Fortunately, silicon is a very abundant material, representing about 25.7% of the earth's Crust. Naturally occurring minerals containing silicon are very impure, so must be refined as well as be converted into the crystalline form .This is usually a multistage process, beginning with quartzite, a type of sand chemically quartzite is $SiO_2$.

The first step in the refining process is to convert the quartzite to Metallurgical Grade Silicon or MGS. This process usually takes place in a furnace in which a mixture of the quartzite and a carbon source (usually coal or coke) is heated to temperatures approaching 2000°C.

A number of reactions take place in the furnace, the overall result of which is that liquid silicon is drawn off and CO is given off as a gas.

The MGS that results about 98% pure, iron and aluminum being the two dominant impurities

$SiO_{2 (solid)}+2C_{(solid)} →Si_{(liquid)}+2CO$ Converting MGS to EGS: MGS reacts with gaseous HCl.

Fine powder of MGS reacted in presence of catalyst at elevated temperature.

This process can form any of a number of SiHCl compounds $(SiH_4- \text{silane}; SiH_3Cl- \text{chlorosilane}; SiH_2Cl_2 - \text{dichlorosilane}; SiHCl_3 -\text{trichlorosilane, or} SiCl_4 -\text{silicon tetrachloride}).$

The formation of SiHCl3 is most commonly used today.

$SiHCl_3$ is a liquid at room temperature, so it can be purified by fractional distillation.

The $SiHCl_3$ is extremely pure and is ready to be converted back to purified polysilicon.

This is accomplished in a large Chemical Vapor Deposition (CVD) reactor using the following reaction:

$2SiHCl_{3 (gas)}+2H_{2 (gas)} → 2Si_{(solid)}+6HCl_{(gas)}$

After this step the polysilicon is obtained which has $10^13-10^14$ ppb impurities. It is not useful in making wafers, therefore it undergoes CZ/FZ process to form pure silicon ingot.

Silicon wafers are cut from this ingot through diamond sawing and are polished using chemical and mechanical polisher to obtain polished wafers which are useful for making devices.