A mercury cadmium telluride device with high consistency working bias voltage and preparation method thereof

Abstract

The present invention belongs to the technical field of mercury cadmium telluride devices, and specifically relates to a mercury cadmium telluride device with a high consistency working bias voltage and a preparation method thereof: a PN junction region is formed on the mercury cadmium telluride absorption region, and the mercury cadmium telluride absorption region and the PN junction region are covered with a first passivation layer; a common electrode hole is provided around the first passivation layer corresponding to the position of the PN junction region, and the common electrode hole is connected to the edge common electrode surrounding the array through a common electrode grid, and the PN junction region is located below the space of the common electrode grid; a second passivation layer is covered on the first passivation layer and the common electrode grid; a PN junction region electrode is provided on the second passivation layer directly above the PN junction region, and the PN junction region electrode extends to the PN junction region; an indium column is provided on the PN junction region electrode. The present invention can not only achieve that the working bias voltage points of the mercury cadmium telluride central pixel and the edge pixel are basically consistent, but also reduce surface leakage and crosstalk by designing the common electrode hole and avoiding direct contact between the common electrode grid and the mercury cadmium telluride absorption region.

Description

Technical Field

[0001] The invention belongs to the technical field of mercury cadmium telluride devices, and in particular relates to a mercury cadmium telluride device with a high-consistency working bias voltage and a preparation method thereof. Background Art

[0002] Mercury cadmium telluride focal plane array devices are the mainstream devices of the second and third generation infrared imaging technology. With the development of military and civilian needs, it is required to obtain more complete and comprehensive information on targets in complex environments, improve the detection and recognition capabilities of targets, especially various large-area medium-wave, long-wave, and two-color mercury cadmium telluride focal plane array devices have become a development trend.

[0003] Among them, the PN junction is the core of the HgCdTe focal plane device. The PN junction needs to be biased to reach the working point when it is working. In the traditional process, the bias voltage is introduced through the common electrodes on the edges, passes through the HgCdTe absorption area, and gradually reaches the working point from the edge pixels to the center pixels. However, since the body resistance of the HgCdTe thin layer is generally in the order of kilohms, under the application conditions of large arrays, small F numbers, long waves, high-energy targets, and high background radiation, when the center pixel gradually reaches the working bias working point, the bias voltage of the edge pixel points of the array will become larger and larger. When the center pixel reaches the bias working point, the edge source pixel points of the array also deviate significantly from the optimal bias voltage working point, resulting in an increase in the bias voltage working point of the focal plane as a whole, which ultimately leads to a decrease in the imaging quality of the HgCdTe focal plane array. Patent No. CN 108922898 A proposes that the common electrode layer surrounds the array and extends into the absorption area within the array area. However, its surrounding design has shortcomings. The surrounding electrode is directly bonded to the p-region over a large area, and the extended common electrode is close to the PN junction area, which can easily lead to serious surface leakage and crosstalk. Summary of the invention

[0004] In order to overcome the deficiencies of the above-mentioned prior art, the object of the present invention is to provide a mercury cadmium telluride device with a highly consistent working bias voltage, which can achieve consistency in the working bias voltage points of the mercury cadmium telluride center pixel and the edge pixel, while also reducing surface leakage and crosstalk, thereby improving the imaging quality of the mercury cadmium telluride focal plane array device.

[0005] To achieve the above-mentioned purpose, the technical solution of the present invention is a mercury cadmium telluride device with a high consistency working bias voltage, comprising a mercury cadmium telluride absorption region, a first passivation layer, a PN junction region, a common electrode hole, a common electrode grid, a second passivation layer, a PN junction region electrode and an indium column; a PN junction region is formed on the mercury cadmium telluride absorption region, and the mercury cadmium telluride absorption region and the PN junction region are covered with a first passivation layer; common electrode holes connected to the mercury cadmium telluride absorption region are arranged around the first passivation layer corresponding to the position of the PN junction region, and the common electrode holes are connected to the edge common electrodes surrounding the array through a common electrode grid, and the PN junction region is located below the space of the common electrode grid; the first passivation layer and the common electrode grid are covered with a second passivation layer; a PN junction region electrode is arranged on the second passivation layer directly above the PN junction region, and the PN junction region electrode extends to the PN junction region; an indium column is arranged on the PN junction region electrode.

[0006] Furthermore, the first passivation layer is composed of cadmium telluride and has a thickness of

[0007] Furthermore, the second passivation layer is composed of zinc telluride and has a thickness of

[0008] Furthermore, the common electrode hole is located at the intersection of the common electrode grid, and the center of the PN junction region is located directly below the center of the space of the common electrode grid.

[0009] Furthermore, the common electrode hole and the common electrode grid are both composed of chromium and gold, and the growth order is first to grow chromium and then to grow gold, and the thickness of chromium is Gold thickness is

[0010] Furthermore, the aperture size of the common electrode hole is 1-4 um, and the line width of the common electrode grid is 2-5 um.

[0011] Furthermore, the PN junction region electrode is composed of tin and gold, and the growth order is to grow tin first and then grow gold.

[0012] The present invention also provides a method for preparing the above-mentioned mercury cadmium telluride device with high consistency working bias voltage, comprising the following steps:

[0013] 1) sequentially growing a first passivation layer and a second passivation layer on the mercury cadmium telluride absorption region;

[0014] 2) forming a PN junction region on the mercury cadmium telluride absorption region by ion implantation;

[0015] 3) removing the second passivation layer;

[0016] 4) completing the opening of the common electrode hole on the first passivation layer around the PN junction area;

[0017] 5) forming a common electrode grid and common electrode holes on the first passivation layer, and forming an edge common electrode at the same time;

[0018] 6) growing a second passivation layer on the first passivation layer and the common electrode grid;

[0019] 7) completing the passivation openings of the first passivation layer and the second passivation layer above the PN junction region;

[0020] 8) forming a PN junction region electrode on the passivation opening above the PN junction region;

[0021] 9) Grow an indium column on the PN junction electrode.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention provides common electrode holes around a PN junction region, connects the common electrode holes and edge common electrodes through a common electrode grid, and provides the common electrode grid between a first passivation layer and a second passivation layer, so as to achieve that the working bias voltage points of a central pixel of mercury cadmium telluride and an edge pixel are basically consistent, and at the same time, the contact area of ​​the common electrode with the mercury cadmium telluride in an absorption region is reduced. By designing the common electrode holes to be away from the PN junction region and avoiding direct contact between the common electrode grid and the mercury cadmium telluride absorption region, the effects of reducing surface leakage and crosstalk are achieved, and the problem of inconsistent working bias voltages of a central pixel of mercury cadmium telluride and an edge pixel of mercury cadmium telluride is effectively solved, thereby improving the imaging quality of a mercury cadmium telluride focal plane array device. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 A cross-sectional view of a mercury cadmium telluride device with a high consistency working bias voltage provided by an embodiment of the present invention;

[0026] Figure 2 A top view of a common electrode network of a mercury cadmium telluride device with a high consistency working bias voltage provided by an embodiment of the present invention;

[0027] In the figure: 1. HgCdTe absorption region, 2. first passivation layer, 3. PN junction region, 4. common electrode hole, 5. common electrode grid, 6. second passivation layer, 7. PN junction region electrode, 8. indium column, 9. edge common electrode. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] In the description of the present invention, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0030] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features; in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0031] like Figure 1-Figure 2As shown, this embodiment provides a mercury cadmium telluride device with a high consistency working bias voltage, comprising a mercury cadmium telluride absorption region 1, a first passivation layer 2, a PN junction region 3, a common electrode hole 4, a common electrode grid 5, a second passivation layer 6, a PN junction region electrode 7 and an indium column 8; a PN junction region 3 is formed on the mercury cadmium telluride absorption region 1, and the mercury cadmium telluride absorption region 1 and the PN junction region 3 are covered with the first passivation layer 2; a common electrode hole 4 connected to the mercury cadmium telluride absorption region 1 is provided around the first passivation layer 2 corresponding to the position of the PN junction region 3, and the common electrode hole 4 is connected to the edge common electrode 9 surrounding the array through the common electrode grid 5, and the PN junction region 3 is located below the space of the common electrode grid 5; the first passivation layer 2 and the common electrode grid 5 are covered with the second passivation layer 6; a PN junction region electrode 7 is provided on the second passivation layer 6 directly above the PN junction region 3, and the PN junction region electrode 7 extends to the PN junction region 3; an indium column 8 is provided on the PN junction region electrode 7. In this embodiment, common electrode holes 4 are provided around each PN junction region 3 of the array, and the common electrode holes 4 and the edge common electrodes 9 are connected through the common electrode grid 5. The common electrode grid 5 is provided between the first passivation layer 2 and the second passivation layer 6, so that the working bias voltage points of the central pixel and the edge pixel of the mercury cadmium telluride are basically consistent, and at the same time, the contact area of ​​the common electrode with the mercury cadmium telluride in the absorption region is reduced. By designing the common electrode holes 4 to be away from the PN junction region 3 and avoiding direct contact between the common electrode grid 5 and the mercury cadmium telluride 1 in the absorption region, the effect of reducing surface leakage and crosstalk is achieved, and the inconsistency problem of the working bias voltage of the central pixel and the edge pixel of the mercury cadmium telluride is effectively solved, thereby improving the imaging quality of the mercury cadmium telluride focal plane array device.

[0032] Furthermore, the first passivation layer 2 is composed of cadmium telluride and has a thickness of

[0033] Furthermore, the second passivation layer 6 is composed of zinc telluride and has a thickness of

[0034] Furthermore, the common electrode hole 4 is located at the intersection of the common electrode grid 5, and the center of the PN junction region 3 is located directly below the center of the space of the common electrode grid 5. Figure 2 As shown, the four sides of the common electrode grid 5 are connected to the edge common electrode 9, the intersection of the common electrode grid 5 is connected to the common electrode hole 4, and the center of the PN junction area 3 is located directly below the center of the space of the common electrode grid 5, so that the common electrode hole 4 is further away from the PN junction area 3, further reducing surface leakage and crosstalk.

[0035] Furthermore, the common electrode hole 4 and the common electrode grid 5 are both composed of chromium and gold to improve metal adhesion. The growth order is to grow chromium first and then grow gold. The thickness of chromium is Gold thickness is

[0036] Furthermore, the aperture size of the common electrode hole 4 is 1-4 um, and the line width of the common electrode grid 5 is 2-5 um.

[0037] Furthermore, the PN junction region electrode 7 is composed of tin and gold, and the growth order is first growing tin and then growing gold.

[0038] This embodiment also provides a method for preparing the above-mentioned mercury cadmium telluride device with high consistency working bias voltage, comprising the following steps:

[0039] 1) sequentially growing a first passivation layer 2 and a second passivation layer 6 on the mercury cadmium telluride absorption region 1;

[0040] 2) forming a PN junction region 3 on the mercury cadmium telluride absorption region 1 by ion implantation;

[0041] 3) Removing the zinc sulfide passivation layer;

[0042] 4) forming a common electrode hole 4 on the first passivation layer 2 corresponding to the PN junction region 3 by a dry method or a wet method through photolithography-development-opening-gold growth, and the common electrode hole 4 extends to the surface of the epitaxial layer of the mercury cadmium telluride absorption region 1;

[0043] 5) Connecting the metal wires to the common electrode holes 4 by photolithography-development-gold growth, forming a common electrode grid 5 on the first passivation layer 2, and forming an edge common electrode 9 surrounding the array;

[0044] 6) growing a second passivation layer 6 on the first passivation layer 2 and the common electrode grid 5;

[0045] 7) completing the passivation opening of the PN junction region of the first passivation layer 2 and the second passivation layer 6 on the PN junction region 3 by a dry method or a wet method through photolithography-development-opening;

[0046] 8) Through photolithography-development-stripping, the PN junction region electrode 7 is grown on the passivation opening;

[0047] 9) Through photolithography-development-stripping, an indium column 8 is grown on the PN junction region electrode 7.

[0048] Example 1

[0049] This embodiment provides a method for preparing a mercury cadmium telluride device with a highly consistent working bias voltage, comprising the following steps:

[0050] 1) Grown sequentially on the mercury cadmium telluride absorption region 1 Cadmium telluride passivation layer and Zinc sulfide passivation layer;

[0051] 2) On the P-type HgCdTe absorption region 1, through B + Ion implantation forms a PN junction region 3;

[0052] 3) Wet removal of zinc sulfide passivation layer;

[0053] 4) Photolithography of the P-region contact electrode hole, wet etching of the 2 μm common electrode hole 4, and removal of the photoresist;

[0054] 5) Photolithography, 3um wide common electrode metal grid, growth Cr, Au common electrode grid 5, gold wire stripping, photoresist removal, and at the same time forming edge common electrodes 9 surrounding the array;

[0055] 6) Growth Zinc sulfide passivation layer;

[0056] 7) Photolithography of the N-region passivation hole, and wet method to complete the passivation opening;

[0057] 8) Photolithography of PN junction region electrode pattern to complete the growth of PN junction region electrode 7;

[0058] 9) Complete the photolithography, growth and stripping of the indium column 8.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A mercury cadmium telluride device with a high consistency working bias voltage, characterized in that: The invention comprises a mercury cadmium telluride absorption region, a first passivation layer, a PN junction region, a common electrode hole, a common electrode grid, a second passivation layer, a PN junction region electrode and an indium column; a PN junction region is formed on the mercury cadmium telluride absorption region, and the mercury cadmium telluride absorption region and the PN junction region are covered with a first passivation layer; common electrode holes connected to the mercury cadmium telluride absorption region are arranged around the first passivation layer corresponding to the position of the PN junction region, and the common electrode holes are connected to the edge common electrodes surrounding the array through a common electrode grid, and the PN junction region is located below the space of the common electrode grid; the first passivation layer and the common electrode grid are covered with a second passivation layer, and the common electrode grid is located on the first passivation layer; a PN junction region electrode is arranged on the second passivation layer directly above the PN junction region, and the PN junction region electrode extends to the PN junction region; an indium column is arranged on the PN junction region electrode.

2. The mercury cadmium telluride device with a high consistency working bias voltage as claimed in claim 1, characterized in that: The first passivation layer is composed of cadmium telluride and has a thickness of 3. The mercury cadmium telluride device with a high consistency working bias voltage as claimed in claim 1, characterized in that: The second passivation layer is composed of zinc telluride and has a thickness of 4. The mercury cadmium telluride device with a high consistency working bias voltage as claimed in claim 1, characterized in that: The common electrode hole is located at the intersection of the common electrode grid, and the center of the PN junction area is located directly below the center of the space of the common electrode grid.

5. The mercury cadmium telluride device with a high consistency working bias voltage as claimed in claim 1, characterized in that: The common electrode hole and the common electrode grid are both composed of chromium and gold, and the growth order is to grow chromium first and then grow gold. The thickness of chromium is Gold thickness is 6. The mercury cadmium telluride device with a high consistency working bias voltage as claimed in claim 1, characterized in that: The aperture size of the common electrode hole is 1-4 um, and the line width of the common electrode grid is 2-5 um.

7. The mercury cadmium telluride device with a high consistency working bias voltage as claimed in claim 1, characterized in that: The PN junction region electrode is composed of tin and gold, and the growth order is to grow tin first and then grow gold.

8. A method for preparing a mercury cadmium telluride device with a high consistency working bias voltage as claimed in any one of claims 1 to 7, characterized in that: The steps include: 1) sequentially growing a first passivation layer and a third passivation layer on the mercury cadmium telluride absorption region; 2) forming a PN junction region on the mercury cadmium telluride absorption region by ion implantation; 3) removing the third passivation layer; 4) completing the opening of the common electrode hole on the first passivation layer around the PN junction area; 5) forming a common electrode grid and common electrode holes on the first passivation layer, and forming an edge common electrode at the same time; 6) growing a second passivation layer on the first passivation layer and the common electrode grid; 7) completing the passivation openings of the first passivation layer and the second passivation layer above the PN junction region; 8) forming a PN junction region electrode on the passivation opening above the PN junction region; 9) Grow an indium column on the PN junction electrode.

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