Investigation on the material removal mechanism of sapphire wafer by novel green slurry in semi-fixed abrasive polishing

Abstract

It is a great challenge to produce ultra-smooth surface of sapphire wafers at high material removal rate (MRR) using green slurry in semi-fixed abrasive polishing. A novel environmentally friendly polishing slurry was developed by preparing abrasives and complexing agents to improve surface quality and polishing efficiency. The SiO₂ and diamond/SiO₂ composite abrasives were successfully prepared by a simplified sol-gel strategy, exhibiting high purity, homogeneous particle size, and excellent dispersibility. Based on the semi-fixed polishing technology, the green polishing performance of sapphire wafers using different types of abrasives alone and in combination with complexing agents was investigated. The experimental results demonstrated that the novel slurry containing triisopropanolamine (TIPA) and diamond/SiO₂ composite abrasive had superior polishing performance. Compared with the traditional diamond slurry, the surface roughness of the novel slurry was reduced by 24.4 % to 6.2 nm (Ra), while the MRR was increased by 65.4 %. Through electrochemical experiments, molecular simulations, and infrared analysis, the improved polishing performance of the composite abrasives with TIPA may be attributed to the complexation of TIPA and the optimization of interfacial contact behavior. The analysis of wear debris and polished sapphire wafer surface further pointed out that the deformation reduced the indentation depth while enhancing the reactivity of the friction chemistry. The diamond/SiO₂ composite abrasives with TIPA slurry accelerated the generation and removal of the reaction layer consisting of AlOOH, Al-OH, and Al₂Si₂O₇, realizing the optimal synergy between mechanical wear and tribochemistry, which significantly improved the polishing quality.