JP2007163253A - Hydrogen gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrogen gas sensor which enhances the poisoning resistance of a catalyst, without having to heat a substrate, is reduced in power consumption and has high sensitivity and high-speed responsiveness. <P>SOLUTION: The hydrogen gas sensor is equipped with a pair of the electrodes 5a and 5b formed on a semiconductor substrate 1, the sensing film 8 for detecting a hydrogen gas formed on the upper part between the electrodes 5a and 5b via a gate insulating film 2 for insulating the electrodes 5a and 5b and a gate electrode 7 for applying a bias voltage to the semiconductor substrate 1, formed on the other surface of the semiconductor substrate 1 in a facing relation to the gate insulating film 2. The sensing film 8 is provided with a catalyst having action for adsorbing hydrogen gas to dissociate the same into a proton (H<SP>+</SP>) and an electron (e) and a metal oxide changing the potential of the sensing film by the reaction of the protons (H<SP>+</SP>) and the electrons (e) produced by the dissociation action. The catalyst has a particle structure that particles, smaller than the particles of the metal oxide constituting the sensing film in diameter, are dispersed and supported on the particles of the metal oxide. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a hydrogen gas detection sensor using a detection film in which a catalyst is dispersedly supported on a metal oxide, and by reaction of protons (H ⁺ ) generated by dissociating hydrogen gas with a catalyst and electrons (e), The present invention relates to a hydrogen gas detection sensor that utilizes the characteristic that metal oxides are reduced to change electrical characteristics, and in particular, containers, pipes, automobiles, fuel cells, hydrogen that require monitoring of gas leakage including hydrogen gas for safety. The present invention relates to a hydrogen gas detection sensor installed in a fuel reformer or the like.

  In recent years, from the viewpoint of protecting the global environment and preventing the depletion of fossil fuels, it is desired to use clean and recyclable energy, and hydrogen gas is attracting attention as a substitute. Hydrogen gas is a potentially abundant fuel and has the advantage of low environmental impact, but is highly explosive (explosion limit concentration is wide from 4% to 75%) and is known to be a dangerous gas. It has been. In order to spread hydrogen gas as an energy source in the future, safety measures for using the system with confidence are indispensable. Therefore, a hydrogen gas detection sensor having high-speed response, high sensitivity, and excellent reliability is desired.

  Currently, there are a catalytic combustion method, a semiconductor method, a solid electrolyte method, a light detection method, and the like as a hydrogen gas detection sensor, and a semiconductor method using a metal oxide is representative.

In a conventional semiconductor-type hydrogen gas detection sensor, for example, as shown in FIG. 10 a, a pair of electrodes 302 and 303 are provided on an insulating substrate 301, and the detection layer 304 extends over the electrodes 302 and 303. A hydrogen gas detection sensor (see, for example, Patent Document 1) in which tungsten oxide (WO ₃ ) is provided and platinum (Pt) or palladium (Pd) as the catalyst layer 305 is further formed thereon, or tungsten trioxide (WO ₃ ) a detection film comprising as a main component, an electrode disposed on the surface of the detection layer, and a catalyst layer for dissociating hydrogen gas provided on the surface of the detection film, and further heating the detection layer, A layered hydrogen gas detection sensor in which a detection layer provided with a heater and a catalyst layer are stacked in order to prevent a decrease in sensitivity due to a decrease in ambient temperature is known. (For example, see Patent Document 2.)
Further, a platinum dispersion in which a detection film in which a platinum (Pt) catalyst is dispersedly supported on tungsten trioxide (WO ₃ ) is formed on an insulating substrate, and an electrode is formed on the tungsten trioxide (WO ₃ ) with platinum (Pt). Research has been conducted on hydrogen gas detection sensors of type tungsten oxide. (For example, refer nonpatent literature 1.)
These hydrogen gas detection sensors dissociate hydrogen gas into protons (H ⁺ ) and electrons (e) by a catalyst, and protons (H ⁺ ), electrons (e) and tungsten trioxide (WO ₃ ) generated by the catalyst. As a result, tungsten bronze is formed, and the conductivity of the detection film changes accordingly, and hydrogen gas is detected by detecting the conductivity.
JP-A-60-212348 JP 2003-240746 A Nanako Yamamoto, 3 others, “Detection characteristics and optimization of room-temperature hydrogen sensor using Pt / WO3 film”, Chemical Sensors, Chemical Society of Electrochemical Society, Vol. 18, Supplement A (2002)

However, in the sensor in which the detection film and the catalyst film are laminated, when palladium (Pd) is used for the catalyst film, the shape changes irreversibly, such as cracking in the palladium (Pd) film when hydrogen exposure is repeated. However, there is a problem that sensor characteristics deteriorate. In addition, when platinum (Pt) is used for the catalyst film, platinum (Pt) has a property of strongly binding to carbon monoxide (CO). Therefore, if carbon monoxide (CO) is present in the atmospheric gas, platinum (Pt) There is a problem in that the surface of Pt) is poisoned by carbon monoxide (CO), hydrogen gas cannot be dissociated into protons (H ⁺ ) and electrons (e), and hydrogen gas cannot be detected.

  In general, the response time for detecting hydrogen gas needs to be high-speed response in order to ensure safety, but there is also a problem that the response time is very slow. A structure in which the detection film is heated to a predetermined temperature by a heater provided below the detection film has been proposed, but heating has problems in terms of safety and power consumption. The above problem is particularly serious in fuel cell vehicles.

  Furthermore, the electrical characteristics of the hydrogen gas sensor due to variations in the electrical conductivity of the sensing film itself due to the structure of the sensing film itself and the variations in the contact resistance between the sensing film and a pair of electrodes provided for measuring the electrical conductivity As a result, the responsiveness of the sensor varies, and the yield of the sensor decreases and the cost increases.

  The present invention solves the problems of the conventional hydrogen gas detection sensor, improves the poisoning resistance of the catalyst, enables high sensitivity and high-speed response with low power consumption without heating the substrate, and An object of the present invention is to provide a hydrogen gas detection sensor capable of correcting characteristic variations of the detection film.

In order to solve the conventional problems, the hydrogen gas detection sensor of the present invention is a hydrogen gas detection sensor for detecting hydrogen gas, and insulates the pair of electrodes from a pair of electrodes formed on a semiconductor substrate. A detection film for detecting hydrogen gas formed above the pair of electrodes through the gate insulating film, and a bias applied to the semiconductor substrate formed on the other surface of the semiconductor substrate so as to face the gate insulating film A gate electrode for applying a voltage, and the detection film adsorbs hydrogen gas to dissociate it into protons (H ⁺ ) and electrons (e) and a proton (H ⁺ generated by the action). ) And electrons (e) are made of a metal oxide in which the potential of the detection film changes, and the catalyst uses particles having a diameter smaller than the metal oxide particles constituting the detection film as the metal oxide particles. Disperse supported on top Out those that have been characterized by having a particulate structure.

The hydrogen gas detection sensor of the present invention is a hydrogen gas detection sensor for detecting hydrogen gas, and includes a gate electrode formed on an insulating substrate and a first gate insulation formed so as to cover the gate electrode. A film, a semiconductor film formed on the first gate insulating film, a pair of electrodes formed in contact with the semiconductor film, and a second gate insulating film that insulates the pair of electrodes A detection film for detecting hydrogen gas formed on the upper part between the pair of electrodes, and the detection film has an action of adsorbing hydrogen gas and dissociating it into protons (H ⁺ ) and electrons (e). It consists of a metal oxide in which the potential of the detection film changes due to the reaction between the catalyst and protons (H ⁺ ) and electrons (e) generated by the action, and the catalyst is made up of metal oxide particles constituting the detection film. The small particle size of the metal oxide particles Is obtained is characterized by having a particle structure of dispersed and carried on.

The hydrogen gas detection sensor of the present invention is a hydrogen gas detection sensor for detecting hydrogen gas, a gate insulating film formed on a semiconductor substrate, a pair of electrodes formed on the gate insulating film, A detection film for detecting hydrogen gas formed on the gate insulating film in contact with a pair of electrodes, and for applying a bias to the semiconductor substrate formed opposite to the gate insulating film on the other surface of the semiconductor substrate comprising a gate electrode, the sensing film, protons generated in the catalyst and the effect of having the action of dissociating the adsorbed hydrogen gas and protons (H ⁺⁾ to the electrons (e) (H ⁺⁾ and electrons (e And the catalyst has a particle structure in which particles having a diameter smaller than the metal oxide particles constituting the detection film are dispersed and supported on the metal oxide particles. Having It is obtained by the features.

The hydrogen gas detection sensor of the present invention is a hydrogen gas detection sensor for detecting hydrogen gas, a gate electrode formed on an insulating substrate, a gate insulating film formed to cover the gate electrode, A pair of electrodes formed on the gate insulating film, and a detection film that detects hydrogen gas formed on the gate insulating film in contact with the pair of electrodes, the detection film containing hydrogen gas a metal oxide adsorbed to protons (H ⁺⁾ and electrons protons generated in the catalyst and the effect it has the effect of dissociation in (e) (H ⁺⁾ and conductivity by reaction with electrons (e) increases The catalyst has a particle structure in which particles having a diameter smaller than the metal oxide particles constituting the detection film are dispersedly supported on the metal oxide particles.

According to the hydrogen gas detection sensor of the present invention, the conductivity of the semiconductor film can be controlled by applying a bias voltage from the gate electrode even if the generated potential of the hydrogen gas detection film varies. In addition, by applying a bias voltage, a hydrogen gas detection sensor with low power consumption, high sensitivity, and high speed response can be realized without heating the sensor.
Further, according to the hydrogen gas detection sensor of the present invention, the conductivity of the semiconductor film can be controlled by applying a bias voltage to the gate electrode even if the generated potential of the hydrogen gas detection film varies. By applying a bias voltage, a hydrogen gas detection sensor with low power consumption, high-speed response and high sensitivity can be realized without heating the sensor. Furthermore, by using an insulating substrate such as a quartz substrate or a ceramic substrate, an inexpensive hydrogen gas detection sensor can be provided compared to a semiconductor substrate.
Furthermore, the hydrogen gas detection sensor of the present invention is capable of correcting the conductivity variation of the hydrogen gas detection film by the voltage at the gate, and has low power consumption, high speed response and high sensitivity without heating the sensor. A gas detection sensor can be realized.
The catalyst has a particle structure in which particles having a diameter smaller than the metal oxide particles constituting the detection film are dispersed and supported on the metal oxide particles, thereby exposing the hydrogen gas detection sensor to carbon monoxide gas. However, it is possible to provide a highly sensitive detection film that does not deteriorate the sensitivity of hydrogen gas.

  Embodiments of the hydrogen gas detection sensor of the present invention will be described below in detail with reference to the drawings.

  In Example 1, the structure, material, operation principle, and manufacturing method of the hydrogen gas detection sensor of the present invention will be described, and the hydrogen gas detection sensor of the present invention will be used for resistance to poisoning, responsiveness, and the structure of the detection film. The results of evaluating the chemical state are described.

  The structure of the hydrogen gas detection sensor will be described with reference to FIG.

As shown in FIG. 1, the main components of the hydrogen gas detection sensor of the present invention are formed in contact with the gate electrode 7, the semiconductor substrate 1, the gate insulating film 2, the insulating film 3, and the semiconductor substrate 1. a pair of electrodes 4a to be, 4b, 5a, 5b and the pair of electrodes 5a, the pair of electrodes 4a 5b a through the gate insulating film 2 for insulating is formed to 4b upper finally protons (H ⁺ ) And electrons (e), a sensing film 8 made of a metal oxide whose potential changes due to a reaction between protons (H ⁺ ) and electrons (e) generated by the action, and a protective film 6. It consists of The lower electrodes 4a and 4b are low resistance doping layers provided to improve the contact resistance with the semiconductor substrate 1 electrodes 5a and 5b. The protective film 6 functions as a gas barrier layer for preventing gas adsorption and dissociation at the electrodes 5a and 5b, and also has a function of insulating the detection film 8 from the electrodes 5a and 5b.

  Next, materials and manufacturing methods for forming the hydrogen gas detection sensor will be described.

A p-type silicon semiconductor substrate 1 having a substrate thickness of 525 μm and a specific resistance of 8-12 Ωcm (100) is thermally oxidized at 1000 ° C. in an oxygen atmosphere, and a gate insulating film 2 made of a silicon oxide (SiO ₂ ) film having a thickness of 20 nm to 300 nm. Form. Subsequently, as the insulating film 3, a 200 nm-thick silicon nitride (Si ₃ N ₄ ) film serving as a mask layer for ion implantation is formed by plasma vapor phase epitaxy (P-CVD). Then, the insulating film 3 made of a silicon nitride (Si ₃ N ₄ ) film and the gate insulating film 2 made of a silicon oxide film corresponding to the source electrode 5a and drain electrode 5b portions are patterned and etched.

  Although FIG. 1 shows a structure penetrating the insulating film 3 and the gate insulating film 2 in the source electrode 5a and drain electrode 5b portions, the gate insulating film 2 is not limited to this structure, and the source electrode 5a. And the drain electrode 5b and a conductive doping layer 4a and 4b. It is desirable to form the detection film 8 so as to partially overlap the doping layers 4a and 4b. Further, it may be formed on the semiconductor substrate 1 via the gate insulating film 2 so that the detection film 8 and the source electrode 5a and the drain electrode 5b are in contact and are not electrically connected.

Thereafter, a pair of electrodes is formed. The pair of electrodes includes a low resistance doping layer and a metal electrode. Specifically, phosphorus (P) is ion-implanted at a dose of 10 ¹⁵ cm ⁻² to form n-type low resistance doping layers 4a and 4b. Next, as a metal electrode material 5a, 5b, a laminated film composed of a titanium (Ti) lower electrode having a thickness of 20 nm and an upper electrode having a thickness of 500 nm platinum (Pt) is formed by sputtering deposition, and photolithography is performed. Pattern with Further, as the protective film 6, a laminated film of a silicon nitride (Si ₃ N ₄ ) film having a thickness of 100 nm and a silicon oxide (SiO ₂ ) film having a thickness of 200 nm is formed by plasma vapor deposition (P-CVD). Form. Next, the opening of the detection film 8 is patterned using photolithography, and the silicon nitride (Si ₃ N ₄ ) film of the protective film 6 is etched.

Next, a detection film 8 for detecting hydrogen gas is formed on the upper portion between the source electrode doping layer 4a and the drain electrode doping layer 4b via the gate insulating film 2 made of a silicon oxide (SiO ₂ ) film. The detection film 8 is formed at a position partially overlapping with the source electrode doping layer 4a and the drain electrode doping layer 4b so that the potential generated by the detection film 8 is uniformly applied to the conductive channel formed between the source and drain electrodes. can do.

  Lift-off is used for pattern formation of the detection film 8. Specifically, a positive resist is applied, and the resist is removed only in a predetermined detection film 8 pattern portion. Thereafter, a sol-gel solution serving as a detection film is applied, dried in air at 80 ° C. for 10 minutes, and then the resist is removed, whereby the pattern of the detection film 8 can be formed. Thereafter, the detection film 8 is fabricated by temporarily firing the detection film under predetermined conditions and then performing main firing. The detection film 8 is not electrically connected to the electrodes 5a and 5b.

  The pattern forming method of the detection film 8 is not limited to the lift-off, and can be formed by etching.

  After the detection film 8 is baked, aluminum (Al) having a film thickness of 300 nm is deposited on the other surface of the semiconductor substrate as the gate electrode 7 for applying a bias voltage to the semiconductor substrate so as to face the gate insulating film. In FIG. 1, the source electrode drain electrode is formed so as to penetrate through the gate insulating film 2. However, the drain electrode 5 b is used as a voltage source and the source electrode 5 a is used as a current source by a lead wire in a region other than the detection portion. Connect to a meter (not shown).

FIG. 2 shows a schematic diagram of the detection film 8. Any method may be used as long as it is a formation method in which the catalyst 21 is dispersedly supported on the metal oxide 20 and can form such a structure. For example, a vapor deposition method, a dipping method, a sol-gel method, etc. can be raised. This time, the sol-gel method was used. Sodium ions (Na ⁺ ) and protons (H ⁺ ) are exchanged with a cation exchange resin in an aqueous solution of a metal salt (for example, sodium salt) as a precursor for forming a metal oxide using the sol-gel method. A sol-gel solution was prepared, and a solution in which a metal complex salt as a catalyst precursor was dissolved in pure water was added to the sol-gel solution, and dispersed and mixed uniformly to synthesize a sol-gel solution.

  As a method for applying the detection film 8, a spin coating method, a dip coating method, a dispensing method, a screen printing method, or the like can be used.

As the detection film 8, a catalyst is platinum (Pt), and a metal oxide is tungsten trioxide (WO ₃ ). First, 41.2 g of sodium tungstate dihydrate (Na ₂ WO ₄ · 2H ₂ O: Junsei Kagaku Co., Ltd.) is placed in a volumetric flask and adjusted to 250 mL with pure water. A colorless transparent sodium tungstate (Na ₂ WO ₄ ) aqueous solution of / L is obtained. Next, a cation exchange resin (Amberlite IR120B Na: Organo Co., Ltd.) is packed in a column tower, and an aqueous solution of sodium tungstate (Na ₂ WO ₄ ) is passed through to form sodium in the aqueous solution of sodium tungstate (Na ₂ WO ₄ ). Ions (Na ⁺ ) are exchanged for protons (H ⁺ ) to obtain a pale yellow tungstic acid (H ₂ WO ₄ ) aqueous solution. Furthermore, hexachloroplatinic acid (H ₂ PtCl ₆ .6H ₂ O: Wako Pure Chemical Industries, Ltd.), which is a catalytic metal, was dissolved in 13 mL of an aqueous solution of tungstic acid (H ₂ WO ₄ ) in pure water at 0.5 mol / L. 4 mL of an aqueous solution and 8 mL of ethanol (C ₂ H ₅ OH) are added and uniformly dispersed and mixed to synthesize a sol-gel solution of platinum-dispersed tungsten oxide.
The sol-gel solution is applied to the pattern portion of the detection film 8 using a spin coater. Thereafter, after drying in air at 80 ° C. for 10 minutes, the resist is removed, whereby the pattern of the detection film 8 is formed. Next, after pre-baking at 200 ° C. for 1 hour using an electric furnace, baking is further performed at a baking temperature of 350 ° C. to 500 ° C. for 5 hours in a flow state of air at 50 mL / min, and then cooled to room temperature. The coating conditions are set so that the thickness of the detection film 8 at this time is 200 nm.

  Next, the operation of the detection film will be described.

  In FIG. 2, the detection film 8 is composed of an aggregate of particulate metal oxides 20 having a particle diameter of 15 nm to 100 nm and has a gap. The gap is formed by evaporating the solvent component of water or alcohol contained in a sol-gel solution that is a synthetic material of the metal oxide 20 described later when heat treatment is performed when the detection film 8 is synthesized. The gap between the metal oxide 20 aggregates 8 is related to gas adsorption, and as the gap increases, the hydrogen gas adsorption area increases and the hydrogen gas sensitivity improves. A catalyst 21 having a particle diameter of 1 nm to 35 nm is dispersed and supported on the surface of the metal oxide 20. As shown in FIG. 2, the dispersion support means that the catalyst 21 is dispersed in the metal oxide 20 as particles, and a part of the catalyst 21 on the surface of the metal oxide 20 is the surface of the metal oxide 20. It shows the state of being adsorbed in the state where it came out.

  The catalyst 21 has a particle structure in which particles having a diameter smaller than the metal oxide particles constituting the detection film 8 are dispersed and supported on the metal oxide 20 particles.

The catalyst 21 particles adsorbed on the metal oxide 20 particles preferably have a smaller catalyst 21 particle size than the particle size of the metal oxide 20, and the catalyst 21 has an area exposed on the surface of the metal oxide 20 particles. The wider, the greater the adsorption / dissociation action of hydrogen gas, and the more proton (H ⁺ ) production occurs. In FIG. 2, the plurality of catalysts 21 are shown to exist on the surface of the metal oxide 20 particles, but the number of the catalysts 21 on the surface of the metal oxide 20 particles is not limited.

Detection film 8 is finally protons by adsorbing hydrogen gas (H ⁺⁾ and electrons protons generated by the action as a catalyst 21 having an effect of dissociation in (e) (H ⁺⁾ and electrons (e) It is formed by being dispersedly supported on the metal oxide 20 whose potential changes by the reaction, and as the material of the catalyst 21 in the detection film 8, it adsorbs hydrogen gas and dissociates into protons (H ⁺ ) and electrons (e). Any material can be used, and palladium (Pd), iridium (Ir), and platinum (Pt) can be preferably used. Further, the metal oxide 20 material in the detection film 8 may be any material as long as the potential is changed by protons (H ⁺ ) and electrons (e) dissociated by the catalyst 21. Preferably, a proton (H ⁺ ) and an electron (e) are injected to form a non-stoichiometric compound, which is a metal oxide that changes potential, molybdenum trioxide (MnO ₃ ), tungsten trioxide (WO _3). ), Titanium dioxide (TiO ₂ ), vanadium pentoxide (V ₂ O ₅ ), nickel oxide (NiO ₂ ), iridium hydroxide (Ir (OH) _n ), and the like.

The operation principle of the field effect transistor of the hydrogen gas detection sensor will be described below with reference to FIG. A semiconductor substrate 1 is generated by applying a drain voltage V _D from a power source 9b to one of the pair of electrodes 5a, and generating a predetermined gate voltage V _G and a potential ΔV of the detection film from the power source 9a to the gate electrode 7.
The change in conductivity of the conductive channel 11 is measured with an ammeter 10. The gate voltage V _G is a bias voltage, and is set to a predetermined voltage so that the rate of change in conductivity due to the potential ΔV of the detection film is increased. Therefore, the conductive channel 11 having a desired conductivity can be formed in the semiconductor substrate 1 regardless of the potential variation of the detection film 8 due to the gate voltage V _G.

Next, a mechanism for generating the potential ΔV of the detection film will be described.
In the detection film 8, hydrogen gas is dissociated and adsorbed on the catalyst particles 21 dispersedly supported on the metal oxide 20, and becomes adsorbed hydrogen atoms (H _ad ) as shown in the following equation.

H ₂ → 2H _ad
As shown in the following equation, the adsorbed hydrogen atoms diffuse from the catalyst particles 21 onto the metal oxide 20 which is the main component of the detection film 3 due to spillover, and finally protons (H ⁺ ) and electrons (e). Into the oxide 20.

H _ad → H ^{+ +} e ^{-
_{XH + + Xe - + M y}} O z → H x M y O z (M: metal)
The main component is a metal oxide of the sensing film 8 (M _y O _z) is substantially an insulator, in the atmosphere there is no hydrogen, the sensing film 8 has an electrically high resistance, the potential of the detection film 8 is a 0V, the reaction occurs in the presence of hydrogen, the non-stoichiometric compound (H _x M _y O _z) is generated for generating an electric potential.

When the metal oxide is tungsten trioxide (WO ₃ ), the potential ΔV of the detection film is about 1 V at the maximum.
Change. Accordingly, the potential ΔV of the detection film 8 generates a gate voltage between 0 V and a maximum of about 1 V in proportion to the amount of tungsten bronze generated by the hydrogen gas concentration.
On the other hand, be returned to the atmosphere there is no hydrogen gas, as shown in the following equation, non-stoichiometric compound (H _x M _y O _z) is oxidized by oxygen gas atmosphere, the metal oxide (M _y O _z) is Reproduce. As a result, the potential ΔV of the detection film 8 decreases and returns to the original 0V state. _{H x M y O z + (} X / 4) O 2 → M y O z + (X / 2) H 2 O
According to the operation principle as described above, the detection film 8 acts as the second gate electrode in accordance with the hydrogen gas contained in the atmospheric gas, and the electric conductivity of the semiconductor film conductive channel at the interface between the semiconductor film and the gate insulating film is increased. The structure that can detect hydrogen gas by measurement is not limited to the above structure.
As the gate electrode 7, a material having electrical conductivity can be used. Preferably, aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), nickel (Ni), copper (Cu), niobium (Nb), molybdenum (Mo), ruthenium ( Use metals and alloys such as Ru), rhodium (Rh), silver (Ag), tantalum (Ta), osmium (Os), iridium (Ir) platinum (Pt), gold (Au), carbon (C), etc. Is possible.
As a method for forming the metal film, a known resistance heating vapor deposition method, sputtering vapor deposition method, ion plating vapor deposition method or the like is used. Further, the chemical vapor deposition method is used for the carbon film.

If a low resistance substrate such as a silicon carbide (SiC) substrate, a diamond substrate, or a gallium nitride (GaN) substrate is used as the semiconductor substrate 1, a hydrogen gas detection sensor excellent in heat resistance can be provided.
For the upper electrodes of the electrode materials 5a and 5b, a material that is stable at about 700 ° C. or higher, which is the sintering temperature of the detection film 8, can be used. Specifically, in addition to platinum (Pt), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), nickel (Ni), copper (Cu), niobium (Nb), molybdenum (Mo), Metals and alloys such as ruthenium (Ru), rhodium (Rh), silver (Ag), tantalum (Ta), osmium (Os), iridium (Ir) platinum (Pt), and gold (Au) can be used. The lower electrodes of the electrode materials 5a and 5b are intended to improve the adhesion between the semiconductor substrate 1 and the upper metal electrode material. In addition to titanium (Ti), chromium (Cr), nickel (Ni), molybdenum (Mo ) Or an alloy film or multilayer film thereof.
The gate insulating film 2 includes a silicon nitride (Si ₃ N ₄ ) film, a silicon oxide (SiO ₂ ) film, a silicon oxynitride (SiON) film, aluminum nitride (AlN), alumina (Al ₂ O ₃ ), oxidation It is possible to use tantalum (Ta ₂ O ₅ ), zirconia oxide (ZrO ₂ ), etc., or a composite film or laminated film thereof.
As the protective film 6, a silicon nitride (Si ₃ N ₄ ) film, a silicon oxide (SiO) film, a silicon oxynitride (SiON) film, aluminum nitride (AlN), alumina (Al ₂ O ₃ ), tantalum oxide (Ta ₂₎ O ₅ ), inorganic films such as zirconia oxide (ZrO ₂ ) films, and composite films thereof, resin films such as polyimide films, epoxy films, and polyfluorinated ethylene films, or laminated films and composite films of the inorganic films and resin films. Can be used.
Next, the evaluation result of the hydrogen gas detection sensor of the present invention will be described.

Using a hydrogen gas detection sensor with a gate length L (μm) and gate width W (μm) of W / L = 500/50, drain voltage V _D (9b) is ± 1 V, 1 KHz, humidity 50%, hydrogen FIG. 3 shows the dependence of the conductivity G on the gate voltage V _G (9a) when an air dilution gas having a gas concentration of 0%, 0.5%, and 1% is introduced. The conductivity G is determined by G = (I _D L) / (V _D W) from the drain current I _D (10), the drain voltage V _D (9b), the gate length L (μm), and the gate width W (μm). Calculate from
The dependence of conductivity G on the gate voltage V _G (9a) is shown in FIG. As can be seen from FIG. 3, as the hydrogen gas concentration increases, the conductivity G vs. gate voltage V _G (9a) characteristic shifts to the negative side of the gate potential V _G (9a). Therefore, it can be seen that a positive potential is effectively generated in the detection film 8 with the hydrogen gas exposure, and the conductivity G increases.

FIG. 4 shows the dependence of the conductivity G on the hydrogen gas concentration when the drain voltage V _D (9b) is ± 1 V, 1 KHz, and the gate voltage V _G (9a) is −0.5 V, 0.5 V, 1 V. . Hydrogen gas sensitivity of the conductivity G by setting the gate voltage V _G from Figure 4 it can be seen that change. As the gate voltage V _G (9a) is increased, the conductivity G with respect to the hydrogen gas concentration increases. When the gate voltage V _G (9a) is 0.5 V, the rate of change of the conductivity G with respect to the hydrogen gas concentration is maximized. When the gate potential V _G (9a) is 1 V, the absolute value of the conductivity G with respect to the hydrogen gas concentration is large, but the rate of change of the conductivity G is small.

From the above, it can be seen that the absolute sensitivity to the hydrogen gas concentration of the hydrogen gas detection sensor and the rate of change of sensitivity can be controlled by the gate voltage V _G (9a). In addition, by using a semiconductor substrate as the substrate, it becomes easy to miniaturize the sensor, to integrate the communication function of the hydrogen gas detection sensor, the control circuit, and the like.

  Next, the evaluation results of the structure of the detection film 8 and the hydrogen gas sensitivity will be described.

FIG. 5 shows the relationship between the hydrogen gas sensitivity of the present invention and the metal oxide average particle size dependency when exposed to an air dilution gas having a hydrogen gas concentration of 1% at room temperature of 25 ° C. The drain voltage V _D is ± 1 V, 1 KHz, the gate voltage V _G is 0.5 V, and shows the hydrogen gas sensitivity calculated from the conductivity _G with and without hydrogen gas. FIG. 5 also shows the hydrogen gas sensitivity when the hydrogen gas is detected as a comparative example without the gate electrode that is a conventional sensor, that is, without bias (V _G = 0 V) when no gate voltage is applied. In the detection film 8, the main component of the catalyst is platinum (Pt), and the main component of the metal oxide is tungsten trioxide (WO ₃ or less, abbreviated as tungsten oxide). The average particle diameter of the detection film 8 is controlled by changing the firing temperature from 350 ° C. to 700 ° C. with firing conditions of 50 mL / min in air, a firing time of 5 hours. The average particle diameter of the detection film 8 formed at each firing temperature is calculated from the particle diameter frequency distribution of 100 tungsten oxide (WO ₃ ) fine particles by a scanning electron microscope (SEM). The average particle diameter of tungsten oxide (WO ₃ ) is about 10 nm at a firing temperature of 350 ° C., increases with the firing temperature, and becomes about 120 nm at a firing temperature of 700 ° C. The average particle size of the platinum (Pt) catalyst formed at each firing temperature is smaller than that of tungsten oxide as shown in FIG. 2, and the platinum (Pt) catalyst is partially supported by tungsten oxide with its surface exposed. ing.

In the comparative example of FIG. 5, the average particle diameter of tungsten oxide (WO ₃ ) 20 which is the main component of the detection film 8 having a sensitivity of 10 or more is 30 nm to 50 nm, but a gate voltage of 0.5 V is applied according to the present invention. Thus, the hydrogen gas sensitivity of the detection film having the average particle diameter is 100 or more in any of the average particle diameters from 15 nm to 80 nm, and high sensitivity of hydrogen gas can be realized.

  The setting of the gate voltage is not limited to the above 0.5 V, and may be set so as to obtain a predetermined hydrogen gas sensitivity in consideration of variations in the detection film 8.

Further, the composition ratio of the constituent atoms of the tungsten oxide (WO ₃ ) 20 and the platinum (Pt) catalyst constituting the detection film 8 according to the present invention and the chemical state of each constituent atom are X-ray photoelectron spectroscopy (hereinafter abbreviated as XPS). Use to measure. For XPS measurement, an X-ray electron spectrometer (model number AXIS-HSU) manufactured by Shimadzu is used, and MgΚα; 1253.6 eV is used as an X-ray source, and measurement conditions are 15 KV and 300 W.

FIG. 6 shows the relationship between the ratio of the number of oxygen atoms and the number of tungsten atoms, which are constituent atoms of tungsten oxide (WO ₃ ) determined by XPS, “O” / “W” hydrogen gas sensitivity.

  “O” / “W” of the detection film is 2.54 at the firing temperature of 350 ° C., and increases with the firing temperature. At a gate voltage of 0 V, the hydrogen gas sensitivity of about 10 was obtained when “O” / “W” of the detection film 8 was in the range of 2.55 to 2.60. However, by applying the gate voltage, 2.55 or more. It can be seen that a hydrogen gas sensitivity of 100 or more is obtained.

  FIG. 7 shows the relationship between the chemical state of the platinum (Pt) catalyst and the hydrogen gas sensitivity. The platinum (Pt) catalyst shows that 18% of the platinum (Pt) catalyst is in an oxidized state at a firing temperature of 350 ° C., and the oxidized state tends to increase with the firing temperature. This is thought to be because the oxidation potential of tungsten oxide serving as a base for dispersion support increases with the firing temperature, and the tungsten oxide becomes a solid acid. At a gate voltage of 0 V, the oxidation state of the platinum (Pt) catalyst of the detection film was 40% to 70%, and a hydrogen gas sensitivity of 10 or more was obtained. However, by applying a gate voltage, the hydrogen gas sensitivity increased. When the oxidation state of the platinum (Pt) catalyst is 18% or more, a hydrogen gas sensitivity of 100 or more can be obtained.

  Next, the gate voltage dependence of the hydrogen gas detection sensor response of the present invention was examined. The response time is measured using the time from the introduction of the air dilution gas having a humidity of 50% and a hydrogen gas concentration of 1% until the conductivity is stabilized.

  As can be seen from FIG. 8, the response time is shortened as the gate voltage increases, and a high-speed response of 5 seconds or less can be obtained when the gate voltage is 0.5 V or more. However, when a gate voltage is further applied, a semiconductor conductive channel is always formed, resulting in a low resistance, resulting in a decrease in hydrogen gas sensitivity. Therefore, an optimum voltage of the gate voltage exists according to the variation of the detection film 8. In practice, the gate voltage may be set in consideration of the desired hydrogen gas sensitivity and response time.

FIG. 9 shows the results of the poisoning resistance experiment of the hydrogen gas detection sensor of the present invention. As a comparative example, a detection film is formed of tungsten trioxide (WO ₃ ) that does not contain a catalyst, and then a laminated film in which platinum (Pt) is formed is used as the catalyst layer. Other than the above, the structure is the same. The drain voltage is set to ± 1 V and 1 KHz, and the gate voltage is set so that the sensitivity of hydrogen gas is maximized and the response is 5 seconds or less. Each hydrogen gas detection sensor is installed in a container kept at room temperature, 100% pure carbon monoxide gas is introduced into the container from a carbon monoxide gas cylinder, and each hydrogen gas detection sensor is exposed in the above atmosphere for 12 hours. Then, after evacuating carbon monoxide, the conductivity was measured when exposed to an air dilution gas having a hydrogen gas concentration of 1%. The vertical axis in FIG. 9 represents the rate of decrease in conductivity when exposed to a hydrogen gas concentration of 1% after being exposed to carbon monoxide, based on the output before being exposed to the carbon monoxide atmosphere. In FIG. 9, when the conventional stacked hydrogen gas detection sensor is exposed to carbon monoxide (CO), the conductivity is reduced by 80% compared to the conductivity before the exposure. The gas detection sensor shows that the drain current does not change before and after exposure. As described above, the hydrogen gas detection sensor is exposed to the carbon monoxide gas by having a particle structure in which catalyst particles having a diameter smaller than the metal oxide particles constituting the detection film are dispersedly supported on the metal oxide particles. However, it is possible to provide a hydrogen gas detection sensor having excellent poisoning resistance and no deterioration of hydrogen gas sensitivity.

Another embodiment is shown in FIG. The difference from Example 1 is that an insulating substrate is used as the substrate. Other configurations and manufacturing methods are the same as those in the first embodiment. The structure and the manufacturing method thereof will be described below with reference to FIG. A gate electrode 102 made of tantalum (Ta) with a thickness of 200 nm on a quartz substrate, which is an insulating substrate 101, and an oxide with a thickness of 20 nm to 300 nm, which is a first gate insulating film 103 formed so as to cover the gate electrode 102 Phosphorus (P) is formed so as to form an ohmic contact between a silicon (SiO ₂ ) film, a 100 nm-thick polycrystalline silicon (Si) film as the semiconductor film 104, and a pair of electrodes formed in contact with the polycrystalline silicon film. N-type low resistance doping layers 105 and 106 formed by ion implantation at a dose of 10 ¹⁵ cm ⁻² , and a film thickness of 20 nm-titanium (Ti) / film thickness of 500 nm-platinum (Pt) on both the regions. A source electrode 107 and a drain electrode 108 constituted by a pair of electrodes made of a laminated film, and the semiconductor film 1 insulating the source electrode 107 and the drain electrode 108. And the second gate insulating film 109 made of silicon oxide (SiO ₂ ) having a thickness of 20 nm to 300 nm and the second gate insulating film 109 that insulates the pair of electrodes. A detection film 110 having a thickness of 200 nm is formed on the upper part. The detection film 110 is not electrically connected to the source electrode 107 and the drain electrode 108. As the protective film 111, a silicon nitride (Si ₃ N ₄ ) film having a thickness of 200 nm is used.

  By using the insulating substrate 101 as a support, it can be formed on a large-area substrate as compared with the case of a semiconductor substrate, and an effect of cost reduction can be obtained.

  In addition, the source electrode 107 and the drain electrode 108 that constitute a pair of electrodes formed of a stacked film of 20 nm-titanium (Ti) / 500 nm-platinum (Pt) are provided between the first gate insulating film and the semiconductor 104. Even if configured, the same characteristics as the above structure can be obtained. That is, after forming the first gate insulating film 103, a stacked film of 20 nm-titanium (Ti) / 500 nm-platinum (Pt) is formed, and the source electrode 107 and the drain which are a pair of electrodes are formed by etching. The pattern of the electrode 108 is formed. Alternatively, a lift-off method can be used in which after the first gate insulating film 103 is formed, a metal stacked film that forms a pair of electrodes is formed after a pattern is formed with a resist, and the resist is removed. Thereafter, a semiconductor film 104 is formed over the pair of electrodes. The semiconductor film 104 may be formed in contact with the pair of electrodes and does not limit the shape of the semiconductor film (not shown).

The insulating substrate 101 may be any material as long as it has insulating properties. However, since the heating temperature during sintering of the detection film 110 is about 700 ° C. or higher, it needs to be a material having high heat resistance. . Preferably, quartz (SiO ₂ ), surface-insulated (eg, silicon oxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), aluminum nitride (AlN), alumina (Al ₂ O ₃ ), or these A silicon (Si) substrate, a silicon carbide (SiC) substrate, an aluminum nitride (AlN) substrate, an alumina (Al ₂ O ₃ ) substrate, a ceramic substrate, or the like on which a composite film is formed can be used.

  As the gate electrode 102, a material that is electrically conductive and is stable at a sintering temperature of the detection film 110 of about 700 ° C. or more can be used. Preferably, titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), nickel (Ni), copper (Cu), niobium (Nb), molybdenum (Mo), ruthenium (Ru), rhodium ( It is possible to use metals and alloys such as Rh), silver (Ag), tantalum (Ta), osmium (Os), iridium (Ir) platinum (Pt), and gold (Au). The electrode can be formed by a printing method or an ink jet method other than a vapor deposition method such as sputtering vapor deposition or ion plating vapor deposition.

As the first gate insulating film 103 and the second gate insulating film 109, a silicon nitride (Si ₃ N ₄ ) film, a silicon oxide (SiO) film, a silicon oxynitride (SiON) film, an aluminum nitride (AlN), Alumina (Al ₂ O ₃ ), tantalum oxide (Ta ₂ O ₅ ), zirconia oxide (ZrO ₂ ), etc., or a composite film thereof can be used. As the formation method, reactive sputter deposition, reactive ion plating deposition, chemical vapor deposition (CVD), metal organic chemical deposition (MOCVD), molecular beam epitaxy (MBE), or the like is used.

The polycrystalline silicon film of the semiconductor film 104 is formed to a thickness of 100 nm by low pressure vapor deposition (LPCVD) using a substrate temperature of 500 ° C. and hydrogen diluted disilane gas (Si ₂ H ₆ ).

As the semiconductor film 104, an amorphous silicon (α-Si) film can also be used. The amorphous silicon film can be formed by plasma vapor phase epitaxy (P-CVD) using hydrogen diluted silane gas (SiH ₄ ) at a substrate temperature of about 300 ° C.

  In order to improve ohmic contact in the source electrode 107 and drain electrode 108 regions, phosphorus (P) is ion-implanted to form an n-type doping layer. As the n-type doping source, arsenic (As) can also be used. On the other hand, the source electrode 107 and the drain electrode 108 may be formed after ion implantation of boron (B) to form the p-type doping layer. Instead of ion implantation, an n-type or p-type doped layer may be formed by plasma doping.

As an electrode material of the source electrode 107 and the drain electrode 108, titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), nickel (Ni), copper (Cu), niobium as well as platinum (Pt). Metals such as (Nb), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), silver (Ag), tantalum (Ta), osmium (Os), iridium (Ir) platinum (Pt), gold (Au) And alloys can be used. The lower electrodes of the electrode materials 107 and 108 are intended to improve the adhesion between the semiconductor film and the upper metal electrode material. In addition to titanium (Ti), chromium (Cr), nickel (Ni), molybdenum (Mo) Alternatively, these alloy films or multilayer films can be used.
As the protective film 111, a silicon nitride (Si ₃ N ₄ ) film, a silicon oxide (SiO) film, a silicon oxynitride (SiON) film, aluminum nitride (AlN), alumina (Al ₂ O ₃ ), tantalum oxide (Ta ₂₎ O ₅ ), inorganic films such as zirconia oxide (ZrO ₂ ) films, and composite films thereof, resin films such as polyimide films, epoxy films, and polyfluorinated ethylene films, or laminated films and composite films of the inorganic films and resin films. Can be used.
By using an insulating substrate as compared with Example 1, a hydrogen gas detection sensor can be realized at a lower cost than a semiconductor substrate. Similar to the case of the first embodiment, tungsten bronze is formed on the detection film 110 according to the hydrogen gas concentration to generate a potential. Since the conductivity of the conductive channel formed at the interface between the semiconductor film 104 and the second gate insulating film 109 changes depending on the potential generated by the hydrogen gas concentration, the hydrogen gas concentration can be measured. As in the first embodiment, the absolute sensitivity to the hydrogen gas concentration and the rate of change in sensitivity can be controlled by the gate electrode 102. Moreover, the poisoning resistance with respect to carbon monoxide gas is also confirmed by the detection film | membrane of this invention.

  That is, the potential generated in the detection film 110 when hydrogen gas is detected acts on the conductive channel formed between the doping layers 105 and 106 below the interface between the semiconductor film 104 and the second gate insulating film 109. Since the conductivity is changed, the hydrogen gas concentration can be measured.

  Another embodiment is shown in FIG. The difference from the first and second embodiments is that the detection film 206 is electrically connected to a source electrode and a drain electrode, which are a pair of electrodes, and functions as a current source. That is, a conductive channel is formed in the detection film itself according to the hydrogen gas concentration.

A p-type silicon (Si) semiconductor substrate 201 having a specific resistance of 8-12 Ωcm (100), a gate insulating film 202 made of a silicon oxide (SiO ₂ ) film having a thickness of 300 nm formed on the semiconductor substrate by a thermal oxidation method, A pair of electrodes 203 and 204 are formed of a laminated film of a lower electrode made of titanium (Ti) with a thickness of 20 nm and an upper electrode made of platinum (Pt) with a thickness of 500 nm formed on the gate insulating film 202. The drain electrode and the source electrode are formed on the lower electrode for obtaining good conductivity with the gate insulating film 202, and any one of 203 and 204 may be used as the drain electrode or the source electrode in terms of structure. The detection film 206 is formed on the gate insulating film 202 while being in contact with each of a pair of electrodes including a drain electrode and a source electrode. The detection portion of the hydrogen gas is adsorbed hydrogen gas finally protons (H ⁺⁾ and protons generated in the action as a catalyst 21 having an action to dissociate the electrons (e) (H ⁺⁾ and electrons (e ) And a protective film 205 formed by dispersing and supporting the metal oxide 20 whose conductivity is increased by the reaction. The detection film 206 is electrically connected to the source electrode and the drain electrode.

  For the gate electrode 207, a material that is electrically conductive and is stable at about 700 ° C. or higher, which is the sintering temperature of the detection film 208, can be used. Preferably, titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), nickel (Ni), copper (Cu), niobium (Nb), molybdenum (Mo), ruthenium (Ru), rhodium ( Metals and alloys such as Rh), silver (Ag), tantalum (Ta), osmium (Os), iridium (Ir) platinum (Pt), and gold (Au) can be used. If the detection film is fired, a low-melting-point metal such as aluminum (Al) can be used after the natural oxide film of the semiconductor silicon substrate is etched as the gate electrode 207 and then vacuum deposition or sputter deposition is used.

An n-type silicon (Si) semiconductor substrate can be used instead of the p-type silicon (Si) semiconductor constituting the gate electrode.
In addition to the silicon oxide (SiO ₂ ) film, the gate insulating film 202 includes a silicon nitride (Si ₃ N ₄ ) film, a silicon oxynitride (SiON) film, aluminum nitride (AlN), alumina (Al ₂ O ₃ ), tantalum oxide ( Ta ₂ O ₅ ), zirconia oxide (ZrO ₂ ), or the like, or a composite film or a laminated film thereof can be used. As the formation method, reactive sputter deposition, reactive ion plating deposition, chemical vapor deposition (CVD), metal organic chemical deposition (MOCVD), molecular beam epitaxy (MBE), or the like is used.

As a material of the upper electrode 204 of the source electrode and the drain electrode, in addition to platinum (Pt), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), nickel (Ni), copper (Cu), Niobium (Nb), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), silver (Ag), tantalum (Ta), osmium (Os), iridium (Ir) platinum (Pt), gold (Au), etc. Metals and alloys can be used. The lower electrode 203 is for the purpose of improving the adhesion between the semiconductor substrate 201 and the upper metal electrode 204. In addition to titanium (Ti), chromium (Cr), nickel (Ni), molybdenum (Mo), or these Alloy film or multilayer film can be used.
Detection film 206, by reacting the adsorbed hydrogen gas and protons (H ⁺⁾ and electrons protons generated in the catalyst and the effect it has the effect of dissociation in (e) (H ⁺⁾ and electrons (e) As will be described later, the catalyst particles are dispersed and supported on a metal oxide whose conductivity increases (or changes) depending on the hydrogen gas concentration. As shown in FIG. It is composed of an aggregate of 15 to 100 nm particulate metal oxide 20 and has a gap. The gap is formed by evaporating the solvent components of water and alcohol contained in a sol-gel solution that is a synthetic material of the metal oxide 20 described later when heat treatment is performed during the synthesis of the detection film 206. The gaps between the aggregates of the metal oxides 20 are related to gas adsorption, and as the gaps increase, the hydrogen gas adsorption area increases and the hydrogen gas sensitivity improves. A catalyst 21 having a particle diameter of 1 nm to 35 nm is dispersed and supported on the surface of the metal oxide 20. As shown in FIG. 2, the dispersion support means that the catalyst 21 is dispersed in the metal oxide 20 as particles, and a part of the catalyst 21 on the surface of the metal oxide 20 is the surface of the metal oxide 20. It shows the state of being adsorbed in the state where it came out.

  The catalyst 21 has a particle structure in which particles having a diameter smaller than the metal oxide particles constituting the detection film 206 are dispersed and supported on the metal oxide 20 particles.

The catalyst 21 particles adsorbed on the metal oxide 20 particles preferably have a smaller catalyst 21 particle diameter than the metal oxide 20 particle diameter. The catalyst 21 is exposed on the surface of the metal oxide 20 particles. The wider, the greater the adsorption / dissociation action of hydrogen gas, and the more proton (H ⁺ ) production. In FIG. 2, the plurality of catalysts 21 are shown to exist on the surface of the metal oxide 20 particles, but the number of the catalysts 21 on the surface of the metal oxide 20 particles is not limited.

The catalyst 21 material in the detection film 206 may be any material that adsorbs hydrogen gas and dissociates into protons (H ⁺ ) and electrons (e), and preferably palladium (Pd), iridium (Ir), platinum ( Pt) can be used. The metal oxide 20 material in the detection film 206 may be any material as long as the conductivity is increased by protons (H ⁺ ) and electrons (e) dissociated by the catalyst 21. Preferably, by injecting protons (H ⁺ ) and electrons (e), a non-stoichiometric compound is formed, and molybdenum trioxide (MnO ₃ ) or tungsten trioxide (WO ₃ ), titanium dioxide (TiO ₂ ), vanadium pentoxide (V ₂ O ₅ ), nickel oxide (NiO ₂ ), iridium hydroxide (Ir (OH) _n ), and the like can be used.

As the protective film 205, a silicon nitride (Si ₃ N ₄ ) film, a silicon oxide (SiO) film, a silicon oxynitride (SiON) film, aluminum nitride (AlN), alumina (Al ₂ O ₃ ), tantalum oxide (Ta ₂₎ O ₅ ), inorganic films such as zirconia oxide (ZrO ₂ ) films, and composite films thereof, resin films such as polyimide films, epoxy films, and polyfluorinated ethylene films, or laminated films and composite films of the inorganic films and resin films. Can be used. As the protective film, a material having low gas permeability is desirable. As for the method of forming the inorganic film, reactive sputtering deposition, reactive ion plating deposition, chemical vapor deposition (CVD), metal organic chemical deposition (MOCVD), molecular beam epitaxy are used as in the gate insulating film. (MBE) or the like is used. As a method for forming the resin film, a pattern can be formed using a coating process such as a spin coating method, a dip coating method, a dispensing method, a screen printing method, and photolithography.

  The operation principle of the hydrogen gas detection sensor of the present invention will be described.

As an operation principle, when hydrogen gas is present in the atmospheric gas, first, the hydrogen gas is dissociated and adsorbed on the catalyst 21 particles, and becomes an adsorbed hydrogen atom (H _ad ) as shown in the following equation.

H ₂ → 2H _ad
As shown in the following equation, the adsorbed hydrogen atoms diffuse from the catalyst 21 particles onto the metal oxide 20 which is the main component of the detection film 206 by spillover, and finally protons (H ⁺ ) and electrons (e). Into the oxide 20.

H _ad → H ^{+ +} e ^{-
_{XH + + Xe - + M y}} O z → H x M y O z (M: metal)
The main component metal oxide which is a detection film 206 (M _y O _z) 20 is substantially an insulator, in the atmosphere there is no hydrogen, detection film 206 has an electrically high resistance. The reaction takes place in the presence of hydrogen, non-stoichiometric compound is a good conductor (H _x M _y O _z) is produced.

On the other hand, Returning to the atmosphere there is no hydrogen, as shown in the following equation, non-stoichiometric compound with oxygen gas in the atmosphere (H _x M _y O _z) is oxidized, a metal oxide (M _y O _z) is Reproduce. Along with this, the electric conductivity of the detection film 206 is lowered and returns to the original insulating state.

_{H x M y O z + (} X / 4) O 2 → M y O z + (X / 2) H 2 O
Based on the operation principle as described above, the sensing film 206 acts as a current source according to the hydrogen gas contained in the atmospheric gas, and the electrical conductivity of the sensing film conductive channel at the interface between the sensing film 206 and the gate insulating film 202 is measured. By doing so, it becomes possible to detect hydrogen gas.

If the electric conductivity of the detection film 206 varies, a proton accumulation layer (or a layer formed on the detection film 206 at the interface between the gate insulating film 202 and the detection film 206 is applied by applying a desired potential to the gate electrode 207 (or Since the electron storage layer can be controlled, variations in the electrical conductivity of the sensing film 206 can be corrected.
The experimental results of the hydrogen gas detection sensor in the present invention are shown below.

Similarly to Example 1, the detection film 206 is a detection film in which the main component of the catalyst is platinum (Pt) and the main component of the metal oxide is tungsten trioxide (WO ₃ or less, abbreviated as tungsten oxide). Use. The average particle size of the detection film 206 is controlled by changing the firing temperature from 350 ° C. to 700 ° C. with firing conditions of 50 mL / min in air, a firing time of 5 hours.

  FIG. 12 shows the dependence of the conductivity G on the gate voltage VG when exposed to an air dilution gas having a humidity of 50% and a hydrogen gas concentration of 0%, 0.5%, and 1%. Unlike Example 1, the conductivity G increases with the gate voltage almost symmetrically with respect to the gate voltage.

FIG. 13 shows the dependence of the conductivity on the hydrogen gas concentration. In FIG. 13, the gate voltage is plotted as a parameter. FIG. 13 shows that the conductivity at the time of hydrogen gas exposure increases with the gate voltage. When the gate voltage is 0.5 V, the change of the conductivity with respect to the hydrogen gas concentration becomes maximum, and when the gate voltage is further increased, the conductivity increases, but the change rate of the conductivity with respect to the hydrogen gas concentration is small. Therefore, according to the present invention, it can be seen that the gate voltage can be adjusted so that the sensitivity of the hydrogen gas detection sensor and the rate of change in sensitivity are maximized. The inventor considers the reason why the conductivity of the detection film increases as follows. That is, in the structure of the present invention, proton (H ⁺ ) and electron (e) can be separated according to the polarity of the bias applied to the gate electrode, so that the probability of proton (H ⁺ ) and electron (e) coupling can be reduced, Their life expectancy becomes longer, and as a result, low resistance (high conductivity) of the sensing film can be realized. Therefore, high sensitivity and high speed can be achieved with low power consumption without heating the sensing film.
Moreover, the effect of the gate voltage of the average particle diameter of the metal oxide constituting the detection film of the hydrogen gas detection sensor according to the present invention is also the same as in Example 1 by applying a desired gate voltage, so that the sensitivity of hydrogen gas is high. It is confirmed that can be realized.

Further, as for the oxidation state of the catalyst particles of the detection film, the hydrogen gas sensitivity tends to increase as the oxidation number increases as in Example 1, and the main component of the detection film catalyst is platinum (Pt), In the case where the main component of the metal oxide is a detection film made of tungsten trioxide (WO ₃ or less, abbreviated as tungsten oxide), the hydrogen gas sensitivity is 100 when platinum is oxidized by 18% or more at a predetermined gate voltage. The above is obtained.

  From the structure of the detection film of the present invention, it has been confirmed that it has poisoning resistance to carbon monoxide gas as in Examples 1 and 2.

  Another embodiment is shown in FIG. The present embodiment is a current source type hydrogen gas detection sensor that is theoretically the same as the third embodiment. Compared to the third embodiment, an insulating substrate is used as the substrate. Other configurations and manufacturing methods are the same as those in the third embodiment.

The structure and the manufacturing method thereof will be described below with reference to FIG. A gate electrode 302 made of tantalum (Ta) having a thickness of 200 nm on a quartz substrate which is an insulating substrate 301, and a gate insulating film made of a silicon oxide (SiO ₂ ) film having a thickness of 300 nm formed so as to cover the gate electrode 302 A source electrode constituting a pair of electrodes 303, a lower electrode 304 made of titanium (Ti) with a thickness of 20 nm formed in contact with the gate insulating film 303, and an upper electrode 305 made of platinum (Pt) with a thickness of 500 nm A 200 nm-thickness detection film 308 formed on the gate insulating film 303 and a 200 nm-thickness silicon nitride (Si ₃ N ₄ ) film protection film 306 in contact with the pair of electrodes. Become.

Further, after forming the gate insulating film 303, a detection film 307 is formed so as to overlap the gate electrode 302. After pattern formation, a lower electrode 304 made of titanium (Ti) with a thickness of 20 nm and platinum (Pt with a thickness of 500 nm) are formed. A source electrode and a drain electrode that constitute a pair of electrodes may be formed by the upper electrode 305 made of (not shown). In this structure, when a metal active against hydrogen gas, such as platinum, palladium, or iridium, is used, a protective film that covers the metal electrode and serves as a hydrogen gas barrier layer is required. The protective film is preferably a silicon nitride (Si ₃ N ₄ ) film having a thickness of 200 nm.

The insulating substrate 301 may be made of any material as long as it has insulating properties. However, since the heating temperature during sintering of the detection film 308 is about 700 ° C. or higher, the insulating substrate 301 needs to be a material having high heat resistance. . Preferably, quartz (SiO ₂ ), surface-insulated (eg, silicon oxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), aluminum nitride (AlN), alumina (Al ₂ O ₃ ), or these A silicon (Si) substrate, a silicon carbide (SiC) substrate, an aluminum nitride (AlN) substrate, an alumina (Al ₂ O ₃ ) substrate, a ceramic substrate, or the like on which a composite film is formed can be used.

  As the gate electrode 302, a material that has electrical conductivity and is stable at about 700 ° C. or higher, which is the sintering temperature of the detection film 307, can be used. Preferably, titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), nickel (Ni), copper (Cu), niobium (Nb), molybdenum (Mo), ruthenium (Ru), rhodium ( Rh), silver (Ag), tantalum (Ta), osmium (Os), iridium (Ir) platinum (Pt), gold (Au), and other metals and alloys can be used. The electrode can be formed by a printing method or an ink jet method other than a vapor deposition method such as sputtering vapor deposition or ion plating vapor deposition.

As the gate insulating film 303, a silicon oxide (SiO ₂ ) film, a silicon nitride (Si ₃ N ₄ ) film, a silicon oxynitride (SiON) film, aluminum nitride (AlN), alumina (Al ₂ O ₃ ), tantalum oxide ( Ta ₂ O ₅ ), zirconia oxide (ZrO ₂ ), or the like, or a composite film thereof can be used. As the formation method, reactive sputter deposition, reactive ion plating deposition, chemical vapor deposition (CVD), metal organic chemical deposition (MOCVD), molecular beam epitaxy (MBE), or the like is used.

As the material of the upper electrode 305 of the source electrode and the drain electrode, in addition to platinum (Pt), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), nickel (Ni), copper (Cu), Niobium (Nb), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), silver (Ag), tantalum (Ta), osmium (Os), iridium (Ir) platinum (Pt), gold (Au), etc. Metals and alloys can be used. The lower electrode 304 is intended to improve the adhesion between the gate insulating film 303 and the upper metal electrode material. In addition to titanium (Ti), chromium (Cr), nickel (Ni), molybdenum (Mo), or these Alloy film or multilayer film can be used.
As the protective film 306, silicon nitride (Si ₃ N ₄ ) film, silicon oxide (SiO) film, silicon oxynitride (SiON) film, aluminum nitride (AlN), alumina (Al ₂ O ₃ ), tantalum oxide (Ta ₂₎ O ₅ ), inorganic films such as zirconia oxide (ZrO ₂ ) films, and composite films thereof, resin films such as polyimide films, epoxy films, and polyfluorinated ethylene films, or laminated films and composite films of the inorganic films and resin films. Can be used. As the protective film, a material having low gas permeability is desirable. As for the method of forming the inorganic film, reactive sputtering deposition, reactive ion plating deposition, chemical vapor deposition (CVD), metal organic chemical deposition (MOCVD), molecular beam epitaxy are used as in the gate insulating film. (MBE) or the like is used. As a method for forming the resin film, a pattern can be formed using a coating process such as a spin coating method, a dip coating method, a dispensing method, a screen printing method, and photolithography.

  By using an insulating substrate compared to Example 3, a hydrogen gas detection sensor can be realized at a lower cost than a semiconductor substrate. As in the case of the third embodiment, electrons and protons are injected into the metal oxide of the detection film 307 according to the hydrogen gas concentration to form a non-stoichiometric compound, and the conductivity of the detection film 307 increases. In particular, when a gate voltage is applied by the gate electrode 302, the conductive channel is formed at the interface of the detection film 307 on the gate insulating film 303 side, and the conductive channel can be controlled by the gate voltage. Therefore, the hydrogen gas detection sensor having desired characteristics can be provided by adjusting the gate voltage in consideration of the sensitivity of the hydrogen gas detection sensor and the rate of change in sensitivity. Moreover, the poisoning resistance to carbon monoxide gas was confirmed by the detection film of the present invention as in Examples 1, 2, and 3.

  Any of the hydrogen gas detection sensors of the present invention is useful as a hydrogen gas detection sensor capable of stably detecting leakage of hydrogen gas at low cost, low power consumption, high sensitivity, and high speed under any environment.

  In the hydrogen gas detection sensor of the present invention, a comparative hydrogen gas detection sensor provided with at least a plurality of hydrogen gas detection sensors on the same substrate, and provided with a gas barrier layer that does not expose one of the detection films to the gas, On the other hand, a hydrogen gas detection sensor free from manufacturing variations and environmental variations can be provided by relatively comparing the outputs with the measurement hydrogen gas detection sensor exposed to the gas.

  Further, the sensing membrane is composed of a conductive fine fiber structure, the catalyst of the present invention, and the catalyst is an aggregate supported on a metal oxide that forms a non-stoichiometric compound having a diameter larger than the particle diameter of the catalyst, A hydrogen gas detection sensor with higher sensitivity and faster response can be provided by dispersing and supporting the aggregate on the conductive fine fiber structure.

  Further, since the hydrogen gas detection sensor of the present invention uses protons or electrons, hydrogen sulfide gas (H2S), ammonia (NH3), flammable gases such as nitrogen monoxide (NO), carbon monoxide (CO). It can be used for a gas detection sensor, a volatile organic mixed gas sensor with hydrogen gas desorption, and a radical sensor.

  By providing a heater in the hydrogen gas detection sensor of the present invention, it is possible to finely adjust the hydrogen gas sensitivity and responsiveness by adjusting the substrate temperature and the gate voltage. It goes without saying that power consumption can be reduced compared to a structure without a date electrode structure.

The figure which shows the structure of the hydrogen gas detection sensor in Example 1 of this invention. The figure which shows typically the structure of the detection film | membrane of the hydrogen gas detection sensor in Example 1 of this invention. The figure for demonstrating the gate voltage dependence of the electrical conductivity of the hydrogen gas detection sensor in Example 1 of this invention The figure which shows the relationship with the hydrogen gas concentration of the electrical conductivity of the hydrogen gas detection sensor in Example 1 of this invention. The figure which shows the average particle diameter dependence of the detection film tungsten trioxide of the hydrogen gas sensitivity in Example 1 of this invention The figure which shows the number of oxygen atoms and tungsten atom number ratio dependence of the detection film tungsten trioxide of the hydrogen gas sensitivity in Example 1 of this invention The figure which shows the oxidation state dependence of the platinum in a platinum metal catalyst as a catalyst metal contained in the surface of the detection film tungsten trioxide of the hydrogen gas sensitivity in Example 1 of this invention The figure which shows the gate voltage dependence of the hydrogen gas detection sensor responsiveness in Example 1 of this invention The figure for demonstrating the poisoning resistance of the hydrogen gas detection sensor in Example 1 of this invention The figure which shows the structure of the hydrogen gas detection sensor in Example 2 of this invention. The figure which shows the structure of the hydrogen gas detection sensor in Example 3 of this invention. The figure which shows the gate voltage dependence of the hydrogen gas detection sensor in Example 3 of this invention. The figure which shows the hydrogen gas concentration dependence of the electrical conductivity of the hydrogen gas detection sensor in Example 3 of this invention The figure which shows the structure of the hydrogen gas detection sensor in Example 4 of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Gate insulating film 3 Insulating film 4a Low resistance doping layer 4b Low resistance doping layer 5a Electrode 5b Electrode 6 Protective film 7 Gate electrode 8 Detection film 9a Power supply 9b Power supply 10 Ammeter 11 Conductive channel 20 Metal oxide 21 Catalyst 101 Insulating substrate 102 Gate electrode 103 Gate insulating film 104 Semiconductor film 105 Low resistance doping layer 106 Low resistance doping layer 107 Electrode 108 Electrode 109 Gate insulating film 110 Detection film 111 Protection film 201 Semiconductor substrate 202 Gate insulation film 203 Electrode 204 Electrode 205 Protection Film 206 Sensing film 207 Gate electrode 301 Insulating substrate 302 Gate electrode 303 Gate insulating film 304 Electrode 305 Electrode 306 Protective film 307 Sensing film

Claims (10)

A hydrogen gas detection sensor for detecting hydrogen gas,
A pair of electrodes formed on a semiconductor substrate;
A detection film for detecting hydrogen gas formed above the pair of electrodes via a gate insulating film that insulates the pair of electrodes;
A gate electrode for applying a bias voltage to the semiconductor substrate formed on the other surface of the semiconductor substrate facing the gate insulating film;
With
The sensing membrane, detection film by the reaction of the adsorbed hydrogen gas and protons (H ⁺⁾ and electrons protons generated in the catalyst and the effect it has the effect of dissociation in (e) (H ⁺⁾ and electrons (e) Consisting of a metal oxide whose potential changes
The hydrogen gas detection sensor, wherein the catalyst has a particle structure in which particles having a diameter smaller than the metal oxide particles constituting the detection film are dispersedly supported on the metal oxide particles. A hydrogen gas detection sensor for detecting hydrogen gas,
A gate electrode formed on an insulating substrate;
A first gate insulating film formed to cover the gate electrode;
A semiconductor film formed on the first gate insulating film;
A pair of electrodes formed in contact with the semiconductor film;
A detection film for detecting hydrogen gas formed above the pair of electrodes through a second gate insulating film that insulates the pair of electrodes;
With
The sensing membrane, detection film by the reaction of the adsorbed hydrogen gas and protons (H ⁺⁾ and electrons protons generated in the catalyst and the effect it has the effect of dissociation in (e) (H ⁺⁾ and electrons (e) Consisting of a metal oxide whose potential changes
The hydrogen gas detection sensor, wherein the catalyst has a particle structure in which particles having a diameter smaller than the metal oxide particles constituting the detection film are dispersedly supported on the metal oxide particles. A hydrogen gas detection sensor for detecting hydrogen gas,
A gate insulating film formed on a semiconductor substrate;
A pair of electrodes formed on the gate insulating film;
A detection film for detecting hydrogen gas formed on the gate insulating film in contact with the pair of electrodes;
A gate electrode for applying a bias to the semiconductor substrate formed on the other surface of the semiconductor substrate so as to face the gate insulating film,
The sensing film, the conductivity by the reaction of the adsorbed hydrogen gas and protons (H ⁺⁾ and electrons protons generated in the catalyst and the effect it has the effect of dissociation in (e) (H ⁺⁾ and electrons (e) Consisting of increasing metal oxides,
The hydrogen gas detection sensor, wherein the catalyst has a particle structure in which particles having a diameter smaller than the metal oxide particles constituting the detection film are dispersedly supported on the metal oxide particles. A hydrogen gas detection sensor for detecting hydrogen gas,
A gate electrode formed on an insulating substrate;
A gate insulating film formed to cover the gate electrode;
A pair of electrodes formed on the gate insulating film;
A detection film for detecting hydrogen gas formed on the gate insulating film in contact with the pair of electrodes;
With
The sensing film, the conductivity by the reaction of the adsorbed hydrogen gas and protons (H ⁺⁾ and electrons protons generated in the catalyst and the effect it has the effect of dissociation in (e) (H ⁺⁾ and electrons (e) Consisting of increasing metal oxides,
The hydrogen gas detection sensor, wherein the catalyst has a particle structure in which particles having a diameter smaller than the metal oxide particles constituting the detection film are dispersedly supported on the metal oxide particles. The claim according to any one of claims 1 to 4, wherein the metal oxide is composed of an aggregate of crystal fine particles and has a particle structure in which an oxidized catalyst is dispersedly supported on the metal oxide. The hydrogen gas detection sensor according to item. The detection film has a particle structure in which the average particle diameter of the catalyst is 2 nm to 35 nm,
6. The hydrogen gas detection sensor according to claim 5, wherein the catalyst particles have a structure in which the particles are dispersed and supported on metal oxide particles having an average particle diameter of 15 nm to 80 nm. The hydrogen gas detection sensor according to claim 5, wherein 18% or more of the total amount of the catalyst contained in the metal oxide is in an oxidized state. The catalyst is one of palladium (Pd), iridium (Ir), and platinum (Pt), or a mixture containing at least one of these. 5. The hydrogen gas detection sensor according to 5. The main components of the metal oxide are molybdenum trioxide (MoO ₃ ), tungsten trioxide (WO ₃ ), titanium dioxide (TiO ₂ ), iridium hydroxide (Ir (OH) _n ), vanadium pentoxide (V 2 O 5), The hydrogen gas detection sensor according to claim 5, wherein the hydrogen gas detection sensor is made of any one of nickel oxide (NiO ₂ ). In the detection film, the main component of the catalyst is platinum (Pt),
The hydrogen gas detection sensor according to claim 5, wherein a main component of the metal oxide is tungsten trioxide (WO ₃ ).

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