The influence of argon pressure on the structure of sputtered molybdenum: From porous amorphous to a new type of highly textured film

Abstract

The density of the low-rate (<0.1 nm/s) sputtered molybdenum films can be controlled between 48% and 96% of the bulk material by the variation of argon pressure from 4.7 to 0.45 Pa. Small angle x-ray scattering shows the existence of columnar voids with a typical size of 10 nm, especially in the low-density films, whereas a high concentration of primary voids with a diameter of 1 nm is found independent of the density. The conductivity of the films decreases monotonically with decreasing density from 2.4×104 to 2.1×102 (Ω cm)−1, with a strong decay below a density of 55%. Films of about 30 nm thickness are amorphous or nanocrystalline with a (110) texture for high- and low-pressure sputter deposition, respectively. Upon increasing the film thickness up to 3 μm, the low-density films become nanocrystalline, too, and develop the common (110) fiber texture. In contrast, increasing the thickness of the high-density films results in a turnover of texture from a (110) type to a (211) mosaiclike texture.