Effects and mechanisms of different types of surfactants on sapphire ultrasonic polishing

The effects of three different types of surfactants, including cationic surfactant cetyltrimethylammonium bromide (CTAB), anionic surfactant sodium dodecyl benzene sulfonate (SDBS), and nonionic surfactant fatty alcohol polyoxyethylene ether (AEO), on sapphire ultrasonic polishing (UV-CMP) were studied. Through XPS, SEM, surface tension, zeta potential and particle size analysis, the implications of surfactants on the chemical products, abrasive adsorption, and material removal rate (MRR) of sapphire surface were investigated. The findings indicate that AEO and SDBS result in a certain degree of abrasive agglomeration and slight particle size increase due to hydrogen bonding and electrostatic repulsion respectively. The cationic surfactant CTAB exhibits significant agglomeration of abrasive particles due to electrostatic attraction, and causes the increase in particle size. The slurry’s surface tension is directly proportional to sapphire MRR within a certain range. The polishing effects are the best when 0.10% CTAB is added. Sapphire MRR is 80.50 nm/min, which is nearly twice as much as that of the slurry without surfactants. The surface roughness is 0.200 nm after polishing.