Design of a capacitance sensor in 0.18um CMOS technology for biomedical application

To determine the existence of a certain target molecules, antibody molecules can be placed on a set of parallel electrodes for binding the target molecules. Detection of target molecules bound to the antibody can be achieved by measuring changes in capacitance between the electrodes. A capacitive sensor used for this purpose must have high accuracy and preferably be low power. This paper describes the design of a capacitive sensor which is capable of detecting as small as 10fF change in capacitance. The design was implemented in a 0.18μm CMOS process.