JPH04150076A - Manufacture of thin film termoelectric device - Google Patents

Abstract

PURPOSE:To obtain a thermocouple device which is small-sized and excellent in high sensibility and heat resistant properties by forming an oxidation preventive film on an electrode pattern which connects a hot section with a cold section out of a thermocouple pattern and then forming into an oxide semiconductor an exposed section of metal thin film through a heat treatment. CONSTITUTION:An Ni metal-made film 2 is formed on an SiO2 substrate 1 based on an RF sputtering process, using a mask. Then, An SiO2 film, which serves as an oxidation preventative film, is formed on a portion equivalent to an electrode section based on the RF sputtering process. When the substrate is heat-treated at a temperature ranging from about 1,000 to 1,200 deg.C in the atmosphere, the SiO2-coated portion is not oxidized but it functions as an electrode section while the Ni film whose portion is not SiO2-coated is oxidized and turned into a p-type oxide semiconductor NiO4, thereby forming a thermocouple with an electrode pattern 3.

Description

DETAILED DESCRIPTION OF THE INVENTION (Al Industrial Field of Application) This invention relates to a method for manufacturing thin film thermoelectric elements used in infrared sensors, temperature sensors, thermal sensors, etc.

(bl) Prior Art Conventionally, so-called thermoelectric elements of the so-called thermomobile type, in which a large number of thermocouples are connected in series, have been developed to be used as infrared sensors, temperature sensors, thermal sensors, etc.

In general, a thermoelectric element of a thermomobile type has a structure in which a large number of thermoelectric materials are connected in series, and thermoelectromotive force generated from a temperature difference is added, and a large thermoelectromotive force can be obtained. As a result, it can be used as a highly efficient thermoelectric conversion element or a highly sensitive infrared, temperature, or thermal sensor that detects minute temperature differences. In particular, thin-film thermoelectric elements are mainly used for sensor applications in order to achieve smaller size, higher sensitivity, and faster response speed.

Thermoelectric materials for conventional thin film thermoelectric elements include Constance-Nichrome (Japanese Patent Publication No. 57-40154), As-Te (Japanese Patent Publication No. 53-132282), Si, and Ge (Japanese Patent Publication No. 53-132282).
No. 77172), B1-5b-Te (Japanese Unexamined Patent Publication No. 61-22
No. 676) and other metal alloys or compound semiconductor materials have been used.

(C) Problems to be Solved by the Invention These conventional thermoelectric materials have the advantage of low resistivity and high thermoelectric conversion efficiency, but have the disadvantage that they cannot be used at high temperatures because they have a small Seebeck coefficient and are easily oxidized. have.

SUMMARY OF THE INVENTION An object of the present invention is to solve these conventional problems and provide a method for manufacturing a thin film thermoelectric element that is thin, has a high thermoelectromotive force, and can be used even in a high temperature range.

(Means for solving the d1 problem) In order to achieve the above objective, it is necessary to use a material that can be used at high temperatures and has a high Kazehehe coefficient. Although it has a high Seebehuku coefficient and high heat resistance, its resistivity is more than two orders of magnitude higher than that of alloys and compound semiconductors, and its figure of merit, which evaluates heat-to-power conversion efficiency, is more than two orders of magnitude lower, making it suitable for use as a thermoelectric element. has not been applied much.

However, for applications of sensors that detect infrared rays, temperature, and heat flow, it is more important to have a large See-Tsk coefficient than to increase heat-to-power conversion efficiency.

The inventors have discovered that the above object can be achieved by forming a thin film of an oxide semiconductor material that has a larger Seebeck coefficient than conventional alloys or compound semiconductors and is stable even at high temperatures.

A method for manufacturing a thin film thermoelectric element according to claim (1) of the present invention includes forming a thermocouple pattern of a metal thin film on an insulating substrate, and forming an electrode pattern connecting hot and cold junctions of the thermocouple pattern. The method is characterized in that after an oxidation-preventing film is formed thereon, the exposed portion of the metal thin film is converted into an oxide semiconductor by heat treatment.

Further, the method for manufacturing a thin film thermoelectric element according to claim (2) of the present invention includes forming a thermocouple pattern including a laminate of an impurity layer and a metal thin film layer on an insulating substrate, and The present invention is characterized in that after an oxidation prevention film is formed on the electrode pattern connecting the contact portions, the oxidation prevention film-free portion is subjected to a heat treatment to diffuse impurities and convert it into an oxide semiconductor.

(e) Effect In the method for manufacturing a thin film thermoelectric element according to claim (1), a thermocouple pattern is formed by a metal thin film layer on an insulating substrate,
An oxidation prevention film is formed on the electrode pattern connecting the hot and cold junctions of the thermocouple pattern, and then heat treatment is performed to oxidize the exposed portion of the metal thin film and convert it into an oxide semiconductor. Therefore, a thin film thermoelectric element can be obtained by a pattern made of an oxide semiconductor film and an electrode pattern connecting the hot and cold junctions thereof.

Further, in the method for manufacturing a thin film thermoelectric element according to claim (2) of the present invention, a thermocouple pattern including a laminate of an impurity layer and a metal thin film layer is formed on an insulating substrate, and among this thermocouple pattern, hot and cold An oxidation prevention film is formed on the electrode pattern connecting the contact parts, and then, by heat treatment, impurities in the impurity layer are diffused into the metal thin film layer and oxidized to become an oxide semiconductor. As a result, a thin film thermoelectric element is obtained by the pattern made of the oxide semiconductor film and the electrode pattern connecting the hot and cold junctions thereof. According to the method for manufacturing a thin film thermoelectric element according to claim (2), even metal materials that are unstable or cannot be sufficiently converted into a semiconductor by oxidation treatment alone can be easily converted into a semiconductor.

(fl Example) A first example of the present invention will be explained in the order of manufacturing steps based on the diagrams shown in FIGS. 1 to 4.

First, as shown in FIG. 1, a Ni metal film 2 is formed on a SiO□ substrate 1 by RF sputtering using a mask. The sputtering conditions at this time are as follows.

Substrate temperature: 150℃ High frequency output = 500W ~ 1.5KW Rate: 1 ~ 10. ljm/hr Next, SiO is applied as an anti-oxidation film to the part 6 corresponding to the electrode part.
2 is formed into a film by RF sputtering. The sputtering conditions at this time are as follows.

Substrate temperature = 150℃ High frequency ratio: 500W to 1.5KW: 0. 5 ~2+Um/hr
Subsequently, the substrate is heat-treated at 1000 to 1200° C. in the atmosphere. As a result, as shown in FIG. 3, the part coated with 5IOz is not oxidized and functions as an electrode part, and the part of the Ni film not coated with 5iOz is oxidized, forming the p-type oxide semiconductor Ni04. becomes. As a result, a thermocouple is formed together with the electrode pattern 3.

Thereafter, as shown in FIG. 4, the lead attachment portion 5iQ2 is removed by polishing to form the lead attachment terminal 5.

In the embodiments shown above, the number of logarithms is reduced to make the drawings clearer, but the thermoelectromotive force can be increased by connecting a large number of thermocouples in series. In the structure shown in FIG. 4, a temperature difference of 5° C. was applied between both ends of the thermoelectric element in which 100 lines of Ni film were formed, and the See-\tsk coefficient was measured, and a value of 70 mV/K was obtained.

Next, the second embodiment will be explained in the order of manufacturing steps based on the diagrams shown in FIGS. 3 to 9.

First, a paste made by adding 50 g of Fes to 1.33 g of Nbzo was prepared as an impurity paste.

In FIG. 5, l is an Al z03 substrate, on which the NbzOs paste 7 is printed.

Next, as shown in FIG. 6, using a mask, the Ti metal 8 is
A film is formed using the F Svantha method. The sputtering conditions at this time are as follows.

Substrate temperature: 150℃ High frequency ratio crab 500W”1.5 KW sylate:
1 to 10 μm/hr Next, a film of SiO□ is formed as an oxidation prevention film on the portion 6 corresponding to the electrode portion by RF sputtering. The sputtering conditions at this time are as follows.

Substrate temperature: 150℃ High frequency ratio: 500W to 1.5KW Rate: 0. 5 to 2 μm/h
rSubsequently, the substrate is heat-treated at 800 to 1000°C in the atmosphere. As a result, as shown in FIG. 8, the part coated with SiO2 is not oxidized and remains as the electrode 3, and the part of the Tl film not coated with SiO2 undergoes oxidation and impurity diffusion, resulting in an n-type oxide. This becomes a Tie2 film 9 which is a semiconductor. This forms a thermocouple together with the electrode 3.

Thereafter, as shown in FIG. 9, the 3jO□ film at the lead attachment portion is removed by polishing to form a lead attachment terminal 10.

In the structure shown in Fig. 9, 100 lines of Ti0z (
5 at both ends of the thermoelectric element (containing Nb as an impurity)
When the Seebeck coefficient was measured by applying a temperature difference of ℃, it was 80.
mV/K was obtained.

(g) Effects of the Invention According to the present invention, by using an oxide semiconductor thin film, it is possible to obtain a thermoelectric element that is small, has a high degree of anger, and has excellent heat resistance. In addition, the deposition rate can be significantly increased compared to, for example, a thin film forming method by sputtering using a ceramic tertiary material, thereby reducing manufacturing costs.

[Brief explanation of drawings]

1 to 4 are diagrams showing the state of the substrate surface in each step of the method for manufacturing a thin film thermoelectric element according to the first embodiment of the present invention. Moreover, FIGS. 5 to 9 are diagrams showing the state of the substrate surface in each step of the method for manufacturing a thin film thermoelectric element according to the second embodiment. 1-Insulating substrate, 2. 8-Metal film/3-Electrode pattern, 4.9-Oxide semiconductor film, 5-10-Lead attachment terminal, 6-Anti-oxidation film (SiO□ film), 7-Impurity film pattern . Applicant Murata Manufacturing Co., Ltd.

Claims (2)

[Claims] (1) A thermocouple pattern made of a metal thin film is formed on an insulating substrate, and an oxidation prevention film is formed on the electrode pattern connecting the hot and cold junctions of the thermocouple pattern, and then the metal thin film is formed by heat treatment. 1. A method for manufacturing a thin film thermoelectric element, characterized in that an exposed portion of the element is made into an oxide semiconductor. (2) After forming a thermocouple pattern including a laminate of an impurity layer and a metal thin film layer on an insulating substrate, and forming an oxidation prevention film on an electrode pattern connecting hot and cold junctions of the thermocouple pattern. . A method for manufacturing a thin film thermoelectric element, comprising diffusing impurities and converting the portion where the anti-oxidation film is not formed into an oxide semiconductor by heat treatment.