Micro-electromechanical system (MEMS) switch

Abstract

An electromechanical switch includes an actuation electrode, a cantilever electrode, a contact, a suspended conductor, and a signal line. The actuation electrode is mounted to a substrate, the cantilever electrode is suspended proximate to the actuation electrode, and the contact is mounted to the cantilever electrode. The suspended conductor is coupled to the contact and straddles a portion of the cantilever electrode. The signal line is positioned to form a closed circuit with the contact and the suspended conductor when an actuation voltage is applied between the actuation electrode and the cantilever electrode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified.

FIG. 1A is a schematic diagram illustrating a plan view of a micro-electromechanical system (“MEMS”) switch, in accordance with an embodiment of the invention.

FIG. 1B is a schematic diagram illustrating a cross-sectional view of a MEMS switch, in accordance with an embodiment of the invention.

FIG. 2A is a schematic diagram illustrating a plan view of a micro-electromechanical system (“MEMS”) switch, in accordance with an embodiment of the invention.

FIG. 2B is a schematic diagram illustrating a cross-sectional view of a MEMS switch illustrating a top stopper and excluding a conductive tether, in accordance with an embodiment of the invention.

FIG. 2C is a schematic diagram illustrating a cross-sectional view of a MEMS switch illustrating top stoppers and excluding a conductive tether, in accordance with an embodiment of the invention.

FIG. 3 is a flow chart illustrating a process of operation of a MEMS switch, in accordance with an embodiment of the invention.

FIG. 4A is a schematic diagram illustrating a first bending phase of a MEMS switch in an open circuit position, in accordance with an embodiment of the invention.

FIG. 4B is a schematic diagram illustrating a second bending phase of a MEMS switch in a closed circuit position, in accordance with an embodiment of the invention.

FIG. 5 illustrates line graphs of uni-polar voltage actuation and alternating polarity voltage actuation of a MEMS switch, in accordance with an embodiment of the invention.

FIG. 6 is a plan view illustrating a circuit layout of a MEMS switch including a conductive tether following an alternative path, in accordance with an embodiment of the invention.

FIG. 7 is a functional block diagram illustrating a demonstrative device implemented with a MEMS switch array, in accordance with an embodiment of the invention.

Claims

1. An apparatus, comprising: an actuation electrode mounted to a substrate;a cantilever electrode suspended proximate to the actuation electrode;a contact mounted to the cantilever electrode;a suspended conductor coupled to the contact and straddling a portion of the cantilever electrode; anda signal line positioned to form a closed circuit with the contact and the suspended conductor when an actuation voltage is applied between the actuation electrode and the cantilever electrode.

2. The apparatus of claim 1, further comprising a top stopper mounted to the substrate and straddling a portion of the cantilever electrode to prevent the cantilever electrode from bending away from the actuation electrode more than a fixed distance.

3. The apparatus of claim 2, wherein the top stopper is positioned to prevent the cantilever electrode from touching the suspended conductor.

4. The apparatus of claim 2, wherein the top stopper includes: a cap portion straddling a portion of the cantilever electrode, the cap portion positioned within a plane including the suspended conductor; anda stopper stub protruding from the cap portion towards the cantilever electrode to prevent the cantilever electrode from touching the suspended conductor.

5. The apparatus of claim 2, wherein the top stopper comprises a first top stopper and further comprising a second top stopper, the first and second top stoppers positioned on either side of the contact, both the first and second top stoppers positioned to restrain the cantilever electrode along an axis substantially passing through a contact mount mounting the contact to the cantilever electrode.

6. The apparatus of claim 1, further comprising an anchor mounted to the substrate, the anchor supporting the cantilever electrode at a first end, wherein the cantilever electrode is configured to progressively bend toward the actuation electrode, when the actuation voltage is applied, starting from a distal end of the cantilever electrode and moving toward the first end.

7. The apparatus of claim 6, wherein the cantilever electrode comprises polysilicon.

8. The apparatus of claim 7, wherein the cantilever electrode includes a plurality of stopper stubs protruding from an underside of the cantilever electrode, and wherein the actuation electrode includes a plurality of stopper butts disposed within the actuation electrode but electrically isolated from the actuation electrode, the stopper butts positioned to abut the stopper stubs when the cantilever electrode bends towards the actuation electrode to prevent the cantilever electrode from electrically contacting the actuation electrode when the actuation voltage is applied.

9. The apparatus of claim 6, further comprising another anchor, and wherein the cantilever electrode comprises two narrow members coupled to a plate member at first ends and mounted to the anchors at opposite ends.

10. The apparatus of claim 6, wherein the contact protrudes below the cantilever electrode between the anchor and a middle of the cantilever electrode, and wherein the cantilever electrode includes multiple spring constants, a first of the multiple spring constants to provide a first restoring force to open circuit the signal line with the contact when the actuation voltage is removed and a second of the multiple spring constants to provide a second restoring force smaller than the first restoring force to separate the distal end of the cantilever electrode from the actuation electrode after the actuation voltage is removed.

11. The apparatus of claim 10, wherein the suspended conductor provides a third restoring force asserted on the cantilever electrode via the contact, the third restoring force being smaller than the first restoring force.

12. The apparatus of claim 1, wherein the suspended conductor follows an indirect path over the cantilever electrode.

13. The apparatus of claim 1, wherein the apparatus comprises a micro-electromechanical system (“MEMS”) radio frequency switch.

14. A method of operating an electromechanical switch, comprising: propagating a signal along a signal line;applying an actuation voltage, between an actuation electrode and a cantilever electrode suspended proximate to the actuation electrode by an anchor, to progressively bend the cantilever electrode toward the actuation electrode starting from a distal end of the cantilever electrode and moving towards the anchor;close circuiting the signal line with a conductive tether straddling a portion of the cantilever electrode through a contact mounted to the actuation electrode while the actuation voltage is applied; andpropagating the signal between the signal line and the conductive tether through the contact.

15. The method of claim 14, wherein applying the actuation voltage to progressively bend the cantilever electrode toward the actuation electrode comprises electrostatically collapsing the cantilever electrode toward the actuation electrode with a zipper-like motion starting from the distal end and moving toward the anchor.

16. The method of claim 14, wherein the actuation voltage comprises a digital logic level voltage.

17. The method of claim 14, further comprising restraining the cantilever electrode from bending away from the actuation electrode more than a fixed distance, when the actuation voltage is not applied.

18. The method of claim 14, wherein the actuation voltage is applied between the actuation electrode and the cantilever electrode with alternating polarity between instances of close circuiting the signal line with the conductive tether, through the contact.

19. A system, comprising: an amplifier;an antenna; anda micro-electromechanical system (“MEMS”) switch coupled in series with the amplifier and the antenna, the MEMs switch including: an actuation electrode mounted to a substrate;a cantilever electrode suspended proximate to the actuation electrode;a contact mounted to the cantilever electrode;a suspend conductor coupled to the contact and straddling a portion of the cantilever electrode, the suspend conductor electrically coupled; anda signal line positioned to form a closed circuit with the contact and the suspended conductor when an actuation voltage is applied between the actuation electrode and the cantilever electrode.

20. The system of claim 19, wherein the MEMs switch further includes a top stopper mounted to the substrate and positioned to prevent the cantilever electrode from bending away from the actuation electrode more than a fixed distance.

21. The system of claim 20, wherein the cantilever electrode comprises polysilicon.

22. The system of claim 21, further comprising control logic coupled to generate the actuation voltage, wherein the control logic is configured to generate the actuation voltage having a logic level voltage used by logic elements of the control logic.