Preparation method of absorption region fully-depleted high-temperature operation medium-wave avalanche detector structure

Abstract

The invention discloses a preparation method of an absorption region fully-depleted high-temperature operation medium-wave avalanche detector structure, and the method comprises the steps: employing a back high-component mutual diffusion tellurium-cadmium-mercury material, carrying out the ion implantation to form an n + region, carrying out the push junction annealing to form an n-multiplication region of an avalanche detector, and controlling the push junction annealing time and temperature, thereby achieving the full-depleted high-temperature operation medium-wave avalanche detector structure. The multiplication region is concentrated in the low component region to obtain the maximum gain and the medium wave response, and a built-in electric field formed by the forbidden band width difference of the absorption region exhausts the thickness of the absorption region, so that the medium wave avalanche detector in high-temperature operation is formed by weakening diffusion current.

Description

Technical field:

[0001] The present invention relates to the technical field of photoelectric detectors, and in particular to a method for preparing a medium-wave avalanche detector structure with full depletion in the absorption region and high temperature operation. Technical background:

[0002] Mid-wave infrared detectors (MWIR) are widely used in various fields, including missile warning and tracking, night vision imaging, target identification, environmental monitoring, astronomical observation, scientific research, and medical and biological applications. However, light absorption caused by carbon dioxide and water vapor in the atmosphere can greatly attenuate the system signal. In addition, accurate long-distance detection and tracking of weak targets in low light and complex environments requires devices that can amplify the signal during the detection process to improve the signal-to-noise ratio at the receiver output. Avalanche photodiodes (APDs) integrate the detection stage and the inherent gain stage into one device, greatly improving the detection accuracy and resolution, and therefore play a vital role in such weak signal application systems. MWIR APD devices usually operate at low temperatures. In order to reduce cost and power consumption, make them more suitable for harsh environments, and pave the way for expanding their versatility in commercial, scientific and civilian fields, MWIR APD systems need to operate at higher temperatures. Therefore, the development of the next generation of MWIR APDs must have the characteristics of high temperature operation (HOT), low dark current and low excess noise.

[0003] Mercury cadmium telluride (Hg 1-x Cd x As the most mature avalanche detector, HgCdTe MWIR APD has the characteristics of single carrier impact ionization, exponential high gain, and extremely low excess noise. However, the current planar homogeneous structure HgCdTe MWIR APD usually works at low temperature of liquid nitrogen and cannot work at higher temperature due to the limitation of high electron diffusion current. Moreover, there is no literature report on the medium-wave avalanche detector structure that can achieve high temperature operation at home and abroad. Summary of the invention:

[0004] The purpose of the present invention is to provide a method for preparing a medium-wave avalanche detector structure with full depletion in the absorption region and high temperature operation, so as to overcome the defect that the prior art cannot operate under the conditions of high operating temperature, low dark current and excess noise.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A method for preparing a medium-wave avalanche detector structure with full depletion in the absorption region and high temperature operation, comprising the following steps:

[0007] The first step is the back / surface interdiffusion of HgCdTe materials: the HgCdTe materials grown on CdZnTe substrates are subjected to interdiffusion annealing to obtain a surface passivation layer with a composition gradient and a back composition gradient region, and SIMS calibration is performed on the companion wafers.

[0008] The second step is to perform p + Type annealing for p + Type annealing doping: P-type Hg vacancy doping of the material after interdiffusion;

[0009] The third step is to photolithographically form ion injection holes: on the HgCdTe heterogeneous material on which the ZnS barrier layer and alignment marks have been prepared, ion injection holes are obtained by photolithography using positive photoresist;

[0010] The fourth step is boron ion implantation. After implantation, the photoresist is removed by immersion in acetone and the surface ZnS barrier layer is removed by immersion in pure hydrochloric acid to obtain n + district;

[0011] The fifth step is rapid push-through annealing, and the component distribution is obtained according to SIMS calibration. - doubling zone;

[0012] Step 6: Passivation and corrosion + / n + Electrode holes: CdTe / ZnS double-layer passivation process is used; positive photoresist is used to open the etching electrode holes in each injection hole and p-type area, and the holes are etched in freezing point pure hydrochloric acid and hydrobromic acid;

[0013] Step 7: Preparation of metal electrodes: Use electron beam evaporation equipment to prepare Cr / Au with a thickness of 50nm / 100nm respectively, then soak in acetone, and then perform metal stripping and remove photoresist;

[0014] Step 8: Preparation of In column by reverse soldering: Use positive photoresist to open In column preparation area in each injection area electrode hole and common electrode, first use electron beam evaporation to prepare UBM metal Cr / Au with thickness of 100nm / 100nm, then thermally evaporate In column on UBM metal Cr / Au, soak it in acetone after production, and then perform metal stripping and remove photoresist;

[0015] Step 9, device reverse soldering: interconnect the structure made in step 8 with the external gemstone substrate through the In column reverse soldering;

[0016] Step 10. Current-voltage and multiplication gain test: Use a variable temperature Dewar test system to test the light / dark current-voltage characteristics of devices of different areas.

[0017] The interdiffusion annealing treatment is performed at a temperature of 300-500° C. and for a time of 1 h-48 h.

[0018] The p+ type annealing treatment is performed at a temperature of 250-400° C. and for a time of 24 h to 72 h.

[0019] The size of the ion injection hole ranges from 5 μm to 50 μm.

[0020] The boron ion energy is 120-180 KeV and the dose is 1×10 13 -1×10 15 cm -2 , the beam current is 50-200μA.

[0021] The push-junction annealing temperature is 150-250° C., and the time is 120-250 seconds.

[0022] After the push-in annealing, n - The width of the multiplication zone is 1-4 μm.

[0023] The beneficial effects of the present invention are as follows: 1. The present invention uses a high-component inter-diffused HgCdTe material on the back to form n + Avalanche detector formed by push-up junction annealing - The multiplication zone is concentrated in the low-component zone by controlling the push-junction annealing time and temperature to obtain the maximum gain and medium-wave response, while the built-in electric field formed by the difference in the bandgap width of the absorption zone depletes the thickness of the absorption zone, and the device forms a high-temperature operating medium-wave avalanche detector by weakening the diffusion current; 2. By cleverly introducing a component gradient distribution in the conventional mercury cadmium telluride avalanche detector structure, the built-in electric field in the absorption zone realizes the full depletion state of the absorption zone, solves the limitation of the existing homogeneous structure dark current electron diffusion, and the multiplication zone adopts a narrow bandgap width material to achieve a greater gain; 3. The structure breaks through the high-temperature dark current limitation of the homogeneous junction medium-wave avalanche detector, combined with the characteristics of adjustable mercury cadmium telluride components, lattice matching, high gain, single carrier multiplication, etc., it can realize a medium-wave avalanche detector device with high temperature operation, low noise, low dark current and high gain; 4. The medium-wave avalanche detector prepared by the present invention has the characteristics of clear principle, simple process, convenient operation, intuitive judgment result and great market application potential. Description of the drawings:

[0024] Figure 1 is a process flow chart;

[0025] Figure 2 A structural diagram of a medium-wave avalanche detector formed by the present invention;

[0026] Figure 3 A distribution diagram of components of a medium-wave avalanche detector formed by the present invention;

[0027] Figure 4 The electric field distribution diagram of the medium-wave avalanche detector formed by the present invention, in which the absorption region is completely depleted.

[0028] Figure 5 The dark current density diagrams at 80K and high temperature 160K that can be achieved by the device with a cut-off wavelength of 4.2μm.

[0029] Figure 6 This is the gain normalized dark current density (GNDCD) that can be achieved at 80K and high temperature 160K for devices with a cutoff wavelength of 4.2μm. Specific implementation method:

[0030] In order to more concisely describe the present embodiment, some parts known to those skilled in the art but not related to the main content of the present invention are omitted in the drawings or descriptions. In addition, for the convenience of description, some parts in the drawings are omitted, enlarged or reduced, but they do not represent the size or entire structure of the actual product.

[0031] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings 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 should fall within the scope of protection of the present invention.

[0032] The present invention is further described below in conjunction with the accompanying drawings, which are only used for exemplary description and cannot be understood as limiting the present invention.

[0033] The present invention will now be further described with reference to the embodiments and the accompanying drawings:

[0034] The present invention relates to a method for preparing a medium-wave avalanche detector structure with full depletion in the absorption region and high temperature operation, such as Figure 1 As shown, the following steps are included:

[0035] The first step is the back / surface interdiffusion of HgCdTe materials: the HgCdTe materials grown on CdZnTe substrates are subjected to interdiffusion annealing treatment at a temperature of 300-500°C for 1h-48h to obtain a surface passivation layer with a composition gradient change and a back composition gradient region, and SIMS calibration is performed on the companion wafers; Figure 2 , Figure 3 shown.

[0036] The second step is to perform p + Type annealing for p + Annealing doping: P-type Hg vacancy doping is performed on the inter-diffused material at a temperature of 250-400°C for 24h-72h;

[0037] The third step is to photolithographically form ion injection holes: on the HgCdTe heterogeneous material on which the ZnS barrier layer and alignment marks have been prepared, a series of ion injection holes of different sizes are obtained by photolithography using positive photoresist, and the size range of the ion injection holes is 5μm-50μm;

[0038] The fourth step is boron ion implantation, with an ion energy of 120-180 KeV and a dose of 1×10 13 -1×10 15 cm -2 , the beam current is 50-200μA, after injection, the photoresist is removed by immersion in acetone, and the surface ZnS barrier layer is removed by immersion in pure hydrochloric acid, and a series of n + district;

[0039] The fifth step is rapid push-junction annealing at a temperature of 150-250°C for 120-250s. The component distribution is calibrated by SIMS to obtain n with a width of 1-4μm. - Multiplication zone, such as Figure 2 As shown;

[0040] Step 6: Passivation and corrosion + / n + Electrode holes: CdTe / ZnS double-layer passivation process is used; positive photoresist is used to open the etching electrode holes in each injection hole and p-type area, and the holes are etched in freezing point pure hydrochloric acid and hydrobromic acid;

[0041] Step 7: Preparation of metal electrodes: Use electron beam evaporation equipment to prepare Cr / Au with thickness of 50nm / 100nm respectively, that is, use electron beam evaporation equipment to prepare a Cr metal layer with a thickness of 50nm, and then use electron beam evaporation equipment to prepare an Au metal layer with a thickness of 100nm on the Cr metal layer, and then soak it in acetone, and then perform metal stripping and remove the photoresist;

[0042] Step 8: Preparation of In column by reverse soldering: Use positive photoresist to open In column preparation area in each injection area electrode hole and common electrode, first use electron beam evaporation to prepare UBM metal Cr / Au with thickness of 100nm / 100nm, then thermally evaporate In column on UBM metal Cr / Au, soak it in acetone after production, and then perform metal stripping and remove photoresist;

[0043] Step 9, device reverse soldering: interconnect the structure made in step 8 with the external gemstone substrate through the In column reverse soldering;

[0044] Step 10. Current-voltage and multiplication gain test: Use a variable temperature Dewar test system to test the light / dark current-voltage characteristics of devices of different areas.

[0045] from Figure 4The electric field distribution diagram shows that the absorption zone of the medium-wave avalanche detector formed by the present invention is completely depleted, and the collision ionization of carriers generated by the high electric field in the multiplication zone. Figure 5 , Figure 6 It can be seen that for the device with a cut-off wavelength of 4.2 μm, the dark current density at a small bias voltage (gain) of 160 K is less than 8×10 -6 A / cm 2 , which is significantly lower than the theoretical minimum limit of electron diffusion current. Even at a gain of -13V 189 when GNDCD is 160K, the overall current is still less than 2×10 -6 A / cm 2 , low dark current and high gain level ensure that the avalanche detector can still work well even at 160K.

[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. That is, any equivalent changes and modifications made according to the content of the patent application scope of the present invention should be within the technical scope of the present invention.

Claims

1. A method for preparing a medium-wave avalanche detector structure with full depletion in the absorption region and high temperature operation, characterized in that: The steps include: The first step is the back / surface interdiffusion of HgCdTe materials: the HgCdTe materials grown on CdZnTe substrates are subjected to interdiffusion annealing to obtain a surface passivation layer with a composition gradient and a back composition gradient region, and SIMS calibration is performed on the companion wafers. The second step is to perform p + Type annealing doping: P-type Hg vacancy doping of the material after interdiffusion; The third step is to photolithographically form ion injection holes: on the HgCdTe heterogeneous material on which the ZnS barrier layer and alignment marks have been prepared, ion injection holes are obtained by photolithography using positive photoresist; The fourth step is boron ion implantation. After implantation, the photoresist is removed by immersion in acetone and the surface ZnS barrier layer is removed by immersion in pure hydrochloric acid to obtain n + district; The fifth step is rapid push-through annealing, and the component distribution is obtained according to SIMS calibration. - doubling zone; Step 6: Passivation and corrosion + / n + Electrode hole: CdTe / ZnS double-layer passivation process is adopted; Positive photoresist was used to open etching electrode holes in each injection hole and p-type region, and then etched in pure hydrochloric acid and hydrobromic acid at freezing point; Step 7: Preparation of metal electrodes: Use electron beam evaporation equipment to prepare Cr / Au with a thickness of 50nm / 100nm respectively, then soak in acetone, and then perform metal stripping and remove photoresist; Step 8: Preparation of In column by reverse soldering: Use positive photoresist to open In column preparation area in each injection area electrode hole and common electrode, first use electron beam evaporation to prepare UBM metal Cr / Au with thickness of 100nm / 100nm, then thermally evaporate In column on UBM metal Cr / Au, soak it in acetone after production, and then perform metal stripping and remove photoresist; Step 9, device reverse soldering: interconnect the structure made in step 8 with the external gemstone substrate through the In column reverse soldering; Step 10. Current-voltage and multiplication gain test: Use a variable temperature Dewar test system to test the light / dark current-voltage characteristics of devices of different areas.

2. The method for preparing the high-temperature operation medium-wave avalanche detector structure with full depletion in the absorption region according to claim 1 is characterized in that: The interdiffusion annealing treatment is performed at a temperature of 300-500° C. and for a time of 1 h-48 h.

3. The method for preparing the high-temperature operation medium-wave avalanche detector structure with full depletion in the absorption region according to claim 1 is characterized by: The p+ type annealing treatment is performed at a temperature of 250-400° C. and for a time of 24 h to 72 h.

4. The method for preparing the absorption region fully depleted high temperature operation medium wave avalanche detector structure according to claim 1, characterized in that: The size of the ion injection hole ranges from 5 μm to 50 μm.

5. The method for preparing the absorption region fully depleted high temperature operation medium wave avalanche detector structure according to claim 1, characterized in that: The boron ion energy is 120-180 KeV and the dose is 1×10 13 -1×10 15 cm -2 , the beam current is 50-200μA.

6. The method for preparing the absorption region fully depleted high temperature operation medium wave avalanche detector structure according to claim 1, characterized in that: The push-junction annealing temperature is 150-250° C., and the time is 120-250 seconds.

7. The method for preparing the absorption region fully depleted high temperature operation medium wave avalanche detector structure according to claim 1, characterized in that: After the push-in annealing, n - The width of the multiplication zone is 1-4 μm.

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