INERTIAL SENSOR AND MANUFACTURING METHOD OF THE SAME

• US 20080196502A1
• Filed: 06/15/2007
• Published: 08/21/2008
• Est. Priority Date: 06/30/2006
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Fujimori, Tsukasa, Hanaoka, Yuko, FUKUDA, Hiroshi
• Granted Patent: US 7,658,109 B2
• Time in Patent Office: Days
• US Class Current: 73/514.38
• CPC Class Codes: G01P 15/08 with conversion into electric or magnetic values
• 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 2015/0814 for translational movement of the mass, e.g. shuttle type
• CPC Class Codes: G01P 2015/0828 the mass being of the paddle type being suspended at one of its longitudinal ends
• CPC Class Codes: G01P 2015/084 the mass being suspended at more than one of its sides, e.g. membrane-type suspension, so as to permit multi-axis movement of the mass
• CPC Class Codes: Y10T 29/49117 Conductor or circuit manufacturing

Abstract

A weight of an inertial sensor if formed from a plurality of divided weights, and the divided weights are connected to each other by elastically deformable beams. A movable range and a mass of each of the divided weights and a rigidity of each of the beams are adjusted and a plurality of deformation modes having different sensitivity ranges with respect to the acceleration are used in combination. By this means, it is possible to improve a detecting sensitivity of an acceleration and widen an acceleration response range.

Claims

1. An inertial sensor comprising:

(a) a cavity portion formed on a substrate;

(b) a weight suspended in the cavity portion via an elastically deformable elastic body; and

(c) a fixed electrode provided in the cavity portion,

wherein a position change of the weight due to an acceleration is detected on the basis of a change of an electrostatic capacitance between the weight and the fixed electrode, and

the weight is divided into a plurality of divided weights, and each of the plurality of divided weights is connected to each other by elastically deformable elastic bodies.

2. The inertial sensor according to claim 1,

wherein some of the plurality of divided weights are connected only to other divided weights via the elastic bodies.

3. The inertial sensor according to claim 1, further comprising:

a lid which seals the cavity portion; and

a support portion which supports the lid and is provided inside the cavity portion,

wherein the support portion is formed among the plurality of divided weights.

4. The inertial sensor according to claim 1,

wherein masses of the plurality of divided weights are equal to each other, and rigidities of the plurality of elastic bodies which connect the plurality of divided weights are also equal to each other.

5. The inertial sensor according to claim 1,

wherein masses of the plurality of divided weights are different from each other, and rigidities of the plurality of elastic bodies which connect the plurality of divided weights are also different from each other.

6. The inertial sensor according to claim 1,

wherein there is a limit to a movable range of the plurality of divided weights.

7. The inertial sensor according to claim 1,

wherein the movable structure body constituted by the plurality of divided weights and the plurality of elastic bodies which connect the plurality of divided weights has a plurality of deformation modes having different sensitivity regions to an acceleration.

8. The inertial sensor according to claim 1,

wherein the plurality of divided weights are arranged on the substrate in a two-dimensional manner.

9. The inertial sensor according to claim 1,

wherein the plurality of divided weights are arranged on the substrate in a one-dimensional manner.

10. A manufacturing method of an inertial sensor comprising:

(a) a step of forming a fixed electrode on a semiconductor substrate;

(b) a step of forming a first interlayer insulating film on the fixed electrode;

(c) a step of forming a first thin film on the first interlayer insulating film;

(d) a step of patterning the first thin film to form a plurality of divided weights functioning as a movable electrode and a plurality of elastic bodies which connect the plurality of divided weights;

(e) a step of forming a second interlayer insulating film on the patterned first thin film;

(f) a step of forming a second thin film on the second interlayer insulating film;

(g) a step of patterning the second thin film to form first etching holes in the second thin film; and

(h) a step of forming a cavity portion by etching a part of the first interlayer insulating film and a part of the second interlayer insulating film through the first etching holes, so that the plurality of divided weights are suspended in the formed cavity portion via the plurality of elastic bodies.

11. The manufacturing method of an inertial sensor according to claim 10, further comprising:

a step of sealing the first etching holes, after the step (h).

12. The manufacturing method of an inertial sensor according to claim 11,

wherein, in the step of sealing the first etching holes, the first etching holes are sealed by a step of depositing a film on the second thin film in which the first etching holes are formed.

13. The manufacturing method of an inertial sensor according to claim 10,

wherein, in the step (g), the first etching holes are formed on the second thin film existing on a forming region of the plurality of divided weights and the plurality of elastic bodies.

14. The manufacturing method of an inertial sensor according to claim 13,

wherein, in the step (h), the cavity portion is formed in a forming region of the plurality of divided weights and the plurality of elastic bodies, and a support portion which supports the cavity portion is formed by leaving the first interlayer insulating film and the second interlayer insulating film below a region in which the first etching holes are not formed.

15. The manufacturing method of an inertial sensor according to claim 14,

wherein the support portion is formed in a region among the plurality of divided weights.

16. The manufacturing method of an inertial sensor according to claim 10,

wherein, in the step (d), second etching holes are formed in the plurality of divided weights at the same time of forming the plurality of divided weights.

17. The manufacturing method of an inertial sensor according to claim 10, further comprising:

a step of forming an MISFET and a wiring layer between the semiconductor substrate and the fixed electrode.

18. A manufacturing method of an inertial sensor comprising:

(a) a step of forming a fixed electrode on a semiconductor substrate;

(b) a step of forming a first interlayer insulating film on the fixed electrode;

(c) a step of forming a first thin film on the first interlayer insulating film;

(d) a step of patterning the first thin film to form a weight functioning as a movable electrode and a plurality of elastic bodies connected to the weight;

(e) a step of forming a second interlayer insulating film on the patterned first thin film;

(f) a step of forming a second thin film on the second interlayer insulating film;

(g) a step of patterning the second thin film to form etching holes in the second thin film existing on a forming region of the weight and the plurality of elastic bodies and not to form the etching hole in the second thin film existing on regions other than the forming region of the weight and the plurality of elastic bodies; and

(h) a step of forming a cavity portion by etching a part of the first interlayer insulating film and a part of the second interlayer insulating film through the first etching holes, so that the weight is suspended in the formed cavity portion via the plurality of elastic bodies, and a support portion which supports the cavity portion is formed by leaving a part of the first interlayer insulating film and a part of the second interlayer insulating film below a region of the second thin film in which the etching hole is not formed.

19. The manufacturing method of an inertial sensor according to claim 18,

wherein, in the step (d), a plurality of divided weights functioning as a movable electrode and a plurality of elastic bodies which connect the plurality of divided weights are formed.

20. The manufacturing method of an inertial sensor according to claim 19,

wherein, the step (h), the support portion is formed among the plurality of divided weights.