Localization of gate oxide integrity defects in silicon metal-oxide-semiconductor structures with lock-in IR thermography

Abstract

A technique to image gate oxide integrity (GOI) defects across large gate areas has been developed. First, a low-ohmic bias pulse is used in order to break down nearly all GOI defects in a large area metal-oxide-semiconductor (MOS) structure. Then a periodic bias of typically 2 V is applied and the local heating caused by the leakage current through the broken GOI defects is imaged by infrared (IR) lock-in thermography. This method allows us to detect very small temperature variations down to 10 μK at a lateral resolution down to 10 μm. The determined defect densities in Czochralski silicon materials with various densities of crystal originated particles are in good agreement with charge-to-breakdown measurements of small area MOS capacitors. In conclusion, IR lock-in thermography provides a fast and reliable imaging technique of the lateral GOI defect distribution across the entire wafer area.