Reff wave phononic crystal resonator based on lithium tantalate single crystal film

Abstract

The invention relates to the technical field of surface acoustic wave devices, and discloses a lithium tantalate single crystal film-based Loff wave photonic crystal resonator, which comprises a functional substrate and a piezoelectric film layer on the upper surface of the functional substrate, an interdigital transducer is arranged in the middle area of the upper surface of the piezoelectric film layer, and photonic crystals are arranged on the two sides of the interdigital transducer; the piezoelectric thin film layer is a lithium tantalate single crystal thin film, and the tangential direction of the lithium tantalate single crystal thin film is any one of Y cuts, including 0-degree Y, 36-degree Y, 42-degree Y, 50-degree Y, 64-degree Y and 128-degree Y cuts. The photonic crystal is used for replacing a reflecting grating in a traditional surface acoustic wave resonator, higher sound velocity and lower longitudinal loss are achieved through a material system constructed by combining the functional substrate and the lithium tantalate single crystal film, and the photonic crystal resonator has the advantages of being simple in structure, small in size and easy to prepare and integrate. And compared with a Bragg reflection grating resonator with the same size, the resonator has a higher Q value.

Description

Technical Field

[0001] The invention relates to the technical field of surface acoustic wave devices, in particular to a Love wave phononic crystal resonator based on a lithium tantalate single crystal film. Background Art

[0002] Phononic crystals are a new type of artificial periodic material used to control and manipulate the propagation of sound waves. They can be formed by periodically arranging scatterers embedded in a medium, where the periodically arranged scatterers can be made of any material different from the substrate, including air slots / holes. Phononic crystals have special properties such as band gaps and anisotropic propagation. The band gap is the frequency range in which sound waves cannot propagate, and has the function of strong obstruction and strong localization of acoustic signals. This property has been observed in bulk acoustic waves, surface acoustic waves, and Lamb waves in various phononic crystal structures. In recent years, based on the band gap characteristics of phononic crystals, researchers have proposed surface acoustic wave devices such as filters and resonators.

[0003] Surface acoustic wave devices have the advantages of low transmission loss, high energy conversion efficiency, and compact structure. They are key components in modern high-frequency and high-speed communication systems and sensing applications. Surface acoustic waves mainly include Rayleigh waves and Love waves. With the development of multilayer piezoelectric composite substrates, various high-performance surface acoustic wave devices based on Love waves have been developed and applied. One of the key performance indicators of surface acoustic wave resonators is the quality factor (Q), which determines the rectangularity and insertion loss of the filter, the phase noise of the oscillator, and the sensitivity of the sensor. Therefore, resonators with higher Q values ​​have always been one of the goals pursued by researchers. The existing Bragg reflector resonator requires more metal reflectors, while phononic crystals with strong acoustic wave blocking function can be used to replace the reflectors in traditional surface acoustic wave resonators, which can enhance the energy localization effect of the resonator (i.e., reduce the mode volume of the resonator), thereby reducing the energy loss of the resonator (i.e., increase the Q value of the surface acoustic wave resonator). At the same time, using phononic crystals to replace the reflectors in traditional surface acoustic wave resonators can reduce the device area, which is conducive to the realization of more compact and more integrated surface acoustic wave resonators and filters.

[0004] In addition, among the piezoelectric materials used in surface acoustic wave devices, lithium tantalate has shown great advantages. It has high temperature stability, high acid and alkali corrosion resistance, a wide frequency range, and a relatively mature preparation process, etc., and has important application value in surface acoustic wave devices.

[0005] In summary, how to improve the surface acoustic wave resonator based on the advantages of lithium tantalate and phononic crystals has become an important research topic in this field. Summary of the invention

[0006] The purpose of the present invention is to provide a Love wave phononic crystal resonator based on a lithium tantalate single crystal film, which utilizes phononic crystals to replace the reflection grating in a traditional surface acoustic wave resonator, and achieves higher sound speed and lower longitudinal loss by combining a material system constructed with a functional substrate and a lithium tantalate single crystal film. The Love wave phononic crystal resonator has the characteristics of simple structure, small size, easy preparation and integration, and has a higher Q value than a Bragg reflection grating resonator of the same size.

[0007] To achieve the above object, the present invention provides the following solutions: A Love wave phononic crystal resonator based on a lithium tantalate single crystal film, wherein the Love wave phononic crystal resonator comprises a functional substrate and a piezoelectric film layer located on the upper surface of the functional substrate, an interdigital transducer is arranged in the middle area of ​​the upper surface of the piezoelectric film layer, and phononic crystals are arranged on both sides of the interdigital transducer; The piezoelectric film layer is a lithium tantalate single crystal film, and the tangent direction of the lithium tantalate single crystal film is any one of the Y-cuts, including 0°Y, 36°Y, 42°Y, 50°Y, 64°Y, and 128°Y.

[0008] Furthermore, the frequencies of the main resonance peak and the anti-resonance peak of the Love wave phononic crystal resonator are both within the forbidden band of the phononic crystal.

[0009] Furthermore, the phononic crystal is formed by etching a periodic or non-periodic hole or groove structure on the surface of the lithium tantalate single crystal film, or by growing a periodic or non-periodic column structure on the surface of the lithium tantalate single crystal film.

[0010] Furthermore, the cross-sectional shapes of the hole or groove structure and the column structure are one or more combinations of circular, elliptical, triangular, polygonal or other irregular shapes.

[0011] Furthermore, the material of the column structure is lithium tantalate, silicon, silicon dioxide, silicon nitride or a metal material, and the metal material includes aluminum, copper, nickel, and chromium; and the height of the column structure is 0-1000 microns.

[0012] Furthermore, the lattice of the phononic crystal is a triangular lattice, a tetragonal lattice, a honeycomb lattice, a cage lattice or other lattices with symmetry, and the lattice period ranges from 0 to 1000 microns.

[0013] Furthermore, the material of the functional substrate is one or more of silicon carbide, sapphire, quartz, diamond, silicon dioxide, polycrystalline silicon, and single crystal silicon.

[0014] Furthermore, the lithium tantalate single crystal film has a thickness of 0-10 microns.

[0015] Furthermore, the spacing between the interdigital transducer and the phononic crystal is greater than 1 / 2 times of the electrode period.

[0016] According to the specific embodiment provided by the present invention, the Love wave phononic crystal resonator based on lithium tantalate single crystal film provided by the present invention discloses the following technical effects: (1) Using phononic crystals to replace the reflection grating in the traditional surface acoustic wave resonator can enhance the energy localization effect of the resonator (i.e., reduce the mode volume of the resonator), thereby reducing the energy loss of the resonator (i.e., increase the Q value of the surface acoustic wave resonator). At the same time, it can reduce the device area, which is conducive to the realization of a more compact and more integrated Love wave phononic crystal resonator.

[0017] (2) By combining a functional substrate with a lithium tantalate single crystal film to construct a material system, a higher sound velocity and lower longitudinal loss can be achieved. The Love wave based on lithium tantalate is a horizontal shear wave, which lacks a displacement component perpendicular to the substrate surface and can significantly reduce the energy transmission loss. This is conducive to the exploration of Love wave phononic crystal resonators with ultra-large bandwidth and small temperature drift.

[0018] In summary, the Love wave phononic crystal resonator provided by the present invention has a relatively simple structure, a small volume, and is easy to prepare and integrate. The phononic crystal has a wide Love wave directional band gap. On the basis of not affecting the heat dissipation and working bandwidth of the surface acoustic wave device, the quality factor of the Love wave phononic crystal resonator prepared based on this phononic crystal is significantly improved compared with the Bragg reflector resonator of the same size, which is of great significance for realizing a new generation of high-performance and miniaturized microwave acoustic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0020] Figure 1 It is a schematic diagram of the top view of the structure of the Love wave phononic crystal resonator based on the lithium tantalate single crystal film of the present invention; Figure 2 It is a schematic cross-sectional view of the Love wave hole type phononic crystal resonator along the section line AA' of Example 1 of the present invention; Figure 3 It is a schematic cross-sectional view of the Love wave column type phononic crystal resonator along the section line AA' of Example 2 of the present invention; Figure 442°Y direction surface acoustic wave band gap structure of the Love wave phononic crystal resonator in Example 1 of the present invention; wherein (a) is a schematic diagram of the Love mode band gap along the Brillouin Г-X direction of the phononic crystal, and (b) and (c) are respectively a top view and a front view of the acoustic field distribution in the phononic crystal unit cell; Figure 5 The energy field distribution comparison diagram at the main resonance peak corresponding to the Love wave phononic crystal resonator based on lithium tantalate single crystal film and the traditional reflection grating resonator of Example 1 of the present invention and the respective admittance comparison diagrams, wherein (a) and (b) are energy field distribution diagrams at the main resonance peak corresponding to the traditional reflection grating resonator and the Love wave phononic crystal resonator based on lithium niobate single crystal film, respectively, and (c) and (d) are admittance diagrams at the main resonance peak corresponding to the traditional reflection grating resonator and the Love wave phononic crystal resonator based on lithium niobate single crystal film, respectively; Figure 6 It is a schematic cross-sectional view of the Love wave hole type phononic crystal resonator along the section line AA' of Example 3 of the present invention; Figure 7 It is a schematic cross-sectional view of the Love wave column type phononic crystal resonator along the section line AA' of Example 4 of the present invention; Figure 8 42°Y direction surface acoustic wave band gap structure of the Love wave phononic crystal resonator in Example 3 of the present invention; (a) is a schematic diagram of the Love mode band gap along the Brillouin Г-X direction of the phononic crystal, (b) and (c) are respectively a top view and a front view of the acoustic field distribution in the phononic crystal unit cell; Fig. 9 This is a comparison diagram of the admittances of the Love wave phononic crystal resonator based on lithium tantalate single crystal film and the traditional reflection grating resonator according to Example 3 of the present invention, wherein (a) and (b) are the admittance diagrams at the main resonance peak corresponding to the traditional reflection grating resonator and the Love wave phononic crystal resonator based on lithium niobate single crystal film, respectively; Fig.10 It is a schematic cross-sectional view of the Love wave hole type phononic crystal resonator along the section line AA' of Example 5 of the present invention; Fig.11 It is a schematic cross-sectional view of the Love wave column type phononic crystal resonator along the section line AA' of Example 6 of the present invention; Fig.12 42°Y direction surface acoustic wave band gap structure of the Love wave phononic crystal resonator in Example 5 of the present invention; wherein (a) is a schematic diagram of the Love mode band gap along the Brillouin Г-X direction of the phononic crystal, and (b) and (c) are respectively a top view and a front view of the acoustic field distribution in the phononic crystal unit cell; Fig.13This is a comparison diagram of the admittance corresponding to the Love wave phononic crystal resonator based on lithium tantalate single crystal film and the traditional reflection grating resonator in Example 5 of the present invention, wherein (a) and (b) are the admittance diagrams corresponding to the traditional reflection grating resonator and the Love wave phononic crystal resonator based on lithium niobate single crystal film, respectively.

[0021] Description of reference numerals: 1, phononic crystal region; 1', microporous phononic crystal; 1", micropillar phononic crystal; 2, interdigital transducer; 3, piezoelectric film layer; 4, 5, 6, 7, functional substrate. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] In the description of invention patents, it is necessary to understand that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", "center", "longitudinal", "lateral", "vertical", "horizontal", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. When an element is referred to as being "fixed to" another element, it may be directly on the other element or there may also be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time.

[0024] The purpose of the present invention is to design a Love wave phononic crystal resonator with a relatively simple structure and a small size, while the existing Bragg reflector resonator requires a large number of metal reflectors. The device is easy to prepare and integrate, and has a higher Q value than a Bragg reflector resonator of the same size.

[0025] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] like Figure 1 , Figure 2 , Figure 3 , Figure 6 , Figure 7 , Fig.10 , Fig.11As shown, a Love wave phononic crystal resonator based on a lithium tantalate single crystal film provided by the present invention comprises a functional substrate (a substrate having one or more layers that can realize a high sound velocity or temperature compensation function) and a piezoelectric film layer 3 located on the upper surface of the functional substrate, an interdigital transducer 2 is arranged in the middle area of ​​the upper surface of the piezoelectric film layer 3, and phononic crystals are arranged in the phononic crystal regions 1 on both sides of the interdigital transducer 2; the frequencies of the main resonance peak and the anti-resonance peak are both within the forbidden band of the phononic crystal; Preferably, the piezoelectric film layer 3 is a lithium tantalate single crystal film, and the tangent direction of the lithium tantalate single crystal film is any one of the Y-cuts, including 0°Y, 36°Y, 42°Y, 50°Y, 64°Y, and 128°Y. For example, the tangent direction of the lithium tantalate is 42°Y, and the electrode periodic direction is parallel to the X direction. The Love wave on the lithium tantalate in this tangent direction has a large electromechanical coupling coefficient.

[0027] The frequencies of the main resonance peak and the anti-resonance peak of the Love wave phononic crystal resonator are both within the forbidden band of the phononic crystal.

[0028] For example, the material of the functional substrate is one (one layer) or more (multiple layers) of (4-H, 6-H or 3-C) silicon carbide, sapphire, (AT cut or BT cut or SC cut) quartz, diamond, silicon dioxide, polycrystalline silicon, and single crystal silicon. Different layers of the substrate may use different materials.

[0029] For example, the lithium tantalate single crystal film has a thickness of 0-10 microns.

[0030] For example, the phononic crystal is formed by etching a periodic or non-periodic hole or groove structure on the surface of the lithium tantalate single crystal film (i.e., the hole or groove structure is located in the body of the lithium tantalate single crystal film), or by growing a periodic or non-periodic column structure on the surface of the lithium tantalate single crystal film (i.e., the column structure is located on the upper surface of the lithium niobate single crystal film). The depth of the etched hole or groove may be less than the thickness of the lithium tantalate single crystal film, equal to the thickness of the lithium tantalate single crystal film, or greater than the thickness of the lithium tantalate single crystal film (i.e., the phononic crystal structure is located not only in the lithium tantalate single crystal film, but also in the functional substrate).

[0031] The cross-sectional shape of the hole or groove structure and the column structure is one or more combinations of a circle, an ellipse, a triangle, a polygon or other irregular shapes. The polygon includes a quadrilateral (square, rhombus, rectangle), a pentagon, a hexagon and the like.

[0032] For example, the material of the column structure is lithium tantalate (the same source as the piezoelectric film layer), silicon, silicon dioxide, silicon nitride or a metal material, and the metal material includes aluminum, copper, nickel, and chromium; for example, the height of the column structure is 0-1000 microns.

[0033] The lattice of the phononic crystal is a triangular lattice, a tetragonal lattice, a honeycomb lattice, a kagome lattice or other lattices with symmetry, and the lattice period ranges from 0 to 1000 microns.

[0034] For example, the spacing between the interdigital transducer and the phononic crystal is greater than 1 / 2 times of the electrode period.

[0035] Specifically, the interdigital transducer includes at least 2 pairs of interdigital electrodes, the interdigital electrodes are metal electrodes with a thickness of 0-5000 nanometers, and the material of the interdigital electrodes is an alloy of one or more combinations of gold, silver, aluminum, titanium, nickel and chromium; the electrode period of the interdigital electrodes is 0-1000 microns, and the electrode width is 0-250 microns.

[0036] Example 1 Figure 1 A top view of a Love wave phononic crystal resonator provided in Example 1 of the present invention. In Example 1 of the present invention, the phononic crystal is formed by etching periodic or non-periodic holes or groove structures on the surface of the lithium tantalate single crystal film. The lattice of the phononic crystal is a tetragonal lattice with C4 symmetry, and the lattice period is 1.5 microns. The etched hole structure forms a microporous phononic crystal 1'. The shape of the micropore is circular, that is, a circular hole. The diameter of the circular hole is 1 micron and the depth is 300 nanometers, forming a Love wave hole-type phononic crystal resonator. The cross-sectional view of the Love wave hole-type phononic crystal resonator along the section line A-A' is shown in FIG. Figure 2 In this embodiment, a functional substrate 4 is provided with a layer, and the substrate 4 can be 4-H, 6-H or 3-C silicon carbide.

[0037] In this embodiment 1, the interdigitated electrodes are gold electrodes, the electrode period is 1 micron, the electrode thickness is 120 nanometers, and the effective electrode aperture is 70 lattice periods, i.e. 70 microns. The interdigitated electrode region can excite Love waves that vibrate in a horizontal plane perpendicular to the propagation direction.

[0038] The Love wave hole type phononic crystal resonator in the embodiment of the present invention has a Love mode bandgap along the Brillouin Г-X direction of the phononic crystal, and the bandgap range is 1.714 GHz-2.125 GHz, such as Figure 4 As shown in (a). Love waves are horizontal shear waves, the acoustic energy is mainly distributed on the surface of the piezoelectric substrate, and the wave vibration direction is perpendicular to the wave propagation direction. In this embodiment, the top view and the front view of the acoustic field distribution in the phononic crystal unit cell are shown in FIG. Figure 4 As shown in (b) and (c).

[0039] The spacing between the electrode region and the reflective region is one of the important factors affecting the quality factor. In the embodiment of the present invention, the spacing between the electrode region and the reflective region is defined as the distance L between the middle of the outermost metal electrode and the center of the innermost circular hole, such as Figure 2 As shown, the spacing L is preferably 7 / 4 times the electrode period, ie, 1.75 microns.

[0040] The Love wave phononic crystal resonator based on lithium tantalate single crystal film provided in Example 1 of the present invention has obvious technical advantages over the traditional reflection grating resonator: like Figure 5 As shown in (a) and (b), the energy field distribution of the Love wave phononic crystal resonator at the main resonance peak frequency of 1.851 GHz is mainly concentrated in the interdigital electrode area. It can be seen that the phononic crystal has a very strong local effect on energy; in contrast, the energy of the traditional reflection grating resonator will have a more serious energy leakage in the direction of Love wave propagation; it can be seen that the Love wave phononic crystal resonator provided by the present invention has a stronger energy localization effect than the traditional reflection grating resonator.

[0041] The admittance of Love wave phononic crystal resonator and traditional reflection grating resonator is as follows Figure 5 As shown in (c) and (d), the main resonance peak frequency of the Love wave phononic crystal resonator is 1.851 GHz and the anti-resonance peak frequency is 1.879 GHz, both of which are within the phononic crystal band gap (1.714 GHz-2.125 GHz). Compared with the admittance of the traditional reflection grating resonator, it can be seen that the main and anti-resonance peaks of the admittance of the phononic crystal resonator are sharper. According to the quality factor calculation formula Q=f s / f 3dB , where f s is the main resonance peak frequency, f 3dB The 3dB bandwidth at the resonance peak, the main and anti-resonance peak Q values ​​of the Love wave phononic crystal resonator in the embodiment of the present invention are 158.2 and 163.4 respectively, while the main and anti-resonance peak Q values ​​of the traditional resonator are 146.9 and 150.3 respectively, indicating that the Love wave phononic crystal resonator described in the present invention can have a higher quality factor while keeping the electromechanical coupling coefficient unchanged compared with the traditional reflection grating resonator.

[0042] Example 2 In this embodiment 2, the phononic crystal is formed by growing a periodic or non-periodic column structure on the surface of the lithium tantalate single crystal film. The column structure forms a micro-column phononic crystal 1", the micro-column is a cylinder, the cylinder height is 50 nanometers, the material is aluminum, the lattice period is 1.5 microns, the cylinder diameter is 1 micron, and a Love wave column type phononic crystal resonator is formed. For the Love wave column type phononic crystal resonator, its cross-sectional view along the section line A-A' is as follows Figure 3shown.

[0043] Example 3 In Example 3 of the present invention, the phononic crystal is formed by etching periodic or non-periodic holes or groove structures on the surface of the lithium tantalate single crystal film. The lattice of the phononic crystal is a tetragonal lattice with C4 symmetry, and the lattice period is 1.5 microns. The etched hole structure forms a microporous phononic crystal 1'. The shape of the micropore is circular, that is, a circular hole, the diameter of the circular hole is 1 micron, and the depth is 300 nanometers, forming a Love wave hole type phononic crystal resonator. The cross-sectional view of the Love wave hole type phononic crystal resonator along the section line A-A' is shown in FIG. Figure 6 In this embodiment, the functional substrate is provided with three layers, namely 5-silicon dioxide, 6-polycrystalline silicon, and 7-monocrystalline silicon, and other different materials may also be used.

[0044] In this embodiment 3, the interdigitated electrodes are gold electrodes, the electrode period is 3.2 micrometers, the electrode thickness is 45 nanometers, and the effective electrode aperture is 70 lattice periods, i.e., 224 micrometers. The interdigitated electrode region can excite Love waves that vibrate in a horizontal plane perpendicular to the propagation direction.

[0045] The Love wave hole type phononic crystal resonator in the third embodiment of the present invention has a Love mode bandgap along the Brillouin Г-X direction of the phononic crystal, and the bandgap range is 1.1 GHz-1.44 GHz, such as Figure 8 As shown in (a). Love waves are horizontal shear waves, the acoustic energy is mainly distributed on the surface of the piezoelectric substrate, and the wave vibration direction is perpendicular to the wave propagation direction. In this embodiment, the top view and the front view of the acoustic field distribution in the phononic crystal unit cell are shown in FIG. Figure 8 As shown in (b) and (c).

[0046] The spacing between the electrode region and the reflective region is one of the important factors affecting the quality factor. In the embodiment of the present invention, the spacing between the electrode region and the reflective region is defined as the distance L between the middle of the outermost metal electrode and the center of the innermost circular hole, such as Figure 6 As shown, the spacing L is preferably 3 / 4 times the electrode period, ie, 2.4 microns.

[0047] The Love wave phononic crystal resonator based on lithium tantalate single crystal film provided in this embodiment 3 has obvious technical advantages compared with the traditional reflection grating resonator: The admittance of Love wave phononic crystal resonator and traditional reflection grating resonator is as follows Fig. 9As shown in (a) and (b), the main resonance peak frequency of the Love wave phononic crystal resonator is 1.177 GHz and the anti-resonance peak frequency is 1.223 GHz, both of which are within the phononic crystal band gap (1.1GHz-1.44 GHz). Compared with the admittance of the traditional reflection grating resonator, it can be seen that the main resonance peak of the admittance of the phononic crystal resonator is sharper. According to the quality factor calculation formula Q=f s / f 3dB The main resonance peak Q value of the Love wave phononic crystal resonator in the embodiment of the present invention is 561, while the main resonance peak Q value of the traditional resonator is 392, and the parasitic mode is eliminated, indicating that the Love wave phononic crystal resonator described in the present invention can have a higher quality factor while keeping the electromechanical coupling coefficient unchanged compared with the traditional reflection grating resonator.

[0048] Example 4 In this embodiment 4, the phononic crystal is formed by growing a periodic or non-periodic column structure on the surface of the lithium tantalate single crystal film. The column structure forms a micro-column phononic crystal 1", the micro-column is a cylinder, the cylinder height is 50 nanometers, the material is aluminum, the lattice period is 1.5 microns, the cylinder diameter is 1 micron, and a Love wave column type phononic crystal resonator is formed. For the Love wave column type phononic crystal resonator, its cross-sectional view along the section line A-A' is as follows Figure 7 shown.

[0049] Example 5 In Example 5 of the present invention, the phononic crystal is formed by etching periodic or non-periodic holes or groove structures on the surface of the lithium tantalate single crystal film. The lattice of the phononic crystal is a tetragonal lattice with C4 symmetry, and the lattice period is 1.5 microns. The etched hole structure forms a microporous phononic crystal 1'. The shape of the micropore is circular, that is, a circular hole, the diameter of the circular hole is 1 micron, and the depth is 300 nanometers, forming a Love wave hole type phononic crystal resonator. The cross-sectional view of the Love wave hole type phononic crystal resonator along the section line A-A' is shown in FIG. Fig.10 In this embodiment, the functional substrate is provided with two layers, 5-silicon dioxide and 7-monocrystalline silicon, and other different materials may also be used.

[0050] In this embodiment 5, the interdigitated electrodes are gold electrodes, the electrode period is 3.2 micrometers, the electrode thickness is 45 nanometers, and the effective electrode aperture is 70 lattice periods, i.e., 224 micrometers. The interdigitated electrode region can excite Love waves that vibrate in a horizontal plane perpendicular to the propagation direction.

[0051] The Love wave hole type phononic crystal resonator in the embodiment of the present invention has a Love mode bandgap along the Brillouin Г-X direction of the phononic crystal, and the bandgap range is 1.10 GHz-1.46 GHz, such as Fig.12As shown in (a). Love waves are horizontal shear waves, the acoustic energy is mainly distributed on the surface of the piezoelectric substrate, and the wave vibration direction is perpendicular to the wave propagation direction. In this embodiment, the top view and the front view of the acoustic field distribution in the phononic crystal unit cell are shown in FIG. Fig.12 As shown in (b) and (c).

[0052] The spacing between the electrode region and the reflective region is one of the important factors affecting the quality factor. In the embodiment of the present invention, the spacing between the electrode region and the reflective region is defined as the distance L between the middle of the outermost metal electrode and the center of the innermost circular hole, such as Figure 6 As shown, the spacing L is preferably 3 / 4 times the electrode period, ie, 2.4 microns.

[0053] The Love wave phononic crystal resonator based on lithium tantalate single crystal film provided in this embodiment 5 has obvious technical advantages compared with the traditional reflection grating resonator: The admittance of Love wave phononic crystal resonator and traditional reflection grating resonator is as follows Fig.13 As shown in (a) and (b), the main resonance peak frequency of the Love wave phononic crystal resonator is 1.181 GHz and the anti-resonance peak frequency is 1.172 GHz, both of which are within the phononic crystal band gap (1.10 GHz-1.46 GHz). Compared with the admittance of the traditional reflection grating resonator, it can be seen that the main resonance peak of the admittance of the phononic crystal resonator is sharper. According to the quality factor calculation formula Q=f s / f 3dB The main resonance peak Q value of the Love wave phononic crystal resonator in the embodiment of the present invention is 586, while the main resonance peak Q value of the traditional resonator is 394, and the parasitic mode is eliminated, indicating that the Love wave phononic crystal resonator described in the present invention can have a higher quality factor while keeping the electromechanical coupling coefficient unchanged compared with the traditional reflection grating resonator.

[0054] Example 6 In this embodiment 6, the phononic crystal is formed by growing a periodic or non-periodic column structure on the surface of the lithium tantalate single crystal film. The column structure forms a micro-column phononic crystal 1", the micro-column is a cylinder, the cylinder height is 50 nanometers, the material is aluminum, the lattice period is 1.5 microns, the cylinder diameter is 1 micron, and a Love wave column type phononic crystal resonator is formed. For the Love wave column type phononic crystal resonator, its cross-sectional view along the section line A-A' is as follows Fig.11 shown.

[0055] In summary, the Love wave phononic crystal based on the functional substrate and the lithium tantalate single crystal film provided by the present invention has a wider directional band gap of the Love wave. Without affecting the heat dissipation and working bandwidth of the surface acoustic wave device, the quality factor of the Love wave phononic crystal resonator invented based on the phononic crystal is significantly improved compared with the Bragg reflection grating resonator of the same size, which is of great significance for realizing a new generation of high-performance and miniaturized microwave acoustic devices.

[0056] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A Love wave phononic crystal resonator based on lithium tantalate single crystal film, characterized in that: The Love wave phononic crystal resonator comprises a functional substrate and a piezoelectric film layer located on the upper surface of the functional substrate, an interdigital transducer is arranged in the middle area of ​​the upper surface of the piezoelectric film layer, and phononic crystals are arranged on both sides of the interdigital transducer; The piezoelectric film layer is a lithium tantalate single crystal film, and the tangent direction of the lithium tantalate single crystal film is any one of the Y-cuts, including 0°Y, 36°Y, 42°Y, 50°Y, 64°Y, and 128°Y.

2. The Love wave phononic crystal resonator based on lithium tantalate single crystal thin film according to claim 1, characterized in that: The frequencies of the main resonance peak and the anti-resonance peak of the Love wave phononic crystal resonator are both within the phononic crystal band gap, and the frequency range of the phononic crystal band gap is 1.714 GHz-2.125 GHz.

3. The Love wave phononic crystal resonator based on lithium tantalate single crystal thin film according to claim 1, characterized in that: The phononic crystal is formed by etching a periodic or non-periodic hole or groove structure on the surface of the lithium tantalate single crystal film, or by growing a periodic or non-periodic column structure on the surface of the lithium tantalate single crystal film.

4. The Love wave phononic crystal resonator based on lithium tantalate single crystal thin film according to claim 3, characterized in that: The cross-sectional shapes of the hole or groove structure and the column structure are one or more combinations of circular, elliptical, triangular, polygonal or other irregular shapes.

5. The Love wave phononic crystal resonator based on lithium tantalate single crystal thin film according to claim 3, characterized in that: The material of the column structure is lithium tantalate, silicon, silicon dioxide, silicon nitride or metal material, and the metal material includes aluminum, copper, nickel, and chromium; the height of the column structure is 0-1000 microns.

6. The Love wave phononic crystal resonator based on lithium tantalate single crystal thin film according to claim 3, characterized in that: The lattice of the phononic crystal is a triangular lattice, a tetragonal lattice, a honeycomb lattice, a cage lattice or other lattices with symmetry, and the lattice period ranges from 0 to 1000 microns.

7. The Love wave phononic crystal resonator based on lithium tantalate single crystal thin film according to claim 1, characterized in that: The material of the functional substrate is one or more of silicon carbide, sapphire, quartz, diamond, silicon dioxide, polycrystalline silicon, and single crystal silicon.

8. The Love wave phononic crystal resonator based on lithium tantalate single crystal thin film according to claim 1, characterized in that: The thickness of the lithium tantalate single crystal film is 0-10 microns.

9. The Love wave phononic crystal resonator based on lithium tantalate single crystal thin film according to claim 1, characterized in that: The spacing between the interdigital transducer and the phononic crystal is greater than 1 / 2 times of the electrode period.

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