Single photon avalanche diode, manufacturing method and electronic device

Abstract

A single photon avalanche diode, a manufacturing method and an electronic device belong to the technical field of semiconductors, and are characterized by comprising a substrate, a doped layer, a first doped region, a second doped region, a first electrode, a second electrode and a third electrode; the first doped region extends from the upper surface of the doped layer to the inside of the doped layer; the second doped region is spaced around the first doped region and extends from the upper surface of the doped layer to the inside of the doped layer; the first electrode is arranged on the upper surface of the first doped region; the second electrode is arranged on the upper surface of the second doped region; the third electrode is arranged on the upper surface of the doped layer and surrounds the second electrode; the first electrode and the second electrode have the same polarity, and the first electrode and the third electrode have opposite polarities; the first doped region and the second doped region are of a first type, and the substrate and the doped layer are of a second type; a multi-electrode mode is adopted to realize a high dynamic range; an electrical isolation mode is adopted to realize the separation of the avalanche region, effectively reduce the dark count rate and the after-pulse probability, and ensure a high signal-to-noise ratio.

Description

Technical Field

[0001] This application belongs to the field of semiconductor technology, and in particular relates to a single-photon avalanche diode, its manufacturing method, and an electronic device. Background Technology

[0002] A single-photon avalanche diode (SPAD) is an avalanche diode operating in Geiger mode, possessing single-photon response capability, i.e., weak light detection capability. Unlike integrator-type photodetectors (i.e., those that output an electrical signal only after the photogenerated charge has accumulated to a certain value) such as charge-coupled devices (CCDs) and complementary metal-oxide-semiconductor (CMOS) image sensors, SPAD detectors are photon-counting photodetectors. The single photogenerated charge can be multiplied within the SPAD device through the avalanche effect, thus a single photon can output a pulse signal. The back-end circuitry uses the number of pulse signals to provide feedback on the incident light intensity.

[0003] Single-photon avalanche diodes (SPADs), as photoelectric conversion elements with single-photon detection sensitivity, exhibit excellent photoelectric response characteristics in image sensor arrays within the 0.001-0.01 lux illuminance range, making them particularly suitable for low-light security monitoring scenarios. However, in nighttime outdoor environments including automotive lighting devices, road lighting systems, and commercial illuminated signs, local illuminance can reach the order of 10^5 lux. Therefore, to meet the needs of common monitoring scenarios, SPAD image sensors or cameras need to achieve a high dynamic range of 160 dB, while existing SPAD imaging devices cannot achieve full-spectrum reconstruction due to their limited dynamic range.

[0004] Therefore, there is an urgent need to provide a high dynamic range single-photon avalanche diode to significantly reduce the design and implementation difficulty of circuit, optics and algorithm aspects of high dynamic range SPAD image sensors. Summary of the Invention

[0005] The purpose of this application is to provide a single-photon avalanche diode, a manufacturing method, and an electronic device, aiming to solve the problem of small dynamic range of related single-photon avalanche diodes.

[0006] This application provides a single-photon avalanche diode, comprising:

[0007] Substrate;

[0008] A doped layer is disposed on the upper surface of the substrate; the substrate and the doped layer form the light-absorbing region of the single-photon avalanche diode;

[0009] A first doped region extending from the upper surface of the doped layer into the interior of the doped layer;

[0010] A second doped region surrounds the first doped region and extends from the upper surface of the doped layer into the interior of the doped layer; the second doped region and the first doped region have a first spacing distance between them.

[0011] The first electrode is disposed on the upper surface of the first doped region;

[0012] The second electrode is disposed on the upper surface of the second doped region;

[0013] A third electrode surrounds the second electrode and is disposed on the upper surface of the doped layer;

[0014] When the reverse voltage applied to the single-photon avalanche diode reaches the reverse breakdown voltage, the first electrode and the first doped region and the doped layer below it form a first avalanche junction; the second electrode and the second doped region and the doped layer below it form a second avalanche junction; photogenerated carriers enter the first avalanche junction and the second avalanche junction to induce the avalanche effect, thereby outputting an avalanche current;

[0015] Wherein, the first electrode and the second electrode have the same polarity, and the first electrode and the third electrode have opposite polarities; the first doped region and the second doped region are of the first type, and the substrate and the doped layer are of the second type; the first type and the second type are P-type and N-type, respectively.

[0016] This application also provides a method for manufacturing a single-photon avalanche diode, the method comprising:

[0017] A doped layer is formed on the upper surface of a substrate; the substrate and the doped layer together form the light-absorbing region of the single-photon avalanche diode.

[0018] A first doped region is formed on the upper surface of the doped layer, and at least one second doped region is formed on the upper surface of the doped layer, sequentially surrounding the first doped region;

[0019] A first electrode is formed on the upper surface of the first doped region, and at least one second electrode is formed on the upper surface of at least one second doped region, and a third electrode is formed on the upper surface of the doped layer surrounding the second electrode;

[0020] Specifically, when the reverse voltage applied to the single-photon avalanche diode reaches the reverse breakdown voltage, the first electrode and the first doped region and the doped layer below it form a first avalanche junction; the second electrode and the second doped region and the doped layer below it form a second avalanche junction.

[0021] This application provides a single-photon avalanche diode, comprising:

[0022] Substrate;

[0023] A doped layer is disposed on the upper surface of the substrate; the substrate and the doped layer form the light-absorbing region of the single-photon avalanche diode;

[0024] A first doped region extending from the upper surface of the doped layer into the interior of the doped layer;

[0025] A second doped region surrounds the first doped region and extends from the upper surface of the doped layer into the interior of the doped layer; the second doped region and the first doped region have a first spacing distance between them.

[0026] The first electrode is disposed on the upper surface of the first doped region;

[0027] A second electrode is disposed inside the second doped region and located on the upper surface of the doped layer; the second electrode has a second spacing distance from the first doped region;

[0028] A third electrode surrounding the second doped region and disposed on the upper surface of the doped layer;

[0029] When the reverse voltage applied to the single-photon avalanche diode reaches the reverse breakdown voltage, the first doped region below the first electrode and the doped layer form an avalanche junction; the second doped region acts as a barrier.

[0030] Wherein, the third electrode and the second electrode have the same polarity, and the first electrode and the third electrode have opposite polarities; the first doped region and the second doped region are of the first type, and the substrate and the doped layer are of the second type; the first type and the second type are P-type and N-type, respectively.

[0031] This application also provides a method for manufacturing a single-photon avalanche diode, the method comprising:

[0032] A doped layer is formed on the upper surface of the substrate;

[0033] A first doped region is formed on the upper surface of the doped layer, and at least one second doped region is formed on the upper surface of the doped layer, sequentially surrounding the first doped region;

[0034] A first electrode is formed on the upper surface of the first doped region, and at least one second electrode is formed inside at least one second doped region on the upper surface of the doped layer, and a third electrode is formed around the second doped region on the upper surface of the doped layer.

[0035] When the reverse voltage applied to the single-photon avalanche diode reaches the reverse breakdown voltage, the first doped region below the first electrode and the doped layer form an avalanche junction; the second doped region acts as a barrier; the substrate and the doped layer form the light-absorbing region of the single-photon avalanche diode.

[0036] This application also provides an electronic device, which includes the single-photon avalanche diode described above.

[0037] The beneficial effects of this invention compared to the prior art are as follows: When the reverse voltage applied to the single-photon avalanche diode reaches the reverse breakdown voltage, the first electrode and the first doped region and doped layer below it form a first avalanche junction; the second electrode and the second doped region and doped layer below it form a second avalanche junction; both the substrate and the doped layer can serve as light-absorbing regions; photons entering the light-absorbing regions have a certain probability of being absorbed and converted into photogenerated electrons and photogenerated holes as photogenerated charge carriers; photogenerated charge carriers enter the first and second avalanche junctions, triggering an avalanche effect and thus outputting an avalanche current; therefore, at least one of the first and second electrodes can be connected to the power supply, thereby causing at least one avalanche junction to undergo an avalanche effect. The avalanche current is output by selecting different electrodes and the number of electrodes connected to the power supply, thereby adjusting the dynamic range of the single-photon avalanche diode. This achieves a wide dynamic range for the photon avalanche diode, reducing the design and implementation difficulty of circuitry, optics, and algorithms in high dynamic range SPAD image sensors. Simultaneously, by using a second doped region to surround the first doped region and extend from the upper surface of the doped layer into the interior of the doped layer, the avalanche junctions are isolated using the doped layer. This achieves the separation of avalanche regions through electrical isolation, reducing lattice dangling bonds caused by the use of an insulating isolation layer. This effectively reduces the dark count rate and afterpulse probability, ensuring a high signal-to-noise ratio for the device. Attached Figure Description

[0038] To more clearly illustrate the technical inventions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 and Figure 2 A schematic diagram of a single-photon avalanche diode provided in Embodiment 1 of this application;

[0040] Figure 3 This is a schematic diagram of another structure of the single-photon avalanche diode provided in Embodiment 1 of this application;

[0041] Figure 4This is a schematic diagram of another structure of the single-photon avalanche diode provided in Embodiment 1 of this application;

[0042] Figure 5 This is a schematic diagram of another structure of the single-photon avalanche diode provided in Embodiment 1 of this application;

[0043] Figure 6 This is a schematic diagram of another structure of the single-photon avalanche diode provided in Embodiment 1 of this application;

[0044] Figure 7 This is a schematic diagram of another structure of the single-photon avalanche diode provided in Embodiment 1 of this application;

[0045] Figure 8 and Figure 9 This is a schematic diagram of a single-photon avalanche diode provided in Embodiment 2 of this application;

[0046] Figure 10 This is a schematic diagram of another structure of the single-photon avalanche diode provided in Embodiment 2 of this application;

[0047] Figure 11 This is a schematic diagram of another structure of the single-photon avalanche diode provided in Embodiment 2 of this application;

[0048] Figure 12 This is a schematic diagram of another structure of the single-photon avalanche diode provided in Embodiment 2 of this application;

[0049] Figure 13 This is a schematic diagram of another structure of the single-photon avalanche diode provided in Embodiment 2 of this application;

[0050] Figure 14 An equivalent circuit diagram of the optoelectronic unit provided in the embodiments of this application;

[0051] Figure 15 A block diagram illustrating the module principle of an electronic device provided in an embodiment of this application. Detailed Implementation

[0052] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0053] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0054] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0055] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0056] The related single-photon avalanche diode pixel structure includes a silicon substrate with a first-type doping type and an avalanche junction doped region with a second-type doping type. The avalanche junction region at the bottom is separated into multiple regions by an insulating layer. The silicon substrate has a pixel top heavily doped region with a first-type doping type at the top, pixel sidewall heavily doped regions with a first-type doping type on both sides, and a pixel bottom heavily doped region with a first-type doping type at the bottom. It also includes: a first electrode located within the pixel sidewall heavily doped region, a sidewall electrode extending downward along the pixel sidewall heavily doped region, and a second electrode located within the avalanche junction region. Therefore, the discrete distribution of the avalanche junction reduces the avalanche junction area and junction capacitance, suppresses after-pulse events, and reduces the dead time during device detection. However, this scheme has the following drawbacks: 1) The insulating isolation layer is close to the avalanche region. The insulating isolation layer is prepared by depositing silicon oxide after etching trench structures on the silicon substrate. There are high-density etching defects at the silicon oxide-silicon substrate interface. The insulating isolation layer close to the avalanche region will inevitably cause high noise problems, including high dark count rate and high afterpulse probability, and cannot achieve the goal of suppressing afterpulse proposed in the patent; 2) The etching depth of the insulating isolation layer is small, generally 0.2-0.4μm. In other words, the avalanche junction that the insulating isolation layer can isolate can only be a shallow junction close to the device surface; there are a large number of lattice dangling bonds on the device surface. Dangling bonds will cause high dark count rate and high afterpulse problems in shallow junction devices; among them, the outermost layer of silicon atoms has 4 electrons, so the substrate generally forms 4 covalent bonds. Since one side of the silicon atoms on the surface is other materials, some electrons cannot form bonds, resulting in so-called dangling bonds. Dangling bonds have the ability to trap and release charges.

[0057] Example 1

[0058] Figure 1 and Figure 2The diagram illustrates a structure of a single-photon avalanche diode according to Embodiment 1 of the present invention. For ease of explanation, only the parts relevant to the embodiment of the present invention are shown, and are described in detail below:

[0059] The aforementioned single-photon avalanche diode includes a substrate 100, a doped layer 90, a first doped region 11, a second doped region 12, a first electrode 21, at least one second electrode 22, and a third electrode 23.

[0060] A doped layer 90 is disposed on the upper surface of the substrate 100; the substrate 100 and the doped layer 90 form the light-absorbing region of the single-photon avalanche diode;

[0061] The first doped region 11 extends from the upper surface of the doped layer 90 into the interior of the doped layer 90;

[0062] The second doped region 12 surrounds the first doped region 11 and extends from the upper surface of the doped layer 90 into the interior of the doped layer 90; the second doped region 12 and the first doped region 11 have a first spacing distance between them;

[0063] The first electrode 21 is disposed on the upper surface of the first doped region 11;

[0064] The second electrode 22 is disposed on the upper surface of the second doped region 12;

[0065] The third electrode 23 surrounds the second electrode 22 and is disposed on the upper surface of the doped layer 90;

[0066] When the reverse voltage applied to the single-photon avalanche diode reaches the reverse breakdown voltage, the first electrode 21 and the first doped region 11 and the doped layer 90 below it form a first avalanche junction; the second electrode 22 and the second doped region 12 and the doped layer 90 below it form a second avalanche junction.

[0067] Among them, the first electrode 21 and the second electrode 22 have the same polarity, and the first electrode 21 and the third electrode 23 have opposite polarities; the first doped region 11 and the second doped region 12 are of the first type, and the substrate 100 and the doped layer 90 are of the second type; the first type and the second type are P-type and N-type, respectively.

[0068] When the first type is N-type and the second type is P-type, the first electrode 21 and the second electrode 22 are the cathodes of the single-photon avalanche diode, and the third electrode 23 is the anode of the single-photon avalanche diode.

[0069] When the first type is P-type and the second type is N-type, the first electrode 21 and the second electrode 22 are the anodes of the single-photon avalanche diode, and the third electrode 23 is the cathode of the single-photon avalanche diode.

[0070] It is understandable that the aforementioned N-type semiconductor regions are formed by implanting group V elements (such as P, As, Sb); while the P-type semiconductor regions are all formed by implanting group III elements (such as B, Ga).

[0071] It should be noted that the second doped region 12, the second electrode 22 and the third electrode 23 are annular, and the annular shape includes octagonal annular, circular, square and rounded square, which are not limited here.

[0072] Taking the first type as N-type and the second type as P-type as an example, when the reverse voltage applied to the single-photon avalanche diode reaches the reverse breakdown voltage, a first avalanche junction is formed by the first electrode 21 and the first doped region 11 and doped layer 90 below it; a second avalanche junction is formed by the second electrode 22 and the second doped region 12 and doped layer 90 below it; both the substrate 100 and the doped layer 90 can serve as light-absorbing regions; photons entering the light-absorbing regions have a certain probability of being absorbed and converted into photogenerated electrons and photogenerated holes as photogenerated charge carriers. The photogenerated charge carriers enter the first and second avalanche junctions, triggering an avalanche effect and thus outputting an avalanche current. In specific implementations, at least one electrode of the first electrode 21 and at least one second electrode 22 can be connected to a power supply, thereby causing at least one avalanche junction to exhibit an avalanche effect and outputting an avalanche current; it can be understood that by selecting different electrodes and selecting the number of electrodes connected to the power supply, the dynamic range of the single-photon avalanche diode can be adjusted, thus achieving a wide dynamic range for the photon avalanche diode.

[0073] Among them, dynamic range refers to the dynamic range of the SPAD detector. I max and I min These represent the maximum and minimum incident illuminance at which the SPAD detector can respond normally. The dead time of the SPAD device and its associated circuitry limits the upper limit of the detector's photon count rate, thus limiting I... max Using filters can effectively reduce the intensity of light incident on the SPAD, thereby improving I. max However, it will also increase I min This limits the detector's ability to detect in low light.

[0074] To achieve isolation between the first and second avalanche junctions, as well as between each second avalanche junction, adjacent doped regions need to maintain a certain distance. Furthermore, the doped regions undergo significant energy injection to allow avalanche junctions to form at a deeper location away from the device surface. Of course, the spacing between doped regions and the depth of the avalanche junctions can be flexibly adjusted according to the device size and doping process parameters, which will not be elaborated upon here.

[0075] It should be noted that in the device structure of this application, the doped regions at different locations are fabricated using the same implantation process. By optimizing the mask size and implantation parameters, it can be ensured that both the first and second avalanche junctions are centrally broken down. In other words, the reverse breakdown voltages BV of the two junctions are equal, and there will be no problem of poor consistency in reverse breakdown voltage BV. Since each avalanche junction has the same reverse breakdown voltage, only one power supply circuit is needed to power all avalanche junctions. That is, only one power supply circuit design is needed, which will greatly reduce the difficulty of circuit design and layout routing; only a simple "gating" circuit design is needed to achieve the switching of different photon detection efficiencies.

[0076] For example, simulation results under the same design parameters with different photon detection efficiencies can be categorized into three cases.

[0077] In the first case, it is used for detecting strong light signals such as 100klux; at this time, when the first electrode 21 is turned on, the avalanche breakdown probability distribution range is S1, the reverse breakdown voltage is 22.2V, and the photon detection efficiency corresponding to the 3.3V overbias voltage is 0.1%.

[0078] In the second case, it is used for medium-intensity optical signal detection. In this case, when the second electrode 22 is selected, the avalanche breakdown probability distribution range is S2, the reverse breakdown voltage is 22.1V, and the photon detection efficiency corresponding to the 3.3V overbias voltage is 11.2%.

[0079] In the third case, it is used for weak light signal detection. At this time, the first electrode 21 and the second electrode 22 are selected at the same time. The avalanche breakdown probability distribution range is S1+S2, the reverse breakdown voltage is 22.1V, and the photon detection efficiency corresponding to the 3.3V overbias voltage is 11.3%.

[0080] Therefore, by simply gating two electrodes, a dynamic range adjustment of 20log11.3 / 0.1 = 41dB can be achieved at the single-device level.

[0081] like Figure 3 As shown, the aforementioned single-photon avalanche diode also includes an isolation structure 40.

[0082] The isolation structure 40 surrounds the third electrode 23 and extends from the upper surface of the doped layer 90 to the lower surface of the substrate 100.

[0083] The isolation structure 40 is filled with materials such as polycrystalline silicon or tungsten metal, which serves to isolate optical and electrical crosstalk between pixels, achieving electrical and optical isolation and potential control between pixels. The tungsten metal filling inside can absorb photons, reducing optical crosstalk between pixels; furthermore, the tungsten metal can be connected to a potential, allowing for the control of the electric field on the side of the device. Various oxide dielectric materials are deposited between tungsten and Si, which not only act as a transition layer between Si and tungsten to reduce stress and improve tungsten adhesion, but also affect the incident photon reflection path, improving photon utilization.

[0084] The above technical solution reduces the possibility of crosstalk between individual single-photon avalanche diodes in the single-photon avalanche diode array, thereby improving the detection accuracy of each single-photon avalanche diode.

[0085] like Figure 4 As shown, the above-mentioned single-photon avalanche diode also includes a deeply doped region 50.

[0086] The deep doped region 50 is disposed between the second doped region 12 and the isolation structure 40 and extends downward from the lower surface of the third electrode 23 to the substrate 100.

[0087] The doping type of the deep doped region 50 is the same as that of the doped layer 90.

[0088] It should be noted that the deep doped region 50 prevents carriers on the etch damage defects of the isolation structure 40 from entering the depletion region, thereby reducing the dark count rate and the probability of afterpulse to a certain extent. Therefore, the deeper the implantation of the deep doped region 50, the better.

[0089] The afterpulse probability refers to the probability that a afterpulse will occur after the base pulse, which is a normal photon pulse. Afterpulses are pulses that form later than the base pulse due to the release of carriers trapped in defects. These are noise signals that are desirable to eliminate. The afterpulse probability is positively correlated with the defect concentration and the junction capacitance of the device.

[0090] Dark count rate refers to the count rate of SPADs in the absence of light. It is caused by the avalanche triggered by the initial charge carriers generated by mechanisms such as thermal excitation, direct tunneling, defect-assisted thermal excitation, and defect-assisted tunneling under the acceleration of an electric field. It is positively correlated with defect concentration and electric field strength and is the device background noise that is expected to be eliminated.

[0091] like Figure 5 As shown, the above-mentioned single-photon avalanche diode also includes a first heavily doped region 31, a second heavily doped region 32, and a third heavily doped region 33.

[0092] The first heavily doped region 31 is disposed between the first electrode 21 and the first doped region 11;

[0093] The second doped region 32 is disposed between the second electrode 22 and at least one second doped region 12;

[0094] The third doped region 33 is disposed between the third electrode 23 and the deep doped region 50. The third doped region 33 and the second doped region 12 have a second spacing distance between them.

[0095] Among them, the doping type of the first heavily doped region 31 is the same as that of the first doped region 11, the doping type of the second heavily doped region 32 is the same as that of the second doped region 12, and the doping type of the third heavily doped region 33 is the same as that of the deep doped region 50.

[0096] Heavily doped N+ regions are formed by implantation or thermal diffusion of group V elements (such as P, As, Sb). To form the cathode ohmic contact, the N+ surface is also treated with silicon metallization. Heavily doped P+ regions are formed by implantation or thermal diffusion of higher concentrations of group III elements (such as B or Ga). To form the cathode ohmic contact, the P+ surface is also treated with silicon metallization.

[0097] like Figure 6 As shown, the aforementioned single-photon avalanche diode also includes a first pad layer 60 and a first lens 70.

[0098] The first pad layer 60 is disposed on the lower surface of the substrate 100;

[0099] The first lens 70 is disposed on the lower surface of the first padding layer 60.

[0100] The padding layer is a multi-layered composite structure located between the SPAD image sensor surface and the focusing lens. It is typically composed of transparent dielectric materials (such as silicon dioxide or silicon nitride) or optical adhesives (such as epoxy resin), with a thickness ranging from micrometers to sub-millimeters. Its core function is to achieve optical path coupling and physical isolation, while matching the refractive index differences of different materials (such as the glass of the lens and the InGaAs / Si material of the SPAD chip).

[0101] like Figure 7 As shown, the above-mentioned single-photon avalanche diode also includes a dielectric layer 80, a second pad layer 61, and a second lens 71.

[0102] The dielectric layer 80 covers the upper surface of the first electrode 21, the upper surface of the second electrode 22, the upper surface of the third electrode 23, and the upper surface of the doped layer, respectively.

[0103] The second pad layer 61 is disposed on the upper surface of the dielectric layer;

[0104] The second lens 71 is disposed on the upper surface of the second pad layer 61.

[0105] It should be noted that the first padding layer 60 and the second padding layer 61 can be inorganic media materials such as SiO2, or organic materials such as optical resin and plexiglass. Generally speaking, such materials are required to have a moderate refractive index n (between 1.5 and 1.8), an extinction coefficient k close to 0, and good processing characteristics and stability to meet the requirements of high light transmittance and high stability.

[0106] like Figure 1 and Figure 2 The single-photon avalanche diode shown achieves more levels or smaller ranges of photon detection efficiency control by increasing the number of avalanche junctions and changing the overbias voltage. Further increasing the number of avalanche junctions is difficult to achieve in small-sized pixels, and overbias voltage is not within the scope of device structure design. Therefore, this application provides... Figure 6 and Figure 7 The solution shown is as follows. As is well known, lenses can redistribute incident photons within the avalanche zone. For example, spherical lenses are often used to focus incident light to improve photon detection efficiency; multifocal Fresnel lenses can be used for multifocal focusing of incident light, etc. By adjusting parameters such as the lens's refractive index, camber, radius of curvature, and the thickness of the padding layer, the number of photons incident on the first and second avalanche nodes can be adjusted. A suitable lens design can not only further increase the upper limit of SPAD's photon detection efficiency but also solve the aforementioned problem of varying photon detection efficiency levels. Here, photon detection efficiency is the probability that an incident photon is detected and a photon count is generated.

[0107] Understandable, Figure 6 It features a backlit design; Figure 7 The front-illuminated design is the most advanced type of light source. In practical applications, the back-illuminated design has better light reception efficiency, noise level, resolution and image quality, but the manufacturing process is more complex and the cost is higher. The front-illuminated design has a simpler manufacturing process and lower cost, but the light reception efficiency, noise level, resolution and image quality are worse.

[0108] Corresponding to one embodiment of a single-photon avalanche diode, the present invention also provides an embodiment of a method for manufacturing a single-photon avalanche diode.

[0109] A method for manufacturing a single-photon avalanche diode includes steps 110 to 130.

[0110] In step 110, a doped layer is formed on the upper surface of the substrate; the substrate and the doped layer form the light-absorbing region of the single-photon avalanche diode;

[0111] A doped layer is formed on the upper surface of a substrate by sputtering or vapor deposition.

[0112] In step 120, a first doped region is formed on the upper surface of the doped layer, and at least one second doped region is formed on the upper surface of the doped layer, sequentially surrounding the first doped region;

[0113] A first doped region is formed on the upper surface of the doped layer by ion implantation, and at least one second doped region is formed on the upper surface of the doped layer in sequence surrounding the first doped region.

[0114] Since the first and second doped regions are prepared using the same implantation process, it ensures that both types of avalanche junctions (the first and second avalanche junctions) are stable with central breakdown. Using two equal and highly consistent independent avalanche junctions significantly reduces the difficulty of power circuit design and layout routing, and improves the tolerance of process errors, resulting in low cost advantages and high mass production potential.

[0115] In step 130, a first electrode is formed on the upper surface of the first doped region, and at least one second electrode is formed on the upper surface of at least one second doped region, and a third electrode is formed on the upper surface of the doped layer surrounding the second electrode.

[0116] Specifically, when the reverse voltage applied to the single-photon avalanche diode reaches the reverse breakdown voltage, the first electrode and the first doped region and doped layer below it form a first avalanche junction, and the second electrode and the second doped region and doped layer below it form a second avalanche junction.

[0117] In practice, step 100 is included before step 110.

[0118] In step 100, a deep doped region surrounding the second doped region is formed on the upper surface of the doped layer.

[0119] A deep doped region surrounding the second doped region is formed on the upper surface of the doped layer through ion implantation and thermal diffusion.

[0120] In practice, step 120 is followed by steps 120-2 and 120-3.

[0121] In step 120-2, a first heavily doped region is formed on the upper surface of the first doped region, and at least one second heavily doped region is formed on the upper surface of at least one second doped region;

[0122] A first heavily doped region is formed on the upper surface of a first doped region by ion implantation, and at least one second heavily doped region is formed on the upper surface of at least one second doped region.

[0123] In step 120-3, a third doped region is formed on the upper surface of the deeply doped region.

[0124] A third doped region is formed on the upper surface of the deeply doped region by ion implantation.

[0125] In practice, step 120 is followed by step 120-4.

[0126] An isolation structure is formed around the deeply doped region, extending from the upper surface of the doped layer to the lower surface of the substrate.

[0127] Specifically, deep trenches are etched in the silicon epitaxial layer by plasma etching. These deep trenches form around a deeply doped region and extend from the upper surface of the doped layer to the substrate. Then, an oxide medium and metal W are deposited sequentially in the trenches.

[0128] Example 2

[0129] Figure 8 and Figure 9 Another structure of the single-photon avalanche diode provided in Embodiment 2 of the present invention is shown. For ease of explanation, only the parts related to the embodiments of the present invention are shown, and are described in detail below:

[0130] The single-photon avalanche diode includes a substrate 100, a doped layer 90, a first doped region 11, at least one second doped region 12, a first electrode 21, at least one second electrode 22, and a third electrode 23.

[0131] A doped layer 90 is disposed on the upper surface of the substrate 100; the substrate 100 and the doped layer 90 form the light-absorbing region of the single-photon avalanche diode;

[0132] The first doped region 11 extends from the upper surface of the doped layer 90 into the interior of the doped layer 90;

[0133] The second doped region 12 surrounds the first doped region 11 and extends from the upper surface of the doped layer 90 into the interior of the doped layer 90; the second doped region 12 and the first doped region 11 have a first spacing distance between them;

[0134] The first electrode 21 is disposed on the upper surface of the first doped region 11;

[0135] The second electrode 22 is disposed inside the second doped region 12 and located on the upper surface of the doped layer 90; the second electrode 22 and the first doped region 11 have a second spacing distance;

[0136] The third electrode 23 surrounds the second doped region 12 and is disposed on the upper surface of the doped layer 90;

[0137] When the reverse voltage applied to the single-photon avalanche diode reaches the reverse breakdown voltage, the first doped region 11 and the doped layer 90 below the first electrode 21 form an avalanche junction; the second doped region 12 acts as a barrier.

[0138] Among them, the third electrode 23 and the second electrode 22 have the same polarity, and the first electrode 21 and the third electrode 23 have opposite polarities; the first doped region 11 and the second doped region 12 are of the first type, and the substrate 100 and the doped layer 90 are of the second type; the first type and the second type are P-type and N-type, respectively.

[0139] When the first type is N-type and the second type is P-type, the first electrode 21 is the cathode of the single-photon avalanche diode, and the second electrode 22 and the third electrode 23 are the anodes of the single-photon avalanche diode.

[0140] When the first type is P-type and the second type is N-type, the first electrode 21 is the anode of the single-photon avalanche diode, and the second electrode 22 and the third electrode 23 are the cathodes of the single-photon avalanche diode.

[0141] In a specific implementation, when the first type is N-type and the second type is P-type, the cathode of the first electrode 21, the third electrode 23 and at least one second electrode 22 are the anodes of a single-photon avalanche diode.

[0142] In the case where the first type is P-type and the second type is N-type, the first electrode 21 is the anode of the single-photon avalanche diode, and the third electrode 23 and at least one second electrode 22 are the cathodes of the single-photon avalanche diode.

[0143] Taking the first type as N-type and the second type as P-type as examples, when the reverse voltage applied to the single-photon avalanche diode reaches the reverse breakdown voltage, the first doped region 11 and the doped layer 90 below the first electrode 21 form an avalanche junction; the second doped region 12 acts as a barrier; the substrate 100 and the doped layer 90 region can serve as light-absorbing regions; photons entering the light-absorbing region have a certain probability of being absorbed and converted into photogenerated electrons and photogenerated holes as photogenerated charge carriers. The photogenerated charge carriers entering the avalanche junction have a certain probability of triggering an avalanche effect, thereby outputting an avalanche current. In specific implementations, at least one electrode from the third electrode 23 and at least one of the second electrodes 22 can be connected to the power supply to adjust the avalanche junction to generate an avalanche effect and output an avalanche current. It can be understood that by selecting different electrodes and the number of electrodes connected to the power supply, adjusting the anode-cathode spacing can achieve the control of the avalanche electric field distribution. Changes in the avalanche electric field distribution will cause changes in the avalanche breakdown probability distribution. Therefore, by selecting the second electrode 22 and the third electrode 23, different photon detection efficiencies can be achieved. The introduction of the second doped region 12 between the two anodes is to electrically isolate the two anodes, ensuring that the distribution of the avalanche junction electric field will be significantly different when the two anodes are selected, thereby achieving the function of adjusting the dynamic range of the single-photon avalanche diode and realizing the wide dynamic range of the photon avalanche diode.

[0144] Among them, dynamic range refers to the dynamic range of the SPAD detector. Imax and I min These represent the maximum and minimum incident illuminance at which the SPAD detector can respond normally. The dead time of the SPAD device and its associated circuitry limits the upper limit of the detector's photon count rate, thus limiting I... max Using filters can effectively reduce the intensity of light incident on the SPAD, thereby improving I. max However, it will also increase I min This limits the detector's ability to detect in low light.

[0145] To achieve separation between the various second electrodes 22 and the third electrode 23, adjacent doped regions need to maintain a certain distance. Furthermore, a large energy injection is used in the doped regions to allow avalanche junctions to form at a deeper location away from the device surface. Of course, the spacing between doped regions and the depth of the avalanche junctions can be flexibly adjusted according to the device size and doping process parameters, which will not be elaborated upon here.

[0146] In one embodiment, the second doped region 12, the second electrode 22, and the third electrode 23 are annular, and the annular shape includes an octagonal annular shape, a circle, a square shape, and a rounded square shape.

[0147] like Figure 10 As shown, the above-mentioned single-photon avalanche diode also includes a first heavily doped region 31, at least one second heavily doped region 32, and a third heavily doped region 33.

[0148] The first heavily doped region 31 is disposed between the first electrode 21 and the first doped region 11;

[0149] The second doped region 32 is disposed between the second electrode 22 and the doped layer 90;

[0150] The third doped region 33 is disposed between the third electrode 23 and the doped layer 90. The third doped region 33 and the second doped region 12 have a third spacing distance.

[0151] The doping type of the first doped region 31 is the same as that of the first doped region 11, and the doping types of the second doped region 32 and the third doped region 33 are the same as those of the doped layer.

[0152] Heavily doped N+ regions are formed by implantation or thermal diffusion of group V elements (such as P, As, Sb). To form the cathode ohmic contact, the N+ surface is also treated with silicon metallization. Heavily doped P+ regions are formed by implantation or thermal diffusion of higher concentrations of group III elements (such as B or Ga). To form the cathode ohmic contact, the P+ surface is also treated with silicon metallization.

[0153] like Figure 11As shown, the aforementioned single-photon avalanche diode also includes an isolation structure 40.

[0154] The isolation structure 40 surrounds the third electrode 23 and extends from the upper surface of the doped layer 90 to the lower surface of the substrate 100.

[0155] The isolation structure 40 is filled with materials such as polycrystalline silicon or tungsten metal, which serves to isolate optical and electrical crosstalk between pixels, achieving electrical and optical isolation and potential control between pixels. The tungsten metal filling inside can absorb photons, reducing optical crosstalk between pixels; furthermore, the tungsten metal can be connected to a potential, allowing for the control of the electric field on the side of the device. Various oxide dielectric materials are deposited between the tungsten and Si, which not only act as a transition layer between Si and Si to reduce stress and improve tungsten adhesion, but also affect the incident photon reflection path, improving photon utilization.

[0156] The above technical solution reduces the possibility of crosstalk between individual single-photon avalanche diodes in the single-photon avalanche diode array, thereby improving the detection accuracy of each single-photon avalanche diode.

[0157] like Figure 12 As shown, the aforementioned single-photon avalanche diode also includes a first pad layer 60 and a first lens 70.

[0158] The first pad layer 60 is disposed on the lower surface of the substrate 100;

[0159] The first lens 70 is disposed on the lower surface of the first padding layer 60.

[0160] The padding layer is a multi-layered composite structure located between the SPAD image sensor surface and the focusing lens. It is typically composed of transparent dielectric materials (such as silicon dioxide or silicon nitride) or optical adhesives (such as epoxy resin), with a thickness ranging from micrometers to sub-millimeters. Its core function is to achieve optical path coupling and physical isolation, while matching the refractive index differences of different materials (such as the glass of the lens and the InGaAs / Si material of the SPAD chip).

[0161] like Figure 13 As shown, the above-mentioned single-photon avalanche diode also includes a dielectric layer 80, a second pad layer 61, and a second lens 71.

[0162] The dielectric layer 80 covers the upper surface of the first electrode 21, the upper surface of the second electrode 22, the upper surface of the third electrode 23, and the upper surface of the doped layer, respectively.

[0163] The second pad layer 61 is disposed on the upper surface of the dielectric layer 80;

[0164] The second lens 71 is disposed on the upper surface of the second pad layer 61.

[0165] It should be noted that the first padding layer 60 and the second padding layer 61 can be inorganic media materials such as SiO2, or organic materials such as optical resin and plexiglass. Generally speaking, such materials are required to have a moderate refractive index n (between 1.5 and 1.8), an extinction coefficient k close to 0, and good processing characteristics and stability to meet the requirements of high light transmittance and high stability.

[0166] like Figure 8 and Figure 9 The single-photon avalanche diode shown can control the avalanche electric field distribution by adjusting the anode-cathode spacing. Changes in the avalanche electric field distribution, along with alterations to the over-bias voltage, allow for more levels or smaller ranges of photon detection efficiency control. Further adjusting the anode-cathode spacing is challenging in small pixels, and over-bias voltage is outside the scope of device structure design. Therefore, this application provides... Figure 10 and Figure 11 The solution shown is as follows. As is well known, lenses can redistribute incident photons within the avalanche zone. For example, spherical lenses are often used to focus incident light to improve photon detection efficiency; multifocal Fresnel lenses can be used for multifocal focusing of incident light, etc. By adjusting parameters such as the lens's refractive index, camber, radius of curvature, and the thickness of the padding layer, the number of photons incident on the avalanche junction can be adjusted. A suitable lens design can not only further increase the upper limit of SPAD's photon detection efficiency but also solve the aforementioned problem of photon detection efficiency levels. Photon detection efficiency refers to the probability that one incident photon is detected and a photon count is generated.

[0167] Understandable, Figure 12 It features a backlit design; Figure 13 The front-illuminated design is the most advanced type of light source. In practical applications, the back-illuminated design has better light reception efficiency, noise level, resolution and image quality, but the manufacturing process is more complex and the cost is higher. The front-illuminated design has a simpler manufacturing process and lower cost, but the light reception efficiency, noise level, resolution and image quality are worse.

[0168] Corresponding to Embodiment 2 of a single-photon avalanche diode, the present invention also provides another embodiment of a method for manufacturing a single-photon avalanche diode.

[0169] A method for manufacturing a single-photon avalanche diode includes steps 210 to 230.

[0170] In step 210, a doped layer is formed on the upper surface of the substrate;

[0171] A doped layer is formed on the upper surface of a substrate by sputtering or vapor deposition.

[0172] In step 220, a first doped region is formed on the upper surface of the doped layer, and at least one second doped region is formed on the upper surface of the doped layer, sequentially surrounding the first doped region;

[0173] A first doped region is formed on the upper surface of the doped layer by ion implantation, and at least one second doped region is formed on the upper surface of the doped layer in sequence surrounding the first doped region.

[0174] In step 230, a first electrode is formed on the upper surface of the first doped region, and at least one second electrode is formed inside at least one second doped region on the upper surface of the doped layer, and a third electrode is formed around the second doped region on the upper surface of the doped layer.

[0175] When the reverse voltage applied to the single-photon avalanche diode reaches the reverse breakdown voltage, the first doped region and the doped layer below the first electrode form an avalanche junction; the second doped region acts as a barrier; the substrate and the doped layer form the light-absorbing region of the single-photon avalanche diode.

[0176] In practice, step 220 is followed by steps 220-2 and 220-3.

[0177] In step 220-2, a first heavily doped region is formed on the upper surface of the first doped region;

[0178] A first heavily doped region is formed on the upper surface of the first doped region by ion implantation.

[0179] In step 220-3, at least one second heavy doping region is formed inside at least one second doping region on the upper surface of the doped layer, and a third heavy doping region is formed around the second doping region on the upper surface of the doped layer.

[0180] At least one second doped region is formed on the upper surface of the doped layer by ion implantation inside at least one second doped region, and a third doped region is formed on the upper surface of the doped layer around the second doped region.

[0181] Step 230 specifically involves: forming the first electrode on the upper surface of the first heavily doped region, forming at least one second electrode on the upper surface of the doped layer inside at least one second heavily doped region, and forming the third electrode on the upper surface of the third heavily doped region.

[0182] In practice, step 220 is followed by step 220-4.

[0183] In step 240, an isolation structure is formed around the third doped region, extending from the upper surface of the doped layer to the lower surface of the substrate.

[0184] Specifically, deep trenches are etched in the silicon epitaxial layer by plasma etching. These deep trenches surround the deeply doped region and extend from the upper surface of the doped layer to the substrate. Then, an oxide medium and tungsten metal are deposited sequentially in the trenches.

[0185] This application embodiment also provides an optoelectronic unit, the optoelectronic unit including a first switching transistor and at least one second switching transistor, the optoelectronic unit further including the single-photon avalanche diode provided in Embodiment 1 of the present invention or the single-photon avalanche diode provided in Embodiment 2 of the present invention;

[0186] When the single-photon avalanche diode provided in Embodiment 1 of the present invention is included, the first switching transistor is electrically connected to the first electrode of the single-photon avalanche diode, and each of the second switching transistors is electrically connected to each of the second electrodes of the single-photon avalanche diode.

[0187] Taking the first type as N-type and the second type as P-type as an example, it can be understood that the first and second electrodes are the cathodes of the single-photon avalanche diode, and the third electrode is the anode of the single-photon avalanche diode; in this case, the equivalent circuit diagram of the photoelectric unit is as follows. Figure 14 As shown, the first switch M1 and each of the second switches M2 can be turned on or off to adjust the detection efficiency.

[0188] When the single-photon avalanche diode provided in Embodiment 2 of the present invention is included, the first switch is electrically connected to the second electrode of the single-photon avalanche diode, and each of the second switch diodes is electrically connected to each of the third electrodes of the single-photon avalanche diode.

[0189] By integrating the first switch, the second switch, and the single-photon avalanche diode into a single optoelectronic unit, one or more of the first switch and the various second switches can be selectively activated, and at least one of the first electrode and at least one of the at least two second electrodes can be selectively connected to the power supply. This adjusts the number of activated avalanche junctions and achieves different photon detection efficiencies. Furthermore, the integration of the first switch, the second switch, and the single-photon avalanche diode into a single optoelectronic unit improves ease of use.

[0190] Taking the first type as P-type and the second type as N-type as examples, it can be understood that the first electrode is the anode of the single-photon avalanche diode, and the second and third electrodes are the cathodes of the single-photon avalanche diode. The equivalent circuit diagram of the photoelectric unit is as follows: Figure 14 As shown, the first switch M1 and each of the second switches M2 can be turned on or off to adjust the detection efficiency.

[0191] By integrating the first switch, the second switch, and the single-photon avalanche diode into a single optoelectronic unit, one or more of the first and second switches can be selectively turned on. The third electrode and at least one of the at least two second electrodes can be selectively connected to the power supply. Adjusting the avalanche electric field distribution allows for modulation of the avalanche electric field distribution. Changes in the avalanche electric field distribution cause changes in the avalanche breakdown probability distribution. Therefore, by selecting the second and third electrodes, the avalanche effect of the avalanche junction can be adjusted to output an avalanche current, achieving different photon detection efficiencies. Furthermore, integrating the first switch, the second switch, and the single-photon avalanche diode into a single optoelectronic unit improves ease of use.

[0192] This application also provides an electronic device, such as... Figure 15 As shown, the electronic device includes an interactive circuit 02, a control circuit 03, and a pixel array 01, wherein the pixel array includes a plurality of the aforementioned photoelectric units;

[0193] Interactive circuit 02, connected to pixel array 01, is used to record the number of photons detected by the pixel array within a preset time period and transmit the photon count information to control circuit 03;

[0194] The control circuit 03 is connected to multiple photoelectric units and is used to compare the number of photons with a set threshold and output a control signal according to the comparison result to control the first switch and the second switch to be turned on or off.

[0195] Understandably, electronic devices can fall into two categories.

[0196] In the first case, the interactive circuit and the pixel array are set in a photodetector. The interactive circuit in the photodetector outputs a signal of the number of photons to the control circuit, and the control circuit outputs a control signal to the photodetector to control the pixel array in the photodetector.

[0197] In the second scenario, the control circuit, interaction circuit, and pixel array are all housed within the photodetector. In this case, the control circuit and the original control module within the photodetector share a single microprocessor.

[0198] In summary, electronic devices may include photodetectors, where the photodetector may be a SPAD detector.

[0199] It should be noted that the control circuit 03 is specifically used to compare the number of photons with multiple set thresholds, determine the target level based on the comparison results, query the control word corresponding to the target level, and output a control signal based on the control word.

[0200] In one embodiment, the range between the first set threshold (upper limit) and the second set threshold (lower limit) constitutes the first gear level; the range above the first set threshold is the second gear level, which falls within the high photon count range. In this range, the PDE needs to be reduced to ensure the photon count rate does not saturate, corresponding to the low photon detection efficiency range; the range below the second set threshold is the third gear level, which falls within the low photon count range. In this range, the photon detection efficiency needs to be increased to achieve high-quality detection with lower light intensity, corresponding to the high photon detection efficiency range. Each gear level corresponds to a corresponding control word. The value of each bit in the control word (binary) is related to the level of each sub-control signal in the control signal. Each sub-control signal is used to control a switch, including a first switch and a second switch. For example, when the target gear level is the third gear level, the control word corresponding to the third gear level is 11, so all sub-control signals are at a high level to control both the first and second switches to be turned on.

[0201] The above technical solution improves the accuracy of photon detection level control.

[0202] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0203] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A single-photon avalanche diode, characterized in that, include: Substrate; A doped layer disposed on the upper surface of the substrate; The substrate and the doped layer form the light-absorbing region of the single-photon avalanche diode; A first doped region extending from the upper surface of the doped layer into the interior of the doped layer; A second doped region surrounds the first doped region and extends from the upper surface of the doped layer into the interior of the doped layer; the second doped region and the first doped region have a first spacing distance between them. The first electrode is disposed on the upper surface of the first doped region; A second electrode is disposed inside the second doped region and located on the upper surface of the doped layer; the second electrode has a second spacing distance from the first doped region; A third electrode surrounding the second doped region and disposed on the upper surface of the doped layer; When the reverse voltage applied to the single-photon avalanche diode reaches the reverse breakdown voltage, the first doped region below the first electrode and the doped layer form an avalanche junction; the second doped region acts as a barrier. The third electrode and the second electrode have the same polarity, while the first electrode and the third electrode have opposite polarities; the first doped region and the second doped region are of the first type, and the substrate and the doped layer are of the second type; the first type and the second type are P-type and N-type, respectively. The first interval distance is greater than the second interval distance; By introducing the second doped region between the second electrode and the third electrode, the second electrode and the third electrode are electrically isolated. When the second electrode and the third electrode are respectively selected, the distribution of the avalanche junction electric field will be significantly different, thereby achieving the effect of adjusting the dynamic range of the single-photon avalanche diode.

2. The single-photon avalanche diode as described in claim 1, characterized in that, Also includes: A first heavily doped region is disposed between the first electrode and the first doped region; A second heavily doped region is disposed between the second electrode and the doped layer; A third doped region is disposed between the third electrode and the doped layer; the third doped region and the second doped region have a third spacing distance; The doping type of the first heavily doped region is the same as that of the first doped region, and the doping types of the second heavily doped region and the third heavily doped region are the same as those of the doped layer.

3. The single-photon avalanche diode as described in claim 1, characterized in that, Also includes: An isolation structure surrounding the third electrode and extending from the upper surface of the doped layer to the lower surface of the substrate; The isolation structure is filled with polycrystalline silicon or tungsten material.

4. The single-photon avalanche diode as described in claim 1, characterized in that, Also includes: A first pad layer is disposed on the lower surface of the substrate; A first lens is disposed on the lower surface of the first pad layer; The first pad layer is made of transparent dielectric material or optical adhesive.

5. The single-photon avalanche diode as described in claim 1, characterized in that, Also includes: A dielectric layer covering the upper surface of the first electrode, the upper surface of the second electrode, the upper surface of the third electrode, and the upper surface of the doped layer, respectively; A second pad layer is disposed on the upper surface of the dielectric layer; A second lens is disposed on the upper surface of the second pad layer; The second padding layer is made of transparent dielectric material or optical adhesive.

6. The single-photon avalanche diode as described in any one of claims 2 to 5, characterized in that, The second doped region, the second electrode, and the third electrode are ring-shaped, including octagonal rings, circles, squares, and rounded squares.

7. A method for manufacturing a single-photon avalanche diode as described in any one of claims 2 to 6, characterized in that, The manufacturing method includes: A doped layer is formed on the upper surface of the substrate; A first doped region is formed on the upper surface of the doped layer, and at least one second doped region is formed on the upper surface of the doped layer, sequentially surrounding the first doped region; A first electrode is formed on the upper surface of the first doped region, and at least one second electrode is formed inside at least one second doped region on the upper surface of the doped layer, and a third electrode is formed around the second doped region on the upper surface of the doped layer. When the reverse voltage applied to the single-photon avalanche diode reaches the reverse breakdown voltage, the first doped region below the first electrode and the doped layer form an avalanche junction; the second doped region acts as a barrier; the substrate and the doped layer form the light-absorbing region of the single-photon avalanche diode.

8. The method for manufacturing a single-photon avalanche diode according to claim 7, characterized in that, After forming a first doped region on the upper surface of the doped layer, and forming at least one second doped region sequentially surrounding the first doped region on the upper surface of the doped layer, the method further includes: A first heavily doped region is formed on the upper surface of the first doped region; At least one second heavily doped region is formed inside at least one second doped region on the upper surface of the doped layer; A third doped region is formed on the upper surface of the doped layer surrounding the second doped region; The specific steps involve forming a first electrode on the upper surface of the first doped region, forming at least one second electrode inside at least one second doped region on the upper surface of the doped layer, and forming a third electrode around the second doped region on the upper surface of the doped layer as follows: The first electrode is formed on the upper surface of the first heavily doped region, and at least one second electrode is formed inside at least one second heavily doped region located on the upper surface of the doped layer, and the third electrode is formed on the upper surface of the third heavily doped region; the step of forming the first doped region on the upper surface of the doped layer and forming at least one second doped region sequentially surrounding the first doped region on the upper surface of the doped layer further includes: An isolation structure is formed around the third doped region, extending from the upper surface of the doped layer to the lower surface of the substrate.

9. A photoelectric unit, characterized in that, The optoelectronic unit includes a first switching transistor and at least one second switching transistor, and the optoelectronic unit further includes a single-photon avalanche diode as described in any one of claims 1 to 6; The first switch is electrically connected to the second electrode of the single-photon avalanche diode, and each of the second switches is electrically connected to the third electrode of the single-photon avalanche diode.

10. An electronic device, characterized in that, The electronic device includes an interactive circuit, a control circuit, and a pixel array, wherein the pixel array includes a plurality of photoelectric units as described in claim 9; The interactive circuit is connected to the pixel array and is used to record the number of photons detected by the pixel array within a preset time period, and transmit the information of the number of photons to the control circuit. The control circuit is connected to multiple photoelectric units and is used to compare the number of photons with a set threshold and output a control signal according to the comparison result to control the first switch and the second switch to be turned on or off.

11. The electronic device according to claim 10, characterized in that, The control circuit is specifically used to compare the number of photons with multiple set thresholds, determine the target level based on the comparison results, query the control word corresponding to the target level, and output the control signal based on the control word.

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