Often very small but precisely measured amounts of As, P or B can also be incorporated into the growing polysilicon.

The next step is to convert this poly-Si to a single crystal. There are two methods for crystal growth used in this case; Czochralski or crucible grown crystals (CZ crystals) and Float zone (FZ) crystals. The FZ method produces crystals with the highest purity, but cannot be used to produce crystals with large diameters.

Czochralski or crucible (CZ) method of crystals growth :

The Czochralski method, invented by the Polish scientist J. Czochralski in 1916, is the method of choice for high volume production of Si single crystals. A schematic drawing of a crystal growth by Czochralski method is given in Fig.3.10.