Method for fabricating a tuning fork gyroscope

• US 7,172,919 B2
• Filed: 10/20/2004
• Issued: 02/06/2007
• Est. Priority Date: 10/05/2001
• Status: Expired due to Term

• Current Assignee: Charles Stark Draper Laboratory Incorporated
• Original Assignee: Charles Stark Draper Laboratory Incorporated
• Inventors: Borenstein, Jeffrey T., Weinberg, Marc S., Duwel, Amy E., Kourepenis, Anthony S., Sawyer, William D., Lento, Christopher M., Cousens, James R., Connelly, James H.
• Primary Examiner(s): PERT, EVAN T
• Application Number:
  US10/970,067
• Publication Number:
  US 20050081631A1
• Time in Patent Office: 839 Days
• Field of Search: 438/50, 438/51
• US Class Current: 438/50
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: H01L 21/6835 using temporarily an auxiliary support
• CPC Class Codes: H01L 2924/19041 being a capacitor
• CPC Class Codes: H01L 2924/30105 Capacitance
• CPC Class Codes: H01L 2924/3025 Electromagnetic shielding

Abstract

A method for reducing errors in a tuning fork gyroscope includes determining a first distance, g_t, between an upper sense plate and a proof mass and a second distance, g_b, between a lower sense plate and the proof mass. The method further includes applying a first voltage, V_t, to the upper sense plate and a second voltage, V_b, to the lower sense plate, wherein the ratio of the first voltage and the second voltage is a function of the first distance and the second distance.

Claims

1. A method for fabricating a tuning fork gyroscope with upper and lower sense plates, the method comprising:

providing a silicon substrate;

etching the silicon substrate to provide at least one recess in the silicon substrate;

producing a structure layer having a predetermined thickness;

etching the structure layer to provide at least one proof mass;

applying a metal coating to the silicon substrate beneath a portion of each proof mass;

providing a glass substrate;

etching the glass substrate to provide at least one recess in the glass substrate;

depositing a multimetal layer to the at least one recess;

electrostatically bonding the silicon substrate to the glass substrate; and

etching the silicon substrate down to the structure layer.

2. The method of claim 1 wherein the proof masses have a thickness in the range of 5 to 100 μ

m.

3. The method of claim 1 wherein the multimetal layer is chosen from the group consisting of Ti/Pt/Au and Ti/Pt.

4. The method of claim 1 in which producing a structure layer includes diffusing boron onto a surface of the silicon substrate.

5. The method of claim 4 in which diffusing boron onto a surface of the silicon substrate includes diffusing boron-geranium silicon to define structural thickness.

6. The method of claim 1 in which producing a structure layer includes growing epitaxial silicon with boron onto a surface of the silicon substrate to define structural thickness.

7. The method of claim 4 in which boron is diffused into a silicon substrate to define structural thickness.

8. The method of claim 4 including the further step of applying KOH thinning prior to etching the silicon substrate.

9. The method of claim 4 in which diffusing boron onto a surface of the silicon substrate includes diffusing silicon-on-insulator to define structural thickness.

10. The method of claim 1 wherein the silicon substrate includes a lightly doped layer and a highly doped epitaxial layer.

11. The method of claim 10 wherein the thickness of said highly doped epitaxial layer is between 5 and 100 μ

m thick.

12. The method of claim 1 wherein the etching of the silicon substrate is plasma enhanced ion etching.

13. The method of claim 1 wherein the structure layer is 5 to 100 μ

m thick.

14. The method of claim 1 wherein the structure layer is 5 to 20 μ

m thick.

15. The method of claim 1 wherein connecting posts between the silicon substrate and the glass substrate are defined by reactive ion etching.

16. The method of claim 1 wherein the recesses in the glass substrate are approximately 1700 Å

deep.

17. The method of claim 1 further including:

providing a second glass substrate;

etching said second glass substrate to provide at least one indentation in the second glass substrate;

depositing at least one metal run in said at least one indentation in the second glass substrate;

cutting a gap between said at least one proof mass and said second glass substrate;

exposing at least one bonding pad; and

bonding said second glass substrate to said structure layer.

18. The method of claim 1 wherein exposing at least one bonding pad includes water drilling.