Silicon crystal growth. Artwork showing the industrial Czochralski process used to grow silicon crystals. Polycrystalline silicon (top left) is melted with dopants to create a semiconductor material with the right electronic properties. A seed crystal on a rod (centre left) is added to trigger crystal growth (lower left). The rod is rotated and slowly withdrawn to form a large single-crystal ingot (right, cutaway view of furnace). Silicon used in microchips needs to be precisely engineered for structure and purity. Circular wafers will be machined from this ingot. For the production stages, see C014/7165 to C014/7167.