高压快速软恢复二极管(Fast and Soft Recovery Diode，FSRD)在功率转换电路中为感性负载提供续流回路。随着IGBT开关性能的不断改善，要求与之反并联高压FSRD不仅具备低损耗、快速软恢复特性，而且具有高抗浪涌电流和动态雪崩能力。目前高压FSRD在性能与可靠性，尤其是在抗浪涌电流和动态雪崩之间很难进行良好的折中。此外，器件内部存在的电场偏移、电流丝演变及其抑制、终端失效等问题亟需深入地研究。针对上述问题，本文对高压FSRD的关键技术进行了研究。主要内容如下： 1.分析了高压p⁺pn⁻nn⁺二极管的静、动态特性。重点讨论了影响零温度系数点(ZTC)、浪涌电流和反向恢复特性的关键因素，研究了在静态雪崩后正、负微分电阻和Egawa场的形成机制，以及三级动态雪崩的诱导因素。 2.建立了电场梯度解析模型，分析了高压FSRD雪崩后结处峰值电场偏移的原因，研究了峰值电场偏移诱导的正微分电阻对电流丝的抑制机理,采用合适的缓冲层掺杂浓度可以提高器件的动态坚固性。探索了电流丝的演变过程，分析了载流子寿命分布对电流丝的影响，表明局部的低载流子浓度可以抑制电流丝。 3.提出了阳极短路二极管(ASD),研究了器件的工作机理，导出了阳极侧寄生npn晶体管的导通条件，分析了电子注入效率的影响因素。在高通态电流密度下，新结构具有低的正向压降，从而提高了抗浪涌电流能力；在反向恢复期间，两侧寄生的晶体管导通，注入的电子和空穴会分别抑制pn⁻结和n⁻n结的峰值电场，提高了抗动态雪崩能力。 4.通过电热仿真研究了高压FSRD结终端的失效机理。在反向恢复期间，高电场穿通到终端表面，使此处的电流丝、高电场强度和碰撞电离形成正反馈，引起局部温度升高，导致终端失效。 5.为了解决结终端的失效问题，基于上述失效机理，提出了一种沟槽-场限环(T-FLR)终端新结构和一种波状p型电阻区(CP-FLR)终端新结构，不仅降低了终端边缘的电流丝，而且将峰值电场转移到体内，避免了正反馈的形成。电热仿真表明，两种新终端的动态坚固性都得到提高。 6.通过工艺研究和仿真，制定了3.3kV/100A FSRD的工艺实施方案，并进行了流片实验。测试结果表明，在100A的额定电流下，正向压降为2.192V,反向击穿电压达到3.5kV,反向恢复时间为652ns,软度因子为0.67,获得了较好的快速软恢复特性。 ①*本研究得到国家高等学校博士点项目基金(编号：20136118110004)的资助 关键词：快速软恢复二极管；软度；雪崩；浪涌；电流丝

 The fast and soft recovery diode (FSRD) provides a freewheeling loop for the inductive load in the power conversion circuit. With the development of high voltage IGBT, the performances of anti-parallel diodes, including the low loss, the fast and soft recovery characteristic, the ruggedness and the surge current capability, should be improved. At present, the high voltage FSRD is difficult to make a better compromise between high surge current and dynamic avalanche capabilities. In addition, there are several problems such as the electric field shifting, the current filament evolution and inhibition, the junction termination failure to be explored urgently. Based on the above problems, the key technologies of high voltage FSRD are studied in this paper, and the main contents are as follows: Firstly, the static and dynamic characteristics of high voltage p⁺pn⁻nn⁺ diode are investigated. The key factors affecting the zero temperature coefficient point (ZTC), the surge current characteristic and the reverse recovery characteristic are analyzed. Moreover, the formation mechanisms of positive and negative differential resistances and Egawa-field after static avalanche, and the induced factors of three-degree dynamic avalanches are discussed. Secondly, the mechanisms of the peak electric field shifting at the junctions after avalanche in high voltage FSRD are analyzed by establishing the electric field gradient analytical models, and the inhibition mechanism of the positive differential resistance induced by the peak electric field shifting on the current filament is studied. It points out that the appropriate buffer doping concentration is important to improve the dynamic ruggedness of the device. Simultaneously, the influence of carrier lifetime distributions on the evolution of current filaments and the inhibition of local low carrier concentration on current filaments are explored. Thirdly, a novel anode shorted diode (ASD) is proposed, and the operating mechanism of the device is analyzed. The conduction condition of the parasitic npn transistor at the anode side is derived, and the factors affecting the electron injection efficiency are given. The results show that the diode exhibits a low forward voltage drop at high on-state current density, improving the surge current capability. During reverse recovery, the parasitic transistors of both sides conduct, injecting electrons and holes into the pn⁻ junction and nn⁻ junction to inhibit the peak electric fields, respectively. This improves the dynamic avalanche capacity. Fourthly, the failure mechanism of the junction termination of high voltage FSRD is studied by electrothermal simulation. During reverse recovery, high electric field will punch through the termination surface, resulting in the positive feedback process maintaining among the current filament, high electric field strength, and impact ionization. This causes an increase in temperature at the local region, leading to the termination failure. Then, in order to solve the termination failure, and based on the above-mentioned failure mechanism, two new termination structures including the improved trench-field limiting ring and the corrugated p-type resistance region are proposed, which reduces the current filament at the termination surface and transfers the peak electric field into the body, avoiding the positive feedback process. Electrothermal simulation shows that the dynamic ruggedness of both terminations are improved. Finally, the process implementation scheme of 3.3 kV/100A FSRD is developed by the process research and simulation, and the experiments are carried out. The test results show that the forward voltage drop of 2.192 V at a rated current of 100 A, the reverse breakdown voltage of 3.5 kV, the reverse recovery time of 652 ns, and the softness factor of 0.67 are obtained, and it shows a fast and soft recovery characteristic. ①*This work was supported by Specialized Research Fund for the Doctoral Program of Higher Education of China [grant number 20136118110004]. Key words:fast and soft recovery diode,softness,avalanche,surge,current filament