Surface acoustic wave filter, radio frequency module and electronic equipment

Abstract

The embodiment of the invention provides a surface acoustic wave filter, a radio frequency module and electronic equipment, and relates to the technical field of electronic equipment. The surface acoustic wave filter comprises a piezoelectric layer, a multi-layer electrode layer and a functional layer. The multiple electrode layers are arranged on the piezoelectric layer, and the multiple electrode layers are stacked in the direction perpendicular to the piezoelectric layer. And at least part of the functional layer is arranged on the surface, close to the piezoelectric layer, of the at least one electrode layer. Wherein the lattice structure of the functional layer is matched with the lattice structure of the electrode layer in contact with the functional layer. According to the structural design, the stress borne by the electrode layer is effectively reduced, the problems of warping, layering and the like of the electrode layer are avoided, and the structural stability and the electrical performance of the surface acoustic wave filter are improved.

Description

Technical Field

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

[0002] In wireless communication systems, antennas, RF front ends, RF transceiver modules, and baseband signal processors are generally included. With the advent of the 5G era, the demand for antennas and RF front ends has increased rapidly. The RF front end is the basic component for converting digital signals into wireless RF signals, and it is also a core component of wireless communication systems. Among them, the RF filter plays an important role in frequency selection and interference filtering, and is one of the most important devices. In order to meet higher power tolerance and smaller macroscopic size, the design and manufacture of multi-layer metal electrodes in RF filters has become particularly important. Summary of the invention

[0003] The embodiments of the present application provide a surface acoustic wave filter, a radio frequency module and an electronic device, the purpose of which is to reduce the stress on the electrode layer, avoid problems such as warping and delamination of the electrode layer, and improve the structural stability and electrical performance of the surface acoustic wave filter.

[0004] To achieve the above objectives, the embodiments of the present application adopt the following technical solutions:

[0005] In a first aspect, a surface acoustic wave filter is provided. The surface acoustic wave filter includes a piezoelectric layer, a multilayer electrode layer, and a functional layer.

[0006] The plurality of electrode layers are arranged on the piezoelectric layer, and the plurality of electrode layers are stacked in a direction perpendicular to the piezoelectric layer. At least part of the functional layer is arranged on a surface of at least one electrode layer close to the piezoelectric layer.

[0007] The lattice structure of the functional layer matches the lattice structure of the electrode layer that the functional layer contacts.

[0008] The surface acoustic wave filter provided in the embodiment of the present application effectively improves the connection strength between the functional layer and the electrode layer by arranging a functional layer on the side of at least one electrode layer facing the piezoelectric layer, and arranging the lattice structure of the functional layer to match the lattice structure of the electrode layer contacted by the functional layer, thereby providing a tensile force parallel to the piezoelectric layer on the side of the electrode layer facing the piezoelectric layer, slowing down the tendency of the electrode layer to warp in a direction away from the piezoelectric layer, and effectively avoiding stratification between the electrode layer and the piezoelectric layer, thereby improving the reliability of the surface acoustic wave filter and optimizing the electrical performance of the surface acoustic wave filter.

[0009] In a possible implementation of the first aspect, the bonding strength between the functional layer and the electrode layer in contact with the functional layer is greater than or equal to 500 Mpa, thereby further enhancing the connection strength between the functional layer and the electrode layer, further slowing down the tendency of the electrode layer to warp away from the piezoelectric layer, avoiding delamination between the electrode layer and the piezoelectric layer, and improving the reliability of the surface acoustic wave filter.

[0010] In a possible implementation manner of the first aspect, an absolute value of a difference between an atomic radius of an element with the highest content in the functional layer and an atomic radius of an element with the highest content in an electrode layer contacting the functional layer is less than or equal to 20 pm.

[0011] That is, the atomic radius of the element with the highest content in the functional layer is set to be approximately the same as the atomic radius of the element with the highest content in the electrode layer that the functional layer contacts, thereby increasing the bonding strength between the two so that the bonding strength between the two is greater than or equal to 500Mpa.

[0012] In a possible implementation manner of the first aspect, at least a portion of the functional layer is disposed between the electrode layer closest to the piezoelectric layer among the multiple electrode layers and the piezoelectric layer.

[0013] That is, a functional layer is provided between the multilayer electrode layer as a whole and the piezoelectric layer, thereby alleviating the warping tendency of the multilayer electrode layer as a whole and avoiding stratification between the multilayer electrode layer as a whole and the piezoelectric layer, thereby improving the reliability of the surface acoustic wave filter.

[0014] In a possible implementation manner of the first aspect, at least a portion of the functional layer is disposed between two adjacent electrode layers.

[0015] That is, at least part of the functional layer can also be arranged on the surface of the electrode layer facing the piezoelectric layer in the multi-layer electrode layer, which is away from the piezoelectric layer, to effectively alleviate the warping tendency of the electrode layer with a higher probability of warping in the multi-layer electrode layer, avoid delamination of the electrode layer and the lower electrode layer, or cause delamination between the lower electrode layer and the piezoelectric layer, thereby also improving the reliability of the surface acoustic wave filter.

[0016] In a possible implementation of the first aspect, the functional layer includes a first sublayer and a second sublayer. The first sublayer is disposed on a surface of at least one electrode layer close to the piezoelectric layer; the second sublayer is disposed on a side surface of at least one electrode layer; and the first sublayer and the second sublayer are disposed integrally.

[0017] By arranging functional layers on the surface of the electrode layer facing the piezoelectric layer and on the side of the electrode layer, and arranging the two parts of the functional layers (i.e., the first sublayer and the second sublayer) as an integrated whole, the bonding strength between the electrode layer and the functional layer is strong, and the electrode layer can be effectively constrained from the surface of the electrode layer facing the piezoelectric layer and on the side of the electrode layer, further reducing the warping tendency of the electrode layer and improving the electrical performance of the surface acoustic wave filter.

[0018] In a possible implementation manner of the first aspect, the functional layer surrounds all surfaces of each electrode layer in the at least one electrode layer.

[0019] That is, among the multi-layer electrode layers, the electrode layer whose warping tendency needs to be alleviated is completely surrounded by the functional layer, thereby constraining the electrode layer from multiple directions, avoiding deformation such as warping of the electrode layer, and further improving the structural stability and electrical performance of the surface acoustic wave filter.

[0020] In a possible implementation manner of the first aspect, the functional layer surrounds the entire surface of the multi-layer electrode layer.

[0021] In this embodiment, the functional layer encloses a cavity to constrain the multi-layer electrode layer as a whole, avoiding deformation such as warping of the electrode layer, and also improving the structural stability and electrical performance of the surface acoustic wave filter. In addition, in this embodiment, while suppressing the warping tendency, the functional layer surrounds the multi-layer electrode layer to improve the bonding ability between adjacent electrode layers, thereby avoiding delamination between two adjacent electrode layers, further optimizing the electrical performance and structural stability of the surface acoustic wave filter.

[0022] In a possible implementation of the first aspect, the ratio of the thickness of the functional layer to the thickness of the electrode layer in contact with the functional layer is greater than or equal to 0.04 and less than or equal to 1. Functional layers of appropriate thickness are provided corresponding to electrode layers of different thicknesses, which can effectively control the mechanical stress of the multi-layer electrode layer as a whole to be less than 500Mpa, thereby avoiding the delamination problem of the electrode layer and ensuring the structural stability of the surface acoustic wave filter.

[0023] In a possible implementation of the first aspect, the resistivity of the functional layer is less than or equal to 1×10-6Ωm. This allows the functional layer to achieve a good conductive effect while avoiding defects such as warping and delamination of the electrode layer, and avoids excessive increase in the overall square resistance of the IDT due to the setting of the functional layer, thereby avoiding the problem of severe heating of the IDT when the power is increased, resulting in a decrease in the quality factor of the surface acoustic wave filter.

[0024] In a possible implementation manner of the first aspect, a grain size of a surface of the functional layer is smaller than a grain size of a surface of an electrode layer that the functional layer contacts.

[0025] That is, compared with the electrode layer, the functional layer has higher flatness. Especially when the functional layer is arranged between the piezoelectric layer and the electrode layer, the functional layer with higher flatness is in contact with the piezoelectric layer, which can effectively improve the quality factor of the surface acoustic wave filter.

[0026] In a possible implementation manner of the first aspect, the material of at least one electrode layer includes at least one of platinum and tungsten or an alloy of at least one of the two.

[0027] In a possible implementation manner of the first aspect, the material of the functional layer includes at least one of vanadium, manganese, zinc, molybdenum, tellurium, silver and aluminum, or an alloy of at least one of them.

[0028] In a possible implementation manner of the first aspect, the surface acoustic wave filter further includes a first adhesion layer, and the first adhesion layer is provided between the piezoelectric layer and the multilayer electrode layer.

[0029] By setting the first adhesive layer, the multi-layer electrode layer can be provided with an adhesive force toward the piezoelectric layer, thereby improving the connection strength between the electrode layer and the piezoelectric layer, further alleviating the tendency of the electrode layer to warp away from the piezoelectric layer, and effectively avoiding stratification between the electrode layer and the piezoelectric layer, thereby improving the reliability of the surface acoustic wave filter and optimizing the electrical performance of the surface acoustic wave filter.

[0030] In a possible implementation of the first aspect, the surface acoustic wave filter further includes a second adhesive layer, which is disposed between two adjacent electrode layers, thereby enhancing the connection strength between the two adjacent electrode layers, and also reducing the probability of warping of the electrode layers, thereby improving the structural stability of the surface acoustic wave filter.

[0031] In a second aspect, a radio frequency module is provided, the radio frequency module comprising a power amplifier and a surface acoustic wave filter provided by any one of the embodiments in the first aspect, wherein the surface acoustic wave filter is coupled to the power amplifier.

[0032] In a third aspect, an electronic device is provided, the electronic device comprising a circuit board and a surface acoustic wave filter provided by any one of the embodiments in the first aspect, wherein the surface acoustic wave filter is arranged on the circuit board.

[0033] The technical effects brought about by the RF module in the second aspect and the electronic device in the third aspect can be referred to the technical effects brought about by the design method of the surface acoustic wave filter in the first aspect, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application;

[0035] Figure 2 A schematic diagram of the structure of a surface acoustic wave filter provided in an embodiment of the present application;

[0036] Figure 3 Another schematic diagram of the structure of the surface acoustic wave filter provided in the embodiment of the present application;

[0037] Figure 4 For along Figure 3 A cross-sectional view of the section line AA' in;

[0038] Figure 5 For along Figure 3 Another cross-sectional view of the section line AA' in FIG.

[0039] Figure 6 For along Figure 3 Another cross-sectional view of the section line AA' in FIG.

[0040] Figure 7 For along Figure 3 Another cross-sectional view of the section line AA' in FIG.

[0041] Figure 8 For along Figure 3 Another cross-sectional view of the section line AA' in FIG.

[0042] Fig. 9 For along Figure 3 Another cross-sectional view of the section line AA' in FIG.

[0043] Fig.10 For along Figure 3 Another cross-sectional view of the section line AA' in FIG. DETAILED DESCRIPTION

[0044] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in some embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments provided by the present application, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present application.

[0045] In the description of the present application, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0046] Unless the context requires otherwise, throughout the specification and claims, the term "including" is interpreted as an open, inclusive meaning, that is, "including, but not limited to". In the description of the specification, the terms "one embodiment", "some embodiments", "exemplary embodiments", "exemplarily" or "some examples" and the like are intended to indicate that specific features, structures, materials or characteristics associated with the embodiment or example are included in at least one embodiment or example of the present application. The schematic representation of the above terms does not necessarily refer to the same embodiment or example. In addition, the specific features, structures, materials or characteristics may be included in any one or more embodiments or examples in any appropriate manner.

[0047] In the following, the terms "first", "second", etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present application, unless otherwise specified, "multiple" means two or more.

[0048] When describing some embodiments, the expressions "coupled", "connected" and their derivatives may be used. The terms "coupled" and "connected" should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. The embodiments disclosed herein are not necessarily limited to the contents of this document.

[0049] “At least one of A, B, and C” has the same meaning as “at least one of A, B, or C” and both include the following combinations of A, B, and C: A only, B only, C only, the combination of A and B, the combination of A and C, the combination of B and C, and the combination of A, B, and C.

[0050] “A and / or B” includes the following three combinations: A only, B only, and a combination of A and B.

[0051] As used herein, "parallel", "perpendicular", and "equal" include the situations described and situations similar to the situations described, and the range of the similar situations is within the acceptable deviation range, wherein the acceptable deviation range is determined by a person of ordinary skill in the art taking into account the measurement in question and the errors associated with the measurement of a particular quantity (i.e., the limitations of the measurement system). For example, "parallel" includes absolute parallelism and approximate parallelism, wherein the acceptable deviation range of approximate parallelism may be, for example, a deviation within 5°; "perpendicular" includes absolute perpendicularity and approximate perpendicularity, wherein the acceptable deviation range of approximate perpendicularity may also be, for example, a deviation within 5°. "Equal" includes absolute equality and approximate equality, wherein the acceptable deviation range of approximate equality may be, for example, the difference between the two equalities is less than or equal to 5% of either one.

[0052] Exemplary embodiments are described herein with reference to cross-sectional views and / or plan views that are idealized exemplary drawings. In the drawings, the thickness of layers and regions are exaggerated for clarity. Therefore, variations in shape relative to the drawings due to, for example, manufacturing techniques and / or tolerances are conceivable. Therefore, the exemplary embodiments should not be interpreted as being limited to the shapes of the regions shown herein, but include deviations in shape due to, for example, manufacturing. Therefore, the regions shown in the drawings are schematic in nature, and their shapes are not intended to illustrate the actual shapes of regions of the device, and are not intended to limit the scope of the exemplary embodiments.

[0053] In addition, the scenarios described in the embodiments of the present application are intended to more clearly illustrate the technical solutions of the embodiments of the present application, and do not constitute a limitation on the technical solutions provided in the embodiments of the present application. A person of ordinary skill in the art can appreciate that, with the emergence of new scenarios, the technical solutions provided in the embodiments of the present application are also applicable to similar technical problems.

[0054] The embodiment of the present application provides an electronic device, and the technical solution of the present application can be applied to various electronic devices including filters. The electronic device can be deployed on land, including indoors or outdoors, handheld or vehicle-mounted. It can also be deployed on the water surface (such as a ship, etc.). It can also be deployed in the air (for example, on an airplane, a balloon, and a satellite, etc.). For example, the electronic device can be a terminal or a base station. For example, the terminal includes but is not limited to: mobile phones, tablet computers, laptop computers, PDAs, mobile Internet devices (MID), wearable devices (such as smart watches, smart bracelets, pedometers, etc.), vehicle-mounted devices (such as cars, bicycles, electric vehicles, airplanes, ships, trains, high-speed railways, etc.), virtual reality (VR) equipment, augmented reality (AR) equipment, wireless terminals in industrial control, smart home devices (such as refrigerators, televisions, air conditioners, electric meters, etc.), intelligent robots, workshop equipment, wireless terminals in self-driving, wireless terminals in remote medical surgery, wireless terminals in smart grids, wireless terminals in transportation safety, wireless terminals in smart cities, or wireless terminals in smart homes, flight equipment (such as intelligent robots, hot air balloons, drones, airplanes), RF front-end modules, etc.

[0055] Figure 1 The structure diagram of an electronic device 1000 provided by way of example in the present application is shown in FIG. Figure 1 As shown, the electronic device 1000 includes a surface acoustic wave filter 100 and a circuit board 200 .

[0056] See also Figure 1 , the surface acoustic wave filter 100 can be set on a circuit board 200 .

[0057] For example, see Figure 1 The electronic device 1000 may further include a radio frequency module 300 , and the aforementioned surface acoustic wave filter 100 may be integrated in the radio frequency module 300 .

[0058] It is understandable that the surface acoustic wave filter 100 can also be independently disposed on the circuit board 200 as a component.

[0059] The electronic device 1000 may further include a system on chip (SOC), a radio frequency chip, etc., which are arranged on the circuit board 200 .

[0060] The circuit board 200 is used to carry the system-level chip, the radio frequency chip, etc., and is electrically connected to the system-level chip, the radio frequency chip, etc. Among them, the radio frequency chip may include components such as filters and processors. The processor is used to process various signals, and the filter (including the surface acoustic wave filter 100) is an important part of radio frequency signal processing, which is used to pass signals of specific frequencies and block signals of other frequencies.

[0061] For example, see Figure 1 , the electronic device 1000 may further include an antenna 500 .

[0062] For example, see Figure 1 , the antenna 500 can be coupled to the RF module 300.

[0063] It should be noted that the "coupling" here may refer to a direct connection between the RF module 300 and the antenna 500, or may refer to an indirect connection between the RF module 300 and the antenna 500, or may refer to a non-contact but mutual influence between the RF module 300 and the antenna 500. The embodiments of the present application do not limit the specific coupling method between the RF module 300 and the antenna 500.

[0064] The antenna 500 is used to radiate the radio frequency signal transmitted in the radio frequency module 300 to the outside.

[0065] It can be understood that the electronic device 1000 may include one or more antennas 500 .

[0066] When the electronic device 1000 includes multiple antennas 500, one antenna 500 may correspond to one RF module 300, one antenna 500 may correspond to multiple RF modules 300, or multiple antennas 500 may share one RF module 300. Application scenarios in related technologies are all applicable to the embodiments of the present application.

[0067] Understandably, Figure 1 The structure of the electronic device 1000 shown in the figure does not constitute a specific limitation on the electronic device 1000. The electronic device 1000 may include, for example, Figure 1 The components shown may be more or less than the components shown, for example, a packaging structure and auxiliary components (such as passive devices IPD or transmission lines) may also be included (not shown in the figure), or a combination of the following may be used: Figure 1 Some of the components shown, or may be combined with Figure 1 The components shown are arranged differently.

[0068] The embodiment of the present application further provides a radio frequency module 300, illustratively, referring to Figure 1 The RF module 300 can be applied to the above-mentioned electronic device 1000, for example, in the RF chip in the electronic device 1000, or, exemplarily, the RF module 300 provided in the embodiment of the present application can also be used as a separate component, or, can also be used in other structures.

[0069] See also Figure 1 The RF module 300 may include a surface acoustic wave filter 100 and a power amplifier 400. The surface acoustic wave filter 100 is coupled to the power amplifier 400 to process and transmit the RF signal.

[0070] The power amplifier 400 is used to amplify the RF signal, and the RF module 300 transmits the amplified RF signal to the antenna 500 .

[0071] The embodiment of the present application further provides a surface acoustic wave filter 100 .

[0072] Exemplarily, the surface acoustic wave filter 100 may be applied to the electronic device 1000 described above, for example, applied to a radio frequency chip in the electronic device 1000 .

[0073] Exemplarily, the surface acoustic wave filter 100 is not limited to being integrated in the electronic device 1000. The surface acoustic wave filter 100 can also be used as a component alone, or the surface acoustic wave filter 100 can also be integrated with components such as the power amplifier 400 into a device (such as a radio frequency device, a radio frequency module 300, a surface acoustic wave filter module, etc.).

[0074] Exemplarily, the SAW filter 100 provided in the embodiment of the present application may be a low-pass SAW filter, a high-pass SAW filter, a band-pass SAW filter, a band-stop SAW filter or an active SAW filter.

[0075] Figure 2 FIG. 1 is a structural diagram of a surface acoustic wave filter 100 provided in an embodiment of the present application. Figure 2 As shown, the surface acoustic wave filter 100 may include a plurality of cascaded surface acoustic wave resonators 10. The plurality of surface acoustic wave resonators 10 may have different resonance frequencies and may be cascaded together in a series-parallel manner. The performance of the surface acoustic wave filter 100 is closely related to the performance of the surface acoustic wave resonators 10. Figure 2 When a plurality of surface acoustic wave resonators 10 are cascaded together in a series-parallel manner, Figure 2 The signal input terminal Vi, the signal output terminal Vo and the ground terminal GND of the surface acoustic wave filter 100 are also shown.

[0076] The surface acoustic wave resonator 10 is small in size and good in performance, and is often used in various radio frequency terminal devices. The surface acoustic wave filter 100 formed by connecting surface acoustic wave resonators 10 with different resonant frequencies in series and parallel has the advantages of small passband insertion loss, high out-of-band steepness and strong power tolerance.

[0077] Figure 3 It is a schematic structural diagram of a surface acoustic wave filter 100 (for example, a surface acoustic wave resonator 10 in the surface acoustic wave filter 100 ) provided in an embodiment of the present application.

[0078] like Figure 3 As shown, the surface acoustic wave filter 100 may include a piezoelectric layer 1 and an interdigital transducer (ITD) 2 , and the ITD 2 is arranged on one side of the piezoelectric layer 1 .

[0079] It should be noted that Figure 3 Only a part of the structure of the surface acoustic wave filter 100 is shown as an example. Figure 3 Only the structure of one surface acoustic wave resonator 10 in the surface acoustic wave filter 100 is shown. It can be understood that the surface acoustic wave filter 100 can also include a plurality of surface acoustic wave resonators 10, that is, the surface acoustic wave filter 100 can also include a plurality of surface acoustic wave resonators 10. Figure 3 The structure shown.

[0080] The piezoelectric layer 1 is used to excite surface acoustic waves under the action of the interdigital transducer 2 .

[0081] For example, the material of the piezoelectric layer 1 may include LiNbO 3 (Lithium Niobate), LiTaO 3 One or more of piezoelectric materials such as lithium tantalate, AlN (aluminum nitride), ZnO (zinc oxide), quartz, etc.

[0082] Exemplarily, the material of the piezoelectric layer can be various tangential. Exemplarily, the material of the piezoelectric layer 1 is 128°YX-LiNbO3. Alternatively, the material of the piezoelectric layer 1 is 42°YX-LiTaO3.

[0083] The resonance characteristics of the surface acoustic wave resonator 10 can be improved by setting the Euler angle of the material of the piezoelectric layer 1 .

[0084] See also Figure 3 The IDT 2 is disposed on the piezoelectric layer 1 , for example, the IDT 2 is disposed on the surface of the piezoelectric layer 1 .

[0085] like Figure 3As shown, the above-mentioned interdigital transducer 2 includes a first busbar 1a and a second busbar 2a that are arranged opposite to each other, a plurality of first electrode fingers 1b, and a plurality of second electrode fingers 2b. The extension direction of the first busbar 1a and the second busbar 2a is parallel to the first direction X, the extension direction of the first electrode finger 1b is parallel to the second direction Y, the first electrode finger 1b protrudes from the first busbar 1a to the second busbar 2a, the plurality of first electrode fingers 1b are arranged in sequence along the extension direction of the first busbar 1a (first direction X), and the plurality of first electrode fingers 1b are coupled to the first busbar 1a. The extension direction of the second electrode finger 2b is parallel to the second direction Y, the second electrode finger 2b protrudes from the second busbar 2a to the first busbar 1a, the plurality of second electrode fingers 2b are arranged in sequence along the extension direction of the second busbar 2a (first direction X), and the plurality of second electrode fingers 2b are coupled to the second busbar 2a.

[0086] The plurality of first electrode fingers 1b and the plurality of second electrode fingers 2b are alternately arranged in sequence between the first bus bar 1a and the second bus bar 2a along the extending direction of the first bus bar 1a and the second bus bar 2a, and the first electrode fingers 1b and the second electrode fingers 2b are not in contact with each other.

[0087] The above-mentioned “multiple first electrode fingers 1b and multiple second electrode fingers 2b are alternately arranged in sequence between the first bus bar 1a and the second bus bar 2a along the extension direction of the first bus bar 1a and the second bus bar 2a” means: between the first bus bar 1a and the second bus bar 2a, a first electrode finger 1b, a second electrode finger 2b, a first electrode finger 1b, a second electrode finger 2b, a first electrode finger 1b, a second electrode finger 2b, etc. are arranged in sequence.

[0088] There is no limitation on the number of first electrode fingers 1 b and the number of second electrode fingers 2 b in the IDT 2 , and they can be set as required.

[0089] The plurality of first electrode fingers 1b may be arranged at equal intervals or at non-equal intervals. Similarly, the plurality of second electrode fingers 2b may be arranged at equal intervals or at non-equal intervals. Taking the first electrode fingers 1b as an example, the non-equal interval arrangement of the plurality of first electrode fingers 1b means that the interval between at least one pair of adjacent first electrode fingers 1b is different from the interval between another pair of adjacent first electrode fingers 1b.

[0090] In addition, the plurality of first electrode fingers 1b and the plurality of second electrode fingers 2b are alternately arranged in sequence, and the spacings between adjacent first electrode fingers 1b and second electrode fingers 2b may be the same; or the spacings between a plurality of adjacent pairs of first electrode fingers 1b and second electrode fingers 2b may not be exactly the same, that is, the spacing between at least one pair of adjacent first electrode fingers 1b and second electrode fingers 2b is different from the spacing between another pair of adjacent first electrode fingers 1b and second electrode fingers 2b.

[0091] It should be noted that the embodiment of the present application does not limit the widths of the first electrode finger 1 b and the second electrode finger 2 b , and they can be reasonably set according to needs.

[0092] It can be understood that the pitch between the first electrode finger 1b and the second electrode finger 2b and the finger width of the first electrode finger 1b and the second electrode finger 2b are mainly affected by the lithography and development processes. By adjusting the pitch between the first electrode finger 1b and the second electrode finger 2b and the finger width of the first electrode finger 1b and the second electrode finger 2b, the passband frequency of the surface acoustic wave resonator 20 can be changed.

[0093] It should be noted that the first bus bar 1a, the first electrode finger 1b, the second bus bar 2a, and the second electrode finger 2b can be manufactured at the same time. Alternatively, the first bus bar 1a and the first electrode finger 1b can be manufactured first, and then the second bus bar 2a and the second electrode finger 2b can be manufactured. Alternatively, the second bus bar 2a and the second electrode finger 2b can be manufactured first, and then the first bus bar 1a and the first electrode finger 1b can be manufactured.

[0094] Regardless of whether the first bus bar 1a, the first electrode finger 1b, the second bus bar 2a and the second electrode finger 2b are manufactured at the same time, the film layer structures of the first bus bar 1a, the first electrode finger 1b, the second bus bar 2a and the second electrode finger 2b may be the same.

[0095] With the large-scale commercial use of the fifth generation mobile communication technology (5G) network, 5G terminals have a large amount of high-speed data transmission, which requires the surface acoustic wave filter 100 to have higher reliability and power tolerance performance.

[0096] However, during the operation of the SAW filter 100, when the SAW propagates, the IDT 2 generates mechanical vibrations on the surface of the piezoelectric layer 1. As the input power increases, the vibration amplitude of the IDT 2 increases, and the mechanical stress at the interface between the IDT 2 and the piezoelectric layer 1 also increases.

[0097] Figure 4 For related technologies Figure 3 A cross-sectional view of the section line AA' in.

[0098] In related art, see Figure 4 The surface acoustic wave filter 100' comprises a piezoelectric layer 1' and a multi-layer electrode layer 3' (ie, an interdigital transducer). The multi-layer electrode layer 3' is stacked in a direction away from the piezoelectric layer 1'.

[0099] like Figure 4 As shown, in the related art, the electrode layer 3 usually warps on the side under the action of mechanical stress (such as Figure 4 ), resulting in delamination between the electrode layer 3' and the piezoelectric layer 1', reducing the reliability of the surface acoustic wave filter 100' and causing the performance of the surface acoustic wave filter 100' to deteriorate rapidly.

[0100] Even if Figure 4 As shown in the figure, when a first adhesive layer 51' is set between the multi-layer electrode layer 3' and the piezoelectric layer 1' to improve the adhesion between the piezoelectric layer 1' and the electrode layer 3', warping and delamination will still occur between the electrode layer 3' and the first adhesive layer 51', or the electrode layer 3' will drive the first adhesive layer 51' to warp from the surface of the piezoelectric layer 1', affecting the electrical performance of the surface acoustic wave filter 100.

[0101] Especially with the gradual miniaturization of the surface acoustic wave filter 100', the electrode layer 3' tends to use platinum material or tungsten material that can effectively reduce the sound velocity and reduce the size of the surface acoustic wave filter 100'. In this case, the electrode layer 3' with high-density platinum material or tungsten material aggravates the problem of side warping under the influence of its own weight, which is not conducive to the further development of the surface acoustic wave filter 100'.

[0102] In order to solve the above technical problems, the structure of the surface acoustic wave filter 100 is designed as follows in the embodiment of the present application:

[0103] Figures 5 to 10 For along Figure 3 Some other cross-sectional views along the section line AA' in FIG.

[0104] In some embodiments, Figures 5 to 10 As shown, the surface acoustic wave filter 100 includes a plurality of electrode layers 3 and a functional layer 4 in addition to the piezoelectric layer 1 .

[0105] It can be understood that the multilayer electrode layer 3 and the functional layer 4 are used to form the aforementioned first bus bar 1a, first electrode finger 1b, second bus bar 2a or second electrode finger 2b. Figures 5 to 10Only the electrode layer 3 and the functional layer 4 corresponding to a part of the structure (such as the first electrode finger 1b and the second electrode finger 2b) are shown exemplarily. It can be understood that other structures (such as the first bus bar 1a or the second bus bar 2a) may also include Figure 5 A multilayer of electrode layers 3 and functional layers 4 is shown.

[0106] Among them, see Figures 5 to 10 The multi-layer electrode layer 3 is arranged on the piezoelectric layer 1, and the multi-layer electrode layer 3 is stacked along a direction perpendicular to the piezoelectric layer 1 (ie, the third direction Z).

[0107] The multiple electrode layers 3 are used to apply voltage to the piezoelectric layer 1 . The electrode layers 3 corresponding to the first electrode finger 1 b and the second electrode finger 2 b respectively apply different voltages to the piezoelectric layer 1 to form a potential difference, thereby generating a piezoelectric effect and realizing the filtering function of the surface acoustic wave filter 100 .

[0108] Exemplarily, among the multiple electrode layers 3 , the material of any one of the electrode layers 3 may include at least one of platinum and tungsten or an alloy of at least one of the two.

[0109] By setting the material of the electrode layer 3 to be platinum metal or tungsten metal or an alloy of either metal, the acoustic velocity can be effectively reduced, and the size of the surface acoustic wave filter 100 can be reduced, which is conducive to realizing a miniaturized design of the surface acoustic wave filter 100 .

[0110] Exemplarily, in the multilayer electrode layer 3, the material of any electrode layer 3 may also include at least one of conductive metals such as aluminum, copper, platinum, gold, nickel, titanium, silver, germanium, molybdenum, tungsten and thallium, or an alloy of at least one of them, for example, it may include metal alloys such as AlCu alloy, AlTi alloy, AlW alloy, etc.

[0111] It is understandable that the material compositions of different electrode layers 3 may not be completely the same, and this is not limited here.

[0112] By adjusting the material or other parameters of the multi-layer electrode layer 3 , the desired resonance characteristics of the surface acoustic wave filter 100 can be adjusted and controlled.

[0113] See also Figures 5 to 10 At least part of the functional layer 4 is disposed on the surface of at least one electrode layer 3 close to the piezoelectric layer 1, that is, Figures 5 to 10 Based on the orientation in the figure, the functional layer 4 can be arranged on the lower surface of at least one electrode layer 3.

[0114] For example, Figure 8 and Fig.10 As shown, the functional layer 4 can be disposed on the lower surface of each electrode layer 3 .

[0115] Alternatively, illustratively, the functional layer 4 may be provided only on the lower surface of the electrode layer 3 having high density or high weight, for example, the functional layer 4 may be provided on the lower surface of the electrode layer 3 including platinum element or tungsten element.

[0116] It can be understood that the functional layer 4 is conductive, so that when at least part of the functional layer 4 is arranged on the surface of at least one electrode layer 3 close to the piezoelectric layer 1, the voltage transmitted on the electrode layer 3 can still be smoothly loaded to the piezoelectric layer 1 through the functional layer 4, thereby avoiding the setting of the functional layer 4 affecting the electrical performance of the surface acoustic wave filter 100.

[0117] The lattice structure of the functional layer 4 matches the lattice structure of the electrode layer 3 that the functional layer 4 contacts (ie, lattice matching).

[0118] The "matching of lattice structures" here can be understood as that the lattice structure of the material of the functional layer 4 is the same as or similar to the lattice structure of the material of the electrode layer 3 that the functional layer 4 contacts. For example, the lattice constants of the two can be roughly the same, and / or the crystal directions of the two can be matched, that is, the normal directions at the interface where the two contact each other are consistent or parallel, and / or the lattice parameters of the two are integer multiples, and / or the symmetry of the crystals of the two is the same or similar.

[0119] By arranging a functional layer 4 on the side of at least one electrode layer 3 facing the piezoelectric layer 1, and arranging the lattice structure of the functional layer 4 to match the lattice structure of the electrode layer 3 contacted by the functional layer 4, the connection strength between the functional layer 4 and the electrode layer 3 is effectively improved, thereby providing a tensile force parallel to the piezoelectric layer 1 on the side of the electrode layer 3 facing the piezoelectric layer 1, slowing down the tendency of the electrode layer 3 to warp away from the piezoelectric layer 1, and effectively avoiding stratification between the electrode layer 3 and the piezoelectric layer 1, thereby improving the reliability of the surface acoustic wave filter 100 and optimizing the electrical performance of the surface acoustic wave filter 100.

[0120] In some embodiments, the bonding strength between the functional layer 4 and the electrode layer 3 in contact with the functional layer 4 can be set to be greater than or equal to 500 MPa, thereby further enhancing the connection strength between the functional layer 4 and the electrode layer 3, slowing down the tendency of the electrode layer 3 to warp away from the piezoelectric layer 1, avoiding stratification between the electrode layer 3 and the piezoelectric layer 1, improving the reliability of the surface acoustic wave filter 100, and optimizing the electrical performance of the surface acoustic wave filter 100.

[0121] For example, the atomic radius of the element with the highest content in the functional layer 4 can be set to be approximately the same as the atomic radius of the element with the highest content in the electrode layer 3 that the functional layer 4 contacts, thereby improving the bonding strength between the two so that the bonding strength between the two is greater than or equal to 500 MPa.

[0122] For example, the absolute value of the difference between the atomic radius of the element with the highest content in the functional layer 4 and the atomic radius of the element with the highest content in the electrode layer 3 contacted by the functional layer 4 is less than or equal to 20 pm. That is, the difference between the atomic radii of the two can be greater than or equal to -20 pm and less than or equal to 20 pm.

[0123] For example, the difference between the atomic radii of the two may be greater than or equal to -20 pm and less than or equal to 10 pm.

[0124] For example, the absolute value of the difference may be 0 pm, 3.5 pm, 10 pm, 13.75 pm, or 20 pm, etc.

[0125] For example, when the element with the highest content in the electrode layer 3 contacted by the functional layer 4 is platinum or tungsten, the atomic radius of platinum is approximately 138pm, and the atomic radius of tungsten is approximately 137pm, then the atomic radius of the element with the highest content in the functional layer 4 can be approximately 118pm~158pm. For example, the material of the functional layer 4 can include at least one of vanadium (V, atomic radius is approximately 134pm), manganese (Mn, atomic radius is approximately 124pm), zinc (Zn, atomic radius is approximately 125pm), molybdenum (Mo, atomic radius is approximately 136.2pm), tellurium (Te, atomic radius is approximately 140pm), silver (Ag, atomic radius is approximately 144pm) and aluminum (AL, atomic radius is approximately 143pm) or an alloy of at least one of them.

[0126] In some embodiments, Figure 5 As shown, at least part of the functional layer 4 is disposed between the electrode layer 3 closest to the piezoelectric layer 1 among the multi-layer electrode layers 3 and the piezoelectric layer 1 .

[0127] That is, a functional layer 4 is provided between the multilayer electrode layer 3 as a whole and the piezoelectric layer 1 to mitigate the warping tendency of the multilayer electrode layer 3 as a whole and avoid stratification between the multilayer electrode layer 3 as a whole and the piezoelectric layer 1, thereby improving the reliability of the surface acoustic wave filter 100.

[0128] In some embodiments, Figure 6 As shown, at least part of the functional layer 4 is arranged between two adjacent electrode layers 3 .

[0129] That is, at least part of the functional layer 4 can also be arranged on the surface of the electrode layer 3 facing the piezoelectric layer 1 in the multilayer electrode layer 3, which is away from the piezoelectric layer 1, so as to reduce the tendency of the electrode layer 3 to warp in the direction away from the piezoelectric layer 1. Figure 6When the material of the upper electrode layer 3 includes platinum or tungsten, the upper electrode layer 3 is greatly affected by mechanical stress and is more likely to warp. By providing a functional layer 4 on the surface of the upper electrode layer 3 facing the piezoelectric layer 1, the warping tendency of the electrode layer 3 (i.e., the upper electrode layer 3) with a higher probability of warping in the multi-layer electrode layers 3 can be effectively alleviated, thereby avoiding delamination of the electrode layer 3 and the lower electrode layer 3, or causing delamination between the lower electrode layer 3 and the piezoelectric layer 1, thereby also improving the reliability of the surface acoustic wave filter 100.

[0130] In some embodiments, Fig.10 As shown, a functional layer 4 can also be set on the surface of each electrode layer 3 facing the piezoelectric layer, so as to suppress the warping tendency of the electrode layer 3 layer by layer, keep each electrode layer 3 flat (that is, each electrode layer 3 is parallel to the piezoelectric layer 1), thereby further enhancing the ability to alleviate the overall warping tendency of the multi-layer electrode layer 3 and effectively improving the reliability of the surface acoustic wave filter 100.

[0131] In some embodiments, Figure 7 As shown, the functional layer 4 includes a first sublayer 41 and a second sublayer 42 .

[0132] See also Figure 7 The first sublayer 41 is arranged on the surface of at least one electrode layer 3 close to the piezoelectric layer 1, and the second sublayer 42 is arranged on the side of at least one electrode layer 3 (ie, perpendicular to the surface of the piezoelectric layer 1).

[0133] That is, a portion of the functional layer 4 (i.e., the first sublayer 41) is arranged on the surface of at least one electrode layer 3 (for example, an electrode layer 3 whose material contains platinum or tungsten) facing the piezoelectric layer 1, and another portion of the functional layer 4 (i.e., the second sublayer 42) is arranged on the side of the at least one electrode layer 3.

[0134] It is understood that the "side" here can refer to Figure 7 Taking the orientation in the figure as an example, at least one of the left side surface, the right side surface, the front side surface and the rear side surface (the front and rear side surfaces are not shown in the figure) of the electrode layer 3.

[0135] See also Figure 7 The first sub-layer 41 and the second sub-layer 42 are integrally arranged.

[0136] By arranging the functional layer 4 on the surface of the electrode layer 3 facing the piezoelectric layer 1 and on the side of the electrode layer 3, and arranging the two parts of the functional layer 4 (i.e., the first sublayer 41 and the second sublayer 42) as an integrated whole, the bonding strength between the electrode layer 3 and the functional layer 4 is relatively strong, and the electrode layer 3 can be effectively constrained from the surface of the electrode layer 3 facing the piezoelectric layer 1 and the side of the electrode layer 3, thereby further alleviating the warping tendency of the electrode layer 3 and improving the electrical performance of the surface acoustic wave filter 100.

[0137] For example, see Figure 7 The portion of the functional layer 4 disposed on the side of the electrode layer 3 may be disposed on the side of only one electrode layer 3 , or may be disposed on the side of multiple electrode layers 3 .

[0138] In some embodiments, Figure 8 As shown, the functional layer 4 surrounds all surfaces of each electrode layer 3 in the at least one electrode layer 3. That is, the functional layer 4 is arranged on all surfaces of each electrode layer 3 in the at least one electrode layer 3, for example, on the surface of each electrode layer 3. Figure 8 The directions in the figure are, for example, the upper surface, the lower surface, the left side surface, the right side surface, the front side surface and the rear side surface (the front and rear side surfaces are not shown in the figure).

[0139] That is, among the multilayer electrode layers 3, the electrode layer 3 whose warping tendency needs to be alleviated is completely surrounded by the functional layer 4, thereby constraining the electrode layer 3 from multiple directions, avoiding deformation such as warping of the electrode layer 3, and further improving the structural stability and electrical performance of the surface acoustic wave filter 100.

[0140] For example, in Figure 8 In the case where the material of the upper electrode layer 3 includes platinum or tungsten, the functional layer 4 may be disposed only around the upper electrode layer 3, or illustratively, see Figure 8 In the multi-layer electrode layer 3 , each electrode layer 3 is surrounded by a functional layer 4 .

[0141] In some embodiments, Fig. 9 As shown, the functional layer 4 surrounds the entire surface of the multilayer electrode layer 3. That is, the multilayer electrode layer 3 is taken as a whole, and the functional layer 4 surrounds the upper surface, the lower surface, the left side surface, the right side surface, the front side surface and the right side surface of the multilayer electrode layer 3 as a whole, and two adjacent electrode layers 3 can be in direct contact with each other.

[0142] In this embodiment, the functional layer 4 encloses a cavity to constrain the multilayer electrode layer 3 as a whole, avoiding deformation such as warping of the electrode layer 3, and also improving the structural stability and electrical performance of the surface acoustic wave filter 100. In addition, in this embodiment, while suppressing the warping tendency, the functional layer 4 surrounds the multilayer electrode layer 3 to improve the bonding ability between adjacent electrode layers 3, thereby avoiding delamination between two adjacent electrode layers 3, and further optimizing the electrical performance and structural stability of the surface acoustic wave filter 100.

[0143] In some embodiments, the ratio of the thickness of the functional layer 4 to the thickness of the electrode layer 3 contacting the functional layer 4 is greater than or equal to 0.04 and less than or equal to 1.

[0144] For example, when the material of the functional layer 4 is Ag, the ratio of the thickness of the functional layer 4 to the thickness of the electrode layer 3 in contact with the functional layer 4 may be greater than or equal to 0.02 and less than or equal to 1. Or, for example, when the material of the functional layer 4 is Zn, Mo or Te, the ratio of the thickness of the functional layer 4 to the thickness of the electrode layer 3 in contact with the functional layer 4 may be greater than or equal to 0.03 and less than or equal to 1. Or, for example, when the material of the functional layer 4 is V, the ratio of the thickness of the functional layer 4 to the thickness of the electrode layer 3 in contact with the functional layer 4 may be greater than or equal to 0.035 and less than or equal to 1. Or, for example, when the material of the functional layer 4 is Mn, Al or AlCu, the ratio of the thickness of the functional layer 4 to the thickness of the electrode layer 3 in contact with the functional layer 4 may be greater than or equal to 0.04 and less than or equal to 1. In the above examples, the material of the electrode layer 3 in contact with the functional layer 4 may be Pt or W.

[0145] For example, the ratio of the thicknesses of the two may be approximately 0.04, 0.0765, 0.38, 0.579, 0.8 or 1.

[0146] For example, when the thickness of the electrode layer 3 to which the functional layer 4 contacts is 370 nm, the thickness of the functional layer 4 may be 20 nm.

[0147] It should be noted that the “thickness of the functional layer 4” here can be understood as the size of the functional layer 4 in the direction perpendicular to the surface of the electrode layer 3 in contact with the functional layer 4. For example, the thickness of the portion of the functional layer 4 arranged on the side of the electrode layer 3 is the size of the functional layer 4 in the direction perpendicular to the side of the electrode layer 3. For example, the thickness of the portion of the functional layer 4 arranged on the lower surface of the electrode layer 3 is the size of the functional layer 4 in the direction perpendicular to the lower surface of the electrode layer 3.

[0148] Exemplarily, the thickness of the functional layer 4 is proportional to the thickness of the electrode layer 3 that the functional layer 4 contacts.

[0149] By setting the thickness of the functional layer 4 so that the ratio of the thickness of the electrode layer 3 in contact with the functional layer 4 is greater than or equal to 0.04 and less than or equal to 1, the electrode layers 3 of different thicknesses are correspondingly provided with functional layers 4 of appropriate thickness, and the mechanical stress of the multi-layer electrode layer 3 as a whole can be effectively controlled to be less than 500Mpa, thereby avoiding the delamination problem of the electrode layer 3 and ensuring the structural stability of the surface acoustic wave filter 100.

[0150] In some embodiments, the grain size of the surface of the functional layer 4 is smaller than the grain size of the surface of the electrode layer 3 (ie, the orientation consistency of metal grains).

[0151] That is, compared with the electrode layer 3, the functional layer 4 has a higher flatness. Especially when the functional layer 4 is arranged on the piezoelectric layer 1 and the electrode layer 3, the functional layer 4 with higher flatness is in contact with the piezoelectric layer 1, which can effectively improve the quality factor of the surface acoustic wave filter 100.

[0152] In addition, the material of the functional layer 4 includes at least one or an alloy of at least one of vanadium, manganese, zinc, molybdenum, tellurium, silver and aluminum, and its preparation and deposition are relatively easy, and it is easy to obtain a functional layer 4 with high flatness, thereby ensuring that the surface acoustic wave filter 100 has a good quality factor.

[0153] In some embodiments, Figures 5 to 10 As shown, the surface acoustic wave filter 100 may further include a first adhesive layer 51 , which is disposed between the piezoelectric layer 1 and the multilayer electrode layer 3 .

[0154] For example, see Figure 6 The first adhesive layer 51 may be directly disposed on the surface of the electrode layer 3 closest to the piezoelectric layer 1 in the multi-layer electrode layer 3 and facing the piezoelectric layer 1 .

[0155] Or, for example, see Figure 5 When at least part of the functional layer 4 is disposed between the electrode layer 3 closest to the piezoelectric layer 1 among the multilayer electrode layers 3 and the piezoelectric layer 1 , the first adhesive layer 51 is disposed between the at least part of the functional layer 4 and the piezoelectric layer 1 .

[0156] By setting the first adhesive layer 51, the multi-layer electrode layer 3 can be provided with an adhesive force toward the piezoelectric layer 1, thereby improving the connection strength between the electrode layer 3 and the piezoelectric layer 1, further alleviating the tendency of the electrode layer 3 to warp away from the piezoelectric layer 1, and effectively avoiding stratification between the electrode layer 3 and the piezoelectric layer 1, thereby improving the reliability of the surface acoustic wave filter 100 and optimizing the electrical performance of the surface acoustic wave filter 100.

[0157] See also Figure 6By arranging the combined functional layer 4 and the first adhesive layer 51 between the electrode layer 3 and the piezoelectric layer 1, the functional layer 4 is used to prevent the electrode layer 3 from warping and delamination, and the first adhesive layer 51 is used to achieve bonding between the functional layer 4 and the piezoelectric layer 1, thereby obtaining a surface acoustic wave filter 100 with a stable structure.

[0158] Exemplarily, there can be multiple combinations of materials for the first adhesion layer 51 and the functional layer 4. For example, the combination of materials for the first adhesion layer 51 / functional layer 4 can be Ti / V, Ti / Mn, Ti / Zn, Ti / Mo, Ti / Te, Ti / Ag, Ti / Al, Ti / Au, Ti / AlCu alloy, Cr / V, Cr / Mn, Cr / Zn, Cr / Mo, Cr / Te, Cr / Ag, Cr / Al, Cr / Au, Cr / AlCu alloy, etc.

[0159] In some embodiments, Fig.10 As shown, the surface acoustic wave filter 100 may further include a second adhesive layer 52 .

[0160] See also Fig.10 The second adhesive layer 52 is disposed between two adjacent electrode layers 3 , thereby enhancing the connection strength between the two adjacent electrode layers 3 , and also reducing the probability of warping of the electrode layers 3 , thereby improving the structural stability of the surface acoustic wave filter 100 .

[0161] It can be understood that, in other embodiments, the second adhesive layer 52 can be disposed between any two electrode layers 3 , or between any electrode layer 3 and the functional layer 4 , so as to improve the structural stability of the surface acoustic wave filter 100 .

[0162] Exemplarily, the materials of the first adhesive layer 51 and the second adhesive layer 52 may be the same.

[0163] Exemplarily, the materials of the first adhesion layer 51 and the second adhesion layer 52 may include materials such as Ti, Cr, and Ni that have good wetting effects and have adhesion and conductivity.

[0164] Exemplarily, the thickness of the first adhesive layer 51 and the second adhesive layer 52 may be 0 nm to 10 nm.

[0165] In some embodiments, the resistivity of the functional layer 4 is less than or equal to 1×10-6Ωm. For example, the resistivity of the functional layer 4 may be less than or equal to 0.42×10-6Ωm.

[0166] By setting the resistivity of the functional layer 4 to be less than or equal to 1×10-6Ωm, the functional layer 4 can achieve a better conductive effect while avoiding defects such as warping and delamination of the electrode layer 3, thereby avoiding the setting of the functional layer 4 to excessively increase the overall square resistance of the IDT 2, thereby avoiding the problem of severe heating of the IDT 2 when the power is increased, resulting in a reduction in the quality factor of the surface acoustic wave filter 100.

[0167] It is understandable that the thickness and material of the functional layer 4, electrode layer 3, first adhesion layer 51 and second adhesion layer 52 may also be other values ​​or other combinations. The parameters and combinations in the aforementioned embodiments are only illustrative examples and do not constitute a limitation on their specific thickness or materials.

[0168] The present application also provides the following specific embodiments to analyze the beneficial effects of the surface acoustic wave filter 100:

[0169] Embodiment 1

[0170] In this embodiment, a first adhesion layer 51 , a functional layer 4 , a first electrode layer 3 , a second adhesion layer 52 and a second electrode layer 3 are sequentially arranged on the piezoelectric layer 1 , wherein the material combination corresponding to each film layer is Ti / Al / Pt / Ti / Al.

[0171] Among them, the thickness of the first adhesion layer 51 (made of Ti) is set to 5nm, the thickness of the functional layer 4 (made of Al) is set to 20nm, the thickness of the first electrode layer 3 (made of Pt) is set to 370nm, the thickness of the second adhesion layer 52 (made of Ti) is set to 20nm, and the thickness of the second electrode layer 3 (made of Al) is set to 200nm.

[0172] The overall stress of the structure provided in the first embodiment is about 470Mpa. Compared with the structure in the related art where the material of the first adhesion layer is NiCr and the functional layer 4 is not provided, the overall stress of the structure provided in the first embodiment is reduced by about 30%, which effectively reduces the probability of problems such as warping and delamination of the electrode layer 3. In addition, the square resistance of the structure provided in the first embodiment is about 160mΩ / square, which is reduced by about 20% compared with the related art, and has a good positive benefit on the power tolerance of the surface acoustic wave filter 100.

[0173] Embodiment 2

[0174] In this embodiment, a first adhesion layer 51, a functional layer 4, a first electrode layer 3, a second adhesion layer 52 and a second electrode layer 3 are sequentially arranged on the piezoelectric layer 1, wherein the material combination corresponding to each film layer is Ti / Ag / Pt / Ti / Al.

[0175] Among them, the thickness of the first adhesion layer 51 (made of Ti) is set to 5nm, the thickness of the functional layer 4 (made of Ag) is set to 20nm, the thickness of the first electrode layer 3 (made of Pt) is set to 370nm, the thickness of the second adhesion layer 52 (made of Ti) is set to 20nm, and the thickness of the second electrode layer 3 (made of Al) is set to 200nm.

[0176] The overall stress of the structure provided in the second embodiment is about 490Mpa. Compared with the structure in the related art where the material of the first adhesion layer is NiCr and the functional layer 4 is not provided, the overall stress of the structure provided in the first embodiment is reduced by about 25%, and the probability of problems such as warping and delamination of the electrode layer 3 is also reduced. In addition, the square resistance of the structure provided in the second embodiment is about 150mΩ / square, which is reduced by about 30% compared with the related art, further increasing the power tolerance of the surface acoustic wave filter 100.

[0177] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that a person skilled in the art can think of within the technical scope disclosed in the present disclosure should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A surface acoustic wave filter, characterized in that: include: Piezoelectric layer; A multi-layer electrode layer is disposed on the piezoelectric layer, and the multi-layer electrode layer is stacked along a direction perpendicular to the piezoelectric layer; a functional layer, at least a portion of which is disposed on a surface of at least one electrode layer close to the piezoelectric layer; The lattice structure of the functional layer matches the lattice structure of the electrode layer that the functional layer contacts.

2. The surface acoustic wave filter according to claim 1, characterized in that The bonding strength between the functional layer and the electrode layer contacted by the functional layer is greater than or equal to 500 MPa.

3. The surface acoustic wave filter according to claim 1 or 2, characterized in that: The absolute value of the difference between the atomic radius of the element with the highest content in the functional layer and the atomic radius of the element with the highest content in the electrode layer contacting the functional layer is less than or equal to 20 pm.

4. The surface acoustic wave filter according to any one of claims 1 to 3, characterized in that At least a portion of the functional layer is disposed between an electrode layer closest to the piezoelectric layer among the multi-layer electrode layers and the piezoelectric layer.

5. The surface acoustic wave filter according to any one of claims 1 to 4, characterized in that At least part of the functional layer is arranged between two adjacent electrode layers.

6. The surface acoustic wave filter according to any one of claims 1 to 5, characterized in that The functional layer includes a first sublayer and a second sublayer; The first sublayer is arranged on the surface of the at least one electrode layer close to the piezoelectric layer; the second sublayer is arranged on the side of the at least one electrode layer; The first sublayer and the second sublayer are integrally arranged.

7. The surface acoustic wave filter according to any one of claims 1 to 6, characterized in that The functional layer surrounds all surfaces of each electrode layer in the at least one electrode layer.

8. The surface acoustic wave filter according to any one of claims 1 to 7, characterized in that The functional layer surrounds the entire surface of the multi-layer electrode layer.

9. The surface acoustic wave filter according to any one of claims 1 to 8, characterized in that The ratio of the thickness of the functional layer to the thickness of the electrode layer contacted by the functional layer is greater than or equal to 0.04 and less than or equal to 1.

10. The surface acoustic wave filter according to any one of claims 1 to 9, characterized in that The resistivity of the functional layer is less than or equal to 1×10- 6 Ωm.

11. The surface acoustic wave filter according to any one of claims 1 to 10, characterized in that: The grain size of the surface of the functional layer is smaller than the grain size of the surface of the electrode layer that the functional layer contacts.

12. The surface acoustic wave filter according to any one of claims 1 to 11, characterized in that: The material of the at least one electrode layer includes at least one of platinum and tungsten or an alloy of at least one of the platinum and tungsten.

13. The surface acoustic wave filter according to any one of claims 1 to 12, characterized in that: The material of the functional layer includes at least one of vanadium, manganese, zinc, molybdenum, tellurium, silver and aluminum or an alloy of at least one of the above.

14. The surface acoustic wave filter according to any one of claims 1 to 13, characterized in that: Also includes: A first adhesion layer is provided between the piezoelectric layer and the multi-layer electrode layer.

15. The surface acoustic wave filter according to any one of claims 1 to 14, characterized in that: Also includes: The second adhesive layer is arranged between two adjacent electrode layers.

16. A radio frequency module, characterized in that: include: The surface acoustic wave filter according to any one of claims 1 to 15; A power amplifier is provided, and the surface acoustic wave filter is coupled to the power amplifier.

17. An electronic device, characterized in that: include: The surface acoustic wave filter according to any one of claims 1 to 15; A circuit board, wherein the surface acoustic wave filter is arranged on the circuit board.

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