Capacitive acceleration sensor

• US 8,312,770 B2
• Filed: 05/12/2008
• Issued: 11/20/2012
• Est. Priority Date: 07/06/2007
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: Fukaura, Teruya
• Primary Examiner(s): Kwok, Helen C.
• Application Number:
  US12/119,057
• Publication Number:
  US 20090007669A1
• Time in Patent Office: 1,653 Days
• Field of Search: 735/143.2, 735/143.6, 735/143.8, 735/142.9
• US Class Current: 73/514.32
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 3/0008 Structures for avoiding electrostatic attraction, e.g. avoiding charge accumulation
• CPC Class Codes: B81C 2203/0118 Bonding a wafer on the substrate, i.e. where the cap consists of another wafer
• CPC Class Codes: B81C 2203/031 Anodic bondings
• CPC Class Codes: G01P 1/023 for acceleration measuring devices
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0814 for translational movement of the mass, e.g. shuttle type

Abstract

A capacitive acceleration sensor that prevents sticking of a mass body, made of silicon, to a first sealing substrate or a second sealing substrate, made of glass. The capacitive acceleration sensor includes a first sealing substrate and a second sealing substrate each made of glass. The mass body is suspended between the first and second sealing substrates by a beam attached to a substrate, and one or both of the sealing substrates is processed such that the mass body only contacts with a subsection of the substrate surface.

Claims

1. A capacitive acceleration sensor including a first sealing substrate and a second sealing substrate each made of glass, the sensor comprising therebetween:

an acceleration detecting portion, made of silicon, including;

a mass body supported in the air to have predetermined gaps each to the first sealing substrate and to the second sealing substrate,

a beam, connected to the mass body for supporting the mass body in the air, having elasticity to enable the mass body to be displaced, and

a fixed electrode provided to face the mass body with a predetermined gap thereto;

a bonding frame, made of silicon, provided so as to surround the periphery of the acceleration detecting portion; and

one of the first sealing substrate and the second sealing substrate including, at a position thereof facing the mass body, a contact portion with which only at least one peripheral portion of the mass body comes into contact, the contact portion being level with a portion of the one of the first sealing substrate and the second sealing substrate facing the fixed electrode in a direction parallel with the mass body.

2. A capacitive acceleration sensor as recited in claim 1, wherein the one of the first sealing substrate and the second sealing substrate including the contact portion is provided with a concavity at a position thereof facing the mass body, to contact the at least one peripheral portion of the mass body.

4. A capacitive acceleration sensor as recited in any one of claims 1 through 3, wherein a contact range of the contact portion with which the mass body comes into contact is determined, in such a way that at the position where the mass body comes into contact with the contact portion, sticking force by which the mass body is stuck to the contact portion becomes lower than recovery force due to the elasticity of the beam that is intended for taking the mass body away from the contact portion.

8. A capacitive acceleration sensor as recited in claim 1, wherein the at least one of the first sealing substrate and the second sealing substrate including the contact portion is anodically bonded to the bonding frame.

9. A capacitive acceleration sensor as recited in claim 2, wherein the depth of the concavity is such that the mass body is prevented from contacting the deepest part of the concavity.

3. A capacitive acceleration sensor including a first sealing substrate and a second sealing substrate each made of glass, the sensor comprising therebetween:

an acceleration detecting portion, made of silicon, including;

a mass body supported in the air to have predetermined gaps each to the first sealing substrate and to the second sealing substrate,

a beam, connected to the mass body for supporting the mass body in the air, having elasticity to enable the mass body to be displaced, and

a fixed electrode provided to face the mass body with a predetermined gap thereto;

a bonding frame, made of silicon, provided so as to surround the periphery of the acceleration detecting portion, wherein

at least one of the first sealing substrate and the second sealing substrate including a contact portion with a protrusion at a position thereof facing the mass body, to contact only a center of the mass body.

5. A capacitive acceleration sensor including a first sealing substrate made of silicon, and a second sealing substrate made of glass, the sensor comprising therebetween:

an acceleration detecting portion, made of silicon, including;

a mass body supported in the air to have predetermined gaps each to the first sealing substrate and to the second sealing substrate,

a beam, connected to the mass body for supporting the mass body in the air, having elasticity to enable the mass body to be displaced, and

a fixed electrode provided to face the mass body with a predetermined gap thereto;

a bonding frame, made of silicon, provided to surround the periphery of the acceleration detecting portion; and

the second sealing substrate including, at a position thereof facing the mass body a contact portion with which a part of the mass body comes into contact, wherein

the second sealing substrate is provided with a concavity at a position thereof facing the mass body, to contact only at least one peripheral portion of the mass body, the contact portion being level with a portion of the second sealing substrate facing the fixed electrode in a direction parallel with the mass body.

7. A capacitive acceleration sensor as recited in any one of claim 5 or 6, wherein a contact range of the contact portion with which the mass body comes into contact is determined, in such a way that at the a position where the mass body comes into contact with the contact portion, sticking force by which the mass body is stuck to the contact portion becomes lower than recovery force due to the elasticity of the beam that is intended for taking the mass body away from the contact portion.

6. A capacitive acceleration sensor as including a first sealing substrate made of silicon, and a second sealing substrate made of glass, the sensor comprising therebetween:

an acceleration detecting portion, made of silicon, including;

a mass body supported in the air to have predetermined gaps each to the first sealing substrate and to the second sealing substrate,

a beam, connected to the mass body for supporting the mass body in the air, having elasticity to enable the mass body to be displaced, and

a fixed electrode provided to face the mass body with a predetermined gap thereto;

a bonding frame, made of silicon, provided to surround the periphery of the acceleration detecting portion; and

the second sealing substrate including, at a position thereof facing the mass body a contact portion with which a part of the mass body comes into contact, wherein

the second sealing substrate is provided with a protrusion at the contact portion thereof facing the mass body, to contact only a center of the mass body.