Title page for etd-0827108-123254


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URN etd-0827108-123254
Author Chia-hsu Hsieh
Author's Email Address No Public.
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Department Electrical Engineering
Year 2007
Semester 2
Degree Master
Type of Document
Language zh-TW.Big5 Chinese
Title A Study on High-linearity and Low-hysteresis
Capacitive Humidity Microsensors
Date of Defense 2008-07-18
Page Count 77
Keyword
  • Polyimide (PI)
  • Low Hysteresis
  • High Linearity
  • Capacitive Relative Humidity (RH) Microsensor
  • Relative Humidity (RH)
  • Abstract People for long term exposed to an air-conditioned but highly humid environment
    are vulnerable to hyper-sensitivity or asthma triggered by fungi or dust mites. This
    thesis aims to develop a high-linearity and low-hysteresis capacitive relative humidity
    (RH) microsensor to more precisely accommodate the humidity of living spaces.
    To reduce the hysteresis and enhance the linearity, this research uses not only one
    polyimide (PI) thin film as a humidity sensing layer but also utilizes another PI thin
    film as a protecting layer of the top electrodes. To improve further the RH sensitivity
    and responding speed, interlacing out-of-plane electrodes are designed in the RH
    microsensor. The main processing steps of the RH sensor developed in this study
    involve at least five photolithographic and four thin film deposition processes. The
    influences of sensing area, number of electrode pairs and testing temperature on the
    sensitivity and sensing linearity of humidity microsensors were investigated.
    Based on the measurement results, the sensitivity apparently increase as well as
    the sensing area (2 mm × 2 mm: 0.12 pF/%RH, 3 mm × 3 mm: 0.48 pF/%RH, 5 mm ×
    5 mm: 1.09 pF/%RH), and decrease with the number of electrode pairs (40 pairs: 0.51
    pF/%RH, 20 pairs: 0.4 pF/%RH) and increase with the testing temperature. The thesis
    has demonstrated that the capacitance of the RH sensor vary from the relative
    humidity with a very linear relationship (linearity: 98.8%~99.99%) over the range of
    30~70%RH. Finally, to increase effectively the surface area and to reduce further the
    hysteresis, three-dimensional (3D) moisture entrances and exits were designed and a
    very low hysteresis value (0.5%RH) can be achieved.
    Advisory Committee
  • Y.C. Lin - chair
  • Wei-Leun Fang - co-chair
  • Jin-Chern Chiou - co-chair
  • Ruey-Shing Huang - co-chair
  • I-Yu Huang - advisor
  • Files
  • etd-0827108-123254.pdf
  • indicate in-campus access in a year and off_campus not accessible
    Date of Submission 2008-08-27

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