Features of the triggering mechanism for single event burnout of power MOSFETs

The feedback mechanism leading to second breakdown and burnout in a power MOSFET is reviewed, and critical device design parameters are identified and chosen with regard to electrical specifications. Assuming typical parameters, the avalanching conditions in the space-charge region of the collector current densities. It is shown that the space charge associated with the collector current density modifies the electric field profile so that with increasing collector current, the avalanche multiplication factor rises in a peak, then declines to a valley, and eventually rises monotonically. This behavior can be explained in simple terms and could lead to a stable avalanching condition with a current density too low to damage the structure. This condition can be initiated by heavy ions with energies below a certain threshold. Ion energies beyond the threshold drive the avalanching process into the region of monotonic increase of the avalanche multiplication factor and lead to runaway and burnout. The threshold for runaway varies widely with changing configurations of the p/sup +/-plug and the p-body region, suggesting the possibility of configurations that are immune to burnout. Threshold currents in a typical hex cell are assessed.>