Modeling copper CMP removal rate dependency on wafer pressure, velocity, and dissolved oxygen concentration

A controlled atmosphere polishing system (CAP) was used to identify differences in copper chemical mechanical polishing (CMP) removal characteristics by changing oxygen partial pressure. A two-step kinetic mechanism was proposed, including a copper surface passivation layer formation and subsequent removal. A semiempirical, two-parameter model has been developed to simulate removal rates for multiple wafer pressures, pad-wafer velocities, and oxygen concentrations. The model accurately predicts removal trends with calculated root-mean-square errors of 77-125 Amin. A major advantage of the CAP system is that a point-of-use gaseous oxidant was successfully used to polish copper substrates, and slight changes in oxidant partial pressure were found to significantly affect removal rate trends.