JP2982275B2 - Manufacturing method of thin film thermoelectric element - Google Patents

Description

The present invention relates to a method for manufacturing a small and highly sensitive thermoelectric element used for an infrared sensor, a temperature sensor, a heat sensor and the like.

(B) Conventional technology Conventionally, a so-called thermopile type thermoelectric element, which is used as an infrared sensor, a temperature sensor, a heat sensor, or the like and has a plurality of thermocouples connected in series, has been developed.

Generally, a thermopile type thermoelectric element has a structure in which a large number of thermoelectric materials are connected in series, and a 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 high-efficiency thermoelectric power conversion element or a highly sensitive infrared, temperature, or heat sensor for detecting a minute temperature difference. In particular, thin-film thermoelectric elements are mainly used for sensor applications in order to reduce the size, increase the sensitivity, and increase the response speed.

In a conventional thin-film thermoelectric element, a thin wire pattern made of an n-type thermoelectric material and a thin wire pattern made of a p-type thermoelectric material are formed on a substrate, and thermocouples are connected in series by forming electrodes.

The thermoelectric materials of such conventional thin film thermoelectric elements include Constantan-Nichrome (Japanese Patent Publication No. 57-40154), As-Te
(JP-A-53-132282), Si, Ge (JP-A-57-7172).
Semiconductor materials such as Bi-Sb-Te (Japanese Patent Application Laid-Open No. 61-22676).

(C) Problems to be Solved by the Invention These conventional thermoelectric materials have the advantage of low specific resistance and high thermoelectric conversion efficiency, but have a small Seebeck coefficient,
Further, it has a drawback that it cannot be used at high temperatures because it is easily oxidized.

An object of the present invention is to provide a method of manufacturing a thin-film thermoelectric element for a sensor which can solve such a conventional problem and can obtain a thin film and high thermoelectromotive force and can be used even in a high temperature range.

(D) Means for Solving the Problems In order to achieve the above object, a material that can be used at a high temperature and has a high Seebeck coefficient is required.

Silicide semiconductors have a high Seebeck coefficient of 300 to 700 μV / K, have high heat resistance, and are attracting attention as thermoelectric power conversion elements at high temperatures.

The inventors have found that a thermopile type thermoelectric element which can be used even at high temperature with high sensitivity can be obtained by thinning an iron silicide semiconductor material.

The method for manufacturing a thin-film thermoelectric element according to the present invention includes the steps of: The method is characterized in that the impurity is thermally diffused into the iron silicide film to form a thermocouple pattern of the iron silicide n-type semiconductor film and the iron silicide p-type semiconductor film.

(E) Function In the method for manufacturing a thin film thermoelectric element of the present invention, a thermocouple pattern of an iron silicide film and a thermocouple pattern of an impurity film are formed as thin films on the insulating substrate, respectively. Then, the impurities are thermally diffused into the iron silicide film by the heat treatment, the part where the donor is diffused becomes an n-type semiconductor, and the region where the acceptor is diffused becomes a p-type semiconductor. Thus, a thermocouple pattern of the iron silicide n-type semiconductor film and the iron silicide p-type semiconductor film is formed on the insulating substrate. As described above, since the intrinsic silicide iron silicide film and the impurity as a donor or an acceptor thereof are formed into thin films in a thermocouple pattern, respectively.
The amount of each composition can be accurately controlled, and a thin-film thermoelectric element made of an iron silicide semiconductor film having a desired carrier concentration can be obtained.

(F) Embodiment An embodiment of the present invention will be described in the order of manufacturing steps with reference to FIGS.

First, the powders of Fe and Si were mixed, and the
Melted at ℃, cast into a disk-shaped mold and cooled. Thereby, a disk-shaped iron silicide ingot is obtained. Then, the surface is polished to obtain an iron silicide target.

Next, as shown in FIG. 1, the above-mentioned iron silicide target is subjected to RF sputtering in Ar using a mask on the SiO ₂ substrate 1 to form an iron silicide thin film 2 in a thermocouple pattern.
The sputtering conditions at this time are as follows.

Substrate temperature: 300 ° C. High frequency output: 500 W to 1.5 kW Rate: 1 to 10 μm / hr Next, as shown in FIG.
RF sputtering in. The sputtering conditions at this time are as follows.

Substrate temperature: 150 ° C. High frequency output: 500 W to 1.5 kW Rate: 2 to 20 μm / hr As a result, as shown in FIG. Be deposited.

Subsequently, as shown in FIG. 4, a mask 5 having an opening formed in a portion where an acceptor is diffused was used as an acceptor.
RF sputtering Mn in Ar. The sputtering conditions at this time are as follows.

Substrate temperature: 150 ° C. High frequency output: 500 W to 1.5 kW Rate: 1 to 15 μm / hr As a result, as shown in FIG.
An Mn thin film 6 is deposited.

Thereafter, the entire substrate is heat-treated at 1200 to 1300 ° C. in a vacuum. As a result, as shown in FIG. 6, Co, M
The n is diffused into n, p-type semiconductor thin films 7 and 8, respectively, to form a thermopile in which a plurality of thermocouples each having a hot / cold junction are connected in series at the center and the periphery of the substrate.

Finally, as shown in FIG. 7, the lead mounting terminals 10 and 11 are formed by vapor-depositing an electrode material using a mask 9 having notches formed in the terminal forming portions, as shown in FIG.

In the above-described embodiments, the number of thermocouples is reduced in order to clarify the drawing.However, since each pattern is formed by a thin film by a sputtering method or the like, by miniaturizing the thermocouple pattern, The thermoelectromotive voltage can be increased. For example, in the structure shown in FIG.
A thermoelectric element having 100 pairs of iron silicide thermocouples was prepared on an m-square substrate, and its sensitivity was measured. As a result, it was about 100 V / W. Even when the device was left at 700 ° C. for 1000 hours, the characteristics did not change.

(G) Effects of the Invention According to the present invention, a thin-film thermoelectric element having a small size, high sensitivity and excellent heat resistance can be obtained, and thus can be applied to, for example, a non-contact temperature sensor or heat sensor for an automobile engine or a blast furnace. . In addition, since a target containing impurities is not used in forming the thin film, the impurity concentration of the semiconductor film can be easily controlled, and a thin film thermoelectric element having uniform characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 to FIG. 7 are plan views showing states on a substrate in respective steps in manufacturing a thin film thermoelectric element according to an embodiment of the present invention.
FIG. 8 is a plan view of the completed thin film thermoelectric element. DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Iron silicide thin film, 3,5,9 ... Mask, 4 ... Impurity (donor) film, 6 ... Impurity (acceptor) film, 7 ... Iron silicide n-type semiconductor film, 8 ...... Iron silicide p-type semiconductor film, 10, 11 ... Lead mounting terminals.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-47850 (JP, A) JP-A-53-117962 (JP, A) JP-A-62-177985 (JP, A) 31985 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 35/32 H01L 35/14 H01L 35/34

Claims (1)

(57) [Claims] 1. A thin-film thermocouple pattern in which impurities as donors and acceptors are alternately arranged and a thin-film thermocouple pattern of an iron silicide film are respectively formed on an insulating substrate, and heat treatment is performed on the silicide film. A method for manufacturing a thin-film thermoelectric device, comprising: performing thermal diffusion of impurities to form a thermocouple pattern of an iron silicide n-type semiconductor film and an iron silicide p-type semiconductor film.