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 m askless polymer-coating step. An on-chip sigma-delta modulator measure s the difference between the sensing and reference capacitors, perform s offset and gain calibration and provides a digital output signal. Ex perimental data have been obtained in a series of measurements, in whi ch several transducers covered with different polymer films (polyether urethane, PUT, polycyanopropylmethyl siloxane, PCM, ethylcellulose, EC , and polyepichlorohydrine, PECH) are exposed to various organic gases at different concentrations. The sensor signals show a clear linearit y and low hysteresis for both polar and non-polar gases, thus confirmi ng the feasibility of smart capacitive chemical sensors in IC technolo gy.