Edge trimming for surface activated dielectric bonded wafers

Abstract

The impact of the edge trimming process on permanently bonded wafers is described. The edge trimming process is a blade sawing process applied on the Si wafer edge and bevel, removing the fragile edge of the wafer prior to grinding. We investigated two routes for the integration on permanently bonded Si wafers, edge-trim before bonding and edge-trim after bonding. The impact on the subsequent processes for both integration routes is assessed. For the case of edge-trim before bonding, a combination of functional water cleaning such as ozone dissolved in water and ammoniac scrub cleaning shows a significant effect to remove Si residues, enabling void free dielectric bonding. For the case of edge-trim after bonding, utilizing a small grit diamond blade shows no mechanical failures into the dielectric bonding interface. These proposed processes are a very promising for the fabrication of extreme thinned Si without mechanical failure at wafer edge.