Gas detector

Patent metadata

Field	Value
Publication number	US-9829455-B2
Application number	US-201414555010-A
Country	US
Kind code	B2
Filing date	Nov 26, 2014
Priority date	Nov 29, 2013
Publication date	Nov 28, 2017
Grant date	Nov 28, 2017

Abstract

A gas detector includes a gas detection element having a protection layer formed of an oxide film mainly containing tantalum oxide (Ta 2 O 5 ). Since the protection layer has excellent condensed-water resistance, even when water droplets adhere thereto, the morphology thereof does not change from dense to porous. Thus, since a change in property of the protection layer, which would otherwise be caused by adhesion of water droplets, can be reduced in the gas detector, even when water droplets adhere to the outermost surface layer of the gas detection element, impurities can be prevented from entering the protection layer (the outermost surface layer), whereby a change in thermal capacity of the gas detection element can be reduced. Thus, the gas detection element of the gas detector has excellent alkali resistance and condensed-water resistance.

First claim

The invention claimed is:

1. A gas detector comprising:
a gas detection element configured such that at least a heat-generating resistor and an insulation layer are laminated on a semiconductor substrate, and the insulation layer covers the heat-generating resistor; and
a controller that controls energization of the heat-generating resistor and detects a target gas on the basis of resistance of the energized heat-generating resistor, wherein
the gas detection element has a gas impermeable oxide film laminated on a surface of the insulation layer in such a manner as to cover the insulation layer,
the oxide film contains at least one of Ta, Nb, and Hf, and forms an outermost surface layer which comes into contact with a gaseous atmosphere containing the target gas,
an adhesion-enhancing film is formed between the heat-generating resistor and the insulation layer, and
the insulation layer is made of a material different from a material of the oxide film.

2. The gas detector according to claim 1 , wherein the oxide film mainly contains tantalum oxide.

3. The gas detector according to claim 1 , wherein the insulation layer has a surface layer formed of silicon nitride.

4. The gas detector according to any one of claims 1 to 3 , wherein the oxide film has a thickness equal to or greater than one-fiftieth of a thickness of the heat-generating resistor as measured in a direction perpendicular to front and back surfaces of the semiconductor substrate.

5. The gas detector according to any one of claims 1 to 3 , wherein the oxide film has a thickness of 5 to 200 nm.

6. The gas detector according to claim 4 , wherein the thickness of the oxide film is a distance between the surface of the insulation layer and a surface of the oxide film which comes into contact with the gaseous atmosphere.

7. The gas detector according to claim 1 or 2 , wherein the oxide film is formed through a sputtering process.

8. The gas detector according to claim 1 or 2 , wherein the target gas is hydrogen gas.

9. The gas detector according to claim 1 or 2 , which is configured such that at least the gas detection element is disposed at a specific position on a fuel cell system that generates electricity from hydrogen and oxygen, and is adapted to detect hydrogen gas used in the fuel cell system.

10. The gas detector according to claim 2 , wherein the insulation layer has a surface layer formed of silicon nitride.

11. The gas detector according to claim 5 , wherein the thickness of the oxide film is a distance between the surface of the insulation layer and a surface of the oxide film which comes into contact with the gaseous atmosphere.

12. The gas detector according to claim 1 , wherein the adhesion-enhancing film is made of tantalum.

13. The gas detector according to claim 1 , further comprising a platinum film formed on the adhesion-enhancing film, wherein the adhesion-enhancing film is provided to enhance the adhesion between the platinum film and the insulation layer.

14. The gas detector according to claim 1 , wherein the insulation layer is made of either silicon dioxide or silicon nitride.

Assignees

• Ngk Spark Plug Co

Inventors

• Watanabe Masaya
• Kitanoya Shoji
• Ichikawa Daisuke
• Yamashita Masahiro
• Matsukura Yusuke

Classifications

• Y02E60/50

  Fuel cells · CPC title

• G01N25/18 Primary

  by investigating thermal conductivity (by calorimetry G01N25/20; by measuring change of resistance of an electrically-heated body G01N27/18) · CPC title

• G01N27/18

  caused by changes in the thermal conductivity of a surrounding material to be tested (G01N27/20 takes precedence) · CPC title

• G01N27/16 Primary

  caused by burning or catalytic oxidation of surrounding material to be tested, e.g. of gas · CPC title