Monte Carlo simulation of the MoS₂ sputtering process and the influence of the normalized momentum on residual stresses

Titelangaben

Vierneusel, Bernd ; Tremmel, Stephan ; Wartzack, Sandro:
Monte Carlo simulation of the MoS₂ sputtering process and the influence of the normalized momentum on residual stresses.
In: Journal of Vacuum Science & Technology A. Bd. 33 (2015) Heft 6 . - 061501.
ISSN 1520-8559
DOI: https://doi.org/10.1116/1.4926383

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Abstract

The film growth of sputtered MoS2 coatings is highly sensitive to the deposition conditions. Therefore, the effects of the deposition parameters on the resulting film structure have been studied excessively over recent decades. There is wide consensus in the literature that dense and hard MoS2 coatings show the best tribological behavior. Therefore, high-energy particle fluxes are typically favored due to momentum-induced film densification. Although particle flux ϕ and particle energy E are considered to be the most relevant for MoS2 film growth, the relationship between the process parameters and the resulting particle energetics has not yet been investigated. In this study, results from Monte Carlo simulations show the effect of cathode voltage and process pressure on the resulting particle energetics as a function of the target–substrate distance. Due to its relevance for the stress state, the normalized momentum according to Windischmann's intrinsic stress law has been investigated as a function of the deposition parameters. Based on the calculated results, it is assumed that the highest degree of particle induced densification and intrinsic stress formation can be expected at low process pressures, low target–substrate distances and high cathode voltages. However, the intensified densification effect of increased cathode voltages decreases with increasing distances to the target. In this study, the calculated results are compared with experimental residual stress data from literature. For this purpose, different ϕE1/2-factors have been calculated for 13 parameter combinations according to a Box–Behnken design by varying the parameters cathode voltage, process pressure and target–substrate distance on three different levels. A strong correlation between these calculated data and experimentally determined stresses has been found, which confirms the approach of the simulation procedure.