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Mask topography effects of hole patterns on hyper-NA lithography

The purpose of this work was to find the specific effects of hole patterns in 32nm node logic by analyzing in the Fourier domain and to clarify the mechanism of mask topography effects. Our focus patterns extend from the lines and spaces (LS) to the contact hole (CH). We also attempt to perform factor analyses of mask topography effects. Intensities of LS and CH patterns are simulated using three mask models. For each of the three models, the method of approximating the mask topography effect is different. As a result, a serious difference among the three mask models has been found with respect to the intensity profile for 32nm node and beyond, though the mask sizes for all models are the same. As the accuracy of mask model improved, it was found that the image contrast tends to decrease on LS patterns while increasing on CH patterns. The qualitative interpretation of the trend of contrast variations can be described by analyzing in the Fourier domain. The mask topography effects can be separated into waveguide and shadowing effects using scatter graphs. It is concluded from the result that one of the major differences between LS and CH is attributable to phase differences between 0th order and 1st order diffractions, because the size of effects for CH have been larger than that for LS.