Acoustic resonator device

Abstract

To provide methods of fabricating a bulk acoustic wave resonator structure for a fluidic device.SOLUTION: A fabrication method has a first step of disposing a first conductive material over a portion of a first surface of a substrate to form at least a portion of a first electrode. Then, a piezoelectric material may be disposed over the first electrode. Next, a second conductive material can be disposed over the piezoelectric material to form at least a portion of a second electrode. An acoustic energy management structure is then disposed over a first side of a bulk acoustic wave resonator. Next, a third conductive material that extends beyond the bulk acoustic wave resonator is disposed over a portion of the second conductive material. Finally, a portion of the second surface of the substrate is removed to expose a chemical mechanical connection at the first electrode at a second side of the bulk wave acoustic resonator.SELECTED DRAWING: Figure 1H

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application is a nonprovisional adaptation of U.S. Provisional Patent Application No. 62 / 844,000, filed May 6, 2019, the entire disclosure of which is incorporated herein by reference.

[0002] SUMMARY The present disclosure relates generally to acoustic resonator devices, including acoustic sensors and fluidic devices incorporating acoustic resonators, and related systems suitable for biosensing or biochemical sensing applications. [Background technology]

[0003] A biosensor (or biological sensor) is an analytical device that includes a biological component and a transducer that converts a biological reaction into an electrical signal. Some biosensors include a selective biochemical reaction between a specific binding substance (e.g., an antibody, a receptor, a ligand, etc.) and a target species (e.g., a molecule, a protein, DNA, a virus, a bacterium, etc.), and the product of this highly specific reaction is converted into a measurable quantity by the transducer. Other sensors may utilize non-specific binding materials that can bind to multiple types or classes of molecules or other moieties that may be present in a sample. The term "functionalization material" may be used generally herein in reference to both specific and non-specific binding materials. The transduction methods used with biosensors may be based on various principles, such as electrochemical, optical, electrical, acoustic, etc. Of these, acoustic transduction offers many potential advantages, such as high sensitivity, as well as being real-time, label-free, and low cost.

[0004] Sonic devices use acoustic waves that propagate through or on the surface of a particular binding material, such that any changes to the properties of the propagation path affect the velocity and / or amplitude of the wave. Sonic devices are typically fabricated by microelectromechanical systems (MEMS) fabrication techniques, as they must provide suitable microscale features to facilitate high frequency operation. The presence of a functionalized material over the active area of ​​the acoustic device allows analytes to bind to the functionalized material, which changes the mass that is vibrated by the acoustic waves, changing the wave propagation properties (e.g., velocity and therefore resonant frequency). The change in velocity can be monitored by measuring the frequency, magnitude, and / or phase properties of the acoustic device, and can be related to the physical quantity being measured.

[0005] Typically, BAW devices are fabricated by microelectromechanical systems (MEMS) fabrication techniques, as they must provide suitable microscale features to facilitate high frequency operation. In the context of biosensors, functionalization materials (e.g., specific binding materials, also known as bioactive probes or drugs) can be deposited on the sensor surface by a variety of techniques, such as microarray spotting (also known as microarray printing). Functionalization materials that provide non-specific binding utility (e.g., allowing for the binding of multiple types or species of molecules) can also be used in certain situations, such as chemical sensing. Summary of the Invention [Problem to be solved by the invention]

[0006] Existing processes for fabricating arrays of resonators include many challenges. For example, when multiple rows of resonators are placed in a fluid path, the length of the electrical leads increases. For example, if there are four resonators across the width of the fluid path, the lead length to the resonator in the center of the fluid path becomes long, making it difficult to apply to high density resonator sensor arrays. As an example, sensor arrays can range from 2 x 2 (four resonators total) to 50 x 50 (2500 resonators total). Furthermore, the fluid height in the sensor flow path is directly related to the height of the laminate substrate.

[0007] It may be desirable to provide a high density BAW sensor array, which offers the advantages of short electrical leads, low flow path height, and high reliability by isolating the fluidic interface and electrical connections on opposite sides of the BAW die. Those skilled in the art will appreciate the scope of the present disclosure and realize additional aspects thereof upon reading the following detailed description in conjunction with the accompanying drawings. [Means for solving the problem]

[0008] The disclosed technology generally relates to a method for manufacturing a device including a bulk acoustic wave resonator sensor that can be more effectively and easily electrically connected to a printed circuit board. The method may include forming a bulk acoustic wave resonator on a first surface of a substrate and removing a portion of the substrate from an opposing surface of the substrate. The method may also optionally include flip chip mounting.

[0009] Some aspects according to the principles of the present disclosure relate to a method of manufacturing a bulk acoustic wave resonator structure for a fluidic device. The method may include a first step of disposing a first conductive material on a portion of a first surface of a substrate, the substrate having a second surface opposite the first surface, to form at least a portion of a first electrode. A piezoelectric material may then be disposed on the first electrode. A second conductive material may then be disposed on the piezoelectric material to form at least a portion of the second electrode. The second conductive material extends substantially parallel to the first surface of the substrate and at least partially on the first conductive material. An area where the first conductive material, the piezoelectric material, and the second conductive material overlap forms a bulk acoustic wave resonator, the bulk acoustic wave resonator having a first side and an opposite second side. An acoustic energy management structure is then disposed on the first side of the bulk acoustic wave resonator. A third conductive material is then disposed over a portion of the second conductive material that extends beyond the bulk acoustic wave resonator, the third conductive material forming an interconnect above the acoustic energy management structure and extending in a direction substantially perpendicular to the first surface of the substrate. Finally, a portion of the second surface of the substrate is removed to expose a chemical-mechanical connection at the first electrode on the second side of the bulk acoustic wave resonator.

[0010] Another aspect according to the principles of the present disclosure relates to a method of manufacturing a bulk acoustic wave resonator structure for a fluidic device. The method may include a first step of disposing a first conductive material on a portion of a first surface of a substrate, the substrate having a second surface opposite the first surface, to form at least a portion of a first electrode. A piezoelectric material may then be disposed on the first electrode. A second conductive material may then be disposed on the piezoelectric material to form at least a portion of the second electrode. The second conductive material extends substantially parallel to the first surface of the substrate and at least partially on the first conductive material. The overlapping region of the first conductive material, the piezoelectric material, and the second conductive material forms a bulk acoustic wave resonator, the bulk acoustic wave resonator having a first side and an opposite second side. A reflector structure, which functions as an acoustic energy management structure, is then disposed on the first side of the bulk acoustic wave resonator. A third conductive material is then disposed over the portion of the second conductive material that extends beyond the bulk acoustic wave resonator, the third conductive material forming an interconnect above the reflector structure and extending in a direction substantially perpendicular to the first surface of the substrate. Finally, a portion of the second surface of the substrate is removed to expose a chemical-mechanical connection at the first electrode on the second side of the bulk acoustic wave resonator.

[0011] Another aspect according to the principles of the present disclosure relates to a method of manufacturing a bulk acoustic wave resonator structure for a fluidic device. The method may include a first step of disposing a first conductive material on a portion of a first surface of a substrate, the substrate having a second surface opposite the first surface, to form at least a portion of a first electrode. A piezoelectric material may then be disposed on the first electrode. A second conductive material may then be disposed on the piezoelectric material to form at least a portion of the second electrode. The second conductive material extends substantially parallel to the first surface of the substrate and at least partially on the first conductive material. The overlapping region of the first conductive material, the piezoelectric material, and the second conductive material forms a bulk acoustic wave resonator, the bulk acoustic wave resonator having a first side and an opposite second side. An air cavity, which functions as an acoustic energy management structure, is then disposed on the first side of the bulk acoustic wave resonator. A third conductive material is then disposed over a portion of the second conductive material that extends beyond the bulk acoustic wave resonator, the third conductive material forming an interconnect above the air cavity and extending in a direction substantially perpendicular to the first surface of the substrate. Finally, a portion of the second surface of the substrate is removed to expose a chemical-mechanical connection at the first electrode on the second side of the bulk acoustic wave resonator.

[0012] The details of one or more aspects of this disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the techniques described in this disclosure will become apparent from the description, drawings, and claims.

[0013] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate several aspects of the present disclosure and, together with the description, serve to explain various principles of the present disclosure. [Brief description of the drawings]

[0014] [Figure 1A] 1A-1D are schematic diagrams of an apparatus at various stages in an exemplary method of making a bulk acoustic wave containing structure according to aspects of the present disclosure. [Figure 1B] 1A-1D are schematic diagrams of an apparatus at various stages in an exemplary method of making a bulk acoustic wave containing structure according to aspects of the present disclosure. [Figure 1C] 1A-1D are schematic diagrams of an apparatus at various stages in an exemplary method of making a bulk acoustic wave containing structure according to aspects of the present disclosure. [Figure 1D] 1A-1D are schematic diagrams of an apparatus at various stages in an exemplary method of making a bulk acoustic wave containing structure according to aspects of the present disclosure. [Figure 1E] 1A-1D are schematic diagrams of an apparatus at various stages in an exemplary method of making a bulk acoustic wave containing structure according to aspects of the present disclosure. [Figure 1F] 1A-1D are schematic diagrams of an apparatus at various stages in an exemplary method of making a bulk acoustic wave containing structure according to aspects of the present disclosure. [Figure 1G] 1A-1D are schematic diagrams of an apparatus at various stages in an exemplary method of making a bulk acoustic wave containing structure according to aspects of the present disclosure. [Figure 1H] 1A-1D are schematic diagrams of an apparatus at various stages in an exemplary method of making a bulk acoustic wave containing structure according to aspects of the present disclosure. [Figure 1I] 1A-1D are schematic diagrams of an apparatus at various stages in an exemplary method of making a bulk acoustic wave containing structure according to aspects of the present disclosure. [Figure 1J] 1A-1D are schematic diagrams of an apparatus at various stages in an exemplary method of making a bulk acoustic wave containing structure according to aspects of the present disclosure. [Diagram 2] 1A-1C are schematic cross-sectional views illustrating a sacrificial layer and a silicon substrate in a method of forming an exemplary bulk acoustic wave structure according to an aspect of the present disclosure. [Diagram 3] 3 is a schematic cross-sectional view showing a silicon oxide layer on the layer of FIG. 2 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Figure 4] 4 is a schematic cross-sectional view showing a silicon nitride layer on the layer of FIG. 3 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Diagram 5] 5 is a schematic cross-sectional view illustrating optional removal of a sacrificial layer over the layers of FIG. 4 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Figure 6]6 is a schematic cross-sectional view showing electrodes and silicon oxide on the layers of FIG. 5 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Figure 7] 7 is a schematic cross-sectional view showing a tilted shear axis piezoelectric film on the layer of FIG. 6 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Figure 8] 8 is a schematic cross-sectional view illustrating a second electrode layer on the piezoelectric layer of FIG. 7 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Figure 9] 9 is a schematic cross-sectional view illustrating a build-up layer on the layer of FIG. 8 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Figure 10] 10 is a schematic cross-sectional view showing a protective layer over the layers of FIG. 9 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Figure 11] 11 is a schematic cross-sectional view illustrating an acoustic energy management structure extending across a portion of the layer of FIG. 10 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Figure 12] 11 is a schematic cross-sectional view showing interconnects for electrical connection to a substrate disposed relative to the layers of FIG. 10 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Figure 13] 13 is a schematic cross-sectional view illustrating the removal of a portion of a substrate to reduce its thickness compared to the layers of FIG. 12 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Figure 14A] 14 is a schematic cross-sectional view illustrating dry etching of additional portions of the substrate to form fluid paths to the layers of FIG. 13 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Figure 14B] 14 is a perspective view illustrating dry etching of additional portions of the substrate to form fluid paths for the layers of FIG. 13 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. FIG. [Figure 14C]14 is a perspective view illustrating dry etching of additional portions of the substrate to form fluid paths for the layers of FIG. 13 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. FIG. [Figure 15A] 15 is a schematic cross-sectional view showing a BAW die flip chip attached to a substrate with respect to the bulk acoustic wave structure of FIG. 14 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Figure 15B] 15 is a schematic cross-sectional view showing a BAW die flip chip attached to a substrate with respect to the bulk acoustic wave structure of FIG. 14 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Figure 15C] 15 is a perspective view of a BAW die flip chip attached to a substrate for the bulk acoustic wave structure of FIG. 14 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. FIG. [Figure 15D] 15 is a cross-sectional view of the BAW die flip chip attached to a substrate for the bulk acoustic wave structure of FIG. 14 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Figure 15E] 15 is a cross-sectional view of the BAW die flip chip attached to a substrate for the bulk acoustic wave structure of FIG. 14 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Figure 16] 15 is a schematic cross-sectional view illustrating attachment of a fluidic wall structure to the bulk acoustic wave structure of FIG. 14 in a method of forming an exemplary fluidic device according to an embodiment of the present disclosure. [Figure 17A] 17 is a schematic cross-sectional view showing underfill wicked under a flip chip attached die for the apparatus of FIG. 16 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. FIG. [Figure 17B] 17 is a schematic cross-sectional view showing underfill wicked under a flip chip attached die for the apparatus of FIG. 16 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. FIG. [Figure 17C]17 is a schematic cross-sectional view showing underfill wicked under a flip chip attached die for the apparatus of FIG. 16 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. FIG. [Figure 18] 18A-18C are schematic cross-sectional views illustrating the printing and spotting of silanized and functionalized bodies onto the apparatus of FIG. 17 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Figure 19A] FIG. 20 is a schematic cross-sectional view showing a fluid chamber cover attached onto a fluid wall structure for the apparatus of FIG. 18 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Figure 19B] FIG. 20 is a schematic cross-sectional view showing a fluid chamber cover attached onto a fluid wall structure for the apparatus of FIG. 18 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Figure 19C] 19 is a cross-sectional view showing a fluid chamber cover attached onto a fluid wall structure for the apparatus of FIG. 18 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Figure 20] 20 is a schematic diagram illustrating an additional method of attaching a fluid chamber cover onto a fluid wall structure with respect to the apparatus of FIG. 18 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Figure 21] 1 is a schematic cross-sectional view of a silicon substrate having silicon oxide and silicon nitride films deposited thereon in a method of forming an exemplary bulk acoustic wave structure according to an aspect of the present disclosure. [Figure 22] In a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure, and with reference to FIG. 21, a schematic cross-sectional view of an electrode formed, having silicon oxide deposited thereon, and having the surface planarized in a CMP process is shown. [Diagram 23] In a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure, with reference to FIG. 22, a schematic cross-sectional view of a deposited tilted shear axis piezoelectric film is shown. [Figure 24]23 is a schematic cross-sectional view illustrating deposition and patterning of a second electrode on a piezoelectric layer in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. FIG. [Diagram 25] 24 is a schematic cross-sectional view illustrating deposition and patterning of build-up layers in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. FIG. [Figure 26] 25 is a schematic cross-sectional view showing deposition and pattern protection layers in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. FIG. [Figure 27] In a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure, with reference to FIG. 26, a schematic cross-sectional view illustrates the creation of an acoustic reflector on a resonator. [Figure 28] In a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure, with reference to FIG. 27, a schematic cross-sectional view illustrates the creation of bumps for electrical connection to a substrate. [Figure 29] In a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure, with reference to FIG. 28, a schematic cross-sectional view illustrating backgrinding of a portion of a substrate to reduce a thickness of the substrate. [Diagram 30] In a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure, and with reference to FIG. 29, a schematic cross-sectional view illustrating dry etching of a portion of a substrate to form a fluid path in a zone of a resonator. [Diagram 31] In a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure, with reference to FIG. 30, a schematic cross-sectional view showing a BAW biosensor die flip chip attached to a printed circuit board. [Figure 32A] 31 is a schematic cross-sectional view illustrating attachment of a separate fluidic wall structure in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. FIG. [Figure 32B] 31 is a perspective view illustrating attachment of a separate fluidic wall structure in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. FIG. [Diagram 33]In a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure, with reference to FIGS. 32A and 32B, a schematic cross-sectional view of the device after underfill has been wicked under a flip chip attached die is shown. [Diagram 34] 33 is a schematic cross-sectional view showing completed silanization, functionalization, printing, and spotting in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. FIG. [Diagram 35] In a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure, with reference to FIG. 34, a schematic cross-sectional view showing a fluid chamber cover attached onto a fluid wall structure. [Diagram 36] 1A-1C are schematic top views of the exposed resonator side and free-standing walls of a BAW sensor die in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Figure 37] 32 is a schematic cross-sectional view illustrating an alternative method of attaching a cover to the BAW die of FIG. 31 in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Figure 38] 1 is a schematic cross-sectional view of a silicon-on-insulator (SOI) wafer that can be used in a method for forming an exemplary bulk acoustic wave structure according to an aspect of the present disclosure. [Figure 39] 38 is a schematic cross-sectional view illustrating a patterned hard mask and wet etching of top silicon in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Diagram 40] In a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure, with reference to FIG. 39, a schematic cross-sectional view of a deposited silicon nitride film is shown. [Diagram 41] In a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure, and with reference to FIG. 40, a schematic cross-sectional view of an electrode formed, having silicon oxide deposited thereon, and having the surface planarized in a CMP process is shown. [Diagram 42] In a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure, with reference to FIG. 41, a schematic cross-sectional view of a deposited tilted shear axis piezoelectric film is shown. [Diagram 43] 42 is a schematic cross-sectional view illustrating deposition and patterning of electrodes on a piezoelectric layer in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Diagram 44] 43 is a schematic cross-sectional view illustrating deposition and patterning of build-up layers in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. FIG. [Diagram 45] In a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure, with reference to FIG. 44, a schematic cross-sectional view illustrates the creation of an air cavity, which is an example of an acoustic energy management structure on a resonator. [Figure 46] In a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure, with reference to FIG. 45, a schematic cross-sectional view showing the creation of bumps for electrical connection to a substrate. [Figure 47] In a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure, with reference to FIG. 46, a schematic cross-sectional view illustrating backgrinding of a substrate to reduce its thickness is shown. [Figure 48] 47 is a schematic cross-sectional view of a BAW biosensor die flip chip attached to a substrate in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. FIG. [Figure 49A] 48, a schematic cross-sectional view showing the attachment of an independent fluidic wall structure. [Figure 49B] With reference to FIG. 48, a schematic plan view showing the mounting of the independent fluidic wall structures is shown. [Figure 50] 49 is a schematic cross-sectional view of an exemplary method of forming a bulk acoustic wave structure according to an embodiment of the present disclosure, showing underfill wicked under a die attached to a flip chip. [Figure 51] 50 is a schematic cross-sectional view showing the printing and spotting of silanized bodies, functionalized bodies in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Figure 52A]In a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure, with reference to FIG. 51, a schematic cross-sectional view showing a fluid chamber cover attached to a fluid wall structure. [Figure 52B] In a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure, with reference to FIG. 51, a top cross-sectional view of a fluid chamber cover attached to a fluid wall structure. [Figure 53] In a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure, and with reference to FIG. 44, a schematic cross-sectional view illustrates the creation of an acoustic mirror, which is an example of an acoustic energy management structure on a resonator. [Figure 54] In a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure, with reference to FIG. 53, a schematic cross-sectional view showing the creation of bumps for electrical connection to a substrate. [Figure 55] In a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure, with reference to FIG. 54, a schematic cross-sectional view illustrating backgrinding of a substrate to reduce its thickness is shown. [Figure 56] 55 is a schematic cross-sectional view of a BAW biosensor die flip chip attached to a substrate in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. FIG. [Figure 57] 56 is a schematic cross-sectional view illustrating attachment of an independent fluidic wall structure in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. FIG. [Figure 58] 57 is a schematic cross-sectional view of an exemplary method of forming a bulk acoustic wave structure according to an embodiment of the present disclosure, showing underfill wicked under a die attached to a flip chip. [Figure 59] 58 is a schematic cross-sectional view showing the printing and spotting of silanized bodies, functionalized bodies in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. [Figure 60] 59 is a schematic cross-sectional view of a fluid chamber cover attached to a fluid wall structure in a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure. FIG. [Figure 61] 1 is a schematic plan view of a free-standing wall and an interconnect side of a BAW sensor die after a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure is completed. FIG. [Figure 62] 1 is a schematic top view of a free-standing wall and exposed resonator side of a BAW sensor die after a method of forming an exemplary bulk acoustic wave structure according to an embodiment of the present disclosure is completed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The drawings are not necessarily to scale. Like reference numbers used in the drawings refer to like components. However, it will be understood that the use of a reference number to refer to a component in a figure is not intended to limit the component in another figure labeled with the same reference number.

[0016] In the following detailed description, several specific embodiments of compounds, compositions, devices, systems and methods are disclosed. It is to be understood that other embodiments are contemplated and can be made without departing from the scope or spirit of the present disclosure. Thus, the following detailed description is not to be taken in a limiting sense.

[0017] In this specification, the terms first, second, etc. may be used to describe various elements, but it will be understood that these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, a first element can be referred to as a second element, and similarly, a second element can be referred to as a first element, without departing from the scope of the present disclosure. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0018] Relative terms such as "lower," "upper," "upper side," "lower," "top," "bottom," "horizontal," or "vertical" may be used herein to describe the relationship of one element, layer, or region to another element, layer, or region as shown in the figures. It will be understood that these terms, and those discussed above, are intended to encompass different orientations of the device in addition to the orientation of the figures.

[0019] The terms used herein are for the purpose of describing particular embodiments only and are not intended to be limiting of the disclosure. As used herein, the singular forms "a," "an," and "the" are intended to include the plural unless the context clearly indicates otherwise. As used herein, the terms "comprises," "comprising," "include," and / or "including" specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. As used herein, the terms "adjacent" and "adjacent" as applied to a particular layer or element refer to the state of being close to or adjacent to another layer or element and include the possibility of the presence of one or more intervening layers or elements abutting or directly contacting the other layer or element, unless otherwise stated herein.

[0020] In the case of piezoelectric crystal resonators, the acoustic waves can embody either bulk acoustic waves (BAW), which propagate inside the substrate, or surface acoustic waves (SAW), which propagate on the surface of the substrate. SAW devices involve the conversion of acoustic waves (generally including two-dimensional Rayleigh waves) utilizing interdigital transducers along the surface of the piezoelectric material, with the waves being limited to a penetration depth of approximately one wavelength. Three wave modes can propagate in BAW devices: one longitudinal mode (embodying shear waves, also called compression / extension waves) and two shear modes (embodying shear waves, also called transverse waves), with the longitudinal and shear modes respectively identifying vibrations in which the particle motion is parallel or perpendicular to the wave propagation direction. The longitudinal modes are characterized by compression and extension in the wave propagation direction, whereas the shear modes are composed of motion perpendicular to the propagation direction. The longitudinal and shear modes are composed of motion perpendicular to the longitudinal action direction.

[0021] The present disclosure relates to an acoustic resonating device including a bulk acoustic wave (BAW) resonator disposed on a substrate, and a method of forming the device. The BAW resonator includes a first conductive material forming a first electrode, a piezoelectric material, and a second conductive material forming a second electrode, the piezoelectric material being disposed between the two electrodes. An acoustic energy management structure operable to reduce or prevent dissipation of acoustic waves into the substrate is formed over at least a portion of an active area on one surface of the BAW resonator, and an interface layer is formed on an opposite surface of at least a portion of the active area of ​​the BAW resonator, thereby enabling subsequent functionalization of the active area.

[0022] According to aspects of the present disclosure, acoustic wave structure devices can be fabricated using microelectromechanical systems (MEMS) techniques suitable for generating microscale geometries suitable for biosensors, functionalization materials (e.g., certain binding materials), etc. Deposition techniques such as atomic layer deposition (ALD), chemical vapor deposition (CVD), or physical vapor deposition (PVD) can be used in combination with one or more masks (e.g., photolithography masks) to pattern various portions of the device being formed.

[0023] The method for manufacturing a BAW device includes the following steps. 1. Fabricate a resonator with a reflective base, a bottom electrode, a tilted shear axis A A N , and a top electrode. 2. Fabricate flip chip interconnect bumps such as copper pillars with tin. 3. Deposit a water vapor barrier layer to protect the electrodes. Examples of suitable materials are CVD Si3N4 or ALD Al2O3. 4. An adhesion layer for a self-assembled monolayer (SAM) is deposited onto the water vapor barrier layer. Examples of suitable materials include SiO2, TiO2, or HfO2. These materials can be deposited by atomic layer deposition (ALD) or chemical vapor deposition (CVD). 5. The die is attached to the laminate substrate over the slots in the substrate that define the fluidic channels. Additional components such as switches, capacitors and resistors are attached onto the substrate to create the RF sensor module. 6. Deposit a self-assembled monolayer (SAM). An example of a suitable material is 3-glycidoxypropyltrimethoxysilane. This SAM coating is applied to improve the bonding or adhesion between the SiO2 layer and the organic polymer. 7. Functionalized bodies, also called bioreceptors, are printed with microarray spotting needles. 8. Chemically block the unlabeled areas of the SAM. This prevents unwanted attachment of analytes to the SAM when the sample is tested. Unbound excess chemical blocking material is washed off the device. 9. The fluid package is manufactured. An example of a fluid package is multiple layers of punched or laser cut laminate with adhesive. The layers are pre-cut and machined, then attached and held together with a pressure sensitive adhesive. 10. The analyte passes through the sensor cavity and binds to the functionalized body, the resonator is driven at the shear RF frequency, and the frequency shift of the bound analyte is detected.

[0024] Such methods produce devices with long electrical leads to isolate the electrical bumps from the fluidic channels. Furthermore, it is difficult to form a dense array of resonators with fluidic and electrical connections on the same side as the die. Flip-chip mounting of the BAW sensor formed as above to a printed circuit board is one way to connect the sensor to the substrate. The die containing the BAW is eventually mounted in a slot in the substrate that will form the fluidic channel. The thickness of the PCB determines the height of the fluidic channel. Reducing the height of the fluidic channel requires reducing the thickness of the PCB.

[0025] These issues are accentuated when considering arrays of sensors. When multiple rows of resonators are placed in a fluid path, the length of the electrical leads increases. For example, if there are four resonators across the width of the fluid path, the lead length to the resonator in the center of the fluid path will be long. This makes it difficult to address high density resonator sensor arrays. For example, sensor arrays can range from 2×2 (4 total) to 50×50 (2500 total). Even arrays as small as 3×3 (9 total), which offer favorable cost / performance tradeoffs, are difficult to fabricate with previously utilized methods. Current thicknesses of typically used PCBs are on the order of 200 micrometers, thus determining the thickness of the fluid channel.

[0026] According to aspects of the disclosure, the embodiments employ flip-chip connections with interconnect pillars to electrically and / or mechanically connect with a circuit board. An acoustic energy management structure, such as an air cavity or an acoustic mirror, can be used on a first side of the resonator. An opposite second side of the resonator can be exposed for use as the active portion of the sensor. The disclosed method also includes removing a portion of the substrate material. The timing of removing the portion of the substrate is important because removing it too early in the process can make the substrate fragile and difficult to handle in some operations.

[0027] Apparatuses at various stages of manufacture according to several methods are disclosed, for example, in Figures 1A-1G. Figure 1A shows a substrate 102 having a first surface 103 and an opposing second surface 104. The substrate 102 may comprise, for example, silicon. The substrate may have various structures or layers formed on either surface and may be utilized in the disclosed methods.

[0028] FIG. 1B shows the substrate 102 after a first conductive material 106 has been disposed on at least a portion of the first surface 103 of the substrate 102. The first conductive material 106, or a first electrode formed therefrom, can be described as having a first surface 105 adjacent or proximate to the substrate 102 and a second surface 107 opposite the first surface 103. The step of disposing the first conductive material can include a deposition step, a patterning step, or any combination thereof. In some embodiments, the conductive material can be deposited on at least a portion of the first surface of the substrate, or on any structure or device formed on the first surface of the substrate, and the conductive material can then be patterned in one or more steps after deposition. A deposition technique such as atomic layer deposition (ALD), chemical vapor deposition (CVD), or physical vapor deposition (PVD), in combination with one or more masks (e.g., photolithography masks), can be used to pattern portions of the first conductive material, and, if desired, any other layer, material, or structure discussed herein. In some embodiments, the first conductive material may include multiple materials, multiple layers, or combinations thereof. In some embodiments, the first conductive material may include aluminum (Al), copper (Cu), gold (Au), platinum (Pt), combinations thereof, alloys thereof, or combinations thereof. In some embodiments, the first conductive material includes Al, an alloy thereof, or a multi-layer structure including at least one Al layer. In some embodiments, the first conductive material may include a bi-layer structure including, for example, Al or at least one AlCu layer and a tungsten (W) layer.

[0029] 1C shows the device after disposing a piezoelectric material 110 on at least a portion of the first electrode. In some embodiments, the piezoelectric material can be deposited on all portions of the first electrode. In some embodiments, the piezoelectric material can be deposited on all portions of the first electrode that are not disposed on the first surface of the substrate or any devices or structures formed on the first surface. In some embodiments, a tilted c-axis hexagonal structure piezoelectric material (e.g., AlN or ZnO) can be utilized as the piezoelectric material.

[0030] In some embodiments, the piezoelectric material may include an aluminum nitride or zinc oxide material that includes a c-axis with an orientation distribution that is primarily non-parallel (and may also be non-perpendicular) to the normal to the plane of the substrate. Such a c-axis orientation distribution allows for the generation of shear displacements, which beneficially enables operation of MEMS resonating devices with liquids, such as in sensors and / or microfluidic devices. In some embodiments, the piezoelectric material includes a c-axis with a longitudinal orientation.

[0031] A method for forming a piezoelectric material with a hexagonal structure including a c-axis with an orientation distribution that is primarily non-parallel to the normal to the plane of the substrate is disclosed in U.S. Patent Application No. 15 / 293,063, filed October 13, 2016, which is incorporated herein by reference. A further method for forming a piezoelectric material with a tilted c-axis orientation is disclosed in U.S. Patent No. 4,640,756, issued February 3, 1987, which is incorporated herein by reference.

[0032] FIG. 1D shows the device after disposing a second conductive material on at least a portion of the piezoelectric material. Disposing the second conductive material may include a deposition step, a patterning step, or any combination thereof. In some embodiments, a conductive material can be deposited on at least a portion of the piezoelectric material, and the conductive material can then be patterned in one or more steps after deposition to form a second electrode 112, as shown in FIG. 1D. The second conductive material extends substantially parallel to the first surface of the substrate. At least a portion of the second electrode 112 overlaps the first electrode 106. The stack of the first electrode 106, the piezoelectric material 110, and the second electrode 112 in the triple overlap region forms a bulk acoustic wave resonator 114. The bulk acoustic wave resonator 114 has a first side 112 that is parallel to and furthest from the first surface 103 of the substrate 102.

[0033] 1E shows the device after forming an acoustic management structure 116 on a portion of the first side of the bulk acoustic wave resonator 114. The acoustic energy management structure may include, for example, an air cavity or a stack of reflectors. The purpose of the acoustic management structure is to contain the acoustic energy within the device. The reflector stack acts as an acoustic mirror and has the advantage of good mechanical strength. An air cavity works well for energy containment, but may work with an overall mechanically weaker device, i.e. other structures can be added to address the lack of mechanical strength.

[0034] In some embodiments, the energy management structure is an air gap or void cavity. The cavity can be formed by forming two sidewalls and a "roof" layer, thereby forming a cavity under and between the roof and the walls, respectively. The walls and roof can be formed using photolithographic materials, such as photoimageable materials, such as photoimageable epoxy materials. Specific examples of such materials can include TMMF® (Tokyo Ohka Kogyo Co., Ltd.) or SU-8 (MicroChem Inc, Newton, Massachusetts). The wall and roof features can have thicknesses of, for example, 3 to 80 micrometers, or 10 to 30 micrometers. The wall width dimension (e.g., the distance from one wall to the other) can be, for example, 3 to 30 micrometers, or 5 to 15 micrometers. The roof area can be, for example, 100 to 500,000 square micrometers, or 2500 to 200,000 square micrometers.

[0035] In some embodiments, the acoustic energy management structure is an acoustic reflector. The acoustic reflector serves to reflect acoustic waves, thus reducing or preventing the dissipation of acoustic waves in the substrate. In some embodiments, the acoustic reflector can include alternating layers of different materials (e.g., silicon oxide carbide [SiOC], silicon nitride [Si3N4], silicon dioxide [SiO2], aluminum nitride [AlN], tungsten [W], and molybdenum [Mo]), and can optionally be incorporated into a quarter-wave Bragg mirror. In some embodiments, other types of acoustic reflectors can also be used.

[0036] Further details regarding possible embodiments of acoustic energy management structures are discussed below with respect to specific embodiments of the disclosed methods.

[0037] FIG. 1F shows the device after depositing a third conductive material 118 on a portion of the second conductive material 112. It should be noted that the first, second and third conductive materials may be the same or different from each other. The third conductive material is deposited on a portion of the second conductive material that extends beyond the bulk acoustic wave resonator 112. In other words, the third conductive material does not overlap any portion of the bulk acoustic wave resonator, but overlaps a portion of the second conductive material. The third conductive material forms an interconnect that extends above the acoustic energy management structure (in a direction perpendicular to the first surface 103 of the substrate 102). The third conductive material may be described or formed as a pillar structure 118, which may be electrically connected to another device or structure in contact therewith.

[0038] FIG. 1G shows the apparatus after the next step, which includes removing a portion of the substrate 102 to expose the first surface 105 of the first electrode 106. The step of removing a portion of the substrate may include one or more processes. In some embodiments, removing a portion of the substrate may include both a mechanical processing step and a chemical processing step. In some embodiments, the first step of removing a portion of the substrate may remove a substantially constant thickness across the entire substrate. In some embodiments, this first step may be followed by additional removal of substrate material only in some portions of the substrate. In some embodiments, the mechanical removal step may be followed by, for example, a chemical removal step. In such embodiments, the first step may leave the substrate with a thickness of 100-600 micrometers, 100-550 micrometers, 200-400 micrometers, or 250-350 micrometers, or about 300 micrometers. An exemplary initial thickness of the substrate may be about 725 micrometers.

[0039] The step of exposing the first surface 105 of the first electrode 106 exposes the second side of the bulk acoustic wave sensor 114 for use or further processing. It should be noted that at this point, the second surface of the bulk acoustic wave resonator 114 may expose the electrode material 106, or some other layer that was disposed on the substrate before the first electrode material was deposited on the substrate.

[0040] Additional layers that may be exposed (or applied) at this point may include an interface layer. The interface layer may act to enable or more easily enable functionalization of the active surface of the bulk acoustic wave resonator 114. In some embodiments, the interface layer may be patterned or available to receive a self-assembled monolayer (SAM) over the entire active area of ​​the bulk acoustic wave resonator, thereby allowing the SAM and functionalization (e.g., specific binding) material applied on the interface layer to overlap the entire active area. In other embodiments, a blocking layer may be patterned on the interface layer, or only a portion of the interface layer may be available to receive a SAM over only a portion of the active area, thereby allowing the SAM and functionalization material applied on the interface layer to overlap only a portion of the active area.

[0041] In some embodiments, photolithography can be used to facilitate patterning of the interface or blocking material on a portion of the MEMS resonator. Photolithography involves the use of light to transfer a geometric pattern from a photomask to a light-sensitive chemical photoresist on a substrate and is a process well known to those skilled in the art of semiconductor manufacturing. Typical steps employed in photolithography include cleaning the wafer, applying a photoresist (including either positive or negative photoresist), aligning the mask, and exposing and developing. After features are defined in the photoresist on the desired surface, the interface layer can be patterned by etching one or more gaps in the photoresist layer, and then the photoresist layer can be removed (e.g., using a liquid photoresist stripper, by ashing via application of an oxygen-containing plasma, or by other removal processes).

[0042] In some embodiments, the interface layer may include a hydroxylated oxide surface suitable for forming an organosilane SAM layer. A preferred interface material that includes a hydroxylated oxide surface is silicon dioxide [SiO2]. Alternative materials that include a hydroxylated oxide surface for forming an interface layer include titanium dioxide [TiO2] and tantalum pentoxide [Ta2O5]. Other alternative materials that include a hydroxylated oxide surface are known to those skilled in the art, and these alternative materials are considered to be within the scope of the present disclosure.

[0043] In other embodiments, the interface layer comprises gold or other noble metals suitable for receiving a thiol-based SAM (eg, ruthenium, rhodium, palladium, osmium, iridium, platinum, or silver).

[0044] In certain embodiments involving electrode materials subject to corrosion, a hermetic layer may also be provided between the upper electrode and the interface layer. If a noble metal (e.g., gold, platinum, etc.) is used for the upper electrode, a hermetic layer may not be necessary. If provided, the hermetic layer preferably has a low water vapor transmission rate (e.g., less than 0.1 (g / m 2 Following deposition of these layers, a SAM can be formed on the interface layer, the SAM preferably comprising an organosilane material. The hermetic layer protects the reactive electrode material (e.g., aluminum or aluminum alloy) from attack in the corrosive liquid environment, and the locally patterned interface layer promotes proper chemical bonding of the SAM.

[0045] In an embodiment, the hermetic layer and / or the interface layer may be applied by one or more deposition processes, such as atomic layer deposition (ALD), chemical vapor deposition (CAV) or physical vapor deposition (PVD). Of the above processes, ALD is suitable for at least the deposition of the hermetic layer (and may also be preferred for the deposition of the interface layer) due to its ability to provide excellent conformal coatings with good step coverage to the device features and to provide a pinhole-free layer structure. Furthermore, ALD can form uniformly thin layers that provide relatively little damping of acoustic vibrations that degrade device performance. Adequacy of coverage is important for the hermetic layer (if present) to avoid corrosion of the underlying electrodes. When ALD is used to deposit the hermetic layer, in an embodiment, the hermetic layer may include a thickness in the range of about 10 nm to about 25 nm. In an embodiment, the hermetic layer has a thickness of about 15 nm, or about 12 nm to about 18 nm. Conversely, if other processes such as CVD are used, the hermetic layer may include a thickness in the range of about 80 nm to about 150 nm or more, or in the range of about 80 nm to about 120 nm. Considering both of the above processes, the hermetic layer thickness may range from about 5 nm to about 150 nm. If ALD is used to deposit the interface layer, the interface layer may include a thickness in the range of about 5 nm to about 15 nm. In an embodiment, the interface layer may be about 10 nm thick, or may include a thickness in the range of about 8 nm to about 12 nm. In an embodiment, other interface layer thickness ranges may be used, or other deposition techniques other than ALD may be used. In an embodiment, the hermetic layer and the interface layer may be applied sequentially in a vacuum environment, thereby promoting a high quality interface between the two layers.

[0046] The airtight layer, if provided, according to certain embodiments, functions as a dielectric material and has a low water vapor transmission rate (e.g., less than 0.1 (g / m 2The hermetic layer may comprise an oxide, nitride or oxynitride material having a surface roughness (Sr / d) or less. In some embodiments, the hermetic layer comprises at least one of Al2O3 or SiN. In some embodiments, the interface layer comprises at least one of SiO2, TiO2 or Ta2O5. In some embodiments, multiple materials may be integrated into a single hermetic layer and / or the hermetic layer may comprise multiple sublayers of different materials. Preferably, the hermetic layer is further selected to promote compatibility with the reactive metal (e.g. aluminum or aluminum alloy) electrode structure of the underlying acoustic resonator structure. Although aluminum or aluminum alloys are frequently used as the electrode material for bulk acoustic wave resonators, a variety of transition and post-transition metals can be used for such electrodes.

[0047] Following deposition of the interface layer (optionally disposed on an underlying hermetic layer), a SAM is preferably formed on the interface layer. The SAM is typically formed by exposing the solid surface to an amphiphilic molecule that has chemical groups that exhibit a strong affinity for the solid surface. When an interface layer that includes a hydroxylated oxide surface is used, an organosilane SAM layer is particularly preferred for attachment to the hydroxylated oxide surface. The organosilane SAM promotes surface bonding via silicon-oxygen (Si--O) bonds. More specifically, organosilane molecules contain hydrolysis-sensitive groups and organic groups, and are therefore useful for bonding inorganic materials to organic polymers. The organosilane SAM can be formed by exposing a hydroxylated surface to an organosilane material in the presence of trace amounts of water to form intermediate silanol groups. These groups then react with free hydroxyl groups on the hydroxylated surface to covalently immobilize the organosilane. Examples of possible organosilane-based SAMs compatible with interface layers including hydroxylated oxide surfaces include 3-glycidoxypropyltrimethoxysilane (GPTMS), 3-mercaptopropyltrimethoxysilane (MPTMS), 3-aminopropyltrimethoxysilane (APTMS), and octadecyltrimethoxysilane (OTMS), including their ethoxy and chloro variants. Additional silanes that can be used in the SAM include poly(ethylene glycol) (PEG)-conjugated variants. Those skilled in the art will recognize that other alternatives exist, which are considered to be within the scope of the present disclosure. Exemplary SAMs can include thicknesses ranging from at least 0.5 nm or greater. Preferably, the SAMs bond readily to the locally patterned interface layer, but not to other adjacent material layers (e.g., hermetic layers, piezoelectric materials, and / or blocking material layers).

[0048] When using an interface layer that includes gold or other noble metals, a thiol-based (e.g., alkanethiol-based) SAM layer can be used. Alkanethiols are molecules with an alkyl chain as the backbone, a tail group, and an S--H head group. Thiols are sometimes used for interface layers of noble metals due to the strong affinity of sulfur for these metals. Examples of thiol-based SAMs that can be used include, but are not limited to, 1-dodecanethiol (DDT), 11-mercaptoundecanoic acid (MUA), and hydroxyl-terminated (hexaethylene glycol) undecanethiol (1-UDT). These thiols contain the same backbone but different end groups, i.e., a methyl group (CH3) for DDT, a carboxyl group (COOH) for MUA, and a hydroxyl-terminated hexaethylene glycol group (HO--(CH2CHO)6). In an embodiment, a SAM can be formed by incubating a gold surface in a thiol solution using a suitable solvent, such as absolute ethanol.

[0049] Following formation of the SAM, the SAM can be biologically functionalized, such as by receiving at least one functionalization (e.g., specific binding) material. In some embodiments, the specific binding material can be applied onto the SAM using a microarray spotting needle or other suitable method. The SAM and the underlying interface layer are patterned with high dimensional tolerances (e.g., using photolithography to define the interface layer) onto only a portion of the resonator structure (including the substrate), and then the applied specific binding material preferably adheres only to the SAM. Thus, higher dimensional tolerances can be achieved in the positioning of the specific binding material than can be achieved from microarray spotting alone.

[0050] FIG. 1H shows the device after additional processing. The device of FIG. 1H is flipped over and then placed on a second substrate 120, for example, to make electrical connections to other devices. The device is electrically connected to the second substrate 120, which may be, for example, a printed circuit board (PCB). The second substrate 120 can be connected to the device, for example, via electrical contact pads 122. The device of FIG. 1H also includes a fluidic wall 122 formed on the second substrate 120. The fluidic wall can be formed of any suitable material, such as a laser-cut "stencil" layer of thin polymeric material and / or laminate, and optionally includes one or more self-adhesive surfaces (e.g., adhesive tape). Optionally, such a wall can be formed prior to depositing the SAM layer, functionalization layer, and / or blocking layer with SU-8 negative epoxy resist or other photoresist material. The device of FIG. 1H also includes a cover 124 or cap layer. The cover 124 can be formed by defining ports (e.g., by laser cutting or water jet cutting) in a layer of a suitable material (e.g., a preferably substantially inert polymer, glass, silicon, ceramic, etc.) and adhering a cover or cap layer to the top surface of the fluidic wall 122. The combination of the cover 124 and the fluidic wall 122 forms the fluidic channel 126.

[0051] FIG. 1I shows the device after functionalization, indicated by YYYY, and blocking, indicated by XXXXX. Examples of specific binding materials for functionalization include, but are not limited to, antibodies, receptors, ligands, and the like. The specific binding materials are preferably configured to accept a predetermined target species (e.g., molecules, proteins, DNA, viruses, bacteria, and the like). The functionalization layer comprising the specific binding materials may comprise a thickness ranging from about 5 nm to about 1000 nm, or from about 5 nm to about 500 nm. In certain embodiments, an array of different specific binding materials may be provided on different active regions of a multiple resonator device (i.e., a resonator device comprising multiple active regions), which may optionally be combined with one or more active regions lacking specific binding materials to serve as comparison (or "reference") regions. In certain embodiments, the functionalization material may provide non-specific binding utility.

[0052] 1J provides an alternative example of forming the fluidic wall to which the cover 124 is attached. In this embodiment, the cover 124 is attached directly to the electrode material that forms the channel 128.

[0053] 2-20 illustrate a more specific method of forming a fluidic device including a bulk acoustic wave resonator according to one embodiment of the present disclosure. Generally, a deposition technique such as atomic layer deposition (ALD), chemical vapor deposition (CVD) or physical vapor deposition (PVD), or other techniques can be used to deposit materials. One or more masks (e.g., photolithography masks), stop layers, etch layers, etc. can also be used to pattern portions of any material deposited herein to form the disclosed layers or structures. The structures and devices illustrated in FIGS. 2-20 illustrate a method of forming three resonator structures, associated electrical connections, and structures, although for clarity, only one of the generally repeated structures is given a reference number.

[0054] 2 generally shows a substrate 200 having a first surface 201 and a second surface 202. A sacrificial layer 203 is formed on a portion of the first surface 201. The sacrificial layer may protect the resonator device formed by the described method when the second side 202 of the substrate 200 is partially removed. The substrate is for example a silicon substrate and the sacrificial material is for example aluminium. The sacrificial layer is typically deposited and patterned in the areas where the resonators are to be formed.

[0055] FIG. 3 shows the structure after steps intended to form a planar surface for additional process steps to be performed. In particular, additional silicon oxide material can be deposited on the sacrificial material 202 and the exposed portion of the first surface 201 of the substrate 200. The deposition of the silicon oxide material can be followed by a chemical mechanical polishing (CMP) process to form, for example, a planar silicon oxide layer 204 having a top surface flush with the sacrificial layer 203. In other words, the top surface of the silicon oxide layer 204 is planar with the top surface of the sacrificial layer 202 deposited and patterned in the step shown in FIG. 2. The silicon oxide layer 204, the sacrificial layer, or both, can function not only as a planarized layer for forming additional structures, but also as a silicon etch stop layer, a functionalized bonding surface, or both, during later steps in the disclosed process. Optionally, the silicon oxide material, if it is thicker, can also provide some temperature compensation properties. For example, a silicon oxide material having a thickness of at least 300 nanometers can be useful for temperature compensation of the device. The particular thickness of the silicon oxide material may depend, at least in part, on, for example, the operating frequency of the device, the materials within the device, the thicknesses of various materials within the device, or a combination thereof.

[0056] 4 shows the structure after a passivation layer 206 is formed over the sacrificial layer 202 and the silicon oxide layer 204. The passivation layer 206 may function, for example, as a moisture barrier layer. Exemplary passivation layers may include, for example, silicon nitride, and aluminum oxide (e.g., ALD deposited AlO). The passivation layer may provide moisture barrier properties that may help protect the device.

[0057] FIG. 5 shows the structure after the sacrificial layer 202 has been removed. The sacrificial layer 202 can be removed, for example, by etching the sacrificial layer 202 from the non-substrate side of the structure to form the resonator gap 208. In some particular embodiments, a photoresist pattern can be applied and a hole (not shown) can be etched through the passivation layer 206 above the sacrificial layer 202. A hole (not shown) can be etched. An exemplary etchant that can be utilized for this particular set of materials can include "16-1-1-2," which represents a composition that includes 16 parts by volume of H3PO4:1 HNO3:1 CH3COOH:2 H2O. This composition does not etch silicon nitride or silicon, but does etch aluminum oxide. Those skilled in the art will be aware of possible etchant compositions if other materials are used for the passivation layer 206 and the sacrificial layer 202. The formation of the resonator gap 208 allows the ultimately formed resonator to be probed and trimmed for final use.

[0058] 6 shows the structure after a first electrode 210 has been formed thereon. Formation or deposition of the first electrode 210 may include deposition of a material, patterning of a material, or any combination thereof. A silicon oxide material 212 is then deposited over the structure and planarized (e.g., using CMP) to form a planar surface for subsequent process steps. Suitable conductive materials for the first electrode may include, for example, aluminum, aluminum copper alloy, tungsten, or combinations of these materials.

[0059] FIG. 7 shows the structure after deposition of piezoelectric material 214 on the exposed surface of silicon oxide material 212. One example of a suitable material useful as a tilted shear axis piezoelectric film is aluminum nitride, which may be deposited at an angle different from the normal to the substrate. An optional tilted piezoelectric seed layer may also be used prior to deposition of the bulk piezoelectric material. The tilted shear axis piezoelectric film may be composed of an aluminum nitride seed layer deposited at an angle and a bulk aluminum nitride piezoelectric film deposited perpendicular to the substrate. The tilted seed layer may promote tilting of the microstructure of the bulk shear film, thus providing shear piezoelectric properties.

[0060] 8 shows the device after forming or depositing the second electrode 216 on the piezoelectric layer 214. Forming the second electrode 216 may include depositing a material, patterning a material, or any combination thereof. Suitable conductive materials for the first electrode may include, for example, aluminum, aluminum copper alloy, tungsten, or combinations of these materials. The material of the second electrode 216 may be the same as or different from the material of the first electrode 210. The area(s) where the first electrode 210, the piezoelectric layer 210, and the second electrode 216 overlap form a bulk acoustic wave resonator 220.

[0061] 9 shows the device after formation of a build-up layer 122. A build-up layer is any structure that can reduce parasitic losses along the length of the lead extending from the second electrode. Some examples of suitable build-up materials include aluminum, aluminum copper alloy, tungsten, or combinations of these metals.

[0062] 10 shows the device after formation of the second passivation layer 224. The second passivation layer 224 may include materials as described with respect to the first passivation layer and may provide the same or similar functions as the first passivation layer. The materials, properties and characteristics (e.g., thickness, etc.) may be the same as or different from the first passivation layer. The second passivation layer is not deposited or is not present in the active area (e.g., on the bulk acoustic wave resonator 220) or on the second electrode where the interconnects are formed, as described further below.

[0063] FIG. 11 shows the device after formation of the acoustic energy management structure 226. The acoustic energy management structure 226 in this example is an air cavity. The acoustic energy management structure covers the resonator and can also protect it from materials, chemicals, or both that may come into contact with and attenuate the resonator. Materials that can be used to fabricate the acoustic energy management structure can include, for example, photoresists or photoimageable epoxies, such as TMMF® (Tokyo Ohka Kogyo Co., Ltd.) or SU-8 (MicroChem Inc, Newton, Massachusetts). The acoustic energy management structure including the air cavity 226 can be fabricated in two structures, for example, a wall layer and a roof layer.

[0064] 12 shows the device after the next step, i.e., formation of interconnects 228 disposed on at least a portion of the second electrode material in areas not overlapping the bulk acoustic wave resonator 220. The interconnects 228 function to provide electrical, mechanical, or electrical and mechanical connections between the acoustic wave resonator 220 and other structures or devices. The interconnects can be formed as electrical interconnect bumps. The interconnects can be formed, for example, with tin-containing copper pillars. Fabrication of tin-containing plated copper pins includes using photoresist to pattern areas, depositing an optional plating seed layer such as titanium or copper, plating the interconnects, and removing any plating seed layer and photoresist.

[0065] FIG. 13 shows the device after a portion of the second surface 202 of the substrate has been removed to expose a modified second surface 230. This step can be achieved by a thinning step or a non-selective localized removal step such as a backgrinding process. The backgrinding provides the desired substrate thickness. In some instances, such as when the height of the final microfluidic channel is defined by the distance from this back surface 230 to the top of the independently formed walls (see later process steps), the thickness of the substrate at this point is important. Fluidic channels are described further below. In some optional embodiments, the substrate can be thinned early and then a temporary carrier may be utilized to provide mechanical stability for some processing steps.

[0066] 14A shows the structure after selective portions of the substrate have been removed from the modified second surface 230 to form an upper substrate surface 233. In particular, the areas of the substrate that are removed are those that underlie the acoustic wave resonator 220. Optionally, material beyond the perimeter of the acoustic wave resonator 220 can also be removed. Once the substrate material has been removed, a hermetic layer, such as silicon nitride, is exposed, and an interface layer, such as silicon oxide, is exposed.

[0067] In embodiments where the sacrificial layer has not yet been removed, it may be removed at this point. This is shown in the apparatus of FIG. 14A. If the sacrificial layer is still intact due to the removal of the substrate, it may help protect the electrodes during the backside dry etch. A particular process for accomplishing this selective removal of a portion of the substrate involves a dry silicon etch over the area of ​​the resonator 220. One particular exemplary method for completing this process is to coat the backside of the wafer with photoresist, typically for dry etching this may be a resist on the order of 5-10 micrometers thick. An alignment tool on the backside may be registered to the alignment marks on the frontside and the photoresist may be exposed. The photoresist may be developed and the silicon may be etched by deep reactive ion etching (DRIE) through alternating sulfur hexafluoride (SF6) and octafluorocyclobutane (C4F8) passivation layers. An alternative masking process for the photoresist is to deposit aluminum on the backside and open the pattern with laser machining. Other useful silicon etching processes may include anisotropic wet chemical etching using potassium hydroxide (KOH) or tetramethylammonium hydroxide (TMAH) to selectively remove the substrate along the active area. In this case, the wall profile is 54.7 degrees, e.g., the silicon in the substrate. <111> It is a wall that continues onto the surface.

[0068] Figure 14B shows the device as the substrate 200 is viewed from the second surface 202. Figure 14B shows the acoustic wave resonator 220 and the trench 235 formed to expose the acoustic wave resonator 220. Figure 14C shows the device as the substrate 200 is viewed from the first surface 201. From this surface, the acoustic energy management structures, exemplified as air cavities 226 and pillars 228, are visible.

[0069] 15A shows the device after flip chip attachment to a sensor board 240. In one embodiment, the interconnect pillars 228 are electrically connected by soldering, for example, tin on copper pads 242 with an organic solderability preservative (OSP). Other alternatives may include solder balls on the die soldered onto the bond pads. There is no fluid on the side of the die with the interconnect bumps.

[0070] Figure 15B shows a cross-section of the device of Figure 15A, showing the sensor board 240 and the substrate 200. Figure 15C shows the structure as viewed from the second surface 202 of the substrate 200, showing the trench 235 exposing the acoustic wave resonator 220.

[0071] Figure 15D shows a view from the bottom surface 241 of the sensor board, showing the respective locations of the pillars 228, air cavity 226 and acoustic wave resonator 220. Figure 15E shows a view from the top surface 243 of the sensor board, showing the respective locations of the remaining substrate 200 and acoustic wave resonator 220. Finally, area 245 shows where the substrate will be etched to a depth that exposes the first electrode layer 210 of the acoustic wave resonator 220, thereby forming the bottom of the fluidic channel.

[0072] 16-19 show one method of forming a fluidic channel with independent walls. FIG. 16 shows the device after forming or attaching a fluidic wall structure 250 to the sensor board 240. In some exemplary embodiments, the fluidic wall structure 250 can be attached to the sensor board 240 with adhesive 252. The fluidic wall structure can be formed from injection molding of resin, machining of metal or glass, or other suitable methods. In mass production, an automated robotic system can be used to dispense the adhesive at the location where the fluidic wall structure is to be placed. The wall structure can be received on the adhesive in either a tape and reel format or in a tray. The wall structure can be placed on the adhesive. The adhesive is cured in an oven. The fluidic wall structure is configured to correspond to the desired fluidic channel height from the resonator to the top of the wall. The channel height 254 of the final fluidic channel can be described as from the surface of the first electrode 210 to the top of the fluidic wall structure 250.

[0073] FIG. 17A shows the structure after an adhesive underfill 256 has been deposited under the flip-chip mounted die. FIG. 17B shows a first cross-section of the structure, showing the adhesive underfill 256. FIG. 17C shows an isometric view of the structure, also showing the adhesive underfill 256. The adhesive from the dispenser tip can be placed near the face of the die. The adhesive under the mounted die is wicked by capillary forces. A bake step can then be performed to harden the adhesive. A bake step can be completed to harden both the underfill and the fluidic wall structure adhesive. The purpose of the underfill adhesive is to protect the raised areas of the die from chemical attack by fluids used during use of the sensor.

[0074] FIG. 18 shows the structure after functionalization (illustrated as YYY in FIG. 18) and blocking (illustrated as XXXXXX in FIG. 18). FIG. 18 shows chemical functionalization on the sensor. First a silanization step is performed to coat the surface with a monolayer of adhesion promoter, then functionalization bodies can be printed onto the resonator, and finally, the non-functionalized surface can be blocked to prevent non-specific binding. The functionalization bodies can be bioreceptors configured to bind the analyte of interest. The functionalization can be, for example, a protein.

[0075] Figures 19A and 19B (cross section) show the structure after a fluid channel cover 260 has been attached to the fluid wall structure 250. The structure of Figures 19A and 19C also shows a fluid inlet 262 and a fluid outlet 264. Examples of suitable fluid chamber covers are adhesive tape or stickers. The cover can be punched or laser machined for dimensions, inlet and outlet ports. The cover can be attached in place, for example, by applying pressure.

[0076] FIG. 20 shows an alternative to FIGS. 16-19 for forming fluid channels. In FIG. 20, a fluid chamber cover 260 is flip chip mounted and attached to the substrate (220) / sensor board (240) structure with underfill adhesive 256. In this embodiment, the fluid chamber cover 260 can be attached directly to the upper substrate surface 233. In this embodiment, the fluid chamber cover 260 can be an adhesive tape or a sticker. The fluid chamber cover 260 can be punched or laser machined for the dimensions and formation of the inlet and outlet ports. The fluid chamber cover 260 can be attached in place, for example, by applying pressure.

[0077] In this view, the resonator can be seen in an etched trench in the substrate, and the edge area of ​​the die can be further etched to make space for inlet and outlet fluid ports. The etched silicon portion of the substrate provides a channel for fluid flow adjacent to the resonator. To complete testing of the sensor, fluid is flowed into the fluid inlet of the cover, and then the fluid is flowed across the resonator and out the fluid outlet. The etched silicon portion of the substrate provides a channel for fluid flow adjacent to the resonator. Analytes of interest can bind to the chemical functionalization, changing the amplitude-magnitude characteristics of the bulk acoustic wafer device.

[0078] 21-36 illustrate another exemplary method of fabricating a fluidic device that includes a bulk acoustic wave resonator and a reflecting mirror as the wave management structure. Those skilled in the art will appreciate that the fabrication processes described above (e.g., as shown in FIGS. 2-10) may be used in conjunction with this method to form structures that include alternative reflecting mirrors and devices.

[0079] Figure 21 shows a substrate such as silicon with silicon oxide and silicon nitride deposited on its surface. The silicon oxide acts as a silicon etch stopper as well as a functionalized bonding surface for the device. Additionally, a thicker silicon oxide layer can act as a temperature compensation layer for the device. The silicon nitride layer is a moisture barrier to protect the device.

[0080] 22 shows the addition of electrode material and silicon oxide, followed by a CMP process of the silicon oxide to make the surface planar. Suitable electrode materials may include aluminum, aluminum copper alloy, tungsten, or combinations of these metals.

[0081] FIG. 23 illustrates the deposition of a piezoelectric film, for example a tilted shear axis piezoelectric film. Suitable materials may include aluminum nitride. The shear axis film may include a seed layer to promote tilting of the bulk shear film.

[0082] Figure 24 shows the deposition and patterning of electrodes on a piezoelectric body. Suitable electrode materials may include aluminum, aluminum copper alloy, tungsten, or combinations of these metals. The area where the two electrodes overlap the piezoelectric material forms a resonator.

[0083] Figure 25 shows the deposition and patterning of the build-up layer. The purpose of the build-up layer is to reduce parasitic losses over the length of the lead. Suitable build-up materials may include aluminum, aluminum copper alloy, tungsten, or combinations of these metals.

[0084] Figure 26 shows the deposition and patterning of a protective layer. An example of a suitable protective layer is silicon nitride. The protective layer is not deposited in the active areas or where the copper pillars will be formed.

[0085] FIG. 27 shows the deposition and patterning of an acoustic reflector in the area of ​​the resonator. The purpose of the acoustic reflector is to return the acoustic energy back to the resonator, improving the performance of the device. The acoustic reflector can be made of alternating layers of silicon oxide and patterned tungsten, or alternating layers of silicon oxide and aluminum nitride.

[0086] Figure 28 illustrates the creation of electrical interconnect bumps. Suitable materials include copper pillars with tin. The production of plated copper pins with tin includes patterning areas using photoresist, depositing a plating seed layer such as titanium or copper, plating the interconnect bumps, and removing the plating seed layer and photoresist.

[0087] Figure 29 shows the apparatus after the substrate has been background. The purpose of backgrinding is to achieve the required substrate thickness. For free-walled fluids, the substrate thickness defines the height of the fluidic channels adjacent to the resonator sensor. For etched die substrate fluids, the substrate thickness defines the channel height of the fluidic channels. The diagram below makes this clear.

[0088] Figure 30 shows the device after the substrate has been dry silicon etched in the zone of the resonator. One way to complete this process is to coat the backside of the wafer with photoresist, typically for dry etching the thickness of the resist is around 5-10 micrometers. An alignment tool on the backside is used that aligns to the alignment marks on the frontside to expose the photoresist. The photoresist is developed. Deep reactive ion etching (DRIE) the silicon alternately with SF6 and C4F8 passivation layers to etch the straight sidewalls. An alternating masking process for the photoresist is to deposit aluminum on the backside and open the pattern with laser machining.

[0089] Figure 31 shows the device after flip chip attachment to the substrate. One interconnect embodiment is copper pillars on the die with tin soldered onto copper pads with an organic solderability preservative (OSP). Another method is solder balls on the die soldered onto gold bond pads.

[0090] 32-36 show examples including fluidic channels defined by separate walls. FIG. 32A shows attachment of the fluidic walls to a substrate. The fluidic wall structures can be formed from injection molding of resin, machining of metal or glass. In mass production, a robot is used to apply adhesive at the site where the fluidic wall structures are to be placed. In mass production, the wall structures are received either in tape and reel format or in trays. The wall structures are placed on the adhesive by the robot. The adhesive is cured in an oven. The fluidic wall structures are configured to achieve the desired fluidic channel height from the resonator to the top of the wall. No fluid is present on the side of the die that includes the interconnect bumps. The fluidic wall structures are not shown to size scale, and in practice the width of the walls will be wider to allow for bonding of the fluidic cover. FIG. 32B shows a plan view of both the side of the die opposite the interconnect bumps and the separate wall structures. In this view, the resonators are seen in the etched portion of the substrate. The cover tape is not shown, but the inlet and outlet openings of the cover are shown. To complete a sensor test, fluid flows into the fluid inlet, across the die with the resonators, and out the fluid outlet. Etched silicon portions of the substrate provide channels for the fluid to flow adjacent to the resonators.

[0091] Figure 33 shows adhesive underfill under a flip chip attached die. The adhesive from the dispense tip is placed near the face of the die. Capillary forces wick the adhesive under the attached die. A bake step is performed to harden the adhesive. The purpose of the underfill adhesive is to protect the raised areas of the die from chemical attack from fluids used during sensor use.

[0092] Figure 34 shows the functionalization chemistry of the biosensor. First, a silanization step is completed to coat a monolayer of adhesion promoter on the surface, then the functionalization bodies are printed onto the resonator, and then the surface is blocked to prevent non-specific binding. The functionalization bodies are bioreceptors configured to bind the analytes of interest. The functionalization bodies can be, for example, proteins.

[0093] FIG. 35 shows the device after the fluid chamber cover has been attached. Examples of suitable fluid chamber covers are adhesive tape or stickers. The cover is punched or laser cut depending on the dimensions, inlet and outlet ports. The cover is attached in place using pressure. FIG. 35 shows the device after the fluid chamber cover has been attached to the BAW die. Examples of suitable fluid chamber covers are adhesive tape or stickers. The cover is punched or laser cut depending on the dimensions, inlet and outlet ports. The cover is attached in place using pressure.

[0094] FIG. 36 shows a plan view of the side of the die opposite the interconnect bumps. In this view, the resonators are seen in the etched portion of the substrate, and the edge region of the die is further etched to provide space for fluid inlet and outlet ports. The etched silicon portion of the substrate provides a channel for fluid flow adjacent to the resonator. To complete the sensor test, fluid flows into the fluid inlet of the cover, then it crosses the resonator and flows out the fluid outlet. The etched silicon portion of the substrate provides a channel for fluid flow adjacent to the resonator. Analytes of interest bind to the chemical functionalization and change the amplitude-magnitude characteristics of the bulk acoustic wafer device.

[0095] 32-36 show an example including fluid channels defined by independent walls, and FIG. 37 is an alternative example of those process steps. In FIG. 37, the fluid chamber cover 260 is flip chip mounted and attached to the substrate (220) / sensor board (240) structure with underfill adhesive 256. In this embodiment, the fluid chamber cover 260 can be attached directly to the upper substrate surface 233. In this embodiment, the fluid chamber cover 260 can be an adhesive tape or a sticker. The fluid chamber cover 260 can be punched or laser machined for the dimensions and formation of the inlet and outlet ports. The fluid chamber cover 260 can be attached in place, for example, by applying pressure.

[0096] In this view, the resonator can be seen in an etched trench in the substrate, and the edge region of the die can be further etched to provide space for inlet and outlet fluid ports. The etched silicon portion of the substrate provides a channel for fluid flow adjacent to the resonator. To complete testing of the sensor, fluid can be flowed into the fluid inlet of the cover, and then the fluid can be flowed across the resonator and out the fluid outlet. The etched silicon portion of the substrate provides a channel for fluid flow adjacent to the resonator. Analytes of interest can bind to the chemical functionalization, changing the amplitude-magnitude characteristics of the bulk acoustic wafer device.

[0097] Figures 38-54 illustrate another method of fabricating a fluidic device including a bulk acoustic wave resonator. Figure 38 illustrates a silicon-on-insulator (SOI) wafer substrate. Those skilled in the art will appreciate that any portion of the fabrication process described above may be used with this method.

[0098] FIG. 39 shows patterning of a hard mask such as silicon dioxide or silicon nitride and anisotropically wet etching the top silicon. The wet etch can be done using TMAH or KOH. FIG. 40 shows removal of the wet etched silicon oxide hard mask and deposition of a silicon nitride layer. The silicon nitride layer is a moisture barrier to protect the device. FIG. 41 shows application of electrodes. Suitable electrode materials include aluminum, aluminum copper alloy, tungsten, or combinations of these metals. FIG. 42 shows deposition of a tilted shear axis piezoelectric film. A suitable material is aluminum nitride. The shear axis film may include a seed layer to promote tilting of the bulk shear film. FIG. 43 shows deposition and patterning of electrodes on the piezoelectric. Suitable electrode materials include aluminum, aluminum copper alloy, tungsten, or combinations of these metals. The area where the two electrodes overlap the piezoelectric material forms the resonator. FIG. 44 shows deposition and patterning of a build-up layer. The purpose of the build-up layer is to reduce parasitic losses over the lead length. Suitable build-up materials include aluminum, aluminum copper alloy, tungsten, or combinations of these metals. Figure 45 shows the creation of a protective cavity for the resonator. The purpose of the protective cavity is to prevent materials from contacting and damping the resonator. Suitable materials for the creation of the cavity include TMMF, which can be photoimaged. This can be achieved with two layers: a wall layer and a roof layer. Figure 46 shows the creation of the electrical interconnect bumps. Suitable materials include tin-containing copper pillars. The fabrication of tin-containing plated copper pins includes patterning areas using photoresist, depositing a plating seed layer such as titanium or copper, plating the interconnect bumps, and removing the plating seed layer and photoresist. Figure 47 shows the device after the substrate has been removed. The thinning or removal process can be completed by etching the silicon by dry etching (SF6) or wet etching (TMAH). Another option is to back-grind the wafer to remove the substrate.

[0099] Figure 48 shows the device after flip chip attachment to the board. One interconnect embodiment is copper pillars with tin on the die soldered onto copper pads with an organic solderability preservative (OSP). Another alternative is solder balls on the die soldered to gold bond pads.

[0100] FIG. 49A shows the attachment of the fluidic wall to the substrate. The fluidic wall structure can be formed from injection molding of resin, machining of metal or glass. In mass production, the adhesive is applied using a robot at the site where the fluidic wall structure is placed. In mass production, the wall structure is received either in tape and reel format or in a tray. The wall structure is placed on the adhesive by the robot. The adhesive is cured in an oven. The fluidic wall structure is configured to achieve the desired fluidic channel height from the resonator to the top of the wall. FIG. 49B shows a top view of the side of the BAW sensor die flip-chip attached to the substrate and the free-standing wall structure. There is no fluid present on the side of the die with the interconnect bumps. The fluidic wall structure is not shown to size scale, in reality the width of the wall would be wider to allow for bonding of the fluidic cover.

[0101] Figure 50 shows adhesive underfill under a die attached to a flip chip. The adhesive from the dispense tip is placed near the face of the die. Capillary forces wick the adhesive under the attached die. A bake step is performed to harden the adhesive. The purpose of the underfill adhesive is to protect the raised areas of the die from chemical attack from fluids used during sensor use.

[0102] Figure 51 shows the functionalization chemistry of the biosensor. First, a silanization step is completed to coat a monolayer of adhesion promoter onto the surface, then the functionalization entities are printed onto the resonator, followed by blocking of the surface to prevent non-specific binding. The functionalization entities are bioreceptors configured to bind the analytes of interest. The functionalization entities can be, for example, proteins.

[0103] FIG. 52A shows the device after the fluid chamber cover has been attached. Examples of suitable fluid chamber covers are adhesive tape or stickers. The cover is punched or laser cut depending on the dimensions, inlet and outlet ports. The cover is attached in place with pressure. FIG. 52B shows a top view of the side of the die opposite the interconnect bumps and free-standing wall structure. In this view, the resonator is seen within the etched portion of the substrate. The cover tape is not shown, but the inlet and outlet openings of the cover are shown. To complete the sensor test, fluid flows into the fluid inlet, across the die with the resonator, and out the fluid outlet. The etched silicon portion of the substrate provides a channel for the fluid to flow adjacent to the resonator.

[0104] The process illustrated in Figures 38-44 can be completed using the process steps illustrated in Figures 53-62, thereby forming a device that includes a resonator mirror in place of the air cavity formed by Figures 38-44. Upon completion of the process steps performed by Figures 38-44, the structure has an acoustic mirror formed thereon, as illustrated in Figures 53-62. Thus, the process of Figures 38-44 and 53-62 illustrates another exemplary method of fabricating a fluidic device that includes a bulk acoustic wave resonator. According to this embodiment, the fluidic device includes an etched silicon-on-insulator (SOI) wafer and an acoustic reflector. Those skilled in the art will appreciate that the fabrication processes described above can also be used in this method.

[0105] Figure 53 shows the device after fabricating an acoustic mirror over the resonator. The purpose of the acoustic reflector is to return acoustic energy back to the resonator, improving the performance of the device. The acoustic reflector can be made of alternating layers of silicon oxide and patterned tungsten, or alternating layers of silicon oxide and aluminum nitride.

[0106] Figure 54 illustrates the creation of electrical interconnect bumps. Suitable materials include copper pillars with tin. The creation of plated copper pins with tin includes patterning areas using photoresist, depositing a plating seed layer such as titanium or copper, plating the interconnect bumps, and removing the plating seed layer and photoresist.

[0107] Figure 55 shows the device after the substrate has been removed. The thinning or removal process can be completed by etching the silicon with a dry etch (SF6) or a wet etch (TMAH). Another option is to backgrind the wafer and remove the substrate.

[0108] Figure 56 shows the device after flip chip attachment to the substrate. One interconnect embodiment is copper pillars with tin on the die soldered onto copper pads using an organic solderability preservative (OSP). Another method is solder balls on the die soldered onto gold bond pads.

[0109] FIG. 57 shows attachment of the fluidic wall to the substrate. The fluidic wall structure can be formed from injection molding of resin, machining of metal or glass. In mass production, a robot is used to dispense adhesive onto the site where the fluidic wall structure is to be placed. In mass production, the wall structure is received either in tape and reel format or in a tray. The wall structure is placed onto the adhesive by the robot. The adhesive is cured in an oven. The fluidic wall structure is configured to achieve the desired fluidic channel height from the resonator to the top of the wall.

[0110] Figure 58 shows adhesive underfill under a flip chip attached die. The adhesive from the dispense tip is placed near the face of the die. Capillary forces wick the adhesive under the attached die. A bake step is performed to harden the adhesive. The purpose of the underfill adhesive is to protect the raised areas of the die from chemical attack from fluids used during sensor use.

[0111] Figure 59 shows the functionalization chemistry of the biosensor. First, a silanization step is completed to coat a monolayer of adhesion promoter on the surface, then the functionalization bodies are printed onto the resonator, and then the surface is blocked to prevent non-specific binding. The functionalization bodies are bioreceptors configured to bind the analytes of interest. The functionalization bodies can be, for example, proteins.

[0112] Figure 60 shows the device after the fluid chamber cover has been attached. Examples of suitable fluid chamber covers are adhesive tape or stickers. The cover is punched or laser cut depending on the dimensions, inlet and outlet ports. The cover is attached in place using pressure.

[0113] Figure 61 shows a plan view of the side of the BAW sensor die flip-chip attached to the substrate and the free-standing wall structures. No fluid is present on the side of the die with the interconnect bumps. The fluidic wall structures are not shown to size scale, and in practice the width of the walls would be wider to allow for attachment of the fluidic cover.

[0114] Figure 62 shows a top view of both the side of the die opposite the interconnect bumps and the free-standing wall structure. In this view, the resonators are seen in the etched portion of the substrate. The cover tape is not shown, but the inlet and outlet openings in the cover are shown. To complete the sensor test, fluid flows into the fluid inlet, across the die with the resonator, and out the fluid outlet. The etched silicon portion of the substrate provides a channel for the fluid to flow adjacent to the resonator.

[0115] It should be understood that the various aspects disclosed herein may be combined in different combinations than those specifically presented in the detailed description and accompanying drawings. Depending on the embodiment, certain acts or events in any process or method described herein may be performed in a different order, added, combined, or omitted entirely (e.g., not all acts or events described may be required to perform the technique). The present invention is defined in the claims. However, the following is a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of other examples, embodiments, or aspects described herein.

[0116] Example 1 is a method of manufacturing a bulk acoustic wave resonator structure for a fluidic device, comprising the steps of: disposing a first conductive material on a portion of a first surface of a substrate to form at least a portion of a first electrode, the substrate having a second surface opposite the first surface; disposing a piezoelectric material on the first electrode; and disposing a second conductive material on the piezoelectric material to form at least a portion of the second electrode, the second conductive material extending substantially parallel to the first surface of the substrate and at least partially over the first conductive material, the overlapping area of ​​the first conductive material, the piezoelectric material, and the second conductive material being forming a bulk acoustic wave resonator, the bulk acoustic wave resonator having a first side and an opposite second side; disposing an acoustic energy management structure on the first side of the bulk acoustic wave resonator; disposing a third conductive material over a portion of the second conductive material and extending beyond the bulk acoustic wave resonator, the third conductive material forming an interconnect above the acoustic energy management structure in a direction substantially perpendicular to the first surface of the substrate; and removing a portion of the second surface of the substrate to expose a chemical-mechanical connection at a first electrode on the second side of the bulk acoustic wave resonator.

[0117] Example 2 is a method in which the step of placing a reflector structure on a first side of the bulk acoustic wave resonator in Example 1 includes forming walls and a top from a photoresist material to define a protective cavity over the bulk acoustic wave resonator.

[0118] Example 3 is the method of example 1, wherein forming a reflector structure on a first side of the bulk acoustic wave resonator includes disposing a layer of material to form an acoustic mirror on the bulk acoustic wave resonator.

[0119] Example 4 is the method of example 1, further including disposing and patterning a sacrificial layer over the substrate and disposing a passivation layer over the sacrificial layer, where the passivation layer is disposed prior to disposing the first conductive material, and disposing the first conductive material over the first portion of the substrate includes patterning the first conductive material such that the first conductive material is aligned over the sacrificial layer, and the passivation layer forms at least a portion of the first electrode in an area overlapping the first conductive material.

[0120] Example 5 is the method of example 4, further comprising removing the sacrificial layer adjacent to the passivation layer.

[0121] Example 6 is the method of example 1, wherein removing a portion of the substrate includes reducing a thickness of the substrate.

[0122] Example 7 is a method of manufacturing a fluidic device, the method including forming a bulk acoustic wave resonator structure and attaching the bulk acoustic wave resonator structure to a base, the forming the bulk acoustic wave resonator structure comprising the steps of disposing a first conductive material on a portion of a first surface of a substrate to form at least a portion of a first electrode, disposing a piezoelectric material on the first conductive material, and disposing a second conductive material on the piezoelectric material to form at least a portion of a second electrode, the second conductive material extending substantially parallel to the first surface of the substrate and at least partially over the first conductive material, the first conductive material, the piezoelectric material, and the piezoelectric material forming at least a portion of a first electrode. and a second conductive material overlapping the first electrode to form a bulk acoustic wave resonator; disposing a reflector structure on a first side of the bulk acoustic wave resonator; disposing a third conductive material over a portion of the second conductive material and extending beyond the bulk acoustic wave resonator, the third conductive material forming an interconnect above the reflector structure and extending in a direction substantially perpendicular to the first surface of the substrate; and removing a portion of the substrate to expose the first electrode on the second side of the bulk acoustic wave resonator, wherein attaching the bulk acoustic wave resonator structure to a base includes connecting the interconnect to the base.

[0123] Example 8 is the method of example 7, further comprising disposing an adhesive between the bulk acoustic wave reflector structure and the base.

[0124] Example 9 is the method of example 7, further comprising disposing a functionalization material over the second electrode.

[0125] Example 10 is the method of example 7, further comprising attaching a chamber wall surrounding a periphery of the bulk acoustic wave resonator structure to the base.

[0126] Example 11 is the method of example 10, further comprising disposing a cover over the chamber wall, the cover having a fluid inlet and a fluid outlet.

[0127] Example 12 is the method of example 7, further comprising defining a fluid pathway in the substrate adjacent to the second electrode.

[0128] Example 13 is the method of example 7, wherein removing a portion of the substrate includes reducing a thickness of the substrate.

[0129] Example 14 is the method of example 7, further comprising disposing a functionalization material on the second electrode after attaching the bulk acoustic wave resonator to the base.

[0130] Example 15 is a fluidic device comprising: a bulk acoustic wave resonator structure disposed below a substrate, the bulk acoustic wave resonator having a first electrode disposed on a portion of a first surface of the substrate, a piezoelectric material disposed on the first electrode, and a second electrode disposed on the piezoelectric material, the bulk acoustic wave resonator being formed by an overlapping region of the first electrode, the piezoelectric material, and the second electrode; a reflector structure disposed on a first side of the bulk acoustic wave resonator; and an interconnect disposed on a portion of the second electrode, the interconnect extending beyond the bulk acoustic wave resonator and extending above a height of the reflector structure in a direction substantially perpendicular to the first surface of the substrate, the substrate having an opening extending from the second surface of the substrate to the first electrode; a functionalization material disposed on the first electrode at the opening; a base electrically connected to the interconnect; a chamber wall extending from the base and surrounding the bulk acoustic wave resonator structure; and a fluid chamber at least partially bonded to the substrate and the chamber wall.

[0131] Example 16 is the fluidic device of Example 15, wherein the bulk acoustic wave resonator structure includes a cavity reflector.

[0132] Example 17 is the fluidic device of Example 15, wherein the bulk acoustic wave resonator structure is a film bulk acoustic wave resonator.

[0133] Example 18 is the fluidic device of Example 15, wherein the substrate includes a fluidic channel.

[0134] Example 19 is a fluidic device according to Example 15, wherein the bulk acoustic wave resonator structure has a plurality of bulk acoustic wave resonators, each of the bulk acoustic wave resonators having an associated reflector structure and an interconnect, and the interconnect individually and electrically connects each bulk acoustic wave resonator to a base.

[0135] Example 20 is the fluidic device of example 19, wherein the plurality of bulk acoustic wave resonators are arranged in a pattern of rows and columns along the substrate.

[0136] Although the present disclosure has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the present disclosure.

Claims

1. 1. A method of manufacturing a bulk acoustic wave resonator structure for a fluidic device, comprising: disposing a first conductive material over a portion of a first surface of a substrate to form at least a portion of a first electrode, the substrate having a second surface opposite the first surface; disposing a piezoelectric material over the first electrode; disposing a second conductive material over the piezoelectric material to form at least a portion of a second electrode, the second conductive material extending substantially parallel to the first surface of the substrate and at least partially over the first conductive material, an overlapping region of the first conductive material, the piezoelectric material and the second conductive material forming a bulk acoustic wave resonator, the bulk acoustic wave resonator having a first side and an opposite second side; disposing an acoustic energy management structure on a first side of the bulk acoustic wave resonator; disposing a third conductive material over a portion of the second conductive material and extending beyond the bulk acoustic wave resonator, the third conductive material forming an interconnect above the acoustic energy management structure and extending in a direction substantially perpendicular to the first surface of the substrate; removing a portion of the second surface of the substrate to expose a chemical-mechanical connection at the first electrode on a second side of the bulk acoustic wave resonator; The method includes:

2. 2. The method of claim 1 , wherein the step of disposing the energy management structure on a first side of the bulk acoustic wave resonator comprises forming at least one wall structure and a roof from a photoimageable material to define an air cavity above the bulk acoustic wave resonator.

3. The method of claim 1 , wherein forming the energy management structure on a first side of the bulk acoustic wave resonator comprises disposing a layer of material to form an acoustic mirror over the bulk acoustic wave resonator.

4. depositing and patterning a sacrificial layer over the substrate; and disposing a passivation layer over the sacrificial layer; the passivation layer is disposed prior to disposing the first conductive material; disposing the first conductive material over the first portion of the substrate includes patterning the first conductive material such that the first conductive material is aligned over the sacrificial layer; The method of any one of claims 1 to 3, wherein the passivation layer forms at least a part of the first electrode in the area overlying the first conductive material.

5. The method of claim 4 , further comprising removing the sacrificial layer adjacent to the passivation layer.

6. The method of any one of claims 1 to 3, wherein removing a portion of the substrate comprises reducing a thickness of the substrate.

7. The method of claim 6 , wherein the thickness of the substrate is reduced to between 200 micrometers and 400 micrometers.

8. 4. The method of claim 1, further comprising: mounting the bulk acoustic wave resonator to a base, and wherein mounting the bulk acoustic wave resonator comprises at least electrically connecting the interconnect to the base.

9. 1. A method of manufacturing a fluidic device, comprising the steps of: forming a bulk acoustic wave resonator structure; and attaching the bulk acoustic wave resonator structure to a base; forming the bulk acoustic wave resonator structure disposing a first conductive material over a portion of a first surface of a substrate to form at least a portion of a first electrode; disposing a piezoelectric material over the first conductive material; disposing a second conductive material over the piezoelectric material to form at least a portion of a second electrode, the second conductive material extending substantially parallel to the first surface of the substrate and at least partially over the first conductive material, an overlapping region of the first conductive material, the piezoelectric material and the second conductive material forming a bulk acoustic wave resonator; forming an acoustic reflector on a first side of the bulk acoustic wave resonator; disposing a third conductive material over a portion of the second conductive material and extending beyond the bulk acoustic wave resonator, the third conductive material forming an interconnect above the reflector structure and extending in a direction substantially perpendicular to the first surface of the substrate; removing a portion of the substrate to expose the first electrode on a second side of the bulk acoustic wave resonator; Including, The method, wherein attaching the bulk acoustic wave resonator structure to a base includes connecting the interconnect to the base.

10. The method of claim 9 , further comprising disposing an adhesive between the bulk acoustic wave resonator and the base.

11. The method of claim 9 , further comprising disposing a functionalization material over the second electrode.

12. attaching a chamber wall to the base, the chamber wall circumscribing the bulk acoustic wave resonator structure; The method of claim 9 , further comprising: disposing a cover over the chamber wall, the cover having a fluid inlet and a fluid outlet.

13. The method of claim 9 , wherein removing a portion of the substrate comprises reducing a thickness of the substrate.

14. A method according to any one of claims 9 to 13, wherein the step of forming the acoustic reflector comprises depositing alternating layers of material.

15. The alternating layers of the material are silicon oxide carbide [SiOC], silicon nitride [Si ３ N ４ ], silicon dioxide [SiO ２ ], aluminum nitride [AlN], tungsten [W] and molybdenum [Mo].

16. The method of claim 13 , wherein the thickness of the substrate is reduced to between 200 micrometers and 400 micrometers.

17. 1. A method of manufacturing a fluidic device, comprising the steps of: forming a bulk acoustic wave resonator structure; and attaching the bulk acoustic wave resonator structure to a base; forming the bulk acoustic wave resonator structure disposing a first conductive material over a portion of a first surface of a substrate to form at least a portion of a first electrode; disposing a piezoelectric material over the first conductive material; disposing a second conductive material over the piezoelectric material to form at least a portion of a second electrode, the second conductive material extending substantially parallel to the first surface of the substrate and at least partially over the first conductive material, an overlapping region of the first conductive material, the piezoelectric material and the second conductive material forming a bulk acoustic wave resonator; forming an air cavity on a first side of the bulk acoustic wave resonator; disposing a third conductive material over a portion of the second conductive material and extending beyond the bulk acoustic wave resonator, the third conductive material forming an interconnect above the reflector structure and extending in a direction substantially perpendicular to the first surface of the substrate; removing a portion of the substrate to expose the first electrode on a second side of the bulk acoustic wave resonator; Including, The method, wherein attaching the bulk acoustic wave resonator structure to a base includes connecting the interconnect to the base.

18. The method of claim 17 , further comprising disposing an adhesive between the bulk acoustic wave resonator and the base.

19. The method of claim 18 , further comprising disposing a functionalization material over the second electrode.

20. attaching a chamber wall to the base, the chamber wall circumscribing the bulk acoustic wave resonator structure; The method of any one of claims 17 to 19, further comprising disposing a cover over the chamber wall, the cover having a fluid inlet and a fluid outlet.

21. The method of claim 17 , wherein removing a portion of the substrate comprises reducing a thickness of the substrate.

22. 22. The method of claim 21, wherein the thickness of the substrate is reduced to between 200 micrometers and 400 micrometers.

23. The method of any one of claims 17 to 19, 21 and 22, wherein forming the air cavity comprises forming at least one of the wall and the roof from a photoimageable material.

24. 24. The method of claim 23, wherein the area of ​​the roof is from 100 square micrometers to 500,000 square micrometers.

25. 1. A bulk acoustic wave resonator structure comprising: a bulk acoustic wave resonator disposed beneath the substrate, the bulk acoustic wave resonator having a first electrode disposed over a portion of a first surface of the substrate, a piezoelectric material disposed over the first electrode, and a second electrode disposed over the piezoelectric material, the bulk acoustic wave resonator being defined by an overlapping region of the first electrode, the piezoelectric material, and the second electrode; an acoustic energy management structure disposed on a first side of the bulk acoustic wave resonator; an interconnect disposed over a portion of the second electrode, extending beyond the bulk acoustic wave resonator and extending above a height of the acoustic energy management structure in a direction substantially perpendicular to the first surface of the substrate; the substrate having an opening extending from a second surface of the substrate to the first electrode; a functionalization material disposed on the first electrode in the opening; a base electrically connected to the interconnect; a chamber wall extending from the base and surrounding the bulk acoustic wave resonator structure; a fluid chamber at least partially bonded to the substrate and to the chamber wall; A fluid device having:

26. 26. The fluidic device of claim 25, wherein the acoustic energy management structure has at least one wall and a roof comprising a photoimageable material.

27. 27. The fluidic device of claim 26, wherein the roof area is between 100 square micrometers and 500,000 square micrometers.

28. The fluidic device of claim 25 , wherein the acoustic energy management structure comprises an acoustic reflector.

29. The acoustic reflector is made of silicon oxide carbide [SiOC], silicon nitride [Si ３ N ４ ], silicon dioxide [SiO ２ 29. The fluidic device of claim 28, comprising alternating layers of a material selected from the group consisting of AlN, Tungsten [W] and Molybdenum [Mo].

30. A fluidic device according to any one of claims 25 to 30, wherein the substrate has a thickness of from 200 micrometers to 400 micrometers.

31. 31. A fluidic device according to any one of claims 25 to 30, wherein the bulk acoustic wave resonator structure comprises a plurality of bulk acoustic wave resonators, each of the bulk acoustic wave resonators having an associated acoustic energy management structure and an interconnect, the interconnect individually and electrically connecting each bulk acoustic wave resonator to the base.

32. The fluidic device of claim 31 , wherein the plurality of bulk acoustic wave resonators are arranged in a pattern of rows and columns along the substrate.

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