CAPACITIVE MICROMECHANICAL SENSOR STRUCTURE AND MICROMECHANICAL ACCELEROMETER

• US 20150316581A1
• Filed: 06/25/2014
• Published: 11/05/2015
• Est. Priority Date: 06/28/2013
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: LIUKKU, Matti, RYTKONEN, Ville Pekka
• Granted Patent: US 9,547,020 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 2201/033 Comb drives
• CPC Class Codes: B81B 3/0078 Constitution or structural means for improving mechanical properties not provided for in B81B3/007 - B81B3/0075
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/131 with electrostatic counterbalancing means
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/0814 for translational movement of the mass, e.g. shuttle type
• CPC Class Codes: G01P 2015/0871 using stopper structures for limiting the travel of the seismic mass

Abstract

The invention relates to a capacitive micromechanical sensor structure comprising a stator structure rigidly anchored to a substrate and a rotor structure movably anchored by means of spring structures to the substrate. The stator structure has a plurality of stator finger support beams and the rotor structure has a plurality of rotor finger support beams. Stator fingers along the stator finger support beam of the stator structure extend into rotor gaps along the rotor finger support beam of the rotor structure, and rotor fingers along the rotor finger support beam of the rotor structure extend into stator gaps along the stator finger support beam of the stator structure.

Claims

1. A capacitive micromechanical sensor structure comprising:

a stator structure rigidly anchored to a substrate and a rotor structure movably anchored by spring structures to the substrate,

the stator structure having a plurality of stator finger support beams,

the rotor structure having a plurality of rotor finger support beams,

a stator finger support beam of the stator structure comprising a stator finger structure along at least one side of the stator finger support beam, wherein the stator finger structure comprises a plurality of stator fingers and stator gaps between two adjacent stator fingers,

a rotor finger support beam of the rotor structure comprising a rotor finger structure along at least one side of the rotor finger support beam, wherein the rotor finger structure comprises a plurality of rotor fingers and rotor gaps between two adjacent rotor fingers,

stator fingers along the stator finger support beam of the stator structure extending into rotor gaps along the rotor finger support beam of the rotor structure,

rotor fingers along the rotor finger support beam of the rotor structure extending into stator gaps along the stator finger support beam of the stator structure;

characterized by

a stator fingertip gap between the stator fingers of the stator finger structure and the rotor finger support beam being in unloaded state of the capacitive micromechanical sensor structure one to three times a finger side gap between the stator fingers of the stator finger structure and the rotor fingers of the rotor finger structure, and

a rotor fingertip gap between the rotor fingers of the rotor finger structure and the stator finger support beam being in unloaded state of the capacitive micromechanical sensor structure one to three times the finger side gap between the stator fingers of the stator finger structure and the rotor fingers of the rotor finger structure, and

the rotor structure being movably anchored to the substrate in such way that the rotor structure can be deflected at least parallel with the plane of the substrate so that the rotor fingertip gap between the rotor fingers along at least one side of the rotor finger support beam and the stator finger support beam changes, the stator fingertip gap between the stator fingers along at least one side of the stator finger support beam and the rotor finger support beam changes, and a finger overlap length changes, the finger overlap length being the length the stator fingers of the stator finger structure extend into the rotor gaps of the rotor finger structure, or alternatively the length the rotor fingers of the rotor finger structure extend into the stator gaps of the stator finger structure.

2. The capacitive micromechanical sensor structure according to claim 1, wherein the stator finger support beam of the stator structure comprises a stator finger structure along two opposite sides of the stator finger support beam, wherein each stator finger structure comprises a plurality of stator fingers and stator gaps between two adjacent stator fingers.

3. The capacitive micromechanical sensor structure according to claim 1, wherein a rotor finger support beam of the rotor structure comprises a rotor finger structure along two opposites side of the rotor finger support beam, wherein each rotor finger structure comprises a plurality of rotor fingers and rotor gaps between two adjacent rotor fingers.

4. The capacitive micromechanical sensor structure according to claim 1, wherein

the stator fingers of the stator finger structure of the stator finger support beam extend perpendicularly from the stator finger support beam, and

the rotor fingers of the rotor finger structure of the rotor finger support beams extend perpendicularly from a rotor finger support beam.

5. The capacitive micromechanical sensor structure according to claim 1, wherein the capacitive micromechanical sensor structure has reflectional symmetry with respect to a first central axis of the capacitive micromechanical sensor structure.

6. The capacitive micromechanical sensor structure according to claim 5, wherein the stator finger support beams of the stator structure and the rotor finger support beams of the rotor structure extend perpendicularly with respect to the first central axis of the capacitive micromechanical sensor structure.

7. The capacitive micromechanical sensor structure according to claim 5, wherein

the stator fingers of the stator finger structure of the stator finger support beam are parallel with the first central axis of the capacitive micromechanical sensor structure, and

the rotor fingers of the rotor finger structure of the rotor finger support beams are parallel with the first central axis of the capacitive micromechanical sensor structure.

8. The capacitive micromechanical sensor structure according to claim 5, wherein

the rotor structure is movably anchored to the substrate by spring structures comprising a first spring structure and a second spring structure, and

the first spring structure and the second spring structure are disposed at a first central axis of the capacitive micromechanical sensor structure, and to have reflectional symmetry with respect to a second central axis of the capacitive micromechanical sensor structure.

9. The capacitive micromechanical sensor structure according to claim 1, wherein

the capacitive micromechanical sensor structure has reflectional symmetry with respect to a first central axis of the capacitive micromechanical sensor structure and reflectional symmetry with respect to a second central axis of the capacitive micromechanical sensor structure, and

the first central axis of the capacitive micromechanical sensor structure and the second central axis of the capacitive micromechanical sensor structure are perpendicular and cutting each other at a center of mass CM of the capacitive micromechanical sensor structure.

10. The capacitive micromechanical sensor structure according to claim 9, wherein

the stator finger support beams of the stator structure and the rotor finger support beams of the rotor structure are parallel with the second central axis of the capacitive micromechanical sensor structure, and

the rotor fingers of the rotor fingers structure and the stator fingers of the stator finger structure are parallel with the first central axis of the capacitive micromechanical sensor structure.

11. The capacitive micromechanical sensor structure according to claim 1, wherein

the capacitive micromechanical sensor structure comprises a rotor frame surrounding the stator structure and the rotor structure,

the rotor frame is movably anchored to the substrate by spring structures,

the rotor finger support beams of the rotor structure are rigidly connected to the rotor frame, and

the rotor frame is arranged symmetrically with respect to a center of mass of the capacitive micromechanical sensor structure.

12. The capacitive micromechanical sensor structure according to claim 1, wherein

the stator finger support beams of the stator finger structure are vertical comb electrodes,

the rotor finger support beams of the rotor finger structure are vertical comb electrodes,

the stator fingers of the stator finger support beams of the stator finger structure are vertical comb electrodes, and

the rotor fingers of the rotor finger support beams of the rotor finger structure are vertical comb electrodes.

13. The capacitive micromechanical sensor structure according to claim 1, wherein

the stator finger support beam comprises a stator finger structure along a side of the stator finger support beam, and the rotor finger support beam comprising a rotor finger structure along a side of the rotor finger support beam, forming a comb pair,

the comb structure of the capacitive micromechanical sensor structure comprises a plurality of such comb pairs, and

third spaces between two adjacent comb pairs.

14. The capacitive micromechanical sensor structure according to claim 13, wherein

the sides of the stator finger support beams that face a third space are free of a stator finger structure, and

the sides of the rotor finger support beams that face a third space are free of a rotor finger structure.

15. The capacitive micromechanical sensor structure according to claim 13, wherein

the capacitive micromechanical sensor structure has reflectional symmetry with respect to a first central axis of the capacitive micromechanical sensor structure and reflectional symmetry with respect to a second central axis of the capacitive micromechanical sensor structure,

the first central axis of the capacitive micromechanical sensor structure and the second central axis of the capacitive micromechanical sensor structure are perpendicular and cutting each other at a center of mass CM of the capacitive micromechanical sensor structure,

the comb pairs are grouped in four groups of comb pairs each comprising the same number of comb pairs, and

the groups of comb pairs are disposed in reflectional symmetry with respect to the first central axis of the capacitive micromechanical sensor structure, with respect to the second central axis of the capacitive micromechanical sensor structure and with respect to the center of mass of the capacitive micromechanical sensor structure.

16. The capacitive micromechanical sensor structure according to claim 1, wherein

stopper bumps configured to prevent excess movement of the rotor structure with respect to the stator structure but allowing the rotor structure to move in two opposite directions a distance corresponding to a stopper gap that is 0.25 to 2.5, preferably 0.7 to 1 times, the finger side gap between stator fingers of the stator finger structure along the side of the stator finger support beam and a rotor fingers of the rotor finger structure along the side of the rotor finger support beam.

17. The capacitive micromechanical sensor structure according to claim 16, wherein

the capacitive micromechanical sensor structure comprises a rotor frame surrounding the stator structure and the rotor structure,

the rotor frame is movably anchored to the substrate by spring structures,

the rotor finger support beams of the rotor structure is rigidly connected to the rotor frame,

the rotor frame is configured symmetrically with respect to the center of mass of the capacitive micromechanical sensor structure, and wherein

the stopper bumps are configured to prevent excess movement of the rotor structure with respect to the stator structure by preventing excess movement of the rotor frame with respect to the stator structure but allowing the rotor frame to move in two opposite directions a distance corresponding to a stopper gap that is 0.25 to 1.5, preferably 0.7 to 1 times, the finger side gap between a stator fingers of the stator finger structure along the side of the stator finger support beam and a rotor fingers of the rotor finger structure along the side of the rotor finger support beam.

18. A micromechanical accelerometer comprising two capacitive micromechanical sensor structures according to claim 1, wherein

the micromechanical accelerometer comprises a substrate having a plane,

said two capacitive micromechanical sensor structures form a first micromechanical sensor and a second micromechanical sensor in the micromechanical accelerometer,

the first micromechanical sensor is configured to measure acceleration along an x-axis parallel to the plane of the substrate, and wherein

the second micromechanical sensor is configured to measure acceleration along an y-axis parallel to the plane of the substrate and perpendicular to the x-axis.

19. The micromechanical accelerometer according to claim 18, wherein

the micromechanical accelerometer comprises a third central axis C,

the first micromechanical sensor is configured in the micromechanical accelerometer so that a first central axis of the first micromechanical sensor and the third central axis C of the micromechanical accelerometer are parallel, and

the second micromechanical sensor is configured in the micromechanical accelerometer so that a first central axis of the second micromechanical sensor and the third central axis C of the micromechanical accelerometer are perpendicular.

20. The micromechanical accelerometer according to claim 18, further comprising at least one third micromechanical sensor for measuring acceleration along an z-axis that is perpendicular to the plane of the substrate and perpendicular to the x-axis and to the y-axis.