Preferred orientation of TiN films studied by a real time synchrotron x-ray scattering

Abstract

The orientational crossover phenomena in a radio frequency (rf) sputtering growth of TiN films were studied in in situ, real time synchrotron x-ray scattering experiments. For the films grown with pure Ar sputtering gas, the crossover from the (002)-oriented grains to the (111)-oriented grains occurred as the film thickness was increased. As the sputtering power was increased, the crossover thickness, at which the growth orientation changes from the 〈002〉 to the 〈111〉 direction, seemed to decrease. The addition of N2 besides Ar as sputtering gas suppressed the crossover, and consequently resulted in the (002) preferred orientation without exhibiting the crossover. We attribute the observed crossover phenomena to the competition between the surface and the strain energy. The x-ray powder diffraction, the x-ray reflectivity, and the ex situ atomic force microscopy surface topology studies consistently suggest that the microscopic growth front was in fact always the (002) planes. In the initial stage of growth, the (002) planes were aligned to the substrate surface to minimize the surface energy. At later stages, however, the (002) growth front tilted away from the surface by about 60° to relax the strain, which caused the crossover of the preferred growth direction to the 〈111〉 direction.