U.S. patent application number 09/734014 was filed with the patent office on 2002-09-12 for apparatus and methods to control the uniformity of electroplated workpiece.
Invention is credited to Landry, Gerard Raymond, Uzoh, Cyprian Emeka.
Application Number | 20020125140 09/734014 |
Document ID | / |
Family ID | 21753228 |
Filed Date | 2002-09-12 |
United States Patent
Application |
20020125140 |
Kind Code |
A1 |
Uzoh, Cyprian Emeka ; et
al. |
September 12, 2002 |
Apparatus and methods to control the uniformity of electroplated
workpiece
Abstract
An electroplating system for plating at least one metal on at
least one substrate. At least one plating tank contains a plating
solution including the at least one metal to be plated on the at
least one substrate. At least one anode is arranged in the at least
one plating tank. The at least one anode is at least partially
immersed within the plating solution during plating of the at least
one metal. At least one cathode includes at least one workpiece
portion in contact with the at least one substrate and at least one
thief portion arranged in the vicinity of at least one portion of
the at least one substrate for controlling plating of the at least
one metal on the at least one portion of the at least one
substrate. At least one power supply is connected to the at least
one cathode. At least one controller separately controls a flow of
power to the at least one workpiece portion of the cathode and the
at least one thief portion of the cathode.
Inventors: |
Uzoh, Cyprian Emeka;
(Hopewell Junction, NY) ; Landry, Gerard Raymond;
(New Windsor, NY) |
Correspondence
Address: |
INTERNATIONAL BUSINESS MACHINES CORPORATION
DEPT. 18G
BLDG. 300-482
2070 ROUTE 52
HOPEWELL JUNCTION
NY
12533
US
|
Family ID: |
21753228 |
Appl. No.: |
09/734014 |
Filed: |
December 12, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09734014 |
Dec 12, 2000 |
|
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|
09012069 |
Jan 22, 1998 |
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6168693 |
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Current U.S.
Class: |
205/82 ; 205/83;
205/96 |
Current CPC
Class: |
Y10S 204/07 20130101;
C25D 21/12 20130101 |
Class at
Publication: |
205/82 ; 205/83;
205/96 |
International
Class: |
C25D 021/12 |
Claims
We claim:
1. An electroplating system for plating at least one metal on at
least one substrate, said electroplating system comprising: at
least one plating tank containing a plating solution including said
at least one metal to be plated on said at least one substrate; at
least one anode arranged in said at least one plating tank, said at
least one anode being at least partially immersed within said
plating solution during plating of said at least one metal; at
least one cathode including at least one workpiece portion in
contact with said at least one substrate and at least one thief
portion arranged in the vicinity of at least one portion of said at
least one substrate for controlling plating of said at least one
metal on said at least one portion of said at least one substrate;
at least one power supply connected to said at least one cathode;
and at least one controller for separately controlling a flow of
power to said at least one workpiece portion of said cathode and
said at least one thief portion of said cathode.
2. The electroplating system according to claim 1, wherein said at
least one controller includes a first timer for controlling a flow
of power to said workpiece portion of said at least one cathode and
said at least one substrate, and a second timer for controlling a
flow of power to said at least one thief portion of said at least
one cathode.
3. The electroplating system according to claim 1, further
comprising: a power supply for each portion of said cathode.
4. The electroplating system according to claim 1, wherein said at
least one controller includes at least one timer for controlling a
flow of power to each of said portions of said at least one
cathode.
5. The electroplating system according to claim 2, further
comprising: a third timer for controlling a flow of power to said
second timer.
6. The electroplating system according to claim 5, wherein said
third timer delays the flow of power to said at least one thief
portion of said at least one cathode to a point in time after power
has been supplied to said at least one workpiece portion of said at
least one cathode and said at least one substrate.
7. A control system for controlling uniformity of electroplating of
at least one metal on at least one substrate in an electroplating
system including at least one plating tank containing a plating
solution including said at least one metal to be plated on said at
least one substrate, at least one anode arranged in said at least
one plating tank, said at least one anode being at least partially
immersed within said plating solution during plating of said at
least one metal, at least one cathode including at least one
workpiece portion in contact with said at least one substrate and
at least one thief portion arranged in the vicinity of at least one
portion of said at least one substrate for controlling plating of
said at least one metal on said at least one portion of said at
least one substrate, at least one power supply connected to said at
least one cathode, said control system comprising: at least one
controller for separately controlling a flow of power to said at
least one workpiece portion of said at least one cathode and said
at least one thief portion of said at least one cathode.
8. The control system according to claim 7, wherein said at least
one controller includes a first timer for controlling a flow of
power to said workpiece portion of said at least one cathode and
said at least one substrate, and a second timer for controlling a
flow of power to said at least one thief portion of said at least
one cathode.
9. The control system according to claim 7, wherein said
electroplating system further includes a power supply for each
portion of said cathode.
10. The control system according to claim 7, wherein said at least
one controller includes at least one timer for controlling a flow
of power to each of said portions of said at least one cathode.
11. The control system according to claim 8, further comprising: a
third timer for controlling a flow of power to said second
timer.
12. The control system according to claim 11, wherein said third
timer delays the flow of power to said at least one thief portion
of said at least one cathode to a point in time after power has
been supplied to said at least one workpiece portion of said at
least one cathode and said at least one substrate.
13. A method of electroplating at least one metal on at least one
substrate in an electroplating system including at least one
plating tank containing a plating solution including said at least
one metal to be plated on said at least one substrate, at least one
anode arranged in said at least one plating tank, said at least one
anode being at least partially immersed within said plating
solution during plating of said at least one metal, at least one
cathode including at least one workpiece portion in contact with
said at least one substrate and at least one thief portion arranged
in the vicinity of at least one portion of said at least one
substrate for controlling plating of said at least one metal on
said at least one portion of said at least one substrate, at least
one power supply connected to said at least one cathode, said
method comprising the steps of: controlling a flow of power to said
at least one workpiece portion of said at least one cathode; and
controlling a flow of power to said at least one thief portion of
said at least one cathode separately from said flow of power to
said at least one workpiece portion of said at least one
cathode.
14. The method according to claim 13, wherein the flow of power to
said at least one thief portion of said at least one cathode is
delayed to a point in time after power has been supplied to said at
least one workpiece portion of said at least one cathode.
15. The method according to claim 13, wherein controlling a flow of
power to said at least one workpiece portion of said at least one
cathode and said at least one thief portion of said at least one
cathode includes controlling at least one parameter selected from
the group consisting of current density and a time period that the
current is applied.
16. The method according to claim 15, further comprising the steps
of: supplying current to said at least one workpiece portion of
said at least one cathode at a first current density for a first
period of time; and supplying current to said at least one thief
portion of said at least one cathode at a second current density
for a second period of time; wherein said first current density,
said second current density, said first period of time, and said
second period of time are selected to result in a desired plating
uniformity.
17. A method of electroplating at least one metal on at least one
substrate in an electroplating system, said method comprising the
steps of: providing an electroplating system including: at least
one plating tank containing a plating solution including said at
least one metal to be plated on said at least one substrate; at
least one anode arranged in said at least one plating tank, said at
least one anode being at least partially immersed within said
plating solution during plating of said at least one metal; at
least one cathode including at least one workpiece portion in
contact with said at least one substrate and at least one thief
portion arranged in the vicinity of at least one portion of said at
least one substrate for controlling plating of said at least one
metal on said at least one portion of said at least one substrate;
at least one power supply connected to said at least one cathode;
and at least one controller for separately controlling a flow of
power to said at least one workpiece portion of said cathode and
said at least one thief portion of said cathode; utilizing said at
least one controller to control a flow of power to said at least
one workpiece portion of said at least one cathode; and utilizing
said at least one controller to control a flow of power to said at
least one thief portion of said at least one cathode separately
from said flow of power to said at least one workpiece portion of
said at least one cathode.
18. The method according to claim 17, wherein said at least one
controller includes a first timer for controlling a flow of power
to said workpiece portion of said at least one cathode and said at
least one substrate, and a second timer for controlling a flow of
power to said at least one thief portion of said at least one
cathode.
19. The method according to claim 17, wherein said at least one
controller further includes a third timer for controlling flow of
power to said second timer, and said method further comprises the
step of: utilizing said third timer to control the controlling of
the flow of power to said at least one thief portion of said at
least one cathode.
20. The method according to claim 17, wherein the flow of power to
said at least one thief portion of said at least one cathode is
delayed to a point in time after power has been supplied to said at
least one workpiece portion of said at least one cathode.
21. The method according to claim 17, wherein controlling a flow of
power to said at least one workpiece portion of said at least one
cathode and said at least one thief portion of said at least one
cathode includes controlling at least one parameter selected from
the group consisting of current density and a time period that the
current is applied.
22. A method of electroplating at least one metal on at least one
substrate in an electroplating system including at least one
plating tank containing a plating solution including said at least
one metal to be plated on said at least one substrate, at least one
anode arranged in said at least one plating tank, said at least one
anode being at least partially immersed within said plating
solution during plating of said at least one metal, at least one
cathode including at least one workpiece portion in contact with
said at least one substrate and at least one thief portion arranged
in the vicinity of at least one portion of said at least one
substrate for controlling plating of said at least one metal on
said at least one portion of said at least one substrate, at least
one power supply connected to said at least one cathode, said
method comprising the step of: decoupling a uniformity of said at
least one metal deposited on said at least one substrate and a
thickness of said at least one metal deposited on said at least one
substrate.
23. The method according to claim 22, wherein said decoupling is
accomplished by providing said electroplating system with at least
one controller for separately controlling a flow of power to said
at least one workpiece portion of said at least one cathode and
said at least one thief portion of said at least one cathode, and
said method further comprises the steps of: utilizing said at least
one controller to control a flow of power to said at least one
workpiece portion of said at least one cathode; and utilizing said
at least one controller to control a flow of power to said at least
one thief portion of said at least one cathode.
24. The method according to claim 23, wherein said at least one
controller includes a first timer for controlling flow of power to
said at least one workpiece portion of said at least one cathode,
and a second timer for controlling flow of power to said at least
one thief portion of said at least one cathode.
25. The method according to claim 24, wherein said at least one
controller further includes a third timer for controlling flow of
power to said second timer, and said method further comprises the
step of: utilizing said third timer to control the controlling of
the flow of power to said at least one thief portion of said at
least one cathode.
26. The method according to claim 25, wherein said third timer
delays the flow of power to said at least one thief portion of said
at least one cathode to a point in time after power has been
supplied to said at least one workpiece portion of said at least
one cathode.
27. The method according to claim 23, wherein controlling a flow of
power to said at least one workpiece portion of said at least one
cathode and said at least one thief portion of said at least one
cathode includes controlling at least one parameter selected from
the group consisting of current density and a time period that the
current is applied.
Description
FIELD OF THE INVENTION
[0001] The invention relates to the electroplating metal on
substrates, a system for electroplating metal on substrates, and
control system for controlling electroplating on substrates and a
method of electroplating metal on substrates.
BACKGROUND OF THE INVENTION
[0002] In the production of microelectronic devices, metal may be
plated on a substrate for a variety of purposes. Typically, metal
is plated on the substrates in cells or reservoirs that hold a
plating solution that includes at least one metal to be plated on
the substrate.
[0003] In microelectronic device manufacture, it is often desirable
for metal to be uniformly deposited across a substrate. In
electrodeposition of metals, uniformity of the deposited metals is
typically coupled to thickness of the deposited metal. This is
particularly so in electrodeposition of metals on thin seed layers.
electrodeposition of metals on thin seed layers. Simultaneous
control of deposited metal thickness and uniformity on various thin
seed layers is rather difficult.
[0004] Typically, for a given thin seed layer thickness,
electroplated metal uniformity improves with increasing metal
thickness. For example, in copper deposition, for ULSI
interconnection, the uniformity of a deposit of about 500 nm is
about 13%. This percentage indicates the percentage of standard
deviation in metal thickness with respect to average metal
thickness over the surface of the substrate. The uniformity for a
deposit of about 1,000 nm is about 9% and about 3% for a deposit of
about 2,000 nm. The above illustrates the strong connection between
metal uniformity and metal thickness.
[0005] Lack of uniformity of deposited metal also presents problems
in metal damascene processes. In the damascene process, after metal
deposition, the metal overburden is planarized to define the
interconnection features or structure.
[0006] In such cases, good metal uniformity may actually pose a
problem. For example, depending upon the nature of polishing pads,
arrangements, choice of slurry, pressure table rotation and other
polishing parameters, good metal uniformity may not be desirable.
For example a 2 .mu. Cu or Al film with the uniformity of 3% may
present a problem for polishing.
[0007] During chemical-mechanical polishing (CMP) the edges of
wafers may tend to clear before the center of a wafer. Premature
exposure of the chips at the wafer edge may cause the chips to be
overpolished. As a result, the resistance of metal lines near a
wafer edge may tend to be higher than the resistance of those
further away from the edge.
SUMMARY OF THE PRESENT INVENTION
[0008] An object of the present invention is to provide a method
and apparatus for controlling uniformity of at least one metal
electroplated on a substrate or workpiece.
[0009] Accordingly, the aspects of the present invention provide an
electroplating system for plating at least one metal on at least
one substrate or workpiece. The system includes at least one
plating tank containing a plating solution including at least one
metal to be plated on the at least one substrate or cathode. At
least one anode is arranged in the at least one plating tank. The
at least one anode is at least partially immersed within the
plating solution during plating of the at least one metal. A
cathode assembly includes at least one thief and at least one
workpiece portion. In the cathode assembly, the at least one thief
portion is arranged in the vicinity of at least one workpiece to be
plated. The at least one thief controls plating of the at least one
metal on the at least one portion of the at least one substrate. At
least one power supply is connected to the at least one cathode. At
least one controller separately controls a flow of power to the at
least one workpiece portion of the cathode and the at least one
thief portion of the cathode.
[0010] The present invention also includes a control system for
controlling uniformity of at least one metal electroplated on at
least one substrate in the electroplating system. The
electroplating system includes at least one plating tank containing
a plating solution including the at least one metal to be plated on
the at least one substrate. At least one anode is arranged in the
at least one plating tank. The at least one anode is at least
partially immersed within the plating solution during plating of
the at least one metal. The system also includes at least one
cathode including at least one workpiece portion in contact with
the at least one substrate and at least one thief portion arranged
in the vicinity of at least one portion of the at least one
substrate for controlling plating of the at least one metal on the
at least one portion of the at least one substrate. At least one
power supply is connected to the at least one cathode. The control
system includes at least one controller for separately controlling
a flow of power to the at least one workpiece portion of the
cathode and the at least one thief portion of the cathode.
[0011] Furthermore, aspects of the present invention include a
method of electroplating at least one metal on at least one
substrate in an electroplating system including at least one
plating tank containing a plating solution including the at least
one metal to be plated on the at least one substrate. At least one
anode is arranged in the at least one plating tank. The at least
one anode is at least partially immersed within the plating
solution during plating of the at least one metal. The system also
includes at least one cathode including at least one workpiece
portion in contact with the at least one substrate and at least one
thief portion arranged in the vicinity of at least one portion of
the at least one substrate for controlling plating of the at least
one metal on the at least one portion of the at least one
substrate. At least one power supply is connected to the at least
one cathode. At least one controller separately controls a flow of
power to the at least one workpiece portion of the cathode and the
at least one thief portion of the cathode. The method includes
controlling a flow of power to the at least one workpiece portion
of the at least one cathode. A flow of power to the at least one
thief portion of the at least one cathode is controlled separately
from the flow of power to the at least one workpiece portion of the
at least one cathode.
[0012] Still further aspects of the present invention provide a
method of electroplating at least one metal on at least one
substrate in an electroplating system. The method includes the step
of providing an electroplating system including at least one
plating tank containing a plating solution including the at least
one metal to be plated on the at least one substrate. At least one
anode is arranged in the at least one plating tank. The at least
one anode is at least partially immersed within the plating
solution during plating of the at least one metal. The system also
includes at least one cathode including at least one workpiece
portion in contact with the at least one substrate and at least one
thief portion arranged in the vicinity of at least one portion of
the at least one substrate for controlling plating of the at least
one metal on the at least one portion of the at least one
substrate. At least one power supply is connected to the at least
one cathode. At least one controller separately controls a flow of
power to the at least one workpiece portion of the cathode and the
at least one thief portion of the cathode. The method also includes
utilizing the at least one controller to control a flow of power to
the workpiece portion of the cathode. Additionally, the method
includes utilizing the at least one controller to control a flow of
power to the at least one thief portion of the at least one cathode
separately from the flow of power to the at least one workpiece
portion of the at least one cathode.
[0013] Aspects of the present invention also include a method of
electroplating at least one metal on at least one substrate in an
electroplating system including at least one plating tank
containing a plating solution including the at least one metal to
be plated on the at least one substrate. At least one anode is
arranged in the at least one plating tank. The at least one anode
is at least partially immersed within the plating solution during
plating of the at least one metal. The system also includes at
least one cathode including at least one workpiece portion in
contact with the at least one substrate and at least one thief
portion arranged in the vicinity of at least one portion of the at
least one substrate for controlling plating of the at least one
metal on the at least one portion of the at least one substrate. At
least one power supply is connected to the at least one cathode.
The method includes the step of decoupling a uniformity of the at
least one metal deposited on the at least one substrate and the
thickness of the at least one metal deposited on the at least one
substrate.
[0014] Still other objects and advantages of the present invention
will become readily apparent by those skilled in the art from the
following detailed description, wherein it is shown and described
only the preferred embodiments of the invention, simply by way of
illustration of the best mode contemplated of carrying out the
invention. As will be realized, the invention is capable of other
and different embodiments, and its several details are capable of
modifications in various obvious respects, without departing from
the invention. Accordingly, the drawings and description are to be
regarded as illustrative in nature and not as restrictive.
DESCRIPTION OF THE FIGURES
[0015] The above-mentioned objects and advantages of the present
invention will be more clearly understood when considered in
conjunction with the accompanying drawings, in which:
[0016] FIG. 1 represents a graph illustrating the uniformity
distribution dependence on the thickness of an electroplated film
on a large substrate;
[0017] FIG. 2 represents a graph illustrating the effect of current
density ratios Id/Iw on a profile of plated copper on a
substrate;
[0018] FIG. 3 represents a graph illustrating the effect of plated
metal thickness on uniformity of a plated film;
[0019] FIG. 4 represents a graph illustrating the effect of an
embodiment of the present invention on the uniformity of
electroplated metal deposited on a substrate;
[0020] FIG. 5 schematically represents a known electroplating
cell;
[0021] FIG. 6 schematically represents an embodiment of an
electroplating cell according to the present invention; and
[0022] FIG. 7 illustrates three embodiments of timer control modes
according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0023] As stated above, the present invention provides a method and
apparatus for controlling uniformity of metal electroplated on
substrates. According to the present invention, uniformity of metal
may be controlled by decoupling metal uniformity from metal
thickness in the electrodeposited metal. The required uniformity of
metal plated on a substrate may vary from application to
application.
[0024] For example, the optimum metal profile for CMP may require
an electroplated metal to be deposited thicker at the periphery of
a substrate rather than at the center of a substrate, or a concave
metal profile. Alternatively, various processes including CMP may
require the opposite, with the metal thicker at the center of a
substrate as compared to the periphery, or a convex metal profile.
The present invention makes it possible to create any desired metal
profile by making uniformity of the deposited metal independent
from thickness of the deposited metal.
[0025] FIG. 1 illustrates the relationship between the uniformity
of electrodeposited copper expressed as the percent standard
deviation with respect to average seed layer thickness. The results
shown in FIG. 1 may be divided into three sections. In section A,
the plated film is thinner than 700 nm. The effect of the seed
layer thickness is very strong in this region. The standard
deviation of the thickness, the measurement of uniformity in this
case, is typically higher than about 8%. The uniformity degrades
further as the thickness of the seed layer decreases.
[0026] In zone B, where the thickness of the deposited copper is
from about 750 to about 1500 nm. The effect of the seed layer
thickness on uniformity is intermediate to strong in this
region.
[0027] In zone C, the thickness of the plated film is above about
1800 nm. In such cases, the impact of the seed layer tends to be
weak.
[0028] FIG. 1 illustrates the dependence of uniformity distribution
on the thickness of electroplated film on a substrate. In general,
the thinner the seed layer, the worse the deposit uniformity.
Conversely, the thicker the seed layer, typically the better the
deposit uniformity. For seed layers thicker than about 250 nm,
specifically for copper, the effect of the seed layer on deposit
uniformity is weak.
[0029] The graph shown in FIG. 2 illustrates the relationship
between the ratio of current density supplied to the cathode
contacting a substrate that metal is being electroplated on
(I.sub.D) and current density supplied to the thief or deflector
(I.sub.W) with respect to the ratio of plated metal thickness at
the wafer center (X.sub.O) and mean plated metal thickness (X).
[0030] At the critical value for the ratio of current densities,
the mean thickness is equal to the thickness at the center of the
wafer, in other words, X.sub.O/X is equal to about one. At lower
current density ratios, the deposit is thinnest at the center. In
such an example, the ratio of thickness is less than about 1.0. The
deposit profile in this case is concave.
[0031] For larger values of the current density ratio greater than
the critical value, the deposit is thicker at the center.
Therefore, X.sub.O is larger than X. In such a case, the deposit is
concave.
[0032] FIG. 3 illustrates the effect of plated metal thickness on
uniformity of plated film. Uniformity is again expressed as the
percentage standard deviation. Plated metal thickness may also be
alternately expressed as plating time since thickness typically
increases with time in an electroplating system.
[0033] In the case shown in FIG. 3, a seed layer of about 50 nm was
used. Initial uniformity at about 2,000 nm was about 4%. The plated
metal profile was convex. The ratio of thickness at the wafer
center and mean thickness was less than about 1.0.
[0034] FIG. 4 illustrates the effect of an electroplating system
according to the present invention including multiple timers for
controlling uniformity of electrodeposited metal. The dotted line
shown in FIG. 4 represents the profile for a single time control.
The solid line represents the profile according to typical known
electroplating system.
[0035] The top dashed line shown in FIG. 4 represents a profile of
metal plated according to the present invention. Although the
dashed line shown in FIG. 4 represents a much more consistent
uniformity regardless of metal thickness, a range of uniformity is
obtainable with an apparatus according to the present invention for
any given metal thickness. The present invention permits deposit
profile across a workpiece to be controlled according to CMP or
metal etching needs.
[0036] For example, to obtain the best plating uniformity may
require plating in the condition in which x/x.sub.O equals about 1
in FIG. 2. Depending on the area of the workpiece with respect to
the thief, this best uniformity plating conditions may require
I.sub.D/I.sub.W to equal about 1.15. This current density on the
thief is about 15% higher than that of the workpiece or wafer.
[0037] However, this typically applies only when the plating time
for both the thief and the workpiece are about the same as in the
prior art with single timer and controller. The present invention,
which includes the use of separate time controllers for the thief
and the workpiece, can increase metal deposition at the edge of the
workpiece, simply by decreasing the length of time power is applied
to the thief only. For example, for a plating time of about 300
seconds, may be plated for about 300 seconds, while the thief may
be plated for only about 240 seconds. Thus, by controlling the
percentage of time the thief current is on, a much larger range of
uniformity can be obtained, as shown in FIG. 4.
[0038] One of the problems of not tuning plating metal uniformity
or profile to the needs of metal planarization is that a greater
variation in line or via resistance across a wafer produces a
correspondingly large variation in chip performance across the
wafer. In addition to the problem of a large variation in chip
performance, other defects may be caused by lack of uniformity or
lack of controlled uniformity of plated metal are severe dishing,
yield losses, shorts and leakages at subsequent metal levels,
erosion of dielectric adjacent wide metal features, overpolishing
among others. All of these problems can be attributed to the
interplay between metal deposit uniformity and metal CMP. Various
requirements involved in wafer production may require deposited
metal to be thicker at the periphery, as compared to the center
where they are reversed. Such requirements may include high wafer
yield and narrow resistance distribution across a wafer. According
to another example, optimum metals distribution may require
excellent metal uniformity across an entire wafer.
[0039] Electroplating systems typically include a variety of
arrangements to control electroplated metal uniformity. For
example, typical arrangements may include anode and/or cathode
shields, baffles, and/or thieves to control electroplated metal
uniformity. To control electroplated metal thickness, typical
systems rely on current density and plating time. Typical
electroplating systems include a single timer to control metal
deposition. As a result, uniformity of the deposited metal
typically is related to deposit thickness on a thin seed layer,
especially on large substrates.
[0040] To avoid problems existing in the prior art, the present
invention utilizes an electroplating system that decouples plated
metal uniformity and thickness. The present invention is effective
whether utilizing a thin or thick metal seed layer and independent
of the size of the substrate. To accomplish this goal, the present
invention utilizes at least one controller for independently
controlling flow of current and/or the characteristics of the
current. The at least one controller may include a plurality of
timers for controlling power flow to the electroplating system.
[0041] Accordingly, an electroplating system according to the
present invention for plating at least one metal on at least one
substrate may include at least one plating tank containing a
plating solution including the at least one metal to be plated on
the at least one substrate. At least one anode is provided in the
at least one plating tank. The at least one anode is at least
partially immersed within the plating solution during plating of
the at least one metal.
[0042] The electroplating system also includes at least one
cathode. The at least one cathode includes at least two separate
portions. In particular, the at least one cathode includes at least
one workpiece portion. The at least one workpiece portion contacts
the at least one substrate and provides current thereto so as to
result in the electroplating of the at least one metal on the at
least one substrate.
[0043] The at least one cathode also includes at least one thief
portion for controlling plating of the at least one metal on at
least a portion of the at least one substrate. Typically, the at
least one thief portion of the at least one cathode is arranged in
the vicinity of at least one portion of a substrate that at least
one metal is to be plated on. As the thief is supplied with
current, metal plates out of the solution on to the thief rather
than the substrate.
[0044] At least one power supply is connected to the at least one
cathode, including the workpiece portion of the cathode and the
thief portion of the cathode. At least one controller separately
controls flow of power to the at least one cathode. In other words,
the at least one controller supplies power and may also vary the
characteristics of the power supplied to the at least one workpiece
portion of the cathode separately from the at least one thief
portion of the cathode.
[0045] One purpose of the present invention is to control a current
output level directed to the two portions of the cathode prior to
application of the current to the at least one cathode. Hence, the
at least one controller may include at least one component for
separately varying the characteristics of the current supplied to
portions of the at least one cathode. The at least one controller
may also include at least one electronic timer for separately
controlling the duration of the application of current to portions
of the at least one cathode. Accordingly, the at least one power
supply may be interconnected with the electroplating system through
timers for controlling the duration of the application of the
power.
[0046] According to one embodiment, the present invention includes
three timers. A first timer controls duration of application of
power to the at least one workpiece cathode and, hence, controls
metal deposited on the at least one substrate. A second timer
controls a duration of application of power to the thief portion of
the cathode. A third timer may be utilized to offset the starting
time of the second timer. For example, the third timer may delay
the starting of the second timer.
[0047] By controlling the three timers, the present invention may
decouple electroplated metal deposit uniformity and metal
thickness. Such an embodiment has been utilized to electroplate
copper in the range of from about 500 to about 3,000 nm and even
thicker with a uniformity of about 12%.
[0048] The present invention may include at least one separate
power supply for each cathode portion, at least one separate timer
for controlling flow of power through each separate cathode portion
and/or at least one separate element for controlling
characteristics of the power, such as current density, supplied to
each separate portion of the at least one cathode. However, it is
only necessary that the present invention include separate timers
for independently controlling flow of power to the cathode
portions. The present invention may also include a pulse timer or
programmable pulse timer to control flow of power to the thief
portion of the cathode. Furthermore, multiplex timers may be
utilized for controlling metal distribution on a workpiece.
[0049] Another embodiment of the present invention includes two
timer sections. Each timer section may include a pair of timers.
Each timer section may also include an operating switch, such as a
toggle switch. The two timer sections may be identified as T1 and
T2. The pair of timers may include one timer for minutes and one
timer for seconds. The controller may include other controls
including a main power switch/circuit breaker, a start/reset
button, a mode switch, to control at the mode of operation, which
will be discussed in greater detail below, and a delta mode
timer.
[0050] Internally, this embodiment of the control system of the
present invention for controlling uniformity of electroplated
metal(s) in an electroplating system may include, of course, the
timers. Additionally, the present invention may include at least
one relay. According to one example, the control system includes
three relays, a first relay that is a control relay, and two output
relays. The two output relays may include snubber type networks
across the contacts to limit voltage spiking to the electroplating
system when a change of state in the relays occurs.
[0051] This embodiment of the timer includes a plurality of outputs
for supplying power to various portions of the electroplating
system. The output of each power supply may be initiated by the
start/reset button. According to one embodiment, when the
start/reset button is closed, the timing circuit becomes active.
The timers may be illuminated to indicate that they are
operational. The timers may be illuminated and, hence, power
supplied to them, until the start/reset button is pushed again.
Pushing the start/reset button again may reset the control and turn
the power off. When the start/reset button is in a reset position
or off position, the timers may not be illuminated.
[0052] The duration that the timers permit power to be supplied to
various portions of the electroplating system, such as various
cathode portions, may be set by knobs on each timer unit. According
to one embodiment, once the timers are started, they begin to count
down the time period while simultaneously supplying power to
various portions of the electroplating system. When time has run
out on a timer, the control system may be in a "time out" standby
mode until the start/reset button is again operated to deactivate
or reset the control system. According to this embodiment, the
start/reset button may be operated again to provide power to the
timers so that they may be "reset" and begin another countdown
sequence.
[0053] Of course, those skilled in the art would know a variety of
ways to configure and construct a control system according to the
present invention once aware of the basic concept of the present
invention.
[0054] Regardless of the elements included in the hardware of an
electroplating system/control system according to the present
invention, the present invention may be operated in a variety of
modes. According to perhaps the simplest method, the present
invention may be manually operated. In other words, each timer of
the control system may be set and energized separately. The timers
may be turned on and off manually.
[0055] According to another mode of operating the present
invention, each timer may simultaneously be supplied with power and
supplies the electroplating system with power. In the embodiment
described above that includes separate seconds and minutes timers,
when the power is supplied to the timers only the minutes portion
of the timers may be supplied with power. At the end of the
programmed number of minutes, the second timers may be energized to
supply the electroplating system with power for the programmed
number of seconds. After the seconds are counted down on the timer,
the power may be cut off from the electroplating system.
[0056] In the embodiment described above, the two output relays may
be controlled by the application of power to the minutes timers.
After the minutes timers count down, a set of timed contacts
energize the second timers. When the second timers are finished
counting down, a set of contacts may open. Opening of the contacts
at the end of the second timers count down de-energizes relays
supplying power to the system, thus cutting off power to the
system.
[0057] According to a third mode of operation, the present
invention may include an additional timer to offset the starting of
one timer section, typically the timer controlling output power to
the thief cathode. When power is supplied to the control system,
power may be supplied to the minute timer of the first timer
section in the embodiment described above. Simultaneous with
activation of the minute timer, one of the output relays may be
energized. At this point in the operation of the electroplating
system, output is supplied only to the tool through one power
supply by way of the first relay. When the minute timer expires,
the second relay becomes energized, supplying power to the
electroplating cell through the second relay.
[0058] The present invention includes an electroplating system and
a control system for controlling an electroplating system. The
present invention also includes methods of electroplating at least
one metal on a substrate. The methods according to the present
invention may include providing an electroplating system as
described above.
[0059] According to the methods of the present invention, the flow
of power to portions of the at least one cathode are separately
controlled. All parameters relating to the flow of power may be
controlled. For example, the current density and time period during
which power is supplied to the portions of the cathode may be
controlled.
[0060] Power may be supplied in various current densities for
various time periods to each portion of the cathode of the
electroplating system. Power may be supplied to each portion of the
cathode for multiple time periods at multiple current densities to
achieve desired characteristics of the plated metal. According to
one example, flow of power to the thief portion of the cathode may
be delayed to a point in time after power has been supplied to the
at least one workpiece portion of the cathode.
[0061] Preferably, the characteristics of the current and time
periods are selected to achieve a desired predetermined plating
uniformity. Additionally, preferably, the electroplating is
controlled such that the uniformity of the at least one metal
deposit on the at least one substrate and the thickness of the at
least one metal deposited on the at least one substrate are
decoupled.
[0062] Another method to control the decoupling of the workpiece
and thief or deflector plating times, may be by the use of a
Programmable Logic Controller, or PLC as they are sometimes called.
This configuration could be used in place of the above disclosed
discreet timer controls.
[0063] Any other arrangements, configurations, or physical layouts,
or hardware layouts, software and software controls, or any
combination or combinations thereof, which are used to
independently or separately control the plating times of the
workpiece with respect to the thief, or deflector may also be
utilized according to the present invention. Any configurations of
hardware or software that can be used to mimic or achieve the
independent control of the plating time of the workpiece with
respect to the thief may also be utilized according to the present
invention.
[0064] The foregoing description of the invention illustrates and
describes the present invention. Additionally, the disclosure shows
and describes only the preferred embodiments of the invention, but
as aforementioned it is to be understood that the invention is
capable of use in various other combinations, modifications, and
environments and is capable of changes or modifications within the
scope of the inventive concept as expressed herein, commensurate
with the above teachings, and/or the skill or knowledge of the
relevant art. The embodiments described hereinabove are further
intended to explain best modes known of practicing the invention
and to enable others skilled in the art to utilize the invention in
such, or other, embodiments and with the various modifications
required by the particular applications or uses of the invention.
Accordingly, the description is not intended to limit the invention
to the form disclosed herein. Also, it is intended that the
appended claims be construed to include alternative
embodiments.
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