Simulation of Fatigue Damage in Clusters of DMOS Cells Subjected to Non-Uniform Transient Thermo-Mechnical Loading

Numerical predictions of thermo-mechanical fatigue in power semiconductors are carried out under consideration of transient thermo-mechanical loading conditions. An existing approach to model bulk fatigue damage is extended towards the usage of more general transient thermal loading conditions. To fully capture the effects of the forming fatigue cracks, a transient simulation of the thermal fields is sequentially coupled with the calculation of mechanical fields. This enables the application of the fatigue framework in larger structures featuring complex thermal boundary conditions and allows to capture the effect of fatigue cracks on thermal fields. For demonstration purposes, the developed bulk fatigue approach is applied to a generic copper-on-silicon geometry which is exposed to temperature pulses similar to cyclic overload switching in DMOS cells. Results of such generic copper-on-silicon geometries under various transient thermo-mechanical loading conditions are presented. The results highlight the novel capabilities of the extended framework and provide some qualitative statements regarding the influence of non-trivial temperature fields in power semiconductors on the thermo-mechanical fatigue behavior.