Turbomolecular pump and method and apparatus for controlling the pressure in a process chamber

Abstract

A turbomolecular pump and method and apparatus for controlling the pressure in a process chamber using such a pump is disclosed. The turbomolecular comprises: a rotor comprising a plurality of blades on a rotatable shaft; a control motor for driving the rotatable shaft; wherein the control motor is sized to output a power that is more than three times larger than a power required to drive the shaft at a constant velocity that is sufficiently high to provide an exhaust pressure of 5 millibars.

1 . A turbomolecular pump comprising:
 a rotor comprising a plurality of blades on a rotatable shaft;   a control motor for driving said rotatable shaft; wherein   said control motor is sized to output a power that is three or more times larger than a power required to drive said shaft at a constant velocity that is sufficiently high to provide an exhaust pressure of 5 millibars.   
     
     
         2 . The turbomolecular according to  claim 1 , wherein said turbomolecular pump comprises a drag stage. 
     
     
         3 . The turbomolecular according to  claim 1 , wherein said turbomolecular pump does not comprise a drag stage. 
     
     
         4 . The turbomolecular pump according to  claim 1 , said rotor further comprising a skirt portion extending in an axial direction beyond said blades of said rotor and having an annular cross section coaxial with and surrounding said shaft, said skirt portion forming a rotor of said control motor. 
     
     
         5 . The turbomolecular pump according to  claim 4 , wherein said turbomolecular pump comprises a Holweck drag stage, said skirt portion comprising a skirt of said Holweck drag stage. 
     
     
         6 . The turbomolecular pump according to  claim 4 , wherein said skirt portion comprises magnets. 
     
     
         7 . The turbomolecular pump according to  claim 4 , wherein said skirt portion comprises a smaller cross section adjacent to said blades of said rotor and a larger cross section remote from said blades. 
     
     
         8 . The turbomolecular pump according to  claim 4 , wherein said stator of said control motor is arranged inside said skirt portion and around said shaft. 
     
     
         9 . The turbomolecular pump according to  claim 4 , wherein said stator of said control motor is arranged around said skirt portion. 
     
     
         10 . The turbomolecular pump according to  claim 4 , wherein said pump comprises a pump housing and said control motor is located within said pump housing. 
     
     
         11 . The turbomolecular pump according to  claim 4 , said turbomolecular pump comprising a further motor for driving said shaft, said further motor and shaft forming a drive spindle and said control motor being formed around said drive spindle. 
     
     
         12 . The turbomolecular pump according to  claim 11 , wherein said further motor is configured to drive said rotor during steady state operation and said control motor is configured to drive said rotor during acceleration and deceleration of said rotor of said turbomolecular pump. 
     
     
         13 . The turbomolecular pump according to  claim 4 , wherein said pump comprises control circuitry for controlling a pressure at an inlet of said turbomolecular pump, said control circuitry being configured to control said control motor to control a speed of said rotor and thereby a pressure at an inlet of said turbomolecular pump. 
     
     
         14 . The turbomolecular pump according to  claim 13 , wherein said turbomolecular pump comprises an exhaust valve, said control circuitry being configured to control said exhaust valve to increase pressure at an exhaust of said turbomolecular pump in conjunction with controlling said control motor to slow said rotor. 
     
     
         15 . The turbomolecular pump according to  claim 13 , said turbomolecular pump comprising a purge gas inlet at an exhaust, wherein said control circuitry is configured to control addition of a purge gas at said exhaust in conjunction with controlling said control motor to slow said rotor. 
     
     
         16 . A turbomolecular pump comprising:
 a rotor comprising a plurality of blades mounted on a rotatable shaft;   a control motor for driving said rotatable shaft; wherein   said rotor further comprises a skirt portion extending in an axial direction beyond said blades of said rotor and having an annular cross section, said skirt portion forming a rotor of said control motor and being coaxial with and surrounding said shaft.   
     
     
         17 . The turbomolecular pump according to  claim 16 , wherein said skirt portion comprises a smaller cross section adjacent to said blades of said rotor and a larger cross section remote from said blades. 
     
     
         18 . The turbomolecular pump according to  claim 16 , wherein said stator of said control motor is arranged inside said skirt portion and around said shaft. 
     
     
         19 . The turbomolecular pump according to  claim 16 , wherein said stator of said control motor is arranged around said skirt portion. 
     
     
         20 . The turbomolecular pump according to  claim 16 , wherein said skirt portion has an inner diameter substantially equal to an inner diameter of the most downstream blade of said turbomolecular pump. 
     
     
         21 . The turbomolecular pump according to  claim 16 , wherein said turbomolecular pump comprises a drag stage. 
     
     
         22 . The turbomolecular according to  claim 16 , wherein said turbomolecular pump does not comprise a drag stage. 
     
     
         23 . The turbomolecular pump according to  claim 21 , wherein said turbomolecular pump comprises a Holweck drag stage, said skirt portion comprising a skirt of a Holweck drag stage. 
     
     
         24 . The turbomolecular pump according to  claim 15 , wherein said skirt portion comprises magnets. 
     
     
         25 . The turbomolecular pump according to  claim 15 , wherein said pump comprises a pump housing and said control motor is located within said pump housing. 
     
     
         26 . The turbomolecular pump according to  claim 15 , said turbomolecular pump comprising a further motor for driving said shaft, said further motor and shaft forming a drive spindle and said control motor and skirt portion being formed around said drive spindle. 
     
     
         27 . The turbomolecular pump according to  claim 26 , wherein said motor is configured to drive said rotor during steady state operation and said control motor is configured to drive said rotor during acceleration and deceleration of said rotor of said turbomolecular pump. 
     
     
         28 . The turbomolecular pump according to  claim 16 , wherein said pump comprises control circuitry for controlling a pressure at an inlet of said turbomolecular pump, said control circuitry being configured to control said control motor to control a speed of said rotor and thereby a pressure at an inlet of said turbomolecular pump 
     
     
         29 . The turbomolecular pump according to  claim 28 , wherein said turbomolecular pump comprises an exhaust valve, said control circuitry being configured to control said exhaust valve to increase pressure at an exhaust of said turbomolecular pump in conjunction with controlling said control motor to slow said rotor. 
     
     
         30 . The turbomolecular pump according to  claim 28 , said turbomolecular pump comprising a purge gas inlet at said exhaust, wherein said control circuitry is configured to add a purge gas at said exhaust in conjunction with controlling said control motor to slow said rotor. 
     
     
         31 - 32 . (canceled) 
     
     
         33 . A method of controlling the pressure in a process chamber, the method comprising:
 in response to determining a pressure is to be decreased in said process chamber accelerating a turbomolecular pump connected to said process chamber; and   in response to determining a pressure is to be increased in said process chamber decelerating a turbomolecular pump connected to said process chamber; wherein   said acceleration and deceleration of said turbomolecular pump is done by a control motor that is sized to output a power that is more than three times larger than a power required to drive a shaft at a constant velocity that is sufficiently high to provide an exhaust pressure of 5 millibars.