用于Tof-3D图像传感器的SPAD像素设计

发布时间：2018-03-03 20:16

本文选题：Tof图像传感器　切入点：SPAD　出处：《深圳大学》2017年硕士论文　论文类型：学位论文

【摘要】：Tof图像传感器由于在激光三维成像、自动驾驶、机器人视觉、手势识别等方面的广阔应用前景成为研究的热点。和基于间接时差测距法的Tof图像传感器对比,基于直接时差测距法的Tof图像传感器有成像速度快,受光子噪声影响小等优点,因而更多的适用于快速运动场景成像和远距离探测,其精度主要由单光子雪崩二极管(SPAD)探测器性能和时间数字转换(TDC)电路精度决定,这也是该技术的发展难点,本文针对该问题做了深入的研究。第一,传统技术的SPAD普遍器件面积大,雪崩击穿电压高,不利于高度集成。本文基于SMIC 0.13μm CIS工艺,优化设计出具有较低雪崩击穿电压和较小器件面积的SPAD结构,通过Silvaco TCAD工艺器件特性仿真证明该结构设计满足边缘电场低等要求,并根据不同的结构尺寸,设计了11个SPAD版本,根据流片测试结果来实际验证。第二,SPAD淬灭电路的设计。根据设计要求,本文采用改进型的主动淬灭电路,通过电流控制模式以提高电路的响应速度,利用低压CMOS晶体管实现了性能良好的主动淬灭电路。将整体死时间控制在了5ns,具有迅速淬灭、结构简单,版图面积小、高集成度的优点,并由时序要求设计了精确的延时电路,从而对复位开关进行复位控制。第三,高精度TDC电路设计,本文根据直接计数法和游标法,设计了由粗精度测量和细精度测量组成的TDC电路,其中细精度测量是设计重点,通过游标法两级延时链的方式来实现,从而达到ps量级的时间分辨率。本文优化设计的SPAD具有较低雪崩击穿电压,淬灭电路具有很快的淬灭速度,整体死时间约为5ns,达到目前文献报道中最好的性能。同时整体像素结构版图所占面积很小,从而具有很高的集成度。目前国外对Tof图像传感器的研究较为领先。国内研究成果和理论水平都与国外有较大差距,大多停留在软件仿真层面上,本设计在完成像素单元设计后通过SMIC 0.13μm CIS工艺流片来实际验证,关于这方面的研究,对提高我国在该领域的研究水平有着非常重要的意义。
[Abstract]:Tof image sensor has become a hot research area because of its wide application prospect in laser 3D imaging, autopilot, robot vision, gesture recognition and so on, and compared with Tof image sensor based on indirect time difference ranging. The Tof image sensor based on direct moveout ranging method has the advantages of fast imaging speed and less influence by photon noise, so it is more suitable for fast moving scene imaging and remote detection. Its precision is mainly determined by the performance of single photon avalanche diode (SPAD) detector and the precision of time-digital converter (TDC) circuit. This is also a difficult point in the development of this technology. Traditional SPAD devices have large area and high avalanche breakdown voltage, which is not conducive to high integration. Based on SMIC 0.13 渭 m CIS process, the SPAD structure with lower avalanche breakdown voltage and smaller device area is optimized and designed in this paper. The simulation results of Silvaco TCAD process show that the design meets the requirements of low edge electric field, and 11 SPAD versions are designed according to different structure sizes. The second is the design of Spad quenching circuit. According to the design requirements, the improved active quenching circuit is adopted in this paper, and the response speed of the circuit is improved by current control mode. The active quenching circuit with good performance is realized by using low voltage CMOS transistor. The whole dead time is controlled at 5ns, which has the advantages of rapid quenching, simple structure, small layout area and high integration, and the precise delay circuit is designed according to the timing requirement. Thirdly, the high precision TDC circuit is designed. According to the direct counting method and the Vernier method, the TDC circuit composed of coarse precision measurement and fine precision measurement is designed, in which fine precision measurement is the key point of the design. By using the two-stage delay chain of Vernier method, the time resolution of PS is achieved. The optimized design of SPAD has lower avalanche breakdown voltage, and the quench circuit has fast quenching speed. The overall dead time is about 5 ns, which is the best performance reported in the current literature. At the same time, the size of the overall pixel structure is very small. So it has a high level of integration. At present, the research of Tof image sensor in foreign countries is leading. There is a big gap between domestic research results and theoretical level, and most of them stay on the level of software simulation. The design is verified by SMIC 0.13 渭 m CIS process after completing the pixel unit design. The research on this aspect is of great significance to improve the research level in this field in China.
【学位授予单位】：深圳大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP391.41;TP212

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