Presentation 3 Manufacturing of semiconductors

Presentation 3 Manufacturing of semiconductors -...

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Manufacturing of Semiconductors Edge Profiling Wire Cutting Rod Grinding Crystal Pulling Laser Inspection Polishing Lapping Epitaxy
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Crystal Growth • i used for crystal growth is purified from SiO2(sand) through The first step in the refining S used o c ysta g o t s pu ed o S O (sa d) t oug refining, fractional distillation and CVD. process involves reducing the silica (silicon dioxide) into silicon and carbon monoxide. This is chieved y eating e w achieved by heating the raw silica in a furnace containing an appropriate amount of carbon, pically e rm f oal oke typically in the form of coal, coke, or wood. Once the reaction has finished, and the silicon has been separated, the result will be about 98% pure. Metallurgical Grade Silicon g (MGS)
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Crystal Growth •Si used for crystal growth is purified from SiO2(sand) through refining, fractional distillation and CVD.
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Crystal Growth Since the product of the previous reduction step is in the form of a solid, the 98% pure silicon is typically ground into a powder and combined with hydrogen chloride (HCl) to form the aqueous solution SiHCl 3 . The resulting iHCl uid p 2 ) from its impurities through an iterative process of SiHCl 3 liquid (bp 32 o C) from its impurities through an iterative process of fractional distillation. f 2 3 H (gas) H (gas) SiHCl (gas) 3HCl (solid) Si + + +
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Crystal Growth Finally, the pure SiHCl 3 can be converted into electronic grade silicon by inserting the SiHCl 3 into a chemical vapor deposition (CVD) reactor containing an appropriate amount of hydrogen gas. The SiHCl 3 will recombine with the hydrogen gas to form EGS (Electronic Grade Silicon) and hydrogen chloride gas. This process was first proposed by Siemens in the 1950's and is consequently referred to as the Siemens process. The resulting EGS material is usually deposited into a 1-4" rod for later onversion to single crystal silicon conversion to single crystal silicon.
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Crystal Growth Once the raw silica material has been refined into EGS, the crystalline structure of the EGS must be refined into Single Crystal Silicon (SCS) . This requires that the orientation of the polysilicon EGS material be aligned so that the crystalline structure is uniform There are currently realigned so that the crystalline structure is uniform. There are currently two popular methods for converting EGS into SCS, the Czochralski (CZ) Technique, and the Float Zone (FZ) Technique, both of which utilize a " rystal- ulling" device to grow the final crystal. Typically, a opant also crystal pulling device to grow the final crystal. Typically, a dopant is also introduced during this step to modify the electrical characteristics of the silicon material. he raw material contains < 1 ppb impurities Pulled crystals Float Zone (FZ) Czochralski (CZ) •The raw material contains < 1 ppb impurities. Pulled crystals contain O ( 10 18 cm -3 ) and C ( 10 16 cm -3 ), plus any added dopants placed in the melt.
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Czochralski Growth
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Czochralski Growth • All Si wafers used for ICs today come from Czochralski grown crystals.
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This note was uploaded on 10/27/2009 for the course ENGR MSE 401 50 taught by Professor Drwang during the Fall '09 term at LA Tech.

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Presentation 3 Manufacturing of semiconductors -...

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