INVESTIGATION OF AEROSOL SPATIAL DISTRIBUTIONS DOWNSTREAM OF A CRITICAL ORIFICE AT LOW-PRESSURE

The spatial distribution of aerosol particles downstream of a critical orifice has been experimentally investigated. The measurements were p erformed by filtering the aerosol and visualizing the filter deposits. Measurements were made for a range of flow rates, pressures, and part icle sizes. The most significant observation was that the particle spa tial distributions changed from uniform to nonuniform when the downstr eam pressure was lowered below about 10 torr. Similar observations wer e made using in-situ particle monitors. These results may have signifi cance for understanding particulate contamination in vacuum-based semi conductor process equipment. (C) 1998 American Association for Aerosol Research.