JPH0882613A - Manufacture for electrode film for sensor - Google Patents

Abstract

PURPOSE: To provide a method for manufacturing a a electrode film for a sensor whereby, when a thin film of a noble metal is formed as an electrode on an insulating substrate such as an oxide substrate or the like, a layer of a strong adhering force and formed of a material hard to mutually diffuse to the noble metal is layered therebetween. CONSTITUTION: After silicon and a noble metal are sequentially piled on an insulating substrate, the pile is held in the air of about 500-900 deg.C, whereby the sensor electrode film is manufactured. The obtained sensor electrode film enhances an adhering force between the insulating substrate and the noble metal electrode film and at the same time, keeps a specific resistance constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an electrode film for a sensor. More specifically, the present invention relates to a method for manufacturing a sensor electrode film having improved adhesion to an insulating substrate on which an electrode film is formed.

[0002]

2. Description of the Related Art Conventionally, electrodes used for various sensors are made of gold, which is highly stable because it is difficult to form an oxide in the atmosphere.
Noble metals such as platinum and palladium are used as electrode materials. These noble metal electrode materials are deposited on an insulating substrate, generally an oxide substrate such as SiO ₂ or Al ₂ O ₃ in a thin film form to form an electrode. There is a problem that it is scarce and peels off during processing or over time. There is a theory that it is difficult to form a metal oxide between these oxides and a noble metal, but it is not clear.

[0003] As a method of improving the adhesion between the two, a metal layer having a strong adhesion to an oxide substrate is generally provided. At this time, unless the sensor used as an electrode is exposed to a high temperature in a manufacturing stage or a use stage, no special consideration is given thereto, and chromium having a strong adhesive force is often used.

[0004] However, some sensors are annealed at the stage of manufacturing the sensor, and temperature sensors are often used at a high temperature, and the gas sensor must operate at a high temperature. Very often, sensors are exposed to high temperatures.

When a noble metal thin film electrode having a metal layer having strong adhesion is exposed to a high temperature, diffusion between the metals becomes remarkable and the resistivity changes. Further, when the atmosphere is an oxidizing atmosphere such as air, oxidation of the metal diffused in the noble metal occurs, which also affects the resistivity. Therefore, it is necessary to form the layer for improving the adhesive force from a material that hardly causes mutual diffusion with the noble metal.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to form a noble metal thin film as an electrode film on an insulating substrate such as an oxide substrate, in which the noble metal is made of a material that is hard to interdiffuse and has strong adhesion. It is to provide a method of manufacturing an electrode film for a sensor in which layers are laminated.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
This is achieved by sequentially depositing silicon and a noble metal on an insulating substrate, and then maintaining the atmosphere in the atmosphere at about 500 to 900 ° C. to manufacture an electrode film for a sensor.

As the insulating substrate, the above-mentioned SiO ₂ , Al ₂ O _{3 are used.}
In addition to oxide substrates such as glass substrates, glass substrates and the like can be used. The silicon and the noble metal can be deposited by any method generally used for forming a thin film such as a vacuum vapor deposition method, a sputtering method, an ion plating method, and the stepwise deposition thereof can be performed by the same reaction apparatus. Can be performed stepwise. The Si layer generally has a thickness of about 0.5-100 nm, preferably about 5-50 nm, and the noble metal layer generally has a thickness of about 50 nm.
It is formed with a film thickness of ~ 500 nm, preferably about 100-300 nm.

The noble metal / Si laminated film thus formed on the insulating substrate is exposed to the atmosphere of about 500 to 900 ° C., preferably about 600 to 800 ° C., in order to enhance the adhesive force with the insulating substrate. Hold for about 0.5-10 hours. At a holding temperature lower than this, the effect of improving the adhesive force is not sufficient, while at a temperature higher than this, grain growth of the noble metal thin film itself becomes remarkable. Moreover, by applying such high temperature holding, the sensor electrode film exhibits a constant resistivity.

[0010]

EFFECTS OF THE INVENTION When a noble metal thin film is formed as an electrode film on an insulating substrate such as an oxide substrate, a silicon thin film having a strong adhesive force is laminated between them, and the thin film is exposed to a high temperature atmosphere. By holding it, the adhesive force between the insulating substrate and the noble metal electrode film can be increased and the resistivity can be made constant, so this can be used for temperature sensors, gas sensors and other sensors. It can be effectively used as an electrode.

[0011]

Next, the present invention will be described by way of examples.

EXAMPLE A Si crucible and a Pt crucible for vacuum deposition were placed in a vacuum deposition apparatus in which an alumina flat plate was placed on a substrate holder, and the apparatus was evacuated to 5 × 10 ^-6 Torr or less. Then S with electron beam
i is heated to deposit 50 nm of Si on the alumina flat plate, and while maintaining the vacuum state, Pt is continuously heated by an electron beam to deposit Pt of 300 nm to deposit the Pt / Si laminated film on the alumina flat plate. Formed.

This Pt / Si laminated film forming alumina flat plate was
The adhesive force of the Pt / Si laminated film to the alumina flat plate was measured by a tensile test method by holding each in the atmosphere of ℃, 600 ℃, 700 ℃ or 800 ℃ for 5 hours. The relationship between the holding temperature and the adhesive force is shown in the graph of FIG. The relationship between the holding temperature and the resistivity is shown in the graph of FIG.

Comparative Example In the example, the Pt film (thickness 3
Only 00 nm) was formed on an alumina plate. The adhesion and resistivity of the Pt film to the alumina plate are also shown in the graphs of FIGS. 1 and 2.

From the above results, the following can be said. (1) Pt / Si laminated film has 2.7 times more adhesive force than Pt film, even if high temperature holding of 600 ° C or higher is not applied.
By applying the above high temperature holding, sufficient adhesive force of 600 kgf / cm ² or more is exhibited. (2) When the high temperature holding of 500 ℃ or more is not applied, the resistivity of Pt film is 1.5 × 10 ^-5 Ωcm, whereas the Pt / Si laminated film is 2.9 × 10 ^-5.
Although it was Ω · cm, by applying a high temperature holding of 500 ° C. or more, it becomes to show an almost constant resistivity of about 2 × 10 ⁻⁵ Ω · cm.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between holding temperature and adhesive force in an example.

FIG. 2 is a graph showing the relationship between the holding temperature and the resistivity in the example.

Claims (1)

[Claims] 1. A method for producing an electrode film for a sensor, which comprises sequentially depositing silicon and a noble metal on an insulating substrate and then holding the same in the atmosphere at about 500 to 900 ° C.