Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
2001-08-10
2004-09-21
Hail, III, Joseph J. (Department: 3723)
Abrading
Abrading process
Glass or stone abrading
C451S059000, C451S285000, C451S286000, C451S288000, C451S309000
Reexamination Certificate
active
06793558
ABSTRACT:
TECHNICAL FIELD
The present invention relates to methods and apparatuses for planarizing microelectronic substrates and, more particularly, to polishing pads having non-horizontal planarizing surfaces.
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 substrates and substrate assemblies.
FIG. 1
schematically illustrates a conventional CMP machine
10
having a platen
20
. The platen
20
supports a planarizing medium
40
that can include a polishing pad
41
having a planarizing surface
42
on which a planarizing liquid
43
is disposed. The polishing pad
41
may be a conventional polishing pad made from a continuous phase matrix material (e.g., polyurethane), or it may be a fixed-abrasive polishing pad made from abrasive particles fixedly dispersed in a suspension medium. The planarizing liquid
43
may be a conventional CMP slurry with abrasive particles and chemicals that remove material from the wafer, or the planarizing liquid may be a planarizing solution without abrasive particles. In most CMP applications, conventional CMP slurries are used on conventional polishing pads, and planarizing solutions without abrasive particles are used on fixed abrasive polishing pads.
The CMP machine
10
can also include an underpad
25
attached to an upper surface
22
of the platen
20
and the lower surface of the polishing pad
41
. A drive assembly
26
rotates the platen
20
(as indicated by arrow A), and/or it reciprocates the platen
20
back and forth (as indicated by arrow B). Because the polishing pad
41
is attached to the underpad
25
, the polishing pad
41
moves with the platen
20
.
A wafer carrier
30
is positioned adjacent the polishing pad
41
and has a lower surface
32
to which a substrate
12
may be attached via suction. Alternatively, the substrate
12
may be attached to a resilient pad
34
positioned between the substrate
12
and the lower surface
32
. The wafer carrier
30
may be a weighted, free-floating wafer carrier, or an actuator assembly
33
may be attached to the wafer carrier to impart axial and/or rotational motion (as indicated by arrows C and D, respectively).
To planarize the substrate
12
with the CMP machine
10
, the wafer carrier
30
presses the substrate
12
face-downward against the polishing pad
41
. While the face of the substrate
12
presses against the polishing pad
41
, at least one of the platen
20
or the wafer carrier
30
moves relative to the other to move the substrate
12
across the planarizing surface
42
. As the face of the substrate
12
moves across the planarizing surface
42
, material is continuously removed from the face of the substrate
12
.
FIG. 2
is a partially schematic isometric view of a conventional web-format planarizing machine
10
a
that has a table
11
with a support surface
13
. The support surface
13
is a generally rigid panel or plate attached to the table
11
to provide a flat, solid workstation for supporting a portion of a web-format planarizing pad
40
a
in a planarizing zone “E” during planarization. The planarizing machine
10
a
also has a pad advancing mechanism, including a plurality of rollers, to guide, position, and hold the web-format pad
40
a
over the support surface
13
. The pad advancing mechanism generally includes a supply roller
24
, 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
a
across the support surface
13
along a travel path T-T. The motor can also drive the supply roller
24
. The first idler roller
21
a
and the first guide roller
22
a
press an operative portion of the pad
40
a
against the support surface
13
to hold the pad
40
a
stationery during operation.
The planarizing machine
10
a
also has a carrier assembly
30
a
to translate the substrate
12
over the pad
40
a
. In one embodiment, the carrier assembly
30
a
has a head
31
to pick up, hold and release the substrate
12
at appropriate stages of the planarizing process. The carrier assembly
30
a
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
31
via a terminal shaft
39
. The actuator
36
orbits the head
31
about an axis F—F (as indicated by arrow R
1
) and can rotate the head
31
(as indicated by arrow R
2
) to move the substrate
12
over the polishing pad
40
a
while a planarizing fluid
43
a
flows from a plurality of nozzles
45
in the head
31
. The planarizing fluid
43
a
may be a conventional CMP slurry with abrasive particles and chemicals that etch and/or oxidize the substrate
12
, or the planarizing fluid
43
a
may be a non-abrasive planarizing solution without abrasive particles, as was discussed above with reference to FIG.
1
.
In the operation of the planarizing machine
10
a
, the polishing pad
40
a
moves across the support surface
13
along the travel path T-T either during or between planarizing cycles to change the particular portion of the polishing pad
40
a
in the planarizing zone E. For example, the supply and take-up rollers
24
and
23
can drive the polishing pad
40
a
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
24
and
23
may drive the polishing pad
40
a
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 polishing pad
40
a
from the planarizing zone E. The rollers
23
and
24
may also continuously drive the polishing pad
40
a
at a slow rate during a planarizing cycle such that the point P moves continuously across the support surface
13
during planarization. In any case, the motion of the polishing pad
40
a
is generally relatively slow when the substrate
12
engages the polishing pad
40
a
, and the relative motion between the substrate
12
and the polishing pad
40
a
is primarily due to the motion of the head
31
. In a preferred method of operation, the polishing pad
40
a
is oriented horizontally to ensure that it is perpendicular to the orbit axis F-F of the head
31
, and to keep the planarizing fluid
43
a
on the polishing pad
40
a.
CMP processes should consistently and accurately produce a uniform, planar surface on substrates 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 microns. Focussing photo-patterns to such small tolerances, however, is difficult when the planarized surfaces of the substrates are not uniformly planar. Thus, to be effective, CMP processes should create highly uniform, planar surfaces on the substrates.
One drawback with the arrangement shown in
FIG. 2
is that it can be inefficient to periodically remove and replace the polishing pad
40
a
. For example, it can be awkward and time consuming to thread the polishing pad
40
a
from a new supply roller
24
, through the idler rollers
21
a
and
21
b
, through the guide rollers
22
a
and
22
b
and then attach the polishing pad
40
a
to the take-up roller
23
.
Another drawback with the arrangements shown in both
FIGS. 1 and 2
is that the material removed from the substrate and/or the polishing pad can remain on the polishing pad as the planarizing operation continues. The removed material can damage the substrate, for example, by becoming caught between the polishing pad
Dorsey & Whitney LLP
Hail III Joseph J.
Micro)n Technology, Inc.
Ojini Anthony
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