Control of flow, thermal and pollutant concentration fields by entrainer air streams to improve fresh air quality intake into a semiconductor manufacture/ processing plant

Abstract

Simulations of turbulent flow, thermal and concentration fields around a semiconductor manufacture/processing plant are reported. Monitored pollutants are ammonia (NH 3 ), hydrofluoric acid (HF), total volatile organic compounds (TVOC) and PM 2.5 that are released from chimneys on the roofs of various buildings. Some of the fresh air for the plant is supplied by the make-up air units (MAU) located on the roofs of the buildings. Returned pollutants through the MAUs can end up in the cleanroom thus decreasing the quality of wafer products. A 3-D transient large eddy simulation model was developed to predict the environment near the plant and transport of pollutants during the summer and winter seasons. Concentrations of pollutants at the inlet planes of the MAUs exhibited marked variations during the day. Pollutants with concentrations higher than industry thresholds were generally re-directed back into the plant through the six MAUs except two that were free of HF and TVOC. Modified flow, thermal and pollutant concentration fields in the vicinity of the plant brought about by introducing 12 vertically-oriented entrainer air streams (EAS) into the environment were also studied in order to quantify their effects on reducing the concentrations of pollutants at the inlet planes of the MAUs below accepted industry thresholds. It is shown that dispersion of the pollutants was markedly affected by the introduction of these novel entrainer air streams. Ingestion of pollutants into the plant was completely eliminated during (i) summer and (ii) winter except for MAU5 (NH 3 ) and MAU6 (NH 3 and TVOC) that exhibited noticeable reduction of concentrations by at least 73.3%. The proposed system can lead to cleaner production practices through eliminating product rejection, lower utilization of raw materials, reduced introduction of pollutants in the environment, etc.