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.