Controlling pressure in a process chamber by variying pump speed and a regulator valve, and by injecting inert gas

Abstract

A gas pumping system of the invention enables gas to be pumped from a process chamber ( 1 ) in order to regulate its pressure as a function of process steps. The system comprises a primary pump ( 2 ), a secondary pump ( 8 ), an inert gas injection device ( 6 ), and a regulator valve ( 4 ). The primary and/or secondary pump ( 2 and/or 8 ) is controlled in speed in order to regulate variations of greater amplitude. The regulator valve ( 4 ) is controlled in opening in order to regulate variations that are small amplitude and fast. The inert gas injection ( 6 ) is controlled in flow rate in order to regulate medium amplitude variations. This provides great reaction stability and a wide range of possible variation for the conditions in the process chamber ( 1 ).

1 . A system for pumping gas from a process chamber ( 1 ), the system comprising a primary pump ( 2 ), a secondary pump ( 8 ), an inert gas injection device ( 6 ), and a regulator valve ( 4 ), in which: 
 the primary and/or secondary pump ( 2  and/or  8 ) is controlled in speed;    the regulator valve ( 4 ) is controlled in opening and is connected to the inlet of the primary pump ( 2 ); and    the inert gas injection ( 6 ) is controlled in flow rate, and is provided upstream from the regulator valve ( 4 ).    
   
   
       2 . A pumping system according to  claim 1 , in which the regulator valve ( 4 ) is controlled so as to compensate for fast variations of small amplitude in conditions of pressure and gas injection flow rate in the process chamber ( 1 ), inert gas injection ( 6 ) is controlled to compensate for larger amplitude variations in conditions of pressure and gas injection flow rate in the process chamber ( 1 ), and primary and/or secondary pump ( 2  and/or  8 ) speed is controlled so as to compensate for longer-term trends and greater variations in the amplitude of conditions of pressure and gas injection flow rate in the process chamber ( 1 ).  
   
   
       3 . A pumping system according to  claim 2 , in which the speed(s) of the primary and/or secondary pump ( 2  and/or  8 ) and the rate of inert gas injection ( 6 ) are determined so as to place the regulator valve ( 4 ) in a mean position of appropriate intermediate opening in which the regulator valve presents appropriate reaction sensitivity.  
   
   
       4 . A pumping system according to  claim 1 , in which: 
 the primary and/or secondary pump ( 2  and/or  8 ) is connected to control means ( 3  or  11 ) for controlling the primary and/or secondary pump ( 2  and/or  8 ) at adjustable speed;    the regulator valve ( 4 ) is associated with control means ( 5 ) for controlling the regulator valve ( 4 );    the inert gas injection ( 6 ) injects inert gas from an inert gas source ( 7 ) via an injection pipe ( 7   a ) provided with an injection valve ( 7   b ) and control means ( 7   c ) for controlling the injection valve ( 7   b ); and    central control means ( 10 ) such as a microprocessor or a microcontroller control the respective control means ( 3 ,  11 ,  5 ,  7   c ) for the primary and/or secondary pump ( 2  and/or  8 ), for the regulator valve ( 4 ), and for the injection valve ( 7   b ).    
   
   
       5 . A pumping system according to  claim 4 , in which the central control means ( 10 ) generate the signals which control the respective control means ( 3 ,  11 ,  5 ,  7   c ) as a function of a reference signal received from reference means ( 13 ), as a function of information concerning the opening positions of the regulator valve ( 4 ) and of the injection valve ( 7   b ), and as a function of measurements of the pressure in the process chamber ( 1 ) as issued by a pressure sensor ( 12 ).  
   
   
       6 . A system for fabricating semiconductor or microelectronic mechanical systems (MEMS), the installation including at least one process chamber ( 1 ) and a pumping system according to  claim 1 .  
   
   
       7 . A method of fabricating semiconductor or microelectronic mechanical systems (MEMS), in which the atmosphere inside a process chamber ( 1 ) is pumped using a pumping system according to  claim 1 .  
   
   
       8 . A method according to  claim 7 , characterized in that the opening of the regulator valve ( 4 ) is controlled in such a manner as to compensate for rapid variations of small amplitude in the conditions of pressure and gas injection flow rate in the process chamber ( 1 ), the inert gas injection ( 6 ) is controlled in flow rate so as to compensate for larger amplitude variations in the conditions of pressure and gas injection flow rate in the process chamber ( 1 ), and the speed of the primary and/or secondary pump ( 2  and/or  8 ) is controlled in such a manner as to compensate for longer-term trends and for variations of large amplitude in the conditions of pressure and/or gas injection flow rate into the process chamber ( 1 ).