Effect of Ru crystal orientation on the adhesion characteristics of Cu for ultra-large scale integration interconnects

The adhesion of Cu on Ru substrates with different crystal orientations was evaluated. The crystal orientation of sputter deposited Ru could be changed from (100) to (001) by annealing at 650°C for 20min. The adhesion of Cu was evaluated by the degree of Cu agglomeration on Ru. Cu films on annealed Ru films with the (001) crystal orientation showed 28% lower RMS values and 50% lower Ru surface coverage than Cu as-deposited on Ru having the (100) crystal orientation after annealing at 550°C for 30min, which suggest that Cu wettability on the Ru(001) was better than that on the Ru(100) plane. The low lattice misfit of 4% between Cu(111) and Ru(001) may be the reason for this good adhesion property.