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.
Optimization of gas utilization in plasma processes
The reduction of chemical usage in semiconductor manufacturing has been a topic of wide discussion over the past several years. The aim of this study is to optimize plasma efficiency as chemical reactions by using the Taguchi method. In short, the function of plasma is to serve as an etchant that reacts with films. The results of the reaction are discharged. The main point of optimization was to use a main etchant to increase the amount of desirable main reaction and to decrease the amount of unreacted gas in order to keep the undesirable side reaction to a minimum. We found chemical vapor deposition cleaning conditions that improve plasma efficiency up to 200%, perfluorocompounds (PFC) gas usage to one-third, and PFC gas emission to 25%. We also found nitride etching conditions that improve plasma efficiency up to 350%, SF/sub 6/ usage to 25%, SF/sub 6/ emission to 22%, and selectivity to oxide up to 145% over the previous conditions.
Clozapine derived 2,3-dihydro-1H-1,4- and 1,5-benzodiazepines with D4 receptor selectivity: synthesis and biological testing.
Novel 4-arylpiperazin-1-yl-substituted 2,3-dihydro-1H-1,4- and 1H-1,5-benzodiazepines and their aza-analogues were synthesized as debenzoclozapine derivatives for evaluation as potential D4-ligands. While Ki values of some of the title compounds came within the range of clozapine, they showed an impressively greater selectivity over other dopamine receptor subtypes, especially D2. For the most promising compounds, intrinsic activity and binding properties to serotonin 5-HT1A and 5-HT2 were also determined.