Abrading – Machine – Combined
Reexamination Certificate
2001-03-20
2004-05-25
Ostrager, Allen (Department: 3725)
Abrading
Machine
Combined
C451S287000, C451S288000
Reexamination Certificate
active
06739955
ABSTRACT:
TECHNICAL FIELD
The present invention relates to conditioning polishing pads used in mechanical and/or chemical-mechanical planarization of microelectronic-device substrate assemblies. More particularly, the invention relates to retarding deterioration of conditioning elements and reducing contamination of polishing pads.
BACKGROUND OF THE INVENTION
Mechanical and chemical-mechanical planarizing processes (collectively “CMP”) are used in the manufacturing of microelectronic devices for forming a flat surface on semiconductor wafers, field emission displays and many other microelectronic-device substrate assemblies.
FIG. 1
schematically illustrates a planarizing machine
10
with a circular platen or table
20
, a first carrier assembly
30
, a polishing pad
40
having a planarizing surface
42
, and a planarizing fluid
44
on the planarizing surface
42
. The planarizing machine
10
may also have an under-pad
25
attached to an upper surface
22
of the table
20
for supporting the polishing pad
40
. In many planarizing machines, a drive assembly
26
rotates (arrow A) and/or reciprocates (arrow B) the table
20
to move the polishing pad
40
during planarization.
The first carrier assembly
30
controls and protects a substrate assembly
12
during planarization. The first carrier assembly
30
typically has a carrier head or substrate holder
32
with a pad
34
that holds the substrate
12
to the carrier head
32
. A drive assembly
36
typically rotates and/or translates the carrier head
32
(arrows C and D, respectively). The carrier head
32
, however, may be a weighted, free-floating disk (not shown) that slides over the polishing pad
40
.
The polishing 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 assembly
12
. The planarizing machine
10
can use a fixed-abrasive polishing pad having a plurality of abrasive particles fixedly bonded to a suspension material. The planarizing solutions
44
used with fixed-abrasive pads are generally “clean solutions” without abrasive particles because an abrasive slurry may ruin the abrasive surface of fixed-abrasive pads. In other applications, the polishing pad
40
may be a nonabrasive pad composed of a polymeric material (e.g., polyurethane), a resin, or other suitable materials without abrasive particles. The planarizing solutions
44
used with nonabrasive polishing pads are typically “slurries” that contain abrasive particles.
CMP processes should consistently and accurately produce a uniformly planar surface on the substrate assembly
12
to enable precise fabrication of circuits and photo-patterns. For example, during the fabrication of transistors, contacts, interconnects and other components, many substrate assemblies develop large “step heights” that create a highly topographic surface across the substrate assembly
12
. To enable the fabrication of integrated circuits with high densities of components, it is necessary to produce a highly planar surface at several stages of processing the substrate assembly
12
because non-planar surfaces significantly increase the difficulty of forming submicron features. For example, it is difficult to accurately focus photo-patterns to within tolerances of 0.1 &mgr;m on nonplanar surfaces because submicron photolithographic equipment generally has a very limited depth of field. Thus, CMP processes often transform a topographical surface into a highly uniform, planar surface.
In the competitive semiconductor industry, it is also highly desirable to have a high yield of operable devices after CMP processing. CMP processes should thus quickly remove material from the substrate assembly
12
to form a uniformly planar surface at a desired endpoint. For example, when a conductive layer on the substrate assembly
12
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
12
. Additionally, when a substrate assembly
12
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 processes should quickly remove material until the desired endpoint is reached.
To provide consistent results and produce planar surfaces, one aspect of CMP processing is maintaining the condition of the planarizing surface
42
on the polishing pad
40
. The condition of the planarizing surface
42
changes because residual matter collects on the planarizing surface
42
of the polishing pad
40
. The residual matter, for example, can be from the substrate assembly
12
, the planarizing solution
44
and/or the polishing pad
40
. In certain applications, residual matter from the substrate assembly
12
can even glaze over sections of the planarizing surface
42
(e.g., planarizing doped silicon dioxide layers). The substrate assemblies can also wear depressions into the planarizing surface
42
that create a non-planar planarizing surface. In many CMP applications, therefore, polishing pads are accordingly “conditioned” periodically to bring the planarizing surface into a desired condition for planarizing the substrate assemblies.
To condition the planarizing surface
42
, the planarizing machine
10
can include a conditioning system
50
that rubs an abrasive conditioning stone
60
against the planarizing surface
42
of the polishing pad
40
between planarizing cycles. The conditioning stone
60
typically includes a metal plate
62
, a layer of nickel
64
covering the bottom surface of the metal plate
62
, and a plurality of diamond particles
66
embedded in the nickel layer
64
. The metal plate
62
is attached to a second carrier assembly
70
that presses the diamond particles
66
against the polishing pad
40
and sweeps the conditioning stone over the planarizing surface
42
.
One problem with conventional conditioning stones
60
is that they wear out and can adversely affect the conditioning of the polishing pad
40
. Conventional conditioning stones, for example, may contaminate the planarizing surface
42
with material from the nickel layer
64
or the diamond particles
66
. The nickel layer
64
may wear during the conditioning cycle, which leaves residual nickel on the planarizing surface
42
and reduces the amount of nickel holding the diamond particles
66
to the plate
62
. The diamond particles
66
can thus break away from the nickel layer
64
and remain on the planarizing surface
42
after the conditioning cycle. The residual materials from the conventional conditioning stones
60
that remain on the planarizing surface
42
may produce defects on the substrate assemblies
12
during the planarizing cycle. Moreover, the loss of diamond particles
66
from the conditioning stones
60
changes the abrasiveness of the conditioning stones
60
, which can cause inconsistent conditioning of the planarizing surface
42
. Thus, there is a need to improve conditioning systems and processes to condition polishing pads
40
.
SUMMARY OF THE INVENTION
The present invention is directed toward conditioning systems and methods for conditioning polishing pads used in mechanical and chemical-mechanical planarization of microelectronic-device substrate assemblies. In one aspect of the invention, a conditioning system includes a conditioning element or conditioning member having a conditioning face configured to engage a polishing pad. The conditioning face preferably includes a bonding medium covering at least a portion of the conditioning face and a plurality of conditioning particles attached to the bonding medium. The conditioning system also includes a corrosion-inhibiting unit that can be coupled to the conditioning element and/or a liquid on the polishing pad. The corrosion-inhibiting unit preferably retards corrosion of the bonding medium in the presence of chemicals on the pol
Dorsey & Whitney LLP
Hong William
Ostrager Allen
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