Bacterial immobilization and detection using porous silicon platform and CMOS sensory circuit

The paper presents the design of MEMS-based sensory system for real-time bacteria detection. The principle of functioning is based on monitoring the variation in capacitance signals owing to the adherence of target bacteria to the sensing interface. The system is designed using custom-based technology and it consists of comb finger capacitor structures made out of doped polysilicon. Aiming at improving the detection efficiency, the space between the comb fingers, forming the two electrodes of the capacitive sensor, will be made porous through a post-processing with Xenon Difluoride (XeF2) dry etching technique. This allows entrapping bacteria in between the electrodes thus increasing the variation of capacitance. This latter, is acquired using a Charge Based Capacitance Measurement (CBCM) sensory circuit built with to the 0.13 μm CMOS technology. The circuit is able to detect a difference in capacitance as low as 0.75 fF.