DIAMOND 2008, 19^th European Conference on Diamond, Diamond-Like Materials, Carbon Nanotubes, and Nitrides, 07.09-11.09.2008, Sitges, Spanien

Topic D Diamond like carbon, including carbon nitride

Title:

Sputter deposition of single layer Si-C-N films: molecular dynamics simulation and experimental validation of structure-property-correlations

Authors & affiliations:

C. Ziebert¹, J. Ye¹, S. Ulrich¹, A. Prskalo², C. Kohler², S. Schmauder²

¹ Institute for Materials Research I, Forschungszentrum Karlsruhe, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany

² Institute for Materials Testing, Materials Science and Strength of Materials (IMWF), University of Stuttgart, Pfaffenwaldring 32, 70569 Stuttgart, Germany

Abstract:

Thin films of silicon carbide (SiC) and silicon carbon nitride (SiCN) have been deposited on Si and hard metal substrates by RF magnetron sputtering from a SiC target. These experiments have been supported by molecular dynamics simulations using IMD and Materials Explorer software with modified Tersoff potentials in order to get more insight into the sputter process, the film deposition, growth and phase formation and to calculate the elastic properties. At first substrate temperature (200 to 800 °C) and bias voltage (0 to -70 V) have been varied in pure Ar atmosphere to investigate the influence on the composition, the constitution and the mechanical properties of SiC films. At second the nitrogen content was varied between 0 and 33 vol.% at 800 °C without bias voltage to investigate its influence on the structure and properties of SiCN films. The films have been characterized by EMPA, XRD and TEM. Hardness, residual stress and critical load of failure in dependence of the film thickness have been investigated by nanoindentation, wafer bending and scratch test. The topographical changes in dependence of the N₂ content have been studied by AFM. Even at a substrate temperature of 800 °C all films deposited in pure Ar were amorphous with a maximum hardness value of 30 GPa and low residual stress of -0.4 GPa. However, even a very small N₂ addition of 0.2 vol.% removed the oxygen contamination and enabled the formation of crystalline films. At a N₂ concentration of 0.4 % a two-phase microstructure of phases similar to alpha-SiC and beta-SiC with nanocrystalline grains of 5-10 nm is formed. This nanostructure results in a superhard film with 45 GPa hardness, however residual stress also rises up from 0.6 to 2.4 GPa. At 33% nitrogen the films become amorphous and the hardness decreases to 20 GPa.

Keywords: sputter deposition, silicon carbon nitride, molecular dynamics simulation, atomic force microscopy