Fluorine-to-carbon ratio

Figure C2.13.7. Change between polymerizing and etching conditions in a fluorocarbon plasma as detennined by tire fluorine-to-carbon ratio of chemically reactive species and tire bias voltage applied to tire substrate surface [36].

The fluorine to carbon ratio (F/C) of the "active species" can be used 40) to explain observed etch results (Figure 10). This model does not con-... 

Fluorine-to-Carbon Ratio (F/C) of Gas Phase Etching Species... 

Figure 10, Schematic of the influence of fluorine to carbon ratio and electrode bias on etching versus polymerization processes in fluorocarbon plasmas, (Reproduced with permission from Ref, 40 J...

Fig. 3.10. Schematic representation of the boundary region between etching and polymerization as influenced by the fluorine-to-carbon ratio of the etching species and the bias applied to the surface of interest (see text for discussion)...

FIC Ratio Model. The fluorine-to-carbon ratio (F/C) of the active species can be used (92) to explain the observed etch results (Figure 8). This model does not consider the specific chemistry occurring in a glow discharge but, rather, views the plasma as a ratio of fluorine species to carbon species that can react with a silicon surface. The generation or elimination of the active species by various processes or gas additions then modifies the initial F/C ratio of the inlet gas. 

The films deposited in various substrates after plasma treatment in the presence of perfluorinated olefins were subject to partial removal with extraction. Generally, after extraction, the fluorine to carbon ratio, determined through XPS analysis, decreased to 0.2 1 to 0.3 1 regardless of the applied power and residence time used during the fonnation of the film. In all cases a moderate but consistent amount of oxygen was detected in the fluorocarbon film. The oxygen to carbon ratio 0.12 1 to O.l t before extraction and 0.08 1 to 0.1 1 after extraction. 

The data in Table 7.6 reveal a large increase in the bond strength of PVF and ECTFE after flame treatment. The fluorine-to-carbon ratio (F/C) of PVF remained unchanged but the oxygen-to-carbon (0/C) ratio increased significantly. In the case of PTFE, the F/C ratio actually increased which could explain the drop in the bond strength as a result of flame treatment. The flame probably removed contamination that had previously masked (covered) some of the F atoms on the surface. 

Certain fluorocarbon processing aids are known to partially alleviate melt defects in extrudable thermoplastic hydrocarbon polymers and allow for faster, more efficient extrusion. Blatz first described the use of fluorocarbon polymer process aids with melt extrudable hydrocarbon polymers wherein the fluorinated polymers are homopolymers and copolymers of fluorinated olefins having an atomic fluorine to carbon ratio of at least 1 2, wherein the fluorocarbon polymers have melt flow characteristics similar to that of the hydrocarbon polymers (4). 

This first systematic XPS analysis has shown that it is possible to sputter-deposit compounds whose surface properties (fluorine to carbon ratio, cross-linking and branching) can be varied over a large range of values, as it has already been observed for polymer films prepared by plasma polymerization. We note here that a film very similar to polytetrafluoroethylene... 

Figure 5. Fluorine to carbon ratio versus percentage of CFa in Argon atmosphere measured for polymers sputtered at 1.5 10 Torr, with Vj = - 1200 V (Series B).

If we compare stoichiometry and composition of fluoropolymer films prepared by RF sputtering (this work) and by plasma polymerization, we note thatbythe latter method polymers with high j or low > fluorine to carbon ratio could be prepared integrated peak intensities corresponding to CF formula of X - 2.06 to 2.36, X - 0.96 to 2.18, X = 0.94 to and X = 0.75 to 1.43 were... 

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