A thin-film surface acoustic wave filter for suppressing transverse modes and a manufacturing method thereof

Abstract

The present application discloses a transverse mode suppression thin film surface acoustic wave filter and a manufacturing method thereof. It relates to the technical field of filtering. Among them, the interdigital electrode structure in the transverse mode suppression thin film surface acoustic wave filter is arranged on the side of the piezoelectric thin film layer away from the substrate, and the transverse mode suppression electrode structure is ingeniously arranged between the piezoelectric thin film layer and the substrate, making full use of the original piezoelectric thin film layer in the thin film surface acoustic wave filter as the isolation layer between the transverse mode suppression electrode and the interdigital electrode, without the need to additionally add an isolation layer, and also ensuring the close distance between the interdigital electrode and the piezoelectric thin film layer, avoiding the negative effect on the filtering effect of the filter caused by the increased distance. Moreover, the transverse mode suppression electrode structure overlaps at least with the free ends of a plurality of interdigital electrodes in the direction perpendicular to the main surface of the piezoelectric thin film layer, thereby changing the sound velocity field of the transverse propagation of the thin film surface acoustic wave filter, effectively suppressing the transverse mode, and improving the transverse mode suppression ability of the thin film surface acoustic wave filter.

Description

Technical Field

[0001] This application relates to the technical field of filtering, and particularly to a thin-film surface acoustic wave filter for suppressing transverse modes and a manufacturing method thereof. Background Art

[0002] With the rapid development of mobile communication technology, surface acoustic wave (SAW) filters have become increasingly important in the radio frequency front-end due to their small size and good performance. SAW filters include thin-film surface acoustic wave (TF-SAW) filters and temperature-compensated surface acoustic wave (TC-SAW) filters. In current mainstream thin-film surface acoustic wave (TF-SAW) filters, due to the structural limitations of thin-film surface acoustic wave filters, interdigital electrodes will inevitably excite higher-order transverse clutter in a stacked-structure surface acoustic wave filter. As can be seen from the admittance curve, there will be many spikes in the high-frequency direction of the resonance frequency, resulting in the deterioration of the flatness of the resonator or filter.

[0003] In order to suppress the transverse clutter of the surface acoustic wave filter, a current transverse mode suppression scheme is to form an interdigital electrode above the piezoelectric substrate, and deposit a passivation layer above the interdigital electrode to form a transverse mode suppression electrode. The passivation layer isolates the transverse mode suppression electrode from the interdigital electrode to prevent the interdigital electrode from sending a short-circuit fault. However, this layout of setting the transverse mode suppression electrode above the interdigital electrode has a problem: the transverse mode suppression electrode is uneven and the suppression effect is poor.

[0004] Another transverse mode suppression scheme is to construct a transverse mode suppression electrode on the piezoelectric substrate, then cover a layer of non-metallic dielectric layer, and finally set an interdigital electrode on this layer. However, this structural design has a problem: the interdigital electrode is isolated from the piezoelectric substrate by the transverse mode suppression electrode and the non-metallic dielectric layer, resulting in the interdigital electrode being relatively far from the piezoelectric substrate (especially when the piezoelectric substrate adopts a composite structure composed of a piezoelectric thin film, silicon dioxide and a silicon substrate). This layout causes the electrical signal generated by the interdigital electrode to be significantly attenuated when reaching the piezoelectric thin film, thereby having an adverse effect on the performance of the filter and reducing the filtering effect.

[0005] Therefore, there is an urgent need for a technical solution that can improve the transverse mode suppression ability of a thin-film surface acoustic wave filter without affecting its filtering effect. Summary of the Invention

[0006] Embodiments of the present disclosure provide a thin film surface acoustic wave filter for suppressing transverse modes and a manufacturing method thereof.

[0007] According to one aspect of the embodiments of the present disclosure, a thin film surface acoustic wave filter for suppressing transverse modes is provided, including a substrate, a piezoelectric thin film layer, and an interdigital electrode structure; the piezoelectric thin film layer is formed on the substrate; the interdigital electrode structure is disposed on a side of the piezoelectric thin film layer away from the substrate, and includes an electrode lead-out portion and a plurality of interdigital electrodes extending in a first direction and alternately arranged in a second direction intersecting with the first direction. One end of the interdigital electrode is a free end, and the other end of the interdigital electrode is connected to the electrode lead-out portion; the thin film surface acoustic wave filter further includes a transverse mode suppression electrode structure disposed between the piezoelectric thin film layer and the substrate, and at least a part of the transverse mode suppression electrode structure overlaps with the free ends of the plurality of interdigital electrodes in a third direction perpendicular to the main surface of the piezoelectric thin film layer.

[0008] Optionally, the plurality of interdigital electrodes include first interdigital electrodes and second interdigital electrodes extending in a first direction and alternately arranged in a second direction intersecting with the first direction; the transverse mode suppression electrode structure includes a first transverse mode suppression electrode and a second transverse mode suppression electrode; the first transverse mode suppression electrode extends in the second direction, and at least a part of the first transverse mode suppression electrode overlaps with the free ends of the first interdigital electrodes in the third direction; the second transverse mode suppression electrode extends in the second direction, and at least a part of the second transverse mode suppression electrode overlaps with the free ends of the second interdigital electrodes in the third direction.

[0009] Optionally, the first transverse mode suppression electrode overlaps with the free ends of the first interdigital electrodes in the third direction and also overlaps with the gaps between adjacent interdigital electrodes in the plurality of interdigital electrodes; and the second transverse mode suppression electrode overlaps with the free ends of the second interdigital electrodes in the third direction and also overlaps with the gaps between adjacent interdigital electrodes in the plurality of interdigital electrodes.

[0010] Optionally, a plurality of first separation gaps are provided on the first transverse mode suppression electrode, and the first separation gaps divide the first transverse mode suppression electrode into a plurality of first transverse mode suppression blocks arranged at intervals, and the first transverse mode suppression blocks overlap with the free ends of the first interdigital electrodes in the third direction; and a plurality of second separation gaps are provided on the second transverse mode suppression electrode, and the second separation gaps divide the second transverse mode suppression electrode into a plurality of second transverse mode suppression blocks arranged at intervals, and the second transverse mode suppression blocks overlap with the free ends of the second interdigital electrodes in the third direction.

[0011] Optionally, the thin film surface acoustic wave filter further includes a dielectric layer; the dielectric layer is located between the substrate and the piezoelectric thin film layer and buries the transverse mode suppression electrode structure; wherein the transverse mode suppression electrode structure is not in contact with the substrate and the piezoelectric thin film layer; or one side of the transverse mode suppression electrode structure close to the piezoelectric thin film layer is in contact with the piezoelectric thin film layer, and the side of the transverse mode suppression electrode structure away from the piezoelectric thin film layer is not in contact with the substrate; or one side of the transverse mode suppression electrode structure close to the piezoelectric thin film layer is not in contact with the piezoelectric thin film layer, and the side of the transverse mode suppression electrode structure away from the piezoelectric thin film layer is in contact with the substrate.

[0012] Optionally, the material of the dielectric layer is SiO2.

[0013] Optionally, the thin film surface acoustic wave filter further includes a first reflection grating and a second reflection grating disposed on opposite sides of the interdigital electrode structure in the second direction, wherein each reflection grating includes a plurality of reflection electrodes and bus bars, the plurality of reflection electrodes extend in the first direction and are arranged at intervals in the second direction, the bus bars extend in the second direction and are connected to the plurality of reflection electrodes; the first transverse mode suppression electrode further overlaps with the plurality of reflection electrodes of each reflection grating in the third direction; and the second transverse mode suppression electrode further overlaps with the plurality of reflection electrodes of each reflection grating in the third direction.

[0014] Optionally, the electrode lead-out portion includes a first electrode lead-out portion and a second electrode lead-out portion that are oppositely arranged and extend in the second direction, the first electrode lead-out portion is connected to the first interdigital electrode, and the second electrode lead-out portion is connected to the second interdigital electrode.

[0015] According to another aspect of the embodiments of the present disclosure, there is also provided a method for manufacturing a thin film surface acoustic wave filter for suppressing transverse modes, including: providing a substrate; forming a transverse mode suppression electrode structure on one side of the substrate; forming a piezoelectric thin film layer on the side of the transverse mode suppression electrode structure away from the substrate; and forming an interdigital electrode structure on the side of the piezoelectric thin film layer away from the substrate, the interdigital electrode structure includes an electrode lead-out portion and a plurality of interdigital electrodes that extend in a first direction and are alternately arranged in a second direction intersecting the first direction, one end of the interdigital electrode is a free end, and the other end of the interdigital electrode is connected to the electrode lead-out portion; wherein at least a part of the transverse mode suppression electrode structure overlaps with the free ends of the plurality of interdigital electrodes in a third direction perpendicular to the main surface of the piezoelectric thin film layer.

[0016] Optionally, the plurality of interdigital electrodes include a first interdigital electrode and a second interdigital electrode that extend in a first direction and are alternately arranged in a second direction intersecting the first direction; the transverse mode suppression electrode structure includes a first transverse mode suppression electrode and a second transverse mode suppression electrode; the first transverse mode suppression electrode extends in the second direction, and at least a part of the first transverse mode suppression electrode overlaps at least the free end of the first interdigital electrode in a third direction; the second transverse mode suppression electrode extends in the second direction, and at least a part of the second transverse mode suppression electrode overlaps the free end of the second interdigital electrode in the third direction.

[0017] Optionally, the first transverse mode suppression electrode overlaps the free end of the first interdigital electrode in the third direction and also overlaps the gap between adjacent interdigital electrodes among the plurality of interdigital electrodes; and the second transverse mode suppression electrode overlaps the free end of the second interdigital electrode in the third direction and also overlaps the gap between adjacent interdigital electrodes of the plurality of interdigital electrodes.

[0018] Optionally, a plurality of first separation gaps are provided on the first transverse mode suppression electrode, and the first separation gaps divide the first transverse mode suppression electrode into a plurality of first transverse mode suppression blocks arranged at intervals, and the first transverse mode suppression blocks overlap the free end of the first interdigital electrode in the third direction; and a plurality of second separation gaps are provided on the second transverse mode suppression electrode, and the second separation gaps divide the second transverse mode suppression electrode into a plurality of second transverse mode suppression blocks arranged at intervals, and the second transverse mode suppression blocks overlap the free end of the second interdigital electrode in the third direction.

[0019] Optionally, the manufacturing method further includes: manufacturing a dielectric layer; the dielectric layer is located between the substrate and the piezoelectric thin film layer and buries the transverse mode suppression electrode structure; wherein the transverse mode suppression electrode structure is not in contact with the substrate and the piezoelectric thin film layer; or one side of the transverse mode suppression electrode structure close to the piezoelectric thin film layer is in contact with the piezoelectric thin film layer, and the side of the transverse mode suppression electrode structure far from the piezoelectric thin film layer is not in contact with the substrate; or one side of the transverse mode suppression electrode structure close to the piezoelectric thin film layer is not in contact with the piezoelectric thin film layer, and the side of the transverse mode suppression electrode structure far from the piezoelectric thin film layer is in contact with the substrate.

[0020] Optionally, the material of the dielectric layer is SiO2.

[0021] Optionally, the manufacturing method further includes: forming a first reflective grating and a second reflective grating on a side of the piezoelectric thin film layer away from the substrate, the first reflective grating and the second reflective grating being disposed on opposite sides of the interdigital electrode structure in the second direction, wherein each reflective grating includes a plurality of reflective electrodes and bus bars, the plurality of reflective electrodes extending in the first direction and being arranged at intervals in the second direction, the bus bars extending in the second direction and connected to the plurality of reflective electrodes; wherein, the first transverse mode suppression electrode further overlaps with the plurality of reflective electrodes of each reflective grating in the third direction; and the second transverse mode suppression electrode further overlaps with the plurality of reflective electrodes of each reflective grating in the third direction.

[0022] Optionally, the electrode lead-out portion includes a first electrode lead-out portion and a second electrode lead-out portion which are oppositely arranged and extend in the second direction, the first electrode lead-out portion being connected to the first interdigital electrode, and the second electrode lead-out portion being connected to the second interdigital electrode.

[0023] In the thin film surface acoustic wave filter for suppressing transverse modes proposed in the present application, the interdigital electrode structure is disposed on a side of the piezoelectric thin film layer away from the substrate, and the transverse mode suppression electrode structure is ingeniously disposed between the piezoelectric thin film layer and the substrate. This design makes full use of the original piezoelectric thin film layer in the thin film surface acoustic wave filter as an isolation layer between the transverse mode suppression electrode and the interdigital electrode, without the need to additionally add an isolation layer, and at the same time ensures a close distance between the interdigital electrode and the piezoelectric thin film layer, thereby avoiding the negative effect on the filtering effect of the filter caused by the increased distance. Moreover, the transverse mode suppression electrode structure overlaps at least with the free ends of the plurality of interdigital electrodes in a direction perpendicular to the main surface of the piezoelectric thin film layer. Therefore, the transverse mode suppression electrode structure can change the sound velocity field propagating transversely in the thin film surface acoustic wave filter, effectively suppress the transverse mode, and significantly improve the transverse mode suppression ability of the thin film surface acoustic wave filter. Description of the Drawings

[0024] The drawings described herein are used to provide a further understanding of the present disclosure, and constitute a part of the present application. The schematic embodiments of the present disclosure and their descriptions are used to explain the present disclosure and do not constitute an improper limitation to the present disclosure. In the drawings:

[0025] Figure 1 is a schematic structural diagram of a thin film surface acoustic wave filter for suppressing transverse modes provided in the first embodiment of the present invention;

[0026] Figure 2 is used to present Figure 1 a planar schematic diagram of the correlation relationship between the interdigital electrode structure, the reflective grating and the transverse mode suppression electrode structure in all directions in the thin film surface acoustic wave filter for suppressing transverse modes provided;

[0027] Figures 3 - 6 These are schematic diagrams of various structures in the manufacturing process of the thin-film surface acoustic wave filter for suppressing transverse modes provided in the first embodiment of the present invention;

[0028] Figure 7 This is a schematic diagram of the structure of the thin-film surface acoustic wave filter for suppressing transverse modes provided in the second embodiment of the present invention;

[0029] Figure 8 This is a schematic diagram of the structure of the thin-film surface acoustic wave filter for suppressing transverse modes provided in the third embodiment of the present invention;

[0030] Figure 9 This is a schematic diagram of the structure of the thin-film surface acoustic wave filter for suppressing transverse modes provided in the fourth embodiment of the present invention;

[0031] Figure 10 This is a schematic diagram of the structure of the thin-film surface acoustic wave filter for suppressing transverse modes provided in the fifth embodiment of the present invention;

[0032] Figure 11 This is a schematic diagram of the structure of the thin-film surface acoustic wave filter for suppressing transverse modes provided in the sixth embodiment of the present invention. Detailed implementation manners

[0033] In order to enable those skilled in the art to better understand the technical solutions of the present disclosure, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present disclosure.

[0034] It should be noted that the terms "first", "second", etc. in the specification and claims of the present disclosure and the above-mentioned accompanying drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present disclosure described here can be implemented in an order other than those illustrated or described here. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0035] Secondly, the present application will be described in detail with reference to the schematic diagrams. When describing the embodiments of the present application, for the convenience of explanation, the cross-sectional views showing the device structure will be enlarged locally not in accordance with the general scale, and the schematic diagrams are only examples and should not limit the scope of protection of the present application herein. In addition, in actual production, three-dimensional spatial dimensions including length, width, and depth should be included.

[0036] Next, with reference to specific embodiments, the thin-film surface acoustic wave filter for suppressing transverse modes and its manufacturing method provided by the embodiments of the present application will be described.

[0037] Embodiment 1

[0038] As Figure 1 and Figure 2 shown, the thin-film surface acoustic wave filter for suppressing transverse modes provided by the embodiments of the present application includes: a substrate 100, a piezoelectric thin film layer 130, and an interdigital electrode structure 140. The piezoelectric thin film layer 130 is formed on the substrate 100; the interdigital electrode structure 140 is disposed on a side of the piezoelectric thin film layer 130 away from the substrate 100, and includes an electrode lead-out portion 141 and a plurality of interdigital electrodes 142 arranged alternately along a first direction D1 and along a second direction D2 intersecting the first direction D1. One end of the interdigital electrode 142 is a free end, and the other end of the interdigital electrode 142 is connected to the electrode lead-out portion 141. Moreover, the thin-film surface acoustic wave filter further includes a transverse mode suppression electrode structure 120, which is disposed between the piezoelectric thin film layer 130 and the substrate 100, and at least a part of the transverse mode suppression electrode structure 120 overlaps with the free ends of the plurality of interdigital electrodes 142 in a third direction D3 perpendicular to the main surface of the piezoelectric thin film layer 130.

[0039] Among them, the material of the transverse mode suppression electrode structure 120 can be an alloy or composite structure of metals such as titanium, copper, aluminum, gold, silver, platinum, etc. The material of the deposited piezoelectric thin film layer 130 can be LiNO3 or LaTO3. The material of the interdigital electrode structure 140 is a metal, and its forming method can be a lithography process.

[0040] In this article, the overlapping of a plurality of components in a certain direction means that the orthographic projections of the plurality of components in the direction overlap with each other. That is to say, the orthographic projections of the transverse mode suppression electrode structure 120 and the free ends of the plurality of interdigital electrodes 142 overlap with each other in a third direction D3 perpendicular to the main surface of the piezoelectric thin film layer 130.

[0041] As Figure 2As shown, the interdigital electrode structure 140 includes first interdigital electrodes 142a and second interdigital electrodes 142b that extend along a first direction D1 and are alternately arranged along a second direction D2 intersecting the first direction D1; the transverse mode suppression electrode structure 120 includes a first transverse mode suppression electrode 121 and a second transverse mode suppression electrode 122. The first transverse mode suppression electrode 121 extends along the second direction D2, and at least a part of the first transverse mode suppression electrode 121 overlaps with the free end of the first interdigital electrode 142a in a third direction D3. The second transverse mode suppression electrode 122 extends along the second direction D2, and at least a part of the second transverse mode suppression electrode 122 overlaps with the free end of the second interdigital electrode 142b in the third direction D3.

[0042] Continuing as Figure 2 As shown, the first transverse mode suppression electrode 121 overlaps with the free end of the first interdigital electrode 142a in the third direction D3 and also overlaps with the gap between adjacent interdigital electrodes (e.g., adjacent first interdigital electrodes 142a and second interdigital electrodes 142b) among the plurality of interdigital electrodes 142. The second transverse mode suppression electrode 122 overlaps with the free end of the second interdigital electrode 142b in the third direction D3 and also overlaps with the gap between adjacent interdigital electrodes (e.g., adjacent first interdigital electrodes 142a and second interdigital electrodes 142b) among the plurality of interdigital electrodes 142.

[0043] Continuing as Figure 1 As shown, the thin film surface acoustic wave filter for suppressing the transverse mode proposed in this embodiment further includes a dielectric layer 110. The dielectric layer 110 is located between the substrate 100 and the piezoelectric thin film layer 130 and buries the transverse mode suppression electrode structure 120. Among them, the material of the dielectric layer 110 is SiO2.

[0044] Continuing as Figure 2As shown in the figure, the thin film surface acoustic wave filter for suppressing transverse modes proposed in this embodiment further includes a first reflection grating 143 and a second reflection grating 144 disposed on opposite sides of the interdigital electrode structure 142 in the second direction D2. The first reflection grating 143 includes a plurality of first reflection electrodes 143a and a first bus bar 143b. The plurality of first reflection electrodes 143a extend along the first direction D1 and are arranged at intervals along the second direction D2. The first bus bar 143b extends along the second direction D2 and is connected to the plurality of first reflection electrodes 143a. The second reflection grating 144 includes a plurality of second reflection electrodes 144a and a second bus bar 144b. The plurality of second reflection electrodes 144a extend along the first direction D1 and are arranged at intervals along the second direction D2. The second bus bar 144b extends along the second direction D2 and is connected to the plurality of second reflection electrodes 144a. Moreover, the first transverse mode suppression electrode 121 overlaps with the plurality of first reflection electrodes 143a and the plurality of second reflection electrodes 144a in the third direction D3; and the second transverse mode suppression electrode 122 also overlaps with the plurality of first reflection electrodes 143a and the plurality of second reflection electrodes 144a in the third direction D3.

[0045] Continue as Figure 2 As shown in the figure, the electrode lead-out portion 141 includes a first electrode lead-out portion 141a and a second electrode lead-out portion 141b that are oppositely arranged and extend along the second direction. The first electrode lead-out portion 141a is connected to the first interdigital electrode 142a, and the second electrode lead-out portion 141b is connected to the second interdigital electrode 142b.

[0046] In summary, in the thin film surface acoustic wave filter for suppressing transverse modes proposed in this embodiment, the interdigital electrode structure is disposed on the side of the piezoelectric thin film layer away from the substrate, and the transverse mode suppression electrode structure is ingeniously disposed between the piezoelectric thin film layer and the substrate. This design makes full use of the original piezoelectric thin film layer in the thin film surface acoustic wave filter as the isolation layer between the transverse mode suppression electrode and the interdigital electrode, without the need to add an additional isolation layer, and at the same time ensures the close distance between the interdigital electrode and the piezoelectric thin film layer, thus avoiding the negative effect on the filtering effect of the filter caused by the increased distance. Moreover, the transverse mode suppression electrode structure overlaps with at least the free ends of the plurality of interdigital electrodes in the direction perpendicular to the main surface of the piezoelectric thin film layer. Therefore, this transverse mode suppression electrode structure can change the sound velocity field of the transverse propagation of the thin film surface acoustic wave filter, effectively suppress the transverse mode, and significantly improve the transverse mode suppression ability of the thin film surface acoustic wave filter.

[0047] In addition, in combination with Figures 1 - 6 As shown in the figure, this embodiment also discloses a manufacturing method for implementing the above-mentioned thin film surface acoustic wave filter for suppressing transverse modes, which includes the following steps:

[0048] As shown Figure 3 in FIG. 1, a substrate 100 is provided, and then a dielectric layer 110 is formed on one side surface of the substrate 100. Among them, the substrate 100 is a silicon substrate, a silicon-on-insulator substrate, a silicon carbide substrate, etc. The material of the dielectric layer can be SiO2, and its formation method can be a thermal oxidation process, a physical vapor deposition (PVD) process, a chemical vapor deposition (CVD) process, etc.

[0049] As shown Figure 4 in FIG. 2, a transverse mode suppression electrode structure 120 is formed on the side of the dielectric layer 110 away from the substrate 100. Among them, the transverse mode suppression electrode structure 120 can be fabricated on the side of the dielectric layer 110 away from the substrate 100 by a photolithography coating process, and its material can be an alloy or composite structure of metals such as titanium, copper, aluminum, gold, silver, platinum, etc. It should be particularly noted that the photolithography coating process is a conventional process in the current semiconductor field. By using this process, a transverse mode suppression electrode structure 120 with a specified pattern can be formed on the side of the dielectric layer 110 away from the substrate 100.

[0050] As shown Figure 5 in FIG. 3, the dielectric layer 110 is continuously deposited to bury the transverse mode suppression electrode structure 120 in the dielectric layer.

[0051] As shown Figure 6 in FIG. 4, a piezoelectric thin film layer 130 is deposited on the side of the dielectric layer 110 away from the substrate 100. That is to say, the transverse mode suppression electrode structure 120 is neither in direct contact with the piezoelectric thin film layer 130 nor in direct contact with the substrate 100. Among them, the material of the deposited piezoelectric thin film layer 130 is LiNO3 or LaTO3.

[0052] As shown Figure 1 in FIG. 5, an interdigital electrode structure 140 is formed on the side surface of the piezoelectric thin film layer 130 away from the substrate 100. Among them, the material of the interdigital electrode structure 140 is metal, and its formation method can be an overlay process.

[0053] As shown Figure 2 in FIG. 6, the interdigital electrode structure 140 includes a first interdigital electrode 142a and a second interdigital electrode 142b that extend along a first direction D1 and are alternately arranged along a second direction D2 intersecting with the first direction D1, a first electrode lead-out portion 141a and a second electrode lead-out portion 141b that are oppositely arranged and extend along the second direction D2, and a first reflection grating 143 and a second reflection grating 144 that are arranged on opposite sides of the interdigital electrode structure 142 in the second direction D2. One end of the first interdigital electrode 142a and the second interdigital electrode 142b is a free end, and the other ends of the first interdigital electrode 142a and the second interdigital electrode 142b are respectively connected to the first electrode lead-out portion 141a and the second electrode lead-out portion 141b.

[0054] As shown Figure 2 in the figure, the transverse mode suppression electrode structure 120 includes a first transverse mode suppression electrode 121 and a second transverse mode suppression electrode 122. The first transverse mode suppression electrode 121 extends along the second direction D2, and at least a part of the first transverse mode suppression electrode 121 overlaps with the free end of the first interdigital electrode 142a in the third direction D3. The second transverse mode suppression electrode 122 extends along the second direction D2, and at least a part of the second transverse mode suppression electrode 122 overlaps with the free end of the second interdigital electrode 142b in the third direction D3.

[0055] Wherein, the widths of the first transverse mode suppression electrode 121 and the second transverse mode suppression electrode 122 (i.e., the widths extending along the first direction D1) are equal, and there is a certain correlation between this width and the acoustic wave wavelength of the thin film surface acoustic wave filter (i.e., the wavelength of the acoustic wave generated by the interdigital transducer), and its expression is as follows:

[0056] ;

[0057] Wherein, y is the width of the first transverse mode suppression electrode 121 and the second transverse mode suppression electrode 122; x is the acoustic wave wavelength of the thin film surface acoustic wave filter, and this acoustic wave wavelength is usually twice the finger pitch of the interdigital transducer; k0, k1, and k2 are coefficients determined in advance based on the design of experiments (DOE) and the particle swarm algorithm.

[0058] Therefore, before manufacturing the first transverse mode suppression electrode 121 and the second transverse mode suppression electrode 122, it is also necessary to determine their widths according to the above formula. Specifically, it includes: first determining the finger pitch of the interdigital transducer, that is, the distance between the first interdigital electrode 142a and the second interdigital electrode 142b, then determining the acoustic wave wavelength of the thin film surface acoustic wave filter according to this distance, and finally substituting this acoustic wave wavelength into the above formula to calculate the widths of the first transverse mode suppression electrode 121 and the second transverse mode suppression electrode 122.

[0059] In the embodiment of the present invention, the specific steps for determining k0, k1, and k2 based on the design of experiments (DOE) and the particle swarm algorithm are as follows:

[0060] (1) According to the design of experiments (DOE), determine m groups of data ; wherein, each group of data is used to indicate that when ensuring that the transverse mode suppression ability of the thin film surface acoustic wave filter meets the requirements, when a selected acoustic wave wavelength is the corresponding widths of the first transverse mode suppression electrode 121 and the second transverse mode suppression electrode 122 are .

[0061] (2) Based on the obtained m groups of data, define the objective function of the particle swarm algorithm as:

[0062] ;

[0063] (3) Initialize the particle swarm: Each particle j represents a potential coefficient combination , randomly generate the initial position and velocity of each particle, initialize the individual best position (Pbest) as the initial position of each particle, and initialize the global best position (Gbest) as the position with the optimal fitness among all particles;

[0064] (4) Calculate the fitness value of each particle, that is, the value of the above objective function at the current particle position.

[0065] (5) Update the individual best position and the global best position: If the fitness value at the current position is better than the fitness value of the individual historical best position, then update the individual historical best position, and in the entire particle swarm, find the particle with the best fitness value and use its position as the global best position.

[0066] (6) Update the velocity and position of the particle according to the current position, velocity, individual historical best position, and global best position of the particle. Among them, the update formulas for the velocity and position of the particle are:

[0067] V j k+1 = ω k V j k + c 1 r 1( P j k - X j k ) + c 2 r 2( G k - X j k );

[0068] X j k+1 = X j k + V j k+1 ;

[0069] Among them, k represents the number of iterations that have been performed; j represents the particle number; V j k and X j k are respectively the velocity and position of the particle j before update; V j k+1 and X j k+1 are respectively the velocity and position of the particle j after update; P j k and G k are respectively the individual best position of the particle j and the global best position of the population; ω k represents the inertia weight after update using a preset PID module; c 1, c 2 represent learning factors; r 1, r 2 represent random numbers between 0 and 1.

[0070] (7) Repeat the steps of evaluating fitness, updating the individual and population best positions, and updating velocity and position until a predetermined number of iterations is reached or a preset stop condition is met (such as the fitness reaching a preset threshold).

[0071] (8) Finally, output the found global best position, that is, the optimal coefficient combination .

[0072] As Figure 2 shown, the first transverse mode suppression electrode 121 overlaps with the free end of the first interdigital electrode 142a in the third direction D3, and overlaps with the gap between adjacent interdigital electrodes (for example, adjacent first interdigital electrodes 142a and second interdigital electrodes 142b) among the multiple interdigital electrodes 142. The second transverse mode suppression electrode 122 overlaps with the free end of the second interdigital electrode 142b in the third direction D3, and overlaps with the gap between adjacent interdigital electrodes (for example, adjacent first interdigital electrodes 142a and second interdigital electrodes 142b) among the multiple interdigital electrodes 142.

[0073] As Figure 2As shown, the first reflection grating 143 includes a plurality of first reflection electrodes 143a and a first bus bar 143b. The plurality of first reflection electrodes 143a extend along the first direction D1 and are arranged at intervals along the second direction D2. The first bus bar 143b extends along the second direction D2 and is connected to the plurality of first reflection electrodes 143a. The second reflection grating 144 includes a plurality of second reflection electrodes 144a and a second bus bar 144b. The plurality of second reflection electrodes 144a extend along the first direction D1 and are arranged at intervals along the second direction D2. The second bus bar 144b extends along the second direction D2 and is connected to the plurality of second reflection electrodes 144a. Moreover, the first transverse mode suppression electrode 121 overlaps with the plurality of first reflection electrodes 143a and the plurality of second reflection electrodes 144a in the third direction D3; and the second transverse mode suppression electrode 122 overlaps with the plurality of first reflection electrodes 143a and the plurality of second reflection electrodes 144a in the third direction D3.

[0074] After adopting the above technical solution, the effect of the present invention is: Using this manufacturing method can change the sound velocity field of the surface acoustic wave filter propagating transversely, effectively suppressing the transverse mode, and at the same time not affecting the filtering effect of the filter.

[0075] Embodiment 2

[0076] As Figure 7 shown, the invention solution in this embodiment is basically the same as that in Embodiment 1, except that in the invention solution, the side of the transverse mode suppression electrode structure 120 close to the piezoelectric thin film layer 130 is directly in contact with the piezoelectric thin film layer 130, while the side of the transverse mode suppression electrode structure 120 far from the piezoelectric thin film layer 130 is not in contact with the substrate 100.

[0077] Embodiment 3

[0078] As Figure 8 shown, the invention solution in this embodiment is basically the same as that in Embodiment 1, except that in the invention solution, the side of the transverse mode suppression electrode structure 120 close to the piezoelectric thin film layer 130 is not in contact with the piezoelectric thin film layer 130, while the side of the transverse mode suppression electrode structure 120 far from the piezoelectric thin film layer 130 is directly in contact with the substrate 100.

[0079] Embodiment 4

[0080] As Figure 9As shown, the inventive concept in this embodiment is basically the same as that in the first embodiment, except that in the inventive concept of this embodiment, a plurality of first separation gaps and second separation gaps are respectively provided on the first transverse mode suppression electrode 121 and the second transverse mode suppression electrode 122. The first separation gaps divide the first transverse mode suppression electrode 121 into a plurality of first transverse mode suppression blocks 121a arranged at intervals, and the second separation gaps divide the second transverse mode suppression electrode 122 into a plurality of second transverse mode suppression blocks 122a arranged at intervals.

[0081] Among them, the first transverse mode suppression block 121a overlaps with the free end of the first interdigital electrode 142a in the third direction D3. The second transverse mode suppression block 122a overlaps with the free end of the second interdigital electrode 142b in the third direction D3. The first transverse mode suppression block 121a and the second transverse mode suppression block 122a also overlap with the plurality of first reflection electrodes 143a and the plurality of second reflection electrodes 144a in the third direction D3.

[0082] Among them, Figure 9 The first transverse mode suppression block 121a and the second transverse mode suppression electrode 122 in

[0083] Embodiment Five

[0084] As Figure 10 shown, the inventive concept in this embodiment is basically the same as that in the fourth embodiment, except that in the inventive concept of this embodiment, the side of the transverse mode suppression electrode structure 120 close to the piezoelectric thin film layer 130 is directly in contact with the piezoelectric thin film layer 130, while the side of the transverse mode suppression electrode structure 120 far from the piezoelectric thin film layer 130 is not in contact with the substrate 100.

[0085] Embodiment Six

[0086] As Figure 11 shown, the inventive concept in this embodiment is basically the same as that in the fourth embodiment, except that in the inventive concept of this embodiment, the side of the transverse mode suppression electrode structure 120 close to the piezoelectric thin film layer 130 is not in contact with the piezoelectric thin film layer 130, while the side of the transverse mode suppression electrode structure 120 far from the piezoelectric thin film layer 130 is directly in contact with the substrate 100.

[0087] The foregoing description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A thin-film surface acoustic wave filter for suppressing transverse modes, comprising a substrate, a piezoelectric thin-film layer, and an interdigital electrode structure; the piezoelectric thin-film layer is formed on the substrate; the interdigital electrode structure is disposed on a side of the piezoelectric thin-film layer away from the substrate and includes an electrode lead-out portion and a plurality of interdigital electrodes extending along a first direction and alternately arranged along a second direction intersecting with the first direction, one end of the interdigital electrode being a free end, and the other end of the interdigital electrode being connected to the electrode lead-out portion; characterized in that: It further includes a transverse mode suppression electrode structure disposed between the piezoelectric thin-film layer and the substrate, and at least a part of the transverse mode suppression electrode structure overlaps with the free ends of the plurality of interdigital electrodes in a third direction perpendicular to the main surface of the piezoelectric thin-film layer; wherein, the piezoelectric thin-film layer is reused as an isolation layer between the transverse mode suppression electrode structure and the interdigital electrode structure.

2. The thin film surface acoustic wave filter according to claim 1, wherein the plurality of interdigital electrodes include a first interdigital electrode and a second interdigital electrode that extend along a first direction and are alternately arranged along a second direction intersecting the first direction; characterized in that, The transverse mode suppression electrode structure includes a first transverse mode suppression electrode and a second transverse mode suppression electrode; the first transverse mode suppression electrode extends along the second direction, and at least a part of the first transverse mode suppression electrode overlaps with the free end of the first interdigital electrode in the third direction; the second transverse mode suppression electrode extends along the second direction, and at least a part of the second transverse mode suppression electrode overlaps with the free end of the second interdigital electrode in the third direction.

3. The thin film surface acoustic wave filter according to claim 2, characterized in that, The first transverse mode suppression electrode overlaps with the free end of the first interdigital electrode in the third direction and also overlaps with the gap between adjacent interdigital electrodes among the plurality of interdigital electrodes; and The second transverse mode suppression electrode overlaps with the free end of the second interdigital electrode in the third direction and also overlaps with the gap between adjacent interdigital electrodes of the plurality of interdigital electrodes.

4. The thin film surface acoustic wave filter according to claim 2, wherein A plurality of first separation gaps are provided on the first transverse mode suppression electrode, and the first separation gaps divide the first transverse mode suppression electrode into a plurality of first transverse mode suppression blocks arranged at intervals, and the first transverse mode suppression blocks overlap with the free ends of the first interdigital electrodes in the third direction; and A plurality of second separation gaps are provided on the second transverse mode suppression electrode, and the second separation gaps divide the second transverse mode suppression electrode into a plurality of second transverse mode suppression blocks arranged at intervals, and the second transverse mode suppression blocks overlap with the free ends of the second interdigital electrodes in the third direction.

5. The thin film surface acoustic wave filter according to claim 1, wherein It further includes a dielectric layer; the dielectric layer is located between the substrate and the piezoelectric thin-film layer and buries the transverse mode suppression electrode structure; wherein The transverse mode suppression electrode structure does not contact the substrate and the piezoelectric thin-film layer; or The side of the transverse mode suppression electrode structure close to the piezoelectric thin-film layer contacts the piezoelectric thin-film layer, and the side of the transverse mode suppression electrode structure away from the piezoelectric thin-film layer does not contact the substrate; or The side of the transverse mode suppression electrode structure close to the piezoelectric thin-film layer does not contact the piezoelectric thin-film layer, and the side of the transverse mode suppression electrode structure away from the piezoelectric thin-film layer contacts the substrate.

6. The thin-film surface acoustic wave filter according to claim 5, wherein, The material of the dielectric layer is SiO2.

7. The thin film surface acoustic wave filter according to claim 3 or 4, wherein the thin film surface acoustic wave filter further includes a first reflection grating and a second reflection grating disposed on opposite sides of the interdigital electrode structure in the second direction, each reflection grating including a plurality of reflection electrodes and a bus bar, the plurality of reflection electrodes extending in the first direction and being spaced apart in the second direction, the bus bar extending in the second direction and connected to the plurality of reflection electrodes; characterized in that: The first transverse mode suppression electrode further overlaps with the plurality of reflection electrodes of each reflection grating in the third direction; and The second transverse mode suppression electrode further overlaps with the plurality of reflection electrodes of each reflection grating in the third direction.

8. The surface acoustic wave filter according to claim 2, wherein The electrode lead-out portion includes a first electrode lead-out portion and a second electrode lead-out portion that are oppositely disposed and extend in the second direction, the first electrode lead-out portion being connected to the first interdigital electrode, and the second electrode lead-out portion being connected to the second interdigital electrode.

9. A manufacturing method of a thin-film surface acoustic wave filter for suppressing transverse modes, characterized in that, Comprising: Providing a substrate; Forming a transverse mode suppression electrode structure on one side of the substrate; Forming a piezoelectric thin film layer on a side of the transverse mode suppression electrode structure away from the substrate; And Forming an interdigital electrode structure on a side of the piezoelectric thin film layer away from the substrate, the interdigital electrode structure including an electrode lead-out portion and a plurality of interdigital electrodes extending in a first direction and alternately arranged in a second direction intersecting the first direction, one end of the interdigital electrode being a free end, and the other end of the interdigital electrode being connected to the electrode lead-out portion; Wherein, at least a part of the transverse mode suppression electrode structure overlaps with the free ends of the plurality of interdigital electrodes in a third direction perpendicular to the main surface of the piezoelectric thin film layer; Wherein, the piezoelectric thin film layer is reused as an isolation layer between the transverse mode suppression electrode structure and the interdigital electrode structure.

10. The manufacturing method according to claim 9, characterized in that, The plurality of interdigital electrodes include a first interdigital electrode and a second interdigital electrode extending in the first direction and alternately arranged in a second direction intersecting the first direction; the transverse mode suppression electrode structure includes a first transverse mode suppression electrode and a second transverse mode suppression electrode; the first transverse mode suppression electrode extends in the second direction, and at least a part of the first transverse mode suppression electrode overlaps with the free end of the first interdigital electrode in the third direction; the second transverse mode suppression electrode extends in the second direction, and at least a part of the second transverse mode suppression electrode overlaps with the free end of the second interdigital electrode in the third direction; Wherein, the first transverse mode suppression electrode overlaps with the free end of the first interdigital electrode in the third direction and also overlaps with the gap between adjacent interdigital electrodes among the plurality of interdigital electrodes; and the second transverse mode suppression electrode overlaps with the free end of the second interdigital electrode in the third direction and also overlaps with the gap between adjacent interdigital electrodes of the plurality of interdigital electrodes; or A number of first separation gaps are provided on the first transverse mode suppression electrode, and the first separation gaps divide the first transverse mode suppression electrode into a number of first transverse mode suppression blocks arranged at intervals, and the first transverse mode suppression blocks overlap with the free ends of the first interdigital electrodes in the third direction; and a number of second separation gaps are provided on the second transverse mode suppression electrode, and the second separation gaps divide the second transverse mode suppression electrode into a number of second transverse mode suppression blocks arranged at intervals, and the second transverse mode suppression blocks overlap with the free ends of the second interdigital electrodes in the third direction.

11. The manufacturing method according to claim 10, characterized in that, The manufacturing method further includes: manufacturing a dielectric layer; the dielectric layer is located between the substrate and the piezoelectric thin film layer and buries the transverse mode suppression electrode structure; wherein the transverse mode suppression electrode structure is not in contact with the substrate and the piezoelectric thin film layer; or one side of the transverse mode suppression electrode structure close to the piezoelectric thin film layer is in contact with the piezoelectric thin film layer, and the side of the transverse mode suppression electrode structure far from the piezoelectric thin film layer is not in contact with the substrate; or one side of the transverse mode suppression electrode structure close to the piezoelectric thin film layer is not in contact with the piezoelectric thin film layer, and the side of the transverse mode suppression electrode structure far from the piezoelectric thin film layer is in contact with the substrate; wherein the material of the dielectric layer is SiO2.

12. The manufacturing method according to claim 11, characterized in that, The manufacturing method further includes: forming a first reflection grating and a second reflection grating on the side of the piezoelectric thin film layer away from the substrate, the first reflection grating and the second reflection grating are arranged on opposite sides of the interdigital electrode structure in the second direction, wherein each reflection grating includes a plurality of reflection electrodes and bus bars, the plurality of reflection electrodes extend in the first direction and are arranged at intervals in the second direction, the bus bar extends in the second direction and is connected to the plurality of reflection electrodes; wherein, the first transverse mode suppression electrode further overlaps with the plurality of reflection electrodes of each reflection grating in the third direction; and the second transverse mode suppression electrode further overlaps with the plurality of reflection electrodes of each reflection grating in the third direction; and The electrode lead-out part includes a first electrode lead-out part and a second electrode lead-out part which are oppositely arranged and extend in the second direction, the first electrode lead-out part is connected to the first interdigital electrode, and the second electrode lead-out part is connected to the second interdigital electrode.

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