Transient roughening behaviour and spontaneous pattern formation during plasma etching of nanoporous silica

摘要

We investigate the roughening of methylsilsesquioxane-derived nanoporous silica ( NPS) during the early stages of reactive ion etching. Etching between 0 - 400 nm produces a dramatic roughening of the surface. We find that the time dependence in this technologically relevant transient regime is not well described by predictions by models of kinetic roughening based on conventional scaling theory. Using lithographic patterning to perturb the NPS/plasma interface at a series of length scales we demonstrate both persistence at a preferred wavelength and evidence for period doubling. Our atomic force microscopy images reveal the dominant role of trench formation, possibly nucleated at nanopores during etching.