Molecular-scale change in the surface properties of silica and copper in pure water with time

We aimed to understand one of the fundamentals of how silica and copper surfaces are flattened on the molecular scale by the chemical mechanical polishing (CMP) method, which is used in the fabrication of semiconductors. In particular, we examined whether even pure water affects the properties of silica and copper surfaces. This study used the atomic force microscope to detect how the morphologies, normal interaction, and friction forces of the silica and copper surfaces changed with their exposure time to water. We found that the surface properties of even the silica surfaces changed on the molecular scale when the surfaces were exposed to water for a sufficiently long time. In the case of copper, the surface properties were observed to undergo rapid changes. Gel-like layers were detected on the copper surface within a few minutes, even though copper surfaces oxidized by ambient air are considered to be rather stable to water.