Investigating the Performance of Amorphous W/WN Bilayer as a Cu Diffusion Barrier in Si.

Tungsten/tungsten nitride bilayer with amorphous structure was deposited on the silicon / silicon oxide substrate by high vacuum thermal evaporation method. To investigate the thermal stability of this bilayer as a diffusion barrier layer, the Cu/W/WN/SiO2/Si multilayer was heated at different temperatures and the results were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and four-point probe (FPP) methods. According to the XRD results, formation of the cupper silicide at 800° C indicates diffusion of copper from the W/WN bilayer in the Si. The formation of a Cu3Si with insulation phase leads to a sudden increase in electrical resistance (212 Ω/cm2) and will disrupt the performance of the W/WN barrier layer as a diffusion barrier. The diffusion of copper into silicon is often through undesirable grain boundaries that occur during the heating treatment of the W/WN bilayer by changing its phase from amorphous to polycrystalline and shown in X-ray diffraction results. At high temperatures, the electron microscope image has shown fracture, cracking and flaking of the surface of the copper layer, which is caused by thermal stress between the penetration barrier/copper surfaces or the volume of the layers. [ABSTRACT FROM AUTHOR]