JPH04170001A - Thin-film thermistor and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a thin-film thermistor with improved stability at a temperature at least exceeding 300 deg.C by forming a heat-sensitive resistance film with a specific ratio of iron and silicon for the remaining part. CONSTITUTION:In a thin-film thermistor 1, a pair of electrodes 3, 3 are provided on an electrical insulation substrate 2 and a heat-sensitive resistance film 4 is provided on an upper surface of these electrodes 3, 3 and that on the substrate 2 where no electrode is provided. Then, this heat-sensitive resistance film 4 consists of an iron 29.0-37.0atom.% and silicon for the remaining part. If the iron is less than 29.0atom.% or exceeds 37.0atom.%, B constant becomes 1000K or less and is not desirable in terms of thermistor characteristics, thus enabling reproducibility of heat-sensitive property at a temperature exceeding 300 deg.C to be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thin film thermistor whose heat-sensitive resistive film is made of iron and silicon, and a method for manufacturing the same. In particular, the present invention relates to a thin film τ mister suitable for high temperature applications and a method for manufacturing the same.

[Prior Art] Conventionally, a heat-sensitive resistance film of a thin film thermistor is made of an oxide material or a non-oxide material. The former oxide material includes metal composite oxides of Mn, Co, and Ni or Mn, C
Metal composite oxides are known in which one or more components of A, Cr, Cu, Fe, etc. are added to two or three components of O, Ni (for example, Japanese Patent Laid-Open No. 62-291002. Tokukai Showa 6
2-293701. Tokukaihei! -50501). Silicon carbide is also known as the latter non-oxide material (
For example, Japanese Patent Publication No. 56-26965, Japanese Patent Publication No. 61-24
5502. JP 1-130503).

[Problems to be Solved by the Invention] In general, materials for thermistors require a B constant, which is a temperature coefficient, of about 2000 to 5000.

However, in the case of the former oxide material, its resistivity is generally several tens of Ω·cm or more at 25°C within the above B constant range, so it is necessary to provide at least one pair of base electrodes on an electrically insulating substrate. Since the film thickness of a thermistor formed with a thin film is approximately 2 μm or less, the resistance value at 25° C. is several tens of Ω or more, which poses the problem that only high-resistance thermistors can be manufactured. In addition, if a high-temperature thermistor is made from the former oxide material to take advantage of this high resistance, since its composition is an oxide, the oxidation state changes at high temperatures, causing the thermistor's characteristics to become unstable. there were.

In the case of the latter, silicon carbide, this material has high thermal stability and can withstand high temperatures, but on the other hand, its resistivity is relatively high, and even if the film thickness is several micrometers, the resistance value at 25 degrees Celsius is several micrometers. L
The problem was that only high resistance thermistors could be made. Also, silicon carbide has a B constant of 25
Since the temperature coefficient is as low as 2,500° C., there is a problem in that unlike oxide materials, it is not possible to create a thin film thermistor with a moderate temperature coefficient. Furthermore, when using silicon carbide as a material for a thermistor, it is difficult to change the composition ratio of silicon and carbon due to its structure, so the characteristics of the thermistor can only be changed by changing the film formation conditions, making it possible to fine-tune the characteristics of the thermistor. However, there was a problem that made it difficult to obtain a thermistor with a wide range of characteristics.

An object of the present invention is to solve the above-mentioned problems, and to provide a thermistor comprising at least one pair of base electrodes on an electrically insulating substrate and a thin film formed thereon.
or at least 100 OK or more, and the film thickness is about 0.1 to 2 μm and the resistance is 10Ω to several MkΩ.
It is an object of the present invention to provide a thin film thermistor that has a resistance value of 1,000, has a wide range of characteristics, and is stable at temperatures of at least 300°C or higher, and a method for manufacturing the same.

[Means to solve the problem] The present inventors developed FeSi as a heat-resistant material.

The bulk material of the system has excellent oxidation resistance and is a high-temperature thermoelectric material that can be used in the atmosphere (R.

Kieffer, F., Benesovsky and
C, Konopicky: Ber.

Deunt, Keram, Ges, 31 (19
54) 223, etc.), and is a stable material on the phase diagram up to 986°C (J.

P, Piton and M, F, Fay: C, R,
Acad, Sci., C266 (1968) 154
), L.Komo focused on the fact that this material is also used as a semiconductor material, and by making this material into a thin film,
The inventors have discovered that the above object can be achieved and have arrived at the present invention.

As shown in FIG. 1, the thin film thermistor 1 of the present invention includes a pair of electrodes 3.3 provided on an electrically insulating substrate 2.
A heat-sensitive resistive film 4 is provided on the upper surface of these electrodes 3.3 and on the upper surface of the substrate 2 where no electrodes are provided. This heat-sensitive resistive film 4 is characterized in that it consists of 29.0 to 37.0 atomic percent iron and the balance silicon. There may be two or more pairs of electrodes 3.3, and the electrodes 3.3 may be provided on the upper surface of the heat-sensitive resistive film 4.

To manufacture this thin film thermistor, iron 29.
A heat-sensitive resistive film consisting of ~37.0 atomic % and the remainder silicon is formed.

The electrically insulating substrate of the present invention has heat resistance, has a coefficient of thermal expansion close to that of iron silicide (IOX 10""deg'" 1), and has high adhesion of iron silicide. For example, a substrate made of any material such as alumina, forsrite, stearite, beryllia, or Mg-An spinel is preferable.

Further, the electrodes are made of a conductive material with excellent heat resistance and corrosion resistance. Examples include silver, gold, platinum, platinum-gold, gold-palladium-platinum, and the like. This electrode is formed by printing and baking the metal paste on the edge of the substrate.

Furthermore, heat-sensitive resistive films can be produced using vapor phase growth method, electron beam evaporation method,
It is formed by ion beam evaporation, vacuum evaporation, sputtering evaporation, or the like. Sputtering deposition is preferred because it is suitable for mass production.

Sputtering deposition is performed in an inert gas atmosphere such as Ar gas, and a target containing iron and silicon powders in a predetermined ratio and powder metallurgized into a disk shape is used. Due to the crystal structure of the vapor-deposited resistive film, it is necessary to form a Fe5it compound.
It is preferable to perform the vapor deposition under heating at a temperature of °C. However, after vapor deposition at room temperature, Fe
5ii compounds may be obtained.

The heat-sensitive resistive film of the present invention is characterized in that it consists of 29.0 to 37.0 atomic percent iron and the balance silicon. When iron is less than 29.0 atom% or more than 37.0 atom%, the B constant is 1.
00OK or less, which is unfavorable in terms of the characteristics of the thermistor.

The thickness of this resistive film is made in the range of 0.1 to 2 μm depending on the purpose of the thermistor. If it is less than 0.1 μm, it will be affected by the electrical resistance of the lead wire connected to the electrode.
If the thickness exceeds 2 .mu.m, the film tends to peel off due to the difference in coefficient of thermal expansion from the substrate, so it is made within the above range.

After sputtering and vapor deposition, it is preferable to heat-treat the electrically insulating substrate on which the heat-sensitive resistive film is formed at a temperature in the range of 400 to 985° C., since this results in good reproducibility of heat sensitivity as a thermistor and excellent thermal stability. This heat treatment is preferably performed in an inert gas atmosphere or in vacuum in order to obtain more stable characteristics, but it is also preferable to perform this heat treatment in the air because the characteristics are stable. Further, if the heat treatment temperature is less than 400°C, the effect will be poor, and if the temperature exceeds 985°C, the resistive film will be easily damaged by heat.

[Function] By sputtering and depositing a heat-sensitive resistive film on a substrate while changing the composition ratio of iron and silicon within a predetermined range, desired characteristics can be obtained from among the B constant and resistance value generally required for thermistors. can be equipped. In addition, the iron silicide thin film formed on the substrate has excellent heat resistance and oxidation resistance.
Moreover, since it is a high-temperature thermoelectric material that can be used in the atmosphere,
The reproducibility of heat sensitivity becomes good even at temperatures of 300° C. or higher.

[Effects of the Invention] As described above, the Fe-5L thin film thermistor of the present invention has a B constant of over 1000 and close to 5000, which is a wide range of desirable values for a thermistor, depending on the composition ratio of iron and silicon. Moreover, since the resistivity at room temperature is 10 Ω·cm or less, which is lower than that of conventional thermistors, the resistance value at room temperature in a thin film state has a wide range of values from several tens of Ω to several MΩ, which is extremely preferable as a thermistor resistance element. As a result, a thermistor having characteristics that precisely correspond to the intended use can be obtained.

In particular, if the thin film is trimmed, the resistance can be further increased, and the characteristics at high temperatures can be further improved. Further, since iron silicide has excellent heat resistance, the thin film thermistor of the present invention is suitable for use at high temperatures.

[Example] Next, examples of the present invention will be described together with comparative examples.

<Example 1> In this example, an alumina substrate was selected as the electrically insulating substrate. A so-called glass frit-containing platinum paste mixed with glass powder was printed on the top surface of the substrate by screen printing and baked in the air at a temperature of 1000°C for 1 hour.
A counter electrode was formed.

After preparing seven of these substrates, a FeSi thin film was formed on the upper surface of each substrate by high frequency sputtering to produce seven types of thin film thermistors. That is, seven types of targets with different atomic ratios of iron and silicon were prepared, each target was separately placed on the cathode of a high-frequency sputtering device, and a
High frequency power 300W in Ar gas atmosphere of about orr
A thin film was formed on the upper surface of the substrate by sputtering at a deposition rate of 3 μm/hour.

After the vapor deposition, the substrate on which the thin film was formed was heat-treated at a temperature of 600°C.

Comparative Example 1> Of the seven types of targets in Example 1, a target with an iron atomic ratio lower than the lowest one and a target with an iron atomic ratio higher than the highest one were used. Two types of thin film thermistors were manufactured in the same manner as in Example 1.

Table 1 shows the characteristics of the thermistors manufactured in Example 1 and Comparative Example 1. All of the nine types of thin film thermistors had a film thickness of about 1 μm, a distance between electrodes of 1 mm, and a thin film width of 1 mm.

Table 1 From the results in Table 1, the atomic percent of iron is 29. If it falls below O or exceeds 37.0, the B constant will be below 1000,
It was found that this was not desirable as a thermistor.

In addition, each of the seven types of thin film thermistors in Example 1 had a
The B constant is almost constant from 0 to 500℃, and 5
It was thermally stable even at high temperatures up to 00°C. When the temperature exceeds 500° C., the B constant tends to increase, and these characteristics are extremely favorable results for a high temperature thermistor.

On the other hand, the two types of thin film thermistors of Comparative Example 1 have a B constant of 10.
Since it has a small temperature coefficient of 0OK or less, it is not suitable as a temperature sensor or a thermistor for temperature compensation.

<Example 2> A thin film thermistor was produced in the same manner as in Example 1 except that the distance between the electrodes of the thermistor in Example 1 was set to 0.1 mm. As a result, the resistance value of the thermistor of Example 2 was approximately one tenth of the resistance value of Example 1.

<Example 3> A thin film thermistor was produced in the same manner as in Example 1 except that the film thickness of the thermistor in Example 1 was changed to 100 OA. As a result, the resistance value of the thermistor of Example 3 was approximately 10 times that of Example 1.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a thin film thermistor manufactured by the method of the present invention. 1: thin film thermistor, 2: electrically insulating substrate, 3: electrode, 4: heat-sensitive resistance film. Patent applicant Mitsubishi Mining Cement Co., Ltd. 1 Thin film thermistor Figure 1 Procedural amendment (August 5, 1991 2, Title of invention Thin film thermistor and its manufacturing method 3,
Relationship with the case of the person making the amendment Patent applicant address (residence) 6-1 Otemachi-chome, Chiyoda-ku, Tokyo Name: Mitsubishi Materials Corporation 4, Agent 8, Contents of amendment (1) Specification No. Page 2, line 20, change “...2000 to 5000K...” to “...10
00-5000K..." I corrected it. (2) On page 3, line 20 of the specification, "...because it is as low as 2,500..." is replaced with "...
・It is about 2,500, and...'' I corrected it. (3) Change "...2000 to 5000K..." from page 4, line 11 of the specification to [...10
00-2500K...]. (4) On page 4, line 12 of the specification, "...more than 100 OK..." is corrected to "...more than 500...". (5) On page 7, line 11 of the specification, "...100 OK or less..." is corrected to "...500 or less...". (6) ``More than 1000 and close to 5000...'' in the first line of page 9 of the specification is r500
That's close to 2,500...'' he corrected. (7) Table 1 on page 11 of the specification is corrected as Table 1 (hereinafter referred to as the margin of this page). (8) On page 11 of the specification, line 4 from the bottom, ``...100OJ is corrected to ``...500J.'' (9) On page 12 of the specification, line 7, ``...1000 or less...''・" is corrected to "...less than 500...".

Claims (1)

[Claims] 1) A heat-sensitive resistive film (4) on an electrically insulating substrate (2), and at least one pair of electrodes (3, 3) provided on the upper or lower surface of this resistive film (4), respectively. Thin film thermistor (1)
, the heat-sensitive resistive film (4) is made of iron 29.0-37
．． A thin film thermistor comprising 0 atomic % and the remainder silicon. 2) In an inert gas atmosphere, a heat-sensitive resistive film consisting of 29.0 to 37.0 atomic percent iron and the balance silicon is formed on an electrically insulating substrate by sputtering deposition using a target consisting of iron and silicon. Method for manufacturing thin film thermistors. 3) After sputtering and vapor deposition, the electrically insulating substrate on which the heat-sensitive resistive film has been formed is heated in an inert gas atmosphere or in a vacuum.
3. The method for manufacturing a thin film thermistor according to claim 2, wherein the heat treatment is carried out at a temperature range of 00 to 985°C.