PC Gamer - UK 2020-04)

per cent may actually make it to the face of the silicon wafer
once it has been bounced through a series of mirrors that,
helpfully, also absorb the EUV.
It’s enough though. Owners of very recent Hauwei phones
with Kirin 990 5G (TSMC, 7nm) chipsets, or the 7nm Exynos
9825 in Samsung’s Galaxy Note 10, are already benefitting
from the lower power requirements and smaller chip
footprints that the tighter process brings.

CIRCUIT TRAINING
So now you’re finished firing lasers to make plasma glow, what
do you do to etch the circuits mapped out by the photoresist?
You have to use a bit more
plasma, of course.
First, a solvent is used to
remove some of the
photoresist that wasn’t
exposed to the EUV light.
Then the silicon wafer is
baked at anything up to
180°C for as long as 30
minutes, depending on the process being used. Then it’s
dunked in plasma (this is known as a ‘dry’ process, as
opposed to wet liquid chemicals) to remove the top layer of
the wafer in areas not exposed to the EUV light. Then the
remaining photoresist is removed with a chemical stripper.
The shrinking of chip pathways was probably most clearly
seen during Intel’s ‘tick-tock’ years, where the CPU giant
would release a new architecture on a familiar process one
year, then shrink it to a new, smaller, technology node the next
year, fixing a few things as it went and calling it a new
generation. So for every Sandy Bridge we got an Ivy Bridge, all
the way up to Skylake, where they stalled. The same 14nm

process introduced with Broadwell (a shrink from Haswell’s

22nm node) was used for Skylake, Kaby Lake, Amber Lake,

Whiskey Lake, Coffee Lake, Cascade Lake, and Comet Lake.

The last of those is being sold today as part of Intel’s10th

Generation Core chips, a hugely confusing choice as ‘10th

Gen’ also includes Ice Lake chips built on a 10nm process

and a new architecture – Sunny Cove. Meanwhile AMDwon

the war of the little numbers by getting a 7nm chip into

production with Zen 2 (Ryzen 3000).

This obviously can’t go on forever. Eventually, transistors

will shrink to the point that they no longer function, or thatit’s

no longer possible to etch them with exotic lights and

chemicals. One avenueof

future development is the

photonic circuit, which uses

light instead of electricity.

Within a chip, photons

travel up to 20 times faster

than electrons, so makingthe

switch would have immediate

benefits. Then there aresome

alternate materials, such as carbon nanotubes (see boxout),

that could replace the silicon itself.

Make a transistor too small, and quantum effects startto

affect the way it works – electrons tunnel out of the gate

they’re meant to be in and into another. The smallest ever

transistor, made in 2016 by Lawrence Berkeley National

Laboratory, shows that traditional silicon chip manufacturing

only has a few generations left in it, and this means new

solutions should begin to be tested any time soon. Don’t

expectthemtofilter down to consumer level right away,but

It’sanexcitingtime nonetheless.

Ian Evenden

FARLEFT:Ascanof

IBMResearch

Alliance’s5nm

transistor,builtusing

anindustry-first

processtostack

siliconnanosheetsas

thedevicestructure.

LEFT:Productionand

cleanroomfacilities

atworkinIntel’sD1D/

D1XplantinHillsboro,

Oregon,whichmakes

chipson14, 10 and

7nmprocesses.

TEENY TINY Other things measured in nanometres

3

CPUTRANSISTOR

OnIntel’s14nmprocess,thegap

betweentransistorfins,andtherefore

betweengates,isaround70nm.These

havebeenusedinApple’sMacBooks

andMacBookPros.

2

DNA MOLECULE

A molecule of DNA is 2.5

nanometres across and about 5

centimetres long. If harnessed for data

storage, a single gram could hold 1

zettabyte (9.7 billion terabytes) of data.

4

HUMANHAIR

Rangingfrom50,000to100,000

nanometresacross,thehumanhairhas

no computingordatastorage

capabilitiesweknowof.Ifitdid,barbers

would berakingitin.

1

CARBON NANOTUBE

A single-walled carbon nanotube

measures just one nanometre across.

Theyaretentimesasstrongasregular

carbonandalsohavegreattensile

strengthand thermal conductivity.

WITHIN A CHIP, PHOTONS

TRAVEL UP TO 20 TIMES FASTER

THAN ELECTRONS

Image credit: Intel Corporation

Image credit: IBM

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