Methods and systems for simultaneously fabricating multi-frequency MEMS devices

• US 6,978,673 B2
• Filed: 02/07/2003
• Issued: 12/27/2005
• Est. Priority Date: 02/07/2003
• Status: Expired due to Fees

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Arch, David K., Johnson, Burgess R., Weber, Mark W., Glenn, Max C., Platt, William P.
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US10/360,962
• Publication Number:
  US 20040154400A1
• Time in Patent Office: 1,054 Days
• Field of Search: 735/041.2, 735/041.4, 735/041.6, 438/50, 438/52
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5656 the devices involving a micromechanical structure
• CPC Class Codes: G01R 33/0286 comprising microelectromechanical systems [MEMS] MEMS devices in general B81B

Abstract

A method for providing micro-electromechanical systems (MEMS) devices with multiple motor frequencies and uniform motor-sense frequency separation is described. The devices each include at least one proof mass, each proof mass being connected to a substrate by a system of suspensions. The method includes controlling the resonant frequencies of the MEMS device by adjusting at least two of a mass of the proof masses, a bending stiffness of the proof masses, a length of the suspensions, and a width of the suspensions.

Claims

1. A method for fabricating a plurality of micro-electromechanical systems (MEMS) devices on a wafer, the MEMS devices having multiple motor frequencies and uniform motor-sense frequency separation, each device including at least one proof mass suspended above a substrate by a plurality of suspensions, said method comprising adjusting a bending stiffness of the suspensions utilizing at least one fusible link attached to at least one of the suspensions as compared to at least some of the other suspensions formed on the wafer.

2. A method according to claim 1 wherein adjusting a bending stiffness of the suspensions utilizing a fusible link attached to at least one of the suspensions comprises:

fabricating at least one fusible link which is attached to at least one suspension; and

burning through the at least one fusible link to adjust a resonant frequency of the device.

3. A method according to claim 1 further comprising adjusting at least one of a mass of the proof mass, a bending stiffness of the proof mass, a length of the suspensions, and a width of the suspensions as compared to at least some of the other proof masses and suspensions formed on the wafer.

4. A method according to claim 3 further comprising fabricating at least one hole within the at least one proof mass to adjust both a mass and a bending stiffness of the at least one proof mass.

5. A method according to claim 4 further comprising adjusting at least one of a position, a size, and a number of holes within the at least one proof mass.

6. A method according to claim 3 wherein adjusting a mass of a proof mass comprises depositing a thin film of material onto at least one surface of the at least one proof mass.

7. A method according to claim 6 wherein the thin film material comprises at least one of silicon dioxide, silicon nitride, and polysilicon.

8. A method according to claim 3 wherein adjusting a mass of a proof mass comprises etching away a portion of at least one surface of the at least one proof mass.

9. A method according to claim 3 wherein a width of the suspensions is controlled using at least one of photolithography and etching processes.

10. A method according to claim 3 wherein a length of the suspensions is controlled using at least one of photolithography and etching processes.

11. A method according to claim 3 wherein adjusting a length of the suspensions comprises adjusting at least one of a length of proof mass suspensions, a length of corner suspensions, and a length of center suspensions.

12. A method according to claim 3 wherein adjusting a width of the suspensions comprises adjusting at least one of a width of proof mass suspensions, a width of corner suspensions, and a width of center suspensions.

13. A micro-electromechanical systems device formed on a wafer, said device comprising:

a substrate;

at least one sense plate attached to said substrate;

at least one proof mass separated from said sense plate;

a plurality of suspensions connecting said proof mass to said substrate, at least a portion of said suspensions configured to provide separation between said sense plate and said proof mass; and

at least one anchor connecting at least one of said suspensions to said substrate, wherein to control resonant frequencies of said device, said device further comprises an adjusted bending stiffness of said suspensions based on one or more fusible links attached to said suspensions as compared to at least one other suspension for other MEMS devices formed on the wafer.

14. A micro-electromechanical systems device according to claim 13 wherein said proof mass comprises:

a top surface;

a bottom surface; and

a thin film material deposit on at least one of said top surface and said bottom surface.

15. A micro-electromechanical systems device according to claim 13 wherein said proof mass comprises:

a top surface;

a bottom surface; and

at least one of said top surface and said bottom surface having a portion removed through etching.

16. A micro-electromechanical systems device according to claim 13 wherein said proof mass comprises a plurality of holes formed in said proof mass, said holes being of a number, a location, and a diameter to provide a desired bending stiffness for said proof mass.

17. A micro-electromechanical systems device according to claim 13 wherein resonant frequencies of said device are controlled by adjusting at least one of a deposition of epitaxial silicon, a photolithography process, and an etching process during fabrication of said suspensions.

18. A micro-electromechanical systems device according to claim 13 further comprising a stiffener beam, said at least one fusible link extending between said stiffener beam and one of said suspensions.

19. A micro-electromechanical systems device according to claim 18 comprising:

a plurality of said stiffener beams; and

at least one of said fusible links extending between each said stiffener beam and a respective one of said suspensions.

20. A micro-electromechanical systems device according to claim 18 comprising a plurality of said stiffener beams attached to one or more of said suspensions, said stiffener beams connected together by one of said fusible links.

21. A micro-electromechanical systems device according to claim 13 wherein said device is one or more of a gyroscope, an accelerometer, and an inertial measurement unit.

22. A micro-electromechanical systems device according to claim 13 wherein said suspensions comprise at least one of proof mass suspensions, corner suspensions, and center suspensions.

23. A micro-electromechanical systems device comprising:

at least one proof mass;

a plurality of suspensions attached to said proof mass and configured to suspend said proof mass;

at least one stiffener beam coupled to at least one of said suspensions; and

at least one fusible link extending from each said stiffener beam, where removing said fusible link changes one or more resonant frequencies of said device by adjusting a stiffness of said suspensions.

24. A micro-electromechanical systems device according to claim 23 further comprising at least two stiffener beams, said fusible link extending therebetween, said stiffener beams both attached to a single one of said suspensions.

25. A micro-electromechanical systems device according to claim 23 further comprising an anchor, said at least one fusible link extends between said stiffener beam and said anchor, said fusible link attached to said anchor either directly or through a second said stiffener beam.

26. An inertial measurement unit comprising three orthogonally situated micro-electromechanical systems gyroscopes, each said gyroscope comprising:

at least one sense plate;

at least one proof mass separated from said sense plate;

a plurality of suspensions attached to said proof mass, at least a portion of said suspensions configured to provide separation between said sense plate and said proof mass; and

at least one anchor connecting at least one of said suspensions to said substrate, wherein to control resonant frequencies of said device, said device further comprises an adjusted bending stiffness of said suspensions based on one or more fusible links attached to said suspensions as compared to at least one other suspension for other MEMS devices formed on the wafer.

27. An inertial measurement unit according to claim 26 wherein at least one of said gyroscopes comprises a stiffener beam and at least one of said fusible links extending between said stiffener beam and one of said suspensions, resonant frequencies of said gyroscope are controlled by removing at least one of said fusible links.

28. An inertial measurement unit according to claim 26 wherein said proof mass comprises:

a top surface;

a bottom surface; and

a thin film material deposit on at least one of said top surface and said bottom surface.

29. An inertial measurement unit according to claim 26 wherein said proof mass comprises:

a top surface;

a bottom surface; and

at least one of said top surface and said bottom surface having a portion removed through an etching process.

30. An inertial measurement unit according to claim 26 wherein said proof mass comprises a plurality of holes formed therein, said holes varying in at least one of a size, a number, and a position for controlling a mass and a bending stiffness of said proof mass.

31. An inertial measurement unit according to claim 26 wherein said suspensions comprise at least one of proof mass suspensions, corner suspensions, and center suspensions.

32. A method for providing micro-electromechanical systems (MEMS) devices with multiple motor frequencies and uniform motor-sense frequency separation, the devices each including at least one proof mass suspended above a substrate by suspensions, said method comprising:

fabricating at least one fusible link coupled to at least one suspension; and

burning through the at least one fusible link to adjust a resonant frequency of the device.