Patent Publication Number: US-11388496-B2

Title: Microelectromechanical microphone having a stoppage member

Description:
PRIORITY APPLICATION 
     This application claims the benefit of and priority to U.S. Provisional Application No. 63/002,021, filed Mar. 30, 2020, the content of which application is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     There are situations in which a diaphragm of a microelectromechanical microphone can be subjected to sudden, large changes in air pressure. For example, the microelectromechanical microphone can fall on a hard surface during assembly into a device, such as a mobile telephone or wireless earbuds. Those sudden, large changes in air pressure can cause a substantial deformation of the diaphragm, resulting in damage to the diaphragm. 
     For some types of microelectromechanical microphones, overpressure valves in the diaphragm can be used to relieve some of the air pressure to which the microelectromechanical microphone is subjected. An overpressure valve can open during high-pressure load and, by relieving pressure, damage to the diaphragm can be avoided. 
     Unfortunately, overpressure valves can be detrimental to low frequency roll-off (LFRO) of a microelectromechanical microphone. In addition, overpressure valves can have rather slow opening times that may render them inadequate for abrupt, large changes in air pressure. Therefore, improved technologies for the reduction of damage to diaphragms in microelectromechanical microphones may be desired. 
     SUMMARY 
     The following presents a simplified summary of one or more of the embodiments in order to provide a basic understanding of one or more of the embodiments. This summary is not an extensive overview of the embodiments described herein. It is intended to neither identify key or critical elements of the embodiments nor delineate any scope of embodiments or the claims. The sole purpose of this Summary is to present some concepts of the embodiments in a simplified form as a prelude to the more detailed description that is presented later. 
     In an embodiment, the disclosure provides a microelectromechanical microphone device. The microelectromechanical microphone device includes a flexible plate configured to be deformed by a pressure wave. The microelectromechanical microphone device also includes a rigid plate mechanically coupled to the flexible plate. The rigid plate defines multiple openings that permit passage of the pressure wave. The microelectromechanical microphone device further includes a stoppage member affixed to the rigid plate and extending perpendicularly relative to a surface of the rigid plate opposite a surface of the flexible plate. The stoppage member has a distal surface that is separated from the surface of the flexible plate by a clearance distance. The stoppage member limits motion of the flexible plate in response to the pressure wave including a threshold amplitude. 
     In another embodiment, the disclosure provides a microelectromechanical microphone device. The microelectromechanical microphone device includes a substrate defining an opening to receive a pressure wave. The microelectromechanical microphone device also includes a flexible plate mechanically coupled to the substrate and configured to be deformed by the pressure wave. The microelectromechanical microphone device further includes a stoppage member affixed to the flexible plate and extending perpendicularly relative to a surface of the flexible plate opposite a surface of the substrate. The stoppage member has a distal surface that is separated from the surface of the substrate by a clearance distance. The stoppage member limits motion of the flexible plate in response to the pressure wave including a threshold amplitude. 
     In yet another embodiment, the disclosure provides a device. The device includes a microelectromechanical microphone device including a substrate defining a first opening to receive a pressure wave; a flexible plate mechanically coupled to the substrate and configured to be deformed by the pressure wave; a rigid plate mechanically coupled to the flexible plate, the rigid plate defining multiple openings that permit passage of the pressure wave; and at least one stoppage member assembled in a spatial relationship with the flexible plate. The at least one stoppage member limiting motion of the flexible plate in response to the pressure wave including a threshold amplitude. The device also includes a circuit coupled to the microelectromechanical microphone device and configured to receive a first signal indicative of a capacitance representative of an amplitude of the pressure wave. The circuit is further configured to generate a second signal representative of an amplitude of the pressure wave. 
     Other embodiments and various examples, scenarios and implementations are described in more detail below. The following description and the drawings set forth certain illustrative embodiments of the specification. These embodiments are indicative, however, of but a few of the various ways in which the principles of the specification may be employed. Other advantages and novel features of the embodiments described will become apparent from the following detailed description of the specification when considered in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a cross-sectional view of an example of a microelectromechanical microphone die, in accordance with one or more embodiments of the disclosure. 
         FIG. 2  illustrates an example of a scenario in which the microelectromechanical microphone die illustrated in  FIG. 1  is subjected to high pressures. 
         FIG. 3  illustrates a cross-sectional view of an example of a microelectromechanical microphone die, in accordance with one or more embodiments of the disclosure. 
         FIG. 4  illustrates an example of a scenario in which the microelectromechanical microphone die illustrated in  FIG. 3  is subjected to high pressures. 
         FIG. 5  illustrates a perspective view of an example for stoppage member, in accordance with one or more embodiments of this disclosure. 
         FIG. 6  illustrates a cross-sectional view of the stoppage member illustrated in  FIG. 5 , in accordance with one or more embodiments of this disclosure. 
         FIG. 7  illustrates examples of stoppage members, in accordance with one or more embodiments of this disclosure. 
         FIG. 8  illustrates examples of other stoppage members, in accordance with one or more embodiments of this disclosure. 
         FIG. 9  illustrates various projection views of example of stoppage members, in accordance with one or more embodiments of this disclosure. 
         FIG. 10  illustrates an example of a configuration of stoppage members affixed to a flexible plate, in accordance with one or more embodiments of this disclosure. 
         FIG. 11  illustrates an example of a stoppage member affixed to a flexible plate, in accordance with one or more embodiments of this disclosure. 
         FIG. 12  illustrates an example of a method for providing a microelectromechanical microphone having a stoppage member, in accordance with one or more embodiments of this disclosure. 
         FIG. 13A  illustrates a top perspective view of a packaged microphone having a microelectromechanical microphone die in accordance with one or more embodiments of this disclosure. 
         FIG. 13B  illustrates a bottom perspective view of the packaged microphone illustrated in  FIG. 13A . 
         FIG. 13C  illustrates a cross-sectional view of the packaged microphone illustrated in  FIG. 13A . 
         FIG. 13D  illustrates a cross-sectional view of another example of a packaged microphone having a microelectromechanical microphone die in accordance with one or more embodiments of this disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of this disclosure address the issue of breakage of elements of microelectromechanical microphones when subjected to an abrupt, large change in air pressure. A microelectromechanical microphone can be subjected to substantial changes in air pressure during assembly of the microelectromechanical microphone into a device (such as a mobile telephone or a tablet computer) or during usage of the device, after assembly. In some situations, the microelectromechanical microphone can fall onto a hard surface in an assembly line. In other situations, the device containing the microelectromechanical microphone can fall. Substantial changes in air pressure can deflect a diaphragm of the microelectromechanical microphone by several or even tens of microns. Those changes can result in substantial stress in a vicinity of a suspension interface between the diaphragm and a support member within the microelectromechanical microphone. That stress can be particularly elevated in large microelectromechanical microphones with high signal-to-noise (SNR) ratio and fully suspended diaphragms. High stress may lead to the breakage of the diaphragm, with the ensuing failure of the microelectromechanical microphone. 
     Embodiments of this disclosure provide microelectromechanical microphones having stoppage members that limit a range of motion of diaphragms in the microelectromechanical microphones. In some embodiments, a stoppage member can be affixed to a backplate of the microelectromechanical microphone. The stoppage member can extend perpendicularly relative to a surface of the backplate opposite a surface of a diaphragm of the microelectromechanical microphone. The stoppage member can have a distal surface that is separated from the surface of the diaphragm by a clearance distance. The stoppage member can limit motion of the diaphragm in response to a pressure wave including a threshold amplitude. The threshold amplitude represents a threshold pressure (e.g., 0.1 bar, 0.5 bar, 1 bar, or 2 bar). 
     In other embodiments, a stoppage member can be affixed to the diaphragm of a microelectromechanical microphone. The stoppage member can extend perpendicularly relative to a surface of the diaphragm opposite a surface of a substrate of the microelectromechanical microphone. The stoppage member can have a distal surface that is separated from the surface of the substrate by a clearance distance. The stoppage member can limit motion of the diaphragm in response to a pressure wave including a threshold amplitude. 
     Regardless of the type of plate—diaphragm or backplate—to which a stoppage member is affixed to, the clearance distance can be uniform and can be within a range from about 10 nm to about 1 μm. Greater clearance distances can be implemented for microelectromechanical microphones that operate in rugged environments, whereas lesser clearance distances can be implemented for more fragile microelectromechanical microphones. In addition, in some embodiments, the stoppage member can be embodied in a discrete, localized structure. In other embodiments, the stoppage member can be embodied in an extended structure, such as an annular structure. Regardless of its structure, the stoppage member can have a uniform thickness within a range from about 0.5 μm to about 5.0 μm. 
     A stoppage member can be affixed to a plate, either a diaphragm or backplate, of a microelectromechanical microphone in numerous ways. In some cases, the stoppage member can be monolithically integrated into the plate. Further, a stoppage member can be formed from a same material as the material that constitutes the plate. In other embodiments, the stoppage member can be formed from a material that is different from the material that constitutes the plate. Simply as an illustration, the stoppage member can be formed from a dielectric material, such as silicon dioxide, aluminum oxide, silicon nitride, or aluminum nitride. 
     In contrast to conventional technologies, the incorporation of a stoppage member in a microelectromechanical microphone can provide fast response times to an intense pressure pulse, or train of pressure pulses, impinging on the diaphragm of the microelectromechanical microphone. Because the stoppage member can limit a range of motion of the diaphragm by structural contact with the diaphragm as the diaphragm deforms in response to a pressure pulse, a response time associated with inhibiting breakage of the diaphragm is comparable, if not the same as, the time duration of the air pressure pulse. 
     Further, the incorporation of a stoppage member into a microelectromechanical microphone does not alter a motion of the diaphragm responsive to acoustic waves having amplitudes corresponding to normal sound pressure intensities. Thus, the incorporation of one or several stoppage members is not detrimental to the performance of the microelectromechanical microphone. 
     With reference to the drawings,  FIG. 1  illustrates various cross-sectional views of an example of a microelectromechanical microphone die  100  in accordance with one or more embodiments of the disclosure. The microelectromechanical microphone die  100  can constitute a microelectromechanical microphone device. The microelectromechanical microphone die  100  includes a substrate  110  that defines an opening to receive a pressure wave  106 . The pressure wave  106  has amplitudes indicating respective pressures that can be greater than or less than atmospheric pressure. In some embodiments, rather than being relative to atmospheric pressure, those pressures can be relative to a reference pressure of the environment of the microelectromechanical microphone die  100 . In some cases, the pressure wave  106  can correspond to an acoustic wave. Thus, the pressure wave  106  can have a waveform representative of an audio signal, such as an audible signal or an ultrasonic signal, or both. The audible signal can represent natural speech, an utterance, or environmental noise, for example. In other cases, the pressure wave  106  can have a waveform defining a single pulse or a train of pulses of large amplitude. 
     In some embodiments, the opening defined by the substrate  110  can be axially symmetric about an axis  102  (denoted as z, for the sake of nomenclature). For instance, the opening can have a circular perimeter. In other embodiments, the opening can be centrosymmetric relative to a geometric center of the opening. For instance, the opening can have a square perimeter or a hexagonal perimeter. 
     The substrate  110  can be formed from, or can include, a semiconducting material or an electrically insulating material (silicon dioxide, aluminum oxide (such as sapphire), or aluminum nitride, for example). In some embodiments, the semiconducting material can include silicon (amorphous, polycrystalline or crystalline); germanium; a semiconductor compound formed from an element in group III and another element in group V (referred to as a III-V semiconductor); a semiconductor compound formed from an element in group II and an element in group VI (referred to as a II-VI semiconductor); or a combination of two or more of the foregoing materials. Such a combination can be embodied in an alloy or a composite. In one example, the substrate  110  can be embodied in a silicon substrate. In another example, the substrate  110  can be embodied in a GaAs substrate. In yet another example, the substrate  110  can be embodied in a sapphire substrate. In still another example, the substrate  110  can be embodied in ZnS substrate. 
     The microelectromechanical microphone die  100  also includes a flexible plate  120  that is mechanically coupled to the substrate  110 . A dielectric member  114  mechanically couples the flexible plate  120  to the substrate  110 . The dielectric member  114  can be referred to as a “bottom spacer” and extends between the substrate  110  and the flexible plate  120 . 
     The flexible plate  120  can embody, or can constitute, a diaphragm of a microelectromechanical microphone that includes the microelectromechanical microphone die  100 . In some embodiments, the flexible plate  120  can be formed from a semiconductor or an electrically conducting material (such as a doped semiconductor or a metal). For example, the flexible plate  120  can be formed from silicon (amorphous, polycrystalline or crystalline); germanium; a III-V semiconductor; a II-VI semiconductor; or a combination (such as an alloy) of two or more of the foregoing materials. As another example, the flexible plate  120  can be formed from gold, silver, platinum, titanium, other types of noble metals, aluminum, copper, tungsten, chromium, or an alloy of two or more of the foregoing metals. In other embodiments, the flexible plate  120  can be formed from a composite material containing a dielectric (e.g., silicon dioxide, aluminum oxide, silicon nitride, or similar) and a semiconductor as is disclosed herein. In yet other embodiments, the flexible plate  120  can be formed entirely from a dielectric material. In such embodiments, the dielectric material is charged and operates as an electret material. 
     The electromechanical microphone die  100  also includes a rigid plate  130  that is mechanically coupled to the flexible plate  120 . A dielectric member  124  mechanically couples the rigid plate  130  to the flexible plate  120 . The dielectric member  124  can be referred to as an “airgap spacer” and extends between the rigid plate  130  and the flexible plate  120 . 
     The rigid plate  130  can define multiple openings that can permit passage of air that transports the pressure wave  106 . More generally, such openings can permit passage of a fluid that transports the pressure wave  106 . As is illustrated in  FIG. 1 , the openings include a first opening  134   a , a second opening  134   b , a third opening  134   c , a fourth opening  134   d , and a fifth opening  134   e.    
     The rigid plate  130  can embody, or can constitute, a backplate of the microelectromechanical microphone that includes the microelectromechanical microphone die  100 . In some embodiments, the rigid plate  130  can be formed from a semiconductor or an electrically conducting material (e.g., a doped semiconductor or a metal). For example, the rigid plate  130  can be formed from silicon (amorphous, polycrystalline, or crystalline); germanium; a semiconductor compound from group III; a III-V semiconductor; a II-VI semiconductor; or a combination (such as an alloy) of two or more of the foregoing. As another example, the rigid plate  130  can be formed from gold, silver, platinum, titanium, other types of noble metals, aluminum, copper, tungsten, chromium, or an alloy of two or more of the foregoing metals. In other embodiments, the rigid plate  130  can be formed from a composite material containing a dielectric (e.g., silicon dioxide, aluminum oxide, silicon nitride, or similar) and a semiconductor as is disclosed herein. In yet other embodiments, the rigid plate  130  can be formed entirely from a dielectric material. In such embodiments, the dielectric material is charged and operates as an electret material. 
     The dielectric member  124  can be formed from an electrically insulating material, e.g., amorphous silicon, silicon dioxide, aluminum oxide, silicon nitride, or similar insulators. In some embodiments, as is depicted in  FIG. 1 , the dielectric member  114  and the dielectric member  124  can be formed from the same electrically insulating material, e.g., amorphous silicon, silicon dioxide, silicon nitride, or the like. In other embodiments, a particular combination of different materials can be utilized. 
     In some embodiments, the rigid plate  130  and the flexible plate  120  can be formed from the same electrically conducting material, e.g., a doped semiconductor or a metal. More generally, the rigid plate  130  can be formed from the same or similar material(s) as the flexible plate  120 . For example, the rigid plate  130  can be formed from amorphous silicon, polycrystalline silicon, crystalline silicon, germanium, an alloy of silicon and germanium, a III-V semiconductor, a II-VI semiconductor, a dielectric (e.g., silicon dioxide, aluminum oxide, silicon nitride, aluminum nitride, and so forth), or a combination (such as an alloy or a composite) of two or more of the foregoing materials. 
     The flexible plate  120  can be configured to be deformed by the pressure wave  106 . Specifically, the flexible plate  120  can include a suspended section that covers the opening defined by the substrate  110 . In some embodiments, the suspended section also can be axially symmetric about the axis  102 . For example, the suspended section also can have a circular perimeter. The dielectric member  114  and the dielectric member  124  can serve as suspension supports about which the suspended section of the flexible plate  120  can bend in response to the pressure wave  106 . As is illustrated in  FIG. 1 , in some embodiments, the flexible plate  120  can define an opening at, or near, the geometric center of the suspended section. 
     The microelectromechanical microphone die  100  also includes a first stoppage member  140   a  that can be affixed to the flexible plate  120 . The stoppage member  140   a  extends perpendicularly relative to a surface of the flexible plate  120 , where the surface is opposite and essentially parallel to a surface of the substrate  110 . The stoppage member  140   a  can be formed from a material that is different from the material that constitutes the flexible plate  120 . For example, the material that constitutes the stoppage member  140  can be embodied in an electrically insulating material, such as silicon dioxide, aluminum oxide, silicon nitride, or aluminum nitride. In other embodiments, the stoppage member  140   a  can be formed from a same material as the material that constitutes the flexible plate  120 . 
     The microelectromechanical microphone die  100  also includes a second stoppage member  140   b  that can be affixed to the flexible plate  120 . The stoppage member  140   b  also extends perpendicularly relative to a surface of the flexible plate  120 , where the surface is opposite and essentially parallel to a surface of the substrate  110 . The stoppage member  140   b  can be formed from a material that is different from the material that constitutes the flexible plate  120 . For example, the material that constitutes the stoppage member  140   b  can be embodied in an electrically insulating material, such as silicon dioxide, aluminum oxide, silicon nitride, or aluminum nitride. In other embodiments, the stoppage member  140   b  can be formed from a same material as the material that constitutes the flexible plate  120 . 
     Diagram  150  in  FIG. 1  illustrates a detail of a section of the microelectromechanical microphone die  100 . As is shown in diagram  150 , the stoppage member  140   a  can be placed at a particular distance D (a real number in units of length) from the dielectric member  114 , toward the geometric center of the flexible plate  120 . 
     In addition, diagram  180  in  FIG. 1  illustrates another detail of the flexible plate  120 , including the stoppage member  140   a . As is shown in diagram  180 , the stoppage member  140   a  can have a thickness t (a real number in units of length) and a height h (a real number in units of length). In some cases, t can have a magnitude within a range from about 0.5 μm to about 5 μm. The stoppage member  140   a  can be assembled to have a defined clearance from a surface of the substrate  110 . The defined clearance can determine a range of motion of the flexible plate  120 . More specifically, the stoppage member  140   a  can have a distal surface that is separated from the surface of the substrate  110  by a clearance distance d c  (a real number in units of length). In some cases, d c  can have a magnitude in a range from about 10 nm to about 1 μm, in some cases. The closer the stoppage member  140   a  is positioned toward the geometric center of the flexible plate  120 , the greater the clearance distance can be. 
     While not shown in  FIG. 1 , the stoppage member  140   b  can have similar structural characteristics as the stoppage member  140   a . Specifically, the stoppage member  140   b  can be placed at the distance D from the dielectric member  114 , towards the geometric center of the flexible plate  120 . The stoppage member  140   b  also can have the thickness t and the height h. The stoppage member  140   b  also can be assembled to have a defined clearance from a surface of the substrate  110 . The defined clearance also can determine a range of motion of the flexible plate  120 . More specifically, the stoppage member  140   b  also can have a distal surface that is separated from the surface of the substrate  110  by the clearance distance d c . 
       FIG. 2  illustrates an example of a scenario in which the microelectromechanical microphone die  100  ( FIG. 1 ) can be subjected to high pressure. As is shown in diagram  200 , the stoppage member  140   a  can limit the motion of the flexible plate  120  in response to the pressure wave  106  including a threshold amplitude representing a threshold pressure. Simply as an illustration, the threshold pressure can be in a range from about 0.1 bar to 2 bar. In some cases, the threshold pressure can about 1 bar. Under negative pressure P (−) —e.g., pressure that is less than atmospheric pressure or a pressure of an environment in which the microelectromechanical microphone  100  operates—the flexible plate  120  can be deflected away from the rigid plate  130 , in a negative direction along the axis  102 . When the magnitude of P (−)  is equal to or greater than the threshold pressure, such a deflection can cause the stoppage member  140  to contact a surface of the substrate  110 . By contacting the surface of the substrate  110  the stoppage member  140  can limit the range of motion of the flexible plate  120 . As a result, stress in a vicinity of a bending point at the interface between the suspended section of the flexible plate  120  and the dielectric member  114  can be maintained below a threshold amount that results in fracture of the flexible plate  120 . 
     Under positive pressure P (+)  relative to atmospheric pressure (or the pressure of an environment in which the microelectromechanical microphone  100  operates), the flexible plate  120  can be deflected towards the rigid plate  130 , in a positive direction along the axis  102 . When the magnitude of P (+)  is equal to or greater than the threshold pressure, the flexible plate  120  can deform the rigid plate  130  and the stoppage member  140  does not limit the range of motion of the flexible plate  120 . 
     A stoppage member in accordance with aspects of this disclosure need not be assembled in a diaphragm of a microelectromechanical microphone in order to limit a range of motion of the diaphragm. The stoppage member also can be assembled in a backplate of the microelectromechanical microphone in order to limit the range of motion of the diaphragm. 
       FIG. 3  illustrates various cross-sectional views of an example of a microelectromechanical microphone die  300  having a stoppage member  140   a  assembled in a rigid plate  310 , in accordance with one or more embodiments of the disclosure. The microelectromechanical microphone die  300  can constitute a microelectromechanical microphone device. The rigid plate  310  can embody, or can constitute, a backplate of a microelectromechanical microphone that includes the microelectromechanical microphone die  300 . The microelectromechanical microphone die  300  includes the substrate  110  defining an opening to receive pressure waves  106 . As mentioned, in some embodiments, the opening can be axially symmetric about the axis  102 . For instance, the opening can have a circular perimeter. Again, the substrate  110  can be formed from a semiconducting material or an electrically insulating material (sapphire or silicon dioxide, for example). 
     The electromechanical microphone die  300  also includes a flexible plate  320  that is mechanically coupled to the substrate  110 . The dielectric member  304  mechanically couples the flexible plate  320  to the substrate  110 . As is illustrated in  FIG. 3 , the dielectric member  304  extends between the substrate  110  and the flexible plate  320 . 
     The flexible plate  320  can embody, or can constitute, a diaphragm of a microelectromechanical microphone that includes the microelectromechanical microphone die  300 . In some embodiments, the flexible plate  320  can be formed from a semiconductor or an electrically conducting material (such as a doped semiconductor or a metal). For example, the flexible plate  320  can be formed from silicon (amorphous, polycrystalline or crystalline); germanium; a III-V semiconductor; a II-VI semiconductor; or a combination (such as an alloy) of two or more of the foregoing materials. As another example, the flexible plate  320  can be formed from gold, silver, platinum, titanium, other types of noble metals, aluminum, copper, tungsten, chromium, or an alloy of two or more of the foregoing metals. In other embodiments, the flexible plate  320  can be formed from a composite material containing a dielectric (e.g., silicon dioxide, aluminum oxide, silicon nitride, or similar) and a semiconductor as is disclosed herein. In yet other embodiments, the flexible plate  320  can be formed entirely from a dielectric material. In such embodiments, the dielectric material is charged and operates as an electret material. 
     As noted, the electromechanical microphone die  300  includes the rigid plate  310  mechanically coupled to the flexible plate  320 . The dielectric member  124  mechanically couples the rigid plate  310  to the flexible plate  120 . The dielectric member  124  extends between the rigid plate  310  and the flexible plate  320 . 
     The rigid plate  310  defines multiple openings that can permit passage of air that transports the pressure wave  106 . As mentioned, more generally, such openings can permit passage of a fluid that transports the pressure wave  106 . As is illustrated in  FIG. 3 , the openings include a first opening  314   a , a second opening  314   b , a third opening  314   c , a fourth opening  314   d , and a fifth opening  314   e.    
     In some embodiments, the rigid plate  310  can be formed from a semiconductor or an electrically conducting material (e.g., a doped semiconductor or a metal). For example, the rigid plate  310  can be formed from silicon (amorphous, polycrystalline or crystalline); germanium; a semiconductor compound from group III; a III-V semiconductor; a II-VI semiconductor; or a combination (such as an alloy) of two or more of the foregoing. As another example, the rigid plate  310  can be formed from gold, silver, platinum, titanium, other types of noble metals, aluminum, copper, tungsten, chromium, or an alloy of two or more of the foregoing metals. In other embodiments, the rigid plate  310  can be formed from a composite material containing a dielectric (e.g., silicon dioxide, aluminum oxide, silicon nitride, or similar) and a semiconductor as is disclosed herein. In yet other embodiments, the movable plate  110  can be formed entirely from a dielectric material. In such embodiments, the dielectric material is charged and operates as an electret material. 
     In some embodiments, the rigid plate  310  and the flexible plate  320  can be formed from the same electrically conducting material, e.g., a doped semiconductor or a metal. More generally, the rigid plate  310  can be formed from the same or similar material(s) as the flexible plate  320 . For example, the rigid plate  310  can be formed from amorphous silicon, polycrystalline silicon, crystalline silicon, germanium, an alloy of silicon and germanium, a III-V semiconductor, a II-VI semiconductor, a dielectric (silicon dioxide, silicon nitride, aluminum oxide, aluminum nitride, and so forth), or a combination (such as an alloy or a composite) of two or more of the foregoing materials. 
     The flexible plate  320  can be configured to be deformed by the pressure wave  106 . Specifically, the flexible plate  320  can include a suspended section that covers the opening defined by the substrate  110 . The suspended section also can be axially symmetric about the axis  102 . For example, the suspended section also can have a circular perimeter. The dielectric member  304  and the dielectric member  124  can serve as suspension supports about which the suspended section of the flexible plate  320  can bend in response to the pressure wave  106 . As is illustrated in  FIG. 3 , in some embodiments, the flexible plate  320  can define an opening at, or near, the geometric center of the suspended section. 
     As mentioned, the microelectromechanical microphone  300  also includes the stoppage member  140   a  affixed to the rigid plate  310 . The stoppage member  140   a  extends perpendicularly relative to a surface of the rigid plate  310 , where the surface is opposite and essentially parallel to a surface of the flexible plate  320 . The stoppage member  140   a  can be formed from a material that is different from the material that constitutes the rigid plate  310 . For example, the material that constitutes the stoppage member  140   a  can be embodied in an electrically insulating material, such as silicon dioxide, aluminum oxide, silicon nitride, or aluminum nitride. In other embodiments, the stoppage member  140   a  can be formed from a same material as the material that constitutes the rigid plate  310 . 
     The microelectromechanical microphone die  300  also includes the second stoppage member  140   b  affixed to the rigid plate  310 . The stoppage member  140   b  also extends perpendicularly relative to a surface of the rigid plate  310 , where the surface is opposite and essentially parallel to a surface of the flexible plate  320 . The stoppage member  140   b  can be formed from a material that is different from the material that constitutes the rigid plate  310 . For example, the material that constitutes the stoppage member  140   b  can be embodied in an electrically insulating material, such as silicon dioxide, aluminum oxide, silicon nitride, or aluminum nitride. In other embodiments, the stoppage member  140   b  can be formed from a same material as the material that constitutes the rigid plate  310 . 
     Diagram  350  in  FIG. 3  illustrates a detail of a section of the microelectromechanical microphone die  300 . As is shown in diagram  350 , the stoppage member  140   a  can be placed at a particular distance D′ (a real number in units of length) from the dielectric member  124 , toward the geometric center of the rigid plate  310 . 
     In addition, diagram  380  in  FIG. 3  illustrates another detail of the rigid plate  310  and the flexible plate  320 , including the stoppage member  140   a . As is shown in diagram  380 , the stoppage member  140   a  can have the thickness t and the height h. As mentioned, in some cases, t can have a magnitude within a range from about 0.5 μm to about 5 μm. The stoppage member  140   a  can be assembled to have a defined clearance from a surface of the flexible plate  320 . The defined clearance can determine a range of motion of the flexible plate  320 . More specifically, the stoppage member  140   a  can have a distal surface that is separated from the surface of the flexible plate  320  by the clearance distance d c . In some cases, d c  can have a magnitude in a range from about 10 nm to about 1 μm, in some cases. The closer the stoppage member  140   a  is positioned toward the geometric center of the rigid plate  310 , the greater the clearance distance can be. 
       FIG. 4  illustrates an example of a scenario in which the microelectromechanical microphone die  300  ( FIG. 3 ) can be subjected to high pressure. The stoppage member  140  can limit the motion of the flexible plate  320  in response to the pressure wave  106  including a threshold amplitude representing a threshold pressure. As mentioned, the threshold pressure can be in a range from about 0.1 bar to 2 bar. In some cases, the threshold pressure can about 1 bar. Under negative pressure P (−) —e.g., pressure that is less than atmospheric pressure or a pressure of an environment in which a microelectromechanical microphone including the die  300  operates—the flexible plate  320  can be deflected away from the rigid plate  310 , in a negative direction along the axis  102 . The stoppage member  140   a  does not limit the range of motion of the flexible plate  320  in such condition. 
     Under positive pressure P pressure that is greater than atmospheric pressure or a pressure of an environment in which a microelectromechanical microphone including the die  300  operates—the flexible plate  320  can be deflected towards the rigid plate  130 , in a positive direction along the axis  102 , as is shown in diagram  450 . When the magnitude of P (+)  is equal to or greater than the threshold pressure, such a deflection may cause the flexible plate  320  to deform the rigid plate  310 . Such a deflection also can cause the stoppage member  140   a  to contact a surface of the flexible plate  320 , as is shown in the diagram  450 . By contacting the surface of the flexible plate  320 , the stoppage member  140   a  can limit the range of motion of the flexible plate  320 . As a result, although the flexible plate  320  may deform the rigid plate  130 , stress in a vicinity of the interface between the suspended section of the flexible plate  320  and the dielectric member  124  can be maintained below a threshold amount that results in fracture of the flexible plate  320 . 
     Regardless of type of plate—e.g., diaphragm or backplate—the stoppage member can be affixed to the plate in numerous ways. In one example, the stoppage member can be affixed by fusing a base of the stoppage member to a surface of the plate by means of a glue or another type of adhesive. In another example, the stoppage member can be affixed by monolithically integrating the stoppage member into the plate. 
     To that point,  FIG. 5  illustrates a perspective view of an example of a stoppage member  510 , in accordance with one or more embodiments of this disclosure. The stoppage member  510  can be monolithically integrated in into a plate  520 . In some embodiments, the plate  520  embodies a diaphragm (such as the flexible plate  120  or the flexible plate  320 ) of a microelectromechanical microphone. In other embodiments, the plate  520  embodies a backplate (such as the rigid plate  130  or the rigid plate  310 ) of the microelectromechanical microphone. Accordingly, the plate  520  can be formed from a semiconductor or an electrically conducting material (e.g., a doped semiconductor or a metal). For example, the plate  520  can be formed from silicon (amorphous, polycrystalline or crystalline); germanium; a semiconductor compound from group III; a III-V semiconductor; a II-VI semiconductor; or a combination (such as an alloy) of two or more of the foregoing. As another example, the plate  520  can be formed from gold, silver, platinum, titanium, other types of noble metals, aluminum, copper, tungsten, chromium, or an alloy of two or more of the foregoing metals. In other embodiments, the plate  520  can be formed from a composite material containing a dielectric (e.g., silicon dioxide, aluminum oxide, silicon nitride, or similar) and a semiconductor as is disclosed herein. In yet other embodiments, the plate  520  can be formed entirely from a dielectric material. In such embodiments, the dielectric material is charged and operates as an electret material. 
     The stoppage member  510  is embodied in an object of revolution and, thus, can have axial symmetry about an axis  504  that pierces the stoppage member  510  perpendicularly to a first planar surface  514  of the stoppage member  510 . Because the stoppage member  510  is monolithically integrated into the plate  520 , the stoppage member  510  has a section embedded into the plate  520 . Such a section can be tapered, ending in a second planar surface  518  interfacing with a portion of the plate  520 . It is noted that stoppage member  510  lack a portion with a distinct interface to the plate  520 . 
     Similar to other stoppage members of this disclosure, a first material that forms the stoppage member  510  can be different from a second material that forms the plate  520 . In some cases, the first material is a dielectric material and the second material is an electrical conductor material (such as polycrystalline silicon or a doped semiconductor). In one example, the dielectric material can be alumina, silicon nitride, or aluminum nitride 
     As is illustrated in  FIG. 6 , the distal planar surface  514  can be located at a clearance distance d c  from a surface  604  of a second plate  610 . The plate  520  and the second plate  610  can constitute, at least partially, a microelectromechanical microphone. In an embodiment in which the plate  520  embodies a diaphragm (e.g., the flexible plate  120  ( FIG. 1 )) of the microelectromechanical microphone, the plate  610  can embody a backplate (e.g., the rigid plate  130  ( FIG. 1 )) of the microelectromechanical microphone. In an embodiment in which the plate  520  embodies the backplate, the plate  610  can embody the diaphragm. 
     Stoppage members in accordance with aspects of this disclosure are not limited to objects of revolution. A stoppage member can have one of many shapes.  FIG. 7  illustrates examples of stoppage members, in accordance with one or more embodiments of this disclosure. Each one of the illustrated stoppage members has axial symmetry (or is axially-symmetric) about an axis  704 . As is illustrated in  FIG. 7 , a stoppage member  710  can be shaped as a truncated cone, a stoppage member  720  can be shaped as a cylinder, a stoppage member  730  can be an object of revolution, and a stoppage member  740  can be a dome. A stoppage member shaped as a dome can be assembled in a diaphragm or a backplate in embodiments in which a separation between the diaphragm and the backplate is small, e.g., less than 5 μm. Each one of those stoppage members can have cross-sections of cylindrical symmetry about the axis  704 , as is shown in the top-view projections depicted in diagram  715 , diagram  725 , diagram  735 , and diagram  745 . 
     Stoppage member  710  can include a first planar surface  714  and a second planar surface  718  having respective circular perimeters. Diagram  715  presents a projection of the stoppage member  710  on a plane perpendicular to the axis  704 , to illustrate the first planar surface  714  and the second planar surface  718 . Stoppage member  720  can include a first planar surface  724  and a second planar surface  728  having respective circular perimeters. Diagram  725  presents a projection of the stoppage member  720  on a plane perpendicular to the axis  704 , to illustrate the first planar surface  724  and the second planar surface  728 . Stoppage member  730  can include a first planar surface  734  and a second planar surface  738  having respective circular perimeters. Diagram  735  presents a projection of the stoppage member  730  on a plane perpendicular to the axis  704 , to illustrate the first planar surface  734  and the second planar surface  738 . Diagram  745  presents a projection of the stoppage member  740  on a plane perpendicular to the axis  704 , to illustrate the cross-section of the planar base  744 . 
       FIG. 8  illustrates examples of other types of stoppage members, in accordance with one or more embodiments of this disclosure. Each one of the stoppage members has rotational symmetry about an axis  804 . Both of the illustrated stoppage members have a C 4  cyclic symmetry group, for example. The stoppage member  810  is shaped as a parallelepiped. Accordingly, the stoppage member  810  has a cross-section that is rectangular, as is shown in diagram  815 . The stoppage member  810  includes a first planar surface  814  and a second planar surface  818  having rectangular perimeters. Diagram  815  presents a projection of the stoppage member  810  on a plane perpendicular to the axis  804 , to illustrate the first planar surface  814  and the second planar surface  818 . The stoppage member  820  has a truncated pyramid shape. The stoppage member  820  includes a first planar surface  824  and a second planar surface  828  having respective rectangular perimeters. Diagram  825  presents a projection of the stoppage member  820  on a plane perpendicular to the axis  804 , to illustrate the first planar surface  824  and the second planar surface  828 . 
     Stoppage members having other cross-sections geometries also can be fabricated.  FIG. 9  illustrates various projection views of various example of stoppage members, in accordance with one or more embodiments of this disclosure. Diagram  910  depicts a stoppage member having a uniform pentagonal cross-section. Diagram  920  depicts a stoppage member having a uniform hexagonal cross-section. Diagram  930  depicts a stoppage member having a uniform octagonal cross-section. While not depicted in  FIG. 9 , stoppage members can have other respective polygonal cross-sections having a perimeter embodied in a regular polygon or an irregular polygon. Diagram  940  depicts a stoppage member having a uniform ellipsoidal cross-section. 
     Embodiments of this disclosure are not limited to microelectromechanical microphones having a specific number of stoppage members. A microelectromechanical microphone in accordance with this disclosure can have a single stoppage member or multiple stoppage members. In embodiments in which the microelectromechanical microphone has multiple stoppage member, those members can be arranged in one of many configurations. 
     As an illustration,  FIG. 10  depicts an example of a configuration of stoppage members on a flexible plate  1010 , in accordance with one or more embodiments of this disclosure. The stoppage members include a first stoppage member  1020 ( 1 ), a second stoppage member  1020 ( 2 ), a third stoppage member  1020 ( 3 ), a fourth stoppage member  1020 ( 4 ), a fifth stoppage member  1020 ( 5 ), a sixth stoppage member  1020 ( 6 ), a seventh stoppage member  1020 ( 7 ), and an eight stoppage member  1020 ( 8 ). The stoppage members are arranged on a symmetric configuration about an opening  1030  at a geometric center of the flexible plate  1010 . As is illustrated in  FIG. 10 , the stoppage members are arranged uniformly along an arcuate path along a periphery  1040  that separates a suspended section of the flexible plate  1010  from a stationary section of the flexible plate  1010  attached to a dielectric space member (such as dielectric member  114  or dielectric member  304 ; not depicted in  FIG. 10 ). 
     The arrangement of the illustrated stoppage members is not exclusive. In addition, although eight stoppage members are illustrated in  FIG. 10 , the disclosure is not limited in that respect. In some embodiments, a number of stoppage members that is greater or less than eight stoppage members can be assembled. 
     It is noted that in some scenarios, a large number of stoppage members can be justified by a rugged nature of an environment in which the microphone device having stoppage members can operate. In other scenarios, however, a microelectromechanical microphone can be expected to operate in an environment in which such a device is unlikely to experience abrupt, large changes in atmospheric pressure. 
     In some embodiments, instead of being discrete, localized structures, a stoppage member can be extended across a plate—a diaphragm or a backplate—that constitutes a microelectromechanical microphone.  FIG. 11  illustrates an example of a stoppage member  1120  on a flexible plate  1110 , in accordance with one or more embodiments of this disclosure. The flexible plate  1110  can embody the flexible plate  120  or the flexible plate  310 , or both. The stoppage member  1120  can have an annular shape that has circular symmetry about an axis that pierces the flexible plate  1110  through an opening  1130  at the geometric center of the flexible plate  1110 . A surface of the stoppage member  1120  is located at a distance D from a periphery  1140  that separates a suspended section of the flexible member  1110  from a stationary section of the flexible plate  1110  attached to a dielectric space member (such as dielectric member  114  or dielectric member  304 ; not depicted in  FIG. 11 ). The stoppage member  1120  can have a uniform height h and a uniform thickness t. A magnitude of t can be within a range from about 0.5 μm to about 5.0 μm. 
     The disclosure is not limited to annular shapes. Stoppage members that are extended can have other closed-loop structures having non-circular perimeters. 
       FIG. 12  illustrates an example of a method  1200  for limiting a range of motion of a diaphragm in a microelectromechanical microphone, in accordance with one or more embodiments of this disclosure. At block  1210 , a substrate defining an opening to receive a pressure wave can be provided. In some embodiments, the opening can have a perimeter that axially-symmetric perimeter about an axis that is perpendicular to a planar surface of the substrate and pierces the planar surface at its geometric center. In other embodiments, the opening can have a perimeter that is centrosymmetric relative to that geometric center. In one example, the substrate can be embodied in the substrate  110  ( FIG. 1 ) and the pressure wave can be embodied in the pressure wave  106  ( FIG. 1 ). 
     At block  1220 , a flexible plate mechanically coupled to the substrate can be formed. The flexible plate can be deformed by the pressure wave. The flexible plate can embody the diaphragm in the microelectromechanical microphone. The flexible plate can be formed from a semiconductor or an electrically conducting material. At block  1230 , a rigid plate mechanically coupled to the flexible plate can be formed. The rigid plate defines multiple openings that permit passage of a fluid that transports the pressure wave. The rigid plate can be formed from a semiconductor or an electrically conducting material. The rigid plate can embody a backplate in the microelectromechanical microphone. In some embodiments, the rigid plate can embody the rigid plate  130  ( FIG. 1 ). In other embodiments, the rigid plate can embody the rigid plate  310  ( FIG. 3 ). 
     At block  1240 , a stoppage member mechanically coupled to one of the flexible plate or the rigid plate can be formed. It is noted that, in some embodiments, block  1240  can be implemented during the implementation of block  1220  or block  1230 , depending on whether the stoppage member is mechanically coupled to the flexible plate or the rigid plate. In some embodiments in which the stoppage member is mechanically coupled to the flexible plate, a pattern for the stoppage member can be defined before formation (e.g., deposition) of the flexible plate. Similarly, in some embodiments in which the stoppage member is mechanically coupled to the rigid plate, a pattern for the stoppage member can be defined before formation (e.g., deposition) of the rigid plate. 
     The formed stoppage member limits motion of the flexible plate in response to the pressure wave including a threshold amplitude. The stoppage member can be embodied in one of the stoppage member  140   a  or the stoppage member  140   b  ( FIG. 1 ); the stoppage member  510  ( FIG. 5 ); or the stoppage member  1120  ( FIG. 11 ), for example. In some embodiments, the stoppage member is affixed to the rigid plate and extends perpendicularly relative to a surface of the rigid plate, where the surface is opposite a surface of the flexible plate. In addition, as mentioned, the stoppage member can have a distal surface that is separated from the surface of the flexible plate by a first clearance distance. The first clearance distance can have a magnitude in a range from about 10 nm to about 1 μm. In other embodiments, the stoppage member is affixed to the flexible plate and extends perpendicularly relative to a surface of the flexible plate, where the surface is opposite a surface of the substrate. In addition, as also mentioned, the stoppage member has a distal surface that is separated from the surface of the substrate by a second clearance distance. The second clearance distance can have a magnitude in a range from about 10 nm to about 1 μm. 
     Regardless of type of plate—e.g., flexible plate or rigid plate—the stoppage member can be affixed to the plate in numerous ways. In some embodiments, the stoppage member can be affixed by fusing a base of the stoppage member to a surface of the plate by means of a glue or another type of adhesive. In other embodiments, the stoppage member can be affixed by monolithically integrating the stoppage member into the plate. See  FIG. 5 , for example. In one of those embodiments, when the stoppage member is affixed to the flexible member, block  1220  and block  1240  can be implemented subsequently, followed by block  1230 . 
     The microelectromechanical microphones having stoppage members in accordance with this disclosure can be packaged for operation within an electronic device (a mobile phone, a tablet computer, or a wireless earbud, for example) or other types of devices including consumer electronics and appliances, for example. As an illustration,  FIG. 13A  presents a top, perspective view of a packaged microphone  1310  that can include a microelectromechanical microphone die in accordance with one or more embodiments of this disclosure (such as the microelectromechanical microphone die  100  shown in  FIG. 1  or the microelectromechanical microphone die  300  shown in  FIG. 3 ). In addition,  FIG. 13B  presents a bottom, perspective view of the packaged microphone  1310 . 
     As is illustrated, the packaged microphone  1310  has a package base  1312  and a lid  1314  that form an interior chamber or housing that contains a microelectromechanical microphone chipset  1316 . In addition, or in other embodiments, such a chamber can include a separate microphone circuit chipset  1318 . The chipsets  1316  and  1318  are depicted in  FIG. 13C  and  FIG. 13D  and are discussed hereinafter. In the illustrated embodiment, the lid  1314  is a cavity-type lid, which has four walls extending generally orthogonally from a top, interior face to form a cavity. In one example, the lid  1314  can be formed from metal or other conductive material to shield the microelectromechanical microphone die  1316  from electromagnetic interference. The lid  1314  secures to the top face of the substantially flat package base  1312  to form the interior chamber. 
     As is illustrated, the lid  1314  can have an audio input port  1320  that is configured to receive audio signals (e.g., audible signals and/or ultrasonic signals) and can permit such signals to ingress into the chamber formed by the package base  1312  and the lid  1314 . In additional or alternative embodiments, the audio port  1320  can be placed at another location. For example, the audio port  1312  can be placed at the package base  1312 . As another example, the audio port  1312  can be placed at one of the side walls of the lid  1314 . Regardless of the location of the audio port  1312 , audio signals entering the interior chamber can interact with the microelectromechanical microphone chipset  1316  to produce an electrical signal representative of at least a portion of the received audio signals. With additional processing via external components (such as a speaker and accompanying circuitry), the electrical signal can produce an output audible signal corresponding to an input audible signal contained in the received audio signals. 
       FIG. 13B  presents an example of a bottom face  1322  of the package base  1312 . As illustrated, the bottom face  1322  has four contacts  1324  for electrically (and physically, in many use cases) connecting the microelectromechanical microphone chipset  1316  with a substrate, such as a printed circuit board or other electrical interconnect apparatus. Although four contacts  1324  are illustrated, the disclosure is not limited in that respect and other number of contacts can be implemented in the bottom face  1322 . The packaged microphone  1310  can be used in any of a wide variety of applications. For example, the packaged microphone  1310  can be used with mobile telephones, landline telephones, computer devices, video games, hearing aids, hearing instruments, biometric security systems, two-way radios, public announcement systems, and other devices that transduce acoustic signals. In a particular implementation, the packaged microphone  1310  can be used within a speaker to produce audible signals from electrical signals. 
     In certain embodiments, the package base  1312  shown in  FIG. 13A  and  FIG. 13B  can be embodied in, or can contain, a printed circuit board material, such as FR-4, or a premolded, leadframe-type package (also referred to as a “premolded package”). Other embodiments may use or otherwise leverage different package types, such as ceramic cavity packages. Therefore, it is noted that this disclosure is not limited to a specific type of package. 
       FIG. 13C  illustrates a cross-sectional view of the packaged microphone  1310  across line  13 C- 13 C in  FIG. 13A . As illustrated and discussed herein, the lid  1314  and base  1312  form an internal chamber or housing that contains a microelectromechanical microphone chipset  1316  and a microphone circuit chipset  1318  (also referred to as “microphone circuitry  1318 ”) used to control and/or drive the microelectromechanical microphone chipset  1316 . In certain embodiments, electronics can be implemented as a second, stand-alone integrated circuit, such as an application specific integrated circuit (e.g., an “ASIC die  1318 ”) or a field programmable gate array (e.g., “FPGA die  1318 ”). It is noted that, in some embodiments, the microelectromechanical microphone chipset  1316  and the microphone circuit chipset  1318  can be formed on a single die. 
     Adhesive or another type of fastening mechanism can secure or otherwise mechanically couple the microelectromechanical microphone chipset  1316  and the microphone circuit chipset  1318  to the package base  1312 . Wirebonds or other type of electrical conduits can electrically connect the microelectromechanical microphone chipset  1316  and microphone circuit chipset  1318  to contact pads (not shown) on the interior of the package base  1312 . 
     While  FIGS. 13A to 13C  illustrate a top-port packaged microphone design, some embodiments can position the audio input port  1320  at other locations, such as through the package base  1312 . For instance,  FIG. 13D  illustrates a cross-sectional view of another example of a packaged microphone  1310  where the microelectromechanical microphone chipset  1316  covers the audio input port  1320 , thereby producing a large back volume. In other embodiments, the microelectromechanical microphone chipset  1316  can be placed so that it does not cover the audio input port  1320  through the package base  1312 . 
     It is noted that the present disclosure is not limited with respect to the packaged microphone  1310  illustrated in  FIGS. 13A to 13D . Rather, discussion of a specific packaged microphone is for merely for illustrative purposes. As such, other microphone packages including a microelectromechanical microphone having one or multiple stoppage members in accordance with this disclosure are contemplated herein. 
     Various aspects of the embodiments of this disclosure are described herein with reference to flowchart illustrations and/or block diagrams of methods. The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of devices, methods, and products according to various embodiments of this disclosure. In this regard, each block in the flowchart or block diagrams can represent one or several operations for implementing the specified function(s). In some implementations, the functions noted in the blocks can occur out of the order noted in the Figures. For example, two blocks shown in succession can, in fact, be implemented substantially concurrently, or the blocks can sometimes be implemented in the reverse order. 
     In the present specification, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or.” That is, unless specified otherwise, or clear from context, “X employs A or B” is intended to mean any of the natural inclusive permutations. That is, if X employs A; X employs B; or X employs both A and B, then “X employs A or B” is satisfied under any of the foregoing instances. Moreover, articles “a” and “an” as used in this specification and annexed drawings should generally be construed to mean “one or more” unless specified otherwise or clear from context to be directed to a singular form. 
     In addition, the terms “example” and “such as” are utilized herein to mean serving as an instance or illustration. Any embodiment or design described herein as an “example” or referred to in connection with a “such as” clause is not necessarily to be construed as preferred or advantageous over other embodiments or designs. Rather, use of the terms “example” or “such as” is intended to present concepts in a concrete fashion. The terms “first,” “second,” “third,” and so forth, as used in the claims and description, unless otherwise clear by context, is for clarity only and doesn&#39;t necessarily indicate or imply any order in time. 
     What has been described above includes examples of one or more embodiments of the disclosure. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing these examples, and it can be recognized that many further combinations and permutations of the present embodiments are possible. Accordingly, the embodiments disclosed and/or claimed herein are intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the detailed description and the appended claims. Furthermore, to the extent that the term “includes” is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term “comprising” as “comprising” is interpreted when employed as a transitional word in a claim.