E-BEAM PLASMA SOURCE WITH PROFILED E-BEAM EXTRACTION GRID FOR UNIFORM PLASMA GENERATION
A plasma, reactor that relies on an electron beam as a plasma source employs a profiled electron beam extraction grid in an electron beam source to improve uniformity.
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This application claims the benefit of U.S. Provisional Application Ser. No. 61/549,346, filed Oct. 20, 2011 entitled E-BEAM PLASMA SOURCE WITH PROFILED E-BEAM EXTRACATION GRID FOR UNIFORM PLASMA GENERATION, by Leonid Dorf, et al.
BACKGROUNDA plasma reactor for processing a workpiece can employ an electron beam (e-beam) as a plasma source. Such a plasma reactor can exhibit non-uniform distribution of processing results (e.g., distribution of etch rate across the surface of a workpiece) due to non-uniform distribution of electron density and/or kinetic energy within the electron beam. Such non-uniformities can be distributed along a direction transverse to the beam propagation direction.
SUMMARYA plasma reactor for processing a workpiece comprises a workpiece processing chamber having a processing chamber enclosure comprising a ceiling and a side wall and an electron beam opening in the side wall, a workpiece support pedestal in the processing chamber having a workplace support surface facing the ceiling and defining a workplace processing region between the workpiece support surface and the ceiling, the electron beam opening facing the workpiece processing region. Further, there is provided an electron beam source chamber comprising an electron beam source chamber enclosure and an emission opening between the electron beam source chamber and the workpiece processing chamber facing the electron beam opening, and a profiled extraction grid is disposed in the emission opening and comprising plural grid openings each extending through the extraction grid, the grid openings having a non-uniform distribution of a number of grid openings per unit length along an axis parallel with a plane of the workpiece support surface.
In one embodiment, the non-uniform distribution of the grid openings is a decreasing function of a proximity of the grid openings to an edge of the profiled extraction grid along the axis. In another embodiment, the non-uniform distribution of the grid openings is an increasing function of a proximity of the grid openings to an edge of the profiled extraction grid along the axis. Optionally, the grid openings may be arranged in regular row and columns, the columns being distributed along the axis, the rows extending parallel to the axis, wherein the number of grid, openings in each the column varies with location of each column along the axis.
The reactor in one embodiment further comprises a voltage source coupled to the extraction grid, the extraction grid comprising a conductive material.
The non-uniform distribution of the number of grid openings per unit length in one embodiment is complementary relative to a non-uniformity in plasma distribution along the axis in the electron beam source chamber
The plasma reactor in one embodiment further comprises an electron beam source gas supply coupled to the electron beam source chamber, a workplace process gas supply coupled to the workplace processing chamber, a supply of plasma source power coupled to the electron beam source chamber and an electron beam extraction voltage supply coupled to the extraction grid.
The plasma reactor in one embodiment further comprises an acceleration grid in the emission opening and located between the extraction grid and the workpiece processing chamber. The acceleration grid comprises plural acceleration grid openings having a non-uniform distribution of a number of grid openings per unit length along the axis parallel with a plane of the workpiece support surface. In one embodiment, the non-uniform distribution of the acceleration grid openings conforms with the non-uniform distribution of the extraction grid openings.
In one embodiment, the emission opening is located
on one side of the workpiece processing chamber, and a beam dump is disposed at a side of the workpiece processing chamber opposite the one side, the beam dump comprising a conductor electrically coupled to a potential attractive to an electron beam. In one embodiment, the beam dump is electrically coupled to the processing chamber enclosure.
The profiled extraction grid in certain embodiments comprises (a) a conductive sheet having the grid openings formed therethrough, or (b) a conductive mesh.
So that the manner in which the exemplary embodiments of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. It is to be appreciated that certain well known processes are not discussed herein in order to not obscure the invention.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
DETAILED DESCRIPTIONReferring to
The plasma is generated in process region 118 by an electron beam from an electron beam source 120. The electron beam source 120 includes a plasma generation chamber 122 outside of the process chamber 100 and having a conductive enclosure 124. The conductive enclosure 124 has a gas inlet or neck 125. An electron beam source gas supply 127 is coupled to the gas inlet 125. The conductive enclosure 124 has an opening 124a facing the process region 118 through an opening 102a in the sidewall 102 of the process chamber 100.
The electron beam source 120 includes a profiled extraction grid 126 (best seen in
The electron beam source 120 further includes a pair of electromagnets 134-1 and. 134-2 aligned with the electron beam source 120, and producing a magnetic field parallel to the direction of the electron beam. The electron beam flows across the processing region 118 over the workpiece 110, and is absorbed on the opposite side of the processing region 118 by a beam dump 136. The beam dump 136 is a conductive body having a shape adapted to capture the wide thin electron beam. The beam dump may be held at a selected electrical potential, such a ground.
A negative terminal of a plasma B.C. discharge voltage supply 140 is coupled to the conductive enclosure 124, and a positive terminal of the voltage supply 140 is coupled to the extraction grid 126. In turn, a negative terminal of an electron beam acceleration voltage supply 142 is connected to the extraction grid 126, and a positive terminal of the voltage supply 142 is connected to the grounded sidewall 102 of the process chamber 100. A coil current supply 146 is coupled to the electromagnets 134-1 and 134-2. Plasma is generated within the chamber 122 of the electron beam source 120 by a B.C. gas discharge produced by power from the voltage supply 140, to produce a plasma throughout the chamber 122. This D.C. gas discharge is the main plasma source of the electron beam source 120. Electrons are extracted from the plasma in the chamber 122 through the extraction grid 126 and the acceleration grid 128 to produce an electron beam that flows into the processing chamber 100. Electrons are accelerated to energies equal to the voltage provided by the acceleration voltage supply 142. Referring to
Distribution of the plasma ion density and plasma electron density across the chamber 122 affects the uniformity of the electron beam that is introduced into the process zone 118 of the processing chamber 100. Thus, non-uniformity in plasma distribution in the chamber 122 causes non-uniformity of the electron beam propagating through the process zone 118. The distribution of electron density across the width of the beam (i.e., along an axis, labeled “X” in
In the embodiments of
In the example of an edge-dense plasma distribution in the chamber 122, a center-dense profiled extraction grid such as that illustrated in
While the illustrated embodiment involve an ordered distribution of the grid openings 126-3 in regular rows and columns arranged along an X-axis, the profiling of the number of grid openings per unit length along the X-axis may be realized without necessarily arranging the grid openings 126-3 in regular rows and column. Instead, the grid openings 126-3 may be arranged irregularly while still realising the desired profiling of the number of grid openings per unit length along the X-axis, as center-dense, or edge-dense or any other desired profile.
In one embodiment, the acceleration grid 128 has a structure identical to that of extraction grid 126. For example, the acceleration grid may be formed as a conductive sheet with openings formed therethrough and distributed in the manner of the openings 126-3 of the extraction grid of
While the main plasma source in the electron beam source 120 is a D.C. gas discharge produced by the voltage supply 140, any other suitable plasma source may be employed instead as the main plasma source. For example, the main plasma source of the electron beam source 120 may be a toroidal RF plasma source, a capacitively coupled RF plasma source, or an inductively coupled RF plasma source.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
Claims
1. A plasma reactor for processing a workpiece, comprising:
- a workpiece processing chamber having a processing chamber enclosure comprising a ceiling and a side wall and an electron beam opening in said side wall, a workpiece support pedestal in said processing chamber having a workpiece support surface facing said ceiling and defining a workpiece processing region between said workpiece support surface and said ceiling, said electron beam opening facing said workpiece processing region;
- an electron beam source chamber comprising an electron beam source chamber enclosure and. an emission opening between said electron beam source chamber and said workpiece processing chamber facing said electron beam opening; and
- a profiled grid in said emission opening and comprising plural grid, openings each extending through said profiled grid, said grid openings having a non-uniform distribution of a number of grid openings per unit length along an axis parallel with a plane of said workpiece support surface.
2. The plasma reactor of claim 1 wherein said non-uniform distribution of said grid openings is a decreasing function of a proximity of said, grid openings to an edge of said profiled grid along said axis.
3. The plasma reactor of claim 1 wherein said non-uniform distribution of said, grid openings is an increasing function of a proximity of said grid openings to an edge of said profiled grid along said axis.
4. The plasma reactor of claim 1 wherein said grid openings are arranged in regular row and columns, said columns being distributed along said axis, said rows extending parallel to said axis, wherein the number of grid openings in each said column varies with location of each column along said axis.
5. The plasma reactor of claim 1 further comprising a voltage source coupled to said profiled grid, said profiled grid comprising a conductive material.
6. The plasma reactor of claim 1 wherein said non-uniform distribution of a number of grid openings per unit length is complementary relative to a non-uniformity in plasma distribution along said axis in said electron beam source chamber.
7. The plasma reactor of claim 1 further comprising:
- an electron beam source gas supply coupled to said electron beam source chamber;
- a workpiece process gas supply coupled to said workpiece processing chamber;
- a supply of plasma source power coupled to said electron beam source chamber; and
- an electron beam extraction voltage supply coupled to said profiled grid.
8. The plasma reactor of claim 7 wherein said profiled grid comprises an extraction grid and said grid openings comprises extraction grid openings, said plasma reactor further comprising an acceleration grid in said emission opening and located between said extraction grid and said workpiece processing chamber.
9. The plasma reactor of claim 8 wherein said acceleration grid comprises plural acceleration grid openings having a non-uniform distribution of a number of grid openings per unit length along said axis parallel with a plane of said workpiece support surface.
10. The plasma reactor of claim 9 wherein said non-uniform distribution of said acceleration grid openings conforms with the non-uniform distribution of said extraction grid openings.
11. The plasma reactor of claim 1 wherein said emission opening is located on one side of said workpiece processing chamber, said plasma reactor further comprising:
- a beam dump at a side of said workpiece processing chamber opposite said one side, said beam dump comprising a conductor electrically coupled to a potential attractive to an electron beam.
12. The plasma reactor of claim 11 wherein said beam dump is electrically coupled to said processing chamber enclosure.
13. The plasma reactor of claim 1 wherein said profiled extraction grid comprises one of:
- (a) a conductive sheet having said grid openings formed therethrough; or
- (b) a conductive mesh.
14. For use in a plasma reactor that includes a workpiece processing chamber having a workpiece support pedestal in said processing chamber with a workpiece support surface, an electron beam source chamber coupled to said workpiece processing chamber through a chamber-to-chamber opening:
- a profiled extraction grid adapted for placement in said chamber-to-chamber opening and comprising plural grid openings, each of said grid openings extending through said profiled extraction grid, said grid openings having a non-uniform distribution of a number of grid openings per unit length along an axis parallel with a plane of said workpiece support surface.
15. The profiled extraction grid of claim 14 wherein said non-uniform distribution of said grid openings is a decreasing function of a proximity of said grid openings to an edge of said profiled extraction grid along said axis.
16. The profiled extraction grid of claim 14 wherein said non-uniform distribution of said grid openings is an increasing function of a proximity of said grid openings to an edge of said profiled extraction grid along said axis.
17. The profiled extraction grid of claim 14 wherein said grid openings are arranged in regular row and columns, said columns being distributed along said axis, said, rows extending parallel to said, axis, wherein the number of grid openings in each said column varies with location of each column along said axis.
18. A plasma reactor comprising:
- a workpiece processing chamber having a workpiece support pedestal in said processing chamber with a workpiece support surface;
- an electron beam source chamber and a supply of plasma source power coupled to said electron beam source chamber;
- a chamber-to-chamber opening between said workpiece processing chamber and said electron beam source chamber; and
- a profiled extraction grid in said chamber-to-chamber opening and comprising plural grid openings, each of said grid openings extending through said profiled extraction grid, said grid openings having a non-uniform distribution of a number of grid openings per unit length along an axis parallel with a plane of said workpiece support surface; and
- a beam extraction voltage supply coupled to said profiled extraction grid.
19. The plasma reactor of claim 18 wherein said non-uniform distribution of said grid openings is a decreasing function of a proximity of said grid openings to an edge of said profiled extraction grid along said axis.
20. The plasma reactor of claim 18 wherein said non-uniform distribution of said grid openings is an increasing function of a proximity of said grid openings to an edge of said profiled extraction grid along said axis.
Type: Application
Filed: Aug 27, 2012
Publication Date: Apr 25, 2013
Applicant: Applied Materials, Inc. (Santa Clara, CA)
Inventors: Leonid Dorf (San Jose, CA), Shahid Rauf (Pleasanton, CA), Kenneth S. Collins (San Jose, CA), Nipun Misra (San Jose, CA), James D. Carducci (Sunnyvale, CA), Gary Leray (Mountain View, CA), Kartik Ramaswamy (San Jose, CA)
Application Number: 13/595,252
International Classification: C23F 1/08 (20060101);