Stacked Polysilicon/Metal Capacitors Failure Analysis

摘要

Poly/metal stacked capacitors present challenges in terms of capacitor access and defect localization. The challenge of access can be overcome using parallel lapping to expose the contact and using chemicals to remove the dielectric. As for defect localization, LC or thermal localization (also OBIRCH/TIVA) and PVC are used. PVC was found to be effective in terms of finding the bad stacked capacitor and a bad capacitor within the stack. Internal probing between the capacitors within a stack allowed the differentiation between capacitor leakage and capacitor-capacitor shorting. For capacitor leakage, the defect can be identified by parallel lapping to remove the upper capacitor plate. For capacitor-capacitor short, if there is no visual defect seen, Pt chemical etch can be applied for PVC inspection.