A method of manufacturing a semiconductor includes applying a planarization material to a substrate and forming an opening in the planarization material. The opening is filled with polysilicon. A plurality of etching modulation sequences are applied to the substrate, each of the etching modulation sequences including: applying a first etching process to the substrate, wherein the first etching process is more selective to polysilicon than the planarization material; and applying a second etching process to the substrate, wherein the second etching process is more selective to the planarization material than the polysilicon.