We investigated an all-dry etching process of the development-free vapor photolithography (DFVP) with a 351 nm XeF excimer laser. After masked exposure, SiO2 on a silicon wafer and under a microlithographically exposed photoaccelerator polymer film can be directly etched by a vapor containing a mixture of HF, water, and N-2. Patterns with 0.4 mu m resolution were obtained. In this article, effects of the etching temperature and time, exposure energy, and the concentration of 5-nitroacenaphthene in polymer on the resolution, as well as the mechanism of DFVP, are discussed.