U.S. patent application number 10/671502 was filed with the patent office on 2004-07-01 for polishing method for semiconductor device, method for fabricating semiconductor device and polishing system.
This patent application is currently assigned to MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.. Invention is credited to Hamanaka, Masashi, Ito, Fumitaka, Shirakashi, Eigo.
Application Number | 20040127148 10/671502 |
Document ID | / |
Family ID | 32652661 |
Filed Date | 2004-07-01 |
United States Patent
Application |
20040127148 |
Kind Code |
A1 |
Hamanaka, Masashi ; et
al. |
July 1, 2004 |
Polishing method for semiconductor device, method for fabricating
semiconductor device and polishing system
Abstract
A method for fabricating a semiconductor device, which includes
the process step of polishing a substrate using CMP. To suppress
the generation of scars and scratches on a wafer surface, in the
polishing process, a tube-type slurry supply pump 15 is used to
supply slurry. Then, in the tube-type slurry supply pump 15, a
vinyl chloride type tube is used as a tube 12 for supplying a
slurry.
Inventors: |
Hamanaka, Masashi; (Nara,
JP) ; Shirakashi, Eigo; (Kyoto, JP) ; Ito,
Fumitaka; (Kyoto, JP) |
Correspondence
Address: |
Jack Q. Lever, Jr.
McDERMOTT, WILL & EMERY
600 Thirteenth Street, N.W.
Washington
DC
20005-3096
US
|
Assignee: |
MATSUSHITA ELECTRIC INDUSTRIAL CO.,
LTD.
|
Family ID: |
32652661 |
Appl. No.: |
10/671502 |
Filed: |
September 29, 2003 |
Current U.S.
Class: |
451/60 |
Current CPC
Class: |
B24B 37/04 20130101;
B24B 57/02 20130101 |
Class at
Publication: |
451/060 |
International
Class: |
B24B 007/22 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 25, 2002 |
JP |
2002-373582 |
Claims
What is claimed is:
1. A polishing method which is part of a method for fabricating a
semiconductor device, the fabrication method including the process
step of polishing a substrate using CMP, wherein in the polishing
process step, a tube-type slurry supply pump is used for supplying
a slurry, and wherein in the tube-type slurry supply pump, a vinyl
chloride type tube is used as a tube for supplying the slurry.
2. The polishing method of claim 1, wherein the vinyl chloride type
tube substantially does not contain fine particles for reinforcing
the strength of the tube.
3. A polishing method which is part of a method for fabricating a
semiconductor device, the fabrication method including the process
step of polishing a substrate using CMP, wherein in the polishing
process step, a tube-type slurry supply pump is used for supplying
a slurry, and wherein in the tube-type slurry supply pump, a tube
including the inner surface formed of a vinyl chloride type tube
and the outer surface formed of a rubber type tube is used as a
tube for supplying the slurry.
4. The polishing method of claim 3, wherein the vinyl chloride type
tube substantially does not contain fine particles for reinforcing
the strength of the tube.
5. A polishing method which is part of a method for fabricating a
semiconductor device, the fabrication method including the process
step of polishing a substrate using CMP, wherein in the polishing
process step, a tube-type slurry supply pump is used for supplying
a slurry, and wherein a filter for removing aggregate particles and
a foreign substance contained in the slurry is disposed downstream
of the slurry supply pump.
6. The polishing method of claim 5, wherein in the tube-type slurry
supply pump, a tube in which at least the inner surface is formed
of a vinyl chloride material is used as a tube for supplying the
slurry.
7. A polishing method which is part of a method for fabricating a
semiconductor device, the fabrication method including the process
step of polishing a substrate using CMP, wherein in the polishing
process step, a tube-type slurry supply pump is used for supplying
a slurry, and wherein in the tube-type slurry supply pump, a tube
which substantially does not contain fine particles for reinforcing
the strength of the tube is used as a tube for supplying the
slurry.
8. The polishing method of claim 7, wherein the tube is a vinyl
chloride type tube or a silicon rubber type tube.
9. A method for fabricating a semiconductor device, comprising the
polishing method of any one of claims 1 through 8.
10. A system for polishing a substrate using CMP, comprising: a CMP
apparatus for polishing the substrate; and a tube-type slurry
supply pump for supplying a slurry during polishing, wherein a tube
for the tube-type slurry supply pump is a tube in which at least
the inner surface is formed of a vinyl chloride material.
11. The polishing system of claim 10, wherein the tube has a
two-layer structure, and wherein the inner surface of the tube is
formed of a vinyl chloride material and the outer surface of the
tube is formed of a rubber material.
12. A system for polishing a substrate using CMP, comprising: a CMP
apparatus for polishing the substrate; a slurry supply apparatus
for supplying a slurry to the CMP apparatus; a pipe for connecting
the slurry supply apparatus and the CMP apparatus; and a tube-type
slurry supply pump disposed in part of the pipe, wherein a filter
for removing at least aggregate particles or a foreign substance
contained in the slurry is disposed between the tube-type slurry
supply pump and the CMP apparatus.
13. The polishing system of claim 12, wherein a tube for the
tube-type slurry supply pump is a tube in which at least the inner
surface is formed of a vinyl chloride material.
14. A system for polishing a substrate using CMP, comprising: a CMP
apparatus for polishing the substrate; and a tube-type slurry
supply pump for supplying a slurry during polishing, wherein a tube
for the tube-type slurry supply pump substantially does not contain
fine particles for reinforcing the strength of the tube.
Description
BACKGROUND OF THE INVENTION
[0001] In recent years, as the size of semiconductor devices has
been reduced, improvement of the flatness of interlevel insulating
films has become essential to ensuring DOF (depth of focus) in
lithography processes. This requires planarization with a CMP
(chemical mechanical polishing) technique. Also, a Cu interconnect
is desired to be used in order to reduce interconnect resistance.
In forming a Cu interconnect, polishing using CMP is necessary
because dry-etching is difficult to be performed.
[0002] In CMP, a wafer surface is brought into direct contact with
a polishing cloth to perform polishing. Thus, scars or scratches
are quite possibly generated, and therefore reducing scratches is
the most important challenge in CMP. Up until now, several measures
for reducing scratches have been proposed. Specifically, scratching
on a wafer surface is prevented by breaking abrasive, aggregate
particles generated in a slurry into pieces with an ultrasonic wave
or removing aggregate particles with a filter (see, e.g., Japanese
Unexamined Patent Publication No. 2001-150346).
[0003] FIG. 1 is a diagram illustrating a slurry supply apparatus
disclosed in the above-described publication. The slurry supply
apparatus of FIG. 1 includes a slurry supply unit 101, a slurry
circulation line 102 connected to the inlet and outlet of the
slurry supply unit 101 and an ultrasonic-wave generator 103. A
slurry in the slurry circulation line 102 is circulated by a first
pump 106. The ultrasonic-wave generator 103 for irradiating the
slurry with an ultrasonic wave is connected to the slurry
circulation line 102.
[0004] The slurry circulation line 102 and a CMP apparatus 105 are
connected with each other by a pipe 110. Along the pipe 110, a
filter 104 for filtering condensed slurry particles is provided.
Moreover, in the pipe 110, a second pump 108 for drawing a slurry
from the slurry circulation line 102 and supplying it to the CMP
apparatus 105 is provided. Note that a valve 107 for adjusting the
amount of the slurry to be supplied to the CMP apparatus 105 while
controlling slurry supply to the CMP apparatus and stop of the
slurry supply is provided between the filter 104 and the second
pump.
[0005] In the slurry supply apparatus shown in FIG. 1, an
ultrasonic-wave generator 103 is provided on the slurry circulation
line 102 and the slurry circulating in the slurry circulation line
102 is irradiated with an ultrasonic wave. Thus, condensation of
slurry particles can be prevented. That is to say, although fine
silica aggregate particles contained in the slurry are tend to link
together to form large aggregate particles in the slurry
circulation line 102, linked particles in large aggregate particles
can be separated by an ultrasonic wave generated by the
ultrasonic-wave generator 103. Thus, a slurry containing fine
particles can be stably supplied to the CMP apparatus 105.
Moreover, dusts or the like contained in the slurry can be removed
by the filter 104 so that a clean slurry can be supplied to the CMP
apparatus 105. Furthermore, the slurry contains no large, aggregate
particle, so that the life of the filter 104 can be improved.
SUMMARY OF THE INVENTION
[0006] In the above-described publication, it is described that
condensation of slurry particles can be prevented with the
ultrasonic-wave generator 103 shown in FIG. 1. However, the present
inventors conducted experiments to find that even if the
ultrasonic-wave generator 103 is provided, scars and scratches are
generated on a wafer surface in CMP. Moreover, the present
inventors also found that even if a filter is provided, there are
cases where the generation of scars and scratches on a wafer
surface can not be prevented.
[0007] As has been described, with reduction in the size of
semiconductor devices, CMP has become an essential technique.
Therefore, it is very difficult to determine not to use a CMP
technique because scars and scratches are very possibly generated
during CMP.
[0008] In view of the above-described problems, the present
invention has been devised and it is therefore a main object of the
present invention to provide a polishing system in which the
generation of scars and scratches on a wafer surface is suppressed.
Another object of the present invention is to provide a CMP
technique and a polishing method for a semiconductor device in
which the generation of scars and scratches on a wafer surface is
suppressed and also to provide a method for fabricating a
semiconductor device including the polishing method.
[0009] A first polishing method for a semiconductor device in
accordance with the present invention is a polishing method which
is part of a method for fabricating a semiconductor device, the
fabrication method including the process step of polishing a
substrate using CMP, and characterized in that in the polishing
process step, a tube-type slurry supply pump is used for supplying
a slurry, and in the tube-type slurry supply pump, a vinyl chloride
type tube is used as a tube for supplying the slurry.
[0010] It is preferable that the vinyl chloride type tube
substantially does not contain fine particles for reinforcing the
strength of the tube.
[0011] A second polishing method for a semiconductor device in
accordance with the present invention is a polishing method which
is part of a method for fabricating a semiconductor device, the
fabrication method including the process step of polishing a
substrate using CMP, and characterized in that in the polishing
process step, a tube-type slurry supply pump is used for supplying
a slurry, and in the tube-type slurry supply pump, a tube including
the inner surface formed of a vinyl chloride type tube and the
outer surface formed of a rubber type tube is used as a tube for
supplying the slurry.
[0012] It is preferable that the vinyl chloride type tube
substantially does not contain fine particles for reinforcing the
strength of the tube.
[0013] A third polishing method for a semiconductor device in
accordance with the present invention is a polishing method which
is part of a method for fabricating a semiconductor device, the
fabrication method including the process step of polishing a
substrate using CMP, characterized in that in the polishing process
step, a tube-type slurry supply pump is used for supplying a
slurry, and a filter for removing aggregate particles and a foreign
substance contained in the slurry is disposed downstream of the
slurry supply pump.
[0014] In the tube-type slurry supply pump, a tube in which at
least the inner surface is formed of a vinyl chloride material may
be used as a tube for supplying the slurry.
[0015] A fourth polishing method for a semiconductor device in
accordance with the present invention is a polishing method which
is part of a method for fabricating a semiconductor device, the
fabrication method including the process step of polishing a
substrate using CMP, and characterized in that in the polishing
process step, a tube-type slurry supply pump is used for supplying
a slurry, and in the tube-type slurry supply pump, a tube which
substantially does not contain fine particles for reinforcing the
strength of the tube is used as a tube for supplying the
slurry.
[0016] In an embodiment of the present invention, the tube is a
vinyl chloride type tube or a silicon rubber type tube.
[0017] A method for fabricating a semiconductor device in
accordance with the present invention includes any one of the
polishing methods.
[0018] A first polishing system in accordance with the present
invention is a system for polishing a substrate using CMP and
includes: a CMP apparatus for polishing the substrate; and a
tube-type slurry supply pump for supplying a slurry during
polishing. In the system, a tube for the tube-type slurry supply
pump is a tube in which at least the inner surface is formed of a
vinyl chloride material.
[0019] In another embodiment of the present invention, the tube has
a two-layer structure, the inner surface of the tube is formed of a
vinyl chloride material and the outer surface of the tube is formed
of a rubber material.
[0020] A second polishing system in accordance with the present
invention is a system for polishing a substrate using CMP and
included: a CMP apparatus for polishing the substrate; a slurry
supply apparatus for supplying a slurry to the CMP apparatus; a
pipe for connecting the slurry supply apparatus and the CMP
apparatus; and a tube-type slurry supply pump disposed in part of
the pipe. In the system, a filter for removing at least aggregate
particles or a foreign substance contained in the slurry is
disposed between the tube-type slurry supply pump and the CMP
apparatus.
[0021] It is preferable that a tube for the tube-type slurry supply
pump is a tube in which at least the inner surface is formed of a
vinyl chloride material.
[0022] A third polishing system in accordance with the present
invention is a system for polishing a substrate using CMP and
includes: a CMP apparatus for polishing a substrate; and a
tube-type slurry supply pump for supplying a slurry during
polishing. In the system, a tube for the tube-type slurry supply
pump substantially does not contain fine particles for reinforcing
the strength of the tube.
[0023] According to the present invention, in fabricating a
semiconductor device with a method including the process step of
polishing a substrate using CMP, a vinyl chloride type tube is used
as a tube for supplying a slurry in a tube-type slurry supply pump
used in the polishing process. Thus, the generation of scars and
scratches on a wafer surface can be suppressed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a diagram illustrating the configuration of a
known slurry supply apparatus.
[0025] FIG. 2 is a view illustrating an example on how a slurry is
supplied.
[0026] FIG. 3 is a view illustrating another example on how a
slurry is supplied.
[0027] FIG. 4 is an enlarged cross-sectional view partially
illustrating a tube-type slurry supply pump.
[0028] FIG. 5 is a diagram schematically illustrating the
configuration of a polishing system in accordance with a first
embodiment of the present invention.
[0029] FIG. 6 is an enlarged cross-sectional view partially
illustrating a tube-type slurry supply pump.
[0030] FIG. 7 is a view schematically illustrating the
configuration of a measurement apparatus for measuring particles
generated from a tube.
[0031] FIG. 8 is a graph showing the relationship between each tube
type and the number of released particles.
[0032] FIG. 9 is a graph showing the number of microscratches after
a tube is change to a rubber type tube or a vinyl chloride type
tube.
[0033] FIG. 10 is a graph showing product yield when a rubber type
tube and a vinyl chloride type tube are actually used.
[0034] FIG. 11 is a view illustrating a cross-sectional structure
of a tube having a two-layer structure.
[0035] FIG. 12 is a view schematically illustrating the
configuration of a polishing system in accordance with a second
embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0036] Hereinafter, embodiments of the present invention will be
described in detail with reference to the accompanying drawings.
Note that the present invention is not limited to the following
embodiments.
[0037] First, description will be made on a phenomenon in which
scars and scratches are generated on a wafer surface in performing
CMP and which the present inventors examined, before embodiments of
the present invention.
[0038] Large particles resulting from cohesion of a slurry and a
foreign substance existing in a slurry are considered to be
possible causes of the generation of scars and scratches on a wafer
surface in CMP. As measures for coping with this, a technique for
eliminating large particles in which aggregate particles are broken
into pieces so as to be fine particles and a technique for removing
large particles and a foreign substance with a filter have been
used.
[0039] FIG. 2 schematically illustrates the configuration of a
system using the former technique. Meanwhile, FIG. 3 schematically
illustrates the configuration of a system using the latter
technique.
[0040] Each of the configurations of FIGS. 2 and 3 includes a
slurry supply apparatus 1, a CMP apparatus 3 and a pipe 2 for
delivering a slurry to the CMP apparatus 3. The slurry supply
apparatus 1 is an apparatus for adjusting or buffering a slurry and
supplying the slurry to the CMP apparatus 3. Moreover, the CMP
apparatus 3 is an apparatus for polishing the surface of a
substrate (e.g., a wafer on which a semiconductor integrated
circuit has been formed) by chemical mechanical polishing (CMP) to
planarize the surface. The slurry in the pipe 2 is pushed out by a
tube-type pump 15 and then supplied to a polishing mechanism unit
of the CMP apparatus 3.
[0041] Note that in the configuration of FIG. 2, an ultrasonic-wave
generator 4 for breaking aggregate slurry particles into pieces is
provided. On the other hand, in the configuration of FIG. 3, a
filter 5 for catching aggregate slurry particles and a foreign
substance in a slurry is provided.
[0042] A polishing slurry is mixed with, for example, an oxidizer,
or merely held as a buffer in the slurry supply apparatus 1. At
this time, the slurry is, in general, intermittently stirred to
prevent precipitation of abrasive particles generated due to
polishing. However, with mechanical pressure applied, aggregation
of abrasive particles occurs, thereby generating large particles in
the slurry. Then, the slurry containing large particles is
delivered to the CMP apparatus 3 through the pipe 2 by the
tube-type pump 15.
[0043] With the configuration of FIG. 2, if large particles are
broken into pieces by irradiating the slurry with an ultrasonic
wave by the ultrasonic-wave generator 4, the slurry containing no
large particles should be supplied to the CMP apparatus 3, thus
preventing scratches on a wafer surface. On the other hand, with
the configuration of FIG. 3, if large particles and a foreign
substance in the slurry are caught by the filter 5, a slurry
containing no large particles and no foreign substance should be
supplied to the CMP apparatus 3, thus preventing scratches on a
wafer surface.
[0044] However, in both of the configurations of FIGS. 2 and 3,
actually, scratches on a wafer surface could not be completely
prevented. The present inventors, then, made the following
assumption. Although it has been considered that aggregate
particles and a foreign substance in a slurry largely cause scars
on a wafer surface, there should be some other causes of scars on
the surface.
[0045] The present inventors conducted a further examination to
find that a foreign substance generated in the CMP apparatus 3 or
the tube-pump-type slurry supply pump 15 located in the vicinity of
the CMP apparatus 3 induced scratches on a wafer surface. FIG. 4 is
an enlarged view partially illustrating the tube-type slurry supply
pump 15 shown in FIGS. 2 and 3.
[0046] As shown in FIG. 4, the tube-type slurry supply pump 15
includes a pump-body-side receiver 6 and a fluid delivery pump
roller 7. The pump-body-side receiver 6 is a member to which a tube
is pressed for delivering a slurry 10, and the fluid delivery pump
roller 7 has the function of pressing a slurry delivery tube 8 to
the pump-body-side receiver 6 and squeezing the tube to push the
slurry out. That is to say, the fluid delivery roller 7 rolls in
the direction of the arrow of FIG. 4 and thereby squeezes the tube
8 to deliver the slurry 10. Note that the slurry delivery tube 8 is
connected to the pipe 2.
[0047] As shown in FIG. 4, the tube-type pump which is provided in
the CMP apparatus 3 or in the proximity of the CMP apparatus 3 and
is used for supplying a slurry presses the slurry delivery tube 8
to the pump-body-side receiver 6 with the fluid delivery roller 7
and squeezes the tube to deliver the slurry 10. As the slurry
delivery tube 8, a rubber type tube with high mechanical strength
is used in many cases. In such a case, the rubber slurry delivery
tube 8 contains a reinforcing material for attaining elasticity.
Such reinforcement materials include particles 9 of SiO.sub.2,
Al.sub.2O.sub.3 or the like, in general. In other words, to
reinforce the mechanical strength of the tube, the rubber type tube
is made to contain the fine particles 9 of SiO.sub.2,
Al.sub.2O.sub.3 or the like. The size of the particles 9 is from
several .mu.m to several hundred .mu.m.
[0048] The slurry delivery tube 8 is pressed to the pump-body-side
receiver 6 by the fluid delivery roller 7. Thus, the particles 9 in
the tube 8 are diffused as particles 11 in the slurry 10. Then, the
slurry 10 containing the particles 9 is supplied to the CMP
apparatus shown in FIGS. 2 and 3, thus resulting in the generation
of scars and scratches on a wafer surface in polishing.
[0049] In this case, even if an ultrasonic wave is irradiated or a
filter is provided right after the slurry supply apparatus
(immediately downstream of the slurry supply apparatus), a foreign
substance generated from the tube pump can not be removed.
Accordingly, scratches can not be reduced.
[0050] Then, the present inventors have completed, based on the
above-described findings, a CMP technique which allows reduction in
scars and scratches on a wafer surface to reach the present
invention.
[0051] Hereinafter, embodiments of the present invention will be
described with reference to the accompanying drawings. In the
drawings, components with the same function are identified by the
same reference numeral for simplicity of description. Note that the
present invention is not limited to the following embodiments.
Embodiment 1
[0052] A first embodiment of the present invention will be
described with reference to FIGS. 5 and 6. FIG. 5 is a view
schematically illustrating the configuration of a polishing system
in accordance with the present invention. FIG. 6 is a partially
enlarged view schematically illustrating the cross-sectional
structure of a tube-type slurry supply pump 15.
[0053] The polishing system of FIG. 5 is a system for polishing a
substrate using CMP and includes a CMP apparatus 3 for polishing a
substrate and a tube-type slurry supply pump 15 for supplying a
slurry during polishing. The tube-type slurry supply pump 15 is
connected to a slurry supply apparatus 1 by a pipe 2.
[0054] The tube-type slurry supply pump (which will be herein
referred to as the "tube-type pump") 15 is a pump for supplying a
slurry to a polishing mechanism unit of the CMP apparatus 3. In
this embodiment, as a tube (slurry delivery tube) 12 for the
tube-type pump 15, a vinyl chloride type tube made of vinyl
chloride resin is used. The vinyl chloride type tube 12 does not
contain fine particles (SiO.sub.2, Al.sub.2O.sub.3 or the like) as
a reinforcement material which has been conventionally needed for a
rubber type tube. Accordingly, fine particles are not diffused in
the slurry 10, as shown in FIG. 6. Since there is no fine particle
in the slurry 10, a slurry containing no fine particle (i.e., no
foreign substance) is supplied to the CMP apparatus 3 of FIG. 3. As
a result, polishing can be performed without generating scars and
scratches on a wafer surface. Thus, polishing method and system for
a semiconductor device with which product yield is not reduced can
be provided.
[0055] Next, an experiment which the present inventors conducted to
confirm effects of the CMP technique of the first embodiment of the
present invention and the results of the experiment will be
described.
[0056] First, before confirming the generation of scratches on a
wafer surface due to polishing, how particles are to be generated
from a tube was examined for six types of tubes. The six types of
tubes were: four types of rubber type tubes (A through D); a type
of silicon tube (E); and a type of vinyl chloride type tube
(F).
[0057] FIG. 7 is a view schematically illustrating the
configuration of a measurement apparatus used for measuring
particles generated from the tubes. As shown in FIG. 7, a tube 40
of each type was installed to the tube-type slurry supply pump 15
and then pure water was delivered. The delivered pure water was
measured with an in-fluid-particle counter 30 connected to a
downstream region of the tube. In this manner, it has been
confirmed how particles with a size of 0.2 .mu.m or more are
generated. The results of the measurement are shown in FIG. 8.
[0058] FIG. 8 is a graph showing the number of particles (the
number of particles with a size of 0.2 .mu.m or more) released into
pure water after consecutive 12-hour deliverly of pure water. As
can be seen from FIG. 8, in the rubber type tubes which are of a
type presently used, a large quantity of particles (about 1000
particles/ml) were released into pure water even after 12 hours. On
the other hand, as for each of the vinyl chloride type tube and the
silicon tube, the number of particles released into pure water was
about 0.5 particles/ml. That is to say, the numbers of released
particles in the vinyl chloride type tube and the silicon type tube
were the level at which almost no particle was detected.
[0059] Herein, a rubber type tube which is presently used means to
be an ethylene propylene rubber tube containing ethylene propylene
terpolymer as a main component. The tube contains inorganic fillers
such as SiO.sub.2 and Al.sub.2O.sub.3. Other rubber type tubes also
contain inorganic fillers. Tubes containing inorganic fillers cause
the generation of scars and scratches on a wafer surface due to the
same mechanism.
[0060] The vinyl chloride type tube used in this embodiment is a
polyvinyl chloride (PVC) tube and contains a plasticizer and a
stabilizer. The polyvinyl chloride type tube contains no inorganic
filler and has a good resistance to wear. As for even a tube other
than vinyl chloride type tubes, as long as it contains no inorganic
filler, fine particles are not diffused in a slurry, so that the
generation of scars and scratches on a wafer surface can be
prevented.
[0061] The results shown in FIG. 8 indicate that it is possible to
reduce the number of particles by using the vinyl chloride type
tube and the silicon type tube of the six tubes. When the vinyl
chloride type tube and the silicon type tube are compared to each
other, the life of the vinyl chloride type tube is about 10 times
longer than that of the silicon type tube. Therefore, in view of
practical use, it is preferable to use the vinyl chloride type tube
as a tube for the tube-type pump 15 of this embodiment. Needless to
say, the silicon type tube can be used to perform CMP if life and
costs are not considered. Note that the vinyl chloride type tube is
advantageously at a lower price than that of the silicon type
tube.
[0062] Since a tube for the tube-type slurry supply pump has been
required to have as a long life as possible, rubber type tubes with
higher mechanical strength than those of other types of tubes have
been presently used. Moreover, rubber type tubes are low in cost
and no adverse effect resulting from rubber type tubes has been yet
reported. Therefore, rubber type tubes are still widely used
today.
[0063] As has been described, the present inventors found problems
in using a rubber type tube. Thus, in order to prevent the
generation of scars and scratches on a wafer surface, the inventors
have decided to use a tube (specifically, a vinyl chloride type
tube) which substantially does not contain fine particles for
reinforcing the strength of the tube, even if life properties of
the tube are reduced.
[0064] Next, results obtained by examining with an optical defect
inspector the number of microscratches generated on a wafer surface
after tube exchange are shown in FIG. 9. As can be seen from the
examination results of scratches on a wafer surface shown in FIG.
9, scratches on the surface of a wafer immediately after tube
exchange could be reduced from several hundred scratches per wafer
to about 10 scratches per wafer by changing a rubber type tube to a
vinyl chloride type tube.
[0065] Moreover, FIG. 10 is a graph showing product yield when the
rubber type tube and the vinyl chloride type tube were actually
used in a CMP process. That is to say, the results shown in FIG. 10
indicate the effect of improving product yield achieved by using
the vinyl chloride type tube. As can be seen from FIG. 10, actual
product yield was improved by 10%-20% at most by changing the
rubber type tube to the vinyl chloride type tube. In this
embodiment, a tube having an outer diameter of 6.35 mm and an inner
diameter of 3.18 mm was used. However, the present invention is not
limited thereto. Preferable outer and inner diameters may be
appropriately selected considering the type of a pump or the
like.
[0066] As has been described, by changing a tube to the vinyl
chloride type tube, scratches on a wafer surface can be reduced,
thus resulting in improved product yield. According to the
examinations which the present inventors conducted, it has been
confirmed that inorganic fillers are released out most at the time
when a rubber type tube is exchanged with new one. Therefore,
immediately after the rubber type tube has been exchanged with new
one, a large number of particles with a size of 0.2 .mu.m are
generated and thus the CMP apparatus can not be immediately set to
be in an operation state. In order to suppress filler release,
running has to be performed. To perform running, several days are
required and a particle check also has to be performed for several
times. Therefore, the CMP apparatus can not be immediately set to
be in an operation state.
[0067] As in this embodiment, however, if the vinyl chloride type
tube is used, the generation of particles can be suppressed even
immediately after tube exchange. Accordingly, the CMP apparatus can
be immediately set to be in an operation state. Moreover, the vinyl
chloride type tube releases far less particles than the rubber type
tube in a stable state. Therefore, use of the vinyl chloride type
tube is more advantageous than use of the rubber type tube. Thus,
it should be noted that even if the life of the vinyl chloride type
tube is shorter than that of a rubber type tube and thus the number
of tube exchanges in a predetermined period is increased, the vinyl
chloride type tube has a great significance from a technical view
point because less particles are generated even immediately after
tube exchange in the case of the vinyl chloride type tube.
[0068] With reduction in the size of semiconductor devices,
particles, scars, scratches or the like on a wafer surface, which
cause reduction in yield, have to be controlled at a finer level.
At the conventional or present level, it is required in many cases
to control particles with a size of 0.3 .mu.m or more on an oxide
film. However, it will be required to control components having a
smaller size. For example, particles with a size of about 0.2 .mu.m
are preferably controlled. The present invention has been devised
to achieve a CMP technique at a level at which particles, scars and
scratches are not detected even if a control is performed using a
measurement apparatus with higher accuracy. This target, then, has
been successfully achieved by using the vinyl chloride type tube as
the slurry delivery tube.
[0069] Note that the reason why the tube-type slurry supply pump is
used as the pump 15 for pushing the slurry out is that in addition
to the fact that this type of pump is low in cost, the pump has
high metering accuracy in supplying a slurry and less pulsating
flows. The tube-type slurry supply pump presses a tube to push the
slurry out. Thus, if a tube made of a rubber material (e.g., raw
rubber) which does not contain a reinforcement material such as
inorganic fillers is used, the mechanical strength of the tube is
so small that the tube can not be used, as it is, as a tube for the
tube-type slurry supply pump. Therefore, it is necessary to make a
rubber material contain a reinforcement material such as inorganic
fillers. In contrast, since a vinyl chloride material has
sufficient mechanical strength, it is not needed to make the vinyl
chloride material contain inorganic fillers or the like, while it
is preferable to make it contain a plasticizer to increase
flexibility.
[0070] Examples of the process step of polishing a substrate by CMP
included in a method for fabricating a semiconductor device are the
process step of forming an STI (shallow trench isolation), the
process step of planarizing an interlevel insulating film, the
process step of forming a tungsten plug or a silicon plug, the
process step of forming a damascene interconnect (e.g., the process
step of forming a Cu interconnect), and the like. With recent
reduction in the size of semiconductor devices, a Cu interconnect
technique is essential in a 0.15 .mu.m design rule or smaller (more
specifically, a 0.13 .mu.m design rule or smaller). Therefore, the
technical significance of the CMP technique in which the generation
of scars and scratches on a wafer surface is suppressed is very
important. In other words, the CMP technique of embodiments of the
present invention is particularly useful in fabricating a
semiconductor device of a 0.15 .mu.m design rule or smaller (more
specifically, a 0.13 .mu.m or smaller). Moreover, the CMP technique
of embodiments of the present invention exhibits greater effects in
fabricating a semiconductor device using a copper interconnect than
in fabricating a semiconductor device using an aluminum
interconnect.
[0071] A substrate to be polished by the CMP apparatus 3 is
typically a semiconductor wafer (a silicon wafer or an SOI
substrate) on which a semiconductor integrated circuit has been
formed. In many cases, a single or multiple layers are formed on
the semiconductor wafer. In this specification, if another layer is
formed on a substrate, the substrate and said another layer as a
whole may be called "substrate" for the purpose of convenience. As
for a semiconductor wafer on which a semiconductor integrated
circuit has been formed, even if the semiconductor wafer is not
completed as a final product (e.g., a semiconductor chip or an IC
chip), the wafer may be called "semiconductor device".
[0072] In the above-described embodiment, a tube entirely made of a
vinyl chloride material is used as the tube 12 of the tube-type
slurry supply pump 15. However, part of the tube which does not
contain fine particles such as inorganic fillers has to exist only
in the inner surface of the tube which has a contact with the
slurry. Therefore, a tube having the inner surface made of a vinyl
chloride material and the outer surface made of some other material
may be used. FIG. 11 is a view illustrating a cross-sectional
structure of a tube having a two-layer structure. The tube of FIG.
11 includes an inner pipe 13 (e.g., a vinyl chloride type tube)
made of the same material (e.g., vinyl chloride) as that of a tube
containing no particles of a reinforcement material or the like and
an outer pipe 14 formed so as to cover the inner pipe 13. The outer
pipe 14 is, for example, a rubber type tube which contains
particles of, for example, a material for reinforcing the tube but
has high mechanical strength.
[0073] As has been described, even if a tube in which at least the
inner surface is made of a vinyl chloride material is used, a
slurry in which no foreign substance is diffused can be supplied to
the CMP apparatus 3, as in the same manner as in the case where the
vinyl chloride type tube is used. Thus, polishing can be performed
without causing the generation of scars and scratches on a wafer
surface. Moreover, a material with high mechanical strength is used
for the outer surface, so that the life of the tube can be
increased. Note that it is also possible to provide another outer
layer so as to form three- or more-layer structure.
[0074] Note that the configurations of FIGS. 2 and 3 have been
described as examples in which a rubber type tube is used. However,
if a vinyl chloride type tube is used as a tube for the tube-type
pump 15, the ultrasonic-wave generator 4 and the filter 5 can be
used for the purpose of dividing aggregate particles of the slurry
and removing dusts or the like contained in the slurry, as shown in
FIGS. 2 and 3.
Embodiment 2
[0075] A second embodiment of the present invention will be
described with reference to FIG. 12. In the first embodiment, the
vinyl chloride type tube is used as the tube 12 of the tube-type
slurry supply pump 15, thereby suppressing the generation of scars
and scratches on a wafer surface. In the second embodiment, as
shown in FIG. 12, a filter 16 is provided downstream of the slurry
supply pump 15 to suppress the generation of scars and scratches on
a wafer surface.
[0076] The filter 16 functions to remove aggregate particles and a
foreign substance contained in a slurry. If a rubber type tube is
used for the tube of the tube-type slurry supply pump 15, the
filter 16 functions to remove a foreign substance (e.g., inorganic
fillers) diffused from the rubber type tube. The tube-type pump 15
is disposed in the CMP apparatus 3 in FIG. 12. However, the
tube-type pump 15 may be disposed in the vicinity or in the
proximity of the CMP apparatus 3. Moreover, the filter 16 may be
disposed in the CMP apparatus 3, or in the vicinity or in the
proximity of the CMP apparatus 3, as long as it is disposed
downstream of the tube-type pump 15.
[0077] Next, operations of the configuration of the polishing
system in accordance with this embodiment.
[0078] Polishing slurry is mixed with, for example, an oxidizer, or
merely held as a buffer in the slurry supply apparatus 1. At this
time, the slurry is, in general, intermittently stirred to prevent
deposition of abrasive particles generated by polishing. However,
with mechanical pressure applied, aggregation of abrasive particles
occurs, thus generating large particles in the slurry. Moreover, a
foreign substance mixed into the slurry is diffused in the slurry
by the stirring. Then, the slurry containing large particles and
the foreign substance is delivered to the CMP apparatus 3 through
the pipe 2. Moreover, in the tube-type slurry pump 15, the slurry
is supplied by pressing the tube, so that a foreign substance might
be mixed into the slurry from the tube. In this embodiment, the
filter 16 is disposed downstream of the tube-type slurry pump 15,
thus substantially all of the large particles and the foreign
substance contained in the slurry and the foreign substance
generated in the tube-type pump 15 can be caught.
[0079] Note that in the configuration shown in FIG. 1, a filter is
disposed not downstream of (after) a pump but upstream of (before)
the pump. The following is a possible reason for this. The filter
for removing dusts or the like in a slurry has higher resistance to
slurry delivery when loadings occur in the filter. The tube-type
slurry pump is used to suppress pulsating flows and allow high,
stable metering accuracy at a low cost. Thus, the filter whose
resistance to slurry delivery might vary has to be located upstream
of the pump. For the same reason, in the configuration shown in
FIG. 3, the filter is located upstream of the pump.
[0080] The examination conducted by the present inventors revealed
that a foreign substance such as inorganic fillers is generated
from the rubber type tube by the tube-type slurry pump 15.
Therefore, the generation of scars and scratches on a wafer surface
can not be suppressed in the configurations of FIGS. 1 and 3. Thus,
the filter 16 has to be provided in part of the pipe 2 located
between the tube-type slurry pump 15 and the CMP apparatus 3 even
if the filter's resistance to slurry delivery might vary. Note that
to reduce the generation of a foreign substance as well as to
prevent the occurrence of loadings in the filter 16, it is
preferable to use a tube in which at least the inner surface is
made of a vinyl chloride material as a tube to be passed through
the tube-type slurry pump 15. If the occurrence of loadings in the
filter 16 is prevented, the life of the filter 16 can be
advantageously increased.
[0081] The present invention has been described by showing
preferred embodiments. However, the description which has been made
herein does not limit the present invention and various kinds of
modification are possible. For example, the two-layer structure for
a tube as a modified example of the first embodiment and the
configuration described in the second embodiment may be
combined.
[0082] As has been described, according to embodiments of the
present invention, it is possible to suppress the generation of a
foreign substance from a tube-type slurry supply pump, so that the
generation of scars and scratches in CMP can be prevented.
Therefore, polishing method and system for a semiconductor device,
which allows high yield, can be provided. Moreover, it is also
possible to use a tube from which a foreign substance is not
generated while ensuring a long life for the tube. Accordingly, the
generation of scars and scratches in CMP can be prevented.
Therefore, polishing method and system for a semiconductor device,
which allows high yield, can be provided. Furthermore, even if a
foreign substance is diffused in a slurry, the diffused foreign
substance can be caught. Accordingly, the generation of scars and
scratches in CMP can be prevented. Therefore, polishing method and
system for a semiconductor device, which allows high yield, can be
provided.
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