Folded spring based micro electromechanical (MEM) RF switch

• US 6,307,452 B1
• Filed: 09/16/1999
• Issued: 10/23/2001
• Est. Priority Date: 09/16/1999
• Status: Expired due to Term

• Current Assignee: North Star Innovations Inc. (Wi-LAN Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Sun, Xi-Qing
• Primary Examiner(s): Bettendorf, Justin P.
• Assistant Examiner(s): Takaoka, Dean O
• Application Number:
  US09/397,313
• Time in Patent Office: 768 Days
• Field of Search: 361/233, 333/101, 333/105, 333/262, 257/418
• US Class Current: 333/262
• CPC Class Codes: H01G 5/16 using variation of distance between electrodes
• CPC Class Codes: H01H 2001/0084 with perpendicular movement of the movable contact relative to the substrate
• CPC Class Codes: H01H 2059/0018 Special provisions for avoiding charge trapping, e.g. insulation layer between actuating electrodes being permanently polarised by charge trapping so that actuating or release voltage is altered
• 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 59/0009 making use of micromechanics
• CPC Class Codes: H01P 1/127 Strip line switches

Abstract

A micro electromechanical switch is formed on a substrate using a microplatform structure suspended on a spring suspension. The spring suspension is attached on one end to an anchor structure and extends in a substantially octagonal direction over a signal line. The microplatform has a shorting bar positioned facing a gap in the signal line and an electrical corset is formed on the signal fine to form a capacitor structure which is electrostatically attractable toward a bottom electrode upon application of a selected voltage. The switch functions from DC to at least 50 GHz with an electrical isolation of 35 dB and an insertion loss of 0.5 dB at 20 GHz. The RF switch has applications in telecommunications including wireless communications.

Claims

1. A micro electromechanical switch formed on a substrate comprising:

(a) an anchor structure, a bottom electrode, and at least one separate signal line formed on the substrate, the signal line having a gap forming an open circuit;

(b) a spring suspension attached on one end to the anchor structure and extending in a substantially orthogonal direction toward the bottom electrode, the spring suspension having a second end;

(c) a microplatform structure attached by four spring suspensions to a second end of the spring suspension and having a shorting bar formed on a portion remote form the spring suspension, the shorting bar positioned facing the gap in the signal line; and

(d) an electrical contact post formed on the signal line and positioned to face the shorting bar and forming a capacitor structure electrostatically attractable toward the bottom electrode upon selective application of a voltage on the shorting bar.

2. The micro electromechanical switch according to claim 1 wherein the microplatform is symmetrical.

3. The microelectromechanical switch according to claim 1 wherein the spring suspension comprises a single film comprising a metal layer.

4. The micro electromechanical switch according to claim 1 wherein the microplatform comprises an electrical insulation layer and an electrically conductive film.

5. The micro electromechanical switch according to claim 4 wherein the electrical insulation layer is formed of a dielectric material selected from the group consisting of silicon oxide, silicon nitride, silicon oxynitride, silicon carbide and mixtures thereof.

6. The microelectromechanical switch according to claim 4 wherein the electrically conductive film is formed of a material selected from the group consisting of tantalum silicide, tungsten, gold, platinum and mixtures thereof.

7. The micro electromechanical switch according to claim 1 wherein the substrate comprises an electrically isolated material selected from the group consisting of silicon, glass, gallium arsenide, ceramic, and printed circuits board.

8. The microelectromechanical switch according to claim 1 wherein the spring suspension comprises a composite film comprising an electrical insulation layer on bottom and an electrical conductive layer on top.

9. A microelectromechanical RF switch formed on a substrate comprising:

(a) an anchor structure, a bottom electrode, and at least one separate signal line formed on the substrate, the signal line having a gap forming an open circuit;

(b) a spring suspension attached on one end to the anchor structure and extending in a substantially orthogonal direction toward the bottom electrode, the spring suspension having a second end;

(c) a platform structure attached by four spring suspensions to a second end of the spring suspension and having a shorting bar formed on an end remote from the spring suspension, the shorting bar positioned facing the gap in the signal line; and

(d) an metal contact formed on the signal line and positioned to face the shorting bar and forming a capacitor structure; and

(e) a voltage selectively applied to the top electrode generating an electrostatic force attracting the capacitor structure toward the bottom electrode wherein, the metal contact on the microplatform closes the gap in the signal line.

10. The micro electromechanical RF switch according to claim 9 wherein the substrate comprises an electrically isolated material selected from the group consisting of silicon, glass, gallium arsenide, ceramic, and printed circuits board.

11. The micro electromechanical RF switch according to claim 9 wherein the microplatform is symmetrical.

12. The microelectromechanical RF witch according to claim 9 wherein the spring suspension comprises a composite film comprising an electrical insulation layer on bottom and an electrical conductive layer on top.

13. The micro electromechanical RF switch according to claim 9 wherein the microplatform comprises an electrical insulation layer and an electrically conductive film.

14. The micro electromechanical RF switch according to claim 13 wherein the electrical insulation layer is formed of a dielectric material selected from the group consisting of silicon oxide, silicon nitride, silicon oxynitride, silicon carbide and mixtures thereof.

15. The microelectromechanical RF switch according to claim 13 wherein the electrically conductive film is formed of a material selected from the group consisting of tantalum silicide, tungsten, gold, platinum and mixtures thereof.