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26 June 2003 Evaluating scanner lens spherical aberration using scatterometer
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Lens spherical error is an important lens aberration used to characterize lens quality and also has a significant contribution to across chip line width variation (ACLV). It also impacts tool-to-tool matching efforts especially when the optical lithography approaches sub-half wavelength geometry. Traditionally, spherical error is measured by using CD SEM with known drawbacks of poor accuracy and long cycle time. At Texas Instruments, an in-house scatterometer-based lens fingerprinting technique (ScatterLith) performs this tedious job accurately and quickly. This paper presents across slit spherical aberration signatures for ArF scanners collected using this method. The technique can successfully correlate these signatures with Litel lens aberration data and Nikon OCD data for spherical aberration errors as small as 10mλ. ACLV contributions from such small spherical errors can be quantified using this method. This provides the lithographer with an important tool to evaluate, qualify and match advanced scanners to improve across chip line width variation control.
© (2003) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Changan Wang, Gary Zhang, Colin L. Tan, Chris Atkinson, Mark A. Boehm, Jay M. Brown, David Godfrey, Michael E. Littau, and Christopher J. Raymond "Evaluating scanner lens spherical aberration using scatterometer", Proc. SPIE 5040, Optical Microlithography XVI, (26 June 2003);

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