Microelectromechanical sensor with improved mechanical decoupling of sensing and driving modes

• US 8,042,396 B2
• Filed: 09/11/2008
• Issued: 10/25/2011
• Est. Priority Date: 09/11/2007
• Status: Expired

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Coronato, Luca, Zerbini, Sarah, Ludovico, Alessandro Balzelli
• Primary Examiner(s): Kwok; Helen C.
• Application Number:
  US12/208,980
• Publication Number:
  US 20090064780A1
• Time in Patent Office: 1,139 Days
• Field of Search: 735/040.8, 735/040.9, 735/041.1, 735/040.4, 735/041.2, 735/041.4, 735/143.2, 735/141.6, 735/142.9
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/14 by making use of gyroscopes gyroscopes per se G01C19/00
• 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

Abstract

A driving mass of an integrated microelectromechanical structure is moved with a rotary motion about an axis of rotation, and a sensing mass is connected to the driving mass via elastic supporting elements so as to perform a detection movement in the presence of an external stress. The driving mass is anchored to a first anchorage arranged along the axis of rotation by first elastic anchorage elements. The driving mass is also coupled to a pair of further anchorages positioned externally thereof and coupled to opposite sides with respect to the first anchorage by further elastic anchorage elements; the elastic supporting elements and the first and further elastic anchorage elements render the driving mass fixed to the first sensing mass in the rotary motion, and substantially decoupled from the sensing mass in the detection movement, the detection movement being a rotation about an axis lying in a plane.

Claims

1. An integrated microelectromechanical structure, comprising:

a substrate;

a driving mass designed to be moved with a rotary motion about an axis of rotation and having a central aperture;

a first anchorage arrangement positioned in the central aperture and structured to anchor the driving mass to the substrate;

a first opening provided within said driving mass;

a first sensing mass of a first type arranged inside said first opening;

first elastic supporting elements connecting said first sensing mass to said driving mass and configured to enable the first sensing mass to perform a first detection movement in the presence of a first external stress;

a second anchorage arrangement positioned externally of said driving mass and coupled to a first side of the driving mass;

a third anchorage arrangement positioned externally of said driving mass and coupled to a second side of the driving mass, the second side being opposite to the first side;

wherein said first elastic supporting elements and said first, second and third anchorage arrangements are so configured that said driving mass is fixed to said first sensing mass of the first type in said rotary motion, and is decoupled therefrom in said detection movement.

2. The structure according to claim 1, wherein said driving mass has an annular shape extending substantially in a plane, said axis of rotation is perpendicular to said plane, and said first anchorage arrangement includes:

a central anchorage arranged substantially at a center of said driving mass in the central aperture defined by said annular shape, and

central elastic anchorage elements coupling said central anchorage to said driving mass, extending in said central aperture; and

wherein said second side is opposite to said first side with respect to said central aperture.

3. The structure according to claim 2, wherein said second and third anchorage arrangements are diametrically opposite and symmetric with respect to said central aperture.

4. The structure according to claim 1, wherein each of said second and third anchorage arrangements comprises an external anchorage coupled to the substrate, and an external elastic anchorage element coupling said external anchorage to said driving mass, extending outside said driving mass.

5. The structure according to claim 4, wherein said external elastic anchorage element comprises a folded spring.

6. The structure according to claim 1, wherein each of said second and third anchorage arrangements comprises a pair of external anchorages coupled to the substrate, and a pair of folded springs connecting a respective one of said external anchorages to said driving mass.

7. The structure according to claim 1, wherein said external stress is a Coriolis force acting in a direction perpendicular to a plane of said driving mass, and said first detection movement is a rotation outside said plane about an axis defined by said elastic supporting elements.

8. The structure according to claim 1, wherein said driving mass extends substantially in a plane and the structure further comprises:

a second sensing mass of the first type, which is aligned with said first sensing mass of the first type along a first axis of detection lying in said plane and is arranged in a second opening provided within said driving mass, said first and second sensing masses of the first type being enclosed in overall dimensions of said driving mass in said plane; and

detection means associated with each of said first and second sensing masses of the first type for detecting said first detection movement, said first detection movement being a rotational movement about an axis lying in said plane and perpendicular to said first axis of detection.

9. The structure according to claim 8, wherein said detection means are configured to implement a differential detection scheme.

10. The structure according to claim 8, wherein said detection means include detection electrodes which are set facing said first and second sensing masses of the first type.

11. The structure according to claim 1, further comprising:

a second sensing mass of the first type, forming with said first sensing mass of the first type a first pair of sensing masses of the first type aligned along a first axis of detection lying in a plane on opposite sides with respect to said first anchorage arrangement; and

a second pair of sensing masses of the first type aligned along a second axis of detection lying in said plane and orthogonal to said first axis of detection, on opposite sides of said first anchorage arrangement.

12. The structure according to claim 1, further comprising:

a sensing mass of a second type arranged inside a second opening provided within said driving mass; and

second elastic supporting elements coupled between the driving mass and the sensing mass of the second type and configured to enable the sensing mass of the second type to perform a second detection movement in a presence of a second external stress, said first detection movement being a rotational movement about a first axis lying in a plane of said driving mass, and said second detection movement being a linear movement along a second axis lying in said plane.

13. The structure according to claim 12, wherein said second external stress is a Coriolis force acting in a radial direction, and said linear movement is directed along said radial direction.

14. The structure according to claim 12, defining a triaxial gyroscope, further including:

a second sensing mass of the first type, forming with said first sensing mass of the first type a first pair of sensing masses of the first type aligned along a first axis of detection lying in a plane on opposite sides with respect to said first anchorage arrangement; and

a second pair of sensing masses of the first type aligned along a second axis of detection lying in said plane and orthogonal to said first axis of detection, on opposite sides of said first anchorage arrangement,

wherein said first and second pairs of sensing masses of the first type are configured to detect, respectively, a first external angular velocity and a second external angular velocity about said first and second axis of detection, and said sensing mass of the second type is configured to detect a third external angular velocity about a third axis of detection orthogonal to said plane.

15. A sensor device comprising:

a microelectromechanical structure including;

a driving mass designed to be moved with a rotary motion about an axis of rotation;

a first anchorage positioned along said axis of rotation;

first elastic anchorage elements anchoring said driving mass to said first anchorage;

a first opening provided within said driving mass;

a first sensing mass arranged inside said first opening;

first elastic supporting elements connecting said first sensing mass to said driving mass and configured to enable said first sensing mass to perform a first detection movement in the presence of an external stress;

a second anchorage positioned externally of said driving mass; and

a second elastic anchorage element coupling an external side of the driving mass to said second anchorage;

wherein said first elastic supporting elements and said first and second elastic anchorage elements are so configured that said first sensing mass is fixed to said driving mass in said rotary motion, and is substantially decoupled from said driving mass in said detection movement.

16. The sensor device according to claim 15, further comprising a read stage configured to switch a mode of operation of said microelectromechanical structure between a gyroscope mode and an accelerometer mode.

17. The sensor device of claim 15, wherein the second elastic anchorage element couples a first side of the driving mass to said second anchorage, the sensor device further comprising:

a third anchorage positioned externally of said driving mass; and

a third elastic anchorage element coupling a second side of the driving mass to said third anchorage.

18. The sensor device according to claim 15, wherein the first sensing mass is of a first type, the microelectromechanical structure further comprising:

a sensing mass of a second type arranged inside a second opening provided within said driving mass; and

second elastic supporting elements coupled between the driving mass and the sensing mass of the second type and configured to enable the sensing mass of the second type to perform a second detection movement in a presence of a second external stress, said first detection movement being a rotational movement about a first axis, and said second detection movement being a linear movement along a second axis.

19. The sensor device according to claim 18, defining a triaxial gyroscope, the microelectromechanical structure further including:

a second sensing mass of the first type, forming with said first sensing mass of the first type a first pair of sensing masses of the first type aligned along a first axis of detection on opposite sides with respect to said first anchorage; and

a second pair of sensing masses of the first type aligned along a second axis of detection orthogonal to said first axis of detection, on opposite sides of said first anchorage,

wherein said first and second pairs of sensing masses of the first type are configured to detect, respectively, a first external angular velocity and a second external angular velocity about said first and second axis of detection, and said sensing mass of the second type is configured to detect a third external angular velocity about a third axis of detection orthogonal to first and second axes of detection.

20. A microelectromechanical device comprising:

a first anchorage;

first elastic anchorage elements;

a driving mass operable to move in a rotary motion about an axis of rotation, the driving mass being anchored via the first elastic anchorage elements to the first anchorage positioned along the axis of rotation and the driving mass substantially extending in a plane perpendicular to the axis of rotation;

a first opening disposed within the driving mass;

first elastic supporting elements;

a first sensing mass of a first type disposed within the first opening and coupled to the driving mass via the first elastic supporting elements to allow for a first detection movement in response to a first external stress, the first detection movement being a rotational movement outside the plane about an axis lying in the plane;

a pair of further anchorages positioned externally of the driving mass;

further elastic anchorage elements coupling the further anchorages to opposite sides of said driving mass;

the first elastic supporting elements and the first and further elastic anchorage elements being configured to fix the first sensing mass to the driving mass during said rotary motion, and wherein the first and further elastic anchorage elements are configured to prevent said driving mass from undergoing said rotational movement outside the plane in response to said first external stress.

21. The device according to claim 20, further comprising:

a second sensing mass of the first type, which is aligned with said first sensing mass of the first type along a first axis of detection lying in said plane and is arranged in a second opening provided within said driving mass, said first and second sensing masses of the first type being enclosed in overall dimensions of said driving mass in said plane; and

detection means associated with each of said first and second sensing masses of the first type for detecting said first detection movement, said first detection movement being a rotational movement about an axis lying in said plane and perpendicular to said first axis of detection.

22. The device according to claim 20, further comprising a sensing mass of a second type arranged inside a second opening provided within said driving mass and connected to said driving mass via second elastic supporting elements in such a manner so as to perform a second detection movement in a presence of a second external stress, said first detection movement being a rotational movement about a first axis lying in said plane, and said second detection movement being a linear movement along a second axis lying in said plane.

23. The device according to claim 22, wherein said second external stress is a Coriolis force acting in a radial direction, and said linear movement is directed along said radial direction.

24. The device according to claim 22, defining a triaxial gyroscope, further including:

a second sensing mass of the first type, forming with said first sensing mass of the first type a first pair of sensing masses of the first type aligned along a first axis of detection lying in a plane on opposite first and second sides with respect to said first anchorage; and

a second pair of sensing masses of the first type aligned along a second axis of detection lying in said plane and orthogonal to said first axis of detection, on opposite third and fourth sides of said first anchorage,

wherein said first and second pairs of sensing masses of the first type are configured to detect, respectively, a first external angular velocity and a second external angular velocity about said first and second axes of detection, and said sensing mass of the second type is configured to detect a third external angular velocity about a third axis of detection orthogonal to said plane.