Transverse clutter mode suppression structure and suppression method for surface acoustic wave device

Abstract

The invention discloses a transverse clutter mode suppression structure and suppression method for a surface acoustic wave device, the suppression structure comprises a busbar, a false finger assembly, a gap and a finger strip assembly, the finger strip assembly comprises a plurality of finger strips arranged along the axial direction, the false finger assembly comprises a plurality of false finger parts arranged along the axial direction, and the gaps are arranged between the finger strips and the false finger parts. The finger strips are in one-to-one correspondence with the artificial finger parts, each artificial finger part comprises at least one artificial finger arranged in the vertical direction, and the axial widths of different positions of the artificial fingers are not completely equal. By optimizing the structural design of the busbars, the false finger assemblies, the gaps and the finger strip assemblies, clutter mode parasitism of all orders is suppressed, and meanwhile a high-Q-value sound wave mode can be excited. Therefore, the performance of low loss, high flatness of the passband and the like of the surface acoustic wave filter can be realized, the requirements of high-speed mobile communication, national defense military industry and other terminals on the high-performance surface acoustic wave filter are met, and the preparation process used by the structure is easy to realize and easy to popularize on a large scale.

Description

Technical Field

[0001] The invention relates to the technical field of surface acoustic wave devices, and in particular to a surface acoustic wave device lateral clutter mode suppression structure and a suppression method. Background Art

[0002] RF filter devices that work using surface acoustic waves (SAW) convert RF signals into sound waves and vice versa to achieve RF signal filtering functions. They are key components of today's communication equipment.

[0003] Sound waves are mechanical vibrations transmitted by physical media. Due to the different properties of physical media, the transmission characteristics of sound waves vary. Surface acoustic waves were discovered due to the study of the serious damage caused by underground earthquakes to humans. Its characteristics are: the energy of sound waves is only transmitted within a few sound wavelength layers on the solid surface, and the transmission loss is low. This is how the engineering application of surface acoustic waves began.

[0004] Surface acoustic wave devices are electronic devices based on the (inverse) piezoelectric effect of piezoelectric materials, which use surface acoustic waves on the surface of piezoelectric materials. They use interdigital transducers (a metal electrode periodic structure, shaped like crossed hands) made on the surface of piezoelectric materials to generate and receive surface acoustic waves on their surface. Under the guidance of relevant device theories, the electrode period, aperture and cross-sectional geometry of the interdigital transducer are designed to achieve the desired electrical performance.

[0005] The structure of a surface acoustic wave device generally includes a substrate layer, a piezoelectric layer, and an electrode finger layer, and the electrode finger layer includes a bus, a dummy finger assembly, and a finger assembly. The noise mode suppression design of the surface acoustic wave device mainly includes the parasitic noise and lateral noise mode suppression design. Among them, the parasitic noise mode suppression depends on its piezoelectric material and its tangent, the electrode material and size, the membrane layer topology, etc., while the lateral noise mode suppression depends on the structure and material design in the finger and aperture direction. With the increasing demand for high-performance surface acoustic wave devices with low loss and high flatness in high-speed mobile communications, achieving noise mode suppression of surface acoustic wave devices has also become a technical problem that needs to be solved urgently. Summary of the invention

[0006] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is: how to provide a structure and method for suppressing the lateral noise mode of a surface acoustic wave device, which can suppress the parasitic noise modes of various orders while exciting high-Q value acoustic wave modes to achieve the performance of low loss, high passband flatness and the like of the surface acoustic wave device.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions: A lateral noise mode suppression structure for a surface acoustic wave device comprises a bus, a dummy finger assembly, a gap and a finger assembly, characterized in that the finger assembly comprises a plurality of fingers arranged along the axial direction, the dummy finger assembly comprises a plurality of dummy finger components arranged along the axial direction, the fingers correspond to the dummy finger components one by one, the dummy finger components comprise at least one dummy finger arranged along the vertical direction, and the axial widths of each of the dummy fingers at different positions are not completely equal.

[0008] Preferably, the side of the fake finger component adjacent to the finger strip has an axial width equal to that of the finger strip at the corresponding position.

[0009] Preferably, the fake finger includes a first step portion away from the finger direction and a second step portion close to the finger direction, the first step portion and the second step portion are both rectangular structures as a whole, and the axial width of the first step portion is greater than the axial width of the second step portion.

[0010] Preferably, the fake finger component comprises a plurality of fake fingers arranged along the vertical direction, and the maximum axial width of the plurality of fake fingers gradually decreases from a position away from the finger strip to a position close to the finger strip.

[0011] Preferably, the fake finger includes a first step portion away from the finger direction and a second step portion close to the finger direction, the first step portion and the second step portion are both rectangular structures as a whole, and the axial width of the first step portion is smaller than the axial width of the second step portion.

[0012] Preferably, the fake finger component comprises a plurality of fake fingers arranged along the vertical direction, and the maximum axial widths of the plurality of fake fingers gradually increase from a position away from the finger strip to a position close to the finger strip.

[0013] Preferably, the axial width of the fake finger gradually decreases from an end away from the finger strip to an end close to the finger strip.

[0014] Preferably, the axial width of the fake finger gradually increases from an end away from the finger strip to an end close to the finger strip.

[0015] Preferably, one end of the fake finger component away from the finger strip is connected to the bus, one end of the finger strip away from the fake finger is connected to the bus, and two adjacent fake finger components are staggered in the axial direction, and two adjacent fingers are staggered in the axial direction.

[0016] A method for suppressing lateral clutter modes of a surface acoustic wave device adopts the lateral clutter mode suppression structure of the surface acoustic wave device.

[0017] Compared with the prior art, the present invention optimizes the structure of the bus, the dummy finger assembly, the gap, and the finger assembly, so that the aperture direction presents a discontinuous structure, resulting in a difference in acoustic impedance. This difference causes acoustic wave reflection, constrains the main mode in the finger area, greatly excites the main mode, and suppresses the lateral mode. In addition, while suppressing the parasitics of each order of clutter modes, it can also achieve low loss and high Q value. Therefore, it is conducive to achieving the low loss and high passband flatness of the surface acoustic wave filter, meeting the requirements of high-speed mobile communications and national defense and military terminals for high-performance surface wave filters, and the preparation process used in the structure is easy to implement and easy to promote on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic structural diagram of a lateral clutter mode suppression structure of a surface acoustic wave device in Embodiment 1 of the present invention; Figure 2 It is a schematic structural diagram of a lateral clutter mode suppression structure of a surface acoustic wave device in Embodiment 2 of the present invention; Figure 3 It is a schematic structural diagram of a lateral clutter mode suppression structure of a surface acoustic wave device in Embodiment 3 of the present invention; Figure 4 It is a schematic structural diagram of a lateral clutter mode suppression structure of a surface acoustic wave device in Embodiment 4 of the present invention.

[0019] Description of reference numerals: busbar 1, dummy finger 2, gap 3, finger strip 4. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment 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. Unless otherwise defined, the technical terms or scientific terms used herein should be the common meaning understood by people with general skills in the field to which the present invention belongs.

[0021] The words "first", "second" and similar words used in the patent application specification and claims of the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, unless the context clearly indicates otherwise, the singular forms of "a", "an" or "the" and other similar words do not indicate a quantitative limitation, but indicate the existence of at least one. Words such as "include" or "comprise" mean that the elements or objects appearing before "include" or "comprise" cover the features, wholes, steps, operations, elements and / or components listed after "include" or "comprise", and do not exclude the existence or addition of one or more other features, wholes, steps, operations, elements, components and / or their collections. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0022] Embodiment 1: The surface acoustic wave device includes a substrate layer, a piezoelectric film layer and an electrode finger layer. The electrode finger layer is located on the surface of the piezoelectric film layer. The piezoelectric film layer is a single-layer or multi-layer structure. The piezoelectric film layer is located on the substrate layer. The substrate layer can adopt a substrate-free structure, or the substrate layer contains a single-layer or multi-layer material structure.

[0023] The lateral noise mode suppression structure of the surface acoustic wave device of this scheme is mainly an improvement on the electrode finger layer structure. In this scheme, as shown in the attached Figure 1 As shown, the electrode finger layer includes a bus 1, a dummy finger assembly, a gap 3 and a finger assembly. The finger assembly includes a plurality of fingers 4 arranged along the axial direction. The dummy finger assembly includes a plurality of dummy finger components arranged along the axial direction. The fingers 4 correspond to the dummy finger components one by one. The dummy finger components include at least one dummy finger 2 arranged along the vertical direction, and the axial widths of each dummy finger 2 at different positions are not completely equal.

[0024] In this embodiment, the side of the fake finger component adjacent to the finger strip 4 has an axial width equal to that of the finger strip 4 at the corresponding position, that is, w1=w2 in the figure.

[0025] In this embodiment, the fake finger 2 includes a first step portion away from the finger bar 4 and a second step portion close to the finger bar 4. The first step portion and the second step portion are both rectangular structures as a whole, and the axial width of the first step portion is greater than the axial width of the second step portion. The vertical height relationship of the first step portions of different fake fingers 2 is h1=n1*h3, and the vertical height relationship of the second step portions of different fake fingers 2 is h2=n2*h4, where n1=n2, n1, n2 are constants.

[0026] In this embodiment, the fake finger component includes a plurality of fake fingers 2 arranged along the vertical direction, and the maximum axial width of the plurality of fake fingers 2 gradually decreases from a position far from the finger bar 4 to a position close to the finger bar 4 .

[0027] In this embodiment, the end of the fake finger component away from the finger bar 4 is connected to the bus 1, and the end of the finger bar 4 away from the fake finger 2 is connected to the bus 1, and two adjacent fake finger components are staggered in the axial direction, and two adjacent finger bars 4 are staggered in the axial direction, that is, as shown in the attached Figure 1 As shown, the upper end of the leftmost dummy finger component is connected to the bus 1, and the lower end of the adjacent dummy finger component is connected to the bus 1, the lower end of the leftmost finger bar 4 is connected to the bus 1, and the lower end of the adjacent finger bar 4 is connected to the bus 1.

[0028] In this embodiment, the electrode finger strip layers are all interdigitated electrodes, and the interdigitated electrodes are made of at least one of the following materials: aluminum Al, copper Cu, gold Au, platinum Pt, titanium Ti, chromium Cr and copper-aluminum alloy.

[0029] In this embodiment, the piezoelectric film layer is made of at least one of the following materials: lithium niobate LiNbO 3 、Lithium Tantalate LiTaO 3 , Quartz, lithium tetraborate, lanthanum gallium silicate, lanthanum gallium niobate.

[0030] In this embodiment, the substrate layer is made of at least one of the following materials: silicon Si, sapphire Sapphire, silicon carbide SiC, diamond Diamond, and spinel.

[0031] A method for suppressing lateral clutter modes of a surface acoustic wave device adopts the lateral clutter mode suppression structure of the surface acoustic wave device.

[0032] Embodiment 2 The difference from the first embodiment is that in this embodiment, as shown in the attached Figure 2 As shown, the fake finger 2 includes a first step portion away from the finger bar 4 and a second step portion close to the finger bar 4. The first step portion and the second step portion are both rectangular structures as a whole, and the axial width of the first step portion is smaller than the axial width of the second step portion.

[0033] In this embodiment, the fake finger component includes a plurality of fake fingers 2 arranged along the vertical direction, and the maximum axial width of the plurality of fake fingers 2 gradually increases from a position far from the finger bar 4 to a position close to the finger bar 4 .

[0034] Embodiment 3 The difference from the first embodiment is that in this embodiment, as shown in the attached Figure 3 As shown, the axial width of the fake finger 2 gradually decreases from the end away from the finger strip 4 to the end close to the finger strip 4 .

[0035] Embodiment 4 The difference from the third embodiment is that in this embodiment, as shown in the attached Figure 4 As shown, the axial width of the fake finger 2 gradually increases from the end away from the finger strip 4 to the end close to the finger strip 4 .

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the technical solution. Those skilled in the art should understand that those modifications or equivalent substitutions of the technical solution of the present invention that do not depart from the purpose and scope of the technical solution should be included in the scope of the claims of the present invention.

Claims

1. A surface acoustic wave device lateral clutter mode suppression structure, comprising a bus, a dummy finger assembly, a gap and a finger assembly, It is characterized in that The finger assembly includes a plurality of fingers arranged along the axial direction, and the fake finger assembly includes a plurality of fake finger parts arranged along the axial direction. The finger bars correspond to the fake finger parts one by one. The fake finger parts include at least one fake finger arranged along the vertical direction, and the axial width of each fake finger at different positions is not completely equal.

2. The lateral noise mode suppression structure of a surface acoustic wave device according to claim 1, It is characterized in that The side of the fake finger component adjacent to the finger strip has an axial width equal to that of the finger strip at a corresponding position.

3. The lateral noise mode suppression structure of a surface acoustic wave device according to claim 2, It is characterized in that The fake finger includes a first step portion away from the finger direction and a second step portion close to the finger direction. The first step portion and the second step portion are both rectangular structures as a whole, and the axial width of the first step portion is greater than the axial width of the second step portion.

4. The lateral noise mode suppression structure of a surface acoustic wave device according to claim 3, It is characterized in that The fake finger component includes a plurality of fake fingers arranged along a vertical direction, and the maximum axial width of the plurality of fake fingers gradually decreases from a position away from the finger strip to a position close to the finger strip.

5. The lateral noise mode suppression structure of a surface acoustic wave device according to claim 2, It is characterized in that The fake finger includes a first step portion away from the finger direction and a second step portion close to the finger direction. The first step portion and the second step portion are both rectangular structures as a whole, and the axial width of the first step portion is smaller than the axial width of the second step portion.

6. The lateral noise mode suppression structure of a surface acoustic wave device according to claim 5, It is characterized in that The fake finger component includes a plurality of fake fingers arranged along a vertical direction, and the maximum axial widths of the plurality of fake fingers gradually increase from a position away from the finger strip to a position close to the finger strip.

7. The lateral noise mode suppression structure of a surface acoustic wave device according to claim 2, It is characterized in that The axial width of the fake finger gradually decreases from an end away from the finger strip to an end close to the finger strip.

8. The lateral noise mode suppression structure of a surface acoustic wave device according to claim 2, It is characterized in that The axial width of the fake finger gradually increases from an end away from the finger strip to an end close to the finger strip.

9. The lateral noise mode suppression structure of a surface acoustic wave device according to claim 1, It is characterized in that One end of the fake finger component away from the finger bar is connected to the bus, and one end of the finger bar away from the fake finger is connected to the bus, and two adjacent fake finger components are staggered in the axial direction, and two adjacent fingers are staggered in the axial direction.

10. A method for suppressing lateral clutter modes of surface acoustic wave devices. It is characterized in that A lateral noise mode suppression structure for a surface acoustic wave device as claimed in any one of claims 1 to 9 is adopted.

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