Physics / mechanism
Etch removes material from a wafer surface with atomic-scale precision. Plasma etch ionises a process gas (Cl₂, HBr, CF₄, SF₆ etc.) into reactive radicals and ions; the former provide chemical selectivity, the latter provide directional energy. Key parameters: selectivity (target:mask:stop-layer removal ratios, ideally >50:1), aspect-ratio-dependent etch (ARDE) uniformity, line-edge roughness (LER, <1 nm 3σ for leading-edge), and damage depth. Atomic Layer Etching (ALE) takes this to the limit—self-limiting half-cycles (adsorption then energetic desorption) give <1 Å/cycle control. ALE is now production-relevant at 3 nm and below; LETI/IMEC roadmaps require it for gate-all-around and backside power rail patterning. Lam Research, Applied Materials, and TEL dominate capital-equipment supply; Hitachi and Oxford Instruments serve compound-semiconductor and photonics niches.
Competitive landscape
Wet etch (HF, KOH, TMAH) is cheaper but isotropic—unsuitable for sub-10 nm critical dimensions. Laser ablation handles thick-film removal or singulation but lacks selectivity. Ion-beam etch (IBE/CAIBE) offers angstrom control for photonics facets and MEMS but throughput is too low for front-end logic. The key competitive axis is selectivity vs. throughput vs. damage budget.
Companies using
Connected ideas
Sources
Frontier (open questions)
- To be added.