Anisotropic Etching

Synonyms

Bosch process; Deep reactive-ion etching (DRIE); Etching single crystalline materials; Physical-chemical etching; Potassium hydroxide (KOH) etching; Silicon etching

Definition

Anisotropic etching is a subtractive microfabrication technique that aims to preferentially remove a material in specific directions to obtain intricate and often flat shapes. Wet techniques exploit the crystalline properties of a structure to etch in directions governed by crystallographic orientation. Dry techniques utilize an inhibitor to protect the sidewalls of a cavity during ion bombardment to obtain high aspect ratios.

Overview

In contrast to isotropic etching, anisotropic etching is a fabrication technique that removes material in specific directions allowing for the production of geometric characteristics such as sharp corners, flat surfaces, and deep cavities. Relative to microfabrication, selectivity can be defined as the ratio of the etch rate of the target material to the etch rate of other...