3D Printing Integrated Circuits: What's Possible Now and in the Future?

The last news in the news section of the libresilicon site you linked was from 2018 - is it in active development still?

The best actually-printed-by-an-inkjet-printer circuits I know of are simple ring oscillators of at most ten transistors or so (e.g., [1]---and they're pretty bad transistors at that), and even the simplest microcontrollers require thousands of transistors.

The paper [2] is a good review of the difficulties. Inkjet printing has at best a ≈20um minimum feature size (vs. 0.01um current transistor sizes), and the material choice is really hard: instead of silicon, you need to make semiconducting inks using funky organic molecules like 6,13‐bis(triisopropylsilylethynyl) pentacene (TIPS‐pentacene). [3] is a good recent paper trying to work around some of these limitations. So everything is still very much in the research phase.

Although inkjet printed circuits won't be anywhere near current silicon circuitry anytime soon if ever (and inkjetting transistors is the best (and kinda the only) method of 3D printing circuits we currently have), the different form factor may be useful. Circuits---even if only a few thousand transistors---could be printed on 3D geometry for interesting microfluidics capabilities, flexible circuits might make good healthcare sensors, and [4] is even studying flexible spacecraft via printed electronics for surprisingly economical space debris removal. And combining all this with 3D printed mechanical parts (via, e.g., the impressive PolyJet [5], which is basically inkjetting layers and lacks only the right materials to print electronics) will be fun.

(as to the source's Air Force Research Lab printed chips, yeah, I can't find further info, either, and agree it was probably sandpapering away most of the spare silicon bulk of an integrated circuit [impressive, useful, but not printing])

[1] https://doi.org/10.1021/acsnano.6b06041 [2] https://doi.org/10.1002/admt.201700063 [3] https://doi.org/10.1038/s41598-017-01391-2 [4] https://www.nasa.gov/feature/brane-craft/ [5] https://www.stratasys.com/polyjet-technology

> Unless the author is proposing printing billions of gates and wires one by one ...

Just to point out, it wouldn't necessarily have to be in the "one by one" serial kind of approach of FDM 3d printing.

Something like the "one whole layer at a time" patterning approach of Stereolithography (SLA) 3D printers might turn out to work.

The closing piece of the article does say:

  The future of 3D printing integrated circuits will likely
  adapt a photolithography process or functional self-assembly
  process to produce integrated circuits with competitive
  resolution.

In a sense it is "additive", they're adding a CPU ... but then that's just what a pick and place machine does - it's how we've made PCBs for decades now

Well, two layer anyway. People have printed overlapping traces into 3d printed volumes before, but it's a very flawed process. High currents are basically out of the question (resistance too high), analog voltages are very hard (inconsistent resistance), complex circuits struggle with connecting traces, and high speed circuits struggle with grounding/shielding. It's possible to achieve shockingly good results by electroplating (https://youtu.be/Tx2B5hI4w1U) but there are heavy caveats.

There isn't really a process that approaches pcbs in a single area, much less all of them. Unfortunately that's more limiting than you'd expect- even very cheap ARM processors will probably be unstable without a ground plane and low resistance traces.

I hear there's some interesting stuff coming in 2021 (can't tie rumors to my real name) and lots of people are working on this kind of thing, but the solutions are non-obvious. SLA is having a lot of trouble because it's hard to include a lot of conductive powder without degrading resin quality (and worse, it blocks the light), sintered stuff struggles with mixed powders, and resin stuff struggles with density and continuous lines/planes.

Thomas Sanladerer had a video on this, essentially using the 3d printer as a plotter for PCBs. It creates an mask but the usual etching process is still there.

https://m.youtube.com/watch?v=sL0LZFcNaow

That's relatively easily achievable, a stepping stone on the path to ICs, and serves a large market that already exists.

Yet, I think there are no commercial offers, and no companies focused on building it (differently from ICs). Go figure.

Sure. Heidelberg's recently made [1] some cool tools ("maskless aligners") that can expose a ≈150mm wafer in an hour or so down to ≈500nm resolution, which is very convenient when rapidly iterating through one-off low-resolution designs or something in a research lab (for comparison, electron beam lithography does the same to ≈10nm resolution in maybe a day). It's still part of the whole fabricate-everything-as-2D-layers-on-a-wafer paradigm, though, and has the same limitations (e.g., temperature limits) as standard silicon circuitry made with conventional photolithography.

[1] https://heidelberg-instruments.com/en/#products

There's been lots of progress on DIY/academic maskless photolithography by using TI digital micromirror devices from projectors to reflect light into a microscope for exposing photoresist. They even sell a UV version that is just for this purpose (maskless light manipulation in general). As usual, the bigger issue is alignment between steps and the etchants.

Still don't know what it has to do with 3d printing, except the article sounds like GPT3 mindlessly connecting lithographic resin 3d printers and semiconductor photolithography, with a Google Scholar search on those terms as a data set.

Lithographic printers already exist and are now cheap. You are likely reading this comment through a photomask right now :)

I was curious too, and it turns out that Nano Dimension is publicly traded, has seen its market cap collapse over the last four years, and oddly seen a massive spike in trading volume over the last four months. I suspect this is another Microvision-like scenario where a stock on the verge of dropping into the pink sheets is getting gamed by people trying to convince others that it is the next big thing.

Another possibility: just loading the page pegs my cpu even with javascript disabled for as long as the tab is open or until I zap a bunch of elements. Could it be a new innovation in cryptocurrency mining?

Both FIB deposition and its cousin Focused Electron Beam-Induced Deposition (FEBID) are pretty nifty; they can cut/add materials down to maybe 1nm (!) resolution. However, they're extremely slow: they can only affect a single spot at a time and move at maybe only 100nm/s movement, so patterning a useful circuit may take days; it's mostly useful for research work. I don't think I've seen anyone figure out the chemistry to use it to print doped semiconductors, so transistors might not be doable anyway.

Really the only other sub-micrometer 3D printing category right now is two-photon lithography (shine a laser to cure a liquid resin into a solid, like common resin 3D printing), which can generally only use a single, even-more-specialized-than-required-for-inkjet material---almost always an insulating polymer---for an entire structure.

What quantity? With a traditional fab process it costs a million dollars to create the setup for your chip, but once you have that the cost of each chip is five cents. I suspect that there is basically no setup costs for this but each chips probably runs in the range of 100 each to make (I'm guessing here, but it looks to me like there is a lot of labor watching the printer). If you need only a few chips the printed process is cheaper, if you need millones the traditional process is cheaper.