The effectiveness of CVD thin film backside gettering on n-type CZ silicon wafers for CMOS technology has been investigated using optical techniques for bulk microdefect analyses and transmission electron microscopy for interfacial structure study. The deposition of LPCVD polysilicon (500-2000 nm), silicon nitride (150 nm), or poly/nitride films on the backside of Si wafers was found to enhance the bulk precipitation. Bulk microdefect density increased as the thickness of polysilicon increased. At the polysilicon/silicon interface, no extended line defects from polysilicon were observed. Based on the results of minority carrier lifetime and oxide breakdown measurements, the best gettering efficiency was given by 1300 nm polysilicon backside gettering scheme.