Reducing edge roll-off during polishing of substrates

Demand for reducing edge roll-off during polishing of substrates such as silicon wafers and glass disks has currently exceeded the capabilities of existing technologies. To address this problem, in previous studies, we have proposed that the use of double-layered polishing pads with a thin upper layer can reduce the edge roll-off of workpieces, resulting in improving surface flatness near the workpiece edge. However, such polishing pads have serious problems for practical use. In this study, we investigate the polishing factors required to suppress the concentration of contact stress near the workpiece edge. Based on the results, we propose two types of polishing pads and a polishing condition. Polishing experiments on silicon wafers reveal that the proposed polishing pads and polishing condition effectively improve edge-site flatness.