Wet Etching: Crystal Structure and Anisotropy

This lecture covers the crystal structure of silicon, including the diamond lattice representation and covalent bonding. It explains the anisotropy in etching rates due to different plane orientations and bonding strengths. The lecture also delves into the etch mechanisms for silicon atoms in different crystal planes, focusing on KOH etching and its reaction rates. Anisotropic etching profiles and etching baths like KOH, EDP, and TMAH are discussed, highlighting their compositions and anisotropy ratios. A case study on a thermo-mechanical micro-actuator demonstrates the practical application of anisotropic etching. Overall, the lecture provides insights into the fundamental principles and practical aspects of wet etching in micro and nanofabrication.