Leakage monitoring and control with an advanced e-beam inspection system

Abstract

Junction leakage control is studied with electron beam (e-beam) defect inspection after tungsten chemical mechanical polishing (WCMP). Leakage-induced bright voltage contrast (BVC) defects are detected. For both wafer to wafer (WtW) and within wafer (WiW), e-beam inspection results strongly correlate with leakage results of wafer acceptance test (WAT). Failure analysis results showed that the junction leakage was caused by lateral diffusion of nickel silicide (NiSi) underneath the spacer. The extrusion length correlates with gray levels of the tungsten plug very well. In this study we found the optimized condition to suppress junction leakage and also confirmed that post WCMP e-beam inspection can be used to monitor and control junction leakage.