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, KNO
₃
, KCl and K
₂
S
₂
O
₈
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, K
₂
S
₂
O
₈
is slightly better than the other two in the same condition. Furthermore, the removal mechanism of potassium salts for sapphire CMP was analyzed briefly.