Patent GB-1246775-A (GB)
Title: Improvements in semiconductor devices
IPC: H01L27/02
Filed: 1970-04-09
Abstract: 1,246,775. Semi-conductor devices. INTERNATIONAL BUSINESS MACHINES CORP. 9 April, 1970 [12 May, 1969], No. 16820/70. Heading H1K. In a switching circuit (Fig. 1, not shown) comprising first and second transistors with parallel collectors and emitters, common collector supply resistors and first and second base input terminals, with a third transistor having a third base input terminal connected to a reference voltage; with a collector supply resistor, and an emitter connection to voltage supply negative in common with the remaining emitters over resistor R2; and the outputs being taken from the collectors; false operation due to parasitic voltage drop over a common conducting path is avoided by providing separate individual collector supply resistors by diffusion or ion implantation in the substrate of an integrated circuit semi-conductor extending from an earthed positive back electrode to electrodes at the front surface of the substrate which are connected through terminal resistors therein to supply points of the integrated transistor circuits (Figs. 4, 5, not shown). Individual channels are provided by diffusion or ion implantation extending through the substrate from the positive earthed base layer and metal heat sink of e.g. gold plated molybdenum bonded on a silicon wafer to terminal resistors interconnected with terminal electrodes of the several circuit devices, whereby mutual voltage drop between separate circuits is avoided. Additional semi-conductor layers may be applied in the formation of specific devices, e.g. transistors and resistors, for the integrated circuitry (Figs. 6, 7, not shown). In operation (Fig. 1, not shown), the third transistor is driven conductive to produce a reduced output voltage if the first and second input levels are reduced, and is driven non- conductive if either first or second input is applied; so that the output develops full positive. Current traverses the first or the second collector resistance but not both. The construction (Figs. 8C, 8D) comprises a polished N+ silicon substrate 8D doped with As, P, or Sb, which is thermally oxidized, coated with photo-resist, etched to open windows in the oxide layer at a predetermined location for heat diffusion of P from PDCl 3  through the windows; the oxide films being etch stripped leaving three channels 82-1, 82-2, 82-3 in the substrate doped to low resistivity. An epitaxial layer 85 of intrinsic material with P impurity is deposited, followed by oxidation to layer 86, deposition of further photo-resist, and etching to open windows over the area to be diffused, overlying areas 82-1, 82-2, 82-3; into which P is heat-diffused from POCI 3  with formation of oxide layer 88 to form channel extensions 82A, 82B, 82C. The surface oxide layer is etched off, a second N-type epitaxial layer 90 is formed on layer 85, oxidized, and a photo-resist is deposited. Further windows are etched overlying the respective channels to define further N-type extensions of the channels. Selectively located P+ boron diffusions isolate the N channels. Monolithic semi-conductor circuits or devices may be formed by diffusion into the second epitaxial layer, and interconnected into required circuitry with voltage connections between selected electrodes and the N channels.