Effect of amino acid complexing agents on chemical mechanical polishing performance and action mechanism of C-plane sapphire: Combining experiments and theoretical calculations

Chemical mechanical polishing (CMP) of sapphire faces greater challenges as the performance and processing requirements of sapphire devices continue to improve. Amino acids are often used as complexing agents on CMP because of their high water solubility, environmental friendliness and strong complexing ability. In this study, a combination of experimental techniques and theoretical calculations were used to investigate the effects of glycine (Gly), serine (Ser) and lysine (Lys) as complexing agents on the CMP properties of C-plane sapphire. The existence forms of three amino acid molecules under alkaline conditions were analyzed, and their possible binding modes to sapphire were discovered. Experimentally, it can be found that all three amino acids can improve the performance of C-plane sapphire CMP in different degrees. The measure results of X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) show that the three amino acids can be complexed with the Al(OH)4‒ ions produced by the sapphire to form soluble substance, thus speeding up the removal of sapphire. By calculation, it can be shown that the process of complexation is that the –NH2 and –OH groups in amino acids form covalent bonds with Al atom in Al(OH)4‒. Finally, the complexation capacity of the three amino acids is in the following order: Gly < Ser < Lys. Therefore, this study can confirm that amino acids as complexing agent have a good complexing effect on sapphire CMP, and the addition of –NH2 and –OH groups can help to enhance the complexing ability of the complexing agent, which has a certain good guiding significant for the selection of sapphire CMP complexing agent.