Wet Etching: Sacrificial Layers

This lecture covers the process of wet etching sacrificial layers in micro and nanofabrication, involving the removal of a sacrificial layer beneath a functional layer. It explains the steps of patterning the sacrificial layer, depositing a polySi layer, and etching SiO2 in a HF bath. The instructor discusses the challenges of microstructure deformation during drying and rinsing, proposing a solution with supercritical point drying. Additionally, the lecture explores the process of supercritical point drying, where the sacrificial layer is etched in a HF bath, followed by a series of steps involving deionized water, ethyl alcohol, and CO2 gas. The stress in surface-machined microstructures is also addressed, along with the use of ring crossbar test structures for diagnosing tensile or compressive stress.