The interactions between magnetron-sputtered Cu and plasma-enhanced chemical-vapour-deposited a-SiCOF film have been investigated via x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and scanning electron microscopy (SEM). High-resolution C 1s, Cu 2p, O 1s, Si 2p and F 1s XPS spectra for the samples before and after annealing are collected. The results show that the C-Cu bond is not observed at the interface of Cu/a-SiCOF before or after the annealing. Moreover, the annealing causes the obvious shifts of Cu 2p3/2, C 1s, O 1s and Si 2p photoelectron peaks toward higher binding energy, and the underlying reasons are discussed in detail. The AES spectra of Cu L3M4, 5M4, 5 with the etching time reveal that some chemical reactions take place at the interface during the sputtering deposition of copper on the a-SiCOF film, and possible reaction mechanisms are also presented. The Cu 2p3/2 XPS spectra and the SEM graphs demonstrate that the annealing enhances the interdiffusion between Cu and a-SiCOF film.