Patent GB-966340-A (GB)
Title: Monolithic semiconductor devices and methods of preparing same
IPC: H01L21/00
Filed: 1961-11-02
Abstract: 966,340. Solid semi-conductor circuits. WESTINGHOUSE ELECTRIC CORPORATION. Nov. 2, 1961 [Nov. 29, 1960], No. 39290/61. Heading H1K. A solid circuit consists of a semi-conductor wafer with layers of different conductivity types forming at least one PN junction extending parallel to the wafer faces, functionally different regions of the wafer being isolated by at least one slot extending through the thickness of the wafer and at least one discontinuity formed in the layer on one face and terminating at a slot. A typical circuit consisting of a capacitor and resistor in parallel (Fig. 4) is formed from a 5 ohm cm. N-type silicon wafer by heating at 1100-1250‹ C. in the vapour of indium, gallium, aluminium or boron to form a P-type surface layer. Surfaces to remain P-type are masked during the process or the layer subsequently etched or abraded away. Overlapping grooves 57, 58 are ultrasonically drilled or etched in opposite faces of the resultant PN structure, the overlapping parts together forming slot 56. If the grooves are etched in separate steps they may differ in depth. Ohmic contacts 61, 62 are subsequently attached and leads 63, 64 alloyed or compression bonded thereto. The capacitance is constituted by the PN junction in part 59 and the resistance by the thin layer of semi-conductor between one groove and the opposite face of the wafer. The multivibrator circuits of Figs. 6 and 19 are embodied in the solid blocks shown in Figs. 11 and 22, and Fig. 20, respectively. In each case a 0.1-10 cm. N-type germanium wafer has acceptor impurity diffused into both faces to form a PNP structure which is then provided with the various slot and groove configurations shown by etching or sandblasting through masks or ultrasonic drilling. In the Fig. 11 structure regions 90, 91 constitute transistors T 1 , T 2  (Fig. 6), the centre-tapped limb 93 forms resistors 72, 77, the parts of the PN junctions between adjacent grooves in limbs 94, 95 form capacitors 74, 76 and treated surfaces of the junctions the shunting resistors 69, 79. Resistors 75, 78 are formed by parts of the middle N-type region beneath the grooves in limbs 94, 95 and ohmic contacts are made to the body at points corresponding to 70 and 73 and earth. A modification of the structure with R.C. networks between the transistor emitters and earth is formed by modifying limb 92, as shown in Fig. 18. The corresponding parts of Fig. 22 may similarly be identified with parts of the circuit. In the block shown in Fig. 20 the centre-tapped limbs 181, 182 perform the function of resistors 168, 169 and 163, 167, respectively (Fig. 19), parts 173, 174 are the transistors, ohmic contact 186 constitutes the inter-emitter connection and the lower junctions in end regions 192, 193 form capacitors 162, 164. The solid blocks shown in Figs. 26 and 30 formed by similar techniques to those outlined above constitute twin T filter networks. Parts of the PN junction (indicated by the broken line) underlying ohmic contacts 452, 454, 456 (518, 514, 516) respectively form the three capacitors and the marked limbs the resistors. In all the above arrangements apart from that shown in Fig. 30 discontinuities in the surface layers are formed by grooves but mechanically stronger constructions may be provided by extending an underlying layer to the surface where a discontinuity is required. This may be done by providing a rib on a body of one conductivity type at the site of a discontinuity, diffusing impurity into the whole surface to form a PN junction at a depth less than that of the rib and then removing the rib to expose the underlying layer. Alternatively the discontinuity is formed by masking the site during the diffusion. A further possibility is to form a groove in one face, diffuse impurities into both faces so that the two surface layers thus formed merge in the groove and then remove the layers around the groove. Specification 889,058 is referred to.