Hardmasks are necessary when the material being etched is itself an organic polymer.
This arises, for instance, in the patterning of low-κ dielectric insulation layers used in VLSI fabrication.
First, the hardmask material is deposited and etched into the required pattern using a standard photoresist process.
Finally the hardmask is removed with a further etching process.
[3] However, SiOCH (carbon doped hydrogenated silicon oxide), a material used to insulate copper interconnects,[4] requires an etchant that attacks silicon compounds.