A focused-ion-beam-assisted procedure with the aim of frequency tuning thin-film bulk acoustic resonators (FBARs) is presented. The procedures of focused-ion-beam-based deposition and milling on the FBAR are described, detailing calibration and alignment issues. A C/Pt/Ga composite was locally deposited on the top electrode of the FBAR by means of ion-assisted deposition. Selected areas of the electrode were chosen to deposit the localized composite, having micrometer dimensions and nanometer thicknesses. Based on the mass-loading principle, a down-shifting in the resonance frequency was observed. The achieved responsivity of 7.4 × 10-19 g Hz-1 was demonstrated to be at least one order of magnitude better than for the thin-film deposition case. Different localized-mass-loading configurations were tested and the possible effects of the ion beam on the physical properties of the resonator analyzed. It was found that responsivity is dependent on the size of the tuning mass and that the Q factor does not suffer significant variation due to the i-beam operation. © 2007 IOP Publishing Ltd.
|Journal||Journal of Micromechanics and Microengineering|
|Publication status||Published - 1 Nov 2007|