Multi-axis acceleration sensor and manufacturing method thereof

• US 6,201,284 B1
• Filed: 02/18/1998
• Issued: 03/13/2001
• Est. Priority Date: 08/08/1997
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Konno, Nobuaki, Hirata, Yoshiaki, Tsugai, Masahiro
• Primary Examiner(s): Saadat, Mahshid
• Assistant Examiner(s): Wilson, Allan R.
• Application Number:
  US09/025,247
• Time in Patent Office: 1,119 Days
• Field of Search: 257/414, 257/415, 257/417-420, 438/50, 438/52
• US Class Current: 257/415
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/082 for two degrees of freedom of movement of a single mass

Abstract

A movable electrode structure is formed in a single sensor element, and this movable electrode structure can be displaced along two axes within a plane, and one axis outside the plane. A detecting fixed electrode is provided via a constant space with each of these detecting axes, and a change in capacitances between the movable electrodes and the fixed electrodes is detected. As a result, the acceleration components of the two axes, or the three axes are detected. The dynamic characteristic of the sensor is controlled based on the mass of the variable electrode, the structure and length of the beam for supporting the movable electrode, and also the ratio of the length to the section of this beam.

Claims

1. A multi-axis acceleration sensor for detecting acceleration along directions of plural axes comprising:

at least one mass body made of a single crystal silicon wafer and arranged on a plane of said silicon wafer;

at least two cantilever beams arranged in parallel to each other capable of displacing said mass body along a plurality of directions and of holding said mass body in such a manner that direction of displacement of said mass body is defined to be parallel with respect to the plane of said wafer and one end of each of said cantilever beams, said one end being connected with respective end of said mass body and another end of each of said cantilever beams being supported by a supporting unit;

at least one fixed electrode which is electrically insulated from said cantilever beams and said mass body and is arranged each direction, opposite to each other via a constant space every acceleration detecting direction of said mass body so as to detect displacement of said mass body caused by the acceleration along the plural directions; and

displacement detecting means for detecting the displacement of said mass body by applying a constant voltage between said fixed electrode and said mass body, wherein;

said multi-axis acceleration sensor includes a mass body “

a”

displaced with respect to one axis within the wafer plane, and a beam structure holding this mass body “

a”

;

an edge portion of this beam structure is connected to a mass body “

b”

formed at a peripheral portion of said mass body “

a”

;

the beam structure for holding the mass body “

b”

owns such a structure that said beam structure is displaced perpendicular to a displacement direction of said mass body “

a”

;

more than one fixed electrodes are provided via a constant space and positioned opposite to the acceleration detecting directions within the wafer plane of the respective mass bodies; and

the respective fixed electrodes are electrically insulated from the beam and the mass bodies to thereby detect the acceleration of two axes along the detecting directions within the wafer plane.

4. The multi-axis acceleration sensor as claimed in claim 1, further comprising at least one self-diagnostic actuation electrode for performing self-diagnose of sensitivity of the sensor.

5. The multi-axis acceleration sensor of claim 4, wherein two self-diagnostic actuation electrodes are provided for performing self-diagnose along two directions.

6. The multi-axis acceleration sensor of claim 4, wherein three self-diagnostic actuation electrodes are provided for performing self-diagnose along three directions.

2. A multi-axis acceleration sensor for detecting acceleration along directions of plural axes, comprising:

at least one mass body made of a single crystal silicon wafer and arranged on a plane of said silicon wafer;

at least two cantilever beams arranged in parallel to each other, capable of displacing said mass body along a plurality of directions and of holding said mass body in such a manner that direction of displacement of said mass body is defined to be parallel with respect to the plane of said wafer and one end of each of said cantilever beams, said one end being connected with respective end of said mass body and another end of each of said cantilever beams being supported by a supporting unit;

at least one fixed electrode which is electrically insulated from said cantilever beams and said mass body, and is arranged each direction opposite to each other via a constant space every acceleration detecting direction of said mass body so as to detect displacement of said mass body caused by the acceleration along the plural directions; and

displacement detecting means for detecting the displacement of said mass body by applying a constant voltage between said fixed electrode and said mass body, wherein;

said multi-axis acceleration sensor includes a mass body “

a”

displaced with respect to one axis within the wafer plane, and a beam structure holding this mass body “

a”

;

an edge portion of this beam structure is connected to a mass body “

b”

formed at a peripheral portion of said mass body “

a”

;

the beam structure for holding the mass body “

b”

owns such a structure that said beam structure is displaced perpendicular to a displacement direction of said mass body “

a”

;

an edge portion of a beam of said mass body “

b”

is connected to a mass body “

c”

formed at a peripheral portion of the mass body “

b”

;

a beam structure for holding the mass body “

c”

owns a structure displaced along the detecting direction outside the plane;

more than one fixed electrodes are provided via a constant space and positioned opposite to the acceleration detecting directions within the wafer plane of the respective mass bodies; and

the respective fixed electrodes are electrically insulated from the beam and the mass bodies to thereby detect the acceleration of two axes along the detecting directions within the wafer plane, and also one axis along the detecting direction outside the wafer plane.

7. The multi-axis acceleration sensor as claimed in claim 2, further comprising at least one self-diagnostic actuation electrode for performing self-diagnose of sensitivity of the sensor.

8. The multi-axis acceleration sensor of claim 7, wherein two self-diagnostic actuation electrodes are provided for performing self-diagnose along two directions.

9. The multi-axis acceleration sensor of claim 7, wherein three self-diagnostic actuation electrodes are provided for performing self-diagnose along three directions.

3. A multi-axis acceleration sensor for detecting acceleration along directions of plural axes comprising:

at least one mass body made of a single crystal silicon wafer and arranged on a plane of said silicon wafer;

at least two cantilever beams arranged in parallel to each other, capable of displacing said mass body along a plurality of directions and of holding said mass body in such a manner that direction of displacement of said mass body is defined to be parallel with respect to the plane of said wafer and one end of each of said cantilever beams, said one end being connected with respective end of said mass body and another end of each of said cantilever beams being supported by a supporting unit;

at least one fixed electrode which is electrically insulated from said cantilever beams and said mass body, and is arranged each direction opposite to each other via a constant space every acceleration detecting direction of said mass body so as to detect displacement of said mass body caused by the acceleration along the plural directions; and

displacement detecting means for detecting the displacement of said mass body by applying a constant voltage between said fixed electrode and said mass body, wherein;

said multi-axis acceleration sensor includes a mass body “

a”

displaced with respect to one axis outside the wafer plane, and a beam structure holding this mass body “

a”

;

an edge portion of this beam structure is connected to a mass body “

b”

formed at a peripheral portion of said mass body “

a”

;

a beam structure for holding a mass body “

b”

is such a structure displaced with respect to one axis within the wafer plane, a beam edge portion of the mass body “

b”

is connected to a mass body “

c”

formed at a peripheral portion of the mass body “

b”

;

a beam structure for holding the mass body “

c”

owns such a displacement structure positioned perpendicular to the displacement direction of the mass body “

b”

within the wafer plane;

more than one fixed electrodes are provided via a constant space and positioned opposite to the acceleration detecting directions within the wafer plane of the respective mass bodies; and

the respective fixed electrodes are electrically insulated from the beam and the mass bodies to thereby detect the acceleration of two axes along the detecting directions within the wafer plane, and also the acceleration of one axis along the detecting direction outside the wafer plane.

10. The multi-axis acceleration sensor as claimed in claim 3, further comprising at least one self-diagnostic actuation electrode for performing self-diagnose of sensitivity of the sensor.

11. The multi-axis acceleration sensor of claim 10, wherein two self-diagnostic actuation electrodes are provided for performing self-diagnose along two directions.

12. The multi-axis acceleration sensor of claim 10, wherein three self-diagnostic actuation electrodes are provided for performing self-diagnose along three directions.