Sensor with high-resolution SPAD array for lidar using a micro-assembly process

Abstract

A light sensor comprises an integrated circuit containing an array of time-to-digital converters and an array of first connections connected to the time-to-digital converter array. A plurality of single-photon avalanche photodiode circuits comprises a second connection. Each of the plurality of single-photon avalanche photodiode circuits corresponds to a single pixel. The plurality of single-photon avalanche photodiode circuits are individually arranged on the integrated circuit, with the second connection of the plurality of single-photon avalanche photodiode circuits connected to a corresponding first connection of the integrated circuit.

Description

Introduction

[0001] The information provided in this section serves the purpose of presenting the general context of the disclosure. The work of the inventors mentioned herein, insofar as it is described in this section, as well as aspects of the description that cannot be classified as prior art at the time of filing, are neither expressly nor implicitly recognized as prior art with respect to the present disclosure.

[0002] The present disclosure relates to light sensors and in particular to a light sensor comprising an array of single photon avalanche photodiodes (SPADs) formed using micro-assembly techniques.

[0003] Vehicles may include driver assistance controllers that support modes for fully or partially autonomous driving. These vehicles incorporate one or more sensors, such as radio detection and ranging (radar) and / or laser detection and ranging (lidar), which emit radio or light pulses and receive reflected signals from objects in the vehicle's path. In some examples, a lidar sensor receiver comprises an array of single-photon avalanche photodiodes (SPADs) monolithically mounted on an integrated circuit. Summary

[0004] A sensor comprises an integrated circuit that includes an array of time-to-digital converters and an array of interconnects connected to the time-to-digital converter array. A plurality of single-photon avalanche photodiode circuits comprises a second interconnect. Each of the plurality of single-photon avalanche photodiode circuits corresponds to a single pixel. The plurality of single-photon avalanche photodiode circuits are individually arranged on the integrated circuit, with the second interconnect of the plurality of single-photon avalanche photodiode circuits connected to a corresponding first interconnect of the integrated circuit.

[0005] In other features, the multitude of single-photon avalanche photodiode circuits on the integrated circuit are spaced at a fixed distance. The multitude of single-photon avalanche photodiode circuits on the integrated circuit are spaced at a variable distance. The first and second connections of the multitude of single-photon avalanche photodiode circuits comprise hybrid copper connections. The integrated circuit also includes a compound layer.

[0006] In other features, the interconnect layer is arranged between the array of time-to-digital converters and the array of first connections. The sensor forms part of a receiver for laser light-based detection and distance measurement.

[0007] A sensor comprises a backplane substrate. A plurality of integrated circuits includes a time-to-digital converter and a first connection that provides a link to the time-to-digital converter, with each of the plurality of integrated circuits corresponding to a single pixel. A plurality of single-photon avalanche photodiode circuits comprises a second connection. Each of the plurality of single-photon avalanche photodiode circuits corresponds to a single pixel. The plurality of single-photon avalanche photodiode circuits are individually arranged on the plurality of integrated circuits, with the second connection of the plurality of single-photon avalanche photodiode circuits connected to a corresponding connection of the first connection of the integrated circuit. The plurality of integrated circuits is arranged on the backplane substrate.

[0008] In other features, the multitude of single-photon avalanche photodiode circuits and the multitude of integrated circuits are spaced at a fixed distance on the backplane substrate. The multitude of single-photon avalanche photodiode circuits and the multitude of integrated circuits are spaced at a variable distance on the backplane substrate. The first and second connections comprise hybrid copper connections. The multitude of integrated circuits further comprises an interconnect layer. The interconnect layer is located between the time-to-digital converter and the first connection.

[0009] In other characteristics, the backplane substrate is either planar or non-planar. The sensor forms part of a receiver for laser light-based detection and distance measurement.

[0010] A vehicle comprises a laser-based detection and distance measurement sensor with an integrated circuit that includes an array of time-to-digital converters and an array of first connections connected to the time-to-digital converter array. A plurality of single-photon avalanche photodiode circuits each includes a second connection. Each of the plurality of single-photon avalanche photodiode circuits corresponds to a single pixel. The plurality of single-photon avalanche photodiode circuits are individually arranged on the integrated circuit, with the second connection of each plurality of single-photon avalanche photodiode circuits connected to a corresponding first connection of the integrated circuit.A controller with an autonomous driving module configured to support partially and / or fully autonomous driving in response to the sensor for laser light-based detection and distance measurement.

[0011] In other features, the multitude of single-photon avalanche photodiode circuits are spaced at a fixed distance on the integrated circuit. The multitude of single-photon avalanche photodiode circuits are spaced at a variable distance on the integrated circuit. The first and second connections of the multitude of single-photon avalanche photodiode circuits comprise hybrid copper connections.

[0012] In other features, the integrated circuit also includes an interconnect layer. The interconnect layer is located between the array of time-to-digital converters and the array of first connections.

[0013] Further applications of the present disclosure will become apparent from the detailed description, the claims, and the drawings. The detailed description and the specific examples serve only for illustration and are not intended to limit the scope of the disclosure. Brief description of the drawings

[0014] The present disclosure is more fully understood from the detailed description and the accompanying drawings, whereby: Fig. 1 a functional block diagram of an example of a vehicle with a sensor for laser light-based detection and distance measurement (Lidar) according to the present disclosure; Fig. 2A is a side cross-section of an example of a substrate with a multitude of pixels with single-photon avalanche photodiodes (SPADs); Fig. 2B is a side cross-section of an example of the SPAD pixels after a division according to the present disclosure; Fig. 2C is a side cross-section of an example of the SPAD pixel according to the present disclosure; Fig. 3 a side cross-section of an example of a substrate with an integrated circuit comprising a time-digital circuit array and an interconnect layer according to the present disclosure; Fig. 4 A side cross-section of an example of the substrate of Fig. 3 with SPAD pixels attached at a fixed distance using a micro-assembly process according to the present disclosure; Fig. 5 a side cross-section of an example of the substrate of Fig. 3 with the SPAD pixels attached using a micro-assembly process with a variable spacing according to the present disclosure; Fig. 6 is a side cross-section of an example of SPAD pixels mounted on respective time-to-digital converter (TDC) integrated circuits (ICs) and arranged on a planar backplane substrate according to the present disclosure; Fig. 7 is a side cross-section of an example of SPAD pixels mounted on respective TDC-integrated circuits and arranged on a curved backplane substrate according to the present disclosure; and Fig. 8A and Fig. 8B Examples of methods for manufacturing SPAD arrays according to the present disclosure are.

[0015] Reference numerals can be reused in the drawings to identify similar and / or identical elements. Detailed description

[0016] While the following description refers to a laser light-based detection and distance measurement (Lidar) sensor for a vehicle, the Lidar sensor can be used in stationary or other applications.

[0017] Some lidar sensors incorporate a monolithic substrate with a SPAD array. The SPAD array comprises a multitude of single-photon avalanche photodiode (SPAD) macropixels (or pixels). Each SPAD pixel may contain subpixels (or micropixels). In some examples, each SPAD pixel is associated with a time-to-digital converter (TDC) (e.g., nominally one TDC per SPAD macropixel). The substrate includes an array of contacts (corresponding to each SPAD pixel) bonded to contacts of a monolithic integrated circuit (IC), which includes a time-to-digital converter for each SPAD pixel and is optionally cured or annealed.

[0018] The physical size of the time-to-digital converter (TDC) for each pixel is larger than the SPAD pixel, which complicates the development of high-resolution SPAD arrays. The unique approach described here decouples the dimensional limitations of the SPAD array and the TDC IC using microassembly techniques. As a result, SPAD arrays with higher resolution (e.g., a higher pixel count) can be fabricated.

[0019] Individual SPAD pixels are manufactured and separated or divided. The SPAD pixels are then placed onto the TDC IC using microassembly techniques, bonded, and optionally annealed. This approach enables high-resolution arrays and allows the creation of non-uniform SPAD arrays that compensate for optical distortion. This approach allows for better optimization to maintain resolution across a field of view in lidar applications. Training SPAD arrays using microassembly processes also provides a faster route to custom array configurations, avoiding the up to 1.5 years required for the design, layout, and fabrication of custom monolithic SPAD arrays.

[0020] Referring now to Fig. 1 comprises a vehicle 10 a controller 8 which contains a module 12 for autonomous driving which is configured to support modes for fully and / or partially autonomous driving based on data acquired by means of a sensor 24 for laser light-based detection and distance measurement (Lidar), one or more radar sensors 22 and / or one or more cameras 23.

[0021] The lidar sensor 24 optionally includes one or more scanners 28, one or more lasers 30, and one or more arrays of single-photon avalanche photodiodes (SPADs) containing SPAD pixels. In some examples, the laser 30 includes one or more vertical cavity surface-emitting lasers (VCSELs). In some examples, the VCSELs are operated in a flash mode without scanners. The lidar sensor 24 further includes an IC 38 with time-to-digital converters (TDCs) configured to determine the elapsed time from the generation of the light pulses to their return. The lidar sensor 24 optionally includes a point cloud generator / storage unit 42 configured to store a point cloud based on the return data.In some examples, data from the lidar sensor 24 and / or other controllers are used to generate an obstacle grid containing object data in the path of the vehicle 10. In some examples, the lidar sensor 24 measures the calibrated target reflectivity for each return.

[0022] The vehicle 10 may further include a global positioning system / compass 20 configured to provide GPS coordinates and / or the vehicle's orientation. The vehicle 10 may further include a radio-based detection and distance measurement system (radar) 22 configured to generate radio signals and receive the feedback. The vehicle 10 includes control elements 50 such as a steering wheel, accelerator pedal, brake pedal, turn signals, etc.

[0023] Now on Fig. Referring to 2A to 2C, a substrate 114 is fabricated such that it comprises a plurality of pixels 110-1, 110-2, ..., 110-N with single-photon avalanche photodiodes (SPADs) (collectively SPAD pixels 110). While in Fig. 2A shows a single row, the SPAD pixels 110 can be arranged in an array of M x N pixels, where M and N are integers greater than zero.

[0024] In Fig. 2B, the SPAD pixels 110-1, 110-2, ..., 110-N are separated into individual SPAD pixels 110-1, 110-2, ..., 110-N. The individual SPAD pixels 110-1, 110-2, ..., 110-N are separated or divided into individual SPAD pixels 110 using established wafer singulation or sectioning techniques (mechanical, laser, etc.) and loaded into a cassette or other carrier compatible with a microassembly process.

[0025] In Fig. 2C comprises the SPAD pixel 110, a lens 130, and light guide sections 134 that direct lidar feedback between sidewalls 136 onto an avalanche area 144 located above an (n+) area 146 situated between (p+) areas 138 and 140 of diodes. Contacts 148, arranged in an insulating layer 149, are made of a conductive material and are connected to the (n+) area 146 and / or the (p+) areas 138 and 140. One or more contact pads 150 connect the contacts 148 of one or more of the (n+) areas 146 and / or the (p+) areas 138 and 140 to the TDC IC.

[0026] Now on Fig. Referring to Figure 3, a substrate 200 comprises a TDC IC 222 with a TDC array and / or the point cloud generator / memory. A connection layer 210 is arranged on one side of the TDC ICs 222 and includes contact pads 214 for connecting to the contact pads 150 of the SPAD pixels 110. In some examples, the contact pads 214 and 150 comprise hybrid copper connections. In some examples, one or both of the contact pads 214 and 150 are made of copper and are surrounded by a dielectric layer (e.g., an oxide layer such as silicon dioxide (SiO2)) prior to microassembly and annealing.

[0027] In some examples, a multitude of individual SPAD pixels are connected to a single digital logic IC using a fixed or variable spacing. In other examples, a multitude of individual SPAD pixels are connected to individual TDC ICs and then mounted on a backplane substrate using a fixed or variable spacing. The individual digital logic ICs can be fabricated in a similar manner to the individual SPAD pixels (fabrication of an array followed by dissecting individual TDC ICs).

[0028] Now on Fig. 4 referring to the substrate 200 of Fig. Figure 3 shows SPAD pixels 110 arranged at a fixed distance (d1) using a microassembly process. After microassembly, a curing or...

[0029] A tempering step is performed to strengthen the bond connecting the contact pads 214 and 150.

[0030] Now on Fig. 5 referring to the substrate 200 is made of Fig. Figure 3 shows SPAD pixels 110 arranged using a microassembly process with variable spacing (e.g., d1 < d2 < d3 ... , d1 > d2 > d3 ... or other patterns). In this example, the spacing increases from the center to the edge of the SPAD array. However, other patterns with variable spacing can be used. After microassembly, an annealing step can be performed to strengthen the bond connecting the contact pads 214 and 150.

[0031] Now on Fig. 6 and Fig. Referring to section 7, the SPAD pixels and the TDC ICs can be fabricated on a substrate and then cut apart as described above to form individual SPAD pixels and TDC circuits 310-1, 310-2, ... and 310-N. The SPAD pixels and TDC ICs 310-1, 310-2, ... and 310-N each comprise a compound layer 314-1, 314-2, ... and 314-N and a TDC layer 318-1, 318-2, ... and 318-N. The SPAD pixels and TDC ICs 310-1, 310-2, ... and 310-N are arranged on a planar backplane substrate 322. Fig. 7 The SPAD pixels and TDC ICs 310-1, 310-2, ... and 310-N are arranged on a curved backplane substrate 332 to compensate for optical distortion.

[0032] Now on Fig. 8A and Fig. Reference to Section 8B shows examples of methods for fabricating SPAD arrays. Fig. In step 410, a large number of SPAD pixels are fabricated on a substrate. In step 414, the SPAD pixels are cut to separate individual pixels. In step 418, the SPAD pixels are placed on a substrate containing a compound layer and digital logic circuitry (e.g., the TDC ICs and / or the point cloud memory). In step 422, annealing is optionally performed to strengthen the bonds.

[0033] In Fig. In step 510, a large number of SPAD pixels, interconnects, and TDC ICs are fabricated on a substrate. In step 514, the SPAD pixels, interconnects, and TDC ICs are cut to separate individual SPAD pixels, interconnects, and TDC ICs. In step 518, the SPAD pixels, interconnects, and ICs are placed on a backplane substrate. In step 522, annealing is optionally performed to strengthen the bonds.

[0034] While the preceding description refers to a light sensor used in a receiver of a lidar sensor, the light sensor can also be used for near-infrared imaging.

[0035] The preceding description is merely illustrative and intended to limit the scope of the revelation, its application, or uses. The comprehensive doctrine of revelation can be implemented in a multitude of forms. Therefore, although this revelation contains particular examples, the true scope of the revelation should not be so limited, since other modifications will become apparent upon study of the drawings, the description, and the following claims. It should be understood that one or more steps within a process may be carried out in a different order (or simultaneously) without altering the principles of the present revelation.Furthermore, although each of the embodiments described above is characterized by certain features, one or more of these features described in relation to any embodiment of the disclosure may be implemented in one of the other embodiments and / or combined with features of one of the other embodiments, even if this combination is not expressly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more embodiments with each other remain within the scope of this disclosure.

[0036] Spatial and functional relationships between elements (for example, between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including "connected," "interlocked," "coupled," "adjacent," "near or beside," "on," "above," "below," and "arranged." Unless explicitly described as "direct," when a relationship between first and second elements is described in the above disclosure, this relationship may be a direct relationship, in which no other intervening elements exist between the first and second elements, or it may be an indirect relationship, in which one or more intervening elements (either spatial or functional) exist between the first and second elements.As used here, the phrase “at least one of A, B and C” should be understood to mean a logical (A OR B OR C) using a non-exclusive logical OR, and should not be understood to mean “at least one of A, at least one of B and at least one of C”.

[0037] In the diagrams, the direction of an arrow, as indicated by its tip, generally illustrates the flow of information (e.g., data or instructions) that is relevant to the illustration. For example, if Element A and Element B exchange a variety of information, but information transferred from Element A to Element B is important for the illustration, the arrow may point from Element A to Element B. This unidirectional arrow does not imply that no other information is transferred from Element B to Element A. Furthermore, Element B may send requests for, or acknowledgments of, information to Element A in connection with the information transferred from Element A to Element B.

[0038] In this application, including the definitions below, the term "module" or the term "controller" may be replaced by the term "circuit". The term "module" may refer to, be part of, or include an application-specific integrated circuit (ASIC); a digital, analog, or mixed analog / digital discrete circuit; a digital, analog, or mixed analog / digital integrated circuit; a combinational logic circuit; a field-programmable gate array (FPGA); a processor circuit (shared, dedicated, or group) that executes code; a memory circuit (shared, dedicated, or group) that stores code executed by the processor circuit; other suitable hardware components that provide the described functionality; or a combination of some or all of the above components, such as in a system-on-a-chip.

[0039] The module may contain one or more interface circuits. In some examples, the interface circuits may include wired or wireless interfaces connected to a local area network (LAN), the internet, a wide area network (WAN), or combinations thereof. The functionality of any given module of this disclosure may be distributed among multiple modules connected via interface circuits. For example, multiple modules may enable load balancing. In another example, a server module (also known as a remote or cloud module) may perform some functions for a client module.

[0040] The term "code," as used above, can include software, firmware, and / or microcode, and can refer to programs, routines, functions, classes, data structures, and / or objects. The term "shared processor circuit" refers to a single processor circuit that executes some or all of the code from multiple modules. The term "group processor circuit" refers to a processor circuit that, in combination with additional processor circuits, executes some or all of the code from one or more modules. References to multiple processor circuits include multiple processor circuits on separate chips, multiple processor circuits on a single chip, multiple cores of a single processor circuit, multiple threads of a single processor circuit, or a combination of the above.The term shared memory circuit refers to a single memory circuit that stores some or all of the code from multiple modules. The term group memory circuit refers to a memory circuit that, in combination with additional memory, stores some or all of the code from one or more modules.

[0041] The term storage circuit is a subset of the term computer-readable medium. The term computer-readable medium, as used here, does not include transitory electrical or electromagnetic signals that propagate through a medium (such as on a carrier wave); the term computer-readable medium can therefore be considered material and non-transient.Non-restrictive examples of a non-transient, physical, computer-readable medium include non-volatile memory circuits (such as a flash memory circuit, a erasable programmable read-only memory circuit, or a mask read-only memory circuit), volatile memory circuits (such as a static random access memory circuit or a dynamic random access memory circuit), magnetic storage media (such as an analog or digital magnetic tape or a hard disk drive), and optical storage media (such as a CD, a DVD, or a Blu-ray Disc).

[0042] The devices and methods described in this application can be partially or fully implemented by means of a special-purpose computer created by configuring a general-purpose computer to perform one or more specific functions embodied in computer programs. The functional blocks, flowchart components, and other elements described above serve as software specifications that can be translated into computer programs through the routine work of a person skilled in the art or a programmer.

[0043] Computer programs contain instructions executable by processors, stored on at least one non-transient, physical, computer-readable medium. Computer programs may also contain or rely on stored data. Computer programs may include a basic input / output system (BIOS) that interacts with the computer's special-purpose hardware, device drivers that interact with specific devices of the computer for special purposes, one or more operating systems, user applications, background services, background applications, etc.

[0044] The computer programs can contain: (i) descriptive text to be parsed, such as HTML (Hypertext Markup Language), XML (Extensible Markup Language), or JSON (JavaScript Object Notation); (ii) assembly code; (iii) object code generated from source code by a compiler; (iv) source code for execution by an interpreter; (v) source code for compilation and execution by a just-in-time compiler; etc. For example, source code can be written using the syntax of languages ​​such as C, C++, C#, Objective-C, Swift, Haskell, Go, SQL, R, Lisp, Java®, Fortran, Perl, Pascal, Curl, OCaml, Javascript®, HTML5 (Hypertext Markup Language 5th Revision), Ada, ASP (Active Server Pages), PHP (PHP: Hypertext Preprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Flash®, and Visual Basic®. Include Lua, MATLAB, SIMULINK and Python®.

Claims

[1] Sensor, encompassing: an integrated circuit that includes: an array of time-to-digital converters; and an array of first connections that are linked to the array of time-to-digital converters; and a multitude of single-photon avalanche photodiode circuits, each comprising a second connection, where each of the multitude of single-photon avalanche photodiode circuits corresponds to a single pixel, wherein the plurality of single-photon avalanche photodiode circuits is individually arranged on the integrated circuit, wherein the second connection of the plurality of single-photon avalanche photodiode circuits is connected to a corresponding one of the first connections of the integrated circuit. [2] Sensor according to claim 1, wherein the plurality of single-photon avalanche photodiode circuits on the integrated circuit are spaced apart at a fixed distance. [3] Sensor according to claim 1, wherein the plurality of single-photon avalanche photodiode circuits on the integrated circuit is spaced apart at a variable distance. [4] Sensor according to claim 1, wherein the first connections and the second connection of the plurality of single-photon avalanche photodiode circuits comprise hybrid copper connections. [5] Sensor according to claim 1, wherein the integrated circuit further comprises a connection layer. [6] Sensor according to claim 5, wherein the interconnect layer is arranged between the array of time-to-digital converters and the array of first interconnects. [7] Sensor according to claim 1, wherein the sensor forms part of a receiver of a sensor for laser light-based detection and distance measurement. [8] Light sensor, comprehensive: a backplane substrate; a variety of integrated circuits, each comprising: a time-to-digital converter; and a first connection that provides a link to the time-to-digital converter, with each of the multitude of integrated circuits corresponding to a single pixel; and a plurality of single-photon avalanche photodiode circuits, each comprising a second connection, wherein each of the plurality of single-photon avalanche photodiode circuits corresponds to a single pixel, wherein the plurality of single-photon avalanche photodiode circuits is individually arranged on the plurality of integrated circuits, wherein the second connection of the plurality of single-photon avalanche photodiode circuits is connected to a corresponding connection of the first connection of the integrated circuit and the multitude of integrated circuits are arranged on the backplane substrate. [9] Sensor according to claim 8, wherein the plurality of single-photon avalanche photodiode circuits and the plurality of integrated circuits are spaced apart at a fixed distance on the backplane substrate. [10] Sensor according to claim 8, wherein the plurality of single-photon avalanche photodiode circuits and the plurality of integrated circuits are spaced apart on the backplane substrate with a variable distance.

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