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WO2025182618A1 - Résonateur à ondes élastiques, filtre à ondes élastiques, module frontal et dispositif de communication - Google Patents

Résonateur à ondes élastiques, filtre à ondes élastiques, module frontal et dispositif de communication

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Publication number
WO2025182618A1
WO2025182618A1 PCT/JP2025/005030 JP2025005030W WO2025182618A1 WO 2025182618 A1 WO2025182618 A1 WO 2025182618A1 JP 2025005030 W JP2025005030 W JP 2025005030W WO 2025182618 A1 WO2025182618 A1 WO 2025182618A1
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WO
WIPO (PCT)
Prior art keywords
polarization
layer
thickness
mixed
polarization direction
Prior art date
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Pending
Application number
PCT/JP2025/005030
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English (en)
Japanese (ja)
Inventor
敬 岩本
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Murata Manufacturing Co Ltd
Original Assignee
Murata Manufacturing Co Ltd
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Filing date
Publication date
Application filed by Murata Manufacturing Co Ltd filed Critical Murata Manufacturing Co Ltd
Publication of WO2025182618A1 publication Critical patent/WO2025182618A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
    • H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator

Definitions

  • the present invention relates to an acoustic wave resonator, an acoustic wave filter, a front-end module, and a communication device.
  • Patent Document 1 describes an acoustic wave resonator in which two piezoelectric layers are stacked between upper and lower electrodes. The polarization directions of the two piezoelectric layers are opposite to each other.
  • the present invention aims to provide an acoustic wave resonator, an acoustic wave filter, a front-end module, and a communication device that can improve resonator characteristics.
  • an acoustic wave resonator comprises a support member having a support substrate, a piezoelectric layer provided on a main surface of the support member, and a plurality of functional electrodes provided on opposing main surfaces of the piezoelectric layer.
  • the piezoelectric layer has a first polarization layer whose polarization direction is a first direction, a second polarization layer provided between the first polarization layer and the main surface of the support member and whose polarization direction is a second direction opposite to the first direction, and a first polarization direction mixed layer disposed between the first polarization layer and the second polarization layer and including a first portion whose polarization direction is the first direction and a second portion whose polarization direction is the second direction.
  • the first polarization layer, the second polarization layer, and the first polarization direction mixed layer are single crystals made of the same material.
  • An acoustic wave filter includes the above-described acoustic wave resonator.
  • a front-end module includes the above-described acoustic wave filter.
  • a communication device includes the above-described front-end module.
  • the acoustic wave resonator, acoustic wave filter, front-end module, and communication device of the present invention can improve resonator characteristics.
  • FIG. 1 is a plan view showing an elastic wave resonator according to a first preferred embodiment of the present invention.
  • FIG. 2 is a cross-sectional view taken along line II-II' of FIG.
  • FIG. 3 is a schematic cross-sectional view for explaining the polarization direction of the piezoelectric layer.
  • FIG. 4 is an explanatory diagram for explaining the polarization direction of the first polarizing layer in a plane along the line IV-IV' in FIG.
  • FIG. 5 is an explanatory diagram for explaining the polarization direction of the first polarization direction mixed layer in a plane taken along line V-V' in FIG.
  • FIG. 6 is an explanatory diagram for explaining the polarization direction of the first polarization direction mixed layer in a plane taken along line VI-VI' in FIG.
  • FIG. 7 is an explanatory diagram for explaining the polarization direction of the second polarizing layer in a plane along the line VII-VII' in FIG.
  • FIG. 8 is an explanatory diagram for explaining the relationship between the piezoelectric layer and the stress distribution of the bulk wave.
  • FIG. 9 is a graph showing the relationship between the thickness of the polarization direction mixed layer and the energy loss rate of the bulk wave.
  • FIG. 10 is a diagram illustrating a method for manufacturing an elastic wave resonator according to the first embodiment.
  • FIG. 11 is a cross-sectional view showing an elastic wave resonator according to the second preferred embodiment of the present invention.
  • FIG. 12 is a cross-sectional view showing an elastic wave resonator according to a third preferred embodiment of the present invention.
  • FIG. 13 is a cross-sectional view showing an elastic wave resonator according to a fourth preferred embodiment of the present invention.
  • FIG. 14 is a diagram showing the configuration of a communication device according to the fifth embodiment.
  • FIG. 15 is a cross-sectional view showing an elastic wave resonator according to a modified example.
  • Fig. 1 is a plan view showing an elastic wave resonator according to a first embodiment.
  • Fig. 2 is a cross-sectional view taken along line II-II' of Fig. 1.
  • An elastic wave resonator 10 according to the first embodiment is a resonator that utilizes bulk waves, i.e., a BAW (Bulk Acoustic Wave) element.
  • BAW Bulk Acoustic Wave
  • the acoustic wave resonator 10 has a support member 13, a piezoelectric layer 20, an upper electrode 31, a lower electrode 32, and connection electrodes 41 and 42.
  • the lower electrode 32, the piezoelectric layer 20, the upper electrode 31, and the connection electrodes 41 and 42 are layered in this order on the support member 13.
  • the thickness direction of the piezoelectric layer 20 is referred to as the Z direction
  • the direction perpendicular to the Z direction is referred to as the X direction
  • the direction perpendicular to the Z and X directions is referred to as the Y direction.
  • the X and Y directions are each parallel to the surface (first main surface 20a) of the piezoelectric layer 20.
  • a planar view refers to the positional relationship when viewed from a direction perpendicular to the first main surface 20a of the piezoelectric layer 20 (Z direction).
  • the support member 13 is disposed opposite the second main surface 20b of the piezoelectric layer 20.
  • the support member 13 comprises a support substrate 11 and an intermediate layer 12.
  • the support substrate 11 is made of silicon (Si), quartz, or the like.
  • the intermediate layer 12 is disposed between the support substrate 11 and the piezoelectric layer 20.
  • the intermediate layer 12 is formed of an insulating material such as silicon oxide. Note that the support member 13 may not have the intermediate layer 12, and the piezoelectric layer 20 may be disposed on the support substrate 11. In other words, the piezoelectric layer 20 is bonded to the support substrate 11 directly or via the intermediate layer 12 (insulating layer).
  • a recess 14 (hollow portion) is formed on the surface of the support member 13 (intermediate layer 12) facing the second main surface 20b of the piezoelectric layer 20.
  • the recess 14 is arranged so as to overlap, in plan view, with the excitation region of the resonator, which is formed by overlapping the piezoelectric layer 20, upper electrode 31, and lower electrode 32. This reduces energy loss of the bulk wave during excitation, resulting in good resonance characteristics.
  • the piezoelectric layer 20 is a flat plate having a first main surface 20a and a second main surface 20b opposite to the first main surface 20a.
  • the piezoelectric layer 20 is a substrate made of a single crystal of lithium niobate ( LiNbO3 ) or lithium tantalate ( LiTaO3 ).
  • the thickness of the piezoelectric layer 20 is not particularly limited, but is preferably 1 ⁇ m or less.
  • the piezoelectric layer 20 has a first polarization layer 21, a second polarization layer 22 provided between the first polarization layer 21 and the main surface of the support member 13, and a first mixed polarization layer 23 disposed between the first polarization layer 21 and the second polarization layer 22. That is, the piezoelectric layer 20 is configured by stacking the second polarization layer 22, the first mixed polarization layer 23, and the first polarization layer 21 in this order on the support member 13.
  • the first polarization layer 21, the first mixed polarization layer 23, and the second polarization layer 22 are single crystals made of the same material. The detailed configurations of the first polarization layer 21, the first mixed polarization layer 23, and the second polarization layer 22 will be described later with reference to Figure 3 and subsequent figures.
  • the term "single crystal" for the first polarization layer 21, first polarization direction mixed layer 23, and second polarization layer 22 constituting the piezoelectric layer 20 means that all crystal orientations can be identified in each layer.
  • the first polarization layer 21, first polarization direction mixed layer 23, and second polarization layer 22 constituting the piezoelectric layer 20 are lithium niobate or lithium tantalate, these layers can be said to be single crystals of lithium niobate or lithium tantalate if the a-axis and c-axis of the crystal can be identified.
  • the piezoelectric layer 20 is not limited to being single crystal, and may include partially amorphous regions and regions with defects or grain boundaries due to manufacturing variations, etc.
  • the upper electrode 31 and lower electrode 32 are provided on the opposing first and second major surfaces 20a and 20b of the piezoelectric layer 20, respectively. Specifically, the upper electrode 31 is provided on the first major surface 20a of the piezoelectric layer 20. The lower electrode 32 is provided on the second major surface 20b of the piezoelectric layer 20.
  • a portion of the upper electrode 31 and a portion of the lower electrode 32 overlap in the region that overlaps with the recess 14.
  • the piezoelectric layer 20 is disposed between the upper electrode 31 and the lower electrode 32 in the Z direction. This allows bulk waves to propagate between the upper electrode 31 and the lower electrode 32.
  • the region where the upper electrode 31 and the lower electrode 32 overlap in a planar view may be described as the excitation region of the resonator.
  • the upper electrode 31 extends in the X direction from the region overlapping with the recess 14 and is connected to a connection electrode 41 separate from the upper electrode 31.
  • the lower electrode 32 also extends from the region overlapping with the recess 14 to the opposite side of the upper electrode 31 and is connected to the connection electrode 42 through an opening OP formed in the piezoelectric layer 20.
  • the upper electrode 31 and the lower electrode 32 are formed of a metal such as aluminum (Al), platinum (Pt), copper (Cu), tungsten (W), or molybdenum (Mo), or an alloy containing at least one of these materials.
  • the upper electrode 31 and the lower electrode 32 may be laminated films. Furthermore, there may be an adhesion layer of Ti, NiCr, or the like between them and the support member 13 (intermediate layer 12).
  • FIG. 15 is a cross-sectional view showing an elastic wave resonator according to a modified example.
  • an acoustic multilayer film 15 may be provided on the support member 13 instead of the recess 14.
  • the acoustic multilayer film 15 has a laminated structure of low acoustic impedance layers 15a, 15c, and 15e, each having a relatively low acoustic impedance, and high acoustic impedance layers 15b and 15d, each having a relatively high acoustic impedance.
  • the low acoustic impedance layers 15a, 15c, and 15e are, for example, dielectric films made of SiO 2 , SiOC, or a polymer, or metal layers made of Al or the like.
  • the high acoustic impedance layers 15b and 15d are, for example, metal layers made of W, Pt, Mo, or the like, or dielectric layers made of hafnium oxide, tantalum oxide, tungsten oxide, or aluminum nitride.
  • the upper electrode 31, the lower electrode 32, and the recess 14 are each rectangular, but this is not limited to this and they may be other shapes, such as circular.
  • Figure 3 is a schematic cross-sectional view for explaining the polarization direction of the piezoelectric layer.
  • arrow P1 indicates the polarization direction of the first polarization layer 21.
  • Arrow P2 indicates the polarization direction of the second polarization layer 22.
  • Arrows P3 and P4 indicate the polarization direction of the first polarization direction mixed layer 23.
  • the first polarization layer 21 is provided in contact with the upper electrode 31 and is located in the uppermost layer of the piezoelectric layer 20.
  • the polarization direction (arrow P1) of the first polarization layer 21 is the first direction D1.
  • the second polarization layer 22 is provided in contact with the lower electrode 32 and is located in the lowermost layer of the piezoelectric layer 20.
  • the polarization direction (arrow P2) of the second polarization layer 22 is the second direction D2, opposite to the first direction D1.
  • the first polarization direction mixed layer 23 is located in an inner layer between the first polarization layer 21 and the second polarization layer 22.
  • the first polarization direction mixed layer 23 includes a first portion 23a whose polarization direction (arrow P3) is the first direction D1 and a second portion 23b whose polarization direction (arrow P4) is the second direction D2.
  • first direction D1 and the second direction D2 are directions that intersect with the X direction, Y direction, and Z direction, respectively. That is, the polarization directions of the first polarization layer 21, the first polarization direction mixed layer 23, and the second polarization layer 22 intersect with the thickness direction (Z direction) of the piezoelectric layer 20. Note that the first direction D1 and the second direction D2 may be parallel to the Z direction. Also, in Figure 3, the boundary between the first portion 23a and the second portion 23b of the first polarization direction mixed layer 23 is shown as a zigzag dashed line. However, Figure 3 is merely a schematic illustration, and the boundary between the first portion 23a and the second portion 23b may be formed with a random pattern including straight and curved portions.
  • the polarization direction (first direction D1) of the first portion 23a is opposite to the polarization direction (second direction D2) of the second portion 23b. Furthermore, the polarization direction (first direction D1) of the first portion 23a of the first polarization direction mixed layer 23 is the same as the polarization direction (first direction D1) of the first polarization layer 21. Furthermore, the polarization direction (second direction D2) of the second portion 23b of the first polarization direction mixed layer 23 is the same as the polarization direction (second direction D2) of the second polarization layer 22.
  • the first portion 23a of the first polarization direction mixed layer 23 is in direct contact with the first polarization layer 21.
  • the second portion 23b of the first polarization direction mixed layer 23 is in direct contact with the second polarization layer 22.
  • the area ratio of the first portion 23a to the second portion 23b increases as it approaches the first polarization layer 21 in the Z direction.
  • the area ratio of the second portion 23b to the first portion 23a increases as it approaches the second polarization layer 22 in the Z direction.
  • the polarization directions of the first polarization layer 21, the first polarization direction mixed layer 23, and the second polarization layer 22 will be described separately as a Z-direction component and a horizontal direction component (a direction parallel to a plane defined by the X and Y directions).
  • the Z-direction component of the polarization direction of the first polarization layer 21 (first direction D1) is opposite to the Z-direction component of the polarization direction of the second polarization layer 22 (second direction D2).
  • the horizontal direction component of the polarization direction of the first polarization layer 21 (first direction D1) is opposite to the horizontal direction component of the polarization direction of the second polarization layer 22 (second direction D2).
  • the Z-direction component of the polarization direction (first direction D1) of the first portion 23a is oriented in the opposite direction to the Z-direction component of the polarization direction (second direction D2) of the second portion 23b. Furthermore, the horizontal component of the polarization direction (first direction D1) of the first portion 23a is oriented in the opposite direction to the horizontal component of the polarization direction (second direction D2) of the second portion 23b.
  • the Z-direction component of the polarization direction (first direction D1) of the first portion 23a of the first polarization direction mixed layer 23 is oriented in the same direction as the Z-direction component of the polarization direction (first direction D1) of the first polarization layer 21.
  • the horizontal direction component of the polarization direction (first direction D1) of the first portion 23a of the first polarization direction mixed layer 23 is oriented in the same direction as the horizontal direction component of the polarization direction (first direction D1) of the first polarization layer 21.
  • the Z-direction component of the polarization direction (second direction D2) of the second portion 23b of the first polarization direction mixed layer 23 is oriented in the same direction as the Z-direction component of the polarization direction (second direction D2) of the second polarization layer 22.
  • the horizontal direction component of the polarization direction (second direction D2) of the second portion 23b of the first polarization direction mixed layer 23 is oriented in the same direction as the horizontal direction component of the polarization direction (second direction D2) of the second polarization layer 22.
  • Figure 4 is an explanatory diagram illustrating the polarization direction of the first polarization layer in a plane taken along line IV-IV' in Figure 3.
  • Figure 5 is an explanatory diagram illustrating the polarization direction of the first polarization direction mixed layer in a plane taken along line V-V' in Figure 3.
  • Figure 6 is an explanatory diagram illustrating the polarization direction of the first polarization direction mixed layer in a plane taken along line VI-VI' in Figure 3.
  • Figure 7 is an explanatory diagram illustrating the polarization direction of the second polarization layer in a plane taken along line VII-VII' in Figure 3.
  • Figures 4 to 7 show the results of observing the polarization directions of the first polarization layer 21, the first polarization direction mixed layer 23, and the second polarization layer 22 using a scanning probe microscope (SPM). Specifically, in PRM (Piezo Response Microscope) images of the horizontal surfaces of the first polarization layer 21, the first polarization direction mixed layer 23, and the second polarization layer 22, regions with different polarization directions appear as regions showing different colors.
  • SPM scanning probe microscope
  • the polarization direction of the first polarization layer 21 is the first direction D1 throughout the entire region.
  • the polarization direction of the second polarization layer 22 is the second direction D2, opposite to the first direction D1, throughout the entire region.
  • the first polarization direction mixed layer 23 is composed of a first portion 23a whose polarization direction is the first direction D1 and a second portion 23b whose polarization direction is the second direction D2. Furthermore, the ratio of the area of the first portion 23a to the area of the second portion 23b varies depending on the position of the first polarization direction mixed layer 23 in the Z direction.
  • the area of the first portion 23a whose polarization direction is the first direction D1 is larger than the area of the second portion 23b whose polarization direction is the second direction D2.
  • the area of the second portion 23b whose polarization direction is the second direction D2 is larger than the area of the first portion 23a whose polarization direction is the first direction D1.
  • the first polarization direction mixed layer 23 is formed so that the area proportion of the first portion 23a increases the closer it is to the first polarization layer 21 in the Z direction, and the area proportion of the second portion 23b increases the closer it is to the second polarization layer 22.
  • Figure 8 is an explanatory diagram illustrating the relationship between the piezoelectric layer and the stress distribution of the bulk wave.
  • Figure 9 is a graph showing the relationship between the thickness of the polarization direction mixed layer and the energy loss rate of the bulk wave.
  • the thickness t1 of the first polarization layer 21 is equal to the thickness t2 of the second polarization layer 22.
  • the thickness t3 of the first polarization direction mixed layer 23 is thinner than the thickness t1 of the first polarization layer 21 and the thickness t2 of the second polarization layer 22.
  • the thickness t1 of the first polarization layer 21 and the thickness t2 of the second polarization layer 22 are each approximately 50 nm or more and 500 nm or less.
  • the thickness t3 of the first polarization direction mixed layer 23 is approximately 5 nm or more and 120 nm or less.
  • the thickness t3 of the first polarization direction mixed layer 23 is preferably set to a thickness that ensures that lithium tantalate crystal and lithium niobate crystal exhibit sufficient piezoelectricity, and that ensures that three or more elementary lattices are included in the c-axis direction in lithium tantalate crystal and lithium niobate crystal, which have a pseudo-ilmenite structure, i.e., a thickness of 5 nm or more.
  • the thickness t3 of the first polarization direction mixed layer 23 is thinner than 1/8 of the sum of the thicknesses of the first polarization layer 21 and the second polarization layer 22 (t1 + t2). Furthermore, the total thickness (t1 + t3 ⁇ 1/2) of the thickness t1 of the first polarization layer 21 and 1/2 of the thickness t3 of the first polarization direction mixed layer 23 in contact with the first polarization layer 21 is equivalent to the total thickness (t2 + t3 ⁇ 1/2) of the thickness t2 of the second polarization layer 22 and 1/2 of the thickness t3 of the first polarization direction mixed layer 23 in contact with the second polarization layer 22.
  • the main bulk wave resonates at half the wavelength in each of the first polarization layer 21 and the second polarization layer 22.
  • the stress in the piezoelectric layer 20 caused by the main bulk wave is greatest at the center in the Z direction of the first polarization layer 21 and the center in the Z direction of the second polarization layer 22. Furthermore, the stress in the piezoelectric layer 20 caused by the main bulk wave is least at the position where it overlaps with the first polarization direction mixed layer 23. As a result, even when the piezoelectric layer 20 has a configuration including the first polarization direction mixed layer 23, energy loss of the main bulk wave is suppressed.
  • the elastic wave resonator 10 of this embodiment can reduce the spurious waves while suppressing deterioration of the main bulk wave. As a result, the elastic wave resonator 10 of this embodiment can improve the resonator characteristics.
  • examples of unwanted waves that differ from the main bulk waves include waves in modes influenced by the ends of the upper electrode 31 or lower electrode 32, and waves in modes influenced by the edges of the membrane portion of the piezoelectric layer 20.
  • the first polarization layer 21, the first polarization direction mixed layer 23, and the second polarization layer 22 are integrally formed from the same piezoelectric material. In other words, there is no piezoelectric material or conductive material different from that of the first polarization layer 21, the first polarization direction mixed layer 23, and the second polarization layer 22 between the layers of the piezoelectric layer 20.
  • the different elements may diffuse into the piezoelectric layers 20 and affect the piezoelectric properties of the piezoelectric layers 20, which could cause the resonance characteristics to change over time. Furthermore, the different material will become a layer that does not contribute to excitation, which could result in a deterioration of the resonance characteristics. Furthermore, if a conductive material is provided as the different material, parasitic capacitance may be generated, which could significantly deteriorate the resonator characteristics. Alternatively, if an amorphous piezoelectric material is provided as the different material, it will become a layer that does not contribute to excitation, which could result in a deterioration of the resonator characteristics.
  • the first polarization layer 21, the first polarization direction mixed layer 23, and the second polarization layer 22 are integrally formed from the same piezoelectric material, which makes it possible to suppress deterioration of the resonator characteristics compared to when different materials are provided between the layers.
  • the horizontal axis of the graph shown in Figure 9 is the thickness t3 of the first polarization direction mixed layer 23, and the vertical axis is the energy loss rate of the main bulk wave.
  • the energy loss rate of the main bulk wave is suppressed to a range of approximately 10% or less.
  • the thickness t3 of the first polarization direction mixed layer 23 is greater than 172.5 nm, the energy loss rate of the main bulk wave becomes greater than 10%.
  • the configuration of the elastic wave resonator 10 described above is merely an example and can be modified as appropriate.
  • the thickness t1 of the first polarization layer 21, the thickness t2 of the second polarization layer 22, the thickness t3 of the first polarization direction mixed layer 23, the resonant frequency, and other values are merely examples and can be modified as appropriate depending on the characteristics required of the elastic wave resonator 10.
  • (Manufacturing method) 10 is an explanatory diagram illustrating a manufacturing method of an acoustic wave resonator according to the first embodiment.
  • a transfer substrate 50 e.g., a silicon substrate
  • a piezoelectric layer 20 is directly bonded to a main surface of the transfer substrate 50 (step ST1).
  • the piezoelectric layer 20 is, for example, a lithium niobate (LiNbO 3 ) single crystal substrate.
  • the polarization direction (arrow P0) of the piezoelectric layer 20 is such that the +c plane faces the surface opposite to the bonding surface (first main surface 20 a) with the transfer substrate 50.
  • the second main surface 20b of the piezoelectric layer 20 is ground to thin it (step ST2). At this time, multiple recesses are formed in the second main surface 20b of the piezoelectric layer 20.
  • a metal layer 51 is formed on the second main surface 20b of the piezoelectric layer 20 (step ST3).
  • the metal layer 51 is patterned so as not to be electrically connected to the transfer substrate 50. Note that in steps ST3 and ST4, the piezoelectric layer 20 is shown enlarged in the thickness direction compared to step ST2 to make the drawings easier to see.
  • a reference potential Vref (e.g., ground potential) is supplied to the transfer substrate 50, and while heating, a positive potential Vp is supplied to the metal layer 51. This applies an electric field to the piezoelectric layer 20.
  • step ST4 the polarization direction on the second main surface 20b side of the piezoelectric layer 20 is reversed (step ST4).
  • step ST4 the electric field strength is controlled to be greater than the coercive electric field of the piezoelectric layer 20, thereby reversing the polarization direction from the second main surface 20b side.
  • the polarization direction is then reversed from the second main surface 20b to the center of the thickness direction of the piezoelectric layer 20, forming a second polarization layer 22.
  • a first polarization layer 21 is formed from the center of the thickness direction of the piezoelectric layer 20 to the first main surface 20a, with the polarization direction in the initial state being maintained.
  • the thickness of the second polarization layer 22 formed in step ST4 can be controlled by the electric field strength.
  • the second polarization layer 22 becomes thicker by increasing the positive potential Vp applied to the metal layer 51, and becomes thinner by decreasing the positive potential Vp.
  • the areas where the recesses are formed form starting points for polarization direction reversal, making the polarization direction reversal more likely to progress than in areas where no recesses are formed.
  • a first polarization direction mixed layer 23 in which polarization directions are mixed, is formed in the center of the thickness direction of the piezoelectric layer 20.
  • the above steps form the first polarization layer 21, the second polarization layer 22, and the first mixed polarization direction layer 23 disposed between the first polarization layer 21 and the second polarization layer 22.
  • the polarization direction, thickness, etc. of the first polarization layer 21, the second polarization layer 22, and the first mixed polarization direction layer 23 can be controlled by applying an electric field to one piezoelectric layer 20. Therefore, there is no need to provide a different material, such as another piezoelectric material or a conductive material, between the piezoelectric layers 20. As a result, a piezoelectric layer 20 can be formed that has excellent reliability, moisture resistance, and good resonance characteristics.
  • FIG 10 only shows the manufacturing process of the piezoelectric layer 20, after step ST4, a lower electrode 32 and various wiring are formed on the second main surface 20b of the piezoelectric layer 20, and it is then bonded to the main surface of the support member 13 (see Figure 2).
  • the piezoelectric layer 20 is laminated on the support member 13 in the order of the second polarization layer 22, first mixed polarization direction layer 23, and first polarization layer 21 (see Figure 1).
  • the transfer substrate 50 is removed, an upper electrode 31 and various wiring are formed, and a recess 14 is formed in the support member 13, completing the manufacturing of the elastic wave resonator 10.
  • any method may be used for the processes from step ST4 onwards.
  • Second Embodiment 11 is a cross-sectional view showing an elastic wave resonator according to the second embodiment.
  • an elastic wave resonator 10A according to the second embodiment differs from the first embodiment in that a piezoelectric layer 20A further includes a third polarization layer 24 and a second polarization direction mixed layer 25.
  • the third polarization layer 24 is provided below the second polarization layer 22. That is, the third polarization layer 24 is provided between the second polarization layer 22 and the main surface of the support member 13 (see Figure 2), and its polarization direction is the first direction D1.
  • the second polarization direction mixed layer 25 is disposed between the second polarization layer 22 and the third polarization layer 24. Like the first polarization direction mixed layer 23, the second polarization direction mixed layer 25 includes a first portion whose polarization direction is the first direction D1 and a second portion whose polarization direction is the second direction D2.
  • the thickness t1 of the first polarization layer 21 is equal to the thickness t4 of the third polarization layer 24.
  • the thickness t2 of the second polarization layer 22 is thicker than the thickness t1 of the first polarization layer 21 and the thickness t4 of the third polarization layer 24.
  • the bulk wave energy of the main resonance leaks to the functional electrode from the topmost and bottommost polarization layers in contact with the functional electrode (here, the first polarization layer 21 and the third polarization layer 24 are referred to as the outer layers).
  • the outer layer and the inner layer (the polarization layer located between the topmost and bottommost polarization layers, here the second polarization layer 22) have the same thickness, unwanted waves will be generated due to the energy leaking to the functional electrode. Therefore, taking into consideration that bulk wave energy leaks to the functional electrode in the outer layer, the thickness of the outer layer is made thinner than the thickness of the inner layer so that the node of the main bulk wave stress is located at the functional electrode, thereby suppressing unwanted waves caused by bulk wave energy leaking to the functional electrode.
  • the total thickness (t1 + t3 ⁇ 1/2) of the thickness t1 of the first polarization layer 21 and 1/2 of the thickness t3 of the first mixed polarization layer 23 in contact with the first polarization layer 21 is equal to the total thickness (t4 + t5 ⁇ 1/2) of the thickness t4 of the third polarization layer 24 and 1/2 of the thickness t5 of the second mixed polarization layer 25 in contact with the third polarization layer 24.
  • the midpoint of the mixed polarization layer is the stress node of the main bulk wave.
  • the energy lost by the main bulk wave due to the mixed polarization layer is minimized, and good resonance characteristics can be obtained.
  • the elastic wave resonator 10A according to the second embodiment can also suppress energy loss in the main bulk waves and reduce unwanted waves.
  • the piezoelectric layer 20A has three or more polarization layers including the first polarization layer 21 and the second polarization layer 22, and two or more polarization direction mixed layers including the first polarization direction mixed layer 23, which are provided between the three or more polarization layers.
  • the total thickness of the uppermost polarization layer (e.g., first polarization layer 21) in contact with the upper electrode 31 (one of the functional electrodes) and half the thickness of the mixed polarization layer (e.g., first polarization layer 23) in contact with the uppermost polarization layer is equal to the total thickness of the lowermost polarization layer (e.g., third polarization layer 24) in contact with the lower electrode 32 (the other functional electrode) and half the thickness of the mixed polarization layer (e.g., second polarization layer 25) in contact with the lowermost polarization layer.
  • (Third embodiment) 12 is a cross-sectional view showing an elastic wave resonator according to a third embodiment.
  • the piezoelectric layers 20 and 20A have two polarized layers and one mixed-polarization layer, or three polarized layers and two mixed-polarization layers, but are not limited to this.
  • an elastic wave resonator 10B according to the third embodiment differs from the first and second embodiments described above in that the piezoelectric layer 20B further includes a fourth polarized layer 26 and a third mixed-polarization layer 27.
  • the fourth polarization layer 26 is provided below the third polarization layer 24. That is, the fourth polarization layer 26 is provided between the third polarization layer 24 and the main surface of the support member 13 (see Figure 2), and its polarization direction is the second direction D2.
  • the third polarization direction mixed layer 27 is disposed between the third polarization layer 24 and the fourth polarization layer 26. Like the first polarization direction mixed layer 23 and the second polarization direction mixed layer 25, the third polarization direction mixed layer 27 includes a first portion whose polarization direction is the first direction D1 and a second portion whose polarization direction is the second direction D2.
  • the thickness t1 of the first polarization layer 21 is equal to the thickness t6 of the fourth polarization layer 26.
  • the thickness t2 of the second polarization layer 22, which is the inner layer between the first polarization layer 21 and the fourth polarization layer 26, is equal to the thickness t4 of the third polarization layer 24.
  • the thickness t2 of the second polarization layer 22 and the thickness t4 of the third polarization layer 24 are thicker than the thickness t1 of the first polarization layer 21 and the thickness t6 of the fourth polarization layer 26.
  • the total thickness (t1 + t3 ⁇ 1/2) of the thickness t1 of the first polarization layer 21 and 1/2 of the thickness t3 of the first polarization direction mixed layer 23 in contact with the first polarization layer 21 is equal to the total thickness (t6 + t7 ⁇ 1/2) of the thickness t6 of the fourth polarization layer 26 and 1/2 of the thickness t7 of the third polarization direction mixed layer 27 in contact with the fourth polarization layer 26.
  • the total thickness (t2 + t3 ⁇ 1/2 + t5 ⁇ 1/2) of the thickness t2 of the second polarization layer 22, 1/2 of the thickness t3 of the first polarization direction mixed layer 23 in contact with the second polarization layer 22, and 1/2 of the thickness of the second polarization direction mixed layer 25 in contact with the second polarization layer 22 is equivalent to the total thickness (t4 + t5 ⁇ 1/2 + t7 ⁇ 1/2) of the thickness t4 of the third polarization layer 24, 1/2 of the thickness t5 of the second polarization direction mixed layer 25 in contact with the third polarization layer 24, and 1/2 of the thickness t7 of the third polarization direction mixed layer 27 in contact with the third polarization layer 24.
  • the piezoelectric layer 20B has four or more polarization layers including the first polarization layer 21 and the second polarization layer 22, and three or more polarization direction mixed layers including the first polarization direction mixed layer 23, which are provided between the four or more polarization layers.
  • the sum of the thickness of each of the multiple inner polarization layers e.g., second polarization layer 22, third polarization layer 24 located between the topmost polarization layer and the bottommost polarization layer and half the thickness of the mixed polarization layers in contact with each of the multiple inner polarization layers (first polarization direction mixed layer 23 and second polarization direction mixed layer 25 in contact with the second polarization layer 22, and second polarization direction mixed layer 25 and third polarization direction mixed layer 27 in contact with the third polarization layer 24) is equal to each other.
  • FIG. 13 is a cross-sectional view showing an elastic wave resonator according to a fourth embodiment.
  • the piezoelectric layer 20B includes four polarization layers and three mixed polarization layers.
  • the present invention is not limited to this.
  • an elastic wave resonator 10C according to the fourth embodiment differs from the first to third embodiments in that the piezoelectric layer 20C further includes a fifth polarization layer 28 and a fourth mixed polarization layer 29.
  • the fifth polarization layer 28 is provided below the fourth polarization layer 26. That is, the fifth polarization layer 28 is provided between the fourth polarization layer 26 and the main surface of the support member 13 (see Figure 2), and its polarization direction is the first direction D1.
  • the fourth polarization direction mixed layer 29 is disposed between the fourth polarization layer 26 and the fifth polarization layer 28. Like the first polarization direction mixed layer 23 to the third polarization direction mixed layer 27, the fourth polarization direction mixed layer 29 includes a first portion whose polarization direction is the first direction D1 and a second portion whose polarization direction is the second direction D2.
  • the thickness t1 of the first polarization layer 21 is equal to the thickness t8 of the fifth polarization layer 28.
  • the thickness t2 of the second polarization layer 22, which is the inner layer between the first polarization layer 21 and the fifth polarization layer 28, is equal to the thickness t4 of the third polarization layer 24 and the thickness t6 of the fourth polarization layer 26, respectively.
  • the thickness t2 of the second polarization layer 22, the thickness t4 of the third polarization layer 24, and the thickness t6 of the fourth polarization layer 26 are thicker than the thickness t1 of the first polarization layer 21 and the thickness t8 of the fifth polarization layer 28.
  • the total thickness (t1 + t3 ⁇ 1/2) of the thickness t1 of the first polarization layer 21 and 1/2 of the thickness t3 of the first polarization direction mixed layer 23 in contact with the first polarization layer 21 is equal to the total thickness (t8 + t9 ⁇ 1/2) of the thickness t8 of the fifth polarization layer 28 and 1/2 of the thickness t9 of the fourth polarization direction mixed layer 29 in contact with the fifth polarization layer 28.
  • the total thickness (t2 + t3 ⁇ 1/2 + t5 ⁇ 1/2) of the thickness t2 of the second polarization layer 22, 1/2 of the thickness t3 of the first polarization direction mixed layer 23 in contact with the second polarization layer 22, and 1/2 of the thickness of the second polarization direction mixed layer 25 in contact with the second polarization layer 22 is 1/2 of the thickness t4 of the third polarization layer 24, 1/2 of the thickness t5 of the second polarization direction mixed layer 25 in contact with the third polarization layer 24, and and the total thickness (t6 + t7 ⁇ 1/2 + t9 ⁇ 1/2) of the thickness t6 of the fourth polarization layer 26, 1/2 of the thickness t7 of the third polarization direction mixed layer 27 in contact with the fourth polarization layer 26, and 1/2 of the thickness t9 of the fourth polarization direction mixed layer 29 in contact with the fourth polarization layer 26.
  • the number of layers, thicknesses, and thickness relationships between layers of the multiple polarized layers and multiple polarization direction mixed layers are merely examples and can be changed as appropriate.
  • the communication device 100 according to the fifth embodiment is, for example, a mobile terminal such as a mobile phone, a smartphone, or a tablet terminal, or a personal computer equipped with a communication function.
  • the communication device 100 may be a backhaul communication device that performs communication between base stations and communication between a base station and a core network.
  • the communication device 100 includes a front-end module 101, an antenna 102, an RF-IC (Radio Frequency Integrated Circuit) 104, and a BB-IC (Baseband Integrated Circuit) 105.
  • RF-IC Radio Frequency Integrated Circuit
  • BB-IC Baseband Integrated Circuit
  • BB-IC105 constitutes a baseband signal processing circuit.
  • BB-IC105 supplies baseband signals to RF-IC104.
  • RF-IC104 performs high-frequency signal processing of transmitted and received signals.
  • the front-end module 101 is connected between the antenna 102 and the RF-IC 104.
  • high-frequency transmission signals are output from the front-end module 101 to the antenna 102, and high-frequency reception signals from the antenna 102 can be received by the front-end module 101.
  • the front-end module 101 includes a switch SW, power amplifiers 111a and 111b, matching circuits 112a and 112b, transmit filters 113a and 113b, a multiplexer 114, matching circuits 115a and 115b, and low-noise amplifiers 116a and 116b.
  • switch SW When transmitting a high-frequency signal, switch SW is switched to transmit filter 113a or transmit filter 113b.
  • the high-frequency transmit signal output from RF-IC 104 is amplified by power amplifier 111a or power amplifier 111b, and input to transmit filter 113a or transmit filter 113b via matching circuits 112a, 112b.
  • the band of transmit filter 113a is, for example, n77 of the 5G NR (New Radio) standard.
  • the frequency range of n77 for 5G NR is from 3.3 GHz to 4.2 GHz.
  • the band of transmit filter 113b is, for example, n79 of the 5G NR standard.
  • the frequency range of n79 for 5G NR is from 4.4 GHz to 5.0 GHz.
  • the high-frequency transmission signal that passes through transmission filter 113a or transmission filter 113b is fed to antenna 102.
  • Multiplexer 114 When receiving a high-frequency signal, switch SW is switched to the multiplexer 114 side.
  • Multiplexer 114 includes receive filters 117a and 117b and a matching circuit 118.
  • the band of receive filter 117a is, for example, n77 of the 5G NR standard.
  • the band of receive filter 117b is, for example, n79 of the 5G NR standard.
  • the received signal from antenna 102 passes through receiving filter 117a or 117b via matching circuit 118.
  • the high-frequency received signal that passes through receiving filter 117a or 117b is transmitted to RF-IC 104 via matching circuits 115a, 115b and low-noise amplifier 116a or 116b.
  • At least one of the transmit filters 113a, 113b and the receive filters 117a, 117b of the multiplexer 114 is an acoustic wave filter that includes any one of the acoustic wave resonators 10, 10A, 10B, and 10C described above.
  • the front-end module 101 includes at least one of the transmit filters 113a, 113b and the receive filters 117a, 117b of the multiplexer 114.
  • the communication device 100 also includes the front-end module 101.
  • this disclosure can also be configured as follows.
  • a support member including a support substrate; a piezoelectric layer provided on a main surface of the support member; a plurality of functional electrodes provided on opposing principal surfaces of the piezoelectric layer,
  • the piezoelectric layer a first polarization layer having a polarization direction in a first direction; a second polarization layer provided between the first polarization layer and the main surface of the support member, the second polarization layer having a polarization direction in a second direction opposite to the first direction; a first polarization direction mixed layer disposed between the first polarization layer and the second polarization layer, the first polarization direction mixed layer including a first portion whose polarization direction is the first direction and a second portion whose polarization direction is the second direction;
  • the elastic wave resonator wherein the first polarization layer, the second polarization layer, and the first polarization direction mixed layer are single crystals made of the same material.
  • the total thickness of the first polarization layer and half the thickness of the first polarization direction mixed layer in contact with the first polarization layer is The elastic wave resonator according to any one of (1) to (3), wherein the thickness of the second polarization layer is equal to the total thickness of the second polarization layer and half the thickness of the first polarization direction mixed layer in contact with the second polarization layer.
  • the piezoelectric layer has three or more polarization layers including the first polarization layer and the second polarization layer, and two or more polarization direction mixed layers including the first polarization direction mixed layer provided between the three or more polarization layers,
  • the elastic wave resonator according to any one of (1) to (4), wherein the total thickness of the uppermost polarization layer among the plurality of polarization layers that is in contact with one of the functional electrodes and half the thickness of the mixed polarization direction layer in contact with the uppermost polarization layer is equal to the total thickness of the lowermost polarization layer among the plurality of polarization layers that is in contact with the other functional electrode and half the thickness of the mixed polarization direction layer in contact with the lowermost polarization layer.
  • the piezoelectric layer has four or more polarization layers including the first polarization layer and the second polarization layer, and three or more polarization direction mixed layers including the first polarization direction mixed layer provided between the four or more polarization layers,
  • the elastic wave resonator according to any one of (1) to (5), wherein, among the plurality of polarization layers, except for the uppermost polarization layer in contact with one of the functional electrodes and the lowermost polarization layer in contact with the other functional electrode, the sum of each thickness of the plurality of inner polarization layers located between the uppermost polarization layer and the lowermost polarization layer and half the thickness of the mixed polarization direction layer in contact with each of the plurality of inner polarization layers is equal to each other.
  • the piezoelectric layer is a third polarization layer provided between the second polarization layer and the main surface of the support member, the third polarization layer having a polarization direction in the first direction; and a second polarization direction mixed layer disposed between the second polarization layer and the third polarization layer, the second polarization direction mixed layer including a first portion whose polarization direction is the first direction and a second portion whose polarization direction is the second direction.
  • the total thickness of the first polarization layer and half the thickness of the first polarization direction mixed layer in contact with the first polarization layer is The elastic wave resonator according to (7), wherein the thickness is equal to the total thickness of the third polarization layer and half the thickness of the second polarization direction mixed layer in contact with the third polarization layer.
  • the piezoelectric layer is a fourth polarization layer provided between the third polarization layer and the main surface of the support member, the fourth polarization layer having a polarization direction in the second direction; a third polarization direction mixed layer disposed between the third polarization layer and the fourth polarization layer, the third polarization direction mixed layer including a first portion whose polarization direction is the first direction and a second portion whose polarization direction is the second direction;
  • the total thickness of the first polarization layer and half the thickness of the first polarization direction mixed layer in contact with the first polarization layer is The elastic wave resonator according to (9), wherein the thickness is equal to the total thickness of the fourth polarization layer and half the thickness of the third polarization direction mixed layer in contact with the fourth polarization layer.
  • the total thickness of the thickness of the second polarization layer, half the thickness of the first polarization direction mixed layer in contact with the second polarization layer, and half the thickness of the second polarization direction mixed layer in contact with the second polarization layer is The elastic wave resonator according to (9), wherein the thickness of the third polarization layer is equal to the total thickness of the third polarization layer, half the thickness of the second polarization direction mixed layer in contact with the third polarization layer, and half the thickness of the third polarization direction mixed layer in contact with the third polarization layer.
  • the piezoelectric layer is a fifth polarization layer provided between the fourth polarization layer and the main surface of the support member, the fifth polarization layer having a polarization direction in the first direction; a fourth polarization direction mixed layer disposed between the fourth polarization layer and the fifth polarization layer, the fourth polarization direction mixed layer including a first portion whose polarization direction is the first direction and a second portion whose polarization direction is the second direction;
  • the elastic wave resonator according to (9), (13) The total thickness of the first polarization layer and half the thickness of the first polarization direction mixed layer in contact with the first polarization layer is The elastic wave resonator according to (12), wherein the thickness is equal to the total thickness of the fifth polarization layer and half the thickness of the fourth polarization direction mixed layer in contact with the fifth polarization layer.
  • the total thickness of the thickness of the second polarization layer, half the thickness of the first polarization direction mixed layer in contact with the second polarization layer, and half the thickness of the second polarization direction mixed layer in contact with the second polarization layer is a total thickness of the thickness of the third polarization layer, half the thickness of the second polarization direction mixed layer in contact with the third polarization layer, and half the thickness of the third polarization direction mixed layer in contact with the third polarization layer; and

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  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)

Abstract

La présente invention concerne un résonateur à ondes élastiques qui comprend : un élément de support comprenant un substrat de support ; une couche piézoélectrique disposée sur une surface principale de l'élément de support ; et une pluralité d'électrodes fonctionnelles disposées respectivement sur des surfaces principales opposées de la couche piézoélectrique. La couche piézoélectrique comprend : une première couche de polarisation ayant une direction de polarisation dans une première direction ; une deuxième couche de polarisation disposée entre la première couche de polarisation et la surface principale de l'élément de support et ayant une direction de polarisation dans une deuxième direction opposée à la première direction ; et une première couche mixte de direction de polarisation disposée entre la première couche de polarisation et la deuxième couche de polarisation et comprenant une première partie ayant une direction de polarisation dans la première direction et une deuxième partie ayant une direction de polarisation dans la deuxième direction. La première couche de polarisation, la deuxième couche de polarisation et la première couche mixte de direction de polarisation sont des monocristaux constitués du même matériau.
PCT/JP2025/005030 2024-02-27 2025-02-14 Résonateur à ondes élastiques, filtre à ondes élastiques, module frontal et dispositif de communication Pending WO2025182618A1 (fr)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01158811A (ja) * 1987-12-15 1989-06-21 Fujitsu Ltd 圧電振動子の製造方法
JPH1051262A (ja) * 1996-04-16 1998-02-20 Matsushita Electric Ind Co Ltd 圧電振動子とその製造方法
JP2003133891A (ja) * 2001-10-26 2003-05-09 Tayca Corp 積層圧電振動子
JP2017224969A (ja) * 2016-06-15 2017-12-21 学校法人早稲田大学 圧電素子及び圧電変換装置
US20230108824A1 (en) * 2021-10-01 2023-04-06 Skyworks Global Pte. Ltd. Bulk acoustic wave device with piezoelectric layer formed by atomic layer deposition

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01158811A (ja) * 1987-12-15 1989-06-21 Fujitsu Ltd 圧電振動子の製造方法
JPH1051262A (ja) * 1996-04-16 1998-02-20 Matsushita Electric Ind Co Ltd 圧電振動子とその製造方法
JP2003133891A (ja) * 2001-10-26 2003-05-09 Tayca Corp 積層圧電振動子
JP2017224969A (ja) * 2016-06-15 2017-12-21 学校法人早稲田大学 圧電素子及び圧電変換装置
US20230108824A1 (en) * 2021-10-01 2023-04-06 Skyworks Global Pte. Ltd. Bulk acoustic wave device with piezoelectric layer formed by atomic layer deposition

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