Elastic wave filter and RF front-end structure

Abstract

This application relates to an elastic wave filter and a radio frequency front-end structure, and relates to the radio frequency field. This application sets a lithium tantalate layer with Euler angles of (0±10°, 132°±10°, 0°±10°) on a non-piezoelectric substrate, sets a conductive material film pattern on the lithium tantalate layer, and sets an interdigital transducer electrode with a thickness of h m Under the premise that the thickness of the lithium tantalate layer h is 4h m ≤h≤(32 / 7)h m , the IDT electrodes do not have any weighting form. In this case, the elastic wave filter and RF front-end structure provided by the present application have better transverse mode suppression and simpler manufacturing process.

Description

Technical Field

[0001] The present application relates to the field of radio frequency technology, and in particular to an elastic wave filter and a radio frequency front-end structure. Background Art

[0002] Mobile communications have become an integral part of our lives. The rapidly growing demand for multifunctional wireless communication systems is driving the development of RF front-ends. RF transmitters and receivers require miniature filtering modules that cover the current mobile communication frequency bands.

[0003] Elastic wave devices, characterized by low cost, compact size, and multiple functions, have found widespread application in radar, communications, navigation, and other fields. The most commonly used elastic wave devices in mobile phone and base station communications include elastic wave filters and elastic wave duplexers and multiplexers, which are composed of multiple elastic wave filters. In any type of elastic wave filter, a thin film of conductive material is patterned on a piezoelectric functional material to define multiple IDT electrodes, multiple reflector electrodes, and multiple conductive traces and pad electrodes for electrically connecting the IDT electrodes. Bandpass characteristics are achieved by utilizing the frequency characteristics of the IDT electrode's conversion function, which converts electrical signals into elastic waves.

[0004] As frequency source devices, elastic wave filters often experience spurious waves caused by transverse modes, which can degrade device performance. Currently, the industry often employs interdigital transducer (IDT) electrodes with varying weighting to suppress transverse modes. However, this approach has several drawbacks: Firstly, the weighting of the IDT electrodes reduces the Q factor of the device itself, thereby increasing losses in the elastic wave filter and hindering its application in RF front-ends. Secondly, the weighting method increases the difficulty of device fabrication. Summary of the Invention

[0005] The purpose of this application is to provide an elastic wave filter and a radio frequency front-end structure to solve the problems existing in the above-mentioned prior art.

[0006] To achieve the above objectives, the technical solutions adopted in this application are:

[0007] In a first aspect, the present application provides an elastic wave filter, comprising:

[0008] non-piezoelectric substrates;

[0009] A lithium tantalate layer disposed on the non-piezoelectric substrate, wherein the Euler angles of the lithium tantalate layer are (0±10°, 132°±10°, 0°±10°); and

[0010] a conductive material thin film pattern disposed on the lithium tantalate layer, the conductive material thin film pattern being formed with a plurality of interdigital transducer electrodes, a plurality of reflector electrodes, a plurality of conductive traces and pad electrodes for achieving electrical connections between the plurality of interdigital transducer electrodes;

[0011] The IDT electrode comprises a plurality of first electrode fingers and a plurality of second electrode fingers interlaced with each other, and a first bus bar and a second bus bar facing each other in the extending direction of the first electrode fingers and the second electrode fingers; the pad electrode comprises an input terminal, an output terminal and at least one ground terminal; when the thickness of the IDT electrode is set to h m Under the premise that the thickness h of the lithium tantalate layer is 4h m ≤h≤(32 / 7)h m ; There is no weighting form for the interdigital transducer electrodes.

[0012] In a possible implementation, the elastic wave filter is applicable to a frequency band ranging from 2300 MHz to 2400 MHz.

[0013] In a possible implementation, the elastic wave filter has a chip-scale packaging structure.

[0014] In one possible implementation, the non-piezoelectric substrate includes:

[0015] a low acoustic velocity material layer disposed directly below the lithium tantalate layer, a capture material layer disposed directly below the low acoustic velocity material layer, and a support substrate disposed directly below the capture material layer; or

[0016] A low acoustic velocity material layer is disposed directly below the lithium tantalate layer, and a support substrate is disposed directly below the low acoustic velocity material layer.

[0017] In one possible implementation, the sound velocity of the body wave propagating in the low-acoustic-velocity material layer is lower than the sound velocity of the body wave propagating in the lithium tantalate layer; the sound velocity of the body wave propagating in the supporting substrate is higher than the sound velocity of the body wave propagating in the lithium tantalate layer.

[0018] In a possible implementation, the low-acoustic-velocity material layer is composed of one or more combinations of relatively low-acoustic-velocity materials such as silicon dioxide, glass, silicon oxynitride, tantalum oxide, or silicon dioxide with a compound containing fluorine, carbon, or boron as the main component added thereto; when the thickness of the interdigital transducer electrode is set to h m Under the premise that the thickness h of the low sound velocity material layer is (23 / 7)h m ≤h≤(27 / 7)h m .

[0019] In a possible implementation, the capture material layer is formed by a combination of one or more materials selected from amorphous silicon, polycrystalline silicon, amorphous germanium, and polycrystalline germanium; when the thickness of the IDT electrode is set to h m Under the premise that the thickness of the capture material layer is (50 / 7)h m .

[0020] In one possible implementation, the conductive material film pattern includes a first conductive material film pattern and a second conductive material film pattern, the second conductive material film pattern partially overlaps with the first conductive material film pattern, and the second conductive material film pattern has a different pattern and film thickness from the first conductive material film pattern.

[0021] In a possible implementation, the reflector electrodes are arranged on both sides of the IDT electrode along the propagation direction of the elastic wave.

[0022] In a second aspect, the present application provides a radio frequency front-end structure, comprising any elastic wave filter as described above.

[0023] The beneficial effects of the technical solution provided by this application include at least:

[0024] The present invention provides a lithium tantalate layer with Euler angles of (0±10°, 132°±10°, 0°±10°) on a non-piezoelectric substrate, and provides a conductive material film pattern on the lithium tantalate layer. m Under the premise that the thickness of the lithium tantalate layer h is 4h m ≤h≤(32 / 7)h m , the IDT electrodes do not have any weighting form. In this case, the elastic wave filter and RF front-end structure provided by the present application have better transverse mode suppression and simpler manufacturing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings are used to provide a further understanding of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the present application and do not constitute a limitation of the present application. In the accompanying drawings:

[0026] Figure 1 A three-dimensional schematic diagram of an elastic wave filter 100 applied to the TX40 frequency band provided in the first embodiment of the present application is shown;

[0027] Figure 2 Schematic top view and cross-sectional view of the elastic wave resonator 200 provided in the first embodiment of the present application are shown;

[0028] Figure 3The figure shows an insertion loss-frequency curve of the elastic wave filter 100 applied to the TX40 frequency band provided in the first embodiment of the present application;

[0029] Figure 4 A standing wave ratio-frequency curve of the elastic wave filter 100 applied to the TX40 frequency band provided in the first embodiment of the present application is shown;

[0030] Figure 5 The following diagram shows three common weighting methods for elastic wave resonators in the industry;

[0031] Figure 6 shows an unweighted schematic diagram of an elastic wave resonator;

[0032] Figure 7 1 shows a layout of an elastic wave filter 100 applied to the TX40 frequency band provided in the first embodiment of the present application;

[0033] Figure 8 The insertion loss-frequency curve of the elastic wave filter applied to the TX40 frequency band after resonator weighting is shown;

[0034] Figure 9 A comparison diagram of the standing wave ratio-frequency of an elastic wave filter applied to the TX40 frequency band after resonator weighting and the elastic wave filter 100 is shown;

[0035] Figure 10 The figure shows the admittance / conductance-frequency curves of the elastic wave resonator 200 with different lithium tantalate thicknesses provided in the first embodiment of the present application;

[0036] Figure 11 The figure shows the admittance / conductance-frequency curves of the elastic wave resonator 200 with different silicon dioxide thicknesses provided in the first embodiment of the present application;

[0037] Figure 12 FIG2 shows a cross-sectional schematic diagram of an elastic wave filter 100 with a chip-scale packaging structure provided in the first embodiment of the present application;

[0038] Figure 13 A three-dimensional schematic diagram of an elastic wave filter 100 with a chip-scale packaging structure provided in the first embodiment of the present application is shown;

[0039] Figure 14 A three-dimensional schematic diagram of an elastic wave filter 300 applied to the TX40 frequency band provided in the second embodiment of the present application is shown;

[0040] Figure 15 The insertion loss-frequency curve of the elastic wave filter 300 applied to the TX40 frequency band provided in the second embodiment of the present application is shown. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0042] Among them, the same parts are represented by the same figure marks. It should be noted that the words "front", "rear", "left", "right", "up" and "down" used in the following description refer to the directions in the drawings of the present application specification, and the words "bottom" and "top", "inside" and "outside" refer to directions toward or away from specific parts, respectively. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present application specification, the meaning of "multiple" is two or more.

[0043] Example 1:

[0044] Figure 1 The following is a three-dimensional schematic diagram of an elastic wave filter 100 applied to the TX40 frequency band provided in the first embodiment of the present application. Figure 1 The direction parallel to the x-axis in the coordinate system is the direction of elastic wave propagation, and the definition is Figure 1 The direction parallel to the y-axis in the coordinate system is the extension direction of the electrode finger, and it is defined as Figure 1 The direction parallel to the z-axis in the coordinate system is the height direction of the elastic wave filter 100 .

[0045] Specifically, the elastic wave filter 100 includes a non-piezoelectric substrate 23 , a piezoelectric layer 10 disposed on the non-piezoelectric substrate 23 , and a conductive thin film pattern disposed on the piezoelectric layer 10 .

[0046] Specifically, the non-piezoelectric substrate 23 is disposed below the piezoelectric layer 10 and includes, from top to bottom, a low-acoustic-velocity material layer 11, a capture material layer 13, and a support substrate 14. The low-acoustic-velocity material layer 11 is located below the piezoelectric layer 10, and the acoustic velocity of the bulk waves propagating in the low-acoustic-velocity material layer 11 is lower than the acoustic velocity of the bulk waves propagating in the piezoelectric layer 10. The capture material layer 13 is located below the low-acoustic-velocity material layer 11. The support substrate 14 is located below the capture material layer 13, and the acoustic velocity of the bulk waves propagating in the support substrate 14 is higher than the acoustic velocity of the bulk waves propagating in the piezoelectric layer 10.

[0047] Furthermore, the conductive material film pattern includes a first conductive material film pattern and a second conductive material film pattern (not shown in the figure), the second conductive material film pattern (not shown in the figure) partially overlaps with the first conductive material film pattern, and the second conductive material film pattern (not shown in the figure) has a pattern and film thickness different from those of the first conductive material film pattern.

[0048] In detail, the first conductive material film pattern is realized with a thickness of h m The second conductive material film pattern is realized with a thickness of 20h m Aluminum; the piezoelectric layer 10 is realized as a thickness of 4h m ~(32 / 7)h m 42YX-lithium tantalate, the Euler angle is (0°, 132°, 0°); the low acoustic velocity material layer 11 is realized with a thickness of (23 / 7)h m ~(27 / 7)h m silicon dioxide; the capture material layer 13 is realized as thick (50 / 7)h m The supporting substrate 14 is realized as 250 μm silicon.

[0049] As common knowledge, the piezoelectric layer is cut so as to be consistent with the front and back crystal axes of the relative piezoelectric layer, so that the piezoelectric layer has different tangent options. We often use Euler angles to define its tangent. For example, the Euler angles of the piezoelectric layer cut with 15°Y are (0°, 105°, 0°), the Euler angles of the piezoelectric layer cut with Z are (0°, 0°, 0°), the Euler angles of the piezoelectric layer cut with 128°Y are (0°, 38°, 0°), and the Euler angles of the piezoelectric layer cut with 32°Y45°X are (0°, 122°, 45°).

[0050] Furthermore, a conductive material film pattern is provided above the piezoelectric layer 10, and the conductive material film pattern includes a series arm resonator 21 and a parallel arm resonator 22 formed by a plurality of interdigital transducer electrodes, a signal input pad 15, a signal output pad 16, a ground pad (17, 18), and a plurality of conductive tracks (series arm 19, parallel arm 20). It should be noted that Figure 1 Not shown, the conductive material film pattern has a certain thickness in the z direction.

[0051] Figure 2 Figure 2 shows a schematic top view and cross-sectional view of an elastic wave resonator 200 provided in Example 1 of the present application. The elastic wave resonators used in the TX40 band elastic wave filter are divided into series-arm resonators and parallel-arm resonators. In recent years, elastic wave resonators 200 based on piezoelectric composite substrates composed of a piezoelectric layer 10 and a non-piezoelectric substrate 23 have garnered widespread attention due to their high Q performance and have been applied in numerous fields, including radar, communications, and navigation.

[0052] Specifically, elastic wave resonator 200 based on a piezoelectric composite substrate comprises a piezoelectric layer 10 and a conductive thin film pattern formed on a piezoelectric composite substrate, which is a non-piezoelectric substrate 23. Piezoelectric layer 10 is a thin single-crystalline layer of piezoelectric material with a thickness h. The piezoelectric material may be lithium niobate, lithium tantalate, gallium nitride, aluminum nitride, or zinc oxide.

[0053] Admittance: A physical quantity that describes the response of a circuit element to alternating current and voltage, usually represented by the symbol Y. For a circuit element, its admittance Y is equal to the ratio of its conductance G to its susceptance B, i.e., Y = G + jB, where j is an imaginary unit. In this embodiment, admittance (dB) can be calculated by the formula Y = 20 × log 10 |Y| is obtained.

[0054] The non-piezoelectric substrate 23 is a single-layer or multi-layer substrate made of a high-acoustic-velocity material, and is therefore also referred to as a high-acoustic-velocity component. The acoustic velocity of bulk waves propagating in the high-acoustic-velocity component is higher than the acoustic velocity of elastic waves propagating in the piezoelectric layer. This increases the acoustic velocity of the elastic waves in the piezoelectric layer and the device's frequency. Furthermore, the high-acoustic-velocity component effectively confines the elastic waves propagating in the piezoelectric layer, preventing them from leaking, thereby improving the device's Q factor.

[0055] Specifically, the non-piezoelectric substrate 23 is disposed below the piezoelectric layer 10 and includes, from top to bottom, a low-acoustic-velocity material layer 11, a capture material layer 13, and a support substrate 14. The low-acoustic-velocity material layer 11 is located below the piezoelectric layer 10, and the acoustic velocity of the bulk waves propagating in the low-acoustic-velocity material layer 11 is lower than the acoustic velocity of the bulk waves propagating in the piezoelectric layer 10. The capture material layer 13 is located below the low-acoustic-velocity material layer 11. The support substrate 14 is located below the capture material layer 13, and the acoustic velocity of the bulk waves propagating in the support substrate 14 is higher than the acoustic velocity of the bulk waves propagating in the piezoelectric layer 10.

[0056] Furthermore, the conductive material film pattern includes an interdigital transducer (IDT) electrode 2a, a reflector electrode 2b, an IDT bus bar 4a and a reflector bus bar 4b, and has a thickness of h m . The IDT electrode 2a includes a plurality of first electrode fingers and a plurality of second electrode fingers that are interlaced with each other, and a first bus bar and a second bus bar that are opposite to each other in the direction in which the first electrode fingers and the second electrode fingers extend. The distance λ between adjacent first (or second) electrode fingers is usually referred to as the "wavelength" of the IDT. The distance AP where the first and second electrode fingers overlap is usually referred to as the "aperture" of the IDT. The reflector electrode 2b includes a plurality of third electrode fingers and a plurality of fourth electrode fingers that are interlaced with each other, and a third bus bar and a fourth bus bar that are opposite to each other in the direction in which the third electrode fingers and the fourth electrode fingers extend.

[0057] Figure 3The insertion loss-frequency curve of the elastic wave filter 100 applied to the TX40 frequency band provided in Example 1 of the present application is shown. As can be seen from the curve, the elastic wave filter 100 has a center frequency of 2351 MHz, a 1 dB bandwidth of 94 MHz, and a minimum insertion loss of -0.38 dB.

[0058] Figure 4 A graph showing the standing wave ratio (SWR) versus frequency for elastic wave filter 100, provided in Example 1 of the present application and applied to the TX40 frequency band, shows that the SWR of elastic wave filter 100 within the passband is less than 2, indicating minimal fluctuations in the filter's passband and essentially no transverse mode response.

[0059] Transverse mode: It is the regular fluctuation between the resonant frequency and the antiresonant frequency of the resonator, usually caused by the diffraction of elastic waves during propagation.

[0060] Figure 5 Schematics showing three common weighting schemes for elastic wave resonators in the industry. However, while some weighting schemes can suppress the transverse modes of an elastic wave resonator, they can also reduce the resonator's Q factor and increase losses. Furthermore, resonator weighting doesn't necessarily suppress transverse modes completely and may even increase the difficulty of device fabrication.

[0061] Figure 6 FIG1 shows a schematic diagram of an unweighted elastic wave resonator. In this embodiment, all resonators adopt the interdigital transducer form of this type.

[0062] Figure 7 The layout of the elastic wave filter 100 applied to the TX40 frequency band is shown. By observing the layout, we can see that Figure 1 Although not shown in the figure, elastic wave filter 100 further includes a capacitor portion.

[0063] Figure 8 The insertion loss vs. frequency curve of an elastic wave filter applied to the TX40 band after resonator weighting is shown. The curve shows that the elastic wave filter has a center frequency of 2349 MHz, a 1 dB bandwidth of 61 MHz, and a minimum insertion loss of -0.46 dB.

[0064] Figure 9 A comparison chart of the standing wave ratio (SWR) of an elastic wave filter applied to the TX40 frequency band after resonator weighting and elastic wave filter 100 is shown. Curve 70 shows the SWR-frequency curve of the elastic wave filter applied to the TX40 frequency band after resonator weighting, and curve 80 shows the SWR-frequency curve of the elastic wave filter 100 applied to the TX40 frequency band.

[0065] from Figure 8and Figure 9 It can be seen that after the resonator is weighted, the bandwidth of the filter is significantly reduced, the loss is significantly increased, and the fluctuation within the passband is also increased, which shows that the weighting has worsened the transverse mode of the resonator and caused the in-band fluctuation of the filter to increase.

[0066] Figure 10 The figure shows the admittance / conductance-frequency curves of the elastic wave resonator 200 with different lithium tantalate thicknesses provided in the first embodiment of the present application. The structural parameters of the elastic wave resonator 200 are the same as those of the resonator in the elastic wave filter 100. As can be seen from the figure, after the lithium tantalate thickness changes to (30 / 7)h, the transverse mode between the resonant frequency and the antiresonant frequency of the resonator intensifies. Therefore, when the lithium tantalate thickness is (30 / 7)h, the transverse mode between the resonant frequency and the antiresonant frequency of the resonator intensifies. m When , the resonator structure just achieves the best suppression effect on the lateral mode.

[0067] Figure 11 The figure shows the admittance / conductance-frequency curves of the elastic wave resonator 200 with different silicon dioxide thicknesses provided in Example 1 of the present application. The structural parameters of the elastic wave resonator 200 are the same as those of the resonator in the elastic wave filter 100. As can be seen from the figure, after the silicon dioxide thickness changes, the transverse mode between the resonant frequency and the antiresonant frequency of the resonator is intensified. Therefore, when the silicon dioxide thickness is (25 / 7)h m When , the resonator structure just achieves the best suppression effect on the lateral mode.

[0068] It can be seen from this that the lateral mode suppression of the elastic wave resonator does not necessarily need to be achieved through weighting. The suppression effect can also be achieved by optimizing the thickness of different layers. Moreover, this method will not increase the difficulty of device preparation or reduce the Q value of the device, and will not damage the performance of the device.

[0069] In this embodiment, when the first conductive material film pattern is realized to have a thickness of h m The second conductive material film pattern is realized with a thickness of 20h m Aluminum; the piezoelectric layer 10 is realized as a thickness of 4h m ~(32 / 7)h m 42YX-lithium tantalate, the Euler angle is (0°, 132°, 0°); the low acoustic velocity material layer 11 is realized with a thickness of (23 / 7)h m ~(27 / 7)h m silicon dioxide; the capture material layer 13 is realized as thick (50 / 7)h m When the supporting substrate 14 is realized as 250μm silicon, the lateral mode of the resonator of this structure is weak and does not deteriorate the in-band fluctuation of the elastic wave filter.

[0070] In addition, the conductive material film pattern used in this embodiment is aluminum. If copper is used as the conductive material film pattern, the thickness of copper needs to be converted accordingly. Copper as the conductive material film pattern is also within the protection scope of this patent.

[0071] Package Structure: To adapt the elastic wave filter 100 for the TX40 frequency band to RF front-end architectures, it also features a package structure. In the industry, three common elastic wave filter packaging structures exist: surface mount packaging, chip-scale packaging, and wafer-level packaging.

[0072] Surface mount packaging: In a surface mount package, the filter chip is typically wire-bonded to a metal leadframe and then overmolded with epoxy. The overmolding compound is a mixture of solid epoxy resin, hardener, filler, and additives that is heated and polymerized.

[0073] Chip-level packaging: In the chip-level packaging structure, the center pin form of the filter chip effectively shortens the signal transmission distance, and its attenuation is reduced accordingly. The chip's anti-interference and anti-noise capabilities can also be greatly improved.

[0074] Wafer-level packaging: Among various packaging formats, wafer-level packaging offers the smallest area, thickness, and volume. In wafer-level packaging, filter chip protection is typically achieved through a cover and multi-part packaging process. The cover is passive, lacks an electrical path, and must allow for through-connections to the chip pads.

[0075] In this embodiment, the elastic wave filter 100 adopts a chip-scale packaging structure. Figure 12 FIG. 1 is a cross-sectional view of an elastic wave filter 100 with a chip-scale packaging structure according to a first embodiment of the present application, wherein the elastic wave filter 100 is within the dotted-line frame.

[0076] In order to more clearly show the morphology of the elastic wave filter after packaging, Figure 13 FIG2 shows a three-dimensional schematic diagram of an elastic wave filter 100 with a chip-scale package structure according to a first embodiment of the present application. The elastic wave filter 100 is fixed inside the package structure by flip-chip mounting.

[0077] Example 2:

[0078] Figure 14 The following is a three-dimensional schematic diagram of an elastic wave filter 300 applied to the TX40 frequency band provided in the second embodiment of the present application. Figure 13 The direction parallel to the x-axis in the coordinate system is the direction of elastic wave propagation, and the definition is Figure 13 The direction parallel to the y-axis in the coordinate system is the extension direction of the electrode finger, and it is defined as Figure 13The direction parallel to the z-axis in the coordinate system is the height direction of the elastic wave filter 300 .

[0079] Specifically, the non-piezoelectric substrate 23 is disposed below the piezoelectric layer 10 and includes, from top to bottom, a low-acoustic-velocity material layer 11 and a supporting substrate 14. The low-acoustic-velocity material layer 11 is located below the piezoelectric layer 10, and the acoustic velocity of the bulk waves propagating in the low-acoustic-velocity material layer 11 is lower than the acoustic velocity of the bulk waves propagating in the piezoelectric layer 10. The supporting substrate 14 is located below the low-acoustic-velocity material layer 11, and the acoustic velocity of the bulk waves propagating in the supporting substrate 14 is higher than the acoustic velocity of the bulk waves propagating in the piezoelectric layer 10.

[0080] Furthermore, the conductive material film pattern includes a first conductive material film pattern and a second conductive material film pattern (not shown in the figure), the second conductive material film pattern (not shown in the figure) partially overlaps with the first conductive material film pattern, and the second conductive material film pattern (not shown in the figure) has a pattern and film thickness different from those of the first conductive material film pattern.

[0081] In detail, the first conductive material film pattern is realized with a thickness of h m The second conductive material film pattern is realized with a thickness of 20h m Aluminum; the piezoelectric layer 10 is realized as a thickness of 4h m ~(32 / 7)h m 42YX-lithium tantalate, the Euler angle is (0°, 132°, 0°); the low acoustic velocity material layer 11 is realized with a thickness of (23 / 7)h m ~(27 / 7)h m The support substrate 14 is realized as 250 μm silicon.

[0082] Furthermore, a conductive material film pattern is provided above the piezoelectric layer 10, and the conductive material film pattern includes a series arm resonator 21 and a parallel arm resonator 22 formed by a plurality of interdigital transducer electrodes, a signal input pad 15, a signal output pad 16, a ground pad (17, 18), and a plurality of conductive tracks (series arm 19, parallel arm 20). It should be noted that Figure 1 Not shown, the conductive material film pattern has a certain thickness in the z direction.

[0083] Figure 15 The insertion loss-frequency curve of the elastic wave filter 300 applied to the TX40 frequency band provided in the second embodiment of the present application is shown. As can be seen from the curve, the elastic wave filter 300 has a center frequency of 2351 MHz, a 1 dB bandwidth of 89 MHz, and a minimum insertion loss of -0.38 dB.

[0084] For the same reasons as those in the first embodiment, the elastic wave filter 300 has a small passband fluctuation and substantially no transverse mode response.

[0085] In summary, the present invention sets a lithium tantalate layer with Euler angles of (0±10°, 132°±10°, 0°±10°) on a non-piezoelectric substrate, sets a conductive material film pattern on the lithium tantalate layer, and sets the thickness of the interdigital transducer electrode to h. m Under the premise that the thickness of the lithium tantalate layer h is 4h m ≤h≤(32 / 7)h m , the IDT electrodes do not have any weighting form. In this case, the elastic wave filter and RF front-end structure provided by the present application have better transverse mode suppression and simpler manufacturing process.

[0086] In the embodiments disclosed herein, terms such as "installed," "connected," "connected," and "fixed" should be interpreted broadly. For example, "connected" may refer to a fixed connection, a detachable connection, or an integral connection; and "connected" may refer to a direct connection or an indirect connection via an intermediary. Those skilled in the art will understand the specific meanings of the above terms in the embodiments disclosed herein based on specific circumstances.

[0087] The above is only a preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. An elastic wave filter, characterized in that: include: non-piezoelectric substrates; A lithium tantalate layer, which is disposed on the non-piezoelectric substrate, wherein the Euler angle of the lithium tantalate layer is (0±10°, 132°±10°, 0°±10°); and a conductive material thin film pattern disposed on the lithium tantalate layer, the conductive material thin film pattern being formed with a plurality of interdigital transducer electrodes, a plurality of reflector electrodes, a plurality of conductive traces and pad electrodes for achieving electrical connections between the plurality of interdigital transducer electrodes; The IDT electrode comprises a plurality of first electrode fingers and a plurality of second electrode fingers interlaced with each other, and a first bus bar and a second bus bar facing each other in the extending direction of the first electrode fingers and the second electrode fingers; the pad electrode comprises an input terminal, an output terminal and at least one ground terminal; when the thickness of the IDT electrode is set to h m Under the premise that the thickness h of the lithium tantalate layer is 4h m ≤h≤(32 / 7)h m ; The IDT electrodes do not have any weighting form; The non-piezoelectric substrate includes a low acoustic velocity material layer directly disposed below the lithium tantalate layer, and the thickness of the interdigital transducer electrode is set to h m Under the premise that the thickness h of the low sound velocity material layer is (23 / 7)h m ≤h≤(27 / 7)h m .

2. The elastic wave filter according to claim 1, wherein The elastic wave filter is applicable to a frequency band ranging from 2300 MHz to 2400 MHz.

3. The elastic wave filter according to claim 1, wherein The elastic wave filter has a chip-level packaging structure.

4. The elastic wave filter according to claim 1, wherein The non-piezoelectric substrate comprises: a capture material layer disposed directly below the low acoustic velocity material layer, and a support substrate disposed directly below the capture material layer; or A support substrate is disposed directly below the low acoustic velocity material layer.

5. The elastic wave filter according to claim 4, wherein The acoustic velocity of the bulk wave propagating in the low-acoustic-velocity material layer is lower than that of the bulk wave propagating in the lithium tantalate layer; the acoustic velocity of the bulk wave propagating in the supporting substrate is higher than that of the bulk wave propagating in the lithium tantalate layer.

6. The elastic wave filter according to claim 4, wherein The low acoustic velocity material layer is composed of one or more combinations of relatively low acoustic velocity materials such as silicon dioxide, glass, silicon oxynitride, tantalum oxide, or silicon dioxide with a compound mainly composed of fluorine, carbon, or boron.

7. The elastic wave filter according to claim 4, wherein The capture material layer is formed by a combination of one or more materials selected from amorphous silicon, polycrystalline silicon, amorphous germanium, and polycrystalline germanium; when the thickness of the interdigital transducer electrode is set to h m Under the premise that the thickness of the capture material layer is (50 / 7)h m .

8. The elastic wave filter according to claim 1, wherein The conductive material film pattern includes a first conductive material film pattern and a second conductive material film pattern, the second conductive material film pattern partially overlaps with the first conductive material film pattern, and the second conductive material film pattern has a different pattern and film thickness from the first conductive material film pattern.

9. The elastic wave filter according to claim 1, wherein The reflector electrodes are arranged on both sides of the IDT electrode along the propagation direction of the elastic wave.

10. A radio frequency front-end structure, comprising the elastic wave filter according to any one of claims 1 to 9.

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