Non-ambipolar electric pressure plasma uniformity control

Abstract

This disclosure relates to a plasma processing system for controlling plasma density near the edge or perimeter of a substrate that is being processed. The plasma processing system may include a plasma chamber that can receive and process the substrate using plasma for etching the substrate, doping the substrate, or depositing a film on the substrate. This disclosure relates to a plasma processing system that may be configured to enable non-ambipolar diffusion to counter ion loss to the chamber wall. The plasma processing system may include a ring cavity coupled to the plasma processing system that is in fluid communication with plasma generated in the plasma processing system. The ring cavity may be coupled to a power source to form plasma that may diffuse ions into the plasma processing system to minimize the impact of ion loss to the chamber wall.

What is claimed is: 
     
         1 . An apparatus for treating a substrate, comprising:
 a plasma processing chamber ;   a substrate holder, disposed in the processing chamber, that can receive a substrate to be treated;   a gas supply system for supplying a gas mixture to the processing chamber;   a plasma source in the plasma processing chamber that can energize the gas mixture into a plasma;   a ring-shaped cavity disposed in the side wall of the plasma processing chamber, above the substrate holder, the ring-shaped cavity being in fluid communication with the plasma processing chamber via a plurality of openings disposed in the sidewall, the ring-shaped cavity comprising an electrode;   a DC power supply for biasing the electrode.   
     
     
         2 . The apparatus of  claim 1 , wherein the plurality of openings comprises a plurality of slits. 
     
     
         3 . The apparatus of  claim 2 , wherein the plurality of openings are substantially vertical. 
     
     
         4 . The apparatus of  claim 2 , wherein the plurality of openings are substantially horizontal. 
     
     
         5 . The apparatus of  claim 1 , wherein the plurality of openings comprises an array of holes. 
     
     
         6 . The apparatus of  claim 1 , wherein the ring-shaped cavity is configured to drive non-ambipolar diffusion across the plurality of openings, when a DC bias is applied to the electrode. 
     
     
         7 . The apparatus of  claim 6 , wherein the DC bias is a positive DC bias. 
     
     
         8 . The apparatus of  claim 1 , wherein the plurality of openings is made of a dielectric material. 
     
     
         9 . The apparatus of  claim 8 , wherein the dielectric material is quartz. 
     
     
         10 . The apparatus of  claim 1 , wherein the plasma source is a surface wave plasma (SWP) source. 
     
     
         11 . A method for treating a substrate, comprising:
 loading a substrate onto a substrate holder disposed inside a plasma processing chamber, the plasma processing chamber being enclosed by one or more chamber walls and comprising:
 a plasma source configured to energize plasma inside the plasma processing chamber, the plasma processing chamber further comprising: 
 a ring-shaped cavity in fluid communication with the plasma processing chamber via a plurality of openings disposed on a wall of the ring-shaped cavity, the ring-shaped cavity comprising an electrode that is configured to be in fluid communication with the plasma, and 
 a power supply for biasing the electrode; 
   forming a first plasma inside the plasma processing chamber using the plasma source, the plasma having a first plasma density profile; and   forming a second plasma inside the ring-shaped cavity based, at least in part, on, the power supply biasing the electrode, the ring-shaped cavity being in fluid communication with the plasma processing chamber, the second plasma enabling non-ambipolar diffusion of electrons and ions across the plurality of openings.   
     
     
         12 . The method of  claim 13 , wherein the second plasma comprises a second plasma density profile that is different from the first density profile. 
     
     
         13 . The method of  claim 12 , wherein the non-ambipolar diffusion comprises diffusing the electrons from the first plasma to the second plasma and diffusing the ions from the second plasma to the first plasma, the diffusion of the electrons and the ions being based, at least in part, on a potential difference between the first plasma and the second plasma. 
     
     
         14 . An apparatus for treating a substrate, comprising:
 a plasma chamber comprising a sidewall and a substrate holder that can support the substrate;   a gas distribution system that provides gases to the plasma chamber;   a power supply that can apply power to a plasma source in the plasma chamber, such that a first plasma region can be formed using the gases;   a diffusion component in fluid communication with the plasma chamber, the diffusion component comprising an electrode that can enable non-ambipolar diffusion in the plasma chamber; and   a power source that can bias the electrode to generate the second plasma region.   
     
     
         15 . The apparatus of  claim 13 , wherein the bias comprises a potential difference of at least 100 volts. 
     
     
         16 . The apparatus of  claim 13 , wherein the ring-shaped cavity is disposed inside the plasma processing chamber and around the substrate holder. 
     
     
         17 . The apparatus of  claim 13 , wherein the ring-shaped cavity is disposed in an annular pumping duct of the plasma processing chamber. 
     
     
         18 . The apparatus of  claim 13 , wherein power source comprises a combined power source that can provide radio frequency power, positive direct current power, or negative direct current power. 
     
     
         19 . The apparatus of  claim 13 , wherein the combined power source comprises a switching assembly that is in electrical communication with the electrode and enables applying one of the following power sources: a RF power source, a positive DC power source, or a negative DC power source. 
     
     
         20 . The apparatus of  claim 13 , further comprising a ground electrode surrounding the substrate holder and disposed proximate to the diffusion component.