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.

The pressure dependence of the deposition rate for magnetron sputter deposition of various elemental semiconductors and metals was investigated by x-ray measurements on sputtered films and quartz monitor measurements. It was found that for all elements investigated the dependence of the rate Φ on pressure-distance (pd) is well described by Φ=Φ0(1−e−cpd)/cpd. The value of c equals the inverse characteristic pressure-distance product (pd)0, which is the characteristics of the exponential decay of rate with pressure for low pressures. The experimental data of (pd)0 vary from 4.6 Pa cm for aluminum to 120 Pa cm for tungsten. It is shown that (pd)0 depend on both material specific properties and process parameters. The material specific properties are mainly the atomic mass and diameter, and the surface binding energy. The process parameters target voltage and power density act via the increase of the mean free path and the reduction of gas density, respectively, on (pd)0. As a first approximation, the characteristic pressure-distance product for argon as sputtering gas is proportional to the product of target atomic mass, average atomic energy and thermal mean free path.

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