Effect of gate dielectric on the performance of ISFET with SU-8 encapsulation

The design and fabrication of open gated ISFETs with different gate dielectric is reported. A comparative analysis of three different sensing layers SiO₂, SiO₂/Si₃N₄ stack and SiO₂/Al₂O₃stack is presented. The focus is on the simple fabrication technique, SU-8 encapsulation and its application as a pH sensor. The SU-8 encapsulation process is developed for the creation of liquid well to enable efficient interaction with biological fluid. For pH analysis the ISFET was tested in buffer solutions with different pH values. A platinum wire was used as the reference electrode for liquid gating. The pH response is evaluated from the IV characteristics and ISFETs with SiO₂/Si₃N₄ stack and SiO₂/Al₂O₃ stack showed better pH response with sensitivity of 59.33 mV/pH and 55.68 mV/pH, respectively as against sensitivity of 48.9 mV/pH in ISFETs with SiO₂.