Abrading – Machine – Rotary tool
Reexamination Certificate
2000-10-19
2002-09-10
Hail, III, Joseph J. (Department: 3723)
Abrading
Machine
Rotary tool
C451S036000, C451S285000, C451S287000, C451S060000
Reexamination Certificate
active
06447381
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polishing apparatus for use in polishing a semiconductor substrate and more particularly to a polishing apparatus which allows recycling of slurry on the polishing pad.
2. Description of the Related Art
Generally, to reduce the cost in polishing processes, abrasives or slurries (liquid abrasives) containing abrasives are recycled for repeated use.
An abrasive has been suggested which is suitable for such recycling in that the abrasive provides less reduction in efficiency of polishing and secures a sufficient rate of polishing when recycled (Japanese Patent Laid-Open Publication No. Hei 4-313224). On the other hand, various techniques for recycling slurries have been suggested (Japanese Patent Laid-Open Publications No. Hei 7-156045 and No. Hei 9-314466, and Japanese Patent No. 2903980).
FIG. 1
illustrates a prior-art ultrasonic abrasives polishing apparatus disclosed in Japanese Patent Laid-Open Publication No. Hei 7-156045. An ultrasonic propagation liquid
106
is filled in an ultrasonic propagation tank
105
with an ultrasonic vibrator
102
arranged on the bottom thereof. In addition, an abrasive tank
100
in which an abrasive liquid
101
is filled is immersed in the ultrasonic ropagation liquid
106
in the ultrasonic propagation tank
105
. The abrasive liquid
101
is adapted to return to an agitator tank
103
via a pipe and a valve, which are provided under the bottom of the abrasive tank
100
. In the agitator tank
103
, provided is a magnetic separator
104
for filtering out foreign substances in the abrasive liquid. After the foreign substances in the abrasive liquid
101
have been filtered out, the abrasive liquid
101
stored in the agitator tank
103
is forced by a pump
107
to a vacuum deaerator
108
, where the abrasive liquid
101
is deaerated by the vacuum deaerator
108
. Thereafter, the abrasive liquid
101
is fed to the abrasive tank
100
. Thus, the abrasive liquid
101
is circulated for use.
In addition, in Japanese Patent Laid-Open Publication No. Hei 9-314466, disclosed is a semiconductor wafer polishing apparatus which filters out impurities in an abrasive liquid to circulate the abrasive liquid.
FIG. 2
is a schematic view illustrating the prior-art polishing apparatus. In the polishing apparatus, a platen
112
, to the upper surface of which a polishing pad
113
is affixed, is adapted to be rotationally driven by rotary drive means (not shown). A weight
111
is adapted to press a wafer
110
against the upper surface of the platen
112
. Under the platen
112
, provided is a slurry pan
114
for receiving a slurry
116
drained from the polishing pad
113
. The slurry pan
114
is coupled to a slurry tank
117
via a slurry collecting pipe
115
. The lower end of a feed pipe
122
is immersed in the slurry
116
in the slurry tank
117
. The feed pipe
122
is connected to heavy metal ion filter means
120
via a pump
121
. Heavy metal ions generated during polishing are trapped and filtered out with the filter means
120
, and thereafter the slurry
116
is fed through the feed pipe
122
onto the polishing pad
113
from a slurry feed port
119
. Incidentally, the heavy metal ion filter means
120
comprises a column with polymers filled and sealed therein, being adapted to filter out heavy metal ions with the polymers. Thus, the slurry
116
is circulated for use.
FIG. 3
illustrates a prior-art polishing apparatus described in Japanese Patent No. 2903980. There are provided a reservoir
136
for storing a slurry
131
at the center of a platen
137
and a polishing pad
138
on the upper surface of the platen
137
. A wafer
130
is adapted to be pressed against the polishing pad
138
. On the outer circumference surface of the platen
137
, a funnel
139
for collecting the slurry is provided around the platen
137
. Further outside the funnel
139
, provided is a receiver tank
140
for receiving a spill-over of the spilt slurry
131
. In addition, a waste liquid tank
132
collects a waste liquid, which has been used for polishing, from the receiver tank
140
. The slurry waste liquid in the waste liquid tank
132
is drained to the outside via a drain pipe (not shown). In addition, the slurry
131
collected in the funnel
139
returns to the reservoir
136
through a pipe
141
which connects the funnel
139
to the reservoir
136
. This allows the slurry
131
to be recycled.
A slurry tank
135
stores the slurry
131
, which is fed to the reservoir
136
by means of a pump
133
. Furthermore, the slurry
131
in the reservoir
136
is fed onto the polishing pad
138
by means of a pump
134
.
In this prior art, only the same amount of the slurry
131
as that used for polishing is fed by the pump
134
from the reservoir
136
onto the polishing pad
138
. The slurry
131
collected in the funnel
139
is returned by a pump (not shown) to the reservoir
136
through the pipe
141
. The slurry collected in the receiver tank
140
is then collected in the waste liquid tank
132
. Only the same amount of slurry as that of the slurry drained to the waste liquid tank
132
is fed from the slurry tank
135
to the reservoir
136
by means of the pump
133
. This allows the level of the liquid to be kept generally constant in the reservoir
136
. That is, the polishing apparatus collects, for recycling, part of the waste liquid that has been used for polishing and drains the remaining waste liquid to the waste liquid tank
132
, the remaining waste liquid being then disposed of outside. Thus, part of the slurry
131
is circulated for use.
However, any one of the prior art polishing apparatuses described above needs to be provided with a circulation system for circulating the slurry. This presents a problem of limiting the reduction in cost of facilities in the polishing process .
Furthermore, the polishing apparatus described in Japanese Patent No. 2903980 recycles only part of the waste liquid after polishing. This also presents a problem of limiting the reduction in cost of slurries.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a polishing apparatus which provides reduced processing cost in the polishing process and obviates the need for a slurry circulation system.
The polishing apparatus according to the present invention comprises a polishing pad to be rotationally driven for polishing a ground material; a ground material carrier for sustaining the ground material; slurry feed means for feeding a slurry onto the polishing pad; a filter, disposed upstream from the ground material in a direction of rotation of the polishing pad, for trapping swarf generated on the polishing pad; and a defense barrier, provided around the polishing pad, for retaining the slurry on the polishing pad during polishing, for allowing the slurry on the polishing pad to be drained to outside after polishing is completed.
According to the present invention, the slurry fed onto the polishing pad by the slurry feed means is prevented from spilling out therefrom and thus retained on the polishing pad. Then, the swarf generated during polishing diffuses into the slurry, however, the swarf is trapped by the filter, thereby allowing the ground material to be always ground with a clean slurry from which the swarf has been removed. Then, after the polishing is completed, the slurry on the polishing pad is allowed to flow out therefrom and thus drained. As described above, according to the present invention, the swarf generated on the polishing pad is trapped by the filter on the polishing pad, and the defense barrier retains the slurry on the polishing pad to polish the predetermined number of ground materials. This allows the slurry to be recycled on the polishing pad, thereby reducing the processing cost in the polishing process. Furthermore, according to the present invention, devices such as a circulation system provided for a prior art polishing apparatus for circulating the slurry is not required, except for the polishing apparatus. T
NEC Corporation
Wilson Lee
Young & Thompson
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