The plasma abatement system co-developed by Rf Environmental, Inc. and Texas A & M University has been effective at destroying the global warming gases CF4 and C4F8. The destruction of greenhouse gases, specifically perfluorocompounds, hydrofluorocompounds, chlorofluorocompounds (PFCs, HFCs, CFCs) and SF6, is paramount to significantly affecting atmospheric pollution. The premise of this study was to examine the design of the plasma abatement system for Global Warming Gases (GWGs) and its abatement potential for these gases. The first goal was to reduce the cost of ownership by examining the cooling system. The cost of an air cooling design was $1400/yr. The intent was to reduce the amount of air used or use a different medium that would produce the same amount of heat transfer. A liquid cooling system design had a cost of only $150/yr. A C4F8 abatement experiment was run on the liquid cooling design. The abatement process resulted in a destruction removal efficiency (DRE) of C4F8 of 97.5 percent. A lower operational cost unit was developed, but the operational performance was less than previous investigations. The second goal was to simulate the semiconductor radio frequency etching process and abate the output gases of the C4F8 and SiO2 reaction. The outcomes of this experiment included a microwave simulation of the radio frequency etching reaction and an abatement that resulted in a 99.98 plus/minus .05 percent DRE for C4F8 with no formation of any other CFC gases. The third goal was to simulate the etching process and abate the output gas, CF4 using H2O vapor as the additive gas. The outcomes of this experiment included a microwave simulation of the radio frequency etching reaction and an abatement that resulted in a 99.96 plus/minus .05 percent DRE for CF4 with no formation of any other CFC gases. A low cost of ownership and effective abatement levels will make this system viable for commercial use. The latest data shows the amount of PFC emissions from the semiconductor industry was 3.6 Tg CO2 Eq. The use of this or a similar abatement technology will have a significant impact on reducing environmental pollution.

Nitrogen trifluoride (NF3) is frequently used as a source of fluorine in the electronics device manufacturing industry as a dry etchant during plasma assisted etching of silicon wafers, or during the plasma cleaning of chemical vapor deposition chambers. As a result of the electrochemical synthesis procedures in which carbon anodes are used in a fluorine-rich environment, NF3 product streams are frequently contaminated with ppm-amounts of carbon tetrafluoride (CF4). The electronics manufacturing industry, however, requires NF3 of exceptional purity, i.e. so-called VLSI-grade (very large scale integration) NF3, with CF4 concentrations of 20 ppm and below. Due to the close chemical and physical similarities of the two compounds, the removal of CF4 from NF3 has proven to be rather difficult, and current NF3 purification technologies are relatively inefficient. Although membrane gas separation has proven to be competitive in terms of operating costs and energy efficiency, its use for the purification of NF3 seems to have remained unexplored to date. In this study, the use of high free volume glassy perfluoropolymers of Teflon AF2400, Teflon AF1600, and Hyflon AD60 was therefore investigated. To be able to measure the pure and mixed gas permeabilities and selectivities of the solution-cast membranes towards NF3 and CF4, a custom built experimental setup was used, in which a newly developed gas chromatographic (GC) analysis method was implemented. Using divinylbenzene-styrene co-polymer stationary phases in the form of Super Q, a reliable quantification of mixtures of NF3 and CF4 were achieved without requiring additional fluorocarbon liquid stationary phases, as is commonly used in NF3 production environments. Furthermore, by implementing a dual-channel configuration it was possible to quantify a wide range of NF3 and CF4 concentrations. Using the newly developed technique, NF3 and CF4 concentrations of ca. 1 mol% and upwards could be quantified using a Thermal Conductivity Detector (TCD) on one channel, and NF3 and CF4 concentrations of between ca. 40 vppm and 4000 vppm could be measured using a Pulsed Discharge Helium Ionisation Detector (PDHID) on the second channel of the GC method. The glassy perfluoropolymer membranes of Teflon AF2400, Teflon AF1600, and Hyflon AD60 were prepared by a solution casting method, and it was found that annealing at sufficiently high temperatures (170 – 200 °C) ensured optimum permeability selectivity. In contrast, thermal analysis of the solution-cast Hyflon AD60 membranes that were heated to only 95 °C confirmed that the polymer matrix was significantly swollen due to a residual amount of the casting solvent. Consequently, considerably reduced selectivity and increased permeability of both NF3 and CF4 were observed for such solvent-swollen Hyflon AD60 membranes in comparison with the non-swollen membranes that were annealed at 170 °C. Nonetheless, the measured He/N2 permeability and permeability selectivity of all the membranes studied compared favourably with literature values, and selectively permeated NF3 rather than CF4 wherein the pure and mixed gas permeability selectivity displayed a clear dependence on the fractional free volume (FFV) of the polymer matrices. Thus, in accordance with the decreasing FFV of the perfluoropolymers in the order Teflon AF2400 > Teflon AF1600 > Hyflon AD60, the NF3 permeability decreased from 227 Barrer for Teflon AF2400, to 29 Barrer for Teflon AF1600, to 1.9 Barrer for Hyflon AD60. In contrast, the NF3/CF4 selectivity, α(NF3/CF4), increased inversely from 4.5 for Teflon AF2400, to 6.0 for Teflon AF1600, to the highest selectivity of 12 which was obtained using Hyflon AD60. To elucidate the mechanism of separation, the transport properties of NF3 and CF4 in Teflon AF2400 and Teflon AF1600 w.r.t. diffusion and solubility were studied using Molecular Dynamics (MD), Grand Canonical Monte Carlo (GCMC), and statistical thermodynamic techniques. The results indicated that NF3/CF4 diffusion selectivity (DNF3/DCF4) was favoured by the lower free volume of Teflon AF1600, whereas poor correlation was achieved between the GCMC calculated sorption isotherms of CF4 and the experimentally determined isotherms as reported in the literature. Consequently, the non-equilibrium lattice fluid (NELF) model, which more accurately described the sorption isotherms of CF4, was used to evaluate the solubility selectivity. It was found that by adjusting the NELF model interaction parameter, Ψ, favourable NF3/CF4 solubility selectivities (SNF3/SCF4) were predicted. Furthermore, by combining the solubility selectivity values with the diffusion selectivities calculated from the MD results, permeability selectivity predictions that correlated well with the experimentally determined values were obtained. Based on a semi-quantitative technological evaluation, it was concluded that although good NF3/CF4 mixed gas permeability selectivity was obtained with Hyflon AD60, further research into improving the NF3 solubility, and hence permeability will aid in the development of an efficient membrane gas separation process for the purification of NF3. / PhD (Chemistry),North-West University, Potchefstroom Campus, 2013.

Nitrogen trifluoride (NF3) is frequently used as a source of fluorine in the electronics device manufacturing industry as a dry etchant during plasma assisted etching of silicon wafers, or during the plasma cleaning of chemical vapor deposition chambers. As a result of the electrochemical synthesis procedures in which carbon anodes are used in a fluorine-rich environment, NF3 product streams are frequently contaminated with ppm-amounts of carbon tetrafluoride (CF4). The electronics manufacturing industry, however, requires NF3 of exceptional purity, i.e. so-called VLSI-grade (very large scale integration) NF3, with CF4 concentrations of 20 ppm and below. Due to the close chemical and physical similarities of the two compounds, the removal of CF4 from NF3 has proven to be rather difficult, and current NF3 purification technologies are relatively inefficient. Although membrane gas separation has proven to be competitive in terms of operating costs and energy efficiency, its use for the purification of NF3 seems to have remained unexplored to date. In this study, the use of high free volume glassy perfluoropolymers of Teflon AF2400, Teflon AF1600, and Hyflon AD60 was therefore investigated. To be able to measure the pure and mixed gas permeabilities and selectivities of the solution-cast membranes towards NF3 and CF4, a custom built experimental setup was used, in which a newly developed gas chromatographic (GC) analysis method was implemented. Using divinylbenzene-styrene co-polymer stationary phases in the form of Super Q, a reliable quantification of mixtures of NF3 and CF4 were achieved without requiring additional fluorocarbon liquid stationary phases, as is commonly used in NF3 production environments. Furthermore, by implementing a dual-channel configuration it was possible to quantify a wide range of NF3 and CF4 concentrations. Using the newly developed technique, NF3 and CF4 concentrations of ca. 1 mol% and upwards could be quantified using a Thermal Conductivity Detector (TCD) on one channel, and NF3 and CF4 concentrations of between ca. 40 vppm and 4000 vppm could be measured using a Pulsed Discharge Helium Ionisation Detector (PDHID) on the second channel of the GC method. The glassy perfluoropolymer membranes of Teflon AF2400, Teflon AF1600, and Hyflon AD60 were prepared by a solution casting method, and it was found that annealing at sufficiently high temperatures (170 – 200 °C) ensured optimum permeability selectivity. In contrast, thermal analysis of the solution-cast Hyflon AD60 membranes that were heated to only 95 °C confirmed that the polymer matrix was significantly swollen due to a residual amount of the casting solvent. Consequently, considerably reduced selectivity and increased permeability of both NF3 and CF4 were observed for such solvent-swollen Hyflon AD60 membranes in comparison with the non-swollen membranes that were annealed at 170 °C. Nonetheless, the measured He/N2 permeability and permeability selectivity of all the membranes studied compared favourably with literature values, and selectively permeated NF3 rather than CF4 wherein the pure and mixed gas permeability selectivity displayed a clear dependence on the fractional free volume (FFV) of the polymer matrices. Thus, in accordance with the decreasing FFV of the perfluoropolymers in the order Teflon AF2400 > Teflon AF1600 > Hyflon AD60, the NF3 permeability decreased from 227 Barrer for Teflon AF2400, to 29 Barrer for Teflon AF1600, to 1.9 Barrer for Hyflon AD60. In contrast, the NF3/CF4 selectivity, α(NF3/CF4), increased inversely from 4.5 for Teflon AF2400, to 6.0 for Teflon AF1600, to the highest selectivity of 12 which was obtained using Hyflon AD60. To elucidate the mechanism of separation, the transport properties of NF3 and CF4 in Teflon AF2400 and Teflon AF1600 w.r.t. diffusion and solubility were studied using Molecular Dynamics (MD), Grand Canonical Monte Carlo (GCMC), and statistical thermodynamic techniques. The results indicated that NF3/CF4 diffusion selectivity (DNF3/DCF4) was favoured by the lower free volume of Teflon AF1600, whereas poor correlation was achieved between the GCMC calculated sorption isotherms of CF4 and the experimentally determined isotherms as reported in the literature. Consequently, the non-equilibrium lattice fluid (NELF) model, which more accurately described the sorption isotherms of CF4, was used to evaluate the solubility selectivity. It was found that by adjusting the NELF model interaction parameter, Ψ, favourable NF3/CF4 solubility selectivities (SNF3/SCF4) were predicted. Furthermore, by combining the solubility selectivity values with the diffusion selectivities calculated from the MD results, permeability selectivity predictions that correlated well with the experimentally determined values were obtained. Based on a semi-quantitative technological evaluation, it was concluded that although good NF3/CF4 mixed gas permeability selectivity was obtained with Hyflon AD60, further research into improving the NF3 solubility, and hence permeability will aid in the development of an efficient membrane gas separation process for the purification of NF3. / PhD (Chemistry),North-West University, Potchefstroom Campus, 2013.

ÿþD / The intense radiation environment in the HERA-B experiment, being comparable to that of LHC experiments, requires that the detector be very resistant to high radiation loads. The Outer Tracker of HERA-B consists of drift tubes folded from polycarbonate foils (honeycomb) and is operated with a CF4-containing gas mixture. Aging tests made in HERA-B, under hadronic irradiation, using prototype drift chambers showed a rapid rise of self-sustaining dark currents (Malter effect). Extensive aging studies were carried out with the objective to find an appropriate set of construction materials as well as optimal operational parameters. It was shown that the gain loss (anode aging) and the Malter effect could be avoided after replacing the methane in the counting gas, Ar/CF4/CH4, by CO2 and applying cathode coating. However, other, relatively less known aging effects appeared: rising conductivity of the wire-supporting strips and wire corrosion. These two aging effects could also be prevented keeping water at a proper concentration. The aging tests showed that a too high water content (above about 500 ppm) gives rise to strip conductivity, conversely, a too low water content (below about 100 ppm) enhances anode wire corrosion. In an attempt to interpret the test results, plasma phenomena like quenching by different admixtures, production of molecular species, concentration of long-lived HF produced via CF4 dissociation in the avalanche were semi-quantitatively estimated. This work contains also a comprehensive summary of all aging studies for the Outer Tracker and an overview of the literature on wire chamber aging, in particular with CF4-based counting gas mixtures.

This thesis deals with the silicon etching technology. It Examines using of water solution of potassium hydroxide. It focuses on plasma etching of silicon using mixture of CF4 and O2 as the dry way of etching. Important parameters of etching like etching rate of silicon and masking materials, etching selectivity, surface roughness and underetching of mask are determined for both ways. Some additional processes has been examined as well, namely creating of mask of resist and silicon dioxide, lithography process and etching of resist using oxygen plasma.

Le détecteur MUNU, destiné à l'étude de la diffusion neutrino sur électron à l'aide des antineutrinos émis par un réacteur nucléaire, est constitué d'une chambre à projection temporelle (TPC) contenant du gaz CF4. L'objectif de la thèse était de déterminer si un détecteur basé sur le même principe pouvait être envisagé pour mesurer le spectre en énergie des neutrinos solaires de basse énergie. Pour cette étude, trois aspects étaient essentiels : la résolution en énergie, la résolution angulaire et le bruit de fond du détecteur. Les deux premiers car l'énergie du neutrino est reconstituée à partir de l'énergie et de la direction initiale de l'électron de recul. Le troisième car le faible nombre d'interactions attendu impose un niveau de bruit de fond très bas. Dans un premier temps, une revue détaillée de la physique des neutrinos solaires du point de vue théorique mais aussi expérimental est réalisée puis les caractéristiques du détecteur MUNU et son principe de fonctionnement sont exposés. Ensuite, les performances du détecteur sont abordées successivement : les méthodes d'étalonnage en énergie développées et la résolution en énergie qui en découle ; la détermination de la direction initiale des électrons et la résolution angulaire associée ; et enfin les différentes sources de bruit de fond rencontrées ainsi que les taux d'événements induits. Finalement, les résultats de la simulation de la détection des neutrinos solaires sont présentés. Ils mettent en évidence les améliorations nécessaires et les points exigeant des études supplémentaires.

Le document présente la problématique de la détection directe de matière noire dans le cadre des expériences XENON100 et MIMAC. Après une introduction générale sur la matière noire et sur les signaux attendus dans un détecteur terrestre, les deux projets sont passés en revue en se concentrant sur les aspects expérimentaux. L'accent est mis particulièrement sur la caractérisation des performances des détecteurs et sur les bruits de fonds associés.

Herstellung anwendungsbezogener SiO2- Grabenstrukturen im sub-μm-Bereich durch RIE und ICP-Prozesse.

Herstellung anwendungsbezogener SiO2- Grabenstrukturen im sub-μm-Bereich durch RIE und ICP-Prozesse.