UN METODO DE FABRICACION DE UN DISPOSITIVO SEMICONDUCTOR.

摘要

1,235,177. Insulated gate field effect transistors. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 5 June, 1968 [8 June, 1967], No. 26718/68. Heading H1K. In a silicon IGFET with source and drain regions formed as juxtaposed inclusions in the face of a body or zone of opposite conductivity type an insulating layer of varying thickness overlies that face. Where the layer overlies the source and drain regions it is thicker than it is under the gate and consists of silicon oxide inset in the surface of the silicon. Such a device can be made from a 200 Áthick 10 ohm. cm. P-type silicon wafer by depositing overall a À2 Á silicon nitride layer from silane and ammonia, removing it except from the gate area, oxidizing the exposed areas in steam, forming windows in the oxide and diffusing phosphorus derived from phosphorus-doped silicon powder through them to form the source and drain, and then reoxidizing the surface. The nitride can be used as gate insulation but is preferably removed in hot phosphoric acid and the underlying silicon heated in steam to form an oxide layer the thickness and electrical properties of which may be improved by successive heat treatments in oxygen, nitrogen and wet nitrogen. If the surface is oxidized before provision of the nitride masking the oxide is re-exposed at this stage by etching and improved as described above. Another possibility is to convert the nitride directly to oxide by anodic treatment. In alternative methods the nitride is first applied also to the source and drain areas or even over the entire water face and the diffusion holes etched in it. In both cases the source and drain areas are oxidized after diffusion as described above. Apertures are formed in the oxide overlying the source and drain regions and aluminium gate, source and drain electrodes applied in conventional manner. Etching of the oxide layers is effected with a saturated aqueous solution of ammonium fluoride to which hydrofluoric acid has been added as this etches the nitride only slowly. Use of a layer of nitride on oxide as gate insulation is mentioned.