Effect of Structurally Modified Toluene Diisocyanate-Based Polyurethane Pads on Chemical Mechanical Polishing of 4H Silicon Carbide Substrate.

Abstract

This study investigates the impact of polycarbonate diol (PCDL)-modified toluene diisocyanate (TDI)-based polyester polyurethane polishing pads on the chemical mechanical polishing of 4H silicon carbide (4H-SiC) substrates. Employing a unique metho, PCDL alters the ratio of polyurethane soft and hard segments, facilitating the one-step synthesis of a polishing pad via chemical foaming. The extent of the reaction of isocyanate groups was characterized by Fourier transform infrared spectroscopy, while the changes in the glass transition temperature of the material before and after modification were evaluated using differential scanning calorimetry. The mechanical properties and surface morphology of the modified pad have been systematically characterized. The results showed that compared with the polyurethane polishing pad without PCDL, tensile strength was augmented by a factor of 2.1, the elastic modulus surged by a factor of 4.2, the elongation at break improved by a factor 1.6, and the wear index decreased by a factor of 0.5 by 40 wt.% PCDL loading. Furthermore, the modified pad demonstrated a 14.5% increase in material removal rate and a reduction in surface roughness of 4H-SiC from 0.124 nm to 0.067 nm. Additionally, the compact surface pore structure and enhanced chemical stability in the strong oxidizing slurry of the modified pad enabled superior polishing performance, achieving an ultrasmooth 4H-SiC surface. The study highlights the potential of tailored polyurethane formulations in enhancing polishing efficiency and surface finish in semiconductor manufacturing processes.