Isotropy and Anisotropy
When a material is attacked by a liquid or vapor etchant, the material will be removed isotropically (uniformly in all directions) or through anisotropic etching (uniformity in vertical direction). The difference between isotropic etching and anisotropic etching is shown in Fig. 1. Material removal rate for wet etching is usually faster than the rates for many dry etching processes and can easily be changed by varying temperature or the concentration of active species.
(a) Completely anisotropic etching of a semiconductor (b) Isotropic etching where the semiconductor is etched all around uniformly if not masked
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Ombaba, M., Inayat, S.B., Islam, M.S. (2015). Wet Chemical and Electrochemical Etching Processes. In: Bhushan, B. (eds) Encyclopedia of Nanotechnology. Springer, Dordrecht. https://doi.org/10.1007/978-94-007-6178-0_431-2
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