碳化硅漂移阶跃超快恢复器件基础技术研究

By researching into the drift step superfast recovery effect of the SiC DSRD(drift step recovery diode) with the voltage rate of 10kV, considering the conditions of the high electric field, the heavy injection and the incomplete ionization, etc., analyzing the current commutation principle based on the controllable plasma layer, the physical models of the chips are established and the packaging parameters are abstracted to achieve the united simulations. The research scheme of the single high voltage device and the low voltage devices in series for the p+-p-n0-n+diode structure is proposed. The body structure and the junction termination structure for the device are optimally designed, and the super junction structure is proposed for the first time to control the charges on the two dimensions, so as to solve the problem of cutting off high current within sub-nanosecond in principle. The key process including the dry etching, ion implantation, electrode fabrication and junction termination protection is studied, and then the whole process for the SiC DSRD chip is integrated. The key technology of packaging which is fit for the switch feature of the high voltage, high temperature and high speed is researched into. The device sample of SiC DSRD with the breakdown voltage higher than 10kV and the current pulse front edge shorter than 1ns is developed. The pulse discharge test platform for the opening switch is established. The dynamic characteristics of the switch is tested and the systematic evaluation method is formed. In all, this work will provide the experimental basis and serial technologies for the design, fabrication and application for the SiC DSRD.

通过研究万伏级SiC DSRD（drift step recovery diode）器件漂移阶跃超快恢复效应，考虑强电场、大注入和不完全电离等条件，分析基于可控等离子层换流原理，建立芯片物理级模型，并提取封装参数完成联合仿真。提出针对p+-p-n0-n+二极管结构的单只高压器件和低压器件串联研究方案，优化设计器件体结构和终端结构，并首次提出采用超结结构从二维上对电荷进行调控，探索从原理上解决亚纳秒时间截断大电流问题。研究包括干法刻蚀、离子注入、电极制备和终端保护等在内的关键工艺并对SiC DSRD芯片全套工艺进行整合，研究适应开关高压、高温、高速特点封装关键技术，研制出阻断电压10kV以上、换流脉冲前沿小于1ns的SiC DSRD器件原型样品，构建断路开关的脉冲放电检测平台，测试开关动态性能并形成系统评价方法，为SiC DSRD器件的设计、制造及应用提供试验依据和系列技术。

本项目针对脉冲功率领域重要的开关器件碳化硅漂移阶跃恢复二极管（SiC DSRD）展开研究，进行了包括该断路型开关的工作机理、结构设计、工艺制备及封装测试等方面的基础技术研究。基于可控等离子层换流原理，从理论上分析了SiC DSRD的漂移阶跃恢复效应和大电流快速截断机理。利用TCAD仿真建立了SiC DSRD的二维数值模型，分析了不同物理效应对动态特性的影响，研究发现禁带宽度变窄和不完全电离是决定负载电压波形形状的两个主要因素。讨论了SiC-DSRD的动态特性影响因素，包括正向电流脉宽、载流子寿命、正向电压、反向电压等。基于4H-SiC DSRD模型，针对kV级SiC DSRD，设计并优化了Mesa-JTE、Bevel-JTE、Etched-JTE三种终端结构。对于10kV级SiC DSRD，通过仿真优化，获得了具有纳秒开关速度和三阶刻蚀JTE终端的二极管结构参数。首次将超结（SJ）结构应用于SiC DSRD，以提高恢复硬度，结果表明与常规的SiC DSRD相比、SJ SiC DSRD能够以更高的上升率前沿输出高压脉冲。在工艺制备中，解决了微沟槽、刻蚀顺序、深槽刻蚀等多种刻蚀关键问题。为高压SiC DSRD设计了堆叠压接式和双面焊接式的封装结构，进行了多物理场仿真分析并完成器件封装。在此基础上，设计并搭建了基于SiC DSRD的脉冲功率测试电路，综合评价了SiC DSRD的动静态特性。本项目成功研制出阻断电压10.4kV（泄漏电流4.4μA）的器件样品，动态测试中负载输出脉冲电压的上升前沿为0.816ns，电流峰值4.28kA。以上工作为SiC DSRD器件在超宽带雷达、探地雷达等国防领域以及空气净化、表面等离子体清洁等民用领域的推广应用奠定了基础。