Perhaps someone can explain to me, why aren't x-rays or another high frequency EMF used? Sure we can't bounce x-rays off mirrors like we can light (or can we?), but seems like a logical step we've never taken for some reason I'm ignorant to.
You need the mirrors to focus the light. X-rays have been tried and they had problems, such as requiring the use of gold to block the x-rays in the mask.
Russia tries to create a lithography machine using X-rays. I'd take that with a grain of salt, but researches were done, so I guess it's possible, probably other approaches made more commercial sense at the time.
