A global model has been developed for low-pressure, inductively coupled plasma (ICP) SF6/O2/Ar mixtures. This model is based on a set of mass balance equations for all the considered species, coupled with the discharge power balance equation and the charge neutrality condition. The present study is an extension of the kinetic global model previously developed for SF6/Ar ICP plasma discharges [Lallement et al., Plasma Sources Sci. Technol. 18, 025001 (2009)]. It is focused on the study of the impact of the O2 addition to the SF6/Ar gas mixture on the plasma kinetic properties. The simulation results show that the electron density increases with the %O2, which is due to the decrease of the plasma electronegativity, while the electron temperature is almost constant in our pressure range. The density evolutions of atomic fluorine and oxygen versus %O2 have been analyzed. Those atomic radicals play an important role in the silicon etching process. The atomic fluorine density increases from 0 up to 40% O2 where it reaches a maximum. This is due to the enhancement of the SF6 dissociation processes and the production of fluorine through the reactions between SFx and O. This trend is experimentally confirmed. On the other hand, the simulation results show that O(3p) is the preponderant atomic oxygen. Its density increases with %O2 until reaching a maximum at almost 40% O2. Over this value, its diminution with O2% can be justified by the high increase in the loss frequency of O(3p) by electronic impact in comparison to its production frequency by electronic impact with O2.
Global kinetic models combined with Monte Carlo sheath models are developed for SF 6 and C 4 F 8 plasma discharges for silicon etching under the Bosch process. In SF 6 plasma, the dominant positive ions are SF + 5 , SF + 4 , SF + 3 and F + while in C 4 F 8 the dominant positive ions are CF + 3 and C 2 F + 3 . The simulation results show that the electrical parameters, such as the electron density and electron temperature, clearly affect the sheath dynamics and consequently the ion energy distribution function evolutions. In this context, we showed the effects of the operating conditions, such as the pressure and the radiofrequency power, on the electron density and electron temperature evolutions as well as the reactive particle fluxes (neutral and positive ions) involved in the plasma surface interactions for etching/deposition under the Bosch process. Ion energy distribution functions obtained from SF 6 and C 4 F 8 plasmas are compared with each other as regards the electrical properties of their associated plasmas. The simulation results show that the bimodal peaks of ion energy distribution functions are wider for SF 6 plasma than for C 4 F 8 plasma due to the high sheath thickness of SF 6 compared to that of C 4 F 8 . This is explained by the low electron density due to the high electronegativity of SF 6 in comparison to that of C 4 F 8 . The simulations also reveal that the bimodal peak of the ion energy distribution function is wider when the ion mass is low.
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