Czochralski process
Silicon ingots of single crystal are pulled from a crucible melt of pure molten polycrystalline silicon - Czochralski process.
The growth of Czochralski crystal involves the solidification of atoms from a liquid phase at an interface.
Controlled amount of impurities are added to the melt to provide the crystal with the required electrical properties.
The crystal orientation is determined by a seed crystal that is dipped into the melt to initiate single crystal growth.
The melt is contained in quartz crucible , which is surrounded by the graphite radiator.
The silicon is melted at temperature above 1425 degree C
After the seed is dipped into the melt , the seed is gradually withdrawn vertically from the melt while simultaneously being rotated.
The molten polycrystalline silicon melts the tip of the seed and refreezing occurs.
The melt freezes gradually by decreasing temperature and it assumes the single crystal form of the seed.
The diameter of the ingot is determined by the seed withdrawal rate and the seed rotation rate.
Dopants
- Adding boron makes p type silicon
- Adding phosphorous makes n type silicon
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