Method for fabricating insulated-gate field effect transistor

1,095,412. Making IGFET. INTERNATIONAL BUSINESS MACHINES CORPORATION. Aug. 4, 1965 [Aug. 26, 1964], No. 33292/65. Heading H1K. In the manufacture of an IGFET impurities are introduced into the gate insulation which is then subjected to an electric field while the transistor is heated. This process leads to a redistribution of charges in the insulation and consequent alternation of the induced charge carrier density in the channel region. The Specification describes a transistor formed on a high resistivity silicon body and having phosphorus diffused source and drain regions and having grown oxide gate insulation. Before the application of the metallic electrodes the transistor is heated in an oxygen atmosphere into which is introduced a boron or aluminium compound which decomposes to form a layer of oxide on the silicon oxide gate insulation. The layer material is diffused into the insulation, and gate, source and drain electrodes applied by vapour deposition. By applying a suitable uniform electric field between gate electrode and substrate and suitably heating the structure the characteristics of the transistor may be made of the deep enhancement type or deep depletion type or any intermediate type. These characteristics remain stable during normal operation of the transistor. If during the treatment potentials are also applied to the source and drain electrodes it is possible to produce a shaped conduction channel. An apparatus is described (Fig. 2, not shown) which is used for applying the heat-field treatment to a plurality of transistors on a single substrate so that each may have a desired type of characteristic.