U.S. patent application number 10/464223 was filed with the patent office on 2004-07-01 for retaining ring having reduced wear and contamination rate for a polishing head of a cmp tool.
Invention is credited to Kramer, Jens, Marxsen, Gerd, Nitsche, Rene.
Application Number | 20040123951 10/464223 |
Document ID | / |
Family ID | 32602440 |
Filed Date | 2004-07-01 |
United States Patent
Application |
20040123951 |
Kind Code |
A1 |
Kramer, Jens ; et
al. |
July 1, 2004 |
Retaining ring having reduced wear and contamination rate for a
polishing head of a CMP tool
Abstract
A retaining member for a polishing head in a CMP apparatus
comprises a bottom surface with silicon carbide. Due to the
superior characteristics of silicon carbide, a low wear rate of the
retaining member is secured, wherein, additionally, accumulation of
electrostatic charges is substantially avoided due to the
conductivity of silicon carbide. Consequently, cost of ownership is
reduced, while at the same time process stability over a large
number of substrates is increased.
Inventors: |
Kramer, Jens; (Dresden,
DE) ; Marxsen, Gerd; (Radebeul, DE) ; Nitsche,
Rene; (Neukirch, DE) |
Correspondence
Address: |
J. Mike Amerson
Williams, Morgan & Amerson, P.C.
Suite 1100
10333 Richmond
Houston
TX
77042
US
|
Family ID: |
32602440 |
Appl. No.: |
10/464223 |
Filed: |
June 18, 2003 |
Current U.S.
Class: |
156/345.12 |
Current CPC
Class: |
B24B 53/017 20130101;
B24B 53/12 20130101; B24B 37/32 20130101 |
Class at
Publication: |
156/345.12 |
International
Class: |
C23F 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 27, 2002 |
DE |
102 61 306.0 |
Claims
What is claimed:
1. A retaining member for a polishing head, the retaining member
being partially comprised of silicon carbide.
2. The retaining member of claim 1, having an upper portion and a
lower portion, the lower portion having a bottom surface that is
comprised of silicon carbide.
3. The retaining member of claim 1, wherein a plurality of slurry
channels are formed in a bottom surface of said retaining
member.
4. The retaining member of claim 2, wherein said bottom surface
comprises a surface topography configured to obtain a conditioning
effect in a polishing pad during operation.
5. The retaining member of claim 2, wherein said upper portion
includes a flexible material.
6. The retaining member of claim 4, wherein said surface topography
includes a plurality of protrusions.
7. The retaining member of claim 4, wherein said surface topography
includes portions having a roughness on a microstructure scale.
8. A polishing head for a CMP apparatus, comprising: a support
surface configured to receive a substrate; and a retaining member
configured to laterally fix the substrate on the support surface,
the retaining member being partially comprised of silicon
carbide.
9. The polishing head of claim 8, wherein said retaining member
comprises an upper portion and a lower portion, the lower portion
having a bottom surface that is comprised of silicon carbide.
10. The polishing head of claim 8, wherein a plurality of slurry
channels are formed in a bottom surface of said retaining
member.
11. The polishing head of claim 9, wherein said bottom surface
comprises a surface topography configured to obtain a conditioning
effect in a polishing pad during operation.
12. The polishing head of claim 9, wherein said upper portion
includes a flexible material.
13. The polishing head of claim 11, wherein said surface topography
includes a plurality of protrusions.
14. The polishing head of claim 11, wherein said surface topography
includes portions having a roughness on a microstructure scale.
15. A CMP apparatus, comprising: a polishing pad attached to a
polishing platen; a polishing head including a retaining member
that is partially comprised of silicon carbide; and a pad
conditioner having a surface portion in contact with the polishing
pad and comprised of silicon carbide.
16. A retaining member, comprising: a lower portion formed of a
conductive non-metal material; and an upper portion formed of a
material other than said non-metal material, wherein said
conductive non-metal material is more rigid than said other
material.
17. The retaining member of claim 16, wherein said non-metal
comprises silicon carbide.
18. The retaining member of claim 16, wherein a plurality of slurry
channels are formed in a bottom surface of said retaining
member.
19. The retaining member of claim 18, wherein said bottom surface
comprises a surface topography configured to obtain a conditioning
effect in a polishing pad during operation.
20. The retaining member of claim 18, wherein said upper portion
includes a flexible material.
21. The retaining member of claim 19, wherein said surface
topography includes a plurality of protrusions.
22. The retaining member of claim 19, wherein said surface
topography includes portions having a roughness on a microstructure
scale.
23. The retaining member of claim 16, wherein said lower portion
comprises a material having a hardness of 15.0 GPa or more.
24. A polishing head for a CMP apparatus, comprising: a support
surface configured to receive a substrate; and a retaining member
configured to laterally fix said substrate on said support surface,
said retaining member comprising a lower portion including a
conductive nonmetal material, and an upper portion formed of a
material other than said conductive non-metal material, wherein
said other material is less rigid than said conductive non-metal
material.
25. The polishing head of claim 24, wherein said non-metal material
comprises silicon carbide.
26. The polishing head of claim 24, wherein a plurality of slurry
channels are formed in a bottom surface of said retaining
member.
27. The polishing head of claim 24, wherein a bottom surface of
said retaining member comprises a surface topography configured to
obtain a conditioning effect in a polishing pad during
operation.
28. The polishing head of claim 24, wherein said upper portion
includes a flexible material.
29. The polishing head of claim 27, wherein said surface topography
includes a plurality of protrusions.
30. The polishing head of claim 27, wherein said surface topography
includes portions having a roughness on a microstructure scale.
31. The polishing head of claim 24, wherein at least a bottom
surface of said lower portion is comprised of a material having a
hardness of 15.0 GPa or more.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] Generally, the present invention relates to the fabrication
of microstructures, such as integrated circuits, and, more
particularly, to the chemical mechanical polishing of substrates
for removing excess material and planarizing the substrate
surface.
[0003] 2. Description of the Related Art
[0004] In manufacturing microstructures and especially integrated
circuits, it is typically necessary to form layers of different
materials, such as semiconductors, insulators, metals, and the
like, on an appropriate substrate and to subsequently pattern one
or more of these layers by photolithography and etch techniques,
thereby producing microstructure elements, such as transistors,
capacitors, resistors, inductors, conductors and the like. With
increasing complexity of the microstructures, especially of the
integrated circuits, the number of material layers to be deposited
and to be patterned on the substrate also increases and thus leads
to an increasingly non-planar surface topography of the patterned
material layers.
[0005] As there is an ongoing tendency to steadily shrink the
dimensions of the circuit elements, the requirements posed on the
photolithography and etch techniques may not sufficiently be met
without periodically planarizing the substrate surface. For
instance, the fabrication of highly sophisticated CPUs requires the
formation of a plurality of metallization layers stacked on top of
each other and having trenches and vias, i.e., vertical
interconnects between the individual metallization layers, with
feature sizes on the order of 0.2 .mu.m and less with an aspect
ratio of greater than 8. A plurality of these metallization layers
may not readily be formed as a layer stack without providing a
well-planarized surface prior to the formation of a next level.
[0006] Chemical mechanical polishing (CMP) has become one of the
most frequently used techniques in planarizing substrates during
various manufacturing stages. In planarizing a substrate by
chemical mechanical polishing, the substrate is typically mounted
on a polishing head, wherein the surface to be polished is exposed
so that it may be placed against a polishing pad, which in turn is
mounted on a rotatable polishing platen. Usually a motion of the
substrate relative to the polishing pad is generated by rotating
the polishing head and the polishing platen. Simultaneously, a
so-called slurry is supplied to the polishing pad, which typically
includes at least one chemical reagent, allowing a chemical
reaction with the material to be removed so that the effectiveness
of material removal is significantly enhanced compared to a pure
mechanical polishing technique. Depending on the type of polishing
pad used, i.e., a standard pad or a fixed-abrasive pad, the slurry
may additionally comprise abrasive particles to promote the removal
of the material or materials from the substrate surface. By
applying a controllable pressure on the substrate to press it
against the polishing pad, by controlling the magnitude of the
relative motion between the polishing pad and the substrate, by
selecting an appropriate slurry with well-defined characteristics,
such as pH value, type of reagent, type of abrasive particles,
temperature, and the like, the rate of removal of material from the
substrate may be adjusted.
[0007] In addition to a high removal rate for a
high-throughput-polishing process, the final "quality" of the
polished surface on a small scale, that is, the residual surface
roughness and topography over adjacent circuit elements, as well as
on a large scale, that is, the uniformity of material removal
across the entire substrate surface, is also of great importance in
view of tightly-set design requirements. Furthermore, chemically
mechanically polishing a plurality of substrates sequentially is a
challenging task as the polishing process per se is subjected to
non-uniformity owing to wear of consumables such as the polishing
pad, components of the polishing head in contact with the polishing
pad, and the like. Additionally, the slurry consistency may change
due to the accumulation of continuously removed material in the
slurry during the polish process. For this reason, so-called pad
conditioners are usually provided that move across the polishing
pad during or after the polishing of the substrate in order to
rework the surface of the polishing pad in an attempt to provide
substantially stable conditions for a plurality of substrates.
[0008] Since chemical mechanical polishing has become a standard
process in manufacturing integrated circuits, and since the
substrate diameter is steadily increasing, for example, in
fabricating modern integrated circuits, wafers of 200 mm diameter
are used with the prospect of 300 mm substrates in the near future,
with an ever increasing demand of improved throughput of the
polishing tools, great efforts are being made to steadily improve
the polishing process, i.e., to provide enhanced polish uniformity
across large diameter substrates and to also improve process
uniformity over a plurality of subsequently processed
substrates.
[0009] For example, U.S. Pat. No. 6,251,215 describes a carrier
head for a CMP tool having a multi-layer retaining ring with a
lower portion for contacting the polishing pad during the
polishing, which is made of a first material, and having an upper
portion made of a second material which is more rigid than the
first material. The first material is made of a plastic, e.g.,
polyphenylene sulfide, polyethylene terephthalate, and the like.
The second material may be a metal, e.g., steel, aluminum or
molybdenum, or a ceramic. The reduced rigidness of the first
material is intended to reduce the so-called edge effect, i.e., the
tendency of a different etch rate at the substrate perimeter
compared to the center of the substrate. Although the provision of
a material with improved elasticity may lead to a more uniform
removal rate during the processing of an individual substrate, the
relatively soft plastic material exhibits a significant wear rate
so that substrate contamination by particles may become a major
issue during the polishing of a plurality of substrates.
Additionally, the relatively high wear rate requires frequent
changing of the retaining ring and thus contributes to a reduced
tool utilization and increased cost of ownership.
[0010] In view of the above-identified problems, a need exists for
an improved technique that allows an increased CMP tool utilization
while at the same time improving process quality.
SUMMARY OF THE INVENTION
[0011] Generally, the present invention is directed to a polishing
head and/or a retaining member that laterally fixes a substrate
mounted on the polishing head during the polishing, wherein at
least a portion of the retaining member is formed of a durable
non-metal exhibiting a certain degree of conductivity so that
contamination of the substrate is significantly reduced due to the
extremely low wear rate and the substantial lack of metal, wherein
the conductivity additionally substantially prevents electrostatic
charges from accumulating on the retaining member during the
polishing process.
[0012] According to one illustrative embodiment of the present
invention, a polishing head for a CMP apparatus comprises a support
surface configured to receive a substrate. A retaining member is
configured to laterally fix the substrate on the support surface,
wherein the retaining member is at least partially comprised of
silicon carbide.
[0013] According to another illustrative embodiment of the present
invention, a retaining member for use in a polishing head is
partially comprised of silicon carbide.
[0014] In accordance with still another illustrative embodiment of
the present invention, a polishing head for a CMP apparatus
comprises a support surface that is configured to receive a
substrate. Moreover, a retaining member is configured to laterally
fix the substrate on the support surface, wherein the retaining
member comprises an upper portion made of a first material and a
lower portion formed of a conductive non-metal. The conductive
non-metal is more rigid than the first material.
[0015] According to still a further illustrative embodiment of the
present invention, a retaining member for a polishing head includes
an upper portion formed of a first material and a lower portion
formed of a conductive non-metal, wherein the conductive non-metal
is more rigid than the first material.
[0016] According to yet another illustrative embodiment of the
present invention, a CMP apparatus comprises a polishing pad
attached to a polishing plate and a polishing head including a
retaining member that is partially comprised of silicon carbide.
The apparatus further comprises a pad conditioner having a surface
portion in contact with the polishing pad and comprised of silicon
carbide.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The invention may be understood by reference to the
following description taken in conjunction with the accompanying
drawings, in which like reference numerals identify like elements,
and in which:
[0018] FIG. 1a schematically shows a polishing tool (in a
simplified manner);
[0019] FIG. 1b depicts a portion of the polishing head of the
apparatus shown in FIG. 1a in more detail;
[0020] FIGS. 2a and 2b are a plan view and a side view,
respectively, of a ring-shaped retaining member usable in the
apparatus shown in FIG. 1a; and
[0021] FIGS. 3a and 3b schematically depict various forms of
ring-shaped retaining members according to further illustrative
embodiments of the present invention.
[0022] While the invention is susceptible to various modifications
and alternative forms, specific embodiments thereof have been shown
by way of example in the drawings and are herein described in
detail. It should be understood, however, that the description
herein of specific embodiments is not intended to limit the
invention to the particular forms disclosed, but on the contrary,
the intention is to cover all modifications, equivalents, and
alternatives falling within the spirit and scope of the invention
as defined by the appended claims.
DETAILED DESCRIPTION OF THE INVENTION
[0023] Illustrative embodiments of the invention are described
below. In the interest of clarity, not all features of an actual
implementation are described in this specification. It will of
course be appreciated that in the development of any such actual
embodiment, numerous implementation-specific decisions must be made
to achieve the developers' specific goals, such as compliance with
system-related and business-related constraints, which will vary
from one implementation to another. Moreover, it will be
appreciated that such a development effort might be complex and
time-consuming, but would nevertheless be a routine undertaking for
those of ordinary skill in the art having the benefit of this
disclosure.
[0024] The present invention will now be described with reference
to the attached figures. Although the various regions and
structures of a semiconductor device are depicted in the drawings
as having very precise, sharp configurations and profiles, those
skilled in the art recognize that, in reality, these regions and
structures are not as precise as indicated in the drawings.
Additionally, the relative sizes of the various features and doped
regions depicted in the drawings may be exaggerated or reduced as
compared to the size of those features or regions on fabricated
devices. Nevertheless, the attached drawings are included to
describe and explain illustrative examples of the present
invention. The words and phrases used herein should be understood
and interpreted to have a meaning consistent with the understanding
of those words and phrases by those skilled in the relevant art. No
special definition of a term or phrase, i.e., a definition that is
different from the ordinary and customary meaning as understood by
those skilled in the art, is intended to be implied by consistent
usage of the term or phrase herein. To the extent that a term or
phrase is intended to have a special meaning, i.e., a meaning other
than that understood by skilled artisans, such a special definition
will be expressly set forth in the specification in a definitional
manner that directly and unequivocally provides the special
definition for the term or phrase.
[0025] FIG. 1a schematically depicts a CMP apparatus 100 in a
simplified manner. The CMP apparatus 100 comprises a polishing
platen 101 supported and driven by a drive assembly 102. A
polishing pad 103 is attached to the polishing platen 101. A slurry
supply 104 is arranged in such a manner to allow the supply of a
slurry 105 to the polishing pad 103. A pad conditioner 106 is
mounted on a respective drive means 107. A polishing head 120 is
radially moveably and rotatably supported by a respective drive
assembly (not shown) and may further be movable so as to receive a
substrate 108 and to bring the substrate into contact with the
polishing pad 103. The polishing head 120 comprises a retaining
member 150, which in the present example is provided as a generally
annular element attached to a base member 121 of the polishing head
120. The polishing head 120 may further comprise a plurality of
fluid lines and manifolds (not shown) to provide gases and/or
vacuum to a substrate receiving portion 122 enclosed by the
retaining member 150.
[0026] FIG. 1b illustrates the encircled portion of FIG. 1a in more
detail. In the substrate receiving portion 122, a flexible membrane
123 is in contact with the back side of the substrate 108. A
support member 124 is arranged such that the membrane 123 is fixed
thereto and provides a sealed space 125, which is connected to a
gas supply (not shown), for providing an overpressure within the
space 125. The substrate 108 is laterally held in place by the
retaining member 150, which comprises an upper portion 151 made of
a first material, such as aluminum, stainless steel, molybdenum,
and the like. A lower portion 153 of the retaining member 150 has a
surface 154, at least a portion thereof may contact the polishing
pad 103 during the operation of the CMP apparatus 100. The lower
portion 153 or at least the surface 154 being in contact with the
polishing pad 103 may be comprised of a material having a high
durability and thus a low wear rate during the operation of the
apparatus 100. In one particular embodiment, the surface 154 may
comprise silicon carbide. In other embodiments, the surface 154 may
be comprised of a conductive material having a Vickers hardness of
approximately 15.0 GPa or more at room temperature. In still other
embodiments, the lower portion 153 may be substantially completely
made of silicon carbide and/or of a material having the
above-identified hardness. Since silicon carbide exhibits a
hardness that is comparable to that of diamond, the wear rate
thereof is extremely low. Contrary to diamond, silicon carbide is
conductive and therefore allows the drain-off of electrostatic
charges that would otherwise build up in an insulating material.
Furthermore, silicon carbide has a high heat conductivity exceeding
that of steel and may therefore effectively conduct heat from and
to the polishing pad 103 via the slurry 105. The lower portion 153
may be attached to the upper portion 151 by a layer of adhesive
152, for example in the form of an epoxy adhesive.
[0027] In operation, the substrate 108 is placed into the substrate
receiving portion 122, for example by moving the polishing head 120
to a respective substrate storage location (not shown) and
establishing a vacuum in the portion 122 to fix the substrate 108
therein. Thereafter, the polishing head 120 is placed against the
polishing pad 103, which rotates at a predefined angular speed.
Typically, the polishing head 120 is also rotated, wherein usually
the rotation of the polishing head 120 and/or of the polishing pad
103 is controlled so as to achieve a substantially uniform relative
motion across the entire substrate surface. To this end, the
polishing head 120 may also be moved radially with respect to the
polishing pad 103, thereby allowing adjustment of the relative
speed and also to improve the utilization of the polishing pad 103
so as to use substantially the whole surface thereof. During the
polishing process, the substrate 108 is laterally fixed by the
retaining member 150, wherein the dimensions of the retaining
member 150 and especially the dimensions of the lower portion 153
are selected so as to minimize a clearance of the substrate 108
within the substrate receiving portion 122, thereby reducing the
risk for any damage of the substrate 108. During the polishing
process, a pressurized gas may be supplied to the space 125 to
exert a pressure via the membrane 123 onto the back side of the
substrate 108. Depending on the type of polishing head used, the
space 125 may be divided into several sub-portions, allowing
pressurization of different substrate areas with a different
pressure. Since the removal rate during the polishing process is
among others determined by the downforce exerted on the substrate
108, pressurizing the back side of the substrate 108 with different
pressures may assist in obtaining a desired removal rate at
specified substrate areas. Moreover, the retaining member 150 may
also be pressurized so as to exert a specified downforce on the
polishing pad 103 to thereby establish predefined polishing
conditions at the perimeter of the substrate 108.
[0028] Prior to and/or during contacting the substrate 108 with the
polishing pad 103 by moving the polishing head 120, the slurry
supply 104 provides the slurry 105 so that a layer of slurry is
established on the polishing pad 103. Depending on the type of
polishing pad used, i.e., a standard pad or a fixed abrasive pad,
the slurry includes at least one chemical reagent and possibly
abrasive particles to create a chemical reaction and promote a
mechanical removal of the one or more materials to be polished off
the substrate 108. As previously noted, silicon carbide is highly
resistive against a plurality of chemical reagents and also
exhibits excellent gliding qualities so that material removal by
chemical reaction and/or abrasion at the surface 154 of the lower
portion 153 is remarkably reduced compared to materials used in
conventional devices, such as metal and plastic materials.
Moreover, electrostatic charges that may build up owing to the
friction between the substrate 108, the surface 154 and the
polishing pad 103 may not accumulate in the lower portion 153 due
to the semiconductive qualities of the material that comprises the
lower portion 153, e.g., silicon carbide. In one embodiment, the
lower portion 153 is substantially comprised of silicon carbide and
the lower portion 153 may be electrically connected to ground, so
that any electrostatic charge created during the polishing process
may effectively be removed. For example, the adhesive layer 152 may
comprise an electrically conductive component so that the charge
carriers may effectively be drained off via the lower portion 153,
the electrically conductive adhesive layer 152 and the upper
portion 151. Thus, an influence of electrostatic charging, on the
slurry components as well as on the substrate 108, may
significantly be reduced.
[0029] Prior to and/or during and/or after polishing the substrate
108, the conditioner 106 may be activated to rework the surface of
the polishing pad 103 to provide substantially similar polishing
conditions on the pad 103 at least for some substrates 108 that
have to be polished sequentially in the apparatus 100. Typically,
the conditioner 106 comprises a surface contacting the polishing
pad 103 which exhibits an appropriate profile or topography to
obtain the desired "conditioning" effect. Since substantially the
same criteria apply to the conditioner 106 with regard to wear
rate, resistivity against corrosion and particle contamination of
the substrate 108 and electrostatic charge accumulation, in one
embodiment, the conditioner 106 includes a silicon carbide surface
portion.
[0030] After a required amount of material is removed from the
substrate 108, that is, the polishing process has been carried out
for a specified time under the process conditions as explained
above, the polishing pad 103 and thus the substrate 108 may be
rinsed and/or the substrate 108, with or without the polishing head
120, may be conveyed to another polishing station for a further CMP
sequence with differently adjusted process parameters. Due to the
reduced wear rate of the retaining member 150, i.e., the reduced
amount of particles created during the polishing process, and due
to its enhanced resistivity against the chemical agents contained
in the slurry 105, substantially stable process conditions may be
maintained for a plurality of substrates 108. For example, a
thickness 155 of the lower portion 153 varies only slowly over a
large number of substrates due to the low wear rate. Consequently,
relatively stable polishing conditions especially at the substrate
edge are maintained even if the retaining member 150 is not
separately vertically pressurized and is pressed against the
polishing pad 103 along with the substrate 108, since a height
difference between the surface 154 and the exposed substrate
surface, for example with respect to the beginning of each polish
process, varies only slightly over time.
[0031] FIG. 2a is a plan view of a retaining member 250 provided as
a ring-shaped element and FIG. 2b shows a schematic cross-sectional
view of the retaining member 250 according to a further embodiment
of the present invention. The retaining member 250 comprises an
upper portion 251, for example made of aluminum, steel, plastic,
ceramic, and the like, with openings 256 for receiving bolts,
screws, and the like, to attach the retaining member 250 on the
base of a polishing head. A lower portion 253 having a bottom
surface 254 and substantially comprised of silicon carbide is
attached to the upper portion 251. Channels or grooves 257 are
formed in the lower portion 253, wherein the channels 257 may be
inclined with respect to the radial direction, as shown in FIG. 2a,
to promote slurry transportation during operation, when the
retaining member 250 is rotated. Due to the increased hardness and
the low wear rate of the lower portion 253, a large number of
channels 257 may be provided compared to conventional devices. FIG.
2a shows twelve channels 257, wherein, however, more than twelve
channels 257 may be provided. In other embodiments, the surface 254
may be provided substantially without any channels 257 so as to act
as an "outer perimeter" of a substrate to be polished, thereby
creating substantially similar polish conditions at the actual
substrate perimeter and inner substrate areas.
[0032] FIG. 3a schematically shows a further cross-sectional view
of a retaining member 350 that may be attached to a polishing head,
such as polishing head 120 shown in FIG. 1a. The retaining member
350 comprises a lower portion 353 with a bottom surface 354,
wherein at least the bottom surface 354 is comprised of a
conductive durable material such as silicon carbide. The lower
portion 353 is attached to an upper portion 351 by means of an
intermediate portion 352 having an increased elasticity so that the
intermediate portion 352 may allow minute deformations in vertical
and lateral directions. The elasticity of the intermediate portion
352 may thus reduce the risk of damage, such as cracks, in the
lower portion 353 despite the high rigidness thereof. The
intermediate portion 352 may be comprised of an adhesive providing
a certain amount of elasticity, or may comprise any other
appropriate elastic material attached to the upper portion 351 and
the lower portion 353 by a suitable adhesive. In one embodiment,
the intermediate portion 352 may comprise a conductive component or
flexible conductive element to allow the application of a reference
potential to the surface 354 to drain off charge carriers created
by friction during the polishing process.
[0033] FIG. 3b schematically shows the retaining member 350,
wherein the surface 354 has a specified profile. The profile may be
selected so as to provide enhanced slurry supply to and from a
substrate and/or may be provided to create a certain "conditioning"
effect on a polishing pad. For example, the profiled surface 354
may comprise a plurality of naps 358 that allow slurry supply and
removal and also rework the polishing pad. Due to the low wear rate
of the lower portion 353 and especially of the naps 358, the risk
of particle contamination of the adjacent substrate is minimal,
although wear of protruding regions is conventionally increased.
Therefore, contrary to conventional retaining rings, an advanced
"slurry channel" topography and/or a conditioning effect may be
provided by the present invention. The specific shape as well as
the dimensions of the naps 358 may be adapted to the specific
requirements in view of enhanced slurry transportation or
conditioning effect. Moreover, different areas having a different
surface profile may be formed on the lower portion 353. For
instance, the lower portion 353 may comprise a substantially flat
bottom surface portion adjacent to the substrate perimeter and,
radially spaced from the substrate, profiled portions for an
enhanced conditioning effect. In other embodiments, the surface 354
may be treated to receive a specified surface roughness, which
allows enhanced slurry transport and conditioning effect at the
same time. The surface roughness may differ from the profiled
surface 354 shown in FIG. 3b in that the roughness is provided on a
microstructure scale, providing protrusions with a height of some
hundred nanometers to a few micrometers and with a lateral distance
of the same order of magnitude. A corresponding surface roughness
may be obtained by well-established etch techniques.
[0034] As a result, the present invention allows significant
stabilization of the process conditions during the chemical
mechanical polishing of a plurality of substrates in that a
retaining member of a polishing head is made of a conductive
material having a high hardness so that its wear rate and thus
particle contamination of the substrate is significantly
reduced.
[0035] The particular embodiments disclosed above are illustrative
only, as the invention may be modified and practiced in different
but equivalent manners apparent to those skilled in the art having
the benefit of the teachings herein. For example, the process steps
set forth above may be performed in a different order. Furthermore,
no limitations are intended to the details of construction or
design herein shown, other than as described in the claims below.
It is therefore evident that the particular embodiments disclosed
above may be altered or modified and all such variations are
considered within the scope and spirit of the invention.
Accordingly, the protection sought herein is as set forth in the
claims below.
* * * * *