Electrothermal self-latching MEMS switch and method

• US 6,882,264 B2
• Filed: 11/08/2002
• Issued: 04/19/2005
• Est. Priority Date: 11/09/2001
• Status: Expired due to Fees

• Current Assignee: WiSpry, Inc (AAC Technologies Holdings Inc.)
• Original Assignee: WiSpry, Inc (AAC Technologies Holdings Inc.)
• Inventors: Cunningham, Shawn Jay
• Primary Examiner(s): Vortman, Anatoly
• Application Number:
  US10/290,807
• Publication Number:
  US 20030117257A1
• Time in Patent Office: 893 Days
• Field of Search: 337/12, 337/14, 337/36, 337/139, 337/140, 337/141, 337/339, 337/343, 337/393, 337/298, 60527-529, 310306-309
• US Class Current: 337/139
• CPC Class Codes: B81B 2201/014 having a cantilever fixed on one side connected to one or more dimples
• CPC Class Codes: B81B 2201/018 Switches not provided for in B81B2201/014 - B81B2201/016
• CPC Class Codes: B81B 2203/0118 Cantilevers
• CPC Class Codes: B81B 2203/04 Electrodes
• CPC Class Codes: B81B 2207/07 Interconnects
• CPC Class Codes: B81B 3/0024 Transducers for transforming thermal into mechanical energy or vice versa, e.g. thermal or bimorph actuators electric motors using thermal effects H02N10/00
• CPC Class Codes: B81B 3/0051 For defining the movement, i.e. structures that guide or limit the movement of an element mechanical arrangements for preventing or damping vibration or shock H01H3/60
• CPC Class Codes: B81C 1/0015 Cantilevers switches using MEMS H01H1/0036; electrostatic relays using micromechanics H01H59/0009; microelectro-mechanical resonators H03H9/02244
• CPC Class Codes: B81C 2201/0107 Sacrificial metal
• CPC Class Codes: B81C 2201/0108 Sacrificial polymer, ashing of organics
• CPC Class Codes: B81C 2201/0109 Sacrificial layers not provided for in B81C2201/0107 - B81C2201/0108
• CPC Class Codes: H01H 1/04 Co-operating contacts of different material
• CPC Class Codes: H01H 1/504 by thermal means
• CPC Class Codes: H01H 2001/0042 Bistable switches, i.e. having two stable positions requiring only actuating energy for switching between them, e.g. with snap membrane or by permanent magnet
• CPC Class Codes: H01H 2001/0063 having electrostatic latches, i.e. the activated position is kept by electrostatic forces other than the activation force
• CPC Class Codes: H01H 2001/0089 Providing protection of elements to be released by etching of sacrificial element; Avoiding stiction problems, e.g. of movable element to substrate
• CPC Class Codes: H01H 2059/0072 with stoppers or protrusions for maintaining a gap, reducing the contact area or for preventing stiction between the movable and the fixed electrode in the attracted position
• CPC Class Codes: H01H 2061/006 Micromechanical thermal relay
• CPC Class Codes: H01H 59/0009 making use of micromechanics
• CPC Class Codes: H01H 61/04 wherein the thermally-sensitive member is only heated directly
• CPC Class Codes: H01L 23/3735 : Laminates or multilayers, e.g. direct bond copper ceramic substrates
• CPC Class Codes: H01L 23/522 : including external interconnections consisting of a multilayer structure of conductive and insulating layers inseparably formed on the semiconductor body
• CPC Class Codes: H01L 27/1203 : the substrate comprising an insulating body on a semiconductor body, e.g. SOI three-dimensional layout H01L27/0688
• CPC Class Codes: H01L 2924/00 : Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 : Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/09701 : Low temperature co-fired ceramic [LTCC]
• CPC Class Codes: H02N 1/006 : of the gap-closing type H02N1/004 takes precedence
• CPC Class Codes: H02N 10/00 : Electric motors using thermal effects motors using expansion or contraction of bodies due to heating or cooling F03G7/06
• CPC Class Codes: Y10T 29/49222 : forming array of contacts or terminals

Abstract

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.

Claims

1. A method for fabricating a self-latching microscale switch, the method comprising:

(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.