A three-dimensional structure disposed on a substrate is processed so as to alter the etch rate of material disposed on at least one surface of the structure. In some embodiments, a conformal deposition of material is performed on the three-dimensional structure. Subsequently, an ion implant is performed on at least one surface of the three-dimensional structure. This ion implant serves to alter the etch rate of the material deposited on that structure. In some embodiments, the ion implant increases the etch rate of the material. In other embodiments, the ion implant decreases the etch rate. In some embodiments, ion implants are performed on more than one surface, such that the material on at least one surface is etched more quickly and material on at least one other surface is etched more slowly.