The thermal properties of 10 nm W-Mo alloy films as copper diffusion barrier on porous SiOCH were studied. The GIXRD results show that this layer has great barrier capabilities against copper penetration. Cross-sectional TEM image and EDS line profiles taken from TEM sample indicate Mo and W still accumulate at the interface. Sharp decline of Cu and Si concentrations at interface and lack of Cu penetrations to porous SiOCH, indicating that W-Mo barrier was effective for sample annealed at 600°C for 30min. Cu agglomeration occurred after 5 min 700°C annealing, suggesting that Cu had poor adhesion to underneath barrier. The 10nm W-Mo layer could be a potential barrier candidate for advanced copper interconnects.