Capacitive sensor

• US 8,176,782 B2
• Filed: 04/25/2007
• Issued: 05/15/2012
• Est. Priority Date: 04/28/2006
• Status: Active Grant

• Current Assignee: Mosaid Technologies Incorporated (MOSAID Technologies Inc. (f/k/a Conversant Intellectual Property Management))
• Original Assignee: Panasonic Electric Works Company Limited (Panasonic Holdings Corporation)
• Inventors: Furukubo, Eiichi, Wakabayashi, Daisuke, Miyajima, Hisakazu, Aoki, Ryo, Ohbuchi, Masao
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US12/296,554
• Publication Number:
  US 20090266164A1
• Time in Patent Office: 1,847 Days
• Field of Search: 735/143.2, 735/10, 735/041.2, 361/280
• US Class Current: 73/514.32
• CPC Class Codes: G01P 1/023 for acceleration measuring devices
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0831 the mass being of the paddle type having the pivot axis between the longitudinal ends of the mass, e.g. see-saw configuration

Abstract

A capacitive sensor includes a fixed electrode and a movable electrode that is movably supported by an anchor portion through a beam portion. The fixed electrode and the movable electrode are opposed to each other with a gap interposed therebetween, thereby constituting a detecting unit. A capacitance suitable for a size of the gap is detected to detect a predetermined physical value. At least one of an end of the beam portion connected to the anchor portion and an end of the beam portion connected to the movable electrode is provided with a stress moderating unit that moderates a stress.

Claims

1. A capacitive sensor, comprising:

a first detector movably supported by a fixed portion of a semiconductor layer through a beam portion such that an asymmetric weight balance is kept, in which a first movable electrode that moves according to displacement of a physical value in a thickness direction of the semiconductor layer and a first fixed electrode formed on a support substrate that supports the semiconductor layer are opposed to each other with a gap interposed therebetween, the first detector detecting the physical value based on a capacitance detected according to a size of the first movable electrode and the first fixed electrode, the semiconductor layer being a single crystal silicon layer, a movable mechanism of the first movable electrode comprising the fixed portion, the beam portion and the first movable electrode being formed by vertically etching the single crystal silicon layer; and

a second detector having;

a second movable electrode movably supported by the fixed portion of the semiconductor layer through a beam portion, and that is operated according to displacement of physical values in both directions of the semiconductor layer; and

a second fixed electrode formed by the semiconductor layer, wherein the second movable electrode and the second fixed electrode are opposed to each other through a gap, the second detector detecting a physical value based on a capacitance detected according to a size of the gap between the second movable electrode and the second fixed electrode,

wherein the first movable electrode of the first detector has a shape surrounding the second detector.