U.S. patent application number 10/688420 was filed with the patent office on 2005-04-21 for electroplating compositions and methods for electroplating.
This patent application is currently assigned to Semitool, Inc.. Invention is credited to Chen, Linlin, Klocke, John L..
Application Number | 20050081744 10/688420 |
Document ID | / |
Family ID | 34521165 |
Filed Date | 2005-04-21 |
United States Patent
Application |
20050081744 |
Kind Code |
A1 |
Klocke, John L. ; et
al. |
April 21, 2005 |
Electroplating compositions and methods for electroplating
Abstract
Disclosed are electroplating compositions and methods for
filling recessed microstructures of a microelectronic workpiece,
such as a semiconductor wafer, with metallization. The
electroplating compositions may comprise a mixture of copper and
sulfuric acid wherein the ratio of copper concentration to sulfuric
acid concentration is equal to from about 0.3 to about 0.8 g/L
(grams per liter of solution). The disclosed electroplating
compositions may also comprise a mixture of copper and sulfuric
acid wherein the copper concentration is near its solubility limit
when the sulfuric acid concentration is from about 65 to about 150
g/L. Such electroplating compositions may also include conventional
additives, such as accelerators, suppressors, halides and/or
levelers. Methods for electrochemically depositing conductive
materials in features, such as trenches and/or contact holes formed
on semiconductor workpieces are disclosed, including methods suited
for use in multiple anode reactors using the disclosed
electroplating solutions.
Inventors: |
Klocke, John L.; (Kalispell,
MT) ; Chen, Linlin; (Plano, TX) |
Correspondence
Address: |
KLARQUIST SPARKMAN, LLP
121 SW SALMON STREET
SUITE 1600
PORTLAND
OR
97204
US
|
Assignee: |
Semitool, Inc.
|
Family ID: |
34521165 |
Appl. No.: |
10/688420 |
Filed: |
October 16, 2003 |
Current U.S.
Class: |
106/1.18 ;
205/291; 257/E21.175; 257/E21.585 |
Current CPC
Class: |
C25D 5/48 20130101; C25D
3/38 20130101; C25D 7/123 20130101; H01L 21/2885 20130101; H01L
21/76877 20130101 |
Class at
Publication: |
106/001.18 ;
205/291 |
International
Class: |
C25D 003/38 |
Claims
1. An aqueous-based electroplating composition comprising: about 35
to about 60 g/L copper; about 65 to about 150 g/L sulfuric acid; a
glycol-based suppressor.
2. The composition of claim 1 wherein the glycol-based suppressor
is present at a concentration of from about 2 to about 30 ml/L.
3. The composition of claim 1 further comprising a
copper-deposition accelerator present at a concentration of from
about 2 to about 30 ml/L.
4. The composition of claim 1 further comprising from about 10 to
about 100 ppm halide ion.
5. The composition of claim 4 further comprising from about 30 to
about 60 ppm HCl.
6. An electroplating composition comprising: about 35 to about 60
g/L copper; about 65 to about 150 g/L sulfuric acid; and about 2 to
about 30 ml/L of a copper-deposition suppressor; wherein the
balance of the composition is water.
7. The composition of claim 6 further comprising a
copper-deposition accelerator at a concentration of from about 2 to
about 30 ml/L.
8. The composition of claim 6 wherein the copper-deposition
suppressor is a random or block copolymer.
9. The composition of claim 6 wherein the copper-deposition
suppressor is copper bath viaform suppressor or Shipley C-3100
suppressor.
10. The composition of claim 6 wherein the copper-deposition
suppressor is glycol-based.
11. The composition of claim 6 further comprising a
copper-deposition accelerator.
12. The composition of claim 11 wherein the copper-deposition
accelerator is copper bath viaform accelerator or Shipley B-3100
accelerator.
13. The composition of claim 11 wherein the copper-deposition
accelerator is SPS.
14. The composition of claim 6 further comprising from about 10 to
about 100 ppm HCl.
15. An aqueous electroplating composition comprising: about 35 to
about 60 g/L copper; about 65 to about 150 g/L sulfuric acid; about
2 to about 30 ml/L copper-deposition accelerator; about 2 to about
30 ml/L copper-deposition suppressor; and about 40 to about 60 ppm
hydrogen chloride.
16. The composition of claim 15 wherein the copper-deposition
suppressor is glycol-based.
17. The composition of claim 15 wherein the copper-deposition
accelerator is a sulphur containing compound.
18. The composition of claim 1 further comprising about 50 ppm
HCl.
19. An electroplating composition comprising: about 45 to about 55
g/L copper; about 75 to about 120 g/L sulfuric acid; a
copper-deposition suppressor; and a copper-deposition
accelerator.
20. The composition of claim 19 wherein the glycol-based suppressor
is at a concentration of from about 2 to about 10 ml/L.
21. The composition of claim 19 further comprising a
copper-deposition accelerator present at a concentration of from
about 2 to about 8 ml/L.
22. The composition of claim 19 further comprising from about 10 to
about 100 ppm halide ion.
23. The composition of claim 19 further comprising from about 30 to
about 60 ppm HCl.
24. The composition of claim 21 wherein the copper-deposition
accelerator is a sulphur containing compound.
25. The composition of claim 19 further comprising a leveler.
26. An electroplating composition comprising: an aqueous mixture of
copper and sulfuric acid wherein the ratio in g/L of solution of
copper to acid is equal to about 0.4 to about 0.8; a
copper-deposition suppressor; and a copper-deposition
accelerator.
27. The composition of claim 26 wherein the copper-deposition
suppressor is a random or block copolymer.
28. The composition of claim 26 wherein the copper-deposition
suppressor is copper bath viaform suppressor or Shipley C-3 100
suppressor.
29. The composition of claim 26 wherein the copper-deposition
suppressor is glycol-based.
30. The composition of claim 26 further comprising a
copper-deposition accelerator present in a concentration of from
about 2 to about 30 ml/L.
31. The composition of claim 26 wherein the copper-deposition
accelerator is copper bath viaform accelerator or Shipley B-3100
accelerator.
32. The composition of claim 26 wherein the copper-deposition
accelerator is SPS.
33. The composition of claim 26 further comprising from about 10 to
about 100 ppm HCl.
34. An electroplating composition comprising: an aqueous-based
mixture of copper and sulfuric acid wherein the ratio in g/L
solution of copper to acid is equal to about 0.3 to about 0.8; a
copper-deposition suppressor; a copper-deposition accelerator;
wherein only electroplating compositions comprising a mixture of
copper and sulfuric acid wherein the ratio in g/L of copper to acid
is equal to about 0.3 to about 0.8 are used to deposit copper on a
workpiece.
35. An electroplating composition comprising: an aqueous mixture of
copper and sulfuric acid wherein the copper concentration in the
composition is within about 60% to about 90% of its solubility
limit when the sulfuric acid concentration is from about 65 to
about 150 g/L; a copper-deposition suppressor; and a
copper-deposition accelerator.
36. The composition of claim 35 wherein the copper-deposition
suppressor is present at a concentration of from about 2 to about
30 ml/L.
37. The composition of claim 35 further comprising a
copper-deposition accelerator present at a concentration of from
about 2 to about 30 ml/L.
38. The composition of claim 36 further comprising from about 10 to
about 100 ppm halide ion.
39. The composition of claim 36 further comprising from about 30 to
about 60 ppm HCl.
40. The composition of claim 36 wherein the copper-deposition
suppressor is at a concentration of from about 2 to about 10
ml/L.
41. The composition of claim 36 further comprising a
copper-deposition accelerator present at a concentration of from
about 2 to about 8 ml/L.
42. The composition of claim 36 wherein the copper-deposition
accelerator is a sulphur containing compound.
43. The composition of claim 36 wherein the copper-deposition
suppressor is glycol-based.
44. An electroplating composition comprising: about 40 g/L copper;
about 100 g/L sulfuric acid; a copper-deposition suppressor; and a
copper-deposition accelerator.
45. The composition of claim 44 wherein the copper-deposition
suppressor is present at a concentration of from about 2 to about
30 ml/L.
46. The composition of claim 44 further comprising a
copper-deposition accelerator present at a concentration of from
about 2 to about 30 ml/L.
47. The composition of claim 44 further comprising from about 10 to
about 100 ppm halide ion.
48. The composition of claim 44 further comprising from about 30 to
about 60 ppm HCl.
49. The composition of claim 44 wherein the copper-deposition
suppressor is at a concentration of from about 2 to about 10
ml/L.
50. The composition of claim 44 further comprising a
copper-deposition accelerator present at a concentration of from
about 2 to about 8 ml/L.
51. The composition of claim 44 wherein the copper-deposition
accelerator is a sulphur containing compound.
52. The composition of claim 44 wherein the copper-deposition
suppressor is glycol-based.
53. An aqueous electroplating composition comprising: about 50 g/L
copper; about 80 g/L sulfuric acid; about 2 to about 10 ml/L
copper-deposition suppressor; and about 2 to about 8 ml/L
copper-deposition accelerator.
54. The composition of claim 53 further comprising from about 10 to
about 100 ppm halide ion.
55. A method for plating a workpiece comprising: providing a
workpiece having a plurality of device features including a seed
layer wherein the plurality of device features is to be metallized;
depositing copper within the plurality of device features utilizing
an electroplating composition comprising about 35 to about 60 g/L
copper, about 65 to about 150 g/L sulfuric acid, and a glycol-based
suppressor.
56. The method of claim 55 further comprising a seed enhancement
procedure.
57. The method of claim 55 further comprising rinsing and drying
the workpiece during processing, wherein the rinsing and/or the
drying occurs in a chamber in which the deposition of copper is
performed.
58. The method of claim 55 further comprising selective etching of
copper deposited on the workpiece.
59. The method of claim 55 further comprising cleaning the backside
of the workpiece after copper is deposited on the workpiece.
60. The method of claim 55 further comprising annealing the
workpiece at temperatures below about 100.degree. C.
61. The method of claim 55 further comprising precleaning the
workpiece prior to depositing copper wherein the precleaning of the
workpiece is performed in the same plating tool in which the
deposition is performed.
62. The method of claim 55 wherein the electroplating composition
comprises from about 35 to about 60 g/L copper, from about 65 to
about 150 g/L sulfuric acid, and from about 2 to about 30 ml/L of a
copper-deposition suppressor.
63. A method for plating a workpiece comprising: providing a
workpiece having a plurality of device features including a seed
layer wherein the plurality of device features is to be metallized;
depositing copper within the plurality of device features utilizing
an electroplating composition comprising from about 35 to about 60
g/L copper, from about 65 to about 150 g/L sulfuric acid, from
about 2 to about 30 ml/L copper-deposition accelerator, from about
2 to about 30 ml/L copper-deposition suppressor; and from about 40
to about 60 ppm hydrogen chloride.
64. The method of claim 63 wherein the electroplating composition
comprises a mixture of copper and sulfuric acid wherein the ratio
in g/L of copper to acid is equal to about 0.4 to about 0.8, a
copper-deposition suppressor, and a copper-deposition
accelerator.
65. The method of claim 63 wherein the electroplating composition
comprises a mixture of copper and sulfuric acid wherein the ratio
in g/L of copper to acid is equal to about 0.3 to about 0.8, a
copper-deposition suppressor, and a copper-deposition accelerator
and wherein only electroplating compositions comprising a mixture
of copper and sulfuric acid wherein the ratio in g/L of copper to
acid is equal to about 0.3 to about 0.8 are used to deposit copper
on the workpiece.
66. A process for applying a metallization interconnect structure,
comprising: providing a workpiece on which a metal seed layer has
been formed using a first deposition process; repairing the seed
layer by electrochemically depositing additional metal on the seed
layer within a principal fluid chamber of a reactor to provide an
enhanced seed layer using a deposition process comprising supplying
electroplating power to a plurality of concentric anodes disposed
at different positions within the principal fluid flow chamber
relative to the workpiece; and electrolytically depositing a metal
on the enhanced seed layer utilizing an electroplating composition
comprising about 35 to about 60 g/L copper, about 65 to about 150
g/L sulfuric acid, and a glycol-based suppressor.
67. The process of claim 66 wherein the electroplating composition
comprises from about 35 to about 60 g/L copper, from about 65 to
about 150 g/L sulfuric acid, and from about 2 to about 30 ml/L of a
copper-deposition suppressor.
68. A process for applying a metallization interconnect structure,
comprising: providing a workpiece on which a metal seed layer has
been formed; repairing the seed layer by electrochemically
depositing additional metal on the seed layer within a principal
fluid chamber of a reactor to provide an enhanced seed layer using
a deposition process comprising supplying electroplating power to a
plurality of electrodes within the principal fluid flow chamber,
independently controlling the supply of electrical power to the at
least two electrodes during repair of the seed layer; and
electrolytically depositing copper on the enhanced seed layer under
conditions in which the deposition rate of the electrolytic
deposition process is substantially greater than the deposition
rate of the process used to repair the metal seed utilizing an
electroplating composition comprising a mixture of copper and
sulfuric acid wherein the ratio in g/L of copper to acid is equal
to about 0.4 to about 0.8, a copper-deposition suppressor, and a
copper-deposition accelerator.
69. The method of claim 68 wherein the electroplating composition
comprises a mixture of copper and sulfuric acid wherein the ratio
in g/L of copper to acid is equal to about 0.3 to about 0.8.
Description
FIELD
[0001] This invention relates generally to electroplating
compositions and methods for depositing conductive materials in
features, such as trenches and/or contact holes formed on
semiconductor workpieces.
BACKGROUND
[0002] In the production of semiconductor integrated circuits and
other microelectronic articles from microelectronic workpieces,
such as semiconductor wafers or semiconductor wafer substrates, it
is often necessary to provide metal layers on a workpiece to serve
as interconnect metallization that electrically connects various
devices on the integrated circuit to one another.
[0003] Electrical interconnects have been conventionally formed in
semiconductor devices by first depositing a conducting layer on a
semiconductor workpiece (e.g., a wafer) surface using sputtering or
similar techniques. Unnecessary portions of the conducting layer
are removed through a chemical dry etch process with a pattern mask
formed of photoresist or the like.
[0004] In earlier devices, aluminum or an aluminum alloy was used
to form the wiring circuits. To keep up with the increased
complexity of semiconductor devices, however, wiring in
semiconductor devices has had to be made smaller and smaller. This
in turn has lead to higher current densities and reduced lifetimes
due to electromigration. In addition to this, shrinking lines
result in higher resistance increasing RC (resistance/capacitance)
delays.
[0005] To avoid excessive RC delays and device failures due to
electromigration, metals having superior conductivity and high
electromigration resistance, such as copper, have been used to form
the wiring. It is, however, difficult to perform dry etching on
copper or a copper alloy that has been deposited over the entire
workpiece surface (as in the process described above). Thus, a new
approach known as damascene processing is used. For copper wires,
first trenches or canals are formed according to a predetermined
pattern in the workpiece surface for the wiring. In dual-damascene
processing, contact holes or vias are also cut into the workpiece
to connect one layer of metal to the overlying or underlying metal
layer. Those trenches and/or contact holes are then filled with
copper or a copper alloy. This method eliminates the process of
removing unnecessary parts of the conductive layer by etching,
requiring only that the surface of the workpiece be polished to
remove the overburden of plated metal.
[0006] However the shapes of such wiring trenches and/or contact
holes in today's device designs have a considerably high aspect
ratio (the ratio of depth to width of the trenches and/or contact
holes) as the width of the wiring gets smaller. The small
dimensions (e.g., sub 1 .mu.m or even sub 0.25 .mu.m) of device
features, such as trenches and/or contact holes, make it difficult
to fill the features with an even layer of metal using conventional
sputtering methods for deposition of the metal. Chemical vapor
deposition (CVD) has been used for depositing various materials,
but it is difficult to prepare an appropriate gas material for
copper or a copper alloy.
[0007] Electrolytic plating by immersing a workpiece into a plating
solution has since been used to fill the trenches and/or contact
holes with the necessary conductive material, typically copper or a
copper alloy. Electroplating methods typically require a thin,
continuous electrically conductive seed layer be deposited on the
workpiece prior to the plating process. The seed layer generally is
formed of a conductive metal, such as copper. Electroplating the
desired metal is then generally accomplished by applying an
electrical bias to the seed layer and exposing the workpiece, such
as a wafer substrate, to an electroplating solution containing
metal ions that will plate over the seed layer in the presence of
the electrical bias.
[0008] An electroplating composition comprising copper (e.g.,
copper sulfate) and an acid or a conductive salt (e.g., sulfuric
acid) may be used. The acid, such as sulfuric acid, is added to the
electroplating composition to provide the high ionic conductivity
to the plating composition necessary to achieve high throwing
power. "Throwing power" refers to the ability of an electroplating
composition to deposit metal uniformly on a workpiece, such as a
wafer substrate. The acid does not participate in the electrode
reactions, but provides conformal coverage of the plating material
over the surface of the workpiece because acid reduces resistivity
within the electroplating composition. If the composition has a low
concentration of copper and a high concentration of acid, throwing
power of the composition is improved.
[0009] A problem encountered with conventional plating solutions is
that the deposition process within high aspect ratio trenches
and/or contact holes is also influenced by mass transport, i.e.,
diffusion of the metal into the trenches and/or contact holes
affects the kinetics of the deposition reaction in addition to the
magnitude of the electric field (as is common on larger feature
devices). Thus, the rate at which plating ions are provided to the
surface of the workpiece can limit the plating rate, irrespective
of the voltage or current density applied to the plating surface.
Highly conductive electroplating compositions (e.g., high acid
concentration compositions) that provide good throwing power do not
obtain good coverage and fill within relatively small features on a
device, i.e., sub-micron sized trenches and/or contact holes. This
often causes a reduction in the quality of the deposit and leads to
fill defects, typically voids. Voids are often formed when using
such compositions for filling relatively small trenches and/or
contact holes. In order to obtain good quality deposition, the
deposition process must have high mass-transfer rates and low
depletion of the reactant concentration near or within the small
trenches and/or contact holes. However, in typical high acid
plating baths the transport rates are limited by the relatively low
metal ion concentration.
[0010] Transport of the metal ion to be plated is directly related
to the concentration of the plated metal ion in the electroplating
composition. A higher metal ion concentration results in a higher
rate of transport of the metal into small features and in a higher
metal ion concentration within the depletion layer, i.e., the
boundary layer at the cathode surface hence, faster and better
quality depositions may be achieved.
[0011] When using a plating composition superior in throwing power
and coating uniformity to fill copper in the trenches and/or
contact holes of a substrate having relatively large aspect ratios,
however, as mentioned above the filling capability of the
composition is poor. The inlets of the trenches and/or contact
holes are often blocked before the trenches and/or contact holes
are filled, thereby tending to form voids. Voids may also be caused
by other forces, such as non-uniform nucleation at the seed layer
during a plating process, inadequate nucleation, and large grain
formation during plating. Unfortunately, using a typical low acid,
high metal plating composition provides inferior throwing power and
suppressed additive activity, resulting in unplated areas within
features.
[0012] A significant number of voids and/or non-uniform deposition
typically result in a detrimentally lowered conductivity as well as
poor electromigration resistance. In some cases, the void(s) and/or
non-uniformity may be sufficiently large to cause an open circuit
and the device fails.
[0013] Put simply, as known to those of ordinary skill in the
relevant art, if the plating composition has a low concentration of
copper and a high concentration of acid, the plating composition
will have high conductivity and good polarization, thereby
improving throwing power. In contrast, if the plating composition
has a high concentration of copper and a low concentration of acid,
it is known that the composition will have good transport of the
metal ions. In other words, the concentration of metal ions will be
sufficient at bottom of the high aspect ratio trenches and/or
contact holes to allow good feature filling.
[0014] Attempts to address the problems introduced using the
conventional plating compositions (i.e., compositions having a low
concentration of copper and a high concentration of acid or visa
versa) have not been completely satisfactory. For example, various
additives have been used, such as particular suppressors,
accelerators, and/or levelers in various concentrations. Other
additives used include halide ions, such as chloride. The additives
used depend upon whether the plating composition is a low copper
concentration with a high acid concentration or the opposite, as is
known to those persons of ordinary skill in the art. Certain
additives may decrease the deposition rate of metal atoms at a
given potential, thereby inhibiting the deposition process, whereas
other additives may increase the deposition rate of metal ions at a
given potential, thereby accelerating the deposition rate.
Unfortunately, the available plating compositions have not
sufficiently resolved the feature filling problems when dealing
with the relatively high aspect ratio features in which the
transport of metal ions is somewhat limited.
SUMMARY
[0015] The electroplating compositions and electroplating methods
of this invention, as described in detail hereinafter, provide
surprisingly superior fill capabilities and ensure superior copper
deposition with bottom-up fill capabilities for high aspect ratio
features of submicron size such that the presence of voids is
reduced or substantially eliminated altogether.
[0016] The electroplating compositions and methods may be utilized
to electroplate a metal into device features, such as high aspect
ratio semiconductor device trenches and/or contact holes on a
semiconductor workpiece. The disclosed compositions and methods are
applicable to a wide range of steps used in the manufacture of a
metallization layer in a workpiece. For ease of explanation, the
compositions and methods are discussed primarily in relation to
metallization of features formed in a semiconductor wafer processed
to form integrated circuits or other microelectronic components.
The compositions and methods disclosed are not limited to such
semiconductor wafers and features but may be used in connection
with any semiconductor workpiece wherein metallization is required.
The term "workpiece" is not limited to semiconductor wafers, but
rather refers to substrates having generally parallel planar first
and second surfaces and that are relatively thin, including
semiconductor wafers, ceramic wafers, and other substrates upon
which microelectronic circuits or components, data storage elements
or layers, and/or micromechanical elements are formed.
[0017] The electroplating compositions include copper and acid at
previously avoided relative concentrations. The electroplating
compositions provide surprisingly superior fill capabilities,
particularly copper deposition bottom-up fill capabilities for high
aspect ratio features having submicron dimensions (e.g., 0.12 .mu.m
trenches) such that the presence of voids is reduced or
substantially eliminated altogether. Additionally, the
electroplating compositions are less corrosive toward seed layers,
also providing superior fill capabilities.
[0018] The electroplating compositions may comprise an aqueous
mixture of copper and sulfuric acid wherein the ratio of copper
concentration to sulfuric acid concentration (concentrations in
g/L) is equal to from about 0.3 to about 0.8. They may also
comprise an aqueous mixture of copper and sulfuric acid wherein the
copper concentration is near its solubility limit when the sulfuric
acid concentration is from about 65 to about 150 g/L. These
compositions may also include conventional additives, such as
accelerators, suppressors, halides and/or levelers.
[0019] The disclosed methods utilize the electroplating
compositions for depositing copper onto semiconductor workpieces.
The methods further ensure superior copper deposition with
bottom-up fill capabilities for high aspect ratio features of
submicron size such that the presence of voids is reduced or
substantially eliminated altogether.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a graph illustrating the solubility of copper
sulfate in sulfuric acid at about 25.degree. C.
[0021] FIGS. 2(a)-2(e) are scanning electron microscope (SEM)
photographs of copper semiconductor interconnects measuring from
about 0.12 .mu.m to about 0.15 .mu.m in width at half the height of
the interconnect formed by using various embodiments of the
electroplating compositions wherein the copper concentration was
varied while the acid concentration was about 80 g/L.
[0022] FIG. 2(f) is a pictured leverage plot showing feature fill
results when comparing varied acid/copper electroplating
compositions, where the copper concentration was increased in
successive samples.
[0023] FIGS. 3(a)-3(d) are SEM photographs of copper semiconductor
interconnects measuring about 0.15 .mu.m in width at half the
height of the interconnect formed using various embodiments of the
electroplating compositions wherein the acid concentration was
varied while the copper concentration was about 20 g/L (in FIGS.
3(a)-(b)) and about 50 g/L (in FIGS. 3(c)-(d)).
[0024] FIG. 3(e) is an SEM photograph of an interconnect trench
measuring about 0.023 .mu.m in width at half the height of the
interconnect trench prior to electroplating.
[0025] FIG. 3(f) is a pictured leverage plot showing the feature
fill results when comparing varied acid/copper electroplating
compositions, wherein the acid concentration was increased in
successive samples.
[0026] FIGS. 4(a)-4(c) are SEM photographs of copper semiconductor
interconnects measuring about 0.25 .mu.m in width at half the
interconnect height formed using a prior art electroplating
composition wherein the copper concentration was about 50 g/L while
the acid concentration was about 10 g/L.
[0027] FIGS. 4(d)-4(f) are SEM photographs of copper semiconductor
interconnects measuring about 0.25 .mu.m in width at half the
interconnect height formed using an embodiment of the
electroplating compositions of this invention wherein the copper
concentration was about 50 g/L while the acid concentration was
about 80g/L.
[0028] FIG. 5(a) is an SEM photograph of copper semiconductor
interconnects measuring about 0.2 .mu.m in width at half the height
of the interconnect formed using a prior art electroplating
composition wherein the copper concentration was about 20 g/L while
the acid concentration was about 180 g/L
[0029] FIG. 5(b) is an SEM photo of copper semiconductor
interconnects measuring about 0.2 .mu.m in width at half the height
of the interconnect formed using an embodiment of the
electroplating compositions of this invention wherein the copper
concentration was about 50 g/L while the acid concentration was
about 80g/L.
[0030] FIG. 6(a) is an SEM photograph of a copper semiconductor via
measuring about 0.16 .mu.m in width at half the height of the via
formed using a prior art electroplating composition wherein the
copper concentration was about 20 g/L while the acid concentration
was about 180 g/L.
[0031] FIG. 6(b) is an SEM photograph of a copper semiconductor via
measuring about 0.16 .mu.m in width at half the height of the via
formed using an embodiment of the electroplating compositions of
this embodiment of this invention wherein the copper concentration
was about 40 g/L while the acid concentration was about 100
g/L.
[0032] FIG. 7(a) is a cross-sectional view of a representative
electroprocessing station having a processing chamber or reactor
for use in a processing tool with which the electrochemical
compositions may be utilized.
[0033] FIG. 7(b) is a cross-sectional view of a portion of a
representative processing chamber or reactor with which the
electrochemical compositions may be utilized.
[0034] FIGS. 8(a)-8(d) are representative process flow charts
illustrating a few of many possible manners of implementing
metallization of a semiconductor workpiece utilizing the
electrochemical compositions and methods of this invention.
[0035] FIGS. 9(a) and 9(b) illustrate two representative processing
tools with which the electroplating compositions may be
utilized.
DETAILED DESCRIPTION
[0036] Conventional electroplating compositions of copper and acid,
such as sulfuric acid, comprise either a relatively low acid
concentration whenever there is a relatively high copper
concentration to reduce the terminal effect and provide reasonable
filling capability, or a relatively high acid concentration
whenever there is a relatively low copper concentration so that the
plating composition will have good throwing power. The
electroplating compositions of this invention do not follow such
conventional wisdom. Instead, they include copper concentrations
more equivalent to the acid concentrations.
[0037] In particular embodiments the electroplating compositions
formulated in accordance with this invention comprise an aqueous
mixture of copper and sulfuric acid wherein the ratio of the copper
concentration to the sulfuric acid concentration (all
concentrations listed in g/L are grams per liter of solution) is
equal to from about 0.3 to about 0.8 g/L. In other particular
embodiments the electroplating compositions comprise a mixture of
copper and sulfuric acid wherein the ratio of the copper
concentration to the sulfuric acid concentration is equal to from
about 0.4 to about 0.7 g/L. In yet other embodiments the
electroplating compositions comprise a mixture of copper and
sulfuric acid wherein the ratio of the copper concentration to the
sulfuric acid concentration is equal to from about 0.5 to about 0.6
g/L.
[0038] In other embodiments the electroplating compositions
comprise an aqueous mixture of copper and sulfuric acid wherein the
copper concentration in the composition is within about 60% to
about 90% of its solubility limit when the sulfuric acid
concentration is from about 65 to about 150 g/L. In yet other
embodiments the electroplating compositions comprise an aqueous
mixture of copper and sulfiic acid wherein the copper concentration
in the composition is within about 60 % to about 90 % of its
solubility limit when the sulfinic acid concentration is from about
70 to about 120 g/L. In other particular embodiments the
compositions comprise an aqueous mixture of copper at a
concentration of from about 35 to about 60 g/L and sulfuric acid at
a concentration of from about 65 to about 150 g/L. In other
embodiments the compositions comprise an aqueous mixture of copper
at a concentration of from about 45 to about 55 g/L and sulfuric
acid at a concentration of from about 75 to about 120 g/L.
[0039] Although any electroplating composition having acid and
copper within the above disclosed ranges will provide superior fill
capabilities, particularly useful electroplating compositions
comprise an aqueous mixture of about 40 g/L copper and about 100
g/L sulfuric acid or about 50 g/L copper and about 80 g/L sulfuric
acid. Other exemplary embodiments comprise aqueous mixtures of
about 60 g/L copper and about 65 g/L sulfuric acid or about 47 g/L
copper and about 70 g/L sulfuric acid.
[0040] The copper source used in the electroplating compositions of
this invention may be, for example, a copper salt such as copper
sulfate, copper fluoborate, copper gluconate, copper sulfamate,
copper sulfonate, copper pyrophosphate, copper chloride, copper
cyanide, combinations thereof, and the like. Although copper
sulfate is primarily mentioned herein, it is to be understood that
copper from any suitable source may be used in the disclosed
compositions.
[0041] The electroplating compositions may contain other mineral
acids in combination with or in place of sulfuric acid, such as
fluoboric acid and the like, organic acids, such as methane
sulfonic (MSA), amidosulfuric, aminoacetic, and combinations
thereof, and the like, combinations of mineral acids and organic
acids. The electroplating compositions may include further
additives such as suppressors, accelerators, and levelers to assist
in filling small features.
[0042] The electroplating compositions may also contain additives
such as halide ions, for example chloride, bromide, iodide,
combinations thereof, and the like. In certain embodiments of the
disclosed compositions chloride is added in combination with
certain suppressing additives (e.g., polyethers) in an amount
sufficient to interact and suppress deposition of copper at
constant voltage, or to increase the over potential for a given
applied current density. As is known to those persons of ordinary
skill in the art, the concentrations of halides added are typically
determined by the operating parameters chosen for the particular
hardware. In certain embodiments of the disclosed compositions the
halogen concentration is from about 10 ppm to about 100 ppm. For
example, about 50 ppm HCl may be added to an electroplating
composition comprising about 50 g/L copper and about 80 g/L
sulfuric acid. In another embodiment, about 20 ppm HCl is added to
an electroplating composition comprising about 40 g/L copper and
about 100 g/L sulfuric acid. Other suitable additives (as known to
those persons of ordinary skill in the art) used to aid the
suppressor in decreasing the deposition rate and/or to aid the
accelerator in increasing the deposition rate may be added.
[0043] Suppressors generally increase cathodic polarization and
adsorb on the substrate surface to inhibit or reduce copper
deposition in the adsorbed areas. Suppressors added to the plating
composition may include, e.g., two-element polyethylene glycol
based suppressors, such as suppressors made of random/block
copolymers of ethylene oxide and propylene oxide mixed in a wide
range of ratios. For example, CUBATH ViaForm Suppressor (DF75),
available from Enthone, Inc. of West Haven, Conn., or Shipley
C-3100 suppressor, available from Shipley Company of Marlborough,
Mass., may be used.
[0044] Embodiments of the electroplating compositions may include
any suitable suppressor type and concentration. For example, CUBATH
ViaForm DF75 suppressor at a concentration of from about 2 ml/L to
about 30 ml/L, or about 2 to about 10 may be used. As further
example, Shipley C-3 100 suppressor at a concentration of from
about 5 ml/L to about 25 ml/L, or about 10 to about 20 may be used.
In one particular embodiment, about 2 ml/L of the CUBATH suppressor
is used in an electroplating composition comprising about 50 g/L
copper and about 80 g/L sulfuric acid. In another example, about
17.5 ml/L of Shipley C-3100 suppressor, available from Shipley
Company of Marlborough, Mass., is used in an electroplating
composition comprising about 40 g/L copper and about 100 g/L
sulfuric acid.
[0045] Accelerators reduce cathodic polarization and compete with
suppressers for adsorption sites to accelerate copper growth in the
adsorbed areas. The accelerators used in the plating composition
may include, e.g., sulphur containing compounds, such as bis(sodium
sulfopropyl)disulfide (SPS). Accelerators, with smaller molecular
dimensions can diffuse faster than suppressors. For example, CUBATH
ViaForm Accelerator (DF74) available from Enthone or Shipley B-3
100 accelerator (available from Shipley), may be used. Embodiments
of the electroplating compositions may include, for example, an
accelerator such as the CUBATH ViaForm DF74. Such an accelerator
may be used in any suitable concentration of from about 2 ml/L to
about 30 ml/L, from about 2 to about 8 ml/L. For example, about 5
ml/L may be used in an electroplating composition comprising about
50 g/L copper and about 80 g/L sulfuric acid. For seed layers with
superior coverage such as CVD, about 8 ml/L of this accelerator may
be used. For seed layers with poor bottom coverage (e.g., bottom
voids), about 2 ml/L of the DF74 or a like accelerator may be used.
In another embodiment, about 10 ml/L of Shipley B-3100 accelerator
(available from Shipley) is used in an electroplating composition
comprising about 40 g/L copper and about 100 g/L sulfuric acid.
[0046] Suppressors and accelerators heavily populate around the
features and since the suppressors inhibit the copper growth, a
small overhang of the seed layer can close the mouth of the feature
leading to a void in the feature. Therefore, an electroplating
composition where the suppression is mostly active on the top of
the topographical features and the accelerators dominate the
suppressors in activity inside features so as to achieve bottom up
growth may be particularly useful.
[0047] The concentrations of such components may vary to be
optimized for particular hardware and/or operating conditions as
desired. Suitable concentration ranges for additives (e.g.,
halides, accelerators, suppressors, optional levelers) to the
electroplating compositions may vary depending upon the specific
operating conditions for a particular chosen process and/or tool
(e.g., temperature, spin speed, flow rate, current density) as is
known to those persons of ordinary skill in the art.
[0048] Continued acceleration after filling the features may result
in excess growth of copper over the features creating surface
protrusions. Thus, the addition of a leveler, such as CUBATH
ViaForm Leveler DF79, available from Enthone, or Shipley U-3 100
leveler (available from Shipley) may be added to the electroplating
compositions disclosed herein. Other suitable levelers may be used
to suppress the current at the protrusions to provide a leveled
surface. Specific embodiments of the electroplating compositions
include a leveler concentration of from about 0.5 ml/L to about 3
ml/L, or from about 1.0 to about 3.0 ml/L. For example, about 2.5
ml/L of the DF79 leveler may be used in an electroplating
composition comprising about 50 g/L copper and about 80 g/L
sulfuric acid. In another example, about 2 ml/L of Shipley U-3100
leveler (available from Shipley) may be used in an electroplating
composition comprising about 40 g/L copper and about 100 g/L
sulfuric acid.
[0049] The operating temperatures of electroplating compositions of
this invention may range from about 15.degree. C. to about
30.degree. C. or from about 22.degree. C. to about 27.degree. C.
For example, an operating temperature of an electroplating
composition comprising about 50 g/L copper and about 80 g/L
sulfuric acid of about 25.degree. C. has been found useful.
[0050] The plating methods using electroplating compositions of
this invention may be carried out, for example, in a fountain style
plating reactor of the type currently marketed by Semitool, Inc. of
Kalispell, Mont., Novellus Systems, Inc., of San Jose, Calif., or
Applied Materials, Inc. of Santa Clara, Calif. These tools
typically incorporate plating reactors having an anode system that
functions as a single anode, either by employing a single disc-like
anode or a basket of anode particles.
[0051] However, the plating methods carried out in a multiple anode
reactor of the type described in U.S. Pat. Nos. 6,497,801,
6,569,297, 6,565,729 and in published PCT Application WO 00/61498
are particularly suited to using the electroplating compositions
described herein. U.S. Pat. Nos. 6,497,801, 6,569, 297, 6,565,729,
and PCT Application WO 00/61498 are herein incorporated by
reference.
[0052] FIG. 7(a) illustrates a partial schematic, cross-sectional
view of a representative plating station 110. A support member 140
includes a spin motor 144 and a rotor 142 coupled to the spin motor
144. The rotor 142 supports a contact assembly 160. The rotor 142
may include a backing plate 145 and a seal 141. The backing plate
145 moves transverse to a workpiece 101 (arrow T) between a first
position (shown in solid lines in FIG. 7(a)) in which the backing
plate 145 contacts a backside of the workpiece 101 and a second
position (shown in broken lines in FIG. 7(a)) in which it is spaced
apart from the backside of the workpiece 101.
[0053] The contact assembly 160 may include a carrier 162, a
plurality of contacts 164 carried by the carrier 162, and a
plurality of shafts 166 extending between the carrier 162 and the
rotor 142. The contacts 164 can be ring-type spring contacts or
other types of contacts that are configured to engage a portion of
the seed-layer on the workpiece 101. Commercially available support
members 140 and contact assemblies 160 can be used. Particular
suitable support members 140 and contact assemblies 160 are
disclosed in U.S. Pat. Nos. 6,228,232 and 6,080,691 and in U.S.
application Ser. Nos. 09/385,784; 09/386,803; 09/386,610;
09/386,197; 09/501,002; 09/733,608; and 09/804,696, all of which
are herein incorporated by reference.
[0054] The plating station 110 may include a reactor vessel 130
having an outer housing or chamber 131 and an inner chamber 132
(both shown schematically in FIG. 7(a)) disposed within the outer
chamber 131. The inner chamber 132 carries at least one electrode
(not shown in FIG. 7(a)) and directs a flow of processing liquid,
such as an embodiment of the electroplating compositions of this
invention, to the workpiece 101. The processing liquid flows over a
weir (as indicated by arrow F) and into the outer chamber 131,
which captures the processing liquid for recirculation, recycling
or disposal.
[0055] In operation, the support member 140 holds the workpiece 101
at a workpiece-processing site (such as a workpiece plane) of the
reactor vessel 130 so that at least a plating surface of the
workpiece 101 engages the processing liquid. An electrical field is
established in the processing liquid by applying an electrical
potential between the plating surface of the workpiece 101 and one
or more electrodes (described in greater detail below with
reference to FIG. 7(b)) positioned in the inner vessel 132. For
example, in one process the contact assembly 160 is biased with a
negative potential with respect to the electrode(s) in the inner
chamber 132 to plate conductive materials onto the workpiece 101.
In one aspect of this process, one of the electrodes (a "thieving"
electrode) is also biased with a negative potential with respect to
the other electrodes to control the uniformity with which materials
are applied to the workpiece 101.
[0056] FIG. 7(b) is a schematic illustration of an embodiment of
the reactor vessel 130 having multiple electrodes, including a
thieving electrode. The reactor vessel 130 includes a helical drain
channel 134 between the inner chamber 132 and the outer chamber
131. The drain channel 134 receives processing liquid, such as an
embodiment of the electroplating compositions of this invention,
overflowing the inner chamber 132 and guides the processing liquid
toward a liquid outlet 135. Liquid enters the inner chamber 132
through a primary inlet 136a and a secondary inlet 136b. The
primary inlet 136a is coupled to a primary flow channel 137 that
directs a portion of the processing liquid within the inner chamber
132 to a primary flow guide 170. The primary flow guide 170
includes apertures 171 that direct the flow toward a central axis
139 of the inner chamber 132. The flow then proceeds upwardly from
the primary flow guide 170 toward the workpiece feature to be
filled.
[0057] The secondary inlet 136b may be coupled to a distributor 189
that directs a secondary liquid, for example the same or a
different embodiment of the electroplating compositions of this
invention, to a plurality of electrodes. The inner chamber 132
includes four concentric electrodes 180. A controller 183 is
operatively coupled to the electrodes 180a-d to individually
control the current applied to each electrode, and accordingly
control the corresponding conductive paths between the electrodes
and the workpiece feature.
[0058] The electrodes 180 are housed in a field shaping unit 176
having a corresponding plurality of electrode compartments 177
(shown as compartments 177a-177d) separated by partitions 178. The
distributor 189 directs the secondary liquid into each compartment
177 via a corresponding plurality of distributor channels 179
(shown as distributor channels 179a-179d). Accordingly, the
secondary liquid proceeds through the distributor 189, past the
electrodes 180, and upwardly toward the workpiece feature. The
effect of the field shaping unit 176 on the electrical field
produced by the electrodes 180 is as if the electrodes 180 were
positioned at the exits of each compartment 177, as shown by
virtual electrode positions 181a-181d.
[0059] The primary flow guide 170 forms an inwardly facing vessel
wall 138 (indicated in dashed lines in FIG. 7(b)) that extends
upwardly and outwardly from the primary fluid inlet 136a. A shield
184 having an aperture 182 can be positioned between the electrodes
180 and the workpiece 101 feature to control the interaction
between the workpiece feature and the fluid flow and electrical
field within the reactor vessel 130.
[0060] In the reactor vessel 130 shown in FIG. 7(b), each
compartment 177 has one or more apertures 174 (e.g., holes and/or
slots) through which liquid and gas bubbles pass. Accordingly, gas
bubbles trapped in each compartment 177 proceed radially outwardly
through the apertures 177 of each compartment until they exit the
inner chamber 132. Each compartment 177 may include an interface
member 175. The interface members 175 may include a filter or other
element configured to trap air bubbles and other particulates,
while allowing the secondary liquid to pass toward the workpiece
feature. In another embodiment, the interface members 175 include
ion membranes that allow ions to pass toward the workpiece feature,
while preventing or substantially preventing the secondary fluid
from passing toward the feature. Instead, the secondary fluid
passes through the apertures 174 and out of the inner chamber 132
via the helical drain channel 134. The first fluid can be collected
at a separate drain (not shown). In another embodiment, the ion
membrane allows the fluid as well as ions to pass through.
[0061] One or more of the foregoing reactor assemblies may be
readily integrated in a processing tool that is capable of
executing a plurality of methods on a workpiece, such as a
semiconductor microelectronic workpiece. One such processing tool
is an electroplating apparatus available from Semitool, Inc. of
Kalispell, Mont. FIGS. 9(a) and 9(b) illustrate such
integration.
[0062] The system of FIG. 9(a) includes a plurality of processing
stations 210. These processing stations include one or more
rinsing/drying stations and one or more electroplating stations.
(Other suitable immersion-chemical processing tools may be used
with the electroplating compositions.) The system includes thermal
processing stations, such as at 215, which include at least one
thermal reactor that is adapted for rapid thermal processing
(RTP).
[0063] The workpieces are transferred between processing stations
210 and the RTP station 215 using one or more robotic transfer
mechanisms 220 that are disposed for linear movement along a
central track 225. One or more of the stations 210 may also
incorporate structures that are adapted for executing an in-situ
rinse. All of the processing stations as well as the robotic
transfer mechanisms may be disposed in a cabinet provided with
filtered air at a positive pressure to thereby limit airborne
contaminants that may reduce the effectiveness of the
microelectronic workpiece processing.
[0064] FIG. 9(b) illustrates another representative processing tool
in which the electroplating compositions of this invention may be
used. The processing tool shown in FIG. 9(b) includes an RTP
station 235 located in portion 230 that includes at least one
thermal reactor, may be integrated into a tool set. Unlike the
processing tool of FIG. 9(a), at least one thermal reactor is
serviced by a dedicated robotic mechanism 240. The dedicated
robotic mechanism 240 accepts workpieces that are transferred to it
by the robotic transfer mechanisms 220. Transfer may take place
through an intermediate staging door/area 245. As such, it becomes
possible to hygienically separate the reactor portion 230 of the
processing tool from other portions of the tool. Additionally,
using such a construction, an annealing station may be implemented
as a separate module that is attached to upgrade an existing tool
set.
[0065] The electroplating compositions of this invention may be
utilized with any of a myriad of workpiece metallization processing
methods for forming interconnects and vias in a workpiece. For
example, FIGS. 8(a)-8(d) illustrate several possible
electrochemical deposition metallization process flows wherein the
disclosed electroplating compositions may be used to form
interconnects, vias or other such features.
[0066] A typical Damascene process flow is illustrated in FIG.
8(a). In the Damascene process, the workpiece is first provided
with a metallic seed layer and a barrier/adhesion layer that are
disposed over a dielectric layer into which trenches (or other
device features) are formed. The seed layer is used to conduct
electrical current during a subsequent metal electroplating step.
Typically the seed layer is a very thin layer of metal that can be
applied using one of several methods. For example, the seed layer
of metal can be laid down using physical vapor deposition or
chemical vapor deposition methods to produce a layer on the order
of about 500 .ANG. thick. The seed layer can also be formed of
copper, gold, nickel, palladium, and most or all other metals. The
seed layer is formed over a surface that is convoluted by the
presence of the trenches, or other device features, which are
recessed into the dielectric substrate.
[0067] In certain methods, before using the electroplating
compositions of this invention, an electrochemical (electroless or
electrolytic) seed layer repair or enhancement step is performed
(not shown in FIG. 8(a)). Specifically, a seed layer, such as an
ultra-thin seed layer, may be repaired if needed to render the seed
layer suitable for a subsequent metal deposition, or enhanced by
depositing additional metal on the existing seed layer, in a
separate deposition step to provide an "enhanced" seed layer. The
enhanced seed layer typically has a thickness at all points on
sidewalls of substantially all recessed features distributed within
the workpiece that is equal to or greater than about 10% of the
nominal seed layer thickness over an exteriorly disposed surface of
the workpiece. For example a seed layer enhancement process may be
performed as disclosed in U.S. Pat. Nos. 6,290,833 and 6,565, 729,
which are incorporated herein by reference. When a seed layer
enhancement process is performed, it may be followed by a rinsing
step.
[0068] With continued reference to FIG. 8(a), a copper layer is
electroplated onto the seed layer in the form of a blanket layer.
The blanket layer is plated to an extent which forms an overlying
layer, to provide a copper layer that fills the trenches (or other
device features) used to form the interconnect wiring. The copper
layer may optionally then be rinsed, typically in DI water and
(optionally) dried. The rinsing/drying, if performed, may occur in
the chamber in which the electrochemical plating occurs or in
separate chambers depending upon the plating tool used.
[0069] Subsequently, excess copper is removed by transferring the
workpiece to a stripping unit to, e.g., bevel-etch the excess
copper. In certain methods using the electroplating compositions
disclosed herein, excess copper is selectively removed from, for
example, a backside of the workpiece and/or a peripheral edge of a
process side of a workpiece, using methods such as those disclosed
in U.S. Pat. No. 6,413,436, which is incorporated herein by
reference. The bevel etched and back side cleaned workpiece may
then be rinsed. The backside clean and initial DI rinse can occur
simultaneously.
[0070] Each of the plating, rinsing and etching steps can be
performed in the same chamber or can be performed in separate
chambers. The etched workpiece is subsequently annealed. The
workpiece may be rinsed with, e.g., DI water, prior to annealing.
The workpiece may be annealed using any suitable method. For
example, the workpiece may be annealed using conventional furnace
methods or may be annealed at temperatures below 100.degree. C., or
even at ambient room temperature, using methods such as those
disclosed in U.S. Pat. No. 6,508,920, which patent is incorporated
herein by reference. The workpiece may then be chemically
mechanically polished to, for example, remove copper that is
deposited in excess of what is desired for the device features.
[0071] As shown in FIG. 8(b), an alternative process utilizing the
electroplating compositions of this invention may include a
preclean or pre-wet step prior to copper plating so as to limit
surface defects and remove waste materials therefrom. As shown in
FIG. 8(b), the preclean or pre-wet step, copper plating, backside
clean and/ or bevel etch and DI rinsing steps may all take place in
the plating tool. The anneal and CMP steps may then follow outside
the plating tool.
[0072] In another possible process suitable for use of the
electroplating compositions of this invention, a seed layer repair
or enhancement step may be performed prior to copper plating (FIG.
8c)). The seed layer repair step may comprise electrochemically
depositing a second seed layer followed by a DI rinse. The second
seed layer deposition may be performed by any suitable means, such
as discussed above. As shown in FIG. 8(c), the seed repair, copper
plating, backside clean and/or bevel etch and DI rinsing steps may
all take place in the plating tool. The anneal and CMP steps may
then follow outside the plating tool.
[0073] As shown in FIG. 8(d), in another alternative process
utilizing the electroplating compositions of this invention, the
copper plating, back side clean/bevel etch, DI rinsing and anneal
steps may all take place in the plating tool. CMP may then be
performed outside the plating tool.
[0074] As discussed above, the electroplating compositions of this
invention may be used in a number of electroplating tools using any
of a variety of workpiece metallization processing methods. In
addition, a number of process parameters may be used for the
metallization process using the electroplating compositions
disclosed herein. The process parameters utilized depend upon the
features to be filled, the tool being used and other such variables
as know to those persons skilled in the art. One possible process
is set forth below as a representative example only.
[0075] During the electrochemical deposition of copper into device
features, such as interconnects and/or vias on a workpiece
(according to one of the methods discussed above or any other
suitable method) acidic electroplating compositions can corrode
(etch) thin seed layers leading to the formation of voids.
Accordingly, a workpiece loading bias, for example, from about 0.1
V to about 1.0 V may be applied to the workpiece plating surface
while the workpiece is being immersed in an embodiment of the
disclosed electroplating composition. For example, a loading bias
of about 0.4 V or greater for 200 mm workpieces have been found to
provide a void free fill of the features. To further enhance
plating, for example, for plating a 1.0 .mu.m copper deposition on
a 200 mm wafer, the wafer may be rotated upon immersion into the
electroplating composition between about 40 rpm and about 200 rpm.
Upon plating, the wafer is rotated between about 10 rpm and about
150 rpm. Exemplary embodiments of the plating methods rotate the
wafer upon immersion at about 75 rpm and upon plating at about, 75
rpm at 1.0 amp for 5 seconds, 40 rpm at 1.0 amp for 25 seconds, and
40 rpm at 4.5 amps for the remaining time necessary to deposit the
desired thickness. As is known to persons skilled in the art, the
rotation speeds, biases, and time periods utilized depend upon the
plating tool used and the device to be formed.
[0076] To further enhance plating, for example, for plating a 0.85
.mu.m copper deposition on a 200 mm wafer, the wafer was rotated
upon immersion into the plating composition at between about 40 rpm
and about 200 rpm. Upon plating the wafer is rotated between about
10 rpm and about 150 rpm. Exemplary embodiments of the plating
methods rotate the wafer upon immersion at about 75 rpm and upon
plating at about, 75 rpm at 1.0 amp for 5 seconds, 40 rpm at 1.0
amp for 5 seconds, 40 rpm at 2.0 amp for 39 seconds, and 60 rpm at
8.22 amp until the desired thickness is achieved.
[0077] Alternatively, and using current density designations for
further description of possible plating enhancing methods, a 1
.mu.m copper deposition may be deposited on 200 mm wafer having a
copper seed layer of about 400 .ANG.. The wafer may be rotated at
about 150 rpm. The current density may be from about 2
mAmps/cm.sup.2 to about 70 mAmps/cm.sup.2. Alternatively, the
current density may be from about 3 mAmps/cm.sup.2 to about 25
mAmps/cm.sup.2 for a time period in which the desired thickness is
achieved. Of course, the current density utilized can be varied
during the plating process, typically but not exclusively starting
at a low current density and finishing with a higher current
density.
EXAMPLE 1 AND COMPARATIVE DATA
[0078] A representative embodiment of the electroplating
composition of this invention is shown in Table 1.
1 TABLE 1 Component Concentration g/L Cu 50 H.sub.2SO.sub.4 80
Accelerator (DF74) 5.0 Suppressor (DF75) 2.0 Leveler (DF79) 2.5 HCL
50* *Halogen concentration in ppm.
[0079] With suitable current densities (such as those set forth
above), void free filling was achieved with this embodiment of the
electrochemical composition, as illustrated in the results shown in
FIGS. 2(e), 3(d), 4(d)-4(f) and 5(b).
[0080] For comparison purposes, prior art electroplating
compositions were tested under the same conditions with identical
additives at the identical concentrations. Features having voids,
as can be seen in FIGS. 4(a)-4(c) were obtained. Specifically,
prior art electroplating compositions comprising the conventional
high copper and low acid combination (i.e., 50 g/L Cu and 10 g/L
sulfuric acid) produced vias having visible voids. A comparison of
the results shown in FIGS. 4(a)-(c) versus 4(d)-(f) reveal that the
prior art high copper/low acid electroplating compositions (FIGS.
4(a)-(c)) result in the formation of interconnects having
significant voids, seen as dark spots in the micrographs at the
lower regions of the interconnects. Although the filling of the
interconnects using one embodiment of the electroplating
compositions of this invention as shown in FIG. 4(d) was halted
prior to completely filling the interconnect trench, as can be seen
in the micrograph of 4(d), the interconnects were forming without
visible voids--a significant improvement over the conventional
electroplating composition results. Additionally, although the
interconnects formed using an embodiment of the electroplating
compositions as shown in FIG. 4(f) show some voiding, the number
and size of the voids in the interconnects are significantly fewer
and smaller as compared to the resulting voiding in interconnects
formed using the prior art high copper/low acid electroplating
composition, as can be seen in the microphotograph of FIG.
4(c).
[0081] For further comparison, another prior art electroplating
composition (i.e., a conventional low copper/high acid composition)
was tested under the same conditions with identical additives (at
identical concentrations) resulting in trenches having seam voids
as is illustrated in FIG. 5(a). Specifically, a prior art
electroplating composition comprising 20 g/L Cu and 180 g/L
sulfuric acid produced seam voids in metallized trenches. In
comparison, an embodiment of the electrochemical plating
compositions of this invention, specifically a composition
comprising 80 g/L sulfuric acid and 50 g/L Cu, produced void free
features in the identical size trenches (as shown in FIG.
5(b)).
EXAMPLE 2 AND COMPARATIVE DATA
[0082] Another embodiment of the electroplating composition of this
invention is shown in Table 2.
2 TABLE 2 Component Concentration g/L Cu 40 H.sub.2SO.sub.4 100
Accelerator (B-3100) 10.0 Suppressor (C-3100) 17.5 Leveler (U-3100)
3.0 HCL 20* *Halogen concentration in ppm.
[0083] With suitable current densities, such as those set forth
above, void free filling of a via was achieved with this embodiment
of the electroplating composition of this invention as is
illustrated in FIG. 6(b).
[0084] For comparison purposes, a prior art electroplating
composition was tested under the same conditions with identical
additives (at identical concentrations) as was Example 2. A via
fill having voids, as can be seen in FIG. 6(a), was obtained with
the prior art composition. Specifically, the prior art
electroplating composition compared had the conventional high acid
and low copper combination (i.e., 20 g/L Cu and 180 g/L sulfuric
acid) producing a via having visible voids, as shown in FIG. 6(a)
while the embodiments of the electroplating compositions of this
invention showed surprisingly superior results, a void-free via
filling was achieved, as shown in FIG. 6(b).
EXAMPLE 3
[0085] As shown in FIGS. 2(a) through 2(e), copper semiconductor
interconnect trenches measuring about 0.12 to about 0.15 .mu.m in
width at half the height of the interconnect were filled using
various embodiments of the electroplating compositions wherein the
copper concentration was varied while the acid concentration was
about 80 g/L and were compared to various prior art compositions.
Specifically, as shown in FIGS. 2(a) and 2(c), interconnect
trenches were filled utilizing a prior art electroplating
composition comprising 20 g/L copper and 80 g/L acid. As can be
seen in the micrographs of these figures, the prior art low
copper/high acid compositions result in devices having visible
voids. In comparison, however, as shown in FIGS. 2(b) and (d), the
electroplating compositions of this invention having copper and
acid concentrations near the copper solubility limit resulted in
devices having a relatively low number of voids formed.
Specifically, as shown in FIGS. 2(b) and 2(d), interconnect
trenches were filled utilizing an electroplating composition
comprising 35 g/L copper and 80 g/L acid providing superior
results.
EXAMPLE 4
[0086] As the FIG. 2(f) tabulated results show a number of example
electroplating compositions tested wherein the copper concentration
was increased step-wise and the acid concentrations were kept
relatively low. This increase in copper concentration relative to
the low acid concentration (contrary to conventional wisdom) again
gave surprisingly superior results.
[0087] Specifically, the additive concentrations and halide
concentrations were held constant while the acid and copper
concentrations were varied from 10 g/l to 150g/l and from 20 g/l to
50 g/l, respectively. After plating, the plated wafers were
cross-sectioned and examined for the presence of voids. For each
example of electroplating compositions tested, five filled features
at each of three sizes (0.12, 0.15, 0.20 .mu.ms) were examined. The
number of features filled out of five was tallied for each size. A
perfect score would be 5 at each size. This data was then entered
into a statistical analysis software tool (i.e., a JMP statistical
analysis software program) that generated the pictured leverage
plot shown in FIG. 2(f). As can be seen from FIG. 2(f),
electroplating compositions wherein the copper concentration was
relatively high and the acid concentration was relatively low
(i.e., embodiments of the electroplating compositions of this
invention wherein copper concentrations were near solubility
limits) provide a statistically significant improvement in feature
bottom-up fill capabilities
EXAMPLE 5 AND COMPARATIVE DATA
[0088] As shown in FIGS. 3(a)-3(d), copper semiconductor
interconnect trenches measuring about 0.15 .mu.m in width at half
the height of the interconnect were filled using electroplating
compositions wherein the sulfuric acid concentration was varied
while the copper concentration was 20 g/L or 50 g/L (20 g/L Cu and
80 and 150 g/L acid, respectively in FIGS. 3(a)-(b)) and 50 g/L Cu
with 10 and 80 g/L acid, respectively in FIGS. 3(c)-(d)). As shown
in FIG. 3(a), an interconnect trench was filled utilizing an
electroplating composition comprising 20 g/L copper and 80 g/L
acid.
[0089] For comparison purposes, as shown in FIG. 3(b), an
interconnect trench was filled utilizing an electroplating
composition comprising 20 g/L copper and 150 g/L sulfuric
acid--like the typical conventional high acid/low copper
compositions. Again, inferior results are achieved with such a
composition.
[0090] For further comparison purposes, as shown in FIG. 3(c), an
interconnect trench was filled utilizing an electrochemical
composition comprising 50 g/L copper and 10 g/L sulfuric acid.
Results are shown in FIG. 3(c). (The results shown in FIG. 3(d)
show the superior results achieved with the electroplating
composition of this invention as described above in Example 1.)
EXAMPLE 6
[0091] As the FIG. 3(f) tabulated results further demonstrate,
increasing the acid concentration while increasing the copper
concentration so that it is at or near its solubility limit
provides a statistically significant improvement in feature fill. A
number of example electroplating compositions where tested wherein
the acid concentration was increased step-wise and the copper
concentrations were kept relatively high--near its solubility
limits for the particular acid concentrations.
[0092] Specifically, the additive concentrations and halide
concentrations were held constant while the acid and copper
concentrations were varied from 10 g/l to 150 g/l and from 20 g/l
to 50 g/l, respectively. After plating, the plated wafers were
cross-sectioned and examined for the presence of voids. For each
example of electroplating composition tested, five filled features
at each of three sizes (0.12, 0.15, 0.20 .mu.ms) were examined. The
number of features filled out of five was tallied for each size. A
perfect score would be 5 at each size. This data was then entered
into a statistical analysis software tool (i.e., a JMP statistical
analysis software program) that generated the pictured leverage
plot shown in FIG. 3(f). As can be seen from FIG. 3(f),
electroplating compositions wherein the copper concentration was at
or near its solubility limit provide statistically significant
improvement in feature bottom-up fill capabilities.
[0093] Whereas the electroplating compositions and methods of this
invention have been described with reference to multiple
embodiments and examples, it will be understood that the invention
is not limited to those embodiments and examples. On the contrary,
the invention is intended to encompass all modifications,
alternatives, and equivalents as may be included within the spirit
and scope of the invention as defined by the appended claims.
* * * * *