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Eric K. Lin, Wen-li Wu, Ronald L. Jones & Chengqing Wang, NIST, USA
Kwang-Woo Choi, George M. Thompson & Bryan J. Rice, Intel Corp., USA

ABSTRACT

While enormous effort has been expended in developing the optical lithography tools to print ever-finer features, significant advances have also been required to measure the shape and dimensions of the printed features. Currently, scanning electron microscopy and optical scatterometry methods are the primary metrology tools for gate stack, source-drain via, and interconnect metrology.  Atomic force microscopy is used in special situations because of its ability to extract unambiguous three-dimensional information.  However, significant challenges arise for the application of these methods for structures with dimensions less than 50nm.  In addition, the continuing development of new materials such as extreme ultraviolet photoresists, nanoporous low-k dielectrics, and metallic interconnects require high precision dimensional measurements for process development and optimization.  To address these challenges, we are developing an x-ray based metrology termed Critical Dimension Small Angle X-ray Scattering (CD-SAXS).  In this article, we review the capability of CD-SAXS for non-destructive measurements of the pitch, line-width, sidewall angle, average cross section, and line edge roughness in line:space grating patterns, and discuss its potential into the future.