MICROELECTROMECHANICAL INTEGRATED SENSOR STRUCTURE WITH ROTARY DRIVING MOTION

• US 20070214883A1
• Filed: 03/09/2007
• Published: 09/20/2007
• Est. Priority Date: 03/10/2006
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Zerbini, Sarah, Durante, Guido, Ludovico, Alessandro
• Granted Patent: US 7,694,563 B2
• Time in Patent Office: Days
• US Class Current: 73/504.40
• 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 and anchored via elastic anchorage elements to an anchorage arranged along said axis of rotation;

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

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.

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 at least one 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 detects a rotational movement about an axis lying in said plane, and said second detection movement detects 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 a first type, which is aligned to said first sensing mass of the first type along a first axis of detection lying in said plane and is arranged in a respective 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 to each of said first and second sensing masses of the first type for detecting said first detection movement, said first detection movement detects a rotational movement about an axis lying in said plane and perpendicular to said first axis of detection.

6. The structure according to claim 5, comprising connection means configured to electrically connect the detection means associated to said first sensing mass of the first type to the detection means associated to said second sensing mass of the first type, 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 7, wherein said detection means comprises a first detection electrode and a second detection electrode, which are set facing each of said first and second sensing masses of the first type, and said connection means comprises:

a first switch element and a second switch element which connect to one another, respectively, said first detection electrode and said second detection electrode facing said first and second sensing masses of the first type, and a third switch and a fourth switch which connect said first and second electrodes facing said first sensing mass of the first type respectively to said second and first electrodes facing said second sensing mass of the first type, 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 further including 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 a 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 sensor device comprising a microelectromechanical structure including:

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 the axis of rotation;

at least one first opening being provided within the driving mass; and

a first sensing mass of a first type arranged inside the at least one first opening and connected to the 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, the first elastic supporting elements and the elastic anchorage elements being configured in a manner such that the first sensing mass of the first type is fixed to the driving mass in the rotary motion, and is substantially decoupled from the driving mass in the first 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 according to claim 16, wherein said microelectromechanical structure comprises:

detection means for detecting said first detection movement; and

connection means for establishing an electrical connection of said detection means wherein said read stage is configured to interact with said connection means for switching said mode of operation of said microelectromechanical structure.

18. 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.

19. The microelectromechanical device of claim 18 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.

20. The microelectromechanical device of claim 18 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 at least 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.