GB918816A - Semiconductor device - Google Patents

Abstract

918,816. Semi-conductor devices. WESTINGHOUSE ELECTRIC CORPORATION. May 11, 1961, No. 17219/61. Class 37. A switching device comprises a semi-conductor wafer having a first region of one conductivity type disposed between second and third regions of opposite conductivity type, and a plurality of fourth regions of said one type forming PN junctions with the second region, electrodes in ohmic contact with the second and third regions and a plurality of electrodes joined to the fourth regions. As shown, Fig. 3, a circular wafer 10 of N-type Si, which may be cut from a rod pulled from a donor-doped Si melt and lapped and/or etched, or may be cut from a dendrite prepared as described in Specification 913,674 is disposed in a diffusion furnace of maximum temperature 1100-1250‹ C. in the vapour of an acceptor material, such material being maintained at 500-1250 C., in an example, Ga vapour is diffused into the flat parallel faces of the wafer at a maximum temperature of 1200‹ C. to produce P-type regions 18, 20. A collector contact 34 and a base contact 30, each of acceptor metal or an alloy thereof, e.g. Au-Ga, Ag-Sn-In, Ag-In (90: 10%), or preferably Au-B (99: 1%), are placed on opposite faces of the wafer (in an example the collector contact 34 is placed on a Mo disc), an annular emitter contact 32 of donor metal or an alloy thereof, e.g. Au-As, Ag-As, Ag-Sb, or preferably Au-Sb (99.5: 0.5%) is placed around base contact 30, and the contacts are fused to the wafer by heating in a vacuum of 10<SP>-2</SP> to 10<SP>-5</SP> mm. Hg or an inert atmosphere, e.g. at 750‹ C. for 15 minutes. The emitter annulus is then partially masked with wax, rubber, or resin, and etched with aqua regia and then with a mixture of HNO 3 , HF, and acetic acid to form a plurality of discrete wedge-shaped emitter regions as shown in Fig. 6; alternatively, the emitter regions may be circular, elliptical, rectangular &c., and may be formed by fusing a plurality of individual foils to the wafer. Metal, e.g. Cu or Ag, contacts are fused to the emitter regions and leads are joined thereto and to base and collector contacts. In a modification in which a row of emitter regions are formed on a rectangular wafer, two or more base contacts are provided. In operation, all emitter-collector paths become conductive when any one is fired, and remain conductive until all are rendered non-conductive simultaneously. A suggested application is for checking rocketry components during count-down. The semiconductor wafer may be of Ge, SiC, or a III-V compound such as GaAs, GaSb, InAs, InSb. Specification 913,674 is referred to.