Study of capacitive structures for amplifying the sensitivity of FET-based chemical sensors

This paper reports on the development of ion sensitive field effect capacitors (ISFEC) as microsensors. ISFEC/(metal/oxide/semiconductor) field effect transistor (MOSFET) amplifying structures are designed and studied in order to improve the sensitivity of field effect transistor (FET)-based chemical sensors (CHEMFETs). Demonstration is performed through the characterisation of SiO2/Si3N4 ISFEC sensors for pH measurement. Linear responses and high detection sensitivities are evidenced on wide pH ranges. Theoretical and experimental studies are in agreement, clarifying dynamic phenomena, lower experimental amplification ratios and measurement drawbacks. Such amplifying structures will lead to further improvements for FET-based microsensors.