| 摘要 |
A pure fused body of silicon is produced by electrically heating silicon in powdered form in an electrically non-conductive heat-resistant container in vacuo or in a protective gas atmosphere so as to form a sintered body, removing the sintered body from the container, and subjecting to a zone melting process. The protective gas may be argon or a decomposable gaseous silicon compound, e.g. SiHCl3 or SiCl4, which may be in admixture with hydrogen. Heating may be by an induction coil or by passage through the powder of a direct or alternating current. As shown, the vessel comprises a vertical quartz tube formed in two parts 2, 3 which are held together by a few fused points and which can be readily separated. Tube 2, 3 is enclosed by a further quartz tube which may be evacuated or filled with protective gas via pipe 8. An induction heating coil 9 surrounds tube 5 and may be moved upwards or downwards at 1-10 mm/min. Heating is initiated in a short fused rod 17 of silicon. If the rod is sufficiently impure, it may be directly heated by the induction heating coil. If the rod is pure, however, it must be indirectly heated, e.g. by means of a radiation heating element 18 of Mo or W which is itself heated by the induction heating coil. In a modification (Fig. 2, not shown) powder is confined in a horizontal tube under pressure by means of two graphite plates which act as electrodes for the passage of an electric current. The current may be maintained constant by means of a resistance. Radiation heating may initially be employed. A protective gas is passed through the powder in the tube.
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