28 August 2016 Reduction of batwing effect in white light interferometry for measurement of patterned sapphire substrates (PSS) wafer
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Abstract
Patterned sapphire substrates (PSS) wafers are used in LED manufacturing to enhance the luminous conversion of LED chips. The most critical characteristics in PSS wafers are height, width, pitch and shape of the pattern. The common way to measure these characteristics is by using surface electron microscope (SEM). White light interferometry is capable to measure dimension with nanometer accuracy and it is suitable for measuring the characteristics of PSS wafers. One of the difficulties in measuring PSS wafers is the aspect ratio and density of the features. The high aspect ratio combined with dense pattern spacing diffracts incoming lights and reduces the accuracy of the white light interferometry measurement. In this paper, a method to improve the capability of white light interferometry for measuring PSS wafers by choosing the appropriate wavelength and microscope objective with high numerical aperture. The technique is proven to be effective for reducing the batwing effect in edges of the feature and improves measurement accuracy for PSS wafers with circular features of 1.95 um in height and diameters, and 700 nm spacing between the features. Repeatability of the measurement is up to 5 nm for height measurement and 20 nm for pitch measurement.
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Abraham Mario Tapilouw, Yi-Wei Chang, Long-Yo Yu, Hau-Wei Wang, "Reduction of batwing effect in white light interferometry for measurement of patterned sapphire substrates (PSS) wafer", Proc. SPIE 9960, Interferometry XVIII, 996006 (28 August 2016); doi: 10.1117/12.2236874; https://doi.org/10.1117/12.2236874
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