Copper Chemical Mechanical Polishing Performances of Polystyrene/Ceria Hybrid Abrasives with a Core/Shell Structure

The core/shell structured hybrid abrasives, featuring polystyrene (PS, 280-300 nm in size) cores and ceria (CeO2, 10-20 nm in thickness) shells, were introduced into copper chemical mechanical polishing (CMP) processes. The slurry chemistry based on the synergy among glycine-hydrogen peroxide-benzotriazole was used in combination with the obtained polystyrene/ceria (PS/CeO2) abrasives. Moreover, the use of a medium/high-hardness pad (IC-1000) was compared to the use of a soft pad (MD-Chem). The copper CMP characteristics were evaluated in terms of material removal rate, surface roughness as well as cross-sectional profile analyses. After CMP with PS/CeO2 hybrids in combination with a soft pad, the average roughness of copper layer decreased from 1.89 to 0.56 nm, and a mean removal rate of 254 nm/min was achieved. With respect to conventional ceria particles, the PS/CeO2 hybrid abrasives contributed to the reduction of the mechanical damage and the number/depth of scratch/pit. The improved copper CMP performances might result from the reduced overall hardness and elastic modulus of PS/CeO2 hybrid particles. These experimental results revealed that the PS/CeO2 composite abrasives further presented potential CMP applications for mechanically challenging materials such as copper and low-k dielectrics.