METHOD FOR DIFFUSING ZN INTO COMPOUND SEMICONDUCTOR OF INP SYSTEM

摘要

PURPOSE:To enable very stable and excellently reproducible diffusion having as a source Zn3P2 which is a product from thermal decomposition of ZnP2, by locally heating the ZnP2 portion after vacuum sealing to cause it to decompose, allowing it to condensate on the inner wall of a quartz tube, and then diffusing it. CONSTITUTION:Weighted ZnP2 5 is placed in a quartz tube 1 at one end thereof, and a InP wafer 3 is placed in the center of the tube 1. After vacuum sealing in a vacuum below 1X10-6 torr, only the ZnP2 5 portion is heated with a burner 7 to decompose and allowed to condensate on a cooling portion 6. Thereafter, it is placed in a heat treatment furnace of 500 deg.C for, e.g., 20 minutes, thereby forming P-type layer which is about 2mum deep. At this time, if the amount of ZnP2 to be enclosed exceeds 0.2mg/cm3, the decomposition product of ZnP2 does not become Zn3P2, and the diffusion depth becomes shallow. Further, if the amount is less than 0.005mg/cm3, the saturated vapor pressure at 500 deg.C is not reached, thus providing inferior reproductivity of diffusion depth. Accordingly, if the amount of ZnP2 is set within the range of 0.005mg/cm3-0.2mg/cm3, ZnP2 decomposes into Zn3P2 and P4 and becomes easy to vaporize, exhibiting very good reproductivity.