Integrated gyroscope of semiconductor material with at least one sensitive axis in the sensor plane

• US 20040035204A1
• Filed: 05/21/2003
• Published: 02/26/2004
• Est. Priority Date: 04/27/2001
• Status: Active Grant

• Current Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Merassi, Angelo, Zerbini, Sarah, Durante, Guido Spinola
• Granted Patent: US 6,928,872 B2
• Time in Patent Office: Days
• US Class Current: 73/504.04
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis

Abstract

An integrated gyroscope, including an acceleration sensor formed by: a driving assembly; a sensitive mass extending in at least one first and second directions and being moved by the driving assembly in the first direction; and by a capacitive sensing electrode, facing the sensitive mass. The acceleration sensor has an rotation axis parallel to the second direction, and the sensitive mass is sensitive to forces acting in a third direction perpendicular to the other directions. The capacitive sensing electrode is formed by a conductive material region extending underneath the sensitive mass and spaced therefrom by an air gap.

Claims

1. An integrated gyroscope, including an acceleration sensor comprising:

a driving assembly;

a sensitive mass extending in a first direction and a second direction, said sensitive mass being moved by said driving assembly in said first direction; and

a capacitive sensing electrode, facing said sensitive mass;

wherein said acceleration sensor has a rotation axis parallel to said second direction, and said sensitive mass is sensitive to forces acting in a third direction perpendicular to said first and second directions.

2. The gyroscope according to claim 1 wherein said capacitive sensing electrode comprises a conductive material region extending underneath and at a distance, in said third direction, from said sensitive mass.

3. The gyroscope according to claim 2 wherein said driving assembly comprises a driving element connected to said sensitive mass through a mechanical linkage, which enables, at least to one part of said sensitive mass, a movement having a component in said third direction.

4. The gyroscope according to claim 3 wherein said sensitive mass can be translated parallel to said third direction.

5. The gyroscope according to claim 4 wherein said sensitive mass and said capacitive sensing electrode have a reciprocal facing area that is constant in presence of movements of said sensitive mass in said first direction or in said second direction.

6. The gyroscope according to claim 4 wherein said driving element surrounds, at least partially, said sensitive mass, said sensitive mass and said capacitive sensing electrode having a rectangular shape, a first one between said sensitive mass and said capacitive sensing electrode having a length in said first direction greater than another one between said sensitive mass and said capacitive sensing electrode, and a second one between said sensitive mass and said capacitive sensing electrode having a length in said second direction greater than another one between said sensitive mass and said capacitive sensing electrode.

7. The gyroscope according to claim 3 wherein said driving element has an open concave shape partially surrounding said sensitive mass, and said sensitive mass has a peripheral portion not facing said driving element.

8. The gyroscope according to claim 7, further comprising movable sensing electrodes extending from said peripheral portion of said sensitive mass in said first direction, said movable sensing electrodes being comb-fingered to fixed sensing electrodes for detecting movements of said sensitive mass in said second direction.

9. The gyroscope according to claim 3 wherein said sensitive mass can turn about an eccentric axis parallel to said second direction.

10. The gyroscope according to claim 9 wherein said driving element surrounds at least partially said sensitive mass, said sensitive mass has a first centroid, and said mechanical linkage comprises a first pair of supporting arms aligned to one another and defining said eccentric axis, said supporting arms of said first pair extending between said driving element and said at least one sensitive mass, eccentrically with respect to said first centroid.

11. The gyroscope according to claim 10 wherein said driving element is E-shaped and comprises first and second oscillating arms and an intermediate arm extending parallel to said first direction, said sensitive mass extending between said first oscillating arm and said intermediate arm, a second sensitive mass extending between said second oscillating arm and said intermediate arm, having a second centroid and being supported by a second pair of supporting arms, said supporting arms of said second pair extending eccentrically with respect to said second centroid.

12. The gyroscope according to claim 11 wherein said supporting arms of said second pair are misaligned with respect to said supporting arms of said first pair.

13. The gyroscope according to claim 11 wherein said sensitive mass and said second sensitive mass have a generally rectangular shape and comprise a first portion that is smaller and a second portion that is larger, arranged on opposite sides with respect to the respective supporting arms, and wherein a differential sensing electrode faces a respective one of said first and second portions of said sensitive mass and said second sensitive mass.

14. The gyroscope according to claim 3 wherein said driving element and said sensitive mass are formed in a same structural layer.

15. The gyroscope according to claim 14 wherein said driving element and said sensitive mass extend on top of a conductive material body and are spaced therefrom by an air gap, and said capacitive sensing electrode is formed by a semiconductor material region extending on top of said conductive material body and insulated therefrom, said semiconductor material region extending beneath said air gap.

16. The gyroscope according to claim 3 wherein said driving assembly further comprises a plurality of movable driving electrodes extending from said driving element and comb-fingered to a plurality of fixed driving electrodes.

17. The gyroscope according to claim 1, further comprising two symmetrical parts connected by central springs and each including an own driving assembly, an own sensitive mass, and an own capacitive sensing electrode.

18. A device, comprising:

a semiconductor substrate;

a first electrode formed in a first layer of the substrate; and

a first sensing mass, mechanically coupled to the substrate and capacitively coupled to the first electrode, formed in a second layer of the substrate, the first sensing mass being configured to oscillate along a first axis lying in a first plane parallel to the first layer, and further configured to move along a second axis perpendicular to the first layer in response to angular movements of the substrate about a third axis perpendicular to the first axis and lying in the first plane.

19. The device of claim 18, further comprising a processing circuit configured to detect a magnitude of angular velocity of the substrate about the third axis by detecting changes in the capacitive coupling of the first sensing mass and the first electrode.

20. The device of claim 18, said first sensing mass being further configured to oscillate along said third axis in response to angular movements of the substrate about said second axis.

21. A device, comprising:

a semiconductor substrate;

a first electrode formed in a first layer of the substrate;

a first sensing mass, mechanically coupled to the substrate and capacitively coupled to the first electrode, formed in a second layer of the substrate, the first sensing mass being configured to oscillate along a first axis lying in a first plane parallel to the first layer, and further configured to oscillate about a second axis lying in the first layer in response to forces acting along a third axis perpendicular to the first and second axes.

22. The device of claim 21, further comprising:

a second electrode formed in the first layer;

a second sensing mass, mechanically coupled to the substrate and capacitively coupled to the second electrode, formed in the second layer of the substrate, the second sensing mass configured to oscillate along the first axis lying in the first plane, and further configured to oscillate about the second axis in response to forces acting along the third axis; and

wherein the first sensing mass and first electrode comprise a first sensing capacitor and the second sensing mass and second electrode comprise a second sensing capacitor.

23. The device of claim 22, further comprising a processing circuit configured to detect a magnitude of angular velocity of the substrate about the third axis by subtracting changes in capacitive values of the first sensing capacitor from the second sensing capacitor, such that changes of like polarities tend to cancel each other and changes of opposing polarities are additive.

24. A method, comprising:

oscillating a sensing mass in a first axis lying in a first plane relative to a surface of a semiconductor material body, the sensing mass mechanically couple to the body;

moving the semiconductor material body about a second axis perpendicular to the first axis and lying in the same plane; and

detecting the movement of the semiconductor material body by detecting changes in a capacitive coupling between the sensing mass and an electrode formed on the surface of the semiconductor body, due to movements of the body in an axis perpendicular to the first plane.