An indium antimonide flat focal plane detector chip and its preparation

Abstract

The present invention relates to an indium antimonide planar focal plane detector chip and its preparation, belonging to the field of infrared detector technology. The chip includes an indium antimonide wafer, a first P-type doping region, a second P-type doping region, a passivation film and a metal electrode; the passivation film is deposited on a surface of the indium antimonide wafer containing the first P-type doping region and the second P-type doping region, and the passivation film region corresponding to the first P-type doping region is processed with an ohmic hole, and the metal electrode is deposited on the passivation film in and around the ohmic hole, and the deposited metal electrode does not contact the passivation film region corresponding to the second P-type doping region. The present invention solves the crosstalk problem between pixel regions by designing the structure of the P-type doping region inside the chip, and can also reduce leakage current; and the preparation process of the chip is simple, with good operability and feasibility, providing an effective way to optimize chip crosstalk and leakage current, and promoting the development of the infrared detector industry.

Description

Technical Field

[0001] The invention relates to an indium antimonide planar focal plane detector chip and preparation thereof, belonging to the technical field of infrared detectors. Background Art

[0002] InSb is a III-V narrow-bandgap compound semiconductor and is an important semiconductor material for the development of 3μm to 5μm infrared focal plane arrays. In the field of medium-wave detection, InSb focal plane detectors have unique advantages such as low production cost, high uniformity, and stable performance. At present, there are two structures of InSb focal plane chips on the market: table structure and planar structure. Among them, the table-type InSb focal plane chip has the advantages of simple process, small crosstalk, and controllable junction area, but it has extremely high requirements for passivation process and the surface leakage current is not easy to control; the planar structure can better make up for the shortcomings of the table structure, but the planar structure InSb focal plane chip has large crosstalk, which seriously affects the performance of the detector. Summary of the invention

[0003] In view of the shortcomings of the above-mentioned two InSb focal plane chip structures, the present invention provides an indium antimonide planar focal plane detector chip and its preparation. On the basis of the traditional structure, by adding a first P-type doping region in the central area of ​​the pixel and adding a second P-type doping region between two pixels, the crosstalk between the pixels of the detector chip can be effectively suppressed, and the leakage current can also be reduced, thereby greatly improving the performance of the detector; the preparation process of the chip described in the present invention is simple and can be extended to the preparation of other photovoltaic infrared focal plane detectors, providing an effective way to optimize their crosstalk and leakage current.

[0004] The objectives of the present invention are achieved through the following technical solutions.

[0005] An indium antimonide planar focal plane detector chip, the detector chip comprising an indium antimonide wafer, a first P-type doping region, a second P-type doping region, a passivation film and a metal electrode;

[0006] The conductivity type of the InSb wafer is N-type; the number of scratches on the surface of the InSb wafer is preferably less than 3, and the density of corrosion pits is preferably less than 25 / cm 2 ;

[0007] The first P-type doping region is doped to P-type in the center region of the pixel of the indium antimonide wafer, and the second P-type doping region is doped to P-type in the non-doped region between two adjacent first P-type doping regions, and the first P-type doping region and the second P-type doping region are not in contact;

[0008] The passivation film is one of a silicon oxide film, a silicon nitride film or an aluminum oxide film, and the thickness is preferably 100nm to 700nm;

[0009] The metal electrode is a composite film composed of a gold (Au) film, a platinum (Pt) film, a nickel (Ni) film, and a titanium (Ti) film in order from top to bottom. The thickness of the gold film is preferably 150nm to 200nm, the thickness of the platinum film is preferably 30nm to 60nm, the thickness of the nickel film is preferably 20nm to 40nm, and the thickness of the titanium film is preferably 20nm to 40nm.

[0010] A passivation film is deposited on a surface of an indium antimonide wafer containing a first P-type doping region and a second P-type doping region. An ohmic hole is processed in the passivation film region corresponding to the first P-type doping region. A metal electrode is deposited on the passivation film in and around the ohmic hole, and the deposited metal electrode does not contact the passivation film region corresponding to the second P-type doping region. Under the cooperation of the first P-type doping region and the second P-type doping region, the detector chip only relies on the built-in electric field of the PN junction to collect the photogenerated carriers generated in the N region, prevents the mutual diffusion of carriers between the two pixel regions, and greatly suppresses the crosstalk between the pixel regions.

[0011] Furthermore, the doping sources of the first P-type doping region and the second P-type doping region are both beryllium ions, and the doping method is preferably ion implantation. Accordingly, the implantation energy is preferably 100keV to 200keV, and the implantation dose is preferably (1 to 8)×10 14 / cm 3 .

[0012] Furthermore, the distance between the centers of two adjacent pixel areas is 10μm to 30μm; the shape of the first P-type doping area in the pixel area is preferably circular or square, and the diameter of the circle or the diameter of the inscribed circle of the square is preferably 5μm to 25μm; the shape of the second P-type doping area is preferably a long rectangle, and the width of the long rectangle is preferably 1μm to 2μm.

[0013] The method for preparing the indium antimonide planar focal plane detector chip of the present invention comprises the following steps:

[0014] (1) firstly preparing an indium antimonide ingot by a Czochralski method, and then slicing it to obtain an indium antimonide wafer;

[0015] (2) using PECVD (plasma enhanced chemical vapor deposition) technology or ICPCVD (inductively coupled plasma chemical vapor deposition) technology to deposit a protective film on the surface of the indium antimonide wafer to be doped;

[0016] (3) depositing a diffusion barrier film on the protective film using PECVD technology or ICPCVD technology;

[0017] (4) etching the diffusion barrier film and the protective film by ICP etching (inductively coupled plasma etching) or RIE etching (reactive ion etching) to form a diffusion region to be doped; using beryllium ions as a doping source, ion implantation is used to perform diffusion doping in the diffusion region to be doped, and a first P-type doping region and a second P-type doping region are formed accordingly;

[0018] (5) removing the diffusion barrier film and protective film on the indium antimonide wafer by wet etching;

[0019] (6) depositing a passivation film on the surface of the indium antimonide wafer containing the first P-type doping region and the second P-type doping region by using PECVD technology, ICPCVD technology or ALD (atomic layer deposition) technology;

[0020] (7) etching the passivation film in the passivation film region corresponding to the first P-type doping region using an ICP etching technique or a RIE etching technique to form an ohmic hole in the passivation film;

[0021] (8) A magnetron sputtering process is used to sputter titanium film, nickel film, platinum film, and gold film in the order from the inside of the ohmic hole to the surface of the passivation film, and then a metal stripping method is used to form a metal electrode, thereby completing the preparation of the detector chip described in the present invention.

[0022] The protective film is a silicon oxide film or a silicon nitride film, and the thickness is preferably 80nm to 120nm; the diffusion barrier film is a silicon oxide film or a silicon nitride film, and the thickness is preferably 500nm to 700nm.

[0023] Furthermore, in step (4), the etching power of the diffusion barrier film and the protective film is 100W to 300W.

[0024] Furthermore, in step (5), a mixed solution of hydrofluoric acid (HF) and water in a volume ratio of 1: (1-5) is selected as the wet etching solution, and the etching time is preferably 5 min to 15 min.

[0025] Furthermore, in step (7), the etching power of the passivation film is 100W to 300W.

[0026] Beneficial effects:

[0027] (1) The present invention mainly designs the structure of the P-type doping region inside the detector chip, that is, adding a first P-type doping region in the central area of ​​the pixel and adding a second P-type doping region between two pixels, and preparing a metal electrode in the area corresponding to the first P-type doping region and not preparing a metal electrode in the area corresponding to the second P-type doping region, and only relying on the built-in electric field of the PN junction to collect the photogenerated carriers generated in the N region, preventing the mutual diffusion of carriers between the two pixel regions, thereby greatly suppressing the crosstalk between the pixel regions, and at the same time reducing the leakage current, thereby improving the performance of the detector.

[0028] (2) The preparation process of the detector chip described in the present invention is simple, has good operability and feasibility, and can be extended to the preparation of other photovoltaic infrared focal plane detectors, providing an effective way to optimize their crosstalk and leakage current, and promoting the development of the infrared detector industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the structure of the indium antimonide planar focal plane detector chip described in Example 1.

[0030] Figure 2 Schematic diagram of the structure of the first P-type doping region and the second P-type doping region in Example 1.

[0031] Among them, 1-InSb wafer, 2-P type doping region, 201-first P type doping region, 202-second P type doping region, 3-passivation film, 4-ohmic hole, 5-metal electrode. DETAILED DESCRIPTION

[0032] The present invention is further described below in conjunction with specific embodiments, wherein the methods are conventional methods unless otherwise specified, and the raw materials can be obtained from public commercial channels unless otherwise specified.

[0033] Example 1

[0034] An indium antimonide planar focal plane detector chip, the detector chip comprising an indium antimonide wafer 1, a first P-type doping region 201, a second P-type doping region 202, a passivation film 3 and a metal electrode 5, such as Figure 1 As shown;

[0035] The specific preparation steps of the detector chip are as follows:

[0036] (1) First, an indium antimonide ingot is prepared by a Czochralski method, and then sliced ​​to obtain an indium antimonide wafer 1 of N-type conductivity. The surface of the indium antimonide wafer 1 has two scratches and a density of 20 scratches / cm 2 No corrosion pits and no sticky dirt;

[0037] (2) using ICPCVD technology to deposit a 100 nm thick silicon oxide film as a protective film on the surface of the indium antimonide wafer 1 to be doped;

[0038] (3) Using ICPCVD technology to deposit a 600 nm thick silicon nitride film on the protective film as a diffusion barrier film;

[0039] (4) The distance between the centers of the two pixel regions is 15 μm. A photolithography machine and a mask are used to print the diffusion hole on the diffusion barrier film. Then, an RIE etching device is used to etch the pixel regions corresponding to the diffusion barrier film and the protective film. A square with a side length of 9 μm is formed at 200 W as the first diffusion region to be doped. An RIE etching device is used to etch the region between the two pixel regions corresponding to the diffusion barrier film and the protective film. A long rectangle with a width of 1.5 μm is formed at 200 W as the second diffusion region to be doped. Beryllium ions are used as the doping source. Ion implantation is used to diffuse doping in the first diffusion region to be doped and the second diffusion region to be doped. The implantation energy is 120 keV and the implantation dose is 3×10 14 / cm 3 , and accordingly form a P-type doping region 2 (including a first P-type doping region 201 and a second P-type doping region 202, such as Figure 2 shown);

[0040] (5) using a mixed solution prepared by mixing hydrofluoric acid and water in a volume ratio of 1:2 as an etching solution, and removing the diffusion barrier film and the protective film on the indium antimonide wafer 1 by wet etching, the etching time being 8 minutes;

[0041] (6) using PECVD technology to deposit a 400 nm thick silicon oxide film as a passivation film 3 on the surface of the indium antimonide wafer 1 containing the P-type doping region 2;

[0042] (7) using RIE etching technology to etch the passivation film 3 in the area of ​​the passivation film 3 corresponding to the first P-type doping region 201, the etching power is 150 W, the etching time is 14 min, and an ohmic hole 4 is formed on the passivation film 3;

[0043] (8) A magnetron sputtering process is used to sputter a titanium film with a thickness of 20 nm, a nickel film with a thickness of 30 nm, a platinum film with a thickness of 40 nm, and a gold film with a thickness of 150 nm in sequence from the inside of the ohmic hole 4 to the surface of the passivation film 3; then, the film is soaked in pure acetone for 10 minutes, and then washed with ethanol for 5 minutes to remove excess metal and acetone residues on the surface of the passivation film 3 to form a metal electrode 5, thereby completing the preparation of the detector chip.

[0044] Example 2

[0045] An indium antimonide planar focal plane detector chip, the detector chip comprising an indium antimonide wafer 1, a first P-type doping region 201, a second P-type doping region 202, a passivation film 3 and a metal electrode 5;

[0046] The specific preparation steps of the detector chip are as follows:

[0047] (1) First, an indium antimonide ingot is prepared by a Czochralski method, and then sliced ​​to obtain an indium antimonide wafer 1 of N-type conductivity. The surface of the indium antimonide wafer 1 has 3 scratches and a density of 23 scratches / cm 2 No corrosion pits and no sticky dirt;

[0048] (2) using PECVD technology to deposit a 110 nm thick silicon oxide film as a protective film on the surface of the indium antimonide wafer 1 to be doped;

[0049] (3) Using ICPCVD technology to deposit a 500 nm thick silicon nitride film on the protective film as a diffusion barrier film;

[0050] (4) The distance between the two pixel regions is 15 μm. The diffusion hole is firstly printed on the diffusion barrier film by using a photolithography machine and a mask. Then, the diffusion barrier film and the protective film are etched by using an RIE etching device. A circle with a diameter of 8 μm is formed at 180 W as the first diffusion region to be doped. The area between the two pixel regions corresponding to the diffusion barrier film and the protective film is etched by using an RIE etching device. A long rectangular strip with a width of 2 μm is formed at 180 W as the second diffusion region to be doped. Beryllium ions are used as the doping source. Ion implantation is used to diffuse doping in the first diffusion region to be doped and the second diffusion region to be doped. The implantation energy is 160 keV and the implantation dose is 2×10 14 / cm 3 , a P-type doping region 2 (including a first P-type doping region 201 and a second P-type doping region 202) is formed accordingly;

[0051] (5) using a mixed solution prepared by mixing hydrofluoric acid and water in a volume ratio of 1:3 as an etching solution, and removing the diffusion barrier film and the protective film on the indium antimonide wafer 1 by wet etching, the etching time being 10 minutes;

[0052] (6) using PECVD technology to deposit a 300 nm thick silicon nitride film as a passivation film 3 on the surface of the indium antimonide wafer 1 containing the P-type doping region 2;

[0053] (7) using RIE etching technology to etch the passivation film 3 in the area of ​​the passivation film 3 corresponding to the first P-type doping region 201, the etching power is 200 W, the etching time is 9 minutes, and an ohmic hole 4 is formed on the passivation film 3;

[0054] (8) A magnetron sputtering process is used to sputter a titanium film with a thickness of 20 nm, a nickel film with a thickness of 20 nm, a platinum film with a thickness of 40 nm, and a gold film with a thickness of 180 nm in sequence from the inside of the ohmic hole 4 to the surface of the passivation film 3; then, the film is soaked in pure acetone for 10 minutes, and then washed with ethanol for 5 minutes to remove excess metal and acetone residues on the surface of the passivation film 3 to form a metal electrode 5, thereby completing the preparation of the detector chip.

[0055] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An InSb flat focal plane detector chip, characterized in that: The detector chip includes an indium antimonide wafer, a first P-type doping region, a second P-type doping region, a passivation film and a metal electrode; The conductivity type of the indium antimonide wafer is N-type; The first P-type doping region is doped to P-type in the center region of the pixel of the indium antimonide wafer, and the second P-type doping region is doped to P-type in the non-doped region between two adjacent first P-type doping regions, and the first P-type doping region and the second P-type doping region are not in contact; The passivation film is one of a silicon oxide film, a silicon nitride film or an aluminum oxide film; The metal electrode is a composite film composed of a gold film, a platinum film, a nickel film, and a titanium film in order from top to bottom; A passivation film is deposited on one surface of an indium antimonide wafer containing a first P-type doping region and a second P-type doping region, an ohmic hole is processed in a passivation film region corresponding to the first P-type doping region, a metal electrode is deposited on the passivation film in and around the ohmic hole, and the deposited metal electrode does not contact the passivation film region corresponding to the second P-type doping region; The number of scratches on the surface of InSb wafer is less than 3, and the density of corrosion pits is less than 25 / cm 2 ; The thickness of the passivation film is 100 nm~700 nm.

2. The InSb flat focal plane detector chip according to claim 1, characterized in that: Among the metal electrodes, the thickness of the gold film is 150 nm~200 nm, the thickness of the platinum film is 30 nm~60 nm, the thickness of the nickel film is 20 nm~40 nm, and the thickness of the titanium film is 20 nm~40 nm.

3. The InSb flat focal plane detector chip according to claim 1, characterized in that: The doping sources of the first P-type doping region and the second P-type doping region are both beryllium ions.

4. The InSb flat focal plane detector chip according to claim 3, characterized in that: Ion implantation is used for beryllium ion doping. Correspondingly, the implantation energy is 100 keV~200 keV and the implantation dose is (1~8)×10 14 / cm 3 .

5. The InSb flat focal plane detector chip according to claim 1, characterized in that: The distance between the centers of two adjacent pixel areas is 10 μm~30 μm; the shape of the first P-type doped area in the pixel area is circular or square, and the diameter of the circle or the inscribed circle of the square is 5 μm~25 μm; the shape of the second P-type doped area is a long rectangle, and the width of the long rectangle is 1 μm~2 μm.

6. A method for preparing the InSb2 planar focal plane detector chip according to any one of claims 1 to 5, characterized in that: The method steps are as follows: (1) First, prepare an indium antimonide ingot by the Czochralski method, and then slice it to obtain an indium antimonide wafer; (2) Using PECVD technology or ICPCVD technology to deposit a protective film on the surface of the indium antimonide wafer to be doped; (3) Depositing a diffusion barrier film on the protective film using PECVD technology or ICPCVD technology; (4) Using ICP etching technology or RIE etching technology to etch the diffusion barrier film and protective film to form a diffusion area to be doped; Using beryllium ions as a doping source, ion implantation is used to perform diffusion doping in the diffusion region to be doped, and a first P-type doping region and a second P-type doping region are formed accordingly; (5) Using wet etching to remove the diffusion barrier film and protective film on the indium antimonide wafer; (6) Depositing a passivation film on the surface of the indium antimonide wafer containing the first P-type doping region and the second P-type doping region by using PECVD technology, ICPCVD technology or ALD technology; (7) etching the passivation film in the passivation film region corresponding to the first P-type doping region using ICP etching technology or RIE etching technology to form an ohmic hole in the passivation film; (8) sputtering a titanium film, a nickel film, a platinum film, and a gold film in sequence from the inside of the ohmic hole to the surface of the passivation film by a magnetron sputtering process, and then forming a metal electrode by a metal lift-off method, thereby completing the preparation of the detector chip; The protective film is a silicon oxide film or a silicon nitride film, and the diffusion barrier film is a silicon oxide film or a silicon nitride film.

7. The method for preparing an InSb flat focal plane detector chip according to claim 6, characterized in that: The thickness of the protective film is 80 nm~120 nm, and the thickness of the diffusion barrier film is 500 nm~700 nm.

8. The method for preparing an InSb flat focal plane detector chip according to claim 6, characterized in that: In step (5), a mixed solution of hydrofluoric acid and water in a volume ratio of 1: (1-5) is selected as the etching solution for wet etching.

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