The PR(Photoresist) flow process after the development step has been used for patterning of sub-200nm contact holes as the design rule decreases rapidly. To optimize the layout design and process parameters, we develop the new viscous PR flow model which is verified for various PRs by experimental results. Using the model and simulation, we demonstrate the close agreement with VSEM(vertical scanning electron microscope) of the top corner rounding profile of PR and investigate the effect of the dominant variables such as the contact size, surrounding bulk density, and temperature. This model is also integrated with lithography simulator. The layout design and process condition of patterns with various contact sizes are optimized by using our new methodology. The viscous flow model linked to the lithography simulator can be effectively used in predicting the contact patterning process and optimizing the layout as well as analyzing defects.