U.S. patent application number 11/404591 was filed with the patent office on 2006-08-31 for methods and apparatus for removing conductive material from a microelectronic substrate.
This patent application is currently assigned to Micron Technology, Inc.. Invention is credited to Scott E. Moore.
Application Number | 20060191800 11/404591 |
Document ID | / |
Family ID | 24614195 |
Filed Date | 2006-08-31 |
United States Patent
Application |
20060191800 |
Kind Code |
A1 |
Moore; Scott E. |
August 31, 2006 |
Methods and apparatus for removing conductive material from a
microelectronic substrate
Abstract
A method and apparatus for removing conductive material from a
microelectronic substrate. In one embodiment, a support member
supports a microelectronic substrate relative to first and second
electrodes, which are spaced apart from each other and spaced apart
from the microelectronic substrate. One or more electrolytes are
disposed between the electrodes and the microelectronic substrate
to electrically link the electrodes to the microelectronic
substrate. The electrodes are then coupled to a source of varying
current that electrically removes the conductive material from the
substrate. The microelectronic substrate and/or the electrodes can
be moved relative to each other to position the electrodes relative
to a selected portion of the microelectronic substrate, and the
electrodes can be integrated with a planarizing portion of the
apparatus to remove material from the conductive layer by
chemical-mechanical planarization.
Inventors: |
Moore; Scott E.; (Meridian,
ID) |
Correspondence
Address: |
PERKINS COIE LLP;PATENT-SEA
PO BOX 1247
SEATTLE
WA
98111-1247
US
|
Assignee: |
Micron Technology, Inc.
Boise
ID
|
Family ID: |
24614195 |
Appl. No.: |
11/404591 |
Filed: |
April 14, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09651779 |
Aug 30, 2000 |
7074113 |
|
|
11404591 |
Apr 14, 2006 |
|
|
|
Current U.S.
Class: |
205/674 |
Current CPC
Class: |
B23H 5/08 20130101 |
Class at
Publication: |
205/674 |
International
Class: |
B23H 3/00 20060101
B23H003/00 |
Claims
1-32. (canceled)
33. A method for removing an electrically conductive material from
a microelectronic substrate, comprising: positioning a first
conductive electrode proximate to the conductive material of the
microelectronic substrate; positioning a second conductive
electrode proximate to the conductive material of the
microelectronic substrate and spaced apart from the first
conductive electrode; disposing a first electrolyte adjacent to at
least one of the first and second electrodes; disposing a second
electrolyte different than the first electrolyte adjacent to the
conductive material of the microelectronic substrate; at least
restricting motion of the second electrolyte toward the one
electrode; and removing the conductive material from the
microelectronic substrate by passing a varying current through the
first and second electrodes while the first and second electrodes
are spaced apart from the conductive material of the
microelectronic substrate.
34. The method of claim 33 wherein at least restricting motion of
the second electrolyte includes disposing a permeable membrane
between the one electrode and the microelectronic substrate and
passing the first electrolyte through the membrane.
35. The method of claim 33, further comprising selecting the first
electrolyte to include sodium chloride, potassium chloride, and/or
or copper sulfate.
36. The method of claim 33, further comprising selecting the second
electrolyte to include hydrochloric acid.
37-81. (canceled)
Description
TECHNICAL FIELD
[0001] This invention relates to methods and apparatuses for
removing conductive material from microelectronic substrates.
BACKGROUND OF THE INVENTION
[0002] Microelectronic substrates and substrate assemblies
typically include a semiconductor material having features, such as
memory cells, that are linked with conductive lines. The conductive
lines can be formed by first forming trenches or other recesses in
the semiconductor material, and then overlaying a conductive
material (such as a metal) in the trenches. The conductive material
is then selectively removed to leave conductive lines extending
from one feature in the semiconductor material to another.
[0003] Electrolytic techniques have been used to both deposit and
remove metallic layers from semiconductor substrates. For example,
an alternating current can be applied to a conductive layer via an
intermediate electrolyte to remove portions of the layer. In one
arrangement, shown in FIG. 1, a conventional apparatus 60 includes
a first electrode 20a and a second electrode 20b coupled to a
current source 21. The first electrode 20a is attached directly to
a metallic layer 11 of a semiconductor substrate 10 and the second
electrode 20b is at least partially immersed in a liquid
electrolyte 31 disposed on the surface of the metallic layer 11 by
moving the second electrode downwardly until it contacts the
electrolyte 31. A barrier 22 protects the first electrode 20a from
direct contact with the electrolyte 31. The current source 21
applies alternating current to the substrate 10 via the electrodes
20a and 20b and the electrolyte 31 to remove conductive material
from the conductive layer 11. The alternating current signal can
have a variety of wave forms, such as those disclosed by
Frankenthal et al. in a publication entitled, "Electroetching of
Platinum in the Titanium-Platinum-Gold Metallization on Silicon
Integrated Circuits" (Bell Laboratories), incorporated herein in
its entirety by reference.
[0004] One drawback with the arrangement shown in FIG. 1 is that it
may not be possible to remove material from the conductive layer 11
in the region where the first electrode 20a is attached because the
barrier 22 prevents the electrolyte 31 from contacting the
substrate 10 in this region. Alternatively, if the first electrode
20a contacts the electrolyte in this region, the electrolytic
process can degrade the first electrode 20a. Still a further
drawback is that the electrolytic process may not uniformly remove
material from the substrate 10. For example, "islands" of residual
conductive material having no direct electrical connection to the
first electrode 20a may develop in the conductive layer 11. The
residual conductive material can interfere with the formation
and/or operation of the conductive lines, and it may be difficult
or impossible to remove with the electrolytic process unless the
first electrode 20a is repositioned to be coupled to such
"islands."
[0005] One approach to addressing some of the foregoing drawbacks
is to attach a plurality of first electrodes 20a around the
periphery of the substrate 10 to increase the uniformity with which
the conductive material is removed. However, islands of conductive
material may still remain despite the additional first electrodes
20a. Another approach is to form the electrodes 20a and 20b from an
inert material, such as carbon, and remove the barrier 22 to
increase the area of the conductive layer 11 in contact with the
electrolyte 31. However, such inert electrodes may not be as
effective as more reactive electrodes at removing the conductive
material, and the inert electrodes may still leave residual
conductive material on the substrate 10.
[0006] FIG. 2 shows still another approach to addressing some of
the foregoing drawbacks in which two substrates 10 are partially
immersed in a vessel 30 containing the electrolyte 31. The first
electrode 20a is attached to one substrate 10 and the second
electrode 20b is attached to the other substrate 10. An advantage
of this approach is that the electrodes 20a and 20b do not contact
the electrolyte. However, islands of conductive material may still
remain after the electrolytic process is complete, and it may be
difficult to remove conductive material from the points at which
the electrodes 20a and 20b are attached to the substrates 10.
SUMMARY
[0007] The present invention is directed toward methods and
apparatuses for removing conductive materials from microelectronic
substrates. A method in accordance with one aspect of the invention
includes positioning a first conductive electrode proximate to the
microelectronic substrate and positioning a second conductive
electrode proximate to the microelectronic substrate and spaced
apart from the first conductive electrode. The method further
includes removing the conductive material from the microelectronic
substrate by applying a varying current to at least one of the
first and second electrodes while the first and second electrodes
are spaced apart from the conductive material of the
microelectronic substrate.
[0008] In a further aspect of the invention, the method can include
disposing a dielectric layer between the microelectronic substrate
and the first electrode and/or varying an amplitude of the current
at a first frequency while superimposing on the first frequency an
amplitude and/or polarity variation having a second frequency less
than the first frequency. The rate at which conductive material is
removed from the microelectronic substrate can be controlled by
controlling a distance between at least one of the electrodes and
the microelectronic substrate. The microelectronic substrate and/or
the electrodes can be moved relative to each other to position the
electrode at a selected position relative to the microelectronic
substrate. In yet another aspect of the invention, a first
electrolyte adjacent to the electrodes can be separated from a
second electrolyte adjacent to the microelectronic substrate while
maintaining an electrical connection between the electrolytes.
[0009] The invention is also directed toward an apparatus for
removing conductive material from a microelectronic substrate. The
apparatus can include a support member having at least one engaging
surface to support the microelectronic substrate, and first and
second electrodes. The first and second electrodes are spaced apart
from the support member and the microelectronic substrate when the
microelectronic substrate is supported by the support member, and
at least one of the first and second electrodes is coupleable to a
source of varying current. The electrodes can have a planform shape
that corresponds to a planform shape of a portion of the
microelectronic substrates and they can be arranged in pairs with
the pairs distributed to control the distance between the
electrodes and the microelectronic substrate. The apparatus can
further include a sensor positioned at least proximate to the
support member to detect the rate at which the conductive material
is removed from the microelectronic substrate and/or the amount of
conductive material remaining on the microelectronic substrate. In
still a further aspect of this embodiment, a polishing pad can be
positioned proximate to the support member and can include a
polishing surface for removing material from the microelectronic
substrate by chemical and/or chemical-mechanical planarization as
the polishing pad and/or the microelectronic substrate move
relative to each other.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a partially schematic, side elevational view of an
apparatus for removing conductive material from a semiconductor
substrate in accordance with the prior art.
[0011] FIG. 2 is a partially schematic side, elevational view of
another apparatus for removing conductive material from two
semiconductor substrates in accordance with the prior art.
[0012] FIG. 3 is a partially schematic, side elevational view of an
apparatus having a support member and a pair of electrodes for
removing conductive material from a microelectronic substrate in
accordance with an embodiment of the invention.
[0013] FIG. 4 is a partially schematic, side elevational view of an
apparatus for removing conductive material and sensing
characteristics of the microelectronic substrate from which the
material is removed in accordance with another embodiment of the
invention.
[0014] FIG. 5 is a partially schematic, side elevational view of an
apparatus that includes two electrolytes in accordance with still
another embodiment of the invention.
[0015] FIG. 6 is a partially schematic, plan view of a substrate
adjacent to a plurality of electrodes in accordance with still
further embodiments of the invention.
[0016] FIG. 7 is a cross-sectional, side elevational view of an
electrode and a substrate in accordance with yet another embodiment
of the invention.
[0017] FIG. 8A is a partially schematic, isometric view of a
portion of a support for housing electrode pairs in accordance with
still another embodiment of the invention.
[0018] FIGS. 8B-8C are isometric views of electrodes in accordance
with still further embodiments of the invention.
[0019] FIG. 9 is a partially schematic, side elevational view of an
apparatus for both planarizing and electrolytically processing
microelectronic substrates in accordance with yet another
embodiment of the invention.
[0020] FIG. 10 is a partially schematic, partially exploded
isometric view of a planarizing pad and a plurality of electrodes
in accordance with still another embodiment of the invention.
[0021] FIG. 11 is a partially schematic, side elevational view of
an apparatus for both planarizing and electrolytically processing
microelectronic substrates in accordance with still another
embodiment of the invention.
[0022] FIGS. 12A-B schematically illustrate a circuit and wave form
for electrolytically processing a microelectronic substrate in
accordance with yet another embodiment of the invention.
DETAILED DESCRIPTION
[0023] The present disclosure describes methods and apparatuses for
removing conductive materials from a microelectronic substrate
and/or substrate assembly used in the fabrication of
microelectronic devices. Many specific details of certain
embodiments of the invention are set forth in the following
description and in FIGS. 3-12B to provide a thorough understanding
of these embodiments. One skilled in the art, however, will
understand that the present invention may have additional
embodiments, or that the invention may be practiced without several
of the details described below.
[0024] FIG. 3 is a partially schematic, side elevational view of an
apparatus 160 for removing conductive material from a
microelectronic substrate or substrate assembly 110 in accordance
with an embodiment of the invention. In one aspect of this
embodiment, the apparatus 160 includes a vessel 130 containing an
electrolyte 131, which can be in a liquid or a gel state. A support
member 140 supports the microelectronic substrate 110 relative to
the vessel 130 so that a conductive layer 111 of the substrate 110
contacts the electrolyte 131. The conductive layer 111 can include
metals such as platinum, tungsten, tantalum, gold, copper, or other
conductive materials. In another aspect of this embodiment, the
support member 140 is coupled to a substrate drive unit 141 that
moves the support member 140 and the substrate 110 relative to the
vessel 130. For example, the substrate drive unit 141 can translate
the support member 140 (as indicated by arrow "A") and/or rotate
the support member 140 (as indicated by arrow "B").
[0025] The apparatus 160 can further include a first electrode 120a
and a second electrode 120b (referred to collectively as electrodes
120) supported relative to the microelectronic substrate 110 by a
support member 124. In one aspect of this embodiment, the support
arm 124 is coupled to an electrode drive unit 123 for moving the
electrodes 120 relative to the microelectronic substrate 110. For
example, the electrode drive unit 123 can move the electrodes
toward and away from the conductive layer 111 of the
microelectronic substrate 110, (as indicated by arrow "C"), and/or
transversely (as indicated by arrow "D") in a plane generally
parallel to the conductive layer 111. Alternatively, the electrode
drive unit 123 can move the electrodes in other fashions, or the
electrode drive unit 123 can be eliminated when the substrate drive
unit 141 provides sufficient relative motion between the substrate
110 and the electrodes 120.
[0026] In either embodiment described above with reference to FIG.
3, the electrodes 120 are coupled to a current source 121 with
leads 128 for supplying electrical current to the electrolyte 131
and the conductive layer 111. In operation, the current source 121
supplies an alternating current (single phase or multiphase) to the
electrodes 120. The current passes through the electrolyte 131 and
reacts electrochemically with the conductive layer 111 to remove
material (for example, atoms or groups of atoms) from the
conductive layer 111. The electrodes 120 and/or the substrate 110
can be moved relative to each other to remove material from
selected portions of the conductive layer 111, or from the entire
conductive layer 111.
[0027] In one aspect of an embodiment of the apparatus 160 shown in
FIG. 3, a distance D.sub.1 between the electrodes 120 and the
conductive layer 111 is set to be smaller than a distance D.sub.2
between the first electrode 120a and the second electrode 120b.
Furthermore, the electrolyte 131 generally has a higher resistance
than the conductive layer 111. Accordingly, the alternating current
follows the path of least resistance from the first electrode 120a,
through the electrolyte 131 to the conductive layer 111 and back
through the electrolyte 131 to the second electrode 120b, rather
than from the first electrode 120a directly through the electrolyte
131 to the second electrode 120b. Alternatively, a low dielectric
material (not shown) can be positioned between the first electrode
120a and the second electrode 120b to decouple direct electrical
communication between the electrodes 120 that does not first pass
through the conductive layer 111.
[0028] One feature of an embodiment of the apparatus 160 shown in
FIG. 3 is that the electrodes 120 do not contact the conductive
layer 111 of the substrate 110. An advantage of this arrangement is
that it can eliminate the residual conductive material resulting
from a direct electrical connection between the electrodes 120 and
the conductive layer 111, described above with reference to FIGS. 1
and 2. For example, the apparatus 160 can eliminate residual
conductive material adjacent to the contact region between the
electrodes and the conductive layer because the electrodes 120 do
not contact the conductive layer 111.
[0029] Another feature of an embodiment of the apparatus 160
described above with reference to FIG. 3 is that the substrate 110
and/or the electrodes 120 can move relative to is the other to
position the electrodes 120 at any point adjacent to the conductive
layer 111. An advantage of this arrangement is that the electrodes
120 can be sequentially positioned adjacent to every portion of the
conductive layer to remove material from the entire conductive
layer 111. Alternatively, when it is desired to remove only
selected portions of the conductive layer 111, the electrodes 120
can be moved to those selected portions, leaving the remaining
portions of the conductive layer 111 intact.
[0030] FIG. 4 is a partially schematic, side elevational view of an
apparatus 260 that includes a support member 240 positioned to
support the substrate 110 in accordance with another embodiment of
the invention. In one aspect of this embodiment, the support member
240 supports the substrate 110 with the conductive layer 111 facing
upwardly. A substrate drive unit 241 can move the support member
240 and the substrate 110, as described above with reference to
FIG. 3. First and second electrodes 220a and 220b are positioned
above the conductive layer 111 and are coupled to a current source
221. A support member 224 supports the electrodes 220 relative to
the substrate 110 and is coupled to an electrode drive unit 223 to
move the electrodes 220 over the surface of the support conductive
layer 111 in a manner generally similar to that described above
with reference to FIG. 3. In one aspect of the embodiment shown in
FIG. 4, the apparatus 260 further includes an electrolyte vessel
230 having a supply conduit 237 with an aperture 238 positioned
proximate to the electrodes 220. Accordingly, an electrolyte 231
can be deposited locally in an interface region 239 between the
electrodes 220 and the conductive layer 111, without necessarily
covering the entire conductive layer 111. The electrolyte 231 and
the conductive material removed from the conductive layer 111 flow
over the substrate 110 and collect in an electrolyte receptacle
232. The mixture of electrolyte 231 and conductive material can
flow to a reclaimer 233 that removes most of the conductive
material from the electrolyte 231. A filter 234 positioned
downstream of the reclaimer 233 provides additional filtration of
the electrolyte 231 and a pump 235 returns the reconditioned
electrolyte 231 to the electrolyte vessel 230 via a return line
236.
[0031] In another aspect of the embodiment shown in FIG. 4, the
apparatus 260 can include a sensor assembly 250 having a sensor 251
positioned proximate to the conductive layer 111, and a sensor
control unit 252 coupled to the sensor 251 for processing signals
generated by the sensor 251. The control unit 252 can also move the
sensor 251 relative to the substrate 110. In a further aspect of
this embodiment, the sensor assembly 250 can be coupled via a
feedback path 253 to the electrode drive unit 223 and/or the
substrate drive unit 241. Accordingly, the sensor 251 can determine
which areas of the conductive layer 111 require additional material
removal and can move the electrodes 220 and/or the substrate 110
relative to each other to position the electrodes 220 over those
areas. Alternatively, (for example, when the removal process is
highly repeatable), the electrodes 220 and/or the substrate 110 can
move relative to each other according to a pre-determined motion
schedule.
[0032] The sensor 251 and the sensor control unit 252 can have any
of a number of suitable configurations. For example, in one
embodiment, the sensor 251 can be an optical sensor that detects
removal of the conductive layer 111 by detecting a change in the
intensity, wavelength or phase shift of the light reflected from
the substrate 110 when the conductive material is removed.
Alternatively, the sensor 251 can emit and detect reflections of
radiation having other wavelengths, for example, x-ray radiation.
In still another embodiment, the sensor 251 can measure a change in
resistance or capacitance of the conductive layer 111 between two
selected points. In a further aspect of this embodiment, one or
both of the electrodes 220 can perform the function of the sensor
251 (as well as the material removal function described above),
eliminating the need for a separate sensor 251. In still further
embodiments, the sensor 251 can detect a change in the voltage
and/or current drawn from the current supply 221 as the conductive
layer 111 is removed.
[0033] In any of the embodiments described above with reference to
FIG. 4, the sensor 251 can be positioned apart from the electrolyte
231 because the electrolyte 231 is concentrated in the interface
region 239 between the electrodes 220 and the conductive layer 111.
Accordingly, the accuracy with which the sensor 251 determines the
progress of the electrolytic process can be improved because the
electrolyte 231 will be less likely to interfere with the operation
of the sensor 251. For example, when the sensor 251 is an optical
sensor, the electrolyte 231 will be less likely to distort the
radiation reflected from the surface of the substrate 110 because
the sensor 251 is positioned away from the interface region
239.
[0034] Another feature of an embodiment of the apparatus 260
described above with reference to FIG. 4 is that the electrolyte
231 supplied to the interface region 239 is continually
replenished, either with a reconditioned electrolyte or a fresh
electrolyte. An advantage of this feature is that the
electrochemical reaction between the electrodes 220 and the
conductive layer 111 can be maintained at a high and consistent
level.
[0035] FIG. 5 is a partially schematic, side elevational view of an
apparatus 360 that directs alternating current to the substrate 110
through a first electrolyte 331a and a second electrolyte 331b. In
one aspect of this embodiment, the first electrolyte 331a is
disposed in two first electrolyte vessels 330a, and the second
electrolyte 331b is disposed in a second electrolyte vessel 330b.
The first electrolyte vessels 330a are partially submerged in the
second electrolyte 33 lb. The apparatus 360 can further include
electrodes 320, shown as a first electrode 320a and a second
electrode 320b, each coupled to a current supply 321 and each
housed in one of the first electrolyte vessels 330a. Alternatively,
one of the electrodes 320 can be coupled to ground. The electrodes
320 can include materials such as silver, platinum, copper and/or
other materials, and the first electrolyte 331a can include sodium
chloride, potassium chloride, copper sulfate and/or other
electrolytes that are compatible with the material forming the
electrodes 320.
[0036] In one aspect of this embodiment, the first electrolyte
vessels 330a include a flow restrictor 322, such as a permeable
isolation membrane formed from Teflon.TM., sintered materials such
as sintered glass, quartz or sapphire, or other suitable porous
materials that allow ions to pass back and forth between the first
electrolyte vessels 330a and the second electrolyte vessel 330b,
but do not allow the second electrolyte 330b to pass inwardly
toward the electrodes 320 (for example, in a manner generally
similar to a salt bridge). Alternatively, the first electrolyte
331a can be supplied to the electrode vessels 330a from a first
electrolyte source 339 at a pressure and rate sufficient to direct
the first electrolyte 331 a outwardly through the flow restrictor
322 without allowing the first electrolyte 331 a or the second
electrolyte 330b to return through the flow restrictor 322. In
either embodiment, the second electrolyte 331b remains electrically
coupled to the electrodes 320 by the flow of the first electrolyte
331a through the restrictor 322.
[0037] In one aspect of this embodiment, the apparatus 360 can also
include a support member 340 that supports the substrate 110 with
the conductive layer 111 facing toward the electrodes 320. For
example, the support member 340 can be positioned in the second
electrolyte vessel 330b. In a further aspect of this embodiment,
the support member 340 and/or the electrodes 320 can be movable
relative to each other by one or more drive units (not shown).
[0038] One feature of an embodiment of the apparatus 360 described
above as reference to FIG. 5 is that the first electrolyte 331a can
be selected to be compatible with the electrodes 320. An advantage
of this feature is that the first electrolyte 331a can be less
likely than conventional electrolytes to degrade the electrodes
320. Conversely, the second electrolyte 331b can be selected
without regard to the effect it has on the electrodes 320 because
it is chemically isolated from the electrodes 320 by the flow
restrictor 322. Accordingly, the second electrolyte 331b can
include hydrochloric acid or another agent that reacts aggressively
with the conductive layer 111 of the substrate 110.
[0039] FIG. 6 is a top plan view of the microelectronic substrate
110 positioned beneath a plurality of electrodes having shapes and
configurations in accordance with several embodiments of the
invention. For purposes of illustration, several different types of
electrodes are shown positioned proximate to the same
microelectronic substrate 110; however, in practice, electrodes of
the same type can be positioned relative to a single
microelectronic substrate 110.
[0040] In one embodiment, electrodes 720a and 720b can be grouped
to form an electrode pair 770a, with each electrode 720a and 720b
coupled to an opposite terminal of a current supply 121 (FIG. 3).
The electrodes 770a and 770b can have an elongated or strip-type
shape and can be arranged to extend parallel to each other over the
diameter of the substrate 110. The spacing between adjacent
electrodes of an electrode pair 370a can be selected to direct the
electrical current into the substrate 110, as described above with
reference to FIG. 3.
[0041] In an alternate embodiment, electrodes 720c and 720d can be
grouped to form an electrode pair 770b, and each electrode 720c and
720d can have a wedge or "pie" shape that tapers inwardly toward
the center of the microelectronic substrate 110. In still another
embodiment, narrow, strip-type electrodes 720e and 720f can be
grouped to form electrode pairs 770c, with each electrode 720e and
720f extending radially outwardly from the center 113 of the
microelectronic substrate 110 toward the periphery 112 of the
microelectronic substrate 110.
[0042] In still another embodiment, a single electrode 720g can
extend over approximately half the area of the microelectronic
substrate 110 and can have a semicircular planform shape. The
electrode 720g can be grouped with another electrode (not shown)
having a shape corresponding to a mirror image of the electrode
720g, and both electrodes can be coupled to the current source 121
to provide alternating current to the microelectronic substrate in
any of the manners described above with reference to FIGS. 3-5.
[0043] FIG. 7 is a partially schematic, cross-sectional side
elevational view of a portion of the substrate 110 positioned
beneath the electrode 720c described above with reference to FIG.
6. In one aspect of this embodiment, the electrode 720c has an
upper surface 771 and a lower surface 772 opposite the upper
surface 771 and facing the conductive layer 111 of the substrate
110. The lower surface 772 can taper downwardly from the center 113
of the substrate 110 toward the perimeter 112 of the substrate 110
in one aspect of this embodiment to give the electrode 720c a
wedge-shaped profile. Alternatively, the electrode 720c can have a
plate-type configuration with the lower surface 772 positioned as
shown in FIG. 7 and the upper surface 771 parallel to the lower
surface 772. One feature of either embodiment is that the
electrical coupling between the electrode 720c and the substrate
110 can be stronger toward the periphery 112 of the substrate 110
than toward the center 113 of the substrate 110. This feature can
be advantageous when the periphery 112 of the substrate 110 moves
relative to the electrode 720c at a faster rate than does the
center 113 of the substrate 110, for example, when the substrate
110 rotates about its center 113. Accordingly, the electrode 720c
can be shaped to account for relative motion between the electrode
and the substrate 110.
[0044] In other embodiments, the electrode 720c can have other
shapes. For example, the lower surface 772 can have a curved rather
than a flat profile. Alternatively, any of the electrodes described
above with reference to FIG. 6 (or other electrodes having shapes
other than those shown in FIG. 6) can have a sloped or curved lower
surface. In still further embodiments, the electrodes can have
other shapes that account for relative motion between the
electrodes and the substrate 110.
[0045] FIG. 8A is a partially schematic view of an electrode
support 473 for supporting a plurality of electrodes in accordance
with another embodiment of the invention. In one aspect of this
embodiment, the electrode support 473 can include a plurality of
electrode apertures 474, each of which houses either a first
electrode 420a or a second electrode 420b. The first electrodes
420a are coupled through the apertures 474 to a first lead 428a and
the second electrodes 420b are coupled to a second lead 428b. Both
of the leads 428a and 428b are coupled to a current supply 421.
Accordingly, each pair 470 of first and second electrodes 420a and
420b defines part of a circuit that is completed by the substrate
110 and the electrolyte(s) described above with reference to FIGS.
3-5.
[0046] In one aspect of this embodiment, the first lead 428a can be
offset from the second lead 428b to reduce the likelihood for short
circuits and/or capacitive coupling between the leads. In a further
aspect of this embodiment, the electrode support 473 can have a
configuration generally similar to any of those described above
with reference to FIGS. 1-7. For example, any of the individual
electrodes (e.g., 320a, 320c, 320e, or 320g) described above with
reference to FIG. 6 can be replaced with an electrode support 473
having the same overall shape and including a plurality of
apertures 474, each of which houses one of the first electrodes
420a or the second electrodes 420b.
[0047] In still a further aspect of this embodiment, the electrode
pairs 470 shown in FIG. 8A can be arranged in a manner that
corresponds to the proximity between the electrodes 420a, 420b and
the microelectronic substrate 110 (FIG. 7), and/or the electrode
pairs 470 can be arranged to correspond to the rate of relative
motion between the electrodes 420a, 420b and the microelectronic
substrate 110. For example, the electrode pairs 470 can be more
heavily concentrated in the periphery 112 of the substrate 110 or
other regions where the relative velocity between the electrode
pairs 470 and the substrate 110 is relatively high (see FIG. 7).
Accordingly, the increased concentration of electrode pairs 470 can
provide an increased electrolytic current to compensate for the
high relative velocity. Furthermore, the first electrode 420a and
the second electrode 420b of each electrode pair 470 can be
relatively close together in regions (such as the periphery 112 of
the substrate 110) where the electrodes are close to the conductive
layer 111 (see FIG. 7) because the close proximity to the
conductive layer 111 reduces the likelihood for direct electrical
coupling between the first electrode 420a and the second electrode
420b. In still a further aspect of this embodiment, the amplitude,
frequency and/or waveform shape supplied to different electrode
pairs 470 can vary depending on factors such as the spacing between
the electrode pair 470 and the microelectronic substrate 110, and
the relative velocity between the electrode pair 470 and the
microelectronic substrate 110.
[0048] FIGS. 8B-8C illustrate electrodes 820 (shown as first
electrodes 820a and second electrodes 820b) arranged concentrically
in accordance with still further embodiments of the invention. In
one embodiment shown in FIG. 8B, the first electrode 820a can be
positioned concentrically around the second electrode 820b, and a
dielectric material 829 can be disposed between the first electrode
820a and the second electrode 820b. The first electrode 820a can
define a complete 3600 arc around the second electrode 820b, as
shown in FIG. 8B, or alternatively, the first electrode 820a can
define an arc of less than 360.degree..
[0049] In another embodiment, shown in FIG. 8C, the first electrode
820A can be concentrically disposed between two second electrodes
820b, with the dielectric material 829 disposed between neighboring
electrodes 820. In one aspect of this embodiment, current can be
supplied to each of the second electrodes 820b with no phase
shifting. Alternatively, the current supplied to one second
electrode 820b can be phase-shifted relative to the current
supplied to the other second electrode 820b. In a further aspect of
the embodiment, the current supplied to each second electrode 820b
can differ in characteristics other than phase, for example,
amplitude.
[0050] One feature of the electrodes 820 described above with
respect to FIGS. 8B-8C is that the first electrode 820a can shield
the second electrode(s) 820b from interference from other current
sources. For example, the first electrode 820a can be coupled to
ground to shield the second electrodes 820b. An advantage of this
arrangement is that the current applied to the substrate 110 (FIG.
7) via the electrodes 820 can be more accurately controlled.
[0051] FIG. 9 schematically illustrates an apparatus 560 for both
planarizing and electrolytically processing the microelectronic
substrate 110 in accordance with an embodiment of the invention. In
one aspect of this embodiment, the apparatus 560 has a support
table 580 with a top-panel 581 at a workstation where an operative
portion "W" of a planarizing pad 582 is positioned. The top-panel
581 is generally a rigid plate to provide a flat, solid surface to
which a particular section of the planarizing pad 582 may be
secured during planarization.
[0052] The apparatus 560 can also have a plurality of rollers to
guide, position and hold the planarizing pad 582 over the top-panel
581. The rollers can include a supply roller 583, first and second
idler rollers 584a and 584b, first and second guide rollers 585a
and 585b, and a take-up roller 586. The supply roller 583 carries
an unused or pre-operative portion of the planarizing pad 582, and
the take-up roller 583 carries a used or post-operative portion of
the planarizing pad 582. Additionally, the first idler roller 584a
and the first guide roller 585a can stretch the planarizing pad 582
over the top-panel 581 to hold the planarizing pad 582 stationary
during operation. A motor (not shown) drives at least one of the
supply roller 583 and the take-up roller 586 to sequentially
advance the planarizing pad 582 across the top-panel 581.
Accordingly, clean pre-operative sections of the planarizing pad
582 may be quickly substituted for used sections to provide a
consistent surface for planarizing and/or cleaning the substrate
110.
[0053] The apparatus 560 can also have a carrier assembly 590 that
controls and protects the substrate 110 during planarization. The
carrier assembly 590 can include a substrate holder 592 to pick up,
hold and release the substrate 110 at appropriate stages of the
planarizing process. The carrier assembly 590 can also have a
support gantry 594 carrying a drive assembly 595 that can translate
along the gantry 594. The drive assembly 595 can have an actuator
596, a drive shaft 597 coupled to the actuator 596, and an arm 598
projecting from the drive shaft 597. The arm 598 carries the
substrate holder 592 via a terminal shaft 599 such that the drive
assembly 595 orbits the substrate holder 592 about an axis E-E (as
indicated by arrow "R.sub.1"). The terminal shaft 599 may also
rotate the substrate holder 592 about its central axis F-F (as
indicated by arrow "R.sub.2").
[0054] The planarizing pad 582 and a planarizing solution 587
define a planarizing medium that mechanically and/or
chemically-mechanically removes material from the surface of the
substrate 110. The planarizing pad 582 used in the apparatus 560
can be a fixed-abrasive planarizing pad in which abrasive particles
are fixedly bonded to a suspension medium. Accordingly, the
planarizing solution 587 can be a "clean solution" without abrasive
particles because the abrasive particles are fixedly distributed
across a planarizing surface 588 of the planarizing pad 582. In
other applications, the planarizing pad 582 may be a non-abrasive
pad without abrasive particles, and the planarizing solution 587
can be a slurry with abrasive particles and chemicals to remove
material from the substrate 110.
[0055] To planarize the substrate 110 with the apparatus 560, the
carrier assembly 590 presses the substrate 110 against the
planarizing surface 588 of the planarizing pad 582 in the presence
of the planarizing solution 587. The drive assembly 595 then orbits
the substrate holder 592 about the axis E-E and optionally rotates
the substrate holder 592 about the axis F-F to translate the
substrate 110 across the planarizing surface 588. As a result, the
abrasive particles and/or the chemicals in the planarizing medium
remove material from the surface of the substrate 110 in a chemical
and/or chemical-mechanical planarization (CMP) process.
Accordingly, the planarizing pad 582 can smooth the substrate 110
by removing rough features projecting from the conductive layer 111
of the substrate 110.
[0056] In a further aspect of this embodiment, the apparatus 560
can include an electrolyte supply vessel 530 that delivers an
electrolyte to the planarizing surface of the planarizing pad 582
with a conduit 537, as described in greater detail with reference
to FIG. 10. The apparatus 560 can further include a current supply
521 coupled to the support table 580 and/or the top-panel 581 to
supply an electrical current to electrodes positioned in the
support table 580 and/or the top-panel 581. Accordingly, the
apparatus 560 can electrolytically remove material from the
conductive layer 111 in a manner similar to that described above
with reference to FIGS. 1-8C.
[0057] In one aspect of an embodiment of the apparatus 560
described above with reference to FIG. 9, material can be
sequentially removed from the conductive layer 111 of the substrate
110 first by an electrolytic process and then by a CMP process. For
example, the electrolytic process can remove material from the
conductive layer 111 in a manner that roughens the conductive layer
111. After a selected period of electrolytic processing time has
elapsed, the electrolytic processing operation can be halted and
additional material can be removed via CMP processing.
Alternatively, the electrolytic process and the CMP process can be
conducted simultaneously. In either of these processing
arrangements, one feature of an embodiment of the apparatus 560
described above with reference to FIG. 9 is that the same apparatus
560 can planarize the substrate 110 via CMP and remove material
from the substrate 110 via an electrolytic process. An advantage of
this arrangement is that the substrate 110 need not be moved from
one apparatus to another to undergo both CMP and electrolytic
processing.
[0058] Another advantage of an embodiment of the apparatus 560
described above with reference to FIG. 9 is that the processes,
when used in conjunction with each other, is expected to remove
material from the substrate 110 more quickly and accurately than
some conventional processes. For example, as described above, the
electrolytic process can remove relatively large amounts of
material in a manner that roughens the microelectronic substrate
110, and the planarizing process can remove material on a finer
scale in a manner that smoothes and/or flattens the microelectronic
substrate 110.
[0059] FIG. 10 is a partially exploded, partially schematic
isometric view of a portion of the apparatus 560 described above
with reference to FIG. 9. In one aspect of an embodiment shown in
FIG. 10, the top-panel 581 houses a plurality of electrode pairs
570, each of which includes a first electrode 520a and a second
electrode 520b. The first electrodes 520a are coupled to a first
lead 528a and the second electrodes 520b are coupled to a second
lead 528b. The first and second leads 528a and 528b are coupled to
the current source 521 (FIG. 9). In one aspect of this embodiment,
the first electrode 520a can be separated from the second
electrodes 520b by an electrode dielectric layer 529a that includes
Teflon.TM. or another suitable dielectric material. The electrode
dielectric layer 529a can accordingly control the volume and
dielectric constant of the region between the first and second
electrodes 520a and 520b to control electrical coupling between the
electrodes.
[0060] The electrodes 520a and 520b can be electrically coupled to
the microelectronic substrate 110 (FIG. 9) by the planarizing pad
582. In one aspect of this embodiment, the planarizing pad 582 is
saturated with an electrolyte 531 supplied by the supply conduits
537 through apertures 538 in the top-panel 581 just beneath the
planarizing pad 582. Accordingly, the electrodes 520a and 520b are
selected to be compatible with the electrolyte 531. In an alternate
arrangement, the electrolyte 531 can be supplied to the planarizing
pad 582 from above (for example, by disposing the electrolyte 531
in the planarizing liquid 587) rather than through the top-panel
581. Accordingly, the planarizing pad 582 can include a pad
dielectric layer 529b positioned between the planarizing pad 582
and the electrodes 520a and 520b. When the pad dielectric layer
529b is in place, the electrodes 520a and 520b are isolated from
physical contact with the electrolyte 531 and can accordingly be
selected from materials that are not necessarily compatible with
the electrolyte 531.
[0061] In either of the embodiments described above with reference
to FIG. 10, the planarizing pad 582 can provide several advantages
over some conventional electrolytic arrangements. For example, the
planarizing pad 582 can uniformly separate the electrodes 520a and
520b from the microelectronic substrate 110 (FIG. 9), which can
increase the uniformity with which the electrolytic process removes
material from the conductive layer 111 (FIG. 9). The planarizing
pad 582 can also have abrasive particles 589 for planarizing the
microelectronic substrate 110 in the manner described above with
reference to FIG. 9. Furthermore, the planarizing pad 582 can
filter carbon or other material that erodes from the electrodes
520a and 520b to prevent the electrode material from contacting the
microelectronic substrate 110. Still further, the planarizing pad
582 can act as a sponge to retain the electrolyte 531 in close
proximity to the microelectronic substrate 110.
[0062] FIG. 11 is a partially schematic, cross-sectional side
elevational view of a rotary apparatus 660 for planarizing and/or
electrolytically processing the microelectronic substrate 110 in
accordance with another embodiment of the invention. In one aspect
of this embodiment, the apparatus 660 has a generally circular
platen or table 680, a carrier assembly 690, a planarizing pad 682
positioned on the table 680, and a planarizing liquid 687 on the
planarizing pad 682. The planarizing pad 682 can be a fixed
abrasive planarizing pad or, alternatively, the planarizing liquid
687 can be a slurry having a suspension of abrasive elements and
the planarizing pad 682 can be a non-abrasive pad. A drive assembly
695 rotates (arrow "G") and/or reciprocates (arrow "H") the platen
680 to move the planarizing pad 682 during planarization.
[0063] The carrier assembly 690 controls and protects the
microelectronic substrate 110 during planarization. The carrier
assembly 690 typically has a substrate holder 692 with a pad 694
that holds the microelectronic substrate 110 via suction. A drive
assembly 696 of the carrier assembly 690 typically rotates and/or
translates the substrate holder 692 (arrows "I" and "J,"
respectively). Alternatively, the substrate holder 692 may include
a weighted, free-floating disk (not shown) that slides over the
planarizing pad 682.
[0064] To planarize the microelectronic substrate 110 with the
apparatus 660, the carrier assembly 690 presses the microelectronic
substrate 110 against a planarizing surface 688 of the planarizing
pad 682. The platen 680 and/or the substrate holder 692 then move
relative to one another to translate the microelectronic substrate
110 across the planarizing surface 688. As a result, the abrasive
particles in the planarizing pad 682 and/or the chemicals in the
planarizing liquid 687 remove material from the surface of the
microelectronic substrate 110.
[0065] The apparatus 660 can also include a current source 621
coupled with leads 628a and 628b to one or more electrode pairs 670
(one of which is shown in FIG. 11). The electrode pairs 670 can be
integrated with the platen 680 in generally the same manner with
which the electrodes 520a and 520b (FIG. 10) are integrated with
the top panel 581 (FIG. 10). Alternatively, the electrode pairs 670
can be integrated with the planarizing pad 682. In either
embodiment, the electrode pairs 670 can include electrodes having
shapes and configurations generally similar to any of those
described above with reference to FIGS. 3-10 to electrolytically
remove conductive material from the microelectronic substrate 110.
The electrolytic process can be carried out before, during or after
the CMP process, as described above with reference to FIG. 9.
[0066] FIG. 12A is a schematic circuit representation of some of
the components described above with reference to FIG. 10. The
circuit analogy can also apply to any of the arrangements described
above with reference to FIGS. 3-11. As shown schematically in FIG.
12A, the current source 521 is coupled to the first electrode 520a
and the second electrode 520b with leads 528a and 528b
respectively. The electrodes 520a and 520b are coupled to the
microelectronic substrate 110 with the electrolyte 531 in an
arrangement that can be represented schematically by two sets of
parallel capacitors and resistors. A third capacitor and resistor
schematically indicates that the microelectronic substrate 110
"floats" relative to ground or another potential.
[0067] In one aspect of an embodiment shown in FIG. 12A, the
current source 521 can be coupled to an amplitude modulator 522
that modulates the signal produced by the current source 521, as is
shown in FIG. 12B. Accordingly, the current source 521 can generate
a high-frequency wave 804, and the amplitude modulator 522 can
superimpose a low-frequency wave 802 on the high-frequency wave
804. For example, the high-frequency wave 804 can include a series
of positive or negative voltage spikes contained within a square
wave envelope defined by the low-frequency wave 802. Each spike of
the high-frequency wave 804 can have a relatively steep rise time
slope to transfer charge through the dielectric to the electrolyte,
and a more gradual fall time slope. The fall time slope can define
a straight line, as indicated by high-frequency wave 804, or a
curved line, as indicated by high-frequency wave 804a. In other
embodiments, the high-frequency wave 804 and the low-frequency wave
802 can have other shapes depending, for example, on the particular
characteristics of the dielectric material and electrolyte adjacent
to the electrodes 420, the characteristics of the substrate 110,
and/or the target rate at which material is to be removed from the
substrate 110.
[0068] An advantage of this arrangement is that the high frequency
signal can transmit the required electrical energy from the
electrodes 520a and 520b to the microelectronic substrate 110,
while the low frequency superimposed signal can more effectively
promote the electrochemical reaction between the electrolyte 531
and the conductive layer 111 of the microelectronic substrate 110.
Accordingly, any of the embodiments described above with reference
to FIGS. 3-11 can include an amplitude modulator in addition to a
current source.
[0069] From the foregoing, it will be appreciated that, although
specific embodiments of the invention have been described herein
for purposes of illustration, various modifications may be made
without deviating from the spirit and scope of the invention.
Accordingly, the invention is not limited except as by the appended
claims.
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