Verfahren zur Herstellung von Silizium-Halbleiterelementen und nach dem Verfahren hergestellter Silizium-Leistungsgleichrichter

摘要

820,190. Semi-conductor devices. STANDARD TELEPHONES & CABLES Ltd. July. 5, 1957 [July 6, 1956], No. 21378/57. Class 37. A molybdenum-silicon structure comprises a silicon body, a molybdenum body adjacent said silicon body and a layer of a material consisting predominantly of gold disposed therebetween and in intimate contact therewith joining said bodies to form an adherent bond. The silicon power rectifier shown comprises a molybdenum base' 2 on which an N-type silicon disc 4 is mounted by means of antimony-doped gold solder 3. An acceptor impurity material such as aluminium 5 is fused to the upper surface of the silicon disc. A molybdenum electrode 6 is attached to the aluminium 5 and a nickel-clad copper wire 7 is welded to the electrode 6. The acceptor type impurity material may contain other Group III elements of the Periodic Table such as B, Ga, In and Tl. The silicon may be P-type, in which case various donor impurities or alloys thereof selected from Group V elements such as P, As, Sb and Bi may be used. In preparing the rectifier a single-crystal silicon ingot is sliced into wafers which are then etched. An aluminium and a molybdenum disc and a gold foil containing 1% antimony are cleaned by etching and the molybdenum outgassed. The cleaning of the bottom surface of the molybdenum disc prepares it for soldering to a copper heat sink. The components of the rectifier are then placed under compression in a helical spring holder which is placed on a tungsten strip through which current is passed to heat the assembly to about 750‹ C. for about 15 secs. in an atmosphere of pure hydrogen or other non- oxidizing gas such as helium, neon, argon or nitrogen, thus forming a P-N junction and simultaneously bonding the molybdenum to the silicon. The temperature to which the assembly is heated is below the melting points of silicon, molybdenum and gold, but is above the eutectic temperature of gold-silicon alloy. Prior to encapsulation the junction may be treated to improve the rectification characteristics, and the rectifier may also be subjected to a known electrical forming operation.