xLight Obtains Funding For Next-Gen EUV Light Source
The funding will enable xLight to develop a light source based on a free electron laser technology for EUV lithography
By Mark LaPedus
xLight, a startup that is developing a next-generation light source technology for EUV lithography, has raised $40 million in venture capital funding.
The funding will enable xLight to further develop its free electron laser (FEL) light source technology for use in extreme ultraviolet (EUV) lithography. The funding round was led by Playground Global, a venture capital firm. Boardman Bay Capital Management, Morpheus Ventures, Marvel Capital and IAG Capital Partners also joined the round.
Pat Gelsinger, the former chief executive of Intel, was recently named executive chairman of xLight. Gelsinger is also a general partner at Playground Global.
Formed in 2021, xLight is developing a new and different way to generate light in ASML’s EUV lithography systems. Basically, EUV lithography uses light to print tiny patterns on chips, which is a fundamental step in manufacturing leading-edge devices. ASML’s EUV systems incorporate a light source, which generates light at 13.5nm wavelengths.
But the light source is inefficient in meeting the power demands of future lithographic systems, according to xLight. Based in Palo Alto, Calif., xLight is building a particle accelerator driven FEL technology, which is designed to replace the current way that light is generated in today’s EUV lithography systems.
Basically, an FEL is a high-power light source, which uses electrons to produce light at different wavelengths. A particle accelerator is a system that propels charged particles.
Still in R&D, xLight’s technology is designed to generate EUV light in an FEL-driven particle accelerator. xLight’s EUV FEL light source produces 4x more power than today’s systems.
There is a catch. The company’s FEL particle accelerator is a large system, which resides in a standalone building. This building is located next to a separate semiconductor fab facility. xLight has developed a way to transport EUV light from the particle accelerator plant to the EUV lithography tools in the fab.
The company is building a feature-complete prototype that will be operational and printing wafers by 2028. It’s an innovative but complex technology. It will likely require a new and expensive infrastructure.
What is EUV?
Before discussing xLight’s technology in depth, let’s look at today’s EUV lithography. Basically, chipmakers (i.e. Intel, Samsung, TSMC, others) manufacture chips using various equipment in a large facility called a fab.
Lithography, one key equipment type, is used to process chips in a fab. Lithography systems pattern the tiny features in chips. ASML, a supplier of equipment based in the Netherlands, is the sole supplier of EUV lithography systems in the market.
Starting around 2018, Samsung and TSMC began using ASML’s EUV lithography systems in the fab. EUV systems are used to process advanced chips at the 7nm node and beyond.
Generating light with a wavelength of 13.5nm, ASML’s EUV systems incorporate a 0.33 numerical aperture (NA) lens with 13nm resolutions. The 0.33 NA system is called low-NA EUV.
ASML’s EUV systems integrate several components in the same unit, including a vacuum chamber, reflective optics and reticle/wafer stages. In the scanner, ASML also incorporates a laser produced plasma (LPP) system, which serves as the light source for the EUV tool. The LPP light source consists of three subsystems—a drive laser, a beam transport system and a source vessel.
The drive laser unit is situated in the sub-fab, which is located beneath the cleanroom in the fab. In EUV lithography, the process starts with the drive laser unit, which generates a pulse. The high-power laser pulse is then routed to ASML’s EUV systems, which are located in the cleanroom portion of the fab.
Initially, the laser pulse is routed into the source vessel unit in the EUV system. The source vessel consists of a droplet generator unit. “In our laser produced plasma (LPP) source, molten tin droplets of around 25 microns in diameter are ejected from a generator at 70 meters per second. As they fall, the droplets are hit first by a low-intensity laser pulse that flattens them into a pancake shape. Then a more powerful laser pulse vaporizes the flattened droplet to create a plasma that emits EUV light. To produce enough light to manufacture microchips, this process is repeated 50,000 times every second,” according to ASML.
After the LPP unit generates EUV light, the light is then routed to a separate vacuum chamber inside the EUV system. At that point, EUV light bounces off several reflective mirrors inside the chamber.
Then, the light hits a mask in the EUV system. The imaged light from the mask is then projected onto a wafer in the system, thereby creating tiny patterns on the wafer. From there, the wafer undergoes a multitude of other process steps in the fab, which in turn creates finished chips.
Soon, it will become too complicated to make chips using 0.33 NA EUV. So, ASML is developing a next-generation lithography system called high-numerical aperture (high-NA) EUV. Still in R&D, high-NA EUV systems incorporate a different 0.55 NA lens with 8nm resolutions.
Like low-NA EUV, high-NA EUV lithography also incorporates several components in the same unit, including an LPP light source. The LPP light source unit has some limitations for both low-NA (0.33) and high-NA (0.55) EUV lithography.
“Today’s EUV light source--laser produced plasma (LPP)–only provides 25% of the light required by current lithography technology and is physically incapable of meeting the power demands of future lithography technologies and techniques,” according to xLight.
FEL EUV light sources
ASML continues to make improvements on its LPP unit, but xLight believes that there is a better solution—a particle accelerator driven FEL.
xLight is working on this technology with various partners, including Cornell, Los Alamos National Laboratory, Fermi National Accelerator Laboratory and others.
FELs and particle accelerators aren’t new. For years, companies, R&D organizations and universities have owned and operated particle accelerators, which are used to generate tiny sub-atomic particles like protons, neutrons and quarks. These systems are generally used in physics and other scientific applications. FELs have been around for a long time.
xLight is putting a new spin on the technology. Based on an animation video from xLight, the company’s FEL particle accelerator would reside in a large standalone facility. That facility is located 50 to 1,500 meters away from a semiconductor fab facility.
In xLight’s technology, electrons are first injected in the particle accelerator and then into the FEL. “FELs use electrons from a particle accelerator and passes them through undulators with a periodic magnetic field to generate coherent, high-intensity light beams,” according to xLight.
In simple terms, EUV light is generated in the accelerator. Then, EUV light is transported from the particle accelerator facility to the fab using what looks like a photon pipeline.
At that point, EUV light is routed into the sub-fab. In the sub-fab, there are various standalone systems called “turning stations.” Based on xLight’s video, each turning station is dedicated to one EUV tool on the fab floor above.
In operation, EUV light is transported to each turning station in the sub-fab. Then, each turning station takes the light and directs it to an EUV system on the fab floor above. This in turn generates the power in the EUV tool.
In this scenario, the EUV lithography tool itself doesn’t incorporate an LPP light source. Instead, EUV light is generated in the particle accelerator and then transported to the EUV tools in the fab. That’s a simple way to describe a complex process.
Nonetheless, xLight’s FEL light source produces 4x more power than today’s LPP units. “By delivering up to 4x higher EUV power, fabs can optimize patterning improvements, productivity, and yield, unlocking billions in additional annual revenue per scanner and ~50% per wafer cost reduction,” according to xLight. “Additionally, a single xLight system can support up to 20 ASML systems with a 30-year operating lifetime, reducing capital and operating expenditures by more than 3x.”
In theory, xLight’s technology could be used for low-NA EUV, high-NA EUV or even hyper-NA EUV. In R&D, ASML is developing 0.75 hyper-NA EUV technology, which is targeted for the distant future.
There is another possible insertion point for xLight. The company is a member of the Blue-X Consortium. Organized by EUV Litho, Blue-X is proposing EUV lithography using a 6.7nm wavelength. 6.7nm EUV is also a futuristic technology. At present, Blue-X comprises of 70 member organizations.
Still, the questions are clear: Will xLight’s technology work? And who will build and fund all of the necessary components in xLight’s system? That remains unclear.