Deposition of diamondlike carbon films by plasma enhanced chemical vapour deposition

Diamondlike carbon (DLC) films have been deposited by various techniques including remote plasma enhanced chemical vapor deposition (RPECVD), cyclic and noncyclic deposition by PECVD. Ar gas was exploited as the plasma gas, while CH₄/H₂/He mixture was for the deposition of the DLC film. CF₄ and He were introduced for etching the deposited DLC film. With increasing hydrogen content, the optical bandgap increases and the hardness of the film decreases. The optical bandgap of the DLC films grown by RPECVD, noncyclic and cyclic PECVD techniques are 2-3.8, 1.2 and 1.2-1.4 eV, respectively. We find out that the films deposited either by RPECVD or noncyclic PECVD techniques contain hydrogen in a significant amount, while the film deposited by cyclic PECVD film contains no hydrogen. Assuming that graphite phase (sp²) and diamondlike phase (sp³) are simultaneously deposited during growth, the graphitic phase related to hydrogen seems then to be etched away during the etching cycle by CF₄.