Demonstration of Inverse Acoustic Band Gap Structures in AlN and Integration with Piezoelectric Contour Mode Transducers
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Electro-Mechanical Systems
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This paper presents the first design and demonstration of a novel inverse acoustic band gap (IABG) structure in aluminum nitride (AlN) and its direct integration with piezoelectric contour-mode transducers. The experimental results indicate that the IABG structure has a stop band from 185 MHz to 240 MHz and is centered around 219 MHz with maximum rejection of 30 dB. The ABG-induced phonon scattering causes a frequency band gap that prohibits the propagation of certain acoustic wavelengths. In this work, the IABG unit cell consists of a high acoustic velocity (V) center material, which is formed by 2-μm-thick AlN sandwiched by 200-nm-thick platinum (Pt) and is held by four thin tethers and surrounded by a low acoustic velocity material (air). This cell arrangement enlarges the frequency band gap and eases the requirements on the thickness (d) to lattice constant (a) ratio, which was imposed by previous ABG demonstration in the very high frequency range. The finite element method (FEM) analysis indicates that the IABG can produce a gap-to-midgap ratio of 13.5% even when the d/a ratio is as small as 0.23. This advantage further allows the direct integration of the IABG with high frequency bulk acoustic wave (BAW) transducers.
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Suggested Citation: Nai-Kuei Kuo, Chengjie Zuo, and Gianluca Piazza. "Demonstration of Inverse Acoustic Band Gap Structures in AlN and Integration with Piezoelectric Contour Mode Transducers" The 15th International Conference on Solid-State Sensors, Actuators and Microsystems (Transducers 2009) (2009): 2334-2337. ©2009 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.