Surface acoustic wave resonator, filter, multiplexer and radio frequency front-end circuit

Abstract

The invention discloses a surface acoustic wave resonator, a filter, a multiplexer and a radio frequency front-end circuit. The surface acoustic wave resonator includes: a piezoelectric substrate; the interdigital transducer comprises a transition metal layer, a main metal layer and a protective layer, the transition metal layer is arranged on one side of the piezoelectric substrate, the main metal layer is arranged on one side, far away from the piezoelectric substrate, of the transition metal layer, and the protective layer is arranged on one side, far away from the piezoelectric substrate, of the main metal layer; the main metal layer comprises at least one elemental metal layer; the protective layer comprises a metal protective layer; and the mass density of the simple substance metal layer is greater than that of the metal protection layer. According to the invention, the main metal layer of the interdigital transducer is composed of the elemental metal layer whose mass density is greater than the mass density of the metal protection layer, so that miniaturization of the surface acoustic wave resonator can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of acoustic devices, and in particular to a surface acoustic wave resonator, a filter, a multiplexer and a radio frequency front-end circuit. Background Art

[0002] Surface acoustic wave resonators are widely used in base station and mobile terminal radio frequency systems in the field of communications. In recent years, multi-band systems have been used to increase the data transmission speed of mobile phones. Since multiple frequency bands can be used for transmission and reception, multiple filtering devices for high-frequency signals passing through different frequency bands are set up in the front-end circuit of the mobile phone. In this case, since the installation space allowed by the RF front-end circuit is limited, the surface acoustic wave resonator used is required to be small in size and have low passband loss.

[0003] The interdigital transducer of the surface acoustic wave resonator in the prior art includes a stacked transition metal layer, a main metal layer and a protective layer, the protective layer including a metal protective layer, which usually adopts the material of the metal protective layer (such as aluminum) as the manufacturing material of the main metal layer of the interdigital transducer. However, since the mass density of the material of the metal protective layer (such as aluminum) is relatively low and the mass load response is weak, the wave velocity of the surface acoustic wave in the surface acoustic wave resonator in the prior art is high. According to the formula v=λ×f, the higher the wave velocity of the surface acoustic wave, the larger the wavelength λ of the surface acoustic wave, the larger the period of the interdigital transducer that determines the wavelength λ of the surface acoustic wave, and the larger the volume of the surface acoustic wave resonator, which is not conducive to the miniaturization of the surface acoustic wave resonator. Summary of the invention

[0004] The present invention provides a surface acoustic wave resonator, a filter, a multiplexer and a radio frequency front-end circuit to solve the problem that the existing surface acoustic wave resonator is difficult to miniaturize.

[0005] In a first aspect, an embodiment of the present invention provides a surface acoustic wave resonator, the surface acoustic wave resonator comprising:

[0006] Piezoelectric substrate;

[0007] An interdigital transducer comprises a transition metal layer, a main metal layer and a protective layer; the transition metal layer is arranged on one side of the piezoelectric substrate, the main metal layer is arranged on a side of the transition metal layer away from the piezoelectric substrate, and the protective layer is arranged on a side of the main metal layer away from the piezoelectric substrate;

[0008] The main metal layer includes at least one single metal layer; the protective layer includes a metal protective layer; and the mass density of the single metal layer is greater than the mass density of the metal protective layer.

[0009] Optionally, the main metal layer includes at least two layers of the single metal layer;

[0010] Along the direction where the transition metal layer approaches the protective layer, the mass density of the single metal layer gradually decreases.

[0011] Optionally, the single metal layer includes a copper metal layer, a platinum metal layer, a chromium metal layer, a molybdenum metal layer, a silver metal layer or a gold metal layer.

[0012] Optionally, the protective layer further comprises a metal oxide protective layer; the metal oxide protective layer is arranged on a side surface of the metal protective layer away from the main metal layer and a side surface of the metal protective layer;

[0013] The equivalent thickness of the interdigital transducer satisfies the following relationship:

[0014] ;

[0015] in, represents the equivalent thickness of the IDT, represents the thickness of the transition metal layer, represents the mass density of the transition metal layer, represents the thickness of the main metal layer, represents the mass density of the main metal layer, represents the thickness of the protective layer, represents the average mass density of the protective layer, represents the mass density of the metal protective layer.

[0016] Optionally, the minimum value of the equivalent thickness of the interdigital transducer is negatively correlated with the mass density of the single metal layer;

[0017] The maximum value of the equivalent thickness of the IDT is negatively correlated with the mass density of the single metal layer.

[0018] Optionally, the transition metal layer includes a titanium metal layer; the protective layer includes an aluminum protective layer and an aluminum oxide protective layer;

[0019] When the single metal layer includes a copper metal layer, the equivalent thickness h0 of the IDT satisfies 0.065×λ≤h0≤0.085×λ;

[0020] When the single metal layer includes a molybdenum metal layer, the equivalent thickness h0 of the interdigital transducer satisfies 0.05×λ≤h0≤0.08×λ;

[0021] When the single metal layer includes a platinum metal layer, the equivalent thickness h0 of the interdigital transducer satisfies 0.045×λ≤h0≤0.065×λ;

[0022] Here, λ represents the wavelength of the surface acoustic wave in the surface acoustic wave resonator.

[0023] Optionally, the piezoelectric substrate includes a supporting substrate and a piezoelectric layer disposed between the supporting substrate and the interdigital transducer;

[0024] A speed at which a surface acoustic wave propagates in the supporting substrate is different from a speed at which the surface acoustic wave propagates in the piezoelectric layer.

[0025] Optionally, the piezoelectric substrate comprises a supporting substrate, an intermediate layer and a piezoelectric layer which are stacked; the piezoelectric layer is arranged between the intermediate layer and the interdigital transducer;

[0026] The speed at which the surface acoustic wave propagates in the intermediate layer is different from the speed at which the surface acoustic wave propagates in the piezoelectric layer;

[0027] A speed at which the surface acoustic wave propagates in the intermediate layer is different from a speed at which the surface acoustic wave propagates in the supporting substrate.

[0028] Optionally, the surface acoustic wave resonator further includes a first dielectric film layer and a second dielectric film layer; the piezoelectric substrate includes a piezoelectric layer;

[0029] The first dielectric film layer is arranged on a side of the IDT away from the piezoelectric layer and a side of the piezoelectric layer close to the IDT; wherein the frequency temperature coefficient of the first dielectric film layer is opposite in polarity to the frequency temperature coefficient of the piezoelectric layer;

[0030] The second dielectric film layer is arranged on a side of the first dielectric film layer away from the interdigital transducer; wherein the thickness of the second dielectric film layer is negatively correlated with the frequency of the surface acoustic wave in the surface acoustic wave resonator.

[0031] In a second aspect, an embodiment of the present invention provides a surface acoustic wave filter, which includes the surface acoustic wave resonator as described in the first aspect.

[0032] In a third aspect, an embodiment of the present invention provides a surface acoustic wave multiplexer, the surface wave multiplexer comprising an antenna, at least one receiving unit and at least one transmitting unit;

[0033] The antenna is communicatively connected to the receiving unit and the sending unit respectively;

[0034] At least one of the receiving unit and the sending unit includes the surface acoustic wave filter as described in the second aspect.

[0035] In a fourth aspect, an embodiment of the present invention provides a radio frequency front-end circuit, which includes the surface acoustic wave multiplexer as described in the third aspect.

[0036] Compared with the technical solution of using the material of the metal protective layer, that is, the material with a smaller mass density as the material constituting the main metal layer, the technical solution of the embodiment of the present invention, by setting the main metal layer of the interdigital transducer to be composed of a single metal layer with a mass density greater than the mass density of the metal protective layer, is beneficial to reducing the wave velocity of the surface acoustic wave, reducing the period of the interdigital transducer, and thereby realizing the miniaturization of the surface acoustic wave resonator.

[0037] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0039] Figure 1 A schematic structural diagram of a surface acoustic wave resonator provided by an embodiment of the present invention;

[0040] Figure 2 A schematic cross-sectional structure diagram of a surface acoustic wave resonator provided by an embodiment of the present invention;

[0041] Figure 3 A schematic cross-sectional structure diagram of another surface acoustic wave resonator provided by an embodiment of the present invention;

[0042] Figure 4 A schematic cross-sectional structure diagram of another surface acoustic wave resonator provided by an embodiment of the present invention;

[0043] Figure 5 A schematic cross-sectional structure diagram of another surface acoustic wave resonator provided by an embodiment of the present invention;

[0044] Figure 6 A schematic cross-sectional structure diagram of another surface acoustic wave resonator provided by an embodiment of the present invention;

[0045] Figure 7 A schematic structural diagram of a surface acoustic wave filter provided by an embodiment of the present invention;

[0046] Figure 8 A schematic diagram of the structure of another surface acoustic wave filter provided by an embodiment of the present invention;

[0047] Fig. 9 A schematic structural diagram of a surface acoustic wave multiplexer provided in an embodiment of the present invention;

[0048] Fig.10 A schematic structural diagram of a radio frequency front-end circuit provided in an embodiment of the present invention.

[0049] Explanation of the reference numerals: 10, surface acoustic wave resonator; 11, piezoelectric substrate; 12, interdigital transducer; 12A, transition metal layer; 12B, main metal layer; 12C, protective layer; 12C1, metal protective layer; 121, first interdigital electrode; 122, second interdigital electrode; 123, first pseudo-finger electrode; 124, second pseudo-finger electrode; 125, first bus bar; 126, second bus bar; X, first direction; Y, second direction; Z, third direction; 13, first reflection grating; 14, second reflection grating; 12B1, first single metal layer; 12B2, second single metal layer; 12C2, metal oxide protective layer; 111, supporting substrate; 112, piezoelectric layer; 113, intermediate layer; 1131, first sub-intermediate layer; 1132, second sub-intermediate layer; 1133, third sub-intermediate layer; 15, first dielectric film layer; 16, a second dielectric film layer; 20, a surface acoustic wave filter; in, a signal input terminal; out, a signal output terminal; 21, a series arm resonator; 22, a parallel arm resonator; 23, a series-parallel resonator; DMS, a dual-mode surface acoustic wave resonator; 30, a surface acoustic wave multiplexer; 31, an antenna; 32, a receiving unit; 33, a transmitting unit; P1, a receiving terminal; P2, a transmitting terminal; 40, a radio frequency front-end circuit; 41, including a switch; 42, a first surface acoustic wave filter; 43, a second surface acoustic wave filter; 44, a first duplexer transmitting filter; 45, a first duplexer receiving filter; 46, a second duplexer transmitting filter; 47, a second duplexer receiving filter; 48, a low noise amplifier; 49, a power amplifier; 50, a radio frequency communication device; 51, an antenna terminal; 52, a radio frequency signal processing circuit; 53, a baseband signal processing circuit. DETAILED DESCRIPTION

[0050] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0051] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices. The orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", etc. is based on the orientation or positional relationship shown in the drawings, and is only used to illustrate the relative positional relationship between the components or components, and does not particularly limit the specific installation orientation of the components or components.

[0052] Figure 1 A schematic diagram of the structure of a surface acoustic wave resonator provided by an embodiment of the present invention, Figure 2 A schematic cross-sectional structure diagram of a surface acoustic wave resonator provided by an embodiment of the present invention, referring to Figure 1 and Figure 2 The surface acoustic wave resonator 10 in the embodiment of the present invention includes a piezoelectric substrate 11 and an interdigital transducer 12. The interdigital transducer 12 includes a transition metal layer 12A, a main metal layer 12B and a protective layer 12C. The transition metal layer 12A is arranged on one side of the piezoelectric substrate 11, the main metal layer 12B is arranged on the side of the transition metal layer 12A away from the piezoelectric substrate 11, and the protective layer 12C is arranged on the side of the main metal layer 12B away from the piezoelectric substrate 11. The main metal layer 12B includes at least one single metal layer. The protective layer 12C includes a metal protective layer 12C1. The mass density of the single metal layer is less than the mass density of the metal protective layer 12C1.

[0053] Exemplary, reference Figure 1The interdigital transducer 12 includes a plurality of first interdigital electrodes 121, a plurality of second interdigital electrodes 122, a plurality of first pseudo-finger electrodes 123, a plurality of second pseudo-finger electrodes 124, a first bus bar 125, and a second bus bar 126; the first interdigital electrodes 121 and the first pseudo-finger electrodes 123 are both connected to the first bus bar 125, and along the direction in which the first bus bar 125 extends, i.e., the first direction X, the first interdigital electrodes 121 and the first pseudo-finger electrodes 123 are alternately arranged; the second interdigital electrodes 122 and the second pseudo-finger electrodes 124 are both connected to the second bus bar The second bus bar 126 is connected, and along the direction in which the second bus bar 126 extends, that is, the first direction X, the second interdigitated electrodes 122 and the second pseudo-finger electrodes 124 are alternately arranged; along the direction in which the first interdigitated electrodes 121 and the second pseudo-finger electrodes 124 extend, that is, the second direction Y, the first interdigitated electrodes 121 and the second pseudo-finger electrodes 124 correspond one to one; along the direction in which the second interdigitated electrodes 122 and the first pseudo-finger electrodes 123 extend, that is, the second direction Y, the second interdigitated electrodes 122 and the first pseudo-finger electrodes 123 correspond one to one; wherein the first direction X and the second direction Y intersect, Figure 1 The first direction X and the second direction Y are perpendicular to each other. The wavelength λ of the surface acoustic wave in the surface acoustic wave resonator 10 is determined by the period D of the IDT 12 , which refers to the distance between two adjacent first interdigital electrodes 121 or the distance between two adjacent second interdigital electrodes 122 .

[0054] Continue to refer Figure 1 The surface acoustic wave resonator 10 in the embodiment of the present invention further includes a first reflection grating 13 and a second reflection grating 14. The first reflection grating 13 and the second reflection grating 14 are respectively located on two opposite sides of the interdigital transducer 12 along the first direction X. The piezoelectric substrate 11 can be vibrated by applying an electrical signal to the first bus bar 125 and the second bus bar 126 to generate a surface acoustic wave. Ideally, the surface acoustic wave should only propagate on the piezoelectric substrate 11 corresponding to the active area of ​​the interdigital transducer 12, wherein the active area of ​​the interdigital transducer 12 refers to the area where the first interdigital electrode 121 and the second interdigital electrode 122 overlap along the second direction Y. However, in reality, a part of the surface acoustic wave will propagate outside the surface acoustic wave resonator along the first direction Y and the direction opposite to the first direction Y. By setting the first reflection grating 13 and the second reflection grating 14 in the embodiment of the present invention, the leakage of the surface acoustic wave to the position where the first reflection grating 13 and the second reflection grating 14 are set can be reduced, which is conducive to improving the Q value of the surface acoustic wave resonator.

[0055] refer to Figure 2, the main metal layer 12B includes only one single metal layer, namely, the first single metal layer 12B1. It should be noted that the single metal layer refers to a metal layer composed of only one metal element. Along the thickness direction of the interdigital transducer 12, namely, the third direction Z, the transition metal layer 12A, the first single metal layer 12B1 and the protective layer 12C are stacked in sequence on the piezoelectric substrate 11.

[0056] Exemplarily, the transition metal layer 12A includes a titanium metal layer, which is used to increase the adhesion between the main metal layer 12B and the piezoelectric substrate 11, so that the transducer 12 and the piezoelectric substrate 11 can be tightly fixed together. The first single metal layer 12B1 includes a copper metal layer, a platinum metal layer, a chromium metal layer, a molybdenum metal layer, a silver metal layer or a gold metal layer. The protective layer 12C includes an aluminum protective layer, that is, the metal protective layer 12C1 is an aluminum protective layer, and the exposed surface of the aluminum protective layer can form an aluminum oxide protective layer in an environment containing oxygen. The aluminum oxide protective layer can protect the main metal layer 12B from being oxidized or corroded, which is beneficial to improving the stability and service life of the surface acoustic wave resonator.

[0057] Compared with the technical solution of using aluminum material as the material for constituting the main metal layer 12B, the embodiment of the present invention arranges the main metal layer 12B of the interdigital transducer 12 to be composed of a single metal layer whose mass density is greater than the mass density of the aluminum protective layer, which is beneficial to reducing the wave velocity of the surface acoustic wave and reducing the period of the interdigital transducer 12, thereby realizing the miniaturization of the surface acoustic wave resonator 10.

[0058] Based on the above embodiments, Figure 3 A schematic cross-sectional view of another surface acoustic wave resonator provided by an embodiment of the present invention, referring to Figure 3 The main metal layer 12B includes at least two single metal layers. The mass density of the single metal layer gradually decreases along the direction from the transition metal layer 12A to the protective layer 12C.

[0059] refer to Figure 3 The main metal layer 12B includes two single metal layers, namely, a first single metal layer 12B1 and a second single metal layer 12B2. Along the thickness direction of the IDT 12, namely, the third direction Z, the transition metal layer 12A, the first single metal layer 12B1, the second single metal layer 12B2 and the protective layer 12C are sequentially stacked on the piezoelectric substrate 11.

[0060] Exemplarily, the first single metal layer 12B1 includes a copper metal layer, a platinum metal layer, a chromium metal layer, a molybdenum metal layer, a silver metal layer or a gold metal layer. The second single metal layer 12B2 includes a copper metal layer, a platinum metal layer, a chromium metal layer, a molybdenum metal layer, a silver metal layer or a gold metal layer. The mass density of the first single metal layer 12B1 is greater than that of the second single metal layer 12B2. According to the principle that in an elastic medium, the greater the density, the smaller the wave velocity, the wave velocity of the surface acoustic wave transmitted in the first single metal layer 12B1 is smaller than the wave velocity of the surface acoustic wave transmitted in the first single metal layer 12B2.

[0061] In the embodiment of the present invention, the main metal layer 12B is arranged to include at least two single metal layers, and is arranged along the direction of the transition metal layer 12A close to the protective layer 12C, that is, the third direction Z. The mass density of the single metal layer gradually decreases, which is beneficial to improving the local stress concentration in the grains of each layer of material during the manufacturing process of the interdigital transducer 12, smoothing the microstructure at the transition interface of each layer of material, and improving the structural strength and durability of the electrode.

[0062] Based on the above embodiments, Figure 2 and Figure 3 The protective layer 12C further includes a metal oxide protective layer 12C2. The metal oxide protective layer 12C2 is disposed on a side surface of the metal protective layer 12C1 away from the main metal layer 12B and on a side surface of the metal protective layer 12C1. The equivalent thickness of the interdigital transducer 12 satisfies the following relationship: .in, represents the equivalent thickness of the interdigital transducer 12, represents the thickness of the transition metal layer 12A, represents the mass density of the transition metal layer 12A, represents the thickness of the main metal layer 12B, represents the mass density of the main metal layer 12B, represents the thickness of the protective layer 12C, represents the average mass density of the protective layer 12C, represents the mass density of the metal protective layer 12C1.

[0063] Exemplarily, the protective layer 12C includes an aluminum protective layer and an aluminum oxide protective layer, that is, the metal protective layer 12C1 is an aluminum protective layer, and the metal oxide protective layer is an aluminum oxide protective layer. Specifically, the steps of making the protective layer 12C are as follows: an aluminum layer is prepared on the side of the main metal layer 12B away from the piezoelectric substrate 11, oxygen is introduced to oxidize the surface of the aluminum layer, so as to form an aluminum oxide protective layer on the exposed surface of the aluminum layer.

[0064] It should be noted that the equivalent thickness of the interdigital transducer 12 is related to the propagation speed of the surface acoustic wave in the surface acoustic wave resonator 10. The equivalent thickness of the interdigital transducer 12 can be set according to the requirement for the propagation speed of the surface acoustic wave in the surface acoustic wave resonator 10, and then the thickness and density of each layer in the interdigital transducer 12 can be set.

[0065] Based on the above embodiment, the minimum value of the equivalent thickness of the IDT 12 is negatively correlated with the mass density of the single metal layer. The maximum value of the equivalent thickness of the IDT 12 is negatively correlated with the mass density of the single metal layer.

[0066] Further, the transition metal layer 12A includes a titanium metal layer, and the protective layer 12C includes an aluminum protective layer and an aluminum oxide protective layer. When the single metal layer includes a copper metal layer, the equivalent thickness h0 of the interdigital transducer 12 satisfies 0.065×λ≤h0≤0.085×λ. When the single metal layer includes a molybdenum metal layer, the equivalent thickness h0 of the interdigital transducer 12 satisfies 0.05×λ≤h0≤0.08×λ. When the single metal layer includes a platinum metal layer, the equivalent thickness h0 of the interdigital transducer 12 satisfies 0.045×λ≤h0≤0.065×λ. Wherein, λ represents the wavelength of the surface acoustic wave in the surface acoustic wave resonator 10.

[0067] It can be understood that the mass density of the copper metal layer is smaller than the mass density of the molybdenum metal layer, and the mass density of the molybdenum metal layer is smaller than the mass density of the platinum metal. According to the fact that the minimum value of the equivalent thickness of the interdigital transducer 12 is negatively correlated with the mass density of the single metal layer, and the maximum value of the equivalent thickness of the interdigital transducer 12 is negatively correlated with the mass density of the single metal layer, it can be known that when the main metal layer adopts the copper metal layer, the minimum value of the equivalent thickness h0 of the interdigital transducer 12 corresponding to the main metal layer is greater than the minimum value of the equivalent thickness h0 of the interdigital transducer 12 corresponding to the main metal layer adopts the molybdenum metal layer, and the minimum value of the equivalent thickness h0 of the interdigital transducer 12 corresponding to the main metal layer adopts the molybdenum metal layer is greater than the minimum value of the equivalent thickness h0 of the interdigital transducer 12 corresponding to the main metal layer adopts the molybdenum metal layer. Greater than the minimum value of the equivalent thickness h0 of the interdigital transducer 12 corresponding to when the main metal layer adopts a platinum metal layer; the maximum value of the equivalent thickness h0 of the interdigital transducer 12 corresponding to when the main metal layer adopts a copper metal layer is greater than the maximum value of the equivalent thickness h0 of the interdigital transducer 12 corresponding to when the main metal layer adopts a molybdenum metal layer, and the maximum value of the equivalent thickness h0 of the interdigital transducer 12 corresponding to when the main metal layer adopts a molybdenum metal layer is greater than the maximum value of the equivalent thickness h0 of the interdigital transducer 12 corresponding to when the main metal layer adopts a platinum metal layer.

[0068] Specifically, under the premise that the transition metal layer 12A includes a titanium metal layer, and the protective layer 12C includes an aluminum protective layer and an aluminum oxide protective layer. If the main metal layer includes a single metal layer, and the single metal layer is a copper metal layer, the equivalent thickness h0 of the interdigital transducer 12 satisfies 0.065×λ≤h0≤0.085×λ. If the main metal layer includes a single metal layer, and the single metal layer is a molybdenum metal layer, the equivalent thickness h0 of the interdigital transducer 12 satisfies 0.05×λ≤h0≤0.08×λ. If the main metal layer includes a single metal layer, and the single metal layer is a platinum metal layer, the equivalent thickness h0 of the interdigital transducer 12 satisfies 0.045×λ≤h0≤0.065×λ.

[0069] Based on the above embodiments, Figure 4 A schematic cross-sectional structure diagram of another surface acoustic wave resonator provided in an embodiment of the present invention, referring to Figure 4 The piezoelectric substrate 11 includes a support substrate 111 and a piezoelectric layer 112 disposed between the support substrate 111 and the IDT 12. The speed at which a surface acoustic wave propagates in the support substrate 111 is different from the speed at which a surface acoustic wave propagates in the piezoelectric layer 112.

[0070] Exemplarily, the material of the piezoelectric layer 112 may include LiNbO3, LiTaO3, AlN, ZnO, PZT or quartz. The material of the support substrate 111 may include single crystal silicon, sapphire, diamond or SiC, quartz crystal, which has a high resistivity (generally greater than 2000Ω·m) and a high sound velocity. By setting the speed of the surface acoustic wave propagating in the support substrate 111 to be different from the speed of the surface acoustic wave propagating in the piezoelectric layer 112, for example, the speed of the surface acoustic wave propagating in the support substrate 111 is greater than the speed of the surface acoustic wave propagating in the piezoelectric layer 112, a surface acoustic wave reflection grating may be formed at the contact point between the support substrate 111 and the piezoelectric layer 112, and the surface acoustic wave reflection grating may reflect the surface acoustic wave propagating toward the support substrate 111 into the piezoelectric layer 112, which is beneficial to reduce the leakage of the surface acoustic wave energy in the direction opposite to the third direction Z.

[0071] Based on the above embodiments, Figure 5 A schematic cross-sectional structure diagram of another surface acoustic wave resonator provided in an embodiment of the present invention, referring to Figure 5 The piezoelectric substrate 11 includes a stacked support substrate 111, an intermediate layer 113, and a piezoelectric layer 112. The piezoelectric layer 112 is disposed between the intermediate layer 113 and the interdigital transducer 12. The speed at which a surface acoustic wave propagates in the intermediate layer 113 is different from the speed at which a surface acoustic wave propagates in the piezoelectric layer 112. The speed at which a surface acoustic wave propagates in the intermediate layer 113 is different from the speed at which a surface acoustic wave propagates in the support substrate 111.

[0072] Exemplarily, the middle layer 113 may include a plurality of sub-middle layers, for example, Figure 5 The intermediate layer 113 in the structure includes a first sub-intermediate layer 1131, a second sub-intermediate layer 1132 and a third sub-intermediate layer 1133. Along the thickness direction of the surface acoustic wave resonator 10, i.e., the third direction Z, the supporting substrate 111, the first sub-intermediate layer 1131, the second sub-intermediate layer 1132 and the third sub-intermediate layer 1133 and the piezoelectric layer 112 are stacked in sequence. It should be noted that along the third direction Z, the propagation speed of the surface acoustic wave between any two adjacent sub-intermediate layers is different, and the propagation speed of the surface acoustic wave in the first sub-intermediate layer 1131 is different from the propagation speed of the surface acoustic wave in the supporting substrate 111, and the propagation speed of the surface acoustic wave in the third sub-intermediate layer 1133 is also different from the propagation speed of the surface acoustic wave in the piezoelectric layer 112. In this way, surface acoustic wave reflection gratings can be formed where the supporting substrate 111 contacts the third sub-middle layer 1133, where the third sub-middle layer 1133 contacts the second sub-middle layer 1132, where the second sub-middle layer 1132 contacts the first sub-middle layer 1131, and where the first sub-middle layer 1131 contacts the piezoelectric layer 112, thereby further reducing the leakage of surface acoustic wave energy in the direction opposite to the third direction Z.

[0073] As a feasible implementation manner, the material of the sub-intermediate layer may include SiO2, SiC, Si3N4, SiFO2, AlN or Al2O3.

[0074] Based on the above embodiments, Figure 6 A schematic cross-sectional structure diagram of another surface acoustic wave resonator provided in an embodiment of the present invention, referring to Figure 6 , the surface acoustic wave resonator 10 further includes a first dielectric film layer 15 and a second dielectric film layer 16. The piezoelectric substrate 11 includes a piezoelectric layer 112. The first dielectric film layer 15 is disposed on a side of the interdigital transducer 12 away from the piezoelectric layer 112 and on a side of the piezoelectric layer 112 close to the interdigital transducer 12. The polarity of the frequency temperature coefficient of the first dielectric film layer 15 is opposite to that of the frequency temperature coefficient of the piezoelectric layer 112. The second dielectric film layer 16 is disposed on a side of the first dielectric film layer 15 away from the interdigital transducer 12. The thickness of the second dielectric film layer 16 is negatively correlated with the frequency of the surface acoustic wave in the surface acoustic wave resonator 10.

[0075] Exemplarily, the first dielectric film layer 15 can be made of a silicon oxide film, the frequency temperature coefficient of the silicon oxide film is a positive value, and the resonant frequency will increase with the increase of temperature. The piezoelectric layer 112 can be made of a lithium tantalate film, and when the frequency temperature coefficient of the lithium tantalate film is a negative value, the resonant frequency will decrease with the increase of temperature. By setting the frequency temperature coefficient of the first dielectric film layer 15 to be opposite to the polarity of the frequency temperature coefficient of the piezoelectric layer 112, the influence of temperature on the resonant frequency can be reduced, which is conducive to improving the performance of the elastic wave resonator.

[0076] Exemplarily, the second dielectric film layer 16 may be made of a silicon nitride film. The thickness of the second dielectric film layer 16 is negatively correlated with the frequency of the surface acoustic wave in the surface acoustic wave resonator 10, and the frequency correction can be achieved by changing the thickness of the second dielectric film layer 16. The second dielectric film layer 16 is disposed on a side of the first dielectric film layer 15 away from the interdigital transducer 12, and can serve as a passivation protective layer of the surface acoustic wave resonator to protect the surface acoustic wave resonator.

[0077] Based on the same inventive concept, the embodiment of the present invention further provides a surface acoustic wave filter 20, which includes the surface acoustic wave resonator 10 in the above embodiment. Therefore, the surface acoustic wave filter 20 includes the technical features of the surface acoustic wave resonator 10 and has the beneficial effects of the surface acoustic wave resonator 10. The same points can be referred to the above description.

[0078] Figure 7 A schematic diagram of the structure of a surface acoustic wave filter provided by an embodiment of the present invention, referring to Figure 7 The surface acoustic wave filter 20 adopts a ladder topology structure type surface acoustic wave filter, including a signal input terminal in, a signal output terminal out, at least one series arm resonator 21 and at least one parallel arm resonator 22. The series arm resonator 21 and the parallel arm resonator 22 both adopt the surface acoustic wave resonator 10 provided by any of the above embodiments of the present invention. The number of series arm resonators 21 is the same as or different from the number of parallel arm resonators 22. Exemplarily, a series arm resonator 21 and a parallel arm resonator 22 can be defined as a group of series-parallel resonators 23. The surface acoustic wave filter 20 may include at least one series-parallel resonator 23, and each series-parallel resonator 23 is sequentially connected in series between the signal input terminal in and the signal output terminal out. It should be noted that Figure 7 The number of the series-parallel resonators 23 shown is 4, and this embodiment is only an example and is not limiting.

[0079] Figure 8 A schematic diagram of another surface acoustic wave filter provided by an embodiment of the present invention, referring to Figure 8The surface acoustic wave filter adopts a longitudinally coupled resonator type surface acoustic wave filter, including a signal input terminal in, a signal output terminal out, at least one dual-mode surface acoustic wave resonator DMS, at least one series arm resonator 21 and at least one parallel arm resonator 22. The series arm resonator 21 and the parallel arm resonator 22 both adopt the surface acoustic wave resonator 10 provided by any of the above embodiments of the present invention. At least one dual-mode surface acoustic wave resonator DMS, at least one series arm resonator 21 and at least one parallel arm resonator 22 are electrically connected between the signal input terminal in and the signal output terminal out. The position of the dual-mode surface acoustic wave resonator DMS between the input terminal and the output terminal is not limited. The series arm resonator 21 is connected in series between the signal input terminal in and the signal output terminal out, one end of the parallel arm resonator 22 is connected between the signal input terminal in and the signal output terminal out, and the other end of the parallel arm resonator 22 is grounded. It should be noted that the number of dual-mode surface acoustic wave resonators DMS and the series arm resonator 21 and the number of parallel arm resonators 22 can be the same or different. Figure 8 The number of the series arm resonators 21 and the number of the parallel arm resonators 22 shown are both 2, and the number of the dual-mode surface acoustic wave resonators DMS is 1. This embodiment is only an example and is not limiting.

[0080] Based on the same inventive concept, the embodiment of the present invention further provides a surface acoustic wave multiplexer 30, Fig. 9 A schematic diagram of a surface acoustic wave multiplexer provided in an embodiment of the present invention, referring to Fig. 9 The surface acoustic wave multiplexer 30 in the embodiment of the present invention includes an antenna 31, at least one receiving unit 32 and at least one transmitting unit 33. The antenna 31 is connected to the receiving unit 32 and the transmitting unit 33 for communication. At least one of the receiving unit 32 and the transmitting unit 33 includes the surface acoustic wave filter 20 in the above embodiment. Therefore, the surface acoustic wave multiplexer 30 includes the technical features of the surface acoustic wave filter 20 and has the beneficial effects of the surface acoustic wave filter 20. The similarities can be referred to the above description.

[0081] Exemplarily, the surface acoustic wave multiplexer 30 is taken as a surface acoustic wave duplexer for example, the receiving unit 32 is arranged between the antenna 31 and the receiving terminal P1, and forms a first passband of the surface acoustic wave duplexer, and the transmitting unit 33 is arranged between the antenna 31 and the transmitting terminal P2, and forms a second passband of the surface acoustic wave duplexer. It should be noted that the receiving unit 32 may include the following: Figure 7 The ladder topology structure type surface acoustic wave filter shown in the figure may also include Figure 8 The longitudinally coupled resonator type surface acoustic wave filter shown in FIG. Figure 7 The ladder topology structure type surface acoustic wave filter shown in the figure may also include Figure 8The longitudinally coupled resonator type surface acoustic wave filter shown.

[0082] It can be understood that when the surface acoustic wave multiplexer 30 is a quadplexer, the quadplexer includes four terminals, an antenna and four surface acoustic wave filters 20, a passband is formed between each terminal and the antenna, and at least one of the four surface acoustic wave filters 20 includes the surface acoustic wave resonator 10 in the above embodiment.

[0083] Based on the same inventive concept, an embodiment of the present invention further provides a radio frequency front-end circuit 40, Fig.10 A schematic diagram of a radio frequency front-end circuit according to an embodiment of the present invention is provided. Fig.10 The radio frequency front-end circuit 40 in the embodiment of the present invention includes the surface acoustic wave multiplexer 30 in the above embodiment.

[0084] refer to Fig.10 The RF front-end circuit 40 includes a switch 41, a first surface acoustic wave filter 42, a second surface acoustic wave filter 43, a first duplexer (the first duplexer includes a first duplexer transmit filter 44 and a first duplexer receive filter 45), a second duplexer (the second duplexer includes a second duplexer transmit filter 46 and a second duplexer receive filter 47), a low noise amplifier 48 and a power amplifier 49.

[0085] Specifically, the RF front-end circuit 40 is connected to the RF signal processing circuit 52 and the baseband signal processing circuit 53 to form the RF communication device 50 .

[0086] Further, the switch 41 is used to control the RF signal, connect the antenna terminal 51 to at least one signal path corresponding to a given frequency band, and the at least one signal path connected to the antenna terminal 51 may also be multiple signal paths (corresponding to multiple filters and duplexers). The RF front-end circuit 40 can support carrier aggregation technology. The low noise amplifier 48 amplifies the RF signal fed via the antenna terminal 51, the switch 41, the first duplexer receiving filter 45, and the second duplexer receiving filter 47, and feeds the amplified signal to the RF signal processing circuit 52. The power amplifier 49 amplifies the RF signal provided by the RF signal processing circuit 52 and feeds the amplified signal to the antenna terminal 51 via the first duplexer transmitting filter 44, the second duplexer transmitting filter 46, and the switch 41 for transmission.

[0087] The RF signal processing circuit 52 in the RF communication device 50 performs signal processing on the RF reception signal provided from the antenna terminal 51 via the reception signal path, and feeds the reception signal generated by the signal processing. The RF signal processing circuit 52 performs signal processing on the transmission signal fed thereto, and feeds the RF transmission signal generated by the signal processing to the power amplifier 49.

[0088] The RF front-end circuit 40 further includes a first SAW filter 42 and a second SAW filter 43 . The first SAW filter 42 and the second SAW filter 43 are connected between the RF signal processing circuit 52 and the switch 41 without passing through the low noise amplifier 48 or the power amplifier 49 .

[0089] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A surface acoustic wave resonator, characterized in that: include: Piezoelectric substrate; An interdigital transducer comprises a transition metal layer, a main metal layer and a protective layer; The transition metal layer is arranged on one side of the piezoelectric substrate, the main metal layer is arranged on a side of the transition metal layer away from the piezoelectric substrate, and the protective layer is arranged on a side of the main metal layer away from the piezoelectric substrate; The main metal layer includes at least one single metal layer; the protective layer includes a metal protective layer; and the mass density of the single metal layer is greater than the mass density of the metal protective layer.

2. The surface acoustic wave resonator according to claim 1, characterized in that: The main metal layer includes at least two layers of the single metal layer; Along the direction where the transition metal layer approaches the protective layer, the mass density of the single metal layer gradually decreases.

3. The surface acoustic wave resonator according to claim 1, characterized in that: The single metal layer includes a copper metal layer, a platinum metal layer, a chromium metal layer, a molybdenum metal layer, a silver metal layer or a gold metal layer.

4. The surface acoustic wave resonator according to claim 1, characterized in that: The protective layer further comprises a metal oxide protective layer; the metal oxide protective layer is arranged on a side surface of the metal protective layer away from the main metal layer and a side surface of the metal protective layer; The equivalent thickness of the interdigital transducer satisfies the following relationship: ； in, represents the equivalent thickness of the IDT, represents the thickness of the transition metal layer, represents the mass density of the transition metal layer, represents the thickness of the main metal layer, represents the mass density of the main metal layer, represents the thickness of the protective layer, represents the average mass density of the protective layer, represents the mass density of the metal protective layer.

5. The surface acoustic wave resonator according to claim 4, characterized in that: The minimum value of the equivalent thickness of the interdigital transducer is negatively correlated with the mass density of the single metal layer; The maximum value of the equivalent thickness of the IDT is negatively correlated with the mass density of the single metal layer.

6. The surface acoustic wave resonator according to claim 5, characterized in that: The transition metal layer includes a titanium metal layer; the protective layer includes an aluminum protective layer and an aluminum oxide protective layer; When the single metal layer includes a copper metal layer, the equivalent thickness h0 of the IDT satisfies 0.065×λ≤h0≤0.085×λ; When the single metal layer includes a molybdenum metal layer, the equivalent thickness h0 of the interdigital transducer satisfies 0.05×λ≤h0≤0.08×λ; When the single metal layer includes a platinum metal layer, the equivalent thickness h0 of the interdigital transducer satisfies 0.045×λ≤h0≤0.065×λ; Here, λ represents the wavelength of the surface acoustic wave in the surface acoustic wave resonator.

7. The surface acoustic wave resonator according to claim 1, characterized in that: The piezoelectric substrate comprises a supporting substrate and a piezoelectric layer disposed between the supporting substrate and the interdigital transducer; A speed at which a surface acoustic wave propagates in the supporting substrate is different from a speed at which the surface acoustic wave propagates in the piezoelectric layer.

8. The surface acoustic wave resonator according to claim 1, characterized in that: The piezoelectric substrate comprises a supporting substrate, an intermediate layer and a piezoelectric layer which are stacked; the piezoelectric layer is arranged between the intermediate layer and the interdigital transducer; The speed at which the surface acoustic wave propagates in the intermediate layer is different from the speed at which the surface acoustic wave propagates in the piezoelectric layer; A speed at which the surface acoustic wave propagates in the intermediate layer is different from a speed at which the surface acoustic wave propagates in the supporting substrate.

9. The surface acoustic wave resonator according to claim 1, characterized in that: The surface acoustic wave resonator further comprises a first dielectric film layer and a second dielectric film layer; the piezoelectric substrate comprises a piezoelectric layer; The first dielectric film layer is arranged on a side of the IDT away from the piezoelectric layer and a side of the piezoelectric layer close to the IDT; wherein the frequency temperature coefficient of the first dielectric film layer is opposite in polarity to the frequency temperature coefficient of the piezoelectric layer; The second dielectric film layer is arranged on a side of the first dielectric film layer away from the interdigital transducer; wherein the thickness of the second dielectric film layer is negatively correlated with the frequency of the surface acoustic wave in the surface acoustic wave resonator.

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

11. A surface acoustic wave multiplexer, characterized in that: comprising an antenna, at least one receiving unit and at least one transmitting unit; The antenna is communicatively connected to the receiving unit and the sending unit respectively; At least one of the receiving unit and the transmitting unit includes the surface acoustic wave filter according to claim 10.

12. A radio frequency front end circuit, characterized in that: It comprises the surface acoustic wave multiplexer as claimed in claim 11.

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