In the semiconductor lithography process, the thermal flow process after development resolves the patterning of sub-100-nm contact holes and the cost problem of resolution-enhancement technology. In this study, resist flowing behavior and contact hole shrinkage are described by using the thermal reflow length of the boundary-movement method and the analysis of image process. The viscosity variable affects the shrinkage of critical dimensions. This variable is extracted from the experimental data by using a proposed equation. These results agree well with the experimental results in both contact hole size and the vertical wall of profile according to the baking temperature and time. Although the most effective process of the 193-nm chemically amplified resist is the postexposure bake process for critical dimension, the parameter of the development process-the inhibition reaction order of the enhanced Mack model-is shown as the most controllable parameter for critical dimension in the thermal reflow process. (c) 2006 American Vacuum Society.