Fabrication of Differently Shaped Polymeric Nanoneedle Arrays via Multistep Plasma Etching Using Silica Microparticles as Masks

We established a method to produce differently shaped polymeric nanoneedle arrays using silica microparticles by using multistep plasma etch processes. The etching conditions of each step were determined by exploring etching parameters such as power, bias power, gas composition and amount, pressure and time. The silica microparticles became unstable and irregular nanoneedle arrays were formed due to difference of etching rates between silica and polymer when silica microparticles were etched continuously in one step. Through the introduction of stabilization step in which selective etching is done on silica microparticle to reduce the diameter of silica microparticles and hence to move the center of mass of the silica microparticle inward, the instability of silica mask was removed and irregularity of nanostructures was minimized. As a result, multistep etching process to fabricate polymeric nanoneedle arrays was established. Depending on the conditions of each step, polymeric nanostructure arrays with various morphology were fabricated.