Patent GB-1310412-A (GB)
Title: Semiconductor devices
IPC: H01L21/22
Filed: 1970-03-26
Abstract: 1310412 Semi-conductors HITACHI Ltd 26 March 1970 [28 March 1969] 14967/70 Heading H1K A silicon transistor is manufactured from an N-type silicon monocrystalline substrate 12 whose major surface is covered by insulant film 14 of e.g. silicon oxide into which an opening is etched to admit selective diffusion of a differing Group IV element, e.g. Ga, Sn, Ti, Zr, Hf or Pb, to form N-type region 18 on the surface of which a further oxide film is formed; and which is limited by interface 20. Openings are etched in film 14 and the new oxide film to partially expose the surface of region 18 and another region of substrate 12, into which a P-type element, e.g. B, is diffused to form regions 26, 28 to differing depths, and new oxide films are formed on the exposed surfaces. P-N junctions 30, 32 are thus defined. Further openings are etched in film 14 and the new oxide films to expose the surfaces of P-type regions 26, 28 and N-type elements, e.g. P, Sb, As, are diffused thereinto to form N-type regions 38, 40 of equal depths; the region 38 containing Ge from region 26. Further openings are formed in film 14 including the newly formed oxide film to expose surfaces of regions 38, 26, 40, 28 and, e.g. Al, contacts are evaporated thereon (Fig. 1e) so that the two NPN transistors T 1 , T 2  are fabricated in substrate 12 having N-type emitter regions 38, 40; P-type base regions 26, 28; and N-type collector regions 50, 52 having different base widths W 1  for power transistor T 1  and W 2  for H.F. amplification transistor T 2 . The transistors are isolated by PN junctions or dielectrics in collector regions 50, 52 of substrate 12. Ge or Sn are diffusible from halides in a quartz tube furnace containing semi-conductor wafers on a quartz support which is surrounded by a heater and through which flows halide vapour in a carrier gas of N 2  and O 2  (Fig. 5, not shown) and Ge is diffusible from the oxide contained in a quartz boat in the furnace tube, which also contains the semi-conductor wafers and is traversed by a carrier gas of mixed O 2  and N 2 ; the oxide and the wafers being surrounded by separate heaters (Figs. 6a, 6b, not shown). Ge may also be diffused from powdered Ge-Si alloy in a heated closed quartz tube, together with the semi-conductor wafers, at low vapour pressure. B may be diffused to a shallower or deeper extent (Figs. 2, 3, 4, not shown). Diffused resistors with metallic contacts may be formed through the oxide layers in P-type regions 26, 28, differing in depth one from the other. A PNP lateral transistor may be fabricated by the same method (Fig. 8, not shown) wherein the first diffused region is ring-shaped and openings are etched through the insulant film into the diffused regions and the area of the substrate within the ring, to which a circular emitter and annular collector are applied by evaporation, a base being applied to the bottom surface or the major surface of the substrate. A semi-conductor integrated circuit device (Fig. 9f) is fabricated in a P-type silicon monocrystalline substrate 90 having insulant, e.g. oxide film, into which a lattice opening is formed for Ge or Sn diffusion into the substrate to form a first region 96, superimposed with a new oxide film. The oxide insulant is etched off and an epitaxial layer 100 of N-type silicon is grown on the major surface, into which further diffusion from the previously diffused regions may occur, and an oxide insulant layer 102 is formed on the epitaxial layer. An opening is formed therein of lattice shape over the first diffused region 96, through which Ge or Sn is diffused into the epitaxial layer to form a second region 106 in contact therewith; a new overlying oxide film being formed. Openings are formed in the oxide film to expose portions of second region 106 and layer 100 into which P-type impurity, e.g. B, is diffused more deeply into the region 100, then into layer 100, to form P-type regions 110 and 112 in one step, with overlying thin oxide films. Further openings are formed in film 102 into which P is selectively diffused to form N-type regions 116, 118, 120, 122, and e.g. Al contacts 124, 126, 128, 130, 132, 134 are evaporated to contact regions 120, 116, 112, 122, 118, 114 respectively, the P-type region 100 isolating the two transistors. A buried NŒ-type layer 98 may be formed in the substrate to lower the collector resistance. A PNP transistor is fabricated by building a P - -type Si epitaxial layer 142 on a P + -type Si monocrystal substrate 140 overlain by SiO 2  insulant film 144 with a ring-shaped opening, Ge or Sn being diffused through the opening to form a first diffused region 148 with an overlying oxide film, and an opening is formed in film 144 to expose the centre of the epitaxial layer, into which an N-type impurity, e.g. As or Sb, is diffused to form region 154 with overlying SiO 2  layer. Two further openings in film 144 expose the surface of the first region 148 and that of region 154, through which B is diffused to form P + -type diffused region 162 and P + -type emitter region 164, having overlying new oxide films. Metal collector and emitter electrodes 166, 168 and base electrode 170 are formed to contact regions 162, 164, 154 (Fig. 10e). An insulated gate FET (Fig. 11a, not shown) fabricated (Fig. 11b) by covering an N-type Si substrate 180 with insulant, e.g. SiO 2  film 182, forming source and drain openings, diffusing Ge or Sn through them into the substrate to form first regions 184, 186 covered with new oxide films; forming three openings in the film to partially expose the surface of the first diffused regions 184, 186 and a portion of the substrate surface, diffusing B into regions 184, 186 and into the substrate to form P-type diffused regions 188, 190, 192; applying metal electrodes 194, 196, 198, 200, 202 and electrically interconnecting a gate electrode 196 with electrode 200. The B is diffused deeply at 184, 186 into the Ge or Sn diffused regions and shallowly into the substrate at 192. The differing diffusion depths are produced at the same time by the same diffusion step. The substrate may be Ge with Si, C, Sn, Ti, Pb, Hf, or Zr as the nonconductivity type producing impurity.