Tunability of Alluminum Nitride Acoustic Resonators: A Phenomenological Approach

Abstract

A phenomenological approach is developed to identify the physical parameters causing the dc-voltage-induced tunability of aluminum nitride (AlN) acoustic resonators, widely used for RF filters. The typical resonance frequency of these resonators varies from 2.038 GHz at -200 V to 2.062 GHz at +200 V. This indicates, based on these RF measurements versus dc bias and the model used, that the AlN stiffness variation versus dc bias is the prominent effect because both resonance and antiresonance experience a similar variation, respectively, 24 MHz and 19 MHz at 400 V. Picosecond ultrasonics were also used to prove independently that the acoustic velocity (and therefore AlN stiffness) is sensitive to dc bias and that the variation induced is comparable to that extracted from the resonance measurements. It turned out that the stiffness relative variation for an electric field of 1 V/μm extracted from picosecond ultrasonics is 54 ppm-μm/V. This is in good agreement with the value extracted from the RF measurements, namely 57.2 ppm-μm/V. The overall tunability of these AlN resonators reaches 1.1%, which is an interesting figure, although probably not high enough for genuine applications.

4-inch transparent plates based on thin-film AlN actuators for haptic applications

“…The material properties used in the FEM model are given in Table 1 . The AlN mechanical material properties are coming from picosecond ultrasonics measurement (details on this measurement technique can be found in [14][15] ), whereas the Glass material properties are coming from the data sheet of this commercial material (EAGLE XG ® ). The piezoelectric coefficient e 31, f is extracted from electromechanical measurements performed on an AlN-actuated cantilever, in particular using an AixACCT tool [16] .…”

Thin film bulk acoustic wave resonators tuning from first principles

“…We include in our treatment a nonlinear electrostrictive coefficient m which was previously considered as a higherorder correction and customarily neglected, 18 but which actually plays an important role in the antiresonance frequency tuning of tunable FBARs. [15][16][17] Let us consider a tunable FBAR operating in the TE mode based on a [001]-oriented BST thin ferroelectric film in the paraelectric phase.…”

Universal modeling of the bulk acoustic wave devices

“…In particular, the focus of the attention remained up till now on tunability which is provided when external variable bias voltage is applied to FBAR. This voltage influences the BAW velocity in the layers forming the system and therefore on its resonant frequencies (Vorobiev & Gevorgian, 2010;Defaÿ, E. et al, 2011).…”