CN118921038B - Acoustic wave resonator, method for preparing acoustic wave resonator, and electronic device - Google Patents
Acoustic wave resonator, method for preparing acoustic wave resonator, and electronic device Download PDFInfo
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
- H03H9/15—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
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
- H03H3/04—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks for obtaining desired frequency or temperature coefficient
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
- H03H9/02—Details
- H03H9/125—Driving means, e.g. electrodes, coils
- H03H9/145—Driving means, e.g. electrodes, coils for networks using surface acoustic waves
- H03H9/14544—Transducers of particular shape or position
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
- H03H3/04—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks for obtaining desired frequency or temperature coefficient
- H03H2003/0414—Resonance frequency
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Abstract
本申请公开了一种声波谐振器、声波谐振器的制备方法和电子设备，该声波谐振器，包括：衬底、压电层和至少两个叉指电极；所述压电层，设置于所述衬底的表面，且所述压电层和所述衬底接触的一侧或背离所述衬底的一侧设置多个凹槽，所述多个凹槽的深度均小于所述压电层的厚度，所述凹槽的数量与所述叉指电极的数量相同，所述多个凹槽中的每个凹槽内设置一个叉指电极。如此，叉指电极更深入压电层的内部，使得激发的声波的振动模态可以更趋近于体波，即在整个介质内部传播。因此，在提高频率的过程中，无需改变叉指电极的尺寸，使得叉指电极的电阻不被增大，从而避免声波谐振器的品质因数降低，实现了高品质的声波谐振器。
The present application discloses an acoustic wave resonator, a method for preparing an acoustic wave resonator, and an electronic device. The acoustic wave resonator includes: a substrate, a piezoelectric layer, and at least two interdigital electrodes; the piezoelectric layer is arranged on the surface of the substrate, and a plurality of grooves are arranged on the side where the piezoelectric layer contacts the substrate or on the side away from the substrate, the depths of the plurality of grooves are all less than the thickness of the piezoelectric layer, the number of the grooves is the same as the number of the interdigital electrodes, and a interdigital electrode is arranged in each of the plurality of grooves. In this way, the interdigital electrodes penetrate deeper into the interior of the piezoelectric layer, so that the vibration mode of the excited acoustic wave can be closer to the body wave, that is, propagating inside the entire medium. Therefore, in the process of increasing the frequency, there is no need to change the size of the interdigital electrodes, so that the resistance of the interdigital electrodes is not increased, thereby avoiding the reduction of the quality factor of the acoustic wave resonator and realizing a high-quality acoustic wave resonator.
Description
Technical Field
The application relates to the technical field of resonators, in particular to an acoustic wave resonator, a preparation method of the acoustic wave resonator and electronic equipment.
Background
At present, the acoustic wave resonator is widely applied to the communication industry due to the characteristics of small volume, large bandwidth and high quality factor (Q value). However, as communication technology advances, the currently used frequency band becomes increasingly crowded, and wireless communication technology with higher frequencies needs to be further explored, so research into acoustic wave resonators with higher frequencies is also important.
Taking an interdigital acoustic wave resonator as an example, in practical application, in the process of continuously increasing the frequency of the interdigital acoustic wave resonator, the interdigital electrode is reduced, so that the resistance of the interdigital electrode is increased, and the quality factor is seriously reduced by a larger resistance, so that the quality of the acoustic wave resonator is reduced.
Disclosure of Invention
The embodiment of the application provides an acoustic wave resonator, a preparation method of the acoustic wave resonator and electronic equipment, which are used for avoiding quality factor reduction in the process of improving the frequency of an interdigital acoustic wave resonator.
In a first aspect, an embodiment of the present application provides an acoustic wave resonator, including a substrate, a piezoelectric layer, and at least two interdigital electrodes;
The piezoelectric layer is arranged on the surface of the substrate, a plurality of grooves are formed in one side, which is contacted with the substrate or away from the substrate, of the piezoelectric layer, the depth of each groove is smaller than the thickness of the piezoelectric layer, the number of the grooves is the same as that of the interdigital electrodes, and one interdigital electrode is arranged in each groove of the grooves.
Optionally, a ratio of a depth of each groove of the plurality of grooves to a thickness of each interdigitated electrode is 1:1, 2:1, 3:1, or 9:8.
Optionally, the acoustic wave resonator is configured to operate at a frequency of 5.3 gigahertz with a ratio of the depth of each recess to the thickness of each interdigital electrode of 1:1;
The acoustic resonator is configured to operate at a frequency of 6.6 gigahertz with a ratio of the depth of each recess to the thickness of each interdigital electrode of 2:1;
The acoustic wave resonator is configured to operate at a frequency of 8.3 gigahertz with a ratio of the depth of each recess to the thickness of each interdigital electrode of 3:1;
the acoustic wave resonator is configured to operate at a frequency of 14.5 gigahertz with a ratio of the depth of each recess to the thickness of each interdigital electrode of 9:8.
Optionally, the depth of each groove is 10-10000 nanometers, the thickness of each interdigital electrode is 10-10500 nanometers, and the thickness of the piezoelectric layer is 10-10000 nanometers.
Optionally, in a case that a plurality of grooves are formed on a side, facing away from the substrate, of the piezoelectric layer, one side, facing away from the substrate, of the at least two interdigital electrodes is covered with a silicon dioxide layer, and the thickness of the silicon dioxide layer is 1-300 nanometers.
Optionally, the piezoelectric layer is a lithium niobate layer, and the Euler angle of the lithium niobate layer is-90 degrees to 90 degrees.
Optionally, each interdigital electrode is a metal having a conductivity greater than 5 x 10 6 siemens per meter.
Optionally, the substrate comprises at least one of silicon, aluminum oxide, silicon oxide, glass, aluminum nitride, scandium aluminum nitride, quartz, or silicon carbide.
In a second aspect, an embodiment of the present application provides a method for manufacturing an acoustic wave resonator, including:
Providing a substrate;
Forming a piezoelectric layer on the surface of the substrate;
Etching a plurality of grooves on one side of the piezoelectric layer, which is contacted with the substrate, or one side of the piezoelectric layer, which is away from the substrate, wherein the depth of the grooves is smaller than the thickness of the piezoelectric layer;
an interdigital electrode is formed in each of the plurality of grooves.
In a third aspect, an embodiment of the present application provides an electronic device, including any implementation manner of the acoustic wave resonator described above.
From the above technical solutions, the embodiment of the present application has the following advantages:
In an embodiment of the present application, an acoustic wave resonator including a substrate, a piezoelectric layer, and at least two interdigital electrodes may be provided. The piezoelectric layer is arranged on the surface of the substrate, a plurality of grooves are formed in one side, which is contacted with the substrate, or one side, which is away from the substrate, of the piezoelectric layer, the depth of each groove is smaller than the thickness of the piezoelectric layer, the number of the grooves is the same as that of the interdigital electrodes, and one interdigital electrode is arranged in each groove of the grooves. In this way, the interdigital electrode can be embedded in the groove of the piezoelectric layer to extend deeper into the piezoelectric layer, so that the vibration mode of the excited sound wave can be closer to the bulk wave, namely, propagate in the whole medium. Therefore, even in the process of increasing the frequency, the size of the interdigital electrode does not need to be changed, so that the resistance of the interdigital electrode is not increased, the quality factor of the acoustic wave resonator is prevented from being reduced, and the acoustic wave resonator with high quality is realized.
Drawings
FIG. 1 is a schematic cross-sectional view of an acoustic wave resonator according to an embodiment of the present application;
FIG. 2 is a schematic cross-sectional view of another acoustic wave resonator according to an embodiment of the present application;
FIG. 3 is a schematic cross-sectional view of another acoustic wave resonator according to an embodiment of the present application;
FIG. 4 is a schematic cross-sectional view of another acoustic wave resonator according to an embodiment of the present application;
FIG. 5 is a schematic diagram of Euler angle rotation according to an embodiment of the present application;
FIG. 6 is a schematic cut-away view of an acoustic wave resonator for operating at a frequency of 5.3 gigahertz provided in accordance with an embodiment of the present application;
FIG. 7 is a simulated admittance curve for an acoustic wave resonator operating at a frequency of 5.3 gigahertz provided by an embodiment of the present application;
FIG. 8 is a schematic cut-away view of an acoustic wave resonator for operating at a frequency of 6.6 gigahertz according to an embodiment of the present application;
FIG. 9 is a simulated admittance curve for an acoustic wave resonator operating at a frequency of 6.6 gigahertz provided by an embodiment of the present application;
FIG. 10 is a schematic cut-away view of an acoustic wave resonator for operating at a frequency of 8.3 gigahertz, according to an embodiment of the present application;
FIG. 11 is a simulated admittance curve for an acoustic wave resonator operating at a frequency of 8.3 gigahertz provided by an embodiment of the present application;
FIG. 12 is a simulated admittance curve for an acoustic wave resonator operating at a frequency of 14.5 gigahertz provided by an embodiment of the present application;
FIG. 13 is a schematic cross-sectional view of an acoustic wave resonator with a silicon dioxide layer on a side of at least two interdigital electrodes facing away from a substrate, according to an embodiment of the present application;
FIG. 14 is a schematic cross-sectional view of another acoustic resonator according to an embodiment of the present application having a silicon dioxide layer on a side of at least two interdigital electrodes facing away from the substrate;
FIG. 15 is a schematic cross-sectional view of another acoustic wave resonator having a silicon dioxide layer on a side of at least two interdigital electrodes facing away from a substrate, in accordance with an embodiment of the present application;
FIG. 16 is a top view of an internal structure of an acoustic wave resonator according to the present application;
fig. 17 is a flowchart of a method for manufacturing an acoustic wave resonator according to an embodiment of the present application.
Detailed Description
As mentioned above, with the continuous development of communication technology, the functions of the communication system are increasingly complex. Particularly, with the rise of the fifth generation mobile communication technology, the communication system needs to support multiple modes such as the global system for mobile communication (Global System for Mobile Communications, GSM), wideband code division multiple access (Wideband Code Division Multiple Access, WCDMA), long term evolution (Long Term Evolution, LTE), new Radio (NR), wi-Fi, and bluetooth, and also needs to cover multiple frequency bands. In order to effectively suppress mutual interference between adjacent frequency bands, a communication system needs to have a specific high isolation. In addition, compared with LTE, the uplink and downlink throughput of the NR mode is greatly improved, which requires that the radio frequency front end system has the performance of ultra-low signal delay, ultra-large data transmission, and ultra-low bit error rate. In addition, the bandwidth of the NR frequency band is far beyond LTE, e.g., the n77 frequency band relative bandwidth is up to 24%. Therefore, the rf front-end filter needs to have low insertion loss, high out-of-band rejection, high squareness, high roll-off, and large bandwidth to accommodate the high performance requirements of the 5G NR system.
Based on the above requirements, it is important to design an acoustic wave resonator with a higher quality factor, since the quality factor of the acoustic wave resonator is closely related to the low loss and high rejection of the filter, the low phase noise of the oscillator, and the high sensitivity of the sensor.
In the process of continuously increasing the frequency of the traditional interdigital acoustic wave resonator, the interdigital electrode is reduced, so that the resistance of the interdigital electrode is increased. And a larger resistance would severely deteriorate the quality factor, resulting in degradation of the quality of the acoustic wave resonator. Therefore, how to increase the quality factor of the acoustic wave resonator in the process of increasing the frequency is a problem that needs to be solved by those skilled in the art.
Based on this, in order to solve the above-described problems, an embodiment of the present application provides an acoustic wave resonator that may include a substrate, a piezoelectric layer, and at least two interdigital electrodes. The piezoelectric layer is arranged on the surface of the substrate, a plurality of grooves are formed in one side, which is contacted with the substrate, or one side, which is away from the substrate, of the piezoelectric layer, the depth of each groove is smaller than the thickness of the piezoelectric layer, the number of the grooves is the same as that of the interdigital electrodes, and one interdigital electrode is arranged in each groove of the grooves.
In this way, the interdigital electrode can be embedded in the groove of the piezoelectric layer to extend deeper into the piezoelectric layer, so that the vibration mode of the excited sound wave can be closer to the bulk wave, namely, propagate in the whole medium. Therefore, even in the process of increasing the frequency, the size of the interdigital electrode does not need to be changed, so that the resistance of the interdigital electrode is not increased, the quality factor of the acoustic wave resonator is prevented from being reduced, and the acoustic wave resonator with high quality is realized. And, because the interdigital electrode is arranged in the groove of the piezoelectric layer, the interdigital electrode is closer to the center of the piezoelectric layer, and the quality factor of the acoustic wave resonator can be further improved by increasing the thickness of the interdigital electrode in the groove so as to increase the cross section of the interdigital electrode, thereby reducing the resistance of the interdigital electrode.
In order to make the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are only some embodiments of the present application, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
Fig. 1 is a schematic cross-sectional view of an acoustic wave resonator according to an embodiment of the present application, fig. 2 is a schematic cross-sectional view of another acoustic wave resonator according to an embodiment of the present application, fig. 3 is a schematic cross-sectional view of another acoustic wave resonator according to an embodiment of the present application, and fig. 4 is a schematic cross-sectional view of another acoustic wave resonator according to an embodiment of the present application. As shown in fig. 1 to 4, an acoustic wave resonator according to an embodiment of the present application may include a substrate 1, a piezoelectric layer 2, and at least two interdigital electrodes 3.
Wherein, piezoelectric layer 2 sets up in the surface of substrate 1, and the one side of piezoelectric layer 2 and substrate 1 contact or the one side that deviates from substrate 1 sets up a plurality of recesses, and the degree of depth of a plurality of recesses is all less than piezoelectric layer 2's thickness, and the quantity of recess is the same with the quantity of interdigital electrode 3, sets up an interdigital electrode 3 in every recess in a plurality of recesses.
Alternatively, in an embodiment of the present application, the substrate 1 may include at least one of silicon, aluminum oxide, silicon oxide, glass, aluminum nitride, scandium aluminum nitride, quartz, or silicon carbide.
The number of the plurality of grooves may be 2 to 500, for example, the number of the plurality of grooves may be 2, 100, 200, 250, 380 or 500. The depth of each groove may be 10 nm to 10000 nm, for example, the depth of each groove may be 10 nm, 100 nm, 2900 nm, 5000 nm, 8900 nm, 10000 nm, or the like. The width of each groove may be 0.001 microns to 5 microns, for example, the width of each groove may be 0.001 microns, 1 micron, 2.6 microns, 4.1 microns, or 5 microns. The length of each groove may be 1 micron to 500 microns, for example, the length of each groove may be 1 micron, 80 microns, 250 microns, 360 microns, 499 microns, or 500 microns.
The interdigital electrode 3 can be a metal having a conductivity greater than 5 x 10 6 siemens per meter. For example, the interdigital electrode 3 may be gold, silver, copper, aluminum, molybdenum, chromium, nickel, platinum, or an alloy composed of titanium gold, titanium aluminum, chromium gold, and chromium aluminum.
In practical applications, the interdigital electrodes may be arranged in pairs. Accordingly, since the number of grooves is the same as that of the interdigital electrodes 3, the number of interdigital electrodes and the grooves described above are both an even number. Based on this, the number of the interdigital electrodes 3 may be 2 to 500, for example, the number of the interdigital electrodes 3 may be 2, 100, 200, 250, 380, or 500. The thickness of each of the interdigital electrodes 3 may be 10 nm to 10500 nm, for example, the thickness of each of the interdigital electrodes 3 may be 10 nm, 100 nm, 2900 nm, 5000 nm, 8900 nm, 10000 nm, 10500 nm, or the like. The width of each of the interdigital electrodes 3 may be 0.001 to 10 micrometers, for example, the width of each of the interdigital electrodes 3 may be 0.001 micrometers, 1 micrometer, 2.6 micrometers, 4.1 micrometers, 7 micrometers, 9.6 micrometers or 10 micrometers. The length of each of the interdigital electrodes 3 may be 1 to 500 micrometers, for example, the length of each of the interdigital electrodes 3 may be 1, 80, 250, 360, 499 or 500 micrometers.
In addition, since the interdigital electrode is disposed in the groove of the piezoelectric layer, the interdigital electrode is closer to the center of the piezoelectric layer, and the quality factor of the acoustic wave resonator can be further improved by increasing the thickness of the interdigital electrode in the groove so as to increase the cross section of the interdigital electrode, thereby reducing the resistance of the interdigital electrode. Based on this, in the embodiment of the present application, the thickness of the interdigital electrode and the depth of the groove are adaptively increased in the corresponding value range.
As an example, as shown in connection with fig. 1, a plurality of grooves may be provided on the side of the piezoelectric layer 2 facing away from the substrate 1. The plurality of grooves may be etched to be rectangular. For each groove, the thickness of the interdigital electrode 3 arranged in the groove is smaller than the depth of the groove.
As another example, as shown in connection with fig. 2, a plurality of grooves may be provided on the side of the piezoelectric layer 2 facing away from the substrate 1. The plurality of grooves may be etched to be rectangular. For each recess, the thickness of the interdigital electrode 3 provided in the recess may be greater than the depth of the recess.
As yet another example, as shown in connection with fig. 3, a plurality of grooves may be provided at a side where the piezoelectric layer 2 contacts the substrate 1. The plurality of grooves may be etched to be rectangular. For each recess, the thickness of the interdigital electrode 3 provided in the recess may be equal to the depth of the recess.
As a further example, as shown in connection with fig. 4, a plurality of grooves may be provided on the side of the piezoelectric layer 2 facing away from the substrate 1. The plurality of grooves may be etched into a trapezoid shape. For each groove, the interdigital electrode 3 in the groove can be attached along the shape of the groove and extend out of the groove to cover the upper surface of the piezoelectric layer 2.
In the embodiment of the present application, the shape of the recess and the interdigital electrode 3 may not be specifically limited, and may be, for example, rectangular, trapezoidal, triangular, elliptical, circular, or the like. The above is only illustrated by way of example in terms of a number of possible embodiments.
The thickness of the piezoelectric layer 2 is 10 nm to 10000 nm, for example, the thickness of the piezoelectric layer 2 may be 10 nm, 100 nm, 2900 nm, 5000 nm, 8900 nm, 10000 nm, or the like.
Accordingly, the piezoelectric layer 2 may be a lithium niobate layer. Further, fig. 5 is a schematic diagram of euler angle rotation according to an embodiment of the present application. Referring to fig. 5, in the embodiment of the present application, an angle formed between a horizontal electric field direction +y' formed by the interdigital electrode 3 and a y-axis direction in the coordinate system of the piezoelectric layer 2 may be regarded as euler angle α. Correspondingly, the Euler angle alpha of the lithium niobate layer is-90 degrees to 90 degrees.
Optionally, in order to further improve the electromechanical coupling coefficient of the acoustic wave resonator, the value range of the Euler angle alpha of the lithium niobate layer can be set to be-20 degrees to 20 degrees or-80 degrees to 40 degrees.
Further, in the embodiment of the present application, the ratio of the depth of each groove to the thickness of each interdigital electrode 3 in the plurality of grooves ranges from 0.5 to 10, for example, the ratio of the depth of each groove to the thickness of each interdigital electrode 3 is 1:1, 2:1, 3:1, or 9:8. For easy understanding, the following exemplary embodiments corresponding to the above ratios are described with reference to examples and drawings, respectively.
As a possible implementation, fig. 6 is a schematic cut-away view of an acoustic wave resonator for operating at a frequency of 5.3 gigahertz provided by an embodiment of the present application. Referring to fig. 6, for the case where the ratio of the depth d of each groove to the thickness t e of each interdigital electrode 3 is 1:1, the depth d of each groove is 90 nm, the thickness t e of each interdigital electrode 3 is 90 nm, and the interdigital electrode 3 in each groove is completely embedded in the groove. A plurality of grooves are formed in the side where the piezoelectric layer 2 contacts the substrate 1, and the surfaces of the grooves in which the interdigital electrodes 3 are embedded are flush with the side where the piezoelectric layer 2 contacts the substrate 1. In the case where a plurality of grooves are provided on the side of the piezoelectric layer 2 facing away from the substrate 1, the surface of the groove in which the interdigital electrode 3 is embedded is on the same plane as the side of the piezoelectric layer 2 facing away from the substrate 1. The duty ratio of each of the interdigital electrodes 3 (i.e., the ratio of the width and the pitch of the electrode fingers included in each interdigital electrode 3) is 50%. The piezoelectric layer 2 may be tangentially X-cut lithium niobate, the euler angle of the piezoelectric layer 2 being-5 °. The sum of 2 times the width of the interdigital electrode 3 and 2 times the pitch of the adjacent interdigital electrode 3 is used as a horizontal wavelength λ, which is 900 nm, and the ratio of the horizontal wavelength λ to the thickness t LN of the piezoelectric layer 2 is 3:1. Based on the above design, acoustic wave resonators can be used to operate at frequencies of 5.3 gigahertz.
Fig. 7 is a simulated admittance curve for an acoustic wave resonator operating at a frequency of 5.3 gigahertz provided by an embodiment of the present application. In the simulated admittance curve, the horizontal axis represents Frequency (Frequency/GHZ) and the vertical axis represents admittance (ADMITTANCE/dB) as shown in FIG. 7. The electromechanical coupling coefficient is about 40% when the acoustic wave resonator is operated at a frequency of 5.3 gigahertz. Wherein the electromechanical coupling coefficient can be calculated by the following formula (1):
(1)
Wherein k 2 is the electromechanical coupling coefficient, f s is the frequency of the highest point of admittance in the true admittance curve, and f p is the frequency of the lowest point of admittance in the simulated admittance curve.
As another possible implementation, fig. 8 is a schematic cut-away view of an acoustic wave resonator for operating at a frequency of 6.6 gigahertz provided by an embodiment of the present application. Referring to fig. 8, for the case where the ratio of the depth d of each groove to the thickness t e of each interdigital electrode 3 is 2:1, the depth d of each groove is 180 nm, the thickness t e of each interdigital electrode 3 is 90 nm, and the interdigital electrode 3 in each groove is completely embedded in the groove. The duty cycle of each interdigital electrode 3 is 50%. The piezoelectric layer 2 may be tangentially X-cut lithium niobate, the euler angle of the piezoelectric layer 2 being-5 °. The sum of 2 times the width of the interdigital electrode 3 and 2 times the pitch of the adjacent interdigital electrode 3 is used as a horizontal wavelength λ, which is 900 nm, and the ratio of the horizontal wavelength λ to the thickness t LN of the piezoelectric layer 2 is 3:1. Based on the above design, acoustic wave resonators can be used to operate at a frequency of 6.6 gigahertz.
Fig. 9 is a simulated admittance curve for an acoustic wave resonator operating at a frequency of 6.6 gigahertz provided by an embodiment of the present application. In the simulated admittance curve, the horizontal axis represents Frequency (Frequency/GHZ) and the vertical axis represents admittance (ADMITTANCE/dB) as shown in FIG. 9. When the acoustic wave resonator is operated at a frequency of 6.6 gigahertz, the electromechanical coupling coefficient is greater than 26%. Wherein, the electromechanical coupling coefficient can be calculated by the above formula (1).
As yet another possible implementation, fig. 10 is a schematic cut-away view of an acoustic wave resonator for operating at a frequency of 8.3 gigahertz provided by an embodiment of the present application. Referring to fig. 10, for the case where the ratio of the depth d of each groove to the thickness t e of each interdigital electrode 3 is 3:1, the depth d of each groove is 270 nm, the thickness t e of each interdigital electrode 3 is 90 nm, and the interdigital electrode 3 in each groove is completely embedded in the groove. The duty cycle of each interdigital electrode 3 is 50%. The piezoelectric layer 2 may be tangentially X-cut lithium niobate, the euler angle of the piezoelectric layer 2 being-5 °. The sum of 2 times the width of the interdigital electrode 3 and 2 times the pitch of the adjacent interdigital electrode 3 is used as a horizontal wavelength λ, which is 900 nm, and the ratio of the horizontal wavelength λ to the thickness t LN of the piezoelectric layer 2 is 3:1. Based on the above design, acoustic wave resonators can be used to operate at 8.3 gigahertz frequencies.
FIG. 11 is a simulated admittance curve for an acoustic wave resonator operating at a frequency of 8.3 gigahertz provided by an embodiment of the present application. In the simulated admittance curve, the horizontal axis represents Frequency (Frequency/GHZ) and the vertical axis represents admittance (ADMITTANCE/dB) as shown in FIG. 11. When the acoustic wave resonator is operated at a frequency of 8.3 gigahertz, the electromechanical coupling coefficient is greater than 9%. Wherein, the electromechanical coupling coefficient can be calculated by the above formula (1).
As yet another possible embodiment, for the case that the ratio of the depth d of each groove to the thickness t e of each interdigital electrode 3 is 9:8, the depth d of each groove is 90 nm, the thickness t e of each interdigital electrode 3 is 80 nm, and the interdigital electrode 3 within each groove is completely embedded in the groove. The duty cycle of each interdigital electrode 3 is 50%. The piezoelectric layer 2 may be tangentially X-cut lithium niobate, the euler angle of the piezoelectric layer 2 being-5 °. The sum of 2 times the width of the interdigital electrode 3 and 2 times the pitch of the adjacent interdigital electrode 3 is used as a horizontal wavelength λ, which is 900 nm, and the ratio of the horizontal wavelength λ to the thickness t LN of the piezoelectric layer 2 is 9:1. Based on the above design, acoustic wave resonators can be used to operate at a frequency of 14.5 gigahertz.
Fig. 12 is a simulated admittance curve for an acoustic wave resonator operating at a frequency of 14.5 gigahertz provided by an embodiment of the present application. In the simulated admittance curve, the horizontal axis represents Frequency (Frequency/GHZ) and the vertical axis represents admittance (ADMITTANCE/dB) as shown in FIG. 12. The electromechanical coupling coefficient is about 79% when the acoustic wave resonator is operated at a frequency of 14.5 gigahertz. Wherein, the electromechanical coupling coefficient can be calculated by the above formula (1).
Based on the above embodiment, in the embodiment of the present application, by designing the groove depth of the piezoelectric layer, the thickness of the interdigital electrode, and the duty ratio, the interdigital electrode is embedded in the groove of the piezoelectric layer, and is deeper into the piezoelectric layer, so that the vibration mode of the excited sound wave is more similar to that of the bulk wave, that is, propagates in the whole medium, therefore, even in the process of increasing the frequency, the size of the interdigital electrode is not required to be changed, so that the resistance of the interdigital electrode is not increased, thereby avoiding the quality factor of the sound wave resonator from being reduced, and realizing the sound wave resonator with high quality. And when the ratio of the horizontal wavelength to the thickness of the piezoelectric layer is kept unchanged, the working frequency of the acoustic wave resonator can be from tens of MHz to tens of GHz, and a larger quality factor is kept, so that the performance requirements of the current frequency band on the high frequency and the high quality of the filter can be well met.
Further, in order to further improve the frequency temperature coefficient of the acoustic wave resonator, in the embodiment of the present application, in the case where a plurality of grooves are provided on the side of the piezoelectric layer 2 facing away from the substrate 1, a silicon dioxide layer may be further covered on the side of the at least two interdigital electrodes 3 facing away from the substrate 1. The thickness of the silicon dioxide layer is 1-300 nm, for example, the thickness of the silicon dioxide layer can be 1nm, 99 nm, 250 nm or 300 nm. For ease of understanding, the following description is made with reference to the accompanying drawings and the various possible embodiments.
As a possible implementation, fig. 13 is a schematic cross-sectional view of an acoustic resonator provided by an embodiment of the present application, where at least two interdigital electrodes 3 are covered with a silicon dioxide layer on a side facing away from the substrate 1. As shown in connection with fig. 13, in case the interdigitated electrodes 3 in each recess are completely embedded in the recess, and there is still an unfilled portion in the recess, it is possible to cover the silicon dioxide layer (shown as SiO 2 in the figure) only on the side of at least two of the interdigitated electrodes 3 facing away from the substrate 1.
As another possible implementation, fig. 14 is a schematic cross-sectional view of another acoustic resonator provided by an embodiment of the present application, where at least two interdigital electrodes 3 are covered with a silicon dioxide layer on a side facing away from the substrate 1. As shown in connection with fig. 14, in case the interdigitated electrodes 3 in each recess are completely embedded in the recess, and there is still an unfilled portion in the recess, it is possible to cover the side of at least two of the interdigitated electrodes 3 facing away from the substrate 1 with a silicon dioxide layer (shown as SiO 2 in the figure) and the side of the piezoelectric layer 2 facing away from the substrate 1 with a silicon dioxide layer.
As a further possible implementation, fig. 15 is a schematic cross-sectional view of a further acoustic resonator provided by an embodiment of the present application, wherein at least two interdigital electrodes 3 are covered with a silicon dioxide layer on the side facing away from the substrate 1. In the case where the interdigital electrode 3 in each groove is not completely embedded in the groove, as shown in fig. 15, in the case where there is a portion beyond the groove, the side of the interdigital electrode 3 beyond the groove may be covered with a silicon oxide layer (shown as SiO 2 in the figure), and the side of the piezoelectric layer 2 facing away from the substrate 1 may be covered with a silicon oxide layer.
Further, fig. 16 is a top view of an internal structure of an acoustic wave resonator according to the present application. As shown in fig. 16, an acoustic wave resonator according to an embodiment of the present application may include a substrate (not shown), a piezoelectric layer 2, interdigital electrodes 3, and a reflective grating 4.
In fig. 16, the interdigital electrodes 3 include two groups, the two groups of interdigital electrodes 3 are staggered and distributed in a periodic manner, and each group of interdigital electrodes 3 is connected with a bus bar.
The reflective grating 4 also comprises two groups, and the two groups of reflective gratings 4 are respectively arranged at two sides of the interdigital electrode 3, and the positions are shown in fig. 16. Each reflective grating 4 comprises a plurality of pairs of metal grating bars, and the number of pairs of metal grating bars can be 10-60, for example, 10, 15, 30, 45 or 60. The thickness of each metal grid may be 10 nm to 10500 nm, for example, the thickness of each metal grid may be 10 nm, 100 nm, 2900 nm, 5000 nm, 8900 nm, 10000 nm, 10500 nm, or the like. The width of each metal grid may be 0.001 to 10 microns, for example, the width of each metal grid may be 0.001, 1, 2.6, 4.1, 7, 9.6 or 10 microns. The length of each metal grid may be 1 micron to 500 microns, for example, the length of each metal grid may be 1 micron, 80 microns, 250 microns, 360 microns, 499 microns or 500 microns.
The metal bars of the reflective grating 4 are made of the same material as the interdigital electrode 3, and have a conductivity of more than 5×10 6 siemens per meter.
In practical application, the interdigital electrodes can be designed into various shapes, and only two groups of interdigital electrodes are required to be staggered and distributed according to the period. Fig. 16 is merely an exemplary illustration, and does not limit the specific shape of the interdigital electrode in the embodiment of the present application.
Based on the above description of the acoustic wave resonator, in an embodiment of the present application, an acoustic wave resonator including a substrate, a piezoelectric layer, and at least two interdigital electrodes may be provided. The piezoelectric layer is arranged on the surface of the substrate, a plurality of grooves are formed in one side, which is contacted with the substrate, or one side, which is away from the substrate, of the piezoelectric layer, the depth of each groove is smaller than the thickness of the piezoelectric layer, the number of the grooves is the same as that of the interdigital electrodes, and one interdigital electrode is arranged in each groove of the grooves. In this way, the interdigital electrode can be embedded in the groove of the piezoelectric layer to extend deeper into the piezoelectric layer, so that the vibration mode of the excited sound wave can be closer to the bulk wave, namely, propagate in the whole medium. Therefore, even in the process of increasing the frequency, the size of the interdigital electrode does not need to be changed, so that the resistance of the interdigital electrode is not increased, the quality factor of the acoustic wave resonator is prevented from being reduced, and the acoustic wave resonator with high quality is realized. Because the interdigital electrode is arranged in the groove of the piezoelectric layer, the interdigital electrode is closer to the center of the piezoelectric layer, and the quality factor of the acoustic wave resonator can be further improved by increasing the thickness of the interdigital electrode in the groove so as to increase the cross section of the interdigital electrode, thereby reducing the resistance of the interdigital electrode.
Further, based on the acoustic wave resonator provided in the above embodiment, the embodiment of the present application may also provide a method for manufacturing the acoustic wave resonator. The method of manufacturing the acoustic wave resonator will be described below with reference to examples and drawings, respectively.
Fig. 17 is a flowchart of a method for manufacturing an acoustic wave resonator according to an embodiment of the present application. Referring to fig. 17, a method for manufacturing an acoustic wave resonator according to an embodiment of the present application may include:
s1701, providing a substrate.
S1702, forming a piezoelectric layer on a surface of a substrate.
And S1703, etching a plurality of grooves on the side, which is contacted with the substrate or is away from the substrate, of the piezoelectric layer, wherein the depth of the grooves is smaller than the thickness of the piezoelectric layer.
And S1704, forming an interdigital electrode in each of the plurality of grooves.
Optionally, a ratio of a depth of each groove of the plurality of grooves to a thickness of each interdigitated electrode is 1:1, 2:1, 3:1, or 9:8.
Optionally, the acoustic wave resonator is configured to operate at a frequency of 5.3 gigahertz with a ratio of the depth of each recess to the thickness of each interdigital electrode of 1:1;
The acoustic resonator is configured to operate at a frequency of 6.6 gigahertz with a ratio of the depth of each recess to the thickness of each interdigital electrode of 2:1;
The acoustic wave resonator is configured to operate at a frequency of 8.3 gigahertz with a ratio of the depth of each recess to the thickness of each interdigital electrode of 3:1;
the acoustic wave resonator is configured to operate at a frequency of 14.5 gigahertz with a ratio of the depth of each recess to the thickness of each interdigital electrode of 9:8.
Optionally, the depth of each groove is 10-10000 nanometers, the thickness of each interdigital electrode is 10-10500 nanometers, and the thickness of the piezoelectric layer is 10-10000 nanometers.
Optionally, in a case that a plurality of grooves are formed on a side, facing away from the substrate, of the piezoelectric layer, one side, facing away from the substrate, of the at least two interdigital electrodes is covered with a silicon dioxide layer, and the thickness of the silicon dioxide layer is 1-300 nanometers.
Optionally, the piezoelectric layer is a lithium niobate layer, and the Euler angle of the lithium niobate layer is-90 degrees to 90 degrees.
Optionally, each interdigital electrode is a metal having a conductivity greater than 5 x 10 6 siemens per meter.
Optionally, the substrate comprises at least one of silicon, aluminum oxide, silicon oxide, glass, aluminum nitride, scandium aluminum nitride, quartz, or silicon carbide.
Further, based on the acoustic wave resonator provided in the above embodiment, the embodiment of the present application may also provide an electronic device. The electronic device comprises the acoustic wave resonator provided by any one of the embodiments.
In this specification, each embodiment is described in a progressive manner, or a parallel manner, or a combination of progressive and parallel manners, and each embodiment focuses on the differences from other embodiments, and the same similar parts between the embodiments are referred to each other. For the preparation method disclosed in the embodiment, since the preparation method corresponds to the acoustic wave resonator disclosed in the embodiment, the description is simpler, and the relevant points are only needed to be referred to the description of the acoustic wave resonator.
It is further noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises an element.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (8)
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