Reactive ion etching of glasses: Composition dependence

Magnetically enhanced reactive ion etching (MERIE) of silicate and phosphate glasses was examined in CF₄/CHF₃ and Ar plasmas. The etch depths were measured by profilometery to obtain etching rates as a function of plasma power, plasma composition and glass composition. It was found that in fluorocarbon plasmas, the etch rate of glasses decreases as the concentration of less-volatile oxides in the glass increases. These etching rates were interpreted in terms of ion-enhanced chemical reaction and physical sputtering. The compositions of the etched surfaces were determined with X-ray photoelectron spectroscopy (XPS). A high chemical reaction rate between the reactive (ion) species in the plasma and the glass surface was observed during the early stages of etching which lead to depletion of highly volatile species (SiF₄ and BF₃) and accumulation of less volatile species (AlF₃, BaF₂, NaF, etc.). At longer times, the glass surface reached a steady state composition (of the less volatile species) and subsequent etching was dominated by physical sputtering.