Abrading – Machine – Rotary tool
Reexamination Certificate
1999-04-29
2002-07-02
Rachuba, M. (Department: 3724)
Abrading
Machine
Rotary tool
C451S453000, C451S456000
Reexamination Certificate
active
06413156
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and an apparatus for polishing a workpiece, and more particularly to a method and an apparatus for polishing a workpiece such as a semiconductor wafer, a glass substrate, or a liquid crystal panel which is required to be highly cleaned.
2. Description of the Related Art
As semiconductor devices become more highly integrated in recent years, circuit interconnections become finer and the distances between those interconnections also become smaller. Photolithographic processes for producing interconnections that are 0.5 &mgr;m wide or smaller, particularly, require a flat image-focusing plane for the stepper because the depth between focal points is small. If a dust particle whose size is greater than the distances between the interconnections is present on a semiconductor substrate, then an undesirable short circuit tends to occur between interconnections through the dust particle.
Therefore, it is important that the workpiece processing must produce a flat and clean workpiece. These processing requirements apply equally to other workpiece materials, such as glass substrates for photo-masking or liquid crystal display panels.
One conventional polishing apparatus is shown in
FIG. 9
of the accompanying drawings. As shown in
FIG. 9
, the conventional polishing apparatus includes a polishing unit
10
, a loading/unloading unit
21
, a feed robot
22
, and two cleaning machines
23
a
,
23
b
. As shown in
FIG. 10
of the accompanying drawings, the polishing unit
10
comprises a turntable
12
with a polishing cloth
11
attached to an upper surface thereof, and a top ring
13
for holding a workpiece
1
such as a semiconductor wafer and pressing the workpiece
1
against the polishing cloth
11
on the turntable
12
.
In operation, the workpiece
1
is supported on the lower surface of the top ring
13
, and pressed by a lifting/lowering cylinder against the polishing cloth
11
on the turntable
12
which is being rotated. A polishing solution (abrasive solution) Q is supplied from a polishing solution nozzle
14
onto the polishing cloth
11
and retained by the polishing cloth
11
. The lower surface of the workpiece
1
is polished by the polishing cloth
11
while the polishing solution Q is being present between the workpiece
1
and the polishing cloth
11
.
The turntable
12
and the top ring
13
rotate at respective speeds that are independent of each other. The top ring
13
holds the workpiece
1
with its edges being spaced distances “a”, “b” from the center and the circumferential edge of the turntable
12
. Thus, the entire lower surface of the workpiece
1
is uniformly polished at a high polishing rate. The workpiece
1
has a diameter “d”. The turntable
12
has a diameter “D” which is selected to be at least twice the diameter “d” of the workpiece
1
, as indicated by the following equation:
D
=2(
d+a +b
)
After having been polished, the workpiece
1
is cleaned in one or more cleaning processes and dried by the cleaning machines
23
a
,
23
b
, and then housed in a delivery cassette
24
of the loading/unloading unit
21
. When the workpiece
1
is cleaned, it may be scrubbed by a brush of nylon, mohair or the like, or a sponge of PVA (polyvinyl alcohol).
In the conventional polishing apparatus, since the relative displacement between the turntable
12
and the top ring
13
is large, and the relative sliding speed between them is also large, the workpiece
1
can be polished efficiently to a flat finish. However, the polished surface of the workpiece
1
tends to have large surface roughness.
In order to produce a polished workpiece of better surface quality, consideration may be given to using two turntables which are operated by varying the surface roughnesses of the polishing cloths, rotational speeds and types of polishing solutions. However, as mentioned above, the diameter of the turntable is larger than twice that of the workpiece diameter, and each apparatus takes up a large floor space area which leads to higher facility costs. These problems becomes more ignorable as the semiconductor manufacturing industry seeks larger diameter substrates.
While it is possible to use one turntable to produce a superior surface quality by varying the type of polishing solution and lowering the rotational speed of the turntable, it is obvious that such an approach leads not only to a potential increase in the cost of polishing solution but also to inevitable lowering in the production efficiency due to a prolonged polishing operation.
In order to make the workpiece clean, there are some cases where scrubbing process is carried out after the workpiece
1
has been polished using the polishing solution Q. However, such scrubbing process fails to remove submicron particles from the polished surface of the workpiece
1
, and is not effective enough to clean the polished workpiece
1
if remaining particles are bonded to the workpiece
1
by large bonding strength.
Further, the conventional polishing apparatus of the type described above has an advantage that the entire surface of the workpiece is polished uniformly, because the elasticity of the polishing cloth
11
moderates the effects of undulation and bowing in the workpiece. However, the workpiece such as a semiconductor wafer is susceptible to edge wear caused by excessive polishing around the peripheral edge of the wafer. Further, in order to polish semiconductor wafers with printed wiring patterns, it is required to obtain a polished surface having flatness of less than 1,000 angstrom by removing any micro-protrusions from uneven surface of the semiconductor wafer. However, the polishing cloth
11
is unable to meet this requirement because the elasticity of the polishing cloth allows the cloth itself to deform and the material from recessed regions as well as from protruding regions is removed.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method and an apparatus for polishing a workpiece such as a semiconductor wafer to a smooth flat finish with improved surface roughness, while effectively removing minute particles from the polished surface.
Another object of the present invention is to provide a compact polishing apparatus to produce a high degree of flatness of a workpiece such as a semiconductor wafer.
According to one aspect of the present invention, there is provided a method for polishing a workpiece, comprising: polishing a surface of the workpiece by pressing the workpiece against a polishing surface; and processing a polished surface of the workpiece by pressing the workpiece against a processing surface, the processing surface making relative translational motion relative to the workpiece.
According to another aspect of the present invention, there is also provided an apparatus for polishing a workpiece, comprising: a polishing unit for polishing a surface of the workpiece by pressing the surface of the workpiece against a polishing surface; a processing unit for processing a polished surface of the workpiece by pressing the workpiece against a processing surface, the processing surface making relative translational motion relative to the workpiece.
According to the present invention, the relative translational motion includes a relative motion of two surfaces of many patterns. The typical pattern is circular or circulative, i.e., repeating itself, and has a circular trace without respective rotational motion. However, it may include a respective rotation of a relatively large period of rotation compared to that of the circulative translation between the two surfaces. The trace of translation motion can be a linear translation pattern, a polygonal pattern or an elliptical pattern, but from the practical standpoint of polishing or processing efficiency and mechanical ease, a circular pattern would be optimum. In the circulative translation motion, all the regions of the workpiece are subjected to the same pattern.
In the present invention, a hig
Kimura Norio
Shimizu Noburu
LandOfFree
Method and apparatus for polishing workpiece does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for polishing workpiece, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for polishing workpiece will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2899993