Semiconductor devices

摘要

959,447. Junction transistors. RADIO CORPORATION OF AMERICA. Aug. 4, 1960 [Aug. 24, 1959], No. 27116/60. Heading H1K. A transistor is formed from a semi-conductor wafer of one conductivity type having on one face a surface layer of the opposite type produced by diffusion and forming a gradual junction with the rest of the wafer. Impurity is diffused into both wafer faces to form a thin high conductivity layer of the opposite type on each face and then leads are attached to each layer and to the part of the wafer of said one conductivity type. A typical transistor of this type is made from a wafer of 1-20 ohm cm. P-type germanium by masking one of its surfaces, immersing it in germanium powder doped with 4 X 1016 atoms/c.c. of antimony and heating to 800‹ C. for an hour. Masking may be effected by heating the wafer for 10- 15 minutes at 700‹ C. in a current of argon containing triethoxysilane, the latter decomposing to form a silicon oxide layer which is then removed except from one face by treatment in 5% hydrofluoric acid. Alternatively, during the heat treatment one face of the wafer is protected from the gas flow by being stuck to a glass plate. After removal from the doped powder the wafer is reheated in nitrogen to 850‹ C. for 20 hours to produce a gradual PN-junction 34 (Fig. 3b) by further diffusion. The masking layer is then etched away and the wafer immersed in a powder consisting of 95% by weight germanium and 5% arsenic and heated for an hour at 800 C. in a nitrogen swept furnace to form an N+ layer over its entire surface. After etching the wafer to the form shown in Fig. 3d, the collector region 35 is attached to copper header 17, Fig. 3e, with lead antimony solder. A ring-shaped base contact 13 of indium-coated nickel and emitter contact of nickel coated with tin lead are then attached to connect the respective zones to wires 15, 16 sealed through the header, and the device encapsulated. The use of silicon, silicon germanium alloys, and alloys of phosphorus, antimony and arsenic with aluminium, gallium and indium instead of germanium is suggested.