Study of ISFET Sensitivity to pH Variations using Silvaco TCAD for Biomedical Applications

Chemical sensors have become increasingly popular in medical fields because of their potential benefits. These benefits include a small footprint, extreme durability, low output impedance, and lightning-fast response. This research aims to create a biosensor for measuring pH using an ion-sensitive field-effect transistor (ISFET). Silvaco software was used for both the design and modelling of this ISFET. In this work, the ISFET operating between pH 2 and 12 is designed and simulated for biomedical applications. The sensitivity was measured using the critical pH value and the threshold voltage parameters for different channel lengths of 250 nm, 200 nm, and 50 nm, respectively. The thickness of the sensing membrane changed between 3 nm, 10 nm, and 20 nm. The results show that titanium dioxide (TiO2) has the maximum sensitivity of 57.98 mV/pH, followed by hafnium(IV) oxide (HfO2) with 57.46 mV/pH, then tantalum pentoxide (Ta2O5) with 57.36 mV/pH, followed by aluminium oxide (Al2O3) with 55.05 mV/pH, and lastly silicon nitride (Si3N4) with 54.75 mV/Ph. All readings were obtained using a gate channel length of 200 nm and a sensing membrane thickness of 3 nm. According to the results, TiO2 was the most sensitive material, followed by HfO2, Ta2O5, Al2O3, and Si3N4. These results show that ISFETs, particularly those with TiO2 sensing membranes, have great potential as a robust and precise pH monitoring sensing platform in the biomedical industry.