ELASTIC BEHAVIOR OF TIN THIN-FILMS

Thin films are increasingly being used in many technological areas. On e of the problems in practical applications is the level of internal f ilm stress, which, in severe cases, can lead to coating failure. In ou r laboratories we are currently studying the effect of deposition para meters and of post-deposition treatments on the stress behaviour of so me coatings obtained by magnetron sputtering techniques and by ion bea m assisted deposition (IBAD). In this work we concentrate on TIN since this compound is particularly valuable as a study system, in view of the good understanding of its physical properties and its wide range o f applications, ranging from barrier layers in microelectronics to gas diffusion inhibition, and from optical coatings to sliding wear reduc tion. We have deposited thin films (ranging in thickness from 100 nm u p to a few microns) of TiN in different experimental conditions, by d. c. magnetron reactive sputtering and by IBAD, and we have characterize d the coatings with respect to composition, structure and microstructu re by scanning electron microscopy, Auger electron spectroscopy and X- ray diffraction. The elastic response of the films has been studied in detail by surface Brillouin light scattering. Our results are in gene ral agreement with other works in the literature; however, the Rayleig h wave velocities for IBAD samples are much lower than expected. Some preliminary explanations of this fact are presented.