Preparation method of long-distance ranging chip based on silicon-based germanium single-photon detector

Abstract

The invention provides a preparation method of a long-distance ranging chip based on a silicon-based germanium single-photon detector. A circuit wafer, an SPAD wafer and a laser wafer capable of generating 1550 nm laser pulses are prepared based on the circuit principle of the long-distance ranging chip of the silicon-based germanium single-photon detector; processing the SPAD wafer, and laminating the processed SPAD wafer and the circuit wafer to form a preliminarily bonded wafer; carrying out low-temperature annealing treatment on the wafer to prepare a circuit SPAD integrated wafer; segmenting the corresponding wafer to obtain a plurality of independent circuit SPAD integrated chips and laser chips; any laser chip and any circuit SPAD integrated chip are welded through a substrate, and optical window design is carried out in the area where the laser chip is located and the area where the silicon-based germanium SPAD detector is located, so that the long-distance ranging chip based on the silicon-based germanium single-photon detector is obtained, monolithic integration is realized, the system integration degree is improved, and the cost is reduced. And the miniaturization of a long-distance ranging system is realized.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor optoelectronic integration, and in particular to a method for preparing a long-distance ranging chip based on a silicon-based germanium single-photon detector. Background Art

[0002] The emergence of time of flight (ToF) distance measurement technology has greatly promoted the development of fields such as drone mapping, autonomous driving, machine vision, and aerospace. LiDAR technology developed with time of flight ranging technology is playing a greater role in application fields such as autonomous driving, industrial automation, and smart homes due to its high precision, fast response, and broad application prospects. With the continuous development of semiconductor technology, the requirements for further improvement of the integration of distance detection sensor technology and higher performance, longer distance, and lower cost distance information detection are getting higher and higher.

[0003] The traditional long-distance ranging solution uses traditional avalanche photodetectors of indium gallium arsenide InGaAs / indium phosphide InP. Its advantage is good performance and is currently used in high-end application fields such as scientific research, military or industry. Its disadvantage is that it is difficult to integrate into a single chip, is expensive, and requires low-temperature cooling to reduce dark current and noise, making long-distance ranging difficult to apply to the field of lightweight and highly integrated consumer electronics. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides a method for preparing a long-distance ranging chip based on a silicon-based germanium single-photon detector, which specifically includes:

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

[0006] The circuit part of the long-distance ranging chip based on silicon-based germanium single-photon detector is processed and prepared on a wafer using a standard silicon complementary metal-oxide-semiconductor (CMOS) process to make a circuit wafer. The circuit part 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] Silicon-based germanium SPAD detectors based on long-distance ranging chips of silicon-based germanium single-photon detectors are made into SPAD wafers;

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

[0009] Thinning the SPAD wafer, removing the redundant silicon substrate portion without the device structure, cleaning the thinned SPAD wafer and the circuit wafer, removing impurities on the surface, and obtaining a cleaned SPAD wafer and a cleaned circuit wafer;

[0010] Flip the cleaned circuit wafer, and align the cleaned SPAD wafer and the flipped circuit wafer based on design requirements;

[0011] Bonding the cleaned SPAD wafer and the flipped circuit wafer at room temperature to form a preliminary bonded wafer;

[0012] Performing low temperature annealing on the preliminarily bonded wafers to obtain low temperature annealed bonded wafers;

[0013] Performing surface treatment on the bonded wafer after low temperature annealing to produce a circuit SPAD integrated wafer;

[0014] Splitting the circuit SPAD integrated wafer to obtain multiple independent circuit SPAD integrated chips;

[0015] Splitting the laser wafer to obtain multiple independent laser chips;

[0016] By adopting flip-chip technology, using thermal conductive glue and low-temperature welding materials, any laser chip and any circuit SPAD integrated chip are welded through the substrate, and optical-grade resin is used to design optical windows for the target areas on the welded chips. The target areas include 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-distance ranging chip based on silicon-based germanium single-photon detector is obtained.

[0017] In a second aspect, the present invention further provides a long-distance ranging chip based on a silicon-based germanium single-photon detector, wherein the long-distance ranging chip based on a silicon-based germanium single-photon detector is prepared by any preparation method provided in the first aspect,

[0018] Long-distance ranging chip based on silicon-based germanium single-photon detector, including:

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

[0020] A laser driving circuit, used for providing a driving signal for a laser device;

[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, and set 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-germanium SPAD detectors for detecting reflected single-photon counting signals;

[0023] A SPAD readout and quenching circuit, used for sending a plurality of single photon counting signals detected by the silicon-germanium SPAD in a current working cycle to a TDC circuit, wherein the plurality of single photon counting signals include a signal reflected by a target to be detected;

[0024] A TDC circuit is used to count 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-distance ranging chip based on the silicon-based germanium single-photon detector and the target to be measured according to the distribution situation.

[0026] In a third aspect, the present invention further provides a long-distance ranging method based on a silicon-based germanium single-photon detector, which is applied to any long-distance ranging chip based on a silicon-based germanium single-photon detector as provided in the second aspect, and 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-distance ranging method based on silicon-based germanium single-photon detector, including:

[0028] Through the laser control circuit and the laser driving circuit, the laser device is controlled to generate and emit a laser pulse with a wavelength of 1550nm, and the current time is synchronously recorded, and the current time is set 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 by a silicon-based germanium SPAD detector;

[0030] Sending multiple single photon counting signals detected by the silicon-germanium SPAD in the current working cycle to the TDC circuit through the SPAD readout and quenching circuit, wherein the multiple single photon counting signals include signals reflected by the target to be measured;

[0031] The distribution of multiple single photon counting signals detected by the silicon-based germanium SPAD detector is counted by the TDC circuit;

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

[0033] In a fourth aspect, the present invention provides a long-distance device based on a silicon-based germanium single-photon detector, including any long-distance ranging chip based on a silicon-based germanium single-photon detector as provided in the second aspect.

[0034] Beneficial effects of the present invention:

[0035] The invention provides a method for preparing a long-distance ranging chip based on a silicon-based germanium single-photon detector. The circuit part of the long-distance ranging chip based on the silicon-based germanium single-photon detector is processed and prepared on a wafer by a standard silicon CMOS process to form a circuit wafer, wherein the circuit part 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; a silicon-based germanium SPAD detector of the long-distance ranging chip based on the silicon-based germanium single-photon detector is formed into a SPAD wafer; a laser wafer is prepared, and the laser wafer can generate a laser pulse with a wavelength of 1550nm; the SPAD wafer is thinned to remove excess silicon substrate parts without device structures, and the thinned SPAD wafer and circuit wafer are cleaned to remove impurities on the surface to obtain a cleaned SPAD wafer and a cleaned circuit wafer; the cleaned circuit wafer is flipped over, and the cleaned SPAD wafer and the flipped circuit wafer are aligned based on design requirements; the cleaned SPAD wafer and the flipped circuit wafer are bonded at room temperature circuit wafers to form preliminary bonded wafers; low-temperature annealing treatment is performed on the preliminary bonded wafers to obtain low-temperature annealed bonded wafers; surface treatment is performed on the low-temperature annealed bonded wafers to form circuit SPAD integrated wafers; the circuit SPAD integrated wafers are divided to obtain multiple independent circuit SPAD integrated chips; the laser wafers are divided to obtain multiple independent laser chips; flip-chip welding technology is adopted, and any laser chip is welded to any circuit SPAD integrated chip through a substrate using thermal conductive adhesive and low-temperature welding materials, and optical-grade resin is used to design optical windows for target areas on the welded chips, the target areas include the area where the laser chip is located and the area where the silicon-based germanium SPAD detector is located, and a long-distance ranging chip based on silicon-based germanium single-photon detector is obtained through system-level packaging, which realizes monolithic integration, breaks through the material and packaging limitations of the existing technology, reduces the chip scale, and at the same time, reduces parasitic capacitance and timing delay, which helps to improve the accuracy and working speed of the detection system and realize higher frequency system operation.

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0038] Figure 2 A schematic flow chart of a method for preparing a long-distance ranging chip based on a silicon-based germanium single-photon detector provided by the present invention;

[0039] Figure 3 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-distance ranging chip based on a silicon-based germanium single-photon detector provided by the present invention;

[0041] Figure 5 A schematic diagram of the distribution of a single photon counting signal provided by the present invention. DETAILED DESCRIPTION

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

[0043] The atmospheric background light noise in the 1550nm band is relatively low, and the interference from ambient light and other light sources is small. In addition, 1550nm is the projection window of the atmosphere, with less absorption in the atmosphere and strong penetration ability. Therefore, the application of 1550nm semiconductor lasers and SPADs can greatly improve the distance of ranging, the accuracy and stability of ranging in complex environments. However, there is currently no long-distance ranging solution integrating 1550nm lasers and SPADs. Existing solutions usually use 905nm wavelength lasers and silicon detectors to achieve close-range distance detection. Some solutions also use 1064nm wavelength lasers and InGaAs / InP avalanche photodiode (APD) detectors.

[0044] The 905nm ranging solution can usually only support short-distance detection within 2km. Due to the power limit of human eye safety, the light divergence angle of 905nm laser is large and the emission power is limited, that is, the propagation distance is very limited. In addition, the background of 905nm in ambient light is larger, and the penetration ability and anti-interference ability are poor. Under various restrictions, the application effect of longer-distance detection in the field of distance detection requiring 250m and above in the field of autonomous driving is not good. The penetration ability and human eye safety power of 1064nm are higher than those of 905nm, and its detection distance potential is also greater than that of the 905nm solution, but the detection efficiency of silicon-based avalanche detectors at 1064nm is very low, only about 1%, so the InGaAs / InP avalanche detector solution is generally used. However, the lattice constant of InGaAs / InP materials is quite different from that of silicon materials, and it is difficult to integrate on-chip with modules such as readout circuits and TDC circuits made by silicon-based CMOS processes to reduce volume and cost. The cost of InGaAs / InP detector itself is also relatively high. In order to improve detection efficiency, InGaAs / InP detector also needs electric cooling to reduce dark current and noise, resulting in limited potential for further reduction of its volume and cost. The existing single-photon ranging scheme of 905nm and 1064nm wavelengths, each module is designed separately, or at most the detector unit and the circuit supporting the detector work are integrated on silicon monolithic chip, and then each module is integrated by printed circuit board (PCB) and other methods, with low integration, which is not conducive to realizing low cost, miniaturization, and high system reliability of sensor. However, non-monolithic integrated circuits and devices have many problems such as parasitic capacitance and timing delay, resulting in the operating frequency of the system being affected by interference and interconnection delay, and its operating frequency is usually low. Such measurement systems are not only easily disturbed and difficult to support long-distance detection, but also because of their low operating frequency, the closest distance that can be detected is also greatly limited.

[0045] Germanium (Ge) material has a bandgap of 0.67eV, and an absorption band from 400nm to 1700nm, which can be used for laser detection at wavelengths of 1064nm / 1310nm / 1550nm. China has abundant Ge mineral reserves, and the price of raw materials is very cheap compared to other infrared detection materials. Germanium materials are easily compatible with silicon-based CMOS processes, and can manufacture silicon-based germanium absorption multiplication and separation SPADs. In addition, SPAD readout circuits, quenching circuits, time-to-digital converters (TDCs), signal processing, and laser drive and control circuits can be integrated on the same silicon (Si) chip, which is conducive to reducing costs and has great yield and cost advantages in the field of single-photon long-distance detection and integrated ranging. Silicon-based germanium detectors are an effective solution for low-cost integration of 1064nm and even longer-band long-distance ranging because Ge can absorb infrared light up to 1700nm, are compatible with silicon-based CMOS processes, and can achieve room-temperature single-photon detection. However, the existing silicon-based germanium SPAD adopts the selective epitaxial preparation scheme, which is complex and difficult to integrate with silicon-based CMOS process. The SPAD array scheme adopted by some schemes often encounters the influence of array crosstalk and saturation. At the same time, the SPAD array requires a precise optical coupling structure to achieve uniform light distribution, which greatly increases the difficulty and volume of packaging.

[0046] In order to solve the problems existing in the prior art, the present invention provides a method for preparing a long-distance ranging chip based on a silicon-based germanium single-photon detector, which is used to prepare Figure 1 The long-distance ranging chip based on silicon-based germanium single-photon detector is shown in FIG. Figure 2 As shown, the method includes:

[0047] S201. The circuit part of the long-distance ranging chip based on silicon-based germanium single-photon detector is processed and prepared on a wafer using a standard silicon CMOS process to form a circuit wafer.

[0048] The circuit part includes silicon-germanium SPAD readout and quenching circuit, TDC circuit, control and signal processing circuit, laser driving circuit and laser control circuit.

[0049] S202. A silicon-based germanium SPAD detector based on a long-distance ranging chip of a silicon-based germanium single photon detector is made into a SPAD wafer.

[0050] S203, preparing a laser wafer.

[0051] Among them, the laser wafer is capable of generating laser pulses with a wavelength of 1550nm.

[0052] Compared with 905nm and 1064nm, the infrared light solution with a wavelength of 1550nm has stronger penetration, higher eye-safe power, and a smaller light divergence angle, and is suitable as a laser and detector solution for long-distance single-photon distance detection. The background noise in the 1550nm band is lower than that of 905nm, 1064nm, etc., and is more suitable for distance detection needs in strong sunlight environments. Therefore, the chip prepared by the preparation method of the long-distance ranging chip based on silicon-based germanium single-photon detector provided by the present invention is suitable for longer-distance laser ranging solutions required in the fields of drones, space exploration, remote mapping, etc.

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

[0054] A1. Epitaxially grow intrinsic Si on substrate 1 to form an epitaxial silicon layer.

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

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

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

[0058] A3. Epitaxially grow intrinsic Si 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. Epitaxially grow Ge on the buffer layer 4 to form a Ge layer.

[0061] Specifically, Ge is epitaxially grown on the buffer layer 4 to form a Ge layer for efficiently absorbing photons larger than 1100 nm.

[0062] Ge material has a bandgap width of 0.67eV, which is very conducive to the absorption of 1064nm / 1310nm / 1550nm wavelengths. The silicon-based germanium absorption and multiplication separated SPAD wafer designed according to this design is more suitable for the detection of 1550nm light.

[0063] A5, implant P into the entire surface of the Ge layer away from the buffer layer 4 +, forming P + Type Ge layer 6.

[0064] Specifically, P is implanted into the entire surface of the Ge layer away from the buffer layer 4. + , forming P + Type Ge layer 6, P is not injected into the Ge layer + The region forms a normal Ge layer 5, and then a P + -I has a built-in electric field, which can transfer electrons to the multiplication layer through the electric field for avalanche multiplication while absorbing photons larger than 1100nm. Specifically, the Ge layer absorbs photons larger than 1100nm, such as 1550nm, to generate electron-hole pairs, and the P + -I's built-in electric field extracts electrons into the multiplication layer below through the electric field.

[0065] A6, respectively, for the common Ge layer 5 and P + The P-type Ge layer 6, the multiplication layer 2 and the P-type silicon layer 3 are etched to prepare electrodes to form a SPAD wafer with separated silicon-based germanium absorption and multiplication.

[0066] Specifically, the Ge-containing ordinary Ge layer 5 and P + The P-type Ge layer 6, the silicon-containing multiplication layer 2 and the P-type silicon layer 3 are etched to expose the electrode positions, and then electrodes 7 and 8 are prepared to form a silicon-based germanium absorption and multiplication separated SPAD wafer.

[0067] The SPAD wafer adopts a design of separated absorption, gradient charge layer and multiplication region, in which epitaxial Ge material is used as the absorption layer, and high-efficiency absorption of 1550nm wavelength is achieved through epitaxial Ge or GeSi material, and the germanium component gradient is optimized to reduce lattice mismatch defects. Through design doping, the high electric field region of avalanche multiplication is designed in the intrinsic silicon layer 2, and the dark current is significantly reduced.

[0068] The SPAD wafer prepared by this method adopts the design of separated absorption, gradient charge layer and multiplication region, in which the epitaxial Ge material is used as the absorption layer to achieve efficient absorption of 1550nm wavelength, and the grown Si buffer layer greatly optimizes the contact interface between Si and Ge, reducing defects and mismatch. The silicon-based high electric field region is used, prepared by CMOS compatible process, and avalanche gain is achieved, and dark current is reduced.

[0069] S204, thinning the SPAD wafer, removing the redundant silicon substrate portion without device structure, cleaning the thinned SPAD wafer and circuit wafer, removing impurities on the surface, and obtaining a cleaned SPAD wafer and a cleaned circuit wafer.

[0070] Specifically, the SPAD wafer and the circuit wafer are cleaned to remove impurities such as organic matter and metal ions on the surface.

[0071] S205 , flipping the cleaned circuit wafer, and aligning the cleaned SPAD wafer and the flipped circuit wafer based on design requirements.

[0072] Design requirements include but are not limited to the shape and area of ​​the circuit wafer being the same as the SPAD wafer, mirror-symmetrical distribution of unit shapes, electrical connection design and cutting paths.

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

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

[0075] S207 , performing low temperature annealing on the preliminarily bonded wafers to obtain low temperature annealed bonded wafers.

[0076] Optionally, the temperature of the low temperature annealing treatment is 200-400°C.

[0077] Low temperature annealing can enhance the bonding strength while preventing impurity diffusion.

[0078] S208, performing surface treatment on the bonded wafers after low-temperature annealing to produce a circuit SPAD integrated wafer.

[0079] Specifically, the bonded wafers after low-temperature annealing are subjected to surface treatment, such as removing an oxide layer or residue on the surface to improve surface flatness and cleanliness.

[0080] Through the above steps, the circuit wafer and the SPAD wafer are finally integrated into a single chip to form a circuit SPAD integrated wafer. By utilizing the technical characteristics of epitaxial growth of germanium on silicon-based wafers, the silicon-based germanium SPAD detector and the circuit part are integrated on-chip to reduce parasitic capacitance and timing delay, greatly improve the accuracy of the detection results of the long-distance ranging chip based on the silicon-based germanium single-photon detector, and increase the detection speed to achieve a higher detection frequency.

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

[0082] S210, using flip-chip technology, using thermal conductive glue and low-temperature welding materials to weld any laser chip and any circuit SPAD integrated chip through a substrate, and using optical-grade resin to design an optical window for the target area on the welded 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-distance ranging chip based on silicon-based germanium single-photon detector is obtained.

[0083] like Figure 1 As shown, the prepared long-distance ranging chip based on silicon-based germanium single-photon detector includes a laser device part and a detector and circuit part. Among them, the laser device part corresponds to a laser chip, and the detector and circuit part corresponds to a circuit SPAD integrated chip. The circuit SPAD integrated chip is obtained by dividing the circuit SPAD integrated wafer, and the circuit SPAD integrated wafer is obtained by monolithic integration of the circuit wafer and the SPAD wafer. Accordingly, the circuit SPAD integrated chip consists of two parts from the circuit wafer and the SPAD wafer, that is, Figure 1 As shown, the detector and circuit part include a silicon circuit wafer and a silicon-based germanium SPAD wafer.

[0084] Specifically, laser cutting or etching is used to divide the laser wafer into independent chips, micro solder balls are deposited in the laser interconnection area, and flip-chip technology is used to connect the laser chip and the circuit SPAD integrated chip through substrate welding, which not only realizes electrical interconnection, but also facilitates heat conduction. After mechanical alignment, thermal conductive glue and low-temperature welding materials are used to enhance thermal management and mechanical stability. Furthermore, optical-grade resin is used to design optical windows for the laser emission and detection parts to ensure that the laser light and the detector detection reflected light are not blocked. This system-level packaging method can greatly improve the system integration, which is conducive to the miniaturization of long-distance detection system solutions. At the same time, it can also reduce interconnection delays and improve the operating speed of the system.

[0085] The present invention provides a method for preparing a long-distance ranging chip based on a silicon-based germanium single-photon detector. The technical characteristics of silicon-based germanium are used to bond a silicon-based germanium SPAD detector wafer with a circuit wafer including a detector auxiliary circuit, a distance detection related circuit, and a laser drive and control circuit to achieve a system-level package of the laser device part, the detector, and the related circuit part. The on-chip integrated design of the circuit reduces parasitic capacitance and timing delay, helps to improve the accuracy and working speed of the detection system, and achieves a higher frequency system operation. In addition, in the prior art, the InGaAs detector cannot be integrated with the CMOS circuit on a single chip due to the incompatibility of the material with the silicon process, and an additional refrigeration module is required; and the conventional silicon-based detector has extremely low efficiency in the 1550nm band. The present invention realizes the full-function integration of 1550nm efficient detection and signal processing on a single silicon chip for the first time through the silicon-based germanium absorption and multiplication separation structure design and system-level packaging process, improves the system integration, and realizes the miniaturization of the long-distance ranging system.

[0086] The present invention also provides a long-distance ranging chip based on a silicon-based germanium single-photon detector. The long-distance ranging chip based on a silicon-based germanium single-photon detector is prepared by any preparation method of a long-distance ranging chip based on a silicon-based germanium single-photon detector provided by the present invention, such as Figure 4 As shown, the long-distance ranging chip based on 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 driving circuit is used to provide a driving signal 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 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.

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

[0090] The SPAD readout and quenching circuit is used to send multiple single-photon counting signals detected by the silicon-germanium SPAD in the current working cycle to the TDC circuit, and the multiple single-photon counting signals include signals reflected by the target to be measured.

[0091] The TDC circuit is used to count 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-distance ranging chip based on the silicon-based germanium single-photon detector and the target to be measured according to the distribution situation.

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

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

[0095]

[0096] Wherein, D represents the distance between the long-distance ranging chip based on silicon-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 period corresponding to the signal reflected by the target to be measured, and T1 represents the start time of the current working cycle.

[0097] The present invention also provides a long-distance ranging method based on silicon-based germanium single-photon detector, which is applied to any long-distance ranging chip based on silicon-based germanium single-photon detector provided by the present invention. The long-distance ranging chip based on 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-distance distance measurement method based on silicon-based germanium single-photon detector includes the following steps B1-B5:

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

[0100] The total duration of the working cycle is preset according to the detection distance.

[0101] For example, for 3km distance detection, the duty cycle length TC can be set at 30 microseconds, which is about 1.5 times the round-trip distance of 9km that light needs to travel. For detection distances as short as 1m or even smaller, the duty cycle needs to be significantly reduced and can be set at 10ns. The response speed of the silicon-based germanium SPAD detector and the accuracy of the TDC circuit limit the minimum distance that can be detected.

[0102] In a working cycle TC, the control circuit controls the laser device to generate 1550nm laser pulses, and synchronously records the time signal T1, which is set as the beginning of the working cycle. The working cycle is from T1 to (T1+TC). After the laser is emitted, it propagates to the object to be measured, and is reflected back, and then the silicon-based germanium SPAD detector performs single photon detection.

[0103] B2. Detect the reflected single photon counting signal through a silicon-germanium SPAD detector.

[0104] B3. Send multiple single-photon counting signals detected by the silicon-germanium SPAD in the current working cycle to the TDC circuit through the SPAD readout and quenching circuit, where the multiple single-photon counting signals include signals reflected by the target to be measured.

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

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

[0107] B5. The control and signal processing circuit calculates the distance between the long-distance ranging chip based on silicon-germanium single-photon detector and the target to be measured according to the distribution situation.

[0108] Optionally, the distribution of multiple single-photon counting signals detected by the silicon-based germanium SPAD detector is counted through a TDC circuit, including: dividing the current working cycle into multiple time periods by the TDC circuit, and based on the division result, determining the temporal distribution of the multiple single-photon counting signals detected by the silicon-based germanium SPAD detector, and determining the time period corresponding to the peak value as the round-trip time period corresponding to the signal reflected by the target to be measured;

[0109] Correspondingly, the control and signal processing circuit calculates the distance between the long-distance ranging chip based on silicon-based germanium single-photon detector and the target to be measured according to the distribution, including:

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

[0111]

[0112] Wherein, D represents the distance between the long-distance ranging chip based on silicon-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 period 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 distribution diagram of the single photon counting signal shown in FIG. 1 shows that the working cycle length TC is divided into N equal parts, and N time segments of length TC / N are obtained. The statistical distribution of the single photon arrival time is obtained according to the time segments. The peak segment is the most likely round-trip time range of the target reflection signal, and the corresponding midpoint of the time segment is recorded as T2, and the distance D is calculated.

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

[0115] For each embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the specific contents and beneficial effects and other related parts are referenced to each other.

[0116] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the scope of protection of the present invention.

Claims

1. A method for preparing a long-distance ranging chip based on silicon-based germanium single-photon detector, characterized in that: include: The circuit part of the long-distance ranging chip based on silicon-based germanium single-photon detector is processed and prepared on a wafer using a standard silicon CMOS process to make a circuit wafer, wherein the circuit part includes silicon-based germanium SPAD readout and quenching circuit, TDC circuit, control and signal processing circuit, laser drive circuit and laser control circuit; A silicon-based germanium SPAD detector based on the long-distance ranging chip based on silicon-based germanium single-photon detector is manufactured into a SPAD wafer; Preparing a laser wafer, wherein the laser wafer is capable of generating laser pulses with a wavelength of 1550 nm; Thinning the SPAD wafer to remove excess silicon substrate portions without device structures, cleaning the thinned SPAD wafer and the circuit wafer to remove surface impurities, and obtaining a cleaned SPAD wafer and a cleaned circuit wafer; Flipping the cleaned circuit wafer, and aligning the cleaned SPAD wafer and the flipped circuit wafer based on design requirements; Laminating the cleaned SPAD wafer and the flipped circuit wafer at room temperature to form a preliminarily bonded wafer; Performing low temperature annealing on the preliminarily bonded wafers to obtain low temperature annealed bonded wafers; Performing surface treatment on the bonded wafers after low temperature annealing to produce a circuit SPAD integrated wafer; dividing the circuit SPAD integrated wafer to obtain a plurality of independent circuit SPAD integrated chips; dividing the laser wafer to obtain a plurality of independent laser chips; By adopting flip-chip technology, using thermal conductive glue and low-temperature welding materials, any of the laser chips and any of the circuit SPAD integrated chips are welded through a substrate, and optical-grade resin is used to design an optical window for the target area on the welded 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-distance ranging chip based on silicon-based germanium single-photon detector is obtained.

2. The method for preparing a long-distance ranging chip based on silicon-based germanium single-photon detector according to claim 1, characterized in that: The silicon-based germanium SPAD detector of the long-distance ranging chip based on the silicon-based germanium single-photon detector is made into a SPAD wafer, comprising: Epitaxially growing intrinsic Si on the substrate to form an epitaxial silicon layer; Performing P-type doping on a region of the epitaxial silicon layer away from the substrate by ion implantation to form a P-type silicon layer, and forming a multiplication layer on a region of the epitaxial silicon layer that is not P-doped; epitaxially growing intrinsic Si on the P-type silicon layer to form a buffer layer; epitaxially growing Ge on the buffer layer to form a Ge layer; P is implanted into the entire surface of the Ge layer away from the buffer layer. + , forming P + Type Ge layer, the Ge layer is not implanted with P + The region forms a common Ge layer; For the ordinary Ge layer and the P + The type Ge layer, the multiplication layer and the P-type silicon layer are etched to prepare electrodes to form a silicon-based germanium absorption and multiplication separated SPAD wafer.

3. The method for preparing a long-distance ranging chip based on 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 preparing a long-distance ranging chip based on silicon-based germanium single-photon detector according to claim 3, characterized in that: The temperature of the low temperature annealing treatment is 200-400°C.

5. A long-distance ranging chip based on silicon-based germanium single-photon detector, characterized in that: The long-distance ranging chip based on silicon-based germanium single-photon detector is prepared by any method for preparing a long-distance ranging chip based on silicon-based germanium single-photon detector as claimed in any one of claims 1 to 3. The long-distance ranging chip based on silicon-based germanium single-photon detector comprises: Laser devices, silicon-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 a driving signal for 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, and set 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 silicon-based germanium SPAD detector is used to detect the reflected single photon counting signal; The SPAD readout and quenching circuit is used to send a plurality of single-photon counting signals detected by the silicon-germanium SPAD in the current working cycle to the TDC circuit, wherein the plurality of single-photon counting signals include a signal reflected by the target to be measured; The TDC circuit is used to count 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-distance ranging chip based on silicon-germanium single-photon detector and the target to be measured according to the distribution condition.

6. The long-distance ranging chip based on silicon-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 result, determine the temporal distribution of multiple single-photon counting signals detected by the silicon-based germanium SPAD detector, and determine the time period corresponding to the peak value as the round-trip time period corresponding to the signal reflected by the target to be measured; Correspondingly, the control and signal processing circuit is specifically used to calculate the distance between the long-distance ranging chip based on silicon-based germanium single-photon detector and the target to be measured according to the round-trip time period corresponding to the signal reflected by the target to be measured and the start time of the current working cycle, which is expressed as: Wherein, D represents the distance between the long-distance ranging chip based on silicon-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 period 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 distance measurement method based on silicon-based germanium single-photon detector, characterized in that: Applicable to any long-distance ranging chip based on silicon-based germanium single-photon detector as claimed in claim 5 or 6, wherein the long-distance ranging chip based on silicon-based germanium single-photon detector comprises 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 distance measurement method based on silicon-based germanium single-photon detector comprises: Through the laser control circuit and the laser driving circuit, the laser device is controlled to generate and emit a laser pulse with a wavelength of 1550nm, and the current time is synchronously recorded, and the current time is set as the start time of the current working cycle. The total duration of the working cycle is preset according to the detection distance; Detecting the reflected single photon counting signal by the silicon-based germanium SPAD detector; Sending a plurality of single-photon counting signals detected by the silicon-germanium SPAD in the current working cycle to the TDC circuit through the SPAD readout and quenching circuit, wherein the plurality of single-photon counting signals include a signal reflected by the target to be measured; Counting the distribution of multiple single photon counting signals detected by the silicon-based germanium SPAD detector through the TDC circuit; The control and signal processing circuit calculates the distance between the long-distance ranging chip based on silicon-germanium single-photon detector and the target to be measured according to the distribution condition.

8. The long-distance distance measurement method based on silicon-germanium single-photon detector according to claim 7 is characterized in that: The counting of distribution of multiple single photon counting signals detected by the silicon-based germanium SPAD detector by the TDC circuit includes: The current working cycle is equally divided into a plurality of time periods by the TDC circuit, and based on the division result, the temporal distribution of a plurality of single-photon counting signals detected by the silicon-based germanium SPAD detector is determined, and the time period corresponding to the peak value is determined as the round-trip time period corresponding to the signal reflected by the target to be measured; Correspondingly, the distance between the long-distance ranging chip based on the silicon-based germanium single-photon detector and the target to be measured is calculated by the control and signal processing circuit according to the distribution, including: The control and signal processing circuit calculates the distance between the long-distance ranging chip based on silicon-based germanium single-photon detector and the target to be measured according to the round-trip time period corresponding to the signal reflected by the target to be measured and the start time of the current working cycle, which is expressed as: Wherein, D represents the distance between the long-distance ranging chip based on silicon-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 period 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 silicon-based germanium single-photon detector, characterized in that: A long-distance ranging chip based on a silicon-germanium single-photon detector as claimed in any one of claims 5 or 6.

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