Extreme ultraviolet lithography (EUVL or simply 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.
, ASML is the only company that produces and sells EUV systems for chip production, targeting 5 nanometer (nm) and 3 nm process nodes, though Reuters reported in December 2025 that China had developed its own prototype EUV lithography system, China is also pursuing alternative EUV light-source approaches, including accelerator based Steady-state microbunching (SSMB) and laser-induced discharge plasma (LDP).
The EUV wavelengths that are used in EUVL are near 13.5 nanometers (nm), to produce a pattern by using a reflective photomask to expose a substrate covered by photoresist.
History and economic impact In the 1960s, visible light was used for the production of integrated circuits, with wavelengths as short 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 towards shorter wavelengths was called extreme UV, or EUV. 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. While working at Nippon Telegraph and Telephone (NTT) in mid-1980s Japan, engineer Hiroo Kinoshita first proposed the concept of EUV. He tested the idea and successfully demonstrated the first EUV images at a 1986 Japan Society of Applied Physics (JSAP) meeting. Despite initial skepticism in Japan, Kinoshita continued EUV research at NTT and organized 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 (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". Their 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.
ASML subsequently became the leading supplier in the production of scanners which contributed to a record turnover of 27.4 billion euros in 2021. Because of the technology's importance, the United States licenser pressured Dutch authorities to restrict the sale of 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 has invested into a domestic EUV project, and Chinese companies such as Huawei and SMEE also filed patents for their alternative proposals relevant to EUV technologies.Stefano Lovati. February 11, 2025. China Invests €37 Billion to Develop Domestic EUV Lithography Systems Power Electronics News In December 2025, Reuters reported that China had secretly completed a prototype EUV machine in Shenzhen, which was expected to produce working chips between 2028 and 2030.
Types of EUV Light Sources Extreme ultraviolet (EUV) lithography requires radiation at 13.5 nm(≈92 eV) to match the peak reflectivity band of molybdenum/silicon (Mo/Si) multilayers mirrors. In plasma-based EUV sources, ionization precedes much of the EUV emission. The thermal production of multicharged positive ions requires a hot, dense plasma, which can itself strongly absorb EUV radiation.
Laser-produced plasma (LPP) Laser-produced plasma, or LPP, is the dominant light-source architecture used in commercial high-volume manufacturing (HVM) EUV lithography. The source architecture centers on a droplet generator that ejects ~25 μm diameter molten tin droplets at ~70 m/s through a vacuum chamber. A dual-pulse carbon dioxide(CO2) laser system (operating at a wavelength of 10.6 μm, pulse duration ~15–25 ns, intensity ~10¹¹ W/cm²) then targets each droplet. A low-energy "pre-pulse" strikes the droplet first, expanding it into a low-density pancake-like cloud of tin vapor. A high-energy "main pulse" then strikes this vapor, ionizing it into a high-temperature plasma with electron temperatures of 20–50 eV and electron densities of 10²⁰–10²¹ cm⁻³.
Within this plasma, tin ions in charge states Sn IX through Sn XIV undergo 4p⁶4dⁿ → 4p⁵4dⁿ⁺¹ + 4dⁿ⁻¹4f transitions, producing strong emission lines clustered around 13.5 nm with a 2% full-width at half-maximum (FWHM) bandwidth. The source operates at a repetition rate of ~50 kHz and conversion efficiency of ~5–6%. Current-generation LPP sources deliver approximately 250 W of in-band EUV power at intermediate focus with plasma size of ~100 μm and an etendue below 1 mm²·sr. With high-NA systems targeting ≥500 W in the near future.
ASML NXE:3400B illuminator features a smaller pupil fill ratio (PFR) down to 20% without transmission loss.M. van de Kerkhof et al., Proc. SPIE 10143, 101430D (2017). PFR is maximized and greater than 0.2 around a metal pitch of 45 nm.Y. Chen et al., J.Vac. Sci. Tech. B35, 06G601 (2017).
A critical engineering challenge is tin debris management. The plasma generates high-energy tin ions (up to several keV), neutral atoms, and sub-micron droplets that deposit on the first collector mirror, degrading its multilayer reflectivity by 0.1–0.3% per billion pulses. To mitigate this, the source vessel is maintained in a hydrogen ambient (H₂ pressure ~1–10 Pa). Atomic hydrogen reacts with deposited tin via Sn(s) + 4H(g) → SnH₄(g), forming stannane gas that is pumped away, enabling in-situ collector cleaning. A superconducting magnet may also be employed to confine ion debris trajectories. Despite these measures, collector mirror replacement remains necessary approximately annually.
Steady-state microbunching (SSMB) SSMB-EUV is a accelerator-based light-source being developed by China's Tsinghua University designed to produce high-average-power, continuous-wave (CW) EUV radiation from a storage ring electron beam — bridging the gap between conventional CW storage rings (high repetition rate but incoherent) and linac-based free-electron lasers (high peak power but pulsed).
An external high-power laser is fired at a circulating relativistic electron beam inside a modulator undulator, imposing a periodic energy modulation on the beam. As the beam then traverses a dispersive section (magnetic chicane or achromatic arc), this energy modulation is converted into a spatial density modulation — forming microbunches at a length scale comparable to the EUV wavelength (or one of its harmonics).
In a conventional storage ring, electrons are randomly distributed → fields add incoherently → radiated power ∝ N (number of electrons), In SSMB, electrons are compressed into microbunches spaced at exactly the modulating laser wavelength → fields add coherently → radiated power scales orders of magnitude more strongly than incoherent synchrotron radiation. A precise turn-by-turn phase correction maintains a steady-state condition where quantum excitation and radiation damping are balanced, allowing sub-wavelength microbunches to remain intact indefinitely. Each turn, these microbunches pass through a radiator (undulator or bending magnet) and emit highly coherent, narrow-bandwidth 13.5 nm EUV at megahertz repetition rates. SSMB requires highly specialized low-alpha (low momentum compaction) magnet lattices to maintain the microbunches. Scaling to a full-power, multi-kilowatt commercial lithography source also requires the development of high-power optical enhancement cavities to sustain the modulating laser continuously, also maintaining nanometer-scale or sub-nanometer-scale longitudinal microbunching in a high-current storage ring is difficult. The electron beam is affected by intrabeam scattering, space-charge effects, wakefields, quantum excitation, radiation damping, energy spread growth, and collective instabilities. The source requires precise control of beam energy, emittance, bunch length, current, and synchronization with any modulation laser. High-current operation also creates challenges for vacuum systems, beam diagnostics, feedback control, and component lifetime.
A landmark proof-of-principle experiment validating the SSMB mechanism was conducted in 2021 at the Metrology Light Source (MLS) in Berlin, Germany, in collaboration between Tsinghua University and German partners — confirming the physics. A prototype is being constructed in Xiong'an New Area (雄安新区), Hebei, China, near Beijing.
Free-electron laser (FEL) Free electron laser is another accelerator-based approach to generate EUV light proposed for future high-power lithography. KEK's compact ERL (cERL) in Tsukuba, Japan and Socol–Budker FEL + multiturn ERL serves as the prototype testbed for this technology.
A superconducting radio-frequency (SRF) linac accelerates high-repetition-rate electron bunches (e.g., 162.5 MHz repetition) — generated from a photocathode gun — to highly relativistic energies of 600–800 MeV. The beam is longitudinally compressed and injected into an undulator: a long periodic array of alternating dipole magnets. Inside the undulator, the alternating magnetic field forces electrons into a sinusoidal transverse trajectory, to emit synchrotron radiation. The emitted wavelength is governed by the FEL resonance (undulator).
where λᵤ is the undulator period, γ is the relativistic Lorentz factor, and K is the undulator deflection parameter. By tuning the electron-beam energy, undulator gap, harmonic number, or optical cavity conditions, the output wavelength can be precisely adjusted — targeting 13.5 nm for EUV lithography, and potentially shorter wavelengths for future nodes. through Self-Amplified Spontaneous Emission (SASE) — or alternatively seeded/oscillator operation — the emitted light feeds back on the electron bunch, causing microbunching and massive coherent exponential amplification, producing intense, spectrally bright EUV pulses at 13.5 nm.
Energy Recovery linac