Ten types of Al-based layered metallization were prepared and were investigated in order to discover how a refractory metal under-layer affected the crystallographic characteristics of an Al layer and therefore the electromigration resistance of the metallization. Both the Al grain size and the Al(111) preferred orientation were compared with the electromigration lifetime by using 3 interconnect line-widths. A W-group under-layer was found to change the Al grain size, while maintaining the preferred orientation. In particular, a WN under-layer increased the Al grain size more than did a SiO2 under-layer; resulting in long electromigration lifetimes. On the other hand, a Ti-group under-layer improved the Al(111) preferred orientation while maintaining the grain size.

S.Kondo, O.Deguchi, K.Hinode: Journal of Applied Physics, 1995, 78[11], 6534-8