Abrading – Flexible-member tool – per se
Reexamination Certificate
2000-08-30
2003-07-15
Eley, Timothy V. (Department: 3724)
Abrading
Flexible-member tool, per se
C051S298000, C451S550000
Reexamination Certificate
active
06592443
ABSTRACT:
TECHNICAL FIELD
This invention relates to planarizing pads and to methods and apparatuses for forming and using planarizing pads, such as disposable and/or conditionless planarizing pads for mechanical and chemical-mechanical planarization of microelectronic substrates.
BACKGROUND
Mechanical and chemical-mechanical planarization processes (“CMP”) are used in the manufacturing of electronic devices for forming a flat surface on semiconductor wafers, field emission displays and many other microelectronic-device 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
schematically illustrates an existing web-format planarizing machine
10
for planarizing a substrate
12
. The planarizing machine
10
has a support table
14
with a top-panel
16
at a workstation where an operative portion (A) of a planarizing pad
40
is positioned. The top-panel
16
is generally a rigid plate to provide a flat, solid surface to which a particular section of the planarizing pad
40
may be secured during planarization.
The planarizing machine
10
also has a plurality of rollers to guide, position and hold the planarizing pad
40
over the top-panel
16
. The rollers include 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 take-up roller
23
. The supply roller
20
carries an unused or pre-operative portion of the planarizing pad
40
, and the take-up roller
23
carries a used or post-operative portion of the planarizing pad
40
. Additionally, the first idler roller
21
a
and the first guide roller
22
a
stretch the planarizing pad
40
over the top-panel
16
to hold the planarizing pad
40
stationary during operation. A motor (not shown) drives at least one of the supply roller
20
and the take-up roller
23
to sequentially advance the planarizing pad
40
across the top-panel
16
. Accordingly, clean pre-operative sections of the planarizing pad
40
may be quickly substituted for used sections to provide a consistent surface for planarizing and/or cleaning the substrate
12
.
The web-format planarizing machine
10
also has a carrier assembly
30
that controls and protects the substrate
12
during planarization. The carrier assembly
30
generally has a substrate holder
32
to pick up, hold and release the substrate
12
at appropriate stages of the planarizing process. Several nozzles
33
attached to the substrate holder
32
dispense a planarizing solution
44
onto a planarizing surface
42
of the planarizing pad
40
. The carrier assembly
30
also generally has a support gantry
34
carrying a drive assembly
35
that translates along the gantry
34
. The drive assembly
35
generally 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 substrate holder
32
via a terminal shaft
39
such that the drive assembly
35
orbits the substrate holder
32
about an axis B—B (as indicated by arrow R
1
). The terminal shaft
39
may also rotate the substrate holder
32
about its central axis C—C (as indicated by arrow R
2
).
The planarizing pad
40
and the planarizing solution
44
define a planarizing medium that mechanically and/or chemically-mechanically removes material from the surface of the substrate
12
. The planarizing pad
40
used in the web-format planarizing machine
10
is typically a fixed-abrasive planarizing pad in which abrasive particles are fixedly bonded to a suspension material. In fixed-abrasive applications, the planarizing solution is a “clean solution” without abrasive particles because the abrasive particles are fixedly distributed across the planarizing.surface
42
of the planarizing pad
40
. In other applications, the planarizing pad
40
may be a non-abrasive pad without abrasive particles, composed of a polymeric material (e.g., polyurethane) or other suitable materials. The planarizing solutions
44
used with the non-abrasive planarizing pads are typically CMP slurries with abrasive particles and chemicals to remove material from a substrate.
To planarize the substrate
12
with the planarizing machine
10
, the carrier assembly
30
presses the substrate
12
against the planarizing surface
42
of the planarizing pad
40
in the presence of the planarizing solution
44
. The drive assembly
35
then orbits the substrate holder
32
about the axis B—B and optionally rotates the substrate holder
32
about the axis C—C to translate the substrate
12
across the planarizing surface
42
. As a result, the abrasive particles and/or the chemicals in the planarizing medium remove material from the surface of the substrate
12
.
The CMP processes should consistently and accurately produce a uniformly planar surface on the substrate assembly to enable precise fabrication of circuits and photo-patterns. During the fabrication of transistors, contacts, interconnects and other features, many substrate assemblies develop large “step heights” that create a highly topographic surface across the substrate assembly. Yet, as the density of integrated circuits increases, it is necessary to have a planar substrate surface at several intermediate stages during substrate assembly processing because non-uniform substrate surfaces significantly increase the difficulty of forming sub-micron features. For example, it is difficult to accurately focus photo patterns to within tolerances approaching 0.1 micron on non-uniform substrate surfaces because sub-micron photolithographic equipment generally has a very limited depth of field. Thus, CMP processes are often used to transform a topographical substrate surface into a highly uniform, planar substrate surface.
One problem with conventional CMP methods is that the planarizing surface
42
of the planarizing pad
40
can become glazed with accumulations of slurry and/or material removed from the substrate
12
or the planarizing pad
40
. One conventional approach to addressing this problem is to remove the accumulations by conditioning the planarizing pad
40
, for example, by abrading the planarizing pad
40
with an abrasive disk (not shown). A drawback with this approach is that the equipment required for conditioning the planarizing pad
40
adds complexity to the planarizing machine
10
and, if the conditioning operation is performed separately from the planarizing operation, it reduces the time that the planarizing pad
40
is available for planarizing. Conventional conditioning processes can thus limit the overall efficiency of the apparatus.
One approach to address this drawback is to eliminate the need to condition the pad by making the planarizing surface or the entire planarizing pad disposable. For example, U.S. application Ser. No. 09/001,333 discloses a disposable planarizing pad film made from materials such as Mylar or polycarbonate. The pads disclosed in Application Ser. No. 09/001,333 can have microfeatures of different heights that entrap small volumes of an abrasive slurry and maintain the slurry in contact with the substrate. The microfeatures can be formed using a variety of techniques, such as embossing or photo-patterning.
One conventional method for photo-patterning is shown schematically in
FIGS. 2A-2E
. As shown in
FIG. 2A
, a photopolymer composite
50
is formed by disposing a photopolymer resist material
53
on a substrate polymer
52
which is supported by support layer
51
. The photopolymer resist material
53
is then exposed to a radiation source
63
. A mask
60
having opaque portions
61
and transmissive portions
62
blocks the radiation emitted from the radiation source
63
from striking unexposed portions
55
of the photopolymer resist material
53
, while allowing the radiation to strike exposed portions
54
.
As shown schematically in
FIG. 2B
, the exposed portions
54
change chemical characteristics as a result of being exposed to the radiation so
Joslyn Michael J.
Kramer Stephen J.
Eley Timothy V.
Perkins Coie LLP
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