Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
2002-11-05
2003-10-21
Eley, Timothy V. (Department: 3724)
Abrading
Abrading process
Glass or stone abrading
C451S059000, C451S063000
Reexamination Certificate
active
06634932
ABSTRACT:
TECHNICAL FIELD
The present invention generally relates to planarizing semiconductor wafers, field emission displays, and other microelectronic substrate assemblies used in the fabrication of microelectronic devices. More particularly, the invention is directed towards web-format polishing pads, and methods for making and using web-format polishing pads in mechanical and/or chemical-mechanical planarization of microelectronic substrates.
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 substrate assemblies.
FIG. 1
schematically illustrates a planarizing machine
10
with a circular platen or table
20
, a carrier assembly
30
, a circular polishing pad
40
, and a planarizing fluid
44
on the polishing pad
40
. The planarizing machine
10
may also have an under-pad
25
attached to an upper surface
22
of the platen
20
for supporting the polishing pad
40
. In many planarizing machines, a drive assembly
26
rotates (arrow A) and/or reciprocates (arrow B) the platen
20
to move the polishing pad
40
during planarization.
The carrier assembly
30
controls and protects a substrate
12
during planarization. The carrier assembly
30
typically has a substrate holder
32
with a pad
34
that holds the substrate
12
via suction. A drive assembly
36
of the carrier assembly
30
typically rotates and/or translates the substrate holder
32
(arrows C and D, respectively). The substrate holder
32
, however, may be a weighted, free-floating disk (not shown) that slides over the polishing pad
40
.
The combination of the polishing pad
40
and the planarizing fluid
44
generally define a planarizing medium that mechanically and/or chemically-mechanically removes material from the surface of the substrate
12
. The polishing pad
40
may be a conventional polishing pad composed of a polymeric material (e.g., polyurethane) without abrasive particles, or it may be an abrasive polishing pad with abrasive particles fixedly bonded to a suspension material. In a typical application, the planarizing fluid
44
may be a CMP slurry with abrasive particles and chemicals for use with a conventional nonabrasive polishing pad. In other applications, the planarizing fluid
44
may be a chemical solution without abrasive particles for use with an abrasive polishing pad.
To planarize the substrate
12
with the planarizing machine
10
, the carrier assembly
30
presses the substrate
12
against a planarizing surface
42
of the polishing pad
40
in the presence of the planarizing fluid
44
. The platen
20
and/or the substrate holder
32
then move relative to one another 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 must consistently and accurately produce a uniformly planar surface on the substrate to enable precise fabrication of circuits and photo-patterns. Prior to being planarized, many substrates have large “step heights” that create a highly topographic surface across the substrate. Yet, as the density of integrated circuits increases, it is necessary to have a planar substrate surface at several stages of processing the substrate because non-uniform substrate surfaces significantly increase the difficulty of forming sub-micron features or photo-patterns to within a tolerance of approximately 0.1 &mgr;m. Thus, CMP processes must typically transform a highly topographical substrate surface into a highly uniform, planar substrate surface (e.g., a “blanket surface”).
One particularly promising planarizing machine to enhance the planarity of the substrates is a web-format machine that uses a long, flexible polishing pad.
FIG.2
is a schematic isometric view of a web-format planarizing machine
100
similar to a machine manufactured by EDC Corporation. The planarizing machine
100
may have a support table
110
with a base
112
at a workstation A defining a planarizing zone. The base
112
is generally a rigid panel or plate attached to the table
110
to provide a flat, solid surface to which a portion of a web-format plagiarizing pad
140
is supported during planarization. The planarizing machine
100
also has a plurality of rollers to guide, position, and hold the web-format pad
140
over the base
112
. The rollers generally include a supply roller
120
, first and second idler rollers
121
a
and
121
b
, first and second guide rollers
122
a
and
122
b
, and a take-up roller
123
. The supply roller
120
carries an unused or pre-operative portion of the web
140
, and the take-up roller
123
carries a used or post-operative portion of the web
140
. A motor (not shown) drives at least one of the supply and take-up rollers to sequentially advance the web
140
across the base
112
. As such, unused portions of the web
140
may be quickly substituted for worn sections. The first idler roller
121
a
and the first guide roller
122
a
stretch the web
140
over the base
112
to hold the web
140
stationary during operation.
The planarizing machine
100
also has a carrier assembly
130
to translate the substrate
12
across the web
140
. In one embodiment, the carrier assembly
130
has a substrate holder
132
to pick up, hold and release the substrate
12
at appropriate stages of the planarizing process. The carrier assembly
130
may also have a support gantry
134
carrying a drive assembly
135
. The drive assembly
135
generally translates along the gantry
134
, and the drive assembly
135
has an actuator
136
, a drive shaft
137
coupled to the actuator
136
, and an arm
138
projecting from the drive shaft
137
. The arm
138
carries the substrate holder
132
via another shaft
139
. The drive assembly
135
may also have another actuator (not shown) to rotate the shaft
139
and the substrate holder about an axis C—C as the actuator
136
orbits the substrate holder
132
about the axis B—B.
One processing concern associated with web-format planarizing machines is that the web-format polishing pad
140
may produce surface asperities on the substrates, such as gouges, scratches or localized rough areas that exceed normal surface non-uniformities across an adequately planarized substrate. More particularly, conventional web-format polishing pads have a plurality of sections
146
attached to one another along seams
147
. As a substrate passes over the pad
140
, the seams
147
may gouge the substrate and produce asperities on the substrate surface. The seams
147
may even severely damage a substrate in more aggressive CMP processes or on softer materials. Additionally, the planarizing characteristics may vary from one pad section
146
to another. Therefore, conventional web-format polishing pads have several drawbacks that may adversely impact the planarity of the finished substrates.
In addition to such processing concerns, web-format polishing pads also have several manufacturing concerns.
FIG. 3
is a schematic isometric view of a process for making a conventional web-format polishing pad in which a cylindrical body
150
of pad material (e.g., polyurethane) is formed in a mold (not shown). A number of individual circular polishing pads
40
, which are generally used with the rotational planarizing machine
10
shown in
FIG. 1
, are formed from the cylindrical body
150
. Each circular polishing pad
40
is generally formed by cutting the cylindrical body
150
along a cutting line substantially normal to the longitudinal center line “C/L” of the cylindrical body
150
. To adapt the circular pads
40
for use in a web-format planarizing machine, a rectilinear pad section
146
is then cut from a circular polishing pad
40
. The rectilinear pad sections
146
are then attached to one another to form the web-format polishing pad
140
with a plurality
Dorsey & Whitney LLP
Eley Timothy V.
Micro)n Technology, Inc.
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