Polishing Characteristics of Hydrophilic Pad in Chemical Mechanical Polishing Process

This article presents a hydrophilic chemical-mechanical polishing pad that uses a submicron graphite-particle impregnated polyurethane matrix to enhance slurry absorption. We investigated pads containing four different graphite contents of 0, 5, 15, and 25 wt%. Two diamond disks, one brazed, and one polycrystalline, were used to dress the polishing pads to create slurry supply and removal channels. The hydrophilic pad's contact angle, wear rate, slurry flow rate, and dielectric oxide-film removal rate are compared with the corresponding values for a conventional porous polishing pad. Pad contact angle decreases with increasing graphite content. Material removal rate (MRR) increases with graphite content, up to an optimal 15 wt%. Further increases in graphite content lead to a decrease in removal rates. The wear rate of the hydrophilic pad is reduced by approximately 20-30%, compared to the porous pad. The maximum removal rate for the hydrophilic pad is obtained at a slurry flow-rate of 120 mL/min, while that for the porous pad occurs at a flow-rate of 160 mL/min. Slurry and pad consumption account for most of the costs of chemical mechanical polishing (CMP) processing; using the hydrophilic pad afford a reduction in consumable cost. The hydrophilic pad offers the additional benefit of using a polycrystalline diamond disk as the diamond dresser. Our findings can help in the development of more efficient polishing pads, and provide reductions in the number of pads used, and the amounts of slurry consumed.