Improvement of Voltage Sensitivity of pH Sensor Based on Ion Sensitive Field Effect Transistor

Ion sensitive field effect transistor-based pH sensor is used for the measurement of pH in the vast domains of electrolytes. An ISFET works on the principle of changing current through the transistor in accordance with changes in the ion concentration for measuring the pH sensitivity of an electrolytic solution. The ion sheath accumulates charges, which causes a generation of voltage between the substrate of the ISFET and the oxide surfaces. The pH value of the electrolyte changes the concentration of OH- ion groups in the gate material. For the design of this model, Si is used as a base semiconductor material, and Al203 as an oxide layer, which works as a sensing membrane. It proposes a channel length of 2,..,m and an oxide thickness of 30nm as a design criterion that successfully exceeds the remaining sensitivity and achieves a sensitivity of 58.97 m V / pH. This research work also extensively shows the boundary conditions for oxide thickness and channel length, which give a correct criterion for ISFET model design. pH measurement plays a significant role in medical science, such as DNA pH measurement, and it also helps to detect the properties of bacteria and fungi, which are essentially important for diagnosis purposes in the food industry. It also helps in wastewater management, drinking water, and natural water sources.