HfO2 and ZrO2–Based Microchemical Ion Sensitive Field Effect Transistor (ISFET) Sensors: Simulation & Experiment

Microchemical ion-sensitive field effect transistor (ISFET) sensors were designed, simulated, fabricated, and electrically characterized using SiO 2 , ZrO 2 and HfO 2 deposited by different methods as ion-sensitive gate dielectric materials. The SiO 2 films showed a non-linear p H response with a low p H sensitivity (∼10 mV/ p H) around the SiO 2 point of zero charge (pzc) of 3.5 ± 0.5 and a higher p H sensitivity (∼25 mV/ p H) above the pzc. The ZrO 2 and HfO 2 films both showed linear and almost ideal (Nernstian) p H sensitivities (∼55 mV/ p H) over a wide p H range. The pzcs of ZrO 2 and HfO 2 were determined to be 6.7 ± 0.5 and 5.5 ± 0.5 respectively. The theoretically predicted C-V responses obtained by numerically solving electroneutrality and potential continuity equations for the electrolyte oxide semiconductor (EOS) device qualitatively matched the experimental trends. This analysis offers an effective and alternative approach of determining the point of zero charge of metal oxide dielectrics.