Effect of Potassium Salts on the Chemical Mechanical Polishing Efficiency of Sapphire Substrate

Sapphire substrate is the most commonly used material in semiconductor industry for GaN-based light emitting diodes (LEDs). Chemical mechanical polishing (CMP) is one of the most effective methods to achieve atomic-scale smooth surface. The effect of potassium salts on the CMP removal rate and surface roughness of sapphire substrate was investigated. In this paper, KNO3, KCl and K2S2O8 were used as an additive in sapphire slurry, respectively. From the result, it is found potassium salts can significantly improve the removal rate of sapphire substrate. Meanwhile, K2S2O8 is slightly better than the other two in the same condition. Furthermore, the removal mechanism of potassium salts for sapphire CMP was analyzed briefly.