Dual-passband transversely excited bulk acoustic wave resonator and its manufacturing method and filter

Abstract

The embodiments of the present invention provide a dual-passband transversely excited bulk acoustic wave resonator, a manufacturing method thereof, and a filter, wherein the resonator comprises a piezoelectric layer, an electrode layer, and a heterogeneous layer; the material of the heterogeneous layer is different from that of the piezoelectric layer; the electrode layer and the heterogeneous layer are located on two opposite sides of the piezoelectric layer in the thickness direction; the electrode layer comprises an interdigitated electrode and a block electrode, and the overlapping region of the interdigitated electrode and the piezoelectric layer forms an active region; the projections of the heterogeneous layer and the active region in the thickness direction completely overlap; the technical solution of the present invention, by adding a heterogeneous layer under the piezoelectric layer, can change the stress and electric field distribution in the thickness direction of the resonator, so that the even-order modal mechanical-electric interaction energy of the resonator is not zero, thereby solving the problem that the traditional resonator can only excite a single resonant mode, and can simultaneously excite the A2 and A3 resonant modes, which is applied to the filter and is conducive to the miniaturization and high integration of the equipment.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of resonator technology, and in particular to a dual-passband transversely excited bulk acoustic wave resonator and a manufacturing method and a filter thereof. Background Art

[0002] At present, 5G communication technology has gradually matured and commercialized. With the explosive growth of mobile data traffic, the demand for the development of future 6G communication technology is becoming more and more urgent. This requires the core RF front-end module to have better performance, among which the RF filter is the most core component that determines the bandwidth of wireless communication. In recent years, the transversely excited bulk acoustic wave resonator (XBAR) has become the best choice for realizing 5G / 6G RF filters with its unique performance such as high frequency and large bandwidth. However, the existing XBAR RF filter only presents a single-band response due to the single resonance peak of the resonator. In order to meet the needs of RF communication for multiple frequency bands, multiple single-band filters must be embedded in the same space, which significantly increases the size and complexity of the equipment, which is not conducive to miniaturization and high integration. Summary of the invention

[0003] The embodiment of the present invention provides a dual-passband transversely excited bulk acoustic wave resonator and a manufacturing method and a filter thereof. By arranging a heterogeneous layer under the piezoelectric layer of the resonator, the A2 and A3 resonance modes can be excited simultaneously, so that the transversely excited bulk acoustic wave resonator presents a dual-band response.

[0004] In a first aspect, an embodiment of the present invention provides a dual-passband transversely excited bulk acoustic wave resonator, comprising a piezoelectric layer, an electrode layer and a heterogeneous layer; the material of the heterogeneous layer is different from that of the piezoelectric layer;

[0005] The electrode layer and the heterogeneous layer are located on opposite sides of the piezoelectric layer in the thickness direction; the electrode layer includes interdigitated electrodes and block electrodes, and the overlapping area of ​​the interdigitated electrodes and the piezoelectric layer forms an active area; the projections of the heterogeneous layer and the active area in the thickness direction are completely overlapped.

[0006] Optionally, the material of the heterogeneous layer has a positive elastic temperature coefficient.

[0007] Optionally, the material of the heterogeneous layer is any one of BCB, Si, SiN, Al2O3, Au, Al, W, and SiO2.

[0008] Optionally, the material of the piezoelectric layer is any one of AlN, ScAlN, LiNbO3, LiTaO3, and PVDF.

[0009] In a second aspect, an embodiment of the present invention provides a method for preparing a dual-passband transversely excited bulk acoustic wave resonator, comprising:

[0010] providing an insulating substrate;

[0011] stacking a heterogeneous layer and a piezoelectric layer in sequence on the insulating substrate;

[0012] etching the piezoelectric layer;

[0013] An electrode layer is prepared, wherein the electrode layer is located on a side of the piezoelectric layer away from the insulating substrate; an active region is formed in an area where the electrode layer overlaps with the piezoelectric layer;

[0014] The insulating substrate of the active area is removed.

[0015] Optionally, before removing the insulating substrate of the active area, the method further comprises:

[0016] Depositing a silicon dioxide protective layer on a side of the electrode layer away from the piezoelectric layer;

[0017] A silicon dioxide layer is deposited and patterned on a side of the insulating substrate away from the piezoelectric layer; the silicon dioxide layer does not overlap with a projection of the active area in the thickness direction.

[0018] Optionally, removing the insulating substrate of the active area includes:

[0019] The insulating substrate of the active area is removed by using a photolithography process.

[0020] Optionally, the heterogeneous layer is a silicon dioxide layer;

[0021] After removing the insulating substrate of the active area, the method further comprises:

[0022] The silicon dioxide layer is etched by using a BOE solution to control the thickness of the silicon dioxide layer.

[0023] Optionally, preparing an electrode layer comprises:

[0024] An electrode layer is deposited and patterned to form interdigitated electrodes and bulk electrodes.

[0025] Optionally, after preparing the interdigital electrodes, the method further comprises:

[0026] The Au Pad electrode is prepared by adopting a metal lift-off process, and the Au Pad electrode is located on a side of the block electrode away from the piezoelectric layer.

[0027] In a third aspect, the present invention further provides a filter, comprising the resonator described in any one of the first aspects of the present invention.

[0028] The embodiment of the present invention provides a dual-passband lateral excitation bulk acoustic wave resonator and a manufacturing method and a filter, wherein the resonator comprises a piezoelectric layer, an electrode layer and a heterogeneous layer; the material of the heterogeneous layer is different from that of the piezoelectric layer; the electrode layer and the heterogeneous layer are located on two opposite sides of the piezoelectric layer in the thickness direction; the electrode layer comprises interdigitated electrodes and block electrodes, and the overlapping area of ​​the interdigitated electrodes and the piezoelectric layer forms an active area; the projections of the heterogeneous layer and the active area in the thickness direction are completely overlapped. The technical solution of the present invention, by adding a heterogeneous layer under the piezoelectric layer, can change the stress and electric field distribution in the thickness direction of the resonator, so that the even-order modal mechanical-electric interaction energy of the resonator is not zero, thereby solving the problem that the traditional resonator can only excite a single resonant mode, and can simultaneously excite the A2 and A3 resonant modes, and is applied to the filter, which is conducive to the miniaturization and high integration of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic structural diagram of a dual-passband transversely excited bulk acoustic wave resonator provided by an embodiment of the present invention;

[0030] Figure 2 is a schematic structural diagram of a conventional transversely excited bulk acoustic wave resonator provided by an embodiment of the present invention;

[0031] Figure 3 yes Figure 2 The simulated impedance curve of the transversely excited bulk acoustic wave resonator shown;

[0032] Figure 4 is a simulated impedance curve diagram of a dual-passband transversely excited bulk acoustic wave resonator provided by an embodiment of the present invention;

[0033] Figure 5 is a schematic diagram of test results of a dual-passband transversely excited bulk acoustic wave resonator provided by an embodiment of the present invention;

[0034] Figure 6 It is a schematic flow chart of a method for preparing a dual-passband transversely excited bulk acoustic wave resonator provided by an embodiment of the present invention;

[0035] Figure 7 is a process flow chart of preparing a dual-passband transversely excited bulk acoustic wave resonator provided by an embodiment of the present invention;

[0036] Figure 8 It is a schematic structural diagram of a dual-passband transversely excited bulk acoustic wave filter provided by an embodiment of the present invention;

[0037] Fig. 9 It is a schematic diagram of test results of a dual-passband transversely excited bulk acoustic wave filter provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0039] It should be mentioned before discussing exemplary embodiments in more detail that some exemplary embodiments are described as processes or methods depicted as flow charts. Although the flow charts describe various operations (or steps) as sequential processes, many operations therein can be implemented in parallel, concurrently or simultaneously. In addition, the order of various operations can be rearranged. The process can be terminated when its operation is completed, but can also have additional steps not included in the accompanying drawings. The process can correspond to methods, functions, procedures, subroutines, subprograms, etc. In addition, the embodiments in the present invention and the features in the embodiments can be combined with each other without conflict.

[0040] The term “including” and its variations used in the present invention are open inclusions, that is, “including but not limited to.” The term “based on” means “based at least in part on.” The term “one embodiment” means “at least one embodiment.”

[0041] It should be noted that the concepts such as "first" and "second" mentioned in the present invention are only used to distinguish the corresponding contents, and are not used to limit the order or interdependence.

[0042] It should be noted that the modifications of "one" and "plurality" mentioned in the present invention are illustrative rather than restrictive, and those skilled in the art should understand that, unless otherwise clearly indicated in the context, it should be understood as "one or more".

[0043] Figure 1 is a schematic diagram of a dual-passband transversely excited bulk acoustic wave resonator provided by an embodiment of the present invention, with reference to Figure 1 The resonator includes a piezoelectric layer 10, an electrode layer 20 and a heterogeneous layer 30; the material of the heterogeneous layer 30 is different from that of the piezoelectric layer 10; the material of the piezoelectric layer 10 is any one of AlN, ScAlN, LiNbO3, LiTaO3, and PVDF, which is not limited. The electrode layer 20 and the heterogeneous layer 30 are located on two opposite sides of the piezoelectric layer 10 in the thickness direction; the electrode layer 20 includes a forked electrode 21 and a block electrode 22, and the area where the forked electrode 21 overlaps with the piezoelectric layer 10 forms an active area; the projections of the heterogeneous layer 30 and the active area in the thickness direction are completely overlapped.

[0044] Specifically, Figure 2 is a schematic diagram of a conventional transversely excited bulk acoustic wave resonator provided by an embodiment of the present invention, with reference to Figure 2The conventional transversely excited bulk acoustic wave resonator only includes an electrode layer 41 and a piezoelectric layer 42. Figure 3 yes Figure 2 The simulated impedance curve of the transversely excited BAW resonator is shown in Figure 1. Since the impedance at the resonant frequency will change significantly, Figure 3 It can be seen that the resonator has a single resonance peak; in the present application, a heterogeneous layer 30 is added below the piezoelectric layer 10, and the materials of the heterogeneous layer 30 and the piezoelectric layer 10 are different, so that the mechanical performance parameters of the combination of the heterogeneous layer 30 and the piezoelectric layer 10 are different from those of the piezoelectric layer 10; it should be noted that since the area where the interdigitated electrodes 21 overlap with the piezoelectric layer 10 forms an active area, and the active area is an effective resonance area, the heterogeneous layer 30 needs to cover at least the entire active area; in the existing resonator structure, the piezoelectric layer 10 is a symmetrical structure in the thickness direction; the piezoelectric layer 10 is in the thickness direction, The upward stress and the downward stress are of the same magnitude but opposite directions. Under the same electric field force, the mechanical-electric interaction energy of the even-order antisymmetric mode is 0, so only the A1 resonant mode can be excited. After adding the heterogeneous layer 30, the combination of the heterogeneous layer 30 and the piezoelectric layer 10 is an asymmetric structure. In the thickness direction, the upward stress and the downward stress are of different magnitudes. Under the same electric field force, the mechanical-electric interaction energy of the even-order antisymmetric mode is not 0, so the A2 and A3 resonant modes can be excited at the same time. Therefore, the resonator exhibits a dual-band response. Figure 4 is a simulated impedance curve diagram of a dual-passband transversely excited bulk acoustic wave resonator provided by an embodiment of the present invention, Figure 5 is a schematic diagram of test results of a dual-passband transversely excited bulk acoustic wave resonator provided by an embodiment of the present invention, Figure 4 , Figure 5 It can be seen that the dual-passband transversely excited bulk acoustic wave resonator has two resonance peaks. It should be noted that the thickness of the heterogeneous layer 30 is determined according to the designed resonator passband frequency band, that is, after the user determines the required resonator passband frequency band, the thickness of the corresponding heterogeneous layer 30 is designed according to the passband frequency band. After adding the heterogeneous layer 30, the thickness of the resonator is increased, thereby increasing the effective heat dissipation area of ​​the cross section, improving the heat dissipation effect, and increasing the power capacity.

[0045] A dual-passband lateral excitation bulk acoustic wave resonator provided by an embodiment of the present invention includes a piezoelectric layer, an electrode layer and a heterogeneous layer; the material of the heterogeneous layer is different from that of the piezoelectric layer; the electrode layer and the heterogeneous layer are located on two sides of the piezoelectric layer that are opposite to each other in the thickness direction; the electrode layer includes interdigital electrodes and block electrodes, and the overlapping area of ​​the interdigital electrodes and the piezoelectric layer forms an active area; the projections of the heterogeneous layer and the active area in the thickness direction are completely overlapped, and by adding a heterogeneous layer under the piezoelectric layer, the stress and electric field distribution in the thickness direction of the resonator can be changed, so that the even-order modal mechanical-electric interaction energy of the resonator is not zero, which solves the problem that the traditional resonator can only excite a single resonant mode, and can simultaneously excite the A2 and A3 resonant modes. When applied to filters, it is conducive to miniaturization and high integration of equipment.

[0046] In an optional embodiment of the present invention, the material of the heterogeneous layer 30 is any one of BCB, Si, SiN, Al2O3, Au, Al, W, and SiO2. It should be noted that the material of the heterogeneous layer is a material with a positive elastic temperature coefficient. For example, when it is SiO2, the TCF (temperature drift coefficient) of the resonator can be improved, thereby reducing thermal stress.

[0047] Figure 6 is a flow chart of a method for preparing a dual-passband transversely excited bulk acoustic wave resonator provided by an embodiment of the present invention, Figure 7 is a process flow chart of a dual-passband transversely excited bulk acoustic wave resonator provided by an embodiment of the present invention, with reference to Figure 6 , Figure 7 An introduction to the preparation process.

[0048] refer to Figure 6 , the preparation method comprises:

[0049] S110, providing an insulating substrate.

[0050] S120, stacking a heterogeneous layer and a piezoelectric layer in sequence on an insulating substrate.

[0051] The thickness of the heterogeneous layer is determined according to the designed passband frequency band of the resonator, and a heterogeneous layer of corresponding thickness is selected according to the passband frequency band of the resonator to be obtained.

[0052] S130 , etching the piezoelectric layer.

[0053] S140, preparing an electrode layer, wherein the electrode layer is located on a side of the piezoelectric layer away from the insulating substrate; an active region is formed in an overlapping region between the electrode layer and the piezoelectric layer.

[0054] Specifically, in an optional embodiment, refer to Figure 7, the electrode layer can be deposited and patterned to form interdigital electrodes and block electrodes. The Au Pad electrode is prepared by metal lift-off process, and the Au Pad electrode is located on the side of the block electrode away from the piezoelectric layer to reduce ohmic loss.

[0055] S150, removing the insulating substrate of the active area.

[0056] Specifically, the insulating substrate of the active region is removed. Optionally, a photolithography process may be used to remove the insulating substrate of the active region, and the insulating substrate of the non-resonant region is retained as a support.

[0057] It should be noted that the method for preparing a dual-passband lateral excitation bulk acoustic wave resonator provided in an embodiment of the present invention provides an insulating substrate, and stacks a heterogeneous layer and a piezoelectric layer in sequence on the insulating substrate, then etches the piezoelectric layer to prepare an electrode layer, and the electrode layer is located on the side of the piezoelectric layer away from the insulating substrate; the area where the electrode layer and the piezoelectric layer overlap forms an active area, and finally the insulating substrate of the active area is removed. The resonator prepared by the above method can change the stress and electric field distribution in the thickness direction of the resonator by adding a heterogeneous layer under the piezoelectric layer, so that the even-order modal mechanical-electric interaction energy of the resonator is not zero, which solves the problem that the traditional resonator can only excite a single resonant mode, and can simultaneously excite the A2 and A3 resonant modes, and is applied to the filter, which is conducive to the miniaturization and high integration of the equipment.

[0058] Furthermore, in an optional embodiment of the present invention, before removing the insulating substrate of the active area, the method further includes:

[0059] Depositing a silicon dioxide protective layer on a side of the electrode layer away from the piezoelectric layer;

[0060] Specifically, refer to Figure 7 In order to prevent the electrode layer from being damaged when etching the insulating substrate of the active area, a silicon dioxide protection layer 71 needs to be deposited, wherein the insulating substrate is made of silicon.

[0061] A silicon dioxide layer is deposited and patterned on a side of the insulating substrate away from the piezoelectric layer; the projection of the silicon dioxide layer and the active area in the thickness direction do not overlap.

[0062] Specifically, in order to remove the insulating substrate in the active area while retaining part of the insulating substrate as support, a silicon dioxide layer 72 is deposited and patterned on the side of the insulating substrate away from the piezoelectric layer to prevent the insulating substrate covered by the silicon dioxide layer 72 from being etched.

[0063] In an optional embodiment of the present invention, the heterogeneous layer is a silicon dioxide layer; after removing the insulating substrate of the active area, the method further comprises:

[0064] The silicon dioxide layer is etched by using a BOE solution to control the thickness of the silicon dioxide layer.

[0065] Specifically, since the thickness of the heterogeneous layer 30 is determined according to the designed resonator passband frequency band, the silicon dioxide layer can be etched by a BOE solution to control the thickness of the silicon dioxide layer, thereby controlling the resonator passband frequency band.

[0066] Figure 8 is a schematic diagram of the structure of a dual-passband transversely excited bulk acoustic wave filter provided by an embodiment of the present invention, with reference to Figure 8 , which includes two thicknesses of transversely excited bulk acoustic wave resonators, namely resonator 110 and resonator 120, and a SiO2 layer is arranged under the piezoelectric layer of the resonator. The transversely excited bulk acoustic wave resonators of different thicknesses are realized by etching the piezoelectric layer by ion beam etching (IBE), inductively coupled plasma etching (ICP-RIE) or plasma trimming (Trimming) process, wherein the ion beam etching (IBE) process is preferred, which has a higher verticality. Fig. 9 is a schematic diagram of test results of a dual-passband transversely excited bulk acoustic wave filter provided by an embodiment of the present invention, with reference to Fig. 9 , the filter presents a dual-band response. Since the filter includes the resonator provided by the embodiment of the present invention, it has the corresponding beneficial effects of the dual-passband transverse excitation bulk acoustic wave resonator provided by the embodiment of the present invention, which will not be described in detail here.

[0067] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A method for preparing a dual-passband transversely excited bulk acoustic wave resonator, characterized in that: The dual-passband transversely excited bulk acoustic wave resonator comprises a piezoelectric layer, an electrode layer and a heterogeneous layer; the material of the heterogeneous layer is different from that of the piezoelectric layer; The electrode layer and the heterogeneous layer are located on two opposite sides of the piezoelectric layer in the thickness direction; the electrode layer includes interdigital electrodes and block electrodes, and the area where the interdigital electrodes overlap with the piezoelectric layer forms an active area; The projections of the heterogeneous layer and the active region in the thickness direction completely overlap; The method for preparing the dual-passband transversely excited bulk acoustic wave resonator comprises: providing an insulating substrate; stacking a heterogeneous layer and a piezoelectric layer in sequence on the insulating substrate; etching the piezoelectric layer; An electrode layer is prepared, wherein the electrode layer is located on a side of the piezoelectric layer away from the insulating substrate; an active region is formed in an area where the electrode layer overlaps with the piezoelectric layer; removing the insulating substrate of the active area; Before removing the insulating substrate of the active area, the method further comprises: Depositing a silicon dioxide protective layer on a side of the electrode layer away from the piezoelectric layer; A silicon dioxide layer is deposited and patterned on a side of the insulating substrate away from the piezoelectric layer; the silicon dioxide layer does not overlap with a projection of the active area in the thickness direction.

2. The preparation method according to claim 1, characterized in that: The material of the heterogeneous layer has a positive elastic temperature coefficient.

3. The preparation method according to claim 1, characterized in that: The material of the heterogeneous layer is any one of BCB, Si, SiN, Al2O3, Au, Al, W, and SiO2.

4. The preparation method according to claim 1, characterized in that: Removing the insulating substrate of the active area comprises: The insulating substrate of the active area is removed by using a photolithography process.

5. The preparation method according to claim 4, characterized in that: The heterogeneous layer is a silicon dioxide layer; After removing the insulating substrate of the active area, the method further comprises: The silicon dioxide layer is etched by using a BOE solution to control the thickness of the silicon dioxide layer.

6. The preparation method according to claim 1, characterized in that: Preparing an electrode layer, comprising: An electrode layer is deposited and patterned to form interdigitated electrodes and bulk electrodes.

7. The preparation method according to claim 6, characterized in that: After preparing the interdigitated electrodes, the following steps are also included: The Au Pad electrode is prepared by adopting a metal lift-off process, and the Au Pad electrode is located on a side of the block electrode away from the piezoelectric layer.

8. A filter, characterized in that: It comprises a resonator prepared by the preparation method according to any one of claims 1 to 7.

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