Synthesis and bulk acoustic wave properties on the dual mode frequency shift of solidly mounted resonators

Abstract

This study focused on the fabrication and the theoretical analysis of solidly mounted resonators (SMR) concerning dual-mode frequency responses and their frequency shift of bulk acoustic wave (BAW) resonance. For this device fabrication, RF/DC magnetron sputtering and photolithography were employed to constitute the required multilayer structure. For the theoretical analysis, the dualmode frequency shift was characterized by the Sauerbrey's formula, and a modified formula was carried out following the trend for the large frequency shift. In the fabrication of the SMR device, Mo/SiO2 was chosen to construct the Bragg reflector as the high/low acoustic impedance materials, respectively, and aluminum nitride (AlN) was used as a piezoelectric layer. To investigate the characteristics of BAW on the dual-mode frequency shift, the c-axis tilted angle of AlN was altered as well as the various mass loading on the SMR. Based on the experimental results, the dual-resonance frequencies showed a nonlinear decreasing trend with a linear increase of the mass loading. Therefore, a modified formula was carried out. Furthermore, the ratio of the longitudinal-resonant frequency to the shear-resonant frequency remained at a range around 1.76 despite the various c-axis tilted angles of AlN and gradual mass loading on the SMR. The electromechanical coupling coefficient, k2(eff), of the shear resonance rose with the increase of the c-axis tilted angle of AlN.

Fabrication of AlGaN High Frequency Bulk Acoustic Resonator by Reactive RF Magnetron Co-sputtering System

“…The BAW resonator has two kinds of structure, one is the film bulk acoustic resonator (FBAR), and the other is solidly mounted resonator (SMR). The SMR structure does not require an etching process like the FBAR structure; therefore, it is relatively stable, and the process yield of the device can be improved [ 8 , 9 , 10 , 11 , 12 , 13 ].…”

Selection of aptamers to Neisseria meningitidis and Streptococcus pneumoniae surface specific proteins and affinity assay using thin film AlN resonators

“…Gravimetric sensors based on bulk acoustic wave (BAW) resonators work under the principle of the resonant frequency shift due to a mass loading [24]. They have shown significant potential as label-free biosensors [24] due to their high sensitivity, low detection limit, and low cost. Since the sensitivity increases with resonant frequency [25], high frequency resonators are preferred.…”

Biosensor for human IgE detection using shear-mode FBAR devices

“…The backside cavity of FBAR can be used as the detection area for adsorbent matter. Under a mass loading, a frequency shift would be resulted in the frequency response of a FBAR [ 17 ]. The analysis methods were used for biosensor in liquid and tiny mass detection in air through the shear mode and longitudinal mode, respectively.…”