Chiaki Hatsuta

CrOxFy as a material for attenuated phase-shift masks in ArF lithography

We investigated the durability of CrOxFy film, which is used as a shifter for attenuated phase-shift masks (Att- PSMs), under ArF excimer laser irradiation. The phase shift of an as-deposited film decreased and the transmittance increased due to the disappearance of interfaces, which was caused by the migration of atoms. To improve durability, the sample was annealed at 300 degrees C to remove the interfaces, and the surface was etched to recover the decreased transmittance caused by the annealing. As a result, the lifetime became 1.5 years, which is sufficient for practical devices. The depth-of-focus of an ArF photoresist was 1.2 micrometers for a 0.13 micrometers line-and-space pattern and 0.5 micrometers for an 0.13 micrometers isolated contact- hole pattern when Att-PSMs made from CrOxFy film were used.