What is etching?

Etching is a process that uses chemical reactions, or other physical processes (like ion beam milling), to remove layers of material from a substrate. In manufacturing, it's commonly used to create patterns on materials like silicon wafers in semiconductor fabrication, printed circuit boards (PCBs), and other microfabricated devices. There are two main types: wet etching, which uses liquid chemicals, and dry etching, which uses plasmas.