A Frequency-Shift based CMOS Magnetic Biosensor with Spatially Uniform Sensor Transducer Gain

H. Wang, C. Sideris and A. Hajimiri

This paper presents a scalable and ultra sensitive magnetic biosensing scheme based on on-chip LC resonance frequency-shifting. The sensor transducer gain is demonstrated as being location-dependent on the sensing surface and proportional to the local polarization magnetic field strength |B|2 generated by the sensing inductor. To improve the gain uniformity, a bowl-shape stacked coil together with floating shimming metal is proposed for the inductor design. As an implementation example, a 16-cell sensor array is designed in a 45nm CMOS process. The spatially uniform sensor gain of the array is verified by testing micron-size magnetic particles randomly placed on the sensing surface. The Correlated-Double- Counting (CDC) noise cancellation scheme is also implemented in the presented design, which achieves a noise suppression of 10.6dB with no power overhead. Overall, the presented sensor demonstrates a dynamic range of at least 85.4dB.