Microwave plasma reactor for manufacturing synthetic diamond material

• US 8,955,456 B2
• Filed: 12/14/2011
• Issued: 02/17/2015
• Est. Priority Date: 12/23/2010
• Status: Active Grant

• Current Assignee: Element Six (Holdings) Ltd. (Anglo American PLC)
• Original Assignee: Element Six (Holdings) Ltd. (Anglo American PLC)
• Inventors: Cullen, Alexander Lamb, Dodson, Joseph Michael, Williams, Stephen David, Brandon, John Robert
• Primary Examiner(s): Yuan, Dah-Wei D
• Assistant Examiner(s): Hernandez-Diaz, Jose
• Application Number:
  US13/994,836
• Publication Number:
  US 20140308461A1
• Time in Patent Office: 1,161 Days
• Field of Search: 118/723.MW
• US Class Current: 118/723.MW
• CPC Class Codes: C23C 16/274 using microwave discharges
• CPC Class Codes: C23C 16/511 using microwave discharges
• CPC Class Codes: H01J 2237/3321 CVD [Chemical Vapor Deposition]
• CPC Class Codes: H01J 37/32009 Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources plasma generation in general H05H1/24
• CPC Class Codes: H01J 37/32192 Microwave generated discharge H01J37/32357, H01J37/32366, H01J37/32394, H01J37/32403 take precedence
• CPC Class Codes: H01J 37/32211 Means for coupling power to the plasma
• CPC Class Codes: H01J 37/32229 Waveguides
• CPC Class Codes: H01J 37/32238 Windows
• CPC Class Codes: H01J 37/32266 Means for controlling power transmitted to the plasma
• CPC Class Codes: H01J 37/3244 Gas supply means

Abstract

A microwave plasma reactor for manufacturing a synthetic diamond material via chemical vapour deposition, the microwave plasma reactor comprising: a plasma chamber (2); a substrate holder (4) disposed in the plasma chamber for supporting a substrate on which the synthetic diamond material is to be deposited in use; a microwave coupling configuration (12) for feeding microwaves from a microwave generator (8) into the plasma chamber; and a gas flow system (13,16) for feeding process gases into the plasma chamber and removing them therefrom, wherein the microwave coupling configuration for feeding microwaves from the microwave generator into the plasma chamber comprises: an annular dielectric window (18) formed in one or several sections; a coaxial waveguide (14) having a central inner conductor (20) and an outer conductor (22) for feeding microwaves to the annular dielectric window; and a waveguide plate (24) comprising a plurality of apertures (28) disposed in an annular configuration with a plurality of arms (26) extending between the apertures, each aperture forming a waveguide for coupling microwaves towards the plasma chamber.

Claims

1. A microwave plasma reactor for manufacturing a synthetic diamond material via chemical vapour deposition, the microwave plasma reactor comprising:

a plasma chamber;

a substrate holder disposed in the plasma chamber for supporting a substrate on which the synthetic diamond material is to be deposited in use;

a microwave coupling configuration for feeding microwaves from a microwave generator into the plasma chamber; and

a gas flow system for feeding process gases into the plasma chamber and removing them therefrom,

wherein the microwave coupling configuration for feeding microwaves from the microwave generator into the plasma chamber comprises;

an annular dielectric window formed in one or several sections;

a coaxial waveguide having a central inner conductor and an outer conductor for feeding microwaves to the annular dielectric window; and

a waveguide plate comprising a plurality of apertures disposed in an annular configuration with a plurality of arms extending between the apertures, each aperture forming a waveguide for coupling microwaves towards the plasma chamber;

wherein the plurality of arms define one or more channels for supplying coolant and/or process gas,

wherein the one or more channels comprise at least one channel configured to supply process gas to one or more injection ports arranged opposite the substrate holder for injecting process gas towards the substrate holder,

wherein the waveguide plate comprises a central portion which extends across the plasma chamber and is supported by the plurality of arms extending between the apertures, and

wherein the central inner conductor of the coaxial waveguide forms a floating conductor supported by the central portion of the waveguide plate.

2. A microwave plasma reactor according to claim 1, wherein the waveguide plate comprises an odd number of apertures.

3. A microwave plasma reactor according to claim 2, wherein the waveguide plate comprises a prime number of apertures.

4. A microwave plasma reactor according to claim 3, wherein the waveguide plate comprises 3, 5, or 7 apertures.

5. A microwave plasma reactor according to claim 1, wherein the waveguide plate is positioned adjacent the annular dielectric window.

6. A microwave plasma reactor according to claim 1, wherein the waveguide plate is positioned between the coaxial waveguide and the annular dielectric window.

7. A microwave plasma reactor according to claim 1, wherein the annular dielectric window is positioned between the coaxial waveguide and the waveguide plate.

8. A microwave plasma reactor according to claim 1, wherein the annular dielectric window comprises two opposing surfaces through which microwaves are coupled into the plasma chamber and seals are provided on said two opposing surfaces.

9. A microwave plasma reactor according to claim 1, wherein the one or more channels comprise at least one channel configured to supply coolant.

10. A microwave plasma reactor according to claim 1, wherein the plurality of apertures are configured to couple microwaves towards the plasma chamber in a direction parallel to a central axis of the plasma chamber.

11. A microwave plasma reactor according to claim 1, wherein the central portion of the waveguide plate supports a conductive surface disposed opposite the substrate holder, wherein the conductive surface is cone-shaped.

12. A microwave plasma reactor according to claim 1, wherein a plurality of mode cancelling blocks are disposed on an inner wall of the plasma chamber, the mode cancelling blocks being spaced apart so as to be symmetrically related to the aperture configuration.

13. A microwave plasma reactor according to claim 1, wherein a ratio of an annular gap provided by the apertures in the waveguide plate to that of a diameter of the plasma chamber is in the range 1/10 to 1/50, 1/20 to 1/40, 1/25 to 1/35, or is 1/30.