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29 June 1998 Reticle contributions to CD uniformity for 0.25-μm DUV lithography
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The trend in the semiconductor industry is towards superior imaging performance requiring fundamentally tighter control of device Critical Dimensions (CD) and yield. This paper focuses on the analysis of reticle contributions to intrafield CD Uniformity for step and repeat 0.25 micrometer DUV Lithography. A method is described to subtract the reticle fingerprint contribution from the CD measurement data. The method demonstrated that CD Uniformity, in terms of 3(sigma) , is perhaps only a valid statically allowed estimate if it is used after reticle correction. The extensive intrafield CD uniformity evaluation was performed on a typical ASML PAS 5500/300 DUV stepper to determine the impact of various illumination conditions. For APEX-E2408 photoresist, the actual intrafield CD uniformity was 13 nm (3(sigma) ) at best focus and 14 nm (3(sigma) ) over a 0.6 micrometer focus range for 0.25 micrometer dense lines and annular illumination with a NA equals 0.54. Subtracting the reticle fingerprint yields the exposure tool CD component of 8 nm (3(sigma) ) at best focus and 8 nm (3(sigma) ) over a 0.6 micrometer focus range. This is smaller than the reticle CD error component of 10 nm (3(sigma) ) which results from 32 nm (3(sigma) ) mask CD uniformity and a reticle sensitivity factor of 1.3. It is, therefore, imperative to reduce the reticle CD influence to realize further resolution reductions in manufacturing. Subtracting the reticle CD non-uniformity contribution allows us more accurately to determine the lithographic tool contribution to the CD uniformity budget.
© (1998) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Jan Pieter Kuijten, Frank Duray, and Ted der Kinderen "Reticle contributions to CD uniformity for 0.25-μm DUV lithography", Proc. SPIE 3334, Optical Microlithography XI, (29 June 1998);

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