Optical error sensitivities of immersion lithography

Zheng G. Chen; Kafai Lai; Ken Racette

doi:10.1117/12.712333

26 March 2007 Optical error sensitivities of immersion lithography

Zheng G. Chen, Kafai Lai, Ken Racette

Proceedings Volume 6520, Optical Microlithography XX; 652013 (2007) https://doi.org/10.1117/12.712333
Event: SPIE Advanced Lithography, 2007, San Jose, California, United States

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.

Citation Download Citation

Zheng G. Chen, Kafai Lai, and Ken Racette "Optical error sensitivities of immersion lithography", Proc. SPIE 6520, Optical Microlithography XX, 652013 (26 March 2007); https://doi.org/10.1117/12.712333

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