Ultrathin amorphous carbon films for magnetic recording prepared by the mesh hollow cathode plasma source
A novel CVD plasma source is used for deposition of thin and ultrathin a-C:H films. Layers down to 2 nm thickness were deposited on silicon wafers in place of magnetic disks, where such thin films are of enormous importance to ensure sufficient wear and corrosion protection of the magnetic layer. The reduction of film thickness is directly coupled with the aim of rising storage density. The knowledge of deposition rate was necessary for the production of 2-nm a-C:H films. We ascertained an excellent linear relationship between X-ray reflectivity (XRR) film thickness and deposition time with a small offset. The origin of this XRR offset was proven to be a natural silicon dioxide interlayer resulting from storage conditions of the wafers. Further film characterization was done by AFM, secondary ion mass spectrometry and ellipsometry showing high scratch resistance and very low film roughness as well as high uniformity in film composition and lateral film thickness. As indicated by these results the mesh hollow cathode plasma source turns out to be an excellent tool for deposition of thin and ultrathin a-C:H films even down to 2 nm with nearly constant film quality within the investigated thickness range.