Rf choke for gas delivery to an rf driven electrode in a plasma processing apparatus

Abstract

In large area plasma processing systems, process gases may be introduced to the chamber via the showerhead assembly which may be driven as an RF electrode. The gas feed tube, which is grounded, is electrically isolated from the showerhead. The gas feed tube may provide not only process gases, but also cleaning gases from a remote plasma source to the process chamber. The inside of the gas feed tube may remain at either a low RF field or a zero RF field to avoid premature gas breakdown within the gas feed tube that may lead to parasitic plasma formation between the gas source and the showerhead. By feeding the gas through an RF choke, the RF field and the processing gas may be introduced to the processing chamber through a common location and thus simplify the chamber design.

1 . An RF choke assembly, comprising:
 a gas feed tube; and   a ferrite element coupled to and at least partially surrounding the gas feed tube.   
     
     
         2 . The assembly of  claim 1 , wherein the ferrite element comprises a plurality of ferrite disks. 
     
     
         3 . The assembly of  claim 2 , wherein the plurality of ferrite disks are spaced apart. 
     
     
         4 . The assembly of  claim 1 , wherein the ferrite element comprises a plurality of cylinders. 
     
     
         5 . The assembly of  claim 4 , wherein the plurality of cylinders are spaced apart. 
     
     
         6 . The assembly of  claim 1 , wherein the ferrite element comprises a plurality of ferrite rods. 
     
     
         7 . The assembly of  claim 6 , wherein the plurality of ferrite rods are spaced apart. 
     
     
         8 . An apparatus, comprising:
 an RF power source;   a gas source;   a remote plasma source; and   an RF choke assembly coupled between the RF power source and the remote plasma source, the RF choke assembly comprising:
 a gas feed tube; and 
 a ferrite element coupled to the gas feed tube. 
   
     
     
         9 . The apparatus of  claim 8 , wherein the remote plasma source is upstream from the RF choke assembly. 
     
     
         10 . The apparatus of  claim 8 , further comprising:
 a Pi network coupled to the RF choke assembly, the Pi network comprising:
 a load capacitor; 
 a tuning capacitor; and 
 an impedance of the RF choke assembly. 
   
     
     
         11 . The apparatus of  claim 8 , further comprising:
 a reverse L-type matching network coupled to the RF choke assembly, the reverse L-type matching network comprising:
 a load capacitor; 
 a tuning capacitor; and 
 the impedance of the RF choke assembly. 
   
     
     
         12 . The apparatus of  claim 11 , wherein the load capacitor comprises the impedance of the RF choke assembly and an external capacitive load. 
     
     
         13 . The apparatus of  claim 11 , wherein the RF choke assembly is part of the load capacitor. 
     
     
         14 . The apparatus of  claim 8 , further comprising:
 an L-type matching network, the L-type matching network comprising:
 a load capacitor; and 
 a tuning capacitor. 
   
     
     
         15 . The apparatus of  claim 14 , wherein the tuning capacitor comprises the impedance of the RF choke assembly and an external tuning capacitor. 
     
     
         16 . An RF choke assembly, comprising:
 a gas feed tube comprising a metal; and   a ferrite element coupled to the gas feed tube, wherein the gas feed tube at least partially encircles the ferrite element.   
     
     
         17 . An apparatus, comprising:
 an RF power source;   a gas source; and   an RF choke assembly coupled between the RF power source and the gas source, the assembly comprising:
 a gas feed tube comprising a metal, a first end coupled with the gas source, and a second end coupled with the RF power source. 
   
     
     
         18 . The apparatus of  claim 17 , wherein the gas feed tube comprises a coil. 
     
     
         19 . The apparatus of  claim 17 , wherein the gas feed tube comprises aluminum. 
     
     
         20 . The apparatus of  claim 19 , wherein the second end of the gas feed tube is coupled to ground.