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Comment by internalfx | Hacker News Reader

So now a transistor is only like ~35 atoms across!

No.

The feature size is 7nm. That's like saying the tightest radius in your CNC mill's tooling is 3mm. The stuff you make is far larger. Just look at the SRAM area: it's .0269 square microns. And SRAMs are tiny compared to "gate" RAMs, like you'd see in a book.

The first line in that slide still blows me away.

17 million gates per square millimeter.

Yeah. I'm gonna attempt a Fermi analysis to try give an idea of how much room is still "down there". 1 sq um is 100,000,000 sq angstroms. The unit cell of crystalline SI is probably around 50 sq A. That gives about 2,000,000 unit cells per sq micron. My guess would be about 5,000,000 "surface" atoms. The SRAM is .025 of that---perhaps 120000 atoms. SRAMs are cubes, so about 40,000,000 atoms cubically. Assume an SRAM is about the size of 8 transistors (that's a big SRAM): that's about 5,000,000 atoms per transistor. I'm going to fudge it down to 500,000 atoms, to be conservative.

The smallest logic I've heard of is a transistor using 7 atoms in toto. That is a factor of 70,000x, or about 16 generations.

Now, how we'll get there, I don't know. Also, I think the generation gap will probably widen to 5, or more, years. So... 75 to 100 years of "room"?

My understanding is that the active gate region is far smaller already so there is less room to scale than you might think.

The active region is smaller, but this is an argument about total bulk. IBM has shown functioning transistors with only a handful of atoms, already.

Yes, but that's the limit. Quantum effects mean we'll probably never see a single-atom transistor. Even if we did that's only a few more scalings. The rest of the features won't shrink as much anyway.

We can see the end of the road. AFAIK no one has any clue how to even start thinking about 2nm or beyond. No one is even certain we will hit 5nm.

At what point does stray ionizing radiation make devices too error-prone to be useful I wonder?

Yes that is amazing, most biological components are bigger:

https://en.wikibooks.org/wiki/Cell_Biology/Introduction/Cell...

Most biological components function in 3D space, though, not on a surface.

https://en.wikipedia.org/wiki/Multigate_device#Tri-gate_.283...

But you're right, actual stacked chips ("3D" ICs) aren't used much, largely for thermal management reasons.

I understand and agree, but most biological components at a sub-cell scale are membranes and pores in membranes, or even linear or circular structures like RNA/DNA.

IANAB but wouldn't most biological components in a cell be proteins (DNA codes for tens of thousands of proteins)?

Sorry for the delay to answer.

Proteins are indeed incredible little machines and for someone with a computer background, they are the most interesting entities in the biological zoo. And proteins may be very large, some are hundreds of nm.

But by seing proteins as components, one misses the transport and signaling aspects which are important inside and outside the cell. It is a problem of scale, if we focus at some scale level, we miss what is going on at a smaller as well at a larger level. I think there is no easy solution to that problem.

Good to see I wasn't the only one to look at the table of atomic radius to check this.

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