U.S. patent application number 10/194171 was filed with the patent office on 2004-01-15 for electrolyte/organic additive separation in electroplating processes.
This patent application is currently assigned to Applied Materials, Inc.. Invention is credited to Yang, Michael X..
Application Number | 20040007473 10/194171 |
Document ID | / |
Family ID | 30114678 |
Filed Date | 2004-01-15 |
United States Patent
Application |
20040007473 |
Kind Code |
A1 |
Yang, Michael X. |
January 15, 2004 |
Electrolyte/organic additive separation in electroplating
processes
Abstract
A method and apparatus for plating metals, such as copper, on a
substrate. The apparatus generally includes a plating cell having
an anolyte compartment containing an anolyte and a catolyte
compartment containing a catolyte, an anode disposed in the anolyte
compartment, and a dialysis membrane disposed between the anolyte
compartment and the catolyte compartment, wherein the membrane
screens molecules by molecular weight. The method generally
includes supplying an electrolyte solution to a copper plating
cell, plating copper onto a substrate in the plating cell from the
electrolyte solution, and preventing the passage of additives from
a catolyte compartment to an anolyte compartment with an anode
disposed therein by providing a dialysis membrane between the
anolyte compartment and catolyte compartment that is selective to
molecule size.
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: |
30114678 |
Appl. No.: |
10/194171 |
Filed: |
July 11, 2002 |
Current U.S.
Class: |
205/291 ;
204/252 |
Current CPC
Class: |
C25D 17/002 20130101;
C25D 7/12 20130101; C25D 3/38 20130101; C25D 21/00 20130101 |
Class at
Publication: |
205/291 ;
204/252 |
International
Class: |
C25D 017/00 |
Claims
1. A copper plating system, comprising: a plating cell having an
anolyte compartment and a catolyte compartment; an anode disposed
in the anolyte compartment; and a dialysis membrane disposed
between the anolyte compartment and the catolyte compartment,
wherein the dialysis membrane screens molecules by molecular
weight.
2. The copper plating system of claim 1, further comprising
disposing a catolyte in the catolyte compartment having copper
sulfate, sulfuric acid, copper chloride, and organic additives.
3. The copper plating system of claim 1, further comprising
disposing an anolyte in the anolyte compartment having copper
sulfate, sulfuric acid, and copper chloride.
4. The copper plating system of claim 1, wherein the dialysis
membrane has a molecular weight cutoff of about 100.
5. The copper plating system of claim 1, wherein the dialysis
membrane is configured to prevent the passage of organic additives
therethrough.
6. The copper plating system of claim 1, wherein the dialysis
membrane is configured to prevent the passage of suppressors and
levelers therethrough.
7. The copper plating system of claim 1, wherein the dialysis
membrane has a molecular weight cutoff of about 1000.
8. The copper plating system of claim 1, wherein a catolyte and an
anolyte disposed in the plating cell have substantially equivalent
concentrations of copper, acid, and chloride.
9. The copper plating system of claim 1, wherein the dialysis
membrane is disposed a distance away from the anode greater than
about 0.1 mm.
10. A method for plating copper, comprising: supplying an
electrolyte solution to a copper plating cell; plating copper onto
a substrate in the plating cell from the electrolyte solution;
supplying additives the electrolyte solution contained in a
catolyte compartment disposed in the copper plating cell; and
preventing the passage of molecules based on their molecular weight
from a catolyte compartment to an anolyte compartment with an anode
disposed therein.
11. The method of claim 10, wherein the preventing the passage of
molecules includes providing a dialysis membrane between the
anolyte compartment and the catolyte compartment.
12. The method of claim 11, wherein the dialysis membrane has a
molecular weight cutoff of about 1000.
13. The method of claim 11, wherein the dialysis membrane has a
molecular weight cutoff of about 100 or less.
14. The method of claim 11, wherein the dialysis membrane has a
molecular weight cutoff of about 160 or less.
15. The method of claim 10, wherein the electrolyte solution
comprises copper sulfate, sulfuric acid, and copper chloride.
16. The method of claim 11, wherein the dialysis membrane has a
distance from the anode of greater than about 0.1 mm.
17. The method of claim 10, wherein the anolyte and catolyte have
essentially the same copper concentration.
18. A copper plating system, comprising: a plating cell having an
anolyte compartment containing an anolyte and a catolyte
compartment containing a catolyte; an anode disposed in the anolyte
compartment; and a dialysis membrane disposed between the anolyte
compartment and the catolyte compartment, wherein the membrane is
selective to molecules having a molecular weight greater than about
80.
19. The method of claim 18, wherein the dialysis membrane is
selective to molecules having a molecular weight greater than about
150.
20. The method of claim 18, wherein the dialysis membrane is
selective to molecules having a molecular weight greater than about
1000.
21. A method for plating copper, comprising: supplying an
electrolyte solution to a copper plating cell; plating copper onto
a substrate in the plating cell from the electrolyte solution; and
preventing the passage of molecules having a molecular weight
greater than about 100 between a catolyte compartment and an
anolyte compartment with an anode disposed therein.
22. A filtering device for use in a copper plating system,
comprising a dialysis membrane configured to prevent the passage of
organic additives therethrough, wherein the dialysis membrane has a
molecular weight cutoff of about 100.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention generally relates to reducing
degradation and contamination of electrolyte solutions.
[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, ire., 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.
Conventionally, deposition techniques such as chemical vapor
deposition (CVD) and physical vapor deposition (PVD) 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, 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, sub-quarter micron sized high aspect
ratio features formed on a substrate surface may be efficiently
filled with a conductive material, such as copper. ECP plating
processes are generally multi-stage processes, wherein a seed layer
is first formed over the surface features of the substrate, either
by electroplating, physical vapor deposition, or electroless
deposition, 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 as a metal on the seed layer. The plated metal, which
may be copper, for example, grows in thickness and forms a copper
layer over the seed layer that operates to fill the features formed
on the substrate surface.
[0006] In order to facilitate and control this plating process,
several additives may be utilized in the electrolyte plating
solution. For example, a typical electrolyte solution used for
copper electroplating may consist of a copper sulfate solution,
which provides the copper to be plated, having sulfuric acid and
copper chloride added thereto. The sulfuric acid may generally
operate to modify the acidity and conductivity of the solution. The
electrolytic solutions also generally contain various organic
molecules, which may be accelerators, suppressors, levelers, or
brighteners. These organic molecules are generally added to the
plating solution in order to facilitate void-free, super-fill of
high aspect ratio features and planarized copper deposition.
Accelerators, for example, may be sulfide-based molecules that
locally accelerate electrical current at a given voltage where they
absorb. Suppressors may be polymers of polyethylene glycol,
mixtures of ethylene oxides and propylene oxides, or copolymers of
ethylene oxides and propylene oxides, for example, which tend to
reduce electrical current at the sites where they absorb (the upper
edges/corners of high aspect ratio features), and therefore, slow
the plating process at those locations, which reduces premature
closure of the feature before the feature is completely filled.
Levelers, for example, may be nitrogen containing long chain
polymers, which operate to facilitate planar plating. Additionally,
the plating bath usually contains a small amount of chloride,
generally between about 20 and about 60 ppm, which provides
negative ions needed for adsorption of suppressor molecules on the
cathode.
[0007] Although the various organic additives facilitate the
plating process and offer a control element over the interconnect
formation processes, they also present a challenge, as the
additives are known to eventually break down and become contaminate
material in the electrolyte solution. The particulate matter may
deposit on the substrate surface, which can detrimentally affect
subsequent deposition processes and detrimentally affect device
fabrication. Conventional plating apparatuses have traditionally
dealt with these organic contaminants via bleed and feed methods
(periodically replacing a portion of the electrolyte), extraction
methods (filtering the electrolyte with a charcoal filter),
photochemical decomposition methods (using UV in conjunction with
ion exchange and acid-resistant filters), and/or ozone treatments
(dispensing ozone into the electrolyte). However, these
conventional methods are inefficient, expensive to implement and
operate, or bulky, and may generate hazardous materials or other
kinds of contaminants as byproducts.
[0008] Furthermore, conventional systems may utilize a soluble
metal anode to provide a continuous supply to metal ions for
electrolyte replenishment. However, anode dissolution has
disadvantages such as undesirable side products, e.g., sludge and
copper ball formation, and undesirable side effects, e.g., anode
passiviation and non-uniform anode dissolution. Therefore, there is
a need for a method and apparatus for reducing contamination in
semiconductor electroplating solutions, wherein the method and
apparatus addresses the deficiencies of conventional devices.
SUMMARY OF THE INVENTION
[0009] Embodiments of the present invention generally relate to a
copper plating system generally including a plating cell having an
anolyte compartment containing an anolyte and a catolyte
compartment containing a catolyte, an anode disposed in the anolyte
compartment, and a dialysis membrane disposed between the anolyte
compartment and the catolyte compartment, wherein the dialysis
membrane screens molecules by molecular weight.
[0010] Embodiments of the invention further relate to a method for
plating copper generally including supplying an electrolyte
solution to a copper plating cell, plating copper onto a substrate
in the plating cell from the electrolyte solution, and preventing
the passage of additives from a catolyte compartment to an anolyte
compartment with an anode disposed therein by providing a dialysis
membrane between the anolyte compartment and catolyte compartment
that is selective to molecule size.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] So that the manner in which the above recited features,
advantages and objects of the present invention are attained can be
understood in detail, a more particular description of the
invention, briefly summarized above, may be had by reference to the
embodiments thereof, which are illustrated in the appended
drawings. It is to be noted, however, that the appended drawings
illustrate only typical embodiments of this invention and are
therefore not to be considered limiting of its scope, for the
invention may admit to other equally effective embodiments.
[0012] FIG. 1 illustrates an exemplary plating system incorporating
a dialysis membrane of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0013] FIG. 1 illustrates an exemplary plating system 100
incorporating aspects of the present invention. Plating system 100
generally includes a plating cell 101, which may be an
electrochemical plating (ECP) cell, or other plating cell
configuration known in the semiconductor art. The plating cell 101
generally includes an anolyte inlet 105 configured to deliver an
anolyte, e.g., a plating processing fluid, to the plating cell 101,
and an anolyte outlet or drain 106 configured to retrieve anolyte
from plating cell 101. The anolyte is delivered to the plating cell
101 via inlet 105, which is generally in fluid communication with
an anolyte storage unit 102. A fluid pump 104 is generally
positioned between the anolyte storage unit 102 and the plating
cell 101 and is configured to deliver the anolyte to plating cell
101 upon actuation thereof. The anolyte generally is contained in
an anolyte compartment 108 with an anode 122 disposed therein.
[0014] The anode 122 may generally be soluble or insoluble. A
consumable anode 122, for example, may be disposed in the cell 101
and configured to dissolve in the electroplating solution under
electrical current in order to provide metal ions to be deposited
onto the substrate from the plating solution. The anode 122
generally does not extend across the entire width of the cell 101,
thus allowing the electroplating solution to flow between the outer
surface of the anode 122 and the anode 122 to the substrate.
Alternatively, an anode 122 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 122 may also be disposed in
the cell 101 so that the electroplating solution may pass
therethrough. However, when a non-consumable anode is included, the
electroplating solution may include a metal supply to continually
replenish the metal to be deposited on the substrate.
[0015] The anolyte compartment 108 is generally separated from a
catolyte compartment 110 having a cathode, e.g., a substrate,
disposed therein, by a dialysis membrane 112. The dialysis membrane
112 generally does not contact the anode 122. Contact with the
anode generally effects plating and anode operation. Therefore, the
dialysis membrane 112 generally has a distance from the anode 122
of greater than about 0.1 mm. The catolyte is generally delivered
to the catolyte compartment 100 via a catolyte inlet 116, which is
generally in fluid communication with a catolyte storage unit 118.
Catolyte compartment 110 further includes a catolyte outlet 114 to
retrieve catolyte from the cell 101.
[0016] The dialysis membrane 112 is configured to permit the
electrolyte solution containing the metal ions to pass through, but
prevent anode by-products from entering the catolyte compartment
110, thereby increasing plating performance by decreasing the
amount of defects present on the plated substrate. In addition, the
dialysis membrane 112 prevents organic additive diffusion from the
catolyte compartment 110 to the anolyte compartment 108. Preventing
additive migration to the anolyte compartment 108 prevents additive
breakdown and contamination generally caused by additive contact
with the anode 122. The dialysis membrane 122 provides additive
control to the cell 101 by screening, and thereby preventing the
passage of molecules by their molecular weight, i.e., large
molecules are unable to pass from one cell compartment to another.
In operation, the metal and chloride concentration of the catolyte
and the anolyte will generally be equivalent, whereas the anolyte
will not contain organic additives.
[0017] Additive control is varied depending on system requirements
by the molecular weight cut off of the membrane. The molecular
weight cut off of the dialysis membrane determines the maximum
molecular weight of the molecules able to permeate the membrane.
For example, dialysis membranes with a molecular weight cut off of
about 1000 prevent the passage of chemicals having a molecular
weight greater than 1000 therethrough, such as
polyethylene-polypropylene oxides having a molecular weight of
about 3000. Different dialysis membranes having various molecular
weight cutoffs (limits) may be selected as required by the additive
composition to be used in each plating process.
[0018] Embodiments of the invention generally employ copper plating
solutions, e.g., both anolyte and catolyte, 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, for example. The acid may include sulfuric
acid, phosphoric acid, and/or derivatives thereof. In addition to
copper sulfate, the plating solution may include other copper
salts, such as copper fluoborate, copper gluconate, copper
sulfamate, copper sulfonate, copper pyrophosphate, copper chloride,
or copper cyanide, for example. However, embodiments of the
invention are not limited to these parameters.
[0019] The anolyte 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 generally
have a molecular weight greater than about 3000 and typically
include polyethers, such as polyethylene glycol, or other polymers,
such as polyethylene-polypropylen- e oxides, which adsorb on the
substrate surface, slowing down copper deposition in the adsorbed
areas. Useful accelerators generally have a molecular weight
greater than about 177 and 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 levelers generally have a
molecular weight greater than about 4000 and typically include
thiadiazole, imidazole, and other nitrogen containing organics.
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
plating 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.
[0020] In contrast to the high molecular weight of the additives,
the additional molecules in the plating solution, such as copper,
chloride ions and sulfate ions, have lower molecular weights. For
example, copper ions have an atomic weight of about 63, chloride
ions have an atomic weight of about 35, and sulfate ions have a
molecular weight of about 96. Therefore, dialysis membranes may be
chosen to prevent the passage of additives into the anolyte
compartment 108, thereby eliminating the additive degradation
caused by the anode. By reducing additive degradation, the plating
solution generally needs to be replaced less frequently, thereby
significantly reducing the cost of plating solutions. Therefore,
embodiments of the invention generally include dialysis membranes
having a molecular weight cutoff of less than about 177 and greater
than about 96. The dialysis membrane generally may have a molecular
weight cutoff of about 100 to prevent the passage of all additives
therethrough. Alternatively, the dialysis membrane may have a
molecular weight cutoff of about 1000 to allow the passage of
accelerators, while preventing the passage of levelers and
suppressors therethrough. Dialysis membranes may be one of many
commercially available membranes. For example, VWR International of
Westchester, Pennsylvania produces dialysis membranes with a
molecular weight cutoff of 1000 under the trade name SPECPOR,
Spectra, and SPC.
[0021] 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.
* * * * *