Vacuum pump

Abstract

The present invention provides a vacuum pump allowing process pressure control with high responsiveness and miniaturization and cost reduction of the overall apparatus, as well as reduction of the running cost. A second pump mechanism portion is equipped on the way of an exhaust passage communicating an exhaust side out of a first pump mechanism portion with a gas outlet. The second pump mechanism portion is constructed to be capable of changing the pump speed of rotation independently of the first pump mechanism portion. When the pump speed of rotation of the second pump mechanism portion is changed, the pressure of the exhaust side out (backing pressure) of the first pump mechanism portion changes. Therefore, efficiency of gas suction from a gas inlet to the first pump mechanism portion side is increased or decreased, and the pressure in a process chamber is changed.

What is claimed is:  
     
         1 . A vacuum pump comprising: 
 a gas inlet connected with a vacuum vessel side,    a first pump mechanism portion for inhaling gas in the vacuum vessel from the gas inlet and for exhausting the gas,    a gas outlet communicated with an exhaust side of the first pump mechanism portion, and    a second pump mechanism portion capable of changing the pump speed of rotation independently of the first pump mechanism portion is provided on the way of an exhaust passage communicating the exhaust side of the first pump mechanism portion with the gas outlet.    
     
     
         2 . A vacuum pump according to  claim 1 , wherein the pressure in the vacuum vessel is controlled by changing the pump speed of rotation of the second pump mechanism portion.  
     
     
         3 . A vacuum pump according to  claim 1 , wherein the second pump mechanism portion having a spiral pump mechanism portion.  
     
     
         4 . A vacuum pump according to  claim 3 , wherein the spiral pump mechanism portion having a spiral impeller.  
     
     
         5 . A vacuum pump according to  claim 4 , wherein the spiral pump mechanism portion having a plurality of spiral impellers.  
     
     
         6 . A vacuum pump according to  claim 4 , wherein the spiral pump mechanism portion having a plurality of spiral impellers, and having a barrier between the spiral impellers.  
     
     
         7 . A vacuum pump according to  claim 1 , wherein the first pump mechanism portion has a compound-type pump construction in which a turbo molecular pump mechanism portion disposed on a high-vacuum side with a thread groove pump mechanism portion disposed at a lower section of this turbo molecular pump mechanism portion are formed integrally.