Surface acoustic wave devices, radio frequency filters, and radio frequency modules

Abstract

In some embodiments, an elastic surface wave device may include a piezoelectric substrate and interdigital transducer electrodes embedded in the surface of the piezoelectric substrate to support a higher-order mode of an elastic surface wave having a wavelength λ and a phase velocity exceeding 8,000 m / s. Such a higher-order mode may include a third-order mode, and the phase velocity may be at least 9,000 m / s. In some embodiments, such an elastic surface wave device may be implemented in products such as radio frequency filters, radio frequency modules, and wireless devices.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims priority to U.S. Provisional Application No. 63 / 346,957, entitled "Elastic Surface Wave Device with High - Speed Higher Modes", filed on May 30, 2022, the disclosure of which is hereby expressly incorporated by reference in its entirety.

[0002] This disclosure relates to elastic surface wave devices and related methods.

Background Art

[0003] An elastic surface wave (SAW) resonator typically includes interdigital transducer (IDT) electrodes mounted on one surface of a piezoelectric layer. Such electrodes include two sets of comb - shaped fingers, and in such a configuration, the distance between two adjacent fingers of the same set is approximately the same as the wavelength λ of the elastic surface wave supported by the IDT electrodes.

[0004] In many applications, the SAW resonator described above can be utilized as a radio frequency (RF) filter based on the wavelength λ. Such a filter can provide a certain number of desired characteristics.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

[0006] According to many embodiments, the present disclosure relates to an elastic surface wave device including a piezoelectric substrate and interdigital transducer electrodes embedded in one surface of the piezoelectric substrate to support a higher-order mode of an elastic surface wave having a wavelength λ and a phase velocity greater than 8,000 m / s.

[0007] In some embodiments, the higher-order mode may include a third-order mode. In some embodiments, the phase velocity may be at least 9,000 m / s. In some embodiments, the interdigital transducer electrodes may include an upper surface that is approximately coplanar with the surface of the piezoelectric substrate.

[0008] In some embodiments, the piezoelectric substrate may include a LiNbO 3 crystal having Euler angles (φ, θ, ψ). The angle θ may be in the range of 100 degrees < θ < 150 degrees.

[0009] In some embodiments, the interdigital transducer electrodes may be formed of aluminum, molybdenum, copper, tungsten, or platinum. In some embodiments, the interdigital transducer electrodes may be formed of copper. Such copper interdigital transducer electrodes may have a thickness in the range of 0.16λ to 0.24λ.

[0010] In some embodiments, the elastic surface wave device may further include a layer mounted on the piezoelectric substrate and the interdigital transducer electrodes, and such a layer may be configured to improve the temperature coefficient of the frequency characteristics of the elastic surface wave device. In some embodiments, the layer may be formed of silicon dioxide (SiO 2 ). The layer may have a first surface that is coplanar with the upper surface of the interdigital transducer electrodes and the surface of the piezoelectric substrate. The layer may have a second surface parallel to the first surface that defines the thickness of the layer. The copper interdigital transducer electrodes may be provided to have a thickness in the range of 0.24λ to 0.5λ.

[0011] In some embodiments, the present disclosure relates to a radio frequency filter including an input node that receives a signal, an output node that provides a filtered signal, and an elastic surface wave device implemented to be electrically present between the input node and the output node. The elastic surface wave device includes a piezoelectric substrate and interdigital transducer electrodes embedded in one surface of the piezoelectric substrate to support a higher-order mode of an elastic surface wave having a wavelength λ and a phase velocity exceeding 8,000 m / s.

[0012] In some embodiments, the higher-order mode may include a third-order mode.

[0013] In some embodiments, the phase velocity can be at least 9,000 m / s.

[0014] In some embodiments, the interdigital transducer electrodes may include an upper surface that is approximately coplanar with the surface of the piezoelectric substrate.

[0015] In some embodiments, the piezoelectric substrate may include a LiNbO crystal having Euler angles (φ, θ, ψ). The angle θ may range from 100 degrees < θ < 150 degrees. 3 crystal. The angle θ may range from 100 degrees < θ < 150 degrees.

[0016] In some embodiments, the interdigital transducer electrodes may be formed of aluminum, molybdenum, copper, tungsten, or platinum.

[0017] In some embodiments, the radio frequency filter may further include a layer mounted on the piezoelectric substrate and the interdigital transducer electrodes, the layer being configured to improve the temperature coefficient of the frequency characteristics of the elastic surface wave device. In some embodiments, the layer is silicon dioxide (SiO 2) may be formed from. The additional layer may have a first surface that is coplanar with the upper surface of the interdigital transducer electrode and the surface of the piezoelectric substrate. The additional layer may have a second surface parallel to the first surface so as to define the thickness of the additional layer.

[0018] In certain implementations, the present disclosure relates to a radio-frequency module. It includes a packaging substrate configured to receive a plurality of components, and a radio frequency circuit mounted on the packaging substrate and configured to support one or both of signal transmission and reception. The radio frequency module further includes a radio frequency filter configured to filter at least some of the signals. This radio frequency filter includes a piezoelectric substrate and interdigital transducer electrodes, and the interdigital transducer electrodes are embedded in one surface of the piezoelectric substrate so as to support a higher-order mode of an elastic surface wave having a wavelength λ and a phase velocity exceeding 8,000 m / s.

[0019] In some teachings, the present disclosure relates to a wireless device including a transceiver, an antenna, and a wireless system electrically implemented between the transceiver and the antenna. The wireless system includes a filter configured to provide a filtering function for the wireless system. This filter includes a piezoelectric substrate and interdigital transducer electrodes, and the interdigital transducer electrodes are embedded in one surface of the piezoelectric substrate so as to support a higher-order mode of an elastic surface wave having a wavelength λ and a phase velocity exceeding 8,000 m / s.

[0020] According to some teachings, the present disclosure relates to a method of fabricating an elastic wave device. The method includes forming or providing a piezoelectric substrate, and embedding interdigital transducer electrodes in one surface of the piezoelectric substrate to support a higher-order mode of a surface elastic wave having a wavelength λ and a phase velocity exceeding 8,000 m / s.

[0021] In some embodiments, the higher order mode may include the third order mode. In some embodiments, the phase velocity may be at least 9,000 m / s.

[0022] In some embodiments, the embedding of the interdigital transducer electrodes may result in an upper surface that is approximately coplanar with the surface of the piezoelectric substrate.

[0023] In some embodiments, the piezoelectric substrate may include a LiNbO crystal having Euler angles (φ, θ, ψ). The angle θ may range from 100 degrees < θ < 150 degrees. 3

[0024] In some embodiments, the interdigital transducer electrodes may be formed from aluminum, molybdenum, copper, tungsten, or platinum. In some embodiments, the interdigital transducer electrodes may be formed from copper. The copper interdigital transducer electrodes may have a thickness in the range of 0.16λ to 0.24λ.

[0025] In some embodiments, the method may further include mounting a layer on the piezoelectric substrate and the interdigital transducer electrodes. This layer improves the temperature coefficient of the frequency characteristics of the surface acoustic wave device. In some embodiments, the layer may be formed from silicon dioxide (SiO). The layer may have a first surface that is coplanar with the upper surface of the interdigital transducer electrodes and the surface of the piezoelectric substrate. The layer may have a second surface parallel to the first surface that defines the thickness of the layer. Copper interdigital transducer electrodes having a thickness in the range of 0.24λ to 0.5λ can be provided. 2

[0026] In some embodiments, the surface acoustic wave device may be part of a radio frequency filter.

[0027] For the purpose of summarizing the present disclosure, certain aspects, advantages, and novel features of the invention have been described herein. It should be understood that not all of the advantages necessarily achieved in accordance with any particular embodiment of the invention. That is, the invention can be embodied or practiced in a manner that achieves or optimizes one advantage or a group of advantages taught herein without necessarily achieving other advantages that may be taught or suggested herein.

Brief Description of the Drawings

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DETAILED DESCRIPTION OF THE INVENTION

[0029] The headings given here are for convenience only and do not necessarily affect the scope or meaning of the claimed invention.

[0030] In some wireless applications, the frequency bands from 700 MHz to 3 GHz used in smartphones and the like are extremely congested. To solve this problem, the fifth-generation mobile communication system (5G) plans to utilize the frequency bands from 3.6 GHz to 4.9 GHz, and further, in the next generation, to utilize frequency bands of 6 GHz or higher.

[0031] To utilize the aforementioned frequency bands, in general elastic wave devices such as surface acoustic wave (SAW) devices, due to power resistance and manufacturing technology constraints, the wavelength (λ) given by the interdigital transducer (IDT) electrodes cannot be reduced, and there are limitations in using high frequencies.

[0032] FIG. 1A is a plan view of a surface acoustic wave (SAW) device 100 having a piezoelectric substrate 101 and an interdigital transducer (IDT) electrode 102 mounted thereon. FIG. 1B shows a side cross-sectional view of the SAW device 100 of FIG. 1A. As shown in FIG. 1B, the IDT electrode 102 can be embedded in the piezoelectric substrate 101 such that the upper surface of the IDT electrode 102 (when viewed as in FIG. 1B) and the upper surface of the piezoelectric substrate 101 (when viewed as in FIG. 1B) are approximately coplanar. It is understood that although various embodiments are described in the context of such a coplanar configuration here, one or more features of the present disclosure can also be implemented in a configuration where the upper surface of the IDT electrode and the upper surface of the piezoelectric substrate are not coplanar.

[0033] Referring to FIGS. 1A and 1B, the distance between two adjacent fingers of the IDT electrode 102 is approximately the same as the wavelength λ of the surface acoustic wave associated with the IDT electrode 102. Further, each finger of the IDT electrode 102 is shown to have a lateral width F, and a gap distance G is shown to be provided between two adjacent fingers that are comb-shaped.

[0034] FIG. 2 shows that in some embodiments, the SAW device 100 of FIGS. 1A and 1B can generate higher-order modes. In the example of FIG. 2, such a SAW device (100 of FIGS. 1A and 1B) is referred to as an embedded IDT configuration. This is contrasted with a baseline IDT configuration in which the corresponding IDT electrodes are not embedded. For both the baseline IDT configuration and the embedded IDT configuration, the piezoelectric substrate is formed from LiNbO 3 (also referred to herein as LN), each having an exemplary Euler angle (0, 120, 0). Further, the IDT electrodes of each of the baseline IDT configuration and the embedded IDT configuration are formed from copper (Cu) and are configured such that the wavelength λ is 2 μm, the width F is 0.20λ, and the thickness h is 0.20λ.

[0035] Configured as described above, FIG. 2 shows, as an example of an admittance coefficient plot, that the third-order mode (designated 110) is generated by the embedded IDT configuration. Such a third-order mode is shown to have a wavelength λ of 2 μm and be at approximately 4.5 GHz, thereby obtaining a phase velocity V = fλ = 9,000 m / s. Note that in some embodiments, such a third-order mode can be utilized in high-frequency filter applications.

[0036] In some embodiments, the SAW devices described herein can be configured to support third-order modes of elastic surface waves having a phase velocity greater than 8,000 m / s. In some embodiments, such elastic surface waves may have a phase velocity of at least 9,000 m / s.

[0037] FIGS. 3A and 3B show an example of a preferred range of the piezoelectric substrate cut angle θ of the Euler angle (φ, θ, ψ). FIG. 3A shows the electromechanical coupling coefficient k when the cut angle θ is swept in 10-degree increments through a range from 70 degrees to 170 degrees. 2 It can be seen that k 2 takes its maximum value when θ is 100 degrees. Also, for the Euler angle configuration (0, 120, 0) of the embedded IDT configuration of FIG. 2, k 2has a relatively large value at θ = 120 degrees, but is slightly smaller than the maximum value (when θ = 100 degrees).

[0038] FIG. 3B shows plots of the quality factors Qs and Qp at the series resonance frequency and the parallel resonance frequency when the cut angle θ is swept in 10-degree increments through the range from 0 degrees to 170 degrees. It can be seen that Qs takes its maximum value when θ is 110 degrees. Also, for the Euler angle configuration (0, 120, 0) of the embedded IDT structure in FIG. 2, Qs has a relatively large value at θ = 120 degrees, but is slightly smaller than the maximum value (when θ = 110 degrees). Also, it can be seen that Qs begins to increase significantly when θ is 80 degrees and returns to a relatively low value when θ is 150 degrees.

[0039] Regarding Qp, it can be seen that the value of Qp begins to increase rapidly when θ is 100 degrees and returns to a relatively low value when θ is 170 degrees.

[0040] Based on the example of FIG. 3B, in some embodiments, it can be seen that a range of cut angles θ between 100 degrees and 150 degrees is desirable. Such a range of cut angles θ also gives a range of relatively high values of the coupling coefficient k 2 as shown in FIG. 3A.

[0041] FIG. 4 shows various plots regarding a SAW device having an embedded IDT structure. It is demonstrated how various parameters of such a SAW device change with the thickness h of the embedded IDT electrode 102. In the example of FIG. 4, the embedded IDT electrode 102 is shown to be made of copper (Cu) and configured to give a wavelength λ of 2 μm and a width F of 0.20λ. Further, the piezoelectric substrate 101 formed from LN is shown to have an Euler angle (0, 120, 0).

[0042] In FIG. 4, the upper left panel shows the plot of the third mode admittance coefficient of the SAW device having thicknesses h of 0.14λ, 0.16λ, 0.18λ, 0.20λ, 0.22λ, and 0.24λ. The upper right panel shows the real part of the admittance of the third mode response for the same thickness h, and the lower left panel shows the Q plot obtained from the peak of such real admittance part. It can be seen that various responses including the Q response are sensitive to the thickness h of the IDT electrode.

[0043] FIG. 5 shows that in some embodiments, to improve the frequency temperature coefficient (TCF) characteristics of the SAW device, the SAW device may include an overcoat layer 105 provided on the IDT electrode 102 and the piezoelectric substrate 101. In the example of FIG. 5, the IDT electrode 102 is embedded in the piezoelectric substrate 101 such that the upper surface of the IDT electrode 102 (when viewed as in FIG. 5) and the upper surface of the piezoelectric substrate 101 are approximately coplanar. That is, in some embodiments, the overcoat layer 105 can completely cover the IDT electrode 102.

[0044] In some embodiments, the overcoat layer 105 can be formed from a material such as silicon dioxide (SiO 2 2) having a constant thickness. In FIG. 5, it is shown that the exemplary SiO 2 overcoat layer 105 has a thickness of 0.20λ. Here, the wavelength λ is 2 μm defined by the exemplary embedded IDT electrode 102, and the embedded IDT electrode 102 is formed from copper (Cu) and has a width F of 0.20λ and a thickness of 0.20λ. In the example of FIG. 5, the piezoelectric substrate 101 is formed from LN having Euler angles (0, 120, 0).

[0045] FIG. 5 shows various plots comparing the aforementioned SAW device having the SiO 2 overcoat layer 105 with a similar SAW device having no SiO 2 overcoat layer. In FIG. 5, the upper left panel shows the SiO 2Plots of the third - mode admittance coefficient of the above SAW device with and without an overcoat layer are shown. The upper - right panel is SiO 2 The real part of the admittance of the third - mode response of the same SAW device with and without an overcoat layer is shown. The lower - left panel shows the Q - plot obtained from the peak of such a real admittance part. Note that the SiO configured as above 2 The implementation of the overcoat layer can improve the TCF performance, but it has been shown that the quality factor Q deteriorates.

[0046] FIG. 6 is similar to the SAW device of the example of FIG. 5, but shows plots of the third - mode admittance coefficient (upper - left panel), plots of the real part of the admittance of the third - mode response (upper - right panel), and Q - plots obtained from the peaks of such real admittance parts (lower - left panel) of SAW devices with different Euler angles (0, θ, 0) cut angles θ of the LN substrate 101. Specifically, the cut angles θ in FIG. 6 are 100 degrees, 110 degrees, 120 degrees, 130 degrees, and 140 degrees. As shown in the Q - plot of FIG. 6, the Q performance does not change significantly even when the angle θ of the LN substrate is changed.

[0047] FIG. 7 is similar to the exemplary SAW device of FIG. 5, but shows plots of the third - mode admittance coefficient (upper - left panel), plots of the real part of the admittance of the third - mode response (upper - right panel), and Q - plots obtained from the peaks of such real admittance parts (lower - left panel) of SAW devices with different thickness values (h) of the IDT electrode 102. Specifically, the thickness values (h) in FIG. 7 are 0.10λ, 0.20λ, 0.30λ, 0.40λ, and 0.50λ. As shown in the Q - plot of FIG. 7, it can be seen that the Q performance improves as the Cu IDT electrode gets thicker.

[0048] In some embodiments, a SAW resonator having one or more of the features described herein can be implemented as a product, and such a product can be included in other products. Examples of such different products are described with reference to FIGS. 8 to 12.

[0049] Figure 8 shows that, in some embodiments, multiple units of SAW resonators can be fabricated while in an array configuration. For example, wafer 200 includes an array of units 100', and such units are processed together through a number of process steps while remaining coupled together.

[0050] Upon completion of the process steps in the wafer format described above, the units 100' of the array can be singulated to provide a number of SAW resonators 100. Figure 8 depicts one such SAW resonator 100, and such SAW resonator can include one or more of the features described herein.

[0051] Figure 9 shows that, in some embodiments, a SAW resonator 100 having one or more of the features described herein can be implemented as part of a packaged device 300. Such a packaged device can include a packaging substrate 302 configured to receive and support one or more components including the SAW resonator 100.

[0052] Figure 10 shows that, in some embodiments, the SAW resonator-based packaged device 300 of Figure 9 can become a packaged filter device 300. Such a filter device can include a packaging substrate 302 suitable for receiving and supporting a SAW resonator 100 configured to provide a filtering function such as an RF filtering function.

[0053] FIG. 11 shows that in some embodiments, a radio frequency (RF) module 400 may include an assembly 406 of one or more RF filters. Such filters may be SAW resonator-based filters 100, package filters 300, or some combination thereof. In some embodiments, the RF module 400 of FIG. 11 may also include, for example, an RF integrated circuit (RFIC) 404 and an antenna switch module (ASM) 408. Such a module may be, for example, a front-end module configured to support wireless operations. In some embodiments, some or all of the components described above may be attached and supported by a packaging substrate 402.

[0054] In some implementations, a device and / or circuit having one or more of the features described herein may be included in an RF device such as a wireless device. Such a device and / or circuit may be implemented directly in a wireless device, implemented in the modular form described herein, or implemented in some combination thereof. In some embodiments, such wireless devices may include, for example, cellular telephones, smartphones, handheld wireless devices with or without telephone functionality, wireless tablets, and the like.

[0055] FIG. 12 depicts an example of a wireless device 500 having one or more of the advantageous features described herein. In the context of a module having one or more of the features described herein, such a module is generally depicted by a dashed square 400 and can be implemented, for example, as a front-end module (FEM). In such an example, one or more of the SAW filters described herein may be included in a filter assembly such as, for example, a duplexer 526.

[0056] Referring to FIG. 12, a plurality of power amplifiers (PAs) 520 can receive corresponding RF signals from transceiver 510. Transceiver 510 can be configured and operate in a well-known manner to generate RF signals to be amplified and transmitted and to process received signals. Transceiver 510 is shown to interact with baseband subsystem 408. Baseband subsystem 408 is configured to provide conversion between appropriate data and / or voice signals for the user and appropriate RF signals for transceiver 510. Transceiver 510 can also communicate with a power management component 506 configured to manage power for the operation of wireless device 500. Such power management can also control the operation of baseband subsystem 508 and module 400.

[0057] Baseband subsystem 508 is shown to be connected to user interface 502 to facilitate various inputs and outputs of voice and / or data provided to and received from the user. Baseband subsystem 508 is also connected to a memory 504 configured to store data and / or instructions to facilitate the operation of the wireless device and / or to store information for the user.

[0058] In an example of wireless device 500, the outputs of the plurality of PAs 520 are shown to be routed to corresponding duplexers 526. Such amplified and filtered signals are routed to antenna 516 via antenna switch 514 for the purpose of transmission. In some embodiments, duplexer 526 enables simultaneous transmission and reception operations using a common antenna (e.g., 516). In FIG. 12, received signals are shown to be routed to an "Rx" path (not shown) that can include, for example, a low noise amplifier (LNA).

[0059] Here, although various examples are described in the context of a piezoelectric substrate including LiNbO 3 (LN), one or more features of the present disclosure are applicable to LiTaO 3It is understood that the present invention can also be implemented using other piezoelectric substrates such as (LT).

[0060] Unless the context clearly requires otherwise, throughout the specification and claims, the terms "comprising", "including", and the like shall be construed in an inclusive sense as opposed to an exclusive or exhaustive sense, i.e., in the sense of "including, but not limited to". The term "coupled" as generally used herein refers to the possibility that two or more elements can be either directly connected or connected via one or more intermediate elements. Additionally, as used in this application, the terms "herein", "above", "below", and terms of similar meaning refer to the entire application and not to any particular part of the application. Where context permits, the terms in the above description using singular or plural numbers may also include the plural or singular numbers respectively. The terms "or" and "or" referring to a list of two or more items cover all of the following interpretations of the term, i.e., any of the items in the list, all of the items in the list, and any combination of the items in the list.

[0061] The foregoing description of embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Specific embodiments and examples of the invention are described above for illustrative purposes, but as will be recognized by those skilled in the art, various equivalent modifications are possible within the scope of the invention. For example, while a process or block is presented in a given order, alternative embodiments can execute a routine having steps in a different order or use a system having blocks in a different order, and some processes or blocks can be deleted, moved, added, subdivided, combined, and / or modified. These processes or blocks may each be implemented in various different manners. Also, while a process or block may be shown as being executed serially, these processes or blocks may instead be executed in parallel or at different times.

[0062] The teachings of the present invention provided herein can be applied to other systems that are not necessarily the systems described above. The elements and operations of the various embodiments described above may be combined to provide further embodiments.

[0063] Although certain embodiments of the invention have been described, these embodiments have been presented by way of example only and are not intended to limit the scope of the disclosure. In fact, the novel methods and systems described herein may be embodied in a variety of other forms, and furthermore, various omissions, substitutions and changes in the forms of the methods and systems described herein may be made without departing from the spirit of the disclosure. The appended claims and their equivalents are intended to cover such forms or modifications as fall within the scope and spirit of the disclosure.

Claims

1. A surface acoustic wave device, Piezoelectric substrate and Interdigital transducer electrode and Includes, A surface acoustic wave device in which the interdigital transducer electrode is embedded on one surface of the piezoelectric substrate to support higher-order modes of surface acoustic waves having a wavelength λ and a phase velocity greater than 8,000 m / s.

2. The surface acoustic wave device according to claim 1, wherein the higher-order mode includes a third-order mode.

3. The surface acoustic wave device according to claim 1, wherein the phase velocity is at least 9,000 m / s.

4. The surface acoustic wave device according to claim 1, wherein the interdigital transducer electrode includes an upper surface that is approximately coplanar with one surface of the piezoelectric substrate.

5. The piezoelectric substrate is LiNbO having Euler angles (φ, θ, ψ). ３ A surface acoustic wave device according to claim 1, comprising a crystal.

6. The surface acoustic wave device according to claim 5, wherein the angle θ is in the range of 100 degrees < θ < 150 degrees.

7. The surface acoustic wave device according to claim 1, wherein the interdigital transducer electrode is formed from aluminum, molybdenum, copper, tungsten, or platinum.

8. The surface acoustic wave device according to claim 7, wherein the interdigital transducer electrode is formed from copper.

9. The surface acoustic wave device according to claim 8, wherein the copper interdigital transducer electrode has a thickness in the range of 0.16λ to 0.24λ.

10. The surface acoustic wave device according to claim 1, further comprising a layer mounted on the piezoelectric substrate and the interdigital transducer electrode, wherein the layer is configured to improve the temperature coefficient of the frequency characteristics of the surface acoustic wave device.

11. The aforementioned layer is silicon dioxide (SiO ２ A surface acoustic wave device according to claim 10, formed from ).

12. The surface acoustic wave device of claim 10, wherein the layer has a first surface that is coplanar with the upper surface of the interdigital transducer electrode and the surface of the piezoelectric substrate.

13. The surface acoustic wave device according to claim 12, wherein the layer has a second surface parallel to the first surface so as to define the thickness of the layer.

14. The surface acoustic wave device according to claim 8, wherein the copper interdigital transducer electrode has a thickness in the range of 0.24λ to 0.5λ.

15. It is a radio frequency filter, An input node that receives a signal, An output node that provides a filtered signal, A surface acoustic wave device is implemented so as to be electrically present between the input node and the output node. Includes, The surface acoustic wave device is a radio frequency filter comprising a piezoelectric substrate and an interdigital transducer electrode embedded on one surface of the piezoelectric substrate to support higher-order modes of surface acoustic waves having a wavelength λ and a phase velocity greater than 8,000 m / s.

16. The radio frequency filter of claim 15, wherein the higher-order mode includes a third-order mode.

17. The radio frequency filter according to claim 15, further comprising a layer mounted on the piezoelectric substrate and the interdigital transducer electrodes, wherein the layer is configured to improve the temperature coefficient of the frequency characteristics of the radio frequency filter.

18. The aforementioned layer is silicon dioxide (SiO ２ A radio frequency filter according to claim 17, formed from ).

19. The radio frequency filter according to claim 17, wherein the layer has a first surface that is coplanar with the upper surface of the interdigital transducer electrode and the one surface of the piezoelectric substrate.

20. A radio frequency module, A package substrate configured to accept multiple components, A radio frequency circuit mounted on the aforementioned package substrate and configured to support either or both transmission and reception of multiple signals, A radio frequency filter configured to filter at least some of the aforementioned plurality of signals Includes, The radio frequency filter is a radio frequency module comprising a piezoelectric substrate and an interdigital transducer electrode, wherein the interdigital transducer electrode is embedded on one surface of the piezoelectric substrate to support higher-order modes of surface acoustic waves having wavelength λ and phase velocity greater than 8,000 m / s.

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