FBAR-CMOS Oscillator Array for Mass-Sensing Applications

Thin-film bulk acoustic resonators (FBAR) are an effective platform for sensitive biological and chemical detection, where their high operating frequencies make them many times more sensitive than a quartz crystal microbalance. Here, we present a monolithic, solidly mounted FBAR oscillator array on CMOS for mass-sensing applications. Through monolithic integration with CMOS drive circuitry, we aim to overcome the spatial and parasitic load limitations of externally coupled resonators to build dense sensor arrays without specialized fabrication techniques. The sensors in this work are constructed in a 6 × 4 array atop a 0.18 ¿m CMOS active substrate, and mass sensitivity comparable to off-chip FBAR sensors is demonstrated.

I. Introduction

Multiplexed protein detection is emerging as an important tool for analyzing cellular networks and characterizing complex diseases, where more traditional nucleic acid assays have proven insufficient [1]. Protein microarrays, a primary multiplex detection platform, have already demonstrated efficacy in analyzing and characterizing colon cancer cells [2], breast cancer biomarkers [3], and a myriad of human autoimmune diseases [4]. These technologies are limited, however, by dependence on fluorescently labeled generic binders, where cross-reactivity at the reporter level bounds assay specificity [1]. Additionally, unbound labeled reporters prevent real-time detection and quantification of binding events, as these must be washed away prior to optical interrogation. These limitations can be surmounted with label-free, mass-based sensing techniques, but only if such techniques can overcome their own technological barriers to multiplexed detection.