Resonator, filter and radio frequency front-end module

Abstract

The utility model discloses a resonator, a filter and a radio frequency front-end module, and relates to the technical field of radio frequency filtering. The resonator comprises a substrate, a first piezoelectric layer, an electrode layer and a second piezoelectric layer; the first piezoelectric layer is arranged on one side of the substrate, the Euler angle of the first piezoelectric layer is that the electrode layer is arranged on one side, far away from the substrate, of the first piezoelectric layer, and the electrode layer comprises an interdigital transducer; the second piezoelectric layer is arranged on the side, away from the first piezoelectric layer, of the electrode layer, the Euler angle of the second piezoelectric layer is the interdigital transducer, the interdigital transducer comprises two comb-shaped electrodes which are oppositely arranged, each comb-shaped electrode comprises a bus bar and a plurality of electrode fingers which are connected with the bus bar and are arranged at intervals, the width of each electrode finger in the first direction is d1, and the width of each electrode finger in the second direction is d2; the gap width between the adjacent electrode fingers is d2, and the first direction is the arrangement direction of the electrode fingers; according to the invention, impure modes in a main mode passband can be reduced, so that the performance of the resonator is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radio frequency filtering, and in particular to a resonator, a filter and a radio frequency front-end module. BACKGROUND

[0002] A 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). In the prior art, the IDT is generally formed on the surface of the piezoelectric layer, and the IDT can be used to convert an electrical signal into an acoustic signal or convert an acoustic signal into an electrical signal.

[0003] However, arranging the IDT on the surface of the piezoelectric layer can cause a large number of spurious modes in the main mode passband of the resonator, thereby affecting the performance of the resonator. CONTENT OF THE UTILITY MODEL

[0004] The present application provides a resonator, a filter and a radio frequency front-end module, which can reduce spurious modes in the main mode passband, thereby improving the performance of the resonator.

[0005] In a first aspect, the present application provides a resonator, which includes a substrate, a first piezoelectric layer, an electrode layer and a second piezoelectric layer.

[0006] The first piezoelectric layer is arranged on one side of the substrate, and the Euler angle of the first piezoelectric layer is

[0007] The electrode layer is arranged on a side of the first piezoelectric layer away from the substrate, and the electrode layer includes an interdigital transducer.

[0008] The second piezoelectric layer is arranged on a side of the electrode layer away from the first piezoelectric layer, and the Euler angle of the second piezoelectric layer is

[0009] The interdigital transducer includes two oppositely arranged comb electrodes, each of which includes a bus bar and a plurality of electrode fingers connected to the bus bar and arranged at intervals, the width of the electrode finger in a first direction being d1, the gap width of adjacent electrode fingers being d2, and the first direction being the arrangement direction of the electrode finger.

[0010] wherein and

[0011] In a second aspect, the present application provides a filter, comprising a plurality of series arm resonators connected in series between an input end and an output end, and a plurality of parallel arm resonators connected at one end to the series arm resonators and at the other end to a ground end, at least one of the series arm resonators and the parallel arm resonators comprising the resonator as described above.

[0012] In a third aspect, the present application provides a radio frequency front-end module, comprising the filter as described above.

[0013] The resonator provided by the present application comprises a substrate, a first piezoelectric layer, an electrode layer and a second piezoelectric layer; the first piezoelectric layer is arranged on one side of the substrate, and the Euler angle of the first piezoelectric layer is The electrode layer is arranged on the side of the first piezoelectric layer away from the substrate, and the electrode layer comprises an interdigital transducer; the second piezoelectric layer is arranged on the side of the electrode layer away from the first piezoelectric layer, and the Euler angle of the second piezoelectric layer is The interdigital transducer comprises two oppositely arranged comb electrodes, each comb electrode comprises a bus bar and a plurality of electrode fingers connected to the bus bar and arranged at intervals, the width of the electrode finger in the first direction is d1, the gap width of adjacent electrode fingers is d2, and the first direction is the arrangement direction of the electrode finger; wherein, and Therefore, by arranging the electrode layer in the form of an interdigital transducer between the first piezoelectric layer and the second piezoelectric layer, and controlling the difference between the Euler angles of the first piezoelectric layer and the second piezoelectric layer within the range of [0, (172°-188°), 0], a large number of reflected spurious modes generated by the first piezoelectric layer and the second piezoelectric layer stacked together can be reduced, thereby effectively reducing the spurs in the main mode passband. In addition, by setting the duty cycle of the electrode finger to be less than or equal to 0.2, the frequency response and impedance characteristics of the resonator can also be improved. BRIEF DESCRIPTION OF DRAWINGS

[0014] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0015] Figure 1 is a cross-sectional structure schematic diagram of a resonator provided by an embodiment of the present application;

[0016] Figure 2 is a structure schematic diagram of an electrode layer provided by an embodiment of the present application;

[0017] Figure 3(a) is a structure schematic diagram of a first piezoelectric layer provided by an embodiment of the present application;

[0018] Fig. 3(b) is a schematic view of a second piezoelectric layer according to an embodiment of the present application;

[0019] Fig. 4(a) is a schematic view of an Euler rotation process according to an embodiment of the present application;

[0020] Fig. 4(b) is a schematic view of another Euler rotation process according to an embodiment of the present application;

[0021] Fig. 4(c) is a schematic view of another Euler rotation process according to an embodiment of the present application;

[0022] Fig. 4(d) is a schematic view of another Euler rotation process according to an embodiment of the present application;

[0023] Figure 5 Fig. 5(a) is a schematic view of a cross-sectional structure of another resonator according to an embodiment of the present application;

[0024] Figure 6 Fig. 5(b) is a schematic view of a cross-sectional structure of another resonator according to an embodiment of the present application;

[0025] Figure 7 Fig. 6 is a schematic view of a harmonic admittance curve comparison between a resonator according to an embodiment of the present application and a resonator according to the related art. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort belong to the scope of the present application.

[0027] The flowcharts shown in the drawings are only exemplary and do not necessarily include all the contents and operations / steps, nor do they have to be executed in the order described. For example, some operations / steps can be further decomposed, combined or partially merged, so the actual execution order can be changed according to the actual situation.

[0028] It should be understood that the terms used in the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the present application specification and the appended claims, unless otherwise clearly indicated by the context, the singular forms "a", "an" and "the" are intended to include the plural forms.

[0029] It should also be understood that the term "and / or" used in the present application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0030] Some embodiments of the present application will be described in detail with reference to the drawings. The following embodiments and features can be combined with each other in the case of no conflict.

[0031] It can be understood that the resonator of the present application is mainly applied to a transversely excited bulk acoustic resonator (XBAR) resonator, which is an acoustic resonator for high frequency and large bandwidth applications, mainly used in radio frequency front-end circuits. The XBAR resonator generates mechanical vibration through the piezoelectric effect, thereby generating resonance phenomenon at a specific frequency, and of course can be other types of resonators, which are not limited in the present application.

[0032] Hereinafter, the resonator is taken as an XBAR resonator for example.

[0033] Please refer to Figure 1 and Figure 2 , Figure 1 is a cross-sectional structure schematic diagram of a resonator provided by an embodiment of the present application, Figure 2 is a structure schematic diagram of an electrode layer provided by an embodiment of the present application.

[0034] As shown in Figure 1 , the resonator 100 includes a substrate 10, a first piezoelectric layer 20, an electrode layer 30 and a second piezoelectric layer 40; the first piezoelectric layer 20 is arranged on one side of the substrate 10, such as can be arranged on the surface of the substrate 10, the substrate 10 is used to support the first piezoelectric layer 20; the electrode layer 30 is arranged on the side of the first piezoelectric layer 20 away from the substrate 10, the electrode layer 30 includes an interdigital transducer 31, the electrode layer 30 is used to support the second piezoelectric layer 40; the second piezoelectric layer 40 is arranged on the side of the electrode layer 30 away from the first piezoelectric layer 20, that is, the interdigital transducer 31 is arranged between the first piezoelectric layer 20 and the second piezoelectric layer 40, so that the first piezoelectric layer 20 and the second piezoelectric layer 40 are arranged on both sides of the electrode layer 30 in the thickness direction.

[0035] As shown in Figure 2 , the interdigital transducer 31 includes two oppositely arranged comb-shaped electrodes, each comb-shaped electrode includes a bus bar 311 and a plurality of electrode fingers 312 connected with the bus bar 311 and arranged at intervals, the width of the electrode finger 312 in the first direction is d1, the gap width of the adjacent electrode fingers 312 is d2, and the first direction is the arrangement direction of the electrode finger 312.

[0036] Among them, the comb-shaped electrodes can be oppositely arranged in the extension direction of the electrode finger 312, the two oppositely arranged comb-shaped electrodes have different polarities, which can include an input electrode and an output electrode, and the electrode fingers 312 of the two comb-shaped electrodes can be alternately arranged in the arrangement direction of the electrode finger 312.

[0037] Exemplarily, the electrode fingers 312 of each comb electrode can be arranged at equal intervals; the electrode fingers 312 of one comb electrode can be arranged at intervals from the electrode fingers 312 of another comb electrode; and the electrode fingers 312 of one comb electrode can also be arranged at intervals from the dummy fingers arranged on another comb electrode. The arrangement of the electrode fingers can be any arrangement, which is not limited herein.

[0038] Exemplarily, the materials of the bus bars 311 and the electrode fingers 312 can be aluminum, molybdenum, copper, gold, platinum, silver, nickel, chromium, tungsten, or the like, which is not limited herein and can be determined according to specific conditions. However, the selected material needs to have good electrical conductivity.

[0039] Exemplarily, the electrode fingers 312 are usually rectangular or strip-shaped, and the cross section of the electrode fingers 312 shaped under the influence of process conditions can also be trapezoidal. In general, the extension line direction of the long side of the electrode fingers 312 is perpendicular to the extension line direction of the bus bars 311. In specific cases, the electrode fingers 312 can also be arranged obliquely relative to the bus bars, and a plurality of electrode fingers 312 are parallel to each other, and a certain gap is left between adjacent electrode fingers 312. In the embodiment of the present application, the electrode fingers 312 need to be in contact with a bus bar 311 to realize electrical connection.

[0040] Specifically,

[0041] Exemplarily, The duty cycle of the electrode fingers 312 can be 0.05, 0.1, 0.15, 0.2, or the like. By controlling the duty cycle of the electrode fingers 312 to be less than or equal to 0.2, the spurs in the main mode passband can be further reduced.

[0042] Specifically, the Euler angle of the first piezoelectric layer 20 is φ a , and the Euler angle of the second piezoelectric layer 40 is φ b , wherein |φ a -φ b | = [0, (172°-188°), 0]. Thus, by controlling the difference between the Euler angle φ a of the first piezoelectric layer 20 and the Euler angle φ b of the second piezoelectric layer 40, the piezoelectric stress constant e 15 of the first piezoelectric layer 20 and the piezoelectric stress constant e′ 15 of the second piezoelectric layer 40 are opposite numbers, and the A1 mode is kept at a larger level, so that a large number of reflected spurs generated by the first piezoelectric layer 20 and the second piezoelectric layer 40 stacked together can be reduced, and the spurs in the main mode passband can be effectively reduced.

[0043] For example, the Euler angles of the first piezoelectric layer 20 and the Euler angles of the second piezoelectric layer 40 satisfy the relationship of wherein the Euler angles of the first piezoelectric layer 20 and the Euler angles of the second piezoelectric layer 40 may be any angle, and the Euler angles of the two are not specifically limited, as long as the Euler angles of the first piezoelectric layer 20 and the Euler angles of the second piezoelectric layer 40 satisfy the above relationship, so that the piezoelectric stress constant e 15 of the first piezoelectric layer 20 15 and the piezoelectric stress constant e' of the second piezoelectric layer 40 are approximately opposite, while the A1 mode is maintained at a relatively large level, so that a large amount of reflected spurious modes generated by stacking the first piezoelectric layer 20 and the second piezoelectric layer 40 together can be reduced, and in turn the spurs in the main mode passband can be effectively reduced.

[0044] wherein the piezoelectric stress constant is a physical quantity describing the stress generated by a piezoelectric material under the action of an electric field or the electric field generated by the piezoelectric material under the action of stress. The piezoelectric stress constant is usually represented by e ij , wherein the subscripts i and j respectively represent the electric field direction (or polarization direction) and the stress direction. Therefore, the piezoelectric stress constant e 15 represents the relationship between the shear stress T5 (i.e. T xz or T yz ) and the electric field E1 (i.e. E x ) or E2 (i.e. E y ).

[0045] The resonator 100 provided in the present application can reduce a large amount of reflected spurious modes generated by stacking the first piezoelectric layer 20 and the second piezoelectric layer 40 together, and in turn effectively reduce the spurs in the main mode passband, by setting the electrode layer 30 in the form of an interdigital transducer 31 between the first piezoelectric layer 20 and the second piezoelectric layer 40, and controlling the difference between the Euler angles of the first piezoelectric layer and the second piezoelectric layer to be within the range of [0, (172°-188°), 0], such as in an example of the present application, the difference between the Euler angles of the first piezoelectric layer 20 and the second piezoelectric layer 40 is set to [0, 180°, 0], and further by setting the duty cycle of the electrode fingers 312 to be less than or equal to 0.2, the frequency response and impedance characteristics and other performances of the resonator 100 can be improved.

[0046] In some embodiments,

[0047] For example, the Euler angles of the first piezoelectric layer 20 and the Euler angles of the second piezoelectric layer 40 satisfy the relationship of In the case of the relationship between the first piezoelectric layer 20 and the second piezoelectric layer 40 being (0, 180°, 0), the Euler angles of the first piezoelectric layer 20 and the second piezoelectric layer 40 can be kept symmetrical, and the piezoelectric stress constant e 15 of the first piezoelectric layer 20 and the piezoelectric stress constant e' 15 of the second piezoelectric layer 40 are opposite numbers, while the A1 mode is maximized, thereby reducing the problem of a large number of reflected spurious modes generated by the first piezoelectric layer 20 and the second piezoelectric layer 40 being stacked together, and effectively reducing the spurs in the main mode passband.

[0048] In some embodiments, the first piezoelectric layer 20 is configured as a lithium niobate (LiNbO3) film, a lithium tantalate (LiTaO3) film, a quartz film, and an aluminum nitride (AlN) film, and / or the first piezoelectric layer 20 includes a (110°-135°) YX-LiNbO3 film and a (-10°-10°) ZX-LiNbO3 film.

[0049] The first piezoelectric layer 20 and the second piezoelectric layer 40 can be configured as a film formed of a piezoelectric material such as a lithium niobate film, a lithium tantalate film, a quartz film, and an aluminum nitride film, and the film types of the first piezoelectric layer 20 and the second piezoelectric layer 40 can be the same or different, which is not specifically limited herein.

[0050] For example, the first piezoelectric layer 20 and the second piezoelectric layer 40 can each be configured as a (110°-135°) YX-LiNbO3 film; or the first piezoelectric layer 20 can be configured as a 125° YX-LiNbO3 film, and the second piezoelectric layer 40 can be configured as a 10° ZX-LiNbO3 film.

[0051] The cut type of the first piezoelectric layer 20 needs to be limited because the A1 vibration mode is mainly used in the XBAR resonator, and in order to make the A1 vibration mode in the XBAR resonator better, the piezoelectric stress constant e 15 of the material needs to be large, and the piezoelectric stress constant e 16 needs to be small. In order to meet the above requirements, the first piezoelectric layer 20 and the second piezoelectric layer 40 can be configured as a (110°-135°) YX-LiNbO3 film or a (-10°-10°) ZX-LiNbO3 film, so that the piezoelectric stress constant e 15 of the first piezoelectric layer 20 is large, and the piezoelectric stress constant e 16 is small, and at the same time, the spurious modes near the main mode energy concentration region are less, the dispersion curve is flat, and the transverse mode is reduced.

[0052] The piezoelectric stress constant e 15 represents the shear stress T5 (i.e., T xz or T yz ) and the electric field E1 (i.e., Ex ) or E2 (i.e. E y The relationship between the piezoelectric stress constant e. 16 This represents the shear stress T6 (i.e., T). xy ) and electric field E1 (i.e. E x ) or E2 (i.e. E y The relationship between the piezoelectric stress constant e and the piezoelectric stress constant e. 15 and piezoelectric stress constant e 16 Although both are piezoelectric stress constants, they describe different directions of shear stress. The piezoelectric stress constant e 15 Shearing involving the xz or yz plane, and the piezoelectric stress constant e 16 This involves shearing in the xy plane.

[0053] Therefore, the following description will be based on the example of both the first piezoelectric layer 20 and the second piezoelectric layer 40 being provided with a (110°-135°) YX-LiNbO3 film or a (-10°-10°) ZX-LiNbO3 film.

[0054] In some embodiments, the difference between the thickness of the first piezoelectric layer 20 and the thickness of the second piezoelectric layer 40 is less than or equal to 50 nm. Therefore, by controlling the thickness relationship between the first piezoelectric layer 20 and the second piezoelectric layer 40, stray particles in the master mode passband can be further reduced.

[0055] For example, the thickness of the first piezoelectric layer 20 can be greater than the thickness of the second piezoelectric layer 40, and the thickness difference between the first piezoelectric layer 20 and the second piezoelectric layer 40 is less than or equal to 50nm, such as 10nm, 30nm or 50nm. Even if the thickness of the first piezoelectric layer 20 is greater than the thickness of the second piezoelectric layer 40, it can still achieve the effect of further reducing stray particles in the main mode passband.

[0056] For example, the thickness of the second piezoelectric layer 40 can be greater than the thickness of the first piezoelectric layer 20, and the thickness difference between the second piezoelectric layer 40 and the first piezoelectric layer 20 is less than or equal to 50nm. For example, the thickness difference between the second piezoelectric layer and the first piezoelectric layer can be any one of 5nm, 25nm or 45nm, so that the thickness of the second piezoelectric layer 40 is greater than the thickness of the first piezoelectric layer 20, so as to further reduce stray particles in the master mode passband by controlling the thickness of the two different piezoelectric layers.

[0057] In some embodiments, the thickness of the first piezoelectric layer 20 is equal to the thickness of the second piezoelectric layer 40. Therefore, by controlling the thicknesses of the first piezoelectric layer 20 and the second piezoelectric layer 40 to be equal, the stray suppression effect in the master mode passband can be optimized.

[0058] For example, the first piezoelectric layer 20 and the second piezoelectric layer 40 are respectively disposed on both sides of the electrode layer 30 and have the same thickness. This not only optimizes the stray suppression effect in the main mode passband, but also stabilizes the structure of the first piezoelectric layer 20 and the second piezoelectric layer 40, so that they are symmetrically disposed on both sides of the electrode layer 30.

[0059] In some embodiments, the thickness of the first piezoelectric layer 20 and the thickness of the second piezoelectric layer 40 can be 200nm-800nm. Therefore, by controlling the thickness of the first piezoelectric layer 20 and the thickness of the second piezoelectric layer 40, stray particles in the main mode passband can be further reduced.

[0060] For example, the thickness of the first piezoelectric layer 20 and the thickness of the second piezoelectric layer 40 can be 200nm, 400nm, 600nm or 800nm. By controlling the thickness of the first piezoelectric layer 20 and the thickness of the second piezoelectric layer 40 within the range of 200nm-800nm, stray particles in the main mode passband can be further reduced.

[0061] For example, the thickness of the first piezoelectric layer 20 and the thickness of the second piezoelectric layer 40 may be different. For example, the thickness of the first piezoelectric layer 20 may be 580 nm, and the thickness of the second piezoelectric layer 40 may be 620 nm, with a thickness difference of 40 nm.

[0062] like Figure 2 As shown, in some embodiments, the distance between two adjacent electrode fingers 312 connected to the same busbar 311 is d3 in a first direction, where the first direction is the arrangement direction of the electrode fingers 312; wherein, the thickness of the first piezoelectric layer 20 and the thickness of the second piezoelectric layer 40 are less than (d1+d3).

[0063] For example, the width of electrode finger 312 in the first direction is d1, and the width of (d1+d3) is the pitch. By controlling the thickness of the first piezoelectric layer 20 and the thickness of the second piezoelectric layer 40 to be less than (d1+d3), it can be ensured that the surface acoustic wave in the resonator 100 is not easily excited, thereby further reducing the spurious waves in the main mode passband.

[0064] For example, if the width of (d1+d3) is 700nm, the thickness of the first piezoelectric layer 20 and the thickness of the second piezoelectric layer 40 will both be controlled within the range of less than 700nm to ensure that the surface acoustic waves in the resonator 100 are not easily excited.

[0065] In some embodiments, the thickness of the first piezoelectric layer 20 and the thickness of the second piezoelectric layer 40 are less than 0.5 × (d1 + d3). This ensures that surface acoustic waves in the resonator 100 are not significantly excited, thereby further reducing stray noise in the main mode passband.

[0066] For example, the thickness of the first piezoelectric layer 20 and the thickness of the second piezoelectric layer 40 can be 0.4x(d1+d3) or 0.3x(d1+d3), etc. If the width of (d1+d3) is 800 nm, the thickness of the first piezoelectric layer 20 and the thickness of the second piezoelectric layer 40 are both controlled in the range of less than 400 nm, so as to ensure that the surface acoustic wave in the resonator 100 is not excited substantially.

[0067] In some embodiments, the thickness of the electrode layer 30 is less than the thickness of the first piezoelectric layer 20 or the second piezoelectric layer 40. Thus, by controlling the thickness of the electrode layer 30, the spurious in the main mode passband can be further reduced.

[0068] In some embodiments, the thickness of the electrode layer 30 is less than the thickness of the first piezoelectric layer 20 or the second piezoelectric layer 40. Thus, by controlling the thickness of the electrode layer 30, the spurious in the main mode passband can be further reduced.

[0069] For example, the thickness of the electrode layer 30 can be less than the thickness of the first piezoelectric layer 20 but not less than the thickness of the second piezoelectric layer 40; or the thickness of the electrode layer 30 can be less than the thickness of the second piezoelectric layer 40 but not less than the thickness of the first piezoelectric layer 20. The above different film thicknesses are examples, and in actual settings, the thickness of the electrode layer 30 can be adjusted according to the product or performance requirements, which will not be described here. Preferably, the thickness of the electrode layer 30 is less than the thickness of the first piezoelectric layer 20 and the second piezoelectric layer 40, so as to further reduce the spurious in the main mode passband.

[0070] In some embodiments, the thickness of the electrode layer 30 is 100 nm-400 nm. Thus, by controlling the thickness of the electrode layer 30, the spurious in the main mode passband can be further reduced.

[0071] For example, the thickness of the electrode layer 30 can be 100 nm, 200 nm, 300 nm or 400 nm. By controlling the thickness of the electrode layer 30 in the range of 100 nm-400 nm, the spurious in the main mode passband can be further reduced.

[0072] In some embodiments, the piezoelectric stress constant of the first piezoelectric layer 20 includes e 15 , the piezoelectric stress constant of the second piezoelectric layer 40 includes e' 15 , the materials of the first piezoelectric layer 20 and the second piezoelectric layer 40 are the same, and e 15 =-(0.95-1.05)e' 15 . Thus, by using the same material for the first piezoelectric layer 20 and the second piezoelectric layer 40, and making the piezoelectric stress constant e 15 of the first piezoelectric layer 20 and the piezoelectric stress constant e' 15The piezoelectric stress constants of the first piezoelectric layer 20 and the second piezoelectric layer 40 are opposite to each other, so that the Euler angles of the first piezoelectric layer 20 and the second piezoelectric layer 40 are kept symmetrical, and the A1 mode is kept in a larger level, so that the problem of a large number of reflected spurious modes generated by stacking the first piezoelectric layer 20 and the second piezoelectric layer 40 together can be reduced, and the spurs in the main mode passband can be effectively reduced.

[0073] In the embodiments of the present application, the piezoelectric stress constant can include e 15 and e 16 , wherein the thickness shear wave mainly utilizes the piezoelectric stress constant e 15 , and the horizontal shear wave mainly utilizes the piezoelectric stress constant e 16 .

[0074] For example, e 15 =-e′ 15 .

[0075] For example, the piezoelectric stress constant e 15 of the first piezoelectric layer 20 can be opposite to the piezoelectric stress constant e′ 15 of the second piezoelectric layer 40, and when they are opposite to each other, the Euler angles of the first piezoelectric layer 20 and the second piezoelectric layer 40 are kept symmetrical, and the resonator is in the A1 vibration mode, and the effect is optimal by setting the duty cycle of the electrode finger to be less than or equal to 0.2, so that the problem of a large number of reflected spurious modes generated by stacking the first piezoelectric layer 20 and the second piezoelectric layer 40 together can be reduced, and the spurs in the main mode passband can be effectively reduced, and the frequency response and impedance characteristics of the resonator can be improved.

[0076] For example, the piezoelectric stress constant e 15 of the first piezoelectric layer 20 can be -0.95e′ 15 , and can also be -1.05e′ 15 , and the specific value is not limited, as long as the piezoelectric stress constant e 15 of the first piezoelectric layer 20 and the piezoelectric stress constant e′ 15 of the second piezoelectric layer 40 are opposite to each other, that is, e 15 =-(0.95-1.05)e′ 15 , so that the Euler angles of the first piezoelectric layer 20 and the second piezoelectric layer 40 are kept symmetrical, and the resonator is in the A1 vibration mode, and the effect is better by setting the duty cycle of the electrode finger to be less than or equal to 0.2, so that the problem of a large number of reflected spurious modes generated by stacking the first piezoelectric layer 20 and the second piezoelectric layer 40 together can be reduced, and the spurs in the main mode passband can be effectively reduced, and the frequency response and impedance characteristics of the resonator can be improved.

[0077] Please refer to FIG. 3(a) and FIG. 3(b), FIG. 3(a) is a structural schematic diagram of a first piezoelectric layer provided by an embodiment of the present application, and FIG. 3(b) is a structural schematic diagram of a second piezoelectric layer provided by an embodiment of the present application.

[0078] As shown in FIG. 3(a) and FIG. 3(b), X and X' are the propagation directions of the acoustic wave, and the Z direction is the thickness direction. The Euler angles of the first piezoelectric layer 20 and the second piezoelectric layer 40 can be expressed as: if the Euler angles of the first piezoelectric layer 20 are (α a ,β a ,γ a ), then the Euler angles of the second piezoelectric layer 40 are (α b ,β b ,γ b ). Since the definition of the shear type is relatively complex, it can be expressed by a simple method, that is, the second piezoelectric layer 40 can first undergo Euler angle rotation and coincide with the first piezoelectric layer 20. Here, we can use the method of rotation matrix. The method of rotating the Euler angles of the second piezoelectric layer 40 to the Euler angles of the first piezoelectric layer 20 can adopt the following way.

[0079] Since obtaining the material parameters of the piezoelectric layer is the first step of calculating the acoustic velocity of the piezoelectric layer material, specifically, we need to obtain the transformation relationship between the current coordinate system and the crystal coordinate system of the piezoelectric layer. Therefore, the Euler angles can be used to represent the transformation relationship from the crystal coordinate system to the current coordinate system. In terms of actual physical meaning, this transformation relationship can also be understood as the process of cutting the crystal raw material in a fixed crystal cutting system, that is, when the tool of the fixed current cutting system is fixed, the piezoelectric layer with a specific shear direction and angle can be obtained by reasonably rotating the direction and angle of the wafer during cutting. When the piezoelectric layer is not rotated, the piezoelectric layer is defaulted to be Z-cut X-propagation. Usually, in order to obtain reasonable device characteristics, the piezoelectric layer needs to be rotated. It should be noted that when the acoustic wave transmission direction deviates from the crystal axis, the response of the periodic grating device will exhibit certain asymmetry, that is, there will be obvious resonance peaks at the non-energizable edge of the forbidden band, so the rotation process needs to be accurately controlled.

[0080] As shown in FIG. 4(a), FIG. 4(b), FIG. 4(c) and FIG. 4(d), the specific rotation process is as follows:

[0081] (1) The initial crystal coordinate system is shown in FIG. 4(a), at this time the crystal coordinate system (xyz) coincides with the Cartesian coordinate system (XYZ), first fix the z axis of the crystal coordinate system, rotate counterclockwise around it according to the right-hand system. At this time, a new coordinate system is obtained as shown in FIG. 4(b), and the corresponding axes are named x'y'z.

[0082] (2) Fix the x' axis of the coordinate system shown in Fig. 4(b) and rotate it counterclockwise according to the right-hand rule At this time, a new coordinate system is obtained as shown in Fig. 4(c), and the corresponding axes are named as x'y"z' respectively.

[0083] (3) Fix the z" axis of the coordinate system shown in Fig. 4(c) and rotate it counterclockwise according to the right-hand rule At this time, a new coordinate system is obtained as shown in Fig. 4(d), and the corresponding axes are named as x"y"z' respectively.

[0084] In the calculation of the material parameters of the piezoelectric layer in any tangential and propagation direction, the coordinate transformation of the related tensors, such as the elastic stiffness coefficients of the piezoelectric layer (fourth-order tensor), the piezoelectric coefficient e ijk (three-order tensor) and the dielectric coefficient ε ij (second-order tensor) is required. Using the direction cosines of the unit vectors of the original coordinate system and the target coordinate system to represent the rotation process, the cosine matrix corresponding to the rotation can be obtained as follows:

[0085]

[0086]

[0087] According to the above definition, the rotation matrix required from the original crystal coordinate system to the new coordinate system is:

[0088]

[0089] The coefficients of each term are as follows:

[0090] R 11 = cos(φ1)cos(φ3) - sin(φ1)cos(φ2)sin(φ3)

[0091] R 12 = sin(φ1)cos(φ3) + cos(φ1)cos(φ2)sin(φ3)

[0092] R 13 = sin(φ2)sin(φ3)

[0093] R 21 = -cos(φ1)sin(φ3) - sin(φ1)cos(φ2)cos(φ3)

[0094] R 22 = -sin(φ1)sin(φ3) + cos(φ1)cos(φ2)cos(φ3)

[0095] R 23= cos(φ1) sin(φ2)

[0096] R 31 = sin(φ1) sin(φ2)

[0097] R 32 = -cos(φ1) sin(φ2)

[0098] R 33 = cos(φ2)

[0099] At this time, the material parameters of the crystal coordinate system piezoelectric coefficient e ijk and dielectric coefficient ε ij to the material parameters of the new coordinate system piezoelectric coefficient e ijk ' and dielectric coefficient ε ij ' can be represented by the conversion matrix R and the Bond transformation matrix M as follows:

[0100] c E ' = M * c E * M T

[0101] e' = R * e * M T

[0102] ε' = R * ε * R T

[0103] Wherein, M is the Bond matrix, used to simplify the matrix operation, and M can be represented as:

[0104]

[0105] And each block matrix expression is:

[0106]

[0107] Due to the anisotropy of the material parameters, piezoelectric stress constant and dielectric coefficient of the piezoelectric layer, the material constants of the piezoelectric layer rotated by different Euler angles have great differences. When we know the original material constants of the crystal and the Euler angles, we can calculate the material constants in the current coordinate system by the above formula.

[0108] Therefore, the Euler angle of the second piezoelectric layer 40 is rotated to the Euler angle of the first piezoelectric layer 20 which is easily obtained as (0, 180°, 0), and the Euler angle of the second piezoelectric layer 40 after a rotation by the corresponding rotation matrix, can be rotated by the same second rotation operation as the Euler angle of the first piezoelectric layer 20 , so as to realize the conversion of the coordinate system.

[0109] In some embodiments, the electrode layer 30 further includes a filling layer 32 disposed in the gap region between the first piezoelectric layer 20 and the second piezoelectric layer 40, and the propagation speed of sound waves in the filling layer 32 is greater than the propagation speed of sound waves in the first piezoelectric layer 20 and the second piezoelectric layer 40. This can further reduce stray light in the master mode passband and improve the support of the electrode layer 30, thereby improving the stability of the resonator 100.

[0110] Among them, the filling layer 32 generally has a good ability to conduct sound waves, so a medium material with high sound velocity is generally selected.

[0111] For example, the material of the filling layer 32 can be a nitride or oxynitride, such as silicon nitride, aluminum nitride or aluminum oxide, so that the material difference between the filling layer 32 and the first piezoelectric layer 20 and the second piezoelectric layer 40 can be used to make the propagation speed of the sound wave in the filling layer 32 greater than the propagation speed of the sound wave in the first piezoelectric layer 20 and the second piezoelectric layer 40.

[0112] Since the filling layer 32 is used to fill the gaps between the electrode layer 31 and the first piezoelectric layer 20 and the second piezoelectric layer 40, the thickness of the filling layer 32 must be at least greater than or equal to the thickness of the electrode layer 31 to completely fill the gaps. For example, the thickness of the filling layer 32 can be the same as the thickness of the electrode layer 31, and the filling layer 32 can also partially cover the first piezoelectric layer 20 and the second piezoelectric layer 40, meaning the thickness of the filling layer 32 can also be greater than the thickness of the electrode layer 31.

[0113] like Figure 5 As shown, in some embodiments, the resonator 100 further includes a dielectric layer 50 disposed between the substrate 10 and the first piezoelectric layer 20; wherein the dielectric layer 50 includes a temperature compensation layer and / or a charge trapping layer.

[0114] For example, the dielectric layer 50 may include a temperature compensation layer, which can improve the negative frequency temperature characteristics of the first piezoelectric layer 20, making the frequency temperature coefficient of the resonator 100 closer to 0. The temperature compensation layer is disposed between the substrate 10 and the first piezoelectric layer 20, that is, the substrate 10, the temperature compensation layer, and the first piezoelectric layer 20 are stacked sequentially. The temperature compensation layer plays a role in temperature compensation, thereby improving the negative frequency temperature characteristics of the first piezoelectric layer 20.

[0115] Exemplarily, the thickness of the temperature compensation layer is similar to the sum of the thicknesses of the first piezoelectric layer 20 and the second piezoelectric layer 40, generally 400 nm-1600 nm. The material of the temperature compensation layer can be silicon oxide, tantalum oxide, silicon oxynitride, or other materials with positive frequency temperature coefficient. Generally, the material of the temperature compensation layer is also a low acoustic velocity material, so as to reduce the leakage of the surface acoustic wave main mode energy to the substrate 10. In the embodiments of the present application, the number of the temperature compensation layer can be one layer or a multi-layer structure stacked, which are all within the protection scope of the present application.

[0116] Exemplarily, the medium layer 50 can include a charge trapping layer. The charge trapping layer can capture the excess electrons at the interface between the substrate 10 and the first piezoelectric layer 20, and the excess electrons will affect the electrical performance of the resonator 100, thereby causing the main mode to fluctuate. The charge trapping layer is arranged between the substrate 10 and the first piezoelectric layer 20, i.e., the substrate 10, the charge trapping layer, and the first piezoelectric layer 20 are sequentially stacked.

[0117] It should be noted that the medium layer 50 can only include the temperature compensation layer, only include the charge trapping layer, or simultaneously include the temperature compensation layer and the charge trapping layer, which are not specifically limited here.

[0118] In some embodiments, the substrate 10 is a single crystal silicon thin film, and the charge trapping layer is a polycrystalline silicon thin film.

[0119] Exemplarily, the substrate 10 is generally a single crystal silicon thin film, so as to support the resonator 100 by using its good support. Preferably, the substrate 10 is a (1, 1, 1) cut silicon thin film.

[0120] Exemplarily, the charge trapping layer is generally a polycrystalline silicon thin film, which has good stability and conductivity, and can effectively conduct charges under the action of an electric field, so that the charge trapping layer can efficiently capture and store charges.

[0121] As shown in FIG. 1, Figure 6 In some embodiments, the substrate 10 includes a first substrate layer 11 and a second substrate layer 12, and the second substrate layer 12 is arranged between the first substrate layer 11 and the first piezoelectric layer 20. The propagation speed of the acoustic wave in the second substrate layer 12 is greater than the propagation speed of the acoustic wave in the first substrate layer 11.

[0122] The second substrate layer 12 generally has good ability to conduct acoustic waves, so it is generally selected from medium materials with high acoustic velocity.

[0123] For example, the first substrate layer 11 can be configured as a single crystal silicon thin film. The second substrate layer 12 can be configured as a polycrystalline silicon thin film, so that the material difference between the single crystal silicon thin film and the polycrystalline silicon thin film can be utilized to make the propagation speed of the acoustic wave in the second substrate layer 12 greater than the propagation speed of the acoustic wave in the first substrate layer 11.

[0124] For example, the thickness of the first substrate layer 11 can be the same as the thickness of the second substrate layer 12, or can be different from the thickness of the second substrate layer 12, such as the thickness of the first substrate layer 11 can be greater than the thickness of the second substrate layer 12, or can be less than the thickness of the second substrate layer 12, which is not specifically limited here.

[0125] In the following, the harmonic admittance curves of the resonator 100 provided in the present application and the resonator provided in the related art will be compared through simulation experiments.

[0126] As shown in Figure 7 For convenience of observation, the curve corresponding to the resonator provided in the present application is moved down by 70 dB, and the comparison can be more intuitive. Through the simulation experiment, it can be seen from the comparison of the real part curves of the admittance of the two that, compared with the resonator provided in the comparative example 1, the real part of the resonator provided in the present application is smaller at the resonance point, indicating that the energy loss is lower at this time, and the real part curve of the admittance is smoother and more symmetrical, indicating that the resonator is well designed and the loss is more stable. It can be seen from the comparison of the amplitude curves of the admittance of the two that the peak value of the amplitude of the admittance at the resonance point is high, and the amplitude at the non-resonance point decreases rapidly, indicating that the resonator has strong suppression ability to non-resonance frequency. It can be seen that the wave ripple between the resonance point and the anti-resonance point of the resonator provided in the present application almost disappears, effectively reducing the large amount of reflected spurious modes generated by the first piezoelectric layer and the second piezoelectric layer stacked together, and further effectively reducing the spurs in the main mode passband, indicating that the resonator provided in the present application has excellent frequency response and impedance characteristics and other performances.

[0127] The present application also provides a filter, which will be described in detail below.

[0128] The filter includes a plurality of series arm resonators 100 connected in series between the input end and the output end, and a plurality of parallel arm resonators 100 connected at one end with the series arm resonators 100 and at the other end with the ground end, and at least one of the series arm resonators 100 and the parallel arm resonators 100 can adopt the resonator 100 provided in any of the above embodiments. The filter can reduce the large amount of reflected spurious modes generated by the first piezoelectric layer 20 and the second piezoelectric layer 40 stacked together, and further effectively reduce the spurs in the main mode passband.

[0129] The application further provides a radio frequency front-end module, which comprises the resonator 100 according to any one of the above embodiments. The radio frequency front-end module can effectively reduce the spurious in the main mode passband, thereby improving the reliability, safety and practicability of the radio frequency front-end module.

[0130] The radio frequency front-end module can comprise an antenna end, a power amplifier, a low-noise amplifier, a switch, a filter and the like, which are not limited herein.

[0131] The above is only a specific embodiment of the application, but the protection scope of the application is not limited thereto, and any person skilled in the art can easily think of various equivalent modifications or replacements within the technical range disclosed by the application, which should be covered in the protection scope of the application. Therefore, the protection scope of the application should be subject to the protection scope of the claims.

Claims

1. A resonator, characterized by, The resonator comprises: a substrate; a first piezoelectric layer disposed on one side of the substrate, the first piezoelectric layer having an Euler angle of an electrode layer disposed on a side of the first piezoelectric layer away from the substrate, the electrode layer comprising an interdigital transducer; a second piezoelectric layer disposed on a side of the electrode layer distal from the first piezoelectric layer, the second piezoelectric layer having an Euler angle of the interdigital transducer comprises two oppositely disposed comb electrodes, each of the comb electrodes comprising a bus bar and a plurality of electrode fingers connected to the bus bar and disposed at intervals, the electrode fingers having a width d1 in a first direction, the first direction being the arrangement direction of the electrode fingers, and adjacent electrode fingers having a gap width d2; wherein and 2. The resonator of claim 1, wherein 3. The resonator of claim 1, wherein a difference between a thickness of the first piezoelectric layer and a thickness of the second piezoelectric layer is less than or equal to 50 nm.

4. The resonator of claim 3, wherein the thickness of the first piezoelectric layer is equal to the thickness of the second piezoelectric layer.

5. The resonator of claim 1, wherein the thickness of the first piezoelectric layer and the thickness of the second piezoelectric layer are 200 nm-800 nm.

6. The resonator of claim 1, wherein a distance between two electrode fingers connected to the same bus bar and adjacent to each other in the first direction is d3, the first direction being the arrangement direction of the electrode fingers; wherein the thickness of the first piezoelectric layer and the thickness of the second piezoelectric layer are less than (d1+d3).

7. The resonator of claim 6, wherein the thickness of the first piezoelectric layer and the thickness of the second piezoelectric layer are less than 0.5×(d1+d3).

8. The resonator of claim 1, wherein a thickness of the electrode layer is less than a thickness of the first piezoelectric layer or the second piezoelectric layer.

9. The resonator of claim 1, wherein the thickness of the electrode layer is 100 nm-400 nm.

10. The resonator of claim 1, wherein, The piezoelectric stress constant of the first piezoelectric layer includes e 15 The piezoelectric stress constant of the second piezoelectric layer includes e' 15 The material of the first piezoelectric layer and the second piezoelectric layer is the same, and e 15 = -(0.95-1.05)e' 15 .

11. The resonator of claim 10, wherein, e 15 = -e' 15 .

12. The resonator of claim 1, wherein, the electrode layer further comprises a filling layer disposed in a gap region between the first piezoelectric layer and the second piezoelectric layer, and a propagation speed of a sound wave in the filling layer is greater than a propagation speed of the sound wave in the first piezoelectric layer and the second piezoelectric layer.

13. The resonator of claim 1, wherein, The resonator further comprises: a dielectric layer disposed between the substrate and the first piezoelectric layer; wherein the dielectric layer comprises a temperature compensation layer and / or a charge trapping layer.

14. The resonator of claim 13, wherein, the substrate is configured as a single-crystal silicon thin film, and the charge trapping layer is configured as a polycrystalline silicon thin film.

15. The resonator of any of claims 1-14, wherein, The substrate comprises: a first substrate layer; a second substrate layer disposed between the first substrate layer and the first piezoelectric layer; wherein a propagation speed of a sound wave in the second substrate layer is greater than a propagation speed of the sound wave in the first substrate layer.

16. The resonator of any one of claims 1-15, wherein, the first piezoelectric layer is configured as any one of a lithium niobate thin film, a lithium tantalate thin film, a quartz thin film, and an aluminum nitride thin film, and / or the first piezoelectric layer comprises any one of a (110°-135°) YX-LiNbO3 thin film and a (-10°-10°) ZX-LiNbO3 thin film.

17. A filter, characterized by a plurality of series arm resonators connected in series between an input terminal and an output terminal, and a plurality of parallel arm resonators connected at one end to the series arm resonators and at the other end to a ground terminal, at least one of the series arm resonators and the parallel arm resonators comprising the resonator as claimed in any one of claims 1-16.

18. A radio frequency front end module, comprising: a filter comprising the resonator as claimed in claim 17.

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