U.S. patent application number 15/632921 was filed with the patent office on 2018-01-11 for deposition ring and electrostatic chuck for physical vapor deposition chamber.
The applicant listed for this patent is Applied Materials, Inc.. Invention is credited to Keith A. MILLER, Muhammad RASHEED, Rongjun WANG.
Application Number | 20180010242 15/632921 |
Document ID | / |
Family ID | 45994641 |
Filed Date | 2018-01-11 |
United States Patent
Application |
20180010242 |
Kind Code |
A1 |
RASHEED; Muhammad ; et
al. |
January 11, 2018 |
DEPOSITION RING AND ELECTROSTATIC CHUCK FOR PHYSICAL VAPOR
DEPOSITION CHAMBER
Abstract
Embodiments of the invention generally relate to a process kit
for a semiconductor processing chamber, and a semiconductor
processing chamber having a kit. More specifically, embodiments
described herein relate to a process kit including a deposition
ring and a pedestal assembly. The components of the process kit
work alone, and in combination, to significantly reduce their
effects on the electric fields around a substrate during
processing.
Inventors: |
RASHEED; Muhammad; (San
Jose, CA) ; MILLER; Keith A.; (Mountain View, CA)
; WANG; Rongjun; (Dublin, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Applied Materials, Inc. |
Santa Clara |
CA |
US |
|
|
Family ID: |
45994641 |
Appl. No.: |
15/632921 |
Filed: |
June 26, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15216389 |
Jul 21, 2016 |
9689070 |
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15632921 |
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13662380 |
Oct 26, 2012 |
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15216389 |
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13280771 |
Oct 25, 2011 |
8911601 |
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13662380 |
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61407984 |
Oct 29, 2010 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C 16/4585 20130101;
C23C 14/3407 20130101; C23C 14/50 20130101; C23C 14/564 20130101;
H01L 21/68735 20130101 |
International
Class: |
C23C 14/50 20060101
C23C014/50; C23C 16/458 20060101 C23C016/458; C23C 14/56 20060101
C23C014/56; H01L 21/687 20060101 H01L021/687; C23C 14/34 20060101
C23C014/34 |
Claims
1. A pedestal assembly for use in a substrate processing chamber,
comprising: a base plate; and a flangeless electrostatic chuck
coupled to the base plate; the flangeless electrostatic chuck
having a height greater than about 0.25 inches, wherein the
flangeless electrostatic chuck has a dielectric body having
electrodes embedded therein.
2. The pedestal assembly of claim 1, wherein the base plate has a
cooling conduit disposed therein.
3. The pedestal assembly of claim 1, wherein the height of the
flangeless electrostatic chuck is between about 0.30 to about 0.75
inches.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] mon This is a continuation application of U.S. patent
application Ser. No. 15/216,389, filed Jul. 21, 2016, which is a
continuation application of U.S. patent application Ser. No.
13/662,380, filed Oct. 26, 2012, which is a divisional application
of U.S. patent application Ser. No. 13/280,771, filed Oct. 25,
2011, which claims benefit of U.S. Provisional Patent Application
Ser. No. 61/407,984, filed Oct. 29, 2010, all of which are
incorporated by reference in their entireties.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] Embodiments of the invention generally relate to an
electrostatic chuck and process kit for a semiconductor processing
chamber, and a semiconductor processing chamber having a process
kit. More specifically, embodiments of the invention relate to a
process kit including at least a deposition ring used in a physical
vapor deposition chamber. Other embodiments relate to a deposition
ring for use with a flangeless electrostatic chuck and processing
chamber having the same.
Description of the Related Art
[0003] Physical vapor deposition (PVD), or sputtering, is one of
the most commonly used processes in the fabrication of electronic
devices. PVD is a plasma process performed in a vacuum chamber
where a negatively biased target is exposed to a plasma of an inert
gas having relatively heavy atoms (e.g., argon (Ar)) or a gas
mixture comprising such inert gas. Bombardment of the target by
ions of the inert gas results in ejection of atoms of the target
material. The ejected atoms accumulate as a deposited film on a
substrate placed on a substrate support pedestal disposed within
the chamber.
[0004] An electrostatic chuck (ESC) may be used to support and
retain substrates within the processing chamber during processing.
The ESC typically includes a ceramic puck having one or more
electrodes therein. A chucking voltage is applied to the electrodes
to electrostatically hold the substrate to the ESC. Further
information on ESC's can be found in U.S. Pat. No. 5909355, issued
Jun. 1, 1999.
[0005] A process kit may be disposed in the chamber to help define
a processing region in a desired region within the chamber with
respect to the substrate. The process kit typically includes a
cover ring, a deposition ring, and a ground shield. Confining the
plasma and the ejected atoms to the processing region helps
maintain other components in the chamber free from deposited
materials and promotes more efficient use of target materials, as a
higher percentage of the ejected atoms are deposited on the
substrate.
[0006] Although conventional ring and shield designs have a robust
processing history, improvements in film uniformity and throughput
are constantly desired. Existing process kit designs position
components in close proximity to the substrates during processing.
The close proximity of the process kit components can affect the
electric fields around the substrates and alter the uniformity of
the films being deposited near the edge of the substrates.
[0007] Therefore, there is a need in the art for an improved
process kit.
SUMMARY OF THE INVENTION
[0008] Embodiments of the invention generally provide a process kit
for use in a physical vapor deposition (PVD) chamber and a PVD
chamber having a process kit.
[0009] In one embodiment, a deposition ring is provided for use in
a substrate processing chamber. The deposition ring generally
includes a first cylinder, a first annular ring, a second cylinder,
and a second annular ring. The first cylinder has a first and
second end, and the second end is coupled to a portion of a top
surface of the first annular ring adjacent an inner diameter of the
first annular ring. The second cylinder has a first and second end.
The first end of the second cylinder is coupled to a portion of a
bottom surface of the first annular ring adjacent an outer diameter
of the first annular ring. The second end of the second cylinder is
coupled to a top surface of the second annular ring near an inner
diameter of the second annular ring. A distance between the first
and second ends of the first cylinder is at least a third of a
distance between the first end of the first cylinder and the bottom
surface of the second annular ring.
[0010] In another embodiment, a process kit for use in a substrate
processing chamber is provided and includes a deposition ring and a
pedestal assembly. The deposition ring generally includes a first
cylinder, a first annular ring, a second cylinder, and a second
annular ring. The first cylinder has a first and second end, and
the second end is coupled to a portion of a top surface of the
first annular ring adjacent an inner diameter of the first annular
ring. The second cylinder has a first and second end. The first end
of the second cylinder is coupled to a portion of a bottom surface
of the first annular ring adjacent an outer diameter of the first
annular ring. The second end of the second cylinder is coupled to a
top surface of the second annular ring near an inner diameter of
the second annular ring. A distance between the first and second
ends of the first cylinder is at least a third of a distance
between the first end of the first cylinder and the bottom surface
of the second annular ring. The pedestal assembly is disposed
within the substrate processing chamber. The pedestal assembly
includes a substrate support coupled to a base plate. The first
cylinder of the deposition ring has a diameter larger than a
diameter of the substrate support. The distance between the first
and second ends of the first cylinder is at least half of a
thickness of the substrate support. The deposition ring is
supported on the pedestal assembly.
[0011] In another embodiment, a ground shield is provided for use
in a substrate processing chamber. The ground shield generally
includes an outer cylindrical ring connected by a base to an inner
cylindrical ring. The outer cylindrical ring has substantially
vertical inner wall and a substantially vertical outer wall.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] 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.
[0013] FIG. 1 is a simplified cross-sectional view of a
semiconductor processing system having one embodiment of a process
kit.
[0014] FIG. 2A illustrates a partial cross-section of the process
kit of FIG. 1.
[0015] FIG. 2B illustrates a partial cross-section of another
embodiment of a process kit.
[0016] FIG. 2C illustrates a partial cross-section of another
embodiment of a process kit.
[0017] FIG. 3A illustrates a partial cross-section of an embodiment
of a ground shield.
[0018] FIG. 3B illustrates a partial top view of FIG. 3A.
[0019] FIG. 3C illustrates a partial sectional view taken through
the section line 3C--3C in FIG. 3B.
[0020] 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
disclosed in one embodiment may be beneficially utilized on other
embodiments without specific recitation.
DETAILED DESCRIPTION
[0021] Embodiments of the invention generally provide a process kit
for use in a physical deposition (PVD) chamber. In one embodiment,
the process kit has reduced effects on the electric fields within
the process cavity, which promotes greater process uniformity and
repeatability.
[0022] FIG. 1 depicts an exemplary semiconductor processing chamber
100 having one embodiment of a process kit 150 capable of
processing a substrate 105. The process kit 150 includes at least a
deposition ring 180 supported on a pedestal assembly 120, and may
also include a one-piece ground shield 160 and an interleaving
cover ring 170. In the version shown, the processing chamber 100
comprises a sputtering chamber, also called a physical vapor
deposition or PVD chamber, capable of depositing metal or ceramic
materials, such as for example, titanium, aluminum oxide, aluminum,
copper, tantalum, tantalum nitride, tantalum carbide, tungsten,
tungsten nitride, lanthanum, lanthanum oxides, titanium nitride,
nickel, and NiPt, among others. One example of a processing chamber
that may be adapted to benefit from the invention is the ALPS.RTM.
Plus and SIP ENCORE.RTM. PVD processing chambers, available from
Applied Materials, Inc. of Santa Clara, Calif. It is contemplated
that other processing chambers including those from other
manufacturers may be adapted to benefit from the invention.
[0023] The processing chamber 100 includes a chamber body 101
having upper adapters 102 and lower adapters 104, a chamber bottom
106, and a lid assembly 108 that enclose an interior volume 110 or
plasma zone. The chamber body 101 is typically fabricated by
machining and welding plates of stainless steel or by machining a
single mass of aluminum. In one embodiment, the lower adapters 104
comprise aluminum and the chamber bottom 106 comprises stainless
steel. The chamber bottom 106 generally contains a slit valve (not
shown) to provide for entry and egress of a substrate 105 from the
processing chamber 100. The lid assembly 108 of the processing
chamber 100 in cooperation with the ground shield 160 that
interleaves with the cover ring 170 confines a plasma formed in the
interior volume 110 to the region above the substrate.
[0024] The pedestal assembly 120 is supported from the chamber
bottom 106 of the chamber 100. The pedestal assembly 120 supports
the deposition ring 180 along with the substrate 105 during
processing. The pedestal assembly 120 is coupled to the chamber
bottom 106 of the chamber 100 by a lift mechanism 122 that is
configured to move the pedestal assembly 120 between an upper and
lower position. Additionally, in the lower position, lift pins (not
shown) are moved through the pedestal assembly 120 to space the
substrate from the pedestal assembly 120 to facilitate exchange of
the substrate with a wafer transfer mechanism disposed exterior to
the processing chamber 100, such as a single blade robot (not
shown). A bellows 124 is typically disposed between the pedestal
assembly 120 and the chamber bottom 106 to isolate the interior
volume 110 of the chamber body 101 from the interior of the
pedestal assembly 120 and the exterior of the chamber.
[0025] The pedestal assembly 120 generally includes a substrate
support 126 sealingly coupled to a base plate 128 which is coupled
to a ground plate 125. The substrate support 126 may be comprised
of aluminum or ceramic. The substrate support 126 may be an
electrostatic chuck, a ceramic body, a heater or a combination
thereof. In one embodiment, the substrate support 126 is an
electrostatic chuck that includes a dielectric body having
electrodes 138 embedded therein. The dielectric body is typically
fabricated from a high thermal conductivity dielectric material
such as pyrolytic boron nitride, aluminum nitride, silicon nitride,
alumina or an equivalent material. As shown in FIG. 2A, the
substrate support 126 has a bottom surface 154. The vertical
distance "V" between the bottom surface 154 and the substrate
receiving surface 127 is between about, such as between about 0.30
to about 0.75 inches (about 0.76 to about 1.91 centimeter), for
example 0.25 inches (0.64 centimeter). Returning to FIG. 1, in one
embodiment, the substrate support 126 is attached to the base plate
128 by a metal foil 112, such as an aluminum foil, which diffusion
bonds the base plate 128 and the substrate support 126.
[0026] The base plate 128 may comprise a material having thermal
properties that are suitably matched to the overlying substrate
support 126. For example, the base plate 128 can comprise a
composite of ceramic and metal, such as aluminum silicon carbide,
which provides better strength and durability than ceramic alone
and also has good heat transfer properties. The composite material
has a thermal expansion coefficient that is matched to the material
of the substrate support 126 to reduce thermal expansion mismatch.
In one version, the composite material comprises a ceramic having
pores that are infiltrated with a metal, which at least partially
fills the pores to form a composite material. The ceramic may
comprise, for example, at least one of silicon carbide, aluminum
nitride, aluminum oxide or cordierite. The ceramic may comprise a
pore volume of from about 20 to about 80 volume % of the total
volume, the remainder volume being of the infiltrated metal. The
infiltrated metal can comprise aluminum with added silicon and may
also contain copper. In another version, the composite may comprise
a different composition of a ceramic and metal, such as metal
having dispersed ceramic particles; or the base plate 128 can be
made from only a metal, such as stainless steel or aluminum. A
cooling plate (not shown) is generally disposed within the base
plate 128 to thermally regulate the substrate support 126, but may
also be disposed within the ground plate 125.
[0027] The ground plate 125 is typically fabricated from a metallic
material such as stainless steel or aluminum. The base plate 128
may be coupled to the ground plate by a plurality of connectors
137. The connectors 137 may be one of a bolt, screw, key, or any
other type of connector. The base plate 128 may be removable from
the ground plate 125 for facilitating easier replacement and
maintenance of the substrate support 126 and base plate 128.
[0028] The substrate support 126 has a substrate receiving surface
127 that receives and supports the substrate 105 during processing,
the surface 127 having a plane substantially parallel to a
sputtering surface 133 of the target 132. The substrate support 126
also has a peripheral edge 129 that terminates before an
overhanging edge of the substrate 105. The peripheral edge 129 of
the substrate support 126 has a diameter between about 275 mm to
about 300 mm. As discussed above, the substrate support 126 is
taller than conventional support, having a height greater than
about 0.25 inches (about 0.64 centimeter), such as between about
0.30 to about 0.75 inches (about 0.76 to about 1.91 centimeter).
The relatively tall height of the substrate support 126
beneficially spaces the substrate vertically from the horizontal
surfaces of a deposition ring 180 of a process kit 150, as further
described below.
[0029] The lid assembly 108 generally includes a target backing
plate 130, a target 132, and a magnetron 134. The target backing
plate 130 is supported by the upper adapters 102 when in a closed
position, as shown in FIG. 1. A ceramic ring seal 136 is disposed
between the target backing plate 130 and upper adapters 102 to
prevent vacuum leakage therebetween.
[0030] The target 132 is coupled to the target backing plate 130
and exposed to the interior volume 110 of the processing chamber
100. The target 132 provides material which is deposited on the
substrate during a PVD process. An isolator ring 198 is disposed
between the target 132, target backing plate 130, and chamber body
101 to electrically isolate the target 132 from the target backing
plate 130 and the upper adapter 102 of the chamber body 101.
[0031] The target 132 is biased with RF and/or DC power relative to
ground, e.g. the chamber body 101, by a power source 140. A gas,
such as argon, is supplied to the interior volume 110 from a gas
source 142 via conduits 144. The gas source 142 may comprise a
non-reactive gas such as argon or xenon, which is capable of
energetically impinging upon and sputtering material from the
target 132. The gas source 142 may also include a reactive gas,
such as one or more of an oxygen-containing gas, a
nitrogen-containing gas, a methane-containing gas, that are capable
of reacting with the sputtering material to form a layer on a
substrate. Spent process gas and byproducts are exhausted from the
chamber 100 through exhaust ports 146 that receive spent process
gas and direct the spent process gas to an exhaust conduit 148
having a throttle valve to control the pressure of the gas in the
chamber 100. The exhaust conduit 148 is connected to one or more
exhaust pumps 149. Typically, the pressure of the sputtering gas in
the chamber 100 is set to sub-atmospheric levels, such as a vacuum
environment, for example, gas pressures of 0.6 mTorr to 400 mTorr.
A plasma is formed from the gas between the substrate 105 and the
target 132. Ions within the plasma are accelerated toward the
target 132 and cause material to become dislodged from the target
132. The dislodged target material is deposited on the
substrate.
[0032] The magnetron 134 is coupled to the target backing plate 130
on the exterior of the processing chamber 100. One magnetron which
may be utilized is described in U.S. Pat. No. 5,953,827, issued
Sep. 21, 1999 to Or et al., which is hereby incorporated by
reference in its entirety.
[0033] Processes performed in the chamber 100 are controlled by a
controller 190 that comprises program code having instruction sets
to operate components of the chamber 100 to facilitate processing
of substrates in the chamber 100. For example, the controller 190
can comprise program code that includes a substrate positioning
instruction set to operate the pedestal assembly 120; a gas flow
control instruction set to operate gas flow control valves to set a
flow of sputtering gas to the chamber 100; a gas pressure control
instruction set to operate a throttle valve to maintain a pressure
in the chamber 100; a temperature control instruction set to
control a temperature control system (not shown) in the pedestal
assembly 120 or lower adapter 104 to set temperatures of the
substrate or lower adapters 104, respectively; and a process
monitoring instruction set to monitor the process in the chamber
100.
[0034] The process kit 150 comprises various components that can be
easily removed from the chamber 100, for example, to clean
sputtering deposits off the component surfaces, replace or repair
eroded components, or to adapt the chamber 100 for other processes.
In one embodiment, the process kit 150 includes at least the
deposition ring 180, but may also include the ground shield 160 and
the cover ring 170. In one embodiment, the cover ring 170 and
deposition ring 180 are placed about the peripheral edge 129 of the
substrate support 126.
[0035] The ground shield 160 is supported by the chamber body 101
and encircles the sputtering surface 133 of a sputtering target 132
that faces the substrate support 126. The ground shield 160 also
surrounds the peripheral edge 129 of the substrate support 126. The
ground shield 160 covers and shadows the lower adapters 104 of the
chamber 100 to reduce deposition of sputtering deposits originating
from the sputtering surface 133 of the sputtering target 132 onto
the components and surfaces behind the ground shield 160.
[0036] FIG. 2A is a partial sectional view of the process kit 150
disposed around the pedestal assembly 120, illustrating the
deposition ring 180, cover ring 170 and ground shield 160 in
greater detail. The deposition ring 180 generally includes a first
cylinder 201, a first annular ring 202, a second cylinder 203, and
a second annular ring 204. The first cylinder 201, first annular
ring 202, second cylinder 203, and second annular ring 204 may be
formed as a unitary structure. The deposition ring 180 may be
fabricated from a ceramic or metal material, such as quartz,
aluminum oxide, stainless steel, titanium or other suitable
material. The first cylinder 201 has a substantially vertical inner
wall 216 that circumscribes the peripheral edge 129 of the
substrate support 126. In one embodiment, the substrate support 126
has a diameter between 275 mm and 300 mm, such as about 280 mm to
295 mm. The first cylinder 201 has a diameter and thickness such
that an outer diameter of the first cylinder 201 does not
substantially protrude past an overhanging edge of the substrate
105. For example, the first cylinder 201 may have an inner diameter
between 280 mm and 305 mm, such as about 290 mm to 300 mm. In
another embodiment the inner wall 216 of the first cylinder may
have a diameter of about 11.615 inches to about 11.630 inches
(about 295 mm). The first cylinder 201 may have an outside diameter
of about 11.720 to about 11.890 inches (about 302 mm). The first
cylinder 201 may have a thickness between about 0.071 to about
0.625 inches (about 0.18 to about 1.59 centimeter), for example
0.29 inches (0.74 centimeter). The first cylinder 201 has a first
end 205 and a second end 206, defining the upper and lower
surfaces. The intersection of the first end 205 and the outer
diameter of the first cylinder 201 may include step or notch 209.
The first cylinder 201 has a height (e.g., distance between the
first and second ends 205, 206) less than that of the substrate
support 126. For example, the first cylinder 201 may have a height
greater than about 0.25 inches (about 0.64 centimeter), for example
between about 0.440 and about 0.420 inches (about 1.12 and about
1.07 cm), such that the first end 205 and substrate 105 are
separated by a gap 251. The gap 251 electrically isolates the
deposition ring 180 from the substrate 105 while minimizing the
possibility for material to be deposited on a back side of the
substrate 105. The notch 209 locally increases the gap 251 at the
edge of the substrate. The gap 251 has a vertical distance "X"
(e.g., distance between first end 205 and the substrate receiving
surface 127) between about 0.001 inches (about 2.54 mm) to about
0.02 inches (about 50.80 mm), for example 0.007 inches (17.78
mm).
[0037] The second end 206 of the first cylinder 201 is coupled to a
top surface 207 of the first annular ring 202 near an inner
diameter of the first annular ring 202. The vertical distance "Y"
between top surface 207 and first end 205 is between about 0.15
inches (about 0.38 centimeter) to about 1.0 inch (about 2.54 cm),
for example 0.343 inches (0.87 centimeter). Increasing the vertical
distance Y reduces the ground potential effect on the edge of the
substrate 105 and creates better deposition uniformity. A first end
220 of the second cylinder 203 is coupled to a bottom surface 208
of the first annular ring 202 near an outer diameter of the first
annular ring 202. A second end 210 of the second cylinder 203 is
coupled to a top surface 211 of the second annular ring 204 near an
inner diameter of the second annular ring 204. In one embodiment,
all vertical or near vertical surfaces of the deposition ring 180
radially outward of the second cylinder 203 are greater than 0.25
inches (0.64 centimeter) vertically below the substrate receiving
surface 127 of the substrate support 126 when the deposition ring
180 is positioned on the pedestal assembly 120.
[0038] In one embodiment, a distance between the first and second
ends 205, 206 of the first cylinder 201 is at least half of a
thickness of the substrate support 126. In another embodiment, the
first cylinder 201 constitutes at least a third of the total
thickness of the deposition ring 180 as defined between the first
end 205 of the first cylinder 201 and a bottom surface 212 of the
second annular ring 204.
[0039] In one embodiment, the bottom surface 208 of the first
annular ring 202 may rest on a ledge of the base plate 128 while
the bottom surface 212 of the second annular ring 204 maintains a
spaced apart relationship with the base plate 128, as shown in FIG.
2A. In another embodiment, a cooling conduit 152 may disposed in
the base plate 128, as shown in FIG. 2A. In another embodiment, the
bottom surface 208 of the first annular ring 202 may rest on a
ledge 217 extending radially outward from the substrate support 126
while the bottom surface 212 of the second annular ring 204
maintains a spaced apart relationship with the base plate 128, as
shown in FIG. 2B. The ledge 217 may be positioned a vertical
distance of 0.25 inches (0.64 centimeter) or greater, such as 0.40
inches (1.02 cm) or greater, from the substrate receiving surface
127 of the substrate support 126. The substrate support may have a
thickness greater than 0.25 inches (0.64 centimeter), for example
greater than 0.40 inches (1.02 cm). The thickness of the substrate
support 126 is configured so that the top surface 207 of the first
annular ring 202 is greater than 0.25 inches (0.64 centimeter), for
example greater than 0.30 inches (0.76 centimeter), vertically from
the substrate receiving surface 127 of the substrate support
126.
[0040] Returning to FIG. 2A, the top surface 211 of the second
annular ring 204 includes a raised annular inner pad 213 separated
from a raised annular outer pad 214 by a groove 215. The raised
annular inner pad 213 extends further above the top surface 211 of
the second annular ring 204 than the raised annular outer pad 214.
The raised annular outer pad 214 supports the cover ring 170. A
portion of the deposition ring 180 may be coated with an Al arc
spray.
[0041] The deposition ring 180 and the cover ring 170 cooperate
with one another to reduce formation of sputter deposits on the
peripheral edges of the substrate support 126 and the overhanging
edge of the substrate 105. The cover ring 170 has a top surface
172. The cover ring 170 encircles and at least partially covers the
deposition ring 180 to receive, and thus, shadow the deposition
ring 180 from the bulk of the sputtering deposits. The cover ring
170 is fabricated from a material that can resist erosion by the
sputtering plasma, for example, a metallic material such as
stainless steel, titanium or aluminum, or a ceramic material, such
as aluminum oxide. In one embodiment, the cover ring 170 is
composed of titanium having a purity of at least about 99.9
percent. In one embodiment, a surface of the cover ring 170 is
treated with a twin-wire aluminum arc-spray coating, such as, for
example, CLEANCOAT.TM., to reduce particle shedding from the
surface of the cover ring 170.
[0042] The cover ring 170 includes a wedge 242 coupled to an
annular body 245. The wedge 242 may include an inclined top surface
244 that is sloped radially inwards and encircles the substrate
support 126. The wedge 242 may also include a projecting bulbous
brim 250 which extends downward toward the raised annular inner pad
213. The projecting brim 250 reduces deposition of sputtering
materials on the outer upper surface of the deposition ring
180.
[0043] The cover ring 170 further comprises a footing 252 extending
downward from the inclined top surface 244 of the wedge 242, to
rest upon the raised annular outer pad 214 of the deposition ring
180. In one embodiment, a dual-stepped surface is formed between
the footing 252 and the lower surface of the projecting brim
250.
[0044] The cover ring 170 further comprises an inner cylindrical
ring 254 and an outer cylindrical ring 256 that extend downwardly
from the annular body 245 to define a gap therebetween that allows
the rings 254, 256 to interleave with the ground shield 160. The
inner and outer cylindrical rings 254 and 256 are located radially
outward of the footing 252 of the annular wedge 242. The inner
cylindrical ring 254 may have a height that is smaller than the
outer cylindrical ring 256. Additionally, both rings 254, 256
extend below the footing 252. The cover ring 170 sits as far
vertically below the substrate 105 as possible to mitigate the
effects that the cover ring 170 may have on electric fields
surrounding the substrate 105. The vertical distance "Z" between
top surface 172 and first end 205 is between about 0.15 inches
(about 0.38 centimeter) to about 1.0 inch (about 2.54 cm), for
example 0.282 inches (0.72 centimeter). Increasing the vertical
distance Z reduces the ground potential effect on the edge of the
substrate 105 and creates better deposition uniformity.
[0045] The ground shield 160 has an inner wall 258. The horizontal
distance "U" between the inner wall 258 and the edge of the
substrate 105 is between about 1.80 inches (about 4.57 cm) to 4.5
inches (11.43 cm), for example 2.32 inches (5.89 cm). A space or
gap 264 between the ground shield 160 and the cover ring 170 forms
a convoluted S-shaped pathway or labyrinth to prevent plasma from
traveling therethrough. The shape of the pathway is advantageous,
for example, because it hinders and impedes ingress of plasma
species into this region, reducing undesirable deposition of
sputtered material.
[0046] In one embodiment, the inside diameter of the ground shield
160 may be increased to space the cover ring 170 farther away from
the substrate 105, as shown in FIG. 2C. Spacing the cover ring 170
from the substrate 105 reduces the effects of the cover ring 170 on
the electric fields near the substrate 105. The increased inside
diameter of the ground shield 160 may increase the substrate 105
deposition uniformity between about 50% to about 75%. The
components of the deposition ring 180 may extend outward by a
greater radial distance to maintain optimum position of the cover
ring 170, for example, a second annular ring 218 may have a greater
radial length as compared to the second annular ring 204 such that
the inside diameter of the cover ring 170 is located radially
outward of the pedestal assembly 120.
[0047] In one embodiment, the ground shield 160 of FIG. 2C may be a
ground shield 300, as shown in FIG. 3A. The ground shield 300 has
an inner cylindrical ring 302 and an outer cylindrical ring 304.
The inner cylindrical ring 302 is connected to the outer
cylindrical ring 304 by a base 326. The outer cylindrical ring 304
has a first top surface 306, a second top surface 308, a bottom
surface 310, a first inner edge 322, and a first outer edge 324.
The first inner edge 322 meets the first outer edge 324 with a
radius between about 0.8 inches (about 2.03 cm) and 0.12 inches
(0.30 centimeter), for example, 0.10 inches (0.25 centimeter). The
first inner edge 322 is adjacent to the first top surface 306, and
the first outer edge 324 is adjacent to the bottom surface 310. The
inner cylindrical ring 302 has a top surface 314. The vertical
distance "U" between the first top surface 306 and bottom surface
310 is between about 0.16 inches (about 0.41 centimeter) to about
0.20 inches (about 0.51 centimeter), for example 0.18 inches (0.46
centimeter). The vertical distance "V" between the first top
surface 306 and the second top surface 308 is between about 0.02
inches (about 0.05 centimeter) to about 0.06 inches (about 0.15
centimeter), for example 0.04 inches (0.10 centimeter). The
vertical distance "W" between the second top surface 308 and the
bottom surface 310 is between about 0.20 inches (about 0.51
centimeter) to about 0.24 inches (about 0.61 centimeter), for
example 0.22 inches (0.56 centimeter). The outer cylindrical ring
body 312 has a thickness of between about 0.11 inches (about 0.28
centimeter) to about 0.15 inches (about 0.38 centimeter), for
example 0.13 inches (0.33 centimeter). The vertical distance "X"
between the top surface 314 of the inner cylindrical ring 302 and
the bottom surface 310 of the outer cylindrical ring 304 is between
about 6.22 inches (about 15.8 cm) to about 6.26 inches (about 15.9
cm), for example 6.24 inches (15.85 cm). The outer cylindrical ring
304 has a substantially vertical first outer wall 316 with an outer
diameter between about 17.87 inches (about 45.39 cm) to about 17.91
inches (about 45.49 cm), for example 17.89 inches (45.44 cm). The
outer cylindrical ring 304 has a second outer wall 328 and a
substantially vertical inner wall 318. The substantially vertical
inner wall 318 may be textured, for example by bead blasting or
other suitable processes that may texture the substantially
vertical inner wall 318. The substantially vertical inner wall 318
may also be sprayed with aluminum arc spray. The substantially
vertical inner wall 318 meets the first inner edge 322, and the
substantially vertical first outer wall 316 meets the first outer
edge 324. The second outer wall 328 is adjacent to the bottom
surface 310 and the second top surface 308.
[0048] FIG. 3B is partial top view of FIG. 3A, and FIG. 3C is
partial sectional view taken through the section line 3C--3C in
FIG. 3B. The ground shield 300 has a notch 340 and a bolt 342
formed in a bottom surface of the notch 344. The bolt 342 is
located in a polar array in the ground shield 300, with about 12
bolts 342 in the ground shield 300. The notch 340 may be formed by
using an end mill or other suitable tools.
[0049] The components of the process kit 150 as described work
alone and in combination to significantly reduce the effects on the
electric fields near the edge of the substrate.
[0050] 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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