DARPA funded a bit in this space a while ago. (Example: https://www.nextbigfuture.com/2011/01/darpa-maskless-nanowri...) I'm not sure how you get over the bandwidth limitations, even with multi-beam.

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amluto 10 hours ago | parent | next [-]

This is a totally different technology.

A free electron laser (FEL) uses free electrons (electrons not attached to a nucleus) as a lasing medium to produce light. The light would shine through a mask and expose photoresist more or less just like the light from ASML’s tin plasma contraption, minus the tin plasma. FELs, in principle, can produce light over a very wide range of wavelengths, including EUV and even shorter.

That DARPA thing is a maskless electron beam lithography system: the photoresist is exposed by hitting it directly with electrons.

Electrons have lots of advantages: they have mass, so much less kinetic energy is needed to achieve short wavelengths. They have charge, so they can be accelerated electrically and they can be steered electrically or magnetically. And there are quite a few maskless designs, which saves the enormous expense of producing a mask. (And maskless lithography would let a factory make chips that are different in different wafers, which no one currently does. And you need a maskless technique to make masks in the first place.) There were direct-write electron-beam research fabs, making actual chips, with resolution comparable to or better than the current generation of ASML gear, 20-30 years ago, built at costs that were accessible to research universities.

But electrons have a huge, enormous disadvantage: because they are charged, they repel each other. So a bright electron beam naturally spreads out, and multiple parallel beams will deflect each other. And electrons will get stuck in electrically nonconductive photoresists, causing the photoresist to (hopefully temporarily) build up a surface charge, interfering with future electron beams.

All of that causes e-beam lithography to be slow. Which is why those research fabs from the nineties weren’t mass-producing supercomputers.

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AlotOfReading 10 hours ago | parent | prev [-]

What bandwidth limitations are you referencing? My understanding is that deep euv lithography is limited by chromatic aberration, so the narrow bandwidth of a single beam FEL would be an advantage. If you need more bandwidth, you can chirp it. Is the bandwidth too high?

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amluto 10 hours ago | parent [-]

They mean bandwidth as in rate at which one can expose a mask using an electron beam, because they’ve confused two different technologies. See my other reply.

P.S. Can you usefully chirp an FEL? I don’t know whether the electron sources that would be used for EUV FELs can be re-tuned quickly enough, nor whether the magnet arrangements are conducive to perturbing the wavelength. But relativistic electron beams are weird and maybe it works fine. Of course, I also have no idea why you would want to chirp your lithography light source.

	▲	AlotOfReading 9 hours ago \| parent [-]
		I don't think it's strictly chirping, but there are methods to achieve that sort of time/ bandwidth trade-off with FELs. I've seen references to it pop up in high speed imaging, though the details of anything that fast and small are quite outside my expertise. Wasn't sure why you would want high bandwidth either, hence my confusion.