U.S. patent application number 10/700745 was filed with the patent office on 2005-05-05 for baths, methods, and tools for superconformal deposition of conductive materials other than copper.
This patent application is currently assigned to Semitool, Inc.. Invention is credited to Hu, Zhongmin, Ritzdorf, Thomas L..
Application Number | 20050092616 10/700745 |
Document ID | / |
Family ID | 34551271 |
Filed Date | 2005-05-05 |
United States Patent
Application |
20050092616 |
Kind Code |
A1 |
Hu, Zhongmin ; et
al. |
May 5, 2005 |
Baths, methods, and tools for superconformal deposition of
conductive materials other than copper
Abstract
Superconformal deposition promoters are used to facilitate the
superconformal deposition of conductive metals other than copper.
Features deposited using the baths, methods, and tools that employ
the superconformal deposition promoters are void free. The
superconformal deposition promoters include sulfonate terminated
alkanethiols, sulfonic acid terminated alkanethiols, carboxylate
terminated alkanethiols, carboxylic acid terminated alkanethiols,
and sulfonate terminated alkanedisulfide compounds.
Inventors: |
Hu, Zhongmin; (Kalispell,
MT) ; Ritzdorf, Thomas L.; (Bigfork, MT) |
Correspondence
Address: |
CHRISTENSEN, O'CONNOR, JOHNSON, KINDNESS, PLLC
1420 FIFTH AVENUE
SUITE 2800
SEATTLE
WA
98101-2347
US
|
Assignee: |
Semitool, Inc.
|
Family ID: |
34551271 |
Appl. No.: |
10/700745 |
Filed: |
November 3, 2003 |
Current U.S.
Class: |
205/266 ;
106/1.13; 204/242 |
Current CPC
Class: |
C25D 3/02 20130101; C25D
3/48 20130101 |
Class at
Publication: |
205/266 ;
204/242; 106/001.13 |
International
Class: |
C25D 005/02; C25D
017/00 |
Claims
The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. A composition for electrolytically depositing a conductive
material other than copper onto a conductive substrate comprising:
ions of the conductive material; a complexing agent; and a
superconformal deposition promoter selected from sulfonate
terminated alkanethiols, sulfonic acid terminated alkanethiols,
carboxylate terminated alkanethiols, carboxylic acid terminated
alkanethiols and sulfonate terminated alkanedisulfide
compounds.
2. The composition of claim 1, wherein the conductive material is
gold.
3. The composition of claim 1, further comprising a grain
refiner.
4. The composition of claim 3, wherein the grain refiner is
thallium.
5. The composition of claim 1 which is free of polyethylene
glycol.
6. The composition of claim 1, further comprising a pH buffer.
7. The composition of claim 6, wherein the pH buffer is a
pyrophosphate.
8. The composition of claim 1, wherein the superconformal
deposition promoter is present in an amount ranging from about 0.05
to 0.3 millimoles.
9. The composition of claim 1, wherein the superconformal
deposition promoter is a sulfonate terminated alkanethiol.
10. The composition of claim 1, wherein the superconformal
deposition promoter is a sulfonic acid terminated alkanethiol.
11. A method for the superconformal deposition of a conductive
material other than copper onto a conductive substrate comprising:
providing a substrate including recessed features to be filled with
the conductive material, a conductive feature being present within
the recessed features; contacting the conductive feature with a
composition for electrolytically depositing the conductive material
into the recessed feature, the composition comprising: (a) ions of
the conductive material; (b) a complexing agent; and (c) a
superconformal deposition promoter selected from sulfonate
terminated alkanethiols, sulfonic acid terminated alkanethiols,
carboxylate terminated alkanethiols, carboxylic acid terminated
alkanethiols, and sulfonate terminated alkanedisulfide compounds;
and depositing the conductive material onto the conductive feature
to fill the recessed feature.
12. The method of claim 11, wherein the conductive material is
gold.
13. The method of claim 11, wherein the composition for
electrolytically depositing the conductive material is free of
polyethylene glycol.
14. The method of claim 11, wherein the superconformal deposition
promoter is present in the composition for electrolytically
depositing the conductive material in an amount ranging from about
0.05 to 0.3 millimoles.
15. The method of claim 11, wherein the superconformal deposition
promoter is a sulfonate terminated alkanethiol.
16. The method of claim 11, wherein the superconformal deposition
promoter is a sulfonic acid terminated alkanethiol.
17. The method of claim 11, wherein the recessed features are
reentrant.
18. The method of claim 11, wherein the conductive material is
deposited onto the conductive feature at a rate ranging from about
0.05 to 0.15 micrometers per minute.
19. A tool for electrolytically depositing a conductive material
other than copper onto a substrate that includes recessed features
that contain a conductive feature and are to be filled with the
conductive material, the tool comprising: a reactor for receiving
the substrate and contacting the conductive features with an
electrolytic deposition bath containing a superconformal deposition
promoter; and a source of the electrolytic deposition bath
containing a superconformal deposition promoter.
20. The tool of claim 19, wherein the electrolytic deposition bath
further comprises: ions of the conductive material; a complexing
agent; and a superconformal deposition promoter selected from
sulfonate terminated alkanethiols, sulfonic acid terminated
alkanethiols, carboxylate terminated alkanethiols, carboxylic acid
terminated alkanethiols, and sulfonate terminated alkanedisulfide
compounds.
21. The tool of claim 19, wherein the conductive material is
gold.
22. The tool of claim 19, wherein the electrolytic deposition bath
is free of polyethylene glycol.
23. The tool of claim 19, wherein the superconformal deposition
promoter is a sulfonate terminated alkanethiol.
24. The tool of claim 19, wherein the superconformal deposition
promoter is a sulfonic acid terminated alkanethiol.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the electrolytic deposition
of conductive materials other than copper, such as gold into
recessed features.
BACKGROUND OF THE INVENTION
[0002] Gold is used in the microelectronics industry as a
conductive material to fill recessed features. Examples of recessed
features include trenches and vias. Trenches filled with gold serve
as conductive lines and vias filled with gold serve as interlayer
interconnects. Decreasing the sizes of conductive features and thus
the recessed features which are used to form such conductive
features places rigorous demands on existing electroplating
chemistry to completely fill the recessed features. The expense of
gold places additional pressure on manufacturers to consistently
achieve void-free fill of recessed features in order to achieve
high yields.
[0003] In certain situations, conventional baths are unable to form
conductive features in recessed structures without voids that
render the conductive features unsatisfactory for most
applications. The presence of voids within the deposited conductive
material is particularly evident when the recessed features are
reentrant, i.e., the opening at the top of the recessed feature is
smaller than the dimension of the recessed feature at the bottom.
The performance of conventional baths can be improved by conducting
electrolytic deposition at optimum conditions such as low
deposition rate, high agitation, or pulse plating. While low
deposition rate, high agitation or pulse plating may improve the
ability of conventional baths to fill reentrant features, even
using such optimum conditions, there continue to be applications
where conventional baths yield features which are not completely
filled. Furthermore, manufacturers prefer not to use low deposition
rates as they contribute to the cost of production.
SUMMARY OF THE INVENTION
[0004] The present invention provides bath compositions, methods
and tools for achieving superconformal filling of recessed features
with a conductive material other than copper, for example gold and
silver. The baths and methods employ a superconformal deposition
promoter selected from sulfonate terminated alkanethiols, sulfonic
acid terminated alkanethiols, carboxylate terminated alkanethiols,
carboxylic acid terminated alkanethiols, and sulfonate terminated
alkanedisulfide compounds. The present inventors have observed that
complete fill of recessed features and the demanding reentrant
features can be achieved without other organic additives such as
polyethylene glycol. In accordance with the present invention,
complete fill is achieved at process conditions that device
manufacturers find attractive.
[0005] Electrolytic plating baths of the present invention include
ions of the conductive material to be deposited, a complexing
agent, and a superconformal deposition promoter described above. In
more specific embodiments, the baths are free of polyethylene
glycol.
[0006] Processes carried out in accordance with the present
invention for the superconformal deposition of a conductive
material other than copper provide a substrate having recessed
features containing a conductive feature, such as a seed layer,
which are to be filled with the conductive material. The conductive
feature within the recessed features is contacted with an
electrolytic plating bath of the type described above. Thereafter,
electroplating power is applied and the conductive material is
deposited onto the conductive features to fill the recessed feature
and provide inlaid features. In more specific embodiments, the
recessed features are reentrant features.
[0007] Tools formed in accordance with the present invention for
the superconformal electrolytic deposition of a conductive material
other than copper include a reactor for receiving the substrate and
contacting conductive features within recessed features with an
electrolytic deposition bath. The electrolytic deposition bath
includes a superconformal deposition promoter described above.
[0008] Through the use of the compositions, methods and tools of
the present invention, conductive materials can be deposited
superconformally into small, e.g., submicron, recessed features at
rates that microelectronic device manufacturers will find
desirable. Device manufacturers will benefit from the increased
productivity and yields achieved by the compositions, methods, and
tools of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The foregoing aspects and many of the attendant advantages
of this invention will become more readily appreciated as the same
become better understood by reference to the following detailed
description, when taken in conjunction with the accompanying
drawings, wherein:
[0010] FIGS. 1A-1J are cross-sectional views illustrating one
embodiment of a process for the superconformal deposition of a
conductive material other than copper into recessed features in
accordance with the present invention;
[0011] FIG. 2 is a process flowchart of the steps for
superconformal deposition of a conductive material other than
copper into a recessed feature in accordance with the embodiment
illustrated in FIGS. 1A-1J;
[0012] FIGS. 3A-3E are cross-sectional views illustrating another
embodiment of a process for the superconformal deposition of a
conductive material other than copper into a recessed feature in
accordance with the present invention;
[0013] FIG. 4 is a process flowchart of the steps for the
superconformal deposition of a conductive material into a recessed
feature in accordance with the embodiment illustrated in FIGS.
3A-3E;
[0014] FIG. 5 is a schematic top plan view of a tool formed in
accordance with the present invention for carrying out processes of
the present invention;
[0015] FIG. 6 is a schematic top plan view of a different tool
formed in accordance with the present invention for carrying out
processes of the present invention; and
[0016] FIG. 7 is a cross-sectional scanning electron microscope
image of conductive features formed in accordance with the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0017] The present invention is now described more fully with
reference to the accompanying drawings, in which specific
embodiments of the invention are shown. The present invention,
however, will be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein. Rather,
the embodiments illustrated in the drawings noted above and
described below are provided so that the description will be
thorough and complete and will convey the scope of the present
invention to those skilled in the art. For example, while the
present invention is described below with respect to particular
arrangements of conductive materials and recessed features, the
present invention is not limited to any one specific arrangement
and the present invention may be embodied in many different
arrangements of various conductive layers and recessed features
such as trenches and vias. In the figures, the thicknesses of the
various layers and regions have been exaggerated for clarity and
are not relative in scope. It should be understood that when an
element, such as a layer, surface, or substrate is referred to as
being over another element, it can be directly on the other element
or there may be intervening elements which may also be present
whether illustrated or not.
[0018] As used throughout the specification, the term "plating"
refers to electrolytic deposition, i.e., electroplating, unless the
context clearly indicates otherwise. The term "feature" refers to a
structure on a substrate.
[0019] As used herein, the term "microelectronic workpiece" or
"workpiece" is not limited to semiconductor wafers, but rather,
refers to workpieces having generally parallel planar first and
second surfaces that are relatively thin, including semiconductor
wafers, ceramic workpieces, and other workpieces upon which
microelectronic circuits or components, including submicron
features, data storage elements or layers, and/or micromechanical
elements are formed.
[0020] As used herein, the term "patterned features" refers to
features that have been formed out of dielectric materials,
including photoresists, which when filled with a conductive
material form inlaid features such as trenches or vias and the like
or construction elements or features.
[0021] As used herein, the term "reentrant features" refers to
patterned features wherein the dimensions, e.g., the width of the
trench, at the top is less than the dimension at the bottom of the
patterned feature, e.g., the width at the bottom of the trench.
[0022] As used herein, the term "conformal" refers to the
deposition of a material into a patterned feature such as a via or
trench wherein the deposition of the material proceeds at all
surfaces of the trench or via at a substantially similar rate.
[0023] As used herein, the term "superconformal" refers to the
deposition of a material into a patterned feature such as a trench
or via wherein a bottom up filling of the feature is achieved as a
result of the deposition occurring at a faster rate at the bottom
of the feature as compared to other surfaces of the feature.
[0024] As used herein, the term "superconformal deposition
promoter" refers to sulfur-containing organic compounds such as:
sulfonate terminated alkanethiols, sulfonic acid terminated
alkanethiols, carboxylate terminated alkanethiols, carboxylic acid
terminated alkanethiols, and sulfonate terminated alkanedisulfide
compounds.
[0025] As discussed above, the present invention relates to
compositions, processes, and tools for the superconformal
deposition of a conductive material other than copper. One example
of an overall plating process to which the aspects of the present
invention can be applied is a blanket plating process described
with reference to FIGS. 1A-1J and FIG. 2. Referring to these
figures, a substrate 20, comprising a dielectric material embedded
with microelectronic structures or a semiconductor material such as
a semiconductor wafer is provided. Substrate 20 may include
electrical contacts for making electrical contact with the
conductive features that are deposited as described below in more
detail. Such electric contacts are not illustrated in FIG. 1A. A
dielectric layer 22 is deposited over substrate 20. Dielectric
material making up layer 22 is deposited by conventional techniques
such as chemical vapor deposition and the like. Dielectric layer 22
can be formed using conventional formation techniques that are well
known to one skilled in the art, and therefore further description
of such techniques are not provided herein.
[0026] Referring to FIG. 1C, a photoresist layer 24 is deposited
over dielectric layer 22. Photoresist layer 24 can be formed using
conventional techniques that are well known to one skilled in the
art, and therefore further description of such techniques is not
provided herein. Deposited photoresist layer 24 is then
photolithographically patterned to provide patterned photoresist
26. Patterning of photoresist layer 24 is carried out using
conventional techniques known to one skilled in the art, and
therefore further description of such techniques is not provided
herein. The patterned photoresist 26 exposes portions of underlying
dielectric layer 22 as illustrated in FIG. 1D.
[0027] Referring to FIG. 1E, the portions of dielectric layer 22
that are not covered by the patterned photoresist 26 are removed
using conventional etching techniques. Referring to FIG. 1F, after
the portions of dielectric 22 that are not covered by patterned
photoresist 26 are etched away. The remaining patterned photoresist
26 is removed using conventional solvents.
[0028] Referring to FIG. 1G, a barrier layer 28 is deposited over
the patterned dielectric elements 30 and the exposed portions of
the underlying substrate 20. Barrier layer 28 inhibits diffusion of
conductive materials deposited subsequently, such as seed layer 32,
described below in more detail, into underlying dielectric 30 and
substrate 20. Barrier layer 28 can be formed from known materials,
such as titanium, tantalum, tungsten and their alloys. Barrier
layer 28 can be formed using conventional techniques, such as
sputtering or any other well known techniques, accordingly, further
description of the formation of barrier layer 28 is not necessary
herein.
[0029] Referring to FIG. 1H, a conductive seed layer 32 is
deposited over barrier layer 28 by conventional techniques such as
electrolytic or electroless deposition. Referring to FIG. 1I, after
formation of seed layer 32 is complete, the structure is placed in
contact with a composition for the superconformal filling of the
patterned features 34. The bath composition which is described
below in more detail includes a superconformal deposition promoter
that promotes the superconformal filling of the patterned features
34 and produces deposited features that are substantially free of
seam voids. After the conductive material 35 is deposited to fill
patterned features 34, planarization is carried out to produce the
inlaid features 36 as illustrated in FIG. 1J. Planarization can be
achieved using conventional techniques such as chemimechanical
planarization.
[0030] The bath compositions, methods, and tools of the present
invention are equally useful in pattern or through-mask plating
processes such as the one described below with reference to FIGS.
3A-3E and FIG. 4. In pattern plating embodiments, referring to FIG.
3A, a substrate 38 similar to substrate 20 described above is
provided with a blanket barrier layer 40 similar to barrier layer
28 described above and a blanket seed layer 42 similar to the seed
layer 32 described above. Over seed layer 42 is deposited a blanket
photoresist layer 44 similar to photoresist 24 described above with
respect to FIG. 1C. Photoresist 44 is patterned to provide the
patterned features 46 illustrated in FIG. 3B. Patterning of
photoresist 44 exposes portions 48 of seed layer 42. These exposed
portions 48 are contacted with the compositions of the present
invention. Electroplating power is applied and the voids 50 between
patterned features 46 are superconformally filled with a conductive
material in accordance with the present invention to provide inlaid
features 52. After inlaid features 52 are formed, the patterned
photoresist features 46 are removed to expose those portions of
seed layer 42 that are not covered by the deposited conductive
material. Referring to FIG. 3E, the portions of seed layer 42 and
barrier layer 40, not covered by feature 52 can then be etched by
conventional techniques to electrically isolate once inlaid
features 52 to provide isolated conductive structures 54.
[0031] In accordance with the present invention, bath compositions
for achieving superconformal deposition of a conductive material
are sulfite or cyanide-based baths that include a source of ions of
the conductive material to be deposited, other than copper,
complexing agent, e.g., sulfite or cyanide, a superconformal
deposition promoter, an optional grain refiner and an optional pH
buffer.
[0032] The source of ions of conductive material will depend upon
the particular conductive material to be deposited. In accordance
with the present invention, the conductive material is a metal
other than copper. Examples of conductive materials other than
copper include gold and silver. The foregoing conductive metals can
be provided in the bath from sources such as sulfite or cyanide
salts, such as sodium gold (I) sulfite, potassium gold (I) cyanide,
silver nitrate, silver sulfate, silver acetate, and silver
tetrafluoroborate.
[0033] Complexing agents are employed in the compositions of the
present invention in order to stabilize ions of the conductive
materials in solution. Examples of suitable complexing agents
include alkali metal sulfites or cyanides such as sodium sulfite,
potassium sulfite, sodium cyanide, or potassium cyanide.
[0034] The bath may optionally contain a grain refiner such as
thallium. An appropriate source of a grain refiner such as thallium
is thallium sulfate.
[0035] Another optional component is a pH buffer. Suitable pH
buffers include phosphoric acid or phosphates and pyrophosphates or
pyrophosphoric acid.
[0036] The superconformal deposition promoters of the present
invention have been briefly described above. They include sulfonate
terminated alkanethiols, sulfonic acid terminated alkanethiols,
carboxylate terminated alkanethiols, carboxylic acid terminated
alkanethiols and sulfonate terminated alkanedisulfide
compounds.
[0037] The sulfonate terminated alkanethiols and the sulfonic acid
terminated alkanethiols can be represented by the general
formula:
HS--R--SO.sub.3X
[0038] wherein R is an alkyl backbone which can be linear, branched
and/or perfluorinated. The length of the alkyl chain can vary from
two to ten carbon atoms. X is either hydrogen or an alkali metal
ion such as sodium or potassium ion. Particular examples of
sulfonate terminated alkanethiols or sulfonic acid terminated
alkanethiols include mercaptopropanesulfonic acid, sodium
3-mercapto-1-propane-sulfonate, potassium
3-mercapto-1-propane-sulfonate, sodium mercaptoethanesulfonate,
potassium mercaptoethanesulfonate, and sodium
10-mercaptodecane-1-sulfona- te. The foregoing are examples of
sulfonate terminated and sulfonic acid terminated alkane thiols. It
should be understood that the use of a suitable sulfonic acid in
combination with sodium hydroxide or potassium hydroxide is
equivalent to the use of a sodium or potassium salt of the
particular sulfonic acid.
[0039] Carboxylate terminated alkanethiols or carboxylic acid
terminated alkanethiols can be represented by the general
formula:
HS--R--CO.sub.2X
[0040] wherein R is an alkyl group containing 2 to 16 carbon atoms
which can be linear, branched, and/or perfluorinated. X represents
hydrogen or an alkali metal ion such as sodium or potassium ion.
Specific examples of this type of superconformal deposition
promoter includes mercaptoacetic acid, 3-mercapto-1-propionic acid,
11-mercapto-1-undecanoic acid, 16-mercapto-1-hexadecanoic acid, and
their alkali metal salts thereof. As with the sulfonate terminated
alkanethiols, the use of a carboxylic acid terminated alkanethiol
and sodium hydroxide or potassium hydroxide is equivalent to the
use of the salt of the corresponding carboxylate terminated
alkanethiol.
[0041] Sulfonate terminated alkanedisulfide compounds are
characterized by terminal sulfate groups and a disulfide linkage.
Such compounds can generally be represented by the formula:
--XO.sub.3S--R--S--S--R--SO.sub.3X
[0042] wherein X is an alkali metal ion such as sodium or potassium
ion, R is an alkyl having 2 to 10 carbon atoms which may be linear,
branched, and/or perfluorinated. A particular example of a
sulfonate terminated alkane disulfide compound is bis-(sodium
sulfopropyl)disulfide. The acid form of this sulfonate terminated
alkane disulfide compound can also be used in accordance with the
present invention by combining it with a base such as sodium
hydroxide or potassium hydroxide.
[0043] The solubility of the respective superconformal deposition
promoter in aqueous solution must be considered in practicing the
present invention. The solubility of the superconformal deposition
promoters in water decreases with the increase in carbon-chain
length. In addition, the solubility of superconformal deposition
promoters terminated with carboxylate or carboxylic acid is
generally lower than the corresponding promoters terminated with
sulfonate or sulfonic acid, especially at lower pHs, because the
sulfonate terminated agents readily deprotonate at low pH as
compared to the tendency of the carboxylate terminated agents to
deprotonate. Accordingly, superconformal deposition promoters
having a short chain length are preferred over those having longer
chain lengths, and sulfonate terminated superconformal deposition
promoters are preferred over those terminated with carboxylate or
carboxylic acid.
[0044] In addition to their low solubility, the longer chain
superconformal deposition promoters, particularly the linear ones,
will have a stronger resistance to heterogeneous electron transfer
taking place on the surface of the substrate during electrolytic
deposition processes. In other words, superconformal deposition
promoters having a longer chain length will function as a stronger
suppressor compared to superconformal deposition promoters that
have a shorter chain length when used as an additive for the
deposition of a conductive material in accordance with the present
invention.
[0045] The bath compositions can be formed as aqueous mixtures. One
way of forming the compositions of the present invention is to
modify a conventional gold plating bath to contain a superconformal
deposition promoter of the present invention. Formation of a bath
of the present invention is described below in the context of a
bath useful for the superconformal deposition of gold. It should be
understood that the foregoing description is equally applicable to
the formation of baths useful for the superconformal deposition of
other conductive materials.
[0046] The bath compositions of the present invention are formed by
adding a superconformal deposition promoter such as sodium
mercaptopropanesulfonate to an electrolytic gold plating bath.
Baths for the electrolytic deposition of gold are available from
numerous commercial sources such as Enthone-OMI, Inc., under the
designation of Neutronex.RTM. 3091 and Neutronex.RTM. 309. Useful
gold plating baths can be alkaline or neutral and can be cyanide or
sulfite based. Such baths include 5 to 20 grams per liter gold, 5
to 40 grams per liter of a complexing agent such as sodium sulfite
and 10-80 grams per liter potassium pyrophosphate or potassium
phosphate as a buffer. The baths have a pH ranging from about 6 to
10. The superconformal deposition promoter such as sodium
mercaptopropanesulfonate can be added to the bath so as to provide
a concentration in the bath ranging from about 0.05-0.3
millimoles.
[0047] When the bath composition is a sulfite-based bath for
plating gold, the bath must be maintained so as to keep the free
gold ion concentration below the threshold concentration when out
plating occurs. Outplating refers to the spontaneous decomposition
of the bath. Maintaining a sufficiently high concentration of free
sulfite ion minimizes the free gold ion concentration and minimizes
out plating. With higher pHs, the sulfite ion concentration
increases and thus, out plating is reduced. The pH of the
sulfite-based gold plating bath can be controlled by a pH buffer
such as potassium pyrophosphoric or pyrophosphoric acid.
[0048] Operating conditions such as the temperature of the bath,
the degree of agitation, and the waveform employed can be varied in
order to achieve the desired deposition rate and the desired
void-free fill. The temperature of the bath can vary over a wide
range. With increasing temperature, the likelihood of plate out
increases. The temperature of the bath can range from 35.degree.
C.-55.degree. C. Generally, the higher the temperature, the better
the mass transfer; however, this must be balanced against the
stability of the bath.
[0049] The bath may be agitated or the substrate may be rotated in
order to impart agitation. Agitation can vary over a wide
range.
[0050] Once the substrate is contacted with the bath, an
electroplating power is applied. The current density can vary over
a wide range. The waveform can include pulse plating or non-pulse
plating. Desirably, the electroplating power provides plating rates
on the order of 0.05-0.2 micrometers per minute. By using the bath
compositions and methods of the present invention, superconformal
void-free filling of patterned features is achieved.
[0051] The superconformal filling of patterned features in
accordance with the present invention may be implemented in a wide
range of tools. Integrated processing tools that incorporate one or
more reactors capable of electrolytic deposition of conductive
materials are particularly suitable for implementing the processes
of the present invention and are available from numerous sources,
including Semitool, Inc., of Kalispell, Mont. Such tools are sold
by Semitool, Inc. under the trademarks Equinox.RTM. and
Paragon.RTM.. Advantageously, the reactors employed in these tools
rotate a workpiece during the electrolytic deposition process
thereby enhancing the uniformity of the deposited material. To
further enhance the quality of the resulting deposited features,
the reactors of these tools may be fitted with an ultrasonic
generator that provides ultrasonic energy to the electroplating
solution during the electrolytic deposition process to enhance the
desired characteristics of the deposited feature.
[0052] In addition to the electrolytic deposition reactors, such
tools frequently include other ancillary processing chambers, such
as, for example, pre-wetting chambers, rinsing chambers, etc., that
are used to perform other processes associated with electrolytic
deposition. Semiconductor wafers, as well as other microelectronic
workpieces, are transferred between the various processing
reactors, as well as between the processing reactors and
input/output stations, by a robotic transfer mechanism. The robotic
transfer mechanism, the electroplating reactors, and the plating
recipes used, as well as other components of the tool, may all be
under the control of one or more programmable processing units.
[0053] Referring to FIG. 5, a tool 100 formed in accordance with
the present invention includes a plurality of workstations for
carrying out pre-wetting, rinsing, electrolytic deposition of a
conductive material and drying steps. The particular arrangement of
the various workstations can vary; however, FIG. 5 illustrates an
exemplary layout. In FIG. 5, workstations 102 and 104 are
spin/rinse/dry chambers capable of applying a medium such as acid,
base or any other kind of aqueous solution to the substrate to be
processed. The spin/rinse/dry stations are also capable of applying
water to the substrate. Pre-wetting of the substrate can be carried
out in spin/rinse/dry chamber 102. From chamber 102, the workpiece
is transferred by the robotic arm 106 between the various
workstations. A workpiece after being pre-wetted in workstation 102
can be transferred to one of the other eight reactors 110, 112,
114, 116, 118, 120, 122, or 124 where electrolytic deposition of
gold in accordance with the present invention is carried out.
Subsequent to the electro-deposition of gold, the workpiece can be
transferred to spin/rinse/dry chamber 104 where it is rinsed and
dried and prepared for further processing.
[0054] Referring to FIG. 6, another tool 126 formed in accordance
with the present invention includes a plurality of workstations for
carrying out pre-wet, spin/rinse/dry, electrolytic deposition of a
conductive material, and electrolytic etching of a conductive
material. The particular arrangement of the various workstations
can vary; however, FIG. 6 illustrates another exemplary layout. In
FIG. 6, workstations 128, 130, 132, and 134 are spin/rinse dry
chambers capable of applying an acid, base, or any other kind of
aqueous solution to the substrate. In addition, the spin/rinse/dry
chambers are capable of rinsing and drying the workpiece. Reactors
136 and 138 are reactors that are useful for electrolytically
etching a conductive material from the workpiece. Workstations 140,
142, 144, and 146, are configured to electrolytically deposit a
conductive material onto a workpiece in accordance with the present
invention. In an exemplary processing sequence, a workpiece is
pre-wetted at one of the four spin/rinse/dry chambers 128, 130,
132, or 134. The workpiece is then delivered to one of the reactors
140, 142, 144, or 146, where electrolytic deposition of the
conductive material using the processes and compositions of the
present invention is carried out. The workpiece is then delivered
to a spin/rinse/dry chamber where it is rinsed and dried in
preparation for other processes such as electrolytic etching of the
conductive material in either of chambers 136 or 138. Following the
electrolytic etching of the conductive material, the workpiece can
be delivered to a spin/rinse/dry chamber for rinsing and
drying.
[0055] It should be understood that there are numerous
configurations of various workstations that can be employed
depending on the particular configuration of conductive and
nonconductive layers to be formed on the substrate. The foregoing
is provided as an example of tool configurations useful for
carrying processes in accordance with the present invention.
EXAMPLE
Superconformal Electrolytic Deposition of Gold into Patterned
Features
[0056] In this example, a silicon wafer including patterned
features having a feature depth of 3.8 .mu.m and an aspect ratio of
4:1 was processed to deposit gold into the patterned features
superconformally. The patterned features included a titanium-based
barrier layer 500 .ANG. thick and a gold seed layer 500 .ANG.
thick. The titanium-based barrier layer and gold seed layer were
deposited by sputtering. The wafer was contacted with the
electroplating bath in an Equinox.RTM. brand single wafer plating
tool available from Semitool, Inc. of Kalispell, Mont. The plating
tool included an inert platinum anode. The plating was carried out
at 50.degree. C. The chemical flow rate was 3.5 gpm and the wafer
was rotated at 40 rpm. The electroplating power was pulsed with 2
ms on and 8 ms off. The peak current density was 8 mA/cm.sup.2 and
an average current density was 1.6 mA/cm.sup.2. This resulted in a
plating rate of about 0.1 .mu.m per minute.
[0057] The wafers were 100 mm in diameter. The wafer included
patterned features that were reentrant in that the width at the top
of the feature is less than the width of the feature at the
bottom.
[0058] The plating bath comprised Enthone Neutronex 3091 with about
0.15 millimoles or 26 ppm sodium mercaptopropanesulfonate. The
plating bath included 50 ppm thallium.
[0059] A cross-sectional scanning electron microscope image is
shown in FIG. 7.
[0060] This example illustrates how the compositions, processes,
and tools of the present invention are able to completely fill
reentrant features.
[0061] While the preferred embodiment of the invention has been
illustrated and described, it will be appreciated that various
changes can be made therein without departing from the spirit and
scope of the invention.
* * * * *