Ikuo Kobayashi

SiC thin-film thermistor

A thermistor using a sputtered SiC film has been developed as a temperature-sensing device which is able to detect temperatures accurately over the wide range of 30-300 degrees C. The thermistor has a unique characteristic in that the B constant increases linearly with an increase of temperature. The typical values of the B constant increase from 1950K at 50 degrees C to 3080K at 250 degrees C. From this unique characteristic, the temperature dependence of resistance was calculated with high accuracy by an experimental equation. The thermistor consists of a thermistor element and a package. The thermistor element comprises the SiC film temperature sensor. The package comprises a small glass tube in which the thermistor element is sealed hermetically. The characteristics of the thermistor are very stable for long periods under various test conditions.

Effects of nitrogen on the electrical properties of sputtered SiCx films

Abstract The electrical properties of r.f.-sputtered SiCx films were studied with a view to thermistor applications. When the sputtering was carried out in an argon atmosphere containing a small amount of nitrogen gas, the electrical properties were strongly affected by the amount of nitrogen gas. For small amounts, less than 2%–3% in concentration, both the resistance and the experimental constant B decreased very rapidly as the amount of nitrogen gas was increased. In contrast, for larger amounts, more than 2%–3% in concentration, both the resistance and B increased rapidly with increasing concentration of nitrogen gas. For all the films sputtered in an argon atmosphere containing various amounts of nitrogen gas up to 9% in concentration, B increased linearly with increasing temperature. From this characteristic, the following experimental equation which represents the dependence of the resistance R of the films on temperature T was obtained: R = AT −n exp ( m T ) where A, n and m are constants determined experimentally.

Rapid response SiC thin‐film thermistor

The thermistor consisted of a rf‐sputtered SiC film deposited on one surface of an alumina ceramic plate. The thermistor element was brazed to the inner surface of a cylindrical metal housing at the closed end. The thermistor can detect temperatures with a thermal time constant of about 0.6 s.

SiC thin film thermistor

Abstract A thermistor using an r.f.-sputtered SiC film has been developed as a temperature-sensing device. The resistance of the SiC film has a unique temperature dependence in that the constant B increases linearly with increasing temperature. Thus the following experimental equation representing the temperature dependence of the resistance R is obtained: R = AT −n exp ( m T ) where A , n and m are experimental constants and T is the absolute temperature. The temperature dependence of the resistance can be obtained with good reproducibility by controlling the substrate temperature and adding a small amount of nitrogen gas to the argon sputtering atmosphere. The thermistor has the advantage of being able to detect temperature with (1) high accuracy over a wide range, (2) rapid response by brazing a thermistor element to a metal housing and (3) good stability for long periods under severe conditions.