凝縮性有機物質の電場によるフラグメント化と表面吸着現象に及ぼす影響のモデル化

概要

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In a corona-discharge field, airborne condensable organic compounds are often decomposed to smaller molecules and generate fragment ions and particles. In order to study the influence of fragmentation on the adsorption of condensable organic compounds, two types of experiments were performed. Through the measurement of abundance ratios of various airborne molecular contaminants at various drift voltages, it was found that the abundance ratio of TCEP was decreased at a high voltage while that of smaller molecules was increased. A chamber test was performed with exposing a semiconductor wafer downstream of corona-discharge type ionizer in unidirectional airflow that contains TCEP vapor. When the voltage between ionizers electrode and the wafer exceeded 10kVs, the adsorption of TCEP was markedly decreased. The reason was that the fragment ions of TCEP generated at a high voltage are responsible for transferring the electric charge in place of TCEP ions. The adsorption of TCEP onto wafer was also simulated by applying Langmuir-type adsorption model. The simulation result well expressed the experimental data when the influence of fragment ions was included.