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Proceedings Paper

Optical error sensitivities of immersion lithography
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Paper Abstract

The imaging of an immersion lithography system has different sensitivities to optical errors such as reticle non-flatness, image plane deviation and laser bandwidth when compared to traditional dry imaging systems. The immersion sensitivities mentioned above are further amplified when higher fluid index is used. The resultant effect of these enhanced sensitivities leads to degraded focal plane flatness centering on wafers and may also lead to larger ACLV and machine to machine CD matching errors than expected. In this paper, we demonstrate the increased sensitivity factors both mathematically and experimentally. We perform a detailed error component analysis to single out an immersion related factor and its impact to CD control. For this purpose we independently quantify the reticle non-flatness directly on the mask. We also identify possible compensation solutions, such as reticle shape correction, improved focal plane setup methodology and the incorporation of focus blur into an OPC model, in order to alleviate an adverse effect of immersion on ACLV and CD stability over time and over different tool sets.

Paper Details

Date Published: 26 March 2007
PDF: 11 pages
Proc. SPIE 6520, Optical Microlithography XX, 652013 (26 March 2007); doi: 10.1117/12.712333
Show Author Affiliations
Zheng G. Chen, IBM Microelectronics (United States)
Kafai Lai, IBM Microelectronics (United States)
Ken Racette, IBM Microelectronics (United States)

Published in SPIE Proceedings Vol. 6520:
Optical Microlithography XX
Donis G. Flagello, Editor(s)

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