Three-dimensional wafer-scale copper chemical–mechanical planarization model

Abstract

Models based on slurry hydrodynamics, mass transport, and reaction kinetics are developed in order to predict the removal rate of copper on a wafer-scale during chemical–mechanical planarization (CMP). The steps in the copper removal model include: mass transport of the oxidizer to the wafer surface; reaction of oxidizer with copper to form a reacted layer; and subsequent removal of the reacted layer by mechanical abrasion. The rates of the chemical reaction and mechanical abrasion steps are described by separate kinetic parameters. For low oxidizer concentrations the chemical step controls the process, while for high concentrations the mechanical step controls. The model shows that mass transport of the oxidizer to the surface controls the removal process at higher removal rates and can cause wafer-scale non-uniformity. Copper CMP experiments with potassium dichromate based slurry are compatible with the proposed surface kinetics steps and showed that the surface kinetics controlled the removal process for this slurry.