Ion-Induced Mesoplasma Formation and Thermal Destruction in 4H-SiC Power MOSFET Devices

Both experiments and simulations have shown that single-event burnout (SEB), a catastrophic event, occurs at less than half of the rated blocking voltage in commercial 4H-SiC power devices under a heavy-ion strike. The failure was shown to be due to significant impact ionization near the epi/substrate interface. Adding a buffer layer between the drift epi and substrate layers reduces the impact ionization effect and changes the thermal failure location. In this article, the SEB phenomenon in a 4H-SiC power MOSFET utilizing a buffer layer is investigated. Heavy-ion transport and 3-D electro-thermal transient simulations were performed to study the device response to a heavy-ion strike. In examining the time evolution of electric field profile, charge carrier dynamics, and thermal heat transfer, it is determined that the failure mode for this design is the location shift of the mesoplasma (or hot spot) to within the drift epi region, away from the high field area. A sensitivity analysis was conducted to identify the dominant electrical or thermal factors contributing to device failure due to second breakdown. From these simulations, it is found that the semiconductor thermal conductivity is the primary material parameter that influences the mesoplasma formation.