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Comment by naasking | Hacker News Reader

That still seems pretty delicate. The lenses and mirrors would have to be aberration-free to an extreme degree so as to not introduce too many artifacts, and moving the mask further from the surface would increase risk of diffraction artifacts, no?

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It is, but that's how modern semiconductor lithography is done. Massive lenses and mirrors (both made of different materials that normal, since they need to have optical properties at wavelengths much smaller than human vision) are manufactured at great cost to ensure that it is free of aberrations. The extremely limited supply of these is actually one of the many factors that restricts the ability to move to newer processes and scale production capability of newer lithographies.

For good telescope optics, we look for something like 1/4 - 1/6 wavelength tolerance, minimum. That's for optical wavelengths, but photolithography is in the UV range, so that's already stricter tolerance in absolute terms because of the shorter wavelength, but how does the tolerance in relative terms compare? Thanks for the info!

Read up on the Zeiss optics that go into the ASML EUV machines. (or at least what is publicly available knowledge). It's truly insane

They go pretty hardcore on the optics. Have a look at their light path:

https://www.asml.com/-/media/asml/images/technology/43679-in...

One youtube video[1] I watched had someone state that if you scaled up one of the curved mirrors to the size of the Earth, the largest imperfection would be the width of a hair.

[1] https://www.youtube.com/watch?v=en7hhFJBrAI around 7:30

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