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Published byRalf Morgan Modified over 8 years ago
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Process stages on the grower and link for main grower units with required process parameters
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Prepare raw material Prepare machine and hot zone Creation vacuum Melting Seeding Growth Detachment Annealing Unloading ingot
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Prepare raw material Verneuil stones scrap Compacted powder (density over 3.3 g/cm^3) Purity 99.998% Check purity under UV lamp (Hg) Size: 20-60 mm Layer by layer dense loading
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Prepare machine and hot zone
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Creation vacuum Diffusion pump Lock Vacuum gauage APG Electromagnetic valve
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Vacuum parameters 1 Initial vacuum 1*10 -2 Pa 2Melting 5*10 -4 Pa 3Annealing 5*10 -5 Pa
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Melting 5 cm melt Crucible material Equilibrium gas concentration in melt Mo x 10 W x 1.1 Ir No change
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Reaction in Al 2 O 3 Al 2 O 3 Al 2 O+AlO Al 2 O 3 Al 2 O+2O Al 2 O 3 Al 2 O 2 +O AlO Al+O AlO 2 Al+2O Al 2 O AlO+Al Al 2 O 2Al+O Al 2 O 2 Al 2 O+O Al 2 O 2 2Al+2O Al 2 O 2 2AlO 2O O 2
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Adjusting temperature field Black seed t melt ~ 100°C =2.88 g/cm 3
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Control parameters Voltage on heater fluctuation 1 mV in the range 5-12 V Voltage decreasing rate 5-15 mV/hour Pulling rate 0.1-0.6 mm/hour, accuracy 1% Accuracy of load measurement 1 g when load100 kg. Temperature change 1 deg/hour when water flow 3.5-4.5 cubic meter/hour and water pressure 4-6 bars
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Adjust melt temperature for seeding Over froozen melt Normal island seed
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Seeding Seed Convection line Island Over heated Normal
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Formation constrictions Heat removal from grown ingot – to provide ingot temperature lower then crucible walls Decreasing dislocations density Decrease inner stress Symmetrical growth
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Shouldering Seed Crystal
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Animation of the temperature along the melt free surface Before seedingSeedingShouldering
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Not symmetrical field HORN
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Melt temperature fluctuations «Blinds» Overheated melt- bubbles accepted by solid interface due to temperature fluctuations «Central cord» too cold melt or too fast growth speed
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Ingots profile 0.3-0.4 mm/hour 0.6-0.7 mm/hour
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After touch of ingot with crucible bottom to increase pulling up rate to 0.5..0.6 mm/hour
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Cycle example- capacity
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Position of seed
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Weight fluctuation
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Weight
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Annealing Voltage-hours
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Unloading ingot
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Prepare machine for next cycle Remove foreign material from crystallizer shields and heater and apply vacuum cleaner for crystallizer Clean elements of hot zone with rectified alcohol Remove and clean windows Clean washer with rectified alcohol
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Optical properties Transmission As grown (b, d) and after X-ray 4 hours (с, e)
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X-ray diffraction диафрагма: b – 5 мм, c –2мм, d-1 мм, e-0,2 мм, f-0,1 мм
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