Nanostructure formation during deposition of TiN/SiN{sub x} nanomultilayer films by reactive dual magnetron sputtering
- Division of Engineering Materials, Lulea ring University of Technology, Lulea ring SE-971 87 (Sweden)
Multilayer thin films consisting of titanium nitride (TiN) and silicon nitride (SiN{sub x}) layers with compositional modulation periodicities between 3.7 and 101.7 nm have been grown on silicon wafers using reactive magnetron sputtering. The TiN and SiN{sub x} layer thicknesses were varied between 2-100 nm and 0.1-2.8 nm, respectively. Electron microscopy and x-ray diffraction studies showed that the layering is flat with distinct interfaces. The deposited TiN layers were crystalline and exhibited a preferred 002 orientation for layer thicknesses of 4.5 nm and below. For larger TiN layer thicknesses, a mixed 111/002 preferred orientation was present as the competitive growth favored 111 texture in monolithic TiN films. SiN{sub x} layers exhibited an amorphous structure for layer thicknesses {>=}0.8 nm; however, cubic crystalline silicon nitride phase was observed for layer thicknesses {<=}0.3 nm. The formation of this metastable SiN{sub x} phase is explained by epitaxial stabilization to TiN. The microstructure of the multilayers displayed a columnar growth within the TiN layers with intermittent TiN renucleation after each SiN{sub x} layer. A nano-brick-wall structure was thus demonstrated over a range of periodicities. As-deposited films exhibited relatively constant residual stress levels of 1.3{+-}0.7 GPa (compressive), independent of the layering. Nanoindentation was used to determine the hardness of the films, and the measurements showed an increase in hardness for the multilayered films compared to those for the monolithic SiN{sub x} and TiN films. The hardness results varied between 18 GPa for the monolithic TiN film up to 32 GPa for the hardest multilayer, which corresponds to the presence of cubic SiN{sub x}. For larger wavelengths, {>=}20 nm, the observed hardness correlated to the layer thickness similar to a Hall-Petch dependence, but with a generalized power of 0.4. Sources of the hardness increase for shorter wavelengths are discussed, e.g., epitaxial stabilization of metastable cubic SiN{sub x}, coherency stress, and impeded dislocation activity.
- OSTI ID:
- 20711733
- Journal Information:
- Journal of Applied Physics, Vol. 97, Issue 11; Other Information: DOI: 10.1063/1.1935135; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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