GoKawiilOne of the key challenges with the development of extreme ultraviolet (EUV) lithography scanners is building a powerful and reliable light source. ASML, which is the only company to manufacture EUV lithography tools, uses rather complicated laser-produced plasma (LPP) technology to generate EUV light. By contrast, numerous companies propose to use a free-electron laser (FEL), which relies on a particle accelerator, for EUV generation. While FEL has its advantages and is even endorsed by Elon Musk, ASML is unlikely to adopt it, according to JPMorgan.
"Given laser advances, ASML sees no reason to try new 'FEL' light source favored by Musk," reports Semi Doped, citing a JPMorgan note for clients.
Modern EUV lithography systems use laser-produced plasma light sources that fire powerful CO₂ laser pulses at tiny droplets of molten tin, around 30 microns in diameter, which turns them into ionized plasma with electron temperatures of several tens of electron volts that emits 13.5-nm EUV radiation. The light is then collected by a roughly 0.5-meter elliptical collector mirror coated with multiple layers of molybdenum and silicon, which selectively reflects as much 13.5-nm radiation as possible and directs it toward the intermediate focus at the entrance to the scanner.
Since virtually all materials absorb EUV radiation — even specialized multilayer mirrors absorb a substantial portion of it — the entire optical path must operate in vacuum and use reflective rather than conventional refractive optics, which is one reason why generating sufficient EUV source power remains challenging.
(Image credit: ASML)
Despite major challenges, ASML has gradually increased the source power of its LPP light sources from around 250W to around 500W and plans to increase it to 1000W in the coming years. In addition, the company plans to almost double the number of generated tin droplets to 100,000 every second.
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(Image credit: ASML)
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