Copper metallization of low-dielectric-constant a-SiCOF films for ULSI interconnects

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.