JPH01208806A - Thin-film temperature sensor - Google Patents

Abstract

PURPOSE:To realize a low-cost thin-film temperature sensor having excellent characteristics by forming a thin-film composed of the same noble metal as a foundation film onto the foundation film attached onto an insulating base body consisting of ceramics, etc. CONSTITUTION:A foundation film 2 attached onto an alumina substrate 1 at a base-body temperature from 750 deg.C to 900 deg.C and consisting of platinum takes a partially massive shape and is formed in insular structure in a plane, but an upper thin-film 3 made up of the same platinum as the foundation film is prepared onto the foundation film 2, thus easily preparing an excellent thin- film temperature sensor, which has resistance temperature characteristics (TCR) at approximately the same value as a value peculiar to a metal and electrical connection of which is also brought to a continuous state. Since the sensor is composed of the thin-film, geometry can be scaled down, thermal responsiveness is reduced and a high resistance value can be shaped.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a thin film temperature sensor that has a correlation between temperature change and resistance value change.

Conventional technology Metal temperature sensors that detect temperature by converting resistance variables into temperature variables using the temperature resistance characteristics (TCR) unique to metals include those that use metal wires and those that use thin films. There are two types. Among these, those that utilize metal wires are used as temperature sensors, such as by simply stretching thin metal wires or by winding the metal wires in a spiral shape onto an insulating substrate.

Also improved measurement accuracy among metal temperature sensors.

Precious metals are particularly used in products intended to ensure reliability, such as improving long-term stability.

Problems to be Solved by the Invention In the above-mentioned temperature sensors that use metal wires, there is a limit to how thin the wires can be. However, it is necessary to sufficiently increase the thickness, which has the disadvantage that the two dimensions of the shape become large. Further, as the dimensions of the shape 9 become larger, the thermal response becomes poorer, which may cause problems as a temperature sensor. - On the other hand, if the two dimensions of the shape are made smaller, the thermal response improves, but since the metal wire becomes shorter, the resistance value obtained becomes lower, and the amount of change in resistance value with respect to temperature changes is small, making it difficult to use as a temperature sensor. The quantity was insufficient.

Also, when comparing the same resistance value, products made using thin films can be made with a smaller shape and one dimension than those made using metal wires, so the thermal response is smaller, or It is also easy to create a relatively high resistance value of up to several XΩ.

It has many advantages. However, if the metal is in the form of a film, the scattering of conduction electrons on the film surface increases, and since the temperature dependence of this scattering is small, the TCR tends to be smaller than the value inherent to the metal.

As a countermeasure to this problem, measures such as increasing the film thickness have been taken, but the product cost is high and it is difficult to provide an inexpensive product.

The present invention has been made in view of the problems of the prior art described above.

The purpose of this invention is to provide a noble metal temperature sensor that is inexpensive and has excellent characteristics.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a substrate temperature of 750°C or higher when depositing a film on an insulating substrate such as ceramics.
On top of the base film deposited at temperatures below 0°C.

A thin film made of the same noble metal as the base film is formed.

The base film deposited on an insulating substrate such as functional ceramics at a substrate temperature of 750°C or more and less than 900"C becomes partially lumpy, and when viewed from above, it takes on an island-like structure and partially becomes discontinuous. The electrical continuity is insufficient compared to that in the continuous state. However, in the lumpy part, there is no phenomenon such as increased scattering of conduction electrons on the film surface, so the TCR value is the same as the value specific to the metal. .Next, by creating a thin film made of the same noble metal as this base film on this base film.

By increasing the electrical connections between lumpy and island-like parts, it is possible to easily create a good metal temperature sensor that has the same TCR value as that unique to metals and has continuous electrical connections. . In addition, since it uses a thin film, it can be made in a small shape with one dimension, and has low thermal response and a high resistance value.

Example The present invention will be explained in detail below.

The thin film was created using a resistance heating vacuum evaporation method.

The thickness of the base film was 4000 angstroms on each side, and the thickness was controlled by monitoring the film deposition using a crystal thickness monitor. The base film and upper thin film were made of the same noble metal, and platinum was used on each side. Base film.

The heating during deposition of the upper thin film was performed by radiation heating using a halogen heater, and the heating was controlled by measuring the substrate surface temperature. Heating during the deposition of the upper thin film was at the substrate surface temperature of 300°C on each side. Heating during the deposition of the base film was at the substrate surface temperature of 700°C in Comparative Example 1, 750°C in Example 1, and 750°C in Example 1. 80 in 2
0°C1 In Example 3, the temperature was 880°C, and in Comparative Example 6, it was 960°C. The thickness of the upper thin film was 1000 angstroms on each side. An alumina substrate with a flatness of 0.2 micron Ra was used as the base. Note that, as a conventional example, one prepared under the same conditions as Example 2 except for the presence of the upper thin film is shown. Table 1 shows the characteristics of each side. Also, Figures 1 to 4
The figure shows a schematic diagram of the sensor made on each side.
1 in the figure is an alumina substrate.

2 is a base film, and 3 is an upper thin film.

Although platinum is used as the noble metal in the embodiment, other noble metals such as palladium can be used.

Further, although an alumina substrate was used as the base, other insulating bases, such as a quartz cylinder, may be used.

(Left below) In Comparative Example 1, as shown in Figure 2, since the deposition temperature of the base film 2 is low, the presence of lumpy parts of the precious metal is small, and the scattering of conduction electrons on the film surface is large ( It is thought that TCR is becoming smaller.

Furthermore, in Comparative Example 2, the lumpy portions are too large as shown in FIG. 3, and the electrical connection between the lumpy portions of the base film 2 depends on the upper thin film 3, so the TOH effect of the upper thin film 3 is large. it is conceivable that.

In Examples 1 to 3, as shown in FIG. 1, the electrical connection of the bulky and island-like portions of the base film 2 is well established by the upper thin film 3, so that the metal-specific TCP is approximately 3.900 pp.
A value close to m/'C is obtained.

As shown in the conventional example, the base film 2 prepared under the same conditions as in Example 2 also did not reach a good TOR because electrical connection through the upper thin film could not be obtained as shown in FIG. This is considered to be effective.

Effects of the Invention As described above, according to the present invention, it is possible to obtain a thin film having a value similar to the TCR specific to metals, and to realize a thin film temperature sensor with excellent characteristics at low cost.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing Examples 1 to 3 of the present invention, and FIG.
The figure is a schematic cross-sectional diagram when the base film deposition temperature is low, Figure 3 is a schematic cross-sectional diagram when the base film deposition temperature is high, and Figure 4 is a schematic cross-sectional diagram showing a conventional example without an upper thin film. be. 1... Alumina substrate, 2... Base film,
3...Top thin film. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 4

Claims (1)

[Claims] Substrate temperature 750 when depositing a film on an insulating substrate such as ceramics
A thin film temperature sensor in which a thin film made of the same noble metal as the base film is formed on top of a base film deposited at a temperature of 0.degree. C. or more and less than 900.degree.