Abrading – Machine – Endless band tool
Reexamination Certificate
2001-09-19
2002-08-06
Eley, Timothy V. (Department: 3723)
Abrading
Machine
Endless band tool
C451S303000
Reexamination Certificate
active
06428404
ABSTRACT:
TECHNICAL FIELD
The present invention relates to methods and apparatuses for planarizing microelectronic substrate assemblies. More particularly, the present invention relates to web-format planarizing machines that stretch a medial region of the polishing pad more than side regions to compensate for uneven wrapping of a used portion of the polishing pad around a take-up roller.
BACKGROUND OF THE INVENTION
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.
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
21
a
and
21
b
, first and second guide rollers
22
a
and
22
b
, 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
21
a
and the first guide roller
22
a
press an operative portion of the pad against the support surface
13
to hold the pad
40
stationary during operation.
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
.
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.
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
1
, I
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.
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 0.1-0.2 &mgr;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 is surfaces on substrate assemblies.
Although web-format planarizing machines show promising results, the polishing pad
40
may develop wrinkles in the planarizing zone A as more of the used portion of the pad wraps around the take-up roller
23
. More specifically, the middle region of the polishing pad
40
wears more than the side regions because the substrate assembly
12
does not contact the side regions during planarization. The middle region of the used portion of the polishing pad
40
is accordingly thinner than the side regions, and the middle region of the portion of the pad
40
wrapped around the take-up roller
23
accordingly has a smaller diameter than the side regions. The torque applied to the take-up roller
23
thus exerts a non-uniform tension across the width of the pad
40
that causes the polishing pad
40
to wrinkle or slip during a planarizing cycle. Additionally, as the polishing pad is transferred from the supply roller
20
to the take-up roller
23
, the torque applied to the take-up roller
23
must be continually adjusted to mitigate wrinkles and slippage in the middle portion of the polishing pad
40
.
SUMMARY OF THE INVENTION
The present invention is directed toward methods and machines for planarizing microelectronic substrate assemblies in mechanical and/or chemical-mechanical planarizing processes. For the purposes of the present application, the term “planarizing” means both planarizing substrate assemblies to form a planar surface and polishing substrate assemblies to form a smooth surface.
One machine in accordance with an embodiment of the invention includes a table having a support surface with a planarizing zone, an elongated polishing pad configured to move across the support surface of the table along a pad travel path, and a pad advancing mechanism coupled to the pad. The elongated pad can have a length along an elongated dimension extending along the pad travel path. The length of the polishing pad, for example, is generally sufficient to extend across the table. The polishing pad further includes an elongated first edge, an elongated second edge opposite the first edge, an elongated first side region extending along the first edge, an elongated second side region extending along the second edge, and an elongated medial region having a width between the first and second side regions. The pad advancing mechanism can include a first roller about which an unused portion of the pad is wrapped and a second roller about which a used portion of the pad is wrapped. At least one of the first and second rollers is driven to advance the pad across the table along the pad travel path for positioning a desired active section of the pad in the planarizing zone.
The planarizing machine can further include a carrier assembly having a head and a drive system. The head is configured to hold a microelectronic substrate assembly, and the drive sys
Moore Scott E.
Walker Michael A.
Dorsey & Whitney LLP
Eley Timothy V.
Nguyen Dung Van
LandOfFree
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