Flow control system and method for multizone gas distribution

Abstract

A multizone gas distribution system configured to be coupled to a process chamber is described. The multizone gas distribution system comprises a first gas distribution element and a second gas distribution element. Additionally, the multizone gas distribution system comprises a flow control system configured to divide a flow of process gas between the first gas distribution element and the second gas distribution element. Further, a system controller coupled to the flow control system is configured to adjust the flow of process gas to the first gas distribution element and the second gas distribution element according to a target flow condition. Further yet, the system controller is configured to monitor the flow control system in order to perform at least one of monitoring a flow rate, adjusting a flow rate, controlling a flow rate, determining a fault condition, and determining an erroneous fault condition.

1 . A multizone gas distribution system configured to be coupled to a process chamber, comprising:
 a multizone gas distribution assembly comprising a first gas distribution element configured to introduce a first flow rate of process gas to said process chamber and a second gas distribution element configured to introduce a second flow rate of process gas to said process chamber;   a flow control system coupled to said multizone gas distribution system, said flow control system comprising:
 a process gas supply system configured to supply said process gas, 
 a process gas supply line having an inlet end coupled to said process gas supply system and an outlet end that splits into a first gas supply branch that supplies said process gas to said first gas distribution element and a second gas supply branch that supplies said process gas to said second gas distribution element, 
 a flow rate controller coupled to said process gas supply line and configured to control the total sum of said first flow rate and said second flow rate, 
 a first flow control valve coupled to said first gas supply branch and configured to adjust said first flow rate, 
 a second flow control valve coupled to said second gas supply branch and configured to adjust said second flow rate, 
 a first pressure measurement device coupled to said first gas supply branch and configured to measure a first pressure, and 
 a second pressure measurement device coupled to said second gas supply branch and configured to measure a second pressure; and 
 a system controller coupled to said flow control system and configured to control said first flow rate and said second flow rate according to a target flow condition by adjusting said first flow control valve and said flow second control valve and monitoring said first pressure and said second pressure. 
   
   
   
       2 . The multizone gas distribution system of  claim 1 , wherein said first pressure measurement device is located on an outlet side of said first flow control valve, and said second pressure measurement device is located on an outlet side of said second flow control valve. 
   
   
       3 . The multizone gas distribution system of  claim 1 , wherein said multizone gas distribution assembly comprises a showerhead gas distribution system, and said first gas distribution element is arranged in a first region while said second gas distribution element is arranged in a second region. 
   
   
       4 . The multizone gas distribution system of  claim 3 , wherein said first region comprises a substantially central region of said shower gas distribution system and said second region comprises a substantially peripheral region surrounding said central region. 
   
   
       5 . The multizone gas distribution system of  claim 3 , wherein said first gas distribution element is pneumatically isolated from said second gas distribution element. 
   
   
       6 . The multizone gas distribution system of  claim 3 , wherein said first gas distribution element comprises a first gas plenum configured to receive said first flow rate of said process gas from said first gas supply branch and a first array of openings formed through a gas injection plate that is configured to introduce said process gas from said first plenum to a process space in said process chamber, and wherein said second gas distribution element comprises a second gas plenum configured to receive said second flow rate of said process gas from said second gas supply branch and a second array of openings formed through said gas injection plate that is configured to introduce said process gas from said second plenum to said process space in said process chamber. 
   
   
       7 . The multizone gas distribution system of  claim 1 , wherein said system controller is configured to determine a fault condition or an erroneous fault condition by monitoring said first pressure, or said second pressure, or a combination of said first pressure and said second pressure. 
   
   
       8 . The multizone gas distribution system of  claim 1 , wherein said system controller is configured to determine a service condition by monitoring said first pressure, or said second pressure, or a combination of said first pressure and said second pressure. 
   
   
       9 . A method of supplying a process gas to a process chamber, comprising:
 initiating a known flow rate of a process gas to a process chamber;   dividing said known flow rate of said process gas into a first flow of said process gas at a first flow rate and a second flow of said process gas at a second flow rate;   measuring a first pressure associated with said first flow of said process gas;   measuring a second pressure associated with said second flow of said process gas; and   controlling said first flow rate and said second flow rate according to a target flow condition by adjusting a first conductance of said first flow of said process gas and a second conductance of said second flow of said process gas and monitoring said first pressure and said second pressure.   
   
   
       10 . The method of  claim 9 , further comprising:
 establishing a first correlation between the sum of said first pressure and said second pressure and the sum of said first flow rate and said second flow rate.   
   
   
       11 . The method of  claim 10 , further comprising:
 establishing a second correlation between a ratio of said first flow rate to said second flow rate and a ratio of said first pressure to said second pressure.   
   
   
       12 . The method of  claim 11 , further comprising:
 determining said first flow rate or said second flow rate or both by using said first correlation, said second correlation, said measurement of said first pressure and said measurement of said second pressure.   
   
   
       13 . The method of  claim 11 , wherein said determining said first flow rate comprises:
 computing the ratio of said first pressure to said second pressure,   determining a flow ratio from said second correlation using the ratio of said first pressure to said second pressure,   computing the sum of said first pressure and said second pressure,   determining a total flow rate using the sum of said first pressure and said second pressure, and   computing said first flow rate using said determined flow ratio and said determined total flow rate or said known flow rate.   
   
   
       14 . The method of  claim 9 , wherein said target flow condition comprises a target ratio of said first flow rate to said known flow rate or a target ratio of said second flow rate to said known flow rate or a target ratio of said first flow rate to said second flow rate, and wherein said controlling said first flow rate and said second flow rate comprises comparing a ratio of said first pressure to said second pressure with said target ratio. 
   
   
       15 . The method of  claim 9 , further comprising:
 determining a fault condition during the supply of said process gas to said process chamber by monitoring said first pressure, or said second pressure, or a combination of said first pressure and said second pressure.   
   
   
       16 . The method of  claim 15 , wherein said determining said fault condition comprises correlating a temporal variation in said first pressure or said second pressure or a combination of said first pressure and said second pressure with a variation in said known flow rate. 
   
   
       17 . The method of  claim 9 , further comprising:
 determining an erroneous fault condition during the supply of said process gas to said process chamber by monitoring said first pressure, or said second pressure, or a combination of said first pressure and said second pressure.   
   
   
       18 . The method of  claim 17 , wherein said determining said fault condition comprises correlating a substantially small temporal variation in said first pressure or said second pressure or a combination of said first pressure and said second pressure with a variation in said known flow rate. 
   
   
       19 . The method of  claim 9 , further comprising:
 determining a service condition during the supply of said process gas to said process chamber by monitoring said first pressure, or said second pressure, or a combination of said first pressure and said second pressure.   
   
   
       20 . The method of  claim 19 , wherein said determining said fault condition comprises detecting a gradual temporal variation in said first pressure or said second pressure or a combination of said first pressure and said second pressure while not varying said known flow rate.