Abstract:
A micro-electromechanical (MEMS) relay decouples a flux path from magnetic actuation from the electrical path through the switch to eliminate signal degradations that result from fluctuations in the current around the core and, thereby the flux. In addition, the MEMS relay has a suspension structure that is independent of the core.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to relays and, more particularly, to a MEMS relay that has a flux path from magnetic actuation that is decoupled from an electrical path through the switch, and a suspension structure that is independent of the core structure, and a method of forming the same. 
     2. Description of the Related Art 
     A switch is a well-known device that connects, disconnects, or changes connections between devices. An electrical switch is a switch that provides a low-impedance electrical pathway when the switch is “closed,” and a high-impedance electrical pathway when the switch is “opened.” A mechanical-electrical switch is a type of switch where the low-impedance electrical pathway is formed by physically bringing two electrical contacts together, and the high-impedance electrical pathway is formed by physically separating the two electrical contacts from each other. 
     An actuator is a well-known mechanical device that moves or controls a mechanical member to move or control another device. Actuators are commonly used with mechanical-electrical switches to move or control a mechanical member that closes and opens the switch, thereby providing the low-impedance and high-impedance electrical pathways, respectively, in response to the actuator. 
     A relay is a combination of a switch and an actuator where the mechanical member in the actuator moves in response to electromagnetic changes in the conditions of an electrical circuit. For example, electromagnetic changes due to the presence or absence of a current in a coil can cause the mechanical member in the actuator to close and open the switch. 
     One approach to implementing actuators and relays is to use micro-electromechanical system (MEMS) technology. MEMS devices are formed using the same fabrication processes that are used to form conventional semiconductor structures, such as the interconnect structures that provide electrical connectivity to the transistors on a die. 
     One drawback of conventional MEMS relays is that the flux path that actuates the device also typically follows the electrical path through the switch. Traditionally, relays are used for power switching, and thus signal attenuation through the switch due to fluctuations in the current around the core and, thereby the flux, has not been a concern. 
     However, when MEMS relays are passing signals with very small amplitudes through the switch, fluctuations in the current around the core and, thereby the flux, can lead to an unacceptable degradation of the signal passing through the switch. Thus, there is a need for a MEMS relay that has a flux path that is decoupled from the electrical path through the switch. 
     Another drawback of conventional MEMS relays is that the suspension structure is typically formed as part of the core structure. The suspension and core structures, however, commonly have conflicting requirements. The ideal geometry of the core structure is a short flux path with a large cross-sectional area. However, the ideal geometry of the suspension structure is a long path with a small cross-sectional area because this reduces the spring stiffness of the beam, and thus the force required to close the switch. Thus, there is also a need for a MEMS relay that has a suspension structure that is independent of the core structure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view illustrating an example of a method  100  of forming a MEMS relay in accordance with the present invention. 
         FIGS. 2A-15A ,  2 B- 15 B,  2 C- 15 C,  2 D- 15 D, and  2 E- 15 E are a series of views that illustrate an example of method  100  in accordance with the present invention.  FIGS. 2A-15A  are plan views.  FIGS. 2B-15B  are cross-sectional views taken along lines  2 B- 2 B of FIGS.  2 A through  15 B- 15 B of  FIG. 15A , respectively.  FIGS. 2C-15C  are cross-sectional views taken along lines  2 C- 2 C of FIGS.  2 A through  15 C- 15 C of  FIG. 15A , respectively.  FIGS. 2D-15D  are cross-sectional views taken along lines  2 D- 2 D of FIGS.  2 A through  15 D- 15 D of  FIG. 15A , respectively.  FIGS. 2E-15E  are cross-sectional views taken along lines  2 E- 2 E of FIGS.  2 A through  15 E- 15 E of  FIG. 15A , respectively. 
         FIGS. 16A-18A ,  16 B- 18 B,  16 C- 18 C,  16 D- 18 D, and  16 E- 18 E are a series of views illustrating a first example of an alternate way of implementing element  110  of method  100  in accordance with the present invention.  FIGS. 16A-18A  are plan views.  FIGS. 16B-18B  are cross-sectional views taken along lines  16 B- 16 B of FIG.  16 A through  18 B- 18 B of  FIG. 18A , respectively.  FIGS. 16C-18C  are cross-sectional views taken along lines  16 C- 16 C of FIG.  16 A through  18 C- 18 C of  FIG. 18A , respectively.  FIGS. 16D-18D  are cross-sectional views taken along lines  16 D- 16 D of FIG.  16 A through  18 D- 18 D of  FIG. 18A , respectively.  FIGS. 16E-18E  are cross-sectional views taken along lines  16 E- 16 E of FIG.  16 A through  18 E- 18 E of  FIG. 18A , respectively. 
         FIGS. 19A-21A ,  19 B- 21 B,  19 C- 21 C,  19 D- 21 D, and  19 E- 21 E are a series of views illustrating a second example of an alternate way of implementing element  110  of method  100  in accordance with the present invention.  FIGS. 19A-21A  are plan views.  FIGS. 19B-21B  are cross-sectional views taken along lines  19 B- 19 B of FIG.  19 A through  21 B- 21 B of  FIG. 21A , respectively.  FIGS. 19C-21C  are cross-sectional views taken along lines  19 C- 19 C of FIG.  19 A through  21 C- 21 C of  FIG. 21A , respectively.  FIGS. 19D-21D  are cross-sectional views taken along lines  19 D- 19 D of FIG.  19 A through  21 D- 21 D of  FIG. 21A , respectively.  FIGS. 19E-21E  are cross-sectional views taken along lines  19 E- 19 E of FIG.  19 A through  21 E- 21 E of  FIG. 21A , respectively. 
         FIGS. 22A-26A ,  22 B- 26 B,  22 C- 26 C,  22 D- 26 D, and  22 E- 26 E are a series of views illustrating an example of an alternate way of implementing element  118  of method  100  in accordance with the present invention.  FIGS. 22A-26A  are plan views.  FIGS. 22B-26B  are cross-sectional views taken along lines  22 B- 22 B of FIG.  22 A through  26 B- 26 B of  FIG. 26A , respectively.  FIGS. 22C-26C  are cross-sectional views taken along lines  22 C- 22 C of FIG.  22 A through  26 C- 26 C of  FIG. 26A , respectively.  FIGS. 22D-26D  are cross-sectional views taken along lines  22 D- 22 D of FIG.  22 A through  26 D- 26 D of  FIG. 26A , respectively.  FIGS. 22E-26E  are cross-sectional views taken along lines  22 E- 22 E of FIG.  22 A through  26 E- 26 E of  FIG. 26A , respectively. 
         FIGS. 27A-27E  are a series of views illustrating an example of sacrificial structure  230  and spring member  254  with a different shape in accordance with the present invention. 
         FIGS. 28A-28E  are a series of views illustrating an example of sacrificial structure  230 , core  236 , intermediate member  246 , and spring member  254  with a different shape in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As described in greater detail below, the present invention is a MEMS relay, and a method of forming the relay, that has a flux path from magnetic actuation which is decoupled from the electrical path through the switch. In addition, the MEMS relay has a suspension structure that is independent of the core structure. 
       FIG. 1  shows an example of a method  100  of forming the MEMS relay in accordance with the present invention. As shown in  FIG. 1 , method  100  begins in  110  by forming a number of spaced-apart lower coil members that form the lower horizontal sections of a to-be-formed coil. In addition, a pair of lower input/output members can optionally be formed at the same time that the lower coil members are formed. 
       FIGS. 2A-15A ,  2 B- 15 B,  2 C- 15 C,  2 D- 15 D, and  2 E- 15 E show a series of views that illustrate an example of method  100  in accordance with the present invention.  FIGS. 2A-3A ,  2 B- 3 B,  2 C- 3 C,  2 D- 3 D, and  2 E- 3 E show a series of views that illustrate an example of method  100  forming a number of spaced-apart lower coil members in accordance with the present invention. 
     As shown in  FIGS. 2A-2E , method  100  utilizes a conventionally formed single-crystal silicon semiconductor wafer  210  that has an overlying base dielectric layer  212 . Base dielectric layer  212  can represent a dielectric layer that includes no metal structures, or a dielectric layer that includes metal structures, such as the dielectric layer of a metal interconnect structure. 
     When formed as the dielectric layer of a metal interconnect structure, base dielectric layer  212  includes levels of metal traces, which are typically aluminum, a large number of contacts that connect the bottom metal trace to electrically conductive regions on wafer  210 , and a large number of inter-metal vias that connect the metal traces in adjacent layers together. Further, selected regions on the top surfaces of the metal traces in the top metal layer function as pads which provide external connection points. 
     In the present example, base dielectric layer  212  represents the dielectric layer of a metal interconnect structure that also includes pads P 1 -P 4 . Pads P 1  and P 2  are selected regions on the top surfaces of two of the metal traces in the top layer of metal traces that provide electrical connections for a to-be-formed coil, while pads P 3  and P 4  are selected regions on the top surfaces of the metal traces that provide electrical input/output connections for a to-be-formed switch. (Only pads P 1 -P 4 , and not the entire metal interconnect structure, are shown in cross-section for clarity.) 
     Referring again to  FIGS. 2A-2E , method  100  begins by forming a metal layer  214  on the top surface of base dielectric layer  212 . In the present example, since base dielectric layer  212  represents the dielectric layer of a metal interconnect structure, metal layer  214  is also formed on the top surfaces of the pads P 1 -P 4 . 
     Metal layer  214  can include, for example, a layer of titanium (e.g., 100 Å thick), a layer of titanium nitride (e.g., 200 Å thick), a layer of aluminum copper (e.g., 1.2 μm thick), a layer of titanium (e.g., 44 Å thick), and a layer of titanium nitride (e.g., 250 Å thick). Once metal layer  214  has been formed, a lower mask  216  is formed and patterned on the top surface of metal layer  214 . 
     As shown in  FIGS. 3A-3E , following the formation and patterning of mask  216 , metal layer  214  is etched to remove the exposed regions of metal layer  214  and form a number of spaced-apart lower coil members  220 . The lower coil members  220 , which have a horseshoe shape, form the lower sides of the to-be-formed coil. Since base dielectric layer  212  represents the dielectric layer of a metal interconnect structure in the present example, the ends of the lower coil members  220  that correspond with the opposite ends of the to-be-formed coil are physically and electrically connected to pads P 1  and P 2 . 
     In addition, the etch can optionally form a pair of lower input/output members  222  that are physically and electrically connected to the input/output pads P 3  and P 4 . After the lower coil members  220  and the pair of lower input/output members  222  have been formed, mask  216  is removed. 
     Returning to  FIG. 1 , once the lower coil members and the pair of lower input/output members have been formed, method  100  moves to  112  to form a lower dielectric layer that touches the lower coil members and the pair of input/output members.  FIGS. 4A ,  4 B,  4 C,  4 D, and  4 E show a series of views that illustrate an example of method  100  forming a lower dielectric layer in accordance with the present invention. 
     As shown in  FIGS. 4A-4E , a lower dielectric layer  224 , such as an oxide layer, is formed on base dielectric layer  212 , the lower coil members  220 , and the pair of lower input/output members  222 . For example, lower dielectric layer can be formed by depositing an oxide, and then chemically-mechanically polishing the oxide to have, for example, a target thickness of, for example, 2000 Å, over base dielectric layer  212 . 
     Referring back to  FIG. 1 , after the lower dielectric layer has been formed, method  100  moves to  114  to form a sacrificial structure that touches the lower dielectric layer.  FIGS. 5A-6A ,  5 B- 6 B,  5 C- 6 C,  5 D- 6 D, and  5 E- 6 E show a series of views that illustrate an example of method  100  forming a sacrificial structure in accordance with the present invention. 
     As shown in  FIGS. 5A-5E , once lower dielectric layer  224  has been formed, a sacrificial layer  226  is formed on the top surface of lower dielectric layer  224 . For example, a layer of amorphous silicon that has a thickness of, for example, 2000 Å, can be formed on the top surface of lower dielectric layer  224 . Once sacrificial layer  226  has been formed, a mask  228  is formed and patterned on the top surface of sacrificial layer  226 . 
     As shown in  FIGS. 6A-6E , following the formation and patterning of mask  228 , sacrificial layer  226  is etched to remove the exposed regions of sacrificial layer  226  and form a sacrificial structure  230 . After sacrificial layer  226  has been etched to form sacrificial structure  230 , mask  228  is removed. 
     Referring again to  FIG. 1 , after the sacrificial structure has been formed, method  100  moves to  116  to form a core, a switch member, and a suspension member that touch the lower dielectric layer. No portion of the switch member touches the core.  FIGS. 7A-9A ,  7 B- 9 B,  7 C- 9 C,  7 D- 9 D, and  7 E- 9 E show a series of views that illustrate an example of method  100  forming a core, a switch member, and a suspension member in accordance with the present invention. 
     As shown in  FIGS. 7A-7E , after the formation of sacrificial structure  230 , a seed layer  232  is formed on the top surface of lower dielectric layer  224  and sacrificial structure  230 . For example, seed layer can be formed by depositing 300 Å of titanium, 3000 Å of copper, and 300 Å of titanium. After seed layer  232  has been formed, a plating mold  234  (shown cross-hatched) is formed and patterned on the top surface of seed layer  232 . 
     Next, following the formation of plating mold  234 , as illustrated in  FIGS. 8A-8E , the top titanium layer is stripped and a magnetic material, such as an alloy of nickel and iron like permalloy, is deposited by electroplating to a thickness of, for example, 10 μm, to form a core  236 , a switch member  238 , and a suspension member  240 . 
     After this, plating mold  234  is removed, followed by the removal of the underlying regions of seed layer  232 . As shown in  FIGS. 9A-9E , core  236 , which mirrors the shape of the to-be-formed coil, also has a horseshoe shape that lies over the lower coil members  220 , while switch member  238  has a contact sidewall  244 . 
     As further shown in  FIGS. 9A-9E , suspension member  240  has an intermediate member  246 . Intermediate member  246  lies between core  236  and switch member  238 , and lies adjacent to the contact sidewall  244  of switch member  238 . As a result, intermediate member  246  is separated from core  236  by an actuation gap  250 , while intermediate member  246  is separated from the contact sidewall  244  of switch member  238  by a contact gap  252 . 
     Actuation gap  250  can be made to be slightly larger than contact gap  252 , thereby ensuring that an electrical connection will always be made when the relay is activated. The sizes of actuation gap  250  and contact gap  252  are defined by the pattern in plating mold  234 . Further, in the present example, intermediate member  246  is also formed to have a half-circle shape, and is oriented towards core  236  to form a racetrack shape. Suspension member  240  also includes a spring member  254 . In the present example, as shown in  FIGS. 9A-9E , spring member  254  is implemented with a base section  256 , which provides the only point where suspension member  240  touches lower dielectric layer  224 , and an extension section  260  that, along with intermediate member  246 , are spaced apart from dielectric layer  224 . 
     Referring again to  FIG. 1 , after the core, the switch member, and the suspension member have been formed, method  100  moves to  118  to form tops and sides that touch the lower coil members to form a coil, a conductive first switch trace that sits over the switch member, and a conductive second switch trace that sits over and rides on the suspension member. No portion of the coil is wrapped around the suspension member. 
       FIGS. 10A-14A ,  10 B- 14 B,  10 C- 14 C,  10 D- 14 D, and  10 E- 14 E show a series of views that illustrate an example of method  100  forming tops and sides that touch the lower coil members to form a coil, a conductive first switch trace that sits over the switch member, and a conductive second switch trace that sits over and rides on the suspension member in accordance with the present invention. 
     As shown in  FIGS. 10A-10E , after the formation of core  236 , switch member  238 , and suspension member  240  have been formed, and after the removal of plating mold  234  and the underlying regions of seed layer  232 , an upper dielectric layer  262 , such as an oxide layer, is formed on lower dielectric layer  224 , core  236 , switch member  238 , and suspension member  240 . For example, upper dielectric layer  262  can be formed by conformally depositing an oxide to a thickness of, for example, 1 μm, over lower dielectric layer  224 . After upper dielectric layer  262  has been formed, a mask  264 , such as a layer of photoresist, is then formed and patterned on the top surface of upper dielectric layer  262 . 
     Following the formation and patterning of mask  264 , as shown in  FIGS. 11A-11E , the exposed regions of the upper dielectric layer  262  and underlying lower dielectric layer  224  are etched to form a number of vertical openings  266 . The vertical openings  266  include via-type openings that expose the top surfaces of the ends of the lower coil members  220  that form the lower sides of the to-be-formed coil. The vertical openings  266  also expose the pair of lower input/output members  222 . In addition, the vertical openings  266  also form a trench that extends from base section  256  around suspension member  240  and back again to base section  256 . 
     In accordance with the present invention, the exposed regions of sacrificial structure  230  are not to be removed during this etch. As a result, vertical openings  266  are formed with an etchant that is highly selective to the material used to form sacrificial structure  230 . In addition, sacrificial structure  230 , which was formed to have the same thickness as lower dielectric layer  224 , can also be formed to be thicker than lower dielectric layer  224  to ensure that a significant portion of the exposed regions of sacrificial structure  230  remain after the etch. Following the etch, mask  264  is then removed. 
     Once mask  264  has been removed, as shown in  FIGS. 12A-12E , a seed layer  270  is formed on the exposed ends of the lower coil members  220 , the exposed input/output members  222 , lower dielectric layer  224 , sacrificial structure  230 , and the top surface of upper dielectric layer  262 . For example, seed layer can be formed by depositing 300 Å of titanium, 3000 Å of copper, and 300 Å of titanium. After seed layer  270  has been formed, a plating mold  272  (shown cross-hatched) is formed and patterned on the top surface of seed layer  270 . The pattern in plating mold  272  is shown hatched in  FIG. 12A . 
     Next, as shown in  FIGS. 13A-13E , following the formation and patterning of plating mold  272 , the top titanium layer is stripped and copper is deposited by electroplating to form a number of copper side sections  274  of the coil, and a number of copper upper sections  276  of the coil. In addition, the electroplating also forms a first switch trace  280  with a sidewall contact  282 , and a second switch trace  284  with a sidewall contact  286 . The first and second switch traces  280  and  284  also touch the input/output members  222  to make an electrical connection. As further shown in  FIGS. 13A-13E , lower coil member  220 - 1 , side section  274 - 1 , and upper section  276 - 1  form three sides of one coil loop. Following this, as shown in  FIGS. 14A-14E , plating mold  272  and the underlying regions of seed layer  270  are removed. 
     Referring again to  FIG. 1 , after the coil, the conductive first switch trace, and the conductive second switch trace have been formed, method  100  moves to  120  to remove the sacrificial structure so that the suspension member moves in response to changes in a current flowing through the coil. 
     In other words, the conductive second switch trace makes and breaks electrical contact with the first conductive switch trace as the suspension member moves in response to changes in a current flowing through the coil. In addition, a magnetic flux passes through a portion of the suspension member and substantially no magnetic flux passes through the first and the second conductive switch traces when a current flows through the coil. 
       FIGS. 15A-15E  show a series of views that illustrate an example of method  100  removing sacrificial structure  230  in accordance with the present invention. As shown in  FIGS. 15A-15E , after the coil, first switch trace  280 , and second switch trace  284  have been formed, sacrificial structure  230  is removed. The removal of sacrificial structure  230  leaves intermediate member  246  and extension section  260  of spring member  254  floating. For example, in the example shown in  FIGS. 15A-15E , intermediate member  246  and extension section  260  each float, connected to lower dielectric layer  224  only via base section  256 . 
     Floating extension section  260  was vertically spaced apart from lower dielectric layer  224  by underlying sacrificial structure  230 , and thereby floats after underlying sacrificial structure  230  has been removed. As a result, the thickness of sacrificial structure  230  determines an offset gap  290 , which is the vertical spacing that lies between lower dielectric layer  224  and floating extension section  260 . 
     Thus, as shown in  FIGS. 15A-15E , the method of the present invention forms a MEMS relay  1500  that includes core  236  and a coil  1510  that is wrapped around core  236 . Coil  1510  can be implemented with the lower coil members  220 , the copper side sections  274 , and the copper upper sections  276 . In addition, both core  236  and coil  1510  touch lower dielectric layer  224 . 
     As further shown in  FIGS. 15A-15E , MEMS relay  1500  also includes a switch structure  1512  and a suspension structure  1514 . Switch structure  1512  can be implemented with switch member  238 , which touches lower dielectric layer  224 , and upper dielectric layer  262 . Suspension structure  1514  can be implemented with suspension member  240 , which touches lower dielectric layer  224 , and upper dielectric layer  262 . Further, no portion of coil  1510  is wrapped around suspension structure  1514 . 
     As additionally shown in  FIGS. 15A-15E , MEMS relay  1500  includes first switch trace  280  that touches and extends along switch structure  1512 , and second switch trace  284  that touches and extends along suspension structure  1514 . Further, first switch trace  280  has a first sidewall contact  282 , and second switch trace  284  has a second sidewall contact  286 . 
     In operation, when no current is present in coil  1510 , suspension structure  1514  lies in a rest position as shown in  FIG. 15A . In addition, suspension structure  1514  and core  236  are spaced apart by a minimum distance X when no current is present in coil  1510 , while first sidewall contact  282  and second sidewall contact  286  are spaced apart by a minimum distance Y when no current is present in coil  1510  that is equal to or less than the minimum distance X. The minimum distance Y, in turn, provides a high-impedance electrical pathway. 
     Thus, one of the advantages of MEMS relay  1500  is that suspension structure  1514  is independent of core  236  (i.e., no portion of suspension structure  1514  touches core  236  when no current flows through coil  1510 ). Thus, the suspension structure  1514  can be optimized to reduce the stiffness of the spring while core  236  can be optimized for a short flux path. 
     On the other hand, when a current flows through coil  1510  and generates an electromagnetic field that is stronger than the spring force of suspension structure  1514 , suspension structure  1514  moves towards core  236  so that the first and second sidewall contacts  282  and  286  touch, thereby providing a low-impedance electrical pathway. 
     Thus, the second sidewall contact  286  of second switch trace  284  moves towards and touches the first sidewall contact  282  of first switch trace  280  when a current flows through coil  1510 , and moves away from the first sidewall contact  282  of first switch trace  280  when no current flows through coil  1510 . Thus, no portion of suspension structure  1514  touches core  236  when no current flows through coil  1510 . 
     Further, as shown in  FIG. 15A , in accordance with the present invention, a magnetic flux  1516  passes through a portion of suspension member  240  when a current flows through coil  1510 , while and substantially no magnetic flux passes through the first and the second switch traces  280  and  284  when a current flows through coil  1510 . Thus, one of the advantages of the present invention is that MEMS relay  1500  is insensitive to fluctuations in the current around the core and, thereby the flux. As a result, signals with very small amplitudes can pass through relay  1500  with no flux-based distortion. 
     Thus, a method of forming a MEMS relay in accordance with the present invention has been described. The elements shown in  FIG. 1  can be implemented in a number of different ways. For example, the spaced-apart lower coil members that form the lower horizontal sections of the coil described in element  110  of  FIG. 1  can be alternately formed. 
       FIGS. 16A-18A ,  16 B- 18 B,  16 C- 18 C,  16 D- 18 D, and  16 E- 18 E show a series of views that illustrate a first example of an alternate way of implementing element  110  of method  100 , which forms a number of spaced-apart lower coil members of the to-be-formed coil, in accordance with the present invention. 
     As with the example shown in  FIGS. 2A-3E , the example shown in  FIGS. 16A-18E  also utilizes single-crystal silicon semiconductor wafer  210  with overlying base dielectric layer  212 . The  FIGS. 16A-18E  example begins by forming a seed layer  1610  on base dielectric layer  212  and the pads P 1 -P 4  which are exposed via openings in base dielectric layer  212 . 
     Once seed layer  1610  has been formed, a plating mold  1612  is formed on the top surface of seed layer  1610 . As shown in  FIGS. 17A-17E , following the formation of plating mold  1612 , copper is deposited by electroplating to form the number of spaced-apart lower coil members  220  and the pair of lower input/output members  222 . 
     As shown in  FIGS. 18A-18E , after the lower coil members  220  and the pair of lower input/output members  222  have been formed, plating mold  1612  is removed, followed by the removal of the underlying regions of seed layer  1610 . As shown, the structure illustrated in  FIGS. 18A-18E  is similar to the structure shown in  FIGS. 3A-3E . 
       FIGS. 19A-21A ,  19 B- 21 B,  19 C- 21 C,  19 D- 21 D, and  19 E- 21 E show a series of views that illustrate a second example of an alternate way of implementing element  110  of method  100 , which forms a number of spaced-apart lower coil members of the to-be-formed coil, in accordance with the present invention. 
     As with the example shown in  FIGS. 2A-3E , the example shown in  FIGS. 19A-21E  also utilizes single-crystal silicon semiconductor wafer  210  with overlying base dielectric layer  212 . The  FIGS. 19A-21E  example begins by forming a mask  1910  on the top surface of base dielectric layer  212 . Following this, the exposed regions of base dielectric layer  212  are etched to form a number of spaced-apart trenches  1912 , which will define the spaced-apart lower coil members of the to-be-formed coil, in the top surface of base dielectric layer  212 . One of the trenches  1912  exposes pad P 1 , while another of the trenches  1912  exposes pad P 2 . In addition, the etch also forms a pair of openings  1914  in base dielectric layer  212  that expose the pair of pads P 3  and P 4 . 
     Following the etch, as shown in  FIGS. 20A-20E , with mask  1910  in place, a copper structure  1916  is formed in the trenches  1912  and the openings  1914  on the exposed regions of base dielectric layer  212 , pads P 1 -P 4 , and mask  1910 . Copper structure  1916  can be formed by, for example, evaporating, in sequence, 300 Å of titanium, 1 μm copper, and 300 Å of titanium. 
     Next, as shown in  FIGS. 21A-21E , after copper structure  1916  has been formed, mask  1910  is stripped which, in turn, lifts off the overlying layer of copper structure  1916 . The removal of mask  1910  leaves the copper structure  1916  only on base dielectric layer  212 , thereby forming the number of spaced-apart lower coil members  220  and the pair of lower input/output members  222 . As shown, other than being recessed, the structure illustrated in  FIGS. 21A-21E  is similar to the structure shown in  FIGS. 3A-3E . 
       FIGS. 22A-26A ,  22 B- 26 B,  22 C- 26 C,  22 D- 26 D, and  22 E- 26 E show a series of views that illustrate an example of an alternate way of implementing element  118  of method  100 , which forms the tops and the sides of the to-be-formed coil and the traces for the switch, in accordance with the present invention. 
     The  FIGS. 22A-26E  example is the same as the  FIGS. 2A-15E  example up through the formation of seed layer  270 , and differs by forming a plating mold  2210  on the top surface of seed layer  270  in lieu of plating mold  272 . Plating mold  2210  differs from plating mold  272  in that plating mold  2210  prevents the first and second sidewall contacts  282  and  286  from being formed from the to-be-formed copper. The pattern in mold  2210  is shown hatched in  FIG. 22A . 
     Next, following the formation of mold  2210 , copper is deposited by electroplating to form the number of copper side sections  274  of the coil, and the number of copper upper sections  276  of the coil. In addition, the electroplating also forms a first switch trace  2212 , which is the same as switch trace  280  except that there is no sidewall contact  282 , and a second switch trace  2214 , which is the same as switch trace  284  except that there is no sidewall contact  286 . Following this, as shown in  FIGS. 23A-23E , mold  2210  and the underlying regions of seed layer  270  are removed. 
     Following this, as shown in  FIGS. 24A-24E , a mask  2216  is formed and patterned on upper dielectric layer  262 , the copper upper sections  276 , first switch trace  2212 , and second switch trace  2214 . Once mask  2216  has been formed and patterned, a conductive layer  2220 , such as a layer of titanium, nickel, or chrome, and an overlying layer of gold, is deposited on the exposed regions of upper dielectric layer  262  that surround switch member  238 , the exposed regions of upper dielectric layer  262  that surround suspension member  240 , the exposed regions of sacrificial structure  230 , and mask  2216 . When sputtered, titanium, nickel, chrome, and gold provide good coverage on the high-aspect ratio (vertical) sidewalls of the switch member  238  and suspension member  240  that face each other. Titanium, nickel, and chrome, in turn, improve the adhesion of gold. 
     As shown in  FIGS. 25A-25E , after conductive layer  2220  has been formed, mask  2216  is stripped which, in turn, lifts off the overlying layer of conductive layer  2220 . The removal of mask  2216  leaves the conductive layer  2220  on the sidewalls of upper dielectric layer  262  over switch member  238  and first switch trace  2212 , and the sidewalls of upper dielectric layer  262  over suspension member  240  and second switch trace  2214 , thereby forming a sidewall contact  2222  of first switch trace  2212  and a sidewall contact of  2224  of second switch trace  2214  that faces sidewall contact  2222 . 
     Following this, as shown in  FIGS. 26A-26E , sacrificial structure  230  is removed. The removal of sacrificial structure  230  leaves intermediate member  246  and extension section  260  of spring member  254  floating as before, but with gold contacts. 
     In addition to the above, the structures can be formed to have different shapes. For example, mask  228  can be formed to have different shapes so that sacrificial structure  230  has different shapes. In addition, plating mold  234  can be formed to have different shapes that correspond with the shapes of sacrificial structure  230  so that core  236 , switch member  238 , and suspension member  240  have different shapes. 
     For example,  FIGS. 27A-27E  show a series of views that illustrate an example of sacrificial structure  230  and spring member  254  with a different shape in accordance with the present invention. In the  FIGS. 27A-27E  example, spring member  254  is formed with a pair of facing structures that each include a base section  256  and a C-shaped extension section  260 . 
     Further,  FIGS. 28A-28E  show a series of views that illustrate an example of sacrificial structure  230 , core  236 , intermediate member  246 , and spring member  254  with a different shape in accordance with the present invention. In the  FIGS. 28A-28E  example, core  236  is formed as a nearly complete doughnut shape, while intermediate member  246  is formed with a wedge or pie shape that fits into the opening in the nearly complete doughnut shape. In addition, spring member  254  is also formed with a pair of facing structures that each include base section  256  and a C-shaped section  260 . 
     As noted above, dielectric layer  212  can represent a dielectric layer that is free of metal structures. When free of metal structures, the electrical connections to coil  1510  can be made, for example, by wire bonding to points on the copper upper sections  276  that represent opposite ends of coil  1510 . In addition, connections to the first and second switch traces  280  and  284  can be made, for example, by wire bonding. Another of the advantages of the present invention is that the present invention requires relatively low processing temperatures. As a result, the present invention is compatible with conventional backend CMOS processes. 
     It should be understood that the above descriptions are examples of the present invention, and that various alternatives of the invention described herein may be employed in practicing the invention. For example, the various seed layers can be implemented as copper seed layers, or as tungsten, chrome, or combination seed layers as need to provide the correct ohmic and mechanical (peel) characteristics. In addition, a double throw switch can be easily fabricated by using two MEMS relays  1500  which are positioned as mirror images of each other. Thus, it is intended that the following claims define the scope of the invention and that structures and methods within the scope of these claims and their equivalents be covered thereby.