Fabrication of Semiconductor Sensor for Immunological Measurement

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Fabrication process of semiconductor sensors for immunological measurement was investigated. The device fabrication-process utilized in this work consists of two steps; (1) deposition of thin organic film by plasma technique, and (2) protein immobilization. It is desirable that the electrical properties of organic film are stable and that high density of protein molecules can be immobilized in an orientation-controlled manner.Electrical property of the organic film was studied using metal/insulator/semiconductor structured capacitors. Plasma-polymerized organic film was deposited onto SiO_2/Si structured substrates. After depositing the Al electrodes, capasitance-voltage characteristics were measured. The hysteresis and the shift of flatband voltage were observed. As far as the technological application to semiconductor sensors is concerned, the above two properties are disadvantageous features. Thus, attempts were made to reduce those effects by heat treatment. The effect was significant. The hysteresis width as well as the shift of flatband voltage were reduced. The best result was obtained in the case of the heat treatment at 200 ゜C for 30 min. in N_2 atmosphere.Immobilization reaction was performed as the following steps; first, amino-groups were introduced to the surface of the plasma-polymerized film by glow-discharge treatment in HH_3, and then, pre-treated antibody molecules (Fab'-SH domain) were covalently immobilized by a bifunctional cross-linking reagent. Using this method, binding sites of the molecule with the supporting material can uniquely be specified. The density of the immobilized antibody molecules was approximately 6 x 10^<11> cm^<-2>, which agreed well with the theoretically estimated one.