Post-WCMP leakage detection and monitoring on 65-nm devices using an advanced e-beam inspection system

N+/P-well junction leakage was studied with an electron beam (e-beam) inspection system by detection of the gray level of the tungsten plug (W-plug) in the defect images of post tungsten chemical mechanical polish (WCMP) inspection. Leakage results of wafer acceptance tests (WAT) show a strong correlation with the e-beam inspection results. Failure analysis results reveal that the junction leakage is caused by lateral diffusion of nickel silicide underneath the spacer. The extrusion length correlates with the gray level of the tungsten plug very well.