A DUAL DAMASCENE HARD METAL CAPPED CU AND AL-ALLOY FOR INTERCONNECT WIRING OF ULSI CIRCUITS

Abstract

This paper extends the application of hard -capped low resistivity metal damascene technology to submicron ULSI circuits utilizing a variety of hard and soft layers which are difficult to etch by conventional RIE process (1-3). The structure results in excellent yields, low via resistance, good corrosion and electromigration resistance by maintaining the planarity at all levels. Also the wear resistance of the soft layer normally difficult to achieve is significantly improved by a hard cap during damascene. The reliability, metal comb-serpentine shorts, opens and via resistances and fill properties of this technique using pitches down to 0.6 μm are evaluated and "real life" product wafers with 1.0 μm pitch are fabricated in the manufacturing environment. The example of this combination is the use of B1/Cu/B2/CVD W (where B1 and B2 are diffusion barriers chosen from PVD Ti/Cr-CrOx, Ti, Ti/Ta sandwich layers) and B3/AI-alloy/B4/CVD W where (B3 and B4 are diffusion barrier chosen from PVD Ti/TiN, Ti, Ti/W layers).