Investigation of the effects of different annealing ambients on Ag/Al bilayers: Electrical properties and morphology

Ag (200 nm)/Al (8 nm) bilayer structures on SiO2 substrates were annealed a t temperatures ranging from 300 degreesC-700 degreesC and for 30 min in He- H, Ar, or NH3 ambient. Upon annealing, Al segregates to the surface where i t reacts with residual oxygen to form an Al-oxide passivation layer. Ruther ford backscattering spectrometry and Auger spectroscopy showed the formatio n of an AlxOy diffusion barrier at the Ag/SiO2 interface. Apart from the su rface passivation that resulted from annealing, the Ag/Al/SiO2 in different ambients, the adhesion of Ag to SiO2 was also improved. A strong correlati on between the resistivity and the residual Al in the Ag film was observed. Resistivity values equivalent to that of the as-deposited sample were obta ined only for temperatures at 700 degreesC or above. Scanning electron micr oscopy (SEM) combined with energy dispersive spectroscopy was used to study the effect of the different ambients on the observed surface morphology. T he SEM studies showed that the passivated surfaces were not uniform but hav e hillocks and holes randomly distributed. In contrast to Ag on SiO2, no ag glomeration was observed in the Ag/Al/SiO2 system. (C) 2001 American Instit ute of Physics.