Reaction Mechanisms in Both a CHF₃/O₂/Ar and CHF₃/H₂/Ar Radio Frequency Plasma Environment

Abstract

A radio frequency (RF) plasma system used to decompose trifluoromethane (CHF 3 or HFC-23) is demonstrated. The CHF 3 decomposition fractions (η CHF 3 ) and mole fractions of detected products in the effluent gas streams of CHF 3 /O 2 /Ar and CHF 3 /H 2 /Ar plasma systems, respectively, have been determined. The effects of four experimental parameters, input power, O 2 /CHF 3 or H 2 / CHF 3 ratio, operational pressure, and the CHF 3 feeding concentration were investigated. The same species detected in the effluent gas streams of both CHF 3 /O 2 /Ar and CHF 3 /H 2 /Ar plasma systems were CH 2 F 2 , CF 4 , HF, and SiF 4 . However, the CO 2 and COF 2 were detected only in the CHF 3 /O 2 /Ar plasma system and the CH 4 , C 2 H 2 , and CH 3 F were detected only in the CHF 3 /H 2 / Ar plasma system. The results of a model sensitivity analysis showed that the input power was the most influential parameter for η CHF 3 both in the CHF 3 /O 2 /Ar and CHF 3 /H 2 /Ar plasma systems. Furthermore, the possible reaction pathways were built up and elucidated in this study. The addition of hydrogen for CHF 3 decomposition can produce a significant amount of HF and the main carbonaceous byproducts were CH 4 and C 2 H 2 . Even though the η CHF 3 in the CHF 3 /H 2 /Ar plasma system is lower than that in the CHF 3 /O 2 /Ar plasma system, but due to the more advantages mentioned above, a hydrogen-based RF plasma system is a better alternative to decompose CHF 3 .

Decomposition of SF6in an RF Plasma Environment

“…13 Figure 2 shows that when no oxygen was added to the reactor (feed O 2 /SF 6 ratio = 0.0), η SF6 clearly increased from 37.79 to 95.68% because of an increase in power from 5 to 20 W. When the power exceeded 40 W, η SF6 exceeded 99%. When oxygen was introduced into the reactor (feed O 2 /SF 6 ratio = 2.0), η SF6 was ~10% less than when no oxygen was added (from 28.61 to 86.09% as the power rose from 5 to 20 W).…”

“…The mole fraction of the product species was determined by comparing with the response of the peak height of standard gas at the same wavenumber. 13,14 However, the concentrations of SF 4 and S 2 F 10 were estimated from data of Heise et al 15 and Wilmshurst and Bernstern. 16 All unreacted F atoms were assumed to be converted into F 2 , 17 and the mole fraction of F 2 was determined using a mass balance.…”

“…The applied power was the most important factor that limited the production of all species. 13 The mole fraction of SiF 4 increased from 0.18 to 0.23% when the input power was varied from 5 to 20 W (Figure 3). Thus, more F radicals were produced, and the etchable wall surface also increased with the plasma contact area under higher input power (Figure 4), which was consistent with the assumption of Breitbarth et al 12 that the SiO 2 etch rate was proportional to the plasma power.…”

Decomposition of Methyl Tert-Butyl Ether by Adding Hydrogen in a Cold Plasma Reactor

“…For example, in the authors' earlier radio-frequency plasma studies (Wang et al, 1999b), the main final products in the C 2 HCl 3 /Ar RF plasma were CO, CO 2 , HCl, and Cl 2 , and the main products in the CCl 2 F 2 /H 2 /Ar plasma were HF, HCl, CH 4 and C 2 H 2 (Wang et al, 1999b).…”

“…(2) Reaction Mechanisms in both a CHF 3 /O 2/ Ar and CHF 3 /H 2 /Ar RF Plasma Environment Wang et al (1999b) studied the decomposition of trifluoromethane (CHF 3 or HFC-23) in a RF plasma system. Wang et al (1999b) obtained some important results and we cited them originally as follows.…”