Silicon nitride is an important material layer in various types of microelectronic devices. Because of continuous integration of devices, patterning of this layer requires a highly selective and anisotropic etching process. Reactive ion etching is one of the most simple and popular plasma processes. The present work is an experimental analysis of primary etch characteristics in reactive ion etching of silicon nitride using chlorine- and/or fluorine-based organic and inorganic chemistries (CCl2F2+O-2, CHF3+O-2, SiF4+O-2, SF6+O-2, and SF6+He) in order to obtain a simultaneous etch selectivity against polysilicon and silicon dioxide. A recipe, in CCl2F2/o(2) plasma chemistry, which provides acceptable etch characteristics, along with a reasonable simultaneous selectivity against polysilicon and silicon dioxide, has been formulated.