US Patent 7709392 Low K dielectric surface damage control

A method of removing a silicon nitride or a nitride-based bottom etch stop layer in a copper damascene structure by etching the bottom etch stop layer is disclosed, with the method using a high density, high radical concentration plasma containing fluorine and oxygen and further optionally N2 and any one of inert gases, to minimize back sputtering of copper underlying the bottom etch stop layer and surface roughening of the low-k interlayer dielectric caused by the plasma.