SEMICONDUCTOR DEVICE WITH GLASS BONDED PREFORM

摘要

1356061 Semi-conductor devices GENERAL ELECTRIC CO 24 May 1971 [22 May 1970] 16755/71 Heading H1K A Si wafer having a junction extending to a peripheral edge surface is mounted within a ceramic (or glass) preform having a surface conforming to the edge surface to which it is secured by means of a layer of glass passivant less than 1 mil. thick. The preform has a coefficient of expansion substantially matching that of Si and the passivant has a coefficient of expansion greater than that of Si but less than 45 x 10-7/�C. and a firing temperature below that of the preform. As shown, Fig. 1, the bevelled edge 13 of a Si rectifier is coated with a soft glass frit, the wafer is fitted into a matching aperture 17 in a preform 15 and the assembly is fired to form a glass passivant layer 19 less than 1 mil. thick. The preform may be a crystalline or a vitreous ceramic (e.g. borosilicate or aluminosilicate glass) or may comprise a glazed ceramic. Contacts are applied by vapour depositing or sputtering on to the Si surfaces and electrodes are soft soldered to the contacts. Alternatively plates of W or Mo may be soft or hard soldered to the wafer and the surrounding surface of the preform. In a modification, Fig. 3 (not shown), the electrodes are the same size as the respective surfaces of the wafer to which they are bonded, the preform is shaped to fit the assembly and is bonded to the electrodes as well as to the edge of the wafer by a layer of glass passivant less than 1 mil. thick. An SCR, Fig. 4 (not shown), may be mounted as in the first embodiment but an aperture is provided in one main electrode for the gate lead. This lead is insulated and the exposed wafer surface is protected by filling the aperture with silicone resin or varnish, a fluorocarbon resin, or a hard glass. Alternatively a small ceramic preform surrounding and bonded to the gate lead is sealed to the wafer and the main electrode by a layer of soft glass passivant, Fig. 5 (not shown). The semi-conductor device may also be a disc, a Schottky diode or a transistor.