Comparative study of novel barrier layers in ULSI copper interconnects

As ULSI dimensions shrink, conventional Ta/TaN barriers will not meet the future demands for ULSI interconnects, i.e. thin conformal layer without overhangs. In this paper, we have compared the material properties of TaN/Ta barriers with Ta only and W based barriers by means of XRD, AFM, Stress and SEM imaging. We found that using a conformal CVD W based barriers has great potential for future ULSI interconnects. It grain size and tensile stress improve resistance to both electromigration and stress migration, extending conductor lifetime.