CF4 plasma

Application of this model to a CF4 plasma results in the chemical scheme indicated by Equations 11-14. 

Depending upon the particular precursors generated in the gas phase, etching, recombination, or film formation (i.e., polymerization) can occur. Also, gas-phase oxidant additives (O2, F2, CI2, etc.) can dissociate and react with unsaturate species. As an example, O2 can undergo the following reactions in a CF4 plasma ... 

Fig. 2.4. Etching and polymerization dependence as a function of pressure in a CF4 plasma. Pressure varied by the different techni iues involving flow rate and residence time...

Although the Novolak resin of the w-cresol-benzaldehyde failed to show a marked increase in CF4 plasma etching resistance, the Novolak resins of hydroxy-naphthalene-hydroxybenzaldehyde showed a remarkable increase in the plasma etching resistance. The resist films also yielded excellent patterns when used together with a diazo-naphthoquinone sensitizer almost non-diluted AZ2401 developer had to be used for image development due to the hydrophobic nature of the naphthalene group. 

In CF4 plasma etching at 0.5 to 1 Torr pressure, the active species are neutral free radicals like F atoms and CF3 (28). Novolak resins have fairly strong CF4 plasma etch resistance (29), which, because of widespread use of the dry etching process, is one of the required features for resins used as resist materials for IC manufacturing processes. 

Reduction in the surface recombination velocity of GaP, from 1.7 x 10s cm/sec to 5xl03 cm/sec, is observed upon exposure to a CF4 plasma in which fluorine is known to be present.20 Again, the product of chemisorption of fluorine on the surface is likely to be a large band gap material such as GaF3, which straddles the edges of the conduction and valence bands of GaP. 

CF, - plasma (Figure S ). As expected, CF4 plasma treatment leads to dramatic effects surface fluorination is seen to be very efficient in regimes "A" and "B , but the fluorine concentration drops rapidly at elevated Vs. The presence of hydrophobic CFX groups maintains high 0a values, as expected r decreases only slowly with increasing substrate bombardment, presumably due to the resulting surface cross-linking. 

Finally, comparing the results for CF4 plasma-treated PC and PVC, we note that substantial adhesion improvement occurs for the former but not for the latter. The fact that both treated surfaces become highly fluorinated and hydrophobic once again underscores the state-... 

Typical range values for plasma parameters in rf diode and high density reactors, (calculation is done for a CF4 plasma assuming Maxwell-Boltzmann distributions)... 

Fig. 3. Measured ion energy distribution in 3 mTorr CF4 plasma (reprinted with permission from J. Appl. Phys., 67 (1990) 1229 [8])..

Fig. 10. Ellipsometry analysis in real-time of Si exposed to a CF4 plasma, V and A as a function of pressure or of gas mixture (reprinted with permission from J. Vac. Sci. Technol., A 11 (1993) 34 [39]).

Reaction set in CF4 plasmas. (Reproduced with permission from Plasma Chem. Plasma Process., 6 (1986) 231 [50]). 

Pai, Y.-H. et al., CF4 plasma treatment for preparing gas diffusion layers in membrane electrode assemblies, J. Power Sources, 161, 275, 2006. 

Air plasma treatment was used to make one surface hydrophilic, and CF4 plasma treatment was used to make the other hydrophobic. Such a fabric with a different set of surface characteristics on each side can be made however, the success of this undertaking is contingent on which treatment is applied first. The sequence dependency of plasma treatments may be explained by the concept of plasma sensitivity of the elements involved in the two steps. Results are summarized in Tables 10.1 and 10.2. 

The efficiency of F incorporation into the surface structure is higher on the surface that is not directly exposed to the CF4 plasma. This trend is found consistently in the data presented in Table 10.2. 

Figure 25.2 depiets the sessile droplet eontaet angle of water on CF4 plasma-treated PET with varying degree of crystallinity, and the influence of water immersion and the subsequent drying. Water-immersed samples were freeze dried to... 

Figure 25.2 Sessile droplet contact angle of water on CF4 plasma treated PET films subsequently treated differently (1) samples kept in air (no water immersion), (2) samples immersed in water for 120 min, (3) water immersed samples heat treated at 100°C for 10 min, (4) water immersed samples heat treated at 180°C for 10 min.

Figure 25.4 Correlation between sessile droplet contact angle of water and XPS F Is intensity of CF4 plasma treated Nylon 6 and PET films.

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