Measurement of ultrafine particle size distributions
A measurement system for microelectronic clean rooms to measureultrafine particle size distribution in the range of 0.002 to 0.2micrometers is provided which includes four screen diffusion stageseach connected in series with a condensation nucleus detector. Theinput to each screen diffusion stage is connected to a localizedarea to be measured, and the output of each condensation nucleusdetector is connected to a vacuum system which simultaneously drawsparticle bearing air through the four channels. The output signalsof the condensation nucleus detectors present particle sizedistributiion. In one embodiment of the present invention, one ormore optical particle detectors are connected in parallel with thediffusion stage-condensation nucleus detectors to expand thedistribution measurements to larger sizes. Other embodimentsinclulde a manifold probe to probe a localized area, an alarmsystem actuated when particle levels exceed a predetermined level,and a manifold assembly to minimize vacuum lines passing throughthe walls of the microelectronic clean room.
Ensor, D., & Sem, G. J. (1991). IPC No. U.S.Measurement of ultrafine particle size distributions (Patent No. 5072626.)