Acoustic wave device and multiplexer

Abstract

To provide an elastic wave device in which the generation of unwanted waves due to third harmonic excitation is suppressed.SOLUTION: A filter 10 includes a plurality of acoustic wave resonators connected to a path connecting terminals 111 and 112. Each of the plurality of acoustic wave resonators has an IDT electrode 54 disposed on a substrate having piezoelectric characteristics. The piezoelectric substrate has a laminated structure of a piezoelectric film 53, a low acoustic velocity film 52, and a high acoustic velocity film. An electrode finger wavelength of the IDT electrode 54 is λ (m), a film thickness of the piezoelectric film 53 is t1 (m), a film thickness of the plurality of electrode fingers is t2 (m), t1 / λ is a film thickness-wavelength ratio A of the piezoelectric film 53, t2 / λ is a film thickness-wavelength ratio B of the plurality of electrode fingers, a density of the piezoelectric film 53 is x (g / cm3), a density of the IDT electrode 54 is y (g / cm3), and (A / x+B / y) is a mass coefficient M, the mass coefficient M of the acoustic wave resonator connected closest to the terminal 111 is greater than or equal to 0.95×0.054 and less than or equal to 1.05×0.054.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to an acoustic wave device and a multiplexer. [Background technology]

[0002] Patent Documents 1 and 2 disclose an electrode structure and a laminated structure of a substrate of a surface acoustic wave resonator using a substrate including a piezoelectric film, a low acoustic velocity film, and a high acoustic velocity film. The above surface acoustic wave resonator can increase the Q value at the resonant frequency and the anti-resonant frequency compared to a surface acoustic wave resonator using a single-layer piezoelectric substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2015 / 098756 [Patent Document 2] JP 2020-48067 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the surface acoustic wave resonators disclosed in Patent Documents 1 and 2 do not sufficiently suppress unwanted waves (triple harmonic excitation) that occur at a frequency three times that of the fundamental wave.

[0005] Therefore, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an acoustic wave device and a multiplexer in which the generation of unwanted waves of third harmonic excitation is suppressed. [Means for solving the problem]

[0006] In order to achieve the above object, an elastic wave device according to one aspect of the present invention includes a first input / output terminal and a second input / output terminal, and a plurality of elastic wave resonators connected to a path connecting the first input / output terminal and the second input / output terminal. Each of the plurality of elastic wave resonators includes an IDT (InterDigital Transistor) disposed on a piezoelectric substrate. The substrate has a piezoelectric film having an IDT electrode formed on one surface thereof, a high acoustic velocity film having a bulk wave acoustic velocity faster than the elastic wave acoustic velocity propagating through the piezoelectric film, and a low acoustic velocity film disposed between the high acoustic velocity film and the piezoelectric film and having a bulk wave acoustic velocity slower than the bulk wave acoustic velocity propagating through the piezoelectric film. The electrode finger wavelength, which is twice the pitch of a plurality of parallel electrode fingers of the IDT electrode, is defined as λ (m), the film thickness of the piezoelectric film is defined as t1 (m), the film thickness of the plurality of electrode fingers is defined as t2 (m), t1 / λ is the film thickness wavelength ratio A of the piezoelectric film, t2 / λ is the film thickness wavelength ratio B of the plurality of electrode fingers, and the density of the piezoelectric film is defined as x (g / cm 3 ) and the density of the IDT electrodes is y (g / cm 3 ) and (A / x+B / y) is the mass coefficient M, the mass coefficient M of the elastic wave resonator connected closest to the first input / output terminal among the multiple elastic wave resonators is equal to or greater than 0.95×0.054 and equal to or less than 1.05×0.054. Effect of the Invention

[0007] According to the present invention, it is possible to provide an acoustic wave device and a multiplexer in which the generation of unwanted waves of third harmonic excitation is suppressed. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a circuit configuration diagram of a multiplexer according to an embodiment. [Figure 2A] 1 is a circuit configuration diagram of an elastic wave device according to an embodiment. [Figure 2B] 11 is a circuit diagram of an elastic wave device according to a modified example of an embodiment. FIG. [Diagram 3] 1A and 1B are a plan view and a cross-sectional view illustrating an elastic wave resonator according to an embodiment of the present invention. [Figure 4]1 is a cross-sectional view of an elastic wave resonator for explaining a mass coefficient. [Diagram 5] 1 is a graph illustrating resonance characteristics of elastic wave resonators according to examples and comparative examples. [Figure 6] 1 is a graph showing the relationship between the mass coefficient of an elastic wave resonator and the phase of a third harmonic excitation signal. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, arrangements and connection forms of the components shown in the following embodiments are merely examples and are not intended to limit the present invention.

[0010] In addition, each figure is a schematic diagram in which emphasis, omission, or adjustment of the ratio is appropriately performed in order to illustrate the present invention, and is not necessarily a strict illustration, and may differ from the actual shape, positional relationship, and ratio. In each figure, the same reference numerals are given to substantially the same configurations, and duplicated explanations may be omitted or simplified.

[0011] In the circuit configuration of the present disclosure, “connected between A and B” and “connected between A and B” mean connected to both A and B between A and B.

[0012] In addition, in the component arrangement of the present disclosure, “component A is arranged in series on path B” means that both the signal input terminal and the signal output terminal of component A are connected to the wiring, electrode, or terminal that constitutes path B.

[0013] In addition, terms indicating the relationship between elements, such as "parallel" and "perpendicular," terms indicating the shape of an element, such as "rectangle," and numerical ranges do not only indicate the strict meaning, but also include a substantially equivalent range, for example, an error of about a few percent.

[0014] Also, in this disclosure, a "terminal" means a point where a conductor within an element terminates, and is to be construed as any point on a conductor between elements or the entire conductor, not just a single point, if the impedance of the conductor between elements is sufficiently low.

[0015] In the following embodiments, the passband of an acoustic wave device or filter is defined as a frequency band between two frequencies that are 3 dB higher than the minimum value of insertion loss in the passband.

[0016] In addition, in the present disclosure, band A and band B refer to frequency bands defined in advance by standardization organizations (e.g., 3GPP (registered trademark), IEEE (Institute of Electrical and Electronics Engineers), etc.) for communication systems built using radio access technology (RAT). In this embodiment, the communication system may be, for example, a Long Term Evolution (LTE) system, a 5th Generation (5G)-New Radio (NR) system, and a Wireless Local Area Network (WLAN) system, but is not limited thereto.

[0017] Additionally, the uplink operating band of Band A refers to the frequency range of Band A designated for uplink use, and the downlink operating band of Band A refers to the frequency range of Band A designated for downlink use.

[0018] (Embodiment) [1. Circuit configuration of multiplexer] 1 is a circuit diagram of a multiplexer 1 according to an embodiment of the present invention. The multiplexer 1 includes filters 10 and 20, a common terminal 100, and input / output terminals 110 and 120.

[0019] The common terminal 100 is connected to, for example, an antenna 2 .

[0020] Filter 10 is an example of an acoustic wave device, is connected to common terminal 100, and has a passband that includes an uplink operating band, for example, band A. Filter 20 is connected to common terminal 100, and has a passband that includes a downlink operating band, for example, band A. Filters 10 and 20 form, for example, a duplexer for band A.

[0021] Note that filter 10 may have a passband including at least one of an uplink operating band and a downlink operating band of band A, and filter 20 may have a passband including at least one of an uplink operating band and a downlink operating band of band B different from band A. In this case, filters 10 and 20 form a diplexer.

[0022] In the present embodiment, the passband of filter 10 is located on the lower frequency side than the passband of filter 20. At least one of the elastic wave resonators constituting filter 10 has a mass coefficient M, which will be described later, of 0.95×0.054 or more and 1.05×0.054 or less, thereby making it possible to reduce unwanted waves of third harmonic excitation. Therefore, even if unwanted waves of third harmonic excitation generated by filter 10 are included in the vicinity of the passband of filter 20, deterioration of the pass characteristic of filter 20 can be suppressed.

[0023] The passband of the filter 10 may be located on the higher frequency side than the passband of the filter 20 .

[0024] 2A is a circuit diagram of a filter 10 according to an embodiment. As shown in the figure, the filter 10 includes series arm resonators 11, 12, 13, and 14, parallel arm resonators 15, 16, 17, and 18, and terminals 111 and 112.

[0025] The terminal 111 is an example of a first input / output terminal and is connected to the common terminal 100. The terminal 112 is an example of a second input / output terminal and is connected to the input / output terminal 110. Each of the series arm resonators 11 to 14 is an elastic wave resonator and is arranged in series on a path connecting the terminal 111 and the terminal 112. The parallel arm resonator 15 is an elastic wave resonator and is connected between the connection point of the series arm resonators 11 and 12 and the ground. The parallel arm resonator 16 is an elastic wave resonator and is connected between the connection point of the series arm resonators 12 and 13 and the ground. The parallel arm resonator 17 is an elastic wave resonator and is connected between the connection point of the series arm resonators 13 and 14 and the ground. The parallel arm resonator 18 is an elastic wave resonator and is connected between the connection point of the series arm resonator 14 and the terminal 112 and the ground. With the above configuration, the filter 10 constitutes, for example, a ladder-type bandpass filter.

[0026] Each of the series arm resonators 11 to 14 and the parallel arm resonators 15 to 18 has an IDT electrode disposed on a piezoelectric substrate.

[0027] 2A is just an example, and the numbers of series arm resonators and parallel arm resonators are not limited to four, but may each be equal to or greater than 1. In addition, an inductor may be connected between the parallel arm resonator and ground.

[0028] Furthermore, filter 10 is not limited to being a ladder-type bandpass filter, and may be, for example, a filter including a longitudinally coupled resonator in which a plurality of acoustic wave resonators are arranged in parallel in the acoustic wave propagation direction, as shown in FIG. 2B.

[0029] 2B is a circuit diagram of a filter 10A according to a modified example of the embodiment. Filter 10A is an example of an acoustic wave device and is connected to a common terminal 100. As shown in FIG. 2B, filter 10A is a filter circuit including a longitudinally coupled resonator 19 including seven acoustic wave resonators, and includes longitudinally coupled resonator 19, series arm resonators 11, 12, and 13, parallel arm resonators 15 and 16, and terminals 111 and 112. Terminal 111 is connected to common terminal 100, and terminal 112 is connected to input / output terminal 120.

[0030] The longitudinally coupled resonator 19 is composed of acoustic wave resonators 191 , 192 , 193 , 194 , 195 , 196 and 197 , and has one end connected to a terminal 111 via series arm resonators 11 and 12 , and the other end connected to a terminal 112 via a series arm resonator 13 .

[0031] Each of the acoustic wave resonators 191 to 197 has an IDT electrode disposed on a piezoelectric substrate. The IDT electrodes of the acoustic wave resonators 191 to 197 are composed of two comb electrodes facing each other. One comb electrode of each of the acoustic wave resonators 191, 193, 195, and 197 is connected to a terminal 111 via the series arm resonators 11 and 12, and the other comb electrode of each of the acoustic wave resonators 191, 193, 195, and 197 is connected to a ground. One comb electrode of each of the acoustic wave resonators 192, 194, and 196 is connected to a terminal 112 via the series arm resonator 13, and the other comb electrode of each of the acoustic wave resonators 192, 194, and 196 is connected to a ground. The acoustic wave resonators 191 to 197 are arranged in the order of 191, 192, 193, 194, 195, 196, and 197 along the acoustic wave propagation direction.

[0032] The series arm resonators 11, 12, and 13 are arranged in series on a path connecting terminals 111 and 112. The parallel arm resonators 15 and 16 are each connected between the above path and ground.

[0033] The filter 20 may be any one of a band-pass filter, a low-pass filter, and a high-pass filter, and includes at least one of an acoustic wave resonator, an inductor, and a capacitor.

[0034] When the filter 20 includes an acoustic wave resonator, the filters 10 and 20 may be formed on the same piezoelectric substrate, which allows the multiplexer 1 to be miniaturized and the manufacturing process to be simplified.

[0035] Furthermore, when the filter 20 includes an acoustic wave resonator, the film thickness of the IDT electrode of the acoustic wave resonator may be the same as the film thickness of the IDT electrode of the acoustic wave resonator that constitutes the filter 10. This can simplify the manufacturing process of the multiplexer 1.

[0036] [2. Structure of elastic wave resonator] Next, the basic structure of each series arm resonator and each parallel arm resonator constituting filter 10 will be described. Fig. 3 is a plan view and a cross-sectional view that typically show an acoustic wave resonator according to an embodiment. The drawings illustrate the basic structure of an acoustic wave resonator constituting filter 10. Note that acoustic wave resonator 60 shown in Fig. 3 is intended to illustrate a typical structure of an acoustic wave resonator constituting filter 10, and the number and length of electrode fingers constituting the electrodes are not limited thereto.

[0037] The acoustic wave resonator 60 is composed of a piezoelectric substrate 50 and comb electrodes 60a and 60b. As shown in FIG. 3(a), a pair of comb electrodes 60a and 60b facing each other is formed on the piezoelectric substrate 50. The comb electrode 60a is composed of a plurality of parallel electrode fingers 61a and a busbar electrode 62a connecting one ends of the plurality of electrode fingers 61a. The comb electrode 60b is composed of a plurality of parallel electrode fingers 61b and a busbar electrode 62b connecting one ends of the plurality of electrode fingers 61b. The plurality of electrode fingers 61a and 61b are formed along a direction perpendicular to the acoustic wave propagation direction (X-axis direction). The busbar electrode 62a and the busbar electrode 62b are arranged facing each other with the electrode fingers 61a and 61b interposed therebetween. The comb electrodes 60a and 60b form an IDT electrode 54.

[0038] The acoustic wave resonator 60 may have reflectors on both ends of the IDT electrode 54 in the acoustic wave propagation direction (X-axis direction).

[0039] As shown in FIG. 3(b), the IDT electrode 54 has a laminated structure of an adhesive layer 540 and a main electrode layer 542, for example.

[0040] The adhesion layer 540 is a layer for improving adhesion between the piezoelectric substrate 50 and the main electrode layer 542, and is made of, for example, Ti. The main electrode layer 542 is made of, for example, Al containing 1% Cu. The protective layer 55 is formed so as to cover the comb-shaped electrodes 60a and 60b. The protective layer 55 is a layer intended to protect the main electrode layer 542 from the external environment, adjust the frequency-temperature characteristics, and increase moisture resistance, and is, for example, a dielectric film whose main component is silicon dioxide.

[0041] The materials constituting the adhesion layer 540, the main electrode layer 542, and the protective layer 55 are not limited to the above-mentioned materials. Furthermore, the IDT electrode 54 does not have to have the above-mentioned laminated structure. The IDT electrode 54 may be made of a metal or alloy such as Ti, Al, Cu, Pt, Au, Ag, or Pd, or may be made of a laminate of multiple layers made of the above-mentioned metals or alloys. Furthermore, the protective layer 55 does not have to be formed.

[0042] Next, a description will be given of the layered structure of the piezoelectric substrate 50. As shown in (c) of Fig. 3, the piezoelectric substrate 50 includes a high acoustic speed support substrate 51, a low acoustic speed film 52, and a piezoelectric film 53, and has a structure in which the high acoustic speed support substrate 51, the low acoustic speed film 52, and the piezoelectric film 53 are layered in this order.

[0043] The piezoelectric film 53 is made of, for example, θ°Y-cut X-propagation LiTaO3 piezoelectric single crystal or piezoelectric ceramics (lithium tantalate single crystal or ceramics cut on a plane whose normal is an axis rotated θ° from the Y axis around the X axis, and whose surface acoustic wave propagates in the X axis direction). Note that the material and cut angle θ of the piezoelectric single crystal used as the piezoelectric film 53 are appropriately selected depending on the required specifications of each filter.

[0044] The high acoustic velocity support substrate 51 is a substrate that supports the low acoustic velocity film 52, the piezoelectric film 53, and the IDT electrode 54. The high acoustic velocity support substrate 51 is an example of a high acoustic velocity film, and is a substrate in which the acoustic velocity of the bulk waves in the high acoustic velocity support substrate 51 is faster than that of the surface waves and boundary waves propagating through the piezoelectric film 53, and functions to confine the surface acoustic waves to the portion where the piezoelectric film 53 and the low acoustic velocity film 52 are laminated, and not to leak below the high acoustic velocity support substrate 51. As the material of the high acoustic velocity support substrate 51, for example, a piezoelectric body such as aluminum nitride, lithium tantalate, lithium niobate, or quartz, a ceramic such as alumina, sapphire, magnesia, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, forsterite, spinel, or sialon, a dielectric material such as aluminum oxide, silicon oxynitride, DLC (diamond-like carbon), or diamond, or a semiconductor such as silicon, or a material mainly composed of the above materials can be used. The spinel includes an aluminum compound containing oxygen and one or more elements selected from Mg, Fe, Zn, Mn, etc. Examples of the spinel include MgAl2O4, FeAl2O4, ZnAl2O4, and MnAl2O4.

[0045] The low acoustic velocity film 52 is a film in which the acoustic velocity of the bulk waves in the low acoustic velocity film 52 is slower than that of the bulk waves propagating through the piezoelectric film 53, and is disposed between the piezoelectric film 53 and the high acoustic velocity support substrate 51. This structure and the property of the acoustic wave concentrating energy in a medium with an essentially low acoustic velocity suppress leakage of surface acoustic wave energy to the outside of the piezoelectric film 53. As the material for the low acoustic velocity film 52, for example, a dielectric material such as glass, silicon oxide, silicon oxynitride, lithium oxide, tantalum oxide, or a compound in which fluorine, carbon, or boron is added to silicon oxide, or a material mainly composed of the above materials can be used.

[0046] The laminated structure of piezoelectric substrate 50 makes it possible to significantly increase the Q value at the resonant frequency and the anti-resonant frequency, compared to a conventional structure using a single-layer piezoelectric substrate. In other words, an elastic wave resonator with a high Q value can be configured, and therefore a filter with low insertion loss can be configured using the elastic wave resonator.

[0047] The high acoustic speed support substrate 51 may have a structure in which a support substrate and a high acoustic speed film in which the acoustic speed of the propagating bulk wave is faster than that of the surface wave and boundary wave propagating through the piezoelectric film 53 are laminated. In this case, the high acoustic speed film is disposed between the support substrate and the low acoustic speed film 52. The material of the high acoustic speed film may be the same as that of the high acoustic speed support substrate 51. The material of the support substrate may be, for example, a piezoelectric material such as aluminum nitride, lithium tantalate, lithium niobate, or quartz; a ceramic material such as alumina, sapphire, magnesia, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, or forsterite; a dielectric material such as diamond or glass; a semiconductor material such as silicon or gallium nitride; or a resin; or a material mainly composed of the above-mentioned material.

[0048] In this specification, the term "major component of a material" refers to a component that accounts for more than 50% by weight of the material. The major component may be in any of the following states: single crystal, polycrystalline, or amorphous, or a mixture of these.

[0049] The piezoelectric substrate on which the IDT electrode 54 is formed may have a structure in which a support substrate, an energy trapping layer, and a piezoelectric film are laminated in this order. The IDT electrode 54 is formed on the piezoelectric film. For example, a LiTaO3 piezoelectric single crystal or a piezoelectric ceramic is used for the piezoelectric film. The support substrate is a substrate that supports the piezoelectric film, the energy trapping layer, and the IDT electrode 54.

[0050] The energy trapping layer is composed of one or more layers, and the speed of the bulk acoustic wave propagating through at least one of the layers is greater than the speed of the acoustic wave propagating near the piezoelectric film. For example, the energy trapping layer may have a laminated structure of a low acoustic speed film and a high acoustic speed film. The low acoustic speed film is a film in which the acoustic speed of the bulk wave in the low acoustic speed film is slower than the acoustic speed of the acoustic wave propagating through the piezoelectric film. The high acoustic speed film is a film in which the acoustic speed of the bulk wave in the high acoustic speed film is faster than the acoustic speed of the acoustic wave propagating through the piezoelectric film. The support substrate may be a high acoustic speed film.

[0051] The energy trapping layer may be an acoustic impedance layer having a configuration in which low acoustic impedance layers having a relatively low acoustic impedance and high acoustic impedance layers having a relatively high acoustic impedance are alternately laminated.

[0052] Here, electrode parameters of the IDT electrodes constituting the acoustic wave resonator 60 will be described.

[0053] The wavelength of the acoustic wave resonator 60 is defined as a wavelength λ, which is a repetition period of the electrode fingers 61a or 61b constituting the IDT electrode 54 shown in FIG. 3B. The wavelength λ is twice the electrode finger pitch, which is the distance between the center of the electrode finger 61a and the center of the electrode finger 61b adjacent to each other. The electrode finger pitch is defined as (W+S), where W is the line width of the electrode fingers 61a and 61b constituting the comb-shaped electrodes 60a and 60b, respectively, and S is the space width between the adjacent electrode fingers 61a and 61b. The duty of the IDT electrode 54 is the line width occupancy rate of the electrode fingers 61a and 61b, which is the ratio of the line width to the sum of the line width and space width of the electrode fingers 61a and 61b, and is defined as W / (W+S). In FIG. 3B, the height of the comb-shaped electrodes 60a and 60b is h.

[0054] In the case where the interval between adjacent electrode fingers in IDT electrode 54 is not constant, the electrode finger pitch of IDT electrode 54 is defined as the average electrode finger pitch of IDT electrode 54. The average electrode finger pitch of IDT electrode 54 is defined as Di / (Ni-1), where the total number of electrode fingers 61a, 61b included in IDT electrode 54 is Ni, and the center-to-center distance between the electrode finger located at one end and the electrode finger located at the other end of IDT electrode 54 in the acoustic wave propagation direction is Di.

[0055] [3. Relationship between mass coefficient M and third harmonic excitation] Next, the relationship between the mass coefficient M and the third harmonic excitation response will be described. The inventors were the first to define the mass coefficient M as a parameter that affects the resonance characteristics of an elastic wave resonator, and found that there is a strong correlation between the mass coefficient M and the third harmonic excitation response.

[0056] FIG. 4 is a cross-sectional view of acoustic wave resonator 60 for explaining mass coefficient M. As shown in the figure, an electrode finger wavelength that is twice the pitch of multiple parallel electrode fingers (electrode fingers 61a and 61b) that constitute IDT electrode 54 is denoted as λ (m). Furthermore, a film thickness of piezoelectric film 53 is denoted as t1 (m), and a film thickness of electrode fingers 61a and 61b is denoted as t2 (m). Further, t1 / λ is a film thickness-wavelength ratio A of piezoelectric film 53, and t2 / λ is a film thickness-wavelength ratio B of IDT electrode 54 (electrode fingers 61a and 61b). Furthermore, a density of piezoelectric film 53 is denoted as x (g / cm 3 ), and the density of the IDT electrode 54 is y (g / cm 3 ) where (A / x+B / y) is defined as the mass coefficient M.

[0057] Mass coefficient M is an effective parameter for optimizing the mass distribution of acoustic wave resonator 60 in the direction perpendicular to the main surface of piezoelectric substrate 50 by adjusting thickness t1 of piezoelectric film 53 and thickness t2 of IDT electrode 54.

[0058] Table 1 shows the structures and parameters of the elastic wave resonators according to the examples and the comparative example.

[0059] [Table 1]

[0060] In Table 1, the mass coefficient M of the elastic wave resonator according to the example is 0.053, and the mass coefficient M of the elastic wave resonator according to the comparative example is 0.044.

[0061] 5 is a graph showing the resonance characteristics of the elastic wave resonators according to the example and the comparative example. As shown in the figure, the resonance characteristics (resonance frequency, anti-resonance frequency, and impedance) of the fundamental wave are almost the same in the elastic wave resonator according to the example and the elastic wave resonator according to the comparative example. In contrast, the strength of the third harmonic excitation response (difference in impedance between the resonant frequency and the anti-resonant frequency) is lower in the elastic wave resonator according to the example than in the elastic wave resonator according to the comparative example.

[0062] Table 2 shows the phase of the third harmonic excitation signal of the elastic wave resonator 60 when the thickness-to-wavelength ratio A of the piezoelectric film 53 and the thickness-to-wavelength ratio B of the IDT electrode 54 are changed. More specifically, Table 2 shows the phase of the third harmonic excitation signal of the elastic wave resonator 60 when the thickness t1 of the piezoelectric film 53 and the thickness t2 of the IDT electrode 54 are changed. Note that in Table 2, the larger the phase of the third harmonic excitation signal (closer to +90°), the higher the intensity of the third harmonic excitation signal, and the smaller the phase of the third harmonic excitation signal (closer to -90°), the lower the intensity of the third harmonic excitation signal.

[0063] [Table 2]

[0064] In calculating the film thickness wavelength ratios A and B in Table 2, the electrode finger wavelength λ is 4.15 (μm). The density y of the IDT electrodes 54 is 2.7 (g / cm 3 ), the electrode duty is 0.625, and the density x of the piezoelectric film 53 is 7.45 (g / cm 3 The material configuration of the IDT electrode 54 and the piezoelectric substrate 50 is the same as the material configuration shown in Table 1.

[0065] From Table 2, when the thickness t1 of the piezoelectric film 53 and the thickness t2 of the IDT electrode 54 are changed, the combinations of t1 and t2 at which the phase of the third harmonic excitation signal is minimized (shown in bold in Table 2) vary.

[0066] 6 is a graph showing the relationship between the mass coefficient M of the elastic wave resonator and the phase of the third harmonic excitation signal. The graph shows the relationship between the mass coefficient M and the phase of the third harmonic excitation signal when the thickness t1 of the piezoelectric film 53 in Table 2 is 700 nm, 800 nm, and 900 nm. Even when the thickness t1 of the piezoelectric film 53 is changed, the phase of the third harmonic excitation signal is minimized at a mass coefficient M of approximately 0.054 in common.

[0067] The mass coefficient M at which the phase of the third harmonic excitation signal is -45° or less is within the range of 0.054±5%. In other words, the mass coefficient M at which the phase of the third harmonic excitation signal is -45° or less is 0.95×0.054 or more and 1.05×0.054 or less.

[0068] This makes it possible to suppress the deterioration of the characteristics of the filter 10 caused by the third harmonic excitation response to a level that does not pose a problem in practical use.

[0069] The elastic wave resonator according to this example corresponds to series arm resonator 11 of the multiple elastic wave resonators constituting filter 10 according to the embodiment. That is, the mass coefficient M of series arm resonator 11 connected closest to terminal 111 of the multiple elastic wave resonators constituting filter 10 is equal to or greater than 0.95×0.054 and equal to or less than 1.05×0.054.

[0070] This effectively prevents the third harmonic excitation signal generated in the filter 10 from adversely affecting other filter circuits connected to the filter 10 at the terminal 111. In the multiplexer 1 according to the embodiment, for example, the reflection loss at the frequency of the third harmonic excitation generated in the filter 10 can be effectively reduced, and therefore the deterioration of the characteristics of the filter 20 at that frequency can be effectively suppressed.

[0071] This is believed to be due to the fact that the mass distribution of the series arm resonators 11 in the direction perpendicular to the main surface of the piezoelectric substrate 50 is optimized by optimizing the mass coefficient M.

[0072] In order to optimize the mass coefficient M, the thickness t1 of the piezoelectric film 53 and the thickness t2 of the IDT electrode 54 are adjusted.

[0073] As a first example of optimizing the mass coefficient M, first, the thickness t1 of the piezoelectric film 53 is optimized in order to adjust the relative band (resonance bandwidth) and higher modes of the elastic wave resonator. By optimizing the thickness t2 of the IDT electrode 54 corresponding to this optimized thickness t1, it becomes possible to adjust the relative band (resonance bandwidth) and higher modes as well as suppress the third harmonic excitation response.

[0074] As a second example of optimizing the mass coefficient M, first, the thickness t2 of the IDT electrode 54 is optimized in order to adjust the stop band width and power durability of the acoustic wave resonator. By optimizing the thickness t1 of the piezoelectric film 53 in correspondence with the optimized thickness t2, it becomes possible to adjust the stop band width and power durability as well as suppress the third harmonic excitation response.

[0075] In filter 10A according to the modified example of the embodiment, the mass coefficient M of series arm resonator 11 connected closest to terminal 111 among the multiple elastic wave resonators constituting filter 10A is not less than 0.95×0.054 and not more than 1.05×0.054.

[0076] In the circuit configuration of filters 10 and 10A, when the elastic wave resonators connected closest to terminal 111 are a parallel arm resonator and a series arm resonator, the mass coefficient M of at least one of the parallel arm resonator and the series arm resonator may be equal to or greater than 0.95×0.054 and equal to or less than 1.05×0.054.

[0077] The elastic wave resonator according to this example may correspond to all of the elastic wave resonators constituting filter 10 according to the embodiment. In other words, the mass coefficient M of all of the elastic wave resonators constituting filter 10 may be equal to or greater than 0.95×0.054 and equal to or less than 1.05×0.054.

[0078] According to this, the third harmonic excitation signal generated in each acoustic wave resonator constituting the filter 10 is suppressed, so that the third harmonic excitation signal generated from the filter 10 can be suppressed to the maximum extent.

[0079] In addition, in filters using elastic wave resonators, a region where the duty is greater than 0.5 is often used to optimize the passband characteristics. However, in a region where the duty is greater than 0.5, unwanted waves of the third harmonic excitation tend to become large.

[0080] In contrast, filter 10 using the acoustic wave resonator according to this embodiment can suppress unwanted waves of third harmonic excitation even in a region where the duty is greater than 0.5.

[0081] Furthermore, one piezoelectric substrate 50 may be shared by all of the acoustic wave resonators that make up filter 10.

[0082] This makes it possible to easily set the mass coefficient M of all of the acoustic wave resonators constituting filter 10 to be equal to or greater than 0.95×0.054 and equal to or less than 1.05×0.054. Furthermore, filter 10 can be made smaller in size.

[0083] Furthermore, the film thickness t2 of the IDT electrode 54 may be the same for all of the acoustic wave resonators that make up the filter 10.

[0084] This makes it possible to easily set the mass coefficient M of all of the acoustic wave resonators constituting filter 10 to be equal to or greater than 0.95×0.054 and equal to or less than 1.05×0.054. Furthermore, the manufacturing process of filter 10 can be simplified.

[0085] [4. Effects, etc.] As described above, filter 10 according to the present embodiment includes terminals 111 and 112 and a plurality of elastic wave resonators connected to a path connecting terminals 111 and 112. Each of the plurality of elastic wave resonators has IDT electrode 54 disposed on a piezoelectric substrate. The piezoelectric substrate includes piezoelectric film 53 having IDT electrode 54 formed on one surface thereof, a high acoustic velocity film having a bulk wave acoustic velocity faster than the acoustic velocity of an elastic wave propagating through piezoelectric film 53, and a high acoustic velocity film having a bulk wave acoustic velocity faster than the acoustic velocity of an elastic wave propagating through piezoelectric film 53. and a low acoustic velocity film 52 disposed between the low acoustic velocity film and the piezoelectric film 53, the low acoustic velocity film 52 having a bulk wave acoustic velocity slower than the bulk wave acoustic velocity propagating through the piezoelectric film 53, an electrode finger wavelength that is twice the pitch of a plurality of parallel electrode fingers of an IDT electrode 54 is defined as λ (m), a film thickness of the piezoelectric film 53 is defined as t1 (m), a film thickness of the plurality of electrode fingers is defined as t2 (m), t1 / λ is a film thickness wavelength ratio A of the piezoelectric film 53, t2 / λ is a film thickness wavelength ratio B of the plurality of electrode fingers, and a density of the piezoelectric film 53 is defined as x (g / cm 3 ), and the density of the IDT electrode 54 is y (g / cm 3 ) and (A / x+B / y) is the mass coefficient M, the mass coefficient M of the first acoustic wave resonator connected closest to terminal 111 among the multiple acoustic wave resonators is equal to or greater than 0.95×0.054 and equal to or less than 1.05×0.054.

[0086] This makes it possible to effectively prevent the unwanted waves of the third harmonic excitation generated in the filter 10 from adversely affecting other filter circuits connected to the filter 10 at the terminal 111.

[0087] For example, in filter 10, the mass coefficient M of each of the multiple acoustic wave resonators is equal to or greater than 0.95×0.054 and equal to or less than 1.05×0.054.

[0088] According to this, the third harmonic excitation signal generated in each elastic wave resonator constituting the filter 10 is suppressed, so that the unnecessary third harmonic excitation wave generated from the filter 10 can be suppressed to the maximum extent.

[0089] Also, for example, in the filter 10, the piezoelectric substrate 50 may be shared among a plurality of acoustic wave resonators.

[0090] This makes it possible to easily set the mass coefficient M of all of the acoustic wave resonators constituting filter 10 to be equal to or greater than 0.95×0.054 and equal to or less than 1.05×0.054. Furthermore, filter 10 can be made smaller in size.

[0091] For example, in filter 10, the film thickness t2 of the electrode fingers is the same for the multiple acoustic wave resonators.

[0092] This makes it possible to easily set the mass coefficients M of all of the acoustic wave resonators constituting filter 10 to be equal to or greater than 0.95×0.054 and equal to or less than 1.05×0.054. Furthermore, the manufacturing process for filter 10 can be simplified.

[0093] Also, for example, in the filter 10, the piezoelectric film 53 contains LiTaO3.

[0094] In the case of an elastic wave resonator using a piezoelectric substrate 50 having a laminated structure including a piezoelectric film 53 containing LiTaO3, a low acoustic velocity film, and a high acoustic velocity film, unwanted waves of higher modes are likely to occur. In contrast, the above-described configuration of the filter 10 makes it possible to suppress unwanted waves of third harmonic excitation even when a piezoelectric substrate 50 having the above-described laminated structure is used.

[0095] For example, in filter 10, the multiple acoustic wave resonators include series arm resonators 11 to 14 arranged in series on a path connecting terminals 111 and 112, and parallel arm resonators 15 to 18 connected between the path and ground.

[0096] This makes it possible to suppress unwanted waves of third harmonic excitation in the ladder-type filter 10.

[0097] For example, in the filter 10A, the multiple acoustic wave resonators include longitudinally coupled resonators.

[0098] This makes it possible to suppress unwanted waves of third harmonic excitation in the filter 10A including the longitudinally coupled resonators.

[0099] For example, multiplexer 1 according to the present embodiment includes common terminal 100, filter 10 or 10A having terminal 111 connected to common terminal 100, and filter 20 connected to common terminal 100.

[0100] This effectively prevents the third harmonic excitation signal generated in the filter 10 from adversely affecting the filter 20 via the common terminal 100.

[0101] Also, for example, in the multiplexer 1 , the filter 20 includes an acoustic wave resonator and is disposed on a piezoelectric substrate 50 .

[0102] This allows the multiplexer 1 to be miniaturized and the manufacturing process to be simplified.

[0103] Also, for example, in multiplexer 1, the acoustic wave resonator of filter 20 has an IDT electrode arranged on piezoelectric substrate 50, and the film thickness of the multiple electrode fingers constituting the IDT electrode of filter 20 is the same as the film thickness of the multiple electrode fingers constituting the IDT electrode of filter 10.

[0104] This allows the manufacturing process of the multiplexer 1 to be simplified.

[0105] Also, for example, in the multiplexer 1, the passband of the filter 20 is located on the higher frequency side than the passband of the filter 10.

[0106] According to this, even if an unwanted wave of third harmonic excitation generated by the filter 10 is included in the vicinity of the passband of the filter 20, deterioration of the passband characteristic of the filter 20 can be suppressed.

[0107] (Other embodiments) Although the elastic wave device and multiplexer according to the present invention have been described above with reference to the embodiments, examples, and modifications, the present invention is not limited to the above-mentioned embodiments, examples, and modifications. The present invention also includes modifications that can be made by those skilled in the art without departing from the spirit of the present invention, and various devices incorporating the elastic wave device and multiplexer according to the present invention.

[0108] Furthermore, for example, in the acoustic wave devices and multiplexers according to the above-described embodiments, examples, and modifications, matching elements such as inductors and capacitors, and switch circuits may be connected between the respective components.

[0109] The resonant frequency and anti-resonant frequency shown in the above-described embodiment, examples, and modified examples are derived, for example, by contacting an RF probe with two input / output electrodes of an acoustic wave resonator and measuring the reflection characteristics.

[0110] The features of the acoustic wave device and the multiplexer described based on the above-mentioned embodiment and example will be described below.

[0111] <1> a first input / output terminal and a second input / output terminal; a plurality of acoustic wave resonators connected to a path connecting the first input / output terminal and the second input / output terminal; Each of the plurality of elastic wave resonators includes The piezoelectric element has an IDT electrode disposed on a substrate having piezoelectricity, The substrate is a piezoelectric film having the IDT electrode formed on one surface thereof; a high acoustic velocity film in which a bulk wave propagates faster than an elastic wave propagating through the piezoelectric film; a low acoustic velocity film disposed between the high acoustic velocity film and the piezoelectric film, the low acoustic velocity film having a bulk wave acoustic velocity slower than the bulk wave acoustic velocity propagating through the piezoelectric film; The electrode finger wavelength, which is twice the pitch of the parallel electrode fingers of the IDT electrode, is defined as λ (m), the film thickness of the piezoelectric film is defined as t1 (m), the film thickness of the electrode fingers is defined as t2 (m), t1 / λ is the film thickness wavelength ratio A of the piezoelectric film, t2 / λ is the film thickness wavelength ratio B of the electrode fingers, and the density of the piezoelectric film is defined as x (g / cm 3 ), and the density of the IDT electrode is y (g / cm 3 ) and (A / x+B / y) is the mass coefficient M, the first elastic wave resonator connected closest to the first input / output terminal among the plurality of elastic wave resonators has a mass coefficient M of not less than 0.95×0.054 and not more than 1.05×0.054.

[0112] <2> a mass coefficient M of each of the plurality of elastic wave resonators is equal to or greater than 0.95×0.054 and equal to or less than 1.05×0.054; <1> The acoustic wave device according to claim 1 .

[0113] <3> the substrate having piezoelectricity is shared among the plurality of elastic wave resonators; <1> or <2> The acoustic wave device according to claim 1 .

[0114] <4> The thicknesses t2 of the electrode fingers are the same for the elastic wave resonators. <1> ~ <3> 2. The acoustic wave device according to claim 1 ,

[0115] <5> The piezoelectric film includes LiTaO3. <1> ~ <4> 2. The acoustic wave device according to claim 1 ,

[0116] <6> The plurality of elastic wave resonators include a series arm resonator arranged in series on a path connecting the first input / output terminal and the second input / output terminal; a parallel arm resonator connected between the path and a ground. <1> ~ <5> 2. The acoustic wave device according to claim 1 ,

[0117] <7> the plurality of elastic wave resonators include longitudinally coupled resonators, <1> ~ <5> 2. The acoustic wave device according to claim 1 ,

[0118] <8> A common terminal; The first input / output terminal is connected to the common terminal. <1> ~ <7> and an elastic wave device according to any one of the preceding claims. a filter connected to the common terminal.

[0119] <9> The filter includes an acoustic wave resonator and is disposed on the substrate. <8> 2. A multiplexer according to claim 1 .

[0120] <10> the acoustic wave resonator of the filter has an IDT electrode disposed on the substrate, a thickness of the plurality of electrode fingers constituting the IDT electrode of the filter is the same as a thickness of the plurality of electrode fingers constituting the IDT electrode of the acoustic wave device; <9> 2. A multiplexer according to claim 1 .

[0121] <11> The filter has a pass band located on the higher frequency side than the acoustic wave device. <8> ~ <10> 2. A multiplexer according to claim 1 . [Industrial Applicability]

[0122] INDUSTRIAL APPLICABILITY The present invention can be widely used as a transmit / receive filter and a multiplexer used in the front end of a wireless communication terminal where low loss within the passband and high attenuation outside the passband are required. [Explanation of symbols]

[0123] 1 Multiplexer 2 Antennas 10, 10A, 20 Filter 11, 12, 13, 14 Series arm resonators 15, 16, 17, 18 Parallel arm resonators 19 Vertically coupled resonator 50 Piezoelectric Substrate 51 High-sonic support substrate 52 Low sound velocity membrane 53 Piezoelectric Film 54 IDT electrode 55 Protective layer 60, 191, 192, 193, 194, 195, 196, 197 Elastic wave resonators 60a, 60b comb-shaped electrode 61a, 61b electrode fingers 62a, 62b Busbar electrodes 100 Common terminal 110, 120 input / output terminals Terminals 111 and 112 540 Adhesion layer 542 Main electrode layer

Claims

1. a first input / output terminal and a second input / output terminal; a plurality of elastic wave resonators connected to a path connecting the first input / output terminal and the second input / output terminal; Each of the plurality of elastic wave resonators includes The piezoelectric transducer has an IDT (InterDigital Transducer) electrode disposed on a piezoelectric substrate, The substrate is a piezoelectric film having the IDT electrode formed on one surface thereof; a high acoustic velocity film in which a bulk wave propagates faster than an elastic wave propagating through the piezoelectric film; a low acoustic velocity film disposed between the high acoustic velocity film and the piezoelectric film, the low acoustic velocity film having a bulk wave acoustic velocity slower than the bulk wave acoustic velocity propagating through the piezoelectric film; The electrode finger wavelength, which is twice the pitch of the parallel electrode fingers of the IDT electrode, is λ (m), the film thickness of the piezoelectric film is t1 (m), the film thickness of the electrode fingers is t2 (m), t1 / λ is the film thickness wavelength ratio A of the piezoelectric film, t2 / λ is the film thickness wavelength ratio B of the electrode fingers, and the density of the piezoelectric film is x (g / cm ３ ), and the density of the IDT electrodes is y (g / cm ３ ) and (A / x+B / y) is the mass coefficient M, a mass coefficient M of an elastic wave resonator connected closest to the first input / output terminal among the plurality of elastic wave resonators is equal to or greater than 0.95×0.054 and equal to or less than 1.05×0.054; Elastic wave device.

2. a mass coefficient M of each of the plurality of elastic wave resonators is equal to or greater than 0.95×0.054 and equal to or less than 1.05×0.054; The acoustic wave device according to claim 1 .

3. the substrate is shared among the plurality of elastic wave resonators; The acoustic wave device according to claim 1 .

4. The thicknesses t2 of the electrode fingers are the same for the elastic wave resonators. The acoustic wave device according to claim 1 .

5. The piezoelectric film is LiTaO ３ Including, The acoustic wave device according to claim 1 .

6. The plurality of elastic wave resonators include a series arm resonator arranged in series on a path connecting the first input / output terminal and the second input / output terminal; a parallel arm resonator connected between the path and a ground. The acoustic wave device according to claim 1 .

7. the plurality of elastic wave resonators include longitudinally coupled resonators, The acoustic wave device according to claim 1 .

8. A common terminal; the first input / output terminal is connected to the common terminal; and a filter connected to the common terminal. Multiplexer.

9. The filter includes an acoustic wave resonator and is disposed on the substrate.

9. The multiplexer of claim 8.

10. The acoustic wave resonator of the filter has an IDT electrode disposed on the substrate, a thickness of the plurality of electrode fingers constituting the IDT electrode of the filter is the same as a thickness of the plurality of electrode fingers constituting the IDT electrode of the acoustic wave device; 10. The multiplexer of claim 9.

11. The filter has a pass band located on the higher frequency side than the acoustic wave device.

9. The multiplexer of claim 8.

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