JPH0354842B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for manufacturing a thin film thermistor used as a temperature detector in, for example, a toner fixing roller of a copying machine or a heat sensitive part of office automation (OA) equipment. Regarding the improvement of

(Prior Art) Conventionally, in the toner fixing roller of a copying machine, the above-mentioned office automation equipment, etc., a thermistor is mechanically brought into contact with the object whose temperature is to be detected, and the temperature is detected in the temperature range of 100°C to 300°C. are doing.

By the way, various types of thermistors of this kind have been developed based on their components, manufacturing methods, etc., such as metal composite oxide sintered thermistors, SiC thin film thermistors, metal composite oxide thin film thermistors, and the like.

Metal composite oxide sintered thermistor is manganese
Mn, Cobalt Co, Nickel Ni or Mn,
It is made by mixing and molding a metal composite oxide whose main components are Co and Ni, with the addition of copper, Cu or iron, and then sintering at a high temperature of 1200°C to 1300°C.

A SiC thin film thermistor is a SiC thin film formed on an alumina substrate by high frequency sputtering in an argon gas atmosphere using a SiC sintered body as a target. The substrate temperature during sputtering is 650°C to 750°C. There are two types of metal composite oxide thin film thermistors, one of which contains chromium Cr or Fe in two to three components of Mn, Co, and Ni. A sintered target is made using the added thermistor material. Furthermore, using this sintered target, a thin film is formed on an alumina substrate by sputtering in an Ar gas atmosphere. Next, heat treatment is performed in the atmosphere to complete the thin film thermistor. Another one is
A thermistor thin film is formed on a high melting point glass substrate using a sintered target of Mn3Co2Ni1 oxide and heated to 400°C to 500°C in a sputtering gas containing Ar mixed with 3% or more oxygen by volume. It is.

(Problems to be Solved by the Invention) However, the thermistor described above has various problems as described below.

Metal composite oxide sintered thermistors are not suitable for miniaturization, and it is difficult to shorten the thermal response time constant.

Next, for SiC thin film thermistors, in order to obtain a stable SiC film with good crystallinity, the temperature of the substrate must be raised to 650℃.
It is necessary to raise the temperature to ~750°C, which undeniably lowers productivity. Also, the thermistor constant is approximately
Since it is small at 2000K and its resistance value changes little due to temperature changes, it is not possible to detect temperature with high accuracy.
Thermistor constant changes depending on temperature. As a result, when temperature is detected over a wide range, linearity is poor. Further, if a small amount of nitrogen is mixed into the sputtering gas, the resistance value changes greatly, making it difficult to obtain a product of constant quality.

Metal composite oxide thin film thermistors are thermally unstable and difficult to use as a thermistor because they remain in the form of spatter. For this reason, it is necessary to perform heat treatment at a high temperature of around 1000°C. Furthermore, the characteristics of the thermistor depend on the heat treatment temperature, making it difficult to set the conditions. In order to obtain a thermally stable thin film thermistor with good crystallinity, it is necessary to raise the substrate temperature to a high temperature (400°C to 500°C), which undeniably reduces productivity as with SiC thin film thermistors.

The present invention has been made in view of the above circumstances, and aims to provide a method for manufacturing a thin film thermistor that has a large thermistor constant, is excellent in thermal stability, has an extremely short thermal response time constant, and is suitable for productivity and mass production. purpose.

(Means for Solving the Problems) The method for manufacturing a thin film thermistor according to the present invention includes forming a composite oxide of Mn, Co, and Ni on an insulating substrate.
Using as a target a sintered body of a composite oxide in which two to three components of Mn, Co, and Ni are added with one or more components of Al, Fe, Cr, and Cu, and heating the substrate. Instead, a thermistor thin film of a composite oxide of the above components is formed by high-frequency sputtering in an Ar gas atmosphere, and then heat-treated in the atmosphere.

(Function) Therefore, according to the method for manufacturing a thin film thermistor using the above means, a metal composite oxide thin film is formed on an insulating substrate without heating the substrate, and then heat treatment is performed in the atmosphere. In order to improve thermal stability, we created a product with a short thermal response time constant.
The manufacturing process is suitable for productivity and mass production.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a cross section of a thin film thermistor, and 1 is an insulating substrate, which is formed by, for example, thermal oxidation on a single crystal silicon substrate.
Silicon oxide using CVD method or sputtering method,
Use a material coated with an insulating layer such as silicon nitride alumina. A thermistor thin film 2 is formed on the upper side of this insulating substrate 1. In forming the thermistor thin film 2, a metal composite oxide of Mn, Co, and Ni or two to three components of Al, Cr, and Mn, Co, and Ni are used.
A metal composite oxide containing one or more of Cu, Fe, etc. is used as a target by sintering. The sintered target may be manufactured using conventional methods for manufacturing conventional thermistor materials. Of course, the metal composite oxide sintered body having the above-mentioned components may be manufactured by other methods. Then, high frequency sputtering is performed in an Ar gas atmosphere using the target as described above to form a thermistor thin film 2 of the metal composite oxide of the above components on the insulating substrate.
During this high frequency sputtering, the insulating substrate 1 is not heated.

After forming the thermistor thin film as described above, silicon oxide is formed by high frequency sputtering.
A protective film 3 made of alumina or the like is formed. The formation of the protective film 3 at this time minimizes the change in specific resistance due to heat treatment and shortens the processing time. The reason why the protective film 3 was provided was to solve the problem that in metal composite oxide thermistors, the proportion of oxygen in the composition changes depending on the temperature, which inhibits the thermal stability of the resistivity. A protective film 3 is provided on the top. Next, heat treatment is performed in the atmosphere at a temperature slightly higher than the operating temperature for 50 to 250 hours. In the figure, 4 indicates an electrode.

Therefore, according to the above manufacturing method, the insulating substrate 1
The metal composite oxide 2 formed above has a fine but stable crystal structure, and by heat treatment for a sufficiently long time even at a relatively low temperature, it can be made thermally stable and does not change over time. can be manufactured.

Next, a specific example of manufacturing the thermistor thin film 2 and the characteristics of the manufactured thin film thermistor will be described.

Regarding the first manufacturing example.

First, a metal oxide sintered body of Mn-35Ni-4Al (wt%) is prepared as a target, and using this target, composite oxide is formed on the insulating substrate 1 by high frequency sputtering in an Ar gas atmosphere at a pressure of 1 mTorr. A thermistor thin film 2 was formed. At this time, the high frequency power was 200W, and the deposition rate was 0.8μm/
It's time. During this sputtering, the substrate 1 is not heated. Furthermore, a protective film 3 was formed using silicon oxide. After that, at 3000℃ in the atmosphere,
Heat treated for 100 hours. As a result, a thin film thermistor with a thermistor constant of 4950K and a specific resistance of 2500Ωcm (at 100°C) was obtained.

Furthermore, when a transmission electron microscope sample was prepared on rock salt under the same conditions as in the above production example and observed using the electron microscope, it became clear that a fine but stable spinel structure had been obtained. (Second
(see figure).

Regarding the second manufacturing example.

The manufacturing method of this thermistor thin film 2 is Mn-
A metal oxide sintered body of 15Co-5Ni (wt%) was prepared as a target, and a thermistor thin film 2 and a protective film 3 were formed on an insulating substrate 1 under substantially the same conditions as in the first manufacturing example. However, the film formation rate was 1 μm/hour. Thereafter, heat treatment was performed at 200°C in the air. FIG. 3 is a diagram showing the relationship between specific resistance and heat treatment time. As is clear from FIG. 3, the change in resistivity at this time increased to about 15% after 200 hours and became constant, indicating thermal stability. This manufacturing method allows the thermistor constant to
A thin film thermistor with a resistivity of 2500Ω・cm (100℃) was obtained at 4500K.

Therefore, according to the method for manufacturing a thin film thermistor of the embodiments described above, the thermistor thin film 2 is, for example,
It can be formed to a thin film thickness of 0.5 to several μm, and the thermistor constant can be as high as 4500 to 5000K. As a result, a thin film thermistor with excellent thermal stability and a short thermal time constant can be obtained. Furthermore, there is no need to heat the insulating substrate 1 when forming the thermistor thin film 2. In particular, heating the insulating substrate 1 in a vacuum requires a long time due to extremely insufficient heat conduction, which significantly reduces productivity, but this manufacturing method 1 does not require heating, and although the heat treatment time in the atmosphere is long, it is possible to process a large amount at once, and when considering the entire manufacturing process, productivity can be significantly improved. .

(Effects of the Invention) As detailed above, according to the present invention, a thermistor with a large constant and excellent thermal stability can be obtained, and the thermal response time constant can be shortened, improving productivity and mass production. It is possible to provide a method for manufacturing a thin film thermistor at a low cost that can be increased.

[Brief explanation of drawings]

Figures 1 to 3 are shown to explain embodiments of the present invention. Figure 1 is a cross-sectional view of a thin film thermistor, and Figure 2 shows the metal structure of the thermistor thin film observed with a transmission electron microscope. 3 are characteristic diagrams showing the relationship between the elapsed time of heat treatment in the atmosphere and the specific resistance of the thermistor thin film. 1... Insulating substrate, 2... Composite oxide thermistor thin film, 3... Protective film.

Claims (1)

[Claims] 1. On an insulating substrate, a composite oxide of Mn, Co, and Ni or 2 to 3 components of Mn, Co, and Ni with Al, Fe, Cr,
Using a sintered body of a composite oxide containing one or more components of Cu as a target, the composite oxide thermistor made of the aforementioned components is produced by high-frequency sputtering in an Ar gas atmosphere without heating the substrate. A method for manufacturing a thin film thermistor, which comprises forming a thin film and then heat-treating it in the atmosphere.