Ambient Dependence of Agglomeration Stability of Cu/Ta Films

Abstract

ABSTRACTWe have investigated the effects of oxygen contamination on the agglomeration of thin Cu films fabricated by physical vapor deposition on Ta barriers. Thin Cu films on clean, ultrahigh vacuum-deposited Ta barriers were stable against agglomeration when annealed for several hours at temperatures as high as T=380°C. However, on Ta barriers intentionally contaminated with oxygen, agglomeration of Cu films occurred within minutes when annealed above 300°C. Time-resolved reflectivity was used to study film evolution and agglomeration in situ. Atomic force microscopy was used for post-growth characterization of agglomeration. Characterization of Ta barriers by X-ray photoelectron spectroscopy and Rutherford backscattering spectrometry demonstrated that clean Cu films on contaminated Ta barriers containing as little as 5% oxygen were unstable against agglomeration.