Diffusion Barrier Reliability with Respect to the Role of Tin Stoichiometry Between Al Metallization and Si Substrate

Abstract

AbstractIn this study, the relation between interdiffusion in Al/ TiN thin film couples and diffusion barrier stability has been investigated. The TiN diffusion barrier was deposited by reactive sputtering in an Ar-N2 gas mixture. The stoichiometry of TiN was achieved by varying the nitrogen-to-argon ratio in the sputtering gas. Interdiffiusion occurred after annealing for 30 minutes at 475°C and 575°C. Diffusion processes and interfacial reactions with respect to TiN stoichiometry were investigated via Auger Electron Spectroscopy (AES) depth profiling and X-ray diffraction (XRD). The barrier reliability with respect to the stoichiometry changes was established; nitrogen-deficient TiN films result in a high degree of interdiffiusion and decomposition at annealing temperatures of 475°C and 575°C. AI3Ti and AlN intermetallic compounds were formed at the interfaces. The sheet resistance of Al films was measured by four-point probe method. Resistance increases for all the annealed films were due to interdiffusion between Al and TiN. The degree of interdiffusion was analyzed by using AES and XRD.