Micro-electro-mechanical system (MEMS) device including an internal anchor area

• US 9,562,926 B2
• Filed: 05/08/2015
• Issued: 02/07/2017
• Est. Priority Date: 12/12/2014
• Status: Active Grant

• Current Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Original Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Inventors: Lin, Chiung-Wen, Lo, Chiung-Cheng, Kang, Yu-Fu
• Primary Examiner(s): Patel, Harshad R
• Assistant Examiner(s): Shah, Samir M
• Application Number:
  US14/708,140
• Publication Number:
  US 20160169927A1
• Time in Patent Office: 641 Days
• US Class Current: 1/1
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/082 for two degrees of freedom of movement of a single mass

Abstract

The invention provides an MEMS device. The MEMS device includes: a substrate, a proof mass, a spring, a spring anchor, a first electrode anchor, and a second electrode anchor, a first fixed electrode and a second fixed electrode. The proof mass is connected to the substrate through the spring and the spring anchor. The proof mass includes a hollow structure inside, and the spring anchor, the first electrode anchor, and the second electrode anchor are located in the hollow structure. The proof mass and the first fixed electrode form a first capacitor, and the proof mass and the second fixed electrode form a second capacitor. There is neither any portion of the proof mass nor any portion of any fixing electrode located between the first electrode anchor, second electrode anchor, and the spring anchor.

Claims

1. An MEMS device, comprising:

a substrate;

a proof mass, including a first movable electrode and a second movable electrode for sensing movements along first and second directions, respectively, wherein the proof mass further includes a hollow space inside;

a spring, a spring anchor, a first electrode anchor, and a second electrode anchor, which are located in the hollow space, wherein the proof mass is connected to the substrate through the spring and the spring anchor; and

a first fixed electrode and a second fixed electrode, respectively connected to the substrate through the first electrode anchor and the second electrode anchor, the first fixed electrode and the first movable electrode forming a first capacitor, and the second fixed electrode and the second movable electrode forming a second capacitor, wherein the first capacitor and the second capacitor are used for sensing movements of the proof mass along the first and second directions, respectively;

wherein there is neither any portion of the proof mass nor any portion of any fixing electrode connected between the spring and the spring anchor.

2. The MEMS device of claim 1, wherein the first movable electrode and the second movable electrode are located at a same side of the spring anchor, and the first movable electrode and the second movable electrode are not directly connected to each other.

3. The MEMS device of claim 1, wherein the first movable electrode and the second movable electrode are located at different sides of the spring anchor, and the first movable electrode and the second movable electrode are not directly connected to each other.

4. The MEMS device of claim 1, wherein the first fixed electrode and the first movable electrode form a plurality of first capacitors which form at least one first differential capacitor, and the second fixed electrode and the second movable electrode form a plurality of second capacitors which form at least one second differential capacitor.

5. The MEMS device of claim 1, wherein the proof mass further includes a third movable electrode for sensing movements along a third direction perpendicular to the first and second directions, and the MEMS device further includes a third fixed electrode forming a third capacitor with the third movable electrode.

6. The MEMS device of claim 1, wherein the movements of the proof mass include an eccentric movement.

7. The MEMS device of claim 1, wherein the spring anchor is located in the middle of the spring, and the spring includes at least two sections each of which includes a first end and a second end, the first end being connected to the spring anchor, the second end being connected to the proof mass, whereby the proof mass can perform an in-plane rotation with respect to a plane formed by the first and second directions and an out-of-plane rotation with respect to the plane formed by the first and second directions.

8. The MEMS device of claim 1, wherein the hollow space includes an internal anchor area which accommodates the first electrode anchor, the second electrode anchor, and the spring anchor therein, and an area size of the internal anchor area occupies less than 5% of a total area size defined by a periphery of the proof mass.

9. The MEMS device of claim 1, wherein the first electrode anchor is connected to the first fixed electrode at a portion of the first fixed electrode which is closest to the spring anchor, and/or the second electrode anchor is connected to the second fixed electrode at a portion of the second fixed electrode which is closest to the spring anchor.

10. The MEMS device of claim 1, wherein the mass of the proof mass is unevenly distributed at two sides of the spring anchor.

11. The MEMS device of claim 1, wherein there is neither any portion of the proof mass nor any portion of any fixing electrode connected between the first electrode anchor, the second electrode anchor, and the spring anchor.