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16 April 2008 Characterization of sub-50-nm line array structures with angle-resolved multiple wavelength scatterometry
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In the sub-90 nm technology nodes, optical metrology techniques are essential for process control of gate formation steps, from lithography to etch layers such as gate, trench, and dielectric interconnect layers and to spacers and straining layer depositions. Conventionally, optical metrology is based on measurements of periodic line or hole arrays (i.e., gratings) using spectroscopic ellipsometers or polarized reflectometers, collecting data across wide wavelength spectra at a single angle of incidence. In this paper, we present results of measurements on periodic etched amorphous-Si gate line arrays using focused beam ellipsometry (FBE), illuminating at three discrete laser wavelengths while data is collected over angles of incidence ranging from 45° to 65°. Results on thoroughly characterized samples representative of 65 and 45 nm technology are presented. These samples include a variety of both line critical dimensions (CDs) (from 18-50 nm) and line pitches (from 200-700nm) for dense and isolated lines arrays. We discuss precision and accuracy in terms of total measurement uncertainty; spot size, navigation, and tool matching are also presented. FBE-based metrology will meet current process control requirements within a substantial margin.
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Michael Kotelyanskii, Fei Shen, Gary Jiang, and Benjamin Bunday "Characterization of sub-50-nm line array structures with angle-resolved multiple wavelength scatterometry", Proc. SPIE 6922, Metrology, Inspection, and Process Control for Microlithography XXII, 69223N (16 April 2008);

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