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7 July 1997 Control and uniformity of 280-nm features in i-line lithography using optical proximity corrections and off-axis illumination
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The feasibility of manufacturing 280 nm gates for ASIC technology using i-line lithography is examined. Off-axis illumination, sub-resolution assist features and proximity effect bias corrections were considered. The experiments were performed with a reticle designed to evaluate the effects of line pitch, bias and field uniformity on the feature dimensions. Results show that dense and isolated features were found to print at about the same linewidth under all three illumination conditions. However, deviations as large as 40 nm were found at intermediate pitches, implying that some form of optical proximity correction is needed to maintain critical dimension (CD) control for a mask pattern with varying feature densities. Sub-resolution assist lines adjacent to isolated 280 nm lines significantly improved the apparent wall angle of the features compared to true isolated features. The use of these features comes at a cost; the sub-resolution features can be printed under certain conditions and could possibly lead to device failure. Multi-dimensional matrices of CD measurements with varying dose, focus, bias and pitch, when displayed in an appropriate manner, are being used to identify the relative advantages of different illumination conditions. Off-axis illumination offers a large depth of focus for all pitches if proximity effect biasing is applied. Conventional illumination with biasing can improve exposure latitude.
© (1997) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Pat G. Watson, Joseph G. Garofalo, M. Hansen, Ilya M. Grodnensky, Ludwik J. Zych, R. Takahashi, Willie J. Yarbrough, Edward Ehrlacher, A. Reim, R. M. Vella, A. Dunbar, Albert Colina, B. Herrero, and D. Castro "Control and uniformity of 280-nm features in i-line lithography using optical proximity corrections and off-axis illumination", Proc. SPIE 3051, Optical Microlithography X, (7 July 1997);


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