Information
-
Patent Grant
-
6561870
-
Patent Number
6,561,870
-
Date Filed
Friday, March 30, 200123 years ago
-
Date Issued
Tuesday, May 13, 200321 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Hail, III; Joseph J.
- Thomas; David B.
Agents
-
CPC
-
US Classifications
Field of Search
US
- 451 10
- 451 41
- 451 296
- 451 303
- 451 307
-
International Classifications
-
Abstract
An adjustable platen is provided. The adjustable platen includes a platen body having a top region and a bottom region. The platen body is oriented under a linear polishing pad of a CMP system. An air bearing is integrated with the platen body at the top region, and the air bearing is configured to apply an air pressure to an underside of the linear polishing pad. A set of bearings are connected to the bottom region of the platen body to enable controlled vertical movement of the top region of the platen body closer or further from the underside of the linear polishing pad depending on the applied air pressure. The applied air pressure is configured to exert a controllable force to the underside of the linear polishing pad. The force is controlled to meet a desired process parameters, while the carrier simply moves the wafer into position over the linear polishing pad.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to chemical mechanical planarization (CMP) systems, and more particularly, to systems having force applying air platens.
2. Description of the Related Art
In the fabrication of semiconductor devices, there is a need to perform Chemical Mechanical Planarization (CMP) operations, including polishing, buffing and wafer cleaning. Typically, integrated circuit devices are in the form of multi-level structures. At the substrate level, transistor devices having diffusion regions are formed. In subsequent levels, interconnect metallization lines are patterned and electrically connected to the transistor devices to define the desired functional device. As is well known, patterned conductive layers are insulated from other conductive layers by dielectric materials, such as silicon dioxide. As more metallization levels and associated dielectric layers are formed, the need to planarize the dielectric material increases. Without planarization, fabrication of additional metallization layers becomes substantially more difficult due to the higher variations in the surface topography. In other applications, metallization line patterns are formed in the dielectric material, and then metal CMP operations are performed to remove excess metallization.
In the prior art, CMP systems typically implement belt, orbital, or brush stations in which belts, pads, or brushes are used to scrub, buff, and polish one or both sides of a wafer. Slurry is used to facilitate and enhance the CMP operation. Slurry is most usually introduced onto a moving preparation surface, e.g., belt, pad, brush, and the like, and distributed over the preparation surface as well as the surface of the semiconductor wafer being buffed, polished, or otherwise prepared by the CMP process. The distribution is generally accomplished by a combination of the movement of the preparation surface, the movement of the semiconductor wafer and the friction created between the semiconductor wafer and the preparation surface.
FIG. 1
illustrates an exemplary prior art CMP system
10
. The CMP system
10
in
FIG. 1
is a belt-type system, so designated because the preparation surface is an endless belt-type polishing pad
18
mounted on two drums
24
which drive the pad in a rotational motion as indicated by belt rotation directional arrows
26
. A wafer
12
is mounted on a carrier
14
. The carrier
14
is rotated in direction
16
, which can be either clockwise or counterclockwise. The rotating wafer
12
is then applied against the polishing pad
18
with a force F to accomplish a CMP process. Some CMP processes require significant force F to be applied and monitored. A platen
22
is provided to stabilize the polishing pad
18
and to provide a support onto which to apply the wafer
12
. The platen
22
is designed with an air bearing
23
, which is designed to supply a constant flow of air during movement of the polishing pad
18
. The constant flow of air therefore provides a consistent cushion over which the polishing pad
18
can traverse. To facilitate polishing, slurry
28
composed of an aqueous solution such as NH
4
OH or DI containing dispersed abrasive particles is introduced upstream of the wafer
12
.
Typically, a load cell (LC) is integrated as part of the carrier
14
to enable monitoring of the pressure being applied to the wafer during processing. In practice, the carrier
14
is lowered onto the polishing pad
18
while the wafer is rotated in the direction
16
. In addition to being lowered, the load cell (LC) is designed to provide pressure data to monitoring electronics. If more or less pressure is needed for a particular process, the spindle is instructed to make the pressure adjustment. Accordingly, not only is the spindle designed to move up and down, rotate at a particular rate, but also continuously adjust the force on the wafer (in the form of pressure) as transmitted by the carrier
14
to achieve the appropriate CMP parameters.
Because the carrier
14
is designed to place a force onto a moving polishing pad
18
, frictional forces will build at the spindle so as to generate mechanical hysteresis. These frictional forces are known to reduce an actuator's (which is designed to apply a force to the carrier
14
) ability to maintain a constant force during small amplitude variations in carrier
14
vertical position during polishing. The challenge of maintaining a constant force during precision polishing operations therefore complicates the design of the carrier
14
and its accompanying electronics and controls. In some cases, even very expensive an complex controls are unable to ensure a uniform application of force since the carrier, which is measuring the forces, is continuously under frictional stress from the moving polishing pad
18
.
In view of the foregoing, a need exists for a chemical mechanical planarization system that can provide a stable and accurate force to a substrate being planarized.
SUMMARY OF THE INVENTION
Broadly speaking, the present invention fills these needs by providing a chemical mechanical planarization system that has an adjustable platen. The adjustable platen is designed to apply a force to an underside of the polishing pad during operation, while the carrier is simply lowered into position over the polishing pad to achieve the appropriate planarization result. It should be appreciated that the present invention can be implemented in numerous ways, including as a process, an apparatus, a system, a device, or a method. Several inventive embodiments of the present invention are described below.
In one embodiment, a chemical mechanical planarization (CMP) system having a polishing pad, a wafer carrier, and an adjustable platen is disclosed. The adjustable platen includes a platen body and an air bearing that is integrated in the platen body for applying air pressure to an underside of the polishing pad. A set of bearings are connected to the platen body to enable movement of the platen body closer and further from the underside of the polishing pad. A load cell is connected to the platen body, and the load cell is configured to output a load signal that is indicative of a force being applied to the underside of the polishing pad. An air supply for applying air flow to the air bearing is also provided. The air flow is adjustable in response to changes in the force being applied to the underside of the polishing pad.
In another embodiment, an adjustable platen is disclosed. The adjustable platen includes a platen body having a top region and a bottom region. The platen body is oriented under a linear polishing pad. An air bearing is integrated with the platen body at the top region, and the air bearing is configured to apply an air pressure to an underside of the linear polishing pad. A set of bearings are connected to the bottom region of the platen body to enable controlled movement of the top region of the platen body closer or further from the underside of the linear polishing pad depending on the applied air pressure. The applied air pressure is configured to exert a controllable force to the underside of the linear polishing pad.
In yet another embodiment, another platen is disclosed. The platen includes a platen body having a top region and a bottom region. The platen body is positioned under a linear polishing pad of a chemical mechanical polishing (CMP) system, and the CMP system is designed to receive a wafer to be polished on a top surface of the linear polishing pad when positioned for processing by a spindle and carrier of the CMP system. An air bearing is coupled with the platen body at the top region, and the air bearing is configured to deliver an air flow to an underside of the linear polishing pad. A set of linear bearings are coupled to the bottom region of the platen body to enable controlled vertical movement of the platen body closer and further from the underside of the linear polishing pad. The vertical movement of the platen body is determined by the air flow, and the air flow is variable so as to set a desired force to the underside of the linear polishing pad.
In still another embodiment, a platen design is disclosed. The platen includes a platen body having a top region and a bottom region. The platen body is positioned under a linear polishing pad of a chemical mechanical polishing (CMP) system, and the CMP system is designed to receive a wafer to be polished on a top surface of the linear polishing pad when positioned for processing by a spindle and carrier of the CMP system. An air bearing is coupled with the platen body at the top region, and the air bearing is configured to deliver a fixed air flow to an underside of the linear polishing pad. A load cell for determining a force being applied to the underside of the linear polishing pad by the fixed air flow is integrated with the platen body. An actuator provided to vertically adjust the platen body closer and further from the underside of the linear polishing pad.
The advantages of the present invention are numerous. Most notably, by having the platen apply controlled forces from under the polishing pad, the spindle controlling the wafer carrier can be greatly simplified, and can eliminate the need for a splined spindle and complicated monitoring and compensating electronics. As is well known, the splines spindle is a mechanical device that allows for rotational motion about it's long axis while allowing for translation about the same axis. Furthermore, the bearing(s) used to guide the platen are not affected by frictional forces, which eliminates the hystersis problems caused by side forces. Additionally, placing the load cell behind the platen as described in one of the possible system configurations would greatly reduce the complexity and cost of the load cell as well as dramatically increase reliability. 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 invention, together with further advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings.
FIG. 1
is an illustration showing an exemplary prior art CMP system.
FIG. 2
shows a chemical mechanical planarization (CMP) system including an adjustable platen, in accordance with one embodiment of the present invention.
FIGS. 3A-3C
show a more detailed views of the adjustable platen relative to the linear polishing pad, in accordance with one embodiment of the present invention.
FIG. 4
illustrates a platen delivering a fixed air flow and being adjustable in vertical position to generate a desired pressure to the underside of the linear polishing pad.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An invention is disclosed for a chemical mechanical planarization system that includes an adjustable air platen. The adjustable platen is designed to apply a force to an underside of the polishing pad during operation. Air is preferably supplied in an adjustable and controlled manner through the platen and directed toward the underside of the polishing pad. The force is preferably monitored by incorporating a load cell into the platen, and adjustments are made to the air flow to appropriately modify the applied force. The carrier, however, is simply designed to move the carrier into position over the polishing pad to achieve the appropriate planarization result. In one specific embodiment, the force applying platen will include an integrated air bearing that provides force to the back of a polishing pad. This force is then transmitted to the wafer through the front of the polishing pad causing the mechanical abrasion forces required for CMP on a linear belt technology system. To apply the force through the platen, an actuator is placed behind the platen. The actuator can take on many forms, such as pneumatic, hydraulic, mechanically driven, or electromagnetically driven.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order not to unnecessarily obscure the present invention.
FIG. 2
shows a chemical mechanical planarization (CMP) system
100
including an adjustable platen
122
, in accordance with one embodiment of the present invention. The CMP system
100
includes a pair of drums
24
which are configured to receive a polishing pad
18
and move the polishing pad linearly around the drums. A carrier
102
is provided, including a wafer
12
that is designed to be lowered over the moving surface of the polishing pad
18
during processing by a spindle. The carrier
102
is connected to a spindle holder
103
that secures a spindle
107
in an aligned position relative to the polishing pad
18
.
In this embodiment, the carrier
102
is designed to have a vertical motion such that the wafer
12
can be moved up and down relative to the polishing pad
18
and also be provided with rotational motion as induced by the spindle on the carrier
14
. Once the carrier
102
is moved to the polishing pad
18
surface and polishing commences, the carrier
102
is no longer monitored for controlled adjustment up or down to achieve a varied pressure for processing the wafer
12
. In this embodiment, the adjustable platen
122
is designed to either apply more or less pressure under the polishing pad
18
in a location directly below the carrier
102
. The applied pressure therefore exerts a force to the underside of the polishing pad
18
. This force, as will be discussed below, can be varied to achieve the desired processing of the wafer
12
. The adjustable platen
122
, as shown has a platen body having a top region and a bottom region. The top region, in one embodiment, can receive an air bearing
126
. Accordingly, the air supplied by the adjustable platen
122
is delivered by way of an air supply line
126
that feeds air into and is distributed by the air bearing
124
. The air bearing
124
can have zones, which are optimized and controlled to deliver optimized air flow to desired regions under the polishing pad
18
. In this manner, the wafer
12
can be polished to the optimum level desired by an end user.
The air bearing
124
, in one embodiment, provides the air to the region between the polishing pad and the adjustable platen
122
. The air forms an air cushion
128
that applies pressure to the under surface of the polishing pad during operation. The adjustable platen
122
is coupled to a reference surface
130
by way of linear bearings
132
. The linear air bearings
132
are, in one embodiment, spring loaded. In this manner, the adjustable platen
122
will naturally be pushed to a neutral uncompressed position that is away from the reference surface. The reference surface
130
also has a connector
134
that is coupled to a load cell
136
. The load cell can by any type of load cell that measures pressure, outputs an analogy signal that can then be digitized for analysis. One example commercially available load cell may be a LPU-500-LRC low profile tension and compression load cell available from Transducer Techniques, located in Temecula, Calif. For more information on load cells and methods for using the same, reference can be made to U.S. Pat. No. 6,083,082, issued Jul. 4, 2000, by Miguel A. Saldana in the name of Assignee Lam Research Corporation. This patent is herein incorporated by reference.
The adjustable height connector
134
is shown in simplified form, and it should be understood that any conventional load cell connector or structure that may be adjusted for platen height by a mechanical device, such as a lead screw, a piston, a shaft, an actuator, and the like can work. The reference surface
130
, as used herein, should be understood to include any surface that can provide support or the adjustable platen
122
. The load cell
136
is designed to measure the amount of force being exerted by the adjustable platen
122
as it pushes downward toward the reference surface
130
. In this embodiment, the load cell
136
is designed to provide a load signal
142
that indicates the amount of loading being experienced by the adjustable platen
122
. The load signal
142
is provided to a comparator
146
. The comparator
146
is further configured to receive a command signal
144
from a control station
145
.
As is well known, a control station
145
can be used to provide a recipe of preprogrammed pressures and other controlling parameters that are appropriate for a given CMP operation. For example, the recipe can be designed for the planarization of oxides, metals, or combinations of oxides and metals. Once the command signal
144
has been provided to the comparator
146
, the comparator and its electronics will then compare the command signal
144
with the load signal
142
to produce a signal
151
that is appropriate for the application and is in conformance with the recipe being applied. As shown, the signal
151
is supplied to a flow controller
150
.
The flow controller
150
is designed to be coupled to an air supply
152
. The air supply
152
can be any air supply, such as one that may be part of a clean room or the like. Once the air flow controller
150
has received the signal
151
, the appropriate amount of air pressure is supplied through the air supply line
126
to the adjustable platen
122
. By applying additional air flow through the air supply line
126
, additional pressure will be exerted to the under surface of the polishing pad
18
during the processing of the wafer
12
. As more air flow is directed to the under surface of the polishing pad
18
, a variable gap
140
will become enlarged, while still exerting additional pressure to the underside of the polishing pad
18
.
It should be noted that all control for additional pressure is controlled by the adjustable platen
122
, and no longer required of the carrier
102
. As such, the carrier design can now be simplified as it only requires the control of up-down parameters and rotational parameters.
FIG. 3A
shows a more detailed diagram of the adjustable platen
122
relative to the polishing pad
118
, in accordance with one embodiment of the present invention. In this illustration, the carrier
102
has been applied to the polishing pad
18
so as to bring the surface of the wafer
12
in contact with the polishing pad
18
. During processing, it is assumed that appropriate amounts of slurry have been applied to the polishing pad
18
to achieve the appropriate level of polishing. In the down position as shown by up-down position
105
, the spindle
107
is designed to be in rotational movement. In this embodiment, the air cushion
128
is shown with an air flow
180
a
that produces a gap
140
a.
The variable air flow
127
is, in this example, applied at a reduced amount since the recipe for the particular CMP operation may not require large pressure from under the polishing pad
18
. During operation, the load cell
136
is providing information by way of load signal
142
, which is supplied to the comparator
146
.
If additional pressure is desired at any time during the polishing operation, the variable air flow
127
will apply additional air flow
180
a
to produce a gap which is slightly larger than
140
a.
In this embodiment, linear bearings
200
enable a shaft
206
to traverse up or down as additional or less air is supplied to the gap
104
a.
In this example, the linear bearings
200
include a cage
204
and a plurality of ball bearings
202
. The ball bearings
202
will allow the shaft
206
to move up and down in a Z direction without introducing an X or Y component. It is also important to note that the frictional forces present in the prior art do not apply to the linear bearings
200
since the platen
102
is not in frictional contact with the polishing pad
18
. Thus, the frictional forces will not impact the measuring of the force through the load cell
136
, and thus, more accurate force results can be measured and in turn applied.
FIG. 3B
shows yet another example of the adjustable platen
122
in which increased air flow is supplied to the air supply line
126
and therefore to the underside of the polishing pad
18
. The air flow
180
b
is illustrated to be more intense than the air flow
180
a
of FIG.
3
A. Similarly, because additional air flow has been provided, the gap
140
a
of
FIG. 3A
is now increased to gap
140
b
as shown in FIG.
3
B. As additional air is supplied through the air supply line
126
, the adjustable platen
122
will move downward toward the reference surface
130
. This movement is also monitored by the load cell in terms of force, thus providing the accurate feedback to the pressure control system.
By way of example, the adjustable platen
122
is shown with shafts
206
in a moved-in position within the linear bearings
200
. As shown in
FIG. 3C
, in one embodiment, the load cell connector
134
will preferably compress a spring
133
or other suitable resistive element. A Z-adjustment
135
can also be included for fine tuning of a reference surface. The Z-adjustment
135
can be, for example, a lead screw, an adjustable connector, a piston, or other suitable device that con provide precision positioning. The spring element
133
may have a mechanical stiffness that can be varied in order to vary the mode of operation of the proposed invention. When the stiffness is low relatively speaking and the spring
133
is compressed for a given pressure setpoint, the adjustable platen
102
will be driven upward when less air is supplied, thus closing the gap between the belt and the platen
102
as the system reaches equilibrium. In a more preferred embodiment, the mechanical stiffness of the spring or resistive element is great as it is replaced by a rigid mechanical connection. Thus, while the air supply rate is dropped, the density of the air between the platen and the belt reduces thereby reducing the resulting pressure on the wafer. Note that in this alternative embodiment, the platen is not driven upward when the air supply is decreased.
Of course, during a CMP operation, the load cell
136
will continue to provide loading information by way of the load signal
142
. If the recipe supplied by the control station
145
requires less pressure to be applied to the underside of the polishing pad
18
, the command signal
144
will be adjusted such that the signal
151
will command the flow controller
150
to apply less air through the air supply line
126
.
FIG. 4
illustrates another embodiment in which an adjustable platen
122
is implemented below a polishing pad
18
, in accordance with one embodiment of the present invention. The adjustable platen
122
includes a load cell
136
which is also configured to produce a load signal
142
. However, instead of coupling the adjustable platen
122
to a reference surface
130
, a shaft
304
coupled to a platen position controller (PPC)
302
is provided. The PPC
302
is configured to receive a position signal
320
from the comparator
142
. The comparator
142
is configured to receive the load signal
142
as well as the command signal
144
from the control station
145
.
As mentioned above, the command signal
144
provided to the comparator
142
is in accordance with a particular recipe that is designed to define the variables for the polishing of the wafer
12
. In this embodiment, the air flow provided by way of the air supply line
126
to the adjustable platen
122
will be fixed
301
, instead of having a variable air flow
127
. Accordingly, it is not the air flow that will move the adjustable platen away form the under surface of the polishing pad
18
, but the platen position controller (PPC). Accordingly, if more force is required, the adjustable platen
122
will be moved closer to the under surface of the polishing pad
18
. If less force is required, the adjustable platen will be moved away since the air flow is fixed. The fixed air flow
301
, however, will still provide the air cushion
128
between the polishing pad
18
and the adjustable platen
122
.
In this embodiment, the shaft
304
can be driven by any type of actuator. For example, the actuator can be a mechanically actuator, a pneumatic actuator, a hydraulic actuator, or an electromagnetic actuator. The controls for such actuator devices may be closed loop servo-driven, this is in fact preferred. The adjustable air platen is then guided by a bearing system that may include one or several bearing guides. The air bearing design may be single zone or multi-zone in either single quadrant or multi-quadrant variations. The spindle is simplified considerably by eliminating the splined shaft requirement and replacing it with a more inexpensive conventional spindle shaft. As described above, closed loop control over force is done using a load cell as a force transducer. In one embodiment, the load cell may be installed either on the carrier wafer head, the platen or at the load application point.
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. A chemical mechanical planarization (CMP) system having a polishing pad, a wafer carrier, and an adjustable platen, the adjustable platen comprising:a platen body; an air bearing integrated in the platen body for applying air pressure to an underside of the polishing pad; a set of bearings connected to the platen body to enable movement of the platen body closer and further from the underside of the polishing pad; a load cell being connected to the platen body, the load cell being configured to output a load signal that is indicative of a force being applied to the underside of the polishing pad; an air supply for applying air flow to the air bearing, the air flow being adjustable in response to changes in the force being applied to the underside of the polishing pad; and a comparator for receiving the load signal and a recipe command, the recipe command being indicative of a desired pressure and the load signal being indicative of an actual pressure.
- 2. A chemical mechanical planarization (CMP) system of claim 1, wherein the platen body has a top region and a bottom region, the top region being proximate to the underside of the polishing pad and separate from the underside of the polishing pad by a gap.
- 3. A chemical mechanical planarization (CMP) system of claim 2, wherein the gap increases as the force applied to the underside of the polishing pad increases, and the gap decreases as the force applied to the underside of the polishing pad decreases.
- 4. A chemical mechanical planarization (CMP) system of claim 2, further comprising:a flow controller for supplying the air flow to the air bearing.
- 5. A chemical mechanical planarization (CMP) system of claim 1, wherein the actual pressure is reduced to approximate the desired pressure.
- 6. An adjustable platen, comprising:a platen body having a top region and a bottom region, the platen body being oriented under a linear polishing pad; an air bearing integrated with the platen body at the top region, the air bearing being configured to apply an air pressure to an underside of the linear polishing pad; and a set of bearings connected to the bottom region of the platen body to enable controlled movement of the top region of the platen body closer or further from the underside of the linear polishing pad depending on the applied air pressure, the applied air pressure being configured to exert a force to the underside of the linear polishing pad.
- 7. An adjustable platen as recited in claim 6, further comprising:a load cell connected to the platen body, the load cell being configured to output a load signal that is indicative of the force being exerted to the underside of the linear polishing pad.
- 8. An adjustable platen as recited in claim 6, further comprising:an air supply being provided to the air bearing, the air supply having a flow rate that defines the air pressure.
- 9. An adjustable platen as recited in claim 8, wherein the air flow is adjustable in response to at least the load signal from the load cell.
- 10. An adjustable platen as recited in claim 8 being integrated into a chemical mechanical planarization (CMP) system, the system including,a carrier for holding a wafer to be processed, the carrier being designed to lower the wafer onto a top surface of the linear polishing pad that is substantially over the adjustable platen.
- 11. An adjustable platen as recited in claim 10, wherein the exerted force to the underside of the linear polishing pad is translated to the wafer being processed.
- 12. A platen, comprising:a platen body having a top region and a bottom region, the platen body being positioned under a linear polishing pad of a chemical mechanical polishing (CMP) system, the CMP system is designed to receive a wafer to be polished on a top surface of the linear polishing pad when positioned for processing by a spindle and carrier of the CMP system; an air bearing coupled with the platen body at the top region, the air bearing being configured to deliver an air flow to an underside of the linear polishing pad; and a set of linear bearings coupled to the bottom region of the platen body to enable controlled vertical movement of the platen body closer and further from the underside of the linear polishing pad, the vertical movement of the platen body determined by the air flow, the air flow being variable so as to set a desired force to the underside of the linear polishing pad.
- 13. A platen as recited in claim 12, further comprising:a load cell integrated in the platen body, the load cell being configured to generate a load signal that is indicative of a current force being exerted to the underside of the linear polishing pad.
- 14. A platen as recited in claim 13, wherein the current force is modified to match the desired force by adjusting the air flow to the underside of the linear polishing pad.
- 15. A platen as recited in claim 12, further comprising:an air supply for providing the air flow to the air bearing, the air supplying being controlled in response to achieve the desired force.
- 16. A platen, comprising:a platen body having a top region and a bottom region, the platen body being positioned under a linear polishing pad of a chemical mechanical polishing (CMP) system, the CMP system is designed to receive a wafer to be polished on a top surface of the linear polishing pad when positioned for processing by a spindle and carrier of the CMP system; an air bearing coupled with the platen body at the top region, the air bearing being configured to deliver a fixed air flow to an underside of the linear polishing pad; a load cell for determining a force being applied to the underside of the linear polishing pad by the fixed air flow; and an actuator vertically adjusting the platen body closer and further from the underside of the linear polishing pad.
- 17. A platen as recited in claim 16, wherein the actuator is one of a mechanical actuator, a pneumatic actuator, a hydraulic actuator, and an electromagnetic actuator.
- 18. A platen as recited in claim 16, wherein a gap is defined between the underside of the linear polishing pad and a top portion of the air bearing, the gap providing an air cushion for the linear polishing pad.
- 19. A platen as recited in claim 16, wherein the spindle and carrier of the CMP system only includes vertical position control and rotation control and excludes pressure sensing and adjustment.
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