MICROELECTROMECHANICAL STRUCTURE WITH ENHANCED REJECTION OF ACCELERATION NOISE

• US 20100281977A1
• Filed: 05/07/2010
• Published: 11/11/2010
• Est. Priority Date: 05/11/2009
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Coronato, Luca, Cazzaniga, Gabriele
• Granted Patent: US 8,342,025 B2
• Time in Patent Office: Days
• US Class Current: 73/504.14
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure
• CPC Class Codes: G01C 19/5747 each sensing mass being connected to a driving mass, e.g. driving frames
• CPC Class Codes: Y10T 29/49002 Electrical device making

Abstract

An integrated MEMS structure includes a driving assembly anchored to a substrate and actuated with a driving movement. A pair of sensing masses suspended above the substrate and coupled to the driving assembly via elastic elements is fixed in the driving movement and performs a movement along a first direction of detection, in response to an external stress. A coupling assembly couples the pair of sensing masses mechanically to couple the vibration modes. The coupling assembly is formed by a rigid element, which connects the sensing masses and has a point of constraint in an intermediate position between the sensing masses, and elastic coupling elements for coupling the rigid element to the sensing masses to present a first stiffness to a movement in phase-opposition and a second stiffness, greater than the first, to a movement in phase, of the sensing masses along the direction of detection.

Claims

1. An integrated MEMS structure, comprising:

a substrate;

a driving assembly anchored to the substrate and configured to be actuated with a driving movement;

a first sensing mass and a second sensing mass suspended above the substrate;

first and second elastic supports, respectively coupling the first and second masses to the driving assembly and configured to enable the sensing masses to perform a movement of detection along a first direction of detection, in response to an external stress; and

a coupling assembly configured to couple mechanically the first sensing mass and the second sensing mass and to couple their vibration modes, the coupling assembly further comprising;

a rigid element between the first and the second sensing masses having a point of constraint in an intermediate position between the first and second sensing masses; and

first and second elastic connectors to connect respective ends of the rigid element to the first and second sensing masses, the first and second elastic connectors and the rigid element being configured to present a first stiffness to a movement in phase-opposition, and a second stiffness, greater than the first stiffness, to a movement in phase of the first and second sensing masses along the first direction of detection.

2. The structure according to claim 1, wherein the second stiffness is configured to inhibit the movement in phase of the first and second sensing masses;

and wherein the point of constraint is fixed with respect to translation during the movement of detection.

3. The structure according to claim 1 wherein the rigid element extends between the first sensing mass and the second sensing mass in a direction transverse to the first direction of detection;

and wherein the first and second elastic connectors and the rigid element are configured to enable in the first sensing mass and the second sensing mass the movement in phase-opposition along lines substantially parallel to one another and to the first direction of detection.

4. The structure according to claim 1 wherein the coupling assembly is configured to cause a separation between a first frequency contribution, associated to the movement in phase-opposition of the first and second sensing masses and to a detection of a first angular velocity, and a second frequency contribution, associated to the movement in phase of the first and second sensing masses and to the detection of a noise acceleration;

the coupling assembly configured to displace to higher frequencies the second frequency contribution, with respect to the first frequency contribution.

5. The structure according to claim 1 wherein the point of constraint of the rigid element is coupled elastically to the substrate via a coupling element.

6. The structure according to claim 5 wherein the coupling element is coupled between the point of constraint of the rigid element and an anchor coupled to the substrate.

7. The structure according to claim 5 wherein the coupling element and the first and second elastic connectors are configured to operate, each, as a hinge at a respective point of connection with the rigid element.

8. The structure according to claim 7 having a main extension in a plane, wherein the coupling element is coupled to a respective pair of elastic elements aligned, one as a prolongation of the other, in the first direction of detection and extending from the point of connection with the rigid element;

the elastic elements being configured to operate in bending-in-the-plane during the movement in phase-opposition of the first and second sensing masses, and to operate in bending-out-of-the-plane during the movement in phase;

the elastic elements configured to present the second stiffness with respect to deformations of bending-out-of-the-plane, and the first stiffness with respect to deformations of bending-in-the-plane.

9. The structure according to claim 1 wherein the driving assembly is configured to be actuated in a plane with the driving movement;

and wherein the first and second sensing masses are configured to perform a respective movement of detection of a linear translation in the plane, in response to a yaw angular velocity applied, during operation, about a first axis transverse to the plane.

10. The structure according to claim 1 wherein the driving assembly is configured to be actuated in a plane with the driving movement;

and wherein the first and second sensing masses are configured to perform a respective movement of detection of a rotation out of the plane, in response to an angular velocity of roll or pitch applied, during operation, about a first or a second axis belonging to the plane and along which the first and second sensing masses are aligned.

11. The structure according to claim 10, further comprising a third sensing mass and a fourth sensing mass suspended above the substrate and coupled to the driving assembly via respective second elastic supports and to the first sensing mass and the second sensing mass, via third elastic supports;

the third sensing mass and fourth sensing mass configured to perform a respective movement of detection of a linear translation in the plane, in response to a yaw angular velocity applied, during operation, about a third axis transverse to the plane.

12. The structure according to claim 10, further comprising a third sensing mass and a fourth sensing mass suspended above the substrate and coupled to the driving assembly via respective second elastic supports;

wherein the rigid element comprises a first frame element, and a second frame element set within, and coupled to, the first frame element, the second frame element constrained at the point of constraint, and the first frame element coupled to the first sensing mass and the second sensing mass via the first and the second elastic connectors, and to the third sensing mass and fourth sensing mass via third and fourth elastic connectors;

the third sensing mass and fourth sensing mass configured to perform a respective movement of detection of a rotation out of the plane in response to an angular velocity of pitch or roll applied, during operation, about the second axis or the first axis belonging to the plane and along which the third sensing mass and fourth sensing mass are aligned.

13. The structure according to claim 12, of a triaxial type, further comprising a fifth sensing mass and a sixth sensing mass suspended above the substrate and coupled to the driving assembly via third elastic supports, and, respectively to the third sensing mass and to the fourth sensing mass, via fifth and sixth elastic connectors;

the fifth and sixth sensing mass configured to perform a respective movement of detection of a linear translation in the plane, in response to a yaw angular velocity applied, during operation, about a vertical axis transverse to the plane.

14. An electronic device, comprising:

an integrated MEMS structure further comprising;

a substrate;

a driving assembly anchored to the substrate and configured to be actuated with a driving movement;

a first sensing mass and a second sensing mass suspended above the substrate;

first and second elastic supports, respectively coupling the first and second masses to the driving assembly and configured to enable the sensing masses to perform a movement of detection along a first direction of detection, in response to an external stress;

a coupling assembly to mechanically connect the first sensing mass and the second sensing mass and to couple their vibration modes, the coupling assembly further comprising;

a rigid element between the first and the second sensing masses having a point of constraint in an intermediate position between the first and second sensing masses; and

first and second elastic connectors to connect respective ends of the rigid element to the first and second sensing masses, the first and second elastic connectors and the rigid element configured to present a first stiffness to a movement in phase-opposition, and a second stiffness, greater than the first stiffness, to a movement in phase of the first and second sensing masses along the first direction of detection; and

a reading stagecoupled to the integrated MEMS structure.

15. The device according to claim 14 wherein the coupling assembly has two vibration modes, one in phase and the other in phase-opposition, having frequencies distinct from one another;

and wherein the reading stage is configured to cancel a contribution of the in-phase mode of vibration, via a low-pass filtering operation.

16. A method, comprising:

forming an integrated MEMS structure, the forming comprising;

forming a driving assembly anchored to a substrate and configured to be actuated with a driving movement;

forming a first sensing mass and a second sensing mass suspended above the substrate;

forming first and second elastic supports, respectively to couple the first and second sensing masses to the driving assembly and configured to enable the sensing masses to perform a movement of detection along a first direction of detection, in response to an external stress; and

forming a coupling assembly mechanically connecting the first sensing mass and the second sensing mass and to couple their vibration modes, forming the coupling assembly further comprising;

forming a rigid element between the first and the second sensing masses having a point of constraint in an intermediate position between the first and second sensing masses; and

forming first and second elastic connectors to connect respective ends of the rigid element to the first and second sensing masses, the first and second elastic connectors and the rigid element to present a first stiffness to a movement in phase-opposition, and a second stiffness, greater than the first stiffness, to a movement in phase of the first and second sensing masses along the first direction of detection.

17. The method of claim 16, further comprising fixing the point of constraint with respect to translation during the movement of detection.

18. The method of claim 16, further comprising forming the rigid element to extend between the first sensing mass and the second sensing mass in a direction transverse to the first direction of detection;

and enabling in the first sensing mass and the second sensing mass the movement in phase-opposition along lines substantially parallel to one another and to the first direction of detection.