Extreme ultraviolet lithography

Extreme ultraviolet lithography (EUVL, also known simply as EUV) is a technology used in the semiconductor industry for manufacturing integrated circuits (ICs). It is a type of photolithography that uses 13.5 nm extreme ultraviolet (EUV) light from a laser-pulsed tin (Sn) plasma to create intricate patterns on semiconductor substrates.

As of 2023, ASML Holding is the only company that produces and sells EUV systems for chip production, targeting 5 nanometer (nm) and 3 nm process nodes.

The EUV wavelengths that are used in EUVL are near 13.5 nanometers (nm), using a laser-pulsed tin (Sn) droplet plasma to produce a pattern by using a reflective photomask to expose a substrate covered by photoresist. Tin ions in the ionic states from Sn IX to Sn XIV give photon emission spectral peaks around 13.5 nm from 4p64dn – 4p54dn+1 + 4dn−14f ionic state transitions.[1]

Image formation mechanism in EUV lithography.
  EUV multilayer of silicon-based glass spacer and molybdenum reflectors
  Absorber
  EUV radiation
  Resist
  Substrate
  Secondary electrons
EUV multilayer and absorber constituting mask pattern for imaging a line. EUV radiation reflected from the mask pattern is absorbed in the resist and substrate, producing photoelectrons and secondary electrons. These electrons increase the extent of chemical reactions in the resist. A secondary-electron pattern that is random in nature is superimposed on the optical image. The unwanted secondary-electron exposure results in loss of resolution, observable line edge roughness and linewidth variation.
  1. ^ O'Sullivan, Gerry; Li, Bowen; D'Arcy, Rebekah; Dunne, Padraig; Hayden, Paddy; Kilbane, Deirdre; McCormack, Tom; Ohashi, Hayato; O'Reilly, Fergal; Sheridan, Paul; Sokell, Emma; Suzuki, Chihiro; Higashiguchi, Takeshi (2015). "Spectroscopy of highly charged ions and its relevance to EUV and soft x-ray source development". Journal of Physics B: Atomic, Molecular and Optical Physics. 48 (144025): 144025. Bibcode:2015JPhB...48n4025O. doi:10.1088/0953-4075/48/14/144025. S2CID 124221931.