Effects of residual stresses on cracking and delamination risks of an avionics MEMS pressure sensor

Abstract

Silicon based pressure sensors often take advantage of piezo-resistive gages which are normally embedded by multiple silicon oxide and silicon nitride layers where gold lines form a Wheatstone bridge. As a result of manufacturing - stepwise deposition of multiple layers - significant layer residual stresses occur in the GPa range in tension and compression. But also anodic bonding of the silicon MEMS device on usually glassy substrates results in additional initial stresses. Especially in avionics MEMS applications such stresses by far exceed the stresses arising under sensor operation and determine the major risks for cracking and delamination. Furthermore, those stresses could lead to a signal drift of the overall sensor over a long period of time - another important trustworthiness risk.