适用于超高压双极型SiC功率器件的二次外延调控中间层覆盖的体终端技术研究

Silicon Carbide (SiC) bipolar devices are practically the only solution for the next-generation power transmission system due to its superior material- and electrical-related properties. Considering the fact that the ultra-high voltage (﹥10kV) SiC bipolar device are suffering from instability in breakdown characteristics due to the surface effect such as the positive charge at the SiC/SiO2 interface, this project proposes a body termination, covered by a regrown epitaxial intermediate layer, to stabilize the breakdown characteristics of the ultra-high voletage SiC PiN power diode, for instance. The regrown layer can be taken as a homoepitaxially passivated-like layer, burying the traditional termination into the bulk SiC, thereby resulting in an intrinsic and stable bulk-breakdown. Through studying on the effect of parameters of the intermediate layer on the breakdown characteristics, an optimized body termination will be proposed. On the other hand, an improved intermediate layer also will be implemented based on the experimental research on the influence of different surface preparation on the quality of the regrown epi-layer. Finally, combining key processes with global structural design, 20-kV-class SiC PiN diodes with quite stable breakdown behavior will be fabricated, simultaneously providing high breakdown efficiency above 90% and high yield above 90% as well in wafer-scale.

碳化硅（SiC）基双极型功率器件以优越的材料和电学特性优势正成为新一代超高压电力传输系统的唯一解决方案。针对目前超高压（﹥10kV）双极型SiC功率器件所面临的SiC/SiO2界面正电荷等表面效应引起击穿特性不稳定的问题，本项目提出利用二次外延形成的调控中间SiC层覆盖传统的表面型终端，并应用于超高压SiC PiN功率二极管，来提高器件的击穿稳定性。由于二次外延创造的同质钝化效果，有效终端区可被控制在SiC体内，从而实现SiC材料固有的、稳定的体击穿优势。通过研究调控中间层参数的影响机理、建立体终端结构的设计优化模型，通过研究不同表面处理工艺对二次外延质量的影响规律、提出改进的中间层质量优化工艺。最后，结合器件关键工艺和整体结构设计优化，研制出具有稳定击穿电压的20 kV级SiC PiN功率二极管，实现击穿效率不低于90%，片内20kV击穿良率达到90%，使器件性能达到国际领先水平。

碳化硅（SiC）基双极型功率器件以优越的材料和电学特性优势正成为新一代超高压电力传输系统的唯一解决方案。针对目前高压SiC功率器件所面临的SiC/SiO2界面正电荷等表面效应引起击穿特性不稳定的问题，本项目提出利用二次外延形成的调控中间SiC层覆盖传统的表面型终端，来提高器件的击穿稳定性，并针对该新型体终端技术系统的开展了相关的基础理论和实验研究。研究内容如下：首先，重点探究了调控中间层的内在作用机理和优化设计规律，内涵包括：1）基于简单单区JTE构造中间层模型，揭示了中间层的电荷补偿机制和对器件击穿行为的调控规律；2）基于复杂多浮区JTE体终端（B-MFZ-JTE）结构，进一步揭示了调控中间层对宏观电场分布的稳定均衡作用及其带来的可显著抵御界面电荷漂移扰动效应的高击穿效率、宽窗稳定耐压优势，建立了体终端参数设计规则和优化方案；其次，基于常规的外延生长工艺优化，并结合前道注入结构特征，开展了二次外延生长调控中间层的实验研究，获得了高质量调控中间层的优化工艺方法。最后，基于关键单步工艺优化和整体工艺流程和版图设计，完成了新型体终端在中高压(3kV)和超高压(10kV) SiC PiN功率二极管上的制备流片，对比验证了调控中间层的有效性。