Single photon avalanche diode, photodetector and detection device

Abstract

Some embodiments of the present disclosure disclose a single photon avalanche diode, a photoelectric detector and a detection device, and relate to the technical field of image sensors, and are used to solve the problem of insufficient dynamic range of the SPAD photoelectric detector in a strong light environment. The single photon avalanche diode comprises a first electrode, a second electrode and a wafer; the wafer comprises a first surface and a second surface; the wafer further comprises a main body part, a first doped part and a second doped part arranged in a stacking manner along a first direction, and a third doped part; the main body part is coupled with the first electrode; the first doped part and the second doped part form a PN junction connected with the main body part; the first doped part is coupled with the second electrode; the third doped part is arranged on a side of the second doped part away from the first doped part; the doping types of the second doped part and the third doped part are opposite; and the single photon avalanche diode provided by some embodiments of the present disclosure is used for photoelectric detection.

Description

Technical Field

[0001] The present disclosure relates to the technical field of image sensors, and in particular to a single-photon avalanche diode, a photodetector, and a detection device. Background Art

[0002] Single Photon Avalanche Diode (SPAD) is a photoelectric detection device. Because it works above the reverse breakdown voltage, the avalanche gain is large, for example, it can reach 10 5 Therefore, the single-photon avalanche diode not only has single-photon detection sensitivity, but also has good time response and time resolution capability of hundreds of picoseconds.

[0003] However, when SPAD photodetectors are used in strong light environments, they suffer from insufficient dynamic range, which manifests as poor linearity of the output response, affecting the final detection and / or imaging effects. Summary of the Invention

[0004] Some embodiments of the present disclosure provide a single-photon avalanche diode, a photodetector, and a detection device for solving the problem of insufficient dynamic range of SPAD photodetectors in strong light environments.

[0005] In a first aspect, a single-photon avalanche diode is provided. The single-photon avalanche diode includes a first electrode, a second electrode and a chip. The first electrode and the second electrode are spaced apart. The chip includes a first surface and a second surface opposite to each other in a first direction, and the first direction is the thickness direction of the chip. The chip also includes: a main body, a first doping part and a second doping part stacked along the first direction, and a third doping part. The main body is coupled to the first electrode. The first doping part is farther away from the second surface than the second doping part; the first doping part and the second doping part form a PN junction connected to the main body, and the doping types of the first doping part and the main body are opposite; the first doping part is coupled to the second electrode. The third doping part is provided on a side of the second doping part away from the first doping part; the doping types of the second doping part and the third doping part are opposite.

[0006] It can be understood that when the single-photon avalanche diode is operating, photogenerated carriers will undergo collision ionization in the avalanche region, producing an avalanche multiplication effect, forming a depletion region within a certain range on the wafer, and the depletion region will expand in the direction of the second doping portion away from the first doping portion. When the single-photon avalanche diode also includes a third doping portion, and the doping types of the second doping portion and the third doping portion are opposite, it is equivalent to forming a low-potential barrier region on the side of the second doping portion away from the first doping portion. In this way, when the absolute value of the overbias voltage is low, the low-potential barrier region formed by the third doping portion will prevent the depletion region from expanding to the side of the third doping portion away from the second doping portion, resulting in a low photon detection efficiency of the single-photon avalanche diode; when the absolute value of the overbias voltage is high, the barrier of the low-potential barrier region formed by the third doping portion will be broken down, causing the depletion region to expand to the side of the third doping portion away from the second doping portion, thereby achieving a higher photon detection efficiency.

[0007] Therefore, by configuring the single-photon avalanche diode to also include a third doping portion, and the second doping portion and the third doping portion to have opposite doping types, the difference between the photon detection efficiency in the two cases of low absolute value of overbias and high absolute value of overbias can be increased. In this way, the photon detection efficiency of the single-photon avalanche diode can be adjusted by adjusting the overbias, and a larger change in photon detection efficiency can be achieved within a smaller overbias adjustment range. For example, a photon detection efficiency adjustment range of more than 20 times can be achieved. In this way, the counting rate of the single-photon avalanche diode can remain in an unsaturated state in a strong light environment, and the output response can be linear, which can solve the problem of insufficient dynamic range of the SPAD photodetector in a strong light environment.

[0008] Optionally, the second doping portion is in contact with the third doping portion.

[0009] Optionally, the second doping portion and the third doping portion are connected through a portion of the main body portion.

[0010] Optionally, a dimension of the first doped portion in the second direction is greater than a dimension of the second doped portion in the second direction, and the second direction is perpendicular to the first direction.

[0011] Optionally, a dimension of the second doping portion in the second direction is greater than a dimension of the third doping portion in the second direction, and the second direction is perpendicular to the first direction.

[0012] Optionally, a surface of the first doped portion away from the second doped portion forms a part of the first surface; and the first doped portion is in contact with the second electrode.

[0013] Optionally, the wafer further includes a fourth doped portion. The fourth doped portion contacts a surface of the first doped portion remote from the second doped portion and is encapsulated by the first doped portion. The fourth doped portion has the same doping type as the first doped portion, and a doping concentration greater than that of the first doped portion. The surface of the fourth doped portion remote from the second doped portion forms a portion of the first surface; the fourth doped portion contacts the second electrode.

[0014] Optionally, the wafer further includes a fifth doped portion. The fifth doped portion is disposed on a side of the main portion and is connected to the main portion. A surface of the fifth doped portion remote from the second surface forms a portion of the first surface. The fifth doped portion is spaced apart from the first doped portion. The doping type of the fifth doped portion is the same as that of the main portion, and the doping concentration of the fifth doped portion is greater than the doping concentration of the main portion. The fifth doped portion is in contact with the first electrode.

[0015] Optionally, the wafer further includes a sixth doping portion. The sixth doping portion is disposed between the fifth doping portion and the main portion, and surrounds the fifth doping portion. The sixth doping portion is spaced apart from the first doping portion. The fifth doping portion and the sixth doping portion have the same doping type, and the doping concentration of the sixth doping portion is greater than the doping concentration of the main portion and less than the doping concentration of the fifth doping portion.

[0016] Optionally, the fifth doping portion and the sixth doping portion are ring-shaped structures, and the first doping portion, the second doping portion, the third doping portion, and the second electrode are arranged inside the fifth doping portion and inside the sixth doping portion. The wafer further includes an isolation portion surrounding the sixth doping portion.

[0017] Optionally, the isolation portion includes a first outer boundary and a second outer boundary opposite to each other in a second direction, the second direction being perpendicular to the first direction, and the first outer boundary and the second outer boundary are separated by a first distance in the second direction. A second distance is separated by a boundary between the first doped portion and the sixth doped portion where the first doped portion and the sixth doped portion are adjacent to each other in the second direction. A ratio of the second distance to the first distance is in a range of 0.02 to 0.5.

[0018] Optionally, the orthographic projection of any one of the first doped portion, the second doped portion, the third doped portion, and the fourth doped portion on the second surface may have a shape including a circle, a square, or a regular octagon. The orthographic projection of the fifth doped portion on the second surface may have a shape including a ring, wherein the inner boundary of the ring is a circle, a square, or a regular octagon, and the outer boundary of the ring is a circle, a square, or a regular octagon.

[0019] Optionally, the doping type of the third doping portion is N-type.

[0020] In a second aspect, a photodetector is provided. The photodetector includes a single-photon avalanche diode provided by the above technical solution and a logic circuit. The logic circuit is coupled to a first electrode and a second electrode, respectively.

[0021] The beneficial effects that can be achieved by the photodetectors provided by some embodiments of the present disclosure are the same as the beneficial effects that can be achieved by the single-photon avalanche diode provided by the above-mentioned technical solution, and will not be repeated here.

[0022] Optionally, the photon detection surface of the single-photon avalanche diode is the second surface. The logic circuit is connected to the first surface of the single-photon avalanche diode.

[0023] In a third aspect, a detection device is provided, which includes the photoelectric detector provided by the above technical solution.

[0024] The beneficial effects that can be achieved by the detection device provided in some embodiments of the present disclosure are the same as the beneficial effects that can be achieved by a photoelectric detector provided by the above technical solution, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings described herein are used to provide a further understanding of the embodiments of the present disclosure and constitute a part of the embodiments of the present disclosure. The exemplary embodiments of the present disclosure and their descriptions are used to explain the present disclosure and do not constitute an improper limitation of the present disclosure. In the drawings:

[0026] Figure 1 A cross-sectional structural diagram of a single-photon avalanche diode provided for some embodiments of the present disclosure;

[0027] Figure 2 A reference diagram of the positions of orthographic projections of some structures of a single-photon avalanche diode provided in some embodiments of the present disclosure on a second surface;

[0028] Figure 3 A device potential distribution simulation diagram of a single-photon avalanche diode provided for some embodiments of the present disclosure;

[0029] Figure 4 A simulation diagram of the avalanche breakdown probability distribution of a single-photon avalanche diode provided in some embodiments of the present disclosure;

[0030] Figure 5 A graph showing a change in potential at each point on the center line of a single-photon avalanche diode as a function of depth, provided in some embodiments of the present disclosure;

[0031] Figure 6 for Figure 5 A partial enlarged view of the middle part of the curve;

[0032] Figure 7 A cross-sectional structural diagram of another single-photon avalanche diode provided for some embodiments of the present disclosure;

[0033] Figure 8A cross-sectional view of another single photon avalanche diode for some embodiments of the present disclosure;

[0034] Figure 9 A position reference diagram of the orthographic projection of some structures of another single photon avalanche diode for some embodiments of the present disclosure on the second surface;

[0035] Figure 10 A position reference diagram of the orthographic projection of some structures of another single photon avalanche diode for some embodiments of the present disclosure on the second surface;

[0036] Figure 11 An arrangement diagram of a single photon avalanche diode of a photodetector for some embodiments of the present disclosure;

[0037] Figure 12 An arrangement diagram of a single photon avalanche diode of a photodetector for some embodiments of the present disclosure;

[0038] Figure 13 An arrangement diagram of a single photon avalanche diode of a photodetector for some embodiments of the present disclosure;

[0039] Figure 14 A structure diagram of a photodetector for some embodiments of the present disclosure;

[0040] Figure 15 A structure diagram of a detection device for some embodiments of the present disclosure. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the drawings. Obviously, the described embodiments are only some of the embodiments of the present disclosure, but not all the embodiments. Based on the embodiments provided by the present disclosure, all other embodiments obtained by those of ordinary skill in the art are within the scope of protection of the present disclosure.

[0042] Unless otherwise required by context, the term "comprises" in the specification and claims is to be construed as an open, inclusive meaning, i.e. "comprises, but not limited to". In the description of the specification, the terms "one embodiment", "some embodiments", "exemplary embodiments", "example", or "some examples" are intended to mean that the particular feature, structure, material, or characteristic being described in connection with this embodiment or example includes in at least one embodiment or example of the present disclosure. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example. In addition, the particular features, structures, materials, or characteristics described can be included in any suitable way in one or more embodiments or examples.

[0043] In the description of the embodiments of the present disclosure, unless otherwise specified, “a plurality of” means two or more.

[0044] As used herein, "parallel", "perpendicular", and "equal" include the situations described and situations similar to the situations described, and the range of the similar situations is within an acceptable deviation range, wherein the acceptable deviation range is determined by a person of ordinary skill in the art taking into account the measurement in question and the errors associated with the measurement of the specific quantity (i.e., the limitations of the measurement system). For example, "parallel" includes absolute parallelism and approximate parallelism, wherein the acceptable deviation range of approximate parallelism can be, for example, a deviation within 5°; "perpendicular" includes absolute perpendicularity and approximate perpendicularity, wherein the acceptable deviation range of approximate perpendicularity can also be, for example, a deviation within 5°. "Equal" includes absolute equality and approximate equality, wherein the acceptable deviation range of approximate equality can be, for example, that the difference between the two equals is less than or equal to 5% of either one.

[0045] 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 the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. Throughout this application, unless otherwise specified, "plurality" means two or more.

[0046] As described in the background, single-photon avalanche diodes (SPADs) are solid-state photodetectors capable of detecting single photons and have attracted considerable attention in recent years. The SPAD's principle of photon detection is as follows: a bias voltage greater than the breakdown voltage is applied to the SPAD. When a photon is incident, electrons in the valence band absorb the photon and transition to the conduction band, generating photogenerated electron-hole pairs. These photogenerated electron-hole pairs are accelerated by an applied electric field and gain sufficient energy to collide with the crystal lattice, generating new electron-hole pairs. This process is called impact ionization. These new electron-hole pairs are further accelerated by the applied electric field and collide with the crystal lattice, generating new electron-hole pairs. This repeated process rapidly increases the number of charge carriers within the SPAD, dramatically increasing the current and generating a large avalanche current. This phenomenon is known as the avalanche multiplication effect.

[0047] According to the principle of SPAD detecting single photons, since SPAD works above the reverse breakdown voltage, compared with avalanche photodiode (APD), SPAD avalanche gain is larger and can reach 10 5 As mentioned above, the signal-to-noise ratio is good, so it not only has single-photon detection sensitivity, but also has good time response and time resolution capabilities, which can realize functions such as ranging. It currently has very important application prospects in the fields of lidar, 3D imaging, medical imaging, etc.

[0048] Figure 1 A cross-sectional structural diagram of a single-photon avalanche diode provided for some embodiments of the present disclosure; Figure 2 A reference diagram of the positions of orthographic projections of some structures of a single-photon avalanche diode on a second surface provided for some embodiments of the present disclosure.

[0049] In some embodiments, as Figure 1 and Figure 2 As shown, the single-photon avalanche diode 100 includes a first electrode 110 and a second electrode 120 , and the first electrode 110 and the second electrode 120 are spaced apart.

[0050] Exemplarily, the first electrode 110 is a metal electrode, such as a copper electrode, an aluminum electrode, or a silver electrode. The first electrode 110 is formed by, for example, an evaporation process, a sputtering process, or a deposition process.

[0051] Exemplarily, the second electrode 120 is a metal electrode, such as a copper electrode, an aluminum electrode, or a silver electrode. The second electrode 120 is formed by, for example, an evaporation process, a sputtering process, or a deposition process.

[0052] The first electrode 110 and the second electrode 120 are spaced apart, which means that there is a gap between the first electrode 110 and the second electrode 120, and they are not in direct contact. For example, the gap between the first electrode 110 and the second electrode 120 can be filled with a material, such as Figure 14 As shown, the gap between the first electrode 110 and the second electrode 120 may be filled with the material of the first dielectric layer 214 described in detail below.

[0053] Through the above configuration, using the first electrode 110 and the second electrode 120 , a low voltage and a high voltage can be respectively connected to the single-photon avalanche diode 100 . The voltage difference between the low voltage and the high voltage is the bias voltage acting on the single-photon avalanche diode 100 .

[0054] In some embodiments, as Figure 1 and Figure 2 As shown, the single-photon avalanche diode 100 further includes a wafer 130 . The wafer 130 includes a first surface 130 a and a second surface 130 b opposite to each other in a first direction X. The first direction X is a thickness direction of the wafer 130 .

[0055] The wafer 130 further includes a main body portion 131 , a first doping portion 132 , and a second doping portion 133 . The main body portion 131 is coupled to the first electrode 110 .

[0056] The first doped portion 132 and the second doped portion 133 are stacked along the first direction X. The first doped portion 132 is further away from the second surface 130 b than the second doped portion 133. The first doped portion 132 and the second doped portion 133 form a PN junction (Positive Negative junction) with the main portion 131, and the first doped portion 132 and the main portion 131 have opposite doping types. The first doped portion 132 is coupled to the second electrode 120.

[0057] In some examples, the first electrode 110 is used to connect a low voltage to the single-photon avalanche diode 100; the second electrode 120 is used to connect a high voltage to the single-photon avalanche diode 100. At this time, the bias voltage is a negative voltage, and the absolute value of the bias voltage is the sum of the absolute value of the breakdown voltage and the absolute value of the overbias voltage.

[0058] For example, the wafer 130 may be a silicon substrate, a germanium substrate, a silicon-germanium substrate, a silicon-on-insulator substrate, an indium gallium arsenide substrate, a gallium arsenide substrate, a silicon carbide substrate, or other suitable materials.

[0059] For example, elements such as boron, indium, and gallium can be doped on the wafer 130 or the epitaxial layer to form a uniform P-type structure; alternatively, elements such as phosphorus, arsenic, and antimony can be doped on the wafer 130 or the epitaxial layer to form a uniform N-type structure, so that the doped portion of the wafer 130 forms the first doped portion 132 or the second doped portion 133, and the PN junction formed by the first doped portion 132 and the second doped portion 133 is connected to the main body 131. The above-mentioned doping process is, for example, an ion implantation process or a diffusion process.

[0060] In some examples, the first doped portion 132 is away from part or all of the surface 132 a of the second doped portion 133 and forms a portion of the first surface 130 a . In this case, at least a portion of the first doped portion 132 is exposed to the first surface 130 a .

[0061] For example, the areas of the first surface 130a and the second surface 130b of the wafer 130 may be the same or different. Furthermore, the first surface 130a and the second surface 130b may be flat, curved, or stepped. For example, the first surface 130a may be a stepped surface. In this case, a surface 132a of the first doped portion 132 away from the second doped portion 133 may be higher than or lower than the main portion 131.

[0062] For example, the first doping portion 132 may be a single-layer structure, or the first doping portion 132 may be a multi-layer structure including a plurality of first sub-doping layers of the same doping type, and the plurality of first sub-doping layers are stacked.

[0063] For example, the second doping portion 133 may be a single-layer structure, or the second doping portion 133 may be a multi-layer structure including a plurality of second sub-doping layers of the same doping type, and the plurality of second sub-doping layers are stacked.

[0064] When the first doping portion 132 and the second doping portion 133 form a PN junction, the doping type of the first doping portion 132 is opposite to the doping type of the second doping portion 133, and the first doping portion 132 and the second doping portion 133 are in contact with each other. When the PN junction formed by the first doping portion 132 and the second doping portion 133 is connected to the main portion 131, the first doping portion 132 and the second doping portion 133 can form a depletion region within the wafer 130. Here, the doping type of the first doping portion 132 is opposite to the doping type of the second doping portion 133, which means that the doping element in the first doping portion 132 is a P-type doping element, and the doping element in the second doping portion 133 is an N-type doping element.

[0065] For example, Figure 1 and Figure 2 As shown, the PN junction formed by the first doping portion 132 and the second doping portion 133 is located in the central area of ​​the wafer 130 .

[0066] Based on the above structure, a reverse bias voltage having an absolute value higher than the reverse breakdown voltage can be applied to the single-photon avalanche diode 100 by using the first electrode 110 and the second electrode 120, so that an avalanche region with a relatively high electric field strength can be formed around the first doped portion 132 and the second doped portion 133. In this way, when a photon is incident on the single-photon avalanche diode 100, it will be absorbed by the main body 131 of the chip 130 and generate photogenerated carriers. These photogenerated carriers may drift to the avalanche region under the action of the electric field, or first diffuse into the depletion region under the action of the concentration difference, and then drift to the avalanche region under the action of the electric field, and undergo collision ionization in the avalanche region, forming an avalanche multiplication effect, generating a large number of carriers, of which electrons flow to the second electrode 120 and holes flow to the first electrode 110, forming a large avalanche current, thereby realizing the function of photodetection.

[0067] Here, the embodiment of the present disclosure does not limit the incident side of the photons. For example, the photons can be incident from the side of the first surface 130a (ie, frontal incidence); Figure 14 As shown, photons may be incident from the second surface 130 b side (ie, back-side incident).

[0068] In related technologies, because SPADs are photon-counting detectors, their unique avalanche-quenching-recovery mechanism limits their maximum count rate. When used in bright light environments, the strong incident light can easily cause the SPAD pixel's count rate to reach saturation, making its output response non-linear. This can affect the ultimate detection and / or imaging performance of the SPAD photodetector (e.g., a SPAD image sensor).

[0069] In some implementations, an ambient light adjustment device applicable to an image sensor is provided, comprising a controller and an adjustment device. The controller is configured to, when the detection intensity value of the image sensor is greater than or equal to a preset threshold, control the adjustment device to reduce the intensity of the light received by the image sensor and / or lower the bias voltage of the image sensor, thereby lowering the intensity value of the light received by the image sensor so that the intensity value of the light received by the image sensor meets the ambient light intensity requirement within the optimal operating range. In this implementation, adjusting the bias voltage of the image sensor is actually intended to adjust the responsiveness of the image sensor. For a SPAD image sensor, this can be understood as adjusting the photon detection efficiency of the SPAD pixel, thereby avoiding saturation of the output count rate.

[0070] However, when the aforementioned control and adjustment device is used to reduce the intensity of light received by the image sensor so that the intensity value of the light received by the image sensor meets the ambient light intensity requirements within the optimal operating range, there are problems such as slow response, high cost, and large size. On the other hand, when the bias voltage of the image sensor is reduced, the adjustable range of the over-bias voltage of the SPAD image sensor is limited due to the threshold voltage and voltage resistance of the MOS, which also limits the adjustable range of the photon detection efficiency. For example, the logic circuit of a SPAD sensor designed based on a mature CMOS process generally provides a narrow over-bias voltage adjustment range (for example, -3.3V to -1.2V). Within this narrow over-bias voltage adjustment range, the adjustable range of the photon detection efficiency is limited.

[0071] The inventors of the present disclosure have discovered that the photon detection efficiency of a single-photon avalanche diode 100 is positively correlated with the amount of photon absorption by the single-photon avalanche diode 100 and the integral value of the avalanche breakdown probability in the depletion region. Specifically, the amount of photon absorption by the single-photon avalanche diode 100 is positively correlated with the thickness of the single-photon avalanche diode 100; and the integral value of the avalanche breakdown probability in the depletion region is positively correlated with the area of ​​the depletion region. Therefore, the photon detection efficiency of the single-photon avalanche diode 100 can be adjusted by adjusting the amount of photon absorption by the single-photon avalanche diode 100 and / or the area of ​​the depletion region.

[0072] However, due to factors such as the device size of the photodetector, the adjustable range of the thickness of the single-photon avalanche diode 100 is relatively small, which also reduces the adjustment range of the photon absorption of the single-photon avalanche diode 100. Therefore, adjusting the area of ​​the depletion region to adjust the photon detection efficiency of the single-photon avalanche diode 100 is a more feasible method.

[0073] Based on this, some embodiments of the present disclosure provide a single photon avalanche diode 100. Figure 1 and Figure 2 As shown, the single-photon avalanche diode 100 further includes a third doping portion 134. The third doping portion 134 is provided on a side of the second doping portion 133 away from the first doping portion 132; the second doping portion 133 and the third doping portion 134 have opposite doping types.

[0074] For example, the third doping portion 134 may be a single-layer structure, or the third doping portion 134 may be a multi-layer structure including a plurality of third sub-doping layers of the same doping type, and the plurality of third sub-doping layers are stacked.

[0075] It should be understood that when the second doping portion 133 and the third doping portion 134 have opposite doping types, the third doping portion 134 and the body portion 131 have opposite doping types.

[0076] For example, Figure 1 As shown, the third doped portion 134 includes a third surface and a fourth surface that are opposite to each other in the first direction X, and also includes at least one side surface connected between the third surface and the fourth surface. The third surface is closer to the second doped portion 133 than the fourth surface. The fourth surface and each side surface of the third doped portion 134 are in contact with the main portion 131.

[0077] It can be understood that when the single-photon avalanche diode 100 is working, the photogenerated carriers will undergo collision ionization in the avalanche region, generating an avalanche multiplication effect, forming a depletion region of a certain range on the chip 130, and the depletion region will expand in the direction of the second doped portion 133 away from the first doped portion 132 (for example, along Figure 1 expansion in the downward direction).

[0078] When the single-photon avalanche diode 100 further includes a third doping portion 134, and the second doping portion 133 and the third doping portion 134 have opposite doping types, a low-potential barrier region is formed on the side of the second doping portion 133 away from the first doping portion 132, for example, a low-potential barrier region is formed between the second doping portion 133 and the main body 131. Thus, when the absolute value of the overbias voltage is low, the low-potential barrier region formed by the third doping portion 134 blocks the depletion region from extending to the side of the third doping portion 134 away from the second doping portion 133, resulting in a low photon detection efficiency of the single-photon avalanche diode 100. When the absolute value of the overbias voltage is high, the barrier of the low-potential barrier region formed by the third doping portion 134 is broken down, causing the depletion region to extend to the side of the third doping portion 134 away from the second doping portion 133, thereby achieving a higher photon detection efficiency.

[0079] Therefore, by configuring the single-photon avalanche diode 100 to also include a third doping portion 134, and the second doping portion 133 and the third doping portion 134 to have opposite doping types, the difference between the photon detection efficiency under the two conditions of low absolute value of overbias voltage and high absolute value of overbias voltage can be increased. In this way, the photon detection efficiency of the single-photon avalanche diode 100 can be adjusted by adjusting the overbias voltage, and a larger change in photon detection efficiency can be achieved within a smaller overbias voltage adjustment range. For example, a photon detection efficiency adjustment range of more than 20 times can be achieved. In this way, the counting rate of the single-photon avalanche diode 100 can remain in an unsaturated state in a strong light environment, thereby making the output response linear, which can solve the problem of insufficient dynamic range of the SPAD photodetector in a strong light environment.

[0080] In some embodiments, combined Figure 1 , for the single photon avalanche diode 100 including the third doping portion 134, under the over-bias voltage V ex For -1.2V and over bias V ex The device potential distribution and avalanche breakdown probability distribution under the condition of -3.3V were simulated and tested respectively. ex When the voltage is -1.2V, the device electrostatic potential distribution simulation diagram of the single photon avalanche diode 100 is as follows: Figure 3 As shown in (a), the avalanche breakdown probability distribution simulation diagram is as follows Figure 4 As shown in (a) in the figure. Over-bias voltage V ex When the voltage is -3.3V, the device electrostatic potential distribution simulation diagram of the single photon avalanche diode 100 is as follows: Figure 3 As shown in (b), the avalanche breakdown probability distribution simulation diagram is as follows Figure 4 As shown in (b) in .

[0081] In addition, the center line of the single photon avalanche diode 100 (the position can be referred to Figure 3 (a) and Figure 3 The potential of each point on the center line of the single photon avalanche diode 100 is measured. Figure 5 and Figure 6 shown; among them, Figure 6 for Figure 5 A partial enlarged view of the dotted box in the middle.

[0082] Combine Figure 1 , refer to Figure 5 and Figure 6 , V ex When V is -1.2 V, the potential below the second doped portion 133 is slightly elevated; ex When V is -3.3V, the potential below the second doped portion 133 continues to decrease; this is because V ex When V is -1.2V, the third doping portion 134 forms a low barrier region and is not broken down, thus forming a blocking effect. ex When the voltage is -3.3 V, the low barrier region formed by the third doping portion 134 is broken down, so that the depletion region can continue to expand downward.

[0083] Combine Figure 1 , refer to Figure 3 (a) in V ex When the voltage is -1.2V, the range of the depletion region is controlled on the side of the third doping portion 134 away from the second surface 130b, indicating that the third doping portion 134 can block the depletion region from extending downward, making the depletion region smaller; Figure 3 (b) in the figure, V ex When the voltage is -3.3 V, the third doped portion 134 forms a low barrier region and is broken down, so that the depletion region can continue to expand downward to the side of the third doped portion 134 close to the second surface 130 b, making the depletion region larger.

[0084] Combine Figure 1 , refer to Figure 4 (a) in V ex When the voltage is -1.2 V, the region where the avalanche breakdown probability is greater than 0 is blocked by the third doping portion 134 and is limited to the side of the third doping portion 134 away from the second surface 130 b and is located in a shallower region; Figure 4 (b) in the figure, V ex When the voltage is -3.3 V, the low barrier region formed by the third doping portion 134 is broken down, and the region on the side of the third doping portion 134 close to the second surface 130 b has an avalanche breakdown probability greater than 0, and the avalanche breakdown probability is relatively high.

[0085] The embodiments of the present disclosure do not limit the doping type of the third doped part 134, as long as the requirement that the doping type of the second doped part 133 and the third doped part 134 are opposite is met.

[0086] In some examples, as shown in FIG. 1B, the doping type of the main part 131 is N type, the doping type of the first doped part 132 is P type, the doping type of the second doped part 133 is N type, and the doping type of the third doped part 134 is P type. Figure 1 In some examples, as shown in FIG. 1B, the doping type of the main part 131 is N type, the doping type of the first doped part 132 is P type, the doping type of the second doped part 133 is N type, and the doping type of the third doped part 134 is P type.The above doping process is, for example, an ion implantation process or a diffusion process.

[0087] In some embodiments, the doping type of the third doped part 134 is N type.

[0088] Through the above arrangement, the doping process (for example, an ion implantation process or a diffusion process) can be used to dope the wafer 130 or the epitaxial layer with elements such as phosphorus, arsenic, and antimony to form a uniform N type structure, so that the doped part of the wafer 130 forms the third doped part 134.

[0089] Since the third doped part 134 is located on the side of the second doped part 133 away from the first doped part 132, the doping depth of the third doped part 134 is deeper. In the process of forming the third doped part 134 by using the N type doping process, it is easier to form the N type doping tailing. In this way, compared with the case where the doping type of the third doped part 134 is P type, the process difficulty of forming the third doped part 134 can be reduced, and the process feasibility of preparing the single-photon avalanche diode 100 is improved.

[0090] It should be understood that, in the case where the third doped part 134 is located on the side of the second doped part 133 away from the first doped part 132, the third doped part 134 can be in direct contact with the second doped part 133, or can be arranged with a spacing.

[0091] In some embodiments, as shown in FIG. 1B, the second doped part 133 is in contact with the third doped part 134. Figure 1

[0092] By such a configuration, the third doping portion 134 can form a blocking effect at the surface of the second doping portion 133 away from the first doping portion 132. In this way, when the absolute value of the over-bias voltage is low, in the first direction X, the boundary of the depletion region can be limited to the surface of the second doping portion 133 away from the first doping portion 132 (that is, the contact surface between the second doping portion 133 and the third doping portion 134). In this way, the area of ​​the depletion region can be made smaller, the photon detection efficiency of the single-photon avalanche diode 100 can be made lower, and the change in the photon detection efficiency under the conditions of low absolute value of the over-bias voltage and high absolute value of the over-bias voltage can be made greater.

[0093] Figure 7 A cross-sectional structural diagram of another single-photon avalanche diode 100 provided for some embodiments of the present disclosure.

[0094] In some embodiments, as Figure 7 As shown, the second doping portion 133 and the third doping portion 134 are connected through a portion of the main body portion 131 .

[0095] Exemplarily, in the first direction X, there is a distance between the third doping portion 134 and the second surface 130 b.

[0096] As described above, the third doping portion 134 can be formed by doping elements on the wafer 130 or the epitaxial layer. In the first direction X, when there is a distance between the third doping portion 134 and the first surface 130a, and between the third doping portion 134 and the second surface 130b, it is necessary to control the doping depth during the formation of the third doping portion 134 so that the third doping portion 134 is within a set depth range. When the second doping portion 133 and the third doping portion 134 are connected by a portion of the main body 131, the doping depth is easier to control during the formation of the third doping portion 134, which is conducive to improving the process feasibility of forming the third doping portion 134.

[0097] Combine Figure 1 The embodiment of the present disclosure does not limit the relative size relationship between the dimension D1 of the first doped portion 132 in the second direction Y and the dimension D2 of the second doped portion 133 in the second direction Y. The second direction Y is perpendicular to the first direction X.

[0098] In some embodiments, a dimension D1 of the first doped portion 132 in the second direction Y is less than or equal to a dimension D2 of the second doped portion 133 in the second direction Y.

[0099] In some cases, combined Figure 1The edge of the first doped portion 132 in the second direction Y has a certain edge concentration enrichment effect, which easily generates a stronger electric field between the edge of the first doped portion 132 in the second direction Y and the surrounding structures. When the dimension D1 of the first doped portion 132 in the second direction Y is less than or equal to the dimension D2 of the second doped portion 133 in the second direction Y, the edge of the first doped portion 132 in the second direction Y is relatively close to the second doped portion 133, which easily generates a certain electric field between them. This can easily cause premature breakdown at the edge of the first doped portion 132, affecting the detection performance of the single-photon avalanche diode 100.

[0100] In some embodiments, as Figure 1 As shown, a dimension D1 of the first doping portion 132 in the second direction Y is greater than a dimension D2 of the second doping portion 133 in the second direction Y.

[0101] Exemplarily, the doping concentration of the second doping portion 133 is greater than the doping concentration of the main body portion 131 .

[0102] Exemplarily, the orthographic projection of the second doping portion 133 on the second surface 130 b is covered by the orthographic projection of the first doping portion 132 on the second surface 130 b .

[0103] Through the above-mentioned setting, the distance between the edge portion of the first doping portion 132 in the second direction Y and the second doping portion 133 can be relatively large, which can avoid the generation of a strong electric field between the two, and further avoid premature breakdown at the edge of the first doping portion 132; moreover, when the doping concentration of the second doping portion 133 is greater than the doping concentration of the main body 131, the edge portion of the first doping portion 132 in the second direction Y can be covered by the main body 131 with a lower doping concentration, and the electric field between the two is weak, which can further avoid premature breakdown at the edge of the first doping portion 132, which is beneficial to improving the detection performance of the single-photon avalanche diode 100.

[0104] The embodiment of the present disclosure does not limit the relative size relationship between the dimension D2 of the second doping portion 133 in the second direction Y and the dimension D3 of the third doping portion 134 in the second direction Y.

[0105] In some examples, a dimension D2 of the second doping portion 133 in the second direction Y is less than or equal to a dimension D3 of the third doping portion 134 in the second direction Y.

[0106] In some embodiments, as Figure 1 As shown, a dimension D2 of the second doping portion 133 in the second direction Y is greater than a dimension D3 of the third doping portion 134 in the second direction Y.

[0107] Exemplarily, the orthographic projection of the third doped portion 134 on the second surface 130b is covered by the orthographic projection of the second doped portion 133 on the second surface 130b.

[0108] In some cases, when the absolute value of the over-bias is high, the middle part of the third doped portion 134 is broken down, while the edge part is not broken down.

[0109] It can be understood that, when the absolute value of the over-bias is high, in the process that the depletion region extends to the side of the third doped portion 134 away from the second doped portion 133, the depletion region also extends to both sides in the second direction Y (i.e. leftward and rightward in Figure 1 In the case that the size D3 of the third doped portion 134 in the second direction Y is large, in the process that the middle part of the third doped portion 134 is broken down, the edge part can not be broken down, so that the unbroken third doped portion 134 can block the extension of the depletion region in the second direction Y, so that the depletion region is small when the absolute value of the over-bias is high, and the change of the photon detection efficiency in the case that the absolute value of the over-bias is low and the case that the absolute value of the over-bias is high can be relatively small.

[0110] Therefore, by the size D2 of the second doped portion 133 in the second direction Y being greater than the size D3 of the third doped portion 134 in the second direction Y, the size D3 of the third doped portion 134 in the second direction Y can be small, so that the third doped portion 134 can be completely broken down when the absolute value of the over-bias is high, so that the depletion region can extend in the second direction Y, and thus the area of the depletion region is large, and the change of the photon detection efficiency in the case that the absolute value of the over-bias is low and the case that the absolute value of the over-bias is high can be larger.

[0111] In the following, the way in which the second electrode 120 is coupled with the first doped portion in the single-photon avalanche diode 100 will be exemplarily described.

[0112] Figure 8 A sectional structure diagram of a single-photon avalanche diode 100 is provided for still another embodiment of the present disclosure.

[0113] In some embodiments, as shown in Figure 8 the surface of the first doped portion 132 away from the second doped portion 133 forms part of the first surface 130a; and the first doped portion 132 is in contact with the second electrode 120.

[0114] By the above arrangement, the first doped portion 132 is in direct contact with the second electrode 120, so that the structure of the single-photon avalanche diode 100 can be simplified.

[0115] In some embodiments, as shown in Figure 1 and Figure 2As shown, the wafer 130 further includes a fourth doped portion 135. The fourth doped portion 135 contacts the surface of the first doped portion 132 remote from the second doped portion 133 and is encapsulated by the first doped portion 132. The doping type of the fourth doped portion 135 is the same as that of the first doped portion 132, and the doping concentration of the fourth doped portion 135 is greater than that of the first doped portion 132. The surface of the fourth doped portion 135 remote from the second doped portion 133 forms a portion of the first surface 130a; the fourth doped portion 135 contacts the second electrode 120.

[0116] Illustratively, the surface of the fourth doping portion 135 close to the second doping portion 133 and the side surface of the fourth doping portion 135 are wrapped by the first doping portion 132. Moreover, the surface of the first doping portion 132 away from the second doping portion and wrapped outside the side surface of the fourth doping portion 135 forms a portion of the first surface 130a.

[0117] It should be understood that, when the doping type of the fourth doping portion 135 is the same as the doping type of the first doping portion 132 , the doping type of the fourth doping portion 135 is the same as the doping type of the third doping portion 134 .

[0118] Exemplarily, the doping concentration of the fourth doping portion 135 is greater than the doping concentration of the third doping portion 134 .

[0119] In some examples, when the first doped portion 132 is in contact with the second electrode 120, the doping concentration of the first doped portion 132 is relatively high, resulting in a relatively strong concentration enrichment effect at the edge of the first doped portion 132 in the second direction Y. This makes it easy for premature corner breakdown to occur with other surrounding structures (such as the fifth doped portion 136 and / or the sixth doped portion 137 described in detail below). To avoid premature corner breakdown, in some cases, the spacing between the first doped portion 132 and other surrounding structures is set within a larger range, thereby reducing the device size of the single-photon avalanche diode 100.

[0120] In some other examples, when the first doped portion 132 is reused as the second electrode 120, the first doped portion 132 is closer to the first surface 130a, so that the PN junction is located in a shallower area. During the avalanche multiplication effect, carriers released by defect energy levels near the surface of the chip 130 (for example, the silicon surface) easily enter the main junction region, resulting in an increase in the dark count rate and a certain amount of noise, which reduces the device signal-to-noise ratio of the single-photon avalanche diode 100.

[0121] It is understood that when the wafer 130 further includes the fourth doped portion 135, on the one hand, the doping concentration of the first doped portion 132 can be made relatively low, so that the concentration enrichment effect at the edge of the first doped portion 132 in the second direction Y is relatively weak, which can reduce the probability of premature breakdown at the corners and reduce the device size of the single-photon avalanche diode 100. On the other hand, the first doped portion 132 can be further away from the first surface 130a. In this way, during the avalanche multiplication effect, carriers released from defect levels near the surface of the wafer 130 are less likely to enter the main junction region, thereby improving the device signal-to-noise ratio of the single-photon avalanche diode 100.

[0122] Hereinafter, the coupling manner between the first electrode 110 and the main body 131 in the single-photon avalanche diode 100 will be described by way of example.

[0123] In some embodiments, as Figure 1 and Figure 2 As shown, the wafer 130 further includes a fifth doped portion 136. The fifth doped portion 136 is disposed on one side of the main portion 131 and is connected to the main portion 131. The surface of the fifth doped portion 136 away from the second surface 130b forms a portion of the first surface 130a. The fifth doped portion 136 is spaced apart from the first doped portion 132. The doping type of the fifth doped portion 136 is the same as that of the main portion 131, and the doping concentration of the fifth doped portion 136 is greater than that of the main portion 131. The fifth doped portion 136 is in contact with the first electrode 110.

[0124] Exemplarily, the main body portion 131 is a portion of the epitaxial layer of the wafer 130 , and the doping concentration of the fifth doping portion 136 may be greater than the doping concentration of the main body portion 131 .

[0125] Through the above-mentioned setting, compared with the case where the first electrode 110 is in contact with the main body 131, the doping concentration of the part in contact with the first electrode 110 can be made relatively higher, which can improve the electrical connection effect between the first electrode 110 and the main body 131, and is beneficial to improving the detection performance of the single-photon avalanche diode 100.

[0126] The embodiment of the present disclosure does not limit the doping concentration and doping depth of the fifth doping portion 136 .

[0127] In some examples, the difference between the doping concentration of the fifth doping portion 136 and the doping concentration of the main portion 131 is relatively large, and the doping depth of the fifth doping portion 136 is relatively shallow, so that the ohmic contact effect between the fifth doping portion 136 and the main portion 131 is relatively poor.

[0128] To this end, in some embodiments, such as Figure 1 and Figure 2As shown, the wafer 130 further includes a sixth doping portion 137. The sixth doping portion 137 is disposed between the fifth doping portion 136 and the main portion 131, and surrounds the fifth doping portion 136. The sixth doping portion 137 is spaced apart from the first doping portion 132. The fifth doping portion 136 and the sixth doping portion 137 have the same doping type, and the doping concentration of the sixth doping portion 137 is greater than the doping concentration of the main portion 131, but less than the doping concentration of the fifth doping portion 136.

[0129] Illustratively, a surface of the fifth doping portion 136 close to the second surface 130 b and a side surface of the fifth doping portion 136 are wrapped by the sixth doping portion 137. Furthermore, a surface of the sixth doping portion 137 away from the second surface 130 b and wrapped around the side surface of the fifth doping portion 136 forms a portion of the first surface 130 a.

[0130] In some examples, the doping type of the main body 131 is N-type, the doping type of the first doping portion 132 is P-type, the doping type of the second doping portion 133 is N-type, the doping type of the third doping portion 134 is P-type, the doping type of the fifth doping portion 136 is N-type, and the doping type of the sixth doping portion 137 is N-type.

[0131] In some examples, the doping type of the main body 131 is P-type, the doping type of the first doping portion 132 is N-type, the doping type of the second doping portion 133 is P-type, the doping type of the third doping portion 134 is N-type, the doping type of the fifth doping portion 136 is P-type, and the doping type of the sixth doping portion 137 is P-type.

[0132] Through the above-mentioned setting, the doping concentrations of the fifth doping part 136, the sixth doping part 137 and the main part 131 are reduced successively. In this way, the sixth doping part 137 can form a transition region between the fifth doping part 136 and the main part 131, which can improve the electrical connection effect between the fifth doping part 136 and the main part 131, and is beneficial to improving the detection performance of the single-photon avalanche diode 100.

[0133] The present disclosure does not limit the shapes of the fifth doping portion 136 and the sixth doping portion 137. For example, the fifth doping portion 136 may be a strip-shaped doping portion, and the number of the fifth doping portion 136 may be one or more.

[0134] Figure 9 and Figure 10 A reference diagram of the positions of orthographic projections of some structures of yet another single-photon avalanche diode 100 on the second surface 130 b provided for some embodiments of the present disclosure.

[0135] In some embodiments, as Figure 1 、 Figure 2 、 Figure 9 and Figure 10 As shown, the fifth doping portion 136 and the sixth doping portion 137 are ring-shaped structures. The first doping portion 132, the second doping portion 133, the third doping portion 134, and the second electrode 120 are disposed inside the fifth doping portion 136 and inside the sixth doping portion 137. The wafer 130 also includes an isolation portion 138 surrounding the sixth doping portion 137.

[0136] For example, the cross-sectional morphology of the fifth doping portion 136 and the cross-sectional morphology of the sixth doping portion 137 may be the same or different. For example, Figure 2 As shown, the fifth doping portion 136 is a ring structure with a circular inner circle and a circular outer circle, and the sixth doping portion 137 is a ring structure with a circular inner circle and a square outer circle; for example, Figure 10 As shown, the fifth doping portion 136 and the sixth doping portion 137 are both ring structures with a square inner circle and a square outer circle.

[0137] For example, Figure 1 As shown, the isolation portion 138 extends through the wafer 130 .

[0138] Exemplarily, the material of the isolation portion 138 includes an isolation dielectric, and the material of the isolation dielectric may be polysilicon or metal tungsten.

[0139] In some examples, such as Figures 11 to 13 As shown, the single-photon avalanche diode 100 is a single-photon avalanche diode 100 in the photodetector 200 , and the photodetector includes a plurality of (eg, a plurality of arranged in an array) single-photon avalanche diodes 100 .

[0140] By providing the fifth doped portion 136 with a ring-shaped structure, a ring-shaped electric field can be formed between the first electrode 110 and the second electrode 120, thereby increasing the distribution range of the electric field and improving the detection efficiency of the single-photon avalanche diode 100. By also providing the wafer 130 with the isolation portion 138, signal interference between the single-photon avalanche diode 100 and adjacent devices (e.g., adjacent single-photon avalanche diodes 100) can be avoided, thereby improving the detection accuracy of the single-photon avalanche diode 100.

[0141] As previously described, the sixth doping portion 137 is spaced apart from the first doping portion 132. The present disclosure does not limit the distance between the sixth doping portion 137 and the first doping portion 132. In practical applications, the distance between the sixth doping portion 137 and the first doping portion 132 can be determined based on device size and doping conditions.

[0142] In some embodiments, as Figure 1As shown, the isolation portion 138 includes a first outer boundary 138 a and a second outer boundary 138 b that are opposite to each other in a second direction Y. The second direction Y is perpendicular to the first direction X. The first outer boundary 138 a and the second outer boundary 138 b are separated by a first distance L1 in the second direction Y. A second distance L2 is formed between the first doped portion 132 and the sixth doped portion 137 at a boundary adjacent to each other in the second direction Y. The ratio of the second distance L2 to the first distance L1 is in a range of 0.02 to 0.5.

[0143] For example, the ratio of the second distance L2 to the first distance L1 may be 0.02, 0.05, 0.1, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.44, or 0.5, etc., which is not limited here.

[0144] It can be understood that when the ratio of the second distance L2 to the first distance L1 is low (e.g., less than 0.02), the distance between the first doped portion 132 and the sixth doped portion 137 is small, making premature breakdown more likely to occur between the edge of the first doped portion 132 and the sixth doped portion 137. When the ratio of the second distance L2 to the first distance L1 is high (e.g., greater than 0.5), the distance between the first doped portion 132 and the sixth doped portion 137 is large, which may result in a relatively small size of the first doped portion 132 and a smaller area of ​​the PN junction formed by the first doped portion 132 and the second doped portion 133, potentially leading to a relatively low detection efficiency of the single-photon avalanche diode 100. Therefore, by setting the ratio of the second distance L2 to the first distance L1 within a range of 0.02 to 0.5, the detection efficiency of the single-photon avalanche diode 100 can be maintained while avoiding premature breakdown between the edge of the first doped portion 132 and the sixth doped portion 137.

[0145] The present embodiment does not limit the shapes of the orthographic projections of the first doping portion 132, the second doping portion 133, the third doping portion 134, the fourth doping portion 135, and the fifth doping portion 136 on the second surface 130b. Furthermore, the shapes of any two of the first doping portion 132, the second doping portion 133, the third doping portion 134, and the fourth doping portion 135 may be the same or different.

[0146] In some embodiments, the orthographic projection of any of the first doped portion 132, the second doped portion 133, the third doped portion 134, and the fourth doped portion 135 on the second surface 130 b may be in the shape of a circle, a square, or a regular octagon. The orthographic projection of the fifth doped portion 136 on the second surface 130 b may be in the shape of a ring, the inner boundary of the ring being a circle, a square, or a regular octagon, and the outer boundary of the ring being a circle, a square, or a regular octagon.

[0147] In some examples, the orthographic projections of the first doping portion 132 , the second doping portion 133 , the third doping portion 134 , and the fourth doping portion 135 on the second surface 130 b have the same shape. Figure 2 As shown, the shapes of the orthographic projections of the first doping portion 132, the second doping portion 133, the third doping portion 134 and the fourth doping portion 135 on the second surface 130b are all circular. Figure 9 As shown, the shapes of the orthographic projections of the first doping portion 132, the second doping portion 133, the third doping portion 134 and the fourth doping portion 135 on the second surface 130b are all regular octagons. Figure 10 As shown, the shapes of the orthographic projections of the first doping portion 132 , the second doping portion 133 , the third doping portion 134 and the fourth doping portion 135 on the second surface 130 b are all square.

[0148] In some other examples, shapes of orthographic projections of at least two of the first doping portion 132 , the second doping portion 133 , the third doping portion 134 , and the fourth doping portion 135 on the second surface 130 b are different from each other.

[0149] In some examples, the inner boundary of the orthographic projection (ring shape) of the fifth doped portion 136 on the second surface 130 b has a shape similar to that of the outer boundary. Figure 2 As shown in FIG, the inner boundary of the ring is circular, and the outer boundary of the ring is circular. Figure 9 As shown, the inner boundary of the ring is a regular octagon, and the outer boundary of the ring is a regular octagon. Figure 10 As shown, the inner boundary of the ring is square and the outer boundary of the ring is square.

[0150] In yet other examples, the inner and outer boundaries of the orthographic projection (annular shape) of the fifth doped portion 136 on the second surface 130 b have different shapes. For example, the inner boundary of the annular shape is circular, while the outer boundary of the annular shape is square. In another example, the inner boundary of the annular shape is a regular octagon, while the outer boundary of the annular shape is square.

[0151] The above arrangement facilitates optimization of the spatial positions of the first doping portion 132, the second doping portion 133, the third doping portion 134, the fourth doping portion 135, and the fifth doping portion 136, thereby making their layout on the wafer 130 more reasonable. Furthermore, when the orthographic projections of the first doping portion 132, the second doping portion 133, the third doping portion 134, the fourth doping portion 135, and the fifth doping portion 136 on the second surface 130b are circular or regular octagonal, compared to when the orthographic projections of the first doping portion 132, the second doping portion 133, the third doping portion 134, the fourth doping portion 135, and the fifth doping portion 136 on the second surface 130b are square, the curvature radius of the first doping portion 132, the second doping portion 133, the third doping portion 134, the fourth doping portion 135, and the fifth doping portion 136 at the edge positions can be larger, thereby reducing the electric field strength in the edge regions and preventing premature breakdown at the edges.

[0152] The following describes an exemplary method for fabricating the single-photon avalanche diode 100, taking the case where the doping type of the third doped portion 134 is N-type as an example. It should be understood that the operations shown in the fabrication method are not exhaustive, and other operations may be performed before, after, or between any of the illustrated operations.

[0153] In some embodiments, a method for preparing the single-photon avalanche diode 100 includes S1:

[0154] S1: A P-type epitaxial layer (P-Epitaxy, P-EPI) is formed by epitaxial growth on the wafer substrate (P-substrate, P-SUB).

[0155] Illustratively, the resistivity of the wafer substrate ranges from 0.01Ω*cm to 100Ω*cm, such as 0.01Ω*cm, 0.1Ω*cm, 0.5Ω*cm, 1Ω*cm, 10Ω*cm, 20Ω*cm, 50Ω*cm, or 100Ω*cm.

[0156] Exemplarily, the resistivity of the P-type epitaxial layer ranges from 0.1Ω*cm to 1000Ω*cm, for example, 0.1Ω*cm, 0.3Ω*cm, 0.5Ω*cm, 1Ω*cm, 10Ω*cm, 50Ω*cm, 100Ω*cm, 300Ω*cm, 500Ω*cm or 1000Ω*cm.

[0157] S2 : performing P-type implantation into the central region of the P-type epitaxial layer, for example, implanting boron (B) atoms to form a second doping portion 133 .

[0158] Illustratively, the implantation energy of the P-type implant in S2 ranges from 300 keV to 800 keV, such as 300 keV, 400 keV, 500 keV, 600 keV, 700 keV, or 800 keV.

[0159] For example, the implantation dose of the P-type implant in S2 is in the range of 1×10 12 cm -2 ~1×10 13 cm -2 , for example, 1×10 12 cm -2 , 2×10 12 cm -2 , 4×10 12 cm -2 , 6×10 12 cm -2 , 8×10 12 cm -2 or 1×10 13 cm -2 wait.

[0160] S3 : performing N-type implantation on the P-type epitaxial layer located on the side of the second doping portion 133 close to the first surface 130 a , for example, implanting phosphorus (P) atoms or arsenic (As) atoms, to form the first doping portion 132 .

[0161] Illustratively, the implantation energy of the N-type implantation in S3 ranges from 100 keV to 500 keV, such as 100 keV, 200 keV, 300 keV, 350 keV, 400 keV, or 500 keV.

[0162] For example, the implantation dose range of the N-type implantation in S3 is 4×10 12 cm -2 ~3×10 13 cm -2 , for example 4×10 12 cm -2 , 6×10 12 cm -2 , 8×10 12 cm -2 , 9×10 12 cm -2 , 1×10 13 cm -2 or 3×10 13 cm -2 wait.

[0163] S4 : Based on the N-type implantation in S3 , a second N-type implantation is performed to form a third doped portion 134 on a side of the second doped portion 133 away from the first doped portion 132 .

[0164] Exemplarily, the implantation dose of the N-type implantation in S4 is higher than that of the N-type implantation in S3. Exemplarily, the implantation energy of the N-type implantation in S4 is higher than that of the N-type implantation in S3. By setting in this way, the tailing of the N-type doping can be utilized to form the third doped part 134.

[0165] Exemplarily, the implantation energy of the N-type implantation in S4 ranges from 100 keV to 500 keV, for example, is 100 keV, 200 keV, 300 keV, 340 keV, 400 keV or 500 keV, etc.

[0166] Exemplarily, the implantation dose of the N-type implantation in S4 ranges from 5×10 12 cm -2 to 5×10 13 cm -2 , for example, is 5×10 12 cm -2 , 6×10 12 cm -2 , 8×10 12 cm -2 , 1×10 13 cm -2 , 3×10 13 cm -2 , or 5×10 13 cm -2 , etc.

[0167] S5: performing a third N-type implantation on the P-type epitaxial layer located on the side of the second doped part 133 close to the first surface 130a, for example, implanting phosphorus (P) atoms or arsenic (As) atoms, to form a fourth doped part 135, and the fourth doped part 135 forms the second electrode 120.

[0168] S6: performing a P-type implantation on the P-type epitaxial layer located on both sides of the first doped part 132, for example, implanting boron (B) atoms, to form an initial sixth doped part.

[0169] S7: performing a P-type implantation on the central region of the initial sixth doped part, for example, implanting boron (B) atoms with a higher concentration, to form a fifth doped part 136, and the region of the initial sixth doped part which is not implanted in S7 forms a sixth doped part 137, and the sixth doped part 137 forms the first electrode 110.

[0170] S8: performing a deep trench etching on the P-type epitaxial layer located on both sides of the sixth doped part 137 to form a full deep trench isolation (FDTI), and filling the full deep trench isolation with polysilicon or tungsten to form an isolation part 138.

[0171] It should be understood that the above S6 to S7 can be performed after S1 to S5 or before S1 to S5.

[0172] It should be understood that the above-mentioned S8 can be performed after S1 to S7 or before S1 to S7.

[0173] It should be noted that the above-listed preparation methods are examples of preparation methods of the single-photon avalanche diode 100 , and are not limitations on the preparation methods of the single-photon avalanche diode 100 .

[0174] Some embodiments of the present disclosure further provide a photodetector 200, such as Figures 11 to 14 As shown, the photodetector 200 includes at least one single-photon avalanche diode 100 provided by the above disclosed embodiment and a logic circuit 211 ; the logic circuit 211 is coupled to the first electrode 110 and the second electrode 120 , respectively.

[0175] Exemplarily, the logic circuit 211 may be configured to respectively input voltage signals to the first electrode 110 and the second electrode 120 .

[0176] The single-photon avalanche diode 100 can convert an optical signal into an electrical signal. In some examples, the logic circuit 211 can be configured to receive the electrical signal generated by the single-photon avalanche diode 100 (eg, read out the charge amount), thereby realizing the photodetection function.

[0177] For example, Figures 11 to 13 As shown, the photodetector 200 includes multiple single-photon avalanche diodes 100 provided by the above-disclosed embodiments, and the multiple single-photon avalanche diodes 100 are arranged in an array (e.g., 4×4, 100×100, or 1280×960), forming a photodiode array. In this case, each single-photon avalanche diode 100 in the photodiode array can constitute a pixel of the photodetector 200, or multiple single-photon avalanche diodes 100 (e.g., 2×2 or 4×4) in the photodiode array can constitute a macropixel of the photodetector 200. When the photodetector 200 includes multiple single-photon avalanche diodes 100, the multiple single-photon avalanche diodes 100 can share a chip 130, and two adjacent single-photon avalanche diodes 100 can share an isolation portion 138.

[0178] In some embodiments, the photodetector 200 may also include an analog-to-digital conversion circuit, a comparison circuit, or an amplification circuit, so as to perform analog-to-digital conversion, comparison, or amplification processing on the electrical signal from the single-photon avalanche diode 100 and output the processed electrical signal.

[0179] In some embodiments, the photodetector 200 further includes a printed circuit board (PCB), on which processing circuits such as a readout circuit, a quenching circuit, an analog-to-digital conversion circuit, a comparison circuit, and an amplifier circuit may be disposed. In some embodiments, multiple processing circuits are provided to perform different processing on the received electrical signal. It is understood that multiple processing circuits may be disposed on the same PCB or on multiple different PCBs.

[0180] In some examples, the photodetector 200 further includes one or more microlenses 220 , wherein one microlens 220 is disposed on a photon detection surface (eg, the second surface 130 b of the wafer 130 ) of the single photon avalanche diode 100 . The microlens 220 can be configured to enhance photon absorption.

[0181] Here, the photon detection surface can be understood as the surface that first receives photons in the single-photon avalanche diode 100. Exemplarily, the photon detection surface of the single-photon avalanche diode 100 can be the first surface 130a or the second surface 130b.

[0182] The beneficial effects that can be achieved by a photodetector 200 provided by some embodiments of the present disclosure are the same as the beneficial effects that can be achieved by a single-photon avalanche diode 100 provided by the above technical solution, and will not be repeated here.

[0183] In some embodiments, as Figure 14 As shown, the photon detection surface of the single-photon avalanche diode 100 is the second surface 130 b , and the logic circuit 211 is connected to the first surface 130 a of the single-photon avalanche diode 100 .

[0184] In a case where the photon detection surface of the single-photon avalanche diode 100 is the second surface 130 b , the photodetector 200 including the single-photon avalanche diode 100 is a back-illuminated structure.

[0185] For example, Figure 14 As shown, the photodetector 200 may further include an inverted pyramid structure 230 disposed on the second surface 130 b . The inverted pyramid structure 230 may be configured to enhance photon absorption.

[0186] For example, Figure 14 As shown, the photodetector 200 may further include a passivation layer 240 disposed on the side of the inverted pyramid structure 230 away from the first surface 130a. In this case, the microlens 220 may be disposed on the passivation layer 240, and the passivation layer 240 may be configured to reduce photon reflection and enhance photon absorption.

[0187] In some examples, such as Figure 14 As shown, the logic circuit 211 is a logic circuit 211 provided on a logic wafer 210. Exemplarily, the logic wafer 210 includes a substrate 212, and the logic circuit 211 is provided on the substrate 212.

[0188] For example, Figure 14 As shown, the logic wafer 210 also includes a first interconnect structure 213 (e.g., a copper-copper interconnect structure) provided between the logic circuit 211 and the first surface 130a; the logic circuit 211 and the first electrode 110, and the logic circuit 211 and the second electrode 120 can be electrically connected through the first interconnect structure 213.

[0189] For example, Figure 14 As shown, the logic wafer 210 also includes one or more first dielectric layers 214 arranged between the first interconnect structure 213 and the first surface 130a. Metal patterns 2141 (for example, metal traces) are distributed in the first dielectric layer 214. The first interconnect structure 213 and the first electrode 110, and the first interconnect structure 213 and the second electrode 120 can be electrically connected through one or more metal patterns 2141.

[0190] For example, Figure 14 As shown, the logic wafer 210 includes a second dielectric layer 215 disposed between the first dielectric layer 214 and the first surface 130 a , and the first electrode 110 and the second electrode 120 are disposed in the second dielectric layer 215 .

[0191] For example, in practical applications, the size and area of ​​the first electrode 110 and / or the second electrode 120 can be set based on the photon detection efficiency and the spacing requirements between the first electrode 110 and the second electrode 120. For example, while ensuring that the distance between the first electrode 110 and the second electrode 120 is greater than a certain spacing (to prevent a short circuit between the two electrodes), the area of ​​the first electrode 110 and / or the second electrode 120 can be set within a larger range. This allows photons that pass through the wafer 130 and strike the first electrode 110 and / or the second electrode 120 to be reflected back into the wafer 130, resulting in secondary absorption, thereby enhancing photon detection efficiency. Furthermore, the larger the area of ​​the first electrode 110 and the second electrode 120, the greater the absorption enhancement effect.

[0192] Exemplarily, the photodetector 200 may further include at least two through-holes (e.g., through-silicon vias, TSVs) formed on the wafer 130. Through-hole contacts 250 are disposed within the through-holes. The ends of the through-hole contacts 250 facing away from the second surface 130b are connected to the logic circuit 211. Of the at least two through-hole contacts 250, one end of the through-hole contact 250 facing away from the logic wafer 210 is connected to an anode pad 261, which is used to at least couple an anode signal to the single-photon avalanche diode 100. Another end of the through-hole contact 250 facing away from the logic wafer 210 is connected to a cathode pad 262, which is used to at least couple a cathode signal to the single-photon avalanche diode 100.

[0193] It can be understood that by connecting the logic circuit 211 to the first surface 130a of the single-photon avalanche diode 100, a wafer (such as a logic wafer) including the logic circuit 211 can be stacked with the chip 130 along the first direction X. In this way, the geometric fill factor and detection efficiency of the photodetector 200 can be improved.

[0194] Some embodiments of the present disclosure further provide a detection device 300, such as Figure 15 As shown, the detection device 300 includes a photodetector 200 provided by the above disclosed embodiment.

[0195] The detection device 300 may include a security inspection device, a medical inspection device, or an industrial nondestructive testing device. The detection device 300 is capable of emitting light, receiving light that has passed through an object to be inspected, converting the received optical signal into an electrical signal, and determining internal and external image information of the object to be inspected based on the electrical signal, thereby achieving a detection function. The present disclosure does not impose any particular limitation on the specific form of the detection device 300. The following describes the structure of the detection device 300 by way of example.

[0196] In some embodiments, as Figure 15 As shown, the detection device 300 includes an emitter 310 , a photodetector 200 and a processor 320 , and the processor 320 is electrically connected to the photodetector 200 .

[0197] Emitter 310 is used to emit light. The disclosed embodiments do not limit the type of light emitted by emitter 310. In some embodiments, emitter 310 can be used to emit invisible light, such as X-rays or gamma rays, to ensure the light's ability to penetrate the object to be detected, thereby improving the detection accuracy of detection device 300. In other embodiments, emitter 310 can also be used to emit visible light.

[0198] In some embodiments, the number of the emitter 310 can be multiple, and the multiple emitters 310 are respectively arranged at different positions, so that the light can be emitted to the object to be detected from different positions, and the use reliability of the detection device 300 is improved.

[0199] In some embodiments, the number of the photodetector 200 can be multiple, so that the light from different directions can be received.

[0200] The processor 320 is electrically connected with the photodetector 200, and the processor 320 can be used to receive the electrical signal from the photodetector 200, and generate the internal image information and the external image information of the object to be detected according to the electrical signal from the photodetector 200. In some embodiments, the processor 320 can be a central processing unit (CPU) or a graphic processing unit (GPU).

[0201] In some embodiments, after the processor 320 generates the image information of the object to be detected, the image information can be transmitted to the outside of the detection device 300. In some other embodiments, the detection device 300 can further include a display device, and the display device is used to display the image information generated by the processor 320. In this way, the user can intuitively obtain the internal image information and the external image information of the object to be detected through the display device, and the use convenience of the detection device 300 is improved.

[0202] Some embodiments of the present disclosure provide a detection device 300, which can achieve the same beneficial effects as the photodetector 200 provided in the above technical solution, and thus the details are not repeated here.

[0203] The above is only a specific embodiment of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical range disclosed in the present disclosure, which should be covered in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be subject to the protection scope of the claims.

Claims

1. A single photon avalanche diode, characterized in that: It includes a first electrode, a second electrode and a chip; the first electrode and the second electrode are spaced apart; The wafer includes a first surface and a second surface opposite to each other in a first direction, wherein the first direction is a thickness direction of the wafer; the wafer further includes: a main body portion, coupled to the first electrode; a first doped portion and a second doped portion stacked along the first direction; the first doped portion being farther from the second surface than the second doped portion; the first doped portion and the second doped portion forming a PN junction connected to the main portion, and the first doped portion and the main portion having opposite doping types; and the first doped portion being coupled to the second electrode; A third doping portion is arranged on a side of the second doping portion away from the first doping portion; the second doping portion and the third doping portion have opposite doping types; the third doping portion is configured to: form a low barrier region on a side of the second doping portion away from the first doping portion; when the absolute value of the overbias voltage is low, the low barrier region blocks the depletion region from extending to the side of the third doping portion away from the second doping portion; when the absolute value of the overbias voltage is high, the barrier of the low barrier region is broken down, causing the depletion region to extend to the side of the third doping portion away from the second doping portion.

2. The single photon avalanche diode according to claim 1, characterized in that The second doping portion is in contact with the third doping portion.

3. The single photon avalanche diode according to claim 1, wherein: The second doping portion and the third doping portion are connected through a portion of the main body portion.

4. The single photon avalanche diode according to claim 1, characterized in that A dimension of the first doping portion in a second direction is greater than a dimension of the second doping portion in the second direction, and the second direction is perpendicular to the first direction.

5. The single photon avalanche diode according to claim 1, characterized in that A dimension of the second doping portion in a second direction is greater than a dimension of the third doping portion in the second direction, and the second direction is perpendicular to the first direction.

6. The single photon avalanche diode according to claim 1, characterized in that A surface of the first doped portion away from the second doped portion forms a portion of the first surface; and the first doped portion is in contact with the second electrode.

7. The single photon avalanche diode according to claim 1, characterized in that: The wafer further comprises: a fourth doping portion, which is in contact with a surface of the first doping portion away from the second doping portion and is wrapped by the first doping portion; the doping type of the fourth doping portion is the same as the doping type of the first doping portion, and the doping concentration of the fourth doping portion is greater than the doping concentration of the first doping portion; the surface of the fourth doping portion away from the second doping portion forms a part of the first surface; and the fourth doping portion is in contact with the second electrode.

8. The single photon avalanche diode according to any one of claims 1 to 6, characterized in that: The wafer further comprises: A fifth doping portion is provided on one side of the main body portion and is connected to the main body portion; a surface of the fifth doping portion away from the second surface forms a part of the first surface; the fifth doping portion is spaced apart from the first doping portion; the doping type of the fifth doping portion is the same as the doping type of the main body portion, and the doping concentration of the fifth doping portion is greater than the doping concentration of the main body portion; the fifth doping portion is in contact with the first electrode.

9. The single photon avalanche diode according to claim 8, characterized in that: The wafer further comprises: A sixth doping portion is arranged between the fifth doping portion and the main portion, and wraps the fifth doping portion; the sixth doping portion is spaced apart from the first doping portion; the fifth doping portion and the sixth doping portion have the same doping type, and the doping concentration of the sixth doping portion is greater than the doping concentration of the main portion and less than the doping concentration of the fifth doping portion.

10. The single photon avalanche diode according to claim 9, characterized in that: The fifth doping portion and the sixth doping portion are ring-shaped structures, and the first doping portion, the second doping portion, the third doping portion and the second electrode are arranged on the inner side of the fifth doping portion and on the inner side of the sixth doping portion; The chip further includes an isolation portion surrounding the sixth doping portion.

11. The single photon avalanche diode according to claim 10, characterized in that: The isolation portion includes a first outer boundary and a second outer boundary opposite to each other in a second direction, the second direction being perpendicular to the first direction, and the first outer boundary and the second outer boundary having a first distance in the second direction; A second distance exists between the boundary between the first doped portion and the sixth doped portion where the first doped portion is close to each other in the second direction, and a ratio of the second distance to the first distance is in a range of 0.02 to 0.

5.

12. The single photon avalanche diode according to any one of claims 1 to 6, characterized in that: The wafer further comprises: a fourth doped portion, contacting a surface of the first doped portion remote from the second doped portion and being wrapped by the first doped portion; the doping type of the fourth doped portion is the same as the doping type of the first doped portion, and the doping concentration of the fourth doped portion is greater than the doping concentration of the first doped portion; the surface of the fourth doped portion remote from the second doped portion forms a portion of the first surface; and the fourth doped portion is in contact with the second electrode; a fifth doped portion, disposed on one side of the main portion and connected to the main portion; a surface of the fifth doped portion away from the second surface forming a portion of the first surface; the fifth doped portion and the first doped portion being spaced apart; a doping type of the fifth doped portion being the same as that of the main portion, and a doping concentration of the fifth doped portion being greater than a doping concentration of the main portion; and the fifth doped portion being in contact with the first electrode; The orthographic projection of any one of the first doping portion, the second doping portion, the third doping portion, and the fourth doping portion on the second surface comprises a circle, a square, or a regular octagon; The orthographic projection of the fifth doping portion on the second surface has a ring shape, an inner boundary of the ring shape is a circle, a square, or a regular octagon, and an outer boundary of the ring shape is a circle, a square, or a regular octagon.

13. The single photon avalanche diode according to any one of claims 1 to 7, characterized in that: The doping type of the third doping portion is N-type.

14. A photoelectric detector, characterized in that: include: At least one single photon avalanche diode according to any one of claims 1 to 13; The logic circuit is coupled to the first electrode and the second electrode respectively.

15. The photodetector according to claim 14, wherein: The photon detection surface of the single-photon avalanche diode is the second surface; the logic circuit is connected to the first surface of the single-photon avalanche diode.

16. A detection device, characterized in that: Comprising a photodetector as claimed in claim 14 or 15.

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