CN117674759A - Elastic wave device - Google Patents
Elastic wave device Download PDFInfo
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- CN117674759A CN117674759A CN202311659407.0A CN202311659407A CN117674759A CN 117674759 A CN117674759 A CN 117674759A CN 202311659407 A CN202311659407 A CN 202311659407A CN 117674759 A CN117674759 A CN 117674759A
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- 239000010409 thin film Substances 0.000 claims abstract description 47
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 claims abstract description 29
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 86
- 239000000758 substrate Substances 0.000 claims description 68
- 239000000463 material Substances 0.000 claims description 64
- 239000000377 silicon dioxide Substances 0.000 claims description 40
- 235000012239 silicon dioxide Nutrition 0.000 claims description 39
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 13
- 229910052802 copper Inorganic materials 0.000 claims description 13
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- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 10
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 claims description 10
- 229910052799 carbon Inorganic materials 0.000 claims description 10
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- 229910001385 heavy metal Inorganic materials 0.000 claims description 8
- 239000007769 metal material Substances 0.000 claims description 8
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 7
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- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 6
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims description 6
- 239000011521 glass Substances 0.000 claims description 6
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims description 6
- 229910052737 gold Inorganic materials 0.000 claims description 6
- 239000010931 gold Substances 0.000 claims description 6
- 229910052750 molybdenum Inorganic materials 0.000 claims description 6
- 239000011733 molybdenum Substances 0.000 claims description 6
- BPUBBGLMJRNUCC-UHFFFAOYSA-N oxygen(2-);tantalum(5+) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Ta+5].[Ta+5] BPUBBGLMJRNUCC-UHFFFAOYSA-N 0.000 claims description 6
- 229910052697 platinum Inorganic materials 0.000 claims description 6
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- 229910052715 tantalum Inorganic materials 0.000 claims description 6
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 claims description 6
- 229910001936 tantalum oxide Inorganic materials 0.000 claims description 6
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 6
- 229910052721 tungsten Inorganic materials 0.000 claims description 6
- 239000010937 tungsten Substances 0.000 claims description 6
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 4
- 229910052732 germanium Inorganic materials 0.000 claims description 4
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 claims description 4
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 4
- 150000001639 boron compounds Chemical class 0.000 claims description 3
- 229910021417 amorphous silicon Inorganic materials 0.000 claims description 2
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- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 description 14
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- WSMQKESQZFQMFW-UHFFFAOYSA-N 5-methyl-pyrazole-3-carboxylic acid Chemical compound CC1=CC(C(O)=O)=NN1 WSMQKESQZFQMFW-UHFFFAOYSA-N 0.000 description 2
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 2
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Landscapes
- Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
Abstract
The application relates to an elastic wave device, and relates to the technical field of elastic waves. The application is realized by arranging the piezoelectric layer into a lithium niobate thin film with Euler angles of (0 DEG + -10 DEG, 122 DEG + -10 DEG, 45 DEG + -10 DEG) or (0 DEG + -10 DEG, 122 DEG + -10 DEG, 135 DEG + -10 DEG); a conductive material film pattern is arranged above the piezoelectric layer, a low sound velocity layer is arranged below the piezoelectric layer, and a Gao Shengsu component is arranged below the low sound velocity layer; on the premise that the thickness of the piezoelectric layer is hLN and the wavelength of the elastic wave is lambda, the piezoelectric layer satisfies that the ratio of lambda to hLN is more than or equal to 0.1 and lambda is less than or equal to 0.3; and satisfying 0.1.ltoreq.h1/λ.ltoreq.0.3 on the premise that the thickness of the low acoustic velocity layer is set to h1 and the wavelength of the elastic wave is set to λ. The problem that the Q value of a longitudinal wave type leaky surface acoustic wave (LLSAW) elastic wave device is too low is solved.
Description
Technical Field
The present invention relates to the field of elastic wave technology, and more particularly, to an elastic wave device that uses a high Q value and a high operating frequency of a longitudinal wave leaky surface acoustic wave (LLSAW).
Background
The elastic wave device has the characteristics of low cost, small volume, multiple functions and the like, and is widely applied to the fields of radar, communication, navigation and the like. The most commonly used elastic wave devices in mobile phone and base station communication are elastic wave resonators, elastic wave filters composed of a plurality of elastic wave resonators, and elastic wave diplexers and elastic wave multiplexers composed of a plurality of elastic wave filters. In any type of elastic wave device, a thin film pattern of a conductive material is provided on a piezoelectric multilayer substrate to determine a plurality of interdigital transducer electrodes and reflective gate electrodes, and bandpass characteristics are obtained by utilizing frequency characteristics of a conversion function of an electric signal of the interdigital transducer electrodes into an elastic wave.
Mobile communication systems are evolving from 3G, 4G to 5G, and their use of frequency bands is evolving toward high frequencies and large bandwidths. In order to increase the frequency of the elastic wave element, the elastic wave wavelength defined by the pitch of the interdigital transducer electrodes can be reduced. The global mobile 5G network deployment already comprises a sub-6G frequency band of 3-7 GHz, and the sound velocity of the piezoelectric crystal material such as lithium niobate and lithium tantalate which are widely used for preparing elastic wave elements at present is about 3000-4000 m/s, so that devices above 3GHz can be hardly manufactured by using the prior photoetching technology on the basis of not greatly improving the cost. In addition, the interdigital electrode is narrowed and thinned under high frequency, the ohmic loss of the electrode is increased, the Q value of the device is reduced, and meanwhile, the electrode material is easy to damage, so that the performance and the reliability of the device are seriously affected. Thus, for increasing the frequency of the elastic wave element, it is important to increase the sound velocity of the elastic wave.
To achieve higher sound speeds, the industry is attempting to use longitudinal wave leaky surface acoustic waves (LLSAW) as the mode of operation in elastic wave elements. However, since the longitudinal leaky surface acoustic wave propagates while leaking to the substrate including the piezoelectric layer, there is a problem that the Q value is low, and the requirement of the high-frequency high-performance filter for the 5G communication cannot be satisfied.
Patent document CN112823473a has studied to provide an acoustic wave device excellent in Q value by efficiently sealing a longitudinal leaky surface acoustic wave to a piezoelectric layer by a specific euler angle and structure of the piezoelectric layer.
However, in the elastic wave device disclosed in patent document CN112823473a, when the main component of the elastic wave propagating is a longitudinal wave, the euler angle of the piezoelectric layer does not cover all ranges, and the Q value, parasitic mode, and other properties of the device are limited by factors such as the interdigital transducer electrode material, the device structure, and the substrate material tangential direction, and therefore, there are disadvantages such as high device manufacturing cost, poor stability, and narrow application range.
Disclosure of Invention
The present application also aims to solve the problem of excessively low Q value of a longitudinal wave leaky surface acoustic wave (LLSAW) acoustic wave device, and has an object to develop an acoustic wave device having a large Q value of the device and a high operating frequency by using a new material euler angle and a new laminated piezoelectric structure.
In order to achieve the above purpose, the technical scheme adopted in the application is as follows:
in a first aspect, the present application provides an elastic wave device comprising:
a piezoelectric layer including a lithium niobate thin film having euler angles of (0°±10°,122°±10°,45°±10°) or (0°±10°,122°±10°,135°±10°), and having first and second main faces opposed to each other;
An interdigital transducer electrode and a reflective gate electrode formed directly or indirectly on the first main face, the interdigital transducer electrode and the reflective gate electrode being composed of a heavy metal material;
a low acoustic velocity layer formed directly or indirectly on the second main surface; and
a high sound speed member located below the low sound speed layer;
wherein, the thickness of the piezoelectric layer is set as h LN On the premise that the wavelength of the elastic wave is lambda, the wavelength is 0.1-h LN Lambda is less than or equal to 0.3; in the case that the thickness of the low sound velocity layer is set to be h 1 On the premise that the wavelength of the elastic wave is lambda, the wavelength is 0.1-h 1 /λ≤0.3。
In one possible implementation, the acoustic velocity of the bulk wave propagating in the Gao Shengsu component is higher than the acoustic velocity of the bulk wave propagating in the piezoelectric layer.
In one possible implementation, the high acoustic speed member includes:
a support substrate for supporting the low acoustic velocity layer; or (b)
A support substrate and a layer of capture material disposed between the support substrate and the low acoustic velocity layer, the layer of capture material being configured to support the low acoustic velocity layer.
In one possible implementation, the support substrate is composed of one or more materials with a sound speed exceeding 6000 m/s.
In one possible implementation, the low sound velocity layer is formed by one or more of silicon dioxide, glass, silicon oxynitride, tantalum oxide, or a material containing fluorine, carbon, or boron compound as a main component added to silicon oxide.
In one possible implementation, the trapping material layer is formed of one or more combinations of amorphous silicon, polysilicon, amorphous germanium, and polycrystalline germanium.
In one possible implementation, the thickness of the trapping material layer is set to h 2 On the premise that the wavelength of the elastic wave is lambda, the value of (h) is 0.1-0 2 +h 1 )/λ≤0.3。
In one possible implementation, the heavy metal material is composed of one or more of copper, platinum, tungsten, gold, silver, molybdenum, tantalum.
In one possible implementation manner, the piezoelectric transducer further comprises a dielectric layer, wherein the dielectric layer is formed by silicon dioxide, silicon nitride or a material with fluorine, carbon or boron compounds as main components added to the silicon oxide, and the dielectric layer is arranged on the piezoelectric layer and covers the interdigital transducer electrode and the reflective gate electrode.
In a second aspect, the present application provides an elastic wave filter or multiplexer, each comprising a resonator on a series arm and a resonator on a parallel arm, wherein:
At least one of said resonators is an elastic wave device as defined in any one of the preceding claims.
The beneficial effects that this application provided technical scheme brought include at least:
by setting the piezoelectric layer to be a lithium niobate thin film having euler angles of (0°±10°,122°±10°,45°±10°) or (0°±10°,122°±10°,135°±10°; a conductive material film pattern is arranged above the piezoelectric layer, a low sound velocity layer is arranged below the piezoelectric layer, and a Gao Shengsu component is arranged below the low sound velocity layer; on the premise that the thickness of the piezoelectric layer is hLN and the wavelength of the elastic wave is lambda, the piezoelectric layer satisfies that the ratio of lambda to hLN is more than or equal to 0.1 and lambda is less than or equal to 0.3; and satisfying 0.1.ltoreq.h1/λ.ltoreq.0.3 on the premise that the thickness of the low acoustic velocity layer is set to h1 and the wavelength of the elastic wave is set to λ. In this case, by using a new material euler angle and a new laminated piezoelectric structure, an elastic wave device having a large device Q value and a high operating frequency is provided, solving the problem that the Q value of a longitudinal wave leaky surface acoustic wave (LLSAW) elastic wave device is too low.
Drawings
The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate the application and together with the embodiments of the application, and not constitute a limitation to the application. In the drawings:
Fig. 1 shows a schematic plan view and a cross-sectional view of a typical Surface Acoustic Wave (SAW) resonator 100;
fig. 2 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 provided in the first embodiment of the application;
fig. 3 shows a vibration mode diagram of two different acoustic modes in a piezoelectric layer of an acoustic wave device (longitudinal wave leaky surface acoustic wave resonator) 200 according to an embodiment of the disclosure, and a change diagram of frequencies corresponding to the two different acoustic modes with wavelength;
fig. 4 is a graph showing the change of piezoelectric coupling coefficients of two different acoustic modes in a piezoelectric layer of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 according to an embodiment of the invention along with euler angles of the piezoelectric layer;
fig. 5 shows a frequency response diagram of an acoustic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 according to an embodiment of the invention;
fig. 6 shows a frequency response diagram of another acoustic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 according to an embodiment of the invention;
fig. 7 shows a frequency response diagram of another acoustic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 according to an embodiment of the invention;
fig. 8 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 300 provided in comparative example one of the present application;
Fig. 9 shows a frequency response diagram of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 300 provided in comparative example one of the present application;
fig. 10 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 400 provided in a comparative example two of the present application;
fig. 11 shows a frequency response diagram of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 400 provided in comparative example two of the present application;
fig. 12 is a graph showing the displacement amount of the LLSAW mode in the support substrate of the elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 provided in the first embodiment of the present application and the elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 300 provided in the first comparative example as a function of the depth (thickness) of the support substrate;
fig. 13 shows a frequency response graph of the elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 according to the first embodiment of the invention as a function of the propagation angle ψ of the piezoelectric layer;
fig. 14 shows a graph of electromechanical coupling coefficient of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 according to a piezoelectric layer propagation angle ψ;
fig. 15 shows a frequency response curve of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 of a pattern of thin films of conductive materials of different materials and thicknesses;
Fig. 16 shows a frequency response curve of another elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 of a pattern of thin films of conductive materials of different materials and thicknesses;
fig. 17 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 500 provided in comparative example three of the present application;
fig. 18 shows a frequency response comparison chart of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 provided in the first embodiment of the invention and an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 500 provided in the third comparative example;
fig. 19 shows a frequency response comparison chart of another elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 provided in the first embodiment of the invention and another elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 500 provided in the third comparative example;
fig. 20 shows a frequency response comparison chart of elastic wave devices (longitudinal wave type leaky surface acoustic wave resonators) 200 of different piezoelectric layer thicknesses;
fig. 21 shows a graph of electromechanical coupling coefficient trends of elastic wave devices (longitudinal wave type leaky surface acoustic wave resonators) 200 of different piezoelectric layer thicknesses;
fig. 22 shows a frequency response comparison chart of elastic wave devices (longitudinal wave type leaky surface acoustic wave resonators) 200 of different low acoustic velocity layer thicknesses;
Fig. 23 shows a graph of electromechanical coupling coefficient trends of elastic wave devices (longitudinal wave type leaky surface acoustic wave resonators) 200 of different low acoustic velocity layer thicknesses;
fig. 24 to 27 are graphs showing frequency response comparisons of acoustic wave devices (longitudinal wave type leaky surface acoustic wave resonators) 200 of different support substrates;
fig. 28 shows a graph of the measured frequency response and Q-value of an acoustic wave device (longitudinal wave leaky surface acoustic wave resonator) 200 according to an embodiment of the invention;
fig. 29 shows a graph of the measured frequency response and Q-value of another acoustic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 according to the first embodiment of the invention;
fig. 30 shows a vibration mode diagram corresponding to a measured frequency response of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 and a transverse mode thereof according to an embodiment of the present disclosure;
FIG. 31 shows a schematic diagram of an inclined interdigital transducer electrode 600;
fig. 32 shows a graph of measured frequency response of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 of different β, and a graph of measured impedance ratio and Q value trend;
FIG. 33 shows a 5G communication-WIFI 6/7 band diagram;
fig. 34 is a schematic diagram showing a topology of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) according to the second embodiment of the invention;
Fig. 35 is a graph showing an actual measurement frequency response of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) according to the second embodiment of the invention;
fig. 36 is a graph showing an actual measurement frequency response of another acoustic wave device (longitudinal wave type leaky surface acoustic wave resonator) according to the second embodiment of the invention;
fig. 37 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 700 provided in a modification of the present application;
fig. 38 is a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 800 according to a second modification of the present application;
fig. 39 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 900 according to a third modification of the present application.
Detailed Description
The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all, of the embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.
Wherein like parts are designated by like reference numerals. It should be noted that the words "front", "rear", "left", "right", "upper" and "lower" used in the following description refer to directions in drawings of the present specification, and the words "bottom" and "top", "inner" and "outer" refer to directions toward or away from, respectively, a specific component. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present specification, the meaning of "plurality" is two or more.
The present application is further described below with reference to the drawings and examples.
Device description:
fig. 1 shows a schematic top view and a cross-sectional view of a typical piezoelectric composite substrate based Surface Acoustic Wave (SAW) resonator 100. In recent years, SAW resonators based on a piezoelectric composite substrate of a piezoelectric layer 101 and a non-piezoelectric substrate 103 have received attention due to their high Q-value performance, and are applied to a variety of fields such as radar, communication, navigation, and the like.
The SAW resonator 100 based on a piezoelectric composite substrate is composed of a piezoelectric layer 101 and a non-piezoelectric substrate 103 on which a thin film pattern of a conductive material is formed. The piezoelectric layer 101 is a thin single crystal layer made of piezoelectric material and has a thickness h LN The piezoelectric material includes, but is not limited to, lithium niobate, lithium tantalate, gallium nitride, aluminum nitride, or zinc oxide. As is known, piezoelectric layer 101 is cut so as to coincide with the crystal axes of the front and back sides of the opposite piezoelectric layer 101, so that piezoelectric layer 101 has different tangential choices, we often define its tangential direction by euler angles, e.g., Z cut piezoelectric layer euler angle (0 °,0 °,0 °), Y128 cut piezoelectric layer euler angle (0 °,38 °,0 °), Y32 ° X45 ° cut piezoelectric layer euler angle (0 °,122 °,45 °).
Quality factor Q:
in acoustic resonators, the quality factor Q is generally defined as the ratio of the peak energy stored during a period of an applied radio frequency signal to the energy dissipated or lost during that period. These dissipated and lost energies include: electrical loss, piezoelectric loss, and mechanical/elastic loss.
The non-piezoelectric substrate 103 is a single-layer or multi-layer substrate made of a high acoustic-velocity material, and is therefore also called a high acoustic-velocity member in which acoustic velocity of bulk waves propagating in the high acoustic-velocity member is higher than acoustic velocity of elastic waves propagating in the piezoelectric layer, so that acoustic velocity of elastic waves in the piezoelectric layer can be raised, and frequency of the device can be raised. In addition, the high sound speed component can effectively seal the elastic wave propagated in the piezoelectric layer without leakage in the piezoelectric layer, so that the Q value of the device is improved.
The conductive material film pattern includes interdigital transducer electrode 102a, reflective gate electrode 102b, interdigital transducer bus bar 104a, and reflective gate bus bar 104b, having a thickness h m . The interdigital transducer electrode 102a includes a plurality of first electrode fingers and a plurality of second electrode fingers that are interposed alternately with each other, and a first bus bar and a second bus bar that are opposed to each other in the extending direction of the first electrode fingers, the second electrode finger fingers. The distance λ between adjacent first (or second) electrode fingers, which is commonly referred to as the "wavelength" of the interdigital transducer. The first and second electrode fingers overlap by a distance AP, which is commonly referred to as the "aperture" of the interdigital transducer. The reflective gate electrode 102b includes a plurality of third electrode fingers and a plurality of fourth electrode fingers interposed alternately with each other, and third bus bars and fourth bus bars opposing each other in the extending direction of the third electrode fingers, the fourth electrode fingers, and the fingers.
Embodiment one:
fig. 2 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 according to an embodiment of the invention. In the present embodiment, the high acoustic velocity member 205 is implemented as a support substrate 204, over which a low acoustic velocity layer 203 is formed and which supports the piezoelectric layer 201, over which a conductive material thin film pattern including interdigital transducer electrodes 202a, reflective gate electrodes 202b, interdigital transducer bus bars (not shown) and reflective gate bus bars (not shown) is formed. A direction parallel to the x-axis in the coordinate system is defined as an electrode finger arrangement direction, which is also an elastic wave propagation direction, a direction parallel to the y-axis in the coordinate system is defined as an electrode finger extending direction (not shown in the figure), and a direction parallel to the z-axis in the coordinate system is defined as a height direction of the elastic wave device 200.
In the present embodiment, the support substrate 204 is composed of a material having a high longitudinal wave sound velocity, such as sapphire, silicon carbide, aluminum nitride, or the like. Table 1 shows the sound speeds of 3 different modes of elastic waves in various materials.
Table 1:
in the present embodiment, the piezoelectric layer 201 is lithium niobate. The pattern of conductive film material is composed of a heavy metal material such as copper, molybdenum, gold, silver, platinum, tantalum, tungsten, and the like. The low acoustic velocity layer 203 is composed of silicon dioxide. The low acoustic velocity layer 203 may be made of, for example, glass, silicon oxynitride, tantalum oxide, or a material containing a compound such as silicon dioxide, in which fluorine, carbon, or boron is added as a main component. The material of the low sound velocity layer 203 may be a material having a relatively low sound velocity.
Fig. 3 shows a diagram of vibration modes of two different acoustic modes in a piezoelectric layer 201 of an acoustic wave device (longitudinal wave leaky surface acoustic wave resonator) 200 according to an embodiment of the disclosure, and a diagram of frequency versus wavelength corresponding to the two different acoustic modes. Wherein SH 0 The mode is a transverse wave mode, the vibration direction of the mode is along the y-axis direction, the propagation direction of the mode is along the x-axis direction, and the two directions are mutually perpendicular; LLSAW mode is a longitudinal wave mode, the vibration direction of the mode is along the x-axis direction, the propagation direction of the mode is along the x-axis direction, and the directions are the same. By observing the frequency versus wavelength plots of the two modes, it can be seen that for a certain fixed wavelength, the LLSAW mode frequency is approximately SH 0 The frequency of the pattern is 1.5 times. Therefore, the LLSAW mode has an unique advantage in realizing a longitudinal wave type leaky surface acoustic wave resonator of a high frequency band. In detail, the piezoelectric layer 201 is implemented as a thin lithium niobate having an euler angle of (0 °,122 °,45 °Film thickness h LN 300nm.
Fig. 4 shows a graph of the piezoelectric coupling coefficients of two different acoustic modes in the piezoelectric layer of the acoustic wave device (longitudinal wave leaky surface acoustic wave resonator) 200 according to the first embodiment of the application as a function of euler angles of the piezoelectric layer. With the euler angle of the piezoelectric layer 201 set to (0 °, θ, ψ), the abscissa in the figure represents the value of the propagation angle ψ of the piezoelectric layer 201, and the ordinate represents the value of the tangential angle θ of the piezoelectric layer 201. The darker the region in the graph, the greater the piezoelectric coupling coefficient of the piezoelectric layer corresponding to the euler angle representing the region.
The piezoelectric constant in the electric field direction and the mechanical stress direction of the piezoelectric layer is set as e, and the rigidity under the zero electric field is set as c E Dielectric constant in electric field direction under zero stress is set as epsilon T On the premise of (a), the piezoelectric coupling coefficient can be represented by the formula e 2 /c E ε T Obtaining the product. Unlike the electromechanical coupling coefficient of a resonator, the piezoelectric coupling coefficient is entirely dependent on material characteristics, rather than being determined by the design and fabrication of the resonator.
Thus, it can be seen from the figure that for SH 0 In mode, the piezoelectric layer has a large piezoelectric coupling coefficient when θ is 90 ° or more and less than or equal to 150 °,0 ° or less than or equal to ψ is 15 ° or 165 ° or less than or equal to ψ is 180 °, preferably, θ=120°, and sh=0° 0 The piezoelectric coupling coefficient of the mode is better; for LLSAW mode, the piezoelectric layer has a larger piezoelectric coupling coefficient at 90 DEG.ltoreq.θ.ltoreq.150 DEG, 30 DEG.ltoreq.ψ60 DEG or 120 DEG.ltoreq.ψ150 DEG, or 15 DEG.ltoreq.θ.ltoreq.45 DEG, 105 DEG.ltoreq.ψ.ltoreq.135 DEG, and preferably, θ=122 DEG, ψ=45 DEG or 135 DEG, the piezoelectric coupling coefficient of LLSAW mode is better.
Fig. 5 shows a frequency response diagram of an acoustic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 according to an embodiment of the invention. Specifically, the piezoelectric layer 201 is realized as a lithium niobate thin film having a thickness of 200nm, the euler angle is (0, 122 °,45 °), the low acoustic velocity layer 203 is realized as a silicon dioxide thin film having a thickness of 200nm, the support substrate 204 is realized as silicon carbide having a thickness of 500 μm, the conductive material thin film pattern is realized as copper having a thickness of 60nm, and the wavelength λ is 1 μm.
Fig. 6 shows a frequency response diagram of another acoustic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 according to an embodiment of the invention. Specifically, the piezoelectric layer 201 is realized as a lithium niobate thin film having a thickness of 200nm, the euler angle is (0, 122 °,45 °), the low acoustic velocity layer 203 is realized as a silicon dioxide thin film having a thickness of 200nm, the support substrate 204 is realized as sapphire having a thickness of 500 μm, the conductive material thin film pattern is realized as copper having a thickness of 60nm, and the wavelength λ is 1 μm.
Fig. 7 shows a frequency response diagram of another acoustic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 according to an embodiment of the invention. Specifically, the piezoelectric layer 201 is realized as a lithium niobate film having a thickness of 200nm, the euler angle is (0, 122 °,45 °), the low acoustic velocity layer 203 is realized as a silicon dioxide film having a thickness of 200nm, the support substrate 204 is realized as aluminum nitride having a thickness of 500 μm, the conductive material film pattern is realized as copper having a thickness of 60nm, and the wavelength λ is 1 μm.
Comparative example one:
fig. 8 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 300 provided in comparative example one of the present application. In the present embodiment, the high acoustic velocity member 305 is implemented as a supporting substrate 304 over which the low acoustic velocity layer 303 is formed and which supports the piezoelectric layer 301, and over which the piezoelectric layer 301 is formed a conductive material thin film pattern including interdigital transducer electrodes 302a, reflective gate electrodes 302b, interdigital transducer bus bars (not shown) and reflective gate bus bars (not shown). A direction parallel to the x-axis in the coordinate system is defined as an electrode finger arrangement direction, which is also an elastic wave propagation direction, a direction parallel to the y-axis in the coordinate system is defined as an electrode finger extending direction (not shown in the figure), and a direction parallel to the z-axis in the coordinate system is defined as a height direction of the elastic wave device 300.
Fig. 9 shows a frequency response diagram of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 300 provided in comparative example one of the present application. Specifically, the piezoelectric layer 301 is realized as a lithium niobate film having a thickness of 200nm, the euler angle is (0, 122 °,45 °), the low acoustic velocity layer 303 is realized as a silicon dioxide film having a thickness of 200nm, the support substrate 304 is realized as silicon having a thickness of 500 μm, the conductive material film pattern is realized as copper having a thickness of 60nm, and the wavelength λ is 1 μm.
Comparative example two:
fig. 10 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 400 provided in a second comparative example of the present application. The elastic wave device has no high sound velocity component, the piezoelectric bulk material 401 is used as a piezoelectric layer and plays a role of supporting, and a conductive material film pattern is formed above the piezoelectric layer 401, wherein the conductive material film pattern comprises interdigital transducer electrodes 402a, reflective gate electrodes 402b, interdigital transducer bus bars 600 (not shown in the figure) and reflective gate bus bars (not shown in the figure). A direction parallel to the x-axis in the coordinate system is defined as an electrode finger arrangement direction, which is also an elastic wave propagation direction, a direction parallel to the y-axis in the coordinate system is defined as an electrode finger extending direction (not shown in the figure), and a direction parallel to the z-axis in the coordinate system is defined as a height direction of the elastic wave device 400.
Fig. 11 shows a frequency response diagram of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 400 provided in comparative example two of the present application. In detail, the piezoelectric layer 401 is realized as lithium niobate having a thickness of 350 μm, the Euler angle is (0, 122 °,45 °), the conductive material thin film pattern is realized as copper having a thickness of 60nm, and the wavelength λ is 1 μm.
Comparative example three:
fig. 17 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 500 provided in comparative example three of the present application. The difference between the third comparative example and the first example is that: whether an intermediate layer (silicon dioxide) is provided between the piezoelectric layer and the support substrate.
And (3) effect verification:
as can be seen from comparison of fig. 5 to 7, 9 and 11, the impedance ratio of the acoustic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 exceeds 70dB, and the spurious modes are small, and the acoustic wave device (longitudinal wave type leaky surface acoustic wave resonator) 300 and the acoustic wave device (longitudinal wave type leaky surface acoustic wave resonator) 400 have better impedance characteristics. With the impedance of the resonator set to Z, the impedance (dB) can be calculated from the equation 20×log 10 And (3) obtaining Z. The impedance ratio is the difference between the impedance (dB) at the resonant frequency of the resonator and the impedance (dB) at the antiresonant frequency. The impedance ratio represents the resonant response of the resonator The larger its value, the stronger the resonance of the resonator, the larger the Q value.
Fig. 12 is a graph showing the displacement amount of the LLSAW mode in the support substrate of the elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 provided in the first embodiment of the present application and the elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 300 provided in the first comparative embodiment as a function of the depth (thickness) of the support substrate. It can be seen from the figure that the displacement of the LLSAW mode in the support substrate of sapphire, silicon carbide or aluminum nitride is substantially 0 when the support substrate is thick, which illustrates that the longitudinal wave type leaky surface acoustic wave resonator can better bind the acoustic wave in the piezoelectric layer when the support substrate is of sapphire, silicon carbide or aluminum nitride, and the Q value of the resonator is large; in contrast, in the supporting substrate of the acoustic wave device (longitudinal wave type leaky surface acoustic wave resonator) 300, the Si substrate has a low acoustic velocity, and the acoustic wave energy leaks into the substrate, so that the resonator Q value is low.
Fig. 13 shows a frequency response graph of the elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 according to the first embodiment of the invention as a function of the propagation angle ψ of the piezoelectric layer. With the euler angle of the piezoelectric layer 201 set to (0, 122 °, ψ), the abscissa in the figure represents the value of the propagation angle ψ of the piezoelectric layer 201. In detail, the piezoelectric layer 201 is realized as a lithium niobate thin film having a thickness of 200nm, the low acoustic velocity layer 203 is realized as a silicon dioxide thin film having a thickness of 200nm, the support substrate 204 is realized as silicon carbide having a thickness of 500 μm, the conductive material thin film pattern is realized as copper having a thickness of 60nm, and the wavelength λ is 1.5 μm. As can be seen from the graph, when the propagation angle ψ of the piezoelectric layer satisfies 25 deg. to 65 deg., the elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 has a large impedance ratio and has a small amplitude of parasitic modes.
Fig. 14 shows a graph of electromechanical coupling coefficient of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 according to an embodiment of the invention as a function of a propagation angle ψ of a piezoelectric layer. With the euler angle of the piezoelectric layer 201 set to (0, 122 °, ψ), the abscissa in the figure represents the value of the propagation angle ψ of the piezoelectric layer 201. Specifically, the piezoelectric layer 201 is a 200nm thick lithium niobate film, and the low-acoustic-velocity layer 203 is a 200nm thick silicon dioxide film, and supports the substrate204 is realized as silicon carbide 500 μm thick, the thin film pattern of conductive material is realized as copper 60nm thick, and the wavelength lambda is 1 μm. As can be seen from the figure, when the propagation angle ψ of the piezoelectric layer satisfies 30+.ltoreq.ψ.ltoreq.65°, the elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 has a large electromechanical coupling coefficient (K t 2 ). At the resonance frequency of the resonator being f s The antiresonant frequency is set to f p On the premise of (1), the electromechanical coupling coefficient can be represented by the formula K t 2 ＝π 2 /4×(f p -f s )/f p Obtaining the product.
Fig. 15 shows a frequency response curve of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 of a pattern of thin films of conductive materials of different materials and thicknesses. Specifically, the piezoelectric layer 201 is a lithium niobate thin film having a thickness of 200nm, the euler angle is (0, 122 °,45 °), the low acoustic velocity layer 203 is a silicon dioxide thin film having a thickness of 200nm, the support substrate 204 is silicon carbide having a thickness of 500 μm, and the wavelength λ is 1 μm.
Fig. 16 shows a frequency response curve of another elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 of a pattern of thin films of conductive materials of different materials and thicknesses. Specifically, the piezoelectric layer 201 is a lithium niobate thin film having a thickness of 200nm, the euler angle is (0, 122 °,45 °), the low acoustic velocity layer 203 is a silicon dioxide thin film having a thickness of 200nm, the support substrate 204 is a sapphire having a thickness of 500 μm, and the wavelength λ is 1 μm.
As can be seen by comparing fig. 15 and fig. 16, the use of the aluminum electrode as the conductive material film pattern is disadvantageous for the realization of the high performance elastic wave element because of the relatively small density, the parasitic mode generated is relatively large, the impedance is relatively small, and the Q value of the device is low. The elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 has cleaner frequency response, fewer parasitic modes and larger impedance ratio, and is more suitable for being used as a material of the longitudinal wave type leaky surface acoustic wave resonator electrode.
Fig. 18 shows a frequency response comparison chart of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 provided in the first embodiment of the present application and an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 500 provided in the third comparative example. In detail, the piezoelectric layer 201 and the piezoelectric layer 501 are realized as lithium niobate thin films having a thickness of 100nm, 150nm, 200nm, or 300nm, the euler angle is (0, 122 °,45 °), the low acoustic velocity layer 203 is realized as a silicon dioxide thin film having a thickness of 200nm, the support substrate 204 and the support substrate 503 are realized as sapphire having a thickness of 500 μm, and the wavelength λ is 1 μm.
Fig. 19 shows a frequency response comparison chart of another elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 provided in the first embodiment of the application and another elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 500 provided in the third comparative example. In detail, the piezoelectric layer 201 and the piezoelectric layer 501 are realized as lithium niobate thin films having a thickness of 100nm, 200nm, or 300nm, the euler angle is (0, 122 °,45 °), the low acoustic velocity layer 203 is realized as silicon dioxide thin films having a thickness of 200nm, the support substrates 204 and 503 are realized as silicon carbide having a thickness of 500 μm, and the wavelength λ is 1 μm.
As can be seen from fig. 18 and 19, the elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 500 lacking an intermediate layer (silicon dioxide) has a relatively low impedance regardless of whether the support substrate is made of sapphire or silicon carbide, and the acoustic wave cannot be confined in the piezoelectric layer, so that energy leaks into the support substrate. In contrast, the acoustic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 having an intermediate layer (silica) has a generally large impedance, and the acoustic wave is well confined in the piezoelectric layer and does not leak to the supporting substrate.
Fig. 20 shows a frequency response comparison chart of elastic wave devices (longitudinal wave type leaky surface acoustic wave resonators) 200 of different piezoelectric layer thicknesses. Fig. 21 shows a graph of electromechanical coupling coefficient trends of elastic wave devices (longitudinal wave type leaky surface acoustic wave resonators) 200 of different piezoelectric layer thicknesses. In detail, the piezoelectric layer 201 is realized as a lithium niobate film having an euler angle of (0, 122 °,45 °), the low acoustic velocity layer 203 is realized as a silicon dioxide film having a thickness of 200nm, the support substrate 204 is realized as silicon carbide having a thickness of 500 μm, and the wavelength λ is 1.5 μm.
Thus, as can be seen from FIGS. 20 and 21, when the ratio of the thickness of the piezoelectric layer to the wavelength λ satisfies 0.1.ltoreq.h LN When lambda is less than or equal to 0.23, elastic wave device (longitudinal wave type leaky surface acoustic wave resonator)) 200 has cleaner frequency response, less parasitic modes and larger impedance; when the ratio of the thickness of the piezoelectric layer to the wavelength lambda satisfies 0.16.ltoreq.h LN When λ is not more than 0.35, the electromechanical coupling coefficient of the elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 is large. Preferably, when the ratio of the thickness of the piezoelectric layer to the wavelength lambda satisfies 0.16.ltoreq.h LN When lambda is less than or equal to 0.23, the elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 has larger electromechanical coupling coefficient and cleaner frequency response and excellent performance.
Fig. 22 shows a frequency response comparison chart of elastic wave devices (longitudinal wave type leaky surface acoustic wave resonators) 200 of different low acoustic velocity layer thicknesses. Fig. 23 shows a graph of electromechanical coupling coefficient trends of elastic wave devices (longitudinal wave type leaky surface acoustic wave resonators) 200 of different low acoustic velocity layer thicknesses. Specifically, the piezoelectric layer 201 is realized as a lithium niobate thin film having a thickness of 200nm, the euler angle is (0, 122 °,45 °), the low acoustic velocity layer 203 is realized as a silicon dioxide thin film, the support substrate 204 is realized as silicon carbide having a thickness of 500 μm, and the wavelength λ is 1.5 μm.
Thus, as can be seen from FIGS. 22 and 23, when the ratio of the thickness of the low acoustic velocity layer to the wavelength λ satisfies 0.067.ltoreq.h SiO2 When lambda is less than or equal to 0.2, the elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 has no acoustic wave leakage phenomenon and has cleaner frequency response; when the ratio of the thickness of the low sound velocity layer to the wavelength lambda satisfies 0.1.ltoreq.h SiO2 When λ is equal to or less than 0.2, the electromechanical coupling coefficient of the elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 is large. Preferably, when the ratio of the thickness of the low acoustic velocity layer to the wavelength lambda satisfies 0.1.ltoreq.h SiO2 When lambda is less than or equal to 0.17, the elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 has larger electromechanical coupling coefficient and cleaner frequency response and excellent performance.
Fig. 24 to 27 show frequency response comparison diagrams of acoustic wave devices (longitudinal wave type leaky surface acoustic wave resonators) 200 of different support substrates. In detail, the piezoelectric layer 201 is realized as a lithium niobate thin film having a thickness of 200nm, the euler angle is (0, 122 °,45 °), the low acoustic velocity layer 203 is realized as a silicon dioxide thin film having a thickness of 200nm, and the support substrate 204 is realized as silicon carbide, sapphire, and aluminum nitride, respectively, having a thickness of 500 μm, and a wavelength λ of 1 μm. By comparison, the three high-sound-speed substrates of silicon carbide, sapphire and aluminum nitride LLSAW have close impedance characteristics, the impedance ratio is more than 70dB, and the performance is excellent. Silicon carbide and aluminum nitride have a large spurious mode on the right side of the passband of the elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 as a supporting substrate, and sapphire has been successfully suppressed on the right side of the passband of the elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 as a supporting substrate.
In addition, the parasitic mode of the vertical wave type leaky surface acoustic wave resonator using silicon carbide as the support substrate is farther from the main mode LLSAW than the vertical wave type leaky surface acoustic wave resonator using aluminum nitride as the support substrate.
Sapphire is therefore a better support substrate material than silicon carbide and aluminum nitride. Silicon carbide is a better support substrate material than aluminum nitride. Preferably, the support substrate 204 is sapphire.
Fig. 28 shows a graph of the measured frequency response and Q-value of an acoustic wave device (longitudinal wave leaky surface acoustic wave resonator) 200 according to an embodiment of the invention. Specifically, the piezoelectric layer 201 is a lithium niobate thin film having a thickness of 300nm, the euler angle is (0, 122 °,45 °), the low acoustic velocity layer 203 is a silicon dioxide thin film having a thickness of 200nm, the support substrate 204 is silicon carbide having a thickness of 500 μm, and the wavelength λ is 1.5 μm. Through calculation, the electromechanical coupling coefficient of the actually prepared elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 is 13.65%, Q max The value is 1022.
Fig. 29 shows a graph of the measured frequency response and Q-value of another acoustic wave device (longitudinal wave leaky surface acoustic wave resonator) 200 according to an embodiment of the invention. Specifically, the piezoelectric layer 201 is realized as a lithium niobate thin film having a thickness of 180nm, the euler angle is (0, 122 °,45 °), the low acoustic velocity layer 203 is realized as a silicon dioxide thin film having a thickness of 200nm, the support substrate 204 is realized as sapphire having a thickness of 250 μm, and the wavelength λ is 1 μm. Through calculation, the electromechanical coupling coefficient of the actually prepared elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 is 14.65%, Q max The value is 850.
By observing the measured frequency response of the acoustic wave device (longitudinal wave leaky surface acoustic wave resonator) 200, it can be seen that there are regular and small spurious modes (transverse modes) in the passband of the resonator that would degrade the performance of the resonator if left unchecked.
Fig. 30 shows a vibration mode diagram corresponding to an actually measured frequency response of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 according to an embodiment of the invention and a transverse mode thereof. As the order of the transverse mode increases, the number of acoustic waves in the transverse direction also increases gradually.
Fig. 31 shows a schematic diagram of an oblique interdigital transducer electrode 600. More specifically, the interdigital transducer bus bar 604a and the reflective grating bus bar 604b are inclined with respect to the propagation direction of the elastic wave by an angle β. Thereby, the lateral mode can be suppressed. Interdigital transducer bus bar 604a and reflective grating bus bar 604b extend in parallel. The interdigital transducer bus bar 604a and the reflective grating bus bar 604b may not necessarily extend in parallel. Similarly, the interdigital transducer electrode 602a and the reflective gate electrode 602b are also inclined with respect to the propagation direction of the elastic wave by an angle β.
Fig. 32 shows graphs of measured frequency responses of acoustic wave devices (longitudinal wave type leaky surface acoustic wave resonators) 200 of different β, and graphs of measured impedance ratios and Q-value trends. By comparison, it can be found that when β is greater than 16 °, the transverse modes within the passband of the resonator are substantially suppressed. When β satisfies 16 ° or more and ψ or less than 20 °, the elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 200 can realize a large impedance ratio and can ensure a high Q value.
Embodiment two:
fig. 33 shows a 5G communication-WIFI 6/7 band diagram. The longitudinal wave type leaky surface acoustic wave has the advantages of high sound velocity and large electromechanical coupling coefficient, and is a suitable scheme for preparing the 5G communication-WIFI 6/7 frequency band filter. The embodiment builds the longitudinal wave type leaky surface acoustic wave filter with high frequency and large bandwidth.
Fig. 34 is a schematic diagram showing a topology of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) according to the second embodiment of the invention. Wherein S1-S4 are series arm resonators, and P1-P5 are parallel arm resonators. In detail, all of the series-arm resonators and the parallel-arm resonators are elastic wave devices (longitudinal wave type leaky surface acoustic wave resonators) 200 according to the first embodiment of the present application.
Fig. 35 is a graph showing an actual measurement frequency response of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) according to the second embodiment of the invention. Specifically, the piezoelectric layer 201 is a lithium niobate thin film having a thickness of 200nm, the euler angle is (0, 122 °,45 °), the low acoustic velocity layer 203 is a silicon dioxide thin film having a thickness of 200nm, and the support substrate 204 is silicon carbide having a thickness of 500 μm. As can be seen, the filter has a center frequency of 5250MHz and a 3dB bandwidth of 300MHz, with a minimum insertion loss of-1 dB and an out-of-band rejection of greater than 40dB.
Fig. 36 shows a graph of an actual measurement frequency response of another acoustic wave device (longitudinal wave type leaky surface acoustic wave resonator) according to the second embodiment of the invention. Specifically, the piezoelectric layer 201 is a lithium niobate thin film having a thickness of 200nm, the euler angle is (0, 122 °,45 °), the low acoustic velocity layer 203 is a silicon dioxide thin film having a thickness of 200nm, and the support substrate 204 is a sapphire having a thickness of 500 μm. As can be seen, the filter has a center frequency of 5625MHz and a 3dB bandwidth of 450MHz, with a minimum insertion loss of-1 dB and an out-of-band rejection of greater than 30dB.
The filter can meet the requirements of UNII-1 and UMII-2C frequency bands in the 5G communication-WIFI 6/7 frequency band. Furthermore, by means of the longitudinal leaky surface acoustic wave, the filter meeting other frequency bands of 5G communication-WIFI 6/7 can be designed and prepared.
For a better understanding of the present application, the present application will be further described with reference to the accompanying drawings and three modifications. The modification can be applied in combination with the above-described embodiments as appropriate.
Modification one:
fig. 37 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 700 according to a modification of the present application. The high acoustic velocity member 705 is implemented as a support substrate 704 over which a low acoustic velocity layer 703 is formed and which supports the piezoelectric layer 701, and over which the piezoelectric layer 701 is formed a thin film pattern of conductive material including interdigital transducer electrodes 702a, reflective gate electrodes 702b, interdigital transducer bus bars (not shown) and reflective gate bus bars (not shown). A direction parallel to the x-axis in the coordinate system is defined as an electrode finger arrangement direction, which is also a direction of propagation of elastic waves, a direction parallel to the y-axis in the coordinate system is defined as an electrode finger extending direction (not shown in the figure), and a direction parallel to the z-axis in the coordinate system is defined as a height direction of the elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 700.
In this modification, the support substrate 704 is made of a material having a high L-wave sound velocity, such as sapphire, silicon carbide, aluminum nitride, or the like. The piezoelectric layer 701 is lithium niobate. The pattern of conductive film material is composed of a heavy metal material such as copper, molybdenum, gold, silver, platinum, tantalum, tungsten, and the like. The low acoustic velocity layer 703 is composed of silicon dioxide. The low acoustic velocity layer 703 may be formed of, for example, glass, silicon oxynitride, tantalum oxide, or a material containing a compound such as silicon dioxide, in which fluorine, carbon, or boron is added as a main component. The material of the low acoustic velocity layer 703 may be a material having a relatively low acoustic velocity.
Preferably, the ratio of the thickness of the piezoelectric layer to the wavelength lambda satisfies 0.16.ltoreq.h LN /λ≤0.23。
Preferably, the ratio of the thickness of the low acoustic velocity layer to the wavelength lambda satisfies 0.1.ltoreq.h SiO2 /λ≤0.2。
The above-described structure is defined as in the first embodiment. The difference between the two is that: a dielectric layer 706 is formed over the conductive material film pattern. Dielectric layer 706 is comprised of silicon dioxide. The dielectric layer 706 may be formed of, for example, silicon nitride or a material containing silicon oxide such as silicon dioxide and a compound containing fluorine, carbon, or boron as a main component. The dielectric layer 706 may be made of a temperature-compensated material or a non-temperature-compensated material.
For the same reason as in the first embodiment, the present modified structure can realize both high-frequency characteristics and high Q value.
Modification II:
fig. 38 shows a cross-sectional view of an acoustic wave device (longitudinal wave type leaky surface acoustic wave resonator) 800 according to a second modification of the present application. The high acoustic velocity member 805 includes a trapping material layer 807 and a support substrate 804 under the trapping material layer 807, and a low acoustic velocity layer 803 is formed over the trapping material layer 807 and supports the piezoelectric layer 801, and a conductive material thin film pattern including interdigital transducer electrodes 802a, reflective gate electrodes 802b, interdigital transducer bus bars (not shown) and reflective gate bus bars (not shown) is formed over the piezoelectric layer 801. A direction parallel to the x-axis in the coordinate system is defined as an electrode finger arrangement direction, which is also a direction of propagation of elastic waves, a direction parallel to the y-axis in the coordinate system is defined as an electrode finger extending direction (not shown in the figure), and a direction parallel to the z-axis in the coordinate system is defined as a height direction of the elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 800.
In this modification, the support substrate 804 is made of a material having a high L-wave sound velocity, such as sapphire, silicon carbide, aluminum nitride, or the like. The piezoelectric layer 801 is lithium niobate. The pattern of conductive film material is composed of a heavy metal material such as copper, molybdenum, gold, silver, platinum, tantalum, tungsten, and the like. The low acoustic velocity layer 803 is composed of silicon dioxide. The low acoustic velocity layer 803 may be formed of, for example, glass, silicon oxynitride, tantalum oxide, or a material containing a compound such as silicon dioxide, in which fluorine, carbon, or boron is added as a main component. The material of the low acoustic velocity layer 803 may be a material having a relatively low acoustic velocity.
Preferably, the ratio of the thickness of the piezoelectric layer to the wavelength lambda satisfies 0.16.ltoreq.h LN /λ≤0.23。
Preferably, the ratio of the sum of the thicknesses of the low acoustic velocity layer and the trapping material layer to the wavelength λ satisfies 0.1.ltoreq.h/λ.ltoreq.0.2.
For the same reason as in the first embodiment, the present modified structure can realize both high-frequency characteristics and high Q value.
Modification three:
fig. 39 shows a cross-sectional view of an elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 900 according to a third modification of the present application. The high acoustic velocity member 705 includes a trapping material layer 907 and a support substrate 904 under the trapping material layer 907, the trapping material layer 907 being formed with a low acoustic velocity layer 903 and supporting the piezoelectric layer 901, the piezoelectric layer 901 being formed with a conductive material thin film pattern including interdigital transducer electrodes 902a, reflective gate electrodes 902b, interdigital transducer bus bars (not shown) and reflective gate bus bars (not shown). A direction parallel to the x-axis in the coordinate system is defined as an electrode finger arrangement direction, which is also a direction of propagation of elastic waves, a direction parallel to the y-axis in the coordinate system is defined as an electrode finger extending direction (not shown in the figure), and a direction parallel to the z-axis in the coordinate system is defined as a height direction of the elastic wave device (longitudinal wave type leaky surface acoustic wave resonator) 900.
In this modification, the support substrate 904 is made of a material having a high L-wave sound velocity, such as sapphire, silicon carbide, aluminum nitride, or the like. The piezoelectric layer 901 is lithium niobate. The pattern of conductive film material is composed of a heavy metal material such as copper, molybdenum, gold, silver, platinum, tantalum, tungsten, and the like. The low acoustic velocity layer 903 is composed of silicon dioxide. The low acoustic velocity layer 903 may be formed of, for example, glass, silicon oxynitride, tantalum oxide, or a material containing a compound such as silicon dioxide, in which fluorine, carbon, or boron is added as a main component. The material of the low sound velocity layer 903 may be a material having a relatively low sound velocity.
Preferably, the ratio of the thickness of the piezoelectric layer to the wavelength lambda satisfies 0.16.ltoreq.h LN /λ≤0.23。
Preferably, the ratio of the sum of the thicknesses of the low acoustic velocity layer and the trapping material layer to the wavelength λ satisfies 0.1.ltoreq.h/λ.ltoreq.0.2.
The above configuration is limited similarly to the modification. The difference between the two is that: a dielectric layer 906 is formed over the thin film pattern of conductive material. Dielectric layer 906 is comprised of silicon dioxide. The dielectric layer 906 may be formed of, for example, silicon nitride, a material containing silicon oxide such as silicon dioxide, a compound containing fluorine, carbon, or boron as a main component, or the like. The dielectric layer 906 may be formed of a temperature compensation material or a non-temperature compensation material.
For the same reason as in the first embodiment, the present comparative example structure can realize both high-frequency characteristics and high Q value.
The foregoing is merely a preferred embodiment of the present application, and it should be noted that: it will be apparent to those skilled in the art that numerous modifications and variations can be made thereto without departing from the principles of the present application, and such modifications and variations are to be regarded as being within the scope of the application.
Claims (10)
1. An elastic wave device, comprising:
a piezoelectric layer including a lithium niobate thin film having euler angles of (0°±10°,122°±10°,45°±10°) or (0°±10°,122°±10°,135°±10°), and having first and second main faces opposed to each other;
an interdigital transducer electrode and a reflective gate electrode formed directly or indirectly on the first main face, the interdigital transducer electrode and the reflective gate electrode being composed of a heavy metal material;
a low acoustic velocity layer formed directly or indirectly on the second main surface; and
a high sound speed member located below the low sound speed layer;
wherein, the thickness of the piezoelectric layer is set as h LN On the premise that the wavelength of the elastic wave is lambda, the wavelength is 0.1-h LN Lambda is less than or equal to 0.3; in the case that the thickness of the low sound velocity layer is set to be h 1 On the premise that the wavelength of the elastic wave is lambda, the wavelength is 0.1-h 1 /λ≤0.3。
2. The elastic wave device according to claim 1, wherein the acoustic velocity of bulk waves propagating in the Gao Shengsu component is higher than the acoustic velocity of bulk waves propagating in the piezoelectric layer.
3. The elastic wave device according to claim 1, wherein the high sound speed member comprises:
a support substrate for supporting the low acoustic velocity layer; or (b)
A support substrate and a layer of capture material disposed between the support substrate and the low acoustic velocity layer, the layer of capture material being configured to support the low acoustic velocity layer.
4. An elastic wave device according to claim 3, wherein the support substrate is composed of one or more materials having a sound speed exceeding 6000 m/s.
5. The elastic wave device according to claim 3, wherein the low sound velocity layer is formed of one or more of silicon dioxide, glass, silicon oxynitride, tantalum oxide, and a material containing fluorine, carbon, or a boron compound as a main component added to silicon oxide.
6. The elastic wave device according to claim 3, wherein the trapping material layer is formed of one or more combinations of amorphous silicon, polysilicon, amorphous germanium, and polycrystalline germanium.
7. An elastic wave device according to claim 3, wherein when the thickness of the trapping material layer is set to h 2 On the premise that the wavelength of the elastic wave is lambda, the value of (h) is 0.1-0 2 +h 1 )/λ≤0.3。
8. The elastic wave device according to claim 1, wherein the heavy metal material is composed of one or more of copper, platinum, tungsten, gold, silver, molybdenum, tantalum.
9. The elastic wave device according to any one of claims 1 to 8, further comprising a dielectric layer made of silicon dioxide, silicon nitride, or a material containing fluorine, carbon, or boron as a main component added to silicon oxide, the dielectric layer being provided on the piezoelectric layer and covering the interdigital transducer electrode and the reflective gate electrode.
10. An elastic wave filter or multiplexer, comprising a resonator on a series arm and a resonator on a parallel arm, wherein:
at least one of said resonators is an elastic wave device according to any one of claims 1 to 9.
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|---|---|---|---|
| CN202311659407.0A CN117674759A (en) | 2023-12-06 | 2023-12-06 | Elastic wave device |
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| CN202311659407.0A CN117674759A (en) | 2023-12-06 | 2023-12-06 | Elastic wave device |
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