Determining the effect of slurry flow rate on the tribological, thermal and removal rate attributes of copper CMP

Chemical mechanical polishing of copper using is examined experimentally and theoretically as a function of slurry flow rate and the product of the applied wafer pressure and relative sliding speed (pV), It is observed that under constant tribological conditions, the removal rate at any fixed value of pV generally decreases as the slurry flow rate increases. This is explained as a reduction in reaction rate due to increased cooling of the wafer surface by the slurry. At a fixed flow rate, it is further observed that the removal rate does not necessarily increase monotonically with pV. The rate may instead depend on the particular pressure and velocity chosen at a fixed value of their product, The dependence occurs through the coefficient for convective heat transfer between the wafer and the slurry, and the heat partition factor, which determines the fraction of the total factional power that heats the wafer. Rates are found to be explainable with a Lagmuir-Hinschelwood model with mechanical and chemical components.