Thermal flow process with a PSM reticle was studied here in order to print a 300mm wafer with dense 120nm contact holes patterns (260nm pitch). This technique is accomplished by a feature size shrinkage using a post development bake. Thus larger features than the final etched ones can be printed which helps maintaining a workable process window. The resist used along this study (XP 11016) is particularly designed for thermal reflow applications by some built-in material properties: (1) Tight polymer molecular weight dispersity for good thermal flow control. (2) Optimized PAG characteristics to get good contact holes resolution and wide process window. (3) Additives to keep contact holes profiles through reflow steps. This study presents a method to defined process setting for different pitches using thermal flow and OPC. The effect of post development bake temperature on resist shrinkage, etch resistance and CD shrinkage was evaluated. Different sizing bias, reflow temperature and optical settings were studied in order to choose the best conditions to print dense or isolated features and finally extract the best overlapping results. The settings obtained using an empirical model make possible to print simultaneously 120nm dense and isolated contact holes.