The effect of H₂, N₂ and N₂O doping on DLC thin films deposited by a PECVD method

Diamond-like carbon (DLC) films were prepared on Si wafers using an rf plasma-enhanced chemical vapor deposition system with the addition of small amount of nitrogen (N₂) and nitrous oxide (N₂O) to the gas mixture of CH₄ and H₂. The deposition rate of films with the addition of N₂O could be decreased at a rf power of 300 W because of the etching of the surface by the increased oxygen. A Raman band at approximately 2200 cm^-1, which can be assigned to the C≡N bond stretching mode, was also observed for films with the addition of N₂. Changes in the Raman intensity with the addition of N₂O gas were noticeable, indicating a decrease because of the etching of the surface by increased oxygen. The effect of various doping types and level on the thickness, structure, optical properties and surface roughness of DLC films was investigated by ellipsometry, Raman, and AFM characterizations.