ZrN and ZrSiN films were prepared in an rf-sputtering apparatus which has a pair of targets facing each other (referred to as the facing target-type rf sputtering). In order to investigate the influence of substrate temperature on the structure and mechanical properties of Zr-Si-N films, the substrate temperature during the deposition was changed from 373 K to 673 K. Only one phase with a cubic 131 NaCl structure, typical for ZrN, can be clearly identified in all Zr-Si-N films in this study. Increasing substrate temperature can improve crystalline quality in all Zr-Si-N films in this study. Grain sizes of all Zr-Si-N thin films, despite the Si content, increase linearly with increasing substrate temperature. However, the grain growth speed with increasing substrate temperature in a pure ZrN thin film is much faster than that in Zr-Si-N thin films, because Si atom occupation of interstitial sites tends to lock diffusion paths and thus stabilize the structure. The hardness of Zr-Si-N film with low Si content, such as 3 at. % Si, decreases after the substrate temperature increases above 600 K because the internal stress drops. In the high Si content Zr-Si-N films, the hardness improved by increasing substrate temperature due to the increased strength in the grain boundaries. (C) 2003 American Vacuum Society.