GB807728A - Semi-conductor translating devices and method of manufacturing the same - Google Patents

Abstract

807,728. Semi-conductor devices. HUGHES AIRCRAFT CO. March 7, 1956 [April 4, 1955], No. 7218/56. Class 37. A method of making PN junction devices comprises forming a zone of one conductivity type on one face of a semi-conductor wafer of the opposite type by the fusion process, and then ohmically affixing to a region of the face surrounding the zone, a backing member of the same basic material and conductivity type as the wafer to facilitate handling in subsequent processing. A large number of PNP-type transistors are made from a circular wafer 10 of N-type Si 1 inch in diameter and 15 mils. thick by fusing A1 bodies to it at spaced points to form local regrown P-type Si zones 11 therein for use as collectors. Ohmic contacts 12 are provided to the eutectic AlSi overlying these regions. The remainder of the wafer surface is provided with a layer of Au 14 containing 0.5 per cent Sb leaving a clearance region 16 round each zone. An apertured wafer 20 of Si doped with sufficient As to give it 10<SP>3</SP> times the conductivity of the wafer 10 and provided on both faces with a layer 21 of Sb doped Au is then applied to wafer 10 and the assembly heated under light pressure to above the eutectic temperature of Au and Si and cooled at a controlled rate to weld the wafers together. The opposite face of wafer 10 is then lapped to reduce it to a thickness of 5 mils and a series of similar but smaller P-type zones for use as emitters formed as on the other face opposite the collector zones. The wafer is then diced to give single PNP units which are etched and provided with emitter, collector and base leads. If ohmic contacts are provided on the lapped surface instead of regrown P-type emitter zones junction rectifiers are produced. Use of a backing member of the same material as the wafer reduces any thermal stresses in operation and also simplifies the etching and dicing processes.