Nanoconfinement Effect on the Mechanical Behavior of Polymer Thin Films

Abstract

AbstractNanoimprint is one of the most promising fabrication techniques for nanoelectronics. The main feature of this process is the compression of a thin film of a polymer resist by a rigid mold to produce a surface pattern. Hence, nanoimprint is essentially a mechanical forming process that depends greatly on the nanoscale mechanical behavior of the plastically deformed polymer film. Consequently, basic understanding of nanoimprint mechanics is imperative for improving pattern quality, reproducibility, and automation. The objective of this study was to elucidate the mechanical response of thin polymer films subjected to nanoindentation loading. Three deformation regimes were identified in the experiments performed with poly(methyl methacrylate) (PMMA) films of thickness in the range of 200-400 nm with a Berkovich tip of nominal radius of curvature equal to 100 nm. A three-layer model consisting of surface, intermediate, and interface layers was introduced to explain the mechanical response of the indented PMMA films. The spatial constraints imposed to the plastic flow of the interface layer by the rigid indenter and substrate surfaces produce a dynamic effect, demonstrated by the loading rate dependence of the deformation response. This phenomenon is of great importance to polymer plastic flow in nanoimprinting.