Inductively coupled plasma apparatus

Abstract

Methods and apparatus for plasma processing are provided herein. In some embodiments, a plasma processing apparatus includes a process chamber having an interior processing volume; a first RF coil disposed proximate the process chamber to couple RF energy into the processing volume; and a second RF coil disposed proximate the process chamber to couple RF energy into the processing volume, the second RF coil disposed coaxially with respect to the first RF coil, wherein the first and second RF coils are configured such that RF current flowing through the first RF coil is out of phase with RF current flowing through the RF second coil.

1 . A plasma processing apparatus, comprising:
 a process chamber having an interior processing volume;   a first RF coil disposed proximate the process chamber to couple RF energy into the processing volume; and   a second RF coil disposed proximate the process chamber to couple RF energy into the processing volume, the second RF coil disposed coaxially with respect to the first RF coil, wherein the first and second RF coils are configured such that RF current flowing through the first RF coil is out of phase with RF current flowing through the second RF coil.   
     
     
         2 . The apparatus of  claim 1 , wherein the first RF coil is wound in a first direction and wherein the second RF coil is wound in a second direction opposite the first direction. 
     
     
         3 . The apparatus of  claim 1 , wherein the second RF coil is coaxially disposed about the first RF coil. 
     
     
         4 . The apparatus of  claim 1 , further comprising:
 a phase shifter coupled to either the first or second RF coil for shifting the phase of the RF current flowing therethrough.   
     
     
         5 . The apparatus of  claim 4 , wherein the phase shifter shifts the phase of the RF current such that the RF current flowing through the first RF coil is about 180 degrees out of phase with RF current flowing through the second RF coil. 
     
     
         6 . A plasma processing apparatus, comprising:
 a process chamber having an interior processing volume;   a first RF coil disposed proximate the process chamber to couple RF energy into the processing volume and wound in a first direction; and   a second RF coil disposed proximate the process chamber to couple RF energy into the processing volume, the second RF coil disposed coaxially with respect to the first RF coil and wound in a second direction opposite the first direction such that RF current flows through the first RF coil in the first direction and through the second RF coil in the second direction.   
     
     
         7 . The apparatus of  claim 6 , wherein RF current flowing through the first RF coil is about 180 degrees out of phase with RF current flowing through the second RF coil. 
     
     
         8 . The apparatus of  claim 6 , wherein the second RF coil is coaxially disposed about the first RF coil. 
     
     
         9 . The apparatus of  claim 8 , wherein the first RF coil further comprises a plurality of symmetrically arranged first coil elements and wherein the second RF coil further comprises a plurality of symmetrically arranged second coil elements. 
     
     
         10 . The apparatus of  claim 9 , wherein the number of first coil elements is two and the number of second coil elements is four. 
     
     
         11 . The apparatus of  claim 9 , wherein the number of first coil elements is four and the number of second coil elements is four. 
     
     
         12 . The apparatus of  claim 11 , further comprising:
 an RF feed structure coupled to each of the first and second coil elements to provide RF power thereto, the RF feed structure coaxially disposed with respect to each of the first and second coil elements.   
     
     
         13 . The apparatus of  claim 12 , wherein the RF feed structure further comprises:
 a first RF feed coupled to each of the first coil elements; and   a second RF feed coaxially disposed about the first RF feed and electrically insulated therefrom, the second RF feed coupled to each of the second coil elements.   
     
     
         14 . The apparatus of  claim 13 , wherein the plurality of first coil elements is symmetrically disposed about the first RF feed and the plurality of second coil elements is symmetrically disposed about the second RF feed. 
     
     
         15 . The apparatus of  claim 13 , wherein the second RF feed further comprises:
 a conductive tube having a first end proximate the first and second coil elements and a second end opposite the first end.   
     
     
         16 . The apparatus of  claim 15 , wherein the first and second end of the conductive tube are separated by a length such that a magnetic field formed by flowing RF current through the first and second RF feeds has substantially no effect on the symmetry of an electric field formed by flowing RF current through the first and second RF coils. 
     
     
         17 . The apparatus of  claim 13 , further comprising:
 a heater element disposed between the first and second RF coils and a dielectric lid of the process chamber.   
     
     
         18 . A method of forming a plasma, comprising:
 providing an RF signal through a first RF coil;   providing the RF signal through a second RF coil coaxially disposed with respect to the first RF coil such that the RF signal flows through the second coil out of phase with respect to the flow of the RF signal through the first coil; and   forming a plasma by coupling the RF signal provided by the first and second RF coils to a process gas disposed in a process chamber.   
     
     
         19 . The method of  claim 18 , wherein the first and second RF coils are wound in opposite directions. 
     
     
         20 . The method of  claim 18 , wherein the RF current flowing through the first and second RF coils are about 180 degrees out of phase.