New ion-sensitive field effect transistors (ISFETs) with backside contacts for flow analysis

Novel back-side contacts structures of ISFETs (ion-selective field effect transistors) are described in this paper. Back-side contact type transducers are especially suitable for the design of chemical sensors for multiparameter flow analysis. The sensor structure requires a specialized flow-head, allowing the measurement of the signals of 10 ISFETs. Unmodified transducers with Si3N4 gate are H+-sensitive and can be used as solid-state pH sensors. Moreover, if the ISFET is covered with an ion-selective membrane it is possible to construct a sensor for the determination of a chosen ion. Measurement properties of the designed transducers and nitrate-sensitive CHEMFET’s were determined in the flow-cell set-up. Constructed microsensors can be applied in water quality monitoring, providing in-situ water analysis without sample preparation.