A plasma developing process for photosensitive polyimide layers has been investigated as an alternative to wet development. Silylation of photoimageable polyimide by applying an organosilicon compound and subsequent ultraviolet exposure using a g-line mask aligner equipment lead, as a consequence, to copolymerization of photoactive functional groups of silylating agents and sensitizer groups of the polyimide-based photoresists. Development of the photoresist layer is carried out by means of oxygen-containing plasma. Interaction of oxygen plasma with a silylated surface of polyimide leads to the formation of a silicon oxide layer that acts as a barrier giving large differences in the etching rates of the photoresist covered and not covered with organosilane. The influence of O-2 plasma etching process parameters on the etching selectivity is studied. The photochemical silylation process and the dry developing method have been characterized by scanning electron microscopy and Fourier transform infrared spectroscopy.