[naasking]

> Interesting. What sort of resolution is that 3D printing though?

Around 50 microns I believe. Not at lithography resolutions obviously, but that's limited by metal powder grain size.

> My guess would be using a single beam?

Electron beams can scan a whole print bed very quickly to heat up the whole top layer [1] which can't be done using lasers. This can be done easily with electrons since they are deflected using magnetic coils, like good old CRT monitors, but this can't be done using lasers because they have to move the mirrors mechanically.

That's why it seemed weird that photolithography would be so much faster, but maybe it's as you say, lasers can be stacked for parallelism to make up for those downsides. Stacked electron beams might interfere with each other because you can't really isolate magnetic fields.

[1] https://www.youtube.com/watch?v=jqjD-FWMexo

[amluto]

Photolithography fabs don’t use scanning lasers — they shine light through a mask and expose a large area at once.

[naasking]

Crazy they have physical masks with features as small as 7nm. I assume those are movable somehow but that seems like incredibly delicate work.

[DougMerritt]

> Crazy they have physical masks with features as small as 7nm.

Everything about this is crazy complex, and the state of the art in any given year is also secret to TSMC and other tiny-feature-size fabs.

But in addition to gradually upping the narrow-bandwidth/phase-coherent illumination frequency every year (which has many problems but continues to see continual progress), they've also long been using techniques to work around the diffraction limit/resolution barrier [1], such as subwavelength metamaterial "hyperlenses" / "superlenses" (previously widely thought to be impossible even in theory) [2][3] and "assist features" and other non-traditional masking elements to pre-compensate for imaging distortions [4]. Plus they fiddle a lot with the chip process to tune it in weird ways to assist with or compensate for the previous issues.

[1] https://en.wikipedia.org/wiki/Diffraction-limited_system

[2] https://en.wikipedia.org/wiki/Superlens#Theory

[3] "Subwavelength-Grating Metamaterial Structures for Silicon Photonic Devices" https://ieeexplore.ieee.org/document/8424820

[4] https://en.wikipedia.org/wiki/Extreme_ultraviolet_lithograph...

[kosievdmerwe]

You can use lenses and curved mirrors to make a larger mask focus the light onto a smaller area.

[naasking]

That still seems pretty delicate. The lenses and mirrors would have to be aberration-free to an extreme degree so as to not introduce too many artifacts, and moving the mask further from the surface would increase risk of diffraction artifacts, no?

[haneefmubarak]

It is, but that's how modern semiconductor lithography is done. Massive lenses and mirrors (both made of different materials that normal, since they need to have optical properties at wavelengths much smaller than human vision) are manufactured at great cost to ensure that it is free of aberrations. The extremely limited supply of these is actually one of the many factors that restricts the ability to move to newer processes and scale production capability of newer lithographies.

[naasking]

For good telescope optics, we look for something like 1/4 - 1/6 wavelength tolerance, minimum. That's for optical wavelengths, but photolithography is in the UV range, so that's already stricter tolerance in absolute terms because of the shorter wavelength, but how does the tolerance in relative terms compare? Thanks for the info!

[Tuna-Fish]

They go pretty hardcore on the optics. Have a look at their light path:

https://www.asml.com/-/media/asml/images/technology/43679-in...

[kosievdmerwe]

One youtube video[1] I watched had someone state that if you scaled up one of the curved mirrors to the size of the Earth, the largest imperfection would be the width of a hair.

[1] https://www.youtube.com/watch?v=en7hhFJBrAI around 7:30

[deelowe]

> That's why it seemed weird that photolithography would be so much faster, but maybe it's as you say, lasers can be stacked for parallelism to make up for those downsides.

The reality of how this is done is so much more complex than I would have thought: https://www.youtube.com/watch?v=f0gMdGrVteI Traditional techniques such as masks don't work when dealing with xrays.