Design, construction, and operation of a laboratory scale reactorfor the production of high-purity, isotopically enriched bulksilicon
The design and operation of a recirculating flow reactor designed to convert isotopically enriched silane to polycrystalline Si with high efficiency and chemical purity is described. The starting material is SiF{sub 4}, which is enriched in the desired isotope by a centrifuge method and subsequently converted to silane. In the reactor, the silane is decomposed to silicon on the surface of a graphite starter rod (3 mm diameter) heated to 700-750 C. Flow and gas composition (0.3-0.5% silane in hydrogen) are chosen to minimize the generation of particles by homogeneous nucleation of silane and to attain uniform deposition along the length of the rod. Growth rates are 5 {micro}m/min, and the conversion efficiency is greater than 95%. A typical run produces 35 gm of polycrystalline Si deposited along a 150 mm length of the rod. After removal of the starter rod, dislocation-free single crystals are formed by the floating zone method. Crystals enriched in all 3 stable isotopes of Si have been made: {sup 28}Si (99.92%), {sup 29}Si (91.37%), and {sup 30}Si (88.25%). Concentrations of electrically active impurities (P and B) are as low as mid-10{sup 13} cm{sup -3}. Concentrations of C and O lie below 10{sup 16} and 10{sup 15} cm{sup -3}, respectively.
- Research Organization:
- Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
- Sponsoring Organization:
- USDOE. Administrator for National Nuclear SecurityAdministration. Nonproliferation and National Security ProgramDirection
- DOE Contract Number:
- AC02-05CH11231
- OSTI ID:
- 862010
- Report Number(s):
- LBNL--56760; BnR: NN4101010
- Country of Publication:
- United States
- Language:
- English
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