GaN电力电子器件钝化关键技术研究

Normally-off AlGaN/GaN HEMT for power switching applications was concerned more and more because its outstanding performances. Unfortunately, the hysteresis in threshold voltage and current collapse, which is even more troublesome than that in microwave power devices, impeded its step for being widely applied. The two above problems can be attributed to how to get better quality of interface between passivation insulator and AlGaN/GaN and reduce the interface states. To solve this, in this project, we would design and fabricate different MIS-HEMTs and testing structures and measured with high quency C-V and quasi-static C-V measurements to analyze the property of the interfaces. Furthermore, the mechanism of the interface states would be research through the profile observation of the testing structures. The technique for improving the passivation would be brought out based on the analysis. The original methods of pulsed DC measurement would be applied to analyze current collapse. Improved passivation technologies would be brought out based on the analysis. Finally, the optimized passivation technology would be combined to obtain hysteresis and current collapse free HEMT for power switching applications.

增强型AlGaN/GaN HEMT电力电子器件因其优异性能越来越引起人们的注意。然而器件本身存在的阈值"回滞"和由于电力电子高压应用环境所导致的比微波功率器件更加棘手的"电流崩塌"严重影响了器件实用化的进度。这两个问题都可以归结为：如何提高钝化介质与衬底界面质量，减少界面态的问题。针对这一目的，本项目利用利用高频C-V结合准静态C-V测试方式，深入研究界面态的性质，并结合剖面形貌分析寻找造成界面态的机理，并提出改进钝化效果的技术方案。利用独创的直流脉冲测试方法分析器件的"电流崩塌"机制,并提出改进的钝化方案。最终，实现无阈值"回滞"和"电流崩塌"的电力电子器件。

本项目就AlGaN/GaN HEMT电力电子器件的钝化过程中的一系列关键技术展开了研究，对PECVD、高温热氧化技术、ICP-CVP、LPCVD等钝化技术以及等离子体和湿法腐蚀前处理进行了系统研究。结合准静态及高频CV测试，XPS、SIMS等表征方式对造成阈值回滞和电流崩塌现象的机制进行了深入探讨，最终确认Ga-O键是造成两种问题的最关键因素。通过比较钝化技术，最终确定以N等离子体原位处理结合LPCVD的钝化最优方案，从而获得了无阈值回滞和电流崩塌的器件，很好地达到预期研究目标。在表征电流崩塌和计算表面态密度方面，也进行了一些不同于既有手段的测试方案。