JP2002131264A - Contact combustion type gas sensor - Google Patents

Abstract

(57) [Abstract] [Problem] Small variation in gas detection sensitivity among products,
Stable flammable gas detection sensitivity is obtained, and the composition ratio of the heat conductive layer and the catalyst layer can be obtained as specified, resulting in stable characteristics and the ability to manufacture in a consistent thin film manufacturing process. The ability to improve manufacturing efficiency. SOLUTION: A gas detecting element 3 is formed in a zigzag shape on a substrate 2 and is a heater 8 for promoting combustion of a combustible gas.
And a heat conductive layer 10 made of a good heat conductor and a catalyst layer 11 which generates heat according to the amount of heat generated by the heater 8 transmitted through the heat conductive layer and acts as a catalyst when combustible gas is burned. And a multilayer film 12 laminated on the heater 8 along the zigzag shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact combustion type gas sensor for measuring a combustible gas by detecting combustion heat generated when a combustible gas is burned by a gas detection element and a compensation element.

[0002]

2. Description of the Related Art FIGS.
No. 811, a contact combustion type gas sensor 100
Is shown. In this contact combustion type gas sensor 100, a gas detecting element 3 and compensating elements 4, 5, 6 are provided adjacent to each other on a substrate 2. Has the function of measuring the amount of combustible gas by detecting the heat of combustion generated when combusting gas. The gas detecting element 3 and the compensating elements 4, 5, 6 are stacked on a dielectric film 7 stacked on the substrate 2.

The gas detecting element 3 includes a heater 8 for promoting the combustion of a combustible gas formed on the substrate 2, and a heat conductive layer 10 which is a thermal conductor provided in thermal contact with the heater 8. And the heater 8 conducted through the heat conducting layer 10
And a catalyst layer 11 that generates heat in accordance with the calorific value of the gas and acts as a catalyst when the combustible gas is burned.

[0004] A compensating element 4 (5, 6) is provided adjacent to the gas detecting element 3 for heating a combustible gas formed on the substrate 2 and a heater 8 for heating the combustible gas. And a thermal conductive layer 10 which is a good thermal conductor provided in contact with the substrate.

The gas detecting element 3 and the compensating element 4
The heaters 5 and 6 are laminated on the dielectric film 7 using platinum, and are connected to separate platinum pads 9 respectively.

In practice, the heat conductive layer 10 in the gas detecting element 3 and the compensating element 4 (5, 6) is formed using an anodic oxide film having a porous film form.

That is, as shown in FIGS. 4 (a) and 4 (b), the heat conductive layer 10 in the gas detection element 3 has a porous anodic oxide film in which a noble metal 11a as a catalyst is dispersed. And laminated on the substrate 2 so as to cover the entire heater 8.

[0008]

However, in the conventional contact combustion type gas sensor 100 configured as described above, the degree of porosity of the heat conduction layer 10 varies between products, and the gas detection element 3 is caused by the variation. There is a problem that the gas detection sensitivity varies among products.

The catalytic efficiency depends on the composition ratio of the heat conduction layer 10 and the catalyst layer 11. In the conventional catalytic combustion type gas sensor 100, the heat conduction layer 10 is formed as an anode having a porous film form. Since it is formed as an oxide film, it is difficult to obtain a composition ratio as designed, and there is a problem that the characteristics are not stable.

Further, a conventional catalytic combustion type gas sensor 1
In 00, since the heat conductive layer 10 was formed as an anodic oxide film having a porous film form,
There is also a problem that the formation process is peculiar and production efficiency is inferior.

Therefore, according to the present invention, the variation in gas detection sensitivity among products is small, stable detection sensitivity of combustible gas can be obtained, and the composition ratio between the heat conductive layer and the catalyst layer can be obtained as specified. It is an object of the present invention to provide a contact-combustion gas sensor which can obtain stable characteristics and can be manufactured in a consistent thin film manufacturing process and can also improve the manufacturing efficiency.

[0012]

According to a first aspect of the present invention, a gas detecting element and a compensating element are provided adjacent to each other on a substrate. In a contact combustion type gas sensor for measuring a combustible gas by detecting combustion heat generated when combustible gas is combusted, the gas detection element is formed in a zigzag shape on the substrate and burns the combustible gas. A heater for promoting the heat, a heat conductive layer made of a good heat conductor, and a catalyst layer acting as a catalyst when burning the combustible gas by generating heat according to the calorific value of the heater conducted through the heat conductive layer. And a multilayer film formed on the heater in a zigzag manner.

For this reason, in the first aspect of the present invention, the multilayer film is laminated on the heater in a zigzag manner, so that the surface area of the catalyst layer can be increased and the sensitivity can be increased. By arbitrarily controlling the number of the heat conduction layer and the catalyst layer to be constituted, the contact area with the flammable gas can be controlled, whereby the sensitivity can be adjusted according to the specification.

The multilayer film can be manufactured by a consistent thin film manufacturing process such as a sputtering method.

According to a second aspect of the present invention, there is provided the catalytic combustion type gas sensor according to the first aspect, wherein the multilayer film is formed by controlling each thickness of the heat conductive layer and the catalyst layer to an atomic level. It is characterized by having.

Therefore, according to the second aspect of the present invention, since the thickness of the catalyst layer is controlled to the atomic level, gas can be detected efficiently.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. Note that the same members or members having the same functions as those in FIGS. 3 and 4 are denoted by the same reference numerals and described.

FIG. 1 is a perspective view of a gas detecting element 3 in a contact combustion type gas sensor 1 according to an embodiment of the present invention, and FIG. 2 is a sectional view thereof.

The catalytic combustion type gas sensor 1 is composed of a combination of a gas detecting element and a compensating element as in the prior art, but has a different element structure. At this time, it is preferable that the compensating element is configured to have the same structure and resistance as the gas detecting element in consideration of a consistent film forming process and characteristics as the compensating element. For this reason, in the present embodiment, the compensation element is formed as having the same structure and resistance as the gas detection element 3, and after formation,
It is used by applying an insulator to lose gas sensitivity.

That is, in the catalytic combustion type gas sensor 1, a gas detecting element 3 and a compensating element (not shown) are provided adjacent to each other on a substrate 2 as in the prior art, and the gas detecting element 3 and the compensating element are combined. It has a function of measuring the combustible gas by detecting the combustion heat generated when the combustible gas is burned.

The gas detecting element 3 of the contact combustion type gas sensor 1 has a heater 8 formed in a zigzag shape on the substrate 2 to promote the combustion of the combustible gas, a heat conductive layer 10 made of a good heat conductor, and a heat conductive layer 10. A catalyst layer 11 that generates heat in accordance with the amount of heat generated by the heater 8 and that acts as a catalyst when combustible gas is burned through the heat conductive layer 10 is alternately stacked on the heater 8 and has a zigzag shape. And a multi-layer film 12 laminated along.

Such a gas detecting element 3 can be formed specifically as follows.

First, the silicon substrate 2 is oxidized to form silicon dioxide (SiO ₂ ) of about 6000 ° on the surface of the substrate 2. The oxidation condition at this time was that the silicon substrate 2 was held at 1100 ° C. for one hour in an oxygen and hydrogen atmosphere.

Next, an electrode (platinum pad 9) and platinum (Pt) to be a heater 8 are formed on the substrate 2 by DC sputtering so that the film thickness becomes 5000 ° by DC sputtering. After that, a multilayer film 12 is formed by alternately laminating alumina (Al ₂ O ₃ ) to be the heat conductive layer 10 by RF sputtering and palladium (Pd) to be the catalyst layer 11 by DC sputtering with an arbitrary film thickness. Further, the heater 8 and the multilayer film 12 are formed in the same zigzag shape by patterning, as shown in FIG.

The gas detection element 3 thus formed is
Since the multilayer film 12 is laminated on the heater 8 along the zigzag shape, high sensitivity can be achieved by enlarging the surface area of the catalyst layer 11, and the heat conductive layer 10 and the catalyst layer constituting the multilayer film 12 can be improved. By arbitrarily controlling the number of 11 layers, the contact area with the flammable gas can be controlled, whereby the sensitivity can be adjusted according to the specification.

The multilayer film 12 can be manufactured by a consistent thin film manufacturing process by a sputtering method.

As a result, the contact combustion type gas sensor 1 having the gas detecting element 3 has a small variation in gas detection sensitivity among products, provides a stable detection sensitivity of combustible gas, and has the same function as the heat conductive layer 10. The composition ratio of the catalyst layer 11 can be obtained as specified, stable characteristics can be obtained, and a consistent thin film manufacturing process can be performed, thereby improving the manufacturing efficiency.

Preferably, the multilayer film 12 is formed by controlling the thickness of each of the heat conductive layer 10 and the catalyst layer 11 to an atomic level.

That is, the multilayer film 12 has a design layer thickness of Al ₂ O ₃ as the heat conductive layer 10 of 48.8 ° and the catalyst layer 1
The film is formed by setting the design layer thickness of Pd as 2.8 °.

At this time, the thickness ratio of Al ₂ O ₃ and Pd can be derived from the optimum composition in the case of a sintered body. Optimum composition, since it is known that a Al ₂ O ₃ -15wt% Pd, when this is converted to volume ratio, Al ₂
O ₃ -5.73 vol% Pd. This volume ratio can be used as a layer thickness ratio. Since the atomic radius of Pd is 1.4 °, the layer thickness of one atom of Pd is 2.8 °, and the volume ratio of Al ₂ O _{3 to} this is 2.8 °. Is 48.8 °. In addition, multilayer film 1
2 can be formed by setting the number of periods of the layer to, for example, 50 periods. In this case, too, the thickness can be reduced by controlling the thickness of each layer at the atomic level.

The gas detecting element 3 configured as above is
Since the thickness of the catalyst layer 11 is controlled to the atomic level, gas can be efficiently detected, which contributes to the increase in sensitivity of the catalytic combustion type gas sensor 1.

In addition, the contact combustion type gas sensor 1 is
The size can be reduced by reducing the thickness of the multilayer film 12, and the power consumption can be reduced.

[0033]

As described above, according to the first aspect of the present invention, since the multilayer film is laminated on the heater along the zigzag shape, the sensitivity can be increased by enlarging the surface area of the catalyst layer. As well as controlling the number of layers of the heat conductive layer and the catalyst layer constituting the multilayer film arbitrarily, the contact area with the flammable gas can be controlled, thereby enabling sensitivity adjustment according to the specification, As a result, the variation in gas detection sensitivity among products is small, stable detection sensitivity of combustible gas can be obtained, and the composition ratio between the heat conductive layer and the catalyst layer can be obtained as specified, and stable characteristics can be obtained. In addition, it is possible to perform manufacturing in a consistent thin film manufacturing process, and it is possible to improve manufacturing efficiency.

According to the second aspect of the present invention, since the thickness of the catalyst layer is controlled at the atomic level, gas detection can be efficiently performed, thereby further increasing the sensitivity. In addition, the size can be reduced by reducing the thickness of the multilayer film, and the power consumption can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view of a gas detection element applied to a contact combustion type gas sensor as one embodiment of the present invention.

FIG. 2 is a cross-sectional view of the gas detection element of FIG. 1 taken along the line II-II.

3A and 3B show a conventional catalytic combustion type gas sensor, in which FIG. 3A is a sectional view and FIG. 3B is a top view thereof.

4A and 4B show a gas detection element applied to a conventional catalytic combustion type gas sensor, wherein FIG. 4A is a perspective view thereof, and FIG.
It is sectional drawing in alignment with the bb line of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Contact combustion type gas sensor 2 Substrate 3 Gas detection element 8 Heater 10 Heat conduction layer 11 Catalyst layer 12 Multilayer film

Claims (2)

[Claims] 1. A gas detecting element and a compensating element are provided adjacent to each other on a substrate, and the gas detecting element and the compensating element detect combustion heat generated when combustible gas is burned, thereby detecting flammable gas. In a contact combustion type gas sensor for measuring gas, the gas detection element is formed in a zigzag shape on the substrate to promote combustion of a combustible gas, a heat conduction layer made of a good heat conductor, and a heat conduction layer formed of a heat conductor. And a catalyst layer that generates heat according to the heat generated by the heater and acts as a catalyst when combustible gas is burned through the heater, and is stacked on the heater in a zigzag manner. A contact combustion type gas sensor comprising a multilayer film. 2. The catalytic combustion type gas sensor according to claim 1, wherein the multilayer film is formed by controlling the thickness of each of the heat conduction layer and the catalyst layer to an atomic level. Contact combustion type gas sensor.