Silicon

This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.

Jöns Jacob Berzelius isolated silicon in 1824 by reducing potassium fluorosilicate with molten potassium and washing the brown powder that resulted. He had no way of knowing that the element he had just purified would, roughly a century and a half later, give its name to a stretch of land south of San Francisco Bay and, through it, to the modern technology economy.

The route from Berzelius's powder to Silicon Valley runs through a specific chemical accident that turned out to be extraordinarily useful. When silicon is exposed to air below about 900 degrees Celsius, it forms a thin, continuous surface layer of silicon dioxide that protects the material beneath from further oxidation, so the reaction is self limiting rather than self sustaining. That protective layer is what let the Fairchild physicist Jean Hoerni build the 1959 planar process: leaving the oxide in place on a silicon wafer to protect the sensitive junctions underneath, then opening and closing precise windows in it for each diffusion step, the technique that made repeatable, mass produced transistor manufacturing possible.

The economic scale that followed is difficult to overstate from where Berzelius stood. Roughly four fifths of the world's elemental silicon production today goes not into electronics at all but into ferrosilicon alloys for steelmaking, an industrial use with no glamour attached to it. It is the much smaller remainder, refined further into semiconductor grade material, that becomes the transistors, integrated circuits and solar cells that a nineteenth century chemist studying an obscure element inside a Swedish laboratory could not have anticipated naming a valley, let alone an age.

This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.

Silicon was not the first choice for semiconductor electronics. Germanium, silicon's neighbor one row down the periodic table, was the material of the first point contact transistor, built at Bell Labs in December 1947, and remained the dominant semiconductor material for transistors into the late 1950s.

Germanium lost that early lead for a reason that traces back to the same self limiting oxide layer that makes silicon useful in the first place. Germanium dioxide, the oxide germanium forms in air, is soluble in water, about 4.5 grams per liter at room temperature, far more soluble than silicon's own oxide, so it cannot be grown into a reliable, permanent insulating layer on a chip the way silicon dioxide can. Without a stable native oxide, germanium devices could not be patterned and etched with anything like the precision silicon's oxide chemistry allowed. Silicon's oxide layer, thin, tough and chemically inert, could be patterned, masked and etched in exact, repeatable steps, which is exactly what building millions of transistors onto a single chip requires.

Silicon also has a wider band gap than germanium, 1.14 electron volts against germanium's 0.67, meaning silicon devices tolerate higher operating temperatures before they start conducting current in ways a circuit designer did not intend, and silicon is vastly more abundant and cheaper to refine, being the second most common element in Earth's crust against germanium's comparative rarity. By the early 1970s the industry had shifted almost entirely to silicon, not because germanium's underlying semiconductor physics was inferior, but because silicon's specific chemistry, an oxide that grows and then stops, turned out to be the property manufacturing at scale actually needed.