Method for processing a semiconductor device

A process for forming backside illuminated devices is disclosed. Specially, the process reduces processing damage to wafers caused by poor bond quality at the wafer edge ring. In one embodiment, a wafer edge trimming step is implemented prior to bonding the wafer to the substrate. A pre-grind blade is used to create a straight edge around the wafer perimeter, eliminating any sharp edge. In another embodiment, edge trimming is performed after the wafer has been bonded to the substrate, and a pre-grind blade is used to remove portion of the wafer edge ring subject to poor bonding quality before grinding. The final thickness of the ground wafer is about 50 microns in either case.