MEMS device and method of reducing stiction in a MEMS device

• US 7,628,072 B2
• Filed: 07/19/2006
• Issued: 12/08/2009
• Est. Priority Date: 07/19/2006
• Status: Expired due to Fees

• Current Assignee: North Star Innovations Inc. (Wi-LAN Inc.)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: McNeil, Andrew C., Koury, Jr., Daniel N.
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): Shah, Samir M
• Application Number:
  US11/489,789
• Publication Number:
  US 20080016964A1
• Time in Patent Office: 1,238 Days
• Field of Search: 735/143.2, 734/88, 735/06, 735/10, 735/140.1, 735/141.6, 735/143.8
• US Class Current: 73/514.32
• CPC Class Codes: B81B 3/001 Structures having a reduced contact area, e.g. with bumps or with a textured surface
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0814 for translational movement of the mass, e.g. shuttle type

Abstract

A MEMS device includes a substrate; a movable mass suspended in proximity to the substrate; and at least one suspension structure coupled to the movable mass for performing a mechanical spring function. The at least one suspension structure has portions that move in tandem when the MEMS device is subject to at least one stimulus in a sensing direction, and further includes at least one link between the portions that move in tandem.

Claims

1. A MEMS device, comprising:

a substrate;

a movable mass suspended in proximity to the substrate; and

at least one suspension structure coupled to the movable mass for performing a mechanical spring function,

wherein the at least one suspension structure has portions that move in tandem when the MEMS device is subject to a stimulus along at least one sensing direction, and wherein the at least one suspension structure further includes at least one link between the portions that move in tandem, wherein the at least one suspension structure has an axial spring constant (K_y) along a longitudinal axis and a transverse spring constant (K_x) along a transverse axis and in the at least one sensing direction, wherein the at least one link does not significantly increase the transverse spring constant (K_x) of the at least one suspension structure.

2. The MEMS device of claim 1, wherein the at least one suspension structure has at least two segments that join to form a first elbow, and wherein the at least one link is provided approximately at the first elbow.

3. The MEMS device of claim 2, wherein the at least one suspension structure has at least two additional segments that join to form a second elbow, and wherein the at least one link is provided approximately between the first and second elbows.

4. The MEMS device of claim 1, wherein the at least one link is a plurality of links.

5. The MEMS device of claim 1, wherein the suspension structure includes a plurality of segments that join to form at least six elbows, and wherein the at least one link includes three links, each linking a pair of elbows.

6. The MEMS device of claim 1, wherein the at least one link is straight.

7. The MEMS device of claim 1, wherein the at least one link is generally U-shaped.

8. The MEMS device of claim 7, wherein the generally U-shaped link is formed by three segments joined at 90°

angles.

9. The MEMS device of claim 1, wherein the at least one link is generally C-shaped.

10. The MEMS device of claim 9, wherein the generally C-shaped link is formed by seven segments joined at 90°

angles.

11. The MEMS device of claim 1, further comprising fixed electrodes supported by the substrate, wherein the movable mass and the fixed electrodes form a plurality of differential capacitor pairs.

12. The MEMS device of claim 1, wherein the at least one link is positioned on a common layer with the at least one suspension structure.

13. A method of reducing stiction in a MEMS device having a substrate, a movable mass suspended in proximity to the substrate, and at least one suspension structure coupled to the movable mass for performing a mechanical spring function and including portions that move in tandem when the MEMS device is subject to a stimulus along at least one sensing direction, wherein the at least one suspension structure has an axial spring constant (K_y) along a longitudinal axis and a transverse spring constant (K_x) along a transverse axis and in the at least one sensing direction, the method comprising:

providing at least one link between the portions that move in tandem such that the at least one link does not significantly increase the transverse spring constant (K_x) of the at least one suspension structure.

14. The method of claim 13, wherein the at least one suspension structure has at least two segments that join to form a first elbow, and

wherein the providing step includes providing the at least one link approximately at the first elbow.

15. The method of claim 14, wherein the at least one suspension structure has at least two additional segments that join to form a second elbow, and wherein the at least one link is provided approximately between the first and second elbows.

16. The method of claim 13, wherein the at least one link is straight.

17. The method of claim 13, wherein the at least one link is generally U-shaped.

18. The method of claim 13, wherein the at least one link is generally C-shaped.

19. The method of claim 13, wherein the MEMS device further includes fixed electrodes supported by the substrate, and wherein the movable mass and the fixed electrodes form a plurality of differential capacitor pairs.

20. A MEMS device, comprising:

a substrate;

a movable mass suspended in proximity to the substrate; and

at least one suspension structure coupled to the movable mass for performing a mechanical spring function,

wherein the at least one suspension structure has a first segment and a second segment that move in tandem when the MEMS device is subject to a stimulus along at least one sensing direction, the first and second segments exhibiting mirror symmetry relative to one another along a symmetry axis, and

wherein the at least one suspension structure further includes at least one link, at least a portion of the at least one link lying on the symmetry axis between the first and second segments.