TCAD Optimisation of 4H-SiC Channel-Doped MOSFET with P-Polysilicon Gate

摘要

Although channel doping is a useful technique for improving the channel mobility of MOSFETs, channel doped MOSFETs display a trade-off between the channel mobility and the threshold voltage. One way to alleviate this compromise is to employ a gate material with a higher work function. In this paper the use of p-type polysilicon gate material, which has a 0.9V higher work-function than those of aluminum and n-type polysilicon, is suggested. TCAD simulations are employed to optimize the doping level and depth of the doped channel layer and to compare the various gate materials. The model for MOSFET channel mobility is enhanced through use of an explicitly defined distribution of surface charge trapping states within the band-gap. This allows good agreement with experimental data to be obtained over a wide range of gate voltage. An improvement of 50cm~2/Vs in the effective channel mobility is realized by using a p-polysilicon gate.