Multi-layer resonator assembly and method of manufacture thereof

Abstract

The method for manufacturing a multi-layer resonator assembly includes the steps of sequentially manufacturing a plurality of vertically stacked resonator layers, including, for each resonator layer of the plurality of resonator layers, depositing a dielectric layer, forming at least one thin film bulk acoustic resonator (FBAR) cavity in the deposited dielectric layer, filling each FBAR cavity of the at least one FBAR cavity with a sacrificial material block, and depositing an FBAR material stack on the at least one FBAR cavity. The deposited FBAR material stack is in contact with the sacrificial material block and the dielectric layer. The method further includes, after the sequential manufacturing of the plurality of resonator layers, removing the sacrificial material block from the at least one FBAR cavity of each resonator layer of the plurality of resonator layers.

Description

[Technical field]

[0001] This application claims priority to U.S. Patent Application No. 17 / 566,144, filed December 30, 2021, which is incorporated by reference in its entirety herein. [Background technology]

[0002] The present disclosure relates generally to radio frequency (RF) filters, and more particularly to multi-layer resonator assemblies that include thin film bulk acoustic resonators (FBARs).

[0003] In many radio frequency (RF) applications, electrical resonators are used in filters to condition signals and improve transmission. Despite continuing efforts to reduce the size and footprint of electrical components, many known filter technologies are not readily conducive to miniaturization. Piezoelectric-based resonators generate acoustic resonant modes in the piezoelectric material, and these sound waves are converted into radio waves for use in electrical applications.

[0004] A type of piezoelectric resonator, the thin film bulk acoustic resonator (FBAR), has a small footprint and can be integrated into integrated circuit (IC) manufacturing processes. As shown in FIGS. 1A-C, the FBAR 100 is an acoustic material stack that may include a piezoelectric material layer 102 sandwiched between two electrodes 104. The FBAR 100 is formed on a substrate 106 that includes the electrodes 104 and a portion of the piezoelectric material 102 suspended above an air gap 108 (e.g., a cavity). Sound waves resonate throughout the acoustic material stack, with the particular resonant frequency being determined by the materials of the layers and the geometry of the electrodes 104.

[0005] However, high density FBAR filter networks can be difficult to manufacture, especially in the small form factors required for today's state-of-the-art RF systems. For example, it can be difficult to manufacture multi-level FBAR architectures that include FBARs and associated cavities on multiple levels (e.g., layers) within the same chip. Thus, there is a need in the art for improved resonator assemblies and related manufacturing methods. Summary of the Invention

[0006] It should be understood that any or all of the features or embodiments described herein can be used or combined in any combination with any other features or embodiments described herein, unless otherwise stated.

[0007] According to an aspect of the present disclosure, a method for manufacturing a multi-layer resonator assembly includes the steps of sequentially manufacturing a plurality of vertically stacked resonator layers, and for each resonator layer of the plurality of resonator layers, the steps include depositing a dielectric layer, forming at least one thin film bulk acoustic resonator (FBAR) cavity in the deposited dielectric layer, filling each FBAR cavity of the at least one FBAR cavity with a sacrificial material block, and depositing an FBAR material stack on the at least one FBAR cavity. The deposited FBAR material stack is in contact with the sacrificial material block and the dielectric layer. The method further includes removing the sacrificial material block from the at least one FBAR cavity of each resonator layer of the plurality of resonator layers after the steps of sequentially manufacturing the plurality of resonator layers.

[0008] In any of the aspects or embodiments described above and herein, filling the at least one FBAR cavity with a sacrificial material block may include depositing the sacrificial material block using one of chemical vapor deposition, physical vapor deposition, or atomic layer deposition.

[0009] In any of the aspects or embodiments described above and herein, removing the sacrificial material block from at least one FBAR cavity of each resonator layer of the plurality of resonator layers may include exposing the plurality of resonator layers to one of a xenon difluoride (XeF), potassium hydroxide (KOH), hydrogen peroxide (H2O2), or oxygen (O2) plasma.

[0010] In any of the aspects or embodiments described above and herein, after fabricating the plurality of resonator layers and prior to removing the sacrificial material block from the at least one FBAR cavity of each resonator layer of the plurality of resonator layers, the sacrificial material block of the at least one FBAR cavity of each resonator layer of the plurality of resonator layers may contact a vertically adjacent sacrificial material block disposed within a vertically adjacent resonator layer of the plurality of resonator layers.

[0011] In any of the aspects or embodiments described above and herein, the method may further include, for each resonator layer of the plurality of resonator layers, after filling each FBAR cavity of the at least one FBAR cavity with the sacrificial material block, planarizing the dielectric layer and the sacrificial material block within each FBAR cavity of the at least one FBAR cavity.

[0012] In any of the aspects or embodiments described above and herein, the method may further include, for each resonator layer of the plurality of resonator layers, forming one or more conductive layers on the dielectric layer.

[0013] In any of the aspects or embodiments described above and herein, the method may further include, for each resonator layer of the plurality of resonator layers, after filling each FBAR cavity of the at least one FBAR cavity with the sacrificial material block and prior to depositing the FBAR material stack over the at least one FBAR cavity, depositing a dielectric coating on the dielectric layer and the sacrificial material block inside each FBAR cavity of the at least one FBAR cavity.

[0014] In any of the aspects or embodiments described above and herein, the method may further include, for each resonator layer of the plurality of resonator layers, removing one or more portions of the dielectric coating prior to depositing the FBAR material stack over the at least one FBAR cavity.

[0015] In any of the aspects or embodiments described above and herein, the FBAR material stack being deposited may include a piezoelectric layer and at least one conductive layer.

[0016] In any of the aspects or embodiments described above and herein, the piezoelectric layer may be sandwiched between an upper conductive layer of the at least one conductive layer and a lower conductive layer of the at least one conductive layer.

[0017] In any of the aspects or embodiments described above and herein, the sacrificial material block may include one of amorphous silicon, polycrystalline silicon, tungsten, titanium nitride (TiN), or polyimide.

[0018] According to another aspect of the present disclosure, a multi-layer resonator assembly includes a plurality of vertically stacked resonator layers including a plurality of thin film bulk acoustic resonators (FBARs). Each resonator layer of the plurality of resonator layers includes a dielectric layer having an upper surface and a lower surface. The dielectric layer defines at least an FBAR cavity within the dielectric layer. The at least one FBAR cavity extends from the upper surface to the lower surface. Each resonator layer of the plurality of resonator layers further includes at least one FBAR of the plurality of FBARs disposed on the upper surface of the dielectric layer. Each FBAR of the at least one FBAR extends across an FBAR cavity of the at least one FBAR cavity. Each FBAR cavity of the at least one FBAR cavity of each resonator layer of the plurality of layers is vertically aligned with a respective FBAR cavity of the at least one FBAR cavity of each vertically adjacent resonator layer of the plurality of resonator layers.

[0019] In any of the aspects or embodiments described above and herein, the multi-layer resonator assembly may further include a plurality of sacrificial material blocks, each sacrificial material block of the plurality of sacrificial material blocks disposed in a respective FBAR cavity of the at least one FBAR cavity of each resonator layer of the plurality of resonator layers.

[0020] In any of the aspects or embodiments described above and herein, each sacrificial material block of the plurality of sacrificial material blocks may contact a vertically-adjacent sacrificial material block of the plurality of sacrificial material blocks of a vertically-adjacent resonator layer of each of the plurality of resonator layers.

[0021] In any of the aspects or embodiments described above and herein, the plurality of sacrificial material blocks may include one of amorphous silicon, polycrystalline silicon, tungsten, titanium nitride (TiN), or polyimide.

[0022] In any of the aspects or embodiments described above and herein, at least some of the FBARs of the plurality of FBARs may be electrically connected to each other in a ladder configuration, the some FBARs including a first sub-portion of the FBARs that may be disposed on a first resonator layer of the plurality of resonator layers and a second sub-portion of the FBARs that may be disposed on a second resonator layer of the plurality of resonator layers that is vertically adjacent to the first resonator layer.

[0023] In any of the aspects or embodiments described above and herein, at least some of the FBARs of the plurality of FBARs may be electrically connected to each other in a lattice configuration, the some FBARs including a first sub-portion of the FBARs that may be disposed in a first resonator layer of the plurality of resonator layers and a second sub-portion of the FBARs that may be disposed in a second resonator layer of the plurality of resonator layers that is vertically adjacent to the first resonator layer.

[0024] In any of the aspects or embodiments described above and herein, at least some of the FBARs of the plurality of FBARs may be electrically connected to each other in a ladder lattice configuration, including a first sub-portion of the FBAR that may be disposed on a first resonator layer of the plurality of resonator layers, a second sub-portion of the FBAR that may be disposed on a second resonator layer of the plurality of resonator layers vertically adjacent to the first resonator layer, and a third sub-portion of the FBAR that may be disposed on a third resonator layer of the plurality of resonator layers vertically adjacent to the second resonator layer.

[0025] In any of the aspects or embodiments described above and herein, one or more of the FBARs of the plurality of FBARs may include a piezoelectric layer sandwiched between an upper conductive layer and a lower conductive layer.

[0026] In any of the aspects or embodiments described above and herein, the multi-layer resonator assembly may further include a base layer disposed vertically adjacent to the plurality of resonator layers, and the base layer may include a high electron mobility transistor (HEMT).

[0027] The present disclosure, as well as all aspects, embodiments, and advantages associated therewith, will become more readily apparent from consideration of the detailed description provided below, including the accompanying drawings. [Brief description of the drawings]

[0028] [Figure 1] 1A-C show cross-sectional views of an exemplary film bulk acoustic resonator (FBAR) mounted on a substrate. [Diagram 2] 1 is a side cutaway view of a portion of a multi-layer resonator assembly in accordance with one or more embodiments of the present disclosure. [Diagram 3] 3 is a top cutaway view of a portion of the multi-layer resonator assembly of FIG. 2 in accordance with one or more embodiments of the present disclosure. [Figure 4] FIG. 1 illustrates a schematic diagram of FBARs electrically connected in a ladder configuration in accordance with one or more embodiments of the present disclosure. [Diagram 5] FIG. 1 shows a schematic diagram of FBARs electrically connected in a lattice configuration in accordance with one or more embodiments of the present disclosure. [Figure 6] 1 shows a schematic diagram of FBARs electrically connected in a ladder lattice configuration in accordance with one or more embodiments of the present disclosure. [Figure 7] 1 illustrates a flowchart of a method for forming a multi-layer resonator assembly in accordance with one or more embodiments of the present disclosure. [Figure 8A] 1A-1D depict a series of side cutaway views of a portion of a multi-layer resonator assembly at various stages of formation in accordance with one or more embodiments of the present disclosure. [Figure 8B] 1A-1D depict a series of side cutaway views of a portion of a multi-layer resonator assembly at various stages of formation in accordance with one or more embodiments of the present disclosure. [Figure 8C] 1A-1D depict a series of side cutaway views of a portion of a multi-layer resonator assembly at various stages of formation in accordance with one or more embodiments of the present disclosure. [Figure 8D] 1A-1D depict a series of side cutaway views of a portion of a multi-layer resonator assembly at various stages of formation in accordance with one or more embodiments of the present disclosure. [Figure 8E] 1A-1D depict a series of side cutaway views of a portion of a multi-layer resonator assembly at various stages of formation in accordance with one or more embodiments of the present disclosure. [Figure 8F] 1A-1D depict a series of side cutaway views of a portion of a multi-layer resonator assembly at various stages of formation in accordance with one or more embodiments of the present disclosure. [Figure 8G] 1A-1D depict a series of side cutaway views of a portion of a multi-layer resonator assembly at various stages of formation in accordance with one or more embodiments of the present disclosure. [Figure 8H] 1A-1D depict a series of side cutaway views of a portion of a multi-layer resonator assembly at various stages of formation in accordance with one or more embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] 2 and 3, a multi-layer resonator assembly 20 (hereinafter "resonator assembly 20") according to the present disclosure includes a plurality of vertically stacked resonator layers 22 configured as an integrated circuit (IC). In some embodiments, the resonator assembly 20 may further include a base layer 24 vertically adjacent the plurality of resonator layers 22. FIGS. 2 and 3 show a portion of an exemplary resonator assembly 20 including a base layer 24 and three resonator layers 22. However, it should be understood that the present disclosure is not limited to the particular configuration of the resonator assembly 20 shown in FIGS. 2 and 3, nor is it limited to any particular number of resonator layers 22. As used herein, the terms "vertical" or "vertically" refer to a direction generally perpendicular to a major plane along which the resonator assembly 20 is processed during fabrication and which can be considered to define a generally horizontal orientation.

[0030] The base layer 24 may be the first layer of an integrated circuit or may be formed on a bare substrate wafer 28 as shown in FIG. 2. Alternatively, the base layer 24 may be the final layer of a more complex IC, such as, for example, a gallium nitride (GaN) switch network. The base layer 24 may generally include a dielectric layer 30, a conductor layer 32, and input / output circuitry 34. Other passive structures, such as, for example, capacitors and inductors, may also be included in the base layer 24. In some embodiments, the base layer 24 may include a GaN high electron mobility transistor (HEMT) and associated IC structures. In some embodiments, the incorporation of a GaN HEMT circuit into the resonator assembly 20 may be accomplished by directly forming multiple resonator layers 22 on top of the GaN HEMT circuit.

[0031] The resonator layers 22 include a plurality of thin film bulk acoustic resonators (FBARs) 36 that are electrically connected to form at least one filter network 38. In some embodiments, the filter network 38 may be configured as a three-dimensional (e.g., multi-layer) FBAR array of the FBARs 36, as described in further detail. Each resonator layer 22 includes a dielectric layer 40 and at least one FBAR 36 of the plurality of FBARs 36. The dielectric layer 40 has a top surface 42 and a bottom surface 44 opposite the top surface 42. The dielectric layer 40 and the dielectric layer 30 may be made of a suitable dielectric material, such as silicon nitride (e.g., SiN or Si3N4), silicon dioxide (SiO2), and the like. The dielectric layer 40 includes at least one FBAR cavity 46 that extends vertically from the top surface 42 to the bottom surface 44 of the dielectric layer 40. Each FBAR 36 of each resonator layer 22 of the multiple resonator layers 22 is positioned such that the each FBAR 36 extends across an FBAR cavity 46 disposed in the respective resonator layer 22. At least a portion of each FBAR 36 of each resonator layer 22 of the multiple resonator layers 22 may contact a top surface 42 of a dielectric layer 40 of the respective resonator layer 22.

[0032] Each FBAR 36 of the plurality of FBARs 36 typically includes a piezoelectric layer 48 and at least one conductive layer 50 (e.g., an electrode). In some embodiments, one or more FBARs 36 of the plurality of FBARs 36 may have a configuration in which the piezoelectric layer 48 is sandwiched between two conductive layers 50 (e.g., an upper conductive layer and a lower conductive layer), as shown, for example, in FIG. 2. In some embodiments, one or more FBARs 36 of the plurality of FBARs 36 may have a "top electrode only" configuration, in which each FBAR 36 of the plurality of FBARs 36 includes a top conductive layer 50 on top of the piezoelectric layer 48 and no conductive layer is present on the bottom of the piezoelectric layer 48. In some embodiments, the top conductive layer 50 may be lithographically patterned to target a particular resonant frequency or other performance requirement of each FBAR 36. Non-limiting examples of materials for the piezoelectric layer 48 include, but are not limited to, aluminum nitride (AlN), scandium-doped aluminum nitride (ScAlN), gallium nitride (GaN), zinc oxide (ZnO), and the like. At least one conductive layer 50 may typically be made of a metallic material. Non-limiting examples of materials for the conductive layer 50 include, but are not limited to, aluminum (Al) or molybdenum (Mo). The multiple FBARs 36 may include FBARs 36 having different thicknesses, sizes, shapes, and configurations depending, for example, on the desired range of frequencies to filter.

[0033] Each resonator layer 22 of the plurality of resonator layers 22 further includes a conductive layer 52 configured to electrically connect components of the resonator assembly 20, including the plurality of FBARs 36. As shown in Figure 2, the conductive layer 52 included in a resonator layer 22 of the plurality of resonator layers 22 may be in electrical contact with the conductive layer 52 of a vertically adjacent resonator layer 22 of the plurality of resonator layers 22. The conductive layer 52 is generally made of a metallic material, such as, for example, copper (Cu) (e.g., copper damascene), aluminum (Al), or the like.

[0034] As shown in Figures 2 and 3, each FBAR cavity 46 of each resonator layer 22 is vertically aligned with one or more FBAR cavities 46 of each vertically adjacent resonator layer 22 of the plurality of resonator layers 22. In other words, at least a portion of each FBAR cavity 46 is vertically aligned with at least a portion of a vertically adjacent FBAR cavity 46 disposed within a vertically adjacent resonator layer 22. Thus, at least one FBAR cavity 46 associated with each resonator layer 22 of the plurality of resonator layers 22 may combine to define one or more uninterrupted etch passages 54 through the plurality of resonator layers 22, for example, from a vertically outermost resonator layer 22 to a vertically innermost resonator layer 22. As shown in Figure 3, one or more FBAR cavities 46 of each resonator layer 22 may be horizontally displaced (e.g., offset) from one or more FBAR cavities 46 of a vertically adjacent resonator layer 22 of the plurality of resonator layers 22.

[0035] The resonator assembly 20 may include a thin capping dielectric coating 56 (hereinafter, "dielectric coating 56") disposed between vertically adjacent ones of the plurality of resonator layers 22, as well as between the base layer 24 and the vertically adjacent ones of the plurality of resonator layers 22. The dielectric coating 56 may be made of a suitable dielectric material, such as silicon nitride (e.g., SiN or Si3N4), and may electrically isolate the components of each resonator layer 22 (e.g., conductive layer 52) from the components of the vertically adjacent ones of the plurality of resonator layers 22. Portions of the dielectric coating 56 may be removed to allow, for example, positioning of the components of the resonator assembly 20 (e.g., the plurality of FBARs 36), electrical contact between the vertically adjacent components (e.g., the conductive layer 52), etc. The resonator assembly 20 may further include one or more pad-out structures 58 in electrical contact with one or more of the FBARs 36 of the plurality of FBARs 36.

[0036] 2 and 3 show partial cutaway views of a portion of an exemplary resonator assembly 20 in which a plurality of FBARs 36 are arranged as a multi-layer array of FBARs, as discussed above. In particular, FIG. 2 shows a side view of the exemplary resonator assembly 20, and FIG. 3 shows a top view of the resonator assembly 20 of FIG. 2. The plurality of resonator layers 22 are shown in FIG. 2 as a first resonator layer 22A, a second resonator layer 22B, and a third resonator layer 22C. For ease of understanding, in FIG. 2 and FIG. 3, the plurality of FBARs 36 are shown as FBARs 36A-F, the FBAR cavities 46 are shown as FBAR cavities 46A-F, and the conductive layers 52 are shown as conductive layers 52A-L.

[0037] 4-6, the plurality of FBARs 36 may be electrically connected with conductive layers 52 to form one or more multi-layer filter networks 38. As shown in FIGS. 4-6, the conductive layers 52 disposed within a first resonator layer 22 of the plurality of resonator layers 22 are generally indicated by dashed lines, the conductive layers 52 disposed within a second resonator layer 22 of the plurality of resonator layers 22 are generally indicated by dotted lines, the conductive layers 52 disposed within a third resonator layer 22 of the plurality of resonator layers 22 are generally indicated by dashed lines, and the conductive layers 52 disposed within a fourth resonator layer 22 of the plurality of resonator layers 22 are generally indicated by solid lines. The FBAR configurations of FIGS. 4-6 are included to illustrate the multi-layer configuration of the filter network 38, and the filter network 38 of the present disclosure is not limited to the FBAR configurations shown in FIGS. 4-6.

[0038] 4, at least some of the FBARs 36 of the plurality of FBARs 36 may be electrically connected to each other in a “ladder configuration.” A first sub-portion of the FBARs 36 may be disposed on a first resonator layer 22A of the plurality of resonator layers 22, and a second sub-portion of the FBARs 36 may be disposed on a second resonator layer 22B of the plurality of resonator layers 22. The first resonator layer 22A may be disposed vertically adjacent to the second resonator layer 22B of the plurality of resonator layers 22.

[0039] 5, at least some of the FBARs 36 of the plurality of FBARs 36 may be electrically connected to each other in a “lattice configuration.” A first sub-portion of the FBARs 36 may be disposed on a first resonator layer 22A of the plurality of resonator layers 22, and a second sub-portion of the FBARs 36 may be disposed on a second resonator layer 22B of the plurality of resonator layers 22. The first resonator layer 22A may be disposed vertically adjacent to the second resonator layer 22B of the plurality of resonator layers 22.

[0040] 6, at least some of the FBARs 36 of the plurality of FBARs 36 may be electrically connected to each other in a "ladder lattice configuration." A first sub-portion of the FBAR 36 may be disposed on a first resonator layer 22A of the plurality of resonator layers 22, a second sub-portion of the FBAR 36 may be disposed on a second resonator layer 22B of the plurality of resonator layers 22, and a third sub-portion of the FBAR 36 may be disposed on a third resonator layer 22C of the plurality of resonator layers 22. The first resonator layer 22A, the second resonator layer 22B, and / or the third resonator layer 22C may be disposed vertically adjacent to another layer of the first resonator layer 22A, the second resonator layer 22B, and the third resonator layer 22C.

[0041] 7 shows a flow chart of a method 700 for manufacturing a multi-layer resonator assembly, such as, but not limited to, resonator assembly 20. Various steps of method 700 will be described with reference to the side cutaway views of Figures 8A-H, which show portions of resonator assembly 20 at various stages of formation.

[0042] In step 702, a dielectric layer 40 for the resonator layer 22 is deposited. The dielectric layer 40 for a first of the resonator layers 22 may be deposited or disposed on the substrate 28 or base layer 24, as shown in FIG. 8A. In some embodiments, step 702 may include planarizing the dielectric layer 40 to define a substantially planar upper surface 42 of the dielectric layer 40. The dielectric layer 40 may be planarized using a chemical mechanical polishing (CMP) method or other suitable IC planarization method.

[0043] In step 704, one or more FBAR cavities 46 are formed in the dielectric layer 40 by removing dielectric material from the dielectric layer 40. For example, the dielectric layer 40 may be etched using a suitable wet etching or dry etching (e.g., plasma etching) process. In step 706, the formed FBAR cavities 46 are filled with a sacrificial material block 60, as shown in FIG. 8A. The sacrificial material block 60 may fill each FBAR cavity 46 and may extend between the lower surface 44 and the upper surface 42 of the dielectric layer 40. The sacrificial material block 60 may be deposited in the FBAR cavities 46 by, for example, chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), or the like. Non-limiting examples of materials for the sacrificial material block 60 may include amorphous silicon, polycrystalline silicon, tungsten, titanium nitride (TiN), or polyimide.

[0044] In step 708, the sacrificial material block 60 deposited in each FBAR cavity 46 may be planarized to be flush with the surrounding dielectric layer 40 (e.g., top surface 42 of dielectric layer 40). In some embodiments, the dielectric layer 40 may alternatively be planarized simultaneously with the planarization of the sacrificial material block 60 in step 708. The sacrificial material block 60 may be planarized using a chemical mechanical polishing (CMP) method or other suitable IC planarization method.

[0045] In step 710, a conductive layer 52 is formed on the dielectric layer 40, as shown in FIG. 8B. Forming the conductive layer 52 may first include etching the dielectric layer 40 to form a channel within which the conductive material of the conductive layer 52 can be deposited. Forming the conductive layer 52 may further include etching one or more portions of the dielectric coating 56 of the preceding vertically adjacent resonator layer 22 to place the conductive layer 52 in electrical contact with the one or more conductive layers 52 of the preceding vertically adjacent resonator layer 22. In step 712, the dielectric layer 40, the conductive layer 52, and the sacrificial material block 60 are covered with the dielectric coating 56, as shown in FIG. 8B. In step 714, one or more portions of the dielectric coating 56 may be etched to form at least one FBAR opening 62 within which the FBAR material can then be deposited, as shown in FIG. 8C.

[0046] In step 716, as shown in FIG. 8C, an FBAR material stack 64 is disposed within each of the at least one FBAR openings 62 such that the FBAR material stack 64 is disposed on top of a sacrificial material block 60 disposed within a respective FBAR cavity 46 of the resonator layer 22. The FBAR material stack 64 may additionally be deposited in contact with the dielectric layer 40 and / or the conductive layer 52. The FBAR material stack 64 may be deposited, for example, using a CMOS-compatible deposition process. Non-limiting examples of CMOS-compatible deposition processes include, but are not limited to, low temperature sputter deposition or physical vapor deposition (PVD), low temperature molecular beam epitaxy (MBE), low temperature atomic layer deposition (ALD), or other chemical or physical deposition processes that may generally be performed below about 350° C. (about 662° F.). However, the temperature compatibility of CMOS devices is not limited to 350° C. For example, higher temperature deposition processes are acceptable if high temperature processing times are kept relatively short. High temperature deposition processes may typically require shorter processing times to prevent CMOS device performance and reliability issues. As previously described with respect to the multiple FBARs 36, the FBAR material stack 64 may also include a piezoelectric layer 48 and at least one conductive layer 50. In step 718, the FBAR material stack 64 of the resonator layer 22 is etched to form the FBARs 36 of the resonator layer 22.

[0047] Steps 702-718 may be repeated for each resonator layer 22 as necessary to sequentially fabricate multiple vertically stacked resonator layers 22 of the resonator assembly 20. FIGS. 8D-G illustrate the sequential fabrication of multiple resonator layers 22 in various successive stages. As the multiple resonator layers 22 are sequentially fabricated, the sacrificial material block 60 of each FBAR cavity 46 of each resonator layer 22 of the multiple resonator layers 22 contacts a vertically adjacent sacrificial material block 60 disposed within a vertically adjacent resonator layer 22 of the multiple resonator layers 22. For example, in the case of a resonator layer 22 fabricated after a first resonator layer 22, each sacrificial material block 60 may be deposited, at least in part, on top of a vertically adjacent sacrificial material block 60 from a preceding vertically adjacent resonator layer 22.

[0048] In step 720, as shown in FIG. 8H, upon completion of the sequential fabrication of the multiple resonator layers 22, a pad-out structure 58 of the resonator assembly 20 is fabricated. The pad-out structure 58 may be electrically connected to one or more of the multiple FBARs 36 to electrically connect the one or more filter networks 38 to an external electrical system or to subsequent layers or other features of the respective IC. The pad-out structure 58 may comprise aluminum (Al), titanium nitride (TiN), or any other suitable conductive material.

[0049] In step 722, the sacrificial material blocks 60 are removed from each FBAR cavity 46 of each resonator layer 22 of the plurality of resonator layers 22, as shown in FIG. 8H. For example, all of the sacrificial material blocks 60 of the resonator assembly 20 are removed from each FBAR cavity 46 adjacent to each FBAR 36 of the plurality of FBARs 36, thereby leaving the plurality of FBARs 36 suspended above their respective FBAR cavities 46 of the plurality of FBAR cavities 46 to complete the filter network 38. As described above, because each of the FBAR cavities 46 of each resonator layer 22 is vertically aligned with one or more FBAR cavities 46 of a vertically adjacent resonator layer 22 of each of the plurality of resonator layers 22, the removal of the sacrificial material can be performed for all of the sacrificial material blocks 60 of all of the resonator layers 22 of the plurality of resonator layers 22. Thus, aspects of the method 700 of the present disclosure allow for all of the FBAR cavities 46 to be formed in a single step (e.g., by removing the sacrificial material blocks 60). Removal of the sacrificial material block 60 from each FBAR cavity 46 may be accomplished using, for example, an etching process. For example, the resonator assembly 20 including the multiple resonator layers 22 may be exposed to an etching compound such as, but not limited to, xenon difluoride (XeF2), potassium hydroxide (KOH), high temperature hydrogen peroxide (H2O2), or oxygen (O2) plasma.

[0050] It should be noted that in the above description and drawings, various connections between multiple elements are shown. It should be noted that these connections are general and may be direct or indirect connections unless otherwise specified, and the specification is not intended to be limiting in this respect. A coupling between two or more entities may refer to a direct connection or an indirect connection. In the case of an indirect connection, one or more intervening entities may be incorporated. It should be further noted that various method or process steps of the embodiments of the present disclosure are described in the following description and drawings. In the description, the method and / or process steps may be presented in a specific order. However, the method or process should not be limited to the specific order of steps described, unless the method or process depends on the specific order of steps described herein. As will be appreciated by those skilled in the art, other orders of steps may be possible. Thus, the specific order of steps described in the description should not be construed as limiting.

[0051] Furthermore, no element, component, or method step of the present disclosure is intended to be publicly disclosed, regardless of whether the element, component, or method step is expressly recited in the claims. No claim element herein should be interpreted under 35 U.S.C. § 112(f) unless the element is expressly recited using the phrase "means for." As used herein, the terms "comprises," "comprising," or any other variation thereof, are intended to refer to a non-exclusive inclusion, such that a process, method, product, or apparatus that includes a list of elements may include not only those elements, but also other elements not expressly recited or other elements specific to such process, method, product, or apparatus.

[0052] Although various aspects of the disclosure have been disclosed, it will be apparent to one of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the disclosure. For example, the disclosure described herein includes several aspects and embodiments that include certain features. These specific features may be described individually, but are within the scope of the disclosure, and some or all of these features may be combined with any one of the aspects and remain within the scope of the disclosure. References to "various embodiments," "one embodiment," "embodiment," "exemplary embodiment," and the like indicate that the described embodiment may include a particular feature, structure, or characteristic, but not every embodiment necessarily includes the particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Furthermore, if a particular feature, structure, or characteristic is described in connection with an embodiment, it is believed to be within the knowledge of one of ordinary skill in the art that such feature, structure, or characteristic is used in connection with another embodiment, whether or not expressly described. Accordingly, the disclosure is not to be limited, except in light of the appended claims and their equivalents.

Claims

1. 1. A method for manufacturing a multi-layer resonator assembly, comprising: Sequentially fabricating a plurality of vertically stacked resonator layers, for each resonator layer of the plurality of resonator layers: depositing a dielectric layer; forming at least one thin film bulk acoustic resonator (FBAR) cavity in the deposited dielectric layer; filling each FBAR cavity of the at least one FBAR cavity with a sacrificial material block; and the sequential fabricating steps including depositing an FBAR material stack over the at least one FBAR cavity, the deposited FBAR material stack in contact with the sacrificial material block and the dielectric layer; and and removing the sacrificial material block from the at least one FBAR cavity of each resonator layer of the plurality of resonator layers after sequentially fabricating the plurality of resonator layers. method.

2. 10. The method of claim 1, wherein filling the at least one FBAR cavity with a sacrificial material block comprises depositing the sacrificial material block using one of chemical vapor deposition, physical vapor deposition, or atomic layer deposition.

3. The step of removing the sacrificial material block from the at least one FBAR cavity in each resonator layer of the plurality of resonator layers includes irradiating the plurality of resonator layers with xenon difluoride (XeF 2 ), potassium hydroxide (KOH), hydrogen peroxide (H 2 O 2 ), or oxygen (O 2 13. The method of claim 1, further comprising exposing the substrate to one of a plasma.

4. 2. The method of claim 1 , after fabricating the plurality of resonator layers and prior to removing the sacrificial material block from the at least one FBAR cavity of each resonator layer of the plurality of resonator layers, the sacrificial material block of the at least one FBAR cavity of each resonator layer of the plurality of resonator layers is in contact with a vertically adjacent sacrificial material block disposed within a vertically adjacent one of the plurality of resonator layers.

5. 10. The method of claim 1 , further comprising, for each resonator layer of the plurality of resonator layers, after filling each FBAR cavity of the at least one FBAR cavity with a sacrificial material block, planarizing the dielectric layer and the sacrificial material block within each FBAR cavity of the at least one FBAR cavity.

6. The method of claim 1 , further comprising forming one or more conductive layers on the dielectric layer for each resonator layer of the plurality of resonator layers.

7. 10. The method of claim 1 , further comprising, for each resonator layer of the plurality of resonator layers, depositing a dielectric coating on the dielectric layer and the sacrificial material block within each FBAR cavity of the at least one FBAR cavity after filling each FBAR cavity of the at least one FBAR cavity with a sacrificial material block and before depositing the FBAR material stack over the at least one FBAR cavity.

8. 8. The method of claim 7, further comprising, for each resonator layer of the plurality of resonator layers, removing one or more portions of the dielectric coating prior to depositing the FBAR material stack over the at least one FBAR cavity.

9. 10. The method of claim 1, wherein the deposited FBAR material stack includes a piezoelectric layer and at least one conductive layer.

10. 10. The method of claim 9, wherein the piezoelectric layer is sandwiched between an upper conductive layer of the at least one conductive layer and a lower conductive layer of the at least one conductive layer.

11. The method of claim 1 , wherein the sacrificial material block comprises one of amorphous silicon, polycrystalline silicon, tungsten, titanium nitride (TiN), or polyimide.

12. 1. A multi-layer resonator assembly comprising: A plurality of vertically stacked resonator layers including a plurality of thin film bulk acoustic resonators (FBARs), each resonator layer of the plurality of resonator layers comprising: a dielectric layer having an upper surface and a lower surface, the dielectric layer defining at least one FBAR cavity therein, the at least one FBAR cavity extending from the upper surface to the lower surface; at least one FBAR of the plurality of FBARs disposed on the top surface of the dielectric layer, each FBAR of the at least one FBAR extending across an FBAR cavity of the at least one FBAR cavity; each FBAR cavity of the at least one FBAR cavity of each resonator layer of the plurality of resonator layers is vertically aligned with a respective FBAR cavity of the at least one FBAR cavity of a vertically adjacent resonator layer of each of the plurality of resonator layers. Multilayer resonator assembly.

13. 13. The multi-layer resonator assembly of claim 12, further comprising a plurality of sacrificial material blocks, each sacrificial material block of the plurality of sacrificial material blocks disposed in a respective FBAR cavity of the at least one FBAR cavity of each resonator layer of the plurality of resonator layers.

14. 14. The multi-layer resonator assembly of claim 13, wherein each sacrificial material block of the plurality of sacrificial material blocks is in contact with a vertically adjacent sacrificial material block of the plurality of sacrificial material blocks of a vertically adjacent resonator layer of each of the plurality of resonator layers.

15. 14. The multi-layer resonator assembly of claim 13, wherein the plurality of sacrificial material blocks comprise one of amorphous silicon, polycrystalline silicon, tungsten, titanium nitride (TiN), or polyimide.

16. 13. The multi-layer resonator assembly of claim 12, wherein at least a portion of the FBARs of the plurality of FBARs are electrically connected to each other in a ladder configuration, the portion of the FBARs including a first sub-portion of FBARs disposed in a first resonator layer of the plurality of resonator layers and a second sub-portion of FBARs disposed in a second resonator layer of the plurality of resonator layers vertically adjacent to the first resonator layer.

17. 13. The multi-layer resonator assembly of claim 12, wherein at least a portion of the FBARs of the plurality of FBARs are electrically connected to each other in a lattice configuration, the portion of the FBARs including a first sub-portion of FBARs disposed in a first resonator layer of the plurality of resonator layers and a second sub-portion of FBARs disposed in a second resonator layer of the plurality of resonator layers vertically adjacent to the first resonator layer.

18. 13. The multi-layer resonator assembly of claim 12, wherein at least a portion of the FBARs of the plurality of FBARs are electrically connected to each other in a ladder lattice configuration, the portion of the FBARs including a first sub-portion of FBARs disposed in a first resonator layer of the plurality of resonator layers, a second sub-portion of FBARs disposed in a second resonator layer of the plurality of resonator layers vertically adjacent to the first resonator layer, and a third sub-portion of FBARs disposed in a third resonator layer of the plurality of resonator layers vertically adjacent to the second resonator layer.

19. 13. The multi-layer resonator assembly of claim 12, wherein one or more FBARs of the plurality of FBARs includes a piezoelectric layer sandwiched between an upper conductive layer and a lower conductive layer.

20. 13. The multi-layer resonator assembly of claim 12, further comprising a base layer disposed vertically adjacent to the plurality of resonator layers, the base layer comprising a high electron mobility transistor (HEMT).

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