Numerical Simulation of Thermal Runaway Phenomena in Silicon Semiconductor Devices

A mathematical model for heat production due to thermal excitation of conductive electrons and positive holes in semiconductor pn junction is derived and discussed. The model is applied to simulate the thermal runaway phenomena in power electronics semiconductor devices. Our discussion focuses especially on the modeling of unexpected huge current due to excessive temperature rise. Calculated dynamics of temperature distributions of silicon wafer while cooling performance decreases proved it possible that silicon wafer might be heated over its melting point in a few miliseconds. Our results indicate that if local hot spot arises in wafer, thermal excitation of intrinsic carries increases diffusion current of minor carriers and recombination current in depletion layer of pn junction. And it appears to be important that cooling performance should be uniform on the wafer to avoid the growth of hot spots and thermal runaway itself.