Patent GB-1398862-A (GB)
Title: Integrated circuits
IPC: H01L27/082
Filed: 1972-05-19
Abstract: 1398862 Integrated circuits PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 19 May 1972 [22 May 1971] 23699/72 Heading H1K [Also in Division H3] In an integrated circuit comprising a plurality of mutually separated semi-conductor island regions in a common substrate of semi-conductor or insulating material, one of the island regions contains at least two transistors the emittercollector paths of which are connected in parallel and base zones of which are provided with bias current by a multi-layer current injector structure. The current injector structure includes at least three layers, including one of the transistor base zones, separated from each other by rectifying junctions and including a first injecting layer and an adjoining second intermediate layer the junction between which two layers is forward biased by a source of potential connected across the two layers so that charge carriers are injected from the former to the latter. Injection and collection of carriers proceeds from each layer of the current injecting structure to the succeeding layer, until the base zone itself collects carriers from its immediate neighbour and is thus provided with the desired bias current. The current injector structure may comprise three layers, including the base zone, but more complex structures comprising four, five, or as manyas seven layers are envisaged. All or part of the bias current may be drawn away from one of the layers of the injector structure by electrodes thereon, and if one of the layers is shorted to both its immediate neighbours in the injector structure, e.g. by a switchable transistor, no injection occurs and no bias current is supplied. The bias current may be otherwise influenced by an electrode (e.g. capacitive) on one of the layers of the structure, and in a seven-layer structure the third and fifth layers may be used independently to control the bias current, e.g. as two inputs of an AND gate. While the layers of the current injector structure are preferably semi-conductor layers of alternating P and N conductivity types, the first injecting layer may alternatively be separated from the second intermediate layer by a layer of insulating material sufficiently thin to permit injection therethrough by tunnelling. Apart from the preferred electrical input, energy may be supplied to the integrated circuit by electromagnetic radiation via a photodiode or a phototransistor. In Fig. 2, which shows a cross-section through part of a master-slave flip-flop circuit (see Division H3), a three-layer current injector structure comprises an elongate P type first injecting layer 20 common to a plurality of transistor pairs, an N type second intermediate layer 21 constituting the common emitter of a transsistor pair, and two P type third layers 5, 10 constituting the base zones of the transistors of the pair. The intermediate layer 21 comprises a relatively high resistivity portion 21b to which the injected biasing current is restricted and lower resistivity portions 21a, 21b which serve firstly as contact regions for the intermediate layer, secondly as isolating regions to prevent parasitic transistor action between adjacent base zones, and thirdly to contain the injected biasing current to a limited area. Conventional techniques and materials are employed in the manufacture of the structure disclosed. A variety of modifications and other circuit applications of the multi-layer current injector structure are described which do not lie within the terms of the present invention but which form the subject-matter of Specifications 1,398,863, 1,398,864, 1,398,865, 1,398,866, 1,398,867 and 1,398,868, all divided from the present Specification.