Synthesis and Characterization of Zr1-xSixN Thin Film Materials

A series of zirconium silicon nitride (Zr1-xSixN) thin films were grown on r-plane sapphire substrates using rf magnetron co-sputtering of Zr and Si targets in a N2/Ar plasma. The films were grown at 200°C and also post-deposition annealed at 1000°C for two hours in vacuum. Face-centered cubic ZrN films grow with high quality (100) heteroepitaxy on the r-plane sapphire substrate as demonstrated by x-ray diffraction (XRD) pole figure analysis. A small amount of Si added to the ZrN lattice, (Si/(Si+Zr) ratio of up to -15%), causes the Zr1-xSixN films to become polycrystalline with one-dimensional (100) oriented crystallographic texture. For a Si/(Si+Zr) ratio above -15%, the films are amorphous. X-ray photoelectron spectroscopy (XPS) measurements were used to determine film stoichiometry and provide information about chemical bonding. No evidence for ZrN/SiN phase separation was found for films deposited at 200°C, and the XPS spectra suggest that homogenous Zr-Si-N films are produced. After the films were annealed at 1000°C, XPS spectra exhibited negligible changes except for a small amount of oxygen contamination that absorbed on the film surface because of degassing in the annealing chamber. N, Zr, and Si Auger parameters, measured from the Zr1-xSixN films after the annealing treatment, decrease as the Si content is increased suggesting the formation of a more polarized bond. Optical microscopy and atomic force microscopy revealed very smooth films except for Si concentrations corresponding to where the film transforms from poly crystalline to amorphous structure. At this transition, evidence is found for regions of film delamination and hillock formation, which is presumably driven by strain at the film-substrate interface. UV-visible optical absorption spectroscopy showed different behavior for Si-rich films compared to Zr-rich films. For Si-rich films (Si/(Si+Zr) ratio above -12%), a direct correlation was found between the location of the absorption edge, and the magnitude of the optical band gap, versus the Si content. For Zr-rich films (below -12%), there is no band gap and the films are highly conductive as determined by four-point probe conductivity measurements