Diffusion barrier performance of amorphous W-Ti-N films in Cu metallization

W-Ti-N films were prepared on a Si wafer by reactive sputter-deposition, followed by a deposition of a Cu thin film by DC magnetron sputtering. The Cu/W-Ti-N/Si samples prepared were annealed at different temperatures under vacuum and then characterized using X-ray diffraction, scanning electron microscopy and auger electron microscopy. The sheet resistivity was determined by four point probe analysis. The results show that the amorphous W-Ti-N film is mainly composed of TiN and W and the crystallization temperature is above 800 °C. W-Ti-N thin films prepared have good thermal stability at 700 °C, but the Cu film tends to agglomerate when the temperature is above 700 °C. A failure mechanism of the diffusion barrier is proposed based on the thermal stress and interface reaction.