4 ms·

The thing I didn't understand after watching that video was why you need such an exotic solution to produce EUV light. We can make lights no problem in the visi

The thing I didn't understand after watching that video was why you need such an exotic solution to produce EUV light. We can make lights no problem in the visible spectrum, we can make xray machines easily enough that every doctors office can afford one, what is it specifically about those wavelengths that are so tricky.

on_the_train 8mo ago
It really is the specific wavelength. Higher or lower is easier. But euv has tricky properties which make it feasible for Lithography (although just barely it you have a look at the optics) but hard to produce with high intensities.
- YetAnotherNick 8mo ago
  Any source to this? I am hearing this for the first time.
  - s0rce 8mo ago
    ITs easy to make X-rays, you just hit a metal target with electrons: https://en.wikipedia.org/wiki/X-ray_tube https://en.wikipedia.org/wiki/X-ray_tube
    - YetAnotherNick 8mo ago
      You can hit metal the same way for EUV.
      - s0rce 8mo ago
        I assume this doesn't work well otherwise everyone would be doing it.
      - on_the_train 8mo ago
        No you can't, or rather you only get a tiny amount in the correct wavelengths
- formerly_proven 8mo ago
  Specifically, what makes x-rays easy to generate are these: https://en.wikipedia.org/wiki/Characteristic_X-ray https://en.wikipedia.org/wiki/Characteristic_X-ray In essence, smashing electrons into atoms allows you to ionize the inner shell of an atom and when an electron drops down from an outer shell, the excess energy is shed as high-energy photons. This constrains the energy range of X-ray tubes ("smash electron into metal") to wavelengths well below 13.5nm. (These emission lines are also what is being used in x-ray spectroscopy to identify elements)
  - s0rce 8mo ago
    You can also generate broad spectrum bremsstrahlung radiation easily, this is widely used for medical X-rays.
zozbot234 8mo ago
There is such a thing as X-ray lithography, but it comes with significant challenges that make it not really worth it compared to EUV.
- bpavuk 8mo ago
  I'd like to hear more about these challenges
  - magicalhippo 8mo ago
    As I understand it, primarly because due to the high energy level of x-rays, light x-ray interacts very differently with materials[1]. Primarily they get absorbed, so very difficult to make mirrors or lenses, which are crucial for litography to redirect and focus the light on a specific miniscule point on the wafer. The primary method is to rely grazing angle reflection, but that per definition only allows you a tiny deflection at a time, nothing like a parabolic mirror or whatnot. [1]: https://en.wikipedia.org/wiki/X-ray_optics https://en.wikipedia.org/wiki/X-ray_optics
    - newswasboring 8mo ago
      All of these problems or equivalent still exist in EUV. Litho industry had to kind of rethink the source and scanner because it went from all lenses to all mirrors in EUV. This is also why low NA and high NA EUV scanners were different phases. As I hear it, the decision had large economic component related to Masks and even OPC.
      - itishappy 8mo ago
        100%. EUV barely works. XRay litho takes all the issues with EUV and cranks them up to 11. It will take comparable effort to EUV, if not more, to get XRay litho up and running, and I'm not aware of anyone approaching this to anywhere near the level of investment that ASML (and others) have pumped into developing EUV tech. We may get there eventually as a species, but we're a ways off.
deleted 8mo ago
[deleted]
KylerAce 8mo ago
The issue isn't in generating short wavelength light, it's in focusing it accurately enough to print a pattern with trillions of nanoscale features with few defects. We can't really use lenses since every material we could use is opaque to high energy photons so we need to use mirrors, which still absorb a lot of the light energy hitting them. Now this only explains why we need all the crazy stuff that asml puts in it's EUV machines to use near x-ray light, but not why they don't use x-ray or higher energy photons. I believe the answer to this is just that the mirrors they can use for EUV are unacceptably bad for anything higher, but I'm not sure
- itishappy 8mo ago
  Photoresist too. XRays are really good at passing through matter, which is a bit of a problem when the whole goal is for them to be absorbed by a 100 nanometer thick film. They tend to ionize stuff, which is actually a mechanism for resist development, but XRay energies are high enough that the reactions become less predictable. They can knock electrons into neighboring resist regions or even knock them out of the material altogether.
generuso 8mo ago
The efficiency of X-ray tubes is proportional to voltage, and is about 1% at 100kV voltage. This is the ballpark for the garden variety Xray machines. But the wavelength of interest for lithography corresponds to the voltage of only about 100V, so the efficiency would be 10 parts per million. The source in the ASML machine produces something like 300-500W of light. With an Xray tube this would then require an electron beam with 50 MW of power. When focused into a microscopic dot on the target this would not work for any duration of time. Even if it did, the cooling and getting rid of unwanted wavelengths would have been very difficult. A light bulb does not work because it is not hot enough. I suppose some kind of RF driven plasma could be hot enough, but considering that the source needs to be microscopic in size for focusing reasons, it is not clear how one could focus the RF energy on it without also ruining the hardware. So, they use a microscopic plasma discharge which is heated by the focused laser. It "only" requires a few hundred kilowatts of electricity to power and cool the source itself.

on_the_train 8mo ago

It really is the specific wavelength. Higher or lower is easier. But euv has tricky properties which make it feasible for Lithography (although just barely it you have a look at the optics) but hard to produce with high intensities.

YetAnotherNick 8mo ago
Any source to this? I am hearing this for the first time.
- s0rce 8mo ago
  ITs easy to make X-rays, you just hit a metal target with electrons: https://en.wikipedia.org/wiki/X-ray_tube https://en.wikipedia.org/wiki/X-ray_tube
  - YetAnotherNick 8mo ago
    You can hit metal the same way for EUV.
    - s0rce 8mo ago
      I assume this doesn't work well otherwise everyone would be doing it.
    - on_the_train 8mo ago
      No you can't, or rather you only get a tiny amount in the correct wavelengths
formerly_proven 8mo ago
Specifically, what makes x-rays easy to generate are these: https://en.wikipedia.org/wiki/Characteristic_X-ray https://en.wikipedia.org/wiki/Characteristic_X-ray In essence, smashing electrons into atoms allows you to ionize the inner shell of an atom and when an electron drops down from an outer shell, the excess energy is shed as high-energy photons. This constrains the energy range of X-ray tubes ("smash electron into metal") to wavelengths well below 13.5nm. (These emission lines are also what is being used in x-ray spectroscopy to identify elements)
- s0rce 8mo ago
  You can also generate broad spectrum bremsstrahlung radiation easily, this is widely used for medical X-rays.

zozbot234 8mo ago

There is such a thing as X-ray lithography, but it comes with significant challenges that make it not really worth it compared to EUV.

bpavuk 8mo ago
I'd like to hear more about these challenges
- magicalhippo 8mo ago
  As I understand it, primarly because due to the high energy level of x-rays, light x-ray interacts very differently with materials[1]. Primarily they get absorbed, so very difficult to make mirrors or lenses, which are crucial for litography to redirect and focus the light on a specific miniscule point on the wafer. The primary method is to rely grazing angle reflection, but that per definition only allows you a tiny deflection at a time, nothing like a parabolic mirror or whatnot. [1]: https://en.wikipedia.org/wiki/X-ray_optics https://en.wikipedia.org/wiki/X-ray_optics
  - newswasboring 8mo ago
    All of these problems or equivalent still exist in EUV. Litho industry had to kind of rethink the source and scanner because it went from all lenses to all mirrors in EUV. This is also why low NA and high NA EUV scanners were different phases. As I hear it, the decision had large economic component related to Masks and even OPC.
    - itishappy 8mo ago
      100%. EUV barely works. XRay litho takes all the issues with EUV and cranks them up to 11. It will take comparable effort to EUV, if not more, to get XRay litho up and running, and I'm not aware of anyone approaching this to anywhere near the level of investment that ASML (and others) have pumped into developing EUV tech. We may get there eventually as a species, but we're a ways off.

deleted 8mo ago

[deleted]

KylerAce 8mo ago

The issue isn't in generating short wavelength light, it's in focusing it accurately enough to print a pattern with trillions of nanoscale features with few defects. We can't really use lenses since every material we could use is opaque to high energy photons so we need to use mirrors, which still absorb a lot of the light energy hitting them. Now this only explains why we need all the crazy stuff that asml puts in it's EUV machines to use near x-ray light, but not why they don't use x-ray or higher energy photons. I believe the answer to this is just that the mirrors they can use for EUV are unacceptably bad for anything higher, but I'm not sure

itishappy 8mo ago
Photoresist too. XRays are really good at passing through matter, which is a bit of a problem when the whole goal is for them to be absorbed by a 100 nanometer thick film. They tend to ionize stuff, which is actually a mechanism for resist development, but XRay energies are high enough that the reactions become less predictable. They can knock electrons into neighboring resist regions or even knock them out of the material altogether.

generuso 8mo ago

The efficiency of X-ray tubes is proportional to voltage, and is about 1% at 100kV voltage. This is the ballpark for the garden variety Xray machines. But the wavelength of interest for lithography corresponds to the voltage of only about 100V, so the efficiency would be 10 parts per million. The source in the ASML machine produces something like 300-500W of light. With an Xray tube this would then require an electron beam with 50 MW of power. When focused into a microscopic dot on the target this would not work for any duration of time. Even if it did, the cooling and getting rid of unwanted wavelengths would have been very difficult. A light bulb does not work because it is not hot enough. I suppose some kind of RF driven plasma could be hot enough, but considering that the source needs to be microscopic in size for focusing reasons, it is not clear how one could focus the RF energy on it without also ruining the hardware. So, they use a microscopic plasma discharge which is heated by the focused laser. It "only" requires a few hundred kilowatts of electricity to power and cool the source itself.