Effect of Texture on Hillock Formation in Aluminum Films

Abstract

Stress voiding describes a phenomenon in thin interconnect lines where hillocks and voids are formed during thermal cycling due to the stresses caused by the difference in the thermal expansion coefficients of metal used in the interconnect lines and the substrate material. The effect of texture on stress voiding in aluminum interconnects is investigated using orientation imaging microscopy (OIM^© ) and scanning electron microscopy. Aluminum films were deposited by PVD deposition onto sublayers of Ti and Ti plus TiN and were analyzed for crystallographic texture and grain boundary structure using OIM^©. These films were later annealed at 400°C for 1 hour and cooled. The specimens were examined for the presence of hillocks and voids using a scanning electron microscope. The results show strongly textured (111) films are more resistant to hillock and void formation.