Floating-gate ion sensitive field-effect transistor for chemical and biological sensing

This paper presents the use of Floating-Gate Ion Sensitive Field-Effect Transistor (FGISFET) as a real-time chemical and biological sensor. The structure of FGISFET is similar to that of an electrically erasable programmable read-only memory (EEPROM). ne floating-gate of a FGISFET is connected to an exposed metallic structure, which serves as a probe for detecting ionic activities. By applying ion-sensitive chemical and biological materials to the floating gate, its threshold voltage can be modulated in the presence of selective chemical or biological targets. As a demonstration, FGISFETs have been fabricated in 1.2 mu m process technology available through MOSIS [1]. Our preliminary measurements confirmed the basic design and operation of FGISFET, and using doped aniline trimer (TANI) as a sensing material, we were able to sense 70ppm of ammonium gas.