lecture_5_chex42

lecture_5_chex42 - Metalurgical Grade Si Production by...

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Metalurgical Metalurgical Grade Grade Si Si Production by Submerged Production by Submerged Electrode Arc Furnace Electrode Arc Furnace ) g ( ) g ( ) ( ) s ( ) s ( energy CO SiO Si SiO C Si Molten ) sand ( SiO ) chips wood coal ( C + + → + + + l 2 2 2 3
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From sand and wood to MG From sand and wood to MG Si Si C SiO CO SiO CO SiC SiO C ) g ( + → + + + 2 2 2 2 3 ) g ( ) g ( ) g ( ) ( CO SiO SiC SiO CO Si SiC SiO + + + + 3 2 2 3 2 2 2 l In Zones 1& 2 (T<1800 o C) In Zone 3 Si is formed by Complete reduction Incomplete reduction: SiO(g) and CO(g) ruse through the bed and condense in upper part of the reactor to give back SiO 2 and C. As SiO and CO rise they cool themselves and heat the descending liquid. A natural recycle.
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Preparation of pure reactants for electronic grade Preparation of pure reactants for electronic grade (EG) (EG) Si Si from MG from MG Si Si Si powder (+ impurities: B, C, Al) H Q & HCl 200-400 o C preheater & vaporizer Fluidized bed reactor Partial condenser c Q & H 2 , HCl, BCl 3 (some) SiHCl 3 SiH 3 Cl SiCl 4 BCl 3 PCl 5 PCl 3 Al 2 Cl 6 CCl 4 Etc. ) g ( ) g ( ) g ( ) s ( ) g ( ) g ( ) g ( ) s ( H SiCl HCl Si H SiHCl HCl Si 2 4 2 3 2 4 3 + → + + + Main Reactions
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Separate various chlorides by distillation Separate various chlorides by distillation SiHCl 3 SiCl 4 BCl 3 PCl 5 PCl 3 Al 2 Cl 6 CCl 4 Etc. SiH 3 Cl (-30.4 o C) BCl 3 (12.7 o C) SiHCl 3 (31.8 o C) SiCl 4 (57 o C) PCl 5 (162 o C) Al 2 Cl 6 (180 o C) PCl 3 (74 o C) Etc. BCl 3 (12.7 o C) SiH 3 Cl (-30.4 o C) SiHCl 3 (31.8 o C) Useful product. Other chlorosilanes are produced by catalytic redistribution of trichlorosilane
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Production of EG Production of EG Si Si by H by H 2 reduction of reduction of cholorosilanes cholorosilanes or or pyrolysis pyrolysis of SiH of SiH 4 4 in a fluidized bed reactor in a fluidized bed reactor Si seed Fluidized bed reactor H 2 , SiHCl 3 Polycrystalline Si particles out gas products ) g ( ) g ( ) s ( C ) g ( ) g ( ) s ( C ) g ( ) g ( Cl HCl Si SiHCl HCl Si H SiHCl o o 2 1000 3 1000 2 3 3 + + → + + ) g ( ) s ( C ) g ( HCl Si Cl SiH o 2 900 2 2 + ) g ( ) s ( C H Si SiH o 2 600 4 2 +
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Bulk Crystal Growth Techniques Bulk Crystal Growth Techniques 1) Czochralski Growth (Most Used; and used for both Si and GaAs) 2) Floating Zone Method (very pure but high cost) 3) Bridgeman technique (for compound semiconductors) http://ruby.chemie.uni-freiburg.de/Vorlesung/angewandte.html
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Czochralski Czochralski Growth Growth http://www.deas.harvard.edu/courses/es154/2001/lectures/lecture_2/materials/materials.html ! Single crystal Si is produced by melting polycrystalline Si and then resolidifying it. ! Electronic grade silicon is loaded into quartz crucible and heated to ~ 1500 o C in presence of Ar inert gas ! T m = 1414 o C http://www.caesar.de/english/research/project_groups/cg_mission.html
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lecture_5_chex42 - Metalurgical Grade Si Production by...

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