U.S. patent application number 12/052431 was filed with the patent office on 2009-09-24 for tunable ground planes in plasma chambers.
Invention is credited to Mohamad Ayoub, Amit Bansal, Dale R. Du Bois, Mark A. Fodor, Karthik Janakiraman, Eller Y. Juco, Hichem M'Saad, Thomas Nowak, Juan Carlos Rocha-Alvarez, Visweswaren Sivaramakrishnan.
Application Number | 20090236214 12/052431 |
Document ID | / |
Family ID | 41087806 |
Filed Date | 2009-09-24 |
United States Patent
Application |
20090236214 |
Kind Code |
A1 |
Janakiraman; Karthik ; et
al. |
September 24, 2009 |
TUNABLE GROUND PLANES IN PLASMA CHAMBERS
Abstract
An apparatus and method are provided for controlling the
intensity and distribution of a plasma discharge in a plasma
chamber. In one embodiment, a shaped electrode is embedded in a
substrate support to provide an electric field with radial and
axial components inside the chamber. In another embodiment, the
face plate electrode of the showerhead assembly is divided into
zones by isolators, enabling different voltages to be applied to
the different zones. Additionally, one or more electrodes may be
embedded in the chamber side walls.
Inventors: |
Janakiraman; Karthik; (San
Jose, CA) ; Nowak; Thomas; (Cupertino, CA) ;
Rocha-Alvarez; Juan Carlos; (San Carlos, CA) ; Fodor;
Mark A.; (Los Gatos, CA) ; Du Bois; Dale R.;
(Los Gatos, CA) ; Bansal; Amit; (Santa Clara,
CA) ; Ayoub; Mohamad; (San Jose, CA) ; Juco;
Eller Y.; (San Jose, CA) ; Sivaramakrishnan;
Visweswaren; (Cupertino, CA) ; M'Saad; Hichem;
(Santa Clara, CA) |
Correspondence
Address: |
PATTERSON & SHERIDAN, LLP - - APPM/TX
3040 POST OAK BOULEVARD, SUITE 1500
HOUSTON
TX
77056
US
|
Family ID: |
41087806 |
Appl. No.: |
12/052431 |
Filed: |
March 20, 2008 |
Current U.S.
Class: |
204/164 ;
118/723R |
Current CPC
Class: |
C23C 16/5096 20130101;
H01J 37/32541 20130101; C23C 16/4586 20130101; C23C 16/458
20130101; H01J 37/32091 20130101; H01J 37/32165 20130101; C23C
16/505 20130101; C23C 16/503 20130101; H01J 37/32532 20130101; C23C
16/4412 20130101; C23C 16/45565 20130101 |
Class at
Publication: |
204/164 ;
118/723.R |
International
Class: |
C23C 16/00 20060101
C23C016/00; H05H 1/24 20060101 H05H001/24 |
Claims
1. An apparatus for processing a substrate, comprising: a substrate
support; one or more electrodes coupled to the substrate support; a
showerhead assembly having a face plate opposing the substrate
support; and one or more ground elements spaced radially away from
the substrate support, wherein the substrate support and the face
plate cooperatively define a processing volume and the one or more
electrodes are adapted to generate a tunable electric field inside
the processing volume having axial and radial components.
2. The apparatus of claim 1, wherein the one or more electrodes is
disposed within the substrate support.
3. The apparatus of claim 1, wherein a portion of at least one of
the one or more electrodes is angled.
4. The apparatus of claim 1, further comprising one or more tunable
circuits coupled to at least one of the one or more ground
planes.
5. The apparatus of claim 4, further comprising one or more tunable
circuits coupled to at least one of the one or more electrodes.
6. The apparatus of claim 1, further comprising a DC power source
coupled to at least one of the one or more electrodes.
7. The apparatus of claim 1, wherein the face plate is divided into
zones separated by one or more isolators.
8. The apparatus of claim 7, further comprising isolators disposed
between the one or more ground planes.
9. The apparatus of claim 1, wherein at least one of the one or
more ground planes is an RF mesh.
10. The apparatus of claim 1, wherein at least one of the one or
more ground planes is the chamber bottom.
11. An apparatus for supporting a substrate in a processing
chamber, comprising: a support surface; a thermal control element
disposed within the support surface; an electrode disposed within
the support surface, wherein the electrode has a first portion
defining a first plane and a second portion defining an angled
surface, and the angled surface intersects the first plane; and a
tuner coupled to the electrode.
12. The apparatus of claim 11, further comprising an electronic
filter coupled to the electrode.
13. The apparatus of claim 11, wherein the support surface defines
a second plane, and the first plane is substantially parallel to
the second plane.
14. The apparatus of claim 11, wherein the electrode is an RF
mesh.
15. A method of controlling the spatial distribution of a
capacitively coupled plasma, comprising: positioning a first
electrode inside a processing chamber; positioning a first ground
plane inside the processing chamber and facing the first electrode
to define a processing volume; and generating an electric field
with axial and radial components inside the processing volume by
application of RF power to the first electrode and DC power to the
first ground plane.
16. The method of claim 15, further comprising positioning a second
ground plane inside the processing chamber.
17. The method of claim 15, further comprising using the first
ground plane to provide a path to ground for the RF power and to
apply a voltage bias inside the processing volume.
18. The method of claim 16, further comprising tuning at least one
of the first and the second ground planes.
19. The method of claim 16, wherein the second ground plane has a
different shape from the first ground plane.
20. The method of claim 15, wherein the ground plane has a shape
defined by a plurality of intersecting surfaces.
Description
BACKGROUND
[0001] 1. Field
[0002] Embodiments of the present invention generally relate to an
apparatus and method for depositing or removing materials on a
substrate. More particularly, embodiments of the present invention
relate to an apparatus and method for controlling the intensity
and/or distribution of a plasma discharge in a plasma chamber.
[0003] 2. Description of the Related Art
[0004] Plasma enhanced processes, such as plasma enhanced chemical
vapor deposition (PECVD) processes, high density plasma chemical
vapor deposition (HDPCVD) processes, plasma immersion ion
implantation processes, and plasma etch processes, have become
common processes used in depositing materials on substrates and/or
removing materials from a substrate to form structures.
[0005] Plasma provides many advantages in manufacturing
semiconductor devices. For example, using plasma enables a wide
range of applications due to lowered processing temperature,
enhanced gap-fill for high aspect ratio gaps, and higher deposition
rates.
[0006] A challenge that is present in conventional plasma
processing systems is the control of the plasma to attain uniform
etching and deposition. A key factor in the etch rate and
deposition uniformity is the spatial distribution of the plasma
during processing. For example, in a conventional PECVD chamber,
which are typically parallel plate reactors, the traditional
factors affecting the spatial distribution of the plasma are
chamber pressure, distance between electrodes, and chemistry, among
other factors. While conventional control of plasma distribution in
PECVD chambers produces satisfactory results, the process may be
improved. One challenge that remains in plasma processing is
non-uniformity or uneven deposition of bulk material, such as
conductive materials, dielectric materials, or semiconductive
materials, to form a thin film on the substrate.
[0007] FIG. 1A (prior art) is a cross-sectional view of a substrate
1 illustrating one challenge caused, at least in part, by
non-uniformity in conventional plasma chambers. The substrate 1
includes a plurality of structures 5, which may be trenches, vias,
and the like, formed therein. A layer 10 of conductive, dielectric,
or semiconductive material formed thereon by a conventional plasma
process substantially covers the substrate 1 and fills the
structures 5. The substrate 1 has a dimension D.sub.1, which may be
a length or width in the case of a rectangular substrate, or an
outside diameter in the case of a round substrate. In this example,
substrate 1 is a round substrate and dimension D.sub.1 is an
outside diameter, which may be equal to about 300 mm or 200 mm.
[0008] As stated above, the layer 10 substantially covers the
substrate 1 but effectively stops at a dimension D.sub.2, which
leaves a peripheral portion of the substrate 1 having little or no
material thereon. In one example, if dimension D.sub.1 is 300 mm,
dimension D.sub.2 may be about 298 mm, which produces about a 1 mm
portion around the periphery of the substrate 1 having little or no
material thereon, which reduces device yield on the substrate 1 as
the periphery of the substrate 1 is effectively unusable. Such
defects are sometimes referred to as edge effects or plasma edge
effects.
[0009] FIG. 1B (prior art) is an exploded cross-sectional view of
substrate 1 of FIG. 1A showing a surface area 20 on the periphery
of the substrate 1 illustrating another challenge caused, at least
in part, by non-uniformity in conventional plasma chambers. The
edge region 25 is shown uncovered due to the device yield reduction
described above. In addition, conventional plasma processes may
produce region 15 along the periphery of the substrate, which may
be an area where excessive deposition and build-up of material
occurs. In subsequent processes, substrate 1 may undergo a chemical
mechanical polishing (CMP) process or other planarization or
polishing process to remove a portion of layer 10. In the
subsequent process, region 15 may create challenges since region 15
must be removed along with layer 10. As region 15 may include a
height D.sub.3 of between a few hundred angstroms (A) to thousands
of A above surface area 20 of layer 10, throughput may be
negatively impacted in the subsequent process. Additionally,
removal of region 15 may cause overpolishing of surface area 20,
which may result in damage to devices or structures formed on
substrate 1.
[0010] Therefore, there is a need for an apparatus and method to
provide enhanced control of the spatial distribution of plasma in a
plasma chamber to address the challenges described above.
SUMMARY OF THE INVENTION
[0011] Embodiments described herein generally provide methods and
apparatus for controlling the spatial distribution of a plasma in a
plasma chamber using a secondary ground plane.
[0012] One embodiment provides an apparatus for processing a
substrate, comprising a substrate support; one or more electrodes
coupled to the substrate support; a showerhead assembly having a
face plate opposing the substrate support; and one or more ground
elements spaced radially away from the substrate support, wherein
the substrate support and the face plate cooperatively define a
processing volume and the one or more electrodes are adapted to
generate a tunable electric field inside the processing volume
having axial and radial components.
[0013] Another embodiment provides an apparatus for supporting a
substrate in a processing chamber, comprising a support surface; a
thermal control element disposed within the support surface; an
electrode disposed within the support surface, wherein the
electrode has a first portion defining a first plane and a second
portion defining an angled surface, and the angled surface
intersects the first plane; and a tuner coupled to the
electrode.
[0014] Another embodiment provides a method of controlling the
spatial distribution of a capacitively coupled plasma, comprising
positioning a first electrode inside a processing chamber,
positioning a first ground plane inside the processing chamber and
facing the first electrode to define a processing volume, and
generating an electric field with axial and radial components
inside the processing volume by application of RF power to the
first electrode and DC power to the first ground plane.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] So that the manner in which the above recited features of
the present invention can be understood in detail, a more
particular description of the invention, briefly summarized above,
may be had by reference to embodiments, some of which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only typical 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.
[0016] FIG. 1A (prior art) is a cross-sectional view of a substrate
treated according to a prior art process.
[0017] FIG. 1B (prior art) is a detail view of the substrate of
FIG. 1A.
[0018] FIG. 2A is a schematic cross-sectional view of a plasma
processing chamber in accordance with one embodiment of the present
invention.
[0019] FIG. 2B is a schematic side view of the plasma processing
chamber of FIG. 2A.
[0020] FIG. 3 is a schematic side view of another embodiment of a
plasma processing chamber according to the present invention.
[0021] FIG. 4 a schematic side view of another embodiment of a
plasma processing chamber according to the present invention.
[0022] FIG. 5 is a schematic side view of another embodiment of a
plasma processing chamber according to the present invention.
[0023] FIG. 6 is a schematic side view of another embodiment of a
plasma processing chamber according to the present invention.
[0024] To facilitate understanding, identical reference numerals
have been used, wherever possible, to designate identical elements
that are common to the figures. It is also contemplated that
elements disclosed in one embodiment may be beneficially utilized
on other embodiments without specific recitation.
DETAILED DESCRIPTION
[0025] The present invention generally provides methods and
apparatus for controlling the spatial distribution of a plasma
during processing of a substrate in a plasma reactor having a
plasma generator with parallel electrodes.
[0026] FIG. 2A is a schematic cross-sectional view of one
embodiment of a plasma enhanced chemical vapor deposition (PECVD)
system 100. The PECVD system 100 generally comprises a chamber body
102 supporting a chamber lid 104 which may be attached to the
chamber body 102 by one or more fasteners, such as screws, bolts,
hinges, and the like. The chamber body 102 comprises chamber
sidewall 112 and a bottom wall 116 defining a processing volume 120
for containing a plasma 103 between a substrate support 128 and a
showerhead assembly 142. A controller 175 is coupled to the system
100 to provide process control, such as gas delivery and exhaust,
transfer functions, among other functions.
[0027] The chamber lid 104 is coupled to a gas distribution system
108 for delivering reactant and cleaning gases into the processing
volume 120 via the shower head assembly 142. The shower head
assembly 142 includes a gas inlet passage 140 which delivers gas
into the processing volume 120 from one or more gas inlets 168,
163, and 169. A remote plasma source (not shown) may be coupled
between the processing volume 120 and the gas inlets 168, 163, and
169. The PECVD system 100 may also include a liquid delivery source
150 and a gas source 172 configured to provide a carrier gas and/or
a precursor gas. A circumferential pumping channel 125 formed in
the sidewall 112 and coupled to a pumping system 164 is configured
for exhausting gases from the processing volume 120 and controlling
the pressure within the processing volume 120. A chamber liner 127,
preferably made of ceramic or the like, may be disposed in the
processing volume 120 to protect the sidewall 112 from the
corrosive processing environment. A plurality of exhaust ports 131
may be formed on the chamber liner 127 to couple the processing
volume 120 to the pumping channel 125.
[0028] A base plate 148 integrates the chamber lid 104, gas
distribution system 108 and shower head assembly 142. A cooling
channel 147 is formed in the base plate 148 to cool the base plate
148 during operation. A cooling inlet 145 delivers a coolant fluid,
such as water or the like, into the cooling channel 147. The
coolant fluid exits the cooling channel 147 through a coolant
outlet 149.
[0029] The substrate support 128 is configured for supporting and
holding a substrate 121 during processing. The substrate support
128 is adapted to move vertically within the processing volume 120,
and may additionally be configured to rotate by a drive system
coupled to a stem 122. Lift pins 161 may be included in the
substrate support 128 to facilitate transfer of substrates into and
out of the processing volume 120. In one embodiment, the substrate
support 128 includes at least one electrode 123 to which a voltage
is applied to electrostatically secure the substrate 121 thereon.
The electrode 123 is powered by a direct current (DC) power source
176 connected to the electrode 123. Although the substrate support
128 is depicted as a monopolar DC chuck, embodiments described
herein may be used on any substrate support adapted to function as
a ground plane in a plasma chamber and may additionally be a
bipolar chuck, a tripolar chuck, a DC chuck, an interdigitated
chuck, a zoned chuck, and the like.
[0030] The substrate support 128 may comprise heating elements 126,
for example resistive heating elements, to heat the substrate 121
positioned thereon to a desired process temperature. The heating
elements 126 may be coupled to an alternating current (AC) power
supply (not shown) configured to provide a voltage, such as about
208 volts to the heating elements 126.
[0031] A radio frequency (RF) power source 165 is coupled to the
showerhead assembly 142 through an impedance matching circuit 173.
The faceplate 146 of the showerhead assembly 142 and the electrode
123, which may be grounded via an electronic filter, such as a
capacitor 190, form a capacitive plasma generator. The RF source
165 provides RF energy to the showerhead assembly 142 to facilitate
generation of a capacitive plasma between the faceplate 146 of the
showerhead assembly 142 and the substrate support 128. Thus, the
electrode 123 provides both a ground path for the RF source 165 and
an electrical bias from DC power source 176 to enable electrostatic
clamping of the substrate 121.
[0032] The substrate support 128 generally comprises a body made of
a ceramic material, such as aluminum oxide (Al.sub.2O.sub.3),
aluminum nitride (AlN), silicon dioxide (SiO.sub.2), or other
ceramic materials. In one embodiment, the body of the substrate
support 128 is configured for use at a temperature in the range of
about -20.degree. C. to about 700.degree. C. The electrode 123 may
be a mesh, such as an RF mesh, or a perforated sheet of material
made of molybdenum (Mo), tungsten (W), or other material with a
substantially similar coefficient of expansion to that of the
ceramic material comprising the body of the substrate support 128.
The electrode 123 embedded in substrate support 128, together with
faceplate 146 of showerhead assembly 142, cooperatively define
processing volume 120.
[0033] The RF source 165 may comprise a high frequency radio
frequency (HFRF) power source, for example a 13.56 MHz RF
generator, and a low frequency radio frequency (LFRF) power source,
for example a 300 kHz RF generator. The LFRF power source provides
both low frequency generation and fixed match elements. The HFRF
power source is designed for use with a fixed match and regulates
the power delivered to the load, eliminating concerns about forward
and reflected power.
[0034] The electrode 123 is coupled to a conductive member 180. The
conductive member 180 may be a rod, a tube, wires, or the like, and
be made of a conductive material, such as molybdenum (Mo), tungsten
(W), or other material with a substantially similar coefficient of
expansion with other materials comprising the substrate support
128. The electrode 123 functions as a return path for RF power and
a biasing electrode to enable electrostatic chucking of the
substrate. In order to provide an electrical bias to the substrate
121, the electrode 123 is in communication with a power supply
system 182 that supplies a biasing voltage to the electrode 123.
The power supply system 182 includes DC power source 176 to supply
a DC signal to the electrode 123 and an electronic filter 186
adapted to filter voltage fluctuations between DC power source 176
and electrode 123. In one embodiment, DC power source 176 is a 24
volt DC power supply and the electrical signal may provide a
positive or negative bias.
[0035] DC power source 176 may be coupled to an amplifier 184 to
amplify the electrical signal from DC power source 176. Voltage
fluctuations are filtered by electronic filter 186 to prevent DC
power source 176 and amplifier 184 from suffering voltage spikes.
In one embodiment, filter 186 may be an inductor 188 with
capacitors 190 and 192 in parallel. The amplified and filtered
electrical signal is provided to the electrode 123 and the
substrate 121 to enable electrostatic clamping of the substrate
121. Capacitors 190 and 192 also allow electrode 123 to function as
a ground member for RF power, wherein RF power is coupled to ground
by connectors 194 and 196. Capacitors 190 and 192 prevent DC power
from DC power source 176 from going to ground, while passing RF
power. In one embodiment, the capacitors 190 and 192 may each be
0.054 micro Farad (.mu.F) capacitors at 10-15 amps and about 2000
volts. In this manner, the electrode 123 functions as a substrate
biasing electrode and a return electrode for RF power.
[0036] As described above, the electrode 123 provides a bias from
DC power source 176 and functions as a ground path for RF energy
from RF power source 165. The capacitively coupled plasma 103
generated in the processing volume 120 may be tuned by the matching
circuit 173 based on signals from the controller 175. However, the
configuration of the electrode 123, in its function as a ground
plane for RF energy, may not provide an acceptable plasma discharge
or spatial distribution. For example, the periphery of the
substrate 121 may encounter only intermittent plasma discharge,
which results in incomplete or reduced deposition at the periphery.
In another example in reference to FIGS. 1A and 1B, the periphery
of the plasma 103 may produce a region 15 along the periphery of
the substrate, which may be an area where excessive deposition and
build-up of deposited material occurs on the substrate 121.
[0037] In the embodiment illustrated by FIG. 2A, the electrode 123
may be shaped to counteract plasma edge effects described in
connection with FIGS. 1A and 1B. Angling the periphery of the
electrode 123, as shown in this embodiment, results in generation
of an electric field having radial as well as axial components
inside the processing volume 120. The potential difference between
the electrode 123 and the face plate 146 is different at different
points on the electrode 123. These potential differences result in
electrostatic forces that push charged particles from the face
plate 146 to the electrode 123, the axial component of the electric
field, and closer to or further from the center of the chamber, the
radial component of the electric field. Additionally, the electrode
123 may be tuned by adjusting DC power to the electrode based on
signals from the controller 175. In this way, the ground plane for
the plasma generator, exemplified in this embodiment by the
electrode 123, is tunable and allows for mitigation of plasma edge
effects.
[0038] FIG. 2B is another schematic side view of the plasma
processing chamber of FIG. 2A, showing the electrode 123 more
distinctly within the substrate support 128. The electric field
creates a plasma 103 by capacitive coupling of a process gas
provided to a processing volume 120 through the face plate 146. In
this embodiment, the electrode 123 features a flat portion 204 and
an angled portion 205. The flat portion 204 of the electrode 123
comprises a first portion that defines a plane, and the angled
portion 205 comprises a second portion that defines a surface. The
substrate support 128 defines a second plane. In this embodiment,
the first plane defined by the flat portion 204 and the second
plane defined by the substrate support 128 are substantially
parallel, while the first plane intersects the surface defined by
the angled portion 205. In this way, the electrode 123 exhibits a
three-dimensional structure that results in an electric field with
radial and axial components. The angled portion 205 of the
electrode 123 curves the electric field lines within the processing
volume 120 in a way that spreads plasma 103 to cover a substrate
121 disposed on the substrate support 128 more completely.
[0039] For embodiments featuring an electrode 123 with an angled
edge, as illustrated by FIG. 2B, the angled portion 205, in
cross-section, will form an angle with the flat portion 204 that is
preferably between about 90.degree. and about 170.degree., such as
about 1350. In the embodiment shown in FIG. 2B, the angled portion
205 of the electrode 123 thus forms an obtuse angle with the flat
portion 204, and is angled away from the surface of the substrate
support 128. In other embodiments, the angled portion 205 may be
angled toward the surface of the substrate support 128, or may be
curved toward or away from the surface of the substrate support
128. In some embodiments, the edges of the electrode 123 may extend
beyond the edges of a substrate disposed on the substrate support
128. In other embodiments, the edges of a substrate may extend
beyond the edges of the substrate support 128 and the electrode
123. In still other embodiments, the electrode 123 is embedded in
the substrate support 128 at a depth such that the distance between
the flat portion 204 of the electrode 123 and the surface of the
substrate support 128 is between about 5 and 10 mm. In some
embodiments, the angled portion 205 may be configured such that the
end of the angled portion 205 furthest from the flat portion 204 is
between about 25% and about 50% further from the surface of the
substrate support 128 than the flat portion 204. In other
embodiments, the portion of the substrate support 128 extending
beyond the edge of the electrode 123 may be between about 1 mm and
about 3 mm in width.
[0040] In other embodiments, portion 205 is an edge portion and
portion 204 is a central portion of electrode 123. Portion 205 may
be raised or lowered relative to portion 204 such that portions 204
and 205 define planes which are substantially parallel, but portion
205 may be closer to, or further from, the surface of substrate
support 128. In some embodiments, portion 205 may be displaced from
portion 204 between about 0.5 mm and about 2 mm. There may be a
sloped portion joining portions 204 and 205, which may form angles
with portions 204 and 205, or may form curved joints with portion
204 and 205.
[0041] Additionally, portion 205, whether angled or not with
respect to portion 204, may have a thickness that is more or less
than portion 204. The thickness of portion 205 may deviate from
that of portion 204 by up to about 0.5 mm, such that portion 205 is
up to 0.5 mm thinner than portion 204, or portion 205 is up to 0.5
mm thicker than portion 204. The thickness of either portions 204
or 205 may also be tapered. For example, portion 205 may be up to
about 3 mm. thick where it joins portion 204, and may taper to a
thickness of 0.5 mm or less at its edge. Portion 205 may likewise
be fitted with a shaped edge, such as a bead with shaped
cross-section, such as a circular bead attached to the edge of
portion 205. The bead may have any advantageous shape in cross
section, such as triangular, square, or trapezoidal.
[0042] FIG. 3 is a schematic side-view of a plasma processing
chamber according to another embodiment. In this embodiment,
chamber 300 features a zoned showerhead assembly 360. The face
plate 146 of the showerhead assembly 360 is separated into discrete
conductive zones by electrical isolators 370. In one embodiment, RF
power is applied to each zone separately by independent RF sources
165 and 330 through independent matching networks 173 and 340,
respectively, all under control of a controller 175. In another
embodiment, a single RF source provides power to each zone, or to
all zones collectively. A voltage bias is applied to the electrode
123, as described above, with the DC biasing source collectively
represented by element 350, which may include filters, such as
filter 186, and amplifiers, such as amplifier 184, as described
above, and is coupled to the electrode 123 by a connector. The
zoned showerhead assembly 360 is coupled to the independent RF
sources 165 and 330, which allows different power levels to be
applied to the zones through the independent impedance matching
networks 173 and 340 to tune the electric field inside the
processing volume 120 to control the spatial distribution of plasma
103.
[0043] FIG. 4 is a schematic side-view of a plasma processing
chamber according to another embodiment of the invention. In this
embodiment, a chamber 400 utilizes an electrode 410 embedded in the
chamber sidewall 112. The chamber wall electrode 410 is made of a
suitable conductive material, such as aluminum, and is isolated
from the sidewall 112 by an isolator 320 and from chamber lid 104
by an isolator 105. Each isolator may be made of any suitable
insulating material, but is preferably made of a material with
thermal characteristics similar to the materials of the chamber
wall. One such material is ceramic. In this embodiment, a voltage
bias is applied to the electrode 123 as above, with DC source,
amplifiers, and filters, as described above in reference to FIG.
2A, collectively represented by DC element 350, which is coupled to
the electrode 123 by a connector. A similar bias generator 420 may
be coupled to the chamber wall electrode 410. The controller 175
may be adapted to control application of RF power to the face plate
146, bias power to the electrode 123, and bias power to the chamber
wall electrode 410 to ensure adequate coverage of a substrate 121
by plasma 103.
[0044] FIG. 5 is a schematic side-view of a plasma processing
chamber 500 according to another embodiment of the invention. In
this embodiment, the chamber wall electrode 410 is not isolated
from the sidewall 112, so plasma 103 may couple directly with the
chamber wall, as well as with the electrode 123, such that the
chamber wall electrode 410, the sidewall 112, and the electrode 123
collectively serve as ground planes. DC bias applied to the chamber
wall electrode 410 is thus applied to the entire chamber wall,
causing plasma 103 to spread toward the periphery of the processing
volume 120 and cover the substrate 121. An insulator 520 is
provided to prevent electric discharges from the sidewall 112, and
an isolator 105 isolates a lid assembly 148 from the rest of the
chamber.
[0045] FIG. 6 is a schematic side-view of a plasma processing
chamber 600 according to another embodiment of the invention. In
this embodiment, two electrodes 623A and 623B are embedded within
the substrate support 128. As before, each electrode is configured
to serve as a ground plane for RF power, while applying DC voltage
bias to clamp a substrate 121 in place. Each electrode is
separately biased by DC bias generators 610 and 620, respectively.
As before, each DC bias generator comprises a DC source with
amplifiers and filters as necessary. The ability to tune the ground
planes independently provides the capability to shape the electric
field inside the processing volume 120 to control the spatial
distribution of plasma 103 to minimize or eliminate plasma edge
effects.
[0046] The embodiments described above are examples incorporating
elements of the invention in demonstrable ways. Any combination of
the above elements may be used to tune and shape plasma 103 inside
the processing volume 120 for complete coverage of a substrate 121
without edge effects. Any combination of multiple electrodes,
shaped or unshaped ground members, bias generators, isolators, and
the like, may be used. For example, multiple shaped ground members,
or a single shaped ground member with a sidewall electrode, may be
used. A zoned showerhead electrode may also be used with one or
more shaped ground members, and with one or more sidewall
electrodes.
[0047] In operation, a substrate is disposed on a substrate support
inside a plasma processing chamber according to any of the
embodiments described above. Process gases are supplied to the
processing chamber through a showerhead assembly, which comprises a
first electrode. RF power is applied to the first electrode by
coupling an RF generator through an impedance matching network to
the first electrode. The RF generator may generate high-frequency
power, such as about 13.56 MHz, or low-frequency power, such as
about 300 kHz. Application of RF power to the first electrode
creates an oscillating electric field inside the processing
chamber, and ionizes the process gases into a plasma.
[0048] The substrate is disposed on a substrate support with a
ground member embedded therein. The ground member serves as an
electrode for coupling DC power to the substrate support, and
together with the first electrode, defines a processing volume in
the processing chamber. DC power is coupled to the electrode using
connectors that run through the substrate support. DC power is
applied to the electrode, creating a voltage bias in the electrode
that results in the substrate being clamped securely to the
substrate support. An electronic filter may be provided between the
DC power source and the electrode disposed in the substrate support
so that the electrode may serve as a path to ground for the RF
power, while applying a DC voltage bias to the substrate. In this
way, the electrode in the substrate support may serve as a ground
member for the RF power. A controller may be used to adjust the
power delivered to the plasma by tuning the impedance of the match
network. The controller may also be used to adjust the power output
of the DC source to tune the electric field inside the processing
chamber. In this way, an electric field having radial as well as
axial components is generated, allowing adjustment of the spatial
distribution of the plasma toward or away from the center of the
chamber for full coverage of the substrate.
[0049] In this embodiment, the ground member is shaped to produce
the desired field properties. For example, the ground member may
feature a first portion substantially parallel to the surface of
the substrate support, and a second portion tapered from the first
portion. The first portion defines a plane, and the second portion
defines a surface that intersects the plane. A shaped ground member
may thus define a plurality of intersecting surfaces.
[0050] In an alternative embodiment, multiple ground members may be
provided. For example, a second ground member having a different
shape from the first ground member may be embedded inside the
substrate support. A controller may separately tune the bias
applied to each ground member to create the desired spatial
distribution of the plasma.
[0051] In another embodiment, a zoned showerhead electrode may be
used to generate a tunable electric field. RF power may be provided
independently through different match networks to the different
zones. A controller may be used to tune the power provided to each
zone by adjusting the impedance of the match networks. A DC voltage
bias is applied to an electrode embedded in the substrate support
to clamp the substrate and provide a path to ground for the RF
power, as discussed above. In this embodiment, tuning the power
delivery to the different zones of the showerhead electrode results
in an electric field having radial as well as axial components, and
allows control of the spatial distribution of the plasma.
[0052] In an alternative embodiment, the electric field and plasma
may be radially adjusted by providing an electrode in the sidewall
of the processing chamber. In some embodiments, the chamber wall
itself may be used as the electrode. The electrode may be grounded
or biased in addition to the electrode embedded in the substrate
support. A controller may be used to independently adjust the bias
of the substrate support electrode, the sidewall electrode, and the
power delivered to the showerhead electrode to adjust the spatial
distribution of the plasma.
[0053] 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.
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