Composition tailored isotropic and anisotropic wet etching of glass

The major composition of any glass substrates consists of more than 70% silicon dioxide with varying concentration of alkali and alkaline earth metals with minor additives such as Al2O3, B2O3 etc. In this study, glass substrates of different compositions were etched successfully using HF based wet etchants. The etch rate as well as the etched profile is greatly dependent on the composition of the glass substrate being used. Two different composition of glasses, wherein the alkali and alkaline earth metals are in different concentrations were used for the etch profile study. One is Borofloat-33 with no free metal ions and the other is Soda lime glass with free metal ions. The etched profile for Borofloat-33 glass had a partial anisotropy with an inclined angle of 33.7 degree while isotropic etch was obtained with soda lime glass. This anisotropy was maintained for Borofloat-33 glass even after continuous agitation during the etch process. The wet etch selectivity of the glass with respect to stack of a-Si/Cr/Au has been established for ∼106 µm deep etching.