Ion-sensitive field-effect transistors fabricated in a commercial CMOS technology

The fabrication of pH-sensitive ISFET devices in an unmodified two-metal co mmercial CMOS technology (1.0 m from Atmel-ES2) is reported. The ISFET devi ces have a gate structure compatible with the CMOS process, with an electri cally floating electrode consisting on polysilicon plus the two metals. The passivation oxynitride layer acts as the pH-sensitive material in contact with the liquid solution. The devices have shown good operating characteris tics, with a 47 mV/pH response. The use of a commercial CMOS process allows the straightforward integration of signal-processing circuitry. An ISFET a mplifier circuit has been integrated with the ISFET sensors. (C) 1999 Elsev ier Science S.A. All rights reserved.