INERTIAL SENSOR

• US 20090183568A1
• Filed: 12/23/2008
• Published: 07/23/2009
• Est. Priority Date: 01/21/2008
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Takano, Hideaki, YAMANAKA, Kiyoko
• Granted Patent: US 8,250,920 B2
• Time in Patent Office: Days
• US Class Current: 73/504.40
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 2201/0242 Gyroscopes
• CPC Class Codes: B81B 7/02 containing distinct electrical or optical devices of particular relevance for their function, e.g. microelectro-mechanical systems [MEMS] B81B7/04 takes precedence
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01P 1/02 Housings
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up

Abstract

An angular rate sensor and an acceleration sensor are sealed at the same sealing pressure. The sealing pressure at this time is put into a reduced pressure state below the atmospheric pressure in view of improving a detection sensitivity of the angular rate sensor. Even in the reduced pressure atmosphere, to improve the detection sensitivity of the acceleration sensor, a shift suppressing portion (damper) for suppressing shifts of a movable body of the acceleration sensor is provided. This shift suppressing portion includes a plurality of protruding portions integrally formed with the movable body and a plurality of protruding portions integrally formed with a peripheral portion, and the protruding portions are alternately disposed separately at equal intervals.

Claims

1. An inertial sensor comprising:

(a) an angular rate sensor which detects an angular rate; and

(b) an acceleration sensor which detects acceleration, wherein

the angular rate sensor includes;

(a1) a first peripheral portion formed on a first semiconductor substrate;

(a2) a first cavity portion formed in the interior of the first peripheral portion;

(a3) a first fixing portion formed in the interior of the first cavity portion;

(a4) a vibrating body formed in the interior of the first cavity portion;

(a5) a first elastic deforming portion which is elastically deformable and connects the first fixing portion and the vibrating body;

(a6) a Coriolis frame formed in the interior of the vibrating body; and

(a7) a second elastic deforming portion which is elastically deformable and connects the vibrating body and the Coriolis frame, wherein

the acceleration sensor includes;

(b1) a second peripheral portion formed on a second semiconductor substrate;

(b2) a second cavity portion formed in the interior of the second peripheral portion;

(b3) a second fixing portion formed in the interior of the second cavity portion;

(b4) a movable body formed in the interior of the cavity portion; and

(b5) a third elastic deforming portion which is elastically deformable and connects the second fixing portion and the movable body, and wherein

the first cavity portion and the second cavity portion are inertial sensors set at a same pressure, and the movable body of the acceleration sensor is provided with a first shift suppressing portion which suppresses shifts with respect to an acceleration.

2. The inertial sensor according to claim 1, wherein

a second shift suppressing portion which suppresses a shift to a Coriolis force is further provided to the Coriolis frame of the angular rate sensor.

3. The inertial sensor according to claim 1, wherein

the first cavity portion and the second cavity portion are sealed, and wherein the first cavity portion and the second cavity portion are set to a pressure below the atmospheric pressure.

4. The inertial sensor according to claim 1, wherein

the first shift suppressing portion has a function of delaying a response to an acceleration as compared with the case where the first shift suppressing portion is not provided.

5. The inertial sensor according to claim 1, wherein

the first shift suppressing portion includes:

(c1) a plurality of first protruding portions formed in the movable body; and

(c2) a plurality of second protruding portions formed in the second peripheral portion, wherein

the plurality of first protruding portions and the plurality of second protruding portions are alternately arranged separately.

6. The inertial sensor according to claim 5, wherein

the plurality of first protruding portions and the plurality of second protruding portions are alternately arranged separately at equal intervals.

7. The inertial sensor according to claim 6, wherein

a spatial distance between the plurality of first protruding portions and the plurality of second protruding portions is a minimum feature size at the time of forming the inertial sensor.

8. The inertial sensor according to claim 5, wherein

the plurality of first protruding portions and the plurality of second protruding portions are configured to protrude in a direction crossing a first shift direction in which the movable body shifts upon receipt of an acceleration, and wherein

the plurality of first protruding portions and the plurality of second protruding portions are arranged in parallel in the first shift direction.

9. The inertial sensor according to claim 1, wherein

the second shift suppressing portion has a function of delaying a response to the Coriolis force as compared with the case where the second shift suppression portion is not provided.

10. The inertial sensor according to claim 1, wherein

the second shift suppressing portion includes:

(d1) a plurality of third protruding portions formed in the Coriolis frame; and

(d2) a plurality of fourth protruding portions formed in a third fixing portion, and

the plurality of third protruding portions and the plurality of fourth protruding portions are alternately arranged separately.

11. The inertial sensor according to claim 10, wherein

the plurality of third protruding portions and the plurality of fourth protruding portions are alternately arranged separately at equal intervals.

12. The inertial sensor according to claim 11, wherein

a spatial distance between the plurality of third protruding portions and the plurality of fourth protruding portions is a minimum feature size in formation of the inertial sensor.

13. The inertial sensor according to claim 10, wherein

the plurality of third protruding portions and the plurality of fourth protruding portions are configured to protrude in a direction crossing a second shift direction in which the Coriolis frame shifts upon receipt of the Coriolis force, and wherein

the plurality of third protruding portions and the plurality of fourth protruding portions are arranged in parallel in the second shift direction.

14. The inertial sensor according to claim 1, wherein

the first semiconductor substrate and the second semiconductor substrate are the same semiconductor substrate, and the angular rate sensor and the acceleration senor are formed on this same semiconductor substrate.

15. The inertial sensor according to claim 14, wherein

the first cavity portion on the angular rate sensor and the second cavity portion on the acceleration sensor are sealed by one cap.

16. The inertial sensor according to claim 15, wherein

the angular rate sensor and the acceleration sensor are formed on the individual chip area formed in a semiconductor wafer, and prior to individualizing the chip area forming the angular rate sensor and the acceleration sensor, the each chip area is sealed by the cap.

17. The inertial sensor according to claim 1, wherein

the acceleration sensor comprises a detecting portion which detects an acceleration of the acceleration sensor, and wherein

the detecting portion includes:

(e1) a fixed electrode formed in the second fixing portion; and

(e2) a detecting electrode formed in the movable body, and wherein

the acceleration of the acceleration sensor is detected by utilizing a change in a capacitance of a capacitor element configured by the fixing electrode and the detecting electrode made as;

the movable body is shifted by adding an acceleration to the acceleration sensor;

a distance between the fixing electrode and the detecting electrode is changed by the movement of the movable body; and

a distance between the fixing electrode and the detecting electrode is changed.

18. The inertial sensor according to claim 17, wherein

the fixing electrode and the detecting electrode are alternately arranged separately, and are arranged so that a distance between the fixing electrode and the detecting electrode formed at one side of the detecting electrode differs from a distance between the fixing electrode and the detection electrode formed at the other side of the detecting electrode.