Method and apparatus for increasing local plasma density in magnetically confined plasma

• US 7,922,880 B1
• Filed: 05/24/2007
• Issued: 04/12/2011
• Est. Priority Date: 05/24/2007
• Status: Active Grant

• Current Assignee: Novellus Systems Incorporated (Lam Research Corporation)
• Original Assignee: Novellus Systems Incorporated (Lam Research Corporation)
• Inventors: Kinder, Ronald L., Pradhan, Anshu A., Hayden, Douglas B., Dulkin, Alexander
• Primary Examiner(s): McDonald; Rodney G
• Application Number:
  US11/807,182
• Time in Patent Office: 1,419 Days
• Field of Search: 204/298.03, 204/298.06, 204/298.08, 204/298.14, 118/723.E, 118/723.ER, 156/345.35, 156/345.43, 156/345.44, 156/345.45, 156/345.47
• US Class Current: 204/298.06
• CPC Class Codes: C23C 14/351 using a magnetic field in close vicinity to the substrate
• CPC Class Codes: H01J 37/3266 Magnetic control means
• CPC Class Codes: H01J 37/3405 Magnetron sputtering
• CPC Class Codes: H01J 37/3461 Means for shaping the magnetic field, e.g. magnetic shunts

Abstract

Local plasma density, e.g., the plasma density in the vicinity of the substrate, is increased by providing an ion extractor configured to transfer ions and electrons from a first region of magnetically confined plasma (typically a region of higher density plasma) to a second region of plasma (typically a region of lower density plasma). The second region of plasma is preferably also magnetically shaped or confined and resides between the first region of plasma and the substrate. A positively biased conductive member positioned proximate the second region of plasma serves as an ion extractor. A positive bias of about 50-300 V is applied to the ion extractor causing electrons and subsequently ions to be transferred from the first region of plasma to the vicinity of the substrate, thereby forming higher density plasma. Provided methods and apparatus are used for deposition and resputtering.

Claims

1. An apparatus for processing material on a semiconductor wafer, comprising:

(a) a process chamber having an inlet for introduction of an inert gas;

(b) a wafer support for holding the wafer in position during processing of the material;

(c) a first magnetic field source configured to generate a first magnetic field capable of shaping plasma in a first plasma region at a first elevation above the wafer support;

(d) a second magnetic field source configured to generate a second magnetic field capable of shaping plasma in a second plasma region at a second elevation above the wafer support, wherein the second elevation is closer to the wafer support than the first elevation; and

(f) an ion extractor positioned within the process chamber and configured to accept a positive DC bias, wherein the ion extractor is configured to increase plasma density and maintain the increased plasma density at the second elevation above the wafer support by transferring electrons generated in the first plasma region to the second plasma region, and wherein the ion extractor is configured to generate an electric field, wherein E vector, characterizing the electric field generated by the positively biased ion extractor crosses with the B vector generated by the second magnetic field source.

2. The apparatus of claim 1, wherein the second elevation is proximate the wafer support.

3. The apparatus of claim 1, wherein the second elevation is within about 3 cm from the wafer support.

4. The apparatus of claim 1, wherein the first elevation is at least about 15 cm from the wafer support.

5. The apparatus of claim 1, wherein the ion extractor is circumferentially positioned proximate the second elevation.

6. The apparatus of claim 1, wherein the ion extractor comprises a conductive member electrically isolated from other members of the process chamber.

7. The apparatus of claim 1, wherein the ion extractor is electrically connected to an ion extractor power supply.

8. The apparatus of claim 1, wherein the ion extractor power supply is a DC power supply.

9. The apparatus of claim 1, wherein the first magnetic field is stronger than the second magnetic field.

10. The apparatus of claim 1, further comprising a target.

11. The apparatus of claim 10, wherein the target is planar.

12. The apparatus of claim 10, wherein the target comprises a particle container, configured for plasma confinement within the target.

13. The apparatus of claim 1, wherein the first magnetic field source and the second magnetic field source comprise electromagnets.

14. The apparatus of claim 1, wherein the first magnetic field source is configured to generate the magnetic field having a strength between about 0.1-1.5 Tesla proximate a target.

15. The apparatus of claim 1, wherein the first magnetic field source is configured to generate an ultra-high magnetic field having a strength of at least about 1 Tesla proximate a target.

16. The apparatus of claim 1, wherein the ion extractor is configured to maintain a plasma density of at least about 10¹¹ electrons/cm³ at the second elevation above the wafer support.

17. The apparatus of claim 1, wherein the ion extractor is configured to maintain a plasma density of at least about 10¹² electrons/cm³ at the second elevation above the wafer support.

18. An apparatus of claim 1 further comprising a controller comprising program instructions for:

(i) positioning the wafer substrate on the wafer support within the process chamber;

(ii) generating a plasma comprising electrons and positively charged ions, said plasma having a first plasma density at the first elevation above the substrate and a second plasma density at the second elevation above the substrate; and

(iii) applying a positive DC bias to the ion extractor circumferentially located proximate the second elevation to thereby extract electrons from the region of the first plasma density to the region of the second plasma density and maintain a high plasma density in the region of the second plasma density.

19. The apparatus of claim 18, further comprising instructions for resputtering a material on the wafer surface.

20. The apparatus of claim 18, further comprising instructions for depositing a material on the wafer surface.

21. The apparatus of claim 18, wherein (iii) comprises applying a bias of between about 50-300V to the ion extractor.

22. The apparatus of claim 18, further comprising instructions for generating an ultra-high magnetic field having a strength of at least about 1 Tesla.

23. The apparatus of claim 18, wherein the program instructions for generating the plasma comprise instructions for producing a chamber pressure of between about 0.5-3 mTorr.

24. The apparatus of claim 1, wherein the E vector and the B vector are substantially orthogonal.

25. The apparatus of claim 1, wherein crossing of electric and magnetic fields in the second plasma region is configured to accelerate trapped electrons.

26. The apparatus of claim 1, wherein the ion extractor and the second magnetic field source are configured to generate a toroidal plasma region above the wafer.

27. The apparatus of claim 1, wherein the ion extractor is configured to accept positive DC bias of at least about 100 V.

28. The apparatus of claim 1, wherein the ion extractor is configured to accept positive DC bias of between about 100-125 V.

29. The apparatus of claim 1, wherein the ion extractor and the second source of magnetic field are disposed at substantially the same elevation above the wafer.

30. The apparatus of claim 29, wherein the second source of magnetic field comprises an electromagnet.