Abrading – Precision device or process - or with condition responsive... – Computer controlled
Reexamination Certificate
2001-08-24
2004-04-20
Rachuba, M. (Department: 3723)
Abrading
Precision device or process - or with condition responsive...
Computer controlled
C451S008000, C451S041000, C451S060000, C451S287000, C451S443000, C451S444000
Reexamination Certificate
active
06722943
ABSTRACT:
TECHNICAL FIELD
The present invention relates to planarizing machines and methods for dispensing planarizing solutions onto a plurality of locations of a processing pad in the fabrication of microelectronic devices.
BACKGROUND
Mechanical and chemical-mechanical planarizing processes (collectively “CMP”) remove material from the surface of semiconductor wafers, field emission displays, read/write heads or other microelectronic workpieces in the production of microelectronic devices and other products.
FIG. 1
schematically illustrates a CMP machine
10
with a platen
20
, a carrier assembly
30
, and a planarizing pad
40
. The CMP machine
10
may also have an under-pad
25
attached to an upper surface
22
of the platen
20
and the lower surface of the planarizing pad
40
. A drive assembly
26
rotates the platen
20
(indicated by arrow F), or it reciprocates the platen
20
back and forth (indicated by arrow G). Since the planarizing pad
40
is attached to the under-pad
25
, the planarizing pad
40
moves with the platen
20
during planarization.
The carrier assembly
30
has a head
32
to which a workpiece
12
may be attached, or the workpiece
12
may be attached to a resilient pad
34
in the head
32
. The head
32
may be a free-floating wafer carrier, or an actuator assembly
36
may be coupled to the head
32
to impart axial and/or rotational motion to the workpiece
12
(indicated by arrows H and I, respectively).
The planarizing pad
40
and a planarizing solution
44
on the pad
40
collectively define a planarizing medium that mechanically and/or chemically-mechanically removes material from the surface of the workpiece
12
. The planarizing pad
40
can be a soft pad or a hard pad. The planarizing pad
40
can also be a fixed-abrasive planarizing pad in which abrasive particles are fixedly bonded to a suspension material. In fixed-abrasive applications, the planarizing solution
44
is typically a non-abrasive “clean solution” without abrasive particles. In other applications, the planarizing pad
40
can be a non-abrasive pad composed of a polymeric material (e.g., polyurethane), resin, felt or other suitable materials. The planarizing solutions
44
used with the non-abrasive planarizing pads are typically abrasive slurries with abrasive particles suspended in a liquid.
To planarize the workpiece
12
with the CMP machine
10
, the carrier assembly
30
presses the workpiece
12
face-downward against the polishing medium. More specifically, the carrier assembly
30
generally presses the workpiece
12
against the planarizing liquid
44
on a planarizing surface
42
of the planarizing pad
40
, and the platen
20
and/or the carrier assembly
30
move to rub the workpiece
12
against the planarizing surface
42
. As the workpiece
12
rubs against the planarizing surface
42
, material is removed from the face of the workpiece
12
.
CMP processes should consistently and accurately produce a uniformly planar surface on the workpiece to enable precise fabrication of circuits and photo-patterns. During the construction of transistors, contacts, interconnects and other features, many workpieces develop large “step heights” that create highly topographic surfaces. 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 surfaces because sub-micron photolithographic equipment generally has a very limited depth of field. Thus, CMP processes are often used to transform a topographical surface into a highly uniform, planar surface at various stages of manufacturing microelectronic devices on a workpiece.
In the highly competitive semiconductor industry, it is also desirable to maximize the throughput of CMP processing by producing a planar surface on a workpiece as quickly as possible. The throughput of CMP processing is a function, at least in part, of the polishing rate of the planarizing cycle and the ability to accurately stop CMP processing at a desired endpoint. Therefore, it is generally desirable for CMP processes to provide (a) a desired polishing rate gradient across the face of a substrate to enhance the planarity of the finished surface, and (b) a reasonably consistent polishing rate during a planarizing cycle to enhance the accuracy of determining the endpoint of a planarizing cycle.
Conventional planarizing machines may not provide consistent polishing rates because of nonuniformities in (a) the distribution of the slurry across the processing pad, (b) the wear of the processing pad, and/or (c) the temperature of the processing pad. The distribution of the planarizing solution across the surface of the processing pad may not be uniform because conventional planarizing machines typically discharge the planarizing solution onto a single point at the center of the pad. This causes a thicker layer of planarizing solution the center of the pad than at the perimeter, which may result in different polishing rates across the pad. Additionally, the nonuniform distribution of the planarizing solution may cause the center region of the pad to behave differently than the perimeter region because many low PH solutions used during planarizing cycles are similar to cleaning solutions for removing stains and waste matter from the pads when polishing metallic surfaces. Such low PH planarizing solutions dispersed locally accordingly may change the physical characteristics differently at the center of the pad than at the perimeter. The nonuniform distribution of planarizing solution also causes a nonuniform temperature distribution across the pad because the planarizing solution is typically at a different temperature than the processing pads. For example, when the planarizing solution is at a lower temperature than the pad, the temperature near the single dispensing point of the planarizing solution is typically lower than other areas of the processing pad.
One concern of manufacturing microelectronic workpieces is that the distribution of the planarizing solution can cause variances in the planarized surface of the workpieces. For example, an inconsistent distribution of planarizing solution between the workpiece and the pad can cause certain areas of the workpiece to planarize faster than other areas. Nonuniform pad wear and nonuniform temperature distributions across the processing pad can also cause inconsistent planarizing results that (a) reduce the planarity and uniformity of the planarized surface on the workpieces, and (b) reduce the accuracy of endpointing the planarizing cycles. Therefore, it would be desirable to develop more consistent planarizing procedures and machines to provide more accurate planarization of microelectronic workpieces.
SUMMARY OF THE INVENTION
The present invention describes machines with solution dispensers for use in chemical-mechanical planarization and/or electrochemical-mechanical planarization/deposition of microelectronic workpieces. One embodiment of such a machine includes a table having a support surface, a processing pad on the support surface, and a carrier assembly having a head configured to hold a microelectronic workpiece. The carrier assembly can further include a drive assembly that carries the head. The machine can also include a solution dispenser separate from the head. The solution dispenser can include a support extending over the pad and a fluid discharge unit or distributor carried by the support. The fluid discharge unit is configured to simultaneously discharge a planarizing solution onto a plurality of separate locations across the pad.
In one particular embodiment, the solution dispenser comprises an elongated support extending over the pad at a location spaced apart from a travel path of the head, a fluid passageway carried by the support through which the planarizing solution can flow, and a plurality of nozzles carried by the support. The nozzles are in flu
Micro)n Technology, Inc.
Perkins Coie LLP
Rachuba M.
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