Method for adjusting resonance frequencies of a vibrating microelectromechanical device

• US 8,505,357 B2
• Filed: 09/16/2011
• Issued: 08/13/2013
• Est. Priority Date: 10/21/2008
• Status: Active Grant

• Current Assignee: Teledyne Scientific & Imaging, LLC (Teledyne Technologies Incorporated)
• Original Assignee: Teledyne Scientific & Imaging, LLC (Teledyne Technologies Incorporated)
• Inventors: DeNatale, Jeffrey F., Stupar, Philip A.
• Primary Examiner(s): LARKIN, DANIEL SEAN
• Application Number:
  US13/235,260
• Publication Number:
  US 20120006789A1
• Time in Patent Office: 697 Days
• Field of Search: 73/13.7, 73/17.7, 735/041.2, 216/41, 216/48, 216/51
• US Class Current: 73/1.37
• CPC Class Codes: G01C 19/56 Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces
• CPC Class Codes: Y10T 29/42 Piezoelectric device making

Abstract

The present invention relates to a method for adjusting the resonant frequencies of a vibrating microelectromechanical (MEMS) device. In one embodiment, the present invention is a method for adjusting the resonant frequencies of a vibrating mass including the steps of patterning a surface of a device layer of the vibrating mass with a mask, etching the vibrating mass to define a structure of the vibrating mass, determining a first set of resonant frequencies of the vibrating mass, determining a mass removal amount of the vibrating mass and a mass removal location of the vibrating mass to obtain a second set of resonant frequencies of the vibrating mass, removing the mask at the mass removal location, and etching the vibrating mass to remove the mass removal amount of the vibrating mass at the mass removal location of the vibrating mass.

Claims

1. A method for adjusting the resonant frequencies of a vibrating MEMS device comprising the steps of:

determining a first resonant frequency of the vibrating MEMS device along a first axis and a second resonant frequency of the vibrating MEMS device along a second axis;

determining a mass removal amount of the vibrating MEMS device and a mass removal location of the vibrating MEMS device to alter the first resonant frequency of the vibrating MEMS device for decreasing a resonant frequency difference between the first resonant frequency and the second resonant frequency;

coating a surface of the vibrating MEMS device with a masking material;

selectively removing the masking material at the mass removal location using laser ablation; and

etching the vibrating MEMS device to remove the mass removal amount of the vibrating MEMS device at the mass removal location of the vibrating MEMS device.

2. The method of claim 1 wherein the vibrating MEMS device is a MEMS resonator.

3. The method of claim 2 wherein the MEMS resonator is a MEMS gyroscope resonator.

4. The method of claim 1 wherein the vibrating MEMS device is formed from Si or quartz.

5. The method of claim 1 wherein the steps of adjusting the resonant frequencies of the vibrating MEMS device is performed at a wafer scale.

6. The method of claim 1 wherein the masking material for coating the surface of the vibrating MEMS device is a conformal masking material.

7. The method of claim 6 wherein the conformal masking material is selected from the group consisting of polymers, oxides, nitrides, and metals.

8. The method of claim 6 wherein the conformal masking material is selected from the family of parylenes (poly-para-xylenes).

9. The method of claim 1 wherein the etching the vibrating MEMS device only removes material from the MEMS device where the masking material has been removed.

10. The method of claim 1 further comprising the step of removing any remaining masking material that is coating the surface of the vibrating MEMS device.

11. The method of claim 10 wherein the removing any remaining masking material that is coating the surface of the vibrating MEMS device is performed by oxygen plasma treatment.

12. The method of claim 1 further comprising repeating any of the steps of adjusting the resonant frequencies of the vibrating MEMS device in order to further adjust the resonant frequencies of the vibrating MEMS device.

13. The method of claim 12 wherein the steps of adjusting the resonant frequencies of the vibrating MEMS device is performed at a wafer scale.

14. The method of claim 1 wherein the selectively removing the masking material at the mass removal location using laser ablation is performed with a laser energy sufficient to remove the masking material without damaging a structural layer of the vibrating MEMS device located below the masking material.

15. The method of claim 1 wherein the etching the vibrating MEMS device at the mass removal location of the vibrating MEMS device is performed using deep reactive ion etching.

16. The method of claim 15 wherein the deep reactive ion etching is performed using time-sequenced etch and passivate chemistry.