Single photon avalanche diode array, receiving sensor and laser radar

Abstract

The invention 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 to the 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, and a second dielectric layer is arranged between the microlens and the SPAD unit. The second dielectric layer is arranged between the SPAD units and the front metal wiring layer, and the front metal wiring layer is electrically connected with the corresponding SPAD units through contact metal wires. The deep groove isolation columns are arranged between the adjacent SPAD units, and the metal filling structures are arranged between the deep groove isolation columns and the back metal grids, so that self-excitation photons generated when the SPAD units are excited by incident light can be isolated, the self-excitation photons are prevented from entering the adjacent SPAD units through grid gaps, the probability of photon crosstalk is reduced, and the optical crosstalk of the device is reduced.

Description

Technical Field

[0001] This application belongs to the technical field of optical devices, and particularly relates to a single-photon avalanche diode array, a receiving sensor, and a lidar. Background Art

[0002] Due to its advantages such as high-sensitivity detection ability for light intensities as low as single photons, high time-resolution ability, and strong anti-interference ability, a silicon photomultiplier (SiPM) formed by connecting at least two single-photon avalanche diode arrays (SPADs) in parallel for single-point use has been widely applied in scenarios such as laser detection and ranging systems (Lidar), autonomous driving, fluorescence lifetime imaging, quantum communication, and biomedical imaging. With the progress of silicon manufacturing technology, the design of single-photon avalanche diode arrays using silicon as the absorption and avalanche material has become a hot topic 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] By combining individual single-photon avalanche diode arrays through circuitry, two typical application forms can be formed. First is the silicon photomultiplier (SiPM), which is composed of at least two single-photon avalanche diode array units (cells) connected in parallel, and outputs a single signal as a whole. Since the pulse signals generated by different photons can be superimposed, SiPM can respond to different light intensities and output a single point. Another typical form is the SPAD array. Each SPAD unit serves as an individual pixel, and the light intensities detected by each pixel can be output separately, having the ability to detect photons in parallel, so it can directly image, and its imaging performance in some low-light environments is very excellent, such as biomedical microscopy, fluorescence lifetime microscopy, Flash lidar, etc.

[0004] However, whether it is SiPM or SPAD array, optical crosstalk is a relatively critical and difficult problem to solve. For SiPM, crosstalk photons cause SPAD units without incident photons to be excited. A relatively large probability of optical crosstalk will lead to an overestimation of the received signal energy, resulting in problems such as incorrect calculation of object reflectivity and increased distance measurement error. For SPAD arrays, phenomena such as imaging expansion and abnormal output in entire rows or columns will occur. Summary of the Invention

[0005] To solve the above technical problems, the embodiments of this application provide a single-photon avalanche diode array and a silicon photomultiplier, aiming to solve the problem that in current single-photon avalanche diode arrays, crosstalk photons cause SPAD units without incident photons to be excited, resulting in a relatively large probability of optical crosstalk.

[0006] In the first aspect of the embodiments of the present application, a single-photon avalanche diode array is provided, and the single-photon avalanche diode array includes:

[0007] At least two SPAD units;

[0008] At least two microlenses, which correspond to at least two of the SPAD units one by one, and the microlenses are used to converge incident light onto the corresponding SPAD units;

[0009] At least two front metal wiring layers, which correspond to at least two of the SPAD units one by one;

[0010] A back metal grid, which is used to connect the SPAD unit to a corresponding external electrode;

[0011] A first dielectric layer is disposed between the microlens and the SPAD unit, and the first dielectric layer is used to reduce the reflection of the incident light;

[0012] A second dielectric layer is disposed between the SPAD unit and the front metal wiring layer; wherein, the front metal wiring layer is electrically connected to the corresponding SPAD unit through a contact metal wire;

[0013] Deep trench isolation pillars are disposed between adjacent SPAD units and are used to isolate adjacent SPAD units;

[0014] A metal filling structure is disposed between the deep trench isolation pillar and the back metal grid and is used to inhibit self-excited photons generated by the excitation of the incident light on the SPAD unit from entering an adjacent SPAD unit through the grid gap.

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

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

[0017] In one embodiment, the vertical cross-section of the back metal grid is an arc-shaped structure and is used to reflect photons irradiating its surface to the SPAD unit.

[0018] In one embodiment, an inter-metal dielectric layer is disposed between adjacent front metal wiring layers, an etch stop layer is disposed between the inter-metal dielectric layer and the deep trench isolation pillar, the deep trench isolation pillar penetrates into the etch stop layer, and the second dielectric layer is divided into at least two dielectric units, and the at least two dielectric units correspond to the SPAD units.

[0019] In one embodiment, an inter-metal dielectric layer is provided between adjacent front metal trace layers, an etch stop layer is provided between the inter-metal dielectric layer and the deep trench isolation pillar, and the length of the part of the deep trench isolation pillar extending into the second dielectric layer is greater than half of the thickness of the second dielectric layer.

[0020] In one embodiment, the SPAD unit includes a first doped region and a second doped region stacked 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 pillar is made of tungsten.

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

[0023] In a second aspect of the embodiments of the present application, there is also provided a silicon photomultiplier tube, which includes the single-photon avalanche diode array as described in any one of the above embodiments.

[0024] In a third aspect of the embodiments of the present application, there is also provided a receiving sensor, which includes the single-photon avalanche diode array as described in any one of the first aspects.

[0025] In a fourth aspect of the embodiments of the present application, there is also provided a receiving sensor, which includes a silicon photomultiplier tube as provided in the second aspect.

[0026] In a fifth aspect of the embodiments of the present application, there is also provided a lidar, which includes a transmitting sensor and the receiving sensors of the third and fourth aspects. The transmitting sensor is used to emit detection laser light, and the receiving sensor is used to receive the echo of the detection laser light, and obtain detection information of the target object according to the echo.

[0027] The beneficial effects of the embodiments of the present application: At least two SPAD units are arranged in an array, the microlens converges the incident light onto the corresponding SPAD unit, the back metal grid connects the SPAD unit with the corresponding external electrode, the first dielectric layer is arranged between the microlens and the SPAD unit, the second dielectric layer is arranged between the SPAD unit and the front metal trace layer, and the front metal trace layer is electrically connected to the corresponding SPAD unit through a contact metal wire. By arranging deep trench isolation pillars between adjacent SPAD units and arranging a metal filling structure between the deep trench isolation pillars and the back metal grid, the self-excited photons generated by the SPAD unit excited by the incident light can be isolated, preventing the self-excited photons from entering the adjacent SPAD unit through the grid gaps, reducing the overflow of self-excited photons, reducing the probability of photon crosstalk, and reducing the optical crosstalk of the device. Description of the Drawings

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

[0029] Figure 2 is a top view schematic diagram of the single-photon avalanche diode array provided by the embodiments of the present application;

[0030] Figure 3 is a schematic diagram of the cross-section AA of the single-photon avalanche diode array provided by the embodiments of the present application;

[0031] Figure 4 is a schematic diagram of the cross-section BB of the single-photon avalanche diode array provided by the embodiments of the present application;

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

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

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

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

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

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

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

[0039] Figure 12 is a schematic diagram of the self-excited crosstalk of the one-dimensional linear array provided by the embodiments of the present application;

[0040] Figure 13 is a schematic diagram of the self-excited crosstalk of the two-dimensional array surface provided by the embodiments of the present application;

[0041] Figure 14 is a schematic diagram of the crosstalk optical field of the traditional structure and the metal filling structure extension scheme provided by the embodiments of the present application;

[0042] Figure 15 Schematic diagram of crosstalk optical field for the traditional structure and deep trench isolation pillar extension solution provided by the embodiments of the present application;

[0043] Figure 16 Schematic diagram of self-excited photon crosstalk of the device structure when the closed-loop solution of deep trench isolation pillar extension and metal filling structure is adopted simultaneously in the embodiments of the present application (such as Figure 9 );

[0044] Figure 17 Schematic diagram of the improvement of self-excited crosstalk of the device structure for the comprehensive solution provided by the embodiments of the present application (such as Figure 11 ). Detailed implementation manners

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

[0046] It should be noted that when an element is referred to as being "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 being "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 orientation or positional relationship indicated by the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present application.

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

[0049] Due to its advantages such as high-sensitivity detection ability for light intensities as low as single photons, high time-resolution ability, and strong anti-interference ability, silicon photomultipliers (SiPMs) composed of at least two single-photon avalanche diodes (SPADs) connected in parallel and used as a single point have been widely applied in scenarios such as lidar (light detection and ranging) systems, autonomous driving, fluorescence lifetime imaging, quantum communication, and biomedical imaging.

[0050] To reduce the crosstalk characteristics of the device, the device can be optimized at the device level, packaging level, and system application level. However, the crosstalk improvement scheme at the application level only avoids the impact of crosstalk on signal reading, at the cost of complex scanning methods and circuit implementation, and does not solve the problem of optical crosstalk. The same is true for the crosstalk improvement scheme at the packaging level. The crosstalk at the device level is the most fundamental, but there are not many available means. Although the crosstalk characteristics of the FSI device (front-illuminated receiving device) are better, its low PDE limits its application, and the industry still uses the back-illuminated (BSI) device with a higher PDE; introducing deep trench isolation pillars (DTI) can greatly reduce optical crosstalk, but it mainly has an obvious effect on reducing the crosstalk of adjacent SPADs, and the distal SPAD can still be crosstalked through other paths. In particular, for SiPM devices, it may cause chain avalanche triggering, resulting in crosstalk of a large area of the device.

[0051] To solve the above technical problems, the embodiments of the present application provide a single-photon avalanche diode array. See Figure 1 As shown, the single-photon avalanche diode array in this embodiment 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, deep trench isolation pillars 400, and a metal filling structure 140.

[0052] In this embodiment, at least two SPAD units 500 are arranged adjacent to each other. At least two microlenses 100 respectively correspond to at least two SPAD units 500 one by one. The microlenses 100 are used to converge incident light onto the corresponding SPAD units 500. At least two front metal trace layers 130 correspond to at least two SPAD units 500 one by one. The back metal grid 200 is used to connect the SPAD units 500 to the corresponding external electrodes. The first dielectric layer 310 is disposed between the microlenses 100 and the SPAD units 500, and the first dielectric layer 310 is used to reduce the reflection of incident light. The second dielectric layer 320 is disposed between the SPAD units 500 and the front metal trace layers 130. Wherein, the front metal trace layer 130 is electrically connected to the corresponding SPAD unit 500 through a contact wire 900. The deep trench isolation pillars 400 are disposed between adjacent SPAD units 500, and the deep trench isolation pillars 400 are used to isolate adjacent SPAD units 500. The metal filling structure 140 is disposed between the deep trench isolation pillars 400 and the back metal grid 200, and the metal filling structure 140 is used to suppress self-excited photons generated by the SPAD units 500 excited by incident light from entering adjacent SPAD units 500 through the grid gaps.

[0053] In this embodiment, the microlenses 100 play a role in converging light, converging incident light onto the corresponding SPAD units 500. The back metal grid 200 plays a role in leading out one of the electrodes of the SPAD units 500 from the back. By arranging the deep trench isolation pillars 400 between adjacent SPAD units 500 and arranging the metal filling structure 140 between the deep trench isolation pillars 400 and the back metal grid 200, the deep trench isolation pillars 400 can electrically isolate adjacent SPAD units 500. Self-excited photons generated by the SPAD units 500 excited by incident light can be reflected when they irradiate on the deep trench isolation pillars 400. While increasing absorption, it also prevents self-excited photons from crosstalking into adjacent SPAD units 500, which is an important way to improve crosstalk. The metal filling structure 140 can isolate self-excited photons generated by the SPAD units 500 excited by incident light, reduce the crosstalk of self-excited photons from the gap between the back metal grid 200 and the deep trench isolation pillars 400 into adjacent SPAD units 500, reduce the overflow of self-excited photons, reduce the probability of photon crosstalk, and reduce the optical crosstalk of the device.

[0054] In one embodiment, when there are multiple SPAD units 500, the multiple SPAD units 500 are arranged in an array. For example, in the case of 4 SPAD units 500, the 4 SPAD units 500 are arranged in an array.

[0055] Figure 2A top view schematic diagram of the SPAD unit 500. At least two SPAD units 500 form an SPAD array. A corresponding microlens 100 is provided on each SPAD unit 500. The metal filling structure 140 is the metal connecting the deep trench isolation column 400 and the back metal grid 200. Figure 3 is Figure 2 a cross-sectional schematic diagram at the AA position of the device cross-section in Figure 4 is Figure 2 a cross-sectional schematic diagram at the BB position of the device cross-section in. As Figure 4 shown, due to the presence of the metal filling structure 140 at the BB position of the cross-section, crosstalk photons cannot enter the adjacent SPAD unit 500 through the dielectric gap between the back metal grid 200 and the deep trench isolation column 400. And at the AA position of the cross-section where the metal filling structure 140 is not filled (as Figure 3 shown), there will be a lot of unabsorbed light or photons generated by self-excitation entering the adjacent SPAD unit 500 through this gap to generate crosstalk.

[0056] In one embodiment, the metal filling structure 140 is a ring structure. As Figure 5 shown, the shape of the metal filling structure 140 is the same as the shape of the back metal grid 200. The metal filling structure 140 can completely fill the gap between the back metal grid 200 and the deep trench isolation column 400 around the SPAD unit 500, which can avoid the gap appearing at the AA position of the cross-section as Figure 2 shown. At this time, the gap appearing at the AA position of the cross-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 to the Si material of the substrate for re-absorption. 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 grid 200 and the deep trench isolation column 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 column 400 can be made of tungsten metal, and a dielectric material is filled around the deep trench isolation column 400. The presence of the deep trench isolation column 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 less than the width of the deep trench isolation column 400.

[0059] In some embodiments, by selecting appropriate first and second dielectric layers 310 and 320 and designing different refractive indices and film thicknesses of the dielectric layers, the first dielectric layer 310 and the second dielectric layer 320 can form an optical filter to absorb or reflect photons of different wavelengths in the self-excited photons, thereby reducing crosstalk in the device.

[0060] In some embodiments, in an array-packaged SiPM device, crosstalk between SiPMs can be reduced by etching a trench structure in the packaging structure.

[0061] In one embodiment, the SPAD unit 500 includes a first doped region 600 and a second doped region 700 stacked on the second dielectric 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 with 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 where the electric field of the PN junction is the strongest. The amplification region 800 is mainly used for the generation and amplification of avalanches. The depletion region is the space charge region generated by the device under a certain voltage. Electrons or holes generated therein can enter the amplification region 800 through drift motion under the electric field to generate avalanches.

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

[0064] The path of optical crosstalk is as Figure 3 shown. Since the back metal grid 200 has a positive trapezoidal morphology, photons are reflected by the sidewalls of the back metal grid 200 and thus have a high probability of entering other SPAD units. Moreover, this crosstalk may be transmitted to a relatively far place due to the small reflection of the lens, causing crosstalk to remote devices and exacerbating the avalanche chain of crosstalk. As Figure 6 shown, in this embodiment, the inverted trapezoidal back metal grid 200 is adopted. At this time, the interface of the back metal grid 200 inclined inward will reflect the incident light back into its own device, reducing the overflow of photons and lowering the crosstalk probability of self-excited photons.

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

[0066] In this embodiment, the vertical cross-section of the back metal grid 200 is a multi-layer stepped structure, and the width of the multi-layer stepped structure increases step by step, causing the back metal grid 200 to incline inward, reflecting the incident light back into its own device, reducing the overflow of photons, and lowering the crosstalk probability of self-excited photons.

[0067] In one embodiment, the widths of the multi-layer stepped structure increase step by step, and the widths of the multi-layer stepped structure are set as an arithmetic progression.

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

[0069] In this embodiment, by setting the vertical cross-section of the back metal grid 200 as an arc-shaped structure, a total reflection interface inclined towards the inner SPAD unit 500 can be formed at the interface between the back metal grid 200 and the microlens 100, reflecting the photons irradiating its surface to the SPAD unit 500 (i.e., the interval of the SPAD unit 500 itself), reducing the overflow of self-excited photons and reducing the crosstalk probability of self-excited photons.

[0070] In one embodiment, referring to Figure 8 As shown, an inter-metal dielectric layer 120 is provided between adjacent front metal trace layers 130, an etch stop layer 110 is provided between the inter-metal dielectric layer 120 and the deep trench isolation pillar 400, the deep trench isolation pillar 400 penetrates into the etch stop layer 110, and divides the second dielectric layer 320 into at least two dielectric units. The at least two dielectric units correspond to the SPAD unit 500, and can block the crosstalk light reflected by the front metal trace layer 130 and the etch stop layer 110.

[0071] In one embodiment, since the first doping region 600 and the second doping region 700 have a certain thickness, and the deep trench isolation pillar 400 penetrates into the second dielectric layer 320, when the length of the part where the deep trench isolation pillar 400 penetrates into the second dielectric layer 320 is greater than half of the thickness of the second dielectric layer 320, the crosstalk light reflected by the front metal trace layer 130 and the etch stop layer 110 can be blocked.

[0072] In specific applications, the length of the part where the deep trench isolation pillar 400 penetrates into the second dielectric layer 320 can be set according to the width of the deep trench isolation pillar 400.

[0073] In one embodiment, the thickness of the part where the deep trench isolation pillar 400 penetrates into the second dielectric layer 320 can be less than the thickness of the second dielectric layer 320.

[0074] In one embodiment, in the single-photon avalanche diode array, the metal filling structure 140 is a ring structure, which can completely fill the gap between the back metal grid 200 and the deep trench isolation pillar 400 around the SPAD unit 500, and can avoid such as Figure 2The gap that appears at the position of the middle cutting plane AA. At this time, this part of crosstalk will be completely suppressed, and in combination with the deep trench isolation pillar 400 extending deep into the etch stop layer 110, a crosstalk prevention combination scheme of deep trench isolation extension and metal filling structure ring is formed, as Figure 9 shown.

[0075] In one embodiment, in the single-photon avalanche diode array, as Figure 10 shown, the back metal grid 200 presents an inverted trapezoidal morphology. At this time, the interface of the back metal grid 200 inclined inward will reflect the incident light back into its own device, reducing the overflow of photons and reducing the crosstalk probability of self-excited photons. At the same time, in combination with the deep trench isolation pillar 400 extending deep into the etch stop layer 110, the probability of photons crosstalking from the bottom is reduced. Through the crosstalk prevention combination scheme composed of deep trench isolation extension and the inverted trapezoidal back metal grid 200, the interference of crosstalk photons to adjacent SPAD units 500 can be effectively reduced.

[0076] In one embodiment, on the basis that the metal filling structure 140 is a ring structure and the deep trench isolation pillar 400 extends deep into the etch stop layer 110, the cross-section of the back metal grid is set as an inverted trapezoid, and a crosstalk prevention combination scheme of deep trench isolation extension, metal filling structure ring and inverted trapezoidal back metal grid can be formed, as Figure 10 shown.

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

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

[0079] In some embodiments, the etch stop layer 110 can be made of silicon carbonitride (SiCN) material.

[0080] In one embodiment, the deep trench isolation pillar 400 is made of tungsten.

[0081] In this embodiment, when the self-excited photons generated by the SPAD unit 500 after being irradiated by light propagate in the device, the light incident on the surrounding deep trench isolation pillars 400 will be repeatedly reflected, increasing absorption while also preventing photons from crosstalking into adjacent units. Therefore, setting the deep trench isolation pillars 400 around the SPAD unit 500 is also an important way to improve crosstalk.

[0082] In one embodiment, the back metal grid 200 is made of aluminum.

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

[0084] To illustrate the improvement effect and level of optical crosstalk of the single-photon avalanche diode array in the above embodiments, the optical crosstalk of the single-photon avalanche diode array is simulated and verified below.

[0085] The calculation formula for the optical crosstalk probability OXT is:

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

[0087] Wherein, G(r) is the carrier rate generated after the adjacent SPAD unit 500 absorbs the crosstalk light of the SPAD unit 500 at the absorption center; ATP(r) is the carrier avalanche probability in the depletion region; Gain is the number of carriers released each time an avalanche occurs in the SPAD unit 500, that is, the gain; PPS(λ) is the avalanche photon generation spectrum, and its physical meaning is the distribution of the average number of photons released by each carrier per avalanche as a function of wavelength.

[0088] In the calculation, G(r) can be obtained by optical simulation, that is, random photons are placed in the central SPAD unit 500, the spectral width of the random photons is 0.4 - 1um, the intensity of each photon is set according to PPS(λ), referring to the spontaneous spectrum of avalanche photons, and then the optical power absorbed in the adjacent SPAD unit 500 is monitored and converted into the carrier generation rate. ATP(r) can be calculated according to the electric field magnitude of the SPAD unit 500 using the McIntyre model to calculate the probability of avalanche triggering at different positions. The Gain gain is set to 0.8M during the calculation. During the simulation, since the self-excited photons have position randomness and radiation direction randomness, in the simulation, the present application sets the self-excited photons to be generated at 3 different positions (left, middle, and right of the device), and at the same time, 3 dipole polarization directions (X, Y, Z) are used for the radiation direction of the photons, and the average of 9 simulation results is taken as the OXT radiation probability.

[0089] When calculating the overall crosstalk of a one-dimensional long array of SPADs, since it is difficult to directly perform optical simulation on a large number of SPADs, this application uses a 4-spads model to approximate the one-dimensional long array, as shown in Figure 11 For easy understanding, first consider the crosstalk situation when there are 3 devices, that is, consider the crosstalk situation of SPAD2. After self-excited photons are generated by SPAD0, SPAD1 avalanches with a certain probability. The avalanche of SPAD1 also has a chance to generate photons to further trigger the avalanche of SPAD2. Therefore, the crosstalk of SPAD2 can be directly generated by SPAD0 (with a probability of χ2), or can be generated by 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, which can be expressed by Formula 2, where χ1 is the probability of direct crosstalk between adjacent two SPADs:

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

[0091] Furthermore, this simulation model is extended to 4-spads. The crosstalk chain can be referred to Figure 10 as shown. Therefore, under the 4-spads model, the crosstalk of the SPAD unit 500 of the one-dimensional array can be calculated by Formula 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 of SPAD0 directly generating crosstalk to the i-th SPAD unit 500, which can be obtained by optical simulation combined with Formula 1. Thus, the optical crosstalk model of the one-dimensional long-line array of SPADs is obtained.

[0094] On this basis, this application uses a similar method to extend it to a 2D array, as shown in Figure 13 The crosstalk received by SPAD0 comes from 8 directions around. According to symmetry, only the horizontal direction crosstalk ρ 1 and the crosstalk ρ 2 in the diagonal direction need to be simulated and calculated.

[0095] This application uses an approximate method to simulate an infinite two-dimensional array, that is, a one-dimensional 4-spads model is used to obtain an approximate horizontal crosstalk ρ 1 , which is used for equivalent calculation Figure 11 the crosstalk of SPAD1 and SPAD2 to SPAD0 in Figure 12 ; Then, the crosstalk magnitude of the SPAD in the diagonal direction is simulated to obtain ρ2, which is equivalent to

[0096] the crosstalk of SPAD3 to SPAD0 in

[0097] OXT -2D = 4ρ 1 + 4ρ 2 + 4(ρ 1 ·ρ 2 - ρ 1 ·ρ 1 ·ρ 2 ); (Formula 4)

[0098] According to the crosstalk improvement effect in this application, sequential simulation verification is carried out, and the crosstalk improvement effect is compared with the crosstalk performance of the traditional device structure simulation. Refer to Table 1

[0099] Table 1

[0100]

[0101] From the simulation data in Table 1, it can be clearly seen that the crosstalk performance has been significantly improved. When only optimizing the deep trench isolation pillar 400 process, the crosstalk probability in both the horizontal direction and the diagonal direction has decreased significantly, and finally the total OXT has decreased to 60% of the original; When only adopting the optimization scheme of the metal filling structure 140 closed loop, the same improvement effect is also achieved; When both the deep trench isolation extension scheme and the metal filling structure 140 closed loop scheme are adopted, the crosstalk performance is further reduced, especially the χ1 probability, that is, the crosstalk suppression of the nearest neighboring SPAD unit 500 is obvious, and the OXT has decreased to 46% of the original; While adopting the comprehensive scheme proposed in this application (as Figure 11 shown), the OXT has decreased to 36% of the original, and the improvement of the nearest neighboring SPAD unit 500 is the most significant

[0102] Figures 14 - 17 More intuitively shows the improvement effect of the optical crosstalk of the scheme in this application Figure 14The crosstalk situation of the self-excited light of the traditional structure and the crosstalk situation of the extended structure of the metal-filled structure 140 are shown. Figure 14 In the leftmost SPAD unit 500 in [reference], self-excited photons are generated by avalanche. Figure 14 The situation where the position of the photon is shown on the left side of the device is presented. By comparing the left and right figures, it can be intuitively seen that the scheme of the closed-loop of the metal-filled structure 140 (such as Figure 1 ) significantly suppresses the crosstalk light of this path.

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

[0104] Figure 16 The crosstalk situation of the self-excited photons when the extended structure of the deep trench isolation and the closed-loop scheme of the metal-filled structure 140 (such as Figure 9 ) are adopted simultaneously is presented. It is not difficult to see that the crosstalk light directly under the back metal grid 200 and at the bottom of the deep trench isolation column 400 has been greatly reduced, and the main crosstalk comes from the lens part.

[0105] Figure 17 The situation when the comprehensive improvement scheme (such as Figure 11 ) is adopted is presented. The back metal grid 200 adopts an inverted trapezoid, so that a large part of the crosstalk light is reflected back into its own SPAD unit, and the optical crosstalk of the adjacent devices is significantly suppressed, thus reducing the optical crosstalk of the entire two-dimensional array. In particular, a smaller gain is adopted in the model calculation of this scheme, and the value of the radiation spectrum of the self-excited photons is also relatively small. Therefore, for the actually fabricated device, when the incident light intensity is increased and the overvoltage is increased, the improvement degree of the optical crosstalk performance will be more significant.

[0106] The embodiments of the present application also provide a silicon photomultiplier tube, which includes a single-photon avalanche diode array as described in any one of the above embodiments.

[0107] Beneficial effects of the embodiments of the present application: The incident light is converged onto the corresponding SPAD unit through a micro-lens. The back metal grid connects the SPAD unit with the corresponding external electrode. The first dielectric layer is arranged between the micro-lens and the SPAD unit, and the second dielectric layer is arranged between the SPAD unit and the front metal wiring layer. The front metal wiring layer is electrically connected to the corresponding SPAD unit through a contact metal wire. By arranging deep trench isolation columns between adjacent SPAD units and arranging a metal-filled structure between the deep trench isolation columns and the back metal grid, the self-excited photons generated by the incident light excitation of the SPAD unit can be isolated, preventing the self-excited photons from entering the adjacent SPAD units through the grid gaps, reducing the overflow of the self-excited photons, reducing the probability of photon crosstalk, and reducing the optical crosstalk of the device.

[0108] The embodiment of the present application further includes a receiving sensor, and the receiving sensor may include one or more of the above-mentioned single-photon avalanche diode arrays or one or more of the above-mentioned silicon photomultipliers.

[0109] The embodiment of the present application further includes a lidar, and the lidar includes a transmitting sensor and the above-mentioned receiving sensor. The transmitting sensor is used to emit detection laser, and the receiving sensor is used to receive the echo of the detection laser, and a target object is obtained according to the echo.

[0110] Those skilled in the art can clearly understand that, for the convenience and conciseness of description, only the above-mentioned division of each functional device area and module is used as an example for illustration. In practical applications, the above-mentioned functions can be allocated to 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 distinction and do not limit the protection scope of the present application. The specific working processes of the units and modules in the above system can refer to the corresponding processes in the foregoing method embodiments and will not be elaborated herein.

[0112] In the above embodiments, the descriptions of each embodiment have their own emphases. For the parts not detailed or recorded in a certain embodiment, reference can be made to the relevant descriptions 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 and do not limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some 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 each embodiment of the present application, and should all 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 includes: at least two SPAD units; At least two microlenses, respectively corresponding to at least two of the SPAD units one by one, and the microlenses are used to converge incident light onto the corresponding SPAD units; At least two front metal wiring layers, at least two of the front metal wiring layers corresponding to at least two of the SPAD units one by one; A back metal grid for connecting the SPAD units to corresponding external electrodes; A first dielectric layer disposed between the microlens and the SPAD unit, and the first dielectric layer is used to reduce the reflection of the incident light; A second dielectric layer disposed between the SPAD unit and the front metal wiring layer; wherein, the front metal wiring layer is electrically connected to the corresponding SPAD unit through a contact wire; Deep trench isolation pillars are disposed between adjacent SPAD units for isolating adjacent SPAD units; A metal filling structure is disposed between the deep trench isolation pillars and the back metal grid for suppressing self-excited photons generated by the SPAD units excited by the incident light from entering adjacent SPAD units through the grid gaps.

2. The single-photon avalanche diode array according to claim 1, Characterized in that, The vertical cross-section of the back metal grid is an inverted trapezoid.

3. The single-photon avalanche diode array according to claim 1, Characterized in that, The vertical cross-section of the back metal grid is a multi-layer stepped structure, and the width of each step in the multi-layer stepped structure gradually increases.

4. The single-photon avalanche diode array according to claim 1, Characterized in that, The vertical cross-section of the back metal grid is an arc-shaped structure for reflecting photons irradiating its surface to the SPAD unit.

5. The single-photon avalanche diode array according to any one of claims 1-4, Characterized in that, An inter-metal dielectric layer is disposed between adjacent front metal wiring layers, an etch stop layer is disposed between the inter-metal dielectric layer and the deep trench isolation pillar, the deep trench isolation pillar penetrates into the etch stop layer, and divides the second dielectric layer into at least two dielectric units, and at least two dielectric units correspond to the SPAD units.

6. The single-photon avalanche diode array according to any one of claims 1-4, Characterized in that, An inter-metal dielectric layer is disposed between adjacent front metal wiring layers, an etch stop layer is disposed between the inter-metal dielectric layer and the deep trench isolation pillar, and the length of the part of the deep trench isolation pillar penetrating into the second dielectric layer is greater than one half of the thickness of the second dielectric layer.

7. The single-photon avalanche diode array according to any one of claims 1-4, Characterized in that, The SPAD unit includes a first doping region and a second doping region stacked on the second dielectric layer, and the first doping region and the second doping region form a PN junction.

8. The single-photon avalanche diode array according to any one of claims 1-4, Characterized in that, The deep trench isolation pillar is tungsten.

9. A receiving sensor, Characterized in that, The receiving sensor includes a single-photon avalanche diode array as described in any one of claims 1-8.

10. A lidar, characterized in that, the lidar includes a transmitting sensor and a receiving sensor as described in claim 9; the transmitting sensor is configured to emit detection laser light; the receiving sensor is configured to receive the echo of the detection laser light and obtain detection information of a target object based on the echo.

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