Ion sensitive field effect transistor with evaluating circuit|has insulated gate field effect transistor in which gate comprises layer(s) of a non-metallic gas sensitive material

    Research output: Patent

    Abstract

    A gas sensor comprises an insulated gate FET in which the gate comprises 1 layer of a non-metallic gas sensitive material. The capacitance and/or the work function of the material is altered by exposure of the material to certain gases. At least one layer is in direct contact with a gate insulating layer (14). Also claimed are (i) a gas sensing arrangement in which the outputs of a first and second insulated gate FET are differentially amplified, only the gas sensitive material or materials of the first FET being exposed to the gas; and (ii) a method of fabricating a gas sensor by providing a gateless FET and depositing 1 layer of a non-metallic gas sensitive material to form a gate.The gas sensitive material comprises semiconducting polymer (12a). A first layer of semiconducting polymer is deposited by chemical polymerisation, which comprises spin coating a gateless FET with a solution containing an oxidising agent, exposing the coated FET to monomer vapour and etching the polymer layer, or by photopolymerisation. The etching is by chemical or plasma etching. Specifically, the first layer is of polypyrrole. A second layer of semiconducting polymer is deposited by electro-polymerisation. The gas sensor is an integral part of CMOS, PMOS or NMOS devices.USE - Sensor is used in gas detection.ADVANTAGE - The device is of simple and more practical design and can support large polymer coated gate dimensions.
    Original languageEnglish
    Patent numberWO9841853-A; WO9841853-A1; EP966675-A1
    Publication statusPublished - 1998

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