Defect reduction of replacement metal gate aluminum chemical mechanical planarization at 28 nm technology node

Abstract

The replacement metal gate (RMG) defectivity control is very challenging for high-k metal gate (HKMG) RMG chemical mechanical polishing (CMP) processes. In this study, three major defect types, including fall on particle, micro-scratch and corrosion, post Al metal CMP process have been investigated to provide the total solutions for preventing the formation of these defects. The fall on particles were fully removed as a repulsive force created between the surfaces of the Al metal gate and polishing abrasives by introducing appropriate acid based slurries and chemical solutions. Furthermore, the micro-scratches could be significantly eliminated as implementing a reliable soft pad at the final polishing step. Severe integranular corrosion and pitting issues on the surface of the RMG structures were also found to be effectively prevented by creating a capable passivation layer with minimized micro-galvanic corrosion level on the top surface of the Ti-doped Al metal gate structures.