Stoichiometry effects in TiN diffusion barriers

Abstract

TiN diffusion barriers were deposited via reactive sputtering in an ArN 2 gas mixture. Several TiN films with variation in the stoichiometry were produced and used as a diffusion barrier between a silicon substrate and an aluminium alloy film in order to prevent Al-Si interdiffusion (“spiking”). The quality of the barrier films during further anneal steps was investigated by detection of the diffusion processes and interfacial reactions using Auger electron spectroscopy (AES) depth profiling and by testing the spiking directly on wafers with contact hole structures (“spiking tests”). A correlation between TiN stoichiometry and barrier quality was established; the use of nitrogen-deficient TiN films resulted in a high degree of interdiffusion and a clear tendency towards spiking. In order to counteract barrier failure due to substoichiometric TiN a barrier post-treatment in N 2 was performed and characterized with AES. With this post-treatment an improvement in the barrier performance for substoichiometric TiN films could be achieved.