U.S. patent application number 11/558926 was filed with the patent office on 2007-06-07 for sputtering target for titanium sputtering chamber.
This patent application is currently assigned to Applied Materials, Inc.. Invention is credited to Ilyoung (Richard) Hong, Alan Alexander Ritchie, Kathleen A. Scheible, Donny Young.
Application Number | 20070125646 11/558926 |
Document ID | / |
Family ID | 38208042 |
Filed Date | 2007-06-07 |
United States Patent
Application |
20070125646 |
Kind Code |
A1 |
Young; Donny ; et
al. |
June 7, 2007 |
SPUTTERING TARGET FOR TITANIUM SPUTTERING CHAMBER
Abstract
A sputtering target for a sputtering chamber comprises a backing
plate and titanium sputtering plate mounted on the backing plate.
The sputtering plate comprises a central cylindrical mesa having a
plane, and a peripheral inclined annular rim surrounding the
cylindrical mesa, the annular rim being inclined relative to the
plane of the cylindrical mesa by an angle of at least about
8.degree..
Inventors: |
Young; Donny; (San Jose,
CA) ; Ritchie; Alan Alexander; (Pleasanton, CA)
; Hong; Ilyoung (Richard); (San Jose, CA) ;
Scheible; Kathleen A.; (San Francisco, CA) |
Correspondence
Address: |
JANAH & ASSOCIATES, P.C.
650 DELANCEY STREET, SUITE 106
SAN FRANCISCO
CA
94107
US
|
Assignee: |
Applied Materials, Inc.
|
Family ID: |
38208042 |
Appl. No.: |
11/558926 |
Filed: |
November 12, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60739658 |
Nov 25, 2005 |
|
|
|
60788378 |
Mar 30, 2006 |
|
|
|
Current U.S.
Class: |
204/298.12 |
Current CPC
Class: |
H01J 37/3497 20130101;
H01J 37/3408 20130101; H01J 37/3423 20130101; H01J 37/34 20130101;
C23C 14/3407 20130101; H01J 37/3426 20130101; H01J 37/3435
20130101; H01J 37/32477 20130101 |
Class at
Publication: |
204/298.12 |
International
Class: |
C23C 14/00 20060101
C23C014/00 |
Claims
1. A sputtering target for a sputtering chamber, the sputtering
target comprising: (a) a backing plate; and (b) a titanium
sputtering plate mounted on the backing plate, the sputtering plate
comprising: (i) a central cylindrical mesa having a plane; and (ii)
a peripheral inclined annular rim surrounding the cylindrical mesa,
the annular rim being inclined relative to the plane of the
cylindrical mesa by an angle of at least about 8.degree..
2. A target according to claim 1 wherein the annular rim of the
sputtering plate is inclined at an angle of from about 10.degree.
to about 20.degree..
3. A target according to claim 1 further comprising an inclined
sidewall surrounding the annular rim, the sidewall being inclined
relative to the plane of the cylindrical mesa by an angle of at
least about 60.degree..
4. A target according to claim 1 wherein sidewall is inclined at an
angle of from about 75.degree. to about 85.degree..
5. A target according to claim 1 wherein the titanium sputtered
plate comprises titanium having a purity of at least about
99.9%.
6. A target according to claim 1 wherein the backing plate
comprises a peripheral ledge.
7. A target according to claim 1 wherein the backing plate
comprises an alloy composed of copper and zinc.
8. A target according to claim 7 wherein the backing plate
comprises an alloy composed of copper in an amount of from about 59
to about 62 wt %, and zinc in an amount of from about 38% to about
41%.
Description
CROSS-REFERENCE
[0001] This application claims priority to U.S. Provisional
Application Serial No. 60/739,658, filed Nov. 25, 2005; and U.S.
Provisional Application No. 60/788,378, filed Mar. 30, 2006; both
of which are incorporated herein by reference in their
entireties.
BACKGROUND
[0002] Embodiments of the present invention relate to a target and
process kit components for a titanium sputtering chamber.
[0003] In the manufacture of integrated circuits and displays, a
substrate, such as a semiconductor wafer or display panel, is
placed in a process chamber and processing conditions are set in
the chamber to deposit or etch material on the substrate. A typical
chamber comprises an enclosure wall that encloses a plasma zone, a
gas supply to provide a process gas in the chamber, a gas energizer
to energize gas to process the substrate, a substrate support to
support a substrate, and a gas exhaust to maintain a gas pressure
in the chamber. Such chambers can include, for example, sputtering
or PVD, CVD, and etching chambers. In a magnetron PVD sputtering
chambers, a target is sputtered in a magnetic field causing
sputtered target material to deposit on a substrate facing the
target. In the sputtering process, a process gas comprising an
inert or reactive gas is supplied into the chamber, and the target
is electrically biased while the substrate maintained at an
electrical floating potential to generate charged plasma species in
the chamber which sputter the target.
[0004] In one type of process, a sputtering chamber is used to
deposit a layer comprising titanium or a titanium compound on a
substrate for a variety of applications. For example, a sputtered
titanium layer can be used as a barrier layer to inhibit the
diffusion of an overlying material into the layers below the
barrier layer. The titanium layers can be used by themselves, or in
combination with other layers, for example, Ti/TiN stacked layers
are often used as liner barrier layers, and to provide contacts to
the source and drain of a transistor. In another example, a
titanium layer is deposited on a silicon wafer and portions of the
titanium layer in contact with the silicon are converted to
titanium silicide layers by annealing. In another configuration,
the diffusion barrier layer below a metal conductor, includes a
titanium oxide layer formed by sputter depositing titanium on the
substrate and then transferring the substrate to an oxidizing
chamber to oxidize the titanium by heating it in an oxygen
environment to form titanium oxide. Titanium oxide can also be
deposited by introducing oxygen gas into the chamber while titanium
is being sputtered. Similarly, titanium nitride can be deposited by
reactive sputtering methods by introducing a nitrogen containing
gas into the chamber while sputtering titanium.
[0005] Conventional sputtering targets which are shaped as
right-cylinders have several problems when used for titanium
sputtering. One problem arises because titanium material sputtered
from the vertical sidewalls of such a target accumulate on adjacent
surfaces of the chamber. The accumulated sputtered material
eventually flakes off with process heating/cooling cycles to fall
upon and contaminate the substrate. Also, in certain chambers, a
dielectric isolator ring is located adjacent to the target to
isolate the electrical potential applied to the target from the
potential applied to the chamber walls and/or support. However, the
sputtered titanium material accumulating on the dielectric isolator
eventually forms a continuous film that can cause electrical shorts
between the chamber walls and target. Another problem arises
because conventional targets made by bonding a sputtering material
plate onto a stainless steel backing plate, often debond from the
backing plate due to thermal expansion stresses. Thus, it is
desirable to have a sputtering target that provides reduced
sidewall sputtering and which does not easily debond.
[0006] The sputtering chamber also includes a process kit
comprising components arranged about the substrate support and
chamber sidewalls to receive sputtering deposits which would
otherwise accumulate on the side surfaces of the support or on the
backside surface of the substrate. The process kit can include, for
example, a deposition ring, cover ring, and shadow ring, located
about the periphery of the substrate. The process kit can also
include shields and liners which serve as a receiving surface to
receive sputtering deposits which would otherwise deposit on the
sidewalls of the chamber. The process kit components also reduce
erosion of the internal chamber structures by the energized plasma.
The components are also often designed to be easily removable for
cleaning of accumulated deposits.
[0007] However, conventional process kit components often do not
allow sufficient amounts of sputtered deposits to accumulate
thereon. The process deposits often flake off due to thermal
stresses and contaminate the substrate after a limited number of
process cycles. Increasing the amount of sputtered deposits that
can accumulate on these components allows a greater number of
substrates to be sequentially processed in the chamber without
shutting down the chamber to dismantle the components for cleaning
them. Each time the chamber requires cleaning, the resultant
downtime of the chamber increases the cost of processing
substrates. Thus it is desirable to have process chamber components
that maximize the amount of time the chamber can be operated
without shutting down the chamber, especially for titanium
sputtering processes. Also, the chamber components should be able
to receive sputtered deposits without causing the components to
stick to one another or to other components which can result in
damage to the substrate or components when they are attempted to be
removed from the support.
[0008] Thus it is desirable to have a sputtering target that limits
the formation and deposition of sputtered material from its
sidewalls on adjacent chamber surfaces. It is further desirable to
have process kit components that minimize chamber down time so that
the chamber can be operated to sputter deposit material on a
greater number of substrates without shutting down the chamber to
clean the components. It is further desirable to have process kit
components that can allow deposits to accumulate on their surfaces
without causing sticking of the components to each other or to the
substrate.
SUMMARY
[0009] A sputtering target for a sputtering chamber comprises a
backing plate and titanium sputtering plate mounted on the backing
plate. The sputtering plate comprises a central cylindrical mesa
having a plane, and a peripheral inclined annular rim surrounding
the cylindrical mesa, the annular rim being inclined relative to
the plane of the cylindrical mesa by an angle of at least about
8.degree..
[0010] A deposition ring is also provided for placement about a
substrate support in a substrate processing chamber that has a
substrate receiving surface with a plane and a peripheral wall that
terminates before an overhanging edge of the substrate. The
deposition ring comprises an annular band having an exposed surface
surrounding the peripheral wall of the support, the exposed surface
comprising a surface roughness average of 150.+-.50 microinches.
The annular band comprises an inner lip extending transversely from
the annular band, the inner lip being substantially parallel to the
peripheral wall of the support and terminating below the
overhanging edge of the substrate. The annular band also has a
raised ridge that is substantially parallel to the plane of the
receiving surface of the substrate support. The annular band also
has an inner open channel between the inner lip and the raised
ridge, the inner open channel extending at least partially below
the overhanging edge of the substrate, and a ledge radially outward
of the raised ridge.
[0011] A cover ring comprises an annular plate comprising a footing
which rests on a surface about the substrate support, and an
exposed surface that is substantially parallel to the receiving
surface of the substrate support, the exposed surface comprising a
surface roughness average of 175.+-.75 microinches. The annular
plate also comprises first and second cylindrical walls that extend
downwardly from the annular plate. The first cylindrical wall has a
first length that is shorter than a second length of the second
cylindrical wall by at least about 10%.
[0012] A ring assembly for placement about a substrate support in a
sputtering chamber, comprises the deposition ring and the cover
ring.
[0013] A shield assembly is capable of encircling a sputtering
plate of a sputtering target. The shield comprises an upper shield
comprising a support lip, and an annular band having a first
cylindrical surface with a first diameter sized to encircle the
sputtering plate of the sputtering target, a second cylindrical
surface with a second diameter sized smaller than the first
diameter, and a sloped surface between the first and second
surfaces. The lower shield comprises a support ledge, a cylindrical
outer band extending below the upper shield, a base plane extending
radially inward from the bottom end of the cylindrical outer band,
and a cylindrical inner band joined to the base plate and at least
partially surrounding the substrate support.
DRAWINGS
[0014] These features, aspects and advantages of the present
invention will become better understood with regard to the
following description, appended claims, and accompanying drawings,
which illustrate examples of the invention. However, it is to be
understood that each of the features can be used in the invention
in general, not merely in the context of the particular drawings,
and the invention includes any combination of these features,
where:
[0015] FIG. 1 is a schematic sectional side view of a sputtering
chamber showing a target and process kit components comprising a
cover ring, deposition ring and shield assembly;
[0016] FIG. 2 is a sectional side view of a titanium sputtering
target suitable for the chamber of FIG. 1;
[0017] FIG. 3 is a detail (3) of the sectional side view of the
sputtering target shown in FIG. 2; and
[0018] FIG. 4 is a sectional side view of the deposition ring,
cover ring and lower shield around a substrate support.
DESCRIPTION
[0019] An example of a sputtering process chamber 100 capable of
processing a substrate 104 is shown in FIG. 1. The chamber 100
comprises enclosure walls 108 that enclose a plasma zone 106 and
include sidewalls 116, a bottom wall 120, and a ceiling 124. The
chamber 100 can be a part of a multi-chamber platform (not shown)
having a cluster of interconnected chambers connected by a robot
arm mechanism that transfers substrates 104 between the chambers
106. In the version shown, the process chamber 100 comprises a
sputtering chamber, also called a physical vapor deposition or PVD
chamber, which is capable of sputter depositing titanium on a
substrate 104. However, the chamber 100 can also be used for other
purposes, such as for example, to deposit aluminum, copper,
tantalum, tantalum nitride, titanium nitride, tungsten or tungsten
nitride; thus, the present claims should not be limited to the
exemplary embodiments described herein to illustrate the
invention.
[0020] The chamber 100 comprises a substrate support 130 to support
the substrate 104 which comprises a pedestal 134. The pedestal 134
has a substrate receiving surface 138 that receives and supports
the substrate 104 during processing, the surface 138 having a plane
substantially parallel to a sputtering surface 135 of an overhead
sputtering target 136. The support 130 also has a peripheral wall
139 that terminates before an overhanging edge of the substrate
104, as shown in FIG. 4. The support 130 can also include an
electrostatic chuck 132 to electrostatically hold the substrate 104
and/or a heater (not shown), such as an electrical resistance
heater or heat exchanger. In operation, a substrate 104 is
introduced into the chamber 100 through a substrate loading inlet
(not shown) in the sidewall 116 of the chamber 100 and placed on
the substrate support 130. The support 130 can be lifted or lowered
to lift and lower the substrate onto the support 130 during
placement of a substrate 104 on the support 130. The pedestal 134
can be maintained at an electrically floating potential or grounded
during plasma operation.
[0021] The sputtering surface 135 of the sputtering target 136
facing the substrate 104, comprises the titanium material to be
sputtered onto the substrate 104. Referring to FIGS. 2 and 3, the
sputtering target 136 comprises a titanium sputtering plate 137
mounted on a backing plate 141. In one version, the titanium
sputtering plate 137 comprises a central cylindrical mesa 143
having the sputtering surface 135 that forms a plane that is
parallel to the plane of the substrate 104. A peripheral inclined
annular rim 145 surrounds the cylindrical mesa 143. The annular rim
145 is inclined relative to the plane of the cylindrical mesa 143
by an angle .alpha. of at least about 8.degree., for example, from
about 10.degree. to about 20.degree., for example, 15.degree.. A
peripheral inclined sidewall 146 having a step 133 surrounds the
annular rim 145. The peripheral sidewall 146 is inclined relative
to the plane of the cylindrical mesa 143 by an angle .beta. of at
least about 60.degree., for example, from about 75.degree. to about
85.degree.. The step 133 occurs between a slightly protruding first
slope 129 and a slightly recessed second slope 131, the step 133
joining the surfaces 129, 131 at a cutback angle of about 35. The
complex shape of the peripheral annular rim 145 and sidewall 146
that is adjacent to the upper shield 147 forms a convoluted gap 149
that serves as a labyrinth that impedes the passage of sputtered or
plasma species through the gap 149. The titanium sputtering plate
137 comprises titanium in a purity of at least about 99.9%, or even
at least about 99.99% purity.
[0022] The backing plate 141 comprises a support surface 151 to
support the sputtering plate 137 and has a peripheral ledge 154
that extends beyond the radius of the sputtering plate 137. The
peripheral ledge 154 comprises an outer footing 155 that rests on
an isolator 144 in the chamber 100, as shown in FIG. 1. The
isolator 144 electrically isolates and separates the backing plate
141 from the chamber 100, and is typically a ring made from a
ceramic material, such as aluminum oxide. The peripheral ledge 154
is shaped to inhibit the flow or migration of sputtered material
and plasma species through the gap 149 between the target 136 and
the isolator 144, to impede the penetration of low-angle sputtered
deposits into the gap 149. The backing plate 141 can be made from
stainless steel or aluminum. In a preferred version, the backing
plate 141 comprises an alloy composed of copper and zinc, which
comprises for example, copper in an amount of from about 59 to
about 62 wt % and zinc in an amount of from about 38% to about
41%.
[0023] The sputtering plate 137 is mounted on the backing plate 141
by diffusion bonding by placing the two plates 137, 141 on each
other and heating the plates to a suitable temperature, typically
at least about 200.degree. C. Also, the peripheral edge 154 of the
target 136 can be coated with a protective coating, for example, a
twin-wire arc sprayed aluminum coating 157. Before coating, the
peripheral edge 154 is degreased and ground with a silicon carbide
disc to achieve a roughness of 200 to 300 microinches. The coating
157 extends to cover the peripheral sidewall 146 of the sputtering
plate 137 and the peripheral ledge 154 of the backing plate 141.
The coating 151 has a final surface roughness of 700.+-.200
microinches, and a thickness of from about 5 to about 10 mils. The
coating 157 protects the edges of the target 136 provides better
adhesion of the sputtered material and reduces flaking of the
material from these surfaces.
[0024] Referring back to FIG. 1, the target 136, support 130, and
upper shield 147 are electrically biased relative to one another by
a power supply 148. The target 136, upper shield 147, support 130,
and other chamber components connected to the target power supply
148 operate as a gas energizer 152 to form or sustain a plasma of
the sputtering gas. The gas energizer 152 can also include a source
coil (not shown) that is powered by the application of a current
through the coil. The plasma formed in the plasma zone 106
energetically impinges upon and bombards the sputtering surface 135
of the target 136 to sputter material off the surface 135 onto the
substrate 104.
[0025] The sputtering gas is introduced into the chamber 100
through a gas delivery system 160 provides gas from a gas supply
162 via conduits 164 having gas flow control valves 166, such as a
mass flow controllers, to pass a set flow rate of the gas
therethrough. The gases are fed to a mixing manifold (also not
shown) in which the gases are mixed to form a desired process gas
composition and fed to a gas distributor 168 having gas outlets in
the chamber 100. The process gas source 169 may comprise a
non-reactive gas, such as argon or xenon, which is capable of
energetically impinging upon and sputtering material from a target.
The process gas source 169 may also include a reactive gas, such as
one or more of an oxygen-containing gas and a nitrogen-containing
gas, that are capable of reacting with the sputtered material to
form a layer on the substrate 104. Spent process gas and byproducts
are exhausted from the chamber 100 through an exhaust 170 which
includes exhaust ports 172 that receive spent process gas and pass
the spent gas to an exhaust conduit 174 having a throttle valve 176
to control the pressure of the gas in the chamber 100. The exhaust
conduit 174 is connected to one or more exhaust pumps 178.
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 1 mtorr to 400 mtorr.
[0026] The chamber 100 is controlled by a controller 180 that
comprises program code having instruction sets to operate
components of the chamber 100 to process substrates 104 in the
chamber 100. For example, the controller 180 can comprise program
code that includes a substrate positioning instruction set to
operate the substrate support 130 and substrate transport; a gas
flow control instruction set to operate gas flow control valves 166
to set a flow of sputtering gas to the chamber 100; a gas pressure
control instruction set to operate the throttle valve 174 to
maintain a pressure in the chamber 100; a gas energizer control
instruction set to operate the gas energizer 152 to set a gas
energizing power level; a temperature control instruction set to
control a temperature control system (not shown) in the support 134
or wall 108 to set temperatures of the substrate 104 or walls 108,
respectively; and a process monitoring instruction set to monitor
the process in the chamber 100.
[0027] The chamber further comprises a process kit 200 comprising
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 for other processes. In one version, the process kit 200
comprises a ring assembly 202 for placement about a peripheral wall
139 of the substrate support 130 that terminates before an
overhanging edge 206 of the substrate, as shown in FIG. 4. The ring
assembly 202 comprises a deposition ring 208 and a cover ring 212
that cooperate with one another to reduce formation of sputter
deposits on the peripheral walls 139 of the support 130 or the
overhanging edge 206 of the substrate 104.
[0028] The deposition ring 208 can be easily removed to clean
sputtering deposits from the exposed surfaces of the ring so that
the support 130 does not have to be dismantled to be cleaned. The
deposition ring 208 protects the exposed side surfaces of the
support 130 to reduce their erosion by the energized plasma
species. In the version shown in FIG. 4, the deposition ring 208
comprises an annular band 216 that extends about and surrounds the
peripheral wall 139 of the support 130. The annular band 216
comprises an inner lip 218 which extends transversely from the band
and is substantially parallel to the peripheral wall 139 of the
support 130. The inner lip 218 terminates immediately below the
overhanging edge 206 of the substrate 104. The inner lip 218
defines an inner perimeter of the deposition ring 208 which
surrounds the periphery of the substrate 104 and support 130 to
protect regions of the support 130 that are not covered by the
substrate 104 during processing. For example, the inner lip 218
surrounds and at least partially covers the peripheral wall 139 of
the support 130 that would otherwise be exposed to the processing
environment to reduce or even entirely preclude deposition of
sputtering deposits on the peripheral wall 139.
[0029] The annular band 216 of the deposition ring 208 also has a
raised ridge 224 that extends along the central portion of the band
216. The raised ridge 224 has a flat top surface 228 that is
substantially parallel to the plane of the receiving surface 138 of
the substrate support 130, and spaced apart from the cover ring 212
to form a narrow gap 229 therebetween. The narrow gap acts as a
labyrinth to reduce penetration of plasma species into the gap or
the regions at the end of the gap. of the raised ridge. An open
inner channel 230 lies between the inner lip 218 and the raised
ridge 224. The open inner channel 230 extends radially inward to
terminate at least partially below the overhanging edge 206 of the
substrate 104. The inner channel 230 has a first rounded corner 232
joining to the inner lip 218 and a gently sloped surface 234
joining to the raised ridge 224. The smooth corner 232 and sloped
surface 234 facilitate the removal of sputtering deposits from
these portions during cleaning of the deposition ring 208. The
deposition ring 208 also has a ledge 236 which extends radially
outward of the raised ridge 224, and serves to support the cover
ring 212. Unlike prior art designs, pins are not needed in the
deposition ring 208 to retain the substrate 104 in the event that
the substrate 104 slides or is misplaced in the chamber 100, due to
accurate positioning of the substrate in the chamber during its
transportation into the chamber.
[0030] In one version, the deposition ring 208 is made by shaping
and machining a ceramic material, such as aluminum oxide.
Preferably, the aluminum oxide has a purity of at least about
99.5%, to reduce contamination of the chamber by undesirable
elements such as iron. The ceramic material is molded and sintered
using conventional techniques such as isostatic pressing, followed
by machining of the molded sintered preformed using suitable
machining methods to achieve the shape and dimensions required.
[0031] In one preferred version, the annular band 216 of the
deposition ring 208 comprises an exposed surface 217 that is bead
blasted to achieve a predefined level of surface roughness while
adjacent surfaces are masked off to prevent accidental bead
blasting of these surfaces. In the bead blasting process, aluminum
oxide grit is blasted through a nozzle of a grit blaster (not
shown) toward the exposed surface of the deposition ring. The grit
blaster can be a pressure driven grit blaster which is powered
using compressed gas at a pressure of from about 20 to about 45
psi. Alternatively, a siphon driven grit blaster can be used at an
operating pressure of from about 60 to about 80 psi. The nozzle of
the grit blaster is maintained at an angle of about 45.degree.
relative to the plane of the exposed surface, and at a distance of
about four to 6 inches. Grit blasting is performed with a grit size
suitable to achieve the predefined surface roughness. The grit
blasted surface roughness average of 150.+-.50 microinches provides
a suitable surface for strong adhesion of sputtered titanium
deposits.
[0032] The surface roughness average is the mean of the absolute
values of the displacements from the mean line of the peaks and
valleys of the roughness features along the exposed surface. The
roughness average, skewness, or other properties may be determined
by a profilometer that passes a needle over the exposed surface 217
and generates a trace of the fluctuations of the height of the
asperities on the surface, or by a scanning electron microscope
that uses an electron beam reflected from the surface to generate
an image of the surface. To measure the surface roughness average,
the exposed surface of a test deposition ring 208 can be cut into
coupons and one or more measurements are made on each coupon. These
measurements are then averaged to determine an average surface
roughness of the exposed surface 217. In one embodiment, three
coupons are used and four traces of the changes in the heights of
the peaks and valleys of the features of the surface roughness are
made on each coupon.
[0033] The cover ring 212 of the ring assembly 202 comprises an
undersurface 219 that is spaced apart from, overlies, and at least
partially covers the raised ridge 224 of the deposition ring 208 to
define the narrow gap 229 which impedes travel of plasma species
through the gap. The constricted flow path of the narrow gap 229
restricts the build-up of low-energy sputter deposits on the mating
surfaces of the deposition ring 208 and cover ring 212, which would
otherwise cause them to stick to one another or to the peripheral
overhang edge 206 of the substrate 104.
[0034] The cover ring 212 comprises an annular plate 244 which has
a footing 246 which rests on a surface about the substrate support
130, such as on the ledge 236 of the deposition ring 208. The
footing 246 extends downwardly from the plate 244 to press against
the ledge 236 on the deposition ring 208. The annular plate 244
serves as a boundary to contain the sputtering plasma within the
process zone between the target 136 and the support 130, receives
the bulk of the sputtering deposits, and shadows the deposition
ring 208. The annular plate terminates in a projecting brim 252
which overlies the raised ridge 224 of the deposition ring 208. The
projecting brim 252 terminates in a rounded edge 256 and has a
planar bottom surface 260 which is the undersurface of the cover
ring. The projecting brim 252 inhibits the deposition of sputtering
deposits on the overhang edge 206 of the substrate and also reduces
deposits on the peripheral walls 139 of the support 130.
[0035] The cover ring 212 also has a pair of cylindrical walls
260a,b that extend downwardly from the annular plate 244. The
cylindrical walls 260a,b are located radially outward of the
footing 246 of the wedge 244,. The inner cylindrical wall 260a has
a smaller length than the outer wall 260b. For example, the inner
wall 260a can have a first length that is shorter than a second
length of the outer wall 260b second leg by at least about 10%. The
walls 260a, 260b are spaced apart to form yet another convoluted
pathway 266 which impedes travel of plasma species and glow
discharges to the surrounding area. In one version, the inner wall
260a has a length of about 0.7 inches.
[0036] The cover ring 212 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 version, the cover
ring 212 is made from stainless steel and has an exposed surface
247 that is substantially parallel to the receiving surface 138 of
the substrate support 130. The exposed surface 247 is bead blasted
to obtain a surface roughness of 175.+-.75 microinches. The bead
blasted surface is prepared in the same manner as the bead blasting
process for the exposed surface 217 of the deposition ring 208 as
described above with suitable modifications to the grit size to
achieve the desired roughness values.
[0037] The process kit 200 can also includes a shield assembly 150
that encircles the sputtering surface of a sputtering target 136
and the peripheral edge 139 of the substrate support 130, as shown
in FIG. 1, to reduce deposition of sputtering deposits on the
sidewalls 116 of the chamber 100 and the lower portions of the
support 130. The shield assembly 150 reduces deposition of
sputtering material on the surfaces of support 130, and sidewalls
116 and bottom wall 120 of the chamber 100, by shadowing these
surfaces. In one version, the shield assembly 150 comprises an
upper shield 147 and a lower shield 182 that cooperate together to
shadow the wall surfaces and lower portion of the chamber 100. The
upper shield 147 comprises a support lip 183 which rests on a ledge
185 of an upper adapter 186 in the chamber. The upper adapter 186
can serve as the sidewall of the chamber 100. The upper shield 147
also has an annular band 187 with a first cylindrical surface 189
having a first diameter sized to encircle the sputtering plate of
the sputtering target, a second cylindrical surface 190 with a
second diameter sized smaller than the first diameter, and a sloped
surface 191 between the first and second surfaces 189, 190.
[0038] The lower shield 182 also has a support ledge 192 which
rests on a circumferential lip 193 of the lower adapter 194 to
support the lower shield 182. The lower shield 182 comprises a
cylindrical outer band 195 that extends below the second
cylindrical surface 190 of the upper shield 147, a base plate 196
that extends radially inward from the bottom end of the cylindrical
outer band 195, and a cylindrical inner band 196 joined to the base
plate 195 which at least partially surrounds the substrate support
130, as shown in FIG. 4. The inner band 196 comprises a height that
is smaller than the outer band 195, for example, the inner band 196
can have a height which is 0.8 times smaller than the height of the
outer band 195. The gaps between the inner and outer bands 196,195,
respectively, and the outer wall 260b and inner wall 260a of the
cover ring 212 serve to hinder and impede ingress of plasma species
into this region.
[0039] The upper and lower shields 147,182 are fabricated from a
conductor, such as a metal, for example, aluminum. In one version,
the shields 147, 182 have exposed surfaces 198, 199, respectively,
facing the plasma zone 106 in the chamber 100. The exposed surfaces
198,199 are bead blasted to have a surface roughness of 175.+-.75
microinches. The bead blasted surface is prepared in the same
manner as the bead blasting process used for the exposed surface
217 of the deposition ring 208 as described above with suitable
modifications to the grit size to achieve the desired roughness
values.
[0040] The design of the components of the process kit 200 and the
target 136 significantly increase the number of process cycles and
process on-time that the process kit can be used in the chamber
without removing the process kit for cleaning in the sputtering of
titanium. The components of the process kit 200 and target 136 are
also designed to allow increased power and pressure in the
sputtering zone 106 to yield higher deposition throughput by
reducing the temperature in the darkspace region which is near the
upper shield 147 and target 136. The present invention has been
described with reference to certain preferred versions thereof;
however, other versions are possible. For example, the process kit
200 can be used in other types of applications, as would be
apparent to one of ordinary skill, for example, etching, CVD and
etching chambers. Other shapes and configurations of the target
136, deposition ring 208, cover ring 212, and shield assembly 150
can also be used. Therefore, the spirit and scope of the appended
claims should not be limited to the description of the preferred
versions contained herein.
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