Aluminum Nitride-Based Adjustable Effective Electromechanical Coupling Coefficient Film Bulk Acoustic Resonator

Abstract

The arrival of the 5G era has promoted the need for filters of different bandwidths. Thin-film bulk acoustic resonators have become the mainstream product for applications due to their excellent performance. The Keff2 of the FBAR greatly influences the bandwidth of the filter. In this paper, we designed an AlN-based adjustable Keff2 FBAR by designing parallel capacitors around the active area of the resonator. The parallel capacitance is introduced through the support column structure, which is compatible with conventional FBAR processes. The effects of different support column widths on Keff2 were verified by finite element simulation and experimental fabrication. The measured results show that the designed FBAR with support columns can achieve a Keff2 value that is 25.9% adjustable.

Aluminum Nitride Out-of-Plane Piezoelectric MEMS Actuators

“…Comparing our devices with the published works, despite the extensive use of piezoelectric transducers in several applications, including energy harvesters [ 43 ], microphones [ 55 ], inertial sensors [ 56 ], and bulk acoustic resonators [ 57 ], to the best of our knowledge, there are no works focusing on the PIC waveguide alignment application. The only report found for PICs’ alignment was presented in [ 34 ] to align an optical fiber with a photonic device.…”

Reliable formulas for accurately determining the resonance and antiresonance frequencies of thin film bulk acoustic resonators

“…Here, A and Y represent the cross-sectional area and the conductance of the FBAR. After substituting e =a D s and equation (22) into equation (23) and performing a detailed derivation to replace b _ p and b + , p we arrive at a closed-form expression for the total impedance, which accounts for the impedance and phase contributions from the various layers. p are normalized impedances for both electrodes.…”

“…However, a well-behaved RF filter constructed from cascaded FBARs needs a highquality factor and, in some cases, requires wide enough bandwidth (BW) FBARs [17][18][19]. Both achievements in FBAR need smooth, high quality, and highly crystalline orientation of piezoelectric layer, i.e., well c-axis orientation, sandwiched by the top and bottom metal layers accompanying highly effective electromechanical coupling ( ) k eff 2 of the piezoelectric layer [20][21][22]. In general, we can evaluate k eff 2 from the Meson model [23] by the formula, k eff…”