Novel metrology and wafer grinder technologies combine for improved capability for TSV structures

There are significant challenges in obtaining a controlled and consistent remaining silicon thickness (RST) above through silicon vias (TSVs) because of the need to support the thin device wafer, which will often be thinned to less than 100 microns during grinding, by bonding it to a full thickness support wafer made of either silicon or glass. Because grinding systems tend to grind flat surfaces, the challenges arise when the cumulative total thickness variation (TTV) of the various elements in the wafer stack are combined. Rudolph Technologies provides a novel new metrology approach which allows the precise measurement of RST above the vias as well as the ability to characterize the TTV of the adhesive layer and the support substrate. By combining these critical measurements and feeding this information forward to the grinding system, manufactured by Strasbaugh, it is possible to utilize the shape control built into the grinding system to accommodate the unique profiles seen in the stacked wafer combinations and produce a uniform RST regardless of the cumulative error built up in the stack.