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See full abstract here:
http://ocs.ciemat.es/EPS2019ABS/pdf/P2.4006.pdf
Plasma is a multi-component gas, composed of ions, electrons and neutrals. Therefore, collisions between different plasma species must be entertained. Moreover, energy and momentum are redistributed by their presence in the plasma. The presence of negative ions in the system has a huge impact on the characteristics of various quantities like sheath thickness, density and potential profile. Also, their presence plays a crucial role in semiconductor industries, microelectronics industries, plasma cleaning, plasma etching, plasma propulsion and plasma nitriding [1–3]. In this paper, we accomplished a mathematical model to examine the behaviour of charged species present in electronegative plasma under the effect of their finite temperature and collisions with neutral atoms. It is found that collisional parameter as well as temperature have an intense effect on the plasma species profile. These result in the modification of sheath structure and hence, the sheath thickness. In this proposed mathematical model, both the ions, i.e. positive ions and negative ions, are described by fluid equations considering their drift term with collisional and pressure gradient terms. Here, we considered the CF4 electronegative plasma [4], primarily composed of CF3+ and F- ions where former ions are produced by the ionization and later ions by the attachment of electrons with neutral CF4. Rate of detachment of electrons from F- ions, which results in reduction of negative ions, is also taken into consideration. Therefore, ionization, attachment and detachment frequencies are also included in proposed model to execute real behaviour of charge species. CF4 plasma is adopted because of its increasing applications in etching and film deposition processes.
References
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