Influence of substrate properties on the growth of titanium films:: Part II

Abstract

In situ internal stress measurements were used to investigate the influence of the chemical properties of the substrate on the growth of a titanium film deposited under UHV conditions. The substrate films used were titanium films evaporated at different water partial pressures. When the titanium film is evaporated at substrate temperatures of 130 °C and higher the shape of the stress vs thickness curve is interpreted to indicate island growth. Comparing the internal stress curve of titanium on Al 2O 3 and Ti/H 2O substrates it is seen that the initial tensile stress is significantly larger on the Ti/H 2O substrate film. This larger tensile stress is interpreted to originate from a redistribution of oxygen at the substrate interface during the early growth stage of the clean titanium film. A compressive stress contribution at higher thickness of the titanium film is interpreted to be due to hydrogen interdiffusion from the substrate into the titanium film. Annealing of the Ti/H 2O substrate films at 350 °C for 20 min reduces the concentration of the surface oxygen species and the amount of hydrogen incorporated in the films. Dosing of previously annealed Ti/H 2O substrate films with water affects both the oxygen concentration on the surface of these substrate films and the amount of hydrogen incorporated in the films. Oxygen dosing of these films only increases the concentration of the oxygen species on the substrate surface; thus only the initial tensile stress built up in the titanium film is affected. Dosing the films with hydrogen, on the other hand, only increases the amount of hydrogen incorporated in the substrate film, which by way of interdiffusion into the growing titanium film gives rise to a larger compressive stress at higher film thickness.