Barrier crystallographic texture control and its impact on copper interconnect reliability

The impacts of barrier micro-structure on Cu seed and electro copper plating (ECP) film have been investigated in terms of seed sheet resistance (R_s) stability, crystal orientation, and wetting properties; ECP film surface morphology and CMP defects. We have studied the effect of these parameters using 4-point probe, X-ray diffraction (XRD), scanning electron microscopy (SEM), and SEM vision. We also studied barrier impact on via resistance and interconnect reliability using E-test measurement and stress migration test. It was found that barrier layer micro-structure can manipulate seed layer and ECP film properties, which affect E-test performance. The seed layer deposited on highly <110>-oriented α-Ta underlayer shows better Cu <111> orientation, resulting in a seed with stable R_s, better wetting properties, smoother ECP film, and lower defects. In addition, it shows lower via resistance and better interconnection reliability.