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Chen G.,Tsinghua University | Chen G.,Guangdong Provincial Key Laboratory of Optomechatronics | Luo G.,Tsinghua University | Luo G.,Guangdong Provincial Key Laboratory of Optomechatronics | And 5 more authors.
Micro and Nano Letters | Year: 2016

Colloidal silica with different dispersion states during silicon chemical mechanical polishing (CMP) are investigated in detail. As the dispersion of colloidal silica is improved, the roughness (Ra) decreases gradually during polishing. The silicon surface has a minimum Ra of 0.118 nm when the polydispersity index of particles is 0.078. Comparing with surface polished by colloidal silica in poor dispersion, the surface quality has great improvement. The important role of dispersant is presented by the results of investigations. The research results indicate that dispersant makes aggregate micelles dispersed into many smaller uniform colloidal silica particles. The uniformly dispersed colloidal silica forms a thin film between the surfaces of silicon and polishing pad during CMP, which is beneficial for the stability of friction, and therefore greatly decreases roughness of silicon surface after polishing. © The Institution of Engineering and Technology 2016. Source

Zhou Y.,Tsinghua University | Zhou Y.,Guangdong Provincial Key Laboratory of Optomechatronics | Pan G.,Tsinghua University | Pan G.,Guangdong Provincial Key Laboratory of Optomechatronics | And 8 more authors.
Journal of Materials Science: Materials in Electronics | Year: 2015

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 (Al2Si2O7·2H2O) is generated on the polished sapphire surface by SiO2 slurry, otherwise alumina hydrate (AlO(OH)) on the polished surface by H2O 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 SiO2 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 H2O. Thus, except for atomic scale mechanical abrading, the abrasive SiO2 nanoparticle is used for anticipating in the chemical reaction, resulting in superior surface finish of sapphire wafer with high efficiency. © 2015 Springer Science+Business Media New York Source

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