High Q-large tuning range micro-electro mechanical system (MEMS) varactor for broadband applications

• US 6,635,919 B1
• Filed: 08/17/2000
• Issued: 10/21/2003
• Est. Priority Date: 08/17/2000
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Williams, Byron, Lin, Tsen-Hwang, Melendez, Jose L.
• Primary Examiner(s): Loke, Steven
• Assistant Examiner(s): Kang, Donghee
• Application Number:
  US09/640,410
• Time in Patent Office: 1,160 Days
• Field of Search: 438/379, 438/50, 438/52, 438/53, 257/312, 257/595, 257/600, 257/602, 257/618, 257/619, 257/621, 200/181, 200/600, 333/101, 333/108, 333/262, 737/15, 737/18, 737/24, 361/277, 361/278, 361/280, 361/281
• US Class Current: 257/312
• CPC Class Codes: H01G 5/16 using variation of distance between electrodes

Abstract

A Micro Electro-Mechanical System (MEMS) varactor (100, 200) having a bottom electrode (116) formed over a substrate (112) and a dielectric material (130) disposed over the bottom electrode (116). A pull-down electrode (122) is formed over spacer (120) and the dielectric material (130). The MEMS varactor (100, 200) is adapted to operate in a stiction mode, with at least a portion of pull-down electrode (122) in contact with dielectric material (130). The MEMS varactor (100, 200) has a high Q, large tuning range, and high sensitivity.

Claims

1. A Micro Electro-Mechanical System (MEMS) varactor, comprising:

a bottom electrode formed over a substrate;

a dielectric material disposed over said bottom electrode;

a spacer Proximate said bottom electrode; and

a pull-down electrode over said spacer and said dielectric material, wherein said MEMS varactor is adapted to operate in a stiction mode,

wherein said pull-down electrode maintains contact with said dielectric material over a range of voltage signals, and

wherein said range of voltage signals is from approximately 3 V to 10 V, wherein a capacitance in the range of 13 to 25 pF is produceable by said MEMS varactor in response to said range of voltage signals.

2. The MEMS varactor according to claim 1 wherein a first voltage signal applied across said bottom electrode and said pull-down electrode produces a first capacitance.

3. The MEMS varactor according to claim 2 wherein said a second voltage signal applied across said bottom electrode and said pull-down electrode produces a second capacitance.

4. The MEMS varactor according to claim 1 further comprising an insulating layer disposed over said substrate beneath said bottom electrode, wherein a distance D₁ is defined between said insulating layer and said pull-down electrode.

5. The MEMS varactor according to claim 4 wherein said distance D₁ is approximately 0.5-2.0 micrometers.

6. The MEMS varactor according to claim 4 wherein said distance D₁ is greater than 2.0 micrometers.

7. The MEMS varactor according to claim 4 wherein said distance D₁ is approximately 0.5-2.0 micrometers.

8. The MEMS varactor according to claim 4 wherein said distance D₁ is greater than 2 micrometers.

9. A Micro Electro-Mechanical System (MEMS) varactor, comprising:

a bottom electrode formed over a substrate;

a dielectric material disposed over said bottom electrode;

a spacer proximate said bottom electrode; and

a pull-down electrode over said spacer and said dielectric material, wherein said MEMS varactor is adapted to operate in a stiction mode, wherein a voltage signal applied across said bottom electrode and said pull-down electrode produces a capacitance,

wherein said pull-down electrode maintains contact with said dielectric material over a range of voltage signals in said stiction mode, and

wherein said range of voltage signals is from approximately 3 V to 10 V, wherein a capacitance in the range of 13 to 25 pF is produceable by said MEMS varactor in response to said range of voltage signals.

10. The MEMS varactor according to claim 9 further comprising an insulating layer disposed over said substrate beneath said bottom electrode, wherein a distance D₁ is defined between said insulating layer and said pull-down electrode.

11. The MEMS varactor according to claim 10 wherein said distance D₁ is approximately 0.5-2.0 micrometers.

12. The MEMS varactor according to claim 10 wherein said distance D₁ is greater than 2.0 micrometers.

13. A method of operating a MEMS varactor having a bottom electrode formed on a substrate, a dielectric material disposed over the bottom electrode, a spacer formed on the substrate supporting a pull-down electrode, wherein a voltage applied across the bottom electrode and the pull-down electrode responsively changes the capacitance of the varactor, comprising:

applying a voltage signal across the bottom electrode and the pull-down electrode to produce a Predetermined capacitance across said bottom and pull-down electrode, wherein at least a portion of said pull-down electrode is adapted to contact said dielectric material during a stiction mode,

wherein said applying a voltage signal comprises applying a voltage of approximately 3 V to 10 V to produce a varactor capacitance in the range of 13 to 25 pF.

14. The method according to claim 13 wherein the area of said pull-down electrode portion in contact with said dielectric material varies responsively to changes in said voltage signal.