CAPACITIVE SENSORS IN CMOS TECHNOLOGY WITH POLYMER COATING

In this paper we report the fabrication of a new integrated capacitive chemical sensor by industrial CMOS technology, followed by a single maskless polymer-coating step. An on-chip sigma-delta modulator measures the difference between the sensing and reference capacitors, performs offset and gain calibration and provides a digital output signal. Experimental data have been obtained in a series of measurements, in which several transducers covered with different polymer films (polyetherurethane, PUT, polycyanopropylmethyl siloxane, PCM, ethylcellulose, EC, and polyepichlorohydrine, PECH) are exposed to various organic gases at different concentrations. The sensor signals show a clear linearity and low hysteresis for both polar and non-polar gases, thus confirming the feasibility of smart capacitive chemical sensors in IC technology.