Flash heating in chemical-mechanical polishing

The chemical reaction temperature in the chemical step of chemical-mechanical polishing can be modeled by a simple compact model in which the temperature rise above ambient has the form of a power law in the sliding speed. Analytical modeling of heating of the wafer by pad asperities suggests that the local wafer temperature rise above ambient is approximately the sum of a pad leading edge temperature increment plus a flash heating increment. One of the factors in the flash temperature rise is the fraction of frictional heat transferred to the pad. Finite element heat transfer analysis of lubricated sliding contact of an asperity against a workpiece indicates that the heat transfer factor can be approximated very well by a power law in the velocity, explaining why the simple compact model works. Furthermore, the detailed thermal analysis makes it possible to relate reaction temperature parameters to basic pad, slurry and lubrication layer physical properties. Applications are shown for copper polishing.