Development of texture in interconnect thin film stacks

Interconnect metallization, used for the fabrication of silicon (Si) semiconductor devices, utilizes sputtered stacks often composed of thin (less than or equal to 100 nm) titanium (Ti), titanium nitride (TiN), or Ti/TiN underlayer(s), covered by aluminum (Al) alloy conductors 400-1000 nm in thickness. The texture (preferred orientation) in such films is an important consideration for both processing and reliability. Two aspects of texture are addressed in this study: (1) the effect of processing parameters on Ti and Ti/TiN underlayer texture development, and (2) the effect of underlayer texture on the texture of the Al alloy subsequently deposited. An increase in the substrate temperature causes a transition in Ti texture from [0002] to [10 (1) over bar 1]. When TiN is reactively sputtered on Ti, the Ti[0002] induces a TiN[111], while the Ti[10 (1) over bar 1] correlates with the formation of TiN[311]. Under the deposition conditions for the Al alloys that were studied, the presence of only a titanium underlayer sharpens the Al(111) texture but does not introduce a crystallographic texture component other than the Al(111). In contrast, the textured TiN in a Ti/TiN underlayer stack promotes texture inheritance, where TiN[111]-->Al[111] and TiN[311]-->Al[311] are orientation correlations indicated by the data. The orientation of a film in a stack depends on the surface energy of the top layer and on the interfacial energy between layers. Atomic bonding in the underlayer strongly affects the minimization of the interfacial energy and determines whether local, grain scale lattice matching between the underlayer and the top layer is operative. (C) 1998 American Vacuum Society.