JPS6233755B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an infrared sensing element,
In particular, the present invention relates to a method of manufacturing a small, highly sensitive photoconductive infrared sensing element.

Generally, a photoconductive type sensing element is known as a type of infrared sensing element constructed of a compound semiconductor made of indium antimony (InSb), which detects infrared rays by utilizing changes in the resistivity of the semiconductor due to light. The device has good sensitivity and quick response.

Conventionally, in order to obtain this type of infrared sensing element, for example, as shown in FIG.
After fixing a compound semiconductor substrate 2 made of InSb, polishing and etching the substrate 2 to a thickness of about several tens of μm, patterning the substrate 2 into a predetermined shape as shown in FIG. A thick electrode layer 3 made of gold (Au) is deposited on the upper surface of the substrate by vapor deposition using a metal mask, for example, so as to define a light receiving section 4 as shown in the figure. Thereafter, as shown in the cross-sectional view of FIG. 3 and the top view of FIG. It is configured to take out the signal output of the sensing element formed by the lead wire 5.

Incidentally, the above-mentioned infrared detection element is generally vacuum-sealed in an airtight container with a dewar structure, and is operated by cooling with a refrigerant such as liquid nitrogen, so it can be used for heat measurement in various industries, detection of pollution gas, etc. In order to implement it in a measuring device and use it continuously for a long time for these measurements, there is a limit to the retention time of the liquid refrigerant, which limits the usage time, making it difficult to use. There is some inconvenience. Recently, electronically cooled infrared detectors using Peltier elements, which are small and easy to cool, have been put into practical use and can satisfy the above problems. A sensing element is desired. However, in order to manufacture such a small infrared element for electronic cooling, the thickness of the element must be 10 μm to increase sensitivity.
If the light receiving surface is not kept extremely thin and the light receiving surface is kept in a very clean state, the recombination speed of carriers generated by infrared light near the surface of the light receiving surface will increase, resulting in a significant decrease in sensitivity. Therefore, after the light-receiving area is defined by an electrode pattern, it is necessary to clean the light-receiving surface by etching or the like, but the conventional manufacturing method has the disadvantage that the electrode peels off and the light-receiving area increases due to the peeling. It was hot. In addition, bonding lead wires to such elements has the problem that the element thickness cannot withstand the bonding pressure, and the element resistance is several tens of ohms, about 1/1000 of the element resistance of conventional types. Very good ohmic connections are required for the line connections.

SUMMARY OF THE INVENTION An object of the present invention is to overcome the above-mentioned problems and provide a novel manufacturing method capable of constructing a small and highly sensitive infrared sensing element for electronic cooling. In order to achieve such an object, the manufacturing method of the present invention involves connecting lead wires by solder to the electrode formation area on an infrared sensing chip made of a compound semiconductor, and then coating the entire surface of the chip with a metal conductive film. The metal conductive film is formed, and then the metal conductive film is selectively removed to provide a light receiving portion of a predetermined area on the chip.

Preferred embodiments of the manufacturing method of the present invention will be described in detail below with reference to the drawings.

FIGS. 5 to 8 are cross-sectional views showing one embodiment of the method for manufacturing a cooled photoelectric conversion element according to the present invention in the order of steps. First, as shown in FIG. 5, an element substrate 22 made of InSb is fixed on a support plate 21 made of, for example, sapphire or high-resistivity silicon with an epoxy resin adhesive, and the substrate 22 is
The substrate 22 is polished and etched to a predetermined thickness of μm or less, and the substrate 22 is patterned into a predetermined shape, and gold (Au) is applied to the electrode formation area on the substrate 22 (hereinafter referred to as a chip) using indium solder 23.
A lead wire 24 consisting of the following is connected ohmicly. Next, as shown in FIG. 6, a metal conductive film 25 made of indium (In), tin (Sn), etc. is coated with infrared light over the entire surface of the support plate including the chip 22 to which the lead wires 24 are connected. The metal conductive film 25 is formed to have a thickness of several μm so that no light is transmitted therethrough, and a resist film 26 is further applied on the metal conductive film 25. Thereafter, the resist film 26 is patterned into a predetermined pattern, and as shown in FIG. 7, the exposed metal conductive film 25 is selectively etched away to form an electrode portion 251. A light receiving section 27 having a predetermined area is provided on the chip 22 in a defined manner. Subsequently, the resist film 26
Using the pattern as a mask, only the light receiving portion 27 is etched as shown in FIG. 8, the thickness is adjusted to the desired element resistance, and the light receiving surface is cleaned. By removing it, the ohmic connection of the lead wire 24 can be reliably preserved, and a highly sensitive infrared sensing element can be obtained which has a light receiving area with good dimensional accuracy and a light receiving part 27 with a clean surface condition. It becomes possible. In particular, according to the method of this embodiment, a light-receiving surface up to about 30 μm square can be formed with high precision, making it easy to miniaturize the device.

Note that the above-described selective etching of the metal conductive film 25 and the light receiving portion 27 may be performed successively using a common etching solution.

As is clear from the above explanation, according to the method for manufacturing a cooled infrared sensing element according to the present invention, a method is used in which lead wires are connected directly to the element using indium solder, so a perfect ohmic connection can be obtained. . In addition, it is possible to precisely define a light-receiving surface with a shape of up to about 30 μm square through the photolithography process, and in the final process, the light-receiving region can be etched to a predetermined thickness without damaging the electrode portion. It has the advantage of being able to easily manufacture small, highly sensitive infrared sensing elements, such as being able to have a clean finish, and is extremely advantageous when applied to the manufacturing of small photoconductive infrared sensing elements for electronic cooling. It is.

[Brief explanation of the drawing]

FIGS. 1 to 4 are cross-sectional views and top views illustrating a conventional method for manufacturing an infrared sensing element in the order of steps. FIGS. 5 to 8 are an embodiment of the method for manufacturing an infrared sensing element according to the present invention. FIG. In the figure, 21 is a support plate, 22 is an element substrate (chip), 23 is indium solder, 24 is a lead wire, 25 is a metal conductive film, 251 is an electrode part, 26 is a resist film, and 27 is a light receiving part.

Claims (1)

[Claims] 1. After connecting a lead wire with solder to a portion of an infrared sensing chip made of a compound semiconductor where electrodes are to be formed, a metal conductive film is deposited on the entire surface of the chip, and then the metal conductive film is selectively removed. A method for manufacturing an infrared sensing element, characterized in that a light receiving portion of a predetermined area is provided on the chip.