Measurement of ultrafine particle size distributions
A measurement system for microelectronic clean rooms to measure ultrafine particle size distribution in the range of 0.002 to 0.2 micrometers is provided which includes four screen diffusion stages each connected in series with a condensation nucleus detector. The input to each screen diffusion stage is connected to a localized area to be measured, and the output of each condensation nucleus detector is connected to a vacuum system which simultaneously draws particle bearing air through the four channels. The output signals of the condensation nucleus detectors present particle size distributiion. In one embodiment of the present invention, one or more optical particle detectors are connected in parallel with the diffusion stage-condensation nucleus detectors to expand the distribution measurements to larger sizes. Other embodiments inclulde a manifold probe to probe a localized area, an alarm system actuated when particle levels exceed a predetermined level, and a manifold assembly to minimize vacuum lines passing through the walls of the microelectronic clean room.