Agglomeration of Cu electroplating seed layers on ultra-thin Ta, Ta1-XNX, Ta1-XOX, contaminated Ta, and composite Ta/Ta1-XNX diffusion barriers

The agglomeration of thin (10 nm) Cu films suitable for use as electroplating seed layers has been investigated on ultrathin (<4 nm) Ta, Ta1-xNx, Ta1-xOx, and composite Ta, Ta1-xNx diffusion barriers. Copper films on clean 3.6nm Ta barriers deposited by ultrahigh vacuum sputter deposition at up to 120 degrees C are stable against agglomeration during 30 minute anneals at 360 degrees C and display strong (022) crystallographic texture. Similar Cu films deposited on thinner Ta, Ta0.85N0.15, Ta0.95O0.05, and residual gas contaminated (similar to 1 Langmuir) Ta barriers agglomerate during annealing, and Cu films on Ta0.85N0.15 and contaminated Ta have random biaxial crystallographic texture. The density of agglomerated regions in Cu films on SiO2 and Ta0.85N0.15 is characterized as a function of thickness of an ultrathin Ta adhesion layer.