Inertial sensor

• US 8,250,920 B2
• Filed: 12/23/2008
• Issued: 08/28/2012
• Est. Priority Date: 01/21/2008
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Yamanaka, Kiyoko, Takano, Hideaki
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US12/342,137
• Publication Number:
  US 20090183568A1
• Time in Patent Office: 1,344 Days
• Field of Search: 735/10, 735/040.4, 735/041.2, 735/143.2
• US Class Current: 73/510
• 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 second cavity portion;

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

(b6) an acceleration detection portion which detects acceleration applied to the acceleration sensor,

wherein the first cavity portion and the second cavity portion are at a same pressure,

wherein the acceleration sensor is provided with a first shift suppressing portion, which is separate from the acceleration detection portion and is constructed to provide a damping function for suppressing shifts of the movable body with respect to an acceleration,

wherein the angular rate sensor further includes an angular rate detecting portion that detects a Coriolis force caused by an angular rate applied to the angular rate sensor, and

wherein the angular rate sensor is provided with a second shift suppressing portion, which is separate from the angular rate detecting portion and is constructed to provide a damping function for suppressing shifts of the Coriolis frame with respect to the Coriolis force.

2. 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.

3. 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.

4. The inertial sensor according to claim 1, wherein

the first shift suppressing portion includes:

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

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

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

5. The inertial sensor according to claim 4, wherein

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

6. The inertial sensor according to claim 4, 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.

7. 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.

8. The inertial sensor according to claim 1, wherein

the second shift suppressing portion includes:

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

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

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

9. The inertial sensor according to claim 8, wherein

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

10. The inertial sensor according to claim 8, 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.

11. 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 sensor are formed on this same semiconductor substrate.

12. The inertial sensor according to claim 11, wherein

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

13. The inertial sensor according to claim 12, 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.

14. The inertial sensor according to claim 1, wherein

the acceleration detection portion includes:

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

(e2) a detecting electrode formed on 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 fixed electrode and the detecting electrode made as;

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

a distance between the fixed electrode and the detecting electrode is changed by the movement of the movable body.

15. The inertial sensor according to claim 14, wherein

the fixed electrode is arranged between a pair of the detecting electrodes such that a distance between the fixed electrode and one of the pair of the detecting electrodes differs from a distance between the fixed electrode and the other of the pair of the detecting electrodes.

16. The inertial sensor according to claim 1, wherein:

the first shift suppressing portion includes;

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

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

the plurality of first protruding portions and the plurality of second protruding portions being arranged alternately at equal intervals; and

the acceleration detection portion includes;

(d1) a plurality of fixed electrodes formed on the second fixing portion; and

(d2) a plurality of detecting electrodes formed on the movable body,

the plurality of detecting electrodes and the plurality of fixed electrodes being arranged alternately with successive intervals therebetween being unequal.

17. The inertial sensor according to claim 1, wherein:

the angular rate sensor has a driving direction associated with vibration of the vibrating body,

the acceleration sensor has a displacement direction associated with shifting of the movable body, and

the driving direction and the displacement direction are parallel to each other.