RF-MEMS switch and its fabrication method

• US 20050099252A1
• Filed: 07/30/2004
• Published: 05/12/2005
• Est. Priority Date: 11/10/2003
• Status: Active Grant

• Current Assignee: Hitachi Media Electronics Co., Ltd. (Hitachi, Ltd.)
• Original Assignee: Hitachi Media Electronics Co., Ltd. (Hitachi, Ltd.)
• Inventors: Matsumoto, Hisanori, Asai, Kengo, Isobe, Atsushi, Uchiyama, Hiroyuki, Terano, Akihisa
• Granted Patent: US 7,242,273 B2
• Time in Patent Office: Days
• US Class Current: 335/78
• CPC Class Codes: H01H 1/20 Bridging contacts for circuit breakers H01H73/045
• CPC Class Codes: H01H 59/0009 making use of micromechanics
• CPC Class Codes: H01P 1/127 Strip line switches

Abstract

An inexpensive MEMS switch which stably operates at low voltage and its fabrication method are provided. The switch comprises: a first anchor 7-2-1 formed over a substrate 3; a first spring 7-3-1 connected to the first anchor; an upper electrode 7-1 which is connected to the first spring and makes a motion above the substrate, elastically deforming the first spring; a lower electrode 1 formed over the substrate, positioned under the upper electrode; a second spring 7-3-2 connected to the upper electrode; and a second anchor 7-2-2 connected to the second spring. When voltage is applied to between the upper electrode and the lower electrode and the upper electrode makes a downward motion, the second anchor is brought into contact with the substrate. As a result, the second spring is elastically deformed. When the upper electrode is subsequently brought into contact with the lower electrode, thereby the upper electrode and the lower electrode are electrically connected with each other. The first and second anchors, first and second springs, and upper electrode are formed of identical metal in integral structure to constitute a membrane 7.

Claims

1. A MEMS switch comprising:

a substrate;

a first anchor formed over said substrate;

a first spring connected to said first anchor;

an upper electrode which is connected to said first spring and makes a motion above said substrate, elastically deforming said first spring;

a lower electrode formed over said substrate and positioned under said upper electrode;

a second spring connected to said upper electrode; and

a second anchor connected to said second spring,

wherein when voltage is applied to between said upper electrode and said lower electrode and said upper electrode makes a downward motion, said second anchor is brought into contact with said substrate and said second spring is elastically deformed, and when said upper electrode is subsequently brought into contact with said lower electrode, thereby said upper electrode and said lower electrode are electrically connected with each other.

2. The MEMS switch according to claim 1,

wherein said first spring, said first anchor, said second spring, said second anchor, and said upper electrode are constituted in integral structure and are formed of a continuous metallic body.

3. The MEMS switch according to claim 1,

wherein said lower electrode contains an insulator film in its surface, and when said upper electrode is brought into contact with said lower electrode containing the insulator film in its surface, thereby electrical capacitance is produced between said upper electrode and said lower electrode.

4. The MEMS switch according to claim 2,

wherein said metal is a metal predominantly comprised of aluminum.

5. The MEMS switch according to claim 1,

wherein the major restoring force of said first spring is elastic force of a solid against torsion, and the major restoring force of said second spring is elastic force of a solid against flexure.

6. The MEMS switch according to claim 1,

wherein a metallic body is formed over said substrate under said second anchor.

7. The MEMS switch according to claim 1,

wherein said upper electrode has dips greater than the thickness of the upper electrode.

8. The MEMS switch according to claim 1,

wherein said upper electrodes, said second spring, and said second anchor are attached in this order on both sides of said first spring to form push-pull structure.

9. A fabrication method for a MEMS switch,

wherein the MEMS switch comprises:

a substrate;

a first anchor structure formed over said substrate;

a first spring connected to said first anchor structure;

an upper electrode which is connected to said first spring, and makes a motion above said substrate, elastically deforming said first spring;

a lower electrode formed over said substrate, positioned under said upper electrode;

a second spring connected to said upper electrode; and

a second anchor connected to said second spring,

wherein when voltage is applied to between said upper electrode and said lower electrode and said upper electrode makes a downward motion, said second anchor is brought into contact with said substrate and said second spring is elastically deformed, and when said upper electrode is subsequently brought into contact with said lower electrode, thereby said upper electrode and said lower electrode are electrically connected with each other,

the method comprising the steps of;

forming said lower electrode over said substrate;

carrying out film formation and patterning over said substrate with said lower electrode formed thereover to form at least two layers of sacrificial films;

forming a metallic film over said sacrificial film once and patterning it to form said first spring, said first anchor, said second spring, said second anchor, and said upper electrode in integral structure; and

removing said sacrificial films.