Symmetrical plural-coil plasma source with side RF feeds and RF distribution plates
A plasma reactor has an overhead inductively coupled plasma source with two coil antennas and symmetric and radial RF feeds and cylindrical RF shielding around the symmetric and radial RF feeds. The radial RF feeds are symmetrically fed to the plasma source.
1. A plasma reactor comprising:
a window assembly;
first and second coil antennas adjacent said window assembly;
a first current distributor coupled to said first coil antenna and a second current distributor coupled to said second coil antenna;
first and second RF feed terminals;
a conductive feed plate lying in a plane above said first and second coil antennas and coupled to said second RF feed terminal, and a plurality of axial rods coupled between a peripheral annular zone of said conductive feed plate and said second current distributor;
a conductive ground plate in a plane between said conductive feed plate and said first current distributor;
a first radial conductive feed rod lying in a plane above said conductive ground plate and having an inner end coupled to said first current distributor and an outer end coupled to said first RF feed terminal.
2. The plasma reactor of claim 1 wherein said first coil antenna comprises an inner coil antenna overlying said window assembly and said second coil antenna comprises an outer coil antenna surrounding said window assembly.
3. The plasma reactor of claim 2 wherein said second RF feed terminal lies above said conductive feed plate, said plasma reactor further comprising:
an upper axial center conductor connected between said second RF feed terminal and said conductive feed plate.
4. The plasma reactor of claim 3 further comprising:
a lower axial center conductor connected between said inner end of said first radial conductive feed rod and said first current distributor.
5. The plasma reactor of claim 4 further comprising an axial center shield surrounding said lower axial center conductor.
6. The plasma reactor of claim 5 further comprising a first radial cylindrical shield surrounding said first radial conductive feed rod.
7. The plasma reactor of claim 6 further comprising a plurality of axial cylindrical shields surrounding respective ones of said plurality of axial rods.
8. The plasma reactor of claim 1 wherein said first coil antenna comprises an inner coil antenna overlying said window assembly and said second coil antenna comprises a middle coil antenna overlying said window assembly.
9. The plasma reactor of claim 8 further comprising:
a second radial conductive feed rod lying in a plane above said conductive ground plate and having an inner end coupled to said conductive feed plate and an outer end coupled to said second RF feed terminal.
10. The plasma reactor of claim 9 further comprising:
a first axial center rod connected between said inner end of said first radial conductive feed rod and said first current distributor; and
a second axial center rod connected between said inner end of said second radial conductive feed rod and said conductive feed plate.
11. The plasma reactor of claim 10 further comprising an axial center shield surrounding said first and second axial center rods.
12. The plasma reactor of claim 11 further comprising a first radial cylindrical shield surrounding said first radial conductive feed rod.
13. The plasma reactor of claim 12 further comprising a second radial cylindrical shield surrounding said second radial conductive feed rod.
14. The plasma reactor of claim 13 further comprising a plurality of axial cylindrical shields surrounding respective ones of said plurality of axial rods.
15. The plasma reactor of claim 14 wherein said plurality of axial cylindrical shields are grounded to said conductive ground plate.
16. The plasma reactor of claim 11 further comprising an inner coil shield surrounding said first coil antenna and lying between said first and second coil antennas.
17. The plasma reactor of claim 16 wherein said inner coil shield is grounded and wherein said first and second coil antennas comprise ground return ends connected to said inner coil shield.
18. The plasma reactor of claim 1 wherein said conductive ground plate comprises plural openings, said plurality of axial rods extending through respective ones of said plural openings.
19. The plasma reactor of claim 1 wherein:
said peripheral annular zone of said a has an inner diameter which is at least 85% of the diameter of said conductive feed plate.
20. The plasma reactor of claim 1 further comprising:
a first RF impedance match coupled to said first RF feed terminal; and
a second RF impedance match coupled to said second RF feed terminal.