The present disclosure pertains to a method for 
plasma etching a 
semiconductor patterning stack. The patterning stack includes at least one layer comprising either a 
dielectric-comprising antireflective material or an 
oxygen-comprising material. In many instances the 
dielectric-comprising antireflective material will be an 
oxygen-comprising material, but it need not be limited to such materials. In one preferred embodiment of the method, the 
chemistry enables the 
plasma etching of both a layer of the 
dielectric-comprising antireflective material or 
oxygen-comprising material and an adjacent or underlying layer of material. In another preferred embodiment of the method, the layer of dielectric-comprising antireflective material or oxygen-comprising material is etched using one 
chemistry, while the adjacent or underlying layer is etched using another 
chemistry, but in the same process chamber. Of particular interest is 
silicon oxynitride, an oxygen-comprising material which functions as an antireflective material. A preferred embodiment of the method provides for the use of a source of carbon and an appropriate 
halogen-comprising 
plasma, to achieve selective etch of one oxygen-containing material compared with another material which contains a more limited amount of oxygen.