Si-based composite microstructure photoelectric detector and forming method thereof

Abstract

The invention discloses a Si-based composite microstructure photoelectric detector and a forming method thereof, and relates to the technical field of photoelectric detection. The Si-based composite microstructure photoelectric detector comprises a signal acquisition first terminal, a light enhancement absorption microstructure and a light transmissible signal acquisition second terminal. The enhanced light absorption microstructure is composed of a short-wave-band visible light enhanced absorption circular light sensitive area, a middle-wave-band visible light enhanced absorption inner ring light sensitive area and a long-wave-band visible light enhanced absorption outer ring light sensitive area. According to the invention, the composite light sensitive unit with an eagle-eye bionic structure is designed, and low reflection and high absorption of light of different wavebands are realized by regulating and controlling the geometric shapes and arrangement modes of the rod-shaped, prismatic table-shaped and conical subunits in the microstructure, so that the light response characteristic of the photoelectric detector is improved.

Description

Technical Field

[0001] The 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 forming method thereof. 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, and the electrical signals are 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] Photoelectric detectors are widely used in various fields of military and national economy. In the visible light or near-infrared band, they are mainly used for ray measurement and detection, industrial automatic control, photometry, etc. In the infrared band, they are mainly used for missile guidance, infrared thermal imaging, infrared remote sensing, etc. With the continuous expansion of the application fields of photoelectric detectors, the demand for high-performance and high-sensitivity photoelectric detectors is increasing, especially the demand for high-sensitivity and high-gain photoelectric detectors is growing rapidly.

[0004] As the cornerstone of integrated device manufacturing, silicon material is widely used in the field of integrated circuit manufacturing due to its abundant reserves, excellent semiconductor properties, mature preparation technology and other advantages. At the same time, it exhibits excellent optical properties and high compatibility with CMOS processes, which undoubtedly makes it the preferred material for preparing integrated high-sensitivity photoelectric detection and optical imaging devices. However, in the prior art of silicon-based photodetectors, photodetectors using planar silicon as light-sensitive materials have low light absorption rates after light irradiation, and produce relatively few effective holes-electrons, resulting in low photoelectric response and poor photoelectric performance of silicon-based photodetectors in the prior art, which limits the application of silicon-based photodetectors in the prior art in high-sensitivity and high-accuracy detection environments. Summary of the invention

[0005] In order to develop high-performance silicon-based photodetectors, the present invention designs a silicon-based photodetector structure and processes the surface of silicon material into a composite microstructure with micro-nano absorption enhancement. On the one hand, it effectively improves the equivalent optical path to suppress the reflection of incident light and improves the utilization rate of light; on the other hand, by manipulating the incident light beam on an extreme sub-wavelength scale, it realizes the coupling resonance of light in the microstructure, breaks through the light absorption limit of traditional materials, improves the quantum efficiency of the photodetector, and improves the photoelectric conversion efficiency. This solves the problem of poor photoelectric performance and low photoelectric response of silicon-based photodetectors in the prior art.

[0006] The present invention provides a Si-based composite microstructure photoelectric detector and a method for forming the same. In order to achieve the above-mentioned purpose, the technical solution of the present invention is as follows: The Si-based composite microstructure photodetector includes a first signal acquisition terminal, a light response area of ​​different wavelengths, and a second signal acquisition terminal. The composite microstructure unit for photodetection is composed of a short-wave visible light enhanced absorption circular light sensitive area, a mid-wave visible light enhanced absorption inner ring light sensitive area, and a long-wave visible light enhanced absorption outer ring light sensitive area. The geometric shape and arrangement of the microstructure subunits distributed in different light sensitive areas are determined according to the wavelength of the detection light in the area.

[0007] As a preferred embodiment, the microstructure of the short-wave visible light enhanced absorption circular light sensitive area is composed of a cone subunit array, and the subunit array is a parallelogram or rhombus formed by 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. 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 range of 100-150 μm; 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, and the subunit array is a parallelogram or rhombus formed by 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 distance between adjacent subunits is 0.4-0.5 μm; 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; 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, and the subunit array is a parallelogram or rhombus formed by 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 distance between adjacent subunits is 0.5-0.7 μm; As a preferred embodiment, the rod-shaped subunit in the composite microstructure unit is arranged outside the prism-shaped light-sensitive region, and the annular width is 150-200 μm; The present invention also provides a method for forming the above-mentioned Si-based composite microstructure photoelectric detector, comprising the following steps: 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; Step 2: Apply photoresist on the polished surface of the substrate, and after baking, use a stepper photolithography machine to expose the mask, transfer the pattern designed on the mask to the photoresist on the surface of the silicon wafer according to a certain proportion, and dissolve the photoresist at the ultraviolet exposure position through a development process after exposure; 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; 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 ; Step 5: coating the polished surface of the substrate with photoresist for the soft mask layer of the second dry etching, and then using a projection photolithography machine to complete the second mask UV exposure, and developing after exposure to remove the photoresist soft mask layer of the short-wave visible light enhanced absorption circular photosensitive area and the medium-wave visible light enhanced absorption inner ring photosensitive area; 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 etching is 15° / s. Step 7: Complete the second B on the substrate through the mask + Ion implantation doping, the doping area is a short-wave visible light enhanced absorption circular photosensitive area and a medium-wave visible light enhanced absorption inner ring photosensitive area, and the doping concentration range is 1×10 5 ion / cm 3 ~5×10 5 ion / cm 3 ; Step 8: After the second doping is completed, a soft mask layer is formed on the substrate surface by the same spin coating process as step 5; then the third mask UV exposure is completed by a projection lithography machine, and after the exposure, the photoresist soft mask at the position of the short-wave visible light enhanced absorption circular light sensitive area is removed by development; Step 9: Perform the third 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 110°. In the second etching cycle, the angle between the substrate and the plasma incident direction is 70°. The sample rotation speed during etching is 25° / s. Step 10: First, an annular first signal collection terminal is formed around the outer ring light sensitive area of ​​the composite microstructure unit with long-wave visible light enhanced absorption by inkjet printing process. Then, a transparent conductive layer is coated on the top layer of the composite microstructure unit by spin coating process to obtain a second signal collection terminal.

[0008] The basic working principle of the present invention is: through the study of biological vision mechanism and retinal structure, it is found that in the photosensitive area of ​​the retinal fovea, human eyes only contain cones, while the owl's retina has both rods and cones. Because of this unique structure, owls are highly sensitive to moving targets in low-light environments. Inspired by this, the photoresponse area of ​​the photodetector adopts a bionic eagle eye retinal structure design, and the rod-shaped, prism-shaped, and cone-shaped composite microstructure processing is achieved through the etching process combining ICP-RIE and variable-angle IBE. When the detector is working, after light enters the device, the light reflection is reduced through the microstructure. When the light propagates inside the detector, the nano-microstructures set in different areas produce coupled resonance to enhance the absorption of light in different bands, thereby generating more photogenerated carriers to form photogenerated current or voltage.

[0009] The beneficial effects of the present invention are as follows: compared with existing silicon-based photodetectors, the light response area of ​​the detector adopts a composite microstructure design of a rod array, a prism array, and a cone array, which significantly increases the absorption of light in different bands. By regulating the arrangement and geometric shape of the microstructure subunits, the reflection of the incident light is effectively suppressed and the utilization rate of light is improved. At the same time, the micro-nano absorption enhancement structure can effectively improve the equivalent optical path, regulate the incident light beam on an extreme subwavelength scale, induce coupled resonance, break through the light absorption limit of traditional materials, and improve the quantum efficiency of the photodetector. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 A side view of a photodetector structure according to an embodiment of the present invention; Figure 2 is a cross-sectional schematic diagram of a photoelectric detector according to an embodiment of the present invention; Figure 3 A schematic diagram of the first photolithography step of forming a photodetector according to an embodiment of the present invention; Figure 4 This is a schematic diagram of ICP-RIE etching of a method for forming a photodetector according to an embodiment of the present invention; Figure 5 A schematic diagram of the second photolithography step of forming a photodetector according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the first IBE etching of the method for forming a photodetector according to an embodiment of the present invention; Figure 7 A schematic diagram of the third photolithography step of forming a photodetector according to an embodiment of the present invention; Figure 8 This is a schematic diagram of the second IBE etching of the method for forming a photodetector according to an embodiment of the present invention; Fig. 9 A schematic diagram of preparing a signal collection terminal of a photodetector forming method according to an embodiment of the present invention; Fig.10 This is a SEM image of the composite microstructure of the photodetector according to an embodiment of the present invention; Fig.11 A diagram showing the light reflection performance of a photoelectric detector according to an embodiment of the present invention; Fig.12 A diagram showing the light absorption performance of a photodetector according to an embodiment of the present invention; In the figure: 101-central light-sensitive area, 102-inner ring light-sensitive area, 103-outer ring light-sensitive area; 201- single crystal silicon substrate; 301- first signal acquisition terminal, 302- second signal acquisition terminal; 401-composite microstructure unit; 501-AZ1500 photoresist soft mask layer, 502-second dry etching soft mask layer, 503-soft mask layer 601-prism-shaped microstructure, 701-rod-shaped microstructure, 801-cone-shaped microstructure. DETAILED DESCRIPTION

[0011] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0012] 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-sectional view along the radial R-R' direction. The structure of the detector 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 first annular signal collection terminal 301, an enhanced absorption microstructure unit 401, and a light-transmitting signal collection second terminal 302 prepared on the top layer of the enhanced absorption microstructure unit 401. Among them, the different wavelength light enhanced absorption microstructure unit 401 consists of a short-wave visible light enhanced absorption central light sensitive region 101, a mid-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.

[0013] 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.

[0014] In this embodiment, the inner ring photosensitive area 102 of the enhanced absorption microstructure unit 401 is composed of a prism-shaped subunit array, in which the bottom diameter of a single subunit in the prism-shaped microstructure array is 0.4-0.5 μm and the height is 0.4-0.5 μm; the distribution mode of the prism-shaped microstructure array is: diamond array distribution, and the spacing between adjacent subunits is 0.5 μm. The inner ring photosensitive area 102 of the enhanced absorption microstructure unit 401 is arranged adjacent to the central photosensitive area 101, and is distributed in an annular shape, and the width of the annular distribution is 100-150 μm.

[0015] In this embodiment, the outer ring light sensitive area 103 of the enhanced absorption microstructure unit 401 is composed of a rod-shaped subunit array, in which the bottom diameter of a single subunit in the rod-shaped microstructure array is 0.5-0.7 μm and the height is 0.5-0.7 μm; the distribution mode of the rod-shaped microstructure array is a diamond array distribution, and the spacing between adjacent subunits is 0.7 μm. The outer ring light sensitive area 103 of the enhanced absorption microstructure unit 401 is arranged adjacent to the inner ring light sensitive area 102, in an annular distribution, and the width of the annular distribution is 100-150 μm.

[0016] 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.

[0017] 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.

[0018] 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 with IPA, acetone, anhydrous ethanol, and deionized water in sequence, then baked in a vacuum environment at 120°C, and finally surface treated with oxygen plasma.

[0019] Step 2: See attached Figure 3 A layer of AZ1500 photoresist soft mask layer 501 with a thickness of 400-500 nm is coated on the polished surface of the substrate by a spin coating process, and then pre-baked on a 95°C heating plate for 90 seconds. 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 ultraviolet exposure position is dissolved by a development process, and finally post-baked on a 120°C heating plate for 2 minutes.

[0020] Step 3: Refer to the attached Figure 4The substrate after step 2 is placed in an ICP-RIE etching system and the single crystal silicon at the position not protected by the photoresist is deeply etched with etching gas. The etching depth is 0.5-0.7 μm. The etching process gas is SF6, C4F8, O2 and Ar. After the etching is completed, the photoresist soft mask is removed with NMP degumming liquid to form rod-shaped microstructures 701, 702, and 703 of different sizes perpendicular to the substrate on the substrate.

[0021] 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 .

[0022] 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 spin coating process for the soft mask layer 502 of the second dry etching, and baked on a heating 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.

[0023] Step 6: Refer to the attached Figure 6 The 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 area 101 and the inner ring photosensitive area 102 of the enhanced absorption microstructure unit 401.

[0024] 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 .

[0025] Step 8: Refer to the attached Figure 7 After the second doping is completed, the photoresist soft mask on the surface of the substrate is removed, and a soft mask layer 503 is prepared on the surface of the substrate using the same spin coating process as step 5; then the third mask UV exposure is completed by 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 light sensitive area 101.

[0026] Step 9: Refer to the attached Figure 8 After step 8, the substrate is placed in the AVP-IBE etching system for a second plasma etching. The specific etching process is as follows: in the first etching cycle, the angle between the substrate and the plasma incident direction is 110°, the sample rotation speed is 15° / s, and the etching time is 90s; in the second etching cycle, the angle between the substrate and the plasma incident direction is 70°, the sample rotation speed is 15° / s, and the etching time is 110s; the intracavity etching parameters are consistent with step 6. After etching, the photoresist soft mask layer is removed using NMP degumming solution, and a cone-shaped microstructure 801 is obtained at the central photosensitive area 101 of the enhanced absorption microstructure unit 401.

[0027] Step 10: Refer to the attached Fig. 9 , an annular first signal acquisition terminal 301 is formed around the central light sensitive area 101 of the enhanced absorption microstructure unit 401 by inkjet printing process, and the first signal acquisition terminal is formed by conductive silver paste with a thickness of 2.5μm. Then, a Ag-NWs solution with a concentration of 6mg / mL is applied to the top layer of the enhanced absorption microstructure unit 401 by spin coating process to form a transparent second signal acquisition terminal 302, and the diameter of the Ag nanowire in the Ag-NWs solution is not greater than 30nm.

[0028] Fig.10 4 is an electron micrograph of the cone-shaped microstructure 801, the prism-shaped microstructure 601, and the rod-shaped microstructure 701 constituting the Si-based enhanced absorption microstructure unit 401 obtained in this embodiment.

[0029] Fig.11 , 12 The light reflection and light absorption test results of this embodiment and the traditional planar structure photoelectric detector are shown in Figure 2. Fig.11 According to the light reflection test results, the reflectivity of the composite microstructure designed in the present invention in the wavelength range of 380 to 1100 nm is much lower than that of the planar structure. Fig.12The light absorption results show that within the wavelength range of 380 to 1100 nm, the average light absorption of the traditional planar structure photodetector is about 48%, while the average light absorption of the composite microstructure photodetector proposed in the present invention reaches 90%. Combining 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 the photodetector device. 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 to improve the propagation path of light and promote 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 visible light enhanced absorption microstructure unit of different wavelengths (401), and a light-transmissive signal acquisition second 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 mid-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), the three light sensitive regions being successively nested from the inside to the outside; the signal collection first terminal (301) is located outside the enhanced absorption microstructure unit (401), and the signal collection second 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 area (101) to the outer ring photosensitive area (103).

2. The Si-based composite microstructure photodetector according to claim 1, characterized in that: The microstructure of the short-wave visible light enhanced absorption central light sensitive region (101) is composed of a cone-shaped subunit array.

3. The Si-based composite microstructure photodetector according to claim 2, 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.

4. The Si-based composite microstructure photodetector according to claim 1, characterized in that: The microstructure of the mid-wavelength visible light enhanced absorption inner ring photosensitive region (102) is composed of a prism-shaped subunit array.

5. The Si-based composite microstructure photodetector according to claim 4, characterized in that: The bottom diameter of the prism-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 prism-shaped microstructure array.

6. The Si-based composite microstructure photodetector according to claim 1, characterized in that: The microstructure of the outer ring photosensitive region (103) with enhanced absorption of long-wavelength visible light is composed of an array of rod-shaped subunits.

7. The Si-based composite microstructure photodetector according to claim 6, 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.

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

9. A method for forming a Si-based composite microstructure photodetector according to any one of claims 1 to 8, characterized in that: First, the ICP-RIE process is used to obtain nanorod-shaped microstructures with different characteristic sizes. Then, the IBE variable-angle etching is used to step-by-step realize the preparation of prism-shaped and cone-shaped nano-microstructures, and gradually realize the preparation of the central photosensitive area (101), the inner ring photosensitive area (102) and the outer ring photosensitive area (103).

10. The method for forming a Si-based composite microstructure photodetector according to claim 9, characterized in that: 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: Spin-coating a photoresist soft mask layer on the polished surface of the substrate and performing the first baking, then using an ultraviolet exposure process 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, with an etching 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 substrate without mask for the first time B + Diffusion doping, doping concentration range is 2×10 12 ion / cm 3 ~5×10 15 ion / 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 ultraviolet 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, and the doping concentration range is 1×10 5 ion / cm 3 ~5×10 5 ion / cm 3 ; Step 8: After the second doping, a soft mask layer is prepared on the substrate surface by the same spin coating process as step 5; then, ultraviolet 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 light sensitive 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 corresponding angles between the substrate and the plasma incident direction are set in the first etching cycle and the second etching cycle, and the angle is smaller than the angle set in step 6. The sample is kept rotating during etching. Step 10: First, an annular first signal collection terminal is formed around the long-wave visible light enhanced absorption outer ring photosensitive area (103) of the composite microstructure unit by using an inkjet printing process; then a transparent conductive layer is coated on the top layer of the composite microstructure unit by using a spin coating process to obtain a signal collection second terminal (302).

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