Stress modification of WSi_2.2 films by concurrent low energy ion bombardment during alloy evaporation

Abstract

The effect of ion bombardment on alloy film stress was studied by coevaporating W and Si in the presence of 100 and 400 eV Ar+ion bombardment at room temperature, 350 and 500 °C. In the absence of ion bombardment, internal stress increases and becomes more tensile as deposition temperature increases. At room temperature, increasing ion bombardment causes the stress to go from tensile to compressive. At 350 6C tensile stress increases as a function of ion flux and decreases slightly at higher flux value. At 500 °C, the effect on stress due to ion bombardment is less pronounced. The correlation between the effect of ion bombardment on stress, deposition temperature, and the structure of the material is discussed using the concept of enhanced surface diffusion and local atomic rearrangement as a mechanism responsible for ion beam stress modification. By using this mechanism, we explain the diminished effect of ion bombardment on stress in the WSi2films that contain compound phases compared to the amorphous WSi2in which ion bombardment is more effective. We also attribute this diminished effect of ion bombardment to the more dominant effect of stress due to phase transformation occurring during deposition. The effect of improving the crystalline order and increasing the grain size due to ion bombardment has also been observed. The modification of stress during deposition has been found to have no consequence on the internal stress obtained after 1000 °C postdeposition annealing. © 1985, American Vacuum Society. All rights reserved.