Patent Publication Number: US-7898371-B2

Title: Electromechanical switch with partially rigidified electrode

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a Continuation of U.S. application Ser. No. 11/472,018, filed Jun. 20, 2006, now U.S. Pat. No. 7,605,675 issued on Oct. 20, 2009. 
    
    
     TECHNICAL FIELD 
     This disclosure relates generally to electromechanical switches, and in particular, relates to micro-electromechanical systems (“MEMS”) switches. 
     BACKGROUND INFORMATION 
     Micro-electromechanical systems (“MEMS”) devices have a wide variety of applications and are prevalent in commercial products. One type of MEMS device is a MEMS radio frequency (RF) switch. A typical MEMS RF switch includes one or more MEMS switches arranged in an RF switch array. MEMS metal-to-metal contact RF switches are ideal for wireless devices because of their low power characteristics and ability to operate in radio frequency ranges. MEMS metal-to-metal contact RF switches are well suited for applications including cellular telephones, wireless networks, communication systems, and radar systems. In wireless devices, MEMS RF switches can be used as antenna switches, mode switches, transmit/receive switches, and the like. 
     Known MEMS switches use an electroplated metal cantilever supported at one end and having an electrical RF metal-to-metal contact near the distal end of the metal cantilever. An actuation electrode is positioned below the electrical RF contact and a direct current (“DC”) actuation voltage applied to either the actuation electrode or the metal cantilever forces the metal cantilever to bend downward and make electrical contact with a bottom RF signal trace. Once electrical contact is established, the circuit is closed and an RF signal can pass through the metal cantilever to the actuation electrode and/or to the bottom RF signal trace. 
     These MEMS switches typically require 40 V or more actuation voltage. If the actuation voltage is reduce much below 40 V, then the spring constant of the cantilever must be reduced. These lower voltage MEMS switches suffer from “stiction” (i.e., stuck in a closed circuit position) and tend to be self-actuated by RF signals or vibrations due to their low spring constants. During fabrication, the electroplated metal cantilever suffers from high stress gradients and therefore has a tendency to curl upwards at the distal end, referred to as switch stress gradient bending. Accordingly, the actuation voltage must be sufficiently large to overcome the larger separation distance due to beam bending and induce electrostatic collapse between the metal cantilever and the actuation electrode below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Non-limiting and non-exhaustive embodiments of the invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. 
         FIG. 1A  is a schematic diagram illustrating a plan view of a switch including a suspended electrode having a rigidification topology localized about a contact, in accordance with an embodiment of the invention. 
         FIG. 1B  is a schematic diagram illustrating a cross-sectional view of a switch including a suspended electrode having a rigidification topology localized about a contact, in accordance with an embodiment of the invention. 
         FIG. 2A  is an expanded perspective view illustrating a 3-dimensional rigidification structure, in accordance with an embodiment of the invention. 
         FIG. 2B  is an expanded cross-sectional view illustrating a 3-dimensional rigidification topology, in accordance with an embodiment of the invention. 
         FIG. 2C  is an expanded perspective view illustrating a 3-dimensional rigidification structure, in accordance with an embodiment of the invention. 
         FIG. 2D  is an expanded cross-sectional view illustrating a 3-dimensional rigidification topology, in accordance with an embodiment of the invention. 
         FIG. 2E  is a plan view illustrating an expanded section of a 3-dimensional rigidification topology using an scanning electron microscope, in accordance with an embodiment of the invention. 
         FIG. 2F  is an expanded perspective view illustrating a 3-dimensional rigidification structure using a scanning electron microscope, in accordance with an embodiment of the invention. 
         FIG. 3  is a flow chart illustrating a process of operation of a switch including a partially rigidified suspended electrode, in accordance with an embodiment of the invention. 
         FIG. 4A  is a schematic diagram illustrating a first bending phase of a switch including a partially rigidified suspended electrode in an open circuit position, in accordance with an embodiment of the invention. 
         FIG. 4B  is a schematic diagram illustrating a second bending phase of a switch including a partially rigidified suspended electrode in a closed circuit position, in accordance with an embodiment of the invention. 
         FIG. 5  illustrates line graphs of uni-polar voltage actuation and alternating polarity voltage actuation of a switch including a partially rigidified suspended electrode, in accordance with an embodiment of the invention. 
         FIG. 6A  is a schematic diagram illustrating a plan view of a switch including a suspended electrode having a rigidification topology localized about a contact and including an alternative RF trace design, in accordance with an embodiment of the invention. 
         FIG. 6B  is a schematic diagram illustrating a cross-sectional view of a switch including a suspended electrode having a rigidification topology localized about a contact and including an alternative RF trace design, in accordance with an embodiment of the invention. 
         FIG. 7A  is a plan view illustrating a circuit layout of a partially fabricated switch including a suspended electrode having a rigidification topology localized about a contact, in accordance with an embodiment of the invention. 
         FIG. 7B  is a plan view illustrating a circuit layout of a fully fabricated switch including a suspended electrode having a rigidification topology localized about a contact, in accordance with an embodiment of the invention. 
         FIG. 8  is a functional block diagram illustrating a demonstrative wireless device implemented with a micro-electromechanical system switch array, in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of an electromechanical switch including a partially rigidified suspended electrode and systems thereof are described herein. In the following description numerous specific details are set forth to provide a thorough understanding of the embodiments. One skilled in the relevant art will recognize, however, that the techniques described herein can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring certain aspects. 
     Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. 
       FIGS. 1A and 1B  are schematic diagrams illustrating a micro-electromechanical (“MEMS”) switch  100 , in accordance with an embodiment of the invention.  FIG. 1A  is a plan view of MEMS switch  100  while  FIG. 1B  is a cross-sectional view of the same. It should be appreciated that the figures herein are not drawn to scale, but rather are merely intended for illustration. 
     The illustrated embodiment of MEMS switch  100  includes a suspended electrode  105 , an actuation electrode  110 , anchors  115 , a contact  120 , an input signal line  125 , and an output signal line  127 . MEMS switch  100  is mounted on a substrate  130 , which includes an insulating layer  135  and a bulk layer  137 . The illustrated embodiment of contact  120  includes a suspended trace  140 , trace mounts  145 , and protruding contacts  150 . The illustrated embodiment of suspended electrode  105  includes narrow members  155  and a plate member  160 . Plate member  160  further includes stopper stubs  161  formed on an underside  163 . Stopper butts  165  are defined within actuation electrode  110 , but electrically insulated therefrom and positioned to abut stopper stubs  161  when suspended electrode  105  collapses onto actuation electrode  110 . Suspended electrode  105  further includes a rigidification structure  167  to reinforce and rigidify a portion of suspended electrode  105 . Actuation electrode  110  includes an input port  170  for applying an actuation voltage between actuation electrode  110  and suspended electrode  105  to electrostatically induce a progressive zipper-like collapse of suspended electrode  105 . Signal lines  125  and  127  each include a bottom electrode  180  and an upper layer  185 . It should be appreciated that in some cases only one or two instances of a component/element have been labeled so as not to crowd the drawings. 
     Substrate  130  may be formed using any material including various semiconductor substrates (e.g., silicon substrate). Insulator layer  135  is provided as a dielectric layer to insulate bottom electrode  180  and actuation electrode  110  from each other and from bulk layer  137 . If bulk layer  137  is an intrinsic insulator then embodiments of the invention may not include insulator layer  135 . Although not illustrated, bulk layer  137  may include a number of sub-layers having signal traces or components (e.g., transistors and the like) integrated therein and electrically coupled to any of signal lines  125  or  127 , anchors  115 , or actuation electrode  110 . In an embodiment where bulk layer  137  includes silicon, insulator layer  135  may include a layer of silicon nitride approximately 0.25 μm thick. The width of signal lines  125  and  127  may be dependent upon the desired impedance to be achieved by a circuit. 
     In one embodiment, signal lines  125  and  127  are formed on insulator layer  135  to propagate radio frequency (“RF”) signals. However, it should be appreciated that embodiments of MEMS switch  100  may be used to switch other frequency signals including direct current (“DC”) signals, low frequency signals, microwave signals, and the like. Bottom electrode  180  and upper layer  185  may be formed using any conductive material, including metal, such as gold (Au). In one embodiment, bottom electrode is approximately 20 μm to 60 μm wide and 0.3-0.5 μm thick, while upper layer  185  is approximately 6 μm thick. 
     Actuation electrode  110  is formed on insulator layer  135  to form a bottom electrode for actuating cantilever electrode  105  and turning on/off MEMS switch  100 . Actuation electrode  110  may be formed of any number of conductive materials, including polysilicon. Input port  170  may also be fabricated of polysilicon and is coupled to actuation electrode  110  to switchably apply the actuation voltage thereto. In one embodiment, actuation electrode  110  has a width W 1  (e.g., ≈200 μm) and a length L 1  (e.g., ≈200 μm) and a thickness of approximately 0.1-0.2 μm. As illustrated, a number of stopper butts  165  are interspersed within actuation electrode  110 . In the illustrated embodiment, stopper butts  165  are electrically insulated from actuation electrode  110  by an air gap (e.g., ≈2-3 μm). 
     As mentioned above, the illustrated embodiment of suspended electrode  105  includes three members: two narrow members  155  and plate member  160 . Narrow members  155  are mounted to anchors  115 , which in turn mount suspended electrode  105  to substrate  130  over actuation electrode  110 . In one embodiment, suspended electrode  105  is fabricated using low stress gradient (“LSG”) polysilicon. LSG polysilicon can be processed without severe upward curling of suspended electrode  105 . In other words, during fabrication of suspended electrode  105  using a LSG polysilicon material, suspended electrode  105  remains relatively parallel to substrate  130  along its length (e.g., less than 25 nm of bending over 350 μm span of suspended electrode  105 ) and therefore distal end  190  experiences relatively minor or no upward curling. 
     Suspended electrode  105  may be fabricated by first defining actuation electrode  110  and anchors  115  on substrate  130 , then forming a sacrificial layer (e.g., deposited oxide) over actuation electrode  110  to fill the air gap between suspended electrode  105  and actuation electrode  110 . Next, suspended electrode  105  may be formed over the sacrificial layer and anchors  115  and contact  120  formed thereon. Subsequently, the sacrificial layer may be etched away with an acid bath (e.g., hydrofluoric acid) to free the bendable portion of suspended electrode  105 . 
     In one embodiment, rigidification structure  167  is formed within suspended electrode  105  by first patterning 3-dimensional topology  169  into substrate  130  underneath rigidification structure  167 . When subsequent layers are disposed over 3-dimensional topology  169  (e.g., insulator layer  135 , actuation electrode  110 , the sacrificial layer, and suspended electrode  105 ), the 3-dimensional topology is copied to each successive layer above. By forming 3-dimensional topology  169  in substrate  130  and actuation electrode  110 , the separation distance between each portion of suspended electrode  105  (including the portion having rigidification structure  167  disposed therein) and actuation electrode  110  is maintained at a constant. Since actuation is electrostatically induced and the electrostatic collapsing force for a given voltage is inversely proportional to the separation distance, maintaining a constant separation distance between the two electrodes reduces the impact of rigidification structure  167  on the actuation voltage. 
     In one embodiment, plate member  160  has approximately the same dimensions, length L 1  and width W 1 , as actuation electrode  110  (perhaps slightly smaller in some embodiments though need not be so) and narrow members  155  have a width W 2  (e.g., ≈30-60 μm) and a length L 2  (e.g., ≈50-150 μm). In one embodiment, suspended electrode  105  is approximately 2-4 μm thick. It should be appreciated that other dimensions may be used for the above components. 
     Stopper stubs  161  are formed on underside  163  of plate member  160  to prevent suspended electrode  105  from collapsing directly onto actuation electrode  110  and forming an electrical connection thereto. If suspended electrode  105  were to form electrical connection with actuation electrode  110  while MEMS switch  100  is closed circuited, then the actuation voltage between the two electrode would be shorted, and MEMS switch  100  would open. Further, allowing actuation electrode  110  and suspended electrode  105  to short circuit results in needless and harmful power dissipation. Accordingly, stopper stubs  161  are positioned on underside  163  to align with the insulated stopper butts  165  so as to prevent an electrical connection between suspended electrode  105  and actuation electrode  110 . 
     In one embodiment, anchor  115  supports suspended electrode  105  approximately 0.5-2.0 μm above actuation electrode  110 . Since polysilicon is a relatively hard substance and due to the multi spring constant nature of suspended electrode  105  (discussed in detail below) and stopping functionality of stopper stubs  161 , very small separation distances between suspended electrode  105  and actuation electrode  110  can be achieved (e.g., 0.6 μm or less). Due to the small air gap between suspended electrode  105  and actuation electrode  110  and the low curling properties of LSG polysilicon, an ultra-low actuation voltage (e.g., 3.0V actuation voltage) MEMS switch  100  can be achieved. 
     The illustrated embodiment of contact  120  includes a suspended trace  140  mounted to suspended electrode  105  via trace mounts  145 . Suspended trace  140  may be coupled to dual protruding contacts  150  that extend below suspended electrode  105  to make electrical contact with bottom electrode  180  when MEMS switch  100  is closed circuited. In one embodiment, contact  120  is fabricated of metal, such as gold (Au). In one embodiment, a insulating layer is disposed between trace mounts  145  and suspended electrode  105 ; however, since trace mounts  145  are relatively small and suspended trace  140  is fabricated of metal being substantially more conductive than suspended electrode  105 , the insulating layer may not be included in some embodiments (as illustrated). In one embodiment, suspended trace  140  is approximately 10 μm wide and 6 μm thick. 
     Contact  120  may be mounted to suspended electrode  105  closer to anchors  115  than to distal end  190 . In one embodiment, contact  120  may be positioned between anchors  115  and a center of plate member  160 . Positioning contact  120  closer to anchors  115  helps prevent stiction and false switching due to self-actuation or vibrations, as is discussed below. 
     It should be appreciated that a number of modifications may be made to the structure of MEMS switch  100  illustrated in  FIGS. 1A and 1B  within the spirit of the present invention. For example, a single anchor  115  and single narrow member  155  may be used to suspend a smaller plate member  160  above actuation electrode  110 . In this alternative embodiment, protruding contacts  150  may straddle each side of this single narrow member  155 . In yet another embodiment, a single protruding contact  150  may be used to make bridging contact with both signal lines  125  and  127 . In yet other embodiments, the specific shapes of suspended electrode  105  and actuation electrode  110 , as well as other components, may be altered. 
       FIGS. 2A and 2B  illustrated expanded views of a demonstrative 3-dimensional rigidification topology, in accordance with an embodiment of the invention.  FIG. 2A  is a perspective view of a portion of rigidification structure  167 , while  FIG. 2B  is a cross-sectional view of the same.  FIGS. 2A and 2B  are not intended to be limiting, but merely demonstrative of a possible 3-dimensional topology that may be formed into a portion of suspended electrode  105  for localized rigidification. 
     In the illustrated embodiments, rigidification structure  167  is a 3-dimensional rigidification topology disposed in plate member  160  and localized about contact  120  to increase the stiffness of plate member  160  about contact  120 . In one embodiment, rigidification structure  167  may include recesses  205  having an approximate depth T 1  of 2μ (micron). By rigidifying the portion of suspended electrode  105  about contact  120 , greater force is transferred from suspended electrode  105  onto contact  120  during actuation. As is discussed below in greater detail, greater contact force between protruding contacts  150  and bottom electrodes  180  of signal lines  125  and  127  reduces switch resistance and insertion loss. Furthermore, greater contact force acts to penetrate thin contamination layers that may accumulate or settle between protruding contacts  150  and bottom electrodes  180  and therefore increase the reliability of MEMS switch  100 . 
     Rigidification structure  167  may assume a variety of 3-dimensional topologies for reinforcing plate member  160  about contact  120 . For example, 3-dimensional rigidification topologies may include an undulated surface, ridges, elongated mesa structures (e.g., T-shaped structures), recesses, trenches, dimples, bumps, or otherwise. The 3-dimensional rigidification topology may be a regular repeated pattern (e.g., checkerboard pattern as illustrated in  FIG. 1A ) or an irregular pattern (as illustrated in  FIGS. 7A and 7B ). 
       FIGS. 2C ,  2 D,  2 E, and  2 F all illustrate an elongated mesa structure embodiment of rigidification structure  167 .  FIG. 2C  is a perspective view sketch,  FIG. 2D  is a cross-sectional sketch,  FIG. 2E  is a plan view using a scanning electron microscope, and  FIG. 2F  a perspective view using a scanning electron microscope of the same embodiment. The illustrated embodiment includes a checkerboard-like pattern of elongated mesa structures (e.g., T-shaped rigidification structures). In one embodiment, T 3 ≅2 μm, T 2 ≅4 μm to 6 μm, D 1 ≅10 μm to 20 μm, and D 2 ≅10 μm to 20 μm. In one embodiment, the overall surface dimension of the illustrated embodiment of rigidification structure  167  is between 40 μm×40 μm to 100 μm×100 μm. It should be appreciated that these dimensions are only representative, and embodiments of the invention may be smaller or larger and have different relative proportions. 
       FIG. 3  is a flow chart illustrating a process  300  for operation of MEMS switch  100 , in accordance with an embodiment of the invention. It should be appreciated that the order in which some or all of the process blocks appear in process  300  should not be deemed limiting. Rather, one of ordinary skill in the art having the benefit of the present disclosure will understand that some of the process blocks may be executed in a variety of orders not illustrated. 
     In a process block  305 , an RF signal is propagated along input signal line  125 . In a process block  310 , an actuation voltage is applied between actuation electrode  110  and suspended electrode  105 . In one embodiment, suspended electrode  105  is electrically grounded through anchors  115  and the actuation voltage is applied to actuation electrode  110  through input port  170 . Alternatively, actuation electrode  110  may be grounded through input port  170  and the actuation voltage applied to suspended electrode  105  through anchors  115 . 
     Referring to  FIG. 5 , either uni-polar voltage actuation (illustrated by line graphs  505 A, B, C) or alternating voltage polarity actuation (illustrated by line graphs  510 A, B, C) may be applied. Since suspended electrode  105  and actuation electrode  110  are substantially electrically decoupled from the RF signal path (e.g., signal lines  125 ,  127  and contact  120 ), the polarity of the voltage actuation may be changed without affecting the RF signal. Line graph  505 A illustrates three consecutive uni-polar actuations of MEMS switch  100  wherein the actuation voltage V A  is applied to actuation electrode  110 . Line graph  505 B illustrates the same three consecutive actuations wherein the voltage of suspended electrode  105  remains grounded. Line graph  505 C illustrates the voltage different between actuation electrode  110  and suspended electrode  105 . 
     Line graphs  510 A and  510 B illustrate three consecutive alternating voltage polarity actuations of MEMS switch  100 . A first actuation  515  of MEMS switch  100  is induced by application of actuation voltage V A  to actuation electrode  110  while suspended electrode  105  remains grounded. A second actuation  520  of MEMS switch  100  is induced by application of actuation voltage V A  to suspended electrode  105  while actuation electrode  110  remains grounded. A third actuation  525  repeats the first actuation instance  515 . Accordingly, line graph  510 C illustrates the potential difference between actuation electrode  110  and suspended electrode  105 . Over many cycles, the actuation voltage between the two electrodes will have a net zero DC component. Use of alternating polarity actuations of MEMS switch  100  may be more desirable when higher actuation voltages V A  are used (e.g., &gt;10V). 
     Returning to process  300 , in a process block  315 , the application of the actuation voltage across suspended electrode  105  and actuation electrode  110  induces suspended electrode  105  to bend or electrostatically collapse toward actuation electrode  110 . This initial bending phase is illustrated in  FIG. 4A . As illustrated, the actuation voltage is sufficient to cause distal end  190  of suspended electrode  105  to progressively collapse to a point where the furthest most stopper stub  161  mates with the furthest most stopper butt  165 . In this sense, suspended electrode  105  acts like a cantilever electrode having a fixed end mounted to anchors  115  and a free moving end at distal end  190 . 
     The actuation voltage is sufficient to overcome the initial restoring force produced by suspended electrode  105  having a first spring constant K 1 . The restoring force of suspended electrode  105  is weakest during this initial bending phase due to the mechanical advantage provided by the cantilever lever arm between distal end  190  and anchors  115 . It should be noted that during this initial bending phase, protruding contacts  150  have not yet formed a closed circuit between signal lines  125  and  127 . 
     In a process block  320 , MEMS switch  100  enters a second bending phase illustrated in  FIG. 4B . Between the point at which distal end  190  make physical contact with one of stopper butts  165  and MEMS switch  100  becomes closed circuited, the restoring force resisting the electrostatic collapsing force increases proportional to a second larger spring constant K 2 . It should be understood that suspended electrode  105  may not have only two abrupt spring constants K 1  and K 2 , but rather K 1  and K 2  represent smallest and largest spring constants, respectively, generated by the cantilever of suspended electrode  105  during the course of one progressive switching cycle. During this second bending phase, suspended electrode  105  begins to collapse inward with a progressive “zipper-like” movement starting at distal end  190  moving towards anchors  115  until protruding electrodes  150  contact bottom electrode  180  forming a closed circuit. As the zipper-like collapsing action continues, the restoring force generated by suspended electrode  105  increases. However, as suspended electrode  105  continues to collapse onto stopper butts  165  the separation distance between the suspended electrode  105  and actuation electrode  110  decreases, resulting in a corresponding drastic increase in the electrostatic collapsing force. This increase in the electrostatic collapsing force is sufficient to overcome the increasingly strong restoring force proportional to the larger spring constant K 2  of suspended electrode  105 . Accordingly, ultra-low actuation voltages equal to digital logic level voltages (e.g., 3.3V or less) can be reliably achieved with embodiments of the invention. 
     Since rigidification structure  167  is localized only about contact  120 , it does not significantly alter the actuation voltage of MEMS switch  100 . However, rigidification structure  167  does act to significantly stiffen suspended electrode  105  about contact  120 , and therefore, impart a greater compressive force onto protruding contacts  150  during the second bending phase. It should be noted that the actuation voltage is primarily determined by the first spring constant K 1  during the first bending phase. However, since the distal end  190  of suspended electrode  105  primarily flexes during the first bending phase, rigidification structure  167  has a less significant impact on the actuation voltage. Accordingly, while the entire suspended contact  105  can be rigidified to increase contact pressure during actuation, doing so increases the actuation voltage. 
     Once MEMS switch  100  is closed circuited, the RF signal can propagate through contact  120  and out output signal line  127  (process block  325 ). To open circuit MEMS switch  100 , the actuation voltage is removed (process block  330 ). Upon removal of the actuation voltage, the electrostatic collapsing force relents, and suspended electrode  105  restores itself to an open circuit position. Initially, stronger spring constant K 2  overcomes contact stiction to restore MEMS switch  100  to the position illustrated in  FIG. 4A , at which point MEMS switch  100  is in deed open circuited (process block  335 ). Subsequently, a weaker restoring force proportional to the spring constant K 1  returns MEMS switch  100  to the fully restored position illustrated in  FIGS. 1A and 1B  (process block  340 ). 
     However, if distal end  190  sticks in the bent position illustrated in  FIG. 4A , MEMS switch  100  is still open circuited since contact  120  is not touching bottom electrode  180 . Therefore, even if stiction does prevent suspended electrode  105  from returning to its fully restored position, MEMS switch  100  will still continue to correctly function as a electromechanical switch. It should be noted that in an embodiment where suspended electrode  105  is fabricated of polysilicon, the relative hardness of polysilicon over traditional metal cantilevers lends itself to reduced incidence of stiction. 
     Due to the zipper-like action of MEMS switch  100 , less wind resistance is generated by the cantilever of suspended electrode  105  while switching, when compared to the flapping motion generated by traditional electromechanical switches. Accordingly, MEMS switch  100  is well suited for high-speed switch applications, as well as, for low-speed applications. In one embodiment, the greater the actuation voltage the faster the zipper-like switch motion. 
       FIGS. 6A and 6B  are schematic diagrams illustrating a MEMS switch  600 , in accordance with an embodiment of the invention.  FIG. 6A  is a plan view of MEMS switch  600  while  FIG. 6B  is a cross-sectional view of the same. MEMS switch  600  is similar to MEMS switch  100  with the exception that input signal line  625  and output signal line  627  are routed over narrow members  155  of suspended electrode  105 . This rerouting of the RF paths avoids lengthy close proximity parallel runs of the RF paths (signal lines  625  and  627 ), which can cause parasitic inductances and capacitances between the RF traces themselves. 
       FIGS. 7A and 7B  are plan views illustrating an example circuit layout of MEMS switch  600 , in accordance with an embodiment of the invention.  FIG. 7A  illustrates a partially fabricated MEMS switch  600 , while  FIG. 7B  illustrates a fully fabricated MEMS switch  600 .  FIG. 7A  illustrates suspended electrode  105  without contact  120  disposed thereon to more fully demonstrate an example placement of rigidification structure  167 . Again, it should be appreciated that the exact size, shape, orientation, and placement of the 3-dimensional rigidification topology may vary from one embodiment to the next. 
       FIG. 8  is a functional block diagram illustrating a demonstrative wireless device  800  implemented with a MEMS switch array, in accordance with an embodiment of the invention. Wireless device  800  may represent any wireless communication device including a wireless access point, a wireless computing device, a cell phone, a pager, a two-way radio, a radar system, and the like. 
     The illustrated embodiment of wireless device  800  includes a MEMS switch array  805 , control logic  810 , signal logic  815 , a low noise amplifier (“LNA”)  820 , a power amplifier  825 , and an antenna  830  (e.g., dipole antenna). MEMS switch array  805  may include one or more MEMS switches  100  or one or more MEMS switches  600 . All or some of the components of wireless device  800  may or may not be integrated into a single semiconductor substrate (e.g., silicon substrate). 
     Control logic  810  may also be referred to as the actuation logic and is responsible for applying the actuation voltage for switching on/off the MEMS switches within MEMS switch array  805 . Control logic  810  couples to actuation electrode  110  and/or suspended electrode  105  of each MEMS switch within MEMS switch array  805 . Since the MEMS switches described herein are capable of ultra-low voltage actuation (e.g., &lt;3.0V), control logic  810  may use logic level voltages (e.g., 3.3 V) to actuate MEMS switch array  805 . In one embodiment, the same logic level voltage used by control logic  810  and/or signal logic  815  to switch transistors therein is also used to switch the MEMS switches of MEMS switch array  805 . 
     During a receive operation, control logic  810  applies the actuation voltage to those MEMS switches coupled to RF input  840  such that an RF signal propagates through MEMS switch array  805  to LNA  820  from antenna  830 . LNA  820  amplifies the RF signal and provides it to signal logic  815 . Signal logic  815  may include analog-to-digital converters to convert the RF signal to a digital signal and further include logic elements to process the digital signal. During a transmit operation, control logic  810  applies the actuation voltage to those MEMS switches coupled to RF output  845  such that an RF signal propagates through MEMS switch array  805  to antenna  830  from power amplifier  825 . Signal logic  815  may further include logic to generate a digital signal and a digital-to-analog converter to convert the digital signal to an RF signal. 
     The above description of illustrated embodiments of the invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. 
     These modifications can be made to the invention in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification. Rather, the scope of the invention is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation.