Abstract:
A micro-electromechanical (MEM) switch capable of inductively coupling and decoupling electrical signals is described. The inductive MEM switch consists of a first plurality of coils on a moveable platform and a second plurality of coils on a stationary platform or substrate, the coils on the moveable platform being above or below those in the stationary substrate. Coupling and decoupling occurs by rotating or by laterally displacing the coils of the moveable platform with respect to the coils on the stationary substrate. Diverse arrangements of coils respectively on the moveable and stationary substrates allow for a multi-pole and multi-position switching configurations. The MEM switches described eliminate problems of stiction, arcing and welding of the switch contacts. The MEMS switches of the invention can be fabricated using standard CMOS techniques.

Description:
BACKGROUND OF INVENTION  
         [0001]    This invention is generally related to micro-electromechanical systems (MEMS) especially MEMS switches, and more specifically, to an inductive MEMS switch utilizing inductive coupling and decoupling, and which is fully compatible with standard CMOS manufacturing materials and processes.  
           [0002]    Switching operations are a fundamental part of many electrical, mechanical and electromechanical applications. MEMS switches have drawn considerable interest over the last few years. Products using MEMS switch technology are widespread in biomedical, aerospace and communications systems.  
           [0003]    MEMS switches have been manufactured using various configurations, they are electrostatically controlled beams that make metal-to-metal contact or a similar structure that uses a dielectric stop to form a capacitive switch. A common feature that characterizes the device is that it is provided with at least one moving element contacting another to complete the circuit.  
           [0004]    In order to better understand the present invention, a conventional MEMS switch will now be described with reference to FIG. 1, showing a cross-section view of a MEMS switch having both ends of a deformable beam  5  anchored on dielectric  2 . The lowest level consists of a dielectric material  1  consisting of conductive elements  3  and  4  which are used to connect or form the various electrical components of the device. Conductors referenced by numerals  3  and  6  are used to provide an operating voltage potential that causes the beam to bend (or deform). Conductor  4 , which conducts an electrical signal, contacts the deformable beam when the MEM switch is in operation. FIG. 2 shows a top-down view of the same conventional switch.  
           [0005]    In a typical implementation of a conventional MEM switch, the contact beam is formed by depositing polysilicon over a dielectric made of, e.g., SiO2. The surrounding material is etched away leaving a raised structure that is attached to silicon beam  5 . The contact element  6 , anchored at one end on silicon beam  5  is suspended at its other end above conductors  3  and  4 , and is preferably made of polysilicon. Subsequently, the device is subjected to electroless plating, usually of gold, that adheres to the polysilicon to complete the fabrication of conductive elements  3 ,  4  and  6 .  
           [0006]    The switch is operated by providing a potential difference between contact beam  6  and electrode  3 . This voltage generates an electrostatic attraction that brings beam  6  in contact with electrode  4 , thus closing the switch. The twist imparted to the anchored beam  5  is used to restore the contact  6  to its open position once the control voltage potential is dropped.  
           [0007]    Generally, all conventional MEMS switches rely upon physical contact, especially metal-to-metal contact to perform the switching operation. This leads to many reliability problems related to arcing, material transfer, micro-welding, station, and the like. It is well known in the art that most of these switches become less reliable at higher frequencies. Some of the metallurgies used, such as gold, that are commonly used in an attempt to alleviate these problems are not compatible with standard CMOS fabrication. The inductive MEMS switch of the present invention which will be described hereinafter lends itself to be operated by any number of well known MEMS actuators.  
           [0008]    Examples of MEMS actuators can be found at the Sandia National Laboratory web site (www.sandia.gov), or in several MEMS patents related to actuators such as U.S. Pat. No. 6,328,903, George E. Vernon, Sr., “Surface-Micromachined Chain for Use in Micro-Mechanical Structures”, issued Dec. 11, 2001. Other patents specifically directed to comb drive systems described hereinafter are to be found, for instance, in U.S. Pat. No. 5,998,906, Jerman et al., “Electrostatic Microactuator and Method for Use Thereof”, issued Dec. 7, 1999.  
           [0009]    In conventional MEMS switches, as described, for instance, in U.S. Pat. No. 6,074,890, Yao et al., Method of Fabricating Suspended Single Crystal Silicon MEMS Devices”, issued Jun. 13, 2000, and further described in IEEE Microwave issued December 2001, typically, at least one electrode in the switching circuit has a DC potential applied as part of the electrostatic actuation. Thus, a distinct need exists to separate the drive system from the switching circuit such that no DC control voltage is applied to at least one contact in order to perform electrostatic actuation.  
         SUMMARY OF INVENTION  
         [0010]    Accordingly, it is an object of the invention to provide an inductive MEMS switch based on inductive coupling and decoupling of electrical signals.  
           [0011]    It is another object to provide an inductive MEMS switch that isolates the control signal from the switched signals by separating the path of the switched signal from the control circuit used to operate the device.  
           [0012]    It is still another object to provide an inductive MEMS switch having an off-state isolation that surpasses a conventional switch in the off-state, and which are typically limited to provide isolation of about 50 dB at 6 GHz.  
           [0013]    It is a further object to provide an inductive MEMS switch that may be configured in a variety of multi-pole, multi-throw arrangements and which is controlled by any number of MEMS linear or rotary drive systems.  
           [0014]    It is yet another object to provide an inductive MEMS switch that can reliably perform “hot-switching”, namely, switching while operating under nominal power levels. Switching can be achieved at 1 watt, 5 watts up to whatever value the remaining part of the circuit cansince the switching is non-contact and, thus, there is no arcing or welding of contacts.  
           [0015]    It is still another object to provide an inductive MEMS switch that operates reliably with no DC potential or physical contact point in the signal path which can potentially lead to arcing, welding or material transfer and degradation.  
           [0016]    It is still a further object to provide an inductive MEMS switch that increases its efficiency at higher frequencies, allowing the size of the coils to decrease when the frequency of the signal increases, the increase in efficiency being achieved by magnetic field coupling between the switch components, thus providing better insertion loss characteristics at higher frequencies without a corresponding decrease in isolation performance.  
           [0017]    It is another object of the invention to provide a switch/transformer combination for achieve impedance matching. By selecting the inductance of each portion of the inductive switch appropriately, the input and output impedance of the switch can be adjusted independently. This adjustment allows for impedance matching and switching at the same time. A special configuration of the transformer can be utilized to create a single-ended to double-ended converter or balun (BAlanced-UNbalanced), providing both switching and signal conversion in a single device.  
           [0018]    It is still a further object to provide an inductive MEMS switch that can be manufactured using CMOS compatible processes and materials.  
           [0019]    In one aspect of the invention, switching of the signal is accomplished by inductive coupling and decoupling between stationary coils and moveable coils. Switching occurs as the moveable coils are or not aligned with respect to the stationary coils.  
           [0020]    A four turn spiral inductor, with a metal thickness of 4 μm, a turn width of 10 μm, and an outer diameter of 150 μm, configured as one element of the switch, is magnetically coupled to another similar spiral, directly above or below, yielding a coupling coefficient of about 0.85. When these spirals are configured as described, a closed-switch insertion loss of 6.6 dB and a opened-switch isolation of 65 dB is achieved at 13 Ghz. This yields an excellent on-off switch ratio tuned to frequencies below 13 Ghz by adding an external tuning capacitor between the two ports of the switch. Similarly, a one and a half turn spiral inductor, with a metal thickness of 4 μm, a turn width of 10 μm, and an outer diameter of 150 μm, configured as one element of the switch, is magnetically coupled to another similar spiral, directly above or below, yielding a coupling coefficient of about 0.85. When the spirals are configured as such, a closed-switch insertion loss of 10 dB and an opened-switch isolation of 60 dB is achieved at 25 Ghz. This yields an excellent on-off switch ratio tuned to frequencies below 25 Ghz by the addition of an external tuning capacitor between the two ports of the switch.  
           [0021]    In another aspect of the invention, the present. MEMS switch solves problems known as stiction, arcing and welding of the switch contacts, all of which are eliminated because of a lack of physical contact between the switching elements. The coils are simply aligned in close proximity such that inductive coupling can transfer the signal between one and the other. In view of this characteristic, the MEMS switch can easily handle switching at full power (hot switching) and, clearly more power than a conventional MEMS switch.  
           [0022]    Multiple switch configurations are realized by varying the number of stationary or moveable coils, and/or by altering the coil geometric configuration of the coils and the corresponding displacement of the moveable elements. Additionally, total isolation from the control signal and the switched signal path is possible since the drive circuit is totally independent of the switching circuit. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0023]    These and other objects, aspects and advantages of the invention will become apparent from the following detailed description of preferred embodiments of the invention, when taken in conjunction with the accompanying drawings.  
         [0024]    [0024]FIGS. 1 and 2 are schematic diagrams respectfully showing a cross-section and a top-down view of a prior art MEMS switch.  
         [0025]    [0025]FIG. 3 shows a first embodiment of the invention, wherein a module of movable inductors rotate about a pivot pin to inductively couple and decouple one set of coils from another. Also shown are comb drives illustrating one possible mode of operation. FIG. 3 illustrates the switch positioned in a decoupled mode to better view the stationary coils.  
         [0026]    [0026]FIG. 4 is the same device shown of FIG. 3, but substantially rotated to illustrate the mode of coupling the moveable inductors to the stationary inductors, in accordance with the present invention.  
         [0027]    [0027]FIG. 5 is a top-down view of the moveable coil arrangement. The delimiter A-A shows the cross-section view to be used in FIG. 6.  
         [0028]    [0028]FIG. 6 is a cross-section view of FIG. 5 through delimiter A-A. Also shown is relevant part of the underlying substrate containing the stationary coils  40  and  50 , the pivot hole and the pivot pin about which the device rotates.  
         [0029]    [0029]FIG. 7 is another top-down view of the same device taken at a different delimiter B-B, to be used in the cross-section shown in FIG. 8.  
         [0030]    [0030]FIG. 8 shows a cross-section of the device of FIG. 7 through delimiter B-B, showing a better perspective of the elements used to connect the moveable coils.  
         [0031]    [0031]FIG. 9 illustrates an arrangement wherein the pivot is moved to the interior of one of the movable coils. Also shown is the coil coupled to stationary coil  40  to provide a multi-throw switch.  
         [0032]    [0032]FIG. 10 shows the MEMS switch configured with coils at one end of a moving fulcrum.  
         [0033]    [0033]FIG. 11 is an extension of FIG. 10 which provides added functionality as a multi-pole switch.  
         [0034]    [0034]FIG. 12 shows an arrangement that uses a rotary drive for a multi-position MEMS switch.  
         [0035]    [0035]FIG. 13 illustrates an arrangement showing a linear (or rack) and pinion drive to provide transversal motion to the MEMS switch of the present invention.  
         [0036]    [0036]FIG. 14 is a cross-sectional diagram of the MEMS switch depicted in FIGS. 3 through 5 with a fully enclosed cavity encapsulating the switch.  
         [0037]    [0037]FIG. 15 shows the MEMS switch of FIG. 14 showing an added upper set of coils to enhance functionality.  
         [0038]    [0038]FIG. 16 is a top-down view of another embodiment of the MEMS device displaying a single turn coil and requiring only one level of wiring in the movable part of the device.  
         [0039]    [0039]FIG. 17 shows a cross-section of the device shown in FIG. 16 as seen from delimiter C-C.  
         [0040]    [0040]FIGS. 18 and 19 depict the ability to fabricate multiple arrangements of moving coils for more demanding applications.  
         [0041]    [0041]FIG. 20 shows an arrangement capable of coupling more than two pairs of coils at a time.  
         [0042]    [0042]FIG. 21 illustrates how a single moveable coil is used to make a switch/balun (BAlanced-UNbalanced) combination.  
         [0043]    [0043]FIG. 22 shows same switch/balun depicted in FIG. 21 in a coupled state.  
         [0044]    [0044]FIG. 23 illustrates a top-down view of a linear arrangement, wherein the coils are constructed vertically (perpendicular) to the plane of the substrate.  
         [0045]    [0045]FIG. 24 shows a cross-section of device shown in FIG. 23 that illustrates how the moveable coil is constructed within the moveable element of the MEMS switch.  
         [0046]    [0046]FIG. 25 is another top-down view of a more complex moveable coil arrangement similar to that shown in FIG. 23.  
         [0047]    [0047]FIG. 26 is a cross-sectional representation of the MEMS switch shown in FIG. 25.  
         [0048]    [0048]FIG. 26A shows a perspective drawing of the three-dimensional coil arrangement as illustrated in FIGS. 25 and 26. 
     
    
     DETAILED DESCRIPTION  
       [0049]    The present invention will now be described more fully with reference to the drawings, in which preferred embodiments are shown.  
         [0050]    [0050]FIG. 3 is a schematic diagram of a first embodiment illustrating the invention in its simplest form. A moveable coil assembly  10  consisting of a substrate, platform or module  15  of moveable inductors  20  and  30  that rotate about pivot pin  70 , inductively coupling and decoupling the moveable coils  20  and  30  to and from stationary coils  40  and  50  positioned on a second substrate above or below platform  15 . Comb drives  8  an  9  provide driving capabilities to the assembly to illustrate one mode of operation, although other drive systems can be used just as effectively. Subsequent figures will show the device positioned in both positions in order to better illustrate the relative position of the moveable coils with respect to the stationary coils.  
         [0051]    The two inductors  20  and  30  are connected to close the circuit through conductors  25  and  35  such that any current flow induced in one coil flows through the other. Pivot pin  70  passes through hole  75  (illustrated in more detail in FIG. 6). Inductors  40  and  50  are positioned on an underlying substrate  7  (shown in FIG. 6), and are connected to other circuitry requiring a switching mechanism, such as a power amp, a receiver and an antenna.  
         [0052]    The mechanism by which rotation is achieved is not an element of the present embodiment. Practitioners of the art will readily recognize that there are any number of MEMS switches that can be accommodated to provide the required movement to device. An example of such a device is found, for instance, in U.S. Pat. No. 6,074,890 “Method of Fabricating Suspended Single Crystal Silicon MEMS devices” to Yao et al., which describes a method of fabricating a simple comb drive or in U.S. Pat. No. 6,465,929 “Micro-electromechanical system actuator for extended linear motion” to Levitan, et al., both of which are incorporated herein be reference.  
         [0053]    [0053]FIG. 4 illustrates the MEMS switch of FIG. 3 rotated to a position where the coils are inductively coupled, namely, moveable inductor  20  to stationary inductor  40  while moveable coil  30  is coupled to stationary coil  50 . In this manner, a signal injected into coil  40  can be inductively transferred to coil  20 . An electric signal is transferred to coil  30  which, in turn, inductively couples it down to coil  50 . Thus, an electric signal from, e.g., a transmitter power amp is applied to coil  40 , and the signal flows through the device to coil  50  which may, in turn, connected to, e.g., an antenna. It should be noted that additional coils may be part of the assembly to achieve additional functionality. This will be illustrated hereinafter with reference to FIGS.  9 - 10 ,  13 , and  18 - 20 .  
         [0054]    [0054]FIG. 5 is a top-down view of assembly  10  illustrating coils  20  and  30  and their inner and outer coil connections  35  and  25 , respectively. Also shown is a delimiter A-A that will be used hereinafter with reference to FIG. 6.  
         [0055]    [0055]FIG. 6 is a cross-section view of FIG. 5 taken through line A-A. Illustrated herein is lower substrate  7  which contains the stationary coils and possibly other related circuitry (not shown herein for clarity). A shoulder  80  surrounding pivot pin  70  is constructed on substrate  7 . This shoulder provides the necessary clearance to allow device  10  to move. The height of the shoulder determines this clearance and to some degree, the level of efficiency of coupling the coils. The shoulder is on the order of 1000 Å to over 2 μm thick, depending on the specific application. The pivot pin  70  is contained within the area of the shoulder and its size is determined by the ability of device  10  to move freely thereat without binding or significant wobble. The diameter of the pivot should be sufficient to provide the necessary mechanical reliability, and it is scaled accordingly. Its diameter is also influenced by the selection of the material and by the process capabilities. Likewise, hole  75  in device  10  is designed to accommodate the pivot pin such that the desired range of motion occurs without binding. The height of the pivot is scaled to conform to the thickness of device  10 . By way of example, if device  10  is 3 μm thick, then the pivot will occupy a substantial portion of the thickness in order to reliably retain the device. Preferentially, the pivot is made slightly taller that the thickness of device  10  so that the top shoulder  85  (see FIG. 14) is contacted by the pivot to enclose and retain the device.  
         [0056]    [0056]FIG. 7 is a top-down view of the moveable portion of device  10  seen from a different position, defined by delimiter B-B, for further use in FIG. 8.  
         [0057]    [0057]FIG. 8 is a cross-section perspective of FIG. 7 seen from delimiter B-B. It specifically illustrates the upper connection  35  between the coils and the studs  60  used to fabricate the multilevel construction needed to form true spiral inductors. In this manner, the internal ends of coils  20  and  30  can be interconnected. The outer connector  25  is built on the same layer as the coils and, therefore, does not require studs. It should be noted that this arrangement is not the only one that is possible. FIGS. 16 and 17 described hereinafter will illustrate coils that are constructed using only one level of wiring.  
         [0058]    [0058]FIG. 9 illustrates a second embodiment of the invention wherein pivot  70  is moved towards one end of the moving portion of the device  10  and additional stationary coils  42  and  45  are incorporated alongside coils  40  and  50 . This illustrates one method of achieving a multi-throw arrangement. In the arrangement shown, output coil  30  can be coupled to any of the stationary coils  42 ,  45 , and  50 . The input to the moveable coils is supplied by coupling the stationary coil  40  to coil  20 . Since pivot pin  70  lies at the center of coil  20 , it remains inductively coupled to  40  as the device  10  rotates, as shown in FIG. 9A, wherein comb drive  13  is engaged and the device rotates counterclockwise, while coils  42  and  30  overlap and become inductively coupled.  
         [0059]    [0059]FIG. 10 shows yet another embodiment of the invention, wherein moveable coils  20  and  30  are constructed at one end of fulcrum  11 . When they are moved, they couple and decouple in pairs with respect to stationary coils  40 ,  42  and  50 . FIG. 10 shows the device  10  in position for coupling to stationary coils  42  and  40 . FIG. 10A illustrates device  10  after being rotated clockwise by comb drive  13  such that coil  42  is decoupled, thus allowing coils  40  and  50  to couple with  20  and  30 , respectively.  
         [0060]    [0060]FIG. 11 illustrates another implementation of the invention, wherein the embodiment of FIG. 10 is extended to include a plurality of movable coils sets to form a multi-pole, multi-throw switch. A symmetrical configuration to the one shown in FIG. 10 is used to replicate the coil arrangement of FIG. 10, wherein stationary coils  42 A,  40 A and  50 A are respectfully coupled to moving coils  20 A and  30 A which are attached to fulcrum  11  and rotated around pivot pin  70 . FIG. 11 illustrates the device such that coils  20  and  30  are inductively coupled to  42  and  40 , respectively. Concurrently, coils  20 A and  30 A are coupled to coils  42 A and  40 A, respectively. In FIG. 11A, the same device is shown in its complementary position after being rotated clockwise by drive  13 . In this position, coils  20  and  30  are shown coupled, respectively, to  40  and  50 , while coils  20 A and  30 A are coupled to  40 A and  50 A, respectively.  
         [0061]    [0061]FIG. 12 shows yet another embodiment of the invention in which the movable coil device  10  is actuated by a rotary drive (not shown) to provide multi-mode switching. This application is especially advantageous, for instance, for band switching on mobile phones. The drives are known in the art, and fully described, e.g., in U.S. Pat. No. 6,404,599 “High Performance Integrated micro-actuator” to Vegan. FIG. 12 shows the device  10  with coils  20  and  30  coupled to stationary coils  42  and  42 A, respectively.  
         [0062]    [0062]FIG. 12A shows the device  10  as it rotates clockwise such that coils  20  and  30  are now coupled to  40  and  40 A, respectively. This clockwise rotation moves the device further such that  20  and  30  are, respectively, coupled to  50  and  50 A. Rotation may further extend in a clockwise direction for other combinations or it may, at this point, be reversed to repeat the stated coupling and decoupling the moving coils  20  and  30  with the respective stationary coils. The rotary motion can be imparted to device  10  by any number of means currently known in the art.  
         [0063]    [0063]FIG. 13 illustrates yet another embodiment on the invention in which device  10  is constrained by rail  16  or trench guide and is moved transversely via a linear drive or as illustrated using rack  17  and pinion  18 . The device as shown includes only one stationary coil  42  and two moveable coils. Other coils may also be incorporated below (or above) device  10  adjacent to stationary coil  42  (similar to  40 A and  50 A in FIG. 15), all of which are not shown herein for clarity. When device  10  moves back and forth, it couples and decouples to and from the various stationary coils positioned below or (above the device). An example of a rack and pinion MEMS device is described in U.S. Pat. No. 6,305,779, “MEMS ink-jet nozzle cleaning and closing mechanism” to Capurso, et al., which is incorporated herein by reference.  
         [0064]    [0064]FIG. 14 is a cross-sectional view of the completed device being totally encapsulated for reliability purposes. The lower stationary coils  40  and  50  are constructed at the bottom dielectric layer  7 . Additionally, lower shoulder  80  is also built on the same layer  7 , and is fabricated with the same material as coplanar dielectric layer  90 . Cavity  12  is formed within dielectric layer  90 , and provides the space necessary for moving device  10 . Upper dielectric layer  100  encases device  10  and provides added mechanical support to the structure, as shown by way of top shoulder  85  contacting pivot pin  70 .  
         [0065]    [0065]FIG. 15 is similar to FIG. 14 except that the former illustrates how additional functionality is attained by incorporating additional coils  40 A and  50 A to the top dielectric  100 .  
         [0066]    [0066]FIG. 16 is a top-down view of device  10  in a simpler one level wiring scheme that eliminates the need for studs (such as  60 , in FIG. 8). This embodiment simplifies the construction of device  10  but does not allow for spiral inductors and, therefore, may have limited use for certain applications. Delimiter C-C provides a reference for the cross-sectional view shown in FIG. 17.  
         [0067]    [0067]FIG. 17 is a diagram representing a cross-sectional view of the structure shown delimiter C-C of FIG. 16. This figure is comparable to the previously described FIG. 8 that illustrates the multilayer wiring needed for spiral inductors.  
         [0068]    [0068]FIG. 18 is yet another embodiment of the invention that utilizes multiple moving devices  10  and  10 A relative to stationary coil  30 . These devices can be formed at different levels of the structure, such that they move as shown in FIG. 19 in a vertical coupling of more than two inductors concurrently. FIG. 18 shows moveable coils  10  and  10 A in a decoupled state, while FIG. 19 illustrates the devices of FIG. 18 in a coupled state.  
         [0069]    [0069]FIG. 20 illustrates the construction of an inductive switch containing more than two coils, the triangular substrate rotating around pivot pin  70 . In the present arrangement, coils  20 ,  21  and  30  are shown coupled to coils  56 ,  41  and  51 , respectively. The misalignment shown is intended for illustration purposes only. If the device is rotated clockwise, then coils  20 ,  21  and  30  end up being aligned with coils  40 ,  50  and  55 , respectively.  
         [0070]    [0070]FIG. 21 illustrates the inductive MEMS switch in a decoupled state, wherein a single moveable coil is used to provide a switch/balun combination. As mentioned previously, impedance matching and Balun functions as well as switching are enabled by providing different inductance values at appropriate locations within the inductive switch.  
         [0071]    [0071]FIG. 22 illustrates the same device of FIG. 21 in the coupled state. Movable coil/balun  20 A couples with both inductors  40  and  50  concurrently.  
         [0072]    [0072]FIG. 23 is a top-down view of a linear arrangement, wherein the stationary coils and the moveable coil are constructed vertically or perpendicular to the plane of the substrate  10 .  
         [0073]    [0073]FIG. 24 shows a cross-section of moveable coil arrangement  10  of FIG. 23 illustrating how the moveable coil is constructed within moveable element  10 . FIG. 24A shows in more detail the construction of a vertical coil. The structure is fabricated in multiple layers with layer A forming the bottom portion of the inductor loops. This process is similar to a standard damascene line level. Layer B contains portions of the outer and inner vertical conductors in the loops as well as the horizontal inner conductor, similar to the dual damascene structures providing vias and interconnected lines. Layer C contains the upper portion of the vertical loops and the upper horizontal conductor which completes the coil(s), again just as in a dual damascene construction. Layer D is just a top insulating layer that also serves the purpose of encapsulating and protecting the metal.  
         [0074]    [0074]FIG. 25 is another top-down view of a more complex moveable coil arrangement similar to the one illustrated in FIG. 23, while FIG. 26 is a cross-section representation of the structure shown in FIG. 25 with coils  20  and  30  in a vertical three-dimensional structure instead of the horizontal two-dimensional coils described earlier. FIG. 26A shows a perspective drawing of the three-dimensional coil arrangement as illustrated in FIGS. 25 and 26. This arrangement is constructed in a manner similar to that described for FIG. 24, wherein the various segments of the coils are constructed in layers as is, typical done in damascene or dual damascene processing.  
         [0075]    The inventive inductive MEMS switch of the invention displays an increased efficiency at higher frequencies, to allow decreasing the size of the coils decreases as the frequency of the signal increases. The increase in efficiency is achieved by the magnetic field coupling between switching components. This magnetic field coupling provides better insertion loss characteristics at higher frequencies without a corresponding decrease in isolation performance. This efficient operation at higher frequencies is contrasted by the increasingly poor performance of typical metal-to-metal and capacitive switches at higher frequencies due to their decreasing isolation performance in the switch-open state. Typical metal-to-metal switches can only handle 2 to 3 GHz reliably whereas the present inventions can readily handle upwards of 25 GHZ. (The efficient operation at higher frequencies is contrasted with the increasingly poor performance of typical metal-to-metal and capacitive switches at higher frequencies due to the decreasing isolation performance in the switch-open state).  
         [0076]    Another advantage of the invention resides in the ability of constructing a switch/transformer combination for built-in impedance matching. By selecting the inductance of each portion of the inductive switch appropriately, the input and output impedance of the switch can be adjusted independently. This adjustment allows for impedance matching and simultaneous switching. A special configuration of the transformer can be utilized to create a single-ended to double-ended converter or balun, providing both switching and signal conversion in a single device.  
         [0077]    While the invention has been described in conjunction with a preferred embodiment, it is to be understood that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the aforementioned description. Accordingly, it is intended to embrace all such alternatives, modifications and variations which fall within the spirit and scope of the appended claims. All matters set forth herein or shown in the accompanying drawings are to be interpreted in an illustrative and non-limiting sense.