Thin film surface acoustic wave filter capable of inhibiting transverse mode and manufacturing method of thin film surface acoustic wave filter

Abstract

The invention discloses a thin film surface acoustic wave filter for inhibiting a transverse mode and a manufacturing method thereof. Relates to the technical field of filtering. An interdigital electrode structure in the film surface acoustic wave filter capable of suppressing the transverse mode is arranged on one side, far away from a substrate, of a piezoelectric film layer, and a transverse mode suppression electrode structure is ingeniously arranged between the piezoelectric film layer and the substrate. According to the thin film surface acoustic wave filter, the original piezoelectric thin film layer in the thin film surface acoustic wave filter is fully utilized as the isolation layer of the transverse mode suppression electrode and the interdigital electrode, the close distance between the interdigital electrode and the piezoelectric thin film layer is ensured without additionally adding the isolation layer, and the negative effect on the filtering effect of the filter due to the increase of the distance is avoided. Moreover, the transverse mode suppression electrode structure is at least overlapped with the free ends of the plurality of interdigital electrodes in the direction perpendicular to the main surface of the piezoelectric film layer, so that the sound velocity field of transverse propagation of the film surface acoustic wave filter is changed, the transverse mode is effectively suppressed, and the transverse mode suppression capability of the film surface acoustic wave filter is improved.

Description

Technical Field

[0001] The present application relates to the field of filtering technology, and in particular 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 RF front-ends due to their small size and good performance. Surface acoustic wave filters include thin-film surface acoustic wave (TF-SAW) filters and temperature compensated SAW (TC-SAW) filters. In the current mainstream thin-film surface acoustic wave (TF-SAW) filters, due to the structural limitations of thin-film surface acoustic wave filters, the interdigitated electrodes in the laminated surface acoustic wave filters will inevitably excite high-order lateral clutter. When reflected in the admittance curve, it can be found that there will be many spikes in the resonant frequency towards the high frequency direction, resulting in the deterioration of the flatness of the resonator or filter.

[0003] In order to suppress the lateral noise of the surface acoustic wave filter, an existing lateral mode suppression scheme is to form a cross-finger electrode on the top of the piezoelectric substrate, and deposit a passivation layer on the cross-finger electrode to form a lateral mode suppression electrode, and the cross-finger electrode and the cross-finger electrode are separated by the passivation layer to prevent the cross-finger electrode from sending a short circuit fault. However, there is a problem with this layout of setting the cross-mode suppression electrode above the cross-finger electrode: the cross-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 it with a non-metallic dielectric layer, and finally set the interdigital electrode on this layer. However, there is a problem with this structural design: the interdigital electrode and the piezoelectric substrate are isolated by the transverse mode suppression electrode and the non-metallic dielectric layer, resulting in the interdigital electrode being remote from the piezoelectric substrate (especially when the piezoelectric substrate adopts a composite structure composed of piezoelectric film, silicon dioxide and silicon substrate). This layout causes the electrical signal generated by the interdigital electrode to be significantly attenuated when it reaches the piezoelectric film, which in turn has an adverse effect on the performance of the filter and reduces the filtering effect.

[0005] Therefore, there is an urgent need for a technical solution that can improve the ability of thin-film surface acoustic wave filters to suppress transverse modes without affecting their 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 method for manufacturing the same.

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

[0008] Optionally, the plurality of interdigitated electrodes include first interdigitated electrodes and second interdigitated electrodes extending along a first direction and alternately arranged along 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 along the second direction, and at least a portion of the first transverse mode suppression electrode overlaps with at least a free end of the first interdigitated electrode in the third direction; the second transverse mode suppression electrode extends along the second direction, and at least a portion of the second transverse mode suppression electrode overlaps with a free end of the second interdigitated electrode in the third direction.

[0009] Optionally, the first transverse mode suppression electrode overlaps with the free end of the first interdigitated electrode in the third direction, and overlaps with the gaps between adjacent interdigitated electrodes among the multiple interdigitated electrodes; and the second transverse mode suppression electrode overlaps with the free end of the second interdigitated electrode in the third direction, and overlaps with the gaps between adjacent interdigitated electrodes among the multiple interdigitated electrodes.

[0010] Optionally, a plurality of first separation gaps are provided on the first transverse mode suppression electrode, the first separation gaps separate 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 interdigitated electrodes in the third direction; and a plurality of second separation gaps are provided on the second transverse mode suppression electrode, the second separation gaps separate 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 interdigitated electrodes in the third direction.

[0011] Optionally, the thin film surface acoustic wave filter also includes a dielectric layer; the dielectric layer is located between the substrate and the piezoelectric 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 film layer; or the side of the transverse mode suppression electrode structure close to the piezoelectric film layer is in contact with the piezoelectric film layer, and the side of the transverse mode suppression electrode structure away from the piezoelectric film layer is not in contact with the substrate; or the side of the transverse mode suppression electrode structure close to the piezoelectric film layer is not in contact with the piezoelectric film layer, and the side of the transverse mode suppression electrode structure away from the piezoelectric 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 also includes a first reflection grating and a second reflection grating arranged on opposite sides of the interdigitated electrode structure in the second direction, wherein each reflection grating includes a plurality of reflection electrodes and a bus bar, the plurality of reflection electrodes extend along the first direction and are arranged at intervals along the second direction, the bus bar extends along the second direction and is connected to the plurality of reflection electrodes; the first transverse mode suppression electrode also overlaps with the plurality of reflection electrodes of each of the reflection gratings in the third direction; and the second transverse mode suppression electrode also overlaps with the plurality of reflection electrodes of each of the reflection gratings 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 which are arranged opposite to each other and extend along 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 an embodiment of the present disclosure, a method for manufacturing a thin-film surface acoustic wave filter that suppresses transverse modes is also provided, comprising: providing a substrate; forming a transverse mode suppression electrode structure on one side of the substrate; forming a piezoelectric film layer on a side of the transverse mode suppression electrode structure away from the substrate; and forming an interdigitated electrode structure on a side of the piezoelectric film layer away from the substrate, the interdigitated electrode structure comprising an electrode lead-out portion and a plurality of interdigitated electrodes extending along a first direction and alternately arranged along a second direction intersecting the first direction, one end of the interdigitated electrode being a free end, and the other end of the interdigitated electrode being connected to the electrode lead-out portion; wherein at least a portion of the transverse mode suppression electrode structure overlaps with the free ends of the plurality of interdigitated electrodes in a third direction perpendicular to the main surface of the piezoelectric film layer.

[0016] Optionally, the plurality of interdigitated electrodes include first interdigitated electrodes and second interdigitated electrodes extending along a first direction and alternately arranged along 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 along the second direction, and at least a portion of the first transverse mode suppression electrode overlaps with at least a free end of the first interdigitated electrode in the third direction; the second transverse mode suppression electrode extends along the second direction, and at least a portion of the second transverse mode suppression electrode overlaps with a free end of the second interdigitated electrode in the third direction.

[0017] Optionally, the first transverse mode suppression electrode overlaps with the free end of the first interdigitated electrode in the third direction, and overlaps with the gaps between adjacent interdigitated electrodes among the multiple interdigitated electrodes; and the second transverse mode suppression electrode overlaps with the free end of the second interdigitated electrode in the third direction, and overlaps with the gaps between adjacent interdigitated electrodes among the multiple interdigitated electrodes.

[0018] Optionally, a plurality of first separation gaps are provided on the first transverse mode suppression electrode, the first separation gaps separate 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 interdigitated electrodes in the third direction; and a plurality of second separation gaps are provided on the second transverse mode suppression electrode, the second separation gaps separate 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 interdigitated electrodes in the third direction.

[0019] Optionally, the manufacturing method also includes: manufacturing a dielectric layer; the dielectric layer is located between the substrate and the piezoelectric 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 film layer; or the side of the transverse mode suppression electrode structure close to the piezoelectric film layer is in contact with the piezoelectric film layer, and the side of the transverse mode suppression electrode structure away from the piezoelectric film layer is not in contact with the substrate; or the side of the transverse mode suppression electrode structure close to the piezoelectric film layer is not in contact with the piezoelectric film layer, and the side of the transverse mode suppression electrode structure away from the piezoelectric 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 reflection grating and a second reflection grating on a side of the piezoelectric film layer away from the substrate, the first reflection grating and the second reflection grating are arranged on opposite sides of the interdigitated electrode structure in the second direction, wherein each reflection grating includes a plurality of reflection electrodes and a bus bar, the plurality of reflection electrodes extend along the first direction and are arranged at intervals along the second direction, the bus bar extends along the second direction and is connected to the plurality of reflection electrodes; wherein the first transverse mode suppression electrode also overlaps with the plurality of reflection electrodes of each of the reflection gratings in the third direction; and the second transverse mode suppression electrode also overlaps with the plurality of reflection electrodes of each of the reflection gratings 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 arranged opposite to each other and extend along 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.

[0023] In the thin film surface acoustic wave filter for suppressing transverse modes proposed in the present application, the interdigitated electrode structure is arranged on the side of the piezoelectric film layer away from the substrate, and the transverse mode suppression electrode structure is cleverly arranged between the piezoelectric film layer and the substrate. This design makes full use of the original piezoelectric film layer in the thin film surface acoustic wave filter as an isolation layer between the transverse mode suppression electrode and the interdigitated electrode, without the need to add an additional isolation layer, while also ensuring the close distance between the interdigitated electrode and the piezoelectric film layer, thereby avoiding the negative effects on the filtering effect of the filter due to the increase in distance. In addition, the transverse mode suppression electrode structure overlaps with at least the free ends of the multiple interdigitated electrodes in the direction perpendicular to the main surface of the piezoelectric film layer, so the 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 capability of the thin film surface acoustic wave filter. BRIEF 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 illustrative embodiments of the present disclosure and their descriptions are used to explain the present disclosure and do not constitute an improper limitation on the present disclosure. In the drawings: Figure 1 It is a schematic structural diagram of a thin-film surface acoustic wave filter for suppressing transverse modes provided in Embodiment 1 of the present invention; Figure 2 It is used to present Figure 1 A schematic plan view of the association relationship between the interdigital electrode structure, the reflection grating and the transverse mode suppression electrode structure in each direction in the provided transverse mode suppression thin film surface acoustic wave filter; Figure 3-Figure 6It is a schematic diagram of various structures in the manufacturing process of the thin film surface acoustic wave filter for suppressing transverse modes provided by the first embodiment of the present invention; Figure 7 It is a schematic structural diagram of a thin-film surface acoustic wave filter for suppressing transverse modes provided by the second embodiment of the present invention; Figure 8 It is a schematic structural diagram of a thin-film surface acoustic wave filter for suppressing transverse modes provided by Embodiment 3 of the present invention; Fig. 9 It is a schematic structural diagram of a thin-film surface acoustic wave filter for suppressing transverse modes provided by a fourth embodiment of the present invention; Fig.10 It is a schematic structural diagram of a thin-film surface acoustic wave filter for suppressing transverse modes provided by Embodiment 5 of the present invention; Fig.11 It is a schematic diagram of the structure of a thin film surface acoustic wave filter for suppressing transverse modes provided in Example 6 of the present invention. DETAILED DESCRIPTION

[0025] 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 drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only embodiments of a part of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present disclosure.

[0026] It should be noted that the terms "first", "second", etc. in the specification and claims of the present disclosure and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present disclosure described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products, or devices.

[0027] 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.

[0028] In the following, in conjunction with specific embodiments, the thin film surface acoustic wave filter for suppressing transverse modes and the method for manufacturing the same provided in the embodiments of the present application are described.

[0029] Embodiment 1 like Figure 1 and Figure 2 As shown, the thin film surface acoustic wave filter for suppressing transverse modes provided in the embodiment of the present application includes: a substrate 100, a piezoelectric film layer 130 and an interdigital electrode structure 140. The piezoelectric film layer 130 is formed on the substrate 100; the interdigital electrode structure 140 is arranged on the side of the piezoelectric film layer 130 away from the substrate 100, and includes an electrode lead-out portion 141 and a plurality of interdigital electrodes 142 extending along a first direction D1 and arranged alternately 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. In addition, the thin film surface acoustic wave filter also includes a transverse mode suppression electrode structure 120, which is arranged between the piezoelectric film layer 130 and the substrate 100, and at least a portion 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 film layer 130.

[0030] The material of the transverse mode suppression electrode structure 120 may be an alloy or composite structure of metals such as titanium, copper, aluminum, gold, silver, platinum, etc. The material of the deposited piezoelectric film layer 130 may be LiNO3 or LaTO3. The material of the interdigital electrode structure 140 is metal, and the formation method thereof may be an overlay process.

[0031] In this context, overlapping of multiple components in a certain direction means that the orthographic projections of the multiple components in the direction overlap each other. That is, the orthographic projections of the free ends of the transverse mode suppression electrode structure 120 and the multiple interdigital electrodes 142 in the third direction D3 perpendicular to the main surface of the piezoelectric film layer 130 overlap each other.

[0032] like Figure 2As shown, the interdigitated electrode structure 140 includes first interdigitated electrodes 142a and second interdigitated electrodes 142b extending along a first direction D1 and 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 portion of the first transverse mode suppression electrode 121 overlaps with the free end of the first interdigitated electrode 142a in the third direction D3, and the second transverse mode suppression electrode 122 extends along the second direction D2, and at least a portion of the second transverse mode suppression electrode 122 overlaps with the free end of the second interdigitated electrode 142b in the third direction D3.

[0033] Continue 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 overlaps with the gap between adjacent interdigital electrodes (for example, 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 overlaps with the gap between adjacent interdigital electrodes (for example, adjacent first interdigital electrodes 142a and second interdigital electrodes 142b) among the plurality of interdigital electrodes 142.

[0034] Continue as Figure 1 As shown, the thin film surface acoustic wave filter for suppressing transverse mode proposed in this embodiment further includes a dielectric layer 110, which is located between the substrate 100 and the piezoelectric film layer 130 and buries the transverse mode suppression electrode structure 120. The material of the dielectric layer 110 is SiO2.

[0035] Continue as Figure 2As shown, the thin film surface acoustic wave filter for suppressing transverse modes proposed in this embodiment also includes a first reflection grating 143 and a second reflection grating 144 arranged 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. Furthermore, the first transverse mode suppression electrode 121 also overlaps with the multiple first reflective electrodes 143a and the multiple second reflective electrodes 144a in the third direction D3; and the second transverse mode suppression electrode 122 also overlaps with the multiple first reflective electrodes 143a and the multiple second reflective electrodes 144a in the third direction D3.

[0036] Continue as Figure 2 As shown, the electrode lead portion 141 includes a first electrode lead portion 141a and a second electrode lead portion 141b which are arranged opposite to each other and extend along the second direction. The first electrode lead portion 141a is connected to the first interdigitated electrode 142a, and the second electrode lead portion 141b is connected to the second interdigitated electrode 142b.

[0037] In summary, in the thin film surface acoustic wave filter for suppressing transverse modes proposed in this embodiment, the interdigitated electrode structure is arranged on the side of the piezoelectric film layer away from the substrate, and the transverse mode suppression electrode structure is cleverly arranged between the piezoelectric film layer and the substrate. This design makes full use of the original piezoelectric film layer in the thin film surface acoustic wave filter as an isolation layer between the transverse mode suppression electrode and the interdigitated electrode, without the need to add an additional isolation layer, while also ensuring the close distance between the interdigitated electrode and the piezoelectric film layer, thereby avoiding the negative effects on the filtering effect of the filter due to the increase in distance. In addition, the transverse mode suppression electrode structure overlaps with at least the free ends of the multiple interdigitated electrodes in the direction perpendicular to the main surface of the piezoelectric film layer, so the 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 capability of the thin film surface acoustic wave filter.

[0038] In addition, combined Figures 1 to 6 As shown, this embodiment also discloses a method for manufacturing a thin film surface acoustic wave filter for suppressing the transverse mode, which comprises the following steps: like Figure 3 As shown, a substrate 100 is provided, and then a dielectric layer 110 is formed on one side surface of the substrate 100. 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 the formation method thereof can be a thermal oxidation process, a physical vapor deposition (PVD) process, or a chemical vapor deposition (CVD) process, etc.

[0039] like Figure 4 As shown, a transverse mode suppression electrode structure 120 is formed on the side of the dielectric layer 110 away from the substrate 100. The transverse mode suppression electrode structure 120 can be made on the side of the dielectric layer 110 away from the substrate 100 by using a photolithography coating process, and its material can be an alloy or a 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 of semiconductors at present, and the transverse mode suppression electrode structure 120 of a specified pattern can be formed on the side of the dielectric layer 110 away from the substrate 100 by using this process.

[0040] like Figure 5 As shown, the dielectric layer 110 is continuously deposited to bury the transverse mode suppression electrode structure 120 in the dielectric layer.

[0041] like Figure 6 As shown, a piezoelectric film layer 130 is deposited on the side of the dielectric layer 110 away from the substrate 100. That is, the transverse mode suppression electrode structure 120 is neither in direct contact with the piezoelectric film layer 130 nor in direct contact with the substrate 100. The material of the deposited piezoelectric film layer 130 is LiNO3 or LaTO3.

[0042] like Figure 1 As shown, an interdigital electrode structure 140 is formed on a surface of the piezoelectric film layer 130 that is away from the substrate 100. The interdigital electrode structure 140 is made of metal and can be formed by an overlay process.

[0043] like Figure 2 As shown, the interdigital electrode structure 140 includes first interdigital electrodes 142a and second interdigital electrodes 142b extending along a first direction D1 and alternately arranged along a second direction D2 intersecting the first direction D1, first electrode lead-out portions 141a and second electrode lead-out portions 141b arranged opposite to each other and extending along the second direction D2, and first reflective grids 143 and second reflective grids 144 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 connected to the first electrode lead-out portion 141a and the second electrode lead-out portion 141b, respectively.

[0044] like Figure 2 As shown, 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 portion of the first transverse mode suppression electrode 121 overlaps with the free end of the first interdigitated electrode 142a in the third direction D3, and the second transverse mode suppression electrode 122 extends along the second direction D2, and at least a portion of the second transverse mode suppression electrode 122 overlaps with the free end of the second interdigitated electrode 142b in the third direction D3.

[0045] 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 the widths are correlated to a certain extent with the wavelength of the sound waves of the thin film surface acoustic wave filter (i.e., the wavelength of the sound waves generated by the interdigital transducer), and the expression is as follows: ; Among them, y is the width of the first transverse mode suppression electrode 121 and the second transverse mode suppression electrode 122; x is the acoustic wavelength of the thin film surface acoustic wave filter, which is usually twice the pitch of the interdigital transducer; k0, k1 and k2 are coefficients determined in advance based on the experimental design method (DOE) and the particle swarm algorithm.

[0046] Therefore, before manufacturing the first transverse mode suppression electrode 121 and the second transverse mode suppression electrode 122, their widths need to be determined according to the above formula. Specifically, the steps include: first determining the interdigital spacing of the interdigital transducer, that is, the spacing between the first interdigital electrode 142a and the second interdigital electrode 142b, and then determining the acoustic wavelength of the thin film surface acoustic wave filter according to the spacing, and finally substituting the acoustic 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.

[0047] In an embodiment of the present invention, the specific steps of determining k0, k1 and k2 based on the experimental design method (DOE) and the particle swarm algorithm are as follows: (1) According to the experimental design method (DOE), determine m groups of data ; Each set of data is used to indicate that a sound wave wavelength is selected under the premise of ensuring that the transverse mode suppression capability of the thin film surface acoustic wave filter meets the requirements. When the width of the first transverse mode suppression electrode 121 and the second transverse mode suppression electrode 122 is .

[0048] (2) Based on the obtained m groups of data, the objective function of the particle swarm algorithm is defined as: ; (3) Initialize the particle swarm: Each particle j Represents a potential combination of coefficients , randomly generate the initial position and speed of each particle, initialize the individual best position (Pbest) as the initial position of each particle, and initialize the group best position (Gbest) as the position with the best fitness among all particles; (4) Calculate the fitness value of each particle, that is, the value of the above objective function at the current particle position.

[0049] (5) Update the individual best position and the group best position: If the fitness value of the current position is better than the fitness value of the individual historical best position, then update the individual historical best position and find the particle with the best fitness value in the entire particle group, and use its position as the global best position.

[0050] (6) Update the particle's speed and position based on the particle's current position, speed, individual historical best position, and global best position. The update formula for the particle's speed and position is: 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 ) ; X j k+1 = X j k + V j k+1 ; in, k Indicates the number of iterations; j represents the particle number; V j k , X jk Particles j Speed ​​and position before update; V j k+1 , X j k+1 Particles j Updated speed and position; P j k , G k Particles j The individual best position of and the global best position of the group; ω k Indicates the use of preset PID Inertia weight after module update; c 1. c 2 represents the learning factor; r 1. r 2 represents a random number between 0 and 1.

[0051] (7) Repeat the steps of evaluating fitness, updating the optimal positions of individuals and groups, and updating speed and position until a predetermined number of iterations is reached or a preset stopping condition is met (such as the fitness reaches a preset threshold).

[0052] (8) The final output is the global optimal position, that is, the optimal coefficient combination. .

[0053] like 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 overlaps with the gap between adjacent interdigital electrodes (for example, 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 overlaps with the gap between adjacent interdigital electrodes (for example, adjacent first interdigital electrodes 142a and second interdigital electrodes 142b) among the plurality of interdigital electrodes 142.

[0054] like Figure 2As shown, the first reflection grid 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 grid 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. In addition, the first transverse mode suppression electrode 121 also 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.

[0055] After adopting the above technical solution, the effect of the present invention is: the manufacturing method can be used to change the sound velocity field of the thin film surface acoustic wave filter in the lateral propagation, effectively suppress the transverse mode, and will not affect the filtering effect of the filter.

[0056] Embodiment 2 like Figure 7 As shown, the invention scheme in this embodiment is basically the same as that in the first embodiment, except that in the invention scheme, the side of the transverse mode suppression electrode structure 120 close to the piezoelectric film layer 130 is directly in contact with the piezoelectric film layer 130, while the side of the transverse mode suppression electrode structure 120 away from the piezoelectric film layer 130 is not in contact with the substrate 100.

[0057] Embodiment 3 like Figure 8 As shown, the invention scheme in this embodiment is basically the same as that in the first embodiment, except that in the invention scheme, the side of the transverse mode suppression electrode structure 120 close to the piezoelectric film layer 130 does not contact the piezoelectric film layer 130, while the side of the transverse mode suppression electrode structure 120 away from the piezoelectric film layer 130 directly contacts the substrate 100.

[0058] Embodiment 4 like Fig. 9 As shown, the invention scheme in this embodiment is basically the same as that in the first embodiment, except that in the invention scheme, a plurality of first separation gaps and a second separation gap are respectively provided on the first transverse mode suppression electrode 121 and the second transverse mode suppression electrode 122, and the first separation gaps separate 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 separate the second transverse mode suppression electrode 122 into a plurality of second transverse mode suppression blocks 122a arranged at intervals.

[0059] 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 reflective electrodes 143a and the plurality of second reflective electrodes 144a in the third direction D3.

[0060] in, Fig. 9 The first transverse mode suppression block 121a and the second transverse mode suppression electrode 122 are rectangular structures. Of course, the shapes of the first transverse mode suppression block 121a and the second transverse mode suppression block 122a separated by the first separation gap and the second separation gap can also be other shapes, such as polygons, or even a combination of different shapes, such as the first transverse mode suppression block 121a is a polygon, and the second transverse mode suppression block 122a is a rectangle.

[0061] Embodiment 5 like Fig.10 As shown, the invention scheme in this embodiment is basically the same as that in the fourth embodiment, except that in the invention scheme, the side of the transverse mode suppression electrode structure 120 close to the piezoelectric film layer 130 directly contacts the piezoelectric film layer 130, while the side of the transverse mode suppression electrode structure 120 away from the piezoelectric film layer 130 does not contact the substrate 100.

[0062] Embodiment 6 like Fig.11 As shown, the invention scheme in this embodiment is basically the same as that in the fourth embodiment, except that in the invention scheme, the side of the transverse mode suppression electrode structure 120 close to the piezoelectric film layer 130 does not contact the piezoelectric film layer 130, while the side of the transverse mode suppression electrode structure 120 away from the piezoelectric film layer 130 directly contacts the substrate 100.

[0063] The above 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 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. 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 thin film surface acoustic wave filter for suppressing transverse modes, comprising a substrate, a piezoelectric film layer and an interdigital electrode structure; the piezoelectric film layer is formed on the substrate; the interdigital electrode structure is arranged on a side of the piezoelectric film layer away from the substrate, comprising an electrode lead-out portion and a plurality of interdigital electrodes extending along a first direction and alternately arranged along 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; characterized in that: It also includes a transverse mode suppression electrode structure, which is arranged between the piezoelectric film layer and the substrate, and at least a portion 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 film layer.

2. The thin film surface acoustic wave filter according to claim 1, wherein the plurality of interdigital electrodes include first interdigital electrodes and second interdigital electrodes extending along a first direction and 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 portion of the first transverse mode suppression electrode overlaps with at least a free end of the first interdigitated electrode in the third direction; the second transverse mode suppression electrode extends along the second direction, and at least a portion of the second transverse mode suppression electrode overlaps with a free end of the second interdigitated 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 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 overlaps with the gaps between adjacent interdigital electrodes of the plurality of interdigital electrodes.

4. The thin film surface acoustic wave filter according to claim 2, characterized in that: A plurality of first separation gaps are provided on the first transverse mode suppression electrode, wherein the first separation gaps separate 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 free ends of the first interdigitated 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 separate 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 interdigitated electrodes in the third direction.

5. The thin film surface acoustic wave filter according to claim 1, characterized in that: It also includes a dielectric layer; the dielectric layer is located between the substrate and the piezoelectric 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 film layer; or The side of the transverse mode suppression electrode structure close to the piezoelectric film layer is in contact with the piezoelectric film layer, and the side of the transverse mode suppression electrode structure away from the piezoelectric film layer is not in contact with the substrate; or A side of the transverse mode suppression electrode structure close to the piezoelectric film layer is not in contact with the piezoelectric film layer, and a side of the transverse mode suppression electrode structure away from the piezoelectric film layer is in contact with the substrate.

6. The thin film surface acoustic wave filter according to claim 5, characterized in that: The material of the dielectric layer is SiO2.

7. The thin film surface acoustic wave filter according to claim 3 or 4, further comprising a first reflection grating and a second reflection grating arranged on opposite sides of the interdigitated electrode structure in the second direction, wherein each reflection grating comprises a plurality of reflection electrodes and a bus bar, the plurality of reflection electrodes extend along the first direction and are arranged at intervals along the second direction, the bus bar extends along the second direction and is connected to the plurality of reflection electrodes; characterized in that: The first transverse mode suppression electrode also overlaps with a plurality of reflection electrodes of each of the reflection gratings in the third direction; and The second transverse mode suppression electrode also overlaps with the plurality of reflection electrodes of each of the reflection gratings in the third direction.

8. The surface acoustic wave filter according to claim 2, characterized in that 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 along the second direction, the first electrode lead-out portion is connected to the first interdigital electrodes, and the second electrode lead-out portion is connected to the second interdigital electrodes.

9. A method for manufacturing a thin film surface acoustic wave filter for suppressing transverse modes, characterized in that: include: providing a substrate; forming a transverse mode suppression electrode structure on one side of the substrate; forming a piezoelectric film layer on a side of the transverse mode suppression electrode structure away from the substrate; as well as An interdigital electrode structure is formed on a side of the piezoelectric film layer away from the substrate, the interdigital electrode structure comprising an electrode lead-out portion and a plurality of interdigital electrodes extending along a first direction and alternately arranged along 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 portion 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 film layer.

10. The manufacturing method according to claim 9, characterized in that: The plurality of interdigital electrodes include first interdigital electrodes and second interdigital electrodes extending along a first direction and alternately arranged along 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 along the second direction, and at least a portion of the first transverse mode suppression electrode overlaps at least a 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 portion of the second transverse mode suppression electrode overlaps 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 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 overlaps with the gap between adjacent interdigital electrodes among the plurality of interdigital electrodes; or A plurality of first separation gaps are arranged on the first transverse mode suppression electrode, and the first separation gaps separate 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 interdigitated electrodes in the third direction; and a plurality of second separation gaps are arranged on the second transverse mode suppression electrode, and the second separation gaps separate 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 interdigitated electrodes in the third direction.

11. The manufacturing method according to claim 10, characterized in that: The manufacturing method also includes: manufacturing a dielectric layer; the dielectric layer is located between the substrate and the piezoelectric 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 film layer; or the side of the transverse mode suppression electrode structure close to the piezoelectric film layer is in contact with the piezoelectric film layer, and the side of the transverse mode suppression electrode structure away from the piezoelectric film layer is not in contact with the substrate; or the side of the transverse mode suppression electrode structure close to the piezoelectric film layer is not in contact with the piezoelectric film layer, and the side of the transverse mode suppression electrode structure away from the piezoelectric 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 a side of the piezoelectric film layer away from the substrate, the first reflection grating and the second reflection grating are arranged on opposite sides of the interdigitated electrode structure in the second direction, wherein each reflection grating includes a plurality of reflection electrodes and a bus bar, the plurality of reflection electrodes extend along the first direction and are arranged at intervals along the second direction, the bus bar extends along the second direction and is connected to the plurality of reflection electrodes; wherein the first transverse mode suppression electrode also overlaps with the plurality of reflection electrodes of each of the reflection gratings in the third direction; and the second transverse mode suppression electrode also overlaps with the plurality of reflection electrodes of each of the reflection gratings in the third direction; and 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 along the second direction, the first electrode lead-out portion is connected to the first interdigital electrodes, and the second electrode lead-out portion is connected to the second interdigital electrodes.

Images