U.S. patent application number 10/814587 was filed with the patent office on 2004-12-30 for retaining ring for holding semiconductor wafers in a chemical mechanical polishing apparatus.
This patent application is currently assigned to Ensinger Kunststofftechnoligie GbR. Invention is credited to Ensinger, Wilfried.
Application Number | 20040261945 10/814587 |
Document ID | / |
Family ID | 43706234 |
Filed Date | 2004-12-30 |
United States Patent
Application |
20040261945 |
Kind Code |
A1 |
Ensinger, Wilfried |
December 30, 2004 |
Retaining ring for holding semiconductor wafers in a chemical
mechanical polishing apparatus
Abstract
A retaining ring to be fitted on a chemical mechanical polishing
apparatus for semiconductor wafers is disclosed, the retaining ring
comprising a carrier ring made of a first material and having
fitting elements for fitting the carrier ring on the polishing
apparatus; and a bearing ring comprising a plastic material,
arranged concentrically on the carrier ring, the bearing ring
resting with a first front side on a polishing surface of the
polishing apparatus and being held on its side axially opposed to
the first front side releasably, non-rotatably, with a positive
and/or frictional connection and without adhesive on the carrier
ring; wherein the first material has a higher rigidity than the
plastic material of the bearing ring.
Inventors: |
Ensinger, Wilfried;
(Nufringen, DE) |
Correspondence
Address: |
LEYDIG VOIT & MAYER, LTD
700 THIRTEENTH ST. NW
SUITE 300
WASHINGTON
DC
20005-3960
US
|
Assignee: |
Ensinger Kunststofftechnoligie
GbR
Nufringen
DE
|
Family ID: |
43706234 |
Appl. No.: |
10/814587 |
Filed: |
April 1, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10814587 |
Apr 1, 2004 |
|
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10322427 |
Dec 19, 2002 |
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Current U.S.
Class: |
156/345.12 |
Current CPC
Class: |
B24B 37/32 20130101 |
Class at
Publication: |
156/345.12 |
International
Class: |
B24B 005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 2, 2002 |
DE |
102 47 179.7 |
Claims
What is claimed is:
1. A retaining ring to be fitted on a chemical mechanical polishing
apparatus for semiconductor wafers, comprising: a carrier ring made
of a first material and having fitting elements for fitting the
carrier ring on the polishing apparatus; and a bearing ring made of
a plastic material, arranged concentrically on the carrier ring,
the bearing ring resting with a first front side on a polishing
surface of the polishing apparatus and being held on its side
axially opposed to the first front side releasably, non-rotatably,
with a positive and/or frictional connection and without adhesive
on the carrier ring; the first material having a higher rigidity
than the plastic material of the bearing ring.
2. The retaining ring in accordance with claim 1, wherein the
releasable, non-rotatable, positive and/or frictional connection of
bearing ring and carrier ring is made in the area of an outer
circumferential surface of the bearing ring.
3. The retaining ring according to claim 2, wherein the bearing
ring has adjacent to the side of the carrier ring a step set back
from the circumference and following the circumference for
receiving the carrier ring, and the outer circumferential surface
for establishing the positive and/or frictional connection is a
circumferential surface of the step.
4. The retaining ring according to claim 3, wherein the carrier
ring with its outer circumferential surface is substantially in
alignment with the outer circumferential surface of the bearing
ring.
5. The retaining ring according to claim 3, wherein the bearing
ring has a flange extending around the circumference, projecting
radially outwardly and enlarging the bearing surface of the front
side of this ring.
6. The retaining ring according to claim 1, wherein, in the joined
state, the bearing ring and the carrier ring lie surface-to-surface
against one another in predetermined surface portions, and the
bearing ring and the carrier ring have complementary projections
and recesses for centering the bearing ring and the carrier
ring.
7. The retaining ring according to claim 6, wherein the surface
portions in which carrier ring and bearing ring lie
surface-to-surface against one another have a radial
orientation.
8. The retaining ring according to claim 6, wherein the
complementary projections and recesses of bearing ring and carrier
ring are arranged on the surface portions on which carrier ring and
bearing ring lie against one another.
9. The retaining ring according to claim 8, wherein the projections
and recesses of bearing ring and carrier ring are connectable with
a press fit.
10. The retaining ring according to claim 1, wherein the bearing
ring has on its outer circumference a circumferential collar
pointing in axial direction away from the first front side, lying
against the outer circumferential surface of the carrier ring and
covering the carrier ring over substantially the entire surface
thereof.
11. The retaining ring according to claim 1, wherein the carrier
ring has on its surface portion contacting the bearing ring- a ring
groove having a substantially axially parallel wall with a threaded
section thereon, and the bearing ring has on its side axially
opposed to the first front side one or several projections arranged
complementarily to the ring groove and having a threaded section of
complementary design to the threaded section of the axially
parallel wall of the groove.
12. The retaining ring according to claim 1, wherein the bearing
ring and carrier ring are provided with cooperating detent means
which, when the rings are in the fitted state, form a detent
connection and secure the rings against axially acting forces in
the fitted state.
13. The retaining ring according to claim 12, wherein the detent
connection is designed as securing means against rotation.
14. The retaining ring according to claim 1, wherein the carrier
ring and the bearing ring have surface portions of complementary
design with which they lie against one another in the fitted state,
and the surface portions have projections and recesses of
complementary design for joining the rings by a shrinking-in or
shrinking-on process.
15. The retaining ring according to claim 1, wherein the bearing
ring has on its circumferential surface a ring groove opening
radially outwardly, and the carrier ring comprises several ring
segments including a flange portion of essentially complementary
design to the ring groove and one or more fitting sections which
are provided for fitting the carrier ring on the polishing
apparatus in axial direction from the side facing away from the
bearing surface of the bearing ring.
16. The retaining ring according to claim 15, wherein the fitting
sections comprise elements projecting axially from the flange
portions.
17. The retaining ring according to claim 16, wherein the groove
has in its groove wall facing axially away from the bearing surface
of the bearing ring recesses in which the elements of the fitting
sections are engageable radially from the outside.
18. The retaining ring according to claim 1, wherein the bearing
ring and the carrier ring have complementary surfaces which in the
fitted state are in alignment with one another and form between
them a ring channel which is sealed off by ring-shaped sealing
elements, and the carrier ring has a closable opening accessible
from the outside and leading into the ring channel for evacuation
of the ring channel.
19. The retaining ring according to claim 1, wherein the bearing
ring and the carrier ring have on at least one surface portion on
which these rings lie against one another a cavity formed by
recesses in both the surface of the bearing ring and the surface of
the carrier ring and fillable with a curable material.
20. The retaining ring according to claim 1, wherein the bearing
ring and the carrier ring are rotationally fixedly connected to one
another by a bolt engaging recesses on both the bearing ring and
the carrier ring.
21. The retaining ring according to claim 20, wherein the bolt is a
threaded bolt, and the recess has an internal threaded section
complementary to the outer thread of the threaded bolt.
22. The retaining ring according to claim 20, wherein the bolt is
insertable in axial or radial direction into the recess.
23. The retaining ring according to claim 1, wherein the plastic
material comprises at least one of a thermoplastic material, a
thermosetting plastic material and an elastomer.
24. The retaining ring according to claim 23, wherein the plastic
material is a reinforced plastic material.
25. The retaining ring according to claim 24, wherein the plastic
material is a fiber-reinforced, plastic material.
26. The retaining ring according to claim 23, wherein
abrasion-reducing and/or wear-reducing additives are admixed with
the plastic material.
27. The retaining ring according to claim 1, wherein the bearing
ring comprises at least two layers or components.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This patent application claims the benefit of copending U.S.
patent application Ser. No. 10/322,427, filed Dec. 19, 2002, which
is incorporated by reference, and which claims the benefit of
German Patent Application No. 102 47 179.7, filed Oct. 2, 2002,
which is incorporated by reference.
FIELD OF THE INVENTION
[0002] The invention relates to a retaining ring for holding
semiconductor wafers in a chemical mechanical polishing
apparatus.
BACKGROUND OF THE INVENTION
[0003] Nowadays, integrated circuits are typically formed on
semiconductor substrates, particularly silicon wafers, by the
sequential deposition of conductive, semiconductive and insulative
layers on the wafer. After deposition of each layer, etching is
performed to create the circuitry functions. After a series of
layers have been sequentially deposited and etched, the uppermost
surface of the semiconductor substrate, i.e., the outer surface of
the substrate, becomes increasingly non-planar. This non-planar
surface presents problems in the photolithographic steps of the
integrated circuit fabrication process. Therefore, there is a need
to periodically planarize or level off the semiconductor substrate
surface.
[0004] So-called chemical mechanical polishing (CMP) is one of the
accepted methods for this. This planarization method typically
requires that the substrate, i.e., the semiconductor wafer, be
mounted on a carrier or polishing head. The exposed surface of the
substrate is then pressed against a rotating polishing pad. A
controlled force is exerted on the substrate via the carrier head
to press the substrate against the polishing pad. A polishing agent
containing at least one chemically reactive substance and abrasive
particles is supplied to the surface of the polishing pad.
[0005] A recurring problem in the CMP process is the so-called edge
effect, i.e., the tendency to polish the edge of the substrate at a
different rate than the center of the substrate. This typically
results in over-polishing at the edge, i.e., the removal of too
much material from the edge, particularly at the outermost 5 to 10
mm of a wafer of 200 mm in diameter.
[0006] Over-polishing reduces the overall flatness of the substrate
and makes the edge of the substrate unsuitable for integrated
circuit fabrication and therefore decreases the process yield.
[0007] To solve this problem, U.S. Pat. No. 6,251,215 discloses a
retaining ring be made of two portions, a first portion being made
of a rigid material, namely a metal portion, and a second portion
of a plastic material, which is less rigid, so that, on the one
hand, it can be subjected to abrasion, and, on the other hand, it
will not damage the semiconductor wafer when contacting it.
[0008] Owing to the edge conditions that prevail in chemical
mechanical polishing, U.S. Pat. No. 6,251,215 discloses that the
plastic portion of the retaining ring and the metal ring are bonded
to one another with an epoxy adhesive. Alternatively, it is
disclosed that the two portions are joined together with a press
fit.
[0009] In practice, both solutions prove to be inadequate.
[0010] While the plastic portion is held securely on the metal
portion when the two portions are bonded with epoxy adhesive, the
reconditioning of the retaining ring after the plastic portion has
been subjected to a certain amount of abrasion presents problems.
The current practice is to send the complete retaining rings to the
manufacturer where the plastic portion is mechanically removed and
the metal portion is then heated up to approximately 200.degree. C.
to thermally decompose the adhesive residues thereon. Subsequently,
the metal portion has to be sandblasted in order to remove final
residues of the adhesive, and only then can a new plastic ring be
adhesively attached thereto.
[0011] Owing to this time-consuming and costly procedure, the
retaining rings as such become very expensive. In addition, the
metal portions, which are more expensive to produce than the
plastic portions, only withstand a small number of cycles of
reconditioning, in particular, on account of the temperature
treatment for thermal decomposition of the adhesive and the
sandblasting treatment that is subsequently required.
[0012] Exchanging a used plastic ring when metal and plastic
portions are joined with a press fit is easier, but a press fit for
joining the plastic and metal portions has proven unsuitable for
reliably withstanding the forces that occur during the polishing
process.
[0013] The present invention, relating to a retaining ring that can
be manufactured more cost-effectively and, in particular, fitted
more cost-effectively with a new plastic part, provides for
ameliorating at least some of the disadvantages of the prior art.
These and other advantages of the present invention will be
apparent from the description as set forth below.
BRIEF SUMMARY OF THE INVENTION
[0014] In an embodiment, the invention provides a retaining ring
comprising a carrier ring made of a first material and having
fitting elements for fitting the carrier ring on the polishing
apparatus; and a bearing ring made of a plastic material and
arranged concentrically on the carrier ring, the bearing ring
resting with a first front side on a polishing surface of the
polishing apparatus and being held at its side axially opposed to
the first front side releasably, non-rotatably, with a positive
and/or frictional connection and without adhesive on the carrier
ring; the first material having a higher rigidity than the plastic
material of the bearing ring.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIGS. 1A to 1D show a first embodiment of a retaining ring
according to the invention;
[0016] FIGS. 2A to 2D show a further embodiment of the retaining
ring according to the invention;
[0017] FIGS. 3A to 3D show a further embodiment of the retaining
ring according to the invention;
[0018] FIGS. 4A to 4D show a further embodiment of the retaining
ring according to the invention;
[0019] FIGS. 5A to 5D show a further embodiment of the retaining
ring according to the invention;
[0020] FIGS. 6A to 6D show a further embodiment of the retaining
ring according to the invention;
[0021] FIGS. 7A to 7D show a further embodiment of the retaining
ring according to the invention;
[0022] FIGS. 8A to 8D show a further embodiment of the retaining
ring according to the invention;
[0023] FIGS. 9A to 9D show a further embodiment of the retaining
ring according to the invention;
[0024] FIGS. 10A to 10F show a further embodiment of the retaining
ring according to the invention;
[0025] FIGS. 11A to 11D show a further embodiment of the retaining
ring according to the invention;
[0026] FIGS. 12A and 12B show a further embodiment of a retaining
ring according to the invention; and
[0027] FIGS. 13A and 13B show a further embodiment of a retaining
ring according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0028] In accordance with an embodiment of the present invention, a
retaining ring comprises a carrier ring made of a first material
and having fitting elements for fitting the carrier ring on the
polishing apparatus; and a bearing ring made of a plastic material
and arranged concentrically on the carrier ring, the bearing ring
resting with a first front side on a polishing surface of the
polishing apparatus and being held at its side axially opposed to
the first front side releasably, non-rotatably, with a positive
and/or frictional connection and without adhesive on the carrier
ring; the first material having a higher rigidity than the plastic
material of the bearing ring.
[0029] The releasable, non-rotatable, positive and/or frictional
connection of bearing ring and carrier ring in the retaining ring
according to the invention is preferably made in the area of an
outer circumferential surface of the bearing ring. This allows
optimum conditions for absorbing the forces acting on the carrier
ring during the chemical mechanical polishing process.
[0030] The bearing ring is seated particularly securely on the
carrier ring when the bearing ring has on the side towards the
carrier ring a step which follows the circumference and receives
the carrier ring therein. The circumferential surface for
establishing the positive and/or frictional connection is then a
circumferential surface of the step. The step can extend right
around the circumference or consist of ring-segment-like step areas
disposed over the circumference.
[0031] The carrier ring with its outer circumferential surface will
preferably be substantially in alignment with the outer
circumferential surface of the bearing ring. The carrier ring is
thereby protected to a large extent from soiling and, in
particular, also from subsequent corrosion problems because the
surfaces of the carrier ring pointing towards the polishing surface
are covered by the bearing ring.
[0032] In a variant of the retaining ring according to the
invention, provision may be made for the bearing ring to have a
flange extending around the circumference, projecting radially
outwardly and enlarging the bearing surface of the front side of
this ring. This outwardly projecting flange of the bearing ring
offers the carrier ring additional protection against soiling
during the chemical mechanical polishing process. In particular,
the idea of designing the carrier ring, which is more expensive to
manufacture, as a part which will last as long as possible and be
reusable, and of only exchanging the bearing ring regularly as
required by its state of wear, is thereby realized in an economic
form.
[0033] In this variant of the retaining ring according to the
invention, provision may be made, depending on the rigidity of the
material of the bearing ring, for the carrier ring to also comprise
an outwardly projecting flange for stabilizing the flange of the
bearing ring in its geometrical shape. Depending on what rigidity
the material of the bearing ring exhibits, the flange of the
carrier ring may support the flange of the bearing ring partially
or also over its entire surface.
[0034] Provision is made in a further preferred embodiment of the
present invention for the bearing ring and the carrier ring to lie
in the joined state surface-to-surface against one another in
predetermined surface portions, and for the bearing ring and the
carrier ring to have complementary projections and recesses for
centering the bearing ring and the carrier ring. In particular,
when fitting the bearing ring on the carrier ring, this helps to
achieve exact concentric arrangement and thereby also facilitates
the exchanging of worn bearing rings.
[0035] The surface portions on which bearing ring and carrier ring
lie surface-to-surface against one another preferably have a radial
orientation and form a planar base and hence support for the
bearing ring on the carrier ring.
[0036] Alternatively, a slightly conical configuration of these
surface portions is also conceivable without any major
disadvantages.
[0037] The complementary projections and recesses of bearing ring
and carrier ring for centering the bearing ring with respect to the
carrier ring are preferably arranged in the area of the surface
portions on which carrier ring and bearing ring lie
surface-to-surface against one another.
[0038] In a further preferred embodiment, the complementary
projections and recesses of bearing ring and carrier ring may be
used for making a connection with a press fit.
[0039] In yet another preferred embodiment provision is made for
the bearing ring to have at its outer circumference a
circumferential collar pointing in axial direction away from the
first front side, resting against the outer circumferential surface
of the carrier ring and covering the carrier ring over
substantially the entire surface thereof. This embodiment has the
advantage that the material of the carrier ring is shielded even
better from influences of the chemical mechanical polishing
process, which permits a larger choice of materials for
manufacturing the carrier ring. At the same time, an exact
centering can be ensured by the circumferential collar of the
bearing ring. It is also conceivable to design the collar for a
press fit connection with the carrier ring.
[0040] Provision is made in an alternative embodiment of the
present invention for the carrier ring to have on its surface
portion that contacts the bearing ring a ring groove having a
substantially axially parallel wall with a threaded section
thereon, for the bearing ring to have on its side axially opposed
to the first front side one or several projections arranged
complementarily to the ring groove and having a threaded section of
complementary design to the threaded section of the axially
parallel wall of the groove. This makes it possible for the carrier
ring to be screwed to the bearing ring, and in one variant the
bearing ring has a collar extending around the circumference as
projection with a threaded section.
[0041] Alternatively, the ring collar may be divided up into
several ring segments spaced from one another.
[0042] A further alternative for joining bearing ring and carrier
ring includes providing these with cooperating detent means which
in the fitted state of the rings form a detent connection and
secure the rings against axially acting forces in the fitted state.
The detent connection is preferably designed so as to
simultaneously act as securing means against rotation. To this end,
several snap connections may, for example, be disposed over the
circumference of the ring, with detent noses engaging individual
recesses and thereby preventing rotation of the bearing ring
relative to the carrier ring in the snapped-in state.
[0043] Provision is made in a further alternative embodiment of the
present invention for the carrier ring and the bearing ring to have
surface portions of complementary design with which they rest
against each other in the fitted state, and for the surface
portions to have projections and recesses of complementary design
for joining the rings by a shrinking-in or shrinking-on process.
Here, too, the connection between bearing ring and carrier ring can
simultaneously be secured against rotation by corresponding design
of the projections and recesses.
[0044] Yet another alternative embodiment of the present invention
makes provision for the bearing ring to have on its circumferential
surface a ring groove opening radially outwardly, and for the
carrier ring to be made up of several ring segments including a
flange portion of essentially complementary design to the ring
groove and one or several fitting sections which are provided for
fitting the carrier ring on the polishing apparatus in axial
direction from the side facing away from the bearing surface of the
bearing ring.
[0045] In the simplest case, the carrier ring consists of two ring
segments, i.e., of two ring halves, as it were, which are pushed in
radial direction onto the bearing ring. Here the flange portions
simultaneously act as the reinforcement of the bearing ring and
thereby ensure that it retains its shape. At the same time, the
flange portions carry several fitting sections with which the
entirety of bearing ring and carrier ring can then be attached to
the polishing apparatus. These fitting sections, may, for example,
comprise simple bushings with an internal thread.
[0046] Alternatively, the flange portions may also have bores with
an internal thread into which fitting bolts are directly
screwable.
[0047] As an alternative to the two ring halves, several ring
segments may be disposed over the circumference so as to form the
carrier ring. These ring segments do not necessarily have to be
directly adjacent to one another, but may be spaced from one
another. The size of the spacing between the individual ring
segments or their flange portions in circumferential direction
depends on the rigidity of the material of the bearing ring.
[0048] In a preferred embodiment, the groove is designed so as to
have recesses in its groove wall facing axially away from the
bearing surface of the bearing ring. Elements of the fitting
sections are then radially insertable from the outside into these
recesses which point in the direction towards the polishing
apparatus. These may, for example, be bushings which are placed on
the flange portions. The recesses may, however, also make bores
with an internal thread, which are formed in the flange itself,
accessible.
[0049] An embodiment of the present invention which differs
significantly from the previously described embodiments provides
for the bearing ring and the carrier ring to have complementary
surfaces which in the fitted state are in alignment with one
another and form between them a ring channel which is sealed off
from the environment by ring-shaped sealing elements, and for the
carrier ring to have a closable opening accessible from the outside
and leading into the ring channel for evacuation of the ring
channel.
[0050] Alternatively, the closable opening leading into the ring
channel could, of course, also be arranged on the bearing ring. For
cost reasons it is, however, preferable to provide this on the
carrier ring.
[0051] A frictional connection between bearing ring and carrier
ring can then be made by evacuation of the ring channel. The
bearing ring can be removed and exchanged by simple aeration of the
ring channel.
[0052] In each embodiment described hereinabove, a securing against
rotation is preferably achieved by providing on the bearing ring
and the carrier ring on at least one surface portion on which these
rings lie against one another, a cavity which is formed by recesses
in both the surface of the bearing ring and the surface of the
carrier ring. This cavity can then be filled with a curable
material. Once the curable material has hardened, this prevents
rotational movement between bearing ring and carrier ring. A
securing of the carrier ring on the bearing ring and vice-versa in
axial direction can also be provided by corresponding design and
arrangement of such a cavity.
[0053] As an alternative to this, the bearing ring and the carrier
ring can be rotationally fixedly connected to one another by a bolt
engaging recesses on both the bearing ring and the carrier ring.
Here it is preferable to use a threaded bolt which at the same time
can then be secured by tightening it in the recess.
[0054] Such screw bolts can be inserted in both axial and radial
direction into corresponding recesses and similarly serve in any
case to prevent rotation.
[0055] In a preferred embodiment, the plastic material includes a
thermoplastic material, a thermosetting plastic material, an
elastomer and/or a plastic composition.
[0056] It is advantageous for the plastic material to be a
reinforced, in particular a fiber-reinforced, plastic material.
[0057] To improve the tribological properties, it has proven
expedient to admix abrasion-reducing and/or wear-reducing
additives, for example, PTFE, polyimide, molybdenum disulfide,
graphite, boron nitride, nanoparticles or the like with the plastic
material.
[0058] It is of particular advantage for the bearing ring to be
made up like a sandwich of at least two layers or components.
[0059] A simple but cost effective means for providing a retaining
ring according to the invention is to form the carrier ring from a
plastics material of increased mechanical stability whereas the
bearing ring contacting the polishing surface of the polishing
apparatus is made of a less hard plastics material. In one step the
carrier ring of said plastic material of high mechanical stability,
especially a reinforced plastic material, is producted while in
another step said bearing ring is manufactured of a plastic
material which has been optimized for contacting the polishing
surface of the polishing apparatus.
[0060] The plastic resin on which the plastics materials of the
carrier ring and the bearing ring is based may be the same or
different and may form a matrix in which a reinforcing and a wear
reducing compound are accommodated, respectively.
[0061] The resin for the bearing ring may be selected independently
from the matrix forming resin of the carrier ring, however, use of
the same resin is preferred.
[0062] The resin of the bearing ring may be modified in order to
reduce wear and to optimize tribological properties as herein
before described in connection with another embodiment of the
invention.
[0063] The carrier and bearing rings can be releasably attached to
one another by a friction welding process.
[0064] In accordance with another embodiment of the retaining ring
of the invention the carrier ring may be a metal ring which may be
pretreated on at least a portion of its surface by metal spraying
it with metal plasma.
[0065] Using this technology a coating of metal beads is formed on
the surface portions of the carrier ring to be pretreated. The
coating of metal beads can be applied as a so-called mono-layer,
however, superimposed multiple layers are preferred.
[0066] Very good results are obtained when a coating of a thickness
of 700 .mu.m or more is applied, the preferred average diameter of
the metal beads being 300 .mu.m to 600 .mu.m, more preferably 400
.mu.m to 500 .mu.m.
[0067] The thickness of the coating may be up to 1 mm or more.
However, thicknesses in excess of 1 mm do not provide for further
advantages.
[0068] The metal beads coating produced by the metal spraying
process provides for numerous microscopic recesses and interstices
into which the plastic material flows when the bearing ring is
injection moulded onto the carrier ring.
[0069] The plastic material is made to partially enter the recesses
and interstices only so as to establish a releasable interlocking
bonding between the plastic material of the bearing ring and the
metal beads coating of the carrier ring.
[0070] Each of the components of the invention will now be
described in more detail below, wherein like components have like
reference numbers.
[0071] FIG. 1A shows in a plan view from the side facing the
polishing apparatus a retaining ring 10 according to the invention
for assembly on a chemical mechanical polishing apparatus for
semiconductor wafers. The retaining ring 10 comprises a carrier
ring 12 made of a first material, in particular, metallic materials
and/or plastic materials with a stability like that of metallic
materials, in particular, fiber-reinforced plastics.
[0072] Arranged concentrically on the carrier ring 12 is a bearing
ring 14 made of a plastic material. The first material has a higher
rigidity than this plastic material.
[0073] At regular angular intervals on its side lying towards the
polishing apparatus, the carrier ring 12 has threaded bores 16 for
attaching the retaining ring to the chemical mechanical polishing
apparatus.
[0074] On its side pointing towards the polishing apparatus, the
carrier ring 12 also has an opening 18 into which a projection (not
shown) on the polishing apparatus extends when the retaining ring
is fitted on the polishing apparatus, so that provision is always
made for a defined assembly position of the retaining ring in the
polishing apparatus. This is facilitated, in particular, by the
alignment of the threaded bores 16 with corresponding through-holes
on the polishing apparatus, through which threaded bolts are
screwed into the threaded bores 16 and the retaining ring is
thereby attached to the polishing apparatus.
[0075] FIG. 1B shows a sectional view of the retaining ring 10 of
FIG. 1A along line A-A and elucidates the principle according to
which the bearing ring made of plastic material is held without
adhesive, releasably, non-rotatably, with a positive and/or
frictional connection on the carrier ring. For this purpose, the
bearing ring 14 has on its side facing the carrier ring 12 a step
22 set back from the outer circumference 20, as shown in the
enlarged, more detailed illustration in FIG. 1C. In order to
releasably and non-rotatably join the carrier ring and the bearing
ring to one another with a frictional connection, the carrier ring,
which, in the given example, is made of steel, is shrunk onto the
bearing ring which is made of plastic. The plastic material of the
bearing ring is preferably a polyphenylene sulfide material (PPS),
a PEEK, PAI, PI, PA, POM, PET or a PBT in pure or modified form. To
improve the tribological properties, abrasion-reducing and/or
wear-reducing additives, for example, PTFE, polyimide, molybdenum
disulfide, graphite, boron nitride, nanoparticles or the like, may
be added.
[0076] An excellent overall stability is imparted to the retaining
ring 10 by the greater rigidity of the steel material of the
carrier ring 12, whereas the plastic material of the bearing ring
14 lies slidingly on the abrasion surface of the chemical
mechanical polishing apparatus, and the semiconductor wafer is held
within the ring space 24 defined by the bearing ring during the
polishing process. The advantage of this embodiment resides, in
particular, in that the steel ring can be shrunk onto the plastic
bearing ring 14, and a frictional, releasable but nevertheless
non-rotatable connection is obtained. When the bearing ring 14 is
worm, it can be removed very easily from the carrier ring 12 and
replaced by a new bearing ring 14. The exchanging procedure is
significantly easier than is the case with the prior art, and there
is no need for removal of any adhesive residues, etc. There is also
no need for the carrier ring 12 to be specially prepared before
being equipped with a new bearing ring 14, and it itself therefore
undergoes considerably less wear.
[0077] The circumferential surface 20 of the retaining ring 10 is
substantially free of steps, i.e., the outer circumference of the
bearing ring 14 is in alignment with the outer circumference of the
carrier ring 12. Owing to the bearing ring 14 extending radially
further inwards than the carrier ring 12 and, in addition,
receiving the carrier ring 12 in a step 22 (FIG. 1C) set back from
the outer circumference 20, the ring space 24 is essentially
delimited exclusively by the bearing ring 14. The semiconductor
wafer to be polished in the chemical mechanical polishing apparatus
therefore only comes into contact with the relatively soft plastic
material of the bearing ring 14, which minimizes the risk of damage
occurring to the edge of the semiconductor wafer.
[0078] FIG. 1D again shows a perspective view of the retaining ring
10, which, in particular, illustrates that the inner space of the
retaining ring 10 is mainly delimited by the bearing ring 14.
[0079] FIGS. 2A to 2D show a further variant of a retaining ring 30
according to the invention, which, like the retaining ring 10 of
FIGS. 1A to 1D, comprises a carrier ring 32 made of steel and a
bearing ring 34 made of plastic material. At regular angular
intervals, the carrier ring 32 has threaded bores 36 which serve to
attach the retaining ring 30 to the chemical mechanical polishing
apparatus. An opening 38 ensures a defined assembly position of the
retaining ring in the chemical mechanical polishing apparatus by a
projection on this apparatus engaging the opening 38 in the fitted
state. The threaded bores 36 are therefore in alignment with the
corresponding attachment elements on the polishing apparatus, and
the fitting can then be carried out in a simple way with screw
bolts. The outer circumference of the retaining ring 30 is designed
such that the outer circumferential surfaces of carrier ring 32 and
bearing ring 34 are in alignment with one another. The bearing ring
34 extends in a radial direction further towards the center than is
the case with the carrier ring 32.
[0080] A step 42 set back from the outer circumference 40 is
provided on the bearing ring 34 for receiving the carrier ring 32
(FIG. 2C). Therefore, an inner space 44 formed by the retaining
ring 30 is again essentially delimited exclusively by the bearing
ring 34, i.e., by its relatively soft plastic material. As shown in
FIG. 2B, this is apparent from the sectional view taken along line
A-A in FIG. 2A. This is also illustrated, in particular, in FIG.
2D. In the area of the step 42, the bearing ring 34 has on its
radial surface contacting the carrier ring 32 a ring-shaped rib 43
which engages a complementary ring groove 45 on the underside of
the carrier ring 32.
[0081] In this embodiment of the retaining ring according to the
invention, the connection between the bearing ring 34 and the
carrier ring 32 can be made with a press fit by the ring-shaped rib
43 being pressed into the ring groove 45.
[0082] The carrier ring and the bearing ring are thereby joined
with a positive and frictional connection, which results in a
non-rotatable connection without adhesive. This connection is
releasable in the event of abrasive wear of the bearing ring 34,
and the carrier ring 32 can be equipped with a new bearing ring 34
with a press fit without the carrier ring 32 having to be prepared
to any great extent for the insertion of the new bearing ring 34.
In particular, the troublesome removal of adhesive residues, as is
necessary in the prior art and also results in wear of the carrier
ring itself, is dispensed with.
[0083] Owing to the inventive design of the retaining ring 30, in
principle, any number of bearing rings 34 can be used with a single
carrier ring 32. The costs for the chemical mechanical polishing of
semiconductor wafers can thereby be drastically reduced, in
particular, also because the bearing ring 34 as part which is
subjected to wear can be manufactured considerably more
cost-effectively than the carrier ring 32 which involves relatively
high manufacturing expenditure.
[0084] With this retaining ring, too, the carrier ring 32 again
assumes the task of mechanically stabilizing the ring and thereby
ensuring a fixed geometry thereof. The bearing ring 34 with its
relatively soft material protects the semiconductor wafers against
contact with the carrier ring 32 and thereby obviates damage to the
edge of the semiconductor wafers.
[0085] A further variant of a retaining ring 50 according to the
invention is shown in FIGS. 3A to 3D. Here, too, a carrier ring 52
assumes the task of mechanically stabilizing the retaining ring 50
and guaranteeing its exact geometry. It is preferably made of
steel.
[0086] On its side pointing towards the bearing surface of the
chemical mechanical polishing apparatus, the carrier ring 52
carries a bearing ring 54 which again is made of plastic
material.
[0087] On its side lying towards the polishing apparatus, the
carrier ring 52 has at regular angular intervals threaded bores 56
via which the retaining ring 50 can be joined by threaded bolts to
the polishing apparatus. The carrier ring 52 also has on its side
facing the polishing apparatus an opening 58 for defined insertion
of the retaining ring 50 in the chemical mechanical polishing
apparatus, so that the threaded bores 56 align with corresponding
through-holes on the polishing apparatus and screw bolts can be
easily inserted and screwed in here.
[0088] FIG. 3B shows a sectional view of a retaining ring 50
according to the invention taken along line A-A of FIG. 3A. Here it
is apparent that the outer circumference 60 of the retaining ring
50 is formed by a collar 66 carried by the bearing ring 54,
extending in axial direction and essentially covering the outer
circumferential surface of the carrier ring 52 completely. The
carrier ring 52 is therefore arranged in a ring channel 62 of the
bearing ring 54 and substantially covered by the plastic material
of the bearing ring on its surfaces extending in axial
direction.
[0089] This opens up the possibility for the designer to use a more
advantageous metallic material which has the same mechanical
properties as the steel material referred to previously, but is
more cost-effective, in particular, also for the manufacturing
processes of the carrier ring 52. The plastic material of the
bearing ring 54 protects the surfaces of the carrier ring 52 in
those areas in which it might possibly come into contact with the
chemical agents used for the chemical mechanical polishing process.
Therefore, corrosion does not occur at the surface of the carrier
ring even when more cost-effective materials are used.
[0090] In the embodiment of a retaining ring 50 shown in FIG. 3,
the carrier ring 52 is joined to the bearing ring 54 with a press
fit, so that here again there is an adhesive-free connection. The
frictional connection between the carrier ring 52 and the bearing
ring 54 is normally sufficient to also ensure a rotationally fixed
connection here.
[0091] In the event of special stresses, a means for preventing
rotation can, however, be provided, as shown by way of example in
FIG. 3D. For this purpose, there are provided at one or several
locations on the carrier ring 52 and the bearing ring 54 at
intervals over the circumference of the retaining ring 50 recesses
which together form a cavity which can be filled with a curable
organic or inorganic material. When fitting the carrier ring 52 on
the bearing ring 54, the material is still soft and shapeable and
therefore substantially fills out the cavities formed by the
recesses on the bearing ring 54 and the carrier ring 52. The
material in the recesses is then cured and thus forms a securing
means against rotation. At the same time, a kind of securing means
is created to prevent the bearing ring 54 from being readily
detachable from the carrier ring 52.
[0092] The choice of curable materials as filler 69 for filling the
cavity 68 is very wide as these materials are completely shielded
from the environment and merely have to meet the mechanical
requirements specified by the mechanical strain during the
polishing process. It is preferable for thermally curable materials
to be used.
[0093] In this variant, too, the bearing ring 54 extends so far
inwards in radial direction of the retaining ring 50 that the inner
space 64 thereby created is substantially delimited by the
relatively soft material of the bearing ring 54 and the
semiconductor wafers held therein cannot become damaged at their
edges during the chemical mechanical polishing process.
[0094] The means for preventing rotation in the retaining rings
according to the invention as described hereinabove with reference
to FIG. 3B can also be applied to the embodiments of the retaining
rings 10 and 30, which had already been previously described, and
likewise to the majority of the retaining rings discussed
hereinbelow, even though specific mention is no longer made of
this.
[0095] FIGS. 4A to 4D show a further variant of a retaining ring 70
according to the invention, which is essentially comprised of two
parts, namely a carrier ring 72 and a bearing ring 74. The carrier
ring 72 again has at regular angular intervals threaded bores 76
and an opening 78 whose function corresponds to the threaded bores
and openings of the previously described retaining rings. Here,
too, the bearing ring 74 extends radially further inwards than the
carrier ring 72 and thereby provides an inner space 84 which is
substantially delimited by the plastic material of the bearing ring
74 and is therefore gentle on the semiconductor wafers accommodated
therein. Here again the outer circumference 80 of the retaining
ring 70 is formed by the plastic material of the bearing ring 74
and its collar 86 so that the material of the carrier ring 72 can
be selected solely from the point of view of the required
stability, irrespective of whether it is sufficiently non-reactive
to the chemical agents used in the chemical mechanical polishing
process. The collar 86 protects the outer surface of the carrier
ring 72 against any possible attack by these materials. In
addition, the carrier ring 72 is pressed into a ring channel 82, as
is best shown in the detailed illustration in FIG. 4B, which
represents a sectional view taken along line A-A in FIG. 4A, and
similarly in FIG. 4C.
[0096] The detailed illustration in FIG. 4C also shows a special
feature of this variant of the retaining ring 70, which is
otherwise similar in design to the retaining ring 50 of FIGS. 3A to
3D.
[0097] A detent connection 85 consisting of a nose 87 held
resiliently on the bearing ring 74 and a recess therefor arranged
in the inner circumferential wall of the carrier ring 72 is
provided on the inner circumferential wall of the ring channel 82
at at least one location, but even better at regular angular
intervals over the entire circumference of the ring channel 82.
[0098] On pressing the carrier ring 72 into the ring channel 82 of
the bearing ring 74, the detent connection 85 engages in the end
position, i.e., the nose 87 snaps into the complementary recess on
the carrier ring 72 and thereby provides a safeguard against
detachment, on the one hand, and establishes a non-rotatable
connection between carrier ring 72 and bearing ring 74, on the
other hand.
[0099] Adequate non-rotational fixing is usually already achieved
by pressing the carrier ring 72 into the bearing ring 74, so that
the detent connection 85 merely constitutes an additional securing
against rotation.
[0100] Here, too, it is possible to easily detach the bearing ring
74 from the carrier ring 72 in the event of excessive wear and
replace it with a new bearing ring 74. In this case, too, it is not
necessary to specially clean or prepare the carrier ring 72 before
a new bearing ring 74 can be fitted.
[0101] FIGS. 5A to 5D show a further variant of a retaining ring 90
according to the invention. The retaining ring 90 is comprised of a
carrier ring 92 and a bearing ring 94, and the carrier ring 92 is
again preferably made of steel, and the bearing ring 94 of a
plastic material, in particular, of polyphenylene sulfide, PEEK,
PAI, PI, PA, POM, PET or of PBT in pure or modified form. Again,
abrasion-reducing and/or wear-reducing additives, for example,
PTFE, polyimide, molybdenum disulfide, graphite, boron nitride,
nanoparticles or the like, may be added to improve the tribological
properties.
[0102] Here the outer circumference 100 of the retaining ring 90 is
formed by the outer surfaces of carrier ring 92 and bearing ring 94
in alignment with one another.
[0103] Differently from the variants previously presented, no
recessed step is provided on the bearing ring 94, but instead a
radial surface 102 which is located opposite the carrier ring 92.
This radial surface 102 contains one or several, in the illustrated
case five, concentric ring-shaped ribs 103 protruding in axial
direction from the radial surface 102. The surface of the carrier
ring 92 which is complementary to the radial surface 102 has
corresponding concentric undercuts 104 for receiving the ribs
103.
[0104] The ribs 103 are preferably incorporated in the undercuts
104 by a shrinking-on or shrinking-in process. Either the metallic
material of the carrier ring 92 is first heated so that the
undercuts 104 expand, the bearing ring 94 with its ribs 103 is then
placed on the carrier ring 92 and the ribs are inserted into the
undercuts, and as the carrier ring 92 cools down the undercuts
contract and thereby hold the ribs 103 with a positive and
frictional connection. Or the plastic material can be cooled down
and the ribs 103 inserted into the undercuts 104.
[0105] In this way, a positive and frictional connection can be
made between the carrier ring 92 and the bearing ring 94 in this
variant.
[0106] Here, too, the positive and frictional connection provides a
safeguard against rotation, which can, however, be further
improved, as shown in the previous variants, for example, by
provision of further securing means against rotation.
[0107] The design of the retaining ring 90 is apparent, in
particular, from FIG. 5B, which represents a sectional view taken
along line A-A of FIG. 5A, and from the detailed illustration of
FIG. 5C.
[0108] FIGS. 6A to 6D show a further variant of the retaining ring
110 according to the invention with a carrier ring 112 and a
bearing ring 114.
[0109] The special feature of this embodiment is that the carrier
ring 112 is segmented, i.e., no longer of integral design, as was
the case with the previously discussed retaining rings 10, 30, 50,
70 and 90.
[0110] The bearing ring 114 has on its outer circumference a
radially recessed step 116 having on its radially outer
circumferential wall a ring groove 118 extending radially inwardly.
The carrier ring 112 has at its end facing the bearing ring 114 a
radially inwardly projecting flange 120 which is pressed into the
ring groove 118 of the bearing ring 114 when assembling the
retaining ring 110. FIG. 6B shows this in detail in the sectional
view taken along line A-A of FIG. 6A. This is also apparent from
the enlarged detailed illustration of FIG. 6C.
[0111] Finally, FIG. 6D shows the segmentation of the carrier ring
112 into two semicircular segments 122 which together form the
carrier ring 112. Here again threaded bores 124 via which the
carrier ring 112 can be screwed to the polishing apparatus are
provided in the carrier ring segments 122. An opening 126 on the
upper side of the carrier ring 112 again ensures a correct assembly
position for the retaining ring on the polishing apparatus.
[0112] In this variant, separation of the carrier ring 112 from the
bearing ring 114 is particularly simple, and, again, no further
preparation work is required before connecting a new bearing ring
114 to the carrier ring 112.
[0113] FIGS. 7A to 7D show a further variant of a retaining ring
130 according to the invention with a carrier ring 132 and a
bearing ring 134. In this variant, the concept of segmentation of
the carrier ring 132, as already realized in the embodiment of
FIGS. 6A to 6D, is further developed, and a total of 12 segments
133 are present herein (cf., in particular, the spatial
illustration in FIG. 7D together with the carrier ring 132).
[0114] The bearing ring 134 is of integral design and has on its
outer circumference 136 a slot 137 extending around the
circumference (cf. sectional view taken along line A-A of FIG. 7A
as shown in FIG. 7B) and on the side pointing towards the polishing
apparatus, at regular angular intervals, open slot-like recesses
138 extending from the outer circumference and in axial direction
towards the polishing apparatus.
[0115] The carrier ring segments 133 include a flange portion 139
which may, for example, be made of flat material. On its surface
pointing towards the polishing apparatus, the flange portion 139
carries a threaded bushing 140 which engages the slot-like recesses
138 upon inserting the flange portion 139 into the ring slot 137
and is thus accessible from the polishing apparatus side for screw
connection of the retaining ring 130 (FIG. 7C).
[0116] Upon inserting the flange portions 139 into the ring slot
137 on the outer circumference 136 of the bearing ring 134, the
flange portions 139 are pressed in so that these are held with a
press fit in the bearing ring 134. A securing against rotation is
achieved automatically by engagement of the threaded bushings 140
in the slot-like recesses 138 so that no further measures for
preventing rotation are necessary here.
[0117] In this case, to ensure a specific positioning of the
retaining ring 130 in the polishing apparatus, the bearing ring 134
has an opening 142 in which a projection on the polishing apparatus
(not shown) engages and thereby effects a definite positioning of
the retaining ring 130 in the polishing apparatus.
[0118] A further variant of a retaining ring 150 according to the
invention with a segmented carrier ring 152 is shown in FIGS. 8A to
8D. Again the bearing ring 154 has in the area of a step 156 a ring
groove 158 opening radially outwardly, while the carrier ring 152,
which is made up of ring segments 153, carries at its end pointing
towards the bearing surface a segment flange pointing radially
inwardly. In the fitted state, this ring segment flange 160 engages
the ring groove 158 and is pressed in there. Differently from the
variant shown in FIGS. 7A to 7D, the threaded bores 162 are
incorporated in the ring segments 153, and a corresponding opening
164 is likewise formed by the ring segments 153.
[0119] FIGS. 9A to 9D show a further variant of a retaining ring
170 according to the invention with an integral carrier ring 172
and an integral bearing ring 174. In this variant, the carrier ring
172 is provided with a concentric ring groove 176 with a
substantially axially parallel wall 178, which is most clearly
apparent from the sectional view in FIG. 9B (sectional illustration
taken along line A-A of FIG. 9A) and from the detailed illustration
in FIG. 9C.
[0120] A threaded section 179 is machined in the axially parallel
wall 178. The bearing ring 174 has on its side pointing towards the
carrier ring side a ring-shaped rib 180 which may also include ring
segments. This means that the rib 180 does not have to be provided
throughout the entire range of 360.degree., but can also be formed
in sections only. This rib 180 has on its inner, axially parallel
wall an internal threaded section with which the bearing ring 174
can be screwed to the carrier ring 172.
[0121] In this way, too, carrier ring 172 and bearing ring 174 can
be joined with a positive and frictional connection, and, as a
rule, a rotationally fixed connection can also be achieved by
appropriate choice of the force or torque with which the threaded
connection is tightened at the end. The rotationally fixed
connection between carrier ring 172 and bearing ring 174 can also
be additionally secured by resorting to securing means such as
those described in conjunction with FIG. 3D. Again, threaded bores
182 are arranged at regular angular intervals on the carrier ring
172 to enable the retaining ring 170 as a whole to be fitted on the
polishing apparatus. An opening 184 for engagement with a
corresponding projection on the polishing apparatus again ensures
correct orientation of the retaining ring when being fitted on the
polishing apparatus.
[0122] FIGS. 10A to 10F show a further variant of a retaining ring
190 according to the invention, in which the positive and
frictional connection between a carrier ring 192 and a bearing ring
194 is also made by a screw connection. The carrier ring 192 is
accommodated in a step 198 set back from the outer circumference
196 and having an axially parallel wall 199 with a threaded section
200 integrated therein. The carrier ring 192 also has on its inner
axially parallel surface a threaded section with which it can be
screwed to the bearing ring 194. Here again a positive and
frictional connection between the carrier ring 192 and the bearing
ring 194 can be established by the screw connection, and, as a
rule, this connection is adequately fixed against rotation.
[0123] To achieve additional securing against rotation, either
flowable, curable material can be introduced into recesses, as
shown in FIG. 3D, and cured after assembly has been completed, or,
as shown in the variants of FIGS. 10D and 10E, rotation of bearing
ring 194 in relation to carrier ring 192 can be prevented by a
securing pin or a securing bolt. As shown in FIG. 10D, a radially
inserted bolt 202 is provided so as to both extend in radial
direction through the carrier ring 192 and engage the bearing ring
194.
[0124] An alternative variant for this kind of securing is shown in
FIG. 10E, where a securing bolt 204 is inserted in axially parallel
arrangement into a bore which is jointly formed by a recess on the
carrier ring 192 and a recess on the bearing ring 194. Threaded
bores 206 are again arranged on the carrier ring 192 to enable
attachment of retaining ring 190 to the polishing apparatus. An
opening 208 ensures correct assembly of the retaining ring 190 on
the polishing apparatus.
[0125] Finally, FIGS. 11A to 11D show a further variant of a
retaining ring 210 according to the invention, which is formed by a
carrier ring 212 and a bearing ring 214. The carrier ring again has
threaded bores 216 arranged at regular angular intervals on its
surface pointing towards the polishing apparatus and an opening 218
for ensuring correct positioning of the retaining ring 210 on the
polishing apparatus. Here the carrier ring 212 and the bearing ring
214 lie with two substantially parallel surfaces opposite one
another, and one or several, in the present case three, concentric
ring channels 221, 222, 223 are machined in the surface of the
carrier ring 212 (cf. enlarged detailed illustration in FIG. 11C).
Arranged adjacent to the radially outer areas of the carrier ring
212, in the shape of rings and concentrically are grooves 224, 225
which receive sealing elements 226, 227. The ring channels 221,
222, 223 are in flow connection with one another (not shown in
detail). At at least one location, the carrier ring 212 has a
radial bore 228 which meets an axial bore 230 leading from the
surface of the carrier ring 212 facing away from the bearing ring
214 into at least one of the ring channels 221, 222 or 223.
[0126] A plug 232 can be screwed into the axial bore 230 and
initially held in an only slightly screwed-in state in the bore
230. Once the bearing ring 214 is joined to the carrier ring 212, a
vacuum can be applied via the radial bore 228 and the volume of the
ring channels 221, 222, 223 thereby evacuated. Owing to the vacuum
created in the ring channels, the bearing ring 214 can then be
readily held on the carrier ring 212. The plug 232 can then be
screwed further into the bore 230 so that the radial bore 228 is
closed. The vacuum is thus maintained in the ring channels 221,
222, 223 without any need for further evacuation via the radial
bore 228. This provides a very simple, releasable connection
between the carrier ring 212 and the bearing ring 214, which with a
frictional connection ensures a rotationally fixed connection
between these two parts of the retaining ring 210.
[0127] When exchanging the worn bearing ring 214, the plug 232 then
only has to unscrewed until aeration of the ring channels 221, 222,
223 is possible via the radial bore 228. The bearing ring 214 can
then be removed from the carrier ring 212 without applying force,
and a new bearing ring 214 can be fitted to the carrier ring 212 in
the previously described manner.
[0128] FIGS. 12A and 12B show another embodiment of the invention
where a retaining ring 250 is composed of a carrier ring 252 which
is made of a first plastic material, and a bearing ring 254 made of
a second plastic material. A number of threaded bushings 256 are
incorporated at regular angular intervals in the carrier ring
252.
[0129] The carrier ring 252 and bearing ring 254 are attached to
one another via a bonding layer 258. The faces of the first and
second ring portions 252 and 254 which meet at the bonding layer
258 are essentially identical in their radial extensions.
[0130] The bonding layer 258 is created when friction welding the
carrier and the bearing rings together to form a releasable
bonding.
[0131] While the first plastic material is selected such that it
provides high stability to the carrier ring 252, the second plastic
material is selected to optimize wear and tribological properties
of the bearing ring 254. The first plastic material is preferably a
reinforced plastic resin while the second plastic material
incorporates preferably no or a lower amount of reinforcing
component. The second plastic material preferably contains wear
reducing components since it is designed to contact the polishing
surface of the polishing apparatus.
[0132] The plastic resin used in the first and second plastic
materials may be the same or different forming a matrix to hold the
reinforcing and wear reducing components, respectively. Preferably
the basic resin for the first and second plastic material is the
same.
[0133] FIGS. 13A and 13B show a further embodiment of a retaining
ring 260 of the invention. The retaining ring 260 comprises a metal
carrier ring 262 which carries a bearing ring 264 made of a
plastics material. The metal carrier ring 262 is preferably made of
steel. On a surface of the metal ring 262 contacting the bearing
ring 264 a coating 266 of metal beads, preferably of copper or a
copper alloy, is deposited, which provides for numerous
micro-interstices which allow the plastic material to partially
flow into the coating 266 thereby providing a releasable positive
connection between the metal carrier ring 262 and the bearing ring
264 upon the injection moulding process.
[0134] The surface portion of the metal carrier ring 262 having the
coating 266 is preferably limited by a rim 268 the height of which
may be approximately 1 mm. The metal beads forming the coating 266
preferably have an average diameter of 400 .mu.m to 500 .mu.m. The
metal beads may be deposited on the surface portion of the metal
carrier ring 262 as a mono-layer, however, a multiple layer
structure as schematically indicated in FIG. 13B is preferred.
[0135] For creating a releasable bond or releasable positive lock
between the metal carrier ring 262 and the bearing ring 264 it is
essential that the plastics material fills only part of the voids
volumes of the interstices between the metal beads.
[0136] All references, including publications, patent applications,
and patents, cited herein are hereby incorporated by reference to
the same extent as if each reference were individually and
specifically indicated to be incorporated by reference and were set
forth in its entirety herein.
[0137] The use of the terms "a" and "an" and "the" and similar
referents in the context of describing the invention (especially in
the context of the following claims) are to be construed to cover
both the singular and the plural, unless otherwise indicated herein
or clearly contradicted by context. Recitation of ranges of values
herein are merely intended to serve as a shorthand method of
referring individually to each separate value falling within the
range, unless otherwise indicated herein, and each separate value
is incorporated into the specification as if it were individually
recited herein. All methods described herein can be performed in
any suitable order unless otherwise indicated herein or otherwise
clearly contradicted by context. The use of any and all examples,
or exemplary language (e.g., "such as") provided herein, is
intended merely to better illuminate the invention and does not
pose a limitation on the scope of the invention unless otherwise
claimed. No language in the specification should be construed as
indicating any non-claimed element as essential to the practice of
the invention.
[0138] Preferred embodiments of this invention are described
herein, including the best mode known to the inventors for carrying
out the invention. Of course, variations of those preferred
embodiments will become apparent to those of ordinary skill in the
art upon reading the foregoing description. The inventors expect
skilled artisans to employ such variations as appropriate, and the
inventors intend for the invention to be practiced otherwise than
as specifically described herein. Accordingly, this invention
includes all modifications and equivalents of the subject matter
recited in the claims appended hereto as permitted by applicable
law. Moreover, any combination of the above-described elements in
all possible variations thereof is encompassed by the invention
unless otherwise indicated herein or otherwise clearly contradicted
by context.
* * * * *