Micromechanical inertial sensor

• US 6,907,782 B2
• Filed: 11/30/2001
• Issued: 06/21/2005
• Est. Priority Date: 12/02/2000
• Status: Expired due to Fees

• Current Assignee: EADS Deutschland GmbH (Airbus SE)
• Original Assignee: EADS Deutschland GmbH (Airbus SE)
• Inventors: Lentner, Konrad, Sassen, Stefan, Schalk, Josef
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US10/433,335
• Publication Number:
  US 20040045354A1
• Time in Patent Office: 1,299 Days
• Field of Search: 735/040.4, 735/041.2, 735/040.2, 735/10
• US Class Current: 73/504.04
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure
• CPC Class Codes: G01C 21/166 Mechanical, construction or arrangement details of inertial navigation systems
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/0828 the mass being of the paddle type being suspended at one of its longitudinal ends
• CPC Class Codes: G01P 2015/0831 the mass being of the paddle type having the pivot axis between the longitudinal ends of the mass, e.g. see-saw configuration

Abstract

A micromechanical inertial sensor that includes three component planes, namely a bottom part, a center part and a cover part. The center part is a silicon wafer in which a cardan-type (i.e. gimbal) structure with two oscillating elements is formed. A plate is formed in the silicon wafer which can be pivoted about a rotational axis lying in the wafer plane. Metallized portions or conductive layers form an exciter unit and set the gimbal structure oscillating. The inventive sensor further comprises a device for detecting the displacement of the plate. In addition, a method for manufacturing a micromechanical inertial sensor.

Claims

1. A micromechanical inertial sensor comprising:

a gimbal structure formed from a single wafer having a wafer plane, the gimbal structure including a first oscillating element having a first axis of oscillation coupled to a second oscillating element having a second axis of oscillation aligned substantially perpendicular to the first axis of oscillation,

an exciter unit configured to oscillate the first oscillating element;

a first sensing device configured to sense a deflection of the second oscillating element;

a first plate formed from the single wafer, the first plate being pivotable about a first axis of rotation and deflectable by an acceleration acting perpendicular to the first axis of rotation;

a second sensing device configured to sense a deflection of the first plate;

a first mass element attached to the first plate, wherein a common center of gravity of the first plate and the first mass element is offset from the first axis of rotation in a direction of the wafer plane; and

a second plate formed in the single wafer and a third sensing device, the second plate being pivotable about a second axis of rotation and deflectable by an acceleration acting perpendicular to the second axis of rotation, the third sensing device configured to sense a deflection of the second plate.

2. The micromechanical inertial sensor as recited in claim 1, further comprising an additional mass element attached to the gimbal structure or the second plate.

3. The micromechanical inertial sensor as recited in claim 1, further comprising a top wafer defining a top plane and a bottom wafer defining a bottom plane, the single wafer being secured between the top and bottom wafers.

4. The micromechanical inertial sensor as recited in claim 3, wherein the single wafer includes silicon, and the bottom wafer or the top wafer include glass.

5. The micromechanical inertial sensor as recited in claim 1, further comprising a plurality of twisting suspension means formed in the single wafer for suspending the gimbal structure, the first plate or the second plate.

6. The micromechanical inertial sensor as recited in claim 1, wherein the first, second or third sensor is configured to sense capacitively.

7. The micromechanical inertial sensor as recited in claim 1, wherein the first, second or third sensor includes a plurality of capacitive elements disposed so as to produce a measuring signal in response to deflection, the measuring signal corresponding to a change in capacitance in opposite directions.

8. The micromechanical inertial sensor as recited in claim 1, wherein the second oscillating element is a frame and the second axis of oscillation lies in the wafer plane and is aligned perpendicular to the first axis of oscillation.

9. The micromechanical inertial sensor as recited in claim 1, wherein the first oscillating element includes at least two mass elements disposed symmetrically to the wafer plane and the first axis of oscillation is aligned parallel to the wafer plane.

10. The micromechanical inertial sensor as recited in claim 1, further comprising an additional mass element attached to the second plate such that a common center of gravity of the second plate and the additional mass element is offset from the second axis of rotation in a direction perpendicular to the wafer plane.

11. The micromechanical inertial sensor as recited claim 10, wherein the second axis of rotation runs through a center of the second plate, and the additional mass element is disposed at the center of the second plate and protruding from the wafer plane.

12. The micromechanical inertial sensor as recited in claim 1, further comprising a plurality of conductive layers disposed in a plane parallel to the wafer plane.

13. The micromechanical inertial sensor as recited in claim 1, wherein the single wafer is disposed in a hermetically sealed interior space and further comprising a plurality external contact elements and a plurality of electric feed-throughs, each of the feed-throughs connecting a respective one of the plurality of external contact elements to the single wafer.

14. The micromechanical inertial sensor as recited in claim 1, wherein the single wafer includes a depression, the first mass element including a spherical shape being secured to the single wafer in the depression.

15. A method for manufacturing a micromechanical inertial sensor comprising the steps of:

providing a single wafer defining a wafer plane;

forming a gimbal structure in the single wafer, the gimbal structure including a first and a second oscillating element;

forming a first plate in the single wafer such that the plate is pivotable about an axis of rotation lying in the wafer plane and is deflectable by an acceleration force, wherein the forming of the first plate and the forming of the gimbal structure are performed by patterning the single wafer using a micromachining technique;

disposing at least a first mass element on the first plate such that a common center of gravity of the plate and the additional mass element is offset from the axis of rotation a direction of the wafer plane;

forming an exciter unit for exciting the gimbal structure to oscillations;

forming a first sensing device for measuring a deflection of the gimbal structure;

forming a second sensing device for measuring a deflection of the first plate; and

forming a second plate in the single wafer such that the second plate is pivotable about a second axis of rotation and deflectable by an acceleration acting perpendicular to the second axis of rotation.

16. The method as recited in claim 15, further comprising:

disposing a top wafer on an upper side of the single wafer; and

disposing a bottom wafer on a lower side of the single wafer, the disposing being performed so as to form a hermetically tight interior space between the top and bottom wafers, the gimbal structure and the plate being located in the interior space.

17. The method as recited in claim 15, further comprising attaching at least one additional mass element to at least one of the second plate and the oscillating element.

18. The method as recited in claim 15, further comprising performing a final module test of the micromechanical inertial sensor, the final mode test including a test of an oscillating of the gimbal structure, a test of a pivoting of the first plate and a test of the entire micromechanical inertial sensor.