Diamond-like carbon films were prepared on radio-frequency (RF) biased substrates of silicon wafer and Coming 7059 glass at low temperature substrate by electron cyclotron resonance microwave plasma chemical vapor deposition using CH4-H-2 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-H-2 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-H-2 System exhibited less damage which demonstrates that the films obtained has a better adherence behavior.