Surface acoustic wave filter and electronic device

Abstract

The utility model provides a surface acoustic wave filter and electronic equipment. The surface acoustic wave filter comprises a substrate; the piezoelectric layer is located on the surface of the substrate, and the substrate and the piezoelectric layer are both made of high-sound-velocity materials; the series arm resonator is located on the partial surface, away from the substrate, of the piezoelectric layer, and the series arm resonator comprises a first IDT electrode; and the parallel arm resonator is located on the partial surface, far away from the substrate, of the piezoelectric layer, and the parallel arm resonator comprises a second IDT electrode. The IPD filter solves the problems that in the prior art, an IPD filter is large in passband insertion loss at a high frequency band and poor in rectangularity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of filters, in particular to a surface acoustic wave filter and an electronic device. BACKGROUND

[0002] With the development of communication technology from 2G to 5G, the number of communication frequency bands gradually increases (from 4 frequency bands of 2G to more than 50 frequency bands of 5G). In order to improve the compatibility of smart phones to different communication systems, the amount of filters required by 5G smart phones will increase significantly, which will promote the large-scale growth of the filter market. With the increasing demand for performance and stability of 5G communication systems, such as N77, N78, N79, 5G Wifi and other frequency bands, the demand for SAW (Surface Acoustic Wave) filter devices to make ultra-high frequency filters is also increasing day by day.

[0003] SAW has been widely used in <3GHz radio frequency filters, but for high frequency bands (>3GHz), most of the current applications are implemented in IPD (Integrated Passive Device). IPD is limited by poor rectangularity and large size, and cannot be applied to high-end devices. As a common filter method applied to high frequency bands, IPD usually has the characteristics of large insertion loss and poor rectangularity in the passband. CONTENT OF THE UTILITY MODEL

[0004] The main purpose of the present application is to provide a surface acoustic wave filter and an electronic device to solve the problem of large insertion loss and poor rectangularity of IPD filter in high frequency band in the prior art.

[0005] In order to achieve the above purpose, according to one aspect of the present application, a surface acoustic wave filter is provided, comprising: a substrate; a piezoelectric layer located on the surface of the substrate, the material of the substrate and the piezoelectric layer is high acoustic velocity material; a series arm resonator located on the part of the surface of the piezoelectric layer away from the substrate, the series arm resonator comprises a first IDT (Interdigital Transducer) electrode; a parallel arm resonator located on the part of the surface of the piezoelectric layer away from the substrate, the parallel arm resonator comprises a second IDT electrode.

[0006] Optionally, the material of the substrate is silicon carbide, and the material of the piezoelectric layer is lithium niobate.

[0007] Optionally, the thickness of the second IDT electrode is greater than the thickness of the first IDT electrode.

[0008] Optionally, the first IDT electrode has a first tilt angle, the second IDT electrode has a second tilt angle, and neither the first tilt angle nor the second tilt angle is 0.

[0009] Optionally, the first IDT electrode has a first rotation angle, the second IDT electrode has a second rotation angle, and neither the first rotation angle nor the second rotation angle is 0.

[0010] Optionally, the series arm resonator comprises the first IDT electrode and a first reflective grating array arranged at two ends of the first IDT electrode.

[0011] Optionally, the parallel arm resonator comprises the second IDT electrode and a second reflective grating array arranged at two ends of the second IDT electrode.

[0012] Optionally, the substrate has a thickness of 200-700 nm.

[0013] Optionally, the piezoelectric layer has a thickness of 100-500 nm.

[0014] According to another aspect of the present application, an electronic device is provided, comprising any of the surface acoustic wave filters.

[0015] According to the technical solution of the present application, the surface acoustic wave filter comprises a substrate, a piezoelectric layer, a series arm resonator and a parallel arm resonator. The piezoelectric layer is located on a surface of the substrate, the series arm resonator and the parallel arm resonator are both located on a part of the surface of the piezoelectric layer away from the substrate, the series arm resonator comprises a first IDT electrode, the parallel arm resonator comprises a second IDT electrode, and the materials of the substrate and the piezoelectric layer are both high acoustic velocity materials. Compared with the IPD filter in the prior art which has a large passband insertion loss and poor rectangularity at a high frequency band, the materials of the substrate and the piezoelectric layer in the present application are both high acoustic velocity materials. A high acoustic velocity means that the SAW device can have a shorter wavelength at the same frequency, which is conducive to realizing a smaller device size, and a high acoustic velocity also helps to reduce the interference of body waves. BRIEF DESCRIPTION OF DRAWINGS

[0016] The drawings accompanying the specification of the present application form a part thereof, serve to provide further understanding of the present application, and together with the specification explain the illustrative embodiments of the present application, and do not limit the present application. In the drawings:

[0017] Figure 1 A cross-sectional schematic view of a surface acoustic wave filter according to an embodiment of the present application is shown;

[0018] Figure 2 A cross-sectional schematic view of a surface acoustic wave filter according to an embodiment of the present application is shown; Figure 1A top view of a corresponding surface acoustic wave filter is shown;

[0019] Figure 3 A wafer diagram is shown according to an embodiment of the present application;

[0020] Figure 4 A diagram of an electrode rotation angle is shown according to an embodiment of the present application;

[0021] Figure 5 A diagram of an electrode tilt angle is shown according to an embodiment of the present application;

[0022] Figure 6 A topological structure diagram of a surface acoustic wave filter is shown according to an embodiment of the present application;

[0023] Figure 7 A performance comparison diagram of a surface acoustic wave filter according to an embodiment of the present application and a filter with an IPD design in the prior art is shown.

[0024] Wherein, the above figures include the following reference signs:

[0025] 10, substrate; 11, piezoelectric layer; 12, series arm resonator; 13, parallel arm resonator; 121, first IDT electrode; 122, first reflector grating array; 131, second IDT electrode; 132, second reflector grating array. DETAILED DESCRIPTION

[0026] It should be noted that the following detailed description is merely exemplary in nature and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0027] It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Additionally, it is to be understood that the terms "comprising", "including", "having" and / or "containing" when used herein, specify the presence of stated features, steps, operations, devices, components and / or combinations thereof, but do not preclude the presence or addition of one or more other features, steps, operations, devices, components and / or combinations thereof.

[0028] It will be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, it can be directly on the other element or intervening elements can also be present. In addition, it will be understood that when an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements can also be present.

[0029] As introduced in the background, the IPD filter in the prior art has large passband insertion loss and poor rectangularity in the high frequency band. To solve the above problems, embodiments of the present application provide a surface acoustic wave filter and an electronic device.

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application.

[0031] The embodiments of the present application provide a surface acoustic wave filter, as shown in the drawings, comprising: Figure 1

[0032] a substrate 10;

[0033] a piezoelectric layer 11 located on a surface of the substrate 10, and the substrate 10 and the piezoelectric layer 11 are both made of high acoustic velocity material;

[0034] a series arm resonator 12 located on a part of the surface of the piezoelectric layer 11 away from the substrate 10, and the series arm resonator 12 comprises a first IDT electrode (not shown);

[0035] a parallel arm resonator 13 located on a part of the surface of the piezoelectric layer 11 away from the substrate 10, and the parallel arm resonator 13 comprises a second IDT electrode (not shown).

[0036] According to the above embodiments, the surface acoustic wave filter comprises a substrate, a piezoelectric layer, a series arm resonator and a parallel arm resonator, wherein the piezoelectric layer is located on the surface of the substrate, the series arm resonator and the parallel arm resonator are both located on a part of the surface of the piezoelectric layer away from the substrate, the series arm resonator comprises a first IDT electrode, and the parallel arm resonator comprises a second IDT electrode, and the substrate and the piezoelectric layer are both made of high acoustic velocity material. Compared with the IPD filter in the prior art which has large passband insertion loss and poor rectangularity in the high frequency band, the substrate and the piezoelectric layer in the present application are both made of high acoustic velocity material, and high acoustic velocity means that the SAW device can have shorter wavelength at the same frequency, which is beneficial to realize smaller device size, and high acoustic velocity also helps to reduce the interference of bulk waves.

[0037] ​In other embodiments, the material of the substrate is silicon carbide, and the material of the piezoelectric layer is lithium niobate. In this embodiment, the material of the substrate is silicon carbide, and the material of the piezoelectric layer is lithium niobate, which is a material with a high electromechanical coupling coefficient, meaning that it can more effectively convert electrical energy into acoustic energy. In a surface acoustic wave (SAW) device, a high electromechanical coupling coefficient can improve the conversion efficiency of the filter and reduce energy loss during signal transmission, thereby achieving low insertion loss. Silicon carbide is a material with very high acoustic velocity, which means that at the same frequency, the SAW device can have a shorter wavelength, which is beneficial for achieving a smaller device size. In addition, high acoustic velocity also helps to reduce the interference of bulk waves, and the low loss characteristics of SIC also help to reduce energy loss during signal transmission.

[0038] Specifically, the surface acoustic wave filter of the present application can realize the application of SAW in high frequency bands such as N77 and N78.

[0039] Specifically, SIC material has high acoustic velocity, and LN (lithium niobate) has a large electromechanical coupling coefficient, so that a large bandwidth filtering performance can be achieved in high frequency bands.

[0040] In an optional solution, as shown in Figure 2 , the thickness of the second IDT electrode 131 is greater than the thickness of the first IDT electrode 121. In this embodiment, a double film thickness technology is adopted, i.e., the thickness of the second IDT electrode is greater than the thickness of the first IDT electrode. By adjusting the electrode thickness, the distance between fs (resonance point) and fu (bulk wave radiation point) can be optimized, thereby achieving lower insertion loss (signal loss) and wider bandwidth in high frequency bands.

[0041] Specifically, the parallel arm and the series arm respectively undertake the responsibilities of out-of-band suppression and in-band transmission in the SAW filter. The thickness of the second IDT electrode is greater than the thickness of the first IDT electrode, which can further improve its suppression ability at out-of-band frequencies while maintaining the low insertion loss characteristics of the series arm, thereby further optimizing the frequency response of the entire filter and further realizing wider bandwidth and lower in-band insertion loss.

[0042] Specifically, in high frequency bands, due to the high bandwidth requirement, bulk waves will be radiated into the passband, resulting in a large loss on the right side of the passband. However, the electrode film thickness is increased, and the distance between fs and fu is increased, which can make the bulk wave radiate to the out-of-band, thereby not affecting the loss on the right side of the passband.

[0043] Specifically, as shown in Figure 1 and Figure 2 , the thickness is the length in the predetermined direction.

[0044] According to some example embodiments of the present application, the first IDT electrode has a first tilt angle, the second IDT electrode has a second tilt angle, and neither the first tilt angle nor the second tilt angle is 0. In this embodiment, the non-zero first tilt angle and the non-zero second tilt angle help to optimize the propagation mode of the surface acoustic wave, reduce the interference of the transverse mode, suppress the unwanted transverse acoustic wave propagation, reduce the wave leakage and reflection, and thus further improve the rectangularity of the filter.

[0045] Specifically, the tilt angle of the resonator is the tilt angle of the IDT electrode in the resonator.

[0046] Specifically, the electrode tilt can effectively suppress the transverse mode.

[0047] In other embodiments, the first IDT electrode has a first rotation angle, the second IDT electrode has a second rotation angle, and neither the first rotation angle nor the second rotation angle is 0. In this embodiment, by setting the non-zero first rotation angle and the non-zero second rotation angle, the vibration mode of the resonator can be adjusted, the Rayleigh mode can be effectively suppressed, and the rectangularity of the filter, i.e., the signal flatness in the passband and the out-of-band suppression capability, can be further optimized.

[0048] Specifically, the electrode rotation can effectively suppress the Rayleigh mode.

[0049] Specifically, in the wafer preparation process, the wafer direction needs to be determined, so a fixed notch is generally left in a certain direction, such as Figure 3 The dashed box in FIG. 1 shows a positive direction for convenience of illustration. Figure 4 FIG. 2 shows the definition of the electrode rotation angle. When the direction of the IDT electrode fingers in the resonator is consistent with the positive direction, it represents that the resonator is 0° rotation at this time. When the direction of the IDT electrode fingers in the resonator is rotated clockwise along the positive direction, it represents that the resonator is positive rotation at this time, and the rotated angle is the positive rotation angle. When the direction of the IDT electrode fingers in the resonator is rotated counterclockwise along the positive direction, it represents that the resonator is negative rotation at this time, and the rotated angle is the negative rotation angle. Figure 5 FIG. 3 shows the definition of the electrode tilt angle. The tilt angle defines that the direction of the IDT electrode fingers in the resonator always remains consistent with the positive direction. When the direction of the IDT electrode fingers in the resonator is consistent with the positive direction, it represents that the resonator is 0° tilt at this time. When the direction of the entire resonator is tilted clockwise along the positive direction (the left side of the reflector array is high and the right side is low), it represents that the resonator is positive tilt at this time, and the tilted angle is the positive tilt angle. When the direction of the entire resonator is tilted counterclockwise along the positive direction (the left side of the reflector array is low and the right side is high), it represents that the resonator is negative tilt at this time, and the tilted angle is the negative tilt angle.

[0050] Specifically, Figure 4 and Figure 5the resonator in Figure 2 the series arm resonator or the parallel arm resonator in Figure 4 and Figure 5 the wafer in Figure 3 the wafer in

[0051] According to some other exemplary embodiments of the present application, as Figure 2 shown in FIG. 2, the series arm resonator 12 includes the first IDT electrode 121 and the first reflector grating array 122 arranged in parallel. In this embodiment, the first reflector grating array is arranged to help reflect the surface acoustic wave and reduce the loss of the wave, thereby enhancing the signal processing capability of the filter.

[0052] In other embodiments, as Figure 2 shown in FIG. 3, the parallel arm resonator 13 includes the second IDT electrode 131 and the second reflector grating array 132 arranged in parallel. In this embodiment, the second reflector grating array is arranged to help further reflect the surface acoustic wave and further reduce the loss of the wave, thereby further enhancing the signal processing capability of the filter.

[0053] Specifically, Figure 1 is a cross-sectional structure diagram of the SAW filter obtained by longitudinally cutting along the dashed line L in Figure 2 Figure 2 the piezoelectric layer 11 in Figure 1 the piezoelectric layer 11 in

[0054] In yet some optional solutions of the present application, the thickness of the substrate is 200 nm to 700 nm.

[0055] In still some optional solutions of the present application, the thickness of the piezoelectric layer is 100 nm to 500 nm.

[0056] Figure 6 A topological structure diagram of a SAW filter according to an embodiment of the present application is shown. As Figure 6 shown in FIG. 4, the series arm resonators 12 are connected in series, the first end of each series arm resonator 12 is electrically connected to the first end of the corresponding parallel arm resonator 13, the second end of each parallel arm resonator 13 is grounded, the first end of the series arm resonator 12 at the front is used to receive a signal, and the second end of the series arm resonator 12 at the back is used to send a signal. Of course, the topological structure of the SAW filter is not limited to the structure shown in Figure 6 FIG. 4.

[0057] Figure 7 A performance comparison diagram of a SAW filter according to an embodiment of the present application and a filter with an IPD design in the prior art is shown.​Figure 7 In the figure, the solid line represents the surface acoustic wave filter of the present application, and the dashed line represents the filter designed by the IPD in the prior art. Figure 7 (a) represents the admittance curve diagram of the whole wave band, Figure 7 (b) represents the admittance curve diagram of the partial wave band corresponding to Figure 7 (a), i.e. the pass band wave band; Figure 7 (a) and Figure 7 In (a) and (b), the abscissa freq represents frequency (Frequency) in GHz, and the ordinate represents admittance gain in decibel (dB). Figure 7 (d) represents the Smith chart of the input end of the filter, Figure 7 (c) represents the Smith chart of the output end of the filter. From Figure 7 (a) and Figure 7 It can be seen from (a) and (b) that the surface acoustic wave filter of the present application (i.e. the solid line) has smaller pass band loss and better out-of-band rejection than the filter designed by the IPD in the prior art (i.e. the dashed line). From Figure 7 (c) and Figure 7 It can be seen from (c) and (d) that the surface acoustic wave filter of the present application (i.e. the solid line) is more convergent at the center and has lower filter impedance than the filter designed by the IPD in the prior art (i.e. the dashed line).

[0058] In summary, the surface acoustic wave filter combined with the high acoustic velocity substrate SIC, the high acoustic velocity piezoelectric layer LN+ double film thickness (i.e. the thickness of the second IDT electrode is greater than the thickness of the first IDT electrode), the tilted electrode and the rotating electrode can be applied to the high frequency band.

[0059] The embodiments of the present application also provide an electronic device comprising any of the above-mentioned surface acoustic wave filters.

[0060] Specifically, the electronic device includes but is not limited to a smart phone, a tablet computer and a sensor.

[0061] From the above description, it can be seen that the above-mentioned embodiments of the present application achieve the following technical effects:

[0062] In the surface acoustic wave filter of the present application, the surface acoustic wave filter comprises a substrate, a piezoelectric layer, a series arm resonator and a parallel arm resonator, wherein the piezoelectric layer is located on the surface of the substrate, the series arm resonator and the parallel arm resonator are both located on the part of the surface of the piezoelectric layer away from the substrate, the series arm resonator comprises a first IDT electrode, the parallel arm resonator comprises a second IDT electrode, and the materials of the substrate and the piezoelectric layer are both high acoustic velocity materials. Compared with the IPD filter in the prior art, which has a large passband insertion loss and poor rectangularity in the high frequency band, the materials of the substrate and the piezoelectric layer in the present application are both high acoustic velocity materials, and high acoustic velocity means that the SAW device can have a shorter wavelength at the same frequency, which is conducive to realizing a smaller device size, and high acoustic velocity also helps to reduce the interference of body waves.

[0063] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Various modifications and changes can be made by those skilled in the art based on the spirit and principles of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A surface acoustic wave filter, characterized by, The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter.

2. The surface acoustic wave filter according to claim 1, characterized by, The application relates to a surface acoustic wave filter.

3. The surface acoustic wave filter according to claim 1, characterized by, The application relates to a surface acoustic wave filter.

4. The surface acoustic wave filter according to claim 1, characterized by, The application relates to a surface acoustic wave filter.

5. The surface acoustic wave filter according to claim 1, wherein The application relates to a surface acoustic wave filter.

6. The surface acoustic wave filter according to claim 1, wherein The application relates to a surface acoustic wave filter.

7. The surface acoustic wave filter according to claim 1, wherein The application relates to a surface acoustic wave filter.

8. The surface acoustic wave filter according to claim 1, characterized by, The application relates to a surface acoustic wave filter.

9. The surface acoustic wave filter according to claim 8, characterized by, The application relates to a surface acoustic wave filter.

10. An electronic device, comprising: The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to

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