| 摘要 |
1,054,360. Semi - conductor devices. SIEMENS - SCHUCKERTWERKE A.G. Dec. 6, 1965 [Dec. 5, 1964], No. 51708/65. Heading H1K. In a diffusion process in which an impurity source and a semi-conductor substrate are sealed in a reaction vessel, the reaction gas comprises an oxide of the semi-conductor material and flows down the temperature gradient to the impurity source with which it reacts forming an oxide of the impurity; this oxide travels by a chemical transport reaction to the semi-conductor substrate with which it reacts depositing the impurity and reforming the semi-conductor oxide; the reaction vessel also has a condensation zone which, when activated precipitates the semi-conductor oxide to terminate or reduce its flow to the impurity source. As shown, Fig. 1, the reaction vessel comprises a sealed quartz tube 1 placed in a furnace 2 and heated by coils 3 to 6. The impurity source 7 comprises a quantity 9 of gallium disposed on a silicon support 9. The substrates 10 are of N-type silicon having P-type surface layers produced by a previous diffusion of aluminium. On heating the substrates, the silicon reacts with the silicon dioxide (quartz) of the tube 1 to form gaseous silicon monoxide which flows down the temperature gradient to source 7 where the silicon is deposited and a gaseous oxide of gallium is formed which travels to the substrates 10 with which it reacts depositing the gallium and reforming the silicon monoxide. Due to the elevated temperature the gallium diffuses into the substrates. Region 12 of the vessel forms a condensation zone so that when its temperature is reduced below that of source 7 the silicon monoxide generated at substrates 10 travels preferentially to region 12 where it is precipitated on the walls of tube 1 thereby reducing or terminating the transfer of gallium from source 7 to substrate 10. Depletion of the surfaces of the substrates is prevented by the presence of gallium vapour in the vessel. In an alternative arrangement, Fig. 2 (not shown), the condensation zone 12 is arranged between the source 7 and the substrates 10. |
