Patent Publication Number: US-2020299127-A1

Title: Composite structures

Description:
The present application relates to structures for supporting one or more components, such as mechanical and/or electrical and/or electromechanical components and to methods of fabricating such structures. In particular, the present application relates to structures for supporting components such as MEMS transducers, circuitry die or mechanical sub-structures. The present application also describes packages for housing one or more components and packaging techniques for the fabrication thereof. 
     Many miniaturised components, such as MEMS transducer die or integrated circuitry die, are mounted and/or supported by a substrate. The substrate may form part of a package structure which allows easy handling and assembly and serves to protect the die from e.g. mechanical damage, RF noise and environmental contamination. The package structure may also provide a means for connecting the package to a circuit board or other elements of a host device. The package typically comprises a cap or cover portion which is provided on a first, or upper, surface of the support substrate. Thus the cover portion is extends in a plane overlying the upper surface of the substrate and defines a chamber of the package within which one or more components—e.g. device or circuitry chips—are housed. 
     Thus, according to previously proposed arrangements one or more die are mounted on a supporting surface of the package substrate. This may be achieved through a process known as discrete die mounting. It will be appreciated that mounting a die to the upper surface of a package substrate results in the component being located within the chamber of the package cavity. Thus, the die occupies volume within the chamber. This has potential consequences for the headroom available within the chamber, the performance of the component(s) and the size—in particular the height—of the packaged component(s). 
     The present aspects and examples relate to structures and/or substrates for supporting one or more components e.g. die. In particular, but not necessarily, the present aspects and examples relate to structures or substrates for supporting at least one semiconductor die. In particular, the present aspects seek to provide arrangements which provide an improvement or gain in the available volume within a package structure. Additionally or alternatively, the present aspects and examples seek to provide support structures which are particularly suitable for wafer and/or batch-level processing techniques. 
     According to at least one example of a first aspect there is provided a substrate for a MEMS transducer package comprising:
         at least one die; and   a frame laterally surrounding and in contact with a side surface of the die.       

     The die may be a silicon die. The frame may be a moulded frame. Within the context of the present invention a die or “chip” may be considered to comprise a portion or unit of material, in particular semiconductor material, which provides a particular function and/or which supports one or more elements or features having a particular function. For example, a die may comprise an integrated circuit (IC), an application specific integrated circuit (ASIC) or a MEMS transducer such as MEMS microphone transducer die. A die may also provide some other function. A further example of a component or die is a port-hole die wherein a die of material comprises a hole which extends through the die from an opening in an upper surface of the die to an opening in a lower surface thereof. 
     According to at least one example a die may be considered to exhibit a footprint which defines a closed shape, which will typically be square or rectangular. The die may be considered to be generally planar in form. Furthermore, the plane of the die may be arranged to be substantially aligned with, or substantially parallel to, the plane of the substrate as a whole. 
     The frame may be formed of a mould material, e.g. an epoxy mould material, a polymer or a polymeric material. The mould material is preferably a hardenable or settable material which may be dispensed or applied in liquid form and manipulated to define the required shape and dimensions of the frame. 
     According to at least one example of the first aspect the die is provided between a first substrate plane defined by an upper surface of the frame and a second substrate plane defined by a lower surface of the frame. The lower surface of the die may be coplanar with the second substrate plane. The distance between the first substrate plane and the second substrate plane can be considered to define a planar height of the substrate. The height of the die may be less than or equal to the planar height of the substrate. 
     According to at least one example one or more through planar vias extend between the first substrate plane and the second substrate plane. The vias, which may be metal plated, facilitate an electrical connection between the first and second substrate planes. Thus, a through planar via may be formed in the die, which may be a silicon die, and will therefore be a through silicon via. Additionally or alternatively, one or more vias may be provided through the moulded frame (TMV). 
     According to at least one example the substrate comprises first and second die. The frame laterally surrounds both first and second die. The first and second die may be considered to be held in fixed positional relationship relative to each other by means of the frame structure. The frame structure may be considered to be a connecting frame. According to at least one example the first die is an ASIC and the second die is a port-hole die. 
     According to at least one example a MEMS microphone transducer is provided on the upper surface of the substrate. The MEMS microphone transducer typically comprises a flexible membrane which deflects in response to a pressure differential across the membrane, and wherein the MEMS microphone transducer is provided such that the flexible membrane overlies a hole provided in the port hole die. 
     According to at least one example of a second aspect there is provided a MEMS transducer package comprising a substrate according to at least one example of the first aspect further comprising a lid portion, the lid portion being provided on the upper surface of the package substrate to define a chamber. 
     According to a further aspect there is provided an electronic device comprising a MEMS transducer package according to an example of the second aspect. For example the device may comprise: a portable device; a battery powered device; an audio device; a computing device; a communications device; a personal media player; a headphone, a mobile telephone; a games device; and a voice controlled device. 
     According to at least one example of a further aspect there is provided a method of fabricating a substrate according to an example of the first aspect. Thus, according to the present method, the frame is formed of a mould material which is applied to a region laterally surrounding the or each die and allowed to harden in order to form a bond between the material of the frame and at least one side surface of the die(s). 
     According to an example of a further aspect there is provided a composite substrate comprising one or more intra-planar die provided in a region between a first plane defined by the upper surface of the composite substrate and a second plane defined by    
    
    
     
       For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made by way of example to the accompanying drawings in which: 
         FIGS. 1 a   - 1   c,  which may be collectively referred to as  FIG. 1 , illustrate a substrate according to a first example; 
         FIGS. 2 a  and 2 b   , which may be collectively referred to as  FIG. 2 , illustrate a substrate according to a second example; 
         FIG. 3  illustrates a substrate according to a third example comprising an ASIC die and a port hole die; 
         FIG. 4  illustrates a substrate as shown in  FIG. 3  and further comprising a MEMS microphone transducer; 
         FIGS. 5 a  and 5 b   , which may be collectively referred to as  FIG. 5 , show a schematic diagram and a perspective view, respectively, of a known capacitive MEMS microphone die which may form the MEMS transducer die illustrated in  FIG. 4 ; 
         FIG. 6  illustrates a package according to one example; 
         FIGS. 7 a   - 7   h,  which may be collectively referred to as  FIG. 7 , illustrate a process flow for fabricating a package according to one example; and 
         FIGS. 8 a   - 8   h,  which may be collectively referred to as  FIG. 8 , illustrate some of the steps in the process flow of  FIG. 7  at single unit level. 
     
    
    
     DETAILED DESCRIPTION 
     The description below sets forth examples and arrangements according to this disclosure. Further examples, arrangements and implementations will be apparent to those having ordinary skill in the art. Further, those having ordinary skill in the art will recognize that various equivalent techniques may be applied in lieu of, or in conjunction with, the examples discussed below, and all such equivalents should be deemed as being encompassed by the present disclosure. 
     Throughout this description any features which are the same or similar to features in other figures have been given the same reference numerals. 
     The present examples relate generally to a substrate suitable for a MEMS transducer package. 
       FIG. 1  illustrates a substrate  10  according to a first example. Specifically,  FIG. 1 a    shows a plan view of the substrate  10  and  FIG. 1 b    shows a cross-sectional view through the line A-A shown in  FIG. 1   a.  The substrate  10  comprises a die  12 , which in this example is generally rectangular in shape, and a frame structure  11 . The frame structure  11  laterally surrounds the die  12  and forms a part of the substrate. Thus, the substrate  10  can be considered to be a composite structure comprising a planar, rigid frame and at least one die formed within the plane of the frame. 
     As shown in  FIG. 1 , the frame  11  is formed in contact with, or is connected to, the side surfaces of the die  12 . The frame  11  defines the overall dimensions of the composite substrate when considered as a whole. Thus, the frame  11  essentially defines the perimeter boundary P of the substrate. Considering  FIG. 1   b,  the frame comprises a first “upper” surface  7  and a second “lower” surface  8 . A first plane X is defined by (i.e. is coincident with) the first upper surface of the frame whilst a lower plane Y is defined by (i.e. coincident with) the second, lower surface of the frame. The planar height Z of the substrate is determined by the distance between the first plane X and the second plane Y of the frame structure. Thus, the die  12  is provided between the first plane X and the second plane Y defined by the frame. In this sense the substrate can be considered to comprise an intra-planar die which is provided such that a lower surface of the intra-planar die is substantially coincident with the lower surface of the substrate, as defined by the frame structure, and wherein the height z of the die is largely or completely accommodated within the planar height Z of the frame. 
     In the present example the die  12  is generally planar in form and exhibits a generally rectangular shape. The dimensions of the die are defined by a length x, a width y and a height z. Thus, according to this particular example the height z of the die  12  is equal to or less than the planar height Z of the substrate. As such, the component can be considered to be provided entirely within the plane of the substrate. In circumstances where the substrate forms a substrate of a package comprising a chamber defined by a lid structure, it will be appreciated that the free volume of the chamber will be enhanced as a consequence of the component being provided within the plane of the package substrate. 
     It will be appreciated that in other examples the die may protrude to some extent above the surface but that a gain in available volume and/or a reduction in package height is nonetheless achieved. 
     The component  12  is illustrated in  FIG. 1   c.  Generally, the component can be considered to be a portion or “die” of material, in particular semiconductor material such as silicon, which provides a particular function and/or which supports one or more elements or features. 
     Thus, the die  12  may be an integrated circuit (IC), the integrated circuit comprising one or more circuitry elements to provide a functional circuit. Alternatively, the die  12  may be a MEMS transducer die such as a MEMS microphone transducer. The die may also comprise both a transducer and circuitry integrated together on the same die. As a further alternative the die  12  may comprise a port-hole die—i.e. a die of material, which comprises a hole which extends through the die from an upper surface to a lower surface thereof. According to at least one arrangement the hole may be intended to form an acoustic port for allowing acoustic pressure waves to travel from the region below the lower surface of the die to the region above the upper surface of the die. Thus, for example, a substrate comprising a port-hole die may be provided for arrangements which require acoustic pressure waves to travel from a region below the die to the region above the die. 
       FIG. 2  illustrates a substrate  20  according to a second example. Specifically,  FIG. 2 a    shows a plan view of the substrate  20  and  FIG. 2 b    shows a cross-sectional view through the line A-A shown in  FIG. 2 a   . The substrate  20  comprises a first die  22   a  and a second die  22   b.  The first and second dies are held in fixed positional relationship by means of a frame structure  21 . The frame structure  21  laterally surrounds each of the first and second die and defines the overall plane of the substrate  20 . Thus, the substrate  20  can be considered to be a composite structure comprising a planar frame and a pair of die formed within the plane of the frame. The substrate can be considered to comprise a pair of intra-planar die. 
       FIG. 3  which shows a substrate  30  comprising an ASIC die  32   a  and a port-hole die  32   b.  The ASIC die  32   a  and the port-hole die  32   b  are held in a fixed positional arrangement by means of a frame structure  31 . The frame structure  31  laterally surrounds both the ASIC die  32   a  and the port hole die  32   b  and defines the overall plane of the substrate  30 . The port-hole die is a die of semiconductor material having a hole  34  which extends through the die from an opening in an upper surface of the die  32   b  to an opening in a lower surface thereof. The ASIC die may optionally comprise a plurality of through silicon vias (TSV)  33 . As will be known by those skilled in the art a TSV is a vertical electrical connection that passes completely through the die and may be used, in conjunction with an associated bond pad, as an electrical interconnect to facilitate connection to an adjacent level or plane of interconnect within a package structure. Thus, a TSV facilitates an electrical connection to be formed through the plane of the die in order to form connections between a region above the upper surface of the die and a region below the surface of the die. In an alternative embodiment a through planar via is formed through the moulded frame and may be considered to be a trans mould via or TMV. Furthermore, at least one redistribution layer (RDL) may be formed on the upper and/or lower surface of the substrate  30 . As will be understood by those skilled in the art an RDL is a metal, e.g. copper, layer which serves to redistribute or relocate electrical connections. 
     The substrate illustrated in  FIG. 3  may be particularly useful in supporting a MEMS transducer since the hole  34  of the port-hole die allows the passage of acoustic pressure waves to a region directly above the upper surface of the substrate. This is illustrated in  FIG. 4  which shows a cross-sectional view of a substrate  30  similar to the substrate illustrated in  FIG. 3  and further comprising a discrete MEMS transducer die  100  provided in a region above the port-hole die. The MEMs transducer die may comprise a MEMS microphone transducer. 
       FIGS. 5 a  and 5 b    show a schematic diagram and a perspective view, respectively, of a known capacitive MEMS microphone die which may form the MEMS transducer die  100  illustrated in  FIG. 4 . The capacitive microphone comprises a membrane layer  101  which forms a flexible membrane which is free to move in response to pressure differences generated by sound waves. A first electrode  102  is mechanically coupled to the flexible membrane, and together they form a first capacitive plate of the capacitive microphone device. A second electrode  103  is mechanically coupled to a generally rigid structural layer or back-plate  104 , which together form a second capacitive plate of the capacitive microphone device. In the example shown in  FIG. 1 a    the second electrode  103  is embedded within the back-plate structure  104 . 
     The capacitive microphone is formed on a substrate  105 , for example a silicon wafer which may have upper and lower oxide layers  106 ,  107  formed thereon. A cavity  108  in the substrate and in any overlying layers (hereinafter referred to as a substrate cavity) is provided below the membrane, and may be formed using a “back-etch” through the substrate  105 . The substrate cavity  108  connects to a first cavity  109  located directly below the membrane. These cavities  108  and  109  may collectively provide an acoustic volume thus allowing movement of the membrane in response to an acoustic stimulus. Interposed between the first and second electrodes  102  and  103  is a second cavity  110 . A plurality of holes, hereinafter referred to as bleed holes  111 , connect the first cavity  109  and the second cavity  110 . 
     A plurality of acoustic holes  112  are arranged in the back-plate  104  so as to allow free movement of air molecules through the back plate, such that the second cavity  10  forms part of an acoustic volume with a space on the other side of the back-plate. The membrane  101  is thus supported between two volumes, one volume comprising cavities  109  and substrate cavity  108  and another volume comprising cavity  110  and any space above the back-plate. These volumes are sized such that the membrane can move in response to the sound waves entering via one of these volumes. Typically the volume through which incident sound waves reach the membrane is termed the “front volume” with the other volume, which may be substantially sealed, being referred to as a “back volume”. 
     In some applications the backplate may be arranged in the front volume, so that incident sound reaches the membrane via the acoustic holes  112  in the backplate  104 . In such a case the substrate cavity  108  may be sized to provide at least a significant part of a suitable back-volume. In other applications, the microphone may be arranged so that sound may be received via the substrate cavity  108  in use, i.e. the substrate cavity forms part of an acoustic channel to the membrane and part of the front volume. In such applications the backplate  4  forms part of the back-volume which is typically enclosed by some other structure, such as a suitable package. 
     It should also be noted that whilst  FIGS. 5 a  and 5 b    shows the backplate being supported on the opposite side of the membrane to the substrate, arrangements are known where the backplate is formed closest to the substrate with the membrane layer supported above it. 
     In use, in response to a sound wave corresponding to a pressure wave incident on the microphone, the membrane is deformed slightly from its equilibrium or quiescent position. The distance between the membrane electrode  102  and the backplate electrode  103  is correspondingly altered, giving rise to a change in capacitance between the two electrodes that is subsequently detected by electronic circuitry (not shown). 
     The membrane layer and thus the flexible membrane of a MEMS transducer generally comprises a thin layer of a dielectric material—such as a layer of crystalline or polycrystalline material. The membrane layer may, in practice, be formed by several layers of material which are deposited in successive steps. Thus, the flexible membrane  101  may, for example, be formed from silicon nitride Si 3 N 4  or polysilicon. Crystalline and polycrystalline materials have high strength and low plastic deformation, both of which are highly desirable in the construction of a membrane. The membrane electrode  102  of a MEMS transducer is typically a thin layer of metal, e.g. aluminium, which is typically located in the centre of the flexible membrane  101 , i.e. that part of the membrane which displaces the most. It will be appreciated by those skilled in the art that the membrane electrode may be formed by depositing a metal alloy such as aluminium-silicon for example. The membrane electrode may typically cover, for example, around 40% of area of the membrane, usually in the central region of the membrane. 
     Thus, known transducer membrane structures are composed of two layers of different material—typically a dielectric layer (e.g. SiN) and a conductive layer (e.g. AlSi). 
     The substrate illustrated in any of  FIG. 1, 2, 3 or 4 , may form part of a package structure. Thus, a lid structure or cover may be provided on top of the substrate in order to define a chamber in the region above the upper surface of the substrate. 
       FIG. 6  shows cross-sectional view through a package  300  comprising a substrate  30  similar to the substrate illustrated in  FIG. 4  and comprising an ASIC die  32   a  and a port hole die  32   b.  A MEMS microphone transducer die  100  is mounted to the upper surface of the substrate such that the flexible membrane  101  of the MEMS transducer overlies the hole  34  provided by the port hole die  32   b.  Thus, the hole  34  acts as an acoustic port of the package and allows the ingress of acoustic pressure waves into the region in front of the flexible membrane transducer. A lid structure, for example a metal lid,  200  is also mounted to the upper surface of the substrate  30  and defines a chamber within which the MEMS transducer  100  is housed. The composite substrate  30  thus serves as the package substrate. A first RDL layer  36   a  is formed on the upper side surface of the substrate  30  and a second RDL layer  36   b  is formed on the lower side surface of the substrate. A bond pad  37  is formed on the upper surface of the substrate and a conductive wire  39  is provided between the contact  37  and the MEMS transducer  100 . 
     From consideration of  FIG. 6  it will be appreciated that the ASIC is fully accommodated within the intra-planar region of the substrate  30 . Thus, the ASIC component of the substrate does not protrude above the surface of the substrate. As a consequence, there is a beneficial gain in head room inside the chamber which forms the back volume of the microphone transducer. 
     Furthermore, according to one or more of the present examples the substrate forms the package substrate, with the lid structure being mounted on the primary substrate and thus obviating the need for a separate package substrate. Thus, a package incorporating a substrate according to one or more the present examples which acts as the package substrate beneficially achieves a reduction in overall package height. 
       FIG. 7  illustrates a process flow for fabricating a package similar to the package shown in  FIG. 6  according to one example. It will be appreciated that the process is a batch assembly process wherein a plurality of packages are fabricated at the same time. 
     In  FIGS. 7 a  to 7 c    and ASIC die  32   a  and a port-hole die  32   b  are mounted side by side on a carrier  51 . Each pair of ASIC die  32   a  and port-hole die  32   b  will form part of a composite substrate. Thus, the carrier tape supports a plurality of die pairs and allows the fabrication of an assembly of composite substrates. In this example the carrier comprises a tape formed on an upper surface of a carrier substrate. A substrate frame  31  is formed in the region laterally surrounding the ASIC and port hole die by a process of film assisted moulding. Specifically, moulding material is applied to the region laterally surrounding the two die e.g. using a film  53  or tool which defines one or more of the boundary surfaces of the intended substrate assembly. The moulding material may comprise e.g. a polymer or epoxy type material. The moulding material is preferably a hardenable or settable material which may be applied in liquid form and which, when hardened, serves to generate a rigid substrate structure. Thus, the ASIC die and the port-hole die are ultimately provided within the plane of the substrate and with a fixed positional relationship between them. 
       FIGS. 7 d  to 7 h    show further batch-level processing steps. To aid understanding, the processing of a single unit is also illustrated in  FIGS. 8 a  to 8 h    which may be reviewed in conjunction with  FIGS. 7 d  to 7 h   . Firstly, the substrate assembly is released from the carrier ( FIG. 7 d   ). As illustrated in  FIG. 7 e   , the surface of the substrate assembly that will form the lower or back side of the substrates is then subject to an RDL process to form an RDL layer  36   b  which is illustrated in more detail in  FIGS. 8 a  to 8 c   . Firstly, as illustrated in  FIG. 8 a    a first layer of insulator (passivation)  61 , e.g. a dielectric material, is applied leaving exposed only the bond pad interface on the ASIC die  32   a.  A copper patterning layer  62  is then applied ( FIG. 8 b   ) which will ensure appropriate electrical connection between the respective bond pad interfaces that will be used for soldering (such as I/O pads). As shown in  FIG. 8 c    a second dielectric layer  63  is applied which will protect the copper surface of the electrical connection from oxidation and finally the bond pads a plated as shown in  FIG. 8   d.    
     As illustrated in  FIG. 7 f    an RDL process is then applied to the other opposite surface of the substrate which will form the upper or top side surface. The steps are illustrated in  FIGS. 8 e  to 8 h    and a similar to the steps of the RDL process carried out on the lower side surface and involve applying an insulator layer (passivation)— FIG. 8 e   , copper patterning— FIG. 8 f   , applying a second insulator layer (passivation)— FIG. 8 g    and plating— FIG. 8   h.    
     Once the RDL processes have been completed, and as illustrated in  FIG. 7 g    a MEMS die  100  is mounted to the upper surface of each of the substrates such that the flexible membrane of the substrate overlies the port hole of the port hole die  32   b  and a wire bond connection is made between the redistributed bond pads and the MEMS transducer. Finally, as shown in  FIG. 7 h   , a lid  200  is attached to each substrate portion in order to define a plurality of packages. In a subsequent step (not shown) the packages are singulated. 
     There are a number of advantages associated with a wafer level fabrication process according to the present examples and as illustrated in  FIGS. 7 and 8 . In particular, the composite substrates are particularly suitable for fabrication by batch-level processing techniques. Embedding the ASIC within the package substrate—which will also be the sound port substrate according to at least one example—allows a bigger backside volume and/or a smaller cavity and/or a reduction in package size (X/Y or Z). 
     It will be appreciated that the sound port of the resultant package is provided by the silicon port-hole die. This beneficially allows improved accuracy in the definition of the sound port which may be formed accurate by silicon processing. Prior arrangements typically involve forming a port hole in a package substrate which comprise a PCB (printed circuit board) substrate. 
     In any of the above examples, it will be appreciated the, or each, component may exhibit a depth z that is less than, equal to, or greater than the depth (z-dimension) of frame which is defined by the distance between the upper and lower surfaces of the frame. Thus, whilst there may be a benefit in being able to fully accommodate the component between the first and second plane defined by the frame, so that the component does not protrude above the upper surface of the substrate, this is not essential. However, it will be appreciated that reducing or minimising the amount by which a component protrudes above the surface of the primary substrate may be particularly advantageous in examples where a chamber is to be defined—e.g. by means of a package lid structure or the like—in the region directly above the upper surface of the substrate and where the volume of that chamber has an impact on the performance of the packaged device. For example, in the case of a composite substrate comprising a port hole substrate as a first component and a circuitry die or ASIC as a second component, wherein a MEMS microphone transducer having a flexible membrane is to be formed so as to overlie the port hole, the chamber will form the back volume of the microphone transducer. Thus, according to one or more of the present examples, it is possible to achieve a gain in headroom inside the chamber and/or a reduction in package height in comparison to previously proposed microphone transducers as a consequence of the circuitry chip being substantially or even totally provided between the first and second plane defined by the frame. 
     Whilst examples of the present aspects are particularly applicable to structures for supporting MEMS sensor transducers, especially capacitive transducers such as MEMS microphones. It will also be appreciated that other types of MEMS capacitive sensors could be implemented, for example accelerometers, pressure sensors, proximity sensors or flow meters. 
     Examples of the present aspects may be implemented in a host device, especially a portable and/or battery powered host device such as a mobile telephone, and audio player, a video player, a PDA, a mobile computing platform such as a laptop computer or tablet and/or a games device for example or in an accessory device, such a headset, earbud (possibly noise-cancelling), or microphone assembly, designed for wired, or wireless connection with such host devices, possibly via multi-wire cables, multi-pole jacks, or optical fibres and connectors. 
     It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. The word “comprising” does not exclude the presence of elements or steps other than those listed in a claim, “a” or “an” does not exclude a plurality, and a single feature or other unit may fulfil the functions of several units recited in the claims. Any reference numerals or labels in the claims shall not be construed so as to limit their scope. 
     As used herein, when two or more elements are referred to as “coupled” to one another, such term indicates that such two or more elements are in electronic communication or mechanical communication, as applicable, whether connected indirectly or directly, with or without intervening elements. 
     This disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that a person having ordinary skill in the art would comprehend. Similarly, where appropriate, the appended claims encompass all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that a person having ordinary skill in the art would comprehend. Moreover, reference in the appended claims to an apparatus or system or a component of an apparatus or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that apparatus, system, or component, whether or not it or that particular function is activated, turned on, or unlocked, as long as that apparatus, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative. Accordingly, modifications, additions, or omissions may be made to the systems, apparatuses, and methods described herein without departing from the scope of the disclosure. For example, the components of the systems and apparatuses may be integrated or separated. Moreover, the operations of the systems and apparatuses disclosed herein may be performed by more, fewer, or other components and the methods described may include more, fewer, or other steps. Additionally, steps may be performed in any suitable order. As used in this document, “each” refers to each member of a set or each member of a subset of a set. 
     Although exemplary embodiments are illustrated in the figures and described below, the principles of the present disclosure may be implemented using any number of techniques, whether currently known or not. The present disclosure should in no way be limited to the exemplary implementations and techniques illustrated in the drawings and described above. 
     Unless otherwise specifically noted, articles depicted in the drawings are not necessarily drawn to scale. 
     All examples and conditional language recited herein are intended for pedagogical objects to aid the reader in understanding the disclosure and the concepts contributed by the inventor to furthering the art, and are construed as being without limitation to such specifically recited examples and conditions. Although embodiments of the present disclosure have been described in detail, it should be understood that various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the disclosure. 
     Although specific advantages have been enumerated above, various embodiments may include some, none, or all of the enumerated advantages. Additionally, other technical advantages may become readily apparent to one of ordinary skill in the art after review of the foregoing figures and description. 
     To aid the Patent Office and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants wish to note that they do not intend any of the appended claims or claim elements to invoke 35 U.S.C. § 112(f) unless the words “means for” or “step for” are explicitly used in the particular claim.