Forming a Micro Electro Mechanical System

• US 20110059566A1
• Filed: 11/17/2010
• Published: 03/10/2011
• Est. Priority Date: 10/20/2006
• Status: Active Grant

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Ramamoorthi, Sriram, Milligan, Donald J.
• Granted Patent: US 8,084,285 B2
• Time in Patent Office: Days
• US Class Current: 438/50
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 2203/051 Translation according to an axis parallel to the substrate
• CPC Class Codes: B81B 2203/053 Translation according to an axis perpendicular to the substrate
• CPC Class Codes: B81C 1/00142 Bridges deformable micromirrors G02B26/0841
• CPC Class Codes: B81C 1/00253 Processes for integrating an electronic processing unit with a micromechanical structure not provided for in B81C1/0023 - B81C1/00246
• CPC Class Codes: B81C 2201/019 Bonding or gluing multiple substrate layers
• CPC Class Codes: B81C 2203/058 Aligning components using methods not provided for in B81C2203/051 - B81C2203/052
• CPC Class Codes: B81C 3/004 Active alignment, i.e. moving the elements in response to the detected position of the elements using internal or external actuators

Abstract

A method of forming a micro-electro mechanical system (MEMS), includes (1) removing material from a first wafer to define a first movable portion corresponding to an x-y accelerometer and a second movable portion corresponding to a z accelerometer, where each movable portion comprises at least one flexure member and at least one proof mass, each proof mass and flexure member being formed by the selective removal of material from a top side and a bottom side of first wafer; (2) bonding the first wafer to a second wafer comprising an electronic circuit, such that a gap is defined between the first wafer and the second wafer. The thickness of the at least one flexure member of the first movable portion is independent of a thickness of the at least one flexure member of the second movable portion and a thickness of the proof mass of the first movable portion is independent of a thickness of the at least one proof mass of the second movable portion.

Claims

1. A method of forming a micro-electro mechanical system (MEMS), comprising:

removing material from a first wafer to define a first movable portion corresponding to an x-y accelerometer and a second movable portion corresponding to a z accelerometer, wherein each said movable portion comprises at least one flexure member and at least one proof mass, each of said proof mass and said flexure member being formed by the selective removal of material from a top side and a bottom side of said first wafer;

bonding said first wafer to a second wafer comprising an electronic circuit, such that a gap is defined between said first wafer and said second wafer;

wherein a thickness of said at least one flexure member of said first movable portion is independent of a thickness of said at least one flexure member of said second movable portion and a thickness of said proof mass of said first movable portion is independent of a thickness of said at least one proof mass of said second movable portion.

2. The method of claim 1, further comprising patterning a circuitry component on a first side of said first wafer

3. The method of claim 1, wherein removing material from said top and bottom sides of said first wafer comprises at least one of etching, trenching, or micromachining said wafer.

4. The method of claim 1, further comprising forming at least one coupling block on said first wafer, wherein said coupling block is configured to couple at least a segment of a said flexure member to an anchoring portion of said first wafer.

5. The method of claim 1, further comprising sealing said MEMS with a protective unprocessed surface or wafer.

6. The method of claim 1, wherein bonding said first wafer to said second wafer comprises applying an adhesive between said first wafer and said second wafer.

7. The method of claim 1, wherein bonding said first wafer to said second wafer comprises optically aligning said first wafer to said second wafer through a window formed in said first wafer.

8. The method of claim 1, wherein said removing material from said first wafer to define at least one flexure member comprises removing a known amount of material to define a height and a width of said flexure member to generate a desired spring constant of said flexure member.

9. The method of claim 8, wherein said first wafer is configured to allow a said proof mass to translate parallel to said second wafer.

10. The method of claim 8, wherein said first wafer is configured to allow a said proof mass to translate perpendicular relative to said second wafer.

11. The method of claim 1, wherein said first wafer comprises a silicon on insulator (SOI) substrate.

12. The method of claim 1, further comprising:

defining a cavity within said first wafer, wherein said cavity is defined by subtracting a height of a said proof mass from an original thickness of said first wafer; and

defining said cavity such that an x-y area of said cavity is larger than an x-y area of that proof mass.

13. A method of forming a micro-electro mechanical system (MEMS), comprising:

selectively removing material from a first wafer to form a first movable portion corresponding to an x-y accelerometer and a second movable portion corresponding to a z accelerometer, wherein each said movable portion comprises at least one flexure member and a proof mass, each of said proof mass and said flexure member being formed by the selective removal of material from a top side and a bottom side of said first wafer; and

bonding a second wafer to said first wafer;

wherein a thickness of said at least one flexure member of said first movable portion is independent of a thickness of said at least one flexure member of said second movable portion and a thickness of said proof mass of said first movable portion is independent of a thickness of said at least one proof mass of said second movable portion.

14. The method of claim 13, further comprising defining a cavity in said top side of said first wafer, wherein said cavity is defined by subtracting a height of a said proof mass from an original thickness of said first wafer.

15. The method of claim 14, further comprising connecting said cavity to an external package volume through a trench.

16. The method of claim 13, further comprising aligning said first and second wafers using a window in said first wafer configured to allow for optical alignment of said first wafer with said second wafer.

17. The method of claim 13, wherein said first wafer comprises a silicon on insulator (SOI) wafer.

18. The method of claim 17, wherein:

a height of said at least one flexure member is defined by a height of a top silicon layer of said SOI wafer; and

a height of said proof mass is defined by a height said top silicon and a height of a processed handle wafer.

19. A method of forming a micro-electro mechanical system (MEMS), comprising:

forming first and second movable portions in a first wafer, wherein each said movable portion comprises at least one electrode, at least one flexure member, and a proof mass, each of said proof mass and said flexure member being formed by the selective removal of material from a top side and a bottom side of said first wafer;

bonding a second wafer to said first wafer, said second wafer comprising at least one electrode corresponding to each said electrode in said first wafer, wherein material is removed from at least a top surface and a bottom surface of said second wafer defining at least one flexure member and at least one proof mass; and

forming at least one circuit operable disposed at least partially within said second wafer and configured to detect lateral movement of said at least one flexure member proof mass of said first movable portion; and

forming at least one circuit disposed at least partially within said second wafer and configured to detect medial movement of said proof mass of said second movable portion;

wherein a thickness of said proof mass of said first movable portion is independent of a thickness of said proof mass of said second movable portion, and a thickness of said at least one flexure member of said first movable portion is independent of a thickness of said at least one flexure member of said second movable portion.

20. The method of claim 19, further comprising:

forming at least one via coupled to said first wafer;

said at least one via providing a path for electrical signals traveling through said first wafer.