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Characterization of a 3-D stacked CMOS SPAD depth sensor in 45/22-nm technology
Optics Express
|May 4, 2026
Summary
This study details a 3-D stacked direct time-of-flight (dToF) depth sensor with 256x128 single-photon avalanche diodes (SPADs). The sensor achieves 100m range finding and improved signal-to-noise ratio for LiDAR applications.
Area of Science:
- Photonics and Sensing
- Integrated Circuits
- LiDAR Technology
Background:
- Advancements in LiDAR require high-resolution, long-range depth sensing.
- Single-photon avalanche diodes (SPADs) are crucial for high-sensitivity photon detection.
Purpose of the Study:
- To characterize a novel 3-D stacked direct time-of-flight (dToF) depth sensor.
- To evaluate its performance for light detection and ranging (LiDAR) applications.
Main Methods:
- Fabrication of a 256x128 SPAD array in 45nm/22nm CMOS technology.
- Utilized digitally synthesized modules with coincidence detection and time-to-digital converters.
- Demonstrated functionality via telemetry, flash 3-D imaging, and full array SPAD characterization.
Main Results:
- Achieved range-finding capability up to 100 meters under 10 klux sunlight.
- Demonstrated 31.7 dB SNR improvement using progressive gating.
- Showcased 17 dB SNR improvement with coincidence photon detection (rank 3).
- Real-time photon counting demonstrated at 25 FPS under 20 klux daylight.
Conclusions:
- The characterized dToF sensor shows promising performance for demanding LiDAR applications.
- The 3-D stacked architecture and advanced SPAD circuitry enable high-resolution, long-range depth sensing.
- The sensor's robustness in bright light conditions and efficient photon-counting capabilities are key advantages.
