As the essential techniques for the CD (Critical Dimension) measurement of the LCD pattern, there
are various modules such as an optics design, auto-focus [1-4], and precise edge detection. Since the
operation of image enhancement to improve the CD measurement repeatability, a ring type of the reflected
lighting optics is devised. It has a simpler structure than the transmission light optics, but it delivers the
same output. The edge detection is the most essential function of the CD measurements. The CD
measurement is a vital inspection for LCDs [5-6] and semiconductors [7-8] to improve the production
yield rate, there are numbers of techniques to measure the CD. So in this study, a new subpixel algorithm
is developed through facet modeling, which complements the previous sub-pixel edge detection algorithm.
Currently this CD measurement system is being used in LCD manufacturing systems for repeatability of
less than 30 nm.
© 2013 Optical Society of Korea
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