Photoelectric detector integrating linear mode and Geiger mode and working method thereof

Abstract

The invention provides a photoelectric detector integrating a linear mode and a Geiger mode and a working method of the photoelectric detector. The photoelectric detector comprises a Geiger mode detector chip located on the upper layer and a linear mode detector chip located on the lower layer. The Geiger mode detector chip and the linear mode detector chip are bonded and integrated through flip-chip bonding in an N electrode area; the Geiger mode detector chip adopts a multi-photon counter (MPPC), and the linear mode detector chip adopts a large photosensitive surface avalanche photodiode (LAAPD). Through the detection process, different working modes are adaptively selected, and the respective advantages of the different working modes are utilized, so that the optimization of resource consumption and system efficiency is achieved as far as possible while a time blind area and a space blind area are eliminated.

Description

Technical Field

[0001] The invention relates to the technical field of photoelectric detection, and in particular to a photoelectric detector integrating a linear mode and a Geiger mode and a working method thereof. Background Art

[0002] Time-of-flight (ToF) imaging sensor chips operating in Geiger mode, such as single-photon avalanche detector (SPAD) arrays and multi-element photon counters (MPPC or SiPM), are a rapidly emerging optoelectronic imaging technology. Since the transmitting power is strictly limited by eye safety regulations, compared with the relatively small detection distance of traditional linear mode avalanche photodiodes (APDs), the biggest advantage of these Geiger mode sensors is that they can quickly generate long-distance environmental depth images using their single-photon level detection sensitivity. Therefore, such low-light sensors are considered to be the key enabling technology for future autonomous driving systems.

[0003] However, the self-sustaining avalanche unique to the Geiger mode, while bringing high gain and high sensitivity, also introduces a recovery time of nanoseconds (Hamamatsu measured data: the recovery time required for a SPAD with a photosensitive surface size of 10μm is 10ns, and the duration is proportional to the size of the photosensitive surface), which greatly limits the time resolution of SAPDs, that is, the ability to capture and track high-speed moving objects; this defect has been alleviated by the gradual application of SiPM, but the "time blind spot" is still of the same order of magnitude, with no essential improvement. In addition, the continuous input of strong light from highly reflective objects appearing at close range causes the Geiger mode sensor to be filled with transients and thus become unusable, and the too close detection time of the emission and return light will also make SPADs unable to distinguish between signal light and stray light, resulting in signal distortion. These introduced "spatial blind spots" will also be a huge safety hazard for application scenarios with frequent emergencies. In reality, autonomous driving is usually equipped with a multi-sensor fusion detection solution to ensure its safety redundancy, so this also has to sacrifice a certain volume, spatial arrangement, energy consumption and system solution efficiency.

[0004] In view of this, the present invention proposes a photoelectric detector integrating linear mode and Geiger mode and a working method thereof. Summary of the invention

[0005] The purpose of the present invention is to propose a high dynamic range detector integrating linear mode and Geiger mode; through the detection process itself, different working modes are adaptively selected, and the respective advantages of different working modes are utilized to optimize resource consumption and system efficiency as much as possible while eliminating "time blind spots" and "spatial blind spots".

[0006] To achieve the above object, the technical solution of the present invention is as follows: A photoelectric detector integrating linear mode and Geiger mode comprises a Geiger mode detector chip located at an upper layer and a linear mode detector chip located at a lower layer. The Geiger mode detector chip and the linear mode detector chip are bonded and integrated by flip-chip welding in an N-electrode region. The Geiger mode detector chip adopts a multi-electrode photon counter MPPC, and the linear mode detector chip adopts a large photosensitive surface avalanche photodiode LAAPD.

[0007] Preferably, the multi-photon counter MPPC and the large photosensitive surface avalanche photodiode LAAPD are both InGaAs / InP material systems; the absorption layer thickness of the multi-photon counter MPPC is 0.5-1.5 μm, and the absorption layer thickness of the large photosensitive surface avalanche photodiode LAAPD is 2-4 μm.

[0008] Preferably, the N-electrode metal of the multi-element photon counter MPPC and the large photosensitive surface avalanche photodiode LAAPD is a multi-layer metal structure, and the multi-layer metal structure includes Ti / Pt / Au, Ni / Pt / Au or AuGe / Ni / Au, wherein Ti / Pt / Au means that the bottom metal is Ti, the middle metal is Pt, and the outer metal is Au; Ni / Pt / Au means that the bottom metal is Ni, the middle metal is Pt, and the outer metal is Au; AuGe / Ni / Au means that the bottom metal is AuGe, the middle metal is Ni, and the outer metal is Au.

[0009] Preferably, the method for preparing the photodetector comprises: S1, prepare two chips, namely, multi-element photon counter MPPC and large photosensitive surface avalanche photodiode LAAPD; S2. According to the selected integration method, an under-ball metal layer (UBM) is prepared by evaporation or sputtering in the N-electrode region of the two chips respectively, and photolithography, indium column evaporation and stripping are performed on the surface of the under-ball metal layer (UBM) of the two chips respectively to complete the preparation of the indium column; S3, the wafer-level multi-element photon counter MPPC and the large photosensitive surface avalanche photodiode LAAPD prepared by the indium pillar array are divided and split respectively, and the appearance of the split chips is inspected and screened, and then the selected qualified MPPC chips and LAAPD chips are flip-chip bonded through the indium pillars; S4, lead the signal lead wire to the ceramic base at the electrode, and inject and cure the optical glue in the gap between the two chips; S5. According to the selected integration method, a microlens array is separately manufactured to align and mount the multi-photon counter MPPC using the microlens array.

[0010] Preferably, the integration method includes a face-to-face integration method and a stacked integration method; In the face-to-face integration method, both the multi-electrode photon counter MPPC and the large photosensitive surface avalanche photodiode LAAPD use coplanar electrodes, and the two chips are integrated in a face-to-face manner with the N-electrode regions; In the stacked integration method, the multi-electrode counter MPPC adopts skew electrodes, the large photosensitive surface avalanche photodiode LAAPD adopts coplanar electrodes, and the two chips are integrated in a face-to-face manner with the N-electrode regions.

[0011] Preferably, the height of the indium column is 4-10 μm, and the diameter of the indium column is 8-15 μm.

[0012] Preferably, S5 is specifically as follows: when the selected integration method is a stacked integration method, a microlens array is manufactured separately, and a suction nozzle is used to move the microlens array until each lens crown coincides with the geometric center of the photosensitive surface of each pixel of the multi-photon counter MPPC, and then the gap between the microlens array and the device is filled and reinforced with insulating optical glue.

[0013] Preferably, the microlens array is replaced with a diffraction grating or a photonic crystal lens to align and mount the multi-element photon counter MPPC.

[0014] Preferably, the microlens array is manufactured based on a wide energy band material substrate through a process flow including thinning, double-sided grinding and polishing, photolithography, hot melt reflow, etching, and optical anti-reflection film coating, and the wide energy band material substrate includes an InP substrate or a GaP substrate.

[0015] A working method of a photoelectric detector integrating a linear mode and a Geiger mode, the method specifically comprising: The optical signal is first received by the upper-layer multi-photon counter MPPC; If the optical signal is a weak light signal reflected from a long distance, it will be received by the multi-photon counter MPPC and converted into an electrical analog signal, and directly sent to the amplifier circuit for subsequent processing, and will not be received by the large photosensitive surface avalanche photodiode LAAPD at the lower layer; If the light signal is a strong light signal reflected from a short distance, after the multi-element photon counter MPPC receives it, multiple pixels enter the dead time zone, and the generated superimposed signal amplitude reaches the preset value, triggering the lower large photosensitive surface avalanche photodiode LAAPD to start working, the multi-element photon counter MPPC stops working, and the strong light detection mode is switched; the remaining strong light energy penetrating the upper multi-element photon counter MPPC is absorbed by the lower large photosensitive surface avalanche photodiode LAAPD absorption layer; The large photosensitive surface avalanche photodiode LAAPD works in the linear region to track high-speed moving targets that produce close-range reflections to eliminate blind spots; When the large photosensitive surface avalanche photodiode LAAPD fails to detect a strong light signal, the upper MPPC is triggered to restart working, and the weak light detection mode is switched.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention adaptively selects different working modes through the detection process itself, and utilizes the respective advantages of different working modes to optimize resource consumption and system efficiency as much as possible while eliminating "time blind spots" and "spatial blind spots". Compared with the application of a single mode detector in the prior art, the present application can eliminate the blind spot; compared with the fusion solution of multiple detectors in the prior art, the present application can save space and energy consumption, and achieve higher system efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The integrated linear mode and Geiger mode photodetector of the face-to-face integration method of the present invention; Figure 2 It is an integrated linear mode and Geiger mode photoelectric detector of the stacked integration method of the present invention; Figure 3 The flowchart of the preparation method of the photoelectric detector integrating the linear mode and the Geiger mode of the present invention; Figure 4 This is a diagram of the adaptive working principle of eliminating blind spots in the present invention.

[0018] In the figure, 1- multi-electrode photon counter MPPC; 2- large photosensitive surface avalanche photodiode LAAPD; 3- N-electrode region of MPPC; 4- N-electrode region of LAAPD; 5- first signal; 6- common N-pole signal; 7- second signal; 8- microlens array. DETAILED DESCRIPTION

[0019] The following is combined with Figure 1-4 , the technical solution of the present invention is specifically described.

[0020] The present invention proposes a photoelectric detector integrating linear mode and Geiger mode. Figure 1-2 , including a Geiger mode detector chip located at the upper layer and a linear mode detector chip located at the lower layer, wherein the Geiger mode detector chip and the linear mode detector chip are bonded and integrated by flip-chip bonding in the N-electrode region; the Geiger mode detector chip adopts a multi-element photon counter MPPC 1, and the linear mode detector chip adopts a large photosensitive surface avalanche photodiode LAAPD 2.

[0021] In this embodiment, the multi-photon counter MPPC 1 and the large photosensitive surface avalanche photodiode LAAPD 2 are both InGaAs / InP material systems; the absorption layer thickness of the multi-photon counter MPPC1 is 0.5-1.5 μm, and the absorption layer thickness of the large photosensitive surface avalanche photodiode LAAPD 2 is 2-4 μm.

[0022] In this embodiment, the N-electrode metal of the multi-element photon counter MPPC 1 and the large photosensitive surface avalanche photodiode LAAPD 2 is a multi-layer metal structure, and the multi-layer metal structure includes Ti / Pt / Au, Ni / Pt / Au or AuGe / Ni / Au, wherein Ti / Pt / Au means that the bottom metal is Ti, the middle metal is Pt, and the outer metal is Au; Ni / Pt / Au means that the bottom metal is Ni, the middle metal is Pt, and the outer metal is Au; AuGe / Ni / Au means that the bottom metal is AuGe, the middle metal is Ni, and the outer metal is Au.

[0023] In this embodiment, the method for preparing the photoelectric detector includes: S1, prepare two chips, namely, multi-element photon counter MPPC and large photosensitive surface avalanche photodiode LAAPD; S2. According to the selected integration method, an under-the-ball metal layer UBM is prepared on the N-electrode region 3 of the multi-electrode photon counter MPPC and the N-electrode region 4 of the large photosensitive surface avalanche photodiode LAAPD by evaporation or sputtering, and photolithography, indium column evaporation and stripping are performed on the surface of the under-the-ball metal layer UBM of the two chips to complete the preparation of the indium column; S3. The wafer-level multi-element photon counter MPPC and large photosensitive surface avalanche photodiode LAAPD that have completed the preparation of the indium pillar array are respectively divided into pieces (dividing and dividing is an industry standard process and will not be described here), and the appearance of the chips after division is inspected and screened, and then the selected qualified MPPC chips and LAAPD chips are flip-chip bonded through the indium pillars.

[0024] S4, lead out signal leads from the electrode to the ceramic base, and inject and solidify the optical glue in the gap between the two chips; wherein the signal leads include a first signal 5, a common N-pole signal 6, and a second signal 7; S5. According to the selected integration method, a microlens array 8 is separately manufactured to align and mount the multi-element photon counter MPPC using the microlens array 8.

[0025] In this embodiment, the integration method includes a face-to-face integration method and a stacked integration method; In the face-to-face integration method, both the multi-electrode photon counter MPPC and the large photosensitive surface avalanche photodiode LAAPD use coplanar electrodes, and the two chips are integrated in a face-to-face manner with the N-electrode regions; In the stacked integration method, the multi-electrode counter MPPC adopts skew electrodes, the large photosensitive surface avalanche photodiode LAAPD adopts coplanar electrodes, and the two chips are integrated in a face-to-face manner with the N-electrode regions.

[0026] In this embodiment, the height of the indium column is 4-10 μm, and the diameter of the indium column is 8-15 μm, so as to perform good flip-chip bonding.

[0027] In this embodiment, Figure 1 The face-to-face integration method can utilize the integrated microlens array integrated on the MPPC substrate to expand the effective light collection area, so there is no need for an additional independent microlens array; otherwise, Figure 2 The stacked integration method requires adding an independent microlens array 8 to expand the effective light-collecting area. Therefore, S5 is specifically as follows: when the selected integration method is the stacked integration method, the microlens array 8 is made separately, and the microlens array 8 is moved by a nozzle until each lens crown coincides with the geometric center of the photosensitive surface of each cell of the multi-element photon counter MPPC, and then the gap between the microlens array 8 and the device is filled and reinforced with insulating optical glue. This step can be completed using standard flip-chip equipment.

[0028] In this embodiment, the microlens array 8 is replaced by a diffraction grating or a photonic crystal lens to align and mount the multi-element photon counter MPPC.

[0029] In this embodiment, the microlens array 8 is manufactured based on a wide energy band material substrate through a process flow including thinning, double-sided grinding and polishing, photolithography, hot melt reflow, etching, and optical anti-reflection film coating. The wide energy band material substrate includes an InP substrate or a GaP substrate.

[0030] The present invention also proposes a working method of a photoelectric detector integrating a linear mode and a Geiger mode, wherein the method is specifically as follows: The optical signal is first received by the upper-layer multi-photon counter MPPC; If the optical signal is a weak light signal reflected from a long distance, it will be fully received by the multi-photon counter MPPC and converted into an electrical analog signal, and directly sent to the amplifier circuit for subsequent processing, and will not be received by the large photosensitive surface avalanche photodiode LAAPD at the lower layer; If the light signal is a strong light signal reflected from a short distance, after the multi-photon counter MPPC receives it, multiple pixels enter the dead time zone, and the generated superimposed signal amplitude reaches the preset value, triggering the lower large photosensitive surface avalanche photodiode LAAPD to start working, and the multi-photon counter MPPC stops working. The system gives priority to dealing with potential dangers at a short distance, and the strong light detection mode is switched. Optionally, the transmitting end can increase the repetition frequency accordingly. Since the thinner absorption layer of the upper multi-photon counter MPPC is not enough to completely absorb, the remaining strong light energy penetrates directly to the lower layer, and is finally fully absorbed by the thicker absorption layer of the lower large photosensitive surface avalanche photodiode LAAPD. LAAPD works in the linear region, has no recovery time limit and can work at a higher sampling frequency, so it has the ability to track high-speed moving targets that produce close-range reflections to eliminate blind spots; When the large photosensitive surface avalanche photodiode LAAPD fails to detect a strong light signal, the upper MPPC is triggered to restart working, and the weak light detection mode is switched.

[0031] The above are preferred embodiments of the present invention. Any changes made according to the technical solution of the present invention, as long as the resulting functions do not exceed the scope of the technical solution of the present invention, belong to the protection scope of the present invention.

Claims

1. A photodetector integrating linear mode and Geiger mode, characterized in that: It comprises a Geiger mode detector chip located at an upper layer and a linear mode detector chip located at a lower layer. The Geiger mode detector chip and the linear mode detector chip are bonded and integrated by flip-chip welding in an N-electrode region. The Geiger mode detector chip adopts a multi-element photon counter MPPC, and the linear mode detector chip adopts a large photosensitive surface avalanche photodiode LAAPD.

2. The photodetector integrating linear mode and Geiger mode according to claim 1, characterized in that: The multi-photon counter MPPC and the large photosensitive surface avalanche photodiode LAAPD are both made of InGaAs / InP material system; the absorption layer thickness of the multi-photon counter MPPC is 0.5-1.5 μm, and the absorption layer thickness of the large photosensitive surface avalanche photodiode LAAPD is 2-4 μm.

3. The photodetector integrating linear mode and Geiger mode according to claim 1, characterized in that: The N-electrode metal of the multi-element photon counter MPPC and the large photosensitive surface avalanche photodiode LAAPD is a multi-layer metal structure, and the multi-layer metal structure includes Ti / Pt / Au, Ni / Pt / Au or AuGe / Ni / Au, wherein Ti / Pt / Au means that the bottom metal is Ti, the middle metal is Pt, and the outer metal is Au; Ni / Pt / Au means that the bottom metal is Ni, the middle metal is Pt, and the outer metal is Au; AuGe / Ni / Au means that the bottom metal is AuGe, the middle metal is Ni, and the outer metal is Au.

4. The photodetector integrating linear mode and Geiger mode according to claim 1, characterized in that: The preparation method of the photodetector comprises: S1, prepare two chips, namely, multi-element photon counter MPPC and large photosensitive surface avalanche photodiode LAAPD; S2. According to the selected integration method, an under-ball metal layer (UBM) is prepared by evaporation or sputtering in the N-electrode region of the two chips respectively, and photolithography, indium column evaporation and stripping are performed on the surface of the under-ball metal layer (UBM) of the two chips respectively to complete the preparation of the indium column; S3, the wafer-level multi-element photon counter MPPC and the large photosensitive surface avalanche photodiode LAAPD prepared by the indium pillar array are divided and split respectively, and the appearance of the split chips is inspected and screened, and then the selected qualified MPPC chips and LAAPD chips are flip-chip bonded through the indium pillars; S4, lead the signal lead wire to the ceramic base at the electrode, and inject and cure the optical glue in the gap between the two chips; S5. According to the selected integration method, a microlens array is separately manufactured to align and mount the multi-photon counter MPPC using the microlens array.

5. The photodetector integrating linear mode and Geiger mode according to claim 4, characterized in that: The integration methods include face-to-face integration and stacked integration. In the face-to-face integration method, both the multi-electrode photon counter MPPC and the large photosensitive surface avalanche photodiode LAAPD use coplanar electrodes, and the two chips are integrated in a face-to-face manner with the N-electrode regions; In the stacked integration method, the multi-electrode counter MPPC adopts skew electrodes, the large photosensitive surface avalanche photodiode LAAPD adopts coplanar electrodes, and the two chips are integrated in a face-to-face manner with the N-electrode regions.

6. The photodetector integrating linear mode and Geiger mode according to claim 4, characterized in that: The height of the indium column is 4-10 μm, and the diameter of the indium column is 8-15 μm.

7. The photodetector integrating linear mode and Geiger mode according to claim 4, characterized in that: Specifically, S5 is as follows: when the selected integration method is a stacked integration method, a microlens array is manufactured separately, and a suction nozzle is used to move the microlens array until each lens crown coincides with the geometric center of the photosensitive surface of each pixel of the multi-photon counter MPPC, and then the gap between the microlens array and the device is filled and reinforced with insulating optical glue.

8. The photodetector integrating linear mode and Geiger mode according to claim 7, characterized in that: The microlens array is replaced with a diffraction grating or a photonic crystal lens to align and mount the multi-photon counter MPPC.

9. The photodetector integrating linear mode and Geiger mode according to claim 7, characterized in that: The microlens array is manufactured based on a wide energy band material substrate through a process flow including thinning, double-sided grinding and polishing, photolithography, hot melt reflow, etching, and optical anti-reflection film coating. The wide energy band material substrate includes an InP substrate or a GaP substrate.

10. A method for operating a photodetector integrating a linear mode and a Geiger mode, characterized in that: The working method of the photoelectric detector is implemented by using a photoelectric detector integrating linear mode and Geiger mode as claimed in any one of claims 1 to 9, specifically: The optical signal is first received by the upper-layer multi-photon counter MPPC; If the optical signal is a weak light signal reflected from a long distance, it will be received by the multi-photon counter MPPC and converted into an electrical analog signal, and directly sent to the amplifier circuit for subsequent processing, and will not be received by the large photosensitive surface avalanche photodiode LAAPD at the lower layer; If the light signal is a strong light signal reflected from a short distance, after the multi-element photon counter MPPC receives it, multiple pixels enter the dead time zone, and the generated superimposed signal amplitude reaches the preset value, triggering the lower large photosensitive surface avalanche photodiode LAAPD to start working, the multi-element photon counter MPPC stops working, and the strong light detection mode is switched; the remaining strong light energy penetrating the upper multi-element photon counter MPPC is absorbed by the lower large photosensitive surface avalanche photodiode LAAPD absorption layer; The large photosensitive surface avalanche photodiode LAAPD works in the linear region to track high-speed moving targets that produce close-range reflections to eliminate blind spots; When the large photosensitive surface avalanche photodiode LAAPD fails to detect a strong light signal, the upper MPPC is triggered to restart working, and the weak light detection mode is switched.

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