Lithography photolithography
Process to transfer patterns (the circuit) to a semiconductor wafer via light + photo-sensitive resist. Defines the entire semiconductor industry's scale.
Wavelength eras: g-line (436 nm, 1980s) → i-line → 248 nm KrF → 193 nm ArF (deep UV, "DUV") → 193nm immersion (water on top of wafer raises effective NA) → 13.5 nm EUV (Extreme UV, since 2018). Multi-patterning is required when feature size is smaller than wavelength. ASML is the sole EUV manufacturer.