Plasma etching of mask materials

Exemplary etching methods may include forming a plasma of a fluorine-containing precursor to produce plasma effluents. A first bias frequency may be applied while forming the plasma. The methods may include contacting a substrate housed in a processing region of a semiconductor processing chamber with the plasma effluents. The substrate may be or include a photomask. The methods may include etching a first layer of the photomask. Etching the first layer of the photomask may expose a second layer of the photomask. The methods may include adjusting the first bias frequency to a second bias frequency while maintaining the plasma of the fluorine-containing precursor. The methods may include etching the second layer of the photomask.