JSSC 2021第11期Image Sensors65nmCMOS Image Sensor

A 1.2-Mpixel Indirect Time-of-Flight Image Sensor With 4-Tap 3.5- μm Pixels for Peak Current Mitigation and Multi-User

一款1.2百万像素间接飞行时间图像传感器，采用4抽头3.5微米像素设计，降低峰值电流并消除多用户干扰。

1.2-Mpixel, 4-tap 3.5-μm pixels, QE 38% at 940 nm, DC 96% at 100 MHz, depth noise <0.92%

间接飞行时间CMOS图像传感器解调像素多用户干扰消除量子效率

▸创新点1：4抽头3.5微米解调像素设计，通过优化像素结构提高量子效率（QE）至38%和解调对比度（DC）至96%/80%（100/200MHz），属于像素级电路创新

▸创新点2：多交织方案通过时序优化降低峰值电流至0.9A以下，同时消除固定模式相位噪声（FPPN）且保持解调对比度稳定，属于系统架构创新

▸创新点3：基于伪随机调制的多用户干扰消除（MUIC）方案，可有效抑制至少两个相邻ToF传感器的信号干扰，属于信号处理算法创新

▸创新点4：采用65nm双die堆叠工艺实现1.2M像素传感器，在full模式和2×2 binning模式下分别实现<0.92%和<0.3%的深度噪声，属于工艺集成创新

Abstract

A 1.2-Mpixel indirect time-of-ﬂight (ToF) CMOS image sensor is presented to lower peak current and to can- cel out multi-user interference. The proposed 4-tap 3.5- µm demodulation pixel is optimally designed to improve quan- tum efﬁciency (QE) and demodulation contrast (DC). A new “multiple-interleaving” scheme is proposed to reduce the peak current and self-compensate ﬁxed-pattern phase noise (FPPN) with the minimal side effect of DC imbalance. To cancel out interference from the other ToF sensors, a multi-user interference cancellation (MUIC) scheme based on pseudorandom modulation is adopted. From the measurement results, we achieve a high QE of 38% at 940 nm and a high DC of 96% and 80% at 100- and 200-MHz modulation frequencies, respectively. With the superior pixel performance, the depth noise of <0.92% and <0.3% is achieved at the full and 2 × 2 binning modes, respectively. The multiple-interleaving scheme suppresses the peak current to less than 0.9 A and removes the column FPPN with constant DC for the whole pixel array. The proposed MUIC proves that at least two interferers can be successfully rejected. The sensor chip is fabricated in a two-stack process with 65 nm for the top die and 65 nm for the bottom die.