Wet Etching: Chemical Reactions and Process Optimization

This lecture covers the isotropic etching of Si using hydrofluoric acid, nitric acid, and acetic acid bath, as well as the chemical reactions involved in the Si etching process. It discusses the generation of SiO2, dissolution of the oxide by HF, and the use of acetic acid as a diluting agent. The lecture also explores the ternary diagram for the HNA bath, iso-etch curves, the Arrhenius plot of the etching rate, mask materials for etching, and the electrochemical etching process. It explains the etching of p-doped and n-doped Si with electrical bias, as well as the etching of n-doped Si with electrical bias and light. The lecture concludes with a summary of the chemistry of isotropic wet etching and the realization of porous Si.