OPTICAL-PROPERTIES OF HYDROGENATED AMORPHOUS-CARBON FILM FOR ATTENUATED PHASE-SHIFT MASK APPLICATIONS

The optical properties of a plasma-deposited amorphous-carbon film have been investigated in the ultraviolet (365 nm) and deep ultraviolet range (248 nm). By varying process conditions, the optical transmission through the films was tuned from 4% to 20% at 365 nm and from 3% to 9% at 248 nm. This tuneability was related to the hydrogen content of the film as affected by the process parameters. The index of refraction n measured by spectroscopic ellipsometry is approximately 2 at the wavelengths used. These optical proper-ties make this film attractive for use in single layer attenuated phase-shift masks for potential application in 0.25 mum lithography at 365 and 248 nm.