Micromechanical detection structure of a MEMS multi-axis gyroscope, with reduced drifts of corresponding electrical parameters

Patent metadata

Field	Value
Publication number	US-10480942-B2
Application number	US-201615273312-A
Country	US
Kind code	B2
Filing date	Sep 22, 2016
Priority date	Mar 31, 2016
Publication date	Nov 19, 2019
Grant date	Nov 19, 2019

Abstract

A multi-axis MEMS gyroscope includes a micromechanical detection structure having a substrate, a driving-mass arrangement, a driven-mass arrangement with a central window, and a sensing-mass arrangement which undergoes sensing movements in the presence of angular velocities about a first horizontal axis and a second horizontal axis. A sensing-electrode arrangement is fixed with respect to the substrate and is set underneath the sensing-mass arrangement. An anchorage assembly is set within the central window for constraining the driven-mass arrangement to the substrate at anchorage elements. The anchorage assembly includes a rigid structure suspended above the substrate that is elastically coupled to the driven mass by elastic connection elements at a central portion, and is coupled to the anchorage elements by elastic decoupling elements at end portions thereof.

First claim

The invention claimed is:

1. A multi-axis MEMS gyroscope, comprising:
a micromechanical detection structure having a main extension in a horizontal plane, the micromechanical detection structure including:
a substrate including semiconductor material;
a driving-mass arrangement configured to be driven in a driving movement;
a driven-mass arrangement having a central window, the driven-mass arrangement coupled elastically to said driving-mass arrangement and configured to be driven in motion by said driving movement;
a sensing-mass arrangement configured to perform, in response to motion of the driven-mass arrangement and in the presence of a first angular velocity about a first horizontal axis of the horizontal plane, a first detection movement of rotation out of the horizontal plane about a second horizontal axis of the horizontal plane, perpendicular to the first horizontal axis, and further configured to perform, in response to motion of the driven-mass arrangement and in the presence of a second angular velocity about the second horizontal axis of the horizontal plane, a second detection movement of rotation out of the horizontal plane about the first horizontal axis;
a sensing-electrode arrangement fixed with respect to the substrate and capacitively coupled to the sensing-mass arrangement; and
an anchorage assembly arranged within the central window of the driven-mass arrangement, the anchorage assembly elastically coupled to the driven-mass arrangement, and configured to constrain the driven-mass arrangement to the substrate at anchorage elements, wherein
said anchorage assembly includes a rigid structure that is suspended above said substrate,
the rigid structure includes a pair of rigid elements that extend along the second horizontal axis and that are arranged symmetrically with respect to the second horizontal axis in the central window,
each of the pair of rigid elements is elastically coupled to the driven-mass arrangement by a respective elastic connection element that extends from a central portion of a respective rigid element to the driven-mass arrangement,
and each of the pair of rigid elements is coupled, at respective terminal ends of the rigid element, to respective anchorage elements by respective elastic decoupling elements, and
said anchorage elements are positioned at a distance from said elastic connection elements and proximate to said sensing-electrode arrangement in the horizontal plane.

2. The multi-axis MEMS gyroscope according to claim 1 , wherein said elastic decoupling elements are configured to elastically decouple said rigid structure from deformations of said substrate due to one or more of thermal drifts, mechanical stresses, and humidity absorption.

3. The multi-axis MEMS gyroscope according to claim 1 , wherein the anchorage elements are positioned proximate to said sensing-electrode arrangement to minimize a mean of the variations of gaps between said sensing-mass arrangement and said sensing-electrode arrangement.

4. The multi-axis MEMS gyroscope according to claim 1 , wherein said anchorage assembly is configured so that said rigid structure is substantially immobile with respect to said first and second angular velocities.

5. The multi-axis MEMS gyroscope according to claim 1 , wherein said driven-mass arrangement comprises a driven mass having internally a first pair of lateral windows set laterally with respect to the central window and aligned along the first horizontal axis; and wherein said sensing-mass arrangement comprises a first pair of sensing masses, each of which is set within a respective lateral window of said first pair of lateral windows, is suspended above the substrate, and is coupled to the driven mass by respective elastic suspension elements; and wherein said elastic suspension elements, of a torsional type, extend parallel to the second horizontal axis on opposite sides of a terminal portion of the respective sensing masses so that said sensing masses are set in cantilever fashion above said substrate.

6. The multi-axis MEMS gyroscope according to claim 5 , wherein said sensing-electrode arrangement comprises a first pair of sensing electrodes set on the substrate underneath said first pair of sensing masses.

7. The gyroscope according to claim 6 , wherein said driven mass further has internally a second pair of lateral windows set laterally with respect to the central window and aligned along the second horizontal axis; and wherein said sensing-mass arrangement comprises a second pair of sensing masses, each of which is set within a respective lateral window of said second pair of lateral windows and is coupled to the driven mass by respective elastic suspension elements suspended in cantilever fashion above said substrate.

8. The multi-axis MEMS gyroscope according to claim 7 , wherein said sensing-electrode arrangement comprises a second pair of sensing electrodes set on the substrate underneath said second pair of sensing masses.

9. The multi-axis MEMS gyroscope according to claim 1 , wherein said driving-mass arrangement is coupled to a set of driving electrodes and is configured to be driven in said driving movement based upon electrical biasing of said set of driving electrodes; wherein said driving movement is a movement of translation along the second horizontal axis such as to drive said driven-mass arrangement into rotation about said vertical axis.

10. The multi-axis MEMS gyroscope according to claim 1 , wherein the elastic connection elements extend within said central window and are aligned to define an axis of rotation out of the horizontal plane for said driven-mass arrangement.

11. An electronic device, comprising:
a MEMS gyroscope including a micromechanical detection structure having a main extension in a horizontal plane, the micromechanical detection structure including:
a substrate including a surface parallel to the horizontal plane;
a driving-mass structure positioned over the surface of the substrate and configured to oscillate in the horizontal plane;
a driven-mass structure positioned over the surface of the substrate and including a central window, the driven-mass structure elastically coupled to the driving-mass structure and configured oscillate, responsive to oscillations of the driving-mass structure in the horizontal plane, in a rotational motion about a vertical axis orthogonal to the horizontal plane;
a sensing-mass structure positioned over the surface of the substrate and configured to detect rotational movement of the driven-mass structure about first and second horizontal axes in the horizontal plane;
a sensing-electrode structure arranged on the surface of the substrate, the sensing-electrode structure capacitively coupled to the sensing-mass structure;
an anchorage assembly arranged within the central window of the driven-mass structure, the anchorage assembly including,
a rigid structure suspended over the surface of the substrate, the rigid structure including a pair of rigid elements that extend along the second horizontal axis and that are arranged symmetrically with respect to the second horizontal axis in the central window;
elastic coupling elements coupling the pair of rigid elements to the driven-mass arrangement, each of the elastic coupling elements extending from a central portion of a respective rigid element to the driven-mass arrangement;
anchorage elements on the surface of the substrate, each anchorage element proximate to the sensing-electrode structure and spaced apart in the horizontal plane from the elastic coupling elements; and
elastic decoupling elements coupled between end portions of the pair of rigid elements and the anchorage elements;

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Assignees

• St Microelectronics Srl

Inventors

• Gattere Gabriele
• Valzasina Carlo
• Falorni Luca Giuseppe

Classifications

• G01C19/5712 Primary

  the devices involving a micromechanical structure · CPC title

• G01C19/5747 Primary

  each sensing mass being connected to a driving mass, e.g. driving frames · CPC title

• G01C19/58 Primary

  Turn-sensitive devices without moving masses · CPC title

• Y10T29/49169

  Assembling electrical component directly to terminal or elongated conductor · CPC title

• G01C25/00

  Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass (testing, calibrating or compensating compasses G01C17/38) · CPC title