Surface acoustic wave device and radio frequency front-end module

Abstract

The invention discloses a surface acoustic wave device, which comprises a substrate, a first dielectric layer, a piezoelectric layer, an interdigital transducer and a second dielectric layer, the first dielectric layer is arranged on the substrate; the piezoelectric layer is arranged on the first dielectric layer; the interdigital transducer is arranged on the surface of the piezoelectric layer, an overlapping area is formed between the two bus bars in the extending direction of the electrode fingers, a gap area is formed between the overlapping area and the bus bars, and the gap area is adjacent to the ends, close to the overlapping area, of the bus bars; the second dielectric layer is located in at least one gap region and covers the piezoelectric layer and the electrode fingers located in the gap region; wherein the propagation speed of the sound waves in the first dielectric layer and the propagation speed of the sound waves in the second dielectric layer are larger than the propagation speed of the sound waves in the piezoelectric layer, and the thickness of the first dielectric layer and the thickness of the second dielectric layer meet the condition that h2 is smaller than or equal to 0.3 h1. The surface acoustic wave device solves the problem that the Q value of the surface acoustic wave device cannot be improved and the high-frequency impure-mode suppression effect near the anti-resonance point cannot be improved in the prior art.

Description

Technical Field

[0001] The present application relates to the field of radio frequency filtering technology, and in particular to a surface acoustic wave device and a radio frequency front-end module. Background Art

[0002] A surface acoustic wave (SAW) device, such as a surface acoustic wave resonator, is a device that converts an electrical signal into an acoustic signal or converts an acoustic signal into an electrical signal. A surface acoustic wave device generally includes a substrate, a piezoelectric layer, and an interdigital transducer (IDT). The IDT is formed on the piezoelectric layer and can be used to convert an electrical signal into an acoustic signal or convert an acoustic signal into an electrical signal.

[0003] At present, the development of radio frequency technology has put higher requirements on the performance of surface acoustic wave devices. Therefore, how to ensure the quality factor (Bode Q) of surface acoustic wave devices while improving the high-frequency clutter mode suppression effect has become a problem that needs to be solved urgently. Summary of the invention

[0004] The present application provides a surface acoustic wave device and a radio frequency front-end module, which solves the problem in the related art that the surface acoustic wave device cannot improve the Q value while also improving the high-frequency clutter mode suppression effect near the anti-resonance point.

[0005] In a first aspect, the present application provides a surface acoustic wave device, the surface acoustic wave device comprising a substrate, a first dielectric layer, a piezoelectric layer, an interdigital transducer, and a second dielectric layer;

[0006] A first dielectric layer is disposed on the substrate;

[0007] The piezoelectric layer is disposed on the first dielectric layer;

[0008] An interdigital transducer is arranged on the surface of the piezoelectric layer, and the interdigital transducer includes two comb-shaped electrodes arranged opposite to each other, each of the comb-shaped electrodes includes a bus bar and a plurality of electrode fingers connected to the bus bar and arranged at intervals, and the electrode fingers of the two comb-shaped electrodes are arranged alternately with each other; in the extension direction of the electrode fingers, there is an overlapping area between the two bus bars, and the overlapping area is the area where the electrode fingers overlap with each other, and a gap area is included between the overlapping area and the bus bar, and the gap area is adjacent to one end of the bus bar close to the overlapping area;

[0009] The second dielectric layer is located in at least one of the gap regions and covers the piezoelectric layer and the electrode fingers located in the gap region;

[0010] Among them, the propagation speed of the sound wave in the first dielectric layer and the propagation speed of the sound wave in the second dielectric layer are greater than the propagation speed of the sound wave in the piezoelectric layer, the thickness of the first dielectric layer is h1, the thickness of the second dielectric layer is h2, and the thickness of the first dielectric layer and the thickness of the second dielectric layer satisfy: h2≤0.3h1.

[0011] In a second aspect, the present application also provides a radio frequency front-end module, comprising the surface acoustic wave device as described above.

[0012] The surface acoustic wave device provided by the present application includes a substrate, a first dielectric layer, a piezoelectric layer, an interdigital transducer and a second dielectric layer; the first dielectric layer is arranged on the substrate; the piezoelectric layer is arranged on the first dielectric layer; the interdigital transducer is arranged on the surface of the piezoelectric layer, the interdigital transducer includes two comb-shaped electrodes arranged opposite to each other, each comb-shaped electrode includes a bus bar and a plurality of electrode fingers connected to the bus bar and arranged at intervals, and the electrode fingers of the two comb-shaped electrodes are arranged alternately with each other; in the extension direction of the electrode fingers, there is an overlapping area between the two bus bars, and a gap area is included between the overlapping area and the bus bar, and the gap area is adjacent to one end of the bus bar close to the overlapping area; the second dielectric layer is located in at least one gap area and covers the piezoelectric layer and the electrode fingers located in the gap area; wherein the propagation speed of the sound wave in the first dielectric layer and the propagation speed of the sound wave in the second dielectric layer are greater than the propagation speed of the sound wave in the piezoelectric layer, the thickness of the first dielectric layer is h1, the thickness of the second dielectric layer is h2, and the thickness of the first dielectric layer and the thickness of the second dielectric layer satisfy: h2≤0.3h1. By setting a first dielectric layer between the substrate and the piezoelectric layer and a second dielectric layer in the gap area, and controlling the thickness relationship between the first dielectric layer and the second dielectric layer, due to the interaction between the first dielectric layer and the second dielectric layer, it is possible to reduce the leakage of the main mode energy of the surface acoustic wave toward the substrate and the bus bar, while also improving the high-frequency stray mode suppression effect at and near the anti-resonance point and improving the Q value of the surface acoustic wave device. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0014] Figure 1 is a schematic structural diagram of a surface acoustic wave device provided in an embodiment of the present application;

[0015] Figure 2 yes Figure 1 Schematic diagram of the cross-sectional structure along the aa direction;

[0016] Figure 3 is a schematic structural diagram of another surface acoustic wave device provided in an embodiment of the present application;

[0017] Figure 4 yes Figure 3 A schematic diagram of the cross-sectional structure along the bb direction;

[0018] Figure 5 is a schematic structural diagram of another surface acoustic wave device provided in an embodiment of the present application;

[0019] Figure 6 is a schematic structural diagram of another surface acoustic wave device provided in an embodiment of the present application;

[0020] Figure 7 yes Figure 6 Schematic diagram of the cross-sectional structure along the cc direction;

[0021] Figure 8 is a schematic structural diagram of another surface acoustic wave device provided in an embodiment of the present application;

[0022] Fig. 9 It is a schematic diagram comparing harmonic admittance curves of the surface acoustic wave device provided in the embodiment of the present application and the surface acoustic wave device provided in the related art;

[0023] Fig.10 It is a schematic diagram comparing Q value variation curves of the surface acoustic wave device provided in the embodiment of the present application and the surface acoustic wave device provided in the related art. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0025] The flowcharts shown in the accompanying drawings are only examples and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps may also be decomposed, combined or partially merged, so the actual execution order may change according to actual conditions.

[0026] It should be understood that the terms used in this application specification are only for the purpose of describing specific embodiments and are not intended to limit the application. As used in this application specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0027] It should also be understood that the term “and / or” used in the specification and appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0028] In conjunction with the accompanying drawings, some embodiments of the present application are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0029] The following is a brief description of the implementation method in the related art.

[0030] Piezoelectric Thin Film SAW device is a SAW device that uses piezoelectric film as piezoelectric functional material. Its main advantages lie in its excellent temperature characteristics and high power tolerance. By bonding the piezoelectric layer and the substrate together, temperature changes are suppressed and heat dissipation is improved, thereby achieving high power tolerance.

[0031] Piezoelectric film SAW devices are particularly important in RF front-end modules because they can provide higher Q values, higher energy efficiency, and lower energy loss than temperature compensated surface acoustic wave (TC-SAW) devices and bulk acoustic wave (BAW) devices. In addition, the process flow of piezoelectric film SAW devices is relatively simple, the cost is lower, and a smaller area and wider bandwidth can be achieved. In terms of performance, the Q value of piezoelectric film SAW devices is greater than 4000, the coupling coefficient (k2) is greater than 8%, and the temperature coefficient of frequency (TCF) is less than 10ppm / ℃.

[0032] In order to improve the Q value, the gap area of ​​the piezoelectric film SAW device is generally shorter, but the shorter gap area will make the method of setting a mass load structure (such as a piston structure or a hammer structure) at the end of the electrode finger in the related technology no longer applicable to the piezoelectric film SAW device. This is because the shorter gap area will change the reflection coefficient at the end of the electrode finger. When the reflection coefficient at the end of the electrode finger changes, it may affect the propagation path and mode of light, and then affect the high-frequency stray mode suppression effect, thereby deteriorating the high-frequency stray mode suppression effect. At the same time, there is also a large amount of lateral acoustic wave energy transmitted to the gap area and the bus bar, which will cause unnecessary stray resonance.

[0033] To this end, the present application provides a surface acoustic wave device and a radio frequency front-end module, the surface acoustic wave device comprising a substrate, a first dielectric layer, a piezoelectric layer, an interdigital transducer and a second dielectric layer; the first dielectric layer is arranged on the substrate; the piezoelectric layer is arranged on the first dielectric layer; the interdigital transducer is arranged on the surface of the piezoelectric layer, the interdigital transducer comprises two comb electrodes arranged opposite to each other, each comb electrode comprises a bus bar and a plurality of electrode fingers connected to the bus bar and arranged at intervals, and the electrode fingers of the two comb electrodes are arranged alternately with each other; in the extension direction of the electrode fingers, there is an overlapping area between the two bus bars, and a gap area is included between the overlapping area and the bus bar, and the gap area is adjacent to one end of the bus bar close to the overlapping area; the second dielectric layer is located in at least one gap area and covers the piezoelectric layer and the electrode fingers located in the gap area; wherein the propagation speed of the sound wave in the first dielectric layer and the propagation speed of the sound wave in the second dielectric layer are greater than the propagation speed of the sound wave in the piezoelectric layer, the thickness of the first dielectric layer is h1, the thickness of the second dielectric layer is h2, and the thickness of the first dielectric layer and the thickness of the second dielectric layer satisfy: h2≤0.3h1. By setting a first dielectric layer between the substrate and the piezoelectric layer, and setting a second dielectric layer in the gap region, the energy dissipation in the thickness direction and the aperture direction can be reduced, thereby improving the Q value of the surface acoustic wave device. By controlling the thickness relationship between the first dielectric layer and the second dielectric layer, the Q value of the surface acoustic wave device can be improved while reducing the passband of the surface acoustic wave device and improving the high-frequency stray mode suppression effect at and near the anti-resonance point. The surface acoustic wave device will be described in detail below.

[0034] It can be understood that the surface acoustic wave device of the present application can be a surface acoustic wave resonator, or a longitudinally coupled resonator, a dual-mode or multi-mode surface acoustic wave filter, or a ladder filter or a duplexer including the above-mentioned surface acoustic wave resonator, etc., and the present application does not make specific limitations.

[0035] In the following, the present application is introduced by taking the surface acoustic wave device as a piezoelectric thin film SAW device as an example.

[0036] See also Figure 1 and Figure 2 , Figure 1 is a schematic structural diagram of a surface acoustic wave device provided in an embodiment of the present application, Figure 2 yes Figure 1 Schematic diagram of the cross-sectional structure along the aa direction.

[0037] like Figure 1 and Figure 2As shown, the surface acoustic wave device 100 includes a substrate 10, a first dielectric layer 20, a piezoelectric layer 30, an interdigital transducer 40 and a second dielectric layer 50; the first dielectric layer 20 is arranged on the substrate 10; the piezoelectric layer 30 is arranged on the first dielectric layer 20; the interdigital transducer 40 is arranged on the surface of the piezoelectric layer 30, and the interdigital transducer 40 includes two comb-shaped electrodes 41 arranged opposite to each other, each comb-shaped electrode 41 includes a bus bar 411 and a plurality of electrode fingers 412 connected to the bus bar 411 and arranged at intervals, and the electrode fingers 412 of the two comb-shaped electrodes 41 are arranged alternately. In the extension direction of the electrode fingers 412, there is an overlapping area A between the two bus bars 411, and there is a gap area B between the overlapping area A and the bus bar 411, and the gap area B is adjacent to one end of the bus bar 411 close to the overlapping area A.

[0038] Wherein, the substrate 10 may include single crystal materials such as silicon and silicon carbide, which are not specifically limited here. The comb electrodes 41 may be arranged relatively to each other in the extension direction of the electrode fingers 412. The two relatively arranged comb electrodes 41 have different polarities and may include an input electrode and an output electrode. The electrode fingers 412 of the two comb electrodes 41 may be arranged alternately with each other in the arrangement direction of the electrode fingers 412. The material of the piezoelectric layer 30 may include at least one of lithium niobate (LiNbO3) and lithium tantalate (LiTaO3). Preferably, 30-50°YX-LiTaO3, 10-50°YX-LN or 110-170°YX-LiNbO3 may be used, so that the main mode energy concentration area (i.e., the overlapping area A) has fewer mixed modes, so that the dispersion curve is flat, thereby reducing the lateral mode. The overlapping area A is the area where the electrode fingers 412 overlap each other.

[0039] Exemplarily, the thickness of the piezoelectric layer 30 may be 0.1λ-0.5λ, where λ is the wavelength of the acoustic wave, so as to confine most of the energy of the surface acoustic wave in the piezoelectric layer 30 .

[0040] Exemplarily, the electrode finger 412 is usually rectangular, and the cross-section of the electrode finger 412 formed under the influence of process conditions may be trapezoidal. Usually, the direction of the extension line of the long side of the electrode finger 412 is perpendicular to the direction of the extension line of the bus bar 411, and the multiple electrode fingers 412 are parallel to each other, and there is a certain gap between adjacent electrode fingers 412. In the embodiment of the present invention, the electrode finger 412 needs to contact with a bus bar 411 to achieve electrical connection, and the metallization rate corresponding to the electrode finger 412 can be 0.3-0.6, and the metallization rate is the ratio of a single finger to half of the finger period.

[0041] Exemplarily, the busbar 411 and the electrode finger 412 may be made of metal materials such as aluminum, molybdenum, copper, gold, platinum, silver, nickel, chromium, and tungsten, which are not specifically limited here and can be determined according to specific circumstances, but the selected materials need to have good electrical conductivity.

[0042] The second dielectric layer 50 is located in at least one gap region B and covers the piezoelectric layer 30 and the electrode fingers 412 located in the gap region B. The propagation speed of the acoustic wave in the first dielectric layer 20 and the propagation speed of the acoustic wave in the second dielectric layer 50 are greater than the propagation speed of the acoustic wave in the piezoelectric layer 30. The thickness of the first dielectric layer 20 is h1, and the thickness of the second dielectric layer 50 is h2. The thickness of the first dielectric layer 20 and the thickness of the second dielectric layer 50 satisfy: h2≤0.3h1.

[0043] Among them, the area between the bus bar 411 and the overlapping area A has two gap areas B, and the two gap areas B are respectively located at the two ends of the overlapping area A, and the two gap areas B are adjacent to one end of the bus bar 411 close to the overlapping area A. The second dielectric layer 50 is located in at least one gap area B, that is, the second dielectric layer 50 can be located in one of the gap areas B, or in both gap areas B at the same time, which can be set according to actual conditions. Since there is a piezoelectric layer 30 and an electrode finger 412 connected to an adjacent bus bar 411 in the gap area B, the second dielectric layer 50 covers the piezoelectric layer 30 and the electrode finger 412 located in the gap area B.

[0044] Specifically, the materials of the first dielectric layer 20 and the second dielectric layer 50 are different from the material of the piezoelectric layer 30, thereby utilizing the material difference between the first dielectric layer 20, the second dielectric layer 50 and the piezoelectric layer 30, so that the propagation speed of the sound wave in the first dielectric layer 20 and the propagation speed of the sound wave in the second dielectric layer 50 are greater than the propagation speed of the sound wave in the piezoelectric layer 30.

[0045] It should be noted that the propagation speed of the sound wave in the first dielectric layer 20 and the second dielectric layer 50 is generally greater than the propagation speed of the sound wave in the substrate 10 .

[0046] The surface acoustic wave device 100 provided in the present application is provided with a first dielectric layer 20 between the substrate 10 and the piezoelectric layer 30 and a second dielectric layer 50 in the gap region B, and the thickness relationship between the first dielectric layer 20 and the second dielectric layer 50 is controlled. When the first dielectric layer 20 and the second dielectric layer 50 simultaneously satisfy the above-mentioned positional relationship and thickness relationship, the surface acoustic wave main mode energy can be reduced from leaking toward the substrate 10 and the bus bar 411, and the high-frequency stray mode suppression effect at and near the anti-resonance point can be improved, as well as the Q value of the surface acoustic wave device 100 can be improved. If the first dielectric layer 20 and the second dielectric layer 50 only satisfy the positional relationship or only satisfy the thickness relationship, the high-frequency stray mode suppression effect at and near the anti-resonance point may be affected, and the suppression effect on acoustic wave energy leakage may also be affected, thereby affecting the working effect of the surface acoustic wave device 100.

[0047] In some embodiments, the materials of the first dielectric layer 20 and the second dielectric layer 50 include silicon nitride, aluminum nitride, and aluminum oxide.

[0048] The materials of the first dielectric layer 20 and the second dielectric layer 50 are materials capable of increasing the propagation speed of sound waves in the first dielectric layer 20 and the second dielectric layer 50 , such as silicon nitride, aluminum nitride, and aluminum oxide.

[0049] For example, if the material of the first dielectric layer 20 can be selected from silicon nitride, aluminum nitride or aluminum oxide, the material difference between the first dielectric layer 20 and the piezoelectric layer 30 can be used to make the propagation speed of the sound wave in the first dielectric layer 20 greater than the propagation speed of the sound wave in the piezoelectric layer 30, and the difficulty of process manufacturing can be reduced, so that the specific size of the resonator in the same frequency band, such as pitch, can be larger. At the same time, the first dielectric layer 20 can also take into account the charge capture layer to capture the excess electrons at the interface between the substrate 10 and the first dielectric layer 20. The excess electrons will affect the electrical properties of the surface acoustic wave device 100, thereby causing the main mode to fluctuate.

[0050] For example, if the material of the second dielectric layer 50 can be selected from materials such as silicon nitride, aluminum nitride or aluminum oxide, the material difference between the second dielectric layer 50 and the piezoelectric layer 30 can be used to make the propagation speed of sound waves in the second dielectric layer 50 greater than the propagation speed of sound waves in the piezoelectric layer 30. The difficulty of process manufacturing can also be reduced, so that the specific dimensions of the resonator in the same frequency band, such as pitch, can be larger.

[0051] It should be noted that the materials of the first dielectric layer 20 and the second dielectric layer 50 may be the same or different, and no specific limitation is made herein.

[0052] like Figure 2As shown, in some embodiments, the IDT 40 further includes a temperature compensation layer 60, and the temperature compensation layer 60 is disposed between the first dielectric layer 20 and the piezoelectric layer 30. Thus, the negative frequency-temperature characteristic of the piezoelectric layer 30 can be improved.

[0053] Specifically, the temperature compensation layer 60 is disposed between the first dielectric layer 20 and the piezoelectric layer 30, that is, the substrate 10, the first dielectric layer 20, the temperature compensation layer 60 and the piezoelectric layer 30 are stacked in sequence. The temperature compensation layer 60 plays a role of temperature compensation, thereby improving the negative frequency temperature characteristics of the piezoelectric layer 30.

[0054] Exemplarily, the material of the temperature compensation layer 60 can be silicon oxide, tantalum oxide, silicon oxynitride or other materials with a positive frequency temperature coefficient. Generally, the propagation speed of sound waves in the temperature compensation layer 60 is slower than that in the first dielectric layer 20 , the second dielectric layer 50 and the piezoelectric layer 30 .

[0055] like Figure 3 and Figure 4 As shown, in some embodiments, the two gap regions B of the IDT 40 both have a second dielectric layer 50. Thus, by simultaneously providing the second dielectric layer 50 in the two gap regions B, the Q value of the surface acoustic wave device 100 can be ensured while further improving the high-frequency stray mode suppression effect at and near the anti-resonance point.

[0056] Exemplarily, the materials of the second dielectric layers 50 in the two gap regions B may be the same or different, which is not specifically limited here. When both gap regions B have the second dielectric layer 50, the Q value and high-frequency heterogeneous mode suppression effect of the surface acoustic wave device 100 are significantly improved.

[0057] In some embodiments, the thickness of the first dielectric layer 20 and the thickness of the second dielectric layer 50 satisfy: 0.035h2≤h1≤0.2h2. Thus, by controlling the thickness relationship between the first dielectric layer 20 and the second dielectric layer 50, the high-frequency stray mode suppression effect at and near the anti-resonance point and the Q value of the surface acoustic wave device 100 can be further improved.

[0058] For example, if the thickness h1 of the first dielectric layer 20 is 600 nm, the thickness h2 of the second dielectric layer 50 is in the range of 21 nm to 120 nm.

[0059] For example, if the thickness h2 of the second dielectric layer 50 is 30 nm, the thickness h1 of the first dielectric layer 20 is in the range of 150 nm to 857 nm.

[0060] In some embodiments, the thickness of the first dielectric layer 20 and the thickness of the second dielectric layer 50 satisfy: 0.05h1≤h2≤0.2h1. Thus, by controlling the thickness relationship between the first dielectric layer 20 and the second dielectric layer 50, the Q value of the surface acoustic wave device 100 and the high-frequency heterogeneous mode suppression effect at and near the antiresonance point can be optimized.

[0061] For example, if the thickness h1 of the first dielectric layer 20 is 600 nm, the thickness h2 of the second dielectric layer 50 is in the range of 30 nm to 120 nm.

[0062] For example, if the thickness h2 of the second dielectric layer 50 is 40 nm, the thickness h1 of the first dielectric layer 20 is in the range of 200 nm to 800 nm.

[0063] In some embodiments, the thickness of the first dielectric layer 20 is 0.2λ-0.8λ, where λ is the wavelength of the sound wave, and / or the thickness of the second dielectric layer 50 is 20nm-45nm. Therefore, the thickness of the first dielectric layer 20 or the second dielectric layer 50 can be adjusted so that the first dielectric layer 20 and the second dielectric layer 50 can meet the thickness requirement, so that the Q value of the surface acoustic wave device 100 and the high-frequency heterogeneous mode suppression effect at the antiresonance point and its vicinity are optimized. If the thickness of the first dielectric layer 20 is less than 0.2λ or the thickness of the second dielectric layer 50 is less than 20nm, based on the thickness relationship between the first dielectric layer 20 and the second dielectric layer 50, the thickness of the first dielectric layer 20 and the second dielectric layer 50 will also become very small, which will affect the high-frequency heterogeneous mode suppression effect and the suppression effect on acoustic wave energy leakage; and if the thickness of the first dielectric layer 20 is greater than 0.8λ or the thickness of the second dielectric layer 50 is greater than 45nm, based on the thickness relationship between the first dielectric layer 20 and the second dielectric layer 50, the thickness of the first dielectric layer 20 and the second dielectric layer 50 will also become very large, which will cause the volume of the surface acoustic wave device 100 to become larger, which is not conducive to the demand for miniaturization.

[0064] Exemplarily, the thickness of the first dielectric layer 20 may be 0.2λ-0.8λ, such as 0.2λ, 0.3λ, 0.3λ, 0.4λ, 0.5λ, 0.6λ, 0.7λ, 0.8λ. If the thickness of the first dielectric layer 20 is 0.5λ, the thickness of the second dielectric layer 50 may be 0.05λ.

[0065] Exemplarily, the thickness of the second dielectric layer 50 may be 20 nm-45 nm, such as 20 nm, 23 nm, 28 nm, 30 nm, 33 nm, 35 nm, 40 nm, or 45 nm. If the thickness of the second dielectric layer is 30 nm, the thickness of the first dielectric layer 20 may be 300 nm.

[0066] See also Figure 3-Figure 5In some embodiments, the interdigital transducer 40 further includes an intermediate electrode 42, which is located between the overlapping region A and the bus bar 411, and a gap region B is formed between the intermediate electrode 42 and the adjacent bus bar 411; along the extension direction of the intermediate electrode 42, the intermediate electrode 42 is connected to the electrode finger 412, and the extension direction of the intermediate electrode 42 intersects with the extension direction of the electrode finger 412.

[0067] like Figure 3 As shown, the interdigital transducer 40 further includes a plurality of intermediate electrodes 42, the intermediate electrodes 42 are located between the overlapping region A and the bus bar 411, a gap region B is formed between the intermediate electrodes 42 and the adjacent bus bar 411, and a connection region C is formed between the intermediate electrodes 42 and the overlapping region A. At this time, the gap region B is connected to the overlapping region A through the connection region C, and the position of the intermediate electrodes 42 is used to divide the gap region B and the connection region C in the extension direction of the electrode finger 412. Along the extension direction of the intermediate electrode 42, the intermediate electrode 42 is connected to at least one electrode finger 412, and the extension direction of the intermediate electrode 42 intersects with the extension direction of the electrode finger 412. By setting the intermediate electrode 42, the stray mode of the gap region B can be suppressed to a certain extent. Preferably, the extension direction of the intermediate electrode 42 is perpendicular or approximately perpendicular to the extension direction of the electrode finger 412.

[0068] like Figure 3 and Figure 4 As shown, illustratively, the IDT 40 further includes a gap electrode 43 , a first end of the gap electrode 43 is connected to the bus bar 411 , and a second end of the gap electrode 43 is connected to the middle electrode 42 .

[0069] In the embodiment of the present application, the first end of the gap electrode 43 is connected to the bus bar 411, the second end of the gap electrode 43 is connected to one end of the intermediate electrode 42, the other end of the intermediate electrode 42 is connected to the electrode finger 412 of the adjacent comb-shaped electrode 41, the electrode finger 412 and the gap electrode 43 are arranged at opposite sides of the intermediate electrode 42 in the extension direction of the intermediate electrode 42, and the gap electrode 43 is also arranged at an interval with the electrode finger 412 of the opposite comb-shaped electrode 41. By setting the gap electrode 43 and the intermediate electrode 42, the mixed mode of the gap area B can be suppressed to a certain extent.

[0070] like Figure 5 As shown, by way of example, the middle electrode 42 is connected to at least two electrode fingers 412 that are spaced apart from each other.

[0071] In the embodiment of the present application, the IDT 40 does not have gap electrodes, the electrode fingers 412 are connected to the bus bar 411 , and the middle electrodes 42 are connected to the electrode fingers 412 .

[0072] Exemplarily, the intermediate electrode 42 is connected to at least two electrode fingers 412 of adjacent comb-shaped electrodes 41 , so that a gap region B is formed between the intermediate electrode 42 and the adjacent bus bar 411 , and a connection region C is formed between the intermediate electrode 42 and the overlapping region A.

[0073] Exemplarily, the middle electrode 42 may be connected to two electrode fingers 412 disposed at intervals, or may be connected to a plurality of electrode fingers 412 disposed at intervals, without specific limitation herein, thereby dividing the gap region B and the connection region C in the extension direction of the electrode fingers 412 .

[0074] It should be noted that the thickness of the middle electrode 42 and the electrode finger 412 are generally the same, that is, the middle electrode 42 and the electrode finger 412 are located on the same plane.

[0075] In some embodiments, Figure 3 and Figure 4 In the corresponding structure, the interdigital transducer 40 may further include a dummy finger; the first end of the dummy finger is connected to the first end of the middle electrode 42 and the second end of the gap electrode 43. By providing the dummy finger, the Q value of the surface acoustic wave device 100 can be improved, energy leakage can be reduced, and the effect of suppressing the heterogeneous mode in the gap region B can be further improved.

[0076] Specifically, the first end of the dummy finger is connected to the first end of the middle electrode 42 and the second end of the gap electrode 43 , and the dummy finger can be arranged on a side close to the overlapping area A, that is, the dummy finger and the gap electrode 43 are arranged on both sides of the middle electrode 42 respectively.

[0077] In some embodiments, Figure 3 and Figure 4 In the corresponding structure, in the extension direction of the electrode finger 412, the second dielectric layer 50 extends from the gap region B to the bus bar 411 and / or the middle electrode 42, and at least partially covers the bus bar 411 and / or the middle electrode 42. This facilitates the preparation process of the second dielectric layer 50 without affecting the performance of the surface acoustic wave device 100.

[0078] Exemplarily, in the extension direction of the electrode finger 412, the second dielectric layer 50 may extend from the gap region B to the bus bar 411, and at least partially cover the bus bar 411; the second dielectric layer 50 may also extend from the gap region B to the middle electrode 42, and at least partially cover the middle electrode 42; the second dielectric layer 50 may extend from the gap region B to the bus bar 411 and the middle electrode 42, respectively, and at least partially cover the bus bar 411 and the middle electrode 42. In this way, the second dielectric layer 50 can be better prepared in the gap region B while ensuring the performance of the surface acoustic wave device 100.

[0079] In some embodiments, Figure 3and Figure 4 In the corresponding structure, the length of the second dielectric layer 50 on the bus bar 411 in the extension direction of the electrode finger 412 is less than or equal to 100 nm, and / or the length of the second dielectric layer 50 on the middle electrode 42 in the extension direction of the electrode finger 412 is less than or equal to 100 nm. In this way, the area of ​​the bus bar 411 and the middle electrode 42 covered by the second dielectric layer 50 can be as small as possible on the basis of facilitating the preparation process of the second dielectric layer 50, so as to avoid affecting the performance of the surface acoustic wave device 100.

[0080] Specifically, the length of the second dielectric layer 50 located on the bus bar 411 in the extension direction of the electrode finger 412 can be controlled to be less than or equal to 100 nm, thereby reducing the area of ​​the bus bar 411 covered by the second dielectric layer 50. The length of the second dielectric layer 50 located on the middle electrode 42 in the extension direction of the electrode finger 412 can also be controlled to be less than or equal to 100 nm, thereby reducing the area of ​​the middle electrode 42 covered by the second dielectric layer 50. This avoids affecting the performance of the surface acoustic wave device 100 while facilitating the preparation process of the second dielectric layer 50.

[0081] In some embodiments, Figure 3 and Figure 5 In the corresponding structure, the overlapping area A includes a middle area A1 and edge areas A2 located on both sides of the middle area A1 in the arrangement direction of the two comb electrodes 41; when a gap area B is formed between the middle electrode 42 and the adjacent bus bar 411, the interdigital transducer 40 also includes an acoustic impedance adjustment structure 44, which is located in the edge area A2, and the acoustic impedance of the edge area A2 is smaller than the acoustic impedance of the middle area A1.

[0082] Specifically, by setting the acoustic impedance adjustment structure 44 in the edge area A2, the acoustic impedance of the edge area A2 is smaller than the acoustic impedance of the middle area A1, so that the propagation speed of the sound wave in the edge area A2 can be made smaller than the propagation speed in the middle area A1, thereby avoiding the leakage of the acoustic wave signal and limiting the acoustic wave signal within the interdigital transducer 40, thereby improving the suppression of the lateral mode of the surface acoustic wave device 100, reducing the acoustic energy loss, increasing the Q value and improving the performance of the surface acoustic wave device 100.

[0083] Exemplarily, the acoustic impedance adjustment structure 44 can be a harmonic suppression structure, such as thickening the electrode finger 412 in the edge area A2 to form a piston thickening structure, widening the electrode finger 412 in the edge area A2, or widening the electrode finger 412 in the edge area A2 and thickening it at the widened position, or widening the electrode finger in the edge area A2 with different widths to form a T-shaped piston structure, or widening a portion of the same electrode finger in the edge area A2 and thickening both the widened portion and the non-widened portion to form a T-shaped piston structure, or adding a mass load bar, without specific limitation herein.

[0084] by Figure 5 Taking the acoustic impedance adjustment structure 44 in the structure as an example, the acoustic impedance adjustment structure 44 is formed by widening and thickening the electrode finger 412 in the edge area A2. In this embodiment, the acoustic impedance adjustment structure 44 is arranged in the thickness direction and the width direction of the electrode finger 412 at the same time. In this way, the electrode finger 412 is equivalent to being widened and thickened at the widened position. The width direction of the electrode finger 412 is perpendicular to the extension direction of the electrode finger 412.

[0085] by Figure 6 Take the acoustic impedance adjustment structure 44 in the structure as an example. At this time, the acoustic impedance adjustment structure 44 is formed by thickening the electrode finger 412 in the edge area A2, that is, the piston thickening structure. In this embodiment, the acoustic impedance adjustment structure 44 is arranged in the thickness direction of the electrode finger 412. In this way, the electrode finger 412 is equivalent to being thickened. Specifically, the acoustic impedance adjustment structure 44 can be located above the electrode finger 412, or below the electrode finger 412, or above and below the electrode finger 412 at the same time.

[0086] by Figure 8 Taking the acoustic impedance adjustment structure 44 in the structure as an example, the acoustic impedance adjustment structure 44 is formed by thickening the electrode finger 412 in the edge area A2 and widening the end of the electrode finger 412, that is, a T-shaped piston structure. In this embodiment, the acoustic impedance adjustment structure 44 is arranged in the thickness direction and the width direction of the electrode finger 412 at the same time. In this way, the electrode finger 412 is also equivalent to widening a part of the same electrode finger in the edge area, and both the widened part and the non-widened part are thickened.

[0087] Exemplarily, the acoustic impedance adjustment structure 44 can also be set only in the width direction of the electrode finger 412. In this way, the electrode finger 412 is equivalent to being widened. Specifically, the acoustic impedance adjustment structure 44 can be located on one side of the electrode finger 412 in the width direction, or can be located on both sides of the electrode finger 412 in the width direction.

[0088] It should be noted that the acoustic impedance adjustment structure 44 can be in direct contact with the electrode finger 412, or the acoustic impedance adjustment structure 44 and the electrode finger 412 can be separated by other membrane layers, wherein the membrane layer used to separate the acoustic impedance adjustment structure 44 and the electrode finger 412 can be at least one of the temperature compensation layer 60 and the frequency modulation layer.

[0089] See also Figure 6-Figure 8 In some embodiments, the overlapping region A includes a middle region A1 and edge regions A2 located on both sides of the middle region A1 in the arrangement direction of the two comb electrodes 41, and gap regions B are formed between the two ends of the overlapping region A and the adjacent bus bars 411 respectively; the interdigital transducer 40 also includes an acoustic impedance adjustment structure 44, and the acoustic impedance adjustment structure 44 is located in the edge region A2, and the acoustic impedance of the edge region A2 is less than the acoustic impedance of the middle region A1.

[0090] In the embodiment of the present application, the acoustic impedance adjustment structure 44 is used to divide the gap area B and the overlapping area A near one end of the bus bar 411. There is no connection area C in the interdigital transducer 40. A gap area B is formed between the acoustic impedance adjustment structure 44 and the adjacent bus bar 411. The gap area B is adjacent to the bus bar 411 and the overlapping area A.

[0091] Specifically, by setting the acoustic impedance adjustment structure 44 in the edge area A2, the acoustic impedance of the edge area A2 is smaller than the acoustic impedance of the middle area A1, so that the propagation speed of the sound wave in the edge area A2 can be made smaller than the propagation speed in the middle area A1, thereby avoiding the leakage of the acoustic wave signal and limiting the acoustic wave signal within the interdigital transducer 40, thereby improving the suppression of the lateral mode of the surface acoustic wave device 100, reducing the acoustic energy loss, increasing the Q value and improving the performance of the surface acoustic wave device 100.

[0092] Exemplarily, the acoustic impedance adjustment structure 44 may be a harmonic suppression structure, such as a piston thickening structure or a T-shaped piston structure, which is not specifically limited herein.

[0093] The relevant embodiments of the acoustic impedance adjustment structure 44 may refer to the above embodiments, which will not be repeated here.

[0094] In some embodiments, when gap regions B are formed between the two ends of the overlapping region A and the adjacent bus bars 411, the second dielectric layer 50 extends from the gap region B to the bus bar 411 in the extension direction of the electrode fingers 412, and at least partially covers the bus bar 411. This facilitates the preparation process of the second dielectric layer 50 without affecting the performance of the surface acoustic wave device 100.

[0095] Specifically, the length of the second dielectric layer 50 on the bus bar 411 in the extension direction of the electrode finger 412 is less than or equal to 100 nm, thereby reducing the area of ​​the bus bar 411 covered by the second dielectric layer 50, thereby facilitating the preparation process of the second dielectric layer 50 and avoiding affecting the performance of the surface acoustic wave device 100.

[0096] In some embodiments, the length of the gap region B in the extension direction of the electrode finger 412 is less than or equal to 1λ, where λ is the wavelength of the acoustic wave, thereby improving the Q value of the surface acoustic wave device 100 .

[0097] Exemplarily, regardless of whether the gap region B is the region between the intermediate electrode 42 and the bus bar 411 or the gap region B is the region between the intermediate electrode 42 and the bus bar 411, the length of the gap region B in the extension direction of the electrode finger 412 can be set to be less than or equal to 1λ, thereby reducing the gap region B and improving the Q value of the surface acoustic wave device 100.

[0098] In some embodiments, the length of the gap region B in the extending direction of the electrode finger 412 is less than or equal to 0.5λ, thereby further improving the Q value of the surface acoustic wave device 100 .

[0099] Exemplarily, no matter the gap region B is the region between the middle electrode 42 and the bus bar 411 or the gap region B is the region between the middle electrode 42 and the bus bar 411, the length of the gap region B in the extension direction of the electrode finger 412 can be set to be less than or equal to 0.5λ, so that the gap region B can be reduced to improve the Q value of the surface acoustic wave device 100. Preferably, when the gap region B is the region between the middle electrode 42 and the bus bar 411, the length of the gap region B in the extension direction of the electrode finger 412 is generally set to be less than or equal to 0.5λ.

[0100] like Figure 2 As shown, in some embodiments, the thickness of the second dielectric layer 50 is smaller than the thickness of the electrode finger 412 .

[0101] Specifically, the thickness of the second dielectric layer 50 is h2, and the thickness of the electrode finger 412 is h3. Generally, h2 <h3。

[0102] In some embodiments, the second dielectric layer 50 covers the electrode fingers 412 located in the gap region B; in the gap region B, the thickness of the second dielectric layer 50 located on the electrode fingers 412 is equal to the thickness of the second dielectric layer 50 located outside the electrode fingers 412. This facilitates the preparation process of the second dielectric layer 50, further improves the Q value of the surface acoustic wave device 100, reduces the stray modes in the passband of the surface acoustic wave device 100, and improves the high-frequency stray mode suppression effect at and near the anti-resonance point.

[0103] Specifically, there will be electrode fingers 412 of adjacent comb-shaped electrodes 41 in the gap region B, so the second dielectric layer 50 will cover the piezoelectric layer 30 located in the gap region B and the electrode fingers 412 located in the gap region B. In the gap region B, there will be the second dielectric layer 50 on both the electrode fingers 412 and the piezoelectric layer 30, and because the electrode fingers 412 have a certain thickness, the overall height of the second dielectric layer 50 located on the electrode fingers 412 is higher than the overall height of the second dielectric layer 50 on the piezoelectric layer 30. However, the thickness of the second dielectric layer 50 located on the electrode fingers 412 is equal to the thickness of the second dielectric layer 50 located outside the electrode fingers 412, that is, in the gap region B, the thickness of the second dielectric layer 50 at any position is equal.

[0104] It should be noted that, in the gap region B, the thickness of the second dielectric layer 50 located on the electrode finger 412 may be equal to or different from the thickness of the second dielectric layer 50 located outside the electrode finger 412. In order to further facilitate the preparation process of the second dielectric layer 50, further improve the Q value of the surface acoustic wave device 100, reduce the stray modes in the passband of the surface acoustic wave device 100, and improve the high-frequency stray mode suppression effect at and near the anti-resonance point, the thickness of the second dielectric layer 50 located on the electrode finger 412 is generally set to be equal to the thickness of the second dielectric layer 50 located outside the electrode finger 412.

[0105] The following will compare the harmonic admittance curves of the surface acoustic wave device 100 provided in the present application with those of the surface acoustic wave device provided in the related art through simulation experiments.

[0106] like Fig. 9As shown, it can be seen that in some frequency bands, such as the frequency band near the resonance point, the SAW device 100 provided in the present application has basically the same heterodyne intensity as the SAW device provided in the related art, and especially in the frequency band corresponding to 2.42-2.48 GHz, that is, the frequency band near the antiresonance point, it can be seen that the heterodyne intensity of the SAW device 100 provided in the present application is significantly weaker than the heterodyne intensity of the SAW device provided in the related art. Therefore, it can be seen that the ripples between the resonance point and the antiresonance point of the SAW device 100 provided in the embodiment of the present application almost disappear, reducing the heterodyne modes in the passband of the SAW device 100, that is, achieving the suppression of high-frequency heterodyne modes, and at the same time, the high-frequency heterodyne mode suppression effect at the antiresonance point and its vicinity is better than that of the SAW device provided in the related art.

[0107] The following will compare the Q value variation curves of the surface acoustic wave device 100 provided in the present application and the surface acoustic wave device provided in the related art through simulation experiments.

[0108] like Fig.10 As shown, it can be seen that in most frequency bands, the Q value of the surface acoustic wave device 100 provided by the present application is greater than the Q value of the surface acoustic wave device provided in the related art, especially on the left side of the resonance point and near the anti-resonance point, the Q value of the surface acoustic wave device 100 provided by the present application is much greater than the Q value of the surface acoustic wave device provided in the related art. Especially in the frequency band corresponding to 2.42-2.48GHz, that is, the frequency band near the anti-resonance point, it can be seen that the Q value of the surface acoustic wave device 100 provided by the present application is significantly stronger than the Q value of the surface acoustic wave device provided in the related art. It can be seen that the surface acoustic wave device 100 provided by the embodiment of the present application can greatly improve the Q value compared with the surface acoustic wave device provided in the related art, thereby improving the performance of the surface acoustic wave device 100.

[0109] In the case where the surface acoustic wave device 100 is a filter, the filter provided in the embodiment of the present application will be described in detail below.

[0110] The filter includes a plurality of series-arm surface acoustic wave devices 100 connected in series between an input end and an output end, and a plurality of parallel-arm surface acoustic wave devices 100 connected to the series-arm surface acoustic wave device 100 at one end and connected to a ground end at the other end, and at least one of the series-arm surface acoustic wave device 100 and the parallel-arm surface acoustic wave device 100 can be the surface acoustic wave device 100 provided by any of the above-mentioned embodiments. The filter can reduce the stray modes in the passband while improving the Q value, and improve the high-frequency stray mode suppression effect at and near the anti-resonance point.

[0111] The embodiment of the present application also provides a radio frequency front-end module, which includes the surface acoustic wave device 100 described in any one of the above embodiments. The radio frequency front-end module can reduce the stray modes in the passband while improving the Q value, and improve the high-frequency stray mode suppression effect at and near the anti-resonance point, thereby improving the reliability, safety and practicality of the radio frequency front-end module.

[0112] Among them, the RF front-end module may include an antenna end, a power amplifier, a low-noise amplifier, a switch, a filter, etc., which are not specifically limited here.

[0113] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present application, and these modifications or replacements should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A surface acoustic wave device, characterized in that: The surface acoustic wave device comprises: substrate; A first dielectric layer is disposed on the substrate; A piezoelectric layer is disposed on the first dielectric layer; An interdigital transducer is arranged on the surface of the piezoelectric layer, the interdigital transducer comprises two comb-shaped electrodes arranged opposite to each other, each of the comb-shaped electrodes comprises a bus bar and a plurality of electrode fingers connected to the bus bar and arranged at intervals, the electrode fingers of the two comb-shaped electrodes are arranged alternately with each other; in the extension direction of the electrode fingers, there is an overlapping area between the two bus bars, the overlapping area is the area where the electrode fingers overlap with each other, a gap area is included between the overlapping area and the bus bar, and the gap area is adjacent to one end of the bus bar close to the overlapping area; a second dielectric layer, the second dielectric layer being located in at least one of the gap regions and covering the piezoelectric layer and the electrode fingers located in the gap region; Among them, the propagation speed of the sound wave in the first dielectric layer and the propagation speed of the sound wave in the second dielectric layer are greater than the propagation speed of the sound wave in the piezoelectric layer, the thickness of the first dielectric layer is h1, the thickness of the second dielectric layer is h2, and the thickness of the first dielectric layer and the thickness of the second dielectric layer satisfy: h2≤0.3h1.

2. The surface acoustic wave device according to claim 1, characterized in that: Both of the two gap regions of the interdigital transducer have the second dielectric layer.

3. The surface acoustic wave device according to claim 1, characterized in that: The thickness of the first dielectric layer and the thickness of the second dielectric layer satisfy: 0.035h1≤h2≤0.2h1.

4. The surface acoustic wave device according to claim 3, characterized in that: The thickness of the first dielectric layer and the thickness of the second dielectric layer satisfy: 0.05h1≤h2≤0.2h1.

5. The surface acoustic wave device according to claim 1, characterized in that: The thickness of the first dielectric layer is 0.2λ-0.8λ, where λ is the wavelength of the sound wave, and / or the thickness of the second dielectric layer is 20nm-45nm.

6. The surface acoustic wave device according to claim 1, characterized in that: The IDT further includes an intermediate electrode, the intermediate electrode is located between the overlapping region and the bus bar, and the gap region is formed between the intermediate electrode and the adjacent bus bar; The intermediate electrode is connected to the electrode fingers along an extending direction of the intermediate electrode, and the extending direction of the intermediate electrode intersects with an extending direction of the electrode fingers.

7. The surface acoustic wave device according to claim 6, characterized in that: The IDT further includes a gap electrode, a first end of the gap electrode is connected to the bus bar, and a second end of the gap electrode is connected to the middle electrode.

8. The surface acoustic wave device according to claim 6, characterized in that: The middle electrode is connected to at least two of the electrode fingers that are spaced apart from each other.

9. The surface acoustic wave device according to claim 6, characterized in that: In the extension direction of the electrode fingers, the second dielectric layer extends from the gap region to the bus bar and / or the middle electrode, and at least partially covers the bus bar and / or the middle electrode.

10. The surface acoustic wave device according to claim 9, characterized in that: The length of the second dielectric layer on the bus bar in the extending direction of the electrode finger is less than or equal to 100 nm, and / or the length of the second dielectric layer on the intermediate electrode in the extending direction of the electrode finger is less than or equal to 100 nm.

11. The surface acoustic wave device according to claim 1, characterized in that: The overlapping region includes a middle region and edge regions located on both sides of the middle region in the arrangement direction of the two comb-shaped electrodes, and the gap region is formed between the two ends of the overlapping region and the adjacent bus bars respectively; The IDT further includes an acoustic impedance adjustment structure, which is located in the edge region. The acoustic impedance of the edge region is smaller than the acoustic impedance of the middle region.

12. The surface acoustic wave device according to claim 1, characterized in that: The length of the gap region in the extending direction of the electrode finger is less than or equal to 1λ, where λ is the wavelength of the sound wave.

13. The surface acoustic wave device according to claim 12, characterized in that: A length of the gap region in the extending direction of the electrode fingers is less than or equal to 0.5λ.

14. The surface acoustic wave device according to claim 1, characterized in that: The thickness of the second dielectric layer is smaller than the thickness of the electrode fingers.

15. The surface acoustic wave device according to claim 1, characterized in that: The second dielectric layer covers the electrode fingers located in the gap region; In the gap region, the thickness of the second dielectric layer located on the electrode fingers is equal to the thickness of the second dielectric layer located outside the electrode fingers.

16. The surface acoustic wave device according to claim 1, characterized in that: The IDT further includes a temperature compensation layer, which is disposed between the first dielectric layer and the piezoelectric layer.

17. The surface acoustic wave device according to any one of claims 1 to 16, characterized in that: The materials of the first dielectric layer and the second dielectric layer include silicon nitride, aluminum nitride and aluminum oxide, and / or the material of the piezoelectric layer includes 30-50° YX-LiTaO3, 10-50° YX-LiNbO3 or 110-170° YX-LiNbO3.

18. A radio frequency front-end module, characterized in that: Comprising the surface acoustic wave device as described in any one of claims 1-17.

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