Effects of the Ar-N_2 Sputtering Gas Mixture on the Preferential Orientation of sputtered Ru Films

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We have investigated the influence of N_2 addition to the Ar sputtering gas on the crystal orientation of sputtered Ru films. An rf magnetron sputtering apparatus with a Ru target (99.9%) and a glass substrate heated to 100°C or 300°C was used for the deposition. The crystal structure, chemical composition and electrical properties of the resultant films were investigated. X-ray diffraction (XRD) revealed the dominant orientation at 0% N_2 to be the c-axis. With increasing proportion of N_2 in the sputtering gas at a substrate temperature of 100°C, the intensity of the (002) peak decreased, finally disappearing at 50% N_2. This c-axis suppressed Ru film sputtered at 50% N_2 was found to contain nitrogen by Auger electron spectroscopy (AES), but by annealing the film in vacuum at 400°C, the nitrogen in the film was completely removed. The film orientation remained the same as before annealing. Thus, we have demonstrated a new method for depositing Ru films with a controlled preferential orientation of either c-axis oriented or c-axis suppressed.