Photoelectric detection unit, photoelectric detection structure, photoelectric detector and preparation method thereof

Abstract

The present application relates to a photoelectric detection unit, a photoelectric detection structure and a method for preparing the same, a photodetector and a method for preparing the same, wherein the photoelectric detection unit includes a first substrate; a first structure having a first doping type formed on the front surface of the first substrate; a second structure having a second doping type formed within the first structure, the first structure having a bottom wall and side walls surrounding the bottom and side surfaces of the second structure; a first light processing layer having a concave-convex structure formed on the upper surface of the second structure; a heavily doped region having a first doping type formed within the sidewall, the doping concentration of the heavily doped region being greater than the doping concentration of the sidewall; a first electrode electrically connected to the heavily doped region; and a second electrode electrically connected to the second structure. In the present application, the first structure and the second structure form a light detection layer, and a first light processing layer is formed on the light detection layer. The first light processing layer reflects the incident light multiple times to increase the optical path and improve the light absorption efficiency of the light detection layer.

Description

Technical Field

[0001] The present invention relates to the field of photoelectric detection, and in particular to a photoelectric detection unit, a photoelectric detection structure, a method for preparing the photoelectric detection structure, a photoelectric detector, and a method for preparing the photoelectric detector. Background Art

[0002] The photoelectric detection structure is the core structure of equipment such as laser radar, ToF (Time of Flight) equipment and depth imaging equipment. With the advancement of science and technology, the detection accuracy requirements for photoelectric detectors are becoming higher and higher. Factors affecting detection accuracy include light absorption efficiency and internal noise interference of the photoelectric detection structure. According to the positive correlation between light absorption efficiency and light propagation path, the current way to improve light absorption efficiency is mainly to increase the thickness of the light detection layer, and increase the light propagation path by increasing the thickness of the light detection layer. However, increasing the thickness of the light detection layer will, on the one hand, increase the processing difficulty of the photoelectric detection structure and reduce the yield rate. On the other hand, increasing the thickness of the light detection layer will also increase the jitter time, thereby reducing the accuracy of detection. Summary of the Invention

[0003] Based on this, the present application addresses the technical problem that the detection accuracy of the current photoelectric detection structure is difficult to improve, and proposes a new photoelectric detection unit, a photoelectric detection structure and a preparation method, and a photoelectric detector and a preparation method.

[0004] A photoelectric detection unit proposed in this application is:

[0005] A photoelectric detection unit, comprising:

[0006] first base;

[0007] a first structure having a first doping type and formed on the first substrate;

[0008] a second structure having a second doping type and formed within the first structure, the first structure having a bottom wall and side walls surrounding a bottom surface and side surfaces of the second structure;

[0009] a first light treatment layer formed on the upper surface of the second structure, wherein the surface of the first light treatment layer has a concave-convex structure;

[0010] a heavily doped region having a first doping type and formed in the sidewall, wherein the doping concentration of the heavily doped region is greater than the doping concentration of the sidewall;

[0011] a first electrode electrically connected to the heavily doped region; and

[0012] The second electrode is electrically connected to the second structure.

[0013] A photoelectric detection structure proposed in this application is:

[0014] A photoelectric detection structure, comprising:

[0015] A plurality of photoelectric detection units, wherein the photoelectric detection units are any of the photoelectric detection units described above.

[0016] A photodetector proposed in this application is:

[0017] A photodetector comprising:

[0018] a second wafer comprising a second substrate and a processing circuit formed within the second substrate;

[0019] A first chip, the first chip includes any of the above-mentioned photoelectric detection structures, the first electrode and the second electrode are led out from the front side of the first chip, the front side of the first chip is inverted on the second chip, so that the first electrode and the second electrode are electrically connected to the processing circuit.

[0020] A method for preparing a photoelectric detection structure proposed in this application is:

[0021] A method for preparing a photoelectric detection structure, comprising:

[0022] preparing a first substrate, wherein the first substrate includes a light reflecting structure;

[0023] Growing an epitaxial layer on the first substrate, and doping the epitaxial layer to form a plurality of photodetection units, each of the photodetection units comprising a first structure and a second structure formed within the first structure, the first structure of each photodetection unit having a bottom wall and side walls surrounding a bottom surface and side surfaces of the second structure, wherein the first structure has a first doping type, and the second structure has a second doping type;

[0024] doping the sidewalls of each of the photodetection units to form heavily doped regions having a first doping type, wherein the doping concentration of the heavily doped regions is greater than the doping concentration of the sidewalls;

[0025] etching the surface of the second structure to form a first optical processing layer having a concave-convex structure;

[0026] forming an insulating layer covering the sidewall and a portion of the second structure, wherein a quenching circuit is formed in the insulating layer;

[0027] A first electrode is formed through the insulating layer to be electrically connected to the heavily doped region, and a second electrode is formed through the insulating layer to be electrically connected to the quenching circuit and the second structure, respectively.

[0028] A method for preparing a photodetector proposed in this application is as follows:

[0029] A method for preparing a photodetector, comprising:

[0030] Providing a first wafer and a second wafer, wherein the first wafer comprises any one of the above-described photodetection structures, and the first electrode and the second electrode are led out from the front surface of the first wafer; and the second wafer comprises a second substrate and a processing circuit formed in the second substrate;

[0031] placing the front side of the first wafer upside down on the second wafer, so that the first electrode and the second electrode are electrically connected to the processing circuit;

[0032] thinning the back side of the first wafer;

[0033] A second light-processing layer is formed on the back surface of the first wafer, and a surface of the second light-processing layer has a concavo-convex structure.

[0034] The above-mentioned photodetection unit and the photodetection structure and photodetector containing the photodetection unit and the preparation method, the photodetection layer is formed on the first substrate, and the photodetection layer specifically includes a first structure and a second structure. Among them, the first structure with the first doping type and the second structure with the second doping type constitute a PN junction, and an avalanche interface is formed at the contact surface of the PN junction. When avalanche breakdown occurs at the PN junction, the current of the diode is positively correlated with the light intensity. The stronger the light, the greater the current. Therefore, the light intensity is reflected by the current size to achieve photodetection. In the present application, a first light processing layer is formed on the photodetection layer. The surface of the first light processing layer has a concave-convex structure. When the light reaches the photodetection structure, the concave-convex surface of the first light processing layer can reflect the light back and forth, increase the propagation path of the light in the photodetection layer, and improve the light absorption efficiency of the photodetection layer. Compared with traditional technologies, the present application increases the propagation path of the light in the photodetection layer through the first light processing layer, so that the light absorption efficiency can be improved without increasing the thickness of the photodetection layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A side sectional view of the photoelectric detection unit in the first embodiment of the present application;

[0036] Figure 2 A side sectional view of a photoelectric detection unit in a second embodiment of the present application;

[0037] Figure 3 A side sectional view of a photoelectric detection unit in a third embodiment of the present application;

[0038] Figure 4 A side sectional view of a photoelectric detection unit in a fourth embodiment of the present application;

[0039] Figure 5 A side sectional view of a photoelectric detection unit in a fifth embodiment of the present application;

[0040] Figure 6 A side sectional view of a photoelectric detection unit in a sixth embodiment of the present application;

[0041] Figure 7 A side sectional view of a photoelectric detection unit in a seventh embodiment of the present application;

[0042] Figure 8 This is a side sectional view of the photoelectric detection structure in the eighth embodiment of the present application;

[0043] Figure 9 This is a side sectional view of the photoelectric detection structure in the ninth embodiment of the present application;

[0044] Figure 10 This is a side sectional view of the photoelectric detection structure in the tenth embodiment of the present application;

[0045] Figure 11 This is a side sectional view of the photoelectric detection structure in the eleventh embodiment of the present application;

[0046] Figure 12 This is a side sectional view of a photodetector in the twelfth embodiment of the present application;

[0047] Figure 13a This is a flow chart of the steps of a method for preparing a photoelectric detection structure in one embodiment of the present application;

[0048] Figure 13b This is a flowchart of a method for preparing a photoelectric detection structure in another embodiment of the present application;

[0049] Figure 14 This is a flowchart of the steps of a method for preparing a photoelectric detector in one embodiment of the present application;

[0050] Figures 15a to 15e This is a structural schematic diagram corresponding to the relevant steps of the photoelectric detector preparation method in one embodiment of the present application.

[0051] Explanation of symbols

[0052] 100 first substrate; 200 light detection layer; 210 first structure; 211 bottom wall; 212 side wall; 220 second structure; 221 first doped region; 222 second doped region; 223 third doped region; 230 heavily doped region; 231 first heavily doped region; 232 second heavily doped region; 233 third heavily doped region; 234 fourth heavily doped region; 235 fifth heavily doped region; 240 isolation structure; 300 first light processing layer; 410 first electrode; 420 second electrode; 430 quenching circuit; 510 convex lens; 520 anti-reflection layer; 610 second substrate; 620 processing circuit; 700 second light processing layer; 800 passivation layer; J1 first wafer; J2 second wafer. DETAILED DESCRIPTION

[0053] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive disclosure of the present invention.

[0054] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0055] First embodiment:

[0056] like Figure 1 FIG. 1 is a schematic structural diagram of the photoelectric detection unit in the first embodiment.

[0057] The photodetection unit includes a first substrate 100 and a light detection layer 200 formed on the first substrate 100. The light detection layer 200 specifically includes a first structure 210 disposed on the first substrate 100 and a second structure 220 formed within the first structure 210. The side and bottom surfaces of the second structure 220 are enclosed by the first structure 210, and the top surface of the second structure 220 does not contact the first structure 210. That is, the first structure 210 has a bottom wall 211 in contact with the bottom surface of the second structure 220 and a side wall 212 in contact with the side surface of the second structure 220.

[0058] The first light-management layer 300 is disposed on the second structure 220 , and the surface of the first light-management layer 300 has a concavo-convex structure.

[0059] A heavily doped region 230 is formed in the sidewall 212 and extends from the top surface of the sidewall 212 to the inside of the sidewall 212. The doping concentration of the heavily doped region 230 is greater than the doping concentration of the sidewall 212. The heavily doped region 230 is connected to the first electrode 410, and the second structure 220 is connected to the second electrode 420.

[0060] The first structure 210 and the heavily doped region 230 have a first doping type, and the second structure 220 has a second doping type. The first doping type and the second doping type have opposite doping properties. Specifically, the first doping type may be N-type and the second doping type may be P-type, or the first doping type may be P-type and the second doping type may be N-type.

[0061] In the aforementioned photodetection unit, the first structure 210 and the second structure 220 with different doping types actually form a PN junction, which forms the photodetection layer 200. Because the longer the optical propagation path of light in the photodetection layer 200, the higher the absorption efficiency, in this application, a first light processing layer 300 is disposed on the photodetection layer 200. Since the first light processing layer 300 has a concave-convex surface, when light propagates to the first light processing layer 300, the concave-convex surface of the first light processing layer 300 will reflect the light multiple times, thereby increasing the optical propagation path of the light in the photodetection layer 200 and improving the light absorption efficiency of the photodetection structure.

[0062] In one embodiment, the first light processing layer 300 can be a separate layer independent of the second structure 220, or it can be the upper surface layer of the second structure 220, that is, the upper surface of the second structure 220 is processed to form a concave-convex structure. Specifically, the concave-convex structure of the first light processing layer 300 is of nanometer size, and the thickness of the first light processing layer is essentially negligible. Compared to the conventional method of increasing the thickness of the entire light detection layer by increasing the thickness of the first or second structure, thereby increasing the optical path length of light in the light detection layer to improve light absorption efficiency, the present application can improve light absorption efficiency without increasing the thickness of the light detection layer, thus avoiding the many problems mentioned above caused by increasing the thickness of the light detection layer.

[0063] Furthermore, the concave-convex structure can have various shapes. In one embodiment, the longitudinal cross-section of the concave-convex structure is sawtooth-shaped, and the grooves of the concave-convex structure are in the shape of an inverted pyramid. In another embodiment, the longitudinal cross-section of the concave-convex structure is square-wave-shaped, and the cross-sections of the grooves and / or protrusions in the protrusion structure are formed in the shape of at least one of a regular polygon and a circle. Furthermore, a protective layer can be formed on the first light treatment layer 300 to protect the first light treatment layer 300.

[0064] Specifically, the doping types of the first light processing layer 300 and the second structure 220 are opposite, for example, the second structure 220 is N-type doped and the first light processing layer 300 is P-type doped, which is beneficial for controlling the noise carriers generated on the surface to the surface and not entering the depletion layer, thereby effectively reducing the dark count.

[0065] Furthermore, the photodetection unit further includes a quenching circuit 430, which can be specifically a quenching resistor. One end of the second electrode 420 contacts the second structure 220, and the other end is connected to the quenching circuit 430. Specifically, an insulating layer is provided on the top surface of the first structure 210 and the second structure 220, and the insulating layer covers the sidewall 212 of the first structure 210 and a portion of the second structure 220. The quenching circuit 430 is provided in the insulating layer, and the first electrode 410 and the second electrode 420 pass through the insulating layer and are led to the surface of the structure.

[0066] In one embodiment, the first substrate 100 includes a light-reflecting light-emitting structure, specifically a DBR (Bragg reflector) structure. Specifically, the first substrate 100 can be a semiconductor substrate or an SOI (Silicon-On-Insulator) substrate with a buried oxide layer incorporated therein. Alternatively, the first substrate 100 can be a metal substrate. When a metal substrate is used as the first substrate 100, an insulating layer is provided between the metal substrate and the bottom wall 211 for electrical isolation.

[0067] In one embodiment, the doping concentration of the bottom wall 211 of the first structure 210 is higher than that of the side wall 212 , which ensures that the breakdown of the PN junction occurs at the contact surface between the second structure 220 and the bottom wall 211 rather than at the contact surface between the second structure 220 and the side wall 212 .

[0068] In one embodiment, the thickness of the second structure 220 is greater than that of the bottom wall 211 to increase the optical path length of light in the second structure 220. Specifically, the thickness of the light detection layer 200 is in the range of [2 μm, 10 μm], and the thickness of the bottom wall 211 does not exceed 5 μm.

[0069] In one embodiment, the doping concentration of the second structure 220 decreases from top to bottom, that is, the doping concentration at the top of the second structure 220 is greater than the doping concentration at the bottom. A potential difference is formed by different doping concentration gradients, which is conducive to the movement of photogenerated carriers from top to bottom.

[0070] Specifically, the second structure 220 includes a third doping region 223, a second doping region 222, and a first doping region 221, with doping concentrations decreasing in sequence, wherein the first doping region 221 is provided on the bottom wall 211, the second doping region 222 extends from the top surface of the first doping region 221 to the inside of the first doping region 221, the third doping region 223 is located on the upper surface of the second doping region 222, and the first light processing layer 300 is formed on the upper surface of the third doping region 223. Furthermore, the extension depth of the second doping region 222 in the first doping region 221 can be set according to parameters such as avalanche voltage, light absorption efficiency, and pulse response. In this embodiment, as Figure 1 As shown, the first doping region 221 surrounds the bottom surface and side surfaces of the second doping region 222 , and the bottom of the second doping region 222 does not contact the bottom wall 211 .

[0071] The heavily doped region 230 can be designed in various forms. In this embodiment, the heavily doped region 230 includes a second heavily doped region 232 and a first heavily doped region 231. The first heavily doped region 231 is formed within the second heavily doped region 232. The doping concentrations of the sidewall 212, the second heavily doped region 232, and the first heavily doped region 231 increase in sequence. The first electrode 410 is drawn out from the sidewall 212 by the heavily doped region 230, thereby reducing the contact resistance between the first electrode 410 and the sidewall 212.

[0072] Second embodiment:

[0073] like Figure 2 FIG. 1 is a schematic structural diagram of a photoelectric detection unit in the second embodiment.

[0074] The difference between the second embodiment and the first embodiment is that in the second embodiment, the bottom of the second doping region 222 extends to the bottom wall 211 and contacts the bottom wall 211, that is, the second doping region 222 passes through the first doping region 221 and contacts the bottom wall 211, the first doping region 221 covers the side surface of the second doping region 222, and the bottom wall 211 covers the bottom surface of the second doping region 222.

[0075] Third embodiment:

[0076] like Figure 3 FIG. 1 is a schematic structural diagram of a photoelectric detection unit in the third embodiment.

[0077] The third embodiment differs from the first embodiment in that, in the third embodiment, the heavily doped region 230 may include only the first heavily doped region 231 .

[0078] Fourth embodiment:

[0079] like Figure 4 FIG. 4 is a schematic structural diagram of a photoelectric detection unit in the fourth embodiment.

[0080] The fourth embodiment differs from the first embodiment in that, in the fourth embodiment, the heavily doped region 230 may include only the first heavily doped region 231. Meanwhile, the bottom of the second doped region 222 extends to and contacts the bottom wall 211. That is, the second doped region 222 penetrates the first doped region 221 and contacts the bottom wall 211. The first doped region 221 covers the side surfaces of the second doped region 222, and the bottom wall 211 covers the bottom surface of the second doped region 222.

[0081] Fifth embodiment:

[0082] like Figure 5 FIG. 1 is a schematic structural diagram of a photoelectric detection unit in the fifth embodiment.

[0083] The fifth embodiment differs from the first embodiment in that, in the fifth embodiment, the second structure 220 is formed on the upper surface of the first structure 210, the bottom wall thickness of the first structure 210 is greater than that of the second structure 220, and the doping concentration of the first structure 210 gradually decreases from the bottom surface to the top surface of the first structure 210. Furthermore, in this embodiment, the heavily doped region 230 includes a third heavily doped region 233 and a fourth heavily doped region 234, and the doping concentrations of the third heavily doped region 233, the fourth heavily doped region 234, and the first structure 210 decrease in sequence. The fourth heavily doped region 234 is located below and in contact with the third heavily doped region 233, thereby increasing the depth of the heavily doped region 230, making it greater than the depth of the second structure 220. The heavily doped region 230 can not only lead out the first electrode 410 and increase the depth of the heavily doped region 230, but also electrically isolate adjacent photodetection units. Furthermore, a fifth heavily doped region 235 may be formed below the fourth heavily doped region 234 and in contact with the fourth heavily doped region 234 . The fourth heavily doped region 234 and the fifth heavily doped region 235 may be formed by plasma implantation processes with different energies.

[0084] Sixth embodiment:

[0085] like Figure 6 FIG. 1 is a schematic structural diagram of a photoelectric detection unit in the sixth embodiment.

[0086] In some embodiments, as Figure 6 As shown, a convex lens 510 is disposed on top of the first light processing layer 300. The convex lens 510 can converge external light onto the first light processing layer 300 of the photodetection unit, thereby improving the photosensitivity of the photodetection unit. It is understood that the convex lens 510 is specifically disposed on the topmost layer on the side of the photodetection unit that receives light.

[0087] Seventh embodiment:

[0088] like Figure 7 FIG. 1 is a schematic structural diagram of a photoelectric detection unit in the seventh embodiment.

[0089] In some embodiments, as Figure 7 As shown, an anti-reflection layer 520 is disposed on top of the first light processing layer 300. The anti-reflection layer 520 reduces the reflection of light from the structure surface, allowing more light to be incident on the first light processing layer 300, thereby improving the photosensitivity of the photodetection unit. It will be understood that the anti-reflection layer 520 is specifically disposed on the topmost layer on the side of the photodetection unit that receives light.

[0090] The present application also relates to a photoelectric detection structure including the above-mentioned photoelectric detection unit. The photoelectric detection structure may include a plurality of the above-mentioned photoelectric detection units. Specific embodiments are described below.

[0091] Eighth embodiment:

[0092] like Figure 8 FIG. 1 is a schematic structural diagram of the photoelectric detection structure in the eighth embodiment.

[0093] In the eighth embodiment, when the left and right photodetection units are arranged in parallel, the left and right photodetection units share the middle sidewall 212, the heavily doped region 230 within the sidewall 212, and the first electrode 410, i.e., the first electrodes 410 of the left and right photodetection units are connected in parallel. In this embodiment, the photodetection unit can specifically be the photodetection unit of any one of the first to fourth embodiments. The specific structure of the photodetection unit has been described in detail above and will not be repeated here.

[0094] Ninth embodiment:

[0095] like Figure 9 FIG. 1 is a schematic structural diagram of the photoelectric detection structure in the ninth embodiment.

[0096] The difference between the ninth embodiment and the eighth embodiment is that the photoelectric detection unit in the ninth embodiment is the photoelectric detection unit in the fifth embodiment. The specific structure of the photoelectric detection unit has been described above and will not be repeated here.

[0097] Tenth embodiment:

[0098] like Figure 10 FIG. 1 is a schematic structural diagram of the photoelectric detection structure in the tenth embodiment.

[0099] The tenth embodiment differs from the eighth embodiment or the ninth embodiment in that an isolation structure 240 is further provided between adjacent photodetection units. The isolation structure 240 is located between the opposite sidewalls 212 of adjacent photodetection units. Specifically, the isolation structure 240 is spaced apart from the heavily doped region 230. The heavily doped region includes a dielectric material, and adjacent photodetection units can be electrically isolated by the isolation structure 240. Adjacent photodetection units are isolated by the isolation structure 240 to avoid mutual interference of electrical signals between adjacent photodetection units and improve the signal-to-noise ratio.

[0100] Specifically, the isolation structure 240 is formed by filling the trench. The isolation structure 240 specifically includes a dielectric layer formed on the inner wall of the trench and a filling structure filled in the trench. The dielectric layer can be a silicon nitride or silicon oxide layer, and the filling structure can be silicon oxide or polysilicon or metal. When the filling structure is silicon oxide, the isolation structure 240 has an electrical isolation effect. When the filling structure is polysilicon or metal, the isolation structure 240 has electrical isolation and optical isolation effects.

[0101] Specifically, the depth of the isolation structure 240 can be designed based on actual conditions. For example, in this embodiment, the isolation structure 240 extends to and contacts the bottom wall 211 or the first substrate 100 to achieve a good isolation effect. In other embodiments, the depth of the isolation structure 240 can be appropriately reduced, and the isolation structure 240 is located above the bottom wall 211 and does not contact the bottom wall 211.

[0102] Eleventh embodiment:

[0103] like Figure 11 FIG. 1 is a schematic structural diagram of the photoelectric detection structure in the eleventh embodiment.

[0104] The eleventh embodiment differs from the tenth embodiment in that the isolation structure 240 contacts the heavily doped region 230 to minimize the area occupied by the isolation structure 240 and improve device integration. Furthermore, the isolation structure 240 specifically contacts the first heavily doped region 231 in the heavily doped region 230 .

[0105] The present application also relates to a photoelectric detector, which includes any of the above-mentioned photoelectric detection structures.

[0106] Twelfth embodiment:

[0107] like Figure 12 FIG. 1 is a schematic structural diagram of a photoelectric detector in the twelfth embodiment.

[0108] Specifically, such as Figure 12As shown, the photodetector includes a first chip J1 and a second chip J2, wherein the second chip J2 includes a second substrate 610 and a processing circuit 620 formed within the second substrate 610. The first chip J1 includes any of the aforementioned photodetection structures, the core of which is a light detection layer 200 composed of a first structure 210 and a second structure 220, with a first light processing layer 300 formed on the second structure 220. In the first chip J1, the first substrate, which can be specifically a silicon substrate, is located on the back side of the first chip J1. The first electrode 410 and the second electrode 420 are extended from the front side of the first chip J1. The processing circuit 620 in the second chip J2 has connection terminals on the front side of the second chip J2. The front sides of the first chip J1 and the second chip J2 are bonded to each other so that the first electrode 410 and the second electrode 420 contact the connection terminals of the processing circuit 620, thereby achieving an electrical connection between the light detection layer 200 and the processing circuit 620.

[0109] To further enhance the light absorption efficiency of the light detection layer 200, after the front surface of the first wafer J1 is bonded to the second wafer J2, the first substrate on the back surface of the first wafer J1 can be thinned, and a second light treatment layer 700 can be formed on the back surface of the first wafer J1. The surface of the second light treatment layer 700 also has a concave-convex structure. Combining the first light treatment layer 300 and the second light treatment layer 700 can further enhance the light absorption efficiency of the light detection layer 200. Specifically, the morphology of the second light treatment layer 700 is identical to that of the first light treatment layer 300 and is not further described here.

[0110] The present application also relates to a method for preparing a photoelectric detection structure, the method comprising the following steps:

[0111] Preparing a first substrate: preparing a first substrate, wherein the first substrate includes a light reflecting structure;

[0112] Preparing a photodetection layer: growing an epitaxial layer on the first substrate, and doping the epitaxial layer to form a plurality of photodetection units, each of the photodetection units comprising a first structure and a second structure formed within the first structure, and in each of the photodetection units, the first structure has a bottom wall and side walls surrounding the bottom and side surfaces of the second structure, wherein the first structure has a first doping type and the second structure has a second doping type;

[0113] Preparing a heavily doped region: doping the sidewalls in each of the photodetection units to form a heavily doped region having a first doping type, wherein the doping concentration of the heavily doped region is greater than the doping concentration of the sidewalls;

[0114] Preparing a first optical treatment layer: etching the surface of the second structure to form a first optical treatment layer having a concave-convex structure;

[0115] Preparing a quenching circuit: forming an insulating layer covering the sidewall and a portion of the second structure, wherein the quenching circuit is formed in the insulating layer;

[0116] Preparing electrodes: forming a first electrode penetrating the insulating layer to be electrically connected to the heavily doped region, and forming a second electrode penetrating the insulating layer to be electrically connected to the quenching circuit and the second structure respectively.

[0117] It should be noted that the above preparation process does not limit the order of the steps, and the order of the steps can be adjusted according to actual conditions.

[0118] The operation time of the step of preparing the first optical treatment layer can be adjusted according to the specific morphology of the first optical treatment layer.

[0119] In one embodiment, the size of the concavo-convex structure of the first optical processing layer 300 is at the nanometer level, the longitudinal section of the concavo-convex structure is sawtooth-shaped, and the grooves in the concavo-convex structure are in the shape of an inverted pyramid.

[0120] In one embodiment, the above-mentioned preparation steps further include:

[0121] Preparation of isolation structure: opening a trench between the phase photoelectric detection units, forming a dielectric layer on the inner wall of the trench and filling the trench with a filling structure to form an isolation structure.

[0122] At this time, when the size of the concavo-convex structure of the first optical processing layer 300 is at the nanometer level, the longitudinal cross-section of the concavo-convex structure is sawtooth-shaped, and the grooves in the concavo-convex structure are in the shape of an inverted pyramid, the steps for preparing the corresponding photoelectric detection structure are performed according to the flowchart shown in Figure 13a, specifically as follows:

[0123] Step S110: preparing a first substrate, wherein the first substrate includes a light reflective structure.

[0124] Specifically, the first substrate 100 may be an SOI substrate, or the first substrate 100 may have a DBR (Bragg reflector) structure, or the first substrate 100 may include a metal substrate.

[0125] Step S120: growing an epitaxial layer on the first substrate, and doping the epitaxial layer to form a plurality of photodetection units, each of the photodetection units including a first structure and a second structure formed in the first structure, and in each of the photodetection units, the first structure has a bottom wall and side walls surrounding the bottom and side surfaces of the second structure, wherein the first structure has a first doping type, and the second structure has a second doping type.

[0126] For details, please refer to Figure 10, the epitaxial layer on the first substrate 100 is doped to form a plurality of photodetection units, wherein the structure of the photodetection unit has been specifically introduced above and will not be repeated here. In this step, the order of doping the epitaxial layer can be flexibly adjusted. In one embodiment, a bottom epitaxial layer can be formed first, and the bottom epitaxial layer is plasma-implanted to form a bottom wall 211, and then a top epitaxial layer is continued to grow on the bottom wall 211, and then the top epitaxial layer is plasma-implanted to form a second structure 220 located on the bottom wall 211 and a side wall 212 surrounding the side of the second structure 220, respectively. The bottom wall 211 and the side wall 212 both have the first doping type, and the two are connected as a first structure 210. In another embodiment, a complete epitaxial layer can be formed first, and then the above-mentioned first structure 210 and second structure 220 are formed by plasma implantation of different energies.

[0127] Step S130: opening a trench between adjacent photodetection units, forming a dielectric layer on the inner wall of the trench, and filling the trench with a filling structure to form an isolation structure.

[0128] For details, please refer to Figure 10 Through an etching process, trenches are opened between adjacent photodetection units, a dielectric layer is formed on the inner wall of the trenches, and a filling structure is filled in the trenches to form an isolation structure 240.

[0129] Specifically, the depth of the trench can be designed based on actual conditions. In one embodiment, the isolation structure 240 extends to and contacts the bottom wall 211 or the first substrate 100 to achieve a better isolation effect. In other embodiments, the depth of the isolation structure 240 can be appropriately reduced, and the isolation structure 240 is located above the bottom wall 211 and does not contact the bottom wall 211.

[0130] Specifically, the dielectric layer formed on the inner wall of the trench can be silicon oxide, and the filling structure filled in the trench can be silicon oxide, polysilicon, or metal. When the filling material is silicon oxide, the isolation structure 240 only has an electrical isolation effect, but not an optical isolation effect. For example, in a silicon photomultiplier (SiPM), the output signals of all subunits are connected together, and there is only one signal output. The SiPM is not sensitive to which subunit is triggered by the signal light. Therefore, even if there is crosstalk of the signal light, it will not affect the detection performance of the entire device. On the contrary, this crosstalk is more conducive to improving the absorption efficiency of the SiPM in the light trapping structure. When the filling material is polysilicon or metal, the isolation structure 240 can be both electrically isolated and optically isolated. This solution is applicable to both SiPM and single-photon avalanche diode (SPAD array detector).

[0131] Step S140: doping the sidewalls in each of the photodetection units to form heavily doped regions having a first doping type, wherein the doping concentration of the heavily doped regions is greater than the doping concentration of the sidewalls.

[0132] Step S150: etching the surface of the second structure to form a first optical processing layer having a concave-convex structure.

[0133] The surface of the second structure 220 is etched to form a first optical processing layer 300 having a concave-convex structure. The longitudinal section of the concave-convex structure is sawtooth-shaped, and the grooves in the concave-convex structure are in the shape of an inverted pyramid.

[0134] Step S160: forming an insulating layer covering the sidewall and a portion of the second structure, wherein a quenching circuit is formed in the insulating layer.

[0135] Step S170: forming a first electrode penetrating the insulating layer to be electrically connected to the heavily doped region, and forming a second electrode penetrating the insulating layer to be electrically connected to the quenching circuit and the second structure, respectively.

[0136] Through the above steps S110 to S170 , a photoelectric detection structure can be formed.

[0137] In another embodiment, the size of the concavo-convex structure of the first optical processing layer 300 is at the nanometer level, the longitudinal section of the concavo-convex structure is a square waveform, and the cross-sectional shape of the protrusions and / or grooves in the concavo-convex structure is at least one of a regular polygon and a circle. In this case, step S150 in the above preparation process can be merged into step S130, and the corresponding preparation steps of the photoelectric detection structure are performed according to the flowchart shown in Figure 13b, specifically as follows:

[0138] Step S210: preparing a first substrate, wherein the first substrate includes a light reflective structure;

[0139] Step S220: growing an epitaxial layer on the first substrate, and doping the epitaxial layer to form a plurality of photodetection units, each of the photodetection units including a first structure and a second structure formed within the first structure, and in each of the photodetection units, the first structure has a bottom wall and side walls surrounding a bottom surface and side surfaces of the second structure, wherein the first structure has a first doping type, and the second structure has a second doping type;

[0140] Step S230: simultaneously opening trenches between adjacent photodetection units and etching the surface of the second structure to form a first optical processing layer having a concave-convex structure, forming a dielectric layer on the inner wall of the trench and filling the trench with a filling structure to form an isolation structure;

[0141] Step S240: doping the sidewalls of each of the photodetection units to form heavily doped regions having a first doping type, wherein the doping concentration of the heavily doped regions is greater than the doping concentration of the sidewalls;

[0142] Step S250: forming an insulating layer covering the sidewall and a portion of the second structure, wherein a quenching circuit is formed in the insulating layer;

[0143] Step S260: forming a first electrode penetrating the insulating layer to be electrically connected to the heavily doped region, and forming a second electrode penetrating the insulating layer to be electrically connected to the quenching circuit and the second structure, respectively.

[0144] Through steps S210 to S260 , another photodetection structure can be formed.

[0145] This application also relates to a method for preparing a photodetector, such as Figure 14 As shown, the preparation method comprises the following steps:

[0146] Step S310: Provide a first chip and a second chip, the first chip includes a photoelectric detection structure; the second chip includes a second substrate and a processing circuit formed in the second substrate; wherein the photoelectric detection structure includes a first substrate and a first structure, a second structure, a first light processing layer, a heavily doped region, and a first electrode and a second electrode formed on the first substrate, the second structure is formed in the first structure, the first structure has a bottom wall and a side wall surrounding the bottom and side surfaces of the second structure, the first light processing layer is formed on the upper surface of the second structure, the surface of the first light processing layer has a concave-convex structure, the heavily doped region is formed in the side wall, and the doping concentration of the heavily doped region is greater than the doping concentration of the side wall; the first electrode is electrically connected to the heavily doped region; the second electrode is electrically connected to the second structure, the first electrode and the second electrode are led out from the front of the first chip, the first structure and the heavily doped region have a first doping type, and the second structure has a second doping type.

[0147] like Figure 15a As shown, a first chip J1 and a second chip J2 are provided. The second chip J2 includes a second substrate 610 and a processing circuit 620 integrated in the second substrate 610. The first chip J1 includes a first substrate 100 and a light detection layer 200 formed on the front surface of the first substrate 100. Figure 1As shown, the photodetection layer 200 includes a first structure 210 and a second structure 220, which form a PN junction. A first light processing layer 300, located on the second structure 220, is used to perform multiple reflections on light, thereby increasing the optical path length. The detailed description of the photodetection structure has been detailed above and will not be repeated here. It will be appreciated that an insulating layer and a quenching circuit may also be provided on the top layer of the first wafer J1.

[0148] Step S320: The front side of the first chip is flipped onto the second chip, so that the first electrode and the second electrode are electrically connected to the processing circuit.

[0149] like Figure 15b As shown, the front surface of the first wafer J1 is inverted and bonded to the second wafer J2, so that the first electrode and the second electrode are electrically connected to the processing circuit 620. Specifically, in the first wafer J1, the first substrate is located on the back surface of the first wafer J1, and the first electrode and the second electrode are led out from the front surface of the first wafer J1. The processing circuit 620 in the second wafer J2 has a connection terminal on the front surface of the second wafer. The front surface of the first wafer J1 and the front surface of the second wafer J2 are bonded so that the first electrode and the second electrode are in contact with the connection terminals of the processing circuit, thereby achieving an electrical connection between the light detection layer and the processing circuit.

[0150] Step S330: thinning the back side of the first wafer.

[0151] like Figure 15c As shown, after the front side of the first chip J1 is bonded to the second chip J2, the back side of the first chip J1 is thinned, specifically the back side of the first substrate in the first chip J1 is thinned to reduce the light blocking effect of the film layer above the light detection layer 200.

[0152] Step S340: forming a second light treatment layer on the back side of the first wafer, wherein the surface of the second light treatment layer has a concave-convex structure.

[0153] like Figure 15d As shown, a second light processing layer 700 is formed on the back of the first chip J1. The second light processing layer 700 has the same function as the first light processing layer 300, which is to reflect the light multiple times to increase the optical path and improve the light absorption efficiency of the light detection layer 200. Figure 15e As shown, a passivation layer 800 is further formed on the second light-management layer 700 to protect the underlying structure.

[0154] The above embodiments merely illustrate several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A photoelectric detection unit, characterized in that: include: first base; a first structure having a first doping type and formed on the first substrate; a second structure having a second doping type, formed within the first structure, the first structure having a bottom wall and side walls surrounding a bottom surface and side surfaces of the second structure, the doping concentration of the bottom wall being greater than the doping concentration of the side walls; the doping concentration of the first structure gradually decreasing from the bottom surface to the top surface of the first structure; A first structure having a first doping type and a second structure having a second doping type form a PN junction, an avalanche interface is formed at a contact surface of the PN junction, and the avalanche interface is located on the bottom wall; the doping concentration of the second structure decreases from top to bottom, and the second structure includes a third doping region, a second doping region, and a first doping region, each of which has a decreasing doping concentration, and the first doping region is located on the bottom wall; a first light-processing layer formed on the upper surface of the second structure, wherein the surface of the first light-processing layer has a concave-convex structure; and the first light-processing layer and the second structure have opposite doping types; a heavily doped region having a first doping type and formed in the sidewall, wherein the doping concentration of the heavily doped region is greater than the doping concentration of the sidewall; a first electrode electrically connected to the heavily doped region; and The second electrode is electrically connected to the second structure.

2. The photoelectric detection unit according to claim 1, wherein The second doping region extends from the top surface of the first doping region to the inside of the first doping region, the first doping region surrounds the bottom and side surfaces of the second doping region, the third doping region is located on the upper surface layer of the second doping region, and the first light processing layer is formed on the third doping region.

3. The photoelectric detection unit according to claim 1, wherein The second doping region passes through the first doping region from the top surface of the first doping region and contacts the bottom wall. The first doping region covers the side surface of the second doping region. The bottom wall covers the bottom surface of the second doping region. The third doping region is located on the upper surface layer of the second doping region. The first light processing layer is formed on the third doping region.

4. The photoelectric detection unit according to claim 1, wherein The heavily doped region includes a second heavily doped region and a first heavily doped region, the first heavily doped region is formed in the second heavily doped region, the doping concentration of the first heavily doped region is higher than the doping concentration of the second heavily doped region, the doping concentration of the second heavily doped region is higher than the doping concentration of the side wall, and the first electrode is connected to the first heavily doped region.

5. The photoelectric detection unit according to claim 1, wherein: The thickness of the bottom wall is greater than the thickness of the second structure.

6. The photoelectric detection unit according to claim 5, wherein: The heavily doped region includes a third heavily doped region and a fourth heavily doped region, the doping concentration of the third heavily doped region is greater than the doping concentration of the fourth heavily doped region, the doping concentration of the fourth heavily doped region is greater than the doping concentration of the first structure, and the fourth heavily doped region is located below the third heavily doped region and in contact with the third heavily doped region.

7. The photoelectric detection unit according to any one of claims 1 to 6, characterized in that: The size of the concavo-convex structure is at the nanometer level, the longitudinal section of the concavo-convex structure is sawtooth-shaped, and the grooves in the concavo-convex structure are in the shape of an inverted pyramid.

8. The photoelectric detection unit according to any one of claims 1 to 6, characterized in that: The size of the concavo-convex structure is at the nanometer level, the longitudinal section of the concavo-convex structure is a square waveform, and the cross-sectional shape of the protrusions and / or grooves in the concavo-convex structure is at least one of a regular polygon and a circle.

9. A photoelectric detection structure, characterized in that: include: A plurality of photoelectric detection units, wherein the photoelectric detection unit is the photoelectric detection unit according to any one of claims 1 to 8.

10. The photoelectric detection structure according to claim 9, wherein: Also includes: An isolation structure is formed between adjacent photoelectric detection units, and the isolation structure includes a dielectric material.

11. The photoelectric detection structure according to claim 10, wherein: The isolation structure contacts the heavily doped region.

12. The photoelectric detection structure according to claim 10, wherein: The isolation structure is spaced apart from the heavily doped region.

13. The photoelectric detection structure according to claim 10, wherein: The isolation structure extends to the bottom wall or the first substrate and contacts the bottom wall or the first substrate.

14. The photoelectric detection structure according to any one of claims 10 to 13, wherein: The isolation structure is formed by filling the trench, and the isolation structure includes: a dielectric layer formed on an inner wall of the trench; A filling structure is filled in the trench, and the filling structure includes silicon oxide, polysilicon or metal.

15. A photoelectric detector, characterized in that: include: a second wafer comprising a second substrate and a processing circuit formed within the second substrate; A first chip, the first chip includes the photoelectric detection structure according to any one of claims 9 to 14, the first electrode and the second electrode are led out from the front side of the first chip, the front side of the first chip is inverted on the second chip, so that the first electrode and the second electrode are electrically connected to the processing circuit.

16. The photodetector according to claim 15, wherein Also includes: The second light-processing layer is formed on the back surface of the first wafer, and the surface of the second light-processing layer has a concavo-convex structure.

17. A method for preparing a photoelectric detection structure, characterized in that: include: preparing a first substrate, wherein the first substrate includes a light reflecting structure; An epitaxial layer is grown on the first substrate, and the epitaxial layer is doped to form a plurality of photodetection units, each of the photodetection units includes a first structure and a second structure formed in the first structure, the first structure of each photodetection unit has a bottom wall and side walls surrounding the bottom and side surfaces of the second structure, wherein the first structure has a first doping type, and the second structure has a second doping type; the doping concentration of the first structure gradually decreases from the bottom surface to the top surface of the first structure; the doping concentration of the bottom wall is greater than the doping concentration of the side wall; the first structure with the first doping type and the second structure with the second doping type constitute a PN junction, and an avalanche interface is formed at the contact surface of the PN junction, and the avalanche interface is located on the bottom wall; the doping concentration of the second structure decreases from top to bottom, and the second structure includes a third doping region, a second doping region and a first doping region with decreasing doping concentrations, and the first doping region is provided on the bottom wall; doping the sidewalls of each of the photodetection units to form heavily doped regions having a first doping type, wherein the doping concentration of the heavily doped regions is greater than the doping concentration of the sidewalls; etching the surface of the second structure to form a first optical processing layer having a concave-convex structure; forming an insulating layer covering the sidewall and a portion of the second structure, wherein a quenching circuit is formed in the insulating layer; A first electrode is formed through the insulating layer to be electrically connected to the heavily doped region, and a second electrode is formed through the insulating layer to be electrically connected to the quenching circuit and the second structure, respectively.

18. The preparation method according to claim 17, wherein The preparation method further includes: opening a trench between adjacent photoelectric detection units, forming a dielectric layer on the inner wall of the trench, and filling the trench with a filling structure to form an isolation structure.

19. The preparation method according to claim 17, wherein The size of the concavo-convex structure is at the nanometer level, the longitudinal section of the concavo-convex structure is sawtooth-shaped, and the grooves in the concavo-convex structure are in the shape of an inverted pyramid.

20. The preparation method according to claim 18, wherein The size of the concavo-convex structure is at the nanometer level, the longitudinal section of the concavo-convex structure is sawtooth-shaped, and the grooves in the concavo-convex structure are in the shape of an inverted pyramid; The step of forming a groove between adjacent photodetection units and the step of etching the surface of the second structure to form a first optical processing layer having a concave-convex structure are performed separately.

21. The preparation method according to claim 18, wherein The size of the concavo-convex structure is at the nanometer level, the longitudinal section of the concavo-convex structure is a square waveform, and the cross-sectional shape of the protrusions and / or grooves in the concavo-convex structure is at least one of a regular polygon and a circle; While trenches are opened between adjacent photodetection units, the surface of the second structure is etched to form a first optical processing layer having a concave-convex structure.

22. A method for preparing a photodetector, characterized in that: include: A first wafer and a second wafer are provided, wherein the first wafer comprises the photoelectric detection structure according to any one of claims 9 to 14, and the first electrode and the second electrode are led out from the front surface of the first wafer; and the second wafer comprises a second substrate and a processing circuit formed in the second substrate; placing the front side of the first wafer upside down on the second wafer, so that the first electrode and the second electrode are electrically connected to the processing circuit; thinning the back side of the first wafer; A second light-processing layer is formed on the back surface of the first wafer, and a surface of the second light-processing layer has a concavo-convex structure.

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