Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
1999-02-04
2001-01-23
Butler, Rodney A. (Department: 3725)
Abrading
Abrading process
Glass or stone abrading
C451S285000, C451S287000
Reexamination Certificate
active
06176763
ABSTRACT:
TECHNICAL FIELD
The present invention relates to methods and apparatuses for uniformly planarizing a microelectronic substrate using a chemical-mechanical planarization process.
BACKGROUND OF THE INVENTION
Mechanical and chemical-mechanical planarizing processes (collectively “CMP”) are used in the manufacture of microelectronic devices to form a flat surface on semiconductor wafers, field emission displays, and many other microelectronic substrates.
FIG. 1
schematically illustrates a planarizing machine
10
with a table or platen
20
, a carrier assembly
30
above the platen
20
, a polishing pad
21
positioned on the platen
20
, and a planarizing fluid
23
on the polishing pad
21
. 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
21
. In many planarizing machines, a platen drive assembly
26
rotates (arrow A) and/or reciprocates (arrow B) the platen
20
to move the polishing pad
21
during planarization.
The carrier assembly
30
controls and protects a substrate
80
during planarization. The carrier assembly
30
typically has a substrate holder
32
with a pad
34
that holds the substrate
80
via suction. A carrier drive assembly
36
typically translates (arrow C) and/or rotates (arrow D) the substrate holder
32
. Alternatively, the substrate holder
32
may be a weighted, free-floating disk (not shown) that slides over the polishing pad
21
. The combination of the polishing pad
21
and the planarizing fluid
23
generally defines a planarizing medium
28
that mechanically and/or chemically-mechanically removes material from the surface of the substrate
80
. The polishing pad
21
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
23
may be a CMP slurry with abrasive particles and chemicals for use with a conventional non-abrasive polishing pad. In other applications, the planarizing fluid
23
may be a chemical solution without abrasive particles for use with an abrasive polishing pad.
To planarize the substrate
80
with the planarizing machine
10
, the carrier assembly
30
presses the substrate
80
against a planarizing surface
24
of the polishing pad
21
in the presence of the planarizing fluid
23
. The platen
20
and/or the substrate holder
32
move relative to one another to translate the substrate
80
across the planarizing surface
24
. As a result, the abrasive particles and/or the chemicals in the planarizing medium
28
remove material from the surface of the substrate
80
.
CMP processes must consistently and accurately produce a uniform 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 substrate processing because non-uniform substrate surfaces significantly increase the difficulty of forming sub-micron features or photo-patterns to within the tolerance of approximately 0.1 microns. Thus, CMP processes must typically transform a highly topographical substrate surface into a highly uniform, planar substrate surface (e.g., a “blanket surface”).
In one conventional apparatus for planarizing microelectronic substrates, the polishing pad
21
includes a relatively soft polyurethane material. For example, the polishing pad
21
can be a model number IC1000, manufactured by Rodel, Inc. of Newark, Del., and described in U.S. Pat. No. 5,489,233 to Cook et al. The polishing pad
21
can include surface features to increase the polishing rate, as described in Cook et al. and U.S. Pat. No. 5,177,908 to Tuttle. One drawback with the polishing pads described above is that they may tend to conform to the surface of the substrate
80
and may therefore not planarize the substrate surface uniformly. One approach to addressing this drawback is to increase the hardness and elastic modulus of the polishing pad. For example, model number OXP3000 polyurethane polishing pads, having a hardness and elastic modulus greater than the corresponding hardness and elastic modulus of the IC1000 polishing pad, are available from Rodel, Inc.
In another conventional apparatus for planarizing substrates, the planarizing liquid
23
used with relatively soft polishing pads can include a suspension of abrasive fumed silica aggregates
27
, such as are shown in FIG.
2
. For example, model number ILD1300 planarizing liquids having a suspension of fumed silica aggregates
27
such as those shown in
FIG. 2
, are available from Rodel, Inc. The fumed silica aggregates
27
can be formed by reacting SiCl
4
and/or SiH
x
Cl
y
with oxygen in a burning process to form SiO
2
particles. As the SiO
2
particles cool, they collide and adhere to each other, forming the three-dimensional aggregates
27
having a fractal configuration and a relatively large surface area.
One problem with the fumed silica aggregates
27
is that they can scratch or otherwise damage the substrate
80
as a result of their rough, three-dimensional shapes. One approach for addressing this problem has been to form abrasive particles having less surface area and less roughness than the silica aggregates
27
. For example, planarizing liquids having spherical abrasive particles are available from Rodel, Inc. under the trade name Klebosol.
One problem with the planarizing solutions having spherical abrasive particles occurs when they are used with relatively soft polishing pads and/or with polishing pads having a porous planarizing surface. The combination of relatively soft polishing pads and planarizing liquids with spherical particles may not uniformly planarize the surfaces of microelectronic substrates because the polishing pads may conform to the surface of the substrate, as discussed above. The porous polishing pad may not planarize the substrate at an acceptable rate because the pores reduce the surface area of the polishing pad that contacts the substrate.
SUMMARY OF THE INVENTION
The present invention is directed toward methods and apparatuses for uniformly removing material from a microelectronic substrate during planarization. In one aspect of the invention, the apparatus can include a planarizing medium having a polishing pad with a generally non-porous planarizing surface and a planarizing liquid. The polishing pad can have a Shore D hardness in the range of approximately 58 to approximately 70 and/or can have a modulus of elasticity in the range of approximately 5.0×10
8
pascals to approximately 1.5×10
9
pascals. The planarizing liquid can include colloidal particles having a generally smooth external surface and being dispersed in the planarizing liquid to form a colloidal suspension.
In one aspect of the invention, the colloidal particles can have a generally spherical shape. In another aspect of the invention, the colloidal particles can have other shapes with smooth external surfaces, such as a cylindrical shape, a generally cubic shape, a generally hexagonal shape, or other closed polyhedrons. The colloidal particles can be formed from silicon dioxide, manganese oxide and/or cerium oxide and/or can have a surface area that is less than the surface area of a fumed silica aggregate of approximately the same overall size.
REFERENCES:
patent: 3916584 (1975-11-01), Howard et al.
patent: 5177908 (1993-01-01), Tuttle
patent: 5230833 (1993-07-01), Romberger et al.
patent: 5391210 (1995-02-01), Bilkadi et al.
patent: 5489233 (1996-02-01), Cook et al.
patent: 5496386 (1996-03-01), Broberg et al.
patent: 5645471 (1997-07-01), Strecker
patent: 5840090 (1998-11-01), Ho et al.
patent: 5891205 (1999-04-01), Picardi et al.
Brochure; Cabot Corporation, “CAB-O-SIL Untreated Fu
Kramer Stephen J.
Meikle Scott
Butler Rodney A.
Dorsey & Whitney LLP
Micro)n Technology, Inc.
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