Pad surface thermal management during copper chemical mechanical planarization

A pad surface thermal management system was developed to improve copper removal rate within wafer non-uniformity by locally adjusting the pad surface temperature. The system consisted of one or more thermal transfer modules, which contacted the pad surface during polishing. Hot or cold water circulated between the thermal transfer module and an external heater or cooler. With the module placed on the pad surface, heat conduction occurred between the module and the pad surface, producing a localized pad surface with higher or lower temperatures. As such, it was expected that local removal rates would change accordingly due to the temperature-sensitive nature of copper chemical mechanical planarization (CMP). In this study, the system was used to adjust the "center-fast" removal rate profile to illustrate its effect during the process. Results showed that, when two thermal transfer modules were employed, local removal rates in the wafer center region decreased significantly while the removal rates near the wafer edge were maintained thereby significantly improving within wafer removal rate non-uniformity.