Chemical-Mechanical Polishing of Copper Wafers Utilizing an Eco-Friendly Slurry

— Sapphire crystals, renowned for their exceptional mechanical and optical properties, have increasingly found applications in both defense and civilian sectors. These applications demand high processing efficiency and superior surface quality. Fixed abrasive polishing (FAP) technology, utilizing diamond abrasive pads, is widely adopted due to its high efficiency, controllability, cost-effectiveness, and environmental benefits. However, FAP suffers from a rapid decline in polishing efficiency and ineffective self-correction. This study explores the use of free abrasives (alumina and silica particles) to enhance the self-correcting capabilities of FAP in sapphire polishing, leading to the development of a novel polishing process. To investigate the impact of free abrasives on the polishing process, three methods were designed: FAP polishing without free abrasives, FAP polishing with free abrasives, and polishing using only free abrasives. The study compared material removal rates (MRR), surface roughness (Ra), and topography of both the sapphire and FAP (including the distribution of diamond abrasives and the presence of holes due to abrasive drop-out) after polishing. The results indicate that the material removal rate of sapphire is lowest with FAP polishing without free abrasives, intermediate with free abrasive-only polishing, and highest with combined FAP and free abrasives, achieving an MRR of approximately 80.1078 nm/min and an Ra of about 24 nm. The data and topography analysis suggest that free abrasives significantly enhance the self-correcting capability of FAP, thereby increasing the material removal rate.s