Study on extended gate field effect transistor with tin oxide sensing membrane

Ion-sensitive field effect transistor (ISFET) is a device composed of a con ventional ion-sensitive electrode and MOSFET device, applied to the measure ment of ion content in a solution. Extended gate field effect transistor (E GFET) is another structure to isolate FET from chemical environment. In thi s study, the ISFET was separated into two parts. Tin dioxide (SnO2), obtain ed by sputtering, is used as a pH-sensitive membrane for electrode, which i s connected with a commercial MOSFET device in CD4007UB or LF356N. The expe rimental data show that this structure has a linear pH response of about 56 -58 mV/pH in a concentration range between pH 2 and 12. In addition, it is easier to fabricate and package the sensitive membrane structure and the me asurement is simple for the application of disposable biosensor. (C) 2000 E lsevier Science S.A. All rights reserved.