Reactively sputtered Ti-Si-N films I. Physical properties

Abstract

Films of Ti-Si-N were synthesized by reactively sputtering TiSi2, Ti5Si3, or Ti3Si targets in an Ar/N2 gas mixture. They were characterized in terms of their composition by MeV 4He backscattering spectrometry, their atomic density by thickness measurements combined with backscattering data, their microstructure by x-ray diffraction and high-resolution transmission electron microscopy, and their electrical resistivity by four-point-probe measurements. All films have a metal–to–silicon ratio close to that of their respective targets. The as-deposited films are either entirely amorphous or contain inclusions of TiN-like nanometer-sized grains when the overall atomic composition of the films approaches the TiN phase in the ternary Ti-Si-N diagram. A correlation between the resistivity of the as-deposited films and their position in the ternary phase diagram is evident, indicating that at the atomic scale, the spatial arrangement of atoms in the amorphous phase and their bonding character can approximate those of the equilibrium phases. A mixture of nanocrystalline TiN and amorphous Si-N is proposed for some titanium- and nitrogen-rich films. The atomic density of some films exceeds 1023 at./cm3. The resistivity of the films increases with the Si and the N content. A thermal treatment in vacuum at 700 °C for 1 h decreases the resistivity of the Ti-rich films deposited from the Ti5Si3 or the Ti3Si target, but increases that of the Si-rich films deposited from the TiSi2 target when the nitrogen content exceeds about 30 at. %. The effectiveness of these films as diffusion barriers between Si and Al or Cu is reported in Part II.