Single photon avalanche diode array, receiving sensor and lidar

Abstract

The application belongs to the technical field of optical devices, and provides a single-photon avalanche diode array, a receiving sensor and a laser radar. At least two SPAD units are arranged in an array. A microlens converges incident light onto a corresponding SPAD unit. A back metal grid connects the SPAD unit and a corresponding external electrode. A first dielectric layer is arranged between the microlens and the SPAD unit. A second dielectric layer is arranged between the SPAD unit and a front metal trace layer. The front metal trace layer is electrically connected to the corresponding SPAD unit through a contact metal wire. By arranging a deep groove isolation column between adjacent SPAD units and arranging a metal filling structure between the deep groove isolation column and the back metal grid, self-excited photons generated by the SPAD unit excited by incident light can be isolated, the self-excited photons can be prevented from entering adjacent SPAD units through the grid gap, the probability of photon crosstalk can be reduced, and the optical crosstalk of the device can be reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of optical devices, and particularly relates to a single-photon avalanche diode array, a receiving sensor and a laser radar. BACKGROUND

[0002] Single-photon avalanche diode arrays (SPADs) have been widely used in Lidar, autonomous driving, fluorescence lifetime imaging, quantum communication, biomedical imaging and other fields due to their high-sensitivity detection capability for intensity as low as a single photon, high time resolution, strong anti-interference capability, and the like. A silicon photomultiplier (SiPM) is formed by connecting at least two SPADs in parallel and used as a single point. With the advancement of silicon manufacturing technology, SPADs using silicon as the absorption and avalanche material have become a hot spot in the industry. In addition, by using various CMOS manufacturing technologies, SPADs can be easily integrated with different quenching circuits and readout circuits, thus having great technical advantages.

[0003] Two typical application forms can be formed by combining single-photon avalanche diode arrays through circuits. First, a silicon photomultiplier (SiPM) is formed by connecting at least two single-photon avalanche diode array cells in parallel, and outputs a signal as a whole. Since the pulse signals generated by different photons can be superimposed, the SiPM can respond to different light intensities and output a single point. Another typical form is a SPAD array, in which each SPAD cell is used as a separate pixel, and the light intensity detected by each pixel can be output individually. Therefore, the SPAD array has the ability to detect photons in parallel and can directly image. The imaging performance of the SPAD array in some weak light environments is excellent, such as biomedical microscopic imaging, fluorescence lifetime microscopic imaging and Flash radar.

[0004] However, for both SiPM and SPAD array, optical crosstalk is a key and difficult problem to solve. For SiPM, crosstalk photons cause SPAD cells without incident photons to be excited, and a large optical crosstalk probability can cause overestimation of the received signal energy, resulting in problems such as calculation error of object reflectivity, increased distance measurement error, and the like. For the SPAD array, imaging expansion and output abnormality of the entire row or column can occur. SUMMARY

[0005] To solve the above technical problems, the embodiments of the present application provide a single-photon avalanche diode array and a silicon photomultiplier, which are aimed at solving the problem that crosstalk photons in the current single-photon avalanche diode array cause SPAD cells without incident photons to be excited, resulting in a large optical crosstalk probability.

[0006] The first aspect of the embodiment of the present application provides a single photon avalanche diode array, the single photon avalanche diode array comprising:

[0007] at least two SPAD units;

[0008] at least two microlenses corresponding to the at least two SPAD units respectively, the microlenses being configured to converge incident light onto the corresponding SPAD units;

[0009] at least two front metal wiring layers corresponding to the at least two SPAD units respectively;

[0010] a back metal grid configured to connect the SPAD units and corresponding external electrodes;

[0011] a first dielectric layer arranged between the microlenses and the SPAD units, the first dielectric layer being configured to reduce reflection of the incident light;

[0012] a second dielectric layer arranged between the SPAD units and the front metal wiring layers; wherein the front metal wiring layers are electrically connected to the corresponding SPAD units through contact wires;

[0013] a deep trench isolation column arranged between adjacent SPAD units, configured to isolate the adjacent SPAD units;

[0014] a metal filling structure arranged between the deep trench isolation column and the back metal grid, configured to suppress self-excitation photons generated by the SPAD units under excitation of the incident light from entering adjacent SPAD units through grid gaps.

[0015] In one embodiment, a vertical cross-section of the back metal grid is an inverted trapezoid.

[0016] In one embodiment, a vertical cross-section of the back metal grid is a multi-layer stepped structure, and a width of each layer of the multi-layer stepped structure gradually increases.

[0017] In one embodiment, a vertical cross-section of the back metal grid is an arc-shaped structure, configured to reflect photons irradiating a surface thereof to the SPAD units.

[0018] In one embodiment, an intermetallic dielectric layer is arranged between adjacent front metal wiring layers, and an etching stop layer is arranged between the intermetallic dielectric layer and the deep trench isolation column, the deep trench isolation column extends to the etching stop layer and divides the second dielectric layer into at least two dielectric units corresponding to the SPAD units.

[0019] In one embodiment, an intermetallic dielectric layer is arranged between the adjacent front metal wiring layers, an etching stop layer is arranged between the intermetallic dielectric layer and the deep trench isolation column, and a length of the deep trench isolation column that penetrates into the second dielectric layer is greater than one half of a thickness of the second dielectric layer.

[0020] In one embodiment, the SPAD unit includes a first doped region and a second doped region arranged in layers on the second dielectric layer, and the first doped region and the second doped region form a PN junction.

[0021] In one embodiment, the deep trench isolation column is tungsten.

[0022] In one embodiment, the metal filling layer is in a ring structure.

[0023] A second aspect of the embodiments of the present application further provides a silicon photomultiplier, which includes the single-photon avalanche diode array according to any one of the above embodiments.

[0024] A third aspect of the embodiments of the present application further provides a receiving sensor, which includes the single-photon avalanche diode array according to any one of the first aspect.

[0025] A fourth aspect of the embodiments of the present application further provides a receiving sensor, which includes the silicon photomultiplier according to the second aspect.

[0026] A fifth aspect of the embodiments of the present application further provides a laser radar, which includes a transmitting sensor for transmitting a probe laser and the receiving sensor according to the third aspect and the fourth aspect for receiving a return wave of the probe laser, and obtaining probe information of a target object according to the return wave.

[0027] The embodiments of the present application have the following beneficial effects: at least two SPAD units are arranged in an array, a microlens converges incident light onto a corresponding SPAD unit, a back metal mesh connects the SPAD unit and a corresponding external electrode, a first dielectric layer is arranged between the microlens and the SPAD unit, a second dielectric layer is arranged between the SPAD unit and the front metal wiring layer, and the front metal wiring layer is electrically connected to the corresponding SPAD unit through a contact wire. By arranging a deep trench isolation column between the adjacent SPAD units and arranging a metal filling structure between the deep trench isolation column and the back metal mesh, self-excitation photons generated by the SPAD unit excited by the incident light can be isolated, the self-excitation photons can be prevented from entering the adjacent SPAD unit through the mesh gap, the overflow of the self-excitation photons is reduced, the probability of photon crosstalk is reduced, and the optical crosstalk of the device is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a schematic diagram of a single photon avalanche diode array provided by an embodiment of the present application Figure 1 ;

[0029] Figure 2 is a schematic diagram of a single photon avalanche diode array provided by an embodiment of the present application

[0030] Figure 3 is a schematic diagram of a single photon avalanche diode array provided by an embodiment of the present application

[0031] Figure 4 is a schematic diagram of a single photon avalanche diode array provided by an embodiment of the present application

[0032] Figure 5 is a schematic diagram of a single photon avalanche diode array provided by an embodiment of the present application Figure 2 ;

[0033] Figure 6 is a schematic diagram of a single photon avalanche diode array provided by an embodiment of the present application Figure 3 ;

[0034] Figure 7 is a schematic diagram of a single photon avalanche diode array provided by an embodiment of the present application Figure 4 ;

[0035] Figure 8 is a schematic diagram of a single photon avalanche diode array provided by an embodiment of the present application Figure 5 ;

[0036] Figure 9 is a schematic diagram of a single photon avalanche diode array provided by an embodiment of the present application Figure 6 ;

[0037] Figure 10 is a schematic diagram of a single photon avalanche diode array provided by an embodiment of the present application Figure 7 ;

[0038] Figure 11 is a schematic diagram of a single photon avalanche diode array provided by an embodiment of the present application Figure 8 ;

[0039] Figure 12 is a schematic diagram of a single photon avalanche diode array provided by an embodiment of the present application

[0040] Figure 13 is a schematic diagram of a single photon avalanche diode array provided by an embodiment of the present application

[0041] Figure 14 is a schematic diagram of a single photon avalanche diode array provided by an embodiment of the present application

[0042] Figure 15 A traditional structure and deep trench isolation pillar extension scheme crosstalk light field schematic diagram provided for the embodiments of the present application;

[0043] Figure 16 A device structure self-excitation photon crosstalk schematic diagram when a deep trench isolation pillar extension and metal filling structure closed loop scheme (such as Figure 9 ) is simultaneously used for the embodiments of the present application;

[0044] Figure 17 A device structure self-excitation crosstalk improvement schematic diagram when a comprehensive scheme (such as Figure 11 ) is used for the embodiments of the present application. DETAILED DESCRIPTION

[0045] In order to make the technical problems to be solved by the present application, the technical solutions and beneficial effects clearer, the present application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0046] It should be noted that when an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0047] It should be understood that the terms "length", "width", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0048] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, "at least two" means one or more than one, unless otherwise specifically limited.

[0049] Single photon avalanche diode array (SPADs) has been widely used in Lidar, autonomous driving, fluorescence lifetime imaging, quantum communication, biomedical imaging and other fields due to its high sensitivity detection capability for intensity as low as a single photon, high time resolution capability, strong anti-interference capability, etc. A silicon photomultiplier (SiPM) is used as a single point by at least two SPADs connected in parallel.

[0050] In order to reduce the crosstalk characteristics of the device, the device can be optimized from the device level, the packaging level and the system application level. However, the crosstalk improvement scheme at the application level only avoids the influence of crosstalk on signal reading, and the cost is a complex scanning method and circuit implementation, which does not solve the problem of optical crosstalk. The crosstalk improvement scheme at the packaging level is similar. The device level crosstalk is the most essential, but there are not many means that can be used. The crosstalk characteristics of FSI devices (front-side receiver devices) are better, but the low PDE limits their application. The industry still uses back-illuminated (BSI) devices with higher PDE. The introduction of deep trench isolation columns (DTI) can greatly reduce optical crosstalk, but it mainly reduces the crosstalk of adjacent SPADs, and far-end SPADs can still be affected by crosstalk through other paths. In particular, for SiPM devices, it may cause chain avalanche triggering, causing large-area devices to be affected by crosstalk.

[0051] To solve the above technical problems, the single photon avalanche diode array provided by the embodiments of the present application, as shown in Figure 1 The single photon avalanche diode array in the embodiments includes at least two SPAD units 500, at least two microlenses 100, at least two front metal wiring layers 130, a back metal grid 200, a first dielectric layer 310, a second dielectric layer 320, a deep trench isolation column 400 and a metal filling structure 140.

[0052] In the embodiment, the at least two SPAD units 500 are arranged adjacently, the at least two microlenses 100 correspond to the at least two SPAD units 500 one by one, the microlenses 100 are used for converging incident light onto the corresponding SPAD units 500, and the at least two front metal wiring layers 130 correspond to the at least two SPAD units 500 one by one. The back metal grid 200 is used for connecting the SPAD units 500 and the corresponding external electrodes, the first dielectric layer 310 is arranged between the microlenses 100 and the SPAD units 500, and the first dielectric layer 310 is used for reducing reflection of the incident light; the second dielectric layer 320 is arranged between the SPAD units 500 and the front metal wiring layer 130; wherein the front metal wiring layer 130 is electrically connected to the corresponding SPAD unit 500 through the contact wire 900. The deep trench isolation column 400 is arranged between the adjacent SPAD units 500, and the deep trench isolation column 400 is used for isolating the adjacent SPAD units 500; the metal filling structure 140 is arranged between the deep trench isolation column 400 and the back metal grid 200, and the metal filling structure 140 is used for inhibiting self-excitation photons generated by the SPAD units 500 excited by the incident light from entering the adjacent SPAD units 500 through the grid gap.

[0053] In the embodiment, the microlenses 100 play a role of converging light, converging incident light onto the corresponding SPAD units 500, the back metal grid 200 plays a role of leading one electrode of the SPAD units 500 out from the back, the deep trench isolation column 400 can electrically isolate the adjacent SPAD units 500 by being arranged between the adjacent SPAD units 500, and the metal filling structure 140 can isolate self-excitation photons generated by the SPAD units 500 excited by the incident light by being arranged between the deep trench isolation column 400 and the back metal grid 200, so that the self-excitation photons irradiated onto the deep trench isolation column 400 can be reflected, the absorption is increased, and the self-excitation photons cannot crosstalk into the adjacent SPAD units 500, which is an important way to improve crosstalk. The metal filling structure 140 can isolate self-excitation photons generated by the SPAD units 500 excited by the incident light, reduce crosstalk of the self-excitation photons from the gap between the back metal grid 200 and the deep trench isolation column 400 into the adjacent SPAD units 500, reduce overflow of the self-excitation photons, reduce the probability of photon crosstalk, and reduce optical crosstalk of the device.

[0054] In one embodiment, the SPAD units 500 are in a plurality of cases, and the plurality of SPAD units 500 are arranged in an array, for example, in the case of four SPAD units 500, the four SPAD units 500 are arranged in an array.

[0055] Figure 2This is a top view of a SPAD unit 500. At least two SPAD units 500 form a SPAD array. Each SPAD unit 500 is provided with a corresponding microlens 100. The metal filling structure 140 is the metal connecting the deep groove isolation pillar 400 and the back metal mesh 200. Figure 3 for Figure 2 A schematic diagram of the cross-section at position AA of the component. Figure 4 for Figure 2 A schematic diagram of the cross-section at position BB of the component. (See diagram below.) Figure 4 As shown, due to the presence of the metal-filled structure 140 at the BB position, crosstalk photons cannot enter the adjacent SPAD unit 500 through the dielectric gap between the back metal mesh 200 and the deep trench isolation pillar 400. However, at the AA position where the metal-filled structure 140 is not present (e.g....), crosstalk photons cannot enter the adjacent SPAD unit 500. Figure 3 As shown, a considerable amount of unabsorbed light or self-generated photons will enter the adjacent SPAD unit 500 through the gap, causing crosstalk.

[0056] In one embodiment, the metal-filled structure 140 is a ring-shaped structure, such as... Figure 5 As shown, the shape of the metal filling structure 140 is the same as that of the back metal mesh 200. The metal filling structure 140 can completely fill the gap between the back metal mesh 200 and the deep groove isolation pillar 400 around the SPAD unit 500, thus avoiding the gaps such as... Figure 2 The gap appearing at position AA of the mid-section is also filled by the metal filling structure 140. This part of the crosstalk will be completely suppressed, and the photons can be reflected back into the Si material of the substrate for reabsorption. It can also improve the photon detection efficiency (PDE) to a certain extent, reduce the crosstalk of self-excited photons from the gap between the back metal mesh 200 and the deep trench isolation pillar 400 to the adjacent SPAD unit 500, reduce the overflow of self-excited photons, reduce the probability of photon crosstalk, and reduce the optical crosstalk of the device.

[0057] In some embodiments, the deep trench isolation post 400 can be made of tungsten metal, and a dielectric material is filled around the deep trench isolation post 400. The presence of the deep trench isolation post 400 will reflect crosstalk photons, greatly reducing the probability of optical crosstalk.

[0058] In some embodiments, the width of the metal filling structure 140 is smaller than the width of the deep groove isolation post 400.

[0059] In some embodiments, by selecting appropriate first medium layer 310 and second medium layer 320, designing different medium layer refractive index and film thickness, the first medium layer 310 and the second medium layer 320 can form an optical filter to absorb or reflect photons of different wavelengths in the self-excited photons, so as to reduce the crosstalk of the device.

[0060] In some embodiments, in the array package SiPM device, a groove structure can be etched in the package structure to reduce the crosstalk between SiPMs.

[0061] In one embodiment, the SPAD unit 500 includes a first doped region 600 and a second doped region 700 stacked on the second medium layer, and the first doped region 600 and the second doped region 700 form a PN junction.

[0062] In some embodiments, the first doped region 600 and the second doped region 700 are two doped regions of different polarities, and a PN junction is formed between the first doped region 600 and the second doped region 700. The amplification region 800 is the region with the strongest electric field of the PN junction, and is mainly used for avalanche generation and amplification. The depletion region is a space charge region generated under a certain voltage, and the electrons or holes generated therein can drift into the amplification region 800 to generate an avalanche.

[0063] In one embodiment, the vertical section of the back metal grid 200 is an inverted trapezoid.

[0064] The path of optical crosstalk is shown in Figure 3 As the back metal grid 200 presents a trapezoidal appearance, the photons reflected by the sidewall of the back metal grid 200 have a high probability of entering other SPAD units, and this crosstalk can propagate to a remote device due to the small reflection of the lens, thereby increasing the avalanche chain of the crosstalk. As shown in Figure 6 In this embodiment, the back metal grid 200 is an inverted trapezoid, and the inwardly inclined interface of the back metal grid 200 reflects the incident light back into the device itself, reducing the overflow of photons and reducing the crosstalk probability of self-excited photons.

[0065] In one embodiment, referring to Figure 7 As shown, the vertical section of the back metal grid 200 is a multi-layer stepped structure, and the width of each layer of the multi-layer stepped structure gradually increases.

[0066] In this embodiment, the vertical section of the back metal grid 200 is a multi-layer stepped structure, and the width of the multi-layer stepped structure gradually increases, so that the back metal grid 200 is inclined inwardly, reflecting the incident light back into the device itself, reducing the overflow of photons and reducing the crosstalk probability of self-excited photons.

[0067] In an embodiment, the width of the multi-layered stepped structure is arranged in an arithmetic sequence.

[0068] In an embodiment, referring to FIG. 2B, the vertical cross-section of the back metal grid 200 is an arc-shaped structure, which is used to reflect the photons irradiating the surface thereof to the SPAD unit 500. Figure 8

[0069] In the embodiment, by arranging the vertical cross-section of the back metal grid 200 as an arc-shaped structure, the interface between the back metal grid 200 and the microlens 100 can form a total reflection interface that is inclined inwardly to the SPAD unit 500, so as to reflect the photons irradiating the surface thereof to the SPAD unit 500 (i.e. the interval of the SPAD unit 500 itself), reduce the overflow of the self-excitation photons, and reduce the crosstalk probability of the self-excitation photons.

[0070] In an embodiment, referring to FIG. 3B, the intermetallic dielectric layer 120 is arranged between the adjacent front metal wiring layers 130, the etching stop layer 110 is arranged between the intermetallic dielectric layer 120 and the deep trench isolation column 400, the deep trench isolation column 400 penetrates into the etching stop layer 110, and the deep trench isolation column 400 divides the second dielectric layer 320 into at least two dielectric units corresponding to the SPAD unit 500, so as to block the crosstalk light reflected by the front metal wiring layer 130 and the etching stop layer 110. Figure 8

[0071] In an embodiment, since the first doped region 600 and the second doped region 700 have a certain thickness, the deep trench isolation column 400 penetrates into the second dielectric layer 320, and in the case that the length of the part of the deep trench isolation column 400 penetrating into the second dielectric layer 320 is greater than one half of the thickness of the second dielectric layer 320, the crosstalk light reflected by the front metal wiring layer 130 and the etching stop layer 110 can be blocked.

[0072] In a specific application, the length of the part of the deep trench isolation column 400 penetrating into the second dielectric layer 320 can be arranged according to the width of the deep trench isolation column 400.

[0073] In an embodiment, the thickness of the part of the deep trench isolation column 400 penetrating into the second dielectric layer 320 can be less than the thickness of the second dielectric layer 320.

[0074] In an embodiment, in the single-photon avalanche diode array, the metal filling structure 140 is a ring-shaped structure, which can completely fill the gap between the back metal grid 200 and the deep trench isolation column 400 around the SPAD unit 500, and can avoid the situation that the crosstalk light reflected by the front metal wiring layer 130 and the etching stop layer 110 can enter the SPAD unit 500 through the gap between the back metal grid 200 and the deep trench isolation column 400. Figure 2 ​​The gap at the middle cross-section AA position, at this time, this part of the crosstalk will be completely suppressed, and the deep trench isolation column 400 is deep into the etching stop layer 110, forming a deep trench isolation extension and a metal filling structure ring anti-crosstalk combination scheme, as shown in Figure 9

[0075] In one embodiment, in a single photon avalanche diode array, as shown in Figure 10 The back metal grid 200 presents an inverted trapezoidal topography at this time, the interface of the back metal grid 200 tilted inward will reflect the light incident on it back into its own device, reducing the overflow of photons and reducing the probability of self-excited photon crosstalk. At the same time, combined with the deep trench isolation column 400 deep into the etching stop layer 110, the probability of photon crosstalk from the bottom is reduced, and the deep trench isolation extension and the inverted trapezoidal back metal grid 200 form an anti-crosstalk combination scheme, which can effectively reduce the interference of crosstalk photons on adjacent SPAD units 500.

[0076] In one embodiment, on the basis of the metal filling structure 140 being a ring structure and the deep trench isolation column 400 deep into the etching stop layer 110, the cross-section of the back metal grid is set to an inverted trapezoid, which can form a deep trench isolation extension, a metal filling structure ring, and a back metal grid inverted trapezoidal anti-crosstalk combination scheme, as shown in Figure 10

[0077] In the above-mentioned BSI device structure, the deep trench isolation column 400 can block most of the crosstalk photons, but there are still several obvious crosstalk paths that have not been solved, which makes it impossible to further reduce crosstalk.

[0078] As shown in Figure 1 The deep trench isolation column 400 stays above the second dielectric layer 320 at this time, for crosstalk photons, it can be reflected into adjacent SPAD units 500 through the front metal wiring layer 130, or it can be reflected into adjacent SPAD units 500 through the interface formed by the etching stop layer 110 and the second dielectric layer 320. In order to reduce the probability of photon crosstalk from the bottom, the deep trench isolation column 400 is extended downward to the etching stop layer in this embodiment to block the crosstalk photons reflected by the front metal wiring layer 130 and the etching stop layer 110.

[0079] In some embodiments, the etching stop layer 110 can be a silicon carbon nitrogen (SiCN) material.

[0080] In one embodiment, the deep trench isolation column 400 is tungsten.

[0081] ​​In the embodiment, when the self-generated photons of the SPAD unit 500 after being irradiated by light propagate in the device, the light incident on the deep trench isolation column 400 around the SPAD unit 500 is repeatedly reflected, which increases the absorption and prevents the photons from crosstalk into adjacent units. Therefore, the deep trench isolation column 400 around the SPAD unit 500 is also an important way to improve crosstalk.

[0082] In one embodiment, the back metal mesh 200 is aluminum.

[0083] In some embodiments, multiple layers of metal traces can be formed in the front metal trace layer 130, which is used to lead out the other electrode of the SPAD unit 500 to the front electrode, and output the corresponding electrical signal through the front metal trace layer 130.

[0084] In order to illustrate the optical crosstalk improvement effect and level of the single-photon avalanche diode array in the above embodiment, the optical crosstalk of the single-photon avalanche diode array is simulated and verified as follows.

[0085] The calculation formula of the optical crosstalk probability OXT is as follows:

[0086] OXT = ∫PPS(λ)·Gain(∫ v G(r)·ATP(r)dV)dλ; (Formula 1)

[0087] Wherein, G(r) is the carrier rate of the SPAD unit 500 after absorbing the crosstalk light of the adjacent SPAD unit 500; ATP(r) is the avalanche probability of the carriers in the depletion region; Gain is the number of carriers released by the SPAD unit 500 for each avalanche, i.e. gain; PPS(λ) is the avalanche photon generation spectrum, which physically means the distribution of the number of photons released by each carrier for each avalanche with wavelength.

[0088] In the calculation, G(r) can be obtained by optical simulation, that is, a random photon is placed in the center SPAD unit 500, the spectral width of the random photon is 0.4-1um, the intensity of each photon is set according to PPS(λ), the reference avalanche photon spontaneous spectrum is referred to, then the absorbed optical power in the adjacent SPAD unit 500 is monitored, and the carrier generation rate is converted, ATP(r) can be calculated according to the size of the electric field of the SPAD unit 500, the probability of avalanche triggering at different positions is calculated by using the McIntyre model, and the gain is 0.8M in the calculation. In the simulation, since the self-generated photons have position randomness and radiation direction randomness, in the simulation, the self-generated photons are generated in three different positions (left, center and right of the device), and three kinds of dipole polarization directions (X, Y and Z) are used for the radiation direction of the photons, and the average of the nine simulation results is taken as the OXT radiation probability.

[0089] When calculating the overall crosstalk of a one-dimensional long array of SPADs, it is difficult to directly perform optical simulations for a large number of SPADs. Therefore, this application uses a 4-spads model to approximate the one-dimensional long array. Figure 11 As shown. For ease of understanding, let's first consider the crosstalk situation with 3 devices, specifically the crosstalk situation experienced by SPAD2. After SPAD0 generates self-excited photons, it has a certain probability of triggering an avalanche in SPAD1. The avalanche of SPAD1 also has a probability of generating photons that further trigger an avalanche in SPAD2. Therefore, the crosstalk of SPAD2 can be generated directly from SPAD0 (probability χ2), or it can be generated through the SPAD0→SPAD1→SPAD2 link. Since these two paths can occur almost simultaneously, the probability of SPAD2 receiving optical crosstalk is the sum of the probabilities of the two links, minus the probability of simultaneous occurrence. This can be expressed by Formula 2, where χ1 is the probability of direct crosstalk between two adjacent SPADs:

[0090] OXT3-spad=χ1 +(χ2 +χ1·χ1- χ2·χ1·χ1); (Formula 2)

[0091] Furthermore, this simulation model is extended to 4-spads, and its crosstalk chain can be referenced. Figure 10 As shown, therefore, under the 4-spads model, the crosstalk of the one-dimensional array of SPAD cells 500 can be calculated by Equation 3:

[0092] OXT4-spad=χ1+(χ2+χ1·χ1-χ2·χ1·χ1)+χ3+2·χ1·χ2+χ1^3-2·χ1·χ2·χ3-χ3·χ1^3-χ1^ 2·χ2^2-2·χ1^3·χ2+χ1^2·χ2^2·χ3+2·χ1^3·χ2·χ3+χ1^3·χ2^2-χ1^3·χ2^2·χ3; (Formula 3)

[0093] In Formula 3, χi (i = 1, 2, 3) represents the probability that SPAD0 will directly cause crosstalk to the i-th SPAD unit 500, which can be obtained by combining optical simulation with Formula 1. Thus, the optical crosstalk model of a one-dimensional long linear array SPAD is obtained.

[0094] Building upon this, this application employs a similar method to extend it to 2D arrays, referencing... Figure 13 As shown, the crosstalk received by SPAD0 comes from eight surrounding directions. Due to symmetry, only the crosstalk ρ1 in the horizontal direction and the crosstalk ρ2 in the diagonal direction need to be simulated and calculated.

[0095] The application simulates an infinite 2D array by using an approximate method, i.e., using a 1D 4-spads model to obtain an approximate horizontal direction crosstalk ρ1, which is used to equivalently calculate Figure 11 the crosstalk of SPAD1 and SPAD2 to SPAD0; and then simulating the crosstalk of the oblique angle direction SPAD to obtain ρ2, which is equivalent to Figure 12 the crosstalk of SPAD3 to SPAD0.

[0096] At this time, SPAD0 receives two crosstalks, i.e., SPAD1→SPAD0 and SPAD3→SPAD1→SPAD0 two paths, and the model ignores some theoretically possible paths with a very small probability, such as SPAD3→SPAD1→SPAD2→SPAD0, and thus the crosstalk model of the entire 2D surface array is given by formula 4:

[0097] OXT -2D = 4ρ1+4ρ2+4(ρ1·ρ2-ρ1·ρ1·ρ2) (formula 4)

[0098] According to the crosstalk improvement effect in the application, simulation verification is sequentially performed, and the crosstalk improvement effect is compared with the crosstalk performance of the traditional device structure, as shown in Table 1.

[0099] Table 1

[0100]

[0101] From the simulation data in Table 1, it can be obviously seen that the crosstalk performance is significantly improved. When the deep trench isolation column 400 process is optimized alone, the crosstalk probability in both the horizontal direction and the oblique diagonal direction is obviously decreased, and finally the total OXT is decreased to 60% of the original; the optimization scheme of the metal filling structure 140 closed loop is also used alone, and the same improvement effect is achieved; at the same time, the deep trench isolation extension scheme and the metal filling structure 140 closed loop scheme are used, and the crosstalk performance is further reduced, especially the χ1 probability, i.e., the crosstalk suppression to the nearest neighbor SPAD unit 500 is obvious, and the OXT is decreased to 46% of the original; and the comprehensive scheme (as shown in Figure 11 ) proposed in the application is used, the OXT is decreased to 36% of the original, and the improvement to the nearest neighbor SPAD unit 500 is the most significant.

[0102] Figures 14-17 the light crosstalk improvement effect of the scheme of the application is more intuitively presented, Figure 14 the self-excitation light crosstalk of the traditional structure and the crosstalk of the metal filling structure 140 extension structure are shown, Figure 14 the leftmost SPAD unit 500 avalanche generates a self-excitation photon, Figure 14The left and right figures show the photon position in the device. By comparing the left and right figures, it can be seen that the metal filling structure 140 closed loop (such as Figure 1 ) scheme obviously suppresses the crosstalk light of this path.

[0103] Figure 15 The crosstalk of the traditional structure and the deep trench isolation extension structure is shown. When the deep trench isolation extends to the etching stop layer, it can be seen that the bottom crosstalk light is also obviously suppressed.

[0104] Figure 16 For the crosstalk of self-excited photons when the deep trench isolation extension and the metal filling structure 140 closed loop scheme (such as Figure 9 ) are used at the same time, it can be seen that the crosstalk light directly from below the back metal mesh 200 and the bottom of the deep trench isolation column 400 is greatly reduced, and the main crosstalk comes from the lens part.

[0105] Figure 17 For the case of using the comprehensive improvement scheme (such as Figure 11 ), the back metal mesh 200 adopts an inverted trapezoidal shape, which makes a large part of the crosstalk light reflect back into the SPAD cell itself. The optical crosstalk of the adjacent device is significantly suppressed, thus reducing the optical crosstalk of the entire two-dimensional array. In particular, the gain used in the model calculation of this scheme is small, and the value of the self-excited photon radiation spectrum is also small. Therefore, for the actually prepared device, the improvement degree of optical crosstalk performance will be more significant when the incident light intensity is increased and the overvoltage is increased.

[0106] The embodiment of the present application also provides a silicon photomultiplier, which comprises the single-photon avalanche diode array according to any one of the above embodiments.

[0107] The embodiment of the present application has the beneficial effects that: the incident light is converged on the corresponding SPAD cell by the microlens, the back metal mesh connects the SPAD cell and the corresponding external electrode, the first dielectric layer is arranged between the microlens and the SPAD cell, the second dielectric layer is arranged between the SPAD cell and the front metal wiring layer, and the front metal wiring layer is electrically connected to the corresponding SPAD cell through the contact wire. By arranging the deep trench isolation column between the adjacent SPAD cells and arranging the metal filling structure between the deep trench isolation column and the back metal mesh, the self-excited photons generated by the SPAD cell excited by the incident light can be isolated, the self-excited photons entering the adjacent SPAD cell through the grid gap are avoided, the overflow of the self-excited photons is reduced, the probability of optical crosstalk is reduced, and the optical crosstalk of the device is reduced.

[0108] The embodiment of the present application also includes a receiving sensor, which can include one or more single-photon avalanche diode arrays or one or more silicon photomultipliers.

[0109] The embodiment of the present application also includes a laser radar, which comprises a transmitting sensor for transmitting a probe laser and a receiving sensor for receiving a return wave of the probe laser, and a target object is obtained according to the return wave.

[0110] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the division of the above functional device areas and modules is exemplified, and in actual application, the above functions can be completed by different functional device areas and modules according to needs, that is, the internal structure of the device is divided into different functional device areas or modules to complete all or part of the functions described above. Each functional device area and module in the embodiment can be integrated in one device, or each unit can exist physically alone, or two or more units can be integrated in one unit.

[0111] In addition, the specific names of each functional device area and module are only for the convenience of mutual differentiation, and do not limit the protection scope of the present application. The specific working process of the units and modules in the above system can refer to the corresponding process in the foregoing method embodiments, which will not be described here.

[0112] In the above embodiments, the description of each embodiment has its own emphasis, and the parts not described or recorded in detail in a certain embodiment can be referred to the related description of other embodiments.

[0113] In addition, each functional device area in each embodiment of the present application can be integrated in one device, or each unit can exist physically alone, or two or more units can be integrated in one unit.

[0114] The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A single photon avalanche diode array, characterized in that, The single-photon avalanche diode array comprises: at least two SPAD units; at least two microlenses corresponding to the at least two SPAD units respectively, the microlenses being used for converging incident light onto the corresponding SPAD units; at least two front metal wiring layers corresponding to the at least two SPAD units respectively; a back metal mesh used for connecting the SPAD units and corresponding external electrodes, the back metal mesh having an interface inclined from top to bottom towards the inside of the back metal mesh, the width above the back metal mesh being greater than the width below the back metal mesh; a first dielectric layer arranged between the microlenses and the SPAD units, the first dielectric layer being used for reducing the reflection of the incident light; a second dielectric layer arranged between the SPAD units and the front metal wiring layers, wherein the front metal wiring layers are electrically connected to the corresponding SPAD units through contact wires; a deep trench isolation column arranged between adjacent SPAD units, used for isolating adjacent SPAD units, the deep trench isolation column being at least deep into the second dielectric layer; a metal filling structure arranged between the deep trench isolation column and the back metal mesh, used for inhibiting self-excitation photons generated by the SPAD units excited by the incident light from entering adjacent SPAD units through mesh gaps, the metal filling structure being a closed ring structure, and the metal materials used by the back metal mesh and the deep trench isolation column being different.

2. The array of single photon avalanche diodes of claim 1, wherein, The vertical section of the back metal mesh is an inverted trapezoid.

3. The array of single photon avalanche diodes of claim 1, wherein, The vertical section of the back metal mesh is a multilayer step structure, and the width of each layer of the step structure gradually increases.

4. The array of single photon avalanche diodes of claim 1, wherein, The vertical section of the back metal mesh is an arc structure, used for reflecting photons irradiating the surface thereof to the SPAD units.

5. The array of single photon avalanche diodes according to any one of claims 1-4, wherein, An intermetallic dielectric layer is arranged between adjacent front metal wiring layers, and an etching stop layer is arranged between the intermetallic dielectric layer and the deep trench isolation column, the deep trench isolation column being deep into the etching stop layer and dividing the second dielectric layer into at least two dielectric units corresponding to the SPAD units.

6. The array of single photon avalanche diodes according to any one of claims 1-4, wherein, An intermetallic dielectric layer is arranged between adjacent front metal wiring layers, and an etching stop layer is arranged between the intermetallic dielectric layer and the deep trench isolation column, the length of the part of the deep trench isolation column deep into the second dielectric layer being greater than one half of the thickness of the second dielectric layer.

7. The array of single photon avalanche diodes according to any one of claims 1 to 4, wherein, The SPAD unit comprises a first doped region and a second doped region arranged on the second dielectric layer in a stacked manner, and the first doped region and the second doped region form a PN junction.

8. The array of single photon avalanche diodes according to any one of claims 1-4, wherein, The deep trench isolation column is tungsten.

9. A receiving sensor, characterized by The receiving sensor comprises the single-photon avalanche diode array according to any one of claims 1-8.

10. A lidar, comprising: The laser radar comprises a transmitting sensor and the receiving sensor according to claim 9; The transmitting sensor is used for transmitting probe laser; The receiving sensor is used for receiving the echo of the probe laser, and obtaining detection information of a target object according to the echo.

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