A semi-conductor device

摘要

1,018,811. Semi-conductor devices. SIEMENS-SCHUCKERTWERKE A.G. Oct. 17, 1962 [Oct. 31, 1961], No. 39368/62. Heading H1K. In a semi-conductor device a metal member is pressed against an area of at least 10 mm.2 of a semi-conductor body or metallized area thereof with a pressure of more than 50 kg./cm.2. At least one of the contact faces is uniformly pitted to a mean depth of 0À05 to 50 Á and both faces are substantially planar. The member may be of copper coated, on the contact face, with gold, silver, platinum or palladium. For instance a foil of silver may be attached to the copper by heating under pressure during manufacture or in the initial stages of operation. Typically the semi-conductor body is mounted between two pressure contacts but a molybdenum plate may alternatively be soldered to one face of the semi-conductor wafer, if it is of silicon or germanium. At the pressure contact the semi-conductor surface may have metallic conduction due to heavy doping or coating with metals such as nickel, gold, silver, palladium, gallium, aluminium or indium. Such coatings are provided by electroplating or vapour deposition, by attachment of foils or in the case of gallium, by rubbing it on the surface. The typical device shown in Fig. 4 is made first by diffusing phosphorus into both faces of a 200 ohm./cm. P-type silicon wafer from phosphorus pentoxide vapour. After lapping one surface to expose the original wafer material boron is diffused into this from boron trioxide vapour. The edge of the wafer is then removed by spinning the wafer about its axis while a jet of etchant is directed at its edge, and the face roughened to a depth of 0À5-50 Á by lapping. Roughened silver foil 7 and wafer 5 are placed as shown on a molybdenum plate 4 hard soldered to copper base 2 and the sub-assembly with its associated dished springs 14, 15, 16 and mica centring washer 12 clamped over them by turning rim 2a over the lip of cup 17. Finally the metal and ceramic cap 20 is sealed to the base. Triodes, four layer switching devices, photo-elements, and solid circuits based on silicon, silicon carbide and A III BV or A II B VI compounds may be similarly mounted.