JPH10256004A - Thin-film thermistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the adhesive force of an electrode film to a thermosensitive resistor film from being dropped in a heat treatment by a method wherein a PdOx film which is regarded as being oxidized sufficiently is deposited on the lower layer of a composite-layer-structure electrode coming into contact with the thermosensitive resistor film and an Au film is laminated on it. SOLUTION: An SiO2 film 5 and a thermosensitive resistor film 2 are formed on an insulating substrate 1'-PdOx films 6a and a 6b in which Pd atoms are regarded as being oxidized partly are and Pd films 7a and 7b laminated on them. In addition, Au films 8a and 8b which are thicker than the Pd times 7a, 7b are laminated. At this time, as the thermosensitive resistor film 2, a composite oxide which contains two or more kinds of elements selected from among the elements of Mn, Ni, Co, Fe and Cu is used. In addition, as the insulating substrate 1', an alumina substrate which contains 90% or higher of Al2 O3 or a crystallized glass whose coefficient of thermal expansion is in a range of 60 to 100×10<-7> / deg.C is used. Thereby, it is possible to prevent an electrode from being stripped owing to a drop in an adhesive force by a heat treatment in a production process and by the history of a temperature change in the use of an actual apparatus.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film thermistor based on infrared detection or a thin film thermistor capable of measuring the temperature of an object to be measured faster than a conventional thermistor using a bulk material. INDUSTRIAL APPLICABILITY The thin film thermistor of the present invention can be used as a temperature sensor for applications such as measuring the temperature of a copying machine roller, measuring the temperature of an unheated object in a microwave oven, and ensuring the temperature for driving a liquid crystal panel.

[0002]

2. Description of the Related Art The following two types of electrode structures have conventionally been devised or implemented for a thin film thermistor using a composite oxide film of a transition metal.

FIG. 5 is a schematic sectional view of a conventional thin film thermistor, corresponding to a first type of electrode structure. As shown in FIG. 5, a first type of electrode structure has a base metal thin film 3a, 3b such as Cr or Ti on an insulating substrate 1.
Is formed, and the base metal thin films 3a and 3b are used as bases to form Au.
Alternatively, a pair of noble metal thin film electrode patterns 4a, 4 of Pt
b and a pair of noble metal thin film electrode patterns 4a, 4b
It has a structure in which a temperature-sensitive resistor film 2 is formed thereon and patterned.

FIG. 6 is a schematic sectional view of a conventional thin film thermistor, corresponding to a second type of electrode structure. In a second type of electrode structure, as shown in FIG. 6, a temperature-sensitive resistor film 2 is formed on an insulating substrate 1, and a pair of Au or Pt noble metal thin-film electrodes is formed on the temperature-sensitive resistor film 2. It has a structure in which patterns 4a and 4b are formed.

The thin film thermistor having the structure shown in FIGS. 5 and 6 is covered with a protective film as required. Conventionally, an alumina substrate has been used as a substrate for a thin film thermistor. The thin-film thermistor having such a structure is characterized in that it has a faster thermal response and can reduce variation in characteristics as compared with a thermistor element using a conventional bulk material.

The temperature-sensitive resistor film 2 made of a composite oxide film of a transition metal is usually deposited by sputtering using a target of an oxide sintered body. Temperature-sensitive resistor film 2 after vapor deposition
Has insufficient crystallinity and is significantly different from the characteristics of a bulk sintered body having the same composition. Therefore, the deposited temperature-sensitive resistor film 2 is heat-treated at an appropriate temperature of 700 to 1000 ° C.
The crystallinity is improved so that the characteristics are close to those of the bulk sintered body, and the time-dependent changes in the characteristics are sufficiently reduced.

In the case of the first type structure shown in FIG. 5, the base metal thin films 3a and 3b and the noble metal thin film electrode patterns 4a and 4b are heat-treated together with the temperature-sensitive resistor film 2 at a temperature of 700 ° C. or more. . By this heat treatment, the base metal thin film 3
a and 3b are oxidized. Due to the volume expansion due to the oxidation, the adhesion of the noble metal thin film electrode patterns 4a and 4b to the insulating substrate 1 is reduced. For this reason, there is a problem in that when the history of the temperature change is received in the actual machine, the electrode peels off.

In the case of the second type structure shown in FIG. 6, Pt is used as the noble metal thin film electrode patterns 4a and 4b,
In the case of patterning, an extremely oxidizing etchant such as heated aqua regia is required, and the photoresist is attacked. Therefore, metal must be deposited and used as a mask. When this patterning method is used, there is a problem that pattern accuracy, that is, resistance accuracy is low. At the time of etching, the temperature-sensitive resistor film 2 made of a transition metal oxide is dissolved. When Au is used as the noble metal thin film electrode patterns 4a and 4b, it must be deposited by sputtering to obtain a sufficient adhesive force. When an electrode film or an inorganic protective film is sputter-deposited on the temperature-sensitive resistor film 2, the energy of atoms incident on the substrate is large, so that the underlying temperature-sensitive resistor film 2 is distorted and its characteristics are deteriorated. Change. In order to completely recover this characteristic change, it is necessary to perform heat treatment at a temperature of 600 ° C. or higher. On the other hand, Au has a relatively low recrystallization temperature,
When heat treatment is performed at 00 ° C., recrystallization occurs. At this time, the adhesion of the noble metal thin film electrode patterns 4a, 4b made of Au to the temperature-sensitive resistor film 2, which is the base, is not sufficient, and the films are aggregated due to thermal stress and become discontinuous. When a Pd film is used as the noble metal thin film electrode patterns 4a and 4b, there is a problem that the Pd film is oxidized by the heat treatment and the volume expansion due to the heat treatment lowers the adhesion.

In the second type of structure shown in FIG.
Forming an Au electrode with a base metal thin film as a base has the problem that the heat treatment oxidizes the base metal thin film, forms a high-resistance layer at the interface of the temperature-sensitive resistor film, and irreversibly changes the resistance of the thermistor element.

In order to manufacture a thin-film thermistor using a transition metal oxide film as a temperature-sensitive resistor film, at least two heat treatments at a high temperature are required. One is to use a transition metal oxide film
This is a heat treatment performed at an appropriate temperature of 0 to 1000C. This heat treatment improves the crystallinity of the transition metal oxide film,
The resistance in the substrate at the arbitrary temperature can be made uniform and the resistance can be stabilized. Another heat treatment is
Performed at a temperature of 600 ° C. or higher. Unnecessary distortion is given to the temperature-sensitive resistor film due to the formation of the electrode or the protective film, so that the characteristics of the temperature-sensitive resistor film become non-uniform. By performing the heat treatment at a temperature of 600 ° C. or more, the characteristics of the temperature-sensitive resistor film can be recovered and made uniform again.

Further, the thin-film thermistor receives a history of temperature changes during actual use.

The conventional thin film thermistor does not have sufficient reliability against the heat treatment in these manufacturing processes and the temperature change history during actual use. The reason is that the thin-film thermistor electrode is deteriorated by high-temperature heat treatment, and its adhesive force is reduced.

[0013]

SUMMARY OF THE INVENTION In view of the problems of the prior art thin film thermistor electrodes, it is an object of the present invention to provide a heat treatment during the manufacturing process without significantly reducing the adhesion.
It is an object of the present invention to provide a thin-film thermistor with sufficient reliability against the temperature change history during actual use.

[0014]

In order to solve the above-mentioned problems, in a thin film thermistor of the present invention, in a structure in which an electrode is formed on a temperature-sensitive resistor film, the electrode reacts with the thermistor film by high-temperature heat treatment. A multi-layered electrode of a noble metal that does not have any problem is used. The lower layer of the multi-layer electrode in contact with the temperature-sensitive resistor film has good adhesion to the temperature-sensitive resistor film,
A structure is used in which a PdO _x film that can be regarded as sufficiently oxidized is deposited, and an Au film that is not oxidized by heat treatment is stacked as the uppermost layer. By using this multi-layer structure electrode, a heat treatment at a temperature of 600 ° C. or more for recovering the non-uniformity of the temperature-sensitive resistor film characteristics on the substrate caused by the formation of the electrode and the protective film causes the temperature-resistance of the electrode film Adhesion to the body membrane is not significantly reduced. Also, the electrode film does not peel off due to the history of temperature changes during actual use. Since the thin-film thermistor electrode of the present invention does not react with the temperature-sensitive resistor film contacted by the high-temperature heat treatment, the resistance value of the thin-film thermistor can be easily controlled.

The thin film thermistor of the present invention has the following configuration. That is, a temperature-sensitive resistor film (2) is formed on an insulating substrate (1 '), and a portion of P is formed on the temperature-sensitive resistor film (2).
PdO _x film (6a, 6
b), Pd film (7a, 7b), Pd film (7a, 7b) a thicker Au layer (8a, 8b) are sequentially laminated film structure of, or the PdO _X film (6a, 6b) and an Au film (8a ,
8b) is formed as a thin film thermistor having a pair of electrodes formed of a multilayer film configuration in which layers are sequentially laminated.

Alternatively, the temperature-sensitive resistor film (2) is made of M
It has a configuration as a thin film thermistor characterized by being a composite oxide containing at least two or more elements selected from n, Ni, Co, Fe, and Cu elements.

Alternatively, the insulating substrate (1 ') has a thickness of 9
It has a structure as a thin film thermistor characterized by being an alumina substrate containing 0% or more of Al ₂ O ₃ or a crystallized glass having a coefficient of thermal expansion in the range of 60 to 100 × 10 ⁻⁷ / ° C.

Alternatively, between the insulating substrate (1 ') and the temperature-sensitive resistor film (2), the components of the insulating substrate (1') may be transferred to the temperature-sensitive resistor film (2). A structure as a thin film thermistor characterized in that an SiO ₂ film (5) for preventing or suppressing diffusion or a structure in which an SiO ₂ film is laminated on an Al ₂ O ₃ film is formed.

Alternatively, the temperature-sensitive resistor film (2) is formed on the insulating substrate (1 ') and the diffusion preventing film (5), and the pair of the temperature-sensitive resistor films is formed on the temperature-sensitive resistor film (2). And a configuration as a thin-film thermistor characterized by forming the above-mentioned electrode.

Alternatively, the temperature-sensitive resistor film (2) is formed on the insulating substrate (1 ') and the diffusion preventing film (5), and an insulating film is formed on the temperature-sensitive resistor film (2). After forming and patterning (9), the pair of electrodes (6a, 6b, 7) is brought into contact with the pattern end of the insulating film (9) already formed.
a, 7b, 8a, 8b) or after forming the temperature-sensitive resistor film (2) having a thickness of 0.1 μm or less as an adhesion layer, the pair of electrodes (6a, 6b, 7a, 7b, 8) is formed.
a, 8b) is formed as a thin-film thermistor.

Alternatively, the insulating film (9) on the temperature-sensitive resistor film (2) may be made of SiO ₂ , Si ₃ N ₄ , TiO ₂
And a configuration as a thin film thermistor characterized by comprising:

[0022]

The thin-film thermistor of the present invention is formed by sputtering on the temperature-sensitive resistor film, so that the temperature-sensitive resistor film is distorted and its characteristics become non-uniform in the substrate. Therefore, the thin-film thermistor substrate is subjected to a heat treatment at a temperature of 600 ° C. or more after the formation of the electrode pattern or after the formation of the inorganic protective film such as SiO ₂ to make the characteristics uniform and stable, and remains in the temperature-sensitive resistor film. The distortion must be recovered and equalized.

In the case of the thin film thermistor of the present invention, PdO _X
It has a structure in which a Pd film and an Au film are laminated with a film as a base, or a structure in which an Au film is laminated. The phase diagram of Pd and Au is a complete solid solution system, and is relatively easily alloyed. Therefore, diffusion of Pd is observed in the Au film only by continuous film formation usually by sputtering. Pd and A
Since the bonding of u is extremely strong, even if the Au film is recrystallized by the heat treatment, it does not change into a discontinuous film as observed in the Au single film.

Pd in the electrode of the thin film thermistor of the present invention
Is coated with Au, so that Pd is not oxidized at all by heat treatment during the manufacturing process or is suppressed. Therefore, the electrode film does not expand in volume due to the heat treatment, and the adhesive force does not significantly decrease. As a result, the electrode of the thin film thermistor of the present invention has an adhesive force enough to withstand the temperature change history during actual use.

In the electrode of the thin film thermistor of the present invention, Pd and Au do not react with the temperature-sensitive resistor film. Further, since the oxidation of Pd is suppressed during the heat treatment, the increase in the specific resistance of the electrode film is small. After the heat treatment of the electrode film, the surface resistance is sufficiently low.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 of the present invention will be described below.

FIG. 1 is a schematic plan view of a thin film thermistor according to a first embodiment of the present invention. FIG. 2 shows A in FIG.
FIG. 3 is a schematic cross-sectional structure diagram along the line A ′. In the first embodiment,
An SiO ₂ film 5 is formed on the alumina substrate 1 ′ by 0.1 to 0.8 μm.
The film is formed by sputtering with a thickness of m. This SiO ₂
The film 5 is made of alumina (Al ₂ O ₃ ) in the alumina substrate 1 ′.
And functions as a diffusion preventing layer to prevent or suppress the reaction at high temperature of the composite transition metal film that becomes the temperature-sensitive resistor film 2, and the characteristics of the temperature-sensitive resistor film 2 are close to those of a bulk sintered body having the same composition. Necessary to make things. When the SiO ₂ film 5 is not provided, a reaction between the alumina (Al ₂ O ₃ ) and the temperature-sensitive resistor film 2 which has been subjected to the heat treatment in the manufacturing process is recognized, and the resistance of the temperature-sensitive resistor film 2 at an arbitrary temperature and B The constant is higher than the case where the SiO ₂ film 5 as the diffusion preventing layer is inserted.

Even when crystallized glass is used as the insulating substrate 1 ', a diffusion preventing layer is necessary. For the crystallized glass substrate, the above-described configuration in which the SiO ₂ film 5 or the Al ₂ O ₃ film and the SiO ₂ film are laminated is used.

On the diffusion preventing layer 5, a Mn-Ni-Co composite oxide film to be the temperature-sensitive resistor film 2 is formed by high frequency sputtering. The sputtering conditions are as follows. For the sputtering, a parallel plate type magnetron sputtering device is used. The substrate temperature is 100
~ 450 ° C, gas pressure during sputtering is 0.27
１．０1.0 Pa. The thickness of the Mn—Ni—Co composite oxide film is in the range of 0.5 to 3.0 μm. The formed Mn-Ni-Co composite oxide film is represented by X
The crystallinity is insufficient when examined by line diffraction, and the specific resistance at an arbitrary temperature is different from that of a bulk fired body having the same composition. Further, the resistance value at the arbitrary temperature in the substrate has a large variation and the characteristics are non-uniform.

The formed Mn-Ni-Co composite oxide film is heat-treated at an appropriate temperature of 700 to 1000 ° C.
By this heat treatment, the crystallinity of the Mn-Ni-Co composite oxide film is improved, and the specific resistance at an arbitrary temperature is close to that of a bulk sintered body having the same composition. In addition, the variation in the resistance value within the substrate becomes sufficiently small, and the change over time in the resistance becomes small. The temperature-sensitive resistor film 2 formed in this way has uniformity and stability that poses no practical problem.

PdO _x, which can be considered to have been partially oxidized, by reactive sputtering on the temperature-sensitive resistor film 2
The films 6a and 6b are formed in a thickness range of 20 to 40 nm. In this sputtering, in addition to Ar gas, O ₂ gas is introduced into a vacuum chamber of a parallel plate type magnetron sputtering apparatus. Oxygen flow ratio is 1-5
%. PdO _X film 6a, 6b functions as an adhesion layer for the Pd film 7a, 7b and an Au film 8a, the temperature sensitive resistor film 2 of 8b are film subsequently. Pd films 7a, 7b
The Au films 8a and 8b are formed by DC sputtering. The Pd films 7a and 7b have a thickness in the range of 20 to 1000 nm, and the Au film has a thickness in the range of 50 nm or more. The thickness of the Au film was at least twice the thickness of the Pd film.

The PdO _X film 6a, 6b and Pd films 7a, 7
The electrode film composed of b and the Au films 8a and 8b is processed into a pair of electrode patterns that can obtain a desired resistance value by using a photolithography process. PdO _X films 6a, 6
The b and Pd films 7a and 7b and the Au films 8a and 8b were all etched using aqua regia.

After the formation of the pair of electrode patterns, an SiO ₂ film serving as the protective film 9 is formed by high frequency sputtering.
It was processed and patterned using a photolithography process. An HF + NH ₄ F solution or chemical dry etching was used for etching the SiO ₂ film serving as the protective film 9. After patterning of the protective film 9, the substrate is
Heat treatment at a temperature of 0 ° C. or higher. A pair of electrodes and protective film 9
When sputtering is performed, the temperature-sensitive resistor film 2 is distorted because it becomes a base, and its resistance value at an arbitrary temperature increases. By performing the heat treatment at a temperature of 600 ° C. or more, the distortion was removed, and the characteristics of the temperature-sensitive resistor film 2 could be made uniform within the substrate.

Embodiment 2 of the present invention will be described below.

FIG. 3 is a schematic plan view of a thin film thermistor according to a second embodiment of the present invention. FIG. 4 shows B in FIG.
FIG. 4 is a schematic cross-sectional structure diagram along a line B ′. The process of Example 2 is the same as that of Example 1 up to the sputtering film formation of the Mn—Ni—Co oxide film to be the temperature-sensitive resistor film 2.
Also in Example 2, the formed Mn-Ni-Co oxide film is subsequently heat-treated at an appropriate temperature of 700 to 1000C. In the second embodiment, this heat treatment can be omitted.

In Example 2, the temperature-sensitive resistor film 2
₂ film 9 is formed by high frequency sputtering,
The O ₂ film 9 is processed into a pattern so as to obtain a desired resistance value. The etching of the SiO ₂ film 9 is the same as the etching of the protective film 9 (SiO ₂ film) of the first embodiment, as in the case of HF + NH _4.
F solution or chemical dry etching was used. If the pattern size is small and stricter resistance accuracy is required, plasma etching or reactive ion etching and anisotropic etching will not hinder the subsequent process.

After patterning the SiO ₂ film 9, the substrate is heat-treated at a temperature of 700 to 1000 ° C. or less. By this heat treatment, the strain given to the temperature-sensitive resistor film 2 by the high frequency sputtering of the SiO ₂ film 9 is removed. SiO ₂
Even if the Mn-Ni-Co oxide film is not heat-treated before the film 9 is formed, the resistance of the temperature-sensitive resistor film 2 at an arbitrary temperature can be made uniform and stable only by this heat treatment.

In the electrode of the thin film thermistor of the second embodiment, the Mn-Ni-Co oxide films 10a and 10b formed by high frequency sputtering to improve the adhesion to the SiO ₂ film 9 are changed to PdO _x films 6a and 6b. Is inserted below. The Mn-Ni-Co oxide films 10a, 10b
Is generally sufficiently thin because it is formed to a thickness of 100 nm or less, and does not affect the resistance value of the thin film thermistor at an arbitrary temperature. Mn-Ni-Co oxide film 10 as adhesion layer
a, PdO _X film 6a on the 10b, 6b and Pd film 7a,
7b and Au films 8a and 8b are formed. The thickness of these films is the same as the thickness of each film in the first embodiment. After the formation of the electrodes, the electrodes were patterned by a photolithography process, and processed into a pair of electrodes that were in contact with the patterned ends of the SiO ₂ film 9. Pd similar to Example 1
O _X film 6a, 6b and Pd films 7a, 7b and an Au film 8
After the etching of a and 8b, the Mn-Ni-Co oxide film of the adhesion layer was etched.

After patterning the pair of electrodes, the substrate is
Heat treatment was performed at a temperature of 0 ° C. or higher, and the characteristics of the temperature-sensitive resistor film 2 were made uniform within the substrate by forming an electrode.

In both the first and second embodiments, the surface is glass-sealed as necessary to enhance reliability. In the second embodiment, when the pair of electrodes are etched, the temperature-sensitive resistor film 2 is
Since it is covered with the O ₂ film 9, it is not exposed to an etching solution having a strong oxidizing property, so that the resistance value of the temperature-sensitive resistor film 2 can be easily controlled.

[0040]

The thin-film thermistor of the present invention has an advantage that the electrode is not peeled off due to a decrease in the adhesive force due to the history of the temperature change during the heat treatment in the manufacturing process and the actual use of the device. Further, no increase in the specific resistance of the electrode after the manufacturing process including the heat treatment is observed. The surface resistance of the electrode is
It is low enough and there is no practical problem. In the case of the thin-film thermistor of the present invention, the heat treatment can be performed at a sufficiently high temperature even after the electrode is formed, so that the distortion of the temperature-sensitive resistor film caused by the formation of the electrode or the protective film can be recovered after sufficient removal. As a result, the variation in resistance at an arbitrary temperature in the substrate is only the variation in the thickness of the temperature-sensitive resistor film, and can be sufficiently suppressed. The change with time of the resistance is small enough,
The change from the initial value of the resistance value after storage at 00 ° C. for 1000 hours was within 1%.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of a thin-film thermistor according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional structural view of the thin-film thermistor as a first embodiment of the present invention, taken along line AA ′ of FIG. 1;

FIG. 3 is a schematic plan view of a thin film thermistor according to a second embodiment of the present invention.

FIG. 4 is a schematic sectional view of a thin film thermistor according to a second embodiment of the present invention, taken along line BB ′ of FIG. 3;

FIG. 5 is a schematic sectional structural view of a conventional thin film thermistor.

FIG. 6 is a schematic sectional structural view of a conventional thin film thermistor.

[Explanation of symbols]

Reference Signs List 1 Insulating substrate (alumina substrate) 1 'Insulating substrate (alumina substrate or crystallized glass substrate) 2 Temperature-sensitive resistor film 3a, 3b Base metal thin film 4a, 4b Noble metal thin film 5 Diffusion prevention layer (SiO ₂ film) 6a, 6b PdO _X film 7a, 7b Pd film 8a, 8b Au film 9 SiO ₂ film 10a, 10b Mn-Ni-Co oxide film (SiO ₂
Adhesion layer for film)

Claims (7)

[Claims] 1. A temperature-sensitive resistor film is formed on an insulating substrate,
A film configuration in which a PdO _x film in which a part of Pd atoms are considered to be oxidized, a Pd film, and an Au film thicker than the Pd film are sequentially laminated on the temperature-sensitive resistor film, or the PdO _x film and the Au film are sequentially laminated. A thin film thermistor formed with a pair of electrodes having a multi-layered film configuration. 2. The temperature-sensitive resistor film comprises Mn, Ni, Co,
2. The thin film thermistor according to claim 1, wherein the composite oxide contains at least two or more elements selected from the group consisting of Fe and Cu. 3. The insulating substrate according to claim 1, wherein said insulating substrate has 90% or more Al ₂ O.
Alumina substrate containing ₃ or having a coefficient of thermal expansion of 60 to 100
The thin film thermistor according to claim 1, wherein the thin film thermistor is crystallized glass in a range of × 10 ⁻⁷ / ° C. 4. 4. An SiO ₂ film or Al ₂ O ₃ between the insulating substrate and the temperature-sensitive resistor film, which prevents or suppresses diffusion of a component of the insulating substrate into the temperature-sensitive resistor film.
The thin film thermistor according to any one of claims 1 to 3, wherein a structure in which an SiO ₂ film is laminated on the film is formed. 5. The temperature-sensitive resistor film according to claim 2, wherein the temperature-sensitive resistor film according to claim 2 is formed on the insulating substrate and the diffusion prevention film according to claim 3 or 4, and on the temperature-sensitive resistor film. The thin film thermistor, wherein the pair of electrodes is formed. 6. The temperature-sensitive resistor film according to claim 2, formed on the insulating substrate and the diffusion prevention film according to claim 3, and an insulating film formed on the temperature-sensitive resistor film. And forming the pair of electrode patterns according to claim 1 or contacting the temperature-sensitive resistor film according to claim 2 with a thickness of 0.1 μm or less, in contact with pattern ends of the already formed insulating film after patterning. The thin film thermistor according to claim 1, wherein the pair of electrodes is formed after forming the adhesion layer. 7. The method according to claim 7, wherein the insulating film on the temperature-sensitive resistor film is S
iO _2, Si ₃ N _4, a thin film thermistor according to claim 6, characterized in that the more one of TiO _2.