Though the concept of extreme-ultraviolet (EUV) lithography dates to the late 1980s, it is only now, in this contemporary era of semiconductor manufacturing, that EUV sources are firmly in the limelight. The company ASML, whose debut EUV lithography systems released in the 2010s quickly set a benchmark for the industry, is the dominant force in advanced chip fabrication technology. Today, the company stands as the only supplier of EUV lithography machines capable of producing the most advanced chips. Courtesy of ASML. ASML’s journey toward dominance in this technology space has not avoided challenges. Geopolitical pressures and export controls, both ever-present and highly consequential, are indicative of the direct link that chipmaking technology has to the economic competitiveness of global powers. Overcoming technical challenges have also shaped ASML’s history. “The evolution [of EUV sources] was the result of targeted research and development. Achieving the required power was the biggest challenge,” said Marc Assinck, media relations manager at ASML. “Achieving sufficient power at the EUV wavelength was a requirement by the semiconductor industry to make the tools economically viable.” At the core of this transformative technology is the use of the 13.5-nm wavelength, which enables the precise manipulation of materials at the atomic scale. This level of accuracy is driving the next generation of semiconductor devices. Further downstream, advancements in EUV metrology are cementing EUV’s role in quality control in semiconductor fabrication, enabling users to detect defects at resolutions that were impossible to achieve with conventional techniques. The power of 13.5 nm Semiconductor manufacturers have steadily pushed the boundaries of chip design by etching increasingly fine structures onto wafers. While many commercially available microchips rely on wavelengths between 193 and 365 nm, EUV lithography at the 13.5-nm wavelength enables conductor paths to be manufactured in the nanometer range. This is essential to producing the high-performance chips found in cutting-edge graphics cards and high-end smartphones, driving advancements in speed, efficiency, and functionality. Precise mirrors are installed in the optical systems used for high-numerical aperture (NA) extreme-ultraviolet (EUV) technology. Courtesy of ZEISS. A manufactured wafer is exposed in a high-numerical aperture (NA) extreme-ultraviolet (EUV) system (impression). Courtesy of ASML. “EUV has followed a longstanding trend of using shorter and shorter wavelengths for lithography; shorter wavelengths result in higher resolution and smaller feature sizes,” said Don McDaniel, vice president and general manager at Energetiq. The company is a developer and manufacturer of broadband and EUV sources, targeting semiconductor metrology applications. “This increases transistor density and reduces power consumption, both of which are essential for the astounding improvements in computing power and memory density over the past 50 years,” McDaniel said. ASML’s status as a technology pioneer in EUV lithography places it at the center of international trade policies. The company has faced mounting restrictions, particularly as the Dutch government, which is under pressure from the U.S. and others, imposed export controls to prevent the shipment of advanced chip-making technology to certain countries. Despite these restrictions, ASML continues to expand its partnerships and technological reach. An electrodeless Z-Pinch discharge plasma source. The bright spot is the 13.5-nm emitting ‘pinch.’ Three plasma ‘return loops’ emit brightly in the visible region (below). Courtesy of Energetiq. The near monopoly on EUV lithography for chip production that ASML holds has not precluded it from close collaboration with industry leaders. ZEISS, which supplies high-precision optics essential for EUV systems, has fostered a strategic partnership with ASML since 1997, according to Jeannine Rapp, head of communications and implementation of group initiatives at ZEISS SMT. “Together, we bear a significant responsibility: The machines we have codeveloped and built hold an 80% market share, and for the EUV systems — and in the future also for the latest high-numerical aperture (NA)-EUV technology — it is 100%,” Rapp said. Pushing the limits of chip design Widespread adoption of EUV technology in 2019 marked a critical turning point for chip manufacturing and the industries — electronics, photonics, optoelectronics, among others — that enable it. Major semiconductor foundries such as TSMC and Samsung integrated EUV into high-volume production, initiating a shift that triggered massive investments in semiconductor manufacturing. Foundries and equipment suppliers began a shift to ramp up capacity to meet global demand that is still ongoing. Investments continue to reach new high dollar amounts. With EUV lithography only recently entering high-volume manufacturing, McDaniel believes that the industry is about five years into a technology cycle that is likely to run for 20 years. Industry settled on 13.5 nm as the next key wavelength in chip design more than two decades ago, but it was the physics of the optics that determined the course of lithography rather than the physics of the lasers. The challenge was to find suitable sources at this wavelength where there is no laser line available. “Every previous reduction in wavelength has been driven by the physics of available sources, particularly lasers,” McDaniel said. “Below 193 nm, things significantly change as no transparent materials are available. Instead, optical systems have to use reflective optics, especially multilayer mirrors.” These multilayer mirrors are made from alternating layers of two elements, for which there are limited available choices. In turn, a limited number of wavelengths can make mirrors with sufficient reflectivity. “The optical systems used in EUV lithography have been designed to operate in a vacuum and utilize mirrors instead of lenses, which are essential due to the absorption of EUV radiation by air and glass. This innovation allows for near-perfect imaging and high precision in chip manufacturing,” Rapp said. “The mirrors are crafted with extreme precision, allowing for minimal loss of EUV light.” ASML’s high-numerical aperture (NA) extreme-ultraviolet (EUV) system represents the chipmaking industry’s gateway to the invaluable 13.5-nm wavelength. Courtesy of ASML. According to Rapp, this necessary precision is achieved via a complex layering system — creating a Bragg mirror. This element consists of more than 100 atomically precise layers. The best solution for the source was laser-produced plasma, which was developed to achieve the necessary power and brightness at the crucial 13.5-nm wavelength. “The development of a unique light source that generates EUV light by creating a plasma from tin droplets has revolutionized the lithography process,” said Matthias Wissert, head of the department in development at TRUMPF Lasersystems for Semiconductor Manufacturing. “This source operates at extremely high temperatures and can produce EUV radiation at a rate of 50,000 times per second.” McDaniel attributes the race to develop an EUV lithography source to the commercialization of several other source architectures. These include tin sources other than droplet; discharge plasma sources (electrode and electrodeless); hybrid discharge/laser sources; and high-harmonic conversion of pulsed laser sources. “These architectures are now vying for market share with regard to the many inspection metrology needs supporting EUV lithography,” McDaniel said. The EUV metrology challenge The need to innovate for EUV metrology and defect inspection goes hand-in-hand with the incredible levels of precision that are achieved in advanced chipmaking. Companies such as EUV Tech and Energetiq are leaders in this space. EUV Tech, an EUV metrology tools developer based in California’s Bay Area, offers at-wavelength EUV metrology solutions, ensuring that manufacturers can detect defects at the nanoscale. In addition to its EUV sources, Energetiq also provides compact, high-brightness x-ray sources. “Chip production as a whole needs a wide variety of metrology tools, and in order to be effective, many of these metrology tools should use the exact same wavelength as used in the lithography tool, providing another important opportunity for EUV sources,” said Patrick Naulleau, CEO of EUV Tech. “Additionally, the requirements for metrology tool light sources are quite different than those for lithography, so different light sources are required.” Mirrors and mask blanks must be inspected for defects “at wavelength” because buried phase defects cannot be detected by any other method. Until it is possible to produce large, defect-free multilayers, these components will require complete inspection. Today’s mask blanks are delivered with full defect maps. These maps are used to orient the mask pattern so that the defects are not printed. Accordingly, McDaniel said, the inspection of patterned masks is becoming an important application for EUV source developers. But other technologies may have a role to play here as well. “There are a number of competitors to EUV, as [electron beam] and deep-ultraviolet (DUV) technologies are both effective to some degree. All three technologies are likely to gain some traction with cost, relative capability, and throughput, ultimately determining the market share of each,” McDaniel said. The next frontier ASML’s pursuit of industry-best imaging resolution led to the development of what is widely considered the next generation of EUV lithography systems. In collaboration with ZEISS and TRUMPF, ASML shipped the first high-NA EUV system to Intel in December 2023. Series production with an optical resolution of Meanwhile, ASML, ZEISS, and an ecosystem of more than 1200 partners continue to work. So-called hyper-NA is one area currently under study. To support this, EUV source manufacturers are challenged with increasing EUV power to 2 kW — double the best-known lab performance and ~5× the power in currently deployed scanners. The mask industry is challenged, too; it is tasked with doubling mask size to preserve field size as NA increases. Further improvements in photoresist performance are also in development. The same core principles that make EUV effective for patterning nanometer-scale features on silicon wafers also lend themselves to a range of nonlithographic applications. Other industries are capitalizing on EUV’s high-energy, short- wavelength light for advanced imaging, metrology, materials science, and biomedical research. In advanced materials analysis, for example, EUV-based techniques facilitate nondestructive testing of aerospace and automotive components, revealing structural weaknesses at microscopic levels. EUV-based spectroscopy provides critical insights into material properties, supporting the development of next-generation energy solutions, including more efficient solar cells. And with the post-COVID-19 era accelerating demand for advanced imaging and diagnostic tools, EUV microscopy provides ultrahigh-resolution images of biological specimens. The approach enables researchers to study viruses, bacteria, and cellular structures with unprecedented clarity. This technology opens doors for breakthroughs in drug discovery, vaccine development, and medical diagnostics. For McPherson Instruments’ Erik Schoeffel, scaling up existing capabilities is much less exciting than discovering new ones. McPherson Instruments develops purpose-built spectroscopy systems as well as components and services for the soft x-ray and vacuum ultraviolet region. Schoeffel also cites solar — both physics and space weather applications — as an area for which EUV has utility. EUV light derived from novel sources, he said, or test and calibration services requiring EUV light (such as for space projects), belong in a conversation on the prospects for EUV light and EUV sources. Other applications are already in practice, and potential applications hold significant promise, though challenges remain. The cost of EUV systems is an obvious barrier to increased adoption. “Typical challenges that are often overlooked with respect to producing commercially viable EUV light sources include thermal and debris management,” EUV Tech’s Naulleau said. “But as costs come down, it will become viable across a much broader application space.” The need for specialized infrastructure is a further roadblock, as is technical complexity. “It is important to remember that almost everything absorbs EUV, necessitating vacuum sample handling and beamlines. This introduces a level of complexity and cost that is only overcome by a dramatic performance value proposition,” McDaniel said. Assembly and commissioning of an extreme-ultraviolet (EUV) system in a cleanroom. Courtesy of TRUMPF Group. “Consequently, the majority of potential applications outside of semiconductor manufacturing tend to be scientific applications, which have traditionally been performed in national lab facilities using synchrotron sources,” he said. “These sources are tremendously flexible but offer limited availability. A few standalone EUV sources have been installed to supplement synchrotrons, but it would be a bit of a stretch to call this a market at this time.” Industry continues to invest despite these barriers to adoption. Though it will not occur immediately, this will result in more efficient EUV sources, improved optics, more effective contamination control, and, ultimately, new applications and markets. For example, according to Schoeffel, reliable 13.5-nm coherent light sources, and the optical systems capable of delivering them, open the door to exploring fundamental high-harmonic laser technology and attosecond and thermonuclear fusion. “Generally, growth in high-harmonic generation lasers, CMOS detectors, and related technologies enable better experiments throughout the EUV region,” Schoeffel said. “Some applications are enabled by the advancements such as water window physics and attosecond movies.” As EUV applications expand further into metrology, defect inspection, energy, and biomedical research, industry must continue to innovate to overcome challenges. With ongoing advancements in high-NA EUV and research into novel use cases, EUV sources will undoubtedly play an even greater role in shaping future technology landscapes.
