WO2021153734A1 - 弾性波デバイスおよびそれを備えたラダー型フィルタ - Google Patents

弾性波デバイスおよびそれを備えたラダー型フィルタ Download PDF

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Publication number
WO2021153734A1
WO2021153734A1 PCT/JP2021/003249 JP2021003249W WO2021153734A1 WO 2021153734 A1 WO2021153734 A1 WO 2021153734A1 JP 2021003249 W JP2021003249 W JP 2021003249W WO 2021153734 A1 WO2021153734 A1 WO 2021153734A1
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Prior art keywords
resonator
electrode
reflector
value
elastic wave
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PCT/JP2021/003249
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English (en)
French (fr)
Japanese (ja)
Inventor
中村　健太郎
岡田　真一
俊介 木戸
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Murata Manufacturing Co Ltd
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Murata Manufacturing Co Ltd
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Priority to KR1020227022834A priority Critical patent/KR102754581B1/ko
Priority to JP2021574152A priority patent/JP7414080B2/ja
Priority to CN202180010904.0A priority patent/CN115004547A/zh
Publication of WO2021153734A1 publication Critical patent/WO2021153734A1/ja
Priority to US17/869,808 priority patent/US12255635B2/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/125—Driving means, e.g. electrodes, coils
    • H03H9/145—Driving means, e.g. electrodes, coils for networks using surface acoustic waves
    • H03H9/14538—Formation
    • H03H9/14541—Multilayer finger or busbar electrode
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/64—Filters using surface acoustic waves
    • H03H9/6423—Means for obtaining a particular transfer characteristic
    • H03H9/6433—Coupled resonator filters
    • H03H9/6483—Ladder SAW filters
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/02535—Details of surface acoustic wave devices
    • H03H9/02543—Characteristics of substrate, e.g. cutting angles
    • H03H9/02574—Characteristics of substrate, e.g. cutting angles of combined substrates, multilayered substrates, piezoelectrical layers on not-piezoelectrical substrate
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/02535—Details of surface acoustic wave devices
    • H03H9/02637—Details concerning reflective or coupling arrays
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/02535—Details of surface acoustic wave devices
    • H03H9/02818—Means for compensation or elimination of undesirable effects
    • H03H9/02842—Means for compensation or elimination of undesirable effects of reflections
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/125—Driving means, e.g. electrodes, coils
    • H03H9/145—Driving means, e.g. electrodes, coils for networks using surface acoustic waves
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/125—Driving means, e.g. electrodes, coils
    • H03H9/145—Driving means, e.g. electrodes, coils for networks using surface acoustic waves
    • H03H9/14544—Transducers of particular shape or position
    • H03H9/14547—Fan shaped; Tilted; Shifted; Slanted; Tapered; Arched; Stepped finger transducers
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/125—Driving means, e.g. electrodes, coils
    • H03H9/145—Driving means, e.g. electrodes, coils for networks using surface acoustic waves
    • H03H9/14544—Transducers of particular shape or position
    • H03H9/14594—Plan-rotated or plan-tilted transducers
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/25—Constructional features of resonators using surface acoustic waves
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/02535—Details of surface acoustic wave devices
    • H03H9/02637—Details concerning reflective or coupling arrays
    • H03H9/02685—Grating lines having particular arrangements
    • H03H9/02771—Reflector banks

Definitions

  • the present disclosure relates to an elastic wave device and a ladder type filter provided with the elastic wave device, and more specifically, to a technique for miniaturizing the elastic wave device.
  • Patent Document 1 discloses a filter device composed of a plurality of surface acoustic wave (SAW) resonators.
  • SAW surface acoustic wave
  • IDT Interdigital Transducer
  • the filter device using the surface acoustic wave resonator as described above may be used, for example, in a mobile terminal represented by a mobile phone or a smartphone.
  • a mobile terminal represented by a mobile phone or a smartphone.
  • devices constituting the mobile terminal such as a filter device, are also required to be further miniaturized and reduced in height.
  • Patent Document 2 Japanese Patent Application Laid-Open No. 2002-176335
  • a configuration has been proposed to reduce the overall size.
  • the present invention has been made to solve the above problems, and an object of the present invention is to reduce the size of an elastic wave device formed by a plurality of resonators while reducing the influence of spurious in a higher-order mode of the device. Is to realize.
  • the elastic wave device includes a substrate having a piezoelectric layer, first resonators and second resonators arranged on the substrate, and a shared reflector.
  • the second resonator is arranged adjacent to the first resonator on the substrate, and has different frequency characteristics from the first resonator.
  • the common reflector is arranged between the first resonator and the second resonator on the substrate.
  • the first resonator includes a first IDT electrode in which the electrode fingers are formed at the first pitch.
  • the second resonator includes a second IDT electrode in which the electrode fingers are formed at a second pitch.
  • the lower limit frequency of the blocking region of the shared reflector is the same as the lower limit frequency of the blocking region of the first resonator and the lower limit frequency of the blocking region of the second resonator, or the lower limit frequency of the blocking region of the first resonator and the second. It is between the lower limit frequency of the resonator blocking region.
  • the upper limit frequency of the blocking region of the shared reflector is the same as the upper limit frequency of the blocking region of the first resonator and the upper limit frequency of the blocking region of the second resonator, or the upper limit frequency of the blocking region of the first resonator and the second. It is between the upper limit frequency of the resonator blocking region.
  • the higher-order mode frequency of the first resonator coincides with the higher-order mode frequency of the second resonator.
  • the electrode fingers facing the shared reflector in the first IDT electrode have the same polarity as the electrode fingers facing the shared reflector in the second IDT electrode.
  • the electrode finger facing the common reflector in the first IDT electrode has the opposite polarity to the electrode finger facing the common reflector in the second IDT electrode.
  • the elastic wave device includes a substrate having a piezoelectric layer, first resonators and second resonators arranged on the substrate, and a shared reflector.
  • the second resonator is arranged adjacent to the first resonator on the substrate, and has different frequency characteristics from the first resonator.
  • the common reflector is arranged between the first resonator and the second resonator on the substrate.
  • the first resonator includes a first IDT electrode in which the electrode fingers are formed at the first pitch.
  • the second resonator includes a second IDT electrode in which the electrode fingers are formed at a second pitch.
  • the main mode of the first resonator and the second resonator is a vibration mode in which the resonance frequency increases with the increase in the thickness of the piezoelectric layer.
  • the value obtained by multiplying the pitch of the electrode finger, the duty of the electrode finger, the thickness of the electrode finger, and the reciprocal of the thickness of the piezoelectric layer is the first value, respectively.
  • the first value is the same as the second value and the third value, or is between the second value and the third value.
  • the higher-order mode frequency of the first resonator coincides with the higher-order mode frequency of the second resonator.
  • the electrode fingers facing the shared reflector in the first IDT electrode have the same polarity as the electrode fingers facing the shared reflector in the second IDT electrode.
  • the electrode finger facing the common reflector in the first IDT electrode has the opposite polarity to the electrode finger facing the common reflector in the second IDT electrode.
  • the elastic wave device includes a substrate having a piezoelectric layer, first and second resonators arranged on the substrate, and a shared reflector.
  • the second resonator is arranged adjacent to the first resonator on the substrate, and has different frequency characteristics from the first resonator.
  • the common reflector is arranged between the first resonator and the second resonator on the substrate.
  • the first resonator includes a first IDT electrode in which the electrode fingers are formed at the first pitch.
  • the second resonator includes a second IDT electrode in which the electrode fingers are formed at a second pitch.
  • the main mode of the first resonator and the second resonator is a vibration mode in which the resonance frequency decreases as the thickness of the piezoelectric layer increases.
  • the values obtained by multiplying the pitch of the electrode fingers, the duty of the electrode fingers, the thickness of the electrode fingers, and the thickness of the piezoelectric layer are the fourth and fifth values, respectively.
  • the fourth value is the same as the fifth value and the sixth value, or is between the fifth value and the sixth value.
  • the higher-order mode frequency of the first resonator coincides with the higher-order mode frequency of the second resonator.
  • the electrode fingers facing the shared reflector in the first IDT electrode have the same polarity as the electrode fingers facing the shared reflector in the second IDT electrode.
  • the electrode finger facing the common reflector in the first IDT electrode has the opposite polarity to the electrode finger facing the common reflector in the second IDT electrode.
  • a shared reflector that functions as both reflectors is arranged between two elastic wave resonators (first resonator and second resonator), each containing an IDT electrode. NS.
  • the shared reflector has a frequency characteristic between the frequency characteristic of the first resonator and the frequency characteristic of the second resonator.
  • the electrode fingers facing the shared reflector of the two resonators are arranged so as to have the same polarity, and the number of electrode fingers of the shared reflector is increased.
  • the electrode fingers facing the shared reflectors of the two resonators are arranged so as to have opposite polarities.
  • FIG. It is a top view of the elastic wave device of the comparative example. It is a figure for demonstrating the frequency characteristic of the elastic wave device of Embodiment 1.
  • FIG. It is the top view of the elastic wave device when the electrode finger of a common reflector is an odd number. It is the top view of the elastic wave device when the electrode finger of a common reflector is an even number. It is a figure for demonstrating the principle that spurious of a higher order mode is reduced.
  • FIG. 1 is a diagram showing a circuit configuration of a filter device 10 formed by an elastic wave device according to the first embodiment.
  • the filter device 10 is, for example, a filter device used in a transmission side circuit of a communication device, and is a ladder type filter connected between a transmission terminal TX and an antenna terminal ANT.
  • the filter device 10 filters the signal received by the transmission terminal TX and outputs it from the antenna terminal ANT.
  • the filter device 10 includes series arm resonance portions S1 to S5 connected in series between the transmission terminal TX and the antenna terminal ANT, and parallel arm resonance portions P1 to P4.
  • Each resonance portion of the series arm resonance portions S1 to S5 and the parallel arm resonance portions P1 to P4 includes at least one elastic wave resonator.
  • each resonance portion of the series arm resonance portions S1 and S5 and the parallel arm resonance portions P1 to P4 is composed of one elastic wave resonator, and each resonance portion of the series arm resonance portions S2 to S4 is 2. It is composed of two elastic wave resonators.
  • the series arm resonance portion S2 includes elastic wave resonators S21 and S22 connected in series.
  • the series arm resonance portion S3 includes elastic wave resonators S31 and S32 connected in series.
  • the series arm resonance portion S4 includes elastic wave resonators S41 and S42 connected in series.
  • the number of elastic wave resonators included in each resonance portion is not limited to this, and is appropriately selected according to the characteristics of the filter device.
  • an elastic surface wave (SAW) resonator can be used as the surface acoustic wave resonator.
  • One end of the parallel arm resonance portion P1 is connected to a connection point between the series arm resonance portion S1 and the series arm resonance portion S2, and the other end is connected to the ground potential GND.
  • One end of the parallel arm resonance portion P2 is connected to a connection point between the series arm resonance portion S2 and the series arm resonance portion S3, and the other end is connected to the ground potential GND.
  • One end of the parallel arm resonance portion P3 is connected to a connection point between the series arm resonance portion S3 and the series arm resonance portion S4, and the other end is connected to the ground potential GND.
  • One end of the parallel arm resonance portion P4 is connected to a connection point between the series arm resonance portion S4 and the series arm resonance portion S5, and the other end is connected to the ground potential GND.
  • FIG. 2 is a top view of a portion of the elastic wave device 100 in which a shared reflector is formed between adjacent resonators.
  • FIG. 3 is a cross-sectional view of a portion between adjacent resonators.
  • the elastic wave device 100 includes two adjacent elastic wave resonators 101 (first resonator) and elastic wave resonator 102 (second resonator), and a shared reflector REF12. including.
  • the elastic wave resonators 101 and 102 included in the elastic wave device 100 are the resonators included in any of the series arm resonance portions S1 to S5 and the parallel arm resonance portions P1 to P4 in the filter device 10 described with reference to FIG. handle.
  • Surface acoustic wave resonators 101 and 102 are SAW resonators including an IDT electrode.
  • the elastic wave resonator 101 includes an IDT electrode IDT1 and reflectors REF1-1 and REF1-2 arranged at both ends of the IDT electrode IDT1.
  • the elastic wave resonator 102 includes an IDT electrode IDT2 and reflectors REF2-1 and REF2-2 arranged at both ends of the IDT electrode IDT2.
  • the IDT electrode has a configuration in which two comb-shaped electrodes in which electrode fingers are arranged on a bus bar at predetermined intervals are opposed to each other.
  • the IDT electrode IDT1 of the elastic wave resonator 101 includes a bus bar 210 (first bus bar) and a bus bar 211 (second bus bar), and the IDT electrode IDT2 of the elastic wave resonator 102 includes a bus bar 220 (third bus bar) and a bus bar 211 (second bus bar). Includes bus bar 221 (fourth bus bar).
  • the IDT electrode surface acoustic waves propagate in a direction orthogonal to the extending direction of the opposing electrode fingers.
  • the reflector is used to reflect the surface acoustic waves leaking from the end of the IDT electrode and confine it in the IDT electrode. Thereby, the Q value of the elastic wave resonator can be increased.
  • the IDT electrode and the reflector formed by each elastic wave resonator are formed on the substrate 105 having the piezoelectric layer 110.
  • the substrate 105 includes a low sound velocity layer 121, a high sound velocity layer 122, and a support layer 130.
  • the support layer 130 is, for example, a semiconductor substrate made of silicon (Si).
  • the hypersonic layer 122, the low sound velocity layer 121, and the piezoelectric layer 110 are laminated in this order on the support layer 130 in the positive direction of the Z axis of FIG.
  • the piezoelectric layer 110 is formed of, for example, a piezoelectric single crystal material such as lithium tantalate (LiTaO 3 ) or lithium niobate (LiNbO 3 ), or a piezoelectric laminated material composed of aluminum nitride (AlN), LiTaO 3 or LiNbO 3. Will be done.
  • An IDT electrode and a reflector, which are functional elements, are formed on the upper surface of the piezoelectric layer 110 (the surface in the positive direction of the Z axis).
  • lithium tantalate (LT) is used as the piezoelectric layer 110.
  • IDT electrodes and reflectors are made of, for example, a single metal consisting of at least one of aluminum, copper, silver, gold, titanium, tungsten, platinum, chromium, nickel and molybdenum, or a material such as an alloy containing these as main components. There is.
  • the low-pitched sound layer 121 is made of a material in which the bulk wave sound velocity propagating in the low-pitched sound layer 121 is lower than the bulk wave sound velocity propagating in the piezoelectric layer 110.
  • the low sound velocity layer 121 is made of silicon dioxide (SiO 2 ).
  • the bass velocity layer 121 is not limited to silicon dioxide, and may be formed of, for example, other dielectrics such as glass, silicon oxynitride, and tantalum oxide, or a compound obtained by adding fluorine, carbon, boron, etc. to silicon dioxide. good.
  • the hypersonic layer 122 is made of a material in which the bulk wave sound velocity propagating in the hypersonic layer 122 is higher than the elastic wave sound velocity propagating in the piezoelectric layer 110.
  • the hypersonic layer 122 is made of silicon nitride (SiN).
  • the treble speed layer 122 is not limited to silicon nitride, and may be formed of a material such as aluminum nitride, aluminum oxide (alumina), silicon oxynitride, silicon carbide, diamond-like carbon (DLC), and diamond.
  • the low sound speed layer 121 and the high sound speed layer 122 function as a reflection layer (mirror layer) 120. That is, the surface acoustic wave leaking from the piezoelectric layer 110 toward the support layer 130 is reflected by the high sound velocity layer 122 due to the difference in the propagating sound velocity, and is confined in the low sound velocity layer 121. In this way, the loss of acoustic energy of the surface acoustic wave propagated by the reflective layer 120 is suppressed, so that the surface acoustic wave can be efficiently propagated.
  • a reflection layer 120 mirror layer
  • the reflection layer 120 includes a plurality of low sound speed layers 121 and high sound speed layers 122.
  • the configuration may be arranged alternately.
  • the reflector REF1-1 of the elastic wave resonator 101 is arranged so as to face the end portion of the IDT electrode IDT1 on the elastic wave resonator 102 side.
  • the reflector REF1-2 is arranged so as to face the end opposite to the reflector REF1-1 with respect to the IDT electrode IDT1.
  • the electrode fingers of the reflectors REF1-1 and REF1-2 are formed at the same pitch as the electrode fingers of the IDT electrode IDT1.
  • the reflector REF2-1 of the elastic wave resonator 102 is arranged so as to face the end portion of the IDT electrode IDT2 on the elastic wave resonator 101 side.
  • the reflector REF2-2 is arranged so as to face the end opposite to the reflector REF2-1 with respect to the IDT electrode IDT2.
  • the electrode fingers of the reflectors REF2-1 and REF2-2 are formed at the same pitch as the electrode fingers of the IDT electrode IDT2.
  • the shared reflector REF12 is arranged between the reflector REF1-1 of the elastic wave resonator 101 and the reflector REF2-1 of the elastic wave resonator 102.
  • the sum of the number of electrode fingers of the reflector REF1-1 and the number of electrode fingers of the shared reflector REF12 is set to the same number as the number of electrode fingers of the reflector REF1-2.
  • the sum of the number of electrode fingers of the reflector REF2-1 and the number of electrode fingers of the shared reflector REF12 is set to the same number as the number of electrode fingers of the reflector REF2-2.
  • the length of the electrode finger of the common reflector REF12 is longer than the crossing width of the electrode finger in the IDT electrode included in the elastic wave resonator 101 and the elastic wave resonator 102.
  • the frequency characteristic of the shared reflector REF12 has an intermediate frequency characteristic between the frequency characteristic of the elastic wave resonator 101 and the frequency characteristic of the elastic wave resonator 102. With such a configuration, the shared reflector REF12 functions as a reflector for both the elastic wave resonator 101 and the elastic wave resonator 102.
  • At least a part of the electrode fingers of the shared reflector REF12 is the pitch of the electrode fingers of the IDT electrode IDT1 and the reflectors REF1-1 and REF1-2 in the elastic wave resonator 101 (first pitch: PT1). ) And the pitch between the IDT electrode IDT2 in the elastic wave resonator 102 and the pitch of the electrode fingers of the reflectors REF2-1 and REF2-2 (second pitch: PT2) to obtain intermediate frequency characteristics. It has been realized.
  • the pitch of the electrode fingers is the distance between the centers of the adjacent electrode fingers.
  • the frequency characteristics can be measured by bringing the contact pins connected to the network analyzer into contact with each resonator and the wiring connected to the reflector as little as possible.
  • the entire electrode finger may be formed at an intermediate pitch, or the pitch is gradually changed from the elastic wave resonator 101 toward the elastic wave resonator 102. There may be. Further, the pitch may be changed stepwise from the elastic wave resonator 101 toward the elastic wave resonator 102.
  • the reflector REF1-1 in the elastic wave resonator 101 and the reflector REF2-1 in the elastic wave resonator 102 are not always indispensable, and the IDT electrode IDT1 of the elastic wave resonator 101 and the IDT electrode IDT2 of the elastic wave resonator 102
  • the configuration may be such that only the shared reflector REF12 is arranged between the two.
  • the number of electrode fingers of the shared reflector REF12 is preferably the same as the number of electrode fingers of the reflector REF1-2 and the reflector REF2-2.
  • FIG. 4 is a top view of an adjacent resonator in the elastic wave device 100 # of the comparative example.
  • the elastic wave device 100 # includes two adjacent elastic wave resonators 101 # and 102 #.
  • reflectors (REF1-2, REF2-2) having the same shape are arranged at both ends of the IDT electrode in each elastic wave resonator. That is, in each elastic wave resonator, the number of electrode fingers of the reflectors arranged at both ends is the same. Therefore, for example, when the number of electrode fingers of each of the reflectors REF1-2 and REF2-2 is 20, the total number of electrode fingers of the reflector arranged between the two IDT electrodes is 40.
  • the number of electrode fingers of each reflector REF1-1 and REF2-1 is eight, and the number of electrode fingers of the shared reflector REF12 is twelve.
  • the total number of electrode fingers of the reflector REF1-1 and the shared reflector REF12, and the total number of electrode fingers of the reflector REF2-1 and the shared reflector REF12 are 20, respectively, and the reflectors REF1-2 and REF2-2 The number is the same as the number of electrode fingers.
  • the total number of electrode fingers of the reflector arranged between the two IDT electrodes is as small as 28 (8 + 12 + 8).
  • the distance between the two IDT electrodes can be narrowed while maintaining the number of electrode fingers that function as reflectors for each elastic wave resonator and suppressing the decrease in reflectance.
  • the elastic wave device 100 can be miniaturized as compared with the elastic wave device 100 # of the comparative example.
  • spurious in a higher-order mode with a higher frequency than the frequency band (main mode) to be passed may occur.
  • reflectors are generally designed to have a large reflectance coefficient for signals in the main mode frequency band.
  • the reflectance coefficient for the frequency band of the higher-order mode cannot always be increased, and therefore spurious of the higher-order mode may not be sufficiently removed by the reflector. Then, the spurious of the higher-order mode affects the adjacent elastic wave resonators, which may cause ripples in the filter characteristics.
  • the frequency bands of the high-order modes of the adjacent elastic wave resonators are substantially matched via the shared reflector, and the high-order generated from each elastic wave resonator.
  • a configuration is adopted in which the phases of the mode signals are inverted from each other.
  • a plurality of higher-order modes occur, but here, the frequency bands of at least one of the plurality of higher-order modes are matched.
  • the spurs of the higher-order mode leaking from the reflector cancel each other out, so that the influence of the spurs of the higher-order mode can be reduced.
  • the reflection characteristics when a shared reflector is used in the adjacent elastic wave resonators will be described.
  • the frequency characteristic of the reflectance coefficient of the reflector is shown in the upper row
  • the frequency characteristic of the impedance of the resonator is shown in the lower row.
  • the solid line LN50 and the solid line LN60 indicate the series arm resonator
  • the broken line LN51 and the broken line LN61 indicate the parallel arm resonator.
  • the ladder type filter as shown in FIG. 1 it is generally designed so that the resonance frequency of the series arm resonator and the antiresonance frequency of the parallel arm resonator substantially match. .. That is, in the reflector of the series arm resonator, the blocking region in which the reflectance coefficient gradually approaches 1 is between frequencies f2 and f4 (region AR10 in FIG. 5A). On the other hand, in the reflector of the parallel arm resonator, the blocking region where the reflectance coefficient gradually approaches 1 is between frequencies f1 and f3 (region AR11 in FIG. 5B).
  • the reflectance coefficient of the shared reflector is, for example, It becomes like the one-dot chain line LN52 in FIG.
  • the blocking region for the series arm resonator is expanded to the range of frequencies f2 to f31 (region AR16).
  • the blocking region for the parallel arm resonator is extended to the frequency range f11 to f3 (region AR17), as shown in FIG. 5 (b).
  • the lower limit frequency of the blocking region of the shared reflector is between the lower limit frequency of the blocking region of the first resonator and the lower limit frequency of the blocking region of the second resonator
  • the upper limit frequency of the blocking region of the shared reflector is , It is between the upper limit frequency of the blocking region of the first resonator and the upper limit frequency of the blocking region of the second resonator. Therefore, as compared with the case where the electrode finger pitch of the shared reflector is unified to the electrode finger pitch of either resonator, the blocking range in the filter device can be expanded, and as a result, deterioration of the filter characteristics can be suppressed. Can be done.
  • the "blocking region” indicates a frequency range having a reflection coefficient higher than 70% of the peak value of the reflection coefficient.
  • the lower limit frequency of the blocking region corresponds to the resonance frequency of each resonator.
  • the upper limit frequency of the blocking region corresponds to the frequency at which the stopband ripple (regions RG10 and RG11 in FIG. 5) begins to appear in the impedance characteristics of each resonator.
  • FIGS. 6 and 7 are top views of the elastic wave device according to the first embodiment, and FIG. 6 shows a top view of the elastic wave device 100A when the number of electrode fingers of the shared reflector is an odd number.
  • FIG. 7 shows a top view of the elastic wave device 100B when the number of electrode fingers of the shared reflector is even.
  • the two adjacent elastic wave resonators may be series arm resonators or parallel arm resonators.
  • the two elastic wave resonators may be one in series arm resonator and the other in parallel arm resonator.
  • the elastic wave device 100A includes an elastic wave resonators 101A and 102A and a shared reflector REF12A arranged between the elastic wave resonators 101A and 102A.
  • the bus bar 211 of the IDT electrode IDT1A in the elastic wave resonator 101A and the bus bar 221 of the IDT electrode IDT2A in the elastic wave resonator 102A are connected by a wiring pattern 200. That is, the bus bar 211 and the bus bar 221 have the same potential.
  • the pitch, duty, and electrode film thickness of the electrode fingers in the elastic wave resonators 101A and 102A and the common reflector REF12A are all the same. Therefore, the frequency bands of the main mode and higher-order mode signals of the elastic wave resonator 101A and the elastic wave resonator 102A are the same.
  • the shared reflector REF12A is arranged between the reflector REF1A-1 of the elastic wave resonator 101A and the reflector REF2A-1 of the elastic wave resonator 102A.
  • the sum of the number of electrode fingers of the reflector REF1A-1 and the number of electrode fingers of the shared reflector REF12A is the same as the number of electrode fingers of the reflector REF1A-2.
  • the sum of the number of electrode fingers of the reflector REF2A-1 and the number of electrode fingers of the shared reflector REF12A is the same as the number of electrode fingers of the reflector REF2A-2.
  • the number of electrode fingers of the shared reflector REF12A is an odd number.
  • the number of electrode fingers of the reflector REF1A-1 of the elastic wave resonator 101A and the number of electrode fingers of the reflector REF2A-1 of the elastic wave resonator 102A are set to be the same.
  • the electrode finger closest to the elastic wave resonator 102A (the electrode finger in the region RG1A), that is, the electrode finger facing the reflector REF1A-1 is connected to the bus bar 210. ..
  • the electrode finger closest to the elastic wave resonator 101A (the electrode finger in the region RG2A), that is, the electrode finger facing the reflector REF2A-1 is connected to the bus bar 221. ing.
  • the electrode fingers closest to the elastic wave resonator on the other side of the IDT electrode are arranged so that they have opposite potentials (opposite polarities). Will be done.
  • the number of electrode fingers of the shared reflector REF12B arranged between the two elastic wave resonators 101B and 102B is an even number.
  • the electrode finger closest to the elastic wave resonator 102B (the electrode finger in the region RG1B), that is, the electrode finger facing the reflector REF1B-1 is connected to the bus bar 211. ..
  • the electrode finger closest to the elastic wave resonator 101B (the electrode finger in the region RG2B), that is, the electrode finger facing the reflector REF2B-1 is connected to the bus bar 221. ing.
  • the electrode fingers closest to the elastic wave resonator on the other side of the IDT electrode are arranged so as to have the same potential (same polarity). ..
  • an elastic wave device 100B in which the number of electrode fingers of the shared reflector is an odd number will be described as an example.
  • the reflectors REF1A-1,2A-1 are omitted.
  • the electrode finger connected to the bus bar 210 is referred to as the electrode finger 230
  • the electrode finger connected to the bus bar 211 is referred to as the electrode finger 231.
  • the electrode finger connected to the bus bar 220 is referred to as the electrode finger 240
  • the electrode finger connected to the bus bar 221 is referred to as the electrode finger 241.
  • the potentials of the bus bars 210 and 220 are positive electrodes on the high potential side and the potentials of the bus bars 211 and 221 are negative electrodes on the low potential side.
  • the bus bar 211 and the bus bar 221 have the same potential because they are connected by the wiring pattern 200.
  • the pitch of the adjacent electrode fingers is half the wavelength ( ⁇ / 2) of the propagating surface acoustic wave. That is, the surface acoustic wave propagating through each IDT electrode has a high potential at the positive electrode and a low potential at the negative electrode.
  • a signal such as the line LN1 propagates from the IDT electrode IDT1A in the direction of the arrow AR1. Further, a signal such as the line LN2 propagates from the IDT electrode IDT2A in the direction of the arrow AR2. However, since the main mode signal is reflected by the reflector arranged between the two IDT electrodes, it does not reach the IDT electrode on the other side.
  • the higher-order mode signal is not sufficiently reflected by the reflector, and at least a part of it passes through the IDT electrode on the other side.
  • a signal such as the line LN3 propagates from the IDT electrode IDT2A in the direction of the arrow AR3. Since the number of electrode fingers of the shared reflector REF12A is odd (that is, the number of electrode fingers between resonators is odd), in the IDT electrode IDT1A, the positive electrode (electrode finger 230) has a low potential from the IDT electrode IDT2A. Is received, and the high potential signal from the IDT electrode IDT2A is received at the negative electrode (electrode finger 231).
  • the higher-order mode signal generated and propagated at the IDT electrode IDT1A has a high potential at the positive electrode (electrode finger 230) and a low potential at the negative electrode (electrode finger 231). That is, since the high-potential signal from one resonator and the low-potential signal from the other resonator are received at each electrode finger, the high-order mode signals cancel each other out at each electrode finger. Become.
  • the higher-order mode signal generated by the IDT electrode IDT1A is in a phase inverted state when it passes through the reflector. Therefore, for the electrode finger facing the reflector in the IDT electrode IDT2A, the influence of the higher-order mode signal is eliminated by setting the potential (opposite polarity) to the electrode finger facing the reflector in the IDT electrode IDT1A. Can be done.
  • the phase of the higher-order mode signal at the time of passing through the reflector is the same phase as the signal output from the IDT electrode. Therefore, in the elastic wave device 100B, the electrode finger facing the reflector in the IDT electrode IDT2B has the same potential (same polarity) as the electrode finger facing the reflector in the IDT electrode IDT1B, so that the higher-order mode signal can be obtained. The effect can be eliminated.
  • the reflectors arranged between the IDT electrode and the common reflector are designed so that the number of electrode fingers is the same, and therefore, between the IDT electrodes. Whether the number of electrode fingers in the reflector is even or odd is determined by the electrode fingers of the shared reflector.
  • the frequencies of the main modes of the two elastic wave resonators match (that is, the frequencies of the higher-order modes also match), but in the actual design, they are adjacent to each other.
  • the frequencies of the higher-order modes of elastic wave resonators do not always match exactly.
  • the frequency difference of the elastic wave resonator that can eliminate the influence of spurious in the higher-order mode will be described below.
  • the pitch of the electrode fingers is set to the half wavelength ( ⁇ / 2) of the propagating surface acoustic wave.
  • the propagation distance in the shared reflector becomes longer, and the greater the propagating electrode index, the more the IDT electrode of the other party is reached.
  • the phase difference between the two signals is widened. If this phase difference is ⁇ / 4 or less, it can be expected that the influence of the higher-order mode will be eliminated.
  • FIG. 9 is a diagram showing the relationship between the effective propagation distance of the signal and the allowable frequency difference between the two elastic wave resonators.
  • the "effective propagation distance” is the limit distance at which the phase difference of the signals propagating in the two elastic wave resonators can be ⁇ / 4 or less, and is represented by the wavelength ( ⁇ ).
  • the frequency difference between the two elastic wave resonators is 2.5% or less. If so, it can be seen that the influence of the higher-order mode can be eliminated.
  • the longer the surface acoustic wave propagation distance in the shared reflector that is, the larger the electrode index
  • the more the pitch difference of the electrode fingers is integrated so that the two signals when the other party's IDT electrode is reached are integrated.
  • the phase difference of is widened. Therefore, as the propagation distance by the shared reflector becomes longer, the permissible frequency difference becomes smaller, and it is necessary to increase the degree of coincidence between the frequencies of the two elastic wave resonators.
  • the permissible frequency difference can be expressed by the following equation (1), which corresponds to the line LN10 in FIG.
  • Allowable frequency difference [%] 25 / N ... (1)
  • the number of electrode fingers of the shared reflector is n
  • Allowable frequency difference [%] 50 / n ... (2)
  • the higher-order mode frequencies match means that the permissible frequency difference is in the range of 0% to (50 / n)%.
  • the size of the shared reflector is appropriately selected according to the frequency difference between the two resonators and the size of the entire elastic wave device.
  • FIG. 10 is a top view of the elastic wave device 100C according to the modified example.
  • the elastic wave device 100C includes elastic wave resonators 101C and 102C and shared reflectors REF12C arranged between elastic wave resonators 101C and 102C.
  • the elastic wave resonator 101C includes an IDT electrode IDT1C and reflectors REF1C-1 and REF1C-2 arranged at both ends of the IDT electrode IDT1C.
  • the elastic wave resonator 102C includes an IDT electrode IDT2C and reflectors REF2C-1 and REF2C-2 arranged at both ends of the IDT electrode IDT2C.
  • the shared reflector REF12C is arranged between the reflector REF1C-1 and the reflector REF2C-1.
  • the sum of the number of electrode fingers of the reflector REF1C-1 and the number of electrode fingers of the shared reflector REF12C is the same as the number of electrode fingers of the reflector REF1C-2.
  • the sum of the number of electrode fingers of the reflector REF2C-1 and the number of electrode fingers of the shared reflector REF12C is the same as the number of electrode fingers of the reflector REF2C-2.
  • the electrode fingers of the elastic wave resonators 101C and 102C and the shared reflector REF12C are obliquely connected to the bus bar.
  • the angle between the electrode finger and the bus bar is greater than 0 ° and less than 90 °.
  • the surface acoustic wave resonator In the surface acoustic wave resonator, the surface acoustic wave propagates in the direction orthogonal to the electrode finger.
  • the signal from the elastic wave resonator 101C propagates in the direction of the arrow AR11 in FIG. 10
  • the signal from the elastic wave resonator 102C propagates in the direction of the arrow AR12 in FIG.
  • the propagation direction of the elastic surface wave in one elastic wave resonator can be changed to the other elastic wave. It can be outside the cross-width region of the electrode fingers in the IDT electrode of the resonator. Therefore, when the surface acoustic wave leaks from the common reflector, the influence on the other surface acoustic wave resonator can be further reduced.
  • the elastic wave device 100C of FIG. 10 corresponds to a configuration in which the electrode fingers of the elastic wave device 100A of FIG. 6 in which the electrode index of the shared reflector is an odd number are arranged in an inclined manner, but the electrode index of the shared reflector Also for the elastic wave device 100B of FIG. 7 in which is an even number, the electrode fingers may be tilted.
  • the influence of the spurious is affected by adjusting the frequency of the spurious of the higher-order mode while maintaining the frequency of the main mode.
  • the frequency dependence on the structural parameters of the resonator such as wavelength, piezoelectric layer film thickness, electrode film thickness, or duty differs between the main mode and the higher-order mode. Therefore, by utilizing such a characteristic, the frequency of the higher-order mode is shifted while maintaining the frequency of the main mode.
  • FIG. 11 is a diagram showing the frequency sensitivity ratio of the higher-order mode to each structural parameter (wavelength, piezoelectric layer film thickness, electrode film thickness, duty) of the resonator.
  • the frequency sensitivity ratio indicates the rate of change of the frequency in the higher-order mode when the rate of change of the resonance frequency in the main mode is 1.00.
  • the sign of the frequency sensitivity ratio is positive when the resonance frequency of the main mode and / or the frequency of the higher-order mode increases with respect to the increase of each structural parameter of the resonator, and the resonance frequency and / or the higher-order mode of the main mode.
  • the frequency of is decreased, it is expressed as negative.
  • the absolute value of the frequency sensitivity ratio is larger than 1.00, it means that the rate of change of the frequency in the higher-order mode when the structural parameter is changed is larger than the rate of change of the frequency in the main mode.
  • the dependence tendency of the main mode resonance frequency and the higher-order mode frequency on each structural parameter of the resonator changes depending on the material and thickness of the piezoelectric layer.
  • the frequency sensitivity ratio is as follows. That is, when the main mode is, for example, A0 mode (0th order antisymmetric mode) or SH0 mode (0th order shear horizontal mode), the sign of the frequency sensitivity ratio is positive.
  • the frequency The sign of the sensitivity ratio is negative.
  • the higher-order mode is, for example, A0 mode or SH0 mode
  • the sign of the frequency sensitivity ratio is positive
  • the higher-order mode is, for example, S0 mode, SH1 mode, A1 mode, and higher-order vibration mode.
  • the sign of the frequency sensitivity ratio is negative.
  • the absolute value of the frequency sensitivity ratio also changes depending on the vibration mode.
  • the thickness of the piezoelectric layer is in the range of 2 ⁇ to 5 ⁇ , the above-mentioned dependence tendency disappears.
  • FIG. 11 shows the frequency sensitivity ratio when the SH0 mode is used as the main mode and the S0 mode is used as the higher-order mode. It should be noted that also in the first to fourth examples described later, the case where these modes are used is shown.
  • the rate of change of the resonance frequency in the main mode is ⁇ 1.00
  • the rate of change in the frequency in the higher order mode is ⁇ 1.00. It becomes 0.67. That is, when the wavelength is changed, the frequency change becomes smaller in the higher-order mode than in the main mode.
  • the frequency sensitivity ratio of the higher-order mode when the piezoelectric layer film thickness is changed is -2.40.
  • the frequency of the higher-order mode becomes lower to a greater extent than that of the main mode.
  • the frequency sensitivity ratio of the higher-order mode when the duty of the electrode finger is changed is 0.55
  • the frequency sensitivity ratio of the higher-order mode when the film thickness of the electrode finger is changed is 0.70. be. That is, when the duty and film thickness of the electrode fingers are changed, the frequency change rate becomes smaller in the higher-order mode than in the main mode.
  • the frequency sensitivity ratio in the higher-order mode has different characteristics depending on the structural parameters. Therefore, when the resonance frequency of the main mode was changed by a structural parameter other than the wavelength (electrode finger pitch) and then the wavelength was adjusted to restore the resonance frequency of the main mode, the resonance frequency of the main mode was set to the same state. Up to this point, the frequencies of the higher-order mode can be different frequencies.
  • FIG. 12 is a cross-sectional view of the elastic wave device 100D according to the first example of the second embodiment.
  • the elastic wave device 100D includes an elastic wave resonators 101D and 102D and a shared reflector REF12D arranged between the elastic wave resonators 101D and 102D.
  • the frequency of the main mode of the elastic wave resonator 101D is set higher than the frequency of the main mode of the elastic wave resonator 102D. That is, the electrode finger pitch (PT1) of the IDT electrode IDT1D and the reflector REF1D in the elastic wave resonator 101D is narrower than the electrode finger pitch (PT2) of the IDT electrode IDT2D and the reflector REF2D in the elastic wave resonator 102D. At least a part of the electrode fingers of the shared reflector REF12D is formed at a pitch between the electrode finger pitch PT1 and the electrode finger pitch PT2.
  • the film thickness of the piezoelectric layer 110 in the region where the elastic wave resonator 101D is arranged is set to BT1, and the film thickness of the piezoelectric layer 110 in the region where the elastic wave resonator 102D is arranged is BT2 (BT1). > BT2) is set.
  • the piezoelectric layer 110 in at least a part of the region where the shared reflector REF12D is arranged is thinner than the film thickness BT1 of the piezoelectric layer 110 in the region where the elastic wave resonator 101D is arranged, and the elastic wave resonator 102D Is set to be thicker than the thickness BT2 of the piezoelectric layer 110 in the region where is arranged.
  • the film thickness of the electrode finger in the shared reflector REF12D gradually decreases from the elastic wave resonator 101D toward the elastic wave resonator 102D.
  • FIG. 13 is a diagram showing the relationship between the piezoelectric layer film thickness and the plate wave sound velocity in the main mode and the higher-order mode.
  • the horizontal axis shows the film thickness (h / ⁇ ) of the piezoelectric layer 110 standardized by wavelength, and the vertical axis shows the plate wave sound velocity.
  • the solid line LN20 shows the case of the main mode, and the broken line LN21 shows the case of an example of the higher-order mode.
  • the sound velocity (frequency) tends to increase as the film thickness of the piezoelectric layer becomes thinner, and the sound velocity (frequency) tends to decrease as the film thickness of the piezoelectric layer increases. ing.
  • the degree of frequency change (absolute value of frequency sensitivity ratio) with respect to the film thickness of the piezoelectric layer is larger in the higher-order mode than in the main mode, and the change direction (frequency sensitivity ratio). The sign) is reversed. Therefore, when the thickness of the piezoelectric layer is thinned to raise the resonance frequency of the main mode and then the electrode finger pitch is adjusted to restore the resonance frequency of the main mode, the frequency of the main mode is maintained. , The frequency of the higher order mode can be increased.
  • the film thickness of the piezoelectric layer 110 on which the elastic wave resonator 101D is arranged is made thicker than the film thickness of the piezoelectric layer 110 on which the elastic wave resonator 102D is arranged.
  • the frequency of the high-order mode of the elastic wave resonator 101D is lowered to approach the frequency of the high-order mode of the elastic wave resonator 102D.
  • the elastic wave resonator 102D is formed.
  • the frequency of the higher-order mode is increased to bring it closer to the frequency of the higher-order mode of the elastic wave resonator 101D.
  • the frequency of the main mode may change slightly by changing the film thickness of the piezoelectric layer 110. In such a case, it is desired to modify the pitch of the target elastic wave resonator. It can be adjusted to the frequency.
  • the thickness of the piezoelectric layer in which each elastic wave resonator is arranged is different.
  • the frequencies of the signals in the higher-order mode can be matched.
  • the frequency of the main mode is changed by changing the polarity of the electrode fingers arranged on the most shared reflector side in the IDT electrode according to whether the number of electrode fingers of the shared reflector is odd or even. Even if they are different, the influence of spurious in the higher-order mode can be reduced.
  • the entire electrode finger may be formed at an intermediate pitch, or the pitch is gradually changed from the elastic wave resonator 101D toward the elastic wave resonator 102D. There may be. Further, the pitch may be changed stepwise from the elastic wave resonator 101D toward the elastic wave resonator 102D.
  • the film thickness of the piezoelectric layer 110 in the region where the shared reflector REF12D is arranged may be an intermediate film thickness as a whole, or from the elastic wave resonator 101D to the elastic wave resonator 102D as shown in FIG.
  • the film thickness of the piezoelectric layer 110 may be gradually changed toward.
  • the film thickness of the piezoelectric layer 110 may be changed stepwise from the elastic wave resonator 101D toward the elastic wave resonator 102D.
  • it is preferable to set the pitch of the electrode fingers and the film thickness of the piezoelectric layer 110 so that the piezoelectric layer film thickness (h / ⁇ ) standardized by wavelength is substantially constant. ..
  • FIG. 14 is a diagram showing specific specifications of an embodiment of the first example and a comparative example thereof.
  • a comparative example is shown in the upper part (FIG. 14 (a)) of FIG. 14, and an embodiment is shown in the lower part (FIG. 14 (b)).
  • the duty of the electrode finger is 0.5 in both the comparative example and the embodiment.
  • the piezoelectric layer film thicknesses of the resonator 1 and the resonator 2 are both set to 600 nm.
  • the frequency of the main mode of the resonator 1 is 2464.282 MHz, and the frequency of the higher-order mode is 3106.941 MHz.
  • the frequency of the main mode of the resonator 2 is 2361.513 MHz, and the frequency of the higher-order mode is 3019.257 MHz.
  • the piezoelectric layer film thickness of the resonator 2 is changed to 500 nm, and the wavelength is further adjusted to 1.607 ⁇ m. That is, the resonance frequency of the main mode is restored by reducing the thickness of the piezoelectric layer of the resonator 2 to lower the resonance frequency of the main mode and adjusting the wavelength to be shorter.
  • the frequency of the main mode of the resonator 2 is 2361.312 MHz, and the frequency of the higher-order mode of the resonator 2 is as high as 3017.580 MHz.
  • the frequency of the higher-order mode can be matched with that of the resonator 1 while maintaining the frequency of the main mode. In this way, even when the frequencies of the main mode are different, it is possible to eliminate the influence of spurious in the higher-order mode by adjusting the piezoelectric layer film thickness.
  • FIG. 15 is a cross-sectional view of the elastic wave device 100E according to the second example of the second embodiment.
  • the elastic wave device 100E includes an elastic wave resonators 101E and 102E and a shared reflector REF12E arranged between the elastic wave resonators 101E and 102E.
  • the frequency of the main mode of the elastic wave resonator 101E is set lower than the frequency of the main mode of the elastic wave resonator 102E. That is, the electrode finger pitch (PT1) of the IDT electrode IDT1E and the reflector REF1E in the elastic wave resonator 101E is wider than the electrode finger pitch (PT2) of the IDT electrode IDT2E and the reflector REF2E in the elastic wave resonator 102E. At least a part of the electrode fingers of the shared reflector REF12E is formed at a pitch between the electrode finger pitch PT1 and the electrode finger pitch PT2.
  • the entire electrode finger may be formed at an intermediate pitch, or the pitch is gradually changed from the elastic wave resonator 101E toward the elastic wave resonator 102E. There may be. Further, the pitch may be changed stepwise from the elastic wave resonator 101E toward the elastic wave resonator 102E.
  • the duty (first duty) of the electrode finger in the elastic wave resonator 101E is set to DT1
  • the duty (second duty) of the electrode finger in the elastic wave resonator 102E is DT2 (DT1>. It is set to DT2).
  • at least a part of the electrode fingers in the shared reflector REF12E is formed with an intermediate duty between the first duty DT1 and the second duty DT2 described above.
  • at least a part of the electrode fingers in the shared reflector REF12E is formed smaller than the first duty DT1 and larger than the second duty DT2.
  • the duty of the electrode finger of the shared reflector REF12E is set so as to gradually or gradually decrease from the elastic wave resonator 101E toward the elastic wave resonator 102E.
  • FIG. 16 is a diagram for explaining the relationship between the higher-order mode frequency and the duty of the IDT electrode.
  • the horizontal axis shows the wavelength of the main mode
  • the vertical axis shows the higher-order mode frequency.
  • the line LN30 shows the case where the duty of the IDT electrode is 0.4
  • the line LN31 shows the case where the duty of the IDT electrode is 0.5
  • the line LN32 shows the case where the duty of the IDT electrode is 0.
  • the case of 6 is shown. From these, it can be seen that even when the frequency of the main mode is the same, the frequency of the higher-order mode tends to decrease as the duty increases.
  • the resonance frequency of the main mode is basically determined by the pitch of the electrode fingers. However, even if the electrode finger pitch is the same, if the mass of the electrode fingers increases or decreases, the resonance frequency of the main mode may change due to the mass addition effect. Specifically, when the mass of the electrode finger increases, the resonance frequency decreases, and when the mass of the electrode finger decreases, the resonance frequency increases. Therefore, when the duty is changed, the electrode width of the electrode finger changes, the mass increases or decreases, and the resonance frequency of the main mode changes. Then, as shown in FIG. 11, the frequency sensitivity with respect to the duty is smaller in the higher-order mode than in the main mode. Therefore, when the duty of the electrode finger is reduced to increase the resonance frequency of the main mode and then the electrode finger pitch is adjusted to restore the resonance frequency of the main mode, the frequency of the main mode is maintained. The frequency of the higher mode can be lowered.
  • the frequency of the higher-order mode can be adjusted and matched without changing the frequency of the main mode. Therefore, even when the frequency of the main mode of the elastic wave resonator is different, it is possible to remove the spurious of the higher-order mode.
  • FIG. 17 is a diagram showing specific specifications of an embodiment of the second example and a comparative example thereof.
  • a comparative example is shown in the upper part (FIG. 17 (a)) of FIG. 17, and an embodiment is shown in the lower part (FIG. 17 (b)) of FIG.
  • the duties of the resonator 1 and the resonator 2 are both set to 0.5.
  • the frequency of the main mode of the resonator 1 is 2464.282 MHz, and the frequency of the higher-order mode is 3106.941 MHz.
  • the frequency of the main mode of the resonator 2 is 2469.837 MHz, and the frequency of the higher-order mode is 3111.626 MHz.
  • the duty of the resonator 2 is set to 0.4, and the wavelength is further set to 1.559226 ⁇ m.
  • the duty of the electrode finger gradually changes from 0.5 to 0.4 from the resonator 1 toward the resonator 2. That is, the duty of the resonator 2 is reduced to increase the resonance frequency of the main mode, and the wavelength is adjusted to be longer to restore the resonance frequency of the main mode.
  • the frequency of the main mode of the resonator 2 is 2469.837 MHz, and the frequency of the higher-order mode of the resonator 2 is as low as 3106.941 MHz.
  • the frequency of the higher-order mode can be matched with that of the resonator 1 while maintaining the frequency of the main mode. In this way, even when the frequencies of the main mode are different, it is possible to eliminate the influence of spurious in the higher-order mode by adjusting the duty of the electrode finger of the elastic wave resonator.
  • FIG. 18 is a cross-sectional view of the elastic wave device 100F according to the third example of the second embodiment.
  • the elastic wave device 100F includes an elastic wave resonators 101F and 102F and a shared reflector REF12F arranged between the elastic wave resonators 101F and 102F.
  • the frequency of the main mode of the elastic wave resonator 101F is set lower than the frequency of the main mode of the elastic wave resonator 102F. That is, the electrode finger pitch (PT1) of the IDT electrode IDT1F and the reflector REF1F in the elastic wave resonator 101F is wider than the electrode finger pitch (PT2) of the IDT electrode IDT2F and the reflector REF2F in the elastic wave resonator 102F. At least a part of the electrode fingers of the shared reflector REF12F is formed at a pitch between the electrode finger pitch PT1 and the electrode finger pitch PT2.
  • the entire electrode finger may be formed at an intermediate pitch, or the pitch is gradually changed from the elastic wave resonator 101F toward the elastic wave resonator 102F. There may be. Further, the pitch may be changed stepwise from the elastic wave resonator 101F toward the elastic wave resonator 102F.
  • the film thickness of the electrode finger in the elastic wave resonator 101F is set to ET1
  • the film thickness of the electrode finger in the elastic wave resonator 102F is set to ET2 (ET1 ⁇ ET2).
  • At least a part of the electrode fingers in the shared reflector REF12F is formed with an intermediate film thickness between the film thickness ET1 and the film thickness ET2.
  • at least a part of the electrode fingers in the shared reflector REF12F is thicker than the electrode finger thickness ET1 in the elastic wave resonator 101F and thinner than the electrode finger thickness ET2 in the elastic wave resonator 102F.
  • the film thickness of the electrode finger of the shared reflector REF12F is set so as to gradually or gradually increase from the elastic wave resonator 101F toward the elastic wave resonator 102F.
  • FIG. 19 is a diagram for explaining the relationship between the higher-order mode frequency and the film thickness of the IDT electrode.
  • the horizontal axis shows the wavelength of the main mode
  • the vertical axis shows the higher-order mode frequency.
  • the line LN40 shows the case where the film thickness of the IDT electrode is 111 nm
  • the line LN41 shows the case where the film thickness of the IDT electrode is 121 nm
  • the line LN42 shows the case where the film thickness of the IDT electrode is 131 nm. Is shown. From these, it can be seen that even when the frequency of the main mode is the same, the frequency of the higher-order mode tends to decrease as the film thickness of the IDT electrode increases.
  • the frequency sensitivity of the IDT electrode to the film thickness is smaller in the higher-order mode than in the main mode. Therefore, when the IDT electrode is thickened to lower the resonance frequency of the main mode and then the electrode finger pitch is adjusted to restore the resonance frequency of the main mode, the frequency of the main mode is maintained. , The frequency of the higher mode can be lowered.
  • the frequency of the higher-order mode can be adjusted and matched without changing the frequency of the main mode. can. Therefore, even when the frequency of the main mode of the elastic wave resonator is different, it is possible to remove the spurious of the higher-order mode.
  • FIG. 20 is a diagram showing specific specifications of an embodiment of the third example and a comparative example thereof.
  • a comparative example is shown in the upper part (FIG. 20 (a)) of FIG. 20, and an embodiment is shown in the lower part (FIG. 20 (b)).
  • the electrode film thicknesses of the resonator 1 and the resonator 2 are both set to 121 nm.
  • the frequency of the main mode of the resonator 1 is 2464.282 MHz, and the frequency of the higher-order mode is 3106.941 MHz.
  • the frequency of the main mode of the resonator 2 is 2468.655 MHz, and the frequency of the higher-order mode is 3110.626 MHz.
  • the electrode film thickness of the resonator 2 is set to 191 nm, and the wavelength is further set to 1.48439 ⁇ m.
  • the electrode film thickness gradually changes from 121 nm to 191 nm from the resonator 1 toward the resonator 2. That is, the resonance frequency of the main mode is restored by increasing the electrode film thickness of the resonator 2 to lower the resonance frequency of the main mode and adjusting the wavelength to be shorter.
  • the frequency of the main mode of the resonator 2 is 2468.227 MHz, and the frequency of the higher-order mode of the resonator 2 is as low as 3107.036 MHz.
  • the frequency of the higher-order mode can be matched with that of the resonator 1 while maintaining the frequency of the main mode. In this way, even when the frequencies of the main mode are different, it is possible to eliminate the influence of spurious in the higher-order mode by adjusting the duty of the electrode finger of the elastic wave resonator.
  • the frequency of the higher-order mode can be adjusted depending on the thickness of the dielectric layer.
  • FIG. 21 is a cross-sectional view of the elastic wave device 100G according to the fourth example of the second embodiment.
  • the elastic wave device 100G includes an elastic wave resonators 101G and 102G, a shared reflector REF12G arranged between the elastic wave resonators 101G and 102G, and an IDT electrode and a reflector of each resonator. Includes a dielectric layer 140 that covers.
  • the dielectric layer 140 is made of a material such as silicon dioxide, glass, silicon nitride, tantalum oxide, silicon nitride, aluminum nitride, aluminum oxide (alumina), silicon nitride, silicon carbide, diamond-like carbon (DLC), and diamond. Yes, it may be formed of a compound in which fluorine, carbon, boron or the like is added to silicon dioxide.
  • the dielectric layer 140 is arranged so as to cover the functional elements (IDT electrodes, reflectors) arranged on the piezoelectric layer 110 of the substrate 105.
  • the frequency of the main mode of the elastic wave resonator 101G is set higher than the frequency of the main mode of the elastic wave resonator 102G. That is, the electrode finger pitch (PT1) of the IDT electrode IDT1G and the reflector REF1G in the elastic wave resonator 101G is narrower than the electrode finger pitch (PT2) of the IDT electrode IDT2G and the reflector REF2G in the elastic wave resonator 102G. At least a part of the electrode fingers of the common reflector REF12G is formed at a pitch between the electrode finger pitch PT1 and the electrode finger pitch PT2.
  • the entire electrode finger may be formed at an intermediate pitch, or the pitch is gradually changed from the elastic wave resonator 101G toward the elastic wave resonator 102G. There may be. Further, the pitch may be changed stepwise from the elastic wave resonator 101G toward the elastic wave resonator 102G.
  • the film thickness of the dielectric layer 140 in the elastic wave resonator 101G is set to FT1
  • the film thickness of the dielectric layer 140 in the elastic wave resonator 102G is set to FT2 (FT1 ⁇ FT2).
  • At least a part of the electrode fingers in the shared reflector REF12G is formed with an intermediate film thickness between the film thickness FT1 and the film thickness FT2.
  • at least a part of the electrode fingers in the shared reflector REF12G is thicker than the electrode finger thickness FT1 in the elastic wave resonator 101G and thinner than the electrode finger thickness FT2 in the elastic wave resonator 102G.
  • the film thickness of the electrode finger of the shared reflector REF12G is set so as to gradually or gradually increase from the elastic wave resonator 101G toward the elastic wave resonator 102G.
  • the dielectric layer 140 is formed of a material having a bulk wave sound velocity slower than the resonance frequency of the elastic wave resonator 101G or the elastic wave resonator 102G (silicon dioxide, glass, tantalum oxide, niobium oxide, tellurium oxide, etc.).
  • the thicker the dielectric layer 140 arranged on the electrode finger the larger the mass when the electrode finger vibrates. Therefore, the resonance frequency of the resonator and the frequency of the higher-order mode become lower due to the mass addition effect. Therefore, as in the second and third examples, by adjusting the film thickness of the dielectric layer 140 and the pitch of the electrode fingers, the frequency of the higher-order mode is lowered while maintaining the resonance frequency of the main mode. can do.
  • the dielectric layer 140 is made of a material having a bulk wave sound velocity faster than the sound velocity of the resonance frequency of the elastic wave resonator 101G or the elastic wave resonator 102G (glass, silicon nitride, aluminum nitride, alumina, silicon oxynitride, silicon carbide, etc.).
  • the thicker the dielectric layer the higher the resonance frequency of the resonator.
  • the frequency of the higher-order mode can be adjusted while maintaining the resonance frequency of the main mode.
  • the film thicknesses FT1 and FT2 of the dielectric layer 140 are defined as the distance from the upper surface of the electrode finger of the IDT electrode and the reflector to the surface of the dielectric layer 140. .. Further, as shown in FIG. 22, in the dielectric layer 140, the position of the upper surface of the dielectric in the portion with the electrode finger and the position of the upper surface of the dielectric in the portion without the electrode finger may be different.
  • the resonance frequency of the resonator, the frequency of the blocking region (upper limit frequency, lower limit frequency), and the frequency of the reflector (upper limit frequency, lower limit frequency) are the pitch of the electrode finger, the duty of the electrode finger, the thickness of the electrode finger, and the piezoelectricity. The same dependence tendency is shown for each parameter of the layer thickness and the thickness of the dielectric layer. As described above, with respect to the pitch of the electrode finger, the duty of the electrode finger, and the thickness of the electrode finger, the resonance frequency of each resonator and the frequency of the higher-order mode tend to decrease as the value of the parameter increases.
  • pitch ⁇ electrode finger duty ⁇ electrode finger film thickness / piezoelectric layer film thickness are set to the first value, the second value, and the third value, respectively
  • the first value of the shared reflector REF12 is the first value of the elastic wave resonator 101.
  • the main mode is a vibration mode such as S0 mode, SH1 mode, A1 mode, and higher-order vibration modes
  • the electrode finger duty x electrode finger film thickness x piezoelectric layer film thickness are the fourth value, the fifth value, and the sixth value, respectively
  • the fourth value of the shared reflector REF12 is the fifth value of the elastic wave resonator 101.
  • the main mode is not limited to the vibration mode described above, and other vibration modes can also be used.
  • a dielectric layer that covers the elastic wave resonator 101, the elastic wave resonator 102, and the common reflector REF12, and is made of a material having a bulk wave sound velocity slower than the resonance frequency of the elastic wave resonator.
  • the larger the thickness of this dielectric layer, the lower the resonance frequency of each resonator tends to be. Therefore, for the shared reflector REF12 and the elastic wave resonators 101 and 102, the values obtained by multiplying each of the first value, the second value, and the third value by the thickness of the dielectric layer ( electrode finger pitch ⁇ electrode finger duty).
  • a dielectric layer that covers the elastic wave resonator 101, the elastic wave resonator 102, and the common reflector REF12, and is made of a material having a bulk wave sound velocity faster than the sound velocity of the resonance frequency of the elastic wave resonator.
  • the larger the thickness of this dielectric layer, the higher the resonance frequency of each resonator tends to be. Therefore, for the shared reflector REF12 and the elastic wave resonators 101 and 102, the values obtained by multiplying each of the first value, the second value, and the third value by the inverse of the thickness of the dielectric layer ( electrode finger pitch ⁇ electrode).
  • the 4b value of the shared reflector REF12 is an elastic wave resonator. It is set so as to be between the 5b value of 101 and the 6b value of the elastic wave resonator 102.
  • the dielectric layer 140 is made of a material having a bulk sound velocity slower than the sound velocity of the resonance frequency of the elastic wave resonator, and the duty of each elastic wave resonator is 0.65 or less. Conditions are required.

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  • Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
PCT/JP2021/003249 2020-01-31 2021-01-29 弾性波デバイスおよびそれを備えたラダー型フィルタ Ceased WO2021153734A1 (ja)

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EP4459867A4 (en) * 2022-01-24 2025-08-06 Huawei Tech Co Ltd ACOUSTIC FILTER AND ELECTRONIC DEVICE

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US20240364305A1 (en) * 2023-04-06 2024-10-31 Skyworks Solutions, Inc. Acoustic wave device with interdigital transducer electrodes having two bus bars
KR102844660B1 (ko) * 2023-07-25 2025-08-11 (주)와이솔 질량 부가막이 전극 상에 형성된 표면 탄성파 필터
CN119602738B (zh) * 2024-10-28 2025-12-05 锐石创芯(重庆)微电子有限公司 声表面波器件及射频前端模组
CN121308715A (zh) * 2025-01-08 2026-01-09 锐石创芯(重庆)微电子有限公司 滤波器、射频前端模组和电子设备

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