Defect detection in unpolished Si wafers by digital shearography

Abstract

Defects in silicon wafers have been of great scientific and technological interest since beforethe earliest days of the silicon transistor. Recently much attention has been focused oncrystal originated pits on the polished surface of the wafer. These defects have been shownto contribute to gate dielectric breakdown. The present work relates to surface and/orsubsurface defect inspection systems for semiconductor industries and particularly to aninspection system for defects such as swirl defects and groups of particles in unpolishedsilicon wafers before the wafer reclamation and/or the wafer fabrication process using adigital shearography technique. The method described here relates specifically tosemiconductor wafers, but may be generalized to any other samples. In the present work,surface or subsurface defects are detected and evaluated by stressing the silicon waferwhile looking for defect-induced anomalies in a fringe pattern, generated by theinterference of two speckle patterns, in the CCD camera and digital image processing.