Effect of Alkali Metal Ion on Chemical Mechanical Polishing of LiTaO₃

Abstract

Low material removal rate (MRR) and poor surface quality are the two main problems in ultra-precision machining of LiTaO3 wafer. In order to improve the MRR of LiTaO3 in chemical mechanical polishing (CMP), the effect of alkaline metal ion in slurry on the MRR of LiTaO3 was studied. The results show that adding an appropriate concentration of alkali metal ions to the slurry can increase the abrasive particle size and reduce the electrostatic repulsion between the abrasive and the wafer surface so as to enhance the mechanical effect. At mean time, Li+ replaced by K+ on the LiTaO3 wafer to produce easily removed KTaO3. Adding a certain amount of alkaline metal ion to the slurry improves the MRR of LiTaO3 wafer. Finally, when CMP was performed in slurry (pH 9) with a composition of 10 wt% SiO2 and 0.07 M KCl, the MRR of LiTaO3 is 111 nm/min and the surface roughness (Sq) is 0.3 nm.