A lamb wave acoustic device spurious mode suppression structure

Abstract

The application discloses a Lamb wave acoustic device clutter mode suppression structure, which comprises an electrode finger strip layer, a piezoelectric film layer and a support substrate layer, the electrode finger strip layer comprises busbars and finger strips, the electrode finger strip layer is located on the piezoelectric film layer, the piezoelectric film layer is located on the support substrate layer, the support substrate layer comprises two support substrates arranged along an axial direction, the two support substrates are arranged at two ends of the piezoelectric film layer along the axial direction, the end face of the support substrate close to the outer side of the piezoelectric film layer is flush with the outer end face of the piezoelectric film layer, and the end face of the support substrate close to the inner side of the piezoelectric film layer is located below the end face of the finger strip. The application can improve the suppression effect on the clutter mode, and further realizes the design of a high-performance Lamb wave acoustic device with low loss, high flatness and the like.

Description

Technical Field

[0001] This invention relates to the field of surface acoustic wave (SAW) devices, and more specifically to a clutter mode suppression structure for Lamb wave acoustic devices. Background Technology

[0002] Lamb wave-based acoustic devices possess characteristics such as high frequency, large bandwidth, small size, good consistency, high reliability, low loss, and excellent filtering performance. They have become the most mainstream RF front-end devices in radar, satellite communication electronics, and mobile terminals. With the development of high-speed mobile communications, the demand for high-performance Lamb wave acoustic devices with low loss and high flatness is increasing.

[0003] Lamb wave acoustic devices exhibit various types of clutter during operation. Clutter mode suppression design for lamb wave acoustic devices mainly includes the suppression of parasitic clutter and transverse clutter modes. Parasitic clutter mode suppression primarily depends on the piezoelectric material and its tangential orientation, electrode material and dimensions, and film topology; while transverse clutter mode suppression mainly depends on the structural and material design along the finger and aperture directions. The presence of various clutter modes limits the application of lamb wave acoustic devices in the field of high-performance components. Therefore, how to improve the suppression effect of clutter modes, and thus achieve the design of high-performance lamb wave acoustic devices with low loss and high flatness, has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the existing technology, the technical problem to be solved by the present invention is: how to provide a Lamb wave acoustic device clutter mode suppression structure that can improve the suppression effect of clutter modes, thereby realizing the design of high-performance Lamb wave acoustic devices with low loss and high flatness.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A clutter mode suppression structure for a Lamb wave acoustic device includes an electrode finger layer, a piezoelectric thin film layer, and a support substrate layer. The electrode finger layer includes a busbar and fingers. The electrode finger layer is located on the piezoelectric thin film layer, which is located on the support substrate layer. The support substrate layer includes two support substrates arranged axially at both ends of the piezoelectric thin film layer. The end faces of the support substrates near the outer side of the piezoelectric thin film layer are flush with the outer end face of the piezoelectric thin film layer, and the end faces of the support substrates near the inner side of the piezoelectric thin film layer are located below the end faces of the fingers.

[0006] Preferably, the axial distance between the end face of the supporting substrate near the inner side of the piezoelectric thin film layer and the end face of the finger strip is greater than or equal to 0.

[0007] Preferably, the end face of the supporting substrate near the inner side of the piezoelectric thin film layer is flush with the end face of the finger in the vertical direction.

[0008] Preferably, the end face of the support substrate near the inner side of the piezoelectric thin film layer protrudes inward from the end face of the finger end.

[0009] Preferably, the end face of the supporting substrate near the inner side of the piezoelectric thin film layer is connected to the piezoelectric thin film layer through a transition connection portion, and the axial distance between the end face of the transition connection portion near the inner side of the piezoelectric thin film layer and the end face of the finger strip is W1, and W1≥0.

[0010] Preferably, the transition connection portion is an angular transition area formed by gradually tilting inward from bottom to top along the vertical direction at the corresponding end face of the supporting substrate.

[0011] Preferably, the transition connection portion is an arc-shaped transition area formed by the corresponding end face of the supporting substrate extending gradually inward from bottom to top in the vertical direction.

[0012] Preferably, the transition connection portion is a multi-level stepped transition area formed by the corresponding end face of the supporting substrate extending gradually inward from bottom to top in the vertical direction.

[0013] Preferably, the piezoelectric thin film layer is made of at least one of the following materials: lithium niobate, lithium tantalate, quartz, lithium tetraborate, lanthanum gallium silicate, and lanthanum gallium niobate.

[0014] Preferably, the supporting substrate is made of at least one of the following materials: silicon, sapphire, silicon carbide, diamond, spinel.

[0015] Preferably, the electrode finger layer is located on the surface of the piezoelectric thin film layer and is an interdigitated electrode, and the electrode finger layer is made of at least one of the following materials: aluminum, copper, gold, platinum, titanium, chromium, and copper-aluminum alloy.

[0016] Preferably, the piezoelectric thin film layer can be in the form of a single layer or multiple layers, and the supporting substrate layer can be in the form of a single layer or multiple layers.

[0017] Compared with the prior art, the present invention has the following advantages: 1. Lamb waves propagate in piezoelectric materials. Sound waves often have a certain energy flux angle, and surface acoustic waves (SAWs) scatter in the aperture direction, resulting in transverse clutter within the passband or near the adjacent band of the SAW device. This degrades the device's passband flatness, insertion loss, and other performance characteristics. Therefore, in this invention, the end face of the supporting substrate near the inner side of the piezoelectric thin film layer is positioned below the end face of the finger strip. Since the sound velocity of Lamb waves in the piezoelectric thin film layer decreases with increasing film thickness, this structure creates a low-velocity region at the finger tip, thereby reducing the sound propagation speed at the finger tip. This confines more Lamb wave energy to the central region of the SAW resonator, reducing scattering of SAWs in the aperture direction and improving the suppression of clutter modes, thus achieving low loss and high flatness.

[0018] 2. When Lamb waves propagate in a piezoelectric thin film layer, the sound waves undergo continuous reflection and transmission at the boundaries of the piezoelectric thin film layer, while simultaneously undergoing interconversion of sound wave modes, thus forming Lamb waves with very complex propagation modes. Lamb waves propagating in piezoelectric materials often exhibit a certain energy flux angle, and the sound waves are scattered along the aperture direction. By incorporating transition connections with varying transition regions of different shapes, the parasitic clutter modes can be effectively suppressed, resulting in Lamb wave devices exhibiting better flatness and insertion loss.

[0019] 3. This invention optimizes the structure of Lamb wave acoustic devices to suppress parasitic clutter modes of all orders while exciting high-Q (quality factor) acoustic modes. This facilitates the achievement of low-loss, high passband flatness, and other performance characteristics of Lamb wave acoustic devices, meeting the requirements of high-speed mobile communications and defense industries for high-performance surface wave devices. Furthermore, the fabrication process used in this structure is easy to implement and readily applicable for large-scale deployment. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the clutter mode suppression structure of the Lamb wave acoustic device in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the clutter mode suppression structure of the Lamb wave acoustic device in Embodiment 2 of the present invention; Figure 3 This is a schematic diagram of the clutter mode suppression structure of the Lamb wave acoustic device in Embodiment 3 of the present invention.

[0021] Explanation of reference numerals in the attached drawings: 1. Busbar; 2. Finger bar; 3. Piezoelectric thin film layer; 4. Supporting substrate; 5. Transition connection. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art to which this invention pertains.

[0023] The terms "first," "second," and similar words used in the specification and claims of this patent application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, unless the context clearly indicates otherwise, the singular forms of "an," "a," or "the," etc., do not indicate a quantity limitation, but rather indicate the presence of at least one. Terms such as "comprising" or "including" mean that the element or object preceding "comprising" encompasses the features, integrals, steps, operations, elements, and / or components listed following "comprising" or "including," and do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or collections thereof. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; these relative positional relationships may change accordingly when the absolute position of the described object changes.

[0024] Example 1: As attached Figure 1 As shown, a clutter mode suppression structure for a Lamb wave acoustic device includes an electrode finger layer, a piezoelectric thin film layer 3, and a support substrate layer. The electrode finger layer includes a busbar 1 and a finger 2. The electrode finger layer is located on the piezoelectric thin film layer 3, which is located on the support substrate layer. The support substrate layer includes two support substrates 4 arranged axially. The two support substrates 4 are arranged at both ends of the piezoelectric thin film layer 3 along the axial direction, and the end face of the support substrate 4 near the outer side of the piezoelectric thin film layer 3 is flush with the outer end face of the piezoelectric thin film layer 3. The end face of the support substrate 4 near the inner side of the piezoelectric thin film layer 3 is located below the end face of the finger 2.

[0025] In this embodiment, the axial distance between the end face of the support substrate 4 near the inner side of the piezoelectric thin film layer 3 and the end face of the finger strip 2 is greater than or equal to 0. Specifically, the end face of the support substrate 4 near the inner side of the piezoelectric thin film layer 3 can be flush with the end face of the finger strip 2 in the vertical direction, or the end face of the support substrate 4 near the inner side of the piezoelectric thin film layer 3 can protrude inward from the end face of the finger strip 2.

[0026] In this embodiment, the end face of the support substrate 4 near the inner side of the piezoelectric thin film layer 3 is connected to the piezoelectric thin film layer 3 through the transition connection portion 5. The axial distance between the end face of the transition connection portion 5 near the inner side of the piezoelectric thin film layer 3 and the end face of the finger strip 2 is W1, and W1≥0.

[0027] In this embodiment, the transition connection portion 5 is an angular transition area formed by gradually tilting inward from bottom to top along the vertical direction at the corresponding end face of the supporting substrate 4.

[0028] In this embodiment, the piezoelectric thin film layer 3 is made of at least one of the following materials: lithium niobate, lithium tantalate, quartz, lithium tetraborate, lanthanum gallium silicate, and lanthanum gallium niobate.

[0029] In this embodiment, the four supporting substrate layers are made of at least one of the following materials: silicon, sapphire, silicon carbide, diamond, and spinel.

[0030] In this embodiment, the electrode finger layer is located on the surface of the piezoelectric thin film layer 3 and is an interdigitated electrode, and the electrode finger layer is made of at least one of the following materials: aluminum, copper, gold, platinum, titanium, chromium, and copper-aluminum alloy.

[0031] In this embodiment, the piezoelectric thin film layer 3 can be a single-layer or multi-layer structure, and the supporting substrate layer 4 can be a single-layer or multi-layer structure.

[0032] Example 2: As attached Figure 2 As shown, the difference from Embodiment 1 is that in this embodiment, the transition connection portion 5 is an arc-shaped transition area formed by the corresponding end face of the supporting substrate 4 extending gradually inward from bottom to top in the vertical direction.

[0033] Example 3: As attached Figure 3 As shown, the difference from Embodiment 1 is that in this embodiment, the transition connection portion 5 is a multi-level stepped transition area formed by the corresponding end face of the supporting substrate 4 extending gradually inward from bottom to top in the vertical direction.

[0034] Compared with the prior art, the Lamb wave propagates in the piezoelectric material of the present invention. The sound wave often has a certain energy flow angle. The surface acoustic wave is scattered in the aperture direction, which leads to transverse clutter in the passband or near the adjacent band of the surface acoustic wave device, which degrades the performance of the device such as passband flatness and insertion loss.

[0035] tan(θ) = β y / β x Where θ is the energy flux angle. β yWavenumber in the aperture direction β x Let be the wave number in the direction of sound propagation.

[0036] Therefore, in this invention, the end face of the support substrate 4 near the inner side of the piezoelectric thin film layer 3 is positioned below the end face of the finger strip 2. Since the sound velocity of the Lamb wave in the piezoelectric thin film layer 3 decreases with increasing film thickness, the structure of the support substrate 4 near the inner side of the piezoelectric thin film layer 3 positioned below the end face of the finger strip 2 can create a low-velocity region at the finger tip, thereby reducing the sound propagation speed at the finger tip and confining more of the Lamb wave energy to the central region of the surface acoustic wave resonator, thus reducing the scattering of the surface acoustic wave in the aperture direction, thereby improving the suppression effect on clutter modes and achieving performance such as low loss and high flatness. When the Lamb wave propagates in the piezoelectric thin film layer 3, the sound wave continuously undergoes reflection and transmission at the boundary of the piezoelectric thin film layer 3, and there is mutual conversion of sound wave modes, thus forming a Lamb wave with a very complex propagation mode. Lamb waves propagate in piezoelectric materials. Sound waves often exhibit a certain energy flux angle and scattering along the aperture direction. By incorporating a transition connection 5 with transition regions of different shapes, the parasitic clutter modes can be effectively suppressed, resulting in Lamb wave devices with better flatness and insertion loss. This invention, through optimization of the Lamb wave acoustic device structure, achieves suppression of parasitic clutter modes of various orders while simultaneously exciting high-Q (quality factor) sound wave modes. This facilitates the achievement of low-loss, high passband flatness, and other performance characteristics in Lamb wave acoustic devices, meeting the requirements of high-speed mobile communications and defense applications for high-performance surface wave devices. Furthermore, the fabrication process used in this structure is easy to implement and readily applicable for large-scale deployment.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A clutter mode suppression structure for a Lamb wave acoustic device, characterized in that, The device includes an electrode finger layer, a piezoelectric thin film layer, and a support substrate layer. The electrode finger layer includes a busbar and fingers. The electrode finger layer is located on the piezoelectric thin film layer, which is located on the support substrate layer. The support substrate layer includes two support substrates arranged axially at both ends of the piezoelectric thin film layer. The end faces of the support substrates near the outer side of the piezoelectric thin film layer are flush with the outer end face of the piezoelectric thin film layer, and the end faces of the support substrates near the inner side of the piezoelectric thin film layer are located below the end faces of the fingers. The end face of the support substrate near the inner side of the piezoelectric thin film layer is connected to the piezoelectric thin film layer through a transition connection portion. The axial distance between the end face of the transition connection portion near the inner side of the piezoelectric thin film layer and the end face of the finger strip is W1, and W1≥0.

2. The clutter mode suppression structure for Lamb wave acoustic devices according to claim 1, characterized in that, The axial distance between the end face of the support substrate near the inner side of the piezoelectric thin film layer and the end face of the finger strip is greater than or equal to 0.

3. The clutter mode suppression structure for Lamb wave acoustic devices according to claim 1, characterized in that, The end face of the supporting substrate near the inner side of the piezoelectric thin film layer is flush with the end face of the finger in the vertical direction.

4. The clutter mode suppression structure for Lamb wave acoustic devices according to claim 1, characterized in that, The end face of the support substrate near the inner side of the piezoelectric thin film layer protrudes inward from the end face of the finger end.

5. The clutter mode suppression structure for Lamb wave acoustic devices according to claim 1, characterized in that, The transition connection portion is an angular transition area formed by gradually tilting inward from bottom to top along the vertical direction at the corresponding end face of the supporting substrate.

6. The clutter mode suppression structure for Lamb wave acoustic devices according to claim 1, characterized in that, The transition connection portion is an arc-shaped transition area formed by the corresponding end face of the supporting substrate extending gradually inward from bottom to top in the vertical direction.

7. The clutter mode suppression structure for Lamb wave acoustic devices according to claim 1, characterized in that, The transition connection portion is a multi-level stepped transition area formed by the corresponding end face of the supporting substrate extending gradually inward from bottom to top in the vertical direction.

8. The clutter mode suppression structure for Lamb wave acoustic devices according to claim 1, characterized in that, The piezoelectric thin film layer is made of at least one of the following materials: lithium niobate, lithium tantalate, quartz, lithium tetraborate, lanthanum gallium silicate, and lanthanum gallium niobate.

9. The clutter mode suppression structure for Lamb wave acoustic devices according to claim 1, characterized in that, The supporting substrate is made of at least one of the following materials: silicon, sapphire, silicon carbide, diamond, spinel.

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