CN114094981A - Double-surface acoustic wave filter, double-frequency assembly and manufacturing method thereof - Google Patents
Double-surface acoustic wave filter, double-frequency assembly and manufacturing method thereof Download PDFInfo
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- CN114094981A CN114094981A CN202111339423.2A CN202111339423A CN114094981A CN 114094981 A CN114094981 A CN 114094981A CN 202111339423 A CN202111339423 A CN 202111339423A CN 114094981 A CN114094981 A CN 114094981A
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/46—Filters
- H03H9/64—Filters using surface acoustic waves
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/08—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of resonators or networks using surface acoustic waves
- H03H3/10—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of resonators or networks using surface acoustic waves for obtaining desired frequency or temperature coefficient
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/125—Driving means, e.g. electrodes, coils
- H03H9/145—Driving means, e.g. electrodes, coils for networks using surface acoustic waves
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Abstract
The invention provides a dual surface acoustic wave filter, comprising: a piezoelectric substrate; arranging a first filter element and a second filter element on the same piezoelectric substrate; a first filter element responsive to a first frequency of the surface acoustic wave, the first filter element including a plurality of first IDT electrodes having a first metal film of a first thickness; a second filter element responsive to a second frequency of the acoustic surface, the second filter element comprising a plurality of second IDT electrodes having 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 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 invention can realize the dual surface acoustic wave filter with high power tolerance and high reliability.
Description
Technical Field
The invention relates to the field of semiconductor manufacturing, in particular to a double-surface acoustic wave filter, a double-frequency component and a manufacturing method thereof.
Background
In recent years, with the rapid development of wireless communication systems, various terminal devices have widely supported various communication protocols such as 2G, 3G, LTE, Wi-Fi, GPS, and the like. To achieve this, in the prior art, the rf front end of the communication device is composed of a plurality of rf circuits, each of which contains independent filters, amplifiers, etc. with different center frequencies and bandwidths. Filters with different center frequencies are selected for communication using the radio frequency switch. While this scheme can support simultaneous operation of multiple communication standards, it adds to the size, power consumption, and cost of the communication system.
In order to solve the problems of the scheme, a dual-frequency component is adopted as soon as possible, and the dual-frequency component is composed of a high-speed broadband A/D converter and two single-passband surface acoustic wave filters, so that the size of a communication system can be reduced to a certain extent. However, because the two single-passband saw filters are located on separate substrates, the two single-passband saw filters are generally implemented by adopting a composite substrate splicing process, but the reliability of the junction is poor and the processing cost is high. Meanwhile, the two single-passband surface acoustic wave filters adopt a switch to switch channels, signals are likely to be lost, and the reliability of the double-frequency component is poor.
How to improve the reliability of the dual-frequency component, further reduce the volume of the dual-frequency component, and improve the frequency selectivity and the passband isolation of the dual-frequency component becomes the problem to be solved by the technical personnel in the field.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a double-surface acoustic wave filter, a double-frequency component and a manufacturing method thereof.
The purpose of the invention is mainly realized by the following technical scheme: according to a first aspect of the present invention, a dual surface acoustic wave filter includes: a piezoelectric substrate; arranging a first filter element and a second filter element on the same piezoelectric substrate; the first filter element is responsive to a first frequency of a surface acoustic wave, the first filter element including a plurality of first IDT electrode fingers having a first metal film of a first thickness, the plurality of first IDT electrode fingers being mounted on the piezoelectric substrate along a surface acoustic wave propagation direction; the second filter element responsive to a second frequency of the acoustic surface, the second filter element comprising a plurality of second IDT electrode fingers having a second metal film of a second thickness, the plurality of second IDT electrode fingers mounted on the piezoelectric substrate along a surface acoustic wave propagation direction; the first frequency is different from the second frequency; the first thickness is different from the second thickness; and the surface acoustic wave propagation path of the first filter element is parallel to or intersected with the surface acoustic wave propagation path of the second filter element.
In some embodiments, a first thickness of the first metal film is defined as H1, a 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, a frequency response speed of the first frequency is defined as v1, and a 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 equations: 7% < H1 × f1/v1< 12%; 8% < H2 f2/v2< 13%.
In some embodiments, a duty cycle of a filter element is defined as a ratio of a width of each of a plurality of electrode fingers to a sum of a width of each of the plurality of electrode fingers and a space between adjacent electrode fingers included in the plurality of 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 0.2 or more and 0.7 or less, and the second duty cycle is 0.3 or more and 0.9 or less.
In some embodiments, the first IDT electrode finger has a first duty cycle and the second IDT electrode finger has a second duty cycle, the first IDT electrode finger and the second IDT electrode finger are each provided with a metal thin-film structure comprising a first metal layer comprising Al and a second metal layer being one of Cu, W, Mo, Cr, Ag, Au, Pt, Ga, Nb, Ta, Au, Si, Sc.
In some embodiments, the piezoelectric substrate is a piezoelectric single crystal substrate, which is lithium tantalate or lithium niobate; the first IDT electrode fingers and the second IDT electrode fingers are formed on the same surface of the piezoelectric single crystal substrate.
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 fingers are formed on the first surface, and the second IDT electrode fingers are formed on the second surface.
In some embodiments, the piezoelectric substrate comprises: the orientation angle between the first filter element and the piezoelectric single crystal substrate is psi 1, psi 1 is 0 °, the orientation angle between the second filter element and the piezoelectric single crystal substrate is psi 2, and psi 2 is in the range of (-5, +5 °).
In some embodiments, the piezoelectric substrate comprises: the first filter element and the second filter element are positioned on the same surface of the piezoelectric single crystal film; the junction layer is arranged on the surface of the piezoelectric single crystal film, which is far away from the first filter element, and has a positive temperature compensation coefficient; and the supporting substrate is arranged on the surface of the junction layer, which is far away from the piezoelectric single crystal film, and is a single crystal silicon substrate.
According to a second aspect of the present invention, there is provided a dual band package comprising the dual surface acoustic wave filter according to any one of claims 1 to 8, wherein a package structure accommodating the dual surface acoustic wave filter is connected to the dual surface acoustic wave filter by bumps.
According to a third aspect of the present invention, there is provided a method of manufacturing a dual surface acoustic wave filter, the method comprising: providing a piezoelectric substrate; arranging a first filter element and a second filter element on the same piezoelectric substrate by using a metal evaporation method; wherein the first filter element is responsive to a first frequency of the surface acoustic wave, the first filter element including a plurality of first IDT electrode fingers having a first metal film of a first thickness, the plurality of first IDT electrode fingers being mounted on the piezoelectric substrate along a surface acoustic wave propagation direction; the second filter element responsive to a second frequency of the acoustic surface, the second filter element comprising a plurality of second IDT electrode fingers having a second metal film of a second thickness, the plurality of second IDT electrode fingers mounted on the piezoelectric substrate along a surface acoustic wave propagation direction; the first frequency is different from the second frequency; the first thickness is different from the second thickness; and the surface acoustic wave propagation path of the first filter element is parallel to or intersected with the surface acoustic wave propagation path of the second filter element.
In some embodiments, providing a first filter element and a second filter element on the same piezoelectric substrate by a metal evaporation method includes: dividing the piezoelectric substrate into a first setting region for forming a first filter element and a second setting region for forming a second filter element; covering a layer of metal film in a first set area and a second set area of the piezoelectric substrate; laying photoresist on the metal film of the first set area, and stripping redundant photoresist by utilizing a photoetching method to form an electrode pattern forming a first IDT electrode finger; covering a metal film on the first IDT electrode finger and the second setting area; and spreading photoresist on the metal film of the second set area, and stripping the redundant photoresist by using a photoetching method to form an electrode pattern which is thicker than the electrode pattern of the first IDT electrode finger and forms the second IDT electrode finger.
In some embodiments, providing a first filter element and a second filter element on the same piezoelectric substrate by a metal evaporation method includes: dividing the piezoelectric substrate into a first setting region for forming a first filter element and a second setting 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 of the first set area, and stripping redundant photoresist by utilizing a photoetching method to form an electrode pattern forming a first IDT electrode finger; and spreading photoresist on the metal film of the second set area, and stripping the redundant photoresist by using a photoetching method to form an electrode pattern which is thinner than the electrode pattern of the first IDT electrode finger and forms the second IDT electrode finger.
In some embodiments, the piezoelectric substrate is a piezoelectric single crystal substrate, the method further comprising: coating a metal film on the upper surface of the piezoelectric single crystal substrate; laying photoresist on the metal film, and stripping redundant photoresist by utilizing a photoetching method to form an electrode pattern forming a first IDT electrode finger; turning the piezoelectric single crystal substrate to face upwards; coating a metal film on the lower surface of the piezoelectric single crystal; laying photoresist on the metal film, and stripping redundant photoresist by utilizing a photoetching method to form an electrode pattern forming a second IDT electrode finger; wherein a thickness of the electrode pattern constituting the first IDT electrode finger is larger than that of the electrode pattern constituting the second IDT electrode finger.
In some embodiments, fabrication of a piezoelectric substrate is implemented to include: implanting an ionized element into the piezoelectric substrate; forming a bonding layer containing silicon dioxide on at least one side of a support substrate supporting the piezoelectric substrate or the piezoelectric substrate; and bonding the bonding layer, the piezoelectric substrate and the support substrate to generate the piezoelectric substrate.
The invention has the following beneficial effects:
according to the method for manufacturing the dual surface acoustic wave filter, the IDT electrodes with different thicknesses can be arranged on one piezoelectric substrate to meet the setting of high and low frequency areas required by the dual surface acoustic wave filter, and the dual surface acoustic wave filter with more different requirements can be met by designing the IDT electrode structure and setting the piezoelectric substrate.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic diagram of a prior art dual surface acoustic wave filter according to the present invention;
FIG. 2 is a schematic diagram of a dual surface acoustic wave filter according to the present invention;
FIG. 3 is a schematic diagram of a multilayer electrode structure of a dual surface acoustic wave filter of the present invention;
fig. 4 is a schematic diagram of an IDT electrode finger structure of a dual surface acoustic wave filter according to the present invention;
FIG. 5 is a schematic diagram of different tangential Euler angle configurations of a dual surface acoustic wave filter of the present invention;
FIG. 6 is a graph of low-end frequency waveform performance of a prior art pre-integrated dual-frequency component;
FIG. 7 is a graph of the performance of the high-side frequency waveform of a prior art dual-frequency device before integration;
FIG. 8 is an overall waveform performance graph of a prior art dual-frequency assembly;
FIG. 9 is a graph of the waveform performance of a dual surface acoustic wave filter of the present invention;
FIG. 10 is a schematic diagram of another dual surface acoustic wave filter configuration of the present invention;
FIG. 11 is a schematic diagram of a dual acoustic surface filter according to yet another embodiment of the present invention;
FIG. 12 is a schematic diagram of a dual-band package according to the present invention;
FIG. 13 is a schematic diagram of a package structure of a dual-band device according to still another embodiment of the present invention;
FIG. 14 is a schematic flow chart of a dual surface acoustic wave filter fabrication process of the present invention;
fig. 15 is a schematic diagram of a process for fabricating a dual surface acoustic wave filter according to yet another embodiment of the present invention.
Wherein, the correspondence between the reference numbers and the part names in fig. 1 to 15 is:
11-single pass band surface acoustic wave filter, 12-adhesive layer;
1-a piezoelectric substrate, 21-a first IDT electrode finger, 22-a second IDT electrode finger;
31-piezoelectric single crystal thin film, 32-bonding layer, 33-support substrate;
41-buffer layer, 42-metal layer;
8-package structure, 801-first package structure, 802-second package structure;
a first layer of an 802-1 second package structure, a second layer of an 802-2 second package structure;
9-bump, 901-base electrode, 902-middle bump electrode, 903-package electrode;
10-double surface acoustic wave filter.
Detailed Description
So that the manner in which the above recited objects, features and advantages of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. It should be noted that the embodiments and features of the embodiments of the present application may be combined with each other without conflict.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those specifically described herein, and therefore the scope of the present invention is not limited by the specific embodiments disclosed below.
In the prior art dual saw filter structure, as shown in fig. 1, a high-speed wideband a/D converter and two single-passband saw filters 11 are usually adopted, which can support operation to reduce the volume of the communication system to some extent. However, because the two single-passband saw filters 11 are located on separate substrates, the two single-passband saw filters are generally spliced by using a composite substrate, for example, a process of adding the adhesive layer 12 is adopted, but the reliability of the interface is poor and the processing cost is high. Meanwhile, the two single-passband surface acoustic wave filters adopt a switch to switch channels, signals are likely to be lost, and the reliability of the double-frequency component is poor.
Example 1
An embodiment of the present invention, as shown in fig. 2, discloses a schematic structural diagram of a dual surface acoustic wave filter, which includes:
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 is responsive to a first frequency of the surface acoustic wave, the first filter element includes a plurality of first IDT electrode fingers 21, the first IDT electrode fingers 21 have a first metal thin film of a first thickness, and the plurality of first IDT electrode fingers 21 are mounted on the piezoelectric substrate along a surface acoustic wave propagation direction.
Further, a second filter element responsive to a second frequency of the acoustic surface, the second filter element including a plurality of second IDT electrode fingers 22 having a second metal film of a second thickness, the plurality of second IDT electrode fingers being mounted on the piezoelectric substrate along the surface acoustic wave propagation direction.
Wherein 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 the surface acoustic wave propagation path of the second filter element.
The first IDT electrode finger or the second IDT electrode finger mentioned for the present application is substantially referred to as an IDT transducer.
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 thin films having different thicknesses can be used as a dual surface acoustic wave filter having different frequencies, thereby reducing the design difficulty of the dual surface acoustic wave filter and obtaining IDT electrode fingers having different center frequencies on the same substrate. Illustratively, the metal film thickness of the first IDT electrode is 200um larger than that of the second IDT electrode, the opposing electrode is formed such that the first IDT electrode is the high center frequency electrode in the dual surface acoustic wave filter, and the second IDT electrode is formed such that the low center frequency electrode in the dual surface acoustic wave filter is 100 um.
Further, as for the structures of the first IDT electrode 21 and the second IDT electrode 22, both of them may be provided with a metal thin film structure, as shown in fig. 3, for example, the metal thin film structure may 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, may be implemented as Si, Cu. The second metal layer 42 includes one of Cu, W, Mo, Cr, Ag, Au, Pt, Ga, Nb, Ta, Au, Si, and Sc, and the thickness of the buffer layer is 0.5% λ or less when λ is a wavelength of an elastic wave determined by an electrode period of the IDT electrode.
In other embodiments, the first metal layer 41 and the second metal layer 42 have the same composition and thickness, for example, both are titanium or both are chromium, or are a titanium-chromium alloy with the same composition ratio, and both have the same thickness.
Further, as for the structures of the first IDT electrode 21 and the second IDT electrode 22, it is also possible to provide IDT electrodes each including an aluminum electrode under which a metal thin film of a different metal element is provided to realize a strong support structure. The IDT electrodes of the strong support structure have an aluminum element as a base, and specifically, each IDT electrode includes a first buffer layer disposed on a piezoelectric substrate and a first metal layer disposed on the first buffer layer. The first buffer layer includes at least one of metallic titanium and chromium, and has a thickness of 0.5% λ or less when λ is a wavelength of an elastic wave determined by an electrode period of the IDT electrode. The first metal layer comprises metallic aluminum, and the thickness of the Al layer ranges from 1% to 30% of the wavelength of the surface acoustic wave.
When the wavelength λ of the elastic wave determined by the electrode period of the IDT electrode is 2 μm, the thickness of the first buffer layer is 10nm or less, and 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 thin film has a uniform and dense structure, the critical load is increased, and the adhesion to the piezoelectric substrate is significantly enhanced.
In addition, a titanium buffer layer is provided between the Al electrode and the substrate, and migration of Al to the substrate can be prevented.
The thickness of the first metal layer Al layer is designed, and the metal Al layer with the thickness of 1% -30% lambda and the Ti buffer layer are adopted to form the IDT electrode finger together, so that the IDT electrode finger has the advantages of good electromigration resistance and stable chemical property.
As a preferred embodiment, as shown in the upper part of fig. 4, the first thickness of the first metal thin film is defined as H1, the second thickness of the second metal thin 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 thin film, the first frequency and the frequency response speed of the first frequency satisfy: 7% < H1 × f1/v1< 12%; the second thickness of the second metal film, the second frequency and the frequency response speed of the second frequency satisfy: 8% < H2 f2/v2< 13%. In the present embodiment, the first thickness of the first metal thin film and the corresponding first frequency, and the second thickness of the second metal thin film and the corresponding second frequency are associated with each other, and thereby, the frequency shift of the dual surface acoustic wave filter can be suppressed, and the insertion loss on the high frequency side in the passband can be reduced.
As a preferred embodiment, as shown in the lower diagram of fig. 4, the duty ratio of the filter element is defined as the ratio of the width of each of the plurality of electrode fingers to the sum of the width of each of the plurality of electrode fingers and the interval between adjacent electrode fingers included in the plurality of electrode fingers, wherein the first filter element has a first duty ratio different from the second duty ratio, the first duty ratio is 0.2 or more and 0.7 or less, and the second duty ratio is 0.3 or more and 0.9 or less. The duty ratio for the first filter element and the second filter element is an average of the duty ratios of the plurality of electrode fingers constituting the filter element. A specific implementation of the duty ratio is a ratio of the IDT electrode finger width W to the sum of the electrode finger width W and the inter-electrode-finger gap G in the first filter or the second filter, i.e., the duty ratio is W/(W + G).
In a preferred embodiment, the piezoelectric substrate is a piezoelectric single crystal substrate, and the first IDT electrode fingers 21 and the second IDT electrode fingers 22 are formed on the same surface of the piezoelectric single crystal substrate. Illustratively, the first IDT electrode finger 21 and the second IDT electrode finger 2 may be disposed in parallel on the same surface of the same piezoelectric single crystal substrate, and further, may be disposed on the same surface of the same piezoelectric single crystal substrate in a range where an IDT electrode finger angle ψ is (-5 °, +5 °), the piezoelectric single crystal substrate is lithium tantalate or lithium niobate, and a LiTaO3 substrate cut in the Y direction at 36 degrees to 52 degrees and propagating in the X direction, that is, an euler angle is (0 °, 36 ° -52 °, ψ). The piezoelectric single crystal substrate comprises a first frequency band region and a second frequency band region which have different tangential Euler angles, the orientation angle between the first filter element and the piezoelectric single crystal substrate is psi 1, psi 1 is 0 DEG, and psi 1 is 0 DEG (not shown), wherein the fact that a surface acoustic wave propagation path of the first filter element is parallel to a surface acoustic wave propagation path of the second filter element is represented. The orientation angle between the second filter element and the piezoelectric single crystal substrate is ψ 2, ψ 2 being in the range of (-5 °, +5 °). As shown in fig. 5, when ψ 2 is located in the range of (-5 °, +5 °), the surface acoustic wave propagation path representing the first filter element intersects with the surface acoustic wave propagation path of the second filter element.
As an example of the application effect of this embodiment, please refer to fig. 6, fig. 7, fig. 8 and fig. 9, before the content of this embodiment is adopted, a frequency waveform performance graph of two single-pass filters of a dual-band component in the prior art can be sequentially referred to as fig. 6 and fig. 7, and a frequency waveform performance graph of combining two single-pass filters into a dual-band component through an adhesive layer can be referred to as fig. 8. It can be seen that the total isolation of the projection and the low end of 2185MHZ is 28dB due to the low frequency at the high end of the 1995MHZ filter, although the isolation of the dual-frequency component with the high end and the low end integrated by the adhesive layer at the low end of 2185MHZ can reach 30dB, and the overall isolation is less than 30dB, the dual-frequency component still does not meet the specification of dual-frequency communication. However, in the dual-filter frequency waveform performance diagram of FIG. 9 under an embodiment of the present application, the structure of the 1995MHZ high-end resonator is adjusted so that the "small bump" is close to the low end of the 2185MHZ, for example, the waveform after the pole-zero reconstruction method is used. It can be seen that at this point, not only the high-end isolation of 1995MHZ is increased to 31dB, but also the low-end isolation of 2185MHZ is increased to 33dB, and the overall level of passband isolation exceeds the required 30 dB.
Further, the euler angles of different frequency band regions may be formed by forming a gully or slope shape on the piezoelectric film by dry etching or wet etching to form a plurality of different euler cut angles. Therefore, a plurality of different Euler cut angles are formed on the same piezoelectric film, so that the requirements of high and low frequency bands and two bandwidths required by the double-surface acoustic wave filter are met, the piezoelectric film is prevented from being cut twice, and the manufacturing cost is effectively reduced.
Example 2
An embodiment of the present invention further discloses a structural schematic diagram of a dual surface acoustic wave filter, as shown in fig. 10, the dual surface acoustic wave filter includes:
the first IDT electrode fingers 21 are formed on the upper surface of the piezoelectric single-crystal substrate, and the second IDT electrode fingers 22 are formed on the lower surface of the piezoelectric single-crystal substrate. The whole IDT electrode fingers are arranged on the piezoelectric single crystal substrate in a concave-convex mode. The depth of the concave-convex structure is less than or equal to that of the piezoelectric single crystal substrate. Specifically, the arrangement of the concavo-convex structure corresponding to the surface IDT electrodes is realized either in a staggered arrangement with the IDT electrodes or in a width corresponding to one IDT electrode finger per two concavities and convexities, whereby the insertion loss can be reduced.
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 having a roughness of 0.2 μm to 0.4 μm, and the average height difference between the peaks and valleys on the rough bottom surface may be 2.5 μm, preferably greater than 4.5 μm. The bottom surface of the substrate is roughened to reduce reflection of acoustic waves back into the bulk dual surface acoustic wave filter. The average lateral distance between peaks and valleys on the roughened substrate surface may be less than 0.05 μm, preferably less than 0.03 μm. The roughening of the bottom surface may be achieved by mechanical roughening. In other embodiments, the roughening of the bottom surface may be achieved by sanding. In other embodiments, the roughening of the bottom surface may also be achieved by etching, preferably wet etching. The effect of the roughening of the bottom surface of the substrate is that the acoustic wave generated by the acoustic wave filter reaching the bottom surface of the substrate is substantially scattered at the roughened bottom surface. Accordingly, the acoustic wave portion that actually reflects the dual surface acoustic wave filter is reduced, which in turn improves the performance characteristics of the dual surface acoustic wave filter. In this way, the dual surface acoustic wave filter can achieve a similar level of performance as the bridge filter, but avoids the disadvantages of the bridge filter in terms of production complexity. The roughening step may be performed simultaneously with the thinning of the substrate. In this case, no additional process step, in particular no additional etching step, is required, reducing the cost of the dual surface acoustic wave filter substrate.
Example 3
One embodiment of the present invention, as shown in fig. 11, discloses a structural schematic diagram of another dual surface acoustic wave filter, which includes a piezoelectric substrate, the piezoelectric substrate includes:
the piezoelectric single crystal film 31, the first filter element and the second filter element are located on the same surface of the piezoelectric single crystal film.
A bonding layer 32, which is arranged on the surface of the piezoelectric monocrystalline film remote from the first filter element, has a positive temperature compensation coefficient TCF and can be realized, for example, as silicon dioxide. And a support substrate 33 provided on a surface of the bonding layer 32 remote from the piezoelectric single crystal thin film, the support substrate being a single crystal silicon substrate. Thus, the dual surface acoustic wave filter can be formed on a substrate having a high-low sound velocity layer.
Example 4
In an embodiment of the present invention, as shown in fig. 12, a dual-band package is disclosed, which includes the dual surface acoustic wave filters according to the first to third embodiments, wherein a package structure 8 for accommodating the dual surface acoustic wave filters is shown in fig. 12, and the package structure is connected to the dual surface acoustic wave filter 10 through bumps 9.
The package structure 8 includes a first package structure 801 and a second package structure 802, the first package structure 801 and the second package structure 802 form a hollow structure, and the dual surface acoustic wave filter 10 is located in the hollow structure.
The bump 9 may be plural. In order to improve the connection strength between the bump 9 and the package structure 8 and the dual surface acoustic wave filter 10, the bump 9 has a three-layer composite bump structure. Each bump 9 includes a substrate electrode 901, an intermediate bump electrode 902, and a package electrode 903, wherein the substrate electrode 901 is disposed on the surface of the dual surface acoustic wave filter, the substrate electrode 901 is made of NiCr alloy and has a thickness of 10nm, the intermediate bump electrode 902 is connected to the substrate electrode 901 by a ball bonding method, the intermediate bump electrode 902 is a spherical or ellipsoidal structure made of Au or an alloy containing Au, and the package electrode 903 is connected to the intermediate bump electrode 902 by an ultrasonic bonding process. By adopting the three-layer composite bump, the stress applied to the surface of the surface acoustic wave filter element 1 can be reduced, the mechanical strength and the reliability of the packaging structure are improved, and the device failure caused by substrate fracture is reduced.
Further, in another embodiment, as shown in fig. 13, the second package structure 802 is a two-layer structure, and includes a first layer 802-1 and a second layer 802-2, the second layer 802-2 is embedded in an inner surface of the first layer 802-1, a thickness of the second layer 802-2 is smaller than that of the first layer 802-1, and the support layer 203 is in contact with the second layer 802-2, so that the saw filter element 10 has good heat dissipation and sealing properties.
Example 5
In an embodiment of the present invention, as shown in fig. 14, a method for manufacturing a dual surface acoustic wave filter is provided, the method including:
401. a piezoelectric substrate is provided.
And selecting a piezoelectric substrate for preparing the double-surface acoustic wave filter, and cleaning the surface of the piezoelectric substrate.
402. A first filter element and a second filter element are provided on the same piezoelectric substrate by a metal vapor deposition method. Wherein the first filter element is responsive to a first frequency of the surface acoustic wave, the first filter element includes a plurality of first IDT electrode fingers having a first metal film with a first thickness, the plurality of first IDT electrode fingers being mounted on the piezoelectric substrate along a surface acoustic wave propagation direction. A second filter element responsive to a second frequency of the acoustic surface, the second filter element including a plurality of second IDT electrode fingers having a second metal film of a second thickness, the plurality of second IDT electrodes being mounted on the piezoelectric substrate along the surface acoustic wave propagation direction; 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 the surface acoustic wave propagation path of the second filter element.
Specifically, forming a first IDT electrode finger and a second IDT electrode finger on the same piezoelectric substrate by a metal evaporation method is realized to include: the piezoelectric substrate is divided into a first setting area for forming a first IDT electrode and a second setting area for forming a second IDT electrode finger, a high-frequency area and a low-frequency area of the double-surface acoustic wave filter are generally divided in advance according to frequency requirements, so that the problems of complicated design and inconvenient operation caused by designing the electrode frequency of the high-frequency area and the low-frequency area after the conventional double-surface acoustic wave filter is integrally manufactured are solved, then a metal film is covered in the first setting area and the second setting area of the piezoelectric substrate, the covered metal film can be realized to contain Al, Cu, Zr, Mg and other elements or compounds, and the material of the metal film is not limited. And then, laying photoresist on the metal film of the first set area, stripping redundant photoresist by using a photoetching method to form an electrode pattern forming the first IDT electrode finger, realizing first electrode coating processing, then, covering a layer of metal film on the first IDT electrode finger and the second set area, laying photoresist on the metal film of the second set area by adopting a rotary gluing method, stripping redundant photoresist by using the photoetching method to form an electrode pattern forming the second IDT electrode finger, wherein the electrode pattern is thicker than the electrode pattern forming the first IDT electrode finger, and realizing second electrode coating processing. When the photoresist is stripped, the piezoelectric wafer can be immersed into glass liquid to remove the residual photoresist and the redundant metal coating film on the residual photoresist. Therefore, the electrode areas of the multilayer structures with two designed frequencies are obtained in one operation flow by basically performing the processes of coating and laying the photoresist, so that the optimal performance of the double-surface acoustic wave filter is realized.
Specifically, when a first IDT electrode finger and a second IDT electrode finger, which are strong support structures, are formed on the same piezoelectric substrate by a metal evaporation method, the method includes: the piezoelectric substrate is divided into a first setting area for forming a first IDT electrode finger and a second setting area for forming a second IDT electrode finger, the high frequency area and the low frequency area of the dual-surface acoustic wave filter are generally divided in advance according to the frequency requirement, so as to avoid the problems of complicated design and inconvenient operation caused by designing the electrode frequency of the high frequency area and the low frequency area after the whole manufacturing of the existing dual-surface acoustic wave filter is completed, and then a multilayer metal film is covered in the first setting area and the second setting area of the piezoelectric substrate, the multilayer metal film can be realized as a double-layer result of taking an aluminum element as a base, in other embodiments, a structure that a metal film is continuously stacked on the base and can also comprise a gold (Au) element and a molybdenum (Mo) element, wherein the stacked metal film comprises the metal film elements required by the first IDT electrode finger and the second IDT electrode finger, then, a photoresist is applied to the metal film of the first set area, an excess photoresist is removed by photolithography to form an electrode pattern constituting the first IDT electrode finger, and then a photoresist is applied to the metal film of the second set area, and an excess photoresist is removed by photolithography to form an electrode pattern constituting the second IDT electrode finger, which is thinner than the electrode pattern constituting the first IDT electrode finger. Therefore, the electrode areas of the strong supporting structures with two designed frequencies are obtained in one operation flow by basically performing the processes of coating and laying the photoresist on one block, so that the optimal performance of the double-surface acoustic wave filter is realized.
In other preferred embodiments, the piezoelectric substrate may be implemented as a piezoelectric single crystal substrate, and the method further includes: firstly, coating a metal film on the upper surface of a piezoelectric single crystal substrate, then spreading photoresist on the metal film, stripping redundant photoresist by utilizing a photoetching method to form an electrode pattern forming a first IDT electrode finger, turning the piezoelectric single crystal substrate to the lower surface upwards, coating the metal film on the lower surface of the piezoelectric single crystal, then spreading photoresist on the metal film, stripping redundant photoresist by utilizing the photoetching method to form an electrode pattern forming a second IDT electrode finger, wherein the thickness of the electrode pattern forming the first IDT electrode finger is larger than that of the electrode pattern forming the second IDT electrode finger. Thus, a piezoelectric single crystal having an IDT electrode structure with irregularities can be realized, and the piezoelectric single crystal can be applied to more choices of the double surface acoustic wave filters.
Example 6
In an embodiment of the present invention, as shown in fig. 15, there is provided a method for manufacturing a dual surface acoustic wave filter, the method including:
501. the piezoelectric substrate is implanted with an ionized element.
The piezoelectric substrate may be a piezoelectric body such as lithium tantalate or lithium niobate, and the defect layer may be formed in a region of a predetermined depth from the surface of the piezoelectric substrate by implanting ions into the surface of the piezoelectric substrate. For example, H + ions are implanted into a LiTaO3 piezoelectric substrate. The implantation energy was 150KeV and the dose was 9X 1016 cm-1. At this time, a high-sound-velocity support layer in which H + ions are distributed at a depth of about 1 μm from the surface of the piezoelectric substrate is formed.
502. A bonding layer containing silicon dioxide is formed on at least one side of a support substrate supporting a piezoelectric substrate or the piezoelectric substrate.
503. And bonding the bonding layer, the piezoelectric substrate and the support substrate to generate the piezoelectric substrate.
Then, a double surface acoustic wave filter is fabricated on the piezoelectric substrate by the method disclosed in the above embodiment, whereby a double surface acoustic wave filter having a supporting substrate can be obtained.
In the present invention, the terms "first", "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance; the term "plurality" means two or more. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (14)
1. A dual surface acoustic wave filter, comprising:
a piezoelectric substrate;
arranging a first filter element and a second filter element on the same piezoelectric substrate;
the first filter element is responsive to a first frequency of a surface acoustic wave, the first filter element including a plurality of first IDT electrode fingers having a first metal film of a first thickness, the plurality of first IDT electrode fingers being mounted on the piezoelectric substrate along a surface acoustic wave propagation direction;
the second filter element responsive to a second frequency of the acoustic surface, the second filter element comprising a plurality of second IDT electrode fingers having a second metal film of a second thickness, the plurality of second IDT electrode fingers mounted on the piezoelectric substrate along a surface acoustic wave propagation direction;
the first frequency is different from the second frequency;
the first thickness is different from the second thickness;
and the surface acoustic wave propagation path of the first filter element is parallel to or intersected with the surface acoustic wave propagation path of the second filter element.
2. The dual surface acoustic wave filter of claim 1, wherein a first thickness of the first metal film is defined as H1, a 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, a frequency response speed of the first frequency is defined as v1, and a 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 meet the following requirements:
8％<H2f2/v2<13％。
3. the dual surface acoustic wave filter of claim 1, wherein a 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 the width of each of the plurality of electrode fingers and a spacing of adjacent electrode fingers included in the plurality of electrode fingers;
the first filter element has a first duty ratio, 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 0.2 or more and 0.7 or less, and the second duty ratio is 0.3 or more and 0.9 or less.
4. The dual surface acoustic wave filter of claim 1, wherein the first IDT electrode finger has a first duty cycle and the second IDT electrode finger has a second duty cycle, wherein the first IDT electrode finger and the second IDT electrode finger are each provided with a metal thin-film structure comprising a first metal layer and a second metal layer, wherein the first metal layer comprises Al and the second metal layer is one of Cu, W, Mo, Cr, Ag, Au, Pt, Ga, Nb, Ta, Au, Si, Sc.
5. The dual surface acoustic wave filter of any of claims 1-4, wherein the piezoelectric substrate is a piezoelectric single crystal substrate, the piezoelectric single crystal substrate being lithium tantalate or lithium niobate;
the first IDT electrode fingers and the second IDT electrode fingers are formed on the same surface of the piezoelectric single crystal substrate.
6. The dual surface acoustic wave filter of any of claims 1-4, wherein 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 fingers are formed on the first surface, and the second IDT electrode fingers are formed on the second surface.
7. The dual surface acoustic wave filter of claim 5, wherein the piezoelectric substrate comprises:
the orientation angle between the first filter element and the piezoelectric single crystal substrate is psi 1, psi 1 is 0 °, the orientation angle between the second filter element and the piezoelectric single crystal substrate is psi 2, and psi 2 is in the range of (-5 °, +5 °).
8. The dual surface acoustic wave filter of claim 5, wherein the piezoelectric substrate comprises:
the first filter element and the second filter element are positioned on the same surface of the piezoelectric single crystal film;
the junction layer is arranged on the surface of the piezoelectric single crystal film, which is far away from the first filter element, and has a positive temperature compensation coefficient;
and the supporting substrate is arranged on the surface of the junction layer, which is far away from the piezoelectric single crystal film, and is a single crystal silicon substrate.
9. A dual-band module comprising the dual surface acoustic wave filter according to any one of claims 1 to 8, wherein a package structure for housing the dual surface acoustic wave filter is connected to the dual surface acoustic wave filter by bumps.
10. A method of making a dual surface acoustic wave filter, the method comprising:
providing a piezoelectric substrate;
arranging a first filter element and a second filter element on the same piezoelectric substrate by using a metal evaporation method;
wherein the first filter element is responsive to a first frequency of the surface acoustic wave, the first filter element including a plurality of first IDT electrode fingers having a first metal film of a first thickness, the plurality of first IDT electrode fingers being mounted on the piezoelectric substrate along a surface acoustic wave propagation direction;
the second filter element responsive to a second frequency of the acoustic surface, the second filter element comprising a plurality of second IDT electrode fingers having a second metal film of a second thickness, the plurality of second IDT electrode fingers mounted on the piezoelectric substrate along a surface acoustic wave propagation direction;
the first frequency is different from the second frequency;
the first thickness is different from the second thickness;
and the surface acoustic wave propagation path of the first filter element is parallel to or intersected with the surface acoustic wave propagation path of the second filter element.
11. The method of manufacturing a dual surface acoustic wave filter according to claim 10, wherein the step of providing the first filter element and the second filter element on the same piezoelectric substrate by metal vapor deposition comprises:
dividing the piezoelectric substrate into a first setting region for forming a first filter element and a second setting region for forming a second filter element;
covering a layer of metal film in a first set area and a second set area of the piezoelectric substrate;
laying photoresist on the metal film of the first set area, and stripping redundant photoresist by utilizing a photoetching method to form an electrode pattern forming a first IDT electrode finger;
covering a metal film on the first IDT electrode finger and the second setting area;
and spreading photoresist on the metal film of the second set area, and stripping the redundant photoresist by using a photoetching method to form an electrode pattern which is thicker than the electrode pattern of the first IDT electrode finger and forms the second IDT electrode finger.
12. The method of manufacturing a dual surface acoustic wave filter according to claim 10, wherein the step of providing the first filter element and the second filter element on the same piezoelectric substrate by metal vapor deposition comprises:
dividing the piezoelectric substrate into a first setting region for forming a first filter element and a second setting 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 of the first set area, and stripping redundant photoresist by utilizing a photoetching method to form an electrode pattern forming a first IDT electrode finger;
and spreading photoresist on the metal film of the second set area, and stripping the redundant photoresist by using a photoetching method to form an electrode pattern which is thinner than the electrode pattern of the first IDT electrode finger and forms the second IDT electrode finger.
13. The method of manufacturing a dual surface acoustic wave filter according to claim 10, wherein the piezoelectric substrate is a piezoelectric single crystal substrate, the method further comprising:
coating a metal film on the upper surface of the piezoelectric single crystal substrate;
laying photoresist on the metal film, and stripping redundant photoresist by utilizing a photoetching method to form an electrode pattern forming a first IDT electrode finger;
turning the piezoelectric single crystal substrate to face upwards;
coating a metal film on the lower surface of the piezoelectric single crystal;
laying photoresist on the metal film, and stripping redundant photoresist by utilizing a photoetching method to form an electrode pattern forming a second IDT electrode finger;
wherein a thickness of the electrode pattern constituting the first IDT electrode finger is larger than that of the electrode pattern constituting the second IDT electrode finger.
14. The method of fabricating a dual surface acoustic wave filter as claimed in any one of claims 10 to 13, wherein the fabrication of the piezoelectric substrate is implemented to include:
implanting an ionized element into the piezoelectric substrate;
forming a bonding layer containing silicon dioxide on at least one side of a support substrate supporting the piezoelectric substrate or the piezoelectric substrate;
and bonding the bonding layer, the piezoelectric substrate and the support substrate to generate the piezoelectric substrate.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116566349A (en) * | 2023-04-17 | 2023-08-08 | 无锡市好达电子股份有限公司 | Surface acoustic wave device based on piston mode and preparation method |
| CN116722838A (en) * | 2023-06-29 | 2023-09-08 | 北京超材信息科技有限公司 | Surface acoustic wave filter, surface acoustic wave filter set, multiplexer and radio frequency module |
| CN116996042A (en) * | 2023-09-26 | 2023-11-03 | 北京超材信息科技有限公司 | Filtering element, filter and radio frequency module |
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2021
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116566349A (en) * | 2023-04-17 | 2023-08-08 | 无锡市好达电子股份有限公司 | Surface acoustic wave device based on piston mode and preparation method |
| CN116566349B (en) * | 2023-04-17 | 2023-11-17 | 无锡市好达电子股份有限公司 | Surface acoustic wave device based on piston mode and preparation method |
| CN116722838A (en) * | 2023-06-29 | 2023-09-08 | 北京超材信息科技有限公司 | Surface acoustic wave filter, surface acoustic wave filter set, multiplexer and radio frequency module |
| CN116996042A (en) * | 2023-09-26 | 2023-11-03 | 北京超材信息科技有限公司 | Filtering element, filter and radio frequency module |
| CN116996042B (en) * | 2023-09-26 | 2024-03-01 | 北京超材信息科技有限公司 | Filtering element, filter and radio frequency module |
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