U.S. patent application number 10/186056 was filed with the patent office on 2004-01-01 for cu ecp planarization by insertion of polymer treatment step between gap fill and bulk fill steps.
This patent application is currently assigned to Applied Materials, Inc.. Invention is credited to Yang, Michael X..
Application Number | 20040000488 10/186056 |
Document ID | / |
Family ID | 29779805 |
Filed Date | 2004-01-01 |
United States Patent
Application |
20040000488 |
Kind Code |
A1 |
Yang, Michael X. |
January 1, 2004 |
CU ECP planarization by insertion of polymer treatment step between
gap fill and bulk fill steps
Abstract
The method generally includes filling features in a substrate by
plating metal ions from a gap fill solution onto the substrate,
reducing plating activity in the features in a polymer treatment
step by conditioning the substrate surface with a conditioning
solution, and plating the substrate surface to a desired thickness
by plating metal ions from a bulk fill solution onto the substrate
surface. The method may also include treating the substrate with a
conditioning solution comprising suppressors after a seed layer
deposition to substantially eliminate conformal deposition in
features of the substrate and plating metal ions from a plating
solution onto the substrate.
Inventors: |
Yang, Michael X.; (Palo
Alto, CA) |
Correspondence
Address: |
PATENT COUNSEL
APPLIED MATERIALS, INC.
Legal Affairs Department
P.O. BOX 450A
Santa Clara
CA
95052
US
|
Assignee: |
Applied Materials, Inc.
|
Family ID: |
29779805 |
Appl. No.: |
10/186056 |
Filed: |
June 28, 2002 |
Current U.S.
Class: |
205/96 ;
205/118 |
Current CPC
Class: |
C25D 7/123 20130101;
C25D 17/001 20130101; C25D 5/02 20130101 |
Class at
Publication: |
205/96 ;
205/118 |
International
Class: |
C25D 005/00; C25D
005/02 |
Claims
What is claimed is:
1. A method for plating metal onto a substrate, comprising:
substantially filling features in the substrate by plating metal
ions from a gap fill solution onto the substrate; and reducing
plating activity in the features prior to completely filling the
features and plating a surface of the substrate by conditioning the
substrate surface with a conditioning solution.
2. The method of claim 1, further comprising plating the substrate
with metal ions from a bulk fill solution.
3. The method of claim 1, wherein the conditioning solution
comprises deionized water.
4. The method of claim 1, wherein the conditioning solution
comprises suppressors.
5. The method of claim 1, wherein the gap fill solution comprises
accelerators and suppressors.
6. The method of claim 1, wherein the reducing plating activity
occurs during substrate transfer from a gap fill cell to a bulk
fill cell by rinsing the substrate with the conditioning
solution.
7. The method of claim 2, wherein the substrate is transferred from
a gap fill cell to a conditioning cell and then to a bulk fill
cell, wherein the bulk fill solution comprises levelers and
accelerators.
8. The method of claim 2, wherein the bulk fill solution and the
conditioning solution are contained in a bulk fill cell.
9. The method of claim 2, wherein the reducing plating activity
comprises providing a period of no-current for a time sufficient to
allow diffusion of the gap fill solution to form the bulk fill
solution.
10. The method of claim 1, further comprising pre-treatment of the
substrate with a solution comprising suppressors to substantially
eliminate conformal deposition in the features prior to
substantially filling the features.
11. A method for plating metal onto a substrate, comprising:
disposing a substrate in a gap fill solution to substantially fill
features in the substrate by plating metal ions onto the substrate;
rinsing the substrate with a conditioning solution to substantially
terminate plating activity in the features; transferring the
substrate from the gap fill solution to a bulk fill solution; and
then plating metal ions from the bulk fill solution onto the
substrate.
12. The method of claim 11, wherein the conditioning solution
comprises suppressors.
13. The method of claim 11, wherein the conditioning solution
comprises deionized water.
14. The method of claim 11, wherein the gap fill solution comprises
accelerators and suppressors.
15. The method of claim 11, wherein the bulk fill solution
comprises levelers and accelerators.
16. A method for plating metal onto a substrate, comprising:
disposing a substrate in a gap fill cell containing a gap fill
solution to substantially fill features in the substrate by plating
metal ions from the gap fill solution onto the substrate;
transferring the substrate from the gap fill cell to a conditioning
cell containing a conditioning solution to substantially terminate
plating activity in the features; and transferring the substrate
from the conditioning cell to a bulk fill cell containing a bulk
fill solution to plate a surface of the substrate to a desired
thickness by plating metal ions from the bulk fill solution onto
the substrate surface.
17. The method of claim 16, wherein the conditioning solution
comprises suppressors.
18. The method of claim 16, wherein the conditioning solution
comprises deionized water.
19. The method of claim 16, wherein the gap fill solution comprises
accelerators and suppressors.
20. The method of claim 16, wherein the bulk fill solution
comprises levelers and accelerators.
21. A method for plating metal onto a substrate, comprising:
disposing a substrate in a plating cell containing a gap fill
solution to substantially fill features in the substrate by plating
metal ions from the gap fill solution onto the substrate; draining
the gap fill solution from the plating cell upon completion of
substantially filling the features; rinsing the substrate with a
conditioning solution; filling the plating cell with a bulk fill
solution; and plating the surface for the substrate to a desired
thickness by plating metal ions from the bulk fill solution onto
the substrate.
22. The method of claim 21, wherein the conditioning solution
comprises suppressors.
23. The method of claim 21, wherein the conditioning solution
comprises deionized water.
24. The method of claim 21, wherein the gap fill solution comprises
accelerators and suppressors.
25. The method of claim 21, wherein the bulk fill solution
comprises levelers and accelerators.
26. A method for plating metal onto a substrate, comprising:
disposing a substrate in a plating cell containing a plating
solution; applying an electrical current to the plating cell to
substantially fill features in the substrate by plating metal ions
from the plating solution onto the substrate; terminating an
electrical current supplied to the plating cell for a time
sufficient to allow diffusion of the plating solution to a point of
equilibrium; and then providing the electrical current to the
plating cell to plate the substrate to a desired thickness.
27. A method for plating metal onto a substrate, comprising:
treating the substrate with a conditioning solution comprising
suppressors after a seed layer deposition to substantially
eliminate conformal deposition in features of the substrate; and
plating metal ions from a plating solution onto the substrate.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention generally relates to a method for
plating a metal on a substrate, whereby feature overspill is
reduced.
[0003] 2. Description of the Related Art
[0004] Metallization for sub-quarter micron sized features is a
foundational technology for present and future generations of
integrated circuit manufacturing processes. In devices such as
ultra large scale integration-type devices, i.e., devices having
integrated circuits with more than a million logic gates, the
multilevel interconnects that lie at the heart of these devices are
generally formed by filling high aspect ratio interconnect features
with a conductive material, such as copper or aluminum, for
example. Conventionally, deposition techniques such as chemical
vapor deposition (CVD) and physical vapor deposition (PVD), for
example, have been used to fill these interconnect features.
However, as interconnect sizes decrease and aspect ratios increase,
void-free interconnect feature fill via conventional metallization
techniques becomes increasingly difficult. As a result thereof,
plating techniques, such as electrochemical plating (ECP) and
electroless plating, for example, have emerged as viable processes
for filling sub-quarter micron sized high aspect ratio interconnect
features in integrated circuit manufacturing processes.
[0005] In an ECP process, for example, sub-quarter micron sized
high aspect ratio features formed into the surface of a substrate
may be efficiently filled with a conductive material, such as
copper. ECP plating processes are generally two stage processes,
wherein a seed layer is first formed over the surface features of
the substrate, and then the surface features of the substrate are
exposed to an electrolyte solution while an electrical bias is
simultaneously applied between the substrate and an anode
positioned within the electrolyte solution. The electrolyte
solution is generally rich in ions to be plated onto the surface of
the substrate. Therefore, the application of the electrical bias
causes these ions to be urged out of the electrolyte solution and
to be plated onto the seed layer.
[0006] FIG. 1 (Prior Art) illustrates feature filling in a
conventional electroplating process. Conventional electroplating
fill processes generally include depositing a conformal layer 102
in the features 100, which generally lasts up to about 20 seconds.
The conformal layer 102 is generally followed by bottom-up fill 104
to substantially fill the feature 100. However, one challenge
associated with ECP processes is that the surface over the sub
micron features 100 after filling may be higher than the field
areas, i.e., the areas between the features. The uneven substrate
topography occurs as a result of an accelerated feature growth rate
that is achieved for bottom-up fill 104, as the accelerated feature
growth generally continues beyond filling of the feature, thereby
resulting in overspill 106, e.g., raised locations above the filled
features.
[0007] The overspill is subsequently removed, such as by a
planarization process, wherein the excess metal is removed from the
entire surface of the substrate to form an even, planar surface.
During the planarization process, a substantially uneven substrate
topography may lead to substrate defects, such as excess shear and
incompatibility with non-abrading removal processes, e.g.,
electropolishing and chemical dissolution. Therefore, there is a
need for an apparatus and method for reducing feature
overspill.
SUMMARY OF THE INVENTION
[0008] Embodiments of the invention generally relate to a method
for plating metal onto a substrate. The method generally includes
substantially filling features in the substrate by plating metal
ions from a gap fill solution onto the substrate, reducing plating
activity in the features prior to completely filling the features
by conditioning the substrate with a conditioning solution.
[0009] Embodiments of the invention further include a method for
plating a metal on a substrate. The method generally includes
plating a substrate with metal ions from a gap fill solution to
substantially fill features in the substrate, rinsing the substrate
with a conditioning solution to substantially terminate plating
activity in the features, and then plating the substrate with metal
ions from a bulk fill solution.
[0010] Embodiments of the invention further include disposing a
substrate in a plating cell containing a plating solution, applying
an electrical current to the plating cell to substantially fill
features in the substrate by plating metal ions from the plating
fill solution onto the substrate, terminating an electrical current
supplied to the plating cell for a time sufficient to allow
diffusion of the plating solution to a point of equilibrium, and
providing the electrical current to the plating cell to plate the
substrate to a desired thickness.
[0011] Embodiments of the invention further include treating the
substrate with a conditioning solution comprising suppressors after
a seed layer deposition to substantially eliminate conformal
deposition in features of the substrate, and plating metal ions
from a plating solution onto the substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] So that the manner in which the above-recited features of
the present invention are obtained may be understood in detail, a
more particular description of the invention briefly summarized
above may be had by reference to the embodiments thereof, which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only exemplary embodiments of
the invention, and are therefore, not to be considered limiting of
its scope, for the invention may admit to other equally effective
embodiments.
[0013] FIGS. 1A-1C (Prior Art) illustrate conventional
electroplating feature fill.
[0014] FIG. 2 illustrates a perspective view of an exemplary
electroplating system.
[0015] FIG. 3 illustrates a cross sectional view of a cell for
electroplating a metal onto a substrate.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0016] FIG. 2 illustrates a perspective view of an electroplating
system 200 including a mainframe 214, an electroplating solution
replenishing system 220, and a control system 222. The mainframe
generally includes a thermal anneal chamber 211, a loading station
210, a spin rinse dry station 212, and a plurality of processing
stations 218. The loading station 210 generally includes one or
more substrate cassette receiving areas 224, generally known as pod
loaders, one or more loading station transfer robots 228, and at
least one substrate orientor 230. Each processing station 218
includes one or more processing cells 240.
[0017] The control system 222 may be a programmable microprocessor
configured to interface with the various components of the system
200 and provide controlling signals thereto. The electroplating
solution replenishing system 220 is positioned adjacent to the
electroplating system 200 in fluid communication with the process
cells 240 in order to circulate electroplating solution to the
cells 240.
[0018] FIG. 3 illustrates a partial cross sectional schematic view
of an exemplary electroplating cell 240 of the invention. The
exemplary electroplating cell 240 may be used for all of the steps
described in detail below, such as polymer treatment, gap fill, and
bulk fill. In addition, other plating cells known to those skilled
in the art may be used for any of the above steps. The
electroplating cell 240 generally includes a container body 342
having an opening on a top portion of the container body 342 to
receive and support a pivotally mounted lid 344. The container body
342 may be manufactured from an electrically insulative material,
such as a plastic, Teflon, or ceramic, for example. The lid 344
serves as a top cover having a substrate supporting surface 346
disposed on the lower portion thereof. A substrate 348 is shown in
parallel abutment to the substrate supporting surface 346, and may
be secured in this orientation via conventional substrate chucking
methods, such as vacuum chucking, for example. The container body
342 may be cylindrically shaped in order to accommodate a generally
circular substrate 348 at one end thereof. However, other substrate
shapes can be used as well.
[0019] An electroplating solution inlet 350 may be disposed at the
bottom portion of the container body 342. An electroplating
solution may be pumped into the container body 342 by a suitable
pump 351 connected to the inlet 350. The solution may flow upwardly
inside the container body 342 toward the substrate 348 to contact
the exposed deposition surface 354. A consumable anode 356, for
example, may be disposed in the container body 342 and configured
to dissolve in the electroplating solution in order to provide
metal particles to be deposited onto the substrate 348 to the
plating solution. The anode 356 generally does not extend across
the entire width of the container body 342, thus allowing the
electroplating solution to flow between the outer surface of the
anode 356 and the inner surface of the container body 342 to the
deposition surface 354. Alternatively, an anode 356 consisting of
an electrode and consumable metal particles may be encased in a
fluid permeable membrane, such as a porous ceramic plate, to
provide metal particles to be deposited onto the substrate to the
plating solution. A porous non-consumable anode may also be
disposed in the container body 342 so that the electroplating
solution may pass therethrough. However, when a non-consumable
anode is included, the electroplating solution may include a metal
particle supply to continually replenish the metal particles to be
deposited on the substrate 348.
[0020] The container body 342 generally includes an egress gap 358
bounded at an upper limit by a shoulder 364 of a cathode contact
ring 352. The gap 358 generally leads to an annular weir 343 that
is substantially coplanar with (or slightly above) the substrate
seating surface 368, and thus, the deposition surface 354. The weir
343 is positioned to ensure that the deposition surface 354 is in
contact with the electroplating solution when the electroplating
solution is flowing out of the egress gap 358 and over the weir
343. During processing, the substrate 348 may be secured to the
substrate supporting surface 346 of the lid 344 by a plurality of
vacuum passages 360 formed in the surface 346, wherein passages 360
are generally connected at one end to a vacuum pump (not shown).
The cathode contact ring 352, which is shown disposed between the
lid 344 and the container body 342, may be connected to a power
supply 349 to provide power to the substrate 348. The contact ring
352 generally has a perimeter flange 362 partially disposed through
the lid 344, a sloping shoulder 364 conforming to the weir 343, and
an inner substrate seating surface 368, which defines the diameter
of the deposition surface 354. The shoulder 364 is provided so that
the inner substrate seating surface 368 is located below the flange
362. This geometry allows the deposition surface 354 to come into
contact with the electroplating solution before the solution flows
into the egress gap 358 as discussed above. However, as noted
above, the contact ring design may be varied from that shown in
FIG. 1 without departing from the scope of the present invention.
Thus, the angle of the shoulder portion 364 may be altered or the
shoulder portion 364 may be eliminated altogether so that the
contact ring is substantially planar. Where a planar design is
used, seals may be disposed between the contact ring 352, the
container body 342 and/or the lid 344 to form a fluid tight seal
therebetween.
[0021] The substrate seating surface 368 preferably extends a
minimal radial distance inward below a perimeter edge of the
substrate 348, but a distance sufficient to establish electrical
contact with a metal seed layer on the substrate deposition surface
354. The exact inward radial extension of the substrate seating
surface 368 may be varied according to application. However, in
general this distance is minimized so that a maximum deposition
surface 354 is exposed to the electroplating solution. In an
exemplary embodiment, the radial width of the seating surface 368
may be between about 2 mm and about 5 mm from the edge of the
substrate 348, for example.
[0022] In operation the contact ring 352 is negatively charged to
act as a cathode and is configured to electrically communicate with
the substrate 348. Therefore, as electroplating solution flows
across the substrate surface 354, the ions in the electroplating
solution are attracted to the surface 354 by the negative charge.
The ions then plate the surface 354 and form the desired film. In
addition to the anode 356 and the cathode contact ring 352, an
auxiliary electrode 367 may be used to control the shape of the
electrical field over the deposition surface 354. An auxiliary
electrode 367 is shown disposed through the container body 342
adjacent an exhaust channel 369. By positioning the auxiliary
electrode 367 adjacent to the exhaust channel 369, the electrode
367 is able to maintain contact with the electroplating solution
during processing and affect the electrical field.
[0023] Substrates 348 generally include small scale, e.g., sub
quarter micron, dense clusters of features. These features are
typically about 1 micron deep and are generally separated by field,
i.e., non-patterned, areas, which are typically tens of microns in
width. Embodiments of the invention generally include a seed layer
deposition step, one or more metal deposition steps, and a
planarization step. The metal deposition steps include a gap fill
step and a bulk fill step. The gap fill step generally continues
for a time sufficient to substantially fill the substrate features,
utilizing methods known in the art for bottom up fill. The bulk
fill step generally follows the gap fill step and continues to
plate the surface of the substrate to a desired level.
[0024] Embodiments of the invention generally employ copper plating
solutions having copper sulfate at a concentration between about 5
g/L and about 100 g/L, an acid at a concentration between about 5
g/L and about 200 g/L, and halide ions, such as chloride, at a
concentration between about 10 ppm and about 200 ppm. The acid
generally includes sulfuric acid, phosphoric acid, and/or
derivatives thereof. In addition to copper sulfate, the
electroplating solution generally includes other copper salts, such
as copper fluoborate, copper gluconate, copper sulfamate, copper
sulfonate, copper pyrophosphate, copper chloride, or copper
cyanide.
[0025] The electroplating solution may further include one or more
additives. Additives, which may be, for example, levelers,
inhibitors, suppressors, brighteners, accelerators, or other
additives known in the art, are typically organic materials that
adsorb onto the surface of the substrate being plated. Useful
suppressors typically include polyethers, such as polyethylene,
glycol, or other polymers, such as polypropylene oxides, which
adsorb on the substrate surface, slowing down copper deposition in
the adsorbed areas. Useful accelerators typically include sulfides
or disulfides, such as bis(3-sulfopropyl) disulfide, which compete
with suppressors for adsorption sites, accelerating copper
deposition in adsorbed areas. Useful inhibitors typically include
sodium benzoate and sodium sulfite, which inhibit the rate of
copper deposition on the substrate. During plating, the additives
are consumed at the substrate surface, but are being constantly
replenished by the electroplating solution. However, differences in
diffusion rates of the various additives result in different
surface concentrations at the top and the bottom of the features,
thereby setting up different plating rates in the features.
Ideally, these plating rates should be higher at the bottom of the
feature for bottom-up fill. Thus, an appropriate composition of
additives in the plating solution is required to achieve a
void-free fill of the features.
[0026] Generally, embodiments of the invention further include a
polymer treatment step. The polymer treatment step generally
operates to condition the substrate surface with a polymer, e.g., a
conditioning solution, in order to reduce the plating activity over
the features. The conditioning solution may include any combination
of polymers capable of suppressing the plating activity, such as
suppressors, including polyethylene and polypropylene.
Alternatively, the conditioning solution may include deionized
water in order to flush out the localized high concentration of
accelerators at the feature openings.
[0027] The gap fill step and the bulk fill step may occur in
separate processing cells 240, utilizing different plating
solutions. For example, the gap fill solution may include
accelerators and suppressors, while the bulk fill solution
generally may include levelers and accelerators. In addition, the
polymer treatment step may occur while the substrate is being
transferred from a gap fill cell to a bulk fill cell. The substrate
may be rinsed with the conditioning solution upon removal from the
gap fill cell. The polymer treatment may alternatively occur in an
intermediate polymer treatment cell containing the conditioning
solution. An alternative embodiment may include a solution having a
high suppressor concentration in the bulk fill cell, thereby
removing the need for a separate polymer treatment step.
[0028] The gap fill step and the bulk fill steps may alternatively
occur in the same processing cell 240. The polymer treatment step
may comprise turning off the electrical current applied to the
plating solution, upon completion of the gap fill step. The period
of no current may last for a time sufficient to allow diffusion of
the plating solution to a point of equilibrium, for example, from
about 1 second to about 100 seconds. The deposition process within
the features is generally controlled by diffusion of the reactants
to the feature. Therefore, diffusion is significant in conformal
plating and filling of the features. Reducing the additive
diffusion in the feature thereby reduces the plating activity in
the feature. As a result of the diffusion, the accelerators no
longer dominate the reaction within the features, thereby reducing
the areas of local high accelerator concentration at the
features.
[0029] Alternatively, the plating solution may be drained from the
cell upon completion of the gap fill step. The substrate may then
be rinsed with the conditioning solution for a time sufficient to
stop the accelerator reaction at the features. The substrate may be
rinsed in a separate rinsing cell. Alternatively, the cell may be
rinsed in the same cell if the cell volume is small. The cell may
then be filled with a bulk fill solution that is different than the
gap fill and conditioning solutions.
[0030] Although not wishing to be bound by theory, it is believed
that conformal plating attributes to the time generally necessary
for the additives to diffuse to the substrate surface. Therefore,
to eliminate the effect of conformal plating and provide immediate
bottom up fill, embodiments of the invention may, in addition to,
or alternatively include a polymer pre-treatment step between a
seed layer step and a metal plating step. The metal plating step is
generally continuous when the polymer treatment step between the
gap fill and bulk fill steps is not included. The polymer
pre-treatment step may reduce the conformal deposition at the
outset of plating. The polymer pre-treatment step may include
conditioning the surface of the substrate with a suppressor rich
solution either by rinsing or by soaking the substrate in a cell
containing the suppressor rich conditioning solution. The cell may
be the same cell as is used for the plating step, or,
alternatively, may be a separate cell, whereby the substrate is
transferred to the plating cell.
[0031] While the foregoing is directed to embodiments of the
present invention, other and further embodiments of the invention
may be devised without departing from the basic scope thereof, and
the scope thereof is determined by the claims that follow.
* * * * *