Surface acoustic wave resonator and filter

Abstract

The invention discloses a surface acoustic wave resonator and a filter. The surface acoustic wave resonator comprises a piezoelectric layer; the electrode layer is arranged on the piezoelectric layer; the electrode layer comprises an interdigital transducer; the interdigital transducer comprises two interdigital electrodes which are oppositely arranged in a first direction; each interdigital electrode comprises a bus bar, a plurality of interdigital strips which are connected with the bus bar, extend in the first direction and are arranged in the second direction, and a plurality of sinking false fingers which are positioned on one side, far away from the bus bar, of each interdigital strip and extend in the first direction; the first direction intersects with the second direction; and each sinking false finger sinks into the piezoelectric layer. According to the technical scheme, clutters of a transverse mode can be effectively restrained, meanwhile, the process steps are simplified, and device miniaturization is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of resonators, and particularly to a surface acoustic wave resonator and a filter. Background Art

[0002] Surface Acoustic Wave (SAW) technology plays an important role in the signal separation and filtering processes of mobile communications. Among them, the working principle of a surface acoustic wave resonator is as follows: two interdigital transducers are arranged at intervals on a piezoelectric material layer. First, an electrical signal is transmitted to one interdigital transducer, and based on the piezoelectric effect, the input electrical signal is converted into an acoustic wave signal and the acoustic wave is processed. Then, the acoustic wave signal is converted back into an electrical signal and output through the other interdigital transducer.

[0003] Such devices will have problems of transverse spurious modes and transverse energy leakage, which affect the performance of the resonator. The main mode of the resonator at the resonant frequency is the shear horizontal wave. However, the resonance caused by Rayleigh waves will trigger spurious frequencies below the resonant frequency, the resonance caused by fast shear horizontal waves will trigger spurious frequencies above the anti-resonant frequency, and the velocity change between different regions (such as the bus bar region, the gap region, the virtual finger region, and the interdigital bar region) on the resonator will cause transverse energy leakage.

[0004] To improve the above problems, existing research has means to adjust the velocity change at the interdigital ends or the gap region, such as adding a material mass loading layer with different densities in such regions. However, due to the limitations of material properties, the mass loading layer must have a certain thickness to achieve a better effect of reducing the acoustic wave propagation velocity in a specific region, resulting in an increase in the device volume, and the thickness is difficult to accurately control, increasing the process difficulty and being not conducive to large-scale production. Therefore, how to propose an effective method for suppressing transverse spurious modes without increasing additional process difficulty and process cost is a technical problem to be solved urgently. Summary of the Invention

[0005] The present invention provides a surface acoustic wave resonator and a filter to solve the problems existing in the prior art, achieve effective suppression of the transverse clutter modes of the surface acoustic wave resonator, and at the same time, simplify the process steps and is conducive to the miniaturization of the device.

[0006] In a first aspect, the present invention provides a surface acoustic wave resonator, comprising:

[0007] A piezoelectric layer;

[0008] An electrode layer disposed on the piezoelectric layer; the electrode layer includes an interdigital transducer; the interdigital transducer includes two interdigital electrodes disposed opposite to each other in a first direction; each of the interdigital electrodes includes a bus bar, a plurality of interdigital fingers connected to the bus bar and extending in the first direction and arranged in a second direction, and a plurality of sinking dummy fingers located on a side of each interdigital finger away from the bus bar and extending in the first direction; the first direction and the second direction intersect;

[0009] Each of the sinking dummy fingers sinks into the piezoelectric layer.

[0010] Optionally, there is a gap between the sinking dummy finger and the corresponding interdigital finger, and / or there is a gap between the sinking dummy finger and the adjacent bus bar; the relationship between the total length L of the gap and the length dummy_L of the sinking dummy finger satisfies: 0 ≤ L ≤ 1 / 5 dummy_L.

[0011] Optionally, the relationship between the thickness T of the piezoelectric layer and the depth dummy_T to which the sinking dummy finger sinks into the piezoelectric layer satisfies: 1 / 3 T ≤ dummy_T ≤ T.

[0012] Optionally, the relationship between the width w of the interdigital finger in the second direction and the width dummy_w of the sinking dummy finger in the second direction satisfies: w ≤ dummy_w ≤ 3w.

[0013] Optionally, the piezoelectric layer is provided with a plurality of grooves; the grooves are located on a side of the piezoelectric layer close to the electrode layer; in a third direction, each groove corresponds to one of the sinking dummy fingers; the third direction is perpendicular to the first direction and the second direction;

[0014] The sinking dummy finger is formed by the groove.

[0015] Optionally, the piezoelectric layer is provided with a plurality of grooves; the grooves are located on a side of the piezoelectric layer close to the electrode layer; in a third direction, each groove corresponds to one of the sinking dummy fingers; the third direction is perpendicular to the first direction and the second direction;

[0016] The groove is filled with a dummy finger structure, and the sinking dummy finger is formed by the groove and the dummy finger structure.

[0017] Optionally, the dummy finger structure includes at least one of silicon dioxide, silicon nitride, tantalum pentoxide, aluminum, copper, magnesium, beryllium, molybdenum, and tungsten.

[0018] Optionally, along the third direction, the relationship between the thickness T1 of the electrode layer, the depth T2 of the groove, and the height T3 of the dummy finger structure satisfies: T3 ≤ T1 + T2.

[0019] Optionally, the electrode layer further includes a first reflector and a second reflector; along the second direction, the first reflector, the interdigital transducer, and the second reflector are arranged in sequence.

[0020] In a second aspect, the present invention further provides a filter, including the surface acoustic wave resonator described in any one of the above.

[0021] According to the technical solution of the present invention, the surface acoustic wave resonator includes a piezoelectric layer and an electrode layer disposed on the piezoelectric layer, and the electrode layer includes an interdigital transducer. The interdigital transducer includes two interdigital electrodes oppositely disposed in a first direction. Each interdigital electrode includes a bus bar, a plurality of interdigital bars connected to the bus bar and extending in the first direction and arranged in the second direction, and a plurality of sinking dummy fingers located on the side of each interdigital bar away from the bus bar and extending in the first direction. Each sinking dummy finger sinks into the piezoelectric layer, so that in the transverse direction, the sound velocity in the area of the sinking dummy fingers increases, thereby suppressing the transverse spurious mode of the surface acoustic wave resonator. At the same time, since the sinking dummy fingers can be obtained by directly etching the piezoelectric layer, there is no need for additional material deposition and complex pattern lithography, and there is no need to increase the thickness, which can simplify the manufacturing process of the surface acoustic wave resonator and is beneficial to the miniaturization of the surface acoustic wave resonator.

[0022] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0024] Figure 1 It is a schematic structural diagram of a surface acoustic wave resonator provided by an embodiment of the present invention;

[0025] Figure 2 It is a cross-sectional view of a surface acoustic wave resonator provided by an embodiment of the present invention along the line A - A';

[0026] Figure 3 It is a cross-sectional view of a surface acoustic wave resonator provided by an embodiment of the present invention along the line B - B';

[0027] Figure 4 It is a cross-sectional view of another surface acoustic wave resonator provided by an embodiment of the present invention along the line A - A';

[0028] Figure 5 A cross-sectional view along line B-B' of another surface acoustic wave resonator provided by an embodiment of the present invention;

[0029] Figure 6 A cross-sectional view along line B-B' of another surface acoustic wave resonator provided by an embodiment of the present invention;

[0030] Figure 7 An impedance curve diagram of a surface acoustic wave resonator with a basic structure in the prior art;

[0031] Figure 8 An impedance curve diagram of a surface acoustic wave resonator provided by an embodiment of the present invention;

[0032] Figure 9 A schematic structural diagram of another surface acoustic wave resonator provided by an embodiment of the present invention;

[0033] Figures 10 - 12 Cross-sectional views along line A-A' of another three surface acoustic wave resonators provided by an embodiment of the present invention;

[0034] Figures 13 - 15 Cross-sectional views along line B-B' of another three surface acoustic wave resonators provided by an embodiment of the present invention;

[0035] Figure 16 A schematic structural diagram of a filter provided by an embodiment of the present invention. Detailed implementation manners

[0036] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0037] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein.

[0038] Embodiment 1

[0039] This embodiment provides a surface acoustic wave resonator, Figure 1 A schematic structural diagram of a surface acoustic wave resonator provided by an embodiment of the present invention,Figure 2 A cross-sectional view along line A-A' of a surface acoustic wave resonator provided by an embodiment of the present invention, Figure 3 A cross-sectional view along line B-B' of a surface acoustic wave resonator provided by an embodiment of the present invention. With reference to the combination shown, Figures 1 to 3 the surface acoustic wave resonator 01 includes a piezoelectric layer 10 and an electrode layer 20. The electrode layer 20 is disposed on the piezoelectric layer 10, and the electrode layer 20 includes an interdigital transducer 3. The interdigital transducer 3 includes two interdigital electrodes oppositely disposed in a first direction L1. Each interdigital electrode includes a bus bar 100, a plurality of interdigital bars 102 connected to the bus bar 100 and extending in the first direction L1 and arranged in a second direction L2, and a plurality of sinking dummy fingers 101A located on a side of each interdigital bar 102 away from the bus bar 100 and extending in the first direction L1. The first direction L1 and the second direction L2 intersect; each sinking dummy finger 101A sinks into the piezoelectric layer 10.

[0040] Among them, the piezoelectric layer 10 can be prepared from piezoelectric materials such as piezoelectric crystals and piezoelectric ceramics. In an exemplary embodiment, the material for preparing the piezoelectric layer 10 may include one or more of lithium tantalate and lithium niobate, etc. It should be noted that the above is only an exemplary description of the piezoelectric layer 10, rather than a limitation on the piezoelectric layer 10.

[0041] In an alternative embodiment, the surface acoustic wave resonator mainly includes a substrate (such as a silicon substrate), a buried layer (such as silicon dioxide or amorphous silicon, etc.), a piezoelectric layer 10, an electrode layer 20, and a temperature compensation layer. Among them, the substrate layer, the buried layer, and the temperature compensation layer are not shown in the drawings provided by this embodiment.

[0042] The interdigital electrodes of the interdigital transducer 3 are oppositely disposed in the first direction L1, and each interdigital bar 102 of each interdigital electrode extends in the first direction L1 and is arranged in the second direction L2. The first direction L1 and the second direction L2 intersect, so that the interdigital transducer 3 can achieve acoustic-electric conversion. The intersection of the first direction L1 and the second direction L2 may include an acute angle, a right angle, or an obtuse angle formed between the straight lines where the first direction L1 and the second direction L2 are located. In an exemplary embodiment, the straight lines where the first direction L1 and the second direction L2 are located form a right angle, so as to reduce the manufacturing difficulty of the interdigital bars 102. The bus bar 100 mainly functions as an electrical connection and needs to be prepared from a material with good conductivity. In an alternative embodiment, the bus bar 100 and the interdigital bars 102 of the interdigital electrode can be prepared from a metal material or an alloy material. Exemplarily, the materials for preparing the bus bar 100 and the interdigital bars 102 may include at least one of aluminum, copper, magnesium, beryllium, molybdenum, or aluminum-copper alloy, etc. It should be noted that the materials of the bus bar 100 and the interdigital bars 102 may be the same or different, and this embodiment does not limit this, as long as the function of the interdigital transducer 3 can be achieved.

[0043] It is understandable that Figure 1 and Figure 2 only the case where each interdigital electrode includes 5 interdigital fingers 102 is exemplarily shown, and the number of the interdigital fingers 102 is not limited; in this embodiment, the number of the interdigital fingers 102 is not specifically limited. In an alternative embodiment, the number of the interdigital fingers 102 can be set according to the performance requirements of the surface acoustic wave resonator. For ease of understanding, the following embodiments will be described by taking the case where each interdigital electrode includes 5 interdigital fingers 102 as an example.

[0044] In an alternative embodiment, the electrode layer 20 further includes a first reflector 1 and a second reflector 2; along the second direction L2, the first reflector 1, the interdigital transducer 3, and the second reflector 2 are arranged in sequence, so that the acoustic wave in the passband can be placed between the first reflector 1 and the second reflector 2, so that the acoustic wave propagates between the interdigital transducers 3, realizing the function of the surface acoustic wave resonator. Exemplarily, the materials for preparing the first reflector 1 and the second reflector 2 may include at least one of aluminum, copper, magnesium, beryllium, molybdenum, or aluminum-copper alloy, etc. In an exemplary embodiment, to simplify the preparation steps of the surface acoustic wave resonator, the first reflector 1, the second reflector 2, and each interdigital electrode are prepared from the same material.

[0045] Each sunken dummy finger 101A sinks into the piezoelectric layer 10 and is arranged corresponding to each interdigital finger 102 one by one. The sunken dummy finger 101A is located on the side of each interdigital finger 102 away from the bus bar 100 and extends in the first direction L1, which is beneficial to increasing the sound velocity of the acoustic wave at each sunken dummy finger 101A, thereby increasing the potential barrier of the acoustic wave at each sunken dummy finger 101A, and further reducing the lateral loss of the acoustic wave.

[0046] It should be noted that each sunken dummy finger 101A sinks into the piezoelectric layer 10 can be understood as that each sunken dummy finger 101A is located in part or all of the piezoelectric layer 10 Figure 2 and Figure 3 only the case where the sunken dummy finger 101A is located in part of the piezoelectric layer 10 is exemplarily shown, and the depth of the sunken dummy finger 101A sinking into the piezoelectric layer 10 is not limited. In other embodiments Figure 4 is a cross-sectional view along the A-A' line of another surface acoustic wave resonator provided by an embodiment of the present invention Figure 5 is a cross-sectional view along the B-B' line of yet another surface acoustic wave resonator provided by an embodiment of the present invention. With reference to Figure 4 and Figure 5 as shown, the sunken dummy finger 101A can also be located in all of the piezoelectric layer 10, that is, the sunken dummy finger 101A penetrates the piezoelectric layer 10, thereby further increasing the sound velocity of the acoustic wave at each sunken dummy finger 101A.

[0047] It should also be noted thatFigure 1 , Figure 3 and Figure 5 Only an example is given where the width of the sinking false finger 101A along the second direction L2 is the same as the width of the interdigital finger 102 along the second direction L2, which does not limit the width of the sinking false finger 101A along the second direction L2. In this embodiment, the width of the sinking false finger 101A along the second direction L2 may be the same as or different from the width of the interdigital finger 102 along the second direction L2, as long as the core inventive point of the present invention can be achieved. In other embodiments, Figure 6 is a cross-sectional view along the B-B' line of another surface acoustic wave resonator provided by an embodiment of the present invention. Refer to Figure 6 As shown, the width of the sinking false finger 101A along the second direction L2 may also be greater than the width of the interdigital finger 102 along the second direction L2, so as to further increase the sound velocity of the sound wave at each sinking false finger 101A.

[0048] This embodiment does not limit the specific method of sinking each sinking false finger 101A into the piezoelectric layer 10. In an optional embodiment, each sinking false finger 101A is formed at the corresponding position of the piezoelectric layer 10 by etching the piezoelectric layer 10.

[0049] Figure 7 is an impedance curve diagram of a surface acoustic wave resonator with a basic structure in the prior art. Figure 8 is an impedance curve diagram of the surface acoustic wave resonator provided by an embodiment of the present invention. Combining with reference to Figure 7 and Figure 8 it can be seen that there are obvious spurious modes in the passband of the surface acoustic wave resonator with the basic structure in the prior art. At the same time, there is a certain degree of lateral energy leakage, which will seriously affect the performance of the surface acoustic wave resonator; while the dispersion response existing in the passband of the surface acoustic wave resonator provided by this embodiment is significantly improved. At the same time, the resonance frequency, electromechanical coupling coefficient and quality factor of the resonator basically remain unchanged, and there is no obvious performance degradation. The above shows that the surface acoustic wave resonator provided by this embodiment can suppress the lateral spurious modes without affecting other performances, and has a simple process and low cost.

[0050] In this embodiment, the surface acoustic wave resonator includes a piezoelectric layer and an electrode layer arranged on the piezoelectric layer, and the electrode layer includes an interdigital transducer, the interdigital transducer includes two interdigital electrodes arranged opposite to each other in a first direction, each interdigital electrode includes a bus bar, a plurality of interdigital bars connected to the bus bar and extending in the first direction and arranged in the second direction, and a plurality of sunken dummy fingers located on a side of each interdigital bar away from the bus bar and extending in the first direction, each sunken dummy finger sinks into the piezoelectric layer, so that the sound velocity in the sunken dummy finger area in the lateral direction is increased, thereby suppressing the lateral stray mode of the surface acoustic wave resonator; at the same time, since the sunken dummy fingers can be obtained by directly etching the piezoelectric layer, there is no need for additional deposition of materials and complex pattern lithography, and there is no need to increase the thickness, the preparation process of the surface acoustic wave resonator can be simplified, which is conducive to the miniaturization of the surface acoustic wave resonator.

[0051] It should be noted that the interdigital strip 102 and the sunken dummy finger 101A, as well as the sunken dummy finger 101A and the adjacent bus bar 100 can be arranged closely or with a gap therebetween, as long as the sound speed in the sunken dummy finger 101A area is different from that in the interdigital strip 102 area.

[0052] Optionally, there is a gap between the sunken dummy finger 101A and the corresponding interdigital bar 102, and / or there is a gap between the sunken dummy finger 101A and the adjacent bus bar 100, and the relationship between the total length L of the gap and the length dummy_L of the sunken dummy finger 101A satisfies: 0≤L≤1 / 5dummy_L.

[0053] Wherein, the gap region is not provided with the sunken false fingers 101A or the interdigitated strips 102, so that the transverse sound waves can propagate in the gap region, and the transverse loss of the sound waves in the gap region cannot be reduced. The existence of a gap between the sinking dummy finger 101A and the corresponding interdigitated bar 102, and / or the existence of a gap between the sinking dummy finger 101A and the adjacent bus bar 100 can be understood as: there is a gap between the sinking dummy finger 101A and the corresponding interdigitated bar 102, while there is no gap between the sinking dummy finger 101A and the adjacent bus bar 100, that is, the sinking dummy finger 101A and the adjacent bus bar 100 are arranged adjacent to each other, or, there is no gap between the sinking dummy finger 101A and the corresponding interdigitated bar 102, that is, the sinking dummy finger 101A and the corresponding interdigitated bar 102 are arranged adjacent to each other, while there is a gap between the sinking dummy finger 101A and the adjacent bus bar 100, or, there are gaps both between the sinking dummy finger 101A and the corresponding interdigitated bar 102 and between the adjacent bus bar 100. Figure 1 , Figure 2 and Figure 4Only an example shows that there is a gap between the sunken dummy finger 101A and the corresponding bus bar 100, and the case where the sunken dummy finger 101A is arranged adjacent to the adjacent bus bar 100 does not limit the relative positions among the sunken dummy finger 101A, the interdigital finger bars, and the bus bar 100.

[0054] Specifically, the shorter the total length of the gap is, the better the suppression effect on the transverse wave is. However, limited by the precision of the manufacturing process, it is difficult for the length of the gap to be 0. On the contrary, when the total length L of the gap is greater than 1 / 5 dummy_L, since the total length L of the gap is too long, the lateral loss of the acoustic wave cannot be effectively reduced, and thus the transverse clutter mode of the surface acoustic wave resonator cannot be effectively suppressed. Therefore, by making the relationship between the total length L of the gap and the length dummy_L of the sunken dummy finger 101A satisfy 0 ≤ L ≤ 1 / 5 dummy_L, the transverse clutter mode of the surface acoustic wave resonator can be effectively suppressed.

[0055] Optionally, the relationship between the thickness T of the piezoelectric layer 10 and the depth dummy_T at which the sunken dummy finger 101A sinks into the piezoelectric layer 10 satisfies: 1 / 3T ≤ dummy_T ≤ T.

[0056] Specifically, the greater the depth dummy_T at which the sunken dummy finger 101A sinks into the piezoelectric layer 10 is, the greater the sound velocity of the acoustic wave in the area of the sunken dummy finger 101A is, and the greater the potential barrier of the acoustic wave at the sunken dummy finger 101A is, so that the transverse clutter mode of the surface acoustic wave resonator can be more effectively suppressed. However, due to the limitation of the thickness T of the piezoelectric layer 10, the maximum depth dummy_T at which the sunken dummy finger 101A sinks into the piezoelectric layer 10 can be the same as the thickness T of the piezoelectric layer 10, that is, the sunken dummy finger 101A can penetrate the piezoelectric layer 10, so that the transverse clutter mode of the surface acoustic wave resonator can be suppressed to the greatest extent. When the depth dummy_T at which the sunken dummy finger 101A sinks into the piezoelectric layer 10 is less than 1 / 3T, since the depth dummy_T at which the sunken dummy finger 101A sinks into the piezoelectric layer 10 is too small, the potential barrier of the acoustic wave at the sunken dummy finger 101A is too small, and thus the transverse clutter mode of the surface acoustic wave resonator cannot be effectively suppressed. Therefore, by making the relationship between the thickness T of the piezoelectric layer 10 and the depth dummy_T at which the sunken dummy finger 101A sinks into the piezoelectric layer 10 satisfy 1 / 3T ≤ dummy_T ≤ T, the transverse clutter mode of the surface acoustic wave resonator can be effectively suppressed, thereby improving the performance of the surface acoustic wave resonator.

[0057] Optionally, the relationship between the width w of the interdigital finger bar 102 in the second direction L2 and the width dummy_w of the sunken dummy finger 101A in the second direction L2 satisfies: w ≤ dummy_w ≤ 3w.

[0058] Specifically, the larger the width dummy_w of the sinking dummy finger 101A in the second direction L2, the greater the sound velocity of the sound wave in the area of the sinking dummy finger 101A, and the greater the potential barrier of the sound wave at the sinking dummy finger 101A. Thus, the lateral clutter mode of the surface acoustic wave resonator can be more effectively suppressed. However, due to the limited gap between two adjacent finger bars and the fact that the piezoelectric layer 10 under the finger bars is not easily removed, the edge of the sinking dummy finger 101A cannot cross the adjacent finger bars. When the width dummy_w of the sinking dummy finger 101A in the second direction L2 is smaller than the width w of the finger bar 102 in the second direction L2, since the width dummy_w of the sinking dummy finger 101A is too small, the potential barrier of the sound wave at the sinking dummy finger 101A is too small, and thus the lateral clutter mode of the surface acoustic wave resonator cannot be effectively suppressed. Therefore, by making the relationship between the width w of the finger bar 102 in the second direction L2 and the width dummy_w of the sinking dummy finger 101A in the second direction L2 satisfy w ≤ dummy_w ≤ 3w, the lateral clutter mode of the surface acoustic wave resonator can be effectively suppressed, thereby improving the performance of the surface acoustic wave resonator.

[0059] Optionally, a plurality of grooves 10A are provided in the piezoelectric layer 10; the grooves 10A are located on the side of the piezoelectric layer 10 close to the electrode layer 20, and in the third direction, each groove 10A corresponds to a sinking dummy finger 101A one by one. The third direction is perpendicular to the first direction L1 and the second direction L2.

[0060] Among them, the plurality of grooves 10A in the piezoelectric layer 10 can be formed by an etching method. The position of the groove 10A in the piezoelectric layer 10 is the position of the part where the sinking dummy finger 101A sinks into the piezoelectric layer 10. The third direction is the thickness direction of the surface acoustic wave resonator.

[0061] In an alternative embodiment, referring to Figures 1 - 6 as shown, the sinking dummy finger 101A is formed by the groove 10A, so that the sinking dummy finger 101A can be formed without further deposition and etching processes, thereby simplifying the manufacturing process of the surface acoustic wave resonator and suppressing the lateral stray mode of the surface acoustic wave resonator at the same time.

[0062] In another alternative embodiment, Figure 9 is a schematic structural diagram of another surface acoustic wave resonator provided by an embodiment of the present invention, Figures 10 - 12 is a cross-sectional view along the A-A' line of another three surface acoustic wave resonators provided by an embodiment of the present invention, Figures 13 - 15 is a cross-sectional view along the B-B' line of another three surface acoustic wave resonators provided by an embodiment of the present invention. With reference to Figures 9 - 15 as shown, the groove 10A is filled with a finger structure, and the sinking dummy finger 101A is formed by the groove 10A and the finger structure.

[0063] Among them, the density of the dummy finger structure is different from that of the piezoelectric layer 10 and the interdigital electrodes, such that the density of the sunken dummy finger 101A is different from that of the piezoelectric layer 10 and the interdigital electrodes, so that the sound velocity of the sound wave in the area of the sunken dummy finger 101A is different, thereby also being able to suppress the lateral spurious modes of the surface acoustic wave resonator.

[0064] In an alternative embodiment, the material forming the dummy finger structure includes but is not limited to at least one of silicon dioxide, silicon nitride, tantalum pentoxide, aluminum, copper, magnesium, beryllium, molybdenum, and tungsten.

[0065] Optionally, along the third direction, the relationship among the thickness T1 of the electrode layer 20, the depth T2 of the groove 10A, and the height T3 of the dummy finger structure satisfies: T3 ≤ T1 + T2.

[0066] Among them, the relationship among the thickness T1 of the electrode layer 20, the depth T2 of the groove 10A, and the height T3 of the dummy finger structure satisfying T3 ≤ T1 + T2 means that the height T3 of the dummy finger structure can be less than or equal to the depth T2 of the groove 10A, that is, the upper surface of the dummy finger structure is lower than the upper surface of the piezoelectric layer 10 or is on the same horizontal plane as the upper surface of the piezoelectric layer 10, or can be greater than the depth T2 of the groove 10A but less than or equal to the sum of the thickness T1 of the electrode layer 20 and the depth T2 of the groove 10A, that is, the upper surface of the dummy finger structure is higher than the upper surface of the piezoelectric layer 10 but lower than the upper surface of the electrode layer 20.

[0067] It should be noted that Figure 10 、 Figures 12 - 15 only the case where the height T3 of the dummy finger structure is equal to the depth T2 of the groove 10A is exemplarily shown, Figure 11 only the case where the height T3 of the dummy finger structure is greater than the depth T2 of the groove 10A but less than or equal to the sum of the thickness T1 of the electrode layer 20 and the depth T2 of the groove 10A is exemplarily illustrated, and it does not limit the relationship among the height T3 of the dummy finger structure, the thickness T1 of the electrode layer 20, and the depth T2 of the groove 10A.

[0068] Based on the same inventive concept, Figure 16 is a schematic structural diagram of a filter provided by an embodiment of the present invention. The embodiment of the present invention also provides a filter. Referring to Figure 16 as shown, the filter includes the surface acoustic wave resonator provided in any of the above embodiments.

[0069] Since the filter provided by the embodiment of the present invention includes the surface acoustic wave resonator provided in this embodiment, it has the corresponding structures and characteristics of the surface acoustic wave resonator, and can achieve the beneficial effects of the surface acoustic wave resonator provided in any embodiment of the present invention. The same parts can refer to the above description.

[0070] In an alternative embodiment, the embodiment of the present invention further provides a multiplexer, which includes the surface acoustic wave resonator provided in any of the above embodiments. Therefore, it has the corresponding structures and features of the surface acoustic wave resonator and can achieve the beneficial effects of the surface acoustic wave resonator provided in any embodiment of the present invention. For the same parts, reference can be made to the above description.

[0071] The above specific embodiments do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A surface acoustic wave resonator, characterized in that: include: Piezoelectric layer; An electrode layer disposed on the piezoelectric layer; the electrode layer includes an interdigital transducer; the interdigital transducer includes two interdigital electrodes disposed opposite to each other in a first direction; Each of the interdigitated electrodes comprises a bus bar, a plurality of interdigitated bars connected to the bus bar and extending in the first direction and arranged in the second direction, and a plurality of sunken false fingers located on a side of each of the interdigitated bars away from the bus bar and extending in the first direction; the first direction and the second direction intersect; Each of the sunken fingers sinks into the piezoelectric layer.

2. The surface acoustic wave resonator according to claim 1, characterized in that: There is a gap between the sunken dummy finger and the corresponding interdigitated bar, and / or there is a gap between the sunken dummy finger and the adjacent bus bar; the relationship between the total length L of the gap and the length dummy_L of the sunken dummy finger satisfies: 0≤L≤1 / 5dummy_L.

3. The surface acoustic wave resonator according to claim 1, characterized in that: The relationship between the thickness T of the piezoelectric layer and the depth dummy_T of the sunken dummy finger into the piezoelectric layer satisfies: 1 / 3T≤dummy_T≤T.

4. The surface acoustic wave resonator according to claim 1, characterized in that: The relationship between the width w of the interdigitated strip in the second direction and the width dummy_w of the sunken dummy finger in the second direction satisfies: w≤dummy_w≤3w.

5. The surface acoustic wave resonator according to any one of claims 1 to 4, characterized in that: The piezoelectric layer is provided with a plurality of grooves; the grooves are located on a side of the piezoelectric layer close to the electrode layer; in a third direction, each of the grooves corresponds to a sinking finger one by one; the third direction is perpendicular to the first direction and the second direction; The sunken false fingers are formed by the grooves.

6. The surface acoustic wave resonator according to any one of claims 1 to 4, characterized in that: The piezoelectric layer is provided with a plurality of grooves; the grooves are located on a side of the piezoelectric layer close to the electrode layer; in a third direction, each of the grooves corresponds to a sinking finger one by one; the third direction is perpendicular to the first direction and the second direction; The groove is filled with a dummy finger structure, and the sunken dummy finger is formed by the groove and the dummy finger structure.

7. The surface acoustic wave resonator according to claim 6, characterized in that: The pseudo-finger structure includes at least one of silicon dioxide, silicon nitride, tantalum pentoxide, aluminum, copper, magnesium, beryllium, molybdenum, and tungsten.

8. The surface acoustic wave resonator according to claim 6, characterized in that: Along the third direction, the relationship between the thickness T1 of the electrode layer, the depth T2 of the groove and the height T3 of the dummy finger structure satisfies: T3≤T1+T2.

9. The surface acoustic wave resonator according to claim 1, characterized in that: The electrode layer further includes a first reflector and a second reflector; along the second direction, the first reflector, the IDT and the second reflector are arranged in sequence.

10. A filter, characterized in that: The invention comprises a surface acoustic wave resonator as claimed in any one of claims 1 to 9.

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