SiNx avalanche photodetector preparation method and device

Abstract

The invention provides a SiNx avalanche photodetector preparation method and device, and relates to the technical field of semiconductor device processing, and the method comprises the steps: providing a first doping type substrate, and carrying out the specific concentration doping of the first doping type on the substrate to form a first epitaxial layer; performing doping of a first doping type on the first epitaxial layer to form a second intrinsic epitaxial layer; performing ion implantation of a second doping type on the second intrinsic epitaxial layer to form a first region; performing ion implantation of a second doping type on the second intrinsic epitaxial layer to form a protection ring region; wherein the first epitaxial layer and the first region form an avalanche junction region.

Description

Technical Field

[0001] The present application relates to the field of semiconductor device technology, and in particular to a method for preparing a SiNx avalanche photodetector and a device. Background Art

[0002] Currently, with the continuous advancement of Si material technology, UV-enhanced Si-based single-photon avalanche diodes (SPADs) can be easily integrated with readout circuits. However, the band gap of Si material is relatively narrow, only 1.12eV, which limits its performance in high-temperature environments. Specifically, Si-based devices have high dark current levels, and as the temperature rises, the intrinsic carrier concentration increases significantly, causing the dark current to increase rapidly. This increase in dark current directly affects the sensitivity of the SPAD and reduces its detection performance. In order to ensure the normal operation of Si-based SPADs under high temperature conditions, expensive cooling systems are usually required for temperature control. In addition, Si-based SPADs are not visible light blind or daylight blind, which means that when performing UV light detection, expensive visible light blind or daylight blind filters are required to filter out unwanted light to ensure detection accuracy. Therefore, SiNx avalanche photodetectors came into being.

[0003] SiNx avalanche photodetectors (APDs) are widely used in ultraviolet (UV) detection, LiDAR, bio-detection, and military applications due to their high sensitivity, low noise, wide spectral response range, high-temperature operation, and strong radiation resistance. When operating under reverse bias, the internal electric field distribution of a SiNx APD is non-uniform. This is particularly true at the device's edges, where the field is often higher due to the device's geometry and the distribution of electric field lines.

[0004] In the prior art, by changing the geometric shape of the device edge, the edge electric field can be effectively reduced, thereby suppressing premature breakdown or performance degradation caused by the edge electric field effect. The tilted mesa structure helps to ensure that the device remains stable under normal operating conditions and avoids performance fluctuations or failures due to uneven electric field distribution. However, a significant disadvantage of the tilted mesa structure is the low duty cycle of the device. Since the tilted part is ineffective for photon detection, this area cannot be counted as the effective detection area. A low duty cycle means that the effective utilization area of ​​the chip is small, which limits the detection efficiency and performance of the device. Therefore, how to increase the effective avalanche area of ​​the SiNx avalanche photodetector and improve the single-photon detection performance of the device is a technical problem that needs to be solved urgently. Summary of the Invention

[0005] The present application provides a method for preparing a SiNx avalanche photodetector and a device, which solves the technical problems of small photosensitive area and low detection performance of SiNx avalanche photodetectors in the prior art.

[0006] In order to achieve the above-mentioned objectives, in a first aspect, an embodiment of the present application provides a method for preparing a SiNx avalanche photodetector, comprising: providing a first doping type substrate, performing a specific concentration of doping of the first doping type on the substrate to form a first epitaxial layer; performing a first doping type of doping on the first epitaxial layer to form a second intrinsic epitaxial layer; performing a second doping type of ion implantation on the second intrinsic epitaxial layer to form a first region; forming a guard ring region by performing a second doping type of ion implantation on the second intrinsic epitaxial layer; wherein, the first epitaxial layer and the first region form an avalanche junction region.

[0007] Optionally, a dielectric layer is formed above the second intrinsic epitaxial layer, and a cathode of the SiNx avalanche photodetector is formed in the dielectric layer through interconnecting metal; and an anode of the SiNx avalanche photodetector is formed on the second surface of the substrate.

[0008] Optionally, the second intrinsic epitaxial layer is the electron-hole multiplication layer of the SiNx avalanche photodetector.

[0009] Optionally, the thickness of the second intrinsic epitaxial layer is smaller than the thickness of the first epitaxial layer.

[0010] Optionally, the doping concentration of the second intrinsic epitaxial layer is less than the doping concentration of the first epitaxial layer.

[0011] Optionally, the guard ring area is adjacent to the first area.

[0012] Optionally, the junction depth of the guard ring region is greater than the junction depth of the first region.

[0013] In a second aspect, an embodiment of the present application provides a SiNx avalanche photodetector device, which is prepared using the SiNx avalanche photodetector preparation method as described in any one of the first aspects. The SiNx avalanche photodetector device includes: a first doping type substrate, a first epitaxial layer of a first doping type arranged on the first doping type substrate, a second intrinsic epitaxial layer of a first doping type arranged on the first epitaxial layer, a first region of a second doping type arranged on the second intrinsic epitaxial layer, and a guard ring region of a second doping type arranged in the intrinsic epitaxial layer.

[0014] Optionally, the SiNx avalanche photodetector device further includes a dielectric layer disposed above the second intrinsic epitaxial layer, a cathode of the SiNx avalanche photodetector disposed in the dielectric layer through interconnecting metal, and an anode of the SiNx avalanche photodetector disposed on the second surface of the substrate.

[0015] Optionally, the SiNx avalanche photodetector devices are isolated from each other by shallow trench isolation.

[0016] Optionally, the second intrinsic epitaxial layer is the electron-hole multiplication layer of the SiNx avalanche photodetector.

[0017] Optionally, the thickness of the second intrinsic epitaxial layer is smaller than the thickness of the first epitaxial layer.

[0018] Optionally, the doping concentration of the second intrinsic epitaxial layer is less than the doping concentration of the first epitaxial layer.

[0019] Optionally, the junction depth of the guard ring region is greater than the junction depth of the first region.

[0020] The embodiment of the present application provides a new method for preparing a SiNx avalanche photodetector, which provides stable P-type conductive properties by growing a P-type high-concentration epitaxial layer on a P-type SiNx substrate through epitaxial technology. Subsequently, a layer of intrinsic concentration epitaxial layer is epitaxially grown on this P-type high-concentration epitaxial layer. This layer serves as the core area of ​​avalanche multiplication and is crucial for achieving high-sensitivity single-photon detection. In the intrinsic epitaxial layer, ion implantation technology is used to inject N-type ions of different concentrations, thereby forming a NIP-type structure. The design of this structure enables the device to produce an avalanche multiplication effect under reverse bias, thereby achieving high-sensitivity detection of single photons.

[0021] To further enhance device performance, the present invention employs lateral ion implantation to create a virtual guard ring. This technique effectively addresses the drawback of the tilted mesa structure, which reduces the photosensitive area. By creating a guard ring structure without adding additional material, the device's effective avalanche area is maximized. This not only improves the device's single-photon detection performance but also makes the device structure more compact and stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic diagram of a process for preparing a SiNx avalanche photodetector provided in an embodiment of the present application;

[0023] Figure 2A-2E Each of them is a schematic cross-sectional view of a SiNx avalanche photodetector device during a process of preparing a SiNx avalanche photodetector device provided in an embodiment of the present application;

[0024] Figure 3A A schematic cross-sectional view of a SiNx avalanche photodetector device provided in an embodiment of the present application;

[0025] Figure 3BA schematic cross-sectional view of another SiNx avalanche photodetector device provided in an embodiment of the present application;

[0026] Figure 4 A schematic diagram of the passive quenching and passive reset circuit principle of a SiNx avalanche photodetector provided in an embodiment of the present application. DETAILED DESCRIPTION

[0027] In the following description, specific details such as specific system structures and technologies are provided for illustrative purposes rather than for limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application can also be implemented in other embodiments without these specific details. In other cases, the well-known working principles of SPADs are omitted to avoid obscuring the description of the present application with unnecessary details.

[0028] The terms used in the following embodiments are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the specification and appended claims of this application, the singular expressions "a," "said," "above," and "the" are intended to also include expressions such as "one or more," unless the context clearly indicates otherwise.

[0029] SiNx avalanche photodetectors (APDs) are widely used in ultraviolet (UV) detection, LiDAR, bio-detection, and military applications due to their high sensitivity, low noise, wide spectral response range, high-temperature operation, and strong radiation resistance. When operating under reverse bias, the internal electric field distribution of a SiNx APD is non-uniform. The edge electric field is particularly high at the device's edges due to its geometry and the distribution of electric field lines. However, conventional SiNx APDs typically employ a tilted mesa structure to suppress the effects of the device's edge electric field.

[0030] Specifically, conventional SiNx avalanche photodetectors utilize a tilted mesa structure to avoid performance fluctuations or failures caused by uneven electric field distribution. However, a significant drawback of the tilted mesa structure is the device's low duty cycle. Because the tilted portion is ineffective for photon detection, this area is not counted as part of the active detection area. This low duty cycle reduces the effective chip area, limiting the device's detection efficiency and performance.

[0031] Therefore, an embodiment of the present application proposes a new method for preparing a SiNx avalanche photodetector, which provides stable P-type conductive properties by growing a P-type high-concentration epitaxial layer on a P-type SiNx substrate through epitaxial technology. Subsequently, a layer of intrinsic concentration epitaxial layer is continued to be epitaxially grown on this P-type high-concentration epitaxial layer. This layer serves as the core area of ​​avalanche multiplication and is crucial for achieving high-sensitivity single-photon detection. In the intrinsic epitaxial layer, ion implantation technology is used to inject N-type ions of different concentrations, thereby forming a NIP-type structure. The design of this structure enables the device to produce an avalanche multiplication effect under reverse bias, thereby achieving high-sensitivity detection of single photons.

[0032] To further enhance device performance, the present invention employs lateral ion implantation to create a virtual guard ring. This technique effectively addresses the drawback of the tilted mesa structure, which reduces the photosensitive area. By creating a guard ring structure without adding additional material, the device's effective avalanche area is maximized. This not only improves the device's single-photon detection performance but also makes the device structure more compact and stable.

[0033] Among them, the preparation method of SiNx avalanche photodetector may include: providing a first doping type substrate, performing a specific concentration doping of the first doping type on the substrate to form a first epitaxial layer; performing a first doping type doping above the first epitaxial layer to form a second intrinsic epitaxial layer; performing a second doping type ion implantation on the second intrinsic epitaxial layer to form a first region; forming a guard ring region by performing a second doping type ion implantation on the second intrinsic epitaxial layer; wherein, the first epitaxial layer and the first region form an avalanche junction region.

[0034] The following first introduces the method for preparing the SiNx avalanche photodetector provided in the embodiment of the present application, see Figure 1 , Figure 1 A schematic flow chart of a method for preparing a SiNx avalanche photodetector provided in an embodiment of the present application. Figure 1 As shown, the method includes the following steps:

[0035] S101 , providing a substrate of a first doping type, and performing doping of a first doping type at a specific concentration on the substrate to form a first epitaxial layer.

[0036] Specifically, see Figure 2AIn the semiconductor manufacturing process, a substrate 201 having a first doping type is first provided. This substrate serves as the foundation for the entire device, and its doping type is determined according to requirements, for example, it can be P-type or N-type, depending on the functional requirements of the subsequent device. On this basis, the substrate further includes an epitaxial layer 202, which is formed on the substrate surface using epitaxial growth technology. Its structure, composition, and thickness are precisely controlled to meet specific performance requirements. In the embodiment of the present application, the preferred thickness of substrate 201 is 300μm.

[0037] In particular, for the SiNx avalanche photodetector device manufacturing method of this embodiment, the first epitaxial layer 202 of the first doping type provided must have a specific doping concentration. This concentration has been accurately calculated and experimentally verified, and is intended to provide the best electrical performance foundation for the subsequent double avalanche junction structure. At the same time, the epitaxial layer not only helps to form a high-quality interface, but also can adjust the depletion region width of the device to a certain extent, thereby optimizing the conditions for the occurrence of the avalanche multiplication effect. In the embodiment of the present application, the preferred doping concentration of the first epitaxial layer is: 1e18 cm-3 ~ 1e19 cm-3, and the thickness is 5μm.

[0038] S102 , performing doping of a first doping type on the first epitaxial layer to form a second intrinsic epitaxial layer.

[0039] Specifically, see Figure 2B , a second intrinsic epitaxial layer 203 is formed on the first epitaxial layer 202 by epitaxial growth technology. The second intrinsic epitaxial layer is doped with the first doping type, and its doping concentration is less than that of the first epitaxial layer, and its thickness is also less than that of the first epitaxial layer. In the embodiment of the present application, preferably, the doping concentration of the second intrinsic epitaxial layer is 1e12cm-3, and the thickness is 1.5μm. That is to say, the doping concentration of the second intrinsic epitaxial layer is less than the doping concentration of the first epitaxial layer; the thickness of the second intrinsic epitaxial layer is less than the thickness of the first epitaxial layer. It should be noted that the second intrinsic epitaxial layer serves as the light absorption coefficient layer and the electron-hole multiplication layer of the SiNx avalanche photodetector.

[0040] S103 , implanting ions of a second doping type into the second intrinsic epitaxial layer to form a first region.

[0041] Specifically, see Figure 2C. The second intrinsic epitaxial layer 203 is subjected to a precisely controlled ion implantation process. In this process, a dopant different from the first doping type of the substrate is used (for example, if the substrate is P-type, an N-type dopant is used), and the dopant is implanted into a certain depth of the epitaxial layer by setting the ion beam parameters (such as energy, dose and angle), thereby forming a first region 204 with a specific doping concentration in the epitaxial layer. In the embodiment of the present application, N-type ion arsenic doping is used to form an N-type region for avalanche, and preferably, the doping concentration is 1e18~1e19cm-3. The junction depth of the first region should be less than the thickness of the second intrinsic epitaxial layer, but not too shallow. A deeper junction depth can increase the breakdown voltage of the device, but may increase leakage current, resulting in increased power consumption and reduced device efficiency. A shallower junction depth can reduce leakage current, but the breakdown voltage may be lower, affecting the stability and reliability of the device. In the embodiment of the present application, the preferred junction depth of the first region 204 is 1 / 3 of the thickness of the second intrinsic epitaxial layer 203. This junction depth can reduce leakage current while maintaining a certain breakdown voltage, achieving an optimal balance in device performance. Furthermore, it is neither too deep nor too shallow, which facilitates process control and production stability.

[0042] S104 , forming a guard ring region by performing ion implantation of a second doping type on the second intrinsic epitaxial layer.

[0043] Specifically, see Figure 2D . In semiconductor devices, edge breakdown is a common problem, which may cause device performance degradation or even failure. In order to prevent edge breakdown, the embodiment of the present application forms an N-type guard ring area with a specific doping concentration in the edge area of ​​the device. This guard ring area can effectively disperse the electric field and reduce the electric field strength in the edge area, thereby improving the breakdown voltage and stability of the device. In the present application, lateral ion implantation is used to introduce dopant atoms in the form of ions into the second intrinsic epitaxial layer to form a virtual guard ring area 205. In the manufacture of semiconductor devices, ion implantation technology is widely used to form various doping regions. By precisely controlling the type, energy and dose of ions, precise control of the doping region concentration and junction depth can be achieved. Specifically, a suitable N-type ion arsenic is selected as a dopant. The arsenic ion is accelerated to a certain energy so that it can penetrate to a specified depth of the semiconductor material. In a vacuum system, the accelerated arsenic ion is injected into the edge area of ​​the semiconductor material. As Figure 2DAs shown, the guard ring region is adjacent to the first region. By adjusting the dose and energy of ion implantation, the concentration and junction depth of the doped region can be controlled. In an embodiment of the present application, the doping concentration of the guard ring region is 1e17~5e17cm-3. The selection of the junction depth of the guard ring region needs to take into account the thickness of the intrinsic epitaxial layer. In this example, the junction depth of the guard ring region is set to 1 / 2 of the thickness of the second intrinsic epitaxial layer. Such a choice can avoid excessive impact on the internal structure of the device while ensuring sufficient protection effect. The junction depth of the guard ring region is greater than the junction depth of the first region. It should be noted that the first epitaxial layer and the first region form the avalanche junction region of the SiNx avalanche photodetector.

[0044] It should also be noted that in the semiconductor preparation process, after the required avalanche junction area is formed, such as all the processes in the above steps in the embodiment, the metallization process and the dielectric layer process are immediately entered, aiming to achieve electrical connection between the internal circuit of the wafer and the outside world (such as package pins, circuit boards, etc.), and provide necessary electrical isolation and protection.

[0045] The dielectric layer is located above the second intrinsic epitaxial layer and plays the role of electrical isolation. These dielectric layers are usually composed of insulating materials (such as silicon dioxide, silicon nitride, etc.) and are formed by chemical vapor deposition (CVD), physical vapor deposition (PVD) and other methods. The dielectric layer also contains through holes and contact holes, which are etched out so that the subsequent metallization process can form a vertical electrical connection. In the embodiment of the present application, aluminum can be used as an interconnect metal for the conduction of electrical signals. In this embodiment of the present application, N++SiNx (first region) is the cathode. The anode is the second surface (back) electrode Ni electrode of the first epitaxial layer, see for details. Figure 2E .

[0046] It should be noted that the embodiments of the present application achieve device isolation through STI (shallow trench isolation).

[0047] The following is a detailed introduction to the SiNx avalanche photodetector device provided in the embodiment of the present application. Figure 3A and Figure 3B , Figure 3A A schematic cross-sectional view of a SiNx avalanche photodetector device provided in an embodiment of the present application is shown in FIG. Figure 3B A cross-sectional schematic diagram of another SiNx avalanche photodetector device provided in an embodiment of the present application. Figure 3A As shown, the SiNx avalanche photodetector device may include: a substrate 201 of a first doping type (such as P-type), covered with a first epitaxial layer 202 of the same type (P-type), and a second intrinsic epitaxial layer 203 of the first doping type above the first epitaxial layer.

[0048] On the second intrinsic epitaxial layer, a first region 204 of the second doping type (e.g., N-type) is first formed through a specific doping process (e.g., ion implantation or diffusion). Subsequently, a guard ring region 205 of the second doping type is formed within the intrinsic epitaxial layer through ion implantation. The first region 204 and the first epitaxial layer form an avalanche junction region.

[0049] like Figure 3A The dielectric layer shown is located above the second intrinsic epitaxial layer and serves as an electrical isolation layer. These dielectric layers are usually composed of insulating materials (such as silicon dioxide, silicon nitride, etc.) and are formed by methods such as chemical vapor deposition (CVD) and physical vapor deposition (PVD). The dielectric layer also includes through holes and contact holes, which are etched out so that the subsequent metallization process can form a vertical electrical connection. In the embodiment of the present application, aluminum can be used as an interconnect metal for conducting electrical signals. In this embodiment of the present application, N++SiNx (first region) is the cathode. The anode is the second surface (back) electrode Ni electrode of the first epitaxial layer. In addition, the embodiment of the present application achieves device isolation through STI (shallow trench isolation).

[0050] In other embodiments, see Figure 3B , its device structure and Figure 3A The following is similar and will not be described here. Figure 3B The second intrinsic epitaxial layer 203 is a photon absorption layer and an electron-hole multiplication layer of the SiNx avalanche photodetector device.

[0051] Figure 4 The schematic diagram of the passive quenching and passive reset circuit principle of a SiNx avalanche photodetector provided in the embodiment of the present application. Of course, the SiNx avalanche photodetector can also use active quenching, which is not specifically limited in the embodiment of the present application. Figure 4 The SiNx avalanche photodetector shown in FIG1 operates under a reverse bias voltage. When it receives a light signal of sufficient intensity, an avalanche multiplication effect occurs, generating a large amount of electrical signals.

[0052] The reverse bias voltage (VH and GND) is provided to the SiNx avalanche photodetector to make it operate in the avalanche multiplication region.

[0053] During the avalanche multiplication process, when the current generated by the SiNx avalanche photodetector reaches a certain threshold, the quenching resistor (R q ) begins to consume current, thereby reducing the gain of the SiNx avalanche photodetector and achieving a quenching effect. This process is "passive" because it does not rely on external control signals.

[0054] After quenching, the reset capacitor provides a short discharge path to restore the output signal of the SiNx avalanche photodetector to its initial state, preparing for the next trigger. This process is also "passive" because it also does not rely on external control signals.

[0055] In summary, the embodiment of the present application proposes a method for preparing a SiNx avalanche photodetector device, which provides stable P-type conductive properties by growing a P-type high-concentration epitaxial layer on a P-type SiNx substrate through epitaxial technology. Subsequently, a layer of intrinsic concentration epitaxial layer is continued to be epitaxially grown on this P-type high-concentration epitaxial layer. This layer serves as the core area of ​​avalanche multiplication and is crucial for achieving high-sensitivity single-photon detection. In the intrinsic epitaxial layer, ion implantation technology is used to inject N-type ions of different concentrations, thereby forming a NIP-type structure. The design of this structure enables the device to produce an avalanche multiplication effect under reverse bias, thereby achieving high-sensitivity detection of single photons.

[0056] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0057] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0058] In the embodiments provided in this application, it should be understood that the disclosed devices / equipment and methods can be implemented in other ways. For example, the device / equipment embodiments described above are merely schematic. For example, the division of the modules or units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0059] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or collections thereof.

[0060] It will also be understood that the term "and / or" used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0061] As used in this specification and the appended claims, the term "if" can be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]," depending on the context.

[0062] In addition, in the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0063] References to "one embodiment" or "some embodiments" in this specification mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in one or more embodiments of the present application. Thus, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," and "in other embodiments" appearing in various places in this specification do not necessarily refer to the same embodiment, but rather mean "one or more but not all embodiments," unless otherwise specifically emphasized. The terms "including," "comprising," "having," and variations thereof all mean "including but not limited to," unless otherwise specifically emphasized.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a SiNx avalanche photodetector, characterized in that: include: Providing a first doping type substrate, and performing doping of a first doping type at a specific concentration on the substrate to form a first epitaxial layer; Performing doping of a first doping type on the first epitaxial layer to form a second intrinsic epitaxial layer; Performing ion implantation of a second doping type on the second intrinsic epitaxial layer to form a first region; Forming a guard ring region by performing ion implantation of a second doping type on the second intrinsic epitaxial layer; The first epitaxial layer and the first region form an avalanche junction region.

2. The method for preparing a SiNx avalanche photodetector according to claim 1, characterized in that: A dielectric layer is formed above the second intrinsic epitaxial layer, and a cathode of the SiNx avalanche photodetector is formed in the dielectric layer through interconnecting metal; and an anode of the SiNx avalanche photodetector is formed on the second surface of the substrate.

3. The method for preparing a SiNx avalanche photodetector according to claim 1, characterized in that: The second intrinsic epitaxial layer is an electron-hole multiplication layer of the SiNx avalanche photodetector. 4 . The method for preparing a SiNx avalanche photodetector according to claim 1 , wherein the thickness of the second intrinsic epitaxial layer is smaller than the thickness of the first epitaxial layer.

5. The method for preparing a SiNx avalanche photodetector according to claim 1, characterized in that: The doping concentration of the second intrinsic epitaxial layer is less than the doping concentration of the first epitaxial layer.

6. The method for preparing a SiNx avalanche photodetector according to claim 1, characterized in that: The guard ring region is adjacent to the first region.

7. The method for preparing a SiNx avalanche photodetector according to claim 1, characterized in that: The junction depth of the guard ring region is greater than the junction depth of the first region.

8. A SiNx avalanche photodetector device, characterized in that: The SiNx avalanche photodetector device is prepared using the SiNx avalanche photodetector preparation method as described in any one of claims 1 to 7, and the SiNx avalanche photodetector device includes: a first doping type substrate, a first epitaxial layer of a first doping type arranged on the first doping type substrate, a second intrinsic epitaxial layer of a first doping type arranged on the first epitaxial layer, a first region of a second doping type arranged on the second intrinsic epitaxial layer, and a guard ring region of a second doping type arranged in the intrinsic epitaxial layer.

9. The SiNx avalanche photodetector device according to claim 8, characterized in that: The SiNx avalanche photodetector device also includes a dielectric layer arranged above the second intrinsic epitaxial layer, a cathode of the SiNx avalanche photodetector is arranged in the dielectric layer through interconnecting metal, and an anode of the SiNx avalanche photodetector is arranged on the second surface of the substrate.

10. The SiNx avalanche photodetector device according to claim 8, characterized in that: The SiNx avalanche photodetector device achieves isolation between devices through shallow trench isolation.

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