Merie plasma reactor with overhead RF electrode tuned to the plasma with arcing suppression

• US 20050236377A1
• Filed: 04/12/2005
• Published: 10/27/2005
• Est. Priority Date: 03/17/2000
• Status: Active Grant

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Ye, Yan, Hoffman, Daniel J., Buchberger, Douglas A. Jr., Miller, Matthew L., Katz, Dan, Zhao, Xiaoye, Chiang, Kang-Lie, Hagen, Robert B.
• Granted Patent: US 7,186,943 B2
• Time in Patent Office: Days
• US Class Current: 219/121.430
• CPC Class Codes: H01J 37/32082 Radio frequency generated discharge H01J37/32357, H01J37/32366, H01J37/32394 and H01J37/32403 take precedence
• CPC Class Codes: H01J 37/32183 Matching circuits
• CPC Class Codes: H01J 37/3244 Gas supply means
• CPC Class Codes: H01J 37/3266 Magnetic control means

Abstract

A plasma reactor for processing a semiconductor workpiece, includes a reactor chamber having a chamber wall and containing a workpiece support for holding the semiconductor support, the electrode comprising a portion of the chamber wall, an RF power generator for supplying power at a frequency of the generator to the overhead electrode and capable of maintaining a plasma within the chamber at a desired plasma ion density level. The overhead electrode has a capacitance such that the overhead electrode and the plasma formed in the chamber at the desired plasma ion density resonate together at an electrode-plasma resonant frequency, the frequency of the generator being at least near the electrode-plasma resonant frequency. The reactor further includes a set of MERIE magnets surrounding the plasma process area overlying the wafer surface that produce a slowly circulating magnetic field which stirs the plasma to improve plasma ion density distribution uniformity.

Claims

1. A plasma reactor for processing a semiconductor workpiece, comprising:

a reactor chamber having a chamber wall and containing a workpiece support for holding the semiconductor workpiece;

an overhead electrode overlying said workpiece support;

an RF power generator for supplying power at a frequency of said generator;

said overhead electrode having a reactance that forms a resonance with the plasma at an electrode-plasma resonant frequency which is at or near said frequency of said generator;

a source of a magnetic field; and

a fixed impedance matching element coupled to said RF power generator and to said overhead electrode.

2. The reactor of claim 1 wherein said magnetic field is sufficiently small in magnitude so that the electron cyclotron frequency associated with said magnetic field is less than the frequency of said RF power generator.

3. The reactor of claim 2 wherein said electron cyclotron frequency is at least 5% less than said RF power generator frequency.

4. The reactor of claim 2 wherein said frequency of said RF power generator is a VHF frequency.

5. The reactor of claim 1 further comprising:

an insulating layer formed on a surface of said overhead electrode facing said workpiece support.

6. The reactor of claim 5 further comprising:

a capacitive insulating layer between said RF power generator and said overhead electrode.

7. The reactor of claim 6 further comprising:

a metal foam layer overlying and contacting a surface of said overhead electrode that faces away from said workpiece support.

8. The reactor of claim 5 further comprising a silicon-containing coating covering said insulating layer.

9. The reactor of claim 8 wherein said silicon-containing coating comprises one of silicon or silicon carbide.

10. The reactor of claim 7 wherein said insulating layer provides a capacitance sufficient to suppress arcing within said gas injection ports.

11. The reactor of claim 10 wherein said capacitive insulating layer has a sufficient capacitance to block D.C. current from a plasma within said chamber from flowing through said overhead electrode.

12. The reactor of claim 11 wherein:

said electrode has plural gas injection orifices therein generally facing said workpiece support; and

said metal foam layer is of a sufficient thickness to suppress an axial electric field within said gas injection orifices.

13. The reactor of claim 5 wherein said overhead electrode comprises aluminum and said insulating layer is formed by anodization.

14. The reactor of claim 6 wherein said capacitive insulating layer forms a capacitance that provides a low impedance path to ground through said overhead electrode for plasma sheath generated harmonics.

15. The reactor of claim 6 further comprising:

a gas inlet to said overhead electrode;

a gas baffling layer within said overhead electrode between said gas inlet and at least a first set of said gas injection orifices.

16. The reactor of claim 15 wherein said gas baffling layer comprises a layer of metal foam.

17. The reactor of claim 13 further comprising thermal control fluid passages within said overhead electrode.

18. The reactor of claim 17 further comprising an optical window in said overhead electrode generally facing said wafer support and a light carrying medium coupled to said window and extending through said overhead electrode.

19. A plasma reactor for processing a semiconductor workpiece, comprising:

a reactor chamber containing a workpiece support for holding the semiconductor workpiece;

an overhead electrode overlying said workpiece support;

an RF power generator for supplying power at a frequency of said generator to said overhead electrode and capable of maintaining a plasma within said chamber at a desired plasma ion density level; and

said overhead electrode having a reactance that forms a resonance with the plasma at an electrode-plasma resonant frequency which is at or near said frequency of said generator.

20. The reactor of claim 19 further comprising a fixed impedance match coupled between said RF power generator and said overhead electrode.