Abrading – Precision device or process - or with condition responsive... – Computer controlled
Reexamination Certificate
2000-08-09
2003-02-18
Eley, Timothy V. (Department: 3724)
Abrading
Precision device or process - or with condition responsive...
Computer controlled
C451S010000, C451S009000, C451S041000, C451S059000, C451S288000, C451S550000
Reexamination Certificate
active
06520834
ABSTRACT:
TECHNICAL FIELD
This invention relates to analyzing and controlling performance parameters of a planarizing cycle of a microelectronic substrate in mechanical and/or chemical-mechanical planarization processes.
BACKGROUND
Mechanical and chemical-mechanical planarization 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 device 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
schematically illustrates an existing web-format-planarizing machine
10
for planarizing a substrate
12
. The planarizing machine
10
has a support table
14
with a top-panel
16
at a workstation where an operative portion (A) of a planarizing pad
40
is positioned. The top-panel
16
is generally a rigid plate to provide a flat, solid surface to which a particular section of the planarizing pad
40
may be secured during planarization.
The planarizing machine
10
also has a plurality of rollers to guide, position and hold the planarizing pad
40
over the top-panel
16
. The rollers include a supply roller
20
, idler rollers
21
, guide rollers
22
, and a take-up roller
23
. The supply roller
20
carries an unused or pre-operative portion of the planarizing pad
40
, and the take-up roller
23
carries a used or post-operative portion of the planarizing pad
40
. Additionally, the left idler roller
21
and the upper guide roller
22
stretch the planarizing pad
40
over the top-panel
16
to hold the planarizing pad
40
stationary during operation. A motor (not shown) generally drives the take-up roller
23
to sequentially advance the planarizing pad
40
across the top-panel
16
, and the motor can also drive the supply roller
20
. Accordingly, clean pre-operative sections of the planarizing pad
40
may be quickly substituted for used sections to provide a consistent surface for planarizing and/or cleaning the substrate
12
.
The web-format-planarizing machine
10
also has a carrier assembly
30
that controls and protects the substrate
12
during planarization. The carrier assembly
30
generally has a substrate holder
32
to pick up, hold and release the substrate
12
at appropriate stages of the planarizing process. Several nozzles
33
attached to the substrate holder
32
dispense a planarizing solution
44
onto a planarizing surface
42
of the planarizing pad
40
. The carrier assembly
30
also generally has a support gantry
34
carrying a drive assembly
35
that can translate along the gantry
34
. The drive assembly
35
generally 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 substrate holder
32
via a terminal shaft
39
such that the drive assembly
35
orbits the substrate holder
32
about an axis B—B (as indicated by arrow R
1
). The terminal shaft
39
may also rotate the substrate holder
32
about its central axis C—C (as indicated by arrow R
2
).
The planarizing pad
40
and the planarizing solution
44
define a planarizing medium that mechanically and/or chemically-mechanically removes material from the surface of the substrate
12
. The planarizing pad
40
used in the web-format planarizing machine
10
is typically a fixed-abrasive planarizing pad in which abrasive particles are fixedly bonded to a suspension material. In fixed-abrasive applications, the planarizing solution is a “clean solution” without abrasive particles because the abrasive particles are fixedly distributed across the planarizing surface
42
of the planarizing pad
40
. In other applications, the planarizing pad
40
may be a non-abrasive pad without abrasive particles that is composed of a polymeric material (e.g., polyurethane) or other suitable materials. The planarizing solutions
44
used with the non-abrasive planarizing pads are typically CMP slurries with abrasive particles and chemicals to remove material from a substrate.
To planarize the substrate
12
with the planarizing machine
10
, the carrier assembly
30
presses the substrate
12
against the planarizing surface
42
of the planarizing pad
40
in the presence of the planarizing solution
44
. The drive assembly
35
then orbits the substrate holder
32
about the axis B—B, and optionally rotates the substrate holder
32
about the axis C—C, 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
.
The CMP processes should consistently and accurately produce a uniformly planar surface on the substrate assembly to enable precise fabrication of circuits and photo-patterns. During the fabrication of transistors, contacts, interconnects and other features, many substrate assemblies develop large “step heights” that create a highly topographic surface across the substrate assembly. Such highly topographical surfaces can impair the accuracy of subsequent photolithographic procedures and other processes that are necessary for forming sub-micron features. For example, it is difficult to accurately focus photo-patterns to within tolerances approaching 0.1 micron on topographic 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 a highly uniform, planar substrate surface at various stages of manufacturing the microelectronic devices.
One concern of CMP processing is that it is difficult to consistently produce a highly planar surface because the polishing rate and other parameters of CMP processing can vary across the substrate
12
during the planarizing cycle. The polishing rate can vary because properties of the polishing pad and/or the planarizing solution can change during a planarizing cycle. The polishing rate can also vary locally across the substrate surface because of non-uniformities in the (a) distribution of planarizing solution, (b) planarizing surface of the pad, (c) relative velocity between the pad and substrate assembly, and (d) several other dynamic factors that are difficult to monitor or evaluate during a planarizing cycle. The polishing rate even varies because the topography of the wafer changes during the planarizing cycle. Therefore, it would be desirable to be able to monitor and/or control at least some of these dynamic factors during a planarizing cycle.
One proposed technique for monitoring the status of a planarizing cycle is to measure static normal forces between the planarizing pad and the substrate. The normal static forces can be measured by placing an array of piezoelectric sensors laminated within a tiny plastic sheet on the polishing pad, and then pressing the substrate assembly against the plastic sheet. The Tekscan Company currently manufactures a thin plastic piezoelectric array for this purpose. One drawback with the Tekscan device, however, is that the substrate must be disengaged from the polishing pad to place the piezoelectric array in the planarizing zone on the pad. The Tekscan device is thus generally used to take “before” and “after” measurements of a normal force distribution, but not during the planarizing cycle. The static normal forces measured by the Tekscan device when the substrate is stationary may not provide accurate and useful data because the static normal forces can be significantly different than the dynamic normal forces and shear forces exerted when the substrate
12
rubs against the planarizing surface
42
of the planarizing pad
40
during a planarizing cycle. The Tekscan device, therefore, may not provide accurate or useful data for monitoring and controlling a planarizing cycle.
SUMMARY OF THE INVENTION
The present invention is directed toward methods and apparatuses for
Eley Timothy V.
Micro)n Technology, Inc.
Perkins Cole LLP
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