Methods and structures for producing smooth electrodes and electrode structures with uniform smooth surfaces

Abstract

Resonator structures, as well as methods and structures for producing smooth electrodes and electrode structures having uniform smooth surfaces, are provided.

Description

[0001] Cross-reference to related applications

[0002] This application is related to and claims the benefit of the priority date of U.S. Provisional Application No. 63 / 478,567, filed on January 5, 2023, entitled “Methods And Structures For Generating Smooth Electrodes And Electrode Structures With A Uniformly Smooth Surface,” which is incorporated herein by reference in its entirety. Technical Field

[0003] The present invention relates to resonator structures and, more particularly, to methods and structures for producing smooth electrodes and electrode structures having uniformly smooth surfaces. Background Art

[0004] Acoustic wave devices utilize acoustic waves that propagate through or on the surface of a specific binding material, whereby any change in the characteristics of the propagation path affects the speed and / or amplitude of the wave. The presence of a functionalized material on or above the active area of the acoustic wave device allows the analyte to bind to the functionalized material, thereby changing the mass vibrated by the acoustic wave and changing the wave propagation characteristics (e.g., speed, thereby changing the resonant frequency). Changes in speed can be monitored by measuring the frequency or phase characteristics of the sensor and can be correlated with the physical quantity being measured.

[0005] Hexagonal piezoelectric materials, such as AlN and ZnO, are of commercial interest due to their piezoelectric and electroacoustic properties. Electroacoustic technology is primarily used in telecommunications (e.g., oscillators, filters, delay lines, etc.). Recently, there has been growing interest in using electroacoustic devices in high-frequency sensing applications due to the potential for high sensitivity, resolution, and reliability. However, in certain sensor applications, particularly those operating in liquid or viscous media (e.g., chemical and biochemical sensors), the application of electroacoustic technology is non-trivial, as longitudinal and surface waves exhibit significant acoustic leakage into such media, resulting in reduced resolution.

[0006] In the case of a piezoelectric crystal resonator, the acoustic waves can manifest as bulk acoustic waves (BAWs) that propagate through the interior (or "bulk") of the piezoelectric material, or surface acoustic waves (SAWs) that propagate on the surface of the piezoelectric material. SAW devices involve transducing acoustic waves (typically comprising two-dimensional Rayleigh waves) using interdigital transducers along the surface of the piezoelectric material, where the waves are confined to a penetration depth of approximately one wavelength.

[0007] BAW devices typically involve the use of electrodes arranged on opposing top and bottom surfaces of a piezoelectric material to transduce acoustic waves. In a BAW device, different vibration modes can propagate in the bulk material, including a longitudinal mode and two differently polarized shear modes, where the longitudinal and shear bulk modes propagate at different velocities. The longitudinal modes are characterized by compression and tension in the direction of propagation, while the shear modes consist of motion perpendicular to the direction of propagation with no local changes in volume. The propagation characteristics of these bulk modes depend on the material properties and propagation direction of the corresponding crystallographic axis orientations. Because shear waves exhibit very low penetration depths into liquids, devices with purely or predominantly shear modes can operate in liquids without significant radiation losses (compared to longitudinal waves, which can radiate in liquids and exhibit significant propagation losses). Reiterating, shear mode vibrations are advantageous for operating acoustic wave devices with fluids because the shear waves do not impart significant energy to the fluid.

[0008] Certain piezoelectric films are capable of exciting both longitudinal and shear mode resonances. To excite waves containing shear modes using standard sandwiched electrode configurations, the polarization axis in the piezoelectric film must typically be non-perpendicular to the film plane (e.g., tilted relative to the film plane). Hexagonal crystal structured piezoelectric materials such as (but not limited to) aluminum nitride (AlN) and zinc oxide (ZnO) tend to have their polarization axis (i.e., c-axis) perpendicular to the film plane because the (0001) plane typically has the lowest surface density and is thermodynamically preferred. Certain high-temperature (e.g., vapor phase epitaxy) processes can be used to grow c-axis tilted films, but providing full compatibility with microelectronic structures such as metal electrodes or traces requires low-temperature deposition processes (e.g., typically below about 300°C).

[0009] One consequence of the lack of c-axis tilt angle uniformity in the AlN film structure above the substrate is that if the AlN film-covered substrate is cut into individual chips, the individual chips will exhibit significant variations in c-axis tile angles and concomitant variations in acoustic wave propagation properties. Such variations in c-axis tile angles make it difficult to efficiently produce large numbers of resonator chips with consistent and repeatable performance.

[0010] Typically, BAW devices are manufactured using microelectromechanical systems (MEMS) manufacturing technology due to the need to provide micron-scale features suitable for facilitating high-frequency operation. In the context of biosensors, functionalized materials (e.g., specific binding materials; also referred to as bioactive probes or reagents) can be deposited on the sensor surface by various techniques, such as microarray spotting (also referred to as microarray printing). Functionalized materials that provide nonspecific binding utility (e.g., allowing the binding of molecules of various types or species) can also be used in certain situations, such as chemical sensing. A biosensor (biosensor or biological sensor) is an analytical device comprising a biological element that converts a biological reaction into an electrical signal. Certain biosensors involve a selective biochemical reaction between a specific binding material and a binding target (e.g., a molecule, protein, DNA, virus, bacteria, etc.), and the product of this specific binding reaction is converted into a measurable amount by a transducer. Other sensors can utilize nonspecific binding materials that can bind to various types or categories of molecules or other parts that may be present in a sample. The transduction method used with a biosensor can be based on various principles, such as electrochemistry, optics, electricity, acoustics, etc. Among them, acoustic transduction offers many potential advantages, such as real-time, label-free, low-cost, and high sensitivity. In the case of filters, BAW devices can be used in a wide range of applications, such as mobile products, radar systems, and communication systems, among other applications. BAW filters operate by converting electrical energy into acoustic or mechanical energy on piezoelectric materials. BAW filters can operate at high frequencies and are less sensitive to temperature than SAW filters. Furthermore, BAW filters offer superior performance and low insertion loss at higher frequency levels.

[0011] Fabricating a BAW resonator device may involve depositing an acoustic reflector on a substrate, followed by depositing a bottom-side electrode, then growing (e.g., via sputtering or other suitable methods) the piezoelectric material, and then depositing the top-side electrode. The piezoelectric material can be grown by chemical vapor deposition (CVD), reactive RF magnetron sputtering (e.g., sputtering Al ions in a nitrogen environment), and the like. These techniques can form layers of uniform thickness (e.g., forming a layer of piezoelectric material via sputtering), but some layers may have portions of varying heights, depending on the surface morphology of the underlying material deposition surface. For example, the bottom-side electrode may not cover the entire underlying acoustic reflector, such that the material deposition surface including the aforementioned layer above the substrate may include bottom-side electrode material that is slightly elevated relative to the top surface of the acoustic reflector. When a uniform thickness of piezoelectric material is applied above the material deposition surface, the portion of the piezoelectric material located above the bottom-side electrode will be elevated relative to other portions of the piezoelectric material that do not cover the bottom-side electrode.

[0012] Improved methods and systems for producing bulk films having a c-axis tilt have been described, wherein the c-axis tilt of the bulk layer is controlled primarily by controlling the deposition angle. For example, apparatus and methods for depositing seed and bulk layers having tilted c-axes are described in U.S. Patent Application Publication No. 2017 / 0110300, entitled “Deposition System for Growth of Inclined C-Axis Piezoelectric Material Structures”; U.S. Patent No. 10,574,204, entitled “Acoustic Resonator Structure with Inclined C-Axis Piezoelectric Bulk and Crystalline Seed Layers”; and U.S. Patent Application No. 10,063,210, entitled “Methods for Producing Piezoelectric Bulk and Crystalline Seed Layers of Different c-Axis Orientation Distributions.”

[0013] Further improvements are desired to provide, for example, one or more of the following: reduced initial surface roughness of the electrodes, reduced electrode rounding, increased surface uniformity of the electrode structures, enhanced detectability of the processes used to create the electrode structures, reduced short-range frequency variations, increased repeatability of resonator spurious content across the wafer, enhanced control over the crystal c-axis angle in the bulk material layer, improved properties such as mechanical quality factor and coupling coefficient; and improved manufacturing efficiency of the bulk material layer. Summary of the Invention

[0014] Aspects of the present disclosure relate to methods and structures for producing smooth electrodes and electrode structures having uniformly smooth surfaces.

[0015] In some aspects, a method for producing an electrode structure comprising one or more smooth electrodes includes producing one or more electrodes comprising an initial surface roughness on a first portion of a substrate. In some embodiments, the method includes producing a sacrificial cover cap on each of the one or more electrodes. In some embodiments, the method includes producing a planarization film on the substrate and on at least a portion of the sacrificial cover cap. In some embodiments, the method includes performing a first planarization procedure to remove at least a portion of the planarization film and at least a first portion of the sacrificial cover cap. In some embodiments, the method includes removing at least a second portion of the sacrificial cover cap to prepare the electrode for reducing the initial surface roughness. In some embodiments, the method includes performing a second planarization procedure to remove at least a third portion of the sacrificial cover cap and reduce the initial surface roughness of the one or more electrodes, thereby smoothing the one or more electrodes.

[0016] In some embodiments, the sacrificial cover comprises a C-bridge. In some embodiments, at least a portion of the C-bridge remains on the electrode structure after the second planarization process. In some embodiments, the C-bridge connects the one or more electrodes to an acoustic energy management layer embedded in the substrate.

[0017] In some embodiments, the sacrificial cap includes a bottom aluminum nitride layer disposed directly on the electrode, a tungsten layer disposed above the bottom aluminum nitride layer, and a top aluminum nitride layer disposed above the tungsten layer. In some embodiments, the first portion of the sacrificial cap removed using the first planarization procedure includes the top aluminum nitride layer and at least a first portion of the tungsten layer. In some embodiments, removing at least the second portion of the sacrificial cap includes removing at least the second portion of the tungsten layer using a wet or dry etch. In some embodiments, the dry etch includes a plasma etch, and the wet etch includes a solution-based etch. In some embodiments, the third portion of the sacrificial cap removed using the second planarization procedure includes at least the first portion of the bottom aluminum nitride layer.

[0018] In some embodiments, the one or more electrodes include a tungsten layer disposed above a layer comprising a metal, a metal alloy, or any combination thereof. In some embodiments, the metal is selected from the group consisting of tungsten (W), aluminum (Al), copper (Cu), titanium (Ti), molybdenum (Mo), platinum (Pt), ruthenium (Ru), iridium (Ir), and any combination thereof. In some embodiments, the metal alloy is an aluminum-copper (AlCu) alloy or a titanium-tungsten (TiW) alloy.

[0019] In some embodiments, the substrate includes a planarizing film. In some embodiments, the planarizing film includes silicon dioxide, TEOS, or any combination thereof. In some embodiments, a plurality of acoustic energy management layers are embedded in the substrate. In some embodiments, the plurality of acoustic energy management layers include a plurality of acoustic reflector layers. In some embodiments, the first planarizing procedure includes chemical mechanical polishing (CMP), or wherein the second planarizing procedure includes chemical mechanical polishing (CMP), or wherein the first planarizing procedure and the second planarizing procedure include chemical mechanical polishing (CMP). In some embodiments, the one or more electrodes are configured to deposit a piezoelectric material layer on a top surface of the one or more electrodes, the piezoelectric material layer including a c-axis having an orientation substantially perpendicular to the top surface of the one or more electrodes.

[0020] In some embodiments, producing the one or more electrodes comprises depositing the one or more electrodes, patterning the one or more electrodes, or any combination thereof. In some embodiments, producing the sacrificial cap on each of the one or more electrodes comprises depositing the sacrificial cap, patterning the sacrificial cap, or any combination thereof. In some embodiments, producing the planarization film comprises depositing the planarization film on the substrate, patterning the planarization film, or any combination thereof. In some embodiments, patterning comprises performing a photolithography process, an etching process, or any combination thereof.

[0021] In some aspects, a method for producing an electrode structure comprising a uniform smooth surface includes producing one or more electrodes on a first portion of a substrate, wherein each of the one or more electrodes comprises an initial surface roughness. In some embodiments, the method includes producing a sacrificial cover cap on each of the one or more electrodes. In some embodiments, the method includes producing a planarization film on the substrate and on at least a portion of the sacrificial cover cap. In some embodiments, the method includes performing a first planarization procedure to remove at least a portion of the planarization film and at least a first portion of the sacrificial cover cap, wherein the sacrificial cover cap maintains the uniformity of the surface of the electrode structure during the first planarization procedure. In some embodiments, the method includes removing at least a second portion of the sacrificial cover cap to prepare the electrode for reducing the initial surface roughness. In some embodiments, the method includes performing a second planarization procedure to remove at least a third portion of the sacrificial cover cap and reduce the initial surface roughness of each of the one or more electrodes, thereby producing an electrode structure comprising a uniform smooth surface.

[0022] In some embodiments, the method further includes depositing a layer of piezoelectric material onto the top surface of the one or more electrodes, the piezoelectric material layer including a c-axis having an orientation substantially perpendicular to the top surface of each of the one or more electrodes. In some embodiments, the sacrificial cover includes a c-bridge. In some embodiments, at least a portion of the c-bridge remains on the structure after performing the second planarization procedure. In some embodiments, the c-bridge connects the one or more electrodes to an acoustic energy management layer embedded in the substrate. In some embodiments, the piezoelectric material layer includes a seed layer and a main material layer. In some embodiments, depositing the piezoelectric material layer includes depositing the seed layer onto the top surface of each of the one or more electrodes before depositing the main material layer. In some embodiments, the piezoelectric material layer includes a material selected from the group consisting of: AlN, ScAlN, ZnO, PZT, and any combination thereof.

[0023] In some embodiments, the sacrificial cap includes a bottom aluminum nitride layer disposed directly on the electrode, a tungsten layer disposed above the bottom aluminum nitride layer, and a top aluminum nitride layer disposed above the tungsten layer. In some embodiments, the first portion of the sacrificial cap removed using the first planarization process includes a first portion of the top aluminum nitride layer and at least a first portion of the tungsten layer.

[0024] In some embodiments, removing the second portion of the sacrificial cap comprises removing the second portion of the tungsten layer using a wet or dry etch. In some embodiments, the dry etch comprises a plasma etch, and the wet etch comprises a solution-based etch. In some embodiments, the third portion of the sacrificial cap removed using the second planarization procedure comprises at least a first portion of the bottom aluminum nitride layer.

[0025] In some embodiments, each of the one or more electrodes comprises a tungsten layer disposed over a layer comprising a metal, a metal alloy, or any combination thereof. In some embodiments, the metal is selected from the group consisting of tungsten (W), aluminum (Al), copper (Cu), titanium (Ti), molybdenum (Mo), platinum (Pt), ruthenium (Ru), iridium (Ir), and any combination thereof. In some embodiments, the metal alloy is an aluminum-copper (AlCu) alloy or a titanium-tungsten (TiW) alloy.

[0026] In some embodiments, the substrate includes a planarization film. In some embodiments, the planarization film includes silicon dioxide, TEOS, or any combination thereof. In some embodiments, multiple acoustic energy management layers are embedded in the substrate. In some embodiments, the multiple acoustic energy management layers include multiple acoustic reflector layers. In some embodiments, the multiple acoustic reflector layers include tungsten, silicon dioxide, aluminum-copper alloy, or any combination thereof.

[0027] In some embodiments, the first planarization process comprises chemical mechanical polishing (CMP), or the second planarization process comprises chemical mechanical polishing (CMP), or the first planarization process and the second planarization process comprise chemical mechanical polishing (CMP). In some embodiments, generating one or more electrodes comprises depositing the one or more electrodes, patterning the one or more electrodes, or any combination thereof. In some embodiments, generating the sacrificial cap on each of the one or more electrodes comprises depositing the sacrificial cap, patterning the sacrificial cap, or any combination thereof.

[0028] In some embodiments, generating the planarization film comprises depositing the planarization film on the substrate, patterning the planarization film, or any combination thereof. In some embodiments, patterning comprises performing a photolithography process, an etching process, or any combination thereof.

[0029] In some aspects, a protected structure for producing an electrode structure comprising a uniformly smooth surface comprises a substrate, one or more electrodes disposed on at least a portion of the substrate, and a sacrificial cover disposed on each of the one or more electrodes, wherein the sacrificial cover comprises a c-bridge.

[0030] In some embodiments, the C-bridge connects the one or more electrodes to an acoustic energy management layer embedded in the substrate. In some embodiments, the sacrificial cap includes a bottom aluminum nitride layer disposed directly on the electrodes, a tungsten layer disposed above the bottom aluminum nitride layer, and a top aluminum nitride layer disposed above the tungsten layer.

[0031] In some embodiments, the one or more electrodes include a tungsten layer disposed above a layer comprising a metal, a metal alloy, or any combination thereof. In some embodiments, the metal is selected from the group consisting of tungsten (W), aluminum (Al), copper (Cu), titanium (Ti), molybdenum (Mo), platinum (Pt), ruthenium (Ru), iridium (Ir), and any combination thereof. In some embodiments, the metal alloy is an aluminum-copper (AlCu) alloy or a titanium-tungsten (TiW) alloy.

[0032] In some embodiments, the substrate includes a planarization film. In some embodiments, the planarization film includes silicon dioxide, TEOS, or any combination thereof. In some embodiments, multiple acoustic energy management layers are embedded in the substrate. In some embodiments, the multiple acoustic energy management layers include multiple acoustic reflector layers. In some embodiments, the multiple acoustic reflector layers include tungsten, silicon dioxide, aluminum-copper alloy, or any combination thereof.

[0033] In some aspects, an electrode structure comprising a uniformly smooth surface comprises: a substrate; a planarization film disposed on the substrate, the planarization film comprising an upper surface; and one or more electrodes disposed on the substrate, wherein a sacrificial cover on each of the one or more electrodes maintains the uniformity of the surface of the electrode structure during a first planarization process, and wherein the one or more electrodes and the upper surface of the planarization film are smoothed by a second planarization process.

[0034] In some embodiments, the sacrificial cover comprises a C-bridge. In some embodiments, the electrode structure further comprises at least a portion of the C-bridge. In some embodiments, the one or more electrodes comprise a tungsten layer disposed above a layer comprising a metal, a metal alloy, or any combination thereof. In some embodiments, the metal is selected from the group consisting of tungsten (W), aluminum (Al), copper (Cu), titanium (Ti), molybdenum (Mo), platinum (Pt), ruthenium (Ru), iridium (Ir), and any combination thereof. In some embodiments, the metal alloy is an aluminum-copper (AlCu) alloy or a titanium-tungsten (TiW) alloy.

[0035] In some embodiments, the substrate includes a planarization film. In some embodiments, the planarization film includes silicon dioxide, TEOS, or any combination thereof. In some embodiments, multiple acoustic energy management layers are embedded in the substrate. In some embodiments, the multiple acoustic energy management layers include multiple acoustic reflector layers. In some embodiments, the multiple acoustic reflector layers include tungsten, silicon dioxide, aluminum-copper alloy, or any combination thereof.

[0036] In some aspects, a piezoelectric structure with increased surface uniformity includes an electrode structure described herein and a piezoelectric material layer disposed on a top surface of the one or more electrodes, the piezoelectric material layer including a c-axis having an orientation substantially perpendicular to the top surface of each of the one or more electrodes.

[0037] In some embodiments, the piezoelectric material layer includes a seed layer and a host material layer. In some embodiments, the piezoelectric material layer includes a material selected from the group consisting of: AlN, ScAlN, ZnO, PZT, and any combination thereof.

[0038] These and other aspects are further explained in the remainder of this disclosure, including the examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 and Figure 2 Schematic cross-sectional view of a protected structure for producing an electrode structure with a uniformly smooth surface.

[0040] Figure 3 After performing a first planarization process to remove at least a portion of the planarization film and at least a first portion of the sacrificial cover Figure 2 Schematic cross-section of a protected structure.

[0041] Figure 4 is a schematic cross-sectional view of an electrode structure including a smooth electrode with reduced surface roughness configured for depositing an on-axis piezoelectric material layer after performing a second planarization procedure.

[0042] Figure 5 is a schematic illustration of a method for producing an electrode structure comprising one or more smooth electrodes.

[0043] Figure 6 1 is an upper external perspective view of a reactor 600 of a deposition system for growing a hexagonal crystal structure piezoelectric material having a c-axis oriented substantially perpendicular to one or more electrodes, the system comprising a linear sputtering apparatus, a movable substrate stage for supporting multiple substrates, and a collimator.

[0044] Figure 7 for Figure 6 A top perspective view of some elements of a reactor including a linear sputtering apparatus, a translation track for translating a movable substrate stage for supporting a plurality of substrates, and a collimator.

[0045] Figures 8A to 8C Schematic cross-sectional view of a process for depositing a piezoelectric material layer including on-axis tilt onto the top surface of an electrode.

[0046] Figure 8D Schematic illustration of a piezoelectric structure after deposition of a layer of piezoelectric material including an on-axis tilt.

[0047] Figures 9A to 9C is a schematic cross-sectional view of a process for depositing a piezoelectric material layer onto the top surface of an electrode, the piezoelectric material layer comprising a seed layer with an on-axis tilt and a host material layer.

[0048] Figure 9D Schematic illustration of a piezoelectric structure after deposition of a layer of piezoelectric material including an on-axis tilt.

[0049] Figure 10 is a schematic illustration of a method for producing an electrode structure comprising a uniformly smooth surface.

[0050] Figure 11 is the shear coupling coefficient (K) that varies with the c-axis tilt angle of AlN s ) and longitudinal coupling coefficient (K l ) curve graph.

[0051] Figure 12 Two box plots are shown, each with the short-range frequency change (MHz) shown on the y-axis. The box plot on the left is the short-range frequency change of a device using previously known techniques, while the box plot on the right is the short-range frequency change of a device using the methods and structures described herein (right side). The x-axis lists the number of devices tested to obtain the data for each box plot.

[0052] Figure 13A is a true cross-sectional view of the protected structure after a first planarization process is performed to remove at least a portion of the planarization film and at least a first portion of the sacrificial cover.

[0053] Figure 13B is an actual cross-sectional view of the electrode structure after removing at least a second portion of the sacrificial cover to prepare the electrode for reducing the initial surface roughness.

[0054] Figure 13C FIG. 1 is a true cross-sectional view of the electrode structure after a second planarization process is performed to remove at least a third portion of the sacrificial cap and reduce the initial surface roughness of the electrode, thereby smoothing the electrode.

[0055] Figure 14 is a true cross-sectional view of an electrode structure produced using an electrode exhibiting a rounded electrode structure.

[0056] Figure 15 are actual cross-sectional views of electrode structures produced using the methods and structures described herein, having uniformly smooth surfaces and smooth electrodes exhibiting reduced rounding.

[0057] Figure 16 Schematic illustration of the axes of a hexagonal system. DETAILED DESCRIPTION

[0058] Unless otherwise indicated, the practice of the present invention will adopt conventional techniques of silicon fabrication in the field of biosensors. Such techniques are fully explained in the literature, such as "Acoustic-Based Biosensors" (Durmus et al., 2014); "Recent Advances in Acoustic Wave Biosensors for the Detection of Disease-related Biomarkers: A review" (Zhang et al., 2021); and "Acoustic Biosensors and Microfluidic Devices in the Decennium: Principles and Applications" (Nair et al., 2021).

[0059] When a range of values is provided, it is understood that the invention encompasses every intervening value between the upper and lower limits of that range (to the tenth of the unit of the lower limit unless the context clearly indicates otherwise) and any other stated or intervening value in that stated range. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges and are also encompassed within the invention, subject to any specifically excluded limits in the stated range. When the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also encompassed within the invention.

[0060] In the following description, numerous specific details are set forth to provide a more thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention can be practiced without one or more of these specific details. In other instances, well-known features and procedures well known to one skilled in the art have not been described to avoid obscuring the present invention.

[0061] All references cited throughout this disclosure, including patent applications and publications, are hereby incorporated by reference in their entirety.

[0062] I. definition

[0063] "Comprising" means that the recited elements are required in the composition / method / kit etc., but other elements may also be included to form a composition / method / kit etc. within the scope of the claim.

[0064] "Consisting essentially of" means limiting the scope of a described composition or method to specified materials or steps that do not materially affect the basic and novel characteristics of the invention.

[0065] "Consisting of" means removing from the composition, method or kit any elements, steps or ingredients not specified in the claims.

[0066] "Angle of incidence" means the angle at which particles are deposited onto a substrate, measured as the angle between the deposition path and the normal to the substrate surface plane.

[0067] "Substrate" means a material on which a seed layer or a bulk material layer may be deposited. The substrate may be, for example, a wafer, or may be a portion of a resonator device composite or wafer, which may also include other components, such as an electrode structure disposed over at least a portion of the substrate. In the examples of the present disclosure, the seed layer is not considered a "substrate."

[0068] Depositing the crystal "on a substrate" means that there may be intervening layers (eg, a seed layer) between the substrate and the crystal. However, the expression "directly on the substrate" or "on the surface of the substrate" is intended to exclude any intervening layers.

[0069] "Piezoelectric material layer" means a portion of a bulk material layer, a bulk material layer, a seed layer and a portion of a bulk material layer, or the seed layer and the bulk material layer, or any combination thereof.

[0070] "Pre-seed layer" means a layer deposited before the seed layer and which may be used to control at least one property of the seed layer formed thereon.

[0071] "Seed layer" means a layer upon which a layer of bulk material may be deposited.

[0072] "Body material layer" or "body layer" means a crystalline layer deposited on an electrode or a seed layer. The body material layer can be formed in one or more steps.

[0073] "c-axis" means the crystal growth direction that originates from the same origin as the "a" axis and is perpendicular to the plane of the "a" axis of the hexagonal system, such as Figure 12 The c-axis is usually the longitudinal axis of the crystal.

[0074] "C-axis tilt," "c-axis orientation," or "c-axis inclination" means the angle of the c-axis relative to the normal to the top surface of the electrode, e.g. Figure 8A , as angle alpha (α). It will be appreciated that even given a single angle value, the crystals in a deposited crystal layer (e.g., a seed layer or a layer of a bulk material) may exhibit a distribution of angles. The distribution of angles generally follows approximately a normal (e.g., Gaussian) distribution that can be displayed graphically, for example, as a two-dimensional graph similar to a bell curve or by a bar graph.

[0075] As defined herein, "on-axis" or "on-axis tilt" means a c-axis tilt, c-axis orientation, or c-axis inclination that is substantially perpendicular to the top surface of the electrode.

[0076] "Off-axis" or "off-axis tilt" means a c-axis tilt, c-axis orientation, or c-axis inclination that is not substantially perpendicular to the top surface of the electrode, as defined herein.

[0077] "Perpendicular" and "substantially perpendicular" relative to the orientation, tilt or inclination of the c-axis of the electrode means that the c-axis of the deposited crystal is substantially perpendicular to the top surface of the electrode.

[0078] "Substantially" means the same as "almost entirely" and can be understood to modify the subsequent term by at least about 90%, at least about 95%, or at least about 98%.

[0079] "Parallel" and "substantially parallel" with respect to the resulting piezoelectric material layer crystals mean that the resulting piezoelectric material layer crystals have the same or similar c-axis tilts.

[0080] “Electrode structure” means a structure in which at least one electrode is disposed on a substrate but no piezoelectric material is disposed thereon.

[0081] "Piezoelectric structure" means a structure in which an electrode structure has a piezoelectric material disposed thereon.

[0082] A “sacrificial cover” is understood to mean a material or a combination of materials disposed on an electrode that maintains the uniformity of the electrode and / or the surface uniformity of the electrode structure.

[0083] The “first planarization process” means a process of removing at least a portion of the planarization film and / or at least a portion of the sacrificial cover.

[0084] The “second planarization process” means a process of reducing the initial surface roughness of each of the one or more electrodes.

[0085] "Functionalized materials" are meant generally in relation to both specific and nonspecific binding materials.

[0086] “About” used in connection with a numerical value is meant to include the normal variation in measurements as would be expected by one skilled in the art and should be understood to have the same meaning as “substantially” and encompass the typical margin of error, eg, ±5% of the stated value.

[0087] Unless otherwise specified, all scientific and technical terms used herein have the meanings commonly used in the art. The definitions provided herein are to aid in understanding certain terms frequently used herein and are not intended to limit the scope of the present disclosure.

[0088] As used herein, the singular forms "a," "an," and "the" encompass instances having plural referents unless the context clearly dictates otherwise.

[0089] As used herein, the term "or" is generally used in its general sense including "and / or" unless the context clearly dictates otherwise. The term "and / or" means one or all of the listed elements or a combination of any two or more of the listed elements.

[0090] As used herein, “have,” “having,” “include,” “including,” “comprise,” “comprising,” and the like are used in their open sense and generally mean “including, but not limited to.” It is understood that “consisting essentially of,” “consisting of,” and the like are encompassed by “comprising,” and the like. As used herein, “consisting essentially of,” as it relates to a composition, product, method, or the like, means that the components of the composition, product, method, or the like are limited to the listed components and any other components that do not materially affect the basic and novel characteristics of the composition, product, method, and the like.

[0091] The words "preferred" and "preferably" refer to embodiments of the invention that may offer certain benefits under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not applicable, and is not intended to exclude other embodiments from the scope of the present disclosure (including the claims).

[0092] The recitation of numerical ranges by endpoints includes all numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.8, 4, 5, etc., or 10 or less includes 10, 9.4, 7.6, 4.3, 2.9, 1.62, 0.3, etc.) When a range of values is stated "up to" a particular value, that value is included in that range.

[0093] Any directions referred to herein, such as "top," "bottom," "left," "right," "upper," "lower," and other directions and orientations, are described herein for clarity with reference to the figures and are not intended to limit the actual device or system or use of the device or system. A device or system as described herein can be used in many directions and orientations.

[0094] II. Detailed description

[0095] The present disclosure provides methods and structures for producing smooth electrodes and electrode structures with uniformly smooth surfaces. Compared to conventional resonator structures, manufacturing methods, and deposition systems, various embodiments of the present disclosure reduce initial surface roughness of electrodes, reduce electrode rounding, increase surface uniformity of electrode structures, reduce short-range frequency variations, improve resonator spurious content repeatability across wafers, enhance control of the crystal c-axis angle in the bulk material layer, improve properties such as mechanical quality factor and coupling coefficient, and improve bulk material layer manufacturing efficiency.

[0096] The examples and embodiments described herein may be used, for example, with the methods and devices described in, for example, U.S. Patent No. 11,369,960 to Rivas et al. (filed May 6, 2020), entitled “Acoustic Resonator Device”; U.S. Patent No. 10,063,210 to McCarron et al. (filed October 13, 2016), entitled “Methods for Producing Piezoelectric Bulk and Crystalline Seed Layers of Different c-Axis Orientation Distributions”; and U.S. Patent No. 10,541,663 to McCarron et al. (filed October 13, 2016), entitled “Multi-Stage Deposition System for Growth of Inclined C-Axis Piezoelectric Material Structures.” All of the above U.S. patents are incorporated herein by reference in their entirety.

[0097] Figures 1 to 4 The various stages of a method for producing an electrode structure comprising one or more smooth electrodes and a uniformly smooth surface are presented. In particular, Figure 1 and 2 Protected structures 101 and 102 are shown for producing an electrode structure comprising one or more smooth electrodes and a uniformly smooth surface. Figure 3 The first planarization process is performed to remove at least a portion of the planarization film and at least a first portion of the sacrificial cover 150. Figure 1 and 2 The resulting structure 103 of structures 101 and 102. Figure 4An electrode structure 104 having a uniform smooth surface is shown, comprising an electrode having a smooth surface. Figure 5 Steps are shown for producing an electrode structure comprising one or more smooth electrodes (eg, where the original surface roughness has been reduced).

[0098] In some examples, the acoustic resonator structure is prepared in a deposition system, and at least one wafer including the substrate 100 is received by a support surface (not shown).

[0099] electrode

[0100] Aspects of the present invention include electrode structures that can be used in conjunction with the methods and systems described herein. One or more electrodes 110 can be generated on a first portion of a substrate 100. Generating the electrodes 110 can include depositing electrodes, patterning electrodes, or any combination thereof. One or more electrodes 110 can include an initial surface roughness. The initial surface roughness of the electrodes 110 can be the same or can be changed during generation. In some embodiments, the electrode 110 includes a tungsten layer disposed above a layer comprising a metal, a metal alloy, or any combination thereof. For example, the electrode material can include W, Al, Cu, AlCu, Mo, Pt, Ru, Ti, TiW, and / or Ir. It should be understood that an aluminum-copper (AlCu) alloy can be any alloy comprising aluminum and copper in different ratios. Similarly, any alloy mentioned or described can include the included metals in different ratios.

[0101] In a preferred embodiment, the electrode 110 is a bottom electrode in a set of top and bottom electrodes of an acoustic resonator device. The electrode 110 can be produced so that it is configured for depositing a piezoelectric material layer including an on-axis tilt on the top surface of the electrode. This will be discussed below with respect to Figures 8A to 8D as well as Figures 9A to 9D Describe in further detail.

[0102] substrate

[0103] Aspects of the present invention include substrates that can be used in conjunction with the methods and systems described herein. A substrate 100 can be received by a support surface and include a planarization film 120. In other examples, the planarization film 120 is produced on the substrate 100. Producing the planarization film 120 on the substrate 100 can include depositing the planarization film, patterning the planarization film, or any combination thereof. The planarization film can include silicon, silicon dioxide, or any other semiconductor material, as well as any other suitable material that can be used in semiconductor manufacturing processes.

[0104] In some embodiments, substrate 100 includes one or more acoustic energy management layers 130 embedded below electrode 110 and above the upper surface of substrate 100. In some embodiments, acoustic energy management layer 130 may be embedded in planarization film 120 of substrate 100 or embedded within planarization film 120 formed on substrate 100. In some embodiments, acoustic energy management layer 130 may include one or more acoustic reflector layers 140. For example, in some embodiments, there are seven acoustic reflector layers. In some embodiments, there may be two or five acoustic reflector layers, for example. The number of acoustic reflector layers and energy management layer may vary depending on the application. Acoustic reflector layer 140 may include W, SiO2, and / or AlCu. Acoustic reflector layer 140 serves to reflect acoustic waves and, thereby, reduce or prevent their dissipation within substrate 100. In some embodiments, acoustic reflector layer 140 is a Bragg reflector.

[0105] In other embodiments, substrate 100 may define one or more recesses (not shown), with a support layer disposed above the recesses. The recesses may serve a similar purpose as acoustic reflector layer 140, namely, reflecting sound waves and reducing or preventing their dissipation within substrate 100. It should be understood that while the acoustic reflector layer and the recesses have similar purposes, they may be implemented separately or together.

[0106] The examples and embodiments described herein may be used, for example, with the structures and methods described in the following U.S. patent application publication: U.S. patent application publication No. 2022 / 0274104 to Rivas et al. (filed on May 19, 2022), entitled “Acoustic Resonator Device,” which is incorporated herein by reference in its entirety.

[0107] Sacrificial cover

[0108] Aspects of the present invention include one or more sacrificial caps that can be used in conjunction with the methods and systems described herein. In some embodiments, a sacrificial cap 150 is generated on each of the one or more electrodes 110. Generating the sacrificial cap 150 on the electrode 110 can include depositing the sacrificial cap, patterning the sacrificial cap, or any combination thereof. The sacrificial cap 150 can maintain the uniformity of the electrode 110, maintain the uniformity of the electrode structures 101-104, prepare the electrode 110 for reducing initial surface roughness and reducing rounding, as well as other features described herein.

[0109] In some embodiments, sacrificial cap 150 may include a bottom aluminum nitride layer disposed directly on electrode 110, a tungsten layer disposed above the bottom aluminum nitride layer, and a top aluminum nitride layer disposed above the tungsten layer. In some embodiments, the top aluminum nitride layer may serve as an etch stop during the planarization film patterning. In some embodiments, the bottom aluminum nitride layer may protect electrode 110 during the removal of the tungsten layer. The desired thickness of the tungsten layer may vary depending on the thickness of the aluminum nitride layer and the planarization process used. Ensuring that the tungsten layer of sacrificial cap 150 is at least a minimum thickness ensures that the sacrificial cap 150 is not penetrated during the first planarization process. If the sacrificial cap 150 is penetrated during the first planarization process, the surface uniformity of the electrode and electrode structure may not be maintained. In some embodiments, the minimum thickness of the tungsten layer of sacrificial cap 150 ranges from 200 angstroms to 2000 angstroms, for example, approximately 250 angstroms, 500 angstroms, 750 angstroms, 1000 angstroms, 1250 angstroms, 1500 angstroms, or 1750 angstroms.

[0110] In some embodiments, the sacrificial cover may include a c-bridge 190. The c-bridge may connect one or more electrodes to the acoustic energy management layer 130 embedded in the substrate. Connecting the c-bridge of one or more electrodes to the acoustic energy management layer 130 can reduce the resistance of the material by placing two resistors in parallel. The examples and embodiments described herein can be used, for example, with the methods and devices described in the following U.S. patent application publication: U.S. Patent Application Publication No. 2022 / 0131521 to Yusuf et al. (filed on February 16, 2022), entitled "Bulk Acoustic Wave Filter Structure with Conductive Bridge Forming Electrical Loopwith an Electrode", which is incorporated herein by reference in its entirety.

[0111] planarization film

[0112] Aspects of the present invention include planarization films that can be used in conjunction with the methods and systems described herein. Figure 1 In FIG. 1 , the planarization film 120 has been produced on the substrate 100 , but has not yet been produced on a portion of the sacrificial cap 150 . Figure 2The planarizing film 120 is shown produced on at least a portion of the substrate and the sacrificial cover cap 150. Producing the planarizing film 120 on at least a portion of the sacrificial cover cap 150 can occur simultaneously with producing the planarizing film 120 on the substrate 100. Alternatively, the planarizing film 120 can be produced on the sacrificial cover cap 150 after producing the planarizing film 120 on the substrate 100. In still other embodiments, the planarizing film 120 and the sacrificial cover cap 150 are both part of the substrate 100 when the substrate is received by the support surface.

[0113] exist Figure 2 In the embodiment of the present invention, a planarization film 120 is formed on at least a portion of the substrate 100 and the sacrificial cap 150. When the planarization film 120 is formed (which may include silicon dioxide or tetraethyl orthosilicate (TEOS; tetraethoxysilane), as well as other materials and combinations), a TEOS opening 160 may be formed. The TEOS opening 160 may be formed using an etching process, such as a dry etching process. The width of the TEOS opening 160 may range from about 10 μm to about 1000 μm, for example, about 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, or 900 μm. In addition, in some embodiments, a TEOS fence 170 may be formed. In some embodiments, the TEOS fence 170 may be formed by patterning the planarization film and etching partially over the bottom electrode using a photolithography and / or etching process. In some embodiments, the pits may be generated due to the surface morphology of the incoming substrate. The width of the TEOS fence 170 can range from about 100 nm to about 5000 nm (5 μm), for example, about 500 nm, 1000 nm, 1500 nm, 2000 nm, 2500 nm, 3000 nm, 3500 nm, 4000 nm, or 4500 nm. In some embodiments, the intermediate opening 180 between the sacrificial caps can be naturally formed. In some embodiments, the TEOS fence corners promote the effectiveness of planarization processes such as chemical mechanical polishing (CMP). Non-limiting examples of planarization processes are described herein.

[0114] First planarization process

[0115] Aspects of the present invention include one or more first planarization processes that can be used in conjunction with the methods and systems described herein. In some embodiments, the first planarization process can be used to planarize substrate 100, planarizing film 120, and / or sacrificial cap 150 to a desired level. The desired level can be a level within the sacrificial cap, such that the sacrificial cap is configured to be removed by one or more subsequent etching processes. The first planarization process can also be used to remove a portion of sacrificial cap 150 while promoting uniformity of the planarizing film 120, electrode 110, and electrode structure on substrate 100.

[0116] Figure 3 The first planarization process is performed to remove at least a portion of the planarization film 120 and at least a first portion of the sacrificial cover 150. Figure 2 Sometimes, the first planarization process has a target stop level within the sacrificial cap 150 or within a specific layer of the sacrificial cap 150 (e.g., a tungsten layer). During the first planarization process, the sacrificial cap 150 maintains the uniformity of the electrode and the surface uniformity of the electrode structure. In some embodiments, at least the first portion of the sacrificial cap 150 removed using the first planarization process includes the top aluminum nitride layer and at least a first portion of the tungsten layer.

[0117] During the first planarization procedure, the material of the planarization film 120 and the sacrificial cap 150 may be removed at different rates, depending on the materials used and the type of first planarization procedure used. For example, an aluminum nitride layer may degrade faster than a tungsten layer. A planarization film 120 comprising silicon dioxide may degrade faster than the aluminum nitride layer of the sacrificial cap 150. The different rates at which material is removed during the first planarization procedure indicate the accuracy with which the first planarization procedure can be performed. For example, in some embodiments, at least a portion of the sacrificial cap 150, such as the tungsten layer, may be removed at a much lower rate than the rate at which the planarization film 120 is removed. The different rates of removal ensure that the sacrificial cap 150 withstands the first planarization procedure and protects the electrode, preparing it for removal of the initial surface roughness. A non-limiting example of a first planarization procedure is chemical mechanical polishing (CMP). Other forms of first planarization procedures are also contemplated.

[0118] Remove the second portion of the sacrificial cover

[0119] As summarized above, in order to maintain uniformity of the surface of the electrode and electrode structure, a sacrificial cap 150 is employed. After removing at least a portion of the planarizing film 120 and at least a first portion of the sacrificial cap 150 during the first planarization process, a second portion of the sacrificial cap 150 can be removed to prepare the electrode 110 for reducing the initial surface roughness.

[0120] Removing the second portion of the sacrificial cap 150 to prepare the electrode 110 for reducing the initial surface roughness may include using wet or dry etching, or both. In some embodiments, where the sacrificial cap 150 prior to the first planarization process includes a bottom aluminum nitride layer, a tungsten layer, and a top aluminum nitride layer, the second portion of the sacrificial cap 150 is removed by removing the tungsten layer using wet or dry etching. In some embodiments, the bottom aluminum nitride layer may also be removed using wet or dry etching. In some examples, a wet, solution-based chemical etch is used to remove the aluminum nitride layer of the sacrificial cap 150, while a dry chemical etch is used to remove the tungsten layer of the sacrificial cap 150.

[0121] During the first planarization process, the sacrificial cap maintains uniformity of the electrode 110, increases uniformity of the surface of the electrode structure 101, and reduces rounding of the electrode 110. A second portion of the sacrificial cap is removed in a manner that prepares the electrode 110 for reducing the initial surface roughness while continuing to maintain uniformity of the electrode 110, maintain surface uniformity of the electrode structure, and reduce rounding of the electrode 110. After preparing the electrode 110 for reducing the initial surface roughness, a second planarization process may occur.

[0122] Second planarization process

[0123] Aspects of the present invention include a second planarization process that can be used in conjunction with the methods and systems described herein. In some embodiments, the second planarization process can be used to remove at least a third portion of the sacrificial cap 150 and reduce the initial surface roughness (smoothing and repairing) of the electrode 110 and the electrode structure including the planarization film 120, thereby configuring the electrode for deposition of a piezoelectric material layer. The second planarization process can include chemical mechanical polishing (CMP), among other processes. After the first, second, or third portion of the sacrificial cap 150 has been removed and / or after the second planarization process has been performed, at least a portion of the c-bridge 190 can remain on the electrode structure, thereby improving the ability to detect the electrode structure production process used. The second planarization process reduces the initial surface roughness of the electrode, resulting in a smooth electrode configured for deposition of a piezoelectric material layer onto the top surface of one or more electrodes. The smooth electrode can be particularly suitable for depositing a piezoelectric material layer that includes a c-axis oriented substantially perpendicular to the top surface of each of the one or more electrodes. Figure 4 An electrode structure is presented that includes a smooth electrode with reduced surface roughness configured for depositing an on-axis piezoelectric material layer after performing a second planarization procedure.

[0124] Aspects of the present invention include methods for producing an electrode structure comprising one or more smooth electrodes using a series of steps, such as e.g. Figure 5 As shown in . Figure 5The steps of a process 500 for producing an electrode structure comprising one or more smooth electrodes (i.e., wherein the initial surface roughness has been reduced) are shown. In step 510, one or more electrodes may be produced on a substrate, the one or more electrodes comprising an initial surface roughness. The one or more electrodes may be produced on a portion of the substrate. In step 520, a sacrificial cap is produced on the one or more electrodes. The sacrificial cap may include a C-bridge. Producing the sacrificial cap may include depositing the sacrificial cap, patterning the sacrificial cap, or any combination thereof. In step 530, a planarizing film may be produced on the substrate and on at least a portion of the sacrificial cap. In step 540, a first planarizing process may be performed to remove at least a portion of the planarizing film and at least a first portion of the sacrificial cap. The first planarizing process may be a chemical mechanical polishing (CMP) process. The sacrificial cap may be sufficiently thick so that the planarizing process does not penetrate the sacrificial cap, thereby maintaining the uniformity of the electrodes and the surface uniformity of the electrodes. In step 550, the sacrificial cap may be removed to prepare the electrodes for reducing the initial surface roughness. At step 560, a second planarization process may be performed to remove at least a third portion of the sacrificial cap and reduce the initial surface roughness of the electrode, thereby smoothing the electrode. This can reduce short-range frequency variations and increase the repeatability of resonator spurious content across the wafer. After the second planarization process, portions of the C-bridge may remain on the electrode structure, thereby enhancing the detectability of the process used to create the electrode structure.

[0125] Piezoelectric material layer

[0126] The examples and embodiments described herein may be used, for example, with the structures and methods described in the following U.S. patent application publications: U.S. Patent Application Publication No. 2019 / 0296710 to Deniz et al. (filed on March 20, 2019), entitled “Piezoelectric Bulk Layers With Tilted C-Axis Orientation and Methods for Making the Same,” and U.S. Patent Application Publication No. 2019 / 0296710 to Deniz et al. (filed on March 20, 2019), entitled “Piezoelectric Bulk Layers With Tilted C-Axis Orientation and Methods for Making the Same,” each of which is incorporated herein by reference in its entirety.

[0127] Figure 6A reactor 600 is shown according to an embodiment of a deposition system for growing a hexagonal crystal structure piezoelectric material having a c-axis oriented substantially perpendicular to a top surface of a substrate or electrode, the reactor 600 including a first tubular portion 610, a second tubular portion 620, and a third tubular portion 630 for accommodating various elements for depositing the material onto a substrate.

[0128] Figure 7 exhibit Figure 6 Some elements of the reactor 600 include a linear sputtering apparatus 710, a translation track 720 for translating a movable substrate stage for supporting a plurality of substrates, and a collimator assembly 730.

[0129] Figures 8A to 8D An example of a two-step piezoelectric material layer deposition process is shown.

[0130] Figure 8A and 8B A first growth step is shown, which comprises depositing a substrate from a linear sputtering apparatus (e.g. Figure 7 The target 812 of the linear sputtering apparatus 710 of FIG. 811 ejects metal atoms to react with gas species forming a deposition flux 812 to be received by the substrate 810 and any objects that have been generated on the substrate. The deposition system may include a multi-aperture collimator (e.g., a plurality of apertures) disposed between the target 811 and the substrate 810. Figure 7 collimator 730).

[0131] The deposition flux 812 can be directed through the aperture of the collimator 730 to help control the angle of incidence during deposition. The deposition flux 812 strikes the substrate 810 at a first angle of incidence α, forming a first portion 813A of the body material layer 813 (shown in FIG. Figure 8D ). For example, the first incident angle α can be about 0 degrees (i.e., normal to and substantially perpendicular to the surface plane of the substrate 810 or the electrode). The crystals of the first portion 813A of the body material layer 813 include an on-axis tilt. In some embodiments, the body material layer 813 including the on-axis tilt is deposited onto the top surface of an electrode structure including a smooth surface. The body material layer 813 can be deposited onto the top surface of an electrode configured for depositing a body material layer including an on-axis tilt.

[0132] Figure 8C and 8DA second growth step is shown in which metal atoms are ejected from target 811 to react with gas species and are received by first portion 813A deposited onto substrate 810. Target 111 may be the same or different from the target from which the metal atoms were ejected in the first growth step. In the second growth step, target 111 may be positioned so that the second angle of incidence β is the same as, greater than, or less than the first angle of incidence α. For example, the second angle of incidence β may be approximately 0 degrees (i.e., orthogonal and substantially perpendicular to the surface plane of substrate 810 or the electrode). The deposited flux 812 in the second growth step forms a second portion 813B of a bulk material layer 813. The crystals of second portion 813B of bulk material layer 813 include an on-axis tilt. The first and second portions of bulk material layer 813 together form a piezoelectric material layer. The second growth step may be accomplished with or without a collimator.

[0133] The first portion 813A, the second portion 813B, or both may be a layer of piezoelectric material. The piezoelectric material layer may also include a seed layer or a pre-seed layer, as described below with respect to Figures 9A to 9D In some embodiments, the body material layer 813 comprises more than the first portion and the second portion. The body material layer 813 can be deposited in many different steps to produce many portions.

[0134] In some embodiments, the on-axis tilt of the second portion 813B follows or substantially follows the on-axis tilt of the first portion 813A of the host material layer 813. In some embodiments, the on-axis tilt of the first portion 813A and the second portion 813B is aligned, or at least substantially aligned, with the first angle of incidence α used during the first growth step. The resulting piezoelectric material layer crystals of the first portion 813A and the second portion 813B can be substantially parallel to each other and at least substantially aligned with the desired on-axis tilt. The resulting piezoelectric material layer crystals of the first portion 813A and the second portion 813B can also be substantially parallel within each portion. For example, at least 50%, at least 75%, or at least 90% of the crystals of the first portion 813A can have an on-axis tilt within 0 to 10 degrees of the average on-axis tilt and an orientation within 0 to 60 degrees, or within 0 to 20 degrees, of the average crystal direction. Similarly, at least 50%, at least 75%, or at least 90% of the crystals of the second portion 813B may have an on-axis tilt within 0 to 10 degrees of the average on-axis tilt, and an orientation within 0 to 60 degrees or within 0 to 20 degrees of the average crystal direction.

[0135] Optionally, as Figures 9A to 9DAs shown in , a first portion 913A of a body material layer 913 can be deposited onto a seed layer 914 that has been deposited onto the substrate 110 or any object produced thereon, such as an electrode. In some embodiments, the seed layer 914 is deposited onto the top surface of the electrode before depositing the body material layer 913. In some examples, a pre-seed layer is deposited before depositing the seed layer 914. The resulting piezoelectric material layer can include a seed layer 914 with an on-axis tilt and a body material layer. As shown, the body material layer 913 can have a first portion and a second portion, or any number of portions, depending on the number of deposition steps used during the piezoelectric material layer deposition process.

[0136] Figure 10 The steps of a process 1000 for producing an electrode structure comprising a uniform, smooth surface are shown. In step 1010, one or more electrodes may be produced on a substrate, the one or more electrodes comprising an initial surface roughness. The one or more electrodes may be produced on a portion of the substrate. In step 1020, a sacrificial cap may be produced on the one or more electrodes. Producing the sacrificial cap may include depositing the sacrificial cap, patterning the sacrificial cap, or any combination thereof. In step 1030, a planarizing film may be produced on the substrate and on at least a portion of the sacrificial cap. In step 1040, a first planarizing process may be performed to remove at least a portion of the planarizing film and at least a first portion of the sacrificial cap, wherein the sacrificial cap maintains uniformity of the electrodes and the surface uniformity of the electrode structure during the first planarizing process. The first planarizing process may be a chemical mechanical polishing (CMP) process. The sacrificial cap may be sufficiently thick so that the first planarizing process does not penetrate the sacrificial cap and prepares the electrodes for removal of the initial surface roughness while maintaining the surface uniformity of the electrode structure. In step 1050, at least a second portion of the sacrificial cap may be removed. At step 1060, a second planarization process may be performed to remove at least a third portion of the sacrificial cap and reduce the initial surface roughness of the electrode, thereby smoothing the electrode. After the second planarization process, portions of the C-bridge may remain on the electrode structure, thereby enhancing the detectability of the electrode structure production process. In some embodiments, a piezoelectric material including an on-axis tilt may be deposited on the top surface of one or more electrodes, a substrate, an object produced thereon, or any combination thereof, thereby producing a piezoelectric structure with an enhanced longitudinal mode piezoelectric response.

[0137] Figure 11 The shear mode coupling coefficient (K) varies with the c-axis tilt angle of AlN. s ) and longitudinal coupling coefficient (K l As shown in the figure, the longitudinal mode coupling coefficient is the main mode at least when the c-axis of the piezoelectric material layer is tilted between 0 and 20 degrees.

[0138] Figure 12 Two box plots are shown, with the short-range frequency variation (MHz) shown on the y-axis. The box plot on the left shows the short-range frequency variation during recording, while the box plot on the right shows the short-range frequency variation when using the methods and structures described herein (right side). The x-axis lists the number of devices used to obtain the box plot data. As shown, the short-range frequency variation is reduced using the methods and structures described herein.

[0139] Aspects of the present invention include structures incorporating the various elements described herein. For example, aspects of the present invention include protected structures for producing electrode structures comprising uniformly smooth surfaces, electrode structures comprising uniformly smooth surfaces, and piezoelectric structures having increased surface uniformity, among other structures.

[0140] For example, in some embodiments, a protected structure for producing an electrode structure comprising a uniformly smooth surface comprises a substrate, one or more electrodes disposed on at least a portion of the substrate, and a sacrificial cap disposed on the electrodes, wherein the sacrificial cap comprises a c-bridge.

[0141] In other embodiments, an electrode structure including a uniform smooth surface includes: a substrate; a planarization film disposed on the substrate, the planarization film including an upper surface; and one or more electrodes disposed on the substrate, wherein a sacrificial cover on each of the one or more electrodes maintains the uniformity of the surface of the electrode structure during a first planarization process, and wherein the one or more electrodes and the upper surface of the planarization film are smoothed by a second planarization process.

[0142] How to use

[0143] Aspects of the present invention include methods for reducing the initial surface roughness of electrodes, reducing electrode rounding, increasing the surface uniformity of electrode structures, enhancing the detectability of the process used to produce the electrode structures, reducing short-range frequency variations, increasing the repeatability of resonator spurious content across the wafer, enhancing control over the crystal c-axis angle in the bulk material layer, improving properties such as mechanical quality factor and coupling coefficient; and improving the manufacturing efficiency of the bulk material layer.

[0144] Examples

[0145] Example 1: Figure 13A FIG1 is an example of an actual cross-sectional view of protected structure 1303A after performing a first planarization process to remove at least a portion of planarization film 1320 and at least a first portion of sacrificial cap 1350. As shown in this example, the first planarization process may have a target stop level within sacrificial cap 1350 or within a specific layer of sacrificial cap 1350 (e.g., a tungsten layer).

[0146] Example 2: Figure 13B is an example of an actual cross-sectional view of electrode structure 1303B after removing at least a second portion of sacrificial cap 1350. As shown, third portion 1311 of the sacrificial cap and the initial surface roughness of electrode 1310 may remain after removing the second portion of sacrificial cap 1350.

[0147] Example 3: Figure 13C FIG1 is an example of an actual cross-sectional view of electrode structure 1303C after a second planarization process is performed to remove at least a third portion 1311 of sacrificial cap 1350 and reduce the initial surface roughness of electrode 1310, thereby smoothing electrode 1310. As shown, after the second planarization process, electrode 1310 has a smooth surface 1312. The resulting electrode structure includes a uniformly smooth surface.

[0148] Example 4: Figure 14 As an example of a realistic cross-sectional view of an electrode structure produced using previously known techniques, the electrodes of the electrode structure exhibit rounding, as shown by 1401 .

[0149] Example 5: Figure 15 is a realistic cross-sectional view of an electrode structure produced using the methods and structures described herein, the electrode structure having a smooth electrode with reduced rounding (as shown at 1402) and the electrode structure having a uniformly smooth surface.

[0150] Although preferred embodiments of the present invention have been shown and described herein, it will be understood by those skilled in the art that such embodiments are provided by way of example only. Those skilled in the art may conceive of many variations, changes, and substitutions without departing from the present invention. It should be understood that various alternatives to the embodiments of the present invention described herein may be employed in practicing the present invention. The following technical solutions are intended to define the scope of the present invention and therefore encompass methods and structures within the scope of these technical solutions and their equivalents.

[0151] Now that the invention is fully described, it will be apparent to those skilled in the art that many changes and modifications can be made therein without departing from the spirit or scope of the invention.

[0152] All references and disclosures cited herein are hereby expressly incorporated by reference in their entirety into this disclosure, to the extent that they may not directly contradict this disclosure. Although specific examples and embodiments have been illustrated and described herein, it will be appreciated by those skilled in the art that a variety of alternative and / or equivalent embodiments may be substituted for the specific exemplary embodiments shown and described without departing from the scope of this disclosure. It should be understood that this disclosure is not intended to be unduly limited by the exemplary examples and embodiments described herein, and such examples and embodiments are presented as examples only, and the scope of this disclosure is intended to be limited only by the claims set forth herein.

Claims

1. A method for producing an electrode structure comprising one or more smooth electrodes, the method comprising: producing one or more electrodes including an initial surface roughness on a first portion of a substrate; creating a sacrificial cap over each of the one or more electrodes; producing a planarization film on the substrate and on at least a portion of the sacrificial cover; performing a first planarization process to remove at least a portion of the planarization film and at least a first portion of the sacrificial cover; removing at least a second portion of the sacrificial cover to prepare the electrode for reducing the initial surface roughness; as well as A second planarization process is performed to remove at least a third portion of the sacrificial cap and reduce the initial surface roughness of the one or more electrodes, thereby smoothing the one or more electrodes. The method of claim 1 , wherein the sacrificial cover comprises a c-bridge. 3 . The method according to claim 2 , wherein after performing the second planarization process, at least a portion of the C-bridge remains on the electrode structure. 4 . The method of claim 2 , wherein the c-bridge connects the one or more electrodes to an acoustic energy management layer embedded within the substrate.

5. The method of claim 1 , wherein the sacrificial cover comprises: a bottom aluminum nitride layer disposed directly on the electrode; a tungsten layer disposed above the bottom aluminum nitride layer; as well as A top aluminum nitride layer is disposed over the tungsten layer. 6 . The method of claim 5 , wherein the first portion of the sacrificial cap removed using the first planarization process includes the top aluminum nitride layer and at least a first portion of the tungsten layer. 7 . The method of claim 5 , wherein removing at least the second portion of the sacrificial cap comprises removing at least the second portion of the tungsten layer using a wet or dry etch.

8. The method of claim 7, wherein the dry etching comprises plasma etching and the wet etching comprises solution-based etching. 9 . The method of claim 5 , wherein the third portion of the sacrificial cap removed using the second planarization process comprises at least a first portion of the bottom aluminum nitride layer.

10. The method of claim 1, wherein the one or more electrodes comprise a tungsten layer disposed over a layer comprising a metal, a metal alloy, or any combination thereof.

11. The method of claim 10, wherein the metal is selected from the group consisting of tungsten (W), aluminum (Al), copper (Cu), titanium (Ti), molybdenum (Mo), platinum (Pt), ruthenium (Ru), iridium (Ir), and any combination thereof. 12 . The method of claim 10 , wherein the metal alloy is an aluminum-copper (AlCu) alloy or a titanium-tungsten (TiW) alloy. The method according to claim 1 , wherein the substrate comprises a planarization film. The method of claim 13 , wherein the planarization film comprises silicon dioxide, TEOS, or any combination thereof.

15. The method of claim 1, wherein a plurality of acoustic energy management layers are embedded within the substrate.

16. The method of claim 15, wherein the plurality of acoustic energy management layers comprises a plurality of acoustic reflector layers.

17. The method of claim 1, wherein the first planarization process comprises chemical mechanical polishing (CMP), or wherein the second planarization process comprises chemical mechanical polishing (CMP), or wherein the first planarization process and the second planarization process comprise chemical mechanical polishing (CMP).

18. The method of claim 1, wherein the one or more electrodes are configured to deposit a layer of piezoelectric material on a top surface of the one or more electrodes, the layer of piezoelectric material comprising a c-axis having an orientation substantially perpendicular to the top surface of the one or more electrodes.

19. The method of claim 1, wherein producing the one or more electrodes comprises depositing the one or more electrodes, patterning the one or more electrodes, or any combination thereof.

20. The method of claim 1, wherein creating the sacrificial cap on each of the one or more electrodes comprises depositing the sacrificial cap, patterning the sacrificial cap, or any combination thereof.

21. The method of claim 1, wherein generating the planarization film comprises depositing the planarization film on the substrate, patterning the planarization film, or any combination thereof.

22. The method of any one of claims 19 to 21, wherein patterning comprises performing: a photolithography process, an etching process, or any combination thereof.

23. A method for producing an electrode structure comprising a uniformly smooth surface, the method comprising: creating one or more electrodes on a first portion of a substrate, wherein each of the one or more electrodes comprises an initial surface roughness; creating a sacrificial cap over each of the one or more electrodes; producing a planarization film on the substrate and on at least a portion of the sacrificial cover; performing a first planarization process to remove at least a portion of the planarization film and at least a first portion of the sacrificial cover, wherein the sacrificial cover maintains uniformity of the surface of the electrode structure during the first planarization process; removing at least a second portion of the sacrificial cover to prepare the electrode for reducing the initial surface roughness; as well as A second planarization process is performed to remove at least a third portion of the sacrificial cap and reduce the initial surface roughness of each of the one or more electrodes, thereby producing an electrode structure including a uniformly smooth surface.

24. The method of claim 23, further comprising depositing a layer of piezoelectric material onto a top surface of the one or more electrodes, the layer of piezoelectric material comprising a c-axis having an orientation substantially perpendicular to the top surface of each of the one or more electrodes.

25. The method of claim 23, wherein the sacrificial cover comprises a c-bridge. 26 . The method of claim 25 , wherein after performing the second planarization process, at least a portion of the c-bridge remains on the electrode structure.

27. The method of claim 25, wherein the c-bridge connects the one or more electrodes to an acoustic energy management layer embedded within the substrate.

28. The method of claim 24, wherein the piezoelectric material layer comprises a seed layer and a host material layer.

29. The method of claim 28, wherein depositing the layer of piezoelectric material comprises depositing the seed layer onto the top surface of each of the one or more electrodes before depositing the layer of bulk material.

30. The method of claim 24, wherein the piezoelectric material layer comprises a material selected from the group consisting of: AlN, ScAlN, ZnO, PZT, and any combination thereof.

31. The method of claim 23, wherein the sacrificial cover comprises: a bottom aluminum nitride layer disposed directly on the electrode; a tungsten layer disposed above the bottom aluminum nitride layer; as well as A top aluminum nitride layer is disposed over the tungsten layer.

32. The method of claim 31 , wherein the first portion of the sacrificial cap removed using the first planarization process comprises a first portion of the top aluminum nitride layer and at least a first portion of the tungsten layer.

33. The method of claim 31 , wherein removing the second portion of the sacrificial cap comprises removing the second portion of the tungsten layer using a wet or dry etch.

34. The method of claim 33, wherein the dry etching comprises plasma etching and the wet etching comprises solution-based etching.

35. The method of claim 31, wherein the third portion of the sacrificial cap removed using the second planarization process comprises at least a first portion of the bottom aluminum nitride layer.

36. The method of claim 23, wherein each of the one or more electrodes comprises a tungsten layer disposed over a layer comprising a metal, a metal alloy, or any combination thereof.

37. The method of claim 36, wherein the metal is selected from the group consisting of tungsten (W), aluminum (Al), copper (Cu), titanium (Ti), molybdenum (Mo), platinum (Pt), ruthenium (Ru), iridium (Ir), and any combination thereof.

38. The method of claim 36, wherein the metal alloy is an aluminum-copper (AlCu) alloy or a titanium-tungsten (TiW) alloy.

39. The method of claim 23, wherein the substrate comprises a planarization film.

40. The method of claim 39, wherein the planarization film comprises silicon dioxide, TEOS, or any combination thereof.

41. The method of claim 23, wherein a plurality of acoustic energy management layers are embedded within the substrate.

42. The method of claim 41, wherein the plurality of acoustic energy management layers comprises a plurality of acoustic reflector layers.

43. The method of claim 42, wherein the plurality of acoustic reflector layers comprises tungsten, silicon dioxide, an aluminum-copper alloy, or any combination thereof.

44. The method of claim 23, wherein the first planarization process comprises chemical mechanical polishing (CMP), or wherein the second planarization process comprises chemical mechanical polishing (CMP), or wherein the first planarization process and the second planarization process comprise chemical mechanical polishing (CMP).

45. The method of claim 23, wherein producing one or more electrodes comprises depositing the one or more electrodes, patterning the one or more electrodes, or any combination thereof.

46. The method of claim 23, wherein creating the sacrificial cap on each of the one or more electrodes comprises depositing the sacrificial cap, patterning the sacrificial cap, or any combination thereof.

47. The method of claim 23, wherein generating a planarization film comprises depositing the planarization film on the substrate, patterning the planarization film, or any combination thereof.

48. The method of any one of claims 45 to 47, wherein patterning comprises performing: a photolithography process, an etching process, or any combination thereof.

49. A protected structure for producing an electrode structure comprising a uniformly smooth surface, the protected structure comprising: substrate; one or more electrodes disposed on at least a portion of the substrate; as well as A sacrificial cover is disposed on each of the one or more electrodes, wherein the sacrificial cover comprises a c-bridge.

50. The protected structure of claim 49, wherein the c-bridge connects the one or more electrodes to an acoustic energy management layer embedded within the substrate.

51. The protected structure of claim 49, wherein the sacrificial cover comprises: a bottom aluminum nitride layer disposed directly on the electrode; a tungsten layer disposed above the bottom aluminum nitride layer; as well as A top aluminum nitride layer is disposed over the tungsten layer.

52. The protected structure of claim 49, wherein the one or more electrodes comprise a tungsten layer disposed over a layer comprising a metal, a metal alloy, or any combination thereof.

53. The protected structure of claim 52, wherein the metal is selected from the group consisting of tungsten (W), aluminum (Al), copper (Cu), titanium (Ti), molybdenum (Mo), platinum (Pt), ruthenium (Ru), iridium (Ir), and any combination thereof.

54. The protected structure of claim 52, wherein the metal alloy is an aluminum-copper (AlCu) alloy or a titanium-tungsten (TiW) alloy.

55. The protected structure of claim 49, wherein the substrate comprises a planarization film.

56. The protected structure of claim 55, wherein the planarization film comprises silicon dioxide, TEOS, or any combination thereof.

57. The protected structure of claim 49, wherein a plurality of acoustic energy management layers are embedded within the substrate.

58. The protected structure of claim 57, wherein the plurality of acoustic energy management layers comprises a plurality of acoustic reflector layers.

59. The protected structure of claim 58, wherein the plurality of acoustic reflector layers comprises tungsten, silicon dioxide, an aluminum-copper alloy, or any combination thereof.

60. An electrode structure comprising a uniform and smooth surface, the electrode structure comprising: substrate; a planarization film disposed on the substrate, the planarization film including an upper surface; and One or more electrodes are provided on the substrate, wherein a sacrificial cap on each of the one or more electrodes maintains uniformity of the surface of the electrode structure during a first planarization process, and The upper surface of the one or more electrodes and the planarization film are smoothed by a second planarization process.

61. The electrode structure of claim 60, wherein the sacrificial cap comprises a c-bridge.

62. The electrode structure of claim 61, further comprising at least a portion of the c-bridge.

63. The electrode structure of claim 60, wherein the one or more electrodes comprise a tungsten layer disposed over a layer comprising a metal, a metal alloy, or any combination thereof.

64. The electrode structure of claim 63, wherein the metal is selected from the group consisting of tungsten (W), aluminum (Al), copper (Cu), titanium (Ti), molybdenum (Mo), platinum (Pt), ruthenium (Ru), iridium (Ir), and any combination thereof.

65. The electrode structure of claim 63, wherein the metal alloy is an aluminum-copper (AlCu) alloy or a titanium-tungsten (TiW) alloy.

66. The electrode structure of claim 60, wherein the substrate comprises a planarization film.

67. The electrode structure of claim 66, wherein the planarization film comprises silicon dioxide, TEOS, or any combination thereof.

68. The electrode structure of claim 60, wherein a plurality of acoustic energy management layers are embedded within the substrate.

69. The electrode structure of claim 68, wherein the plurality of acoustic energy management layers comprises a plurality of acoustic reflector layers.

70. The electrode structure of claim 69, wherein the plurality of acoustic reflector layers comprises tungsten, silicon dioxide, an aluminum-copper alloy, or any combination thereof.

71. A piezoelectric structure having increased surface uniformity, the piezoelectric structure comprising: The electrode structure according to claim 60; as well as A layer of piezoelectric material is disposed on the top surface of the one or more electrodes, the layer of piezoelectric material including a c-axis having an orientation substantially perpendicular to the top surface of each of the one or more electrodes.

72. The piezoelectric structure of claim 71, wherein the piezoelectric material layer comprises a seed layer and a host material layer.

73. The piezoelectric structure of claim 72, wherein the piezoelectric material layer comprises a material selected from the group consisting of: AlN, ScAlN, ZnO, PZT, and any combination thereof.

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