Negative Piezoelectric-Based Electric-Field-Actuated Mode-Switchable Multilayer Ferroelectric FBARs for Selective Control of Harmonic Resonances Without Degrading Keff²
Negative Piezoelectric-Based Electric-Field-Actuated Mode-Switchable Multilayer Ferroelectric FBARs for Selective Control of Harmonic Resonances Without Degrading Keff²
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基于负压电的电场驱动模式可切换多层铁电 FBAR，用于在不降低 Keff² 的情况下选择性控制谐波谐振
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发表时间：
2020
期刊：
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通讯作者：
A. Mortazawi
中科院分区：
文献类型：
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作者：
M. Koohi;A. Mortazawi
提出了一种可切换模式的铁电薄膜体声谐振器。这种谐振器基于具有大电伸缩系数的复合多层铁电体（如钛酸锶钡（BST））的动态非均匀有效压电性工作。当机电耦合系数(<inline-formula> < text -math notation="LaTeX">$ extit {nf}_{o}$ </ text -math></inline-formula>) ="LaTeX">${K}_{mathm {eff}}^{{{2}}}$ </ text -math></inline-formula>)等于基模时，可以选择性地激发多层铁电体声波（BAW）谐振器的谐波共振模式（<inline-formula> < text -math notation="LaTeX">$ extit {nf}_{o}$ </ text -math></inline-formula>）。这与传统压电BAW谐振器呈现的<inline-formula> < text -math符号="LaTeX">${K}_{mathm {eff}}^{{{2}}} proto {1}/{n}^{{{2}}}$ </ text -math></inline-formula>的趋势相反。通过在铁电层上施加一组适当的直流控制电压，产生与每种模式的应力场成比例的非均匀压电系数的图案，可以选择性地将这种器件设置为在其不同的谐振谐波上共振。这样的谐振器允许设计一种新型的带开关滤波器。作为实验验证，首次设计并制作了基于双层铁电BST结构的可切换模式FBAR和带切换梯形滤波器。双层BST fbar不仅可以开启或关闭，而且通过选择不同的偏置配置，可以选择性地激发2 GHz和3.6 GHz两个共振模式，其<inline-formula> < text -math符号="LaTeX">${K}_{mathm {eff}}}^{{{2}}}$ </ text -math></inline-formula>分别为8%和7%。
Mode-switchable ferroelectric thin-film bulk acoustic resonators (FBARs) are presented. Such resonators operate based on a dynamic nonuniform effective piezoelectricity in composite multilayer ferroelectrics with large electrostriction coefficients, like barium strontium titanate (BST). Harmonic resonance modes (<inline-formula> <tex-math notation="LaTeX">$ extit {nf}_{o}$ </tex-math></inline-formula>) of a multilayer ferroelectric bulk acoustic wave (BAW) resonator can be selectively excited with an electromechanical coupling coefficient (<inline-formula> <tex-math notation="LaTeX">${K}_{mathrm {eff}}^{{{2}}}$ </tex-math></inline-formula>) equal to the fundament mode, which is contrary to the trend <inline-formula> <tex-math notation="LaTeX">${K}_{mathrm {eff}}^{{{2}}}propto {1}/{n}^{{{2}}}$ </tex-math></inline-formula> exhibited by conventional piezoelectric BAW resonators. Such a device can selectively be set to resonate at its different resonance harmonics by generating a pattern of nonuniform piezoelectric coefficient proportional to the stress field of each mode with an application of a proper set of dc control voltages applied across the ferroelectric layers. Such a resonator allows for the design of a new class of band-switching filters. As an experimental validation, a mode-switchable FBAR and a band-switching ladder-type filter based on a bilayer ferroelectric BST structure are designed and fabricated for the first time. The bilayer BST FBARs not only can be switched ON or OFF but also by choosing different bias configurations, two resonance modes at 2 and 3.6 GHz can be selectively excited having <inline-formula> <tex-math notation="LaTeX">${K}_{mathrm {eff}}^{{{2}}}$ </tex-math></inline-formula> of 8% and 7%, respectively.