Single photon avalanche diode, receiving chip, receiving sensor and lidar

Abstract

This application belongs to the field of optical device technology and provides a single-photon avalanche diode, a receiving chip, a receiving sensor, and a lidar. By setting a second type of guard ring doped region in a first type of doped epitaxial absorption layer, the distance between the inner side of the second type of guard ring doped region and the avalanche main junction is greater than 0.1 μm and less than 0.6 μm, and the outer side of the second type of guard ring doped region is in contact with a second type of doped conductive region. The doping concentration of the second type of guard ring doped region is greater than that of the second type of doped conductive region, thereby enabling electrons moving from the back to the front of the device to form a high potential region. Photogenerated charge carriers move laterally into the main junction, and by generating an electric field convergence, the avalanche collection efficiency of charge carriers is improved.

Description

Technical Field

[0001] This application belongs to the field of optical device technology, and particularly relates to a single-photon avalanche diode, a receiving chip, a receiving sensor, and a lidar. Background Technology

[0002] A single-photon avalanche diode (SPAD) is a special PN structure sensor operating in Geiger mode. It can absorb, convert, and output electrical pulse signals at light intensities down to the single-photon level, exhibiting extremely high detection sensitivity. Photon detection efficiency (PDE) and dark count rate (DCR) are two important technical indicators of SPADs. A higher PDE indicates a stronger detection capability for weak light; a higher DCR introduces more noise, significantly degrading the device's detection capability. Traditional back-illuminated (BSI) planar junction SPAD devices are the mainstream direction for SPAD device structure due to their compatibility with complementary metal-oxide-semiconductor (CMOS) process platforms. However, related back-illuminated planar junction SPAD devices suffer from slow photogenerated carrier transport and large dead zones, making them prone to lateral soft breakdown and affecting the avalanche collection efficiency of the device. Summary of the Invention

[0003] To address the aforementioned technical problems, embodiments of this application provide a single-photon avalanche diode, a receiving chip, a receiving sensor, and a lidar, aiming to solve the problem that related back-illuminated planar junction SPAD device structures are prone to lateral soft breakdown, which affects the carrier avalanche collection efficiency of the device.

[0004] A first aspect of this application provides a single-photon avalanche diode, the single-photon avalanche diode comprising: Avalanche main knot; A first-doped epitaxial absorption layer covers the avalanche main junction; The second doped conductive region covers the first doped epitaxial absorption layer. The second type of guard ring doped region is disposed within the first type of doped epitaxial absorption layer. The distance between the inner surface of the second type of guard ring doped region and the avalanche main junction is greater than 0.1 μm and less than 0.6 μm. The outer surface of the second type of guard ring doped region is in contact with the second type of doped conductive region. The first electrode is electrically connected to the first end of the avalanche main junction; The second electrode is electrically connected to the second doped conductive region between the insulating isolation structures on both sides of the avalanche main junction.

[0005] In some embodiments, the second type of guard ring doped region has a ring structure, and the avalanche master junction is located on the central axis of the ring structure.

[0006] In some embodiments, the concentration of the second type of guard ring doped region near the edge of the avalanche main junction is less than or equal to 5e16 cm⁻¹. -3 .

[0007] In some embodiments, the doping concentration of the second type of guard ring doped region gradually decreases from the second doped type conductive region toward the central axis of the avalanche main junction.

[0008] In some embodiments, the second type of guard ring doped region includes a plurality of horizontally arranged gradient doped regions, the doping concentrations of the plurality of gradient doped regions being arranged in an arithmetic sequence from the second doped type conductive region toward the central axis of the avalanche main junction.

[0009] In some embodiments, the widths of the plurality of gradient doped regions gradually increase or decrease from the second doped type conductive region toward the central axis of the avalanche master junction.

[0010] In some embodiments, the single-photon avalanche diode further includes: A first type of compensation doped layer is disposed within the first type of doped epitaxial absorption layer. The doping concentration of the first type of compensation doped layer is less than the doping concentration of the first type of doped region within the avalanche main junction. The outer surface of the first type of compensation doped layer is flush with the outer surface of the second type of guard ring doped region, and the inner surface of the first type of compensation doped layer is flush with the inner surface of the second type of guard ring doped region.

[0011] In some embodiments, the avalanche master junction includes a first doped type well region and a second doped type well region, wherein the second doped type well region is formed between the first doped type well region and the central region of the first doped type epitaxial absorption layer.

[0012] In some embodiments, the single-photon avalanche diode further includes: A metal mesh on the back is disposed on the insulating isolation structure; and / or The microlens is disposed opposite to the avalanche master junction and is located on the second doped conductive region.

[0013] A second aspect of this application also provides a receiving chip, the receiving chip including a plurality of single-photon avalanche diodes as described in any of the preceding claims, the plurality of single-photon avalanche diodes being arranged in an array.

[0014] A third aspect of this application also provides a receiving sensor, which includes a plurality of receiving chips as described in any of the preceding claims.

[0015] A fourth aspect of this application also provides a lidar, which includes a transmitting sensor and a receiving sensor, wherein the transmitting sensor is used to transmit a detection laser, and the receiving sensor is used to receive the echo of the detection laser and obtain detection information of a target object based on the echo.

[0016] The beneficial effects of this application embodiment are as follows: By setting a second type of guard ring doped region in the first doped epitaxial absorption layer, the distance between the inner side of the second type of guard ring doped region and the avalanche main junction is greater than 0.1 μm and less than 0.6 μm, the outer side of the second type of guard ring doped region is in contact with the second doped conductive region, and the doping concentration of the second type of guard ring doped region is greater than the doping concentration of the second doped conductive region, thereby enabling electrons moving from the back side of the device to the front side to form a high potential region, and photogenerated charge carriers to move laterally into the main junction, thereby improving the avalanche collection efficiency of charge carriers by generating an electric field convergence. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the single-photon avalanche diode provided in the embodiments of this application. Figure 1 ; Figure 2 This is a schematic diagram of the single-photon avalanche diode provided in the embodiments of this application. Figure 2 ; Figure 3 This is a schematic diagram of the single-photon avalanche diode provided in the embodiments of this application. Figure 3 ; Figure 4 This is a schematic diagram of the single-photon avalanche diode provided in the embodiments of this application. Figure 4 ; Figure 5a , 5b 5c and 5d are partial process flow diagrams of the single-photon avalanche diode provided in the embodiments of this application. Detailed Implementation

[0018] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0019] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0020] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0021] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or at least two of that feature. In the description of this application, "at least two" means one or more, unless otherwise explicitly specified.

[0022] Traditional back-illuminated (BSI) planar junction SPAD devices are the mainstream direction for SPAD device structure due to their compatibility with CMOS process platforms. Taking the N-on-P structure as an example (extendable to P-on-N structure), the main structure of the device includes a microlens for incident light focusing, an Al grid, a P-type doped structure to passivate deep trench isolation (DTI) interface defects and optimize potential distribution, a DTI for physical isolation between avalanche main junctions, a lightly doped p-type epitaxial layer main absorption region, a heavily doped p-type region for providing ohmic contacts, an anode electrode, a P-well doped region of the avalanche diode main junction, an N-well doped region of the main junction, a heavily doped N-type region for cathode ohmic contacts and a cathode electrode, and a metal layer for signal extraction. However, in related single-photon avalanche diodes, there is a problem of easy lateral soft breakdown, which affects the carrier avalanche collection efficiency of the device.

[0023] To address the aforementioned technical problems, this application provides a single-photon avalanche diode, see [link to relevant documentation]. Figure 1As shown, the single-photon avalanche diode includes: an avalanche main junction 100, a first-doped epitaxial absorption layer 6, second-doped conductive regions (second-doped conductive regions 4 and 5), a second-type guard ring doped region 7, a first electrode 610, and a second electrode 710. The first-doped epitaxial absorption layer 6 covers the avalanche main junction 100, and the second-doped conductive regions cover the first-doped epitaxial absorption layer 6. The second-type guard ring doped region 7 is disposed within the first-doped epitaxial absorption layer 6. The distance between the inner surface of the second-type guard ring doped region 7 and the avalanche main junction 100 is greater than 0.1 μm and less than 0.6 μm, and the outer surface of the second-type guard ring doped region 7 contacts the second-doped conductive region 4. The first electrode 610 is electrically connected to the first end of the avalanche main junction 100; the second electrode 710 is electrically connected to the second-doped conductive region 4 between the insulating isolation structures 200 on both sides of the avalanche main junction 100.

[0024] In this embodiment, the avalanche main junction 100 includes an avalanche main junction composed of an N-type doped region and a P-type doped region. Since the doping type of the second doped conductive region 4 is opposite to that of the first doped epitaxial absorption layer 6, it forms a naturally depleted region. Under the SPAD loading voltage, a strong electric field is generated in the first doped epitaxial absorption layer 6, which is beneficial for the collection of photogenerated carriers. By setting a second-type guard ring doped region 7 with the same doping type as the second-type doped conductive region 4 and the second-type doped conductive region 5, a high potential region is formed for electrons moving upward from the bottom, allowing photogenerated carriers a and c to move laterally and enter the main junction of the avalanche main junction 100, i.e., to be transported along path 1. Without the second-type guard ring doped region 7, photogenerated carrier a would move along path 2 and not enter the avalanche main junction, but would be directly collected by the cathode, resulting in the inability of photogenerated carriers to be converted into avalanches, which is detrimental to PDE. Therefore, the second-type guard ring doped region 7 is conducive to generating electric field convergence and improving the carrier avalanche collection efficiency of the device.

[0025] In this embodiment, combined with Figure 2As shown, the distance D1 between the inner surface of the second-type guard ring doped region 7 and the avalanche main junction 100 is greater than 0.1 μm and less than 0.6 μm. If D1 is too large, it will not act as an electron barrier, resulting in poor electron collection efficiency of the device. If D1 is too small, edge soft breakdown is likely to occur, affecting the normal operation of the device. Therefore, when the distance D1 between the inner surface of the second-type guard ring doped region 7 and the avalanche main junction 100 is greater than 0.1 μm and less than 0.6 μm, edge breakdown can be avoided. The specific value of the distance D1 can be determined by the critical electric field strength. When the distance is less than D1, the electric field strength at the edge of the avalanche main junction 100 in the device reaches the critical electric field strength, thereby triggering edge breakdown.

[0026] In some embodiments, the doping concentration of the second type guard ring doped region 7 is greater than the doping concentration of the second doped type conductive region 4, and the doping concentration of the second type guard ring doped region 7 gradually decreases from the second doped type conductive region 4 toward the avalanche main junction 100.

[0027] In some embodiments, the distance D1 between the inner side of the second type guard ring doped region 7 and the avalanche main junction 100 is small, which can ensure an effective electronic barrier. In addition, the doping concentration of the second type guard ring doped region 7 closest to the main junction is less than that of the second type guard ring doped region 7 far from the main junction. Since the doping concentration of the second type guard ring doped region 7 closest to the main junction is smaller, the electric field strength at the edge of the main junction is weakened, thereby reducing the probability of PEB occurrence and ensuring that the single-photon avalanche diode (hereinafter also referred to as a SPAD device) can work normally. The distance D1 between the inner side of the second type guard ring doped region 7 (the side closer to the avalanche main junction 100) and the avalanche main junction 100 is related to the first doped type epitaxial absorption layer 6, the second type guard ring doped region 7, the main junction size of the avalanche main junction 100, and the edge curvature of the avalanche main junction 100.

[0028] In some embodiments, the distance D1 between the inner surface of the second type guard ring doped region 7 and the avalanche main junction 100 is greater than one-fifth of the width of the second type guard ring doped region 7.

[0029] In some embodiments, the second doped conductive region 4 is located on both sides of the pixel, the second doped conductive region 5 is located at the bottom of the pixel, the doping type of the first doped epitaxial absorption layer 6 is N-type doped, the doping type of the second doped conductive region 4 and the second doped conductive region 5 is P-type doped, the first electrode 610 is a cathode electrode, and the second electrode 710 is an anode electrode.

[0030] In some embodiments, the doping type of the first doped epitaxial absorption layer 6 is P-type doping, the doping type of the second doped conductive region 4 and the second doped conductive region 5 is N-type doping, the first electrode 610 is an anode electrode, and the second electrode 710 is a cathode electrode.

[0031] In some embodiments, the avalanche master junction 100 includes a first type doped region and a second type doped region, the second type doped region and the first type doped region forming a PN junction.

[0032] In some embodiments, taking the first doping type epitaxial absorption layer 6 as an example where the doping type is N-type and the second doping type conductive region 4 is P-type doping, combined with... Figure 2 The working principle of the single-photon avalanche diode in this embodiment will be explained. In this case, the first electrode 610 is the cathode electrode and the second electrode 710 is the anode electrode. Under zero bias, the first doped epitaxial absorption layer 6 acts as a weak N-type epitaxial absorption layer. A PN structure is formed between the N-type epitaxial absorption layer (first doped epitaxial absorption layer 6) and the P-type hole conducting region (second doped conducting region 4), which can generate lateral and bottom electric fields pointing towards the N-type epitaxial layer (first doped epitaxial absorption layer 6). This assists in the transport of photogenerated electrons to the central region corresponding to the avalanche main junction 100, significantly improving the utilization efficiency of the epitaxial absorption volume and the collection efficiency (CE) of photogenerated carriers. At this time, the PN junction electric field between the P-type region of the avalanche main junction (the P-type region within the avalanche main junction 100) and the N-type epitaxial absorption layer (the first doped type epitaxial absorption layer 6) can help electrons near the avalanche main junction move away from the main junction region and point towards the undepleted central body region (the central region of the first doped type epitaxial absorption layer 6) on the side of the SPAD main junction facing the back of the device (the light-gathering side). After applying a reverse bias voltage (Vbias) to the SPAD device, i.e., the voltage applied at the cathode electrode (first electrode 610) is higher than the voltage at the anode electrode (second electrode 710), as Vbias increases, after the P-type region of the avalanche main junction is completely depleted, the electric field lines below it begin to reverse, i.e., the electron transport path reverses (transmitting from the central region of the first doped epitaxial absorption layer 6 to the avalanche main junction 100). Under the action of the reverse bias voltage, the electron transport path in this region points to the avalanche main junction region. At the same time, as the reverse bias voltage further increases, the undepleted region of the body-center region of the SPAD device (the central region of the first doped epitaxial absorption layer 6) on the side of the avalanche main junction 100 facing the back of the device is gradually completely depleted, and there is no undepleted region remaining in the body. At this time, the electron transport path all points to the avalanche main junction, which significantly improves the carrier collection efficiency.

[0033] In some embodiments, under zero bias, the depletion state of the body-centered region (the central region of the first-doped epitaxial absorber layer 6) of the SPAD device is related to the doping concentration of the first-doped epitaxial absorber layer 6.

[0034] In some embodiments, if the breakdown voltage of the SPAD device is set relatively low, and the body-centered region of the SPAD device is still not completely depleted under reverse bias conditions, a floating body-centered region will form in the central region of the first doped epitaxial absorber layer 6. This floating body-centered region will create a potential pocket in the undepleted region on the back side of the main junction. During the avalanche, the potential pocket will store a large number of charge carriers. During the recovery charging process after the avalanche ends, these charge carriers can transport a large number of charge carriers into the main junction region through random diffusion or with the assistance of a partial electric field, causing a significant afterpulse effect. Therefore, SPAD devices based on N-type epitaxial absorber layers require regulation of potential and electric field. After eliminating potential pockets, increasing the potential drop from the device's longitudinal direction (from the front to the back) or any location on the SPAD to the avalanche junction can further improve carrier collection efficiency. At the same time, the electric field enhancement introduced by the potential gradient can reduce carrier transport time, thereby improving the time jitter characteristics of the SPAD device, eliminating potential pockets in the potential curve, and realizing the potential distribution of the potential curve in the figure.

[0035] In some embodiments, the doping concentration of the first doped epitaxial absorption layer 6 gradually decreases from the avalanche main junction 100 toward the light-incoming side of the single-photon avalanche diode.

[0036] In this embodiment, the single-photon avalanche diode is a back-illuminated planar junction SPAD device, and the light-incoming side of the single-photon avalanche diode is the back side of the device. Figure 1 As shown, a first metal layer 620 and a second metal layer 720 are disposed on the positive side of the single-photon avalanche diode. The first metal layer 620 is connected to the first electrode 610, and the second metal layer 720 is connected to the second electrode 710.

[0037] In some embodiments, taking N-type doping as the first doping type and P-type doping as the second doping type, in order to form the N-type doped first doping type epitaxial absorption layer 6, in the SPAD device process, if the device epitaxial layer is weakly P-type doped, in order to avoid increasing the complexity of the SPAD process, an unobstructed deep N-type well implantation (DNW) step is introduced before the well layer implantation in the SPAD process to achieve the inversion of the well layer. This scheme can achieve greater freedom in the control of the N-type doping field in the epitaxial absorption region.

[0038] In this embodiment, a deep N-type well implantation (DNW) process is used in the P-type epitaxial layer of the SPAD device region. This allows for high-energy implantation of As or P ions from the front side of the device, achieving a conversion of the epitaxial absorption region doping type from weak P-type to weak N-type inversion. The N-type ion doping concentration is controlled at 1-5 E11 cm⁻¹. -2On the order of magnitude, a volume concentration of 1E15 cm⁻¹ can be achieved. -3 The epitaxial absorption region is doped with N-type background at a magnitude of 100%.

[0039] In some embodiments, a deep N-well implantation (DNW) process is used in the P-type epitaxial layer of the SPAD device region. This allows for multiple high-energy ion implantations from the front side of the device, with each high-energy ion implantation having a different implantation energy, thereby achieving relatively uniform N-type doping within the first doped epitaxial absorption layer 6.

[0040] In this embodiment, for near-infrared enhanced SPAD, the epitaxial absorption layer is generally thick (on the order of 4-10 μm). Based on the actual thickness of the absorption layer, multi-step implantation with different energies and doses of DNW can be selected to achieve relatively uniform N-type well background doping.

[0041] In some embodiments, a deep N-well implantation (DNW) process is used in the P-type epitaxial layer of the SPAD device region, which allows for multiple high-energy ion implantations from the front side of the device, with each high-energy ion implantation having a different implantation energy, to achieve a concentration gradient doping in the vertical direction within the first doping type epitaxial absorption layer 6.

[0042] In some embodiments, the second type of guard ring doped region 7 has a ring structure, the avalanche main junction 100 is located on the central axis of the ring structure, and the distance between the inner ring surface of the ring structure and the avalanche main junction 100 is greater than 0.1 μm and less than 0.6 μm.

[0043] In some embodiments, the concentration of the second type guard ring doped region 7 near the edge of the avalanche main junction 100 is less than or equal to 5e16 cm⁻¹. -3 .

[0044] In this embodiment, the concentration of the second type of guard ring doped region 7 near the edge of the avalanche main junction 100 is set to be less than or equal to 5e16 cm⁻¹. -3 This allows the distance D1 between the inner surface of the second type guard ring doped region 7 and the avalanche main junction 100 to be as small as possible, and increases the threshold for edge breakdown of the device. When the distance D1 between the inner surface of the second type guard ring doped region 7 and the avalanche main junction 100 is greater than 0.1 μm and less than 0.6 μm, the electric field strength at the edge of the avalanche main junction 100 inside the device is less than the critical electric field strength. Thus, soft breakdown will not occur in the edge region of the second type guard ring doped region 7 near the avalanche main junction 100, thereby improving the stability of the device.

[0045] In some embodiments, the doping concentration of the second type guard ring doped region 7 gradually decreases from the second doped type conductive region 4 toward the central axis of the avalanche main junction 100.

[0046] In this embodiment, since the second type guard ring doped region 7 absorbs photogenerated carriers d, it needs to undergo a diffusion process before it can be collected by the avalanche junction to generate an avalanche, or it can be directly collected by the cathode electrode without generating an avalanche. This would have a negative impact on the device's PDE. Therefore, by setting the doping concentration of the second type guard ring doped region 7 to gradually decrease from the second doped type conductive region towards the central axis of the avalanche main junction 100, the second type guard ring doped region 7 near the avalanche main junction 100 has a lower doping concentration, so that this part of the doped region can be depleted by the applied reverse voltage.

[0047] In some embodiments, H2 is greater than the thickness of the avalanche main junction 100, and H2 is the distance between the interface between the avalanche main junction 100 and the dielectric layer on the front side of the device and the lateral perimeter of the second type of guard ring doped region 7.

[0048] Due to the photogenerated carriers (e.g.) generated in the portion of the second-type guard ring doped region 7 near the front side of the device, the second type of guard ring doped region 7 is affected. Figure 1 The photogenerated carriers (e) in the region will be directly collected by the cathode, so this region is actually a "dead zone" and cannot contribute to PDE. Therefore, the distance of H2 is crucial. By setting H2 to be greater than the thickness of the avalanche main junction 100, it is possible to prevent the photogenerated carriers generated in the part of the second type guard ring doped region 7 near the front side of the device from being collected by the cathode.

[0049] In some embodiments, the second type of guard ring doped region 7 includes a plurality of horizontally arranged gradient doped regions, the doping concentrations of the plurality of gradient doped regions being arranged in an arithmetic sequence from the second doped type conductive region 4 toward the central axis of the avalanche main junction 100.

[0050] In this embodiment, combined with Figure 3 As shown, the second type of guard ring doped region 7 includes horizontally arranged gradient doped regions 7-1, 7-2, and 7-3, which are referred to as gradient doped regions 7-1, 7-2, and 7-3 from left to right. The doping concentrations of gradient doped regions 7-1, 7-2, and 7-3 are arranged in an arithmetic sequence, and the doping concentration difference between adjacent gradient doped regions is the same, forming a horizontal doping concentration gradient. Through the horizontally gradual gradient doping design, an electric field step is introduced to assist the transport of photogenerated carriers in the second type of guard ring doped region 7. Since the concentration of the gradient doped region 7-3, which is closest to the avalanche main junction 100, is sufficiently low, the gradient doped region 7-3 is depleted by the applied reverse voltage. That is, it is located in the region of the yellow long dotted line. For carriers a and e, outside the depletion region, the concentration gradient facilitates the lateral diffusion and transport of carriers along the gradient direction, reducing the randomness of the movement. However, after entering the depletion region, they are quickly swept into the amplification region by the electric field, generating an avalanche.

[0051] In some embodiments, the widths of the multiple gradient doping regions gradually increase or decrease in the direction from the second-doped-type conductive region towards the central axis of the avalanche main junction 100.

[0052] In this embodiment, in combination with Figure 3 As shown, taking the second-type guard ring doping region 7 including the horizontally arranged gradient doping regions 7-1, 7-2, and 7-3 as an example, from left to right, they are the gradient doping region 7-1, the gradient doping region 7-2, and the gradient doping region 7-3 in sequence. The doping concentrations of the gradient doping regions 7-1, 7-2, and 7-3 gradually fade, forming a lateral doping concentration gradient. Moreover, the widths of the gradient doping regions 7-1, 7-2, and 7-3 gradually decrease in the direction from the second-doped-type conductive region towards the central axis of the avalanche main junction 100. Since the concentration of the gradient doping region 7-3 closest to the main junction of the avalanche main junction 100 is light enough, it is ensured that the gradient doping region 7-3 is depleted by the applied reverse voltage, that is, within the region of the yellow long dotted line.

[0053] In some embodiments, the doping concentrations of the multiple gradient doping regions in the second-type guard ring doping region 7 form a geometric progression. For example, the doping concentrations of the gradient doping regions 7-1, 7-2, and 7-3 are set in a geometric progression. The doping concentration of the gradient doping region 7-1 is twice the doping concentration of the gradient doping region 7-2, and the doping concentration of the gradient doping region 7-2 is twice the doping concentration of the gradient doping region 7-3.

[0054] In some embodiments, in combination with Figure 4 As shown, the single-photon avalanche diode further includes: a first-type compensation doping layer 8. The first-type compensation doping layer 8 is disposed within the first-doped-type epitaxial absorption layer 6. The doping concentration of the first-type compensation doping layer 8 is less than the doping concentration of the first-type doping region within the avalanche main junction 100. The outer side surface of the first-type compensation doping layer is flush with the outer side surface of the second-type guard ring doping region 7, and the inner side surface of the first-type compensation doping layer is flush with the inner side surface of the second-type guard ring doping region 7.

[0055] In this embodiment, one or several first-doped-type doping regions are implanted above the second-type guard ring doping region 7 to form the first-type compensation doping layer 8. The doping type of the first-type compensation doping layer is opposite to the doping type of the second-type guard ring doping region 7. Therefore, compensation doping can be performed to reduce the longitudinal volume of the second-type guard ring doping region 7, and it can make D2’ < D2. In some embodiments, in combination with Figure 4As shown, H1 is the distance between the lateral central axis of the first type of compensation doped layer and the dielectric layer interface on the front side of the device, and H2' is the distance between the lateral central axis of the second type of guard ring doped region 7 and the dielectric layer interface on the front side of the device. By setting the first type of compensation doped layer, H2' H_min is the safe distance to prevent PEB. Due to the addition of the first type of compensation doping layer 8, the region of the second type of guard ring doped region 7 near the front side of the device is compensated with doping, reducing the equivalent width D2 of the second type of guard ring doped region 7. This further reduces the volume of the non-depletion region and further reduces the distance H2, further compressing the dead zone volume above the second type of guard ring doped region 7, which is beneficial for improving PDE and optimizing the device's time jitter characteristics.

[0056] In some embodiments, the doping concentration of the second type of guard ring doped region 7 is less than the doping concentration of the second type of guard ring doped region 7.

[0057] In some embodiments, the doping concentration of the second type of guard ring doped region 7 is half of the doping concentration of the second type of guard ring doped region 7.

[0058] In some embodiments, gradient doped regions 7-1, 7-2, and 7-3 can be formed through multi-step ion implantation. Based on the already implanted doped ions forming the first doped type epitaxial absorption layer 6 and avalanche main junction 100, a photoresist pattern is used as a mask for the ion implantation process. First, under the coverage of the first mask 101, second type doped ions are implanted to form the outermost gradient doped region 7-1 with the highest doping concentration. Figure 5a As shown, the doping concentration in this region can be less than or equal to the concentration of the second doped conductive region 4. After completion, the first mask 101 is removed, and exposure and development are performed again to form the second mask 102. The second type of doped ion implantation process is then performed again to complete the doping of the gradient doped region 7-2, as shown. Figure 5b As shown, the doping concentration of the gradient doped region 7-2 is less than that of the gradient doped region 7-1. The doping concentration of the gradient doped region 7-2 can be half that of the gradient doped region 7-1, or it can be reduced by an order of magnitude. After completion, the second mask 102 is removed again, and exposure and development are performed again to form the third mask 103. The ion implantation process is then performed again to complete the doping of the gradient doped region 7-3. Figure 5c As shown, the concentration in this region is less than that in the gradient doping region 7-2; it can be half or reduced by an order of magnitude. After completion, the third mask 103 is removed again, and exposure and development are performed again to form the fourth mask 104, as shown. Figure 5dAs shown, ion implantation is performed on a first type of compensation doped layer 8, the doping type of which is opposite to that of the second type of guard ring doped region 7, and the doping concentration is less than that of the main junction n-type region within the avalanche main junction 100. After the above process, a lateral second type of guard ring doped region 7 and a first type of compensation doped layer 8 are formed.

[0059] In some embodiments, the avalanche master junction 100 includes a first doped type well region 2 and a second doped type well region 3, wherein the second doped type well region is formed between the first doped type well region and the central region of the first doped type epitaxial absorption layer 6.

[0060] In some embodiments, combined with Figure 1 As shown, the single-photon avalanche diode also includes a back metal mesh 300, which is disposed on the insulating isolation structure 200.

[0061] In some embodiments, the insulating isolation structure 200 may be an STI structure.

[0062] In some embodiments, the back metal mesh 300 can be aluminum.

[0063] In some embodiments, combined with Figure 1 As shown, the single-photon avalanche diode also includes a microlens 400, which is disposed opposite to the avalanche main junction 100 and is located on the second doped conductive region.

[0064] In some embodiments, the device optimization of the single-photon avalanche diode in the above embodiments can be combined with optical astigmatism structures, such as inverted pyramid array (IPA) structures, STI array structures and other optical absorption enhancement measures, to further improve the PDE. This will not be elaborated further in this embodiment.

[0065] This application also provides a receiving chip, which includes a plurality of single-photon avalanche diodes as described above, and the plurality of single-photon avalanche diodes are arranged in an array.

[0066] It is understood that the receiving chip also includes a time-to-digital converter (TDC) for converting the output electrical signal of the SPAD into a digital signal.

[0067] The receiver chip also includes a digital signal processor (DSP) for processing digital signals to output usable depth information or photon count values. This digital signal processing includes histogram analysis, peak extraction, noise filtering, and data compression of the raw time data output by the TDC.

[0068] This application also provides a receiving sensor, which includes the aforementioned receiving chip. As an optional implementation, the receiving sensor further includes a processor, a memory, and a communication interface. The data processor can be a digital signal processor (DSP). The processor can be used to further process the data output by the receiving chip. The processor executes by accessing memory to retrieve instructions.

[0069] This application also provides a lidar, which includes a transmitting sensor and a receiving chip or a receiving sensor. The transmitting sensor is used to emit a detection laser, and the receiving chip or receiving sensor is used to receive the echo of the detection laser and obtain the detection information of the target object based on the echo.

[0070] The lidar may further include a processor for further processing the signals received by the receiving chip or receiving sensor to generate object detection information. This processing includes, but is not limited to, fusing and stitching the detection information. The processor may be a general-purpose processor, digital signal processor (DSP), application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), microcontroller, ARM (Acorn RISC Machine) or other programmable logic devices, discrete gate or transistor logic, discrete hardware components, or any combination of these components.

[0071] Furthermore, the lidar may also include a memory, and the processor executes program instructions in the memory to process signals received by the receiving chip or receiving sensor.

[0072] In this embodiment, a second type of guard ring doped region 7 is provided within the first type of doped epitaxial absorption layer. The distance between the inner side of the second type of guard ring doped region and the avalanche main junction 100 is greater than 0.1 μm and less than 0.6 μm. The outer side of the second type of guard ring doped region 7 is in contact with the second type of doped conductive region. The doping concentration of the second type of guard ring doped region is greater than that of the second type of doped conductive region. This allows electrons moving from the back side of the device to the front side to form a high potential region. Photogenerated carriers then move laterally into the main junction, and by generating an electric field, the avalanche collection efficiency of carriers is improved.

[0073] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional device areas and modules is used as an example. In practical applications, the above functions can be assigned to different functional device areas and modules as needed, that is, the internal structure of the device can be divided into different functional device areas or modules to complete all or part of the functions described above. In the embodiments, the functional device areas and modules can be integrated into one device, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0074] Furthermore, the specific names of each functional device area and module are merely for easy differentiation and are not intended to limit the scope of protection of this application. The specific working processes of the units and modules in the above system can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0075] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0076] In addition, the functional device regions in the various embodiments of this application can be integrated into one device, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0077] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A single-photon avalanche diode, characterized in that, The single-photon avalanche diode includes: Avalanche main knot; A first-doped epitaxial absorption layer covers the avalanche main junction; The second doped conductive region covers the first doped epitaxial absorption layer. The second type of guard ring doped region is disposed within the first type of doped epitaxial absorption layer. The distance between the inner surface of the second type of guard ring doped region and the avalanche main junction is greater than 0.1 μm and less than 0.6 μm. The outer surface of the second type of guard ring doped region is in contact with the second type of doped conductive region. The first electrode is electrically connected to the first end of the avalanche main junction; The second electrode is electrically connected to the second doped conductive region between the insulating isolation structures on both sides of the avalanche main junction.

2. The single-photon avalanche diode as described in claim 1, characterized in that, The second type of guard ring doped region has a ring structure, and the avalanche master junction is located on the central axis of the ring structure.

3. The single-photon avalanche diode as described in claim 1, characterized in that, The concentration of the second type of guard ring doped region near the edge of the avalanche main junction is less than or equal to 5e16 cm⁻¹. -3 .

4. The single-photon avalanche diode as described in claim 1, characterized in that, The doping concentration of the second type of guard ring doped region gradually decreases from the second type of doped conductive region toward the central axis of the avalanche main junction.

5. The single-photon avalanche diode as described in claim 1, characterized in that, The second type of guard ring doped region includes at least two horizontally arranged gradient doped regions, and the doping concentrations of the at least two gradient doped regions are arranged in an arithmetic sequence from the second type of doped conductive region toward the central axis of the avalanche main junction.

6. The single-photon avalanche diode as described in claim 4, characterized in that, The width of the multiple gradient doped regions gradually decreases from the second doped type conductive region toward the central axis of the avalanche master junction.

7. The single-photon avalanche diode as described in any one of claims 1-6, characterized in that, The single-photon avalanche diode also includes: A first type of compensation doping layer is disposed within the first type of doped epitaxial absorption layer. The doping concentration of the first type of compensation doping layer is less than the doping concentration of the first type of doped region within the avalanche main junction. The outer surface of the first type of compensation doping layer is flush with the outer surface of the second type of guard ring doped region, and the inner surface of the first type of compensation doping layer is flush with the inner surface of the second type of guard ring doped region.

8. The single-photon avalanche diode as described in any one of claims 1-6, characterized in that, The avalanche master junction includes a first doped type well region and a second doped type well region, wherein the second doped type well region is formed between the first doped type well region and the central region of the first doped type epitaxial absorption layer.

9. The single-photon avalanche diode as described in any one of claims 1-6, characterized in that, The single-photon avalanche diode also includes: A metal mesh on the back is disposed on the insulating isolation structure; and / or The microlens is disposed opposite to the avalanche master junction and is located on the second doped conductive region.

10. A receiving chip, characterized in that, The receiving chip includes at least one or more of the single-photon avalanche diodes as described in any one of claims 1-9.

11. A receiving sensor, characterized in that, The receiving sensor includes the receiving chip as described in claim 10.

12. A lidar, characterized in that, The lidar includes a transmitting sensor and a receiving sensor as described in claim 11; The emission sensor is used to emit a detection laser; The receiving sensor is used to receive the echo of the detection laser and obtain the detection information of the target object based on the echo.

Images