Reliability of SiC MOSFET Power Modules under Consecutive H3TRB and Power Cycling Stress

Abstract

Power semiconductor modules are subject to both thermo-mechanical stress and electro-chemical stress during field operation. Usually, those stressors are investigated separately and possible interaction of both degradation mechanisms is neglected. In this work, the effect of combined thermo-mechanical and electro-chemical stress is investigated by means of consecutive H3TRB and PCT testing. One test group had been subjected to power cycling before the H3TRB test was performed, while another test group had been exposed to H3TRB stress before the power cycling test. As a reference, devices without preconditioning were tested in both, H3TRB and power cycling and are also used to compare the H3TRB and power cycling performance of the SiC devices to similar silicon devices. The results show, that the SiC devices feature a significantly better H3TRB performance than comparable silicon devices, but are inferior in terms of power cycling performance. Furthermore, the results for both test groups of the combined tests indicate that the failure modes for the previously stressed devices were the same as for the pristine devices and no impact of either preceding stress on the devices' lifetime could be observed. Therefore, the results of this work suggest no interaction between both stressors, at least not for the devices used for this investigation.