In order to prevent excessive motor loading or system overheating due to the accumulation of particulate or dust, from SACVD type CVD processes, in the running clearances of the vacuum pump a vacuum pumping arrangement is provided having a plurality of vacuum pumping stages and comprising a first pump inlet through which process fluid from the vacuum chamber can enter the pump and pass through each of the pumping sections towards a pump outlet, and a second pump inlet through which process fluid can enter the pump and pass through only one or more pumping stages downstream of the most upstream pumping stage, wherein the apparatus configured to conveying process fluid from the vacuum chamber to the first pump inlet for pumping during the second processing step and conveying process fluid from the vacuum chamber to the second pump inlet for pumping during the first processing step.
展开▼
