Elastic Modulus and Hardness as Derived from Nanoindentation of Ni and Mo Films Prepared by Ion Beam Assisted Deposition
- PDF / 256,297 Bytes
- 5 Pages / 414.72 x 648 pts Page_size
- 86 Downloads / 248 Views
A. WROBLEWSKI* x,N. CHECHENIN#, J.BOTTIGER*, J. CHEVALLIER*, N. KARPE+, AND J.P. KROG* * Institute of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark # Institute of Nuclear Physics, Moscow State University, 119899 Moscow, Russia + Department of Solid State Physics, Royal Institute of Technology, 100 44 Stockholm, Sweden x On leave from Moscow Engineering Physics Institute. ABSTRACT Using ion beam assisted deposition, 1.5-2.2 pm thick molybdenum and nickel films were prepared on silicon substrates. Some films were found to be strongly textured. By changing the rate of Ar÷ bombardment during the deposition, the resulting in-plane film stresses could be changed from being strongly tensile to strongly compressive. Using nanoindentation, the hardness and elastic modulus were measured for all films, but no major influence of the film stress or different textures could be found. The elastic modulus of the Ni films was found to be close to its polycrystalline bulk value, and that of Mo was found to be about 70% of its polycrystalline bulk value.
INTRODUCTION For a large number of microelectronic and micromechanical applications, knowledge of mechanical properties of thin films is essential. In this connection, nanoindentations have emerged during the last 2 decade as an important tool for direct investigations of such mechanical properties."' For a specific film preparation technique, many key parameters such as morphology, stress, impurity contents and porosity cannot be varied independently, and their relative importance for the observed mechanical behavior of the film is not readily determined. In particular, the possible influence of stress on the observed hardness and elasticity in a nanoindentation experiment is often masked out by variations in other parameters. For thin films and multilayers, compressive surface stresses have been suggested to lead to a substantially enhanced elastic modulus. 4' Ion Beam Assisted Deposition (IBAD), Le., ion irradiation simultaneously with deposition by evaporation, offers a possibility to vary film stresses over a broad range from being strongly tensile to strongly compressive in the same type of films by only altering the ion bombardment conditions during the deposition. 56 In addition, the ion bombardment gives rise to a high atomic surface mobility during the deposition process, which helps to produce films of high density. In this brief note, the hardness and elastic modulus of bcc molybdenum and fcc nickel films prepared by IBAD are reported. For both elements, stress levels ranging from tensile to compressive have been investigated, but no major influence on the hardness or elastic modulus was observed. These results suggest that the direct stress influence on hardness and elasticity in these metallic films is so small that other factors such as for example porosity in practice are likely to dominate, except perhaps for ultrathin or compositionally modulated films. Most films were found to exhibit a pronounced texture with a characteristic (111) orient
Data Loading...
