Experimental and numerical analysis of an inhibitor containing slurry for copper chemical mechanical planarization

A slurry containing Benzotriazole (BTA) as the inhibitor was analyzed in terms of its frictional, thermal and,kinetic attributes;for copper CMP applications. The frictional analysis indicated that 'boundary lubrication' was the dominant tribological mechanism. Due to the presence of the inhibitor in the slurry, copper removal rate exhibited a highly non-Prestonian behavior. Based on the measured coefficient of friction (COF) and pad temperature data, a proven thermal model was used to predict wafer temperature. The Preston Equation was used to describe the polishing rate when p x V was lower than 11,000 Pa(.)m/s; while a modified Langmuir-Hinshel wood kinetic model was used to simulate the copper removal when p x V was higher than 11,555 Pa(.)m/s. Assuming that the adsorbed inhibitor layer was abraded off instantly from the copper surface when p x V was higher than 11,555 Pa(.)m/s, the modified Langmuir-Hinshelwood kinetic model indicated that copper polishing was chemically limited in this polishing region.