Evaluation of Titanium as a Diffusion Barrier Between Aluminum and Silicon for 1.2 μm CMOS Integrated Circuits

Abstract

Metallurgical, electrical, and reliability evaluations of a Al‐0.5%Cu/Ti interconnect metallization system for use in 1.2 μm CMOS SRAM integrated circuit devices have been performed. The results indicate that the Al‐0.5%Cu/Ti metallization system is superior to both Al‐0.5%Cu and Al‐1%Si‐0.5%Cu metallization systems. It is shown that the presence of titanium has significantly improved the electromigration strength, reduced both the size and density of annealing hillocks, and improved the thermal and electrical stability of the metal‐silicon and metal‐metal contacts. The diffusion barrier behavior of titanium was studied electrically (via junction leakage current measurements) and analytically (via TEM examination of Al/Ti/Si interfaces). It is found that titanium is an effective diffusion barrier to aluminum and silicon as long as it is not completely consumed to produce .