Mask roughness induced LER: geometric model at long correlation lengths

Brittany M. McClinton; Patrick P. Naulleau

doi:10.1117/12.881677

8 April 2011 Mask roughness induced LER: geometric model at long correlation lengths

Brittany M. McClinton, Patrick P. Naulleau

Proceedings Volume 7969, Extreme Ultraviolet (EUV) Lithography II; 79691Y (2011) https://doi.org/10.1117/12.881677
Event: SPIE Advanced Lithography, 2011, San Jose, California, United States

Abstract

Collective understanding of how both the resist and line-edge roughness (LER) on the mask affect the final printed LER has made significant advances. What is poorly understood, however, is the extent to which mask surface roughness couples to image plane LER as a function of illumination conditions, NA, and defocus. Recently, progress has been made in formulating a simplified solution for mask roughness induced LER. Here, we investigate the LER behavior at long correlation lengths of surface roughness on the mask. We find that for correlation lengths greater than 3λ/NA in wafer dimensions and CDs greater than approximately 0.75λ/NA, the previously described simplified model, which remains based on physical optics, converges to a "geometric regime" which is based on ray optics and is independent of partial coherence. In this "geometric regime", the LER is proportional to the mask slope error as it propagates through focus, and provides a faster alternative to calculating LER in contrast to either full 2D aerial image simulation modeling or the newly proposed physical optics model. Data is presented for both an NA = 0.32 and an NA = 0.5 imaging system for CDs of 22-nm and 50-nm horizontal-line-dense structures.

Citation Download Citation

Brittany M. McClinton and Patrick P. Naulleau "Mask roughness induced LER: geometric model at long correlation lengths", Proc. SPIE 7969, Extreme Ultraviolet (EUV) Lithography II, 79691Y (8 April 2011); https://doi.org/10.1117/12.881677

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