Electroacoustic filter component and manufacturing method to reduce the influence of debris

Abstract

An electroacoustic filter component having improved acoustic and / or electroacoustic properties is provided. The component includes a piezoelectric material (PM) having planar sides, preferably without chip defects. The piezoelectric material may be arranged above a carrier substrate (CS). A functional layer (FL) having planar sides may be arranged over an electrode structure (ES) as a trimming layer, a TCF layer, or a passivation layer. In a manufacturing method, the piezoelectric material and the functional layer are removed from a cutting line such that the layers do not chip.

Description

Technical Field

[0001] The present invention relates to electroacoustic filter components and a method of manufacturing such components. Background Art

[0002] Electroacoustic filter components can be used in RF filters, for example, RF filters for wireless communication devices, to separate desired RF signals from undesired RF signals.

[0003] Electroacoustic filter components can use electroacoustic resonators, such as BAW resonators (BAW = bulk acoustic wave) or SAW resonators (SAW = surface acoustic wave), where an electrode structure is in contact with a piezoelectric material, and when an RF signal is applied to the electrode structure, a conversion between an acoustic RF signal and an electromagnetic RF signal takes place.

[0004] Such resonators can be electrically connected to each other to form an RF filter, for example, in a ladder-shaped circuit topology.

[0005] Electroacoustic resonators require a cavity to allow oscillation of the piezoelectric material. Further, the active structure of the electroacoustic resonator must be protected from harmful environmental influences such as dust or water. A thin-film encapsulation including a thin-film layer can be provided, which together with a carrier substrate encloses a cavity in which the active structure can be arranged.

[0006] Typical methods of manufacturing such components involve manufacturing steps that are applied simultaneously to a plurality of components to be separated later. After creating the active structure and the corresponding cavity on a common wafer material, the wafer is singulated into individual elements, for example, by dicing.

[0007] However, such a manufacturing process may lead to defects during certain steps, such that a perfect hermetic seal of the active structure cannot be guaranteed. Summary of the Invention

[0008] Accordingly, there is a desire for a design for an electroacoustic component in which the active structure has better protection, and there is a desire for a method of manufacturing such a component.

[0009] To this end, an electroacoustic filter component and a corresponding manufacturing method according to the independent claims are provided. The dependent claims provide preferred embodiments.

[0010] The electroacoustic filter component includes a piezoelectric material in a piezoelectric layer, an electrode structure in an electrode layer disposed on the piezoelectric layer, and a cavity above the electrode structure. The sides of the piezoelectric material are planar.

[0011] Providing a planar side such as a planar side of a piezoelectric material means that the corresponding side is intact and not damaged, e.g., intact and not damaged during manufacturing. Correspondingly, the side of the piezoelectric material should be as smooth as possible. In this regard, when the top surface of the piezoelectric material in which the electrode structure is arranged is oriented in a horizontal position, the side of the piezoelectric material substantially represents the vertical surface of the piezoelectric material.

[0012] Correspondingly, the planar side of the piezoelectric material may be free of debris.

[0013] During the manufacturing steps of conventional components, singulation typically involves cutting through a carrier substrate and through the materials disposed on the carrier substrate. Since piezoelectric materials and other functional layers are typically disposed directly on the carrier substrate, debris caused by the cutting process can result in defects on the side surfaces of the materials of the piezoelectric material and / or other functional layers. Such defects can significantly reduce the acoustic performance of the resonator, thereby significantly reducing the electroacoustic performance of the corresponding filter component.

[0014] Thus, by providing an intact planar side of the piezoelectric material, the described electroacoustic filter component improves the acoustic performance of the resonator and improves the electroacoustic performance of the filter.

[0015] Correspondingly, the electroacoustic filter component may further include a functional layer. The functional layer may be disposed on or above the electrode structure. The side of the functional layer is also planar.

[0016] Furthermore, the planar side of the functional layer may also be free of debris.

[0017] Preventing debris from occurring at the piezoelectric material or the materials of other functional layers also enhances the hermetic seal of the cavity and the active structure of the component.

[0018] The functional layer may cover the side of the piezoelectric material.

[0019] Then, the piezoelectric material can still be better protected from harmful effects from the environment.

[0020] The functional layer may be a TCF compensation layer (TCF = temperature coefficient of frequency), a trimming layer, or a passivation layer. Other functional layers may include materials selected from or consisting of dielectric materials, nitrides, silicon nitrides, oxides, silicon oxides, silicon dioxides.

[0021] The TCF compensation layer helps to reduce or eliminate temperature-induced characteristic frequency drift, such as the center frequency of a band-pass filter or a band-stop filter, or the characteristic frequency of a resonator, such as the resonance frequency or the anti-resonance frequency.

[0022] The trimming layer can be used to set the characteristic frequency of the resonator, and thus the characteristic frequency of the filter, for example, by trimming the thickness of the trimming layer during the trimming process. The passivation layer can be used to seal the materials below the passivation layer to prevent harmful effects.

[0023] Silicon oxides such as silicon dioxide are materials that are well-suited to provide the TCF compensation layer. The nitride layer is well-suited to provide protection in the form of a passivation layer.

[0024] The electroacoustic filter component may involve a SAW resonator or a BAW resonator. Specifically, the electrode structure can be the electrode structure of one or more SAW resonators, which includes interdigital electrode fingers electrically connected to one of the two busbars of the resonator.

[0025] The cavity may be formed by thin-film encapsulation (TFAP). The thin-film encapsulation is characterized in that the cavity is at least partially enclosed by a thin-film layer. The thin film is composed of a material deposited by using thin-film techniques such as sputtering or includes a layer of such a material.

[0026] A sacrificial material can be used to fabricate the thin-film encapsulation, and the sacrificial material defines the later position and shape of the cavity below the thin-film protection cap.

[0027] The piezoelectric material can be arranged on or above the carrier substrate.

[0028] The carrier substrate can include silicon or be composed of it.

[0029] The carrier substrate can be provided as a wafer material, which is monomerized into individual chips during the cutting process.

[0030] The extension of the piezoelectric material and / or the functional layer in the lateral direction may be less than the extension of the carrier substrate in the corresponding lateral direction.

[0031] This difference in the lateral direction can be obtained through the corresponding structuring process of the material of the piezoelectric material and / or the functional structure. Therefore, at the position of subsequent cutting, there is no material of the piezoelectric layer or other functional layers. Therefore, when cutting is performed, no cutting defects will appear in the material of the piezoelectric material and / or the functional layer. Therefore, the sides of the piezoelectric material and the functional layer remain intact, and there are no debris defects caused by cutting.

[0032] Correspondingly, the carrier substrate may have cut sides. Although it is preferred that the carrier substrate also has no debris defects, the cut sides may include debris defects.

[0033] The component may also include an additional layer between the piezoelectric material and the carrier substrate.

[0034] The additional layer may be a waveguide layer.

[0035] Specifically, the waveguide material for the additional layer may include an oxide, such as silicon oxide, such as silicon dioxide. Preferably, the material of the waveguide layer has a lower acoustic impedance than the piezoelectric material, such that due to reflection at the interface between materials of different acoustic impedances, acoustic energy is confined to the interface region between the electrode structure and the piezoelectric material. Additionally, if the waveguide layer includes silicon dioxide, the waveguide layer may contribute to or result in compensation for temperature-induced drift of the characteristic frequency.

[0036] Corresponding to the features described above, a method of manufacturing an electroacoustic filter component includes the following steps:

[0037] - Providing a wafer material as the material of the carrier substrate,

[0038] - Disposing a piezoelectric material on or above the wafer material,

[0039] - Constructing an electrode structure on the piezoelectric material,

[0040] - Cutting the wafer material into individual pieces.

[0041] When the material is cut into individual pieces, there is no piezoelectric material at specific cutting positions of the wafer material.

[0042] Further, the piezoelectric material may be constructed before cutting such that there is no piezoelectric material at subsequent cutting positions.

[0043] Correspondingly, there may also be no material of the functional layer at subsequent cutting positions. This can be achieved by also constructing the material of the functional layer such that the carrier substrate and the cutting positions of its wafers are free of these materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Central aspects and details of preferred embodiments of the electroacoustic filter component and method are shown in the attached schematic diagrams.

[0045] In the drawings:

[0046] Figure 1 A cross-section of an electroacoustic filter component FC through a complete side including a piezoelectric material is shown;

[0047] Figure 2 The possibility of covering the side of the piezoelectric material with the material of the functional layer is shown;

[0048] Figure 3 The possibility of enclosing the piezoelectric material and the functional layer also in a cavity enclosed by a thin-film encapsulation and a carrier substrate is shown;

[0049] Figure 4 A cross-section of an electroacoustic filter component with fragmentation defects in the piezoelectric material and the functional layer is shown;

[0050] Figure 5 The possibility of arranging a functional layer between a piezoelectric material and a carrier substrate is shown. Detailed description

[0051] Figure 1 A cross-section of an electroacoustic filter component FC with improved acoustic properties is shown. The component includes a carrier substrate CS, on which a piezoelectric material PM is arranged in a piezoelectric layer. An electrode structure ES is arranged on the piezoelectric material PM. The electrode structure ES includes interdigital electrode fingers that extend along a transverse direction y perpendicular to a longitudinal direction x and a vertical direction z. The electrode structure ES is covered with a material of a functional layer FL. The top surface of the active structure including the electrode structure in the piezoelectric material is covered with a thin film cover of a thin film package TFP.

[0052] The lateral extension of the piezoelectric material PM in the longitudinal direction x or the transverse direction y is less than the corresponding extension of the carrier substrate CS, which allows a cutting tool for singulating the sheets of the carrier substrate CS not to contact the piezoelectric material PM. Therefore, the side surfaces of the piezoelectric material PM do not have defects such as chip defects.

[0053] Figure 2 The possibility of extending the functional layer FL around the side surfaces of the piezoelectric material PM to protect the corresponding side surfaces of the piezoelectric material is shown. Thus, the piezoelectric material is completely enclosed within the functional layer FL and the carrier substrate CS.

[0054] Figure 3 The possibility of extending the cover of the thin film TFP to a vertical position z on the top side of the carrier substrate CS such that the hermetic seal is further improved is also shown.

[0055] In contrast, Figure 4 A filter component FC is shown, in which the materials of the piezoelectric material PM and the functional layer FL are substantially flush with the material of the carrier substrate CS in the longitudinal direction (x) and the transverse direction (y). Thus, as Figure 4 shown, chip defects may occur on the side surfaces of the piezoelectric material PM and the side surfaces of the material of the functional layer FL.

[0056] Figure 5 A cross-section of an electroacoustic filter component FC is shown, in which an additional layer is arranged between the carrier substrate CS and the piezoelectric material PM. The additional layer may be a waveguide layer WGL.

[0057] Furthermore, the side surfaces of the piezoelectric material, the side surfaces of the waveguide layer, and the side surfaces at specific positions of the functional layer FL are oriented at an angle between 0° and 90° with respect to the top surface of the carrier substrate. The angle may be in the range of 20° to 70°.

[0058] Furthermore, Figure 5Shows a chip defect CD present on the side surface of the carrier substrate CS, but there are no chip defects in the piezoelectric material PM, the functional layer FL, and the additional waveguide layer WGL.

[0059] The electroacoustic filter component and the manufacturing method of such a component are not limited to the technical details described above or shown in the drawings. The component may include other structural elements, for example, for establishing the desired acoustic wave mode and other electrical connections with other circuit components of the filter or the external circuit environment.

[0060] List of reference numerals

[0061] CD: Chip defect

[0062] CS: Carrier substrate

[0063] ES: Electrode structure

[0064] FC: Electroacoustic filter component

[0065] FL: Functional layer

[0066] PM: Piezoelectric material

[0067] TFCP: Thin film encapsulation

[0068] WGL: Waveguide layer

[0069] x: Longitudinal direction

[0070] z: Vertical direction

Claims

1. An electroacoustic filter component, comprising: Piezoelectric material in a piezoelectric layer, An electrode structure in an electrode layer disposed on the piezoelectric layer, A cavity above the electrode structure, and A functional layer on or above the electrode structure, Wherein the side surface of the piezoelectric material is planar, Wherein the functional layer covers the side surface of the piezoelectric material.

2. The electroacoustic filter component according to claim 1, wherein the planar side surface of the piezoelectric layer is free of debris.

3. The electroacoustic filter component according to claim 1, wherein the side surface of the functional layer is planar.

4. The electroacoustic filter component according to claim 1, wherein the Planar side surface of the functional layer is free of debris.

5. The electroacoustic filter component according to claim 1, wherein the functional layer: - Is a TCF compensation layer, a trimming layer or a passivation layer, - Comprises a material selected from dielectric materials, nitrides, SiN4, oxides, silicon oxide, SiO2 or consists of the same.

6. The electroacoustic filter component according to claim 1, wherein the cavity is formed by a thin film encapsulated TFAP.

7. The electroacoustic filter component according to claim 1, wherein the piezoelectric material is disposed on or above a carrier substrate.

8. The electroacoustic filter component according to claim 7, wherein the piezoelectric material and / or the functional layer extends less in the lateral direction than the carrier substrate.

9. The electroacoustic filter component according to claim 7, wherein the carrier substrate has a cut side surface.

10. The electroacoustic filter component according to claim 7, further comprising an additional layer located between the piezoelectric material and the carrier substrate.

11. The electroacoustic filter component according to claim 10, wherein the additional layer is a waveguide layer.

12. A method of manufacturing an electroacoustic filter component, comprising the steps of: Providing a wafer material as the material of the carrier substrate, Disposing a piezoelectric material on or above the wafer material, Constructing an electrode structure on the piezoelectric material, Forming a functional layer on or above the electrode structure, and Cutting the wafer material into individual pieces, Wherein the functional layer covers the side surface of the piezoelectric material, Wherein when cutting, the wafer material has no piezoelectric material at the cutting position.

13. The method according to claim 12, further comprising: Setting the piezoelectric material and / or the functional layer to extend less in the lateral direction than the carrier substrate.

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