U.S. patent application number 10/128557 was filed with the patent office on 2002-09-26 for polishing apparatus.
Invention is credited to Hirokawa, Kazuto, Hiyama, Hirokuni, Matsuo, Hisanori, Togawa, Tetsuji, Wada, Yutaka.
Application Number | 20020137440 10/128557 |
Document ID | / |
Family ID | 16305614 |
Filed Date | 2002-09-26 |
United States Patent
Application |
20020137440 |
Kind Code |
A1 |
Matsuo, Hisanori ; et
al. |
September 26, 2002 |
Polishing apparatus
Abstract
A polishing apparatus is used for polishing a plate-like
workpiece, such as a semiconductor wafer or a glass substrate. The
polishing apparatus has a polishing table having a polishing
surface thereon, a plurality of workpiece holders each for holding
a workpiece and pressing the workpiece against the polishing
surface, and a dresser for dressing the polishing surface by
pressing a desired position of the polishing surface.
Inventors: |
Matsuo, Hisanori; (Fujisawa,
JP) ; Hiyama, Hirokuni; (Tokyo, JP) ; Wada,
Yutaka; (Chigasaki, JP) ; Hirokawa, Kazuto;
(Chigasaki, JP) ; Togawa, Tetsuji; (Chigasaki,
JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
16305614 |
Appl. No.: |
10/128557 |
Filed: |
April 24, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
10128557 |
Apr 24, 2002 |
|
|
|
09612216 |
Jul 7, 2000 |
|
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|
6398626 |
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Current U.S.
Class: |
451/67 ;
451/339 |
Current CPC
Class: |
B24B 53/017 20130101;
B24D 7/14 20130101; B24D 13/147 20130101; B24B 37/345 20130101 |
Class at
Publication: |
451/67 ;
451/339 |
International
Class: |
B24B 007/00; B24B
009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 7, 1999 |
JP |
11-193299 |
Claims
What is claimed is:
1. A polishing apparatus for polishing a surface of a workpiece,
comprising: a polishing section for polishing a workpiece; and at
least two reversing machines for reversing the workpiece, at least
one of said at least two reversing machines being movable.
2. A polishing apparatus as claimed in claim 1, wherein said
movable reversing machine serves to reverse the dry workpiece, and
another of said at least two reversing machines serves to reverse
the wet workpiece.
3. A polishing apparatus as claimed in claim 1, further comprising
a cleaning section for cleaning and drying the workpiece, said
cleaning section having at least two cleaning units.
4. A polishing apparatus as claimed in claim 3, further comprising:
at least two feed robots for feeding the workpiece, one of said
feed robots being movable along the array of said cleaning
units.
5. A polishing apparatus as claimed in claim 3, further comprising:
a loading/unloading section for housing workpieces which are to be
polished and have been polished; wherein each of said polishing
section, said cleaning section and said loading/unloading section
is accommodated in a housing.
6. A polishing apparatus as claimed in claim 2, wherein said
reversing machine serving to reverse the wet workpiece is housed in
a cover.
7. A polishing apparatus as claimed in claim 2, wherein said
movable reversing machine moves after reversing the workpiece.
8. A polishing apparatus for polishing a workpiece, comprising: a
polishing section for polishing a workpiece; a loading/unloading
section for housing workpieces which are to be polished and have
been polished; a cleaning section having at least two cleaning
units for cleaning and drying the workpiece; at least two feed
robots for feeding the workpiece, one of said feed robots being
movable along the array of said cleaning units; and at least two
reversing machines for reversing the workpiece, at least one of
said reversing machines being movable between a location near said
polishing section and a location near said loading/unloading
section.
9. A polishing apparatus as claimed in claim 8, wherein each of
said polishing section, said cleaning section and said
loading/unloading section is accommodated in a housing.
Description
[0001] This application is a divisional of Ser. No. 09/612,216,
filed Jul. 7, 2000.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a polishing apparatus for
polishing a plate-like workpiece such as a semiconductor wafer or a
glass substrate.
[0004] 2 Description of the Related Art
[0005] Recent rapid progress in semiconductor device integration
demands smaller and smaller wiring patterns or interconnections and
also narrower spaces between interconnections which connect active
areas. One of the processes available for forming such
interconnection is photolithography. Although the photolithographic
process can form interconnections that are at most 0.5 .mu.m wide,
it requires that surfaces of semiconductor wafers on which pattern
images are to be focused by a stepper be as flat as possible
because the depth of focus of the optical system is relatively
small. It is, therefore, necessary to planarize the surfaces of the
semiconductor wafers for photolithography. One customary way of
planarizing the surfaces of the semiconductor wafers is to polish
them with a polishing apparatus.
[0006] FIG. 13 of the accompanying drawings shows a main part of a
conventional polishing apparatus. The polishing apparatus comprises
a rotating polishing table 100 with a polishing cloth 102 made of
urethane or the like attached to an upper surface of the polishing
table 100, a top ring (workpiece holder) 104 for holding a
semiconductor wafer W which is a workpiece to be polished and
pressing the semiconductor wafer W against the polishing table 100
while the top ring 104 is rotated, and a polishing liquid supply
nozzle 106 for supplying a polishing liquid Q to the polishing
cloth 102. The top ring 104 is connected to a top ring shaft 110
through a spherical bearing 108 so that the top ring 104 is
tiltable with respect to the top ring shaft 110. The top ring 104
is provided with an elastic pad 112 made of polyurethane or the
like on its lower surface, and the semiconductor W is held by the
top ring 104 in contact with the elastic pad 112. The top ring 104
also has a cylindrical guide ring 114 mounted on a lower outer
circumferential edge thereof for retaining the semiconductor wafer
W on the lower surface of the top ring 104.
[0007] In operation, the semiconductor wafer W is held against the
lower surface of the elastic pad 112, and pressed against the
polishing cloth 102 on the polishing table 100 by the top ring 104.
The polishing table 100 and the top ring 104 are rotated to move
the polishing cloth 102 and the semiconductor wafer W relative to
each other. At this time, the polishing liquid Q is supplied onto
the polishing cloth 102 from the polishing liquid supply nozzle
106. The polishing liquid Q comprises a chemical solution such as
an alkali solution containing abrasive particles suspended therein.
The semiconductor wafer W is polished by a composite action
comprising a chemical polishing action of the chemical solution and
a mechanical polishing action of the abrasive particles. This
polishing is called chemical mechanical polishing.
[0008] In the chemical mechanical polishing (CMP) apparatus using
the polishing cloth 102, since the polishing cloth 102 is made of
material having elasticity, irregularities of a polished surface of
the semiconductor wafer remain, and the surface of the
semiconductor wafer cannot be sufficiently planarized. Therefore,
the conventional CMP apparatus cannot cope with a demand for a
higher degree of planarization of the semiconductor wafer.
[0009] To be more specific, a device pattern on the upper surface
of the semiconductor wafer W has various irregularities having
various dimensions and steps. When the semiconductor wafer W having
step-like irregularities is planarized by the polishing cloth 102
having elasticity, not only raised regions but also depressed
regions are formed. Hence, irregularities of the polished surface
of the semiconductor wafer are difficult to eliminate, with the
result that a high degree of flatness of the polished surface
cannot be obtained.
[0010] Further, the surface of the polishing cloth 102 tends to
have irregularities, and hence, it is necessary to frequently
perform dressing of the surface of the polishing cloth 102 to
remove glazing of the surface of the polishing cloth 102.
[0011] Furthermore, a considerable proportion of the polishing
liquid Q supplied to the polishing cloth 102 is discharged without
reaching the surface of the semiconductor wafer to be polished.
Consequently, the polishing liquid Q is required to be supplied in
a large quantity, and hence, an operating cost in the polishing
process becomes high because the polishing liquid is expensive and
the cost of a process for treating the polishing liquid is
high.
[0012] Therefore, there has been developed a fixed abrasive type of
polishing apparatus and method in which a polishing surface
comprising an abrading plate, i.e., a fixed abrasive plate is used,
in place of the polishing cloth 102. The abrading plate comprises
abrasive particles such as silica particles and a binder for
binding the abrasive particles, and is formed into a flat plate.
FIG. 14 shows a main part of a conventional polishing apparatus
having such abrading plate. The polishing apparatus comprises a
polishing table 100 with a polishing tool 120 attached to an upper
surface thereof, and liquid supply nozzles 124 connected to a
liquid supply device 122 for supplying water or a chemical liquids
during polishing. The polishing tool 120, attached to the upper
surface of the polishing table 100, comprises a base plate 116 and
an abrading plate 118 attached to the surface of the base plate
116. Other structures of the polishing apparatus shown in FIG. 14
are the same as that of the conventional polishing apparatus shown
in FIG. 13.
[0013] According to the above polishing process, the abrading plate
(fixed abrasive) is harder than the polishing cloth and has less
elastic deformation than the polishing cloth. Hence, only the
raised regions on the semiconductor wafer are polished and
undulation of the polished surface of the semiconductor wafer is
prevented from being formed. Therefore, selective polishing
performance of the raised regions on the semiconductor wafer is
improved, a degree of flatness of the semiconductor wafer is
improved, and an expensive polishing liquid Q is not required to be
used.
[0014] Further, it is confirmed by the inventors of the present
application that in the polishing method using the fixed abrasive,
the polished surface of the semiconductor wafer is planarized once
to a certain level, and then the polishing rate is lowered
extremely to show a self-stop ability of polishing because of
nature of the fixed abrasive. Therefore, the inventors of the
present application have proposed to utilize such self-stop ability
of polishing for detecting an endpoint of polishing or detecting a
thickness of a film formed on the semiconductor wafer W in Japanese
Patent Application Nos. 10-150546 and 10-134432.
[0015] Recently, there have been strong demands in the polishing
apparatus for polishing semiconductor wafers field for an
improvement of productivity per apparatus and improvement of
productivity per unit installation area of the apparatus, as in
other semiconductor manufacturing apparatuses. However, in the
polishing apparatus having a single top ring per polishing table,
the polishing surface on the polishing table is not effectively
utilized, and therefore, the productivity per unit installation
area of the apparatus cannot be improved.
[0016] In order to solve the above problem, it is conceivable that
a plurality of top rings are provided with respect to a single
polishing table for thereby utilizing a polishing surface on the
polishing table efficiently. However, in this case, the polishing
surface on the polishing table is rapidly deteriorated and the
polishing rate is lowered, and frequently conducted dressing
operations lower an operating efficiency of the polishing
apparatus. Particularly, in a case of the fixed abrasive method, it
is necessary to dress the polishing surface on the polishing table
frequently to regenerate and planarize the polishing surface
because the polishing surface is worn away by the polishing
operation and irregularities of the polishing surface are
formed.
[0017] Further, in a case of conducting finish polishing of the
semiconductor wafer, in order to avoid formation of fine scratches
on the polished surface of the semiconductor wafer, it is necessary
to use a fixed abrasive having different compositions or a
different polishing table having a polishing cloth thereon. Hence,
throughput of the semiconductor wafers is greatly lowered.
SUMMARY OF THE INVENTION
[0018] It is therefore an object of the present invention to
provide a polishing apparatus which has a high processing
capability per unit time and unit installation area in a clean room
requiring an expensive operating cost.
[0019] According to an aspect of the present invention, there is
provided a polishing apparatus for polishing a surface of a
workpiece. The polishing apparatus comprises a polishing table
having a polishing surface thereon, a plurality of workpiece
holders each for holding a workpiece and pressing the workpiece
against the polishing surface, and a dresser for dressing the
polishing surface by pressing a desired position of the polishing
surface.
[0020] According to the present invention, when workpieces, such as
semiconductor wafers, are polished by utilizing a polishing surface
efficiently, even if a deteriorating rate of the polishing surface
is high, the workpieces can be efficiently polished to a high
degree of flatness while forming a good polishing surface at all
times and regenerating the polishing surface by dressing.
[0021] In a preferred aspect of the present invention, the
polishing surface has a plurality of polishing positions which have
different dressing effects.
[0022] In the case where the polishing table is a rotating-type
polishing table, the polishing surface has the most efficient
polishing performance at a polishing position immediately
downstream of the dressing position, in a rotational direction of
the polishing table, where dressing of the polishing surface is
performed. The polishing surface has less efficient polishing
performance at other polishing positions where deterioration of the
polishing surface progresses because at least one of the workpieces
has been polished once. By utilizing these characteristics, the
workpieces can be polished under different polishing conditions at
different polishing positions.
[0023] In a preferred aspect of the present invention, the
workpiece is sequentially polished by moving the workpiece to the
plurality of polishing positions sequentially.
[0024] In a preferred aspect of the present invention, an initial
polishing of the workpiece is conducted at the polishing position
where the dressing effect remains large, and a secondary polishing
or a finish polish of the workpiece is conducted at the polishing
position where the dressing effect remains small.
[0025] In a preferred aspect of the present invention, the
polishing pressure applied to the workpiece by the workpiece holder
is controlled on the basis of the dressing effect remaining on the
polishing surface. If the dressing effect remains large at a
certain polishing position, the polishing pressure applied to the
workpiece and/or the relative sliding speed between the workpiece
and the polishing surface are decreased. Conversely, if the
dressing effect remains small at a certain polishing position, the
polishing pressure applied to the workpiece and/or the relative
sliding speed between the workpiece and the polishing surface are
increased.
[0026] In a preferred aspect of the present invention, the
polishing surface has a plurality of polishing positions, and
dressing effects on the plurality of polishing positions by the
dresser are equal to one another.
[0027] With this arrangement, a plurality of polishing positions on
the polishing surface where a plurality of workpiece holders are
located can be kept at a constant polishing performance having a
certain level. Hence, a plurality of workpieces can be polished
under the same polishing condition.
[0028] In a preferred aspect of the present invention, a plurality
of dressers are provided so as to correspond to the plurality of
workpiece holders.
[0029] In a preferred aspect of the present invention, the dresser
is provided so as to dress an entire surface of the polishing
surface.
[0030] A dressing load applied to the polishing surface by the
dresser or the relative speed between the dresser and the polishing
surface may be controlled depending on the number of workpieces
which are polished simultaneously. For example, if the number of
workpieces is large, the dressing load is increased, and if the
number of workpieces is small, the dressing load is decreased.
Thus, the dressing load is controlled according to the degree of
deterioration caused by polishing operation.
[0031] In a preferred aspect of the present invention, the
polishing surface comprises a polishing cloth, or a fixed abrasive
plate having a self-generation function of abrasive particles.
[0032] The above and other objects, features, and advantages of the
present invention will become apparent from the following
description when taken in conjunction with the accompanying
drawings which illustrate preferred embodiments of the present
invention by way of example.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1 is a plan view showing a whole structure of a
polishing apparatus according to a first embodiment of the present
invention;
[0034] FIG. 2A is an enlarged plan view showing essential parts of
the polishing apparatus shown in FIG. 1;
[0035] FIG. 2B is an enlarged side view showing essential parts of
the polishing apparatus shown in FIG. 1;
[0036] FIG. 3 is a plan view of a polishing apparatus according to
a modified embodiment of the polishing apparatus shown in FIG.
1;
[0037] FIGS. 4A and 4B are views showing a polishing apparatus
according to another modified embodiment of the polishing apparatus
shown in FIG. 1, and FIG. 4A is a plan view and FIG. 4B is a front
view;
[0038] FIG. 5 is a plan view of a polishing apparatus according to
still another modified embodiment of the polishing apparatus shown
in FIG. 1;
[0039] FIG. 6 is a plan view showing a whole structure of a
polishing apparatus according to a second embodiment of the present
invention;
[0040] FIG. 7 is a cross-sectional view of a polishing apparatus
according to a modified embodiment of the polishing apparatus shown
in FIG. 6;
[0041] FIG. 8 is a plan view showing a whole structure of a
polishing apparatus according to a third embodiment of the present
invention;
[0042] FIGS. 9A and 9B are views showing a polishing apparatus
according to a modified embodiment of the polishing apparatus shown
in FIG. 8, and FIG. 9A is a front view and FIG. 9B is a plan
view;
[0043] FIGS. 10A and 10B are views showing a polishing apparatus
according to another modified embodiment of the polishing apparatus
shown in FIG. 8, and FIG. 10A is a plan view and FIG. 10B is a
front view;
[0044] FIGS. 11A and 11B are views showing a polishing apparatus
according to still another modified embodiment of the polishing
apparatus shown in FIG. 8, and FIG. 11A is a plan view and FIG. 11B
is a front view;
[0045] FIG. 12 is a plan view showing a polishing apparatus
according to still another modified embodiment of the polishing
apparatus shown in FIG. 8;
[0046] FIG. 13 is a cross-sectional view of a conventional
polishing apparatus according to an example; and
[0047] FIG. 14 is a cross-sectional view of a conventional
polishing apparatus according to another example.
DETAILED DESCRIPTION OF THE INVENTION
[0048] Next, a polishing apparatus according to the present
invention will be described below with reference to the
drawings.
[0049] FIG. 1 shows a polishing apparatus according to a first
embodiment of the present invention. As shown in FIG. 1, the
polishing apparatus has a polishing section A for polishing
semiconductor wafers W, a cleaning section B disposed in front of
the polishing section A for cleaning and drying polished
semiconductor wafers W, and a loading/unloading section D disposed
in front of the cleaning section B and having wafer cassettes C for
housing semiconductor wafers W that are to be polished and have
been polished. Each of the polishing section A, the cleaning
section B, and the loading/unloading section D is accommodated in a
housing.
[0050] In the polishing section A, a polishing table 12 having a
polishing surface 10 is provided. The polishing surface 10
comprises a polishing cloth 102 (see FIG. 13) attached to the upper
surface of the polishing table 12 or an abrading plate 118 (see
FIG. 14) attached to the upper surface of the polishing table 12.
In this embodiment, the polishing table 12 comprises a
rotation-type polishing table which is rotatable about its own
central axis. However, the polishing table 12 may comprise a
scroll-type table which makes a circulative translational motion
(scroll motion) along a circle having a small radius without
rotating about its own axis. The polishing table may include both
of the rotation-type polishing table and the scroll-type table, and
it may be possible to select one of them in accordance with the
essence of the present invention.
[0051] The polishing section A also has a liquid supply nozzle 14
disposed above the polishing table 12 and supported by a nozzle arm
for supplying a polishing liquid or water to the polishing surface
10. Further, the polishing section A has three top rings (workpiece
holders) 16 supported by a top ring support assembly 18 for holding
semiconductor wafers W and keeping surfaces of the semiconductor
wafers W to be polished in contact with the polishing surface 10 on
the polishing table 12 for thereby, polishing the semiconductor
wafers W.
[0052] The top ring support assembly 18 is rotatably and vertically
movably supported on a support column 20 which is disposed at a
central position of the polishing surface 10. The top ring support
assembly 18 has three radial support arms 22, each supporting one
of the top rings 16, a motor for rotating the top ring 16, and an
air cylinder for vertically moving the top ring 16 and pressing the
top ring 16 against the polishing table 12. The air cylinders are
capable of vertically moving the top rings 16 independently of each
other, and also of adjusting their pressing pressures independently
of each other.
[0053] The polishing section A also has a rotary transporter 26
having two pushers 24 for attaching a semiconductor wafer W to and
removing a semiconductor wafer W from a top ring 16. The rotary
transporter 26 is rotatably supported by a support post at an
intermediate position between the two pushers 24. When the support
post rotates about its own axis, either one of the two pushers 24
can move selectively to a transfer position near the polishing
table 12 and a transfer position near the cleaning section B.
[0054] Each of the top rings 16 or the support arm 22 has a moving
mechanism for moving the top ring 16 along the support arm 22
radially across the polishing table 12. When the top ring 16 is
thus moved, it can move selectively to a position above the
polishing surface 10 and a position above the pusher 24 which is
located in the transfer position near the polishing table 12. In
FIG. 1, both of the positions for the top ring 16 are
illustrated.
[0055] The polishing section A further includes a dresser 28 for
dressing the polishing surface 10 on the polishing table 12. The
dresser 28 is mounted on one end of a dresser arm 30. When the
dresser arm 30 is swung about a shaft on the other end thereof, the
dresser 28 can move between a dressing position on the polishing
surface 10 and a standby position outside of the polishing table
12. A cleaning container 29, which stores a cleaning liquid for
cleaning the dresser 28, is disposed in the standby position of the
dresser 28.
[0056] The cleaning section B has three cleaning units 32, 34 and
36, two feed robots 38, 40, and two reversing machines 42, 44. The
cleaning unit 32 has rollers 46 for holding the circumferential
edge of a semiconductor wafer W and rotating the semiconductor
wafer W at a relatively low speed, and sponge rolls 48 for cleaning
both surfaces of the semiconductor wafer W while the semiconductor
wafer W is rotating at the relatively low speed. The cleaning unit
34 has a holder 50 for holding a semiconductor wafer W and rotating
the semiconductor wafer W at a relatively high speed, and applies a
jet of cleaning liquid to both surfaces or a polished surface of
the semiconductor wafer W to clean the semiconductor wafer W while
the holder 50 is rotating at the relatively high speed. The
cleaning unit 36 has a holder 50 for holding a semiconductor wafer
W and rotating the semiconductor wafer W at a relatively high speed
or a high speed, and cleans a polished surface of the semiconductor
wafer W with a pencil-shaped sponge member while the holder 50 is
rotating at the relatively high speed, after which the
semiconductor wafer W is rotated at the high speed to dry the
semiconductor wafer W by way of a spin dry process.
[0057] The two feed robots 38, 40 serve to feed semiconductor
wafers W. Each of the feed robots 38, 40 has a hand for holding a
dry semiconductor wafer W and a hand for holding a wet
semiconductor wafer W. If a robot (first robot) 56 in the
loading/unloading section D is used to remove a semiconductor wafer
W from the cleaning unit in the final stage, then the robot 40 may
only have a hand for holding a wet semiconductor wafer W. The robot
(second robot) 38 is not a mobile robot, but is fixed in a position
near the rotary transporter 26. The robot 38 is rotatable to change
its direction for transferring a semiconductor wafer W. The robot
(third robot) 40 is a mobile robot movable along the array of
cleaning units 32, 34 and 36.
[0058] Of the two reversing machines 42, 44, the reversing machine
42 serves to reverse a dry semiconductor wafer W and is movable
between an end of the cleaning section B near the polishing section
A and an opposite end of the cleaning section B near the
loading/unloading section D. The second reversing machine 44 serves
to reverse a wet semiconductor wafer W, and is housed in a cover
52.
[0059] The loading/unloading section D has an array of cassette
bases 54 for placing thereon wafer cassettes C which house
semiconductor wafers W or which are to house semiconductor wafers
W, and a single robot (first robot) 56 for feeding a semiconductor
wafer W. The robot 56 has a single hand for holding a dry
semiconductor wafer W.
[0060] The polishing section A, the cleaning section B, and the
loading/unloading section D are individually partitioned by walls
so as to form respective chambers. The internal pressures of the
chambers are controlled such that air in a chamber having a
relatively low level of cleanliness does not leak into a chamber
having a relatively high level of cleanliness. The walls have wafer
passages defined therein. Each of the wafer passages has a
vertically movable shutter, which is opened only when a
semiconductor wafer W is to pass therethrough. When air is
discharged from the polishing apparatus, the air is passed through
a HEPA or ULPA filter so as to prevent the environment of a clean
room in which the polishing apparatus is installed, from being
contaminated by the discharged air.
[0061] Operation of the polishing apparatus shown in FIG. 1 will be
described below. First, operation of the polishing section A will
be described below. Since the polishing section A has the single
rotary transporter 26 for replacing semiconductor wafers W on the
110 plural top rings 16, it is most efficient to polish
semiconductor wafers W on three top rings 16 out of phase with each
other. Depending on the material of the semiconductor wafers W and
the polishing process, however, it may be possible to select an
operation control program to polish all semiconductor wafers W
simultaneously in a batch process after the semiconductor wafers W
have been mounted on all the top rings 16.
[0062] The former standard polishing process will be described
below. A wafer cassette C which houses semiconductor wafers to be
polished is automatically or manually supplied from the outside of
the polishing apparatus to the loading/unloading section D, and
placed on one of the cassette bases 54 in the loading/unloading
section D.
[0063] The first robot 56 in the loading/unloading section D
removes a semiconductor wafer W from the supplied wafer cassette C,
and transfers the removed semiconductor wafer W to the reversing
machine (first reversing machine) 42 in the cleaning section B. The
first reversing machine 42 which has received the semiconductor
wafer W reverses the semiconductor wafer W such that its surface to
be polished faces downward, and then moves to a position
confronting the second robot 38.
[0064] The second robot 38 rotates so as to face the first
reversing machine 42, and receives the semiconductor wafer W from
the first reversing machine 42 with the hand which serves to hold a
dry semiconductor wafer. Then, the second robot 3 8 rotates so as
to face the rotary transporter 26 in the polishing section A, and
transfers the semiconductor wafer W to the pusher 24 of the rotary
transporter 26 which is positioned closer to the cleaning section
B, i.e., the pusher 24 closer to the second robot 38.
[0065] In the polishing section A, semiconductor wafers W on three
top rings 16 are polished about 120.degree. out of phase each
other. Specifically, as shown in FIG. 2A, a primary polishing of a
semiconductor wafer W is carried out in a first polishing position
P.sub.1 which confronts the rotary transporter 26 on the polishing
surface 10 of the polishing table 12 for a period of time that is
about one-third of the total polishing time. Then, the top ring
support assembly 18 is turned 120.degree. to transfer the
semiconductor wafer W to a second polishing position P.sub.2 that
is spaced 120.degree. downstream from the first polishing position
P.sub.1 with respect to the direction in which the polishing table
12 is rotated, and then a secondary polishing of the semiconductor
wafer W is carried out in the second polishing position P.sub.2.
Thereafter, the top ring support assembly 18 is further turned
120.degree. to transfer the semiconductor wafer W to a third
polishing position P.sub.3 that is 120.degree. spaced downstream
from the second polishing position P.sub.2 with respect to the
direction in which the polishing table 12 is rotated, and then a
tertiary polishing of the semiconductor wafer W is carried out in
the third polishing position P.sub.3. Since the first polishing
position P.sub.1 is also a semiconductor wafer transfer position,
the period of time in which the semiconductor wafer W is polished
in the first polishing position P.sub.1 is shorter than the periods
of time in which the semiconductor wafer W is polished in the
second and third polishing positions P.sub.2, P.sub.3.
Simultaneously with the polishing of the semiconductor wafer W, the
polishing surface 10 is dressed by the dresser 28. As shown in
FIGS. 2A and 2B, the dresser 28 has a substantially circular plate
having a dressing surface at a lower surface. Diamond particles
capable of dressing or conditioning the polishing surface are
uniformly attached to the entire surface of the dressing surface of
the dresser 28 by electrodeposition. Other dressers in other
embodiments have the same dressing surface comprising
electrodeposited diamond particles.
[0066] The operation of the polishing section A will be described
in greater detail below. When the polishing of the semiconductor
wafer W in the third polishing position P.sub.3 is finished, the
top ring 16 which carries the polished semiconductor wafer W is
lifted, and the top ring support assembly 18 is turned 120.degree.
to bring the top ring 16 to a wafer transfer position, i.e., the
first polishing position P.sub.1. When the top ring support
assembly 18 is turned, the dresser 28 is retracted out of the path
of the top ring support assembly 18, as necessary. Then, the top
ring 16 moves radially outward along the support arm 22 to a
position above the pusher 24 located in the wafer transfer position
near the polishing table 12. The top ring 16 is lowered by an air
cylinder into abutment against the pusher 24 and transfers the
polished semiconductor wafer W to the pusher 24. Then, the top ring
16 is lifted and waits in an upper standby position.
[0067] Depending on the polishing process, the semiconductor wafer
holding surfaces of the top rings 16 from which semiconductor
wafers W have been removed may be cleaned by a liquid such as pure
water or a chemical solution ejected under a given pressure from a
top ring cleaning nozzle (not shown). In addition, a cleaning
liquid may be supplied to clean the liquid supply nozzle 14
depending on the polishing liquid or the polishing process. The
feed robots 38, 40, the reversing machines 42, 44, and the rotary
transporter 26 may have a self-cleaning mechanism for cleaning
themselves with suitable timing depending on the polishing
process.
[0068] After receiving the polished semiconductor wafer W from the
top ring 16, the rotary transporter 26 is turned 180.degree. to
locate the pusher 24 that has received the polished semiconductor
wafer W at the wafer transfer position near the cleaning section B
and locate the pusher 24 that carries a semiconductor wafer W to be
polished at the wafer transfer position near the polishing table
12. The top ring 16 is lowered from the upper standby position,
receives the semiconductor wafer W to be polished under vacuum from
the pusher 24, and is then lifted. Thereafter, the top ring 16
holding the semiconductor wafer W to be polished moves radially
inward along the support arm 22 toward the center of the top ring
support assembly 18 until the top ring 16 is positioned over the
polishing surface 10 of the polishing table 12. When the angular
movement of the rotary transporter 26 finishes, the dresser 28
returns from the retracted position to an operative position, and
dresses the polishing surface 10.
[0069] The top ring 16 is lowered by the air cylinder to press the
surface to be polished of the semiconductor wafer W held by the top
ring 16 against the polishing surface 10 under a predetermined
pressure, and starts polishing the semiconductor wafer W. During
this time and also while the top ring support assembly 18 is
rotating, the other two top rings 16 are continuously polishing
semiconductor wafers W that are carried by these top rings 16. In
order to rotate the top ring support assembly 18 smoothly, the top
ring support assembly 18 may be lifted to space all the
semiconductor wafers W held by the top rings 16 away from the
polishing surface 10.
[0070] Before the top ring 16, which holds an unpolished
semiconductor wafer W or a semiconductor wafer W in the process of
being polished, is lowered to bring the surface to be polished of
the semiconductor wafer W into contact with the polishing surface
10, the top ring 16 starts rotating. The polishing table 12 is
rotated at all times during the polishing process. Therefore, the
semiconductor wafer W is polished while the top ring 16 and the
polishing table 12 are rotating. The polishing surface 10 is
supplied with pure water or at least one polishing liquid (abrasive
liquid) from the liquid supply nozzle 14 during the polishing
process.
[0071] After the polishing of a semiconductor wafer W is finished,
the polished semiconductor wafer W is transferred from the top ring
16 to the rotary transporter 26, and an unpolished semiconductor
wafer W is transferred from the rotary transporter 26 to the top
ring 16. As the polishing of the semiconductor wafers W held by the
three top rings 16 is finished, the polished semiconductor wafers W
are successively transferred from the top rings 16 to the rotary
transporter 26 and unpolished semiconductor wafers W are
successively transferred from the rotary transporter 26 to the top
rings 16. During this operation, the polished and unpolished
semiconductor wafers W are transferred between the rotary
transporter 26 and the second robot 38. Specifically, the second
robot 38 successively removes the polished semiconductor wafers W
from the rotary transporter 26, and successively delivers the
unpolished semiconductor wafers W to the rotary transporter 26.
[0072] In the polishing process, the polishing surface 10 of the
polishing table 12 is steadily dressed by the dresser 28. The
polishing surface 10 is fully regenerated in the first polishing
position P.sub.1, and the regenerated effect of the polishing
surface 10 is reduced progressively in the second and third
polishing positions P.sub.2, P.sub.3. Therefore, when a plurality
of semiconductor wafers W are to be simultaneously polished, the
polishing positions, depending on the remaining dressing effect on
the polishing surface 10, may be selected to polish the
semiconductor wafers W effectively.
[0073] Specifically, in the case where the polishing table 12 is a
rotating-type polishing table, as shown in FIG. 2A and 2B, the
polishing surface 10 has the most efficient polishing performance
at the first polishing position P.sub.1 immediately downstream of
the dressing position, in a rotational direction R of the polishing
table 12, where the dressing of the polishing surface 10 is
performed by the dresser 28. The polishing surface 10 has less
efficient polishing performance at the second and third polishing
positions P.sub.2, P.sub.3, where deterioration of the polishing
surface 10 progresses, because at least one of semiconductor wafers
has been polished once. By utilizing these characteristics, the
semiconductor wafers can be polished under different polishing
conditions at different polishing positions P.sub.1, P.sub.2,
P.sub.3.
[0074] In the case where the polishing surface 10 comprises a fixed
abrasive surface provided by the abrading plate which causes
self-generation of abrasive particles during the polishing process,
the abrasive particles are generated by dressing. In the first
polishing position P.sub.1, the polishing surface 10 polishes a
semiconductor wafer W initially at a high polishing rate to remove
large surface irregularities with the abundant abrasive particles
available in the first polishing position. In the second polishing
position P.sub.2, the polishing surface 10 polishes the
semiconductor wafer W secondarily at a medium polishing rate. In
the third polishing position P.sub.3, the polishing surface 10
conducts a finish polishing of the semiconductor wafer W.
[0075] In the illustrated embodiment, a semiconductor wafer W is
successively moved in one direction to the three polishing
positions P.sub.1, P.sub.2, P.sub.3 and successively polished in
the three polishing positions. However, the semiconductor wafer W
may be moved in different patterns. For example, the semiconductor
wafer W may be moved back from the third polishing position P.sub.3
to the second polishing position P.sub.2. Alternatively,
semiconductor wafers W of different types may be polished only in
their respective polishing positions.
[0076] In the polishing apparatus, it may be desirable to remove
the same amount of material from the semiconductor wafers in the
respective polishing positions P.sub.1, P.sub.2, P.sub.3. This may
be achieved by changing the polishing pressure applied by the top
rings 16, and/or the rotational speed, i.e., the sliding speed, of
the top rings 16. For example, the polishing pressure and/or the
rotational speed of the top ring 16 is reduced in the first
polishing position P.sub.1 where the dressing effect remains large,
and is increased in the second and third polishing positions
P.sub.2, P.sub.3 where the dressing effect remains small, for
thereby eliminating nonuniformity in the amount of material to be
removed among the semiconductor wafers held by the top rings 16. As
described above, the polishing pressure and/or the rotational
speeds of the top rings 16 are adjusted in order to uniformize the
polishing rates in the respective polishing positions P.sub.1,
P.sub.2, P.sub.3. However, the polishing pressure and/or the
rotational speeds of the top rings 16 may be adjusted to
intentionally make the polishing rates in the respective polishing
positions P.sub.1, P.sub.2, P.sub.3 different.
[0077] Further, in this polishing apparatus, the amount of dressing
may be adjusted according to the number of semiconductor wafers
which have been polished. For example, while replacement of the
semiconductor wafer is carried out in one of the three top rings
16, the degree of deterioration of the polishing surface 10 on the
polishing cloth or the amount of self-generated abrasive particles
required for polishing in the abrading plate may be two-thirds of
the case in which the three top rings 16 perform polishing
operation. Therefore, in this case, the dressing load may be
reduced to prevent the polishing cloth from being dressed
excessively or to prevent the abrading plate from being worn
excessively.
[0078] The polished semiconductor wafer W removed from the rotary
transporter 26 by the second robot 38 is delivered to a cleaning
process in the cleaning section B. Specifically, the second robot
38 removes the polished semiconductor wafer W with its hand for
holding a wet semiconductor wafer W, turns 180.degree., and
transfers the polished semiconductor wafer W to the second
reversing machine 44 for reversing a wet semiconductor wafer W.
[0079] The polished semiconductor wafer W is cleaned in the
cleaning B section as follows. The semiconductor wafer W
transferred to the second reversing machine 44 by the second robot
38 is reversed to cause the polished surface to face upward. The
reversed semiconductor wafer W is then removed laterally from the
second reversing machine 44 by the third robot 40 that is movable.
The third robot 40 which has received the semiconductor wafer W
moves to the position confronting the first cleaning unit 32, and
transfers the semiconductor wafer W to the first cleaning unit 32.
The third robot 40 uses its hand for holding a wet semiconductor
wafer W to transfer the semiconductor wafer W to the first cleaning
unit 32. In the first cleaning unit 32, the rollers 46 hold the
circumferential edge of the semiconductor wafer W and rotate the
semiconductor wafer W at a relatively low speed, and the sponge
rolls 48, which are rotating, clean both surfaces of the
semiconductor wafer W while the semiconductor wafer W is rotating
at the relatively low speed.
[0080] After the semiconductor wafer W is cleaned in the first
cleaning unit 32, the third robot 40 removes the cleaned
semiconductor wafer W from the first cleaning unit 32, carries the
cleaned semiconductor wafer W to the second cleaning unit 34, and
transfers the cleaned semiconductor wafer W to the second cleaning
unit 34. In the second cleaning unit 34, the holder 50 holds the
semiconductor wafer W, and a jet of cleaning liquid is applied to
both surfaces or the polished surface of the semiconductor wafer W
to clean the semiconductor wafer W while the holder 50 is rotating
at a relatively high speed.
[0081] After the semiconductor wafer W is cleaned in the second
cleaning unit 34, the third robot 40 removes the cleaned
semiconductor wafer W from the second cleaning unit 34, carries the
cleaned semiconductor wafer W to the third cleaning unit 36, and
transfers the cleaned semiconductor wafer W to the third cleaning
unit 36. The third robot 40 uses its hand for holding a wet
semiconductor wafer W to transfer the semiconductor wafer W to the
third cleaning unit 36. In the third cleaning unit 36, the holder
50 holds the semiconductor wafer W, and the polished surface of the
semiconductor wafer W is cleaned with a pencil-shaped sponge member
while the holder 50 is rotating at a relatively high speed, after
which the semiconductor wafer W is rotated at a high speed to dry
the semiconductor wafer W by way of a spin dry process.
[0082] After the semiconductor wafer W is cleaned and dried in the
cleaning section B, the semiconductor wafer W is removed from the
third cleaning unit 36 by the hand for a dry semiconductor wafer in
the third robot 40 and then returned to the wafer cassette C from
which the semiconductor wafer W was supplied, by the first robot 56
in the loading/unloading section D. Therefore, semiconductor wafers
W are processed by a dry-in and dry-out process in the polishing
apparatus, and then delivered to a next process in the clean
room.
[0083] FIG. 3 shows a polishing apparatus according to a modified
embodiment of the polishing apparatus shown in FIG. 1. In this
embodiment, a dresser 28A comprises a bar-like dresser (dressing
rod) or a plate-like dresser (dressing plate) having a suitable
cross-section, in place of a rotating disk-type of dresser. The
dresser 28A has both ends pressed by a pressing device, such as an
air cylinder, whereby the dresser 28A is brought in sliding contact
with the polishing surface 10 on the polishing table 12. The
dressing surface of the dresser 28A may comprise a suitable
material and a suitable shape. The dresser 28A may comprise a
roller having a circular cross-section which can dress the
polishing surface while the roller is rotating about its own axis.
Although the dresser 28A has a shape and an arrangement different
from the dresser 28, other structures in the dresser 28A shown in
FIG. 3 are the same as those in FIGS. 1 and 2.
[0084] FIGS. 4A and 4B show a polishing apparatus according to
another modified embodiment of the present invention. In this
embodiment, the top ring support assembly (not shown) supports six
top rings 16 so that six semiconductor wafers W can be polished
simultaneously. A dresser 28B is provided so as to be laid
diametrically across the polishing table 12. The dresser 28B has
both ends connected to air cylinders 60, and is pressed downward by
the air cylinders 60. Therefore, in this embodiment, the first
through third polishing position P.sub.1, P.sub.2, and P.sub.3 are
arranged in two rows.
[0085] Further, FIG. 5 shows a polishing apparatus according to a
modified embodiment. The polishing apparatus in this embodiment is
different from that in FIGS. 4A and 4B in that two dressers 28A
each comprising a dressing rod are provided so as to extend
radially from a position close to a center of the polishing table
12 to the periphery of the polishing table 12.
[0086] FIG. 6 shows a polishing apparatus according to a second
embodiment of the present invention. The polishing apparatus
according to the second embodiment has a cleaning section B and a
loading/unloading section D Which are identical to those of the
polishing apparatus according to the first embodiment, and a
polishing section A which differs from that of the polishing
apparatus according to the first embodiment.
[0087] The polishing apparatus has a top ring support body 18
having four support arms 22 each for supporting either a top ring
16 or a dresser 28. That is, two top rings 16 and two dressers 28
are provided on the support arms 22, and the top rings 16 and the
dressers 28 are alternately provided in a circumferential direction
of the polishing table 12. The top rings 16 and the dressers 28 are
radially movable along the support arms 22 which support them.
Thus, one dresser 28 is provided so as to correspond to one top
ring 16, and hence, the polishing surface 10 has the same polishing
condition at respective polishing positions of the respective top
rings 16. Therefore, the semiconductor wafers can be polished in a
uniform quality, and the process control can be easily
conducted.
[0088] In this embodiment, a cleaning container 29 for cleaning the
dresser 28 is disposed at a standby position adjacent to a transfer
position of the semiconductor wafer which is located in
confrontation with the rotary transporter 26. Therefore, while the
top ring 16 performs the replacement work of the semiconductor
wafer, the dresser 28, located upstream of the top ring 16 which
performs the replacement work, is positioned in the cleaning
container 29 in which ground-off particles and the like can be
removed by a certain cleaning mechanism.
[0089] In this embodiment, three top rings 16 may be supported by
the three support arms among four support arms, and one dresser 28
may be supported by remaining support arm. This structure allows
throughput of semiconductor wafers to be increased. In this case,
although the polishing surface 10 has different conditions among
three top rings 16, an adverse effect caused by the different
conditions may be removed by an accurate endpoint detection of
polishing.
[0090] When the polishing of the semiconductor wafer finishes by
one of the top rings 16, the top ring support assembly 18 is
turned, and the top ring 16 which carries the polished
semiconductor wafer W is moved to the wafer transfer position where
the polished semiconductor wafer W is replaced with an unpolished
semiconductor wafer W. Unlike the polishing apparatus according to
the first embodiment, in addition to polishing of the semiconductor
wafers by other top rings, the polishing surface can be dressed by
the dresser 28 while the top ring support assembly 18 is being
turned.
[0091] As shown in FIG. 7, a dresser 28C may comprise a top ring
16. Specifically, the dresser 28C comprises a dressing tool 62
including an attachment portion 62a having a small diameter, and a
dressing portion 62b having a large diameter. The lower surface of
the dressing portion 62b serves as a dressing surface. This
structure allows the top ring 16 to hold the dressing tool 62
instead of the semiconductor wafer, thus forming the dresser 28C,
as required.
[0092] FIG. 8 shows a polishing apparatus according to a third
embodiment of the present invention. The polishing apparatus
according to the third embodiment has a cleaning section B and a
loading/unloading section D which are identical to those of the
polishing apparatus according to the first embodiment, and a
polishing section A which differs from that of the polishing
apparatus according to the first embodiment.
[0093] As shown in FIG. 8, the polishing section A has a plurality
of top rings 16 and one or more dressers 28 which are mounted on a
support member 64. The support member 64 is rotatable in a
horizontal plane about its own axis, and the top rings 16 and the
dresser (or dressers) 28 are disposed around the axis of the
support member 64. The support member 64 is mounted on a distal end
of a swing head 66 that is rotatable in a horizontal plane. In this
embodiment, the three top rings are provided at equal angular
intervals, and one or more (three at the maximum) dressers 28 may
be provided so as to locate each dresser 28 between two top rings.
The swing head 66 is supported at its proximal end by a support
post 68. The support arm 22 has motors and air cylinders for
individually rotating the top ring 16 and the dresser 28 and moving
the top ring 16 and the dresser 28 vertically.
[0094] The polishing section A also has a rotary transporter 70
having six pushers 24 which alternately hold unpolished
semiconductor wafers W and polished semiconductor wafers W. When
the swing head 66 is turned about the support post 68, each of the
top rings 16 can move to a position over the rotary transporter 70
for attachment of a semiconductor wafer W to and removal of a
semiconductor wafer W from the top ring 16.
[0095] In the third embodiment, unpolished semiconductor wafers W
are simultaneously installed on the three top rings 16 and also
simultaneously polished in a batch process. Specific operation of
the polishing apparatus according to the third embodiment will be
described below. The process of carrying an unpolished
semiconductor wafer W with the second robot 38 to the polishing
section A is identical to the corresponding process carried out by
the polishing apparatus according to the first embodiment.
[0096] The second robot 38 that has received the semiconductor
wafer W from the first reversing machine 42 with the hand for
holding a dry semiconductor wafer W is turned so as to face the
rotary transporter 70, and transfers the semiconductor wafer W to a
first loading pusher 24 on the rotary transporter 70. Each time the
rotary transporter 70 receives a semiconductor wafer W, the rotary
transporter 70 is turned 120.degree. clockwise. The above process
is repeated twice. Therefore, unpolished semiconductor wafers W are
placed respectively on three loading pushers (first, second, and
third loading pushers) 24 on the rotary transporter 70.
[0097] Then, the swing head 66 is turned to place the three top
rings 16 over the rotary transporter 70. The rotary transporter 70
is turned 60.degree. clockwise to position the three loading
pushers 24 thereon in alignment with the three top rings 16,
respectively. The air cylinders for vertically moving the top rings
16 are actuated to lower the top rings 16, and then the top rings
16 hold the unpolished semiconductor wafers W under vacuum on the
three loading pushers 24. The top rings 16 that have received the
semiconductor wafers W are lifted, and the swing head 66 is turned
to bring the top rings 16 over the polishing surface of the
polishing table 12. The top rings 16 and the dresser 28 are
lowered, and the semiconductor wafers W supported by the top rings
16 are polished by the polishing surface 10 of the polishing table
12, while the polishing surface 10 is dressed by the dresser 28.
The number of dressers and arrangement of the dressers with respect
to the top rings 16 are the same as the polishing apparatus shown
in FIG. 6.
[0098] While the semiconductor wafers W are being polished, the
semiconductor wafers W that have been polished and placed on the
unloading pushers 24 on the rotary transporter 70 are discharged by
the second robot 38, and semiconductor wafers to be polished next
are supplied to the loading pushers 24 on the rotary transporter 70
according to the process described above.
[0099] When the polishing of the semiconductor wafers W is
completed, the top rings 16 are elevated, and the swing head 66 is
turned to position the top rings 16 over the rotary transporter 70
where the three unloading pushers 24 are positioned in alignment
with the respective top rings 16. The top rings 16 are lowered into
abutment against the unloading pushers 24, and transfer the
polished semiconductor wafers W to the unloading pushers 24.
[0100] After transferring the polished semiconductor wafers W to
the unloading pushers 24, the top rings 16 are lifted to a
predetermined position, after which the rotary transpoter 70 is
turned 60.degree. clockwise to position the loading pushers 24
thereon in alignment with the top rings 16. The top rings 16 are
lowered to receive unpolished semiconductor wafers W from the
loading pushers 24. Thereafter, the top rings 16 are lifted, and
the swing head 66 is turned to position the top rings 16 over the
polishing surface 10, after which the top rings 16 are lowered to
polish the semiconductor wafers W.
[0101] The polished semiconductor wafers W that have been held by
the unloading pushers 24 are successively removed from the
unloading pushers 24 by the second robot 38, and transferred to the
cleaning process in the cleaning section B. At this time, the
second robot 38 delivers the polished semiconductor wafers W one by
one. Specifically, the second robot 38 receives a polished
semiconductor wafer W from a corresponding unloading pusher 24 with
its hand for holding a wet semiconductor wafer W, is turned
180.degree., and transfers the received polished semiconductor
wafer W to the second reversing machine 44.
[0102] During this time, the rotary transporter 70 is turned
120.degree. clockwise to orient an unloading pusher 24, which is
still holding a polished semiconductor wafer W toward the second
robot 38. The second robot 38, which has transferred the
semiconductor wafer W to the second reversing machine 44, is turned
180.degree. to face the rotary transporter 70 again, receives the
next polished semiconductor wafer W, and transfers the received
semiconductor wafer W to the second reversing machine 44. The same
process is repeated once more to deliver three semiconductor wafers
W that have been simultaneously polished in one polishing process,
successively to the cleaning section B. The process of cleaning of
the polished semiconductor wafers W in the cleaning section B and
the subsequent process are identical to the corresponding processes
performed by the polishing apparatus according to the first
embodiment.
[0103] FIGS. 9A and 9B show a polishing apparatus according to
another embodiment of the present invention. In this embodiment,
six top rings 16 are provided on the swing head 66 shown in FIG. 8.
Further, a disk-like dressing plate 28D having substantially the
same diameter as the polishing table 12 is provided, and the
dressing plate 28D has holes at positions corresponding to the
respective top rings 16. The dressing plate 28D is attached to the
swing head 66 through an air cylinder or the like, so that the
dressing plate 28D is capable of being vertically moved and pressed
against the polishing table 12, separately from the top rings
16.
[0104] In this apparatus, when six semiconductor wafers W are
polished simultaneously, by pressing the dressing plate 28D
constituting a dresser against the polishing surface 10 under a
given pressure, the amount of material removed from the polishing
surface 10 is uniformized over the entire polishing surface.
Particularly, in the case where the polishing surface 10 comprises
an abrading plate, i.e., a fixed abrasive plate, the shaping
process of the surface of the abrading plate may be omitted. In the
embodiment, although the dressing plate 28D is supported by the
swing head 66, the dressing plate 28D may be supported by the top
ring support assembly 18 shown in FIGS. 1 and 6.
[0105] FIGS. 10A and 10B show a polishing apparatus according to
still another embodiment. In this embodiment, six top rings 16 are
provided on the swing head 66 shown in FIG. 8. Further, a
ring-shaped dresser 28E (dressing ring) is provided on the outer
peripheral portion of each of the top rings 16. In this embodiment,
the dresser 28E is attached to the top ring 16 through a film (not
shown in the drawing) having a desired elasticity. The dresser 28E
may be supported by a spring or an actuator such as an air
cylinder.
[0106] According to this embodiment, by a relatively simple
structure of the dresser, areas on the polishing surface 10 where
dressing is required can be reliably dressed by utilizing rotation
of the top ring 16. The dresser 28E may have such a structure that
the dresser 28E is not corotated with the top ring 16. Also in this
embodiment, the dressers 28E may be supported by the top ring
support assembly 18 shown in FIGS. 1 and 6.
[0107] FIGS. 11A and 11B shows a polishing apparatus according to
still another embodiment of the present invention. In this
embodiment, six top rings 16 are provided on the swing head 66
shown in FIG. 8, and six dressers 28F are provided between adjacent
top rings 16, so as to extend radially. The dresser 28F comprises a
rod-like member (dressing rod) or a plate-like member (dressing
plate). The dressers 28F are integrally attached to a single
attachment member (not shown in the drawing), or are individually
attached to the swing head 66 through actuators such as air
cylinders. The basic operation of the polishing apparatus in FIGS.
11A and 11B is the same as that of the polishing apparatus in FIGS.
9A and 9B. The dressers 28F may be supported by the top ring
support assembly 18 shown in FIGS. 1 and 6.
[0108] FIG. 12 shows a polishing apparatus according to still
another embodiment of the present invention. In this embodiment, a
support member 64 having a diameter substantially equal to the
radius of the polishing table 12 is provided on the swing head 66
shown in FIG. 8, and three top rings 16 are provided on the support
member 64. Further, a dresser 28G having a dressing surface with a
diameter substantially equal to the radius of the polishing table
12 is swingably provided adjacent to the support member 64. In this
embodiment, a pusher 24 is disposed adjacent to the polishing table
12, and the top ring 16 is movable over the pusher 24 by rotation
of the swing head 66 for thereby replacing the semiconductor wafer
W with a new one.
[0109] According to this embodiment, an initial polishing of the
semiconductor wafer is conducted at a position of the top ring 16a
because the top ring 16a is closest to the dresser 28G, a secondary
polishing of the semiconductor wafer is conducted at the position
of the top ring 16b, and a finish polishing of the semiconductor
wafer is conducted at a position of the top ring 16c, because a
position of the top ring 16c is farthest from the dresser 28G. That
is, by rotating the support member 64 properly, the polishing
process from the initial polishing to the finish polishing can be
performed on the single polishing table.
[0110] As described above, according to the present invention, when
workpieces such as semiconductor wafers are polished by utilizing a
polishing surface efficiently, even if a deteriorating rate of the
polishing surface is high, the workpieces can be efficiently
polished to a high degree of flatness while forming a good
polishing surface at all times and regenerating the polishing
surface by dressing. Therefore, throughput per unit time and unit
installation area in a clean room requiring an expensive operating
cost can be improved.
[0111] Although certain preferred embodiments of the present
invention have been shown and described in detail, it should be
understood that various changes and modifications may be made
therein without departing from the scope of the appended
claims.
* * * * *