A Microwave-Optical Biosensor with 5.4ppm Label/Reference-free Long-term Stability and Single Photon Sensitivity in 28nm Bulk CMOS

This paper presents a hybrid microwave and optical sensing platform for real-time monitoring of biomolecular interactions. The microwave sensing unit is a 39G-42GHz superharmonic coupled QVCO for permittivity detection. A novel tank-perturbation based noise-cancellation readout scheme is proposed to achieve label-and-reference-free 5.4ppm long-term stability (8 hours). The optical sensing unit is an array of SPADs (single-photon-avalanche-diodes) for photon counting. It demonstrates first-time implementation in 28nm bulk CMOS, and achieves DCR (dark count rate) of 500/sec and PDE (photon detection efficiency) of 11.5% (520nm) under 1V excessive bias voltage. An enzyme denaturation experiment is performed to show that multi-parametric sensing provides a better profiling of complex biomolecular processes.