A method for manufacturing a magnetic write pole of a magnetic write head for perpendicular magnetic recording. A magnetic write pole material is deposited, followed by union milling hard mask, a polymer mask under-layer followed by a dielectric hard mask material, followed by a photoresist. The photoresist is patterned to define a write pole shape and the shape of the patterned photoresist is transferred onto the underlying dielectric hard mask by a novel reactive ion etching that is performed in a chemistry that includes one or more fluorine containing gases and He. The presence of He in the reactive ion etching tool helps to improve the profile of the patterned dielectric hard mask. In addition, RIE parameters such a gas ratio (e.g. CF4 to CHF3 gas ratio) and power ratio (e.g. source power to bias power) are adjusted to optimize the profile of the patterned dielectric mask.