Plasma etch method for extreme ultraviolet lithography photomask

Studies on extreme ultraviolet mask etch were carried out by using the Gibbs energy minimization method to select plasma etch chemistries and to determine product volatility when etching absorber material to ensure a clean process and chamber operation. A self-mask method and corresponding etch conditions were proposed and experimentally examined using the antireflective portion of an absorber layer as a hard mask for the bulk absorber layer beneath. This approach overcame the intrinsic soft mask disadvantage of large etch critical dimension (CD) bias and low pattern transfer fidelity, producing significantly reduced etch CD bias (2 nm) and high pattern transfer fidelity. (c) 2007 American Institute of Physics.