Improvements in or relating to evaporation processes for the deposition of metals, particularly for use in the making of semi-conductor devices

摘要

839,081. Coating by vapour deposition. ' WESTINGHOUSE ELECTRIC CORPORATION. Dec. 13, 1957, No. 38775/57. Class 82(2) [Also in Group XXXVI] In a process of evaporating the metal of a metal body to deposit a coating thereof on a member disposed below the metal body, the temperature of the body is raised to the evaporation point so as to effect the evaporation of volatile impurities and metal, the impurities and metal flowing toward the member are collected for an initial time period to prevent them reaching the member, and pure metal is allowed to deposit on the member only after the impurities volatilizable at the evaporation temperature have been driven off. The process is applicable to the deposition of doping material upon a semiconductor such as Ge or Si to provide a P-N junction therein. As shown, Ge wafers 14 are heated by graphite heater 15 and coated with Al by evaporation from body 28, impurities from said body being intercepted during the initial stage of the evaporation by shield 30 which is swung aside when all the impurities have been dissipated. Other metals which may be evaporated are In, As, Sb, Ga and Ag. Pure Al for making a transistor junction may be produced by evaporating Al on to a glass plate and then stripping off the resulting film.