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4 May 2005 Origin of LER and its solution
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We have studied several factors having an effect on LER in terms of resist chemistry, resist process, CD-SEM metrology, numerical aperture and sigma settings of the exposure tool, and the mask pattern. LER is extracted from the developed resist profile. In ArF lithography process, development and rinse process is very critical because ArF resist is relatively hydrophobic compared to KrF resist. It causes heterogeneous interaction at interface of resist and aqueous solution (developer or deionized water). We improved roughness at contact hole pattern by the introduction of wetting process prior to development. Clear and homogeneous rinsing is also needed to remove scum and swelled resist generated at development step. On the other hand, the roughness of mask pattern is one of the important factors of LER on wafer. We confirmed that this global dislocation is a potent influence but local edge roughness of mask is insignificant to wafer LER. This dislocation of pattern is originated from the lack of shot accuracy in E-beam writer using variable shaped beam.
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Geunsu Lee, Tae-Seung Eom, Cheolkyu Bok, Changmoon Lim, Seung-Chan Moon, and Jinwoong Kim "Origin of LER and its solution", Proc. SPIE 5753, Advances in Resist Technology and Processing XXII, (4 May 2005);

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