Methods of facilitating fabrication of circuit structures are provided which include, for instance: providing a structure with a film layer; modifying an etch property of the film layer by implanting at least one species of element or molecule into the upper portion of the film layer, the etch property of the film layer remaining unmodified beneath the upper portion; and subjecting the structure and film layer with the modified etch property to an etching process, the modified etch property of the film layer facilitating the etching process. Modifying the etch property of the upper portion of the film layer may include making the upper portion of the film layer preferentially susceptible or preferentially resistant to the etching process depending on the circuit fabrication approach being facilitated.