Nanohole Morphologies On Photoresist Surface Produced By Low-Energy Ar+ Ion Bombardment Under Normal And Near-Normal Incidence

Random nanohole morphologies on a photoresist surface were produced spontaneously by ion bombardment, from normal to near-normal incidence. At an optimized ion energy, the critical parameters (diameter and depth) and uniformity of these nanoholes can be tailored with multi-ion parameters, including ion fluence (i.e. bombardment time), ion flux, and incidence angle. The temporal evolution of the nanohole structures, at normal incidence, showed growth and stabilization regimes. The mass redistribution effect and the distribution of energy deposition led to the transition from nanoholes to nanoripples, which were deduced from the crater shape evolution at low incidence angles. The incidence angle-dependent evolution of the crater shape (or rim) on the resist surface is consistent with the crater function simulation, and confirms the ion bombardment-induced surface atomic currents and mass redistribution. Finally, X-ray photoelectron spectroscopy characterization confirmed ion bombardment-induced decomposition, in particular, graphitization in the surface layer of the resist.