Investigation on preparation and diffusion barrier properties of W–Ti thin films

An W-10 wt.%Ti alloy target was prepared by the W–Ti ball-milled powders, and W–Ti thin films were deposited by dc magnetron sputtering on Si substrates. Then Cu/W–Ti/Si structures were prepared after Cu films were deposited on the W–Ti/Si structures. The results show that W–Ti alloy has a single phase structure with fine grain size. The structures of W–Ti thin films evolved from an amorphous film to a dual phase structure with bcc W and hcp Ti, followed by W–Ti solid solution with increasing sputtering powers. W–Ti thin films can effectively block against Cu diffusion and maintain good adhesion strength with Cu films at 600 °C. The failure mechanism of the crystal W–Ti films is related to the grain boundary which provides fast diffusion paths for Cu and Si atoms, while the amorphous W–Ti diffusion barrier layer is directly related to the thermal stress and interface reaction.

► A W-10 wt.%Ti alloy target with fine grains and a single W–Ti solid solution was successfully fabricated by high energy balling and sintering under argon atmosphere.
► The emphasis is placed on the investigation of W–Ti thin films prepared by dc sputtering at different powers utilizing this W-10 wt.%Ti target.
► The Cu/W–Ti/Si samples were subsequently annealed at different temperatures ranging from 500 to 800 °C in Ar gas for 1 h. The diffusion barrier properties and thermal stability of W–Ti films were studied, and the failure mechanism was also discussed.