EUV light source - didn't know that :)  - Page 1
Forum section: electronics / general

author: daqq
author_rank: Super Contributor
timestamp: November 09, 2020, 09:18:16 pm
content: So, apparently a normal light bulb ain't gonna cut it, so to get the silly wavelengths required for today's EUV processes ( ~13.5 nm ) you need something special.What they do is:Shoot a microscopic droplet of tin (~30 um) into a vacuum chamber.Hit the droplet at precisely the right time with a CO2 laser.The droplet becomes crazy hot, forms a dense plasma.Plasma blinks at the required wavelength.Light is gathered by insanely polished special mirror.Light travels through the rest of the machine.Rinse and repeat thousands of times per second.Just wanted to share, pretty interesting stuff

author: jogri
author_rank: Frequent Contributor
timestamp: November 09, 2020, 10:02:36 pm
content: I wouldn't want to be the guy responsible for maintaining this thing... A mirror that has to be polished enough to reflect 13 nm light inside what is basically a sputtering system sounds like a fun combo.

author: Cerebus
author_rank: Super Contributor
timestamp: November 09, 2020, 10:42:39 pm
content: Quote from: jogri on November 09, 2020, 10:02:36 pmThat was my immediate first thought: "Hold on,wheredoes all that tin go? How do they keep it off the mirror?"

author: S. Petrukhin
author_rank: Super Contributor
timestamp: November 10, 2020, 12:25:20 am
content: Quote from: Cerebus on November 09, 2020, 10:42:39 pmMaybe they blow it off with a smoke catcher?

author: daqq
author_rank: Super Contributor
timestamp: November 10, 2020, 07:16:51 am
content: I'm pretty sure that the tin removal is one of those things that are the secret sauce of the manufacturerThat said, if you shoot the tin droplet from behind, won't it splatter in the forward direction?

author: filssavi
author_rank: Frequent Contributor
timestamp: November 10, 2020, 07:29:36 am
content: The main reason EUV took so long to get to market (but by far not the only one) is precisely the light source, for many many years there was no light source strong enough to make commercial sense, and even today EUV is being deployed only in the most critical steps of the process, as EUV have a fraction of the throughput with respect to normal DUv machines, mainly due to light source issues

author: Berni
author_rank: Super Contributor
timestamp: November 10, 2020, 07:39:45 am
content: And it doesn't even end there. You need optics to handle the light.Only issue is that we don't have a lens material that works with these wavelengths so all the optics have to be in the form of polished reflective surfaces. This includes optics all the way down to focusing it onto the mask.

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 10, 2020, 12:43:33 pm
content: What's stopping them going to Xrays which are even shorter wavelength but relatively easy to generate?

author: Cerebus
author_rank: Super Contributor
timestamp: November 10, 2020, 12:56:52 pm
content: Argh! I'm being a putz. As far as keeping the mirror clean while ablating tin droplets is concerned it's obvious what's going on once you think about it.The droplets have momentum, so dealing with residualunablated tin is easy, just let it hit a collector on the other side of the chamber. That bit was never too much of a problem as I saw it.As for the stuff that gets really hot and turns into a plasma? Well, that's it, it's not just metal vapour in a vacuum, it's aplasma, it has charge. You can just push it where you want with a electric field.I'm sure that there's a residual bit of tin floating about that eventually reduces the efficiency of the mirror but now I can see how the majority of the tin can be dealt with, rather than the machine being one large chamber for vacuum metallizing everything in it.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 10, 2020, 01:38:36 pm
content: Hmm, that could perhaps do it. The ions are certainly not negative (at least, not many of them?), the energy levels are several times the electron affinity of anything on the Periodic Table. And with the energy levels being around 90eV as mentioned, it should really only take a few hundred to do that, or even thousands of volts, just because. Grids could even be hanging to enforce specific electric fields in the drift area, without sacrificing the optical path too much I think.Quote from: NiHaoMike on November 10, 2020, 12:43:33 pmX-rays tend to cause a lot of damage, both to the resist and the substrate. The beam resolution can be very good indeed (a few atoms, even), though the masks can't be magnified any, they have to be made at 1:1 scale (well, unless you want to take up many meters of beam length with grazing-incidence mirrors, which, eh, it could happen?). But the exposure resolution is limited by the movement of ionized (Auger) electrons in the substrate and resin, some 10-20nm depending. Electron beam writing, same idea, plus the added restriction that you can't really create a mask at all, so you have to scan vector or raster -- very slow indeed!Tim

author: Berni
author_rank: Super Contributor
timestamp: November 10, 2020, 03:06:18 pm
content: Quote from: NiHaoMike on November 10, 2020, 12:43:33 pmI think the problem with those is that they start ignoring the reflective optics and going straight trough it, even if you can get them focused down into a mask then they might go trough the mask itself. Those Xrays are notorisuly hard to wrangle.And yes also possible that large quantieis of Xrays might mess up the silicon chip that is being manufactured, not sure how much energy is needed for that. Maybe they instead move towards shooting electrons at it with an electron gun, tho those can also get destructive once you give them enugh energy.

author: David Hess
author_rank: Super Contributor
timestamp: November 10, 2020, 04:09:31 pm
content: I wonder why they could not use a synchrotron source. Are they too large to be economical?

author: Marco
author_rank: Super Contributor
timestamp: November 10, 2020, 07:10:16 pm
content: Apparently TSMC is the only company which can make it work with decent yields.The debris from the tin ball screws everything up, I wonder how they fix it ... electrostatic filter perhaps?

author: Marco
author_rank: Super Contributor
timestamp: November 10, 2020, 07:13:01 pm
content: Quote from: David Hess on November 10, 2020, 04:09:31 pmAFAIK the industry refused to invest significantly invest in researching Free Electron Lasers mainly because of space requirements. Of course given the delays and yield effects from the tin light sources it might not have been the smartest decision in retrospect.

author: Twoflower
author_rank: Frequent Contributor
timestamp: November 10, 2020, 07:56:57 pm
content: This is provides a bit more information about the EUV process:https://www.youtube-nocookie.com/embed/f0gMdGrVteI?rel=0About the EUV source: At about 6:00 there is some more information. They actually hit the tin droplet twice. Even is a bit marketing-ish with photoshop-fail like video sequences it still contain some impressive information.

author: filssavi
author_rank: Frequent Contributor
timestamp: November 10, 2020, 10:18:08 pm
content: Quote from: NiHaoMike on November 10, 2020, 12:43:33 pmDesigning the optical train and masks for EUV is already extremely difficult ( you can’t use lenses as there is no material transmissive enough to make them with and you need to use only mirrors which is much harder). Doing it for x rays will be nigh on impossiblealso x rays have this pesky ability to pass straight through basically almost any material known to man, thus you will need to use mask sets made out of lead(which does not seem he ideal material).

author: filssavi
author_rank: Frequent Contributor
timestamp: November 10, 2020, 10:30:54 pm
content: Quote from: David Hess on November 10, 2020, 04:09:31 pmI don’t know for shure, but I suspect the sheer amount of money needed to be sunk into such a project are probably a complete showstopper, not only in term if of building the machine itself, but also into the research of how to run it as a factory while turning a profitAs far as I know most, if not all currently operating synchrotrons are research type facilities, and are operated as such (even if they sell beam time), with running periods alternated with periodic downtime for maintenance that can last for month, this is really incompatible with the requirement to get an ROI in term of few months/years, needed in the foundry business

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 11, 2020, 07:59:44 am
content: Quote from: filssavi on November 10, 2020, 10:18:08 pmThis is all solved problems, if perhaps not on the scale of semiconductor production. Any heavy element will do, tungsten, gold, etc. I suppose gold and platinum would be particularly desirable for their corrosion resistance. The mask is made of a low-Z, rigid material, like silicon carbide. I suppose beryllium would be wonderful, but too difficult to handle (it is still used I think, for certain applications like linear accelerator windows, which are used for food sterilization, medical treatment, etc.).X-ray optics use grazing incidence and achieve good efficiency. Chandra X-ray Observatory perhaps most famously, but they see use in synchrotron labs and so on as well.Tim

author: iteratee
author_rank: Contributor
timestamp: November 15, 2020, 03:08:16 am
content: Quote from: T3sl4co1l on November 11, 2020, 07:59:44 amI thought theywereusing the Chandra-like mirrors for EUV. This is the first I've heard of the conventional reflective mirror use. They need dense neutronium mirrors for better smoothness, or a chemical phosphorescence-like effect for dropping the xray energies down to to EUV levels.

author: dmills
author_rank: Super Contributor
timestamp: November 15, 2020, 02:08:35 pm
content: Xray down to EUV is one HELL of a Stokes shift!

author: Doctorandus_P
author_rank: Super Contributor
timestamp: November 22, 2020, 07:46:20 pm
content: It's completely insane technology.Some time ago I heared that each mirror has only about 30% or so refectivity, and there are over 10 mirrors in the system, and after that you still have to have enough light left to develop some kind of photomaterial in ms.