The present invention is generally related to electrical power switching arrays, and, more particularly, to a micro-electromechanical systems (MEMS) switching array, and, even more particularly, to a MEMS switching array having one or more substrates configured with current-conduction functionality, such as may be suitable to improved packing density and/or flexible interconnectivity for the array components.
It is known to connect MEMS switches to form a switching array. An array of switches may be needed because a single MEMS switch may not be capable of either conducting enough current, and/or holding off enough voltage, as may be required for a given switching application.
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In view of the foregoing considerations, it is desirable to provide an improved MEMS switching array that avoids or reduces the drawbacks discussed above.
In one example embodiment thereof, aspects of the present invention are directed to a micro-electromechanical systems (MEMS) switch. The switch may include a first substrate including at least an electrically conductive substrate region. An electrical isolation layer may be disposed on a first surface of the substrate. A substrate contact is electrically coupled to a movable actuator and the electrically conductive region of the first substrate so that a flow of electrical current being switched is established during an electrically-closed condition of the switch. The electrically conductive substrate region of the first substrate defines an electrically conductive path for the flow of electrical current.
In another aspect thereof, a micro-electromechanical systems (MEMS) switch array is provided. A first substrate includes at least an electrically conductive substrate region shared by at least some of the MEMS switch array. An electrical isolation layer may be disposed over a first surface of the first substrate. A plurality of movable actuators is provided. At least one substrate contact is electrically coupled to at least one of the plurality of movable actuators and the electrically conductive region of the first substrate so that a flow of electrical current being switched is established during an electrically-closed condition of the MEMS switch array. The electrically conductive region of the first substrate defines an electrically conductive path for the flow of electrical current.
In yet another aspect thereof, a micro-electromechanical systems (MEMS) switch array is provided. A carrier substrate includes at least an electrically conductive substrate region shared by at least some of the MEMS switch array. An electrical isolation layer may be disposed over a first surface of the carrier substrate. A plurality of movable actuators is provided. At least one substrate contact is electrically coupled to at least one of the plurality of movable actuators so that a flow of electrical current being switched is established during an electrically-closed condition of the MEMS switch array. A cover substrate includes at least an electrically conductive substrate region. The electrically conductive region of the carrier substrate is electrically coupled by way of an interface contact to the electrically conductive region of the cover substrate to define an electrically conductive path for the flow of electrical current during the electrically-closed condition of the switching array.
In accordance with aspects of the present invention, structural and/or operational relationships are described herein, as may be used to establish current flow through a respective thickness of one or more substrates, such as a carrier substrate, or a capping substrate, or both, in a switching array based on micro-electromechanical systems (MEMS) switches. The current flow though the one or more substrates advantageously allows eliminating at least some (or essentially all) of the conductive traces and pads generally constructed on a common surface of the substrate, e.g., a top surface of the substrate. This reduction or elimination of conductive traces and pads is conducive to improving the beam packing density and/or the interconnectivity of a MEMS switching array embodying aspects of the present invention.
Presently, micro-electromechanical systems (MEMS) generally refer to micron-scale structures that for example can integrate a multiplicity of elements, e.g., mechanical elements, electromechanical elements, sensors, actuators, and electronics, on a common substrate through micro-fabrication technology. It is contemplated, however, that many techniques and structures presently available in MEMS devices will in just a few years be available via nanotechnology-based devices, e.g., structures that may be smaller than 100 nanometers in size. Accordingly, even though example embodiments described throughout this document may refer to MEMS-based devices, it is submitted that the inventive aspects of the present invention should be broadly construed and should not be limited to micron-sized devices.
In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of various embodiments of the present invention. However, those skilled in the art will understand that embodiments of the present invention may be practiced without these specific details, that the present invention is not limited to the depicted embodiments, and that the present invention may be practiced in a variety of alternative embodiments. In other instances, well known methods, procedures, and components have not been described in detail.
Furthermore, various operations may be described as multiple discrete steps performed in a manner that is helpful for understanding embodiments of the present invention. However, the order of description should not be construed as to imply that these operations need be performed in the order they are presented, nor that they are even order dependent. Moreover, repeated usage of the phrase “in one embodiment” does not necessarily refer to the same embodiment, although it may. The terms “comprising”, “including”, “having”, and the like, as used in the present application, are intended to be synonymous unless otherwise indicated.
The adjectives “top” and “bottom” may be used for ease of description, e.g., in reference to the drawings; however, use of such adjectives should not be construed as suggestive of spatial limitations. For example, in a practical embodiment, structural features and/or components of the switching array may be arranged partly in one orientation and partly in another. To avoid linguistic constraints, the adjectives “first” and “second” may be used in lieu of the adjectives “top” and “bottom”, although the terms “first” and “second” could also be used in an ordinal sense.
First substrate 22 may be electrically-conductive, as may be formed from a sufficiently doped semiconductor material, such as silicon and germanium, so that the semiconductor behaves as a conductor rather than a semiconductor (a so-called degenerate semiconductor). In one alternate example embodiment, first substrate 22 may be a metallic substrate. An electrical isolation layer 24 may be disposed on a first surface (e.g., a top surface) of first substrate 22. Electrical isolation layer 24 may be formed from silicon nitride, silicon oxide and aluminum oxide. A movable actuator 26 (often referred to as a beam) is provided.
A substrate contact 28 is electrically coupled (ohmic contact) to movable actuator 26 and first substrate 22 so that a flow of electrical current (schematically represented by solid line 30) is established during the electrically-closed condition of the switch. For example, an anchor 48 of MEMS switch 20 may be electrically coupled to a conductive trace (not shown) to receive electrical current to be switched by MEMS switch 20. Arrows 31, in opposite direction to the arrows shown on line 30, are used to symbolically indicate that the current flow may be bidirectional. For example, in one example application the current being switched may flow through movable actuator 26 through contact 28 and downwardly through first substrate 22 and on to an external electrical load (not shown). In another example application, the current may flow upwardly through first substrate 22 to contact 28 and on to movable actuator 26.
Movable actuator 26 may be caused to move toward contact 28 by the influence of a control electrode 29 (also referred to as a gate) positioned on isolation layer 24 below movable actuator 26. As would be appreciated by those skilled in the art, movable actuator 26 may be a flexible beam that bends under applied forces such as electrostatic attraction, magnetic attraction and repulsion, or thermally induced differential expansion, that closes a gap between a free end of the beam and contact 28.
In accordance with aspects of the present invention, first substrate 22 may define an electrically conductive path in the substrate for the flow of electrical current. An interface layer 32, as may be configured to provide ohmic contact to first substrate 22, may be disposed on a second surface (e.g., a bottom surface) of first substrate 22. In one embodiment, the second surface of the substrate is positioned opposite the first surface of the substrate. In the example case of a metallic substrate, interface layer 32 may not be needed since the ohmic contact functionality provided by interface layer 32 may be directly provided by the bottom surface of such a metallic substrate.
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It will be appreciated that the entire substrate 22 need not be an electrically-conductive substrate since, for example, it is contemplated that just a respective substrate region, such as beneath substrate contact 28 and extending across the thickness of the substrate, may be arranged to be electrically conductive. Accordingly, in one example embodiment one can engineer substrate 22 to include a region having a relatively high doping (e.g., the electrically-conductive region beneath substrate contact 28 and through the thickness of the substrate). As described in greater detail below, it will be appreciated that the electrically conductive path provided by first substrate 22 need not be limited to the example arrangement shown in
In one example embodiment, conductive traces 40 and pads 42 located on the top surface of the substrate may be arranged as respective input paths to the current flow, and interface layer 32 (
By way of example, the through-thickness current flow that is established in the electrically conductive substrate advantageously allows to reduce approximately by one-half the structural features (conductive traces and/or pads) previously used on the top surface of the substrate for passing input/output current in the switching array. For comparative purposes, a simple visual comparison of
The description below builds on the concepts described so far in the example context of a first substrate (e.g., a carrier substrate). More particularly, the description below illustrates example embodiments conducive to a MEMS switching array, where a MEMS carrier substrate is arranged with a second substrate (e.g., a capping or cover substrate). For readers desirous of general background information in connection with sealing and packaging of MEMS devices, as may use a carrier substrate and a capping substrate, reference is made to U.S. Pat. No. 7,605,466 commonly assigned to the same assignee of the present invention and herein incorporated by reference.
In accordance with aspects of the present invention, first substrate 22 and second substrate 50 cooperate to jointly define an electrically conductive path for the flow of electrical current (schematically represented by solid line 56), which advantageously allows to eliminate essentially all input/output pads 16, 18 and metal traces 14, 17, (
In accordance with further aspects of the present invention, one may flexibly route gating line 64 to actuate any desired combination of series and/or parallel circuit interconnections of the MEMS switches of the switching array. That is, being that the example embodiment shown in
A non-limiting example application of a MEMS switch array embodying aspects of the present invention may be an alternating current (AC) power switch, where the frequency value of the current being switched comprises a power line frequency, such as 60 Hz or 50 Hz (e.g., a relatively low-frequency, non-radio frequency). Another example application of a MEMS switch array embodying aspects of the present invention may be a direct current (DC) power switch.
It is noted that such power-switching applications may particularly benefit from a MEMS switch array embodying aspects of the present invention. For example, each of the electrically conductive paths in the substrate carries a portion of the overall current being switched by the MEMS switch array. The through-thickness conductivity in the substrate should not be analogized to vertical vias structures commonly constructed in a substrate, where such vias structures are typically electrically isolated from one another to provide signal isolation to the signals carried by such vias. In accordance with aspects of the present invention, no such signal isolation is required being that the electrically conductive paths in the substrate each carries a respective portion of the overall current being switched by the MEMS switch array.
While various embodiments of the present invention have been shown and described herein, it will be understood that such embodiments are provided by way of example only. Numerous variations, changes and substitutions may be made without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.