Source: http://www.google.com/patents/US6882264?ie=ISO-8859-1&dq=5,890,152
Timestamp: 2014-11-23 19:17:06
Document Index: 131640649

Matched Legal Cases: ['Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60']

Patent US6882264 - Electrothermal self-latching MEMS switch and method - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsElectrothermal Self-Latching MEMS Switch and Method. According to one embodiment, a microscale switch having a movable microcomponent is provided and includes a substrate having a stationary contact. The switch can also include a structural layer having a movable contact positioned for contacting the...http://www.google.com/patents/US6882264?utm_source=gb-gplus-sharePatent US6882264 - Electrothermal self-latching MEMS switch and methodAdvanced Patent SearchPublication numberUS6882264 B2Publication typeGrantApplication numberUS 10/290,807Publication dateApr 19, 2005Filing dateNov 8, 2002Priority dateNov 9, 2001Fee statusPaidAlso published asCN1292447C, CN1613128A, CN1613154A, CN1695233A, CN100474519C, CN100550429C, DE60215045D1, DE60215045T2, DE60217924D1, DE60217924T2, DE60222468D1, DE60222468T2, DE60229675D1, DE60230341D1, DE60232471D1, DE60238956D1, EP1454333A1, EP1454333A4, EP1454333B1, EP1454349A2, EP1454349A4, EP1454349B1, EP1461816A2, EP1461816A4, EP1461816B1, EP1717193A1, EP1717193B1, EP1717194A1, EP1717194B1, EP1717195A1, EP1717195B1, EP1721866A1, EP1721866B1, EP1760036A1, EP1760036B1, EP1760746A2, EP1760746A3, EP1760746B1, US6746891, US6847114, US6876047, US6876482, US6917086, US8264054, US8420427, US20030116417, US20030116848, US20030116851, US20030117257, US20030119221, US20040012298, US20040188785, US20040197960, US20070158775, WO2003040338A2, WO2003040338A3, WO2003041133A2, WO2003041133A3, WO2003042721A2, WO2003042721A3, WO2003043038A2, WO2003043038A3, WO2003043042A1, WO2003043044A1Publication number10290807, 290807, US 6882264 B2, US 6882264B2, US-B2-6882264, US6882264 B2, US6882264B2InventorsShawn Jay CunninghamOriginal AssigneeWispry, Inc.Export CitationBiBTeX, EndNote, RefManPatent Citations (12), Referenced by (20), Classifications (57), Legal Events (6) External Links: USPTO, USPTO Assignment, EspacenetElectrothermal self-latching MEMS switch and methodUS 6882264 B2Abstract Electrothermal Self-Latching MEMS Switch and Method. According to one embodiment, a microscale switch having a movable microcomponent is provided and includes a substrate having a stationary contact. The switch can also include a structural layer having a movable contact positioned for contacting the stationary contact when the structural layer moves toward the substrate. An electrothermal latch attached to the structural layer and having electrical communication with the movable contact to provide current flow between the electrothermal latch and the stationary contact when the movable contact contacts the stationary contact for maintaining the movable contact in contact with the stationary contact.
(a) depositing a first conductive layer on a substrate; (b) forming a stationary contact by removing a portion of the first conductive layer; (c) depositing a sacrificial layer on the stationary contact and the first conductive layer; (d) depositing a second conductive layer on the sacrificial layer; (e) forming a movable contact by removing a portion of the second conductive layer; (f) depositing a structural layer on the movable contact and the sacrificial layer; (g) forming a via through the structural layer to the movable contact; (h) depositing a third conductive layer on the structural layer and in the via; (i) removing a portion of the third conductive layer to form an electrothermal latch, wherein the electrothermal latch electrically communicates with the movable contact through the via; and (j) removing a sufficient amount of the sacrificial layer so as to define a first gap between the stationary contact and the movable contact. 2. A self-latching microscale switch having a movable microcomponent, the switch comprising:
(a) a substrate including a stationary contact; (b) a structural layer having a movable contact positioned for contacting the stationary contact when the structural layer moves toward the substrate; (c) an electrothermal latch attached to the structural layer and having electrical communication with the movable contact to provide current flow between the electrothermal latch and the stationary contact when the movable contact contacts the stationary contact for maintaining the movable contact in contact with the stationary contact; and (d) wherein the substrate further includes a stationary electrode and the structural layer further includes a movable electrode for moving the structural layer toward the substrate when a voltage difference is applied across the movable electrode and the stationary electrode. 3. A self-latching microscale switch having a movable microcomponent, the switch comprising:
(a) a substrate including a stationary contact; (b) a structural layer having a movable contact positioned for contacting the stationary contact when the structural layer moves toward the substrate; (c) an electrothermal latch attached to the structural layer and having electrical communication with the movable contact to provide current flow between the electrothermal latch and the stationary contact when the movable contact contacts the stationary contact for maintaining the movable contact in contact with the stationary contact; (d) wherein the substrate further includes a stationary electrode and the structural layer further includes a movable electrode for moving the structural layer toward the substrate when a voltage difference is applied across the movable electrode and the stationary electrode; and (e) wherein the movable electrode comprises a metal material. 4. A self-latching microscale switch having a movable microcomponent, the switch comprising:
(a) a substrate including a stationary contact; (b) a structural layer having a movable contact positioned for contacting the stationary contact when the structural layer moves toward the substrate; (c) an electrothermal latch attached to the structural layer and having electrical communication with the movable contact to provide current flow between the electrothermal latch and the stationary contact when the movable contact contacts the stationary contact for maintaining the movable contact in contact with the stationary contact; (d) wherein the substrate further includes a stationary electrode and the structural layer further includes a movable electrode for moving the structural layer toward the substrate when a voltage difference is applied across the movable electrode and the stationary electrode; and (e) wherein the movable electrode comprises a semiconductive material. 5. A self-latching microscale switch having a movable microcomponent, the switch comprising:
(a) a substrate including a stationary contact; (b) a structural layer having a movable contact positioned for contacting the stationary contact when the structural layer moves toward the substrate; (c) an electrothermal latch attached to the structural layer and having electrical communication with the movable contact to provide current flow between the electrothermal latch and the stationary contact when the movable contact contacts the stationary contact for maintaining the movable contact in contact with the stationary contact; (d) wherein the substrate further includes a stationary electrode and the structural layer further includes a movable electrode for moving the structural layer toward the substrate when a voltage difference is applied across the movable electrode and the stationary electrode; and (e) wherein the movable electrode substantially covers an underside of the structural layer. 6. A self-latching microscale switch having a movable microcomponent, the switch comprising:
(a) a substrate including a stationary contact; (b) a structural layer having a movable contact positioned for contacting the stationary contact when the structural layer moves toward the substrate; (c) an electrothermal latch attached to the structural layer and having electrical communication with the movable contact to provide current flow between the electrothermal latch and the stationary contact when the movable contact contacts the stationary contact for maintaining the movable contact in contact with the stationary contact; (d) wherein the substrate further includes a stationary electrode and the structural layer further includes a movable electrode for moving the structural layer toward the substrate when a voltage difference is applied across the movable electrode and the stationary electrode; and (e) an electrode interconnect attached to a top surface of the structural layer opposite from the movable electrode and having electrical communication with the movable electrode. 7. A self-latching microscale switch having a movable microcomponent, the switch comprising:
(a) a substrate including a stationary contact; (b) a structural layer having a movable contact positioned for contacting the stationary contact when the structural layer moves toward the substrate; (c) an electrothermal latch attached to the structural layer and having electrical communication with the movable contact to provide current flow between the electrothermal latch and the stationary contact when the movable contact contacts the stationary contact for maintaining the movable contact in contact with the stationary contact; (d) wherein the substrate further includes a stationary electrode and the structural layer further includes a movable electrode for moving the structural layer toward the substrate when a voltage difference is applied across the movable electrode and the stationary electrode; (e) an electrode interconnect attached to a surface of the structural layer opposite from the movable electrode and having electrical communication with the moveable electrode; and (f) wherein the movable electrode and electrode interconnect have substantially equal respective coefficients of thermal expansion. 8. A self-latching microscale switch having a movable microcomponent, the switch comprising:
(a) a substrate including a stationary contact; (b) a structural layer having a movable contact positioned for contacting the stationary contact when the structural layer moves toward the substrate; (c) an electrothermal latch attached to the structural layer and having electrical communication with the movable contact to provide current flow between the electrothermal latch and the stationary contact when the movable contact contacts the stationary contact for maintaining the movable contact in contact with the stationary contact; and (d) wherein the electrothermal latch includes first and second terminal ends for communication with a fixed contact for providing electrical communication between the fixed contact and the stationary contact when the movable contact touches the stationary contact. 9. A self-latching microscale switch having a movable microcomponent, the switch comprising:
(a) a substrate including a stationary contact; (b) a structural layer having a movable contact positioned for contacting the stationary contact when the structural layer moves toward the substrate; (c) an electrothermal latch attached to the structural layer and having electrical communication with the movable contact to provide current flow between the electrothermal latch and the stationary contact when the movable contact contacts the stationary contact for maintaining the movable contact in contact with the stationary contact; and (d) wherein the electrothermal latch is attached to a top side of the structural layer for producing heat on the top side of the dielectric layer to deflect the structural layer towards the substrate. 10. A self-latching microscale switch having a movable microcomponent, the switch comprising:
(a) a substrate including a stationary contact; (b) a structural layer having a movable contact positioned for contacting the stationary contact when the structural layer moves toward the substrate; (c) an electrothermal latch attached to the structural layer and having electrical communication with the movable contact to provide current flow between the electrothermal latch and the stationary contact when the movable contact contacts the stationary contact for maintaining the movable contact in contact with the stationary contact; and (d) wherein the electrothermal latch extends substantially the length of the structural layer. 11. A self-latching microscale switch having a movable microcomponent, the switch comprising:
(a) a substrate including a stationary contact; (b) a structural layer having a movable contact positioned for contacting the stationary contact when the structural layer moves toward the substrate; (c) an electrothermal latch attached to the structural layer and having electrical communication with the movable contact to provide current flow between the electrothermal latch and the stationary contact when the movable contact contacts the stationary contact for maintaining the movable contact in contact with the stationary contact; and (d) wherein the electrothermal latch includes at least one conductive path extending substantially the length of the structural layer. 12. A self-latching microscale switch having a movable microcomponent, the switch comprising:
(a) a substrate including a stationary contact; (b) a structural layer having a movable contact positioned for contacting the stationary contact when the structural layer moves toward the substrate; (c) an electrothermal latch attached to the structural layer and having electrical communication with the movable contact to provide current flow between the electrothermal latch and the stationary contact when the movable contact contacts the stationary contact for maintaining the movable contact in contact with the stationary contact; and (d) wherein the electrothermal latch includes two conductive paths extending substantially the length of the structural layer and along the outside of the top surface of the structural layer. 13. A self-latching microscale switch having a movable microcomponent, the switch comprising:
(a) a substrate including a stationary contact; (b) a structural layer having a movable contact positioned for contacting the stationary contact when the structural layer moves toward the substrate; (c) an electrothermal latch attached to the structural layer and having electrical communication with the movable contact to provide current flow between the electrothermal latch and the stationary contact when the movable contact contacts the stationary contact for maintaining the movable contact in contact with the stationary contact; and (d) wherein the electrothermal latch includes at least one resistance path transition effecting an abrupt change in electrical resistance for generating heat at the location of the resistance path transition. 14. A self-latching microscale switch having a movable microcomponent, the switch comprising:
(a) a substrate including a stationary contact; (b) a structural layer having a movable contact positioned for contacting the stationary contact when the structural layer moves toward the substrate; (c) an electrothermal latch attached to the structural layer and having electrical communication with the movable contact to provide current flow between the electrothermal latch and the stationary contact when the movable contact contacts the stationary contact for maintaining the movable contact in contact with the stationary contact; and (d) wherein the electrothermal latch includes at least one resistance path transition positioned adjacent the at least one fixed end for effecting an abrupt change in electrical resistance for generating heat adjacent the at least one fixed end. 15. A self-latching microscale switch having a movable microcomponent, the switch comprising:
(a) a substrate including a stationary contact; (b) a structural layer having a movable contact positioned for contacting the stationary contact when the structural layer moves toward the substrate; (c) an electrothermal latch attached to the structural layer and having electrical communication with the movable contact to provide current flow between the electrothermal latch and the stationary contact when the movable contact contacts the stationary contact for maintaining the movable contact in contact with the stationary contact; and (d) further including a contact interconnect attached on an opposite side of the dielectric layer from the movable contact and having electrical communication with the movable contact. 16. A self-latching microscale switch having a movable microcomponent, the switch comprising:
(a) a substrate including a stationary contact; (b) a structural layer having a movable contact positioned for contacting the stationary contact when the structural layer moves toward the substrate; (c) an electrothermal latch attached to the structural layer and having electrical communication with the movable contact to provide current flow between the electrothermal latch and the stationary contact when the movable contact contacts the stationary contact for maintaining the movable contact in contact with the stationary contact; and (d) further including a contact interconnect attached on an opposite side of the dielectric layer from the movable contact and having electrical communication with the movable contact; and (e) wherein the electrothermal latch is in electrical communication with the contact interconnect. 17. A method for maintaining a microscale switch in a closed position, the method comprising:
(a) providing a stationary contact formed on a substrate; (b) providing a movable microcomponent suspended above the substrate, the microcomponent comprising: (i) a structural layer having a movable contact positioned for contacting the stationary contact when the structural layer is moved towards the substrate; and (ii) an electrothermal latch attached to the structural layer and having electrical communication with the movable contact; (c) moving the structural layer towards the substrate whereby the movable contact moves into contact with the stationary contact; (d) providing current flow between the electrothermal latch and the stationary contact to maintain the movable contact in contact with the stationary contact; and (e) wherein the electrothermal latch is attached to a top side of the structural layer and produces heat on the top side of the dielectric layer to deflect the structural layer towards the substrate. 18. A method for maintaining a microscale switch in a closed position, the method comprising:
(a) providing a stationary contact formed on a substrate; (b) providing a movable microcomponent suspended above the substrate, the microcomponent comprising: (i) a structural layer having a movable contact positioned for contacting the stationary contact when the structural layer is moved towards the substrate; and (ii) an electrothermal latch attached to the structural layer and having electrical communication with the movable contact; (c) moving the structural layer towards the substrate whereby the movable contact moves into contact with the stationary contact; (d) providing current flow between the electrothermal latch and the stationary contact to maintain the movable contact in contact with the stationary contact; and (e) wherein the electrothermal latch includes at least one resistance path transition effecting an abrupt change in electrical resistance for generating heat at the location of the resistance path transition. 19. A method for maintaining a microscale switch in a closed position, the method comprising:
(a) providing a stationary contact formed on a substrate; (b) providing a movable microcomponent suspended above the substrate, the microcomponent comprising: (i) a structural layer having a movable contact positioned for contacting the stationary contact when the structural layer is moved towards the substrate; and (ii) an electrothermal latch attached to the structural layer and having electrical communication with the movable contact; (c) moving the structural layer towards the substrate whereby the movable contact moves into contact with the stationary contact; (d) providing current flow between the electrothermal latch and the stationary contact to maintain the movable contact in contact with the stationary contact; and (e) further including providing a stationary electrode formed on the substrate and a movable electrode attached to the structural layer, and wherein moving the structural layer includes applying a voltage difference between the movable electrode and the stationary electrode to move the structural layer towards the substrate. 20. A self-latching microscale switch having a movable microcomponent, the switch comprising:
(a) a substrate including a stationary contact and a stationary electrode; (b) a multi-layer beam extending at least partially over the substrate and comprising a structural layer and a moveable contact, the moveable contact adapted for movement between an open and a closed position, wherein the beam comprises at least two electrically connected layers and the beam adapted for electrostatic actuation to cause the movable contact to move from the open position, wherein the moveable contact is out of contact with the stationary contact, to the closed position, and wherein the movable contact is in contact with the stationary contact; and (c) a dielectric structural layer positioned at least partially between the two electrically connected layers.
CROSS-REFERENCE TO RELATED APPLICATIONS This nonprovisional application claims the benefit of U.S. Provisional Application No. 60/337,527, filed Nov. 9, 2001; U.S. Provisional Application No. 60/337,528, filed Nov. 9, 2001; U.S. Provisional Application No. 60/337,529, filed Nov. 9, 2001; U.S. Provisional Application No. 60/338,055, filed Nov. 9, 2001; U.S. Provisional Application No. 60/338,069, filed Nov. 9, 2001; U.S. Provisional Application No. 60/338,072, filed Nov. 9, 2001, the disclosures of which are incorporated by reference herein in their entirety. Additionally, the disclosures of the following U.S. Patent Applications, commonly assigned and simultaneously filed herewith, are all incorporated by reference herein in their entirety: U.S. Patent Applications entitled �MEMS Device Having a Trilayered Beam and Related Methods�; �Trilayered Beam MEMS Device and Related Methods�; �MEMS Device Having Contact and Standoff Bumps and Related Methods�; and �MEMS Device Having Electrothermal Actuation and Release and Method for Fabricating�.
TECHNICAL FIELD The present invention generally relates to micro-electro-mechanical systems (MEMS) devices and methods. More particularly, the present invention relates to the design and fabrication of movable MEMS microscale structures.
BACKGROUND ART An electrostatic MEMS switch is a switch operated by an electrostatic charge and manufactured using MEMS techniques. A MEMS switch can control electrical, mechanical, or optical signal flow. MEMS switches have typical application to telecommunications, such as DSL switch matrices and cell phones, Automated Testing Equipment (ATE), and other systems that require low cost switches or low-cost, high-density arrays.
Many current MEMS switch designs employ a cantilievered beam (or plate), or multiply-supported beam geometry for the switching structure. In the case of cantilevered beams, these MEMS switches include a movable, bimaterial beam comprising a structural layer of dielectric material and a layer of metal. Typically, the dielectric material is fixed at one end with respect to the substrate and provides structural support for the beam. The layer of metal is attached on the underside of the dielectric material and forms a movable electrode and a movable contact. The layer of metal can form part of the anchor. The movable beam is actuated in a direction toward the substrate by the application of a voltage difference across the electrode and another electrode attached to the surface of the substrate. The application of the voltage difference to the two electrodes creates an electrostatic field, which pulls the beam towards the substrate. The beam and substrate each have a contact which is separated by an air gap when no voltage is applied, wherein the switch is in the �open� position. When the voltage difference is applied, the beam is pulled to the substrate and the contacts make an electrical connection, wherein the switch is in the �closed� position.
One of the problems that faces current MEMS switches having a bimaterial beam is curling or other forms of static displacement or deformation of the beam. The static deformation can be caused by a stress mismatch or a stress gradient within the films. At some equilibrium temperature, the mismatch effects could be balanced to achieve a flat bimaterial structure, but this does not fix the temperature dependent effects. The mismatch could be balanced through specific processes (i.e., deposition rates, pressures, method, etc.), through material selection, and through geometrical parameters such as thickness. This bimaterial structure of metal and dielectric introduces a large variation in function over temperature, because the metal will typically have a higher thermal expansion rate than the dielectric. Because of the different states of static stress in the two materials, the switch can be deformed with a high degree of variability. Switch failure can result from deformation of the beam. Switch failure results when electrical contact is not established between the movable and stationary contacts due to static deformation or because of the deformation introduced as a function of temperature. A second mode of failure is observed when the movable contact and the stationary contact are prematurely closed, resulting in a �short�. Because of the deformation of the beam, the actuation voltage is increased or decreased depending on whether it is curved away from the substrate or towards the substrate, respectively. Because of this variability, the available voltage may not be adequate to achieve the desired contact force and, thus, contact resistance.
Typically, the beam of a MEMS switch is restored to an �open� position from a �closed� position by reducing the actuation voltage an amount sufficient for the resilient forces of the beam to deflect the beam back to the �open� position. The contacts of a MEMS switch frequently adhere to one another due metallurgical adhesion, cold welding, or hot welding forces. These forces are sometimes greater than the resilient forces of the beam, thus preventing the deflection of the beam to the �open� position. In such cases, switch failure results because the beam does not return to the �open� position. Therefore, it is desired to have a MEMS switch having a mechanism for generating a force to return the beam to an �open� position.
DISCLOSURE OF THE INVENTION According to one embodiment, a self-latching microscale switch having a movable microcomponent is provided. The switch can include a substrate having a stationary contact. The switch can also include a structural layer having a movable contact positioned for contacting the stationary contact when the structural layer moves toward the substrate. An electrothermal latch attached to the structural layer and having electrical communication with the movable contact to provide current flow between the electrothermal latch and the stationary contact when the movable contact contacts the stationary contact for maintaining the movable contact in contact with the stationary contact.
FIG. 1 illustrates a cross-sectional side view of a MEMS switch having electrothermal self-latching in an �open� position;
FIG. 4 illustrates a cross-sectional side view of an electrothermal self-latching MEMS switch in a �closed� position;
DETAILED DESCRIPTION OF THE INVENTION For purposes of the description herein, it is understood that when a component such as a layer or substrate is referred to as being �disposed on�, �attached to� or �formed on� another component, that component can be directly on the other component or, alternatively, intervening components (for example, one or more buffer or transition layers, interlayers, electrodes or contacts) can also be present. Furthermore, it is understood that the terms �disposed on�, �attached to� and �formed on� are used interchangeably to describe how a given component can be positioned or situated in relation to another component. Therefore, it will be understood that the terms �disposed on�, �attached to� and �formed on� do not introduce any limitations relating to particular methods of material transport, deposition, or fabrication.
Contacts, interconnects, conductive vias, electrothermal components and electrodes of various metals can be formed by sputtering, CVD, or evaporation. If gold, nickel or PERMALLOY� (NixFey) is employed as the metal element, an electroplating process can be carried out to transport the material to a desired surface. The chemical solutions used in the electroplating of various metals are generally known. Some metals, such as gold, might require an appropriate intermediate adhesion layer to prevent peeling. Examples of adhesion material often used include chromium, titanium, or an alloy such as titanium-tungsten (TiW). Some metal combinations can require a diffusion barrier to prevent a chromium adhesion layer from diffusing through gold. Examples of diffusion barriers between gold and chromium include platinum or nickel.
As used herein, the term �device� is interpreted to have a meaning interchangeable with the term �component.� As used herein, the term �conductive� is generally taken to encompass both conducting and semi-conducting materials.
Referring to FIGS. 1-5, different views of a MEMS switch, generally designated 100, having electrothermal self-latching are illustrated. Referring specifically to FIG. 1, a cross-sectional side view of MEMS switch, generally designated 100, is illustrated in an �open� position. MEMS switch 100 includes a substrate 102. Non-limiting examples of materials which substrate 102 can comprise include silicon (in single-crystal, polycrystalline, or amorphous forms), silicon oxinitride, glass, quartz, sapphire, zinc oxide, alumina, silica, or one of the various Group III-V compounds in either binary, ternary or quaternary forms (e.g., GaAs, InP, GaN, AlN, AlGaN, InGaAs, and so on). If the composition of substrate 102 is chosen to be a conductive or semi-conductive material, a non-conductive, dielectric layer can be deposited on the top surface of substrate 102, or at least on portions of the top surface where electrical contacts or conductive regions are desired.
MEMS switch 100 further comprises a movable, trilayered beam generally designated 108, suspended over stationary contact 104 and stationary electrode 106. Beam 108 is fixedly attached at one end to a mount 110, which can be fixedly attached to substrate 102. Beam 108 extends substantially parallel to the top surface of substrate 102 when MEMS switch 100 is in an �open� position. Beam 108 generally comprises a dielectric structural layer 112 sandwiched between two electrically conductive layers described in more detail below. Structural layer 112 can comprise a bendable, resilient material, preferably silicon oxide (SiO2, as it is sputtered, electroplated, spun-on, or otherwise deposited), to deflect towards substrate 102 for operating in a �closed� position. Structural layer 112 provides electrical isolation and desirable mechanical properties including resiliency properties. Alternatively, structural layer 112 can comprise silicon nitride (SixNy), silicon oxynitride, alumina or aluminum oxide (AlxOy), polymers, CVD diamond, their alloys, or any other suitable bendable, resilient materials known to those of skill in the art.
Electrodes 106 and 118, contacts 104 and 120, electrothermal latch 126, and interconnects 124 and 128 can comprise similar materials, such as gold, whereby the manufacturing process is simplified by the minimization of the number of different materials required for fabrication. Additionally, electrodes 106 and 118, contacts 104 and 120, electrothermal latch 126, and interconnects 124 and 128 can comprise conductors (platinum, aluminum, palladium, copper, tungsten, nickel, and other materials known to those of skill in the art), conductive oxides (indium tin oxide), and low resistivity semiconductors (silicon, polysilicon, and other materials known to those of skill in the art). These components can include adhesion layers (Cr, Ti, TiW, etc.) disposed between the component and structural material 112. These components can comprise a conductive material and an adhesion layer that includes diffusion barriers for preventing diffusion of the adhesion layer through the electrode material, the conductor material through the adhesion layer or into the structural material. These components can also comprise different materials for breakdown or arcing considerations, for �stiction� considerations during wet chemical processing, or because of fabrications process compatibility issues. Contacts 104 and 120 can comprise a material having good conductive properties and other desirable properties of suitable contacts known to those of skill in the art, such as low hardness and low wear. Preferably, contacts 104 and 120 comprise a material having low resistivity, low hardness, low oxidation, low wear, and other desirable properties of suitable contacts known to those of skill in the art. Preferably, electrothermal latch 126 comprises a material having high resistivity, high softening/melting point, and high current capacity. The preferred properties contribute to high localized heating for development of larger deflections and forces. The high softening/melting point and high current capacity increase the reliability of the device during electrothermal operation. In one embodiment, electrode interconnect 124, electrothermal latch 126, and contact interconnect 128 comprise the same material. Alternatively, electrode interconnect 124, electrothermal latch 126, and contact interconnect 128 can comprise different materials.
MEMS switch 100 provides a switching function that establishes an electrical connection between stationary contact 104 and a fixed contact (not shown) located at mount 110 when beam 108 is moved to a �closed� position. Conversely, when beam 108 is not in a �closed� position, there is no electrical connection between stationary contact 104 and the fixed contact. Movable contact 120 can be suspended over stationary contact 104 in a position such that it will contact stationary contact 104 when beam 108 is deflected to the �closed� position. Movable contact 120 and contact interconnect 128 are electrically connected through structural layer 112 by a second interconnect via 134 (shown with broken lines due to its position within structural layer 112). As stated above, contact interconnect 128 is connected to electrothermal latch 126, which is connected to the fixed contact. Thus, when switch 100 operates in the �closed� position, the fixed contact is provided electrical communication with stationary contact 104 through electrothermal latch 126, contact interconnect 128, second interconnect via 134, and movable contact 120. When switch 100 is not operating in the �closed� position, contacts 104 and 120 are separated by an air gap such that there is no electrical communication between stationary contact 104 and the fixed contact.
Movable contact 120 is dimensioned smaller than stationary contact 104 to facilitate contact when process and alignment variability are taken into consideration. Stationary contact 104 needs to be sized appropriately so that movable contact 120 always makes contact with stationary contact 104 when beam 108 is moved to the �closed� position. A second consideration that determines the size of movable contact 120 and stationary contact 104 is the parasitic response of switch 100. The parasitic actuation response is generated by electric fields produced by potential differences between contacts 104 and 120 that produce electric fields and a force on structural layer 112 which moves movable contact 120. The dimensions of contacts 104 and 120 are related to the dimensions of contact 104 and 120 for achieving a specific ratio of the parasitic actuation to the actuation voltage.
MEMS switch 100 includes an electrothermal self-latching function for maintaining beam 108 in the �closed� position without application of a voltage difference across electrodes 106 and 118. The electrothermal self-latching function operates when contacts 104 and 120 touch and current flows through movable contact 120, first interconnect via 130, contact interconnect 128, and electrothermal latch 126. Electrothermal latch 126 includes resistance path transitions (shown in FIG. 2) for providing an abrupt change in the density of current flow through electrothermal latch 126. Alternatively, the resistance path transition can be realized by a change in thickness rather than a change in width. Alternatively, electrothermal latch 126 can comprise material transitions rather than area transitions to accomplish the resistance path transitions. The material transitions are realized by patterning different materials on either side of the resistance path transition. For example, nickel (Ni) and gold (Au) can be patterned on a first and second side of the resistance path transition. Two different suitable materials having differing thermal and mechanical properties as known to those of skill in the art can be used to form the resistance path transition. The magnitude of the localized heating is determined by the difference in the geometric or material properties. The magnitude of the current density introduces a local temperature gradient on top of the structural layer 112 for elongating the top portion of structural layer 112, thereby increasing the deflection force of beam 108 for pressing together contacts 104 and 120. Beam 108 is �unlatched� when current flow through electrothermal latch 126 is reduced sufficiently such that the resilient force of structural layer 112 overcomes the electrothermal force for restoring beam to the �open� position. Once the contact between contacts 104 and 120 is broken such that beam 108 is not in the �closed� position, beam 108 will deflect to the �open� position.
The self-latching function of MEMS switch 100 is advantageous because it provides a force sufficient to maintain beam 108 in the �closed� position without application of a voltage difference by voltage source 130. Power requirements are reduced because the application of voltage is not required. Additionally, the self-latching function is advantageous because it can reduce the likelihood of welding between contacts 104 and 120. The likelihood of welding is reduced because the contact resistance between contacts 104 and 120 improves due to electrothermal forces. The electrothermal force deflecting structural layer 112 to substrate 102 increases as current flow through electrothermal latch 126 increases, thus improving the contact established between contacts 104 and 120 and reducing the contact resistance between contacts 104 and 120. Because contact resistance decreases with increased contact force, the electrothermal force will provide a switch having lower contact resistance. The lower contact resistance will result in a reduced contact temperature which will reduce the likelihood of welding.
Upon the application of sufficient voltage by voltage source 130, beam 108 moves toward substrate 102 in a stable manner until movable electrode 118 is close enough to stationary electrode 106 for �pull-in� voltage, or �snap-in� voltage, to occur. After �pull-in� voltage occurs, beam 108 is pulled in an unstable manner towards substrate 102 until movable contact 120 touches stationary contact 104, thus establishing an electrical connection. Referring to FIG. 4, a cross-sectional side view of MEMS switch 100 is illustrated in a �closed� position wherein an electrical connection has been established. As shown in the �closed� position, movable contact 120 is touching stationary contact 104. As described below, the components of MEMS switch 100 are dimensioned such that movable electrode 118 does not contact stationary electrode 106 in the �closed� position, thus preventing a short between components 106 and 118. MEMS switch 100 can be maintained in a �closed� position by the electrothermal actuation of electrothermal latch 126. The application of a voltage difference across electrodes 106 and 118 is not required to maintain beam 108 in the �closed� position.
In the �open� position, movable contact 120 is separated from stationary contact 104 by a gap distance a 138 as shown in FIG. 1. Movable electrode 118 is separated from stationary electrode 106 by a gap distance b 140. In this embodiment, distance a 138 is less than distance b 140. If distance a 138 is less than distance b 140, the operation of MEMS switch 100 is more reliable because potential for shorting between stationary electrode 106 and movable electrode 118 is reduced. The length of beam 108 is indicated by a distance c 142. The center of movable contact 120 is a distance d 144 from mount 110 and a distance e 146 from the end of beam 108 that is distal mount 110. The edge of electrode interconnect 124 distal mount 110 is a distance f 148 from mount 110. The edge of electrode interconnect 124 near mount 110 is a distance g 150 from mount 110. In this embodiment, distance a 138 is nominally 1.5 microns; distance b 140 is preferably 2 microns; distance c 142 is preferably 155 microns; distance d 144 is preferably 135 microns; distance e 146 is preferably 20 microns; distance f 148 is preferably 105 microns; and distance g 150 is 10 microns. The distances a 138, b 140, c 142, d 144, e 146, f 148, and g 150 provide desirable functional performance, but other dimensions can be selected to optimize other functional characteristics, manufacturability, and reliability.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS4423401 *Jul 21, 1982Dec 27, 1983Tektronix, Inc.Thin-film electrothermal deviceUS5619177 *Jan 27, 1995Apr 8, 1997Mjb CompanyShape memory alloy microactuator having an electrostatic force and heating meansUS5796152Jan 24, 1997Aug 18, 1998Roxburgh Ltd.Cantilevered microstructureUS5824186Jun 7, 1995Oct 20, 1998The Regents Of The University Of CaliforniaMethod and apparatus for fabricating self-assembling microstructuresUS6046659 *May 15, 1998Apr 4, 2000Hughes Electronics CorporationDesign and fabrication of broadband surface-micromachined micro-electro-mechanical switches for microwave and millimeter-wave applicationsUS6236300 *Mar 26, 1999May 22, 2001R. Sjhon MinnersBistable micro-switch and method of manufacturing the sameUS6316278Mar 16, 1999Nov 13, 2001Alien Technology CorporationMethods for fabricating a multiple modular assemblyUS6324748Jan 19, 1999Dec 4, 2001Jds Uniphase CorporationMethod of fabricating a microelectro mechanical structure having an arched beamUS6348851 *Aug 13, 1999Feb 19, 2002Renata A.G.Breaker switch and battery including the sameUS6367251 *Apr 5, 2000Apr 9, 2002Jds Uniphase CorporationLockable microelectromechanical actuators using thermoplastic material, and methods of operating sameUS6531947 *Sep 12, 2000Mar 11, 20033M Innovative Properties CompanyDirect acting vertical thermal actuator with controlled bendingUS20030048170 *Aug 31, 2001Mar 13, 2003Susan BromleyThermally activated latch* Cited by examinerReferenced byCiting PatentFiling datePublication dateApplicantTitleUS7142087 *Jan 27, 2004Nov 28, 2006Lucent Technologies Inc.Micromechanical latching switchUS7332980Sep 22, 2005Feb 19, 2008Samsung Electronics Co., Ltd.System and method for a digitally tunable impedance matching networkUS7520790Sep 14, 2004Apr 21, 2009Semiconductor Energy Laboratory Co., Ltd.Display device and manufacturing method of display deviceUS7671693Apr 14, 2006Mar 2, 2010Samsung Electronics Co., Ltd.System and method for a tunable impedance matching networkUS7675393 *Feb 12, 2007Mar 9, 2010Kabushiki Kaisha ToshibaMEMS switchUS8026773Feb 19, 2008Sep 27, 2011Samsung Electronics Co., Ltd.System and method for a digitally tunable impedance matching networkUS8044574Mar 18, 2009Oct 25, 2011Semiconductor Energy Laboratory Co., Ltd.Display device and manufacturing method of display deviceUS8066462 *Dec 12, 2006Nov 29, 2011Telezygology, Inc.Development in beam type fastenersUS8154378 *Aug 10, 2007Apr 10, 2012Alcatel LucentThermal actuator for a MEMS-based relay switchUS8264054 *Nov 8, 2002Sep 11, 2012Wispry, Inc.MEMS device having electrothermal actuation and release and method for fabricatingUS8362693Oct 20, 2011Jan 29, 2013Semiconductor Energy Laboratory Co., Ltd.Display device and manufacturing method of display deviceUS8420427Jul 25, 2006Apr 16, 2013Wispry, Inc.Methods for implementation of a switching function in a microscale device and for fabrication of a microscale switchUS8458888Dec 20, 2010Jun 11, 2013International Business Machines CorporationMethod of manufacturing a micro-electro-mechanical system (MEMS)US8685778Dec 20, 2010Apr 1, 2014International Business Machines CorporationPlanar cavity MEMS and related structures, methods of manufacture and design structuresUS8709264Dec 20, 2010Apr 29, 2014International Business Machines CorporationPlanar cavity MEMS and related structures, methods of manufacture and design structuresUS8722445Dec 20, 2010May 13, 2014International Business Machines CorporationPlanar cavity MEMS and related structures, methods of manufacture and design structuresUS8779886 *Nov 30, 2009Jul 15, 2014General Electric CompanySwitch structuresUS20110012703 *Jul 19, 2010Jan 20, 2011Reseaux Mems, Societe En CommanditeMems actuators and switchesUS20110063068 *Jun 30, 2010Mar 17, 2011The George Washington UniversityThermally actuated rf microelectromechanical systems switchUS20120174572 *Jan 9, 2012Jul 12, 2012Donato ClausiMethod for mechanical and electrical integration of sma wires to microsystems* Cited by examinerClassifications U.S. Classification337/139, 60/528, 310/307, 337/12, 257/E27.112, 60/529, 337/36, 337/14International ClassificationH01L21/302, H01L23/522, H02N1/00, H01L23/373, B81B7/00, H01L29/86, B81B3/00, H01H59/00, H02N10/00, H01H61/04, H01H1/50, H01H1/04, H01L27/12Cooperative ClassificationH01H1/504, H01L2924/09701, H01H2061/006, B81B2201/014, H01H1/04, B81B2201/018, B81C2201/0108, H01H2001/0042, H01H2059/0072, B81B3/0051, H02N1/006, H01H61/04, B81B2203/0118, H01L23/3735, B81C2201/0109, B81C1/0015, H01H2001/0063, H01H2001/0089, B81B3/0024, H01L23/522, B81B2207/07, H02N10/00, B81B2203/04, H01H59/0009, H01L27/1203, B81C2201/0107, H01L2924/0002European ClassificationH01L23/373L, B81B3/00K6, B81B3/00H4, H02N1/00B2, B81C1/00C4C, H01L23/522, H01H61/04, H01H59/00B, H02N10/00Legal EventsDateCodeEventDescriptionMay 29, 2014ASAssignmentFree format text: RELEASE OF SECURITY INTEREST;ASSIGNOR:VENTURE LENDING & LEASING IV, INC.;REEL/FRAME:033062/0059Owner name: WISPRY, INC., CALIFORNIAEffective date: 20140228Mar 26, 2014ASAssignmentFree format text: RELEASE BY SECURED PARTY;ASSIGNOR:VENTURE LENDING & LEASING IV, INC.;REEL/FRAME:032527/0950Owner name: WISPRY, INC., CALIFORNIAEffective date: 20140228Oct 17, 2012FPAYFee paymentYear of fee payment: 8May 30, 2008FPAYFee paymentYear of fee payment: 4Oct 6, 2006ASAssignmentOwner name: VENTURE LENDING & LEASING IV, INC., CALIFORNIAFree format text: SECURITY AGREEMENT;ASSIGNOR:WISPRY, INC.;REEL/FRAME:022482/0236Effective date: 20060831Oct 15, 2004ASAssignmentOwner name: WISPRY, INC., CALIFORNIAFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:COVENTOR, INC.;REEL/FRAME:015249/0852Effective date: 20041007Owner name: WISPRY, INC. 7 CORPORATE PARK, SUITE 260IRVINE, CAFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:COVENTOR, INC. /AR;REEL/FRAME:015249/0852RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services©2012 Google