The effects of Si addition on the structure and mechanical properties of ZrN thin films deposited by an r.f. reactive sputtering method

The addition of Si to nitride films such as TiN or WN has been investigated to improve the mechanical properties of films. The aim of this study is to investigate the influence of Si addition on the structure and the mechanical properties of ZrN thin films. Thin films were synthesized by an r.f. reactive sputtering method in a facing target-type sputtering (FTS) machine on the substrates of silicon wafer and aluminum foils. The structure of thin films was studied by means of XRD and TEM. The hardness of the thin films was studied in detail by the nano-indentation system and the internal stress was evaluated by measuring the change of curvature induced in the sample. A study of their structure and mechanical properties has revealed as the following: (1) with increasing Si content, the hardness of the films increases initially, attaining a maximum hardness at approximately 3%, and then decreases to lower hardness than that of ZrN binary films; (2) the hardest film containing approximately 3% Si consists of large crystals in the range of 20–25 nm; (3) the increment in hardness of ZrSiN films by silicon addition cannot be explained by the crystal size; (4) the change of hardness with increasing Si content might be attributed to the change of internal stress.