A 4.5-mW 22-nm CMOS Label-Free Frequency-Shift 3 × 3 × 2 3-D Biosensor Array Using Vertically Stacked 60-GHz LC Oscillators

In this brief, a label-free
$\mathbf {3\times 3\times 2}$
three-dimensional frequency-shift biosensor array with vertically-stacked 60-GHz on-chip LC oscillators is presented. The 60-GHz LC oscillators function as sensor front-end since the frequency downward shifts due to dielectric derived from biomedical sensing targets. The proposed array element consists of the two vertically-stacked LC oscillators and 15-stage dividers necessary for extracting high-frequency output signals with a long distance. The proposed circuit was designed with Spectre RF simulation and the test chip was fabricated in 22-nm CMOS technology. The whole and element chip size is 0.04 mm2 and 0.0035 mm2 respectively. The measurement with thick and thin silicon resin samples successfully demonstrated their vertical and horizontal detection on the same chip while the prior works only achieved two-dimensional detection. The 22-nm CMOS prototype also showed high spatial resolution
$60 ~\mu {\mathrm{ m}} \times 60 ~\mu {\mathrm{ m}} \times 4 ~\mu {\mathrm{ m}}$
and high fill factor 73% while consuming 4.5 mW under 1.2 V per the single-element.