A method for forming a stair-step structure in a substrate is provided. An organic mask is formed over the substrate. A hardmask with a top layer and sidewall layer is formed over the organic mask. The sidewall layer of the hard mask is removed while leaving the top layer of the hardmask. The organic mask is trimmed. The hardmask is removed. The substrate is etched. The forming the hardmask, removing the sidewall layer, trimming the organic mask, and etching the substrate are repeated a plurality of times.
