5 ms·
I know nothing about this area, so this is kind of an ELI5 question, but: If the wavelength of the light defines the lower limit of detail size, why can't they
by 13of40 9y ago
I know nothing about this area, so this is kind of an ELI5 question, but: If the wavelength of the light defines the lower limit of detail size, why can't they switch to actual x-rays, which we already seem to be really good at producing?
- fuzzyfizz 9y agocoherency/focusing
- ben_w 9y agoIIRC, same reason you use a laser rather than a lightbulb in a laser cutter. Conventional x-ray sources don't focus anything like as well.
- sbierwagen 9y agoNot my field, but I'd guess that one problem is that the hotter the photon, the better it is at penetrating matter. EUV photomasks are already a real pain in the butt to make[1], and making them work for shorter wavelengths probably introduces even more excitingly intractable engineering problems. 1: https://www.nist.gov/sites/default/files/documents/pml/div683/conference/Rice_2011.pdf https://www.nist.gov/sites/default/files/documents/pml/div68...
- justinjlynn 9y agoMasks may be a pain, but the pellicle (the part that protects the masks from contamination) is non-existent unless they've made a breakthrough I'm unaware of: https://www.semiwiki.com/forum/content/3720-euv-pellicles.html https://www.semiwiki.com/forum/content/3720-euv-pellicles.ht... basically this means any dust or contamination of the mask by anything bigger than 50-80 nm will possibly ruin the maskset and destroy the yield until it is replaced. It's a huge challenge.
- Animats 9y agoIf you go too far into the X-ray range, the high-energy X-ray photons penetrate the masks.
- sbierwagen 9y agoOne fun fact about EUV lithography that I learned recently: the masks and optics all work by reflection, since EUV photons aren't very "optical"-- you either have a thin film that EUV ghosts right through, or a thick film that stops it. Changing the type of atom doesn't much matter, there's not really anything akin to a pigment for energetic photons that's also thin enough to be used for nanometre lithography. But EUV doesn't like to reflect much, either, so the mirrors are made of stacks of metal films, which absorb a lot of the light and need active cooling. So that's the reason EUV sources have to be so much brighter than LUV sources: the optics eat most of the light getting it to the wafer. EDIT: elaborating on UV optics.
- sytse 9y agoThe optics are reflective because almost everything absorbs EUV.
- sbierwagen 9y agoOr rather, stuff either absorbs EUV or doesn't absorb it. I edited the parent comment to elaborate.
- fuzzyfizz 9y agocoool
- vpribish 9y agoI think it's that we don't have materials that can focus x-rays with refraction the way we do visible wavelengths. The alternatives are tricky.
- deleted 9y ago[deleted]
- deepnotderp 9y agoActually, x-ray lithography was a competing technology to EUV for a long time, but it has its own problems, not the least of which is going through the wafer itself and the fact that optics are ridiculously hard to make for it. Masks are already really hard to write and are projected to explode in price (not that they haven't already). Don't crush chip startups under mask costs ;)
- aphextron 9y ago>why can't they switch to actual x-rays, which we already seem to be really good at producing? The energy level is unnecessary. The lithography process does a "step-down" via electromagnetic lensing which determines the feature size. This becomes exponentially harder to do as you decrease wavelength (i.e. increase energy).