U.S. patent application number 09/810827 was filed with the patent office on 2001-08-09 for endpoint detection apparatus, planarizing machines with endpointing apparatus, and endpointing methods for mechanical or chemical-mechanical planarization of microelectronic-substrate assemblies.
Invention is credited to Moore, Scott E..
Application Number | 20010012750 09/810827 |
Document ID | / |
Family ID | 23526459 |
Filed Date | 2001-08-09 |
United States Patent
Application |
20010012750 |
Kind Code |
A1 |
Moore, Scott E. |
August 9, 2001 |
Endpoint detection apparatus, planarizing machines with endpointing
apparatus, and endpointing methods for mechanical or
chemical-mechanical planarization of microelectronic-substrate
assemblies
Abstract
Endpointing devices, planarizing machines with endpointing
devices, and methods for endpointing mechanical and/or
chemical-mechanical planarization of microelectronic substrate
assemblies. One endpointing apparatus in accordance with the
invention includes a primary support member for supporting either a
polishing pad or a substrate assembly, and a secondary support
member coupled to the primary support member. The primary support
member is movable with respect to the secondary support member in a
lateral motion at least generally parallel to the planarizing plane
in correspondence to the drag forces between the substrate assembly
and the polishing pad. The endpointing apparatus also includes a
force detector attached to at least one of the primary and
secondary support members at a force detector site that can have a
contact surface transverse to the planarizing plane. The force
detector measures lateral forces between the primary support member
and the secondary support member in response to drag forces between
the substrate assembly and the polishing pad. In operation, the
endpoint of CMP processing is detected when the measure lateral
force is equal to a predetermined endpoint force for a particular
CMP application.
Inventors: |
Moore, Scott E.; (Meridian,
ID) |
Correspondence
Address: |
Mark W. Roberts, Esq.
DORSEY & WHITNEY LLP
Suite 3400
1420 Fifth Avenue
Seattle
WA
98101
US
|
Family ID: |
23526459 |
Appl. No.: |
09/810827 |
Filed: |
March 16, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09810827 |
Mar 16, 2001 |
|
|
|
09386645 |
Aug 31, 1999 |
|
|
|
6206754 |
|
|
|
|
Current U.S.
Class: |
451/8 ;
451/41 |
Current CPC
Class: |
B24B 49/16 20130101;
B24B 37/013 20130101; B24B 21/004 20130101 |
Class at
Publication: |
451/8 ;
451/41 |
International
Class: |
B24B 001/00; B24B
049/00; B24B 051/00 |
Claims
1. A machine for planarizing a microelectronic substrate assembly,
comprising: a polishing pad having a planarizing surface defining a
planarizing plane and a backside opposite the planarizing surface;
a carrier assembly having a head configured to hold a substrate
assembly against the planarizing surface; a table including a base
and a primary plate moveable with respect to the base in a lateral
motion corresponding to the lateral drag forces, the base having a
base surface supporting the polishing pad and at least a first stop
surface extending from the base surface transverse to the
planarizing plane, and the primary plate having a bearing surface
facing the backside of the polishing pad to support at least a
portion of the polishing pad in a planarizing zone and at least a
first contact surface adjacent to the first stop surface; a drive
system coupled one of the table and the carrier assembly to move
the substrate assembly relative to the polishing pad in a lateral
direction at least generally parallel to the planarizing plane to
generate lateral drag forces when the substrate assembly engages
the planarizing surface; and at least a first force detector
contacting the first stop surface and the first contact surface at
a first load site to sense lateral forces between the base and the
primary plate.
2. The planarizing machine of claim 1 wherein: the polishing pad
comprises a web format pad having a pre-polish section wrapped
around a supply roller, an operative section in a planarizing zone
over the primary plate, and a post-polish section wrapped around a
take-up roller; the base of the table comprises a sub-platen having
a rectilinear recess including the base surface and a plurality of
walls projecting from the base surface transverse to the
planarizing plane, the plurality of walls including a first
side-wall, a second side-wall opposite the first side-wall, a first
end-wall between one end of the first and second side-walls, and a
second end-wall between the other end of the first and second
side-walls, the first end-wall defining the first stop surface; the
primary plate comprises a platen sized to fit within the
rectilinear recess in the sub-platen, the platen having a first
side-face adjacent to the first side-wall, a second side-face
adjacent to the second side-wall, a first end-face adjacent to the
first end-wall, and a second end-face adjacent to the second
end-wall, the first end-face defining the first contact surface;
and the planarizing machine further includes a second force
detector contacting the first side-face and the first side-wall, a
first dead stop contacting the second end-face and the second
end-wall, and a second dead stop contacting the second side-face
and the second side-wall.
3. The planarizing machine of claim 1 wherein: the polishing pad
comprises a web format pad having a pre-polish section wrapped
around a supply roller, an operative section in a planarizing zone
over the primary plate, and a post-polish section wrapped around a
take-up roller; the base of the table comprises a sub-platen having
a rectilinear recess including the base surface and a plurality of
walls projecting from the base surface transverse to the
planarizing plane, the plurality of walls including a first
side-wall, a second side-wall opposite the first side-wall, a first
end-wall between one end of the first and second side-walls, and a
second end-wall between the other end of the first and second
side-walls, the first end-wall defining the first stop surface; the
primary plate comprises a platen sized to fit within the
rectilinear recess in the sub-platen, the platen having a first
side-face adjacent to the first side-wall, a second side-face
adjacent to the second side-wall, a first end-face adjacent to the
first end-wall, a second end-face adjacent to the second end-wall,
and a back surface facing the base surface of the sub-platen, the
first end-face defining the first contact surface; the planarizing
machine further includes a second force detector contacting the
first side-face and the first side-wall, a first dead stop
contacting the second end-face and the second end-wall, and a
second dead stop contacting the second side-face and the second
side-wall; and the planarizing machine further includes a bearing
assembly between the base surface of the sub-platen and the back
surface of the platen.
4. The machine of claim 1 wherein: the base of the table comprises
a rotatable sub-platen that rotates about a drive axis in a
rotation direction, the sub-platen having a top surface defining
the base surface and at least one tab projecting upwardly from the
top surface, the first stop surface being a surface on the tab
facing in the rotation direction; the primary plate comprises a
platen on the sub-platen, the platen including an upper surface
defining the bearing surface, a lower surface adjacent to the top
surface of the sub-platen, and at least one opening having a face
facing counter to the rotation direction defining the first contact
surface, the tab of the sub-platen being received in the opening of
the platen so that the first stop surface on the tab faces the
first contact surface; and the first force detector contacts the
first stop surface and the first contact surface.
5. The machine of claim 1 wherein: the base of the table comprises
a rotatable sub-platen that rotates about a drive axis in a
rotation direction, the sub-platen having a top surface defining
the base surface and at least one tab projecting upwardly from the
top surface, the first stop surface being a surface on the tab
facing in the direction of rotation; the primary plate comprises a
platen on the sub-platen, the platen including an upper surface
defining the bearing surface, a lower surface adjacent to the top
surface of the sub-platen, and at least one opening having a face
facing counter to the rotation direction defining the first contact
surface, the tab of the sub-platen being received in the opening of
the platen so that the first stop surface on the tab faces the
first contact surface; the first force detector contacts the first
stop surface and the first contact surface; and the planarizing
machine further comprises a bearing assembly between the top
surface of the sub-platen and the lower surface of the platen.
6. The machine of claim 1, further comprising a processor coupled
to the force detector to receive and process electrical signals
from the force detector and to produce data representing the
lateral forces between the base and the primary plate.
7. The machine of claim 1 wherein the primary plate has a back
surface facing the base surface of the base, and wherein the
planarizing machine further comprises a bearing assembly between
the base surface and the back surface to reduce friction between
the base and the primary plate.
8. The machine of claim 1 wherein the primary plate has a back
surface facing the base surface of the base, and wherein the
planarizing machine further comprises a bearing assembly having a
plurality of ball bearings between the base surface and the back
surface to reduce friction between the base and the primary
plate.
9. The machine of claim 1 wherein the first load site is along a
first axis and the planarizing machine further comprises a second
force detector positioned between the base and the primary plate at
a second load site along a second axis orthogonal to the first
axis.
10. A machine for planarizing a microelectronic-device substrate
assembly, comprising: a table having a bearing surface; a polishing
pad having a planarizing zone positioned over the bearing surface
of the table, the polishing pad having a backside supported by the
bearing surface and a planarizing surface in a planarizing plane; a
carrier assembly for controlling a substrate assembly, the carrier
assembly having a head configured to hold the substrate assembly
against the planarizing surface; a drive system having a shaft
pivotally coupled to one of the carrier head or the table to move
at least one of the table or the carrier head in a lateral movement
at least generally parallel to the planarizing plane to impart
relative lateral motion between the substrate assembly and the
polishing pad thereby generating lateral drag forces; and a force
detector attached at a load site to at least one of the carrier
head or the table, and the force detector being positioned at the
load site to provide a signal indicative of the lateral drag
forces.
11. The machine of claim 10 wherein: the head comprises a chuck
having a bottom section including a substrate holder facing the
polishing pad, a top section including a cavity having a side-wall,
and a pivoting joint in the cavity, the shaft having an end section
received in the cavity and attached to the pivoting joint; and the
force detector is attached to one of the side-wall of the cavity or
the end section of the shaft.
12. The machine of claim 10 wherein: the head comprises a chuck
having a bottom section including a substrate holder facing the
polishing pad, a top section including a cavity having a side-wall,
and a pivoting joint in the cavity, the shaft having an end section
received in the cavity and attached to the pivoting joint; and the
force detector comprises a pressure sensitive ring attached to the
side-wall of the cavity.
13. The machine of claim 10 wherein: the head comprises a chuck
having a bottom section including a substrate holder facing the
polishing pad, a top section including a cavity having a side-wall,
and a pivoting joint in the cavity, the shaft having an end section
received in the cavity and attached to the pivoting joint; and the
force detector comprises a pressure sensitive ring attached to the
end section of the shaft.
14. The machine of claim 10 wherein: the head comprises a chuck
having a bottom section including a substrate holder facing the
polishing pad, a top section including a cavity having a side-wall,
and a pivoting joint in the cavity, the shaft having an end section
received in the cavity and attached to the pivoting joint; and the
force detector comprises a pressure sensitive pad attached to the
end section of the shaft.
15. An endpointing apparatus for a chemical-mechanical planarizing
machine having a table, a polishing pad having a planarizing
surface defining a planarizing plane, and a carrier assembly having
a head for holding a microelectronic-device substrate assembly and
a drive system coupled to the head to move the substrate assembly,
the endpointing apparatus comprising: a primary support member for
supporting either the polishing pad or the substrate assembly; a
secondary support member coupled to the primary support member for
holding the primary support member, the primary support member
being moveable with respect to the secondary support member in a
lateral motion at least generally parallel to the planarizing
plane; and at least a first force detector attached to at least one
of the primary and secondary support members at a force detector
site having a contact surface transverse to the planarizing plane,
and the first force detector being positioned at the load site to
contact the other of the primary support member or the secondary
support member as the primary support member moves laterally with
respect to the secondary support member in response to drag forces
between the substrate assembly and the polishing pad during
planarization.
16. The endpointing apparatus of claim 15 wherein the endpointing
apparatus is positioned in the table of the planarizing machine,
the endpointing apparatus including a base portion of the table
defining the secondary support member and a primary plate defining
the primary support member, the primary plate being moveable
laterally with respect to the base in a lateral motion, and the
base having a base surface facing toward the polishing pad and at
least a first stop surface extending from the base surface
transverse to the planarizing plane, and the primary plate having a
bearing surface facing the backside of the polishing pad to support
at least a portion of the polishing pad in a planarizing zone and
at least a first transverse surface defining the first contact
surface, the first contact surface being adjacent to the first stop
surface; and the first force detector contacts the first stop
surface and the first contact surface.
17. The endpointing apparatus of claim 16 wherein: the polishing
pad comprises a web format pad having a pre-polish section wrapped
around a supply roller, an operative section in a planarizing zone
over the primary plate, and a post-polish section wrapped around a
take-up roller; the base of the table comprises a sub-platen having
a rectilinear recess including the base surface and a plurality of
walls projecting from the base surface transverse to the
planarizing plane, the plurality of walls including a first
side-wall, a second side-wall opposite the first side-wall, a first
end-wall between one end of the first and second side-walls, and a
second end-wall between the other end of the first and second
side-walls, the first end-wall defining the first stop surface; the
primary plate comprises a platen sized to fit within the
rectilinear recess in the sub-platen, the platen having a first
side-face adjacent to the first side-wall, a second side-face
adjacent to the second side-wall, a first end-face adjacent to the
first end-wall, and a second end-face adjacent to the second
end-wall, the first end-face defining the first contact surface;
and the planarizing machine further includes a second force
detector contacting the first side-face and the first side-wall, a
first dead stop contacting the second end-face and the second
end-wall, and a second dead stop contacting the second side-face
and the second side-wall.
18. The endpointing apparatus of claim 16 wherein: the polishing
pad comprises a web format pad having a pre-polish section wrapped
around a supply roller, an operative section in a planarizing zone
over the primary plate, and a post-polish section wrapped around a
take-up roller; the base of the table comprises a sub-platen having
a rectilinear recess including the base surface and a plurality of
walls projecting from the base surface transverse to the
planarizing plane, the plurality of walls including a first
side-wall, a second side-wall opposite the first side-wall, a first
end-wall between one end of the first and second side-walls, and a
second end-wall between the other end of the first and second
side-walls, the first end-wall defining the first stop surface; the
primary plate comprises a platen sized to fit within the
rectilinear recess in the sub-platen, the platen having a first
side-face adjacent to the first side-wall, a second side-face
adjacent to the second side-wall, a first end-face adjacent to the
first end-wall, a second end-face adjacent to the second end-wall,
and a back surface facing the base surface of the sub-platen, the
first end-face defining the first contact surface; the planarizing
machine further includes a second force detector contacting the
first side-face and the first side-wall, a first dead stop
contacting the second end-face and the second end-wall, and a
second dead stop contacting the second side-face and the second
side-wall; and the planarizing machine further includes a bearing
assembly between the base surface of the sub-platen and the back
surface of the platen.
19. The endpointing apparatus of claim 16 wherein: the base of the
table comprises a rotatable sub-platen that rotates about a drive
axis in a rotation direction, the sub-platen having a top surface
defining the base surface and at least one tab projecting upwardly
from the top surface, the first stop surface being a surface on the
tab facing in the rotation direction; the primary plate comprises a
platen on the sub-platen, the platen including an upper surface
defining the bearing surface, a lower surface adjacent to the top
surface of the sub-platen, and at least one opening having a face
facing counter to the rotation direction defining the first contact
surface, the tab of the sub-platen being received in the opening of
the platen so that the first stop surface on the tab faces the
first contact surface; and the first force detector contacts the
first stop surface and the first contact surface.
20. The endpointing apparatus of claim 16 wherein: the base of the
table comprises a rotatable sub-platen that rotates about a drive
axis in a rotation direction, the sub-platen having a top surface
defining the base surface and at least one tab projecting upwardly
from the top surface, the first stop surface being a surface on the
tab facing in the direction of rotation; the primary plate
comprises a platen on the sub-platen, the platen including an upper
surface defining the bearing surface, a lower surface adjacent to
the top surface of the sub-platen, and at least one opening having
a face facing counter to the rotation direction defining the first
contact surface, the tab of the sub-platen being received in the
opening of the platen so that the first stop surface on the tab
faces the first contact surface; the first force detector contacts
the first stop surface and the first contact surface; and the
planarizing machine further comprises a bearing assembly between
the top surface of the sub-platen and the lower surface of the
platen.
21. The endpointing apparatus of claim 16, further comprising a
processor coupled to the force detector to receive and process
electrical signals from the force detector and to produce date
representing the lateral forces between the base and the primary
plate.
22. The endpointing apparatus of claim 16 wherein the primary plate
has a back surface facing the base surface of the base, and wherein
the planarizing machine further comprises a bearing assembly
between the base surface of the base and the back surface to reduce
friction between the base and the primary plate.
23. The endpointing apparatus of claim 16 wherein the primary plate
has a back surface facing the base surface of the base, and wherein
the planarizing machine further comprises a bearing assembly having
a plurality of ball bearings between the base surface and the back
surface to reduce friction between the base and the primary
plate.
24. The endpointing apparatus of claim 16 wherein the first load
site is along a first axis and the planarizing machine further
comprises a second force detector positioned between the base and
the primary plate at a second load site along a second axis
orthogonal to the first axis.
25. A method of planarizing a microelectronic substrate assembly,
comprising: removing material from the substrate assembly by
pressing the substrate assembly against a planarizing surface of a
polishing pad and moving at least one of the substrate assembly or
the polishing pad in a planarizing plane; monitoring a lateral drag
force between the substrate assembly and the planarizing surface by
sensing lateral forces between a moveable primary support member
supporting either the polishing pad or the substrate assembly and a
secondary support member holding the primary support member; and
terminating removal of material from the substrate assembly when
the sensed lateral drag force reaches a predetermined endpoint
force.
26. The method of claim 25, further comprising providing a low
friction bearing assembly between the primary support member and
the secondary support member that allows the primary support member
to freely move laterally with respect to the secondary support
member.
27. The method of claim 25 wherein: the secondary support member
comprises a base of a table of a planarizing machine and the
primary support member comprises a primary plate moveably coupled
to the base, the base having a base surface facing toward the
polishing pad and at least a first stop surface extending from the
base surface transverse to the planarizing plane, and the primary
plate having a bearing surface facing the backside of the polishing
pad to support at least a portion of the polishing pad in a
planarizing zone and at least a first contact surface adjacent to
the first stop surface; and monitoring the lateral drag force
comprises providing at least a first force detector contacting the
first stop surface and the first contact surface at a first load
site to sense lateral forces between the base and the primary plate
and processing electrical signals from the first force detector
with a processor to produce data representing the drag force
between the substrate assembly and the polishing pad.
28. The method of claim 25 wherein: the secondary support member
comprises a drive shaft of a carrier assembly of a planarizing
machine and the primary support member comprises a carrier head
pivotally coupled to the drive shaft, the drive shaft having a
lower end with a stop surface orientated transverse to the
planarizing plane and the carrier head having an upper cavity with
a contact surface, the drive shaft being received in the upper
cavity to position the stop surface adjacent to the contact
surface; and monitoring the lateral drag force comprises providing
a force detector contacting the stop surface and the contact
surface at a load site to sense lateral forces between the drive
shaft and the carrier head and processing electrical signals from
the force detector with a processor to produce data representing
the drag force between the substrate assembly and the polishing
pad.
Description
TECHNICAL FIELD
[0001] The present invention relates to methods and apparatuses for
planarizing microelectronic substrate assemblies and, more
particularly, to apparatuses and methods for endpointing mechanical
and/or chemical-mechanical planarization of semiconductor wafers,
field emission displays and other microelectronic substrate
assemblies.
BACKGROUND OF THE INVENTION
[0002] Mechanical and chemical-mechanical planarizing processes
(collectively "CMP") are used in the manufacturing of electronic
devices for forming a flat surface on semiconductor wafers, field
emission displays and many other microelectronic substrate
assemblies. CMP processes generally remove material from a
substrate assembly to create a highly planar surface at a precise
elevation in the layers of material on the substrate assembly.
[0003] FIG. 1 is a schematic isometric view of a web-format
planarizing machine 10 for planarizing a microelectronic substrate
assembly 12. The planarizing machine 10 has a table 11 with a rigid
panel or plate to provide a flat, solid support surface 13 for
supporting a portion of a web-format planarizing pad 40 in a
planarizing zone "A." The planarizing machine 10 also has a pad
advancing mechanism including a plurality of rollers to guide,
position, and hold the web-format pad 40 over the support surface
13. The pad advancing mechanism generally includes a supply roller
20, first and second idler rollers 21a and 21b, first and second
guide rollers 22a and 22b, and a take-up roller 23. As explained
below, a motor (not shown) drives the take-up roller 23 to advance
the pad 40 across the support surface 13 along a travel axis T-T.
The motor can also drive the supply roller 20. The first idler
roller 21a and the first guide roller 22a press an operative
portion of the pad against the support surface 13 to hold the pad
40 stationary during operation.
[0004] The planarizing machine 10 also has a carrier assembly 30 to
translate the substrate assembly 12 across the pad 40. In one
embodiment, the carrier assembly 30 has a head 32 to pick up, hold
and release the substrate assembly 12 at appropriate stages of the
planarizing process. The carrier assembly 30 also has a support
gantry 34 and a drive assembly 35 that can move along the gantry
34. The drive assembly 35 has an actuator 36, a drive shaft 37
coupled to the actuator 36, and an arm 38 projecting from the drive
shaft 37. The arm 38 carries the head 32 via another shaft 39. The
actuator 36 orbits the head 32 about an axis B-B to move the
substrate assembly 12 across the pad 40.
[0005] The polishing pad 40 may be a non-abrasive polymeric pad
(e.g., polyurethane), or it may be a fixed-abrasive polishing pad
in which abrasive particles are fixedly dispersed in a resin or
another type of suspension medium. A planarizing fluid 50 flows
from a plurality of nozzles 49 during planarization of the
substrate assembly 12. The planarizing fluid 50 may be a
conventional CMP slurry with abrasive particles and chemicals that
etch and/or oxidize the surface of the substrate assembly 12, or
the planarizing fluid 50 may be a "clean" non-abrasive planarizing
solution without abrasive particles. In most CMP applications,
abrasive slurries with abrasive particles are used on non-abrasive
polishing pads, and non-abrasive clean solutions without abrasive
particles are used on fixed-abrasive polishing pads.
[0006] In the operation of the planarizing machine 10, the pad 40
moves across the support surface 13 along the pad travel path T-T
either during or between planarizing cycles to change the
particular portion of the polishing pad 40 in the planarizing zone
A. For example, the supply and take-up rollers 20 and 23 can drive
the polishing pad 40 between planarizing cycles such that a point P
moves incrementally across the support surface 13 to a number of
intermediate locations I.sub.1, I.sub.2, etc. Alternatively, the
rollers 20 and 23 may drive the polishing pad 40 between
planarizing cycles such that the point P moves all the way across
the support surface 13 to completely remove a used portion of the
pad 40 from the planarizing zone A. The rollers may also
continuously drive the polishing pad 40 at a slow rate during a
planarizing cycle such that the point P moves continuously across
the support surface 13. Thus, the polishing pad 40 should be free
to move axially over the length of the support surface 13 along the
pad travel path T-T.
[0007] CMP processes should consistently and accurately produce a
uniform, planar surface on substrate assemblies to enable circuit
and device patterns to be formed with photolithography techniques.
As the density of integrated circuits increases, it is often
necessary to accurately focus the critical dimensions of the
photo-patterns to within a tolerance of approximately 0.1 .mu.m.
Focusing photo-patterns to such small tolerances, however, is
difficult when the planarized surfaces of substrate assemblies are
not uniformly planar. Thus, to be effective, CMP processes should
create highly uniform, planar surfaces on substrate assemblies.
[0008] In the highly competitive semiconductor industry, it is also
desirable to maximize the throughput of CMP processing by producing
a planar surface on a substrate assembly as quickly as possible.
The throughput of CMP processing is a function of several factors,
one of which is the ability to accurately stop CMP processing at a
desired endpoint. In a typical CMP process, the desired endpoint is
reached when the surface of the substrate assembly is planar and/or
when enough material has been removed from the substrate assembly
to form discrete components on the substrate assembly (e.g.,
shallow trench isolation areas, contacts, damascene lines, etc.).
Accurately stopping CMP processing at a desired endpoint is
important for maintaining a high throughput because the substrate
assembly may need to be re-polished if it is "under-planarized," or
too much material can be removed from the substrate assembly if it
is "over-polished." For example, over-polishing can cause "dishing"
in shallow-trench isolation structures or completely destroy a
section of the substrate assembly. Thus, it is highly desirable to
stop CMP processing at the desired endpoint.
[0009] One method for determining the endpoint of CMP processing is
described in U.S. Pat. No. 5,036,015 issued to Sandhu ("Sandhu"),
which is herein incorporated by reference. Sandhu discloses
detecting the planar endpoint by sensing a change in friction
between a wafer and the polishing medium. Such a change of friction
may be produced by a different coefficient of friction at the wafer
surface as one material (e.g., an oxide) is removed from the wafer
to expose another material (e.g., a nitride). In addition to the
different coefficients of friction caused by a change of material
at the substrate surface, the friction between the wafer and the
planarizing medium generally increases during CMP processing
because more surface area of the substrate contacts the polishing
pad as the substrate becomes more planar. Sandhu discloses
detecting the change in friction by measuring the change in
electrical current through the platen drive motor and/or the drive
motor for the substrate holder.
[0010] Although Sandhu discloses a viable process for endpointing
CMP processing, the change in electrical current through the platen
and/or drive motor may not accurately indicate the endpoint of a
substrate assembly. For example, the friction between the substrate
assembly and the planarizing medium generally increases
substantially linearly, and thus the change in the motor current at
the endpoint may not be sufficient to provide a definite signal
identifying that the endpoint has been reached. Moreover, friction
losses and other power losses in the motors, gearboxes or other
components may also change the current draw through the motors. The
change in current through the drive motors, therefore, may not
accurately reflect the drag force between the wafer and the
polishing pad because the drag force is not the only factor that
influences the current draw. Thus, it would be desirable to develop
an apparatus and method for more accurately endpointing
planarization of microelectronic substrate assemblies.
SUMMARY OF THE INVETION
[0011] The present invention is directed toward endpointing
apparatuses, planarizing machines with endpointing apparatuses, and
methods for endpointing mechanical and/or chemical-mechanical
planarization of microelectronic substrate assemblies. One
endpointing apparatus in accordance with the invention includes a
primary support member for supporting either a polishing pad or a
substrate assembly, and a secondary support member coupled to the
primary support member. The primary support member is movable with
respect to the secondary support member in a lateral motion at
least generally parallel to a planarizing plane in correspondence
to drag forces between the substrate assembly and the polishing
pad. The primary support member, for example, can rest on a bearing
assembly that provides for relatively frictionless lateral
displacement between the primary and secondary support members. The
endpointing apparatus also includes a force detector attached to
the primary support member and/or the secondary support member at a
force detector site having a contact surface transverse to the
planarizing plane. The force detector measures lateral forces
between the primary support member and the secondary support member
in response to drag forces between the substrate assembly and the
polishing pad. The primary support member can be held with respect
to the secondary support member by dead stops and force detectors,
or by posts attached to both the primary and secondary support
members. In either case, the force detector senses lateral forces
imparted to the primary support member by the substrate assembly
during planarization. In operation, the endpoint of CMP processing
is detected when the measured lateral force is equal to a
predetermined endpoint force for a particular CMP application.
[0012] In one planarizing machine in accordance with the invention,
the primary support member is a moveable primary plate or platen
under the polishing pad, and the secondary support member is a base
or sub-platen under the primary plate. The planarizing machine can
also include a carrier assembly having a head configured to hold a
substrate assembly against the planarizing surface and a drive
system to move the head. At least one of the polishing pad or the
head moves in a lateral motion at least generally parallel to the
planarizing plane. The base can have a base surface facing toward
the polishing pad and a first stop surface projecting from the base
surface transverse to the planarizing plane. The primary plate can
have a bearing surface facing the backside of the polishing pad to
support at least a portion of the polishing pad in a planarizing
zone, and the primary plate can also have a first contact surface
adjacent to the first stop surface on the base. The primary plate
is moveable with respect to the base in a lateral motion
corresponding to the drag forces between the substrate assembly and
the polishing pad. The planarizing machine can further include at
least a first force detector contacting the first stop surface and
the first contact surface at a load site. The force detector is
configured to sense lateral forces between the base and the primary
plate corresponding to the lateral drag forces between the
substrate assembly and the polishing pad.
[0013] The present invention also includes several additional
embodiments in which the force detector is attached at a load site
to at least one of the carrier head or the table. Several of these
embodiments accordingly do not use a table with primary and
secondary support members. The force detector provides a signal
indicative of the lateral drag forces between the substrate
assembly and the polishing pad.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is an isometric view of a web-format planarizing
machine in accordance with the prior art.
[0015] FIG. 2 is a schematic isometric view of a web-format
planarizing machine having a cut-away portion illustrating an
endpointing apparatus in accordance with an embodiment of the
invention.
[0016] FIG. 3 is a schematic cross-sectional view of the
planarizing machine in FIG. 2 along line 3-3.
[0017] FIG. 4 is a graph illustrating the sensed pressure as a
function of the rotational position of the carrier head.
[0018] FIG. 5 is a schematic cross-sectional view of the
planarizing machine in accordance with another embodiment of the
invention.
[0019] FIG. 6 is a schematic cross-sectional view of the
planarizing machine in accordance with still another embodiment of
the invention.
[0020] FIG. 7 is a schematic isometric view of a planarizing
machine in accordance with another embodiment of the invention.
[0021] FIG. 8 is a schematic isometric view of a rotary planarizing
machine with a cut-away section illustrating an endpointing
apparatus in accordance with another embodiment of the
invention.
[0022] FIG. 9 is a schematic cross-sectional view of the
planarizing machine of FIG. 8.
[0023] FIG. 10 is a schematic cross-sectional view of a substrate
holder having an endpointing apparatus in accordance with yet
another embodiment of the invention.
[0024] FIG. 11A is a plan view of a substrate holder having an
endpointing apparatus in accordance with another embodiment of the
invention.
[0025] FIG. 11B is a schematic cross-sectional view of the
substrate holder of 11A taken along line 11B-11B.
[0026] FIG. 12 is a schematic cross-section view of a substrate
holder having an endpointing apparatus in accordance with another
embodiment of the invention.
[0027] FIG. 13 is a schematic cross-section view of a substrate
holder having an endpointing apparatus in accordance with another
embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0028] The present invention relates to endpointing devices,
planarizing machines including endpointing devices, and methods for
predicting the endpoint of planarizing processes in mechanical or
chemical-mechanical planarization of semiconductor wafers, field
emission displays and other microelectronic substrate assemblies.
Many specific details of the invention are described below with
reference to web-format and rotary planarizing machines to provide
a thorough understanding of such embodiments. The present
invention, however, may have additional embodiments or can be
practiced without several of the details described in the following
description.
[0029] FIG. 2 is a schematic isometric view of a web-format
planarizing machine 100 for planarizing a microelectronic substrate
assembly 12 in accordance with an embodiment of the invention. The
planarizing machine 100 includes a table 110, a carrier assembly
130 over the table 110, and a polishing pad 140 on the table 110.
The carrier assembly 130 and the polishing pad 140 can be
substantially the same as those described above with reference to
FIG. 1. The polishing pad 140 is accordingly coupled to a
pad-advancing mechanism having a plurality of rollers 120, 121, 122
and 123. The pad-advancing mechanism can also be the same as that
described above with reference to FIG. 1.
[0030] The planarizing machine 100 also includes an endpointing
apparatus that measures the drag force between the substrate
assembly 12 and the polishing pad 140 during planarization. The
endpointing apparatus generally includes a secondary support member
defined by a sub-platen 150, a primary support member defined by a
platen 170, and at least one force detector 190 between the
sub-platen 150 and the platen 170. The platen 170 and the
sub-platen 150 are generally separate components of the table 110.
The polishing pad 140 is releasably coupled to the platen 170 so
that drag forces between the substrate assembly 12 and the pad 140
exert lateral forces against the platen 170. The platen 170 can
move laterally with respect to sub-platen 150 in correspondence to
drag forces between the substrate assembly 12 and the polishing pad
140, and the force detector 190 can detect the lateral forces that
the platen 170 exerts against the sub-platen 150. In general, the
endpoint of a planarizing cycle is detected when the measured
lateral force between the sub-platen 150 and the platen 170 reaches
a predetermined endpoint force.
[0031] FIG. 3 is a schematic cross-sectional view of the
planarizing machine 100 illustrating the endpointing apparatus in
greater detail. Referring to FIGS. 2 and 3 together, the sub-platen
150 can be a base supporting the platen 170. The sub-platen 150 has
a recess 152 defined by a base surface 153 and a plurality of walls
(identified by reference numbers 154a, 154b, 156a and 156b)
projecting upwardly from the base surface 153 transversely with
respect to a planarizing plane P-P (FIG. 3). For the purposes of
the present disclosure, the term "transverse" means any
non-parallel arrangement and is not limited to a perpendicular
arrangement. The walls can include a first side-wall 154a, a second
side-wall 154b opposite the first side-wall 154a, a first end-wall
156a at one end of the side-walls 154a and 154b, and a second
end-wall 156b at the other end of the side-walls 154a and 154b. The
walls can be configured in a rectilinear pattern or other suitable
patterns to receive the platen 170.
[0032] The platen 170 is positioned in the recess 152 of the
sub-platen 150. The platen 170 can be a plate having a first
side-face 172a, a second side-face 172b opposite the first
side-face 172a, a first end-face 174a between one end of the
side-faces 172a and 172b, and a second end-face 174b between the
other end of the side-faces 172a and 172b. In the embodiment shown
in FIG. 3, the first side-face 172a is adjacent to the first
side-wall 154a, the second side-face 172b is adjacent to the second
side-wall 154b, the first end-face 174a is adjacent to the first
end-wall 156a, and the second end-face 174b is adjacent to the
second end-wall 156b. The platen 170 also includes a bearing
surface 176 facing the backside of the polishing pad 140 to support
at least a portion of the polishing pad 140 in a planarizing zone
under the head 132, and the platen 170 includes a back surface 178
facing the base surface 153 of the sub-platen 150. The polishing
pad 140 is coupled to the bearing surface 176 during planarization
so that the pad transmits lateral forces to the platen 170.
Suitable devices and methods for coupling the polishing pad 140 to
the bearing surface 176 are disclosed in U.S. patent application
Ser. Nos. 09/285,319 filed on Apr. 2, 1999, and Ser. No. 09/181,578
filed on Oct. 28, 1998, both of which are herein incorporated by
reference.
[0033] The platen 170 can move with respect to the sub-platen 150
in a lateral motion L (FIG. 2) at least generally parallel to a
planarizing plane P-P (FIG. 3). In this embodiment, the endpointing
apparatus also includes a bearing mechanism 180 (FIG. 3) to reduce
the friction between the base surface 153 of the sub-platen 150 and
the back surface 178 of the platen 170. The bearing assembly 180
can be a roller mechanism having a plurality of rollers attached to
either the sub-platen 150 or the platen 170 to allow the platen 170
to freely roll across the sub-platen 150. The bearing assembly 180
can also be a low-friction coating or lubricant between the base
surface 153 and the back surface 178, or a flexible bladder (not
shown) between the sub-platen 150 and the platen 170. In still
another embodiment, the bearing assembly 180 can be a frictionless
device having a number of air bearings defined by air holes through
the sub-platen 150 that are connected to a pressurized air source
that provides a continuous layer of air between the sub-platen 150
and the platen 170. In still another embodiment, the bearing
assembly 180 can be a magnetic device including magnetic bearings
that prevent the back surface 178 from contacting the base surface
153 by positioning magnetic fields of a like polarity adjacent to
one another. In operation, the bearing assembly 180 frictionally
isolates the platen 170 from the sub-platen 150 so that the drag
forces between the substrate assembly 12 and the pad 140 drive the
platen 170 laterally with respect to the sub-platen 150 without
substantial friction losses.
[0034] The force detectors 190 (identified by reference numbers
190a-190d) can be positioned between the walls of the recess 152 in
the sub-platen 150 and the faces of the platen 170. Each force
detector 190 can be a contact sensor that contacts both the
sub-platen 150 and the platen 170 to sense the lateral forces
exerted by the platen 170 against the sub-platen 150 in correlation
to the lateral forces exerted by the substrate assembly 12 against
the polishing pad 140 during planarization. Suitable contact force
detectors are strain gauges, piezoelectric elements or other
transducers that generate signals corresponding to the force
exerted by the platen 170 against the sub-platen 150. The force
detectors 190 can be other sensors that generate electrical signals
corresponding to the lateral forces or displacement between the
sub-platen 150 and the platen 170. For example, in other
embodiments in which the force detectors 190 do not contact the
platen 170 and the sub-platen 150 does not have dead stops so that
the platen 170 can move relative to the sub-platen 150, the force
detectors 190 can be lasers, accelerometers, capacitance
displacement sensors, linear variable differential transformers or
other displacement sensors.
[0035] In the particular embodiment of the planarizing machine 100
illustrated in FIGS. 2 and 3, four force detectors are configured
along two orthogonal axes. In other embodiments, the planarizing
machine 100 can have only one force detector positioned along one
axis, or two force detectors positioned along two orthogonal axes,
or any number of force detectors positioned between the walls of
the sub-platen 150 and the faces of the platen 170. For example, in
an embodiment having two force detectors 190 positioned along
orthogonal axes, a first force detector 190a can contact the first
end-wall 156a and the first end-face 174a at a first force detector
site, a second force detector 190b can contact the first side-wall
154a and the first side-face 172a at a second force detector site,
and dead stops can be substituted for the force detectors 190c and
190d. The first end-wall 156a and the first side-wall 154a of the
sub-platen 150 accordingly define first and second stop surfaces,
and the first end-face 174a and the first side-face 172a of the
platen 170 accordingly define first and second contact surfaces. In
still another embodiment, the first and second force detectors 190a
and 190b can be positioned as explained above, and the dead stops
or force detectors 190c and 190d can be eliminated by sizing the
platen 170 such that the second end-face 174b abuts the second
end-wall 156b and the second side-face 172b abuts the second
side-wall 154b.
[0036] The embodiment of the endpointing apparatus described above
with reference to the planarizing machine 100 operates by measuring
the drag force between the substrate assembly 12 and the polishing
pad 140, and comparing the measured drag force with a predetermined
endpoint force. In operation, the carrier assembly 130 presses the
substrate assembly 12 against a planarizing surface 142 of the
polishing pad 140, and the drive system 135 moves the head 132 to
translate the substrate assembly 12 across the planarizing surface
142 in a lateral motion at least generally parallel to the
planarizing plane P-P. The lateral drag forces generated by the
friction between the substrate assembly 12 and the planarizing
surface 142 are transmitted to the platen 170 via the polishing pad
140. The lateral drag forces drive the platen 170 against the force
detectors 190, which generate corresponding electrical signals. The
electrical signals from the force detectors 190 are transmitted to
a processor 199 that converts the electrical signals into data that
can be analyzed.
[0037] FIG. 4, for example, is a graph illustrating the lateral
forces sensed by one of the force detectors 190 during
planarization. In general, the force detector 190 senses the
increase in lateral force that the platen 170 exerts against the
sub-platen 150 from a level A to a level B as the substrate
assembly 12 is planarized. The endpoint of the substrate assembly
12 can be detected by empirically determining the typical load
exerted by the platen 170 against the sub-platen 150 at the
endpoint of the planarizing cycle of a particular application
assembly.
[0038] The planarizing machines described above with reference to
FIGS. 2 and 3 are expected to enhance the accuracy of endpointing
CMP processing because they isolate a drag force parameter that is
not influenced by energy losses unrelated to drag force at the
pad/substrate interface. In contrast to conventional planarizing
processes that endpoint CMP processing using the current of the
drive motors, several embodiments of the planarizing machines
described above with reference to FIGS. 2 and 3 measure the drag
force between the substrate assembly and the polishing pad by
isolating the displacement or the internal forces between either a
platen and sub-platen, or a carrier head and a drive shaft. The
isolated drag force parameter provides a much more accurate
indication of the actual drag force at the pad/substrate interface
than measuring motor current because energy losses and other
factors associated with moving the carrier head or the polishing
pad do not influence or otherwise overshadow the changes in drag
force between the pad and the substrate assembly. The endpointing
apparatuses and monitoring systems described above with reference
to FIGS. 2 and 3, therefore, are expected to enhance the accuracy
of detecting the endpoint in CMP processing.
[0039] The planarizing machine 100 is also expected to enhance the
accuracy of endpointing CMP processing because the bearing assembly
180 frictionally isolates the back surface 178 of the platen 170
from the base surface 153 of the sub-platen 150. The bearing
assembly 180 accordingly reduces friction losses between the
sub-platen 150 and the platen 170 so that the lateral movement of
the platen 170 against the force detectors 190 is influenced
primarily by the drag forces between the substrate assembly 12 and
the polishing pad 140. The endpointing apparatus of the planarizing
machine 100 accordingly avoids measuring the drag force in a manner
in which power and friction losses in the gears and electric drive
motors for the platen and carrier assembly can influence the
measured drag force between the substrate assembly and the
polishing pad. The planarizing machine 100, therefore, is expected
to enhance the accuracy of detecting the endpoint of CMP
processing.
[0040] FIG. 5 is a schematic cross-sectional view of the
planarizing machine 100 in accordance with another embodiment of
the invention. In this embodiment, the sub-platen 150 has a post
155 projecting upwardly from the base surface 153, and the platen
170 is fixedly attached to the post 155. The walls 172/174 of the
platen 170 do not contact either the faces 154/156 of the
sub-platen 150, any dead stops, or other devices that inhibit the
platen 170 from moving with respect to the sub-platen 150. The
movement of the substrate assembly 12 across the polishing pad 140
accordingly displaces the platen 170 relative to the sub-platen 150
and generates torsional forces in the post 155 that are expected to
be proportionate to the drag force between the substrate assembly
12 and the polishing pad 140. The force detector 190 can be a
strain gauge attached to the post 155 to measure the torsional
displacement of the post 155. The force detector 190 senses the
change in the torsional forces exerted on the platen 170 and sends
a signal to the processor 199. In another embodiment, the force
detector 190 can be a displacement sensor at one of the walls
(e.g., end-wall 156a) of the recess 152 in the sub-platen 150.
Thus, this embodiment is also expected to accurately detect the
endpoint of the planarizing process.
[0041] FIG. 6 is a schematic cross-sectional view of the
planarizing machine 100 in accordance with another embodiment of
the invention in which a number of posts 155 attach the platen 170
to the sub-platen 150. The platen 170 can also move laterally with
respect to the sub-platen 150. The posts 155 can be threaded studs
having a diameter of approximately 1.0 inch and a length of 3.0
inches made from metal, high density polymers or other suitable
materials. The posts 155 of this embodiment accordingly do not
frictionally isolate the platen 170 from the sub-platen 150, but
rather they deflect through a small displacement to control the
motion between the platen 170 and the sub-platen 150 in
correspondence to the drag forces between the substrate assembly 12
and the polishing pad 140. The force detectors 190 accordingly
measure the displacement between the platen 170 and the sub-platen
150 to determine the drag forces between the substrate assembly 12
and the polishing pad 140.
[0042] FIG. 7 is an schematic isometric view of a planarizing
machine 100 in accordance with still another embodiment of the
invention. In this embodiment, the planarizing machine 100 has a
circular platen 170 and the recess 152 in the sub-platen 150 has a
single circular wall 154. The platen 170 accordingly has a single,
circular side-face 174. The platen 170 can be coupled to the
sub-platen 150 by any of the bearings 180 or posts 155 described
above with reference to FIGS. 2-6.
[0043] FIG. 8 is a schematic isometric view of a planarizing
machine 200 in accordance with another embodiment of the invention,
and FIG. 9 is a schematic cross-sectional view of the planarizing
machine 200 taken along line 9-9. The planarizing machine 200 has a
sub-platen 250 coupled to a rotary drive mechanism 251 to rotate
the sub-platen 250 (arrow R), a platen 270 movably coupled to the
sub-platen 250, and a polishing pad 240 attached to the platen 270.
The sub-platen 250 has a base surface 253 facing the polishing pad
240 and a tab 254 projecting upwardly from the base surface 253.
The tab 254 has a stop surface 256 facing in the direction of the
rotation of the sub-platen 250. The platen 270 includes an opening
271 having a contact surface 272 facing the stop surface 256 of the
tab 254. The planarizing machine 200 further includes a bearing
assembly 280 that can be the same as the bearing assembly 180
described above with reference to FIG. 3. The planarizing machine
200 also includes a force detector 290 contacting the stop surface
256 of the tab 254 and the contact surface 272 of the platen
270.
[0044] The planarizing machine 200 is expected to enhance the
accuracy of detecting the endpoint of planarizing a substrate
assembly in rotary planarizing applications. In operation, a
carrier assembly 230 (FIG. 9) moves a carrier head 232 to press the
substrate assembly 12 against a planarizing surface 242 of the
polishing pad 240. The rotary drive assembly 251 also rotates the
sub-platen 250 causing the tab 254 to press the force detector 290
against the contact surface 272. The sub-platen 250 accordingly
rotates the platen 270 in the direction R, but the drag force
between the substrate assembly 12 and the polishing pad 240 resists
rotation in the direction R. The bearing assembly 280 allows the
drag forces between the substrate assembly 12 and the planarizing
surface 242 to drive the contact surface 272 of the platen 270
against the force detector 290 in correlation to the drag forces.
As the drag force increases between the substrate assembly 12 and
the planarizing surface 242, the force detector 290 accordingly
detects an increase in the lateral force that the platen 270 exerts
against the tab 254. The force detector 290 is coupled to a
processor 299 to convert the signals from the force detector 290
into data that can be analyzed to determine the endpoint of the
planarizing process.
[0045] FIG. 10 is a schematic cross-sectional view of a carrier
assembly 330 for a planarizing machine in accordance with another
embodiment of the invention. The carrier assembly 330 can include a
carrier head 332 having a lower portion 333 with a lower cavity 334
to receive a substrate assembly 12 and an upper portion 336 with an
upper cavity 338. A pivoting joint 350 is attached to the head 332
in the cavity 338, and a drive-shaft 339 is pivotally attached to
the joint 350. In this embodiment, the endpointing apparatus
includes a primary support member defined by the head 332, a
secondary support member defined by the drive-shaft 339, and a
first contact surface defined by the side-wall of the upper cavity
338. In one embodiment, the joint 350 is a gimbal joint or other
bearing assembly that allows universal pivoting between the head
332 and the shaft 339. The carrier head 332 also includes a force
detector 390 attached to an interior wall of the cavity 338. The
force detector 390, for example, can be an annular piezoelectric
ring.
[0046] In operation, the drag forces between the substrate assembly
12 and the polishing pad 140 cause the shaft 339 to pivot about the
joint 350 such that the lower end of the shaft 339 contacts the
force detector 390. The force exerted by the driveshaft 339 against
the force detector 390 will be proportional to the drag forces
between the substrate assembly 12 and the polishing pad 140.
Accordingly, the force detector 390 is coupled to a processor (not
shown) to detect the endpoint of the planarizing process in a
manner similar to that described above with respect to FIGS.
2-9.
[0047] FIG. 1A is a plan view of a carrier assembly 430 for a
planarizing machine in accordance with another embodiment of the
invention, and FIG. 11B is a schematic cross-section view of the
carrier assembly in FIG. 11A along line 11B-11B. The carrier
assembly 430 can include a carrier head 32 to hold the substrate
assembly 12. A housing 460 is fixedly attached to the carrier head
432 by a number of bolts 461. The carrier assembly 430 also
includes a drive shaft 439 extending through a hole 462 in the
housing 460, and a drive member 450 at the end of the drive shaft
439 in the housing 460. The drive member 450 engages a low friction
pad 470 to press the substrate assembly 12 against the polishing
pad 140. The carrier assembly 430 further includes at least one
force detector 490 and two dead stops 495a/495b (FIG. 11A). The
force detector 490 and the dead stops 495a/495b can be equally
spaced apart from one another around the interior of the housing
460.
[0048] In operation, the drive shaft 439 can be orbited about an
eccentric axis as described above with reference to FIG. 1. The
drive member 450 presses against the force detector 490 and the
dead stops 495a/495b to move the carrier head 432 and substrate
assembly 12 over the polishing pad 140. The force detector 490
accordingly senses drag forces between the substrate assembly 12
and the polishing pad 140.
[0049] FIG. 12 is a schematic cross-sectional view of a carrier
assembly 530 for a planarizing machine in accordance with still
another embodiment of the invention. The carrier assembly 530
includes a carrier head 532 having a retaining ring 560 with an
opening 562. The carrier assembly 530 also includes a drive shaft
539 extending through the opening 562 and a drive member 550 in the
carrier head 532. The carrier assembly 530 can have a force
detector 590 attached to one portion of the drive member 550 and a
number of dead stops 595 attached to other portions of the drive
member 550. The force detector 590 and the dead stops 595 can be
arranged as set forth above with respect to the carrier assembly
430 in FIG. 11A. The carrier assembly 530 can also include a low
friction backing film 570 between the substrate 12 and the drive
member 550. In operation, the drive shaft 539 and the drive member
550 push the housing 560 via the force detector 590 and the dead
stops 595 to move the substrate assembly 12 across the polishing
pad 140. The carrier assembly 530 accordingly detects the lateral
forces between the drive member 550 and the housing 560
corresponding to the drag forces between the substrate assembly 12
and the polishing pad 140.
[0050] FIG. 13 is a schematic cross-section view of another carrier
assembly 630 for a planarizing machine in accordance with an
embodiment of the invention. In this embodiment, the substrate
assembly 630 has a carrier head 632 connected to a drive shaft 639
and a retaining ring 660. A backing member 650 is positioned within
the cavity of the carrier head 632. The carrier assembly 630 also
includes a force detector 690 attached to one portion of the
retaining ring 660 and a number of dead stops 695 attached to other
portions of the retaining ring 660. The backing member 650 contacts
the force detector 690 and the dead stops 695 so that the lateral
movement of the carrier head 632 drives the backing member 650
laterally over the polishing pad 140. A high friction backing
member 670 frictionally couples the backing member 650 to the
substrate assembly 12. In operation, the carrier head 630 drives
the backing member 650 via the force detector 690 and the dead
stops 695 to move the substrate assembly 12 laterally across the
polishing pad 140. The drag forces between the substrate assembly
12 and the polishing pad 140 are accordingly detected by the force
detector 690.
[0051] From the foregoing it will be appreciated that, although
specific embodiments of the invention have been described herein
for purposes of illustration, various modifications may be made
without deviating from the spirit and scope of the invention.
Accordingly, the invention is not limited except as by the appended
claims.
* * * * *