Effect of gradient a-SiCx interlayer on adhesion of DLC films

Diamond-like carbon films were prepared on radio-frequency (RF) biased substrates of silicon wafer and Corning 7059 glass at low temperature substrate by electron cyclotron resonance microwave plasma chemical vapor deposition using CH4–H2 and CH4–Ar as reactant gases. The effects of a-SiCx interlayer prepared by RF-PECVD on the adhesion and failure mode of DLC films were investigated. In CH4–H2 system with the a-SiCx interlayer and RF bias applied to −90 V, the adherence of DLC films was improved significantly and the critical load was increased from 2 N without RF bias to 80 N. The failure mode transferred from spalling failure at lower substrate bias to conformal cracking at higher substrate bias. In CH4–Ar system with a-SiCx interlayer, the critical load was increased to 20 N at RF bias −90 V and the spalling failure mode was revealed. Comparing the DLC films obtained in the two system coated with a-SiCx interlayer and RF bias applied to −90 V, the one deposited in CH4–H2 system exhibited less damage which demonstrates that the films obtained has a better adherence behavior.