U.S. patent application number 13/914960 was filed with the patent office on 2013-10-17 for method of manufacturing semiconductor device.
The applicant listed for this patent is Kabushiki Kaisha Toshiba. Invention is credited to Yukiteru Matsui, Gaku Minamihaba.
Application Number | 20130273817 13/914960 |
Document ID | / |
Family ID | 46966435 |
Filed Date | 2013-10-17 |
United States Patent
Application |
20130273817 |
Kind Code |
A1 |
Minamihaba; Gaku ; et
al. |
October 17, 2013 |
METHOD OF MANUFACTURING SEMICONDUCTOR DEVICE
Abstract
According to one embodiment, the method of manufacturing a
semiconductor device includes contacting a film formed on a
semiconductor substrate with a rotating polishing pad which is
supported on a turntable, and feeding polishing foam to a region of
the polishing pad with which the film is contacted, thereby
polishing the film. The polishing foam is obtained by turning the
aqueous dispersion into a foamy body. The aqueous dispersion
includes 0.01-20% by mass of abrasive grain and 0.01-1% by mass of
foam forming and retaining agent, all based on a total mass of the
aqueous dispersion.
Inventors: |
Minamihaba; Gaku;
(Yokohama-shi, JP) ; Matsui; Yukiteru;
(Yokohama-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kabushiki Kaisha Toshiba |
Tokyo |
|
JP |
|
|
Family ID: |
46966435 |
Appl. No.: |
13/914960 |
Filed: |
June 11, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13236229 |
Sep 19, 2011 |
8480915 |
|
|
13914960 |
|
|
|
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Current U.S.
Class: |
451/111 |
Current CPC
Class: |
B24B 37/044 20130101;
B24B 57/02 20130101; H01L 21/76224 20130101; H01L 21/31053
20130101; C09G 1/02 20130101 |
Class at
Publication: |
451/111 |
International
Class: |
B24B 57/02 20060101
B24B057/02 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 7, 2011 |
JP |
2011-085443 |
Claims
1.-17. (canceled)
18. A polishing apparatus comprising: a rotatable turntable; a
polishing head configured to hold a semiconductor substrate having
a film formed thereon and contact the film with a polishing pad
supported on the rotatable turntable; and a polishing foam
generator configured to accommodate an aqueous dispersion
comprising abrasive grain and a foam forming and retaining agent
and discharge, through a mesh, the aqueous dispersion as a foamy
body to feed the polishing foam to a region of a polishing pad with
which the film is contacted.
19. The apparatus according to claim 18, wherein the mesh is formed
of a material selected from the group consisting of nylon,
polyester and polyethylene.
20. (canceled)
21. The apparatus according to claim 18, wherein an aperture of the
mesh is 100-500 meshes.
22. The apparatus according to claim 18, wherein the polishing foam
generator is constituted by a cylinder unit having a chamber
configured to accommodate the aqueous dispersion.
23. The apparatus according to claim 22, wherein the cylinder unit
is formed of a resin.
24. The apparatus according to claim 22, wherein the cylinder unit
comprises a passageway communicated with the chamber, the aqueous
dispersion being fed via the passageway.
25. The apparatus according to claim 24, wherein the passageway is
configured to supply the chamber with air in addition to the
aqueous dispersion.
26. The apparatus according to claim 25, wherein the polishing foam
generator comprises a regulator configured to regulate a flow rate
of the air supplied to the chamber.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from prior Japanese Patent Application No. 2011-085443,
filed Apr. 7, 2011, the entire contents of which are incorporated
herein by reference.
FIELD
[0002] Embodiments described herein relate generally to a method of
manufacturing a semiconductor device.
BACKGROUND
[0003] In the manufacture of a semiconductor device, there has been
practiced to polish a film deposited on the semiconductor substrate
by chemical mechanical polishing (CMP) using a CMP slurry. The CMP
slurry that has been conventionally employed is formed of, for
example, a dispersion containing abrasive grain wherein pure water
is employed as a dispersion medium. When CMP, a CMP slurry is fed
in the vicinity of central portion of a rotating polishing pad. The
CMP slurry thus fed spreads to the outer peripheral region of the
polishing pad by centrifugal force, thereby the CMP slurry is
utilized for the polishing of a film which is being contacted with
the polishing pad.
[0004] All of the CMP slurry that has been fed to the polishing pad
is not necessarily contribute to the polishing of the film to be
polished. Since the CMP slurry is low in viscosity and part of the
CMP slurry is discharge outside the polishing pad, the CMP slurry
employed in the prior art is not utilized effectively.
[0005] If it is possible to retain the CMP slurry on the polishing
pad without being discharged from the polishing pad, the quantity
of CMP slurry to be used can be reduced, thus leading to the
improvement of utilization efficiency of the CMP slurry.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a perspective view schematically illustrating a
method of manufacturing a semiconductor device according to one
embodiment;
[0007] FIG. 2 is a cross-sectional view schematically illustrating
the construction of a polishing foam generator;
[0008] FIG. 3 is a graph illustrating the relationship between the
content of a foam forming and retaining agent and a foam volume
reduction ratio;
[0009] FIG. 4 is a perspective view schematically illustrating a
method of manufacturing a semiconductor device according to the
prior art;
[0010] FIG. 5 is a perspective view schematically illustrating a
conventional method of manufacturing a semiconductor device wherein
a conventional slurry is used; and
[0011] FIGS. 6A, 6B, and 6C are cross-sectional views illustrating
the manufacturing process of STI.
DETAILED DESCRIPTION
[0012] In general, according to one embodiment, the method of
manufacturing a semiconductor device includes contacting a film
formed on the semiconductor substrate with a rotating polishing pad
which is supported on a turntable; and feeding polishing foam to a
region of the polishing pad with which the film is contacted,
thereby polishing the film. The polishing foam can be obtained by
turning the aqueous dispersion into a foamy body. The aqueous
dispersion includes 0.01-20% by mass of abrasive grain and 0.01-1%
by mass of foam forming and retaining agent, all based on a total
amount of the aqueous dispersion.
[0013] Next, embodiments will be explained with reference to
drawings.
[0014] A method of manufacturing a semiconductor according to one
embodiment will be explained with reference to FIG. 1. As shown in
FIG. 1, a semiconductor substrate 14 which is held on a polishing
head 13 to be driven by a rotating mechanism (not shown) is
contacted with a polishing pad 12 supported on a turntable 11 to be
driven by another rotating mechanism (not shown). By feeding
polishing foam 15 to a prescribed region of the polishing pad 12
while rotating the turntable 11 and the polishing head 13,
respectively at a prescribed rotating speed, the film 10 deposited
on the semiconductor substrate 14 can be polished.
[0015] The region of polishing pad 12 to which the polishing foam
15 is fed among the entire surface of the polishing pad 12 is
confined to a region with which the semiconductor substrate 14 is
contacted. Since the polishing pad 12 is rotated, it can be said
that the region of the polishing pad 12 to which the polishing foam
15 is fed is confined to the region corresponding to the orbital
tract of the semiconductor substrate 14 moving on the polishing pad
12. The polishing foam 15 that has been fed to the polishing pad 12
enters into an interface between the polishing pad 12 and the film
10 to be polished, thereby polishing the film 10.
[0016] The polishing foam 15 utilized in the polishing of the film
10 to be polished can be prepared by turning an aqueous dispersion
containing abrasive grain and foam forming and retaining agent into
a foamy body using a polishing foam generator 16.
[0017] The abrasive grain contained in the aqueous dispersion may
be optionally selected depending on the material of the film to be
polished. For example, if an oxide film such as a thermal oxide
film is polished, it is possible to employ cerium oxide, silicon
oxide, etc. The content of the abrasive grain in the aqueous
dispersion is 0.01-20% by mass based on the total amount of the
aqueous dispersion. When the content of the abrasive grain is less
than 0.01% by mass, it would be impossible to achieve a practical
polishing rate. On the other hand, if the content of the abrasive
grain is more than 20% by mass, it would be no longer possible to
retain a desired volume of polishing foam and the manufacturing
cost would be increased. Preferably, the content of the abrasive
grain in the aqueous dispersion is around 0.1-10% by mass based on
the total amount of the aqueous dispersion.
[0018] An average particle diameter of the abrasive grain is
generally around 10-1,000 nm. The average particle diameter of the
abrasive grain can be determined, for example, by measuring the
individual image of each of abrasive grains which have been
obtained by a transmission electron microscope or by measuring the
specific surface area that has been obtained by BET method using an
automatic fluid type specific surface area-measuring,
apparatus.
[0019] The foam forming and retaining agent makes it possible to
turn an aqueous dispersion into a foamy body by passing the aqueous
dispersion through a polishing foam generator provided with a mesh
and also makes it possible to retain the state of foamy body thus
formed. However, it is necessary to prevent the foam forming and
retaining agent from giving any adverse effects to the polishing of
a film to be polished. Therefore, the foam forming and retaining
agent is selected taking above affairs into consideration. When an
oxide film is polished, it is possible to employ an anionic
surfactant for example as a foam forming and retaining agent. It is
also possible to employ ordinary sodium dodecyl sulfate (SDS) as a
foam forming and retaining agent. It is especially preferable to
employ, as a foam forming and retaining agent, alkyl benzene
sulfonate and salts of alkyl benzene sulfonate. Among the alkyl
benzene sulfonate, it is preferable to employ those having alkyl
group of 8 to 16 carbon atoms. In order to enable the polishing
foam to retain its volume while the influence thereof on the
polishing speed of the film to be polished is taken into
consideration, it is more preferable to employ those having alkyl
group of 10 to 14 carbon atoms. In viewpoint of biodegradation, the
alkyl group of alkyl benzene sulfonate is preferably of straight
chain. As the salts, potassium salt and ammonium are
preferable.
[0020] Specific examples of alkyl benzene sulfonate and salts of
alkyl benzene sulfonate include linear dodecylbenzenesulfonic acid,
potassium linear dodecylbenzenesulfonate, ammonium linear
dodecylbenzenesulfonate, etc.
[0021] The content of the foam forming and retaining agent in the
aqueous dispersion is 0.1-10% by mass. If the content of the foam
forming and retaining agent is less than 0.1% by mass, it would be
impossible to sufficiently secure the effects of enhancing the
polishing speed even though a certain degree of enhancement can be
obtained. Additionally, it would be impossible to create a desired
state of foam. On the other hand, if the content of the foam
forming and retaining agent is more than 10% by mass, the foam may
adhere onto the film to be polished, thereby undesirably decreasing
the polishing speed. Incidentally, by the expression of "a desired
state of foam", it is intended to indicate a state wherein the
volume reduction ratio of foam is 5% or less as the foam is kept
standing for 120 seconds at room temperature. It is more preferable
that the volume reduction ratio of foam is 1% or less as the foam
is kept standing for 120 seconds at room temperature. When the
content of foam forming and retaining agent in the aqueous
dispersion is around 0.5-5% by mass, the aforementioned low volume
reduction ratio of foam can be achieved. Details regarding the
volume reduction ratio of foam and the formation of foam will be
discussed hereinafter.
[0022] Depending on circumstances, resinous particle having a
nonionic functional group on its surface may be co-used. Although
this nonionic functional group in itself is incapable of acting as
a foam-generating agent, it is possible to derive the effects of
suppressing the volume reduction of polishing foam as it is co-used
together with the aforementioned foam forming and retaining agent.
In this case, it is possible to reduce the content required of the
foam forming and retaining agent. Specific materials of the
resinous particle can be selected from, for example, polystyrene,
polymethacrylate, etc. Examples of the nonionic functional group
include, for example, carboxyl group, sulfonyl group, etc.
[0023] The resinous particle having a nonionic functional group on
its surface can be obtained according to the preparation method
described, for example, in Example 4 of JP-A 2000-204353
(KOKAI).
[0024] The aqueous dispersion can be obtained by adding a
predetermined quantity of abrasive grain and of foam forming and
retaining agent to water. As for the water, it is possible to
employ pure water, for example.
[0025] The aqueous dispersion thus prepared contains a foam forming
and retaining agent and abrasive grain and can be turned into a
foamy body by passing it through a polishing foam generator. The
polishing foam generator 16 is constructed, for example, as shown
in FIG. 2. A mixing chamber 20 is provided inside a cylindrical
resinous cylinder block 17 and communicated with a feeding
passageway 18. The aqueous dispersion containing a foam forming and
retaining agent and abrasive grain can be fed, via the feeding
passageway 18, into the mixing chamber 20 and accommodated
therein.
[0026] By supplying air from the feeding passageway 18 to the
interior of the mixing chamber 20, the aqueous dispersion is
agitated and then allowed to pass through a mesh 19, thereby
enabling the aqueous dispersion to turn into a polishing foam. The
polishing foam is then discharged from a discharge opening 21 of
the polishing foam generator 16. With respect to the aperture of
mesh 19, as long as it is around 100-500 meshes, it is possible to
create a desired state of foam. With respect to the materials of
mesh 19, there is not any particular limitation and hence the mesh
19 may be formed of nylon, polyester, polyethylene, etc.
[0027] The supply flow rate of air can be regulated by an
electropneumatic regulator. By blowing air into the aqueous
dispersion containing prescribed quantities of a foam forming and
retaining agent and abrasive grain under appropriate conditions, a
foamy body can be obtained in a desired state. In order to obtain a
foamy body in a desired state, the temperature of the aqueous
dispersion is preferably within the range of 18-30.degree. C. The
air is desirably supplied in such a manner that the volume of air
becomes 2-10 times larger than the volume of the aqueous
dispersion. Further, it is also effective, in order to obtain foam
of desirable state, to supply air through a filter so as to
minimize the impurities in the air.
[0028] The polishing foam created in this manner by the polishing
foam generator is featured in that the volume reduction ratio after
120 seconds is 5% or less. It is more preferable that the volume
reduction ratio after 120 seconds is 1% or less.
[0029] The volume reduction ratio can be defined as follows. First
of all, by the aforementioned polishing foam generator, an aqueous
dispersion is turned into a foamy body, which is then accommodated
in a graduated cylinder to determine the initial volume (V.sub.0)
of the foamy body. The foamy body thus determined is left standing
for 120 seconds under the conditions of windless atmosphere and
room temperature and then the volume (V.sub.120) after 120 seconds
is measured. Thus, volume reduction ratio of the foamy body can be
obtained from {100.times.(V.sub.0-V.sub.120)/V.sub.0}.
[0030] In the ordinary polishing process, the time required for
polishing the film to be polished and being deposited on the
semiconductor substrate is 120 seconds or less. As long as the
polishing foam obtained as a foamy body from an aqueous dispersion
can be kept in a desirable state, the polishing foam stays on the
polishing pad, thus contributing to the polishing of the film to be
polished. Since the polishing foam is reliably utilized for the
polishing of the film to be polished, it is possible to secure a
practical polishing speed. Moreover, the polishing foam applied to
the polishing pad can be prevented from being discharged from the
polishing pad even if the polishing foam is subjected to a
centrifugal force (the rotational speed of the turntable is 10-150
rpm in general), thus making it possible to enhance the utilization
efficiency of the polishing foam.
[0031] The state of the polishing foam can be assessed by the value
of foam volume reduction ratio. It has been found out by the
present inventors that as long as the foam volume reduction ratio
after 120 seconds is 5% or less, it is possible to obtain desired
effects of polishing foam.
Examples
[0032] Next, specific examples of the method of manufacturing a
semiconductor device will be explained.
Embodiment 1
[0033] Abrasive grain was added to a dispersion medium to obtain an
aqueous dispersion containing 0.5% by mass of the abrasive grain.
Cerium oxide having an average particle diameter of 0.1 .mu.m was
employed as the abrasive grain and pure water was employed as a
dispersion medium. The aqueous dispersion thus obtained was
employed as Sample 1. This Sample 1 corresponds to a CMP slurry
which has been conventionally used.
[0034] To this Sample 1 was added predetermined quantities of
potassium linear dodecylbenzenesulfonate as a foam forming and
retaining agent to obtain Samples 2-8. The amount of potassium
linear dodecylbenzenesulfonate were regulated so that these samples
could be formed respectively as polishing foam and that the foam
volume reduction ratio thereof after standing for 120 seconds at
room temperature would be confined respectively to a predetermined
value. In order to create the polishing foam, a polishing foam
generator constructed as shown in FIG. 2 was employed. The capacity
of the mixing chamber 20 was around CO cc and a 300-mesh
polyethylene mesh was employed as the mesh 19. The diameter of the
discharge opening 21 was about 5 mm. Air was supplied controlling
the original pressure thereof to 0.5 MPa by an electropneumatic
regulator.
[0035] The foam volume reduction ratio and the content of each of
the foam forming and retaining agents are summarized in the
following Table 1. Further, the relationship between the content of
foam forming and retaining agent and the foam volume reduction
ratio was plotted as shown in the graph of FIG. 3.
TABLE-US-00001 TABLE 1 Foam Foam forming Sample volume-reduction
and retaining No. ratio (%) agent (mass %) 2 10 0.01 3 6 0.05 4 5
0.1 5 3 1 6 0.7 5 7 0.5 10 8 0.5 15
[0036] Further, a sample exhibiting a volume reduction ratio of
0.5% was obtained as Sample 9. This sample 9 contained resinous
grain having a nonionic surface functional group. The content of
the resinous grain in the Sample 9 was about 0.1% by mass. This
surface functional group was carboxyl group and the resinous grain
was about 50 nm in average particle diameter and formed of
styrene/methacryl copolymer.
[0037] Using Sample 1, a thermal oxide film deposited on the
semiconductor substrate was polished. This thermal oxide film was
300 nm in thickness and the diameter of the semiconductor substrate
was 200 mm. When polishing the thermal oxide film, the polishing
head 13 holding the semiconductor substrate 14 was forced to
contact with the polishing pad 12 at a polishing load of 300 hPa
while driving the turntable 11 having the polishing pad 12 attached
thereto to rotate at rotational speed of 100 rpm as shown in FIG.
4. The rotational speed of the polishing head 13 was 103 rpm. By
following the conventional supply method, Sample 1 constituting the
slurry 25 was fed from the slurry supply nozzle 26 to a central
region of the polishing pad 12. The flow rate of the slurry 25 was
set to 100 cc/min. This flow rate corresponds to the ordinary flow
rate of slurry which has been conventionally employed.
[0038] The slurry 25 applied dropwise to a central region of the
polishing pad 12 spread toward the peripheral region of the
polishing pad due to the centrifugal force, thereby the slurry 25
is utilized for the polishing of the thermal oxide film. The
polishing pad employed herein was formed of IC1000 (Rodel Co.,
Ltd.). The polishing was performed for 60 seconds.
[0039] The thermal oxide film was polished under the same
conditions as described above excepting that the flow rate of the
slurry 25 to be fed from the slurry supply nozzle 26 was changed to
50 cc/min and to 25 cc/min. In this case, the polishing speed was
estimated from the quantity shaved from the thermal oxide film. The
flow rate of Sample 1 and the polishing speed are summarized in the
following Table 2.
TABLE-US-00002 TABLE 2 Flow rate Polishing speed (cc/min) (nm/min)
100 158 50 143 25 102
[0040] As shown in above Table 2, when the flow rate of slurry was
100 cc/min, the polishing speed was 158 nm/min, thus indicating
that it was possible to polish the thermal oxide film at a
practical speed. When the follow rate was decreased, the polishing
speed was also decreased. When the follow rate was 25 cc/min, the
polishing speed was decreased to 102 nm/min. Since the polishing
speed of the thermal oxide film is at least required to be 150
nm/min or more, above-mentioned polishing speed is not
practical.
[0041] Then, using the polishing foam generator 16 shown in FIG. 2,
the samples Nos. 1-9 were respectively fed only to the region of
the polishing pad 12 which corresponds to the orbital tract of the
semiconductor substrate. In every case, the amount of the sample
thus applied was 25 cc. The polishing of the same thermal oxide
film as described above was performed under the same conditions
excepting the quantity of the sample.
[0042] When the samples Nos. 2-9 were respectively feed as
described above, the polishing foam 15 was placed at a
predetermined region of the polishing pad 12 as shown in FIG. 1.
The polishing foam 15 placed on the polishing pad 12 by each of
samples of Nos. 4-9 was substantially incapable of exhibiting
fluidity, thus enabling the polishing foam 15 to remain at the
predetermined region of the polishing pad 12. It was assumed that
the polishing foam 15 thus placed contributed to the polishing of
the film throughout the entire period of polishing.
[0043] The polishing foam 15 created by each of samples of Nos. 2
and 3 was easily fluidized and hence was incapable of being stably
kept in place. The sample of No. 1 was not foamy and a portion 27
thereof was discharged out of the polishing pad as shown in FIG.
5.
[0044] In the same manner as describe above, the polishing speed
was estimated from the quantity shaved from the thermal oxide film.
The polishing speed each of these samples is summarized in the
following Table 3.
TABLE-US-00003 TABLE 3 Sample Polishing speed No. (nm/min) 1 39 2
115 3 120 4 169 5 161 6 157 7 153 8 135 9 166
[0045] Since Sample 1 was an aqueous dispersion, even if it was
fed, using a polishing foam generator, to the region of the
polishing pad which corresponds to the orbital tract of the
semiconductor substrate, Sample 1 was incapable of being stably
kept in place on the polishing pad. Since Sample 1 thus fed was
discharged out of the polishing pad due to centrifugal force, the
degree of Sample 1 that contributes to the polishing of the film
was extremely minimized. Because of this, the polishing speed of
the thermal oxide film was as very low as 39 nm/min. When slurry
formed of an aqueous dispersion is employed, it is impossible to
polish the film at the practical polishing speed unless the slurry
is fed according to the conventional method.
[0046] In the cases of Samples 2 and 3, although they were
respectively turned into a foamy body, the polishing speed thereof
was as low as 120 nm/min or less, thus indicating insufficient
polishing speed. The reason for this is assumed to be attributed to
the fact that since the volume reduction ratio of these foamy
bodies was too large, it was impossible to enable them to
contribute to the polishing of the film to be polished.
[0047] The polishing speed in the cases of Samples 4-7 and 9 was
all not less than the value that was obtained when the Sample 1 was
supplied at a flow rate of 100 cc/min. Since the amount of feeding
these samples was respectively 25 cc, it was possible to obtain a
practical polishing speed even when the feeding amount of these
samples was as small as 1/4 of Sample 1.
[0048] In the case of Sample 8, although it was possible to keep
the volume of foam, the polishing speed was as low as 135 nm/min.
The reason for this was assumed to be attributed to the fact that
since the content of the foam forming and retaining agent was as
large as 15% by mass, the foam adhered to the film to be polished,
thereby decreasing the polishing speed.
[0049] It was found out that when the method of this embodiment was
adopted employing a polishing foam exhibiting a foam volume
reduction ratio of 5% or less, it was possible to polish a film to
be polished at a practical polishing speed even if the quantity of
slurry to be used was reduced.
Embodiment 2
[0050] The method of manufacturing shallow trench isolation (STI)
will be explained with reference to FIGS. 6A to 6C.
[0051] First of all, a semiconductor substrate 30 having a silicon
nitride film 31 deposited thereon and provided with an STI pattern
B as shown in FIG. 6A was prepared. The silicon nitride film 31
acts as a stopper film and the film thickness thereof is 50 nm for
example. A silicon oxide film for example may be interposed between
the semiconductor substrate 30 and the silicon nitride film 31.
Using the silicon oxide film as an etching mask, the semiconductor
substrate 30 is worked together with the silicon nitride film 31 to
form the STI pattern B.
[0052] The width and intervals of this STI pattern B are both 1
.mu.m (line/space: 1/1 .mu.m). Further, the depth of this STI
pattern B is 200 nm for example.
[0053] As shown in FIG. 6B, a silicon oxide film 32 is deposited on
the silicon nitride film 31 by a high-density plasma CVD (HDP-CVD)
method for example. The film thickness of the silicon oxide film 32
is 280 nm and this silicon oxide film 32 is formed all over the
surface of silicon nitride film 31 including the regions other than
the STI pattern B.
[0054] Then, the surface of silicon oxide film 32 is entirely
subjected to CMP to remove the silicon oxide film 32 existing
outside the STI pattern B as shown in FIG. 6C. As a result, the
silicon oxide film 32 is buried in the STI pattern B and the
surface of silicon nitride film 31 is exposed at the regions other
than the STI pattern B.
[0055] On the occasion of performing the CMP, the silicon oxide
film is polished at first under the conditions conventionally
employed. More specifically, the aforementioned Sample 1 is fed at
a flow rate of 100 cc/min and the polishing is performed under the
same conditions as described above. The polishing speed is 158
nm/min.
[0056] Further, using aforementioned Sample 5, the silicon oxide
film is polished under the same conditions as described above.
Namely, using a polishing foam generator, 25 cc of Sample 5 is
turned into a foamy body, which is then applied only to the region
of polishing pad corresponding to the orbital tract of the
semiconductor substrate. The polishing speed is 161 nm/min.
[0057] The time required for exposing the surface of silicon
nitride film 31, the depth of dishing on the surface of silicon
oxide film 32 that was left remain in the STI pattern B and the
number of defectives were investigated, the results being
summarized in the following Table 4. If the depth of dishing is not
more than 30 nm, it is considered as acceptable.
TABLE-US-00004 TABLE 4 Sample Polishing Dishing Number of No. time
(sec) (nm) defectives 1 95 15 23 5 92 18 20
[0058] Above Table 4 indicates that, as in the case of Embodiment
1, even if the quantity of slurry used was reduced to 1/4 of Sample
1, it was possible to obtain almost the same CMP performance.
Embodiment 3
[0059] Silicon oxide having an average particle diameter of 25 nm
is prepared as abrasive grain. This silicon oxide is added to pure
water employed as a solvent to obtain an aqueous dispersion
containing 10% by mass of silicon oxide. The aqueous dispersion
thus obtained is used as Sample 10. This Sample 10 corresponds to a
CMP slurry which has been conventionally used.
[0060] To this Sample 10 is added predetermined amount of ammonium
linear dodecylbenzenesulfonate as a foam forming and retaining
agent to obtain Sample 11 as polishing foam. The foam volume
reduction ratio of this Sample 11 after standing for 120 seconds at
room temperature is 4%.
[0061] In the employment of Sample 10, the polishing of a silicon
oxide film is performed under the same conventional conditions as
described in Embodiment 1. More specifically, Sample 10 is fed at a
flow rate of 10 cc/min and the polishing was performed under the
same conditions as described above. The polishing speed is 108
nm/min.
[0062] On the other hand, in the employment of Sample 11, 25 cc of
Sample 5 is turned into a foamy body using a polishing foam
generator and then applied only to the region of polishing pad
corresponding to the orbital tract of the semiconductor substrate.
The polishing speed is 121 nm/min.
[0063] When compared with cerium oxide, although the polishing
speed to be obtained using silicon oxide was decreased, the
polishing speed was not lowered even if the flow rate thereof was
reduced to 1/4. It was confirmed that even if silicon oxide was
employed as abrasive grain, it was possible to obtain almost the
same effects as in the case of cerium oxide.
[0064] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of the inventions. Indeed, the novel
embodiments described herein may be embodied in a variety of other
forms; furthermore, various omissions, substitutions and changes in
the form of the embodiments described herein may be made without
departing from the spirit of the inventions. The accompanying
claims and their equivalents are intended to cover such forms or
modifications as would fall within the scope and spirit of the
inventions.
* * * * *