| Summary: | 碩士 === 中原大學 === 電子工程研究所 === 89 === The objective of this thesis is to study the stability of extended gate field effect transistor (EGFET) for pH-ISFET or biosensor applications. The major research issues include sensitivity, linearity, hysteresis, time drift, reproducibility and long-term stability. The ion sensitive membrane of the EGFET is split from the field effect transistor. Accordingly, compared to the conventional open-gate ISFET structure, only the sensitive membrane stays in the buffer solution, but the portion of the field effect transistor needs not put into the solution and avoid illumination effects. The low cost of EGFET can be expected because the separated ion sensitive membrane has advantages of simple structure, uncomplicated fabrication and encapsulation.
In the experiments, we studied four types of EGFET with different structures that include SnO2/ITO glass, TiN/SiO2/Si, SnO2/Al/Si and TiN/Al/Si EGFET, where SnO2 and TiN films were deposited using R.F. sputtering method. Besides the stability of each structure has been investigated, the theories and models have been also proposed for hysteresis and drift effects to explain their mechanisms.
From the experimental measurements, overall characteristics of the SnO2/ITO glass EGFET present satisfactory performance for disposable H+ sensing and biosensor applications.
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