Inductively coupled plasma source with multiple dielectric windows and window-supporting structure

1. A plasma reactor comprising:

an enclosure having an axis of symmetry and a workpiece support within the enclosure, said workpiece support and said enclosure defining a processing region;

said enclosure comprising a metallic portion and a dielectric portion comprising plural dielectric windows supported on said metallic portion, each of said dielectric windows extending around said axis of symmetry, said enclosure having a diameter greater than the diameter of at least one of said dielectric windows, a first one of said dielectric windows comprising a disk-shaped dielectric window and a second one of said dielectric windows comprising a cylindrical dielectric window;

plural concentric coil antennas disposed on an external side of said enclosure, respective ones of said coil antennas facing respective ones of said dielectric windows;

a cylindrical chamber body wall surrounding said cylindrical dielectric window;

an annular top gas plate comprising a peripheral portion supported on said chamber body wall, and a central opening through said annular top gas plate, wherein said disk-shaped dielectric window comprises a circular edge portion supported on an edge of said central opening;

a center gas disperser at a center of said disk-shaped dielectric window having a pair of opposing input ports and disposed to introduce gas into said processing region; and

at least a pair of opposing gas flow conduits extending radially across said disk-shaped dielectric window to said opposing input ports of said center gas disperser;

wherein first and second ones of said coil antennas are concentrically disposed over said disk-shaped dielectric window, and a third one of said coil antennas has a diameter exceeding a diameter of said cylindrical dielectric window and surrounds said cylindrical dielectric window;

said reactor further comprising a first heater layer on said disk-shaped dielectric window and comprising a radially outer portion and plural fingers extending radially inwardly from said radially outer portion; and

wherein said pair of opposing gas flow conduits are enclosed in respective ones of said plural fingers of first heater layer.

2. The plasma reactor of claim 1 wherein:

said enclosure has a diameter greater than the diameter of said disk-shaped dielectric window.

3. The plasma reactor of claim 1 wherein said cylindrical dielectric window is below a plane of said disk-shaped dielectric window.

4. The plasma reactor of claim 1 wherein said disk-shaped dielectric window has a diameter less than the diameter of said chamber body wall, and a gap separates said chamber body wall from said disk-shaped dielectric window, said peripheral portion of said top gas plate spanning said gap, and said disk-shaped dielectric window is suspended over said central opening of said top gas plate.

5. The plasma reactor of claim 1 wherein said top gas plate comprises:

plural gas supply ports;

plural gas injection orifices circularly arranged about said peripheral portion;

a first hierarchy of equal length recursive gas flow paths from a first one of said gas supply ports to said plural gas injection orifices.

6. The plasma reactor of claim 5 wherein said top gas plate further comprises:

a second hierarchy of equal length recursive gas flow paths from a second one of said gas supply ports to said pair of gas flow conduits.

7. The plasma reactor of claim 1 further comprising a second heater layer on said cylindrical dielectric window, said second heater layer comprising a grid of axial fingers.

8. The plasma reactor of claim 7 further comprising:

a cylindrical shield coaxial with an axis of symmetry and located between said first and second ones of said coil antennas and facing an inner radial portion of said disk-shaped dielectric window;

a top fan plenum in a central air flow path comprising an axial path passing through an interior of said cylindrical shield and a radial path extending across a surface of said disk-shaped dielectric window, and plural intake fans coupled to said top fan plenum.

9. The plasma reactor of claim 8 further comprising an annular air flow plate overlying said disk-shaped dielectric window and having a center air flow aperture open to said interior of said cylindrical shield and forming a top boundary of said radial path of said central air flow path.

10. The plasma reactor of claim 9 wherein said annular air flow plate confines said radial path to regions between said plural fingers of said first heater layer.

11. The plasma reactor of claim 8 wherein a side air flow passage is defined between said cylindrical dielectric window and said cylindrical chamber body wall, said plasma reactor further comprising:

a side fan plenum at an axial location between the top fan plenum and the cylindrical dielectric window, said side fan plenum open to said side air flow passage and comprising plural side fan plenum openings;

plural exhaust fans at said plural side fan plenum openings.

12. The plasma reactor of claim 11 further comprising:

a first temperature sensor at said disk-shaped dielectric window;

a second temperature sensor at said cylindrical dielectric window;

a controller coupled to said first and second temperature sensors, said controller being coupled to govern levels of power delivered respectively to said first heater layer, said second heater layer, said plural intake fans, said plural exhaust fans, and to respective ones of said coil antennas.

13. The plasma reactor of claim 12 wherein:

said controller is programmed to control the power levels delivered to said first heater layer and said plural intake fans in response to an output of said first temperature sensor; and

said controller is programmed to control the power levels delivered to said second heater layer and said plural exhaust fans in response to an output of said second temperature sensor.

14. The plasma reactor of claim 8 further comprising:

an RF power feed assembly coupled to said plural coil antennas and comprising plural conductive legs;

a ground plate extending radially and having openings through which respective ones of said legs extend, said ground plate providing a boundary between an upper region in which at least some of said plural conductive legs are distributed asymmetrically and a lower region in which said respective ones said legs are distributed symmetrically with respect to said axis of symmetry;

wherein said ground plate comprises a circular center aperture aligned with said axial path of said central air flow path.

15. The plasma reactor of claim 1 further comprising an exhaust chamber assembly, said exhaust chamber assembly comprising:

an exhaust chamber wall defining an evacuation region at a side of said workpiece support opposite said processing region, said exhaust chamber assembly having an exhaust pump port symmetrically located relative to an axis of symmetry; and

plural axial exhaust passages between said processing region and said evacuation region, and symmetrically distributed with respect to said axis of symmetry.