Reaction removal mechanism of polished single crystal sapphire wafers in pure water medium
The atomic-level reaction removal mechanism of SiO2 polishing sapphire in aqueous solution was studied by reactive molecular dynamics simulation,and verified by polishing experiments.Simulation results show that:in the reaction process,H2O molecules will be adsorbed on the sapphire surface,and bonded with the Al atoms of sapphire,forming Al—H2O and Al—OH chemical bonds,so as to achieve the"softening"of the surface of the sapphire substrate.Then,under the action of abrasive particles,the Al atoms of the workpiece are removed in the form of Si-O-Al chains.The surface composition of the processed sapphire wafers was analyzed by XPS,and the abrasive chips were observed by TEM analysis and the atomic energy spectrum was calculated.Experimental results show that there is a chemical reaction between SiO2 and aqueous solution during the processing of sapphire,resulting in the formation of a soft reactive layer consisting of aluminum silicate containing Si-O-Al bonding(Al2SiO5)and hydrated aluminum oxide(AlOOH),which is ultimately removed by the mechanical action of the abrasive.
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