Enhanced EM endurance of TiN/AlCu/TiN/sub x/ interconnection

Abstract

Summary form only given. In submicron devices, TiN is used as a barrier layer in multilayered aluminum interconnection (e.g., TiN/Al/TiN). The conventional TiN layer is formed by reactive sputtering, which shows a columnar grain structure about the size of 10 nm. In this study, we focused on another technique of forming TiN from TiN/sub x/, and compared the electromigration (EM) endurance of the multilayered interconnections using TiN/sub x/ and conventional TiN. In order to investigate the structural aspects of aluminum and the TiN formed from the TiN/sub x/ layer, the samples were prepared as follows. TiN/sub x/ film of 50 nm thickness was reactively deposited on the oxidized (400 nm thick) silicon wafer by using DC magnetron sputtering in a mixed gas atmosphere of argon and nitrogen, in which the volume percent of nitrogen was fixed at 15%. After thermal treatment at 600 /spl deg/C for 20 sec using RTA, Al-0.5%Cu film (500 nm thick) and TiN (40 nm thick) film were sequentially deposited. After patterning of aluminum stripes of 0.4 /spl mu/m width and 1400 /spl mu/m length, the samples were alloyed at 400 /spl deg/C, 30 min in 15% H/sub 2//N/sub 2/ ambient. Finally, a passivation layer consisting of CVD nitride (1.2 /spl mu/m thick) and CVD oxide (0.4 /spl mu/m thick) was deposited. The film properties before and after RTA were analyzed using RBS, XRD, and AES. Such an interconnection showed extremely high EM endurance (MTTF /spl sim/ 10/sup 4/ min) in comparison with that using the conventional TiN as an underlying barrier layer (MTTF /spl sim/10/sup 2/ min). It is suggested that the crystal continuity between the Al and the TiN suppresses interface and grain boundary diffusion of Al atoms to improve the EM endurance.