Mo/Al metallization for VLSI applications

We have investigated the ohmic contact properties of a metallization system made of a thin ( < 50-nm) film of aluminum covered by a thick (≈ 0.4-µm) layer of molybdenum. The thin aluminum film provides good contact characteristics to shallow n⁺-p and p⁺-n junctions in silicon, and good adherence. The thick molybdenum overlayer, which is the primary current carrier, contributes good thermal and metallurgical reliability features. Results of the present study show that the combined Mo/Al metallization system is suitable for use in very large scale integrated circuits, as the first-level metallization in a multilevel interconnect scheme.