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24 March 2006 Scatterometry measurements of line end shortening structures for focus-exposure monitoring
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Spectroscopic critical dimension (SCDTM) metrology on line gratings has previously been shown to be a sensitive and useful technique for monitoring lithographic focus and exposure conditions. Line end shortening (LES) effects are sensitive to focus and potentially more sensitive to focus variation than side wall angle or other profile parameters of line gratings. Rectangular line segment structures that exhibit line-end shortening behavior are arranged in a rectangular two-dimensional (2D) array to provide a scatterometry signal sensitive to the profile of the thousands of line ends in the measurement beam spot. Spectroscopic ellipsometry (SE)-based scatterometry measurements were carried out on 2D array targets of rectangular features exposed in a focus-exposure matrix (FEM). The focus and exposure sensitivities of multiple shape parameters were found to be good and uniquely separable. In addition, the side wall angle of the line ends was found to be nearly linearly dependent on focus and provide necessary focus direction information. Focus and exposure can be determined from SCD measurements by applying a model generated to describe the focus-exposure behavior of multiple shape parameters using KLA Tencor's KT Analyzer software. Several different models based on different combinations of shape parameters were evaluated. Focus measurement precision of 3nm 3σ was obtained, which will be useful for lithography processes with tight depth of focus.
© (2006) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Kelvin Hung, Yung Feng Cheng, Jie Wei Sun, Benjamin Szu-Min Lin, Steven Fu, Thaddeus G. Dziura, Marcelo Cusacovich, and Walter D. Mieher "Scatterometry measurements of line end shortening structures for focus-exposure monitoring", Proc. SPIE 6152, Metrology, Inspection, and Process Control for Microlithography XX, 61521W (24 March 2006);

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