# How is the crystal direction important for etching silicon surfaces?

I am a student of masters study with a background only in electrical engineering, but I have studied Miller indices and crystallographic planes and directions, personally, to help myself understand the process of silicon etching which is required in my current course of study. But, I am unable to understand the following written in my text book:

"When Silicon is etched anisotropically, i.e. depending on crystal direction, and a {1 0 0} surface direction is used, cavities will result which have the same {1 0 0} orientation at the bottom and are determined laterally by {1 1 1} surfaces. The reason is that {1 1 1} surfaces are etched off using a minimal etch rate and this way becomes the most resistant"

• Hello and Welcome to Chemistry.se! While your question is straightforward, I think it would be much appreciated if you edit in the source for your quote. – Martin - マーチン Nov 17 '14 at 2:04