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Capacitance type semiconductor dynamic quantity sensor

  • US 7,275,435 B2
  • Filed: 08/26/2004
  • Issued: 10/02/2007
  • Est. Priority Date: 09/22/2003
  • Status: Active Grant
First Claim
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1. A capacitance type semiconductor dynamic quantity sensor comprising:

  • a support substrate;

    a ben-shaped movable electrode displaceable in response to application of a dynamic quantity to the support substrate; and

    beam-shaped fixed electrodes fixedly supported on the support substrate so that side surfaces thereof face a side surface of the movable electrode, the applied dynamic quantity being detected on the basis of variation in electrostatic capacitance between the side surface of the movable electrode and the side surface of each of the fixed electrodes when the movable electrode is displaced in response to the application of the dynamic quantity, wherein;

    the side surface of one of the movable electrode and the fixed electrodes is equipped with adherence preventing projecting portions projecting from the side surface concerned at sites where the side surfaces of the movable and fixed electrodes face each other so that the projecting portions are arranged along a longitudinal direction of the one of the movable and the fixed electrodes;

    when L represents the length of the movable and fixed electrodes at the sites where the side surfaces of the movable and fixed electrodes face each other, La represents the distance between neighboring projecting portions in the arrangement of the projecting portions, σ

    2(x) represents a sagging amount of one of the movable electrode and the beam-shaped fixed electrodes between the projecting portions, E and I represent the Young'"'"'s modulus of the movable and fixed electrodes and the cross-section quadratic moment, W represents the width of the movable and fixed electrodes, h represents the thickness of the movable and fixed electrodes, d2 represents the height of the projecting portions, V represents the voltage applied between the movable electrode and the fixed electrode, and Fe(x) represents the electrostatic force applied between the movable and fixed electrodes,
    σ

    2(x)=[Fe(x

    La3]/(48·



    I
    )]x(⅝

    )
    I=W3h/12
    Fe(x)=ε

    0·

    V
    2/(2·

    d
    22



    L
    ; and

    La/L, W, d2 are determined so that the sagging amount σ

    2(x) is less than half of the height d2 of the projecting portions (σ

    2(x)<

    d2/2).

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