[sanxiyn]

> ... electron beam lithography ... could theoretically be built out of a hacked scanning electron microscope

Not only theoretically. Sam hacked his own scanning electron microscope and did electron beam lithography in 2018.

http://sam.zeloof.xyz/e-beam-lithography/

[bippingchip]

e-beam litho is anything but fast though: the machines are cheaper but they are much much slower in wafer throughput than the insanely expensive ASML EUV machines.

Now the website claims a fast fab, but leaves it open what that means: fast production of wafers? Or slow production of wafers that run fast?

[cma]

If the machines could be super cheap you could make up for slow by having many run in parallel (~~not parallel beams working on same chip, since electrons deflect each other, but machines running in parallel~~).

Edit: linked below, https://www.ims.co.at/en/products/ , says it uses 512x512 beams with a beam field of only 82um. Is that spacing between beams, or width of all the beams together?

[nwiswell]

The machines themselves couldn't be "super" cheap, that's impossible. You still have to deposit the e-beam resist while keeping the wafers extremely clean. This is non-trivial.

The only route to economic viability is absolutely massive beam parallelism inside the tool. But at that scale, there's serious questions about accuracy/reliability. Just one out of hundreds of thousands (or millions) of beams fails for a microsecond and the chip is ruined. This is a problem that is effectively sidestepped for traditional litho -- the masks themselves are created by (slow) e-beam, but mask inspection tools ensure that the masks are perfect before they are actually used to process product wafers.

[amluto]

> You still have to deposit the e-beam resist while keeping the wafers extremely clean. This is non-trivial.

True, but this is more or less the same process for e-beam and photolithography (as I understand it). I don’t see a fundamental reason why one couldn’t replace one ASML EUV machine with, say, 1000 e-beam machines and run them all in parallel. You would need the e-beam machines to be extremely reliable, but they’re conceptually simple devices and this should be possible.

(With vague ballpark numbers from the Internet, an EUV machine appears to be about 10k times as expensive as a SEM. Building 10k e-beam machines at the same cost as one Alibaba SEM would be an interesting challenge, and there would be factors pushing the price in both directions.)

[nwiswell]

> I don’t see a fundamental reason why one couldn’t replace one ASML EUV machine with, say, 1000 e-beam machines and run them all in parallel.

Fab floorspace is also very expensive, nevermind that's not even close to a realistic price per system (the factory interface alone costs $100k+)

[mrtnmcc]

Could also do multiple parallel e-beams to a chip (within reason). This might amortize some of the cost.

[AaronFriel]

> The machines themselves couldn't be "super" cheap, that's impossible.

There are a few dimensions of cost that can be optimized though, right? My understanding is that ASML is making ~10s of these EUV machines per year because of the extreme complexity of many components.

[nwiswell]

Sure. Chief among those dimensions is the fact that it's not used as a serious production technology, so the manufacturing of these systems doesn't benefit from economy of scale.

E-beam certainly does provide a bounding limit on how expensive EUV can get, but we're not in danger of hitting that limit anytime soon.

I expect that EUV will become cheaper/more productive per dollar in the medium term, unless ASML starts acting uncomfortably monopolistically (and it's probably in their interest to drive EUV adoption to starve out Nikon and Canon, anyway)

[petra]

Maybe the error rate of massively parralel e-beam could be good enough for ML chips?

[nwiswell]

I don't think being an ML chip means the defects are necessarily less fatal. These often interfere with the actual functioning of the chip, cause shorts, etc -- it's not just a matter of the TTL being very slightly messed up somewhere.

You could imagine chips that are engineered for redundancy / defect resistance, but that would make them a lot less performant so it's highly questionable whether that can be justified by any cost savings on litho.

[Zigurd]

Back-of-the-envelope, a beam array of 256k beams could plausibly level that 1 minute vs 1 day ratio.

[zymhan]

I presume meaning "fast turnaround on producing a design", i.e. less time needed to setup tooling.

Like the concept of Fast Fashion

[fsociety]

My short introduction into the fab industry exactly echos this. Allowing US companies to turnaround prototypes quickly is a valuable business. Perhaps they aim to get a foothold with this and slowly ramp up to high volume manufacturing.

[naasking]

e-beam litho just seems strange to me since electron beam 3D printing is just as fast as using lasers, so clearly the scanning part isn't the bottleneck. What is the bottleneck in this case?

[ThePhysicist]

You need to deposit a specific amount of energy into your resin to polymerize it, that takes time as you can't just crank up the amount of charge or the energy / electron in your e-beam as that will usually increase the energy variance and thereby the aberration. It's much easier to produce a coherent beam of light with sufficient energy than a coherent beam of electrons with comparable energy.

[chrisjc]

> since electron beam 3D printing is just as fast as using lasers

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

> What is the bottleneck in this case?

My guess would be using a single beam? Perhaps it's possible to scale this up to multiple beams working on a die or wafer at a time time?

Which brings up another interesting question. Would this process require the same kind of wafer/substrate as traditional EUV machines? Perhaps using this approach opens up the possibility of using different materials that are easier, cheaper and faster to produce?

Dont't traditional kinds of wafers have to be grown and sliced from exotic/rare materials? If so the additional time to "etch" with this new process might be offset by other factors such as what goes in to preparing the wafer?

[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.

[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.

[jjk166]

No the scanning is the bottleneck, scanning laser photolithography is equally slow. For mass production of chips, photolithography is done with a light source that illuminates a "large" area all at once.

[thinkyfish]

EUV can expose a whole chip image in a single shot. Raster scanning electrons takes about 4 hours to do the same image.