Evacuation apparatus

Abstract

The present invention relates to an evacuation apparatus for evacuating a vacuum chamber of a substrate processing apparatus for processing a substrate such as a semiconductor wafer or liquid crystal panel. An evacuation apparatus according to the present invention includes a first vacuum pump connected to a vacuum chamber, and a second vacuum pump connected to the first vacuum pump. The first vacuum pump has a pair of multistage pump rotors.

1 . An evacuation apparatus comprising:
 a booster pump having a pair of multistage pump rotors; and   a main pump coupled to said booster pump, said main pump being arranged downstream of said booster pump.   
     
     
         2 . An evacuation apparatus according to  claim 1 , wherein said main pump has a pair of multistage pump rotors. 
     
     
         3 . A method of operating an evacuation apparatus having a booster pump coupled to a vacuum chamber and a main pump coupled to the booster pump, the booster pump having a pair of multistage pump rotors, said method comprising:
 starting the main pump;   starting the booster pump after a predetermined period of time has passed from said starting of the main pump; and   when current of the booster pump is lowered to a predetermined value, increasing the rotational speed of the booster pump.