JPS6222401A - Thermosensitive element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a temperature sensing element. More specifically, the present invention relates to a temperature-sensitive element with excellent responsiveness and good environmental resistance.

[Conventional technology]

There are many types of temperature sensing elements currently in use, each with its own characteristics. In particular, with the recent trend toward electronics, it is desired that temperature-sensitive elements not only be readable by the human eye, but also be capable of emitting electrical signals that can be used to control temperature and other equipment. . Silicon carbide thin film thermistors are currently used in such applications, but silicon carbide thin films often peel off from the substrate due to thermal shock (chipping).

Because of this, it has drawbacks such as a high product defect rate.

The present inventor has previously found that it has excellent durability, good proportionality and responsiveness to temperature, and can be suitably used for measurements over a wide temperature range from near room temperature to high temperature range. As a temperature-sensing element, we have proposed a thin film made of a silicon carbide alloy resistor formed on an insulating temperature-sensing element substrate (Japanese Patent Application No. 59-774).
No. 34).

[Problem that the invention seeks to solve]

As mentioned above, thin film thermistors made of silicon carbide suffer from chipping, and due to problems such as environmental resistance, they are used in a structure sealed in a glass container. For this reason, the response is poor, and the 90% response up to 300°C is approximately 50 to 6
It requires a sand diameter of 0, and therefore has the disadvantage of not being able to follow rapid temperature changes.

Therefore, in addition to the solution using the silicon carbide alloy resistor thin film described above, the present inventors have found that a temperature-sensitive element with excellent responsiveness and environmental resistance can be obtained by using a thin film of silicon carbide itself. After conducting various studies in search of a solution, we found that this problem could be effectively solved by covering a silicon carbide thin film formed on an insulated silicon substrate with a fluorine-containing polymer thin film. I found it.

[Means for Solving the Problems] and [Operations] Accordingly, the present invention relates to a temperature sensing element, which comprises a silicon carbide thin film in contact with an electrode on the surface of an insulated silicon substrate. is formed, and the silicon carbide thin film is covered with a fluorine-containing polymer thin film.

Insulating a silicon substrate is performed by oxidizing or coating the surface of a silicon substrate, which is generally formed from a silicon wafer with a thickness of about 0.2 to 0.5 mm, with silicon oxide, silicon nitride, etc. .

Oxidation of the silicon substrate surface is performed by thermal oxidation, anodic oxidation, etc., and generally a thermal oxidation method is used. In that case, a silicon substrate such as a silicon wafer is heated to about 800 to 1250° C. for about 1 to 4 hours under oxygen flow to form an insulating film of silicon oxide (SiO□) on its surface.

The thickness of the insulating film formed depends on thermal oxidation conditions, mainly heating temperature and heating time, but is generally about 0.1 to 0.5 μm.

Instead of forming a silicon oxide thin film using such an oxidation method, magnetron
A silicon oxide thin film or a silicon nitride thin film having a similar thickness may be formed by a sputtering method, an ion blating method, or the like, and these coating thin films may be used as an insulating film.

Next, carbonization with a thickness of approximately 0.5 to 1 μm is applied to a portion of the insulating film on the surface of the silicon substrate formed by these various methods by remagnetron sputtering, ion blating, etc. A thin silicon film is formed. Both ends of the formed silicon carbide thin film are in contact with electrodes formed by vapor deposition, for example, aluminum electrodes.

The silicon carbide thin film thus formed is covered with a fluorine-containing polymer thin film so that no exposed portion is exposed on the insulated silicon substrate. This fluorine-containing polymer thin film is generally formed as a fluorine-based plasma polymerized film by plasma polymerization of a fluorocarbon compound.

As a fluorocarbon compound to be plasma polymerized, 1
For example, saturated fluorocarbon compounds such as perfluoroethane, perfluoropropane, and perfluorocyclobutane, or unsaturated fluorocarbon compounds such as perfluoroethylene are used. In these plasma polymerization reactions, a silicon substrate with a silicon carbide thin film formed on its surface is placed in a plasma polymerization reaction apparatus, the pressure inside the reaction vessel is set to 10-4 to 10-' Torr, and then a fluorocarbon compound is added. Predetermined pressure (approximately 0.01 to 0.3
Torr), a constant power is applied by a high-frequency oscillator to generate plasma, and a plasma polymerized film with a thickness of about O,OS to 0.5 μm is formed there. .

FIG. 1 of the drawings is a plan view (a) of one embodiment of a temperature-sensitive element according to the present invention and a cross-sectional view (b) along its center line, in which an insulating film 2 is formed on the surface of a silicon substrate 1. A silicon carbide thin film 3 is formed thereon so as to be in contact with the electrodes 4° 4', and the silicon carbide thin film portion is covered with a fluorine-containing polymer thin film 5. Note that numerals 6 and 6' are silver pastes provided on the electrodes, and 7 and 7' are lead wires drawn out from there.

〔Effect of the invention〕

The temperature-sensitive element according to the present invention uses silicon, which has good thermal conductivity, as a substrate and covers the silicon carbide thin film formed on the surface insulating film with a fluorine-containing polymer thin film, thereby making it a glass-encapsulated type. The observed decrease in responsiveness did not occur, and a good response speed was obtained. Moreover, the fluorine-containing polymer thin film that covers the silicon carbide thin film not only exhibits the stain resistance characteristic of fluorine-containing polymers and is difficult to attract dirt, but also when formed by plasma polymerization. It has no pinholes and therefore is not easily affected by humidity, and has excellent environmental resistance.

〔Example〕

Next, the present invention will be explained with reference to examples.

EXAMPLE A temperature-sensitive element as shown in FIG. 1 was manufactured in a first-order manner.

A thin M (thickness: 0.2 μm) of silicon oxide is formed on a silicon wafer substrate by magnetron sputtering, and by applying magnetron sputtering while covering the excess portion of the insulating film, the center of the insulating film is A silicon carbide thin film of 3 mm x 2 mm x 0.5 μm was formed on the part. The silicon carbide thin film was coated with a thickness of 5cm x 4+nm x 0.5μm by vapor deposition so that both ends of the film were in contact with each other.
After forming a pair of aluminum electrodes, a perfluorocyclobutane plasma polymerized film (thickness: 0.3 μm) was formed to sufficiently cover the silicon carbide thin film portion.

When the resistance of this thermosensitive element was measured at various temperatures in the atmosphere, the results shown in the graph of FIG. 2 were obtained. Moreover, when the response of this temperature sensing element is measured as 90% response time.

6 seconds for 150℃→25℃, and 25℃→150℃
C., a value of 5 seconds was obtained, compared to a value of 50 to 60 seconds for a commercially available silicon carbide thin film thermistor.

It can be seen that the performance has been significantly improved.

[Brief explanation of drawings]

FIG. 1 is a plan view (a
) and its center line sectional view (b). Moreover, FIG. 2 is a graph showing the element resistance value at each temperature of the temperature-sensitive element of the present invention. (Explanation of symbols) 1... Silicon substrate 2... Insulating film on the substrate surface 3... Thin film made of silicon carbide 4... Electrode

Claims (1)

[Scope of Claims] 1. A temperature-sensitive element formed by forming a silicon carbide thin film in contact with an electrode on the surface of an insulated silicon substrate, and covering the silicon carbide thin film with a fluorine-containing polymer thin film. 2. The temperature sensing element according to claim 1, wherein a silicon substrate whose surface is oxidized is used as the insulated silicon substrate. 3. The temperature-sensitive element according to claim 1, wherein a silicon substrate whose surface is coated with silicon oxide or silicon nitride is used as the insulated silicon substrate. 4. The temperature-sensitive element according to claim 1, wherein the fluorine-containing polymer thin film is formed as a fluorine-based plasma polymerized film.