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