High cycle fatigue testing and modelling of sputtered aluminium thin films on vibrating silicon MEMS cantilevers

Abstract

Aluminium is still one of the most important contact metallisations for power electronic chips like MOSFETs or IGBTs. With a large difference in thermal expansion coefficients (CTEs) between aluminium and silicon and the temperatures generated in hot-spots during high power transients, these layers are prone to failure due to thermo-mechanical fatigue. So far, lifetime modelling was done by subjecting dedicated test specimens to the thermal cycling one would expect during normal operation. This paper will propose a novel method for creating accelerated lifetime models of thin aluminium films within the high-cycle fatigue regime by isothermal mechanical loads. The specially designed test stand is suggested to complement or replace expensive and lengthy thermal cycling and allow in-situ monitoring of failure indicators.