Microstructure and properties of dual ion beam sputtered tungsten film

Abstract

The relationship between microstructure and properties of dual ion beam sputtered tungsten film is investigated. Film properties, such as electrical resistivity and residual stress, are found to be dependent significantly on the Ar+sputtering energy from the deposition source and also on the flux density and energy of the assisting beam. Resistivity increases with increasing Ar+sputtering energy, and decreases with increasing assisting flux and energy. Residual stress increases with increasing Ar+sputtering energy and decreasing flux of assisting beam. With high Ar+sputtering energy, such as 1200 eV, a flux of energetic particles including sputtered atoms and reflected argon is directed toward film surface resulting in the atomic peening and sputter etching of growing film, which is a characteristic result of directional sputtering using ion beam. Microstructural analysis shows that this process causes the formation of finer grains, denser microdefects, sharp strain contours, and metastable β-phase tungsten, which correlate consistently with the observed high stress and resistivity. Bombarding the growing film with low-energy assisting Ar+flux reduces both stress and resistivity by mobilizing the sputtered atoms on film surface. It is shown that the presence of assisting flux reduces the density of microdefect and strain contours within the grain, and stabilizes the bcc a-phase tungsten without altering the overall microstructure of the tungsten film. © 1989, American Vacuum Society. All rights reserved.