AVS 51st International Symposium
    Thin Films Monday Sessions
       Session TF-MoA

Paper TF-MoA6
Mechanical Stress in PVD Deposited Chromium Films

Monday, November 15, 2004, 3:40 pm, Room 303C

Session: Mechanical Properties of Thin Films
Presenter: G.C.A.M. Janssen, Delft University of Technology, The Netherlands
Authors: G.C.A.M. Janssen, Delft University of Technology, The Netherlands
J.-D. Kamminga, Netherlands Institute for Metals Research, The Netherlands
S.Y. Grachev, Netherlands Institute for Metals Research, The Netherlands
Correspondent: Click to Email
Thin films on substrates are usually in a stressed state. Apart from the well understood thermal stress - stress occurring due to different thermal expansion coefficient of layer and substrate in combination with an elevated deposition temperature - intrinsic stress can occur resulting from the growth and/or microstructure of the film. In this presentation the mechanisms behind both tensile and compressive intrinsic stress are discussed. A set of chromium films was deposited at room temperature using PVD. These films have a microstructure in zone 2 of the Thornton model. The grain boundary density is high near the substrate-film interface and lower higher up in the film. In fact the grain boundary density as function of height in the film follows a power law. We have shown that tensile stress and grain boundary density co-develop with film thickness. This observation proves the generation of tensile stress at grain boundaries. We calculated the amount of grain boundary shrinkage responsible for the generation of tensile stress to be 0.013 nm. Films deposited at higher Ar pressure exhibit a different power law dependence on thickness. TEM revealed dense grain boundaries and small grains for the films deposited at low pressure and porous grain boundaries, separating larger feather like grains, for films deposited at higher pressures. Grains in those films have less interaction and generate less stress. Stresses in films deposited under a bias voltage were tensile for thin films and compressive for thick films. This is due to a combined effect of atomic peening, leading compressive stress and grain boundary shrinkage leading to tensile stress. It is shown that the dependence of the total stress on film thickness is described by a thickness dependent tensile term and a thickness independent compressive term.