High-Efficiency PFC Abatement System Utilizing Plasma Decomposition and Ca(OH)$_{2}$ /CaO Immobilization
In order to minimize contributions to global warming, it is important to develop a perfluorocompound (PFC) abatement system that can remove PFCs effectively with low electric power. We have developed a new PFC abatement system consisting mainly of a 2-MHz ICP plasma source and two Ca(OH)2/CaO columns operated under a decompression pressure. Reactive fluorinated compounds including SiF4 are immobilized in the Ca(OH)2/CaO columns without a water scrubber. Stable compounds such as CF4 are excited by the 2-MHz ICP plasma. When the emissions from an Si oxidation film etching process chamber were treated by this abatement system, F2 equivalent removal efficiency was 99.6%, which was about one order of magnitude larger than that of a conventional abatement system. But the CO2 equivalent removal efficiency was calculated to be 91.4% because over 95% of CO2 equivalent emissions were caused by the plasma source power consumption of 2.4 kWh. It means that minimization of the plasma source power consumption, depending on PFC emissions, is a very effective method of minimizing contributions to global warming in a manner similar to improving the PFC removal efficiency.
Perfluorocompound Emissions Control and Kinetic Characteristics in Point-of-Use Wet-Thermal-Wet Abatement of Plasma-Enhanced Chemical Vapor Deposition Chamber Cleaning
Electric thermal oxidation of NF<sub>3</sub> is studied in the context of kinetic and activation energy, with an emphasis on correlation with reaction rate. To improve economic feasibility of the wet-thermal-wet abatement process, the effect of NF<sub>3</sub> flow rate, N<sub>2</sub> flow rate, and operational temperature on decomposition of NF<sub>3</sub> are examined. The reactions in question follow first order kinetics. It was found the rate constant is enhanced with increasing flow rate of NF<sub>3</sub> and temperature, and decreased with increasing flow rate of N<sub>2</sub>. The highest rate constant of NF<sub>3</sub> was 0.5501 s<sup>−1</sup> for 13 liter per minute (LPM) NF<sub>3</sub> flow rate, 70 LPM N<sub>2</sub> flow rate, and a temperature of 725 °C. The inlet and outlet concentration of NF<sub>3</sub> was examined utilizing Fourier-transform infrared spectroscopy for estimation of NF<sub>3</sub> decomposition. This paper not only confirms that large amounts of NF<sub>3</sub> can be efficiently decomposed by electric thermal oxidation, but also enhances the feasibility of this technology.
Mechanics of deformable directed surfaces
Abstract The paper develops a simple, yet complete and consistent non-linear dynamic thermo-elastic shell theory based on the concepts of a two-dimensional directed continuum. The constitutive equations are postulated in a general form. Stress-strain relations are derived using the equation of energy balance and the two entropy production inequalities, which are rewritten in a special form. The linear theory is discussed in detail. The structure of the stress-strain relations is presented in the most general form and then specialized to concrete examples, in particular, to the classical shell theory, using their invariance properties with respective to certain symmetry groups. The elastic moduli are determined by demanding the coincidence of the frequency dispersion surfaces obtained using the two-dimensional theory with the lowest foils of the corresponding surfaces resulting from the three-dimensional theory of elasticity.