Abrading – Machine – Combined
Reexamination Certificate
1998-09-02
2001-02-27
Scherbel, David A. (Department: 3723)
Abrading
Machine
Combined
C451S307000, C451S168000, C451S173000
Reexamination Certificate
active
06193588
ABSTRACT:
TECHNICAL FIELD
The present invention relates to mechanical and chemical-mechanical planarization of microelectronic substrates. More particularly, the present invention relates to processing media having a planarizing surface to planarize a microelectronic substrate and a separate finishing surface to clean the microelectronic substrate after planarization.
BACKGROUND OF THE INVENTION
Mechanical and chemical-mechanical planarization processes remove material from the surfaces of semiconductor wafers, field emission displays and many other microelectronic substrates to form a flat surface at a desired elevation.
FIG. 1
schematically illustrates a planarizing machine
10
with a platen or base
20
, a carrier assembly
30
, a planarizing medium
40
, and a planarizing liquid
44
on the planarizing medium
40
. The planarizing machine
10
may also have an under-pad
25
attached to an upper surface
22
of the platen
20
for supporting the planarizing medium
40
. In many planarizing machines, a drive assembly
26
rotates (arrow A) and/or reciprocates (arrow B) the platen
20
to move the planarizing medium
40
during planarization.
The carrier assembly
30
controls and protects a substrate
12
during planarization. The carrier assembly
30
generally has a substrate holder
32
with a pad
34
that holds the substrate
12
via suction. A drive assembly
36
of the carrier assembly
30
typically rotates and/or translates the substrate holder
32
(arrows C and D, respectively). The substrate holder
32
, however, may be a weighted, free-floating disk (not shown) that slides over the planarizing medium
40
.
The planarizing medium
40
and the planarizing liquid
44
may separately, or in combination, define a polishing environment that mechanically and/or chemically-mechanically removes material from the surface of the substrate
12
. The planarizing medium
40
may be a conventional polishing pad composed of a polymeric material (e.g., polyurethane) without abrasive particles, or it may be an abrasive polishing pad with abrasive particles fixedly bonded to a suspension material. In a typical application, the planarizing liquid
44
may be a chemical-mechanical planarization slurry with abrasive particles and chemicals for use with a conventional nonabrasive polishing pad. In other applications, the planarizing liquid
44
may be a chemical solution without abrasive particles for use with an abrasive polishing pad.
To planarize the substrate
12
with the planarizing machine
10
, the carrier assembly
30
presses the substrate
12
against a planarizing surface
42
of the planarizing medium
40
in the presence of the planarizing liquid
44
. The platen
20
and/or the substrate holder
32
then move relative to one another to translate the substrate
12
across the planarizing surface
42
. As a result, the abrasive particles and/or the chemicals in the polishing environment remove material from the surface of the substrate
12
.
Planarizing processes must consistently and accurately produce a uniformly planar surface on the substrate to enable precise fabrication of circuits and photo-patterns. As the density of integrated circuits increases, the uniformity and planarity of the substrate surface is becoming increasingly important because it is difficult to form sub-micron features or photo-patterns to within a tolerance of approximately 0.1 &mgr;m on non-uniform substrate surfaces. Thus, planarizing processes must create a highly uniform, planar surface on the substrate.
To obtain a highly uniform substrate surface, conventional planarizing processes generally involve two separate cycles: (1) a planarizing cycle in which material is abraded and/or etched from the substrate with a primary planarizing medium and a planarizing liquid as set forth above; and (2) a finishing cycle in which very small defects are smoothed-out and waste particles are cleaned from the substrate surface with a secondary finishing medium and an appropriate cleaning fluid (e.g., deionized water). The primary planarizing medium used during the initial planarizing cycle may be a firm polyurethane polishing pad with holes or grooves designed to transport a portion of the planarizing liquid below the substrate surface. The polishing pad may alternatively be an abrasive polishing pad with abrasive particles fixedly bonded to a suspension material. The secondary finishing medium used during the finishing cycle may be a soft, compressible material with a napped fiber surface. For example, the finishing medium may be a compressible, nonabrasive polyurethane pad with a napped surface.
The two separate cycles of conventional planarizing processes are generally performed at two separate work-stations of a single planarizing machine or on two separate machines. For example, a first work-station of a typical planarizing machine has a first platen supporting the primary planarizing medium, and a second work-station has a second platen supporting the secondary finishing medium. In the operation of the planarizing machine
10
shown in
FIG. 1
, the substrate holder
32
initially picks up the substrate
12
from an external stack of substrates (not shown), and then the carrier assembly
30
positions the substrate
12
on the primary planarizing medium
40
of the first work-station to commence the planarizing cycle. After the planarizing cycle has finished, the carrier assembly
30
moves the substrate
12
to the finishing medium (not shown) at the second work-station (not shown). For example, the finishing medium is typically mounted to a second platen (not shown) that moves the finishing medium as a nozzle (not shown) sprays deionized water near the substrate to clean the substrate surface. After the finishing cycle is over, the carrier assembly
30
places the substrate
12
in a measuring machine (not shown) to measure the thickness of particular layers on the substrate. This two-cycle process is then repeated with a new wafer.
In the competitive semiconductor and microelectronic device manufacturing industries, it is desirable to maximize the throughput of finished substrates. One drawback of conventional two-cycle planarizing processes, however, is that the time between the planarizing and finishing cycles reduces the throughput. For example, because conventional planarizing machines have separate planarizing and finishing media at separate work-stations, it typically takes 5-10 seconds to transfer the substrate from the planarizing medium to the finishing medium. Although a 5-10 second delay may not seem important, it results in a significant amount of down-time in large scale operations that manufacture devices on several thousand substrates each year and planarize each substrate several times. Accordingly, it would be desirable to reduce the down-time between the planarizing and finishing cycles.
Another drawback of conventional two-cycle planarization processes is that the finishing cycle increases the time of the overall process for each substrate. In conventional processes, the planarizing cycle typically runs for approximately 60-300 seconds, and the conditioning cycle typically runs for approximately 30-60 seconds. Because the substrate carrier sequentially positions the substrate on the planarizing media and then the finishing media, the planarizing media remains idle during the finishing cycle. The entire finishing cycle, therefore, is down-time for the planarizing medium. Thus, it would be desirable to develop a more efficient process and apparatus for performing the planarizing and finishing cycles.
Still another drawback of conventional two-cycle planarization processes is that the planarizing machines must have two separate work-stations. For example, the conventional planarizing machine described above has two separate platens for individually controlling the planarizing and finishing media. As such, conventional two-station planarizing machines may have duplicative components that do not enhance the throughput of finished substrates.
SUMMARY OF THE INVENTION
The present invention is
Carlson David W.
Moore Scott E.
Southwick Scott A.
Dorsey & Whitney LLP
Micro)n Technology, Inc.
Nguyen G.
Scherbel David A.
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