
The smallest transistor reported to date - upen
http://sciencebulletin.org/archives/6094.html
======
nojvek
If an atom is .1 - .5nm. That means the transistor wires are about 2-10 atoms
thick. About what Richard Feynman predicted in his "plenty of room at the
bottom". This is Amazing.

Is it possible to have a cube of 1nm transistors. Like a 100 million ^ 3. The
cube would have size of 10cm w.d.h.

~~~
Pyxl101
> Is it possible to have a cube of 1nm transistors. Like a 100 million ^ 3.
> The cube would have size of 10cm w.d.h.

Probably, but I suspect operating it would cause it to melt or explode :-) We
could probably manufacturer 3D chips today (or more 3D than they are today),
but from what I understand cooling them starts to become a major issue. (Not
involved in chip design or manufacturing)

~~~
Razengan
A total newb/layman question incoming; what exactly is the process that
generates heat in CPUs?

Are there any known/theoretical ways in which information be transmitted and
processed at the atomic/subatomic/quantum level without generating any heat?

~~~
pjc50
a) Resistance. Every switching action is effectively charging a small
capacitor (the transistor gate) through a wire. The wire has nonzero
resistance. It will also usually be travelling through the gate of one or more
transistors, which have a nonzero resistance ('Rdson').

b) _Theoretically_ , all computing that 'destroys' information (overwriting
one register value with another) costs entropy, although we're nowhere near
that level at the moment - orders of magnitude away.

'Reversible' computing would theoretically not incur that cost.

~~~
lake99
It's been a while since I studied or worked with these things, but I think
your explanation is wrong. A transistor (BJT or FET, doesn't matter)
dissipates very little in either cut-off region or saturation region (Rdson --
in FETs). It's in the active region that the transistor drops the most voltage
across itself and has a fair amount of current flowing through it. I don't
feel like doing the math right now, so I'll just cite something[1]. Anyway,
when you're switching transistor from one state to the other, it invariably
spends a little bit of time going through the active region. This is where it
heats up the most. In the saturation stage, most of the voltage drop is across
pull-up or pull-down resistors, so the V drop across the transistor is quite
small. The higher the frequency, the more time the transistor spends in the
active region, switching between states. This is why a given processor runs
hotter a higher frequency.

But like I said, it's been a while since I worked in this field, so if someone
knows better please correct me.

[1] [http://www.satcure-focus.com/tutor/page4.htm](http://www.satcure-
focus.com/tutor/page4.htm)

~~~
pjc50
I prefer "oversimplified" :)

You're correct that there is more dissipation in the active region, but the
Rdson is not negligable because the transistors are so small and the gate
voltages so low (1.8V or less).

Switching does dissipate power based on switching speed. For "big" macroscopic
FETs driving motors you have a separate gate driver amplifier to handle this.
Within a chip, there's a tradeoff because driving a particular gate fast
requires a bigger transistor to do the driving, which in turn requires a
bigger transistor to drive it - so if you're not careful you spend a lot of
area.

Transistor sizes are individually tuned during the design process (usually 99%
algorithmically, 1% human intervention). There's a whole bunch of tunable
design parameters.

I didn't discuss "leakage" either, so here's Intel on "high k metal gate"
technology:
[http://www.intel.com/pressroom/kits/advancedtech/doodle/ref_...](http://www.intel.com/pressroom/kits/advancedtech/doodle/ref_HiK-
MG/high-k.htm?&wapkw=\(32nm\))

(Basically, for big FETs we pretend that the resistance between gate and
drain-source channel is infinite. For tiny ones it's surprisingly small and
electrons can simply tunnel through your "insulator").

------
Altay-
Perhaps I'm guilty of falling for marketing definitions, but aren't we already
down to 14nm rather than the 20nm the article suggests in the opening
paragraph?

>They knew that the laws of physics had set a 5-nanometer threshold on the
size of transistor gates among conventional semiconductors, about one-quarter
the size of high-end 20-nanometer-gate transistors now on the market.

~~~
ilogik
I think 14nm is the current smallest feature size in modern cpus. Like a
resolution. A transistor is made up of multiple features.

~~~
tinganho
This is correct. And many foundries will be manufacturing 7nm transistors in
2017-2018. So it seems like this article is a bit incorrect.

~~~
tankenmate
When they say that they are manufacturing a 7nm transistor it means the
smallest feature is 7nm across. The gate size isn't always the smallest
feature of a transistor; it typically is, but not always. And sometimes the
larger features can be 4 to 5 times bigger, i.e a drain can be 40~50nm across
because it connects to multiple other transistors or is part of a compound
transistor. Transistors are inherently analog devices and so feature layout
isn't as simple as "I need an XOR gate in this part of the circuit".

------
Phithagoras
Paper at
[http://science.sciencemag.org/content/354/6308/99](http://science.sciencemag.org/content/354/6308/99)
DOI: 10.1126/science.aah4698

~~~
Animats
It's paywalled, even though this was work done at a U.S. Government laboratory
with tax funding. DOE has a 12 month "embargo" before the paper goes on line
for free. There's a previous paper on line, though, which describes the
process by which they get a stable one atom thick layer of molybdenum
disulphide on a silicon substrate.[1] Another paper covers how they got a
semiconductor junction made of molybdenum disulphide.[2] They've clearly been
plugging away at this exotic area of semiconductor device physics for a while.

[1]
[http://www.osti.gov/pages/servlets/purl/1259305](http://www.osti.gov/pages/servlets/purl/1259305)
[2]
[http://www.osti.gov/pages/biblio/1256052-mos2-heterojunction...](http://www.osti.gov/pages/biblio/1256052-mos2-heterojunctions-
thickness-modulation)

~~~
dredmorbius
Appreciating all that, SciHub should provide access.

[http://sci-hub.bz](http://sci-hub.bz)

------
mappu
_> Because electrons flowing through MoS2 are heavier_

Really?

~~~
tinganho
What they mean is that they have less energy and thus less likely to tunnel
between source and drain.

~~~
smaddox
Not quite. They mean they have a higher effective mass, which is a solid-state
physics quantity describing quasi-particles such as electrons and holes in a
crystal. You are correct that high effective mass particles do not quantum
tunnel as easily, though.

------
TheBeardKing
Maybe the headline should be smallest transistor with manufacturing potential.
See [https://www.wired.com/2009/12/functional-molecular-
transisto...](https://www.wired.com/2009/12/functional-molecular-transistor/)
and [http://www.nrl.navy.mil/media/news-
releases/2015/researchers...](http://www.nrl.navy.mil/media/news-
releases/2015/researchers-build-a-transistor-from-a-molecule-and-a-few-atoms)

------
austinlyons
Anyone with access to the full text know if they are reporting results on only
one transistor or if they were able to fabricate and test several transistors?

------
schwede
With transistors getting smaller and smaller, do we better methods to
dissipate heat? It seems like this is a major bottleneck.

~~~
daveguy
Smaller transistors are able to operate at lower voltages which is typically
why the TDP in watts have been dropping or remaining the same with more
compute.

I think manufacturing is the big question mark. One is good as a proof of
concept, but if you can't cram billions on a die then they can't compete.
Hopefully they can work out manufacturing.

~~~
AstralStorm
Producing the gates should be quite easy. The trouble is manufacturing and
embedding the nanotube wires.

------
b34r
I thought I remembered something about circuits of this size being infeasible
due to electrons hopping around?

~~~
marcosdumay
That's specific to a material. The most commonly talked limits are even
specific for MOS-FETs with a few specific insulators.

For alternative materials or designs, things change. Those people choose a
material for exactly this property, it has a bigger resistance, but leaks less
electrons.

There are also designs of transistors that switch on leaking current, never
becoming a classical conductor. Those have negligible leaking when off.

