Large area deposition of hydrogenated amorphous carbon films for optical storage disks

Homogenous wear resistant carbon coatings with an optical gap of 3 eV but low stress are needed to increase the storage density in optical storage disks in order to reach 100 GB in 12-cm diameter disks. Here, hydrogenated amorphous carbon (a-C:H) films are deposited at room temperature using a large area electron cyclotron wave resonance plasma beam source of 14.2-inch diameter. Methane is used as the precursor. The ion flux and energy, plasma pressure, distance between the extraction grid and the substrate were varied. The films are characterized in terms of hydrogen content, stress, optical gap, refractive index, wear resistance, surface roughness and homogeneity by a variety of characterization techniques. Resonant Raman spectroscopy is used in order to non-destructively monitor the disk quality. We show how it is possible to produce homogenous, wear resistant a-C:H coatings with an optical gap of 3 eV and low stress (<500 MPa), without damaging the plastic disks.