AFM and XPS studies on material removal mechanism of sapphire wafer during chemical mechanical polishing (CMP)

• Published in: Journal of materials science. Materials in electronics Vol. 26; no. 12; pp. 9921 - 9928
• Main Authors: Zhou, Yan, Pan, Guoshun, Shi, Xiaolei, Gong, Hua, Xu, Li, Zou, Chunli
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.12.2015; Springer Nature B.V
• Subjects: Atomic force microscopy; Characterization and Evaluation of Materials; Chemistry and Materials Science; Materials Science; Morphology; Optical and Electronic Materials; Original Paper; Polished; Sapphire; Silicon dioxide; Slurries; Wafers; X-ray photoelectron spectroscopy; Atomic Force Microscopy; Chemical Mechanical Polishing; Atomic Step; Sapphire; Material Removal Rate
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1007/s10854-015-3668-x

The material removal mechanism of sapphire wafer during chemical mechanical polishing has been studied through X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) measurements. XPS results indicate that alumina silicate (Al 2 Si 2 O 7 ·2H 2 O) is generated on the polished sapphire surface by SiO 2 slurry, otherwise alumina hydrate (AlO(OH)) on the polished surface by H 2 O solution. Meanwhile, ultra-smooth polished surface with extremely low Ra of below 0.1 nm and atomic step structure morphology via AFM is realized using SiO 2 slurry. Through investigating the variations of the surface characteristics polished by different ingredients via the morphology and force curve measurements, it’s reveals that the product-aluminum silicate with stronger adhesion and lower hardness is more readily to generate and be removed than the product-alumina hydrate induced by H 2 O. Thus, except for atomic scale mechanical abrading, the abrasive SiO 2 nanoparticle is used for anticipating in the chemical reaction, resulting in superior surface finish of sapphire wafer with high efficiency.