Molecular Dynamics Simulation of Single-Crystal Silicon CMP Using Ultrasonic Vibration-Assisted and Hollow Silica Abrasives

Molecular dynamics (MD) simulation of the ReaxFF reaction is used to systematically compare the polishing process of hollow silica abrasive grains on Si (100) substrates under conventional chemical mechanical polishing (CMP) and ultrasonic vibration-assisted chemical mechanical polishing (UV-CMP) methods, revealing the chemical reaction process and material removal mechanism from an atomic point of view. The performance differences between solid silica abrasive grains and hollow silica abrasive grains with different pore sizes were also comparatively analyzed to reveal the influence of the hollow structure characteristics on the polishing performance. It is shown that ultrasonic vibration can accelerate the breaking of chemical bonds on the surface of monocrystalline silicon wafers, which leads to the oxidation reaction with an aqueous solution to generate a lower-hardness oxide layer. Under the parameters of 40 GHz frequency and 12 Å amplitude, optimal removal efficiency and surface quality can be obtained. Under the same loading conditions, the hollow silica abrasive grains exhibit lower hardness and a larger elastic modulus compared with their solid counterparts. As a result, they produce a shallower indentation depth on the single-crystal silicon surface, leading to a reduced atomic removal rate as the hole radius increases. Under an equivalent material removal efficiency, large hollow abrasives can effectively replace smaller solid abrasives. Their larger contact area enhances the chemical reaction efficiency, while the more uniform strain distribution minimizes surface damage. Additionally, their stable thermodynamic stability reduces localized thermal effects and the unique hollow structure helps capture fragmented abrasive grains during polishing to prevent secondary scratches. This study not only deepens the fundamental understanding of ultrasonic vibration-assisted polishing mechanisms but also provides innovative insights for the design of new abrasive grain structures.