An acoustic resonator and a filter for suppressing transverse high-order modes

Abstract

The present invention relates to the field of microelectronic devices, and discloses an acoustic wave resonator and a filter for suppressing transverse higher-order modes, including a support substrate, a piezoelectric thin film disposed on the support substrate, the material of which includes lithium tantalate or lithium niobate, an electrode array disposed on the piezoelectric thin film, the acoustic wave resonator is excited by a transverse electric field, the propagation direction of the generated acoustic wave is the direction of the normal of the electrode array, and the included angle between the acoustic wave propagation direction and the direction where the acoustic wave phase velocity reaches an extreme value is a first included angle, the first included angle range includes [1°, 10°] or [−1°, −10°], the included angle between the acoustic wave energy flow direction and the acoustic wave propagation direction is a second included angle, the second included angle range includes [3°, 15°] or [−3°, −15°]. Based on a heterogeneous integration substrate, in the embodiments of the present invention, only by changing the in-plane orientation of the electrode, the acoustic wave propagation direction is deviated from the direction where the acoustic wave phase velocity takes an extreme value, and the symmetry of the acoustic wave propagation is broken to suppress the transverse higher-order modes.

Description

Technical Field

[0001] The present invention relates to the field of microelectronic devices, and in particular, to an acoustic wave resonator and a filter for suppressing transverse higher-order modes. Background Art

[0002] In the modern communication industry, the requirements for signal quality are getting higher and higher, and the competition for communication spectrum resources is also becoming increasingly fierce. Low loss, wide bandwidth, tunability, and temperature stability have become the common pursuit goals in the communication industry.

[0003] Surface Acoustic Wave (SAW) resonators have been widely used in the communication field due to their small size, large bandwidth, and high Q value. Compared with traditional SAW resonators based on piezoelectric crystals, SAW devices based on piezoelectric hetero-substrates have achieved very significant improvements in terms of Q value, temperature stability, and power capacity.

[0004] However, hetero-substrates often bring additional parasitic modes, such as transverse higher-order modes, which will form ripples in the passband of the corresponding filter. There are many methods for suppressing transverse higher-order modes, such as piston structures, apodization structures, tilted electrode structures, and adjusting the vertical slowness curve. These methods either sacrifice the Q value of the device, require more stringent exposure conditions, increase the device area, or have limited flexibility. Therefore, how to suppress transverse higher-order modes while maintaining a high Q value of the device has become the key to realizing high-performance filters. Summary of the Invention

[0005] Embodiments of the present application provide an acoustic wave resonator and a filter for suppressing transverse higher-order modes. Based on a hetero-integrated substrate, the embodiments of the present application only change the in-plane orientation of the electrode to make the direction of acoustic wave propagation deviate from the direction where the acoustic wave phase velocity takes an extreme value, and break the symmetry of acoustic wave propagation to suppress transverse higher-order modes. At the same time, this method neither changes the geometric shape of the device nor reduces the Q value of the device, and has flexible design.

[0006] On the one hand, an embodiment of the present invention provides an acoustic wave resonator for suppressing transverse higher-order modes, and the acoustic wave resonator includes:

[0007] A support substrate;

[0008] A piezoelectric thin film disposed on the support substrate; the material of the piezoelectric thin film includes lithium tantalate or lithium niobate;

[0009] An electrode array disposed on the piezoelectric thin film;

[0010] The acoustic wave resonator is excited by a transverse electric field;

[0011] The propagation direction of the excited acoustic wave is the normal direction of the electrode array, and the included angle between the propagation direction of the acoustic wave and the direction where the phase velocity of the acoustic wave reaches an extreme value is the first included angle; the first included angle range includes [1°, 10°] or [-1°, -10°];

[0012] The included angle between the energy flow direction of the acoustic wave and the propagation direction of the acoustic wave is the second included angle, and the second included angle range includes [3°, 15°] or [-3°, -15°].

[0013] Optionally, the electrode array includes an interdigital electrode array and a reflection grating electrode array;

[0014] The reflection grating electrode array includes a first reflection grating electrode sub-array and a second reflection grating electrode sub-array;

[0015] The first reflection grating electrode sub-array is arranged at the first end of the interdigital electrode array, and the second reflection grating electrode sub-array is arranged at the second end of the interdigital electrode array.

[0016] Optionally, the interdigital electrode array includes interdigital electrodes and dummy fingers; the interdigital electrodes and the dummy fingers are arranged in one-to-one correspondence;

[0017] The thickness of the piezoelectric thin film is less than or equal to the period of the interdigital electrode; the length of the dummy finger is greater than or equal to half of the period of the interdigital electrode.

[0018] Optionally, the acoustic wave resonator further includes:

[0019] An intermediate layer; the intermediate layer is arranged between the piezoelectric thin film and the support substrate; the material of the intermediate layer includes silicon oxide.

[0020] Optionally, the acoustic wave resonator further includes:

[0021] A rich trap layer; the rich trap layer is located between the intermediate layer and the support substrate; the material of the rich trap layer includes polysilicon or amorphous silicon.

[0022] Optionally, the support substrate includes one of sapphire, silicon, quartz, spinel, silicon carbide, diamond, diamond-like, silicon nitride.

[0023] Optionally, when the mode of the acoustic wave resonator is the horizontal shear surface acoustic wave mode and the piezoelectric thin film is rotated Y-cut lithium tantalate, the direction where the sound velocity reaches an extreme value in the horizontal shear surface acoustic wave mode is the crystal X-axis direction.

[0024] Optionally, when the electrode array of the acoustic wave resonator is an aluminum electrode, the piezoelectric thin film is lithium tantalate, the intermediate layer is silicon oxide, the support substrate is sapphire, and the mode of the acoustic wave resonator is the horizontal shear surface acoustic wave mode, the direction in which the sound velocity reaches the extreme value in the horizontal shear surface acoustic wave mode is the crystal X-axis direction, the first included angle interval includes [2°, 8°] or [-2°, -8°], and the second included angle interval includes [3°, 12°] or [-3°, -12°].

[0025] Optionally, when the electrode array of the acoustic wave resonator is an aluminum electrode, the piezoelectric thin film is lithium tantalate, the intermediate layer is silicon oxide, the rich trap layer is polysilicon, the support substrate is silicon, and the mode of the acoustic wave resonator is the horizontal shear surface acoustic wave mode, the direction in which the sound velocity reaches the extreme value in the horizontal shear surface acoustic wave mode is the crystal X-axis direction, the first included angle interval includes [2°, 8°] or [-2°, -8°], and the second included angle interval includes [3°, 12°] or [-3°, -12°].

[0026] On the other hand, an embodiment of the present invention provides a filter, including a plurality of resonators, and the resonators are the above-mentioned acoustic wave resonators that suppress transverse higher-order modes.

[0027] The acoustic wave resonator and filter for suppressing transverse higher-order modes provided by the embodiments of the present application have the following technical effects:

[0028] The acoustic wave resonator includes a support substrate, a piezoelectric thin film disposed on the support substrate, the material of the piezoelectric thin film includes lithium tantalate or lithium niobate, an electrode array disposed on the piezoelectric thin film, the acoustic wave resonator is excited by a transverse electric field, the propagation direction of the generated acoustic wave is the direction of the normal of the electrode array, and the included angle between the propagation direction of the acoustic wave and the direction in which the acoustic wave phase velocity reaches the extreme value is the first included angle, the first included angle interval includes [1°, 10°] or [-1°, -10°], the included angle between the energy flow direction of the acoustic wave and the propagation direction of the acoustic wave is the second included angle, and the second included angle interval includes [3°, 15°] or [-3°, -15°]. Based on the heterogeneous integration substrate, in the embodiments of the present invention, only by changing the in-plane orientation of the electrodes, the propagation direction of the acoustic wave is deviated from the direction in which the acoustic wave phase velocity takes the extreme value, and the symmetry of the acoustic wave propagation is broken to suppress the transverse higher-order modes. At the same time, this method neither changes the geometric shape of the device nor reduces the Q value of the device, and the design is flexible. Description of the Drawings

[0029] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required to be used in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained according to these drawings without creative efforts.

[0030] Figure 1 is a schematic cross - section of an acoustic wave resonator for suppressing transverse higher - order modes provided by an embodiment of the present application Figure 1 ;

[0031] Figure 2 is a top - view schematic diagram of an acoustic wave resonator for suppressing transverse higher - order modes provided by an embodiment of the present application;

[0032] Figure 3 is a top - view schematic diagram of an acoustic wave resonator without suppressing transverse higher - order modes provided by an embodiment of the present application;

[0033] Figure 4 is a three - dimensional displacement comparison schematic diagram of the anti - resonance frequency obtained in the horizontal shear surface acoustic wave mode of an acoustic wave resonator for suppressing transverse higher - order modes provided by an embodiment of the present application;

[0034] Figure 5 is a schematic diagram provided by an embodiment of the present application for extracting Figure 4 comparison of displacement curves at different positions along the in - plane orientation;

[0035] Figure 6 is a comparison of resonator admittance curves provided by an embodiment of the present application Figure 1 ;

[0036] Figure 7 is a schematic diagram of conductance curve comparison based on the resonator corresponding to the test in Figure 6 and provided by an embodiment of the present application;

[0037] Figure 8 is a relationship diagram of phase velocity with deflection angle θ and energy - flow angle with deflection angle θ in the horizontal shear surface acoustic wave mode of an acoustic wave resonator for suppressing transverse higher - order modes provided by an embodiment of the present application;

[0038] Figure 9 is a conductance curve corresponding to different θ in the horizontal shear surface acoustic wave mode of an acoustic wave resonator for suppressing transverse higher - order modes provided by an embodiment of the present application;

[0039] Figure 10 is a schematic diagram of the electromechanical coupling coefficient k of the resonator corresponding to different θ extracted in the horizontal shear surface acoustic wave mode of an acoustic wave resonator for suppressing transverse higher - order modes provided by an embodiment of the present application 2 schematic diagram;

[0040] Figure 11 is a schematic diagram of the electromechanical coupling coefficient Q of the resonator corresponding to different θ extracted in the horizontal shear surface acoustic wave mode of an acoustic wave resonator for suppressing transverse higher - order modes provided by an embodiment of the present application max schematic diagram;

[0041] Figure 12 The Bode-Q curve comparison obtained by testing the mode of an acoustic wave resonator for suppressing transverse higher-order modes provided by an embodiment of the present application in the horizontal shear surface acoustic wave mode Figure 1 ;

[0042] Figure 13 The cross-sectional schematic diagram of an acoustic wave resonator for suppressing transverse higher-order modes provided by an embodiment of the present application Figure 2 ;

[0043] Figure 14 The comparison of the admittance curves of a resonator provided by an embodiment of the present application Figure 2 ;

[0044] Figure 15 is a schematic diagram of the conductance curve comparison obtained by corresponding testing of the resonator based on the one provided by an embodiment of the present application Figure 14 ;

[0045] Figure 16 The Bode-Q curve comparison obtained by testing the mode of an acoustic wave resonator for suppressing transverse higher-order modes provided by an embodiment of the present application in the horizontal shear surface acoustic wave mode Figure 2 . Detailed implementation manners

[0046] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0047] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above accompanying drawings are used to distinguish similar objects, and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or server including a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0048] Next, a specific embodiment of an acoustic wave resonator for suppressing transverse higher-order modes of the present application will be introduced Figure 1 The cross-sectional schematic diagram of an acoustic wave resonator for suppressing transverse higher-order modes provided by an embodiment of the present applicationFigure 1 , this specification provides a component structure as shown in the embodiments or drawings, but may include more or fewer modules or components based on routine or non-creative labor. The component structures listed in the embodiments are only one way among many component structures and do not represent the only component structure. During actual implementation, the component structure shown in the embodiments or drawings can be followed.

[0049] Specifically, as Figure 1 shown, an acoustic wave resonator for suppressing transverse higher-order modes may include: a support substrate 101, a piezoelectric thin film 102 disposed on the support substrate 101, and an electrode array 103 disposed on the piezoelectric thin film 102.

[0050] Optionally, the material of the piezoelectric thin film may include lithium tantalate LiTaO3 or lithium niobate LiNbO3.

[0051] Optionally, the support substrate may include one of sapphire, silicon, quartz, spinel, silicon carbide, diamond, diamond-like, and silicon nitride.

[0052] Optionally, the acoustic wave resonator may further include: an intermediate layer 104, the intermediate layer 104 is disposed between the piezoelectric thin film 102 and the support substrate 101, and the material of the intermediate layer 104 may include silicon oxide. The intermediate layer provided in the embodiments of the present application can improve the confinement of energy and exist as a temperature compensation medium in the acoustic wave resonator.

[0053] In the embodiments of the present application, Figure 2 is a top view schematic diagram of an acoustic wave resonator for suppressing transverse higher-order modes provided by the embodiments of the present application. As Figure 2 shown, the electrode array may include an interdigital electrode array 201 and a reflection grating electrode array 202. The reflection grating electrode array includes a first reflection grating electrode sub-array 203 and a second reflection grating electrode sub-array 204. The first reflection grating electrode sub-array is disposed at the first end of the interdigital electrode array, and the second reflection grating electrode sub-array is disposed at the second end of the interdigital electrode array. Among them, the interdigital electrode array contains bus bars that can provide electrical signals. The electrical signals generate a transverse electric field, and the transverse electric field will excite acoustic waves. By disposing the first reflection grating electrode sub-array and the second reflection grating electrode sub-array at the two ends of the interdigital electrode array, the acoustic waves excited by the transverse electric field are confined, so that the energy of the acoustic waves is concentrated within the region where the interdigital electrodes exist.

[0054] In the embodiments of the present application, in combination with Figure 2Continuing the description, the interdigital electrode array 201 may include interdigital electrodes 205 and dummy fingers 206. The interdigital electrodes and the dummy fingers are arranged in one-to-one correspondence, and an air gap is formed between the interdigital electrodes and the dummy fingers. The thickness of the piezoelectric thin film provided may be less than or equal to the period of the interdigital electrodes, that is, the wavelength. At the same time, the length of the dummy fingers may be greater than or equal to half of the period of the interdigital electrodes. For example, when the period of the interdigital electrodes is set to λ, the thickness of the piezoelectric thin film cannot exceed 1λ, and the length of the dummy fingers cannot be less than 0.5λ.

[0055] In this application, the dummy fingers set in one-to-one correspondence with the interdigital electrodes are used to reduce the lateral acoustic wave radiation and ensure that the energy of the acoustic wave is concentrated in the interdigital electrode region.

[0056] In the embodiment of this application, combined with Figure 2 Continuing the description, when the acoustic wave resonator is excited by a transverse electric field, the propagation direction of the excited acoustic wave is the direction of the normal of the electrode array. That is to say, the propagation direction of the generated acoustic wave is perpendicular to the extension directions of the interdigital electrodes and the dummy fingers. The propagation direction of the acoustic wave forms an angle θ with the direction in which the acoustic wave phase velocity reaches an extreme value, that is, the first angle.

[0057] In the embodiment of this application, Figure 3 is a top view schematic diagram of an acoustic wave resonator that does not suppress the lateral high-order mode provided by the embodiment of this application. As Figure 3 shown, when the mode of the acoustic wave resonator is the horizontal shear surface acoustic wave mode and the piezoelectric thin film is rotated Y-cut lithium tantalate, the direction in which the sound velocity reaches an extreme value in the horizontal shear surface acoustic wave mode is the crystal X-axis direction.

[0058] In a possible embodiment, Figure 4 is a three-dimensional displacement comparison schematic diagram of the anti-resonant frequency obtained when the mode of the acoustic wave resonator that suppresses the lateral high-order mode provided by the embodiment of this application is the horizontal shear surface acoustic wave mode. As Figure 4 shown, when θ = 0° or θ = 5°, that is, the first angle is 0° or the first angle is 5°, the three-dimensional displacement diagram of the acoustic wave resonator in the horizontal shear surface acoustic wave mode at the anti-resonant frequency is simulated. The electrode array of this acoustic wave resonator is an aluminum electrode, the piezoelectric thin film is lithium tantalate, the intermediate layer is silicon oxide, and the support substrate is sapphire. And when the mode of the acoustic wave resonator is the horizontal shear surface acoustic wave mode, the direction in which the sound velocity reaches an extreme value in the horizontal shear surface acoustic wave mode is the crystal X-axis direction, where the period of the interdigital electrodes is 2.2 μm, that is, the wavelength λ = 2.2 μm.

[0059] Combined with Figure 4Continuing the elaboration, as can be seen from the figure with θ = 0°, the vibration of the acoustic wave is mainly concentrated in the interdigital electrodes, and a small amount of energy penetrates into the reflection grating. At the junction of the interdigital electrodes and the reflection grating, it can be clearly seen that when θ = 0°, the energy flow direction is consistent with the in-plane orientation of the electrodes, that is, the power flow angle PFA = 0°. While from the figure with θ = 5°, the vibration of the acoustic wave is mainly concentrated in the interdigital electrodes, and a small amount of energy penetrates into the reflection grating. At the junction of the interdigital electrodes and the reflection grating, it can be seen that when θ = 5°, the energy flow direction deviates from the in-plane orientation of the electrodes, and the power flow angle PFA at this time is about -9°.

[0060] Figure 5 is a kind provided by the embodiment of the present application which extracts Figure 4 Schematic diagram of the comparison of displacement curves at different positions along the in-plane orientation, as Figure 5 shown. It can be seen that along the electrode direction, the displacement curve shows large fluctuations, which are caused by the transverse higher-order modes. In addition, the displacement curves at different positions basically coincide, indicating that when θ = 0°, the phases of the acoustic waves at different positions are the same, and the propagation has symmetry. While from the figure with θ = 5°, it can be seen that along the electrode direction, the fluctuation amplitude of the displacement curve has been greatly reduced compared with the figure with θ = 0°, which indicates that the transverse higher-order modes are significantly weakened. In addition, the displacement curves at different positions do not coincide, indicating that when θ = 5°, due to the non-zero power flow angle, the phases of the acoustic waves at different positions are inconsistent, which is the result of the broken symmetry of the propagation. It can be concluded from this that a small non-zero power flow angle can suppress the transverse higher-order modes.

[0061] In a possible embodiment, Figure 6 is a comparison of the admittance curves of a resonator provided by the embodiment of the present application Figure 1 , as Figure 6 shown. When θ = 0°, there are transverse higher-order modes in the admittance curve, and when θ = 5°, the transverse higher-order modes are suppressed. Figure 7 is a kind provided by the embodiment of the present application based on Figure 6 Schematic diagram of the comparison of the conductance curves corresponding to the resonator in Figure 7 shown. When θ = 0°, the parasitic mode appearing between the resonance frequency and the anti-resonance frequency is the transverse higher-order mode, while when θ = 5°, the transverse higher-order mode is basically suppressed.

[0062] Based on the above analysis, it can be concluded that by setting a small non-zero power flow angle, that is, the second included angle, the symmetry of the acoustic wave transmission can be broken, so as to suppress the problem of transverse higher-order modes.

[0063] In the embodiment of the present application, Figure 8 is a relationship diagram of the phase velocity, deflection angle θ, power flow angle and deflection angle θ of the horizontal shear surface acoustic wave mode, which is a mode of an acoustic wave resonator for suppressing transverse higher-order modes provided by the embodiment of the present application, asFigure 8 As shown, when θ≠0, it is necessary to ensure that the phase velocity maintains a relatively high magnitude, and at the same time select a relatively small and appropriate non-zero energy flow angle. Combining Figure 8 It can be seen that the range of θ is 1°≤|θ|≤10°, and θ≠0. At this time, the range of the power flow angle (PFA), that is, the angle between the group velocity and the phase velocity, can be selected as 3°≤|PFA|≤15°. That is, the angle between the propagation direction of the sound wave and the direction where the phase velocity of the sound wave reaches the extreme value is the first angle, and the first angle interval can be set as [1°, 10°] or [-1°, -10°]. The angle between the energy flow direction of the sound wave and the propagation direction of the sound wave is the second angle, and the second angle interval can be set as [3°, 15°] or [-3°, -15°]. Within this range, the set energy flow angle is relatively small, and the phase velocity can be ensured to be relatively large, thereby suppressing the transverse higher-order mode.

[0064] Figure 9 is the conductance curve corresponding to different θ in the horizontal shear surface acoustic wave mode of an acoustic wave resonator for suppressing transverse higher-order modes provided by an embodiment of the present application. As Figure 9 shown, with the increase of θ, combining Figure 8 the results of, the power flow angle PFA also increases. Therefore, with the increase of θ, the transverse higher-order mode weakens. When θ≥2°, the transverse higher-order mode has been significantly weakened.

[0065] In the embodiment of the present application, Figure 10 is the electromechanical coupling coefficient k of the resonator corresponding to different θ extracted in the horizontal shear surface acoustic wave mode of an acoustic wave resonator for suppressing transverse higher-order modes provided by an embodiment of the present application 2 schematic diagram. As Figure 10 shown, with the increase of θ, k 2 decreases. When θ is not greater than 8°, k 2 still remains at a relatively high level. Figure 11 is the electromechanical coupling coefficient Q of the resonator corresponding to different θ extracted in the horizontal shear surface acoustic wave mode of an acoustic wave resonator for suppressing transverse higher-order modes provided by an embodiment of the present application max schematic diagram. As Figure 11 shown, under the combined action of various loss mechanisms, Q max is at a relatively high level when θ≤8°.

[0066] In the embodiment of the present application, Figure 12 is the comparison of the Bode-Q curves obtained by testing in the horizontal shear surface acoustic wave mode of an acoustic wave resonator for suppressing transverse higher-order modes provided by an embodiment of the present application Figure 1 , as Figure 12As shown, when θ = 0°, the frequency at which the transverse high-order mode appears corresponds to more undulating peaks in the Bode-Q curve. When θ = 5°, Q max is higher than that when θ = 0°. Therefore, this method suppresses the transverse high-order mode while maintaining a high Q value.

[0067] Based on the above analysis, when the electrode array of the acoustic resonator is an aluminum electrode, the piezoelectric film is lithium tantalate, the intermediate layer is silicon oxide, the supporting substrate is sapphire, and the mode of the acoustic resonator is the horizontal shear surface acoustic wave mode, the direction in which the sound velocity reaches the extreme value in the horizontal shear surface acoustic wave mode is the crystal X-axis direction. It can be set that 2° ≤ |θ| ≤ 8°. At this time, the range of the power flow angle is 3° ≤ |PFA| ≤ 12°, and θ ≠ 0°. That is, the interval of the first included angle is [2°, 8°] or [-2°, -8°], and the interval of the second included angle is [3°, 12°] or [-3°, -12°]. Within this interval, the transverse high-order mode is well suppressed, and it can ensure that the Q value of the device is not reduced, and at the same time, the geometric shape of the device is not changed.

[0068] In another possible embodiment, Figure 13 is a cross-sectional schematic diagram of an acoustic resonator for suppressing transverse high-order modes provided by an embodiment of the present application Figure 2 , as Figure 13 shown, when the supporting substrate is a semiconductor, the acoustic resonator may further include a trap-rich layer 1301, and the trap-rich layer is located between the intermediate layer 104 and the supporting substrate 101. Optionally, the material of the trap-rich layer may include polysilicon or amorphous silicon. Setting a trap-rich layer in the acoustic resonator can reduce radio frequency loss.

[0069] In an optional embodiment, when the electrode array of the acoustic resonator is an aluminum electrode, the piezoelectric film is lithium tantalate, the intermediate layer is silicon oxide, the trap-rich layer is polysilicon, the supporting substrate is silicon, and the mode of the acoustic resonator is the horizontal shear surface acoustic wave mode, the direction in which the sound velocity reaches the extreme value in the horizontal shear surface acoustic wave mode is the crystal X-axis direction, where the period of the interdigital electrode is 2.2 μm, that is, the wavelength λ = 2.2 μm.

[0070] Figure 14 is a comparison of the admittance curves of a resonator provided by an embodiment of the present application Figure 2 , as Figure 14 shown, when θ = 0°, there are transverse high-order modes in the admittance curve. When θ = -6°, the transverse high-order modes are suppressed. Figure 15 is a schematic diagram of the comparison of the conductance curves obtained by testing the resonator corresponding to Figure 14 in an embodiment of the present application, as Figure 15As shown, when θ = 0°, the parasitic mode that appears between the resonant frequency and the anti-resonant frequency is the transverse high-order mode, while when θ = -6°, the transverse high-order mode is basically suppressed.

[0071] Figure 16 is the comparison of the Bode-Q curves obtained by testing the mode of an acoustic wave resonator for suppressing the transverse high-order mode in the horizontal shear surface acoustic wave mode provided by the embodiment of the present application Figure 2 , such as Figure 16 shown, when θ = 0°, the frequency at which the transverse high-order mode appears corresponds to more undulating peaks in the Bode-Q curve, while when θ = -6°, Q max is increased compared to when θ = 0°. Therefore, this method suppresses the transverse high-order mode while maintaining a high Q value.

[0072] Based on the above analysis, when the electrode array of the acoustic wave resonator is an aluminum electrode, the piezoelectric thin film is lithium tantalate, the intermediate layer is silicon oxide, the rich trap layer is polysilicon, the support substrate is silicon, and the mode of the acoustic wave resonator is the horizontal shear surface acoustic wave mode, the direction in which the sound velocity in the horizontal shear surface acoustic wave mode reaches the extreme value is the crystal X-axis direction. It can be set that 2° ≤ |θ| ≤ 8°. At this time, the range of the power flow angle is 3° ≤ |PFA| ≤ 12°, and θ ≠ 0°, that is, the interval of the first included angle is [2°, 8°] or [-2°, -8°], and the interval of the second included angle is [3°, 12°] or [-3°, -12°]. Within this interval, the transverse high-order mode is well suppressed, and it can ensure that the Q value of the device is not reduced, and at the same time, the geometric shape of the device is not changed.

[0073] In the embodiment of the present application, by setting a small non-zero power flow angle, that is, the second included angle, to break the symmetry of acoustic wave transmission, so as to suppress the problem of the transverse high-order mode. And the small non-zero power flow angle can deflect the acoustic wave resonator by an angle, that is, set the first included angle, so that the in-plane orientation of the electrode deviates from the direction where the acoustic wave phase velocity takes the extreme value to achieve. This method neither changes the geometric shape of the device nor reduces the Q value of the device, and the design is relatively flexible.

[0074] On the other hand, the embodiment of the present invention provides a filter, and the filter includes a plurality of resonators, and the resonators are the above-mentioned acoustic wave resonators for suppressing the transverse high-order mode.

[0075] Using the acoustic wave resonator for suppressing transverse higher-order modes provided by the embodiments of the present application, the acoustic wave resonator includes a supporting substrate, a piezoelectric thin film disposed on the supporting substrate, the material of the piezoelectric thin film includes lithium tantalate or lithium niobate, an electrode array disposed on the piezoelectric thin film, the acoustic wave resonator is excited by a transverse electric field, the propagation direction of the generated acoustic wave is the direction of the normal of the electrode array, and the included angle between the propagation direction of the acoustic wave and the direction where the acoustic wave phase velocity reaches an extreme value is a first included angle, the first included angle range includes [1°, 10°] or [-1°, -10°], the included angle between the energy flow direction of the acoustic wave and the propagation direction of the acoustic wave is a second included angle, the second included angle range includes [3°, 15°] or [-3°, -15°]. In the embodiments of the present invention, only by changing the in-plane orientation of the electrodes, the propagation direction of the acoustic wave is deviated from the direction where the acoustic wave phase velocity takes an extreme value, and the symmetry of the acoustic wave propagation is broken to suppress the transverse higher-order modes. At the same time, this method neither changes the geometric shape of the device nor reduces the Q value of the device, and the design is flexible.

[0076] It should be noted that: the above-mentioned sequence of the embodiments of the present application is only for description and does not represent the advantages and disadvantages of the embodiments. And the specific embodiments of the present specification have been described above. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims can be executed in a different order from that in the embodiments and still achieve the desired results. Additionally, the processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0077] Each embodiment in this specification is described in a progressive manner, and the same or similar parts among the embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the device embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiments.

[0078] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An acoustic resonator for suppressing transverse high-order modes, characterized in that, Comprising: A supporting substrate; A piezoelectric thin film disposed on the supporting substrate; The material of the piezoelectric thin film includes lithium tantalate or lithium niobate; An electrode array disposed on the piezoelectric thin film; the electrode array includes an interdigital electrode array; the interdigital electrode array includes interdigital electrodes and dummy fingers; The interdigital electrodes and the dummy fingers are arranged in one-to-one correspondence; the thickness of the piezoelectric thin film is less than or equal to the period of the interdigital electrodes; the length of the dummy fingers is greater than or equal to half of the period of the interdigital electrodes; The acoustic wave resonator is excited by a transverse electric field; The propagation direction of the excited acoustic wave is the direction of the normal of the electrode array, and the included angle between the propagation direction of the acoustic wave and the direction where the acoustic wave phase velocity reaches an extreme value is a first included angle; the first included angle range includes [1°, 10°] or [-1°, -10°]; wherein, when the mode of the acoustic wave resonator is the horizontal shear surface acoustic wave mode and the piezoelectric thin film is rotated Y-cut lithium tantalate, the direction where the sound velocity reaches an extreme value in the horizontal shear surface acoustic wave mode is the crystal X-axis direction; The included angle between the energy flow direction of the acoustic wave and the propagation direction of the acoustic wave is a second included angle, and the second included angle range includes [3°, 15°] or [-3°, -15°].

2. The acoustic wave resonator for suppressing transverse higher-order modes according to claim 1, wherein, The electrode array further includes a reflection grating electrode array; The reflection grating electrode array includes a first reflection grating electrode sub-array and a second reflection grating electrode sub-array; The first reflection grating electrode sub-array is disposed at a first end of the interdigital electrode array, and the second reflection grating electrode sub-array is disposed at a second end of the interdigital electrode array.

3. The acoustic resonator for suppressing transverse higher-order modes according to claim 1, characterized in that, The acoustic wave resonator further includes: An intermediate layer; the intermediate layer is disposed between the piezoelectric thin film and the supporting substrate; the material of the intermediate layer includes silicon oxide.

4. The acoustic resonator for suppressing transverse higher-order modes according to claim 3, wherein The acoustic wave resonator further includes: A rich trap layer; the rich trap layer is located between the intermediate layer and the supporting substrate; the material of the rich trap layer includes polysilicon or amorphous silicon.

5. The acoustic wave resonator for suppressing transverse higher-order modes according to claim 1, wherein, The supporting substrate includes one of sapphire, silicon, quartz, spinel, silicon carbide, diamond, diamond-like, silicon nitride.

6. The acoustic wave resonator for suppressing transverse higher-order modes according to claim 4, wherein, When the electrode array of the acoustic wave resonator is an aluminum electrode, the piezoelectric thin film is lithium tantalate, the intermediate layer is silicon oxide, the supporting substrate is sapphire, and the mode of the acoustic wave resonator is the horizontal shear surface acoustic wave mode, the direction where the sound velocity reaches an extreme value in the horizontal shear surface acoustic wave mode is the crystal X-axis direction, the first included angle range includes [2°, 8°] or [-2°, -8°], and the second included angle range includes [3°, 12°] or [-3°, -12°].

7. The acoustic wave resonator for suppressing transverse higher-order modes according to claim 4, wherein, When the electrode array of the acoustic resonator is an aluminum electrode, the piezoelectric thin film is lithium tantalate, the intermediate layer is silicon oxide, the trap-rich layer is polysilicon, the support substrate is silicon, and the mode of the acoustic resonator is the horizontal shear surface acoustic wave mode, the direction in which the sound velocity reaches an extreme value in the horizontal shear surface acoustic wave mode is the crystal X-axis direction, the first included angle interval includes [2°, 8°] or [-2°, -8°], and the second included angle interval includes [3°, 12°] or [-3°, -12°].

8. A filter, characterized in that, Comprising a plurality of resonators, the resonators being the acoustic resonators for suppressing transverse high-order modes according to any one of claims 1-7.

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