Patent GB-775366-A (GB)
Title: Semiconductor signal translating devices and methods of making them
IPC: H01L23/488
Filed: 1954-05-06
Abstract: 775,366. Semi-conductor devices. WESTERN ELECTRIC CO., Inc. May 6, 1954 [May 11, 1953], No. 13286/54. Class 37. A semi-conductor signal translating device is produced by bonding a metal member to a matrix of semi-conductor material and extracting the member with an adherent portion of the matrix to which a further electrode is applied. The invention enables devices having semi. conductor bodies of small but controlled size to be produced. Fig. 2 shows apparatus for producing a bond-extracted semi-conductor body. A single crystal of germanium or silicon provides the semi-conductor matrix 11 mounted in a housing 13 containing an inert or reducing atmosphere, between a platinum rod electrode 12 and a wire member 10. Member 10 slides in a tube 21 which may be adjusted to the desired position by manipulator 18, and is urged against the matrix by spring 23. Heating is effected by passing current through coil 25 and/or between electrodes 10 and 12. The bonding member 10 preferably consists of material which forms a eutectoid alloy with the semi-conductor such as gold, gold alloy or aluminium, references being made to Specifications 759,012 and 724,930, and should also have a different expansion coefficient from the semi-conductor so as to produce strains on cooling. Acceptor or donor impurities may be included so that the bonded member may form either a rectifying contact (e.g. as described in Specification 759,012) or an ohmic contact (of N + or P + type) with the semi-conductor. The heating and cooling process and the depth of " feed in " of member 10, may be controlled so as to form a eutectic zone of predetermined size, and also to produce strain lines in the adjoining semiconductor material so that when the member 10 is forced away from the semi-conductor matrix 11 by pulling or crushing, a portion 32 (Fig. 4) of the material of predetermined shape adheres to the member. Examples using gold and germanium are given, in which the matrix is heated to temperatures between 300‹ and 400‹ C., a bonding current is passed through the electrodes for periods between 5 and 15 seconds, and the unit is cooled to 100‹ C. in periods varying from 8 secs. to 1 minute. Since the exposed surface lies along a natural cleavage, pressure, junction and other electrodes may be applied directly without lapping or etching. The semi-conductor material may comprise one or more PN junctions near the surface, so that the bond-extracted portion also comprises a PN junction. Fig. 5 shows a bond-extracted semi-conductor used as a diode structure with a point contact or bonded rectifying contact 50, housed in a resinous bead 54 as described in Specification 728,223. Fig. 9 shows a transistor comprising a bond-extracted body 92 supported in an aperture in a frame 90 on base electrode 93 which is soldered to a conductive coating 95 on the frame. Emitter and collector electrodes consist of wires in metal tubes 103 and 104 which are positioned on opposite sides of projection 94 and conductively secured to coatings 96 and 97. The emitter and collector points engage a surface of body 92 which has been flattened by etching. The structure may serve as a jig for bonding the emitter and collector contacts. The whole may be mounted in a glass or metal envelope. An NPN hook collector transistor is also described. A number of bonds may be made simultaneously by heating the matrix by means of a strip heater. Bonds may also be effected by soldering. Specifications 602,140, [Group XL (c)], 632,492, [Group I], 632,980, [Group XL (c)], 706,849, 769,673, [Group III], and 774,270 also are referred to.