Development of EGFET-based microsensors with high-sensitivity and high-linearity for dissolved oxygen and carbon dioxide detection

This study integrated extended-gate field-effect transistor (EGFET) based dissolved oxygen (O
₂
) and carbon dioxide (CO
₂
) microsensors in one silicon chip (with dimension of 1.3 × 1.1 cm
²
) utilizing microelectromechanical systems (MEMS) technology for water quality monitoring applications. All of the manufacturing processes adopted in this work are compatible with standard planar technology and therefore are very suitable for mass production. Under the optimized situation, the EGFET-based O
₂
and CO
₂
microsensors have very high sensitivity (35.36 mV/ppm and 42.3 mV/decade, respectively) and very high sensing linearity (98.8% and 99.2%, respectively).