CN112600529A - Lamb wave resonator with POI structure - Google Patents
Lamb wave resonator with POI structure Download PDFInfo
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- CN112600529A CN112600529A CN202011501937.9A CN202011501937A CN112600529A CN 112600529 A CN112600529 A CN 112600529A CN 202011501937 A CN202011501937 A CN 202011501937A CN 112600529 A CN112600529 A CN 112600529A
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- 235000019687 Lamb Nutrition 0.000 title claims abstract description 52
- 239000000463 material Substances 0.000 claims abstract description 23
- 239000000758 substrate Substances 0.000 claims abstract description 21
- 238000003475 lamination Methods 0.000 claims abstract description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 5
- 229910052681 coesite Inorganic materials 0.000 claims description 4
- 229910052906 cristobalite Inorganic materials 0.000 claims description 4
- 239000000377 silicon dioxide Substances 0.000 claims description 4
- 229910052682 stishovite Inorganic materials 0.000 claims description 4
- 229910052905 tridymite Inorganic materials 0.000 claims description 4
- 230000005284 excitation Effects 0.000 claims description 2
- 229910003327 LiNbO3 Inorganic materials 0.000 abstract description 2
- 239000010410 layer Substances 0.000 description 171
- 230000008878 coupling Effects 0.000 description 77
- 238000010168 coupling process Methods 0.000 description 77
- 238000005859 coupling reaction Methods 0.000 description 77
- 238000010586 diagram Methods 0.000 description 34
- 230000000694 effects Effects 0.000 description 9
- 229910052751 metal Inorganic materials 0.000 description 8
- 239000002184 metal Substances 0.000 description 8
- 238000000034 method Methods 0.000 description 3
- 238000010897 surface acoustic wave method Methods 0.000 description 3
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 230000004075 alteration Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000000593 degrading effect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000010295 mobile communication Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 238000000206 photolithography Methods 0.000 description 1
- 238000000623 plasma-assisted chemical vapour deposition Methods 0.000 description 1
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- 239000004065 semiconductor Substances 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
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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 devices; 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
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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 devices; Electromechanical resonators
- H03H9/25—Constructional features of resonators using surface acoustic waves
Abstract
The invention provides a lamb wave resonator with a POI structure. The lamb wave resonator may include: a substrate of a high acoustic velocity material; and a piezoelectric layer located above the high acoustic velocity material substrate, the piezoelectric layer having an upper surface and a lower surface on which first and second interdigital transducers are respectively disposed, wherein interdigital electrodes of the first and second interdigital transducers are opposed to each other in a lamination direction across the piezoelectric layer, and have the same electrode width, electrode thickness, electrode pitch, duty ratio η, and excited acoustic wave wavelength λ, wherein the duty ratio η ═ electrode width ÷ (electrode width + electrode pitch), the material of the piezoelectric layer is YX-LiNbO3 having a cut angle θ, and wherein the cut angle θ and the duty ratio η take values of: θ is 30 ° ≦ 60 °, and η ≦ 0.2, 0.4-0.6, or 0.8-0.9.
Description
Technical Field
The invention relates to the field of mobile phone radio frequency, in particular to a lamb wave resonator with a POI structure.
Background
The development of 5G handset filters requires lower loss, higher frequencies and greater bandwidth, which presents a significant challenge to existing Surface Acoustic Wave (SAW) and Bulk Acoustic Wave (BAW) technologies, which are generally limited by the effects of spurs. In order to meet the requirement, a Lamb wave structure is proposed recently, which mainly adopts a plate wave mode, has a high acoustic velocity, and shows application advantages in sub-6GHz and millimeter wave mobile communication. In the lamb wave resonator, the main mode is lamb wave, and the rayleigh wave mode is a spurious mode. The presence of spurious modes can affect the performance of the resonator, such as by degrading the Q value (quality factor). How to improve the electromechanical coupling coefficient and inhibit the spurious effect is one of the key problems faced by lamb wave resonators.
Disclosure of Invention
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
To solve the above problems, the present invention aims to provide an improved lamb wave resonator structure having a POI structure, which has advantages of high electromechanical coupling coefficient and small stray.
According to an aspect of the present invention, there is provided a lamb wave resonator having a POI structure, the lamb wave resonator comprising:
a substrate of a high acoustic velocity material; and
a piezoelectric layer located above the high acoustic velocity material substrate, the piezoelectric layer having first and second interdigital transducers respectively arranged on upper and lower surfaces thereof, wherein interdigital electrodes of the first and second interdigital transducers are opposed to each other in a lamination direction across the piezoelectric layer and have the same electrode width, electrode thickness, electrode pitch, duty ratio η, and excitation acoustic wave wavelength λ, wherein
Duty η ═ electrode width ÷ (electrode width + electrode spacing),
the piezoelectric layer is made of YX-LiNbO3 with the cut angle of theta, and
wherein the values of the tangent angle theta and the duty ratio eta are respectively as follows: θ is 30 ° ≦ 60 °, and η ≦ 0.2, 0.4-0.6, or 0.8-0.9.
According to a further embodiment of the present invention, the values of the cut angle θ and the duty cycle η are respectively one of the following combinations:
theta is more than or equal to 30 degrees and less than or equal to 45 degrees, eta is 0.2, 0.4-0.6 or 0.8-0.9;
θ is 50 °, η is 0.2, 0.4-0.6 or 0.9;
50 degrees < theta > 55 degrees, eta > 0.2, 0.4-0.5 or 0.9; and
55 degrees < theta > is less than or equal to 60 degrees, eta is 0.2 or 0.4 to 0.6.
According to a further embodiment of the present invention, the values of the cut angle θ and the duty cycle η are respectively one of the following combinations:
θ is 30 °, η is 0.2 or 0.9;
θ is 35 °, η is 0.4, 0.6 or 0.9;
θ＝40°，η＝0.2；
θ＝45°，η＝0.6；
θ＝50°，η＝0.5；
θ is 55 °, η is 0.8; and
θ is 60 °, η is 0.2 or 0.4.
According to a further embodiment of the present invention, the values of the cut angle θ and the duty ratio η are respectively:
30°≤θ≤60°，η＝0.4。
according to a further embodiment of the invention, the high acoustic speed material is 4H-SiC or 6H-SiC.
According to a further embodiment of the present invention, the lamb wave resonator further comprises: a layer of low acoustic velocity material dielectric disposed between the high acoustic velocity material substrate and the piezoelectric layer.
According to a further embodiment of the invention, the material of low acoustic velocity is SiO2And the thickness is 0.075 lambda-0.1 lambda.
According to a further embodiment of the invention, the wavelength λ is 2 μm.
According to a further embodiment of the invention, the thickness of the substrate of a high acoustic velocity material is 5 λ and the thickness of the piezoelectric layer is 0.6 λ.
According to a further embodiment of the invention, the electrode width is 0.5 λ η, the electrode spacing is 0.5 λ η (1- η), and the electrode thickness is 200 nm.
Compared with the scheme in the prior art, the lamb wave resonator provided by the invention at least has the following advantages:
1. by controlling the electrode duty ratio and the piezoelectric layer cutting angle, the lamb wave resonator can have higher electromechanical coupling coefficient and high Q value, and the main mode has no stray or very small stray;
2. by interposing a dielectric layer of low acoustic velocity material (e.g. SiO) between the piezoelectric layer and the high acoustic velocity substrate2) The Temperature Coefficient of Frequency (TCF) can be reduced; meanwhile, the dielectric layer of the low sound velocity material and the high sound velocity substrate form a reflecting layer to prevent sound waves from leaking from the direction of the substrate, so that the lamb wave resonator has a high Q value.
These and other features and advantages will become apparent upon reading the following detailed description and upon reference to the accompanying drawings. It is to be understood that both the foregoing general description and the following detailed description are explanatory only and are not restrictive of aspects as claimed.
Drawings
So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only some typical aspects of this invention and are therefore not to be considered limiting of its scope, for the description may admit to other equally effective aspects.
Fig. 1 is a schematic diagram of a saw interdigital transducer.
Fig. 2 is a cross-sectional view showing the structure of lamb wave resonator 100 according to one embodiment of the invention.
FIG. 3 is a partially enlarged schematic view of a lamb wave resonator showing the electrode duty cycle.
Fig. 4(a) - (i) show admittance diagrams of lamb wave resonators with a piezoelectric layer cut angle of 30 deg. and duty cycles of 0.1-0.9, respectively.
Fig. 5(a) - (i) show admittance diagrams of lamb wave resonators with a piezoelectric layer cut angle of 35 deg. and duty cycles of 0.1-0.9, respectively.
Fig. 6(a) - (i) show admittance diagrams of lamb wave resonators with a piezoelectric layer cut angle of 40 deg. and duty cycles of 0.1-0.9, respectively.
Fig. 7(a) - (i) show admittance diagrams of lamb wave resonators with a piezoelectric layer cut angle of 45 deg. and duty cycles of 0.1-0.9, respectively.
Fig. 8(a) - (i) show admittance diagrams of lamb wave resonators with a 50 ° cut angle of the piezoelectric layer and duty cycles of 0.1-0.9, respectively.
Fig. 9(a) - (i) show admittance diagrams of lamb wave resonators with a piezoelectric layer cut angle of 55 deg. and duty cycles of 0.1-0.9, respectively.
Fig. 10(a) - (i) show admittance diagrams of lamb wave resonators with a piezoelectric layer cut angle of 60 deg. and duty cycles of 0.1-0.9, respectively.
Fig. 11 is a cross-sectional view showing the structure of a lamb wave resonator 200 according to another embodiment of the invention.
Detailed Description
The present invention will be described in detail below with reference to the attached drawings, and the features of the present invention will be further apparent from the following detailed description.
Fig. 1 is a schematic structural view of a surface acoustic wave interdigital transducer (IDT). As shown in fig. 1, a metal film is deposited on the surface of the piezoelectric substrate, and then a set of comb-shaped crossed metal electrodes is obtained by using a photolithography method in a semiconductor planar process. The metal electrodes in the shape of fingers are arranged in a mutually crossed mode, and bus bars are arranged at two ends of the metal electrodes to be connected together to form two stages of devices respectively, so that the interdigital transducer is obtained. In the example of fig. 1, the 6 metal electrodes numbered 1-6 are shown together, indicating that the interdigital electrode number of this interdigital transducer is 6, wherein the electrodes (also called fingers) numbered odd numbers (1, 3, 5) are connected together to form the positive input (or output) terminal (+ V in the figure) of the interdigital transducer, and the fingers of the electrodes numbered even numbers (2, 4, 6) are connected together to form the positive input (or output) terminal (V in the figure) of the interdigital transducer.
Several main parameters of saw interdigital transducers are: the number of finger pairs N (e.g., 3 for finger pair N in fig. 1), the width d of the metal finger, the half-cycle length L, and the gap width b of the adjacent finger (b-L-d).
Fig. 2 is a cross-sectional schematic view of a lamb wave resonator 100 according to one embodiment of the invention, taken transverse to the lamb wave resonator, along the line a-a, for example, as shown in fig. 1. As shown in FIG. 2, lamb wave resonator 100 may include a substrate 101, which substrate 101 may use a high acoustic velocity material, such as 4H-SiC or 6H-SiC, and constitutes a POI structure.
Above the substrate 101 is a piezoelectric layer 102, and first and second interdigital transducers (IDTs) are provided on the upper and lower surfaces of the piezoelectric layer 102, respectively, wherein interdigital electrodes (also simply referred to as upper and lower electrodes) of the first and second interdigital transducers are opposed to each other in the stacking direction across the piezoelectric layer 102, respectively, and have the same electrode width, electrode thickness, electrode pitch, and excited acoustic wave wavelength λ. As one example, the material of the piezoelectric layer 102 may be YX-LiNbO with a cut angle of θ3The tangent angle theta may be, for example, 30 deg. -60 deg.. The interdigital electrodes of the first and second interdigital transducers may be made of a metal or alloy of Ti, Al, Cu, Au, Pt, Ag, Pd, Ni, or the like, or a laminate of these metals or alloys. It will be understood by those skilled in the art that although only two electrode fingers are shown for both the upper and lower electrodes in fig. 2, this is merely for convenience of illustration, and in practice, the interdigital electrode of a lamb wave resonator typically has more than two electrode fingers (as shown in fig. 1) all having the same electrode width, electrode thickness, electrode spacing, and excited acoustic wave wavelength λ.
FIG. 3 is a partially enlarged schematic view of a lamb wave resonator showing the electrode duty cycle. As shown in fig. 3, assuming that each finger electrode of the interdigital electrodes has an electrode width d and the distance between adjacent finger electrodes is referred to as an electrode pitch b along with the notation in fig. 1, the electrode duty ratio η can be calculated as follows:
duty ratio η ═ electrode width d ÷ (electrode width d + electrode spacing b)
As shown in fig. 1, the sum of the electrode width d and the electrode spacing b is the half-cycle length L of the interdigital transducer. In one example, the sum of the electrode width and the electrode spacing may be 0.5 λ, where λ is the excited acoustic wavelength of the electrode. Accordingly, the electrode width can be expressed as 0.5 λ η, and the electrode spacing as 0.5 λ (1- η). Further, for reference, in the present example, λ may be 2 μm, the electrode thicknesses of the upper and lower electrodes are each 200nm, the thickness of the piezoelectric layer 102 is 0.6 λ, and the thickness of the substrate 101 is 5 λ.
In past attempts to improve on the electromechanical coupling coefficient and the spurious effect, the effect of the electrode duty cycle on the electromechanical coupling coefficient and the spurious effect was never considered and explored, and the effect of the combination of the electrode duty cycle and the piezoelectric layer cut angle on the electromechanical coupling coefficient and the spurious effect was even less considered and explored. FIGS. 4-10 show admittance plots of a lamb wave resonator at different duty cycles, respectively, where the duty cycles are η, fsIs the resonant frequency, fp is the anti-resonant frequency, center frequency f0Can be calculated according to the following formula (1):
f0＝(fs+fp)/2 (1)
coefficient of electromechanical coupling k2It can be calculated by the following formula (2):
k2＝(π2/8)(fp2-fs 2)/fs 2 (2)
fig. 4(a) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 30 ° and the duty ratio η of the upper and lower electrodes is 0.1. As shown in fig. 4(a), in the case where the piezoelectric layer cut angle is 30 ° and the duty ratio η is 0.1, the resonance frequency fsAbout 2163MHz, the antiresonance frequency fpAbout 2435MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 32.95%.
Fig. 4(b) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 30 ° and the duty ratio η of the upper and lower electrodes is 0.2. As shown in fig. 4(b), in the case where the piezoelectric layer cut angle is 30 ° and the duty ratio η is 0.2, the resonance frequency fsAt about 2150MHz, antiresonant frequency fpAbout 2475MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 40.08%.
FIG. 4(c) shows the case where the cut angle of the piezoelectric layer is 30 DEG and the duty ratio eta of the upper and lower electrodes is 0.3Admittance diagram of (1). As shown in fig. 4(c), in the case where the piezoelectric layer cut angle is 30 ° and the duty ratio η is 0.3, the resonance frequency fsAbout 2145MHz, an antiresonant frequency fpAbout 2510MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 45.51%.
Fig. 4(d) shows an admittance diagram for the case where the cut angle of the piezoelectric layer is 30 ° and the duty ratio η of the upper and lower electrodes is 0.4. As shown in fig. 4(d), in the case where the piezoelectric layer cut angle is 30 ° and the duty ratio η is 0.4, the resonance frequency fsAbout 2125MHz, antiresonant frequency fpAbout 2513MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 49.11%.
Fig. 4(e) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 30 ° and the duty ratio η of the upper and lower electrodes is 0.5. As shown in fig. 4(e), in the case where the piezoelectric layer cut angle is 30 ° and the duty ratio η is 0.5, the resonance frequency fsAt about 2153MHz, antiresonant frequency fpAbout 2514MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 44.79%.
Fig. 4(f) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 30 ° and the duty ratio η of the upper and lower electrodes is 0.6. As shown in fig. 4(f), in the case where the piezoelectric layer cut angle is 30 ° and the duty ratio η is 0.6, the resonance frequency fsAbout 2134MHz, the antiresonant frequency fpAbout 2417MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 34.86%.
Fig. 4(g) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 30 ° and the duty ratio η of the upper and lower electrodes is 0.7. As shown in fig. 4(g), in the case where the piezoelectric layer cut angle is 30 ° and the duty ratio η is 0.7, the resonance frequency fsAt about 2078MHz, antiresonant frequency fpIs about 2211MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 16.28%.
Fig. 4(h) shows an admittance diagram for the case where the cut angle of the piezoelectric layer is 30 ° and the duty ratio η of the upper and lower electrodes is 0.8. As shown in fig. 4(h), in the case where the piezoelectric layer chamfer is 30 ° and the duty ratio η is 0.8, the resonance frequency fsAbout 2071MHz, inverse harmonicVibration frequency fpAbout 2330MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 32.75%.
Fig. 4(i) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 30 ° and the duty ratio η of the upper and lower electrodes is 0.9. As shown in fig. 4(i), in the case where the piezoelectric layer chamfer is 30 ° and the duty ratio η is 0.9, the resonance frequency fsAbout 2113MHz, antiresonant frequency fpAbout 2383MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 33.51%.
Fig. 5(a) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 35 ° and the duty ratio η of the upper and lower electrodes is 0.1. As shown in fig. 5(a), in the case where the piezoelectric layer cut angle is 35 ° and the duty ratio η is 0.1, the resonance frequency fsAt about 2158MHz, antiresonant frequency fpAbout 2481MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 39.65%.
Fig. 5(b) shows an admittance diagram for the case where the cut angle of the piezoelectric layer is 35 ° and the duty ratio η of the upper and lower electrodes is 0.2. As shown in fig. 5(b), in the case where the piezoelectric layer chamfer is 35 ° and the duty ratio η is 0.2, the resonance frequency fsAt about 2158MHz, antiresonant frequency fpAbout 2481MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 39.65%.
Fig. 5(c) shows an admittance diagram for the case where the cut angle of the piezoelectric layer is 35 ° and the duty ratio η of the upper and lower electrodes is 0.3. As shown in fig. 5(c), in the case where the piezoelectric layer chamfer angle is 35 ° and the duty ratio η is 0.3, the resonance frequency fsAt about 2152MHz, antiresonant frequency fpAbout 2516MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 45.21%.
Fig. 5(d) shows an admittance diagram for the case where the cut angle of the piezoelectric layer is 35 ° and the duty ratio η of the upper and lower electrodes is 0.4. As shown in fig. 5(d), in the case where the piezoelectric layer chamfer angle is 35 ° and the duty ratio η is 0.4, the resonance frequency fsAbout 2132MHz, the antiresonant frequency fpIs about 2520MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 48.94%.
Fig. 5(e) shows an admittance diagram for the case where the cut angle of the piezoelectric layer is 35 ° and the duty ratio η of the upper and lower electrodes is 0.5. As shown in fig. 5(e), in the case where the piezoelectric layer chamfer angle is 35 ° and the duty ratio η is 0.5, the resonance frequency fsAbout 2160MHz, the antiresonant frequency fpIs about 2522MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 44.77%.
Fig. 5(f) shows an admittance diagram for the case where the cut angle of the piezoelectric layer is 35 ° and the duty ratio η of the upper and lower electrodes is 0.6. As shown in fig. 5(f), in the case where the piezoelectric layer chamfer angle is 35 ° and the duty ratio η is 0.6, the resonance frequency fsAbout 2140MHz, an antiresonant frequency fpAbout 2424MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 34.88%.
Fig. 5(g) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 35 ° and the duty ratio η of the upper and lower electrodes is 0.7. As shown in fig. 5(g), in the case where the piezoelectric layer cut angle is 35 ° and the duty ratio η is 0.7, the resonance frequency fsAbout 2040MHz, antiresonant frequency fpIs about 2220MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 22.71%.
Fig. 5(h) shows an admittance diagram for the case where the cut angle of the piezoelectric layer is 35 ° and the duty ratio η of the upper and lower electrodes is 0.8. As shown in fig. 5(h), in the case where the piezoelectric layer chamfer is 35 ° and the duty ratio η is 0.8, the resonance frequency fsAt about 2078MHz, antiresonant frequency fpAbout 2338MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 32.77%.
Fig. 5(i) shows an admittance diagram for the case where the cut angle of the piezoelectric layer is 35 ° and the duty ratio η of the upper and lower electrodes is 0.9. As shown in fig. 5(i), in the case where the piezoelectric layer chamfer is 35 ° and the duty ratio η is 0.9, the resonance frequency fsAbout 2120MHz, antiresonant frequency fpAbout 2391MHz, at which time the electromechanical coupling coefficient k may be calculated according to equation (2)2About 33.52%.
Fig. 6(a) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 40 ° and the duty ratio η of the upper and lower electrodes is 0.1. As shown in fig. 6(a), in the piezoelectric layerThe resonant frequency f is 40 DEG and the duty ratio eta is 0.1sAbout 2179MHz, antiresonant frequency fpIs about 2443MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 31.67%.
Fig. 6(b) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 40 ° and the duty ratio η of the upper and lower electrodes is 0.2. As shown in fig. 6(b), in the case where the piezoelectric layer chamfer is 40 ° and the duty ratio η is 0.2, the resonance frequency fsAbout 2166MHz, the antiresonance frequency fpAbout 2484MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 38.84%.
Fig. 6(c) shows an admittance diagram for the case where the cut angle of the piezoelectric layer is 40 ° and the duty ratio η of the upper and lower electrodes is 0.3. As shown in fig. 6(c), in the case where the piezoelectric layer chamfer angle is 40 ° and the duty ratio η is 0.3, the resonance frequency fsAbout 2160MHz, the antiresonant frequency fpIs about 2520MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 44.51%.
Fig. 6(d) shows an admittance diagram for the case where the cut angle of the piezoelectric layer is 40 ° and the duty ratio η of the upper and lower electrodes is 0.4. As shown in fig. 6(d), in the case where the piezoelectric layer chamfer angle is 40 ° and the duty ratio η is 0.4, the resonance frequency fsAbout 2140MHz, an antiresonant frequency fpIs about 2524MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 48.20%.
Fig. 6(e) shows an admittance diagram for the case where the cut angle of the piezoelectric layer is 40 ° and the duty ratio η of the upper and lower electrodes is 0.5. As shown in fig. 6(e), in the case where the piezoelectric layer chamfer angle is 40 ° and the duty ratio η is 0.5, the resonance frequency fsAbout 2170MHz, antiresonant frequency fpIs about 2526MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 43.76%.
Fig. 6(f) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 40 ° and the duty ratio η of the upper and lower electrodes is 0.6. As shown in fig. 6(f), in the case where the piezoelectric layer chamfer angle is 40 ° and the duty ratio η is 0.6, the resonance frequency fsAbout 2148MHz, an antiresonant frequency fpIs about 2428MHz, in this caseThe electromechanical coupling coefficient k can be calculated by the formula (2)2Is about 34.23%.
Fig. 6(g) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 40 ° and the duty ratio η of the upper and lower electrodes is 0.7. As shown in fig. 6(g), in the case where the piezoelectric layer chamfer is 40 ° and the duty ratio η is 0.7, the resonance frequency fsAbout 2094MHz, the anti-resonance frequency fpIs about 2227MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 16.15%.
Fig. 6(h) shows an admittance diagram for the case where the cut angle of the piezoelectric layer is 40 ° and the duty ratio η of the upper and lower electrodes is 0.8. As shown in fig. 6(h), in the case where the piezoelectric layer chamfer is 40 ° and the duty ratio η is 0.8, the resonance frequency fsAbout 2087MHz, anti-resonance frequency fpIs about 2344MHz, where the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 32.22%.
Fig. 6(i) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 40 ° and the duty ratio η of the upper and lower electrodes is 0.9. As shown in fig. 6(i), in the case where the piezoelectric layer chamfer angle is 40 ° and the duty ratio η is 0.9, the resonance frequency fsAbout 2129MHz, antiresonant frequency fpAbout 2396MHz, at which time the electromechanical coupling coefficient k may be calculated according to equation (2)2About 32.85%.
Fig. 7(a) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 45 ° and the duty ratio η of the upper and lower electrodes is 0.1. As shown in fig. 7(a), in the case where the piezoelectric layer cut angle is 45 ° and the duty ratio η is 0.1, the resonance frequency fsAbout 2183MHz, the antiresonance frequency fpIs about 2441MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 30.85%.
Fig. 7(b) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 45 ° and the duty ratio η of the upper and lower electrodes is 0.2. As shown in fig. 7(b), in the case where the piezoelectric layer cut angle is 45 ° and the duty ratio η is 0.2, the resonance frequency fsAbout 2175MHz, antiresonant frequency fpAbout 2485MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 37.64%.
FIG. 7(c) shows the piezoelectric layer corner cut of 4And 5 DEG, an admittance diagram under the condition that the duty ratio eta of the upper electrode and the lower electrode is 0.3. As shown in fig. 7(c), in the case where the piezoelectric layer cut angle is 45 ° and the duty ratio η is 0.3, the resonance frequency fsAbout 2169MHz, the antiresonance frequency fpAbout 2519MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 42.98%.
Fig. 7(d) shows an admittance diagram for the case where the cut angle of the piezoelectric layer is 45 ° and the duty ratio η of the upper and lower electrodes is 0.4. As shown in fig. 7(d), in the case where the piezoelectric layer cut angle is 45 ° and the duty ratio η is 0.4, the resonance frequency fsAt about 2150MHz, antiresonant frequency fpIs about 2523MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 46.47%.
Fig. 7(e) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 45 ° and the duty ratio η of the upper and lower electrodes is 0.5. As shown in fig. 7(e), in the case where the piezoelectric layer cut angle is 45 ° and the duty ratio η is 0.5, the resonance frequency fsAbout 2180MHz, the antiresonance frequency fpIs about 2526MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 42.23%.
Fig. 7(f) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 45 ° and the duty ratio η of the upper and lower electrodes is 0.6. As shown in fig. 7(f), in the case where the piezoelectric layer cut angle is 45 ° and the duty ratio η is 0.6, the resonance frequency fsAt about 2157MHz, antiresonant frequency fpAbout 2430MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 33.17%.
Fig. 7(g) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 45 ° and the duty ratio η of the upper and lower electrodes is 0.7. As shown in fig. 7(g), in the case where the piezoelectric layer cut angle is 45 ° and the duty ratio η is 0.7, the resonance frequency fsAbout 2104MHz, antiresonant frequency fpAbout 2234MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 15.70%.
Fig. 7(h) shows an admittance diagram for the case where the cut angle of the piezoelectric layer is 45 ° and the duty ratio η of the upper and lower electrodes is 0.8. As shown in fig. 7(h), in the case where the piezoelectric layer cut angle is 45 ° and the duty ratio η is 0.8, the resonance isVibration frequency fsAbout 2098MHz, anti-resonance frequency fpIs about 2347MHz, where the electromechanical coupling coefficient k can be calculated according to equation (2)2About 30.99%.
Fig. 7(i) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 45 ° and the duty ratio η of the upper and lower electrodes is 0.9. As shown in fig. 7(i), in the case where the piezoelectric layer cut angle is 45 ° and the duty ratio η is 0.9, the resonance frequency fsAbout 2138MHz, the antiresonant frequency fpAbout 2399MHz, at which time the electromechanical coupling coefficient k may be calculated according to equation (2)2Is about 31.93%.
Fig. 8(a) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 50 ° and the duty ratio η of the upper and lower electrodes is 0.1. As shown in fig. 8(a), in the case where the piezoelectric layer chamfer is 50 ° and the duty ratio η is 0.1, the resonance frequency fsAbout 2191MHz, the antiresonant frequency fpAbout 2438MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 29.35%.
Fig. 8(b) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 50 ° and the duty ratio η of the upper and lower electrodes is 0.2. As shown in fig. 8(b), in the case where the piezoelectric layer chamfer is 50 ° and the duty ratio η is 0.2, the resonance frequency fsAbout 2184MHz, the antiresonance frequency fpAbout 2482MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 35.93%.
Fig. 8(c) shows an admittance diagram for the case where the cut angle of the piezoelectric layer is 50 ° and the duty ratio η of the upper and lower electrodes is 0.3. As shown in fig. 8(c), in the case where the piezoelectric layer chamfer is 50 ° and the duty ratio η is 0.3, the resonance frequency fsAbout 2179MHz, antiresonant frequency fpAbout 2515MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 40.94%.
Fig. 8(d) shows an admittance diagram for the case where the cut angle of the piezoelectric layer is 50 ° and the duty ratio η of the upper and lower electrodes is 0.4. As shown in fig. 8(d), in the case where the piezoelectric layer chamfer angle is 50 ° and the duty ratio η is 0.4, the resonance frequency fsAbout 2161MHz, the antiresonance frequency fpAbout 2519MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 44.22%.
Fig. 8(e) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 50 ° and the duty ratio η of the upper and lower electrodes is 0.5. As shown in fig. 8(e), in the case where the piezoelectric layer chamfer is 50 ° and the duty ratio η is 0.5, the resonance frequency fsAbout 2192MHz, antiresonant frequency fpIs about 2522MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 39.90%.
Fig. 8(f) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 50 ° and the duty ratio η of the upper and lower electrodes is 0.6. As shown in fig. 8(f), in the case where the piezoelectric layer chamfer angle is 50 ° and the duty ratio η is 0.6, the resonance frequency fsAbout 2168MHz, the antiresonance frequency fpAbout 2429MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 31.46%.
Fig. 8(g) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 50 ° and the duty ratio η of the upper and lower electrodes is 0.7. As shown in fig. 8(g), in the case where the piezoelectric layer chamfer is 50 ° and the duty ratio η is 0.7, the resonance frequency fsAbout 2115MHz, antiresonant frequency fpAt about 2240MHz, where the electromechanical coupling coefficient k can be calculated according to equation (2)2About 15.00%.
Fig. 8(h) shows an admittance diagram for the case where the cut angle of the piezoelectric layer is 50 ° and the duty ratio η of the upper and lower electrodes is 0.8. As shown in fig. 8(h), in the case where the piezoelectric layer chamfer is 50 ° and the duty ratio η is 0.8, the resonance frequency fsAbout 2109MHz, the antiresonant frequency fpIs about 2347MHz, where the electromechanical coupling coefficient k can be calculated according to equation (2)2About 29.39%.
Fig. 8(i) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 50 ° and the duty ratio η of the upper and lower electrodes is 0.9. As shown in fig. 8(i), in the case where the piezoelectric layer chamfer is 50 ° and the duty ratio η is 0.9, the resonance frequency fsAbout 2149MHz, an antiresonant frequency fpAbout 2398MHz, at which time the electromechanical coupling coefficient k may be calculated according to equation (2)2Is about 30.21%.
FIG. 9(a) shows the conductance for the case where the cut angle of the piezoelectric layer is 55 ° and the duty ratio η of the upper and lower electrodes is 0.1And (4) carrying out nano-graph. As shown in fig. 9(a), in the case where the piezoelectric layer cut angle is 55 ° and the duty ratio η is 0.1, the resonance frequency fsAbout 2196MHz, antiresonant frequency fpAbout 2431MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 27.79%.
Fig. 9(b) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 55 ° and the duty ratio η of the upper and lower electrodes is 0.2. As shown in fig. 9(b), in the case where the piezoelectric layer cut angle is 55 ° and the duty ratio η is 0.2, the resonance frequency fsAbout 2193MHz, antiresonant frequency fpAbout 2476MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 33.86%.
Fig. 9(c) shows an admittance diagram in the case where the cut angle of the piezoelectric layer is 55 ° and the duty ratio η of the upper and lower electrodes is 0.3. As shown in fig. 9(c), in the case where the piezoelectric layer cut angle is 55 ° and the duty ratio η is 0.3, the resonance frequency fsAbout 2189MHz, the antiresonance frequency fpAbout 2508MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 38.54%.
Fig. 9(d) shows an admittance diagram for the case where the piezoelectric layer chamfer is 55 ° and the upper and lower electrode duty ratio η is 0.4. As shown in fig. 9(d), in the case where the piezoelectric layer cut angle is 55 ° and the duty ratio η is 0.4, the resonance frequency fsAbout 2173MHz, antiresonant frequency fpAbout 2511MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 41.32%.
Fig. 9(e) shows an admittance diagram in the case where the cut angle of the piezoelectric layer is 55 ° and the duty ratio η of the upper and lower electrodes is 0.5. As shown in fig. 9(e), in the case where the piezoelectric layer cut angle is 55 ° and the duty ratio η is 0.5, the resonance frequency fsAt about 2204MHz, antiresonant frequency fpAbout 2515MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 37.24%.
Fig. 9(f) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 55 ° and the duty ratio η of the upper and lower electrodes is 0.6. As shown in fig. 9(f), in the case where the piezoelectric layer cut angle is 55 ° and the duty ratio η is 0.6, the resonance frequency fsAbout 2179MHz, antiresonant frequencyRate fpAbout 2426MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 29.52%.
Fig. 9(g) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 55 ° and the duty ratio η of the upper and lower electrodes is 0.7. As shown in fig. 9(g), in the case where the piezoelectric layer cut angle is 55 ° and the duty ratio η is 0.7, the resonance frequency fsAbout 2127MHz, antiresonant frequency fpAt about 2244MHz, where the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 13.93%.
Fig. 9(h) shows an admittance diagram in the case where the cut angle of the piezoelectric layer is 55 ° and the duty ratio η of the upper and lower electrodes is 0.8. As shown in fig. 9(h), in the case where the piezoelectric layer chamfer angle is 55 ° and the duty ratio η is 0.8, the resonance frequency fsAbout 2120MHz, antiresonant frequency fpIs about 2343MHz, and then the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 27.29%.
Fig. 9(i) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 55 ° and the duty ratio η of the upper and lower electrodes is 0.9. As shown in fig. 9(i), in the case where the piezoelectric layer chamfer angle is 55 ° and the duty ratio η is 0.9, the resonance frequency fsAt about 2159MHz, antiresonant frequency fpAbout 2395MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 28.42%.
Fig. 10(a) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 60 ° and the duty ratio η of the upper and lower electrodes is 0.1. As shown in fig. 10(a), in the case where the piezoelectric layer cut angle is 60 ° and the duty ratio η is 0.1, the resonance frequency fsAbout 2198MHz, antiresonant frequency fpAbout 2419MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 26.03%.
Fig. 10(b) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 60 ° and the duty ratio η of the upper and lower electrodes is 0.2. As shown in fig. 10(b), in the case where the piezoelectric layer chamfer is 60 ° and the duty ratio η is 0.2, the resonance frequency fsAt about 2201MHz, antiresonant frequency fpIs about 2467MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 31.59%.
Fig. 10(c) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 60 ° and the duty ratio η of the upper and lower electrodes is 0.3. As shown in fig. 10(c), in the case where the piezoelectric layer chamfer angle is 60 ° and the duty ratio η is 0.3, the resonance frequency fsAt approximately 2202MHz, anti-resonant frequency fpAbout 2496MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 35.11%.
Fig. 10(d) shows an admittance diagram for the case where the cut angle of the piezoelectric layer is 60 ° and the duty ratio η of the upper and lower electrodes is 0.4. As shown in fig. 10(d), in the case where the piezoelectric layer chamfer angle is 60 ° and the duty ratio η is 0.4, the resonance frequency fsAbout 2185MHz, the antiresonance frequency fpIs about 2499MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 37.97%.
Fig. 10(e) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 60 ° and the duty ratio η of the upper and lower electrodes is 0.5. As shown in fig. 10(e), in the case where the piezoelectric layer chamfer angle is 60 ° and the duty ratio η is 0.5, the resonance frequency fsAbout 2216MHz, anti-resonance frequency fpAbout 2504MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 34.12%.
Fig. 10(f) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 60 ° and the duty ratio η of the upper and lower electrodes is 0.6. As shown in fig. 10(f), in the case where the piezoelectric layer chamfer angle is 60 ° and the duty ratio η is 0.6, the resonance frequency fsAbout 2192MHz, antiresonant frequency fpAbout 2420MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 26.97%.
Fig. 10(g) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 60 ° and the duty ratio η of the upper and lower electrodes is 0.7. As shown in fig. 10(g), in the case where the piezoelectric layer cut angle is 60 ° and the duty ratio η is 0.7, the resonance frequency fsAbout 2139MHz, the antiresonant frequency fpAt about 2247MHz, where the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 12.76%.
Fig. 10(h) shows an admittance diagram for the case where the cut angle of the piezoelectric layer is 60 ° and the duty ratio η of the upper and lower electrodes is 0.8. As shown in FIG. 10(h), inWhen the cut angle of the piezoelectric layer is 60 DEG and the duty ratio eta is 0.8, the resonant frequency fsAbout 2131MHz, the antiresonant frequency fpAbout 2336MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2Is about 24.85%.
Fig. 10(i) shows an admittance chart in the case where the cut angle of the piezoelectric layer is 60 ° and the duty ratio η of the upper and lower electrodes is 0.9. As shown in fig. 10(i), in the case where the piezoelectric layer chamfer angle is 60 ° and the duty ratio η is 0.9, the resonance frequency fsAbout 2170MHz, antiresonant frequency fpAbout 2388MHz, at which time the electromechanical coupling coefficient k can be calculated according to equation (2)2About 26.00%.
In table 1 below, the resonant frequency f of the lamb wave resonator at different piezoelectric layer cutting angles and different duty ratios shown in the above figures is countedsAnti-resonance frequency fp and electromechanical coupling coefficient k2Also given are the Q values in each case.
TABLE 1
It can be found that under different combinations of different piezoelectric layer cut angles theta and electrode duty ratios eta, the following groups of values have obvious effect of improving electromechanical coupling coefficients and quality factors Q.
1. When the piezoelectric layer cut angle theta and the electrode duty ratio eta are values in table 2, the electromechanical coupling coefficient of the lamb wave resonator is large and at least above 26.9%, and the main mode has no stray or very small stray.
TABLE 2
2. When the piezoelectric layer cut angle θ and the electrode duty ratio η are the values in table 3, the electromechanical coupling coefficient of the lamb wave resonator is large, at least above 27.3%, and the main mode has no or very small spurious, which means that the spurious effect is suppressed, and as can be seen from the data, the quality factor Q at this time is high, at least above 500.
| Corner cut theta of piezoelectric layer | Duty ratio eta | |
| 30° | 0.2,0.9 | Q≥500 |
| 35° | 0.4,0.6,0.9 | Q≥590 |
| 40° | 0.2 | Q≥620 |
| 45° | 0.6 | Q≥750 |
| 50° | 0.5 | Q≥664 |
| 55° | 0.8 | Q≥740 |
| 60° | 0.2，0.4 | Q≥650 |
TABLE 3
3. When the cut angle theta of the piezoelectric layer is fixed to a specific value and the duty ratio eta of the upper electrode and the lower electrode is 0.4, the electromechanical coupling coefficient k2And max. When the duty ratio eta of the upper electrode and the lower electrode is 0.4, the cut angle theta of the piezoelectric layer is in the range of 30-60 DEG, and the electromechanical coupling coefficient k increases along with the increase of the cut angle theta2And decreases.
| Corner cut theta of piezoelectric layer | Duty ratio eta | Coefficient of electromechanical coupling k2(％) |
| 30° | 0.4 | 49.11％ |
| 35° | 0.4 | 48.9％ |
| 40° | 0.4 | 48.20％ |
| 45° | 0.4 | 46.5％ |
| 50° | 0.4 | 44.2％ |
| 55° | 0.4 | 41.3％ |
| 60° | 0.4 | 38％ |
TABLE 3
Fig. 11 is a cross-sectional view showing the structure of a lamb wave resonator 200 according to another embodiment of the invention. As shown in fig. 11, a lamb wave resonator 200 has a similar structure to the lamb wave resonator 100 except that a dielectric layer 103 is interposed between a high acoustic velocity substrate 101 and a piezoelectric layer 102. The dielectric layer 103 may be formed of a low acoustic impedance material having low acoustic speed, such as SiO2. The temperature coefficient of frequency of the dielectric layer 103 is positive and the temperature coefficient of frequency of the piezoelectric layer 102 is negative, so that the dielectric layer 103 can reduce the lamb wave resonatorTemperature Coefficient of Frequency (TCF). Further, the dielectric layer 103 has a low acoustic velocity and forms a reflective layer with the high acoustic velocity substrate 101, so that the acoustic wave can be prevented from leaking from the direction of the substrate 101, which contributes to obtaining a high Q value. As an example, the dielectric layer 103 may have a thickness of 0.075-0.1 λ.
Optionally, the lamb wave resonator 300 may further be covered with a dielectric layer 104 by PECVD, CVD, or the like, on the piezoelectric layer 102, and the material of the dielectric layer may be SiO2SiN, etc. This dielectric layer 104 may further reduce the Temperature Coefficient of Frequency (TCF) of the lamb wave resonator and may also act as a protective layer for the resonator.
What has been described above includes examples of aspects of the claimed subject matter. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the claimed subject matter, but one of ordinary skill in the art may recognize that many further combinations and permutations of the claimed subject matter are possible. Accordingly, the disclosed subject matter is intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims.
Claims (10)
1. A lamb wave resonator having a POI structure, the lamb wave resonator comprising:
a substrate of a high acoustic velocity material; and
a piezoelectric layer located above the high acoustic velocity material substrate, the piezoelectric layer having first and second interdigital transducers respectively arranged on upper and lower surfaces thereof, wherein interdigital electrodes of the first and second interdigital transducers are opposed to each other in a lamination direction across the piezoelectric layer and have the same electrode width, electrode thickness, electrode pitch, duty ratio η, and excitation acoustic wave wavelength λ, wherein
Duty η ═ electrode width ÷ (electrode width + electrode spacing),
the piezoelectric layer is made of YX-LiNbO with a cut angle theta3And is and
wherein the values of the tangent angle theta and the duty ratio eta are respectively as follows: θ is 30 ° ≦ 60 °, and η ≦ 0.2, 0.4-0.6, or 0.8-0.9.
2. The lamb wave resonator of claim 1, wherein said tangent angle θ and said duty cycle η each take one of the following combinations:
theta is more than or equal to 30 degrees and less than or equal to 45 degrees, eta is 0.2, 0.4-0.6 or 0.8-0.9;
θ is 50 °, η is 0.2, 0.4-0.6 or 0.9;
50 degrees < theta > 55 degrees, eta > 0.2, 0.4-0.5 or 0.9; and
55 degrees < theta > is less than or equal to 60 degrees, eta is 0.2 or 0.4 to 0.6.
3. The lamb wave resonator of claim 1, wherein said tangent angle θ and said duty cycle η each take one of the following combinations:
θ is 30 °, η is 0.2 or 0.9;
θ is 35 °, η is 0.4, 0.6 or 0.9;
θ＝40°，η＝0.2；
θ＝45°，η＝0.6；
θ＝50°，η＝0.5；
θ is 55 °, η is 0.8; and
θ is 60 °, η is 0.2 or 0.4.
4. The lamb wave resonator of claim 1, wherein said tangent angle θ and said duty cycle η each take the values:
30°≤θ≤60°，η＝0.4。
5. the lamb wave resonator of claim 1, wherein said high acoustic speed material is 4H-SiC or 6H-SiC.
6. The lamb wave resonator of claim 1, further comprising: a layer of low acoustic velocity material dielectric disposed between the high acoustic velocity material substrate and the piezoelectric layer.
7. The lamb wave resonator of claim 6, wherein said low acoustic velocity material is SiO2And the thickness is 0.075 lambda-0.1 lambda.
8. The lamb wave resonator of claim 1, wherein said wavelength λ is 2 μm.
9. The lamb wave resonator of claim 1 wherein said substrate of high acoustic velocity material has a thickness of 5 λ and said piezoelectric layer has a thickness of 0.6 λ.
10. The lamb wave resonator of claim 1, wherein said electrode width is 0.5 λ η, said electrode spacing is 0.5 λ η (1- η), and said electrode thickness is 200 nm.
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