"The mirrors guiding this light, made of sandwiched layers of silicon and molybdenum, are ground so precisely that, if scaled to the size of Germany, they would have no bumps bigger than a millimetre" <https://www.economist.com/business/2020/02/29/how-asml-becam...>
Or is it a matter of manufacturing it, testing it, and rejecting some percentage of things that don't fit your requirements due to imprecisions?
Are there any good background resources on how some of these things are done?
Test, measurement and calibration equipment for new technologies (think 5G/UWB, mmWave, even up to CERN LHC) can be right on the cutting edge of technology. Companies who specialize in these areas tend to have large budgets on research and commercialization.
Nice summary:
https://www.youtube.com/watch?v=gNRnrn5DE58 ("Origins of Precision" by "Machine Thinking")
Two stones is not enough, you can then end up with two spherical surfaces. With three this isn't possible (imagine two of them are convex, when you rub them together they will grind eachother down and become less convex).
Is it a strict requirement that one plate remains stationary?
Altough, I disagree with the "random fashion". Alternating the pairs AB -> BC -> CA seems more logical to me.
Also, the order being random wouldn't effect the end result.
however, now my imagination is now running, and thinking about how overkill "true" random might be for this application. something "random" like an orbital sander would probably be enough. you're just trying to get away from side-to-side, left-circle, right-circle, up/down patterns. you're doing this to 3 different surfaces, so they would grind out any slight patterns which is the point. seems like a try crypto random would be as "effecient" as my roomba appears not to be.
Maybe some code then, instead: https://www.dwitter.net/d/20446
I'll add that this depends on the materials having similar properties, so when ground together, they are grinding each other. This means whatever residual shape you have in one of them, it won't be transferred completely to the other.
If the materials had very different hardnesses, one of them would dominate over the other when they're ground together.
https://pearl-hifi.com/06_Lit_Archive/15_Mfrs_Publications/M...
Very reasonable assumption that I used to have too. (Un?)fortunately it's also wrong, or at best, incomplete. :-) e.g., maybe you don't have the technology to make precisely straight lines, but if you can make a flat surface (like paper), then you can fold it in half and get a straight line. Then fold that in half and get a pretty-close-to-90-degree angle.
I also vaguely recall that feedback can increase precision in a system... like you can get 2% accuracy with a circuit that has only 5%-accurate resistors by using feedback (or something along those lines). Unfortunately I no longer recall how this is done. I just remember my mind was blown when I learned it.
You can build a machine like that and most machines are built like that because simply reproducing the precision that is already in the machine is cheaper than building a complex intelligent system that knows how to compensate for flaws in precision. Think about how many 3d printers do auto leveling in software rather than simply make the bed perpendicular to the print head by hand. Those old manual milling machines and lathes didn't have all that fancy software so they simply reproduced their own flaws.
Well, given a smart enough human he can compensate for the flaws in the tools and get to a higher degree of precision.
Scraping https://www.toyoda.com/news-events/rpd-blog-the-importance-o...
[1] https://www.amazon.com/Exactly-Precision-Engineers-Created-M...
For a cultural history of precision see The Perfectionists: How Precision Engineers Created the Modern World by Simon Winchester:
* https://www.goodreads.com/book/show/35068671-the-perfectioni...
Examples of this is the device[1] used for the redefined kilogram[2], LIGO[3] and many others.
[1]: https://www.nist.gov/si-redefinition/kilogram-kibble-balance
[2]: https://en.wikipedia.org/wiki/2019_redefinition_of_the_SI_ba...
[3]: https://www.ligo.caltech.edu/LA/page/faq (first question)
A more general approach is to understand measurement as a process where a minute signal has to be amplified to be more easily evaluated. There are many such methods.
In the case of surface metrology, Coherence scanning interferometry is such a method which uses the properties of interfering light waves to directly visualize surface anomalies as bands of lights. Another, more direct method is to drag a stylus across the surface and to amplify variations in position. Sort of like a turntable does.
"That means if the continental United States was polished smooth to the same tolerances, the entire country – from Maine to California – would not vary in thickness by just over two inches!"
Given the US is roughly 27 times the area of Germany, looks like semiconductor manufacturing requires roughly double the accuracy of space telescopes (1 mm * 27 is slightly more than 1 inch)
[0] https://www.nasa.gov/topics/technology/features/webb-craft.h...
I suspect lot of the production facilities would want to be near them.
https://www.bloomberg.com/news/features/2021-07-13/u-s-and-c...
https://www.intel.com/pressroom/archive/releases/1997/CN0911...
There must be a better way.
Yes, EUV machines are said to increase fab electricity consumption few times over, over regular UV steppers.
> There must be a better way.
The better way may well be worse. The alternative proposal is to build the whole fab around a synchrotron.
That's still better than tens of megawatt light sources.