Molecular composition of films and solid particles polymerized in fluorocarbon plasmas

Abstract

In fluorocarbon ͑C 4 F 8 ) plasmas, formation mechanisms of polymers were investigated by the characterization with x-ray photoelectron spectroscopy ͑XPS͒ and gel permeation chromatography ͑GPC͒. The molecular compositions of the polymers in the films deposited on the substrate and in the particles formed in the gas phase were elucidated by these chemical analyses. The XPS results showed that the particles were carbon-rich and composed of highly branched molecules in contrast to the film composition. From the GPC measurements, the particles were found to contain ultrahigh mass polymers, whose molecular weights were around 100 000. On the contrary, the deposited film contained polymers with molecular weights distributed below 2000, in which oligomers, monomers, and fragmented products were included. Present study suggests that these polymers are involved in the formation of crosslinked networks of the films and the particles via surface reactions, where the crosslinking is enhanced by the ion bombardment.

Nanopowder management and control of plasma parameters in electronegative SiH4 plasmas

“…We note that existing models 26,37 considered averaged plasma parameters, and we investigated self-consistently the cross-sectional profiles of the governing quantities. The model can be straightforwardly extended to other reactive plasmas containing charged powder, such as the hydrocarbon-3 and fluorocarbon-based 63 powder generating systems. In summary, we have studied the role of the plasma parameters in the management of nanosize powder particles in a low-pressure parallel-plate silane discharge.…”

Plasma enhanced CVD of fluorocarbon films by low-pressure dielectric barrier discharge

“…In these r.f. plasmas, FC films may be deposited using various fluorocarbon or FC-containing gases such as CF 4 [6], C 2 F 6 [6,7], C 3 F 8 [8], C 4 F 8 [8,9], C 3 F 6 O [10], CH 2 F 2 [11], C 2 H 2 F 4 [11,12], and CHF 3 [13]. These FC gases were decomposed into various radicals and ions, which resulted in the successful fabrication of the films with low dielectric constants.…”

Group additivity values for enthalpies of formation (298K), entropies (298K), and molar heat capacities (300K<T<1500K) of gaseous fluorocarbons

“…Though this is not as desirable as conducting a least-squares-fit over a large database of molecules, Cohen and Benson [25] found that GAVs determined from accurate data for single molecules were able to reproduce the thermodynamic properties of larger molecules within experimental uncertainty. Given the fluorocarbon-fluorocarbon interaction values determined by Yamada and Bozzelli [18], GAVs for C-[F] 3 2 were found from C 3 F 6 . The results are listed in table 3, which gives GAVs for standard enthalpies of formation and entropies at 298 K, and molar heat capacities over the range 300 to 1500 K. …”

“…Therefore, we supposed that setting the GAVs for C-[F] 3 From these assumptions, a step-by-step approach was used to derive group additivity values from the available database. Though this is not as desirable as conducting a least-squares-fit over a large database of molecules, Cohen and Benson [25] found that GAVs determined from accurate data for single molecules were able to reproduce the thermodynamic properties of larger molecules within experimental uncertainty.…”

“…In the latter case, large radical species would primarily contribute to film growth, due to their high reactivity. Similarly, it is proposed that large fluorocarbon radicals polymerize in the gas phase, leading to powder formation in low-pressure fluorocarbon plasmas commonly used in the microelectronics industry [2,3]. Knowledge of thermodynamic properties of large fluorocarbon molecules and short-lived species, such as radicals, is important for an understanding of these complex chemical processes.…”