Microelectromechanical sensor with improved mechanical decoupling of sensing and driving modes

Patent metadata

Field	Value
Publication number	US-RE45855-E
Application number	US-201314062671-A
Country	US
Kind code	E1
Filing date	Oct 24, 2013
Priority date	Sep 11, 2007
Publication date	Jan 19, 2016
Grant date	Jan 19, 2016

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.

First claim

The invention claimed is:

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 relative to a central axis;
a first anchorage arrangement positioned in the central aperture and structured to anchor the driving mass to the substrate; arranged at the central axis and coupled to the substrate;
a first opening provided within said driving mass;
elastic anchorage elements coupling the driving mass to the first anchorage;
a first sensing mass of a first type arranged inside said first opening;
first elastic supporting elements connecting coupling said first sensing mass to said driving mass and configured to enable the first sensing mass to move in a first direction in response to a first acceleration to perform a first detection movementin the presence of a first external stress;
a second sensing mass that is of a type that is different from the first sensing mass;
second elastic supporting elements coupled between the driving mass and the second sensing mass and configured to enable the second sensing mass to perform a second detection movement in response to a second acceleration, 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;
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 anchorages are so configured so that said driving first sensing mass is fixed to said first sensing driving mass of the first type in said rotary motion and driven relative to the central axis, and the first sensing mass is decoupled therefrom in said detection movement from the driving mass when moving in said first direction.

2. The structure according to claim 1 , wherein said driving mass has an annular shape extending substantially in a plane, and said central 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 of the driving mass with respect to said central aperture axis.

3. The structure according to claim 2 1, wherein said second and third anchorage arrangements anchorages are diametrically opposite and symmetric with respect to said central aperture axis.

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

7. The structure according to claim 1 , wherein said external stress first acceleration is generated by 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 first 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 that 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 located inward 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 a 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 1, wherein said second external stress is acceleration is generated by 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 1, defining a triaxial gyroscope, further including:
a second third 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 second 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

Assignees

• St Microelectronics Srl

Inventors

• Coronato Luca
• Ludovico Alessandro Balzelli
• Zerbini Sarah

Classifications

• G01C19/5712 Primary

  the devices involving a micromechanical structure · CPC title

• G01P15/125

  by capacitive pick-up · CPC title

• G01P15/14

  by making use of gyroscopes (gyroscopes per se G01C19/00) · CPC title

• G01P15/18

  in two or more dimensions · CPC title

• G01P2015/0828

  the mass being of the paddle type being suspended at one of its longitudinal ends · CPC title