A Study On Air Flow Organization And Pollutant Diffusion In A Large-Span Electronic Cleanroom

With the development of precision equipment and the microelectronics industry,large-span electronic clean rooms had been widely used in industries such as semiconductors,transistors,and LCD displays.As the span of clean rooms increases,the control of airflow organization becomes more complex,making the optimization of airflow organization in large-span clean rooms particularly important.In China,the microelectronics industry started relatively late,and the equipment in large-span clean rooms was often centrally placed,which,combined with the large size of microelectronic equipment,can affect the uniformity of airflow organization in clean rooms.Therefore,it is necessary to study the impact of different equipment heights,different equipment placement positions,and the pollution of process equipment on clean rooms,and propose optimization suggestions for airflow organization in large-span clean rooms from the perspectives of reasonable air supply velocity for different heights of equipment,reasonable equipment placement positions,and prevention of pollutant diffusion.This is the focus and purpose of this paper’s research.This article investigated the airflow patterns and their implementation methods commonly used in large-span electronic cleanrooms through a survey of an actual operating facility.A full-scale circulating air model of the large-span cleanroom was established using CFD numerical simulation software.The airflow organization of the cleanroom under empty and static conditions was studied,and the characteristics of the airflow organization in the two types of large-span cleanrooms were compared in accordance with cleanroom design requirements.To optimize the airflow organization in large-span clean rooms,this paper investigated the influence of different FFU air supply velocities(ranging from 0.3 m/s to 0.8 m/s)and equipment heights(ranging from 1 m to 3 m)on the airflow organization in the work area of the clean room.The evaluation of the airflow organization was conducted based on indicators such as the average sectional air velocity,turbulence intensity,and airflow velocity attenuation.The results suggested that the appropriate air supply velocities for different equipment heights are as follows:0.4 m/s to 0.7 m/s for equipment height of 1 m,0.5 m/s to 0.8 m/s for equipment height of 2 m,and 0.6 m/s to 0.8 m/s for equipment height of 3 m.To further optimize the airflow organization in clean rooms,this study investigated the layout of equipment in the clean area,sub-clean area,and return air duct.Specifically,the influence of equipment placement on the airflow organization in the large-span clean room was studied from three aspects:the relative position(0m～1m)between process equipment and air supply outlets in the clean area,the height(3m～13m)of fresh air supply in the return air duct,and the position of electric heating pipes(170w/m~2～200w/m~2)in the sub-clean area.Non-dimensional parameters were proposed for the relative positions of equipment and air supply outlets,as well as for the relative positions of the fresh air height and the return air well height.These parameters can provide references for the layout of equipment in similar large-span clean rooms and optimize the airflow organization.The two non-dimensional parameters was denoted as b~*and a~*,and the optimal ranges are b~*≤0.2 and 0.40≤a~*≤0.72.Finally,this paper studied the diffusion process of contaminants in etching equipment.HCl,a common contaminant during the maintenance phase of the etching equipment,was selected for numerical simulation and compared with literature and experimental results.The study focused on the impact range of HCl diffusion at the highest concentration and the changes in HCl concentration inside the reaction chamber at different times after the introduction of vacuum blow.By comparative analysis,according to the standard,two diffusion ranges of pollutants in the large-span clean room were obtained,which were 1.7m and 2.5m respectively,and three levels of contaminated areas were identified.The use of vacuum blow process was proposed as a preventive measure to reduce HCl leakage from the equipment.This article studied the airflow organization and pollutant diffusion process in large-span clean rooms from different perspectives.Optimization suggestions for the airflow organization in large-span clean rooms were proposed mainly from the aspects of air supply velocity,equipment layout,and pollutant diffusion.These suggestions were of practical significance in reducing the interference of backflow on large-span clean rooms,avoiding harm caused by pollutant diffusion,and ensuring stable airflow inside clean rooms.