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Atomic Force Microscopy of Semiconductor Line Edge Roughness



N G. Orji, Jayaraman Raja, Theodore V. Vorburger


Over the last two decades the width of patterned lines on semiconductor devices has continuously decreased. Based on technology trends predicted by the International Technology Roadmap for Semiconductors (ITRS), the linewidth of isolated gate lines on microprocessor will be reduced to less than 50 nm by 2012. This trend towards smaller feature sizes poses a great challenge to the tools, analysis methods, and calibration techniques used in linewidth measurements. State-of-the-art linewidth measurement involves the use of scanning electron microscopes (SEM), but as the feature sizes decrease, SEM techniques may become inadequate for such measurements. Part of the difficulty of imaging patterned lines with the SEM lies with the uncertainties associated with determining the edges of lines; this can be attributed partly to the deviation of the line edge from the mean line, otherwise known as line edge roughness (LER). Another important part of the problem lies in the fact that the decrease in LER is not proportional to feature size as the industry move toward smaller features because the fundamental causes of LER are material and process dependent rather than size dependent. Errors in the range of 25 nm which were acceptable for linewidths of 500 nm or more will consume over half the lithography error budget for 100 nm linewidths and below. Recent studies have correlated LER with increased current leakage for linewidths below 100 nm, and thus highlight the need for an in-depth characterization of this parameter. This work explores the use of atomic force microscopes (AFM) for characterizing LER. The challenges involved with AFM characterization of LER are highlighted, and various scanning strategies and analysis techniques are presented. The objective of this work is to present some of the measurement and analysis techniques needed to extract valuable LER information using the atomic force microscope.
Conference Dates
October 20-25, 2002
Conference Location
St. Louis, MO, USA
Conference Title
Proceedings of the American Society for Precision Engineering


atomic force microscope, line edge roughness, linewidth


Orji, N. , Raja, J. and Vorburger, T. (2002), Atomic Force Microscopy of Semiconductor Line Edge Roughness, Proceedings of the American Society for Precision Engineering, St. Louis, MO, USA (Accessed April 13, 2024)
Created September 30, 2002, Updated October 12, 2021