Characterization and Optimization of the Cmp Process

In the Chemical Mechanical Polishing (CMP) process used for microelectronics manufacturing, three contact regimes between the wafer surface and the polishing pad may be proposed: direct contact, mixed or partial contact, and hydroplaning. An effective in-situ method for characterizing the wafer/pad contact and a systematic way of relating contact conditions to the process parameters are both lacking. In this work, the interfacial friction force, measured by a load sensor on the wafer carrier, characterizes the contact conditions. Models that relate the friction coefficient to the applied pressure, relative velocity, and slurry viscosity are developed and verified by experiments. Additionally, a correlation between friction coefficient and the material removal rate (MRR) is established. The effects of process parameters on the Preston constant are investigated. Process optimization methods based on extending the high-material-removal regime are also suggested and discussed.