U.S. patent application number 13/740083 was filed with the patent office on 2013-08-01 for substrate cleaning chamber and cleaning and conditioning methods.
The applicant listed for this patent is Karl M. BROWN, Daniel J. Hoffman, Vineet Mehta, Keith A. Miller, Vijay D. PARKHE, John A. Pipitone, Steven C. Shannon. Invention is credited to Karl M. BROWN, Daniel J. Hoffman, Vineet Mehta, Keith A. Miller, Vijay D. PARKHE, John A. Pipitone, Steven C. Shannon.
Application Number | 20130192629 13/740083 |
Document ID | / |
Family ID | 39968423 |
Filed Date | 2013-08-01 |
United States Patent
Application |
20130192629 |
Kind Code |
A1 |
Mehta; Vineet ; et
al. |
August 1, 2013 |
SUBSTRATE CLEANING CHAMBER AND CLEANING AND CONDITIONING
METHODS
Abstract
A substrate cleaning chamber includes a contoured ceiling
electrode having an arcuate surface that faces a substrate support
and has a variable cross-sectional thickness to vary the gap size
between the arcuate surface and the substrate support to provide a
varying plasma density across the substrate support. A dielectric
ring for the cleaning chamber comprises a base, a ridge, and a
radially inward ledge that covers the peripheral lip of the
substrate support. A base shield comprises a circular disc having
at least one perimeter wall. Cleaning and conditioning processes
for the cleaning chamber are also described.
Inventors: |
Mehta; Vineet; (Mountain
View, CA) ; BROWN; Karl M.; (Santa Clara, CA)
; Pipitone; John A.; (Livermore, CA) ; Hoffman;
Daniel J.; (Fort Collins, CO) ; Shannon; Steven
C.; (Raleigh, NC) ; Miller; Keith A.;
(Mountain View, CA) ; PARKHE; Vijay D.; (San Jose,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Mehta; Vineet
BROWN; Karl M.
Pipitone; John A.
Hoffman; Daniel J.
Shannon; Steven C.
Miller; Keith A.
PARKHE; Vijay D. |
Mountain View
Santa Clara
Livermore
Fort Collins
Raleigh
Mountain View
San Jose |
CA
CA
CA
CO
NC
CA
CA |
US
US
US
US
US
US
US |
|
|
Family ID: |
39968423 |
Appl. No.: |
13/740083 |
Filed: |
January 11, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11745451 |
May 8, 2007 |
8435379 |
|
|
13740083 |
|
|
|
|
Current U.S.
Class: |
134/1 |
Current CPC
Class: |
C25F 7/00 20130101; H01J
37/32009 20130101; H01L 21/0206 20130101; B08B 7/0035 20130101;
H01J 37/32541 20130101; H01L 21/02046 20130101 |
Class at
Publication: |
134/1 |
International
Class: |
B08B 7/00 20060101
B08B007/00 |
Claims
1. A process for removing material from one or more substrates,
comprising: (a) removing an amount of material from each substrate
in a first batch of substrates in a process chamber, wherein
removing the material from each substrate in the first batch forms
a first process residue on an internal surface of the process
chamber; (b) depositing a conditioning layer comprising a
conditioning material over the first process residue by sputtering
a material from a surface of a conditioner substrate, the
conditioning material being different than the material removed
from the substrates in the first batch; and (c) removing an amount
of material from each substrate in a second batch of substrates in
the process chamber, wherein removing the material from each
substrate in the second batch forms a second process residue over
the conditioning layer.
2. The process of claim 1, further comprising sequentially
repeating steps (b) and (c) at least 10 times before removing a
process kit on which the internal surface is formed.
3. The process of claim 1, wherein the conditioner substrate
comprises a silicon containing substrate having a layer of material
disposed over a surface, wherein the conditioning material
comprises a metal.
4. The process of claim 1, wherein the conditioning material
comprises aluminum or titanium.
5. The process of claim 1, wherein the material removed from the
first batch of substrates comprises silicon nitride.
6. The process of claim 1, wherein the material removed from the
first batch of substrates comprises polyimide.
7. The process of claim 6, wherein the conditioning material
comprises a metal.
8. The process of claim 1, further comprising: depositing an
additional conditioning layer comprising the conditioning material
over the second process residue by sputtering a material from the
surface of the conditioner substrate, wherein the conditioning
material comprises aluminum or titanium.
9. The process of claim 1, wherein the first process residue has a
thickness of at least about 1 micron.
10. The process of claim 1, wherein the conditioning layer has a
thickness of at least about 500 angstroms.
11. The process of claim 1, wherein step (a) comprises energizing a
cleaning gas in the process chamber by delivering a dual frequency
electrical power to the cleaning gas, the dual frequency electrical
power comprising a power ratio of a first frequency to a second
frequency of at least about 1:2, and the first frequency being less
than the second frequency.
12. The process of claim 11, wherein the first frequency is 13.5
MHz.
13. The process of claim 11, wherein the second frequency is 60
MHz.
14. The process of claim 1, wherein step (a) further comprises
setting a gap between a ceiling electrode and a substrate support,
wherein the gap is set for each of the substrates processed in the
first batch of production substrates during step (a).
15. A process for removing material from one or more substrates,
comprising: (a) removing an amount of material from each substrate
in a first batch of substrates in a process chamber by sputtering,
wherein removing the amount of material from each substrate in the
first batch forms a first process residue comprising silicon on an
internal surface of the process chamber, (b) depositing a
conditioning layer comprising aluminum or titanium over the first
process residue by sputtering a material from a layer disposed on a
surface of a conditioner substrate; and (c) removing an amount of
material from each substrate in a second batch of substrates in the
process chamber by sputtering, wherein removing the amount of
material from each substrate in the second batch forms a second
process residue comprising silicon over the conditioning layer.
16. The process of claim 15, further comprising sequentially
repeating steps (b) and (c) at least 10 times before removing a
process kit component on which the internal surface is formed.
17. The process of claim 15, wherein the conditioner substrate
comprises a silicon containing substrate that has a layer of
material disposed over a surface, wherein the layer of material
comprises aluminum.
18. The process of claim 15, wherein the process residue comprises
silicon nitride.
19. The process of claim 15, wherein the process residue further
comprises polyimide.
20. The process of claim 15, wherein removing the amount of
material from each substrate in the first and the second batch each
further comprise energizing a cleaning gas by delivering a dual
frequency electrical power to the cleaning gas that is disposed in
the process chamber.
21. The process of claim 20, wherein delivering the dual frequency
electrical power comprises delivering a first amount of electrical
power at a first frequency of about 13.5 MHz and delivering a
second amount of electrical power at a second frequency of about 60
MHz.
22. The process of claim 15, wherein step (a) further comprises
setting a gap between a contoured ceiling electrode and a substrate
support, wherein the gap is set for each of the substrates
processed in the first batch of production substrates during step
(a).
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of co-pending U.S. patent
application Ser. No. 11/745,451, filed May 8, 2007, which is hereby
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Embodiments of the present invention relate to a substrate
cleaning chamber, chamber components, and substrate cleaning
method.
[0004] In the manufacture of integrated circuits and displays, a
substrate such as a semiconductor wafer or display, is placed in a
process chamber and processing conditions are set to form various
active and passive features on the substrate. Advanced integrated
circuits and displays use multiple levels of sub-micron sized
interconnects to connect the features formed on a substrate. In
order to improve circuit reliability, the surface features on the
substrate are cleaned prior to the deposition of overlying
materials on the surfaces of the interconnect or other features. A
typical pre-clean or cleaning chamber comprises an enclosure around
a process zone which contains chamber components that include a
substrate support to hold the substrate, a gas supply to provide a
cleaning gas, a gas energizer to energize the cleaning gas to etch
away the surface of the features to clean the substrate, and a gas
exhaust to remove spent gas, as for example, described in U.S. Pat.
No. 6,107,192, issued on Aug. 22, 2000, to Subrahmanyan et al.,
which is incorporated by reference herein and in its entirety.
[0005] However, conventional pre-clean chambers and processes often
do not uniformly clean the surfaces of the ever smaller features
being fabricated on a substrate. Failure to properly clean these
features can result in void formation or increased electrical
resistance between the surface features. For example, a layer of
native oxides and contaminants which are left on the features can
cause void formation by promoting the uneven distribution of
material deposited on the substrate in a subsequent processing
step, or by causing the corners of the features to grow, merge, and
seal off before the feature is filled with the material being
deposited therein. Pre-cleaning processes are especially desirable
to uniformly etch and clean substrate surfaces for subsequent
barrier layer or metal deposition processes.
[0006] It is also desirable to have pre-clean chamber that can
receive ever increasing amounts of accumulated deposits without
causing the chamber components to stick to each other or the
accumulated deposits flaking off between cleaning cycles. During
the etch cleaning process, cleaning residues often deposit on the
exposed internal surfaces in the chamber. Build-up of these
residues is undesirable as the accumulated deposits can flake off
when thermally stressed to fall upon and contaminate the substrate
and other chamber surfaces. Periodic cleaning of the residues off
the chamber components reduces this problem but also requires
disassembly and cleaning of the chamber components and shut-down of
the chamber. Further, when metal-containing process residues
accumulate on the ceiling of a chamber having an external inductor
coil gas energizer to couple induction energy through the ceiling
to energize the cleaning gas, the metal containing residues reduce
or prevent coupling of the induction energy through the ceiling.
Conventional cleaning chambers use a process kit comprising lower
and upper shields, and various deposition or cover rings arranged
about the substrate support to receive such process residues.
Periodically, the process kit components are dismantled and removed
from the chamber for cleaning. However, it is desirable to have a
chamber and internal components which can receive ever larger
amounts of accumulated deposits so that the chamber can be used for
a larger number of process cycles before shut down.
SUMMARY OF THE INVENTION
[0007] A contoured ceiling electrode is used in a cleaning chamber
comprising a substrate support having a substrate receiving surface
and a support electrode. The contoured ceiling electrode comprises
an arcuate surface facing the substrate support. The arcuate
surface has a diameter sized to extend across the substrate
receiving surface of the substrate support and a cross-sectional
thickness that changes across the substrate support to vary a
dimension of a gap formed between the arcuate surface and the
support electrode of the substrate support, thereby allowing a
plasma density of a plasma formed between the arcuate surface and
the substrate support to vary radially across the substrate
support. The ceiling electrode can also have an annular band
extending downwardly from a periphery of the arcuate surface to
encircle the substrate support. A support ledge extends radially
outwardly from the annular band.
[0008] A dielectric ring for the cleaning chamber comprises a base
that rests on a peripheral flange of a dielectric baseplate in the
chamber, to surround the substrate support. The dielectric ring
also has a ridge having a height that is higher than the substrate
receiving surface. A radially inward ledge covers the peripheral
lip of the substrate support.
[0009] A base shield for the substrate cleaning chamber comprises a
circular disc having a top surface to support the dielectric
baseplate, and a plurality of lift pin holes passing through the
circular disc to allow chamber lift pins to extend therethrough.
The base shield also has a perimeter wall extending upward from and
surrounding the circular disc, the perimeter wall being spaced
apart from the peripheral flange of the dielectric baseplate.
[0010] A process for etch cleaning a layer on a substrate in a
cleaning chamber comprises placing a substrate on the substrate
support in the cleaning chamber, setting a gap between the support
and contoured ceiling electrodes, maintaining a pressure of a
cleaning gas in the chamber, and energizing the cleaning gas by
applying a dual frequency electrical power to the ceiling and
support electrodes, the dual frequency electrical power comprising
a power ratio of a first frequency to a second frequency of at
least about 1:2, the first frequency being less than about 20 KHz
and the second frequency being at least about 20 MHz.
[0011] A process for etch cleaning a layer on a substrate in a
cleaning chamber. comprises cleaning a first material on first
batch of production substrates in the cleaning chamber to form
process residues comprising the first material on the internal
surfaces of the cleaning chamber. Thereafter, a conditioning layer
of a second material is deposited over the process residues on the
internal surfaces of the cleaning chamber by etch sputtering a
conditioner substrate comprising a second material in the cleaning
chamber, the second material being a different material than the
first material. The first material on a second batch of production
substrates provided in the cleaning chamber can then be cleaned to
form further process residues comprising the first material on the
conditioning layer. This process delays cleaning of the
chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] 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:
[0013] FIG. 1 is a schematic sectional side view of an embodiment
of a cleaning chamber showing the contoured ceiling electrode,
substrate support, dielectric ring, the electric baseplate, and
lower shield;
[0014] FIG. 2 is a graph of the etch profile obtained on a test
substrate which was etch cleaned using a flat ceiling electrode,
and a corresponding mapping of the arcuate profile selected for a
contoured ceiling electrode that compensates for this etch
profile;
[0015] FIG. 3 is a perspective view of an embodiment of a contoured
ceiling electrode having an arcuate surface comprising a convex
bulge, a peripheral groove, and a peripheral wall;
[0016] FIG. 4 is a sectional side view of a contoured ceiling
electrode having an arcuate surface that is a concave
depression;
[0017] FIG. 5 is a partial sectional view of an embodiment of a
cover ring resting on a dielectric base plate and substrate
support, and showing a substrate positioned on the substrate
support;
[0018] FIG. 6A is a perspective view of an embodiment of a base
shield comprising a circular disc with a surrounding perimeter
wall;
[0019] FIG. 6B is a perspective view of another embodiment of a
base shield comprising a surrounding perimeter wall and an inner
wall that are concentric to one another; and
[0020] FIG. 7 is a contour plot of the uniform cleaning rates
obtained across the surface of a substrate processed in the
cleaning chamber.
DETAILED DESCRIPTION
[0021] An exemplary embodiment of a cleaning chamber 100 capable of
cleaning a surface layer of a substrate 104 is illustrated in FIG.
1. Generally, the cleaning chamber 100 comprises enclosure walls
105 that enclose a process zone 106, the walls 105 include a
ceiling lid 108, sidewall 110, and bottom wall 112. The enclosing
walls of the chamber can be made from a metal, such as aluminum,
stainless steel, copper-chromium or copper-zinc. The ceiling lid
108 comprises a plate 114 with downwardly extending side ledges
116. The side ledges 116 of the ceiling lid 108 rest on a top
surface 118 of the sidewall 110. The sidewall 110 has a gas inlet
124 for introducing a cleaning gas from a cleaning gas source 126
at a flow rate monitored by a gas flow control valve 127, and an
exhaust port 128 for exhausting gas from the chamber 100 past a
throttle valve 129 using an exhaust pump 123. The bottom wall 112
has openings to receive electrical connectors 120 and a lifting
mechanism 122. In the version shown, the cleaning chamber 100 is
particularly suitable for cleaning a metal containing material,
such as a metal or metal compound, off a substrate 104 by etching
away a surface portion of the material. The chamber can be, for
example, a REACTIVE PRE-CLEAN.TM. type cleaning chamber, such as
the DAVINCI chamber, available from Applied Materials, Inc., of
Santa Clara, Calif. The chamber 100 can be a part of a
multi-chamber platform (not shown) having a cluster of
interconnected chambers, such as the family of ENDURA.RTM.,
PRODUCER.RTM. and CENTURA.RTM. processing platforms, all available
from Applied Materials, Inc., of Santa Clara, Calif.
[0022] The chamber 100 also includes a substrate support 130 which
comprises a support electrode 134. The substrate support 130
comprises a raised pedestal 135 having a surrounding peripheral lip
136 about a substrate receiving surface 137. The peripheral lip 136
extends outwardly from the bottom portion of the pedestal 135 and
is at a reduced height. The substrate receiving surface 137 is
planar and sized to receive a substrate 104. In the embodiment
shown, the support electrode 134 and the substrate support 130 are
the same structure; however, in alternative embodiments, the
substrate support 130 can have a dielectric that covers or encloses
(not shown) the support electrode 134. In the version shown, the
substrate support 130 which also serves as the support electrode
134 comprises, or is composed of, a metal, such as for example
aluminum, copper, titanium, or alloys thereof. In one version,
which is desirable for high temperature pre-clean processes, the
support electrode 134 is fabricated from titanium. This version
provides higher operational temperatures compared to conventional
support electrodes 134 which are made from aluminum. To load a
substrate, the substrate support 130 is lowered by a lift motor 131
and lift bellows 132, so that the stationary lift fingers 138
extend through holes in the support 130. 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 lift fingers 138. The substrate support 130 is then raised up
to lift the substrate 104 off the lift fingers 138.
[0023] A contoured ceiling electrode 140 opposingly faces the
substrate support 130 and the support electrode 134. The substrate
support 130 is positioned to set a predetermined gap 139 between
the support electrode 134 and the ceiling electrode 140. The
contoured ceiling electrode 140 has a peripheral edge 141 that
rests on a grounding ring 143 which in turn rests on a ledge 145 of
the chamber lid 108. Both the contoured ceiling electrode 140 and
support are made of a conducting material, such as for example,
aluminum, and are bolted to the chamber body which is also made of
a metal conductor such as aluminum. The contoured ceiling electrode
140 and grounding ring 143 are electrically interconnected and can
be maintained at a floating potential or grounded. The grounding
ring 143 and peripheral edge 141 of the contoured ceiling electrode
140 are shaped to impede the penetration of low-angle sputtered
plasma species and resultant process deposits past their
surfaces.
[0024] Conventional cleaning chambers used an inductor coil wrapped
around a dome shaped dielectric ceiling to inductively couple
energy to the cleaning gas in the chamber to form a plasma which
cleans the substrate 104. However, when cleaning a metal layer on
the substrate 104, process residues containing metal species
deposit on the internal surfaces of the chamber ceiling 114, and
this metal-containing layer disturbs the inductive coupling of
energy through the ceiling 114.
[0025] In the present version of the cleaning chamber, the
conventionally used inductor coil is replaced by a contoured
ceiling electrode 140 which has a contoured profile and which
couples with the support electrode 134 to energize a plasma from
the cleaning gas provided in the chamber 100. The ceiling electrode
140 can receive metal-containing deposits without affecting the
performance of the electrode 140 because the electrode 140 itself
is made of a conductor, such as a metal. This improves performance
of the cleaning chamber 100 in the cleaning of metal-containing
materials on the substrate 104.
[0026] In one version, the contoured ceiling electrode 140
comprises an arcuate surface 144 that faces the substrate support
130, a version of which is illustrated in FIGS. 1 to 4. The arcuate
surface 144 includes a single or multi-radius curved surface which
has a diameter sized sufficiently large to extend across the
substrate receiving surface of the substrate support 130. The shape
of the arcuate surface 144 is selected to control a plasma density
or flux of a plasma formed between the arcuate surface 144 and the
substrate support 130 or support electrode 134. As one example, the
arcuate surface 144 can extend across substantially the entire
substrate receiving surface of the substrate support 130 or support
electrode 134, for example, at least about 70%, or even at least
about 90%, of the substrate receiving surface area of the substrate
support 130.
[0027] The arcuate surface 144 also has a variable cross-sectional
thickness or profile that is shaped to vary a dimension or size of
the gap 139 between the ceiling electrode 140 and the support
electrode 134 of the substrate support 130. This varies the gap
distance between the arcuate surface 144 and the corresponding area
of the substrate support 104 and/or support electrode 134. The
varying gap distance provides a plasma density that varies radially
across an entire surface of a substrate 104 held on the substrate
receiving surface 137 of the substrate support 130. Conventional
ceiling electrodes have a flat surface to provide a uniform
electric flux across the gap between the substrate receiving
surface and the ceiling electrode. In contrast, the contoured
ceiling electrode 140 has a profile 146 that is capable of
generating a non-uniform or variable electric flux across the
process zone 106 of the cleaning chamber 100 which is
counterintuitive to conventional flat electrode designs. This
electrode shape allows a plasma density of a plasma formed between
the arcuate surface 144 and the substrate support 130 to vary
radially across the substrate support 130.
[0028] The shape of an arcuate profile 146 of the arcuate surface
144 of the contoured ceiling electrode 140 is experimentally
determined based on test results obtained for test substrates 104
that are etched using a flat ceiling electrode (not shown). An
etching parameter, such as etch depth or etch rate, is measured at
a number of discrete points across the surface of the test
substrate 104 to obtain a plurality of measurement points that give
an etch profile 148 across the substrate 104. The arcuate profile
146 of the contoured ceiling electrode 140 is then shaped to
compensate for the etch profile obtained with the flat electrode.
For example, the arcuate profile 146 of the contoured ceiling
electrode 140 can be shaped to provide a weaker electric field and
hence higher plasma density at those regions of the substrate 104
measured to have a smaller etch depth or lower etch rate with a
flat electrode, and conversely, shaped to provide a stronger
electric field and hence lower plasma density at those regions of
the substrate 104 that were found to be etched to a greater depth
or with a higher etch rate with the flat electrode. Thus, the
arcuate profile 146 is shaped in relation to the etch depth profile
148 of the substrate 104 so that the gap 139 between the support
electrode 134 and contoured ceiling electrode 140 varies in
relationship to the etch profile 148 of the test substrate 104
obtained using a flat ceiling electrode. At positions where the
etch depth on the substrate 104 is greatest, the arcuate profile
146 of the contoured ceiling electrode 140 is recessed the most to
reduce the electric field and increase the corresponding plasma
density at that region, or vice versa.
[0029] A graph of the etch profile 148 obtained on a test substrate
104 which was etch cleaned using a flat surfaced ceiling electrode,
and a corresponding mapping of the arcuate profile 146 selected for
a contoured ceiling electrode 140 that can compensate for this etch
profile 148, is shown in FIGS. 2 and 3. In the embodiment graphed,
the arcuate profile 146 comprises a convex bulge 150 that forms a
smoothly curving surface which extends across at least about 70% of
the area of the contoured ceiling electrode 140 that is exposed in
the chamber 100 and which faces the substrate support 130. FIG. 1
shows the relationship of the contoured ceiling electrode to the
support electrode 134 in the substrate support 130. The substrate
support 130 comprises central and peripheral regions 152, 154, and
the convex bulge 150 is shaped to increase a plasma density at the
peripheral region 154 relative to the central region 152 during
processing of the substrate 104 in the chamber 100. This is
accomplished by reducing the gap distance between the contoured
ceiling electrode 140 and the substrate receiving surface 137 at
the central region 152 to a first smaller distance decrease a
plasma density therein, and increase the gap distance between the
contoured ceiling electrode 140 and the substrate receiving surface
137 at the peripheral region 154 to a second and higher gap
distance to increase a plasma density therein. The convex bulge 150
sets the gap between the support electrode 134 and contoured
ceiling electrode 140 to be narrower at the central region 152 than
the peripheral region 154 of the substrate support 130. In one
version, the closest distance of the gap between the support
electrode 134 and the apex 156 of the convex bulge 150 of the
contoured ceiling electrode 140 is at least about 3 cm. Thus, the
contoured ceiling electrode 140 compensates for the etch rates that
were measured across the substrate 104 using a flat ceiling
electrode, to result in substantially uniform etch cleaning rates
and etch uniformity across the substrate 104.
[0030] The contoured ceiling electrode 140 can also have a convex
bulge 150 that has other shapes. For example, the convex bulge 150
can have a multi-radius arc 160 that transitions continuously
across different radiuses of curvature, and is surrounded by a
recessed peripheral groove 162 that is concave. In yet another
version, the central portion 164 of the convex bulge 150 can be
slightly flattened. The convex bulge 150 transitions from the
peripheral concave groove 162 to top region 172 via an annular rim
166 that is curved, and which is approximately inclined relative to
the plane of the flattened central portion.
[0031] In another prospective version, as shown in FIG. 4, the
arcuate surface 144 of the contoured ceiling electrode 140 is
shaped to have a concave depression 170 that performs the opposite
function to that obtained from the contoured ceiling electrode
shaped as shown in FIGS. 2 and 3. In this version, the concave
depression 170 is shaped to increase a plasma density at the
central region 152 relative to the peripheral region 154 during
processing of the substrate 104 in the chamber 100. This is
accomplished by increasing the gap distance at the central region
152 to increase plasma density at those regions, and reducing the
gap distance between the contoured ceiling electrode 140 and the
support electrode 134 at the peripheral region 154 to decrease a
plasma density therein. The arcuate surface 144 can also be a
multi-radius arc 160 or have a flattened plateau on its the top
portion. This version of the contoured ceiling electrode 140 also
compensates for etch rates obtained across the substrate 104 using
a flat ceiling electrode when higher etch rates are obtained at the
central region 152 relative to the peripheral region 154 of a test
substrate 104 processed with a flat electrode, to provide an etch
cleaning process in which the substrate is uniformly etch cleaned
across its surface.
[0032] The contoured ceiling electrode 140 also has an annular band
174 that extends downwardly from a periphery of the convex bulge
150 to encircle the substrate receiving surface 137 of the
substrate support 130, as shown in FIGS. 1 and 3. The annular band
174 encircles the process zone 106 that occurs between the arcuate
surface 144 of the contoured ceiling electrode 140 and the
substrate support 130. The annular band 174 extends downward from
the ceiling lid 108 sufficiently to encircle the outer periphery of
the substrate support 130 and shadow the sidewalls 110 of the
chamber 100 during the process cycle. The annular band 174 serves
as an upper shield to reduce or prevent the deposition of process
residues originating from the surface of the substrate 104 that
would otherwise fall on the side walls 110 of the chamber 100 and
other internal surfaces of the chamber 100. The annular band 174
also serves to contain the cleaning plasma on the surface of the
substrate 104. This reduces erosion of internal chamber surfaces by
the cleaning plasma. The peripheral edge 141 of the contoured
ceiling electrode comprises a support ledge 176 that extends
radially outwardly from around the annular band 174, and serves to
support the contoured ceiling electrode 140. In this version, the
contoured ceiling electrode 140 is composed of aluminum, but it can
also be made of other electrical conductors, including metals such
as stainless steel.
[0033] A dielectric baseplate 178 is located below the support
electrode 134 of the substrate support 130 as shown in FIGS. 1 and
5. The dielectric baseplate 178 serves to electrically isolate the
support electrode 134 from the surrounding chamber components. The
dielectric baseplate 178 receives the substrate support 130 having
the support electrode 134 on the top surface. The dielectric
baseplate 178 has a peripheral flange 180 that surrounds the top
surface of the support 130 to insulate a peripheral edge 198 of the
support electrode 134. The peripheral flange 180 has an annular top
surface 182 that encircles a peripheral lip 204 of the support
electrode 134.
[0034] Referring to FIG. 5, a dielectric ring 186 comprises a base
188 that rests on the annular top surface 182 of the peripheral
flange 180 to surround the support electrode 134 of the substrate
support 130. The dielectric ring 186 also has a ridge 196 having a
height that is higher than the substrate receiving surface 137. The
ridge 196 of the dielectric ring 186 serves to contain and focus
the cleaning plasma on the surface of the substrate 104. The ridge
196 also operates in synergy with the contoured profile 146 of the
contoured ceiling electrode 140 to control the plasma density and
the energy of the plasma species at the peripheral edge of the
substrate 104. For example, the dielectric ring 186 can reduce the
plasma ion flux hitting the substrate 104 at the peripheral region
of the substrate 104, thereby reducing etching rates in the
peripheral region as compared to a central region of the substrate
104. This provides more uniform cleaning across the substrate 104
by controlling etching rates across the substrate 104. The
dielectric ring 186 has a radially inward ledge 202 that covers the
peripheral lip 204 of the substrate support 130 and also serves to
enclose and protect the peripheral edge 198 of the support
electrode 134. Further, the radially inward ledge 202 also provides
a step having a reduced height immediately surrounding the
perimeter of the substrate 104 being processed on the substrate
support 130.
[0035] The ridge 196 and a radially inward ledge 202 of the
dielectric ring 186 are joined by an inner face 208 which can be
substantially straight or sloped. In one version, the inner face
208 is substantially straight and perpendicular to the plane of the
substrate surface. In another version, the sloped inner face 208 is
inclined relative to the top surface plane of the ridge 196 by an
angle.about.of at least about 60.degree., for example, from about
82.degree. to about 98.degree.. The sloped inner face 208 provides
a gradual transition region for the plasma formed over the
substrate 104. The sloped inner face 208 also comprises rounded
edges 212 to reduce the stresses that would be otherwise be created
on a coating covering a sharp edge or corner, these stresses being
responsible for causing early flaking off of residues deposited on
these regions. Thus the rounded edges 212 allow an increased
thickness of process residues to be deposited on the dielectric
ring 186. The rounded edges 212 also further reduce the erosive
effect of the cleaning plasma on the edges of the dielectric ring
186.
[0036] A base shield 214 (also known as a lower shield) is used to
support the dielectric baseplate 178 as shown in FIG. 1. Referring
to FIG. 6A, the base shield 214 comprises a circular disc 215
having a top surface 216 with a plurality of lift pin holes 217 for
a plurality of lift pins 138 to extend therethrough. The top
surface 216 of the circular disc 215 is used to support the
dielectric baseplate 178. The top surface 216 can also have a
central hole 213 to allow the electrical connectors 120 and other
structures to extend therethrough. The base shield 214 also has a
perimeter wall 218 extending upwardly from and surrounding the
circular disc 215. The perimeter wall 218 is spaced apart from the
peripheral flange 180 of the dielectric baseplate 178 as shown in
FIG. 1. For example, the perimeter wall 218 can be spaced apart
from the peripheral flange 180 of the dielectric baseplate 178 by a
spacing distance of at least about 1 cm. The perimeter wall 218
also extends substantially vertically from the top surface 216 of
the circular disc 215, for example, to a height of at least about 5
mm. The perimeter wall 218 is also spaced apart from, and parallel
to, the band shield 174 of the contoured ceiling electrode 140. For
example, the perimeter wall 218 can be spaced apart from the band
shield 174 by a spacing distance of at least about 1 cm. The
perimeter wall 218 forms a convoluted passageway with the ban
shield 174 to form a narrow gap 220 therebetween that serves as a
labyrinth to impede the passage of plasma species therethrough. The
constricted flow path of the narrow gap 220 restricts the build-up
of low-energy plasma deposits on the outer radially surfaces of the
chamber such as the sidewalls 110. Also the exposed surfaces of the
perimeter wall 218 of the base shield 214 and the band shield 174
act as deposition surfaces to receive residue deposits before they
access the chamber sidewalls 110. In this manner, the base shield
214 further protects the chamber sidewalls 110 from the process
residues. The base shield 214 can be electrically grounded or
maintained at a floating or other electrical potential. In one
version, the base shield 214 is composed of an electrical
conductor, such as a metal, for example, aluminum, or other
metals.
[0037] Another version of the base shield 214, as shown in FIG. 68,
includes an inner wall 219 between the perimeter wall 218 of the
base shield 214 and the peripheral flange 180 of the dielectric
baseplate 178. In one version, the inner wall 219 also extends
vertically upward from the top surface 216 of the circular disc
215. In one version, the inner wall 219 is spaced apart from the
perimeter wall 218 by a spacing distance of at least about 1 cm,
and the inner wall 219 has a height of at least about 5 mm. The
inner wall 219, like the rest of the base shield 214, can be
composed of an electrical conductor. The inner wall 219 can serve,
for example, to raise the ground plane by providing an electrically
conducting pathway closer to the contoured ceiling electrode 140.
This changes the electric flux or plasma density, and consequently
the etch rate, at the localized region about the inner wall 219 and
the edge of the substrate 104 to achieve a more uniform etch across
the entire substrate 104. Thus the inner wall 219 is adapted to
serve as another form of plasma control in this version of the base
shield 214 for controlling the plasma distribution across the
substrate 104.
[0038] In an exemplary version of a cleaning process, a substrate
104 is placed on the substrate support 130 in the cleaning chamber
100, and the substrate support 130 is moved to set a gap 139
between the support electrode 134 and the contoured ceiling
electrode 140. Cleaning gas is introduced into the chamber 100
through the gas inlet 124 which provides the cleaning gas from a
gas source 126, which can be a single gas supply or a number of gas
supplies that provide different gasses which are mixed together in
a desirable flow ratio. The flow rate of the cleaning gas is
controlled thorough a plurality of gas flow control valves 128,
such as mass flow controllers, to pass a set flow rate of cleaning
gas into the chamber. The gas pressure is set by controlling the
flow of gas to exhaust pumps 123 using the throttle valve 129.
Typically, the pressure of the cleaning gas in the chamber 100 is
set to sub-atmospheric levels, such as a vacuum environment, for
example, gas pressures of from about 1 mTorr to about 1 Torr. The
cleaning gas can include a non-reactive gas which is capable of
being energized to form plasma species and energetically impinging
upon and sputtering material from the substrate 104. The cleaning
gas may also comprise reactive gases, such as oxygen-containing
gases or halogen-containing gases, which are capable of reacting
with native oxides, polymeric residues, or other materials on the
surface of the substrate 104 to form volatile compounds which are
removed from the chamber 100 by the exhaust system.
[0039] One process for removing native oxides and other
contaminants from polysilicon, copper and metal surfaces, uses a
cleaning process step in which the substrate surface is exposed to
an energized cleaning gas, and which can be optionally followed by
a reducing process step in which the substrate surface is exposed
to an energized reducing gas. The cleaning process step uses a
cleaning gas such as oxygen, a mixture of CF4 102, or a mixture
gases such as NF3 and He. Residual native oxides can also be
reduced in a reducing process step by treatment with a plasma which
has hydrogen radicals. During the cleaning process, removal of the
native oxide and other surface contaminants is monitored by taking
reflectivity measurements of the exposed layer on the substrate
104. The surface reflectivity can be used to measure the presence
of native oxides or other contaminants on the substrate because
these materials change the reflectivity of the substrate surface.
Reflectivity is typically measured in cleaning processes using
optical devices.
[0040] The chamber 100 is controlled by a controller 230 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 230 can comprise program
code that includes substrate positioning instruction sets to
operate the lift motor 131 of the substrate support 130 and the
substrate transfer and robot mechanism; gas flow control
instruction sets to operate gas flow control valves 127 to set a
flow of cleaning gas to the chamber 100; gas pressure control
instruction sets to operate the exhaust throttle valve 129 to
maintain a pressure in the chamber 100; gas energizer control
instruction sets to operate the gas energizer comprising the
support electrode 134 and opposing contoured ceiling electrode 140
to set a gas energizing power level; temperature control
instruction sets to control a temperature control system in the
substrate support 130 or a chamber wall 105 to set temperatures of
various components in the chamber 100; and process monitoring
instruction sets to monitor the process in the chamber 100.
[0041] In one cleaning process, the cleaning gas is energized by a
dual frequency electrical power which applies a first electrical
voltage comprising a first frequency and a second electrical
voltage comprising a second frequency, to the support electrode 134
and contoured ceiling electrode 140. The first frequency is lower
than the second frequency, for example, the first frequency can be
lower than the second frequency by at least about 10 KHz. In one
version, the first frequency is less than about 20 KHz and the
second frequency is at least about 20 MHz. For example, the first
frequency can be 13.5 KHz, and a second frequency can be 60
MHz.
[0042] The power ratio of the first frequency to the second
frequency also affects the cleaning process because it is believed
that the first frequency provides increased acceleration of the
plasma species and the second frequency provides additional
ionization and dissociation in the plasma. Thus when the voltage at
the first frequency is supplied at a higher electrical power level
than the voltage at the second frequency, the ratio of the amount
of plasma species to the kinetic energy of the plasma species can
be controlled. Plasma species having a higher kinetic energy
produce increased or deeper penetrating sputtering of the substrate
while an increased number of plasma species produces a greater more
uniform distribution or plasma flux across the surface. For
example, an embodiment of the cleaning process applies voltage at a
first frequency of 13.5 MHz at a power level of from about 200 to
about 200 Watts; and voltage at a second frequency of 60 MHz at a
power level of from about 800 to about 1300 Watts. In this version,
the 60 MHz power contributes to increased plasma density by
creating more ions. In contrast, the 13.56 MHz power contributes to
ion energy by accelerating ions created by the 60 MHz power to
accelerate these ions across the plasma sheath. Too little 60 MHz
power results in insufficient plasma species available, and too
little 13.56 MHz power causes the plasma ions to lack sufficient
levels of kinetic energy to etch the substrate surface. Thus, in
one cleaning process, the power ratio of the first frequency to the
second frequency is set to be at least about 1:2, or even at least
about 1:3.
[0043] FIG. 7 shows a contour plot of the uniform cleaning rates
obtained across the surface of a substrate processed in the
cleaning chamber 100 using the cleaning process described herein.
The substrate 104 was a 300 m silicon wafer coated with a thermal
silicon dioxide layer. The substrate 104 was cleaned using the
following process conditions: 300 W of 13.56 MHz and 1,000 W of 60
MHz power; chamber pressure of 4.5 mT; argon flow. The chamber 100
used a contoured ceiling electrode 140 having an arcuate surface
144 with a convex bulge 150 as shown in FIG. 3. In the cleaning
process, the etch cleaning rate was measured across the substrate
104, as shown in the contour map of FIG. 7. The average etch rate
was found to be about 350 A/minute, and the points shown on the
contour map correspond to the etch rate values that exceed or fall
below the average etch cleaning rate. The contoured ceiling
electrode 140 and dual frequency cleaning process provided a high
etch cleaning uniformity with the etch cleaning rates varying less
than 1.5% across the surface of the substrate.
[0044] In yet another aspect, the process for etch cleaning a layer
on the substrate 104 in the cleaning chamber 100 is further
enhanced by performing a conditioning process which coats a metal
layer on the internal surfaces of the chamber 100 in between
cleaning steps. In the cleaning process step, a first batch of
production substrates 104 is cleaned in the cleaning chamber 100 to
clean and remove contaminants and native oxide off a first material
on the substrates 104. This cleaning step causes process residues
comprising the first material to deposit on the internal surfaces
of the cleaning chamber 100. After processing of a number of
substrates 104, the process residues and deposits on the internal
surfaces of the chamber 100 accumulate to a sufficiently high
thickness that they risk flaking-off in subsequent process cycles
due to a build-up of film stress. At this time, a conditioner
substrate is transferred into the cleaning chamber 100. The
conditioner substrate is etch sputtered in the cleaning chamber 100
by introducing a sputtering gas in the cleaning chamber 100 and
energizing the sputtering gas by capacitively coupling electrical
power to the sputtering gas. The conditioner substrate comprises a
second material that is a different material than the first
material previously cleaned off the production substrates 104. The
sputtering process sputters material from the conditioner substrate
to coat the cleaning chamber 100 with the sputtered "paste"
material that serves as a conditioning layer over the process
residues. The freshly coated internal surfaces of the chamber 100
can now receive additional process residue deposits without flaking
off of these process residue deposits.
[0045] After the chamber conditioning step, a second batch of
production substrates is cleaned in the cleaning chamber 100 to
clean the first material on the substrates 104 to accumulate
additional process residues on the conditioning layer which has
been formed over the previously deposited process residues on the
internal surfaces of the cleaning chamber 100. This process allows
additional process cycles to be conducted before the process kit
components of the chamber 100 have to be dismantled and cleaned,
thereby increasing runtime of the chamber 100. The conditioning
process allows processing of sequential batches of substrates many
times before requiring removal of process kit components in the
cleaning chamber for cleaning. For example, a number of batches of
substrates can be cleaned to accumulate process residues on the
chamber surfaces, and then conditioning layer can be deposited on
the accumulated process residues, and this process can be repeated
at least 2 or more times, before removing the process kit in the
cleaning chamber for cleaning of process residues accumulated
thereon.
[0046] In one embodiment, the production substrates comprise a
first material comprising a first metal-containing material, such
as a silicon containing material, for example, silicon nitride
(SiN), or other materials, such as polyimide. When etch cleaned,
these substrates cause the deposition of process residues composed
of silicon nitride or polyimide on the internal chamber surfaces. A
suitable conditioning material comprises a second material which
can be a second-metal containing material, such as for example,
aluminum or titanium. This second material is sputtered in the
chamber to deposit the conditioning layer on the accumulated
process residues. In one version, the periodic conditioning process
is performed after accumulation of process residues in a thickness
of at least about 1 micron; however, this depends on the type and
sticking quality of the residues and the underlying chamber surface
composition. In one version, the conditioning process is performed
to deposit a conditioning layer in a thickness of at least about
500 angstroms on the internal surfaces of the process chamber.
[0047] In one exemplary version of a conditioning process, a
sputtering gas comprising argon is introduced into the cleaning
chamber, and the gas is energized by capacitively coupling RF
energy at a frequency of 13.56 MHz at a power level of 300 watts;
and RF energy at a frequency of 60 MHz power at a power level of
1000 Watts, for about 2 minutes. The source of the conditioning
material can be the process kit and other components in the chamber
itself; a substrate with a coating of the second material, such as
a silicon wafer with coating of aluminum; or even a sacrificial
pedestal of aluminum that can be sputtered in the chamber. This
sputtering process deposits a conditioning layer having a thickness
of from about 0.08 to about 0.12 microns over the accumulated
process residues which have been formed on the internal chamber
surfaces. The conditioning process can be repeated after cleaning
of from about 50 to about 100 substrates. Advantageously, the
conditioning process can allow processing of a larger number of
substrates, for example, from about 3500 to about 4500 substrates,
without requiring an intervening step of shutting down the chamber
to remove process residues off the chamber components.
[0048] Embodiments of the process kit, cleaning chamber 100, and
cleaning and conditioning processes described herein provide
Significant advantages. The contoured ceiling electrode 140,
dielectric ring 186, substrate support 130, base shield 214, and
other process kit components of the cleaning chamber 100 provide
more uniform cleaning of the surface contaminants and native oxide
layers on the substrate 104, while also allowing for a larger
number of substrate processing cycles between clean cycles. In
addition, the dual frequency, capacitively coupled, cleaning
process provides better cleaning control over both the number of
plasma species or plasma density across the substrate surface as
well as the kinetic energy of the plasma species. Furthermore, the
in-situ metal sputtering process substantially increases the number
of process cycles between chamber clean cycles. Thus, the present
process and apparatus provides significantly better cleaning while
also providing a substantial reduction in the down time of the
cleaning chamber 100 which is required for the opening and removing
chamber components for cleaning the same.
[0049] The present invention has been described with reference to
certain preferred versions thereof; however, other versions are
possible. For example, the contoured ceiling electrode, dielectric
ring, support, and lower shield, can be used in other types of
applications, as would be apparent to one of ordinary skill, for
example, etching chambers, CVD chambers, and PVD chambers.
Therefore, the spirit and scope of the appended claims should not
be limited to the description of the preferred versions contained
herein.
* * * * *