The effect of crystal phase of Ta barrier on via resistance and reliability performance for Cu line

It has been reported that the crystal phase of Ta on TaN barrier depends on the underlying TaN thickness. However the investigation of TaN film thickness dependent about via resistance has not been carried out enough. In this study, we have investigated the influences of crystal phase of Ta barrier at the via bottom on via resistance and reliability performances. We found that the via resistance with 5nm-thick TaN under layer show bi-modal distribution. And we estimated that the bi-modal distribution of via resistance indicates the Ta crystal phase at via bottom become one of a-Ta and b-Ta. Also, we represented that the reliability performance is same for both α-Ta and β-Ta. These results indicate the influence of the phase of Ta in only the distribution of via-resistance.