JPH01236603A - Sic thin film thermistor - Google Patents

Abstract

PURPOSE:To make it possible to suppress irregularity in the resistance value and the thermistor constant of the title thin film thermistor by bringing the degree of surface roughness of a heat-resisting insulated substrate to 1mum or less. CONSTITUTION:The surface roughness of a heat-resisting insulating substrate 1 is formed at 1mum or less by conducting a mirror-polishing work thereon. Then, Pt-Au conductive paste is printed on said substrate 1 using a screen printing method, and after the paste has been dried up, a pair of pectinated electrodes 2 are formed by sintering. Also, a part of said electrodes 2 is used as terminal attaching parts 2a and 2b, and an SiC temperature-sensitive resistance film is formed on the substrate 1, excluding the terminal attaching parts 2a and 2b, and the electrode 2 by conducting a high frequency sputtering method. As the surface roughness of the insulated substrate 1 becomes 1mum or less as above-mentioned, the irreqularity in resistance value and thermistor constant can be made small.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an SIC thin film thermistor that is used as a temperature-sensitive resistance element for a temperature sensor and has excellent bithermal responsiveness and high heat resistance.

Conventional technology temperature sensors include various temperature sensing means, but thermistor elements made of metal oxides are common.

It has been put into practical use in various fields. In recent years, with the expansion of applications, there has been a demand for devices with wider temperature detection ranges, faster response speeds, and higher reliability under various environments.

In response to such demands, thermally extremely stable silicon carbide thermistors have been put into practical use. In view of the intended use, devices made of thin films with excellent thermal responsiveness have been put into practical use.

This SiC thin film thermistor has a configuration as shown in FIG. In FIG. 1, 1 is a heat-resistant insulating substrate with a surface roughness of about 3 μm, and 2 is the heat-resistant insulating substrate 1.
These are a pair of comb-shaped electrodes made of PT gold alloy, etc., which are formed by firing on top of the comb-shaped electrodes.
, 2b. 3 is the terminal mounting section 2a, 2b.
A temperature-sensitive resistance film of silicon carbide (Sin) is formed on the entire surface of the substrate 1 and the electrode 2 except for the electrode 2 by a high-frequency sputtering method.

Problems to be Solved by the Invention However, thin-film thermistors in which the temperature-sensitive resistive film in the conventional configuration is obtained by high-frequency sputtering have large variations in resistance value and thermistor constant, making it difficult to put them into practical use.
Several post-processing steps were required.

The present invention solves these problems, and aims to provide a SiC thin film thermistor that can be produced stably by suppressing variations in resistance value and thermistor constant.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention includes a heat-resistant insulating substrate, a pair of comb-shaped electrodes formed thereon, and a terminal attachment method for a part of the electrodes. The heat-resistant insulating substrate has a surface roughness of 1 μm or less, and includes a SIC temperature-sensitive resistance film formed on the entire surface of the substrate and the electrodes, except for the outer surface of the heat-resistant insulating substrate.

In other words, the present inventors investigated various surface roughness of heat-resistant insulating substrates, and by creating an insulating substrate with a smooth surface, the variation in resistance value and thermistor constant was suppressed. It was derived from experimental results that this is possible.

Effect: According to this configuration, the variation in the resistance value of the thin film thermistor after high-frequency sputtering is reduced to about 2 compared to the conventional method, and the variation in the thermistor constant can also be suppressed to about z.

EXAMPLE An example of the present invention will be described below with reference to the drawings. Here, since the configuration itself is basically the same as the conventional example, it will be explained using FIG. 1.

First, for the heat-resistant insulating substrate 1 shown in FIG. 1, a substrate with an alumina purity of 90% or more was used in consideration of practicality.

This alumina substrate is 50rrrm x 50rrrm
X 0.2t, and the surface roughness was 3 μm. This was mirror-polished and samples were collected at each stage to obtain an alumina substrate with a surface roughness of 0.03 μm to 3 μm.

Next, a pt-AU-based guide paste was printed on this substrate 1 by screen printing, dried at 120'C for 20 minutes, and then fired to form a pair of comb-shaped electrodes 2. The peak temperature at this time is 950°C to 1050°C, the peak holding time is 10 minutes to 20 minutes, and the temperature rise and fall is 800°C/1 hour.
It was r. Further, part of the electrode 2 was designated as portions 2a and 2b with the number of terminals υ. Next, parts 2a and 2 with the number of terminals are
A temperature-sensitive resistance film 3 was formed on the substrate 1 and the electrode 2 except for b. The formation conditions at this time were that sputtering was performed for 6 hours in a murky atmosphere using a target made of silicon carbide.

The sputtering pressure at this time is (2 to 4) x 10” TORR
Met.

R25 of the SiC thin film thermistor thus obtained
The relationship between the surface roughness and the substrate surface roughness was determined, and the result was as shown in FIG. In addition, the relationship between the thermistor constant and the substrate surface roughness is as shown in Figure 3, and for the comparative example (surface roughness 3 μm), both the resistance value and thermistor constant have a substrate surface roughness of 1 μm or less. In this region, the variation suddenly becomes smaller. Note that the electrode 2 in the example has a line spacing of 8
There were 5 pairs of comb-shaped electrodes with a length of 2+++ m.

Here, in the above embodiment, the surface roughness of the insulating substrate 1 is 1 μm.
Although it is not clear why the variations in resistance value and thermistor constant become smaller when the values are below, it is presumed that crystal growth becomes more uniform during sputtering and a homogeneous film is formed.

Furthermore, it is presumed that the same effect as described above can be obtained even if the surface roughness is 0.03 μm or less, but this may be determined as appropriate in view of the effect and economical efficiency.

Effects of the Invention As detailed above, according to the present invention, variations in resistance value and thermistor constant are suppressed, the yield in the manufacturing process is improved, stable production is possible, and its industrial value is outstanding. There is something.

[Brief explanation of the drawing]

Fig. 1 is a plan view for explaining the structure of the present invention and a conventional thin film thermistor, and Fig. 2 is a basic plan view of a SiG thin film thermistor element for explaining the present invention, and the resistance value and substrate surface measured at 25°C. FIG. 3 is an explanatory diagram showing the relationship between the thermistor constant and the substrate surface roughness. DESCRIPTION OF SYMBOLS 1...Heat-resistant insulating substrate, 2...Comb-shaped electrode, 2a, 2b...Terminal extraction part, 3...
...Temperature-sensitive resistance film. Name of agent: Patent attorney Toshio Nakao, and 1 other person - 5 absolute slides in heat-resistant stocks 1 Provisional Figure 1

Claims (1)

[Claims] A heat-resistant insulating substrate, a pair of comb-shaped electrodes formed thereon, and a SiC temperature-sensitive resistance film formed by high-frequency sputtering on the entire surface of the substrate and the electrodes, excluding some terminal attachment portions of the electrodes. An SiC thin film thermistor comprising: and wherein the heat-resistant insulating substrate has a surface roughness of 1 μm or less.