Abstract: Based on the conventional sensitive model of an ion-sensitive structure,a threshold voltage model that uses a silicon nitride passivation layer as the sensitive membrane with a multi-floating gate field effect structure has been built.A pH sensor compatible with CMOS is designed according to the 0.6μm CMOS standard process offered by Shanghua.An integrated control circuit keeps the source drain voltage and source drain current of the MFGFET structure in a steady state.Pattern mode noise in the circuit is reduced through a differential output between the ion-sensitive MFGFET and a reference MFGFET.The test result shows the pH sensor has an average sensitivity of 35.8mV/pH from pH 1 to pH 13.

Key words: pH sensor, MFGFET, sensitivity