Wafer contamination and particles resulting from cooling-pad elastomer

A new, ultrapure silicone formulation recently introduced by Genus contains extremely low amounts of impurities. Front- and back-side levels of contaminants were measured on wafers which were implanted aboard a wheel outfitted with disks coated with the new silicone. The levels were exceedingly low. Levels of backside particles and residual oil on wafers were reduced by pre-conditioning the silicone. The pre-conditioning treatment consists of implanting the silicone itself with phosphorus (P). The implant recipe was determined by using a factorial design-of-experiment (DOE) approach. The independent variables were beam current, energy, and dosage. The dependent variables were particle counts and wafer-cooling power. The resulting implant recipe required some compromise between reduction of contaminants and cooling power of the elastomer