Microelectromechanical integrated sensor structure with rotary driving motion

• US 7,694,563 B2
• Filed: 03/09/2007
• Issued: 04/13/2010
• Est. Priority Date: 03/10/2006
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Durante, Guido Spinola, Zerbini, Sarah, Ludovico, Alessandro Balzelli
• Primary Examiner(s): Kwok; Helen C.
• Application Number:
  US11/684,243
• Publication Number:
  US 20070214883A1
• Time in Patent Office: 1,131 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 15/18 in two or more dimensions

Abstract

A driving mass of an integrated microelectromechanical structure is moved with a rotary motion about an axis of rotation, and a first sensing mass is connected to the driving mass via elastic supporting elements so as to perform a first detection movement in a presence of a first external stress. The driving mass is anchored to an anchorage arranged along the axis of rotation by elastic anchorage elements. An opening is provided within the driving mass and the first sensing mass is arranged within the opening. The elastic supporting and anchorage elements render the first sensing mass fixed to the driving mass in the rotary motion, and substantially decoupled from the driving mass in the first detection movement. A second sensing mass is connected to the driving mass so as to perform a second detection movement in a presence of a second external stress. A first movement is a rotation about an axis lying in a plane, and a second movement is a linear movement along an axis of the plane.

Claims

1. An integrated microelectromechanical structure, comprising:

a driving mass designed to be moved with a rotary motion about an axis of rotation, the driving mass having a central opening, an inner surface defining the central opening, and an outer surface;

an anchorage arranged along said axis of rotation;

elastic anchorage elements configured to anchor the driving mass to the anchorage, the elastic anchorage elements extending between the inner surface of the driving mass and the anchorage;

a first opening provided within said driving mass and positioned between the inner and outer surfaces of the driving mass; and

a first sensing mass of a first type arranged inside said first opening and connected to said driving mass via first elastic supporting elements in such a manner so as to perform a first detection movement in a presence of a first external stress, said first elastic supporting elements and said elastic anchorage elements being configured in a manner such that said first sensing mass of the first type fixedly rotates with said driving mass in said rotary motion, and is substantially decoupled from said driving mass in said first detection movement.

2. The structure according to claim 1, wherein said driving mass extends substantially in a plane and said axis of rotation is perpendicular to said plane, said anchorage being arranged substantially at a center of said driving mass.

3. The structure according to claim 2, further comprising a first 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 an axis lying in said plane, and said second detection movement being a linear movement along the axis lying in said plane.

4. The structure according to claim 3, wherein said second external stress is a Coriolis force acting in a first radial direction, and said linear movement is directed along said first radial direction.

5. The structure according to claim 1, wherein said driving mass extends substantially in a plane and 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;

first detection means associated with said first sensing mass 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; and

second detection means associated with said second sensing mass of the first type for detecting said first detection movement.

6. The structure according to claim 5, comprising connection means configured to electrically connect the first detection means to the second detection means, said connection means being configured to implement, in given operating conditions, a differential detection scheme.

7. The structure according to claim 6, wherein said connection means is further configured to switch a mode of operation of said microelectromechanical structure between a gyroscope mode and an accelerometer mode.

8. The structure according to claim 6, wherein:

said first detection means comprises a first detection electrode and a second detection electrode, which are set facing said first sensing mass of the first type;

said second detection means comprises a third detection electrode and a fourth detection electrode, which are set facing said second sensing mass of the first type; and

said connection means comprises;

a first switch element connecting said first detection electrode and said third detection electrode to one another;

a second switch element connecting said second detection electrode and said fourth detection electrode to one another;

a third switch element connecting said first switch element and said fourth switch element to one another; and

a fourth switch element connecting said second switch element and said third switch element to one another, wherein said first and second switch elements are configured in an open condition and said third and fourth switch elements are configured in a closed condition for implementing said gyroscope mode, and said first and second switch elements are configured in a closed condition and said third and fourth switch elements are configured in an open condition for implementing said accelerometer mode.

9. 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 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 sides of said anchorage.

10. The structure according to claim 9, further comprising a pair of sensing masses of a second type aligned in a first radial direction on opposite sides of said anchorage, said pair of sensing masses of the second type being connected to said driving mass via respective second elastic supporting elements in such a manner as to perform a second detection movement in a presence of a second external stress.

11. The structure according to claim 10 wherein the structure is a triaxial gyroscope, 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 pair of sensing masses of the second type are configured to detect a third external angular velocity about a third axis of detection orthogonal to said plane.

12. 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, which are symmetrical to one another with respect to said anchorage and are set on opposite sides of a first axis of detection lying in said plane;

a second pair of sensing masses of the first type, which are symmetrical with respect to said anchorage and are set on opposite sides of a second axis of detection lying in a plane and orthogonal to said first axis of detection; and

a further pair of sensing masses of the first type for each of said first and second axes of detection, which are symmetrical with respect to said anchorage and are set on opposite sides of a respective one of said first and second axes of detection with respect to a respective one of said first and second pairs of sensing masses of the first type, wherein corresponding sensing masses of the first or the second pairs associated to one and a same axis of detection are set facing one another with respect to said respective axis of detection wherein the first elastic supporting elements are staggered along said respective axis of detection and coupled to the corresponding sensing masses of the first or the second pairs.

13. The structure according to claim 12, wherein said driving mass includes an empty space at a center and further comprises:

an electrical-insulation region, which electrically insulates a driving portion from a detection portion of said driving mass, which are biased, in use, at different voltages, said electrical-insulation region comprising a first ring surrounding at least a portion of said first and second pairs of sensing masses and a second ring surrounding at least another portion of said first and second sensing masses, said first and second rings having an opening at said empty space, wherein a portion of the driving mass surrounded by the first and second rings includes the detection portion while a portion of the driving mass outside the first and second rings includes the driving portion.

14. The structure according to claim 1, wherein said driving mass has in a plane a circular geometry, having a first axis of symmetry and a second axis of symmetry with an empty space at a center of the driving mass, wherein the center of the driving mass is in a position corresponding to said anchorage, said elastic anchorage elements extending within said empty space.

15. A microelectromechanical device comprising:

an anchorage;

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 elastic anchorage elements to the anchorage arranged along the axis of rotation and the driving mass substantially extending in a plane perpendicular to the axis of rotation;

a first opening and a second 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 elastic supporting elements and the elastic anchorage elements being configured to fix the first sensing mass of the first type to the driving mass, and wherein the elastic anchorage elements are substantially decoupled from the driving mass during the first detection movement;

second elastic supporting elements; and

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

16. The microelectromechanical device of claim 15 wherein the second external stress is a Coriolis force acting in a first radial direction and the linear movement is directed along the first radial direction.

17. The microelectromechanical device of claim 15 wherein the driving mass further comprises:

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

detection means for performing the first detection movement of the first and second sensing masses of the first type in response to the first external stress, the first detection movement detects a rotational movement about the axis lying in the plane and perpendicular to the first axis of detection.

18. An integrated microelectromechanical structure, comprising:

a driving mass designed to be moved with a rotary motion about an axis of rotation and anchored via elastic anchorage elements to an anchorage arranged along said axis of rotation;

a first opening being provided within said driving mass;

a first sensing mass of a first type arranged inside said first opening and connected to said driving mass via first elastic supporting elements in such a manner so as to perform a first detection movement in a presence of a first external stress, said first elastic supporting elements and said elastic anchorage elements being configured in a manner such that said first sensing mass of the first type is fixed to said driving mass in said rotary motion, and is substantially decoupled from said driving mass in said first detection movement, wherein said driving mass extends substantially in a plane and said axis of rotation is perpendicular to said plane, said anchorage being arranged substantially at a center of said driving mass; and

a first 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 an axis lying in said plane, and said second detection movement being a linear movement along the axis lying in said plane.

19. The structure according to claim 18, wherein said second external stress is a Coriolis force acting in a first radial direction, and said linear movement is directed along said first radial direction.

20. The structure according to claim 18, further comprising:

a second sensing mass of the first type forming with said first sensing mass of the first type a 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 anchorage; and

a second sensing mass of the second type aligned with the first sensing mass of the second type in a first radial direction on opposite sides of said anchorage, said sensing masses of the second type being connected to said driving mass via respective second elastic supporting elements in such a manner as to perform the second detection movement in a presence of the second external stress.

21. The structure according to claim 18, 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, which are symmetrical to one another with respect to said anchorage and are set on opposite sides of a first axis of detection lying in said plane;

a second pair of sensing masses of the first type, which are symmetrical with respect to said anchorage and are set on opposite sides of a second axis of detection lying in a plane and orthogonal to said first axis of detection;

a third pair of sensing masses of the first type, which are symmetrical with respect to said anchorage and are set on opposite sides of said first axis of detection; and

a fourth pair of sensing masses of the first type, which are symmetrical with respect to said anchorage and are set on opposite sides of said second axis of detection.

22. An integrated microelectromechanical structure, comprising:

a driving mass designed to be moved with a rotary motion about an axis of rotation and anchored via elastic anchorage elements to an anchorage arranged along said axis of rotation, wherein said driving mass extends substantially in a plane;

at least one first opening being provided within said driving mass;

a first sensing mass of a first type arranged inside said at least one first opening and connected to said driving mass via first elastic supporting elements in such a manner so as to perform a first detection movement in a presence of a first external stress, said first elastic supporting elements and said elastic anchorage elements being configured in a manner such that said first sensing mass of the first type is fixed to said driving mass in said rotary motion, and is substantially decoupled from said driving mass in said first detection movement;

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;

first detection means associated with said first sensing mass 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;

second detection means associated with said second sensing mass of the first type for detecting said first detection movement;

connection means configured to electrically connect the first detection means to the second detection means, said connection means being configured to implement, in given operating conditions, a differential detection scheme, wherein said connection means is further configured to switch a mode of operation of said microelectromechanical structure between a gyroscope mode and an accelerometer mode, wherein;

said first detection means comprises a first detection electrode and a second detection electrode, which are set facing said first sensing mass of the first type;

said second detection means comprises a third detection electrode and a fourth detection electrode, which are set facing said second sensing mass of the first type; and

said connection means comprises;

a first switch element connecting said first detection electrode and said third detection electrode to one another;

a second switch element connecting said second detection electrode and said fourth detection electrode to one another;

a third switch element connecting said first detection electrode and said fourth detection electrode to one another; and

a fourth switch element connecting said second detection electrode and said third detection electrode to one another, wherein said first and second switch elements are configured in an open condition and said third and fourth switch elements are configured in a closed condition for implementing said gyroscope mode, and said first and second switch elements are configured in a closed condition and said third and fourth switch elements are configured in an open condition for implementing said accelerometer mode.

23. The structure according to claim 22, further comprising:

a pair of sensing masses of a second type aligned in a first radial direction on opposite sides of said anchorage, said pair of sensing masses of the second type being connected to said driving mass via respective second elastic supporting elements in such a manner as to perform a second detection movement in a presence of a second external stress.

24. The structure according to claim 22, wherein the second sensing mass of the first type forms with said first sensing mass of the first type a first pair of sensing masses of the first type, which are symmetrical to one another with respect to said anchorage and are set on opposite sides of the first axis of detection, the structure further comprising:

a second pair of sensing masses of the first type, which are symmetrical with respect to said anchorage and are set on opposite sides of a second axis of detection lying in a plane and orthogonal to said first axis of detection;

a third pair of sensing masses of the first type, which are symmetrical with respect to said anchorage and are set on opposite sides of said first axis of detection; and

a fourth pair of sensing masses of the first type, which are symmetrical with respect to said anchorage and are set on opposite sides of said second axis of detection.

25. An integrated microelectromechanical structure, comprising:

a driving mass designed to be moved with a rotary motion about an axis of rotation and anchored via elastic anchorage elements to an anchorage arranged along said axis of rotation;

a first opening being provided within said driving mass; and

a first sensing mass of a first type arranged inside said first opening and connected to said driving mass via first elastic supporting elements in such a manner so as to perform a first detection movement in a presence of a first external stress, said first elastic supporting elements and said elastic anchorage elements being configured in a manner such that said first sensing mass of the first type is fixed to said driving mass in said rotary motion, and is substantially decoupled from said driving mass in said first detection movement;

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 anchorage;

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 anchorage; and

a pair of sensing masses of a second type aligned in a first radial direction on opposite sides of said anchorage, said pair of sensing masses of the second type being connected to said driving mass via respective second elastic supporting elements in such a manner as to perform a second detection movement in a presence of a second external stress.

26. The structure according to claim 25 wherein the structure is a triaxial gyroscope, 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 pair of sensing masses of the second type are configured to detect a third external angular velocity about a third axis of detection orthogonal to said plane.

27. An integrated microelectromechanical structure, comprising:

a driving mass designed to be moved with a rotary motion about an axis of rotation and anchored via elastic anchorage elements to an anchorage arranged along said axis of rotation;

a first opening being provided within said driving mass;

a first sensing mass of a first type arranged inside said at least one first opening and connected to said driving mass via first elastic supporting elements in such a manner so as to perform a first detection movement in a presence of a first external stress, said first elastic supporting elements and said elastic anchorage elements being configured in a manner such that said first sensing mass of the first type is fixed to said driving mass in said rotary motion, and is substantially decoupled from said driving mass in said first detection movement, wherein said driving mass extends substantially in a plane and said axis of rotation is perpendicular to said plane, said anchorage being arranged substantially at a center of said driving mass;

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, which are symmetrical to one another with respect to said anchorage and are set on opposite sides of a first axis of detection lying in said plane;

a second pair of sensing masses of the first type, which are symmetrical with respect to said anchorage and are set on opposite sides of a second axis of detection lying in a plane and orthogonal to said first axis of detection; and

a further pair of sensing masses of the first type for each of said first and second axes of detection, which are symmetrical with respect to said anchorage and are set on opposite sides of a respective one of said first and second axes of detection with respect to a respective one of said first and second pairs of sensing masses of the first type, wherein corresponding sensing masses of the first or the second pairs associated to one and a same axis of detection are set facing one another with respect to said respective axis of detection wherein the first elastic supporting elements are staggered along said respective axis of detection and coupled to the corresponding sensing masses of the first or the second pairs.

28. The structure according to claim 27, wherein said driving mass includes an empty space at a center and further comprises:

an electrical-insulation region, which electrically insulates a driving portion from a detection portion of said driving mass, which are biased, in use, at different voltages, said electrical-insulation region comprising a first ring surrounding at least a portion of said first and second pairs of sensing masses and a second ring surrounding at least another portion of said first and second sensing masses, said first and second rings having an opening at said empty space, wherein a portion of the driving mass surrounded by the first and second rings includes the detection portion while a portion of the driving mass outside the first and second rings includes the driving portion.