The effect of using bilayer Ni/Al-1%Cu or Co/Al-1%Cu metallization stacks w
ith regard to hillock formation is investigated in this study and compared
to hillock suppression capabilities of Al-1%Si and Al-1%Cu single layer fil
ms and Ti/Al-1%Cu bilayer metallization stacks. Various heat treatments dur
ing and immediately after depositions were used to study the resistances of
different metallization stack specimens to hillock formation. The densitie
s and sizes of hillocks were characterized using scanning electron microsco
py and atomic force microscopy, while interfacial reactions between the tra
nsition metal layer and Al-1%Cu in the metallization stack were examined us
ing glancing angle x-ray diffraction. Resistivities of the bilayer metalliz
ation stacks were characterized using conventional four-point probe measure
ments. Our studies indicate that metallization processes involving bilayer
metallization stacks of nickel and cobalt with Al-1%Cu are more robust comp
ared to those involving titanium with Al-1%Cu. The mechanism of hillock for
mation is analyzed in light of intermetallic compound formation and stress-
strain considerations. (C) 1999 American Institute of Physics. [S0021-8979(
99)08913-6].