Phononic Film Bulk Acoustic Resonator for High mass-sensitive Biosensing

MEMS technology is widely used for biological applications as a reliable alternative for optical systems. ThinFilm Bulk Acoustic Resonator (FBAR) has been proposed as key device in gravimetric sensing, thanks to the GHz operating frequency with high-quality factor and high sensitivity. However, using FBAR in biosensing is difficult due to the presence of the biological liquid resulting in an increase of the acoustic radiation hence strongly deteriorating the device performance. This paper proposes the integration of phononic nano pillar in the FBAR leading to the so-called innovative P-FBAR device structure. P-FBAR enables the reduction of energy losses and hence preserving the energy at the surface of the device. The paper provides clear evidence of the presence of nano-resonators storing mechanical energy and offering new features including a strongly confined spatial distribution of energy. As a result, an improved quality factor and mass-sensitivity is obtained in the proposed P-FBAR device. The optimum design and performance of the proposed P-FBAR is numerically analyzed through finite element method simulations. The proposed P-FBAR offers an order of magnitude improvement in mass sensitivity and an order of magnitude improvement in quality factor leading to two orders of magnitude enhancement in the Figure of merit compared to the conventional FBAR. The proposed design enables a better in-situ bio detection at lower cost and higher resolution.