Green chemical mechanical polishing of sapphire wafers utilizing h-BN assisted Al2O3 abrasives

Chemical mechanical polishing (CMP) is currently the predominant technique for achieving optical-grade surface planarization of sapphire substrates. However, conventional CMP slurries often contain toxic and corrosive chemicals, raising significant environmental concerns. To address this challenge, this study presents a novel eco-friendly CMP slurry formulation comprising alumina (Al 2 O 3 ), silicon (SiO 2 ), hexagonal boron nitride (h-BN), sorbitol, aminomethyl propanol (AMP), and deionized water. The incorporation of h-BN, with its layered crystalline structure, enhances interfacial shear stress during polishing, thereby improving material removal efficiency. Furthermore, the modulation of friction mechanisms by h-BN reduces ineffective interfacial interactions, minimizing surface scratch formation. Experimental results demonstrate outstanding polishing performance, with the processed sapphire wafers exhibiting an ultra-smooth surface Ra = 0.578 nm) and a high material removal rate (MRR=3.768 µm·h −1 ). Through comprehensive characterization using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR), we elucidate the synergistic CMP mechanism involving the alkaline slurry and h-BN. The alkaline environment promotes the formation of soluble Al(OH) - 4 species from the sapphire surface, while h-BN facilitates the generation of a softened layer that is subsequently removed through sorbitol chelation. This dual mechanism enables simultaneous achievement of high removal rates and exceptional surface quality. The findings of this study provide valuable insights for advancing atomic-level surface planarization technologies for sapphire and other hard materials, while addressing critical environmental considerations in semiconductor manufacturing processes. • Synergistic effect of h-BN shear layer, sorbitol chelation, and mixed abrasives enhances sapphire MRR and reduces roughness.