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.
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.
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.
[1] https://www.nature.com/news/2008/081022/full/news.2008.1185....
Too bad we can't make x-ray leds.
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/