A Si-based composite microstructure photodetector and its forming method

Abstract

The present invention discloses a Si-based composite microstructure photoelectric detector and a method for forming the same, and relates to the field of photoelectric detection technology. The Si-based composite microstructure photoelectric detector includes a first terminal for signal acquisition, a light-enhanced absorption microstructure, and a second terminal for light-transmitting signal acquisition. The enhanced light absorption microstructure is composed of a short-wave visible light enhanced absorption circular photosensitive area, a medium-wave visible light enhanced absorption inner ring photosensitive area, and a long-wave visible light enhanced absorption outer ring photosensitive area. The present invention designs a composite photosensitive unit with an eagle-eye bionic structure, and achieves low reflection and high absorption of light in different bands by regulating the geometric shape and arrangement of the subunits in the microstructure with rod-shaped, prism-shaped, and cone-shaped shapes, thereby improving the light response characteristics of the photoelectric detector.

Description

Technical Field

[0001] The present invention belongs to the technical field of photoelectric detection, and in particular relates to a wide-spectrum photoelectric detector composed of a Si-based composite microstructure capable of enhancing light absorption and a method for forming the same. Background Art

[0002] A photodetector is an electronic device that converts light signals into electrical signals. Its working principle is that the photosensitive layer of the photodetector generates electron-hole pairs after absorbing photons. The electrical signal is obtained by collecting the photogenerated charges under the action of the electric field at the signal acquisition end. It is a detection instrument based on the photoelectric effect.

[0003] Photodetectors are widely used in various fields of military and national economy. In the visible and near-infrared bands, they are mainly used for radiation measurement and detection, industrial automation control, and photometry. In the infrared band, they are mainly used for missile guidance, infrared thermal imaging, and infrared remote sensing. As the application fields of photodetectors continue to expand, the demand for high-performance and high-sensitivity photodetectors is increasing, especially for high-sensitivity and high-gain photodetectors.

[0004] As the cornerstone of integrated device manufacturing, silicon materials are widely used in the field of integrated circuit manufacturing due to their abundant reserves, excellent semiconductor properties, and mature preparation technology. At the same time, they exhibit excellent optical properties and high compatibility with CMOS processes, making them undoubtedly the preferred material for the preparation of integrated high-sensitivity photodetection and optical imaging devices. However, in the existing technology of silicon-based photodetectors, photodetectors using planar silicon as the light-sensitive material have low light absorption rates after light irradiation, resulting in relatively few effective hole-electron pairs. As a result, the photoelectric response of silicon-based photodetectors in the existing technology is low, and the photoelectric performance is poor, which limits the application of silicon-based photodetectors in the existing technology in high-sensitivity and high-accuracy detection environments. Summary of the Invention

[0005] To develop high-performance silicon-based photodetectors, this paper designs a silicon-based photodetector structure and processes the silicon material surface into a composite microstructure with micro-nano absorption enhancement. This effectively improves the equivalent optical path, suppresses the reflection of incident light, and increases light utilization. Furthermore, by manipulating the incident light beam at an extreme subwavelength scale, light generates coupled resonance within the microstructure, surpassing the light absorption limit of traditional materials, increasing the quantum efficiency of the photodetector and improving the photoelectric conversion efficiency. This addresses the poor photoelectric performance and low photoelectric response of existing silicon-based photodetectors.

[0006] The present invention provides a Si-based composite microstructure photodetector and a method for forming the same. To achieve the above-mentioned objectives, the technical solutions of the present invention are as follows:

[0007] A Si-based composite microstructure photodetector includes a first signal acquisition terminal, regions responsive to light of different wavelengths, and a second signal acquisition terminal. The composite photodetection microstructure unit comprises a circular photosensitive region with enhanced absorption of short-wavelength visible light, an inner ring photosensitive region with enhanced absorption of mid-wavelength visible light, and an outer ring photosensitive region with enhanced absorption of long-wavelength visible light. The geometric shape and arrangement of the microstructure subunits distributed in the different photosensitive regions are determined by the wavelength of the light detected in each region.

[0008] As a preferred embodiment, the microstructure of the short-wave visible light enhanced absorption circular light sensitive area is composed of a cone-shaped subunit array, wherein the subunit array is arranged in a parallelogram or rhombus shape with four adjacent subunits; the bottom diameter of a single subunit constituting the array is 0.3-0.4 μm, the height is 0.3-0.4 μm, and the distance between adjacent subunits is 0.3-0.4 μm.

[0009] As a preferred embodiment, the cone-shaped microstructure subunit array is arranged at the center of the composite microstructure unit, and the distribution area is circular with a radius of 100-150 μm;

[0010] As a preferred embodiment, the microstructure of the inner ring photosensitive area of ​​the composite microstructure with mid-band visible light enhanced absorption is composed of a prism-shaped subunit array, wherein the subunit array is arranged in a parallelogram or rhombus shape with four adjacent subunits; the bottom diameter of a single subunit constituting the array is 0.4-0.5 μm, the height is 0.4-0.5 μm, and the spacing between adjacent subunits is 0.4-0.5 μm;

[0011] As a preferred embodiment, the prism-shaped subunit array in the composite microstructure unit is arranged adjacent to the circular area and is distributed in an annular shape, and the width of the annular distribution is 100-150 μm;

[0012] As a preferred embodiment, the microstructure of the outer ring photosensitive area of ​​the composite microstructure with long-wavelength visible light enhanced absorption is composed of a rod-shaped subunit array, wherein the subunit array is arranged in a parallelogram or rhombus shape with four adjacent subunits; the bottom diameter of a single subunit constituting the array is 0.5-0.7 μm, the height is 0.5-0.7 μm, and the spacing between adjacent subunits is 0.5-0.7 μm;

[0013] As a preferred embodiment, the rod-shaped subunits in the composite microstructure unit are arranged outside the pyramid-shaped light-sensitive region, and the ring width is 150-200 μm;

[0014] The present invention also provides a method for forming the above-mentioned Si-based composite microstructure photoelectric detector, comprising the following steps:

[0015] Step 1: Select a thickness of 400μm, <100> The monocrystalline silicon wafer with a crystalline orientation is used as the substrate and is cleaned with IPA, acetone, anhydrous ethanol, deionized water and treated with oxygen plasma;

[0016] Step 2: Apply photoresist to the polished surface of the substrate, bake it, and then use a stepper to expose the mask. The pattern designed on the mask is transferred to the photoresist on the surface of the silicon wafer according to a certain ratio. After exposure, the photoresist at the UV-exposed position is dissolved through a development process.

[0017] Step 3: Complete the first dry etching of the substrate in the ICP-RIE etching system with an etching depth of 0.5~0.7μm. After the etching is completed, use NMP stripping solution to remove the photoresist soft mask;

[0018] Step 4: Use thermal diffusion process to make the first B without mask on the substrate + Diffusion doping, doping concentration range is 2×10 12 ion / cm 3 ~5×10 15 ion / cm 3 ;

[0019] Step 5: Coating a photoresist on the polished surface of the substrate to form a soft mask layer for the second dry etching, then performing a second UV exposure of the mask using a projection photolithography machine, and developing after exposure to remove the photoresist soft mask layer of the short-wavelength visible light enhanced absorption circular photosensitive region and the mid-wavelength visible light enhanced absorption inner ring photosensitive region;

[0020] Step 6: Perform a second dry etching in the AVP-IBE etching system. The etching process is carried out in two cycles. In the first etching cycle, the angle between the substrate and the plasma incident direction is 135°. In the second etching cycle, the angle between the substrate and the plasma incident direction is 45°. The sample rotation speed during the etching period is 15° / s.

[0021] Step 7: Complete the second B through the mask on the substrate + Ion implantation doping, the doping area is the short-wave visible light enhanced absorption circular photosensitive area and the medium-wave visible light enhanced absorption inner ring photosensitive area, the doping concentration range is 1×10 5 ion / cm 3 ~5×10 5 ion / cm 3 ;

[0022] Step 8: After the second doping is completed, a soft mask layer is formed on the substrate surface using the same spin coating process as in step 5; then, a third mask UV exposure is performed using a projection lithography machine, and after exposure, the photoresist soft mask at the position of the short-wavelength visible light enhanced absorption circular photosensitive area is removed by development;

[0023] Step 9: Perform a third dry etch in the AVP-IBE etching system. The etching process is carried out in two cycles. In the first etching cycle, the angle between the substrate and the plasma incident direction is 110°. In the second etching cycle, the angle between the substrate and the plasma incident direction is 70°. The sample rotation speed during the etching is 25° / s.

[0024] Step 10: First, an annular first signal acquisition terminal is formed around the outer ring photosensitive region of the composite microstructure unit with enhanced absorption of long-wavelength visible light using an inkjet printing process. Then, a transparent conductive layer is applied to the top layer of the composite microstructure unit using a spin coating process to form a second signal acquisition terminal.

[0025] The basic operating principle of this invention is that research into biological vision mechanisms and retinal structure has revealed that the human eye contains only cones in the photosensitive area of ​​the fovea, while the owl's retina contains both rods and cones. This unique structure contributes to the owl's high sensitivity to moving targets in low-light conditions. Inspired by this, the photodetector's light-response area is designed to mimic the structure of an eagle's eye retina. A composite microstructure of rods, prisms, and cones is fabricated using an etching process combining ICP-RIE and variable-angle IBE. When the detector is operating, light entering the device passes through the microstructure, minimizing reflections. As light propagates within the detector, nanostructures in different regions generate coupled resonances, enhancing absorption of light at different wavelengths, thereby generating more photogenerated carriers and generating a photogenerated current or voltage.

[0026] The beneficial effects of this invention are as follows: Compared to existing silicon-based photodetectors, the detector's light response region utilizes a composite microstructure design consisting of a rod array, a prism array, and a cone array, significantly increasing the absorption of light across different wavelengths. By manipulating the arrangement and geometry of the microstructure's subunits, the reflection of incident light is effectively suppressed, improving light utilization. Furthermore, the micro-nano absorption-enhancing structure effectively improves the equivalent optical path, modulating the incident light beam at an extreme subwavelength scale, inducing coupled resonance, and surpassing the light absorption limit of traditional materials, thereby improving the quantum efficiency of the photodetector. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A side view of a photodetector structure according to an embodiment of the present invention;

[0028] Figure 2 is a schematic cross-sectional view of a photodetector according to an embodiment of the present invention;

[0029] Figure 3 A schematic diagram of the first photolithography step of the method for forming a photodetector according to an embodiment of the present invention;

[0030] Figure 4Schematic diagram of ICP-RIE etching of a photodetector forming method according to an embodiment of the present invention;

[0031] Figure 5 A schematic diagram of the second photolithography step of forming a photodetector according to an embodiment of the present invention;

[0032] Figure 6 This is a schematic diagram of the first IBE etching process of the photodetector forming method according to an embodiment of the present invention;

[0033] Figure 7 A schematic diagram of the third photolithography step of the method for forming a photodetector according to an embodiment of the present invention;

[0034] Figure 8 This is a schematic diagram of the second IBE etching process of the photodetector forming method according to an embodiment of the present invention;

[0035] Figure 9 A schematic diagram of signal acquisition terminal preparation in a method for forming a photodetector according to an embodiment of the present invention;

[0036] Figure 10 This is a SEM image of the composite microstructure of the photodetector according to an embodiment of the present invention;

[0037] Figure 11 A diagram showing light reflection performance of a photodetector according to an embodiment of the present invention;

[0038] Figure 12 is a diagram showing the light absorption performance of a photodetector according to an embodiment of the present invention;

[0039] In the picture:

[0040] 101-central light-sensitive area, 102-inner ring light-sensitive area, 103-outer ring light-sensitive area;

[0041] 201- single crystal silicon substrate;

[0042] 301- first signal acquisition terminal, 302- second signal acquisition terminal;

[0043] 401-composite microstructure unit;

[0044] 501-AZ1500 photoresist soft mask layer, 502-second dry etching soft mask layer, 503-soft mask layer

[0045] 601-prism-shaped microstructure, 701-rod-shaped microstructure, 801-cone-shaped microstructure. DETAILED DESCRIPTION

[0046] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0047] Please refer to Figure 1 and Figure 2 , Figure 1 This is a side view of a Si-based composite microstructure photodetector. Figure 2 for Figure 1 Schematic cross-section along the radial R-R' direction. The detector structure consists of a single-crystal silicon substrate 201, an n-type heavily doped conductive layer (not shown) grown on the single-crystal silicon substrate 201, a ring-shaped signal collection first terminal 301, an enhanced absorption microstructure unit 401, and a light-transmitting signal collection second terminal 302 fabricated on the top layer of the enhanced absorption microstructure unit 401. Specifically, the enhanced absorption microstructure unit 401 for different wavelengths consists of a central photosensitive region 101 for enhanced absorption of short-wavelength visible light, an inner ring photosensitive region 102 for enhanced absorption of mid-wavelength visible light, and an outer ring photosensitive region 103 for enhanced absorption of long-wavelength visible light.

[0048] In this embodiment, the central light-sensitive area 101 of the enhanced absorption microstructure unit 401 is composed of a conical subunit array, in which the bottom diameter of a single subunit in the conical microstructure array is 0.3~0.4μm and the height is 0.3~0.4μm; the distribution mode of the conical microstructure array is: diamond array distribution, and the distance between adjacent subunits is 0.4μm; the central light-sensitive area 101 of the enhanced absorption microstructure unit 401 is arranged in a circle with a radius of 50~100μm and is located at the center of the enhanced absorption microstructure unit 401.

[0049] In this embodiment, the inner ring photosensitive region 102 of the enhanced absorption microstructure unit 401 is composed of an array of prism-shaped subunits. Each subunit in the prism-shaped microstructure array has a base diameter of 0.4-0.5 μm and a height of 0.4-0.5 μm. The prism-shaped microstructure array is distributed in a diamond array with a spacing of 0.5 μm between adjacent subunits. The inner ring photosensitive region 102 of the enhanced absorption microstructure unit 401 is located adjacent to the central photosensitive region 101 in an annular distribution with a width of 100-150 μm.

[0050] In this embodiment, the outer ring photosensitive region 103 of the enhanced absorption microstructure unit 401 is composed of an array of rod-shaped subunits. Each subunit in the rod-shaped microstructure array has a base diameter of 0.5-0.7 μm and a height of 0.5-0.7 μm. The rod-shaped microstructure array is distributed in a diamond array, with a spacing of 0.7 μm between adjacent subunits. The outer ring photosensitive region 103 of the enhanced absorption microstructure unit 401 is located adjacent to the inner ring photosensitive region 102, forming an annular distribution with a width of 100-150 μm.

[0051] In this embodiment, a composite photosensitive unit with an eagle-eye bionic structure is designed. By regulating the geometric shape and arrangement of the rod-shaped, prism-shaped, and cone-shaped subunits in the microstructure, low reflectivity and high absorption of light in different bands are achieved, thereby improving the light response characteristics of the photodetector.

[0052] In order to realize the above-mentioned Si-based composite microstructure photodetector, a method for forming the composite microstructure photodetector is proposed, which will be described in detail below with reference to the accompanying drawings.

[0053] Step 1: Select a thickness of 400μm, <100> The monocrystalline silicon wafer with a crystalline orientation is used as the substrate. It is first cleaned in sequence with IPA, acetone, anhydrous ethanol, and deionized water, then baked in a vacuum environment at 120°C, and finally surface treated with oxygen plasma.

[0054] Step 2: See attached Figure 3 A layer of AZ1500 photoresist soft mask layer 501 with a thickness of 400~500nm is coated on the polished surface of the substrate through a spin coating process, and then pre-baked on a hot plate at 95℃ for 90s. Then, a stepper photolithography machine is used to expose the mask, and the pattern designed on the mask is transferred to the photoresist on the surface of the silicon wafer according to a certain proportion. After exposure, the photoresist at the UV exposure position is dissolved through a development process, and finally post-baked on a hot plate at 120℃ for 2min.

[0055] Step 3: Refer to the attached Figure 4 The substrate after step 2 was placed in an ICP-RIE etching system. Etching gases were used to perform deep silicon etching on the single-crystal silicon in areas not protected by the photoresist. The etching depth was 0.5 to 0.7 μm. Etching process gases included SF6, C4F8, O2, and Ar. After etching, the photoresist soft mask was removed using an NMP stripping solution, forming rod-shaped microstructures 701, 702, and 703 of varying sizes perpendicular to the substrate.

[0056] Step 4: Use thermal diffusion process to perform maskless first B + Diffusion doping, doping concentration range is 2×10 12 ion / cm 3 ~5×10 15 ion / cm 3 .

[0057] Step 5: Refer to the attached Figure 5 After the first doping is completed, a layer of AZ5214 photoresist is prepared on the surface of the substrate by the spin coating process for the soft mask layer 502 of the second dry etching, and the soft mask layer is baked on a hot plate at 95°C. The thickness of the soft mask layer is 1.2μm. Then, a projection photolithography machine is used to complete the second mask UV exposure. After exposure, the photoresist soft mask layer at the center photosensitive area 101 and the inner ring photosensitive area 102 is removed by development.

[0058] Step 6: Refer to the attached Figure 6The substrate after step 5 was placed in the AVP-IBE etching system for the first plasma dry etching. The specific etching process was as follows: in the first etching cycle, the angle between the substrate and the plasma incident direction was 135°, the sample rotation speed was 15° / s, and the etching time was 90s; in the second etching cycle, the angle between the substrate and the plasma incident direction was 45°, the sample rotation speed was 15° / s, and the etching time was 110s; during the etching process, the etching gas was Ar, the etching protection gas was N2, and the vacuum in the etching process chamber was 3.2×10 7 After etching, the photoresist soft mask is removed by using NMP stripping solution, and prism-shaped microstructures 601 and 602 are obtained at the positions of the central photosensitive region 101 and the inner ring photosensitive region 102 of the enhanced absorption microstructure unit 401.

[0059] Step 7: Use ion implantation to mask the substrate for the second time B + doping, the doping area is the central photosensitive area 101 and the inner ring photosensitive area 102, and the doping concentration range is 1×10 5 ion / cm 3 ~5×10 5 ion / cm 3 .

[0060] Step 8: Refer to the attached Figure 7 After the second doping is completed, the photoresist soft mask on the substrate surface is removed, and a soft mask layer 503 is prepared on the substrate surface using the same spin coating process as step 5; then the third mask UV exposure is completed using a projection lithography machine, and after exposure, a development process is performed to remove the photoresist soft mask layer at the position of the central photosensitive area 101.

[0061] Step 9: Refer to the attached Figure 8 After step 8, the substrate was placed in an AVP-IBE etching system for a second plasma etching process. The specific etching process was as follows: during the first etching cycle, the angle between the substrate and the plasma incident direction was 110°, the sample rotation speed was 15° / s, and the etching time was 90 seconds. During the second etching cycle, the angle between the substrate and the plasma incident direction was 70°, the sample rotation speed was 15° / s, and the etching time was 110 seconds. The intracavity etching parameters remained the same as those in step 6. After the etching, the photoresist soft mask layer was removed using an NMP stripping solution, resulting in a conical microstructure 801 at the central photosensitive region 101 of the enhanced absorption microstructure unit 401.

[0062] Step 10: Refer to the attached Figure 9An inkjet printing process was used to form a ring-shaped first signal acquisition terminal 301 around the central photosensitive region 101 of the enhanced absorption microstructure unit 401. The first signal acquisition terminal was formed from a conductive silver paste with a thickness of 2.5 μm. A 6 mg / mL Ag-NWs solution was then spin-coated onto the top layer of the enhanced absorption microstructure unit 401 to form a transparent second signal acquisition terminal 302. The Ag nanowires in the Ag-NWs solution had a diameter of no greater than 30 nm.

[0063] Figure 10 4 is an electron micrograph of the cone-shaped microstructure 801 , the pyramid-shaped microstructure 601 , and the rod-shaped microstructure 701 constituting the Si-based enhanced absorption microstructure unit 401 obtained in this embodiment.

[0064] Figure 11 、 12 The light reflection and light absorption test results of this embodiment and the traditional planar structure photoelectric detector are compared. Figure 11 The results of the light reflection test show that the reflectivity of the composite microstructure designed in the present invention to light in the wavelength range of 380 to 1100 nm is much lower than that of the planar structure. Figure 12 The light absorption results show that within the wavelength range of 380 to 1100 nm, the average light absorption of conventional planar structure photodetectors is approximately 48%, while the average light absorption of the composite microstructure photodetector proposed in the present invention reaches 90%. Based on the above test results, it can be found that the light absorption of the Si-based composite microstructure photodetector proposed in the present invention is significantly improved, and light reflection is effectively suppressed. The structure proposed in the present invention improves the performance of photodetection devices. On the one hand, the composite microstructure proposed in the present invention effectively suppresses the reflection of light incident on the surface. On the other hand, the design and distribution of the microstructure with a special geometric shape forms a resonant cavity that improves the propagation path of light and promotes the generation and collection of photogenerated electron-hole pairs.

Claims

1. A Si-based composite microstructure photoelectric detector, comprising a first signal acquisition terminal (301), a microstructure unit (401) for enhancing absorption of visible light of different wavelengths, and a light-transmissive second signal acquisition terminal (302); characterized in that: The enhanced light absorption microstructure unit comprises a short-wave visible light enhanced absorption central light sensitive region (101), a medium-wave visible light enhanced absorption inner ring light sensitive region (102), and a long-wave visible light enhanced absorption outer ring light sensitive region (103), wherein the three light sensitive regions are successively nested from the inside to the outside; the first signal acquisition terminal (301) is located outside the enhanced absorption microstructure unit (401), and the second signal acquisition terminal (302) covers the enhanced absorption composite microstructure unit; The enhanced absorption composite microstructure unit is formed by an etching process combining ICP-RIE and variable angle IBE, and the density of the microstructure subunits decreases and the volume of the microstructure increases from the central photosensitive region (101) to the outer ring photosensitive region (103). The microstructure of the short-wavelength visible light enhanced absorption central light-sensitive region (101) is composed of a cone-shaped subunit array; the microstructure of the medium-wavelength visible light enhanced absorption inner ring light-sensitive region (102) is composed of a prism-shaped subunit array; and the microstructure of the long-wavelength visible light enhanced absorption outer ring light-sensitive region (103) is composed of a rod-shaped subunit array.

2. The Si-based composite microstructure photodetector according to claim 1, characterized in that: The bottom diameter of the cone subunit is 0.3-0.4 μm, and the height is 0.3-0.4 μm; adjacent subunits are arranged at a spacing of 0.3-0.45 μm to form a cone microstructure array.

3. The Si-based composite microstructure photodetector according to claim 1, characterized in that: The bottom diameter of the pyramid-shaped subunit is 0.4-0.5 μm, and the height is 0.4-0.5 μm; adjacent subunits are arranged at a spacing of 0.4-0.55 μm to form a pyramid-shaped microstructure array.

4. The Si-based composite microstructure photodetector according to claim 1, characterized in that: The bottom diameter of the rod-shaped subunit is 0.5-0.7 μm, and the height is 0.5-0.7 μm; adjacent subunits are arranged at a spacing of 0.5-0.75 μm to form a rod-shaped microstructure array.

5. The Si-based composite microstructure photodetector according to claim 1, characterized in that: The central light-sensitive region (101) is a circle with a radius of 50 to 100 μm, and is located at the center of the composite microstructure unit; the inner ring light-sensitive region (102) is adjacent to the central light-sensitive region (101) and is distributed in a ring shape, and the width of the ring shape distribution is 100 to 150 μm; the outer ring light-sensitive region (103) is adjacent to the side of the inner ring light-sensitive region (102) and is distributed in a ring shape, and the width of the ring shape distribution is 150 to 200 μm; the doping concentration of the central light-sensitive region (101) and the inner ring light-sensitive region (102) is higher than that of the outer ring light-sensitive region (103).

6. A method for forming a Si-based composite microstructure photodetector according to any one of claims 1 to 5, characterized in that: First, the ICP-RIE process was used to obtain nanorod-shaped microstructures with different characteristic sizes. Then, IBE variable-angle etching was used to step-by-step realize the preparation of prism-shaped and cone-shaped nanostructures, gradually realizing the preparation of the central photosensitive area (101), the inner ring photosensitive area (102) and the outer ring photosensitive area (103).

7. The method for forming a Si-based composite microstructure photodetector according to claim 6, wherein: The following steps are involved: Step 1: Select a single crystal silicon sheet as the substrate, clean and dry it, and then perform surface treatment; Step 2: Apply a photoresist soft mask layer on the polished surface of the substrate by spin coating and perform the first baking. Then, use UV exposure to orthographically project the pattern on the mask onto the photoresist according to the corresponding proportion, followed by development and a second baking. Step 3: Deep silicon etching is performed on the substrate in an ICP-RIE etching system to a depth of 0.5-0.7 μm. After etching, the photoresist soft mask is removed using an NMP stripping solution to obtain rod-shaped microstructures perpendicular to the substrate with different feature sizes. Step 4: Use thermal diffusion process to make the first B without mask on the substrate + Diffusion doping, B + The doping concentration of ions ranges from 2×10 12 / cm 3 ~5×10 15 / cm 3 ; Step 5: After the first doping is completed, a photoresist soft mask layer is coated on the substrate surface by a spin coating process, and then a UV mask exposure is performed by projection lithography to remove the photoresist soft mask at the position of the short-wave visible light enhanced absorption circular photosensitive area and the medium-wave visible light enhanced absorption inner ring photosensitive area (102); Step 6: After completing step 5, two cycles of IBE first dry etching are sequentially performed to form a prism-shaped microstructure at the position of the circular photosensitive area and the inner ring photosensitive area (102); different angles are set between the substrate and the plasma incident direction in the first etching cycle and the second etching cycle, and the sample is kept in a rotating state during the etching; Step 7: Use ion implantation to mask the substrate for the second time B + Doping, the doping area is the circular area and the inner ring area, B + The doping concentration of ions ranges from 1×10 5 / cm 3 ~5×10 5 / cm 3 ; Step 8: After the second doping, a soft mask layer is prepared on the substrate surface using the same spin coating process as in step 5; then, ultraviolet mask exposure is performed by projection lithography to remove the photoresist soft mask at the location of the short-wavelength visible light enhanced absorption circular photosensitive area; Step 9: After step 8, two cycles of IBE dry etching are performed for the second time to form a conical microstructure at the circular photosensitive area. The angle between the substrate and the plasma incident direction is set to be smaller than the angle set in step 6 during the first and second etching cycles. The sample is kept in a rotating state during the etching. Step 10: First, an annular first signal acquisition terminal is formed around the long-wavelength visible light enhanced absorption outer ring photosensitive area (103) of the composite microstructure unit by an inkjet printing process; then, a transparent conductive layer is coated on the top layer of the composite microstructure unit by a spin coating process to obtain a signal acquisition second terminal (302).

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