A surface acoustic wave filter and a communication device

Abstract

The utility model provides a kind of effectively inhibiting transverse mode's acoustic surface filter and communication equipment.The acoustic surface filter includes: IDT metal electrode being arranged on piezoelectric substrate, IDT metal electrode surface is covered with temperature compensation layer, the IDT metal electrode includes finger electrode, load layer is arranged in the finger electrode end head area along the direction of sound wave propagation, the load layer uses following structure one: structure one, single continuous strip shape;Structure two, multiple continuous strip shape;Structure three, multiple intermittent strip shape;Finger electrode two ends end head area does not simultaneously use structure one.The utility model utilizes the multiple strip load layer of being arranged to block or reflect transverse mode propagation, to effectively inhibit transverse wave mode, improve the performance of TC- SAW filter, also have the advantage that Q value is higher.

Description

Technical Field

[0001] This utility model relates to the field of surface acoustic wave (SAW) filter technology, specifically to a SAW filter and communication device. Background Technology

[0002] Surface acoustic wave (SAW) filters are widely used in wireless communication due to their high selectivity, low insertion loss, and miniaturization. TC-SAW filters employ a temperature compensation layer (such as SiO2, fluorinated SiO2, or Si3N4) and a passivation layer successively coated on the metal electrodes of the interdigital transducer (IDT) to compensate for the negative temperature coefficient of the piezoelectric substrate (LiNbO3, LiTaO3, etc.) and improve frequency stability. However, the introduction of the temperature compensation layer alters the acoustic wave propagation conditions in TC-SAW filters, easily leading to standing waves along the length of the interdigital transducer fingers. This results in significant transverse mode propagation, causing fine ripples in the passband and a decrease in Q value, such as... Figure 2 As shown, numerous spikes are formed within the passband, corresponding to different orders of transverse modes. Traditional transverse mode suppression methods mainly include:

[0003] 1. Adjust the dummy pointer to the overlap region of the length-weighted IDT;

[0004] 2. Increase the mass load by widening or thickening the metal electrodes at the finger ends of the interdigital transducer.

[0005] However, the above solutions generally have the following drawbacks: adjusting the dummy finger reduces the coupling efficiency of the master mode and lowers the Q value; widening / thickening the electrode process is difficult, prone to short circuits, and reduces yield. Utility Model Content

[0006] In order to overcome the defects existing in the prior art, the purpose of this utility model is to provide a surface acoustic wave (SAW) filter and communication device that can effectively suppress transverse modes.

[0007] To achieve the above-mentioned objectives of this utility model, this utility model provides a surface acoustic wave (SAW) filter, comprising: a piezoelectric substrate, an IDT metal electrode disposed on the piezoelectric substrate, wherein the surface of the IDT metal electrode is covered with a temperature compensation layer, and the IDT metal electrode includes a finger strip electrode;

[0008] A load layer is provided in the region of the finger electrode tip along the direction of sound wave propagation, and the load layer adopts one of the following structures:

[0009] Structure 1: A single, continuous strip;

[0010] Structure 2: Multiple continuous strips;

[0011] Structure 3: Multiple discontinuous bands;

[0012] Structure 1 is used when the end regions of the two ends of the finger electrode are different.

[0013] This surface acoustic wave (SAW) filter utilizes multiple strip-shaped load layers to block or reflect transverse mode propagation, thereby effectively suppressing transverse wave modes, improving the performance of the TC-SAW filter, achieving better performance, and also having the advantage of a high Q value.

[0014] Optionally, the load layer is disposed on or in the temperature compensation layer, and the load layer does not contact the IDT metal electrode;

[0015] Alternatively, the load layer may be disposed within the piezoelectric substrate;

[0016] Alternatively, the load layer is located between the IDT metal electrode and the temperature compensation layer, the load layer is in close contact with and covers the IDT metal electrode, and the load layer is a dielectric material.

[0017] In this optional solution, the strip load layer can be configured with various structures, allowing for more flexible structural design.

[0018] Optionally, in structure two, the continuous strip-shaped load layers of the same finger electrode tip are arranged in parallel with equal or unequal spacing, wherein the length direction edge of the first strip-shaped load layer is flush with the projection of the edge of the finger electrode tip.

[0019] This alternative solution further enhances the suppression of shear wave modes by utilizing multi-interface reflections, building upon the original approach.

[0020] Optionally, in structure three, multiple discontinuous strip load layers are set without intervals between the same finger electrode tip, and the edge of each load layer segment in each discontinuous strip load layer is flush with the edge projection of the finger electrode tip.

[0021] The load layer segments of multiple discontinuous strip-shaped load layers on the same finger electrode tip alternately cover and expose the area of ​​the finger electrode tip at the discontinuity.

[0022] This alternative solution achieves the elimination of transverse wave modes through multiple reflections, building upon the original approach.

[0023] Optionally, the multiple discontinuous strip-shaped load layers in structure three can be integrated into a single structure.

[0024] Optionally, in structure two, the number of consecutive strip-shaped load layers in the surface acoustic wave filter is 3 to 10.

[0025] This alternative solution can achieve optimal transverse mode suppression while ensuring the coupling efficiency of the master mode.

[0026] Optionally, in structure three, the number of discontinuous strip-shaped load layers in the surface acoustic wave filter is 4 to 6.

[0027] This alternative solution can achieve optimal transverse mode suppression while ensuring the coupling efficiency of the master mode.

[0028] Optionally, in structure one, the width of the strip-shaped load layer is 0.125λ–0.5λ, and the thickness is 0.01λ–0.02λ.

[0029] Optionally, in structure two, the width of the strip load layer is 0.125λ–0.375λ, the thickness is 0.01λ–0.02λ, and the spacing between adjacent strip load layers is 0.1λ–0.5λ.

[0030] Optionally, in structure three, the width of the strip-shaped load layer is 0.275λ–0.35λ, and the thickness is 0.01λ–0.02λ.

[0031] Optionally, the load layer is a metallic material or a dielectric material.

[0032] Optionally, a passivation layer is also included, wherein when the load layer is disposed on the temperature compensation layer, the passivation layer covers both the temperature compensation layer and the load layer;

[0033] When the load layer is disposed in the temperature compensation layer, or between the IDT metal electrode and the temperature compensation layer, the passivation layer covers the temperature compensation layer;

[0034] When the load layer is disposed within the piezoelectric substrate, the passivation layer covers the temperature compensation layer.

[0035] This alternative is beneficial for environmental protection and oxidation prevention.

[0036] This application also proposes a communication device including the aforementioned surface acoustic wave (SAW) filter that effectively suppresses transverse modes. This communication device possesses all the advantages of the aforementioned SAW filter.

[0037] The beneficial effects of this utility model are:

[0038] This application suppresses transverse wave modes by setting a load layer at and near the finger electrode tip. This load layer has a specific shape and height, which, through the shape and height described in this application, blocks the propagation of transverse wave modes in the IDT region, thereby preventing transverse parasitic modes from affecting the main modes in the IDT metal electrode. In particular, when the load layer is set on or within the surface of the temperature compensation layer, the load layer does not directly contact the finger electrode of the IDT metal electrode, avoiding negative impacts on the Q value of the main mode. At the same time, the structure of the continuous or discontinuous strip-shaped load layer is simple, and there is no complicated processing technology, which can reduce production costs and complexity.

[0039] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0040] The above and / or additional aspects and advantages of this utility model will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0041] Figure 1 This is a structural schematic diagram of Embodiment 1;

[0042] Figure 2 This is the admittance curve of a standard TC-SAW filter without transverse mode suppression;

[0043] Figure 3 It is a graph showing the relationship between the width of multiple continuous strip-shaped load layers and the shear wave mode;

[0044] Figure 4 It is a graph showing the relationship between the number of multiple continuous strip-shaped load layers and the shear wave mode;

[0045] Figure 5 This is a structural schematic diagram of Embodiment 2.

[0046] Figure 6 It is a graph showing the relationship between the width of multiple discontinuous strip-shaped load layers and the shear wave mode;

[0047] Figure 7 This is a structural schematic diagram of Embodiment 3;

[0048] Figure 8 This is a schematic diagram of the structure of Embodiment 4.

[0049] Explanation of icon numbers:

[0050] 1 is the finger electrode, 2 is the busbar, 3 is the temperature compensation layer, and 4 is the strip-shaped load layer. Detailed Implementation

[0051] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0052] In the description of this utility model, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two components. They can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0053] Example 1

[0054] like Figure 1 As shown, this utility model provides an embodiment of a surface acoustic wave (SAW) filter, which is particularly suitable for TC-SAW filters.

[0055] The surface acoustic wave (SAW) filter in this embodiment includes: a piezoelectric substrate, an IDT metal electrode disposed on the piezoelectric substrate, the IDT metal electrode including a finger bar electrode 1 and a busbar 2 disposed at both ends of the finger bar electrode 1, the surface of the IDT metal electrode is covered with a temperature compensation layer 3, and multiple continuous strip-shaped load layers 4 are disposed along the direction of sound wave propagation in the end region of the finger bar electrode 1 to block or reflect the propagation of transverse modes, thereby suppressing transverse modes. Here, "continuous" means that the strip-shaped load layer 4 is a complete strip-shaped load layer 4.

[0056] The strip-shaped load layer 4 can be disposed on or within the temperature compensation layer 3. The strip-shaped load layer 4 does not contact the IDT metal electrode. A passivation layer covers both the strip-shaped load layer 4 and the temperature compensation layer 3 for environmental protection and oxidation prevention. In other embodiments, the strip-shaped load layer 4 can also be disposed within the temperature compensation layer 3, or between the IDT metal electrode and the temperature compensation layer 3, in which case the passivation layer covers the temperature compensation layer 3; or the strip-shaped load layer 4 can also be disposed within the piezoelectric substrate (in these two structures, the load layer uses a metallic or dielectric material). Alternatively, the load layer can be located between the IDT metal electrode and the temperature compensation layer, with the load layer closely adhering to and covering the IDT metal electrode (in this structure, the load layer uses a dielectric material).

[0057] The choice of piezoelectric substrate depends on the master mold to be used; it can be lithium tantalate (LiTaO3) with various cuts (Euler angles (0°, -60° to -30°, 0°)), lithium niobate (LiNbO3) with various cuts (Euler angles (0°, 0° to 175°, 0°)), or other materials such as quartz. The IDT metal electrode can be made of Ti, Al, Cu, etc., and fabricated using equipment such as photolithography, electron beam evaporation, or magnetron sputtering. The temperature compensation layer 3 can be one or any combination of SiO2, fluorinated SiO2, and Si3N4 deposited by PVD or PECVD, with a thickness of 0.1λ–0.5λ.

[0058] The strip-shaped load layer 4 can be a metallic material or a dielectric material. When it is a metallic material, metals such as Ti, Al, Cu, Au, Pt, and W can be selected; when it is a dielectric material, dielectrics such as SiO2, Si3N4, PI, Al2O3, Ta2O5, Cr2O3, and TiO2 can be selected.

[0059] In this embodiment, such as Figure 1As shown, the strip-shaped load layers 4 at the same finger electrode 1 end are arranged in parallel with equal or unequal spacing. The edge of the first strip-shaped load layer 4 (that is, the one that is located on the same side of the surface acoustic wave filter and is farthest from the busbar 2 in the figure) along its length direction (the direction of surface acoustic wave propagation) is flush with the projection of the edge of the finger electrode 1 end, so as to further enhance the suppression effect by utilizing multi-interface reflection.

[0060] In the surface acoustic wave (SAW) filter of this embodiment, the width 'a' of each strip of the load layer 4 is 0.125λ–0.375λ, the thickness 'h' is 0.01λ–0.02λ, and the spacing 'd' between adjacent strip load layers 4 is 0.1λ–0.5λ. λ refers to the wavelength of the surface acoustic wave propagating in the piezoelectric substrate. At least one finger electrode 1 end must have at least two strip load layers 4 to ensure the main mode coupling efficiency while achieving optimal transverse mode suppression. Preferably, the number of continuous strip load layers 4 on one side is 3 to 10 (the number of strip load layers located on the same side of the SAW filter).

[0061] like Figure 2 As shown, this is a comparison of the admittance curves of a conventional TC-SAW filter without a load layer for transverse mode suppression. In the figure, the blue solid line represents the admittance amplitude curve, and the green dotted line represents the real part of the admittance curve. It can be seen from the figure that the conventional TC-SAW structure, due to the introduction of a thick temperature compensation layer in the transverse mode, exhibits more severe transverse mode propagation, forming numerous spikes in the passband, corresponding to different orders of transverse modes, such as... Figure 2 As shown by the green dotted line in the middle, the load layer fabricated on the surface of the temperature compensation layer in this invention suppresses these shear wave modes and improves the performance of the TC-SAW transducer. The amplitude and real part of the admittance curves are relatively smooth, and the shear wave modes are well suppressed.

[0062] like Figure 3 As shown, this figure illustrates the relationship between transverse mode amplitude and the width of the connected strip-load layer 4. The piezoelectric substrate of the filter corresponding to this figure is made of LiNbO3 material. The spacing between the finger electrodes 1 in the IDT metal electrode is 2 μm (wavelength λ is 4 μm), the metal film thickness is 3300 angstroms, and Cu electrodes are used. The temperature compensation layer 3 is made of SiO2 material, with a thickness of approximately 0.3 wavelengths. The strip-load layer 4 has 3 strips on each side, a thickness h of 65 nm (approximately 0.015 wavelengths), and a width a that varies from 0.5 μm to 1.5 μm (0.125λ~0.375λ). The spacing d between adjacent strip-load layers 4 is the same as the width a. The transverse mode suppression effect is obtained through finite element simulation. Figure 3As shown, when the width of the strip-loaded layer 4 is 1µm, a relatively smooth amplitude and real part curve of the admittance curve are obtained. When the width of the strip-loaded layer 4 is small, there is more transverse mode residue and incomplete suppression. When the width is large, the transverse mode is over-suppressed, affecting the principal mode and producing a split peak in the principal mode peak of the admittance curve. However, compared with... Figure 2 As can be seen from the green dotted lines, the strip-shaped load layer 4 in this embodiment can suppress the transverse wave mode, improve the performance of the TC-SAW transducer, and the amplitude value and real part curve of the admittance curve are smoother than those without the load layer.

[0063] like Figure 4 As shown, it illustrates the relationship between the transverse mode amplitude and the number of continuous strip load layers 4. The other geometric parameters of the filter corresponding to this figure are... Figure 3 The thickness h of the strip-loaded layer 4 is 65nm and the width is 1um. The number of strip-loaded layers 4 varies from 2 to 9. When the number of strip-loaded layers 4 is 6, the suppression effect is the best and the amplitude of the transverse wave mode is the lowest.

[0064] Example 2

[0065] like Figure 5 As shown, this embodiment is similar to Embodiment 1, except that multiple discontinuous strip-shaped load layers 4 are arranged along the sound wave propagation direction in the end region of the finger electrode 1. These discontinuous strip-shaped load layers 4 are arranged without gaps at the end of the same finger electrode 1. The edge of each load layer segment in the length direction (sound wave propagation direction) of each strip-shaped load layer 4 is flush with the projection of the edge of the end of the finger electrode 1, eliminating transverse modes through multiple reflections. The load layer segments of the multiple discontinuous strip-shaped load layers 4 at the end of the same finger electrode 1 alternately cover the exposed end region of the finger electrode 1 at the discontinuity points; that is, the discontinuities of adjacent discontinuous strip-shaped load layers 4 are not adjacent and do not overlap. Thus, the multiple discontinuous strip-shaped load layers 4 form a meandering, folded patterned structure. In some alternative embodiments, the multiple discontinuous strip-shaped load layers 4 are an integral structure, meaning that adjacent discontinuous strip-shaped load layers 4 are seamlessly connected at the non-discontinuity points, and can be integrally molded during fabrication.

[0066] In a surface acoustic wave (SAW) filter, at least one finger electrode 1 must have at least two discontinuous strip-shaped load layers 4. Preferably, the number of discontinuous strip-shaped load layers 4 on one side is 4 to 6 (the number of strip-shaped load layers on the same side of the SAW filter). The width a of each discontinuous strip-shaped load layer 4 is 0.275λ–0.35λ, and the thickness d is 0.01λ–0.02λ.

[0067] like Figure 6 As shown, it illustrates the relationship between the transverse mode amplitude and the width of the discontinuous strip load layer 4. The other geometric parameters of the filter corresponding to this figure are the same as those in Embodiment 1. Figure 3 ,4 Similarly, the thickness h of the discontinuous strip-shaped load layer 4 is also approximately 0.015 wavelengths. The difference lies in the width a of the discontinuous strip-shaped load layer 4, which varies from 1.1 μm to 1.6 μm (0.275λ~0.4λ). Its transverse mode suppression effect is obtained through finite element simulation. Figure 7 As can be seen, the best suppression effect is achieved when a = 1.3 μm. Throughout the width variation range, the suppression effect of the transverse wave mode is less sensitive to changes than that of the multiple continuous strip-shaped load layers 4. Therefore, this structure will be more stable in practical use.

[0068] Example 3

[0069] This embodiment is based on Embodiment 1, but replaces the multiple continuous strip-shaped load layers 4 at one end of the finger strip electrode of the surface acoustic wave filter provided in Embodiment 1 with a single continuous strip-shaped load layer 4, such as... Figure 7 As shown, the width of a single continuous strip-shaped load layer 4 is 0.125λ–0.5λ, and the thickness is 0.01λ–0.02λ.

[0070] Example 4

[0071] This embodiment is based on Embodiment 2, but replaces the multiple discontinuous strip-shaped load layers 4 at one end of the finger strip electrode of the surface acoustic wave filter provided in Embodiment 2 with a single continuous strip-shaped load layer 4, such as... Figure 8 As shown, the width of a single continuous strip-shaped load layer 4 is 0.125λ–0.5λ, and the thickness is 0.01λ–0.02λ.

[0072] Example 5

[0073] This embodiment is based on Embodiment 2. In addition to multiple discontinuous strip-shaped load layers 4, a single continuous strip-shaped load layer 4 is also provided at one end of the finger bar electrode of the surface acoustic wave filter provided in Embodiment 1. The width of the single continuous strip-shaped load layer 4 is 0.125λ–0.5λ, and the thickness is 0.01λ–0.02λ.

[0074] Example 6

[0075] This embodiment is based on Embodiments 1 and 2. Multiple continuous strip-shaped load layers 4 are provided on one end region of the finger electrode 1 along the direction of sound wave propagation, and multiple discontinuous strip-shaped load layers 4 are provided on the other end region of the finger electrode 1 along the direction of sound wave propagation.

[0076] Example 7

[0077] The third embodiment provided in this application is a communication device, which includes the surface acoustic wave filter that can effectively suppress transverse modes as described in Embodiment 1 and / or Embodiment 2.

[0078] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0079] Although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A surface acoustic wave (SAW) filter, comprising: A piezoelectric substrate, an IDT metal electrode disposed on the piezoelectric substrate, the surface of the IDT metal electrode being covered with a temperature compensation layer, the IDT metal electrode including finger electrodes, characterized in that... A load layer is provided in the region of the finger electrode tip along the direction of sound wave propagation, and the load layer adopts one of the following structures: Structure 1: A single, continuous strip; Structure 2: Multiple continuous strips; Structure 3: Multiple discontinuous bands; Structure 1 is used when the end regions of the two ends of the finger electrode are different.

2. The surface acoustic wave filter according to claim 1, characterized in that, The load layer is disposed on or in the temperature compensation layer, and the load layer does not contact the IDT metal electrode. Alternatively, the load layer may be disposed within the piezoelectric substrate; Alternatively, the load layer is located between the IDT metal electrode and the temperature compensation layer, the load layer is in close contact with and covers the IDT metal electrode, and the load layer is a dielectric material.

3. The surface acoustic wave filter according to claim 1, characterized in that, In structure two, the continuous strip-shaped load layers of the same finger electrode tip are arranged in parallel with equal or unequal spacing, wherein the edge of the first strip-shaped load layer along its length direction is flush with the projection of the edge of the finger electrode tip.

4. The surface acoustic wave (SAW) filter according to claim 1, characterized in that, In structure three, multiple discontinuous strip load layers are set without intervals between the same finger strip electrode head, and the edge of each load layer segment in each discontinuous strip load layer is flush with the edge projection of the finger strip electrode head. The load layer segments of multiple discontinuous strip-shaped load layers on the same finger electrode tip alternately cover and expose the area of ​​the finger electrode tip at the discontinuity.

5. The surface acoustic wave filter according to claim 4, characterized in that, In Structure 3, the multiple discontinuous strip-shaped load layers are integrated into a single structure.

6. The surface acoustic wave filter according to claim 1, characterized in that, In structure two, the number of continuous strip-shaped load layers in the surface acoustic wave filter is 3 to 10.

7. The surface acoustic wave (SAW) filter according to claim 1, characterized in that, In structure three, the number of discontinuous strip-shaped load layers in the surface acoustic wave filter is 4 to 6.

8. The surface acoustic wave (SAW) filter according to claim 1, characterized in that, In structure one, the width of the strip-shaped load layer is 0.125λ–0.5λ, and the thickness is 0.01λ–0.02λ.

9. The surface acoustic wave (SAW) filter according to claim 1, characterized in that, In structure two, the width of the strip-shaped load layer is 0.125λ–0.375λ, the thickness is 0.01λ–0.02λ, and the spacing between adjacent strip-shaped load layers is 0.1λ–0.5λ.

10. The surface acoustic wave filter according to claim 1, characterized in that, In structure three, the width of the strip-shaped load layer is 0.275λ–0.35λ, and the thickness is 0.01λ–0.02λ.

11. The surface acoustic wave filter according to claim 1, characterized in that, The load layer is made of metallic or dielectric material.

12. The surface acoustic wave filter according to claim 2, characterized in that, It also includes a passivation layer. When the load layer is disposed on the temperature compensation layer, the passivation layer covers both the temperature compensation layer and the load layer; When the load layer is disposed in the temperature compensation layer, or between the IDT metal electrode and the temperature compensation layer, the passivation layer covers the temperature compensation layer; When the load layer is disposed within the piezoelectric substrate, the passivation layer covers the temperature compensation layer.

13. A communication device, characterized in that, Includes the surface acoustic wave filter as described in any one of claims 1 to 12.

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