Surface acoustic wave resonator, filter and electronic equipment

Abstract

The invention discloses a surface acoustic wave resonator, a filter and electronic equipment, and relates to the technical field of radio frequency, on the basis that at least one of two oppositely arranged bus bars is inclined relative to a main acoustic mode propagation direction to suppress a transverse spurious mode, a silicon dioxide laminated layer is arranged between a substrate and a piezoelectric layer, and the piezoelectric layer is arranged between the substrate and the piezoelectric layer; the silicon dioxide laminated layer comprises at least two silicon dioxide layers, and any two adjacent silicon dioxide layers have different densities, so that any two adjacent silicon dioxide layers with different densities form a sound velocity gradient by utilizing different sound velocities of the silicon dioxide layers with different densities, energy is better limited in the piezoelectric layer, the Q value of the resonator is improved, and the dielectric constant of the resonator is improved. The transverse stray mode of the surface acoustic wave resonator is effectively suppressed, the Q value of the resonator is improved, and the insertion loss of a communication system is reduced.

Description

Technical Field

[0001] The present application relates to the field of radio frequency technology, and in particular to a surface acoustic wave resonator, a filter and an electronic device. Background Art

[0002] Surface acoustic wave (SAW) resonator is a device widely used in the radio frequency field. It combines low insertion loss and good suppression performance with a small size. It mainly uses the piezoelectric effect to convert electrical energy and mechanical energy into each other, which is used to combine and realize the gating characteristics of signal transmission.

[0003] There are many types of SAW resonators, such as SAW resonators with dummy fingers in IDT, SAW resonators with reflection gratings on both sides of IDT, temperature-compensation SAW (TC-SAW) resonators, and thin-film SAW (TC-SAW) resonators. For any type of SAW resonator, the laterally propagating sound waves will cause the resonator to have a lateral resonant mode, that is, the clutter that appears in and near the passband. This clutter will increase the device loss, cause the Q value to fluctuate greatly, and reduce the performance of the resonator and filter. In addition, the Q value of the resonator is directly related to the insertion loss of the filter. In the RF link, it is usually required that the insertion loss of each component is as small as possible to ensure that the signal has sufficient strength and quality, thereby ensuring the reliability and stability of the communication system.

[0004] Therefore, how to effectively suppress the lateral spurious modes of the surface acoustic wave resonator while improving the Q value of the resonator to reduce the insertion loss of the communication system is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0005] To solve the above technical problems, the embodiments of the present application provide a surface acoustic wave resonator, a filter and an electronic device, so as to effectively suppress the lateral spurious mode of the surface acoustic wave resonator, improve the Q value of the resonator and reduce the insertion loss of the communication system.

[0006] To achieve the above objectives, the present application provides the following technical solutions:

[0007] A surface acoustic wave resonator, comprising:

[0008] substrate;

[0009] A silicon dioxide stack located on one side of the substrate, the silicon dioxide stack comprising at least two silicon dioxide layers, and any two adjacent silicon dioxide layers have different densities;

[0010] a piezoelectric layer located on a side of the silicon dioxide stack facing away from the substrate;

[0011] an interdigital transducer located on a side of the piezoelectric layer facing away from the substrate;

[0012] The IDT comprises a first bus bar and a second bus bar which are arranged opposite to each other along a first direction, a first electrode finger connected to the first bus bar and a second electrode finger connected to the second bus bar are arranged between the first bus bar and the second bus bar, the first electrode finger and the second electrode finger extend along the first direction and are alternately arranged along a second direction, the first direction and the second direction are parallel to the plane where the substrate is located, and the first direction and the second direction are perpendicular;

[0013] An extending direction of at least one of the first bus bar and the second bus bar intersects with the second direction.

[0014] Optionally, in the silicon dioxide stack, the density of each silicon dioxide layer gradually decreases or increases along a direction away from the substrate and close to the piezoelectric layer.

[0015] Optionally, the silicon dioxide stack includes a first silicon dioxide layer and a second silicon dioxide layer, the second silicon dioxide layer is located on a side of the first silicon dioxide layer away from the substrate, and the density of the first silicon dioxide layer is greater than that of the second silicon dioxide layer.

[0016] Optionally, a ratio RA of the thickness of the first silicon dioxide layer in a direction perpendicular to the plane where the substrate is located to the thickness of the silicon dioxide stack in a direction perpendicular to the plane where the substrate is located satisfies: 0<RA≤75%.

[0017] Optionally, the first silicon dioxide layer is prepared by a chemical vapor deposition process or a sputtering process;

[0018] The second silicon dioxide layer is prepared by a physical vapor deposition process.

[0019] Optionally, the surface acoustic wave resonator further includes:

[0020] The high acoustic velocity layer is located between the silicon dioxide stack and the piezoelectric layer, and the acoustic velocity of the high acoustic velocity layer is greater than the acoustic velocity of each silicon dioxide layer in the silicon dioxide stack.

[0021] Optionally, the material of the high acoustic velocity layer includes at least one of silicon nitride and aluminum nitride.

[0022] A filter comprises the above-mentioned surface acoustic wave resonator.

[0023] An electronic device comprises the above filter.

[0024] Compared with the prior art, the above technical solution has the following advantages:

[0025] The surface acoustic wave resonator provided by the embodiment of the present application includes a substrate, a piezoelectric layer located on one side of the substrate, and an interdigital transducer located on the side of the piezoelectric layer away from the substrate. The interdigital transducer includes a first bus bar and a second bus bar arranged opposite to each other along a first direction. A first electrode finger connected to the first bus bar and a second electrode finger connected to the second bus bar are arranged between the first bus bar and the second bus bar. The first electrode finger and the second electrode finger extend along the first direction and are alternately arranged along the second direction. The first direction and the second direction are parallel to the plane where the substrate is located, and the first direction and the second direction are perpendicular. By setting the extension direction of at least one of the first bus bar and the second bus bar to intersect with the second direction, that is, at least one of the first bus bar and the second bus bar is inclined relative to the second direction, the lateral stray mode can be effectively suppressed; and the larger the inclination angle of the first bus bar and / or the second bus bar relative to the second direction, the better the suppression effect of the lateral stray mode.

[0026] Further consideration is given that when the optimal lateral mode suppression effect is achieved by tilting the busbar, the optimal tilt angle of the busbar is usually too large, which will lead to a decrease in the Q value of the resonator. Based on this, a silicon dioxide stack is arranged between the substrate and the piezoelectric layer. The silicon dioxide stack includes at least two silicon dioxide layers, and the densities of any two adjacent silicon dioxide layers are different. The different sound velocities of the silicon dioxide layers with different densities are utilized to form a sound velocity gradient between any two adjacent silicon dioxide layers with different densities, which better confines the energy in the piezoelectric layer, improves the Q value of the resonator, and has no effect on the lateral mode. Ultimately, the Q value of the resonator is improved while the lateral stray mode of the surface acoustic wave resonator is effectively suppressed, thereby reducing the insertion loss of the communication system.

[0027] Further optionally, a high sound velocity layer is added between the silicon dioxide stack and the piezoelectric layer, and the sound velocity of the high sound velocity layer is greater than the sound velocity of each silicon dioxide layer in the silicon dioxide stack. In this way, not only there is a sound velocity gradient in the silicon dioxide stack, but the silicon dioxide stack and the high sound velocity layer also form a sound velocity gradient, which additionally increases the sound velocity gradient of the sound wave propagating on the resonator, thereby further improving the Q value of the resonator. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 It is a top view schematic diagram of a common existing surface acoustic wave resonator;

[0030] Figure 2 for Figure 1 Schematic diagram of the cross-sectional structure of the SAW resonator along the AA' section;

[0031] Figure 3 It is a top view schematic diagram of another existing surface acoustic wave resonator;

[0032] Figure 4 is a top view schematic diagram of another existing surface acoustic wave resonator;

[0033] Figure 5 It is a schematic diagram of the cross-sectional structure of another existing surface acoustic wave resonator;

[0034] Figure 6 It is a schematic diagram of the cross-sectional structure of another existing surface acoustic wave resonator;

[0035] Figure 7 A schematic top view of another existing surface acoustic wave resonator;

[0036] Figure 8 is a top view schematic diagram of another existing surface acoustic wave resonator;

[0037] Fig. 9 A schematic top view of another existing surface acoustic wave resonator;

[0038] Fig.10 A schematic top view of an existing surface acoustic wave resonator with a tilted interdigital transducer;

[0039] Fig.11 for Fig.10 Schematic diagram of simulation results of the surface acoustic wave resonator shown;

[0040] Fig.12 A schematic cross-sectional structure diagram of a surface acoustic wave resonator provided in an embodiment of the present application;

[0041] Fig.13 A schematic top view of a surface acoustic wave resonator provided in an embodiment of the present application;

[0042] Fig.14It is a schematic diagram of the cross-sectional structure of an existing surface acoustic wave resonator;

[0043] Fig.15 for Fig.12 The surface acoustic wave resonator (Example 1) and Fig.14 A comparison chart of the frequency response simulation results of the surface acoustic wave resonator (comparative example 1) shown;

[0044] Fig.16 for Fig.12 The surface acoustic wave resonator (Example 1) and Fig.14 A comparison chart of the Bode Q curve simulation results of the surface acoustic wave resonator (comparative example 1) shown;

[0045] Fig.17 is a curve schematic diagram showing how the Q value of the resonator changes with the change in the ratio RA of the thickness d1 of the first silicon dioxide layer in the silicon dioxide stack along the direction perpendicular to the plane where the substrate is located to the thickness d0 of the silicon dioxide stack along the direction perpendicular to the plane where the substrate is located;

[0046] Fig.18 A schematic cross-sectional structure diagram of another surface acoustic wave resonator provided in an embodiment of the present application;

[0047] Fig.19 A schematic top view of another surface acoustic wave resonator provided in an embodiment of the present application;

[0048] Fig. 20 A schematic top view of another surface acoustic wave resonator provided in an embodiment of the present application. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0050] In the following description, many specific details are set forth to facilitate a full understanding of the present application, but the present application may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0051] Secondly, the present application is described in detail with reference to the schematic diagram. When describing the embodiments of the present application in detail, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present application. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0052] Figure 1 FIG. 1 shows a top view of a common surface acoustic wave resonator. Figure 2 Shows Figure 1 Schematic diagram of the cross section of the SAW resonator along the AA' section, combined with Figure 1 and Figure 2 As shown, the existing surface acoustic wave resonator includes a substrate 01 and an interdigital transducer 02 located on the substrate 01, wherein the interdigital transducer 02 includes two bus bars 021 and 022 parallel to the main acoustic mode propagation direction X0, and two electrode fingers 023 and 024 located between the two bus bars 021 and 022 and alternately arranged along the main acoustic mode propagation direction X0, and the electrode finger 023 is connected to the bus bar 021, and the electrode finger 024 is connected to the bus bar 022.

[0053] Figure 3 A schematic top view of another existing surface acoustic wave resonator is shown. Figure 1 Compared with the SAW resonator shown in Figure 3 In the surface acoustic wave resonator shown, the interdigital transducer 02 also includes a dummy finger 025 arranged opposite to the electrode finger 023 and a dummy finger 026 arranged opposite to the electrode finger 024, and the dummy finger 025 is connected to the bus bar 022, and the dummy finger 026 is connected to the bus bar 021, that is, dummy fingers 025 and 026 are added to the interdigital transducer 02. With such an arrangement, the lateral mode can be reflected through the sound velocity mutation boundary of the dummy finger area to avoid the formation of resonance conditions and achieve better resonator performance, but it also requires occupying a larger space.

[0054] Figure 4 A schematic top view of another existing surface acoustic wave resonator is shown. Figure 1 Compared with the SAW resonator shown in Figure 4 In the surface acoustic wave resonator shown, reflection gratings 03 and 04 are added on opposite sides of the interdigital transducer 02 along the main acoustic mode propagation direction X0, so as to utilize the reflection gratings 03 and 04 to reflect sound waves, help form better resonance in the main resonance area, and improve the transmission performance of the resonator.

[0055] Figure 5 A cross-sectional schematic diagram of another existing surface acoustic wave resonator is shown. Figure 2 Compared with the SAW resonator shown in Figure 5The surface acoustic wave resonator shown is a temperature compensated surface acoustic wave resonator TC-SAW, and a temperature compensation layer 05 is arranged above the electrode finger. The temperature compensation layer 05 can be a SiO2 layer. The temperature drift coefficient of the temperature compensation layer 05 is opposite to that of the piezoelectric material, which is used to overcome the temperature drift problem and improve the temperature stability of the resonator.

[0056] Figure 6 A cross-sectional schematic diagram of another existing surface acoustic wave resonator is shown. Figure 2 Compared with the SAW resonator shown in Figure 6 The surface acoustic wave resonator shown is a thin film surface acoustic wave resonator TC-SAW, wherein a piezoelectric film 011 is arranged on a substrate 01 , and an interdigital transducer 02 is located on a side of the piezoelectric film 011 away from the substrate 01 .

[0057] As described in the background technology section, for any type of surface acoustic wave resonator, laterally propagating sound waves will cause lateral resonance modes to appear in the resonator, that is, noise appearing in and near the passband. This noise will increase device losses, cause large fluctuations in the Q value, and reduce the performance of the resonator and filter.

[0058] In the prior art, a tilted interdigital transducer (IDT) design has been used to suppress lateral spurious modes (or in-band spurious modes). For example, referring to the invention patent No. CN114614794A previously applied by the applicant, a schematic diagram of the structure is shown in FIG. Figure 7 As shown; the invention patent number is CN114710134A, and its brief structural diagram is as follows Figure 8 As shown in the invention patent with patent number CN117375564A, its brief structural diagram is as follows Fig. 9 As shown, busbars 021 and 022 adopt a zigzag structure. Specifically, busbars 021 and 022 are inclined at a certain angle relative to the propagation direction X0 of the main acoustic mode, so as to reduce the lateral resonance film and improve the suppression effect of the resonator on clutter.

[0059] However, the inventors have found that although the greater the inclination angle of the bus bar relative to the propagation direction of the main acoustic mode, the better the suppression effect on the lateral stray mode, when the inclination angle exceeds a certain angle, the Q value, electromechanical coupling coefficient and effective area of ​​the surface acoustic wave resonator will decrease, thereby causing a contradiction between suppressing the lateral stray mode and improving the Q value, electromechanical coupling coefficient and effective area.

[0060] For example, Fig.10 FIG. 4 shows a top view of a conventional surface acoustic wave resonator with a tilted interdigital transducer. Fig.10As shown, the busbar 021 and the busbar 022 are arranged in parallel, and the angle between the extension direction of the busbar 021 and the busbar 022 and the propagation direction X0 of the main acoustic mode is the inclination angle theta of the busbar 021 and the busbar 022. Fig.11 Shows Fig.10 The simulation results of the interdigital transducer are shown in Figure 1. Fig.11 As shown in the figure, when the inclination angle theta of busbar 021 and busbar 022 is 7 degrees, the left side of the resonance peak is smooth, but the spurious suppression on the right side of the resonance peak is incomplete. At this time, the inclination angle theta of busbar 021 and busbar 022 is usually increased to make the band smooth. For example, the inclination angle theta of busbar 021 and busbar 022 is increased to 10 degrees, but from Fig.11 It can be seen that although the right side of the resonance peak of the tilt angle theta = 10 degrees is smoother than that of the tilt angle theta = 7 degrees, the overall curve of the tilt angle theta = 10 degrees is worse, which usually leads to a decrease in the Q value, electromechanical coupling coefficient and effective area of ​​the resonator.

[0061] That is, when the best transverse mode suppression effect is achieved by tilting the busbars, the best tilt angle theta of the busbars is usually too large, which will lead to a decrease in the Q value, electromechanical coupling coefficient and effective area of ​​the resonator.

[0062] Among them, the Q value of the resonator is directly related to the insertion loss of the filter. In the RF link, it is usually required that the insertion loss of each component is as small as possible to ensure that the signal has sufficient strength and quality, thereby ensuring the reliability and stability of the communication system. Therefore, improving the Q value of the resonator is an effective means to reduce the insertion loss of the communication system and thus improve the signal quality.

[0063] However, when suppressing the transverse mode by tilting the busbar, the Q value of the resonator is reduced because the tilt angle of the busbar corresponding to the optimal transverse mode suppression effect is usually too large. Therefore, how to improve the Q value of the resonator while ensuring the suppression effect of the tilted busbar on the transverse mode to reduce the insertion loss of the communication system is a technical problem that needs to be urgently solved by technical personnel in this field.

[0064] In view of this, an embodiment of the present application provides a surface acoustic wave resonator. Fig.12 FIG. 4 shows a schematic cross-sectional structure diagram of a surface acoustic wave resonator provided in an embodiment of the present application, such as Fig.12 As shown, the surface acoustic wave resonator comprises:

[0065] Substrate 10;

[0066] A silicon dioxide stack 20 located on one side of the substrate 10, wherein the silicon dioxide stack 20 includes at least two silicon dioxide layers 201, and any two adjacent silicon dioxide layers 201 have different densities;

[0067] a piezoelectric layer 30 located on the side of the silicon dioxide stack 20 facing away from the substrate 10;

[0068] The interdigital transducer 40 is located on the side of the piezoelectric layer 30 facing away from the substrate 10 .

[0069] The substrate 10 may be a silicon substrate.

[0070] The piezoelectric layer 30 may be a single crystal piezoelectric layer. Under the action of electric field excitation, the piezoelectric layer 30 excites acoustic waves through the inverse piezoelectric effect. The material of the piezoelectric layer 30 includes but is not limited to lithium tantalate (LiTaO3), lithium niobate (LiNbO3), etc. The thickness of the piezoelectric layer 30 in the direction perpendicular to the plane where the substrate 10 is located may be about 0.1 to 20 wavelengths.

[0071] The deposition method of the piezoelectric layer 30 may include single crystal slicing, chemical vapor deposition (CVD) and physical vapor deposition (PVD), etc., wherein the single crystal slicing process for preparing the piezoelectric layer 30 also requires related processes such as ion implantation and bonding.

[0072] Each silicon dioxide layer 201 in the silicon dioxide stack 20 is an oxide buried layer, which has a low acoustic velocity and has a temperature compensation function. Its excellent insulation properties can effectively isolate the top piezoelectric layer 30 and the bottom substrate 10, ensuring excellent electrical properties and acoustic performance.

[0073] The thickness of the silicon dioxide stack 20 in a direction perpendicular to the plane where the substrate 10 is located may be about 0.1 micrometers to 10 micrometers.

[0074] Fig.13 FIG. 4 shows a schematic top view of a surface acoustic wave resonator provided in an embodiment of the present application. Figure 2 As shown, the interdigital transducer 40 includes a first bus bar 41 and a second bus bar 42 which are arranged opposite to each other along a first direction Y. A first electrode finger 43 connected to the first bus bar 41 and a second electrode finger 44 connected to the second bus bar 42 are arranged between the first bus bar 41 and the second bus bar 42. The first electrode finger 43 and the second electrode finger 44 extend along the first direction Y and are alternately arranged along the second direction X. The first direction Y and the second direction X are parallel to the plane where the substrate 10 is located, and the first direction Y and the second direction X are perpendicular. The extension direction of at least one of the first bus bar 41 and the second bus bar 42 intersects with the second direction X.

[0075] In the present application, the first direction Y is the direction in which the first bus bar 41 and the second bus bar 42 are relatively arranged, and is also the direction in which the first electrode fingers 43 and the second electrode fingers 44 extend as a whole; the second direction X is the direction in which the first electrode fingers 43 and the second electrode fingers 44 are alternately arranged, and is also the propagation direction of the main acoustic mode.

[0076] In the present application, the extension direction of at least one of the first bus bar 41 and the second bus bar 42 intersects with the second direction X, that is, at least one of the first bus bar 41 and the second bus bar 42 is inclined relative to the second direction X, that is, the first bus bar 41 is inclined relative to the second direction X, or the second bus bar 42 is inclined relative to the second direction X, or, both the first bus bar 41 and the second bus bar 42 are inclined relative to the second direction X.

[0077] When the first bus bar 41 and the second bus bar 42 are both inclined relative to the second direction X, the angle at which the first bus bar 41 is inclined relative to the second direction X and the angle at which the second bus bar 42 is inclined relative to the second direction X may be equal or unequal. Fig.13 In the example, the first bus bar 41 and the second bus bar 42 are both inclined relative to the second direction X, and the angle of inclination of the first bus bar 41 relative to the second direction X is equal to the angle of inclination of the second bus bar 42 relative to the second direction X, that is, the first bus bar 41 and the second bus bar 42 are arranged in parallel, wherein the angle of inclination of the first bus bar 41 and the second bus bar 42 relative to the second direction X is theta. It can be understood that Fig.12 for Fig.13 Schematic cross-sectional view of CC'.

[0078] In the present application, at least one of the first bus bar 41 and the second bus bar 42 is tilted relative to the second direction X (i.e., the propagation direction of the main acoustic mode) to suppress the lateral stray mode. However, considering that, although the greater the inclination angle of the bus bar relative to the propagation direction of the main acoustic mode, the better the suppression effect on the lateral stray mode, when the inclination angle exceeds a certain angle, the Q value, electromechanical coupling coefficient and effective area of ​​the surface acoustic wave resonator will be reduced, thereby causing a contradiction between suppressing the lateral stray mode and improving the Q value, electromechanical coupling coefficient and effective area; in other words, when the best lateral mode suppression effect is achieved by tilting the bus bar, the optimal inclination angle theta corresponding to the bus bar is usually too large, which will lead to a decrease in the Q value, electromechanical coupling coefficient and effective area of ​​the resonator.

[0079] Based on this, in this application, Fig.12 As shown, a silicon dioxide stack 20 is disposed between the substrate 10 and the piezoelectric layer 30, and the silicon dioxide stack 20 includes at least two silicon dioxide layers 201, and the densities of any two adjacent silicon dioxide layers 201 are different. For comparison, Fig.14 The cross-sectional structure diagram of an existing surface acoustic wave resonator is shown, wherein only one silicon dioxide layer 202 is provided between the substrate 10 and the piezoelectric layer 30, and the silicon dioxide layer 202 is a single-density low-acoustic-velocity layer.

[0080] contrast Fig.12 and Fig.14 It can be seen that the surface acoustic wave resonator provided in the embodiment of the present application is provided with a silicon dioxide stack 20 between the substrate 10 and the piezoelectric layer 30. The silicon dioxide stack 20 includes at least two silicon dioxide layers 201, and the density of any two adjacent silicon dioxide layers 201 is different. The different sound velocities of the silicon dioxide layers 201 with different densities are utilized, so that any two adjacent silicon dioxide layers 201 with different densities form a sound velocity gradient, which better confines the energy in the piezoelectric layer 30, improves the Q value of the resonator, and has no effect on the lateral mode. Ultimately, the lateral stray mode of the surface acoustic wave resonator is effectively suppressed, while the Q value of the resonator is improved, and the insertion loss of the communication system is reduced.

[0081] Fig.15 Shows Fig.12 The surface acoustic wave resonator (Example 1) and Fig.14 The comparison chart of the frequency response simulation results of the surface acoustic wave resonator (comparative example 1) shows that Fig.12 The admittance curve of the surface acoustic wave resonator (Example 1) shown in FIG. Fig.14 There is no obvious difference in the admittance curves of the surface acoustic wave resonator (Comparative Example 1) shown, indicating that Fig.12 In the surface acoustic wave resonator shown, the silicon dioxide stack 20 including at least two silicon dioxide layers 201 with different densities arranged between the substrate 10 and the piezoelectric layer 30 has almost no effect on the lateral mode, thereby being able to maintain the suppression effect of the first bus bar 41 and / or the second bus bar 42 being inclined relative to the second direction X on the lateral stray mode.

[0082] Fig.16 Shows Fig.12 The surface acoustic wave resonator (Example 1) and Fig.14 The Bode Q curve simulation results of the surface acoustic wave resonator (Comparative Example 1) shown in the figure show that compared with Fig.14 The surface acoustic wave resonator shown (Comparative Example 1), Fig.12 The Q value of the surface acoustic wave resonator (Example 1) is significantly improved.

[0083] Optionally, in some embodiments of the present application, reference Fig.12As shown, in the silicon dioxide stack 20, the density of different silicon dioxide layers 201 is different, or in other words, the density of each silicon dioxide layer 201 is different, which can further better confine the energy in the piezoelectric layer 30 and improve the Q value of the resonator.

[0084] Optionally, in some embodiments of the present application, reference Fig.12 As shown, in the silicon dioxide stack 20, the density of each silicon dioxide layer 201 gradually decreases along the direction away from the substrate 10 and close to the piezoelectric layer 30, so that the sound velocity of each silicon dioxide layer 201 gradually increases, forming a gradient of gradually increasing sound velocity, which can further better confine the energy in the piezoelectric layer 30 and improve the Q value of the resonator.

[0085] Optionally, in some other embodiments of the present application, refer to Fig.12 As shown, in the silicon dioxide stack 20, the density of each silicon dioxide layer 201 gradually increases along the direction away from the substrate 10 and close to the piezoelectric layer 30, so that the sound velocity of each silicon dioxide layer 201 gradually decreases, forming a gradient of gradually decreasing sound velocity, which can further better confine the energy in the piezoelectric layer 30 and improve the Q value of the resonator.

[0086] In other embodiments of the present application, the density of each silicon dioxide layer 201 in the silicon dioxide stack 20 may not gradually decrease or increase in the direction away from the substrate 10 and close to the piezoelectric layer 30. Instead, as long as the density of any two adjacent silicon dioxide layers 201 is different, a sound velocity gradient can be formed to better confine the energy in the piezoelectric layer 30, thereby improving the Q value of the resonator.

[0087] Specifically, in some embodiments of the present application, Fig.12 As shown, the silicon dioxide stack 20 includes a first silicon dioxide layer 21 and a second silicon dioxide layer 22, and the second silicon dioxide layer 22 is located on the side of the first silicon dioxide layer 21 away from the substrate 10, that is, in the stacked first silicon dioxide layer 21 and the second silicon dioxide layer 22, the first silicon dioxide layer 21 is located on the side close to the substrate 10, and the second silicon dioxide layer 22 is located on the side close to the piezoelectric layer. The density of the first silicon dioxide layer 21 is greater than the density of the second silicon dioxide layer 22. In this way, the sound velocity of the first silicon dioxide layer 21 is less than the sound velocity of the second silicon dioxide layer 22, that is, the sound velocity of the second silicon dioxide layer 22 is greater than the sound velocity of the first silicon dioxide layer 21. The first silicon dioxide layer 21 and the second silicon dioxide layer 22 form a sound velocity gradient to better confine the energy in the piezoelectric layer 30 and improve the Q value of the resonator.

[0088] The inventor further studied and found that reference Fig.12As shown, the Q value of the resonator changes with the change of the ratio RA of the thickness d1 of the higher density first silicon dioxide layer 21 in the silicon dioxide stack 20 along the direction perpendicular to the plane where the substrate 10 is located to the thickness d0 of the silicon dioxide stack 20 along the direction perpendicular to the plane where the substrate 10 is located, RA=d1 / d0.

[0089] Fig.17 The diagram shows a curve diagram of how the Q value of the resonator changes with the change in the ratio RA of the thickness d1 of the first silicon dioxide layer 21 with higher density in the silicon dioxide stack 20 along the direction perpendicular to the plane where the substrate 10 is located to the thickness d0 of the silicon dioxide stack 20 along the direction perpendicular to the plane where the substrate 10 is located. It can be seen that as the ratio RA of the thickness d1 of the first silicon dioxide layer 21 with higher density in the silicon dioxide stack 20 along the direction perpendicular to the plane where the substrate 10 is located to the thickness d0 of the silicon dioxide stack 20 along the direction perpendicular to the plane where the substrate 10 is located increases, the Q value of the resonator first increases and then decreases; when 0<RA≤75%, the silicon dioxide stack 20 including the first silicon dioxide layer 21 and the second silicon dioxide layer 22 is arranged between the substrate 10 and the piezoelectric layer 30 in the present application, compared with the existing low-acoustic-velocity silicon dioxide layer with only a single density arranged between the substrate 10 and the piezoelectric layer 30, can improve the Q value of the resonator; in particular, when RA is about 25%, the Q value of the resonator is improved the most, by about 25%.

[0090] In the present application, silicon dioxide layers 201 with different densities can be prepared by different deposition techniques. Optionally, the first silicon dioxide layer 21 with a higher density near the substrate 10 can be prepared by a chemical vapor deposition (CVD) process or a sputtering process; the second silicon dioxide layer 22 with a lower density near the piezoelectric layer 30 can be prepared by a physical vapor deposition (PVD) process. The stack composed of the first silicon dioxide layer 21 and the second silicon dioxide layer 22 is bonded to the bottom substrate 10 by a bonding process.

[0091] It is understandable that in some embodiments of the present application, the silicon dioxide stack 20 may include three or more silicon dioxide layers 201, and any two adjacent silicon dioxide layers 201 have different densities, which can also form a sound velocity gradient and improve the Q value of the resonator.

[0092] Based on any of the above embodiments, optionally, in some embodiments of the present application, such as Fig.18As shown, the surface acoustic wave resonator provided by the embodiment of the present application may also include a high acoustic velocity layer 50 located between the silicon dioxide stack 20 and the piezoelectric layer 30. The acoustic velocity of the high acoustic velocity layer 50 is greater than the acoustic velocity of each silicon dioxide layer 201 in the silicon dioxide stack 20, that is, the acoustic velocity of the high acoustic velocity layer 50 is greater than the acoustic velocity of the entire silicon dioxide stack 20. Optionally, the material of the high acoustic velocity layer 50 may include at least one of silicon nitride (Si3N4) and aluminum nitride (AlN). In this way, after the high acoustic velocity layer 50 is added between the silicon dioxide stack 20 and the piezoelectric layer 30, not only does the silicon dioxide stack 20 have an acoustic velocity gradient, but the silicon dioxide stack 20 and the high acoustic velocity layer 50 also form an acoustic velocity gradient, which additionally increases the acoustic velocity gradient of the sound wave propagating on the resonator, thereby further improving the Q value of the resonator.

[0093] It can be understood that, by arranging a silicon dioxide stack 20 between the substrate 10 and the piezoelectric layer 30, the silicon dioxide stack 20 includes at least two silicon dioxide layers 201, and the densities of any two adjacent silicon dioxide layers 201 are different, so as to form a sound velocity gradient, better confine the energy in the piezoelectric layer 30, and improve the Q value of the resonator; and then adding a high sound velocity layer 50 between the silicon dioxide stack 20 and the piezoelectric layer 30, additionally increasing the sound velocity gradient, and further improving the Q value of the resonator; on this basis, the inclination angle of the first bus bar 41 and / or the second bus bar 42 relative to the second direction X can be further increased to improve the suppression effect of the lateral stray mode.

[0094] like Fig.13 As shown, the surface acoustic wave resonator may further include a reflection grating 60 located on two opposite sides of the interdigital transducer 40 along the second direction X, the reflection grating 60 includes a first short-circuit bar 61 and a second short-circuit bar 62 arranged opposite to each other along the first direction Y, and a third electrode finger 63 located between the first short-circuit bar 61 and the second short-circuit bar 62, the third electrode finger 63 extends along the first direction Y and is arranged along the second direction X.

[0095] Optionally, the reflection grating 60 can refer to the design of the inclined interdigital transducer 40, and the structure of the reflection grating 60 can be the same as the structure of the interdigital transducer 40, that is, the extension direction of the first short-circuit bar 61 and / or the second short-circuit bar 62 in the reflection grating 60 can also intersect with the second direction X, that is, the first short-circuit bar 61 and / or the second short-circuit bar 62 in the reflection grating 60 is inclined relative to the second direction X.

[0096] Optional, such as Fig.19As shown, the interdigital transducer 40 may also include a first dummy finger 45 connected to the first bus bar 41 and a second dummy finger 46 connected to the second bus bar 42, the first dummy finger 45 and the second electrode finger 44 are arranged relatively to each other along the first direction Y, and the first dummy finger 45 and the first electrode finger 43 are arranged alternately along the second direction X, the second dummy finger 46 and the first electrode finger 43 are arranged relatively to each other along the first direction Y, and the second dummy finger 46 and the second electrode finger 44 are arranged alternately along the second direction X.

[0097] Further optional, such as Fig.19 As shown, at least one of the two sides of the dummy finger connected to the inclined bus bar along the second direction X is inclined relative to the first direction Y. For example, the first bus bar 41 is inclined at a certain angle theta relative to the second direction X, and the first dummy finger 45 connected to the first bus bar 41 is inclined at a certain angle beta relative to the first direction Y along at least one of the two sides along the second direction X. Similarly, the second bus bar 42 can also be inclined at a certain angle theta relative to the second direction X, and the second dummy finger 46 connected to the second bus bar 42 can also be inclined at a certain angle beta relative to the first direction Y along at least one of the two sides along the second direction X. In this way, the suppression of the lateral stray mode within the resonator band can be enhanced, the optimal inclination angle of the bus bar can be reduced, and the reduction of the resonator Q value, electromechanical coupling coefficient and effective area due to the excessively large optimal inclination angle of the bus bar can be avoided.

[0098] Further optional, such as Fig. 20 As shown, at least one of the two sides opposite to each other along the second direction X along the end portion (corresponding to the dummy finger portion on the same side) of the electrode finger connected to the inclined bus bar can also be tilted relative to the first direction Y. For example, at least one of the two sides opposite to each other along the second direction X along the end portion (corresponding to the first dummy finger 45 portion) of the first electrode finger 43 connected to the first bus bar 41 can be tilted relative to the first direction Y, and / or at least one of the two sides opposite to each other along the second direction X along the end portion (corresponding to the second dummy finger 46 portion) of the second electrode finger 44 connected to the second bus bar 42 can be tilted relative to the first direction Y, so as to further enhance the suppression of the lateral stray mode within the resonator band, thereby further reducing the optimal tilt angle of the bus bar, and avoiding the reduction of the resonator Q value, electromechanical coupling coefficient and effective area due to the excessively large optimal tilt angle of the bus bar.

[0099] Based on any of the above embodiments, optionally, a piston structure can be provided at one end of the first electrode finger 43 close to the second dummy finger 46, and a piston structure can be provided at one end of the second electrode finger 44 close to the first dummy finger 45, so as to further improve the heterogeneous mode suppression effect of the resonator without affecting the excitation and propagation of the main acoustic mode.

[0100] Correspondingly, an embodiment of the present application further provides a filter, comprising the surface acoustic wave resonator provided by any of the above embodiments.

[0101] Furthermore, an embodiment of the present application also provides an electronic device, comprising the above-mentioned filter.

[0102] Since the surface acoustic wave resonator has been described in detail in the aforementioned embodiments, it will not be described again here.

[0103] The various parts in this manual are described in a combination of parallel and progressive manners. Each part focuses on the differences from other parts, and the same or similar parts between the various parts can be referenced to each other.

[0104] With respect to the above description of the disclosed embodiments, the features described in the embodiments in this specification may be replaced or combined with each other, so that professionals in the field can implement or use the present application. Various modifications to these embodiments will be apparent to professionals in the field, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A surface acoustic wave resonator, characterized in that: include: substrate; A silicon dioxide stack located on one side of the substrate, the silicon dioxide stack comprising at least two silicon dioxide layers, and any two adjacent silicon dioxide layers have different densities; a piezoelectric layer located on a side of the silicon dioxide stack facing away from the substrate; an interdigital transducer located on a side of the piezoelectric layer facing away from the substrate; The IDT comprises a first bus bar and a second bus bar which are arranged opposite to each other along a first direction, a first electrode finger connected to the first bus bar and a second electrode finger connected to the second bus bar are arranged between the first bus bar and the second bus bar, the first electrode finger and the second electrode finger extend along the first direction and are alternately arranged along a second direction, the first direction and the second direction are parallel to the plane where the substrate is located, and the first direction and the second direction are perpendicular; An extending direction of at least one of the first bus bar and the second bus bar intersects with the second direction.

2. The surface acoustic wave resonator according to claim 1, characterized in that: In the silicon dioxide stack, the density of each silicon dioxide layer gradually decreases along a direction away from the substrate and close to the piezoelectric layer.

3. The surface acoustic wave resonator according to claim 1, characterized in that: In the silicon dioxide stack, the density of each silicon dioxide layer gradually increases along a direction away from the substrate and close to the piezoelectric layer.

4. The surface acoustic wave resonator according to claim 1, characterized in that: The silicon dioxide stack includes a first silicon dioxide layer and a second silicon dioxide layer, wherein the second silicon dioxide layer is located on a side of the first silicon dioxide layer away from the substrate, and a density of the first silicon dioxide layer is greater than a density of the second silicon dioxide layer.

5. The surface acoustic wave resonator according to claim 4, characterized in that: A ratio RA of the thickness of the first silicon dioxide layer in a direction perpendicular to the plane where the substrate is located to the thickness of the silicon dioxide stack in a direction perpendicular to the plane where the substrate is located satisfies: 0<RA≤75%.

6. The surface acoustic wave resonator according to claim 4, characterized in that: The first silicon dioxide layer is prepared by a chemical vapor deposition process or a sputtering process; The second silicon dioxide layer is prepared by a physical vapor deposition process.

7. The surface acoustic wave resonator according to any one of claims 1 to 6, characterized in that: The surface acoustic wave resonator further comprises: The high acoustic velocity layer is located between the silicon dioxide stack and the piezoelectric layer, and the acoustic velocity of the high acoustic velocity layer is greater than the acoustic velocity of each silicon dioxide layer in the silicon dioxide stack.

8. The surface acoustic wave resonator according to claim 7, characterized in that: The material of the high acoustic velocity layer includes at least one of silicon nitride and aluminum nitride.

9. A filter, characterized in that: The surface acoustic wave resonator comprises the surface acoustic wave resonator according to any one of claims 1 to 8.

10. An electronic device, characterized in that: Comprising the filter as claimed in claim 9.

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