Design, Construction, and Operation of a Laboratory Scale Reactorfor the Production of High-Purity, Isotopically Enriched Bulksilicon

Ager, J. W., III ; Beeman, J. W. ; Hansen, W. L. ; Haller, E. E.

Lawrence Berkeley National Laboratory

关键词: Removal;    Centrifuges;    08 Hydrogen;    36 Materials Science;    Production;   

DOI  :  10.2172/862010
RP-ID  :  LBNL--56760
RP-ID  :  DE-AC02-05CH11231
RP-ID  :  862010

美国|英语

来源: UNT Digital Library

【 摘 要 】

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.