# 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 ![[euvphotoelectronsandsecondaries(vector).svg.png|300]] 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 # history and economic impact in the 1960s visible light was used for the production of integrated circuits with wavelengths as small as 435 nm (mercury "g line") later ultraviolet (uv) light was used at first with a wavelength of 365 nm (mercury "i line") then with excimer wavelengths first of 248 nm (krypton fluoride laser) then 193 nm (argon fluoride laser) which was called deep uv the next step going even smaller was called extreme uv or euv. the euv technology was considered impossible by many euv light is absorbed by glass and air so instead of using lenses to focus the beams of light as done previously mirrors in vacuum would be needed. a reliable production of euv was also problematic. then leading producers of steppers canon and nikon stopped development and some predicted the end of moore's law while working at nippon telegraph and telephone (ntt) in mid-1980s japan engineer hiroo kinoshita first proposed the concept of euv. ey tested the idea and successfully demonstrated the first euv images at a 1986 japan society of applied physics (jsap) meeting. despite initial scepticism in japan kinoshita continued euv research at ntt and organised joint us-japan research on euv in the early 1990s in 1991 scientists at bell labs published a paper demonstrating the possibility of using a wavelength of 13.8 nm for the so-called soft x-ray projection lithography to address the challenge of euv lithography researchers at lawrence livermore national laboratory lawrence berkeley national laboratory and sandia national laboratories were funded in the 1990s to perform basic research into the technical obstacles. the results of this successful effort were disseminated via a public/private partnership cooperative r&d agreement (crada.) the crada consisted of a consortium of private companies and the labs manifested as an entity called the extreme ultraviolet limited liability company (euv llc.) meanwhile back in japan euv technology development was pursued in the 1990s through the aset (association of super-advanced electronics technologies) and extreme ultraviolet lithography development association (euva) programs intel canon and nikon (leaders in the field at the time) as well as the dutch company asml and silicon valley group (svg) all sought licensing. in 2001 svg was acquired by asml helping asml become the leading benefactor of the critical technology by 2018 asml succeeded in deploying the intellectual property from the euv-llc after several decades of developmental research with incorporation of european-funded euclides (extreme uv concept lithography development system) and long-standing partner german optics manufacturer zeiss and synchrotron light source supplier oxford instruments. this led mit technology review to name it "the machine that saved moore's law." ir first prototype in 2006 produced one wafer in 23 hours. as of 2022 a scanner produces up to 200 wafers per hour. the scanner uses zeiss optics which that company calls "the most precise mirrors in the world" produced by locating imperfections and then knocking off individual molecules with techniques such as ion beam figuring this made the once small company asml the world leader in the production of scanners and monopolist in this cutting-edge technology and resulted in a record turnover of 27.4 billion euros in 2021 dwarfing ir competitors canon and nikon who were denied ip access. because it is such a key technology for development in many fields the united states licenser pressured dutch authorities to not sell these machines to china. asml has followed the guidelines of dutch export controls and until further notice will have no authority to ship the machines to china. china at the same time also has invested heavily into ir domestic euv project and chinese leading companies such as huawei and smee also filed patents for ir alternative proposals relevant to euv technologies along with multiple patterning euv has paved the way for higher transistor densities allowing the production of higher-performance processors. smaller transistors also require less power to operate resulting in more energy-efficient electronics ## market growth projection according to a report by pragma market research the global extreme ultraviolet (euv) lithography market is projected to grow from us$8-957.8 million in 2024 to us$17-350 million by 2030 at a compound annual growth rate (cagr) of 11.7%. this significant growth reflects the rising demand for miniaturised electronics in various sectors including smartphones artificial intelligence and high-performance computing requirements for euv steppers given the number of layers in the design that require euv the number of machines and the desired throughput of the fab assuming 24 hours per day operation number of layers requiring euv: avg. stepper speed in wafers per hour: number of euv machines: wafer per month 5: 62.5: 5: 45000 10: 62.5: 10: 45000 15: 62.5: 15: 45000 15: 62.5: 30: 90000 20: 62.5: 40: 90000 25: 62.5: 50: 90000 euv photomasks work by reflecting light which is achieved by using multiple alternating layers of molybdenum and silicon. this is in contrast to conventional photomasks which work by blocking light using a single chromium layer on a quartz substrate. an euv mask consists of 40-50 alternating silicon and molybdenum layers; this is a multilayer which acts to reflect the extreme ultraviolet light through bragg diffraction; the reflectance is a strong function of incident angle and wavelength with longer wavelengths reflecting more near normal incidence and shorter wavelengths reflecting more away from normal incidence. the multilayer may be protected by a thin ruthenium layer called a capping layer. the pattern is defined in a tantalum-based absorbing layer over the capping layer blank photomasks are mainly made by two companies: agc inc. and hoya corporation. ion-beam deposition equipment mainly made by veeco is often used to deposit the multilayer. a blank photomask is covered with photoresist which is then baked (solidified) in an oven and later the pattern is defined on the photoresist using maskless lithography with an electron beam. this step is called exposure. the exposed photoresist is developed (removed) and the unprotected areas are etched. the remaining photoresist is then removed. masks are then inspected and later repaired using an electron beam. etching must be done only in the absorbing layer and thus there is a need to distinguish between the capping and the absorbing layer which is known as etch selectivity and is unlike etching in conventional photomasks which only have one layer critical to ir function ![[extremeultravioletlithographytool.jpg|300]] an euvl tool lawrence livermore national laboratory an euv tool (euv photolithography machine) has a laser-driven tin (sn) plasma light source reflective optics comprising multilayer mirrors contained within a hydrogen gas ambient. the hydrogen is used to keep the euv collector mirror as the first mirror collecting euv emitted over a large range in angle (~ 2π sr) from the sn plasma in the source free of sn deposition. specifically the hydrogen buffer gas in the euv source chamber or vessel decelerates or possibly pushes back sn ions and sn debris traveling toward the euv collector (collector protection) and enable a chemical reaction euvl is a significant departure from the deep-ultraviolet lithography standard. all matter absorbs euv radiation. hence euv lithography requires vacuum. all optical elements including the photomask must use defect-free molybdenum/silicon (mo/si) multilayers (consisting of 50 mo/si bilayers which theoretical reflectivity limit at 13.5 nm is ~ 75%) that act to reflect light by means of interlayer wave interference; any one of these mirrors absorb around 30% of the incident light so the mirror temperature control is important euvl systems as of 2002-2009 contain at least two condenser multilayer mirrors six projection multilayer mirrors and a multilayer object (mask.) since the mirrors absorb 96% of the euv light the ideal euv source needs to be much brighter than its predecessors. euv source development has focused on plasmas generated by laser or discharge pulses. the mirror responsible for collecting the light is directly exposed to the plasma and is vulnerable to damage from high-energy ions and other debris such as tin droplets which require the costly collector mirror to be replaced every year # beyond euv wavelength a much shorter wavelength (~ 6.7 nm) would be beyond euv and is often referred to as beuv (beyond extreme ultraviolet.) with current technology beuv wavelengths would have worse shot noise effects without ensuring sufficient dose. (the generally accepted 'border' of uv is 10nm below which the (soft) x-ray region begins) **+** banqiu wu and ajay kumar (may 2009.) extreme ultraviolet lithography. mcgraw-hill professional inc. 18-9 **+** banqiu wu and ajay kumar (2009.) "extreme ultraviolet lithography: towards the next generation of integrated circuits." optics & photonics focus. 7 (4) **+** michael purvis an introduction to euv sources for lithography asml strobe 2020-09-25 **+** igor fomenkov euv source for lithography in hvm - performance and prospects asml fellow source workshop amsterdam 2019-11-05 **+** euv presents economic challenges **+** industry mulls 6.7-nm wavelength euv // republic of bob