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Electrostatic capacitance detecting device

  • US 7,078,917 B2
  • Filed: 04/16/2004
  • Issued: 07/18/2006
  • Est. Priority Date: 04/17/2003
  • Status: Active Grant
First Claim
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1. An electrostatic capacitance detection device for reading surface contours of an object by detecting an electrostatic capacitance, which changes according to a distance with the object, comprising:

  • M individual power supply lines and N individual output lines, arranged in a matrix of M rows×

    N columns, and electrostatic capacitance detection elements provided on crossing points of the individual power supply lines and the individual output lines,each of the electrostatic capacitance detection elements being formed of a signal detection element and a signal amplification element,the signal detection element being formed of a capacitance detecting electrode, a capacitance detecting dielectric layer and a reference capacitor,the reference capacitor being formed of a reference capacitor first electrode, a reference capacitor dielectric layer and a reference capacitor second electrode, andthe signal amplification element being formed of a MIS type thin film semiconductor device for signal amplification, including a gate electrode, a gate insulating layer and a semiconductor layer,using an area of the reference capacitor electrode of SR

    m2), a gate electrode area of the MIS type thin film semiconductor device for signal amplification of ST

    m2), a thickness of the reference capacitor dielectric layer of tR

    m), a dielectric constant of the reference capacitor dielectric layer of ∈

    R, a thickness of the gate insulating layer of tox

    m), and a dielectric constant of the gate insulating layer of ∈

    ox, a capacitance CR (reference capacitor capacitance) of the reference capacitor and a transistor capacitance CT of the MIS type thin film semiconductor device for signal amplification are defined as
    CR=∈

    0·



    R·

    S
    R/tR,
    CT=∈

    0·



    ox·

    S
    T/toxwhere ∈

    0 is permittivity in vacuum, respectively; and

    using an area of the capacitance detecting electrode of SD

    m2), a thickness of the capacitance detecting dielectric layer of tD

    m), and a dielectric constant of the capacitance detecting dielectric layer of ∈

    D, an element capacitance CD of the signal detection element is defined as
    CD=∈

    0·



    D·

    S
    D/tDwhere ∈

    0 is permittivity in vacuum, andthe element capacitance CD being sufficiently larger than CR+CT, a summation of the capacitance CR of the reference capacitor and the transistor capacitance CT.

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