A method for forming a chlorine containing plasma etched patterned layer. There is first provided a substrate 10 employed within a microelectronics fabrication. There is then formed over the substrate a blanket target layer 12 formed of a material susceptible to etching within a second plasma employing a chlorine containing etchant gas composition. There is then formed upon the blanket target a blanket hard mask layer 14 formed of a material selected from the group consisting of silsesquioxane spin-on-glass (SOG) materials and amorphous carbon materials. There is then formed upon the blanket hard mask layer a patterned photoresist layer 16. There is then etched while employing the patterned photoresist layer as a first etch mask layer and while employing a first plasma employing a fluorine containing etchant gas composition the blanket hard mask layer to form a patterned hard mask layer. Finally, there is then etched while employing at least the patterned hard mask layer as a second etch mask layer and while employing the second plasma employing the chlorine containing etchant gas composition the blanket target layer to form the patterned target layer.