The dry development of 0.25 mu m diffusion-enhanced silylated resist structures produced in a LAM Research Corporation TCP(TM)400((TM)) inductively coupled plasma etcher is studied. The processes consist of a low-selectivity, C2F6- containing, descum step followed by an oxygen-based main and overetch step. An extensive study, based on statistically designed experiments, shows the effect of different process parameters on anisotropy, selectivity, and the etch rates of silylated and unsilylated resist that occur when using different dry development chemistries. Solutions that independently control and enhance the selectivity and the anisotropy, while maintaining Vertical profiles and acceptable etch rates, are demonstrated. Optimal processes for the different chemistries are compared. The effect that the different chemistries exert on the lithographic performance is quantified, and the strong reduction of the proximity effect, both in terms of linewidth and profiles, resulting from SO2 addition is studied. It has been demonstrated that the results also apply to sub-0.25 mu m geometries and that none of the tested chemistries interfere with subsequent etching of the polysilicon substrate.