U.S. patent application number 10/846894 was filed with the patent office on 2005-02-10 for cleaning tantalum-containing deposits from process chamber components.
Invention is credited to Brueckner, Karl.
Application Number | 20050028838 10/846894 |
Document ID | / |
Family ID | 34798987 |
Filed Date | 2005-02-10 |
United States Patent
Application |
20050028838 |
Kind Code |
A1 |
Brueckner, Karl |
February 10, 2005 |
Cleaning tantalum-containing deposits from process chamber
components
Abstract
A method of cleaning tantalum-containing deposits from a copper
surface of a process chamber component involves immersing the
surface of the component in a cleaning solution. The cleaning
solution has HF and an oxidizing agent. The cleaning solution can
have a molar ratio of HF to the oxidizing agent of at least about
6:1, and the oxidizing agent can include at least one of HNO.sub.3,
H.sub.2O.sub.2, H.sub.2SO.sub.3 and O.sub.3. The cleaning solution
removes the tantalum-containing deposits from the surface
substantially without eroding the surface.
Inventors: |
Brueckner, Karl; (Santa
Clara, CA) |
Correspondence
Address: |
Applied Materials, Inc.
Patent Department, M/S 2061
P. O. Box 450A
Santa Clara
CA
95052
US
|
Family ID: |
34798987 |
Appl. No.: |
10/846894 |
Filed: |
May 13, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10846894 |
May 13, 2004 |
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10742604 |
Dec 19, 2003 |
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10742604 |
Dec 19, 2003 |
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10304535 |
Nov 25, 2002 |
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Current U.S.
Class: |
134/3 |
Current CPC
Class: |
C22B 3/065 20130101;
C22B 7/007 20130101; Y02P 10/234 20151101; C23G 1/103 20130101;
Y02P 10/20 20151101; B08B 3/08 20130101; C23G 1/086 20130101; C23G
1/125 20130101; C23G 1/205 20130101; C23C 16/4407 20130101; C22B
34/24 20130101; C23F 1/44 20130101; C23C 14/564 20130101; C23G
1/106 20130101; C23G 1/22 20130101; C23F 1/46 20130101; C23G 1/36
20130101; C23G 1/19 20130101 |
Class at
Publication: |
134/003 |
International
Class: |
C23G 001/02 |
Claims
What is claimed is:
1. A method of cleaning tantalum-containing deposits from a surface
of a process chamber component, the surface comprising copper, the
method comprising: immersing the surface of the component in a
cleaning solution comprising HF and an oxidizing agent, the molar
ratio of HF to the oxidizing agent being at least about 6:1,
whereby the tantalum-containing deposits can be removed from the
surface substantially without eroding the surface.
2. A method according to claim 1 wherein the molar ratio of HF to
oxidizing agent is from about 6:1 to about 40:1.
3. A method according to claim 1 wherein the molar ratio of HF to
oxidizing agent is from about 9:1 to about 20:1.
4. A method according to claim 1 wherein the oxidizing agent
comprises at least one of HNO.sub.3, H.sub.2O.sub.2,
H.sub.2SO.sub.3 and O.sub.3.
5. A method according to claim 4 wherein the oxidizing agent
consists essentially of HNO.sub.3.
6. A method according to claim 1 wherein the cleaning solution
comprises at least about 3 M HF.
7. A method according to claim 6 wherein the cleaning solution
comprises from about 3 M to about 20 M HF.
8. A method according to claim 6 wherein the cleaning solution
comprises from about 0.1 M to about 3 M of the oxidizing agent.
9. A method according to claim 1 further comprising recovering the
tantalum-containing deposits from the cleaning solution.
10. A component cleaned according to the method of claim 1, the
component comprising a portion of one or more of an enclosure wall,
chamber shield, target, cover ring, deposition ring, support ring,
insulator ring, coil, coil support, shutter disk, clamp shield, and
substrate support; and wherein the component is substantially
absent tantalum-containing deposits.
11. A method of cleaning tantalum-containing deposits from a
surface of a process chamber component, the surface comprising
copper, the method comprising: immersing the surface of the
component in a cleaning solution comprising HF and an oxidizing
agent, the oxidizing agent comprising at least one of
H.sub.2O.sub.2, H.sub.2SO.sub.3 and O.sub.3, whereby the
tantalum-containing deposits can be removed from the surface
substantially without eroding the surface.
12. A method according to claim 11 wherein the cleaning solution
comprises at least about 3 M HF.
13. A method according to claim 12 wherein the cleaning solution
comprises from about 3 M to about 20 M HF.
14. A method according to claim 11 wherein the cleaning solution
comprises from about 0.1 M to about 3 M of the oxidizing agent.
15. A component cleaned according to the method of claim 11, the
component comprising a portion of one or more of an enclosure wall,
chamber shield, target, cover ring, deposition ring, support ring,
insulator ring, coil, coil support, shutter disk, clamp shield, and
substrate support; and wherein the component is substantially
absent tantalum-containing deposits.
Description
CROSS-REFERENCE
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 10/742,604, entitled "Cleaning Chamber
Surfaces to Recover Metal-Containing Compounds" to Brueckner et al,
assigned to Applied Materials, Inc. and filed on Dec. 19, 2003,
which is a continuation-in-part of U.S. patent application Ser. No.
10/304,535, entitled "Method of Cleaning a Coated Process Chamber
Component" to Wang et al, assigned to Applied Materials, Inc. and
filed on Nov. 25, 2002, both of which are herein incorporated by
reference in their entireties.
BACKGROUND
[0002] The present invention relates to the cleaning and recovery
of metal-containing residues from the surface of processing chamber
components.
[0003] In the processing of substrates, such as semiconductor
wafers and displays, a substrate is placed in a process chamber and
exposed to an energized gas to deposit or etch material on the
substrate. During such processing, process residues are generated
and deposited on internal surfaces in the chamber. For example, in
sputter deposition processes, material sputtered from a target for
deposition on a substrate also deposits on other component surfaces
in the chamber, such as on deposition rings, cover ring, shadow
rings, inner shield, upper shield, wall liners, and focus rings. In
subsequent process cycles, the deposited process residues can
"flake off" from the chamber component surfaces to fall upon and
contaminate the substrate. Consequently, the deposited process
residues are periodically cleaned from the chamber surfaces.
[0004] However, it is difficult to clean process deposits that
contain metals such as tantalum from chamber components, especially
when the components are made of metal-containing materials. When
tantalum is sputter deposited onto the substrate, some of the
sputtered tantalum deposits upon the adjacent chamber component
surfaces. These tantalum process deposits are difficult to remove
because cleaning solutions suitable for their removal are also
frequently reactive with other metals, such as titanium, that are
used to form chamber components. Cleaning of tantalum-containing
materials from such surfaces can erode the components and require
their frequent replacement. The erosion of metal surfaces can be
especially problematic when cleaning textured metal surfaces, such
as surfaces formed by a "Lavacoat.TM." process. These surfaces have
crevices and pores in which tantalum-containing process residues
get lodged, making it difficult to remove these residues with
conventional cleaning process.
[0005] When conventional cleaning methods are used to clean
tantalum, an amount of the tantalum-containing material generated
in these process is not recovered. It is estimated that in many
tantalum deposition processes, only about one-half of the sputtered
tantalum material is deposited on the substrate, the rest being
deposited on component surfaces within the chamber. Conventional
cleaning methods frequently dispose of the used cleaning solutions
along with the dissolved tantalum material. Thus, a large amount of
tantalum material is wasted after it is cleaned off the chamber
surfaces, resulting in an estimated loss of about 30,000 pounds of
tantalum per year. The disposal of tantalum is environmentally
undesirable and costly because high purity tantalum is expensive
and fresh cleaning solution has to be acquired.
[0006] In one version, it is desirable to be able to use process
chamber components having copper surfaces during the processing of
substrates. Copper surfaces exhibit fewer thermal gradients, and
can thus minimize stresses between the copper surfaces and any
residues deposited on the surfaces. However, it can be difficult to
implement the use of components having copper surfaces because it
can be very difficult to clean process residues from such surfaces.
This is in part because the copper surfaces are typically very
easily etched and eroded by the same cleaning solutions that are
capable of etching and removing tantalum-containing deposits from
the component surfaces. Also, copper surfaces can be undesirably
eroded even by cleaning solutions that do not otherwise excessively
erode other metal surfaces, such as aluminum or stainless steel
surfaces.
[0007] Thus, it is desirable to have a method of cleaning
metal-containing residues and deposits such as tantalum-containing
deposits from surfaces of components without excessively eroding
the surfaces. It is further desirable to have a method of cleaning
tantalum-containing deposits from surfaces of components comprising
copper. It is also desirable to reduce the waste of the tantalum
materials cleaned off the chamber surfaces. It is further desirable
to have a method of recovering cleaning solutions which are used to
clean the tantalum-containing residues.
SUMMARY
[0008] In one version, a method of cleaning tantalum-containing
deposits from a copper surface of a process chamber component
involves immersing the surface of the component in a cleaning
solution having a molar ratio of HF and an oxidizing agent of at
least about 6:1. The cleaning solution removes the
tantalum-containing deposits from the surface substantially without
eroding the surface.
[0009] In another version, a method of cleaning tantalum-containing
deposits from a copper surface of a process chamber component
involves immersing the surface of the component in a cleaning
solution having HF and an oxidizing agent to remove the
tantalum-containing deposits substantially without eroding the
surface. The oxidizing agent includes at least one of
H.sub.2O.sub.2, H.sub.2SO.sub.3 and O.sub.3.
DRAWINGS
[0010] 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:
[0011] FIG. 1 is a schematic side view of an embodiment of a
component having a surface with metal-containing deposits
thereon;
[0012] FIG. 2 is a schematic side view of an embodiment of an
electrochemical etching apparatus;
[0013] FIG. 3a is a flow chart showing an embodiment of a method
for recovering tantalum-containing compounds;
[0014] FIG. 3b is a flow chart showing another embodiment of a
method for recovering tantalum-containing compounds;
[0015] FIG. 4 is a sectional side view of an embodiment of a
process chamber having one or more components that can be cleaned
of metal-containing deposits in a cleaning process;
[0016] FIG. 5 is a comparative graph of the percent weight loss of
copper for increasing cleaning time resulting from the cleaning of
copper surfaces with different cleaning solutions comprising HF and
HNO.sub.3;
[0017] FIG. 6a is a graph of the percent weight loss of copper for
increasing cleaning time resulting from the cleaning of copper
surface with a cleaning solution comprising HF alone, and also with
an improved cleaning solution having a pre-selected ratio of HF to
HNO.sub.3; and
[0018] FIG. 6b is a graph of the percent weight loss of tantalum
for increasing cleaning time resulting from the cleaning of
tantalum surfaces with the cleaning solutions in FIG. 6a.
DESCRIPTION
[0019] A process chamber component 22 having a surface 20 is
cleaned to remove metal-containing process deposits 24, such as
tantalum-containing deposits 24, that are generated during
processing of a substrate 104, as shown for example in FIG. 1. The
tantalum-containing deposits can comprise, for example, at least
one of tantalum metal, tantalum nitride and tantalum oxide.
Performing a cleaning process to remove the tantalum-containing
deposits 24 can reduce the formation of contaminant particles in
the chamber 106, improve substrate yields, and allow recovery of
tantalum from the cleaning solution. The chamber components 22 to
be cleaned are those that accumulate metal and tantalum-containing
process deposits 24, such as for example, portions of a gas
delivery system 112 that provides process gas in the chamber 106, a
substrate support 114 that supports the substrate 104 in the
chamber 106, a gas energizer 116 that energizes the process gas,
chamber enclosure walls 118 and shields 120, or a gas exhaust 122
that exhausts gas from the chamber 106, exemplary embodiments of
which are shown in FIG. 4.
[0020] Referring to FIG. 4, which illustrates an embodiment of a
physical vapor deposition chamber 106, components 22 that can be
cleaned include a chamber enclosure wall 118, a chamber shield 120,
including upper and lower shields 120a,b, a target 124, a cover
ring 126, a deposition ring 128, a support ring 130, insulator ring
132, a coil 135, coil support 137, shutter disk 133, clamp shield
141, and a surface 134 of the substrate support 114. The components
22 can have surfaces 20 comprising metal, such as at least one of
titanium, stainless steel, aluminum, copper and tantalum. The
surfaces 20 can also comprise a ceramic material, such as at least
one of aluminum oxide, aluminum nitride, and silicon oxide.
[0021] A cleaning step to remove process deposits 24 can comprise
exposing the surface 20 of the component 22 to an acidic cleaning
solution that is capable of at least partially removing the process
deposits 24 from the surface 20 of the component 22. The acidic
solution comprises dissolved acidic species that are capable of
reacting with and removing process deposits 24 from the surface 20
of the component 22, for example, by reacting with the process
deposits 24 to form species that readily dissolve in the acidic
solution. However, the acidic solution does not excessively corrode
or otherwise damage the exposed portions of the surface 20 of the
component 22 after the process deposits 24 are removed from that
portion of the component 22. The surface 20 can be exposed to the
acidic solution by dipping, immersing or otherwise contacting
portions of the surface 20 with the acidic solution. The surface 20
of the coated component 22 may be immersed in the acidic solution
for a duration of from about 3 to about 15 minutes, such as about 8
minutes, but may also be immersed for other times depending on the
composition and thickness of the process deposit materials.
[0022] The composition of the acidic cleaning solution is selected
according to the composition of the surface 20, and the composition
of the process deposits 24. In one version, the acidic solution
comprises hydrofluoric acid (HF). Hydrofluoric acid can react with
and dissolve impurities that may have accumulated on the surface
20. The acidic solution may additionally or alternatively comprise
a non-fluorinated acid, such as nitric acid (HNO.sub.3.) The
non-fluorinated agent may provide less aggressive chemical species,
which allows for the cleaning and preparation of the surface 20
with reduced formation of erosion cracks through the underlying
component structure. Additionally, in one version, the acidic
solution provided to clean the surface 20 can comprise a suitably
small concentration of the acidic species to reduce corrosion of
the component 22. A suitable concentration of acidic species may
be, for example, less than about 15 M acidic species, such as from
about 2 to about 15 M acidic species. For a component 22 comprising
a surface 20 comprising aluminum oxide or stainless steel, a
suitable acidic solution may comprise from about 2 M to about 8 M
HF, such as about 5 M HF, and from about 2 M HNO.sub.3 to about 15
M HNO.sub.3, such as about 12 M HNO.sub.3. For a component 22
comprising a surface 20 comprising titanium, a suitable acidic
solution may comprise from about 2 M to about 10 M HNO.sub.3. In
one version, a suitable acidic solution may comprise 5 M HF and 12
M HNO.sub.3.
[0023] It has further been discovered that the cleaning method can
be improved to clean tantalum-containing residues by immersing the
surface 20 in a solution having a ratio of HF to HNO.sub.3 that is
selected to remove the tantalum-containing deposits substantially
without eroding the surface 20, and especially without eroding
metal surfaces 20. In particular, it has been discovered that
selecting a ratio of HF to HNO.sub.3 that is sufficiently low can
reduce erosion of the surface 20, and can especially reduce the
erosion of metal surfaces 20. A suitable ratio of HF to HNO.sub.3
may be a ratio that is less than about 1:8 by weight. For example,
the cleaning solution can comprise a ratio of HF to HNO.sub.3 of
from about 1:8 to about 1:30 by weight, and even from about 1:12 to
about 1:20 by weight, such as about 1:15 by weight. A concentration
of HF in solution is desirably maintained at less than about 10% by
weight, such as from about 2% to about 10% by weight, and even
about 5% by weight. A concentration of HNO.sub.3 in solution is
desirably at least about 60% by weight, such as from about 60% to
about 67% by weight, and even about 65% by weight.
[0024] The improved cleaning results are believed to be at least in
part because the HNO.sub.3 reacts with the surfaces 20, such as
metal surfaces, to form an oxidized and etch-resistant protective
layer on the surface that inhibits etching of the surface 20. At a
sufficiently low ratio, the HNO.sub.3 and HF work in concert to
remove the tantalum-containing deposits substantially without
eroding the surface 20. The HF etches away and dissolves the
tantalum-containing deposits, and thus exposes portions of the
surface 20. The HNO.sub.3 also etches tantalum-containing deposits,
although at a lower etching rate, and as a strong oxidizer further
reacts with and oxidizes the exposed portions of the surface 20 to
form the protective etch-resistant layer. Thus, by maintaining a
concentration of HNO.sub.3 that is sufficiently high with respect
to the concentration of HF in the solution, an excess of HNO.sub.3
can be used to protect the surface 20 from erosion. Cleaning
solutions having the improved ratio of HF to HNO.sub.3 that
provides a sufficiently high concentration of HNO.sub.3 with
respect to HF may be especially suitable for cleaning metal
surfaces 20 comprising, for example, at least one of titanium,
stainless steel, aluminum, and tantalum.
[0025] In the cleaning process, fresh HF can be added to the
cleaning solution to replenish depleted HF. The HF in solution
becomes depleted by, for example, reacting with tantalum-containing
deposits 24 to form tantalum fluoride compounds. The HF depletion
gradually slows down the removal of the tantalum-containing
deposits from the surface 20. Addition of fresh HF allows the
tantalum-containing deposits 24 to be removed from the surface 20
at a desired rate.
[0026] In one version, the composition of the cleaning solution can
be optimized to clean tantalum-containing deposits from metal
surfaces 20 comprising copper. In particular, a cleaning solution
comprising hydrofluoric acid (HF) and an oxidizing agent in a
pre-selected molar ratio has been discovered to provide improved
cleaning of the tantalum-containing deposits 24 without excessively
etching the copper surface 20, and even substantially without
eroding the copper surface 20. In one version, the cleaning
solution comprises a molar ratio of HF to an oxidizing agent of at
least about 6:1, such as at least about 9:1, and even at least
about 20:1. For example, the cleaning solution may comprise a molar
ratio of HF to oxidizing agent of from about 6:1 to about 40:1,
such as from about 9:1 to about 20:1. A suitable concentration of
HF in the cleaning solution may be at least about 3 M, such as from
about 3 M to about 20 M. A suitable concentration of oxidizing
agent in the cleaning solution may be less than about 3 M, such as
from about 0.1 M to about 3 M, and even less than about 1 M, such
as from about 0.1 M to about 1 M. The improved cleaning solution
comprising HF and the oxidizing agent in the pre-selected ratio can
provide a good etching selectivity of the tantalum-containing
deposits 24 to the copper surface 20, such as for example a
selectivity of at least about 40:1, and even at least about
50:1.
[0027] The oxidizing agent comprises a compound that is capable of
oxidizing other compounds and materials, such as the
tantalum-containing deposits, and typically comprises an
oxygen-containing compound. In one version, a suitable oxidizing
agent comprises nitric acid (HNO.sub.3). It has further been
discovered that good cleaning results can be provided with
oxidizing agents comprising at least one of hydrogen peroxide
(H.sub.2O.sub.2), sulfurous acid (H.sub.2SO.sub.3), and ozone
(O.sub.3), any one or combination of which can be provided in
addition to or as an alternative to HNO.sub.3. For example, ozone
can be provided in the cleaning solution in the desired ratio by
bubbling ozone gas into the cleaning solution.
[0028] In one exemplary version of a cleaning solution suitable for
cleaning tantalum-containing deposits from a component surface 20
comprising copper, the oxidizing agent comprises HNO.sub.3. For
example, the cleaning solution may be formed by combining (i) about
45% by volume of a stock solution of HF having a concentration of
about 49% HF by weight, with (ii) from about 5% to about 10% by
volume of a stock solution of HNO.sub.3 having a concentration of
about 70% HNO.sub.3 by weight. The remainder of the solution
comprises water, which is preferably de-ionized. Such a solution
comprises a molar ratio of HF to HNO.sub.3 of from about 9:1, for
the 10% by volume HNO.sub.3 solution, to about 19:1, for the 5% by
volume HNO.sub.3 solution.
[0029] The discovery that a solution comprising HF and an oxidizing
agent in a pre-selected ratio could clean tantalum-containing
deposits 24 without excessively etching copper surfaces 20 was
unexpected, because copper is typically very susceptible to
chemical attack by oxidizing agents such as HNO.sub.3, and thus can
be easily eroded by such agents. Also, tantalum-containing deposits
24 are not typically etched at a desirably high rate by solutions
comprising HF alone. However, it was observed that by combining HF
and an oxidizing agent in the pre-selected molar ratio, a
synergistic effect could be obtained by which improved cleaning of
the tantalum-containing deposits 24 was obtained. Without limiting
the discovery to any specific chemical mechanism, it is postulated
that the oxidizing agent may act to speed up the rate of cleaning
achieved by HF in solution to etch the tantalum-containing deposits
from the surface 20 at a high etching rate. However, the
concentration of oxidizing agent is desirably maintained low with
respect to the HF concentration, as excessive amounts of the
oxidizing agent can otherwise result in rapid etching and erosion
of copper surfaces 20. The improved copper cleaning ability of the
HF and oxidizing agent cleaning solution is further a surprise, as
surfaces 20 of components comprising metals other than copper, such
as for example aluminum or stainless steel surfaces, can often
require cleaning solutions having a substantially lower molar ratio
of HF to HNO.sub.3. Thus, the cleaning of copper surfaces 20 with
the improved cleaning solution having HF and the oxidizing agent in
the pre-selected ratio provides unexpectedly good cleaning results,
and provides for the efficient use of components 22 having copper
surfaces 20 in substrate processing chambers 106.
[0030] FIGS. 5 through 6b show comparative data for the cleaning of
surfaces with different cleaning solutions. FIG. 5 demonstrates
comparative data for cleaning solutions having HF and HNO.sub.3 in
relatively low ratios that are below the desired molar ratio of at
least about 6:1. To obtain the comparative data, copper surfaces 20
were immersed in cleaning solutions comprising HF and HNO.sub.3 in
molar ratios of (i) 2:1 in the solution indicated by line 200, and
(ii) 1:2 in the solution indicated by line 202 on FIG. 5. The
solution indicated by line 200 was formed by combining 1 part by
volume of a 49% by weight stock solution of HF, 1 part by volume of
a 70% by weight stock solution of HNO.sub.3, and 1 part by volume
of de-ionized water. The solution indicated by line 202 was formed
by combining 1 part by volume of the 49% by weight stock solution
of HF with 4 parts by volume of de-ionized water. The weight
percent of copper eroded way from each surface was measured at
different intervals during the cleaning process and this weight
percent was graphed for increasing cleaning duration. FIG. 5
demonstrates that both cleaning solutions yielded undesirably high
levels of erosion of the copper surface, with the cleaning solution
indicated by line 200 eroding away about 20% by weight of the
copper surface after only about 5 minutes, and the solution
indicated by line 202 eroding a little over 25% by weight after
about 5 minutes, and over 30% by weight after about 10 minutes.
Thus, the cleaning solutions provided undesirable results in the
cleaning of the copper surfaces 20.
[0031] FIGS. 6a and 6b demonstrate the unexpectedly good cleaning
results obtained with a solution comprising HF and HNO.sub.3 having
the pre-selected ratio. In FIG. 6a, copper surfaces were immersed
in solutions comprising (i) a comparative solution comprising HF
alone in a concentration of about 15 M, indicated by line 204, and
(ii) an improved solution comprising HF and HNO.sub.3 in a molar
ratio of about 20:1, indicated by line 206. The comparative
solution was formed by combining 1 part by volume of a 49% by
weight stock solution of HF with 1 part by volume of de-ionized
water. The improved cleaning solution was formed by combining 10
parts by volume of a 49% by weight stock solution of HF with 1 part
by volume of a 70% by weight stock solution of HNO.sub.3 and 10
parts by volume of de-ionized water. The weight percent of copper
eroded way from each surface was measured at different intervals
during the cleaning process, and the eroded weight percent was
graphed for increasing cleaning duration.
[0032] FIG. 6a shows the weight percent loss of copper resulting
from the cleaning of copper surfaces 20 with the comparative
cleaning solution comprising HF and the improved cleaning solution
comprising both HF and HNO.sub.3 in the molar ratio of about 20:1.
The comparative solution yielded little or no erosion of the copper
surface. While the improved solution comprising both HF and
HNO.sub.3 did result in minor erosion of the copper surface, the
erosion occurred at a much lower rate and with a much lower copper
percent weight loss than the comparative cleaning solutions
represented by lines 200 and 202 in FIG. 5. For example, for the
improved cleaning solution represented by line 206, the copper
percent weight loss after a little more than 100 minutes of
cleaning was just a little lower than 0.15%. By comparison, after
only 5 minutes of cleaning, the comparative solutions represented
by lines 200 and 202 in FIG. 5 resulted in copper weight loss
percentages of 20% and a little over 25%, which is a percent weight
loss that is over 100 times that of the improved cleaning solution
having the pre-selected ratio of HF to HNO.sub.3. Even after about
350 minutes of cleaning, the improved cleaning solution having the
pre-selected ratio of HF to HNO.sub.3 only yielded a loss of a
little over about 0.20 weight percent of copper from the surface
20. Thus, the improved cleaning solution having the pre-selected
ratio of HF to HNO.sub.3 provides improved cleaning of copper
surfaces 20 substantially without eroding the copper surfaces
20.
[0033] FIG. 6b demonstrates the results from the exposure of
tantalum surfaces to cleaning solutions having the same composition
as those in FIG. 6a. The cleaning results provided by the
comparative solution comprising about 15 M HF are indicated by line
208, and the cleaning results provided by the improved solution
comprising both HF and HNO.sub.3 in the pre-selected ratio of about
20:1 is indicated by line 210. To obtain the data for this figure,
surfaces comprising tantalum were immersed in each of the cleaning
solutions, and the weight percent of tantalum eroded way from each
surface was measured at different intervals during the cleaning
process to determine the cleaning ability of each solution. The
eroded weight percent was graphed for each solution for increasing
cleaning duration.
[0034] The results shown in FIG. 6b demonstrate that the improved
cleaning solution having the pre-selected ratio of HF to HNO.sub.3
provides excellent cleaning of tantalum-containing materials over
solutions having HF alone. For example, after about 150 minutes of
cleaning, the improved solution of HF and HNO.sub.3, represented by
line 210, removed over 5 weight percent of tantalum from the
surface. By comparison, the solution comprising only HF,
represented by line 208, removed only about 1 weight percent of
tantalum in the same time period. Furthermore, a comparison of
FIGS. 6a and 6b demonstrate the high selectivity between tantalum
and copper that is exhibited by the improved cleaning solution
comprising the pre-selected ratio of HF to HNO.sub.3. The improved
cleaning solution resulted in a loss of only about 0.22 weight
percent of copper after a cleaning duration of about 350 minutes,
as shown by line 206 in FIG. 6a, while a little over 11 weight
percent of tantalum was removed from the surface during the same
time period, as shown by line 210 in FIG. 6b. Thus, the improved
cleaning solution is capable of providing a selectivity of tantalum
to copper of about 50:1. Accordingly, a solution having the
pre-selected ratio of HF and oxidizing agent such as HNO.sub.3
provides improved results for the efficient cleaning of
tantalum-containing residues from component surfaces comprising
copper, substantially without eroding the component surfaces.
[0035] In yet another version, tantalum-containing deposits 24 can
be cleaned from a surface 20 by immersing the surface 20 in a
cleaning solution comprising KOH and H.sub.2O.sub.2. The cleaning
solution has a ratio of KOH to H.sub.2O.sub.2 that is selected to
remove the tantalum-containing deposits substantially without
eroding the surface 20, and in particular substantially without
eroding metal surfaces. A suitable ratio of KOH to H.sub.2O.sub.2
is from about 6:1 to about 10:1 by mole, such as about 7.5:1. A
ratio that is lower or higher than the desired ratio range can
reduce the selectivity towards the tantalum-containing deposits,
and result in etching and erosion of the surface 20, respectively.
A suitable concentration of KOH in solution is, for example, from
about 5 M to about 12 M, and even from about 5 M to about 10 M,
such as about 7 M. A suitable concentration of H.sub.2O.sub.2 in
solution is, for example, from about 0.5 M to about 2.5 M, and even
from about 0.5 M to about 2 M, such as about 1 M. Also, it has been
discovered that maintaining a proper temperature of the cleaning
solution comprising KOH and H.sub.2O.sub.2 can improve the removal
of tantalum-containing deposits 24 by increasing the deposit
removal rate. A suitable temperature of the cleaning solution may
be at least about 70.degree. C., such as from about 80 to about
95.degree. C., and even at least about 90.degree. C.
[0036] In yet another version of the cleaning method, a metal
surface 20 is cleaned in an electrochemical etching process. In
this process, the surface 20 of the component 22 serves as an anode
and is connected to a positive terminal 31 of a voltage source 30,
as shown for example in FIG. 2. The metal surface 20 is immersed in
an electrochemical bath 33 having a bath solution comprising
electrolytes. The electrochemical bath solution can also or
alternatively comprise an etching agent that selectively etches the
tantalum-containing deposits, such as at least one of HF,
HNO.sub.3, KOH and H.sub.2O.sub.2. For example, the electrochemical
bath can comprise one of the HF/HNO.sub.3 or KOH/H.sub.2O.sub.2
cleaning solutions described above. The bath solution can also
comprise other cleaning agents such as HCl, H.sub.2SO.sub.4 and
methanol. In one version, the bath selectively electrochemically
etches tantalum-containing deposits with a solution comprising HF,
H.sub.2SO.sub.4 and methanol. A cathode 34 connected to the
negative terminal 32 of the voltage source 30 is also immersed in
the bath 33. Application of a bias voltage to the metal surface 20
and cathode 34 from the voltage source 30 induces a change in
oxidation state of the tantalum-containing residues 24 on the
surface 20 that can change tantalum-containing deposits 24, such as
tantalum metal, into ionic forms that are soluble in the
electrochemical etching bath solution, thus "etching" the
tantalum-containing deposits 24 away from the surface 20. The
electrochemical etching process conditions, such as the voltage
applied to the metal surface 20, the pH of the electrochemical
etching solution, and the temperature of the solution, are
desirably maintained to selectively remove tantalum-containing
deposits from the metal surface 20 substantially without eroding
the metal surface 20.
[0037] These cleaning methods may be particularly suitable for
surfaces 20 that are textured, as shown for example in FIG. 1.
Components 22 having textured surfaces reduce particle generation
in the process chamber by providing a "sticky" surface to which
process residues adhere. In one version, components 22 cleaned of
tantalum-containing deposits include components having surfaces
textured by a "Lavacoat.TM." process, such as for example
components described in U.S. patent application Ser. No. 10/653,713
to West, et al, filed on Sep. 2, 2002, entitled "Fabricating and
Cleaning Chamber Components Having Textured Surfaces," U.S. patent
application Ser. No. 10/099,307, filed Mar. 13, 2002, to
Popiolkowski et al, and U.S. patent application Ser. No.
10/622,178, filed on Jul. 17, 2003 to Popiolkowski et al., all
commonly assigned to Applied Materials, Inc., and all of which are
incorporated herein by reference in their entireties. The
components 22 can also comprise coated components having textured
surfaces, such as plasma sprayed coatings or twin-wire arc sprayed
coatings, as described for example in U.S. patent application Ser.
No. 10/304,535 to Wang et al, filed on Nov. 25, 2002, commonly
assigned to Applied Materials, which is incorporated herein by
reference in its entirety.
[0038] The "Lavacoat.TM." textured metal surface 20 is formed by
generating an electromagnetic energy beam and directing the beam
onto the surface 20 of the component 22. The electromagnetic energy
beam is preferably an electron beam, but can also comprise protons,
neutrons and X-rays and the like. The electron beam is typically
focused on a region of the surface 20 for a period of time, during
which time the beam interacts with the surface 20 to form features
on the surface. It is believed that the beam forms the features by
rapidly heating the region of the surface 20, in some cases to a
melting temperature of the surface material. The rapid heating
causes some of the surface material to be ejected outwards, which
forms depressions 23 in the regions the material was ejected from,
and protuberances 25 in areas where the ejected material
re-deposits. After the desired features in the region are formed,
the beam is scanned to a different region of the component surface
20 to form features in the new region. The final surface 20 can
comprise a honeycomb-like structure of depressions 23 and
protuberances 25 formed in the surface 20. The features formed by
this method are typically macroscopically sized, and the
depressions can range in diameter from about 0.1 mm to about 3.5
mm, such as from about 0.8 to about 1.0 mm in diameter. The
"Lavacoat.TM." textured surface 20 has an overall surface roughness
average of from about 2500 microinches (63.5 micrometers) to about
4000 microinches (101.6 micrometers), the roughness average of the
surface 20 being defined as the mean of the absolute values of the
displacements from the mean line of the features along the surface
20.
[0039] The instant cleaning methods provide surprisingly good
results in cleaning such textured surfaces substantially without
eroding the surfaces 20. For example, for a textured metal surface
20 formed of titanium, the cleaning methods described above may
clean tantalum-containing residues from the surface 20 while
eroding less than about 1 mg/cm.sup.2 per hour of titanium from the
metal surface 20. In contrast, conventional tantalum cleaning
processes can erode more than about 5 mg/cm.sup.2 of titanium from
a titanium surface of a component 22. As another example, a
solution of KOH and H.sub.2O.sub.2 having the selected molar ratio
of from about 6:1 to about 10:1 and a temperature of from about 80
to about 95.degree. C., can clean tantalum-containing deposits at a
rate that is about 20 times faster than the rate at which a
titanium component surface 20 is eroded, allowing the surface 20 to
be cleaned substantially without excessive erosion.
[0040] Once cleaning of the component surface 20 has been
completed, the cleaning solution can be treated to recover
metal-containing materials, such as the tantalum-containing
materials, which may be at least one of tantalum metal and tantalum
oxide. Recovering tantalum-containing materials from the cleaning
solution reduces the pollution of the environment by tantalum
waste, and can also reduce the costs associated with proper
disposal of waste tantalum. The recovered tantalum-containing
materials can be re-used in substrate processing, for example the
recovered tantalum materials can be used to form a
tantalum-containing target for physical vapor deposition processes.
In addition to tantalum recovery, the used cleaning solution can be
treated to allow for re-use of the cleaning solution. For example,
the cleaning solution can be treated to recover a re-useable
solution of HF and HNO.sub.3.
[0041] A flow chart showing one version of a method of cleaning a
component and recovering tantalum-containing materials is shown in
FIG. 3a. In the first step of this method, the component surface 20
is cleaned by immersing in a cleaning solution, which dissolves
tantalum and other metal-containing residues in the solution to
form tantalum and metal-containing compounds, respectively. After
the component surface 20 has been cleaned, a precipitating agent is
added to the cleaning solution to precipitate metal-containing
compounds out of the solution and form mixed solids. The mixed
solids comprise tantalum-containing compounds such as tantalum
oxides, and can also comprise other metal-containing compounds,
such as compounds comprising aluminum, titanium and iron. In one
version, the cleaning solution may be recovered and re-used to
clean subsequent components 22 once the mixed solids have been
precipitated out of and removed from the solution, as indicated by
the arrow in FIG. 3a. In one method of precipitating the mixed
solids, the cleaning solution is neutralized by adding a
precipitating agent comprising an acid or base to bring the pH of
the solution from a pH of less than about 1 to about 7. For
example, for a cleaning solution comprising HF and HNO.sub.3, a
base can be added to neutralize the solution. For a cleaning
solution comprising KOH and H.sub.2O.sub.2, an acid can be added to
neutralize the solution. A suitable neutralizing acid can comprise
at least one of HNO.sub.3, H.sub.2SO.sub.4 and H.sub.3PO.sub.4. A
suitable neutralizing base can comprise at least one of NaOH, KOH
and CaCO.sub.3. The mixed solids are then separated from the
cleaning solution, for example by filtering the mixed solids from
the solution.
[0042] To separate the tantalum-containing compounds from the other
metal-containing compounds, a metal-selective acid solution is
added to the mixed solids. The metal-selective acid solution
comprises a metal-selective acid that dissolves metal-containing
compounds in the acid solution substantially without dissolving the
tantalum-containing compounds. A suitable metal-selective acid can
comprise, for example, HCl. The solid tantalum-containing compounds
are separated from the acid solution having the dissolved
metal-containing compounds by, for example, filtering the
tantalum-containing solids, or by decanting the acid solution from
the tantalum-containing solids. The tantalum-containing compound
can then be converted into tantalum oxide, for example by
heating.
[0043] Yet another method of cleaning a component and recovering
tantalum-containing materials is shown in the flow chart of FIG.
3b. The component surface 20 is cleaned by immersing the surface 20
in an aqueous cleaning solution to dissolve tantalum-containing
compounds from the surface 20. After cleaning the surface,
tantalum-containing compounds are removed from the cleaning
solution in a liquid-to-liquid extraction process. The extraction
process comprises combining the aqueous cleaning solution with an
organic solution that is substantially non-miscible with the
aqueous solution. The organic solution is a solution in which the
tantalum-containing compounds are highly soluble, and that is
capable of extracting the tantalum-containing compounds from the
aqueous solution. A suitable organic solution for extracting the
tantalum-containing compounds can comprise, for example, at least
one of methyl isobutyl ketone, diethyl ketone, cyclohexone,
diisobutyl ketone, and tributyl phosphate. Once the
tantalum-containing compounds have been extracted into the organic
solution, the organic and aqueous solutions are separated, for
example by allowing the solutions to divide into separate organic
and aqueous phases, and draining one of the solutions from the
other. The separated aqueous solution can be retained and re-used
as a cleaning solution, as shown by the arrow in FIG. 3b. For
example, the aqueous solution can comprise HF and HNO.sub.3 that
remain in the aqueous solution during the extractions, and which
can be re-used in subsequent cleaning processes to remove
tantalum-containing residues from metal surfaces 20.
[0044] After the extraction process, the tantalum-containing
compounds in the organic solution can be pyrohydrolytically
decomposed. In the pyrohydrolytic decomposition, the
tantalum-containing compounds are heated to a temperature at which
the compounds react with oxygen to form tantalum oxide compounds,
such as a temperature of at least about 120.degree. C., such as
from about 120.degree. C. to about 180.degree. C. The organic
solution and any decomposition reaction products can be evaporated
from the tantalum oxide compounds during the pyrohydrolytic
decomposition process. Alternatively, the organic solution can be
removed from the tantalum-containing compounds in a separate step.
The tantalum oxide compounds can also be further treated to form
tantalum metal, for example by heating the tantalum oxide compounds
in a furnace.
[0045] An example of a suitable process chamber 106 having a
component that is cleaned to remove metal-containing deposits 24
such as tantalum-containing deposits 24 is shown in FIG. 4. The
chamber 106 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 106 comprises a
sputter deposition chamber, also called a physical vapor deposition
or PVD chamber, that is capable of sputter depositing material on a
substrate 104, such as one or more of tantalum, tantalum nitride,
titanium, titanium nitride, copper, tungsten, tungsten nitride and
aluminum. The chamber 106 comprises enclosure walls 118 that
enclose a process zone 109, and that include sidewalls 164, a
bottom wall 166, and a ceiling 168. A support ring 130 can be
arranged between the sidewalls 164 and ceiling 168 to support the
ceiling 168. Other chamber walls can include one or more shields
120 that shield the enclosure walls 118 from the sputtering
environment.
[0046] The chamber 106 comprises a substrate support 114 to support
the substrate in the sputter deposition chamber 106. The substrate
support 114 may be electrically floating or may comprise an
electrode 170 that is biased by a power supply 172, such as an RF
power supply. The substrate support 114 can also comprise a
moveable shutter disk 133 that can protect the upper surface 134 of
the support 114 when the substrate 104 is not present. In
operation, the substrate 104 is introduced into the chamber 106
through a substrate loading inlet (not shown) in a sidewall 164 of
the chamber 106 and placed on the support 114. The support 114 can
be lifted or lowered by support lift bellows and a lift finger
assembly (not shown) can be used to lift and lower the substrate
onto the support 114 during transport of the substrate 104 into and
out of the chamber 106.
[0047] The support 114 may also comprise one or more rings, such as
a cover ring 126 and a deposition ring 128, that cover at least a
portion of the upper surface 134 of the support 114 to inhibit
erosion of the support 114. In one version, the deposition ring 128
at least partially surrounds the substrate 104 to protect portions
of the support 114 not covered by the substrate 104. The cover ring
126 encircles and covers at least a portion of the deposition ring
128, and reduces the deposition of particles onto both the
deposition ring 128 and the underlying support 114.
[0048] A process gas, such as a sputtering gas, is introduced into
the chamber 106 through a gas delivery system 112 that includes a
process gas supply comprising one or more gas sources 174 that each
feed a conduit 176 having a gas flow control valve 178, such as a
mass flow controller, to pass a set flow rate of the gas
therethrough. The conduits 176 can feed the gases to a mixing
manifold (not shown) in which the gases are mixed to from a desired
process gas composition. The mixing manifold feeds a gas
distributor 180 having one or more gas outlets 182 in the chamber
106. The process gas 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 may also
comprise 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 106 through an exhaust 122 which includes one or
more exhaust ports 184 that receive spent process gas and pass the
spent gas to an exhaust conduit 186 in which there is a throttle
valve 188 to control the pressure of the gas in the chamber 106.
The exhaust conduit 186 feeds one or more exhaust pumps 190.
Typically, the pressure of the sputtering gas in the chamber 106 is
set to sub-atmospheric levels.
[0049] The sputtering chamber 106 further comprises a sputtering
target 124 facing a surface 105 of the substrate 104, and
comprising material to be sputtered onto the substrate 104, such as
for example at least one of tantalum and tantalum nitride. The
target 124 is electrically isolated from the chamber 106 by an
annular insulator ring 132, and is connected to a power supply 192.
The sputtering chamber 106 also has a shield 120 to protect a wall
118 of the chamber 106 from sputtered material. The shield 120 can
comprise a wall-like cylindrical shape having upper and lower
shield sections 120a, 120b that shield the upper and lower regions
of the chamber 106. In the version shown in FIG. 4, the shield 120
has an upper section 120a mounted to the support ring 130 and a
lower section 120b that is fitted to the cover ring 126. A clamp
shield 141 comprising a clamping ring can also be provided to clamp
the upper and lower shield sections 120a,b together. Alternative
shield configurations, such as inner and outer shields, can also be
provided. In one version, one or more of the power supply 192,
target 124, and shield 120, operate as a gas energizer 116 that is
capable of energizing the sputtering gas to sputter material from
the target 124. The power supply 192 applies a bias voltage to the
target 124 with respect to the shield 120. The electric field
generated in the chamber 106 from the applied voltage energizes the
sputtering gas to form a plasma that energetically impinges upon
and bombards the target 124 to sputter material off the target 124
and onto the substrate 104. The support 114 having the electrode
170 and support electrode power supply 172 may also operate as part
of the gas energizer 116 by energizing and accelerating ionized
material sputtered from the target 124 towards the substrate 104.
Furthermore, a gas energizing coil 135 can be provided that is
powered by a power supply 192 and that is positioned within the
chamber 106 to provide enhanced energized gas characteristics, such
as improved energized gas density. The gas energizing coil 135 can
be supported by a coil support 137 that is attached to a shield 120
or other wall in the chamber 106.
[0050] The chamber 106 is controlled by a controller 194 that
comprises program code having instruction sets to operate
components of the chamber 106 to process substrates 104 in the
chamber 106. For example, the controller 194 can comprise a
substrate positioning instruction set to operate one or more of the
substrate support 114 and substrate transport to position a
substrate 104 in the chamber 106; a gas flow control instruction
set to operate the flow control valves 178 to set a flow of
sputtering gas to the chamber 106; a gas pressure control
instruction set to operate the exhaust throttle valve 188 to
maintain a pressure in the chamber 106; a gas energizer control
instruction set to operate the gas energizer 116 to set a gas
energizing power level; a temperature control instruction set to
control temperatures in the chamber 106; and a process monitoring
instruction set to monitor the process in the chamber 106.
[0051] Although exemplary embodiments of the present invention are
shown and described, those of ordinary skill in the art may devise
other embodiments which incorporate the present invention, and
which are also within the scope of the present invention. For
example, other chamber components than the exemplary components
described herein can also be cleaned. Additional cleaning and
recovery steps other than those described could also be performed.
Furthermore, relative or positional terms shown with respect to the
exemplary embodiments are interchangeable. Therefore, the appended
claims should not be limited to the descriptions of the preferred
versions, materials, or spatial arrangements described herein to
illustrate the invention.
* * * * *