具有异质结体二极管和N包围型P柱的4H-SiC超结MOSFET

A superjunction 4H-SiC MOSFET with heterojunction body diode and N-enclosed P-pillar

利用TCAD仿真研究了一种具有异质结体二极管与N包围型P柱超结的4H-SiC UMOSFET(SJH-MOSFET)。通过在SJH-MOSFET中引入异质结和具有电荷平衡的超结结构,能够有效地优化器件的击穿电压、比导通电阻、反向恢复特性。研究结果表明,薄轻掺杂的电流扩展层(CSL)和N型包围使得耗尽区变窄,并为电流的流动提供了两个扩散路径,其中CSL使得电子快速地水平扩散,而N型包围允许电子可以垂直地流动,改进后结构的耐压提升了13.6%,栅槽底部高电场降低了10.5%,比导通电阻降低了10.5%,开启时间降低了38.4%,关断时间降低了44.7%;体区嵌入P+多晶硅与漂移区接触形成异质结体二极管,由于异质结特殊的能带结构,使得体二极管在导通时,P+多晶硅里空穴较少地流入到漂移区,使反向恢复电荷降低了42.96%,反向恢复时间降低了4.17%。

A 4H-SiC superjunction UMOSFET(SJH-MOSFET)with heterojunction body diode and N-enveloped P-pillar was investigated by utilizing Silvaco TCAD simulations.The breakdown voltage(VBR),specific on-resistance(Ron,sp),and reverse recovery characteristics of the device were optimized by introducing heterojunction and superjunction structure with charge balance in SJH-MOSFET.The results show that the thin lightly doped current spreading layer(CSL)and N-type surroundings make the depletion region narrower and provide two diffusion paths for current flow,where the CSL allows for fast horizontal diffusion of electrons and the N-type surroundings allow the electrons to be able to flow vertically.The improved structure has 13.6%higher VBR,10.5%lower high electric field at the bottom of the gate,10.5%lower Ron,sp,38.4%lower turn-on time,and 44.7%lower turn-off time.A heterojunction body diode was formed by P+polysilicon embedded body region in contact with the drift region.Due to the special energy band structure of the heterojunction,less holes in the P+polysilicon flow into the drift region when the body diode is on,which reduces the reverse recovery charge by 42.96%and the reverse recovery time by 4.17%.