Effect of Ceria Abrasives on Planarization Efficiency in STI CMP Process

The strong Ce-O-Si bonding between CeO2 abrasives and SiO2 film surface; i.e., the chemical tooth effect, improved planarization efficiency in CMP using ceria-based slurry as a result of nonlinear behavior of the removal rate. Removal rate is a power function of pressure and relative velocity (i.e., RR = kPαV β ). In particular, the high dependency of removal rate on pressure when α >1 results in a much higher material removal rate in the upper pattern than in the lower pattern. Therefore, the planarization efficiency of ceriabased slurry is better, from initial polishing time to the completion of the polishing step, than that of conventional silica-based slurry with an exponent value of α ≈1.