Nanometer scale high-aspect-ratio trench etching at controllable angles using ballistic reactive ion etching

The authors demonstrate a low pressure reactive ion etching process capable of patterning nanometer scale angled sidewalls and three dimensional structures in photoresist. At low pressure, the plasma has a large dark space region where the etchant ions have very large highly directional mean free paths. Mounting the sample entirely within this dark space allows for etching at angles relative to the cathode with minimal undercutting, resulting in high-aspect ratio nanometer scale angled features. By reversing the initial angle and performing a second etch, the authors create three-dimensional mask profiles. (C) 2013 American Vacuum Society. [http://dx.doi.org/10.1116/1.4773919]