Embodiments of the present disclosure generally relate to a method for forming an opening using a mask. In one embodiment, a method includes forming a mask on a feature layer. The method includes forming a first opening in the mask to expose a portion of the feature layer. The method further includes forming a carbon layer on the mask and the exposed portion of the feature layer. The method also includes removing portions of the carbon layer and a portion of the exposed portion of the feature layer in order to form a second opening in the feature layer.