MICRO-ELECTRO-MECHANICAL DEVICE WITH COMPENSATION OF ERRORS DUE TO DISTURBANCE FORCES, SUCH AS QUADRATURE COMPONENTS

• US 20150377624A1
• Filed: 06/25/2015
• Published: 12/31/2015
• Est. Priority Date: 06/30/2014
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Falorni, Luca Giuseppe, Valzasina, Carlo, Carminati, Roberto, Tocchio, Alessandro
• Granted Patent: US 9,696,157 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B81B 2201/025 Inertial sensors not provided for in B81B2201/0235 - B81B2201/0242
• CPC Class Codes: B81B 2203/0163 Spring holders
• CPC Class Codes: B81B 3/0018 Structures acting upon the moving or flexible element for transforming energy into mechanical movement or vice versa, i.e. actuators, sensors, generators
• CPC Class Codes: B81B 3/0086 Electrical characteristics, e.g. reducing driving voltage, improving resistance to peak voltage
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure
• CPC Class Codes: G01C 19/5733 Structural details or topology
• CPC Class Codes: G01C 19/5747 each sensing mass being connected to a driving mass, e.g. driving frames

Abstract

MEMS device having a support region elastically carrying a suspended mass through first elastic elements. A tuned dynamic absorber is elastically coupled to the suspended mass and configured to dampen quadrature forces acting on the suspended mass at the natural oscillation frequency of the dynamic absorber. The tuned dynamic absorber is formed by a damping mass coupled to the suspended mass through second elastic elements. In an embodiment, the suspended mass and the damping mass are formed in a same structural layer, for example of semiconductor material, and the damping mass is surrounded by the suspended mass.

Claims

1. A MEMS device comprising:

a substrate;

first elastic elements; and

a movable mass system including;

a suspended mass elastically coupled to the substrate by the first elastic elements and subject to disturbance forces along a vibration direction; and

a dynamic absorber elastically coupled to the suspended mass and configured to reduce movements of the suspended mass due to the disturbance forces.

2. The MEMS device according to claim 1, wherein the disturbance forces are quadrature forces that act on the suspended mass in the vibration direction at a natural oscillation frequency of the dynamic absorber.

3. The MEMS device according to claim 2, wherein the dynamic absorber comprises a damping mass coupled to the suspended mass by second elastic elements, the first and second elastic elements being configured to enable the suspended mass and the damping mass to move in the vibration direction.

4. The MEMS device according to claim 3, wherein the damping mass is surrounded by the suspended mass.

5. The MEMS device according to claim 4, wherein the damping mass and the suspended mass are formed in a structural layer of semiconductor material.

6. The MEMS device according to claim 5, wherein the structural layer is suspended over the substrate, wherein the substrate is of semiconductor material.

7. The MEMS device according to claim 1, wherein the MEMS device forms an inertial sensor.

8. The MEMS device according to claim 7, comprising third elastic elements and a driving structure coupled to the suspended mass by the third elastic elements, the driving structure being configured to generate a driving movement in a driving direction that is different from the vibration direction at the natural oscillation frequency.

9. The MEMS device according to claim 7, wherein the inertial sensor is a gyroscope.

10. The MEMS device according to claim 9, wherein:

the gyroscope is a biaxial gyroscope, the suspended mass comprises first and second pairs of sensing masses arranged symmetrically about a first and a second driving axes;

the sensing masses being arranged about a central axis and being elastically coupled to a central anchorage region;

the first and second driving axes being perpendicular to each other, the sensing masses of a first pair being symmetric with respect to the second driving axis and being actuated parallel to the first driving axis, the sensing masses of a second pair being symmetric with respect to the first driving axis and being actuated parallel to the second driving axis; and

each sensing mass surrounding and elastically coupled to a respective damping mass.

11. The MEMS device according to claim 10, comprising:

fourth and fifth elastic elements;

a first driving frame and a second driving frame elastically coupled to the substrate, the first and second driving frames being elastically coupled to the first pair of sensing masses by the fourth elastic elements and configured to transmit a driving movement along the first driving axis, the first and second driving frames being elastically coupled to the second pair of sensing masses by the fifth elastic elements and configured to transmit a driving movement along the second driving axis.

12. The MEMS device according to claim 11, wherein the first and second driving frames each include at least one electrostatic driving unit configured to generate a driving movement for the respective driving frame at a natural oscillation frequency of the damping masses, each of the first and second driving frames including a frequency-detection unit configured to detect an effective driving frequency of the sensing masses.

13. An electronic device comprising:

a controller;

an input/output device coupled to the controller; and

a MEMS device coupled to the controller, the MEMS device including;

a substrate;

first and second elastic elements; and

a movable mass system including;

a suspended mass elastically coupled to the substrate by the first elastic elements; and

a dynamic absorber elastically coupled to the suspended mass by the second elastic elements, the dynamic absorber being configured to absorb at least some disturbance forces that would otherwise act on the suspended mass.

14. The electronic device according to claim 13, wherein the dynamic absorber is located in an opening of the suspended mass.

15. The electronic device according to claim 13, wherein MEMS device includes a driving assembly configured to drive the suspended mass and the damping mass in a first plane, wherein the damping mass is driven at its resonance frequency, wherein the disturbance forces are perpendicular to the first plane.

16. The electronic device according to claim 13, wherein the MEMS device includes at least one of a gyroscope and accelerometer.

17. The electronic device according to claim 13, wherein the electronic device is at least one of a tablet, a laptop, a portable computer, a smartphone, a wearable device, a messaging device, a digital music player, and a digital photo or video camera.

18. The electronic device according to claim 13, wherein the suspended mass extends substantially in a plane, and the dynamic absorber is configured to absorb disturbance forces having a direction that is perpendicular to the plane of the suspended mass.

19. The electronic device according to claim 13, wherein:

the suspended mass comprises first and second pairs of sensing masses arranged symmetrically about a first and a second driving axes, respectively;

the first and second driving axes being perpendicular to each other, the sensing masses of a first pair being symmetric with respect to the second driving axis and being actuated parallel to the first driving axis, the sensing masses of a second pair being symmetric with respect to the first driving axis and being actuated parallel to the second driving axis; and

each sensing mass surrounding by and being elastically coupled to a respective damping mass.

20. The electronic device according to claim 13, wherein the sensing masses being arranged about a central axis and being elastically coupled to a central anchorage region.