Effect of channel width-to-length ratio on isothermal point of MOSFET-ISFET structure

The effect of channel width-to-length (W/L) ratio on MOSFET-ISFET structures was investigated from simulation and experimental approach. A metal-oxide-semiconductor field-effect-transistor (MOSFET) has been adopted to investigate the isothermal point of an ion-sensitive FET (ISFET), which is needed to suit the readout interfacing circuit of an ISFET sensor. The MOSFET structure with different W/L ratio has been characterized in order to see the effect of W/L ratio to the isothermal point. The Keithley 236 Parameter Analyzer and Semi-auto prober micromanipulator system were used to measure the drain-source current (I DS ) versus gate to source voltage (V GS ) curves at various temperatures from 30 °C to 60 °C. The simulation result showed that the reduction of W/L ratio can decrease the isothermal point and this was proven by the actual measurement.