Adhesion and Removal of Silica and Ceria Particles on the Wafer Surfaces in STI and Poly Si CMP

The purpose of this study is to investigate the effects of slurry pH on the adhesion and removal of silica and ceria abrasive particles on the poly Si, TEOS, SiN and SAC (self aligned memory cell contact) and STI (shallow trench isolation) patterned wafer surfaces. The adhesion force of silica and ceria particles were theoretically and experimentally investigated in STI and poly Si CMP process. A stronger adhesion force was observed for silica particles on the poly Si wafer in acidic rather than in alkaline solutions. The adhesion force of ceria particle was lower than that of silica in investigated pH ranges. STI patterned wafer showed lower adhesion force than SAC patterned wafer. Lower adhesion force between particles and surface resulted in a lower level of particle contamination.