacid salt showed the same result.

[0070] In Example 3, carbon dioxide gas sensors using lithium carbonate, sodium carbonate, potassium carbonate, calcium carbonate, strontium carbonate, barium carbonate, and sodium hydrogen carbonate as the ion-conductive oxyacid salts showed equivalent results.

Further, a carbon dioxide gas sensor using another carbonate or bicarbonate as the ion-conductive oxyacid salt showed equivalent results.

In Example 4, a nitrogen dioxide gas sensor using NASICON as a solid electrolyte and sodium nitrite as an ion-conductive oxyacid salt, NASICON as a solid electrolyte, sodium nitrate as an ion-conductive oxyacid salt, and a Pt Nitrogen monoxide gas sensor containing, a carbon dioxide gas sensor using NASICON as a solid electrolyte and lithium carbonate and barium carbonate as an ionic conductive oxyacid salt, a NASICON as a solid electrolyte using sodium hydrogen carbonate as an ionic conductive oxyacid salt The carbon dioxide gas sensor showed good results.

<Comparative Example 2> Gate width 100 μm, gate length 3
A gold electrode or a platinum electrode was provided on a gate control type pn junction diode having a thickness of 000 μm, and the sample was fabricated in a measurement cell in which various concentrations of a test gas were circulated in dry air at 50 to 200 ° C. (here, 150 ° C.). A gas sensor was inserted, and evaluation was performed in the same manner as in Examples 3 and 4. The result is displayed
2 (NO. 120 to 126).

[0074] The gas sensor of the embodiment is more
Excellent in response speed, sensitivity, and selectivity.

Example 5 An ion conductive oxyacid salt (film thickness: 1 mm) shown in Table 3 was provided on a silicon schottky diode having a rectifying barrier electrode area of 25 mm ^{2 and} a silicon carbide schottky diode. 150 ° C, 3 for silicon carbide Schottky diode
At 00 ° C., the gas sensor produced was inserted into a measurement cell in which test gases of various concentrations were circulated in dry air, and 2 V was applied between the rectifying barrier electrode and the back electrode, and 1.V between the rectifying barrier electrode and the current collector. The current (I) flowing between the rectifying barrier electrode and the back electrode when 0 V was applied was measured. This gas sensor was evaluated in the same manner as in Example 1. Table 3 shows the results.

Example 6 A solid electrolyte (film thickness of 10) shown in Table 3 was added to a silicon Schottky diode and a silicon carbide Schottky diode having a rectifying barrier electrode area of 25 mm ^2.
0 μm) and ion conductive oxyacid salt (film thickness 1 mm)
At 150 ° C. for a silicon Schottky diode and 300 ° C. for a silicon carbide Schottky diode, the gas sensor manufactured was inserted into a measurement cell in which test gases of various concentrations were circulated in dry air, and the same as in Example 5 was performed. evaluated. Table 3 shows the results.

[0077]

[Table 3] NO. Semiconductor Test gas Conductive oxyacid salt Collector Response speed Sensitivity Selectivity 127 Si NO2 LiNO2 Au ◎ ◎ ◎ 128 Si NO2 NaNO2 Au ◎ ◎ ◎ 129 Si NO2 KNO2 Au ◎ ◎ ◎ 130 Si NO2 Ba (NO2) 2 Au ○ ○ ○ 131 Si NO2 Sr (NO2) 2 Au ○ ○ ○ 132 Si NO2 NASICON -NaNO2 Au ◎ ◎ ◎ 133 Si NO LiNO3 + Pt Au ◎ ◎ ◎ 134 Si NO NaNO3 + Pt Au ◎ ◎ ◎ 135 Si NO KNO3 + Pt Au ◎ ◎ ◎ 136 SiC NO RbNO3 Au ○ ○ ○ 137 SiC NO Mg (NO3) 2 Au ○ ○ ○ 138 SiC NO Ca (NO3) 2 Au ○ ○ ○ 139 SiC NO Sr (NO3) 2 Au ○ ○ ○ 140 SiC NO Ba (NO3) 2 Au ○ ○ ○ 141 SiC NO Sc (NO3) 3 Au ○ ○ ○ 142 SiC NO Ce (NO3) 3 Au ○ ○ ○ 143 SiC NO Zr (NO3) 4 Au ○ ○ ○ 144 S C NO Fe (NO3) 2 Au ○ ○ ○ 145 SiC NO Co (NO3) 2 Au ○ ○ ○ 146 SiC NO Sn (NO3) 4 Au ○ ○ ○ 147 SiC NO In (NO3) 3 Au ◎ ◎ ◎ 148 SiC NO Ni (NO3) 2 Au ○ ○ ○ 149 SiC NO Bi (NO3) 3 Au ○ ○ ○ 150 Si NO La (NO3) 3 + Pt Au ○ ○ ○ 151 Si NO Pr (NO3) 3 + Pt Au ○ ○ ○ 152 Si NO NASICON − NaNO3-Pt Au ◎ ◎ ◎ 153 SiC CO2 Li2CO3 Au ◎ ◎ ◎ 154 SiC CO2 Na2CO3 Au ◎ ◎ ◎ 155 SiC CO2 K2CO3 Au ◎ ◎ ◎ 156 SiC CO2 Cs2CO3 Au ○ ○ 157 157 SiC CO CaCO3 Au ◎ ◎ ◎ 159 SiC CO2 SrCO3 Au ◎ ◎ ◎ 160 SiC CO2 BaCO3 Au ◎ ◎ ◎ 161 SiC CO2 FeCO3 Au ○ ○ ○ 162 SiC CO2 Cu2CO3 Au ○ ○ 163 SiC CO2 PbCO3 Au ○ ○ ○ 164 SiC CO2 NiCO3 Au ○ ○ ○ 165 SiC CO2 MnCO3 Au ○ ○ ○ 166 SiC CO2 CdCO3 Au ○ ○ ○ 167 SiC CO2 Ag2CO3 Au ○ ○ ○ 168 SiC CO2 CoCO3 Au ○ SiC CO2 La2 (CO3) 3 Au ○ ○ ○ 170 SiC CO2 Ce2 (CO3) 3 Au ○ ○ ○ 171 Si CO2 NASICON -Li2CO3-BaCO3 Au ◎ ◎ ◎ 172 Si CO2 NaHCO3 Au ◎ ◎ ◎ 173 Si CO2 KHCO3 ○ ○ ○ 174 SiC CO2 RbHCO3 Au ○ ○ ○ 175 SiC CO2 CsHCO3 Au ○ ○ ○ 176 Si CO2 NASICON- NaHCO3 Au ◎ ◎ ◎ 177 Si NO2 None Pt × × 178 Si NO2 None Au × × 179 SiC NO None Pt × × 180 Si NO None Au × × 181 SiC CO2 None Pt × × 182 SiC CO2 None Au × ×

In Example 5, the nitrogen dioxide gas sensor using lithium nitrite, sodium nitrite, and potassium nitrite as the ion-conductive oxyacid salts showed equivalent results.

Further, nitrogen dioxide gas sensors using barium nitrite and strontium nitrate as the ion conductive oxyacid salts also showed the same results.

[0080] In Example 5, lithium nitrate, sodium nitrate, potassium nitrate, and indium nitrate were used as the ion-conductive oxyacid salts, respectively, and a nitric oxide gas sensor containing platinum on the surface showed equivalent results.

Further, a nitric oxide gas sensor containing platinum on the surface using another nitrate as the ion-conductive oxyacid salt showed the same result.

In Example 5, carbon dioxide gas sensors using lithium carbonate, sodium carbonate, potassium carbonate, calcium carbonate, strontium carbonate, barium carbonate, and sodium hydrogen carbonate as the ion-conductive oxyacid salts showed equivalent results.

[0083] A carbon dioxide gas sensor using another carbonate or bicarbonate as the ion-conductive oxyacid salt also showed equivalent results.

In Example 6, NASICON was used as the solid electrolyte.
Nitrogen dioxide gas sensor using sodium nitrite as ion-conductive oxyacid salt, NASICON as solid electrolyte using sodium nitrate as ionic conductive oxyacid salt, nitric oxide gas sensor containing Pt on the surface, NASICON as solid electrolyte The carbon dioxide gas sensor using lithium carbonate and barium carbonate as the ion conductive oxyacid salt, and the carbon dioxide gas sensor using NASICON as the solid electrolyte and sodium hydrogen carbonate as the ion conductive oxy acid salt showed good results.

<Comparative Example 3> A gold electrode or a platinum electrode is provided for a silicon schottky diode and a silicon carbide schottky diode having a rectifying barrier electrode area of 25 mm 2, and 150 ° C. for a silicon Schottky diode and 300 ° C. for a silicon carbide Schottky diode. In, the gas sensor manufactured was inserted into a measurement cell in which test gases of various concentrations were circulated in dry air, and evaluation was performed in the same manner as in Examples 5 and 6. The results are shown in Table 3 (Nos. 177 to 182).

[0086] The gas sensor of the example is different from that of the comparative example.
Excellent in response speed, sensitivity, and selectivity.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration example of a gas sensor according to an embodiment in which an ion conductive oxyacid salt is joined to a field effect transistor.

FIG. 2 is a diagram illustrating a configuration example of a gas sensor according to an embodiment in which a solid electrolyte and an ion-conductive oxyacid salt are joined to a field-effect transistor.

FIG. 3 is a diagram illustrating a configuration example of a gas sensor according to an embodiment in which an ion-conductive oxyacid salt is joined to a gate control type pn junction diode.

FIG. 4 is a diagram illustrating a configuration example of a gas sensor according to an embodiment in which a solid electrolyte and an ion-conductive oxyacid salt are joined to a gate control type pn junction diode.

FIG. 5 is a diagram illustrating a configuration example of a gas sensor according to an embodiment in which an ion conductive oxyacid salt is bonded to a silicon Schottky diode.

FIG. 6 is a diagram illustrating a configuration example of a gas sensor according to an embodiment in which a solid electrolyte and an ion conductive oxyacid salt are bonded to a silicon Schottky diode.

FIG. 7 is a diagram illustrating a configuration example of a gas sensor according to an embodiment in which an ion conductive oxyacid salt is bonded to a silicon carbide Schottky diode.

FIG. 8 is a diagram illustrating a configuration example of a gas sensor according to an embodiment in which a solid electrolyte and an ion conductive oxyacid salt are bonded to a silicon carbide Schottky diode.

FIG. 9 shows a nitrogen dioxide gas sensor in which sodium nitrite and a gold current collector are formed in a gate region of a field effect transistor in which a source region, a drain region, and a gate region are formed in a silicon semiconductor substrate, and a nitrogen dioxide gas sensor in a comparative example. FIG. 4 is a characteristic diagram of sensor sensitivity with respect to nitrogen concentration.

FIG. 10 shows a nitric oxide gas sensor in which sodium nitrate containing platinum particles and a gold current collector are formed in a gate region of a field effect transistor in which a source region, a drain region, and a gate region are formed in a silicon semiconductor substrate, and a comparative example. FIG. 4 is a characteristic diagram of a sensor sensitivity to a nitric oxide concentration in a nitric oxide gas sensor.

FIG. 11 shows a solid-state electrolyte of NASICON, a 1: 2 complex salt of sodium carbonate and barium carbonate, and a gold current collector in a gate region of a field-effect transistor in which a source region, a drain region, and a gate region are formed on a silicon semiconductor substrate. FIG. 4 is a characteristic diagram of sensor sensitivity with respect to carbon dioxide concentration of the carbon dioxide gas sensor in which is formed and the carbon dioxide gas sensor of the comparative example.

FIG. 12 shows a carbon dioxide gas sensor in which sodium hydrogen carbonate and a gold current collector are formed in a gate region of a field effect transistor in which a source region, a drain region, and a gate region are formed in a silicon semiconductor substrate, and a carbon dioxide gas sensor in a comparative example. FIG. 5 is a characteristic diagram of sensor sensitivity with respect to carbon concentration.

FIG. 13 shows a gas sensor according to the embodiment shown in FIGS.
FIG. 4 is a characteristic diagram showing a change over time in sensor sensitivity at a nitrogen monoxide gas concentration of 1 ppm in dry air and a carbon dioxide gas concentration of 1000 ppm in dry air.

[Explanation of symbols]

 2 Silicon semiconductor substrate 3 Source region 4 Source electrode 5 Drain region 6 Drain electrode 7 Gate region 8 Ionic conductive oxyacid salt 9 Current collector 10 Solid electrolyte 11 DC power supply 12 DC ammeter 13 p-type region 14 p-type electrode 15 n Type region 16 n-type electrode 17 rectifying barrier electrode 18 back electrode 19 silicon carbide semiconductor substrate

Claims (14)

[Claims] 1. A semiconductor substrate comprising: a source region, a drain region,
A gas sensor, wherein an ion-conductive oxyacid salt and a current collector are formed in a gate region of a field-effect transistor having a gate region. 2. The gas sensor according to claim 1, wherein a solid electrolyte is further formed in said gate region. 3. A gas sensor wherein an ion-conductive oxyacid salt and a current collector are formed in a gate region of a gate control type pn junction diode having a p-type region, an n-type region and a gate region formed on a semiconductor substrate. . 4. The gas sensor according to claim 3, wherein a solid electrolyte is further formed in said gate region. 5. A gas sensor, wherein an ion-conductive oxyacid salt and a current collector are formed on a rectifying barrier electrode of a Schottky diode having a rectifying barrier electrode formed on a semiconductor substrate. 6. The gas sensor according to claim 5, wherein a solid electrolyte is further formed on the rectifying barrier electrode. 7. The gas sensor according to claim 1, wherein said oxyacid salt contains metal nitrite and / or metal nitrate. 8. The method according to claim 1, wherein the metal nitrite is lithium nitrite, sodium nitrite, potassium nitrite, rubidium nitrite,
The gas sensor according to any one of claims 1 to 7, further comprising at least one of cesium nitrite, barium nitrite, and strontium nitrite. 9. The method according to claim 8, wherein the metal nitrate is lithium nitrate, sodium nitrate, potassium nitrate, rubidium nitrate, magnesium nitrate, calcium nitrate, strontium nitrate, barium nitrate, scandium nitrate, cerium nitrate, zirconium nitrate, iron nitrate, copper nitrate, cobalt nitrate The gas sensor according to any one of claims 1 to 7, further comprising at least one of tin nitrate, indium nitrate, nickel nitrate, lead nitrate, bismuth nitrate, and rare earth nitrate. 10. The method according to claim 1, wherein said oxyacid salt contains a metal carbonate and / or a metal bicarbonate.
6. The gas sensor according to any of 6. 11. The metal carbonate is lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, iron carbonate, copper carbonate, lead carbonate, nickel carbonate, Manganese carbonate, cadmium carbonate, silver carbonate,
The gas sensor according to claim 1, wherein the gas sensor contains at least one of cobalt carbonate and a rare earth carbonate. 12. The method according to claim 1, wherein said metal hydrogencarbonate contains at least one of sodium hydrogencarbonate, potassium hydrogencarbonate, rubidium hydrogencarbonate and cesium hydrogencarbonate. Gas sensor. 13. The solid electrolyte according to claim 1, wherein said solid electrolyte is a sodium ion conductor, a lithium ion conductor, a potassium ion conductor,
7. The gas sensor according to claim 2, comprising at least one of a proton conductor, an oxide ion conductor and a fluorine ion conductor. 14. The method according to claim 7, wherein the surface of said metal nitrite or metal nitrate contains platinum particles.
9. The gas sensor according to any of 9.