An approach is presented which eliminates the problems caused by hydrocarbon polymer deposition in etching compound semiconductor with CH4/H2based plasmas. We find that atomic nitrogen, created by the addition of N2to the plasma, inhibits polymer deposition in the chamber and on the sample. Atomic nitrogen has several beneficial effects; the elimination of polymer precursors, the reduction of the atomic hydrogen concentration, and a potential increase of methyl radical concentration. It is also demonstrated that the addition of N2to CH4/H2based electrocyclotron resonance plasmas used to etch HgCdTe eliminates the roughness normally formed during etching. ©1995 American Institute of Physics.