Numerical Analysis on Power Semiconductor Die Passivation Layer Stack Structure Behavior

Wide bandgap power semiconductors are considered as important carbon-neutral enablers due to their high power conversion efficiency with excellent switching performance. As performance approaches higher physical levels, the reliability of wide-bandgap power semiconductors is also of increasing concern. A typical wide bandgap power semiconductor die has layer stack arrangement on top. The thin and brittle layers in this stack layer structure are susceptible to thermomechanical stress during switching of high voltages. The relevant reliability limitations severely impact the commercial sustainability and widespread implementation of high voltage wide bandgap semiconductors.Present study demonstrates a fundamental understanding of cracking in stack layer structure of Z-shape nitride passivation layer. ANSYS Workbench has been utilized with sub model technique. Based on original package design, a series of modifications and improvements are issued and assessed through four representative cases. The layer stack structure multi-component system response mechanism to these modification and further effects on related Z-shape nitride risk regions are investigated. As the three dominant components to determine passivation layer stress, metal layer, EMC and the material atop stack layers are analyzed regarding their contraction direction and extent, as well as resulting impacts on Z-shape passivation layer deformation state. Two behavior categories are summarized which can provide possible improvement directions based on corresponding observations and requirements, and can serve as a reference in future die structure design.