Layered and homogeneous films of aluminum and aluminum/silicon with titanium and tungsten for multilevel interconnects

Layered structures and homogeneous alloy films synthesized by sputter deposition were investigated for use in a VLSI multilevel interconnect technology. Major areas studied include hillock formation, resistivity before and after annealing, film composition and structure, reproducibility, interlevel shorts, and dry etching. It has been demonstrated in this work that aluminum alloyed with silicon and titanium and layered with titanium offers advantages over current technological materials for interconnections in integrated circuits. Measurements of surface roughness and electrical shorts between two levels of metal showed that the hillock densities in the films are significantly reduced when small amounts (one to three atomic percent) of titanium and silicon are present. The resistivity of such homogeneous films, however, is 4.5 to 5.5 µΩ.cm, which is higher than standard metallization alloys. When Al/Si was layered with Ti, no hillocks were observed and the resistivity of the composite films was comparable to standard metallization alloys.