MEMS Bridge

Abstract

The present invention relates to a radio frequency (RF) microelectromechanical system (MEMS) switch comprising a substrate, a first signal conductor on the substrate, ground conductors supported on both sides of the first signal conductor on the substrate, and a MEMS bridge having at least one end mechanically connected to the substrate by at least one anchor, wherein the MEMS bridge comprises a variable capacitor region provided on the first signal conductor, the variable capacitor region comprising a first dielectric layer and a first conductive layer, the first conductive layer positioned on the surface of the first dielectric layer facing the substrate. The RF MEMS switch is provided, comprising a substrate comprising one or more pull-down substrate conductors, the MEMS bridge comprising one or more operable conductors located between an anchor and a variable capacitor region and provided on one or more pull-down substrates, at least one of the one or more operable conductors comprising an embedded portion extending longitudinally along the MEMS bridge between the first and second longitudinal conductive portions.

Description

Technical Field

[0001] The present invention relates to a radio frequency (RF) microelectromechanical system (MEMS) switch including a variable capacitor region, and a method of manufacturing an RF MEMS switch.

Background Art

[0002] A radio frequency (RF) microelectromechanical system (MEMS) switch typically includes a signal conductor supported by a substrate and a bridge extending over the signal conductor, the bridge being movable between an up state and a down state to change one or more electrical characteristics such as the capacitance or resistance of the switch. The present application focuses on capacitive switches where the up and down states of the bridge have different capacitances rather than on / off or open / closed switches.

[0003] US7126447B2 discloses an RF-MEMS switch including a plurality of movable electrodes disposed with a space therebetween in the RF signal conduction direction of an RF signal conduction unit provided on the RF signal conduction unit.

[0004] It is desirable to obtain a large and properly controlled change in capacitance between the up state and the down state. To obtain a high capacitance ratio between the up state and the down state, the gap distance between the bridge and the substrate when the bridge is in the down state should be minimized. Further, the gap distance should ideally be predictable and consistent.

[0005] The present disclosure has been devised in this situation.

Summary of the Invention

[0006] In this specification and the appended claims, a MEMS switch refers to a MEMS device that is switchable between at least a first state and a second state, thereby changing at least one impedance (typically capacitance and / or resistance). In some embodiments, the MEMS device is a capacitive MEMS switch. In the present invention, the MEMS switch comprises a signal line support on a substrate and a MEMS bridge movable with respect to the signal line between a first state and a second state, thereby changing at least one capacitance and / or resistance.

[0007] According to a first aspect of the present invention, an RF MEMS switch is provided, comprising: a substrate; at least one signal conductor supported on the substrate; and a MEMS bridge, at least one end of which is mechanically connected to the substrate via at least one anchor. The MEMS bridge comprises a variable capacitor region provided on the at least one signal conductor. The variable capacitor region comprises a first dielectric layer and a first conductive layer. The first conductive layer is positioned on the surface of the first dielectric layer facing the substrate and is separated into at least a first longitudinal conductive portion and a second longitudinal conductive portion. The first longitudinal conductive portion and the second longitudinal conductive portion are spaced apart in a direction perpendicular to the longitudinal length of the MEMS bridge.

[0008] A second aspect of the present invention provides a method for manufacturing a radio frequency (RF) micro-electromechanical system (MEMS) switch, as described below. The method includes providing a substrate and providing at least one signal conductor supported by the substrate. The method includes providing a MEMS bridge having a variable capacitor region on at least one signal conductor by providing a first dielectric layer and a first conductive layer. The first conductive layer is provided on the surface of the first dielectric layer facing the substrate and is separated into at least a first longitudinal conductive portion and a second longitudinal conductive portion. The first longitudinal conductive portion and the second longitudinal conductive portion are spaced apart in a direction perpendicular to the longitudinal length of the MEMS bridge.

[0009] At least one signal conductor may comprise a first signal conductor and a second signal conductor. The first and second signal conductors may be parts of the same divided signal line. This may be a series configuration of RF MEMS switches.

[0010] A MEMS switch may comprise a first signal conductor and a ground conductor supported on the substrate on both sides of the first signal conductor. A variable capacitor region may be located above the ground conductor. This may be a shunt configuration for an RF MEMS switch.

[0011] Typically, the substrate comprises a first surface on which at least one signal conductor, a ground conductor, and a MEMS bridge are supported. The substrate is typically formed from a material with high resistivity, such as high resistivity undoped silicon. The signal conductor and ground conductor are typically made from conductive materials, such as aluminum, gold, molybdenum, copper, titanium, nickel, platinum, chromium, or aluminum alloys such as Al-Cu, Al-Si, and Al-Nd, which are typically metals.

[0012] The fact that the variable capacitor region is located on at least one signal conductor (and ground conductor) means that, regardless of the orientation of the device, it refers to the direction away from the substrate on which at least one signal conductor (and ground conductor) is formed.

[0013] The signal conductor and the ground conductors on both sides of the signal conductor typically form a coplanar waveguide on the substrate to guide the signal along the signal conductor.

[0014] The MEMS bridge may be deformable from a first position, where the variable capacitance region is spaced apart from each of at least one signal (and ground) conductors, to a second position, where the variable capacitance region is closer to each of at least one signal conductor than in the first position, due to electrostatic ductivity. The capacitance between the variable capacitance region and at least one signal conductor (and ground conductor) may be greater when the MEMS bridge is in the second position than when the MEMS bridge is in the first position.

[0015] In a shunt configuration, a capacitor may be formed between the MEMS bridge and each of the ground conductor and signal conductor. In a series configuration, a capacitor may be formed between the MEMS bridge and each of the signal conductors.

[0016] The first position may be the MEMS bridge in the up position. The second position may be the MEMS bridge in the down position. The first state or up position of a MEMS bridge, switch, or device refers to a state in which the MEMS bridge is separated from the substrate, at least on the signal conductors, and the second state or down position refers to a state in which the MEMS bridge is in contact with the substrate (typically via an intermediate layer).

[0017] Typically, the variable capacitor region is movable from the first position to the second position, for example, in the first and second positions of the MEMS bridge. Typically, in the second position, the variable capacitor region is closer to the substrate than in the first position. Typically, in the second position, the variable capacitor region is closer to the signal conductor (and ground conductor) than in the first position. Typically, in the second position, a portion of the MEMS bridge is closer to the substrate than when the MEMS bridge is in the first position. Typically, in the second position, a portion of the MEMS bridge is closer to the signal conductor (and ground conductor) than when the MEMS bridge is in the first position. Typically, when the MEMS bridge moves from its first position to its second position, the anchor does not move.

[0018] A typical double-layer MEMS bridge contains different materials in each layer. These different materials may have different stress properties. These differences in stress properties can result in large stress differences between the bridge layers. For example, layers may be made of materials with different coefficients of thermal expansion that cause curvature and bending of the bridge when exposed to high temperatures. When the MEMS bridge is operated, torque is applied from the layer with the higher stress parameter to the layer with the lower stress parameter, which can cause transverse strain in the bridge. Stress can be introduced into the bridge during deposition or during further downstream processes that occur at higher temperatures.

[0019] A problem related to transverse distortion is that when a MEMS bridge is distorted transversely, the ratio of capacitance between the MEMS bridges in the up state compared to the down state is smaller than the change in capacitance between the MEMS bridges in the up state compared to the down state when the MEMS bridge is distorted. This is because contact between the bridge and the signal conductor and ground conductor (which may be via an intermediate layer) is reduced, and an air gap is introduced between the substrate and the MEMS bridge.

[0020] Advantageously, the torque applied to the bridge can be controlled by providing the first conductive layer in spaced-out and separate first and second longitudinal conductive portions. Because the torque can be controlled by providing spaced-out and separate longitudinal conductive portions, the distortion of the MEMS bridge is reduced, and it can become substantially flat when down. In particular, the torque exerted by the first conductive layer on the first dielectric layer can be controlled. In the portion of the MEMS bridge where the first conductive layer is provided, the torque is applied to the first dielectric layer. Therefore, when the first conductive layer is dispersed by having separate first and second longitudinal conductive portions, a distributed torque is realized within the bridge. The portion of the bridge where the first conductive layer is absent (i.e., the portion of the bridge formed from the first dielectric layer and located between the longitudinal conductive portion and the centerline of the MEMS bridge) has a bulk modulus that acts to resist the torque applied by the longitudinal conductive portion. Therefore, by arranging longitudinally conductive portions that are spaced laterally across the MEMS bridge, the effect of this dispersed torque on the strain of the MEMS bridge is minimized for a given region of the first conductive layer on the MEMS bridge.

[0021] Generally, it is desirable to achieve a large change in capacitance between the up and down states of a MEMS bridge without increasing the overall size of the MEMS device. The present invention makes it possible to increase the change in capacitance per unit area of ​​a MEMS bridge between the up and down states compared to a MEMS bridge without a first longitudinal conductive portion and a second longitudinal conductive portion. The change in capacitance per unit area between the up and down states of a MEMS bridge is sometimes referred to as the capacitance ratio (e.g., between the up and down states).

[0022] When the MEMS bridge is in the second position, the stress ratio between the first conductive layer and the first dielectric layer may be greater than 1:1.

[0023] Typically, the capacitance of a MEMS bridge changes between up and down states by, for example, at least 5 times, at least 10 times, at least 100 times, or at least 1000 times. Typically, RF MEMS switches are capacitive switches. MEMS switches can be shunts or series capacitive switches. MEMS switches can be used as phase shifters (where the phase of a signal in a signal conductor changes due to a change in impedance (particularly capacitance) between up and down states).

[0024] RF MEMS switches can be configured for use with RF signals at frequencies above 10 GHz. RF MEMS switches can also be configured for use with RF signals at frequencies above 15 GHz and above 20 GHz.

[0025] A MEMS bridge may be cantilevered and have one end mechanically connected to the substrate by a single anchor. A MEMS bridge may also have opposing first and second ends connected to the substrate by their respective anchors. An RF MEMS switch may be a seesaw switch in which the MEMS bridge is mechanically connected to the substrate via a single anchor that acts as a pivot.

[0026] Typically, a MEMS bridge is formed from a spanning portion. The spanning portion may span signal conductors (and ground conductors). When the MEMS bridge is in the up position, the spanning portion may be separated perpendicularly from the substrate by an air gap. The spanning portion may be closer to the substrate when the MEMS bridge is in the down position than when it is in the up position. The spanning portion may include a variable capacitor region. The spanning portion may contact the substrate when the MEMS bridge is in the down position. The spanning portion is typically a variable capacitor region. The spanning portion may typically be connected to one or more anchors.

[0027] Optionally, the MEMS bridge can be cantilevered in that it has one anchor that mechanically connects the spanning portion of the MEMS bridge to the substrate. Optionally, the MEMS bridge (i.e., the spanning portion) can be supported by anchors at opposite ends of the MEMS bridge. The first end can be mechanically connected to the substrate and supported by the first anchor, and the second end can be mechanically connected to the substrate and supported by the second anchor. The first end and the second end are typically edges of the MEMS bridge perpendicular to the longitudinal edges of the MEMS bridge. Typically, when the RF MEMS switch is a seesaw switch, the MEMS bridge is mechanically connected to the substrate, typically via a pivot that also functions as an anchor or to which an anchor can be connected. Optionally, the seesaw switch includes a first signal conductor and a second signal conductor on both sides of the anchor (i.e., the pivot), and optionally, ground conductors can be provided on both sides of each signal conductor, respectively.

[0028] Throughout this application, the term longitudinal (e.g., edge) is intended to refer to the direction in which the longest length (e.g., edge) extends. The term transverse (e.g., edge) is intended to refer to a direction perpendicular to the longitudinal length (e.g., edge), which is the second longest length (e.g., edge). The MEMS bridge (e.g., the variable capacitor region) is typically connected to the anchor along its transverse edge and exposed along its longitudinal edge.

[0029] The variable capacitor region can typically include a variable capacitor. The variable capacitor region can typically include a voltage-controlled variable capacitor (e.g., a MEMS varactor). The MEMS varactor typically provides two or more states having two or more capacitances. The variable capacitor region may function as a phase shifter by applying a phase shift to a signal passing along a signal conductor (e.g., in a shunt configuration), or may function as a switch for establishing / disconnecting a connection between two signal tracks that are normally disconnected within a coplanar waveguide (e.g., in a series configuration).

[0030] Typically, in some examples, the variable capacitor region refers to a portion of the MEMS bridge that can be a spanning portion forming a capacitive connection with the signal conductor and the ground conductor. Typically, in some examples, the variable capacitor region refers to a portion of the MEMS bridge that can be a spanning portion forming a capacitive connection with the signal conductor.

[0031] The variable capacitor region is typically formed from two layers, a first conductive layer and a first dielectric layer. The first conductive layer is typically formed from a conductive material, typically a metal such as aluminum, gold, molybdenum, copper, titanium, nickel, platinum, chromium, or an aluminum alloy such as Al-Cu, Al-Si, and Al-Nd. The first dielectric layer is typically formed from an electrical insulating material (e.g., silicon nitride, strontium titanate (SrTiO3), parylene, polyimide, aluminum oxide, aluminum nitride, silicon dioxide, hafnia, zirconia, etc.). The first dielectric layer is typically above the first conductive layer in a direction away from the substrate.

[0032] The MEMS bridge typically includes an upper surface away from the substrate and a lower surface facing the substrate. The lower surface can be formed from both the first conductive layer and the second conductive layer. The MEMS bridge can have a longitudinal edge of at least 100 microns, at least 200 microns, at least 300 microns, at least 400 microns, at least 450 microns, or at least 500 microns. The MEMS bridge can have a lateral edge of at least 10 microns, at least 20 microns, at least 30 microns, at least 35 microns, at least 40 microns, at least 45 microns, or at least 50 microns. The MEMS bridge can have a thickness of at least 0.5 microns, at least 1 micron, at least 1.5 microns, or at least 2 microns in a direction extending perpendicular to the substrate.

[0033] When the MEMS bridge is in the second position, the first longitudinal conductive portion and the second longitudinal conductive portion each typically contact at least one signal conductor (and ground conductor).

[0034] The first longitudinal conductive portion and the second longitudinal conductive portion are typically parts of the first conductive layer. The first and second longitudinal conductive portions typically have longitudinal edges that are significantly longer than their transverse edges. The first and second conductive portions may have the same length as the longitudinal length of the variable capacitor region, or they may have a length shorter than the longitudinal length of the variable capacitor region.

[0035] Optionally, the first longitudinal conductive portion and the second longitudinal conductive portion may be separated by a portion of the first dielectric layer. That is, the first longitudinal conductive portion and the second longitudinal conductive portion may be integrated into the first dielectric layer. The first longitudinal conductive portion and the second longitudinal conductive portion are separated in the direction of the lateral edge of the variable capacitor region.

[0036] The first longitudinal conductive portion and the second longitudinal conductive portion may extend along opposing longitudinal edges of a variable capacitor region parallel to the longitudinal length of the MEMS bridge. A method for providing the first conductive layer may include providing the first longitudinal conductive portion and the second longitudinal conductive portion extending along opposing longitudinal edges of a variable capacitor region parallel to the longitudinal length of the MEMS bridge.

[0037] Advantageously, by providing a first and a second longitudinal conductive portion along the longitudinal edge of the variable capacitor region, the curvature of the MEMS bridge is reduced when the MEMS bridge is actuated toward the substrate. Both conductive portions generate torque distributed across the MEMS bridge. However, the portion of the MEMS bridge without the first conductive portion resists the bending caused by the torque of the conductive portion. By positioning the conductive portion at the longitudinal edge of the MEMS bridge, a desired capacitance ratio between the up and down states can be achieved while providing a central portion without the first conductive layer that resists bending caused by torque. Thus, the MEMS bridge can function as a variable capacitor while simultaneously optimizing the capacitance ratio between the up and down states achieved by reducing curvature.

[0038] The first longitudinal conductive portion and the second longitudinal conductive portion are typically aligned with the longitudinal edge of the variable capacitor region. The method may include forming the first longitudinal conductive portion and the second longitudinal conductive portion aligned with the longitudinal edge of the variable capacitor region. The first longitudinal conductive portion and the second longitudinal conductive portion are typically aligned with the longitudinal edge (e.g., spanning portion) of the MEMS bridge. The method may include forming the first longitudinal conductive portion and the second longitudinal conductive portion aligned with the longitudinal edge (e.g., spanning portion) of the MEMS bridge. Optionally, a first dielectric layer may be formed between the first longitudinal conductive portion and the second longitudinal conductive portion to form the underside of the MEMS bridge. The method may include forming a first dielectric layer between the first longitudinal conductive portion and the second longitudinal conductive portion to form the underside of the MEMS bridge.

[0039] The first and second longitudinal conductive portions may extend along the entire longitudinal edge of the variable capacitor region. The longitudinal edge of the MEMS bridge may be entirely formed from the longitudinal edge of the variable capacitor region. That is, the variable capacitor region may extend from the first anchor to the second anchor.

[0040] Optionally, the MEMS bridge may comprise one or more extended sections between each anchor and the edge of the variable capacitor region. Optionally, the longitudinal edge of the MEMS bridge may be formed by the longitudinal edge of the variable capacitor region and the longitudinal edges of one or more extended sections. That is, one or more extended sections may comprise a first arm of the MEMS bridge located between a first anchor and a first end of the variable capacitor region, and a second arm of the MEMS bridge located between a second end of the variable capacitor region and a second anchor. Optionally, in some examples, the MEMS bridge (e.g., an extended section) includes one or more operable conductors (considered below) that form a portion of the longitudinal edge of the MEMS bridge between the edge of the variable capacitor region and each anchor.

[0041] The first longitudinal conductive portion and the second longitudinal conductive portion may each extend laterally across the MEMS bridge to less than one-third of the lateral width of the MEMS bridge. The first longitudinal conductive portion and the second longitudinal conductive portion may extend laterally in a direction perpendicular to the longitudinal length of the MEMS bridge.

[0042] Advantageously, when the surface area of ​​the MEMS bridge is larger when there is no first conductive layer than when there is a first conductive layer, the stress parameter of the first dielectric layer is lower than that of the first conductive layer, resulting in greater resistance to the torque generated by the first conductive layer. In other words, the greater the amount of the first dielectric layer exposed on the surface compared to the amount of the first conductive layer, the greater the resistance to the torque generated by the first conductive layer, and the smaller the torque actually applied to the MEMS bridge.

[0043] Typically, the first longitudinal conductive portion and the second longitudinal conductive portion each have an inner longitudinal edge and an outer longitudinal edge. The inner longitudinal edges of the first and second conductive portions may be separated by distances of 3 to 30 microns, e.g., 5 to 25 microns, e.g., 7 to 20 microns, e.g., 10 to 15 microns (e.g., distances perpendicular to the longitudinal direction).

[0044] The electrical length between the first conductive part and the second conductive part may be less than 20% of the RF signal wavelength, for example, less than 25%, for example less than 20%, for example less than 15%. The electrical length between the first conductive part and the second conductive part may be more than 25%, for example more than 33%, for example more than 50% of the RF signal wavelength. The RF signal refers to the RF signal conducted by the signal conductor in use. The RF signal may be the signal on which the RF MEMS switch (e.g., the signal conductor) is composed. The RF signal may be the operating RF signal wavelength.

[0045] The first longitudinal conductive portion and the second longitudinal conductive portion may have a longitudinal length exceeding 400 microns. The first longitudinal conductive portion and the second longitudinal conductive portion may have a longitudinal length exceeding 400 microns, 450 microns, or 500 microns.

[0046] Typically, the lateral edges of the first and second longitudinal conductive portions are shorter than the longitudinal edges of the first and second longitudinal conductive portions. The first and second longitudinal conductive portions may be of equal or different sizes.

[0047] The first longitudinal conductive portion and the second longitudinal conductive portion may each extend the MEMS bridge laterally to less than one-third, less than 25%, less than 20%, less than 15%, or less than 10% of the lateral width of the MEMS bridge.

[0048] Optionally, the underside of the MEMS bridge may have a total area that includes more of the first dielectric layer than the first conductive layer. The underside of the MEMS bridge may have a total area that includes more of the first conductive layer than the first dielectric layer. The underside of the MEMS bridge may have a total area that includes more than 25%, more than 50%, or more than 75% of the first dielectric layer. The underside may have a total area that includes more than 25%, more than 50%, or more than 75% of the first conductive layer. The underside may have a total area that includes equal amounts of the first conductive layer and the first dielectric layer.

[0049] MEMS bridges are typically symmetrical about a central longitudinal axis. In this way, equal amounts of the first conductive layer and the first dielectric layer are present on the undersides on both sides of the central longitudinal axis.

[0050] The first longitudinal conductive portion and the second longitudinal conductive portion may not be electrically connected to each other.

[0051] The MEMS switch comprises a first signal conductor and ground conductors supported on substrates on both sides of the first signal conductor, wherein the first longitudinal conductive portion and the second longitudinal conductive portion may form a separate parallel variable capacitance connection between the signal conductor and the ground conductor. The MEMS switch comprises a first signal conductor and a second signal conductor, wherein the first longitudinal conductive portion and the second longitudinal conductive portion may form a separate parallel variable capacitance connection between the first signal conductor and the second signal conductor.

[0052] By providing a variable capacitor region with separate longitudinal conductive portions in the MEMS bridge, each longitudinal conductive portion forms a capacitive connection between the signal conductor and the ground conductor (in a shunt configuration) or between the signal conductors (in a series configuration). That is, typically, the first longitudinal conductive portion forms a first parallel variable capacitance connection including multiple capacitances, and the second longitudinal conductive portion forms a second parallel variable capacitance connection including multiple capacitances. Typically, in a shunt configuration, the first parallel variable capacitance connection includes a first capacitance between sections of the first longitudinal conductive portion provided on the signal conductor. Typically, in a shunt configuration, the first parallel variable capacitance connection includes a second and third capacitance between sections of the first longitudinal conductive portion provided on the ground conductor. Typically, in a shunt configuration, the second parallel variable capacitance connection includes a fourth capacitance between sections of the second longitudinal conductive portion provided on the signal conductor. Typically, in a shunt configuration, the second parallel variable capacitance connection includes a fifth and sixth capacitance between sections of the second longitudinal conductive portion provided on the ground conductor. Typically, in a series configuration, the first parallel variable capacitance connection includes a first capacitance between sections of the first longitudinal conductive portion provided on the first signal conductor. Typically, in a series configuration, the first parallel variable capacitance connection includes a second capacitance between sections of the first longitudinal conductive portion provided on the second signal conductor. Typically, in a series configuration, the second parallel variable capacitance connection includes a third capacitance between sections of the second longitudinal conductive portion provided on the first signal conductor. Typically, in a series configuration, the second parallel variable capacitance connection includes a fourth capacitance between sections of the second longitudinal conductive portion provided on the second signal conductor.

[0053] Typically, the capacitance between the variable capacitor region (e.g., the longitudinal conductive portion) and the signal conductor (and between the variable capacitor region (e.g., the longitudinal conductive portion) and the ground conductor) is greater when the variable capacitor region (and thereby the MEMS bridge) is in a second position than when it is in a first position.

[0054] Advantageously, since the first longitudinal conductive portion and the second longitudinal conductive portion are not electrically connected to each other and form separate parallel variable capacitance connections between the signal conductors (and ground conductors), it is possible to achieve a higher capacitance area (and therefore a higher change in capacitance) while maintaining a high capacitance ratio between the up and down states.

[0055] Optionally, the first conductive layer may comprise one or more third longitudinal conductive portions extending parallel to the first longitudinal conductive portion and the second longitudinal conductive portion. Each of the one or more third longitudinal conductive portions may extend laterally across the MEMS bridge by less than 25% of the lateral width of the MEMS bridge. The lateral extensions across the MEMS bridge may be oriented perpendicular to the longitudinal length of the MEMS bridge. A method for providing the first conductive layer may include providing one or more third longitudinal conductive portions extending parallel to the first longitudinal conductive portion and the second longitudinal conductive portion.

[0056] Advantageously, by using one or more third longitudinal conductive portions, it is possible to achieve a higher capacitance area (and therefore a greater change in capacitance) while maintaining a high capacitance ratio between the up and down states.

[0057] Typically, one or more third longitudinal portions are substantially the same as the first and second longitudinal conductive portions. The one or more third longitudinal conductive portions are typically separated from each other by the first dielectric layer and also separated from the first and second longitudinal conductive portions. The method may include forming the underside of a MEMS bridge by providing one or more third longitudinal conductive portions separated from each other by the first dielectric layer and also separated from the first and second longitudinal conductive portions. That is, the underside of the MEMS bridge may alternately include strips of longitudinal conductive portions of the first conductive layer and strips of the first dielectric layer extending downward (i.e., toward the substrate) between the longitudinal conductive portions.

[0058] Each of the one or more third longitudinal conductive portions may extend laterally across the MEMS bridge to less than 25%, less than 20%, less than 15%, or less than 10% of the lateral width of the MEMS bridge.

[0059] A MEMS bridge may comprise one or more slots extending longitudinally along the MEMS bridge, and one or more slots extending through both the first dielectric layer and the first conductive layer. The method may include providing one or more slots that extend longitudinally along the MEMS bridge and extend through both the first dielectric layer and the first conductive layer.

[0060] Advantageously, providing slots within the MEMS bridge means that the first dielectric layer is absent, and therefore the first and second conductive portions cannot apply torque to the slots in the MEMS bridge, thus reducing the curvature of the MEMS bridge.

[0061] Optionally, one or more slots may form gaps on the top and bottom surfaces of the MEMS bridge. That is, one or more slots typically extend through the entire thickness of the MEMS bridge. The first and second conductive portions, and, if present, one or more third longitudinal conductive portions, may be separated from each other by one or more slots. The method may include forming the bottom surface of the MEMS bridge by separating the first and second conductive portions, and, if present, one or more third longitudinal conductive portions, from each other by one or more slots. For example, the bottom surface of the MEMS bridge may be formed by a repeating alternating pattern of longitudinal conductive portions and slots across the entire bottom surface of the MEMS bridge. In another example, the bottom surface of the MEMS bridge may be formed by longitudinal conductive portions along each longitudinal edge of the variable capacitor region, with an alternating pattern of slots and strips of the first dielectric layer. Advantageously, this configuration achieves an even higher capacitance ratio, thereby resulting in a flatter MEMS bridge at the second location. Advantageously, for example, by adjusting the change in capacitance to a lower value in order to apply a smaller increment of phase shift to the signal passing along the signal conductor.

[0062] One or more slots may extend laterally across the MEMS bridge by more than 20% of the total lateral width of the MEMS bridge. One or more slots may extend laterally across the MEMS bridge in a direction perpendicular to the longitudinal length of the MEMS bridge.

[0063] Advantageously, if the MEMS bridge has a large surface area formed by slots, less material of the MEMS bridge is subjected to the torque generated by the first and second conductive portions. That is, the lower the amount of the first dielectric layer exposed on the surface of the MEMS bridge compared to the amount of the first conductive layer, the less surface area of ​​the MEMS bridge is subjected to the torque generated by the first conductive layer.

[0064] Typically, one or more slots have a lateral length shorter than the longitudinal conductive portion. However, in some examples, one or more slots may have a lateral length equal to or longer than the longitudinal conductive portion. One or more slots may extend the MEMS bridge laterally by more than 20%, 30%, 40%, or 50% of the total lateral width of the MEMS bridge.

[0065] One or more slots may extend further longitudinally toward each end of the MEMS bridge than at least one longitudinal edge of the variable capacitor region. Providing one or more slots may include providing one or more slots that extend further toward each end of the MEMS bridge than at least one longitudinal edge of the variable capacitor region.

[0066] Optionally, one or more slots may extend longitudinally through at least a portion of the variable capacitor region and at least a portion of one or more slots.

[0067] The substrate may comprise one or more pull-down substrate conductors, and the MEMS bridge may comprise one or more operable conductors located between the anchor and the variable capacitor region. The one or more operable conductors may be provided on top of one or more pull-down substrate conductors. The method may include providing one or more pull-down substrate conductors and one or more operable conductors extending on top of one or more pull-down substrate conductors between the anchor and the variable capacitor region. Optionally, providing one or more operable conductors may include providing embedded portions that extend longitudinally along the MEMS bridge and between a first longitudinal conductive portion and a second longitudinal conductive portion.

[0068] If present, the embedded portion typically extends between the first longitudinal conductive portion and the second longitudinal conductive portion without contacting them. Thus, one or more operable conductors typically remain isolated from the variable capacitor region.

[0069] One or more pull-down substrate conductors and one or more actuated conductors can typically move a MEMS bridge from a first position to a second position. Optionally, the MEMS bridge may comprise a first actuated conductor located on a first pull-down substrate conductor on the substrate, and a second actuated conductor located on a second pull-down substrate conductor on the substrate. Typically, a potential difference is applied between at least one conductor on the substrate (e.g., one or more ground conductors, or signal conductors, or pull-down conductors (conductors configured to selectively pull down the bridge)) and at least one conductor on the MEMS bridge (e.g., a variable capacitor region of the MEMS bridge or an actuated conductor) to move the MEMS bridge from a first position (up) to a second position (down) (typically, the variable capacitor region is closer to the substrate in the second position than in the first position), causing electrostatic action (generating an electrostatic attraction between the conductors on the substrate and the MEMS bridge, thereby pulling down the MEMS bridge). The potential difference (or bias potential) may be DC. For example, a method for operating an RF MEMS switch may involve applying a step change to a DC potential difference. However, the potential difference may be AC, and the frequency will typically be less than 10 kHz (or less than 5 kHz). The potential of the actuatable conductors of a MEMS bridge may be changed (whether DC or AC) to induce electrostatic operation. The potential of pull-down conductors supported on a substrate may be changed (whether DC or AC) to induce electrostatic operation. A DC potential offset may be applied to a conductor carrying an RF signal (e.g., a signal conductor). A bias signal (e.g., a DC signal or AC signal with a frequency typically less than 10 kHz (or less than 5 kHz)) may be applied to a conductor carrying an RF signal (e.g., a signal conductor).

[0070] At least one of the one or more operable conductors may have a recessed portion that extends longitudinally along the MEMS bridge and between a first longitudinal conductive portion and a second longitudinal conductive portion. The recessed portion may be located on at least one of the ground conductors.

[0071] Advantageously, by providing embedded portions in one or more operable conductors, the longitudinal range of the operable conductors is extended, and the curvature of the bridge in the down state is further reduced by increasing the longitudinal range of the bridge that is directly held by the electromagnetic attraction between the conductors.

[0072] Optionally, the embedded portion typically corresponds to a portion of an operable conductor provided on the MEMS bridge between the first and second conductive portions, extending at least a portion of the longitudinal length of the first and second conductive portions. If the MEMS bridge is in the second position, the embedded portion may be in contact (optionally via an intermediate layer) with the respective ground conductors on which they are provided.

[0073] The embedded portion may be provided at least partially on the ground conductor. In this way, at least a portion of the embedded portion is provided vertically on the ground conductor.

[0074] At least one of the one or more operable conductors may have one or more slots that extend longitudinally along a portion of the MEMS bridge. The method may include providing one or more slots in at least one of the one or more operable conductors.

[0075] Typically, each actuarial conductor may have one or more slots. One or more slots in at least one actuarial conductor typically run through the entire thickness of the actuarial conductor. That is, one or more slots may form a gap in the actuarial conductor. One or more slots may extend through the embedded portion of the actuarial conductor. The combined lateral length of one or more slots may be more than 20%, 30%, 40%, or 50% of the longest lateral length of the actuarial conductor. At least one of the one or more slots may have a width of less than 5 microns, less than 3 microns, less than 2 microns, less than 1 micron, or less than 0.5 microns.

[0076] Advantageously, by providing one or more slots, the voltage at which transverse (secondary) collapse occurs is reduced, allowing the bridge to be pulled flat toward the substrate at a lower voltage (e.g., in the ON state).

[0077] An RF MEMS switch may have one or more dimples between one or more actuated conductors and one or more pull-down substrate conductors. The method may include providing one or more dimples between one or more actuated conductors and one or more pull-down substrate conductors.

[0078] Optionally, one or more dimples may be provided on the surface of one or more actuated conductors facing the substrate. Optionally, one or more dimples may be provided on the surface of a pull-down substrate conductor facing a MEMS bridge. The one or more dimples may typically be formed from an insulating material. The one or more dimples may optionally be separate regions of the insulating material formed as a pattern on the pull-down substrate conductor or actuated conductor.

[0079] Advantageously, one or more dimples prevent the pull-down substrate conductor from contacting one or more operable conductors when the MEMS bridge (and variable capacitor region) is in the second position, by acting as a mechanical standoff to prevent a DC short to ground. In addition, the size and spacing of the one or more dimples can be selected to reduce or prevent stiction.

[0080] A MEMS bridge may comprise a second dielectric layer provided between a first conductive layer and at least one signal conductor. The second dielectric layer may be provided on at least one of the signal conductor and the first conductive layer. A MEMS bridge may comprise a second dielectric layer provided between the first conductive layer and the signal conductor and the ground conductor. The second dielectric layer may be provided on at least one of the signal conductor, the ground conductor, and the first conductive layer.

[0081] Typically, the second dielectric layer is a solid electrical insulating layer. The second dielectric layer is provided between the variable capacitor region (i.e., the longitudinal conductive portion) and the signal conductor (to prevent a short circuit between them when the variable capacitor region / MEMS bridge is in the second position). Typically, the second dielectric layer is provided between the variable capacitor region (i.e., the longitudinal conductive portion) and the (respective) ground conductors. Optionally, the second dielectric layer may be provided on the surface of the longitudinal conductive portion facing the substrate, or on the surface of the signal conductor and / or ground conductor facing the MEMS bridge.

[0082] The second dielectric layer may comprise one or more pads on at least one of the signal conductors and ground conductors. The change in capacitance between the first and second positions may depend on the dimensions of the one or more pads. The electric permittivity of the one or more pads may be greater than the relative permittivity of 1 normalized to air.

[0083] Since this in itself is considered novel, a third aspect of the present invention provides a circuit comprising a plurality of radio frequency (RF) micro-electromechanical system (MEMS) switches, the switches comprising: a substrate; signal conductors supported on the substrate; ground conductors supported on the substrate on both sides of the signal conductors; and a MEMS bridge, the MEMS bridge having at least one end mechanically connected to the substrate by at least one anchor. The MEMS bridge comprises a variable capacitor region provided on the signal conductors and the ground conductors. The MEMS bridge is deformable by electrostatic force from a first position where the variable capacitor portion is spaced apart from the respective signal and ground conductors to a second position where the variable capacitor region is closer to the respective signal and ground conductors than in the first position. The capacitance between the variable capacitance region and the signal conductors and ground conductors may be larger when the MEMS bridge is in the second position than when the MEMS bridge is in the first position. The variable capacitor region comprises a first dielectric layer and a first conductive layer. The first conductive layer is located on the surface of the first dielectric layer facing the substrate. The variable capacitor region further comprises a second dielectric layer provided between the first conductive layer, the signal conductor and the ground conductor. The second dielectric layer comprises one or more pads on the signal conductor and the ground conductor. The change in capacitance between the first position and the second position depends on the dimensions of the one or more pads. The circuit comprises an RF MEMS switch comprising one or more pads of different dimensions such that the change in capacitance between the first position and the second position of the RF MEMS switch is different.

[0084] A fourth aspect of the present invention provides a method for manufacturing a circuit according to a third aspect of the present invention. This method includes providing a substrate, providing a signal conductor and a ground conductor on both sides of a signal conductor supported by the substrate, and providing a MEMS bridge having a variable capacitor region on the signal conductor and the ground conductor by providing a first dielectric layer, a first conductive layer, and a second dielectric layer. The first conductive layer is provided on the surface of the first dielectric layer facing the substrate, and the second dielectric layer is provided between the first conductive layer and the signal conductor and the ground conductor. A method for providing the second dielectric layer includes providing one or more pads on the signal conductor and the ground conductor, and providing one or more pads includes selecting a change in capacitance between a first position and a second position, and selecting the dimensions of one or more pads according to the selected change in capacitance.

[0085] Advantageously, the larger the surface area of ​​the contact area between one or more pads and each conductor, the greater the change in capacitance between the up and down states of the MEMS bridge. Since one or more pads are typically formed from a material with a dielectric constant significantly higher than air, such as a dielectric material, one or more pads influence the change in capacitance achieved when the MEMS bridge transitions from the up state to the down state. Therefore, when the MEMS bridge is in the down state, one or more pads form the majority of the capacitive gap, and thus the capacitance increases significantly compared to a capacitor of the same dimensions and spacing where the capacitive gap is filled with air.

[0086] The electrical permittivity of one or more pads may be greater than the relative permittivity of 1.25 normalized to air. The electrical permittivity of one or more pads may be greater than the relative permittivity of 5 normalized to air. The electrical permittivity of one or more pads may be greater than the relative permittivity of 2 normalized to air.

[0087] Advantageously, since the dielectric constant of one or more pads is higher than that of air, the capacitance of the MEMS switch between the first and second positions changes depending on the dimensions of one or more pads. As a result, the change in capacitance is determined by the dimensions of one or more pads. In comparison, if the dielectric constant of one or more pads is the same as that of air, the one or more pads will primarily function as spacers. Although air-bridged capacitance is also produced by the operation of the MEMS switch, this capacitance will be lower than the capacitance of one or more pads.

[0088] One or more pads can typically be three-dimensional. One or more pads can have a surface area (e.g., in a plane extending perpendicular to the direction of movement of the MEMS bridge between a first position and a second position). One or more pads can have a thickness (e.g., in a direction extending parallel to the direction of movement of the MEMS bridge between a first position and a second position).

[0089] A selected change in capacitance may be achieved by changing the dimensions of the pads. One or more pads may have different cross-sectional areas (e.g., in a plane extending perpendicular to the direction of movement of the MEMS bridge between the first and second positions) and a constant thickness. That is, achieving a selected change in capacitance between the first and second positions may involve changing the cross-sectional area of ​​one or more pads.

[0090] One or more pads may be one or more pads having a constant cross-sectional area (e.g., in a plane extending perpendicular to the direction of movement of the MEMS bridge between the first and second positions) and different thicknesses. That is, resulting in a selected change in capacitance between the first and second positions may involve changing the thickness of one or more pads.

[0091] The change in capacitance between the first and second positions may depend on the surface area of ​​one or more pads. The larger the surface area of ​​one or more pads, the greater the change in capacitance between the first and second positions of the MEMS bridge may be.

[0092] The change in capacitance between the first and second positions may depend on the thickness of one or more pads. The greater the thickness of one or more pads, the greater the change in capacitance between the first and second positions of the MEMS bridge may be.

[0093] The dimensions of one or more pads that result in a smaller change in capacitance may include a length of at least 50 microns and a width of up to 4 microns. The dimensions of one or more pads that result in a larger change in capacitance may include a length of at least 50 microns and a width of at least 50 microns. The dimensions of one or more pads that result in a smaller change in capacitance may include up to 10% of the surface area of ​​the region where the variable capacitor overlaps with the coplanar waveguide conductor. The dimensions of one or more pads that result in a larger change in capacitance may include at least 95% of the surface area of ​​the region where the variable capacitor overlaps with the coplanar waveguide conductor.

[0094] Optionally, an RF MEMS switch may have one or more pads on both the signal conductor and the ground conductor. Typically, to maximize the change in capacitance of a given signal, the total area of ​​one or more pads on the ground conductor below the variable capacitor region must be equal to the total area of ​​one or more pads on the signal conductor below the variable capacitor region. By thus reducing the total area of ​​one or more pads below the variable capacitor region, the change in capacitance from when the bridge is up compared to when it is down is reduced, so the dimensions of one or more pads can be used to adjust the change in capacitance in the same bridge design. Using this technique, it is possible to create RF MEMS switches that implement smaller phase shift increments without changing the design of the MEMS bridge.

[0095] One or more pads with variable capacitance regions may be standoffs or dielectric landing pads (DLPs). Typically, one or more pads with a large area relative to the surface of each signal, along with a ground conductor on which one or more pads are located, cause a large change in capacitance between the MEMS bridge at the first position and the MEMS bridge at the second position.

[0096] Any of the features described above with respect to the RF MEMS switch may also be any optional features of other aspects of the present invention, such as the method or circuit of the present invention. The steps of the method may be performed in the order described herein, or possibly in a different order. In some cases, one or more steps of the method may be performed simultaneously.

[0097] Herein, exemplary embodiments of the present invention will be illustrated with reference to the following drawings. [Brief explanation of the drawing]

[0098] [Figure 1-21] The RF MEMS switch according to the present invention will be illustrated as an example. [Figure 1-22] A simplified circuit diagram of key capacitance in a MEMS bridge is illustrated as an example. [Figure 23-24] An example of prior art, specifically an RF MEMS switch, is illustrated. [Figure 25-26] The RF MEMS switch according to the present invention will be illustrated as an example. [Figure 27-28] A flowchart illustrating the method according to the present invention is provided as an example. [Figure 29-30] The RF MEMS switch according to the present invention will be illustrated as an example. [Modes for carrying out the invention]

[0099] Figure 1 illustrates a radio frequency (RF) microelectromechanical (MEMS) switch 100 according to the present invention in a plan view. The RF MEMS switch 100 comprises a substrate 110 that serves as the base for the RF MEMS switch 100. The RF MEMS switch 100 comprises a signal conductor 120 with ground conductors 130a and 130b arranged on both sides. The MEMS bridge is generally indicated by reference numeral 140 and comprises a variable capacitor region 160. The variable capacitor region 160 has a first longitudinal edge 141 and a second longitudinal edge 142. The MEMS bridge 140 is connected to the substrate 110 by anchors 150a and 150b. The variable capacitor region 160 extends over the signal conductor 120 and the ground conductors 130a and 130b. The longitudinal direction extends from left to right in the drawing, and the transverse direction extends from bottom to top in the drawing. The MEMS bridge has a thickness that extends into the drawing.

[0100] Figures 2 and 3 are side views along plane a shown in Figure 1 illustrating the RF MEMS switch 100 according to the present invention. The variable capacitor region 160 comprises a first dielectric layer 161 and a first conductive layer 162. The first conductive layer 162 comprises a first longitudinal conductive portion 162a and a second longitudinal conductive portion 162b that are separated laterally across the variable capacitor region 160. The first dielectric layer 161 extends toward the substrate 110 between the first longitudinal conductive portion 162a and the second longitudinal conductive portion 162b. The first longitudinal conductive portion 162a extends along the first longitudinal edge 141. The second longitudinal conductive portion 162b extends along the second longitudinal edge 142. The first longitudinal conductive portion 162a and the second longitudinal conductive portion 162b extend along the entire longitudinal edge of the variable capacitor region 160. Since the first dielectric layer 161 is insulating, there is no conductive connection between the first longitudinal conductive portion 162a and the second longitudinal conductive portion 162b.

[0101] The first longitudinal conductive portion 162a and the second longitudinal conductive portion 162b are not typically visible in plan views, but are included for illustrative purposes to aid understanding, and are therefore shown using dotted lines in the plan view of Figure 1.

[0102] Figure 2 shows the MEMS bridge 140 in a first position where it is not in contact with the signal conductor 120 or the ground conductors 130a and 130b. Figure 3 shows the MEMS bridge 140 in a second position where it is in contact with the signal conductor 120 and the ground conductors 130a and 130b. In Figure 3, the variable capacitor region 160 is closer to the signal conductor 120 and the ground conductors 130a and 130b than in Figure 2. The MEMS bridge 140 moves between the first and second positions due to electrostatic force.

[0103] Figure 4 shows a MEMS bridge 140 having a first conductive layer 162 comprising a first longitudinal conductive portion 162a and a second longitudinal conductive portion 162b, and five third longitudinal conductive portions 162c parallel to them.

[0104] Figure 5 shows the MEMS bridge 140 of Figure 4 with six slots 163 added that extend longitudinally along the MEMS bridge 140 in the same direction as the longitudinal conductive portions 162a, 162b, and 162c. The slots 163 form gaps within the MEMS bridge 140 because the slots pass through the first dielectric layer 161 and the first conductive layer 162. Figure 6 illustrates the MEMS bridge of Figure 5 in a plan view. As shown in Figure 6, the slots 163 form gaps within the MEMS bridge 160. Typically, although not visible in the plan view, the MEMS bridge 140 in Figure 6 also includes a first longitudinal conductive portion 162a along a first longitudinal edge 141, a second longitudinal conductive portion 162b along a second longitudinal edge 142, and a third longitudinal conductive portion 163c between the first longitudinal conductive portion 162a and the second longitudinal conductive portion 162b.

[0105] Figure 7 shows the MEMS bridge 140 of Figures 2 and 3 with six slots 163 added, consisting only of the first and second conductive portions 162a and 162b. It will be understood that the edges or anchors 150a and 150b of the variable capacitor region 160 are visible in the cross-section where the slots 163 are located. However, for clarity and illustrative purposes, these features are not illustrated.

[0106] Figure 8 shows a MEMS bridge 140 in plan view, having two slots 163. Typically not visible in plan view, the MEMS bridge 140 in Figure 8 also includes a first longitudinal conductive portion 162a along a first longitudinal edge 141 and a second longitudinal conductive portion 162b along a second longitudinal edge 142. The slots extend further longitudinally than the first longitudinal edge 141 and the second longitudinal edge 142 of the variable capacitor region 160.

[0107] Figure 9 shows the MEMS bridge 140 of Figure 1, wherein the substrate 110 comprises two pull-down substrate conductors 170a and 170b. The substrate 110 comprises a pull-down substrate conductor 170a between a first anchor 150a and a first ground conductor 130a, and a pull-down substrate conductor 170b between a second ground conductor 130b and a second anchor 150b. The MEMS bridge 140 comprises two operable conductors 180a and 180b. The MEMS bridge 140 comprises an operable conductor 180a between a first anchor 150a and a variable capacitor region 160. The MEMS bridge 140 comprises an operable conductor 180b between the variable capacitor region 160 and a second anchor 150b. Each operable conductor 180a, 180b is positioned on its respective pull-down substrate conductor 170a, 170b.

[0108] The electrostatic attraction that moves the MEMS bridge 140 between a first position and a second position is provided by applying a bias to the operable conductors 180a and 180b. The operable conductors 180a and 180b are selectively electrostatically attracted to the pull-down substrate conductors 170a and 170b.

[0109] Figure 10 shows the MEMS bridge 140 of Figure 9, in which the operable conductors 180a and 180b each have embedded portions 182a and 182b, respectively. Each embedded portion 182a and 182b extends within the variable capacitor region 160 between the first longitudinal conductive portion 162a and the second longitudinal conductive portion 162b. The embedded portions 182a and 182b are partially formed on the ground conductors 130a and 130b, respectively.

[0110] Figure 11 shows the MEMS bridge 140 of Figure 9, having slots 184 that extend longitudinally through each of the operable conductors 180a, 180b. The slots 184 also partially extend within the variable capacitor region 160.

[0111] Figure 12 shows the MEMS bridge 140 of Figure 10, which has slots 184 extending longitudinally through the embedded portions 182a and 182b of the operable conductors 180a and 180b, respectively.

[0112] Figure 13 shows a cross-section of the MEMS bridge 140 of Figure 9 along plane b at a first position where there is no electrostatic attraction between the pull-down substrate conductor 170a and the operable conductor 180a. Figure 14 shows a cross-section of Figure 13 where the MEMS bridge 140 is at a second position where there is an electrostatic attraction between the pull-down substrate conductor 170a and the operable conductor 180a, so the operable conductor 180a is pulled down toward the pull-down substrate conductor 170a.

[0113] Figure 15 shows a cross-section of the MEMS bridge 140 of Figure 9 along plane b, where the pull-down substrate conductor 170a has a dimple 175 on its upper surface. The MEMS bridge 140 is shown in a first position where there is no electrostatic attraction between the pull-down substrate conductor 170a and the operable conductor 180a. Figure 16 shows a cross-section of Figure 15, where the MEMS bridge 140 is in a second position where there is an electrostatic attraction between the pull-down substrate conductor 170a and the operable conductor 180a. When the MEMS bridge 140 is in the second position, the upper surface of the pull-down substrate conductor 170a is not in contact with the operable conductor 180a. This is because the operable conductor 180a is in contact with the dimple 175, which is located on top of the pull-down substrate conductor 170a.

[0114] Figure 17 shows a cross-section of the RF MEMS switch shown in Figure 1, with the signal conductor 120 along a plane a having a second dielectric layer 125. The second dielectric layer 125 is formed from a single pad. The MEMS bridge 140 is shown in a first position where there is no electrostatic attraction between the MEMS bridge 140 and the substrate 110. Figure 18 shows a cross-section of Figure 17, with the MEMS bridge 140 shown in a second position where there is an electrostatic attraction between the MEMS bridge 140 and the substrate 110. The upper surface of the signal conductor 120 is not in contact with the variable capacitor region 160 because the pad 125 is on top of the signal conductor 120 and the variable capacitor region is in contact with the pad 125.

[0115] Figure 19 shows a cross-sectional view of the MEMS bridge 140 taken along the second longitudinal edge 142. In Figure 19, the MEMS bridge 140 has opposing first and second transverse edges that form the end of the second longitudinal edge 142 and are connected to the substrate 110 by two anchors 150a and 150b, respectively. Figure 20 shows a cross-sectional view of the MEMS bridge 140 taken along the second longitudinal edge 142. In Figure 20, the MEMS bridge 140 has opposing first and second transverse edges that form the end of the second longitudinal edge 142. Only the first end is mechanically connected to the substrate 110 via one anchor 150a. Therefore, the MEMS bridge 140 in Figure 20 is cantilevered. Figure 21 shows a cross-sectional view of the MEMS bridge 140 taken along the second longitudinal edge 142. In Figure 21, the MEMS bridge 140 has opposing first and second transverse edges that form the end of a second longitudinal edge 142. Neither the first nor the second end is connected to an anchor. Instead, the central portion of the MEMS bridge 140 is connected to a central anchor 150c. The substrate 110 in Figure 21 also includes a second set of ground conductors 230a, 230b and a second signal conductor 220. The MEMS bridge 140 is attracted to either the first set of conductors (120, 130a, 130b) or the second set of conductors (220, 230a, 230b). The central anchor 150c acts as a pivot, and the RF MEMS switch 100 is a seesaw switch.

[0116] Figure 22 shows a simplified circuit diagram of the key capacitance in the MEMS bridge 140 from Figure 1. The simplified circuit diagram includes two separate parallel variable capacitance connections between the signal conductor and the ground conductor. The first longitudinal conductive portion 162a forms the first parallel variable capacitance connection 362a, and the second longitudinal conductive portion 162b forms the second parallel variable capacitance connection 362b. The top line represents the signal conductor 120. The bottom line represents the ground conductors 130a and 130b. Taking the first parallel variable capacitance connection 362a, the capacitance 311 is the capacitance between the center of the first longitudinal conductive portion 162a and the signal conductor 120. This capacitance is low when the MEMS bridge 140 (and therefore the variable capacitor region 160) is in the first position, but much higher when the MEMS bridge 140 is in the second position. Capacitors 312 and 313 are the capacitances between the edge of the first longitudinal conductive portion 162a and the ground conductors 130a and 130b. Again, when the bridge is in the second position, these capacitances increase significantly. Capacitors 312 and 313 are in parallel, and the capacitance of their combination is in series with capacitance 311.

[0117] With the second parallel variable capacitance connection 362b, capacitance 314 is the capacitance between the center of the second longitudinal conductive portion 162b and the signal conductor 120. This capacitance is low when the MEMS bridge 140 (and therefore the variable capacitor region 160) is in the first position, but is much higher when the MEMS bridge 140 is in the second position. Capacitors 315 and 316 are the capacitances between the edges of the longitudinal conductive portion 162b and the ground conductors 130a and 130b. Again, these capacitances increase significantly when the bridge is in the second position. Capacitors 315 and 316 are in parallel, and the capacitance of their combination is in series with capacitance 314.

[0118] Figures 23 and 24 illustrate cross-sections of RF switches according to prior art examples. The RF MEMS switch 2200 differs from the RF MEMS switch 100 of the present invention in that the MEMS bridge 2240 has a variable capacitor region 2260 including a first conductive layer 2262 continuous beneath the first dielectric layer 2261. The continuous first conductive layer 2262 covers the entire first dielectric layer 2261. The MEMS bridge 2240 is provided on a signal conductor 2220 supported on a substrate 2210. Figure 23 shows the MEMS bridge 2240 in a first position. Figure 24 shows the MEMS bridge 2240 in a second position. Due to the high stress difference between the first dielectric layer 2261 and the first conductive layer 2262, when the MEMS bridge 2240 is actuated from the first position to the second position, the MEMS bridge 2240 experiences transverse strain caused by the torques of the two layers 2261 and 2262, respectively. This transverse strain reduces the capacitance ratio between the up and down states of the MEMS bridge 2240 and the substrate 2210 compared to when the MEMS bridge 2240 is flat in the second position.

[0119] Figure 25 shows a MEMS bridge 140 having pads 125a on each of the ground conductors 130a, 130b and the signal conductor 120. Figure 26 shows the MEMS bridge 140 of Figure 25, with pads 125b of different sizes on each of the ground conductors 130a, 130b and the signal conductor 120. The MEMS bridges shown in Figures 25 and 26 are identical except for the size of the pads 125a and 125b. As shown, pad 125a is wider than pad 125b. Pad 125a causes a larger change in capacitance between the up and down states of the MEMS bridge than pad 125b. Since the total area under pad 125a is greater than the total area under pad 125b, the change in capacitance between the first and second positions of the MEMS bridge 140 in Figure 25 is greater than the change in capacitance between the first and second positions of the MEMS bridge 140 in Figure 26. In some embodiments, the MEMS bridges shown in Figures 25 and 26 are part of the circuit.

[0120] Figure 27 illustrates method 2600 according to the present invention. In particular, method 2700 is a method for manufacturing an RF MEMS switch as described above. As part of the manufacturing process, a substrate is provided (2710), and signal conductors and ground conductors on both sides of the substrate are provided on the surface of the substrate (2720). Next, a MEMS bridge including a variable capacitor region is provided on the substrate on the signal conductors and ground conductors (2730). The variable capacitor region of the MEMS bridge is formed by providing a first dielectric layer and a first conductive layer 2740. The first conductive layer is formed below the first dielectric layer and from at least two separate conductive portions. Specifically, the first conductive layer is provided by forming at least a first longitudinal conductive portion and a second longitudinal conductive portion that are spaced apart in a direction perpendicular to the longitudinal length of the MEMS bridge.

[0121] Method 2700 may also include further steps of the method, shown by the dashed lines in Figure 27. Step 2750 of the method describes a method (2750) for providing a first conductive layer having a first longitudinal conductive portion and a second longitudinal conductive portion. The first and second conductive portions are provided to extend along opposing longitudinal edges of the variable capacitor region, as shown in Figure 1, the first conductive portion 162a and the second conductive portion 162b.

[0122] Step 2760 of the method is another method (2760) for providing a first conductive layer having one or more third longitudinal conductive portions. These one or more third longitudinal conductive portions are provided so as to extend parallel between the first longitudinal conductive portion and the second longitudinal conductive portion, as shown in the third conductive portion 162c in Figure 4.

[0123] Method 2700 may include step (2770) of a method for providing one or more slots. The slots are provided so as to extend longitudinally along the MEMS bridge through both the first dielectric layer and the first conductive layer, as shown in slot 163 in Figure 5.

[0124] Method 2700 may include providing one or more pull-down substrate conductors and one or more operable conductors (2780). The pull-down substrate conductors are provided on the substrate and one or more operable conductors are provided on the MEMS bridge. One or more operable conductors are provided so as to extend over one or more pull-down substrate conductors between the anchor and the variable capacitor region. Step 2780 of the method of providing one or more operable conductors may, in some embodiments, include providing a recessed portion as shown in Figure 10.

[0125] Figure 28 illustrates Method 2800 according to the present invention. Method 2800 is a method for manufacturing a circuit having a plurality of RF MEMS switches, such as those shown in Figures 25 and 26. Method 2800 includes steps 2810 to 2840 of the method, which are the same as steps 2710 to 2740 of Method 2700 shown in Figure 27. Method 2800 includes step 2845 of the method, which includes providing a second dielectric layer by providing one or more pads on signal conductors and ground conductors, such as pads 125a, 125b shown in Figures 25 and 26.

[0126] The dimensions of the pads provided on the signal conductor and ground conductor are selected such that a desired change in capacitance is obtained when the MEMS bridge moves from a first position to a second position and from the second position to the first position. Thus, method 2800 includes selecting a desired change in capacitance that occurs when the MEMS bridge moves from a first position to a second position and from the second position to the first position 2855. Method 2800 also includes selecting the dimensions of one or more pads 2865 in accordance with the desired change in capacitance. Then, one or more pads are provided on the signal conductor and ground conductor having dimensions corresponding to the desired change in capacitance.

[0127] The above embodiment illustrates a shunt embodiment. However, the MEMS bridge is also useful in a series embodiment. A series of embodiments are shown in Figure 29, which illustrates a radio frequency (RF) micro-electromechanical (MEMS) switch 300 according to the present invention in a plan view. In addition, all of the above exemplary bridges are useful in a series configuration.

[0128] The RF MEMS switch 300 comprises a substrate 310 that serves as the base for the RF MEMS switch 300. The RF MEMS switch 300 comprises a first signal conductor 320a and a second signal conductor 320b. The MEMS bridge is generally indicated by reference number 340 and comprises a variable capacitor region 360. The variable capacitor region 360 has a first longitudinal edge 341 and a second longitudinal edge 342. The MEMS bridge 340 is connected to the substrate 310 by anchors 350a and 350b. The variable capacitor region 360 extends over the first signal conductor 320a and the second signal conductor 320b.

[0129] Figure 30 shows a plan view of a MEMS bridge 340 in a series of embodiments of a device having three slots 363. The slots 363 extend further longitudinally than the first longitudinal edge 341 and the second longitudinal edge 342 of the variable capacitor region 360.

Claims

1. A radio frequency (RF) micro-electromechanical system (MEMS) switch comprising a substrate, a first signal conductor on the substrate, ground conductors supported on both sides of the first signal conductor on the substrate, and a MEMS bridge, at least one end of which is mechanically connected to the substrate by at least one anchor, wherein the MEMS bridge comprises a variable capacitor region provided on the first signal conductor, comprising a first dielectric layer and a first conductive layer, the first conductive layer being positioned on the surface of the first dielectric layer facing the substrate, and the longitudinal length of the MEMS bridge An RF MEMS switch comprising: a MEMS bridge separated into at least a first longitudinal conductive portion and a second longitudinal conductive portion spaced apart in a direction perpendicular thereto, wherein the substrate comprises one or more pull-down substrate conductors, the MEMS bridge comprises one or more operable conductors located between the anchor and the variable capacitor region and provided on the one or more pull-down substrate conductors, at least one of the one or more operable conductors comprising an embedded portion extending longitudinally along the MEMS bridge and between the first longitudinal conductive portion and the second longitudinal conductive portion.

2. The RF MEMS switch according to claim 1, comprising the embedded portion, wherein the embedded portion extends between the first longitudinal conductive portion and the second longitudinal conductive portion without contacting them.

3. The RF MEMS switch according to claim 1 or 2, wherein the embedded portion is at least partially provided on the ground conductor.

4. The RF MEMS switch according to any one of claims 1 to 3, wherein the first longitudinal conductive portion and the second longitudinal conductive portion extend along opposing longitudinal edges of the variable capacitor region parallel to the longitudinal length of the MEMS bridge.

5. The RF MEMS switch according to any one of claims 1 to 4, wherein the first longitudinal conductive portion and the second longitudinal conductive portion are not electrically connected to each other.

6. The RF MEMS switch according to any one of claims 1 to 5, wherein the first longitudinal conductive portion and the second longitudinal conductive portion form a separate parallel variable capacitance connection between the first signal conductor and the ground conductor, and optionally the MEMS switch comprises a second signal conductor, wherein the first longitudinal conductive portion and the second longitudinal conductive portion form a separate parallel variable capacitance connection between the first signal conductor and the second signal conductor.

7. The RF MEM switch according to claim 6, having a series configuration and comprising the second signal conductor, wherein the first longitudinal conductive portion forms a first parallel variable capacitance connection including a plurality of capacitances, the second longitudinal conductive portion forms a second parallel variable capacitance connection including a plurality of capacitances, the first parallel variable capacitance connection includes a first capacitance between sections of the first longitudinal conductive portion provided on the first signal conductor, and the first parallel variable capacitance connection includes a second capacitance between sections of the first longitudinal conductive portion provided on the second signal conductor.

8. The RF MEMS switch according to any one of claims 1 to 7, wherein the first longitudinal conductive portion and the second longitudinal conductive portion each extend laterally across the MEMS bridge in a direction perpendicular to the longitudinal length of the MEMS bridge by less than one-third of the lateral width of the MEMS bridge.

9. The RF MEMS switch according to any one of claims 1 to 8, wherein the first conductive layer comprises one or more third longitudinal conductive portions extending parallel to the first longitudinal conductive portion and the second longitudinal conductive portion, and optionally each of the one or more third longitudinal conductive portions extends laterally across the MEMS bridge in a direction perpendicular to the longitudinal length of the MEMS bridge by less than 25% of the lateral width of the MEMS bridge.

10. The RF MEMS switch according to any one of claims 1 to 9, wherein the MEMS bridge comprises one or more slots extending longitudinally along the MEMS bridge, and the one or more slots extend through both the first dielectric layer and the first conductive layer.

11. The RF MEMS switch according to claim 10, wherein the one or more slots extend across the MEMS bridge in a direction perpendicular to the longitudinal length of the MEMS bridge, exceeding 20% ​​of the total lateral width of the MEMS bridge, and optionally, the one or more slots extend further longitudinally toward each end of the MEMS bridge beyond at least one longitudinal edge of the variable capacitor region.

12. The RF MEMS switch according to claim 10 or 11, wherein the lower surface of the MEMS bridge comprises a first longitudinal conductive portion and a second longitudinal conductive portion, and each longitudinal conductive portion provided along the longitudinal edge of the variable capacitor region further comprises an alternating pattern of slots and strips of the first dielectric layer.

13. The RF MEMS switch according to any one of claims 1 to 12, wherein at least one of the one or more operable conductors comprises one or more slots extending longitudinally along a portion of the MEMS bridge.

14. The RF MEMS switch according to any one of claims 1 to 13, wherein the RF MEMS switch comprises one or more dimples between one or more operable conductors and one or more pull-down substrate conductors.

15. The RF MEMS switch according to any one of claims 1 to 14, wherein the MEMS bridge comprises a second dielectric layer provided between the first conductive layer and the signal conductor, and the second dielectric layer is provided on at least one of the signal conductor and the first conductive layer.

16. The RF MEMS switch according to any one of claims 1 to 15, wherein the MEMS bridge is deformable by electrostatic force from a first position in which the variable capacitor portion is spaced apart from each of the signal conductors to a second position in which the variable capacitor region is closer to each of the signal conductors than the first position, and the capacitance between the variable capacitance region and the signal conductors is greater when the MEMS bridge is in the second position than when the MEMS bridge is in the first position.

17. The RF MEMS switch according to claim 16, as dependent on claim 15, wherein the second dielectric layer comprises one or more pads on at least one of the signal conductor and the ground conductor, the change in capacitance between the first position and the second position depends on the dimensions of the one or more pads, and optionally the electric dielectric constant of the one or more pads is greater than the relative permittivity of 1 normalized to air.

18. The RF MEMS switch according to claim 16 or 17, wherein when the MEMS bridge is in the second position, the stress ratio between the first conductive layer and the first dielectric layer is greater than 1:

1.

19. The RF MEMS switch according to any one of claims 1 to 18, wherein the first longitudinal conductive portion and the second longitudinal conductive portion have a longitudinal length of more than 400 microns.

20. The RF MEMS switch according to any one of claims 1 to 19, wherein the first longitudinal conductive portion and the second longitudinal conductive portion extend along the entire longitudinal edge of the variable capacitor region.

21. The RF MEMS switch is a capacitive switch, and The RF MEMS switch according to any one of claims 1 to 20, wherein the RF MEMS switch is configured to be used with an RF signal having a frequency greater than 10 GHz, or both.

22. The RF MEMS switch according to any one of claims 1 to 21, wherein the MEMS bridge is cantilevered and has one end mechanically connected to the substrate via one anchor, or the MEMS bridge has opposing first and second ends connected to the substrate by their respective anchors, or the RF MEMS switch is a seesaw switch in which the MEMS bridge is mechanically connected to the substrate via one anchor that functions as a pivot.

23. A method for manufacturing a radio frequency (RF) micro-electromechanical system (MEMS) switch according to any one of claims 1 to 22, the method comprising: providing a substrate; providing a first signal conductor supported on the substrate; providing ground conductors supported on both sides of the first signal conductor on the substrate; and providing a MEMS bridge having a variable capacitor region on the first signal conductor by providing a first dielectric layer and a first conductive layer, wherein the first conductive layer is provided on the surface of the first dielectric layer facing the substrate, and the MEMS bridge A method for manufacturing an RF MEMS switch, wherein the bridge is separated into at least a first longitudinal conductive portion and a second longitudinal conductive portion that are spaced apart in a direction perpendicular to the longitudinal length of the bridge, the method further includes providing one or more pull-down substrate conductors and one or more operable conductors extending over the one or more pull-down substrate conductors between the anchor and the variable capacitor region, the provision of the one or more operable conductors includes providing embedded portions that extend longitudinally along the MEMS bridge and between the first longitudinal conductive portion and the second longitudinal conductive portion.

24. A method for manufacturing an RF MEMS switch according to claim 23, wherein providing the first conductive layer includes providing a first longitudinal conductive portion and a second longitudinal conductive portion that extend along opposing longitudinal edges of the variable capacitor region parallel to the longitudinal length of the MEMS bridge.

25. A method for manufacturing an RF MEMS switch according to claim 23 or 24, wherein providing the first conductive layer includes providing one or more third longitudinal conductive portions that extend parallel between the first longitudinal conductive portion and the second longitudinal conductive portion.

26. A method for manufacturing an RF MEMS switch according to any one of claims 23 to 25, comprising providing one or more slots that extend longitudinally along the MEMS bridge and extend through both the first dielectric layer and the first conductive layer.

27. A circuit comprising a plurality of radio frequency (RF) micro-electromechanical system (MEMS) switches, the circuit comprising a substrate, signal conductors supported on the substrate, ground conductors supported on the substrate on both sides of the signal conductors, and a MEMS bridge, wherein at least one end of the MEMS bridge is mechanically connected to the substrate by at least one anchor, and the MEMS bridge comprises a variable capacitor region provided on the signal conductors and the ground conductors. The circuit comprises an RF MEMS bridge, wherein the MEMS bridge is deformable by electrostatic force from a first position in which the variable capacitor portion is spaced apart from the respective signal and ground conductors to a second position in which the variable capacitor region is closer to the respective signal and ground conductors than the first position, and the capacitance between the variable capacitance region and the signal conductor and the ground conductor is greater when the MEMS bridge is in the second position than when the MEMS bridge is in the first position, the variable capacitor region comprises a first dielectric layer and a first conductive layer, the first conductive layer is positioned on the surface of the first dielectric layer facing the substrate, the variable capacitor region further comprises a second dielectric layer provided between the first conductive layer and the signal conductor and the ground conductor, the second dielectric layer comprises one or more pads on the signal conductor and the ground conductor, the change in capacitance between the first position and the second position depends on the dimensions of the one or more pads, and the circuit comprises an RF MEMS switch comprising one or more pads of different dimensions, and therefore the RF The change in capacitance between the first and second positions of the MEMS switch is different in the circuit.

28. A method for manufacturing the circuit according to claim 27, comprising: providing a substrate; providing a signal conductor; providing ground conductors on both sides of the signal conductor supported by the substrate; and providing a MEMS bridge having a variable capacitor region on the signal conductor and the ground conductor by providing a first dielectric layer, a first conductive layer, and a second dielectric layer, wherein the first conductive layer provided on the surface of the first dielectric layer faces the substrate; the second dielectric layer is provided between the first conductive layer and the signal conductor and the ground conductor; providing the second dielectric layer comprises providing one or more pads on the signal conductor and the ground conductor; providing the one or more pads comprises selecting a change in capacitance between a first position and a second position; and selecting the dimensions of the one or more pads in accordance with the selected change in capacitance.

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