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Semiconductor technology happens in factories. They need special materials, "reticles"
(= structures), "know-how" and huge amoundt of money (= capital) as major inputs |
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It's always about money! Only mass production will recover large investments. |
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The materials side always contains semiconductor substrates ("wafers") and often
very dangerous special "raw" materials. | |
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A number tells it all: 500 - 1.000 wafers /day are processed in a large Si "wafer
fab" | |
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Three big steps to Si wafers |
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Sand (SiO2)
Metallurgical Si
Poly-Si |
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Metallurgical Si
clean (doped) poly-Si.
Single crystal / wafer |
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Si single crystal growth is done by "Czochralski process" (CZ). |
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Dislocation-free crystals are possible but "bulk microdefects" and impurities cannot
be totally avoided. | |
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Nearly perfect 300 mm wafers are standard. |
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Growing single crystals of compound semiconductors is far more difficult than
for elemental semiconductors | |
GaAs:
150 mm wafers, encapsulation technique, disl. density (103 - 106) cm–2
GaP, InP
as GaAs but smaller and more expensive
SiC:
100 mm wafers, sublimation technique, several polytypes available, "pipe" defects |
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Precise stoichiometry is important |
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Vapor pressures if the constituents at the melting point might be very different |
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New kinds of defects might be encountered |
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Polytypie might be encountered |
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Major techniques are - Encapsulated CZ
- Sublimation growth
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© H. Föll (Semiconductor Technology - Script)
