Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
1999-07-20
2001-10-23
Eley, Timothy V. (Department: 3723)
Abrading
Abrading process
Glass or stone abrading
C451S285000, C451S286000, C451S287000
Reexamination Certificate
active
06306012
ABSTRACT:
TECHNICAL FIELD
The present invention relates to methods and apparatuses for planarizing microelectronic substrate assemblies and, more particularly, to mechanical and/or chemical-mechanical planarization of such substrate assemblies using non-abrasive planarizing solutions and fixed-abrasive polishing pads.
BACKGROUND OF THE INVENTION
Mechanical and chemical-mechanical planarizing processes (collectively “CMP”) are used in the manufacturing of electronic devices for forming a flat surface on semiconductor wafers, field emission displays and many other microelectronic 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
is a schematic isometric view of a web-format planarizing machine
10
for planarizing a microelectronic substrate assembly
12
. The planarizing machine
10
has a table
11
with a rigid panel or plate to provide a flat, solid support surface
13
for supporting a portion of a web-format planarizing pad
40
in a planarizing zone “A.” The planarizing machine
10
also has a pad advancing mechanism including a plurality of rollers to guide, position, and hold the web-format pad
40
over the support surface
13
. The pad advancing mechanism generally includes 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
. As explained below, a motor (not shown) drives the take-up roller
23
to advance the pad
40
across the support surface
13
along a travel axis T—T. The motor can also drive the supply roller
20
. The first idler roller
21
a
and the first guide roller
22
a
press an operative portion of the pad against the support surface
13
to hold the pad
40
stationary during operation.
The planarizing machine
10
also has a carrier assembly
30
to translate the substrate assembly
12
across the pad
40
. In one embodiment, the carrier assembly
30
has a head
32
to pick up, hold and release the substrate assembly
12
at appropriate stages of the planarizing process. The carrier assembly
30
also has a support gantry
34
and a drive assembly
35
that can move along the gantry
34
. The drive assembly
35
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 head
32
via another shaft
39
. The actuator
36
orbits the head
32
about an axis B—B to move the substrate assembly
12
across the pad
40
.
The polishing pad
40
may be a non-abrasive polymeric pad (e.g., polyurethane), or it may be a fixed-abrasive polishing pad in which abrasive particles are fixedly dispersed in a resin or another type of suspension medium.
FIG. 2A
, for example, is an isometric view of a fixed-abrasive polishing pad having a body
41
including a backing film
42
and a planarizing medium
43
on the backing film
42
. The backing film
42
can be a thin sheet of Mylar® or other flexible, high-strength materials. The abrasive planarizing medium
43
generally includes a resin binder
44
and a plurality of abrasive particles
45
distributed throughout the resin binder
44
. The planarizing medium
43
is generally textured to form a planarizing surface
46
having a plurality of truncated pyramids, cylindrical columns, or other raised features. The 3M Corporation of St. Paul, Minn., for example, manufactures several fixed-abrasive polishing pads having alumina, ceria or other abrasive particles fixedly bonded to a Mylar® backing film
42
by a resin binder.
Referring again to
FIG. 1
, a planarizing fluid
50
flows from a plurality of nozzles
49
during planarization of the substrate assembly
12
. The planarizing fluid
50
may be a conventional CMP slurry with abrasive particles and chemicals that etch and/or oxidize the surface of the substrate assembly
12
, or the planarizing fluid
50
may be a “clean” non-abrasive planarizing solution without abrasive particles. In most CMP applications, abrasive slurries with abrasive particles are used on non-abrasive polishing pads, and non-abrasive clean solutions without abrasive particles are used on fixed-abrasive polishing pads.
In the operation of the planarizing machine
10
, the pad
40
moves across the support surface
13
along the pad travel path T—T either during or between planarizing cycles to change the particular portion of the polishing pad
40
in the planarizing zone A. For example, the supply and take-up rollers
20
and
23
can drive the polishing pad
40
between planarizing cycles such that a point P moves incrementally across the support surface
13
to a number of intermediate locations I
1
, I
2
, etc. Alternatively, the rollers
20
and
23
may drive the polishing pad
40
between planarizing cycles such that the point P moves all the way across the support surface
13
to completely remove a used portion of the pad
40
from the planarizing zone A. The rollers may also continuously drive the polishing pad
40
at a slow rate during a planarizing cycle such that the point P moves continuously across the support surface
13
. Thus, the polishing pad
40
should be free to move axially over the length of the support surface
13
along the pad travel path T—T.
CMP processes should consistently and accurately produce a uniform, planar surface on substrate assemblies to enable circuit and device patterns to be formed with photolithography techniques. As the density of integrated circuits increases, it is often necessary to accurately focus the critical dimensions of the photo-patterns to within a tolerance of approximately 0.1 &mgr;m. Focusing photo-patterns to such small tolerances, however, is difficult when the planarized surfaces of substrate assemblies are not uniformly planar. Thus, to be effective, CMP processes should create highly uniform, planar surfaces on substrate assemblies.
The planarity of the finished substrate surface is a function of several factors, one of which is the distribution of abrasive particles under the substrate assembly during planarization. In certain applications that use a non-abrasive pad and an abrasive slurry, the distribution of abrasive particles under the substrate assembly may not be uniform because the edge of the substrate assembly wipes the slurry off of the pad such that the center region of the substrate assembly does not consistently contact abrasive particles. The center region of the substrate assembly may accordingly have a different polishing rate than the edge region causing a center-to-edge polishing gradient across the substrate assembly.
Fixed abrasive polishing pads, like the one shown in
FIG. 2A
, are relatively new and have the potential to produce highly planar surfaces. The primary technical advance of fixed-abrasive pads is that the distribution of abrasive particles under the substrate assembly is not a function of the distribution of the planarizing solution because the abrasive particles are fixedly attached to the pad. Fixed abrasive pads accordingly provide a more uniform distribution of abrasive particles under the substrate assembly
12
than abrasive slurries on non-abrasive pads. Fixed-abrasive polishing pads, however, may scratch or otherwise produce defects on the finished substrate surface. The particular mechanism that causes scratching and defects is not completely understood, but it is expected that large pieces
47
of the fixed-abrasive planarizing medium
43
(see
FIG. 2
) break away during planarization and scratch the substrate assembly
12
. Fixed-abrasive pads may also produce defects because, unlike abrasive slurries in which the abrasive particles are mobile and can move with the slurry, the abrasive particles in fixed-abrasive pads do not roll or move with the substrate assembly. As such, minor peaks on the raised features of the planarizing surface
46
or disparities in the size or shape of the fixed-abrasive particles
45
may scratch the substrate surface. Theref
Berry Jr. Willie
Dorsey & Whitney LLP
Eley Timothy V.
Micro)n Technology, Inc.
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