A method of etching exposed silicon-nitrogen-and-carbon-containing material on patterned heterogeneous structures is described and includes a remote plasma etch formed from a fluorine-containing precursor and an oxygen-containing precursor. Plasma effluents from the remote plasma are flowed into a substrate processing region where the plasma effluents react with the exposed regions of silicon-nitrogen-and-carbon-containing material. The plasma effluents react with the patterned heterogeneous structures to selectively remove silicon-nitrogen-and-carbon-containing material from the exposed silicon-nitrogen-and-carbon-containing material regions while very slowly removing selected other exposed materials. The silicon-nitrogen-and-carbon-containing material selectivity results partly from the presence of an ion suppression element positioned between the remote plasma and the substrate processing region. The ion suppression element controls the number of ionically-charged species that reach the substrate. The methods may be used to selectively remove silicon-nitrogen-and-carbon-containing material at a faster rate than exposed silicon oxide or exposed silicon nitride.