JP2017129537A - Field effect transistor gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a field effect device, for a gas sensor, which has a gas-sensitive layer and can be easily manufactured; and the gas sensor.SOLUTION: A field effect device 100 for a gas sensor comprises: a gate electrode 24 where gas passes therethrough; a gas absorption layer 22 which is made of an organic and/or complex material selectively absorbing the gas passing through the gate electrode; a gate insulating layer 20 which is arranged opposite to the gate electrode with respect to the gas absorption layer; a source electrode 12S and a drain electrode 12D which are arranged, with a distance therebetween, at positions opposite to the gas absorbing layer with respect to the gate insulating layer; and a semiconductor layer 10 which forms a channel between the source electrode and the drain electrode.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a field effect device for a gas sensor and a gas sensor.

Conventionally, a gas sensor using a field effect transistor (FET) has been proposed.
For example, Patent Document 1 discloses a gas sensor including a field effect transistor including a substrate including a source region, a drain region, and a gate region, and a gas-sensitive layer attached to the gate region via a porous adhesive. Is disclosed. As the gas-sensitive layer, a layer containing a crystalline metal or a nanocrystalline metal is described.
Further, Patent Document 2 is configured as a layer system that is disposed between a substrate, a gas-exposed gate electrode, a source electrode, a drain electrode, and the substrate and the gate electrode disposed on the substrate. A gas sensor is disclosed in which a constant stabilized charge is introduced into at least one layer of the layer system. Aluminum oxide, silicon oxide and the like are described as materials constituting the layer system corresponding to the gas-sensitive layer.

JP 2010-145402 A JP 2014-13239 A

The gas sensor disclosed in Patent Document 1 takes time and effort to manufacture because a gas-sensitive layer containing metal is attached to the gate electrode via a porous adhesive layer.
Since the gas sensor disclosed in Patent Document 2 is formed of a metal, a metal compound, or the like for sensing a specific gas component, the gas sensing layer needs to be formed at a high temperature or patterned by photolithography or the like. There is.
In addition, it is costly and labor-intensive to manufacture a sensor that detects a plurality of types of gases by arraying a plurality of FETs in which gas-sensitive layers are formed of materials having different components.
Furthermore, in the above prior art documents, gas detection selectivity is determined by physical adsorption of gas molecules on a layer containing a crystalline metal or a nanocrystalline metal, or a metal, a metal compound, etc., and the selectivity is greatly changed. It was difficult.

An object of the present invention is to provide a gas sensor field effect device and a gas sensor having a gas-sensitive layer that can be easily manufactured.
Furthermore, the present invention changes the gas detection selectivity, detects the gas with high selectivity, or uses a gas sensor having a plurality of different selectivity, and processes and processes the signals to identify and quantify the gas. An object of the present invention is to provide a gas sensor system capable of easily integrating a plurality of gas sensor devices having different gas selectivity.

In order to achieve the above object, the following means are provided.
<1> a gas-permeable gate electrode;
A gas adsorption layer containing an organic material and / or a complex material that selectively adsorbs the gas that has passed through the gate electrode;
A gate insulating layer disposed on the opposite side of the gas adsorption layer from the gate electrode;
A source electrode and a drain electrode that are spaced apart from each other on the opposite side of the gas adsorption layer with respect to the gate insulating layer;
A semiconductor layer forming a channel between the source electrode and the drain electrode;
A field effect device for a gas sensor.
<2> The gas adsorption layer is
As the organic material, a layer containing a polyethylene glycol, a siloxane compound, or a compound obtained by chemically modifying a polyethylene glycol or a siloxane compound with a functional functional group selected from the group consisting of a benzene ring, a proline, and a secondary amine,
As the complex material, a layer containing a metal organic structure (MOF: Metal Organic Frameworks), or
The field effect device for a gas sensor according to <1>, which is a layer in which the complex material is dispersed in the organic material.

<3> A gas sensor comprising the field-effect device for gas sensor according to <1> or <2>.
<4> The gas sensor according to <3>, including a plurality of field effect devices for the gas sensor, wherein the plurality of field effect devices for the gas sensor are different from each other in at least one of a gas adsorption characteristic and an operating temperature of the gas adsorption layer.

ADVANTAGE OF THE INVENTION According to this invention, the field effect device for sensors and gas sensor which have a gas-sensitive layer which can be manufactured easily can be provided.
Further, according to the present invention, the gas detection selectivity is changed, the gas is detected with high selectivity, or a gas sensor having a plurality of different selectivities is used to process the signals to identify and identify the gas. It is possible to provide a gas sensor system capable of easily integrating a plurality of gas sensor devices having different gas selectivities so that they can be quantified.

It is the schematic which shows an example of a structure of the field effect type device for gas sensors which concerns on embodiment of this invention. It is the schematic which shows an example of the process of forming the gas adsorption layer in the field effect device for gas sensors shown in FIG. It is the schematic which shows an example of the process of forming the gate electrode in the field effect type device for gas sensors shown in FIG. It is the schematic which shows the other structural example of the field effect device for gas sensors which concerns on embodiment of this invention. It is the schematic which shows the other structural example of the field effect device for gas sensors which concerns on embodiment of this invention. It is the schematic which shows an example of a structure of the gas sensor which concerns on embodiment of this invention. It is the schematic which shows an example of a structure of the gas sensor provided with the several field effect type device for gas sensors. It is a photographic image which shows the field effect type device for gas sensors produced in the Example. It is the schematic which shows the electric circuit evaluation system used in the Example. It is a figure which shows the time-dependent change of the output voltage in the electric circuit evaluation type | system | group shown in FIG. 9 of the gas flow in Example 1, and the field effect type device characteristic for gas sensors. It is a figure which shows the influence of temperature about the time-dependent change of the output voltage in the electric circuit evaluation system shown in FIG. 9 of the gas flow in Example 2, and the field effect type device characteristic for gas sensors.

Hereinafter, a field-effect device for a gas sensor (hereinafter sometimes referred to as “device”) and a gas sensor according to an embodiment of the present invention will be described with reference to the accompanying drawings.
In the following description, the numerical range indicated by the symbol “to” means a range including numerical values described as the lower limit value and the upper limit value on both sides of “to”. Moreover, when a unit is attached | subjected only to an upper limit or a lower limit, it means that it is the same unit over the whole numerical range.

[Field-effect device for gas sensor]
A field effect device for a gas sensor according to an embodiment of the present invention includes a gate electrode through which a gas passes, a gas adsorption layer including an organic material that selectively adsorbs the gas that has passed through the gate electrode, and the gas adsorption layer. In contrast, a gate insulating layer disposed on the opposite side of the gate electrode, a source electrode and a drain electrode disposed on the opposite side of the gas insulating layer with respect to the gate insulating layer, and the source A semiconductor layer forming a channel between the electrode and the drain electrode.

  The field-effect device for a gas sensor according to an embodiment of the present invention uses a gas adsorption layer using an organic material that selectively adsorbs components in the gas (hereinafter, may be referred to as “gas-adsorbing organic material”). Therefore, a gas adsorption layer can be formed by applying and drying a solution or dispersion containing a gas adsorbing organic material and a solvent. Therefore, for example, when manufacturing a gas sensor having an array structure in which a plurality of field effect devices for gas sensors exhibiting adsorption characteristics with respect to different components are arranged, a gas adsorbing organic material corresponding to the gas component to be detected is included. An integrated gas sensor capable of detecting a plurality of gas components can be easily manufactured by applying the coating liquid onto the gate insulating layer of each device with a dispenser or the like and drying the coating liquid.

  FIG. 1 is a schematic diagram illustrating an example of a configuration of a field effect device 100 for a gas sensor according to an embodiment of the present invention. A gas sensor field effect device 100 shown in FIG. 1 includes a gate electrode 24 through which a gas passes, a gas adsorption layer 22 containing an organic material that selectively adsorbs the gas that has passed through the gate electrode 24, and a gas adsorption layer 22. On the other hand, a gate insulating layer 20 disposed on the opposite side of the gate electrode 24, and a source electrode 12S and a drain electrode 12D disposed on the opposite side of the gas insulating layer 20 from the gate insulating layer 20 and spaced apart from each other. And a semiconductor layer 10 forming a channel between the source electrode 12S and the drain electrode 12D. Hereinafter, each structure of the field effect type device 100 for gas sensors which concerns on embodiment of this invention is demonstrated concretely.

(Gate electrode)
The gate electrode 24 is made of a conductive material and has a structure that allows gas to pass therethrough.
Examples of the conductive material constituting the gate electrode 24 include metals such as Pt, Ir, Pd, Au, Ag, Al, Cu, Cr, Mo, Ti, Pt alloy, Ir alloy, Pd alloy, Ag alloy, Cu alloy, and the like. And metal oxides such as tin oxide, zinc oxide, indium oxide, indium tin oxide, and zinc indium oxide can be used. Alternatively, a conductive polymer such as a polymer material (PEDOT / PSS) in which PSS (poly3,4-ethylenedioxythiophene) is doped with PSS (polystyrene sulfonic acid) can also be used. The gate electrode 24 may be configured by combining a plurality of materials.

  The gate electrode 24 preferably has a porous structure including through holes from the viewpoint of allowing gas to pass therethrough. For the gate electrode 24 having a porous structure, the gate electrode 24 having a porous structure may be formed at the stage of forming the gate electrode 24, or after forming the gate electrode 24, a hole penetrating in the thickness direction may be formed. You may form a porous structure by forming. The entire surface of the gate electrode 24 preferably has a porous structure. A part of the gate electrode 24 may have a porous structure. The gate electrode 24 may have elasticity.

  The thickness of the gate electrode 24 is not particularly limited, but if the thickness of the gate electrode 24 is too thin, the resistance increases, and if it is too thick, the gas permeability tends to decrease. From this viewpoint, the thickness of the gate electrode 24 is preferably 1 nm to several tens of nm.

(Gas adsorption layer)
The gas adsorption layer 22 includes an organic material (gas adsorbing organic material) that selectively adsorbs the gas that has passed through the gate electrode 24. The gas adsorbing organic material contained in the gas adsorbing layer 22 may be selected according to the polarity, solubility, affinity, hydrophilicity, hydrophobicity, molecular size, etc. of the gas to be detected. From the viewpoint of repeatedly using the gas sensor, the gas adsorbing organic material is preferably a material that selectively adsorbs (captures) one or more gases and desorbs the adsorbed gas by heating.
Further, from the viewpoint of easily forming the gas adsorbing layer 22 by a coating method, the gas adsorbing organic material is preferably a material that can be dissolved or dispersed in a solvent and formed by coating and drying. The solvent may be selected according to the gas adsorbing organic material.

  As the gas adsorbing organic material contained in the gas adsorption layer 22, for example, a siloxane compound having a siloxane bond (Si—O—Si), polyethylene glycol (PEG) can be preferably used. Although the structure of the siloxane compound and polyethylene glycol (PEG) which can comprise the gas adsorption layer 22 is shown below, it is not limited to these. In the formula, n and m represent integers.

For example, a siloxane compound is suitable for adsorption of a low polar or medium polar gas component, and PEG is suitable for adsorption of a high polar gas component.
The gas adsorbing organic material contained in the gas adsorbing layer 22 is not limited to siloxane compounds and PEG, and for example, supramolecules, peptides, etc. can be used. Further, the gas adsorbing organic material is not limited to an organic compound as long as it includes an organic material and can form the gas adsorption layer 22, and may be a material including an organic compound and a metal element. For example, the gas adsorption layer 22 may be formed using a metal organic structure in which an organic ligand is coordinated to a metal ion as a complex material. The metal organic structure is also called a porous coordination polymer (PCP).

The gas adsorbing layer 22 may be configured by using a gas adsorbing organic material exhibiting adsorbing properties for a plurality of types of gases or the complex material. The gas adsorption layer 22 may include a plurality of types of gas adsorbing organic materials, or may include a gas adsorbing organic material and an organic material that does not adsorb gas.
Further, the gas adsorption layer 22 has an organic functional material such as a benzene ring, proline, secondary amine or the like as an organic material such as a siloxane compound or polyethylene glycol as a gas adsorbing organic material in order to enhance gas adsorption selectivity. A layer containing an organic material whose group is chemically modified may be used, or a layer containing a complex material such as a metal organic structure may be used. Alternatively, it is also effective to form a layer in which the complex material is dispersed in the organic material.

  The thickness of the gas adsorption layer 22 is preferably several nm to 1 μm, for example. If the thickness of the gas adsorbing layer 22 is within the above range, formation by a coating method is easy, and gas is detected by capturing a specific gas component that has passed through the gate electrode 24 and affecting the transistor characteristics. Can do.

(Gate insulation layer)
The gate insulating layer 20 is disposed on the opposite side of the gas adsorption layer 22 from the gate electrode 24. The gate insulating layer 20 can be formed of a known material as the gate insulating layer 20 of the FET. Examples thereof include silicon oxide, tantalum oxide, hafnium oxide, aluminum oxide, silicon nitride, and silicon oxynitride.
The gate insulating layer 20 may have a single layer structure or a stacked structure of two or more layers. For example, the field effect device 100 for a gas sensor shown in FIG. 1 includes a silicon oxide film 14, a silicon nitride film 16, and a tantalum oxide film 18 as the gate insulating layer 20, and the gate insulating layer 20 includes a silicon oxide film. 14, the structure which has any one insulating film of the silicon nitride film 16 and the tantalum oxide film 18 may be sufficient, and you may comprise with another insulating material.

  The thickness of the gate insulating layer 20 is preferably about 5 nm to 500 nm, for example. If the thickness of the gate insulating layer 20 is within the above range, insulation between the source electrode 12S and the drain electrode 12D (hereinafter sometimes referred to as “source / drain electrodes 12S, 12D”) is ensured, and When gas is adsorbed to the gas adsorption layer 22, it is easy to detect by a change in current or voltage.

(Passivation layer)
In the field effect device 100 for a gas sensor illustrated in FIG. 1, for example, a passivation layer may be provided between the gas adsorption layer 22 and the gate insulating layer 20 or between the insulating layer 20 and the semiconductor layer 10. By providing the passivation layer, the semiconductor layer 10 can be protected and operational stability can be achieved.
As a material constituting the passivation layer, an insulating inorganic material such as silicon oxide or silicon nitride and a semiconductor inorganic material such as silicon carbide, or an insulating organic material such as polyimide can be used. The passivation layer may be composed of one kind of material or may be composed of two or more kinds of materials. In the gas sensor field effect device 100 shown in FIG. 1, the silicon oxide film 14 and the silicon nitride film 16 constituting the gate insulating layer 20 also serve as a passivation layer.

(Source / drain electrodes)
The source electrode 12S and the drain electrode 12D form a pair of electrodes, and are spaced apart from each other on the side opposite to the gas adsorption layer 22 with respect to the gate insulating layer 20.
The source electrode 12S and the drain electrode 12D are made of a conductive material. Specifically, the source / drain electrodes 12S and 12D can be formed of a conductive material such as a metal, a metal compound, or a conductive polymer exemplified as the material constituting the gate electrode 24.

  Further, for example, a silicon substrate may be used as the semiconductor layer 10 and a source electrode (source region) and a drain electrode (drain region) may be formed by doping. A gas sensor field effect device 100 shown in FIG. 1 uses a p-type silicon substrate serving as both a support substrate and a semiconductor layer 10, and implants (dopes) impurities into a predetermined portion of the silicon substrate to thereby form an n-type source Drain electrodes (source / drain regions) 12S and 12D are formed.

  The thickness of the source / drain electrodes 12S and 12D is, for example, 0.01 to 5 μm from the viewpoint of ease of formation and conductivity.

(Semiconductor layer)
The semiconductor layer 10 is connected to the source electrode 12S and the drain electrode 12D, and a channel is formed between the source electrode 12S and the drain electrode 12D through the semiconductor layer 10. In the device 100 shown in FIG. 1, the source electrode 12S and the drain electrode 12D are in contact with the semiconductor layer 10, but the source electrode 12S and the drain electrode 12D are connected to the semiconductor layer 10 via an ohmic contact layer (not shown). And may be electrically connected.

Examples of the semiconductor layer 10 include compound semiconductors such as silicon, germanium, GaAs, GaP, and InP, oxide semiconductors, and organic semiconductors. Silicon is preferable from the viewpoints of stability, mobility, cost, and the like. Note that an oxide semiconductor and an organic semiconductor are preferable from the viewpoint of low-temperature film formability.
As described above, a silicon substrate may be used as the semiconductor layer 10, and the source electrode (source region) 12S and the drain electrode (drain region) 12D may be formed by doping.

[Method for producing field-effect device for gas sensor]
Although the manufacturing method of the field effect device 100 for gas sensors which concerns on embodiment of this invention is not specifically limited, The field effect device 100 for gas sensors of the structure shown in FIG. 1 can be manufactured with the following method, for example.
First, source / drain electrodes (source / drain regions) 12S and 12D are formed by implanting (doping) impurities such as phosphorus and arsenic into predetermined positions of the p-type silicon substrate.
Next, as the gate insulating layer 20, a SiO ₂ film, a Si ₃ N ₄ film, and a Ta ₂ O ₅ film are sequentially formed. In addition, the device 100 marketed as ISFET (Ion-Sensitive Field Effect Transistor) can also be used for the material which has the semiconductor layer 10 structure.

  Next, the gas adsorption layer 22 is formed on the gate insulating layer 20. FIG. 2 shows an example of a method for forming the gas adsorption layer 22. A coating solution 22A in which a gas adsorbing organic material constituting the gas adsorbing layer 22 is dissolved or dispersed in a solvent is dropped onto the gate insulating layer 20 by a dispenser 30 as shown in FIG. A gas adsorption layer 22 containing an organic material can be formed.

  The method for forming the gas adsorbing layer 22 is not limited to the dispenser method. For example, the inkjet method, the dip coating method, the spray coating method, the spin coating method, the blade coating method, the casting method, the roll coating method, the bar coating method, and the die coating method. A method, a mist method, a screen printing method, a relief printing method, an intaglio printing method, an electrolytic polymerization method, an electrospinning method, and the like may be applied.

Next, a gas permeable gate electrode 24 is formed on the gas adsorption layer 22. For example, the gate electrode 24 is formed on the gas adsorption layer 22 by sputtering using a metal target constituting the gate electrode 24. At this time, if the film is formed with a thickness of 10 nm or less, for example, a porous gate electrode 24 having a gap between the metal particles attached to the gas adsorption layer 22 is formed as shown in FIG. Also gas can be contacted.
Note that the method for forming the gate electrode 24 is not limited to sputtering as long as the gate electrode having gas permeability can be formed without damaging the gas adsorption layer 22 containing an organic material. For example, the gate electrode may be formed by a wet method such as electron beam evaporation, printing, or coating.

1 is an N-channel depletion type (normally on) FET, the field-effect device 100 for gas sensor according to the embodiment of the present invention may be a P-channel. It may be an enhancement type (normally off).
1 has a configuration in which source / drain electrodes 12S and 12D are formed on a silicon substrate by doping, but is not limited to the configuration shown in FIG. 1, and a glass substrate or a resin substrate. The field effect device 100 for a gas sensor according to the embodiment of the present invention may be formed on a support substrate such as a thin film transistor (TFT). When forming the field effect device 100 for a gas sensor according to the embodiment of the present invention on a support substrate, for example, as shown in FIG. 4, the semiconductor layer 10 and the source / drain electrodes 12S are formed on the support substrate 50 such as glass. , 12D, the insulating layer 20, the gas adsorption layer 22, and the gate electrode 24 may be formed sequentially. As shown in FIG. 5, the source / drain electrodes 12S and 12D, the semiconductor layer 10, the insulating layer 10 are formed on the support substrate 50. The layer 20, the gas adsorption layer 22, and the gate electrode 24 may be sequentially formed.

[Gas sensor]
A gas sensor according to an embodiment of the present invention includes the above-described field-effect device 100 for a gas sensor. FIG. 6 schematically shows an example of the configuration of the gas sensor according to the embodiment of the present invention.
In the field effect device 100 for a gas sensor according to the embodiment of the present invention, a specific gas component contained in the gas that has passed through the gate electrode 24 is adsorbed by the gas adsorption layer 22, so that the dielectric constant of the gas adsorption layer 22, etc. The characteristic change occurs. Therefore, gas can be detected by electrically detecting a change in transistor characteristics (voltage and / or current) of the field effect device 100 for gas sensor.

  In addition, a plurality of field-effect devices 100 for gas sensors each having a gas adsorption layer 22 formed using gas adsorbing organic materials having different polarities, solubility, affinity, hydrophilicity, hydrophobicity, molecular size, etc. are arrayed, By integrating, a gas sensor capable of detecting various gases can be obtained.

  FIG. 7 shows an example of a gas sensor including a plurality of gas sensor field effect devices 100 in which at least one of the gas adsorption characteristics and the operating temperature of the gas adsorption layer 22 is different from each other. The gas sensor 300 shown in FIG. 7 has four gas sensor field effect devices 100a, 100b, 100c, and 100d each having a gas adsorbing layer made of gas adsorbing organic materials having different polarities and different gas adsorbing characteristics. A device 44 for measuring the voltage and current, a display 46, and the like are provided, and a change in transistor characteristics of each device 100 can be measured. The gas sensor field effect devices 100a, 100b, 100c, and 100d are arranged in the gas flow cell 40, and the sample gas is introduced into the gas flow cell 40 through the pipes 42A and 42B and discharged. As described above, a plurality of types of gases can be detected if the gas sensor includes a plurality of field effect devices 100 for gas sensors having different polarities of materials used for the gas adsorption layer 22.

The gas adsorbing organic material constituting the gas adsorbing layer 22 of each device 100 may adsorb a plurality of types of gas components, or the same gas component may be adsorbed even if the types of the gas adsorbing organic materials are different. However, if the type of the gas adsorbing organic material is different, the adsorption characteristics for the gas are basically different. Therefore, various gases can be detected if the change in transistor characteristics reflecting the gas adsorption characteristics of each device 100 is examined in advance for the gas component to be detected.
In addition, the device of the present invention changes the gas adsorption / desorption characteristics and the electric characteristics as an FET depending on the temperature. Each device included in the gas sensor of the present invention may be configured such that the operating temperature is different. When the operating temperature of the gas sensor is adjusted and controlled, the desorption characteristics of the adsorbed gas molecules differ depending on the types of molecules, and become an important index for molecular identification. For example, even if the plurality of devices 100 have the gas adsorption layer 22 made of the same material, if the gas sensors are operated at different temperatures, the responses of the sensors are different. By controlling and optimizing the type of gas adsorbing organic material and the operating temperature of the sensor, the accuracy of gas detection can be improved.
In addition, gas can be identified and quantified by changing the gas detection selectivity and detecting the gas with high selectivity, or by using a plurality of gas sensors having different selectivity and processing these signals. As described above, a gas sensor system in which a plurality of gas sensor devices having different gas selectivity can be easily integrated can be provided.

  The gas to be detected by the gas sensor according to the present invention is not particularly limited. For example, the present invention can be applied to detection of toxic gas indoors and outdoors, detection of alcohol contained in exhaled breath, illegal drugs, and the like. It is also conceivable to apply this method when detecting components contained in exhaled breath and diagnosing organs and the like.

  Examples of the present invention will be described below, but the present invention is not construed as being limited to the following examples.

[Example 1]
<Production of Field Effect Device 1 for Gas Sensor>
As a substrate provided with a semiconductor layer, source / drain electrodes, and an insulating layer, a research ISFET manufactured by Ice Fetcom Corp. was used. The configuration of each layer is as follows.
Semiconductor layer: p-Si
Source / drain electrodes: n-Si
Gate insulating layer: SiO ₂ , Si ₃ N ₄ , Ta ₂ O ₅

(Formation of gas adsorption layer)
On the Ta ₂ O ₅ layer, a PEG solution (solvent: pure water, PEG concentration: 0.5 mg / 1 mL) was dropped, and dried at 80 ° C. for 1 hour. As a result, a PEG layer (gas adsorption layer) was formed on the Ta ₂ O ₅ layer.

(Formation of gate electrode)
As a gate electrode, a Pt layer was formed on the gas adsorption layer by sputtering. The sputtering conditions are as follows. The thickness of the Pt layer was 6 nm.
-Sputtering conditions-
・ Target: Pt
・ Film formation pressure: chamber pressure 1Pa
・ Deposition temperature; room temperature ・ deposition atmosphere; Ar gas

  Through the above steps, a field effect device 1 for a gas sensor shown in FIG. 8 was produced.

<Evaluation>
Under the electric circuit evaluation system shown in FIG. 9, the gas sensor field effect device 1 is placed in the gas flow cell, and the gas flow field effect device 1 is turned on at about 250 ° C. while the gas sensor field effect device 1 is heated to about 60 ° C., The output voltage Vout in FIG. 9 was measured after turning OFF. Further, the electric circuit used for the operation of the gas sensor device is not limited to the electric circuit shown in FIG.
The composition and flow rate of the sample gas used are as follows. The heating of the device is to promote desorption of the adsorbed gas.
Sample gas: CH ₃ OH and N ₂ mixed gas (CH ₃ OH concentration: 543 ppm)
Flow rate: 1 L / min

FIG. 10 shows changes over time in gas flow and output voltage in Example 1. As shown in FIG. 10, when the gas flow is turned on, that is, when the sample gas is supplied into the cell, the output voltage increases. When the gas flow is turned off, that is, when the supply of the sample gas into the cell is stopped, the output voltage decreases. This phenomenon was repeated regularly and stably.
From this result, it is possible to detect the gas by detecting the change in the electrical characteristics of the device when the gas containing the CH ₃ OH and the gas adsorption layer of the device interact by using the field effect device 1 for gas sensor. Recognize.

[Example 2]
<Production of field effect device 2 for gas sensor>
An ISFET having the same configuration as in Example 1 was prepared.

(Formation of gas adsorption layer)
A siloxane compound solution (Silicon OV-73, Shinwa Kako Co., Ltd., solvent: toluene, concentration: 0.5 mg / 1 mL) having the following structure was dropped on the Ta ₂ O ₅ layer and dried at room temperature for 1 hour. . Thus, a siloxane compound layer (gas adsorption layer) on the Ta ₂ O ₅ layer was formed.

(Formation of gate electrode)
As a gate electrode, a Pt layer was formed on the gas adsorption layer by sputtering in the same manner as in Example 1.

  The field effect device 2 for gas sensor was produced through the above steps.

<Evaluation>
Under the electric circuit evaluation system of FIG. 9, the gas sensor field effect device 2 is placed in the gas flow cell, and the gas sensor field effect device 2 is heated at about 65 ° C., and the gas flow is turned ON / OFF every 250 s. The output voltage Vout was measured. Further, the electric circuit used for the operation of the gas sensor device is not limited to the electric circuit shown in FIG.
The composition and flow rate of the sample gas used are as follows. The heating of the device is to promote desorption of the adsorbed gas.
Sample gas: CH ₃ OH and N ₂ mixed gas (CH ₃ OH concentration: 543 ppm)
Flow rate: 1 L / min

  The gas flow was turned on and off in the same manner as described above while warming the field effect device 2 for gas sensor at about 70 ° C or about 75 ° C.

FIG. 11 shows changes with time in gas flow and output voltage. As shown in FIG. 11, regardless of the temperature of the device, the phenomenon that the output voltage increases when the sample gas is supplied into the cell and the output voltage decreases regularly when the supply of the sample gas into the cell is stopped. And it was repeated stably.
From this result, it can be seen that a mixed gas of CH ₃ OH and nitrogen can be detected by using the field effect device 2 for gas sensor.

DESCRIPTION OF SYMBOLS 10 Semiconductor layer 12D Drain electrode 12S Source electrode 14 Silicon oxide film 16 Silicon nitride film 18 Tantalum oxide film 20 Gate insulating layer 22 Gas adsorption layer 24 Porous gate electrode 30 Dispenser 50 Support substrate 100 Field effect type device for gas sensors

Claims (4)

A gas permeable gate electrode;
A gas adsorption layer containing an organic material and / or a complex material that selectively adsorbs the gas that has passed through the gate electrode;
A gate insulating layer disposed on the opposite side of the gas adsorption layer from the gate electrode;
A source electrode and a drain electrode that are spaced apart from each other on the opposite side of the gas adsorption layer with respect to the gate insulating layer;
A semiconductor layer forming a channel between the source electrode and the drain electrode;
A field effect device for a gas sensor. The gas adsorption layer is
As the organic material, a layer containing a polyethylene glycol, a siloxane compound, or a compound obtained by chemically modifying a polyethylene glycol or a siloxane compound with a functional functional group selected from the group consisting of a benzene ring, a proline, and a secondary amine,
As the complex material, a layer containing a metal organic structure, or
The field effect device for a gas sensor according to claim 1, which is a layer in which the complex material is dispersed in the organic material.   A gas sensor comprising the field effect device for a gas sensor according to claim 1.   The gas sensor according to claim 3, comprising a plurality of field effect devices for gas sensor, wherein the plurality of field effect devices for gas sensor are different from each other in at least one of a gas adsorption characteristic and an operating temperature of the gas adsorption layer.