Electrochemical Characterization of Ion-Sensitive Capacitors with ALD Al2O3 as the Sensitive Dielectric

Abstract

The design, fabrication and characterization of Ion-Sensitive Capacitive Sensors (ISCAPs) is presented. These sensors were fabricated with a single metal level CMOS process, and they incorporate special capacitive arrangements which help to improve the sensor's response (sensitivity). Specifically, the main advantage of this kind of sensor is that the measurements can be recorded by flat-band voltage shift and maximum capacitance (Cox) changes. Additionally, an integrated quasi-reference electrode has been included in the design, which provides the possibility of making measurements with both: an external or the integrated electrode. Based on previous results of the chemical and morphological characterization of materials after immersion in buffer solutions, ALD aluminum oxide (Al2O3) has been selected as the sensing material, providing both, high sensitivity and stability for measurements in the short term. It is shown that these sensors operate with both sensing mechanisms and with stability when measuring with the included quasi-reference electrode.