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Comment by Animats | Hacker News Reader

A lot of people were hoping someone would come up with a better way to make "extreme ultraviolet" (soft x-rays, really) light than the horrible kludge used now.[1] Syncrotrons were tried. (Whatever happened to Lyncean?[2]) What's used now looks like a physics experiment, not a production process. Drops of tin are hit with lasers to emit X-rays, which are then focused with mirrors on the mask and wafer. This takes a setup the size of a house that produces very little power at the output end.

Much of the industry was hoping something better would come along. But so far, it hasn't.

[1] https://strobe.colorado.edu/wp-content/uploads/STROBE_ASML-E...

[2] https://lynceantech.com/

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What's stopping them from using hard x-rays? Those are really easy to emit. (Genuine question; not trying to suggest that they're all idiots who just never considered using hard x-rays.)

Presumably difficult to make a material that can focus them?

Interaction with the mask material, I imagine. With hard x-rays, most of the photons generated will just sail right through, not interacting at all, or (worse) ionize the material being exposed.

Personally, I'm surprised that there aren't ways to generate this energy by nonlinear mixing of light from two lasers that are separated by the desired frequency.

Lasers are an Electro-Magnetic emission of which the output is a synchronized at a specific and regular frequency.

If you have two lasers at about 700nm and 1000nm, and they 'start' at a synchronized point, then 7mm (7000nm) of emission later they'd have a repeat of the cycle begin again.

During that cycle the interference pattern would probably have an interesting shape, but I very much doubt it'd be useful for semiconductor production. Maybe a math or physics graduate could elaborate on if there's a name for this kind of pattern and if there are any uses I'm not aware of.

https://en.wikipedia.org/wiki/Interference_lithography exists, but it only uses a single laser with beam splitters, and typically for creating large diffraction gratings and such.

That’s a linear mixing, non-linear allows for the absorption of two photons followed by the emission of one with twice the energy. That allows for a laser pumped frequency doubler.

Actually most consumer oriented lasers (for example green lasers) work like this, but I don’t know if it works for frequencies as high as soft x-rays.

https://en.m.wikipedia.org/wiki/Second-harmonic_generation

An option would be to replace the laser and tin with some tape. [1] I know tape is a consumable item but is considerably less professional compared to a laser.

[1] https://www.nature.com/news/2008/081022/full/news.2008.1185....

A laser is not just light. It is a specific wavelength. X-Rays are a spectrum. The EUV/soft X-ray is a part of that spectrum. There's also other properties that you want from the laser. But this tape-x-rays won't be easy to control or uniform in wavelength. Making it not a laser, even if you could collimate it.

https://en.wikipedia.org/wiki/Laser

Thanks for this info. I assumed there was a specific reason they used this setup. I was joking about using tape.

Too bad we can't make x-ray leds.

It's easier to generate hard X-rays than EUV. An X-ray tube is just an electron gun and a copper target.

Wow that's the most interesting power point I have viewed in a long time! What a complex machine!

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