Dynamic Degradation in SiC Trench MOSFET With a Floating p-Shield Revealed With Numerical Simulations
Dynamic Degradation in SiC Trench MOSFET With a Floating p-Shield Revealed With Numerical Simulations
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DOI：
10.1109/ted.2017.2697763
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发表时间：
2017-05
影响因子：
3.1
通讯作者：
Jin Wei;Meng Zhang;Huaping Jiang;Hanxing Wang;K. J. Chen
中科院分区：
文献类型：
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作者：
Jin Wei;Meng Zhang;Huaping Jiang;Hanxing Wang;K. J. Chen
在碳化硅沟槽MOSFET中，通常采用栅沟槽下方的p型屏蔽区(p屏蔽区)，以获得较低的氧化场和反向转移电容(${C}_{rss})$。本文对比研究了接地P形屏蔽体和浮动P形屏蔽体的影响。本文利用Sentaurus TCAD对器件进行了模拟，揭示了器件的内部动力学特性。浮动P屏蔽层可以像接地P屏蔽层那样有效地降低关态氧化场，而不会降低其静态性能。然而，在从关态切换后，带有浮动p-屏蔽的沟槽MOSFET(FS-MOS)的通态氧化场显著升高。与具有接地p屏蔽层的沟槽MOSFET相比，FS-MOS还表现出更高的${C}_{{\Text{RSS}$，因此开关速度较慢。此外，在开关操作过程中，FS-MOS表现出动态${R}_{{\mathm{on}$的退化。然后提出了一种电荷存储机制来解释FS-MOS中的动力学。在高${V}_{{\Text{ds}$时，当穿透由p屏蔽层、p体层和它们之间的n区组成的寄生p-n-p结构时，从浮动p屏蔽层发射孔，即使在移除高${V}_{{\Text{ds}$时，也在浮动p屏蔽层中留下负电荷。基于这一机制，很好地解释了FS-MOS的行为。
A p-type shield region (p-shield) under the gate trench is typically adopted in a SiC trench MOSFET for achieving a lower oxide field and reverse transfer capacitance ( ${C}_{rss})$ . This paper comparatively studies the effects of a grounded p-shield and a floating p-shield. Device simulations using Sentaurus TCAD are carried out in this paper to reveal the devices’ internal dynamics. The floating p-shield can effectively reduce the OFF-state oxide field as a grounded p-shield does, without degrading its static performance. However, after being switched from the OFF-state, the ON-state oxide field in the trench MOSFET with a floating p-shield (FS-MOS) is dramatically elevated. Compared with the trench MOSFET with a grounded p-shield, the FS-MOS also exhibits a higher ${C}_{{{\text {rss}}}}$ and a consequently slower switching speed. Furthermore, the FS-MOS exhibits a degradation of dynamic ${R}_{{ \mathrm{ON}}}$ during switching operation. A charge storage mechanism is then presented to explain the dynamics in FS-MOS. Upon a high ${V}_{{{\text {DS}}}}$ , holes are emitted from the floating p-shield when the parasitic p-n-p structure consisting of p-shield, p-body, and n-region between them is punched through, leaving negative charges in the floating p-shield even when the high ${V}_{{{\text {DS}}}}$ is removed. Based on this mechanism, the behaviors of the FS-MOS are well explained.