Titanium nitride removal

A method of removing titanium nitride hardmasks, the method comprising:

• forming an amorphous carbon-containing layer over low-k dielectric walls over an underlying copper layer on a patterned substrate, wherein the low-k dielectric walls form a via having a via width and a trench having a trench width, wherein the via and the trench are fluidly coupled to one another and the via width is less than the trench width, and the patterned substrate further comprises the titanium nitride hardmasks above the low-k dielectric walls, wherein one of the titanium nitride hardmasks extends over the trench and the amorphous carbon-containing layer fills the via and the trench and also covers the titanium nitride hardmasks;
• placing the patterned substrate in a substrate processing region of a substrate processing chamber;
• flowing a radical-chlorine precursor and a radical-carbon-hydrogen precursor from a remote plasma region, through a showerhead and into the substrate processing region;
• etching away both the amorphous carbon-containing layer overlying the titanium nitride hardmasks and the titanium nitride hardmasks with the radical-chlorine-precursor and the radical-carbon-hydrogen precursor leaving behind a remainder of the amorphous carbon-containing layer inside the via and the trench, wherein the radical-chlorine precursor and the radical-carbon-hydrogen precursor do not make contact with the underlying copper layer as a result of a presence of the remainder of the amorphous carbon-containing layer;
• flowing an oxygen-containing precursor and a second carbon-and-hydrogen-containing precursor into the remote plasma region fluidly coupled to the substrate processing region while forming a second remote plasma in the remote plasma region to produce plasma effluents;
• flowing the plasma effluents into the substrate processing region through through-holes in the showerhead;
• etching away the remainder of the amorphous carbon-containing layer with the plasma effluents from the via and the trench;
• and
• filling the via and the trench with copper after the etching away of the remainder of the amorphous carbon-containing layer.