Substrate temperature and collimator aspect ratio effects in titanium sputtering

We investigated the relationship of substrate temperature and collimator aspect ratio to sputtered titanium thin-film properties. Titanium films were deposited in a configuration with a collimating mesh between the target and substrate over collimator aspect ratios of 0.7–2.0 and substrate temperature ranges of 150–450 °C, respectively. We found that a morphology transition occurs with rising deposition temperature and falling collimator aspect ratio where film stress switches from compressive to tensile, roughness increases 50%, grain size doubles, and resistivity increases 20%. We propose that the transition phenomenon is based on a film growth mechanism where substrate heating and surface bombardment have competing effects on the formation of surface clusters.