MEMS devices having discharge circuits

MEMS devices having discharge circuits. In some embodiments, a MEMS device can include a substrate and an electromechanical assembly implemented on the substrate. The MEMS device can further include a discharge circuit implemented relative to the electromechanical assembly. The discharge circuit can be configured to provide a preferred arcing path during a discharge condition affecting the electromechanical assembly. The MEMS device can be, for example, a switching device, a capacitance device, a gyroscope sensor device, an accelerometer device, a surface acoustic wave (SAW) device, or a bulk acoustic wave (BAW) device. The discharge circuit can include a spark gap assembly having one or more spark gap elements configured to facilitate the preferred arcing path.

BACKGROUND

Field

The present disclosure relates to microelectromechanical systems (MEMS) devices having discharge circuits.

Description of the Related Art

Microelectromechanical systems devices, or MEMS devices, typically include miniaturized mechanical and electro-mechanical elements. Such MEMS devices can include moving elements controlled by a controller to provide desired functionalities. MEMS devices are sometimes referred to as microsystems technology devices or micromachined devices.

SUMMARY

According to a number of implementations, the present disclosure relates to a microelectromechanical systems (MEMS) device that includes a substrate and an electromechanical assembly implemented on the substrate. The MEMS device further includes a discharge circuit implemented relative to the electromechanical assembly. The discharge circuit is configured to provide a preferred arcing path during a discharge condition affecting the electromechanical assembly.

In some embodiments, the MEMS device can be a switching device, a capacitance device, a gyroscope sensor device, an accelerometer device, a surface acoustic wave (SAW) device, or a bulk acoustic wave (BAW) device. In some embodiments, the MEMS device can be a switching device. The switching device can be a contact switching device. The discharge circuit can include a spark gap assembly having one or more spark gap elements configured to facilitate the preferred arcing path. The spark gap assembly can include a first conductor with one or more spark gap elements and a second conductor with one or more spark gap elements. Each of the one or more spark gap elements of the first and second conductors can include a shaped conductive feature. The shaped conductive feature can include a sharp feature to increase the likelihood of arcing. The one or more shaped conductive features of one of the first and second conductors can be laterally offset from the one or more shaped conductive features of the other conductor. The lateral offset of the shaped conductive features of the first and second conductors can be configured to provide the preferred arcing path as one conductor moves relative to the other conductor.

In some embodiments, each of the first and second conductors of the spark gap assembly can be located away from the electromechanical assembly. In some embodiments, one of the first and second conductors of the spark gap assembly can be located away from the electromechanical assembly, and the other conductor can be a part of the electromechanical assembly. In some embodiments, each of the first and second conductors of the spark gap assembly can be a part of the electromechanical assembly.

In some embodiments, the contact switching device can includes a movable first electrode and a stationary second electrode as parts of the electromechanical assembly. The movable first electrode can include a beam having a contact pad. The beam can be configured to be in a first state in which the contact pad is disengaged from the second electrode, and in a second state in which the contact pad is engaged with the second electrode. The contact switch device can further include a gate configured to provide an electrostatic force to the beam to thereby allow the beam to be in the first state or the second state. The spark gap assembly can be configured such that a discharging arc through the preferred arcing path occurs at a first potential difference between the first and second electrodes, with the first potential difference being lower than a potential difference needed to trigger an arc through the contact pad when the beam is in the first state. The spark gap assembly can be further configured so that the first potential difference is lower than a lowest potential difference needed to trigger an arc through the contact pad in a range of motion of the contact pad relative to the second electrode. The spark gap assembly can be configured to provide discharge protection during hot switching operations as well as cold switching operations.

In some embodiments, the contact switching device can include a self-activation functionality, where the self-activation can result from a sufficient voltage difference between the beam and the gate. The self-activation can result in the contact pad engaging the second electrode. The gate can be coupled to ground such that the self-activation results in charge associated with the sufficient voltage difference between the beam and the gate to be dissipated to the ground.

In some embodiments, the discharge condition can include an electrostatic discharge (ESD) event. The contact switching device can be an electrostatic discharge (ESD) protection MEMS device. The ESD protection MEMS device can be configured to have to have either or both functionalities of a faster switching speed and actuation at a lower voltage than other MEMS devices in a circuit.

In some teachings, the present disclosure relates to a method for fabricating a microelectromechanical systems (MEMS) device. The method includes providing a substrate and forming an electromechanical assembly on the substrate. The method further includes forming a discharge circuit relative to the electromechanical assembly. The discharge circuit is configured to provide a preferred arcing path during a discharge condition affecting the electromechanical assembly.

In a number of implementations, the present disclosure relates to a radio-frequency (RF) module that includes a packaging substrate configured to receive a plurality of components, and an RF MEMS device implemented on the packaging substrate. The RF MEMS device includes an electromechanical assembly, and a discharge circuit implemented relative to the electromechanical assembly. The discharge circuit is configured to provide a preferred arcing path during a discharge condition affecting the electromechanical assembly.

In some embodiments, the RF MEMS device can be, for example, a capacitor or an RF switch. In some embodiments, the RF module can be an antenna switch module (ASM).

In a number of teachings, the present disclosure relates to a method for fabricating a radio-frequency (RF) module. The method includes providing a packaging substrate configured to receive a plurality of components. The module further includes mounting or forming an RF MEMS device on the packaging substrate. The RF MEMS device includes an electromechanical assembly, and a discharge circuit implemented relative to the electromechanical assembly. The discharge circuit is configured to provide a preferred arcing path during a discharge condition affecting the electromechanical assembly.

According to a number of implementations, the present disclosure relates to a radio-frequency (RF) device that includes a receiver configured to process an RF signal, and a front-end module (FEM) in communication with the receiver. The FEM includes a switching circuit configured to route the RF signal and having an RF MEMS device. The RF MEMS device includes an electromechanical assembly, and a discharge circuit implemented relative to the electromechanical assembly. The discharge circuit is configured to provide a preferred arcing path during a discharge condition affecting the electromechanical assembly. The RF device further includes an antenna in communication with the FEM. The antenna is configured to receive the RF signal.

In some embodiments, the RF device can be a wireless device such as a cellular phone.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

Disclosed are various examples related to microelectromechanical systems (MEMS) devices and how such devices can include a discharge circuit configured to, for example, provide protection against conditions such as electrostatic discharge (ESD). Although various examples are described in the context of MEMS, it will be understood that one or more features of the present disclosure can also be utilized in other electromechanical systems having dimensions larger or smaller (e.g., NEMS) than typical MEMS dimensions.

FIG. 1shows a block diagram of a MEMS device100having a discharge circuit110. In some embodiments, such a discharge circuit can be implemented substantially within the MEMS boundary and/or volume, and be configured to provide an electrical discharge path under certain conditions (e.g., ESD event).

As is generally understood, a MEMS device typically includes an electromechanical assembly implemented on a substrate. Such an electromechanical assembly can be configured to yield mechanical changes based on electrical inputs; and such mechanical changes can yield changes in electrical properties of the MEMS device. Contact switches and capacitors are examples of devices that can be implemented in MEMS form factors. Although various examples are described herein in the contexts of such switches and capacitors, it will be understood that one or more features of the present disclosure can also be utilized in other MEMS devices.

FIGS. 2A-2Cshow examples of how a discharge circuit110can be implemented relative to an electromechanical assembly104on a MEMS device100.FIG. 2Ashows that in some embodiments, a MEMS device100can include an electromechanical assembly104implemented on a substrate102. A discharge circuit110having one or more features as described herein can be implemented separately from the electromechanical assembly104. Examples related to such a configuration are described herein in greater detail.

FIG. 2Bshows that in some embodiments, a MEMS device100can include an electromechanical assembly104implemented on a substrate102. A discharge circuit110having one or more features as described herein can be implemented as a part of the electromechanical assembly104. Examples related to such a configuration are described herein in greater detail.

FIG. 2Cshows that in some embodiments, a MEMS device100can include an electromechanical assembly104implemented on a substrate102. A discharge circuit110having one or more features as described herein can be implemented partially as a part of the electromechanical assembly104, and partially separately from the electromechanical assembly104. Examples related to such a configuration are described herein in greater detail.

In some embodiments, some or all of the different configurations ofFIGS. 2A-2Ccan be implemented in combination.

As described herein, discharge circuits as described herein can be desirable in MEMS devices for a number of reasons. For example, protecting MEMS devices and circuits from ESD has been an issue in various applications. These devices are typically highly sensitive to electrical overstress, which can cause immediate failures and/or lead to long term reliability issues. An electrical overstress from ESD events can damage, for example, contacts, dielectrics and/or substrates associated with MEMS devices.

FIG. 3shows a plan view of an example MEMS contact switch10without a discharge circuit, andFIGS. 4A-4Cshow side views of the switch10ofFIG. 3in various stages of activation. In the example MEMS switch10, a first electrode20is shown to be implemented as a beam24supported on a post26which is in turn mounted on a substrate12through a base28. The first electrode20is shown to include a contact pad22formed at or near the end opposite from the post26. When the switch10is in an OFF state (FIG. 4A), the beam24can be in its relaxed state such that the contact pad22is separated from a second electrode30by a distance d1. When the switch10is in an ON state (FIG. 4C), the beam24can be in its flexed state such that the contact pad22is touching the second electrode30so as to form an electrical connection between the first electrode20and the second electrode30.

In the example MEMS switch10, transition between the foregoing OFF and ON states can be effectuated by a gate40configured to provide electrostatic actuation. For example, when an actuation signal is applied to the gate40, the gate40can apply an attractive electrostatic force (arrow42) on the beam24to thereby pull on the beam24. Accordingly, the contact pad22of the first electrode20moves closer to the second electrode30(e.g., in an intermediate stage inFIG. 4Bwith a gap distance of d2), until the two physically touch to close the circuit between the first and second electrodes20,30. When the actuation signal is removed from the gate40, the attractive force42is removed. Accordingly, the beam24can return to its relaxed state ofFIG. 4A.

The close proximity of the elements (e.g., the contact pad22and the second electrode30ofFIGS. 3 and 4) in a MEMS device can allow electrical arcing between nearby elements during an ESD event. Such an arcing can damage the MEMS device. For example, contact areas on the contact pad22and the second electrode30of the switch10are relatively close to each other, especially during a transition state (e.g.,FIG. 4B). Accordingly, arcing can damage such contact areas and degrade the performance of the switch, or even worse, make the switch un-usable.

FIGS. 5-15show various examples related to discharge circuits associated with MEMS switches.FIGS. 5 and 6show examples where a discharge circuit can be generally separate from an electromechanical assembly.FIGS. 7-10show examples where a discharge circuit can be considered to be a part of an electromechanical assembly.FIGS. 11-15show examples where a discharge circuit can be considered to be implemented partially as a part of an electromechanical assembly and partially separate from the electromechanical assembly.

Although the examples ofFIGS. 5-15are described in the context of beam-type MEMS switches, it will be understood that one or more features associated with the discharge circuits can also be implemented in other types of MEMS switches. Further, in the examples ofFIGS. 5-15, switching functionality is described in the context of first and second electrodes being coupled to input and output (or output and input). However, it will be understood that one or more features associated with the discharge circuits can also be implemented with other types of switching functionalities. For example, a contact pad on a beam can contact two ends of otherwise separate input and output terminals to thereby close the circuit between the input and output terminals.

FIG. 5shows a more specific example of the configuration ofFIG. 2A, where a discharge circuit110can be implemented to be generally separate from an electromechanical assembly104. InFIG. 5, the discharge circuit110of a MEMS device100is shown to be implemented on a substrate102at a location that is near a portion106(of the electromechanical assembly104) that is susceptible to ESD events. In the context of a beam-type MEMS device100ofFIGS. 6A and 6B, such a portion susceptible to ESD events can include a contact pad122and the corresponding contact surface on an electrode130.

InFIGS. 6A and 6B, switching operations between the contact pad122of a first electrode120and the second electrode130can be achieved in manners similar to the example ofFIGS. 4A-4C. More particularly, the first electrode120can be implemented as a beam124supported on a post126which is in turn mounted on a substrate102through a base128. The contact pad122is shown to be positioned at or near the end of the beam124opposite from the post126. When the switch100is in an OFF state, the beam124can be in its relaxed state such that the contact pad122is separated from the second electrode130. When the switch100is in an ON state, the beam124can be in its flexed state such that the contact pad122is touching the second electrode130so as to form an electrical connection between the first electrode120and the second electrode130.

The foregoing transition between the OFF and ON states can be effectuated by a gate140configured to provide electrostatic actuation. For example, when an actuation signal is applied to the gate140, the gate140can apply an attractive electrostatic force on the beam124to thereby pull on the beam124. Accordingly, the contact pad122of the first electrode120can contact the second electrode130to close the circuit between the first and second electrodes120,130. When the actuation signal is removed from the gate140, the attractive force is removed so as to result in the beam returning to its relaxed state and thereby separating the contact pad122from the second electrode130and thereby opening the circuit between the first and second electrodes120,130.

InFIGS. 6A and 6B, each of the MEMS devices100is shown to include a discharge circuit110positioned near the contact pad (122) end of the beam124. InFIG. 6A, the discharge circuit110can be generally isolated from the electromechanical assembly which includes the first electrode120and the second electrode130. Such a configuration can be implemented if it is desirable to have a discharge such as an ESD be routed to a node other than those connected to the first electrode120and the second electrode130. For example, it may be desirable to have a discharge be shunted to ground away from the first and second electrodes120,130.

InFIG. 6B, the discharge circuit110can be coupled to the first electrode120(through a path170) and the second electrode130(through a path172), essentially providing a discharge path that is electrically parallel with the assembly of the first and second electrodes120,130. Such a configuration can be implemented if it is desirable to have a discharge path, for an event such as an ESD, bypass sensitive portions of the first electrode120and the second electrode130. For example, it may be desirable to have a discharge be routed between the first electrode120and the second electrode130, but not through the contact pad122. As described herein, the discharge circuit110can be configured to allow such a discharge to occur away from the contact pad122.

As shown inFIGS. 6A-6C, the example discharge circuit110can include a first conductor150and a second conductor160configured to provide an arcing path that is more preferable than arcing paths between the first and second electrodes120,130. For example, a spark gap configuration182can be provided where either or both of the first and second conductors150,160includes one or more shaped conductive features that lower the potential difference needed to cause arcing.

In the example shown, each conductor (150or160) includes a plurality of sharp conductive protrusions (152for the first conductor150,162for the second conductor160) that are generally aligned with the counterpart protrusions of the other conductor (160or150). As better shown inFIG. 6D, design parameters such as dimensions of the sharp protrusions (152,162), gap distance (z) between two counterpart protrusions, and spacing (x) between the neighboring protrusions can be selected to provide desired arcing properties.

As shown inFIG. 6C, the foregoing spark gap configuration182can be implemented by positioning the first conductor150at a distance from the second conductor160. If the second conductor160is positioned on the substrate102, the first conductor150can be positioned in such a manner by posts156and their respective bases158.

The discharge circuit110configured in the foregoing manner can provide a structure that results in arcing at lower potential difference levels than that of the electromechanical assembly so that the charge of an ESD event can be dissipated appropriately with little or no damage to the electromechanical assembly. Design of the spark gap configuration182inFIGS. 6A-6Ccan be relatively easier due to the static nature of the discharge circuit110where the protrusions152,162of the first and second conductors150,160generally do not move relative to each other. Accordingly, one set of protrusions (152or162) can remain at a fixed position relative to the other set of protrusions (162or152). For example, the sharp points of the protrusions152can be positioned and remain substantially aligned with the sharp points of the protrusions162.

In some embodiments, some or all of a discharge circuit can be integrated into an electromechanical assembly. For example,FIGS. 7A-Cand8show side and plan views of a MEMS device100having a discharge circuit110integrated into its electromechanical assembly104. The discharge circuit110is shown to include a spark gap configuration between one or more shaped conductive features190on an underside of a first electrode120and one or more shaped conductive features192on an upper side of a second electrode130. The conductive features190,192are shown to be positioned so as to provide one or more arcing paths at location(s) away from the switching contact area (e.g., between a contact pad122and the corresponding area on the second electrode130). Accordingly, in an ESD event, such an arcing through the spark gap can prevent or reduce damage to the switching contact area.

In the example ofFIGS. 7 and 8, the configuration of the first and second electrodes120,130can be similar to those ofFIGS. 6A and 6BandFIGS. 3 and 4, other than the presence of the integrated discharge circuit119inFIGS. 7 and 8. Accordingly, switching operations actuated by a gate140can be performed in similar manners.

In the example discharge circuit110ofFIGS. 6A-6D, the spark gap configuration includes the spark gap elements (e.g., shaped conductor features) arranged in a fixed manner (e.g., with the sharp tips aligned). In the example ofFIGS. 7 and 8, however, relative position of the spark elements (190for the first electrode120, and192for the second electrode130) does not remain constant during a switching operation due to the movement of the beam124. Accordingly, in some embodiments, the spark elements190,192can be arranged so as to provide a preferred arcing path during some or all of the entire movement range of the beam124without making physical contact.

In some embodiments, and as shown inFIGS. 7 and 8, the foregoing arrangement of the spark gap elements190,192can be achieved by providing a lateral offset between the upper spark gap elements190and the lower spark gap elements192. Such an arrangement can allow the beam124to move in its full range of motion while providing desired distances between the spark gap elements190,192without physical contact. Such a spark gap configuration can provide a preferred arcing path over an arcing path involving the contact pad122during some or all of the entire movement range of the beam124.

The foregoing configuration (where arcing is more likely through the preferred arcing path) can be particularly useful for providing discharge protection during hot switching operations. In a hot switching operation, a signal being switched ON or OFF is present on one of the electrodes. When the contact pad122is closer to the second electrode130(e.g.,FIG. 7Bwhen it moves towards the second electrode130to close the switch, or when it moves away from the second electrode upon opening of the switch), arcing is more likely due to the smaller gap. Without the discharge circuit110, arcing resulting from the signal itself can occur; and such arcing during hot switching operation can result in damage to the contact pad122and/or the second electrode130. As described herein, the discharge circuit110can be configured to provide a preferred arcing path, even when the contact pad122is very close to the second electrode130.

FIGS. 9 and 10show side and plan views of a MEMS device100having a discharge circuit110that is similar to the example ofFIGS. 7 and 8. However, in the MEMS device100ofFIGS. 9 and 10, the discharge circuit110is shown to be moved further away from the contact pad122and on the other side of the gate140. To accommodate such a configuration, a conductor structure204can be provided to include one or more lower spark gap elements202(e.g., shaped conductive features). Such lower spark gap elements are shown to be arranged in a laterally offset manner relative to one or more upper spark gap elements200(e.g., shaped conductive features) formed on the underside of the beam124, to accommodate the movement of the beam124.

Similar to the example ofFIGS. 7 and 8, the foregoing spark gap between the upper and lower spark gap elements200,202can provide a preferred arcing path in hot or cold switching operations. The discharge circuit110ofFIGS. 9 and 10being further away from the contact pad122can be useful in, for example, applications where a signal is present in the first electrode120and where arcing during hot switching operation is a concern. The closer proximity of the discharge circuit110to the source of the signal (e.g., the base128), combined with its spark gap configuration providing a preferred arcing path, can make it more likely that arcing due to the signal itself will be routed through the discharge circuit110.

In some embodiments, and as shown inFIG. 10, the lower spark gap elements202are shown to be electrically connected to the second electrode130through the conductor structure204and a conductive path206. Accordingly, the discharge circuit110can be considered to provide a parallel and more preferred arcing path than an arcing path involving the contact pad122. As described herein, the discharge circuit110can be connected in other manners to provide different routing options. For example, the lower spark gap elements202can be connected to ground.

FIG. 11shows a plan view of a MEMS device100having a discharge circuit110that is coupled to the first electrode120but separate from the beam124.FIG. 12shows a side view of the discharge circuit110.

InFIGS. 11 and 12, the electromechanical assembly104can be configured for switching operations in similar manners as the other beam-actuated switch examples described herein. The discharge circuit110is shown to include a spark gap configuration between one or more upper spark gap elements212(e.g., shaped conductive features) and one or more lower spark gap elements222(e.g., shaped conductive features). The upper spark gap elements212can be formed on the underside of a conductor210supported by posts214,216. The post216is shown to be connected to the base128of the electromechanical assembly104. The lower spark elements222can be formed on the upper surface of a conductor structure220. Since the spark gap elements212,222generally do not move, they can be positioned relative to each other to provide a desired arcing property.

In the example ofFIGS. 11 and 12, the lower spark gap elements222are shown to be electrically connected to the second electrode130through the conductive structure220and a conductive path224. Accordingly, the discharge circuit110can be considered to provide a parallel and more preferred arcing path than an arcing path involving the contact pad122. As described herein, the discharge circuit110can be connected in other manners to provide different routing options. For example, the lower spark gap elements222can be connected to ground.

The example ofFIGS. 11 and 12can provide similar discharge functionality as the example ofFIG. 6, utilizing a fixed spark gap configuration. In the example ofFIGS. 11 and 12, the discharge circuit110being further away from the contact pad122and being coupled more directly to the first electrode120can be advantageous in applications where a signal is input through the first electrode120. The discharge circuit110can be configured to provide discharge protection in hot or cold switching operations. For the hot switching operation, the spark gap between the elements212,222can be configured appropriately to provide a preferred arcing path for some or all of the movement range of the contact pad122.

In the various examples described in reference toFIGS. 6-12, the spark gap configurations include spark gap elements that form vertical gaps similar to the vertical arrangement of the first and second electrodes. Other configurations of spark gaps can also be implemented.

For example,FIGS. 13-15show discharge circuits110having lateral spark gap configurations. In each of the examples ofFIGS. 13-15, the electromechanical assembly104can be configured for switching operations in similar manners as the other beam-actuated switch examples described herein.

In the example ofFIG. 13, the discharge circuit110is shown to include a spark gap configuration between one or more spark gap elements230(e.g., shaped conductive features) on a side of the beam124and one or more spark gap elements232(e.g., shaped conductive features) on a side of a conductor structure234. In such a configuration, either or both of the spark gap elements230,232can be configured to accommodate the movements of the beam during switching operations so as to provide a preferred arcing path over an arcing path involving the contact pad, for some or all of the movement range.

In the example ofFIG. 13, the spark gap elements232are shown to be electrically connected to the second electrode130through the conductive structure234and a conductive path236. Accordingly, the discharge circuit110can be considered to provide a parallel and more preferred arcing path than the arcing path involving the contact pad122. As described herein, the discharge circuit110can be connected in other manners to provide different routing options. For example, the spark gap elements232can be connected to ground.

In some applications, it may be desirable to have opposing spark gap elements remain generally fixed relative to each other during movements of the beam of an electromechanical assembly104. In such a configuration, the spark gap elements can remain generally fixed during the movements of the beam. Accordingly, the spark gap elements can be configured to provide a preferred arcing path over an arcing path involving the contact pad, for some or all of the movement range of the beam.FIGS. 14 and 15show non-limiting examples of such a configuration.

In the example ofFIG. 14, the discharge circuit110includes a spark gap configuration between two generally fixed parts. For example, the spark gap configuration of the discharge circuit110is shown to be between one or more spark gap elements240(e.g., shaped conductive features) on a side of a base128of the first electrode120and one or more spark gap elements242(e.g., shaped conductive features) on a side of a conductor structure244. A conductor structure248can be implemented on the base128to elevate the spark gap elements240to a level appropriate for the spark gap elements242.

In the example ofFIG. 14, the spark gap elements242are shown to be electrically connected to the second electrode130through the conductive structure244and a conductive path246. Accordingly, the discharge circuit110can be considered to provide a parallel and more preferred arcing path than the arcing path involving the contact pad122. As described herein, the discharge circuit110can be connected in other manners to provide different routing options. For example, the spark gap elements242can be connected to ground.

In the example ofFIG. 15, the discharge circuit110is similar to the example ofFIG. 14, in that the spark gap configuration is between two generally fixed parts. For example, the spark gap configuration of the discharge circuit110is shown to be between one or more spark gap elements250(e.g., shaped conductive features) and one or more spark gap elements252(e.g., shaped conductive features). In some embodiments, such spark gap elements can be implemented on or near the surface of the substrate102, on one or more conductor structures to elevate the spark gap elements from the substrate102, or any combination thereof.

In the context of the spark gap elements250,252being on conductor structures, the spark gap elements250can be implemented on a side of a conductor structure258, and the spark gap elements252can be implemented on a side of a conductor structure254. In some embodiments, some or all of the conductor structure258can be provided by a post126that supports a beam124of the first electrode120. The conductor structure254can be formed underneath the beam124and adjacent the post126so as to allow the spark gap elements252to be positioned appropriately relative to the spark gap elements250.

In such a configuration, the spark gap elements250,252can remain generally fixed during the movements of the beam124. Accordingly, spark gap elements250,252can be configured to provide a preferred arcing path over an arcing path involving the contact pad122, for some or all of the movement range of the beam124.

In the example ofFIG. 15, the spark gap elements252are shown to be electrically connected to the second electrode130through the conductive structure254and a conductive path256. Accordingly, the discharge circuit110can be considered to provide a parallel and more preferred arcing path than the arcing path involving the contact pad122. As described herein, the discharge circuit110can be connected in other manners to provide different routing options. For example, the spark gap elements252can be connected to ground.

Based on the various examples described herein, one can see that a discharge circuit can be implemented in a MEMS device so as to provide a preferred arcing path from any conductive feature associated with the first and/or second electrodes of an electromechanical assembly. Accordingly, such variations are contemplated in the present disclosure.

As also described herein, a discharge circuit can be implemented in a MEMS device by way of one or more conductive features that are separate from the first and/or second electrodes of an electromechanical assembly. Such conductive feature(s) of the discharge circuit may or may not be electrically coupled to the first and/or second electrodes. Accordingly, variations involving such configurations are contemplated in the present disclosure.

As also described herein, a discharge circuit can be based on one or more conductive features associated with an electromechanical assembly and one or more conductive features generally separate from the electromechanical assembly. Accordingly, variations involving such configurations are contemplated in the present disclosure.

In the various examples described herein, various spark gap configurations are described in the context of an air gap, and at locations above a substrate. However, it will be understood that spark gaps having one or more features as described herein can also be implemented such that some or all of the spark gap elements are within, for example, a substrate, a dielectric material, or any other material that provides electrical isolation between the elements.

In the various examples disclosed herein, various spark gap configurations are describe in the context of being implemented at various locations relative to an electromechanical assembly. It will be understood that a MEMS device can include more than one of such spark gaps at different locations to provide even more robust discharge protection for the MEMS device.

As described herein, at least some of the spark gap configurations of the various discharge circuits can be suitable for providing discharge protection during hot switching operations. Such a feature can be particularly advantageous, especially when one considers typical lifetime expectancies associated with hot-switching (e.g., about 100 million cycles) and cold-switching (e.g., about 5 billion cycles) operations.

In the various examples ofFIGS. 3-15, the MEMS devices are described in the context of switching devices. It will be understood that other types of MEMS devices can also include a discharge circuit having or more features as described herein.

For example,FIG. 16shows a MEMS capacitor100having a discharge circuit110. In the example ofFIG. 16, the MEMS capacitor100is shown to be similar to the switch example ofFIGS. 9 and 10. A dielectric layer260is shown to be formed on the surface of a contact pad122of a first electrode120. Similarly, a dielectric layer262is shown to be formed on the surface of a second electrode130. Accordingly, when the beam is in its relaxed state (e.g., as inFIG. 16), a first capacitance exists between the first and second electrodes120,130. When the beam is in its flexed state due to the actuation by the gate140, the dielectric layer260of the contact pad122comes into physical contact with the dielectric layer262of the second electrode130(but not in electrical contact) thereby yielding a second capacitance that is typically greater than the first capacitance. Values of the first and second capacitances can be adjusted by, for example, materials and/or thicknesses of the dielectrics260,262, and the separation gap when in the relaxed state.

In the example ofFIG. 16, the discharge circuit110is shown to include one or more spark gap elements270(e.g., shaped conductive features) formed on the underside of the beam124, and one or more spark gap elements272(e.g., shaped conductive features) formed on an upper surface of a conductor structure. The spark gap elements270,272may or may not be completely covered by their respective dielectrics.

In some embodiments, the spark gap elements270,272can be configured to add little or minimized capacitance between the elements, so as to not impact the capacitances associated with the first and second electrodes120,130. In some embodiments, the spark gap elements270,272can be configured to contribute to the overall capacitances of the MEMS device in some desirable manner. In the context of switching devices as described herein, the spark gap elements can be configured to add little or minimized capacitance between the elements, so as to reduce or minimize parasitic capacitances associated with the switches.

In the example ofFIG. 16, the spark gap elements270,272are shown to be configured in a laterally offset manner similar to the example ofFIGS. 9 and 10. Accordingly, the MEMS capacitor100can be switched between the two capacitance states while “hot,” and have the discharge circuit110provide a preferred arcing path throughout such transitions.

It will be understood that MEMS capacitors can also be implemented with different discharge circuit configurations, including those examples described herein.

It will also be understood that, although various examples are described herein in the contexts of contact MEMS devices (such as contact switches) and capacitive MEMS devices, one or more features of the present disclosure can also be implemented in other MEMS applications and/or applications involving electromechanical devices. Such applications and/or devices can include, but are not limited to, gyroscopes, accelerometers, surface acoustic wave (SAW) devices, bulk acoustic wave (BAW) devices, and any other MEMS devices that are sensitive to ESD events and/or hot switching problems. In the context of contact switches, other RF and/or non-RF applications can include, for example, load switches in power supplies, voltage converters and regulators (e.g., where MEMS switches can replace FET switches); and power switches such as those configured to handle high power and/or high voltage (e.g., low frequency) signals.

MEMS devices having one or more features as described herein can be utilized in a number of electronic applications, including radio-frequency (RF) applications. In the context of RF applications, electrostatically-actuated MEMS devices, such as the MEMS switches and MEMS capacitors as described herein, can provide desirable characteristics such as low insertion loss, high isolation, high linearity, high power handling capability, and/or high Q factor.

FIG. 17shows an example of an RF application where MEMS devices having one or more features as described herein can be implemented. The example ofFIG. 17includes a multiple port switching configuration involving RF Port1, RF Port2and RF Port3. RF Port1can be, for example, a common antenna port, and RF Ports1and2can be associated with, for example, first and second RF band signal paths. In such an example context, there can be more than two RF bands coupled to the common antenna port.

Each of the three ports is shown to be coupled to a switchable shunt path to ground. For RF Port1, the shunt path can include an ESD protected MEMS switch. For RF Port2, the shunt path can include an ESD protected MEMS switch. For RF Port3, the shunt path can include an ESD protected MEMS switch. In some embodiments, each of such ESD protected MEMS switch can be configured as a self-actuating MEMS switch. Additional details concerning such self-actuating MEMS switches are described herein in greater detail.

InFIG. 17, a MEMS switch (Port1MEMS) can be provided between the second port (RF Port2) and a common node shared by the three ports. Similarly, a MEMS switch (Port2MEMS) can be provided between the third port (RF Port3) and the common node. Such MEMS switches (Port1MEMS and Port2MEMS) are shown to have their gates controlled by a switch gate controller.

In some embodiments, some or all of the foregoing MEMS devices (RF Port1ESD Protection MEMS, RF Port2ESD Protection MEMS, RF Port3ESD Protection MEMS, Port1MEMS, Port2MEMS) can include respective discharge circuits having one or more features as described herein. In the context of the self-actuating MEMS switches (e.g., RF Port1ESD Protection MEMS, RF Port2ESD Protection MEMS, RF Port3ESD Protection MEMS), spark gaps of their respective discharge circuits can be configured to facilitate and/or improve the self-actuating process.

With respect to self-actuation, it is noted that MEMS devices can self-actuate under certain conditions (e.g., higher voltage conditions). Such a property can be undesirable under some operating conditions; however, the same property can be utilized in other operating conditions to provide, for example, a switchable path to ground during ESD events.

In MEMS RF switch devices, such self-actuation can occur in beam-actuated configurations in which a beam is actuated by applying a voltage to the gate to thereby create an electrostatic force on the beam. In such a configuration, a beam can self-actuate, without the force from the gate, if there is a sufficient voltage difference between the beam and the gate.

During a typical ESD event, very high voltages can be applied to a MEMS device. In a MEMS device where the gate and one electrode are grounded, and the other electrode is located on the beam, such a high voltage associated with ESD can allow the beam to self-actuate and close the circuit between the two electrodes. This self-actuation allows the energy associated with the ESD event to be discharged to ground before other elements of the device are harmed. As described herein, use of discharge circuits in such self-actuated MEMS switches can allow the ESD Protection MEMS devices to be designed to actuate at a lower voltage and/or to have faster switching speeds.

In the example ofFIG. 17, suppose there is an ESD event across any two ports. Such an ESD event will likely yield a large voltage differential between the beam and the gate of some or all of the ESD Protection MEMS devices. The affected ESD Protection MEMS device can have its beam self-actuated by the voltage differential; and since the affected gate is grounded, the ESD energy can safely dissipate to ground before damage occurs. Again, use of discharge circuits can allow such ESD Protection MEMS devices to be designed to actuate at a lower voltage and/or to have faster switching speeds to, for example, provide better protection of the rest of the devices (e.g., by activating before the rest of the device and thereby handling the discharge).

As disclosed herein, ESD Protection MEMS devices can be implemented as MEMS switches; and such MEMS switches may or may not include self-actuation functionality. As also disclosed herein, a discharge circuit having one or more features as described herein can be implemented in any of such MEMS devices, including but not limited to, a MEMS device (e.g., a switch) which may or may not be specifically configured to provide ESD protection, and a MEMS switch with or without self-actuation functionality.

FIG. 18shows that in some embodiments, one or more MEMS devices as described herein can be implemented in a module300. The example module300can include a packaging substrate302configured to receive a plurality of components. At least some of such components can include one or more MEMS devices100; and some or all of such MEMS devices can include a discharge circuit110having one or more features as described herein.

In the example ofFIG. 18, five of such MEMS devices100are shown to be implemented on the substrate302and connected between three example ports to provide switching functionalities similar to the example ofFIG. 17. In the example ofFIG. 18, the antenna port (ANT) can be the first port (Port1) ofFIG. 17; and the ports for Band1and Band2can be the second and third ports (Port2, Port3) ofFIG. 17. The five MEMS devices100can be mounted or formed on the substrate302, and such devices can be interconnected to provide desired functionalities. In the example ofFIG. 18, a switch controller component304is also depicted as being on the module300. Other components can also be implemented on the module300.

In some embodiments, the module300can be an antenna switching module (ASM). In some embodiments, the module300can be a front-end module (FEM) in which case other components such as power amplifiers, low-noise amplifiers, matching circuits, and/or duplexers/filters can be included.

In some implementations, an architecture, device and/or circuit having one or more features described herein can be included in an RF device such as a wireless device. Such an architecture, device and/or circuit can be implemented directly in the wireless device, in one or more modular forms as described herein, or in some combination thereof. In some embodiments, such a wireless device can include, for example, a cellular phone, a smart-phone, a hand-held wireless device with or without phone functionality, a wireless tablet, a wireless router, a wireless access point, a wireless base station, etc. Although described in the context of wireless devices, it will be understood that one or more features of the present disclosure can also be implemented in other RF systems such as base stations.

FIG. 19depicts an example wireless device400having one or more advantageous features described herein. In some embodiments, such advantageous features can be implemented in a module300such as an antenna switch module (ASM). In some embodiments, such a module can include more or less components than as indicated by the dashed box.

Power amplifiers (PAs) (collectively depicted as412) (e.g., in a PA module) can receive their respective RF signals from a transceiver410that can be configured and operated to generate RF signals to be amplified and transmitted, and to process received signals. The transceiver410is shown to interact with a baseband sub-system408that is configured to provide conversion between data and/or voice signals suitable for a user and RF signals suitable for the transceiver410. The transceiver410is also shown to be connected to a power management component406that is configured to manage power for the operation of the wireless device400. Such power management can also control operations of the baseband sub-system408and other components of the wireless device400.

The baseband sub-system408is shown to be connected to a user interface402to facilitate various input and output of voice and/or data provided to and received from the user. The baseband sub-system408can also be connected to a memory404that is configured to store data and/or instructions to facilitate the operation of the wireless device, and/or to provide storage of information for the user.

In the example wireless device400, the module300can include one or more MEMS devices configured to provide one or more desirable functionalities as described herein. Such MEMS devices can facilitate, for example, operation of the antenna switch module (ASM)414in a discharge-protected manner. In some embodiments, at least some of the signals received through an antenna420can be routed from the ASM414to one or more low-noise amplifiers (LNAs)418. Amplified signals from the LNAs418are shown to be routed to the transceiver410.

A number of other wireless device configurations can utilize one or more features described herein. For example, a wireless device does not need to be a multi-band device. In another example, a wireless device can include additional antennas such as diversity antenna, and additional connectivity features such as Wi-Fi, Bluetooth, and GPS.

In the various examples disclosed herein, discharge circuits are described as being configured to provide preferred discharge paths by way of, for example, arcing across opposing spark gap elements. It will be understood that use the term arcing or arc can include any transmission of energy such as electrical energy between two or more electrically non-contacting elements. Such transmission of energy can be due to, for example, ionization, and/or conduction; and can be through, for example, gas (including air), semiconductor, electrical insulator, and/or dielectric.