Comment by Someone | Hacker News Reader

Comment by Someone | Hacker News Reader

FTA: “Canon’s nanoimprint lithography — a technology under development for more than 15 years but which the company says is only now commercially viable — stamps chip designs on to silicon wafers rather than etching them using light.”

It seems everything old is new again. https://thechipletter.substack.com/p/leaving-arizona:

“there was a reason the 6800 was expensive. It was made using ‘contact lithography’, where the photomask, containing the image that is to created on the silicon die, comes into direct contact with the silicon wafer. This inevitably led, over time, to damage to the photomask, reducing yields and eventually rendering the expensive photomask unusable. Making a low-cost version of the 6800 would be impossible without a more cost-effective manufacturing process.”

Reading https://en.wikipedia.org/wiki/Contact_lithography and https://en.wikipedia.org/wiki/Nanoimprint_lithography, that problem doesn’t seem to have been solved, but of course, it’s possible that the lower cost more than compensates for it.

Contact (photo)lithography and this nanoimprint lithography are not the same thing.

The 2nd is like embossing, the 1st is like stencil (like other types of photolithography, but the photomask touches the wafer).

Can you be more specific about what the difference is?

With photolithography, what most chips are made with, the resist is developed by exposing it to UV light. A mask is used so that the desired parts of the resist are left behind, and the rest is washed away. Contact photolithography places the mask directly against the silicon wafer because it helps the optics during exposure, but the mask doesn't directly remove the resist.

In nanoimprint lithograhy, a stamp is pressed into the resist on wafer and leaves the desired pattern behind.

The difference is that the resist is removed mechanically instead of chemically.

How does the stamp not get damaged or degrade over time? Or is this part a consumable / easily replaced?

It might help you to look up https://en.wikipedia.org/wiki/Mimeograph and possibly other copying techniques. More approachable examples include CD / DVD https://en.wikipedia.org/wiki/Compact_disc_manufacturing or earlier vinyl record production methods.

For the case of chip lithography they'd probably make source masks, copy the first generation a time or two, and use those secondary source masks to produce consumable 'stamps' for production.

Hopefully the stamps maintain sufficient quality across at least a couple batches (50-100+?) of wafers.

I highly doubt it will be that much initially. Silicon is pretty hard.

The stamp doesn't touch the silicon or any other solid material, it hovers just above.

It only touches a liquid photo-resist that is spread on the wafer. The stamp is transparent, which allows UV light to shine though and exposes the photo-resist, which solidifies into a mask matching the stamp.

Ah ok! I thought the two were actually in contact. Ok, in that case they might get some life out of them.

It's how cheap holograms are made. They are simply stamped into the material rather than that there is a photographic step during mass manufacturing.

How are the masks(molds) created for the Canon process?

https://global.canon/en/technology/nil-2023.html

Would they still have to make a standard photomask and use that to produce a mold using EUV lithography? At which point a cheaper process could be used for production. ASML would still be in that supply chain, but only for mold production.

> In addition to the technology enabling high-accuracy measurement of positional-deviation information, matching technology enabling alignment with lower-layer patterns is also important. Canon has developed a proprietary matching system that achieves alignment by using laser irradiation to thermally deform the wafer (Fig. 2). This system makes it possible to change the heat input pattern and freely deform the wafer by controlling an ultra-fine mirror group called a Digital Micromirror Device (DMD). Instead of assuming that thermal deformation of the wafer worsens alignment precision as is conventionally thought, Canon has applied an innovative new approach to the alignment (Fig. 3).

This is damn cool (hah)! They use a DMD to deposit packets of heat to different parts of the mold to warp to match the underlying layer it needs to imprint for localized nm level positioning. Bad ass.

Am I wrong?

Well, the costs of photolithography have skyrocketed recently, so that's a big part of it. I suspect that plus cost reductions for this tech is why it can be viable despite the masks needing to be remade periodically.

Can you give any sense of numbers because my intuition is telling me the process should be a win.

If it takes N days of very expensive process to make a mask and the mask can be used M times with cheaper process, what are the thresholds where it is not cost effective?

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