Evaluation of double sided lapping using a fixed abrasive pad for sapphire substrates

In this study, the double sided lapping behavior of sapphire substrate using fixed diamond abrasive pad was evaluated. For the lapping process, fixed diamond abrasive pad is used along with the alumina slurry. Triethanolamine (TEA) is used as a dispersant for the alumina slurry. Sapphire removal rate increases with increase in alumina particle to dispersant ratio, lapping pressure and platen speed. However the increase in the sapphire removal rate is highly sensitive to the lapping pressure. The removal rate and surface roughness of sapphire increase with increase in the diamond size used in the pad. The exact role of the diamond and alumina used in the lapping process was identified. The removal rate of sapphire was negligible when the lapping was performed with water. Sapphire removal rate was also found to be negligible when the sapphire was polished using the alumina slurry and IC pad. Thus a synergetic action of diamond particles and alumina abrasives is needed for higher sapphire removal rate. The diamond particles fixed on the pad plays a critical role in the sapphire removal. However, the higher removal rate could be achieved only if the pad surface is conditioned by the alumina particles. Sapphire removal rate of 1 μm/min could be achieved easily at the optimized condition with a good surface quality.