基于标准0.18μm CMOS工艺设计了一种新型单光子雪崩二极管(SPAD)器件。该SPAD以pwell/nwell轻掺杂雪崩结作为器件的核心工作区域, 同时利用三个相邻n阱间的横向扩散在pn结边缘形成n-虚拟保护环以提高器件的性能。采用Silvaco软件对该器件的电场分布、响应度、击穿电压、光子探测效率和暗计数率等性能参数进行了仿真分析。仿真结果表明: 当SPAD器件的光窗口直径为20μm且n阱间隙宽度为1.4μm时, 其雪崩击穿电压为13V; 在过偏压为1V时, 其探测效率峰值和暗计数率分别为37%和0.82kHz; 在450~700nm波长范围器件的响应度较好, 且在500nm处达到峰值0.33A/W。

A novel single photon avalanche diode (SPAD) device was designed based on standard 0.18μm CMOS process. It uses pwell/nwell lightlydoped avalanche junction as the core working region, while uses an lateral diffusion between three adjacent nwells to form an n- virtual guard ring at the edge of the pn junction to improve the device performance. Silvaco software was used to simulate the parameters of the device, such as electric field distribution, responsivity, breakdown voltage, photon detection efficiency and dark count rate. Simulation results show that the avalanche breakdown voltage is 13V when the optical window diameter of the SPAD device is 20μm and the width of the nwell gap is 1.4μm; the maximum detection efficiency and dark count rate are 37% and 0.82kHz respectively when the excess bias is 1V; the responsiveness of the device is good in 450~700nm, and the peak value of 0.33A/W is realized at the wavelength of 500nm.