Bulk acoustic wave resonator device with enhanced power handling capability employing bilayer piezoelectric material

Abstract

Embodiments of the present invention relate to an acoustic wave resonator device (100) with enhanced power processing capability for exciting bulk acoustic waves (BAWs). The acoustic wave resonator device (100) has a composite piezoelectric patch comprising a first piezoelectric layer (110) and a second piezoelectric layer (120), the acoustic impedances of the first piezoelectric layer (110) and the second piezoelectric layer (120) being the same or similar, but the first piezoelectric layer (110) and the second piezoelectric layer (120) having opposite phase wave excitation at a given wave polarization. Thus, the size of the composite piezoelectric patch can be increased at a given static capacitance while maintaining the bandwidth of the acoustic resonator device (100), thereby improving the power handling capacity of the acoustic resonator device (100).

Description

Technical Field

[0001] Embodiments of the present invention relate to an acoustic wave resonator device with enhanced power handling capability for exciting bulk acoustic waves (BAW). Background Art

[0002] A BAW resonator is an electromechanical device in which a standing acoustic wave is generated by an electrical signal in a piezoelectric material between two metal electrodes. For example, BAW resonators can be used as radio frequency (RF) filters or duplexers and are replacing traditional RF filters in many wireless communication applications.

[0003] There are two main types of BAW resonators, film bulk acoustic resonator (FBAR) and solidly mounted resonator (SMR). FBAR devices consist of a piezoelectric sheet sandwiched between two electrodes. The resonant cavity in the FBAR is formed along the thickness of the piezoelectric sheet and the electrodes. In SMR devices, additional layers are placed below the main structure of the device to act as Bragg reflectors and provide structural support. Summary of the invention

[0004] The purpose of the embodiments of the present invention is to provide a solution that can reduce or solve the shortcomings and problems of traditional solutions.

[0005] Another object of embodiments of the present invention is to provide an acoustic wave resonator device with enhanced power handling capability.

[0006] The above objects and other objects are achieved by the subject matter claimed in the independent claims. Further embodiments of the invention are provided in the dependent claims.

[0007] According to a first aspect of the present invention, the above objects and other objects are achieved by an acoustic wave resonator device, the acoustic wave resonator device comprising:

[0008] a first piezoelectric layer and a second piezoelectric layer, wherein a bottom surface of the first piezoelectric layer is attached to a top surface of the second piezoelectric layer, the first piezoelectric layer and the second piezoelectric layer have the same or similar acoustic impedances, and the first piezoelectric layer and the second piezoelectric layer have opposite phase wave excitations at a given wave polarization;

[0009] A first electrode is attached to a top surface of the first piezoelectric layer and a second electrode is attached to a bottom surface of the second piezoelectric layer, wherein the first electrode and the second electrode are used to convert electrical signals into acoustic waves in the first piezoelectric layer and the second piezoelectric layer.

[0010] The advantage of the acoustic wave resonator device according to the first aspect is that the disclosed acoustic wave resonator device can efficiently excite the second thickness plate resonance in the first piezoelectric layer and the second piezoelectric layer. In addition, the acoustic wave resonator device can be optimized so that the contact surface between the first piezoelectric layer and the second piezoelectric layer is located in a low stress region of the standing acoustic wave during resonance to achieve a high Q factor.

[0011] In an implementation of the acoustic wave resonator device according to the first aspect, a ratio of the acoustic impedance of the first piezoelectric layer to the acoustic impedance of the second piezoelectric layer is in a range of 0.8 to 1.2.

[0012] The advantage of this implementation is that the elastic energy at resonance is evenly distributed along the first piezoelectric layer and the second piezoelectric layer, thereby promoting efficient wave excitation in each piezoelectric layer.

[0013] In an implementation of the acoustic wave resonator device according to the first aspect, a thickness d1 of the first piezoelectric layer and a thickness d2 of the second piezoelectric layer are in a range of 0.3λ to 0.7λ, where λ is a wavelength of an acoustic wave at resonance.

[0014] This implementation has the advantage that the second thickness resonance in the acoustic wave resonator device is caused to occur with approximately half the wavelength above the contact surface between the piezoelectric layers and the other half the wavelength below the contact surface, thereby improving the excitation efficiency.

[0015] In an implementation of the acoustic wave resonator device according to the first aspect, the thickness d1 of the first piezoelectric layer and the thickness d2 of the second piezoelectric layer are in the range of 100 nm to 1100 nm.

[0016] An advantage of this implementation is that these layer thicknesses enable the design of an acoustic wave resonator device operating in a desired frequency band.

[0017] In an implementation of the acoustic wave resonator device according to the first aspect, the acoustic wave resonator device is configured to operate in a frequency range of 3 GHz to 10 GHz.

[0018] The advantage of this implementation is that bulk wave resonators are particularly needed in this frequency range. Frequencies below 3 GHz use surface acoustic wave resonators or bulk wave resonators using a single piezoelectric plate. Above 10 GHz, the piezoelectric thickness required for highly coupled resonators is technically not feasible.

[0019] In an implementation of the acoustic wave resonator device according to the first aspect, the acoustic wave resonator device is configured to operate at a second composite plate thickness resonance of the acoustic wave resonator device.

[0020] The advantage of this implementation is that, at the same resonant frequency, the thickness of the acoustic wave resonator device is approximately twice that of a single piezoelectric layer resonator operating on a basic thickness resonance according to conventional schemes. Compared to a single piezoelectric layer resonator, approximately twice the area is required to achieve the same static capacitance. Therefore, the acoustic wave resonator device disclosed herein including two piezoelectric layers is approximately 4 times larger in volume, which is associated with approximately the same reduction in power density and corresponding increase in power handling capability. In addition, due to the elimination of the electrode between the first piezoelectric layer and the second piezoelectric layer, the increase in overall volume is typically greater than 4 times.

[0021] In an implementation of the acoustic wave resonator device according to the first aspect, at least one of the first piezoelectric layer and the second piezoelectric layer is from the 3m point group.

[0022] The advantage of this implementation is that high electromechanical coupling materials such as LiTaO3 and LiNbO3 can be used to excite shear waves or longitudinally polarized waves with large electromechanical coupling.

[0023] In one implementation of the acoustic wave resonator device according to the first aspect,

[0024] The first piezoelectric layer is a negative compressive C-axis AlScN layer and the second piezoelectric layer is a LiNbO3 layer having a rotated Y-cut in the range of -134° to -154°, or vice versa; or

[0025] The first piezoelectric layer is a positive compressive C-axis AlScN layer and the second piezoelectric layer is a LiNbO3 layer having a rotated Y-cut in the range of 26° to 46°, or vice versa.

[0026] The advantage of this implementation is that both the first and second piezoelectric layers primarily support the excitation of highly coupled longitudinally polarized acoustic waves that propagate through the thickness of the plate. The wavelength of acoustic waves in AlScN is significantly larger than that in LiNbO3, which allows thicker resonator stacks to improve power handling. In addition, unlike LiNbO3, AlScN is a material with excellent thermal conductivity.

[0027] In one implementation of the acoustic wave resonator device according to the first aspect, the positive compressive C-axis AlScN layer and the negative compressive C-axis AlScN layer are Al 1–X Sc X N layers, where x>0.2.

[0028] The advantage of this implementation is that a Sc concentration greater than 20% is required to achieve strong electromechanical coupling of longitudinal bulk acoustic waves propagating along the C-axis, ie, about 20% or more.

[0029] In an implementation of the acoustic wave resonator device according to the first aspect, the AlScN layer is grown on the LiNbO 3 layer, and the LiNbO 3 layer is a single crystal layer.

[0030] The advantage of this implementation is that commercially available technology is applied. In addition, it is also envisaged to use an acoustic thin seed layer on LiNbO3 to promote the c-axis growth of AlScN.

[0031] In one implementation of the acoustic wave resonator device according to the first aspect, the first piezoelectric layer is a first LiNbO3 layer, the second piezoelectric layer is a second LiNbO3 layer, or vice versa, the first LiNbO3 layer and the second LiNbO3 layer have a rotated Y-cut in any range of 153° to 173° or –7° to –27°, and the first LiNbO3 layer has an X-axis rotated 180° relative to the X-axis of the second LiNbO3 layer.

[0032] The advantage of this implementation is that these cuts of LiNbO3 specifically promote efficient excitation of bulk acoustic waves with shear polarization, while longitudinal bulk acoustic waves suppress electromechanical coupling. In addition, the excitation phase of the shear wave in the first piezoelectric layer is opposite to the excitation phase in the second piezoelectric layer, while the excitation phase of the longitudinal wave remains the same in the first piezoelectric layer and the second piezoelectric layer.

[0033] In one implementation of the acoustic wave resonator device according to the first aspect, the first piezoelectric layer is a first LiNbO3 layer having a first rotated Y-cut, and the second piezoelectric layer is a second LiNbO3 layer having a second rotated Y-cut, or vice versa, wherein the first rotated Y-cut is rotated 180° around the X-axis of the LiNbO3 layer crystal relative to the second rotated Y-cut, or vice versa.

[0034] In an implementation of the acoustic wave resonator device according to the first aspect, the first LiNbO 3 layer has a rotated Y-cut in the range of 26° to 46°, and the second LiNbO 3 layer has a rotated Y-cut in the range of −134° to −154°.

[0035] The advantage of this implementation is that these cuts of LiNbO3 specifically promote efficient excitation of bulk acoustic waves with longitudinal polarization, while shear bulk acoustic waves suppress electromechanical coupling.

[0036] In an implementation of the acoustic wave resonator device according to the first aspect, the first LiNbO 3 layer has a rotated Y-cut in the range of 153° to 173°, and the second LiNbO 3 layer has a rotated Y-cut in the range of −7° to −27°.

[0037] The advantage of this implementation is that these cuts of LiNbO3 specifically promote efficient excitation of bulk acoustic waves with shear polarization, while longitudinal bulk acoustic waves suppress electromechanical coupling.

[0038] In an implementation of the acoustic wave resonator device according to the first aspect, the first LiNbO 3 layer has an X-axis rotated by 0°, 60°, 90°, 120° or 180° relative to the X-axis of the second LiNbO 3 layer.

[0039] The advantage of this implementation is that it distorts the polarization and excitation phase of the shear wave between the first and second piezoelectric layers, thereby suppressing the shear wave excitation efficiency. This implementation is particularly valuable for resonators operating with longitudinal waves.

[0040] In an implementation of the acoustic wave resonator device according to the first aspect, the first LiNbO 3 layer and the second LiNbO 3 layer are single crystalline layers.

[0041] The advantage of this implementation is that the mechanical quality factor of the single crystal layer is better than that of the polycrystalline layer. Typically, single crystal materials exhibit better power handling capabilities than polycrystalline materials.

[0042] In an implementation of the acoustic wave resonator device according to the first aspect, the first LiNbO 3 layer is attached to the second LiNbO 3 layer by bonding, or vice versa.

[0043] In an implementation of the acoustic wave resonator device according to the first aspect, the second piezoelectric layer is acoustically coupled to a Bragg mirror, wherein the Bragg mirror comprises a plurality of alternating layers with different acoustic impedances.

[0044] In an implementation of the acoustic wave resonator device according to the first aspect, the plurality of alternating layers are arranged on a supporting substrate and are acoustically coupled to the supporting substrate.

[0045] Other applications and advantages of the embodiments of the present invention will become apparent from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The accompanying drawings are intended to illustrate and explain different embodiments of the present invention, in which:

[0047] - Figure 1 The acoustic wave resonator device provided by the embodiment of the present invention is shown;

[0048] - Figure 2 An acoustic wave resonator device provided by another embodiment of the present invention is shown;

[0049] - Figure 3a and Figure 3bThe first piezoelectric layer and the second piezoelectric layer provided by the embodiment of the present invention are shown;

[0050] - Figure 4 The first piezoelectric layer and the second piezoelectric layer provided by the embodiment of the present invention are shown;

[0051] - Figure 5a and Figure 5b The first piezoelectric layer and the second piezoelectric layer provided by the embodiment of the present invention are shown;

[0052] - Figures 6 to 8 Performance results are shown. DETAILED DESCRIPTION

[0053] BAW resonators in the 3 GHz to 10 GHz frequency range require wide bandwidths and low resonator capacitances. For example, BAW resonators below 6 GHz require bandwidths of about 10% and resonator capacitances of about 1 pF and below to achieve good performance.

[0054] In a BAW resonator, as the thickness of the piezoelectric layer decreases, the static capacitance C0 per unit electrode area increases with frequency adjustment, and the resonant frequency also increases. For example, a lithium niobate (LiNbO3) film for fundamental frequency acoustic resonance in the 4 GHz range is expected to require 565 μm 2 Up to 1130μm 2 The area required to achieve a static capacitance in the 1pF range depends on the excitation mode. Therefore, the electrode area is small, about 23um×23um to 33um×33um, and even smaller for FBARs with capacitance C below 1pF. Such small resonators limit power handling and have poor energy confinement.

[0055] In order to improve the power handling capability of BAW resonators, a new composite piezoelectric sheet for efficient excitation of BAW is disclosed. The proposed composite piezoelectric sheet includes two piezoelectric layers and can be used as a component in FBAR devices and SMR devices. For a given static capacitance C0, the composite piezoelectric sheet increases the area and thickness of the FBAR or SMR sheet. As a result, the energy density in the resonator is reduced, and the power handling capability of the resonator is improved compared to conventional solutions.

[0056] therefore, Figure 1 The acoustic wave resonator device 100 provided by an embodiment of the present invention is shown. The acoustic wave resonator device 100 can be used to operate in the frequency range of 3 GHz to 10 GHz, but is not limited thereto, and can be a FBAR device or a SMR device, or a part of a FBAR device or a SMR device. Figure 1, the acoustic wave resonator device 100 includes a first piezoelectric layer 110 and a second piezoelectric layer 120, respectively. The bottom surface 114 of the first piezoelectric layer 110 is attached to the top surface 122 of the second piezoelectric layer 120. The acoustic wave resonator device 100 also includes a first electrode 130 attached to the top surface 112 of the first piezoelectric layer 110 and a second electrode 140 attached to the bottom surface 124 of the second piezoelectric layer 120. The first electrode 130 and the second electrode 140 are used to convert the electric signal ES into the acoustic wave AW in the first piezoelectric layer 110 and the second piezoelectric layer 120. Therefore, the acoustic wave AW is generated in both the first piezoelectric layer 110 and the second piezoelectric layer 120.

[0057] The acoustic impedances of the first piezoelectric layer 110 and the second piezoelectric layer 120 are the same or similar. In an embodiment, the ratio of the acoustic impedance of the first piezoelectric layer 110 to the acoustic impedance of the second piezoelectric layer 120 is in the range of 0.8 to 1.2. Therefore, a uniform energy distribution can be achieved between the first piezoelectric layer 110 and the second piezoelectric layer 120. At a given wave polarization, the first piezoelectric layer 110 and the second piezoelectric layer 120 also have opposite phase wave excitations. In terms of wave propagation, the given wave polarization can be a longitudinal type or a shear type. Only one given wave polarization (i.e., a longitudinal wave polarization or a shear wave polarization) is relevant at a time, and the other wave polarization should be fully suppressed.

[0058] Figure 2 The acoustic wave resonator device 100 provided by an embodiment of the present invention is shown, wherein the acoustic wave resonator device 100 is implemented as an SMR device or a part of an SMR device. The acoustic wave resonator device 100 can be used to operate in a frequency range of 3 GHz to 10 GHz. Figure 1 In addition to the components described, Figure 2 The acoustic wave resonator device 100 provided in the illustrated embodiment includes a Bragg reflector 150 and a support substrate 170 located below the Bragg reflector. Figure 2 , the second piezoelectric layer 120 is acoustically coupled to the Bragg reflector 150. When the electrode is considered to be included in the first layer of the Bragg reflector (for example, if the Bragg reflector starts with a tungsten (W) layer or a molybdenum (Mo) layer), the term acoustic coupling can be understood as a direct connection between the piezoelectric layer and the Bragg reflector. For example, when the electrode is not considered to be part of the Bragg reflector (for example, using an acoustic thin Al electrode, etc.), acoustic coupling can also be performed through the electrode. The Bragg reflector 150 includes a plurality of alternating layers 160 with different acoustic impedances. The plurality of alternating layers 160 are arranged in sequence on a supporting substrate 170 and are acoustically coupled to the supporting substrate 170. The thickness of each layer of the Bragg reflector can be approximately a quarter wavelength, and if the difference between the acoustic impedances of the layers is large, the reflectivity of each layer will be greater. Typical materials with large acoustic impedance differences can be used, such as W / SiO2, Mo / SiO2, and SiN / SiO2.

[0059] The acoustic wave resonator device 100 provided by any of the embodiments described herein may be configured to operate at a second composite plate thickness resonance of the acoustic wave resonator device 100. The second plate thickness resonance may be defined as a resonance when the acoustic wave AW forms a 1λ standing wave along the thickness of the acoustic wave resonator device 100. The thickness may be defined as the sum of all layers of the acoustic wave resonator device 100 including the electrodes. In order for the acoustic wave resonator device 100 to operate at the second composite plate thickness resonance of the acoustic wave resonator device 100, the thickness d1 of the first piezoelectric layer 110 and the thickness d2 of the second piezoelectric layer 120 may be selected (see Figure 1 ) such that the thickness of the acoustic wave resonator device 100 corresponds to the wavelength λ of the acoustic wave at resonance. For example, the thickness of each piezoelectric layer 110, 120 may be approximately half the wavelength of the acoustic wave, i.e., λ / 2. In an embodiment, the thickness d1 of the first piezoelectric layer 110 and the thickness d2 of the second piezoelectric layer 120 are in the range of 0.3λ to 0.7λ, where λ is the wavelength of the acoustic wave at resonance in each material. In addition, the thickness d1 of the first piezoelectric layer 110 and the thickness d2 of the second piezoelectric layer 120 may be in the range of 100nm to 1100nm, as this is technically feasible and may also define resonance in the desired frequency range. The thicknesses d1 and d2 may be considered design parameters and may be used to tune the coupling depending on the asymmetry of the electrodes (different materials, different thicknesses, etc.) and when the piezoelectric materials have different acoustic impedances (i.e., different energy distributions).

[0060] The first piezoelectric layer 110 and the second piezoelectric layer 120 may be selected from one or more crystal symmetry groups, i.e., the first piezoelectric layer 110 and the second piezoelectric layer 120 may belong to the same or different crystal symmetry groups. In an embodiment, at least one of the first piezoelectric layer 110 and the second piezoelectric layer 120 is from the 3m point group. For example, the 3m point group includes LiNbO3 and lithium tantalate (LiTaO3). If only one of the first piezoelectric layer 110 and the second piezoelectric layer 120 is from the 3m point group, the other of the first piezoelectric layer 110 and the second piezoelectric layer 120 may be from the 6mm group including aluminum scandium nitride (AlScN) and Sc-doped AIN.

[0061] In an embodiment where the first piezoelectric layer 110 and the second piezoelectric layer 120 are from different crystal symmetry groups, the first piezoelectric layer 110 can be a negative compression C-axis AlScN layer and the second piezoelectric layer 120 can be a LiNbO3 layer with a rotational Y-cut in the range of -134° to -154°, or vice versa. The first piezoelectric layer 110 can also be a positive compression C-axis AlScN layer and the second piezoelectric layer 120 can be a LiNbO3 layer with a rotational Y-cut in the range of 26° to 46°, or vice versa. In this way, the first piezoelectric layer 110 and the second piezoelectric layer 120 have different crystal orientations, and a combination between positive compression excitation and negative compression excitation is achieved in each layer. The positive compression C-axis AlScN layer and the negative compression C-axis AlScN layer can be Al (1–X) Sc X N layer, wherein x>0.2. 10. The AlScN layer can be grown on the LiNbO3 layer, and the LiNbO3 layer can be a single crystal layer. For example, the AlScN layer can be grown on a single crystal layer LiNbO3 layer manufactured by piezoelectric on insulator (POI) technology or the like using deposition or sputtering technology.

[0062] In an embodiment, the first piezoelectric layer 110 and the second piezoelectric layer 120 are both from the 3m point group. For example, the first piezoelectric layer 110 may be a first LiNbO3 layer and the second piezoelectric layer 120 may be a second LiNbO3 layer, or vice versa. The first LiNbO3 layer and the second LiNbO3 layer may have a rotated Y-cut in any range of 153° to 173° or in the range of –7° to –27°, and the X-axis of the first LiNbO3 layer may be rotated 180° relative to the X-axis of the second LiNbO3 layer. These configurations make the phase excitation in one of the piezoelectric layers opposite to the phase excitation in the other piezoelectric layer and are only effective for shear wave polarizations, and therefore only for the above-mentioned cut types.

[0063] In addition, the first piezoelectric layer 110 may be a first LiNbO3 layer having a first rotated Y-cut, and the second piezoelectric layer 120 may be a second LiNbO3 layer having a second rotated Y-cut, or vice versa, wherein the first rotated Y-cut is rotated 180° about the X-axis of the LiNbO3 layer crystal relative to the second rotated Y-cut, or vice versa. For example, the first LiNbO3 layer may have a rotated Y-cut in the range of 26° to 46°, and the second LiNbO3 layer may have a rotated Y-cut in the range of -134° to -154°. Alternatively, the first LiNbO3 layer may have a rotated Y-cut in the range of 153° to 173°, and the second LiNbO3 layer may have a rotated Y-cut in the range of -7° to -27°. The first LiNbO3 layer may also have an X-axis rotated 0°, 60°, 90°, 120°, or 180° relative to the X-axis of the second LiNbO3 layer. These configurations allow the excitations in the two piezoelectric layers to be in phase with each other for longitudinal and / or shear waves. The electromechanical coupling is strong at the second thickness resonance for the desired wave polarization, while minimizing the coupling of the remaining polarizations.

[0064] The first LiNbO3 layer and the second LiNbO3 layer may be single crystal layers, for example, which may be fabricated on a carrier substrate (eg, a POI substrate) by ion slicing technology. The first LiNbO3 layer may then be attached to the second LiNbO3 layer by bonding, or vice versa.

[0065] 3 to 5 show examples of the above-described embodiments of the first piezoelectric layer 110 and the second piezoelectric layer 120. In the disclosed example, the thickness d1 of the first piezoelectric layer 110 and the thickness d2 of the second piezoelectric layer 120 are approximately half of the wavelength of the acoustic wave at resonance, i.e., 0.5λ. Therefore, the acoustic wave resonator device 100 including the first piezoelectric layer 110 and the second piezoelectric layer 120 can operate at the resonance of the second composite plate thickness of the acoustic wave resonator device 100.

[0066] exist Figure 3a In the embodiment, the first piezoelectric layer 110 is a negative compressive C-axis Al 0.7 Sc 0.3 The N layer, the second piezoelectric layer 120 is a LiNbO 3 layer having a rotated Y-cut in the range of −134° to −154°.

[0067] exist Figure 3b In the embodiment, the first piezoelectric layer 110 is a positive compressive C-axis Al 0.7 Sc 0.3 The N layer, the second piezoelectric layer 120 is a LiNbO 3 layer having a rotated Y-cut in the range of −134° to −154°.

[0068] exist Figure 4, the first piezoelectric layer 110 is a first LiNbO3 layer having a rotated Y-cut in the range of 153° to 173°, and the second piezoelectric layer 120 is a second LiNbO3 layer having a rotated Y-cut in the range of -7° to -27°. The first LiNbO3 layer has an X-axis rotated 180° relative to the X-axis of the second LiNbO3 layer.

[0069] exist Figure 5a , the first piezoelectric layer 110 is a first LiNbO3 layer having a first rotated Y-cut in the range of 26° to 46°, and the second piezoelectric layer 120 can be a second LiNbO3 layer having a second rotated Y-cut in the range of -134° to -154°. The first LiNbO3 layer can also have an X-axis rotated by 0°, 60°, 90°, 120°, or 180° relative to the X-axis of the second LiNbO3 layer.

[0070] exist Figure 5b , the first piezoelectric layer 110 is a first LiNbO3 layer having a first rotated Y-cut in the range of 153° to 173°, and the second piezoelectric layer 120 is a second LiNbO3 layer having a second rotated Y-cut in the range of -7° to -27°. The first LiNbO3 layer may also have an X-axis rotated by 0°, 60°, 90°, 120°, or 180° relative to the X-axis of the second LiNbO3 layer.

[0071] also, Figures 6 to 8 Different performance results of the acoustic wave resonator device 100 provided by the embodiments of the present invention are shown. Figures 6 to 8 The absolute value of the admittance (in dB) is shown as a function of frequency.

[0072] Figure 6 The proposed c-AlScN / -144Y LiNbO3 composite is shown, which has the same BW as a high-coupled c-AlScN (Kt2~20%) single piezoelectric layer resonator, but the capacitance per unit area of ​​the composite is 2.1 less than the latter. The thickness of the composite acoustic wave resonator device 100 is 2.6 times that of the traditional c-AlScN-based device, so the energy density per unit constant capacitance is reduced by 2.1×2.6=5.4 times. Therefore, the disclosed acoustic wave resonator device 100 can be used to enhance the power handling capability of broadband filters that typically use AlScN films. Compared with the 36Y LiNbO3 single piezoelectric layer device, the capacitance per unit area is 6 times smaller, affecting the BW. The thickness of the disclosed acoustic wave resonator device 100 is 3.4 times that of the traditional device, so the energy density at constant capacitance is reduced by 3.4×6=20.4 times. Compared to 36Y LiNbO 3 single piezoelectric layer devices, AlScN further improves the heat dissipation capability of the disclosed acoustic wave resonator device 100 .

[0073] Figure 7 The proposed 36Y LiNbO3 / -144Y LiNbO3 composite is shown, which has a slightly lower BW and a 3x smaller capacitance per unit area than the classic single 36Y LiNbO3 layer structure. The disclosed acoustic wave resonator device 100 is 2.9 times thicker than the conventional single 36YLiNbO3 layer device, so the energy density per unit constant capacitance is reduced by 3×2.9=8.7 times. For example, the disclosed acoustic wave resonator device 100 can be used to enhance the power handling capability of broadband filters.

[0074] Figure 8 The proposed -17Y LiNbO3 / 163Y LiNbO3 composite is shown, which has a slightly lower BW and 3.55 times less capacitance per unit area than the classic single 163Y LiNbO3 layer structure. The disclosed acoustic wave resonator device 100 is 3.5 times thicker than the traditional single 163YLiNbO3 layer device, so the energy density per unit constant capacitance is reduced by 3.55×3.5=12.4 times. For example, the disclosed acoustic wave resonator device 100 can be used to enhance the power handling capability of broadband filters.

[0075] Finally, it should be understood that the present invention is not limited to the embodiments described above, but also relates to and incorporates all embodiments within the scope of the appended independent claims.

Claims

1. An acoustic wave resonator device (100), characterized in that include: A first piezoelectric layer (110) and a second piezoelectric layer (120), wherein a bottom surface (114) of the first piezoelectric layer (110) is attached to a top surface (122) of the second piezoelectric layer (120), the first piezoelectric layer (110) and the second piezoelectric layer (120) have the same or similar acoustic impedance, and under a given wave polarization, the first piezoelectric layer (110) and the second piezoelectric layer (120) have opposite phase wave excitations; A first electrode (130) attached to a top surface (112) of the first piezoelectric layer (110) and a second electrode (140) attached to a bottom surface (124) of the second piezoelectric layer (120), wherein the first electrode (130) and the second electrode (140) are used to convert an electrical signal (ES) into an acoustic wave (AW) in the first piezoelectric layer (110) and the second piezoelectric layer (120).

2. The acoustic wave resonator device (100) according to claim 1, characterized in that A ratio of the acoustic impedance of the first piezoelectric layer (110) to the acoustic impedance of the second piezoelectric layer (120) is in the range of 0.8 to 1.

2.

3. The acoustic wave resonator device (100) according to claim 1 or 2, characterized in that The thickness (d1) of the first piezoelectric layer (110) and the thickness (d2) of the second piezoelectric layer (120) are in the range of 0.3λ to 0.7λ, wherein λ is the wavelength of the sound wave at the time of resonance.

4. The acoustic wave resonator device (100) according to claim 3, characterized in that The thickness (d1) of the first piezoelectric layer (110) and the thickness (d2) of the second piezoelectric layer (120) are in the range of 100 nm to 1100 nm.

5. The acoustic wave resonator device (100) according to any one of the preceding claims, characterized in that The acoustic wave resonator device (100) is adapted to operate in a frequency range of 3 GHz to 10 GHz.

6. The acoustic wave resonator device (100) according to any one of the preceding claims, characterized in that The acoustic wave resonator device (100) is configured to operate at a second composite plate thickness resonance of the acoustic wave resonator device (100).

7. The acoustic wave resonator device (100) according to any one of the preceding claims, characterized in that At least one of the first piezoelectric layer (110) and the second piezoelectric layer (120) is from a 3m point group.

8. The acoustic wave resonator device (100) according to claim 7, characterized in that The first piezoelectric layer (110) is a negative compressive C-axis AlScN layer and the second piezoelectric layer (120) is a LiNbO3 layer having a rotational Y-cut in the range of -134° to -154°, or vice versa; or The first piezoelectric layer (110) is a positive compressive C-axis AlScN layer and the second piezoelectric layer (120) is a LiNbO3 layer having a rotated Y-cut in the range of 26° to 46°, or vice versa.

9. The acoustic wave resonator device (100) according to claim 8, characterized in that The positive compressive C-axis AlScN layer and the negative compressive C-axis AlScN layer are Al (1–X) Sc X N layers, where x>0.

2.

10. The acoustic wave resonator device (100) according to claim 8 or 9, characterized in that The AlScN layer is grown on the LiNbO 3 layer, and the LiNbO 3 layer is a single crystal layer.

11. The acoustic wave resonator device (100) according to claim 7, characterized in that The first piezoelectric layer (110) is a first LiNbO3 layer, the second piezoelectric layer (120) is a second LiNbO3 layer, or vice versa, the first LiNbO3 layer and the second LiNbO3 layer have a rotated Y-cut in any range of 153° to 173° or -7° to -27°, and the first LiNbO3 layer has an X-axis rotated 180° relative to the X-axis of the second LiNbO3 layer.

12. The acoustic wave resonator device (100) according to claim 7, characterized in that The first piezoelectric layer (110) is a first LiNbO3 layer having a first rotated Y-cut, and the second piezoelectric layer (120) is a second LiNbO3 layer having a second rotated Y-cut, or vice versa, wherein the first rotated Y-cut is rotated 180° around the X-axis of the LiNbO3 layer crystal relative to the second rotated Y-cut, or vice versa.

13. The acoustic wave resonator device (100) according to claim 12, characterized in that The first LiNbO 3 layer has a rotated Y-cut in a range of 26° to 46°, and the second LiNbO 3 layer has a rotated Y-cut in a range of −134° to −154°.

14. The acoustic wave resonator device (100) according to claim 12, characterized in that The first LiNbO 3 layer has a rotated Y-cut in a range of 153° to 173°, and the second LiNbO 3 layer has a rotated Y-cut in a range of −7° to −27°.

15. The acoustic wave resonator device (100) according to claim 13 or 14, characterized in that The first LiNbO 3 layer has an X-axis rotated by 0°, 60°, 90°, 120°, or 180° relative to the X-axis of the second LiNbO 3 layer.

16. The acoustic wave resonator device (100) according to any one of claims 12 to 15, characterized in that The first LiNbO 3 layer and the second LiNbO 3 layer are single crystal layers.

17. The acoustic wave resonator device (100) according to claim 16, characterized in that The first LiNbO 3 layer is attached to the second LiNbO 3 layer by bonding, or vice versa.

18. The acoustic wave resonator device (100) according to any one of the preceding claims, characterized in that The second piezoelectric layer (120) is acoustically coupled to a Bragg reflector (150), wherein the Bragg reflector (150) includes a plurality of alternating layers (160) having different acoustic impedances.

19. The acoustic wave resonator device (100) according to claim 18, characterized in that The plurality of alternating layers (160) are disposed on a support substrate (170) and acoustically coupled to the support substrate (170).

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