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24 March 2006 An advanced study for defect disposition through 193-nm aerial imaging
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With decreasing structure sizes on masks also the acceptable CD variation corridor for printing on the wafer and therefore, the maximum allowed defect size is decreasing. This has not only implications to the accuracy and repeatability of front-end processes such as writers, etchers, etc. but also challenges defect inspection and qualification. Defect qualification is usually done by an AIMSTM tool which optically simulates the aerial image of the structures by applying the same illumination conditions as the wafer fabs' scanners. As lithographers continue to produce smaller and smaller structures, the as well decreasing acceptable design variation pushes the AIMSTM evaluation step by step towards a metrology method. Thus, an advanced measurement capability of the AIMSTM tool is mandatory to reliably disposition defects within these small margins. It is influenced by the performance of illumination, imaging homogeneity, and stability. A possible measure for the tool's capability is the (long term) repeatability, i.e. the 3σ-variance of the tool by evaluating the same defect with a certain frequency over several weeks. The AIMSTM fab 193i platform takes into account the tightened requirements with respect to homogeneity and stability by improved optics such as a new beam homogenizer module, new energy monitoring and vibration isolation concept. In this paper we show data on the long term repeatability compared between the first generation AIMSTM fab 193SE and the new AIMSTM fab 193i platform and discuss the implications on the measurement capabilities of the two platforms.
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Arndt C. Dürr, Axel M. Zibold, and Klaus Böhm "An advanced study for defect disposition through 193-nm aerial imaging", Proc. SPIE 6152, Metrology, Inspection, and Process Control for Microlithography XX, 61522M (24 March 2006);

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