Abstract
As radio-frequency (RF) communication becomes more ubiquitous globally, film bulk acoustic resonators (FBAR) have attracted great attention for their superior performance. One of the key parameters of an FBAR, the effective electromechanical coupling coefficient (), has a great influence on the bandwidth of RF filters. In this work, we propose a feasible method to tune the of the FBAR by etching the piezoelectric material to form a trench around the active area of the FBAR. The influence of the position of the etching trench on the of the FBAR was investigated by 3D finite element modeling and experimental fabricating. Meanwhile, a theoretical electrical model was presented to test and verify the simulated and measured results. The of the FBAR tended to be reduced when the distance between the edge of the top electrode and the edge of the trench was increased, but the Q value of the FBAR was not degraded. This work provides a new possibility for tuning the of resonators to meet the requirements of different filter bandwidths.
Highlights
The rapid development of wireless mobile communication has led to higher requirements for radio-frequency (RF) devices
Film bulk acoustic filters have been attracting researchers’ attention in recent years, since the achievable high acoustic velocity, good temperature stability and large electromechanical coupling coefficients (K2 ) of piezoelectric film materials, for example, aluminum nitride (AlN) and scandium-doped AlN (ScAlN), render them suitable to meet the harsh requirements of 5G wireless communication [2]
An adequate Ke2f f bringing in a large bandwidth is achievable by using suitable piezoelectric materials or doping methods which are commonly used in previous process technologies
Summary
The rapid development of wireless mobile communication has led to higher requirements for radio-frequency (RF) devices. Film bulk acoustic filters have been attracting researchers’ attention in recent years, since the achievable high acoustic velocity, good temperature stability and large electromechanical coupling coefficients (K2 ) of piezoelectric film materials, for example, aluminum nitride (AlN) and scandium-doped AlN (ScAlN), render them suitable to meet the harsh requirements of 5G wireless communication [2]. The effective electromechanical coupling coefficient (Ke2f f ) of a film bulk acoustic resonator (FBAR) is a core parameter which influences the bandwidth and cutoff frequency of filters. An adequate Ke2f f bringing in a large bandwidth is achievable by using suitable piezoelectric materials or doping methods which are commonly used in previous process technologies. Moulet et al reported BAW devices fabricated with thin single crystalline
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