U.S. patent application number 11/057297 was filed with the patent office on 2005-07-07 for apparatus for avoiding particle accumulation in electrochemical processing.
This patent application is currently assigned to NUTOOL, INC., a Delaware Corporation. Invention is credited to Basol, Bulent M., Talieh, Homayoun, Uzoh, Cyprian.
Application Number | 20050145484 11/057297 |
Document ID | / |
Family ID | 26960342 |
Filed Date | 2005-07-07 |
United States Patent
Application |
20050145484 |
Kind Code |
A1 |
Basol, Bulent M. ; et
al. |
July 7, 2005 |
Apparatus for avoiding particle accumulation in electrochemical
processing
Abstract
Systems and methods to remove or lessen the size of metal
particles that have formed on, and to limit the rate at which metal
particles form or grow on, workpiece surface influencing devices
used during electrodeposition are presented. According to an
exemplary method, the workpiece surface influencing device is
occasionally placed in contact with a conditioning substrate coated
with an inert material, and the bias applied to the
electrodeposition system is reversed. According to another
exemplary method, the workpiece surface influencing device is
conditioned using mechanical contact members, such as brushes, and
conditioning of the workpiece surface influencing device occurs,
for example, through physical brushing of the workpiece surface
influencing device with the brushes. According to a further
exemplary method, the workpiece surface influencing device is
rotated in different direction during electrodeposition.
Inventors: |
Basol, Bulent M.; (Manhattan
Beach, CA) ; Uzoh, Cyprian; (Milpitas, CA) ;
Talieh, Homayoun; (San Jose, CA) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET
FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Assignee: |
NUTOOL, INC., a Delaware
Corporation
|
Family ID: |
26960342 |
Appl. No.: |
11/057297 |
Filed: |
February 10, 2005 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11057297 |
Feb 10, 2005 |
|
|
|
09982558 |
Oct 17, 2001 |
|
|
|
60280524 |
Mar 30, 2001 |
|
|
|
Current U.S.
Class: |
204/247.2 ;
257/E21.175; 257/E21.583; 257/E21.585 |
Current CPC
Class: |
H01L 21/7684 20130101;
H01L 21/76877 20130101; C25D 17/001 20130101; C25D 5/22 20130101;
B24B 37/04 20130101; B24B 53/017 20130101; B24B 53/001 20130101;
H01L 21/2885 20130101 |
Class at
Publication: |
204/247.2 |
International
Class: |
B23H 007/26 |
Claims
What is claimed is:
1. A processing apparatus for electrochemical mechanical processing
of a workpiece using a solution comprising: an electrochemical
mechanical processing system adapted to operate on the workpiece,
the system including an electrode, a holder adapted to hold the
workpiece, a terminal adapted to make electrical contact with the
workpiece, and a workpiece surface influencing device, wherein the
electrochemical mechanical processing system is adapted to operate
upon the workpiece using the solution, with the workpiece surface
influencing device being disposed in proximity to the workpiece for
a period of time during the electrochemical mechanical processing,
the electrochemical mechanical processing also resulting in
accumulation of particles onto the workpiece surface influencing
device; and a system adapted to operate on the workpiece surface
influencing device and thereby result in one of the number of
accumulated particles being reduced and the size of the accumulated
particles being reduced.
2. The apparatus according to claim 1, wherein the system is
attached to the holder and adapted to permit both the conditioning
of the workpiece surface influencing device and the electrochemical
mechanical processing on the workpiece to occur simultaneously.
3. The apparatus according the claim 1, wherein electrochemical
mechanical processing comprises an electrochemical mechanical
deposition process.
4. The apparatus according to claim 1, wherein electrochemical
mechanical processing comprises an electrochemical mechanical
polishing process.
5. The apparatus according to claim 1, wherein the system is
adapted to condition the workpiece surface influencing device by at
least one of electrochemically etching the accumulated particles
and mechanically contacting the accumulated particles.
6. The apparatus according to claim 1, wherein the particles are
conductive particles.
7. The apparatus according to claim 1, wherein the particles are
non-conductive particles.
8. The apparatus according to claim 1, wherein the system includes
a conditioning substrate with a plurality of brushes thereon, the
plurality of brushes adapted to mechanically contact the workpiece
surface influencing device.
9. The apparatus according to claim 8, wherein the conditioning
substrate attaches to the holder upon removal of the workpiece from
the holder.
10. The apparatus according to claim 1, wherein the system includes
a conditioning conductor layer that will not anodize in the
solution, and the conditioning conductor layer is adapted to be
electrically connected to a potential difference that will cause
the one of the number of accumulated particles to be reduced and
the size of the accumulated particles to be reduced.
11. The apparatus according to claim 10, wherein the conditioning
conductor layer attaches to the holder upon removal of the
workpiece from the holder.
12. The apparatus according to claim 1, wherein the system and the
electrochemical mechanical processing system are located within a
lower chamber of a vertically configured chamber system, the
vertically configured chamber system also including an upper
chamber that includes a cleaning system that cleans the workpiece
and a moveable guard adapted to separate the lower chamber from the
upper chamber when the upper chamber is being used.
13. The apparatus according to claim 12, wherein the system
includes a plurality of brushes attached to a conditioning
substrate and a brush movement assembly, the brush movement
assembly configured to move the plurality of brushes over the
workpiece surface influencing device to operate on the workpiece
surface influencing device.
14. The apparatus according to claim 13, wherein the system is
adapted to operate on the workpiece surface influencing device at
the same time the cleaning system is adapted to operate upon the
workpiece.
15. The apparatus according to claim 13, wherein the plurality of
brushes and the conditioning substrate have a conductive coating
that will not anodize in the solution disposed within the lower
chamber, the conditioning substrate adapted to be electrically
connected to a potential difference that will cause the one of the
number of accumulated particles to be reduced and the size of the
accumulated particles to be reduced.
16. The apparatus according to claim 15, wherein the system is
adapted to operate on the workpiece surface influencing device at
the same time the cleaning system is adapted to operate upon the
workpiece.
17. The apparatus according to claim 15, wherein the conductive
coating is comprised of an inert conductor.
18. The apparatus according to claim 12, wherein the system
includes a conditioning conductor layer that will not anodize in
the solution disposed within the lower chamber, the conditioning
conductor layer adapted to be electrically connected to a potential
difference that will cause the one of the number of accumulated
particles to be reduced and the size of the accumulated particles
to be reduced.
19. The apparatus according to claim 18, wherein the conditioning
conductor layer is comprised of an inert conductor.
20. The apparatus according to claim 12, wherein the system is
adapted to operate on the workpiece surface influencing device at
the same time the cleaning system is adapted to operate upon the
workpiece.
21. The apparatus according to claim 1, wherein the electrochemical
mechanical processing system is located within a lower chamber of a
vertically configured chamber system, the vertically configured
chamber system also including an upper chamber and a moveable guard
adapted to separate the lower chamber from the upper chamber when
the upper chamber is being used.
22. The apparatus according to claim 21, further including a
cleaning system that cleans the workpiece disposed in the upper
chamber.
23. The apparatus according to claim 21, wherein the holder is
further adapted to hold the system when the holder is no longer
holding the workpiece.
24. The apparatus according to claim 23, wherein the system
includes a plurality of brushes attached to a conditioning
substrate, the plurality of brushes configured for relative
movement with the workpiece surface influencing device to condition
the workpiece surface influencing device.
25. The apparatus according to claim 24, wherein the plurality of
brushes and the conditioning substrate have a conductive coating
that will not anodize in the solution disposed within the lower
chamber, the conditioning substrate adapted to be electrically
connected to a potential difference that will cause the one of the
number of accumulated particles to be reduced and the size of the
accumulated particles to be reduced.
26. The apparatus according to claim 25, wherein the conductive
coating is comprised of an inert conductor.
27. The apparatus according to claim 26, wherein the system
includes a conditioning conductor layer that will not anodize in
the solution disposed within the lower chamber, the conditioning
conductor layer adapted to be electrically connected to a potential
difference that will cause the one of the number of accumulated
particles to be reduced and the size of the accumulated particles
to be reduced.
28. The apparatus according to claim 27, wherein the conditioning
conductor layer is comprised of an inert conductor.
29. A system for processing a workpiece and removing particles on a
workpiece surface influencing device, the workpiece surface
influencing device being used in conjunction with a plating
solution to process the workpiece, comprising: a holder adapted to
receive the workpiece and to move the workpiece proximate to the
workpiece surface influencing device; an apparatus adapted to
deposit, via the plating solution, conductive material onto the
workpiece using a first potential difference that is applied
between an electrode and the workpiece with the workpiece surface
influencing device in close proximity to the workpiece; and a
member having a conditioning conductor layer adapted to assist in
removing at least a first portion of the particles that accumulate
on the workpiece surface influencing device during the depositing
of the conductive material using a second potential difference that
is applied between the electrode and the conditioning conductor
layer of the member, the second potential difference being of an
opposite polarity to the first potential difference.
30. The system according to claim 29, wherein the member further
comprises a mechanical contact member to mechanically remove at
least a second portion of the particles that accumulate on the
workpiece surface influencing device.
31. The system according to claim 29, wherein the holder is further
adapted to hold the member when the holder is no longer holding the
workpiece.
32. A system for processing a workpiece and removing particles on a
workpiece surface influencing device, the workpiece surface
influencing device being used in conjunction with a plating
solution to process the workpiece, comprising: an apparatus adapted
to deposit, via the plating solution and with the workpiece surface
influencing device in close proximity to the workpiece, conductive
material onto the workpiece in the presence of a first potential
difference that is applied between an electrode and the workpiece;
a holder adapted to receive the workpiece, to move the workpiece in
close proximity to the workpiece surface influencing device so that
the depositing of the conductive material by the apparatus can take
place, and to remove the workpiece from being in close proximity to
the workpiece surface influencing device upon completion of the
depositing by the apparatus; and a member having at least one
mechanical contact member and adapted to move against a top surface
of the workpiece surface influencing device so that at least a
portion of the particles that accumulate on the workpiece surface
influencing device during the depositing of the conductive material
are mechanically removed from the workpiece surface influencing
device.
33. The system according to claim 32, wherein the apparatus is
further adapted to remove at least a second portion of the
particles that accumulate on the workpiece surface influencing
device during the depositing of the conductive material, and the at
least one mechanical contact layer being comprised of an inert
conductor so that the at least one mechanical contact layer
conductor will not anodize in the plating solution.
34. The apparatus according to claim 32, wherein the holder is
further adapted to hold the member when the holder is no longer
holding the workpiece.
35. A system for processing a workpiece and removing particles on a
workpiece surface influencing device, the workpiece surface
influencing device being used in conjunction with a plating
solution to process the workpiece, comprising: a deposition
apparatus positioned in a lower chamber for depositing conductive
material from the plating solution onto the workpiece with the
workpiece surface influencing device in close proximity to the
workpiece; and a member adapted to be positioned in the lower
chamber and to remove at least a portion of the particles that
accumulate on the workpiece surface influencing device during the
depositing of the conductive material by the deposition apparatus;
and a holder adapted to position the workpiece in the lower chamber
while the deposition apparatus is being used.
36. The system according to claim 35, further comprising a cleaning
system disposed in the upper chamber and wherein the upper and
lower chamber are capable of being separated using a moveable
guard.
37. The system according to claim 35, wherein the member is adapted
for relative movement with the workpiece surface influencing device
so that the conductive particles are mechanically removed from the
workpiece surface influencing device.
38. The system according to claim 35, wherein the member is adapted
to apply a potential difference between the member and the
workpiece surface influencing device to assist in removing the
particles from the workpiece surface influencing device.
39. The system according to claim 35, wherein the holder is adapted
to rotate about a first axis.
40. The system according to claim 39, wherein the holder is further
adapted to move side to side within the lower chamber.
41. The system according to claim 35, wherein the deposition
apparatus comprises an electrochemical mechanical deposition
apparatus.
42. The system according to claim 35, wherein the member comprises
a brush member.
43. The system according to claim 42, further comprising a brush
assembly that moves the brush member connected thereto in a lateral
direction and wherein the brush assembly is disposed in the lower
chamber.
44. The apparatus according to claim 43 wherein the member is
adapted to operate on the workpiece surface influencing device at
the same time another system is operating upon the workpiece in the
upper chamber.
45. The system according to claim 44, wherein the brush assembly
comprises a drive apparatus that moves the brush member in the
lateral direction.
Description
PRIOR APPLICATIONS
[0001] This is a divisional application of U.S. application Ser.
No. 09/982,558 filed Oct. 17, 2001 entitled Method and Apparatus
for Avoiding Particle Accumulation in Electrodeposition, which
claims the benefit of priority to U.S. Provisional Application Ser.
No. 60/280,524 filed Mar. 30, 2001.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method and apparatus for
removing particles from surfaces, and avoiding particle
accumulation on surfaces during, electrochemical mechanical
processing.
[0004] 2. Description of the Related Art
[0005] Conventional semiconductor devices generally include a
semiconductor substrate, usually a silicon substrate, and a
plurality of sequentially formed dielectric interlayers such as
silicon dioxide and conductive paths or interconnects made of
conductive materials. The interconnects are usually formed by
filling a conductive material in trenches etched into the
dielectric interlayers. In an integrated circuit, multiple levels
of interconnect networks laterally extend with respect to the
substrate surface. The interconnects formed in different layers can
be electrically connected using vias or contacts. A conductive
material filling process of such features, i.e., via openings,
trenches, pads or contacts can be called out by depositing a
conductive material over the substrate including such features.
[0006] Copper and copper alloys have recently received considerable
attention as interconnect materials because of their superior
electromigration and low resistivity characteristics. The preferred
method of copper deposition is electrodeposition. During
fabrication, copper is deposited on the substrate that has been
previously coated with a barrier layer and then a seed layer. The
barrier layer coats the vias and the trench as well as the surface
of the dielectric layer to ensure good adhesion and acts as a
barrier material to prevent diffusion of the copper into the
semiconductor devices through the dielectric insulation layer.
Typically, seed layer forms a conductive material base for copper
film growth during the subsequent copper deposition. Typical
barrier materials generally include tungsten, tantalum, titanium,
their alloys, and their nitrides. The deposition process can be
carried out using a variety of processes. After depositing copper
into the features on the semiconductor wafer surface, an etching,
an electropolishing (also called electroetching), an
electrochemical mechanical etching (ECME) or a chemical mechanical
polishing (CMP) step may be employed. These processes remove the
conductive materials off the field regions of the surface, thereby
leaving the conductive materials only within vias, trenches and
other features.
[0007] In conventional electrodeposition techniques, copper is
coated on the wafer surface in a conformal manner. As shown in
FIGS. 1-3, when, for example, a dual damascene structure on the
wafer surface is coated with copper using conventional plating, it
yields a rather conformal film. FIGS. 1-3 show three possible
stages in the conventional process. In a first stage shown in FIG.
1, the dual damascene structure 10 with a wide trench 11, a small
via 12 covered with a barrier layer 13 and a copper seed layer 14
is shown. As the copper film is electroplated in a second stage
shown in FIG. 2, the copper 15 quickly fills the small via 12 but
coats the wide trench and the surface in a conformal manner. When
the deposition process is continued, the wide trench is also filled
with copper in a third stage shown in FIG. 3, but with a resulting
large step `S` and a thick surface copper layer `t`. Thick copper
on the surface presents a problem during the material removal step
such as a CMP step, which is expensive and time consuming.
Techniques that can yield thin surface copper overburden and small
or no `S` step are very attractive, which is exemplified in FIG.
4.
[0008] The importance of overcoming the various deficiencies of the
conventional electrodeposition techniques is evidenced by
technological developments directed to the deposition of planar
copper layers. For example, U.S. Pat. No. 6,176,992, entitled
"Method and Apparatus for Electrochemical Mechanical Deposition"
and commonly owned by the assignee of the present invention,
describes in one aspect an electro chemical mechanical deposition
technique (ECMD) that achieves deposition of the conductive
material into the cavities on the substrate surface while
minimizing deposition on the field regions by polishing the field
regions with a pad as the conductive material is deposited, thus
yielding planar copper deposits. In another aspect, this
application describes an electrochemical mechanical etching (ECME)
or electroetching or electropolishing technique that removes
conductive material from the surface of a workpiece.
[0009] U.S. Pat. No. 6,534,116 for "Plating Method and Apparatus
that Creates a Differential Between Additive Disposed on a Top
Surface and a Cavity Surface of a Workpiece Using an External
Influence," also assigned to the same assignee as the present
invention, describes in one aspect another ECMD method and
apparatus for plating a conductive material onto the substrate by
creating an external influence, such as causing relative movement
between a workpiece and a mask, to cause a differential in
additives to exist for a period of time between a top surface and a
cavity surface of a workpiece. While the differential is
maintained, power is applied between an electrode (in this case
anode) and the substrate to cause greater relative plating of the
cavity surface than the top surface.
[0010] These ECMD methods can deposit metals in and over cavity
sections on a workpiece in a planar manner. Some methods even have
the capability to provide deposits with excess metal in and over
the cavities. In such above-mentioned processes, a pad, a mask or a
sweeper, hereinafter collectively referred to as a
workpiece-surface-influencing device (WSID), can be used during at
least a portion of the electrodeposition process when there may be
physical contact between the workpiece surface and the WSID. The
physical contact, polishing, or the external influence affects the
growth of the metal by effectively reducing the growth rate on the
top surface with respect to the features. During the process step
that involves the WSID being in close proximity to, and typically
in contact with, the metal surface, small particles of the metal
may attach onto the WSID material. These particles may exist
because of the fact that they may be just physically removed from
the substrate surface or they may originate from the plating
solution due to poor filtration of the plating solution. In any
case once the conductive metal particles attach themselves to a
location on the WSID, they may start growing in size because they
become cathodic with respect to the electrode. Further, since they
are conductive they receive coating and thus grow in size.
[0011] ECME methods also use a WSID, and during usage of these
methods, the WSID is also in close proximity to, and typically in
contact with, the metal surface of the workpiece. During ECME, the
potential applied between the workpiece surface and the electrode
is reversed rendering the workpiece surface anodic. Therefore,
material is removed from the workpiece surface. If WSID is not used
during this material removal step, i.e. if there is no mechanical
action on the workpiece surface, the process is referred to as just
electrochemical etching or polishing. It should be noted that in
general both ECMD and ECME processes are referred to as
electrochemical mechanical processing (ECMPR) hereinafter, since
both involve electrochemical processes and mechanical action.
[0012] In addition to conductive particles, there are also
non-conductive particles that may accumulate on the WSID material.
The non-conductive particles may originate from other parts of the
system, such as from the plating solution due to the poor
filtration or from the WSID material itself due to the wear and
tear during processing.
[0013] Presence of such particles on or in close proximity of the
surface of the WSID is undesirable because if they become loose and
find their way to the interface between the WSID and the workpiece
surface, they can cause scratches, inclusions, or other defects on
the workpiece surface or they can actually cause scratches on the
surface of the WSID, especially if the WSID has a non-flat surface
profile.
[0014] Therefore, elimination of such particles, or process steps
to limit their growth, are very important to increase process yield
and the lifetime of the WSID used in planar metal deposition
techniques in which particles may come close to or touch the
workpiece surface, and particularly when particles are disposed on
a WSID that touches the workpiece surface.
SUMMARY OF THE INVENTION
[0015] It is an object of the invention to remove or reduce the
size of particles that have formed on pads, masks, sweepers or
WSIDs used during electrochemical mechanical processing
(ECMPR).
[0016] It is another object of the invention to limit the rate at
which conductive particles form or grow on WSID used during
ECMPR.
[0017] It is yet another object of the invention to reduce defects
on the workpiece.
[0018] Certain of the above objects of the invention, among others,
either singly or in combination, are achieved in one embodiment by
occasionally conditioning the WSID used during ECMPR.
[0019] In one embodiment, this involves placing the WSID in the
presence of a conditioning substrate and applying a bias that will
cause removal of, or reduction in the size of, conductive particles
on the WSID.
[0020] In another embodiment, the WSID is conditioned using
mechanical contact members, such as brushes, and conditioning
occurs, for example, through physical brushing of the WSID with the
brushes.
[0021] In another embodiment, conditioning occurs by rotating the
WSIDs used during electrodeposition in different directions, or by
rotating successive substrates or workpieces in different
directions.
[0022] The above and other embodiments can also be combined, as
described in further detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] These and other objects, features and advantages of the
present invention are better understood by reading the following
detailed description of the preferred embodiment, taken in
conjunction with the accompanying drawings, in which:
[0024] FIGS. 1-4 illustrate various process stages during the
plating of a metal on a semiconductor substrate using
electrodeposition techniques;
[0025] FIG. 5 shows various components of an exemplary
electrochemical mechanical processing system;
[0026] FIG. 6 illustrates an exemplary WSID;
[0027] FIG. 7A illustrates the accumulation of particles on an
exemplary WSID that can be operated upon according to the present
invention;
[0028] FIG. 7B illustrates the accumulation of particles on another
exemplary WSID;
[0029] FIG. 7C illustrates the accumulation of particles on yet
another exemplary WSID;
[0030] FIG. 7D shows a cross-sectional view of the WSID shown in
FIG. 7C;
[0031] FIG. 7E shows the accumulation of particles on the surface
of an exemplary WSID;
[0032] FIG. 7F shows the accumulation of particles on a fatigued
surface of an exemplary WSID;
[0033] FIG. 8 illustrates usage of an exemplary conditioning
substrate according to an embodiment of the present invention;
[0034] FIGS. 9-10 illustrate another exemplary embodiment of the
present invention;
[0035] FIG. 11A illustrates an exemplary conditioning member
according to another embodiment of the present invention;
[0036] FIG. 11B illustrates another exemplary embodiment of the
conditioning member shown in FIG. 11A;
[0037] FIG. 12 illustrates usage of the conditioning member of FIG.
11A;
[0038] FIGS. 13-15 illustrate an exemplary mechanical contact
member and the incorporation of the mechanical contact member into
a plating system having a WSID;
[0039] FIGS. 16-18 show an exemplary WSID that can be cleaned or
conditioned with the present invention; and
[0040] FIGS. 19 and 20 illustrate a conditioning substrate
apparatus that can condition a WSID while also performing
electrochemical mechanical processing.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0041] One way of eliminating the growth of conductive, and
typically metallic, or other particles on the workpiece surface
influencing device (WSID) surface is to use a "particle elimination
step" during electrochemical mechanical processing, either
simultaneous with the electrochemical mechanical processing or when
intermittently stopping the electrochemical mechanical processing.
This step involves using a conditioning system, with a conditioning
member that can assist in removing particles. As described
hereinafter, this conditioning member can take the form of a
conditioning substrate with a plurality of brushes that operates
mechanically, a conductive conditioning substrate with conductive
brushes that operates both mechanically and electrically, or a
conditioning conductor layer that operates electrically. Of course,
modifications of these embodiments can also exist. When operating
electrically, as described hereinafter, the conductor used to coat
is preferably an inert material that cannot be anodized or etched
in the plating solution, under a bias, as will be described further
hereinafter.
[0042] Reference will now be made to the drawings wherein like
numerals refer to like parts throughout. FIG. 5 schematically shows
an exemplary electrochemical mechanical processing (ECMPR) system
100 which can be used for ECMD and ECME processes. The system 100
in our example has an electrode 102 and the workpiece 104 and a
WSID portion 106. When used for ECMD, it will include a plating
solution, containing the ionic species of the metal to be
deposited, that touches the electrode 102 and the work piece 104.
An exemplary copper plating solution may be copper sulfate solution
that is commonly used in the industry. The workpiece 104 may be an
exemplary substrate, preferably a silicon wafer portion, to be
plated with a conductor metal, preferably copper. The substrate 104
comprises a front surface 108 to be plated with copper and a bottom
surface 110 to be held by a carrier head (not shown). The front
surface 108 may comprise the features shown in FIG. 1.
[0043] FIG. 6 illustrates in more detail an exemplary WSID portion
106, which may comprise a top surface 112 and a bottom surface 114.
The WSID 106 also comprises an exemplary channel 116 extending
between the top and the bottom surfaces 112, 114 and defined by
sidewall 118 having a first wall 118a and a second wall 118b. The
channel also laterally extends between a closed end 120 and an open
end 122. Although the channel in this example is V-shaped, it is
understood that any shape channel that allows fluid communication
between the wafer and the electrode can be used.
[0044] During an ECMD process, the front surface 108 of substrate
104 is brought into close proximity, or contact with, the top
surface 112 of the WSID 106 for planar metal deposition. As a
plating solution, depicted by arrows 124, is delivered to the
channel 116, the substrate 104 is rotated about a rotation axis 126
while the front surface 108 contacts the top surface 112 of the
WSID 106 or is in close proximity of the top surface 112. For the
purpose of clarification, the rotation axis 126 may be the point at
which the closed end 120 of the channel 116 is located, thereby
ensuring that rotation of the substrate 104 will result in the
entire front surface 108 of the substrate 104 having uniform
contact with the channel 116. As the solution is delivered and
fills the channel 116, it wets the front surface 108 of the
substrate 104. Under an applied potential between the substrate and
the electrode 102, in the presence of the solution 124 that fills
the channel 116, the conductor or metal, such as copper, is plated
on the front surface 108 of the substrate and the front surface 108
of the substrate 104 is also swept by the top surface 112 of the
WSID 106. This sweeping of the top surface 112 of the WSID 106
assists in obtaining planar deposition of the metal. The solution
124, which is continuously delivered under pressure, will then flow
through the channel 116 in the direction of the arrow 128 towards
the open end 122 of the channel 116, and exits the WSID 106.
[0045] It is noted that the above description described rotation
and movement of the substrate 104, assuming that the WSID 106 was
stationary. It is understood that the system 100, as described
above, will allow for either the substrate or the WSID to move, or
for both of them to move, thereby creating the same relative
effect. For ease of description, however, the invention was
described and will continue to be described in terms of movement of
the substrate. Furthermore, the shapes and forms of the channels
may be different. When the system 100 is used for ECME, although
the same plating solution that is used for the ECMD can still be
used, it can be replaced with an electroetching solution or an
electropolishing solution or an etching solution. In the ECME case,
the WSID will typically contact the workpiece as described above,
but the applied potential between the substrate and the electrode
102 will be opposite to that which is used for plating, and will be
of the same polarity as that used when conditioning the WSID with a
conditioning substrate that uses an applied potential, as discussed
hereinafter.
[0046] FIG. 7A exemplifies how the planar plating process through
the channel 116 progresses as the substrate 104 is rotated about
the rotation axis 126 on the WSID 106 as described above. It should
be understood that, for cathodic ECMD, the ionic species in the
solution 124 are positively charged. Therefore, during deposition
the substrate surface 108 upon which deposition is carried out is
rendered cathodic (more negative) with respect to the electrode
102, which becomes the anode. It should be noted that the electrode
may be an inert electrode (such as Pt, graphite or Pt-coated Ti
etc.) or it may be made of the same metal that is being deposited
onto the substrate surface 108 (consumable electrode). When a
cathodic voltage is applied to the substrate surface 108 metal
deposits out of the plating solution 126 onto the substrate surface
108. However, as mentioned above, as the process progresses,
particles 130 may form on the sidewalls 118 of the channel 116. In
the process of the present invention, the above ECMD process may be
repeated coating metal on certain number of substrate surfaces
until the metal particle growth on the WSID becomes a problem. The
rate at which particle growth occurs depends upon many factors, in
particular how the plating is performed and the applied voltage
used during plating in particular. Generally, however, after
processing 10-100 wafers or typically after processing 20-50
wafers, undesired particles may start becoming a problem.
Similarly, in an ECME process, particles can also attach to the
WSID and become a problem. As previously mentioned, presence of
such particles on or in close proximity of the surface of the WSID
is undesirable because if they become loose and find their way to
the WSID/substrate surface interface, they can cause scratches,
inclusions, or other defects on the surface or they can actually
cause scratches on the surface of the WSID, especially if the WSID
has a non-flat profile. For example, when such particles grow
beyond 0.5 micron size, it is advantageous to remove them or at
least reduce their size using the teachings of the present
invention.
[0047] It should be understood that ECMD, ECME, and other processes
can occur in succession, and that any number of such processes can
occur, with a conditioning step occurring thereafter, and then any
number of such processes can occur again. For example, an ECMD
process, followed by an ECME process, followed by an ECMD process
is typical. It may then be desirable to perform conditioning of the
WSID according to the present invention, and then resume with some
number of processes, for instance another set of ECMD, ECME, and
ECMD processes. Alternately, conditioning may be done after the
ECMD process before the ECME process, etc.
[0048] As mentioned above, channels in a WSID may have different
shapes and sizes. FIG. 7B exemplifies a WSID 500 having channels
502 that are shaped as slits, preferably substantially parallel
slits, and a top surface 503 or a sweeping surface. Channels 502
may have side walls 504. Channels allow an electrolyte, or another
solution to flow between an electrode (not shown) and a front
surface of a wafer 506 (shown in dotted lines) which may be rotated
and also moved in lateral direction. In this example the top
surface 503 of the WSID performs the sweeping action. As the ECMD
or ECME process progresses, particles 508 may get attached on the
side walls 504. However, as can be seen in FIG. 7C in top view and
in FIG. 7D in cross sectional view, a WSID 500A may have a raised
surface 510 which is smaller in comparison to the top surface 503A
of the WSID 500A. In this embodiment the sweeping function is
performed by the raised surface 510. As in the previous case, as
the ECMPR progresses, particles 508 may get attached on side walls
512 of the raised surfaces 510. As will be described more fully
below, such undesired particles are removed using the teachings of
the present invention.
[0049] In the above examples, channel and raised surface side-walls
are described as the main particle growth or presence sites.
However, such unwanted particle may be on other locations of a WSID
for example on the top surface of a WSID. FIG. 7E shows a WSID
portion 600. A top surface 602 of the WSID 600 may have various
surface features 604 that may enhance mechanical sweeping of a
wafer surface (not shown). Features 604 may comprise abrasive
particles. As shown in FIG. 7E, particles may get attached or in
some cases grow over various locations on the surface features as
well, and the particles should be removed using the teachings of
the present invention. As shown in FIG. 7F, during the process,
portions 608 of the top surface 602 of the WSID may be fatigued and
break loose, forming the particles 606, and damage a wafer
surface.
[0050] Therefore, a cleaning process according to the teachings of
the present invention not only cleans such fatigued portions 608
after they are broken off the surface but also removes them safely
once they are weakly attached to the top surface before they are
broken off.
[0051] To that effect, in one embodiment, a conditioning substrate
132, shown in FIG. 8, is coated with a conditioning conductor layer
134 and is substituted in place of the substrate 104. This
embodiment of the conditioning substrate 132 may perform the
electrochemical cleaning of the WSID 106 to remove conductive
particles. As will be described below an alternative embodiment of
the conditioning substrate may have mechanical contact members so
as to mechanically sweep the WSID 106 (see FIG. 11A) and remove
both conductive and non-conductive particles. As will be described
below mechanical contact members may mechanically dislodge the
particles from the locations where they are accumulated. The
surface 136 of the conditioning conductor layer 134 in FIG. 8 is
rendered anodic or more positive compared to the electrode 102 and
an anodic current density of, for example 0.1-100 mA/cm2 and
typically in the range of 1-20 mA/cm2 is applied. This anodic
current may be passed for a period of time sufficient to reduce or
eliminate such particles. This time period may typically be in the
range of 2-10 seconds. The conditioning conductor is a material
that does not get, or at least does not substantially get, anodized
or etched or otherwise change its character in the plating solution
under anodic conditions. It should also not shed any particles. It
should, therefore, be preferably made of a hard coating. Inert
nitrides of titanium (Ti), tungsten (W) and tantalum (Ta), or
platinum (Pt) or Pt-containing alloys, or iridium (Ir) or
Ir-containing alloys are good examples of such conditioning
conductors for metal deposition processes that deposit common
metals or metal alloys containing Cu, Ni, Co or the like. It is
noted that this conditioning conductor does not need to have very
low resistance like copper. A sheet resistance of 0.1-10 ohms per
square is adequate although lower resistances can also be used. In
this respect, the conditioning substrate 132 may be a semiconductor
wafer coated with the conditioning conductor layer 134. When an
anodic voltage is applied to the conditioning conductor layer 134
on the conditioning substrate 132, the metal particles on or near
proximity of the WSID 106 also become anodic with respect to the
electrode 102. Preferably, during this process, the surface of the
conditioning conductor layer makes physical contact to the surface
of the WSID. As described above, the conditioning conductor layer
134 on the conditioning substrate 132 does not become substantially
affected by the anodic voltage, however, the metal particles 130
become anodized and etched into the plating solution 124. This
etching process either causes the particles 130 to completely
dissolve into the solution 124 or to become smaller in size, and
thereby typically loosen from the sites on which they are located,
such as side walls 118 to which they attach themselves, so that the
flowing plating solution 124 can wash them out.
[0052] In another embodiment, a conditioning member may be used to
mechanically dislodge particles of both natures, conductive or
nonconductive. As shown in FIG. 11A, a conditioning member 200 is a
plate, preferably disk shaped, having a front surface 202 and a
back surface 204. The front surface 202 may have mechanical contact
members 206 to mechanically clean the WSID 106. The mechanical
contact members 206 may be brushes, wipers or the like. In this
embodiment, two lines of brushes 206 are attached on the front
surface 202 in a near-perpendicular array so that they cross each
other at the center of the front surface 202. As shown in FIG. 11B,
in another embodiment, a conditioning member 200A has a front
surface 202A and a back surface 204A. In this embodiment, the front
surface may comprise a plurality of mechanical contact members 206A
that are distributed across the front surface 202A of the
conditioning member 200A. Other brush variations can also be used
effectively.
[0053] Brushes 206 and the conditioning member 200 may be made of a
conductive material or an insulator, depending upon whether
conditioning that requires them to conduct is required, as
explained herein. When the WSID needs to be cleaned, the
conditioning member is placed on the wafer carrier, workpiece
holder, or carrier head, and the conditioning member is lowered
onto the WSID while being rotated or otherwise moved. As shown in
FIG. 12, in operation, the mechanical action between the brushes
206 and the particles 130 dislodges the particles, whether
conductive or non conductive, from the sites where they are
located, such as side walls 118. The plating solution flow is
preferably kept on during this process to wash away any particles
that may be dislodged. Although the conditioning member 200 can be
used to mechanically clean the WSID, it can also be used for
electrochemical cleaning as in the first embodiment above. In this
case the conditioning member and the brushes 206 must be made of
conductive materials or they must be coated with conductors that
would not be anodized in the plating solution. An electrical
contact 208 is slidably or otherwise connected to an edge portion
of the back surface 204 so that an anodic potential can be applied
to the conditioning member. Contact may also be made right at the
edge or on the front surface. During the process, application of
the potential allows conductive particles, which contact the
conductive brushes, to be dissolved selectively electrochemically,
while the mechanical action of the brushes removes both the
conductive and non-conductive particles mechanically.
[0054] In the above embodiments, when a work piece is subsequently
processed using the plating solution 124, particles do not present
a threat to the integrity of the film because the surface of the
WSID is substantially free of particles. If copper is being
deposited, for example, without the use of the conditioning
process, particles can grow to more than 10 microns in size after
running more than 20-50 wafers with WSID touching, with the
location of these particles being concentrated along the edges of
the channels. Particle size and the growth rate may vary depending
on the charge used per substrate and the duration of the process
per wafer. In general, a conditioning process may be carried out
after processing some number of wafers, such as 10 to 50 wafers,
although it is understood that the number of wafers to be processed
prior to using the conditioning system requires a balance between
the desired throughput and the concentration of undesired particles
that can be tolerated.
[0055] In another embodiment of the present invention, elimination
of particle accumulation and growth, or at least a reduction in the
formation and/or growth of such particles, along the channels of
the WSID 106 is achieved by controlling the rotation direction of a
substrate or a wafer in the process from run to run. As shown in
FIG. 9, in this embodiment, a first substrate 136 or a wafer is
first rotated in a first direction 138 during the processing of the
first substrate 136. As shown in FIG. 10, during the processing of
a second substrate 140 or a wafer, the substrate 140 is rotated in
a second direction 142 that is directly opposite to the first
direction 138. This way, the particles 130, conductive or
non-conductive, which may start to accumulate along the first
sidewall 118a of the channel 116 will loosen and be pushed into the
channels during the processing cycle of the second substrate 140
without giving them chance to grow and deleteriously affect the
quality of the coating on the substrates. This method has
particular application to ECMD, although it can also be used with
ECME.
[0056] The embodiments described above can also be used together to
further reduce the presence of undesired particles.
[0057] As previously mentioned, the WSID may have different channel
configurations and shapes. As shown in FIGS. 13, 14 and 15, in
another embodiment, a conditioning device 249 comprising a brush
member 250 may be incorporated into an electrochemical mechanical
processing (ECMPR) system 300 having a WSID 400.
[0058] FIGS. 16-18 show an exemplary WSID 400 that can be cleaned
or conditioned with the present invention, although any shape WSID,
such as the one shown in FIG. 7B or 7C, may be used as suitable.
The WSID comprises a channel system 402 comprising recessed channel
regions 404 and raised sweeping or polishing regions 406. The
channel system 402 may preferably be comprised of more than one
channel, such as a first channel 408 and a second channel 410, and
more than one polishing region 406. Each channel 408, 410 is
comprised of a closed end 412 and an open end 414. Closed ends 412
form a center of the WSID 400. The open ends 414 may also be shaped
in other ways without adversely affecting the unique nature of the
invention. Preferably, raised polishing regions 406 are comprised
of a top surface 416 and a side wall 418. The side wall 418
elevates the top surface from a surface 420 of the recessed region
404. The top surfaces of the raised polishing regions are
preferably formed in a coplanar fashion. The top surfaces 416,
which may be abrasive, sweeps the wafer surface during the
processing, whether that is ECMD or ECME. The top surface may be
textured such as shown in FIG. 7E. A number of holes 422 extend
between a bottom surface of the WSID 400 and the recessed regions.
Holes 422 within the channel regions are formed with a shape so
that the inner and outer walls of the holes 422 correspond to the
arc at a given radius from the center of the WSID, and are
progressively smaller in size as they get closer to the center of
the WSID, and are distributed on opposite sides from the center of
the WSID in a staggered manner (hole lines up with space as shown)
to ensure that the entire wafer will receive a uniform application
of electrolyte.
[0059] Referring back to FIG. 14, the system 300 comprises a lower
chamber 302, an upper chamber 304 and a carrier head 305 holding
the wafer. The lower chamber 302 is comprised of a chamber that
includes an electro chemical mechanical processing (ECMPR) unit
306. The ECMPR unit 306 comprises an electrode 308 and a WSID 400.
As mentioned before, during processing, an electrolyte solution 312
contacts the electrode 308 and flows onto and through the WSID 400.
Description of aspects of one such system can be found in U.S. Pat.
No. 6,532,623 entitled "A Vertically Configured Chamber Used For
Multiple Processes" which is commonly owned by the assignee of the
present invention The conditioning device is also incorporated in
the ECMPR unit 306. The upper chamber 304 is separated from the
lower chamber 302 by movable guards or flaps 314. In this
embodiment, the wafer is loaded in the upper chamber 304 and
lowered into the lower chamber 302 for ECMPR. Once the ECMPR is
over, the carrier head retaining the wafer is raised into the upper
chamber 304 and the flaps 314 are closed. While the wafer is rinsed
and dried in the upper chamber 304, the WSID is conditioned in the
lower chamber 302 using a brush member 250.
[0060] Also referring to FIG. 14, the brush member 250 may be moved
on the WSID 400 by a brush assembly 324 which enables the brush
member 250 to move between a first end 326 of the WSID and a second
end of the WSID 328, in the directions of arrows A and B. The brush
assembly is also a part of the conditioning device. The lateral
movement of the brush member on the WSID surface mechanically
cleans the surface from the conductive and non-conductive
particles. The first position is home position of the brush member
250, where the brush member is held when the conditioning process
is over. Although the brush member 250 can be used to mechanically
clean the WSID, it can also be used for electrochemical cleaning as
in one embodiment above. In this case the brush member 250 must be
made of conductive materials or it must be coated with conductors
that would not be anodized in the plating solution. An electrical
contact (not shown) may be connected to the brush member 250 so
that an anodic potential can be applied to it. During the process,
application of the potential allows conductive particles, which
contact the conductive brushes, to be dissolved selectively
electrochemically, while the mechanical action of the brushes
removes both the conductive and non-conductive particles
mechanically
[0061] As shown in FIG. 15, the brush member 250 is mechanically
connected by connectors 330 to the belts 331 of the brush assembly
324. A driving motor 332 moves the belts 331 simultaneously along
the side of the processing unit 306. The motor 332 moves the belts
331, the connectors 330, and hence the brush member 250 connected
to them in the direction of arrows A and B. Belts 324 are connected
to the motor 332 through a shaft 334 and wheels 336. As mentioned
above, the lower chamber 302 is separated from the upper chamber
304 by movable flaps 314. The upper surface of the flaps 314
comprises cleaning and rinsing fluid nozzles 316. In this
embodiment, the cleaning and rinsing is performed in the upper
chamber 304 while the cleaning and rinsing solution is delivered to
the wafer surface through the nozzles 316. Used solution leaves the
system through a drain opening 320. During the process the
substrate carrier or carrier head 305 is rotated. Once the ECMPR
process is over, the wafer is rinsed and dried in the upper chamber
304 while the WSID is conditioned at the lower chamber 302. During
the WSID conditioning, the brush assembly is brought into the
operational position and moved across the WSID to sweep the WSID
surface. As shown in FIG. 15, upon completion of the process, the
brush assembly is moved back into its home position. Although a
specific design is disclosed in FIG. 15, it should be understood
that many different mechanisms can be used to move the brush
members over the WSID to practice the conditioning invention
disclosed here.
[0062] FIGS. 19 and 20 illustrate a side view of yet another
conditioning apparatus 700 that includes a carrier head 702 with
brushes 704, and a bottom view of the conditioning apparatus 700.
As illustrated, the brushes 704 are disposed around the periphery
of the carrier head 702. The brushes 704 provide for conditioning
of the WSID 706 through mechanical movement, in the same manner as
has been discussed previously. In this embodiment, however, ECMPR
of the workpiece 708, whether ECMD or ECME, and conditioning of the
WSID 706 can occur at the same time, during the same process. In
this particular situation, in order to condition the entire WSID
706, the lateral movement the WSID 706 should preferably be equal
or greater than the radius of the carrier head 702 so that the WSID
portion it covers can effectively be cleaned.
[0063] While the present invention has been described herein with
reference to particular embodiments thereof, a latitude of
modification, various changes and substitutions are intended in the
foregoing disclosure. It will thus be appreciated that in some
instances some features of the invention will be employed without a
corresponding use of other features without departing from the
spirit and scope of the invention.
* * * * *