Semiconductor mechanical sensor

• US 6,422,078 B2
• Filed: 12/22/2000
• Issued: 07/23/2002
• Est. Priority Date: 08/21/1992
• Status: Expired due to Fees

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Imai, Masahito
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US09/742,448
• Publication Number:
  US 20010009110A1
• Time in Patent Office: 578 Days
• Field of Search: 745/041.5, 745/143.2, 745/141.6, 745/041.2, 745/041.3, 745/041.4, 361/307, 361/283.3, 361/321.1, 361/321.5, 361/283.1
• US Class Current: 73/514.32
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 7/0006 Interconnects
• CPC Class Codes: C07C 303/32 of salts of sulfonic acids
• CPC Class Codes: C07C 303/44 Separation; Purification
• CPC Class Codes: C07C 309/17 containing carboxyl groups bound to the carbon skeleton
• CPC Class Codes: G01C 19/56 Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces
• CPC Class Codes: G01C 19/5656 the devices involving a micromechanical structure
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0817 for pivoting movement of the mass, e.g. in-plane pendulum
• CPC Class Codes: G01P 2015/0828 the mass being of the paddle type being suspended at one of its longitudinal ends
• CPC Class Codes: Y10T 29/49002 Electrical device making
• CPC Class Codes: Y10T 29/49004 including measuring or testing of device or component part

Abstract

A semiconductor mechanical sensor having a new structure in which a S/N ratio is improved. In the central portion of a silicon substrate 1, a recess portion 2 is formed which includes a beam structure. A weight is formed at the tip of the beam, and in the bottom surface of the weight in the bottom surface of the recess portion 2 facing the same, an electrode 5 is formed. An alternating current electric power is applied between the weight portion 4 and the electrode 5 so that static electricity is created and the weight is excited by the static electricity. In an axial direction which is perpendicular to the direction of the excitation of the weight, an electrode 6 is disposed to face one surface of the weight and a wall surface of the substrate which faces the same. A change in a capacitance between the facing electrodes is electrically detected, and therefore, a change in a physical force acting in the same direction is detected.

Claims

1. A semiconductor mechanical sensor comprising:

a semiconductor substrate;

a beam structure extending in spaced relation over said semiconductor substrate;

a weight connected to said beam structure and including a first mechanical force detect electrode, said weight being movable along a predetermined direction;

a second mechanical force detect electrode facing said first mechanical force detect electrode of said weight;

an oscillation member for oscillating said weight; and

an AM modulation means for superimposing a signal from said first mechanical force detect electrode and said second mechanical force detect electrode on a carrier wave;

wherein movement of said weight produces a change in capacitance between said first mechanical force detect electrode and said second mechanical force detect electrode to enable said sensor to detect mechanical forces acting thereon.

2. A semiconductor mechanical sensor in accordance with claim 1, wherein said oscillation member includes a third electrode and a fourth electrode, said third electrode being formed on said weight and said fourth electrode facing said third electrode.

3. A semiconductor mechanical sensor in accordance with claim 1, which is adapted to be used as a yaw rate sensor.

4. A semiconductor mechanical sensor in accordance with claim 1, wherein said oscillation member oscillates said weight in a direction generally perpendicular to said predetermined direction.