Cosmic ray induced failures in high power semiconductor devices

Abstract

Recently it was discovered that cosmic rays can induce failures in large area, high voltage power semiconductors. The effect is of considerable practical significance and has caused a series of equipment malfunctions in the field. We show that earlier attempts to model the physical process of failure are inadequate and introduce a new model. From the new model we derive a phenomenological law for the failure rate as a function of simple design parameters. The law has only two adjustable parameters and the parameters have a simple physical interpretation. In particular the parameter which describes the slope of the extrapolation curve from test to field conditions can be calculated from first principles and shows good agreement with the experimentally found value. This gives high confidence in the validity of the extrapolation law. We give mathematical expressions and diagrams to quantify the safe operating conditions with respect to the cosmic ray failure mode for all high voltage power devices. This allows the user to design reliable power electronic equipment and the semiconductor manufacturer to design devices virtually immune against this failure mode.