A novel SnO2/Al discrete gate ISFET pH sensor with CMOS standard process

In this paper, we present a method allowing industrial production of integrated ion sensitive field effect transistor (ISFET) sensor. An ASIC CMOS standard process is used to integrate the sensor and signal processing circuit; then the sensor is plated with the sensing membrane (SnO2) by sputtering. The structure of the ISFET is novel SnO2/Al discrete gate. The discrete gate ISFET and the readout circuit were fabricated with a conventional standard CMOS IC process where no extra mask was required. The experimental data show that the SnO2/Al discrete gate ISFET sensors have a high linearity of 58 mV/pH in a concentration ranging from pH 2 to 10. The low offset and low power readout circuit for the discrete gate ISFETs pH sensor was designed and evaluated for monolithic in this study. (C) 2001 Elsevier Science B.V. All rights reserved.