Abrading – Abrading process – With tool treating or forming
Reexamination Certificate
2002-11-19
2004-06-08
Ostrager, Allen (Department: 3725)
Abrading
Abrading process
With tool treating or forming
C451S288000, C451S443000, C451S444000, C451S456000
Reexamination Certificate
active
06746316
ABSTRACT:
TECHNICAL FIELD
The present invention relates to methods and apparatuses for planarizing microelectronic-device substrate assemblies, and to methods for mechanical and chemical-mechanical planarization of such substrate assemblies on planarizing pads.
BACKGROUND OF THE INVENTION
Mechanical and chemical-mechanical planarizing 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 a 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
. As such, 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 cycle. A plurality of 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 another shaft
39
such that the drive assembly
35
orbits the substrate holder
32
about an axis B—B offset from a center point C—C the substrate
12
.
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 offset axis B—B 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
.
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 stages of processing the substrate assembly 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 &mgr;m 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.
In the competitive semiconductor industry, it is also highly desirable to have a high yield in CMP processes by quickly producing a uniformly planar surface at a desired endpoint on a substrate assembly. For example, when a conductive layer on a substrate assembly is under-planarized in the formation of contacts or interconnects, many of these components may not be electrically isolated from one another because undesirable portions of the conductive layer may remain on the substrate assembly over a dielectric layer. Additionally, when a substrate assembly is over planarized, components below the desired endpoint may be damaged or completely destroyed. Thus, to provide a high yield of operable microelectronic devices, CMP processing should quickly remove material until the desired endpoint is reached.
The web-format machine
10
produces good results in applications that use a stationary planarizing pad
40
and orbit the substrate assembly
12
about the offset axis B—B. One problem of CMP processing that the planarizing machine
10
addresses is the center-to-edge planarizing profile produced by conventional planarizing machines that have a rotating platen and a substrate holder that rotates about the center point of the substrate. In conventional rotating platen machines, the rotation of both the planarizing pad and the substrate holder causes the relative velocity between the substrate assembly and the pad to be consistently higher at the perimeter of the substrate assembly than the center. The polishing rate accordingly varies from the center of the substrate assembly to the perimeter causing a center-to-edge planarizing profile. The web-format machine
10
reduces the center-to-edge planarizing profile by orbiting the substrate holder
32
about the offset axis B—B and holding the planarizing pad
40
stationary to reduce the difference in relative velocity between the substrate assembly
12
and the pad
40
across the surface of the substrate assembly
12
.
The web-format planarizing machine
10
also produces highly planar surfaces when substrate assemblies are planarized on a fixed-abrasive planarizing pad
40
and a “clean” planarizing solution
44
, i.e., a planarizing solution without abrasive particles. Because the abrasive particles are fixedly bonded to the pad
40
, the particles cannot agglomerate in the planarizing solution or accumulate on the planarizing
Chopra Dinesh
Meikle Scott G
Dorsey & Whitney LLP
Micro)n Technology, Inc.
Ostrager Allen
Self Shelley
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