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.

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The adhesion force and removal of alumina particles on Cu, Ta, TEOS, SILKTM, Aurora and FSG wafer surfaces were experimentally and theoretically investigated in slurry solutions of different pHs. These wafer surfaces showed negative zeta potentials in the investigated pH ranges with exception of FSG and Ta. However, the zeta potentials of FSG surface drastically decreased with increasing pH. The lowest adhesion force and smallest number of alumina particles were measured between alumina particle and FSG surface in a slurry solution of pH 11. Alkaline slurry was much more desirable in controlling the level of particle contamination during Cu CMP. The pH of the slurry and zeta potentials of the surfaces played important roles in controlling the interaction force.

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