engleski

The influence of deposition conditions on ß-phase occurrence in tungsten thin films

Interest for metallic tungsten films in modern technologies has been motivated by its useful properties, such as high electrical conductivity, high melt temperature, high mechanical strength and corrosion resistance. In many studies the effects of deposition conditions has been noted, and the formation of the metastable A15 b-W phase observed in preference to the equilibrium a-W phase. In this work we report the influence of deposition conditions on appearance of the b-W phase, and correlate it to the amount of strain in thin tungsten films deposited by magnetron sputtering. Tungsten thin films were deposited onto glass substrates (11 mm in diameter; 1.0 or 0.15 mm in thickness; current density at target 4mA/cm2 if one magnetron used or 2 to 2.5 mA/cm2 if two magnetrons used; substrate distance 5 cm; Ar gas pressure 0.7 to 2.8 Pa, substrate temperature LN2, RT and 2500C; deposition duration 15, 30 and 60 min), and the phase and microstructure of the deposited W films were analyzed by X-ray diffraction (XRD). The influence of deposition conditions on the appearance of metastable b-W was examined. The residual lattice micro strain was determined by XRD peak line profile analysis and compared with the results obtained by measurements of glass substrates deformation caused by deposited films. The preliminary results showed that thicker films partly detached from the substrate, compensating the strain. No single b-W phase films were found. The thicker the films, or higher the substrate temperature, the amount of b-W phase is lower. Films deposited on 2500C were of single a-W structure. Further analysis of the deposition parameters on strain states in deposited films is in progress.

magnetron sputtering; beta-tungsten

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