JP2008209390A - Gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas sensor capable of preventing a gas detecting layer from peeling, of electrically connecting the gas detection layer to a detecting electrode via an insulating close contact layer therebetween, and of satisfactorily detecting concentration change in a specific gas. <P>SOLUTION: The close contact layer 7 is formed between the gas detecting layer 4 and a substrate 15 constituted of a silicon substrate 2 and insulating film layers 3, 230, the degree of adhesion is improved, and peeling is prevented. This close contact layer 7 is made of an insulating metal oxide and will not affect the characteristics of the gas detection layer 4. The whole surface 61 of the detecting electrode 6, facing the gas detection layer 4, is in contact with the gas detection layer 4, thereby electrically connecting the gas detection layer 4 to the detecting electrode 6; and consequently, the electrical characteristics of the gas detection layer 4 which change, in response to the concentration change in the specified gas, can be detected satisfactorily. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a gas sensor having a gas detection layer mainly composed of a metal oxide semiconductor.

Conventionally, a precious metal such as platinum (Pt) is supported as a catalyst on a metal oxide semiconductor such as tin oxide (SnO ₂ ), and the electrical characteristics (for example, resistance value) change depending on the gas to be detected. Gas sensors that detect changes in the concentration of a gas to be detected are known. In the gas detection layer of such a gas sensor, the precious metal was dispersed on the surface of the metal oxide semiconductor by impregnating the metal oxide semiconductor powder in the solution containing the precious metal element in the manufacturing process and then firing. It is carried in a state (see, for example, Patent Document 1).

  By the way, when a gas detection layer in which a basic metal oxide is supported as a catalyst on a metal oxide semiconductor is used, high gas sensitivity can be obtained against various odors (especially bad odors) that may be caused by hydrogen sulfide or mercaptans. It is known to show (see, for example, Patent Document 2). However, the basic metal oxide has a high electric resistance value. When the basic metal oxide is supported on each metal oxide semiconductor powder as a catalyst as in Patent Document 1, the electric resistance value of the gas detection layer itself is high. Thus, the circuit design of the gas sensor becomes difficult. Therefore, if a basic metal oxide is supported on the surface of the sintered body (gas detection layer) after sintering the gas detection layer made of metal oxide semiconductor powder, the electrical resistance value of the gas detection layer increases. Can be suppressed (see, for example, Patent Document 3).

On the other hand, the gas detection layer of such a gas sensor does not react with the gas to be detected at room temperature, and is activated by being heated to, for example, 200 to 400 ° C. and reacts with the gas to be detected. Generally, a heating resistor is provided in a substrate such as a semiconductor substrate to be formed. However, when the gas sensor is driven at a high temperature using the heating resistor, there is a possibility that separation at the interface may occur due to a difference in thermal expansion between the gas detection layer and the substrate. Further, in such a gas sensor, in order to obtain high reliability, it is naturally required to increase the mechanical adhesion strength between the gas detection layer and the substrate. Various proposals have been made to form an adhesion layer between the gas detection layer and the substrate. For example, a hafnium oxide layer is formed between a platinum (Pt) heater, which is a thin film resistor, and an underlying insulating film to reduce thermal expansion (see, for example, Patent Document 4) or on a substrate. The surface of the electrode layer is made uneven to increase the surface area of the electrode layer, and between the electrode layer and the gas detection layer, a conductive functionally graded material with a slight change in the material composition of both is intermediate A gas sensor that relaxes the thermal expansion coefficient by using it as a layer has been proposed (see, for example, Patent Document 5).
JP-A 63-279150 Japanese Patent Publication No. 6-27719 Japanese Patent Publication No. 5-51096 JP 2001-91486 A Japanese Patent Laid-Open No. 9-33470

  However, the thermal sensor proposed in Patent Document 4 is effective for improving the adhesion between thin films having a large contact area, but is not effective because the contact area between the thick gas detection layer and the substrate is small. Further, in the gas sensor proposed in Patent Document 5, the adhesion between the base and the gas detection layer is ensured by forming the surface of the electrode layer with irregularities and providing a conductive intermediate layer on the electrode layer. However, because the gas reaction of the gas to be detected occurs at the interface between the detection electrode and the gas detection layer, a conductive intermediate layer having a composition different from that of the gas detection layer is formed between the electrode layer and the gas detection layer. If so, there is a concern of adversely affecting gas sensitivity.

  The present invention has been made to solve the above-described problems, and prevents adhesion of a gas detection layer from a substrate using an adhesion layer, and changes in the concentration of a specific gas without adversely affecting gas sensitivity. An object of the present invention is to provide a gas sensor that detects well.

In order to solve the above problems, a gas sensor according to a first aspect of the present invention is a metal oxide semiconductor that is formed on a substrate and whose electrical characteristics change according to a change in concentration of a specific gas in a gas to be detected. In the gas sensor having a gas detection layer as a component, on the substrate, an insulating adhesion layer that is in contact with the gas detection layer and a detection electrode for detecting a change in electrical characteristics in the gas detection layer are provided. The entire surface of the detection electrode facing the gas detection layer is in contact with the gas detection layer.

  According to a second aspect of the present invention, in addition to the configuration of the first aspect of the invention, the surface of the detection electrode facing the base is in contact with the base.

  According to a third aspect of the present invention, in addition to the configuration of the first aspect of the invention, the gas detection sensor is provided between the adhesion layer and the gas detection layer, and the adhesion of the detection electrode. The surface on the side facing the layer is in contact with the adhesion layer.

According to a fourth aspect of the present invention, there is provided a gas sensor comprising a metal oxide semiconductor as a main component, wherein the gas sensor is formed on a substrate and changes in electrical characteristics in accordance with a change in concentration of a specific gas in a gas to be detected. In the gas sensor having a layer, the substrate includes an insulating adhesion layer that contacts the gas detection layer and a detection electrode that detects a change in electrical characteristics of the gas detection layer , and the detection electrode includes the adhesion electrode A first layer formed between the detection electrode and the gas detection layer; and a surface of the detection electrode facing the adhesion layer. The surface on the side facing the gas detection layer of the detection electrode has a second uneven surface, and the entire surface is in contact with the gas detection layer.

  According to a fifth aspect of the present invention, there is provided a gas sensor according to any one of the first to fourth aspects, wherein the gas detection layer and the adhesion layer are formed from the gas detection layer side formed on the substrate. The projected area when the contact surface is projected is 50% of the projected area when the contact surface between the gas detection layer, the adhesion layer, and the detection electrode is projected from the gas detection layer formed on the substrate. It is characterized by occupying the above.

According to a sixth aspect of the present invention, in the gas sensor according to the sixth aspect of the invention, in addition to the configuration of the first aspect of the invention, the base includes a semiconductor substrate having an opening formed in a plate thickness direction, and the semiconductor substrate. An insulating layer formed on the insulating layer having a partition wall at a portion corresponding to the opening; a heating resistor formed on the partition wall of the insulating layer; and the insulating layer so as to cover the heating resistor The detection electrode, the adhesion layer, and the gas detection layer are formed on the protective layer of the substrate.
According to a seventh aspect of the present invention, in addition to the configuration of the first aspect of the present invention, the detection electrode is a pair of electrodes, and the adhesion layer is the pair of detection electrodes. It is formed in the area | region between.

  In a gas sensor having a gas detection layer mainly composed of a metal oxide semiconductor, a gas reaction occurring at the interface between the detection electrode and the gas detection layer has a relatively large effect on the gas detection. (In other words, it is preferable to adopt a configuration in which no gas is active). On the other hand, if an adhesion layer made of an insulating material is formed on the substrate including the surface of the detection electrode, it becomes impossible to ensure electrical connection between the gas detection layer and the detection electrode. Therefore, in the gas sensor of the invention according to claim 1, the adhesion layer affects the electron conduction of the gas detection layer while the entire surface of the detection electrode facing the gas detection layer is in contact with the gas detection layer. It is made up of no insulating material. As a result, it is possible to obtain an effect that does not exist in the prior art, such that good gas sensitivity to a specific gas can be obtained while effectively improving the adhesion between the substrate and the gas detection layer. In addition, according to the gas sensor of the present invention, it is possible to sufficiently detect the concentration change of the specific gas even if the current flowing through the gas detection layer or the magnitude of the applied voltage is reduced. It is also possible to obtain a secondary effect.

  Further, according to the gas sensor of the invention according to claim 2, since the detection electrode has a configuration that contacts both the base and the gas detection layer, the detection electrode does not cover the adhesion layer. They are formed on the same surface. Accordingly, the detection electrode is provided so as to cover the adhesion layer, and the formation amount of the adhesion layer is reduced as compared with the case where the gas detection layer is formed so as to be in contact with the detection electrode. The effects of the invention can be obtained.

  According to the gas sensor of the invention of claim 3, in addition to the effect of the invention of claim 1, since the surface of the detection electrode on the substrate side is in contact with the adhesion layer, the gas detection layer and the substrate Not only the adhesion but also the adhesion between the detection electrode and the substrate can be ensured.

  According to the gas sensor of the invention according to claim 4, since the surface of the detection electrode on the substrate side is in contact with the adhesion layer, not only the adhesion between the gas detection layer and the substrate but also the detection electrode and the substrate. Adhesion can also be ensured. The adhesion layer is made of an insulating material that does not affect the electron conduction of the gas detection layer while the entire surface of the detection electrode facing the gas detection layer is in contact with the gas detection layer. As a result, it is possible to obtain an effect that does not exist in the prior art, such that good gas sensitivity to a specific gas can be obtained while effectively improving the adhesion between the substrate and the gas detection layer. Furthermore, a second uneven surface is provided on the side of the detection electrode facing the gas detection layer, and the surface on the side facing the detection electrode included in the gas detection layer is an uneven surface of the second uneven surface included in the detection electrode. It has a concavo-convex shape (concave surface) that fits together. For this reason, the contact area is increased as compared with the case where the surface where the detection electrode and the gas detection layer contact is flat, and the adhesion between the detection electrode and the gas detection layer is achieved by the anchor effect of the second uneven surface. Can be further improved. Further, the surface of the detection electrode on the substrate side has an uneven shape (uneven surface) that fits with the unevenness of the first uneven surface provided in the adhesion layer. And since the detection electrode is in contact with the first concavo-convex surface of the adhesion layer on the concavo-convex surface, not only the adhesion between the gas detection layer and the substrate, but also the detection electrode and the substrate, due to the anchor effect of the first concavo-convex surface. Can also be secured. In addition, according to the gas sensor of the present invention, it is possible to sufficiently detect the concentration change of the specific gas even if the current flowing through the gas detection layer or the magnitude of the applied voltage is reduced. It is also possible to obtain a secondary effect.

  According to the gas sensor of the invention of claim 5, in addition to the effect of the invention of any of claims 1 to 4, the projected area of the contact surface between the gas detection layer and the adhesion layer (hereinafter referred to as “first” "Projected area") occupies 50% or more of the projected area (hereinafter referred to as "second projected area") of the contact surface between the gas detection layer, the adhesion layer, and the detection electrode. The first projected area has a positive correlation with the contact area between the gas detection layer and the adhesion layer that is difficult to measure. Similarly, the second projected area has a positive correlation with the contact area between the gas detection layer, the adhesion layer, and the detection electrode that are difficult to measure. Therefore, with the above configuration, the adhesion between the base and the gas detection layer can be obtained more reliably. Further, since the first projected area occupies 50% or more of the second projected area, the projected area of the contact surface between the gas detection layer and the sensing electrode in the second projected area (hereinafter referred to as “third projected area”). )) Will be suppressed. The third projected area has a positive correlation with the contact area between the gas detection layer and the detection electrode, which is difficult to measure. That is, according to the configuration of the present invention, the contact area between the detection electrode acting as a catalyst and the gas detection layer is suppressed. For this reason, it is difficult for the detection electrode to detect a change in the electrical characteristics of the gas detection layer due to a miscellaneous gas other than the specific gas in the gas to be detected, and the change in the concentration of the specific gas can be detected well. Effects can be obtained. The second projected area is a projected area obtained by projecting the contact surface between the gas detection layer and the adhesion layer and the contact surface between the gas detection layer and the detection electrode from the side of the gas detection layer formed on the substrate. Therefore, the sum of the first projected area and the third projected area is the second projected area.

  According to the gas sensor of the invention according to claim 6, in addition to the effect of the invention according to any one of claims 1 to 5, the gas detection layer is formed on the protective layer so as to face the heating resistor. Since this heating resistor is formed at a position corresponding to the opening formed in the semiconductor substrate, the gas detection layer can be efficiently heated and activated, and the concentration change of the specific gas can be improved more effectively. Can be detected.

  Hereinafter, an embodiment of a gas sensor embodying the present invention will be described with reference to the drawings. First, the structure of the gas sensor 1 will be described with reference to FIGS. FIG. 1 is a plan view of the gas sensor 1, and FIG. 2 is a cross-sectional view in the arrow direction of the gas sensor 1 along the line AA shown in FIG. 1. 3 is a plan view of the heating resistor 5 provided in the gas sensor 1, and FIG. 4 is a cross-sectional view in the direction of the arrow of the gas sensor 1 along the line BB shown in FIG. FIG. 5 is a cross-sectional view in the arrow direction of the gas sensor 1 along the line CC shown in FIG. In FIG. 2, the vertical direction is referred to as the vertical direction, and in FIGS. 1 to 5, the horizontal direction is referred to as the horizontal direction.

As shown in FIG. 1, the gas sensor 1 is a gas sensor having a rectangular planar shape with a length of 2.6 mm and a width of 2 mm. As shown in FIG. 2, an insulating coating layer 3 is formed on the upper surface of the silicon substrate 2. The insulating coating layer 3 has a structure in which the heating resistor 5 is included and the adhesion layer 7 and the gas detection layer 4 are formed on the upper surface thereof. The gas detection layer 4 has a property that its own resistance value changes depending on the specific gas in the gas to be detected. Here, in the present gas sensor 1, the gas detection layer 4 is provided by containing 0.2% by weight of calcium oxide as a catalyst in tin dioxide, and the ammonia ( To detect specific gases such as NH ₃ ), hydrogen sulfide (H ₂ S), methyl disulfide ((CH ₃ ) ₂ S ₂ ), methyl mercaptan (CH ₃ SH), trimethylamine ((CH ₃ ) ₃ N) It is configured. The “detection” in the present invention is intended to include not only detecting the presence or absence of a specific gas contained in the gas to be detected, but also detecting a change in the concentration of the specific gas. The silicon substrate 2 corresponds to the “semiconductor substrate” in the present invention, and the silicon substrate 2, the insulating coating layer 3, and the insulating coating layer 230 correspond to the “base” in the present invention. Hereinafter, each member which comprises the gas sensor 1 is explained in full detail.

  The silicon substrate 2 is a silicon flat plate having a predetermined thickness. Further, as shown in FIG. 2, the silicon substrate 2 and a part of the insulating coating layer 230 are removed from the lower surface of the silicon substrate 2 to form an opening 21 in which a part of the insulating layer 31 is exposed as a partition wall 39. ing. That is, in the gas sensor 1, the silicon substrate 2 having the opening 21, the insulating coating layer 3, and the insulating coating layer 230 form the base body 15 having a diaphragm structure. The opening 21 is formed so that the position of the partition wall 39 is a position where the heating resistor 5 embedded in the insulating layers 33 and 34 is disposed when viewed from the opening side of the opening 21. ing.

The insulating coating layer 3 is composed of insulating layers 31, 32, 33, 34 and a protective layer 35 formed on the upper surface of the silicon substrate 2. The insulating layer 31 formed on the upper surface of the silicon substrate 2 is a silicon oxide (SiO ₂ ) film having a predetermined thickness, and a part of the lower surface of the insulating layer 31 is exposed to the opening 21 of the silicon substrate 2. ing. The insulating layer 32 formed on the upper surface of the insulating layer 31 is a silicon nitride (Si ₃ N ₄ ) film having a predetermined thickness. The insulating layer 33 formed on the upper surface of the insulating layer 32 has a predetermined thickness. This is a silicon oxide (SiO ₂ ) film having a thickness of An insulating layer 34 is formed on the upper surface of the insulating layer 33 in addition to a heating resistor 5 to be described later and a lead portion 12 for energizing the heating resistor 5. The insulating layer 34 is a silicon oxide (SiO ₂ ) film having a predetermined thickness. A protective layer 35 made of a silicon nitride (Si ₃ N ₄ ) film having a predetermined thickness is formed on the upper surface of the insulating layer 34. The protective layer 35 plays a role of preventing contamination and damage by being disposed so as to cover a heating resistor 5 described later and a lead portion 12 for energizing the heating resistor 5.

The insulating layer 231 formed on the lower surface of the silicon substrate 2 is a silicon oxide (SiO ₂ ) film having a predetermined thickness, and the insulating layer 232 formed on the lower surface of the insulating layer 231 is nitrided having a predetermined thickness. It is a silicon (Si ₃ N ₄ ) film. The insulating layers 231 and 232 constitute an insulating coating layer 230 provided on the lower surface of the silicon substrate 2.

  As shown in FIGS. 2 and 3, the heating resistor 5 is a portion corresponding to the upper part of the opening 21 of the silicon substrate 2, and has a spiral shape in plan view between the insulating layer 33 and the insulating layer 34. Is formed. Further, a lead portion 12 is embedded between the insulating layer 33 and the insulating layer 34 to be connected to the heating resistor 5 and to energize the heating resistor 5. As shown in FIG. A heating resistor contact portion 9 for connecting to an external circuit is formed at the end of the portion 12. The heating resistor 5 and the lead part 12 have a two-layer structure composed of a platinum (Pt) layer and a tantalum (Ta) layer. The heating resistor contact portion 9 has a structure in which a contact pad 92 made of gold (Au) is formed on the surface of the extraction electrode 91 formed of a platinum (Pt) layer and a tantalum (Ta) layer. . A pair of heating resistor contact portions 9 is provided in the gas sensor 1.

  On the upper surface of the protective layer 35, the detection electrode 6 and the lead portion 10 (see FIG. 4) for energizing the detection electrode 6 so as to be positioned on the heating resistor 5 are respectively in parallel with the silicon substrate 2. It is formed on a plane. Like the lead electrode 91 of the heating resistor contact portion 9, the detection electrode 6 and the lead portion 10 are composed of a tantalum (Ta) layer formed on the protective layer 35 and platinum (Pt) formed on the surface thereof. ) Layer. Further, as shown in FIG. 4, a contact pad 11 made of gold (Au) is formed on the surface of the end of the lead portion 10, and is configured as an oxide semiconductor contact portion 8 for connecting to an external circuit. ing. In addition, as shown in FIGS. 1 and 4, a pair of oxide semiconductor contact portions 8 is provided in the gas sensor 1.

  As shown in FIG. 5, the detection electrode 6 has a comb-like planar shape and is a pair of electrodes for detecting changes in electrical characteristics in the gas detection layer 4. As shown in FIG. 2, the surface 61 of the detection electrode 6 facing the gas detection layer 4 is entirely in contact with the gas detection layer 4, and the gas detection layer 4 and the detection electrode 6 are electrically connected. Yes. Thus, since the gas detection layer 4 and the surface 61 of the detection electrode 6 are in full contact with each other, the gas reaction at the interface between the gas detection layer 4 and the detection electrode 6 is inhibited by other members including the adhesion layer 7. It will not be done. Moreover, since the gas detection layer 4 is heated quickly and satisfactorily by being heated by the heating resistor 5, the gas sensitivity of the gas sensor 1 can be increased also from this viewpoint. On the other hand, the surface 62 of the detection electrode 6 facing the protective layer 35 is in contact with the protective layer 35. The adhesion between the base 15 and the gas detection layer 4 is improved around the detection electrode 6 and excluding the surface 61 of the detection electrode 6, and the gas detection layer 4 is peeled off from the base 15. An adhesion layer 7 for preventing is provided.

  The adhesion layer 7 is a layer for improving the adhesion between the substrate 15 and the gas detection layer 4 and has a structure in which a plurality of particles made of an insulating metal oxide are aggregated. Therefore, the adhesion layer 7 has an irregular surface on its surface, and the adhesion between the base 15 and the gas detection layer 4 formed in a thick film is enhanced by the anchor effect of the irregular surface. The adhesion layer 7 can be obtained, for example, by applying a sol solution in which insulating metal oxide particles are dispersed, baking, and solidifying.

  The adhesion layer 7 is formed in a region between the pair of detection electrodes 6 formed in a comb-teeth shape as shown in the cross-sectional view shown in FIG. On the other hand, as shown in the longitudinal sectional view of FIG. 2, the adhesion layer 7 is not formed between the detection electrode 6 and the gas detection layer 4, and the surface of the detection electrode 6 facing the gas detection layer 4. 61 has a configuration in which the entire surface is in contact with the gas detection layer 4. With such a configuration, the adhesion between the substrate 15 and the gas detection layer 4 is improved without affecting the gas reaction occurring at the interface between the detection electrode 6 and the gas detection layer 4. Further, when the gas detection layer 4 is peeled off, the gas detection layer 4 is often peeled off from the end portion of the gas detection layer 4. Since they are in contact with each other, peeling from the end of the gas detection layer 4 can also be prevented.

Further, the adhesion layer 7 is made of an insulating metal oxide such as alumina (Al ₂ O ₃ ) or silica (SiO ₂ ) so as not to affect the gas reaction occurring at the interface between the detection electrode 6 and the gas detection layer 4. It is composed of things. In order to improve the adhesion between the detection electrode 6 and the gas detection layer 4, the thickness of the adhesion layer 7 is preferably smaller than the thickness of the detection electrode 6. With such a configuration, the thickness of the adhesion layer 7 can be reduced, and the surface 61 of the detection electrode 6 on the side facing the gas detection layer 4 is surely covered with respect to the upper surface of the adhesion layer 7. Therefore, the entire surface 61 can be reliably brought into contact with the gas detection layer 4.

[Example 1]
The gas sensor 1 having the above structure was produced according to the following manufacturing process. In addition, the intermediate body of the gas sensor 1 in the middle of manufacture is called a board | substrate. The numbers in parentheses attached to the process names used in the description of each process indicate the execution order of the processes. For example, “(1) cleaning the silicon substrate 2” is the process performed first. It shows that there is.

(1) Cleaning of the silicon substrate 2 First, the silicon substrate 2 having a thickness of 400 μm was immersed in a cleaning solution and subjected to a cleaning process.

(2) Formation of insulating layers 31 and 231 The silicon substrate 2 is placed in a heat treatment furnace, and the insulating layers 31 and 231 made of a silicon oxide (SiO ₂ ) film having a thickness of 100 nm are formed on the silicon substrate 2 by thermal oxidation. It formed on both surfaces (upper surface and lower surface).

(3) Formation of Insulating Layers 32, 232 Next, a silicon nitride film (Si ₃ N ₄ ) having a thickness of 200 nm using dichlorosilane (SiH ₂ Cl ₂ ) and ammonia (NH ₃ ) as source gases by LP-CVD. Insulating layers 32 and 232 made of films were formed on the surfaces of the insulating layers 31 and 231, respectively.

(4) Formation of Insulating Layer 33 Next, silicon oxide (SiO ₂ ) having a thickness of 100 nm on the surface of the insulating layer 32 using tetraethoxysilane (TEOS) and oxygen (O ₂ ) as a source gas by plasma CVD. An insulating layer 33 made of a film was formed.

(5) Formation of heating resistor 5 and lead portion 12 Thereafter, using a DC sputtering apparatus, a tantalum (Ta) layer having a thickness of 20 nm is formed on the surface of the insulating layer 33, and platinum having a thickness of 220 nm is formed on the layer. A (Pt) layer was formed. After sputtering, the resist was patterned by photolithography, and the pattern of the heating resistor 5 and the lead portion 12 was formed by wet etching.

(6) Formation of Insulating Layer 34 Then, similarly to (4), tetraethoxysilane (TEOS) and oxygen (O ₂ ) are used as a source gas by plasma CVD, and the insulating layer 33, the heating resistor 5 and the lead portion 12 are formed. An insulating layer 34 made of a silicon oxide (SiO ₂ ) film having a thickness of 100 nm was formed on the surface of the substrate. Thus, the heating resistor 5 and the lead portion 12 were embedded in the insulating layer 34 having a thickness of 200 nm.

(7) Formation of Protective Layer 35 Further, similarly to (3), dichlorosilane (SiH ₂ Cl ₂ ) and ammonia (NH ₃ ) are used as source gases by LP-CVD, and the thickness is increased on the upper surface of the insulating layer 34. A protective layer 35 made of a 200 nm silicon nitride (Si ₃ N ₄ ) film was formed.

(8) Formation of Opening of Heating Resistor Contact Part 9 Next, a resist pattern is formed by photolithography, and the protective layer 35 and the insulating layer 34 are etched by a dry etching method to form the heating resistor contact part 9 A hole was made in the lead hole to expose a part of the end of the lead portion 12.

(9) Formation of detection electrode 6, lead portion 10 and extraction electrode 91 Next, using a DC sputtering apparatus, a tantalum (Ta) layer having a thickness of 20 nm is formed on the surface of the protective layer 35, and further on the surface. A platinum (Pt) layer having a thickness of 40 nm was formed. After sputtering, the resist was patterned by photolithography, and the patterns of the comb-like detection electrode 6, the lead portion 10, and the extraction electrode 91 were formed by wet etching.

(10) Formation of Adhesion Layer 7 A sol solution layer that becomes the adhesion layer 7 after firing was formed on the protective layer 35 between and around the comb-shaped detection electrodes 6. The sol solution layer is prepared by preparing a sol solution containing alumina particles having a particle diameter in the range of 10 nm to 20 nm to a predetermined viscosity, applying the sol solution on the protective layer 35 using an ink jet method, and drying the solution. Was formed.

(11) Formation of contact pads 11 and 92 Then, using a DC sputtering apparatus, a gold (Au) layer having a thickness of 400 nm was formed on the electrode-side surface of the substrate on which the electrode part was fabricated. After sputtering, resist was patterned by photolithography, and contact pads 11 and 92 were formed by wet etching.

(12) Formation of opening 21 Next, a resist was patterned by photolithography, and an insulating film serving as a mask was formed by dry etching. Then, the substrate is immersed in a tetramethylammonium hydroxide (TMAH) solution and anisotropic etching of the silicon substrate 2 is performed, so that the lower surface is opened and the insulating layer 31 corresponding to the arrangement position of the heating resistor 5 is formed. The opening 21 was formed so that the portion to be the partition wall 39 was exposed.

(13) Formation of gas detection layer 4 Further, an oxide semiconductor paste mainly composed of tin oxide and added with calcium oxide is applied on the surface of the sol solution layer and the detection electrode 6 by thick film printing, and the thickness is 30 μm. A paste layer was formed. Note that the oxide semiconductor paste was manufactured by the following procedure. First, tin chloride (SnCl ₂ ) was added to pure water and sufficiently stirred and dissolved, and then ammonia water was added dropwise to precipitate tin hydroxide. Thereafter, the precipitated powder was washed several times with pure water to remove ammonium ions and chlorine ions and dried. After drying, the precipitated powder and calcium hydroxide (Ca (OH) ₂ ) were dispersed in pure water, sufficiently stirred, and then dried. At this time, the amount of calcium hydroxide added was 0.2% by weight in terms of calcium oxide (CaO). After drying, it was calcined at 800 ° C. for 5 hours, and 5 g of the obtained powder was pulverized for 1 hour with a raking machine. Then, the organic solvent was mixed and pulverized for 4 hours with a roughing machine (or a pot mill). Further, a binder and a viscosity adjusting agent were added and pulverized for 4 hours to prepare a paste having a viscosity of 140 Pa · s at 25 ° C.

(14) Substrate firing The substrate was inserted into a heat treatment furnace and fired at 650 ° C. for 1 hour to obtain a substrate on which the adhesion layer 7 and the gas detection layer 4 were formed.

(15) Cutting the substrate The substrate was cut using a dicing saw to obtain a gas sensor 1 having a size of 2.6 mm × 2 mm in plan view.

  Next, in order to confirm the effect of the present invention by producing the gas sensor 1 according to the above manufacturing process, the following two types of evaluation and verification were performed.

[Evaluation 1]
As a comparative example, a gas sensor having the same configuration except for the material of the adhesion layer 7 of the gas sensor 1 is manufactured and specified as the gas sensor 1 in which the adhesion layer 7 is configured using insulating alumina (Al ₂ O ₃ ) particles. The gas sensitivity to the gas component was evaluated. The adhesion layer of this comparative example was made of tin oxide (SnO ₂ ), which is an oxide semiconductor constituting the main component of the gas detection layer 4, and did not contain calcium oxide as a catalyst.

The procedure of the evaluation test is as follows. First, a mixed gas of oxygen and nitrogen (N ₂ ) with a temperature of 25 ° C., a relative humidity of 40% RH, and an oxygen (O ₂ ) amount of 20.9% by volume is used as a base gas. The base gas resistance value (Rair) of the gas sensor was measured. The temperature of the heating resistor 5 during this measurement was controlled to be 350 ° C. Then, after measuring the base gas resistance value, 5 ppm of ammonia (NH ₃ ) as a specific gas component to be detected was mixed in the base gas, and after 5 seconds, the electric resistance value (Rgas) of each gas sensor was measured. Then, a ratio (Rgas / Rair) between the base gas resistance value and the measured electric resistance value was calculated and used as gas sensitivity.

  The result of the evaluation 1 performed as described above is shown in FIG. FIG. 6 is a bar graph showing the result of evaluation 1. As shown in FIG. 6, the gas sensitivity of both gas sensors showed a value of less than 0.95, which is considered to have no practical problem, but the gas sensitivity of the gas sensor 1 of the present example is 0.67. Compared with the gas sensitivity of 0.94 in the comparative example, it was confirmed that the gas sensitivity was remarkable. As described above, the gas sensitivity is better in the example made of the insulating metal oxide than in the comparative example in which the adhesion layer is made of the substance that reacts with the specific gas component contained in the gas to be detected. From this, it was suggested that the material of the adhesion layer has a relatively large influence on the gas detection by the reaction occurring at the interface between the detection electrode and the gas detection layer.

[Evaluation 2]
Subsequently, the characteristic with respect to miscellaneous gases other than the specific gas component in the gas sensor 1 of Example 1 was evaluated. The procedure of this evaluation test is as follows. First, similarly to the above evaluation 1, the base gas resistance value (Rair) of the gas sensor 1 in the base gas atmosphere was measured. Then, after measuring the base gas resistance value, 1 ppm of nitrogen dioxide oxide (NO ₂ ) as a miscellaneous gas is mixed in the base gas instead of ammonia as the specific gas component, and after 10 seconds, the electric resistance value (Rgas ′) of the gas sensor 1 is mixed. ) Was measured. Then, a ratio (Rgas' / Rair) between the base gas resistance value and the measured electric resistance value was calculated, and this was defined as the miscellaneous gas characteristic. This miscellaneous gas characteristic is an index indicating that the detection accuracy with respect to the change in the concentration of the specific gas component decreases as the value of the ratio (Rgas ′ / Rair) increases. The miscellaneous gas characteristics are considered to be practically preferably 1.9 or less, particularly preferably 1.5 or less.

As a result of various examinations by the inventors through experiments, it has been newly confirmed that reducing the ratio of the contact area between the detection electrode 6 acting as a catalyst and the gas detection layer 4 is effective in suppressing this miscellaneous gas characteristic. It was done. Specifically, securing the first projected area of 50% or more of the second projected area and reducing the ratio of the contact area between the gas detection layer and the detection electrode may be effective in suppressing miscellaneous gas characteristics. The experimental results suggested it. For example, when the gas sensor 1 is manufactured such that the first projected area is 150,000 μm ² , the second projected area is 250,000 μm ² , and the first projected area occupies 60% of the second projected area, its miscellaneous gas characteristics Was 1.33. The ratio 1.33 indicating the miscellaneous gas characteristics is a value smaller than 1.5, which is particularly preferable in practice, and it was confirmed that the miscellaneous gas characteristics can be satisfactorily suppressed. The upper limit of the ratio of the first projected area to the second projected area is appropriately set to a value less than 100% based on whether or not the minimum concentration change of the specific gas to be detected by the gas sensor can be measured. Is done.

Here, in order to secure 50% or more of the first projected area of the second projected area, the conditions in the manufacturing process of the gas sensor 1 may be set as follows. Hereinafter, the conditions of the manufacturing process will be described by taking as an example the case where the first projected area occupies 60% of the second projected area in Evaluation 2. In “(9) Formation of the detection electrode 6, the lead portion 10, and the extraction electrode 91”, a projection area (third projection area) when the pair of detection electrodes 6 is projected from the gas detection layer 4 side formed on the substrate. The detection electrode 6 was formed so as to be 100,000 μm ² . In addition, “(10) Formation of the adhesion layer 7” means that the adhesion layer 7 is projected from the side of the gas detection layer 4 formed on the substrate so as to include the detection electrode 6 in the region of the gas detection layer 4. The adhesion layer 7 was formed so that the projection area (first projection area) of only the adhesion layer in the projection region was 150,000 μm ² . Further, in “(13) Formation of gas detection layer 4”, the projected area when the contact surface between the gas detection layer 4, the adhesion layer 7 and the detection electrode 6 is projected from the gas detection layer 4 formed on the substrate. The gas detection layer 4 was formed so that (second projected area) was 250,000 μm ² . Thereby, in the gas sensor 1 described above in evaluation 2, the first projected area occupies 50% or more (150,000 μm ² / 250,000 μm ² × 100 = 60%) of the second projected area. .

  As described above in detail, in the gas sensor 1 of the present embodiment, the detection electrode 6 and the gas detection layer 4 are brought into contact with the gas detection layer 4 on the entire surface 61 of the detection electrode 6 facing the gas detection layer 4. An adhesion layer 7 made of an insulating material that does not affect the electron conduction of the gas detection layer 4 is formed between the base 15 and the gas detection layer 4 while ensuring a contact area with the gas detection layer 4. Therefore, according to the gas sensor 1 of the present embodiment, it is possible to obtain an effect that is not found in the prior art that good gas sensitivity can be obtained while improving the adhesion between the base 15 and the gas detection layer 4. . In addition, since the change in the concentration of the specific gas can be sufficiently detected even if the current flowing through the gas detection layer 4 or the applied voltage is reduced, the circuit design of the gas sensor can be made easy and inexpensive. Is also obtained as a secondary. Further, since the heating resistor 5 is formed at a position corresponding to the opening 21 formed in the silicon substrate 2, the gas detection layer 4 can be efficiently heated and activated, and the detection target can be satisfactorily detected. A change in the concentration of a specific gas in the gas can be detected.

The present invention is not limited to the above embodiment, and various modifications may be made without departing from the spirit of the present invention. For example, the silicon substrate 2 forming the base 15 is made of silicon, but may be made of alumina (Al ₂ O ₃ ) or a semiconductor material. Moreover, the planar shape of the produced gas sensor 1 is not limited to a rectangle, but may be a polygon or a circle, and the size, thickness, and arrangement of each member are not limited.

  Moreover, the manufacturing method of the gas sensor 1 is not limited to Example 1, It can change suitably. For example, in Example 1, in “(10) Formation of adhesion layer 7”, the sol solution layer to be the adhesion layer 7 was formed by the ink jet method. However, the dipping method, electrophoresis method, liquid film transfer method, mist transport method are used. Further, it may be formed by other methods such as a screen printing method and a spin coating method. Further, although the adhesion layer 7 is performed after the formation of the detection electrode 6, the lead portion 10, and the extraction electrode 91, it may be performed before the detection electrode 6, the lead portion 10, and the extraction electrode 91 are formed. In that case, for example, after forming a sol solution layer as the adhesion layer 7 on the protective layer 35 in a film shape, the portions where the formation of the detection electrode 6, the lead portion 10 and the extraction electrode 91 are formed are removed by etching or the like. Subsequently, the detection electrode 6, the lead portion 10, and the extraction electrode 91 are formed in the removed portion.

  In the above embodiment, the thickness of the adhesion layer 7 is smaller than the thickness of the gas detection layer 4. However, the surface 61 of the detection electrode 6 facing the gas detection layer 4 is entirely covered. The gas detection layer 4 is not limited to this as long as it is in contact with the gas detection layer 4. Furthermore, in the said embodiment, although the contact | adherence layer 7 was set as the structure formed in the area | region between a pair of detection electrode 6 formed in the comb-tooth shape, and two area | regions of the peripheral part of the detection electrode 6, either one was used. The adhesion layer 7 may be formed only in the region to ensure the adhesion between the gas detection layer 4 and the substrate 15.

  Further, in the above embodiment, the first projected area is secured 50% or more of the second projected area to reduce the ratio of the contact area between the gas detection layer and the detection electrode. It is not limited to. The ratio of the first projected area to the second projected area can be appropriately set according to gas sensitivity, miscellaneous gas characteristics, and the like.

  The insulating coating layer 3 has a multilayer structure made of silicon oxide and silicon nitride, but may have a single layer structure made of silicon oxide or silicon nitride. In the present embodiment, the heating resistor 5 is embedded in the insulating layers 33 and 34. However, the present invention is not limited to this. For example, the heating resistor 5 may be embedded in the insulating layer 32.

Moreover, although the gas detection layer 4 used tin oxide which is a metal oxide semiconductor as a main component, zinc oxide (ZnO), nickel oxide (NiO), titanium oxide (TiO ₂ ), vanadium oxide (VO ₂ ), etc. Other metal oxide semiconductors may be used. The basic metal oxide added to the metal oxide semiconductor includes oxides of alkaline earth metals such as calcium (Ca), magnesium (Mg), strontium (Sr), barium (Ba), and beryllium (Be). Oxides of alkali metals such as sodium (Na), potassium (K), rubidium (Rb) and cesium (Cs), scandium (Sc), yttrium (Y), and other rare earth oxides such as lanthanoid elements It may be used.

  By the way, in the above-described embodiment, the surface of the detection electrode 6 facing the base body 15 has a configuration in contact with the protective layer 35. According to this configuration, there is an advantage that the adhesion between the base 15 and the gas detection layer 4 can be improved while reducing the formation amount of the adhesion layer 7, while the area of the contact surface between the base 15 and the detection electrode 6 is small. If it is large, the adhesion between the substrate 15 and the detection electrode 6 may not be improved. Therefore, the configuration of the adhesion layer may be as in the first modification. Hereinafter, the gas sensor 101 according to the first modification example in which the adhesion layer 7 is formed on the lower surface of the detection electrode 6 will be described with reference to FIG. Since the configuration of the gas sensor 101 is the same as that of the above-described embodiment except for the configuration of the adhesion layer, the description of the same mode is omitted. 7 is a cross-sectional view of the gas sensor 101 corresponding to the cross-sectional view taken along the line AA in FIG. 1 shown in FIG. In FIG. 7, the vertical direction is referred to as the vertical direction, and the horizontal direction is referred to as the horizontal direction.

  As shown in FIG. 7, in the gas sensor 101 according to Modification 1, the entire surface 161 of the detection electrode 106 facing the gas detection layer 104 is in contact with the gas detection layer 104. On the other hand, the surface 162 of the detection electrode 106 on the substrate 15 side, that is, the surface 162 facing the adhesion layer is in contact with the adhesion layer 107. By adopting such a configuration, the adhesion between the detection electrode 106 and the protective layer 35 is improved. Further, in Modification 1, since the area of the contact surface between the protective layer 35 and the adhesive layer 107 constituting the base body 15 is increased as compared with the above-described embodiment, the adhesive layer 107 and the protective layer 35 are more Adhere securely. Therefore, for example, even when the area of the contact surface between the base 15 and the detection electrode 106 is large, the adhesion between the base 15 and the detection electrode 6 can be improved, and the gas detection layer 104 is peeled from the base 15. Can be prevented.

  Next, as Example 2, the manufacturing process of Modification 1 will be described. The manufacturing method of the gas sensor 101 of the first modification is the same as that of the first embodiment described above, and “(9) Formation of the detection electrode 6, the lead portion 10 and the extraction electrode 91” and “(10) Formation of the adhesion layer 7”. Different. A description of the same steps as those of the first embodiment will be omitted, and hereinafter, manufacturing steps different from those of the first embodiment will be described.

[Example 2]
(9) Formation of Adhesion Layer 107 A sol solution layer that becomes the adhesion layer 7 after firing was formed by spin coating at a position on the upper surface of the protective layer 35 corresponding to the heating resistor 5 and the opening 21 and dried. Then, the part which forms the detection electrode 106 in a sol solution layer was removed by etching, and the recessed part was formed.

(10) Formation of the detection electrode 106, the lead portion 10, and the lead electrode 91 Next, a tantalum layer having a thickness of 20 nm is formed on the surface of the concave portion and the protective layer 35 removed by etching the adhesion layer 107 using a DC sputtering apparatus. Further, a platinum layer having a thickness of 40 nm was formed on the surface. After sputtering, the resist was patterned by photolithography, and the patterns of the comb-like detection electrode 106, the lead portion 10, and the extraction electrode 91 were formed by wet etching.

  By the way, in the above-mentioned embodiment and the modification 1, it has the structure which the detection electrode and the gas detection layer contact | abutted directly. When the area of the contact surface between the gas detection layer and the detection electrode is large, the adhesion between the substrate and the detection electrode may not be improved. Therefore, as in Modification 2, the detection electrode is formed between the adhesion layer and the gas detection layer, and the adhesion layer has a first uneven surface on the side facing the detection electrode and the gas detection layer, and the detection electrode. May be provided with a second uneven surface on the side facing the gas detection layer. Hereinafter, the gas sensor 201 according to the modified example 2 will be described with reference to FIGS. 8 and 9. 8 is a cross-sectional view of the gas sensor 201 corresponding to the cross-sectional view taken along the line AA in FIG. 1 shown in FIG. FIG. 9 is an enlarged view of a part of the gas sensor 201 shown in FIG. 8 and 9, the vertical direction is referred to as the vertical direction, and the horizontal direction is referred to as the horizontal direction.

  As shown in FIGS. 8 and 9, the configuration of the gas sensor 201 according to Modification 2 is the same as that of the above-described embodiment except for the configurations of the adhesion layer 207, the detection electrode 206, and the gas detection layer 204. Therefore, the description of the same configuration as that of the above-described embodiment is omitted, and the configurations of the adhesion layer 207, the detection electrode 206, and the gas detection layer 204, which are different from those of the above-described embodiment, will be described in detail below.

  As shown in FIGS. 8 and 9, the adhesion layer 207 of the gas sensor 201 according to the second modification includes a first uneven surface 271 on the surface facing the gas detection layer 204 and the detection electrode 206. The adhesion layer 207 is a layer for improving the adhesion between the substrate 15 and the gas detection layer 204, and has a structure in which a plurality of particles made of an insulating metal oxide are aggregated. In the modified example 2, since the surface of the adhesion layer 207 is an uneven surface, the adhesion layer 207 provides the adhesion between the base 15 and the gas detection layer 204 formed in a thick film shape as the first uneven surface 271. It is enhanced more effectively by the anchor effect. The adhesion layer 207 can be obtained, for example, by applying a sol solution in which insulating metal oxide particles are dispersed, baking, and solidifying.

  The detection electrode 206 includes an uneven surface 261 having unevenness that fits the unevenness of the first uneven surface 271 of the adhesion layer 207 on the base 15 side, that is, the side facing the adhesion layer 207. It is in contact with the first uneven surface 271 of the layer 207. As described above, in the modified example 2, the area of the contact surface between the gas detection layer 204 and the detection electrode 206 and the adhesion layer 207 constituting the base body 15 is increased as compared with the above-described embodiment. In addition, the detection electrode 206 and the adhesion layer 207 adhere more reliably. Therefore, for example, even when the area of the contact surface between the base 15 and the detection electrode 206 is large, the adhesion between the base 15 and the detection electrode 206 can be improved, and the gas detection layer 204 is peeled off from the base 15. Can be prevented.

  The detection electrode 206 includes a second uneven surface 262 on the side facing the gas detection layer 204. On the other hand, the surface 241 that contacts the detection electrode 206 of the gas detection layer 204 is an uneven surface that has unevenness that fits into the unevenness of the second uneven surface 262 provided in the detection electrode 206. The entire surface of the detection electrode 206 facing the gas detection layer 204 is in contact with the surface 241 of the gas detection layer 204 at the second uneven surface 262. For this reason, the contact area between the detection electrode 206 and the gas detection layer 204 is increased as compared with the case where the surface of the detection electrode 206 facing the gas detection layer 204 is flat, and the anchor of the second uneven surface 262 is increased. Due to the effect, the adhesion between the detection electrode 206 and the gas detection layer 204 can be improved. Therefore, for example, even when the area of the contact surface between the gas detection layer 204 and the detection electrode 206 is large, the effect of preventing the gas detection layer 204 from peeling from the base body 15 is increased. The detection electrode 206 provided with the second uneven surface 262 can be obtained, for example, by forming a conductive metal film on the surface of the adhesion layer 207 provided with the first uneven surface 271 by a sputtering method. Further, for example, after the detection electrode is formed, the second uneven surface may be formed by performing mechanical unevenness processing on the surface facing the gas detection layer.

  Next, as Example 3, an example of a manufacturing process of the gas sensor 201 according to Modification 2 will be described. The manufacturing method of the gas sensor 201 of Modification 2 is the same as that of Example 1 described above, “(8) Formation of the opening of the heating resistor contact portion 9”, “(9) Detection electrode 6, lead portion 10 and lead electrode 91. Unlike the “formation”, “(10) formation of the adhesion layer 7” and “(13) formation of the gas detection layer 4”, the other steps are the same as those in the first embodiment in terms of the process contents and the execution order. A description of the same steps as those of the first embodiment will be omitted, and hereinafter, manufacturing steps different from those of the first embodiment will be described.

[Example 3]
(8) Formation of Adhesion Layer 207 An aluminum film having an uneven surface is formed at a predetermined thickness on the upper surface of the protective layer 35 corresponding to the heating resistor 5 and the opening 21 by a sputtering method, and the aluminum film Was oxidized to aluminum oxide. In this step, an adhesion layer 207 having an uneven surface was formed.

(9) Formation of Opening of Heating Resistor Contact 9 Next, resist is patterned by photolithography, and the protective layer 35 and the insulating layer 34 in which the adhesion layer 207 is formed on the upper surface thereof are etched by dry etching. Then, a hole was made in a portion where the heating resistor contact portion 9 was formed, and a part of the end of the lead portion 12 was exposed.

(10) Formation of the detection electrode 206, the lead portion 10, and the lead electrode 91 Next, using a DC sputtering apparatus, a tantalum layer having a thickness of 20 nm is formed on the surface of the adhesion layer 207 and the protective layer 35, and further on the surface A platinum layer with a thickness of 40 nm was formed. After sputtering, the resist was patterned by photolithography, and the patterns of the comb-like detection electrode 206, the lead portion 10, and the extraction electrode 91 were formed by wet etching. In this step, due to the uneven surface on the surface of the adhesion layer 207 formed in “(8) Formation of the adhesion layer 207”, the second uneven surface 262 having unevenness on the upper surface of the detection electrode 206 was formed (FIG. 10).

(13) Formation of gas detection layer 204 Further, an oxide semiconductor paste mainly composed of tin oxide and added with calcium oxide is applied to the upper surfaces of the detection electrode 206 and the adhesion layer 207 by thick film printing, and the thickness is 30 μm. A paste layer was formed. At this time, the second surface of the detection electrode 206 formed in “(10) Formation of the detection electrode 206, the lead portion 10, and the extraction electrode 91” is formed on the surface 241 that is a surface where the gas detection layer 204 and the detection electrode 206 are in contact with each other. Irregularities that fit into the irregularities of the irregular surface 262 were formed (FIG. 11). Note that the oxide semiconductor paste was manufactured in the same procedure as in Example 1.

  Next, in order to confirm the structure of the gas sensor 201 manufactured according to the above manufacturing process, the second uneven surface 262 of the detection electrode 206 and the state where the second uneven surface 262 and the surface 241 of the gas detection layer 204 are in contact with each other are scanned. It confirmed by magnifying 10,000 times with the electron microscope. FIG. 10 is a photograph obtained by enlarging the second uneven surface 262 of the detection electrode 206 with a scanning electron microscope immediately after the formation of the detection electrode 206 (before forming the gas detection layer 204). As shown in the photograph of FIG. 10, a second uneven surface 262 formed by agglomeration of a plurality of metal particles is confirmed on the surface of the detection electrode 206 prepared in accordance with the above manufacturing process on the side facing the gas detection layer 204. It was done. The second uneven surface 262 is an uneven surface formed due to the uneven surface on the surface of the adhesion layer 207 formed in “(8) Formation of the adhesion layer 207”. On the other hand, FIG. 11 is a photograph taken by enlarging the contact surface between the detection electrode 206 and the gas detection layer 204 with a scanning electron microscope. In the photograph of FIG. 11, the layer having relatively large particles seen in the lower part of FIG. 11 is the detection electrode 206, and the layer having relatively small particles seen in the upper part of FIG. 11 is the gas detection layer 204. It is. It was confirmed that the surface 241 of the gas detection layer 204 on the side in contact with the detection electrode 206 is an uneven surface that fits into the unevenness of the second uneven surface 262 included in the detection electrode 206. 10 and 11, the gas sensor 201 according to the modified example 2 is in contact with the detection electrode 206 and the gas detection layer 204 as compared with the case where the surface of the detection electrode 206 facing the gas detection layer 204 is flat. It was confirmed that the area increased.

In the second modification, “(2) Formation of insulating layers 31 and 231” is performed to form the insulating layers 31 and 231. However, this step is omitted, and both surfaces of the silicon substrate 2 are nitrided. The insulating layers 32 and 232 made of a silicon film (Si ₃ N ₄ ) film may be formed. Further, the execution order of each manufacturing process can be changed as necessary. For example, “(9) Formation of opening of heating resistor contact portion 9” is “(10) Detection electrode 206, lead portion 10 and extraction electrode 91”. It may be performed after “formation”.

  The present invention can be applied to a semiconductor gas sensor.

2 is a plan view of the gas sensor 1. FIG. It is arrow sectional drawing in the AA line | wire shown in FIG. It is a top view of the heating resistor 5 with which the gas sensor 1 is provided. It is arrow direction sectional drawing in the BB line shown in FIG. It is arrow sectional drawing in the CC line shown in FIG. 2 of the gas sensor 1. FIG. It is a bar graph showing the result of evaluation 1. It is sectional drawing corresponding to the arrow direction sectional view in the AA line of FIG. 1 of the gas sensor 101 shown in FIG. It is sectional drawing corresponding to the arrow sectional view in the AA of FIG. 1 of the gas sensor 201 shown in FIG. It is the enlarged view to which the wavy line 240 vicinity of the gas sensor 201 shown in FIG. 8 was expanded. It is the photograph which expanded and image | photographed the 2nd uneven | corrugated surface 262 of the detection electrode 206 immediately after formation of the detection electrode 206 (before forming the gas detection layer 204). It is the photograph which expanded and image | photographed the contact surface of the detection electrode 206 and the gas detection layer 204 with the scanning electron microscope.

Explanation of symbols

1, 101, 201 Gas sensor 2 Silicon substrate 3, 230 Insulating coating layer 4, 104, 204 Gas detection layer 5 Heating resistor 6, 106, 206 Detection electrode 7, 107, 207 Adhesion layer 15 Base body 21 Openings 31, 32, 33, 34, 231, 232 Insulating layer 35 Protective layer 39 Separation part 61, 62, 161, 162 surface 261 uneven surface 262 second uneven surface 271 first uneven surface

Claims (6)

In a gas sensor having a gas detection layer mainly composed of a metal oxide semiconductor, which is formed on a substrate and whose electrical characteristics change according to a change in concentration of a specific gas in a gas to be detected,
On the substrate, a detection electrode for detecting a change in electrical characteristics in the gas detection layer and an insulating adhesion layer in contact with the gas detection layer are provided.
The gas sensor according to claim 1, wherein a surface of the detection electrode facing the gas detection layer is entirely in contact with the gas detection layer.   The gas sensor according to claim 1, wherein a surface of the detection electrode facing the base is in contact with the base. The detection electrode is provided between the adhesion layer and the gas detection layer,
2. The gas sensor according to claim 1, wherein a surface of the detection electrode facing the adhesion layer is in contact with the adhesion layer. In a gas sensor having a gas detection layer mainly composed of a metal oxide semiconductor, which is formed on a substrate and whose electrical characteristics change according to a change in concentration of a specific gas in a gas to be detected,
On the substrate, a detection electrode for detecting a change in electrical characteristics in the gas detection layer and an insulating adhesion layer in contact with the gas detection layer are provided.
The detection electrode is provided between the adhesion layer and the gas detection layer,
The surface of the detection electrode facing the adhesion layer is in contact with a first uneven surface formed on the adhesion layer facing the detection electrode and the gas detection layer,
The gas sensor according to claim 1, wherein a surface of the detection electrode facing the gas detection layer has a second concavo-convex surface, and the entire surface is in contact with the gas detection layer.   The projected area when the contact surface between the gas detection layer and the adhesion layer is projected from the gas detection layer side formed on the substrate is calculated from the gas detection layer side formed on the substrate. The gas sensor according to any one of claims 1 to 4, wherein the gas sensor occupies 50% or more of a projected area when a contact surface between a layer, the adhesion layer, and the detection electrode is projected. The base is a semiconductor substrate having an opening formed in the thickness direction;
An insulating layer formed on the semiconductor substrate and having a partition wall at a portion corresponding to the opening;
A heating resistor formed on the partition portion of the insulating layer;
A protective layer formed on the insulating layer so as to cover the heating resistor,
The gas sensor according to claim 1, wherein the detection electrode, the adhesion layer, and the gas detection layer are formed on the protective layer of the base.