EFFECTS OF GRAIN-SIZE AND PREFERRED ORIENTATION ON THE ELECTROMIGRATION LIFETIME OF AL-BASED LAYERED METALLIZATION

Ten kinds of Al-based layered metallizations were fabricated and inves tigated to find out how a refractory metal underlayer affects the crys tallographic characteristics of an Al layer and, in consequence, the e lectromigration resistance of the metallization. Both Al grain size an d Al (111) preferred orientation were compared with electromigration l ifetime by using three interconnect linewidths. A W group underlayer w as found to change the Al grain size while maintaining the preferred o rientation. A WN underlayer, in particular, increases the Al grain siz e more than a SiO2 underlayer does, resulting in long electromigration lifetime. A Ti group underlayer, in contrast, improves Al (111) prefe rred orientation while maintaining the grain size. The crystallographi c characteristics of the layered interconnects were plotted on constan t-lifetime-line figures indicating the direction of the next layered m etallization. (C) 1995 American Institute of Physics.