Design and Electrochemical Characterization of Ion-Sensitive Capacitors With ALD Al2O3 as the Sensitive Dielectric

A process for the fabrication and further characterization of ion-sensitive capacitive sensors is reported. This process is based on a standard 5-μm complementary metal- oxide-semiconductor process, which has been designed to employ a single metal level. These sensors were fabricated with atomic layer deposited thin films of Al
₂
O
₃
, used as the ion-sensitive dielectric. In addition, these devices were designed with a serial capacitive arrangement in order to provide an additional capacitive response. From the electrochemical characterization, it is shown that the capacitive sensors have a sensitivity in terms of the shift in the flat-band voltage of nearly 30-mV · pH
^-1
, and a sensitivity in the maximum capacitance displacement of 0.6-pF · pH
^-1
. It is shown that with these modifications, this kind of sensors are able to provide a response to the pH of a solution as a change in the maximum capacitance, or as a shift in the flat-band voltage while maintaining a simpler fabrication process in comparison with other technologies.