Multiple coil inductively coupled plasma source with offset frequencies and double-walled shielding
A plasma reactor has an overhead multiple coil antennas including a parallel spiral coil antenna 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;
first and second RF power sources coupled to said first and second RF feed terminals respectively;
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; and
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 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.
3. The plasma reactor of claim 2 further comprising:
a lower axial center conductor connected between said inner end of said first radial conductive feed rod and said first current distributor.
4. The plasma reactor of claim 3 further comprising an axial center shield surrounding said lower axial center conductor.
5. The plasma reactor of claim 4 further comprising a first radial cylindrical shield surrounding said first radial conductive feed rod.
6. The plasma reactor of claim 5 further comprising a plurality of axial cylindrical shields surrounding respective ones of said plurality of axial rods.
7. The plasma reactor of claim 1 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.
8. The plasma reactor of claim 7 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.
9. The plasma reactor of claim 8 further comprising an axial center shield surrounding said first and second axial center rods.
10. The plasma reactor of claim 9 further comprising a first radial cylindrical shield surrounding said first radial conductive feed rod.
11. The plasma reactor of claim 10 further comprising a second radial cylindrical shield surrounding said second radial conductive feed rod.
12. The plasma reactor of claim 11 further comprising a plurality of axial cylindrical shields surrounding respective ones of said plurality of axial rods.
13. The plasma reactor of claim 12 wherein said plurality of axial cylindrical shields are grounded to said conductive ground plate.
14. 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.