U.S. patent application number 09/837191 was filed with the patent office on 2002-02-21 for slurry supply apparatus and method.
Invention is credited to Sugai, Kazumi.
Application Number | 20020022441 09/837191 |
Document ID | / |
Family ID | 18631163 |
Filed Date | 2002-02-21 |
United States Patent
Application |
20020022441 |
Kind Code |
A1 |
Sugai, Kazumi |
February 21, 2002 |
Slurry supply apparatus and method
Abstract
A slurry supply apparatus includes a slurry supply tank, CMP
unit, ultrasonic dispersion unit, and filter. In the slurry supply
tank, a slurry obtained by dispersing abrasive grains with a
predetermined grain size in a chemical solution is agitated and
stored. The slurry is supplied from the slurry supply tank to the
CMP unit through a slurry supply line. The ultrasonic dispersion
unit pulverizes the abrasive grains formed by cohesion and supplied
from the slurry supply tank through the slurry supply tank. The
filter removes an abrasive grain with the predetermined grain size
or less, which is supplied from the ultrasonic dispersion unit and
supplies the resultant slurry to the CMP unit. A slurry supply
method is also disclosed.
Inventors: |
Sugai, Kazumi; (Tokyo,
JP) |
Correspondence
Address: |
McGinn & Gibb, PLLC
8321 Old Courthouse Road, Suite 200
Vienna
VA
22182-3817
US
|
Family ID: |
18631163 |
Appl. No.: |
09/837191 |
Filed: |
April 19, 2001 |
Current U.S.
Class: |
451/60 |
Current CPC
Class: |
B24B 57/02 20130101;
B24B 37/04 20130101 |
Class at
Publication: |
451/60 |
International
Class: |
B24B 057/02 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 21, 2000 |
JP |
120336/2000 |
Claims
What is claimed is:
1. A slurry supply apparatus comprising: a slurry supply tank in
which a slurry obtained by dispersing abrasive grains with a
predetermined grain size in a chemical solution is agitated and
stored; a polishing unit to which the slurry is supplied from said
slurry supply tank through a slurry supply line; ultrasonic
dispersion means for pulverizing the abrasive grains formed by
cohesion and supplied from said slurry supply tank through said
slurry supply tank; and filter means for removing an abrasive grain
with not less than the predetermined grain size, which is supplied
from said ultrasonic dispersion means and supplying the resultant
slurry to said polishing unit.
2. An apparatus according to claim 1, wherein said ultrasonic
dispersion means is clamped on a pipe of the slurry supply line,
and adapted to apply ultrasonic vibration to the slurry through the
pipe.
3. An apparatus according to claim 1, wherein said polishing unit
is a chemical mechanical polishing (CMP) unit.
4. An apparatus according to claim 1, wherein said filter means is
formed by connecting in a subordinate manner a plurality of filters
that remove the abrasive grains from those with a large grain size
to those with a small grain size gradually.
5. An apparatus according to claim 1, wherein said ultrasonic
dispersion means has an ultrasonic oscillator which generates
ultrasonic waves in a range of 0.1 W/cm.sup.2 to several 100
W/cm.sup.2 at a frequency of 10 kHz to several GHz.
6. A slurry supply method of supplying a slurry, obtained by
dispersing abrasive grains with a predetermined grain size in a
chemical solution and agitated and stored in a slurry supply tank,
to a polishing unit through a slurry supply line, comprising the
steps of: pulverizing the abrasive grains formed by cohesion and
supplied from the slurry supply tank by using ultrasonic vibration;
and removing an abrasive grain with not less than the predetermined
grain size from the pulverized abrasive grains by using a filter,
and thereafter supplying the slurry containing abrasive grains with
less than the predetermined grain size to the polishing unit.
7. A method according to claim 6, wherein the step of pulverizing
comprises the steps of clamping an ultrasonic dispersion unit for
applying ultrasonic vibration on a pipe of the slurry supply line,
and applying ultrasonic vibration from the ultrasonic dispersion
unit to the slurry through the pipe.
8. A method according to claim 6, wherein the polishing unit is a
chemical mechanical polishing (CMP) unit.
9. A method according to claim 6, wherein the step of pulverizing
has the step of generating ultrasonic vibration of ultrasonic waves
in a range of 0.1 W/cm.sup.2 to several 100 W/cm.sup.2 at a
frequency of 10 kHz to several GHz.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a slurry supply apparatus
and a method therefor and, more particularly, to a slurry supply
apparatus and method for supplying a slurry to a chemical
mechanical polishing (CMP) unit.
[0002] In recent years, as the integration degree and performance
of semiconductor integrated circuits increase, the CMP method is
introduced as a micropatterning technique. The CMP method is a
technique utilized often in planarization of an interlevel
insulating film, metal plug formation, and buried interconnection
formation in an LSI (Large Scale Integrated circuit) manufacturing
process, particularly in a multilevel interconnection forming
process. A CMP unit which polishes a semiconductor wafer
manufactured by this technique is comprised of, e.g., a lower table
to which a polishing cloth is adhered, and a vertically movable,
pivotal and rotatable upper table for supporting the semiconductor
wafer with a backing pad. To polish the semiconductor wafer, a
slurry dispersed with abrasive grains with a predetermined grain
size is supplied onto the polishing cloth of the lower table.
[0003] As the slurry used for polishing a metal, e.g., copper, used
to form an interconnection, one having abrasive grains with a
predetermined grain size and containing an oxidizing material as
main components is generally employed. For example, such a slurry
is formed by dispersing abrasive grains made of SiO.sub.2, alumina,
CeO.sub.2, MnO.sub.2, or Mn.sub.20.sub.3 and with a grain size of
about 0.01 .mu.m to 1 .mu.m in a chemical solution containing about
1 wt % to 10 wt % of an oxidant, e.g., hydrogen peroxide
(H.sub.2O.sub.2), ferric sulfide (Fe(No.sub.3).sub.3), or potassium
periodate (KIO.sub.3), a dispersant, or the like.
[0004] A semiconductor device is polished with such a slurry by
mechanically removing the obtained oxide with abrasive grains while
oxidizing the surface of a metal as a polishing target material by
the oxidizing operation of an oxidizing material. Recent
micropatterned semiconductor devices require polishing with a
uniform surface roughness. The surface roughness is determined by
the grain size of the abrasive grains. Thus, to increase the
uniformity of the surface roughness, the classification precision
of the abrasive grains themselves must be increased. In general,
however, abrasive grains with a predetermined diameter or more are
inevitably mixed in the slurry.
[0005] It is known that, when the grain size of the abrasive grains
decreases, the interface energy of the surface of the single
abrasive grain increases, and the abrasive grains attract each
other to cause cohesion. To prevent this cohesion, surface
treatment or dispersion promoting treatment may be performed. Yet,
when a predetermined period of time has elapsed, cohesion occurs
again. The large grains may form a large scratch on the polishing
target surface or degrade the uniformity of the surface roughness.
For example, when a scratch is formed on the surface of an
insulating film, a polishing agent is left on the surface of the
insulating film to cause heavy metal ion contamination, leading to
an operation error of the semiconductor device. When a scratch is
formed on the surface of a metal film, it causes a conduction error
or degrades the electromigration resistance.
[0006] To remove large grains formed by cohesion of such abrasive
grains, a method of building a filter having pores with a
predetermined diameter in a slurry supply apparatus is known. A
conventional slurry supply apparatus of this type will be described
with reference to FIG. 3. As shown in FIG. 3, a conventional slurry
supply apparatus 1 has a slurry supply tank 3 and slurry supply
line 4. A filter 6 is installed midway along the slurry supply line
4 that connects the slurry supply tank 3 and a polishing unit such
as a CMP unit 2.
[0007] In the slurry supply apparatus 1 with the above arrangement,
the slurry supplied from the slurry supply tank 3 passes through
the filter 6 to remove large grains in it, and is supplied to the
turn table of the CMP unit 2. How the large grains are removed will
be described with reference to FIGS. 4A and 4B.
[0008] Near the outlet of the slurry supply tank 3, abrasive grains
Sa with a small grain size and large grains Sb formed by cohesion
of the abrasive grains in the slurry discharged from the slurry
supply tank 3 of the slurry supply apparatus 1 are distributed with
respective peaks as shown in FIG. 4A. After passing through the
filter 6, the large grains Sb formed by cohesion of the abrasive
grains are removed, as shown in FIG. 4B, to leave only the abrasive
grains Sa with the small grain size, and the slurry with the
uniform abrasive grain size is introduced to the CMP unit 2.
[0009] In the conventional slurry supply apparatus 1 described
above, although the large grains can be removed by the filter 6,
the filter 6 tends to clog and thus has a short service life. For
this reason, the filter 6 must be exchanged often, and accordingly
the down time of the CMP unit 2 and the cost of filter components
increase, leading to an increase in the cost of the semiconductor
devices.
[0010] In order to reduce the load on the filter 6, the slurry in
the slurry supply tank 3 is agitated so the abrasive grains are
dispersed. It is, however, difficult to completely disperse the
abrasive grains in the slurry supply tank 3. Even if the abrasive
grains are dispersed, they cause cohesion again while the slurry
passes through the slurry supply line 4. If the slurry is agitated
strongly or for a long period of time in order to increase the
dispersion properties, the viscosity of the slurry increase. In
this case, the polishing performance itself degrades, e.g., the
polishing speed decreases or the uniformity degrades, and the
slurry supply amount fluctuates.
SUMMARY OF THE INVENTION
[0011] It is an object of the present invention to provide a slurry
supply apparatus and method which do not apply a load on a filter
installed midway along a slurry supply line.
[0012] It is another object of the present invention to provide a
slurry supply apparatus and method which can effectively remove
large grains formed by cohesion of abrasive grains from a
slurry.
[0013] In order to achieve the above objects, according to the
present invention, there is provided a slurry supply apparatus
comprising a slurry supply tank in which a slurry obtained by
dispersing abrasive grains with a predetermined grain size in a
chemical solution is agitated and stored, a polishing unit to which
the slurry is supplied from the slurry supply tank through a slurry
supply line, ultrasonic dispersion means for pulverizing the
abrasive grains formed by cohesion and supplied from the slurry
supply tank through the slurry supply tank, and filter means for
removing an abrasive grain with not less than a predetermined grain
size, which is supplied from the ultrasonic dispersion means and
supplying the resultant slurry to the polishing unit.
DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a view schematically showing the arrangement of a
slurry supply apparatus according to an embodiment of the present
invention;
[0015] FIGS. 2A, 2B, and 2C are graphs showing the distributions of
abrasive grains contained in the slurry at points a, b, and c,
respectively, of the slurry supply line shown in FIG. 1;
[0016] FIG. 3 is a view schematically showing the arrangement of a
conventional slurry supply apparatus; and
[0017] FIGS. 4A and 4B are graphs showing the distributions of
abrasive grains contained in the slurry at points a and b,
respectively, of a conventional slurry supply line.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0018] The present invention will be described in detail with
reference to the accompanying drawings.
[0019] FIG. 1 schematically shows the arrangement of a slurry
supply apparatus according to an embodiment of the present
invention. As shown in FIG. 1, a slurry supply apparatus 11 is
comprised of a slurry supply tank 13, a polishing unit such as a
CMP unit 12 connected to the slurry supply tank 13 through a slurry
supply line 14, an ultrasonic dispersion unit 15 with an ultrasonic
oscillator 15a and disposed midway along the slurry supply line 14,
and at least one filter 16 provided downstream of the ultrasonic
dispersion unit 15.
[0020] In this arrangement, when the slurry supplied from the
slurry supply tank 13 passes through the ultrasonic dispersion unit
15, most of large grains contained in the slurry are pulverized,
and only those large grains which are not pulverized but left in a
small amount are trapped by the filter 16.
[0021] The size of the abrasive grains contained in the slurry is
usually from about 0.01 .mu.m to 1 .mu.m. SiO.sub.2, alumina,
CeO.sub.2, MnO.sub.2, Mn.sub.2O.sub.3, or the like can be used as
the abrasive grains, and is dispersed in a chemical solution
containing about 1 wt % to 10 wt % of a dispersant, oxidant, or the
like. As the oxidant, hydrogen peroxide (H.sub.2O.sub.2), ferric
sulfide (Fe(No.sub.3).sub.3), potassium periodate (KIO.sub.3), or
the like is used.
[0022] How the large grains are removed from the slurry by the
slurry supply apparatus 1 will be described with reference to FIGS.
2A, 2B, and 2C. In FIGS. 2A to 2C, the abscissa represents the
abrasive grain size. The closer to the right side of the graph, the
larger the abrasive grain size. The ordinate represents the
strength, i.e., the number, of abrasive grains.
[0023] As shown in FIG. 2A, the slurry discharged from the slurry
supply tank 13 has both the peak of abrasive grains Sa with a small
grain size and the peak of large grains Sb formed by cohesion of
the abrasive grains. The peak of the large grains Sb is
considerably large. In other words, at this stage, a considerably
large number of large grains are contained in the slurry.
[0024] When the slurry passes through the ultrasonic dispersion
unit 15, the large grains Sb are pulverized by ultrasonic vibration
of the ultrasonic oscillator 15a to improve the dispersion
properties of the abrasive grains, as shown in FIG. 2B. Thus, the
peak of the abrasive grains Sa with the small grain size becomes
large, while the peak of the large grains Sb with the large grain
size, which is formed by cohesion becomes small.
[0025] The ultrasonic oscillator 15a need not be a particularly
specific one, and suffices if it is, e.g., an oscillator that can
generate ultrasonic waves in the range of 0.1 W/cm.sup.2 to several
100 W/cm.sup.2 at a frequency of 10 kHz to several GHz. As a method
of applying the ultrasonic waves, the slurry may be temporarily put
in a tank and ultrasonic waves may be applied to it. Alternatively,
the pipe of the slurry supply line 14 may be clamped, and
ultrasonic waves may be applied. The flow rate of the slurry is
usually about 50 cc/min to 500 cc/min.
[0026] When the slurry in which the large grains with a large grain
size have been pulverized by the ultrasonic dispersion unit 15
further passes through the filter 16, the large grains Sb with the
large grain size are completely removed, as shown in FIG. 2C, and
only the abrasive grains Sa with the small grain size are supplied
to the turn table of the CMP unit 12.
[0027] The mesh size of the filter may be selected in accordance
with the abrasive grain size. The present invention is not limited
to a method that uses one filter matching the grain size of the
abrasive grains to be passed. For example, a plurality of filters
for removing abrasive grains, from those with a large grain size to
those with a small grain size gradually, may be connected in a
subordinate manner, so only abrasive grains with a desired grain
size may be passed through the filters. When the plurality of
filters are to be used, the abrasive grains with the large grain
size are removed by a front filter, and the abrasive grains with
the small grain size are removed by a rear filter. This can prolong
the service life of the filters 16 more than in a case wherein one
filter 16 is used.
[0028] In this manner, since the ultrasonic dispersion unit 15 and
filter 16 are sequentially arranged from the upstream of the slurry
supply line 14 that connects the slurry supply tank 13 and a
polishing unit, e.g., the CMP unit 12, of the slurry supply
apparatus 11, most of the large grains formed by cohesion of the
abrasive grains with the small grain size can be pulverized by the
ultrasonic dispersion unit 15. Since the large grains that are not
pulverized but left can be completely removed by the filter 16
provided immediately before the CMP unit 12, a slurry containing
only uniform-diameter abrasive grains with the small grain size can
be supplied to the CMP unit 12. When compared to the conventional
case wherein only the filter 6 is used, the load to the filter 16
can be reduced, so that the service life of the filter 16 can be
greatly prolonged.
[0029] In the above embodiment, a case wherein the slurry is
supplied to the CMP unit 12 is described. However, the present
invention is not limited to this, and can also be applied to other
polishing apparatus, cutting apparatus, pulverizing apparatus, or
the like using a slurry dispersed with abrasive grains, as a matter
of course.
[0030] As has been described above, according to the present
invention, the serve life of the filter used for removing large
grains is prolonged so that the cost of the filter can be reduced,
and the down time of the apparatus necessary for exchanging the
filters is shortened so that the time efficiency of the apparatus
can increase. Thus, the manufacturing cost of the semiconductor
devices can be reduced.
[0031] This is due to the following reason. Since ultrasonic waves
are applied to the slurry by using the ultrasonic dispersion unit,
the large grains formed by cohesion can be pulverized. This
pulverizing is performed on a supply line close to the use point,
so the dispersion performance of the slurry itself, which is to be
actually supplied to the turn table, can always be maintained at a
high level. Since one or more filters having predetermined mesh
sizes are provided downstream of the ultrasonic dispersion unit,
the large grains formed by cohesion can be completely removed from
the slurry, and the number of large grains reaching the filters is
reduced by the ultrasonic dispersion unit, thereby suppressing
clogging of the filters.
* * * * *