Improvements relating to Contact Electrodes for Semi-Conductor Devices and Methods for the Production Thereof.

摘要

1,189,740. Electrodes for semi-conductor devices. SEMIKRON GES. FUR GLEICHRICHTERBAU UND ELEKTRONIK m.b.H. 22 Nov., 1968 [24 Nov., 1967], No. 55416/68. Heading H1K. An electrode is applied to a semi-conductor body 1 by applying a first metal layer to the body, applying a second layer of a ductile metal over the first layer, and heating the arrangement to a temperature which is lower than the eutectic temperature between the ductile metal and the semi-conductor but higher than that between the ductile metal and the first metal and between the first metal and the semi-conductor. The layer thicknesses and heating conditions are selected so that the major part of the second layer retains its ductility after heating. Thus, as shown, the final structure comprises the semi-conductor body 1, a layer 4 consisting of a ternary alloy of the semi-conductor and both metals and a layer 3 still comprising the ductile metal. Ge, GaAs and SiC are referred to, but the body 1 preferably comprises Si, the first layer being of Al or Mg and the ductile metal being Ag or Pd. Cu may also be used as the ductile metal, in which case a protective coating 6 of Ag or Au is required. Various methods of applying the metal layers are referred to, including vapour deposition while the body 1 is heated to 200- 300‹ C., cathode sputtering and electrolytic or electroless plating. Alloying is effected at 600-700‹ C. in vacuo or a protective gas. The ductile metal may be applied as two successive laminae and a further layer of the first metal may be situated between the laminµ. Electrical connections may be hard soldered to the ductile layer using eutectic Au/Sn, Au/Ge or Au/Si alloy solders. The invention may be applied to rectifiers, transistors or thyristors and the electrodes so formed may be ohmic or rectifying.