High Precision Wafer Thinning Using Ultra-low-TTV Glass Carrier and Novel Temporary Bonding

Wafer thinning is a critical part of device making and advanced packaging in semiconductor manufacturing. Carrier-supported wafer thinning becomes attractive when the final wafer thickness becomes very thin, say <100um, due to handling difficulties. Post-thinning processing (deposition, CMP, bonding etc.) also benefits from having a rigid and thermomechanically stable support structure. In order to achieve very low total thickness variation (hereafter abbreviated as TTV) of the final wafer, both the carrier wafer and the temporary bonding material, typically an adhesive layer, must deliver sufficiently low TTV. The carrier wafer also must have a suitable coefficient of thermal expansion (CTE). In this paper, we describe a glass carrier solution and a novel temporary bonding method that combine to enable low TTV wafer thinning. Feasibility demonstration is done using a 150mm diameter single crystal lithium tantalate wafer, and thinning reaches 5um with wafer grinding alone.