Novel method to remove tall diamond grits and improve diamond disk performance

Abstract

A diamond disk is indispensable to dressing chemical mechanical planarization (CMP) polishing pads. Current CMP diamond disks contain numerous diamond grits (approximately 10,000-25,000) on the flat surface of a metal substrate. Although a diamond disk has a regular distribution of grits on its surface, their tips are not of uniform height. Hence, only a small proportion of the grits can penetrate the flexible pad surface, and a large number of grits remain unused on the disk. In this work, we developed a novel technique to find and remove tall diamond grits on a diamond disk to improve the leveling of the diamond tips and increase the number of working grits. We examined an original diamond disk and disks in which three, five, and seven tall diamond grits were removed. We then evaluated the surface characteristics and pad dressing rates (PDRs) as well as the removal rate for a dielectric oxide film dressed with these diamond disks after the removal of the tall grits. We compared the results with those obtained for the original diamond disk. The removal of the tall diamond grits facilitated diamond leveling and helped increase the number of working grits. The PDR decreased as the number of tall grits removed increased. The experimental results revealed that, after the removal of the tall grits, the diamond disk exhibited better non-uniformity and a lower pad consumption rate without damaging the local circuitry. In addition, the lifetime of the pad and disk was prolonged, which should lower the cost of the CMP process.