Semiconductor device manufacturing: process – Chemical etching – Combined with the removal of material by nonchemical means
Reexamination Certificate
1999-04-09
2002-06-18
Whitehead, Jr., Carl (Department: 2822)
Semiconductor device manufacturing: process
Chemical etching
Combined with the removal of material by nonchemical means
C438S690000, C438S692000
Reexamination Certificate
active
06407000
ABSTRACT:
TECHNICAL FIELD
The present invention relates to bi-modal slurries for planarizing microelectronic-device substrate assemblies, and to methods and apparatuses for making and using such slurries in mechanical and/or chemical-mechanical planarization processes.
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. 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 assembly
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 polishing pad
40
is positioned. The top panel
16
is generally a rigid plate to provide a flat, solid surface to support the operative section of the polishing pad
40
during planarization.
The planarizing machine
10
also has a plurality of rollers to guide, position and hold the polishing 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 preoperative portion of the polishing pad
40
, and the take-up roller
23
carries a used or post-operative portion of the polishing pad
40
. Additionally, the first idler roller
21
a
and the first guide roller
22
a
stretch the polishing pad
40
over the top panel
16
to hold the polishing pad
40
stationary during operation. A drive motor (not shown) drives at least one of the supply roller
20
and the take-up roller
23
to sequentially advance the polishing pad
40
across the top panel
16
. As such, clean preoperative sections of the polishing pad
40
may be quickly substituted for used sections to provide a consistent surface for planarizing the substrate assembly
12
.
The web-format planarizing machine
10
also has a carrier assembly
30
that controls and protects the substrate assembly
12
during planarization. The carrier assembly
30
generally has a carrier head
31
with a plurality of vacuum holes
32
to pick up and release the substrate assembly
12
at appropriate stages of the planarizing cycle. A plurality of nozzles
41
attached to the carrier head
31
dispense a planarizing solution
42
onto a planarizing surface
43
of the polishing 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 actuator
36
, a drive shaft
37
coupled to the actuator
36
, and an arm
38
projecting from the drive shaft
37
. The aim
38
carries the carrier head
31
via another shaft
39
such that the drive assembly
35
orbits the carrier head
31
about an axis B—B offset from a center point C—C of the substrate assembly
12
.
The polishing pad
40
and the planarizing solution
42
define a planarizing medium that mechanically and/or chemically-mechanically removes material from the surface of the substrate assembly
12
. The web-format planarizing machine
10
typically uses a fixed-abrasive polishing pad having a plurality of abrasive particles fixedly bonded to a suspension material. The planarizing solutions
42
used with fixed-abrasive pads are generally “clean solutions” without abrasive particles because the abrasive particles in conventional abrasive CMP slurries 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
42
used with nonabrasive polishing pads are typically “abrasive” CMP slurries with abrasive particles.
To planarize the substrate assembly
12
with the planarizing machine
10
, the carrier assembly
30
presses the substrate assembly
12
against the planarizing surface
43
of the polishing pad
40
in the presence of the planarizing solution
42
. The drive assembly
35
then orbits the carrier head
31
about the offset axis B—B to translate the substrate assembly
12
across the planarizing surface
43
. As a result, the abrasive particles and/or the chemicals in the planarizing medium remove material from the surface of the substrate assembly
12
.
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 substrate surface at several stages of processing the substrate assembly
12
because non-planar substrate 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 substrate surfaces because submicron 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 of operable devices after CMP processing by quickly producing a uniformly planar surface at a desired endpoint on a substrate assembly. 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 processing should quickly remove material until the desired endpoint is reached.
To accurately create highly planar substrate surfaces at the desired endpoint, the particle size distribution of planarizing slurrries should be consistent from one planarizing cycle to another. One problem with CMP processing, however, is that the abrasive particles may be unstable in the slurry. For example, because many types of abrasive particles have a large affinity for one another, individual particles in a liquid solution may agglomerate into larger abrasive elements. The formation of such abrasive elements affects the consistency of the slurry because the extent that the particles agglomerate varies from one batch of slurry to another, or even within a single batch of slurry as it is delivered to the planarizing machine. Additionally, large abrasive elements may scratch the substrate assemblies and produce defects, or they may settle out of the solution. Thus, the agglomeration of abrasive particles is a serious problem for processing substrate assemblies with CMP processing.
One particularly promising CMP slurry being developed by Micron Technology, Inc. is a liquid solution having a plurality of first and second abrasive particles. The first and second abrasive particles are typically composed of the same material, such as ceria or silica treated ceria abrasive particles. The difference between the first and second abrasive particles is the size of the particles. This slurry accordingly has a “bi-modal” distribution of abrasive particles in which the first abrasi
Jr. Carl Whitehead
Vockrodt Jeff
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