ISFET for pH Sensor

• Main Author: M.N. Haron
• Format: Conference Paper
• Language: English
• Published: 2013
• Subjects: ISFET > MOSFET > pH Sensor > Ionic Sensing
• Online Access: http://ddms.usim.edu.my/handle/123456789/6126
• Institution: Universiti Sains Islam Malaysia

ISFET is an ion sensitive field effect transistor that has similar structure to the MOSFET. The physical difference of the ISFET structure is the replacement of the gate electrode of the MOSFET by the series of combination of the reference electrode, electrolyte and ion sensitive layer. For this device, Silicon Nitride is used as a pH sensing membrane which behaves as a gate in contact with the liquid solution that is biased with a reference electrode. In overall fabrication process, 6 masking level are employed with 12 main processes are involved. In MOSFET principle, the operation was controlled by the gate electrode, meanwhile the operation of ISFET was controlled by the ion concentration in the electrolyte. The measurement of the threshold voltage of the ISFETs will give the pH value of the solution and in general will serve as a pH measurement system.