Patent ID: 9726176
Date: 2017-08-08
CPC Classifications: F04C

Claim:
1. A method of evacuating a vacuum process chamber with a vacuum pumping arrangement, the method comprising: conveying process fluid from the vacuum process chamber to a first pump inlet for pumping during a first processing step, wherein the first processing step is performed in the vacuum process chamber at a higher vacuum than a second processing step and generates a smaller amount of particles than the second processing step, and wherein the vacuum pumping arrangement comprises a pump outlet, a plurality of vacuum pumping stages, the first pump inlet through which process fluid from the vacuum process chamber can enter the vacuum pumping arrangement and pass through each of the plurality of vacuum pumping stages towards a pump outlet, and a second pump inlet through which process fluid can enter the vacuum pumping arrangement and pass through only one or more vacuum pumping stages of the plurality of vacuum pumping stages downstream of the most upstream vacuum pumping stage of the plurality of vacuum pumping stages; and conveying process fluid from the vacuum process chamber to the second pump inlet for pumping during the second processing step, wherein the second processing step is performed in the vacuum process chamber at a lower vacuum than the first processing step and generates a larger amount of particles than the first processing step.