Method for producing a p-n junction in a monocrystalline semiconductor member by etching and diffusion

1,049,408. Semi-conductor devices. SIEMENS & HALSKE A.G. Aug. 4, 1964 [July 23, 1963], No. 30697/64. Addition to 966,257. Heading H1K. In making a semi-conductor device a lightly doped monocrystalline semi-conductor layer is deposited on a carrier body of the same material by thermal decomposition of a gaseous compound of the semi-conductor. One or more limited surface zones of the carrier are heavily doped with donor and acceptor impurities. The dominant impurity has the lower diffusion coefficient so that during the annealing process during and/or following deposition the other impurity preferentially diffuses outwards to the surface of the deposited layer to form a PN junction in the layer. The doping of the limited surface zones may be effected by localized deposition or diffusion from the vapour phase through a stencil or oxide mask of both impurities, or of one impurity where the substrate is already doped with the other. Alternatively the impurities are deposited over the entire surface and then etched from the areas where not required. The method may be used to form varactor diodes but is described as applied to the formation of the collector junctions and base zones of a plurality of transistors on a common substrate. In this case the material between the surface zones is doped only with the impurity dominant in those zones and the surface of the layer is coveted with oxide before or during annealing. If the semiconductor is silicon the zones are preferably doped with phosphorus to N type, the minor impurity being boron or aluminium but when germanium is used P-type zones are employed.