Because the surface roughness of a thin film will cause light scattering, the reflectance (R) and transmittance (T) measured using a UV/visible (vis) spectrometer become lower than the actual values. The deviation becomes larger with increasing roughness and decreasing wavelength of incident light. Hence, it is necessary to correct measured R and T using roughness as a modification factor. The refraction (n) and extinction coefficient (k) obtained by the modified R-T method are closer to those results obtained using a variable angle spectroscopic ellipsometer (VASE), which provides more precise results than a n and k analyzer.

Simulations for the optimization of the mask error enhancement factor (MEEF) by using Taguchi's design of experiment (DOE) method in both dry and immersion ArF lithography have been demonstrated here. By DOE, MEEF has been successfully reduced, and the process window has also been enlarged. Furthermore, in immersion lithography, MEEF has been significantly reduced, and resolution is also enhanced. In this study, we determined the optimal process and optical parameters to enlarge the process window and reduce MEEFs for different types of mask by DOE.

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