Clean and repair of EUV photomasks

Regardless at what technology node it will be implemented, extreme ultraviolet (EUV) lithography appears to be the most likely candidate to succeed 193 nm wavelength lithography. However, EUV photomasks present new and different challenges for both repair and clean processes. Among these are different and more complex materials, greater sensitivity to smaller topography differences, and lack of pelliclization to protect critical pattern areas. Solutions developed and recently refined to meet these challenges are reviewed as an integrated solution to make the manufacture and maintenance of this mask type feasible. This proven, integrated solution includes nanomachining, BitClean® and cryogenic clean processes applied for hard (missing pattern) and soft (nanoparticle) defect removals with no damage to underlying multilayers.