US Patent 9269590 Spacer formation

Embodiments of the present invention pertain to methods of forming more symmetric spacers which may be used for self-aligned multi-patterning processes. A conformal spacer layer of spacer material is formed over mandrels patterned near the optical resolution of a photolithography system using a high-resolution photomask. A carbon-containing layer is further formed over the conformal spacer layer. The carbon-containing layer is anisotropically etched to expose the high points of the conformal spacer layer while retaining carbon side panels. The conformal spacer layer may then be etched to form spacers without the traditional skewing of the profile towards one side or the other.