U.S. patent application number 10/605447 was filed with the patent office on 2005-03-31 for integrated pressure control system for workpiece carrier.
This patent application is currently assigned to SPEEDFAM-IPEC CORPORATION. Invention is credited to Herb, John, Korovin, Nikolay, Schultz, Steve.
Application Number | 20050070205 10/605447 |
Document ID | / |
Family ID | 34375681 |
Filed Date | 2005-03-31 |
United States Patent
Application |
20050070205 |
Kind Code |
A1 |
Korovin, Nikolay ; et
al. |
March 31, 2005 |
INTEGRATED PRESSURE CONTROL SYSTEM FOR WORKPIECE CARRIER
Abstract
An integrated pressure control system for a workpiece carrier
includes a multizone carrier workpiece having multiple
pressurizable zones and a pressure control system mounted to the
carrier for controlling pressure provided to the pressurizable
zones. The present invention also includes a workpiece carrier
having a housing, a workpiece bladder coupled to the housing, and
at least one pressure transducer mounted to the carrier housing for
controlling pressure provided to the workpiece bladder.
Inventors: |
Korovin, Nikolay; (Phoenix,
AZ) ; Schultz, Steve; (Gilbert, AZ) ; Herb,
John; (Phoenix, AZ) |
Correspondence
Address: |
SNELL & WILMER
ONE ARIZONA CENTER
400 EAST VAN BUREN
PHOENIX
AZ
850040001
|
Assignee: |
SPEEDFAM-IPEC CORPORATION
305 North 54th Street
Chandler
AZ
|
Family ID: |
34375681 |
Appl. No.: |
10/605447 |
Filed: |
September 30, 2003 |
Current U.S.
Class: |
451/5 ;
451/288 |
Current CPC
Class: |
B24B 37/30 20130101;
B24B 49/16 20130101 |
Class at
Publication: |
451/005 ;
451/288 |
International
Class: |
B24B 049/00; B24B
051/00 |
Claims
1. A workpiece carrier comprising: a carrier housing a workpiece
bladder coupled to said housing, said workpiece bladder having a
surface configured to press against a surface of a workpiece; and
at least one pressure transducer mounted to said carrier housing
for controlling pressure provided to said workpiece bladder.
2. The workpiece carrier of claim 1 wherein said bladder comprises
a plurality of pressurizable zones and each zone has a pressure
transducer for monitoring pressure to that zone.
3. The workpiece carrier of claim 1 further comprising at least one
valve mounted to said carrier.
4. The workpiece carrier of claim 1 further comprising a control
board mounted to said carrier.
5. The workpiece carrier of claim 1 further comprising means for
automatically calibrating said at least one pressure
transducer.
6. An integrated pressure control system for planarizing a
workpiece comprising: a multizone workpiece carrier having a
plurality of pressurizable zones; and a pressure control system
mounted to said carrier for controlling pressure provided to said
plurality of pressurizable zones.
7. The integrated pressure control system of claim 6 further
comprising an automatic calibration system for calibrating said
pressure control system.
8. The integrated pressure control system of claim 6 wherein said
pressure control system comprises at least one pressure
transducer.
9. The integrated pressure control system of claim 8 wherein said
pressure control system further comprises at least one valve.
10. The integrated pressure control system of claim 6 further
comprising a rotary union for connecting electrical lines to said
pressure control system.
11. The integrated pressure control system of claim 10 wherein said
rotary union further connects an air supply line and an air exhaust
line to said pressure control system.
12. A carrier insert for a multizone workpiece carrier comprising:
a pneumatic manifold having a plurality of ports in alignment with
a plurality of pressurizable zones located in said multizone
workpiece carrier; and at least one pressure transducer mounted to
said pneumatic manifold.
13. The carrier insert of claim 12 further comprising at least one
valve mounted to said pneumatic manifold.
14. The carrier insert of claim 13 further comprising a control
board mounted to said pneumatic manifold.
Description
FIELD OF INVENTION
[0001] The present invention generally relates to the art of
planarizing a workpiece against an abrasive surface and, more
particularly, to an integrated pressure control system for a
workpiece carrier that applies pressure to the back surface of a
workpiece during planarization.
BACKGROUND OF THE INVENTION
[0002] The manufacture of many types of workpieces requires the
substantial planarization of at least one surface of the workpiece.
Examples of such workpieces that require a planar surface include
semiconductor wafers, optical blanks, memory disks, and the like.
Without loss of generality, but for ease of description and
understanding, the following description of the invention will
focus on applications to only one specific type of workpiece,
namely a semiconductor wafer. However, the invention is not to be
interpreted as being applicable only to semiconductor wafers.
[0003] In an exemplary conventional method for planarizing a wafer,
the wafer is secured in a carrier that is connected to a shaft in a
chemical mechanical polishing (CMP) tool. The shaft transports the
carrier, and thus the wafer, to and from a load or unload station
and a position adjacent a polishing pad mounted to a platen. A
pressure is exerted on the back surface of the wafer by the carrier
in order to press the wafer against the polishing pad, usually in
the presence of a slurry. The wafer and/or polishing pad may be
rotated, orbited, linearly oscillated or moved in a variety of
geometric or random patterns via motors connected to the shaft
and/or platen.
[0004] The construction of the carrier head and the relative motion
between the polishing pad and the carrier head have been
extensively engineered in an attempt to achieve a uniform or
controlled non-uniform removal of material across the surface of
the workpiece and hence to achieve the desired planar surface. For
example, numerous carrier designs are known in the art for holding
and distributing a pressure on the back surface of the wafer during
the planarization process. Conventional carriers commonly have a
hard flat pressure plate that is used to press against the back
surface of the wafer. As a consequence, the pressure plate is not
capable of applying a uniform polish pressure across the entire
area of the wafer, especially at the edge of the wafer. In an
attempt to overcome this problem, the pressure plate is often
covered by a soft carrier film. The purpose of the film is to
transmit uniform pressure to the back surface of the wafer to aid
in uniform polishing.
[0005] Other conventional carriers implement means for applying
more than one pressure region across the back surface of the wafer.
Specifically, some conventional carriers provide a carrier housing
with a plurality of concentric internal chambers that may be
independently pressurized separated by barriers. By pressurizing
the individual chambers in the top plate to different magnitudes, a
different pressure distribution can be established across the back
surface of the wafer. The pressure control systems used to operate
these multi-zone carriers utilize a design in which the pressure
control components, such as pressure regulators and transducers,
are located remotely from the carriers on a dedicated pneumatic
panel. The regulators and transducers are connected to the
different chambers in the multi-zone carriers via long, narrow
pneumatic tubes through a multi-port rotary union. However, this
architectural design creates a number of problems.
[0006] First, significant drops in pressure can occur across the
pressure lines during employment of the pressure control system.
Second, there is a large response time or lag time in communicating
and correcting for pressure drops in the lines. Third, the
pneumatic rotary union through which the pressure lines are routed
lacks reliability. Fourth, the system is more vulnerable to leaks
between channels and leaks from channels to the
environment/atmosphere outside the channels. Fifth, the pressure
control system lacks the ability to measure pressure at the point
of use, namely in the chamber of the carrier, and therefore lacks
the ability to utilize a closed loop control design.
[0007] All of the above problems cause existing pressure control
systems to be plagued with three major deficiencies. These
deficiencies include low dynamic accuracy, poor static accuracy,
and loss of control at low pressure levels. Accordingly, there is a
need for a workpiece carrier having an integrated pressure control
system that is capable of overcoming these major deficiencies.
SUMMARY OF INVENTION
[0008] The present invention is directed to a workpiece carrier for
planarizing a workpiece having an integrated pressure control
system for applying pressure to the back surface of a workpiece or
wafer. All components for executing the regulation of pressure to
the backside of the wafer are mounted on a common manifold which is
connected to, or comprises part of, the carrier"s housing. These
components include, but are not limited to pressure transducers and
control valves.
[0009] One exemplary embodiment of a workpiece carrier housing in
accordance with the present invention includes a carrier housing, a
workpiece bladder coupled to the housing so that a surface of the
workpiece bladder can press against a back surface of the
workpiece, and at least one pressure transducer mounted to the
carrier housing for monitoring pressure to the workpiece
bladder.
[0010] In one aspect of the invention, the workpiece bladder may
comprise a number of zones that can be pressurized individually
with each zone having a pressure transducer for monitoring pressure
to that zone. In another aspect of the invention, there is at least
one valve mounted to the carrier to manipulate air flow to the
workpiece bladder.
[0011] In yet another aspect of the invention, a control board may
be mounted to the carrier for controlling the components which
regulate pressure provided to the workpiece bladder. Further, in
still another aspect of the invention, the workpiece carrier may
include one or more automatic calibration means for calibrating any
pressure transducers located on the carrier.
[0012] Another exemplary embodiment of the present invention
includes an integrated pressure control system for planarizing a
workpiece which has a multizone workpiece carrier with a plurality
of pressurizable zones and a pressure control system mounted to the
carrier for controlling the pressure that is provided to the
multiple pressurizable zones. The pressure control system may
include at least one pressure transducer and at least one valve.
The pressure control system may also comprise an automatic
calibration system and a rotary union for connecting electrical
lines to the pressure control system. The rotary union may also
function to connect an air supply line and an air exhaust line to
the pressure control system.
[0013] Yet another exemplary embodiment of the invention is
directed to a carrier insert for a multizone workpiece carrier
which includes a pneumatic manifold having a plurality of ports
that are aligned with multiple pressurizable zones located in the
multizone workpiece carrier and at least one pressure transducer
mounted to the pneumatic manifold for directing pressure through
the ports. The carrier insert may also include at least one valve
mounted to the pneumatic manifold and a control board mounted to
the pneumatic manifold.
BRIEF DESCRIPTION OF DRAWINGS
[0014] The present invention is hereinafter described in
conjunction with the appended drawing figures, wherein like
numerals denote like elements, and in which:
[0015] FIG. 1 is a schematic of a pressure control system known in
the prior art;
[0016] FIG. 2 is a schematic of an exemplary integrated pressure
control system in accordance with the present invention;
[0017] FIG. 3 is a more detailed schematic of another embodiment of
the exemplary integrated pressure control system of the present
invention;
[0018] FIG. 4 is a partial perspective view of a workpiece carrier
containing components of the integrated pressure control system of
the present invention;
[0019] FIG. 5 is a cross-sectional view of a workpiece carrier
containing the integrated pressure control system of the present
invention; and
[0020] FIG. 6 is a top plan view of a workpiece carrier containing
the integrated pressure control system of the present
invention.
DETAILED DESCRIPTION
[0021] Preferred embodiments of the present invention include
integrated pressure control systems for wafer carriers used in
planarizing wafers where the components for controlling pressure
applied to the back surface of a wafer are contained on the carrier
itself. The present invention is particularly suited for multizone
carriers which contain multiple zones for applying varying degrees
of pressure to different areas of the back surface of the wafer.
The carrier remains a separate hardware component for CMP where the
integrated pressure control system may be snapped to the carrier
during mounting of the carrier. Alternatively, the pressure control
system of the present invention may be integrated into the
structure of the carrier such that it is not removable from the
carrier.
[0022] The present invention may be used with a variety of CMP
tools such as, for example, the AvantGaard 676, 776 or MV200 or
Auriga C or CE or MV300 made commercially available by Novellus
(formerly SpeedFam-IPEC) located in Chandler, Ariz. The present
invention may also be used with a variety of workpiece or wafer
carriers, and especially multizone carriers such as those described
in U.S. Pat. Nos. 6,390,905 and 6,336,853 and 6,508,694. CMP tools
that may be used to practice the invention are well known in the
art and will not be discussed in detail to avoid confusing the
invention. It should also be understood by those skilled in the art
that wafer carriers that are well known in the art may be used to
practice the invention and that such wafer carriers may be provided
with a removable integrated pressure system or may be singularly
reconfigured and recreated to provide a one piece wafer carrier
that incorporates an integrated pressure control system.
[0023] A wafer carrier in a CMP tool must retain the wafer and
assist in the distribution of a pressing force on the back of the
wafer while the front of the wafer is planarized against an
abrasive surface. The abrasive surface typically comprises a
polishing pad wetted by chemically active slurry with suspended
abrasive particles. The preferred polishing pad and slurry are
highly dependent on the particular process and workpiece being
used. Conventional CMP polishing pads and slurries are made
commercially by Rodel Inc. from Newark, Del. for typical
applications.
[0024] Exemplary embodiments of the present invention will be
discussed in detail with reference to a multizone carrier, i.e. a
wafer carrier having a plurality of pressurizable zones for
contacting the back surface of a wafer during CMP. A prior art
pressure control system 10 for use with a multizone carrier 12 is
shown in FIG. 1. Prior art pressure control systems are not
integrated with the wafer carrier and typically include multiple
channels 14, such as long pneumatic tubes, which are connected to
multizone carrier 12. The number of channels 14 connected to
carrier 12 is equal to the number of pressurizable zones contained
in carrier 12. Pressure regulators 16 and pressure transducers 18
for each channel 14 are located remotely from carrier 12 and
connected to control system 20. Pressure control components such as
pressure regulators 16 and pressure transducers 18 are in turn
connected to multizone carrier 12 through a multi-port rotary union
22. Multi-port rotary union 22 contains as many ports as there are
channels 14.
[0025] Prior art pressure control systems such as that shown in
FIG. 1 possess a number of problems such as experiencing
significant pressure drop across channels 14 and a large response
or lag time between signaling a change in pressure and actual
change in pressure of a pressurizable zone connected to a given
channel 14. In addition, the reliability of pneumatic rotary union
22 is low due to the number of channels 14 passing there through
and leaks between the channels and from the channels are also more
likely to occur due to their location and the increased number of
them passing through rotary union 22. The inability of prior art
system 10 to measure the pressure at the point of use, i.e. in the
chamber of the carrier, also delays response time and efficiency in
changing or adjusting pressure within the zones in multizone
carrier 12. The present invention was designed to overcome these
problems.
[0026] A schematic of an exemplary integrated pressure control
system in accordance with the present invention is shown in FIG. 2.
Integrated pressure control system 30 includes a multizone carrier
32 having a multi-port manifold 33 for association with multiple
channels 34. Multi-port manifold 33 includes multiple inlet valves
35 and exhaust valves 37 such that an inlet valve 35 and exhaust
valve 37 are each paired with a separate zone 34 for pressurizing
that zone. Multiple pressure transducers 38 are also contained on
multi-port manifold 33 so that a pressure transducer 38 is coupled
with each pair of inlet and exhaust valves 35 and 37 for
controlling the pressure flow by inlet and exhaust valves 35 and
37. Inlet valves 35, exhaust valves 37, and pressure transducers 38
are all connected to a control board 44 located on multizone
carrier 32. Control board 44 functions to send and receive
electrical signals for controlling the pressure provided to
separate zones 34 through their respective inlet and outlet valves
35 and 37.
[0027] Each inlet valve 35 located within carrier 32 is connected
to a single pressure line 46 and each exhaust valve 37 located
within carrier 32 is connected to a single exhaust line 48. Single
pressure line 46 and single exhaust line 48 exit carrier 32 and are
coupled to a pressure source and vacuum source, respectively,
through rotary union 42. Rotary union 42 is connected to a control
system 40 which commands and monitors pressure in a zone of the
carrier. Control board 44, which manipulates inlet valves 35 and
exhaust valves 37, is connected to rotary union 48 so that
electrical signals may pass to and from control system 40 and to
and from control board 44 via rotary union 42.
[0028] Integrated system 30 overcomes the problems and deficiencies
present in prior art system 10. More specifically, the components
responsible for air flow manipulation such as valves, flappers, and
variable orifices, are located at the carrier chamber thereby
eliminating dynamic control error, air leaks, and differential
pressure drop. Further, relocation of pressure transducers 38 to
the carrier 32 in integrated system 30 improves static accuracy and
linearity. Rotary union 42 is used to connect pressure line 46 and
exhaust line 48 to carrier 32. The elimination of multiple
pneumatic lines through a rotary union for each chamber 34 in
carrier 32 eliminates the effects that potential leaks and pressure
drops in these lines would have on system operation and
performance. Potential leaks and pressure drops in main pressure
line 46 and main exhaust line 48 are not critical for system
operation since pressure supplied to chambers 34 is controlled at
carrier 32. Rotary union 42 is also used to connect electrical
lines between control system 40 and control board 44. The
reliability and simplicity of this connection is much higher than
for pneumatic lines. Finally, the reduced number of components in
system 30 and their reduced dimensions, along with the simplified
design for rotary union 42, allow for a greater number of channels
and pressurizable chambers in multiple carrier 32, which in turn
improve process performance of carrier 32.
[0029] FIG. 3 shows more detailed schematic of another embodiment
of the integrated pressure control system of the present invention.
Integrated pressure control system 50 includes a carrier head 52
having a plurality of inlet valves 55, a plurality of exhaust
valves 57, and a plurality of pressure transducers 58 all located
on carrier head 52. Carrier head 52 has multiple pressurizable
chambers 54 where each chamber 54 is paired with an inlet valve 55,
and exhaust valve 57, and a pressure transducer 58 each of which
are electrically connected to a rotary union 70. Rotary union 70 is
located on an outer top surface of carrier head 52 and connects
control board with pressure control components located on carrier
head 52.
[0030] A pressure supply source 67 is connected to main pressure
line 66 which is coupled to multiple pressure lines contained in
carrier head 52 via rotary union 72. A vacuum source 74 is
connected to main vacuum line 76, which is in turn connected to
multiple exhaust valves 57 located on carrier head 52 via rotary
union 72. Under normal operation the pressure transducer 58 senses
pressure in the particular chamber and sends electric signal to the
control board via rotary union 70. This signal is compared with
commanded pressure. If chamber pressure is larger than commanded
the control board, according to the control algorithm, preferably
PID, commands inlet valve 58 to close and exhaust valve 57 to open.
If chamber pressure is lower than commanded the control board
commands inlet valve 58 to open and exhaust valve 57 to close. In
the preferred embodiment the inlet and exhaust valves are
proportional valves, meaning that the air flow through the valve is
proportional to the signal commanded to the valve. This ensures
smooth pressure control without fluctuations.
[0031] Exhaust valves 57 are connected to the source of vacuum.
This allows to supply and control vacuum in the carrier chamber.
Controlled vacuum is used in the carrier during wafer acquiring
(wafer chuck).
[0032] A partial perspective view of an exemplary workpiece carrier
containing the components of the integrated pressure control system
of the present invention is shown in FIG. 4. Integrated pressure
control system 80 includes a multi-zone carrier head having a wafer
head mount plate 82 and a multi-port pneumatic manifold 84. Wafer
head mount plate 82 and multi-port pneumatic manifold 84 are rigid
and cylindrical in shape and may comprise, for example, stainless
steel to give the multizone carrier the necessary rigidity and
resistance to corrosion needed in a CMP environment. Wafer head
mount plate 82 may be adapted to be connected to almost any
conventional CMP tool. Most conventional CMP tools have a movable
shaft for transporting a carrier containing a wafer. The movable
shaft typically allows the carrier to move between a wafer loading
and/or unloading station and a position in proximity and parallel
to an abrasive surface in the CMP tool.
[0033] Multi-port manifold 84 has multiple pressure transducers 88
and multiple control valves 90 located thereon so that a pressure
transducer 88 and control valve 90 are associated with each
pressurizable zone contained in the carrier. Although the present
invention has been described as an integrated pressure control
system for a multizone carrier, the present invention is also
intended to include an integrated pressure control system for a
carrier having a single pressurizable zone or chamber where the
pressure control components for that chamber are located on the
carrier. It will also be understood by those skilled in the art
that multi-port manifold 84 may comprises an interchangeable piece
that can be incorporated into existing carrier heads known in the
art. In addition, the integrated pressure control system of the
present invention is intended to include any carrier head or
pressure system where at least any one pressure control component
is located on the carrier head.
[0034] FIG. 5 shows a cross-sectional view of the present invention
which includes a workpiece carrier having an integrated pressure
control system. The multizone carrier 100 includes wafer head mount
plate 102 and multi-port pneumatic manifold 104. Multi-port
pneumatic manifold 104 includes a plurality of pressure transducers
108, a plurality of control valves 110, and a plurality of
pneumatic fittings 112 which connect pressure transducers 108 and
control valves 110 to a wafer module plate 114. Carrier bladder 116
forms a plurality of pressurizable zones, each of which has an
inlet port, an exhaust port, a pressure transducer, and inlet and
exhaust control valves associated therewith.
[0035] The configuration of the integrated pressure control system
of the present invention allows for automatic calibration of the
system. Special calibration fixtures and one external high accuracy
pressure transducer can be used to evaluate the performance of each
individual channel and pressurizable chamber. Miscalibration of
very channel can be estimated during calibration and specific
calibration coefficients can be stored in the memory of the CMP
tool and applied during regular operations.
[0036] A top plan view of a workpiece carrier containing the
integrated pressure control system of the present invention is
shown in FIG. 6. The multi-zone carrier head 120 includes a
multi-port pneumatic manifold 124 which contains a plurality of
pressure transducers 128 and a plurality of control valves 130. A
control board 144 for controlling pressure transducers 128 and
control valves 130 is also located on multi-port pneumatic manifold
124.
[0037] The present invention redesigns the traditional multi
channel pressure control system used with multizone carriers by
relocating one or more pressure control components for the various
pressurizable zones onto the carrier itself. The integrated
pressure control system of the present invention eliminates a
number of critical deficiencies associated with prior art pressure
control systems, enables a significant increase in the number of
control channels for controlling pressure to pressurizable zones,
and allows for automatic calibration and evaluation of the
system.
[0038] Although the foregoing description sets forth preferred
exemplary embodiments and methods of operation of the invention,
the scope of the invention is not limited these specific
embodiments or described methods of operation. Many details have
been disclosed that are not necessary to practice the invention,
but have been included to sufficiently disclose the best mode of
operation and manner and process of making and using the invention.
Modification may be made to specific form and design of the
invention without departing from its spirit and scope as expressed
in the following claims.
* * * * *