| 摘要 |
820,289. Semi-conductors; electrolytic etching and plating. PHILCO CORPORATION. Nov. 26, 1956 [Nov. 25, 1955], No. 36071/56. Classes 37 and 41. An alloy region is produced between a semiconductor body and a metal by depositing the latter electrolytically on the surface of the body and simultaneously heating the interface to produce alloying. The resulting device may be used as a rectifier, or the deposited metal may form the collector or minority-carrier emitter of a transistor, in the latter case two such regions usually being formed on opposite surfaces of the body to act as emitter and collector respectively. The deposition is preferably carried out by directing a jet of electrolyte 13 (Fig. 1) on to the body 8 with or without another jet 14 on the opposite side. A p.d. is established between the two by means of electrodes 22, 24 attached to a source of E.M.F. 26 by a changeover switch 28. Thus the operation may commence with electrolytic etching of the surface of the body to give the desired profile and deposition of metal then caused to begin by reversing the p.d. Heating is produced by radiators 50, 60, supplemented by coils 40, 41 to warm the electrolyte, so that the temperature of the latter may be equal to, higher than or lower than that of the body. The electrolyte temperature should be above the melting point of the metal deposited (or any eutectic formed with the material of the body) and below the decomposition point of the solvent used. The temperature of the body should be equal to or above the eutectic temperature with the alloying metal. When two jets are used the temperatures of the electrolyte and body may differ on the two sides. It is possible to start the hot jet before the electrolytic current, and to terminate the latter first, when additional heating is required. In a typical case the electrolyte consists of indium trichloride and ammonium chloride in ethylene glycol, the operating temperature being between 156‹ C. (M. Pt. of indium) and 197‹ C. (decomposition of glycol); 180‹ C. is suitable. The body is ntype germanium so that the application of two alloy regions produces a p-n-p transistor. Other metals that may be deposited are gallium, caesium, bismuth, or intermetallic compounds such as indium-cadmium. A higher boiling solvent such as glycerol may be used. Initial shaping of the body may be carried out independently, e.g. with a separate jet-etching system or by the method of Specification 805,291. Reference has been directed by the Comptroller to Specification 761,795. |
