U.S. patent application number 12/790558 was filed with the patent office on 2010-09-23 for apparatus for applying a plating solution for electroless deposition.
Invention is credited to John M. Boyd, Yezdi Dordi, Aleksander Owczarz, Fritz C. Redeker, William Thie.
Application Number | 20100239767 12/790558 |
Document ID | / |
Family ID | 38846505 |
Filed Date | 2010-09-23 |
United States Patent
Application |
20100239767 |
Kind Code |
A1 |
Dordi; Yezdi ; et
al. |
September 23, 2010 |
Apparatus for Applying a Plating Solution for Electroless
Deposition
Abstract
An electroless plating chamber is provided. The electroless
plating chamber includes a chuck configured to support a substrate
and a bowl surrounding a base and a sidewall of the chuck. The base
has an annular channel defined along an inner diameter of the base.
The chamber includes a drain connected to the annular channel. The
drain is capable of removing fluid collected from the chuck. A
proximity head capable of cleaning and substantially drying the
substrate is included in the chamber. A method for performing an
electroless plating operation is also provided.
Inventors: |
Dordi; Yezdi; (Palo Alto,
CA) ; Thie; William; (Mountain View, CA) ;
Boyd; John M.; (Woodlawn, CA) ; Redeker; Fritz
C.; (Fremont, CA) ; Owczarz; Aleksander; (San
Jose, CA) |
Correspondence
Address: |
MARTINE PENILLA & GENCARELLA, LLP
710 LAKEWAY DRIVE, SUITE 200
SUNNYVALE
CA
94085
US
|
Family ID: |
38846505 |
Appl. No.: |
12/790558 |
Filed: |
May 28, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11611736 |
Dec 15, 2006 |
7752996 |
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12790558 |
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11513634 |
Aug 30, 2006 |
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11611736 |
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11514038 |
Aug 30, 2006 |
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11513634 |
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11513446 |
Aug 30, 2006 |
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11514038 |
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11382906 |
May 11, 2006 |
7306662 |
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11513446 |
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11427266 |
Jun 28, 2006 |
7297190 |
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11382906 |
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Current U.S.
Class: |
427/372.2 |
Current CPC
Class: |
C23C 18/50 20130101;
H01L 21/76883 20130101; H01L 21/288 20130101; Y10S 134/902
20130101; C23C 18/38 20130101; H01L 21/02074 20130101; C23C 18/1628
20130101; H01L 21/76849 20130101 |
Class at
Publication: |
427/372.2 |
International
Class: |
B05D 3/00 20060101
B05D003/00 |
Claims
1. A method for performing an electroless plating operation within
a single chamber, comprising method operations of; depositing a
plating solution onto a surface of a substrate, the substrate
resting on a chuck; plating a layer onto the surface of the
substrate; rinsing a top surface of the substrate to remove the
plating solution; and drying the top surface of the substrate.
2. The method of claim 1, wherein the method operation of rinsing
and drying a top surface of the substrate includes rotating the
substrate.
3. The method of claim 1, wherein the method operation of rinsing a
top surface of the substrate to remove the plating solution
includes, collecting fluid draining from the top surface of the
substrate into a bowl surrounding the chuck.
4. The method of claim 1, wherein the method operation of plating a
layer onto the surface of the substrate includes, depositing an
electroless copper plating solution consisting essentially of an
aqueous copper salt component, an aqueous cobalt salt component, a
polyamine-based complexing agent, a chemical brightener component,
and a pH-modifying substance in an amount sufficient to make the
electroless copper plating solution have a pH of less than about
8.
5. The method of claim 1, wherein the method operation of plating a
layer onto the surface of the substrate includes, depositing an
electroless cobalt plating solution onto the surface of the
substrate.
6. The method of claim 5, wherein the electroless cobalt plating
solution is selected from a group consisting of CoWB, CoWP, or
CoWBP.
7. The method of claim 1, further comprising: evacuating a chamber
in which the electroless plating operation occurs; pulsing an inert
gas into the chamber; repeating the evacuating and the pulsing to
remove any non-inert gases from the chamber prior to depositing the
plating solution.
8. The method of claim 4, wherein the electroless copper plating
solution includes a halide component.
9. The method of claim 8, wherein the halide component is selected
from a group consisting of potassium bromide, lithium chloride,
potassium iodide, chlorine fluoride, ammonium chloride, ammonium
bromide, ammonium fluoride and ammonium iodide.
10. The method of claim 1 where the environment within the single
chamber is substantially oxygen free.
Description
CLAIM OF PRIORITY
[0001] This application is a divisional of U.S. patent application
Ser. No. 11/611,736, entitled "Apparatus for Applying a Plating
Solution for Electroless Deposition," which is a continuation in
part and claims priority of U.S. patent application Ser. No.
11/513,634, entitled "Processes and Systems for Engineering a
Copper Surface for Selective Copper Deposition," U.S. patent
application Ser. No. 11/514,038, entitled "Processes and Systems
for Engineering a Barrier Surface for Selective Copper Deposition,"
and U.S. patent application Ser. No. 11/513,446, entitled
"Processes and Systems for Engineering a Silicon-Type Surface for
Selective Metal Deposition to Form a Metal Silicide," U.S. patent
application Ser. No. 11/382,906, entitled "Plating Solution for
Electroless Deposition of Copper," U.S. patent application Ser. No.
11/427,266, entitled "Plating Solutions for Electroless Deposition
of Copper," all of which are filed on the same day as the instant
application. The disclosure of these related applications is
incorporated herein by reference in their entireties for all
purposes.
CROSS REFERENCE TO RELATED APPLICATION
[0002] This application is related to U.S. Provisional Application
Ser. No. 60/686,787, titled "High Rate Electroless Plating and
Integration Flow to Form Cu Interconnects," filed on Aug. 31, 2005,
and U.S. application Ser. No. 11/461,415, titled "System and Method
for Forming Patterned Copper lines Through Electroless Copper
Plating," filed on Jul. 27, 2006, both of which are hereby
incorporated by reference.
BACKGROUND
[0003] The fabrication of semiconductor devices such as integrated
circuits, memory cells, and the like, involve a series of
manufacturing operations that are performed to define features on
semiconductor wafers ("wafers"). The wafers include integrated
circuit devices in the form of multi-level structures defined on a
silicon substrate. At a substrate level, transistor devices with
diffusion regions are formed. In subsequent levels, interconnect
metallization lines are patterned and electrically connected to the
transistor devices to define a desired integrated circuit device.
Also, patterned conductive layers are insulated from other
conductive layers by dielectric materials.
[0004] To build an integrated circuit, transistors are first
created on the surface of the wafer. The wiring and insulating
structures are then added as multiple thin-film layers through a
series of manufacturing process steps. Typically, a first layer of
dielectric (insulating) material is deposited on top of the formed
transistors. Subsequent layers of metal (e.g., copper, aluminum,
etc.) are formed on top of this base layer, etched to create the
conductive lines that carry the electricity, and then filled with
dielectric material to create the necessary insulators between the
lines. The process used for producing copper lines is referred to
as a dual Damascene process, where trenches are formed in a planar
conformal dielectric layer, vias are formed in the trenches to open
a contact to the underlying metal layer previously formed, and
copper is deposited everywhere. Copper is then planarized
(overburden removed), leaving copper in the vias and trenches
only.
[0005] Although copper lines are typically comprised of a plasma
vapor deposition (PVD) seed layer (i.e., PVD Cu) followed by an
electroplated layer (i.e., ECP Cu), electroless chemistries are
under consideration for use as a PVD Cu replacement, and even as an
ECP Cu replacement. A process called electroless copper deposition
can thus be used to build the copper conduction lines. During
electroless copper deposition, electrons are transferred from a
reducing agent to the copper ions resulting in the deposition of
reduced copper onto the wafer surface. The formulation of the
electroless copper plating solution is optimized to maximize the
electron transfer process involving the copper ions.
[0006] Conventional formulations call for maintaining the
electroless plating solution at a high alkaline pH (i.e., pH>9)
to enhance the overall deposition rate. The limitations with using
highly alkaline copper plating solutions for electroless copper
deposition are non-compatibility with positive photoresist on the
wafer surface, longer induction times, and decreased nucleation
density due to an inhibition by hydroxylation of the copper
interface (which occurs in neutral-to-alkaline environments). These
are limitations that can be eliminated if the solution is
maintained at an acidic pH environment (i.e., pH<7). One
prominent limitation found with using acidic electroless copper
plating solutions is that certain substrate surfaces, such as
tantalum nitride (TaN), tend to get oxidized readily in an alkaline
environment causing adhesion problems for the reduced copper
resulting in blotchy plating on the TaN surfaces of the wafer.
Efforts to counteract this limitation by seeding the TaN surfaces
with various metals such as palladium and ruthenium have resulted
in minimal levels of success primarily due to increase of the line
resistance. With the growing interest in electroless plating
solutions, is a concomitant interest in chambers capable of
providing the environment for depositing the electroless plating
solutions, especially with regard to solutions that tend to oxidize
easily, e.g., cobalt plating solutions as well as copper plating
solutions.
[0007] In view of the forgoing, there is a need for a chamber that
enables the efficient use of improved formulations of copper
plating solutions for use in electroless copper deposition
processes, as well as other sensitive plating solutions.
SUMMARY
[0008] Broadly speaking, the present invention fills these needs by
providing a chamber for enabling the use of the electroless plating
solutions in a controlled environment. It should be appreciated
that the present invention can be implemented in numerous ways,
including as a method and a chemical solution. Several inventive
embodiments of the present invention are described below.
[0009] In one exemplary embodiment, an electroless plating chamber
is provided. The electroless plating chamber includes a chuck
configured to support a substrate and a bowl surrounding a base and
a sidewall of the chuck. The base has an annular channel defined
along an inner diameter of the base. The chamber includes a drain
connected to the annular channel. The drain is capable of removing
fluid collected from the chuck. A proximity head capable of
cleaning and substantially drying the substrate is included in the
chamber.
[0010] In another aspect of the invention, a method for performing
an electroless plating operation in a single chamber is provided.
The method initiates with depositing a plating solution onto a
surface of a substrate. The method includes plating a layer onto
the surface of the substrate. The top surface of the substrate is
sprayed to remove the plating solution and the top surface of the
substrate is substantially dried. In one embodiment, a proximity
head is used for rinsing and drying the substrate in a
substantially oxygen free environment within the chamber.
[0011] It will be obvious, however, to one skilled in the art, that
embodiments of the present invention may be practiced without some
or all of these specific details. In other instances, well known
process operations have not been described in detail in order not
to obscure the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The present invention will be readily understood by the
following detailed description in conjunction with the accompanying
drawings, and like reference numerals designate like structural
elements.
[0013] FIG. 1 is a flow chart of a method for preparing an
electroless copper plating solution, in accordance with one
embodiment of the present invention.
[0014] FIG. 2 is a high-level schematic diagram illustrating a
manufacturing tool which incorporates an electroless plating
chamber to be used with the solutions described herein in
accordance with one embodiment of the invention.
[0015] FIG. 3A is a simplified schematic diagram showing a cross
sectional view of an electroless deposition module in accordance
with one embodiment of the invention.
[0016] FIG. 3B is a simplified schematic diagram showing an
alternative embodiment of the electroless deposition module of FIG.
3A.
DETAILED DESCRIPTION
[0017] An invention is described for providing improved
formulations of electroless copper plating solutions that can be
maintained in an acidic pH to weakly alkaline environment for use
in electroless copper deposition processes and a chamber for
performing the plating operation therein. It should be appreciated
that while specific plating solutions are described herein, the
chamber may be used for any plating solution and is not limited for
use with the specifically mentioned plating solutions. It will be
obvious, however, to one skilled in the art, that the present
invention may be practiced without some or all of these specific
details. In other instances, well known process operations have not
been described in detail in order not to unnecessarily obscure the
present invention.
[0018] Electroless metal deposition processes used in semiconductor
manufacturing applications are based upon simple electron transfer
concepts. The processes involve placing a prepared semiconductor
wafer into an electroless metal plating solution bath then inducing
the metal ions to accept electrons from a reducing agent resulting
in the deposition of the reduced metal onto the surface of the
wafer. The success of the electroless metal deposition process is
highly dependent upon the various physical (e.g., temperature,
etc.) and chemical (e.g., pH, reagents, etc.) parameters of the
plating solution. As used herein, a reducing agent is an element or
compound in an oxidation-reduction reaction that reduces another
compound or element. In doing so, the reducing agent becomes
oxidized. That is, the reducing agent is an electron donor that
donates an electron to the compound or element being reduced.
[0019] A complexing agent (i.e., chelators or chelating agent) is
any chemical agent that can be utilized to reversibly bind to
compounds and elements to form a complex. A salt is any ionic
compound composed of positively charged cations (e.g., Cu2+, etc.)
and negatively charged anions, so that the product is neutral and
without a net charge. A simple salt is any salt species that
contain only one kind of positive ion (other than the hydrogen ion
in acid salts). A complex salt is any salt species that contains a
complex ion that is made up of a metallic ion attached to one or
more electron-donating molecules. Typically a complex ion consists
of a metallic atom or ion to which is attached one or more
electron-donating molecules (e.g., Cu(II)ethylenediamine2+, etc.).
A protonized compound is one that has accepted a hydrogen ion
(i.e., H+) to form a compound with a net positive charge.
[0020] A copper plating solution for use in electroless copper
deposition applications is disclosed below. The components of the
solution are a copper(II) salt, a cobalt(II) salt, a chemical
brightener component, and a polyamine-based complexing agent. In
one exemplary embodiment, the copper plating solution is prepared
using de-oxygenated liquids. Use of de-oxygenated liquids
substantially eliminates oxidation of the wafer surfaces and
nullifies any effect that the liquids may have on the redox
potential of the final prepared copper plating solution. In one
embodiment, the copper plating solution further includes a halide
component. Examples of halide species that can be used include
fluoride, chloride, bromide, and iodide.
[0021] In one embodiment, the copper(II) salt is a simple salt.
Examples of simple copper(II) salts include copper(II) sulfate,
copper (II) nitrate, copper(II) chloride, copper(II)
tetrafluoroborate, copper(II) acetate, and mixtures thereof. It
should be appreciated that essentially any simple salt of
copper(II) can be used in the solution so long as the salt can be
effectively solubilized into solution, be complexed by a
polyamine-based complexing agent, and oxidized by a reducing agent
in an acidic environment to result in deposition of the reduced
copper onto the surface of the wafer.
[0022] In one embodiment, the copper(II) salt is a complex salt
with a polyamine electron-donating molecule attached to the
copper(II) ion. Examples of complex copper(II) salts include
copper(II) ethylenediamine sulfate, bis(ethylenediamine)copper(II)
sulfate, copper (II) dietheylenetriamine nitrate,
bis(dietheylenetriamine)copper(II) nitrate, and mixtures thereof.
It should be appreciated that essentially any complex salt of
copper(II) attached to a polyamine molecule can be used in the
solution so long as the resulting salt can be solubilized into
solution, be complexed to a polyamine-based complexing agent, and
oxidized by a reducing agent in an acidic environment to result in
deposition of the reduced copper onto the surface of the wafer.
[0023] In one embodiment, the concentration of the copper(II) salt
component of the copper plating solution is maintained at a
concentration of between about 0.0001 molarity (M) and the
solubility limit of the various copper(II) salts disclosed above.
In another exemplary embodiment, the concentration of the
copper(II) salt component of the copper plating solution is
maintained at between about 0.001 M and 1.0 M or the solubility
limit. It should be understood that the concentration of the
copper(II) salt component of the copper plating solution can
essentially be adjusted to any value up to the solubility limit of
the copper(II) salt as long as the resulting copper plating
solution can effectuate electroless deposition of copper on a wafer
surface during an electroless copper deposition process.
[0024] In one embodiment, the cobalt(II) salt is a simple cobalt
salt. Examples of simple cobalt(II) salts include cobalt(II)
sulfate, cobalt(II) chloride, cobalt(II) nitrate, cobalt(II)
tetrafluoroborate, cobalt(II) acetate, and mixtures thereof. It
should be understood that essentially any simple salt of cobalt(II)
can be used in the solution so long as the salt can be effectively
solubilized in the solution, be complexed to a polyamine-based
complexing agent, and reduce a cobalt(II) salt in an acidic
environment to result in the deposition of the reduced copper onto
the surface of the wafer.
[0025] In another embodiment, the cobalt(II) salt is a complex salt
with a polyamine electron-donating molecule attached to the
cobalt(II) ion. Examples of complex cobalt(II) salts include
cobalt(II) ethylenediamine sulfate, bis(ethylenediamine)cobalt(II)
sulfate, cobalt(II) dietheylenetriamine nitrate,
bis(dietheylenetriamine)cobalt(II) nitrate, and mixtures thereof.
It should be understood that essentially any simple salt of
cobalt(II) can be used in the solution so long as the salt can be
effectively solubilized into solution, be complexed to a
polyamine-based complexing agent, and reduce a copper(II) salt in
an acidic environment to result in the deposition of the reduced
copper onto the surface of the wafer.
[0026] In one embodiment, the concentration of the cobalt (II) salt
component of the copper plating solution is maintained at between
about 0.0001 molarity (M) and the solubility limit of the various
cobalt(II) salt species disclosed above. In one exemplary
embodiment, the concentration of the cobalt(II) salt component of
the copper plating solution is maintained at between about 0.001 M
and 1.0 M. It should be understood that the concentration of the
cobalt(II) salt component of the copper plating solution can
essentially be adjusted to any value up to the solubility limit of
the cobalt(II) salt as long as the resulting copper plating
solution can effectuate electroless deposition of copper on a wafer
surface at an acceptable rate during an electroless copper
deposition process.
[0027] In one embodiment, the chemical brightener component works
within the film layer to control copper deposition on a microscopic
level. The brightener tends to be attracted to points of high
electro-potential, temporarily packing the area and forcing copper
to deposit elsewhere in this embodiment. It should be appreciated
that as soon as the deposit levels, the local point of high
potential disappears and the brightener drifts away, i.e.,
brighteners inhibit the normal tendency of the copper plating
solution to preferentially plate areas of high potential which
would inevitably result in rough, dull plating. By continuously
moving between surfaces with the highest potential, brighteners
(also referred to as levelers) prevent the formation of large
copper crystals, giving the highest possible packing density of
small equiaxed crystals (i.e., nucleation enhancement), which
results in a smooth, glossy, high ductility copper deposition in
this embodiment. One exemplary brightener is
bis-(3-sulfopropyl)-disulfide disodium salt (SPS), however, any
small molecular weight sulfur containing compounds that increase
the plating reaction by displacing an adsorbed carrier may function
in the embodiments described herein. In one embodiment, the
concentration of the chemical brightener component is maintained at
between about 0.000001 molarity (M) and the solubility limit for
the brightener. In another embodiment, the chemical brightener
component has a concentration of between about 0.000001 M and about
0.01 M. In still another embodiment, the chemical brightener has a
concentration of about between 0.000141 M and about 0.000282 M. It
should be appreciated that the concentration of the chemical
brightener component of the copper plating solution can essentially
be adjusted to any value up to the solubility limit of the chemical
brightener as long as the nucleation enhancing properties of the
chemical brightener is maintained in the resulting copper plating
solution to allow for a sufficiently dense deposition of copper on
the wafer surface.
[0028] In one embodiment, the polyamine-based complexing agent is a
diamine compound. Examples of diamine compounds that can be
utilized for the solution include ethylenediamine,
propylenediamine, 3-methylenediamine, and mixtures thereof. In
another embodiment, the polyamine-based complexing agent is a
triamine compound. Examples of triamine compounds that can be
utilized for the solution include diethylenetriamine,
dipropylenetriamine, ethylene propylenetriamine, and mixtures
thereof. In still another embodiment, the polyamine-based
complexing agent is an aromatic or cyclic polyamine compound.
Examples of aromatic polyamine compounds include
benzene-1,2-diamine, pyridine, dipyride, pyridine-1-amine. It
should be understood that essentially any diamine, triamine, or
aromatic polyamine compound can be used as the complexing agent for
the plating solution so long as the compound can complex with the
free metal ions in the solution (i.e., copper(II) metal ions and
cobalt(II) metal ions), be readily solubilized in the solution, and
be protonized in an acidic environment. In one embodiment, other
chemical additives including accelerators (i.e., sulfopropyl
sulfonate) and suppressors (i.e., PEG, polyethylene glycol) are
included in the copper plating solution at low concentrations to
enhance the application specific performance of the solution.
[0029] In another embodiment, the concentration of the complexing
agent component of the copper plating solution is maintained at
between about 0.0001 molarity (M) and the solubility limit of the
various diamine-based, triamine-based, and aromatic or cyclic
polyamine complexing agent species disclosed above. In one
exemplary embodiment, the concentration of the complexing agent
component of the copper plating solution is maintained at between
about 0.005 M and 10.0 M, but must be greater than the total metal
concentration in solution.
[0030] Typically, the complexing agent component of a copper
plating solution causes the solution to be highly alkaline and
therefore somewhat unstable (due to too large a potential
difference between the copper(II)-cobalt(II) redox couple). In one
exemplary embodiment, an acid is added to the plating solution in
sufficient quantities to make the solution acidic with a
pH.ltoreq.about 6.4. In another embodiment, a buffering agent is
added to make the solution acidic with a pH.ltoreq.about 6.4 and to
prevent changes to the resulting pH of the solution after
adjustment. In still another embodiment, an acid and/or a buffering
agent is added to maintain the pH of the solution at between about
4.0 and 6.4. In yet another embodiment, an acid and/or a buffering
agent is added to maintain the pH of the solution at between about
4.3 and 4.6. In one embodiment, the anionic species of the acid
matches the respective anionic species of the copper(II) and
cobalt(II) salt components of the copper plating solution, however
it should be appreciated that the anionic species do not have to
match. In yet another embodiment, a pH modifying substance is added
to make the solution weakly alkaline, i.e., a pH of less than about
8.
[0031] Acidic copper plating solutions have many operational
advantages over alkaline plating solutions when utilized in an
electroless copper deposition application. An acidic copper plating
solution improves the adhesion of the reduced copper ions that are
deposited on the wafer surface. This is often a problem observed
with alkaline copper plating solutions due to the formation of
hydroxyl-terminated groups, inhibiting the nucleation reaction and
causing reduced nucleation density, larger grain growth and
increased surface roughness. Still further, for applications such
as direct patterning of copper lines by electroless deposition of
copper through a patterned film, an acidic copper plating solution
helps improve selectivity over the barrier and mask materials on
the wafer surface, and allows the use of a standard positive resist
photomask resin material that would normally dissolve in a basic
solution.
[0032] In addition to the advantages discussed above, copper
deposited using the acidic copper plating solutions exhibits lower
pre-anneal resistance characteristics than with copper deposited
using alkaline copper plating solutions. It should be appreciated
that the pH of the copper plating solutions, as disclosed herein,
can essentially be adjusted to any acidic (i.e., pH<7.0)
environment so long as the resulting deposition rates of copper
during the electroless copper deposition process is acceptable for
the targeted application and the solution exhibits all the
operational advantages discussed above. In general, as the pH of
the solution is lowered (i.e., made more acidic), the copper
deposition rate decreases. However, varying the choice of
complexing agent (e.g., diamine-based, triamine-based, aromatic
polyamine, etc.) plus the concentration of the copper (II) and
cobalt(II) salts can help compensate for any reduction in copper
deposition rate resulting from an acidic pH environment.
[0033] In one embodiment, the copper plating solution is maintained
at a temperature between about 0.degree. Celsius (.degree. C.) and
70.degree. C. during an electroless copper deposition process. In
one exemplary embodiment, the copper plating solution is maintained
at a temperature of between about 20.degree. C. and 70.degree. C.
during the electroless copper deposition process. It should be
appreciated that temperature impacts the nucleation density and
deposition rate of copper (mainly, the nucleation density and
deposition rate of copper is directly proportional to temperature)
to the wafer surface during copper deposition. The deposition rate
impacts the thickness of the resulting copper layer and the
nucleation density impacts void space, occlusion formation within
the copper layer, and adhesion of the copper layer to the
underlying barrier material. Therefore, the temperature settings
for the copper plating solution during the electroless copper
deposition process would be optimized to provide dense copper
nucleation and controlled deposition following the nucleation phase
of the bulk deposition to optimize the copper deposition rate to
achieve copper film thickness targets.
[0034] FIG. 1 is a flow chart of a method for preparing an
electroless copper plating solution, in accordance with one
embodiment of the present invention. Method 100 begins with
operation 102 where the aqueous copper salt component, a portion of
the polyamine-based complexing agent, the chemical brightener
component, the halide component, and a portion of the acid
component of the copper plating solution are combined into a first
mixture. The method 100 proceeds on to operation 104 where the
remaining portion of the complexing agent and the aqueous cobalt
salt component are combined into a second mixture. In one
embodiment, the pH of the second mixture is adjusted so that the
second mixture has an acidic pH. It should be appreciated that the
advantage of keeping the second mixture acidic is that this will
keep the cobalt (II) in an active form. The method 100 then
continues on to operation 106 where the first mixture and the
second mixture are combined into the final copper plating solution
prior to use in a copper plating operation utilizing the system
described below.
[0035] In one embodiment, the first and the second mixtures are
stored in separate permanent storage containers prior to
integration. The permanent storage containers being designed to
provide transport and long-term storage of the first and second
mixtures until they are ready to be combined into the final copper
plating solution. Any type of permanent storage container may be
used as long as the container is non-reactive with any of the
components of the first and the second mixtures. It should be
appreciated that this pre-mixing strategy has the advantage of
formulating a more stable copper plating solution that will not
plate out (that is, resulting in the reduction of the copper) over
time in storage.
[0036] This invention can be further understood in reference to
Example 1 which describes a sample formulation of copper plating
solution, in accordance with one embodiment of the present
invention.
Example 1
Nitrate-based Copper Plating Formulation
[0037] In this embodiment, a nitrate-based formulation of the
copper plating solution is disclosed with a pH of 6.0, a copper
nitrate (Cu(NO.sub.3).sub.2) concentration of 0.05M, a cobalt
nitrate (Co(NO.sub.3).sub.2) concentration of 0.15M, an
ethylenediamine (i.e., diamine-based complexing agent)
concentration of 0.6M, a nitric acid (HNO.sub.3) concentration of
0.875M, a potassium bromide (i.e., halide component) concentration
of 3 millimolarity (mM), and a SPS (i.e., chemical brightener)
concentration of between about 0.000141 M and about 0.000282 M. The
resulting mixture is then deoxygenated using Argon gas to reduce
the potential for the copper plating solution to become
oxidized.
[0038] Continuing with Example 1, in one embodiment, the
nitrate-based formulation of the copper plating solution is
prepared using a pre-mixing formulation strategy that involves
pre-mixing a portion of the ethylenediamine with the copper
nitrate, the nitric acid, and the potassium bromide into a into a
first pre-mixed solution. The remaining portion of the complexing
agent component is pre-mixed with the cobalt salt component into a
second pre-mixed solution. The first premixed solution and second
pre-mixed solution are then added into an appropriate container for
final mixing into the final electroless copper plating solution
prior to use in an electroless copper deposition operation. As
disclosed above, this pre-mixing strategy has the advantage of
formulating a more stable copper plating solution that will not
plate out over time in storage.
[0039] FIG. 2 is a high-level schematic diagram illustrating a
manufacturing tool which incorporates an electroless plating
chamber to be used with the solutions described herein in
accordance with one embodiment of the invention. The system
includes Front Opening Unified Pods (FOUPs) 461 which handle the
incoming and outgoing wafers being delivered into the system and
from the system. Lab ambient module 460 is a module that operates
at ambient temperature with HEPA filtered air. Modules 463, 463',
and 483 operating off of lab ambient module 460 may be cleaning
modules. These cleaning modules can perform either wet cleaning or
dry cleaning operations on substrate 455 as the substrate is
delivered into or taken from system 450. From lab ambient module
460 load lock 465 delivers or transitions substrate 455 between lab
ambient module 460 and vacuum module 470. Off of vacuum module 470
are etch chambers and deposition chambers which require vacuum
processing or low pressure processing. Etch chamber 471 may include
any of the commonly known etch processes and ALD/PVD chamber 473
may perform any of the commonly known deposition processes. From
vacuum module 470, the substrate is transitioned between the vacuum
chamber and controlled ambient chamber 480 by load lock 475.
Controlled ambient chamber 480 and the modules which are associated
with the controlled ambient chamber have highly controlled
environmental conditions. For example, the controlled ambient
chamber may have all oxygen removed, i.e., operate in an inert gas
environment, in order to avoid oxidation for processes sensitive to
oxidation. Off of controlled ambient chamber 480 is cleaning system
483. Cleaning system 483 may be used to planarize copper after
copper fill, i.e., the deposition from ALD/PVD that may be
performed in plasma processing chamber 473. It should be
appreciated that cleaning system 483 that connected to the
controlled ambient module 480, may perform functionally similar
operations to cleaning system 483 that is connected to the ambient
transfer module 460, with the exception that the cleaning is
performed under controlled ambient environmental conditions. For
example, the controlled ambient conditions, may include the lack of
oxygen, regulated temperature, pressure, among control of other
environmental conditions. Electroless deposition module 483 is the
module used to perform the electroless plating with the
formulations described herein. As mentioned above, electroless
deposition module 481 will operate in a controlled ambient
environment where the temperature and gas environment is highly
controlled. In one embodiment, oxygen has been eliminated from the
environment within electroless deposition module 483 in order to
prevent oxidation of the formulations used for the electroless
deposition processes. Thus, system 450 is an exemplary architecture
that allows minimal exposure of substrate surface to oxygen at
critical steps after surface treatment. In addition, since system
450 is an integrated system, the substrate is transferred from one
process station immediately to the next process station, which
limits the duration that for example, a prepared copper surface is
exposed to oxygen. The integrated system 450 can be used to process
substrate(s) through an entire process sequence flow as described
in more detail in U.S. application Ser. No. 11/513,634.
[0040] Still referring to FIG. 2, surface treatments, electroless
deposition of cobalt-alloy, and the optional post-cobalt-alloy
deposition processes involve a mixture of dry and wet processes.
The wet processes are typically operated near atmosphere, while the
dry O.sub.2 plasma, hydrogen plasma, and O.sub.2/Ar sputtering are
all operated at less than 1 Ton. Therefore, integrated system 450
is capable of handling a mixture of dry and wet processes. As
illustrated in FIG. 2, integrated system 450 has 3 substrate
transfer modules (or chambers) 460, 470, and 480. Transfer chambers
460, 470 and 480 are equipped with robots to move substrate 455
from one process area to another process area. It should be
appreciated that the process area could be a substrate cassette, a
reactor, or a loadlock. Substrate transfer module 460 is operated
under lab ambient, which refers to the laboratory (or factory)
environment that is under room temperature, atmospheric pressure
and exposed to air, usually HEPA- or ULPA-filtered to control
particle defects. Module 460 interfaces with substrate loaders (or
substrate cassettes) 461 to bring the substrate 455 into the
integrated system or to return the substrate to the cassette(s) 461
to continue processing outside the system 450.
[0041] In one embodiment, substrate 455 is brought to integrated
system 450 to be deposited with a cobalt-alloy, such as Cobalt
tungsten boron (CoWB), cobalt tungsten phosphide (CoWP), or Cobalt
Tungsten borophosphide (CoWBP), after the substrate has been
planarized by metal CMP to remove excess metal from the substrate
surface and leaves the metal only in the metal trenches. The
surface of substrate 455 is processed to remove surface
contaminants such as Cu-BTA complex and other metal oxide residues.
Cu-BTA and metal oxides can be removed by a wet clean process
involving a cleaning solution, such as a solution containing
tetramethylammonium hydroxide (TMAH) or complexing amines such as,
but not limited to, ethylene diamine or diethylamine triamine.
Following BTA-metal complex removal, metal oxides remaining on the
copper and dielectric surfaces can be removed using a wet clean
process involving a cleaning solution such as a solution containing
citric acid, or other organic acid that can remove copper oxide
more or less selectively to copper. Metal oxides, specifically
copper oxide, can be removed using a weak organic acid such as
citric acid, or other organic or inorganic acids can be used.
Additionally, very dilute (i.e. <0.1%) peroxide-containing
acids, such as sulfuric-peroxide mixtures, can also be used. The
wet clean process can also remove other metal or metal oxide
residues.
[0042] A wet clean module 463 can be integrated with the
lab-ambient transfer module 460, which is operated at lab ambient
condition. The wet clean module 463 can be used to perform a 1-step
or 2-step cleaning process. Alternatively, an additional wet clean
module 463' can be integrated with the lab-ambient transfer module
460 to allow the first step of the 2-step cleaning process to be
performed in module 463 and the second step be performed in module
463'. For example, a cleaning solution containing a chemical such
as TMAH for cleaning Cu-BTA is in module 463 and a cleaning
solution containing a weak organic acid such as citric acid for
cleaning metal oxide is in module 463'. Exemplary cleaning
solutions are described in U.S. Pat. Nos. 6,165,956, 6,593,282,
6,162,301, 6,294,027, 6,303,551, 6,479,443, and 6,927,198 which are
incorporated herein by reference.
[0043] As mentioned above, a lab ambient condition occurs under
atmospheric pressure and open to the environment in the module.
Although the wet clean module 463 can be integrated with the
lab-ambient transfer module 460, this process step can also be
performed right after metal CMP and before the substrate is brought
to integrated system 450 for cobalt-alloy deposition.
Alternatively, the wet cleaning process can be performed in a
controlled ambient process environment, where the controlled
ambient is maintained during and after the wet cleaning step. The
US patent applications related to proximity heads and their use
that are owned by the assignee and specified below provide further
information on the structure used to perform the cleaning process
in one embodiment.
[0044] Organic residues (or contaminants) not removed by the
previous wet cleans can be removed by a dry oxidizing plasma
process, such as oxygen-containing plasma, O.sub.2/Ar sputter, or
Ar sputter following the removal of Cu-BTA and metal oxides in a
reaction chamber. As described above, most plasma or sputtering
processes are operated below 1 Torr; therefore, it is desirable to
couple such systems (or apparatus, or chambers, or modules) to a
transfer module that is operated under vacuum at pressure, such as
under 1 Torr. If the transfer module integrated with the plasma
process is under vacuum, substrate transfer is more time efficient
and the process module is maintained under vacuum, since it does
not require extended time to pump down the transfer module. In
addition, since the transfer module is under vacuum, the substrate
after cleaning by the plasma process is exposed to only very low
levels of oxygen. Assuming the O.sub.2 plasma process is selected
to clean the organic residues, the O.sub.2 plasma process reactor
471 is coupled to a vacuum transfer module 470.
[0045] Since lab-ambient transfer module 460 is operated at
atmosphere and vacuum transfer module 470 is operated under vacuum
(<1 Torr), a loadlock 465 is placed between these two transfer
modules to allow substrate 455 to be transferred between the two
modules, 460 and 470, operated under different pressures. Loadlock
465 is configured to be operated under vacuum at pressure less than
1 Torr, or at lab ambient, or to be filled with an inert gas
selected form a group of inert gases.
[0046] After substrate 455 finishes the oxidizing plasma processing
using O.sub.2, for example, substrate 455 is moved into the
hydrogen-containing reducing plasma reduction chamber (or module)
473. Hydrogen-containing plasma reduction is typically processed at
a low pressure, which is less than 1 Ton; therefore, it is coupled
to the vacuum transfer module 470. Once the substrate 455 is
reduced with hydrogen-containing plasma, the copper surface is
clean and free of copper oxide. In a preferred embodiment, after
substrate 455 finishes the O.sub.2 plasma processing, a H.sub.2 or
H.sub.2/NH.sub.3 plasma reduction step can be performed in-situ,
without removing the wafer from the chamber. In either case, the
substrate is ready for cobalt-alloy deposition after completion of
the reduction process.
[0047] As described above, it is important to control the
processing and transport environments to minimize the exposure of
the copper surface to oxygen after the substrate is reconditioned
by the hydrogen-containing reducing plasma. The substrate 455
should be processed under a controlled environment, where the
environment is either under vacuum or filled with one or more inert
gas to limit the exposure of substrate 455 to oxygen. Dotted line
490 outlines the boundary of a part of the integrated system 450 of
FIG. 4B that show the processing systems and transfer modules whose
environment is controlled. Transferring and processing under
controlled environment 490 limits the exposure of the substrate to
oxygen.
[0048] Cobalt-alloy electroless deposition is a wet process that
involves cobalt species in a solution that is reduced by a reducing
agent, which can be phosphorous-based (e.g. hypophosphite),
boron-based (e.g. dimethylamine borane), or a combination of both
phosphorous-based and boron-based. Typically, the solution that
uses phosphorous-based reducing agent deposits CoWP, and the
solution that uses boron-based reducing agent deposits CoWB.
Accordingly, the solution that uses both phosphorous-based and
boron-based reducing agents deposits CoWBP. In one embodiment, the
cobalt-alloy electroless deposition solution is alkaline-based.
Alternatively, cobalt-alloy electroless deposition solution can
also be acidic. Since wet processes are typically conducted under
atmospheric pressure, the transfer module 480 that is coupled to
the electroless deposition reactor should be operated near
atmospheric pressure. To ensure the environment is controlled to be
free of oxygen, inert gas(es) can be used to fill the
controlled-ambient transfer module 480. Additionally, all fluids
used in the process are de-gassed, i.e. dissolved oxygen is removed
by commercially available degassing systems. Exemplary inert gas
includes nitrogen (N.sub.2), helium (He), neon (Ne), argon (Ar),
krypton (Kr), and xenon (Xe).
[0049] In one embodiment, the wet cobalt-alloy electroless
deposition reactor (or apparatus, or system, or module) is coupled
with a rinse and dry system (or apparatus, or module) to allow the
substrate to be transferred into the electroless deposition system
481 under dry conditions and to come out of the system 481 in a dry
condition (dry-in/dry-out). The dry-in/dry-out requirement allows
the electroless deposition system 481 to be integrated with the
controlled-ambient transfer module 480, and avoids the need of a
wet robotic transfer step to a separate rinse-dry module. The
environment of the electroless deposition system 481 is controlled
to provide low (or limited) levels of oxygen and moisture (water
vapor). Inert gas can also be used to fill the system to ensure low
levels of oxygen are in the processing environment.
[0050] Alternatively, cobalt-alloy electroless deposition can also
be conducted in a dry-in/dry-out manner similar to electroless
copper disclosed recently. A dry-in/dry-out electroless copper
process has been developed for copper electroless deposition. The
process uses a proximity head to limit the electroless process
liquid in contacting with the substrate surface on a limited region
constrained by a liquid meniscus. The substrate surface not under
the proximity process head is dry. Details of such process and
system can be found in U.S. application Ser. No. 10/607, 611,
titled "Apparatus And Method For Depositing And Planarizing Thin
Films On Semiconductor Wafers," filed on Jun. 27, 2003, and U.S.
application Ser. No. 10/879,263, titled "Method and Apparatus For
Plating Semiconductor Wafers," filed on Jun. 28, 2004, both of
which are incorporated herein in their entireties. The electroless
plating of cobalt-alloy can use a proximity head to enable a
dry-in/dry-out process. That is, even though a wet process is
performed, the substrate comes into the module dry and leaves
dry.
[0051] After cobalt-alloy deposition in system 481, substrate 455
can be rinsed and dried within the same cobalt-alloy deposition in
system 481 by a proximity head or can optionally be sent through an
separate post-deposition cleaning chamber. Further information on
the structure of proximity heads and their use may be found in U.S.
Pat. Nos. 6,988,327, 6,954,993, 9,988,326, and patent application
Ser. Nos. 10/330,843, 10/261,839, 60/686,787, and 11/461,415, all
of which are co-owned by the Assignee and are incorporated by
reference. Alternatively, non-brush particle removal processes
described in U.S. publications 2006012860 and 2006012859, both
incorporated by reference herein, may be employed as well. A rinse
and dry system must also be integrated with the brush scrub system
or non-brush methods described in U.S. publications 2006012860 and
2006012859 to allow substrate 455 to be dry-in/dry-out of the wet
cleaning system 483. Other methods of mechanical assisted cleaning
may be utilized, such as a brush scrub using chemistry such as
CP72B or hydroxylamine-based cleaning chemistries or by using other
methods, such as immersion cleaning, or spin-rinse cleaning, Inert
gas(es) is used to fill system 483 to ensure limited (or low)
oxygen is present in the system. In one embodiment, the oxygen
level is below 3 parts per million (ppm). The system 483 is dotted
to illustrate that this system is optional, since the
post-deposition cleaning is optional. Since the post-deposition
clean step is the last process that is to be operated by the
integrated system 450, substrate 455 is brought back into cassette
461 after processing. Therefore, the cleaning system 483 can
alternatively be coupled to the lab-ambient transfer module 460, as
shown in FIG. 4B. If the cleaning system 483 is coupled to the
lab-ambient transfer module 460, the cleaning system 483 is not
operated under controlled environment and inert gas(es) does not
need to fill the system.
[0052] FIG. 3 is a simplified schematic diagram showing a cross
sectional view of an electroless deposition module in accordance
with one embodiment of the invention. Electroless deposition module
481 includes a first chamber wall 300. In one embodiment, the
chamber wall 300 is composed of aluminum. Within chamber 300 is a
second chamber 302. Chamber 302 is composed of a
Polytetrafluoroethylene (PTFE) material in one embodiment, however,
it should be appreciated that the material of composition for
chamber 302 may be any suitable material that is compatible with
the chemicals and operating conditions used herein for the
electroless deposition. Chuck 318 supports wafer 314 within module
481. In one embodiment, chuck 318 is a heated chuck. It should be
noted that chuck 318 may also be referred to as a support. That is,
through any suitable means, e.g., electrical resistance or other
suitable techniques for providing heat from chuck 318, heat is
provided to substrate 455. Chuck 318 is surrounded by bowl 304.
Bowl 304, as illustrated, includes an indentation at the bottom of
chuck 318 and the sidewalls of bowl 304 comes up above the surface
of chuck 318 so as to create a cavity where a solution may reside
on top of a wafer sitting on the chuck and confined by the
sidewalls. The indentation, also referred to as an annular channel
around an inner diameter of the base of bowl 304, will provide for
excess material to be collected and drained from bowl 304 through
drain 312. In essence, the indentation defines an annular ring,
which collects excess material or any material lost from substrate
455, for delivery to drain 312.
[0053] Still referring to FIG. 3, the chemical solutions described
above may be deposited through nozzle 308 or any other suitable
delivery means into the cavity in which substrate 455 sits. The
cavity is defined by the space created by the upper edge of bowl
304 that rises above substrate 455 and the top surface of the
substrate. Of course the delivery of the plating solution may occur
with the reducing agent being provided at the point of use as
mentioned above. Gate valve 310 enables the introduction of the air
or the removal of air from electroless deposition module 481. It
should be appreciated that the vacuum pull down/air removal may
occur in stages or pulses, i.e., a vacuum pulse followed by
introduction of an inert gas, followed by a vacuum pulse, followed
by introduction of an inert gas, etc. In one embodiment, chuck 318
moves in a vertical position as indicated by arrow 301 so as to
provide the ability to perform additional cleaning within
electroless deposition module 481 after the plating operation has
completed. In this embodiment, chuck 318 moves to a first position
above the initial position, after completion of the electroless
deposition in order to remove the plating solution from the upper
surface of wafer 455. Here, a de-ionized water solution may be
sprayed on top of the wafer in order to remove the solution. The
means for spraying the solution may be a nozzle in flow
communication with a reservoir of fluid, similar to the nozzle
described above for delivering the plating solution or preferably a
proximity head may be used to clean, rinse and dry the substrate.
After removal of the solution, chuck 318 may move up to a second
position, above the first position, where a proximity head may be
used to perform a clean and dry operation. Of course, chuck 318 can
remain at the first position for the clean and dry operation by
proximity head(s). It should be appreciated that as chuck 318 lifts
from an initial position, where the electroless deposition takes
place, to the first position where the remnants of the deposition
process are removed, rollers 303 may be used to support the wafer.
One skilled in the art will appreciate that transfer of substrate
455 to rollers 303 may be accomplished through the use of a robot
or other known mechanical means. In an alternative embodiment,
chuck 318 may be able to rotate as an alternative to the rollers.
Of course, for the embodiments using a proximity head, the
proximity head is ca-able of lateral, rotational, translational and
vertical movement.
[0054] FIG. 3B is another embodiment for the deposition module of
FIG. 3A. In FIG. 3B, wafer 455 is raised from an initial position
on chuck 318 to be supported by rollers 303. As illustrated in
FIGS. 3A and 3B, chuck 318 forms a seal against the sidewalls of
bowl 304. Thus, as chuck 318 is moved vertically, the seal against
O-ring 314 breaks, thereby allowing fluid from the electroplating
process to drain through drain 312. It should be appreciated that a
robot or other known mechanical means may transport wafer 455
between chuck 318 and rollers 303. Proximity heads 316 are used to
clean wafer 455 as discussed in U.S. Pat. Nos. 6,988,327,
6,954,993, 9,988,326, and patent application Ser. Nos. 10/330,843,
10/261,839, 60/686,787, and 11/461,415 mentioned above. Proximity
heads 316 are in communication with a vacuum source and fluid
supplies, as illustrated. Thus, within the module of FIGS. 3A and
3B, the rinsing and drying, as well as the plating process all
occur within the same chamber, which can have a controlled
environment, e.g., substantially free from oxygen.
[0055] Although a few embodiments of the present invention have
been described in detail herein, it should be understood, by those
of ordinary skill, that the present invention may be embodied in
many other specific forms without departing from the spirit or
scope of the invention. Therefore, the present examples and
embodiments are to be considered as illustrative and not
restrictive, and the invention is not to be limited to the details
provided therein, but may be modified and practiced within the
scope of the appended claims.
* * * * *