Electronic grade silicon
EGS is the raw material for the preparation of single crystal silicon.
It is a polycrystalline material of high purity and requires doping elements to be in parts per billion range.
Major impurities - boron,phosphorous,carbon.
1st step is metallurgical grade silicon (MGS) production in submerged electrode arc furnace.The furnace is charged with quartzite and carbon.
Reactions taking place in furnace are :
- SiC (solid) + SiO2 (solid) -> Si (liquid) + SiO (gas) +CO (gas)
- Si (solid) + 3HCl (gas) -> SiHCl3 (gas) + H2 (gas) + heat
- 2H2 (gas) + 2SiHCl3 (gas) -> 2Si (solid) + 6HCl (gas)
- SiH4 (gas) + heat -> Si (solid) + 2H2 (gas)
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