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Artillery Row

Letting data live

The secrets of semiconductors

The recent speculations that physicists had discovered a room-temperature superconductor seem to be fruitless, but it gives us an excuse to celebrate another miracle of the modern world: semiconductors. They are as essential to modern life as water pipes and electrical cables. Without them, you wouldn’t just lose your smartphone and laptop: it would mean no television, digital camera, washing machine or ATM. They are used in remote patient monitoring devices. Defence systems rely on them. Video games, microwaves, GPS, fitbits, central heating, digital watches, solar panels, pacemakers, manufacturing machinery — all use semiconductors. So important are they, there are now as many semiconductors as there are stars in the milky way.

To make a computer chip, you first need silicon, which is extracted from sand. This process produces a large ingot of silicon, which is salami sliced into discs, onto which chips can be etched. It is a delicate, sterile process: one speck of dust can ruin a batch. The disc is oxidised, to make it semiconductive and provide a protective film. Then circuits are etched on. This is called photolithography, because it resembles the development of photographs: the circuit pattern is made in a glass substrate, which is put on top of the silicon. Development fluid removes the areas of the disc exposed to light, and the pattern is laid on, ready to be etched out.

Before transistors, we used vacuum tubes

Transistors are essential to the way semiconductors work. They allow the circuits to be turned on and off. A transistor is a switch, and it can therefore store binary — 1s and 0s. Binary is how computers store information. The more transistors you have, the more powerful computers you get. Transistors allow different combinations of binary (bits of information) to be combined by making gates between them. The circuit can therefore make huge numbers of calculations with the binary code.

Before transistors, we used vacuum tubes. These large glass bulb-shaped tubes were able to send or stop sending electrons from the cathode to the anode when heated up. This is the original way that binary was used in computers. An early computer, the ENIAC, had eighteen thousand of them, all liable to overheat and need replacing — and all requiring a lot of energy.

Transistors do this job today. Anyone who remembers using bulky plastic transistors to build basic circuits at school will see the immediate problem: space. The improvement of computer power has been the result of making transistors so small that they are now much smaller than the diameter of a human hair. That’s why computers are so much better today than they were in the 1990s. They have many, many more transistors. We can put billions of them on a single chip.

Silicon is the essential material because the addition of impurities like boron and phosphorus makes it semiconductive. Phosphorus adds electrons to the silicon, and boron lacks an electron relative to silicon, allowing those spare phosphorus electrons to move to fill the gaps left by the boron, similarly to the way electrons flowed through vacuum tubes.

When we invented books, we complained that most were trash

Semiconductors have become geopolitically important. China makes a large proportion of chips — though not the ones used in things like AI. The Biden administration has cut China’s access to complex American semiconductors and invested money in new American facilities to make chips. That might sound like a step towards industrial policy, but remember that the market leader in making semiconductors is in Taiwan, a country China wants to invade and the US has pledged to defend. The ability to manufacture semiconductors isn’t just a question of where your next phone comes from: the modern balance of power is related to the location of these fabrication plants. It is as important for the US to secure its supply of complex semiconductors as it is to secure a supply of energy.

Of all modern miracles discussed in these columns, the semiconductor is the one we feel most ambivalent about. The internet is as much a curse as a blessing. It gave us Wikipedia, blogging and the YouTube back catalogue of the greatest music and television recordings of the last century. It is also full of pornography, hatred and misinformation, however. Smartphones preoccupy people’s attention, often for the worst. The problem of knowing where to put your attention, of being in control of your mind — the problem of keeping on an even keel in a choppy world — this is just a problem of being human, however.

When we invented books, we complained for centuries that most of them weren’t worth reading, that the world was being cluttered up with trash. If anything, that problem has gotten worse. Semiconductors are our books. They are the Milton and pulp fiction, the Bible and the Playboy, the dictionary and the idle comic strip of our age. We live in faster, busier, more variegated intellectual times, but the stakes are still the same. We must find something worth looking at, something that, as Samuel Johnson said, will help you better to enjoy life or to endure it.

Semiconductors give us all far more options to accomplish that. The fault is in us, and it is in our technology.

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