CHARACTERIZATION OF TIN FILMS GROWN BY REACTIVE DC TRIODE SPUTTERING ONTO COPPER SUBSTRATES

TiN films with a thickness varying from 70 to 300 nm were deposited onto Cu substrates by reactive d.c, triode sputtering. The characteristic features of the deposition system are described in detail. In order to vary the structure of the as-deposited films, they were grown with and without substrate heating and with substrate bias. The as-deposited films (unheated substrate) were quasi-stoichiometric, as determined by Auger electron spectroscopy (AES). Transmission electron microscopy (TEM) showed that the latter films were randomly oriented crystal with a grain size between 8 and 12 nm, whereas the films deposited under substrate heating (250-400 degrees C) or under substrate bias (-250 V) had larger grain size, between 50 and 600 nm, consisting of monocrystalline areas with (110) and (100) orientations parallel to the substrate plane. We determined a parameter value of 0.425 nm by electron diffraction as well as by X-ray diffraction for the as-deposited films (unheated substrate). A TEM cross-section of the latter showed a dense void-free columnar structure. It was shown also that this columnar structure is independent of the atomic fraction of the nitrogen. Finally, annealing of samples prepared without substrate bias at 700 degrees C for 30 min showed from the AES depth profiles that there is no diffusion of Cu to the outer surface of the films and also that no reaction occurs at the interface. This behaviour is related to the low pressure and small deposition rate used.