U.S. patent application number 13/595252 was filed with the patent office on 2013-04-25 for e-beam plasma source with profiled e-beam extraction grid for uniform plasma generation.
This patent application is currently assigned to Applied Materials, Inc.. The applicant listed for this patent is James D. Carducci, Kenneth S. Collins, Leonid Dorf, Gary Leray, Nipun Misra, Kartik Ramaswamy, Shahid Rauf. Invention is credited to James D. Carducci, Kenneth S. Collins, Leonid Dorf, Gary Leray, Nipun Misra, Kartik Ramaswamy, Shahid Rauf.
Application Number | 20130098552 13/595252 |
Document ID | / |
Family ID | 48135003 |
Filed Date | 2013-04-25 |
United States Patent
Application |
20130098552 |
Kind Code |
A1 |
Dorf; Leonid ; et
al. |
April 25, 2013 |
E-BEAM PLASMA SOURCE WITH PROFILED E-BEAM EXTRACTION GRID FOR
UNIFORM PLASMA GENERATION
Abstract
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.
Inventors: |
Dorf; Leonid; (San Jose,
CA) ; Rauf; Shahid; (Pleasanton, CA) ;
Collins; Kenneth S.; (San Jose, CA) ; Misra;
Nipun; (San Jose, CA) ; Carducci; James D.;
(Sunnyvale, CA) ; Leray; Gary; (Mountain View,
CA) ; Ramaswamy; Kartik; (San Jose, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Dorf; Leonid
Rauf; Shahid
Collins; Kenneth S.
Misra; Nipun
Carducci; James D.
Leray; Gary
Ramaswamy; Kartik |
San Jose
Pleasanton
San Jose
San Jose
Sunnyvale
Mountain View
San Jose |
CA
CA
CA
CA
CA
CA
CA |
US
US
US
US
US
US
US |
|
|
Assignee: |
Applied Materials, Inc.
Santa Clara
CA
|
Family ID: |
48135003 |
Appl. No.: |
13/595252 |
Filed: |
August 27, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61549346 |
Oct 20, 2011 |
|
|
|
Current U.S.
Class: |
156/345.4 |
Current CPC
Class: |
H01J 2237/06366
20130101; H01J 37/3233 20130101 |
Class at
Publication: |
156/345.4 |
International
Class: |
C23F 1/08 20060101
C23F001/08 |
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.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] 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.
BACKGROUND
[0002] A 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.
SUMMARY
[0003] A 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.
[0004] 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.
[0005] The reactor in one embodiment further comprises a voltage
source coupled to the extraction grid, the extraction grid
comprising a conductive material.
[0006] 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
[0007] 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.
[0008] 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.
[0009] In one embodiment, the emission opening is located
[0010] 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.
[0011] The profiled extraction grid in certain embodiments
comprises (a) a conductive sheet having the grid openings formed
therethrough, or (b) a conductive mesh.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] 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.
[0013] FIGS. 1A, 1B and 1C depict a plasma reactor with an electron
beam plasma source having a profiled e-beam extraction grid, of
which FIG. 1A is a side view, FIG. 1B is an enlarged view of a
portion of FIG. 1A, and FIG. 1C is a cross-sectional view taken
along lines 1C-1C of FIG. 1B, in accordance with a first
embodiment.
[0014] FIGS. 2A, 2B and 2C depict the profiled e-beam extraction
grid in alternative embodiments.
[0015] FIGS. 3A, 3B and 3C depict respective grid opening shapes in
the profiled extraction grid, in accordance with different
embodiments.
[0016] FIGS. 4A and 4B are graphical depictions of the interaction
of an edge-dense profiled extraction grid with a center-dense
electron beam source.
[0017] FIGS. 5A and 5B are graphical depictions of the interaction
of a center-dense profiled extraction grid with an edge-dense
electron beam source.
[0018] 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 DESCRIPTION
[0019] Referring to FIGS. 1A-1C, a plasma reactor includes a
process chamber 100 enclosed by a cylindrical side wall 102, a
floor 104 and a ceiling 106. A workpiece support pedestal 108
supports a workpiece 110, such as a semiconductor wafer, the
pedestal 108 being movable in the axial (e.g., vertical) direction.
A gas distribution plate 112 is integrated with or mounted on the
ceiling 106, and receives process gas from a process gas supply
114. A vacuum pump 116 evacuates the chamber through the floor 104.
A process region 118 is defined between the workpiece 110 and the
gas distribution plate 112. Within the process region 118, the
process gas is ionized to produce a plasma for processing of the
workpiece 110.
[0020] 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.
[0021] The electron beam source 120 includes a profiled extraction
grid 126 (best seen in FIG. 1C) between the opening 124a and the
plasma generation chamber 122, and an acceleration grid 128 between
the extraction grid 126 and the process region 118. The profiled
extraction grid 126 and the acceleration grid 128 may be formed as
separate conductive sheets having apertures or holes formed
therethrough or as meshes, for example. The extraction grid 126 and
the acceleration grid 128 are mounted with insulators 130, 132,
respectively, so as to be electrically insulated from one another
and from the conductive enclosure 124. However, the acceleration
grid 128 is in electrical contact with the side wall 102 of the
chamber 100. The openings 124a and 102a and the extraction and
acceleration grids 126, 128 are mutually congruent, generally, and
define a thin wide flow path for an electron beam into the
processing region 118. The width of the flow path is about the
diameter of the workpiece 110 (e.g., 100-500 mm), while the height
of the flow path is less than about two inches.
[0022] 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.
[0023] 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 FIG. 1C, the extraction grid 126 includes a frame
126-1 and a grid 126-2 with grid openings 126-3. The frame 126-1
defines a narrow aperture whose height H is relatively small (e.g.,
2-4 cm) and whose width W (e.g., on the order of the workpiece
diameter, or 300 mm or more) is generally parallel to the workpiece
support plane of the pedestal 108, so as to produce a
correspondingly thin wide electron beam.
[0024] 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 FIG. 1C) is liable to exhibit non-uniformities. The
X-axis is parallel to the workpiece support surface of the pedestal
108 and perpendicular to the propagation direction of the electron
beam. For example, the electron density distribution along this
axis may be center high (center dense) or edge-high (edge-dense).
This is because the plasma density within the chamber 122 of the
electron beam source 120 may itself exhibit non-uniform
distribution along the X-axis, which may be edge-dense or
center-dense, for example. The profiled extraction grid 126 is
configured to counteract such a non-uniformity, by having a
distribution of the grid openings 126-3 along the X-axis that is
complementary to the plasma electron (or ion) distribution along
the X-axis of plasma in the electron beam source chamber 122. For
example, the grid openings 126-3 through the profiled extraction
grid of FIG. 1C are distributed so that the number of grid openings
126-3 per unit length along the X-axis of FIG. 1C is lower at the
center and higher at each end of the profiled extraction grid. In
this example, the distribution of the grid openings 126-3 along the
X-axis has an edge-high and center low profile, which may be
referred to as an edge-dense profile. Such an edge-dense profile in
the distribution of the openings 126-3 of the extraction grid 126
is suitable for reducing or compensating for center-dense or
center-high non-uniform distribution along the X-axis of plasma
density in the chamber 122. This is because the edge-dense grid
opening profile is complementary to (or is an inverse function of)
the center-dense plasma distribution in the chamber 122.
[0025] FIG. 2A depicts an alternative embodiment of the profiled
extraction grid 126, in which the distribution of the grid openings
126-3 along the X-axis has a center-dense profile. Such a
center-dense profiled extraction grid is useful for countering an
edge-dense non-uniformity in the plasma electron (or ion)
distribution in the electron beam source chamber 122. FIGS. 2B and
2C depict other possible configurations of the profiled extraction
grid 126, in which the profile of the linear density of grid
openings has two spaced-apart density peaks (FIG. 2B) or has a
smoothly varying edge-peaked profile (FIG. 2C).
[0026] In the embodiments of FIGS. 1C, 2A, 2B and 2C, the profile
or distribution of the number of grid openings 126-3 per unit
length along the X-axis is realized by arranging the openings 126-3
in successive side-by-side columns extending parallel with a center
line (labeled "Center" in FIGS. 1C and 2A) and rows extending
parallel with the X-axis. The number of grid openings 126-3 varies
from column to column in accordance with the desired profile. The
desired profile is selected to compensate for a previously
determined non-uniformity in the plasma distribution along the
X-axis within the e-beam source chamber 122. Specifically, in the
example of a center-dense plasma distribution in the chamber 122,
an edge-dense profiled extraction grid such as that illustrated in
FIG. 1C is desired. In this example, the number of grid openings
126-3 per column is minimal at the center of the extraction grid
126 and is maximum at each edge. The number of grid openings 126-3
in each column is an increasing function of the nearness of the
column to either edge of the frame 126-1 along the X-axis or a
decreasing function of the nearness of the column to the center of
the frame 126-1 along the X-axis. The columns may be arranged
symmetrically with respect to the center line of the frame
126-1.
[0027] In the example of an edge-dense plasma distribution in the
chamber 122, a center-dense profiled extraction grid such as that
illustrated in FIG. 2A is desired. In this example, the number of
grid openings 126-3 per column is minimal at the edge of the
extraction grid 126. The number of grid openings 126-3 in each
column is an increasing function of the nearness of the column to
the center of the frame 126-1 along the X-axis or a decreasing
function of the nearness of the column to either edge of the frame
126-1 along the X-axis.
[0028] 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.
[0029] FIGS. 3A, 3B and 3C depict different embodiments of one grid
opening 126-3, including a rectangular shape (FIG. 3A), an oval
shape (FIG. 3B) and a circular shape (FIG. 3C). The grid 126 may be
formed as a metal sheet having the openings 126-3 formed through
the sheet. In other embodiments, the grid 126 and grid openings
126-3 may be formed using a wire-mesh structure, for example.
[0030] FIGS. 4A and 4B graphically depict the effect of using the
edge dense profiled extraction grid of FIG. 1C with a plasma source
having a center-dense distribution along the X-axis, The
non-uniformity or center peak exhibited by the plasma source is
compensated by the profiled extraction grid, resulting in an
electron distribution of the electron beam that has little or no
center peak along the X-axis.
[0031] FIGS. 5A and 5B graphically depict the effect of using the
center dense profiled extraction grid of FIG. 2A with a plasma
source having an edge-dense distribution along the X-axis. The
non-uniformity or peak at each edge exhibited by the plasma source
is compensated by the profiled extraction grid, resulting in an
electron distribution of the electron beam that has little or no
peak at each edge along the X-axis.
[0032] 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 FIGS. 1C, 2A, 2B or 2C. In such a
case, FIGS. 1C, 2A, 2B and 2C are representative of both the
extraction grid 126 and the acceleration grid 128. In another
embodiment, the acceleration grid 128 has a distribution of
openings that is different from that of the extraction grid 126.
For example, the acceleration grid opening distribution may be
uniform along the X-axis, rather than being profiled, while only
the extraction grid opening distribution is profiled. Or, the
reverse may be implemented, in which only the acceleration grid
opening distribution is profiled while the extraction grid opening
distribution is uniform.
[0033] 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.
[0034] 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.
* * * * *