JPS6044801B2 - thin film thermistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermistor, and particularly to a thin film thermistor comprising an electrode film and a temperature-sensitive resistor film formed on an insulating substrate.

Conventionally, this type of thin-film thermistor has used a temperature-sensitive resistor film made of Si or a composite metal oxide such as Fe, Ni, Co, or Mn.

The thermistor constants (hereinafter simply referred to as B constants) of these temperature-sensitive resistor films were almost constant regardless of temperature, similar to the bulk thermistors made of the temperature-sensitive sintered body of the composite oxide.
Therefore, when using this type of thermistor as a circuit element of the electric circuit shown in FIG. 1 to electrically detect temperature,
The disadvantages are that the output voltage does not vary linearly with temperature, or that the detection sensitivity varies widely depending on temperature. In FIG. 1, 1 is a thermistor, and its resistance-temperature characteristic R(T) is shown.

2 is a fixed resistor with a resistance value Ro (constant), 3 is a voltage EaV
4 is the output voltage, and its value is indicated by Eg.

The following equation holds true between these. -Ro Ea-Ro+R(T) Below, for simplicity, it will be treated as Ea■IV, but Ea
It will be clear that in the case of :IV, no essential difference arises.

Ro is the thermistor resistance value R(T
o) is selected to be the same value. To is determined by the detection temperature range, the characteristics of the electric circuit that electrically processes the output voltage Eg, and the like. FIGS. 2 and 3 show a typical relationship between output voltage Eg and temperature T, and a relationship between detection sensitivity dEg/dT and temperature T for a conventional thermistor when To1 is 150°C.

Curves 5 and 7 are B■2000') Curves 6 and 8 are B:50
This is the case for 00. As shown in curves 5 and 6, the output weight range kg changes in a curved manner with respect to the temperature T. Also curve 7
, 8, the detection sensitivity dEg/dT varies widely 7 with respect to the temperature T. These output voltage characteristics and detection sensitivity characteristics with respect to the temperature T have resulted in drawbacks such as the complexity of the electronic circuit for processing the output weight (kg) and the difficulty in circuit design.

Furthermore, if you want to control the amount of heat generated by a heat source by detecting the temperature with a thermistor and comparing it with a set temperature, the electric circuit is usually configured so that the set temperature corresponds to the rotation angle of the rotary shaft of the variable resistor. .

At this time, there was a drawback that the set temperature could not be determined linearly with respect to the rotation angle due to the output voltage characteristics and detection sensitivity characteristics as described above. In the region where detection sensitivity is small, the change in output voltage Eg with respect to temperature T is flat, so if a slight change occurs in the set rotation angle of the variable resistor, that is, a small change occurs in the set output voltage Eg. In this case, large temperature fluctuations occur, while in regions of high detection sensitivity, the opposite is true. As described above, there was a drawback that the accuracy of the set temperature varied depending on the set temperature. Note that when a SiC resistor film is used as the temperature-sensitive resistor film, the B constant has temperature dependence and is not necessarily constant.

However, even in this case, as shown in curves 9 and 10 in FIGS. 2 and 3, the above-mentioned drawbacks could not be avoided. The present invention provides a novel thin film thermistor that eliminates these conventional drawbacks.

The gist of the present invention resides in that at least an electrode film and a temperature-sensitive resistor film are formed on a temperature-sensitive substrate plate, and the resistance-temperature characteristics of the temperature-sensitive substrate and the temperature-sensitive resistor film are different from each other.

FIG. 4 shows a cross section of the thin film thermistor of the present invention.

11 is a temperature-sensitive substrate, 12 is an electrode film, and 13 is a temperature-sensitive substrate. It is a temperature resistor film.

The greatest feature of the thin film thermistor of the present invention is that the temperature-sensitive substrate 1
It is in 1.

That is, conventional thin film thermistors use an insulating substrate. Therefore, the characteristics of this type of thermistor are limited to the temperature-sensitive resistor film 13! You can decide accordingly. On the other hand, since the thin film thermistor of the present invention uses the temperature sensitive substrate 11, its characteristics are affected not only by the temperature sensitive resistor film 13 but also by the temperature sensitive substrate 11. As a result, a four-thin film thermistor with excellent output voltage characteristics and detection sensitivity characteristics can be obtained, as will be described later. The temperature-sensitive substrate 11 is made of Fe, Ni
, CO, Mn, etc. or Ni, Zn, F
The material is preferably selected from the group of oxide semiconductors such as elemental metal oxides such as e and COI, and elemental semiconductors such as Si and Ge.

Among these, composite oxides of Fe, Ni, CO, and Mn are known in particular for their compositions and electrical properties in relatively detailed information, and their production methods have been established, as well as being highly mass-producible and inexpensive. Therefore, it is optimal as the temperature-sensitive substrate 11. The electrode film 12 is made of Au-Pt, Ag-Pd, Au-
Thick film electrode films such as Pd, Au, Ag, G-Au, Cr-
An ordinary conductive film such as a thin film electrode film such as Ag or Cr-Cu may be used.

In principle, the temperature-sensitive resistor film 13 may be made of an oxide semiconductor, an element semiconductor, or a compound semiconductor, similar to the temperature-sensitive substrate 11.

However, when forming a film, considering the difficulty of the formation method and the difficulty of controlling the composition, ・Those selected from the group of metal oxides of Ge, Si, and SiCl are excellent. Among these, SiC is most suitable for the temperature-sensitive resistor film 13 because it is chemically and thermally stable and its electrical properties can be controlled relatively easily. The effects of the thin film thermistor of the present invention will be explained below using Examples.

Example 1 The temperature-sensitive substrate 11 has a specific resistance of about 103Ω-D. , B constant approximately 1
A Cr--Au thin film electrode film 12 was formed on the surface of a Fe, Ni, CO composite oxide having a density of 20Cf1<.

Furthermore, the temperature-sensitive resistor film 1 of e is coated on top of the film by vacuum evaporation.
3 was formed. The G temperature sensitive resistor film 13 has a specific resistance of approximately 80Ω.
- α, B constant was about 4600K. The output voltage characteristics and detection sensitivity characteristics of the thin film thermistor of the present invention thus formed are shown in curves 14 and 15 in FIGS. 2 and 3. As is clear from these figures, the output voltage Eg varied linearly with respect to the temperature T over a wide range of 0 to 240 degrees Celsius. Furthermore, the detection sensitivity DEg/DT was also approximately constant with respect to the temperature T at 1.9±0.14 mV/°C in the same temperature range. This detection sensitivity of about 1.9 TT]V/° C. is a relatively small value, but in practical terms this level is within a range that can be easily detected electrically. Example 2 The temperature-sensitive substrate 11 has a specific resistance of about 2×10 3 Ω-D. ．． Using Fe, Ni, CO composite oxide with a B constant of about 5000'K,
An Au--Pt thick film electrode film 12 was formed on the surface thereof.

Furthermore, a SiC temperature-sensitive resistor film 13 was formed thereon by sputtering. The SiC temperature sensitive resistor film 13 had a specific resistance of about 10 Ω-α. In addition, the B constant is not necessarily constant and changes depending on the measurement temperature, and the measurement temperature range is 50~
The temperature at 140°C was about 900K, and the temperature at 1140-230°C was about 1300'K. The output voltage characteristics and detection sensitivity characteristics of the thin film thermistor of the present invention formed in this manner were
Figure 3 shows curves 16 and 17. As is clear from these figures, the output voltage Eg varies from 0 to 240 with respect to the temperature T.
It varied linearly over a wide range of °C. Also, the detection sensitivity DEg/DT is 1.9 in the same temperature range with respect to temperature T.
It was approximately constant at ±0.17 mV/°C. This detection sensitivity of about 1.9rT1V/°C is a relatively small value, but in practical terms this level is within the range that can be easily detected electrically. In addition, the SiC temperature-sensitive resistor film 13 used in this example
has excellent heat resistance. Therefore, it is particularly suitable for uses that require heat resistance, for example, in cookers such as ovens, where the ambient temperature may be about 350°C. In addition, in the above embodiment, F is used as the temperature-sensitive substrate 11.
Although an example using e, Ni, CO composite oxide has been shown, other oxide semiconductors such as Fe, Mg, Cr oxide, Li
, Ni composite oxide, Li, CO composite oxide, Ni, Li
It is natural that similar effects can be obtained with composite oxides.

Similar effects can also be obtained with elemental semiconductors such as Ge and Si.

As shown above, it is clear that the thin film thermistor of the present invention can eliminate the above-mentioned drawbacks.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing an example of an electric circuit that detects temperature using a thermistor, Figure 2 is a characteristic diagram showing the relationship between temperature T and output voltage Eg, and Figure 3 is temperature T and detection sensitivity DEg/D.
A characteristic diagram showing the relationship with T, and FIG. 4 is a sectional view of the thin film thermistor of the present invention. 11... Temperature-sensitive substrate, 12... Electrode film, 13... Temperature-sensitive resistor film.

Claims (1)

[Claims] 1. At least an electrode film and a temperature-sensitive resistor film are formed on a temperature-sensitive substrate, and the resistance-temperature characteristics of the temperature-sensitive substrate and the temperature-sensitive resistor film are different from each other. thin film thermistor. 2. The thin film thermistor according to claim 1, wherein at least the temperature-sensitive substrate is selected from the group of oxide semiconductors and elemental semiconductors. 3 At least, the temperature-sensitive substrate is Fe, Ni, Co, Mn
3. The thin film thermistor according to claim 2, wherein the thin film thermistor is a composite oxide semiconductor. 4. The thin film thermistor according to claim 1, wherein at least the temperature sensitive resistor film is a SiC resistor film.