Hydrogen gas sensor

Abstract

This invention provides a hydrogen gas sensor that can detect hydrogen gas concentration even during initialization, and that does not pose a risk of damage to the sensor membrane during initialization. [Solution] The hydrogen gas sensor 2 comprises an insulating substrate 4, an insulating film 8 disposed on the surface 4a side of the substrate 4, and a sensor film 10 disposed on the surface 4a side of the substrate 4, the sensor film having properties that change according to the hydrogen gas concentration in contact. The hydrogen gas sensor 2 further comprises a heater film 6 laminated on the surface 4a of the substrate 4 and heated by the flow of current or the application of voltage. The insulating film 8 is laminated on the surface 6b of the heater film 6, and the sensor film 10 is laminated on the surface 8b of the insulating film 8. The insulating film 8 transmits the heat generated when the heater film 6 is heated to the sensor film 10 and insulates the flow of current from the heater film 6 to the sensor film 10.

Description

Technical Field

[0001] The present invention relates to a hydrogen gas sensor for detecting the concentration of hydrogen gas.

Background Art

[0002] Various forms of hydrogen gas sensors for detecting the concentration of hydrogen gas are known. For example, the hydrogen gas sensor disclosed in Patent Document 1 below includes an insulating substrate, a metal film disposed on the surface of the substrate, and a sensor film disposed on the surface of the metal film. Unevenness of 10 nm or more is formed on the surface of the metal film. The material of the sensor film is platinum, and the film thickness of the sensor film is 40 nm or less. In the hydrogen gas sensor, the change in the characteristics of the sensor film when hydrogen gas contacts the sensor film can be increased, and it has sufficient practicality.

[0003] The hydrogen gas sensor also includes an initialization means for returning the characteristics of the sensor film changed by contact with hydrogen gas to the initial state. The initialization means heats the sensor film by flowing a pulsed current through the sensor film or applying a pulsed voltage to the sensor film. As a result, the characteristics of the sensor film can be quickly returned to the initial state as compared with the case where the sensor film is not heated.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the above hydrogen gas sensor has some issues that need improvement. First, in the above hydrogen gas sensor, an electric current is passed through the sensor film or a voltage is applied to the sensor film during initialization, so the hydrogen gas concentration detection function is lost during initialization. Also, since the temperature of the sensor film rises due to the current or voltage during initialization, there is a risk that the sensor film will overheat and the platinum crystal structure will break down, and if the platinum crystal structure breaks down, the hydrogen gas concentration detection function will be lost. Furthermore, depending on the current passed through the sensor film or the voltage applied to the sensor film during initialization, the resistance of the sensor film may increase excessively, or electromigration may cause the sensor film to break.

[0006] The object of the present invention is to provide a hydrogen gas sensor that can detect hydrogen gas concentration even while it is being initialized, and that does not pose a risk of damage to the sensor film during initialization. [Means for solving the problem]

[0007] According to the present invention, the following hydrogen gas sensor is provided that solves the above problems. That is, "A hydrogen gas sensor that detects hydrogen gas concentration, An insulating substrate, An insulating film disposed on the surface side of the substrate, The system comprises a sensor film disposed on the surface side of the substrate, the sensor film having properties that change depending on the hydrogen gas concentration in contact with it, The substrate further comprises a heater film laminated on the surface of the substrate and heated by the passage of current or the application of voltage, The insulating film is laminated on the surface of the heater film, and the sensor film is laminated on the surface of the insulating film. The provided hydrogen gas sensor is characterized in that the insulating film transmits the heat generated when the heater film is heated to the sensor film and insulates the flow of current from the heater film to the sensor film.

[0008] The system includes an initialization means for returning the characteristics of the sensor film, which have been altered by contact with hydrogen gas, to their initial state by passing an electric current through the heater film or applying a voltage, wherein the sensor film is preferably heated to a predetermined temperature by the heat generated by the heating of the heater film by the initialization means, which is transmitted through the insulating film. Preferably, the predetermined temperature is 80°C or higher and 200°C or lower. The initialization means preferably includes a heater electrode that reaches the heater film from the back surface of the substrate. The initialization means may further include a sensor electrode that reaches the sensor film from the back surface of the substrate. The sensor film may be formed in a meandering linear shape when viewed in a direction perpendicular to the surface of the substrate.

[0009] The substrate may be made of glass. The heater film is preferably formed from tantalum nitride, platinum, or titanium. The insulating film may be a silicon oxide film, a porous silica film, or a silicon nitride film. The sensor film may be formed from platinum. [Effects of the Invention]

[0010] In the hydrogen gas sensor of the present invention, the heater film is heated by passing an electric current through it or by applying a voltage to it. The heat generated from the heated heater film is then transferred to the sensor film via an insulating film, thereby heating the sensor film to a predetermined temperature and initializing it. Furthermore, in the hydrogen gas sensor of the present invention, since the heater film and the sensor film are electrically insulated by an insulating film, no electric current flows through the sensor film or a voltage is applied to it during initialization. Therefore, the hydrogen gas concentration can be detected even during initialization, and there is no risk of damage to the sensor film during initialization. [Brief explanation of the drawing]

[0011] [Figure 1] A plan view of the hydrogen gas sensor according to the present invention. [Figure 2] Figure 1 shows an exploded perspective view of the hydrogen gas sensor. [Figure 3] Cross-sectional view of the section where the heater electrodes are installed. [Figure 4] Cross-sectional view of the area where the sensor electrodes are installed. [Modes for carrying out the invention]

[0012] Hereinafter, preferred embodiments of the hydrogen gas sensor according to the present invention will be described with reference to the drawings.

[0013] (Hydrogen gas sensor 2) As shown in Figures 1 and 2, the hydrogen gas sensor 2 comprises an insulating substrate 4, a heater film 6 laminated on the surface 4a (top surface in Figure 2) of the substrate 4 and heated by the application of current or voltage, an insulating film 8 disposed on the surface 4a side of the substrate 4, and a sensor film 10 disposed on the surface 4a side of the substrate 4, the characteristics of which change according to the hydrogen gas concentration in contact. Furthermore, the hydrogen gas sensor 2 of this embodiment includes an initialization means 11 that returns the characteristics of the sensor film 10, which have changed due to contact with hydrogen gas, to their initial state by applying current or voltage to the heater film 6. The initialization means 11 includes a heater electrode 12 (see Figure 3) that reaches the heater film 6 from the back surface 4b of the substrate 4. The initialization means 11 may further include a sensor electrode 14 (see Figure 4) that reaches the sensor film 10 from the back surface 4b of the substrate 4.

[0014] (Circuit board 4) As shown in Figures 1 and 2, the substrate 4 in this embodiment has a rectangular shape in plan view, but the shape of the substrate 4 can be any shape. The substrate 4 can be formed from an electrically insulating material such as glass. Specific materials for the substrate 4 include borosilicate glass, quartz glass, and the like.

[0015] (Heater film 6) The heater film 6 is a film that is heated when a current flows or a voltage is applied when the hydrogen gas sensor 2 is initialized. The heater film 6 is laminated on the surface 4a of the substrate 4. The shape of the heater film 6 in the present embodiment is rectangular, similar to the substrate 4. However, the size of the heater film 6 is smaller than the size of the substrate 4. That is, the longitudinal dimension (X-direction dimension) of the heater film 6 is smaller than the longitudinal dimension of the substrate 4, and the widthwise dimension (Y-direction dimension) of the heater film 6 is smaller than the widthwise dimension of the substrate 4. The heater film 6 can be formed by sputtering, vapor deposition, or the like. Also, the material of the heater film 6 may be any one of tantalum nitride, platinum, or titanium.

[0016] As shown in FIG. 2, the heater film 6 of the present embodiment is provided with a plurality (three in the illustrated form) of circular through-holes 6a for passing the sensor electrodes 14. The through-holes 6a are arranged at intervals in the longitudinal direction (X-direction) of the heater film 6. Note that the X-direction is the direction indicated by the arrow X in FIGS. 1 and 2, and the Y-direction is the direction indicated by the arrow Y in FIGS. 1 and 2, which is a direction orthogonal to the X-direction.

[0017] (Insulating film 8) The insulating film 8 is a film that transmits the heat generated when the heater film 6 is heated to the sensor film 10 and insulates the flow of current from the heater film 6 to the sensor film 10. The insulating film 8 is laminated on the surface 6b (the upper surface in FIG. 2) of the heater film 6. The shape of the insulating film 8 in the present embodiment is rectangular, similar to the substrate 4 and the heater film 6. However, the size of the insulating film 8 is smaller than the size of the substrate 4 and larger than the size of the heater film 6. That is, the longitudinal dimension of the insulating film 8 is smaller than the longitudinal dimension of the substrate 4 and larger than the longitudinal dimension of the heater film 6. Also, the widthwise dimension of the insulating film 8 is smaller than the widthwise dimension of the substrate 4 and larger than the widthwise dimension of the heater film 6. The insulating film 8 can be formed by sputtering, vapor deposition, or the like, similar to the heater film 6. Also, the insulating film 8 may be any one of a silicon oxide film, a porous silica film, or a silicon nitride film.

[0018] As shown in Fig. 2, the insulating film 8 of the present embodiment has a plurality (three in the illustrated form) of circular through-holes 8a for passing the sensor electrodes 14, similar to the heater film 6. The diameter of the through-hole 8a is smaller than the diameter of the through-hole 6a of the heater film 6. As shown in Fig. 4, even at the portion where the through-hole 8a is provided, the insulating film 8 covers the heater film 6, and the heater film 6 and the sensor electrode 14 are electrically insulated by the insulating film 8. Therefore, even though the through-hole 8a is formed, the electrical insulation between the heater film 6 and the sensor film 10 is ensured. In the present embodiment, since the entire heater film 6 on the substrate 4 is covered by the insulating film 8, the heater film 6 is not exposed. However, as long as the heater film 6 and the sensor film 10 are electrically insulated by the insulating film 8, a part of the heater film 6 may be exposed.

[0019] (Sensor film 10) The sensor film 10 is a film whose characteristics (e.g., electrical resistance) change according to the hydrogen gas concentration in contact. The sensor film 10 is laminated on the surface 8b (the upper surface in Fig. 2) of the insulating film 8. The sensor film 10 of the present embodiment is formed in a meandering linear shape when viewed in the direction orthogonal to the surface 4a of the substrate 4. The sensor film 10, similar to the heater film 6 and the insulating film 8, can be formed by sputtering, evaporation, or the like. The material of the sensor film 10 may be platinum. A metal film (e.g., titanium film, chromium film, nickel film) as an adhesive layer may be provided between the sensor film 10 and the insulating film 8.

[0020] As shown in Figs. 1 and 2, the sensor film 10 of the present embodiment is provided with a plurality of electrode connection portions 10a connected to the sensor electrodes 14. In the illustrated electrode connection portions 10a, a total of three are provided at the first end portion, the second end portion, and the intermediate portion between the first end portion and the second end portion of the sensor film 10, but a total of two may be provided at the first and second end portions.

[0021] (Heater electrode 12) The heater electrode 12 is an electrode used to heat the heater film 6. As shown in Figures 2 and 3, in this embodiment, a pair of heater electrodes 12 are connected to the heater film 6, and the pair of heater electrodes 12 are spaced apart in the longitudinal direction (X direction) of the heater film 6. The heater electrode 12 is formed as a through electrode that penetrates the substrate 4, and reaches the heater film 6 from the back surface 4b of the substrate 4. The material of the heater electrode 12 may be copper, titanium, tungsten, silicon, etc. The number of heater electrodes 12 may be one pair as in this embodiment, but three or more may be provided.

[0022] (Sensor electrode 14) The sensor electrode 14 is primarily used to pass an electric current through the sensor film 10 when detecting the hydrogen gas concentration using the sensor film 10. As shown in Figure 2, multiple (three in the illustrated configuration) sensor electrodes 14 are connected to the sensor film 10, and the multiple sensor electrodes 14 are spaced apart in the X direction. As shown in Figure 4, the sensor electrode 14 has a through electrode 14a that penetrates the substrate 4 and a bump 14b located on the surface 4a side of the substrate 4. The bump 14b penetrates the through hole 6a of the heater film 6 and the through hole 8a of the insulating film 8, and is connected to the through electrode 14a. The bump 14b is also connected to the electrode connection portion 10a of the sensor film 10. That is, the sensor electrode 14 reaches the electrode connection portion 10a of the sensor film 10 from the back surface 4b of the substrate 4. The material of the sensor electrode 14 may be copper, titanium, tungsten, silicon, etc. The number of sensor electrodes 14 may be 3 as in this embodiment, but it may also be 2.

[0023] In the hydrogen gas sensor 2 described above, when the characteristics of the sensor film 10, which have been altered by contact with hydrogen gas, are returned to their initial state (initialized), a current is passed through the heater film 6 via the heater electrode 12 of the initialization means 11, or a voltage is applied to the heater film 6 via the heater electrode 12. This heats the heater film 6. As a result, the heat generated from the heating of the heater film 6 is transferred to the sensor film 10 via the insulating film 8, and the sensor film 10 is heated to a predetermined temperature. Consequently, the characteristics of the sensor film 10 are returned to their initial state.

[0024] The above-mentioned predetermined temperature (heating temperature of the sensor film 10 during initialization) is preferably between 80°C and 200°C. If the above-mentioned predetermined temperature is below 80°C, the effect of heating the sensor film 10 is reduced. In other words, there is little significant difference in initialization time compared to when the sensor film 10 is not heated. On the other hand, if the above-mentioned predetermined temperature exceeds 200°C, the sensor film 10 may be damaged. That is, the crystal structure of the material (platinum) of the sensor film 10 may break, or the sensor film 10 may be cut. Therefore, the above-mentioned predetermined temperature is preferably between 80°C and 200°C.

[0025] In the hydrogen gas sensor 2, the heater film 6 and the sensor film 10 are electrically insulated by the insulating film 8. Therefore, even if current flows through the heater film 6 or a voltage is applied to the heater film 6 during initialization, no current flows through the sensor film 10, nor is any voltage applied to the sensor film 10. Consequently, the hydrogen gas sensor 2 can detect the hydrogen gas concentration even during initialization, and there is no risk of damage to the sensor film 10 during initialization.

[0026] Furthermore, if the heater film 6 is not initialized by passing a current through the heater electrode 12 or by applying a voltage to the heater film 6 through the heater electrode 12 due to hydrogen concentration, humidity, contamination, etc., the sensor film 10 may be heated by passing a current through the sensor electrode 14 or by applying a voltage to the sensor electrode 14. In other words, in such cases, the sensor electrode 14 can also be used as the initialization means 11. [Explanation of symbols]

[0027] 2: Hydrogen gas sensor, 4: Substrate, 4a: Surface of substrate, 4b: Back of substrate, 6: Heater film, 6a: Through-hole in heater film, 6b: Surface of heater film, 8: Insulating film, 8a: Through-hole in insulating film, 8b: Surface of insulating film, 10: Sensor film, 10a: Electrode connection part of sensor film, 12: Heater electrode, 14: Sensor electrode, 14a: Through-electrode, 14b: Bump

Claims

1. A hydrogen gas sensor that detects hydrogen gas concentration, An insulating substrate, An insulating film disposed on the surface side of the substrate, The system comprises a sensor film disposed on the surface side of the substrate, the sensor film having properties that change depending on the hydrogen gas concentration in contact with it, The substrate further comprises a heater film laminated on the surface of the substrate and heated by the passage of current or the application of voltage, The insulating film is laminated on the surface of the heater film, and the sensor film is laminated on the surface of the insulating film. The hydrogen gas sensor is characterized in that the insulating film transmits the heat generated when the heater film is heated to the sensor film and insulates the flow of current from the heater film to the sensor film.

2. The system includes an initialization means that restores the characteristics of the sensor film, which have been altered by contact with hydrogen gas, to their initial state by passing an electric current through the heater film or applying a voltage to the heater film. The hydrogen gas sensor according to claim 1, wherein the sensor film is heated to a predetermined temperature by the heat of the heater film generated by the initializing means, which is transmitted through the insulating film.

3. The hydrogen gas sensor according to claim 2, wherein the predetermined temperature is 80°C or more and 200°C or less.

4. The hydrogen gas sensor according to claim 2, wherein the initialization means includes a heater electrode that reaches the heater film from the back surface of the substrate.

5. The hydrogen gas sensor according to claim 4, wherein the initialization means further includes a sensor electrode that reaches the sensor film from the back surface of the substrate.

6. The hydrogen gas sensor according to claim 1, wherein the sensor film is formed in a meandering linear shape when viewed in a direction perpendicular to the surface of the substrate.

7. The hydrogen gas sensor according to claim 1, wherein the substrate is made of glass.

8. The hydrogen gas sensor according to claim 1, wherein the heater film is formed from tantalum nitride, platinum, or titanium.

9. The hydrogen gas sensor according to claim 1, wherein the insulating film is one of a silicon oxide film, a porous silica film, or a silicon nitride film.

10. The hydrogen gas sensor according to claim 1, wherein the sensor film is formed from platinum.

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