In some implementations, a method is provided in a plasma reactor for etching a trench in an organic planarization layer of a resist structure comprising a photoresist mask structure over a hardmask masking the organic planarization layer. This may include introducing into the plasma reactor an etchant gas chemistry including N2, H2, and O2 and etching a masked organic planarization layer using a plasma formed from the etchant gas chemistry. This may include etching through the planarization layer to form a trench with a single etch step.