Verfahren und Vorrichtung zur Rückgewinnung der unverbrauchten Ausgangsstoffe bei der Herstellung von Reinstsilizium mittels Reduktion von Silanen durch Wasserstoff

In the production of ultra-pure silicon by reduction of chlorinated silanes, e.g. SiHCl3 or SiCl4, the residual gaseous mixture of hydrogen, silanes, chlorinated silanes and hydrogen chloride is cooled to a temperature higher than the liquefying temperature of hydrogen chloride (-85 DEG C.) to liquefy most of the silanes and chlorinated silanes, and passed through at least one more cooling trap charged with an adsorbent for adsorbing the remaining silanes and chlorinated silanes. The hydrogen and hydrogen chloride mixture may then be washed with water, which may be very pure, to dissolve out the hydrogen chloride. The gases entering helical tube 3 at 2, where they are pre-cooled by gases passing through tube 8 from cooling trap 1, pass into tube 4, containing metal strips 4a to produce eddying in the gas stream, and are cooled by a solid carbon dioxide-methyl alcohol mixture 6. Silanes and chlorinated silanes are collected at 7 and the remaining gases pass out through tube 8 to further cooling traps 10, 11, charged with an adsorbent, e.g. silica gel. Alternative traps 16, 17 are provided so that traps 10, 11 may be regenerated by passage of hydrogen and the process carried out continuously. The hydrogen chloride is washed out in vessel 25 by water supplied through reservoir 23. The hydrogen is dried in a drying tower 26 filled with glass beads, and compressed in compressor 27. Remaining water is condensed in condenser 28 cooled by ice water, oxygen is removed by passing the hydrogen over a heated platinum or palladium catalyst, and final drying of the hydrogen is effected in trap 30 charged with liquid air or solid carbon dioxide. Silanes and chlorinated silanes may be removed from the first cooling trap by a siphon 35 to a vessel 36, protected from the atmosphere by a barrier device 40 which contains mercury or an oil, and a safety vessel, 42 to prevent this liquid entering vessel 36.