The Impaction of Epitaxy Growth Method on Performance of Low-Voltage UMOS

As we all know that epitaxy (called EPI later) is quite important for traditional UMOS devices to sustain more than 80% of the inverse voltage. In most cases, the EPI is diffused on the high doping concentration substrate to make sure that the EPI can be supported and has better performance, but different EPI growth method leads to different breakdown voltage, which dues to the reduction of actual EPI thickness. In this dissertation, through simulation we found that under the same doping concentration, diffuse temperature and growth time, the EPI growth layers has great impact on the breakdown voltage of low-voltage UMOS devices, the reason is that the substrate's diffusing to EPI is quite different in different EPI growth layers. The more substrate diffuses to EPI, the doping concentration of the interface of substrate and EPI will be higher, the lower voltage EPI can sustain. The EPI which has more layers has higher breakdown voltage and relatively lower threshold voltage, besides the diffusion from substrate to EPI is less when EPI growth's layers are more. Through analysis we found that the real concentration of the interface of substrate and EPI is the main factor which leads to the results. All the simulation is based on a 60 V UMOS process, but takes no account of the industrialized production error. Those results could give researchers a new way to improve the power UMOS device.