Molecular Dynamics Analysis on the Behavior of Water and Alcohol Liquids on a OH-Terminated SiO_2 Surface

摘要

In this study, we carried molecular dynamics (MD) simulations of water and various alcohol liquids on a flat SiO_2 surface terminated by hydroxyl groups in order to examine the microscopic structures of these liquids near the solid surface and diffusion property for the fundamental understanding of the wet process during the semiconductor fabrication. As an equilibrium state, water as well as methanol, ethanol and isopropyl alcohol (IPA) molecules formed a multiple layered structure on the solid surface; however, the microscopic structures were remarkably different between water and IPA liquids because the IPA molecules in the first adsorption layer strongly adsorbed on the solid surface through the hydrogen bond with the surface hydroxyl groups with directing hydrophobic CH_3 groups toward the second layer. Non-equilibrium MD simulations of the dilution of water/IPA adsorption layer by IPA/water solvent revealed that the strongly adsorbed IPA layer can easily be replaced by water molecules.