The Chip a grain of sand that thinks

Take it apart

A stack of rocks, refined

This is a model of a modern AI accelerator: two silicon dies side by side, with eight stacks of memory around them, on a silicon bridge, on a package. Nvidia's Blackwell is built this way, and carries 208 billion transistors across its two dies, made by TSMC.¹

Layer by layer

• Lid copper, plated with nickel, pulls the heat away
• Dies silicon, cut from a single crystal
• Memory eight dies stacked like a deck of cards, wired through with copper
• Interposer a slab of silicon wiring the dies to their memory
• Substrate copper traces in resin
• Solder balls tin, silver and copper

Now open one die

A city in eleven floors

Inside a die, billions of transistors sit on the silicon. Above them, tungsten and cobalt plugs reach up to layer upon layer of copper wiring. Each copper wire is lined with tantalum, because copper left touching silicon would seep in and ruin the transistors.^5,6

Where copper gives up

At the finest layers the wires are only a few dozen atoms wide, and copper's liner takes up too much of the room. Intel moved its two finest wiring layers to cobalt, and GlobalFoundries described a switch from tungsten to cobalt at 7 nanometres.⁵

SiHfWCoCuTaSnAgNi

Quartz

Silicon, chained to oxygen

Quartz is silicon dioxide: every silicon atom held by four oxygens. Silicon is the second most common element in Earth's crust, but it never occurs on its own.

Break the bond

In an arc furnace, quartz is melted with carbon at around 2,000 °C. The carbon takes the oxygen away as gas, leaving liquid silicon metal. China accounted for almost 80% of the world's silicon materials in 2025.⁹

Eleven nines

99.999999999%

Chip-grade polysilicon must be at least this pure.² That's one stray atom for every hundred billion silicon atoms: one second out of 3,000 years.

The crystal

The same pattern as a diamond

Freed of oxygen, each silicon atom bonds to four other silicon atoms in a tetrahedron: the diamond-cubic crystal, 0.543 nanometres from corner to corner. Grown from the melt as one giant crystal, it is sliced into the wafers every chip is printed on.

How it works

A switch, billions of times over

A transistor is a switch with no moving parts. Put a voltage on the gate and a channel opens in the silicon fin; electrons flow from source to drain. Take it away and the flow stops. Every photo, search and AI answer is built from these on-and-off decisions.

The hafnium trick

By the mid-2000s the insulating layer under the gate was so thin that current leaked straight through it. In 2007 Intel replaced it with a hafnium-based material and a metal gate, which it said cut gate leakage more than tenfold.^3,4 Hafnium is recovered almost entirely as a by-product of refining zirconium.

Wired up

Tungsten or cobalt contacts carry the signal up from each transistor to its first copper wire. On a big AI chip this happens more than a hundred billion times, on a slab of silicon about the size of a postage stamp.

Beyond silicon

Gallium meets nitrogen

Grown layer by layer from gallium and nitrogen gases, gallium nitride forms a hard hexagonal crystal that switches power faster and runs hotter than silicon can. It's in compact fast chargers, 5G base stations and modern radar; its cousin gallium arsenide handles radio signals.⁷

One country

99%

China's share of the world's primary gallium in 2025.⁷ Gallium is a by-product of turning bauxite into alumina; refineries elsewhere could recover it, but most of that capacity sits idle.

And germanium

Gallium's neighbour on the periodic table, germanium, goes into fibre optics, infrared lenses and space solar cells. China is the leading producer and exporter of germanium metal.⁸

The cost

AlixPartners forecast, September 2021.¹³

19 March 2021

A fire in the clean room of Renesas's Naka fab in Japan, a major maker of car microcontrollers, cut supply further. TrendForce estimated three months before it was back to full output.¹⁴

Then the minerals

1. Feb 2022Russia invades Ukraine; Cryoin and Ingas halt neon production.¹¹
2. Aug 2023China puts gallium and germanium exports under licence.⁷
3. Sep 2024Hurricane Helene shuts the Spruce Pine quartz plants.¹⁰
4. Dec 2024China bans gallium, germanium and antimony exports to the US.¹⁵
5. Nov 2025China suspends that ban until 27 Nov 2026; licences still apply.¹⁶

Scale

208,000,000,000

Transistors on one Blackwell AI chip.¹ Each dot here is 1 million of them.

A galaxy in your hand

That's about 25 transistors for every person on Earth (8.2 billion in 2024)¹⁷, and in the same range as the 100 to 400 billion stars astronomers estimate for the Milky Way.¹⁸