Core Principle
A maskant (e.g., photoresist, wax, or polymer) is applied to protect areas you want to keep.
Unmasked areas are exposed to an etchant, which chemically reacts with the material (e.g., metal, silicon, glass) and dissolves it.
The reaction proceeds isotropically (removes material equally in all directions) or can be made anisotropic for certain materials (e.g., silicon in KOH).
Typical Process Steps
Cleaning: Degrease and prepare the substrate surface.
Masking: Apply a photoresist or protective layer.
Patterning: Expose the mask to light (photolithography) and develop to remove resist from target areas.
Etching: Immerse or spray with etchant (e.g., ferric chloride for steel, HF for SiO₂, KOH for silicon).
Stripping: Remove the remaining maskant.
Inspection: Verify precision and quality.
Key Applications
Microelectronics & semiconductors: Patterning wafers, etching oxides, and creating MEMS.
Precision metal parts: Shims, springs, filters, medical devices, aerospace components.
Printmaking & art: Traditional intaglio etching on metal plates.
Metallography: Revealing grain structures for material analysis.
Advantages
High precision for thin, intricate parts (down to microns).
Burr-free edges and no mechanical stress.
Works with almost any metal and many non-metals.
Scalable for mass production.
Common Etchants
Metals: Ferric chloride (FeCl₃), nitric acid (HNO₃), hydrochloric acid (HCl).
Silicon: Potassium hydroxide (KOH), tetramethylammonium hydroxide (TMAH).
Silicon dioxide: Hydrofluoric acid (HF).