U.S. patent application number 11/385047 was filed with the patent office on 2006-11-02 for electroless deposition process on a silicide contact.
Invention is credited to Srinivas Gandikota, Avgerinos V. Gelatos, Arulkumar Shanmugasundram, Michael P. Stewart, Timothy W. Weidman, Zhize Zhu.
Application Number | 20060246217 11/385047 |
Document ID | / |
Family ID | 37024527 |
Filed Date | 2006-11-02 |
United States Patent
Application |
20060246217 |
Kind Code |
A1 |
Weidman; Timothy W. ; et
al. |
November 2, 2006 |
Electroless deposition process on a silicide contact
Abstract
Embodiments as described herein provide methods for depositing a
material on a substrate during electroless deposition processes, as
well as compositions of the electroless deposition solutions. In
one embodiment, the substrate contains a contact aperture having an
exposed silicon contact surface. In another embodiment, the
substrate contains a contact aperture having an exposed silicide
contact surface. The apertures are filled with a metal contact
material by exposing the substrate to an electroless deposition
process. The metal contact material may contain a cobalt material,
a nickel material, or alloys thereof. Prior to filling the
apertures, the substrate may be exposed to a variety of
pretreatment processes, such as preclean processes and activations
processes. A preclean process may remove organic residues, native
oxides, and other contaminants during a wet clean process or a
plasma etch process. Embodiments of the process also provide the
deposition of additional layers, such as a capping layer.
Inventors: |
Weidman; Timothy W.;
(Sunnyvale, CA) ; Stewart; Michael P.; (Mountain
View, CA) ; Zhu; Zhize; (Cupertino, CA) ;
Shanmugasundram; Arulkumar; (Sunnyvale, CA) ;
Gandikota; Srinivas; (Santa Clara, CA) ; Gelatos;
Avgerinos V.; (Redwood City, CA) |
Correspondence
Address: |
PATTERSON & SHERIDAN, LLP
3040 POST OAK BOULEVARD, SUITE 1500
HOUSTON
TX
77056
US
|
Family ID: |
37024527 |
Appl. No.: |
11/385047 |
Filed: |
March 20, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60663493 |
Mar 18, 2005 |
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60683599 |
May 23, 2005 |
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60703538 |
Jul 29, 2005 |
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60703633 |
Jul 29, 2005 |
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60709564 |
Aug 19, 2005 |
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60754230 |
Dec 27, 2005 |
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60731624 |
Oct 28, 2005 |
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Current U.S.
Class: |
427/99.5 ;
106/1.22; 106/1.27; 427/443.1 |
Current CPC
Class: |
B82Y 30/00 20130101;
C23C 18/1893 20130101; H01L 21/76874 20130101; H01L 21/76843
20130101; H01L 21/76814 20130101; C23C 18/34 20130101; H01L
21/28518 20130101; H01L 21/76889 20130101; C23C 18/32 20130101;
H01L 21/76855 20130101; H01L 21/76879 20130101; H01L 21/02063
20130101; C23C 18/1651 20130101; H01L 21/288 20130101; H01L
21/76847 20130101; H01L 21/76856 20130101; H01L 21/76802 20130101;
H01L 21/76867 20130101 |
Class at
Publication: |
427/099.5 ;
427/443.1; 106/001.22; 106/001.27 |
International
Class: |
B28B 19/00 20060101
B28B019/00; C23C 18/34 20060101 C23C018/34 |
Claims
1. A method for depositing a material on a substrate, comprising:
positioning a substrate within a process chamber, wherein the
substrate comprises an aperture containing an exposed silicide
contact surface; exposing the exposed silicide contact surface to a
deposition solution to form a metal contact material over the
exposed silicide contact surface during an electroless deposition
process; and filling the aperture with the metal contact material
by continuing the electroless deposition process.
2. The method of claim 1, wherein the exposed silicide contact
surface comprises at least one metal selected from the group
consisting of cobalt, nickel, tungsten, molybdenum, rhenium,
titanium, tantalum, hafnium, zirconium, alloys thereof, and
combinations thereof.
3. The method of claim 2, wherein the metal contact material
comprises a material selected from the group consisting of nickel,
nickel phosphide, nickel boride, cobalt, cobalt tungsten, cobalt
tungsten phosphide, cobalt tungsten boride, cobalt tungsten
phosphide boride, cobalt nickel, cobalt phosphide, cobalt boride,
cobalt nickel phosphide, cobalt nickel boride, derivatives thereof,
alloys thereof, and combinations thereof.
4. The method of claim 1, wherein a capping layer is deposited on
the exposed silicide contact surface prior to filling the aperture
with the metal contact material.
5. The method of claim 4, wherein the capping layer comprises a
material selected from the group consisting of cobalt tungsten
phosphide, cobalt tungsten boride, cobalt tungsten phosphide
boride, derivatives thereof, alloys thereof, and combinations
thereof.
6. The method of claim 5, wherein the capping layer is deposited
during an electroless deposition process.
7. The method of claim 1, wherein the exposed silicide contact
surface is exposed to a preclean process prior to depositing the
metal contact material thereon.
8. The method of claim 7, wherein the substrate is exposed to a
plasma to remove native oxides or contaminants from the exposed
suicide contact surface during the preclean process.
9. The method of claim 8, wherein a thin film is formed on the
substrate by the plasma and the thin film is removed by a vacuum
sublimation process.
10. The method of claim 8, further comprising exposing the
substrate to the plasma and a process gas comprising a gas mixture
of ammonia and nitrogen trifluoride.
11. The method of claim 10, wherein the gas mixture has a molar
ratio of the ammonia to the nitrogen trifluoride within a range
from about 1:1 to about 30:1.
12. The method of claim 7, wherein the preclean process is a wet
clean process.
13. The method of claim 12, wherein the wet clean process comprises
exposing the substrate to a wet clean solution comprising hydrogen
fluoride and a basic compound selected from the group consisting of
ammonium hydroxide, tetramethylammonium hydroxide, ethanolamine,
diethanolamine, triethanolamine, derivatives thereof, salts
thereof, and combinations thereof.
14. The method of claim 13, wherein the wet clean solution
comprises an EA-HF complex, a DEA-HF complex, a TEA-HF complex, a
DEA-EA-HF complex, a DEA-TEA-HF complex, a TEA-EA-HF complex,
derivatives thereof, salts thereof, and combinations thereof.
15. The method of claim 12, wherein the wet clean process comprises
exposing the substrate to a wet clean solution comprising hydrogen
peroxide and a basic compound selected from the group consisting of
ammonium hydroxide, tetramethylammonium hydroxide, ethanolamine,
diethanolamine, triethanolamine, derivatives thereof, salts
thereof, and combinations thereof.
16. The method of claim 12, wherein the wet clean process comprises
exposing the substrate to a wet clean solution comprising hydrogen
peroxide and hydrogen chloride.
17. A method for depositing a material on a substrate, comprising:
positioning a substrate within a process chamber, wherein the
substrate comprises an aperture containing an exposed silicon
contact surface; forming a metal silicide layer on the exposed
silicon contact surface; and exposing the substrate to an
electroless deposition process to fill the aperture with a metal
contact material.
18. The method of claim 17, wherein the metal silicide layer
comprises at least one metal selected from the group consisting of
cobalt, nickel, tungsten, molybdenum, rhenium, titanium, tantalum,
hafnium, zirconium, alloys thereof, and combinations thereof.
19. The method of claim 17, wherein the metal contact material
comprises a material selected from the group consisting of nickel,
nickel phosphide, nickel boride, cobalt, cobalt tungsten, cobalt
tungsten phosphide, cobalt tungsten boride, cobalt tungsten
phosphide boride, cobalt nickel, cobalt phosphide, cobalt boride,
cobalt nickel phosphide, cobalt nickel boride, derivatives thereof,
alloys thereof, and combinations thereof.
20. The method of claim 19, wherein the electroless deposition
process comprises sequentially exposing the substrate to a first
electroless solution containing a cobalt source and to a second
electroless solution containing a nickel source.
21. The method of claim 20, wherein the substrate is rinsed after
each exposure of the first electroless solution and the second
electroless solution.
22. The method of claim 21, wherein a process cycle of the
sequential exposures of the first and second electroless solutions
is repeated to form the metal contact material as a cobalt-nickel
stack material having a predetermined thickness.
23. The method of claim 17, wherein a capping layer is deposited on
the metal silicide layer prior to filling the aperture with the
metal contact material.
24. The method of claim 23, wherein the capping layer comprises a
material selected from the group consisting of cobalt tungsten
phosphide, cobalt tungsten boride, cobalt tungsten phosphide
boride, derivatives thereof, alloys thereof, and combinations
thereof.
25. The method of claim 24, wherein the capping layer is deposited
during an electroless deposition process.
26. The method of claim 17, wherein a self assembled monolayer is
deposited within the aperture prior to forming the metal contact
material.
27. The method of claim 17, wherein the metal silicide layer is
formed from the exposed silicon contact surface by exposing the
substrate to a metal-containing activation solution.
28. The method of claim 27, wherein the metal-containing activation
solution comprises a cobalt source, a fluoride source, and a
hypophosphite source.
29. The method of claim 17, wherein the metal silicide layer is
exposed to a preclean process prior to depositing the metal contact
material thereon.
30. The method of claim 29, wherein the substrate is exposed to a
plasma to remove native oxides or contaminants from the metal
silicide layer during the preclean process.
31. The method of claim 30, wherein a thin film is formed on the
substrate by the plasma and the thin film is removed by a vacuum
sublimation process.
32. The method of claim 30, further comprising exposing the
substrate to the plasma and a process gas comprising a gas mixture
of ammonia and nitrogen trifluoride.
33. The method of claim 29, wherein the preclean process is a wet
clean process that provides exposing the substrate to a wet clean
solution comprising hydrogen fluoride and a basic compound selected
from the group consisting of ammonium hydroxide,
tetramethylammonium hydroxide, ethanolamine, diethanolamine,
triethanolamine, derivatives thereof, salts thereof, and
combinations thereof.
34. The method of claim 33, wherein the wet clean solution
comprises an EA-HF complex, a DEA-HF complex, a TEA-HF complex, a
DEA-EA-HF complex, a DEA-TEA-HF complex, a TEA-EA-HF complex,
derivatives thereof, salts thereof, and combinations thereof.
35. The method of claim 29, wherein the preclean process is a wet
clean process that provides exposing the substrate to a wet clean
solution comprising hydrogen peroxide and a basic compound selected
from the group consisting of ammonium hydroxide,
tetramethylammonium hydroxide, ethanolamine, diethanolamine,
triethanolamine, derivatives thereof, salts thereof, and
combinations thereof.
36. A method for depositing a material on a substrate, comprising:
positioning a substrate within a process chamber, wherein the
substrate comprises an aperture containing an exposed silicide
contact surface; and filling the aperture with a cobalt-nickel
stack material during an electroless deposition process comprising
sequentially exposing the substrate to a first electroless solution
containing a cobalt source and to a second electroless solution
containing a nickel source.
37. The method of claim 36, wherein the cobalt-nickel stack
material comprises a first layer comprising a material selected
from the group consisting of cobalt, cobalt phosphide, cobalt
boride, cobalt tungsten, cobalt tungsten phosphide, cobalt tungsten
boride, cobalt tungsten phosphide boride, derivatives thereof,
alloys thereof, and combinations thereof, and a second layer
comprising a material selected from the group consisting of nickel,
nickel phosphide, nickel boride, derivatives thereof, alloys
thereof, and combinations thereof.
38. A composition of a cobalt deposition solution, comprising: a
cobalt source at a concentration within a range from about 1 mM to
about 150 mM; a reducing agent source at a concentration within a
range from about 1 mM to about 100 mM; and a chelating agent source
at a concentration within a range from about 10 mM to about 500
mM.
39. The composition of claim 38, further comprising: the cobalt
source at a concentration within a range from about 10 mM to about
100 mM; the reducing agent source at a concentration within a range
from about 5 mM to about 50 mM; and the chelating agent source at a
concentration within a range from about 50 mM to about 300 mM.
40. The composition of claim 39, further comprising: the cobalt
source at a concentration within a range from about 20 mM to about
80 mM; the reducing agent source at a concentration within a range
from about 10 mM to about 40 mM; and the chelating agent source at
a concentration within a range from about 75 mM to about 250
mM.
41. The composition of claim 40, further comprising the cobalt
source at a concentration of about 35 mM, the reducing agent source
at a concentration of about 25 mM, and the chelating agent source
at a concentration of about 150 mM.
42. The composition of claim 38, wherein the chelating agent source
is selected from the group consisting of citric acid, lactic acid,
glycine, ethanolamine, diethanolamine, triethanolamine, salts
thereof, derivatives thereof, and combinations thereof.
43. The composition of claim 42, wherein the reducing agent source
comprises dimethylamine-borane complex.
44. The composition of claim 43, further comprising boric acid.
45. The composition of claim 38, further comprising saccharin.
46. The composition of claim 38, further comprising ammonium
fluoride or tetramethylammonium fluoride.
47. The composition of claim 38, further comprising a pH value
within a range from about 8 to about 10.
48. The composition of claim 47, wherein the pH value is about
9.2.
49. A composition of a nickel deposition solution, comprising: a
nickel source at a concentration within a range from about 1 mM to
about 150 mM; a reducing agent source at a concentration within a
range from about 1 mM to about 150 mM; and a chelating agent source
at a concentration within a range from about 10 mM to about 500
mM.
50. The composition of claim 48, further comprising: the nickel
source at a concentration within a range from about 5 mM to about
100 mM; the reducing agent source at a concentration within a range
from about 5 mM to about 100 mM; and the chelating agent source at
a concentration within a range from about 50 mM to about 300
mM.
51. The composition of claim 50, further comprising: the nickel
source at a concentration within a range from about 10 mM to about
80 mM; the reducing agent source at a concentration within a range
from about 10 mM to about 80 mM; and the chelating agent source at
a concentration within a range from about 75 mM to about 200
mM.
52. The composition of claim 51, further comprising the nickel
source at a concentration of about 40 mM, the reducing agent source
at a concentration of about 40 mM, and the chelating agent source
at a concentration of about 150 mM.
53. The composition of claim 49, wherein the chelating agent source
is selected from the group consisting of citric acid, lactic acid,
glycine, ethanolamine, diethanolamine, triethanolamine, salts
thereof, derivatives thereof, and combinations thereof.
54. The composition of claim 53, wherein the reducing agent source
comprises dimethylamine-borane complex.
55. The composition of claim 54, further comprising boric acid.
56. The composition of claim 49, further comprising a pH value
within a range from about 8 to about 10.
57. The composition of claim 56, wherein the pH value is about 9.2.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of U.S. Ser. No. 60/663,493,
filed Mar. 18, 2005 (9916L), U.S. Ser. No. 60/683,599, filed May
23, 2005 (9916L.02), U.S. Ser. No. 60/703,538, filed Jul. 29, 2005
(9916L.03), U.S. Ser. No. 60/703,633, filed Jul. 29, 2005
(9916L.04), U.S. Ser. No. 60/709,564, filed Aug. 19, 2005
(9916L.05), U.S. Ser. No. 60/754,230, filed Dec. 27, 2005
(9916L.06), and U.S. Ser. No. 60/731,624, filed Oct. 28, 2005
(10659L), which are all herein incorporated by reference in their
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Embodiments of the invention generally relate to methods for
depositing materials on substrates, and more specifically to
methods for filling apertures within a high aspect ratio
contact.
[0004] 2. Description of the Related Art
[0005] Multilevel, 45 nm node metallization is one of the key
technologies for the next generation of very large scale
integration (VLSI). The multilevel interconnects that lie at the
heart of this technology possess high aspect ratio features,
including contacts, vias, lines, and other apertures. Reliable
formation of these features is very important for the success of
VLSI and the continued effort to increase quality and circuit
density on individual substrates. Therefore, there is a great
amount of ongoing effort being directed to the formation of
void-free features having high aspect ratios of 10:1 (height:width)
or greater.
[0006] Copper and tungsten are choice metals for filling VLSI
features, such as a submicron high aspect ratio contact (HARC) on a
substrate. Contacts are formed by depositing a conductive
interconnect material, such as copper or tungsten into an aperture
(e.g., via) on the surface of an insulating material disposed
between two spaced-apart conductive layers. A high aspect ratio of
such an opening may inhibit deposition of a conductive interconnect
material to fill an aperture. Although copper and tungsten are
popular interconnect materials, deposition processes for depositing
these materials may suffer by forming a void or a seam within the
contact plug, as illustrated in FIG. 1C.
[0007] FIGS. 1A-1B depict a schematic cross-sectional view of an
integrated circuit device on substrate 100 containing aperture 105
formed in dielectric layer 104 to expose contact layer 102. During
a deposition process that may include chemical vapor deposition
(CVD) or atomic layer deposition (ALD), metal layer 106 is
deposited on dielectric layer 104 and within aperture 105 including
on contact layer 102 and the sidewalls of dielectric layer 104 to
form plug 103. Near opening 107 of plug 103, metal layer 106 may
pinch off, depicted in FIG. 1C, so that plug 103 maintains a seam
or void 108 therein. During a subsequent chemical mechanical
polishing (CMP) process that removes a portion of metal layer 106
and dielectric layer 104 from the surface of substrate 100, void
108 may be breached or exposed to form gap 110 within plug 103, as
illustrated in FIG. 1D. FIG. 1E depicts conductive layer 112 (e.g.,
copper) deposited on substrate 100 forming void 114 by enclosing
gap 110. Substrate 100 may contain additional layers of material
depending on the overall architecture of the electronic device. For
example, dielectric layer 104 may be covered by a barrier layer
(not shown) thereon prior to the deposition of conductive layer 112
or conductive layer 112 may also contain a barrier layer (not
shown) thereon prior to the deposition of layer 120.
[0008] Defects, such as a seam or void 114, may cause a series of
problems during the fabrication of electronic devices depicted
herein. The resistance to current flow through plug 103 is impaired
due to the lack of conductive material in void 114. However, a more
serious obstacle during fabrication is the displacement of voids
from one layer to the next. For example, subsequent fabrication
processes of substrate 100 may include the deposition of layer 120
(e.g., dielectric layer) on conductive layer 112. During subsequent
thermal processing, such as an annealing process, material 116 from
conductive layer 112 may diffuse into void 114 and form void 118
within conductive layer 112. As illustrated in FIG. 1F, material
116 may not diffuse completely to the bottom of void 114. The
defect formed in conductive layer 112, such as void 118, will
increase the resistance of the circuit containing the defect and
thus affect device performance. Ultimately, the defects in
conductive layer 112 can affect the device yield of the fabricated
substrate.
[0009] Therefore, a need exists for a method to fill a contact
level aperture with a conductive contact material, such that the
contact material is deposited free of voids, seams and other
defects.
SUMMARY OF THE INVENTION
[0010] Embodiments as described herein provide methods for
depositing a material on a substrate during electroless deposition
processes. In one embodiment, the substrate contains a contact
aperture having an exposed silicon contact surface. In another
embodiment, the substrate contains a contact aperture having an
exposed silicide contact surface. The apertures are filled with a
metal contact material by exposing the substrate to an electroless
deposition process. The metal contact material may contain a cobalt
material, a nickel material, or alloys thereof. Prior to filling
the apertures, the substrate may be exposed to a variety of
pretreatment processes, such as preclean processes and activations
processes. A preclean process may remove organic residues, native
oxides, and other contaminants during a wet clean process or a
plasma etch process. Embodiments of the process also provide the
deposition of additional layers, such as a capping layer.
[0011] In one embodiment, a method for depositing a material on a
substrate is provided which includes positioning a substrate within
a process chamber, wherein the substrate has an aperture containing
an exposed silicide contact surface, and exposing the exposed
silicide contact surface to a deposition solution to form a metal
contact material over the exposed silicide contact surface during
an electroless deposition process. In another embodiment, the
substrate has an aperture containing an exposed silicon contact
surface, and the method provides forming a metal silicide layer on
the exposed silicon contact surface, and exposing the substrate to
an electroless deposition process to fill the aperture with a metal
contact material. In another embodiment, a metal suicide layer is
formed from the exposed silicon contact surface by exposing the
substrate to a metal-containing activation solution. In one
example, the metal-containing activation solution contains a cobalt
source, a fluoride source, and a hypophosphite source.
[0012] In one example, the contact aperture is filled with the
metal contact material by continuing the electroless deposition
process. The exposed silicide contact surface may contain at least
one metal, such as cobalt, nickel, tungsten, molybdenum, rhenium,
titanium, tantalum, hafnium, zirconium, alloys thereof, or
combinations thereof. The metal contact material may contain
nickel, nickel phosphide, nickel boride, cobalt, cobalt tungsten,
cobalt tungsten phosphide, cobalt tungsten boride, cobalt tungsten
phosphide boride, cobalt nickel, cobalt phosphide, cobalt boride,
cobalt nickel phosphide, cobalt nickel boride, derivatives thereof,
alloys thereof, or combinations thereof.
[0013] In another embodiment, the exposed silicide contact surface
is exposed to a preclean process prior to depositing the metal
contact material thereon. In one example, the substrate is exposed
to a plasma to remove native oxides or contaminants from the
exposed silicide contact surface during the preclean process.
During the plasma etch process, a thin film may be formed on the
substrate by the plasma and subsequently, the thin film is removed
by a vacuum sublimation process. The substrate is usually exposed
to the plasma along with a process gas. In one example, the process
gas contains a gas mixture of ammonia and nitrogen trifluoride. The
gas mixture may have a molar ratio of the ammonia to the nitrogen
trifluoride within a range from about 1:1 to about 30:1.
[0014] In other embodiments, the substrate is exposed to a wet
clean process. In one example, the substrate is exposed to a wet
clean solution containing hydrogen fluoride and a basic compound,
such as ammonium hydroxide, tetramethylammonium hydroxide,
ethanolamine, diethanolamine, triethanolamine, derivatives thereof,
salts thereof, or combinations thereof. In another example, the wet
clean solution contains an EA-HF complex, a DEA-HF complex, a
TEA-HF complex, a DEA-EA-HF complex, a DEA-TEA-HF complex, a
TEA-EA-HF complex, derivatives thereof, salts thereof, or
combinations thereof. In another embodiment, the substrate is
exposed to a wet clean solution containing hydrogen peroxide and a
basic compound. In another example, the wet clean solution contains
hydrogen peroxide and hydrogen chloride.
[0015] In another embodiment, a method for depositing a material on
a substrate is provided which includes positioning a substrate
within a process chamber, wherein the substrate has an aperture
containing either an exposed silicon contact surface or an exposed
silicide contact surface, and the aperture is filled with a
cobalt-nickel stack material during an electroless deposition
process. The substrate may be optionally rinsed after each exposure
of the first electroless solution and the second electroless
solution. Generally, a process cycle of the sequential exposures of
the first and second electroless solutions is repeated to form the
metal contact material as a cobalt-nickel stack material having a
predetermined thickness. The electroless deposition process
includes sequentially exposing the substrate to a first electroless
solution containing a cobalt source and to a second electroless
solution containing a nickel source. The cobalt-nickel stack
material may have a first layer containing cobalt, cobalt
phosphide, cobalt boride, cobalt tungsten, cobalt tungsten
phosphide, cobalt tungsten boride, cobalt tungsten phosphide
boride, derivatives thereof, alloys thereof, or combinations
thereof, and a second layer containing nickel, nickel phosphide,
nickel boride, derivatives thereof, alloys thereof, or combinations
thereof.
[0016] In one embodiment, a capping layer is deposited on the
exposed silicide contact surface prior to filling the aperture with
the metal contact material. The capping layer may contain cobalt
tungsten phosphide, cobalt tungsten boride, cobalt tungsten
phosphide boride, derivatives thereof, alloys thereof, or
combinations thereof. The capping layer may be formed or deposited
by a vapor deposition process, but preferably is deposited during
an electroless deposition process. In another embodiment, a self
assembled monolayer (SAM-layer) may be deposited within the
aperture prior to depositing the metal contact material.
[0017] In one embodiment, a composition of a cobalt deposition
solution is provided which contains a cobalt source at a
concentration within a range from about 1 mM (millimolar,
millimole/L) to about 150 mM, a reducing agent source at a
concentration within a range from about 1 mM to about 100 mM, and a
chelating agent source at a concentration within a range from about
10 mM to about 500 mM. In another example, the cobalt deposition
solution contains the cobalt source at a concentration within a
range from about 10 mM to about 100 mM, the reducing agent source
at a concentration within a range from about 5 mM to about 50 mM,
and the chelating agent source at a concentration within a range
from about 50 mM to about 300 mM. In another example, the cobalt
deposition solution contains the cobalt source at a concentration
within a range from about 20 mM to about 80 mM, the reducing agent
source at a concentration within a range from about 10 mM to about
40 mM, and the chelating agent source at a concentration within a
range from about 75 mM to about 250 mM. In another example, the
cobalt deposition solution contains the cobalt source at a
concentration of about 35 mM, the reducing agent source at a
concentration of about 25 mM, and the chelating agent source at a
concentration of about 150 mM. The chelating agent source may
include citric acid, lactic acid, glycine, ethanolamine,
diethanolamine, triethanolamine, salts thereof, derivatives
thereof, or combinations thereof. In one example the reducing agent
source comprises dimethylamine-borane complex. Other examples
provide that the composition contains boric acid, saccharin,
ammonium fluoride, or tetramethylammonium fluoride. A pH adjusting
agent, such as TMAH, may be added to provide the cobalt deposition
solution having a pH value within a range from about 8 to about 10,
such as about 9.2.
[0018] In another embodiment, a composition of a nickel deposition
solution is provided which contains a nickel source at a
concentration within a range from about 1 mM to about 150 mM, a
reducing agent source at a concentration within a range from about
1 mM to about 150 mM, and a chelating agent source at a
concentration within a range from about 10 mM to about 500 mM. In
another example, the nickel deposition solution contains the nickel
source at a concentration within a range from about 5 mM to about
100 mM, the reducing agent source at a concentration within a range
from about 5 mM to about 100 mM, and the chelating agent source at
a concentration within a range from about 50 mM to about 300 mM. In
another example, the nickel deposition solution contains the nickel
source at a concentration within a range from about 10 mM to about
80 mM, the reducing agent source at a concentration within a range
from about 10 mM to about 80 mM, and the chelating agent source at
a concentration within a range from about 75 mM to about 200 mM. In
another example, the nickel deposition solution contains the nickel
source at a concentration of about 40 mM, the reducing agent source
at a concentration of about 40 mM, and the chelating agent source
at a concentration of about 150 mM. The chelating agent source may
include citric acid, lactic acid, glycine, ethanolamine,
diethanolamine, triethanolamine, salts thereof, derivatives
thereof, or combinations thereof. In one example the reducing agent
source comprises dimethylamine-borane complex. Other examples
provide that the composition contains boric acid. A pH adjusting
agent, such as TMAH, may be added to provide the nickel deposition
solution having a pH value within a range from about 8 to about 10,
such as about 9.2.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] So that the manner in which the above recited features of
the invention are attained and can be understood in detail, a more
particular description of the invention, briefly summarized above,
may be had by reference to the embodiments thereof which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only typical embodiments of
this invention and are therefore not to be considered limiting of
its scope, for the invention may admit to other equally effective
embodiments.
[0020] FIGS. 1A-1F illustrate schematic cross-sectional views of an
integrated circuit formed by a process described in the art;
[0021] FIGS. 2A-2F illustrate schematic cross-sectional views of
integrated circuits formed by deposition processes described within
embodiments herein;
[0022] FIGS. 3A-3Q illustrate schematic cross-sectional views of
integrated circuits formed by other deposition processes described
within embodiments herein;
[0023] FIGS. 4A-4H illustrate schematic cross-sectional views of
integrated circuits formed by another deposition process described
within embodiments herein;
[0024] FIG. 5 illustrates a flow chart depicting a process sequence
as described within embodiments herein;
[0025] FIG. 6 illustrates a flow chart depicting another process
sequence as described within embodiments herein;
[0026] FIG. 7 illustrates a flow chart depicting another process
sequence as described within embodiments herein;
[0027] FIG. 8 illustrates a flow chart depicting an electroless
deposition process as described within embodiments herein;
[0028] FIGS. 9A-9D illustrate a schematic representation of timing
sequences for electroless deposition processes as described within
embodiments herein;
[0029] FIG. 10 illustrates a flow chart depicting an electroless
deposition process as described within embodiments herein; and
[0030] FIG. 11 illustrates a schematic representation of an
alternative timing sequence for an electroless deposition process
as described within an embodiment herein.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0031] Embodiments as described herein provide methods for
depositing a material on a substrate during electroless deposition
processes. In one embodiment, the substrate contains a contact
aperture having an exposed silicon contact surface. In another
embodiment, the substrate contains a contact aperture having an
exposed silicide contact surface. The apertures are filled with a
metal contact material by exposing the substrate to an electroless
deposition process. The metal contact material may contain a cobalt
material, a nickel material, and alloys thereof. Prior to filling
the apertures, the substrate may be exposed to a variety of
pretreatment processes, such as preclean processes and activations
processes. A preclean process may remove organic residues, native
oxides, and other contaminants during a wet clean process or a
plasma etch process. Embodiments of the process also provide the
deposition of additional layers, such as a capping layer.
Metal-Containing Interconnect Processes
[0032] FIG. 2A illustrates a cross-sectional view of substrate 200
having aperture 210 formed into dielectric layer 204. Aperture 210
may include features, such as contact holes, vias, or trenches.
Dielectric layer 204 contains an insulating material that includes
silicon oxide, silicon nitride, silicon on insulator (SOI), silicon
oxynitride, fluorine-doped silicate glass (FSG), or carbon-doped
silicon oxides, such as SiO.sub.xC.sub.y, for example, BLACK
DIAMOND.RTM. low-k dielectric, available from Applied Materials,
Inc., located in Santa Clara, Calif.
[0033] Aperture 210 may be formed in dielectric layer 204 using
conventional lithography and etching techniques to expose
interconnect layer 202, such as a bit line layer. Interconnect
layer 202 contains a conductive metal such as copper, tungsten,
aluminum or alloys thereof. Oxide surface 212 is usually formed
upon the oxidation of interconnect layer 202 subsequent to etching
and ashing processes used to form aperture 210. Oxide surface 212
may be a continuous or a discontinuous layer across the surface of
interconnect layer 202 and includes a surface terminate with
oxygen, hydrogen, hydroxides, metals, or combinations thereof. In
this configuration, interconnect layer 202 may contain oxide
surface 212.
[0034] FIGS. 2A-2C illustrate cross-sectional views of an
electronic device at different stages of an interconnect
fabrication sequence incorporating one embodiment of the invention
for pre-treating and subsequently filling aperture 210 with a
nickel-containing material or a cobalt-tungsten alloy. FIG. 2B
illustrates substrate 200 after exposing oxide surface to a
pretreatment process. Contact surface 214 of interconnect layer 202
is exposed and is free of or substantially free of oxide surface
212. In one aspect, oxide surface 212 may be chemically reduced to
a tungsten metal. For example, oxide surface 212 is exposed to a
hydrogen plasma to remove the oxygen and form an oxide free contact
surface 214. In another example, oxide surface 212 may be exposed
to a vapor deposition process containing diborane to remove oxygen
and form contact surface 214 containing tungsten boride. In another
aspect, oxide surface 212 is exposed to a wet clean process to
further oxidize and remove tungstate ion while leaving behind a
clean contact surface 214. Additives, such as surface chelators,
may be used within the wet clean solution that adhere to the
freshly prepared contact surface 214 and prohibit excess
oxidization.
[0035] A plasma pretreatment process may be conducted for a
predetermined time to reduce oxide surface 212, leaving a
substantially oxide-free contact surface 214. A plasma pretreatment
process may occur for about 5 minutes or less, preferably, within a
range from about 1 second to about 60 seconds, more preferably,
from about 5 seconds to about 30 seconds. During the pretreatment
process, the substrate is maintained at a temperature within a
range from about 20.degree. C. to about 150.degree. C., preferably,
from about 50.degree. C. to about 100.degree. C. The process
chamber may have a pressure within a range from about 0.1 Torr to
about 450 Torr, preferably, from about 1 Torr to about 100 Torr,
and more preferably, from about 10 Torr to about 30 Torr.
[0036] The plasma treatment process may be conducted in a process
chamber capable of plasma vapor deposition techniques. For example,
the substrate may be placed into a plasma enhanced ALD (PE-ALD), a
plasma enhanced CVD (PE-CVD) or high density plasma CVD (HDP-CVD)
chamber, such as the ULTIMA HDP-CVD.RTM., available from Applied
Materials, Inc., located in Santa Clara, Calif. An inductively
coupled plasma generating device, capacitively coupled plasma
generating device, or combination thereof may be used in a plasma
chamber to carryout the plasma treatment process.
[0037] Oxide surface 212 may be exposed to a reducing plasma
containing the reductant to form a substantially oxide-free contact
surface 214. The reductant may be diluted in a carrier gas and
includes hydrogen, diborane, silane, disilane, phosphine,
derivatives thereof, or combinations thereof. During the plasma
pretreatment process, a carrier gas flow is established within the
process chamber and exposed to the substrate. Carrier gases may be
selected so as to also act as a purge gas for the removal of
volatile reactants and/or by-products from the process chamber.
Carrier gases or purge gases include helium, argon, hydrogen,
forming gas, or combinations thereof. The carrier gas may be
provided at a flow rate within a range from about 500 sccm to about
5,000 sccm, preferably, from about 500 sccm to about 2,500 sccm.
The reductant may be provided at a flow rate within a range from
about 5 sccm to about 500 sccm, preferably, from about 10 sccm to
about 100 sccm. The plasma may be formed using an RF power
delivered to the plasma generating devices (e.g., showerhead in a
capacitively coupled chamber or a substrate support) utilized in
the plasma chamber where the RF power ranges from about 100 W to
about 10,000 W at an RF frequency between about 0.4 kHz and about
10 GHz. In one aspect, the plasma is formed using a showerhead RF
power setting and a substrate support RF power setting that is
within a range between about 500 W and about 5,000 W at a frequency
of about 13.56 MHz.
[0038] In an exemplary plasma pretreatment process, the substrate
is heated to about 50.degree. C. and the process chamber is
maintained at a pressure of about 10 Torr, to reduce the oxides
formed on contact surface 214. The substrate may be exposed to a
reducing plasma containing hydrogen at a flow rate of about 1,000
sccm for a time period of about 30 seconds to remove oxide layer
212.
[0039] In another exemplary plasma pretreatment process, a
substrate is heated to about 50.degree. C., the process chamber is
maintained at a pressure of about 10 Torr using a flow rate of
about 50 sccm of diborane and about 450 sccm of a helium carrier
gas to reduce the oxides formed on contact surface 214. The
substrate is exposed to the reducing plasma for about 30 seconds to
remove the oxide layer 212.
[0040] In another embodiment, the pretreatment process may be a
liquid reduction process, whereas oxide surface 212 is exposed to a
reducing solution to form contact surface 214. The reducing
solutions may contain at least one metal-reductant, such as a
compound containing a variable-valence metal. Variable-valence
metals are utilized as metal-reductants due to the availability of
electrons between redox states and include compounds of
Ti.sup.3+/Ti.sup.4+, Fe.sup.2+/Fe.sup.3+, Cr.sup.2+/Cr.sup.3+ and
Sn.sup.2+/Sn.sup.4+. Metal-reductants containing variable-valence
metals may contain a variety of anionic ligands including
complexing agents and halides, such as chlorides, fluorides,
bromides or iodides. Complexing agents that are useful may have
functional groups that include carboxylic acids, dicarboxylic
acids, polycarboxylic acids, amino acids, amines, diamines,
polyamines, alkylamines, alkanolamines and alkoxyamines. Complexing
agents may include citric acid, glycine, ethylenediamine (EDA),
monoethanolamine, diethanolamine (DEA), triethanolamine (TEA),
derivatives thereof, salts thereof or combinations thereof. In one
embodiment, citric acid or a citrate salt is a preferred complexing
agent within a reducing solution. For example, a reducing solution
may contain titanium salts with carboxylic acid ligands, such as a
citrate.
[0041] Generally, the reducing solutions are formed in water by
combining a metal halide (e.g., titanium chloride containing
TiCl.sub.3 and TiCl.sub.4) with a salt containing a predetermined
ligand (e.g., trisodium citrate) to form a metal complex or a metal
salt that contains the predetermined ligand (e.g., titanium
citrate) having a variable-valence state. The reducing solution may
further contain additives such as various chelators, surfactants,
pH adjusting agents, or combinations thereof. Variable-valence
metal compounds and reducing solutions are further described in V.
V. Sviridov et al., "Use of Ti(III) Complexes to reduce Ni, Co, and
Fe in Water Solution," J. Phys. Chem., vol. 100, pp. 19632-19635,
(1996), M. Majima et al., "Development of Titanium Redox
Electroless Plating Method," SEI Technical Review, vol. 54, pp.
67-70, (June 2002), S. Nakao et al., "Electroless Pure Nickel
Plating Process with Continuous Electrolytic Regeneration System,"
Surface and Coatings Technology, vols. 169-170(1), pp. 132-134.,
(Jun. 2, 2003), which are each incorporated by reference to the
extent not inconsistent with the claimed aspects and description
herein.
[0042] In an effort to remove oxide surface 212, substrate 200 is
exposed to a reducing solution for a predetermined time to remove
the oxides from contact surface 214. The liquid reduction process
may occur for about 5 minutes or less, preferably within a range
from about 1 second to about 120 seconds, more preferably, from
about 5 seconds to about 90 seconds. During the liquid reduction
process, the substrate is heated to a temperature within a range
from about 20.degree. C. to about 150.degree. C., preferably, from
about 50.degree. C. to about 100C.
[0043] In another embodiment, the pretreatment process may be a
vapor deposition process, whereas oxide surface 212 is exposed to a
reducing vapor to form contact surface 214. The reductant may
include borane, diborane, borane-alkylsulfides, such as
borane-dimethylsulfide (BH.sub.3.(CH.sub.3).sub.2S), alkyboranes
(e.g., ethylborane), phosphine, alkylposphines (e.g.,
dimethylphosphine), silane, disilane, trisilane, alkylsilanes
(e.g., methylsilane), ammonia, hydrazine, hydrogen, derivatives
thereof, or combinations thereof. Preferably, the reductant is
diborane, phosphine, silane, hydrazine, hydrogen, or combinations
thereof.
[0044] In an effort to remove the oxide surface 212 the substrate
200 is exposed to a reducing vapor process for a predetermined time
to remove the oxides from the contact surface 214. The reducing
vapor process may occur for about 5 minutes or less, preferably
within a range from about 1 second to about 120 seconds, more
preferably, from about 5 seconds to about 90 seconds. During the
reducing vapor process, the substrate is maintained at a
temperature within a range from about 20.degree. C. to about
150.degree. C., preferably, from about 50.degree. C. to about
100.degree. C. The process chamber may have a pressure within a
range from about 0.1 Torr to about 450 Torr, preferably, from about
1 Torr to about 100 Torr, and more preferably, from about 10 Torr
to about 30 Torr.
[0045] In one aspect, the reductant used to remove oxide layer 212
may be diluted in a carrier gas. During the reducing vapor process,
a carrier gas flow is established within the process chamber and
exposed to the substrate. Carrier gases may be selected so as to
also act as a purge gas for the removal of volatile reactants
and/or by-products from the process chamber. Carrier gases or purge
gases include helium, argon, nitrogen, hydrogen, forming gas,
mixtures thereof. The carrier gas may be provided at a flow rate
within a range from about 100 sccm to about 5,000 sccm, preferably,
from about 500 sccm to about 2,500 sccm. The reductant may be
provided at a flow rate within a range from about 5 sccm to about
500 sccm, preferably, from about 10 sccm to about 100 sccm.
[0046] The reducing vapor process may be conducted in a process
chamber capable of vapor deposition, such as an ALD process chamber
or a CVD process chamber. A process chamber useful for ALD during
the reducing vapor process is described in commonly assigned U.S.
Pat. Nos. 6,916,398 and 6,878,206, which are both incorporated
herein by reference.
[0047] In another embodiment, oxide surface 212 is removed by
further oxidizing by a wet clean process which includes dispensing
a wet clean solution across or sprayed on the surface of substrate
200. The wet clean process may be an in situ process performed in
the same processing cell as a subsequent electroless deposition
process. Alternatively, substrate 200 may be wet cleaned in a
separate processing cell from the subsequent electroless deposition
processing cell. The wet clean process usually includes an acidic
wet clean solution with a pH of about 4 or less, preferably, within
a range from about 1.5 to about 3. Oxide surface 212 having a
tungsten oxide typically requires an aggressive cleaning at low pH
values. The pH value of the wet clean solution is usually adjusted
by adding an acid or a base to the predetermined value. The acid
may include hydrochloric acid, sulfuric acid, nitric acid,
phosphoric acid, derivatives thereof, or combinations thereof. The
base may include a hydroxide salt, ammonia or an amine, such as
ethanolamine (EA), diethanolamine (DEA), triethanolamine (TEA),
derivatives thereof, salts thereof, or combinations thereof. The
wet clean solution also contains at least one chelator or
complexing agent, such as a carboxylic acid or carboxylate, for
example, a citrate, oxalic acid, glycine, salts thereof, or
combinations thereof. In one example, the wet clean solution
contains about 0.05 M to about 0.5 M of citric acid and optionally
up to about 0.25 M of methanesulfonic acid.
[0048] Once oxide surface 212 is removed or reduced to reveal
contact surface 214 by the processes described herein, fill
material 220 may be deposited thereon. FIG. 2C illustrates
substrate 200 after fill material 220 has been deposited on contact
surface 214. Fill material 220 is composed of a conductive material
and preferably deposited by an electroless deposition process. A
conductive material deposited as fill material herein includes
nickel, cobalt, tungsten, cobalt-tungsten alloys, alloys thereof,
or combinations thereof. In one example, fill material 220 is a
nickel-containing layer deposited by an electroless deposition
solution. In another example, fill material 220 is a
cobalt-containing layer (e.g., CoW-alloy) deposited by an
electroless deposition solution.
[0049] In an alternative embodiment, FIGS. 2A, 2D-2F illustrate
cross-sectional views of an electronic device at different stages
of an interconnect fabrication sequence to pretreat and
subsequently fill aperture 210 with a conductive material. Nickel
or cobalt-tungsten alloys are used as conductive materials to fill
aperture 210. FIG. 2D illustrates substrate 200 after a
pretreatment process has been performed on the oxide surface 212.
In one aspect of the pretreatment process a ruthenium oxide layer
216 is deposited by exposing substrate 200 and oxide surface 212 to
a ruthenium tetroxide (RuO.sub.4) vapor. Thereafter, ruthenium
oxide layer 216 may be chemically reduced to form
ruthenium-containing layer 218 on oxide surface 212, as illustrated
in FIG. 2E.
[0050] A ruthenium containing layer may be deposited on the
substrate by use of a vapor deposition process, such as an in situ
generated process, or in a liquid deposition process, such as an
aqueous solution or suspension. Preferably, ruthenium tetroxide is
generated in situ by exposing a ruthenium-containing source to an
oxidizing gas prior and exposing the product to oxide surface 212.
Ruthenium tetroxide is a strong oxidant and therefore readily
reacts with any exposed metal oxide (e.g., tungsten oxide) layers
to form a consistent and catalytic active layer of ruthenium
oxide.
[0051] In one example of forming ruthenium tetroxide, ozone gas is
produced by supplying an oxygen source gas into an ozone generator.
The oxygen source may include oxygen (O.sub.2), nitrous oxide
(N.sub.2O), nitric oxide (NO), nitrogen dioxide (NO.sub.2), or
combinations thereof. Preferably, a 12 vol % ozone is generated by
flowing oxygen through the ozone generator. The oxidizing gas
containing ozone may be purified when passed or bubbled through a
silicon gel. Subsequently, the ozone is exposed to a metallic
ruthenium source to form ruthenium tetroxide that is condensed in a
cooled cold trap. The ozone flow is stopped and the cold trap is
purged with an inert gas (e.g., nitrogen) to rid the line of excess
oxygen. Thereafter, the cold trap is warmed to a temperature to
sublime the ruthenium tetroxide while a flow of inert gas is passed
therethrough. The vaporized ruthenium tetroxide saturates the inert
gas to form a deposition gas.
[0052] In an exemplary vapor deposition process, a deposition gas
containing ruthenium tetroxide is delivered to a substrate having a
tungsten oxide layer formed thereon. During the process, the
substrate is maintained at a temperature of about 100.degree. C.
After exposing oxide surface 212 to the ruthenium tetroxide
containing gas for about 30 seconds, ruthenium oxide layer 216 is
formed on the tungsten oxide layer.
[0053] Ruthenium oxide layer 216 may be exposed to a reductant
forming ruthenium-containing layer 218. The ruthenium oxide is
chemically reduced to ruthenium metal. For example, ruthenium oxide
layer 216 may be exposed to a hydrogen plasma to remove the oxygen
and form metallic ruthenium-containing layer 218. In another
example, ruthenium oxide layer 216 may be exposed to a vapor
deposition process containing diborane to remove oxygen and form
ruthenium-containing layer 218 containing ruthenium boride. In
another example, ruthenium oxide layer 216 is exposed to phosphine
through a vapor deposition process to remove oxygen and form
ruthenium-containing layer 218 containing ruthenium phosphide.
[0054] Fill material 220 may be deposited on ruthenium-containing
layer 218 to fill aperture 210 as illustrated in FIG. 2F. Fill
material 220 contains nickel or a cobalt-tungsten alloy. The
electroless deposition process and the composition of fill material
220 are previously described above for substrate 200 depicted in
FIG. 2C.
Silicon-Containing Interconnect Processes
[0055] FIGS. 3A-3Q and 4A-4H illustrate cross-sectional views of
electronic devices disposed on substrates 300 and 400 at different
stages of interconnect fabrication sequences incorporating multiple
embodiments herein. FIGS. 5-7 provide flow charts of processes 500,
600, and 700 that may be used to form substrates 300 and 400 while
correlating with FIGS. 3A-3Q and 4A-4H. Processes 500, 600, and 700
may be used during interconnect fabrication where an exposed
contact surface contains either a silicon surface or a silicide
surface on substrates 300 and 400.
[0056] FIG. 3A illustrates a cross-sectional view of substrate 300
having contact aperture 310 formed within dielectric layer 304.
Dielectric layer 304 contains an insulating material that may
include silicon dioxide and other silicon oxides, silicon on
insulator (SOI), silicon oxynitride, fluorine-doped silicate glass
(FSG), or carbon-doped silicon oxides, such as SiO.sub.xC.sub.y,
for example, BLACK DIAMOND.RTM. low-k dielectric, available from
Applied Materials, Inc., located in Santa Clara, Calif. Contact
aperture 310 may be formed in dielectric layer 304 using
conventional lithography and etching techniques to expose
interconnect layer 302, such as a bit line layer. Alternatively,
dielectric layer 304 may be deposited on interconnect layer 302
forming contact aperture 310 therein. Interconnect layer 302 may
contain pure silicon or a silicon-containing material that contains
germanium, carbon, boron, phosphorous, arsenic, metals, or
combinations thereof, among other dopants. For example,
interconnect layer 302 may contain silicon, silicon carbide,
silicon germanium, silicon germanium carbide, metal silicide, doped
variants thereof, or combinations thereof. In one example,
interconnect layer 302 is a MOS type source or a drain interface
and is generally a doped (e.g., n+ or p+) silicon region of
substrate 300.
[0057] Oxide surface 312 is usually formed upon the oxidation of
interconnect layer 302 during an exposure to air subsequent to
etching and ashing processes used forming contact aperture 310.
Oxide surface 312 may be a continuous layer or a discontinuous
layer across the surface of interconnect layer 302 and include a
surface terminations of oxygen, hydrogen, hydroxide, halide,
metals, or combinations thereof. Oxide surface 312 may also contain
various contaminants, such as organic and inorganic residues and
particulate. Oxide surface 312 formed on interconnect layer 302
generally contains a metastable lower quality oxide (e.g.,
SiO.sub.x, where x is between 0 and 2) compared to the much more
stable oxide materials that are typically used to form dielectric
layer 304 (e.g., SiO.sub.2), such as thermal oxides. The metastable
lower quality oxide (e.g., the "native oxide") is much easier to
remove from interconnect layer 302 than dielectric layer 304,
probably due to a lower activation energy than the material of
dielectric layer 304.
[0058] FIG. 3B illustrates substrate 300 containing exposed surface
314 on interconnect layer 302 subsequent to the removal of oxide
surface 312. Exposed surface 314 may be formed by at least one
pretreatment process during steps 510, 610, or 710 of processes
500, 600, or 700, as described by embodiments herein. In some
embodiments, exposed surface 314 may contain an exposed silicon
contact surface. In other embodiments, exposed surface 314 may
contain an exposed silicide contact surface.
[0059] During steps 510, 610, or 710, substrate 300 may be exposed
to at least one pretreatment process, such as a preclean process,
an activation process, or combinations thereof for forming exposed
surface 314. A preclean process may be used to remove oxide surface
312 and reveal a silicon surface or a suicide surface of exposed
surface 314. In one embodiment, the preclean process may be a wet
clean process, such as a buffered oxide etch (BOE) process, a SC1
process, a SC2 process, or a HF-last process. Alternatively, the
preclean process may be a dry clean process, such as a plasma etch
process. For example, a plasma etch process that may be used during
a preclean process is the SICONI.TM. preclean process, available
from Applied Materials, Inc., located in Santa Clara, Calif.
Pretreatment processes, such as a preclean process and an
activation process for forming exposed surface 314, are further
described below.
[0060] An activation process may also be used as a pretreatment
process to form exposed surface 314. In one embodiment, substrate
300 is exposed to an activation solution containing a cobalt
source, a fluoride source, and a hypophosphite source to transform
oxide surface 312 to a metal silicide surface of exposed surface
314. In another embodiment, substrate 300 is exposed to an
activation solution containing a variable-valence metal reducing
agent that chemically reduces oxide surface 312 to a silicon
surface of exposed surface 314. In another embodiment, substrate
300 is exposed to reducing hydrogen plasma that chemically reduces
oxide surface 312 to a silicon surface of exposed surface 314.
[0061] In one embodiment, FIGS. 3B-3C illustrate substrate 300
before and after contact aperture 310 is filled with metal contact
material 320, during steps 560, 660, or 760 of processes 500, 600,
or 700 (FIGS. 5-7), as described by embodiments herein. Metal
contact material 320 may be deposited on exposed surface 314 of
interconnect layer 302 within contact aperture 310. Metal contact
material 320 is usually deposited on exposed surface 314 during an
electroless deposition process to bottom-up fill contact aperture
310. In one example, the electroless deposition process is
continued until aperture 310 is filled with metal contact material
320.
[0062] Alternatively, a second electroless deposition process, or
multiple deposition processes, may be used to form metal contact
material 320 while filling contact aperture 310. For example, metal
contact material 320 may be formed of different materials to vary
the composition throughout, such as a graded material. In an
alternative embodiment, cobalt-nickel stack material 330 is formed
of at least two types of materials sequentially deposited on each
other, such as layers 322 and 324, as illustrated in FIGS. 4A and
4B by substrate 400 that correlates to substrate 300 in FIGS. 3C
and 3D. In one example, layer 322 may contain a cobalt material and
layer 324 may contain a nickel material. In another example, layer
322 may contain a nickel material and layer 324 may contain a
cobalt material.
[0063] Metal contact material 320 may be formed or deposited during
electroless deposition process described herein. The composition of
metal contact material 320 may vary based on the particular
electronic device requirements. Metal contact material may contain
metallic nickel, nickel phosphide, nickel boride, nickel phosphide
boride, metallic cobalt, cobalt phosphide, cobalt boride, cobalt
phosphide boride, cobalt tungsten, cobalt tungsten phosphide,
cobalt tungsten boride, cobalt tungsten phosphide boride, cobalt
nickel, cobalt nickel phosphide, cobalt nickel boride, cobalt
nickel phosphide boride, silicides thereof, derivatives thereof,
alloys thereof, or combinations thereof. Electroless deposition
processes and solutions for forming or depositing metal contact
material 320 and cobalt-nickel stack material 330, are further
described below.
[0064] FIG. 3D illustrates silicide layer 315 at the interface of
exposed surface 314 and metal contact material 320. Silicide layer
315 may be formed by exposing substrate 300 to an optional thermal
process during steps 580, 680, or 780. Silicide layer 315 may
contain a cobalt silicide, nickel silicide, cobalt tungsten
silicide, cobalt nickel silicide, borides thereof, alloys thereof,
derivatives thereof, or combinations thereof. Silicide layer 315
may be formed prior, during, or after filling of aperture 310 with
metal contact material 320. In one example, substrate 300 is heated
during a thermal process to form silicide layer from silicon atoms
of exposed surface 314 and metal atoms of metal contact material
320. Generally, substrate 300 may be heated to a temperature within
a range from about 150.degree. C. to about 500.degree. C. for a
time period within a range from about 5 seconds to about 10
minutes.
[0065] In another embodiment, FIGS. 3B and 3E-3G illustrate
substrate 300 at different stages of process 500. SAM-layer 350 may
be formed on substrate 300 during optional step 550, as depicted in
FIG. 3E. SAM-layer 350 may be initially deposited over dielectric
layer 304 and exposed surface 314. In one example, SAM-layer 350 is
deposited on exposed surface 314 containing an exposed contact
silicon surface. In another example, SAM-layer 350 is deposited on
exposed surface 314 containing an exposed contact silicide
surface.
[0066] FIGS. 3E-3F illustrate substrate 300 before and after
contact aperture 310 is filled with metal contact material 320,
during step 560 of process 500 (FIG. 5). Metal contact material 320
is deposited on SAM-layer 350 within contact aperture 310. Metal
contact material 320 is with interconnect layer 302. In one
example, substrate 300 may be exposed to a thermal process to form
silicide layer 315 (FIG. 3G). Silicide layer 315 provides higher
electrical conductivity, than without silicide layer 315, at the
interface between interconnect layer 302 and metal contact material
320. In an alternative embodiment, cobalt-nickel stack material 330
may be formed on SAM-layer 350, as illustrated in FIG. 4C by
substrate 400 that correlates to substrate 300 in FIG. 3G.
Deposition processes for depositing SAM-layer 350 on substrate 300
are further described below.
[0067] FIG. 6 depicts a flow graph of process 600 containing steps
610, 650, 660, and 680 that correlate to steps 510, 550, 560, and
580 of process 500. However, process 600 further provides the
formation or deposition of a suicide material during step 620. In
one embodiment of process 500, a silicide material may be formed
during a pretreatment process at step 510. For example, substrate
300 may be exposed to a clean process to remove oxides and
contaminants and subsequently exposed to an activation process to
form a silicide material.
[0068] FIG. 3H depicts substrate 300 containing metal-containing
layer 316 disposed on interconnect layer 302 within contact
aperture 310. Metal-containing layer 316 may contain a metal, a
metal silicide, or an alloy thereof. Metal-containing layer 316 may
be formed or deposited during steps 510, 610, 620, 710, or 720 and
include a metal layer or a metal silicide layer. In one example,
metal-containing layer 316 contains a metallic layer and is
deposited on exposed surface 314 containing an exposed contact
silicon surface. Thereafter, exposed surface 314 and
metal-containing layer 316 form a metal silicide during a thermal
process. In another example, metal-containing layer 316 contains a
metal suicide material deposited or formed on exposed surface 314.
In another example, metal-containing layer 316 contains a metal
silicide material formed either prior to or during steps 620 or
720.
[0069] In one embodiment, metal-containing layer 316 contains a
cobalt material, such as metallic cobalt, cobalt silicide, cobalt
phosphide, cobalt boride, cobalt phosphide boride, cobalt tungsten,
cobalt tungsten phosphide, cobalt tungsten boride, cobalt tungsten
phosphide boride, a cobalt alloy, suicides thereof, or combinations
thereof. In another embodiment, metal-containing layer 316 contains
a cobalt nickel material, such as cobalt nickel, cobalt nickel
phosphide, cobalt nickel boride, derivatives thereof, alloys
thereof, or combinations thereof. In another embodiment,
metal-containing layer 316 contains a nickel material, such as
metallic nickel, nickel silicide, nickel phosphide, nickel boride,
nickel phosphide boride, a nickel alloy, or combinations thereof.
In other embodiments, the exposed silicide contact surface may be
metal-containing layer 316 that contains at least one metal, such
as cobalt, nickel, tungsten, molybdenum, rhenium, titanium,
tantalum, hafnium, zirconium, alloys thereof, or combinations
thereof.
[0070] In one embodiment, metal-containing layer 316 may be formed
by exposing substrate 300 to an activation solution during an
electroless deposition process. In one example, metal-containing
layer 316 may be formed by exposing substrate 300 to an activation
process. In another example, metal-containing layer 316 may be
formed by exposing substrate 300 to a thermal process. In another
example, metal-containing layer 316 may be formed by exposing
substrate 300 to a silicidation process.
[0071] FIGS. 3H-3I illustrate substrate 300 before and after
contact aperture 310 is filled with metal contact material 320,
during step 660 of process 600 (FIG. 6). Metal contact material 320
is deposited on metal-containing layer 316 within contact aperture
310. In an alternative embodiment, cobalt-nickel stack material 330
may be formed on metal-containing layer 316, as illustrated in FIG.
4D by substrate 400 that correlates to substrate 300 in FIG. 3I.
Deposition processes for depositing metal-containing layer 316 on
substrate 300 are further described below.
[0072] In another embodiment, FIGS. 3H and 3J illustrate substrate
300 at different stages of process 600. SAM-layer 350 may be formed
on substrate 300 during optional step 650, as depicted in FIG. 3J.
SAM-layer 350 may be initially deposited over dielectric layer 304
and metal-containing layer 316. In one example, SAM-layer 350 is
deposited on metal-containing layer 316 containing a metallic
surface. In another example, SAM-layer 350 is deposited on
metal-containing layer 316 containing a metal silicide surface.
[0073] FIGS. 3J-3K illustrate substrate 300 before and after
contact aperture 310 is filled with metal contact material 320,
during step 660 of process 600. Metal contact material 320 may be
deposited on SAM-layer 350 within contact aperture 310. In an
alternative embodiment, cobalt-nickel stack material 330 may be
formed on SAM-layer 350, as illustrated in FIG. 4E by substrate 400
that correlates to substrate 300 in FIG. 3K.
[0074] FIG. 7 depicts a flow graph of process 700 containing steps
710, 720, 750, 760, and 780 that correlate to steps 610, 620, 650,
660, and 680 of process 600. However, process 700 further provides
the deposition of capping layer 318 during step 740. In one
embodiment, capping layer 318 may be deposited on substrate 300 as
a barrier layer over metal-containing layer 316, during step 740 of
process 700. In one example, capping layer 318 may be deposited on
SAM-layer 350 covering metal-containing layer 316 within contact
aperture 310 (FIG. 3L). Thereafter, metal contact material 320 may
be deposited on capping layer 318 filling contact aperture 310
(FIG. 3M). In an alternative embodiment, cobalt-nickel stack
material 330 may be formed on capping layer 318, as illustrated in
FIG. 4F by substrate 400 that correlates to substrate 300 in FIG.
3M.
[0075] In another example, capping layer 318 may be deposited
directly on metal-containing layer 316 within contact aperture 310
(FIG. 3N). Thereafter, in one aspect, metal contact material 320
may be deposited on capping layer 318 filling contact aperture 310
(FIG. 3O). In an alternative embodiment, cobalt-nickel stack
material 330 may be formed on capping layer 318, as illustrated in
FIG. 4G by substrate 400 that correlates to substrate 300 in FIG.
3O. In another aspect, SAM-layer 350 may be deposited on capping
layer 318 (FIG. 3P). Subsequently, metal contact material 320 may
be deposited on SAM-layer 350 covering capping layer 318 and
filling contact aperture 310 (FIG. 3Q). In alternative embodiments,
cobalt-nickel stack material 330 may be formed on SAM-layer 350
covering capping layer 318, as illustrated in FIG. 4H by substrate
400 that correlates to substrate 300 in FIG. 3O. Deposition
processes, including electroless deposition processes and solutions
for depositing capping layer 318 on substrate 300, are further
described below.
Pretreatment processes
Wet Clean Processes
[0076] In one embodiment, substrate 300 may be exposed to a wet
clean process to remove oxide surface 312 and to form exposed
surface 314 during steps 510, 610, or 710 of processes 500, 600, or
700. Substrate 300 may be treated by wet clean processes, such as
an acidic cleaning process (e.g., a solution containing
hydrochloric acid and hydrogen peroxide held at elevated
temperature, such as SC2 clean), a basic cleaning process (e.g., a
solution containing ammonium hydroxide and hydrogen peroxide held
at elevated temperature, such as SC1 clean), or a series of wet
cleans containing both acidic and basic cleaning processes. In a
preferred embodiment, substrate 300 is exposed to a SC1 solution
(e.g., TMAH and H.sub.2O.sub.2) to remove organic residues and
other contaminants and subsequently, exposed to a BOE solution
(e.g., 0.5 M of TEA-HF solution) to remove native oxides.
[0077] A wet clean process may include dispensing a wet clean
solution across or sprayed on the surface of substrate 300. The wet
clean process may be an in situ process performed in the same
processing cell as a subsequent electroless deposition process.
Alternatively, substrate 300 may be wet cleaned in a separate
processing cell from the subsequent electroless deposition
processing cell. A wet-clean pretreatment process may occur for
about 10 minutes or less, such as within a range from about 5
seconds to about 5 minutes, preferably, from about 5 seconds to
about 3 minutes, more preferably, from about 10 seconds to about 2
minutes, and more preferably, from about 15 seconds to about 1
minute. During the pretreatment process, the substrate is
maintained at a temperature within a range from about 15.degree. C.
to about 50.degree. C., preferably, about room temperature (e.g.,
20.degree. C.). The wet-clean process may be performed in a
TEMPEST.TM. wet-clean system, available from Applied Materials,
Inc., located in Santa Clara, Calif. Other examples of various
wet-clean processes that may be used to remove oxide surface 312
are further described in commonly assigned U.S. Ser. No. 60/709,564
(APPM 9916.L05), filed Aug. 19, 2005, U.S. Ser. No. 60/703,538
(APPM 9916.L03), filed Jul. 29, 2005, and U.S. Ser. No. 60/663,493
(APPM 9916L), filed Mar. 18, 2005, which are all incorporated by
reference herein in their entirety.
[0078] In one embodiment, oxide surface 312 is removed by a HF-last
solution to form exposed surface 314 as a substantially oxide-free,
silicon hydride surface. In one example, the wet-clean process
utilizes an HF-last solution containing water, HF and optional
additives including chelators, surfactants, reductants, other acids
or combinations thereof. In one example, the hydrogen fluoride
concentration of a wet-clean solution may be within a range from
about 10 ppm to about 5 wt %, preferably, from about 50 ppm to
about 2 wt %, and more preferably, from about 100 to about 1 wt %,
for example, about 0.5 wt %. In another embodiment, oxide surface
312 is removed during a liquid reduction process to form exposed
surface 314 as a substantially oxide-free, silicon-containing
surface.
SC1 and SC2 Processes
[0079] In one embodiment, substrate 300 containing oxide surface
312 may be exposed to a SC1 clean solution to remove contaminants,
such as organic and inorganic residues and particulates during
steps 510, 610, or 710 of processes 500, 600, or 700. In one
example, the SC1 clean solution contains hydrogen peroxide and at
least one basic compound, such as ammonium hydroxide,
tetramethylammonium hydroxide, ethanolamine, diethanolamine,
triethanolamine, derivatives thereof, salts thereof, or
combinations thereof. The substrate may be heated to a temperature
within a range from about 50.degree. C. to about 100.degree. C.,
preferably, from about 70.degree. C. to about 90.degree. C.
[0080] In another embodiment, substrate 300 containing oxide
surface 312 may be exposed to a SC2 clean solution during steps
510, 610, or 710 of processes 500, 600, or 700. In one example, the
SC2 clean solution contains hydrogen peroxide and hydrogen
chloride. The substrate may be heated to a temperature within a
range from about 50.degree. C. to about 100.degree. C., preferably,
from about 70.degree. C. to about 90.degree. C.
BOE Processes and Solutions
[0081] In another embodiment of a preclean process, buffered oxide
etch (BOE) solutions and processes may be used to selectively
remove native oxides and other contaminants from substrate 300
during steps 510, 610, or 710 of processes 500, 600, or 700. The
BOE solutions generally contain alkanolamine compounds and an
etchant, such as hydrogen fluoride. In one embodiment, the
viscosity of the BOE solution may be adjusted by varying a
concentration ratio of at least two alkanolamine compounds. A BOE
solution having a viscosity within a range from about 10 cP to
about 30 cP has superior wetting properties on a substrate surface
during a process to selectively remove native oxide layers
therefrom.
[0082] In one embodiment, a method for selectively removing oxide
surface 312 to form exposed surface 314 on substrate 300. In one
example, substrate 300 may be exposed to a BOE solution containing
about 0.5 M of TEA-HF solution for about 25 seconds at about
20.degree. C. In another example, substrate 300 may be exposed to a
BOE solution containing about 0.5 M of EA-HF solution for about 20
seconds at about 20.degree. C. In another example, substrate 300
may be exposed to a BOE solution containing about 0.5 M of DEA-HF
solution for about 30 seconds at about 20.degree. C. Thereafter,
the excess BOE solution is removed by spinning the substrate for
about 10 seconds.
[0083] In one embodiment, a composition of a BOE solution is
provided which includes, by weight, a first alkanolamine compound
at a concentration within a range from about 0.5% to about 10%, a
second alkanolamine compound at a concentration within a range from
about 0.5% to about 10%, hydrogen fluoride at a concentration
within a range from about 0.5% to about 10%, water at a
concentration within a range from about 80% to about 98%, a pH
value within a range from about 3.5 to about 5, and a viscosity
within a range from about 10 cP to about 30 cP.
[0084] In one example, the first alkanolamine compound is at a
concentration within a range from about 1% to about 5%, the second
alkanolamine compound is at a concentration within a range from
about 1% to about 5%, the hydrogen fluoride is at a concentration
within a range from about 1% to about 5%, the water is at a
concentration within a range from about 85% to about 95%, the pH
value is within a range from about 3.8 to about 4.8, and the
viscosity is within a range from about 12 cP to about 28 cP. In
another example, the first alkanolamine compound is at a
concentration within a range from about 2% to about 3%, the second
alkanolamine compound is at a concentration within a range from
about 2% to about 3%, the hydrogen fluoride is at a concentration
within a range from about 1% to about 3%, the water is at a
concentration within a range from about 88% to about 94%, the pH
value is within a range from about 3.5 to about 5, preferably, from
about 4 to about 4.5, and the viscosity is less than about 50 cP,
such as within a range from about 15 cP to about 25 cP. In another
example, the first alkanolamine compound is at a concentration of
about 3%, the second alkanolamine compound is at a concentration of
about 2%, the hydrogen fluoride is at a concentration of about 2%,
the water is at a concentration of about 92%, the pH value is
within a range from about 4 to about 4.5, and the viscosity is less
than about 50 cP, such as within a range from about 15 cP to about
25 cP.
[0085] In some examples, a weight ratio of the first alkanolamine
compound to the second alkanolamine compound is within a range from
about 1 to about 5, for example, about 1.5, or about 1.1. The first
and second alkanolamine compounds may be different alkanolamine
compounds selected from ethanolamine (EA), diethanolamine (DEA),
triethanolamine (TEA), or derivatives thereof. For example, the
first alkanolamine compound may be DEA and the second alkanolamine
compound may be TEA. In another example, the first alkanolamine
compound is DEA the second alkanolamine compound is EA. In another
example, the first alkanolamine compound is TEA the second
alkanolamine compound is EA. In other examples, the first
alkanolamine compound is DEA at a concentration to have the
viscosity within a range from about 15 cP to about 25 cP or at a
concentration by weight within a range from about 1% to about
15%.
[0086] A BOE solution may contain a first alkanolamine and a second
alkanolamine compound at a weight ratio concentration to form a
viscosity within a range from about 10 cP to about 30 cP, hydrogen
fluoride at a concentration by weight within a range from about
0.5% to about 10%, water at a concentration by weight within a
range from about 80% to about 98%, a pH value within a range from
about 3.5 to about 5, and a viscosity within a range from about 10
cP to about 30 cP. The first and second alkanolamine compounds may
include EA, DEA, TEA, or other alkanolamine derivatives. In one
example, the weight ratio concentration of the first alkanolamine
compound to the second alkanolamine compound is within a range from
about 1 to about 5, such as about 1.5 or about 1.1. In another
example, the viscosity of the BOE solution is within a range from
about 12 cP to about 28 cP, preferably, from about 15 cP to about
25 cP.
[0087] The BOE solution may contain a pH adjusting agent, such as
hydrofluoric acid, additional alkanolamine compounds, sulfuric
acid, ammonium hydroxide, tetramethylammonium hydroxide,
derivatives thereof, or combinations thereof. In one example, the
BOE solution contains the pH adjusting agent at a concentration to
have a pH value within a range from about 3.5 to about 5,
preferably, from about 3.8 to about 4.8, and more preferably, from
about 4 to about 4.5.
[0088] In one example, the buffered oxide etch solution contains a
first alkanolamine compound at a concentration by weight within a
range from about 0.5% to about 10%, a second alkanolamine compound
at a concentration by weight within a range from about 0.5% to
about 10%, hydrogen fluoride at a concentration by weight within a
range from about 0.5% to about 10%, water at a concentration by
weight within a range from about 80% to about 98%, a pH value
within a range from about 3.5 to about 5, and a viscosity within a
range from about 10 cP to about 30 cP.
[0089] In another embodiment, a composition of a BOE solution is
provided which includes DEA at a concentration by weight within a
range from about 0.5% to about 10%, TEA at a concentration by
weight within a range from about 0.5% to about 10%, HF at a
concentration by weight within a range from about 0.5% to about
10%, water at a concentration by weight within a range from about
80% to about 98%, a pH value within a range from about 3.5 to about
5 and a viscosity within a range from about 10 cP to about 30
cP.
[0090] In one example, the composition of the buffered oxide etch
solution contains the DEA at a concentration within a range from
about 1% to about 5%, the TEA at a concentration within a range
from about 1% to about 5%, the HF at a concentration within a range
from about 1% to about 5%, the water at a concentration within a
range from about 85% to about 95%, the pH value within a range from
about 3.8 to about 4.8, and the viscosity within a range from about
12 cP to about 28 cP. In another example, the composition of the
buffered oxide etch solution contains the DEA at a concentration
within a range from about 2% to about 3%, the TEA is at a
concentration within a range from about 2% to about 3%, the HF is
at a concentration within a range from about 1% to about 3%, the
water is at a concentration within a range from about 88% to about
94%, the pH value is within a range from about 4 to about 4.5, and
the viscosity is within a range from about 15 cP to about 25 cP. In
another example, the composition of the buffered oxide etch
solution contains the DEA is at a concentration of about 3%, the
TEA is at a concentration of about 2%, the HF is at a concentration
of about 2%, the water is at a concentration of about 92%, the pH
value is within a range from about 4 to about 4.5, and the
viscosity is within a range from about 15 cP to about 25 cP. The
weight ratio of the DEA to the TEA is within a range from about 1
to about 5, preferably, the weight ratio is about 1.5 or less and
the viscosity is about 23 cP.
[0091] In another embodiment, a method for selectively removing an
oxide layer from a substrate surface is provided which includes
providing a substrate having a native oxide surface and a feature
surface and exposing the substrate to a buffered oxide etch
solution to remove the native oxide surface while forming a native
surface and preserving the feature surface on the substrate. The
BOE solution may contain DEA at a concentration by weight within a
range from about 0.5% to about 10%, TEA at a concentration by
weight within a range from about 0.5% to about 10%, HF at a
concentration by weight within a range from about 0.5% to about
10%, water at a concentration by weight within a range from about
80% to about 98%, a pH value within a range from about 3.5 to about
5, and a viscosity within a range from about 10 cP to about 30 cP.
The pH value of the BOE solution may be adjusted to a point of zero
charge of silicon, such as within a range from about 4 to about
4.5. The BOE solution may have a weight ratio of the DEA to the TEA
within a range from about 1 to about 5. In one example of the BOE
solution, the weight ratio is about 1.5 and the viscosity is about
23 cP.
[0092] The method further provides that substrate 300 is exposed to
the BOE solution for a time period within a range from about 10
seconds to about 120 seconds, preferably, from about 15 seconds to
about 60 seconds, for example, about 30 seconds. Substrate 300 may
be exposed to a rinse solution subsequent to the BOE solution.
Thereafter, a metal-containing material, such as a barrier layer or
a metal silicide layer, may be deposited or formed on the native
surface.
[0093] A wet clean solution may contain hydrogen fluoride and at
least one basic compound, such as ammonium hydroxide,
tetramethylammonium hydroxide, EA, DEA, TEA, derivatives thereof,
salts thereof, or combinations thereof. Examples of the wet clean
solution include an EA-HF complex, a DEA-HF complex, a TEA-HF
complex, a DEA-EA-HF complex, a DEA-TEA-HF complex, a TEA-EA-HF
complex, derivatives thereof, salts thereof, or combinations
thereof. In one example, substrate 300 is exposed to a BOE solution
containing about 0.5 M of TEA-HF solution for about 25 seconds at
about 20.degree. C. Thereafter, the excess BOE solution is removed
by spinning the substrate for about 10 seconds.
Plasma Etch Process
[0094] In another embodiment, substrate 300 is exposed to a plasma
etch process or a plasma clean process remove oxide surface 312 and
to form exposed surface 314 during steps 510, 610, or 710 of
processes 500, 600, or 700. Also, the plasma etch process may be
used to remove native oxides and other contaminants formed on
exposed contact surfaces prior to several processes described
herein, such as an electroless deposition process. Surfaces exposed
to the plasma etch process usually have an improve adhesion of
subsequently deposited metal layers. The plasma etch process is
performed in a chamber adapted to perform a chemical etch clean and
in-situ anneal on substrates.
[0095] An exemplary plasma etch process for removing native oxides
on a surface of the substrate using an ammonia (NH.sub.3) and
nitrogen trifluoride (NF.sub.3) gas mixture performed within a
plasma etch processing chamber will now be described. The plasma
etch process begins by placing a substrate into a plasma etch
processing chamber. During processing, the substrate may be cooled
below 65.degree. C., such as between 15.degree. C. and 50.degree.
C. In another example, the substrate is maintained at a temperature
of between 22.degree. C. and 40.degree. C. Typically, the substrate
support is maintained below about 22.degree. C. to reach the
desired substrate temperatures.
[0096] The ammonia gas and nitrogen trifluoride gas are introduced
into the dry etching chamber to form a cleaning gas mixture. The
amount of each gas introduced into the chamber is variable and may
be adjusted to accommodate, for example, the thickness of the oxide
layer to be removed, the geometry of the substrate being cleaned,
the volume capacity of the plasma and the volume capacity of the
chamber body. In one aspect, the gases are added to provide a gas
mixture having at least a 1:1 molar ratio of ammonia to nitrogen
trifluoride. In another aspect, the molar ratio of the gas mixture
is at least about 3 to about 1 (ammonia to nitrogen trifluoride).
Preferably, the gases are introduced in the dry etching chamber at
a molar ratio of from about 1:1 (ammonia to nitrogen trifluoride)
to about 30:1, more preferably, from about 5:1 (ammonia to nitrogen
trifluoride) to about 30:1. More preferably, the molar ratio of the
gas mixture is of from about 5 to 1 (ammonia to nitrogen
trifluoride) to about 10 to about 1. The molar ratio of the gas
mixture may also fall between about 10:1 (ammonia to nitrogen
trifluoride) and about 20:1. Alternatively, a pre-mixed gas mixture
of the preferred molar ratio may be used during the plasma etch
process.
[0097] A purge gas or carrier gas may also be added to the gas
mixture. Any suitable purge/carrier gas may be used, such as argon,
helium, hydrogen, nitrogen, forming gas, or mixtures thereof.
Typically, the overall gas mixture by volume of ammonia and
nitrogen trifluoride is within a range from about 0.05% to about
20%. The remainder of the process gas may be the carrier gas. In
one embodiment, the purge or carrier gas is first introduced into
the chamber body before the reactive gases to stabilize the
pressure within the chamber body.
[0098] The operating pressure within the chamber body can be
variable. The pressure may be maintained within a range from about
500 mTorr to about 30 Torr, preferably, from about 1 Torr to about
10 Torr, and more preferably, from about 3 Torr to about 6 Torr. An
RF power within a range from about 5 watts to about 600 watts may
be applied to ignite a plasma of the gas mixture within the plasma
cavity. Preferably, the RF power is less than about 100 watts. More
preferable is that the frequency at which the power is applied is
very low, such as less than about 100 kHz, and more preferably,
within a range from about 50 kHz to about 90 kHz.
[0099] The plasma energy dissociates the ammonia and nitrogen
trifluoride gases into reactive species that combine to form a
highly reactive ammonia fluoride (NH.sub.4F) compound and/or
ammonium hydrogen fluoride (NH.sub.4F--HF) which reacts with the
substrate surface. In one embodiment, the carrier gas is first
introduced into the dry etch chamber, a plasma of the carrier gas
is generated, and then the reactive gases, ammonia and nitrogen
trifluoride, are added to the plasma.
[0100] Not wishing to be bound by theory, it is believed that the
etchant gas, NH.sub.4F and/or NH.sub.4F--HF, reacts with the native
oxide surface to form ammonium hexafluorosilicate
((NH.sub.4).sub.2SiF.sub.6), ammonia, and water. The ammonia and
water are vapors at processing conditions and removed from the
chamber by a vacuum pump attached to the chamber. A thin film of
ammonium hexafluorosilicate is left behind on the substrate
surface.
[0101] The thin film of ammonium hexafluorosilicate on the
substrate surface may be removed during a vacuum sublimation
process. The process chamber radiates heat to dissociate or
sublimate the thin film of ammonium hexafluorosilicate into
volatile SiF.sub.4, NH.sub.3, and HF products. These volatile
products are then removed from the chamber by the vacuum pump
attached to the system. In one example, a temperature of about
75.degree. C. or higher is used to effectively sublimate and remove
the thin film from the substrate. Preferably, a temperature of
about 100.degree. C. or more is used, such as between about
115.degree. C. and about 200.degree. C. Once the film has been
removed from the substrate, the chamber is purged and evacuated
prior to removing the cleaned substrate.
[0102] A plasma cleaning processes may be performed using a vacuum
preclean chamber, such as a SICONI.TM. Preclean chamber and
process, both available from Applied Materials, Inc., located in
Santa Clara, Calif. Further description of a plasma-assisted dry
etch chamber and plasma etch process that may be used by embodiment
herein is disclosed in commonly assigned U.S. Ser. No. 11/063,645,
(8802), entitled "In-Situ Dry Clean Chamber For Front End Of Line
Fabrication," filed on Feb. 22, 2005, and U.S. Ser. No. 11/192,993,
(8707.P1), entitled "Integrated Electroless Deposition System,"
filed on Jul. 29, 2005, which are hereby incorporated by reference
in their entirety to the extent not inconsistent with the claimed
invention.
Activation Processes
[0103] In other embodiments, substrate 300 may be exposed to an
activation process to remove oxide surface 312 and to form exposed
surface 314, suicide layer 315, or metal-containing layer 316, or
combinations thereof during steps 510, 610, or 710 of processes
500, 600, or 700. In one embodiment, interconnect layer 302
contains exposed surface 314 has an exposed silicon contact surface
within contact aperture 310. Exposed surface 314 may contain a pure
silicon surface, a silicon hydride-terminus surface, or a mixture
thereof. In another embodiment, interconnect layer 302 contains
exposed surface 314 has an exposed silicide contact surface within
contact aperture 310. The exposed silicide contact surface contains
a silicide surface, such as a cobalt silicide, a nickel silicide, a
cobalt nickel silicide, a cobalt tungsten silicide, alloys thereof,
or combinations thereof. As described by embodiments herein,
exposed surface 314 containing an exposed silicide contact surface,
silicide layer 315, or metal-containing layer 316 may contain at
least one metal silicide material that contains cobalt, nickel,
tungsten, molybdenum, rhenium, titanium, tantalum, hafnium,
zirconium, alloys thereof, or combinations thereof.
[0104] In another embodiment, the activation process may be a
liquid reduction process, whereas oxide surface 312 is exposed to a
reducing solution to form exposed surface 314 during steps 510,
610, or 710 of processes 500, 600, or 700. The reducing solutions
may contain at least one metal-reductant, such as a compound
containing a variable-valence metal. Variable-valence metals are
utilized as metal-reductants due to the availability of electrons
between redox states and include compounds of Ti.sup.3+/Ti.sup.4+,
Fe.sup.2+/Fe.sup.3+, Cr.sup.2+/Cr.sup.3+ and Sn.sup.2+/Sn.sup.4+.
Metal-reductants containing variable-valence metals may contain a
variety of anionic ligands including complexing agents and halides,
such as chlorides, fluorides, bromides or iodides. Complexing
agents that are useful may have functional groups that include
carboxylic acids, dicarboxylic acids, polycarboxylic acids, amino
acids, amines, diamines, polyamines, alkylamines, alkanolamines and
alkoxyamines. Complexing agents may include citric acid, glycine,
ethylenediamine (EDA), monoethanolamine, diethanolamine (DEA),
triethanolamine (TEA), derivatives thereof, salts thereof or
combinations thereof. In one embodiment, citric acid or a citrate
salt is a preferred complexing agent within a reducing solution.
For example, a reducing solution may contain titanium salts with
carboxylic acid ligands, such as a citrate.
[0105] Generally, the reducing solutions are formed in water by
combining a metal halide (e.g., titanium chloride containing
TiCl.sub.3 and TiCl.sub.4) with a salt containing a predetermined
ligand (e.g., trisodium citrate) to form a metal complex or a metal
salt that contains the predetermined ligand (e.g., titanium
citrate) having a variable-valence state. The reducing solution may
further contain additives such as various chelators, surfactants,
pH adjusting agents, or combinations thereof. Variable-valence
metal compounds and reducing solutions are further described in V.
V. Sviridov et al., "Use of Ti(III) Complexes to reduce Ni, Co, and
Fe in Water Solution," J. Phys. Chem., vol. 100, pp. 19632-19635,
(1996), M Majima et al., "Development of Titanium Redox Electroless
Plating Method," SEI Technical Review, vol. 54, pp. 67-70, (June
2002), S. Nakao et al., "Electroless Pure Nickel Plating Process
with Continuous Electrolytic Regeneration System," Surface and
Coatings Technology, vols. 169-170(1), pp. 132-134., (Jun. 2,
2003), which are each incorporated by reference to the extent not
inconsistent with the claimed aspects and description herein.
[0106] In an effort to remove oxide surface 312, substrate 300 is
exposed to a reducing solution for a predetermined time to remove
the oxides from exposed surface 314. The liquid reduction process
may occur for about 5 minutes or less, preferably within a range
from about 1 second to about 120 seconds, more preferably, from
about 5 seconds to about 90 seconds. During the liquid reduction
process, the substrate is heated to a temperature within a range
from about 20.degree. C. to about 150.degree. C., preferably, from
about 50.degree. C. to about 100.degree. C. In one example, the
metal-reductant may be a Ti.sup.3+ compound, such as titanium
citrate. In an alternative embodiment of a pretreatment process,
substrate 300 is exposed to a plasma process for a predetermined
time to reduce oxide surface 312 and form exposed surface 314.
[0107] In another embodiment, the pretreatment process may be a
vapor deposition process, whereas oxide surface 312 is exposed to a
reducing vapor to form exposed surface 314 during steps 510, 610,
or 710 of processes 500, 600, or 700. The reductant may include
borane, diborane, borane-alkylsulfides, such as
borane-dimethylsulfide (BH.sub.3.(CH.sub.3).sub.2S), alkyboranes
(e.g., ethylborane), phosphine, alkylposphines (e.g.,
dimethylphosphine), silane, disilane, trisilane, alkylsilanes
(e.g., methylsilane), ammonia, hydrazine, hydrogen, derivatives
thereof or combinations thereof. Preferably, the reductant is
diborane, phosphine, silane, hydrazine, hydrogen, or combinations
thereof.
Cobalt Activation Process and Solution
[0108] In other embodiments, the activation process may be a
silicidation process, whereas exposed surface 314 is exposed to an
action solution to form metal-containing layer 316 during steps
510, 610, 620, 710, or 720 of processes 500, 600, or 700. In one
embodiment, an activation solution to form metal-containing layer
316 containing a cobalt silicide material on substrate 300 contains
a cobalt source, a fluoride source, and a hypophosphite source.
Useful cobalt sources include cobalt sulfate, cobalt chloride,
cobalt fluoride, cobalt acetate, cobalt phosphate, other Co.sup.2+
compounds, derivatives thereof, hydrates thereof or combinations
thereof. In one example, cobalt sulfate heptahydrate
(COSO.sub.4.7H.sub.2O) is used within the activation solution to
form cobalt-containing materials. The activation solution may have
a cobalt source at a concentration within a range from about 1 mM
to about 500 mM, preferably, from about 1 mM to about 100 mM, more
preferably, from about 5 mM to about 50 mM, and more preferably,
from about 10 mM to about 30 mM, for example, about 22 mM.
[0109] The activation solution further contains a fluoride source.
Useful fluoride sources include hydrogen fluoride, ammonium
fluoride compounds, including alkylammonium fluoride compounds and
metal fluoride compounds, including alkaline fluoride compounds,
rare-earth fluoride compounds, transition metal fluoride compounds,
or combinations thereof. Ammonium fluoride compounds, alkylammonium
fluoride compounds, and alkanolamine fluoride compounds may have a
chemical formula of [R.sub.4N][F], wherein each R is independently
a hydrogen (H), an alkyl group, such as methyl (--CH.sub.3 or Me),
ethyl(--C.sub.2H.sub.5 or Et), propyl(--C.sub.3H.sub.7 or Pr),
butyl(--C.sub.4H.sub.9 or Bu), amyl(--C.sub.5H.sub.11), an alcohol
group, such as methanol (--CH.sub.2OH), ethanol
(--C.sub.2H.sub.2OH), propanol (--C.sub.3H.sub.6OH), butanol
(--C.sub.4H.sub.8OH), pentanol (--C.sub.5H.sub.10OH), derivatives
thereof, or combinations thereof. The activation solution may have
a fluoride concentration within a range from about 1 mM to about 1
M, preferably, from about 10 mM to about 400 mM, more preferably,
from about 20 mM to about 200 mM, and more preferably, from about
50 mM to about 120 mM, for example, about 83 mM.
[0110] In one embodiment, a fluoride source includes an
alkanolamine fluoride compound with a chemical formula of
[(HO(CH.sub.2).sub.n).sub.mNH.sub.4-m][F], wherein n=1, 2, 3, 4, or
5 and m=1, 2, 3, or 4, for example, an ethanolammonium fluoride has
a chemical formula [(HOCH.sub.2CH.sub.2).sub.mNH.sub.4-m][F]. In
one example, a fluoride source is a monoalkanolamine fluoride
compound with a chemical formula of
[(HO(CH.sub.2).sub.n)NH.sub.3][F], wherein n=1, 2, 3, 4, or 5, for
example, ethanolammonium fluoride (EA-HF) with a chemical formula
of [(HOCH.sub.2CH.sub.2)NH.sub.3][F]. In another example, a
fluoride source is a dialkanolamine fluoride compound with a
chemical formula of [(HO(CH.sub.2).sub.n).sub.2NH.sub.2][F],
wherein n=1, 2, 3, 4, or 5, for example, diethanolammonium fluoride
(DEA-HF) with a chemical formula of
[(HOCH.sub.2CH.sub.2).sub.2NH.sub.2][F]. In another example, a
fluoride source is a trialkanolamine fluoride compound with a
chemical formula of [(HO(CH.sub.2).sub.n).sub.3NH][F], wherein n=1,
2, 3, 4, or 5, for example, triethanolammonium fluoride (TEA-HF)
with a chemical formula of [(HOCH.sub.2CH.sub.2).sub.3NH][F]. In
other examples, the fluoride sources include ammonium fluoride
([H.sub.4N][F]) and tetramethylammonium fluoride ([Me.sub.4N][F]).
The fluoride compounds may be added as a fluoride salt or may be
formed to the activation solution. In one embodiment, a fluoride
source may be formed in situ by combining a basic compound to an
acidic compound, such as combining diethanolamine (DEA) and
hydrogen fluoride (HF) to form diethanolammonium fluoride (DEA-HF).
Therefore, the activation solution may contain a fluoride compound
and also a complexing base to form the respective fluoride salt.
The base, such as ammonia, alkylamine compounds, alkanolamine
compounds, or mixtures thereof, may be contained in the activation
solution at a concentration within a range from about 1 mM to about
1 M, preferably, from about 10 mM to about 400 mM, more preferably,
from about 20 mM to about 200 mM, and more preferably, from about
50 mM to about 120 mM, for example, about 80 mM.
[0111] In another embodiment, the activation solution may contain
two, three or more different alkanolamine fluoride compounds,
alkanolamine compounds, other fluoride sources, hydrogen fluoride,
salts thereof, or mixtures thereof. The viscosity of the activation
solution may be adjusted by varying a concentration ratio of at
least two alkanolamine compounds. An activation solution having a
viscosity within a range from about 10 cP to about 30 cP has
superior wetting properties while activating a substrate surface.
In one example, a molar ratio of the first alkanolamine compound to
the second alkanolamine compound is within a range from about 1 to
about 5, preferably, from about 1 to about 1.5, for example, about
1.2. The first and second alkanolamine compounds may be different
alkanolamine compounds selected from ethanolamine (EA),
diethanolamine (DEA), triethanolamine (TEA), or derivatives
thereof. For example, the first alkanolamine compound may be DEA
and the second alkanolamine compound may be TEA. In another
example, the first alkanolamine compound is DEA the second
alkanolamine compound is EA. In another example, the first
alkanolamine compound is TEA the second alkanolamine compound is
EA.
[0112] An activation solution further contains a reductant, such as
a hypophosphite source. Useful hypophosphite sources include sodium
hypophosphite, potassium hypophosphite, lithium hypophosphite,
calcium hypophosphite, ammonium hypophosphite, tetramethylammonium
(TMAH) hypophosphite and other alkylammonium hypophosphites,
derivatives thereof, or combinations thereof. Hypophosphite of
sodium, potassium, ammonium, or alkylammonium may have the chemical
formula of M.sub.nH.sub.3-nPO.sub.2, where n=1, 2, or 3 and M is
sodium, potassium ammonium, alkylammonium (e.g., TMAH), derivatives
thereof, or combinations thereof. In one example, a preferred
hypophosphite source is TMAH hypophosphite or sodium hypophosphite.
The activation solution may have a hypophosphite concentration
within a range from about 1 mM to about 1 M, preferably, from about
10 mM to about 400 mM, more preferably, from about 20 mM to about
200 mM, and more preferably, from about 50 mM to about 120 mM, for
example, about 83 mM.
[0113] In one embodiment, a cobalt activation solution may be used
to form metal-containing layer 316. In one example, the activation
solution may contain a cobalt concentration within a range from
about 1 mM to about 100 mM, a fluoride concentration within a range
from about 10 mM to about 400 mM, and a hypophosphite concentration
within a range from about 5 mM to about 150 mM. Preferably, an
activation solution may contain a cobalt concentration within a
range from about 5 mM to about 50 mM, a fluoride concentration
within a range from about 20 mM to about 200 mM, and a
hypophosphite concentration within a range from about 10 mM to
about 80 mM. More preferably, an activation solution may contain a
cobalt concentration within a range from about 10 mM to about 30
mM, a fluoride concentration within a range from about 50 mM to
about 120 mM, and a hypophosphite concentration within a range from
about 20 mM to about 60 mM. In one example, an activation solution
contains a cobalt concentration of about 22 mM, a fluoride
concentration of about 83 mM, and a hypophosphite concentration of
about 43 mM.
[0114] In one example, an activation solution has a pH value of
about 7 and contains about 22 mM of a cobalt sulfate hexahydrate,
about 70 mM of DEA-HF, about 18 mM of HF, and about 43 mM of a
TMAH-hypophosphite. In another example, an activation solution has
a pH value of about 7 and contains about 22 mM of a cobalt sulfate
hexahydrate, about 70 mM of TEA-HF, about 18 mM of HF, and about 43
mM of a TMAH-hypophosphite. In another example, an activation
solution has a pH value of about 7 and contains about 22 mM of a
cobalt sulfate hexahydrate, about 70 mM of DEA-TEA-HF (DEA:TEA
molar ratio of 1.22), about 18 mM of HF, and about 43 mM of a
TMAH-hypophosphite.
[0115] Generally, the substrate may be exposed to an activation
solution to form a cobalt silicide layer for a time period within a
range from about 1 second to about 90 seconds, preferably, from
about 5 seconds to about 60 seconds, and more preferably, from
about 10 seconds to about 30 seconds, for example, about 20
seconds. The substrate may be heated to a temperature within a
range from about 70.degree. C. to about 95.degree. C., preferably,
from about 80.degree. C. to about 85.degree. C. during the
activation process.
Self Assembled Monolayer and Capping Layer
Self Assembled Monolayer
[0116] In one embodiment, SAM-layer 350 (self-assembled-monolayer)
may be deposited on substrate 300 to provide further barrier
protection between neighboring layers during steps 550, 650, or 750
of processes 500, 600, or 700. An example of a prototypical SAM
material includes, but is not limited to, aminopropyltriethoxy
silane (APTES). A vapor deposition process may be used to form
SAM-layer 350 from APTES. Further description of a process for
depositing a SAM material is disclosed in commonly assigned U.S.
Ser. No. 60/754,230, filed Dec. 27, 2005, (9916L.06), which is
herein incorporated by reference in its entirety.
[0117] Substrate 300 may be exposed to a plasma treatment process
prior to depositing SAM-layer 350, as described in embodiments
herein, such as during optional step 750 of process 700 (FIG. 7). A
plasma treatment process containing water, hydrogen, or
combinations thereof forms a silanol (e.g., Si--OH) terminated
surface for promoting strong adhesion of SAM-layer 350 to an
underlying layer, such as dielectric layer 304, exposed surface
314, silicide layer 315, metal-containing layer 316, capping layer
318, and other surfaces and layers on substrate 300.
[0118] In one embodiment, SAM-layer 350 may be deposited on
substrate 300 covering exposed surface 314 and dielectric layer 304
(FIG. 3E). Metal contact material 320 is formed over SAM-layer 350
(FIG. 3F). Subsequently, substrate 300 is exposed to a thermal
process and silicide layer 315 is formed at the interface between
metal contact material 320 and interconnect layer 302 (FIG. 3G).
The portion of SAM-layer 350 therebetween is decomposed and may
incorporate carbon into silicide layer 315.
[0119] In another embodiment, SAM-layer 350 may be deposited on
substrate 300 covering metal-containing layer 316 and dielectric
layer 304 (FIG. 3J). In one example, metal contact material 320 is
directly formed over SAM-layer 350 (FIG. 3K). In another example,
capping layer 318 is formed over SAM-layer 350 prior to the
deposition of metal contact material 320 (FIG. 3L-3M). The portion
of SAM-layer 350 formed at the interface between metal contact
material 320 and metal-containing layer 316 may be preserved (FIG.
3K), but usually is decomposed and incorporates carbon into nearby
layers, such as metal-containing layer 316 (FIG. 3M). The
composition of SAM-layer 350, the composition of neighboring
layers, and the subsequent process temperatures experienced by
substrate 300 determine the extent the durability or decomposition
of SAM-layer 350.
[0120] In another embodiment, SAM-layer 350 may be deposited on
substrate 300 covering capping layer 318 and dielectric layer 304
(FIG. 3P) and metal contact material 320 is directly formed over
SAM-layer 350 (FIG. 3Q).
Capping Layer
[0121] Capping layer 318 may be formed or deposited on substrate
300, as described in embodiments herein, such as during step 740 of
process 700 (FIG. 7). In one embodiment, a selective deposition
process may be used to form or deposit capping layer 318 over the
exposed areas of metal-containing layer 316 (FIGS. 3L-3Q). The
selective deposition process may include an electroless deposition
process, a CVD process, a PE-CVD process, an ALD process, a PE-ALD
process, a PVD process, or combinations thereof. The selective
process covers metal-containing layer 316 while maintaining
sidewalls of contact aperture 310 free of deposited material.
Capping layer 318, as a barrier layer, eliminates or reduces atomic
diffusion (e.g., silicon) into metal contact materials 320 from
metals or metal suicides contained within metal-containing layer
316.
[0122] In one example, capping layer 318 may be selectively
deposited by use of an electroless deposition process. The
electroless deposition process may be used to form a layer that
contains a binary alloy, a ternary alloy, or a quaternary alloy.
Capping layer 318 may contain cobalt boride (CoB), cobalt phosphide
(CoP), nickel boride (NiB), nickel phosphide (NiP), cobalt tungsten
phosphide (CoWP), cobalt tungsten boride (CoWB), nickel tungsten
phosphide (NiWP), nickel tungsten boride (NiWB), cobalt molybdenum
phosphide (CoMoP), cobalt molybdenum boride (CoMoB), nickel
molybdenum phosphide (NiMoB), nickel molybdenum phosphide (NiMoP),
nickel rhenium phosphide (NiReP), nickel rhenium boride (NiReB),
cobalt rhenium boride (CoReB), cobalt rhenium phosphide (CoReP),
alloys thereof, derivatives thereof, or combinations thereof. The
film composition of the binary or ternary alloys can be preferably
designed to have a resistivity within a range from about 1
.mu..OMEGA.-cm to about 200 .mu..OMEGA.-cm.
[0123] Capping layer 318 containing a cobalt-tungsten alloy or a
nickel-containing material may be deposited during an electroless
deposition process that utilizes either a pre-mixed solution or
solution prepared by an in-line mixing process that combines
componential solutions. In one example, an electroless solution to
deposit a cobalt-tungsten alloy may contain a cobalt source, a
tungsten source, a citrate source, a hypophosphite source, a borane
reductant, and other additives. In another example, an electroless
solution to deposit a nickel-containing material may contain a
nickel source, a citrate source, a borane reductant and other
complexing agents and additives. Other electroless deposition
solutions and processes useful for depositing cobalt-tungsten
alloys are further described in the commonly assigned U.S. Ser. No.
10/967,919, entitled, "Selective Self-initiating Electroless
Capping of Copper with Cobalt-containing Alloys," filed on Oct. 18,
2004, and published as US 2005-0136193, which is incorporated by
reference to the extent not inconsistent with the claimed aspects
and description herein.
Sequential Electroless Deposition Processes for Co--Ni Stack
Material
[0124] In embodiment described herein, FIGS. 4A-4H depict substrate
400 having contact aperture 310 filled with cobalt-nickel stack
material 330 during steps 560, 660, or 760 of processes 500, 600,
or 700. Cobalt-nickel stack material 330 may be formed during a
bottom-up electroless deposition process. Cobalt-nickel stack
material 330 may be formed by a sequential electroless deposition
process containing at least two electroless solutions, such as a
cobalt solution containing a cobalt source and a nickel solution
containing a nickel source. Cobalt-nickel stack material 330 is
formed of sequential layers of at least two types of materials,
layers 322 and 324, wherein layers 322 may contain a cobalt
material and layers 324 may contain a nickel material or vice
versa. Cobalt materials and nickel materials contained within
cobalt-nickel stack material 330 may contain cobalt, nickel,
tungsten, boron or phosphorus and include materials such as
metallic cobalt, cobalt boride, cobalt phosphide, cobalt
borophosphide, metallic nickel, nickel boride, cobalt tungsten
boride, nickel phosphide, nickel borophosphide, nickel tungsten
boride, derivatives thereof, alloys thereof, or combinations
thereof.
[0125] In one example, cobalt-nickel stack material 330 on
substrate 400 (FIG. 4A) may be formed during a sequential
electroless deposition process, instead of forming metal contact
material 320 on substrate 300 (FIG. 3C). Similarly, by substituting
a non-sequential electroless deposition process for the sequential
electroless deposition process, a variety of alternative features
may be formed on substrate 400. In another example, cobalt-nickel
stack material 330 on substrate 400 (FIG. 4B) may be formed during
a sequential electroless deposition process, instead of forming
metal contact material 320 on substrate 300 (FIG. 3D). Other
examples include substituting metal contact material 320 on
substrate 300 for cobalt-nickel stack material 330 on substrate
400, where FIG. 4C correlates to FIG. 3G, FIG. 4D correlates to
FIG. 3I, FIG. 4E correlates to FIG. 3K, FIG. 4F correlates to FIG.
3M, FIG. 4G correlates to FIG. 3O, and FIG. 4H correlates to FIG.
3Q. In one example, cobalt-nickel stack material 330 may be a
graded contact plug by forming layers 322 and 324 closer to
interconnect layer 302 with a different composition than layers 322
and 324 that are further away from interconnect layer 302.
[0126] Sequential electroless deposition processes contain a
variety of sequences for exposing a substrate to deposition
solutions and rinse solutions. FIG. 8 illustrates a flow chart of
process 800 describing one embodiment of a sequential electroless
deposition process. During optional step 810, a substrate may be
exposed to a pretreatment process as described herein to remove
oxide surfaces, form hydride surfaces, form metallic surfaces, form
silicide surfaces, form a SAM material, form a capping layer, by
pre-clean processes, activation processes, reduction processes, or
combinations thereof.
[0127] FIG. 9A depicts a graph to illustrate periods of time for
exposing a substrate to solutions during an electroless process,
such as process 800. During step 820, a cobalt material is formed
by exposing the substrate to a cobalt solution containing a cobalt
source for a time period between to and t.sub.1. Generally, the
cobalt material is deposited to form a layer with a thickness
within a range from about a discontinuous atomic layer to about 100
.ANG., preferably, from about an atomic layer to about 50 .ANG.,
and more preferably, from about 5 .ANG. to about 30 .ANG.. The time
period between t.sub.0 and t.sub.1 may be within a range from about
5 seconds to about 5 minutes, preferably, from about 10 seconds to
about 3 minutes, and more preferably, from about 30 seconds to
about 2 minutes.
[0128] The substrate is exposed to a rinse solution during a rinse
process for a time period between t.sub.1 and t.sub.2 during step
830. The rinse solution is preferably water, such as deionized
water. Alternatively, the rinse solution may contain an additive,
such as a surfactant, a chelator or a mild reductant. The rinse
process removes the remaining cobalt solution and any byproducts.
Generally, the time period between t.sub.1 and t.sub.2 is within a
range from about 5 seconds to about 5 minutes, preferably, from
about 10 seconds to about 3 minutes, and more preferably, from
about 30 seconds to about 2 minutes.
[0129] During step 840, a nickel material is formed by exposing the
substrate to a nickel solution containing a nickel source for a
time period between t.sub.2 and t.sub.3. Generally, the nickel
material is deposited to form a layer with a thickness within a
range from about a discontinuous atomic layer to about 100 .ANG.,
preferably, from about an atomic layer to about 50 .ANG., and more
preferably, from about 5 .ANG. to about 30 .ANG.. The time period
between t.sub.2 and t.sub.3 may be within a range from about 5
seconds to about 5 minutes, preferably, from about 10 seconds to
about 3 minutes, and more preferably, from about 30 seconds to
about 2 minutes.
[0130] The substrate is again exposed to the rinse solution during
a rinse process for a time period between t.sub.3 and t.sub.4
during step 850. The rinse solution may be the same solution as
used during step 830 or the rinse solution may be different,
dependant on the specific chemistries of the cobalt and nickel
solutions. The rinse process removes the remaining nickel solution
and any byproducts. Generally, the time period between t.sub.3 and
t.sub.4 is within a range from about 5 seconds to about 5 minutes,
preferably, from about 10 seconds to about 3 minutes, and more
preferably, from about 30 seconds to about 2 minutes.
[0131] Once the cobalt-nickel material is deposited to a
predetermined thickness, the sequential electroless process is
complete at step 860. However, multiple cycles of steps 820, 830,
840, and 850 may be repeated until the cobalt-nickel material is
formed with the predetermined thickness. For example, a second
cycle of steps 820, 830, 840, and 850 may be completed during
t.sub.4-t.sub.8 and a third cycle of steps 820, 830, 840, and 850
may be completed during t.sub.8-t.sub.12 (FIG. 9A). Usually, the
cobalt-nickel material is deposited onto the substrate to fill any
vias or apertures.
[0132] In other aspects, process 800 may be modified by rearranging
or omitting process steps. For example, step 820 may include a
nickel solution and not a cobalt solution while step 840 includes a
cobalt solution and not a nickel solution. In another example,
steps 820 or 840 may by skipped during a cycle. In an alternative
embodiment, multiple layers of cobalt material may be deposited on
each other or multiple layers of nickel material may be deposited
on each other. A graded cobalt-nickel material may be formed by
selectively manipulating the order or the amount of time of process
steps 820, 830, 840, and 850.
[0133] Therefore, in an alternative embodiment, in reference to
FIGS. 4A-4H, the composition of layers 322 and 324 may vary
throughout cobalt-nickel stack material 330, such as that layers
322 and 324 that are closer to interconnect layer 302 have a
different composition than layers 322 and 324 that are further away
from interconnect layer 302 (FIGS. 4A-4H). Electroless deposition
processes that may be utilized to control composition of
cobalt-nickel materials formed during processes described herein
(e.g., processes 800 and 1000) are further disclosed in commonly
assigned U.S. Ser. No. 11/040,962, entitled "Method and Apparatus
for Selectively Changing Thin Film Composition During Electroless
Deposition in a Single Chamber," filed on Jan. 22, 2005, and
published as US 2005-0181226, which is incorporated by reference to
the extent not inconsistent with the claimed aspects and
description herein.
[0134] FIGS. 9B-9D depict graphs to illustrate periods of time for
exposing a substrate to solutions during various permutations of
the electroless deposition processes. Process 800 may be modified
by omitting step 830 (FIG. 9B), by omitting step 850 (FIG. 9C), or
conducting steps 820 and 840 during the same time and omitting
either step 830 or step 850 (FIG. 9D).
[0135] FIG. 10 illustrates a flow chart of process 1000 describing
another embodiment of a sequential electroless deposition process,
and FIG. 11 depicts a graph to illustrate periods of time for
exposing a substrate to solutions during an electroless deposition
process, such as process 1000. During optional step 1010, a
substrate may be exposed to a pretreatment process and/or
activation process as described for step 810.
[0136] A cobalt-nickel material may be formed by exposing a
substrate to an increasing amount of a cobalt solution while
exposing the substrate to a decreasing amount of a nickel solution
for a time period between t.sub.0 and t.sub.1 during a transition
step. The cobalt-nickel material is deposited to form a layer with
a thickness within a range from about a discontinuous atomic layer
to about 100 .ANG., preferably, from about an atomic layer to about
50 .ANG., and more preferably, from about 5 .ANG. to about 30
.ANG.. The time period between t.sub.0 and t.sub.1 may be within a
range from about 5 seconds to about 5 minutes, preferably, from
about 10 seconds to about 3 minutes, and more preferably, from
about 30 seconds to about 2 minutes.
[0137] During step 1020, a cobalt material is formed by exposing
the substrate to a cobalt solution for a time period between
t.sub.1 and t.sub.2. The cobalt material is deposited to form a
layer with a thickness within a range from about a discontinuous
atomic layer to about 100 .ANG., preferably, from about an atomic
layer to about 50 .ANG., and more preferably, from about 5 .ANG. to
about 30 .ANG.. The time period between t.sub.1 and t.sub.2 may be
within a range from about 5 seconds to about 5 minutes, preferably,
from about 10 seconds to about 3 minutes, and more preferably, from
about 30 seconds to about 2 minutes.
[0138] A cobalt-nickel material may be formed by exposing the
substrate to a decreasing amount of a cobalt solution while
exposing the substrate to an increasing amount of a nickel solution
for a time period between t.sub.2 and t.sub.3 during another
transition step. The cobalt-nickel material is deposited to form a
layer with a thickness within a range from about a discontinuous
atomic layer to about 100 .ANG., preferably, from about an atomic
layer to about 50 .ANG., and more preferably, from about 5 .ANG. to
about 30 .ANG.. The time period between t.sub.2 and t.sub.3 may be
within a range from about 5 seconds to about 5 minutes, preferably,
from about 10 seconds to about 3 minutes, and more preferably, from
about 30 seconds to about 2 minutes.
[0139] A nickel material may be formed by exposing the substrate to
a nickel solution for a time period between t.sub.3 and t.sub.4
during step 1030. The nickel material is deposited to form a layer
with a thickness within a range from about a discontinuous atomic
layer to about 100 .ANG., preferably, from about an atomic layer to
about 50 .ANG., and more preferably, from about 5 .ANG. to about 30
.ANG.. The time period between t.sub.3 and t.sub.4 may be within a
range from about 5 seconds to about 5 minutes, preferably, from
about 10 seconds to about 3 minutes, and more preferably, from
about 30 seconds to about 2 minutes.
[0140] Once the cobalt-nickel material is deposited to a
predetermined thickness, the sequential electroless process may be
complete at step 1040. However, multiple cycles of steps 1020 and
1030 and transition steps are repeated until the cobalt-nickel
material is formed with a predetermined thickness. For example, a
second cycle of steps 1020 and 1030 and transition steps may be
completed during t.sub.4-t.sub.8 and a third cycle of steps 1020
and 1030 and transition steps may be completed during
t.sub.8-t.sub.12 (FIG. 10). Usually, the cobalt-nickel material is
deposited onto the substrate to fill any vias or apertures.
[0141] The substrate may be exposed to a chemical mechanical
polishing (CMP) process prior to the pretreatment and deposition
processes described herein. Usually, the CMP process is conducted
in a first process chamber, the nickel-containing layer or
cobalt-tungsten alloy layer may be deposited in a second process
chamber and the first and second process chambers are on the same
CMP tool. In one example, the first and second process chambers may
be in fluid communication to an in-line mixing system that combines
stock solutions used in the pretreatment process and/or the
electroless deposition processes.
Nickel Electroless Process
[0142] In some embodiments, a nickel-containing material may
deposited as metal-containing layer 316 or metal contact material
320 on substrate 300 during steps 560, 660, or 760 of processes
500, 600, or 700. Nickel-containing materials may be deposited as
capping layers or filling material by an electroless deposition
process throughout embodiments described herein. Nickel-containing
materials include metallic nickel, nickel boride, nickel phosphide,
nickel boride phosphide, or other nickel alloys. The electroless
deposition solution to form nickel-containing materials is an
aqueous solution that generally contains a nickel source, a
reductant, at least one complexing agent, a pH adjusting agent, and
optional additives and surfactants. A nickel-containing material
may be deposited by an electroless process utilizing either a
pre-mixed electroless deposition solution or an in-line mixing
process that combines solution components to generate the
electroless solution.
[0143] The nickel source within the electroless deposition solution
may have a concentration within a range from about 1 mM to about
150 mM, preferably, from about 5 mM to about 100 mM, and more
preferably, from about 10 mM to about 80 mM, such as about 40 mM.
Nickel sources provide nickel ions (e.g., Ni.sup.2+) dissolved
within the electroless solution and later reduced out as the
deposited nickel-containing material. Useful nickel sources include
nickel sulfate, nickel chloride, nickel acetate, nickel phosphate,
derivatives thereof, hydrates thereof, or combinations thereof. In
a preferred embodiment, nickel sulfate hexahydrate
(NiSO.sub.4.6H.sub.2O) is used in the electroless solution to
deposit nickel-containing materials.
[0144] The reductant within the electroless deposition solution may
have a concentration within a range from about 1 mM to about 150
mM, preferably, from about 5 mM to about 100 mM, and more
preferably, from about 10 mM to about 80 mM, such as about 40 mM.
Reductants provide electrons to induce chemical reduction of the
nickel ions that form and deposit the nickel-containing material.
Reductants may include organic reductants (e.g., formaldehyde or
glyoxylic acid), hydrazine, organic hydrazines (e.g., methyl
hydrazine), hypophosphite sources (e.g., hypophosphorous acid
(H.sub.3PO.sub.2), ammonium hypophosphite
((NH.sub.4).sub.4-xH.sub.xPO.sub.2) and salts thereof), borane
sources (e.g., dimethylamine borane complex
((CH.sub.3).sub.2NH.BH.sub.3), DMAB), trimethylamine borane complex
((CH.sub.3).sub.3N.BH.sub.3), TMAB), tert-butylamine borane complex
(.sup.tBuNH.sub.2.BH.sub.3), tetrahydrofuran borane complex
(THF.BH.sub.3), pyridine borane complex (C.sub.5H.sub.5N.BH.sub.3),
ammonia borane complex (NH.sub.3.BH.sub.3), borane (BH.sub.3),
diborane (B.sub.2H.sub.6), derivatives thereof, complexes thereof,
or combinations thereof. In a preferred embodiment, DMAB is used as
a reductant in the electroless solution for depositing
nickel-containing materials.
[0145] Chelators or complexing agents are in the electroless
solution to complex nickel ions thereby stabilizing the solubility
and reduction of nickel ions. The complexing agents may have a
concentration of about 2 M or less, such as within a range from
about 10 mM to about 500 mM, preferably, from about 50 mM to about
300 mM, and more preferably, from about 75 mM to about 200 mM, such
as about 150 mM. Complexing agents generally may have functional
groups, such as carboxylic acids, dicarboxylic acids,
polycarboxylic acids, amino acids, amines, diamines, polyamines,
alkylamines, alkanolamines, or alkoxyamines. Complexing agents may
include citric acid, citrates, glycolic acid, glycine, malonic
acid, maleic acid, lactic acid, ethylenediaminetetraacetic acid
(EDTA), ethylenediamine (EDA), triethylene tetramine (TETA),
diaminoethane, ethanolamine (EA), diethanolamine (DEA),
triethanolamine (TEA), hydroxylamine hydrochloride, ammonia,
ammonium chloride, derivatives thereof, salts thereof, or
combinations thereof. Usually, the electroless solution contains
more than one complexing agent. Preferably, the electroless
solution contains at least citric acid or citrate salts, more
preferably, the electroless solution also contains DEA, glycine,
and/or lactic acid. In one example, the electroless solution
contains about 45 mM of citric acid, about 16 mM of DEA, about 5 mM
of glycine, and about 85 mM of lactic acid.
[0146] A pH adjusting agent may be added to adjust the electroless
solution to a pH value within a range from about 8 to about 10,
preferably, from about 8.5 to about 10, and more preferably, from
about 9.0 to about 9.5, such as about 9.2. The pH adjusting agent
may be an acidic compound to decrease the pH value of the
electroless solution and include hydrochloric acid, sulfuric acid,
phosphoric acid, derivatives thereof, or combinations thereof.
Alternatively, the pH adjusting agent may be a basic compound to
increase the pH value of the electroless solution and include metal
hydroxides, tetraalkylammonium hydroxides (e.g.,
tetramethylammonium hydroxide ((CH.sub.3).sub.4NOH, TMAH) or
tetraethylammonium hydroxide ((CH.sub.3CH.sub.2).sub.4NOH, TEAH)),
ammonium hydroxide, DEA, TEA, derivatives thereof, or combinations
thereof. The pH adjusting agent may be dissolved in water prior to
adjusting the pH value of the electroless solution. In one example,
a 25 wt % aqueous solution of TMAH is used as a pH adjusting agent.
In another example, both TMAH and DEA are used to adjust the pH
value of an electroless solution.
[0147] The optional additives may include levelers, accelerators
and suppressors. Levelers within the electroless solution are used
to achieve different deposition thickness as a function of leveler
concentration and feature geometry while depositing
nickel-containing materials. The leveler within the electroless
deposition solution may have a concentration within a range from
about 20 ppb to about 600 ppm, preferably, from about 100 ppb to
about 100 ppm. Examples of levelers that may be employed in an
electroless solution include, but are not limited to
alkylpolyimines and organic sulfonates, such as
1-(2-hydroxyethyl)-2-imidazolidinethione (HIT), 4-mercaptopyridine,
2-mercaptothiazoline, ethylene thiourea, thiourea, or derivatives
thereof. The electroless deposition solution may contain
brighteners or accelerators and suppressors as alternative
additives to provide further control of the deposition process. The
role of accelerators is to achieve a smoothly deposited surface of
the nickel-containing material. The accelerator within the
electroless deposition solution has a concentration within a range
from about 20 ppb to about 600 ppm, preferably, from about 100 ppb
to about 100 ppm. Accelerators that are useful in an electroless
solution for depositing nickel-containing materials may include
sulfur-based compounds such as bis(3-sulfopropyl)disulfide (SPS),
3-mercapto-1-propane sulfonic acid (MPSA), aminoethane sulfonic
acids, thiourea, derivatives thereof, combinations thereof.
Suppressors are used to suppress nickel deposition by initially
adsorbing onto underlying catalytic surfaces and therefore blocking
access to the catalyst of the reaction. Suppressors generally may
include polyethylene glycol (PEG), polypropylene glycol (PPG),
polyoxyethylene-polyoxypropylene copolymer (POCP), benzotriazole
(BTA), dipyridyl, dimethyl dipyridyl, derivatives thereof, or
combinations thereof. The suppressor within the electroless
deposition solution has a concentration within a range from about
20 ppb to about 600 ppm, preferably, from about 100 ppb to about
100 ppm.
[0148] The electroless solution may contain boric acid as an
additional additive. Boric acid is added to provide additional
buffering and to stabilize the composition of the solution. Boric
acid is an oxidation by-product from the chemical reactions of
borane reductants (e.g., DMAB). Therefore, an electroless solution
containing boric acid is more normalized at the start of the
deposition process since a less steep dissipation gradient exist as
additional boric acid is formed from the borane reductant. Boric
acid is preferably within the electroless deposition solution at
concentration within a range from about 0.1 mM to about 50 mM,
preferably, from about 0.5 mM to about 5 mM, and more preferably,
from about 1 mM to about 3 mM, such as about 2 mM.
[0149] Also, an optional surfactant may be added to the electroless
solution. The surfactant is a wetting agent to reduce the surface
tension between the electroless solution and the substrate surface.
Surfactants are generally added to the electroless solution at a
concentration of about 1,000 ppm or less, preferably about 800 ppm
or less, such as from about 20 ppb to about 600 ppm. The surfactant
may have ionic or non-ionic characteristics. A preferred surfactant
includes dodecyl sulfates, such as sodium dodecyl sulfate (SDS).
Other surfactants that may be used in the electroless deposition
solution include glycol ether based surfactants (e.g., polyethylene
glycol). For example, a glycol ether based surfactants may contain
polyoxyethylene units, such as TRITON.RTM. 100, available from Dow
Chemical Company. A nonylphenol ethoxylate surfactant is useful in
the electroless deposition solution, such as TERGITOL.RTM.,
available from Dow Chemical Company or IGEPAL-630, available from
GAF Corporation. Other useful surfactants may contain phosphate
units, for example, sodium poly(oxyethylene)phenyl ether phosphate,
such as RHODAFAC.RTM. RE-610, available from Rhodia, Inc. The
surfactants may be single compounds or a mixture of compounds of
molecules containing varying length of hydrocarbon chains.
[0150] An electroless process to deposit nickel-containing
materials may utilize an in-line mixing process to form the
electroless solution. The process may contain the addition of two,
three, four or more componential solutions to form the electroless
solution. In one example, the electroless solution is formed by
combining a buffered complexing solution, a nickel-containing
solution, a reducing solution and water, where each solution is a
concentrate and water is added to reach a predetermined
concentration of the final solution. In another example, the
electroless solution is formed by combining a buffered complexing
solution, a nickel-containing solution and a reducing solution,
where each of the solutions are pre-diluted and therefore do not
require additional water. In another example, the electroless
solution is formed by combining a buffered nickel-containing
solution, a reducing solution and water, where a buffered
complexing solution and a nickel-containing solution are combined
to form the buffered nickel-containing solution. Further details of
in-line mixing processes and componential solutions are further
described in the commonly assigned U.S. Ser. No. 10/967,919,
entitled, "Selective Self-initiating Electroless Capping of Copper
with Cobalt-containing Alloys," filed on Oct. 18, 2004, and
published as US 2005-0136193, which is incorporated by reference to
the extent not inconsistent with the claimed aspects and
description herein.
[0151] A buffered complexing solution usually contains water, at
least one complexing agent, additives and a pH adjusting agent. The
complexing agent within the buffered complexing solution is at a
concentration from about 0.1 M to about 3 M, preferably, from about
0.2 M to about 2 M. The additive within the buffered complexing
solution is at a concentration from about 10 mM to about 1 M,
preferably, from about 50 mM to about 500 mM. The pH adjusting
agent is at a concentration to provide the buffered complexing
solution with a pH value within a range from about 8 to about 11,
preferably, from about 9 to about 10, and more preferably, from
about 9.2 to about 9.6, such as about 9.4. In one example, a
buffered complexing solution contains water, about 450 mM of DEA,
about 300 mM of citric acid, about 150 mM of glycine, about 50 mM
of boric acid and a concentration of TMAH to adjust the pH value to
about 9.4. In another example, a buffered complexing solution
contains water, about 1.15 M of DEA, about 375 mM of citric acid,
about 300 mM of glycine, about 100 mM of boric acid and a
concentration of TMAH to adjust the pH value to about 9.4. In
another example, a buffered complexing solution contains water,
about 330 mM of DEA, about 300 mM of citric acid, about 150 mM of
glycine, about 50 mM of boric acid and a concentration of TMAH to
adjust the pH value to about 9.4.
[0152] A nickel-containing solution usually contains water, a
nickel source, at least one complexing agent, and a pH adjusting
agent. The nickel source within the nickel-containing solution is
at a concentration from about 50 mM to about 1 M, preferably, from
about 100 mM to about 500 mM, such as about 300 mM. The complexing
agent within the nickel-containing solution is at a concentration
from about 0.2 M to about 2 M, preferably, from about 0.5 M to
about 1 M. The pH adjusting agent is at a concentration to provide
the nickel-containing solution with a pH value within a range from
about 8 to about 11, preferably, from about 8.5 to about 10, and
more preferably, from about 9 to about 9.5, such as about 9.2. In
one example, a nickel-containing solution contains water, about 100
mM of citric acid, about 275 mM of nickel sulfate, about 567 mM of
85% lactic acid and a concentration of TMAH to adjust the pH value
to about 9.2.
[0153] A reducing solution usually contains water, at least one
reductant, at least one complexing agent and a pH adjusting agent.
The reductant within the reducing solution is at a concentration
from about 10 mM to about 500 mM, preferably, from about 50 mM to
about 300 mM, such as about 200 mM. The complexing agent within the
reducing solution is at a concentration from about 10 mM to about
200 mM, preferably, from about 50 mM to about 150 mM, such as about
100 mM. The pH adjusting agent is at a concentration to provide the
reducing solution with a pH value within a range from about 8 to
about 11, preferably, from about 9 to about 10, and more
preferably, from about 9.0 to about 9.4, such as about 9.2. In one
example, a reducing solution contains water, about 100 mM of citric
acid, about 204 mM of DMAB, and a concentration of TMAH to adjust
the pH value to about 9.2.
[0154] The electroless solution is preferably formed by in-line
mixing process that combines various volumetric ratios of the
buffered complexing solution, the nickel-containing solution, the
reducing solution and water. In one example, one volumetric
equivalent of a buffered complexing solution, two volumetric
equivalents of a nickel-containing solution, two volumetric
equivalents of a reducing solution, and five volumetric equivalents
of deionized water are in-line mixed to form an electroless
solution. That is, the volumetric ratio of the buffered complexing
solution, the nickel-containing solution, the reducing solution,
and the deionized water is 1:2:2:5. In another example of an
electroless solution, a volumetric ratio of the buffered complexing
solution, the nickel-containing solution, the reducing solution,
and the water is 1:1:1:3. In a preferred example, the volumetric
percentages of the buffered complexing solution, the
nickel-containing solution, the reducing solution and the deionized
water is about 3.5%, about 15%, about 20%, and about 61.5%,
therefore, the volumetric ratio is about 1.0 to about 4.3 to about
5.7 to about 17.6.
[0155] In one embodiment, an electroless solution contains: nickel
sulfate with a concentration within a range from about 1 mM to
about 150 mM, preferably, from about 5 mM to about 100 mM, and more
preferably, from about 10 mM to about 80 mM, such as about 40 mM;
DMAB with a concentration within a range from about 1 mM to about
150 mM, preferably, from about 5 mM to about 100 mM, and more
preferably, from about 10 mM to about 80 mM, such as about 40 mM;
citric acid with a concentration within a range from about 5 mM to
about 200 mM, preferably, from about 10 mM to about 100 mM, and
more preferably, from about 30 mM to about 60 mM, such as about 45
mM; DEA with a concentration within a range from about 5 mM to
about 100 mM, preferably, from about 10 mM to about 30 mM, such as
about 16 mM; glycine with a concentration within a range from about
0.5 mM to about 100 mM, preferably, from about 1 mM to about 50 mM,
and more preferably, from about 2 mM to about 10 mM, such as about
5 mM; boric acid with a concentration within a range from about 0.5
mM to about 50 mM, preferably, from about 1 mM to about 20 mM, and
more preferably, from about 1 mM to about 5 mM, such as about 2 mM;
lactic acid with a concentration within a range from about 10 mM to
about 300 mM, preferably, from about 20 mM to about 200 mM, and
more preferably, from about 50 mM to about 150 mM, such as about 85
mM; TMAH with a concentration to adjust the electroless solution to
a have pH value within a range from about 8 to about 11,
preferably, from about 8.5 to about 10, and more preferably, from
about 9.0 to about 9.6, such as about 9.2.
[0156] In one embodiment, citrate is a preferred complexing agent
and is present in each componential solution, such as the buffered
complexing solution, the nickel-containing solution and the
reducing solution. Citrate may be added as citric acid and/or as a
citrate salt. Citrate plays an important role for buffering each of
the individual componential solutions while being combined to form
the plating solution. Citrates generally have poor solubility in
water at high concentrations, while the componential solutions may
have relatively concentrated solutions. If a substantial citrate
concentration of the final electroless solution is desired, a
single componential solution may not be capable of completely
containing all the dissolved citrate. Therefore, the citrate may be
dissolved in each componential solution to assure no formation of
citrate precipitate, and subsequently combined with water forming
the electroless solution at a final concentration.
[0157] The electroless deposition process may be conducted at a
temperature within a range from about 35.degree. C. to about
120.degree. C., preferably, from about 60.degree. C. to about
100.degree. C., and more preferably, from about 75.degree. C. to
about 80.degree. C. The water may be degassed, preheated and/or
deionized water. Degassing the water reduces the oxygen
concentration of the subsequently formed electroless solution. An
electroless solution with a low oxygen concentration (e.g., less
than about 100 ppm) may be used during the deposition process.
Preheated water allows forming the electroless solution at a
predetermined temperature just below the temperature used to
initiate the deposition process, thereby shortening the process
time.
[0158] The processes described herein may be performed in an
apparatus suitable for performing an electroless deposition process
(EDP). A suitable apparatus includes the SLIMCELL.TM. processing
platform that is available from Applied Materials, Inc., located in
Santa Clara, Calif. The SLIMCELL.TM. platform, for example, is an
integrated system capable of etching a native oxide within a
wet-clean cell during a BOE process and depositing
cobalt-containing materials, cobalt-tungsten materials,
cobalt-nickel materials, nickel-containing materials within an EDP
cell. The SLIMCELL.TM. platform generally includes a wet-clean cell
or etch cell and one or more EDP cells as well as one or more
pre-deposition or post-deposition cell, such as spin-rinse-dry
(SRD) cells or annealing chambers. Process systems, platforms,
chambers, and cells useful for wet clean processes and electroless
deposition processes, as described herein, are further disclosed in
commonly assigned U.S. Ser. No. 10/059,572, entitled "Electroless
Deposition Apparatus," filed Jan. 28, 2002, and published as US
2003-0141018, U.S. Ser. No. 10/965,220, entitled, "Apparatus for
Electroless Deposition," filed on Oct. 14, 2004, and published as
US 2005-0081785, U.S. Ser. No. 10/996,342, entitled, "Apparatus for
Electroless Deposition of Metals on Semiconductor Wafers," filed on
Nov. 22, 2004, and published as US 2005-0160990, U.S. Ser. No.
11/043,442, entitled, "Apparatus for Electroless Deposition of
Metals on Semiconductor Wafers," filed on Jan. 26, 2005, and
published as US 2005-0263066, U.S. Ser. No. 11/175,251, entitled,
"Apparatus for Electroless Deposition of Metals on Semiconductor
Wafers," filed on Jul. 6, 2005, and published as US 2005-0260345,
U.S. Ser. No. 11/192,993, entitled, "Integrated Electroless
Deposition System," filed on Jul. 29, 2005, and published as US
2006-0033678, and U.S. Ser. No. 11/040,962, entitled, "Method and
Apparatus for Selectively Changing Thin Film Composition During
Electroless Deposition in a Single Chamber," filed on Jan. 22,
2005, and published as US 2005-0181226, which are each incorporated
by reference to the extent not inconsistent with the claimed
aspects and description herein.
Cobalt and Nickel Electroless Deposition Solutions and Processes
Cobalt
[0159] In some embodiments, a cobalt material or a nickel material
may deposited as metal-containing layer 316 or metal contact
material 320 on substrate 300 during steps 560, 660, or 760 of
processes 500, 600, or 700. In one embodiment, an electroless
solution for depositing metallic cobalt contains: cobalt ions
(Co.sup.2+) with a concentration within a range from about 1 mM to
about 100 mM, preferably, from about 5 mM to about 50 mM, and more
preferably, from about 10 mM to about 20 mM, such as about 15 mM;
hydrazine hydrate with a concentration within a range from about
100 mM to about 2 M, preferably, from about 200 mM to about 1 M,
and more preferably, from about 300 mM to about 400 mM, such as
about 500 mM; citric acid or citrate salt with a citrate
concentration within a range from about 5 mM to about 200 mM,
preferably, from about 10 mM to about 100 mM, and more preferably,
from about 30 mM to about 70 mM, such as about 50 mM; and an
optional pH adjusting agent (e.g., TMAH) with a concentration to
adjust the electroless solution to a have pH value within a range
from about 10 to about 14, preferably, from about 11.5 to about 13,
and more preferably, from about 12.2 to about 12.8, such as about
12.5. In one example, a pH value is about 11.5 or higher,
preferably, about 12.0 or higher, and more preferably, about 12.5
or higher. The electroless deposition process to deposit metallic
cobalt may be conducted at a temperature within a range from about
35.degree. C. to about 100.degree. C., preferably, from about
60.degree. C. to about 90.degree. C., and more preferably, from
about 70.degree. C. to about 80.degree. C., such as about
75.degree. C.
Cobalt Boride
[0160] In one embodiment, an electroless solution for depositing
cobalt boride contains: cobalt ions (Co.sup.2+) with a
concentration within a range from about 1 mM to about 150 mM,
preferably, from about 10 mM to about 100 mM, and more preferably,
from about 20 mM to about 80 mM, such as about 35 mM; DMAB with a
concentration within a range from about 1 mM to about 100 mM,
preferably, from about 5 mM to about 50 mM, and more preferably,
from about 10 mM to about 40 mM, such as about 25 mM; chelating
agent within a range from about 10 mM to about 500 mM, preferably,
from about 50 mM to about 300 mM, and more preferably, from about
75 mM to about 250 mM, such as about 150 mM; ammonium fluoride
within a range from about 1 mM to about 100 mM, preferably, from
about 2 mM to about 50 mM, and more preferably, from about 5 mM to
about 20 mM, such as about 11 mM; and an optional pH adjusting
agent (e.g., TMAH) with a concentration to adjust the electroless
solution to a have pH value within a range from about 8 to about
11, preferably, from about 8.5 to about 10, and more preferably,
from about 9.0 to about 9.6, such as about 9.2. The electroless
deposition process to deposit cobalt boride may be conducted at a
temperature within a range from about 35.degree. C. to about
100.degree. C., preferably, from about 70.degree. C. to about
90.degree. C., and more preferably, from about 75.degree. C. to
about 85.degree. C., such as about 80.degree. C.
[0161] In another embodiment, an electroless solution for
depositing cobalt boride contains: cobalt sulfate with a
concentration within a range from about 1 mM to about 150 mM,
preferably, from about 10 mM to about 100 mM, and more preferably,
from about 20 mM to about 80 mM, such as about 35 mM; DMAB with a
concentration within a range from about 1 mM to about 100 mM,
preferably, from about 5 mM to about 50 mM, and more preferably,
from about 10 mM to about 40 mM, such as about 25 mM; DEA within a
range from about 1 mM to about 300 mM, preferably, from about 10 mM
to about 100 mM, and more preferably, from about 30 mM to about 60
mM, such as about 45 mM; citric acid or citrate salt with a citrate
concentration within a range from about 5 mM to about 500 mM,
preferably, from about 30 mM to about 300 mM, and more preferably,
from about 50 mM to about 150 mM, such as about 67 mM; lactic acid
or lactate salt with a lactate concentration within a range from
about 1 mM to about 100 mM, preferably, from about 10 mM to about
50 mM, and more preferably, from about 15 mM to about 25 mM, such
as about 19 mM; glycine within a range from about 1 mM to about 100
mM, preferably, from about 5 mM to about 50 mM, and more
preferably, from about 10 mM to about 20 mM, such as about 15 mM;
boric acid within a range from about 0.5 mM to about 50 mM,
preferably, from about 1 mM to about 10 mM, and more preferably,
from about 2 mM to about 7 mM, such as about 5 mM; saccharin within
a range from about 0.02 mM to about 0.5 mM, preferably, from about
0.05 mM to about 0.2 mM, and more preferably, from about 0.07 mM to
about 0.15 mM, such as about 0.1 mM; ammonium fluoride within a
range from about 1 mM to about 100 mM, preferably, from about 2 mM
to about 50 mM, and more preferably, from about 5 mM to about 20
mM, such as about 11 mM; and an optional pH adjusting agent (e.g.,
TMAH) with a concentration to adjust the electroless solution to a
have pH value within a range from about 8 to about 11, preferably,
from about 8.5 to about 10, and more preferably, from about 9.0 to
about 9.6, such as about 9.2. The electroless deposition process to
deposit cobalt boride may be conducted at a temperature within a
range from about 35.degree. C. to about 100.degree. C., preferably,
from about 70.degree. C. to about 90.degree. C., and more
preferably, from about 75.degree. C. to about 85.degree. C., such
as about 80.degree. C.
Cobalt Tungsten Boride
[0162] In one embodiment, an electroless solution for depositing
cobalt tungsten boride contains: cobalt ions (Co.sup.2+) with a
concentration within a range from about 1 mM to about 100 mM,
preferably, from about 5 mM to about 50 mM, and more preferably,
from about 10 mM to about 20 mM, such as about 15 mM; tungstic acid
or tungstate salt with a tungstate concentration within a range
from about 0.1 mM to about 10 mM, preferably, from about 0.5 mM to
about 5 mM, and more preferably, from about 1 mM to about 3 mM,
such as about 2 mM; DMAB with a concentration within a range from
about 1 mM to about 200 mM, preferably, from about 10 mM to about
100 mM, and more preferably, from about 30 mM to about 50 mM, such
as about 40 mM; citric acid or citrate salt with a citrate
concentration within a range from about 5 mM to about 500 mM,
preferably, from about 30 mM to about 300 mM, and more preferably,
from about 50 mM to about 150 mM, such as about 100 mM; and an
optional pH adjusting agent (e.g., TMAH) with a concentration to
adjust the electroless solution to a have pH value within a range
from about 8 to about 11, preferably, from about 8 to about 10, and
more preferably, from about 8.5 to about 9.5, such as about 8.9.
The electroless deposition process to deposit cobalt tungsten
boride may be conducted at a temperature within a range from about
35.degree. C. to about 100.degree. C., preferably, from about
60.degree. C. to about 80.degree. C., and more preferably, from
about 65.degree. C. to about 75.degree. C., such as about
70.degree. C.
Nickel Boride
[0163] In one embodiment, an electroless solution contains: nickel
sulfate with a concentration within a range from about 1 mM to
about 150 mM, preferably, from about 5 mM to about 100 mM, and more
preferably, from about 10 mM to about 80 mM, such as about 40 mM;
DMAB with a concentration within a range from about 1 mM to about
150 mM, preferably, from about 5 mM to about 100 mM, and more
preferably, from about 10 mM to about 80 mM, such as about 40 mM;
citric acid with a concentration within a range from about 5 mM to
about 200 mM, preferably, from about 10 mM to about 100 mM, and
more preferably, from about 30 mM to about 60 mM, such as about 45
mM; DEA with a concentration within a range from about 5 mM to
about 100 mM, preferably, from about 10 mM to about 30 mM, such as
about 16 mM; glycine with a concentration within a range from about
0.5 mM to about 100 mM, preferably, from about 1 mM to about 50 mM,
and more preferably, from about 2 mM to about 10 mM, such as about
5 mM; boric acid with a concentration within a range from about 0.5
mM to about 50 mM, preferably, from about 1 mM to about 20 mM, and
more preferably, from about 1 mM to about 5 mM, such as about 2 mM;
lactic acid with a concentration within a range from about 10 mM to
about 300 mM, preferably, from about 20 mM to about 200 mM, and
more preferably, from about 50 mM to about 150 mM, such as about 85
mM; TMAH with a concentration to adjust the electroless solution to
a have pH value within a range from about 8 to about 11,
preferably, from about 8.5 to about 10, and more preferably, from
about 9.0 to about 9.6, such as about 9.2. The electroless
deposition process to deposit nickel boride may be conducted at a
temperature within a range from about 35.degree. C. to about
100.degree. C., preferably, from about 65.degree. C. to about
90.degree. C., more preferably, from about 70.degree. C. to about
85.degree. C., and more preferably, from about 75.degree. C. to
about 80.degree. C.
[0164] In another embodiment, an electroless solution for
depositing nickel boride contains: nickel ions (Ni.sup.2+) with a
concentration within a range from about 1 mM to about 100 mM,
preferably, from about 5 mM to about 50 mM, and more preferably,
from about 10 mM to about 20 mM, such as about 15 mM; DMAB with a
concentration within a range from about 1 mM to about 200 mM,
preferably, from about 10 mM to about 100 mM, and more preferably,
from about 30 mM to about 50 mM, such as about 40 mM; citric acid
or citrate salt with a citrate concentration within a range from
about 5 mM to about 300 mM, preferably, from about 10 mM to about
100 mM, and more preferably, from about 40 mM to about 60 mM, such
as about 50 mM; lactic acid or lactate salt with a lactate
concentration within a range from about 5 mM to about 300 mM,
preferably, from about 10 mM to about 100 mM, and more preferably,
from about 40 mM to about 60 mM, such as about 50 mM; and an
optional pH adjusting agent (e.g., TMAH) with a concentration to
adjust the electroless solution to a have pH value within a range
from about 8 to about 11, preferably, from about 8 to about 10, and
more preferably, from about 8.5 to about 9.5, such as about 8.9.
The electroless deposition process to deposit nickel boride may be
conducted at a temperature within a range from about 35.degree. C.
to about 100.degree. C., preferably, from about 60.degree. C. to
about 80.degree. C., and more preferably, from about 65.degree. C.
to about 75.degree. C., such as about 70.degree. C.
Nickel Tungsten Boride
[0165] In one embodiment, an electroless solution for depositing
nickel tungsten boride contains: nickel ions (Ni.sup.2+) with a
concentration within a range from about 1 mM to about 100 mM,
preferably, from about 5 mM to about 50 mM, and more preferably,
from about 10 mM to about 20 mM, such as about 15 mM; tungstic acid
or tungstate salt with a tungstate concentration within a range
from about 0.1 mM to about 10 mM, preferably, from about 0.5 mM to
about 5 mM, and more preferably, from about 1 mM to about 3 mM,
such as about 2 mM; DMAB with a concentration within a range from
about 1 mM to about 200 mM, preferably, from about 10 mM to about
100 mM, and more preferably, from about 30 mM to about 50 mM, such
as about 40 mM; citric acid or citrate salt with a citrate
concentration within a range from about 5 mM to about 300 mM,
preferably, from about 10 mM to about 100 mM, and more preferably,
from about 40 mM to about 60 mM, such as about 50 mM; lactic acid
or lactate salt with a lactate concentration within a range from
about 5 mM to about 300 mM, preferably, from about 10 mM to about
100 mM, and more preferably, from about 40 mM to about 60 mM, such
as about 50 mM; and an optional pH adjusting agent (e.g., TMAH)
with a concentration to adjust the electroless solution to a have
pH value within a range from about 8 to about 11, preferably, from
about 8 to about 10, and more preferably, from about 8.5 to about
9.5, such as about 8.9. The electroless deposition process to
deposit nickel tungsten boride may be conducted at a temperature
within a range from about 35.degree. C. to about 100.degree. C.,
preferably, from about 60.degree. C. to about 80.degree. C., and
more preferably, from about 65.degree. C. to about 75.degree. C.,
such as about 70.degree. C.
Cobalt Nickel Boride
[0166] In one embodiment, an electroless solution for depositing
cobalt nickel boride contains: cobalt ions (Co.sup.2+) with a
concentration within a range from about 1 mM to about 100 mM,
preferably, from about 5 mM to about 50 mM, and more preferably,
from about 10 mM to about 20 mM, such as about 15 mM; nickel ions
(Ni.sup.2+) with a concentration within a range from about 1 mM to
about 100 mM, preferably, from about 5 mM to about 50 mM, and more
preferably, from about 10 mM to about 20 mM, such as about 15 mM;
DMAB with a concentration within a range from about 1 mM to about
200 mM, preferably, from about 10 mM to about 100 mM, and more
preferably, from about 30 mM to about 50 mM, such as about 40 mM;
citric acid or citrate salt with a citrate concentration within a
range from about 5 mM to about 500 mM, preferably, from about 30 mM
to about 300 mM, and more preferably, from about 50 mM to about 150
mM, such as about 100 mM; and an optional pH adjusting agent (e.g.,
TMAH) with a concentration to adjust the electroless solution to a
have pH value within a range from about 8 to about 11, preferably,
from about 8 to about 10, and more preferably, from about 8.5 to
about 9.5, such as about 8.9. The electroless deposition process to
deposit cobalt nickel boride may be conducted at a temperature
within a range from about 35.degree. C. to about 100.degree. C.,
preferably, from about 60.degree. C. to about 80.degree. C., and
more preferably, from about 65.degree. C. to about 75.degree. C.,
such as about 70.degree. C.
Cobalt Nickel
[0167] In one embodiment, an electroless solution for depositing
cobalt nickel contains: cobalt ions (Co.sup.2+) with a
concentration within a range from about 1 mM to about 100 mM,
preferably, from about 5 mM to about 50 mM, and more preferably,
from about 10 mM to about 20 mM, such as about 15 mM; nickel ions
(Ni.sup.2+) with a concentration within a range from about 1 mM to
about 100 mM, preferably, from about 5 mM to about 50 mM, and more
preferably, from about 10 mM to about 20 mM, such as about 15 mM;
hydrazine hydrate with a concentration within a range from about
100 mM to about 2 M, preferably, from about 200 mM to about 1 M,
and more preferably, from about 300 mM to about 400 mM, such as
about 500 mM; citric acid or citrate salt with a citrate
concentration within a range from about 5 mM to about 500 mM,
preferably, from about 30 mM to about 300 mM, and more preferably,
from about 50 mM to about 150 mM, such as about 100 mM; and an
optional pH adjusting agent (e.g., TMAH) with a concentration to
adjust the electroless solution to a have pH value within a range
from about 10 to about 14, preferably, from about 11.5 to about 13,
and more preferably, from about 12.2 to about 12.8, such as about
12.5. The electroless deposition process to deposit cobalt nickel
may be conducted at a temperature within a range from about
35.degree. C. to about 100.degree. C., preferably, from about
60.degree. C. to about 90.degree. C., and more preferably, from
about 70.degree. C. to about 80.degree. C., such as about
75.degree. C.
Cobalt Activation Solution
[0168] In one embodiment, a cobalt activation solution may be used
to activate silicon-containing surfaces, such as a silicon surface
or a metal silicide surface. The cobalt activation solution may
contain a cobalt concentration within a range from about 1 mM to
about 100 mM, a fluoride concentration within a range from about 10
mM to about 400 mM, and a hypophosphite concentration within a
range from about 5 mM to about 150 mM. Preferably, an activation
solution may contain a cobalt concentration within a range from
about 5 mM to about 50 mM, a fluoride concentration within a range
from about 20 mM to about 200 mM, and a hypophosphite concentration
within a range from about 10 mM to about 80 mM. More preferably, an
activation solution may contain a cobalt concentration within a
range from about 10 mM to about 30 mM, a fluoride concentration
within a range from about 50 mM to about 120 mM, and a
hypophosphite concentration within a range from about 20 mM to
about 60 mM. In one example, an activation solution contains a
cobalt concentration of about 22 mM, a fluoride concentration of
about 83 mM, and a hypophosphite concentration of about 43 mM.
[0169] In one embodiment, citrate is a preferred complexing agent
and may be present in cleaning solutions, reducing solutions (e.g.,
Ti.sup.3+/T.sup.4+ complexes), cobalt-containing solutions,
nickel-containing solutions or cobalt-nickel-containing solutions.
Citrate may be added as citric acid and/or as a citrate salt.
Citrate plays an important role of buffering the aforementioned
solutions.
[0170] A "substrate surface," as used herein, refers to any
substrate or material surface formed on a substrate upon which film
processing is performed. For example, a substrate surface on which
processing may be performed include materials such as
monocrystalline, polycrystalline, or amorphous silicon, strained
silicon, silicon on insulator (SOI), doped silicon, fluorine-doped
silicate glass (FSG), silicon germanium, germanium, gallium
arsenide, glass, sapphire, silicon oxide, silicon nitride, silicon
oxynitride, or carbon doped silicon oxides, such as
SiO.sub.xC.sub.y, for example, BLACK DIAMOND.RTM. low-k dielectric,
available from Applied Materials, Inc., located in Santa Clara,
Calif. Substrates may have various dimensions, such as 200 mm or
300 mm diameter wafers, as well as, rectangular or square panes.
Embodiments as described herein provide processes to deposit
metal-containing layers on many types of substrates and surfaces.
Substrates on which embodiments of the invention may be useful
include, but are not limited to semiconductor wafers, such as
crystalline silicon (e.g., Si<100> or Si<111>), silicon
oxide, strained silicon, silicon germanium, doped or undoped
polysilicon, doped or undoped silicon wafers, and patterned or
non-patterned wafers. Substrates made of glass or plastic, which,
for example, are commonly used to fabricate flat panel displays and
other similar devices, may also be used during embodiments
described herein.
[0171] While foregoing is directed to the preferred embodiment of
the invention, other and further embodiments of the invention may
be devised without departing from the basic scope thereof, and the
scope thereof is determined by the claims that follow.
* * * * *