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17 December 2003 Improving global CD uniformity by optimizing post-exposure bake and develop sequences
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Abstract
Improvements in the final uniformity of masks can be shrouded by error contributions from many sources. The final Global CD Uniformity (GCDU) of a mask is degraded by individual contributions of the writing tool, the Post Applied Bake (PAB), the Post Exposure Bake (PEB), the Develop sequence and the Etch step. Final global uniformity will improve by isolating and minimizing the variability of the PEB and Develop. We achieved this de-coupling of the PEB and Develop process from the whole process stream by using “dark loss” which is the loss of unexposed resist during the develop process. We confirmed a correspondence between Angstroms of dark loss and nanometer sized deviations in the chrome CD. A plate with a distinctive dark loss pattern was related to a nearly identical pattern in the chrome CD. This pattern was verified to have originated during the PEB process and displayed a [Δ(Final CD)/Δ(Dark Loss)] ratio of 6 for TOK REAP200 resist. Previous papers have reported a sensitive linkage between Angstroms of dark loss and nanometers in the final uniformity of the written plate. These initial studies reported using this method to improve the PAB of resists for greater uniformity of sensitivity and contrast. Similarly, this paper demonstrates an outstanding optimization of PEB and Develop processes.
© (2003) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Stephen P. Osborne, Mark Mueller, Homer Lem, David Reyland, and KiHo Baik "Improving global CD uniformity by optimizing post-exposure bake and develop sequences", Proc. SPIE 5256, 23rd Annual BACUS Symposium on Photomask Technology, (17 December 2003); https://doi.org/10.1117/12.518479
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