Improved pH Sensitivity and Reliability for Extended Gate Field-Effect Transistor Sensors Using High- <i>k</i> Sensing Membranes

摘要： In this study, we fabricated extended-gate (EG) ?eld-effect transistor (FET) pH sensors with dual-gate (DG) structures, using a range of dielectric sensing membranes (SiO2, Si3N4, HfO2 and Ta2O5) to vary their sensitivity. The fabricated EGFETs consisted of a silicon-on-insulator (SOI)-based metal-oxide semiconductor ?eld-effect transistor (MOSFET) transducer and an EG sensor. We ampli?ed the sensitivity of the device far beyond the Nernst limit (59 mV/pH), which is the theoretical maximum of conventional ion-selective FET (ISFET) sensing, by applying capacitive coupling. Among the evaluated dielectric sensing membranes, we obtained the highest sensitivity (478 mV/pH), low hysteresis (100.2 mV) and drift rate (24.6 mV/h) from the pH sensor with a Ta2O5 membrane. Hence, we expect DG FET con?gurations using Ta2O5 ?lms as EG sensing membranes to be useful for high performance biosensor applications, as they satisfy the requirements for sensitivity, stability and reliability.