Comment by zozbot234
21 hours 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.
21 hours 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.
I'd like to hear more about these challenges
Stochastic effects become a bigger and bigger problem. At some point (EUV) a single photon has enough energy to ionize atoms, causing a cascade that causes effects to bloom outside of the illumination spot.
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
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.
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There are no normal x-ray mirrors. The only way to focus them is to use special grazing mirrors where the x-rays hit them almost parallel to the surface.
https://science.gsfc.nasa.gov/662/instruments/mirrorlab/xopt...