U.S. patent application number 10/664156 was filed with the patent office on 2004-04-15 for polishing apparatus.
Invention is credited to Ishii, You, Kimura, Norio, Tateyama, Yoshikuni.
Application Number | 20040072512 10/664156 |
Document ID | / |
Family ID | 14179120 |
Filed Date | 2004-04-15 |
United States Patent
Application |
20040072512 |
Kind Code |
A1 |
Kimura, Norio ; et
al. |
April 15, 2004 |
Polishing apparatus
Abstract
A polishing apparatus has a turntable with a polishing cloth
attached thereto and a top ring for holding and pressing a
workpiece to be polished against the polishing cloth under a
certain pressure. The polishing apparatus also has a first dressing
unit having a contact-type dresser for dressing the polishing cloth
by bringing the contact-type dresser in contact with the polishing
cloth, and a second dressing unit having a noncontact-type dresser
for dressing the polishing cloth with a fluid jet applied therefrom
to the polishing cloth. The contact-type dresser comprises a
diamond dresser or an SiC dresser.
Inventors: |
Kimura, Norio;
(Fujisawa-shi, JP) ; Ishii, You; (Yokohama-shi,
JP) ; Tateyama, Yoshikuni; (Hiratsuka-shi,
JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
14179120 |
Appl. No.: |
10/664156 |
Filed: |
September 17, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10664156 |
Sep 17, 2003 |
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09622638 |
Nov 8, 2000 |
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6645053 |
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09622638 |
Nov 8, 2000 |
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PCT/JP99/01543 |
Mar 26, 1999 |
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Current U.S.
Class: |
451/56 |
Current CPC
Class: |
B24B 53/02 20130101;
B24B 53/017 20130101 |
Class at
Publication: |
451/056 |
International
Class: |
B24B 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 26, 1998 |
JP |
10-96971 |
Claims
What is claimed is:
1. A method of polishing a workpiece in a polishing apparatus,
comprising: conditioning a polishing surface by a contact-type
dresser for initial conditioning before starting using said
polishing surface; polishing a workpiece by bringing said workpiece
into contact with said polishing surface after said conditioning;
and dressing said polishing surface after said polishing by a
noncontact-type dresser for removing ground-off particles of said
workpiece.
2. A method according to claim 1, wherein said noncontact-type
dresser and said contact-type dresser are provided in said
polishing apparatus.
3. A method according to claim 1, wherein said noncontact-type
dresser comprises a plurality of fluid jet nozzles for ejecting
fluid jets.
4. A method according to claim 3, wherein the pressure of each of
said nozzles is variable.
5. A method according to claim 1, wherein said contact-type dresser
comprises a diamond dresser.
6. A method according to claim 1, wherein said polishing surface is
dressed by said contact-type dresser before said dressing of said
polishing surface by said noncontact-type dresser.
7. A method according to claim 1, wherein said noncontact-type
dresser is angularly movable to a standby position located
outwardly of said polishing surface.
8. A method according to claim 7, wherein said contact-type dresser
is angularly movable to a standby position located outwardly of
said polishing surface.
9. A method of polishing workpieces in a polishing apparatus,
comprising: attaching a member having a polishing surface to a
table; conditioning said polishing surface by a contact-type
dresser for initial conditioning before starting using said
polishing surface; polishing workpieces repeatedly by bringing each
of said workpieces into contact with said polishing surface after
said conditioning while supplying an abrasive liquid in said
polishing; and dressing said polishing surface between said
polishing of said workpieces by a noncontact-type dresser for
removing ground-off particles of said workpieces.
10. A method according to claim 9, further comprising holding said
each of said workpieces by a vacuum.
11. A method according to claim 9, wherein said noncontact-type
dresser comprises a plurality of fluid jet nozzles for ejecting
fluid jets.
12. A method according to claim 1 wherein the pressure of each of
said nozzles is variable.
13. A method according to claim 9, wherein said contact-type
dresser comprises a diamond dresser.
14. A method according to claim 9, wherein said polishing surface
is dressed by said contact-type dresser before said dressing of
said polishing surface by said noncontact-type dresser.
15. A method of polishing a workpiece in a polishing apparatus,
comprising: attaching a member having a polishing surface to a
table; conditioning said polishing surface for initial conditioning
before starting using said polishing surface; polishing a workpiece
by bringing said workpiece into contact with said polishing surface
after said conditioning; and dressing said polishing surface after
said polishing for removing ground-off particles of said workpiece.
Description
[0001] This application is a divisional application of Ser. No.
09/622,638, filed Nov. 8, 2000, which is a national stage
application of International Application Serial No. PCT/JP99/01543,
filed Mar. 26, 1999.
TECHNICAL FIELD
[0002] The present invention relates to a polishing apparatus for
polishing a workpiece, such as a semiconductor wafer, to a planar
finish, especially to a device pattern on the surface of the
semiconductor wafer by bringing the surface of the semiconductor
wafer in contact with a polishing cloth, and particularly to a
method of conditioning the surface of the polishing cloth attached
to a turntable in the polishing apparatus.
BACKGROUND ART
[0003] 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
interconnections is photolithography. Though the photolithographic
process can form interconnections that are at most 0.5 .mu.m wide,
it requires that surfaces 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.
[0004] It is, therefore, necessary to make the surfaces of
semiconductor wafers flat for photolithography. One customary way
of flattening the surfaces of semiconductor wafers is to polish
them with a polishing apparatus, and such a process is called
Chemical Mechanical Polishing (CMP) in which the semiconductor
wafers are chemically and mechanically polished while supplying an
abrasive liquid comprising abrasive grains and a chemical solution,
such as alkaline solution.
[0005] In the polishing apparatus for polishing the surface of a
semiconductor wafer, especially a device pattern on the upper
surface of the semiconductor wafer, to a planar finish, as a
polishing cloth attached to a turntable, a nonwoven fabric
polishing cloth has heretofore been employed.
[0006] Higher levels of integration achieved in recent years for
ICs and LSI circuits demand smaller steps or surface irregularities
on the polished surface of the semiconductor wafer. In order to
meet such a demand, it has been proposed to employ a polishing
cloth made of a hard material such as polyurethane foam.
[0007] After the semiconductor wafers are contacted with the
polishing cloth and polished by rotating the turntable and the top
ring which holds the semiconductor wafer, the polishing capability
of the polishing cloth is gradually deteriorated due to a deposit
of abrasive grains and ground-off particles of the semiconductor
material, and due to changes in the characteristics of the
polishing cloth. Therefore, if the same polishing cloth is used to
repeatedly polish semiconductor wafers, the polishing rate of the
polishing apparatus is lowered, and the polished semiconductor
wafers tend to suffer polishing irregularities. Therefore, it has
been customary to condition the polishing cloth according to a
process called "dressing" for recovering the surface of the
polishing cloth before, during or after polishing.
[0008] There are basically two types of dressing processes, one of
which is a contact-type dressing process in which a brush or a
diamond dresser is brought into contact with a polishing cloth and
rubs the polishing cloth, and the other of which is a
noncontact-type dressing process in which a fluid jet of water or
gas is applied under high pressure to the surface of the polishing
cloth.
[0009] In the conventional polishing apparatus, either a dressing
unit comprising a brush or a diamond dresser, or a dressing unit
employing a fluid jet has been incorporated therein, depending on
the properties of the polishing cloth.
[0010] It has been found that when a new polishing cloth is used,
it needs to be dressed by a brush or a diamond dresser for initial
conditioning, and while the polishing cloth is being used in a
polishing process, it needs to be dressed by a fluid jet to remove
an aggregate of abrasive slurry or ground-off particles of the
semiconductor material therefrom. Unless the polishing cloth is
dressed by the fluid jet, the polished surface of the semiconductor
wafer is liable to be scratched, resulting in a poor yield of
properly polished semiconductor wafers. For the above reasons,
these two dressing units are required to be replaced with each
other, when necessary, in the conventional polishing apparatus.
Such selective installing and replacing work has been tedious and
time-consuming, and is liable to lower the throughput of the
semiconductor wafers.
DISCLOSURE OF INVENTION
[0011] It is therefore an object of the present-invention to
provide a polishing apparatus which incorporates both a
contact-type dressing unit having a brush or a diamond dresser and
a noncontact-type dressing unit employing a fluid jet.
[0012] Another object of the present invention is to provide a
method of conditioning the surface of a polishing cloth attached to
a turntable in such a polishing apparatus.
[0013] According to one aspect of the present invention, there is
provided a polishing apparatus comprising a turntable with a
polishing cloth attached thereto, a top ring for holding and
pressing a workpiece to be polished against the polishing cloth
under a certain pressure, a first dressing unit having a
contact-type dresser for dressing the polishing cloth by bringing
the contact-type dresser in contact with the polishing cloth, and a
second dressing unit having a noncontact-type dresser for dressing
the polishing cloth with a fluid jet applied thereto.
[0014] According to another aspect of the present invention, there
is provided a method of conditioning a polishing cloth attached to
a turntable for polishing a workpiece. The method comprises
dressing the polishing cloth with a first dressing unit having a
contact-type dresser as initial conditioning when the polishing
cloth starts to be used, and dressing the polishing cloth with a
second dressing unit having a noncontact-type dresser between
polishing processes, each for polishing the workpiece.
[0015] According to still another aspect of the present invention,
there is provided a method of conditioning a polishing cloth
attached to a turntable for polishing a workpiece. The method
comprises dressing the polishing cloth with a first dressing unit
having a contact-type dresser as initial conditioning when the
polishing cloth stalls to be used, and dressing the polishing cloth
first with the first dressing unit and then with a second dressing
unit having a noncontact-type dresser between polishing processes,
each for polishing the workpiece.
[0016] The polishing apparatus is equipped with both the
contact-type dressing unit, such as a diamond dresser, and the
noncontact-type dressing unit, such as a fluid jet dresser.
Therefore, it is not necessary to replace these contact-type and
noncontact-type dressing units with each other on the polishing
apparatus, but the contact-type and noncontact-type dressing units
may be combined to carry out a desired pattern of dressing
processes to dress or condition the polishing cloth.
[0017] 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 a preferred embodiment of the present
invention by way of example.
BRIEF DESCRIPTION OF DRAWINGS
[0018] FIG. 1 is a plan view of a polishing apparatus according to
the present invention;
[0019] FIG. 2 is an elevational view, partly in cross section,
taken along line II-II of FIG. 1;
[0020] FIG. 3A is a bottom view of a diamond dresser in a first
dressing unit incorporated in the polishing apparatus;
[0021] FIG. 3B is a cross-sectional view taken along line a-a of
FIG. 3A;
[0022] FIG. 3C is an enlarged view of an encircled area b in FIG.
3B;
[0023] FIG. 4 is an elevational view of a second dressing unit
comprising a fluid jet dresser incorporated in the polishing
apparatus; and
[0024] FIGS. 5A and 5B are timing charts of different patterns of
polishing and dressing sequences carried out by the polishing
apparatus.
DETAILED DESCRIPTION OF THE INVENTION
[0025] Next, a polishing apparatus according to the present
invention will be described with reference to the drawings.
[0026] As shown in FIGS. 1 and 2, a polishing apparatus according
to the present invention comprises a turntable 20 and a top ring
unit 4 having a top ring 3 for holding a semiconductor wafer 2 to
be polished and pressing the semiconductor wafer 2 against the
turntable 20. The turntable 20 is coupled to a motor 21 by a
vertical shaft, and rotatable about the vertical shaft. A polishing
cloth 5, such as IC-1000 manufactured by Rodel, Inc., is attached
to the tipper surface of the turntable 20.
[0027] A pusher 40 is positioned on one side of the turntable 20
adjacent to the top ring unit 4. The top ring unit 4 is angularly
movable in a horizontal plane to move the top ring 3 between a
transfer position above the pusher 40 where the semiconductor wafer
2 is transferred to and from the pusher 40, a polishing position
over the turntable 20, and a standby position off the turntable 20.
The top ring 3 is coupled to a motor and a lifting/lowering
cylinder (not shown). The top ring 3 is vertically movable by the
lifting/lowering cylinder and is also rotatable about its own axis
by the motor as indicated by the arrows (see FIG. 2). When the top
ring 3 is lowered toward the turntable 20, the top ring 3 presses
the semiconductor wafer 2 against the polishing cloth 5 on the
turntable 20 under a predetermined pressure. The top ring 3 has a
holding mechanism (not shown) for holding the semiconductor wafer 2
by its lower surface under a vacuum. A guide ring 6 is mounted on a
lower outer circumferential surface of the top ring 3, whereby the
semiconductor wafer 2 is retained against removal from the lower
surface of the top ring 3. An abrasive liquid containing abrasive
grains is supplied to the polishing cloth 5 on the turntable 20 by
an abrasive liquid supply nozzle (not shown) which is positioned
above the turntable 20.
[0028] The polishing apparatus also has a first dressing unit 11
having a contact-type dresser 10, and a second dressing unit 16
having a noncontact-type dresser comprising a plurality of water
jet nozzles 15. The first dressing unit 11, which is positioned
diametrically opposite to the top ring unit 4 and the pusher 40
across the turntable 20, is angularly movable in a horizontal plane
between a dressing position over the turntable 20 and a standby
position off the turntable 20. As shown in FIG. 2, the dresser 10
is connected to a motor 17 and a lifting/lowering cylinder 18. The
dresser 10 is vertically movable by the lifting/lowering cylinder
18 and is also rotatable about its own axis by the motor 17 as
indicated by the arrows (see FIG. 2).
[0029] FIGS. 3A, 3B, and 3C show in detail the dresser 10 of the
first dressing unit 11. As shown in FIGS. 3A, 3B and 3C, the
dresser 10 comprises a circular disk-shaped dresser body 12 having
an annular projection 12a extending along a lower circumferential
edge thereof and having a predetermined radial width. The dresser
10 will also be referred to as a diamond dresser 10. The dresser 10
has an electrodeposited diamond ring 13 which comprises fine grains
of diamond electrodeposited on the lower surface of the annular
projection 12a. Specifically, the electrodeposited diamond ring 13
is produced by attaching fine grains of diamond to the lower
surface of the annular projection 12a and then plating the lower
surface of the annular projection 12a with nickel for thereby
fixing the fine grains of diamond with a plated nickel layer.
[0030] In operation, while the turntable 20 and the dresser 10 are
rotated relative to each other, and a dressing liquid such as pure
water or an abrasive liquid is supplied from a nozzle (not shown)
to a substantially central region of the polishing cloth 5, the
lower surface of the electrodeposited diamond ring 13 is held
against the upper surface of the polishing cloth 5 to scrape off a
thin layer of the polishing cloth 5, thereby dressing the polishing
cloth 5.
[0031] The dresser body 12 has a diameter of 250 mm, and the
electrodeposited diamond ring 13 oil the lower end of the annular
projection 12a has a radial width of 6 mm. As shown in FIG. 3A, the
electrodeposited diamond ring 13 comprises a plurality of equal
arcuate sectors (eight in the illustrated embodiment). The diameter
of the dresser body 12 is greater than the diameter of the
semiconductor wafer 2 to be polished. When the semiconductor wafer
2 is polished, therefore, the dressed surface of the polishing
cloth 5 provides an extra margin with respect to the polished
surface of the semiconductor wafer 2 in both radial inward and
outward directions of the turntable 20. The dresser 10 may be
replaced with an SiC dresser having a ring of sectors made of
silicon carbide. The SiC dresser has a structure identical to the
structure shown in FIGS. 3A-3C, and has on the surfaces of its
sectors a number of pyramidal projections each having a height of
about several tens of .mu.m.
[0032] FIG. 4 shows structural details of the second dressing unit
16. As shown in FIG. 4, the second dressing unit 16 comprises an
array of six water jet nozzles 15 positioned over the polishing
cloth 5 and equally spaced radially of the polishing cloth 5. The
water jet nozzles 15 are fixedly mounted oil a water jet nozzle arm
22 having a liquid passage 22a defined therein. Pure water supplied
from a pure water source (not shown) is pressurized by a pump 26
and supplied through a tube 23 and the liquid passage 22a to the
water jet nozzles 15, from which pure water jets are ejected
downward toward the polishing cloth 5.
[0033] The water jet nozzles 15 are positioned and oriented to
apply the pure water jets ejected therefrom to an area of the
polishing cloth 5 which is used to polish the semiconductor wafer
2, i.e., an area of the polishing cloth 5 against which the
semiconductor wafer 2 is pressed so as to be polished. The water
jet nozzle arm 22 is fixed in a position above the polishing cloth
5 by a vertical support 22b. However, the water jet nozzle arm 22
may be angularly movable in a horizontal plane about the vertical
axis of the vertical support 22b for fine positional adjustment
thereof and/or for a standby position located radially outward of
the polishing cloth 5 for maintenance thereof.
[0034] The pure water flowing through the water jet nozzle arm 22
is kept at a predetermined pressure by a controller (not shown) for
the pump 26. The water jet nozzles 15 are identical in structure to
each other, so that they eject respective water jets under
substantially the same pressure at substantially the same rate. The
pressure of the ejected water jets can be maintained in the range
of 5 to 30 kg/cm.sup.2 by controlling the pump 26.
[0035] When the polishing cloth 5 is dressed by the second dressing
unit 16, the turntable 20 and hence, the polishing cloth 5, are
rotated to thereby apply the water jets ejected from the water jet
nozzles 15 to the entire surface of the polishing cloth 5. Since
the polishing cloth 5 is held in contact with the water jets for a
period of time which is progressively shorter in the radially
outward direction, the dressing effect on the polishing cloth 5
which is caused by the water jets may vary depending on the radial
position on the polishing cloth 5. Therefore, in order to
uniformize the dressing effect on the polishing cloth 5, the number
of water jet nozzles 15 may be increased in the radially outward
direction, or the water jet nozzles 15 may eject water jets at a
progressively higher speed in the radially outward direction.
Alternatively, the distance between the nozzle outlet and the
polishing cloth 5 may vary from nozzle to nozzle. Further, the
pressure and the speed at which the water jet is ejected may be
made variable at each of the water jet nozzles 15.
[0036] Polishing and dressing processes which are carried out by
the polishing apparatus shown in FIGS. 1 through 4 will be
described with reference to FIGS. 5A and 5B. FIGS. 5A and 5B are
timing charts of different patterns of polishing and dressing
sequences carried out by the polishing apparatus.
[0037] According to the pattern of polishing and dressing sequences
shown in FIG. 5A, when the polishing cloth 5 starts to be used, it
is first dressed by the diamond dresser 10 for initial
conditioning. Thereafter, a semiconductor wafer 2 is polished using
the dressed polishing cloth 5. Between polishing processes, the
polishing cloth 5 is dressed by the water jet nozzles 15 with water
jets ejected therefrom.
[0038] According to the pattern of polishing and dressing sequences
shown in FIG. 5B, when the polishing cloth 5 starts to be used
(i.e., before it is used for polishing), it is first dressed by the
diamond dresser 10 for initial conditioning. Thereafter, a
semiconductor wafer 2 is polished using the dressed polishing cloth
5. Between polishing processes, the polishing cloth 5 is dressed in
two steps, i.e., first by the diamond dresser 10 and then by the
water jet nozzles 15 with water jets ejected therefrom.
[0039] As shown in FIGS. 5A and 5B, according to the polishing
apparatus of the present invention, after initial conditioning of
the polishing cloth 5 by the diamond dresser 10, a polishing
process of the semiconductor wafer is carried out, and after
completing the polishing process, dressing of the polishing cloth 5
by the wafer jet is carried out. Thereafter, polishing process is
candied out again. Further, between polishing processes, dressing
of the polishing cloth 5 by the diamond dresser and the water jet
may be combined.
[0040] In the illustrated embodiment, the contact-type dresser of
the first dressing unit 11 comprises the diamond dresser 10.
However, the diamond dresser may be replaced with a brush dresser.
Furthermore, pure water is used as the dressing liquid in the first
dressing unit 11 and also as the water jets in the second dressing
unit 16. However, chemicals such as alkaline liquid or
surface-active agent may be used in the first and second dressing
units 11 and 16 for performing a chemical dressing action in
addition to a mechanical dressing action.
[0041] Inasmuch as the polishing apparatus according to the present
invention is equipped with both the first dressing unit 11 having
the contact-type dresser comprising the diamond dresser 10 and the
second dressing unit 16 having the noncontact-type dresser
comprising the water jet nozzles 15, it is not necessary to replace
two dressing units as in the conventional polishing apparatus, and
the two dressing units 11, 16 may be combined to carry out a
desired pattern of dressing processes. If the polishing apparatus
is applied to the fabrication of semiconductor devices, then
semiconductor devices can be manufactured in a high yield with high
productivity.
[0042] Although a certain preferred embodiment of the present
invention has 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.
INDUSTRIAL APPLICABILITY
[0043] The present invention relates to a polishing apparatus for
polishing a workpiece such as a semiconductor wafer to a planar
finish, and is preferably utilized in manufacturing semiconductor
devices.
* * * * *