Information
-
Patent Grant
-
6709322
-
Patent Number
6,709,322
-
Date Filed
Thursday, March 29, 200123 years ago
-
Date Issued
Tuesday, March 23, 200420 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 451 5
- 451 6
- 451 11
- 451 26
- 451 36
- 451 41
- 451 57
- 451 285
- 451 286
- 451 287
- 451 288
- 451 289
- 451 397
-
International Classifications
-
Abstract
A CMP system and methods reduce a cause of differences between an edge profile of a chemical mechanical polished edge of a wafer and a center profile of a chemical mechanical polished central portion of the wafer within the edge. The wafer is mounted on a carrier surface of a wafer carrier so that a wafer axis of rotation is gimballed for universal movement relative to a spindle axis of rotation of a wafer spindle. A retainer ring limits wafer movement on the carrier surface perpendicular to the wafer axis. The retainer ring is mounted on and movable relative to the wafer carrier. A linear bearing is configured with a housing and a shaft so that a direction of permitted movement between the wafer carrier and the retainer ring is only movement parallel to the wafer axis, so that a wafer plane and a retainer ing may be co-planar.
Description
1. FIELD OF THE INVENTION
The present invention relates generally to chemical mechanical polishing (CMP) systems and techniques for improving the performance and effectiveness of CMP operations. Specifically, the present invention relates to a gimbal-mounted plate for carrying wafers, in which edge effects are reduced by aligning a wafer-engaging surface of the wafer carrying plate with a wafer polisher-engaging surface of an active retainer ring.
2. DESCRIPTION OF THE RELATED ART
In the fabrication of semiconductor devices, there is a need to perform chemical mechanical polishing (CMP) operations on semiconductor wafers, such as those made from silicon and configured as disks of 200 mm or 300 mm in diameter. For ease of description, the term “wafer” is used below to describe and include such semiconductor wafers and other planar structures, or substrates, that are used to support electrical or electronic circuits.
Integrated circuit devices may be in the form of multi-level structures fabricated on such wafers. A transistor device may be formed at one level, and in subsequent levels interconnect metallization lines may be patterned and electrically connected to the transistor device to define the desired functional device. Patterned conductive layers are insulated from other conductive layers by dielectric materials. As more metallization levels and associated dielectric layers are formed, there is an increased need to planarize the dielectric material, such as by performing CMP operations. Without such planarization, fabrication of additional metallization layers becomes substantially more difficult due to variations in the surface topography.
A CMP system typically includes a polishing station, such as a belt polisher, for polishing a selected surface of a wafer. In a typical CMP system, the wafer is mounted on a wafer-engaging surface of a carrier (carrier surface). The mounted wafer has a surface (wafer surface) exposed for contact with a polishing surface, e.g., of a polishing belt. The carrier and the wafer rotate in a direction of rotation. The CMP process may be achieved, for example, when the exposed rotating wafer surface and an exposed moving polishing surface are urged toward each other by a force, and when the exposed wafer surface and the exposed polishing surface move relative to each other. The carrier surface is said to define a carrier plane, the exposed wafer surface is said to define a wafer plane, and the exposed polishing surface in contact with the wafer plane is said to define a polishing plane.
In the past, the wafer carrier has been mounted on a spindle that provides rotation and polishing force for the carrier. To enable the wafer carrier to properly position the exposed wafer surface for desired contact with the exposed polishing surface, for example, a gimbal has been provided between the spindle and the wafer carrier. The gimbal allows the carrier plane to tilt relative to a spindle axis around which the wafer carrier rotation occurs. Such tilting allows the carrier plane to be parallel to the polishing plane of the belt. Generally, however, provision of the gimbal results in more mechanical structures between the carrier surface and a force sensor mounted on the spindle. As a result, there is more of an opportunity for friction in the mechanical structures to reduce the force sensed by the sensor.
Others have provided so-called active retainer rings that support the wafer against horizontal forces to retain the wafer on the carrier plate. However, the design of such active retainer rings has not appreciated an adverse feature of such active retainer rings. Thus, such design did not take into account a gimbal-like action of such active retainer rings. Such action of such retainer ring mounted on the carrier may be appreciated in terms of a retainer ring plane defined by an exposed surface of the retainer ring (the ring surface). Such design did not appreciate that a lack of guidance of such active retainer ring allows such retainer ring plane to be positioned axially offset from the wafer plane in response to forces, such as a horizontal force of the belt acting on the ring surface. The amount of the offset may be referred to as a reveal, and if the reveal is positive, the wafer plane is closer than the ring plane to the polishing plane of the belt. In general, a negative reveal is used to properly seat, or position, the wafer on the carrier surface prior to polishing.
As an example of the lack of guidance of such prior active retainer rings, the motor, such as a bladder, that drives such an active retainer ring relative to the wafer has been flexible and allowed the retainer ring plane to move in an uncontrolled manner relative to the carrier plane and relative to the wafer plane. This uncontrolled relative retainer ring-wafer carrier movement has allowed the retainer ring plane to tilt and become out-of-parallel with respect to both the carrier plane and the wafer plane. Unfortunately, in the tilted orientation, the retainer ring is not co-planar with the wafer plane. As a result, such tilting results in the value of the reveal being different at different angles along the circumference of the wafer and of the retainer ring, i.e., around the carrier axis of rotation. Such differences in the values of the reveal are undesirable because, for example, they are uncontrolled and have caused problems in CMP operations. The problems may be understood in terms of the edge of the wafer, which generally includes an annular portion of the wafer surface extending from the outer periphery of the wafer inwardly about 5 to 8 mm, for example. The problems in CMP polishing arise because the variation in the value of the reveal results in the vertical profile of the edge of the polished wafer having a different value for each different value of the reveal.
What is needed then, is a way of allowing the retainer ring to move relative to the wafer plane while limiting the movement of the retainer ring so as to avoid such tilting. What is also needed is a way to prevent the retainer ring plane from becoming out-of-parallel with respect to both the carrier plane and the wafer plane so that the retainer ring plane and the wafer plane may be aligned, i.e., co-planar. What is also needed are structure and methods of allowing the retainer ring to move relative to the wafer plane while avoiding relative movement that results in the value of the reveal being different at different angles of rotation of the wafer and the retainer ring on the carrier axis of rotation. In particular, currently there is an unmet need for structure and methods of providing a uniform profile of the edge of a wafer in CMP operations while retaining the advantages of retainer rings that are actively moved relative to the wafer plane.
SUMMARY OF THE INVENTION
Broadly speaking, the present invention fills these needs by providing CMP systems and methods which implement solutions to the above-described problems, wherein structure and methods are provided for allowing a retainer ring to move relative to a wafer plane while limiting the movement of the retainer ring so as to avoid such tilting that causes the retainer ring plane to become misaligned (i.e., out-of-parallel with respect to both the carrier plane and the wafer plane, or not co-planar with the wafer plane). In such systems and methods, the retainer ring may move relative to the wafer plane, but the relative movement is limited so that for polishing the wafer the retainer ring plane and the wafer plane may be co-planar. In particular, the direction of the relative movement is limited to a direction perpendicular to the wafer plane and the carrier plane, whereby the value of any desired reveal remains the same at different angles around the periphery of the wafer and of the retainer ring, i.e., around the carrier axis of rotation. Thus, the advantages of retainer rings that are actively moved relative to the wafer plane are retained without having the non-uniform reveal problem.
In one embodiment of the systems and methods of the present invention, a carrier plate is provided with a carrier surface to support a wafer. A retainer ring is mounted on and for movement relative to the carrier plate. A linear bearing arrangement is mounted between the carrier plate and the retainer ring. The arrangement is configured to limit the movement of the retainer ring relative to the carrier, wherein permitted movement keeps the retainer ring plane parallel to the wafer plane, or for polishing, co-planar with the wafer plane.
In another embodiment of the systems and methods of the present invention, an assembly including the carrier plate is provided with a gimbal to movably mount the carrier plate relative to a spindle housing. The spindle housing is mounted on a drive spindle. The gimbal allows the carrier plate to move so that the wafer plane may move and become co-planar with the polishing plane during the CMP operations. The retainer ring is mounted on and for movement relative to the carrier plate, and thus may also move relative to the wafer. However, the linear bearing arrangement constrains both such relative movements by permitting only movement of the retainer ring relative to the carrier plate along a path parallel to a central axis of the carrier plate.
In yet another embodiment of the systems and methods of the present invention, the linear bearing arrangement is provided as an array of separate linear bearing assemblies spaced around the wafer carrier.
In still another embodiment of the systems and methods of the present invention, the linear bearing arrangement is provided as an array of separate linear bearing assemblies in conjunction with the retainer ring, wherein a force applied to the retainer ring by the polishing belt is transferred to the carrier plate parallel to an axis of the carrier plate to facilitate calibration of the retainer ring.
In a related embodiment of the systems and methods of the present invention, the linear bearing arrangement is assembled with the retainer ring in conjunction with a motor for moving the retainer ring relative to the wafer mounted on the carrier so that an exposed surface of the wafer and a surface of the retainer ring to be engaged by the polishing pad are co-planar during the polishing operation.
Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements.
FIG. 1
is a schematic elevational view showing an embodiment of the present invention in which a wafer carrier plate supports a wafer and a retainer ring for contact with a chemical mechanical polishing surface;
FIG. 2
is a plan view taken along line
2
—
2
in
FIG. 1
, schematically showing the polishing surface, depicted as a belt, for contact with both the wafer carried by the wafer carrier plate and the retainer ring that surrounds the wafer;
FIG. 3
is a cross sectional view taken along line
3
—
3
in
FIG. 2
schematically showing a gimbal assemblage that allows an axis of rotation of the wafer carrier plate to move relative to an axis of rotation of a spindle, illustrating linear bearing assemblies between the wafer carrier plate and the retainer ring;
FIG. 4A
is a cross sectional view taken along line
4
A—
4
A in
FIG. 2
showing a connector shaft maintaining the retainer ring assembled to the carrier plate and a spring biasing the retainer ring into a position in which a retainer ring reveal has a maximum value for positioning the wafer on the carrier plate;
FIG. 4B
is a cross sectional view similar to
FIG. 4A
, showing a linear motor for moving the retainer ring in opposition to the force of the spring, wherein the retainer ring is shown in a position in which the retainer ring reveal has a zero value for polishing the wafer;
FIG. 4C
is an enlarged view of a portion of
FIG. 4B
, illustrating the zero value of the reveal and co-planarity of the retainer ring plane and the wafer plane;
FIG. 4D
is a cross sectional view similar to
FIGS. 4A and 4B
, illustrating the linear motor having moved the retainer ring to a position a maximum distance away from the wafer carrier to facilitate positioning the wafer on the carrier plate;
FIG. 5
is a cross sectional view taken along line
5
—
5
in
FIG. 2
showing various fasteners for mounting a linear bearing assembly between the carrier plate and the retainer ring so that relative movement between the carrier plate and the retainer ring is limited to a direction perpendicular to the wafer plane and the carrier plane;
FIG. 6
is a cross sectional view taken along line
6
—
6
in
FIG. 2
showing a vacuum and gas supply line provided in the spindle and connected to the wafer carrier plate;
FIG. 7
is a cross sectional view taken along line
7
—
7
in
FIG. 2
showing the gimbal assemblage connected to a load cell and the gimbal assemblage including a drive pin received in a tapered cavity of the wafer carrier plate;
FIG. 8
is a cross sectional view taken along line
8
—
8
in
FIG. 2
showing the retainer ring secured to a retainer ring base;
FIG. 9
is a three dimensional view of the wafer carrier plate, illustrating flanges extending from the wafer carrier plate for four linear bearing assemblies;
FIG. 10
is a three dimensional view of the wafer carrier plate, illustrating a wafer-engaging surface surrounded by the retainer ring;
FIG. 11
depicts a flow chart illustrating operations of a method of the present invention for aligning an exposed surface of the retainer ring with a wafer;
FIG. 12
depicts a flow chart illustrating operations of a method of the present invention for transferring respective forces from the wafer-engaging surface and from the retainer ring surface to the wafer carrier;
FIG. 13
depicts a flow chart illustrating operations of a method of the present invention for calibrating the retainer ring;
FIG. 14
is a graph resulting from calibrating the retainer ring;
FIG. 15
depicts a flow chart illustrating operations of a method of the present invention for using the calibration graph;
FIG. 16
is a flow chart depicting operations of a method of the present invention for reducing a cause of differences between an edge profile of a chemical mechanical polished edge portion of the wafer and a center profile of a chemical mechanical polished central portion of the wafer within the edge portion;
FIG. 17A
is a cross sectional view of the outer edge of a wafer polished using a retainer ring that is not provided with the linear bearing assemblies of the present invention; and
FIG. 17B
is a cross sectional view of the wafer shown in
FIG. 17A
, illustrating a profile of a central portion of the wafer.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An invention is described for a CMP system, and methods, which enable precision controlled polishing of an exposed surface of a wafer. The present invention fills the above-described needs by providing CMP systems and methods which implement solutions to the above-described problems, wherein structure and methods are provided for allowing a retainer ring to move relative to a wafer plane while limiting the movement of the retainer ring so as to avoid tilting that causes the retainer ring plane to become out-of-parallel with respect to both the carrier plane and the wafer plane. In such systems and methods, the retainer ring plane may move relative to the wafer plane, but the relative movement is limited. The direction of the relative movement is limited to a direction perpendicular to the wafer plane and to the carrier plane. As a result, for polishing the wafer, the wafer plane and the retainer ring plane may be co-planar. Also, the value of a desired reveal remains the same at different angles around the periphery of the wafer and of the retainer ring, i.e., around the carrier axis of rotation. Thus, the advantages of retainer rings that are actively moved relative to the wafer plane are retained without having the problem resulting from a non-uniform reveal or lack of such co-planarity.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be understood, however, to one skilled in the art, that the present invention may be practiced without some or all of these details. In other instances, well known process operations have not been described in detail in order not to obscure the present invention.
Referring to
FIGS. 1 and 2
, there is schematically shown an embodiment of the present invention, including a CMP system
200
. The embodiment of
FIGS. 1 and 2
includes a polishing head
202
configured with an endless belt
204
to polish an exposed surface
206
of a wafer
208
mounted on a wafer carrier surface
210
of a wafer carrier
212
. The wafer
208
may be any of the wafers described above, for example. The polishing head
202
is designed to polish the surface
206
of the wafer
208
utilizing the belt
204
. The belt
204
may be made from CMP materials, fixed abrasive pad materials, etc. In general, any pad material that enables the desired polishing levels and precision can be used for the belt
204
. In a preferred embodiment, the belt
204
may have a stainless steel core with an IC
1000
polishing pad, for example.
The polishing belt
204
performs CMP of the wafer
208
, and for this purpose is linearly moved (see arrow
214
) by spaced capstans
216
. The capstans
216
move the belt
204
relative to an axis of rotation
218
of a spindle
220
. The spindle
220
is both rotated around the axis
218
and urged toward the belt
204
parallel to the axis
218
. Referring also to
FIG. 3
, the spindle
220
is mounted to the wafer carrier
212
by a gimbal assembly
222
that allows the wafer carrier
212
to move and position a carrier axis of rotation
224
(
FIG. 3
) at an angle, or tilted, relative to the spindle axis
218
. The wafer carrier
212
is urged by the spindle
220
toward the belt
204
. In turn, the exposed surface
206
of the wafer
208
mounted on the wafer carrier surface
210
is urged by a polishing force (see arrow
225
in
FIG. 1
) against the belt
204
for performing CMP operations. The belt
204
is backed by a belt plate
204
p
to resist the polishing force
225
. A retainer ring
226
is movably mounted on the wafer carrier
212
. The retainer ring
226
may be moved to expose a portion of a peripheral edge
208
E (
FIG. 4A
) of the wafer
208
. The exposed portion of the edge
208
E is referred to as a reveal
227
, and
FIG. 4A
shows a maximum value of the reveal
227
. The retainer ring
226
may be moved away from the carrier
212
to a zero reveal polishing position (FIGS.
4
B and
4
C). In the zero reveal position, there is no exposed portion of the edge
208
E of the wafer
208
, (i.e., no reveal
227
). In
FIGS. 4B and 4C
, an inner peripheral edge
226
I surrounds the edge
208
E of the wafer
208
to hold the wafer
208
centered on the axis
224
against frictional polishing forces (see arrow
228
in
FIG. 1
) exerted by the belt
204
on the surface
206
of the wafer
208
. The retainer ring
226
may be moved further away from the carrier
212
as shown in
FIG. 4D
so that a plane
232
defined by a surface
233
of the ring
226
is positioned beyond a plane
234
defined by the exposed surface
206
of the wafer
208
to facilitate easy mounting of the wafer
208
on the carrier
212
. This is referred to as a wafer mounting position of the retainer ring
226
.
Linear bearing assemblies
230
(shown in dashed lines in
FIG. 1
) are provided between the retainer ring
226
and the wafer carrier
212
to limit the movement of the retainer ring
226
relative to the carrier
212
to movement parallel to the carrier axis
224
and parallel to an axis
231
of symmetry (or rotation) of the wafer
208
. Such limiting assures parallelism among the plane
232
defined by the surface
233
of the retainer ring
226
, and the plane
234
defined by the exposed wafer surface
206
of the wafer
208
mounted on the wafer carrier surface
210
, and a plane
236
defined by the surface
210
on which the wafer
208
is mounted. During polishing, such limiting assures co-planarity of the planes
232
and
234
. Since the gimbal assembly
222
allows the wafer carrier
212
to move and position the carrier axis of rotation
224
(
FIG. 3
) tilted relative to the spindle axis
218
, the retainer ring plane
232
and the wafer plane
234
and the wafer carrier surface plane
236
may move parallel not only to each other but parallel to a plane
238
defined by the portion of the belt
204
engaged by the wafer surface
206
and the ring surface
233
. The limitation of movement imposed by the linear bearing assemblies
230
thus restricts the movement allowed by the gimbal assembly
222
.
As described, the spindle
220
is urged toward the belt
204
parallel to the axis
218
. With the support of the back plate
204
p
, the belt
204
resists such urging and applies a force F
1
(
FIG. 3
) on the exposed wafer surface
206
and a force F
2
on the exposed ring surface
233
. With the retainer ring
226
mounted on the wafer carrier
212
, and the linear bearing assemblies
230
limiting the movement of the retainer ring
226
to movement parallel to the axis of rotation
224
of the carrier
212
, the forces F
1
and F
2
are parallel, and parallel to the axis
224
. These forces F
1
and F
2
combine and a component FC of these forces F
1
and F
2
that is parallel to the spindle axis
218
is sensed by a load cell
240
(shown in dashed lines in FIG.
1
). Signals (not shown) from the load cell
240
in response to the sensed component FC may be used to control the force by which the spindle
220
is urged toward the carrier
212
.
Referring to
FIGS. 3 and 6
, the axis
218
of the spindle
220
is shown. The spindle
220
may include a conventional cam operated connector, or base,
242
. The base
242
is secured in a well-known manner to another connector (not shown) of the spindle
220
so that the base
242
receives the rotation and urging for the CMP operations. The base
242
is provided with a shoulder
244
and a flange
246
. The flange
246
is cut away to define a stepped cavity
248
that receives the load cell
240
. The load cell
240
may be a standard strain gauge such as Model Number LPU-500-LRC sold by Transducer Techniques, of Temecula, Calif. The load cell
240
may have a load sensing range of from about zero pounds of force to 500 pounds of force. More preferably, a more accurate load sensing range may be used, e.g., from about zero to about 400 pounds of force. The load cell
240
is secured to the base
242
by bolts
250
(FIG.
6
). The load cell
240
has an input, or sensor tip,
252
configured for attachment to a first gimbal member, or spherical gimbal socket,
254
of the gimbal assembly
222
. The socket
254
receives a second gimbal member, or gimbal ball,
256
. The ball
256
is mounted to the wafer carrier
212
in a cavity
258
. The cavities
248
and
258
are opposed and are configured to enable the wafer carrier surface
210
to be very close to the input
252
(see dimension
260
, FIG.
3
). Further, as described below, the gimbal assembly
222
provides a minimum of mechanical assemblies between the cavity
248
and the cavity
258
. In this manner, friction losses between the wafer carrier
212
and the load cell
240
are reduced, fostering more accurate measuring of the force FC. In this manner, the force sensed by the load cell
240
is a more accurate representation of the force FC. As described below, calibration operations determine the value of a force FR (
FIGS. 3 and 14
) of the retainer ring
226
corresponding to various actuating pressures PB (
FIG. 14
) applied to a linear motor
300
.
The spindle axis
218
is aligned with a central axis
262
(
FIG. 6
) of the socket
254
. Permitted movement (referred to as gimballing movement) of the ball
256
relative to the socket
254
allows the central axis
224
of the wafer carrier, and the axis of the ball
256
(that is co-axial with the carrier axis
224
), to move relative to the socket axis
262
and to the spindle axis
218
. Space
266
(e.g., an air gap) is provided between the base
242
and the wafer carrier
212
to allow the gimballing movement. The space
266
may be from about 0.100 inches to about 0.050 inches. The component FC of force from the forces F
1
and F
2
is transferred from the wafer carrier
212
to the ball
256
and to the socket
254
to the input
252
to actuate the load cell
240
.
Referring to
FIGS. 3
,
6
and
7
, the wafer carrier
212
is shown having the wafer carrier surface
210
provided with a diameter
268
about equal to the diameter of the wafer (e.g., about 200 or 300 mm.). Such surface
210
is opposite to the cavity
258
. Adjacent to an outer edge
270
of the carrier
212
and at locations spaced from each other by about
90
degrees, tabs, or mounting sections,
272
extend outwardly from the carrier
212
, and upwardly in the FIGs. The tabs
272
extend over a retainer ring base
274
and over the retainer ring
226
.
FIG. 7
shows one of three bores
276
provided in the spindle base
242
aligned with respective threaded bores
278
provided in the respective tabs
272
. Each of the bores
276
is configured with a diameter larger than that of respective screws
280
threaded into the respective threaded bores
278
. The larger diameters provide room to permit the gimballing movement, while respective screw heads
282
keep the wafer carrier
212
attached to the spindle base
242
. Additionally,
FIG. 7
shows one of three sets of opposed bores
284
. Each bore
284
S of the base
242
receives a respective drive pin
286
that extends across the space
266
and into a respective tapered bearing
288
received in one of the bores
284
C. As the carrier
212
may move in the gimballing movement, the shapes of the bearing
288
and the pin
286
avoid interference with the gimballing movement.
FIG. 4A
shows one of four sets of opposed, aligned bores
290
in the tab
272
(see
290
T) and in the retainer ring base
274
(see
290
B). Each bore
290
T of the tab
272
is configured to receive a bolt
292
(having a washer
294
) and a spring
296
. Each bore
290
B of the retainer ring base
274
is configured to receive a threaded end of the bolt
292
. A shoulder
298
is provided in the bore
290
T so that the spring
296
is compressed between the shoulder
298
and the washer
294
. With the bolt
292
threaded into the threaded bore
290
B of the retainer ring base
274
, the compressed spring
296
urges the bolt
292
upwardly in
FIG. 4A
to pull the base
274
and the retainer ring
226
upwardly so that the base
274
normally contacts the tabs
272
. Referring to
FIG. 8
, which shows a portion of the base
274
and the retainer ring
226
, the base
274
and the retainer ring
226
are bolted together by bolts
315
and move together as a unit.
FIG. 4A
shows that with the base
274
in contact with the tabs
272
, the plane
232
of the retainer ring
226
is closer to the tabs
272
than the wafer plane
234
(shown in dashed lines). In this position, it may be said that the value of the reveal
227
is a maximum, or full, indicated by the dimension
331
having a maximum positive value. This maximum value of the dimension
311
may be about one-half of the thickness of the wafer
208
, for example. In contrast,
FIGS. 4B and 4C
show the reveal
227
having a minimum, or zero, value, with the wafer plane
234
co-planar with the retainer ring plane
232
.
To provide movement of the retainer ring
226
(e.g., to change the value of the reveal
227
), the linear motor
300
is mounted between an annular portion
302
of the tabs
272
and the retainer ring base
274
. The linear motor
300
may preferrably be provided in the form of a sealed cavity, or more preferably in the form of a pneumatic motor or an electro-mechanical unit. A most preferred linear motor
300
is shown including a pneumatic bladder
304
supplied with pneumatic fluid (see arrow
306
,
FIG. 3
) through an inlet
308
. As shown in
FIGS. 3
,
4
A and
4
B, the retainer ring base
274
is provided with an annular groove
310
for receiving the bladder
304
. The linear motor
300
is selectively actuated by supplying the fluid
306
to the bladder
300
at the different amounts of pressure PB (
FIG. 14
) according to the amount of a desired stroke of the bladder
304
. Such stroke may in turn provide a particular amount, or value, of the reveal
227
(FIG.
4
A), if any.
FIG. 4D
shows a maximum stroke of the bladder
304
, which for example may be 0.050 inches measured parallel to the axis
224
. Such maximum stroke is from the position shown in
FIG. 4A
(with the maximum reveal
227
), and compares to a vertical dimension (or thickness) of the wafer
208
, which may be 0.030 inches.
For purposes of description, the carrier
212
may be said to be fixed in the vertical direction, such that when the fluid
306
is admitted into the bladder
304
the bladder
304
will urge the retainer ring base
274
downwardly from the full reveal position shown in FIG.
4
A. The amount of the downward movement corresponds to the value of the pressure PB of the fluid
306
(
FIG. 14
) introduced into the bladder
304
. The bladder
304
will thus move the retainer ring base
274
, and thus the retainer ring
226
, down (in this example) relative to the wafer
208
positioned on the wafer carrier surface
210
. The pressure PB of the fluid
306
introduced to the bladder
304
may be one of many pressures, for example. In a general, preliminary, sense, the pressure PB may be selected to move the retainer ring
226
from the full reveal position (
FIG. 4A
) through one of many reveal positions in which the reveal
227
has a positive value, to the zero reveal position shown in
FIGS. 4B and 4C
. Higher values of the pressure PB may be selected to move the retainer ring
226
further downward into the wafer mounting position shown in FIG.
4
D. The pressure PB may be in a range of from zero (in the maximum reveal position shown in
FIG. 4A
) to about fifteen psi. to about seven to ten psi, for example, in the wafer mounting position shown in FIG.
4
D.
The polishing (zero reveal) position is the desired position of the retainer ring
226
during polishing of the wafer
208
. Moreover, in the polishing position shown in
FIGS. 4B and 4C
, because of the operation of the linear bearing assemblies
230
, the wafer plane
234
and the ring plane
232
are co-planar and the reveal
227
has a zero value all around the perimeter of the wafer
208
. As a result, as the belt
204
moves in the direction of the arrow
214
(
FIG. 1
) the ring plane
232
will not be free to tilt relative to the axis
224
. Thus, the ring
226
will not dig into the belt
204
. Further, a portion of the belt
204
will first contact and traverse over the retainer ring
226
. This contact and traverse will cause a dynamic condition of the portion of the belt
204
, e.g., the belt
204
will assume a wave-like shape. However, the continued traverse of the portion of the belt
204
over the retainer ring
226
will tend to allow this wave-like shape to decrease. Therefore, by the time the portion of the belt
204
reaches the outer edge of the wafer
208
the belt
204
will have a relatively flat, non-wave-like shape. Further, with the plane of the ring
226
co-planar with the wafer plane
234
(due to the operation of the linear bearing assemblies
230
), as the portion of the belt
204
crosses from the ring
226
onto the edge of the wafer
208
, there will be a minimum disturbance of the portion of the belt
204
. Such disturbance is significantly less than the disturbance that results from the above-described non-co-planar relationship of the ring plane
232
and the wafer plane
234
. Thus, the relatively flat or planar portion of the belt
204
will more readily start to polish the wafer surface in a desired relatively flat (or planar) profile.
As described above, the four linear bearing assemblies
230
limit the movement of the retainer ring
226
so that the plane
232
of the ring
226
remains parallel to the plane
234
of the wafer
208
and to the plane
236
of the carrier surface
210
.
FIGS. 3 and 5
depict one of the linear bearing assemblies
230
. Each linear bearing assembly
230
includes a main bearing housing
320
provided with a linear ball bearing assembly
321
. The linear ball bearing assembly
321
includes an internal bearing housing
321
H that receives a set of bearing balls
322
held in a cage
323
. The bearing balls
322
receive a bearing shaft
326
that is dimensioned to provide an interference fit with the bearing balls
322
to preload the bearing balls
322
. The linear bearing assemblies
321
may be linear bearing Model Number ML
500-875
sold under the trademark ROTOLIN by RBM of Ringwood, N.J., for example.
The shaft
326
is hardened, such as to at least Rc 60 and is ground to a finish of at least 10 micro inches, for example. Suitable bearing balls
322
may have a one-half inch inside diameter and a length of about one and one half inches, for example. Each linear bearing assembly
321
is open at a bottom
324
to receive the mating bearing shaft
326
. Suitable shafts
326
may have an outside diameter of about just less than 0.500 inch (plus 0.000 and minus 0.0002 inch) so as to provide the interference fit in the bearing balls
322
. The shaft
326
may be about one and one-half inches long. The length
323
L of the cage
323
in a direction parallel to the axis
218
is less than a dimension
321
HD of the internal bearing housing
321
H, and may have a ratio of 3/7 relative to the dimension
321
HD of the internal housing
321
H. The value of the dimension
321
HD is selected according to the desired amount of movement of the shaft
326
in the linear bearing assembly
321
. Each housing
320
extends upwardly from one of the tabs
272
, and is bolted to the tab by bolts
328
. Each shaft
326
extends upwardly from the retainer ring base
274
, to which it is bolted by bolts
330
.
As the shaft
326
moves with the movement of the retainer ring
226
, the shaft
326
is tightly guided by the bearing balls
322
. The bearing balls
322
allow the limited movement of the shaft
326
corresponding to the above-described limited movement of the retainer ring
226
relative to the carrier
212
, which is the movement parallel to the carrier axis
224
and parallel to the axis
231
of symmetry of the wafer
208
. As the shaft
326
so moves, the bearing balls
322
roll against the internal bearing housing
321
H such that the cage
323
moves in the direction of the movement of the shaft
326
. The above-described relative dimensioning of the internal bearing housing
321
H and the cage
323
permits such movement of the cage
323
. Such limited movement assures the parallelism among the plane
232
and the plane
234
, and the plane
236
, and for polishing provides co-planarity of the planes
232
and
234
. As described, the limitation of movement imposed by the linear bearing assembly
321
restricts the movement allowed by the gimbal assembly
222
. Continued operation of the linear bearing assembly
321
in this manner is fostered by seals
325
located at opposite ends of the internal bearing housing
321
H, which are configured to keep foreign matter from entering the housing
321
H.
FIG. 9
shows the linear bearing assemblies
230
as including an array
332
of the linear bearing assemblies
230
. The array
332
is configured to divide the operation of each individual linear ball bearing assembly
321
into parts having a short length in the direction of the axis
231
and small diameters relative to the diameters (e.g., 200 mm or 300 mm) of the wafers
208
. Moreover, such division locates the linear bearing assemblies
230
at uniformly spaced intervals around a circular path (shown in dashed lines
334
). In this manner, as the wafer carrier
212
rotates, there is a rapid succession of individual linear bearing assemblies
230
, for example, located over the belt
204
.
FIG. 9
also shows a uniform spacing of six of the eight bolts
315
around the retainer ring base
274
for holding the base
274
assembled with the retainer ring
226
. Supplementing
FIG. 4A
,
FIG. 9
also shows one of the four bolts
292
that are provided with the springs
296
in each of the four tabs
272
for keeping the base
274
biased against the tab
274
, and to resiliently release the base
274
and the retainer ring
226
when the bladder
304
of the linear motor
300
is pressurized.
FIG. 9
also shows a pneumatic hose
340
that is attached to the inlet
308
of the linear motor
300
. The hose
340
extends to the spindle
220
for connection to a supply (not shown) of the pressurized fluid
306
, e.g., air.
FIG. 10
shows the bottom of the wafer carrier
212
, including the wafer carrier surface
210
. The surface
210
is provided with evenly spaced holes
344
that are either supplied with nitrogen (N2) or connected to a vacuum supply (not shown).
FIG. 6
shows a port
346
with a pneumatic connector
347
that is connected to one of many tees
348
that serve as manifolds to distribute the N2 or vacuum to the holes
344
from the spindle
220
.
FIG. 7
shows an amplifier
352
connected to the load cell
240
to provide an amplified output to an electrical connector
354
. The connector
354
is connected to a conductor that extends through the spindle base
242
to control circuitry (not shown).
Referring now to
FIG. 11
, a method of the present invention is shown including operations of a flow chart
400
for aligning the exposed (or ring) surface
233
of the retainer ring
226
with the wafer carrier surface
210
. The wafer carrier surface
210
may also be referred to as a wafer-engaging surface, and the aligning may be performed during a chemical machining polishing operation. The operations of the flow chart
400
may include an operation
402
of mounting the wafer-engaging surface
210
on the axis
231
of rotation. Operation
402
may include mounting the wafer carrier
212
on the spindle base
242
, for example. The method moves to an operation
404
of mounting the retainer ring
226
on and for movement relative to the wafer-engaging surface
210
and relative to the axis
231
of rotation. Such mounting is with the retainer ring
226
free to move other than parallel to, and parallel to, the axis
231
of rotation, and may be provided, for example, by the bolts
250
. The method moves to an operation
406
of resisting the freedom of the mounted retainer ring
226
to move other than parallel to the axis of rotation. The resisting may, for example, be provided by the four linear bearing assemblies
230
. In resisting such freedom, the linear bearing assemblies
230
only permit the retainer ring
226
to move so that the surface
233
of the retainer ring
226
remains parallel to the surface
210
. With a wafer
208
carried by the wafer carrier
212
, and with the wafer
208
having sides that are parallel to each other, the retainer ring surface
233
is also parallel to or co-planar with the exposed surface
206
of the wafer
208
.
Another aspect of the method of the present invention is described with respect to a flow chart
410
shown in FIG.
12
. The method may start by an operation
412
in which the wafer-engaging surface
210
of the carrier
212
and the ring surface
233
are urged toward the belt
214
. The wafer
208
and the retainer ring
26
contact the bolt
208
. The urging provides the force F
1
on the wafer-engaging surface
210
(via the wafer
208
) and the force F
2
on the retainer ring
226
(e.g., on the surface
233
). The method moves to an operation
414
of transferring the force F
1
from the wafer-engaging surface
210
and the force F
2
from the ring surface
233
to the carrier
212
. The transferring operation
414
may be performed by the retainer ring
226
acting on the base
274
, which acts on the tab
272
of the carrier
212
, for example. The sum of the forces F
1
and F
2
includes the component force FC parallel to the axis
218
. The method may then move to an operation
416
of measuring the respective forces F
1
and F
2
transferred to the carrier
212
. Such measuring is performed by the load cell
240
, which measures the value of the component FC parallel to the axis
218
.
Another aspect of the method of the present invention is described with respect to a flow chart
420
shown in FIG.
13
. The method may be used for calibrating the retainer ring
226
, which due to the action of the motor
300
, is an “active” retainer ring. The retainer ring
226
also has the ring surface
233
, and the ring
226
is movable with respect to the wafer-engaging surface
210
during a chemical machining polishing operation in which the ring surface
233
touches the upper, or polishing, surface of the belt
204
(that defines the plane
238
as shown in FIG.
1
). The method starts with an operation
422
of mounting the wafer-engaging surface
210
on the axis
224
of rotation. The method moves to an operation
423
of mounting the retainer ring
226
on and for movement relative to the wafer-engaging surface
210
and relative to the axis
224
of rotation with the retainer ring
226
free to move other than parallel to, and parallel to, the axis
224
of rotation. The method moves to an operation
424
of resisting the freedom of the mounted retainer ring
226
to move other than parallel to the axis
224
of rotation. As before, the resisting may be provided by the four linear bearing assemblies
230
. In resisting such freedom, the linear bearing assemblies
230
only permit the retainer ring
226
to move so that the surface
233
of the retainer ring
226
remains parallel to the surface
210
. The method moves to an operation
425
of fixing the position of the spindle
220
along the axis
218
. The method moves to an operation
426
of placing the retainer ring
226
in contact with a calibration, or force measuring, fixture. The fixture may be a standard force sensor (not shown) similar to the load cell
240
, and having an annular force sensor plate
427
(
FIG. 3
) configured to contact the retainer ring
226
without touching the wafer
208
or the surface
210
. The method moves to an operation
428
of applying to the linear motor
300
various input pressures PB to cause the bladder
304
to urge the retainer ring
226
axially downward (in the direction of the axis
224
) against the force sensor plate
427
of the calibration fixture. The method may move to an operation
429
in which, for each of the plurality of different ones of the input (e.g., for each of many pressures PB of the air supplied to the bladder
304
), the force measuring fixture measures the value of the forces FR (
FIG. 3
) applied by the retainer ring
226
. Knowing the area of the retainer ring
226
, the forces FR (
FIG. 14
) may be converted to retainer ring pressures PR (
FIG. 14
) on the retainer ring in psi. By this method of flow chart
420
, operation
428
may conclude by preparing a calibration graph
432
(
FIG. 14
) by plotting on one axis such retaining ring forces FR (
FIG. 14
) and on the other axis the corresponding different inputs (pressure PB to the bladder
304
), each as a function of retainer ring pressure PR. Referring to
FIG. 14
, these pressures PB are plotted on the left axis, whereas the forces FR before conversion to pressure (based on a force FR divided by the area of the retainer ring
226
) are plotted on the right axis.
In another aspect of the methods of the present invention, the calibration graph
432
may be used as shown in
FIG. 15
in a flow chart
440
for a next actual polishing operation. An operation
442
selects a pressure PB to be supplied to the bladder
304
according to a polishing process specification for the next polishing operation. The method moves to an operation
443
in which, based on the calibration graph
432
, the selected pressure PB is used to select a corresponding force FR (shown in
FIGS. 3 and 14
) of the retainer ring
226
on the belt
204
. The force FR has the corresponding opposite force F
2
. The method moves to an operation
444
. Operation
444
is performed with the process specification in mind. In the process specification, a polishing force, which may be termed a wafer down force FWD for descriptive purposes (not shown), is specified for the next polishing operation. The wafer down force FWD is the force by which, without the retainer ling
226
, the spindle
220
would normally be urged downwardly in
FIGS. 2 and 3
, for example, to urge the wafer
208
against the belt
204
for polishing. However, because the retainer ring
226
also contacts the belt
204
, applies the force FRR, and receives the opposite force F
2
(FIG.
3
), such wafer down force FWD by which the spindle
220
would normally be urged downwardly is not the force that is applied by the wafer
208
against the belt
204
. Rather, the force FC described above has the two components F
1
and F
2
, and only the component F
1
corresponds to the polishing force (or to the wafer down force FWD) between the wafer
208
and the polishing surface of the belt
204
. In operation
444
, the force FR of the retainer ring
226
is added to this wafer down (normal) force FWD derived from the process specification. In this manner operation
444
provides a value of the total downward force of the spindle
220
that is greater than the normal wafer down force FWD used without the retainer ring
226
. Thus, the spindle
220
is urged downwardly by a force opposed to and equal to the force FC which includes the forces F
1
and F
2
.
Another aspect of the methods of the present invention may be used to reduce a cause of differences between an edge profile (identified by an arrow
450
in
FIG. 8
) of a chemical mechanical polished edge portion
452
of the wafer
208
, and a center profile (identified by an arrow
454
in
FIG. 8
) of a chemical mechanical polished central portion (identified by a bracket
456
) of the wafer
208
. As shown in
FIG. 8
, the edge profile
450
and the center profile
454
have generally the same contour as a result of the present invention. On the other hand,
FIGS. 17A and 17B
show portions of a typical wafer
208
that has been polished using a retainer ring positioned to provide a reveal
227
of about 0.009 inches. Such retainer ring is not provided with the linear bearing assemblies
230
. The portions shown include an edge profile (identified by an arrow
450
P in
FIG. 17A
) of a chemical mechanical polished edge portion
452
P of the wafer
208
, and a center profile (identified by an arrow
454
P in
FIG. 17B
) of a chemical mechanical polished central portion (identified by a bracket
456
P) of the wafer
208
.
FIG. 17B
shows the profile
454
P having a somewhat wavy shape to represent about a three to five percent variation in the height of the profile
454
P (which generally is an acceptable profile). In comparison,
FIG. 17A
shows the edge profile
450
P having a sharp step
457
representing substantially more than the three to five percent variation in the height of the edge profile
454
P. Such step
457
and the corresponding increased variation is an unacceptable edge profile. The edge profile
450
P may result from the dynamics of the belt
204
resulting from the initial contact of the belt
204
and the wafer edge portion
452
P. Such dynamics do not dissipate because the retainer ring that provides the reveal of 0.009 inches does not contact the belt
204
before the belt
204
contacts the edge portion
450
P of the wafer
208
. Further, the above-described tilting of the prior retainer rings (resulting in differences in the values of the reveal around the perimeter of the wafer
208
) were said to be undesirable because they are uncontrolled and have caused problems in CMP operations. One type of problem is the unacceptable edge profile
450
P.
On the other hand, as described above, because a portion of the belt
204
first contacts the retainer ring
226
of the present invention, and because the retainer ring
226
is co-planar with the exposed surface of the wafer
208
during polishing, the dynamics of the portion of the belt
204
resulting from the portion of the belt
204
initially contacting the retainer ring
226
dissipate so that the portion of the belt
204
is substantially in a steady-state condition as the portion of the belt
204
advances past the retainer ring
226
and moves onto the edge of the wafer
208
. In the steady-state condition the belt
204
tends to polish with only about a three to five percent height variation of the edge profile
452
and center profile
454
, in each case without the unacceptable sharp steps (e.g.,
457
) depicted in
FIG. 17A
, for example.
As shown in
FIG. 16
another aspect of the methods of the present invention is depicted in a flow chart
460
. A method includes an operation
462
of mounting the wafer
208
on the carrier surface
210
of the wafer carrier
212
so that the wafer axis
231
of rotation is universally movable relative to the spindle axis
218
of rotation of the wafer spindle
220
. The method moves to an operation
464
for limiting movement of the wafer
208
on the carrier surface
210
in a direction perpendicular to the wafer axis
231
by movably mounting the retainer ring
226
on and relative to the wafer carrier
212
. The limiting operation
464
may be performed by providing the reveal
227
. The method moves to an operation
466
in which, during both the respective mounting and the limiting operations
462
and
464
the relative movement of the retainer ring
226
other than parallel to the wafer axis
231
is resisted. The resisting operation
466
may be performed by configuring components of the linear bearing assemblies
230
so that a direction of the only permitted movement between the wafer carrier
212
and the retainer ring
226
is parallel to the wafer axis
231
. The resisting operation
466
may further include mounting the linear bearing components on the respective wafer carrier
212
and retainer ring
226
.
It may be understood that the cause of the differences between the edge profile
450
P and the center profile
454
P may be a lack of co-planarity of the wafer plane
234
defined by the exposed to-be-polished surface
206
of the wafer
208
, and the ring plane
232
defined by the exposed polishing-member-engaging surface
233
of the retainer ring
226
. The operation
462
of mounting the wafer
208
on the carrier surface
210
renders the wafer plane
234
universally movable relative to the spindle axis
218
, and gives rise to the problem of lack of such co-planarity. The operation
466
of resisting the relative movement of the retainer ring
226
other than parallel to the wafer axis
231
results, for example, in enabling the operation of the bladder
304
to achieve the desired co-planarity of the wafer plane
234
and the ring plane
232
(
FIG. 4B
) during polishing, thus eliminating this cause of the differences between the edge profile
450
P and the center profile
454
P.
Although the foregoing invention has been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications may be practiced within the scope of the appended claims. Accordingly, the present embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims.
Claims
- 1. Apparatus for controlling a positional relationship in a chemical mechanical polishing system, the apparatus comprising:a wafer carrier plate having a carrier plate surface configured to mount a wafer for contact with a chemical mechanical polishing surface; a retainer ring assembly mounted on and for movement relative to the wafer carrier plate to retain the wafer in a desired position on the carrier surface, the retainer ring assembly having a ring surface configured to contact the polishing surface; and a bearing assembly mounted between the wafer carrier plate and the retainer ring assembly to limit the movement of the retainer ring assembly relative to the carrier plate so that the ring surface is positioned parallel to the carrier plate surface.
- 2. Apparatus as recited in claim 1, wherein:the bearing assembly is configured with a bearing housing mounted on one of the wafer carrier plate and the retainer ring, and a bearing shaft is mounted on the other of the wafer carrier plate and the retainer ring assembly, the bearing shaft being received in the bearing housing.
- 3. Apparatus as recited in claim 1, further comprising:a drive mounted between the wafer carrier plate and the retainer ring assembly to control a reveal position of the ring surface relative the carrier plate surface.
- 4. Apparatus as recited in claim 3, wherein:the bearing assembly is effective during the control of the reveal position of the ring surface relative the carrier plate surface to maintain the ring surface parallel to the carrier plate surface.
- 5. Apparatus as recited in claim 1, further comprising:a spindle configured to mount the wafer carrier plate for rotation, the spindle having a base closely adjacent to the wafer carrier plate, the base being configured to receive a first gimbal member; a second gimbal member configured to cooperate with the first gimbal member and secured to the wafer carrier plate to allow the wafer carrier plate to be positioned in any position in a range of polishing positions in which the carrier plate surface is parallel to the polishing surface; and wherein with the carrier plate surface parallel to the polishing surface the bearing assembly is effective to limit the movement of the retainer ring assembly relative to the carrier plate so that the ring surface is positioned co-planar with the polishing surface.
- 6. Apparatus for controlling positional relationships with respect to a chemical mechanical polishing surface, the apparatus comprising:a spindle; a wafer carrier having a wafer carrier surface; a gimbal assembly having a first gimbal member mounted on the spindle and a second gimbal member mounted on the carrier, the second gimbal member mating with the first gimbal member to permit gimballing motion of the carrier relative to the spindle into a polishing position in which the wafer carrier surface is parallel to the polishing surface; a retainer ring assembly mounted on and for movement relative to the wafer carrier, the retainer ring assembly having a ring surface configured to contact the polishing surface; and a bearing assembly mounted between the wafer carrier and the retainer ring assembly, the bearing assembly being configured to limit the movement of the retainer ring assembly relative to the carrier so that the ring surface is positioned parallel to the carrier surface.
- 7. Apparatus as recited in claim 6, further comprising:a drive positioned between the wafer carrier and the retainer ring assembly to move the ring surface relative the carrier surface.
- 8. Apparatus as recited in claim 6, wherein the spindle is configured to provide a rotational force and the gimbal assembly is configured with at least one connector for transferring the rotational force to the carrier.
- 9. Apparatus as recited in claim 6, wherein:the bearing assembly is configured with a linear bearing housing on one of the wafer carrier and the retainer ring assembly and with a linear bearing shaft on the other of the wafer carrier and the retainer ring assembly.
- 10. Apparatus as recited in claim 6, further comprising:a sensor mounted on the spindle and having a force input connected to the first gimbal member to receive a polishing force.
- 11. Apparatus as recited in claim 10, wherein:the spindle is configured with a cavity to receive and position the sensor closely adjacent to the wafer carrier; and the wafer carrier is configured with a recess to receive the first and second gimbal members and enable the force input of the sensor to be closely adjacent to the wafer carrier surface.
- 12. Apparatus for controlling positional relationships in a chemical mechanical polishing system, the apparatus comprising:a spindle configured to provide a rotational force, the spindle having a first gimbal member; a gimbal assembly having a second gimbal member configured to cooperate with the first gimbal member to permit gimballing motion in which the second member moves universally relative to the spindle, the gimbal assembly having a drive connector for transferring the rotational force; a wafer carrier mounted on the second gimbal member and provided with a wafer carrier surface, the gimbal members allowing the gimballing motion of the wafer carrier into a polishing position in which the wafer carrier surface is parallel to the polishing surface, the wafer carrier having a drive socket configured to receive the drive connector and allow the gimballing motion while transferring the rotational force to the carrier; a retainer ring assembly mounted on and for movement relative to the wafer carrier into a reveal position to provide a reveal for retaining the wafer on the wafer carrier surface, the retainer ring assembly having a ring surface configured to contact the polishing surface; and a linear bearing assembly mounted separately from the spindle and between the wafer carrier and the retainer ring assembly to permit only limited movement of the retainer ring assembly relative to the carrier, the limited movement being with the ring surface oriented parallel to the carrier surface during the gimballing motion.
- 13. Apparatus as recited in claim 12, further comprising:a drive positioned between the wafer carrier and the retainer ring assembly to move the ring surface relative to the wafer carrier surface and permit the selection of a value of the reveal.
- 14. Apparatus for controlling structural movement of a semiconductor wafer carrier in chemical mechanical polishing, the apparatus comprising:a carrier plate having a wafer mount surface centered relative to a carrier axis of rotation of the carrier plate; a retainer ring surrounding the wafer mount surface; a connector arrangement configured to mount the retainer ring on and for movement relative to the carrier plate in a plurality of directions including a first direction parallel to the carrier axis and other directions not parallel to the carrier axis; and a linear bearing arrangement having at least one first unit secured to the carrier plate and at least one second unit secured to the retainer ring, the at least one second unit being movable relative to the at least one first unit, the at least one first unit and the at least one second unit being configured to resist all of the movement of the retainer ring relative to the carrier plate in the plurality of directions except movement in the first direction parallel to the carrier axis.
- 15. Apparatus according to claim 14, wherein:the wafer mount surface is configured to be coaxial with the carrier axis and centrally located adjacent to the axis; and the linear bearing arrangement includes an array of linear bearings positioned along an arcuate path around the central wafer mount surface, each of the linear bearings has one of the at least one first units secured to the carrier plate radially outwardly of the wafer mount surface, each of the linear bearings has one of the at least one second units secured to the retainer ring radially outwardly of the wafer mount surface.
- 16. Apparatus according to claim 14, further comprising:a coupler having a drive axis of rotation and configured to rotate the carrier plate, the coupler having a first gimbal surface configured to cooperate with a second gimbal surface; wherein the carrier plate is provided with the second gimbal surface cooperating with the first gimbal surface to permit the carrier plate and the retainer ring on the carrier plate to move relative to the coupler so that the carrier axis may tilt with respect to the drive axis; and wherein during the movement of the carrier plate relative to the coupler the linear bearing arrangement permits movement of the retainer ring relative to the carrier plate only in the first direction parallel to the carrier axis.
- 17. Apparatus according to claim 16, wherein separate polishing forces are applied to the retainer ring and to the carrier plate and each of the separate polishing forces has a parallel component parallel to the carrier axis and a component other than parallel to the carrier axis, the apparatus further comprising:a sensor mounted on the coupler and having a force input, the sensor being configured so that the force input may be contacted by the first gimbal surface; and wherein the configuration of the connector for mounting the retainer ring on and for movement relative to the carrier plate, and the linear bearing arrangement permitting movement of the retainer ring relative to the carrier plate only in the first direction parallel to the carrier axis, enable only the parallel component of the separate polishing force applied to the retainer ring to be applied to the carrier plate for sensing by the sensor.
US Referenced Citations (14)
Foreign Referenced Citations (4)
Number |
Date |
Country |
10156712 |
Jun 1998 |
EP |
2000334655 |
Dec 2000 |
EP |
08320301 |
Nov 1996 |
JP |
11145978 |
May 1999 |
JP |