Fabrication method of long-range ranging chip based on silicon-based germanium single-photon detector

Abstract

This invention provides a method for fabricating a long-range ranging chip based on a silicon-based germanium single-photon detector. The method involves fabricating a circuit wafer, a SPAD wafer, and a laser wafer capable of generating 1550nm laser pulses based on the circuit principle of the long-range ranging chip using a silicon-based germanium single-photon detector. The SPAD wafer is processed, and the processed SPAD wafer is bonded to the circuit wafer to form a preliminary bond. This wafer is then subjected to low-temperature annealing to form a circuit SPAD integrated wafer. The wafer is then divided to obtain multiple independent circuit SPAD integrated chips and laser chips. Any laser chip is soldered to any circuit SPAD integrated chip via a substrate, and optical windows are designed in the areas where the laser chip and the silicon-based germanium SPAD detector are located, thereby obtaining a long-range ranging chip based on a silicon-based germanium single-photon detector. This achieves monolithic integration, improves system integration, and enables miniaturization of the long-range ranging system.

Description

Technical Field

[0001] This invention relates to the field of semiconductor optoelectronic integration technology, and specifically to a method for fabricating a long-range ranging chip based on a silicon-based germanium single-photon detector. Background Technology

[0002] The emergence of Time-of-Flight (ToF) distance measurement technology has greatly promoted the development of fields such as UAV mapping, autonomous driving, machine vision, and aerospace. LiDAR technology, developed using ToF ranging, is playing an increasingly important role in autonomous driving, industrial automation, and smart home applications due to its high precision, fast response, and broad application prospects. With the continuous development of semiconductor technology, the requirements for further improvements in the integration of distance detection sensors and for higher performance, longer range, and lower cost distance information detection are becoming increasingly stringent.

[0003] Traditional long-range ranging solutions use indium gallium arsenide (InGaAs) / indium phosphorus (InP) avalanche photodetectors. Their advantages are good performance, and they are currently used in high-end applications such as scientific research, military, or industry. Their disadvantages are that they are difficult to integrate on a single chip, are expensive, and require low-temperature cooling to reduce dark current and noise, making it difficult to apply long-range ranging to thin, highly integrated consumer electronics. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention provides a method for fabricating a long-range ranging chip based on a silicon-based germanium single-photon detector, specifically comprising:

[0005] In a first aspect, the present invention provides a method for fabricating a long-range ranging chip based on a silicon-based germanium single-photon detector, comprising:

[0006] The circuit portion of the long-range ranging chip based on silicon-based germanium single-photon detectors is fabricated on a wafer using standard silicon complementary metal-oxide-semiconductor (CMOS) technology to form a circuit wafer. The circuit portion includes a silicon-based germanium single-photon avalanche detector (SPAD) readout and quenching circuit, a time-to-digital converter (TDC) circuit, a control and signal processing circuit, a laser driving circuit, and a laser control circuit.

[0007] A silicon-based germanium SPAD detector based on a long-range ranging chip of a silicon-based germanium single-photon detector is fabricated into a SPAD wafer;

[0008] Fabrication of laser wafers, which can generate laser pulses with a wavelength of 1550nm;

[0009] The SPAD wafer is thinned to remove excess silicon substrate without device structure. The thinned SPAD wafer and circuit wafer are then cleaned to remove surface impurities, resulting in a cleaned SPAD wafer and a cleaned circuit wafer.

[0010] Flip the cleaned circuit wafer and align the cleaned SPAD wafer with the flipped circuit wafer according to design requirements;

[0011] At room temperature, the cleaned SPAD wafer and the flipped circuit wafer are bonded together to form a preliminary bonded wafer;

[0012] The pre-bonded wafers are subjected to low-temperature annealing to obtain low-temperature annealed bonded wafers;

[0013] Surface treatment is performed on the bonded wafers after low-temperature annealing to fabricate SPAD integrated circuit wafers;

[0014] By dividing the circuit SPAD integrated wafer, multiple independent circuit SPAD integrated chips are obtained;

[0015] The laser wafer is split to obtain multiple independent laser chips;

[0016] Using flip-chip bonding technology, thermally conductive adhesive and low-temperature soldering materials, any laser chip and any circuit SPAD integrated chip are soldered together through a substrate. Optical-grade resin is used to design optical windows on the target area on the soldered chip. The target area includes the area where the laser chip is located and the area where the silicon-based germanium SPAD detector is located. Through system-level packaging, a long-range ranging chip based on a silicon-based germanium single-photon detector is obtained.

[0017] Secondly, the present invention also provides a long-range ranging chip based on a silicon-based germanium single-photon detector, wherein the long-range ranging chip based on the silicon-based germanium single-photon detector is prepared by any of the preparation methods provided in the first aspect.

[0018] Long-range ranging chips based on silicon-based germanium single-photon detectors include:

[0019] Laser devices, silicon-based germanium SPAD detectors, SPAD readout and quenching circuits, TDC circuits, control and signal processing circuits, laser drive circuits, and laser control circuits;

[0020] Laser driver circuit, used to provide drive signals for laser devices;

[0021] The laser control circuit is used to control the laser device to generate and emit laser pulses with a wavelength of 1550nm, and synchronously record the current time, setting the current time as the start time of the current working cycle. The total duration of the working cycle is preset according to the detection distance.

[0022] Silicon-based germanium SPAD detectors are used to detect reflected single-photon counting signals.

[0023] The SPAD readout and quenching circuit is used to send multiple single-photon count signals detected by the silicon-based germanium SPAD during the current working cycle to the TDC circuit. The multiple single-photon count signals include signals reflected by the target under test.

[0024] The TDC circuit is used to statistically analyze the distribution of multiple single-photon counting signals detected by the silicon-based germanium SPAD detector.

[0025] The control and signal processing circuit is used to calculate the distance between the long-range ranging chip based on the silicon-based germanium single-photon detector and the target to be measured, according to the distribution.

[0026] Thirdly, the present invention also provides a long-distance ranging method based on a silicon-based germanium single-photon detector, which can be applied to any long-distance ranging chip based on a silicon-based germanium single-photon detector as provided in the second aspect. The long-distance ranging chip based on a silicon-based germanium single-photon detector includes a laser device, a silicon-based germanium SPAD detector, a SPAD readout and quenching circuit, a TDC circuit, a control and signal processing circuit, a laser driving circuit, and a laser control circuit.

[0027] Long-range ranging methods based on silicon-based germanium single-photon detectors include:

[0028] The laser control circuit and laser drive circuit control the laser device to generate and emit laser pulses with a wavelength of 1550nm, and simultaneously record the current time, setting the current time as the start time of the current working cycle. The total duration of the working cycle is preset according to the detection distance.

[0029] The reflected single-photon counting signal is detected using a silicon-based germanium SPAD detector;

[0030] The SPAD readout and quenching circuit sends multiple single-photon counting signals detected by the silicon-based germanium SPAD during the current working cycle to the TDC circuit. Among the multiple single-photon counting signals are signals reflected by the target under test.

[0031] The distribution of multiple single-photon counting signals detected by the silicon-based germanium SPAD detector is statistically analyzed using the TDC circuit.

[0032] The distance between the long-range ranging chip based on the silicon-based germanium single-photon detector and the target is calculated by the control and signal processing circuit according to the distribution.

[0033] Fourthly, the present invention provides a long-range device based on a silicon-based germanium single-photon detector, including any of the long-range ranging chips based on a silicon-based germanium single-photon detector as provided in the second aspect.

[0034] The beneficial effects of this invention are:

[0035] This invention provides a method for fabricating a long-range ranging chip based on a silicon-based germanium single-photon detector. The circuit portion of the long-range ranging chip is fabricated on a wafer using standard silicon CMOS technology to create a circuit wafer. The circuit portion includes a silicon-based germanium SPAD readout and quenching circuit, a TDC circuit, a control and signal processing circuit, a laser driving circuit, and a laser control circuit. The silicon-based germanium SPAD detector of the long-range ranging chip is fabricated into a SPAD wafer. A laser wafer is fabricated, capable of generating laser pulses with a wavelength of 1550 nm. The SPAD wafer is thinned to remove excess silicon substrate without device structures. The thinned SPAD wafer and circuit wafer are cleaned to remove surface impurities, resulting in a cleaned SPAD wafer and a cleaned circuit wafer. The cleaned circuit wafer is flipped, and the cleaned SPAD wafer and the flipped circuit wafer are aligned according to design requirements. The cleaned SPAD wafer and the flipped circuit wafer are then bonded together at room temperature. The process involves: forming a preliminary bonded wafer from circuit wafers; subjecting the preliminary bonded wafers to low-temperature annealing to obtain a low-temperature annealed bonded wafer; performing surface treatment on the low-temperature annealed bonded wafers to fabricate a circuit SPAD integrated wafer; dividing the circuit SPAD integrated wafers to obtain multiple independent circuit SPAD integrated chips; dividing the laser wafers to obtain multiple independent laser chips; using flip-chip bonding technology, thermally conductive adhesive and low-temperature soldering material, soldering any laser chip to any circuit SPAD integrated chip through a substrate; and using optical-grade resin to design optical windows on the target areas of the soldered chips, including the area where the laser chip is located and the area where the silicon-based germanium SPAD detector is located. Through system-level packaging, a long-range ranging chip based on a silicon-based germanium single-photon detector is obtained, achieving monolithic integration, breaking through the material and packaging limitations of existing technologies, reducing chip size, and simultaneously reducing parasitic capacitance and timing delay, which helps improve the accuracy and operating speed of the detection system and achieve higher frequency system operation.

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0037] Figure 1 A schematic diagram of the architecture of a long-range ranging chip based on a silicon-based germanium single-photon detector provided by the present invention;

[0038] Figure 2 A schematic flowchart illustrating a method for fabricating a long-range ranging chip based on a silicon-based germanium single-photon detector provided by the present invention.

[0039] Figure 3 This is a schematic diagram of the structure of a SPAD wafer provided by the present invention;

[0040] Figure 4 A schematic diagram of the internal architecture of a long-range ranging chip based on a silicon-based germanium single-photon detector provided by the present invention;

[0041] Figure 5 This is a schematic diagram illustrating the distribution of a single-photon counting signal provided by the present invention. Detailed Implementation

[0042] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0043] The 1550nm wavelength band has relatively low atmospheric background noise, minimal interference from ambient light and other light sources, and is the atmospheric projection window, exhibiting low absorption and strong penetration. Therefore, applying 1550nm semiconductor lasers and SPADs can significantly improve ranging distance, accuracy, and stability in complex environments. However, currently, there is no long-range ranging solution integrating a 1550nm laser and SPAD. Existing solutions typically use 905nm wavelength lasers and silicon detectors, enabling short-range distance detection. Some solutions also employ 1064nm wavelength lasers and InGaAs / InP avalanche photodiode (APD) detectors.

[0044] 905nm ranging solutions typically only support short-range detection within 2km. Due to power limitations for human eye safety, 905nm lasers have a large divergence angle and limited emission power, resulting in a very limited propagation distance. Furthermore, 905nm exhibits a larger background in ambient light and has poor penetration and anti-interference capabilities. Under these constraints, its performance is unsatisfactory for longer-range detection applications, such as those requiring 250m or more in autonomous driving. 1064nm offers higher penetration and human-eye-safe power compared to 905nm, and its detection range potential is also greater. However, silicon-based avalanche detectors have very low detection efficiency at 1064nm, only around 1%. Therefore, InGaAs / InP avalanche detectors are generally used. However, the lattice constant of InGaAs / InP materials differs significantly from that of silicon, making it difficult to integrate them on-chip with silicon-based CMOS readout circuits and TDC circuits to reduce size and cost. InGaAs / InP detectors are inherently expensive. To improve detection efficiency, they require electrical cooling to reduce dark current and noise, limiting the potential for further reductions in size and cost. Existing single-photon ranging schemes at 905nm and 1064nm wavelengths involve individually designed modules, or at most, silicon-based monolithic integration of the detector unit and supporting circuitry, followed by integration via printed circuit boards (PCBs). This low integration level hinders the achievement of low-cost, miniaturized, and highly reliable sensors. However, non-monolithically integrated circuits and devices suffer from parasitic capacitance and timing delays, affecting the system's operating frequency due to interference and interconnect delays, typically resulting in a lower operating frequency. Such measurement systems are not only susceptible to interference and unable to support long-distance detection, but their low operating frequency also significantly limits their minimum detectable distance.

[0045] Germanium (Ge) materials have a bandgap of 0.67 eV and an absorption range from 400 nm to 1700 nm, making them suitable for laser detection at wavelengths of 1064 nm, 1310 nm, and 1550 nm. China possesses abundant Ge mineral reserves, making the raw material very inexpensive compared to other infrared detection materials. Germanium is readily compatible with silicon-based CMOS processes, enabling the fabrication of silicon-based germanium absorption-multiplying discrete SPADs. Furthermore, SPAD readout circuits, quenching circuits, time-to-digital converters (TDCs), signal processing, and laser drive and control circuits can be integrated onto the same silicon (Si) chip, significantly reducing costs. This provides substantial advantages in yield and cost for integrated ranging in the field of single-photon long-range detection. Silicon-based germanium detectors, due to Ge's absorption of infrared light up to 1700 nm and compatibility with silicon-based CMOS processes, enabling room-temperature single-photon detection, are an effective low-cost integrated solution for long-range ranging at wavelengths of 1064 nm and beyond. However, existing silicon-based germanium SPADs employ selective epitaxy (SEEP), a complex and challenging process that is not conducive to integration with silicon-based CMOS processes. Some SPAD array solutions often encounter array crosstalk and saturation issues. Furthermore, SPAD arrays require precise optical coupling structures to achieve uniform light distribution, significantly increasing packaging difficulty and size.

[0046] To address the problems existing in the prior art, this invention provides a method for fabricating a long-range ranging chip based on a silicon-based germanium single-photon detector, used to prepare such a chip. Figure 1 The long-range ranging chip based on a silicon-based germanium single-photon detector shown is, for example... Figure 2 As shown, the method includes:

[0047] S201. The circuit part of the long-range ranging chip based on silicon-based germanium single-photon detector is fabricated on a wafer using standard silicon CMOS technology to form a circuit wafer.

[0048] The circuitry includes a silicon-based germanium SPAD readout and quenching circuit, a TDC circuit, a control and signal processing circuit, a laser drive circuit, and a laser control circuit.

[0049] S202, A silicon-based germanium SPAD detector based on a long-range ranging chip of a silicon-based germanium single-photon detector, fabricated into a SPAD wafer.

[0050] S203, Fabrication of laser wafers.

[0051] Among them, the laser wafer can generate laser pulses with a wavelength of 1550nm.

[0052] Compared to 905nm and 1064nm, the 1550nm infrared wavelength scheme offers stronger penetration, higher power safety for the human eye, and a smaller divergence angle, making it suitable as a laser and detector scheme for long-range single-photon distance detection. The 1550nm band also has lower background noise than 905nm and 1064nm, making it more suitable for distance detection requirements in strong sunlight environments. Therefore, the chip fabricated using the method for fabricating a long-range ranging chip based on a silicon-based germanium single-photon detector provided by this invention is suitable for longer-range laser ranging solutions required in fields such as UAVs, space exploration, and remote mapping.

[0053] In one possible implementation, the structure of the SPAD wafer is as follows: Figure 3 As shown, the corresponding method for fabricating a long-range ranging chip based on a silicon-based germanium single-photon detector according to claim 1, the silicon-based germanium SPAD detector for the long-range ranging chip based on the silicon-based germanium single-photon detector, and the fabrication of a SPAD wafer, includes the following steps A1-A6:

[0054] A1. Intrinsic Si is epitaxially grown on substrate 1 to form an epitaxial silicon layer.

[0055] Optionally, substrate 1 is N-type Si or SOI.

[0056] A2. In the region of the epitaxial silicon layer far from the substrate 1, P-type doping is performed by ion implantation to form a P-type silicon layer 3. In the region of the epitaxial silicon layer that is not P-type doped, a multiplication layer 2 is formed.

[0057] Specifically, after step A2, a PIN-type avalanche multiplication structure is formed inside the silicon layer formed by the substrate 1 and the epitaxial silicon layer.

[0058] A3. Intrinsic Si is epitaxially grown on the P-type silicon layer 3 to form a buffer layer 4.

[0059] This step helps to obtain a better Si-Ge interface.

[0060] A4. Ge is epitaxially grown on buffer layer 4 to form a Ge layer.

[0061] Specifically, Ge is epitaxially grown on buffer layer 4 to form a Ge layer for efficient absorption of photons larger than 1100nm.

[0062] Ge material has a bandgap of 0.67eV, which is very advantageous for absorption at wavelengths of 1064nm / 1310nm / 1550nm. Based on this, the silicon-based germanium absorption and multiplication separation SPAD wafer is more suitable for the detection of 1550nm light.

[0063] A5. Inject P into the entire area of ​​the Ge layer far from buffer layer 4. +, forming P + Type Ge layer 6.

[0064] Specifically, P is injected across the entire surface of the Ge layer in the region far from buffer layer 4. + , forming P + Type 6 Ge layer, no P injected into the Ge layer + In the region, a normal Ge layer 5 is formed, and then, P is formed inside the Ge layer. + The built-in electric field of the -I layer can absorb photons larger than 1100nm while simultaneously transferring electrons into the multiplication layer for avalanche multiplication. Specifically, after absorbing photons larger than 1100nm, such as 1550nm, in the Ge layer, electron-hole pairs are generated, and P0.05 electrons are formed inside the Ge layer. + The built-in electric field of -I draws electrons into the multiplication layer below through the electric field.

[0065] A6. For ordinary Ge layers 5 and P respectively... + The P-type Ge layer 6, as well as the multiplication layer 2 and the P-type silicon layer 3, are etched to prepare electrodes, forming a silicon-based germanium absorption and multiplication separation SPAD wafer.

[0066] Specifically, for ordinary Ge layers 5 and P containing Ge, respectively + The P-type Ge layer 6, as well as the silicon-containing multiplication layer 2 and the P-type silicon layer 3, are etched to expose the electrode positions. Then, electrodes 7 and 8 are fabricated to form a silicon-based germanium absorption and multiplication separation SPAD wafer.

[0067] This SPAD wafer employs a design with separated absorption, a gradient charge layer, and a multiplication region. Epitaxial Ge material is used as the absorption layer, achieving efficient absorption at a wavelength of 1550 nm through epitaxial Ge or GeSi materials. The germanium composition gradient is optimized to reduce lattice mismatch defects. Through design doping, the high-electric-field region of avalanche multiplication is incorporated into intrinsic silicon layer 2, significantly reducing dark current.

[0068] Using this method, the prepared SPAD wafers employ a design of separated absorption, a gradient charge layer, and a multiplication region. The use of epitaxial Ge material as the absorption layer achieves efficient absorption at a wavelength of 1550 nm. The grown Si buffer layer significantly optimizes the Si-Ge interface, reducing defects and mismatches. Avalanche gain is achieved and dark current is reduced by using a silicon-based high-electric-field region fabricated via CMOS-compatible processes.

[0069] S204. Thin the SPAD wafer to remove excess silicon substrate without device structure, clean the thinned SPAD wafer and circuit wafer to remove surface impurities, and obtain a cleaned SPAD wafer and a cleaned circuit wafer.

[0070] Specifically, SPAD wafers and circuit wafers are cleaned to remove impurities such as organic matter and metal ions from their surfaces.

[0071] S205. Flip the cleaned circuit wafer. Based on design requirements, align the cleaned SPAD wafer and the flipped circuit wafer.

[0072] Design requirements include, but are not limited to, the circuit wafer having the same area as the SPAD wafer, mirror-symmetrical cell shape, electrical connection design, and dicing channels.

[0073] Specifically, the circuit wafers are flipped, and high-precision alignment equipment is used to align the processed SPAD wafers and circuit wafers according to design requirements.

[0074] S206. At room temperature, the cleaned SPAD wafer and the flipped circuit wafer are bonded together to form a preliminarily bonded wafer.

[0075] S207. Perform low-temperature annealing on the preliminarily bonded wafer to obtain a low-temperature annealed bonded wafer.

[0076] Optionally, the temperature for low-temperature annealing is 200–400℃.

[0077] Low-temperature annealing can enhance bond strength while preventing impurity diffusion.

[0078] S208. Surface treatment is performed on the bonded wafer after low-temperature annealing to fabricate a circuit SPAD integrated wafer.

[0079] Specifically, the bonded wafers after low-temperature annealing undergo surface treatment, such as removing the oxide layer or residues on the surface, to improve the surface smoothness and cleanliness.

[0080] Through the above steps, the monolithic integration of the circuit wafer and the SPAD wafer was finally achieved, resulting in a circuit-SPAD integrated wafer. Utilizing the technical characteristics of silicon-based wafer epitaxial growth of germanium, the silicon-based germanium SPAD detector and circuitry are integrated on-chip, reducing parasitic capacitance and timing delays. This significantly improves the accuracy of long-range ranging chips based on silicon-based germanium single-photon detectors, increases detection speed, and achieves higher detection frequencies.

[0081] S209. Divide the circuit SPAD integrated wafer to obtain multiple independent circuit SPAD integrated chips, and divide the laser wafer to obtain multiple independent laser chips.

[0082] S210. Using flip-chip bonding technology, any laser chip and any circuit SPAD integrated chip are bonded together through a substrate using thermally conductive adhesive and low-temperature welding materials. Optical-grade resin is used to design optical windows on the target area of ​​the bonded chip. The target area includes the area where the laser chip is located and the area where the silicon-based germanium SPAD detector is located. Through system-level packaging, a long-range ranging chip based on a silicon-based germanium single-photon detector is obtained.

[0083] like Figure 1 As shown, the fabricated long-range ranging chip based on a silicon-based germanium single-photon detector includes a laser device section and a detector and circuit section. The laser device section corresponds to one laser chip, and the detector and circuit section corresponds to one circuit SPAD integrated chip. The circuit SPAD integrated chip is obtained by dicing a circuit SPAD integrated wafer, which is obtained by monolithic integration of a circuit wafer and a SPAD wafer. Accordingly, the circuit SPAD integrated chip consists of two parts from the circuit wafer and the SPAD wafer, as shown below. Figure 1 As shown, the detector and circuitry section includes silicon circuit wafers and silicon-based germanium SPAD wafers.

[0084] Specifically, laser wafers are diced into individual chips using methods such as laser cutting or etching. Micro-solder balls are deposited in the laser interconnect areas, and flip-chip technology is used to connect the laser chips to the SPAD integrated circuit chips via substrate bonding, achieving both electrical interconnection and facilitating heat dissipation. After mechanical alignment, thermally conductive adhesive and low-temperature soldering materials are applied to enhance thermal management and mechanical stability. Furthermore, optical-grade resin is used to design optical windows for the laser emission and detection sections, ensuring that the laser emission and the detected reflected light are not obstructed. This system-level packaging method greatly improves system integration, which is beneficial for the miniaturization of long-distance detection system solutions. At the same time, it can also reduce interconnect latency and improve system operating speed.

[0085] This invention provides a method for fabricating a long-range ranging chip based on a silicon-based germanium single-photon detector. Utilizing the technical characteristics of silicon-based germanium, a silicon-based germanium SPAD detector wafer is monolithically integrated with a circuit wafer containing detector auxiliary circuitry, distance detection-related circuitry, and laser driving and control circuitry. This achieves system-level packaging of the laser device portion with the detector and related circuitry. The on-chip integration design reduces parasitic capacitance and timing delays, helping to improve the accuracy and operating speed of the detection system and enabling higher frequency system operation. Furthermore, in existing technologies, InGaAs detectors cannot be monolithically integrated with CMOS circuits due to material incompatibility with silicon processes and require additional cooling modules; while conventional silicon-based detectors have extremely low efficiency in the 1550nm band. This invention, through a silicon-based germanium absorption and multiplication separation structure design and system-level packaging technology, achieves for the first time full-function integration of high-efficiency 1550nm detection and signal processing on a single silicon chip, improving system integration and enabling miniaturization of long-range ranging systems.

[0086] This invention also provides a long-range ranging chip based on a silicon-based germanium single-photon detector. This long-range ranging chip is prepared using any of the methods provided by this invention for preparing a long-range ranging chip based on a silicon-based germanium single-photon detector, such as... Figure 4 As shown, the long-range ranging chip based on a silicon-based germanium single-photon detector includes: a laser device, a silicon-based germanium SPAD detector, a SPAD readout and quenching circuit, a TDC circuit, a control and signal processing circuit, a laser driving circuit, and a laser control circuit.

[0087] The laser driver circuit is used to provide drive signals for the laser device.

[0088] The laser control circuit is used to control the laser device to generate and emit laser pulses with a wavelength of 1550nm, and to simultaneously record the current time, setting the current time as the start time of the current working cycle. The total duration of the working cycle is preset according to the detection distance.

[0089] Silicon-based germanium SPAD detectors are used to detect reflected single-photon count signals.

[0090] The SPAD readout and quenching circuit is used to send multiple single-photon count signals detected by the silicon-based germanium SPAD during the current working cycle to the TDC circuit. Among the multiple single-photon count signals are signals reflected by the target under test.

[0091] The TDC circuit is used to statistically analyze the distribution of multiple single-photon counting signals detected by the silicon-based germanium SPAD detector.

[0092] The control and signal processing circuit is used to calculate the distance between the long-range ranging chip based on the silicon-based germanium single-photon detector and the target to be measured, according to the distribution.

[0093] Optionally, the TDC circuit is specifically used to divide the current working cycle into multiple time periods, and based on the division results, to determine the temporal distribution of multiple single-photon counting signals detected by the silicon-based germanium SPAD detector, and to determine the time period corresponding to the peak as the round-trip time period corresponding to the signal reflected by the target under test.

[0094] Correspondingly, the control and signal processing circuit is specifically used to calculate the distance between the long-range ranging chip based on the silicon-based germanium single-photon detector and the target, based on the round-trip time corresponding to the signal reflected by the target and the start time of the current working cycle, expressed as:

[0095]

[0096] Where D represents the distance between the long-range ranging chip based on silicon-based germanium single-photon detector and the target to be measured, c represents the speed of light in the air, T2 represents the midpoint of the round-trip time corresponding to the signal reflected by the target to be measured, and T1 represents the start time of the current working cycle.

[0097] This invention also provides a long-range ranging method based on a silicon-based germanium single-photon detector, applicable to any long-range ranging chip based on a silicon-based germanium single-photon detector provided by this invention. The long-range ranging chip based on a silicon-based germanium single-photon detector includes a laser device, a silicon-based germanium SPAD detector, a SPAD readout and quenching circuit, a TDC circuit, a control and signal processing circuit, a laser driving circuit, and a laser control circuit.

[0098] The long-range ranging method based on silicon-based germanium single-photon detectors includes the following steps B1-B5:

[0099] B1. Through the laser control circuit and the laser drive circuit, the laser device is controlled to generate and emit laser pulses with a wavelength of 1550nm, and the current time is recorded synchronously and set as the start time of the current working cycle.

[0100] The total duration of the working cycle is preset based on the detection distance.

[0101] For example, for detection at a distance of 3km, a duty cycle length (TC) can be set to 30 microseconds, approximately 1.5 times the round-trip distance of 9km required for light to travel. For detection distances as short as 1m or even less, the duty cycle needs to be significantly reduced, potentially to 10ns. The response speed of silicon-based germanium SPAD detectors and the accuracy of the TDC circuit limit the minimum detectable distance.

[0102] Within one working cycle TC, the laser device is controlled by the control circuit to generate 1550nm laser pulses, and the time signal T1 is recorded synchronously and set as the start of the working cycle. The working cycle then lasts from the start of T1 to the end of (T1+TC). After being emitted, the laser propagates to the object being measured, is reflected back, and is then detected as a single photon by a silicon-based germanium SPAD detector.

[0103] B2. Detect the reflected single-photon count signal using a silicon-based germanium SPAD detector.

[0104] B3. Through the SPAD readout and quenching circuit, the multiple single-photon counting signals detected by the silicon-based germanium SPAD during the current working cycle are sent to the TDC circuit. The multiple single-photon counting signals include the signal reflected by the target under test.

[0105] Because of the complex environment around the object being measured, the 1550nm light pulse will be reflected back to the detector in other ways. The silicon-based germanium SPAD detector can detect many single-photon count signals within one working cycle TC.

[0106] B4. The distribution of multiple single-photon counting signals detected by the silicon-based germanium SPAD detector is statistically analyzed using the TDC circuit.

[0107] B5. The distance between the long-range ranging chip based on the silicon-based germanium single-photon detector and the target is calculated by the control and signal processing circuit according to the distribution.

[0108] Optionally, the distribution of multiple single-photon counting signals detected by the silicon-based germanium SPAD detector is statistically analyzed through the TDC circuit, including: dividing the current working cycle into multiple time periods through the TDC circuit, and determining the temporal distribution of multiple single-photon counting signals detected by the silicon-based germanium SPAD detector based on the division results, and determining the time period corresponding to the peak as the round-trip time period corresponding to the signal reflected by the target under test.

[0109] Accordingly, the control and signal processing circuit calculates the distance between the long-range ranging chip based on a silicon-based germanium single-photon detector and the target under test according to the distribution, including:

[0110] The distance between the long-range ranging chip based on a silicon-based germanium single-photon detector and the target is calculated by the control and signal processing circuit based on the round-trip time corresponding to the signal reflected by the target and the start time of the current working cycle. This distance is expressed as:

[0111]

[0112] Where D represents the distance between the long-range ranging chip based on silicon-based germanium single-photon detector and the target to be measured, c represents the speed of light in the air, T2 represents the midpoint of the round-trip time corresponding to the signal reflected by the target to be measured, and T1 represents the start time of the current working cycle.

[0113] like Figure 5 The diagram shows the distribution of the single-photon counting signal. Dividing the working period length TC into N equal parts results in N time segments of length TC / N. The statistical distribution of single-photon arrival times is obtained from these time segments. The peak segment represents the most likely round-trip time range of the target reflection signal, and the midpoint of the corresponding time segment is denoted as T2. The distance D is then calculated.

[0114] The present invention also provides a long-range device based on a silicon-based germanium single-photon detector, including any of the long-range ranging chips based on a silicon-based germanium single-photon detector provided by the present invention.

[0115] Since the embodiments are basically similar to the method embodiments, the descriptions are relatively simple, and the specific content and beneficial effects are mutually referential.

[0116] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for fabricating a long-range ranging chip based on a silicon-based germanium single-photon detector, characterized in that, include: The circuit portion of the long-range ranging chip based on silicon-based germanium single-photon detector is fabricated on a wafer using standard silicon CMOS technology to form a circuit wafer. The circuit portion includes a silicon-based germanium SPAD readout and quenching circuit, a TDC circuit, a control and signal processing circuit, a laser driving circuit, and a laser control circuit. Based on the aforementioned long-range ranging chip based on a silicon-based germanium single-photon detector, a silicon-based germanium SPAD detector is fabricated into a SPAD wafer; Fabricating a laser wafer, the laser wafer being capable of generating laser pulses with a wavelength of 1550 nm; The SPAD wafer is thinned to remove excess silicon substrate without device structure. The thinned SPAD wafer and the circuit wafer are cleaned to remove surface impurities, resulting in a cleaned SPAD wafer and a cleaned circuit wafer. Flip the cleaned circuit wafer and align the cleaned SPAD wafer and the flipped circuit wafer according to design requirements; The cleaned SPAD wafer and the flipped circuit wafer are bonded together at room temperature to form a preliminarily bonded wafer; The preliminarily bonded wafer is subjected to low-temperature annealing to obtain a low-temperature annealed bonded wafer; The bonded wafer after low-temperature annealing is surface treated to form a circuit SPAD integrated wafer; The circuit SPAD integrated wafer is divided to obtain multiple independent circuit SPAD integrated chips; The laser wafer is split to obtain multiple independent laser chips; Using flip-chip bonding technology, thermally conductive adhesive and low-temperature soldering material, any of the laser chips and any of the circuit SPAD integrated chips are soldered together through a substrate. Optical-grade resin is used to design an optical window on the target area of ​​the soldered chip. The target area includes the area where the laser chip is located and the area where the silicon-based germanium SPAD detector is located. Through system-level packaging, a long-range ranging chip based on a silicon-based germanium single-photon detector is obtained.

2. The method for fabricating a long-range ranging chip based on a silicon-based germanium single-photon detector according to claim 1, characterized in that, The silicon-based germanium SPAD detector, based on a silicon-based germanium single-photon detector, is fabricated into a SPAD wafer and includes: Intrinsic Si is epitaxially grown on a substrate to form an epitaxial silicon layer; In the region of the epitaxial silicon layer that is far from the substrate, P-type doping is performed by ion implantation to form a P-type silicon layer, and the region of the epitaxial silicon layer that is not P-type doped forms a multiplication layer. Intrinsic Si is epitaxially grown on the P-type silicon layer to form a buffer layer; Ge is epitaxially grown on the buffer layer to form a Ge layer; P is injected across the entire surface of the Ge layer in the region far from the buffer layer. + , forming P + Type Ge layer, wherein no P is injected into the Ge layer. + The region forms a common Ge layer; For ordinary Ge layers and the P layer respectively + The P-type Ge layer, as well as the multiplication layer and the P-type silicon layer, are etched to prepare electrodes, forming a silicon-based germanium absorption and multiplication separation SPAD wafer.

3. The method for fabricating a long-range ranging chip based on a silicon-based germanium single-photon detector according to claim 2, characterized in that, The substrate is N-type Si or SOI.

4. The method for fabricating a long-range ranging chip based on a silicon-based germanium single-photon detector according to claim 3, characterized in that, The temperature for the low-temperature annealing process is 200–400°C.

5. A long-range ranging chip based on a silicon-based germanium single-photon detector, characterized in that, The long-range ranging chip based on a silicon-based germanium single-photon detector is prepared by any of the preparation methods for long-range ranging chips based on silicon-based germanium single-photon detectors as described in claims 1-3. The long-range ranging chip based on a silicon-based germanium single-photon detector includes: Laser devices, silicon-based germanium SPAD detectors, SPAD readout and quenching circuits, TDC circuits, control and signal processing circuits, laser drive circuits, and laser control circuits; The laser driving circuit is used to provide driving signals to the laser device; The laser control circuit is used to control the laser device to generate and emit laser pulses with a wavelength of 1550nm, and synchronously record the current time, setting the current time as the start time of the current working cycle, wherein the total duration of the working cycle is preset according to the detection distance. The silicon-based germanium SPAD detector is used to detect reflected single-photon counting signals; The SPAD readout and quenching circuit is used to send multiple single-photon counting signals detected by the silicon-based germanium SPAD during the current working cycle to the TDC circuit. The multiple single-photon counting signals include signals reflected by the target under test. The TDC circuit is used to statistically analyze the distribution of multiple single-photon counting signals detected by the silicon-based germanium SPAD detector. The control and signal processing circuit is used to calculate the distance between the long-range ranging chip based on the silicon-based germanium single-photon detector and the target to be measured, according to the distribution.

6. The long-range ranging chip based on a silicon-based germanium single-photon detector according to claim 5, characterized in that, The TDC circuit is specifically used to divide the current working cycle into multiple time periods, and based on the division results, to determine the temporal distribution of multiple single-photon counting signals detected by the silicon-based germanium SPAD detector, and to determine the time period corresponding to the peak as the round-trip time period corresponding to the signal reflected by the target under test. Accordingly, the control and signal processing circuit is specifically used to calculate the distance between the long-range ranging chip based on the silicon-based germanium single-photon detector and the target based on the round-trip time period corresponding to the signal reflected by the target and the start time of the current working cycle, expressed as: Where D represents the distance between the long-range ranging chip based on silicon-based germanium single-photon detector and the target to be measured, c represents the speed of light in the air, T2 represents the midpoint of the round-trip time corresponding to the signal reflected by the target to be measured, and T1 represents the start time of the current working cycle.

7. A long-distance ranging method based on a silicon-based germanium single-photon detector, characterized in that, The long-range ranging chip based on a silicon-based germanium single-photon detector as described in claim 5 or 6 includes a laser device, a silicon-based germanium SPAD detector, a SPAD readout and quenching circuit, a TDC circuit, a control and signal processing circuit, a laser driving circuit, and a laser control circuit. The long-distance ranging method based on silicon-based germanium single-photon detectors includes: The laser control circuit and the laser drive circuit control the laser device to generate and emit laser pulses with a wavelength of 1550nm, and simultaneously record the current time, setting the current time as the start time of the current working cycle. The total duration of the working cycle is preset according to the detection distance. The reflected single-photon counting signal is detected by the silicon-based germanium SPAD detector; The SPAD readout and quenching circuit transmits multiple single-photon counting signals detected by the silicon-based germanium SPAD during the current working cycle to the TDC circuit. The multiple single-photon counting signals include signals reflected by the target under test. The distribution of multiple single-photon counting signals detected by the silicon-based germanium SPAD detector is statistically analyzed using the TDC circuit. The control and signal processing circuit calculates the distance between the long-range ranging chip based on the silicon-based germanium single-photon detector and the target under test according to the distribution.

8. The long-distance ranging method based on a silicon-based germanium single-photon detector according to claim 7, characterized in that, The step of statistically analyzing the distribution of multiple single-photon counting signals detected by the silicon-based germanium SPAD detector through the TDC circuit includes: The TDC circuit divides the current working cycle into multiple time periods, and based on the division results, determines the temporal distribution of multiple single-photon counting signals detected by the silicon-based germanium SPAD detector, and determines the time period corresponding to the peak value as the round-trip time period corresponding to the signal reflected by the target under test. Accordingly, the step of calculating the distance between the long-range ranging chip based on the silicon-based germanium single-photon detector and the target under test by the control and signal processing circuit according to the distribution includes: The control and signal processing circuit calculates the distance between the long-range ranging chip based on the silicon-based germanium single-photon detector and the target based on the round-trip time corresponding to the signal reflected by the target and the start time of the current working cycle. This distance is expressed as: Where D represents the distance between the long-range ranging chip based on silicon-based germanium single-photon detector and the target to be measured, c represents the speed of light in the air, T2 represents the midpoint of the round-trip time corresponding to the signal reflected by the target to be measured, and T1 represents the start time of the current working cycle.

9. A long-distance device based on a silicon-based germanium single-photon detector, characterized in that, Includes any of the long-range ranging chips based on silicon-based germanium single-photon detectors as described in claim 5 or 6.

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