Systems and methods for improving wafer etch non-uniformity when using transformer-coupled plasma

1. A substrate processing system, comprising:

a processing chamber including a dielectric window and a pedestal for supporting a substrate during processing;

a gas supply system configured to supply gas to the processing chamber;

a coil arranged outside of the processing chamber adjacent to the dielectric window;

a radio frequency (RF) source configured to supply RF signals to the coil to create RF plasma in the processing chamber;

a gas plenum arranged between the coil and the dielectric window, wherein the gas plenum includes a body; and

N flux attenuating portions arranged in a spaced pattern adjacent to the coil, wherein N is an integer greater than one, wherein at least one of

the N flux attenuating portions are attached to the body of the plenum, and the N flux attenuating portions extend outwardly from the body, and

a ring portion is arranged around the coil, wherein the N flux attenuating portions are attached to the ring and the N flux attenuating portions extend inwardly from the ring portion.

2. The substrate processing system of claim 1 , wherein the N flux attenuating portions are arranged between the coil and the dielectric window.

3. The substrate processing system of claim 1 , wherein the N flux attenuating portions are arranged adjacent to a radially outer edge of the coil.

4. The substrate processing system of claim 2 , wherein the N flux attenuating portions project radially outwardly from the body of the plenum.

5. The substrate processing system of claim 4 , further comprising a gas supply to provide gas to the plenum during operation.

6. The substrate processing system of claim 1 , wherein the N flux attenuating portions are spaced at 360/N degree intervals.

7. The substrate processing system of claim 6 , wherein N is equal to 4.

8. The substrate processing system of claim 1 , wherein the coil includes a first coil that is wound within at least part of a second coil, wherein opposite ends of the first coil are arranged 180 degrees apart, and wherein opposite ends of the second coil are arranged 180 degrees apart.

9. The substrate processing system of claim 8 , wherein N is equal to 4, the N flux attenuating portions are spaced at 90 degree intervals, and the N flux attenuating portions are rotated 30-60 degrees relative to the opposite ends of the first coil and the second coil.

10. The substrate processing system of claim 1 , wherein the N flux attenuating portions are made of at least one of polytetrafluoroethylene, glass-filled polytetrafluoroethylene, polyphenylsulfone, or polyetheretherketone.

11. The substrate processing system of claim 1 , wherein the N flux attenuating portions extend radially inwardly from the ring portion between the coil and the dielectric window.

12. The substrate processing system of claim 1 , further comprising a transformer-coupled capacitive tuning circuit including at least one capacitor, wherein the transformer-coupled capacitive tuning circuit is connected between the RF source and the coil.

13. A method for operating a substrate processing system, comprising:

providing a processing chamber including a dielectric window and a pedestal for supporting a substrate;

arranging a coil adjacent to the dielectric window;

arranging a gas plenum having a body between the coil and the dielectric window;

arranging N flux attenuating portions in a spaced pattern adjacent to the coil, wherein N is an integer greater than one, wherein at least one of

the N flux attenuating portions are attached to the body of the plenum, and the N flux attenuating portions extend outwardly from the body, and

a ring portion is arranged around the coil, wherein the N flux attenuating portions are attached to the ring portion and the N flux attenuating portions extend inwardly from the ring portion;

supplying gas to the processing chamber; and

supplying RF signals to the coil to create RF plasma in the processing chamber.

14. The method of claim 13 , wherein the N flux attenuating portions are arranged between the coil and the dielectric window.

15. The method of claim 13 , wherein the N flux attenuating portions are arranged adjacent to a radially outer edge of the coil.

16. The method of claim 14 , wherein the N flux attenuating portions project radially outwardly in a spaced pattern from the plenum.

17. The method of claim 16 , further comprising providing gas to the plenum during operation.

18. The method of claim 13 , further comprising spacing the N flux attenuating portions at 360/N degree intervals.

19. The method of claim 13 , wherein N is equal to 4.

20. The method of claim 13 , wherein the coil includes a first coil that is wound within at least part of a second coil, and further comprising:

arranging opposite ends of the first coil 180 degrees apart; and

arranging opposite ends of the second coil 180 degrees apart.

21. The method of claim 20 , wherein N is equal to 4, and further comprising:

spacing the N flux attenuating portions at 90 degree intervals; and

rotating the N flux attenuating portions 30-60 degrees relative to the opposite ends of the first coil and the second coil.

22. The method of claim 13 , wherein the N flux attenuating portions are made of at least one of polytetrafluoroethylene, glass-filled polytetrafluoroethylene, polyphenylsulfone, or polyetheretherketone.

23. The method of claim 13 , wherein the N flux attenuating portions extend radially inwardly from the ring portion between the coil and the dielectric window.

24. The method of claim 13 , further comprising connecting a transformer-coupled capacitive tuning circuit between the coil and an RF source generating the RF signals.