| Summary: | 碩士 === 國立交通大學 === 產業安全與防災學程碩士班 === 90 === Abstract
The objective of this study is to verify the method of covering exhaust pipe with heating tape to prevent particles from deposition and to evaluate the deposition efficiency of aerosol particles in the exhaust pipe of the semiconductor dry etching process. The effects of thermophoretic deposition, Brownian diffusion, gravitational settling and impaction loss of aerosol particles on deposition efficiency are also investigated. The experiment was performed in a horizontal stainless-steel pipe including a 90-degree bend with a bend radius of 200 mm and a straight tube of 1200 mm in length, located after the vacuum pump of a dry etcher in a semiconductor factory. The inner diameter of the pipe is 57.2mm. The experiment consists of two conditions. One is that aerosol particles pass through stainless-steel pipe covered with heating tape and operated at temperature of 40、60、80 and 1000C. The other is that the temperature was only keeping at 250C (ambient temperature) under laminar flow condition. The results showed that the deposition efficiency of the aerosol particles is 41~57% at ambient temperature. When the heating tape temperature was at 40、60、80 and 1000C, the deposition efficiency of the aerosol particles was about 40~58%, 31~54%, 17~43% and 6~20%, respectively. It is suggested that, the deposition efficiency of particles will be lower by heating the pipe wall at a higher temperature. With an increasing pipe wall temperature, the deposition efficiency decreases and the pipe cleaning will be less frequent. When the pipe wall is heated to a temperature of 100 oC, which is higher than the inlet gas temperature, 80 oC, the submicron particle deposition efficiency will be reduced substantially. However, it is believed that complete prevention of particle deposition on the wall can¢t be achieved only by increasing the tape temperature due to particle deposition caused by of electrostatic attraction and or other deposition mechanisms.
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