Characterizing the contact evolution through the combination of surface roughness parameters in chemical mechanical polishing using a polyurethane polishing pad

The surface texture of the polishing pad used in chemical mechanical polishing (CMP) governs the contact characteristics during material removal. However, quantifying this texture is challenging because of the porous structural characteristics and viscoelastic behavior of polyurethane polishing pads. In this paper, we propose a novel contact characterization parameter that effectively explains material removal by combining it with the polishing pad surface roughness parameter. Experiments were conducted on three types of pads with different surface microstructures, and various combinations of surface roughness parameters were explored using an exhaustive search method based on the coefficient of determination ($R^2$). A two-dimensional parameter derived as the optimal combination of the root mean square height ($R_q$) and maximum peak height ($R_p$) achieved a maximum accuracy of 94.54 % in explaining variations in the material removal rate. This combined parameter demonstrated enhanced explanatory power over single parameters across diverse pad surface conditions and ensured consistently high $R^2$ values without overfitting, even when compared with higher-dimensional combinations. The proposed parameter, representing the relative peak prominence of the overall roughness, enhances our understanding of material removal mechanisms and provides new insights into the contact behavior of surface degradation during continuous wear processes.