Single photon avalanche diode and photoelectric sensing device

Abstract

A single-photon avalanche diode (SPAD) and a photoelectric sensing device are disclosed, relating to the field of optoelectronic technology, which can reduce the breakdown voltage of an avalanche junction (A). The single-photon avalanche diode (SPAD) includes a substrate (10) and an epitaxial layer (20). The epitaxial layer (20) includes a first-type doped region (21) and a second-type doped region (22), a first-type edge doped region (S1) and a second-type edge doped region (S2). The first-type edge doped region (S1) is disposed around the first-type doped region (21). The second-type edge doped region (S2) includes: located in the second-type... The portion surrounding the doped region (22) and opposite to the first type edge doped region (S1); the first type edge doped region (S1) has the same doping type as the first type doped region (21), and the doping concentration of the first type edge doped region (S1) is less than that of the first type doped region (21); the second type edge doped region (S2) has the same doping type as the second type doped region (22), and the doping concentration of the second type edge doped region (S2) is less than that of the second type doped region (22); the doping types of the first type doped region (21) and the second type doped region (22) are opposite.

Description

Technical Field

[0001] This application relates to the field of optoelectronic technology, and in particular to a single-photon avalanche diode and an optoelectronic sensing device. Background Technology

[0002] A single-photon avalanche diode (SPAD) is an avalanche photodiode that operates in reverse bias and in Geiger mode. Due to its advantages such as high gain, low noise, and insensitivity to electromagnetic fields, it is widely used in single-photon and weak light detection and imaging.

[0003] SPAD includes an avalanche junction, and an absorption region is formed in the area directly opposite the avalanche junction. When the breakdown voltage of the avalanche junction (also known as the Geiger breakdown voltage) increases, the area of ​​the absorption region is compressed, which in turn leads to a decrease in photon detection efficiency (PDE). Summary of the Invention

[0004] This application provides a single-photon avalanche diode and a photoelectric sensing device that can reduce the breakdown voltage of the avalanche junction.

[0005] This application provides a single-photon avalanche diode (hereinafter referred to as SPAD) comprising: a substrate and an epitaxial layer located on the substrate; the epitaxial layer includes: a first type doped region and a second type doped region, as well as a first type edge doped region and a second type edge doped region.

[0006] For the first type doped region and the second type doped region mentioned above, the first type doped region and the second type doped region are stacked along the thickness direction of the epitaxial layer, and the second type doped region is closer to the substrate than the first type doped region; the doping types of the first type doped region and the second type doped region are opposite, that is, the doping types of the first type doped region and the second type doped region are N type and P type respectively; an avalanche junction is formed between the first type doped region and the second type doped region.

[0007] Regarding the aforementioned first-type edge doped region, the first-type edge doped region is disposed around the first-type doped region, and the first-type edge doped region has the same doping type as the first-type doped region, while the doping concentration of the first-type edge doped region is lower than that of the first-type doped region; that is, the same type of low-concentration first-type edge doped region is disposed around the first-type doped region.

[0008] For the aforementioned second-type edge doped region, the second-type edge doped region includes: a portion located around the second-type doped region and disposed opposite to the first-type edge doped region; and the second-type edge doped region has the same doping type as the second-type doped region, and the doping concentration of the second-type edge doped region is lower than that of the second-type doped region; that is, a second-type edge doped region of the same type and low concentration is disposed around the second-type doped region.

[0009] In the SPAD provided in this application, a first-type edge doped region with the same doping type and reduced doping concentration is provided around the first-type doped region, and a second-type edge doped region with the same doping type and reduced doping concentration and positioned opposite to the first-type edge doped region is provided. In this case, on the one hand, since the doping concentration of the first-type edge doped region and the second-type edge doped region is reduced, the edge electric field of the avalanche junction formed by the first-type doped region and the second-type doped region can be reduced; on the other hand, by providing the second-type edge doped region in the opposite region of the first-type edge doped region, the second-type edge doped region can block the depletion region (i.e., the space charge region formed by the recombination of electrons and holes) formed by the first-type edge doped region, thereby reducing the depletion rate of the first-type edge doped region on the epitaxial layer and preventing the first-type edge doped region from being depleted to the absorption region before the first-type doped region is depleted to the absorption region.

[0010] It is understandable here that if the Type II edge doped region does not block the depletion region formed by the Type I edge doped region, when the Type I edge doped region is depleted to the absorption region first, most of the photogenerated carriers generated in the absorption region will enter the Type I edge doped region along the direction of the electric field, and will not enter the avalanche multiplication region (i.e., the avalanche junction region) formed by the Type I and Type II doping regions, thus failing to effectively trigger avalanche multiplication. Furthermore, the depletion of the Type I edge doped region in the absorption region will reduce the actual voltage applied across the avalanche junction, thereby increasing the actual required Geiger breakdown voltage, leading to an increase in the applied supply voltage and an increase in the power consumption of the entire system.

[0011] In other words, the second-type edge doped region in this application can block the depletion region formed by the first-type edge doped region, reducing the depletion rate of the first-type edge doped region on the epitaxial layer. This ensures that the first-type edge doped region is depleted to the absorption region before the first-type doped region is depleted to the absorption region. Consequently, most of the photogenerated carriers generated in the absorption region will enter the avalanche multiplication region formed by the first-type doped region and the second-type doped region along the direction of the electric field, effectively triggering avalanche multiplication. This avoids the voltage drop across the avalanche junction caused by the depletion of the first-type edge doped region in the absorption region, thereby reducing the Geiger breakdown voltage. At the same time, it can also increase the effective area of ​​the absorption region, thereby increasing the fill factor of the absorption region and improving the photon detection efficiency (PDE) of the SPAD.

[0012] Especially for SPADs in small-sized pixels, the setting method of this application can avoid the problems caused by the use of thick silicon technology, such as the area of ​​the effective light absorption area being drastically compressed, the Geiger breakdown voltage being increased, and deviation from the design value. It effectively ensures the requirements of SPADs in small-sized pixels for parameters such as fill factor, PDE, and Geiger breakdown voltage.

[0013] In some possible implementations, the second-type edge doped region contacts the edge region of the second-type doped region; in this case, the second-type edge doped region largely blocks the depletion region (i.e., the space charge region formed by the recombination of electrons and holes) formed by the first-type edge doped region, thereby reducing the depletion rate of the first-type edge doped region on the epitaxial layer.

[0014] In some possible implementations, the aforementioned second-type edge doped region may include at least two doped regions arranged sequentially in a direction away from the second-type doped region, with the doping concentration decreasing sequentially. In this way, the edge electric field can be flexibly adjusted, and in conjunction with the arrangement of the first-type edge doped region, the Geiger breakdown voltage of the avalanche junction can be reduced.

[0015] In some possible implementations, the first-type edge doped region may include at least two doped regions with doping concentrations decreasing sequentially in a direction away from the first-type doped region; this allows for flexible adjustment of the edge electric field and, in conjunction with the setting of the first-type edge doped region, simultaneously achieves the purpose of reducing the Geiger breakdown voltage of the avalanche junction.

[0016] In some possible implementations, the doping depth of the first type edge doped region can be set to gradually increase in the direction away from the first type doped region; the doping depth of the first type edge doped region is greater than or equal to the doping depth of the second type doped region, and the first type edge doped region and the second type edge doped region are in contact in opposite regions.

[0017] In this case, the electric field strength formed between the first-type edge doped region and the second-type edge doped region in the SPAD is less than the electric field strength of the avalanche junction formed by the first-type doped region and the second-type doped region. At the same time, the radius of curvature of the electric field at the edge of the avalanche junction is increased, thereby reducing the edge electric field effect and reducing the surface electric field of the avalanche junction.

[0018] In some possible implementations, the first type edge doped region includes: a first doped region; the doping depth of the first doped region is greater than or equal to the doping depth of the second type doped region; the second type edge doped region includes: a second doped region; the second doped region is disposed opposite to the first doped region and the second doped region is in contact with the first doped region.

[0019] In this case, in the SPAD, the avalanche electric field that causes Geiger breakdown is concentrated between the first-type doped region and the second-type doped region, and the breakdown voltage is determined by the concentration and distribution of the first-type doped region and the second-type doped region. The electric field strength formed between the first-type edge doped region and the second-type edge doped region is less than the avalanche junction electric field strength formed by the first-type doped region and the second-type doped region. At the same time, the radius of curvature at the edge of the electric field is increased, thereby reducing the edge electric field effect and reducing the surface electric field of the avalanche junction.

[0020] In some possible implementations, the second-type edge doped region also includes: a third doped region; the doping concentration of the third doped region is greater than that of the second doped region; the third doped region is located on the side of the second doped region closest to the second-type doped region, and the third doped region is in contact with both the second doped region and the second-type doped region.

[0021] In this scenario, within the SPAD, on one hand, the avalanche electric field is concentrated between the first-type doped region and the second-type doped region. The electric fields between the first and third doped regions, between the first and second doped regions, and between the third doped region and the first-type doped region are all lower than the avalanche electric field between the first and second doped regions. Simultaneously, the radius of curvature at the edge of the electric field is increased, thereby reducing the edge electric field effect and decreasing the surface electric field of the avalanche junction. On the other hand, by adding a third doped region to the side of the second doped region closer to the second-type doped region, the doping position and concentration of the third doped region can be adjusted relatively flexibly. This allows for a reduction in the edge electric field strength of the avalanche region while ensuring that the first doped region does not affect or minimizes its impact on the effective absorption region during depletion.

[0022] In some possible implementations, the third doped region is located on the substrate-proximity side of the second type doped region and is in contact with the substrate-proximity side of the second type doped region. Indicatively, the third doped region may be in contact with the substrate-proximity side of the second type doped region, and this third doped region may be in contact with both the second and first doped regions on the side proximity to the second doped region.

[0023] In some possible implementations, the third doped region is located between the second-type doped region and the first doped region, and the third doped region is in contact with the second-type doped region, the first doped region, and the second doped region. In this configuration, the presence of the third doped region helps to decouple the edge electric field of the avalanche junction, enabling flexible control of the electric field at the edge of the avalanche junction.

[0024] In some possible implementations, the first type edge doped region may further include a fourth doped region in addition to the aforementioned doped regions. This fourth doped region is located on the side of the first doped region away from the first type doped region, and the doping depth of the fourth doped region is greater than or equal to the doping depth of the first doped region, and the doping concentration of the fourth doped region is less than the doping concentration of the first doped region. The second type edge doped region may further include a fifth doped region in addition to the aforementioned doped regions. This fifth doped region is positioned opposite to the fourth doped region and is in contact with both the second and fourth doped regions. Furthermore, the doping concentration of this fifth sub-doped region is less than the doping concentration of the second doped region.

[0025] In this case, the avalanche electric field in the SPAD is concentrated between the first-type doped region and the second-type doped region. The electric fields between the first-type doped region and the second-type doped region, between the first-type doped region and the second-type doped region, between the fourth-type doped region and the second-type doped region, and between the fourth-type doped region and the fifth-type doped region are all lower than the avalanche electric field between the first-type doped region and the second-type doped region. Furthermore, the electric field strength of this uniform transition electric field decreases along the direction away from the avalanche electric field, the potential distribution moves further and further away from the surface of the avalanche junction, and the radius of curvature of the electric field increases. This reduces the influence of the guard ring and the edge depletion region on the avalanche junction and the absorption region, while also reducing the edge electric field effect, decreasing the surface electric field at the edge of the avalanche junction, and reducing the dark current.

[0026] In some possible implementations, the doping depth of the first-type edge doped region is less than that of the first-type doped region, and the doping depth of the first-type edge doped region decreases in the direction away from the first-type doped region; the distance between the first-type edge doped region and the second-type edge doped region gradually increases in the direction away from the first-type doped region.

[0027] In this case, in the SPAD, the doping concentrations of both the first-type edge doped region and the second-type edge doped region decrease along the direction away from the avalanche junction, and the distance between the first-type edge doped region and the second-type edge doped region gradually increases. As a result, the electric field strength formed between the first-type edge doped region and the second-type edge doped region is less than the avalanche junction electric field strength formed by the first-type doped region and the second-type doped region. Furthermore, the electric field strength formed between the first-type edge doped region and the second-type edge doped region decreases along the direction away from the avalanche junction, thereby reducing the edge electric field effect, reducing the surface electric field of the avalanche junction, and reducing the dark current.

[0028] In some possible implementations, the first type edge doped region includes: a sixth doped region and a seventh doped region arranged sequentially along a direction away from the first type doped region; the doping concentration of the seventh doped region is less than the doping concentration of the sixth doped region, and the doping depth of the seventh doped region is less than the doping depth of the sixth doped region; the second type edge doped region includes: an eighth doped region and a ninth doped region arranged sequentially and continuously along a direction away from the second type doped region; the doping concentration of the ninth doped region is less than the doping concentration of the eighth doped region; the sixth doped region is arranged opposite to the eighth doped region, and the seventh doped region is arranged opposite to the ninth doped region; the distance between the seventh doped region and the ninth doped region is greater than the distance between the sixth doped region and the eighth doped region.

[0029] In some possible implementations, the doping thickness of the ninth doped region is less than that of the eighth doped region.

[0030] In some possible implementations, the sixth edge doped region has the same shape and size as the eighth edge doped region; the seventh edge doped region has the same shape and size as the ninth edge doped region; thereby reducing the number of layouts used in the fabrication process.

[0031] In some possible implementations, the first-type edge doped region is in contact with the side of the first-type doped region.

[0032] In some possible implementations, the doping type of the first type doped region is N-type; the doping type of the second type doped region is P-type.

[0033] This application also provides an optoelectronic sensing device, including a sensor array and a logic circuit, wherein at least one sensor in the sensor array includes a single-photon avalanche diode as provided in any of the aforementioned possible implementations; the logic circuit is connected to the single-photon avalanche diode. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of a photoelectric sensing device provided in an embodiment of this application;

[0035] Figure 2 This is a schematic diagram of the structure of a SPAD provided in an embodiment of this application;

[0036] Figure 3 for Figure 2 Top view of the epitaxial layer;

[0037] Figure 4 This is a schematic diagram of the structure of a SPAD provided in an embodiment of this application;

[0038] Figure 5 This is a schematic diagram of the structure of a SPAD provided in an embodiment of this application;

[0039] Figure 6 This is a schematic diagram of the structure of a SPAD provided in an embodiment of this application;

[0040] Figure 7 This is a schematic diagram of the structure of a SPAD provided in an embodiment of this application;

[0041] Figure 8 This is a schematic diagram of the structure of a SPAD provided in an embodiment of this application;

[0042] Figure 9 This is a schematic diagram of the structure of a SPAD provided in an embodiment of this application;

[0043] Figure 10 This is a schematic diagram of the structure of a SPAD provided in an embodiment of this application. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0045] The terms "first," "second," etc., used in the specification, embodiments, claims, and drawings of this application are for distinguishing purposes only and should not be construed as indicating or implying relative importance or order. Terms such as "connected," "linked," etc., are used to express communication or interaction between different components, and may include direct connection or indirect connection through other components. "At least one" means one or more, and "more" means two or more. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, such as including a series of steps or units. A method, system, product, or device is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or devices. Terms such as "upper," "lower," "left," and "right," etc., are used only with respect to the orientation of components in the drawings. These directional terms are relative concepts used for relative description and clarification and may vary accordingly depending on the orientation of the components in the drawings.

[0046] This application provides a photoelectric sensing device. This application does not limit the specific configuration or application field of the photoelectric sensing device. For example, the photoelectric sensing device can be applied to fields such as weak light detection, imaging, and direct time of flight (DTOF) ranging. It realizes photoelectric detection by converting the received light into an electrical signal.

[0047] As illustrated, the aforementioned photoelectric sensing device can be an image sensor; for example, it can be a CMOS (complementary metal oxide semiconductor) chip; of course, the photoelectric sensing device can also be an electronic device containing an image sensor; for example, LiDAR, medical devices, mobile phones, digital cameras, etc.; this application does not limit it in any way.

[0048] In some possible ways of implementation, such as Figure 1 As shown, the above-mentioned photoelectric sensing device includes a sensor array 100 and a logic circuit 200; wherein, the sensor array 100 includes a plurality of single-photon avalanche diodes (SPADs) arranged in an array, and the logic circuit 200 is connected to each SPAD.

[0049] As illustrated, in some possible implementations, the aforementioned SPAD can be a thick silicon SPAD applied to the near-infrared band.

[0050] In the aforementioned photoelectric sensing device, a reverse bias voltage (greater than the Geiger breakdown voltage) is provided to the SPAD in the sensor array 100 through the logic circuit 200, controlling the SPAD to operate in Geiger mode. The avalanche effect is generated by the directional movement of photogenerated carriers in a strong electric field to perform photoelectric detection.

[0051] The photoelectric sensing device provided in this application uses SPADs (partially or entirely) in its sensor array, which have advantages such as high fill factor, high photon detection efficiency (PDE), and low avalanche junction breakdown voltage. This results in a lower external power supply voltage required by the photoelectric sensing device and lower power consumption of the entire system.

[0052] As illustrated, in some possible implementations, all SPADs in the sensor array can adopt the SPAD structure provided in the following embodiments of this application.

[0053] The specific settings of the SPAD provided in the embodiments of this application are described below.

[0054] like Figure 2 , Figure 3 ( Figure 2As shown in the top view of the epitaxial layer, the SPAD includes a substrate 10 and an epitaxial layer 20 located on the substrate 10; wherein, a first type doped region 21 and a second type doped region 22 are provided in the epitaxial layer 20, and an avalanche junction A is formed between the first type doped region 21 and the second type doped region 22.

[0055] The first type doped region 21 and the second type doped region 22 are stacked along the thickness direction of the epitaxial layer 20, with the second type doped region 22 closer to the substrate 10 than the first type doped region 21; in this case, an absorption region C1 is formed below the second type doped region 22. (Illustratively, as shown...) Figure 2 As shown, the first type doped region 21 can be located on the surface of the epitaxial layer 20 away from the substrate 10, and the second type doped region 22 is located below the first type doped region 21.

[0056] For the avalanche junction A formed by the first type doped region 21 and the second type doped region 22, it can be understood that when the doping type of the first type doped region 21 is P-type, the doping type of the second type doped region 22 is N-type; when the doping type of the first type doped region 21 is N-type, the doping type of the second type doped region 22 is P-type; that is, the doping types of the first type doped region 21 and the second type doped region 22 are opposite. The following embodiments of this application are all described with the example of the first type doped region 21 being N-type and the second type doped region 22 being P-type. In this case, the substrate 10 can be a heavily doped P-type semiconductor (such as heavily doped P-type silicon), and the epitaxial layer 20 can be a lightly doped P-type semiconductor (such as a lightly doped P-type thick silicon structure).

[0057] Based on this, refer to Figure 2 As shown, the SPAD also includes: a first-type edge doped region S1 (reference) surrounding the first-type doped region 21. Figure 3 As shown), the doping type of the first type edge doped region S1 is the same as that of the first type doped region 21 (for example, both can be N-type doped), and the doping concentration of the first type edge doped region S1 is less than that of the first type doped region 21.

[0058] Additionally, refer to Figure 2 As shown, the SPAD also includes a second type edge doped region S2 with the same doping type as the second type doped region 21 and a lower doping concentration than the second type doped region 21 (for example, the second type doped region 21 and the second type edge doped region S2 can both be P-type doped). The second type edge doped region S2 includes a portion located around the second type doped region 21 and disposed opposite to the first type edge doped region 21.

[0059] It should be noted here that the first type edge doped region S1 and the second type edge doped region S2 can be in contact in their respective regions (e.g., Figure 2 As shown), it can also be done without contact (e.g. Figure 4 (As shown), this application does not impose any restrictions on this.

[0060] Furthermore, the shape of the first-type edge doped region S1 can be adapted to the shape of the first-type doped region 21, for example, referring to... Figure 3 As shown, when the first type doped region 21 is a circular structure, the first type edge doped region S1 can be a ring-shaped structure (i.e., a circular protective ring structure) arranged around the first type doped region 21; of course, when the first type doped region 21 is a rectangular structure, the first type edge doped region S1 can be a rectangular ring-shaped structure (i.e., a rectangular protective ring structure); similarly, the arrangement of the second type edge doped region S2 can also be a ring-shaped structure, a rectangular ring-shaped structure, etc., that are adapted to the shape of the second type doped region 22.

[0061] In the SPAD provided in this application, a first-type edge doped region S1 with the same doping type and reduced doping concentration is provided around the first-type doped region 21, and a second-type edge doped region S2 with the same doping type and reduced doping concentration as the second-type doped region 22 is provided and is provided opposite to the first-type edge doped region S1. In this case, on the one hand, since the doping concentration of the first-type edge doped region S1 and the second-type edge doped region S2 is reduced, the edge electric field of the avalanche junction A formed by the first-type doped region 21 and the second-type doped region 22 can be reduced; on the other hand, by providing the second-type edge doped region S2 in the opposite region of the first-type edge doped region S1, the second-type edge doped region S2 can block the depletion region (i.e., the space charge region formed by the recombination of electrons and holes) formed by the first-type edge doped region S1, reduce the depletion rate of the first-type edge doped region S1 on the epitaxial layer 20, and prevent the first-type edge doped region S1 from being depleted to the absorption region C1 before the first-type doped region 21 is depleted to the absorption region C1.

[0062] It is understandable here that if the second-type edge doped region S2 does not block the depletion region (i.e., the space charge region formed by the recombination of electrons and holes) formed by the first-type edge doped region S1, when the first-type edge doped region S1 is depleted to the absorption region C1 first, most of the photogenerated carriers generated in the absorption region C1 will enter the first-type edge doped region S1 along the direction of the electric field, and will not enter the avalanche multiplication region (i.e., the region of avalanche junction A) formed by the first-type doped region 21 and the second-type doped region 22, thus failing to effectively trigger avalanche multiplication; and the depletion of the first-type edge doped region S1 in the absorption region C1 will reduce the actual voltage applied across the avalanche junction, thereby increasing the actual required Geiger breakdown voltage, leading to an increase in the applied supply voltage and an increase in the power consumption of the entire system.

[0063] In other words, the second-type edge doped region S2 in this application can block the depletion region (i.e., the space charge region formed by the recombination of electrons and holes) formed by the first-type edge doped region S1, reducing the depletion rate of the first-type edge doped region S1 on the epitaxial layer 20. This ensures that the first-type edge doped region S1 is depleted to the absorption region C1 before the first-type doped region 21 is depleted to the absorption region C1. Consequently, most of the photogenerated carriers generated in the absorption region C1 will enter the avalanche multiplication region formed by the first-type doped region 21 and the second-type doped region 22 along the direction of the electric field, effectively triggering avalanche multiplication. This avoids the voltage drop across the avalanche junction caused by the depletion of the first-type edge doped region S1 in the absorption region C1, thereby reducing the Geiger breakdown voltage. At the same time, it can also increase the effective area of ​​the absorption region C1, thereby increasing the fill factor of the absorption region and improving the photon detection efficiency (PDE) of the SPAD.

[0064] Of course, in order to further block the depletion region (i.e., the space charge region formed by the recombination of electrons and holes) formed by the first edge doped region S1 through the second type edge doped region S2, and to reduce the depletion rate of the first type edge doped region S1 on the epitaxial layer 20, in some possible implementation methods, refer to Figure 2 and Figure 4 As shown, the second type edge doped region S2 can be set to contact the edge region of the second type doped region 22 and extend to the region opposite to the first type edge doped region S1.

[0065] Furthermore, it is understandable that as the lateral size of image sensor pixels decreases, especially when pixel size shrinks to the micrometer level, the area of ​​the effective light absorption region of SPADs using thick silicon technology is drastically compressed, leading to a sharp decrease in PDE, especially for longer wavelength incident photons. At the same time, the reduction in pixel size causes an increase in the Geiger breakdown voltage of the avalanche junction of the thick silicon SPAD, deviating from the design value, and causing significant problems for the use of SPADs in low-power applications. Based on this, the SPAD provided in the embodiments of this application can effectively solve the various drawbacks caused by the reduction in the lateral size of pixels. In other words, the SPAD provided in the embodiments of this application can well meet the requirements of SPADs in small-sized pixels for parameters such as fill factor, PDE, and Geiger breakdown voltage.

[0066] It should also be noted that, in this application, the first type edge doped region S1 can contact the four edges of the first type doped region 21 (e.g., Figure 2 As shown), it can also not contact the periphery of the first type doped region 21 (as shown). Figure 4 As shown in the figure, this application does not impose any restrictions on this, and in practice, it can be set as needed.

[0067] The doping depth of the first-type edge doped region S1 can be greater than the doping depth of the first-type doped region 21 (e.g., Figure 2 As shown), the doping depth can also be smaller than that of the first type doped region 21 (e.g., Figure 4 (as shown); This application does not limit the doping depth of the first type edge doped region S1, which can be set as needed in practice.

[0068] Indicatively, in some possible implementations, both the first type edge doped region S1 and the first type doped region 21 extend downward from the side surface of the epitaxial layer 20 away from the substrate 10, that is, both the first type edge doped region S1 and the first type doped region 21 are obtained by doping from the side surface of the epitaxial layer 20 away from the substrate 10.

[0069] Furthermore, it is understood that SPADs typically include electrodes (E1, E2) and other structures in addition to the aforementioned doped regions. This application does not impose any restrictions on these, and they can be configured as needed in practice. For example, ... Figure 2 , Figure 4 As shown, an insulating dielectric layer can be disposed on the surface of the epitaxial layer 20, and a first electrode E1 (which can be a cathode) connected to the first type doped region 21 is disposed on the surface of the insulating dielectric layer, and a second electrode E2 (which can be an anode) is disposed on the lower surface of the substrate 10 (i.e. the surface away from the epitaxial layer 20).

[0070] For the aforementioned first-type edge doped region S1 with a doping concentration lower than that of the first-type doped region 21:

[0071] Among some possible implementation methods, refer to Figure 2 , Figure 4 , Figure 5 , Figure 6 , Figure 7 As shown, the first type edge doped region S1 can be a doped region with a basically uniform doping concentration.

[0072] In some possible implementations, the doping concentration of the first-type edge doped region S1 can be a doped region in which the doping concentration gradually decreases in the direction away from the first-type doped region 21; for example, the first-type edge doped region S1 can be a doped region in which the doping concentration gradually decreases in the direction away from the first-type doped region 21; as another example, refer to Figure 8 , Figure 9 , Figure 10 As shown, the first type edge doped region S1 can also be a plurality of doped regions with doping concentration decreasing sequentially in the direction away from the first type doped region 21; schematically, each doped region in the first type edge doped region S1 can be a ring structure; of course, when the first type edge doped region S1 includes multiple doped regions, the multiple doped regions may or may not be in contact, and this application does not impose any restrictions on this.

[0073] It should be noted that, compared to Figure 2 , Figure 4 , Figure 5 , Figure 6 , Figure 7 In the case of the first type edge doped region S1, which uses a doped region with a basically uniform doping concentration, Figure 8 , Figure 9 , Figure 10 The first type edge doped region S1 consists of multiple doped regions with the same doping type and decreasing doping concentration in a direction away from the first type doped region 21. In conjunction with the setting of the first type edge doped region S1, the Geiger breakdown voltage of the avalanche junction can be reduced, and the edge electric field can be flexibly adjusted.

[0074] For the second-type edge doped region S2, where the doping concentration is lower than that of the second-type doped region 22:

[0075] Among some possible implementation methods, refer to Figure 2 , Figure 4 As shown, the second type edge doped region S2 can be a doped region with a basically uniform doping concentration.

[0076] In some possible implementations, the doping concentration of the second-type edge doped region S2 can gradually decrease in the direction away from the first-type doped region 21; for example, the second-type edge doped region S2 can be a doped region in which the doping concentration gradually decreases in the direction away from the first-type doped region 21; or, for example, referring to... Figures 8 to 10 As shown, the second type edge doped region S2 can be a plurality of continuously arranged doped regions with doping concentration decreasing sequentially in the direction away from the second type doped region 22; schematically, each doped region in the second type edge doped region S2 can be a ring structure.

[0077] Compared to Figure 2 , Figure 4 , Figure 5 In the case of the second type edge doped region S2, which uses a doped region with a basically uniform doping concentration, Figures 8 to 10 The second type edge doped region S2 consists of multiple consecutively arranged doped regions with the same doping type and decreasing doping concentration in a direction away from the second type doped region 22. In conjunction with the first type edge doped region S1, it can reduce the Geiger breakdown voltage of the avalanche junction and also flexibly adjust the edge electric field.

[0078] The following is a schematic explanation of the specific arrangement of the first-type edge doped region S1 and the second-type edge doped region S2, which, while reducing the Geiger breakdown voltage of the avalanche junction A, also reduces the edge electric field effect and decreases the surface electric field of the avalanche junction A.

[0079] Setup Method 1

[0080] Among some possible implementation methods, refer to Figure 5 , Figure 6 , Figure 7 , Figure 8 As shown, the doping depth of the first type edge doped region S1 can be set to be greater than or equal to the doping depth of the second type doped region 22, and the first type edge doped region S1 and the second type edge doped region S2 are in contact in opposite regions (that is, a PN junction is formed between the first type edge doped region S1 and the second type edge doped region S2). In this case, the electric field strength formed between the first type edge doped region S1 and the second type edge doped region S2 is less than the avalanche junction electric field strength formed by the first type doped region 21 and the second type doped region 22. At the same time, the radius of curvature of the electric field at the edge of the avalanche junction is increased, thereby reducing the edge electric field effect and reducing the surface electric field of the avalanche junction.

[0081] The following specific embodiments illustrate the specific configuration structure of the first type edge doped region S1 and the second type edge doped region S2 under this configuration method.

[0082] Example 1

[0083] like Figure 5 As shown, in this embodiment, the first type edge doped region S1 includes: a first doped region 1; the doping depth of the first doped region 1 is greater than or equal to the doping depth of the second type doped region 22. Figure 5 (This is just an illustrative example, taking the doping depth of the first doped region 1 as being greater than the doping depth of the second type doped region 22 as an example); The second type edge doped region S2 includes: a second doped region 2, which is disposed opposite to the first doped region 1 and is in contact with the first doped region 1.

[0084] In this case, the avalanche electric field that causes Geiger breakdown is concentrated between the first type doped region 21 and the second type doped region 22, and the breakdown voltage is determined by the concentration and distribution of the first type doped region 21 and the second type doped region 22. The electric field strength formed between the first type edge doped region S1 and the second type edge doped region S2 is less than the avalanche junction electric field strength formed by the first type doped region 21 and the second type doped region 22. At the same time, the radius of curvature at the edge of the electric field is increased, thereby reducing the edge electric field effect and reducing the surface electric field of the avalanche junction.

[0085] Example 2

[0086] like Figure 6 , Figure 7As shown, the difference between this second embodiment and the first embodiment is that the second type edge doped region S2 also includes a third doped region 3. This third doped region 3 is located on the side of the second doped region 2 closest to the second type doped region 22, and it is in contact with both the second doped region 2 and the second type doped region 22. The doping concentration of the third doped region 3 is less than that of the second type doped region 22, but greater than that of the second doped region 2. In other words, the second type edge doped region S2 includes two doped regions (3, 2) whose doping concentration decreases along a direction away from the second type doped region 22 and are continuously arranged.

[0087] In this case, by setting the third doped region 3, the edge region of the second type edge doped region S2 can be made to contact the edge region of the second type doped region 22, thereby blocking the depletion region formed by the first type edge doped region S1 to a greater extent and reducing the depletion rate of the first type edge doped region S1 on the epitaxial layer 20.

[0088] It should be noted that the second type doped region 22 and the third doped region 3 may overlap to some extent during the ion implantation process, so special design can be made during layout design.

[0089] Regarding the specific configuration of the third doped region 3 mentioned above:

[0090] In some possible ways of implementation, such as Figure 6 As shown, the third doped region 3 can be located on the side of the second type doped region 2 near the substrate 10, and the third doped region 3 is in contact with the side of the second type doped region 22 near the substrate 10. Furthermore, the third doped region 3 is in contact with both the second doped region 2 and the first doped region 1 on the side near the second doped region 2.

[0091] In some possible ways of implementation, such as Figure 7 As shown, the third doped region 3 can be located between the second type doped region 22 and the first doped region 1, and the third doped region 3 is in contact with the second type doped region 22, the first doped region 1, and the second doped region 2. Of course, the third doped region 3 may or may not be in contact with the first type doped region 21. This application does not impose any restrictions on this, and it can be set as needed in practice. Figure 7 The illustration is merely illustrative, using the contact between the third doped region 3 and the first type doped region 21 as an example.

[0092] In this case, the avalanche electric field is concentrated between the first type doped region 21 and the second type doped region 22. The electric fields between the first doped region 1 and the third doped region 3, between the first doped region 1 and the second doped region 2, and between the third doped region 3 and the first type doped region 21 are all lower than the avalanche electric field between the first type doped region 21 and the second type doped region 22. At the same time, the radius of curvature at the edge of the electric field is increased, thereby reducing the edge electric field effect and decreasing the surface electric field of the avalanche junction.

[0093] It should be noted that, compared to Figure 6 The arrangement of the third doped region 3 shown in the figure adopts... Figure 7 The arrangement of the third doped region 3, as illustrated in the diagram, helps to decouple the edge electric field of the avalanche junction A. The third doped region 3 enables flexible control of the edge electric field of the avalanche junction A.

[0094] Furthermore, it is understandable that, compared to the configuration without a third doped region 3 in Embodiment 1, if the concentration and position of the second doped region 2 are not properly set during the depletion process of the first type doped region 1, under certain conditions, the first doped region 1 may bypass the second doped region 2 and consume the area of ​​the absorption region, which is not conducive to improving the fill factor and reducing the breakdown voltage. In contrast, in this Embodiment 2, by adding a third doped region 3 on the side of the second doped region 2 close to the second type doped region 22, the doping position and concentration of the third doped region 3 can be adjusted relatively flexibly. Thus, while reducing the electric field strength at the edge of the avalanche region, it is ensured that the first doped region 1 does not affect or minimizes its impact on the effective absorption region during the depletion process.

[0095] Example 3

[0096] like Figure 8 As shown, the difference between this third embodiment and the aforementioned first embodiment is that: the first type edge doped region S1 includes the first doped region 1 and also includes a fourth doped region 4 disposed on the side of the first doped region 1 away from the first type doped region 21; the second type edge doped region S2 includes the second doped region 2 and also includes a fifth doped region 5 disposed on the side of the second doped region 2 away from the second type doped region 22.

[0097] The doping depth of the fourth doped region 4 is greater than that of the first doped region 1, and the doping concentration of the fourth doped region 4 is less than that of the first doped region 1; that is, the first type edge doped region S1 includes multiple doped regions (such as 1 and 4) whose doping concentration decreases sequentially and whose doping depth increases sequentially along the direction away from the first type doped region 21. Of course, the fourth doped region 4 and the first doped region 1 can be in contact or have a certain gap, and this application does not limit this.

[0098] The fifth doped region 5 is positioned opposite to the fourth doped region 4, and the fifth doped region 5 is in contact with the second doped region 2 and the fourth doped region 4; the doping concentration of the fifth sub-doped region 5 is less than the doping concentration of the second doped region 2.

[0099] Compared to Embodiment 1, in Embodiment 3, the doping depth of the first doped region 1 is set to be basically the same as that of the second type doped region 21. Furthermore, a fourth doped region 4 and a fifth doped region 5 with lower doping concentrations are set outside the first doped region 1 and the second doped region 2 (also away from the avalanche junction A). Simultaneously, the doping depth of the fourth doped region 4 is set to be greater than that of the first doped region 1. In this case, the avalanche electric field is concentrated between the first type doped region 21 and the second type doped region 22, while the electric field between the first doped region 1 and the second type doped region 22, and the electric field between the first doped region 1 and the second type doped region 22 are concentrated between the two types. The electric fields between the second doped region 2, between the fourth doped region 4 and the second doped region 2, and between the fourth doped region 4 and the fifth doped region 5 are all lower than the avalanche electric field between the first doped region 21 and the second doped region 22. Furthermore, the electric field strength of this uniform transition electric field decreases along the direction away from the avalanche electric field, the potential distribution moves further and further away from the surface of the avalanche junction, and the radius of curvature of the electric field increases. This reduces the influence of the guard ring and the edge depletion region on the avalanche junction and the absorption region, while also reducing the edge electric field effect, decreasing the surface electric field at the edge of the avalanche junction, and reducing the dark current.

[0100] In addition, compared with Example 3, which sets four doped regions (1, 2, 4, 5) around the avalanche junction A, Example 2 sets three doped regions (1, 2, 3) while achieving the same reduction of edge electric field effect. That is, the number of doped regions in Example 2 is reduced, the number of doping implantations is reduced, and the number of photomasks used is reduced, which simplifies the fabrication process and reduces the fabrication cost.

[0101] It should be noted that the above embodiment three is only illustrated by adding a fourth doped region 4 and a fifth doped region 5 to the SPAD used in embodiment one. In other possible implementations, an SAPD including a third doped region 3 can also be used in embodiment two (such as...). Figure 6 , Figure 7 Based on the above, a fourth doping region 4 and a fifth doping region 5 are added; this application does not impose specific restrictions on this, and in practice, it can be set as needed.

[0102] Setting Method 2

[0103] Among some possible implementation methods, refer to Figure 9 and Figure 10As shown, the doping depth of the first-type edge doped region S1 can be set to be less than the doping depth of the first-type doped region 21, and the doping depth of the first-type edge doped region S1 decreases in the direction away from the first-type doped region 21; at the same time, the distance between the first-type edge doped region S1 and the second-type edge doped region S2 gradually increases in the direction away from the first-type doped region 21; in this case, in the direction away from the avalanche junction A, the doping concentrations of the first-type edge doped region S1 and the second-type edge doped region S2 both become smaller and smaller, and the distance between the first-type edge doped region S1 and the second-type edge doped region S2 gradually increases. In this way, the electric field strength formed between the first-type edge doped region S1 and the second-type edge doped region S2 is less than the avalanche junction electric field strength formed between the first-type doped region 21 and the second-type doped region 22, and in the direction away from the avalanche junction A, the electric field strength formed between the first-type edge doped region S1 and the second-type edge doped region S2 becomes smaller and smaller, thereby reducing the edge electric field effect, reducing the surface electric field of the avalanche junction, and reducing the dark current.

[0104] The specific configuration structure of the first type edge doped region S1 and the second type edge doped region S2 in this configuration method 2 will be described below.

[0105] like Figure 9 , Figure 10 As shown, the first type edge doped region S1 may include a sixth doped region 6 and a seventh doped region 7 arranged sequentially in a direction away from the first type doped region 21; wherein, the doping concentration of the seventh doped region 7 is less than the doping concentration of the sixth doped region 6, and the doping concentration of the sixth doped region 6 is less than the doping concentration of the first type doped region 21.

[0106] As illustrated, in some possible implementation methods, such as Figure 9 , Figure 10 As shown, the doping depth of the sixth doped region 6 is less than the doping depth of the first type doped region 21, and the doping depth of the seventh doped region 7 is less than the doping depth of the sixth doped region 6.

[0107] The second-type edge doped region S2 may include an eighth doped region 8 and a ninth doped region 9 sequentially and continuously arranged in a direction away from the second-type doped region 22; wherein the doping concentration of the ninth doped region 9 is less than the doping concentration of the eighth doped region 8; the ninth doped region 9 is arranged opposite to the seventh doped region 7, the eighth doped region 8 is arranged opposite to the sixth doped region 6, and the distance between the ninth doped region 9 and the seventh doped region 7 is greater than the distance between the eighth doped region 8 and the sixth doped region 6.

[0108] As illustrated, in some possible implementation methods, such as Figure 9 , Figure 10As shown, the doping thickness of the eighth doped region 8 is less than that of the second type doped region 22, and the doping thickness of the ninth doped region 9 is less than that of the eighth doped region 8.

[0109] In addition, in order to reduce the number of patterns (such as photomasks) used in the SPAD fabrication process, in some possible implementations, the sixth edge doped region 6 and the eighth edge doped region 8 can be set to have the same shape and size, that is, the sixth edge doped region 6 and the eighth edge doped region 8 can be doped using the same photomask; in some possible implementations, the seventh edge doped region 7 and the ninth edge doped region 9 can be set to have the same shape and size, that is, the seventh edge doped region 7 and the ninth edge doped region 9 can be doped using the same photomask.

[0110] It should be noted that all doped regions involved in the embodiments of this application can be met through relatively accurate calculation and design.

[0111] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A single photon avalanche diode, characterized in that include: Substrate and epitaxial layer located on said substrate; The epitaxial layer includes: A first type doped region and a second type doped region; wherein the first type doped region and the second type doped region are stacked along the thickness direction of the epitaxial layer, and the second type doped region is closer to the substrate than the first type doped region; the first type doped region and the second type doped region have opposite doping types; A first type edge doped region and a second type edge doped region; wherein, the first type edge doped region is disposed around the periphery of the first type doped region; the second type edge doped region includes: a portion located around the periphery of the second type doped region and disposed opposite to the first type edge doped region along the thickness direction of the epitaxial layer; The second type of edge doped region includes at least two doped regions that are sequentially and continuously disposed along a direction away from the second type of doped region, and whose doping concentration decreases sequentially. The first type edge doped region has the same doping type as the first type doped region, and the doping concentration of the first type edge doped region is less than that of the first type doped region; the second type edge doped region has the same doping type as the second type doped region, and the doping concentration of the second type edge doped region is less than that of the second type doped region.

2. The single-photon avalanche diode according to claim 1, characterized in that, The second type edge doped region is in contact with the edge region of the second type doped region.

3. The single-photon avalanche diode according to claim 1, characterized in that, The first type of edge doped region includes at least two doped regions whose doping concentration decreases sequentially along a direction away from the first type of doped region.

4. The single-photon avalanche diode according to claim 1, characterized in that, The doping depth of the first type edge doped region gradually increases along the direction away from the first type doped region; The doping depth of the first type edge doped region is greater than or equal to the doping depth of the second type doped region, and the first type edge doped region and the second type edge doped region are in contact in opposite regions.

5. The single-photon avalanche diode according to claim 1, characterized in that, The doping depth of the first type edge doped region is smaller than the doping depth of the first type doped region, and the doping depth of the first type edge doped region decreases in the direction away from the first type doped region; The distance between the first type edge doped region and the second type edge doped region gradually increases in the direction away from the first type doped region.

6. The single-photon avalanche diode according to any one of claims 1-4, characterized in that, The first type of edge doped region includes: a first doped region; the doping depth of the first doped region is greater than or equal to the doping depth of the second type of doped region; The second type of edge doped region includes: a second doped region; the second doped region is disposed opposite to the first doped region, and the second doped region is in contact with the first doped region.

7. The single-photon avalanche diode according to claim 6, characterized in that, The second type of edge doped region further includes: a third doped region; the doping concentration of the third doped region is greater than the doping concentration of the second doped region; The third doped region is located on the side of the second doped region that is close to the second type doped region, and the third doped region is in contact with both the second doped region and the second type doped region.

8. The single-photon avalanche diode according to claim 7, characterized in that, The third doped region is located on the side of the second type doped region closest to the substrate and is in contact with the side of the second type doped region closest to the substrate; Alternatively, the third doped region is located between the second type doped region and the first doped region, and the third doped region is in contact with the second type doped region, the first doped region, and the second doped region.

9. The single-photon avalanche diode according to claim 6, characterized in that, The first type of edge doped region includes: a fourth doped region; the fourth doped region is located on the side of the first doped region away from the first type of doped region, and the doping depth of the fourth doped region is greater than or equal to the doping depth of the first doped region, and the doping concentration of the fourth doped region is less than the doping concentration of the first doped region; The second type of edge doped region includes: a fifth doped region; the fifth doped region is disposed opposite to the fourth doped region, and the fifth doped region is in contact with the second doped region and the fourth doped region; the doping concentration of the fifth doped region is less than the doping concentration of the second doped region.

10. The single-photon avalanche diode according to any one of claims 1-3 and 5, characterized in that, The first type of edge doped region includes a sixth doped region and a seventh doped region sequentially disposed along a direction away from the first type of doped region; the doping concentration of the seventh doped region is less than the doping concentration of the sixth doped region, and the doping depth of the seventh doped region is less than the doping depth of the sixth doped region; The second type edge doped region includes an eighth doped region and a ninth doped region sequentially and continuously disposed along a direction away from the second type doped region; the doping concentration of the ninth doped region is less than the doping concentration of the eighth doped region; The sixth doped region is disposed opposite to the eighth doped region, and the seventh doped region is disposed opposite to the ninth doped region; the distance between the seventh doped region and the ninth doped region is greater than the distance between the sixth doped region and the eighth doped region.

11. The single-photon avalanche diode according to claim 10, characterized in that, The doping thickness of the ninth doped region is less than that of the eighth doped region.

12. The single-photon avalanche diode according to claim 10, characterized in that, The sixth doped region has the same shape and size as the eighth doped region; The seventh doped region has the same shape and size as the ninth doped region.

13. The single-photon avalanche diode according to any one of claims 1-5, 7-9, and 11-12, characterized in that, The first type of edge doped region is in contact with the side of the first type of doped region.

14. The single-photon avalanche diode according to any one of claims 1-5, 7-9, and 11-12, characterized in that, The first type of doped region is N-type; The doping type of the second type doped region is P-type.

15. An optoelectronic sensing device, characterized in that include: Sensor array and logic circuitry; at least one sensor in the sensor array comprises a single-photon avalanche diode as described in any one of claims 1-14; The logic circuit is connected to the single-photon avalanche diode.

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