The study of fugitive particles during the preventive maintenance of the sputtering facility in a color-filter fab
TFT-LCD (Thin Film Transistor Liquid Crystal Display) has been the mainstream color display technology since the beginning of this century. With rapidly growing market, large amount of chemicals and toxic substances are extensively used in the TFT-LCD industry during the manufacturing process, posing health threats to workers. Therefore, the occupational hygiene and safety problems of the workers deserve attention. The main objective of this study is to investigate fugitive aerosols during the preventive maintenance of the sputtering facility in a color-filter fab. The experiment in this study has three stages. In the first stage, a TSI DustTrak was used to monitor the background level of the particle mass concentration. In the second stage, IOSH (Institute for Occupational Safety and Health) cyclones were used to measure the exposure level of the sputtering workers. In the final stage, the SSPD (Small-Scale Powder Disperser) method was used to disperse the collected particles which were deposited on the wall of the sputter chamber. A TSI SMPS (Scanning Mobility Particle Sizer) and a TSI APS (Aerodynamic Particle Sizer) were used to measure the particle size distributions, and a MOUDI (Multiple-Orifice Uniform Deposit Impactor) was used to measure the mass distributions of the dispersed powders. The exposure level of the operators to the fugitive particles was studied during regular preventive maintenance of the sputtering facility. The average particle concentration was found to be 0.057±0.038mg/m3, and the metallic Indium concentration was 0.034±0.015mg/m3. In addition, the average respirable particle concentration was 0.028±0.011 mg/m3. The results clearly indicated that the aerosol concentration in the current working environment meets the domestic occupational health and safety regulation. However, it was found that using the air blow gun to clean the sputter chamber increased the aerosol concentration which might exceed the exposure threshold value suggested by SEMI. Such cleaning method should be avoided. It was found that particles emitted from the ITO powders were submicron in number distribution with the number median electric mobility diameter of 180nm. In terms of mass concentration, these particles were in the respirable size range with the mass median aerodynamic diameter of 1080 nm.
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