Local metal segregation as root cause for electrical shorts in highly doped pressure sensor devices

Abstract

The fabrication of pressure sensor dies for precise and stable industrial applications requires a critical high dose implantation process strongly affecting the manufacturing yield of these devices. This paper describes a specific critical process related failure mechanism caused by this implantation process generating local electrical shorts within the piezo resistive structures in-built in the doped silicon substrate surface. The defect signature was investigated by applying site specific localization, advanced target preparation strategy and high-resolution electron microscopy to understand its process related root cause. The electrical shorts could be localized by Lock-in Thermography (LIT) and then were prepared by advanced laser and focused ion beam (FIB) based preparation in both cross-section and plan-view direction for in-depth investigation of the crystal defect signature by high resolution transmission electron microscopy (TEM) analysis in combination with energy dispersive X-ray spectroscopy (EDXS). As a result, the defect mechanism could be identified as segregation of embedded metal residues caused by Fe and Ni contamination from the high dose implantation equipment.