When SiO2 is reacted with 'C' at very high temperature in the range of 1800Â°C then the metallargical grade Si (MGS) is formed. This type of Si contains the impurities such as Fe, Al and heavy metals so this is not useful for electronic applications. The metallargical grade Si is refined further to get semiconductor grade or electronic grade Si (EGS) in which the impurities are very less so it is a pure Si.
Next we have to convert the high purity electronic grade Si into single crystal Si ingots or bouls. This is generally done today by a process commonly called as Czochralski method shortly called as 'Cz' method. In Cz crystal growth the shape of the ingot is determined by combination of two physical properties i.e. the tendency of cross section and the influence of surface tension.
The cross section of large ingot is almost circular. Figure below shows the Czochralski (Cz ) process.
After growth the Si ingot is shown in Figure below. The large single crystal ingot provides typically 12 inch diameter silicon wafers when sliced using saw.