Time Evolution of Single-Event Burnout in Vertical Power MOSFETs and Implications for Mitigation Strategies

In this paper, we analyze the thermomechanical effects occurring in a power DMOS transistor after a single-event burnout process. This paper focuses on simulation to determine a safe time at which the device should be disconnected from the power supply to prevent damage. This strategy has been proposed as a means to avoid dangerous values in the temperature or mechanical stress that can produce a catastrophic failure or compromise the reliability of the DMOS. We solve the problem with the finite element method, modeling the DMOS with a detailed simulation structure. In this paper, we show that it is not possible to assume that the temperature and stresses relax after power supply disconnection. Consequently, it is necessary to simulate the power down of the device for analyzing the evolution of the fields after disconnection. The simulation results show the existence of mechanical stress overshoots after disconnection. We show that the upper limit for the disconnection time is considerably different from the reported one in previous research.