In one embodiment a method of method of treating a sidewall layer of a patterned feature includes providing the patterned feature as an etched structure comprising one or more layers disposed on a substrate and generally parallel to a plane of the substrate defined by a front surface of the substrate. The sidewall layer comprises material from the one or more etched layers. The method further includes arranging the substrate proximate a sheath modifier that is adjacent a plasma, and providing ions in an ion dose to the substrate by extracting the ions from the plasma through the sheath modifier, the ions impinging upon the substrate at an angle with respect to a perpendicular to the plane of the substrate.