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6 December 2004 Evaluation of printability of crystal growth defects in a 193nm lithography environment using AIMS
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The frequent occurrence of crystal growth defects on the patterned surface and back glass of critical layer reticles in 193nm lithography has been seen at most advanced fabs around the world. While frequent contamination inspections using regimented sample plans help monitor the growth of crystals and protect yield, no clear solutions have been found to eliminate this progressive defect growth. The recently proposed “Advanced Reticle Defect Disposition Process” (ARDD) was applied successfully for the first time. This process employs a high-throughput inspection system based on the STARlight architecture and - after defect reduction through algorithms - a high-resolution AIMS review system, utilizing the newest networked data connectivity to directly exchange inspection report data and review results. The printability of crystal growth defects is highly variable depending on which surface the defects occur, the size of the defects, and the proximity of the defect to a printing pattern. Crystal growth defects can have different transmittance and phase depending on the lithography wavelength and we found in our investigations a significant change in transmission loss depending on lithography settings like NA and sigma. Such effects may result in severe reduction of the process window, and affect yield. Progressive reticle defects have been characterized on a production reticle applying the ARDD process. It is shown that emulating any given stepper/ scanner settings is necessary to measure the effect of these types of defects on transmittance and that through-focus AIMS evaluation is required to accurately assess the printability of crystal growth defects in terms of process window on wafer. Both features are important components of an overall effective and economical reticle monitor strategy, e.g. in order to optimize the reticle cleaning cycles and thus the reticle lifetime.
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Rainer Schmid, Axel M. Zibold, Kaustuve Bhattacharyya, Xuemei Chen, and Brian J. Grenon "Evaluation of printability of crystal growth defects in a 193nm lithography environment using AIMS", Proc. SPIE 5567, 24th Annual BACUS Symposium on Photomask Technology, (6 December 2004);

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