METHOD OF CONTACTING A MULTISHORT-CIRCUITED EMITTER ZONE OF PNPN SEMICONDUCTOR STRUCTURE

1,206,480. Semi-conductor devices. BROWN BOVERI & CO. Ltd. 27 Dec., 1967 [29 Dec., 1966], No. 58619/67. Heading H1K. The junction between the emitter zone 11 and the control zone 3 of a PNPN device is shortcircuited at a plurality of locations by alloying a metal layer 16 containing dopants of the same conductivity-type as the control zone to the surface, thus forming a degenerate PN junction between the emitter zone 11 and a recrystallized zone 15 through which tunnelling can occur. As shown the N+ type emitter zone 11 of a Si thyristor is alloyed into an outer P-type zone 3 of a wafer using an Au foil containing 1% Sb. Holes are provided in the foil so that the zone 3 emerges at the surface at several points within the emitter zone 11. A foil 16 of Au containing 1% B is then alloyed to the surface, forming a P+ type recrystallized zone 15 which short-circuits the emitter junction by virtue of the tunnelling action through the degenerate junction between the zones 11 and 15. The wafer is alloyed to a carrier plate through an Al slice. The foil 16 preferably overlaps the area occupied by the emitter zone 11, but it may alternatively comprise several pieces of foil situated only at positions where the emitter junction emerges at the surface. In a further modification the Au/Sb foil may be alloyed to the entire face of the control zone, and apertures may be etched through the resulting emitter layer prior to alloying of the foil 16.