Abrading – Machine – Rotary tool
Reexamination Certificate
1999-08-03
2004-04-20
Vo, Peter (Department: 3729)
Abrading
Machine
Rotary tool
C451S177000, C451S208000, C438S691000, C438S692000
Reexamination Certificate
active
06722963
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a carrier having a membrane for engaging microelectronic substrates during mechanical and/or chemical-mechanical planarization.
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 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 new generation 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 under-pad
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 under-pad
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
.
CMP processes should consistently and accurately produce a uniformly planar surface on the substrate to enable precise fabrication of circuits and photo-patterns. During the fabrication of transistors, contacts, interconnects and other features, many substrates develop 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. For example, it is difficult to accurately focus photo-patterns to within tolerances approaching 0.1 &mgr;m on non-uniform substrate surfaces because sub-micron photolithographic equipment generally has a very limited depth of field. Thus, CMP processes are often used to transform a topographical substrate surface into highly uniform, planar substrate surface.
In the competitive semiconductor industry, it is also highly desirable to have a high yield in CMP processes by producing a uniformly planar surface at a desired endpoint on a substrate as quickly as possible. For example, when a conductive layer on a substrate 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 over a dielectric layer. Additionally, when a substrate 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.
The planarity of the finished substrate and the yield of CMP processing is a function of several factors, one of which is the rate at which material is removed from the substrate (the “polishing rate”). Although it is desirable to have a high polishing rate to reduce the duration of each planarizing cycle, the polishing rate should be uniform across the substrate to produce a uniformly planar surface. The polishing rate should also be consistent to accurately endpoint CMP processing at a desired elevation in the substrate. The polishing rate, therefore, should be controlled to provide accurate, reproducible results.
In certain applications, the polishing rate is a function of the relative velocity between the microelectronic substrate
12
and the polishing pad
41
. For example, where the carrier
30
and the substrate
12
rotate relative to the polishing pad
41
, the polishing rate may be higher toward the periphery of the substrate
12
than toward the center of the substrate
12
because the relative linear velocity between the rotating substrate
12
and the polishing pad
41
is higher toward the periphery of the substrate
12
. Where other methods are used to generate relative motion between the substrate
12
and the planarizing medium
40
, other portions of the substrate
12
may planarize at higher rates. In any case, spatial non-uniformity in the polishing rate can reduce the overall planarity of the substrate
12
.
One conventional method for improving the uniformity of the polishing rate across the face of the substrate
12
is to vary the normal force (and therefore the frictional force) between the substrate
12
and the polishing pad
41
to account for the different relative velocities between the two. For example, in one conventional arrangement shown in
FIG. 2
, a carrier
30
a
can include a plurality of downward facing jets
35
(shown schematically in
FIG. 2
) that can direct high pressure air through a small cavity
39
and against the backside of the substrate
12
, pressing the substrate
12
against the polishing pad
41
. In one aspect of this arrangement, selected jets
35
can be closed or opened to vary the normal force applied to the substrate
12
. For example, where it is desirable to reduce the normal force applied toward the periphery of the substrate
12
(relative to the normal force applied to the center of the substrate
12
), selected jets
35
aligned with the periphery of the substrate
12
can be closed. One drawback with this approach is that it may be difficult and/or time consuming to change the number and/or location of the closed jets when the carrier
30
a
planarizes different types of substrates
12
. A further drawback is that it may be difficult to accurately control the pressure applied by the jets because of the flow of gas from the jets
35
in the cavity
39
can be highly turbulent and unpredictable.
Another approach to varying the normal force applied to the substrate
12
is to use pressurized bladders, as shown in FIG.
3
. For example, in one conventional approach, a carrier
30
b
can include a central bladder
36
a
aligned with the central portion of the substrate
12
and an annular peripheral bladder
36
b
aligned with the periphery of the substrate
12
. The carrier
30
b
can also include an annular retaining ring
37
that is biased against the polishing pad
41
by an annular retainer bladder
36
c
. Each of the bladders
36
a
-
36
c
is coupled
Micro)n Technology, Inc.
Tugbang A. Dexter
Vo Peter
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