The ability of ‘‘dry’’ primary vacuum pumps of the roots/claw configuration to handle semiconductor processes which previously could be pumped only with very frequent maintenance and great expense, has represented a quantum advance in pumping technology. A detailed knowledge of the mechanism by which dusty by-products are generated and transported through the machine, together with the characteristics of particulate deposition, is required when such pumps are serving production wafer-processing equipment. Experiments are described which detail the performance of a pump under conditions of high rates of dust loading together with techniques, by which reliability can be enhanced.

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