First observation on the feasibility of scratch formation by pad–particle mixture in CMP process

Micro-scratch formation on a post-chemical mechanical polishing (CMP) wafer surface is one of the critical problems that should be solved for miniaturization and reliability of a semiconductor device. In this study, the mechanism of micro-scratch formation during CMP was investigated through experiments and simulations. When a used pad was utilized in the experiments, it was found that micro-scratches could be generated by the polishing process that was done with DI water and additive only without abrasive particles. In order to analyze these micro-scratches under a used pad process, the change in surface properties of the polishing pad before and after the CMP was investigated using various surface sensitive techniques. In addition, 2-dimensional finite element analysis (FEA) of CMP process was performed to verify the experimental results. Especially, the FE model with a particle put inside a pad pore was considered to examine how it plays a role in micro-scratch generation. In summary, the scientific results from experiments and simulations in this study first revealed that the pad–particle mixture could be formed on the pad surface during CMP process, which would be one of the major factors leading to micro-scratch generation.