Improvements relating to semi-conductor devices

摘要

972,522. Semi-conductor devices. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Sept. 14, 1962 [Nov. 6, 1961], No. 39649/61. Heading H1K. A semi-conductor device having a body of refractory semi-conductor material, e.g. silicon or germanium, with at least one junction between regions of different conductivity or conductivity type has the exposed surface of the junction hermetically sealed by a mass of insulating vitreous material fused to the surface of the body on each side of the junction and apart from terminals provided thereon. In one embodiment (Fig. 2) a silicon controlled rectifier formed of a wafer of N-type silicon 11 with a surface layer 12 of P-type material has part of layer 12 removed by etching to define an island 13 separated from the remainder of the surface layer by an annular portion of the N-type wafer, and the exposed edges of the P-N junction between the layer 12 and wafer 11 are hermetically sealed by glass 22. The island 13 of P-type material has a layer 14 of gold antimony alloyed thereto to form a low voltage P-N junction with a copper terminal member 15 soldered by a lead-tin solder to the goldantimony layer. An aluminium foil 16 is alloyed to the other face of the wafer and to a disc 17 of molybdenum previously coated on its opposite face with gold 19. The copper block 18 acts as a terminal and a heat sink and an aluminium control electrode 21 is secured to the layer 13 by ultrasonic bonding to complete the device. A further embodiment (Fig. 1, not shown) relates to a silicon rectifier in which an N-type silicon wafer with aluminium alloyed to a central region of one surface to form a P-N junction has alloyed to the opposite surface of the body a layer of gold-antimony to which is soldered by lead-tin solder a copper terminal. The aluminium layer is nickel plated (electroless) and then soldered to the copper terminal acting as a heat sink. As before the junction edge is sealed with glass. A final embodiment (Figs. 3 and 4) (Fig. 3, not shown) discloses an arrangement in which an aluminium foil is alloyed to and between faces of adjacent cylinders of N- and P-type material. The surface of the composite semiconductor body formed is oxidized before sealing of the junction edge by a glass annulus. A lower M.Pt. glass may be used in contact with the semi-conductor body, in each embodiment, with a further higher M.Pt. material subsequently applied. Several silicon wafers may be cut ultrasonically from a large silicon slice in which one or more junctions have been formed and sealing of the junction edges effected by a glass layer.