U.S. patent application number 14/212438 was filed with the patent office on 2014-09-18 for non-ambipolar electric pressure plasma uniformity control.
This patent application is currently assigned to Tokyo Electron Limited. The applicant listed for this patent is Tokyo Electron Limited. Invention is credited to Lee Chen, Zhiying Chen, Merritt Funk, Jianping Zhao.
Application Number | 20140273538 14/212438 |
Document ID | / |
Family ID | 51529033 |
Filed Date | 2014-09-18 |
United States Patent
Application |
20140273538 |
Kind Code |
A1 |
Chen; Lee ; et al. |
September 18, 2014 |
NON-AMBIPOLAR ELECTRIC PRESSURE PLASMA UNIFORMITY CONTROL
Abstract
This disclosure relates to a plasma processing system for
controlling plasma density near the edge or perimeter of a
substrate that is being processed. The plasma processing system may
include a plasma chamber that can receive and process the substrate
using plasma for etching the substrate, doping the substrate, or
depositing a film on the substrate. This disclosure relates to a
plasma processing system that may be configured to enable
non-ambipolar diffusion to counter ion loss to the chamber wall.
The plasma processing system may include a ring cavity coupled to
the plasma processing system that is in fluid communication with
plasma generated in the plasma processing system. The ring cavity
may be coupled to a power source to form plasma that may diffuse
ions into the plasma processing system to minimize the impact of
ion loss to the chamber wall.
Inventors: |
Chen; Lee; (Cedar Creek,
TX) ; Chen; Zhiying; (Austin, TX) ; Zhao;
Jianping; (Austin, TX) ; Funk; Merritt;
(Austin, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Tokyo Electron Limited |
Tokyo |
|
JP |
|
|
Assignee: |
Tokyo Electron Limited
Tokyo
JP
|
Family ID: |
51529033 |
Appl. No.: |
14/212438 |
Filed: |
March 14, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61799718 |
Mar 15, 2013 |
|
|
|
Current U.S.
Class: |
438/798 ;
118/723E; 156/345.1 |
Current CPC
Class: |
H01J 37/32431 20130101;
H01L 21/263 20130101; H01J 37/32697 20130101; H01J 37/32568
20130101; H01L 21/67069 20130101 |
Class at
Publication: |
438/798 ;
156/345.1; 118/723.E |
International
Class: |
H01L 21/263 20060101
H01L021/263 |
Claims
1. An apparatus for treating a substrate, comprising: a plasma
processing chamber ; a substrate holder, disposed in the processing
chamber, that can receive a substrate to be treated; a gas supply
system for supplying a gas mixture to the processing chamber; a
plasma source in the plasma processing chamber that can energize
the gas mixture into a plasma; a ring-shaped cavity disposed in the
side wall of the plasma processing chamber, above the substrate
holder, the ring-shaped cavity being in fluid communication with
the plasma processing chamber via a plurality of openings disposed
in the sidewall, the ring-shaped cavity comprising an electrode; a
DC power supply for biasing the electrode.
2. The apparatus of claim 1, wherein the plurality of openings
comprises a plurality of slits.
3. The apparatus of claim 2, wherein the plurality of openings are
substantially vertical.
4. The apparatus of claim 2, wherein the plurality of openings are
substantially horizontal.
5. The apparatus of claim 1, wherein the plurality of openings
comprises an array of holes.
6. The apparatus of claim 1, wherein the ring-shaped cavity is
configured to drive non-ambipolar diffusion across the plurality of
openings, when a DC bias is applied to the electrode.
7. The apparatus of claim 6, wherein the DC bias is a positive DC
bias.
8. The apparatus of claim 1, wherein the plurality of openings is
made of a dielectric material.
9. The apparatus of claim 8, wherein the dielectric material is
quartz.
10. The apparatus of claim 1, wherein the plasma source is a
surface wave plasma (SWP) source.
11. A method for treating a substrate, comprising: loading a
substrate onto a substrate holder disposed inside a plasma
processing chamber, the plasma processing chamber being enclosed by
one or more chamber walls and comprising: a plasma source
configured to energize plasma inside the plasma processing chamber,
the plasma processing chamber further comprising: a ring-shaped
cavity in fluid communication with the plasma processing chamber
via a plurality of openings disposed on a wall of the ring-shaped
cavity, the ring-shaped cavity comprising an electrode that is
configured to be in fluid communication with the plasma, and a
power supply for biasing the electrode; forming a first plasma
inside the plasma processing chamber using the plasma source, the
plasma having a first plasma density profile; and forming a second
plasma inside the ring-shaped cavity based, at least in part, on,
the power supply biasing the electrode, the ring-shaped cavity
being in fluid communication with the plasma processing chamber,
the second plasma enabling non-ambipolar diffusion of electrons and
ions across the plurality of openings.
12. The method of claim 13, wherein the second plasma comprises a
second plasma density profile that is different from the first
density profile.
13. The method of claim 12, wherein the non-ambipolar diffusion
comprises diffusing the electrons from the first plasma to the
second plasma and diffusing the ions from the second plasma to the
first plasma, the diffusion of the electrons and the ions being
based, at least in part, on a potential difference between the
first plasma and the second plasma.
14. An apparatus for treating a substrate, comprising: a plasma
chamber comprising a sidewall and a substrate holder that can
support the substrate; a gas distribution system that provides
gases to the plasma chamber; a power supply that can apply power to
a plasma source in the plasma chamber, such that a first plasma
region can be formed using the gases; a diffusion component in
fluid communication with the plasma chamber, the diffusion
component comprising an electrode that can enable non-ambipolar
diffusion in the plasma chamber; and a power source that can bias
the electrode to generate the second plasma region.
15. The apparatus of claim 13, wherein the bias comprises a
potential difference of at least 100 volts.
16. The apparatus of claim 13, wherein the ring-shaped cavity is
disposed inside the plasma processing chamber and around the
substrate holder.
17. The apparatus of claim 13, wherein the ring-shaped cavity is
disposed in an annular pumping duct of the plasma processing
chamber.
18. The apparatus of claim 13, wherein power source comprises a
combined power source that can provide radio frequency power,
positive direct current power, or negative direct current
power.
19. The apparatus of claim 13, wherein the combined power source
comprises a switching assembly that is in electrical communication
with the electrode and enables applying one of the following power
sources: a RF power source, a positive DC power source, or a
negative DC power source.
20. The apparatus of claim 13, further comprising a ground
electrode surrounding the substrate holder and disposed proximate
to the diffusion component.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] Pursuant to 37 C.F.R. .sctn.1.78(a)(4), this application
claims the benefit of and priority to prior filed co-pending
Provisional Application Ser. No. 61/799,718 filed Mar. 15, 2013,
which is expressly incorporated herein by reference.
FIELD OF THE INVENTION
[0002] This invention relates to semiconductor processing
technology, and more particularly, to apparatus and methods for
controlling plasma properties of a processing system for treating a
substrate.
BACKGROUND OF THE INVENTION
[0003] Plasma uniformity control during plasma processing for
treating semiconductor substrates is important to achieve
patterning structures on a substrate or controlling the amount of
material removed from or deposited on or into the substrate. A
plasma processing system may include a large distance or gap
between the plasma source and the substrate. A chamber wall of the
plasma processing may be disposed between the plasma source and the
substrate. As a result, ions and electrons in the plasma may be
influenced by the potential difference between the plasma and the
chamber wall. The ions proximate to the chamber wall may migrate
towards the chamber wall instead of the substrate. The loss of ions
to the chamber wall may alter the plasma density profile across the
substrate that may introduce processing non-uniformities that may
negatively impact semiconductor devices being built in or on the
substrate. For example, a lower plasma density at the edge of the
substrate may induce a lower etch or deposition rate at the edge of
the substrate than at the center of the substrate. Hence, systems
and methods that improve plasma density profile uniformity may be
desirable.
SUMMARY OF THE INVENTION
[0004] This disclosure relates to a plasma processing system for
controlling plasma density near the edge or perimeter of a
substrate that is being processed. The plasma processing system may
include a plasma chamber that can receive and process the substrate
using plasma for etching the substrate, doping the substrate, or
depositing a film on the substrate.
[0005] The plasma chamber may include one or more plasma sources
that can emit electromagnetic energy to ionize gas that is
delivered via a gas delivery system. The distance between the
plasma and the substrate may sufficiently confine the charted
particles in the plasma to enable a uniform plasma density. The
charged particles may be attracted to potential sources (e.g.,
chamber wall) that prevent charged particles from reaching the
chamber wall. The loss of the charge particles to a potential
boundary or chamber wall may result in plasma density
non-uniformity that leads to substrate processing
non-uniformity.
[0006] One approach to minimizing charged particle (e.g., ions)
loss may be to alter the boundary potential proximate to the
chamber wall in a way that may diffuse ions into the plasma chamber
or push ions away from the chamber wall. The boundary potential or
plasma sheath proximate to the chamber wall may be altered by
including a ring cavity surrounding a portion of the chamber wall
and that is in fluid communication with the plasma chamber via
openings between the ring cavity and the plasma chamber. The ring
cavity may include an electrode along an interior surface of the
ring cavity that may be coupled to one or more power sources (e.g.,
direct current, radio frequency, etc.). The boundary potential or
plasma sheath at the chamber wall may be altered by this
arrangement in way that generates a plasma sheath conditions that
enable the electric pressure concept by diffusing ions into the
plasma chamber. In other words, the electric pressure may be
enabled by forming a potential difference proximate to the chamber
wall that may alter the plasma density or plasma sheath proximate
to the chamber wall, such that the plasma density across the plasma
chamber may be more uniform.
[0007] In one embodiment, this electric pressure may be generated
using non-ambipolar diffusion of ions from a ring cavity or chamber
that is adjacent to the plasma chamber. The non-ambipolar diffusion
may occur between regions of different localized plasma potential.
The diffusion may include the exchange of ions and electrons
between the regions, in that the first region (e.g., inside the
plasma chamber) may diffuse electrons towards a second plasma
region and that the second region (e.g., ring cavity) may diffuse
ions towards the first plasma region in a systematic manner The
diffusion of ions and electrons in opposing directions may enable
an increase in ion density in the first region in the plasma
chamber. The diffusion of the ions may alter the rate of ion loss
from the first plasma region to the plasma chamber wall. In this
way, the plasma density exposed to the substrate may be more
uniform, particularly near the edge of the substrate, such that
substrate processing may be more uniform from the center to the
edge of the substrate.
[0008] The ring cavity may be used alone or in conjunction with one
or more additional plasma sources that may include, but are not
limited to, inductive coupling sources, microwave sources, radio
frequency sources, or a combination thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention and, together with a general description of the
invention given above, and the detailed description given below,
serve to explain the invention. Additionally, the left most
digit(s) of a reference number identifies the drawing in which the
reference number first appears.
[0010] FIG. 1 is an illustration of a representative embodiment of
a plasma processing system that shows a schematic cross-sectional
illustration of a plasma chamber that includes a non-ambipolar
plasma source.
[0011] FIG. 2 is an illustration of a representative embodiment of
a plasma processing system that shows a schematic cross-sectional
illustration of a plasma chamber that includes a non-ambipolar
plasma source and a ground ring.
[0012] FIG. 3 is an illustration of a representative embodiment of
a plasma processing system that shows a schematic cross-sectional
illustration of a plasma chamber that includes a non-ambipolar
plasma source coupled to radio frequency (RF) or alternating
current power source.
[0013] FIG. 4 is an illustration of a representative embodiment of
a plasma processing system that shows a schematic cross-sectional
illustration of a plasma chamber that includes a ring plasma source
coupled to an RF power source, a positive direct current (DC)
source, and a negative DC source.
[0014] FIG. 5 includes illustrations of ring cavity opening
embodiments of the non-ambipolar source.
[0015] FIG. 6 is an illustration of a representative embodiment of
a plasma processing system that shows a schematic cross-sectional
illustration of a plasma chamber that includes a non-ambipolar
plasma source subjacent to a substrate holder.
[0016] FIG. 7 is a flow diagram for a method for implementing a
boundary potential profile in the plasma chamber using the
non-ambipolar source.
DETAILED DESCRIPTION
[0017] The following Detailed Description refers to accompanying
drawings to illustrate exemplary embodiments consistent with the
present disclosure. References in the Detailed Description to "one
embodiment," "an embodiment," "an exemplary embodiment," etc.,
indicate that the exemplary embodiment described can include a
particular feature, structure, or characteristic, but every
exemplary embodiment does not necessarily include the particular
feature, structure, or characteristic. Moreover, such phrases are
not necessarily referring to the same embodiment. Further, when a
particular feature, structure, or characteristic is described in
connection with an embodiment, it is within the knowledge of those
skilled in the relevant art(s) to affect such feature, structure,
or characteristic in connection with other exemplary embodiments
whether or not explicitly described.
[0018] The exemplary embodiments described herein are provided for
illustrative purposes, and are not limiting. Other embodiments are
possible, and modifications can be made to exemplary embodiments
within the scope of the present disclosure. Therefore, the Detailed
Description is not meant to limit the present disclosure. Rather,
the scope of the present disclosure is defined only in accordance
with the following claims and their equivalents.
[0019] The following Detailed Description of the exemplary
embodiments will so fully reveal the general nature of the present
disclosure that others can, by applying knowledge of those skilled
in the relevant art(s), readily modify and/or adapt for various
applications such exemplary embodiments, without undue
experimentation, without departing from the scope of the present
disclosure. Therefore, such adaptations and modifications are
intended to be within the meaning and plurality of equivalents of
the exemplary embodiments based upon the teaching and guidance
presented herein. It is to be understood that the phraseology or
terminology herein is for the purpose of description and not
limitation, such that the terminology or phraseology of the present
specification is to be interpreted by those skilled in relevant
art(s) in light of the teachings herein.
[0020] FIG. 1 depicts a plasma processing system 100 for treating
substrates using plasma (not shown) that is generated in plasma
chamber 102. Plasma may be generated in the plasma chamber 102 by
ionizing gas that is provided by a gas delivery system 104 and
exposing the gas to electromagnetic energy provided by a plasma
power source 106. A vacuum system 108 may also maintain a
sub-atmospheric pressure within the plasma chamber 102 during
plasma generation.
[0021] Plasma generation (e.g., first plasma region 108) may be
done by applying electromagnetic energy to an electrically neutral
gas to cause negatively charged electrons to be released from a gas
molecule that is positively charged as result of the lost electron.
Over time, the electromagnetic energy and the increasing electron
collisions within the gas may increase the density of ionized
molecules within the gas, such that the ionized molecules may be
influenced by potential differences within the plasma chamber 102.
For example, the potential differences within the plasma chamber
102 may direct the ionize molecules towards a substrate (not
shown). The ionized molecules 110 may interact with the substrate
or treat the substrate in a way that may remove a portion of the
substrate or may be deposited unto the substrate. In this way,
patterns may be etched into the substrate or films may be deposited
onto the substrate.
[0022] Plasma density across the plasma chamber 102 may impact the
uniformity of the plasma treatment of the substrate. The plasma
density may be ion molecule 110 density within a volume within the
plasma chamber 102. Plasma processing uniformity may be impacted
when the plasma density varies across the substrate such that
higher plasma density at the center of the substrate may cause a
higher etch rate than the etch rate at the edge of the substrate.
Generally, this process non-uniformity may be the result of ion
loss to the chamber wall 112, specifically for a wide gap between
the plasma source 134 and the substrate holder 118. One approach to
resolve the non-uniformity may be to alter or generate a sheath or
boundary potential (not shown) at the chamber wall 112 that may
minimize the impact ion 108 loss to the chamber wall 112. A cross
sectional view 114 of the plasma chamber 102 illustrates one
embodiment of this approach.
[0023] In this embodiment (e.g., view 114), the sheath or boundary
potential may be altered by using a ring cavity 116 that surrounds
the plasma chamber 102 and may be in fluid communication the
processing region of the plasma chamber 102. The processing region
may be enclosed by the chamber wall 112 or any region that may be
used to treat a substrate (not shown) placed on a substrate holder
118 that may or may not be grounded 122. Although the ring cavity
116 is shown in FIG. 1 to be coupled to the chamber wall 112, the
ring cavity 116 is not required to be coupled to the chamber wall
112.
[0024] The ring cavity 116 may be used to generate a second plasma
region 120 that may provide ions 110 to the first plasma region 108
and may receive electrons 124, via non-ambipolar diffusion, from
the first plasma region 108, as indicated by the arrows on electron
124 and ion 110. The diffusion of ions 110 and electrons 124 may be
done through openings 126 between the ring cavity 116 and the
chamber wall 112. The diffusion rate may be based, at least in
part, on geometry of the openings 126, ring cavity barrier walls
128, and the power applied to an electrode (not shown) in the ring
cavity 116. The power may be supplied by a boundary power source
130 that may include, but is not limited to, a RF power source, a
DC power source, a microwave power source, or a combination thereof
In this embodiment, the plasma chamber 102 may also include a gas
distribution system 132 that provides gas that may be energized by
a plasma source 134 to form the first plasma region 108. In other
embodiments, the first plasma region 108 may be generated by one or
more plasma sources 134 that may include, but are not limited to,
inductive coupling sources, microwave sources, radio frequency
sources, or a combination thereof
[0025] FIG. 2 is a schematic cross-sectional illustration 200 of a
plasma chamber 102 that includes a non-ambipolar plasma source or
ring cavity 116 and a ground ring 202 disposed below or proximate
to the ring cavity 116. The ground ring 202 may be used in
conjunction with the ring cavity 116 to control the plasma sheath
(not shown) proximate to the chamber wall 112. The ground ring 202
may be embedded in the chamber wall 112 or inside the plasma
chamber 102 (see FIG. 4).
[0026] The geometry and magnitude of the plasma sheath (see FIG. 3)
may be used to control the non-ambipolar diffusion rate between
ring cavity and the plasma chamber 102. The non-ambipolar diffusion
rate may also be controlled based, at least in part, on the
geometry of the openings 126 and the ring cavity barrier walls 128.
The ring cavity barrier walls 128 may vary in depth 204 and height
206 and the openings 126 may also vary in opening height 208. As
the opening height 208 increases and the ring cavity barrier wall
depth 204 decreases, the ion diffusion from the ring cavity 116
into the plasma chamber 102 may increase. Likewise, the ion
diffusion may decrease with decreasing opening height 208 and
increasing ring cavity barrier wall depth 204. Although the
openings and the ring cavity barrier walls are shown to be
continuous in FIG. 2, they are not required to be continuous, as
will be discussed in the description of FIG. 5. The ring cavity
barrier walls 128 may be made of a dielectric material, such as
quartz or ceramic, that may enable potential of the ring cavity 116
to float. Hence, the ring cavity barrier walls 128 may be
electrically isolated from the electrode 210. In another
embodiment, the ring cavity barrier walls 128 may be made of metal
that may be covered by a dielectric material such as quartz or
ceramic.
[0027] The power applied to the ring cavity 116 may also impact the
ion diffusion rate. The boundary power supply 130 may be coupled to
an electrode 210 inside the ring cavity 116. In the FIG. 2
embodiment, the electrode 210 may be coupled to the interior wall
212 of the ring cavity 116. The electrode 210 may made of any
conductive material that may be used to energize any gas within the
ring cavity 116. In other embodiments, the electrode may just cover
a portion of the interior wall 212 and is not required to cover the
entire or majority of the interior wall 212, as shown in FIG. 2.
The electrode 210 may also be covered by a dielectric material (not
shown), such as, but not limited to, quartz and/or ceramic, to
prevent etching or sputtering of the electrode 210.
[0028] In this embodiment, a secondary plasma source 214 may also
be used in conjunction with the plasma source 134 to generate the
first plasma region 108. The secondary plasma source 214 may be
incorporated into the chamber wall 112 or may be located away from
the plasma chamber 102 and generate plasma remotely that may be
provided to the plasma chamber 102. In the FIG. 2 embodiment, the
secondary plasma source 214 may be disposed between the substrate
holder 118 and the plasma source 134. This configuration may be
used to control plasma density across the substrate holder 118 in
conjunction with the ring cavity 116. The secondary plasma source
214 may include, but are not limited to, inductive coupling
sources, microwave sources, radio frequency sources, or a
combination thereof
[0029] FIG. 3 is an illustration 300 of a representative embodiment
of a plasma processing system that shows a schematic
cross-sectional illustration of a plasma chamber 102 that includes
a non-ambipolar plasma source (e.g., ring cavity 116) coupled to
radio frequency (RF) or alternating current (AC) power source 302.
The illustration 300 also includes representative plasma density
profiles that may be generated by the first plasma region 108 and a
combination of the first plasma region 108 and the second plasma
region 120. The first plasma density profile 304 indicates that the
plasma density is higher at the center of the substrate holder 118
than at the edge. The first plasma density profile 304 may be
representative of using the plasma source 134 and/or the secondary
plasma source 214 without using the ring cavity 116. In contrast,
the NEP plasma density profile 306 may be generated by the
combination of the effects of the first plasma region 108 (e.g.,
plasma source 134 and/or secondary plasma source 214) and the
second plasma region 120 (e.g., ring cavity 116). As shown in FIG.
3, the NEP plasma density profile 306 is more uniform across the
plasma chamber 102. The uniformity may be driven by the ions 110
that are provided from the ring cavity 116 to the plasma chamber
102 towards the substrate holder 118. The ions 110 provided from
the second plasma region 120 may counteract the loss of ions 110
from the first plasma region 108 to the chamber wall 112. The NEP
plasma density profile 306 may be achieved by enabling the plasma
potential distribution 310 or wall double layer (W-DL) across the
plasma chamber 102. The W-DL may be adjusted to achieve an NEP
plasma density profile 306 that may be flatter than the first
plasma density profile 304. The W-DL may be adjusted up or down
(e.g., vertically) or moved expanded or contracted in a
substantially horizontal manner to achieve a relatively flatter
plasma density profile under a variety of process conditions. The
W-DL may result in an increase of plasma density near the edge of
the substrate due to the diffusion of ions 110 from the ring cavity
116. Generally, the W-DL may be implemented in various ways using
any of the embodiments, or variations of those embodiments,
disclosed in this application to achieve a uniform plasma density
profile (e.g., NEP plasma density profile 306 vs. first plasma
density profile 304) across the plasma chamber 102, or at least the
substrate holder 118.
[0030] Accordingly, the process uniformity during substrate
processing may also be more uniform when the NEP plasma density
profile 306 is achieved. One approach to controlling the ion
diffusion may be based, at least in part, on the power applied to
the ring cavity. For example, the diffusion rate and plasma density
profile may be optimized depending on the process conditions and/or
hardware that generate the first plasma region 108.
[0031] In one embodiment, the RF or AC power source 302 may be used
to alter the diffusion rate or plasma density profile based, at
least in part, on the diffusion between the first plasma region 108
and the second plasma region 120. In one specific embodiment, the
power source 302 may apply an alternating voltage between zero
volts and 400V with a frequency of up to 60 MHz. In this case, the
non-ambipolar diffusion is merely momentary and not constant as in
the DC power embodiment. This momentary diffusion may be due to the
lack of net current flow in the RF power source 302. The momentary
diffusion may due to the electron-ion mobility of the first plasma
region 108 and/or the second plasma region 120 when the plasma
potential is above zero volts. In one specific embodiment to
improve power transmission quality and control, the RF power source
302 may be coupled in parallel with a first capacitor 308 and in
series with an inductor 310, and a second capacitor 312.
[0032] In another embodiment, one approach to controlling the ion
diffusion may be based, at least in part, on the power applied to
the ring cavity. For example, the diffusion rate and plasma density
profile may be optimized depending on the process conditions and/or
hardware that generate the first plasma region 108. Being able to
alter the diffusion rate or profile by varying the power during
substrate processing or when processing different substrates using
the same plasma chamber 102 without substantial mechanical
reconfiguration may be desirable.
[0033] FIG. 4 shows a schematic cross-sectional illustration 400 of
a plasma chamber 102 that includes a ring plasma source 402 coupled
to an integrated power source 404 that enables the distribution of
a variety of power sources to the ring plasma source 402 or the
electrode 210. In one embodiment, the integrated power source 404
RF may include, but is not limited to, a RF power source 302, a
positive DC source 404, and a negative DC source 406. The positive
DC source 404 may be coupled to a first switch 408 that controls
when the positive DC power source 404 may be applied to the ring
plasma source 402. The first switch 408 may be tied to a controller
(not shown) that may open and close the circuit for a specific
duration or may open and close the first switch 408 at a certain
frequency. Further, the negative DC source 406 may be coupled to a
second switch 410 that controls when the negative DC power source
408 may be applied to the ring plasma source 402. The second switch
410 may be tied to a controller (not shown) that may open and close
the circuit for a specific duration or may open and close the
second switch 410 at a certain frequency. In one embodiment, the
plasma processing system 100 may include a controller (not shown)
that may enable the transfer of transmitted power between the
sources of the integrated power source 402 during substrate
processing or during an interval between substrate processing.
[0034] In the FIG. 4 embodiment, the ring plasma source 402 may be
embedded into the chamber wall 112 or may be substituted with the
ring cavity 116 described in previous embodiments. The ring plasma
source 402 may be electrically isolated from the chamber wall 112
that may also include a dielectric 412 (e.g., quartz or ceramic)
film or material disposed along the chamber wall 112 surface. The
ring plasma source 402 may use the integrated power source 404 or
any of the other power sources described in this application.
Likewise, the integrated power source 404 may also be used with the
other plasma chamber 102 embodiments described in this
application.
[0035] Another approach to controlling ion 110 diffusion may
include varying the geometry of the openings 126 between the ring
cavity 116 and the plasma chamber 102.
[0036] FIG. 5 includes illustrations 500 of the opening 126
embodiments that enable fluid communication between the ring cavity
116 and the plasma chamber 102 (e.g., first plasma region 108). The
openings 126 may enable ion 110 diffusion into the first plasma
region 108. The illustrations 500 in FIG. 5 include a perspective
view of the plasma chamber 102 without the ring cavity 116. The
chamber wall 112 is visible in each of the embodiments along with
different types of openings 126 that may be used enable plasma
density uniformity control over the substrate holder 118. In
general, the black lines, or objects, in FIG. 5 proximate to the
center of the chamber wall 112 may be considered openings 126 that
may enable non-ambipolar diffusion described in this
application.
[0037] In the continuous ring embodiment 502, the ring openings 504
may extend around the chamber wall 112 in a continuous manner.
Although only three ring openings 504 are shown in FIG. 5, the
number and size of the ring openings are not limited to this
embodiment within the scope of this disclosure. In fact, in other
embodiments, the ring openings 504 may be disposed in a
non-continuous manner around the chamber wall 112. For example, the
ring openings 504 may form horizontal slits that may be separated
from each other by the chamber wall 112.
[0038] In the slot opening embodiment 506, horizontal slit openings
508 may be arranged around the chamber wall 112 in a substantially
horizontal manner. However, the slit openings may also be angled
between zero and 90 degrees from the orientation shown in FIG. 5.
Horizontal slit openings 508 may also be different shapes besides
rectangular. The shapes may include, but are not limited to,
oblong, elliptical, square, triangular, and the like. Further, the
density of the horizontal slit openings 508 may also be closer
together than as shown in FIG. 5. In other embodiments, the area of
the horizontal slit openings 508 may also vary.
[0039] For example, in the hole embodiment 510, the openings 126
may include holes 512 that are arranged around the chamber wall 112
in a symmetric or asymmetric manner. As shown in FIG. 5, a pair of
holes 512 may proximate to each other and the pattern may repeat
around the chamber wall 112. However, the scope of the claim should
not be limited to this illustrated embodiment. For example, the
pair of holes 512 may be horizontally offset from each other such
that the single holes 512 may each be aligned along distinct or
unique vertical axis.
[0040] In other embodiments, the positioning of the ring cavity 116
relative to the substrate holder 118 may also vary in a variety of
ways and still be able to enable non-ambipolar diffusion. For
example, the ring cavity 116 may be positioned below or
perpendicular to the substrate holder 118.
[0041] FIG. 6 shows a schematic cross-sectional illustration 600 of
a plasma chamber 102 that includes a non-ambipolar plasma source
subjacent to the substrate holder 118. However, in other
embodiments, the orientation of the non-ambipolar source may be
placed in any direction or orientation. In FIG. 6, the subjacent
ring cavity 602 is disposed below the substrate holder 118 with the
subjacent openings 604 and subjacent walls 606 that may a part of a
horizontal plane that is perpendicular or substantially
perpendicular to the substrate holder 118. The subjacent ring
cavity 602 may operate in a similar manner as the ring cavity 116
described in this application. The subjacent ring cavity 602 may
include a subjacent electrode 608 that may be coupled to the
interior wall 610. The subjacent electrode 608 may be coupled to a
boundary power supply 130, coupled to ground 122, that may enable,
at least in part, plasma (not shown) within the subjacent ring
cavity 602. The plasma may diffuse ions 110 towards the substrate
holder 118 or towards plasma that may be generated by the plasma
source 134 and/or the secondary plasma source 214. The subjacent
ring cavity 602 may also be used in conjunction with a ground ring
202 in a similar manner as described in the description of FIG.
2.
[0042] FIG. 7 is a flow diagram 700 for a method for implementing a
boundary potential profile (e.g., plasma potential distribution
310) in the plasma chamber 102 using the non-ambipolar source
(e.g., ring cavity 116). The method may be implemented using one or
more of the hardware embodiments described in the description of
FIGS. 1-6 or any other hardware that may fall within the scope of
the claims as drafted.
[0043] At block 702, a wafer handling mechanism (not shown) may
load a substrate onto a substrate holder 118 that may be disposed
inside a plasma processing chamber 102. The plasma processing
chamber 102 may be enclosed by one or more chamber walls and may
include a plasma source 134 configured to energize plasma (e.g.,
first plasma region 108) within the chamber walls 112. The plasma
processing chamber 102 may also include a ring-shaped cavity 116 in
fluid communication with the plasma processing chamber 102 via a
plurality of openings 126 disposed on the interior wall 212. The
ring-shaped cavity 116 may also include an electrode 210 that can
be in fluid communication with plasma and may receive power from a
power supply 130 that may bias the electrode 210.
[0044] At block 704, the plasma source 134 may receive power from
the plasma power source 106 and gas from the gas delivery system
104. Based at least in part on this combination, a first plasma
region 108 may be formed inside the plasma processing chamber 102.
The first plasma region 108 may form a first plasma density profile
304 indicates that the plasma density is higher at the center of
the substrate holder 118 than at the edge.
[0045] At block 706, the ring cavity 116 may use power provided by
the boundary power supply 130 and gas from the gas delivery system
104 to form a second plasma region 120 proximate to the ring-shaped
cavity 115. In this embodiment, the ring-shaped cavity 116 may be
in fluid communication with the plasma processing chamber through
the openings 126. The interaction between the first plasma region
108 and the second plasma region 120 may enable non-ambipolar
diffusion of electrons 124 and ions 110 across the plurality of
openings 126.
[0046] The non-ambipolar diffusion may enable the formation of the
plasma potential distribution 310 or wall double layer (W-DL)
across the plasma chamber 102 as described in the description of
FIG. 3. As a result of the W-DL, the first plasma density profile
304 may be altered to form the NEP plasma density profile 306 that
is more uniform that the first density profile 304. As shown in
FIG. 3, the NEP plasma density profile 306 is different from the
first density profile 304, in that the plasma density across the
substrate holder 118 may be more uniform or flatter from the center
to the edge of the substrate holder 118.
[0047] In one embodiment, the non-ambipolar diffusion may include,
but is not limited to, the diffusion of the electrons 124 from the
first plasma region 108 to the second plasma region 120 and the
diffusion of the ions 110 from the second plasma region 120 to the
first plasma region 108. The diffusion of the electrons 124 and the
ions 110 being based, at least in part, on a potential difference
between the first plasma region 108 and the second plasma region
120. In one embodiment, the non-ambipolar diffusion direction may
be parallel or substantially parallel to the substrate holder
118.
[0048] It is to be appreciated that the Detailed Description
section, and not the Abstract section, is intended to be used to
interpret the claims. The Abstract section can set forth one or
more, but not all exemplary embodiments, of the present disclosure,
and thus, is not intended to limit the present disclosure and the
appended claims in any way.
[0049] While the present disclosure has been illustrated by the
description of one or more embodiments thereof, and while the
embodiments have been described in considerable detail, they are
not intended to restrict or in any way limit the scope of the
appended claims to such detail. Additional advantages and
modifications will readily appear to those skilled in art. The
invention in its broader aspects is therefore not limited to the
specific details, representative apparatus and method and
illustrative examples shown and described. Accordingly, departures
may be made from such details without departing from the scope of
the general inventive concept.
* * * * *