Comment by CydeWeys | Hacker News Reader

Comment by CydeWeys | Hacker News Reader

I remember reading articles like this a decade ago saying that transistors couldn't get any smaller because they were already the size of visible light. We've since switched to UV light per this article, and there's still much shorter wavelengths available. The size of the atoms that make up the wafer itself could be a potential problem too, but there's other materials we can switch to that are less susceptible to quantum tunneling. And that's not even touching true 3D chip design (right now it's a pile of layers that is essentially 2D).

Point being, there's many billions of dollars in revenue here at stake, and chip companies are doing their damnedest to solve these problems. They've solved every challenge so far, and there's no real reason that these latest challenges are fundamentally unconquerable in ways that the previous ones were not. An article highlighting the current challenges is useful, but one positing that they can't be overcome is sensationalist.

On the contrary, this article omits mentioning most of the limits we're running into, probably because the reporter couldn't understand them. Dennard scaling ended almost a decade ago because of leakage. You can still put more transistors on a chip, but the benefit of doing so is going away: it allows you to put more hardware in there, but you can't afford to run it all the time because it overheats (the "dark silicon" problem), so instead of giving you a parallel speedup, you're limited to providing a wider range of alternative hardware resources. Reversible computing was an attempt to solve the power-dissipation problem, but it doesn't help with leakage currents, and it's also essentially unachievable as a practical reduction in dissipation with current technology.

(I think it's a little strange to call light with a wavelength of under 10nm "ultraviolet". It's 40 times more energetic than the single octave we call visible light; that's five or six octaves away. I think it's usually called "X-rays".)

True 3D chip design is older than 2D chip design. Bardeen and Brattain's transistor was a 3D chip. That's why it was impractical for 12 years until the planar fabrication process in 1959. Planar fabrication is not only technically important, but also necessary for our current approaches to cooling, which is getting gradually more crucial.

I agree that we're not even close to the ultimate limits of computation. If your lambda is 10 nm and your wires are 20 nm across, that's still on the order of 200 atoms across, and it's been demonstrated that you could just use one: that's almost 16 Moore doublings, or 32 years. And certainly when we figure out how to do reversible computation and molecular nanotechnology, we can reach that limit. But CMOS and X-ray lithography aren't on a path to do that.

CMOS had a great run, totally dominating electronics from about 1982 to about 2017, pushing every alternative process to the margins with its low cost and the miracle of Dennard scaling: ECL, Josephson junctions, CCDs, DNA computing, vacuum tubes, core, chalcogenide glasses. But now that's over.

But don't forget that electronics started in 1904. Vacuum tubes, planar bipolar transistors, planar bipolar ICs, and planar CMOS ICs have each had their time in the sun. Whatever comes next will be something totally different, maybe as different as vacuum tubes are from planar transistors, and there's no reason to expect Intel or TSMC to be the one to pioneer it, just as Polaroid, Kodak, and Nikon weren't the companies that pioneered semiconductor imaging sensors or flash memory.

I'd be surprised if it happened in the US or Europe. Israel, China, Korea, or Japan, possibly.

Excellent summary, note that the deep trench transistors (aka FinFets) helped with the leakage problem significantly, but heat will always be an issue.

I've speculated that if we could figure out how to manufacture it, we could get electron scale computation out of an artfully constructed Graphene matrix. Basically a tiny Pachinko machine with electrons for balls. But at that scale you're going to need redundancy to get around quantum effects. We know you can build transistors at 7nm [1] but to what end.

[1] http://arstechnica.com/gadgets/2015/07/ibm-unveils-industrys...

Thank you for both the plaudits and the corrections!

Great talk!

I don't think anyone doubts that we'll continue to make improvements in process technologies until the sun explodes, the main questions are pace and benefits.

Yes, we can create shorter channels using more/different materials. Yes, we can get stronger gate fields using more/different materials. Yes, we can start building vertically and cool the chip using microfluidics. But, all of these things take more time than previous scaling efforts, and are going to have quantum scaling benefits instead of the classical scaling benefits that we had before.

Even now, companies have a difficult choice when switching to 16nm - is it worth the cost and effort? The rules for designing chips have double width each new generation too, making it harder to physically design in addition to the less-manageable transistors. We now have a bad combination of high supply and low demand - new processes double supply due to shrinkage, but reduce demand due to design cost & difficulty.

edit: Newtonian => classical

The opposite of 'quantum' is 'classical', not 'Newtonian'.

> Even now, companies have a difficult choice when switching to 16nm - is it worth the cost and effort?

The alternative is to spread processing power over multiple cores and have programmers write code that takes advantage of that. We have a thirty year-long history of failures in that department. It has gone from "this is how we'll be writing code tomorrow" in the '80s to "this will FINALLY be a nail in the coffin of Moore's law, just wait and see" since the late 1990s.

The cost is worth it because there are a lot of high-profile industries depending on it, and there is no credible alternative yet. Until that alternative -- which will be hardware in nature, not software -- comes up, the current trend is all we have.

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