JPS603793B2 - Infrared sensing element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in the structure of an electrode and a light receiving part of an infrared sensing element, particularly a photoconductive infrared sensing element.

As a constituent material of a semiconductor infrared sensing element, a multicomponent semiconductor having a narrow bandgap, such as mercury cadmium telluride (Hg1-xC Te), is generally used.

As a type of infrared sensing element made of such a multi-component semiconductor, carriers are generated by irradiating infrared rays with a wavelength where the photon energy is greater than the energy gap of the element material, and the electrical conductivity of the element changes based on these carriers. There is a photoconductive sensing element that detects incident infrared rays using

Conventionally, the structure of the electrodes in this type of element is as shown in FIG. The electrode 3 was formed using a metal such as ln by a vapor deposition method or the like, and the element 1 and the electrode 3 were formed so as to be in ohmic contact.

However, when the dimension i between the electrodes of the element becomes smaller, and the minority carriers generated by the optical signal naturally disappear in the light receiving part, which is less than the lifetime time, that is, the diffusion length, the minority carriers will contact the ohmic contact within the lifetime time. Sweep out (Sweep
Since a phenomenon called "out" occurs, if the bias voltage between the electrodes is increased beyond a certain level, the sensitivity of the element to the optical signal will become saturated.

Therefore, in order to eliminate this drawback, a material such as zinc sulfide (ZnS), which transmits infrared light but is an electrical insulator, is deposited on the interface between the element 21 and the electrode 23, as shown in FIG. Dimension 1, which determines the light-receiving area, is determined in the same way as for the slave by the electrodes such as ln, and only the area of ohmic contact is kept away from the light-receiving surface 22, so that the electrode and the insulator layer are separated. It was proposed to have a partially overlapping structure and to configure the structure at a position farther than the carrier diffusion/annihilation length.

However, the electrodes that make up conventional sensing elements not only have the function of detecting electrical signals, but also have the role of determining the light-receiving area. The present invention has been developed by arranging electrodes in positions where the above-mentioned sweep is unlikely to occur, without significantly changing the conventional manufacturing process, and by forming an electrically insulated layer on the electrodes to block infrared light. The present invention aims to provide a novel infrared sensing element defined by a window provided in a material layer.

In order to achieve such an object, the present invention relates to an infrared detector having a structure in which electrodes are provided at both ends of the light-receiving surface side of an infrared detecting element, in which electrodes partially overlap the ends of the electrodes on the infrared element on the light-receiving surface side. The present invention is characterized in that a desired light-receiving portion is formed by a light-shielding insulating layer, and one embodiment of the present invention will be described in detail below with reference to the drawings.

First, as shown in FIG. 3, a wafer for an infrared sensing element made of Hg1-Length Te is bonded onto a support plate 31, such as high resistivity Si, etc. with an adhesive, and then polished and etched to form the desired shape. It is assumed that the chip is 32.

However, the support plate 31 may be made of saphire made of an insulating material. Next, using a metal mask or the like on the chip 32, an electrode 33 is formed by vapor deposition of a metal such as ln. However, at this time, the electrode spacing L does not match the planned width of the light receiving surface A, but is made larger than the width of the light receiving surface. The reason for this will be explained in detail later. Further, on the chip 32 on which the electrode 33 is formed, a material that blocks infrared light and becomes an electrical insulator, such as Si0, is placed so as to partially overlap the electrode end.
A second layer 34 is deposited by chemical vapor deposition, and a window of a predetermined area is opened by photoetching or the like to form a light-receiving surface A.

The electrodes also make good ohmic contact with the chip. In a photoconductive infrared sensing element, a change in the conductivity of the chip, and therefore a change in the resistance value of the element, occurs only while carriers generated by light exist between the two electrodes, and once the carriers disappear, they no longer contribute to the change in resistance. It disappears.

Similarly, when carriers reach the ohmic contact region of the electrode, they disappear, resulting in signal saturation. Therefore, the electrode spacing L of the sensing element needs to be larger than the distance over which the carriers generated in the light receiving section by the incident light diffuse and move before disappearing over the lifetime.

Generally, it is preferable to select the above-mentioned interval L to be 3 to 7 times the width 1 of the light receiving surface. The configuration of the electrode and light receiving section as described above prevents carriers generated by signals incident from the light receiving surface A from disappearing due to sweep-out, and improves the response ability of the sensing element to infrared rays.

Furthermore, the spacing L between the electrodes 33 formed on the sensing element chip 32 is determined by forming the electrodes at a predetermined spacing from the relationship with the light receiving surface width 1 that determines the light receiving area, and then the light shielding insulating layer 33
4, the light receiving area may be determined. Therefore, there is an advantage that sensing elements having various desired light-receiving areas can be manufactured extremely easily by applying conventional manufacturing processes to the electrode portions. Note that the present invention is based on the H
It goes without saying that the present invention can also be applied to photoconductive devices having a sweep-out phenomenon other than photoconductive devices using g1-xCdxTe.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of a conventional infrared sensing element, and FIG. 3 is a cross-sectional view for explaining the structure of an infrared sensing element according to the present invention. 1, 21, 32: infrared sensing element, 2, 22, A: light-receiving surface, 3, 23, 33: electrode, 24: insulator layer, 31: support plate, 34: insulating layer, 1: determining light-receiving area Dimensions, L
: Electrode spacing. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. An infrared sensing element chip made of a multi-component semiconductor is fixed on a support plate made of a high resistivity material, and electrodes are formed on both sides of the expected light receiving window on the top surface of the chip, so that the chips partially overlap on the electrodes. 1. An infrared sensing element, comprising: forming a light-shielding insulating layer; and removing a portion of the insulating layer located between the two electrodes to form a light-receiving window of a predetermined area.