Effects of the Ar–N2 sputtering gas mixture on the preferential orientation of sputtered Ru films

We have investigated the influence of N2 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% N2 to be the c-axis. With increasing proportion of N2 in the sputtering gas at a substrate temperature of 100 °C, the intensity of the (002) peak decreased, finally disappearing at 50% N2. This c-axis-suppressed Ru film sputtered at 50% N2 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.