Correlation of electrical resistivity and grain size in sputtered titanium films

Thin Ti films deposited onto thermal SiO2 by sputtering in Ar or Ne are analyzed accounting for electron scattering at both film and grain boundary surfaces. An intrinsic resistivity of 54 and 63 μΩ cm, and an electron mean free path of 18 and 15 nm is derived for films sputter deposited in Ar and Ne, respectively. For both gases, a grain boundary reflection coefficient of 0.17 is calculated, assuming pure specular electron reflection at the film surfaces. Resistivity lowering is shown to correlate directly with an increase in grain size. Sputtering in Ar results in larger grain size films that have a small 21 μΩ cm residual resistivity and a high 2800 ppm temperature coefficient of resistance. The film grain size is independent of the deposition rate and reduced when sputtered in Ne, or in Ar and an applied negative substrate bias. The Ti film texture is found to be independent of film thickness and the presence of a collimator but sensitive to an applied substrate bias.