Silicon
The silicon
The silicon is extracted from the sand, the latter is taken from the sand quarries
Silicon is very abundant in the earth's crust, immediately after oxygen,
The main compounds it forms are:
-Silicon carbide: obtained at very high temperatures from a reaction between silicon and carbon
-Silica or silicon dioxide: one of the compounds that make up the sand
-Silicates: they can be found in many minerals, especially in magmatic ones
-Silicones: they are inorganic polymers on a silicon chain, thanks to these substances such as silicone or lubricants are produced.
pure silicon is obtained by reducing silica with carbon in the melting reduction furnace at temperatures of about 2000 ° C. The starting material is quartz sand or quartz gravel, but it can also be obtained with other processes.
The structure
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It has a crystalline shape with a cubic lattice (it is a lattice similar to that of a diamond) in which each atom (varies according to the compound it forms) is
bonded to 4 other silicon atoms tetrahedral; has a blue-gray color and features
a metallic sheen.
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crystalline shape with a cubic lattice:
http://www.chimdocet-inorganica.it/file33.htm
Silicon carbide: https://www.azom.com/article.aspx?ArticleID=14
Silicones: https://www.wikiwand.com/en/Organosilicon
Silicates: https://geoetc.com/silicates/
Process Czochralski (CZ):
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The process consists in the vertical lifting of a seed at very low speed
monocrystalline silicon, just immersed in a crucible, that is a container resistant to high temperatures, containing
pure fused silicon.
The monocrystalline seed is instead a rod with a thin one on it
silicon layer in monocrystalline form
The molten silicon atoms, in contact with the monocrystalline seed, are oriented according to the
atomic lattice of the silicon structure;
The temperature of the silicon in the crucible is maintained
at 1414 ° C, and adhering to the monocrystalline seed, it is extracted
gradually
from the molten mass, which solidifies very quickly while retaining the monocrystalline structure of
seed to which it adheres.
Strict control of the temperature of the molten material, of the atmosphere in the chamber, and of the
extraction speed, as well as the absolute absence of vibrations, allows the production of spindles
cylindrical.
The next operation consists in cutting the melt using a diamond disc, obtaining in discs with a thickness of a few tenths of a millimeter called wafers
Wacker process:
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Process in which Silicon is cooled in a mold by means of a gradient
vertical thermal controlled. The block is then cut into large pieces
madinate medinate a sawed slab. The individual loaves are cut into thin slices:
polycrystalline wafers.
Floating zone method (FZ):
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In the float zone method, a crystal with a spurious structure and composition is
moves moves through an area where the material is liquid starting from a
crystalline germ that orients the atoms in the
fused area. This method allows you to
obtain mono-layers of high purity and crystallinity.
In the FZ method the fusion is carried out in vacuum or in inert gas and is ad
zero impurities because the melting zone is not in direct contact with the crucible
as in the CZ procedure.
