Extreme ultraviolet lithography

Extreme ultraviolet lithography is a technology used in the semiconductor industry for manufacturing integrated circuits. It is a type of photolithography that uses 13.5 nm extreme ultraviolet light from a laser-pulsed tin plasma to create intricate patterns on semiconductor substrates.
, ASML Holding is the only company that produces and sells EUV systems for chip production, targeting 5 nanometer and 3 nm process nodes, though Reuters reported in December 2025 that China had developed its own prototype EUV system.
The EUV wavelengths that are used in EUVL are near 13.5 nanometers, using a laser-pulsed tin 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.

History and economic impact

In the 1960s, visible light was used for the production of integrated circuits, with wavelengths as short as 435 nm.
Later, ultraviolet light was used, at first with a wavelength of 365 nm, then with excimer wavelengths, first of 248 nm, then 193 nm, 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 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 meeting. Despite initial scepticism 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. The CRADA consisted of a consortium of private companies and the Labs, manifested as an entity called the Extreme Ultraviolet Limited Liability Company. Meanwhile back in Japan, EUV technology development was pursued in the 1990s through the ASET and Extreme Ultraviolet Lithography Development Association programs.
Intel, Canon, and Nikon, as well as the Dutch company ASML and Silicon Valley Group 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 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.
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 their 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 their domestic EUV project, and Chinese leading companies such as Huawei and SMEE also filed patents for their alternative proposals relevant to EUV technologies. 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.
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.

Fab tool output

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	185	5	135000
10	185	10	135000
15	185	15	135000
15	185	30	270000
20	185	40	270000
25	185	50	270000

Masks

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 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, 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 their function.

Tool

An EUV tool has a laser-driven tin 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 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 and enable a chemical reaction of Sn + 4H -> SnH4 to remove Sn deposition on the collector in the form of SnH4 gas.
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 multilayers 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. 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.

Resource requirements

The required utility resources are significantly larger for EUV compared to 193 nm immersion, even with two exposures using the latter. At the 2009 EUV Symposium, Hynix reported that the wall plug efficiency was ~0.02% for EUV, i.e., to get 200 watts at intermediate focus for 100 wafers per hour, one would require 1 megawatt of input power, compared to 165 kilowatts for an ArF immersion scanner, and that even at the same throughput, the footprint of the EUV scanner was ~3× the footprint of an ArF immersion scanner, resulting in productivity loss. Additionally, to confine ion debris, a superconducting magnet may be required.
A typical EUV tool weighs nearly 200 tons and costs around 180 million USD.
EUV tools consume at least 10× more energy than immersion tools.