The material used in the growth of single crystal silicon is electronic grade polysilicon, which is extracted from quartz (SiO2) and purified to 99.999999999% purity. A crucible made of fused quartz is placed in a vacuumable chamber. The polycrystal is filled in the crucible. The chamber is filled with a protective atmosphere and the crucible is heated to about 1500°C. Next, a small chemically etched seed crystal (about 0.5 cm in diameter and 10 cm in length) is lowered into contact with the polycrystalline melt. The seed crystal must be strictly oriented because it is a replica of the sample on which it is based. A large crystal called a boule will grow on it. Current silicon ingots have a diameter of more than 300mm and a length of 1-2m.