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Pressure-Controlled Transport of Sputtered Atoms in Thin-Film Deposition: Mean-Free-Path and Collision-Probability Analysis |
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PP: 195-202 |
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doi:10.18576/ijtfst/150206
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Author(s) |
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Abdelkader Bouazza,
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Abstract |
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| Sputter deposition involves the generation of energetic target atoms followed by their transport through a background gas toward a substrate. This work examines the pressure dependence of that transport within a two-stage SRIM–SIMTRA framework, in which SRIM describes the sputtering of aluminium, germanium, boron, niobium, antimony and copper targets bombarded at normal incidence by argon, xenon, helium, neon and silicon ions, and SIMTRA describes the subsequent gas-phase transport. The physical link between pressure and trajectory is expressed through the mean free path and the probability of collision during the target-to- substrate flight. These relations are extended to the ballistic survival fraction, the mean collision number, the diffusion coefficient and the ballistic and diffusive transit times, and are supported by a nomenclature table, a Knudsen-number regime classification, a two- dimensional pressure–temperature map and a schematic of the SRIM–SIMTRA workflow. The analysis covers gas temperatures of 300–450 K, the interval over which the calculations were compared with previous work. All pressure-dependent figures in this paper are calculated directly from the stated analytical relations with explicitly specified illustrative parameters; they are not experimental measurements or SRIM/SIMTRA output. For an effective collision diameter of 0.36 nm, a 0.10 m flight path and 300 K, the transport moves from the transitional into the continuum regime at about 1 Pa, and the ballistic and diffusive transit-time estimates cross at a Knudsen number of 1.5.
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