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.
Perfluorocarbon Destruction and Removal Efficiency: Considering the Byproducts and Energy Consumption of an Abatement System for Microelectronics Manufacturing
The purpose of this paper was to estimate the reduction efficiency of an abatement system for perfluorocarbon (PFC) gases produced during semiconductor manufacturing processes. The reduction efficiency currently used in the semiconductor industry, the destruction and removal efficiency (DRE), considers only the destruction ratio of PFC gases. A method estimating the reduction efficiency, which in addition to measure the destruction ratio also considers the energy consumption and byproducts produced during the treatment of PFC gases, was proposed in this paper; this efficiency was defined as the net reduction efficiency (NRE). For the estimation of the reduction efficiency, measurements were made using a plasma-wet type abatement system installed in an actual semiconductor manufacturing plant. The destruction ratio of the PFC gases was measured using Fourier transform infrared spectroscopy and quadrupole mass spectroscopy. The energy consumption was measured using an electricity meter. Based on these measurements, the DRE and the NRE of the PFC gases were calculated and compared. The results indicated that the DRE showed high reduction efficiency while the NRE showed lower values.
APPLICATION OF THE FINITE ELEMENT METHOD TO ROTARY-WING AEROELASTICITY.
Recent research in rotary-wing aeroelasticity has indicated that all fundamental problems in this area are inherently nonlinear. The non-linearities in this problem are due to the inclusion of finite slopes, due to moderate deflections, in the structural, inertia and aerodynamic operators associated with this aeroelastic problem. In this paper the equations of motion, which are both time and space dependent, for the aeroelastic problem are first formulated in P.D.E. form. Next the equations are linearized about a suitable equilibrium position. The spatial dependence in these equations is discretized using a local Galerkin method of weighted residuals resulting in a finite element formulation of the aeroelastic problem. As an illustration the method is applied to the coupled flap-lag problem of a helicopter rotor blade in hover. Comparison of the solutions with previously published solutions establishes the convergence properties of the method. It is concluded that this formulation is a practical tool for solving rotary-wing aeroelastic stability or response problems.