Elastic wave resonator, manufacturing method and communication device

Abstract

The present invention provides an elastic wave resonator, a manufacturing method and a communication device. The elastic wave resonator includes a top electrode, a piezoelectric film layer and a bottom electrode. The top electrode includes a first bus bar, a second bus bar, a first interdigital electrode and a second interdigital electrode. The first interdigital electrode and the second interdigital electrode are both located between the first bus bar and the second bus bar. The piezoelectric film layer is located below the top electrode. The bottom electrode is located below the piezoelectric film layer. In the direction from the first bus bar to the second bus bar, a load bar is provided at the end of the bottom electrode. The extension direction of the load bar is perpendicular to the direction from the first bus bar to the second bus bar. The present invention reduces the speed of sound in the region by providing a load bar at the end of the bottom electrode, thereby suppressing the lateral high-order mode. Since the electric potential of the entire bottom electrode is the same, even if the load bar is a conductive material, there will be no short circuit. The device has high reliability, simple manufacturing process, and low requirements for photolithography accuracy and alignment accuracy.

Description

Technical Field

[0001] The invention belongs to the technical field of microelectronics and relates to an elastic wave resonator, a manufacturing method and communication equipment. Background Art

[0002] Modern wireless communication technology requires RF filters to have low loss, large bandwidth, high frequency and flat passband. Acoustic wave filter technology is currently the most widely used filter technology, in which acoustic wave modes above the 0th order excited by the longitudinal electric field have great advantages in frequency, bandwidth, and capacitance density. However, for all acoustic resonators, transverse high-order modes will appear due to the finite length of the transverse waveguide. They generally appear near the resonant frequency, anti-resonant frequency and between the resonant frequency and anti-resonant frequency of the resonator, resulting in ripples in the passband of the corresponding filter. Therefore, suppressing transverse high-order modes has become an indispensable step in achieving high-performance acoustic filters with flat passbands.

[0003] The first solution is to widen the end of the electrode to form a region with a lower sound velocity to change the displacement distribution of the main mode and achieve the suppression of lateral high-order modes, but this will result in a larger duty cycle in the widened electrode area, increasing the difficulty of lithography; the second solution is to add a load block at the end of the interdigitated top electrode to form a low sound velocity area to suppress the lateral high-order modes. The load block often uses heavy metal materials, and the load blocks must be kept separate. There are high requirements for lithography accuracy and alignment accuracy, otherwise the electrode may short-circuit due to insufficient alignment accuracy; in addition, a solution for preparing an acoustic wave resonator excited by a longitudinal electric field is to form a cavity by etching a supporting substrate from the back, and then form a patterned bottom electrode by depositing metal from the back to avoid parasitic body acoustic waves, but the patterned bottom electrode makes it impossible to perform further operations on the bottom electrode and the area near the bottom electrode, limiting the design flexibility of the device.

[0004] Therefore, how to provide an elastic wave resonator, a manufacturing method and a communication device to suppress lateral high-order modes, reduce process difficulty and improve device reliability has become a technical problem that needs to be urgently solved by those skilled in the art.

[0005] It should be noted that the above introduction to the technical background is only for the convenience of providing a clear and complete description of the technical solutions of the present application and for the convenience of understanding by those skilled in the art. It cannot be considered that the above technical solutions are well known to those skilled in the art simply because they are described in the background technology section of the present application. Summary of the invention

[0006] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide an elastic wave resonator, a manufacturing method and a communication device, which are used to solve the problems of high process precision requirements and poor device reliability of resonators for suppressing lateral high-order modes in the prior art.

[0007] To achieve the above object and other related objects, the present invention provides an elastic wave resonator, comprising:

[0008] A top electrode, the top electrode comprising a first bus bar, a second bus bar, a first interdigital electrode and a second interdigital electrode, the first interdigital electrode and the second interdigital electrode are both located between the first bus bar and the second bus bar, in the direction of acoustic wave propagation, the first interdigital electrodes and the second interdigital electrodes are alternately arranged, the first interdigital electrode is electrically connected to the first bus bar, and the second interdigital electrode is electrically connected to the second bus bar;

[0009] a piezoelectric film layer, located below the top electrode;

[0010] The bottom electrode is located below the piezoelectric film layer. A load bar is provided at the end of the bottom electrode in the direction from the first bus bar to the second bus bar. The extension direction of the load bar is perpendicular to the direction from the first bus bar to the second bus bar.

[0011] Optionally, the load bar is located below an end of the bottom electrode, and the load bar contacts the bottom electrode.

[0012] Optionally, the load bar and the bottom electrode are made of the same material; or the load bar and the bottom electrode are made of different materials.

[0013] Optionally, the load bar is embedded in an end portion of the bottom electrode, and the load bar and the bottom electrode are made of different materials.

[0014] Optionally, the load bar is formed by ion implantation into an end portion of the bottom electrode.

[0015] Optionally, the load bar is located above an end of the bottom electrode, and the load bar is made of the same material as the piezoelectric film layer.

[0016] Optionally, a dielectric layer is further included, which is located below the piezoelectric film layer and covers the bottom electrode and the load bar, wherein the load bar is located below the end of the bottom electrode and the load bar is located in the dielectric layer, and the load bar is in contact with the bottom electrode.

[0017] Optionally, a dielectric layer is further included, which is located below the piezoelectric film layer and covers the bottom electrode and the load bar, wherein the load bar is located below the end of the bottom electrode and in the dielectric layer, and the load bar is not in contact with the bottom electrode.

[0018] Optionally, a dielectric layer is further included, which is located below the piezoelectric film layer and covers the bottom electrode, wherein the load bar is located below the end of the bottom electrode and below the dielectric layer, and the load bar is not in contact with the bottom electrode.

[0019] Optionally, etching grooves are provided in the piezoelectric film layer between adjacent interdigital electrodes.

[0020] Optionally, a supporting substrate is provided under the load bar, and a high acoustic velocity supporting substrate is adopted for the supporting substrate. The center distance between adjacent first interdigitated electrodes is λ, and the center distance between adjacent second interdigitated electrodes is λ. The product of λ and the target mode resonance frequency does not exceed the slow shear wave acoustic velocity of the supporting substrate.

[0021] Optionally, a supporting substrate is also provided under the load bar, and a high acoustic velocity layer is provided between the supporting substrate and the load bar, the center distance between adjacent first interdigitated electrodes is λ, the center distance between adjacent second interdigitated electrodes is λ, the product of λ and the target mode resonance frequency does not exceed the slow shear wave velocity of the high acoustic velocity layer, and the thickness of the high acoustic velocity layer is not less than 0.5λ.

[0022] Optionally, a supporting substrate is further disposed below the load bar, a Bragg reflection layer is disposed between the supporting substrate and the load bar, and the number of layers of the Bragg reflection layer is not less than 2.

[0023] The present invention also provides a communication device, comprising the elastic wave resonator described in any one of the above items.

[0024] The present invention also provides a method for manufacturing an elastic wave resonator, comprising the following steps:

[0025] Providing an auxiliary substrate, the auxiliary substrate comprising a first surface and a second surface arranged opposite to each other, the second surface of the auxiliary substrate having a piezoelectric film layer;

[0026] A bottom electrode is formed on a side of the piezoelectric film layer away from the auxiliary substrate, and a load bar is formed at the end of the bottom electrode in a direction perpendicular to the propagation direction of the acoustic wave, and the extension direction of the load bar is parallel to the propagation direction of the acoustic wave;

[0027] Providing a supporting substrate, bonding the side of the load bar away from the auxiliary base to the supporting substrate;

[0028] The auxiliary substrate is removed, and a top electrode is formed on a side of the piezoelectric film layer away from the supporting substrate.

[0029] Optionally, after forming the load bar, the method further includes forming a dielectric layer on a side of the piezoelectric film layer away from the auxiliary substrate, wherein the dielectric layer covers the bottom electrode and the load bar, and then bonding the dielectric layer to the supporting substrate.

[0030] Optionally, the auxiliary substrate is a piezoelectric substrate, ions are implanted into the piezoelectric substrate at a preset depth to form an ion implantation layer, and the piezoelectric substrate above the ion implantation layer constitutes the piezoelectric film layer; the piezoelectric film layer is retained during the removal of the auxiliary substrate.

[0031] As described above, in the elastic wave resonator, manufacturing method and communication equipment of the present invention, a load bar is set at the end of the bottom electrode to reduce the sound velocity in the area, thereby achieving suppression of lateral high-order modes. Compared with setting the load bar on the top interdigitated electrode, since the electric potential of the entire bottom electrode is the same, even if the load bar is made of conductive material, no short circuit will occur. The device has high reliability, and the manufacturing process is simple, with low requirements for lithography accuracy and alignment accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Shown is a top view of the elastic wave resonator in the first embodiment of the present invention.

[0033] Figure 2 Shown is a cross-sectional view of an elastic wave resonator in Embodiment 1 of the present invention.

[0034] Figure 3 It shows a cross-sectional view of the elastic wave resonator in the second embodiment of the present invention.

[0035] Figure 4 Shown is a cross-sectional view of the elastic wave resonator in the third embodiment of the present invention.

[0036] Figure 5 Shown is a cross-sectional view of an elastic wave resonator in a fourth embodiment of the present invention.

[0037] Figure 6 It shows a cross-sectional view of the elastic wave resonator in the fifth embodiment of the present invention.

[0038] Figure 7 It shows a cross-sectional view of the elastic wave resonator in the sixth embodiment of the present invention.

[0039] Figure 8 It shows a cross-sectional view of the elastic wave resonator in the seventh embodiment of the present invention.

[0040] Fig. 9 It shows a cross-sectional view of the elastic wave resonator in the eighth embodiment of the present invention.

[0041] Fig.10 It shows a cross-sectional view of an elastic wave resonator in Embodiment 9 of the present invention.

[0042] Fig.11 It shows a cross-sectional view of the elastic wave resonator in the tenth embodiment of the present invention.

[0043] Fig.12 It shows a cross-sectional view of an elastic wave resonator in the eleventh embodiment of the present invention.

[0044] Fig.13 Shown is a top view of the elastic wave resonator in comparative example 1.

[0045] Fig.14 Shown is a cross-sectional view of the elastic wave resonator in Comparative Example 1.

[0046] Fig.15 Shown is a cross-sectional view of the elastic wave resonator in Comparative Example 2.

[0047] Fig.16 Shown is a simulated admittance / conductance curve of the elastic wave resonator of comparative example 1.

[0048] Fig.17 Shown is a simulated admittance / conductance curve of the elastic wave resonator of Example 1.

[0049] Fig.18 Shown is a simulated admittance / conductance curve of the elastic wave resonator of comparative example 2.

[0050] Fig.19 Shown is a simulated admittance / conductance curve of the elastic wave resonator of Example 9.

[0051] Fig. 20 It is a schematic diagram showing the provision of an auxiliary substrate in the twelfth embodiment of the present invention.

[0052] Fig.21 It is a schematic diagram showing the formation of an ion implantation layer in the twelfth embodiment of the present invention.

[0053] Fig. 22 It is a schematic diagram showing the formation of a bottom electrode in the twelfth embodiment of the present invention.

[0054] Fig.23 It is a schematic diagram showing the formation of a load bar in the twelfth embodiment of the present invention.

[0055] Fig.24 It is a schematic diagram showing the formation of a dielectric layer in the twelfth embodiment of the present invention.

[0056] Fig.25 It is a schematic diagram showing providing a supporting substrate and bonding a dielectric layer to the supporting substrate in the twelfth embodiment of the present invention.

[0057] Fig.26 It is a schematic diagram showing the removal of the auxiliary substrate in the twelfth embodiment of the present invention.

[0058] Fig. 27 It is a schematic diagram showing the formation of a top electrode in the twelfth embodiment of the present invention.

[0059] Component number description

[0060] 1 Top electrode

[0061] 10 First busbar

[0062] 11 Second bus bar

[0063] 12. First interdigital electrode

[0064] 13. Second interdigital electrode

[0065] 14 Direction of sound wave propagation

[0066] 15 Effective aperture area

[0067] 2 Piezoelectric film layer

[0068] 3 Bottom electrode

[0069] 4 Load bars

[0070] 5 Dielectric layer

[0071] 6 Support substrate

[0072] 60 Support base

[0073] 61 High sound velocity layer

[0074] 7 Bragg reflector

[0075] 8 Auxiliary substrate

[0076] 9 Ion implantation layer DETAILED DESCRIPTION

[0077] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0078] For example, when describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional view showing the device structure will not be partially enlarged according to the general scale, and the schematic view is only an example, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional space dimensions of length, width and depth should be included.

[0079] In the context of the present application, a structure in which a first feature is described as being "above" a second feature may include embodiments in which the first feature and the second feature are formed in direct contact, and may also include embodiments in which additional features are formed between the first feature and the second feature, such that the first feature and the second feature may not be in direct contact.

[0080] See also Figures 1 to 27 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0081] Embodiment 1

[0082] This embodiment provides an elastic wave resonator. Figure 1 and Figure 2 The elastic wave resonator includes a top electrode 1, a piezoelectric film layer 2 and a bottom electrode 3, wherein the top electrode 1 includes a first bus bar 10, a second bus bar 11, a first interdigitated electrode 12 and a second interdigitated electrode 13, wherein the first interdigitated electrode 12 and the second interdigitated electrode 13 are both located between the first bus bar 10 and the second bus bar 11, and in the direction of sound wave propagation 14, the first interdigitated electrodes 12 and the second interdigitated electrodes 13 are alternately arranged, the first interdigitated electrodes 12 are electrically connected to the first bus bar 10, and the second interdigitated electrodes 13 are electrically connected to the second bus bar 11; the piezoelectric film layer 2 is located below the top electrode 1; the bottom electrode 3 is located below the piezoelectric film layer 2, and a load bar 4 is provided at the end of the bottom electrode 3 in a direction from the first bus bar 10 to the second bus bar 11, and an extension direction of the load bar 4 is perpendicular to a direction from the first bus bar 10 to the second bus bar 11.

[0083] As an example, the target mode of the elastic wave resonator is a high-order acoustic wave mode excited by a longitudinal electric field, including one of a high-order Lamb wave, a high-order horizontal shear wave or a high-order Rayleigh mode, wherein a high-order mode refers to a mode above the 0th order, and a load bar 4 is set at the end of the bottom electrode 3 to reduce the speed of sound in the region, thereby suppressing the lateral high-order mode. Compared with setting a load bar at the top interdigitated electrode, the present application sets a load bar 4 at the end of the bottom electrode 3. Since the electric potential of the entire bottom electrode 3 is the same, even if the load bar 4 is a conductive material, there will be no short circuit, thereby improving the reliability of the device, and the manufacturing process is simple, with low requirements for photolithography accuracy and alignment accuracy, which is conducive to large-scale production.

[0084] As an example, one end of the first interdigital electrode 12 is connected to the first bus bar 10, and the other end of the first interdigital electrode 12 is spaced from the second bus bar 11 by a preset distance to form an air gap; one end of the second interdigital electrode 13 is connected to the second bus bar 11, and the other end of the second interdigital electrode 13 is spaced from the first bus bar 10 by a preset distance to form an air gap. In the direction of sound wave propagation 14, the overlapping part of the first interdigital electrode 12 and the second interdigital electrode 13 forms an effective aperture area 15, and in the direction from the first bus bar 10 to the second bus bar 11, the length of the bottom electrode 3 does not exceed the length of the effective aperture area 15, so as to avoid the longitudinal electric field in the non-aperture area causing parasitic body acoustic waves, and energy leakage caused by body acoustic waves.

[0085] As an example, the material of the top electrode 1 includes a combination of one or more of copper, aluminum, gold, silver, tungsten, platinum, nickel, chromium, molybdenum, titanium, graphene, copper-aluminum alloy, and aluminum-silicon alloy; the material of the piezoelectric film layer 2 includes one or more of lithium tantalate, lithium niobate, potassium niobate, aluminum nitride, scandium-doped aluminum nitride, lead zirconate titanate, or lead magnesium niobate-lead titanate; the material of the bottom electrode 3 includes one or more of copper, aluminum, gold, silver, tungsten, platinum, nickel, chromium, molybdenum, titanium, graphene, copper-aluminum alloy, aluminum-silicon alloy, doped silicon, doped silicon carbide, and doped gallium nitride.

[0086] As an example, the load bar 4 is located below the end of the bottom electrode 3 , the load bar 4 is in contact with the bottom electrode 3 , and the load bar 4 and the bottom electrode 3 are made of different materials.

[0087] Specifically, in this embodiment, the top electrode 1 is made of molybdenum with a thickness of 40nm, the center distance λ of adjacent first interdigitated electrodes 12 is 1.5μm, the center distance λ of adjacent second interdigitated electrodes 13 is 1.5μm, and the electrode line width of the first interdigitated electrode 12 and the second interdigitated electrode 13 is 450nm; the piezoelectric film layer 2 is made of lithium niobate, the Euler angle is (90°, 99°, 0°), and the thickness is 250nm; the bottom electrode 3 is made of aluminum with a thickness of 20nm; the load bar 4 is made of gold with a thickness of 10nm, and the width of the load bar 4 in the direction from the first bus bar 10 to the second bus bar 11 is 375nm; the main mode is a first-order antisymmetric Lamb wave mode.

[0088] As an example, the bottom electrode 3 is a suspended bottom electrode, and when the elastic wave resonator is working, the bottom electrode 3 is not connected to an external electrical signal.

[0089] In other examples, the top electrode 1 also includes a pseudo-finger electrode. For example, a first pseudo-finger electrode is arranged in the gap between the first interdigitated electrode 12 and the second bus bar 11, one end of the first pseudo-finger electrode is spaced a preset distance from the first interdigitated electrode 12, and the other end of the first pseudo-finger electrode is connected to the second bus bar 11. A second pseudo-finger electrode is arranged in the gap between the second interdigitated electrode 13 and the first bus bar 10, one end of the second pseudo-finger electrode is spaced a preset distance from the second interdigitated electrode 13, and the other end of the second pseudo-finger electrode is connected to the first bus bar 10. By setting the pseudo-finger electrode, the Q value of the main mode can be improved, thereby reducing the insertion loss of the filter.

[0090] In other examples, reflection gratings are further provided on both sides of the top electrode 1 along the propagation direction of the sound wave, and the extension direction of the reflection gratings is perpendicular to the propagation direction of the sound wave to reflect the sound wave energy, thereby reducing the leakage of the sound wave in the propagation direction.

[0091] In other examples, etched grooves are further provided in the piezoelectric film layer 2 between adjacent interdigitated electrodes for suppressing parasitic modes excited by horizontal electric fields. This is because the horizontal electric field is concentrated in the area between the interdigitated electrodes, and the main mode is excited by the longitudinal electric field. By suppressing the parasitic modes excited by the horizontal electric field, the proportion of the longitudinal electric field area is increased, and the electromechanical coupling coefficient of the main mode is also increased.

[0092] Embodiment 2

[0093] See also Figure 3 This embodiment provides an elastic wave resonator, which is different from the first embodiment in that the load bar 4 is completely embedded in the end of the bottom electrode 3 , and the load bar 4 can be regarded as being located on the side of the end of the bottom electrode 3 .

[0094] Embodiment 3

[0095] See also Figure 4 This embodiment provides an elastic wave resonator, which is different from the first embodiment in that the load bar 4 is made of the same material as the bottom electrode 3 , and the load bar 4 can be regarded as a thickened bottom electrode 3 .

[0096] Embodiment 4

[0097] See also Figure 5 This embodiment provides an elastic wave resonator, which is different from the first embodiment in that the load bar 4 is formed by ion implantation at the end of the bottom electrode 3 based on an ion implantation process, and the load bar 4 can be regarded as an ion implantation region of the bottom electrode 3.

[0098] Embodiment 5

[0099] See also Figure 6 This embodiment provides an elastic wave resonator, which differs from the first embodiment in that: the load bar 4 is located above the end of the bottom electrode 3, the load bar 4 is made of the same material as the piezoelectric film layer 2, and the load bar 4 can be regarded as a thickened piezoelectric film layer 2. Since the piezoelectric film layer 2 at the end of the bottom electrode 3 is thickened, the end of the bottom electrode 3 protrudes from the center of the bottom electrode 3 in the vertical direction (Z direction).

[0100] Embodiment 6

[0101] See also Figure 7 This embodiment provides an elastic wave resonator, which differs from the first embodiment in that: the elastic wave resonator also includes a dielectric layer 5, the dielectric layer 5 is located below the piezoelectric film layer 2, and the dielectric layer 5 covers the bottom electrode 3 and the load bar 4; the dielectric layer 5 can be a single-layer material or a multi-layer material, including but not limited to one or more of silicon oxide, silicon nitride, polycrystalline silicon, amorphous silicon, aluminum oxide, and aluminum nitride; the dielectric layer 5 serves as one or more of a temperature compensation layer, a heat dissipation layer, a trap-rich layer, a bonding layer, and a low sound velocity layer.

[0102] Embodiment 7

[0103] See also Figure 8 This embodiment provides an elastic wave resonator, which is different from the sixth embodiment in that the load bar 4 is located below the end of the bottom electrode 3 and is not in contact with the bottom electrode 3 , and the load bar 4 is located in the dielectric layer 5 .

[0104] Embodiment 8

[0105] See also Fig. 9This embodiment provides an elastic wave resonator, which is different from the sixth embodiment in that the dielectric layer 5 covers the bottom electrode 3 , the load bar 4 is located below the end of the bottom electrode 3 , and the load bar 4 is located below the dielectric layer 5 .

[0106] Embodiment 9

[0107] See also Fig.10 This embodiment provides an elastic wave resonator, which is different from the sixth embodiment in that the elastic wave resonator further includes a support substrate 6, which is located below the dielectric layer 5, and the support substrate 6 adopts a high-acoustic-velocity support substrate, which is a combination of one or more of silicon carbide, diamond, diamond-like carbon, sapphire, aluminum nitride, boron nitride, boron carbide and silicon nitride of different crystal forms and different cuts. The product of the resonant frequency of the target mode and λ does not exceed the slow shear wave sound velocity of the high-acoustic-velocity support substrate, so as to ensure that the target mode will not leak to the support substrate 6 within the resonant frequency range.

[0108] Specifically, in this embodiment, the supporting substrate 6 is silicon carbide, the dielectric layer 5 is silicon oxide, the bottom electrode 3 is tungsten with a thickness of 100nm, the dielectric layer 5 below the bottom electrode 3 is 200nm thick, the load bar 4 is platinum with a thickness of 30nm, and the width of the load bar 4 in the direction from the first bus bar 10 to the second bus bar 11 is 770nm. The piezoelectric film layer 2 is lithium niobate, the Euler angle is (29°, 90°, -90°), and the thickness is 200nm. The top electrode 1 is aluminum / tungsten with a thickness of 78 / 25nm. The center distance λ of adjacent first interdigitated electrodes 12 is 1.5μm, and the center distance λ of adjacent second interdigitated electrodes 13 is 1.5μm. The electrode line width of the first interdigitated electrode 12 and the second interdigitated electrode 13 is 385nm, and the main mode is a first-order horizontal shear mode.

[0109] Embodiment 10

[0110] See also Fig.11, this embodiment provides an elastic wave resonator, which is different from the ninth embodiment in that: the supporting substrate 6 adopts a stacked supporting base 60 and a high acoustic velocity layer 61, the high acoustic velocity layer 61 is located above the supporting base 60, and the product of λ and the target mode resonance frequency does not exceed the slow shear wave acoustic velocity of the high acoustic velocity layer 61. The material of the supporting base 60 includes one or more of quartz, silicon, sapphire, spinel, and yttrium aluminum garnet, and the high acoustic velocity layer 61 is a material that is easy to form and process. The material of the high acoustic velocity layer 61 is one or more of silicon carbide, diamond, diamond-like carbon, aluminum oxide, aluminum nitride, boron nitride, boron carbide, and silicon nitride of different crystal forms and different cuts. Among them, the thickness of the high acoustic velocity layer 61 is not less than 0.5λ, so as to avoid the leakage of the main mode energy through the high acoustic velocity layer 61 into the supporting base 60 when the high acoustic velocity layer 61 is too thin.

[0111] Embodiment 11

[0112] See also Fig.12 This embodiment provides an elastic wave resonator, which is different from the tenth embodiment in that: the high acoustic velocity layer 61 is replaced by a Bragg reflection layer 7, and the Bragg reflection layer 7 is located between the dielectric layer 5 and the supporting substrate 60. The number of layers of the Bragg reflection layer 7 is at least 2, including high acoustic impedance layers and low acoustic impedance layers stacked alternately. Even if the acoustic velocity of the supporting substrate 60 is low, the sound wave can still be confined near the piezoelectric film because the Bragg reflection layer 7 can reflect the sound wave energy.

[0113] Comparative Example 1

[0114] See also Fig.13 and Fig.14 The difference between comparative example 1 and embodiment 1 is that: the elastic wave resonator is not provided with a load bar 4, the material of the top electrode 1 is molybdenum with a thickness of 40nm, the center distance λ of adjacent first interdigitated electrodes 12 is 1.5μm, the center distance λ of adjacent second interdigitated electrodes 13 is 1.5μm, and the electrode line width of the first interdigitated electrode 12 and the second interdigitated electrode 13 is 450nm; the piezoelectric film layer 2 is made of lithium niobate, the Euler angle is (90°, 99°, 0°), and the thickness is 250nm; the material of the bottom electrode 3 is made of aluminum with a thickness of 20nm; and the main mode is a first-order antisymmetric Lamb wave mode.

[0115] Comparative Example 2

[0116] See also Fig.15The difference between the comparative example 2 and the embodiment 9 is that: the elastic wave resonator is not provided with a load bar 4, the supporting substrate 6 is silicon carbide, the dielectric layer 5 is silicon oxide, the bottom electrode 3 is tungsten with a thickness of 100nm, the dielectric layer 5 below the bottom electrode 3 is 200nm thick, the piezoelectric film layer 2 is lithium niobate, the Euler angle is (29°, 90°, -90°), and the thickness is 200nm, the top electrode 1 is aluminum / tungsten with a thickness of 78 / 25nm, the center distance λ of adjacent first interdigitated electrodes 12 is 1.5μm, the center distance λ of adjacent second interdigitated electrodes 13 is 1.5μm, the electrode line width of the first interdigitated electrode 12 and the second interdigitated electrode 13 is 385nm, and the main mode is a first-order horizontal shear mode.

[0117] The beneficial effects that can be achieved by the elastic wave resonator of the present invention are further illustrated below in combination with comparative examples and embodiments.

[0118] (I) Please refer to Fig.16 and Fig.17 , respectively, show the simulated admittance / conductance curves of the elastic wave resonator of the comparative example 1 and the embodiment 1. Fig.16 As shown in FIG. 1 , in comparative example 1, there are a large number of transverse high-order modes between the resonant frequency of the main mode (the frequency corresponding to the maximum point of the admittance curve), and the resonant frequency and the anti-resonant frequency (the frequency corresponding to the minimum point of the admittance curve). These parasitic modes cause the passband fluctuation of the filter. Fig.17 As shown, in the first embodiment, the lateral high-order mode is greatly weakened, the electromechanical coupling coefficient of the resonator is as high as 37.6%, and the frequency is above 6 GHz, that is, by setting the load bar 4 at the end of the bottom electrode 3, it is helpful to realize a high-frequency filter with a flat passband.

[0119] (ii) Please refer to Fig.18 and Fig.19 , respectively, are simulated admittance / conductance curves of the elastic wave resonator of the comparative example 2 and the embodiment 9. Fig.18 As shown, in comparative example 2, there are a large number of transverse high-order modes between the resonant frequency and the anti-resonant frequency of the main mode and near the anti-resonant frequency. These parasitic modes cause the passband fluctuation of the filter. Fig.19 As shown, in the ninth embodiment, the lateral high-order mode is greatly weakened, and the electromechanical coupling coefficient of the resonator is as high as 54.7%. That is, by arranging the load bar 4 at the end of the bottom electrode 3, it is helpful to realize a high-frequency filter with a flat passband.

[0120] The present invention further provides a communication device, the communication device comprising the elastic wave resonator described in any one of Embodiments 1 to 11, the communication device comprising at least one of a filter, a duplexer, and a multiplexer.

[0121] Embodiment 12

[0122] This embodiment provides a method for manufacturing an elastic wave resonator, comprising the following steps:

[0123] S1: providing an auxiliary substrate, wherein the auxiliary substrate comprises a first surface and a second surface arranged opposite to each other, and the second surface of the auxiliary substrate has a piezoelectric film layer;

[0124] S2: forming a bottom electrode on a side of the piezoelectric film layer away from the auxiliary substrate, wherein a load bar is formed at an end of the bottom electrode in a direction perpendicular to the propagation direction of the acoustic wave, and an extension direction of the load bar is parallel to the propagation direction of the acoustic wave;

[0125] S3: providing a supporting substrate, and bonding a side of the load bar away from the auxiliary base to the supporting substrate;

[0126] S4: removing the auxiliary substrate, and forming a top electrode on a side of the piezoelectric film layer away from the supporting substrate.

[0127] First, see Fig. 20 and Fig.21 , performing step S1: providing an auxiliary substrate 8, wherein the auxiliary substrate 8 comprises a first surface and a second surface arranged opposite to each other, and the second surface of the auxiliary substrate 8 has a piezoelectric film layer 2.

[0128] As an example, Fig. 20 As shown, the auxiliary substrate 8 is a piezoelectric substrate; Fig.21 As shown, ions are implanted into the piezoelectric substrate 8 at a preset depth to form an ion implantation layer 9, and the piezoelectric substrate above the ion implantation layer 9 constitutes the piezoelectric film layer 2. In another example, the auxiliary substrate 8 with the ion implantation layer 9 can be replaced by a piezoelectric heterogeneous substrate, which at least includes a support carrier and a piezoelectric film layer located on the support carrier, and the support carrier will be removed after the piezoelectric film layer is transferred.

[0129] Next, see Fig. 22 and Fig.23 , execute step S2: form a bottom electrode 3 on the side of the piezoelectric film layer 3 away from the auxiliary substrate 8, and form a load bar 4 at the end of the bottom electrode 3 in a direction perpendicular to the propagation direction of the sound wave, and the extension direction of the load bar 4 is parallel to the propagation direction of the sound wave.

[0130] As an example, this embodiment only shows the situation that the load bar 4 is located at the end of the bottom electrode 3 away from the piezoelectric film layer 2, and is not limited to this embodiment. Figures 2 to 6 The configuration of the load bar 4 is selected according to the requirements and is not limited to this embodiment.

[0131] As an example, Fig.24As shown in FIG. 1 , after forming the bottom electrode 3 and the load bar 4, a dielectric layer 5 is formed on the side of the piezoelectric film layer 2 away from the auxiliary substrate 8, and the dielectric layer 5 is polished to be flat, and the dielectric layer 5 covers the bottom electrode 3 and the load bar 4. In other examples, after forming the bottom electrode 3 and before forming the load bar 4, a dielectric layer 5 of a preset thickness is formed first, and then the load bar 4 is formed, and then a dielectric layer 5 of a certain thickness is formed (such as Figure 8 or after forming the bottom electrode 3, a dielectric layer 5 of a desired thickness is formed, and then a load bar 4 is formed (as shown in Fig. 9 ), also falls within the scope of protection of this embodiment.

[0132] Next, see Fig.25 , perform step S3: provide a support substrate 6 , and bond the side of the load bar 4 away from the auxiliary base 8 to the support substrate 6 .

[0133] As an example, the support substrate 6 is a high acoustic velocity support substrate. In other examples, the support substrate 6 may also be a stacked support substrate plus a high acoustic velocity layer, or a stacked support substrate plus a Bragg reflection layer, which is not limited to this embodiment.

[0134] As an example, the dielectric layer 5 is formed on a side of the load bar 4 away from the auxiliary base 8 , and the dielectric layer 5 is bonded to the support substrate 6 .

[0135] Next, see Fig.26 and Fig. 27 , executing step S4: removing the auxiliary substrate 8 and forming a top electrode 1 on a side of the piezoelectric film layer 2 away from the supporting substrate 6 .

[0136] As an example, Fig.26 As shown, the piezoelectric film layer 2 together with the bottom electrode 3 etc. are transferred to the supporting substrate 6 by annealing, peeling, polishing and other processes; Fig. 27 As shown, the top electrode 1 is formed on the side of the piezoelectric film layer 2 away from the supporting substrate 6. The structure of the top electrode 1 can be found in the first embodiment and will not be described in detail here.

[0137] As an example, in this embodiment, the bottom electrode 3 is first formed and then transferred onto the supporting substrate 6 together with the piezoelectric film layer 2, which is conducive to further fine design of the bottom electrode structure.

[0138] In summary, in the elastic wave resonator, manufacturing method and communication device of the present invention, the acoustic velocity in the region is reduced by setting a load bar at the end of the bottom electrode, thereby suppressing the lateral high-order mode. Compared with setting the load bar at the top interdigital electrode, since the potential of the entire bottom electrode is the same, even if the load bar is a conductive material, there will be no short circuit. The device has high reliability, and the manufacturing process is simple, with low requirements for photolithography accuracy and alignment accuracy. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0139] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. An elastic wave resonator, characterized in that: include: A top electrode, the top electrode comprising a first bus bar, a second bus bar, a first interdigital electrode and a second interdigital electrode, the first interdigital electrode and the second interdigital electrode are both located between the first bus bar and the second bus bar, in the direction of acoustic wave propagation, the first interdigital electrodes and the second interdigital electrodes are alternately arranged, the first interdigital electrode is electrically connected to the first bus bar, and the second interdigital electrode is electrically connected to the second bus bar; a piezoelectric film layer, located below the top electrode; A bottom electrode is located below the piezoelectric film layer, and is a suspended bottom electrode. A load bar is provided at the end of the bottom electrode in a direction from the first bus bar to the second bus bar to suppress transverse high-order mode sound waves. The load bar is made of conductive material, and an extension direction of the load bar is perpendicular to a direction from the first bus bar to the second bus bar.

2. The elastic wave resonator according to claim 1, characterized in that: The load bar is located below an end of the bottom electrode, and the load bar contacts the bottom electrode.

3. The elastic wave resonator according to claim 2, characterized in that: The load bar is made of the same material as the bottom electrode; Or the load bar and the bottom electrode are made of different materials.

4. The elastic wave resonator according to claim 1, characterized in that: The load bar is embedded in the end of the bottom electrode, and the load bar and the bottom electrode are made of different materials.

5. The elastic wave resonator according to claim 1, characterized in that: It also includes a dielectric layer, which is located below the piezoelectric film layer and covers the bottom electrode and the load bar, wherein the load bar is located below the end of the bottom electrode, and the load bar is located in the dielectric layer, and the load bar is in contact with the bottom electrode.

6. The elastic wave resonator according to claim 1, characterized in that: It also includes a dielectric layer, which is located below the piezoelectric film layer and covers the bottom electrode and the load bar, wherein the load bar is located below the end of the bottom electrode and in the dielectric layer, and the load bar is not in contact with the bottom electrode.

7. The elastic wave resonator according to claim 1, characterized in that: It also includes a dielectric layer, which is located below the piezoelectric film layer and covers the bottom electrode, wherein the load bar is located below the end of the bottom electrode and below the dielectric layer, and the load bar is not in contact with the bottom electrode.

8. The elastic wave resonator according to claim 1, characterized in that: Etched grooves are provided in the piezoelectric film layer between adjacent interdigital electrodes.

9. The elastic wave resonator according to claim 1, characterized in that: A support substrate is also provided under the load bar. The support substrate adopts a high acoustic velocity support substrate. The center distance between adjacent first interdigitated electrodes is λ, and the center distance between adjacent second interdigitated electrodes is λ. The product of λ and the target mode resonance frequency does not exceed the slow shear wave acoustic velocity of the support substrate.

10. The elastic wave resonator according to claim 1, characterized in that: A supporting substrate is also provided below the load bar, and a high acoustic velocity layer is provided between the supporting substrate and the load bar. The center distance between adjacent first interdigitated electrodes is λ, and the center distance between adjacent second interdigitated electrodes is λ. The product of λ and the target mode resonance frequency does not exceed the slow shear wave velocity of the high acoustic velocity layer, and the thickness of the high acoustic velocity layer is not less than 0.5λ.

11. The elastic wave resonator according to claim 1, characterized in that: A supporting substrate is further arranged below the load bar, a Bragg reflection layer is arranged between the supporting substrate and the load bar, and the number of layers of the Bragg reflection layer is not less than 2.

12. A communication device, characterized in that: The communication device comprises the elastic wave resonator according to any one of claims 1 to 11.

13. A method for manufacturing an elastic wave resonator, characterized in that: The following steps are involved: Providing an auxiliary substrate, the auxiliary substrate comprising a first surface and a second surface arranged opposite to each other, the second surface of the auxiliary substrate having a piezoelectric film layer; A bottom electrode is formed on a side of the piezoelectric film layer away from the auxiliary substrate, the bottom electrode is a suspended bottom electrode, a load bar is formed at the end of the bottom electrode in a direction perpendicular to the propagation direction of the sound wave to suppress the transverse high-order mode sound wave, the load bar is a conductive material, and the extension direction of the load bar is parallel to the propagation direction of the sound wave; Providing a supporting substrate, bonding the side of the load bar away from the auxiliary base to the supporting substrate; The auxiliary substrate is removed, and a top electrode is formed on a side of the piezoelectric film layer away from the supporting substrate.

14. The method for manufacturing an elastic wave resonator according to claim 13, characterized in that: After forming the load bar, the method further includes forming a dielectric layer on a side of the piezoelectric film layer away from the auxiliary substrate, wherein the dielectric layer covers the bottom electrode and the load bar, and then bonding the dielectric layer to the supporting substrate.

15. The method for manufacturing an elastic wave resonator according to claim 13, characterized in that: The auxiliary substrate is a piezoelectric substrate, ions are implanted into the piezoelectric substrate at a preset depth to form an ion implantation layer, and the piezoelectric substrate above the ion implantation layer constitutes the piezoelectric film layer; The piezoelectric film layer is retained during the process of removing the auxiliary substrate.

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