Gyroscope and fabrication method thereof

• US 20030159509A1
• Filed: 03/25/2003
• Published: 08/28/2003
• Est. Priority Date: 02/12/2001
• Status: Active Grant

• Current Assignee: Intellimicrons Co., Ltd., Seoul National University R&DB Foundation (Seoul National University)
• Original Assignee: Intellimicrons Co., Ltd.
• Inventors: Kim, Yong-Kweon, Kim, Seong-Hyok
• Granted Patent: US 6,845,668 B2
• Time in Patent Office: Days
• US Class Current: 73/504.03
• CPC Class Codes: B81B 2201/0242 Gyroscopes
• CPC Class Codes: B81B 2203/0136 Comb structures
• CPC Class Codes: B81B 2203/04 Electrodes
• CPC Class Codes: B81B 3/0062 Devices moving in two or more dimensions, i.e. having special features which allow movement in more than one dimension
• CPC Class Codes: B81B 3/0078 Constitution or structural means for improving mechanical properties not provided for in B81B3/007 - B81B3/0075
• CPC Class Codes: G01C 19/5755 the devices having a single sensing mass

Abstract

A gyroscope which comprises: a driving fixed electrode (26) being fixed; a driving displacement electrode (24) being opposite to the driving fixed electrode, and being able to be displaced in a first direction; an inertial mass (23) being connected to the driving displacement electrode (24), being displaced in the first direction according to the first directional displacement of the driving displacement electrode (24), and being displaced in a second direction when an angular rate is applied; a sensing displacement electrode (22) being connected to the inertial mass (23), and being able to be displaced in the second direction according to the second directional displacement of the inertial mass (23); and a sensing fixed electrode (25) being opposite to the sensing displacement electrode and being fixed. The driving displacement electrode (24) is supported by a folded spring (31) movable in the first direction, and the sensing displacement electrode is supported by a folded spring (32) movable in the second direction.

Claims

1. A gyroscope comprising:

a driving fixed electrode being fixed;

a driving displacement electrode being opposite to the driving fixed electrode, and being able to be displaced in a first direction;

an inertial mass being connected to the driving displacement electrode, being displaced in the first direction according to the first directional displacement of the driving displacement electrode, and being displaced in a second direction when an angular rate is applied;

a sensing displacement electrode being connected to the inertial mass, and being able to be displaced in the second direction according to the second directional displacement of the inertial mass; and

a sensing fixed electrode being opposite to the sensing displacement electrode and being fixed.

2. The gyroscope of claim 1, wherein the driving displacement electrode is supported by a folded spring movable in the first direction, and the sensing displacement electrode is supported by a folded spring movable in the second direction.

3. The gyroscope of claim 1, wherein the driving displacement electrode and the inertial mass can be movable in the second direction and are connected by a folded spring having no fixture shaft, and the sensing displacement electrode and the inertial mass can be movable in the first direction and are connected by a folded spring having no fixture shaft.

4. The gyroscope of claim 1, wherein two sensing displacement electrodes are provided, one on each of two sides of the inertial mass, and the gyroscope further comprises an edge gimbal for connecting the two sensing displacement electrodes.

5. The gyroscope of claim 1, wherein a cavity is provided in the center of the inertial mass, and the gyroscope further comprises a displacement limit shaft provided to the center of the cavity and being fixed.

6. The gyroscope of claim 1, wherein the gyroscope further comprises tuning electrodes, symmetrically formed on both sides of the sensing displacement electrode, functioning as electrical springs to vary the resonance frequency of the sensing displacement electrode and control sensing sensitivity.

7. The gyroscope of claim 6, wherein spaced tooth shapes are respectively formed on the sensing displacement electrode'"'"'s surface and on the tuning electrode'"'"'s surface facing the sensing displacement electrode, and tooth portions of the sensing displacement electrode are facing those of the tuning electrode, and spaces between the tooth portions of the sensing displacement electrode are facing those of the tuning electrode.

8. The gyroscope of claim 1, wherein spaced tooth shapes are provided to the facing sides of the driving fixed electrode and the driving displacement electrode, and to those of the sensing fixed electrode and the sensing displacement electrode, to be interspersed with each other.

9. A method for fabricating a gyroscope comprising:

(a) performing anodic bonding on a silicon substrate and a glass substrate;

(b) etching and polishing the silicon substrate to be a predetermined thickness;

(c) forming a metallic layer on the silicon substrate;

(d) performing photolithography on the metallic layer and the silicon substrate to form a silicon structure having a gyroscope pattern;

(e) etching the glass substrate, and separating remaining portions of the silicon structure except a fixture shaft from the glass substrate to form a gyroscope structure; and

(f) performing flip chip bonding on the gyroscope structure to connect it to an external circuit.

10. The method of claim 9, wherein the method further comprises dicing the silicon substrate and the glass substrate and separating them into respective elements between (d) and (e).

11. The method of claim 9, wherein the metallic layer formed in (c) is a double layer of Cr and Au.

12. The method of claim 9, wherein the glass substrate is etched using an HF solution in (e).

13. The method of claim 12, wherein the depth for etching the glass substrate using the HF solution is set to be greater than 10 μ

m so as to minimize air damping and to operate the gyroscope in atmospheric pressure.

14. The method of claim 9, wherein the silicon substrate is etched using a KOH aqueous solution of 36 wt. % at 80°

C. in (b).