How silicon wafers are made

A wafer is sliced from one crystal that can grow two meters long, pulled from a quartz pot used only once.

stations: 6
things upstream: 19
raw sources: 8
steps from the ground: 6

The short version

A silicon wafer is sliced from a single crystal. Pure polysilicon melts in a quartz crucible, a seed crystal is dipped in and slowly pulled up while turning, and a cylinder called a boule grows. A wire saw slices the boule, then the slices are ground flat, etched to remove damage and polished to a mirror.

Melt polysilicon in quartz

Chunks of ultra-pure polysilicon go into a crucible of high-purity quartz and are melted at 1,425 °C. Boron or phosphorus can be added to the melt in exact amounts to set the electrical type of the finished crystal.

1,425 °C

Goes in
Polysilicon Quartz
Pull a single crystal

A seed crystal on a rod is dipped into the melt and lifted slowly while it rotates, under argon gas. The melt freezes onto the seed in the same crystal pattern, and temperature and pulling speed set the width.

Goes in
Argon
Saw the boule apart

The finished cylinder can reach two meters in length and weigh several hundred kilograms. A wire saw slices it into thin disks, and the quartz crucible is usually thrown away after one ingot.
Grind the slices flat

Sawing leaves ripples and a damaged surface, so each disk is machined to improve flatness.
Etch off the damage

A chemical bath dissolves the crystal damage left behind by sawing and grinding.
Polish to a mirror

A final polish leaves a surface flat enough to hold circuit patterns only nanometers wide.

End of the lineSilicon wafer Next it goes into microchip, memory chip, camera sensor and 2 more.

Worth repeating

The quartz crucible is normally thrown away after a single ingot has been pulled from it.
Moving from 200 mm to 300 mm wafers cut the price per die by about 30 to 40%.
Wafer-grade silicon is nearly defect-free single crystal with a purity of 99.9999999% or higher.