JP5043556B2 - Hydrogen gas sensor - Google Patents

Description

  The present invention relates to a hydrogen gas sensor that detects hydrogen gas.

  As a conventional hydrogen gas sensor, a configuration in which a thermoelectric member is provided on a silicon substrate and a platinum-based catalyst material is provided on the thermoelectric member is known (Patent Document 1).

JP 2004-163192 A

  However, in the above-described conventional example, since the heat capacity is large, if the concentration of hydrogen gas to be detected is low, there is a disadvantage that the generated temperature difference in the thermoelectric member is small and the output voltage becomes small. In addition, since the response speed is slow from several seconds to several tens of seconds, there is a disadvantage that the object cannot be sufficiently achieved as a danger prevention sensor. An object of this invention is to provide the hydrogen gas sensor which eliminated such an inconvenience.

  In the hydrogen gas sensor according to the present invention, a cavity is formed in the silicon substrate corresponding to the membrane on the surface of the silicon substrate, and a thermopile is provided on the membrane, and the thermopile has a hot junction corresponding to the upper side of the cavity. In addition to being arranged so as to be located, the cold junction part is arranged so as to correspond to the outside of the cavity, and a blackened catalyst layer made of platinum is formed so as to cover the warm junction part.

The blackened platinum catalyst layer is preferably formed by vapor deposition. Further, the above-mentioned cavity is preferably formed from the silicon substrate surface side and has a bottomed shape, and at this time, it is more preferable to form the platinum catalyst layer from blackened platinum.

  Furthermore, it is preferable that the hydrogen gas sensor having the above-described configuration is provided on the same semiconductor chip as the amplifier that amplifies the output of the thermopile.

  In the configuration in which the platinum catalyst layer is made of blackened platinum, it is preferable that the hydrogen gas sensor is provided on the same semiconductor chip or in the same case as the infrared sensor for detecting the ambient temperature.

  The hydrogen gas sensor according to the present invention has the following effects. First, the heat capacity of the thermopile is reduced and the thermoelectric conversion reaction becomes sensitive. Second, since the platinum catalyst layer is made of blackened platinum, the surface area as a catalyst increases, the reaction of thermoelectric conversion becomes more sensitive, and the detection of diluted hydrogen gas is facilitated. Third, when the cavity is formed from the surface side of the silicon substrate, the membrane can be thinned, so that high-speed response and high sensitivity are possible, and miniaturization is also possible. Further, when the cavity is formed in a bottomed shape, since there is no restriction on the back surface of the semiconductor chip, die bonding (chip bonding) can be handled in the same way as a normal semiconductor chip. Fourth, when the hydrogen gas sensor is installed on the same semiconductor chip as the amplifier that amplifies the thermopile output, the influence of noise due to external factors can be minimized, so malfunctions are reduced. A minute output can be detected, and a high-speed response can be detected even with a low concentration gas. Fifth, when the hydrogen gas sensor is provided on the same semiconductor chip as the infrared sensor for detecting the ambient temperature, the influence of the ambient temperature on the output of the hydrogen gas sensor can be corrected. Sixth, even when the hydrogen gas sensor is arranged in the same case as the infrared sensor for detecting the ambient temperature, the influence of the ambient temperature on the output of the hydrogen gas sensor can be corrected.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a preferred embodiment of the invention will be described with reference to FIGS. Here, FIG. 1 is a sectional view schematically showing the basic structure of a hydrogen gas sensor, FIG. 2 is a plan view showing an arrangement state of thermocouples, and FIG. 3 shows an embodiment in which a hydrogen gas sensor and an amplifier are provided on the same base. FIG. 4 is a schematic plan view, and FIG. 4 is a schematic sectional view showing an embodiment in which a hydrogen gas sensor and an ambient temperature detecting infrared sensor are provided on the same base.

  As shown in FIGS. 1 and 2, the silicon substrate 2 of the hydrogen gas sensor 1 is provided with a membrane 3 formed on the surface by, for example, a silicon nitride film by a CVD method. A bottomed cavity 4 formed by etching from an etching hole (not shown) provided in 3 is provided. A thermopile 6 having a structure in which a plurality of thermocouples 5 made of different kinds of conductive materials are connected in series is provided on the membrane 3.

  The hot contact portion 7 of the thermopile 6 is disposed in the vicinity of the center portion of the silicon substrate 2, and the cold contact portion 8 of the thermopile 6 is disposed in the peripheral portion of the silicon substrate 2. That is, the hot contact portion 7 is located above the cavity 4 and the membrane 3, and the cold contact portion 8 is located outside the cavity 4 and the membrane 3. The thermopile 6 is covered with a flattening insulating film 9 such as SOG (Spin On Glass), for example, and on the flattening insulating film 9, it corresponds to the hot junction part 7 of the thermopile 6, but the cold junction part 8, a platinum catalyst layer 10 formed by blackening platinum and vacuum-depositing it is provided via a lower layer film 11 so as not to correspond to FIG. And the platinum black used as this platinum catalyst layer 10 can also be formed by plating.

  Further, as shown in FIG. 1, a patterned polysilicon film 12 is formed on the membrane 3, and this polysilicon film 12 is formed of an insulating film 13 such as a BPSG (Boron-doped Phospho-Silicate Glass) film, for example. The surface of the insulating film 13 is flattened. Then, an aluminum film 14 is formed on the planarized insulating film 13, and the aluminum film 14 and the polysilicon film 12 are joined to form a thermopile 6 by connecting a plurality of thermocouples 5 in series. Further, the aluminum film 14 is covered with the planarization insulating film 9 described above. In the above description, the thermopile is formed by bonding the aluminum film and the polysilicon film. However, the present invention is not limited to this, and the thermopile can be formed by bonding n-type polysilicon and p-type polysilicon.

  As shown in FIG. 2, the cold junction 8 is disposed on the silicon substrate 2 that acts as a heat sink and is not covered with the platinum catalyst layer 10, so that the platinum catalyst layer 10 comes into contact with hydrogen gas. Although the temperature hardly changes, the hot contact portion 7 is formed on the cavity 4 and the membrane 3 floating from the silicon substrate 2, and therefore has a small heat capacity and is covered with the platinum catalyst layer 10. When layer 10 comes into contact with hydrogen gas, the temperature rises sensitively.

  When the platinum catalyst layer 10 comes into contact with hydrogen gas, the temperature of the hot junction portion 7 of the thermocouple 5 rises, and a temperature difference is generated between the thermocouple 5 and the cold junction portion 8, thereby generating a thermoelectromotive force in each thermocouple 5. . The thermoelectromotive forces of these thermocouples 5 are added, and the output can be taken out from the thermopile extraction electrode 15. By detecting this output, the generation of hydrogen gas can be detected.

  FIG. 3 shows another embodiment of the present invention. The hydrogen gas sensor 1 and the amplifier 22 described above are arranged on the same base 21, and the thermopile lead electrode 15 of the hydrogen gas sensor is connected to the input end of the amplifier 22. It is a thing. According to this configuration, since the output from the thermopile extraction electrode 15 can be amplified and extracted by the amplifier 22, high-speed response detection can be performed even when the hydrogen gas has a low concentration and the output of the thermopile 5 is very small. In addition, since the hydrogen gas sensor 1 and the amplifier 22 are provided on the same base 21, the influence of noise due to external factors can be suppressed, and malfunction due to noise is reduced. If the hydrogen gas sensor 1 and the amplifier 22 are provided on the same semiconductor chip, the effect of suppressing the influence of noise due to external factors and the effect of reducing malfunction caused by noise can be further improved.

  FIG. 4 shows still another embodiment of the present invention, in which the hydrogen gas sensor 1 and the gold-black film infrared sensor 32 for detecting ambient temperature are arranged on the same base 31 and provided in the same case 34. It is a thing. The configuration of the gold black film infrared sensor 32 is the same as that of the hydrogen gas sensor 1 except that the catalyst layer is a gold catalyst layer 33 formed by vacuum vapor deposition of blackened gold. To do.

  The case 34 is provided with a vent 35 for introducing hydrogen gas, and a light shielding plate 36 is provided in the case 34 so that infrared rays or the like are not directly irradiated onto the platinum catalyst layer 10 and the gold catalyst layer 33. The light shielding plate 36 is also provided with a vent 37. In FIG. 4, 38 is a mold member, and 39 and 40 are output terminals of the sensors 1 and 32, respectively.

  In the hydrogen gas sensor 1, the platinum catalyst layer 10 becomes sensitive to infrared rays due to the ambient temperature, and the output of the hydrogen gas sensor 1 is influenced by the infrared rays and is not only due to the detected output of the hydrogen gas. In the embodiment, by detecting the ambient temperature with the gold black film infrared sensor 32, the detection output by the infrared of the hydrogen gas sensor 1 is canceled, the output of the hydrogen gas sensor 1 is corrected, and the influence of the infrared is eliminated. Can do.

  The hydrogen gas sensor 1 and the gold black film infrared sensor 32 are more preferably provided on the same silicon substrate 2 in terms of miniaturization. However, as described above, the two sensors 1 and 32 are separately provided. Even if they are formed on a semiconductor chip and placed in the same case 34 on the same base 31, a predetermined effect can be obtained.

  Further, since the sensor for detecting the ambient temperature is intended to accurately detect the temperature change of the case itself, other infrared sensors can be used in addition to the gold black film infrared sensor using the gold black film. . That is, since the hydrogen gas sensor of the present invention uses a blackened platinum catalyst layer, it reacts sensitively not only to hydrogen gas but also to heat changes (for example, the temperature change of the case itself), so the output change due to that heat. Is the purpose of providing a sensor for detecting the ambient temperature, and any sensor that can achieve this is sufficient. And it is possible to use the same configuration as the hydrogen gas sensor of the present invention as the ambient temperature detection sensor. In that case, the ambient temperature detection sensor is sealed to prevent hydrogen from entering. What is necessary is just to change the structure.

1 is a cross-sectional view schematically showing a basic structure of a hydrogen gas sensor according to the present invention. The top view which similarly shows the arrangement | positioning state of a thermocouple. 1 is a schematic plan view showing an embodiment in which a hydrogen gas sensor and an amplifier are provided on the same base. 1 is a schematic cross-sectional view showing an embodiment in which a hydrogen gas sensor and an ambient temperature detection infrared sensor are provided on the same base.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hydrogen gas sensor 2 Silicon substrate 3 Membrane 4 Cavity 5 Thermocouple 6 Thermopile 7 Hot contact part 8 Cold contact part 9 Planarization insulating layer 10 Platinum catalyst layer 11 Lower layer film 12 Polysilicon film 13 Insulating film 14 Aluminum film 15 Thermopile extraction electrode 21 , 31 Base 22 Amplifier 34 Case 35, 37 Vent 36 Light-shielding plate

Claims (5)

And a membrane formed on a silicon substrate,
A bottomed cavity formed by etching the silicon substrate from an etching hole provided in the membrane ;
The hot junction portion is located above the cavity , the cold junction portion is located outside the cavity, and a thermopile formed on the membrane;
An insulating film formed on the thermopile;
On this insulating film, a catalyst layer made of blackened platinum provided via a lower layer so as not to correspond to the cold junction part while corresponding to the hot junction part of the thermopile ,
A hydrogen gas sensor comprising: The hydrogen gas sensor according to claim 1, wherein the blackened platinum catalyst layer is formed by vapor deposition. 3. A hydrogen gas sensor according to claim 1, wherein the hydrogen gas sensor according to claim 1 is provided on the same semiconductor chip as an amplifier that amplifies the output of the thermopile . Hydrogen gas sensor, characterized in that the hydrogen gas sensor of claim 1 Symbol placement provided on the same semiconductor chip and the infrared sensor for the ambient temperature detected. A hydrogen gas sensor according to claim 1, wherein the hydrogen gas sensor is provided in the same case as the infrared sensor for detecting ambient temperature.

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