A dual surface acoustic wave filter, a dual frequency component and a manufacturing method thereof

Abstract

The present invention proposes a dual surface acoustic wave filter, which includes: a piezoelectric substrate; a first filter element and a second filter element are arranged on the same piezoelectric substrate; the first filter element responds to the first frequency of the surface acoustic wave, the first filter element includes a plurality of first IDT electrodes, and the first IDT electrodes have a first metal film of a first thickness; the second filter element responds to the second frequency of the surface acoustic wave, the second filter element includes a plurality of second IDT electrodes, and the second IDT electrodes have a second metal film of a second thickness; the first frequency is different from the second frequency; the first thickness is different from the second thickness; the surface acoustic wave propagation path of the first filter element is parallel to or intersects with the surface acoustic wave propagation path of the second filter element. Therefore, the dual surface acoustic wave filter and the manufacturing method thereof provided by the present invention can realize a dual surface acoustic wave filter with high power tolerance and high reliability.

Description

Technical Field

[0001] The invention relates to the field of semiconductor manufacturing, and in particular to a dual surface acoustic wave filter, a dual-frequency component and a manufacturing method thereof. Background Art

[0002] In recent years, with the rapid development of wireless communication systems, various terminal devices have widely supported multiple communication protocols such as 2G, 3G, LTE, Wi-Fi, GPS, etc. In order to achieve this goal, in the prior art, the RF front end of the communication equipment is composed of multiple RF circuits, each of which contains independent filters, amplifiers and other devices with different center frequencies and bandwidths. RF switches are used to select filters with different center frequencies for communication. Although this solution can support the simultaneous operation of multiple communication standards, it increases the volume, power consumption and cost of the communication system.

[0003] In order to solve the problems of the above scheme, dual-frequency components came into being. They are composed of a high-speed broadband A / D converter and two single-passband surface acoustic wave filters, which can support the work and reduce the volume of the communication system to a certain extent. However, since the two single-passband surface acoustic wave filters are located on separate substrates, they are generally implemented by splicing composite substrates, which will lead to poor reliability at the junction and high processing costs. At the same time, the two single-passband surface acoustic wave filters use switches to switch channels, and the signal may be lost, and the reliability of the dual-frequency components is poor.

[0004] How to improve the reliability of dual-frequency components, further reduce the size of dual-frequency components, and improve the frequency selectivity and passband isolation of dual-frequency components has become a problem that technical personnel in this field need to solve. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a dual-surface acoustic wave filter, a dual-frequency component and a method for manufacturing the same. The dual-surface acoustic wave filter is arranged on the same substrate and responds to two different center frequencies. It can improve the integration of the surface acoustic wave filter, improve the reliability of the dual-frequency component, further reduce the volume of the dual-frequency component, and improve the frequency selectivity and passband isolation of the dual-frequency component.

[0006] The purpose of the present invention is mainly achieved through the following technical solutions: According to the first aspect of the present invention, a dual surface acoustic wave filter comprises: a piezoelectric substrate; a first filter element and a second filter element are arranged on the same piezoelectric substrate; the first filter element responds to a first frequency of the surface acoustic wave, the first filter element comprises a plurality of first IDT electrode fingers, the first IDT electrode fingers have a first metal film of a first thickness, and the plurality of first IDT electrode fingers are mounted on the piezoelectric substrate along the propagation direction of the surface acoustic wave; the second filter element responds to a second frequency of the surface acoustic wave, the second filter element comprises a plurality of second IDT electrode fingers, the second IDT electrode fingers have a second metal film of a second thickness, and the plurality of second IDT electrode fingers are mounted on the piezoelectric substrate along the propagation direction of the surface acoustic wave; the first frequency is different from the second frequency; the first thickness is different from the second thickness; the surface acoustic wave propagation path of the first filter element is parallel to or intersects with the surface acoustic wave propagation path of the second filter element.

[0007] In some embodiments, the first thickness of the first metal film is defined as H1, the second thickness of the second metal film is defined as H2, the first frequency is defined as f1, the second frequency is defined as f2, the frequency response speed of the first frequency is defined as v1, and the frequency response speed of the second frequency is defined as v2, wherein the first thickness of the first metal film, the second thickness of the second metal film, the first frequency, the second frequency, the frequency response speed of the first frequency, and the frequency response speed of the second frequency satisfy the following formula: 7%

[0008] In some embodiments, the duty cycle of the filter element is defined as the ratio of the width of each of the multiple electrode fingers to the sum of the width of each of the multiple electrode fingers and the intervals between adjacent electrode fingers included in the multiple electrode fingers, the first filter element has a first duty cycle, the second filter element has a second duty cycle, the first duty cycle is different from the second duty cycle, the first duty cycle is greater than 0.2 and less than 0.7, and the second duty cycle is greater than 0.3 and less than 0.9.

[0009] In some embodiments, the first IDT electrode finger has a first duty cycle, the second IDT electrode finger has a second duty cycle, the first IDT electrode finger and the second IDT electrode finger are both provided with a metal thin film structure, the metal thin film structure includes a first metal layer and a second metal layer, the first metal layer includes Al, and the second metal layer is one of Cu, W, Mo, Cr, Ag, Au, Pt, Ga, Nb, Ta, Au, Si, and Sc.

[0010] ​In some embodiments, the piezoelectric substrate is a piezoelectric single crystal substrate, and the piezoelectric single crystal substrate is lithium tantalate or lithium niobate; the first IDT electrode finger and the second IDT electrode finger are formed on the same surface of the piezoelectric single crystal substrate.

[0011] In some embodiments, the piezoelectric substrate is a piezoelectric single crystal substrate, the piezoelectric single crystal substrate is lithium tantalate or lithium niobate, the single crystal piezoelectric substrate has a first surface and a second surface arranged in parallel, the first IDT electrode finger is formed on the first surface, and the second IDT electrode finger is formed on the second surface.

[0012] In some embodiments, the piezoelectric substrate includes: an orientation angle between the first filter element and the piezoelectric single crystal substrate is ψ1, ψ1 is 0°, and an orientation angle between the second filter element and the piezoelectric single crystal substrate is ψ2, ψ2 is in the range of (-5, +5°).

[0013] In some embodiments, the piezoelectric substrate includes: a piezoelectric single crystal film, the first filter element and the second filter element are located on the same surface of the piezoelectric single crystal film; a bonding layer, arranged on the surface of the piezoelectric single crystal film away from the first filter element, and the bonding layer has a positive temperature compensation coefficient; a supporting substrate, arranged on the surface of the bonding layer away from the piezoelectric single crystal film, and the supporting substrate is a single crystal silicon substrate.

[0014] According to a second aspect of the present invention, there is provided a dual-frequency component, comprising a dual-surface acoustic wave filter as described in any one of claims 1 to 8, characterized in that a packaging structure is provided for accommodating the dual-surface acoustic wave filter, wherein the packaging structure is connected to the dual-surface acoustic wave filter via a bump.

[0015] According to a third aspect of the present invention, a method for manufacturing a dual surface acoustic wave filter is provided, the method comprising: providing a piezoelectric substrate; arranging a first filter element and a second filter element on the same piezoelectric substrate by metal evaporation; wherein the first filter element responds to a first frequency of the surface acoustic wave, the first filter element comprises a plurality of first IDT electrode fingers, the first IDT electrode fingers have a first metal film of a first thickness, and the plurality of first IDT electrode fingers are mounted on the piezoelectric substrate along a propagation direction of the surface acoustic wave; the second filter element responds to a second frequency of the surface acoustic wave, the second filter element comprises a plurality of second IDT electrode fingers, the second IDT electrode fingers have a second metal film of a second thickness, and the plurality of second IDT electrode fingers are mounted on the piezoelectric substrate along a propagation direction of the surface acoustic wave; the first frequency is different from the second frequency; the first thickness is different from the second thickness; the surface acoustic wave propagation path of the first filter element is parallel to or intersects with the surface acoustic wave propagation path of the second filter element.

[0016] In some embodiments, a first filter element and a second filter element are arranged on the same piezoelectric substrate by metal evaporation method, including: dividing the piezoelectric substrate into a first set area for forming the first filter element and a second set area for forming the second filter element; covering the first set area and the second set area of ​​the piezoelectric substrate with a layer of metal film; laying photoresist on the metal film in the first set area, and stripping off excess photoresist by photolithography to form an electrode pattern constituting a first IDT electrode finger; covering the first IDT electrode finger and the second set area with a layer of metal film; laying photoresist on the metal film in the second set area, and stripping off excess photoresist by photolithography to form an electrode pattern constituting a second IDT electrode finger that is thicker than the electrode pattern of the first IDT electrode finger.

[0017] In some embodiments, a first filter element and a second filter element are arranged on the same piezoelectric substrate using a metal evaporation method, including: dividing the piezoelectric substrate into a first set area for forming the first filter element and a second set area for forming the second filter element; covering the first set area and the second set area of ​​the piezoelectric substrate with multiple layers of metal film; laying photoresist on the metal film in the first set area, and using photolithography to peel off excess photoresist to form an electrode pattern constituting a first IDT electrode finger; laying photoresist on the metal film in the second set area, and using photolithography to peel off excess photoresist to form an electrode pattern constituting a second IDT electrode finger that is thinner than the electrode pattern of the first IDT electrode finger.

[0018] In some embodiments, the piezoelectric substrate is a piezoelectric single crystal substrate, and the method further includes: coating a metal film on the upper surface of the piezoelectric single crystal substrate; laying photoresist on the metal film, and using photolithography to peel off excess photoresist to form an electrode pattern constituting a first IDT electrode finger; flipping the piezoelectric single crystal substrate so that the lower surface faces upward; coating a metal film on the lower surface of the piezoelectric single crystal; laying photoresist on the metal film, and using photolithography to peel off excess photoresist to form an electrode pattern constituting a second IDT electrode finger; wherein the thickness of the electrode pattern constituting the first IDT electrode finger is greater than the thickness of the electrode pattern constituting the second IDT electrode finger.

[0019] In some embodiments, the production of a piezoelectric substrate includes: injecting ionized elements into the piezoelectric substrate; forming a bonding layer containing silicon dioxide on a supporting substrate supporting the piezoelectric substrate or on at least one side of the piezoelectric substrate; and bonding the bonding layer, the piezoelectric substrate, and the supporting substrate to generate a piezoelectric substrate.

[0020] The beneficial effects achieved by the present invention are as follows:

[0021] According to the present invention, a method for manufacturing a dual surface acoustic wave filter is provided. By arranging IDT electrodes of different thicknesses on a piezoelectric substrate, the setting of high and low frequency regions required by the dual surface acoustic wave filter can be met. Moreover, by designing the IDT electrode structure and setting the piezoelectric substrate, a dual surface acoustic wave filter with more different requirements can be met. The manufacturing process is simple, the design difficulty is low, and it is conducive to achieving the optimal device performance of the dual surface acoustic wave filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0023] Figure 1 It is a schematic diagram of the structure of a dual surface acoustic wave filter in the prior art of the present invention;

[0024] Figure 2 It is a schematic structural diagram of a dual surface acoustic wave filter of the present invention;

[0025] Figure 3 It is a schematic diagram of a multilayer electrode structure of a dual surface acoustic wave filter of the present invention;

[0026] Figure 4 It is a schematic diagram of the IDT electrode finger structure of a dual surface acoustic wave filter of the present invention;

[0027] Figure 5 It is a schematic diagram of the structure of different tangential Euler angles of a dual surface acoustic wave filter of the present invention;

[0028] Figure 6 It is a low-end frequency waveform performance diagram of the dual-frequency component before integration of the prior art;

[0029] Figure 7 It is a high-end frequency waveform performance diagram of the dual-frequency component before integration of the prior art;

[0030] Figure 8 It is an overall waveform performance diagram of a dual-frequency component of the prior art;

[0031] Fig. 9 It is a waveform performance diagram of a dual surface acoustic wave filter of the present invention;

[0032] Fig.10 It is another schematic diagram of the structure of a dual surface acoustic wave filter of the present invention;

[0033] Fig.11 It is a schematic diagram of the structure of another dual acoustic surface filter of the present invention;

[0034] Fig.12It is a schematic diagram of the packaging structure of a dual-frequency component of the present invention;

[0035] Fig.13 It is a schematic diagram of the packaging structure of another dual-frequency component of the present invention;

[0036] Fig.14 It is a schematic diagram of the manufacturing process of a dual surface acoustic wave filter of the present invention;

[0037] Fig.15 It is another schematic diagram of the manufacturing process of a dual surface acoustic wave filter of the present invention.

[0038] in, Figures 1 to 15 The corresponding relationship between the reference numerals and component names in the figure is:

[0039] 11-single passband surface acoustic wave filter, 12-adhesive layer;

[0040] 1-piezoelectric substrate, 21-first IDT electrode finger, 22-second IDT electrode finger;

[0041] 31-piezoelectric single crystal film, 32-bonding layer, 33-support substrate;

[0042] 41- buffer layer, 42- metal layer;

[0043] 8-packaging structure, 801-first packaging structure, 802-second packaging structure;

[0044] 802-1 a first layer of a second encapsulation structure, 802-2 a second layer of a second encapsulation structure;

[0045] 9-bump, 901-substrate electrode, 902-middle bump electrode, 903-packaging electrode;

[0046] 10-Dual SAW filter. DETAILED DESCRIPTION

[0047] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0048] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0049] In the dual surface acoustic wave filter structure in the prior art, such as Figure 1As shown, a high-speed broadband A / D converter and two single-passband surface acoustic wave filters 11 are usually used to support the work and reduce the volume of the communication system to a certain extent. However, since the two single-passband surface acoustic wave filters 11 are located on separate substrates, they are generally spliced ​​by a composite substrate, such as adding an adhesive layer 12, but this will lead to poor reliability at the junction and high processing costs. At the same time, the two single-passband surface acoustic wave filters use switches to switch channels, the signal may be lost, and the reliability of the dual-frequency components is poor.

[0050] Example 1

[0051] A specific embodiment of the present invention, as Figure 2 As shown, a schematic diagram of the structure of a dual surface acoustic wave filter is disclosed, and the dual surface acoustic wave filter includes:

[0052] A piezoelectric substrate 1 is provided with a first filter element and a second filter element on the piezoelectric substrate 1. The first filter element responds to a first frequency of a surface acoustic wave, and the first filter element includes a plurality of first IDT electrode fingers 21, the first IDT electrode fingers 21 have a first metal film of a first thickness, and the plurality of first IDT electrode fingers 21 are mounted on the piezoelectric substrate along a propagation direction of the surface acoustic wave.

[0053] Furthermore, the second filter element responds to the second frequency of the surface acoustic wave, and includes a plurality of second IDT electrode fingers 22, the second IDT electrode fingers have a second metal film of a second thickness, and the plurality of second IDT electrode fingers are mounted on the piezoelectric substrate along the propagation direction of the surface acoustic wave.

[0054] The first frequency is different from the second frequency. The first thickness is different from the second thickness.

[0055] The surface acoustic wave propagation path of the first filter element is parallel to or intersects with the surface acoustic wave propagation path of the second filter element.

[0056] The first IDT electrode finger or the second IDT electrode finger mentioned in the present application actually refers to an IDT transducer.

[0057] Since the first IDT electrode finger 21 and the second IDT electrode finger 22 are formed on the same piezoelectric substrate, the IDT electrode fingers formed by the metal films of different thicknesses achieve a dual surface acoustic wave filter with different frequencies, thereby reducing the design difficulty of the dual surface acoustic wave filter, and obtaining IDT electrode fingers with different center frequencies on the same substrate. Exemplarily, the thickness of the metal film of the first IDT electrode is greater than the thickness of the metal film of the second IDT electrode by 200um, and the relative electrodes formed are the first IDT electrode as the high center frequency electrode in the dual surface acoustic wave filter, and the second IDT electrode as the low center frequency electrode in the dual surface acoustic wave filter by 100um.

[0058] Furthermore, the first IDT electrode 21 and the second IDT electrode 22 may both have a metal thin film structure, such as Figure 3 As shown, illustratively, the metal film structure can be a double-layer structure, including a first metal layer 41 and a second metal layer 42, wherein the first metal layer 41 includes Al, and in other embodiments can be implemented as Si or Cu. The second metal layer 42 includes one of Cu, W, Mo, Cr, Ag, Au, Pt, Ga, Nb, Ta, Au, Si, and Sc. When the wavelength of the elastic wave determined by the electrode period of the IDT electrode is set to λ, the thickness of the buffer layer is less than 0.5%λ.

[0059] In other embodiments, the first metal layer 41 and the second metal layer 42 have the same composition and thickness, for example, both are composed of titanium or chromium, or are titanium-chromium alloys with the same composition ratio, and both have the same thickness.

[0060] Furthermore, the structure of the first IDT electrode 21 and the second IDT electrode 22 can also be set to include aluminum electrodes, and metal films of different metal elements are also arranged under the aluminum electrodes to realize IDT electrodes with strong support structures. The IDT electrode with strong support structure uses aluminum elements as a substrate. Specifically, each IDT electrode includes a first buffer layer arranged on a piezoelectric substrate and a first metal layer arranged on the first buffer layer. The first buffer layer includes at least one of metal titanium or chromium. When the wavelength of the elastic wave determined by the electrode period of the IDT electrode is set to λ, the thickness of the first buffer layer is less than 0.5%λ. The first metal layer includes metal aluminum, and the thickness of the Al layer ranges from 1% to 30% of the wavelength of the surface acoustic wave.

[0061] When the wavelength λ of the elastic wave determined by the electrode period of the IDT electrode is 2μm, the thickness of the first buffer layer is less than 10nm. In a preferred embodiment, the thickness of the first buffer layer can be set to 2nm, so that a strong Al texture can be obtained. The obtained Al film has a uniform and dense structure, an increased critical load, and significantly enhanced adhesion to the piezoelectric substrate.

[0062] In addition, a titanium buffer layer is provided between the Al electrode and the substrate to prevent the migration of Al to the substrate.

[0063] The thickness of the first metal layer Al layer is designed, and a metal Al layer with a thickness between 1%λ and 30%λ is used together with a Ti buffer layer to form an IDT electrode finger, which has the advantages of good anti-electromigration performance and stable chemical properties.

[0064] As a preferred embodiment, Figure 4As shown in the upper part of the figure, the first thickness of the first metal film is defined as H1, the second thickness of the second metal film is defined as H2, the first frequency is defined as f1, the second frequency is defined as f2, the frequency response speed of the first frequency is defined as v1, and the frequency response speed of the second frequency is defined as v2, wherein the first thickness of the first metal film, the first frequency and the frequency response speed of the first frequency meet: 7%

[0065] As a preferred embodiment, Figure 4 As shown in the lower figure, the duty cycle of the filter element is defined as the ratio of the width of each of the multiple electrode fingers to the sum of the width of each of the multiple electrode fingers and the intervals between adjacent electrode fingers contained in the multiple electrode fingers, wherein the first filter element has a first duty cycle, and the second filter element has a second duty cycle, the first duty cycle is different from the second duty cycle, the first duty cycle is greater than 0.2 and less than 0.7, and the second duty cycle is greater than 0.3 and less than 0.9. The duty cycle of the first filter element and the second filter element is the average value of the duty cycle of the multiple electrode fingers constituting the filter element. The specific implementation method of the duty cycle is through the ratio of the IDT electrode finger width W of the first filter or the second filter to the sum of the electrode finger width W and the gap G between the electrode fingers, that is, duty cycle = W / (W+G).

[0066] As a preferred embodiment, the piezoelectric substrate is a piezoelectric single crystal substrate, wherein the first IDT electrode finger 21 and the second IDT electrode finger 22 are formed on the same surface of the piezoelectric single crystal substrate. Exemplarily, the first IDT electrode finger 21 and the second IDT electrode finger 22 can be arranged in parallel on the same surface of the same piezoelectric single crystal substrate, and further, can be arranged on the same surface of the same piezoelectric single crystal substrate with an IDT electrode finger angle ψ in the range of (-5°, +5°), and the piezoelectric single crystal substrate is lithium tantalate or lithium niobate, a LiTaO3 substrate cut in the Y direction at 36 to 52 degrees and propagated in the X direction, that is, the Euler angle is (0°, 36°-52°, ψ). Wherein, the piezoelectric single crystal substrate includes a first frequency band region and a second frequency band region with different tangential Euler angles, and the orientation angle between the first filter element and the piezoelectric single crystal substrate is ψ1, ψ1 is 0°, and ψ1=0° (not shown in the figure) represents that the surface acoustic wave propagation path of the first filter element is parallel to the surface acoustic wave propagation path of the second filter element. The orientation angle between the second filter element and the piezoelectric single crystal substrate is ψ2, and ψ2 is within the range of (-5°, +5°).​ Figure 5 As shown, when ψ2 is within the range of (-5°, +5°), it represents that the surface acoustic wave propagation path of the first filter element intersects with the surface acoustic wave propagation path of the second filter element.

[0067] As an example of the application effect of this embodiment, please refer to Figure 6 , Figure 7 , Figure 8 and Fig. 9 As shown, before adopting the content of this embodiment, the frequency waveform performance diagrams of the two single-passband filters of the dual-frequency component of the prior art can be referred to in sequence. Figure 6 and Figure 7 As shown in the figure, the frequency waveform performance diagram of combining two single passband filters into a dual-frequency component through a bonding layer can be referred to Figure 8 As shown. It can be seen that due to the low frequency at the high end of the 1995MHZ filter, the total isolation after the convex part and the 2185MHZ low end are superimposed is 28dB. Although the dual-frequency component after the high end and the bottom end are integrated through the adhesive layer, the isolation at the low end of 2185MHZ can reach 30dB, the overall isolation is less than 30dB, but it still does not meet the dual-frequency communication index. However, in the embodiment of the present application, Fig. 9 In the dual filter frequency waveform performance diagram shown, the structure of the 1995MHZ high-end resonator is adjusted so that the "small bump" is close to the low end of 2185MHZ, such as the waveform after the zero-pole reconstruction method. It can be seen that at this time, not only the high-end isolation of 1995MHZ is improved to 31dB, but also the low-end isolation of 2185MHZ is increased to 33dB, and the overall level of passband isolation exceeds the required 30dB.

[0068] Furthermore, for the Euler angles in different frequency bands, gullies or slopes can be formed on the piezoelectric film by dry etching or wet etching to form multiple different Euler cutting angles. In this way, multiple different Euler cutting angles are formed on the same piezoelectric film, thereby meeting the requirements of the two high and low frequency bands and two bandwidths required by the dual surface acoustic wave filter, thereby avoiding cutting the piezoelectric film twice, effectively reducing the production cost.

[0069] Example 2

[0070] A specific embodiment of the present invention also discloses a schematic diagram of a dual surface acoustic wave filter structure, as shown in FIG. Fig.10 As shown, the dual surface acoustic wave filter includes:

[0071] The first IDT electrode finger 21 is formed on the upper surface of the piezoelectric single crystal substrate, and the second IDT electrode finger 22 is formed on the lower surface of the piezoelectric single crystal substrate. The entire IDT electrode finger is arranged in a concave-convex configuration on the piezoelectric single crystal substrate. The depth of the concave-convex structure is less than or equal to the depth of the piezoelectric single crystal substrate. Specifically, the concave-convex structure corresponds to the surface IDT electrode configuration, or is staggered with the IDT electrode, or every two concave-convex structures correspond to the width of one IDT electrode finger, thereby reducing the insertion loss.

[0072] Specifically, the surface of the first IDT electrode finger 21 or the second IDT electrode finger 22 away from the piezoelectric single crystal substrate forms a rough bottom surface, the roughness of the rough bottom surface is 0.2μm to 0.4μm, and the average height difference between the peaks and valleys on the rough bottom surface can be 2.5μm, preferably greater than 4.5μm. The bottom surface of the substrate is roughened to reduce the reflection of acoustic waves back to the body double acoustic surface wave filter. The average lateral distance between the peaks and valleys on the roughened substrate surface can be less than 0.05μm, preferably less than 0.03μm. The roughening of the bottom surface can be achieved by mechanical roughening. In other embodiments, the roughening of the bottom surface can be achieved by sanding. In other embodiments, the roughening of the bottom surface can also be achieved by etching, preferably wet etching. The effect of the roughening of the bottom surface of the substrate is that the acoustic waves generated by the acoustic wave filter that reach the bottom surface of the substrate are basically scattered on the roughened bottom surface. Therefore, the portion of the acoustic wave that actually reflects the double acoustic surface wave filter is reduced, which in turn improves the performance characteristics of the double acoustic surface wave filter. In this way, the double SAW filter can achieve a performance level similar to that of a bridge filter, but avoids the disadvantages of the bridge filter in terms of production complexity. The roughening step can be performed simultaneously with the thinning of the substrate. In this case, no additional process steps are required, especially no additional etching steps, which reduces the cost of the double SAW filter substrate.

[0073] Example 3

[0074] A specific embodiment of the present invention, as Fig.11 As shown, another schematic diagram of the structure of a dual surface acoustic wave filter is disclosed, the dual surface acoustic wave filter includes a piezoelectric substrate, and the piezoelectric substrate includes:

[0075] The piezoelectric single crystal thin film 31, the first filter element and the second filter element are located on the same surface of the piezoelectric single crystal thin film.

[0076] The bonding layer 32 is arranged on the surface of the piezoelectric single crystal film away from the first filter element, and the bonding layer has a positive temperature compensation coefficient TCF, and can be realized as silicon dioxide, for example. The supporting substrate 33 is arranged on the surface of the bonding layer 32 away from the piezoelectric single crystal film, and the supporting substrate is a single crystal silicon substrate. Thus, the dual surface acoustic wave filter can be formed on a substrate with a high and low speed layer.

[0077] Example 4

[0078] A specific embodiment of the present invention, as Fig.12 As shown, a dual-frequency component is disclosed, the dual-frequency component has the dual surface acoustic wave filter as in the first to third embodiments, wherein the packaging structure 8 accommodating the dual surface acoustic wave filter is as shown in Fig.12 As shown, the packaging structure is connected to the dual surface acoustic wave filter 10 via the bump 9 .

[0079] The packaging structure 8 includes a first packaging structure 801 and a second packaging structure 802 . The first packaging structure 801 and the second packaging structure 802 form a hollow structure, and the dual surface acoustic wave filter 10 is located in the hollow structure.

[0080] There may be multiple bumps 9. In order to improve the connection strength between the bump 9 and the packaging structure 8 and the dual surface acoustic wave filter 10, the bump 9 adopts a three-layer composite bump structure. Each bump 9 includes a substrate electrode 901, an intermediate bump electrode 902 and a packaging electrode 903, wherein the substrate electrode 901 is arranged on the surface of the dual surface acoustic wave filter, the substrate electrode 901 is made of NiCr alloy, and the thickness is 10nm, the intermediate bump electrode 902 is connected to the substrate electrode 901 by a spherical welding method, the intermediate bump electrode 902 is a spherical or ellipsoidal structure made of Au or an alloy containing Au, and the packaging electrode 903 is connected to the intermediate bump electrode 902 by an ultrasonic pressure welding process. The use of a three-layer composite bump can reduce the stress applied to the surface of the surface acoustic wave filter element 1, improve the mechanical strength and reliability of the packaging structure, and reduce device failure caused by substrate rupture.

[0081] Further, in other embodiments, Fig.13 As shown, the second packaging structure 802 is a double-layer structure, including a first layer 802-1 and a second layer 802-2. The second layer 802-2 is embedded in the inner surface of the first layer 802-1. The thickness of the second layer 802-2 is smaller than the first layer 802-1. The supporting layer 203 is in contact with the second layer 802-2, so that the surface acoustic wave filter element 10 has good heat dissipation and sealing properties.

[0082] Example 5

[0083] A specific embodiment of the present invention, as Fig.14 As shown, a method for manufacturing a dual surface acoustic wave filter is provided, the method comprising:

[0084] 401. Provide a piezoelectric substrate.

[0085] A piezoelectric substrate for preparing a dual surface acoustic wave filter is selected, and the surface of the piezoelectric substrate is cleaned.

[0086] 402. A first filter element and a second filter element are arranged on the same piezoelectric substrate by metal evaporation. The first filter element responds to a first frequency of a surface acoustic wave, comprises a plurality of first IDT electrode fingers, has a first metal film of a first thickness, and the plurality of first IDT electrode fingers are mounted on the piezoelectric substrate along the propagation direction of the surface acoustic wave. The second filter element responds to a second frequency of the surface acoustic wave, comprises a plurality of second IDT electrode fingers, has a second metal film of a second thickness, and the plurality of second IDT electrodes are mounted on the piezoelectric substrate along the propagation direction of the surface acoustic wave; the first frequency is different from the second frequency; the first thickness is different from the second thickness. The surface acoustic wave propagation path of the first filter element is parallel to or intersects with the surface acoustic wave propagation path of the second filter element.

[0087] Specifically, the process of forming the first IDT electrode finger and the second IDT electrode finger on the same piezoelectric substrate by metal evaporation includes: firstly dividing the piezoelectric substrate into a first set area for forming the first IDT electrode and a second set area for forming the second IDT electrode finger. Generally, the high-frequency zone and the low-frequency zone of the dual-surface acoustic wave filter are divided in advance according to the frequency requirements to avoid the problem of complex design and inconvenient operation caused by designing the electrode frequencies of the high-frequency zone and the low-frequency zone of the existing dual-surface acoustic wave filter after the overall manufacturing is completed. Then, a layer of metal film is covered in the first set area and the second set area of ​​the piezoelectric substrate. The covered metal film can be implemented as elements or compounds including Al, Cu, Zr, Mg, etc. The present invention does not limit the material of the metal film. Afterwards, a photoresist is laid on the metal film in the first set area, and the excess photoresist is stripped by photolithography to form an electrode pattern constituting the first IDT electrode finger, thereby achieving the first electrode coating process. Afterwards, a layer of metal film is covered on the first IDT electrode finger and the second set area, and a photoresist is laid on the metal film in the second set area by spin coating, and the excess photoresist is stripped by photolithography to form an electrode pattern constituting the second IDT electrode finger which is thicker than the electrode pattern of the first IDT electrode finger, thereby achieving the second electrode coating process. When stripping the photoresist, the piezoelectric chip can be immersed in glass liquid to remove the remaining photoresist and the excess metal coating thereon. Thus, by basically performing the coating and laying the photoresist process in one piece, two multilayer structure electrode areas with designed frequencies can be obtained under one operation process, so as to achieve the optimal performance of the dual acoustic surface wave filter.

[0088] Specifically, a first IDT electrode finger and a second IDT electrode finger are formed on the same piezoelectric substrate by a metal evaporation method. When the first IDT electrode finger and the second IDT electrode finger are strong support structures, the method includes: firstly dividing the piezoelectric substrate into a first set area for forming the first IDT electrode finger and a second set area for forming the second IDT electrode finger. Generally, the high-frequency area and the low-frequency area of ​​the double-surface acoustic wave filter are divided in advance according to the frequency requirements to avoid the problem of complex design and inconvenient operation caused by designing the electrode frequencies of the high-frequency area and the low-frequency area of ​​the existing double-surface acoustic wave filter after the overall manufacturing is completed. Then, a plurality of layers are covered in the first set area and the second set area of ​​the piezoelectric substrate. Metal film, the multilayer film can be realized as a double-layer result with aluminum element as the substrate. In other embodiments, it can also include gold (Au) element and molybdenum (Mo) element. The structure of metal film is continuously stacked on the substrate, wherein the stacked metal film includes the metal film elements required for the first IDT electrode finger and the second IDT electrode finger. After that, photoresist is laid on the metal film of the first set area, and the excess photoresist is stripped by photolithography to form the electrode pattern of the first IDT electrode finger. Then, photoresist is laid on the metal film of the second set area, and the excess photoresist is stripped by photolithography to form the electrode pattern of the second IDT electrode finger which is thinner than the electrode pattern of the first IDT electrode finger. Thus, by basically performing the coating and laying the photoresist in one piece, two electrode areas with strong support structures of designed frequencies are obtained under one operation process to achieve the optimal performance of the dual acoustic surface wave filter.

[0089] In other preferred embodiments, the piezoelectric substrate can be implemented as a piezoelectric single crystal substrate, and the method further includes: first, coating a metal film on the upper surface of the piezoelectric single crystal substrate, then laying photoresist on the metal film, using photolithography to peel off excess photoresist to form an electrode pattern constituting a first IDT electrode finger, then flipping the piezoelectric single crystal substrate to face the lower surface upward, coating a metal film on the lower surface of the piezoelectric single crystal, then laying photoresist on the metal film, and using photolithography to peel off excess photoresist to form an electrode pattern constituting a second IDT electrode finger, wherein the thickness of the electrode pattern constituting the first IDT electrode finger is greater than the electrode pattern constituting the second IDT electrode finger. Thus, a piezoelectric single crystal with a concave-convex IDT electrode structure can be realized, which can be adapted to the selection of more types of dual acoustic surface wave filters.

[0090] Example 6

[0091] A specific embodiment of the present invention, as Fig.15 As shown, another method for manufacturing a dual surface acoustic wave filter is provided, the method comprising:

[0092] 501. Implant ionized elements into the piezoelectric substrate.

[0093] The piezoelectric substrate can be a piezoelectric such as lithium tantalate or lithium niobate. By injecting ions into the surface of the piezoelectric substrate, a defect layer can be formed in the region of the piezoelectric substrate at a specified depth from the surface. For example, H+ ions are injected into the LiTaO3 piezoelectric substrate. The injection energy is 150KeV and the dose is 9×1016cm-1. At this time, a high-speed support layer is formed, in which the H+ ions are distributed at a depth of about 1μm from the surface of the piezoelectric substrate.

[0094] 502. Form a bonding layer containing silicon dioxide on at least one side of a supporting substrate or a piezoelectric substrate that supports the piezoelectric substrate.

[0095] 503. Join the bonding layer, the piezoelectric substrate and the supporting substrate to generate the piezoelectric substrate.

[0096] Afterwards, a double surface acoustic wave filter is manufactured on the piezoelectric substrate using the method disclosed in the above embodiment, thereby obtaining a double surface acoustic wave filter with a supporting substrate.

[0097] In the present invention, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance; the term "plurality" means two or more. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0098] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A double surface acoustic wave filter, characterized in that: The dual surface acoustic wave filter comprises: Piezoelectric substrate; Disposing a first filter element and a second filter element on the same piezoelectric substrate; The first filter element responds to a first frequency of a surface acoustic wave, the first filter element comprises a plurality of first IDT electrode fingers, the first IDT electrode fingers have a first metal film of a first thickness, and the plurality of first IDT electrode fingers are mounted on the piezoelectric substrate along a propagation direction of the surface acoustic wave; The second filter element is responsive to a second frequency of the surface acoustic wave, the second filter element comprises a plurality of second IDT electrode fingers, the second IDT electrode fingers have a second metal film of a second thickness, and the plurality of second IDT electrode fingers are mounted on the piezoelectric substrate along a propagation direction of the surface acoustic wave; The first frequency is different from the second frequency; The first thickness is different from the second thickness; The surface acoustic wave propagation path of the first filter element is parallel to or intersects with the surface acoustic wave propagation path of the second filter element; The first thickness of the first metal film is defined as H1, the second thickness of the second metal film is defined as H2, the first frequency is defined as f1, the second frequency is defined as f2, the frequency response speed of the first frequency is defined as v1, the frequency response speed of the second frequency is defined as v2, wherein the first thickness of the first metal film, the first frequency, and the frequency response speed of the first frequency satisfy: 7% <H1f1 / v1<12%; The second thickness of the second metal film, the second frequency, and the frequency response speed of the second frequency satisfy: 8% <H2f2 / v2<13%。 2. The double surface acoustic wave filter according to claim 1, characterized in that: The duty cycle of the filter element is defined as a ratio of a width of each of the plurality of electrode fingers to a sum of a width of each of the plurality of electrode fingers and intervals between adjacent electrode fingers included in the plurality of electrode fingers; The first filter element has a first duty ratio, and the second filter element has a second duty ratio, the first duty ratio is different from the second duty ratio, the first duty ratio is greater than 0.2 and less than 0.7, and the second duty ratio is greater than 0.3 and less than 0.

9.

3. The double surface acoustic wave filter according to claim 1, characterized in that: The first IDT electrode finger has a first duty cycle, the second IDT electrode finger has a second duty cycle, the first IDT electrode finger and the second IDT electrode finger are both provided with a metal thin film structure, the metal thin film structure includes a first metal layer and a second metal layer, the first metal layer includes Al, and the second metal layer is one of Cu, W, Mo, Cr, Ag, Au, Pt, Ga, Nb, Ta, Au, Si, and Sc.

4. The double surface acoustic wave filter according to any one of claims 1 to 3, characterized in that: The piezoelectric substrate is a piezoelectric single crystal substrate, and the piezoelectric single crystal substrate is lithium tantalate or lithium niobate; The first IDT electrode finger and the second IDT electrode finger are formed on the same surface of the piezoelectric single crystal substrate.

5. The dual surface acoustic wave filter according to any one of claims 1 to 3, characterized in that: The piezoelectric substrate is a piezoelectric single crystal substrate, the piezoelectric single crystal substrate is lithium tantalate or lithium niobate, the single crystal piezoelectric substrate has a first surface and a second surface arranged in parallel, the first IDT electrode finger is formed on the first surface, and the second IDT electrode finger is formed on the second surface.

6. The double surface acoustic wave filter according to claim 4, characterized in that: The piezoelectric substrate comprises: The orientation angle between the first filter element and the piezoelectric single crystal substrate is ψ1, which is 0°; the orientation angle between the second filter element and the piezoelectric single crystal substrate is ψ2, which is within the range of (-5°, +5°).

7. The double surface acoustic wave filter according to claim 4, characterized in that: The piezoelectric substrate comprises: A piezoelectric single crystal thin film, wherein the first filter element and the second filter element are located on the same surface of the piezoelectric single crystal thin film; A bonding layer is provided on a surface of the piezoelectric single crystal film away from the first filter element, and the bonding layer has a positive temperature compensation coefficient; The supporting substrate is arranged on the surface of the bonding layer away from the piezoelectric single crystal film, and the supporting substrate is a single crystal silicon substrate.

8. A dual-frequency component, comprising a dual surface acoustic wave filter as claimed in any one of claims 1 to 7, characterized in that: A packaging structure for accommodating the dual surface acoustic wave filter, wherein the packaging structure is connected to the dual surface acoustic wave filter via a bump.

9. A method for manufacturing a dual surface acoustic wave filter, wherein the dual surface acoustic wave filter is the dual surface acoustic wave filter according to any one of claims 1 to 7, characterized in that: The method comprises: providing a piezoelectric substrate; Arranging a first filter element and a second filter element on the same piezoelectric substrate by metal evaporation method; The first filter element responds to a first frequency of a surface acoustic wave, and the first filter element includes a plurality of first IDT electrode fingers, the first IDT electrode fingers have a first metal film of a first thickness, and the plurality of first IDT electrode fingers are mounted on the piezoelectric substrate along a propagation direction of the surface acoustic wave; The second filter element responds to a second frequency of the surface acoustic wave, the second filter element comprises a plurality of second IDT electrode fingers, the second IDT electrode fingers have a second metal film of a second thickness, and the plurality of second IDT electrode fingers are mounted on the piezoelectric substrate along a propagation direction of the surface acoustic wave; The first frequency is different from the second frequency; The first thickness is different from the second thickness; The surface acoustic wave propagation path of the first filter element is parallel to or intersects with the surface acoustic wave propagation path of the second filter element.

10. The method for manufacturing a dual surface acoustic wave filter according to claim 9, characterized in that: The method of providing the first filter element and the second filter element on the same piezoelectric substrate by using a metal evaporation method comprises: dividing the piezoelectric substrate into a first set region for forming a first filter element and a second set region for forming a second filter element; Covering a metal film in the first set area and the second set area of ​​the piezoelectric substrate; Laying photoresist on the metal film in the first set area, and stripping off excess photoresist by photolithography to form an electrode pattern constituting a first IDT electrode finger; Covering the first IDT electrode finger and the second set area with a metal film; A photoresist is laid on the metal film in the second set area, and excess photoresist is stripped off by photolithography to form an electrode pattern constituting a second IDT electrode finger which is thicker than the electrode pattern constituting the first IDT electrode finger.

11. The method for manufacturing a dual surface acoustic wave filter according to claim 9, characterized in that: The method of providing the first filter element and the second filter element on the same piezoelectric substrate by using a metal evaporation method comprises: dividing the piezoelectric substrate into a first set region for forming a first filter element and a second set region for forming a second filter element; Covering a plurality of metal films in a first set area and a second set area of ​​the piezoelectric substrate; Laying photoresist on the metal film in the first set area, and stripping off excess photoresist by photolithography to form an electrode pattern constituting a first IDT electrode finger; A photoresist is applied to the metal film in the second set region, and excess photoresist is stripped off by photolithography to form an electrode pattern constituting a second IDT electrode finger which is thinner than the electrode pattern constituting the first IDT electrode finger.

12. The method for manufacturing a dual surface acoustic wave filter according to claim 9, characterized in that: The piezoelectric substrate is a piezoelectric single crystal substrate, and the method further comprises: coating a metal film on the upper surface of the piezoelectric single crystal substrate; Laying photoresist on the metal film, and stripping off excess photoresist by photolithography to form an electrode pattern constituting a first IDT electrode finger; Turning the piezoelectric single crystal substrate over so that the lower surface faces upward; coating a metal film on the lower surface of the piezoelectric single crystal; Laying photoresist on the metal film, and stripping off excess photoresist by photolithography to form an electrode pattern constituting the second IDT electrode finger; The thickness of the electrode pattern constituting the first IDT electrode finger is greater than the thickness of the electrode pattern constituting the second IDT electrode finger.

13. The method for manufacturing a dual surface acoustic wave filter according to any one of claims 9 to 12, characterized in that: The manufacturing of the piezoelectric substrate is implemented by: implanting ionized elements into the piezoelectric substrate; forming a bonding layer containing silicon dioxide on at least one side of a supporting substrate supporting the piezoelectric substrate or the piezoelectric substrate; The bonding layer, the piezoelectric substrate, and the supporting substrate are bonded together to produce a piezoelectric substrate.

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