U.S. patent application number 11/184960 was filed with the patent office on 2006-02-09 for polishing composition.
This patent application is currently assigned to Kao Corporation. Invention is credited to Yuichi Honma, Kazuhiko Nishimoto, Kenichi Suenaga, Kouji Taira.
Application Number | 20060030243 11/184960 |
Document ID | / |
Family ID | 34916449 |
Filed Date | 2006-02-09 |
United States Patent
Application |
20060030243 |
Kind Code |
A1 |
Nishimoto; Kazuhiko ; et
al. |
February 9, 2006 |
Polishing composition
Abstract
A polishing composition containing an abrasive and water,
wherein the polishing composition has a pH of from 0.1 to 7, and
satisfies the following conditions: (1) that the number of
polishing particles having sizes of 0.56 .mu.m or more and less
than 1 .mu.m is 500,000 or less per 1 cm.sup.3 of the polishing
composition; and (2) that the ratio of polishing particles having
sizes of 1 .mu.m or more is 0.001% by weight or less to the entire
polishing particles in the polishing composition. The polishing
composition is suitable for polishing substrates for precision
parts including, for example, recording disk substrates, such as
magnetic disks, optical disks, and opto-magnetic disks, photomask
substrates, optical lenses, optical mirrors, optical prisms and
semiconductor substrates, and the like.
Inventors: |
Nishimoto; Kazuhiko;
(Wakayama-shi, JP) ; Taira; Kouji; (Wakayama-shi,
JP) ; Suenaga; Kenichi; (Wakayama-shi, JP) ;
Honma; Yuichi; (Wakayama-shi, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Assignee: |
Kao Corporation
|
Family ID: |
34916449 |
Appl. No.: |
11/184960 |
Filed: |
July 20, 2005 |
Current U.S.
Class: |
451/41 ; 51/307;
51/308; 51/309; G9B/5.299 |
Current CPC
Class: |
C09K 3/1463 20130101;
G11B 5/8404 20130101; B24B 37/0056 20130101; C09K 3/1409 20130101;
B24B 37/044 20130101; C09G 1/02 20130101 |
Class at
Publication: |
451/041 ;
051/308; 051/307; 051/309 |
International
Class: |
B24D 3/02 20060101
B24D003/02; B24B 1/00 20060101 B24B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 9, 2004 |
JP |
2004-232378 |
Oct 1, 2004 |
JP |
2004-289475 |
Oct 12, 2004 |
JP |
2004-298117 |
Nov 19, 2004 |
JP |
2004-336601 |
Claims
1. A polishing composition comprising an abrasive and water,
wherein the polishing composition has a pH of from 0.1 to 7, and
satisfies the following conditions: (1) that the number of
polishing particles having sizes of 0.56 .mu.m or more and less
than 1 .mu.m is 500,000 or less per 1 cm.sup.3 of the polishing
composition; and (2) that the ratio of polishing particles having
sizes of 1 .mu.m or more is 0.001% by weight or less to the entire
polishing particles in the polishing composition.
2. The polishing composition according to claim 1, wherein the
polishing composition further satisfies the following condition:
(3) that the ratio of polishing particles having sizes of 3 .mu.m
or more is 0.0008% by weight or less to the entire polishing
particles in the polishing composition.
3. The polishing composition according to claim 1, wherein the
abrasive has an average particle size of primary particles of from
1 to 50 nm.
4. The polishing composition according to claim 1, wherein the
abrasive is contained in the polishing composition in an amount of
from 0.5 to 20% by weight.
5. The polishing composition according to claim 1, wherein the
abrasive is colloidal silica.
6. The polishing composition according to claim 1, wherein the
polishing composition is used for a magnetic disk substrate.
7. The polishing composition according to claim 1, wherein the
number of nano scratches of a polished substrate is 1.5 or less per
1 cm.sup.2 according to a standard test.
8. A polishing particle preparation comprising an abrasive and
water, satisfying the following conditions: (i) that the number of
polishing particles having sizes of 0.56 .mu.m or more and less
than 1 .mu.m is 500,000 or less per 1 cm.sup.3 of the polishing
particle preparation; and (ii) that the ratio of polishing
particles having sizes of 1 .mu.m or more is 0.001% by weight or
less to the entire polishing particles in the polishing particle
preparation, wherein the polishing particle preparation is used in
the preparation of the polishing composition as defined in claim
1.
9. A process for producing the polishing composition as defined in
claim 1, comprising the following purification steps of: (I)
filtering a pre-purification polishing composition with a
depth-type filter, to give an intermediate filtrate; and (II)
filtering the intermediate filtrate with a pleated type filter, to
give the polishing composition, wherein the fluctuation range of
the pressure at an inlet of the depth-type filter in the step (I)
is 50 kPa or less.
10. The process according to claim 9, wherein the number of
polishing particles having sizes of 0.56 .mu.m or more and less
than 1 .mu.m is 1,000,000 or less per 1 cm.sup.3 of the
intermediate filtrate obtained after the step (I).
11. The process according to claim 9, wherein the number of
polishing particles having sizes of 0.56 .mu.m or more and less
than 1 .mu.m is 1,000,000 or less per 1 cm.sup.3 of the
intermediate filtrate to be supplied for the step (II).
12. A process for producing the polishing particle preparation as
defined in claim 8, comprising the following purification steps of:
(I') filtering a pre-purification polishing particle preparation
with a depth-type filter, to give an intermediate filtrate; and
(II') filtering the intermediate filtrate with a pleated type
filter, to give the polishing particle preparation, wherein the
fluctuation range of the pressure at an inlet of the depth-type
filter in the step (I') is 50 kPa or less.
13. The process according to claim 12, wherein the number of
polishing particles having sizes of 0.56 .mu.m or more and less
than 1 .mu.m is 1,000,000 or less per 1 cm.sup.3 of the
intermediate filtrate obtained after the step (I').
14. The process according to claim 12, wherein the number of
polishing particles having sizes of 0.56 .mu.m or more and less
than 1 .mu.m is 1,000,000 or less per 1 cm.sup.3 of the
intermediate filtrate to be supplied for the step (II').
15. A method for manufacturing a substrate, comprising the step of
polishing a substrate with a polishing machine using the polishing
composition as defined in claim 1.
16. The method according to claim 15, wherein the substrate is a
magnetic disk substrate.
17. The method according to claim 16, wherein the magnetic disk
substrate is a Ni--P plated aluminum alloy substrate.
18. The method according to claim 15, wherein the method comprising
the step of polishing a substrate to be polished while feeding the
polishing composition to the polishing machine comprising a platen
at a flow rate of 0.06 cm.sup.3/minute or more per 1 cm.sup.2 of an
area to be polished of the substrate.
19. The method according to claim 15, wherein the platen pressure
of the polishing machine is from 3 to 50 kPa.
20. The method according to claim 15, wherein the method comprises
plural polishing steps, wherein the polishing composition is used
for a finish polishing.
21. The method according to claim 15, wherein a difference between
a pH of the polishing composition before polishing and a pH of a
waste liquid after polishing is 2 or less.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a polishing composition and
a polishing particle preparation which is used in the production of
the polishing composition, and processes for producing these
polishing composition and polishing particle preparation, and a
method for manufacturing a substrate with the polishing
composition.
BACKGROUND OF THE INVENTION
[0002] In recent memory hard disk drives, high storage capacity and
miniaturization have been demanded. In order to increase the
recording density, it has been urged to lower the flying height of
a magnetic head and to reduce the unit recording area. Along with
this trend, even in a manufacturing step for a substrate for a
magnetic disk, the surface qualities of the substrate required
after polishing have become severely assessed every year. In other
words, in order to satisfy the lowering of flying height of the
magnetic head, the surface roughness, the microwaviness, the
roll-off and projections are required to be reduced, and in order
to satisfy the reduction in unit recording area, the acceptable
number of scratches per one side of the substrate has been reduced,
and the acceptable sizes and depths of the scratches have become
increasingly smaller.
[0003] Also, in the field of semiconductors, highly integrated
circuits and higher speed at the operating frequencies have been
advanced, and the production of thinner wiring is required
especially in highly integrated circuits. As a result, in the
method for manufacturing a substrate for semiconductors, since the
depth of focus becomes more shallow during the exposure of a
photoresist, even more improvement in surface smoothness and
planarization is desired.
[0004] In order to meet such requirements, in order to achieve the
reduction of damages (scratches and the like) generated on the
surface of the polished object for the purpose of improving the
surface smoothness, JP2000-15560 A, JP2001-271058 A, JP2003-188122
A, or JP2003-155471 A discloses a polishing liquid slurry having
the reduced number of coarse particles; and JP2002-97387 A or
JP-A-Hei-11-57454 discloses a process for producing a polishing
liquid slurry having the reduced number of coarse particles.
Further, in order to achieve reduction in microwaviness and
reduction in micropits of the surface of a polished object for the
purpose of improving surface smoothness, JP2004-204151 A,
JP2004-259421 A, or JP2004-204155 A discloses a polishing
composition which defines a particle size distribution of the
polishing particles.
[0005] However, there has yet been desired to develop a polishing
composition which can meet the requirement of an even higher
densification such as high storage capacity and high
integration.
SUMMARY OF THE INVENTION
[0006] Specifically, the present invention relates to: [0007] [1] a
polishing composition containing an abrasive and water, wherein the
polishing composition has a pH of from 0.1 to 7, and satisfies the
following conditions: [0008] (1) that the number of polishing
particles having sizes of 0.56 .mu.m or more and less than 1 .mu.m
is 500,000 or less per 1 cm.sup.3 of the polishing composition; and
[0009] (2) that the ratio of polishing particles having sizes of 1
.mu.m or more is 0.001% by weight or less to the entire polishing
particles in the polishing composition; [0010] [2] a polishing
particle preparation containing an abrasive and water, satisfying
the following conditions: [0011] (i) that the number of polishing
particles having sizes of 0.56 .mu.m or more and less than 1 .mu.m
is 500,000 or less per 1 cm.sup.3 of the polishing particle
preparation; and [0012] (ii) that the ratio of polishing particles
having sizes of 1 .mu.m or more is 0.001% by weight or less to the
entire polishing particles in the polishing particle preparation,
wherein the polishing particle preparation is used in the
preparation of the polishing composition as defined in the above
item [1]; [0013] [3] a process for producing the polishing
composition as defined in the above item [1], including the
following purification steps of: [0014] (I) filtering a
pre-purification polishing composition with a depth-type filter, to
give an intermediate filtrate; and [0015] (II) filtering the
intermediate filtrate with a pleated type filter, to give the
polishing composition, wherein the fluctuation range of the
pressure at an inlet of the depth-type filter in the step (I) is 50
kPa or less; [0016] [4] a process for producing the polishing
particle preparation as defined in the above item [2], including
the following purification steps of: [0017] (I') filtering a
pre-purification polishing particle preparation with a depth-type
filter, to give an intermediate filtrate; and [0018] (II')
filtering the intermediate filtrate with a pleated type filter, to
give the polishing particle preparation, wherein the fluctuation
range of the pressure at an inlet of the depth-type filter in the
step (I') is 50 kPa or less; and [0019] [5] a method for
manufacturing a substrate, including the step of polishing a
substrate with a polishing machine using the polishing composition
as defined in the above item [1].
DETAILED DESCRIPTION OF THE INVENTION
[0020] The embodiment 1 of the present invention relates to a
polishing composition being capable of giving a polished object
with a small surface roughness, of remarkably reducing nano
scratches which are important factors in high densification, and of
economically polishing the object to be polished; a polishing
particle preparation which is used for producing the polishing
composition; and a method for manufacturing a substrate including
the step of polishing a substrate using the polishing
composition.
[0021] The embodiment 2 of the present invention relates to a
process capable of economically producing the polishing composition
and the polishing particle preparation which is used for producing
the polishing composition.
[0022] The embodiment 3 of the present invention relates to a
method for manufacturing a substrate including a polishing step,
which is capable of remarkably reducing the above-mentioned nano
scratches, which is an important in high densification and also
economically polishing the substrate in the polishing step of a
precision part substrate such as a memory hard disk or
semiconductor element.
[0023] There are exhibited some excellent effects that the
polishing composition of the present invention realizes an
economical polishing rate, gives the polished substrate excellent
surface smoothness, and is capable of remarkably reducing fine nano
scratches by being used, for example, in the polishing step of a
substrate for precision parts for high density or high integration.
Therefore, a high-quality substrate for precision parts, such as a
magnetic disk substrate or a substrate for semiconductor element,
which has excellent surface properties, can be manufactured.
[0024] In addition, by using the processes of the present
invention, there are exhibited some effects that the polishing
composition, or a polishing particle preparation which is used for
producing the polishing composition can be prepared without
impairing its productivity.
[0025] Further, according to the method for manufacturing a
substrate of the present invention, since a remarkable reduction in
nano scratches of the polished substrate can be realized, there are
exhibited some effects that a high-quality substrate for precision
parts, such as a memory hard disk substrate or a substrate for
semiconductor element, which has excellent surface properties, can
be economically manufactured.
[0026] These and other advantages of the present invention will be
apparent from the following description.
Embodiment 1 of the Present Invention
[0027] A feature of the polishing composition of the present
invention resides in that the polishing composition contains an
abrasive and water, wherein the polishing composition has a pH of
from 0.1 to 7, and satisfies the following conditions: [0028] (1)
that the number of polishing particles having sizes of 0.56 .mu.m
or more and less than 1 .mu.m is 500,000 or less per 1 cm.sup.3 of
the polishing composition; and [0029] (2) that the ratio of
polishing particles having sizes of 1 .mu.m or more is 0.001% by
weight or less to the entire polishing particles in the polishing
composition. Since the polishing composition has the above feature,
nano scratches which could cause defects can be remarkably reduced,
whereby a substrate having excellent surface properties can be
provided at an economical polishing rate. The nano scratches are an
important property especially for increasing the recording density
of the memory hard disk substrate or the integration of the
semiconductor substrate. Therefore, a high-quality memory hard disk
substrate or a substrate for semiconductor element having excellent
surface properties can be manufactured by using the polishing
composition of the present invention.
[0030] The term "nano scratches" as used herein refers to fine
scratches on a substrate surface having a depth of 10 nm or more
and less than 100 nm, a width of 5 nm or more and less than 500 nm,
and a length of 100 .mu.m or more. The nano scratches can be
detected with an atomic force microscope (AFM), and can be
quantitatively evaluated as the number of nano scratches by
determination with "MicroMax" commercially available from VISION
PSYTEC a visual inspecting device as described in Examples set
forth below.
[0031] The above-mentioned nano scratches are fine surface defects
which have not been conventionally detected. In other words, when a
conventionally known method is used, the quality of the substrate
for high densification such as an even higher recording capacity or
higher integration has not been satisfactory. The present inventors
have intensively studied the causations therefor. As a result, they
have found for the first time that the reduction in the "nano
scratches" which have not been so far detected are
unsatisfactory.
[0032] The mechanism for reducing the nano scratches is not
elucidated. Although not wanting to be limited by theory, it is
presumed that aggregates of polishing primary particles or coarse
polishing primary particles contained in the polishing composition
are contacted with the surface of an object to be polished by
undergoing a local load under a polishing pressure, whereby the
deep nano scratches are generated. There have been elucidated that
the number of particles having sizes in the order of submicron
influences the nano scratches because scratches are generated by a
single particle or an aggregate of those particles, and that the
weight of the particles having sizes in the order of micron
influences the nano scratches because the larger the particles, the
more likely the occurrences of scratches. The term "polishing
particle(s)" in the polishing composition includes not only primary
particles used herein but also an aggregated particle in which the
primary particles are aggregated.
[0033] In the present invention, the preferred range for the
reduced number of nano scratches of the polished substrate is 1.5
or less per 1 cm.sup.2 according to the nano scratch standard test,
more preferably 1.2 or less, even more preferably 0.9 or less, and
even more preferably 0.6 or less, from the viewpoint of
manufacturing a high-precision substrate.
[0034] Here, the procedures for the nano scratch standard test are
as follows.
Nano Scratch Standard Test
[0035] 1. Substrate to be polished: A Ni--P-plated aluminum alloy
substrate (previously roughly polished with a polishing composition
containing an alumina abrasive, to adjust the average surface
roughness (AFM-Ra) to 10 .ANG. (1 nm)) having a thickness of 1.27
mm, an outer diameter of 95 mm and an inner diameter of 25 mm.
2. Polishing Conditions
[0036] Polishing testing machine: double-sided 9B polishing
machine, commercially available from Speedfam Co., Ltd. [0037]
Polishing pad: a finishing polishing pad made of urethane,
commercially available from FUJIBO (FUJI SPINNING Co., Ltd.)
(thickness: 0.9 mm, average pore size: 30 .mu.m) [0038] Rotational
speed of an upper platen: 32.5 r/min [0039] Feed amount (flow rate)
for a polishing composition: 100 mL/min [0040] Concentration of an
abrasive of a polishing composition: 7% by weight [0041] Polishing
time period: 4 minutes [0042] Polishing pressure: 7.8 kPa [0043]
Number of substrates introduced: 10 3. Determination Conditions for
Nano Scratches [0044] Measurement equipment: "MicroMax VMX-2100CSP"
commercially available from VISION PSYTEC CO., LTD. [0045] Light
source: 2S.lamda. (250 W) and 3P.lamda. (250 W) being both 100%
[0046] Tilt angle: -6.degree. [0047] Magnification: maximum (scope
of vision: 1/120 of the entire area) [0048] Observed range: entire
area (a substrate having an outer diameter of 95 mm and an inner
diameter of 25 mm) [0049] Iris: notch [0050] Evaluation: Four
pieces of substrates are randomly selected from 10 substrates
introduced into the polishing machine, and a total of the number of
nano scratches on each of both sides of the four substrates is
divided by 8 to calculate the number of nano scratches per side of
the substrate. The resulting value is divided by an area (65.97
cm.sup.2) of an object to be polished of one side to calculate and
evaluate the number of nano scratches per 1 cm.sup.2 of the
substrate.
[0051] The number of polishing particles having sizes of 0.56 .mu.m
or more and less than 1 .mu.m is 500,000 or less per 1 cm.sup.3 of
the polishing composition, and preferably 400,000 or less, more
preferably 300,000 or less, even more preferably 200,000 or less,
and even more preferably 100,000 or less, from the viewpoint of
reducing nano scratches. Here, the phrase "having sizes of 0.56
.mu.m or more and less than 1 .mu.m" refers to particle sizes of
the polishing particles.
[0052] In addition, the ratio of polishing particles having sizes
of 1 .mu.m or more is 0.001% by weight or less to the entire
polishing particles in the polishing composition, and the ratio is
preferably 0.0008% by weight or less, more preferably 0.0007% by
weight or less, even more preferably 0.0006% by weight or less, and
even more preferably 0.0005% by weight or less, from the viewpoint
of reducing nano scratches.
[0053] In addition, the ratio of polishing particles having sizes
of 3 .mu.m or more is, for example, 0.0008% by weight or less to
the entire polishing particles in the polishing composition, and
preferably 0.0007% by weight or less, more preferably 0.0006% by
weight or less, even more preferably 0.0005% by weight or less, and
even more preferably 0.0004% by weight or less, from the viewpoint
of reducing nano scratches.
[0054] As to the particle size of the polishing particles in the
polishing composition, Sizing Particle Optical Sensing method can
be employed, and the particle size can be determined by "Accusizer
780" commercially available from Particle Sizing Systems, "Coulter
Counter" commercially available from Coulter, and the like.
[0055] A method of controlling the number of polishing particles
having sizes of 0.56 .mu.m or more and less than 1 .mu.m, or a
content of polishing particles having sizes of 1 .mu.m or more, or
having sizes of 3 .mu.m or more is not limited. A method of general
dispersion or particle removal can be employed during or after the
production of the polishing composition. For example, a dispersion
method using a high-speed dispersion device or a high-pressure
dispersion device such as a high-pressure homogenizer; a
precipitation method by a centrifuge or the like; and a filtration
method such as a precision filtration or ultrafiltration with a
filter material can be utilized. Each of these methods can be used
for the treatment alone or in combination of two or more kinds, and
the order of treatments of the combination is not limited in any
manner. In addition, the treatment conditions and the number of
treatments can be appropriately selected and used.
[0056] Among them, as the method for effectively and economically
removing aggregates of the polishing primary particles and coarse
polishing primary particles contained in the polishing composition,
a precision filtration with a filter is suitably used.
[0057] As the filter material used for a precision filtration, a
depth-type filter or a pleated type filter can be used. As the
depth-type filter, a bag style filter (one commercially available
from Sumitomo 3M Limited or the like), as well as a cartridge style
filter (one commercially available from Advantec Toyo Kaisha, Ltd.,
Nihon Pall Ltd., CUNO Incorporated, Daiwabo Co., Ltd. or the like)
can be used.
[0058] The features of the depth-type filter are that the filter
material has a pore structure that is rough at an inlet side and
fine at an outlet side, and that the pore structure of the filter
material becomes finer continuously or stepwise from the inlet side
towards the outlet side. Specifically, larger particles among the
coarse particles are captured near the inlet side, and smaller
particles among the coarse particles are captured near the outlet
side. In addition, the coarser the particles, the higher the
likelihood of removability of the particles because the particles
are captured in the direction of a thickness of the filter in
multiple steps. The shape of the depth-type filter may be a bag
style in the form of a sac, or a cartridge style in the form of a
hollow cylinder. In addition, since a filter obtained by simply
molding those filter materials having the above-mentioned features
to the pleated form also has the function of the depth-type filter,
the filter is classified as depth-type filters.
[0059] The pleated type filter refers to one produced by forming a
filter material in the pleated form, to give a hollow cylindrical
cartridge style filter. Contrary to the depth-type filter in which
the particles are captured in each portion in the direction of the
thickness of the filter, the feature of the pleated type filter
resides in that the filter has a small thickness of the filter
material, so that it is said that the particles are mainly captured
on the surface of the filter, whereby generally giving a high
filtration precision.
[0060] The filtration method may be a recirculation method in which
filtration is repeatedly carried out, or a one-pass method.
Alternatively, a batch process in which a one-pass method is
repeated may be used. As to the method of passing the liquid, a
pump is preferably used in the recirculation method, and a pressure
filtration method in which an air pressure or the like is
introduced into a tank can be used in addition to the use of the
pump in the one-pass method.
[0061] The particle size of the coarse particles to be removed can
be controlled by properly selecting the pore structure of the
filter.
[0062] The filter system may be a single-step filtration, or a
multiple-step filtration in a combination thereof. The multi-step
filtration has advantages of improving the particle size control
(filtration precision) of the coarse particles to be removed and an
economic advantage by properly selecting a pore size of the filter
and a structure of the filter material, and further properly
selecting the order of the processing of the filter. In other
words, when a filter having a large pore structure is used as the
earlier step, and a filter having a fine pore structure as the
subsequent step, there is an advantage that the life of the filter
can be extended overall. In the structure of the filter material,
when the depth-type filter is used as the earlier step and the
pleated type filter is used as the subsequent step, there is an
advantage that the life of the filter can be extended overall.
[0063] As the abrasive usable in the present invention, the
abrasives that are generally used for polishing can be used. The
abrasive includes metals; carbides of metals or metalloids,
nitrides of metals or metalloids, oxides of metals or metalloids or
borides of metals or metalloids; diamond, and the like. The
elements for metals or metalloids include those elements belonging
to the Group 2A, 2B, 3A, 3B, 4A, 4B, 5A, 6A, 7A or 8 of the
Periodic Table (long period form). Specific examples of the
abrasives include silicon oxide (hereinafter also referred to as
silica), aluminum oxide (hereinafter also referred to as alumina),
silicon carbide, diamond, manganese oxide, magnesium oxide, zinc
oxide, titanium oxide (hereinafter also referred to as titania),
cerium oxide (hereinafter also referred to as ceria), zirconium
oxide, and the like. It is preferable to use one or more kinds of
these abrasives from the viewpoint of an increase in the polishing
rate. Among them, silica, alumina, titania, ceria, zirconium oxide,
and the like are suitable for polishing a substrate for precision
parts such as a substrate for a semiconductor element, or a
substrate for a magnetic disk.
[0064] The polishing particles are preferably colloidal particles
and fumed particles, from the viewpoint of reduction of nano
scratches which are surface defects. Among the polishing particles,
the colloidal particles are preferable, and the colloidal particles
include, for example, colloidal silica particles, colloidal ceria
particles, colloidal alumina particles, and colloidal titania
particles, and the colloidal silica particles are more preferable.
The colloidal silica particles can be prepared by a process of
generating silica particles from, for example, an aqueous silicic
acid solution. In addition, one obtained by surface-modifying or
surface-improving these polishing particles with a functional
group, one obtained by forming composite particles with a
surfactant or other abrasive or the like can be used.
[0065] The abrasive has an average particle size of the primary
particles of preferably from 1 to 50 nm, from the viewpoint of
reducing the nano scratches and lowering the surface roughness
(average surface roughness: Ra, peak-to-valley value: Rmax). The
abrasive has an average particle size of the primary particles of
more preferably from 3 to 50 nm, even more preferably from 5 to 40
nm, and even more preferably from 5 to 30 nm, from the viewpoint of
simultaneously increasing the polishing rate.
[0066] The average particle size of the primary particles of the
abrasive can be obtained as an average particle size according to a
method of obtaining a particle size from an observed image through
a transmission electron microscope (TEM), titration method, or BET
method.
[0067] The content of the abrasive is preferably 0.5% by weight or
more, more preferably 1% by weight or more, even more preferably 3%
by weight or more, and even more preferably 5% by weight or more,
of the polishing composition upon use from the viewpoint of
increasing the polishing rate. In addition, the content of the
abrasive is preferably 20% by weight or less, more preferably 15%
by weight or less, even more preferably 13% by weight or less, and
even more preferably 10% by weight or less, of the polishing
composition upon use, from the viewpoint of economically improving
surface quality. Therefore, the content of the abrasive is
preferably from 0.5 to 20% by weight, more preferably from 1 to 15%
by weight, even more preferably from 3 to 13% by weight, and even
more preferably from 5 to 10% by weight, of the polishing
composition, from the viewpoint of increasing the polishing rate
and economically improving surface quality. The content of the
abrasive may be any content during the production of the polishing
composition and the content upon use. In many cases, the polishing
composition is usually prepared as a concentrate, which is diluted
upon use.
[0068] Water usable in the present invention includes ion exchanged
water, distilled water, ultrapure water and the like. The content
of water which corresponds to the balance excluding the abrasive
and the other components from 100% by weight, is preferably from 60
to 99% by weight, and more preferably from 80 to 97% by weight, of
the polishing composition.
[0069] The polishing composition of the present invention has a pH
of from 0.1 to 7. Under alkaline conditions, the occurrences of
nano scratches are remarkable as compared to those under acidic
conditions. Although not wanting to be limited by theory, although
the mechanism for occurrences of nano scratches is not elucidated,
it is presumably as follows. Under alkaline atmosphere in which the
polishing particles themselves are strongly repulsive to each other
by surface charges, the aggregates of the polishing primary
particles or coarse polishing primary particles contained in the
polishing composition are not densely packed in the polishing
portion, whereby under polishing pressure a local load is more
likely to be generated thereto. The pH is preferably determined
according to the kinds of the objects to be polished and their
required properties. When the material of the object to be polished
is a metallic material, the pH is preferably 6 or less, more
preferably 5 or less, and even more preferably 4 or less, from the
viewpoint of increasing the polishing rate. In addition, the pH is
preferably 0.5 or more, more preferably 1 or more, and even more
preferably 1.4 or more, from the viewpoint of the influence to
human bodies and corrosion resistance of the polishing machine.
Especially, in the substrate for precision parts in which the
material of the object to be polished is a metallic material as in
the case of a nickel-phosphorus (Ni--P) plated aluminum alloy
substrate, the pH is preferably from 0.5 to 6, more preferably from
1.0 to 5, and even preferably from 1.4 to 4, from the
above-mentioned viewpoint.
[0070] The pH can be adjusted with the following acid or a salt
thereof. Specific examples of the acid or a salt thereof include
inorganic acids such as nitric acid, sulfuric acid, nitrous acid,
persulfuric acid, hydrochloric acid, perchloric acid, phosphoric
acid, phosphonic acid, phosphinic acid, pyrophosphoric acid,
tripolyphosphoric acid, and amide sulfuric acid, or salts thereof;
organic phosphonic acids such as 2-aminoethylphosphonic acid,
1-hydroxyethylidene-1,1-diphosphonic acid,
aminotri(methylenephosphonic acid),
ethylenediaminetetra(methylenephosphonic acid),
diethylenetriaminepenta(methylenephosphonic acid),
ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid,
ethane-1-hydroxy-1,1-diphosphonic acid,
ethane-1-hydroxy-1,1,2-triphosphonic acid,
ethane-1,2-dicarboxy-1,2-diphosphonic acids,
methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic
acids, 1-phosphonobutane-2,3,4-tricarboxylic acids, and
.alpha.-methylphophonosuccinic acid, or salts thereof;
aminocarboxylic acids such as glutamic acid, picolinic acid, and
aspartic acid, or salts thereof; carboxylic acids, such as oxalic
acid, nitroacetic acid, maleic acid and oxaloacetic acid, or salts
thereof; and the like. Among them, the inorganic acids, the organic
phosphonic acids and salts thereof are preferable from the
viewpoint of reduction of nano scratches.
[0071] In addition, among the inorganic acids or salts thereof,
nitric acid, sulfuric acid, hydrochloric acid, perchloric acid, or
a salt thereof is more preferable. Among the organic phosphonic
acids or salts thereof, 1-hydroxyethylidene-1,1-diphosphonic acid,
aminotri(methylenephosphonic acid),
ethylenediaminetetra(methylenephosphonic acid),
diethylenetriaminepenta(methylenephosphonic acid), or a salt
thereof is more preferable. These acids or salts thereof may be
used alone or in admixture of two or more kinds.
[0072] The counterion (cation) of these salts is not particularly
limited. Specific examples of the counterion of these salts include
a metal ion, ammonium ion, or an alkylammonium ion. Specific
examples of the metal include the metals belonging to the Group 1A,
1B, 2A, 2B, 3A, 3B, 4A, 6A, 7A or 8 of the Periodic Table (long
period form). The ammonium ion or the metal belonging to the Group
1A of the periodic table is preferable, from the viewpoint of
reduction of nano scratches.
[0073] In addition, there can be added other component to the
polishing composition of the present invention as occasion demands.
The other component includes, for example, thickeners, dispersing
agents, anticorrosive agents, basic substances, surfactants, and
the like. In addition, although it cannot be generally defined
depending upon the materials of the object to be polished, in
general, an oxidizing agent can be added for the metal material,
from the viewpoint of increasing the polishing rate. The oxidizing
agent includes hydrogen peroxide, permanganic acid, chromic acid,
nitric acid, peroxo acid, oxyacid, or salts thereof, and oxidizable
metal salts.
[0074] The polishing composition of the present invention having
the constitution as mentioned above can be prepared by mixing each
of the above-mentioned components with a known method.
[0075] The process for producing a polishing composition includes,
for example, the following two manners. [0076] (1) a method
including the step of adding other components to a mixture prepared
by mixing a polishing particle preparation and water; and [0077]
(2) a method including the step of adding a polishing particle
preparation to a mixture of other components and water.
[0078] Among them, it is preferable from the viewpoint of economic
advantages that the polishing composition of the present invention
is first produced by preparing a polishing particle preparation
(Embodiment A-1) containing an abrasive and water, satisfying the
following conditions: [0079] (i) that the number of polishing
particles having sizes of 0.56 .mu.m or more and less than 1 .mu.m
is 500,000 or less per 1 cm.sup.3 of the polishing particle
preparation; and [0080] (ii) that the ratio of polishing particles
having sizes of 1 .mu.m or more is 0.001% by weight or less to the
entire polishing particles in the polishing particle preparation as
a concentrate, and thereafter formulating other components as
mentioned above to the polishing particle preparation.
[0081] In addition, the process (2) in which the polishing particle
preparation (Embodiment A-1) is added to a mixture of other
components and water is preferable, from the viewpoint of
dispersion stability of the abrasive.
[0082] Here, in the process (1), other components can be used by
diluting with a proper amount of water as occasion demands.
[0083] Therefore, the present invention also relates to a polishing
particle preparation.
[0084] The polishing particle preparation may be those used in the
process (1) or (2) mentioned above for producing the polishing
composition, and includes, besides the above-mentioned Embodiment
A-1, the following embodiments: [0085] (Embodiment A-2) a polishing
particle preparation according to Embodiment A-1, further
satisfying the following conditions: [0086] (iii) that the ratio of
polishing particles having sizes of 3 .mu.m or more is 0.0008% by
weight or less to the entire polishing particles in the polishing
particle preparation; [0087] (Embodiment A-3) a polishing particle
preparation according to Embodiment A-1 or A-2, wherein the
abrasive has an average particle size of primary particles of from
1 to 50 nm; [0088] (Embodiment A-4) a polishing particle
preparation according to any one of Embodiment A-1 to A-3, wherein
the abrasive is contained in the polishing particle preparation in
an amount of from 1 to 60% by weight; [0089] (Embodiment A-5) a
polishing particle preparation according to any one of Embodiment
A-1 to A-4, wherein the abrasive is colloidal silica; [0090]
(Embodiment A-6) a polishing particle preparation according to any
one of Embodiments A-1 to A-5, wherein the polishing particle
preparation is used for producing the polishing composition used
for a magnetic disk substrate; and [0091] (Embodiment A-7) a
polishing particle preparation according to any one of Embodiments
A-1 to A-6, wherein the polishing particle preparation is used for
producing the polishing composition, wherein the number of nano
scratches of a polished substrate is 1.5 or less per 1 cm.sup.2
according to a standard test.
[0092] The content of the abrasive in the polishing particle
preparation is preferably 1% by weight or more, more preferably 5%
by weight or more, and even more preferably 10% by weight or more,
from the viewpoint of increasing the polishing rate, and the
content is preferably 60% by weight or less, and more preferably
50% by weight or less, from the viewpoint of economically improving
the surface quality. Therefore, the content is preferably from 1 to
60% by weight, more preferably from 5 to 50% by weight, and even
more preferably from 10 to 50% by weight.
[0093] In addition, the content of water in the polishing particle
preparation is preferably 40% by weight or more, and more
preferably 50% by weight or more, from the viewpoint of fluidity of
the polishing particle preparation, and the content is preferably
99% by weight or less, more preferably 95% by weight or less, and
even more preferably 90% by weight or less, from the viewpoint of
increasing the polishing rate. Therefore, the content is preferably
from 40 to 99% by weight, more preferably from 50 to 95% by weight,
and even more preferably from 50 to 90% by weight.
[0094] The above-mentioned polishing particle preparation can be
suitably used in the preparation of the polishing compositions of
the following Embodiments 1 to 7: [0095] (Embodiment 1) a polishing
composition containing an abrasive and water, wherein the polishing
composition has a pH of from 0.1 to 7, and satisfies the following
conditions: [0096] (1) that the number of polishing particles
having sizes of 0.56 .mu.m or more and less than 1 .mu.m is 500,000
or less per 1 cm.sup.3 of the polishing composition; and [0097] (2)
that the ratio of polishing particles having sizes of 1 .mu.m or
more is 0.001% by weight or less to the entire polishing particles
in the polishing composition; [0098] (Embodiment 2) the polishing
composition according to Embodiment 1, wherein the polishing
composition further satisfies the following condition: [0099] (3)
that the ratio of polishing particles having sizes of 3 .mu.m or
more is 0.0008% by weight or less to the entire polishing particles
in the polishing composition; [0100] (Embodiment 3) the polishing
composition according to Embodiment 1 or 2, wherein the abrasive
has an average particle size of primary particles of from 1 to 50
nm. [0101] (Embodiment 4) the polishing composition according to
any one of Embodiments 1 to 3, wherein the abrasive is contained in
the polishing composition in an amount of from 0.5 to 20% by
weight; [0102] (Embodiment 5) the polishing composition according
to any one of Embodiments 1 to 4, wherein the abrasive is colloidal
silica; [0103] (Embodiment 6) the polishing composition according
to any one of Embodiments 1 to 5, wherein the polishing composition
is used for a magnetic disk substrate; and [0104] (Embodiment 7)
the polishing composition according to any one of Embodiments 1 to
6, wherein the number of nano scratches of a polished substrate is
1.5 or less per 1 cm.sup.2 according to a standard test.
[0105] The polishing composition of the present invention can be
used while contacting the substrate in the polishing step which
includes the step of feeding the polishing composition between a
polishing pad, such as a nonwoven organic polymer-based polishing
pad and a substrate to be polished, i.e. feeding the polishing
composition to the polishing side of the substrate placed between
polishing platens to which the polishing pad is attached, and
moving the polishing platens and/or the substrate, while applying a
given load. The generation of the nano scratches can be remarkably
suppressed by this polishing step.
[0106] In order to effectively reduce the nano scratches, the
substrate to be polished is polished with the polishing composition
of the present invention, or while a polishing composition being
prepared by mixing each of the components so as to have the
polishing composition of the present invention. By polishing the
substrate to be polished as mentioned above, a substrate having
excellent surface quality can be manufactured, the surface defects
of the substrate, particularly nano scratches, being remarkably
reduced, even more lower surface roughness being lowered.
Therefore, the present invention also relates to a method for
manufacturing a substrate, including the step of polishing a
substrate with a polishing machine using the polishing composition
of the present invention.
[0107] The polishing composition of the present invention can be
preferably used in the manufacture a substrate for precision parts.
For example, the polishing composition is suitable for polishing
substrates for precision parts, including recording disk substrates
such as magnetic disks, opto-magnetic disks and optical disks; and
photomask substrates, optical lenses, optical mirrors, optical
prisms, and semiconductor substrates, and the like. In the
manufacture of the semiconductor substrate, the polishing
composition of the present invention can be used in the steps of
polishing a silicon wafer (bare wafer), forming an embedded metal
line, subjecting an interlayer dielectric to planarization, forming
a film for shallow trench isolation, and forming an embedded
capacitor, and the like.
[0108] The polishing composition of the present invention is
especially effective in the polishing step, and the polishing
composition can be similarly applied to grinding steps other than
this, for example, lapping step, and the like.
[0109] The material of a substrate to be polished, which is
suitably used for the polishing composition of the present
invention, includes, for example, metals or metalloids such as
silicon, aluminum, nickel, tungsten, copper, tantalum and titanium,
and alloys thereof; glassy substances such as glass, glassy carbon
and amorphous carbons; ceramic materials such as alumina, silicon
dioxide, silicon nitride, tantalum nitride, and titanium carbide;
resins such as polyimide resins; and the like. Among them, a
substrate to be polished is preferably made of a metal such as
aluminum, nickel, tungsten or copper, or made of an alloy
containing these metals as the main components. For example, a
Ni--P plated aluminum alloy substrate and a glass substrate made of
crystallized glass, reinforced glass or the like are more
preferable, and a Ni--P plated aluminum alloy substrate is even
more preferable.
[0110] The shape of the substrate to be polished is not
particularly limited. For example, those having shapes containing
planar portions such as discs, plates, slabs and prisms, or shapes
containing curved portions such as lenses can be subjects for
polishing with the polishing composition of the present invention.
Among them, disc-shaped substrates to be polished are even more
preferable for the polishing.
[0111] In addition, the evaluation method for surface roughness,
which is a measure of surface smoothness, is not limited. In the
present invention, the surface roughness is evaluated as roughness
that can be determined at a short wavelength of 10 .mu.m or less in
the AFM (atomic force microscope), and expressed as an average
surface roughness (AFM-Ra). Specifically, the polishing composition
of the present invention is suitable for a polishing step for a
magnetic disk substrate, further for a polishing step for reducing
the surface roughness (AFM-Ra) of the polished surface to 2.0 .ANG.
(0.20 nm) or less.
[0112] When the manufacturing steps for a substrate includes plural
polishing steps, the polishing composition of the present invention
is preferably used in the second or subsequent step among the
multi-polishing steps, and it is more preferable that the polishing
composition of the present invention is used in the polishing step
as a finish-polishing step, from the viewpoint of remarkably
reducing nano scratches and surface roughness, thereby obtaining
excellent surface smoothness. The finish-polishing step refers to
at least one of final polishing steps in a case there are
multi-polishing steps.
[0113] In this polishing step, in order to avoid admixing of the
abrasive or the polishing composition of the earlier step, separate
polishing machines may be used for the individual polishing step.
And when the separate polishing machines are used, it is preferable
to clean the substrate for each step. Here, the polishing machines
are not particularly limited. The substrate manufactured as
described above has a remarkable reduction in the nano scratches,
and excellent surface smoothness. In other words, the surface
roughness (AFM-Ra) of the polished substrate is, for example, 2.0
.ANG. (0.20 nm) or less, preferably 1.8 .ANG. (0.18 nm) or less,
and more preferably 1.5 .ANG. (0.15 nm) or less.
[0114] Here, the surface properties of the substrate before
subjecting to the polishing step with the polishing composition of
the present invention are not particularly limited. For example, a
substrate having surface properties such that AFM-Ra is 10 .ANG.
(1.0 nm) or less is suitable.
[0115] The abrasive usable in the method for manufacturing a
substrate of the present invention may be same one as that usable
in the above-mentioned polishing composition. The above-mentioned
polishing step is carried out in the second or subsequent step
among the plural polishing steps, and it is even more preferable to
carry out the polishing step as a finish-polishing step.
[0116] As described above, the substrate manufactured by using the
polishing composition of the present invention or the method for
manufacturing a substrate of the present invention has excellent
surface smoothness so that a substrate having a surface roughness
(AFM-Ra) of, for example, 2.0 .ANG. (0.20 nm) or less, preferably
1.8 .ANG. (0.18 nm) or less, and more preferably 1.5 .ANG. (0.15
nm) or less may be obtained.
[0117] In addition, the manufactured substrate has very small
number of nano scratches. Therefore, when the substrate is, for
example, a memory hard disk substrate, the substrate can meet the
requirement of a recording density of 120 G bits/inch.sup.2, and
preferably 160 G bits/inch.sup.2. And when the substrate is a
semiconductor substrate, the substrate can meet the requirement of
a wire width of 65 nm, and preferably 45 nm.
[0118] The polishing composition of the present invention can be
produced in the manner as described above, or the polishing
composition can be economically produced according to the
production method described hereinbelow without impairing its
productivity.
[0119] Therefore, the present invention also relates to a process
for producing a polishing composition capable of economically
producing the polishing composition.
Embodiment 2 of the Present Invention
[0120] The feature of the process for producing a polishing
composition of the present invention resides in that the process is
a process for producing the above-mentioned polishing composition,
including the following purification steps of: [0121] (I) filtering
a pre-purification polishing composition with a depth-type filter,
to give an intermediate filtrate; and [0122] (II) filtering the
intermediate filtrate with a pleated type filter, to give the
polishing composition, wherein the fluctuation range of the
pressure at an inlet of the filter in the step (I) is 50 kPa or
less. According to the polishing composition produced by the
process of the present invention, the nano scratches which cause
defects can be remarkably reduced, whereby a substrate having
excellent surface smoothness can be provided.
[0123] As mentioned above, the nano scratches are a property that
is an important factor in high densification and high integration
in the substrate for a memory hard disk substrate or a
semiconductor element. Therefore, by using the above-mentioned
polishing composition obtainable in the present invention, a
high-quality substrate for a memory hard disk or a semiconductor
element having excellent surface properties can be
manufactured.
[0124] As mentioned above, it has been elucidated that the nano
scratches can be reduced by reducing the number of coarse polishing
particles having particular sizes existing in the polishing
composition. However, in the conventionally known technique, the
coarse polishing particles could not be industrially satisfactorily
reduced. For example, the step of filtering with a screen type
filter such as a membrane filter cannot be used on an industrial
scale even though the aggregates of the polishing particles or
coarse polishing particles can be removed. In addition, in the step
of filtering only with the pleated type filter, while the removal
of the aggregate of the polishing particles or coarse polishing
particles is satisfactory, clogging is generated by the coarse
particles, thereby making it difficult to economically obtain a
purified polishing composition.
[0125] In the present invention, there is exhibited an effect that
a polishing composition capable of remarkably reducing the nano
scratches can be economically obtained by filtering first with a
depth-type filter, and thereafter with a pleated type filter, and
adjusting the fluctuation range of the pressure at an inlet of the
depth-type filter to a specified range.
[0126] Here, in the filtration with a filter, when an effective
sieve opening of the filter material is widened due to pressure,
the coarse particles captured or to be captured undesirably pass
through the filter, or on the other hand, the detachment of the
material of filter (fiber or the like) due to pressure may lead to
lowering of the filtration precision. In order to prevent these
phenomena, the controlling the pressure difference between the
pressures at an inlet and at an outlet of the filter to a given
value or lower is generally recommended by the various filter
manufacturers. However, even when the pressure difference is
controlled to a given value or lower, the lowering of the
filtration precision incurred. In view of the above, the present
inventors have intensively progressed in the study. As a result,
the present inventors have found that the pulsating movement of
liquid is generated during the liquid conveying, the fluctuation
range of the pressure at an inlet of the filter is widened, thereby
causing lowering of the filtration precision.
[0127] Therefore, the present inventors have further intensively
progressed in the study. As a result, the capturing efficiency of
the coarse particles and precision of the filter can be increased
in the step for producing a polishing composition by carrying out
filtration first with a depth-type filter, and then with a pleated
type filter, and controlling the fluctuation range of the pressure
at an inlet of the depth-type filter within a given range, whereby
the present inventors have found for the first time that even a
polishing composition in which the amount of the coarse particles
is very strictly controlled as in the present invention can be
produced.
[0128] In the present invention, the fluctuation range of the
pressure at an inlet of the depth-type filter refers to a
difference between the maximum pressure and the minimum pressure
applied to the filter during liquid conveying. When plural
depth-type filters are used, the fluctuation range refers to a
value of the depth-type filter positioned at the most upstream.
[0129] The fluctuation range of the pressure at an inlet of the
depth-type filter in step (I) is 50 kPa or less, and the
fluctuation range is preferably 40 kPa or less, and more preferably
30 kPa or less, from the viewpoint of reducing the load of removing
the coarse particles in the step (II) due to increase in the
filtration precision of the step (I). The fluctuation range of the
pressure at an inlet of the filter can be determined by reading off
the maximum pressure and the minimum pressure during liquid
conveying using, for example, a pressure gauge attached to a filter
housing.
[0130] As one method of reducing the above-mentioned fluctuation
range of the pressure, a method of reducing pulsation generated
from the liquid conveying pump including, for example, a method of
conveying liquid with a non-pulsating pump having small pulsation,
or a method of setting a pressure absorbing device such as damper
at an outlet of the pump for preventing pulsation can be used.
Alternatively, a method of increasing the volume of the pipe in
order to reduce the pulsation of the substance to be filtered
between the liquid conveying pump and the inlet of the filter
including, for example, a method of setting an accumulator or the
like between the outlet of the pump and the filter, a method of
extending the length of the pipe between the pump and the filter,
or a method of widening the pipe diameter can be used. In addition,
the fluctuation range of the pressure can be even made smaller by
using each of these methods alone or in a proper combination of
them according to a filtration apparatus and filtration conditions
and the like.
[0131] In the purification step of the polishing composition, the
depth-type filter in the step (I) may be the same ones as those
used during the control of the content of the coarse particles in
the above-mentioned polishing composition.
[0132] In the step (I), the depth-type filter may be used in a
single step or multi-steps in a combination thereof (for example,
in serial arrangement). In addition, the bag style and cartridge
style depth-type filters may be used in combination. In the
multi-step filtration, the appropriate pore size of the filter and
the structure of the filter material are properly selected
depending upon the number of polishing particles having particle
sizes of 0.56 .mu.m or more and less than 1 .mu.m in the
pre-purification polishing composition, and the order of treatment
of the filter is properly selected, whereby the particle size
control (filtration precision) of the removed coarse particles and
economic advantages can be improved. In other words, when a filter
having a large pore structure is used in a step (upstream side)
earlier than a filter having a finer pore structure, there is an
effect that the life of the filter can be extended in the overall
production steps.
[0133] As the pleated type filter in the step (II), one produced by
forming a filter material into a pleated form to give a hollow
cylindrical cartridge style filter (one commercially available from
Advantec Toyo Kaisha, Ltd., Nihon Pall Ltd., CUNO Incorporated,
Daiwabo Co., Ltd. or the like) can be generally used.
[0134] The pleated type filter usable in the step (II) may be used
in a single step or multi-steps in a combination thereof (for
example, in serial arrangement). In the multi-step filtration, the
appropriate pore size of the filter and the structure of the filter
material are properly selected depending upon the number of
polishing particles having particle sizes of 0.56 .mu.m or more and
less than 1 .mu.m in the intermediate filtrate after the step (I),
and the order of treatment of the filter is properly selected,
whereby the productivity of the polishing composition of the
present invention can be improved. In other words, when a filter
having a large pore structure is used in a step (upstream side)
earlier than a filter having a finer pore structure, the life of
the filter can be extended overall. Further, when plural filters
having the same pore size are used in later step of multi-steps,
there is an effect that the quality of the polishing composition
can be stabilized.
[0135] In the overall filtration steps, when the filtration is
carried out first with the depth-type filter, and thereafter with
the pleated type filter, the life of the filter can be extended
overall, whereby the polishing composition in the present invention
can be produced economically advantageously.
[0136] The pore sizes of these depth-type filter and pleated type
filter are generally expressed as a precision of filtration capable
of 99% removal, for example, the pore size of 1.0 .mu.m refers to a
filter capable of removing particles having a diameter of 1.0 .mu.m
at a ratio of 99%.
[0137] The depth-type filter usable in the step (I) of the present
invention has a pore size of preferably 5.0 .mu.m or less, more
preferably 3.0 .mu.m or less, and even more preferably 2.0 .mu.m or
less, from the viewpoint of reducing loads of removing coarse
particles in the step (II).
[0138] In addition, in the case where plural depth-type filters are
used in the step (I) (in, for example, serial arrangement), when a
final filter has a pore size in the order of submicron or less, the
loads of removing coarse particles in the step (II) are more
reduced, thereby improvement in the productivity can be
achieved.
[0139] The pleated type filter usable in the step (II) in the
present invention has a pore size of preferably 1.0 .mu.m or less,
more preferably 0.8 .mu.m or less, even more preferably 0.6 .mu.m
or less, and even more preferably 0.5 .mu.m or less, from the
viewpoint of reducing the content of coarse particles.
[0140] The number of the polishing particles having particle sizes
of 0.56 .mu.m or more and less than 1 .mu.m per 1 cm.sup.3 in the
intermediate filtrate after the step (I) is preferably 1,000,000 or
less, and the number is more preferably 800,000 or less, even more
preferably 700,000 or less, and even more preferably 600,000 or
less, from the viewpoint of reducing the loads of removing coarse
particles in the step (II).
[0141] The number of the polishing particles having particle sizes
of 0.56 .mu.m or more and less than 1 .mu.m per 1 cm.sup.3 in the
polishing composition after the step (II) is 500,000 or less, and
the number is preferably 400,000 or less, even more preferably
300,000 or less, even more preferably 200,000 or less, and even
more preferably 100,000 or less, from the viewpoint of reducing
nano scratches.
[0142] As the filtration methods in the step (I) and the step (II),
the same filtration method as the filtration method usable during
the control of the content of the coarse particles in the
above-mentioned polishing composition can be used. In a pressure
filtration method in which an air pressure or the like is
introduced into a tank, the fluctuation range of the pressure at an
inlet of the filter can be reduced.
[0143] In the intermediate filtrate to be supplied in the step
(II), the number of polishing particles having sizes of 0.56 .mu.m
or more and less than 1 .mu.m is preferably 1,000,000 or less per 1
cm.sup.3. In order to realize this, besides passing through the
step (I), a general dispersion or particle removal step may be
provided before and/or after the step (I). For example, a
dispersion method using a high-speed dispersion device or a
high-pressure dispersion device such as a high-pressure
homogenizer, a precipitation method with a centrifuge or the like
can be utilized. When these methods are used, the methods may be
used alone or in combination of two or more kinds, and the order of
the methods (treatments) in the combination is not limited in any
way. In addition, the treatment conditions and the number of
treatments can be properly selected.
[0144] As the supplying pressure to the filter in the step (I) and
the step (II), it is preferable that the filtration is carried out
at a pressure or lower than that recommended by the manufacturers
for the filter used, from the viewpoint of filtration precision. In
addition, by making the pressure difference between the pressures
at the inlet and at the outlet of the filter larger, the effective
sieve opening of the filter material is widened, which leads to
lowering the filtration precision. Therefore, it is preferable that
the pressure difference is controlled at a given value or less.
[0145] The pressure difference of the depth-type filter in the step
(I) is preferably 200 kPa or less, more preferably 170 kPa or less,
and even more preferably 150 kPa or less, from the viewpoint of
filtration precision. The pressure difference of the pleated type
filter in the step (II) is preferably 250 kPa or less, more
preferably 200 kPa or less, and even more preferably 170 kPa or
less, from the viewpoint of filtration precision. Here, using, for
example, a pressure gauge attached to a filter housing at the inlet
and the outlet, the pressure difference applied to the filter
during the liquid conveying can be calculated from a difference of
their averages.
[0146] Here, the filtration conditions other than those mentioned
above in the steps (I) and (II) are not particularly limited.
[0147] The pre-purification polishing composition in the present
invention refers to a composition containing an abrasive containing
polishing particles, before being supplied to the above-mentioned
step (I). The pre-purification polishing composition includes, for
example, a composition prepared by mixing an abrasive, water, and
other components as occasion demands. In addition, the
pre-purification polishing composition is preferably in a state in
which the polishing particles are dispersed.
[0148] In the present invention, a polishing composition can be
produced by subjecting the pre-purification polishing composition
to steps (I) and (II). Specifically, a polishing composition can be
produced by subjecting a composition prepared by mixing an
abrasive, water, and other components to the steps (I) and (II); or
produced by subjecting the pre-purification polishing composition
containing an abrasive and water to the steps (I) and (II) to give
a filtrate, and thereafter mixing other components to the
filtrate.
[0149] In addition, since the present invention is a process for
producing the above-mentioned polishing composition, the abrasive,
the polishing particles and water, and their contents usable in the
present invention may be the same as the abrasive, the polishing
particles and water, and their contents usable in the
above-mentioned polishing composition.
[0150] In the present invention, an acid or a salt thereof, or an
alkali which can be used in the pH adjustment of the polishing
composition may be the same ones as those used in the pH adjustment
of the above-mentioned polishing composition. Further, other
components which may be the same components as those that can be
formulated in the above-mentioned polishing composition as occasion
demands can be formulated.
[0151] Examples of the polishing composition after the step (II)
produced in the present invention include, for example, the
polishing compositions (Embodiments 1 to 7) in the above-mentioned
polishing compositions.
[0152] In the present invention, the polishing composition after
the step (II) satisfies the following conditions (2): [0153] (2)
that the ratio of polishing particles having sizes of 1 .mu.m or
more is 0.001% by weight or less to the entire polishing particles
in the polishing composition, and it is preferable that the
polishing composition further satisfies the following conditions
(3): [0154] (3) that the ratio of polishing particles having sizes
of 3 .mu.m or more is 0.0008% by weight or less to the entire
polishing particles in the polishing composition, from the
viewpoint of reducing nano scratches.
[0155] The above-mentioned polishing composition obtained by the
process of the present invention can be used in the manner as
described above.
[0156] Here, the surface properties of the substrate before
subjecting to a polishing step using the polishing composition
after the step (II) of the present invention are not particularly
limited, and, for example, a substrate having surface properties
such that AFM-Ra is 10 .ANG. (1 nm)) or less is preferable.
[0157] The substrate manufactured using the polishing composition
obtained by the process of the present invention has excellent
surface properties, so that a substrate having a surface roughness
(AFM-Ra) of 2.0 .ANG. (0.20 nm) or less, preferably 1.8 .ANG. (0.18
nm) or less, and more preferably 1.5 .ANG. (0.15 nm) or less can be
obtained.
[0158] Further, the substrate manufactured by using the polishing
composition obtained by the process of the present invention has
very small number of nano scratches. Therefore, when the substrate
is, for example, a memory hard disk substrate, the substrate can
meet the requirement of a recording density of 120 G
bits/inch.sup.2, and preferably 160 G bits/inch.sup.2. And when the
substrate is a semiconductor substrate, the substrate can meet the
requirement of a wire width of 65 nm, and preferably 45 nm.
[0159] In addition, the above-mentioned polishing particle
preparations (Embodiments A-1 to A-7) can be produced economically
advantageously in the same manner as in the process for producing
the polishing composition of the present invention without
impairing the productivity.
[0160] Therefore, the present invention also relates to a process
for producing a polishing particle preparation capable of
economically advantageously producing the above-mentioned polishing
particle preparation.
[0161] The feature of the process for producing a polishing
particle preparation of the present invention resides in that the
process includes the following purification steps of: [0162] (I')
filtering a pre-purification polishing particle preparation with a
depth-type filter, to give an intermediate filtrate; and [0163]
(II') filtering the intermediate filtrate with a pleated type
filter, to give the polishing particle preparation, wherein the
fluctuation range of the pressure at an inlet of the depth-type
filter in the step (I') is 50 kPa or less.
[0164] The fluctuation range of the pressure at an inlet of the
depth-type filter in the step (I') is 50 kPa or less, and the
fluctuation range of the pressure is preferably 40 kPa or less, and
more preferably 30 kPa or less, from the viewpoint of reducing the
loads of removing coarse particles in the step (II') due to
improvement in the filtration precision of the step (I'). The
determination method for the fluctuation range of the pressure at
an inlet of the filter, and the method of reducing the fluctuation
range of the pressure may be the same as those of the
above-mentioned process for producing the polishing
composition.
[0165] In the purification step of the polishing particle
preparation, the filter to be used and the embodiments of use of
the filter may be the same as those of the above-mentioned process
for producing the polishing composition.
[0166] The number of polishing particles having sizes of 0.56 .mu.m
or more and less than 1 .mu.m is preferably 1,000,000 or less per 1
cm.sup.3 of the intermediate filtrate obtained after the step (I'),
and the number of polishing particles is more preferably 800,000 or
less, even more preferably 700,000 or less, and even more
preferably 600,000 or less, from the viewpoint of reducing the
loads of removing coarse particles in the step (II').
[0167] The number of polishing particles having sizes of 0.56 .mu.m
or more and less than 1 .mu.m is 500,000 or less per 1 cm.sup.3 of
the polishing particle preparation obtained after the step (II'),
and the number of polishing particles is preferably 400,000 or
less, more preferably 300,000 or less, even more preferably 200,000
or less, and even more preferably 100,000 or less, from the
viewpoint of reducing the nano scratches.
[0168] In addition, the ratio of polishing particles having sizes
of 1 .mu.m or more is 0.001% by weight or less to the entire
polishing particles in the polishing particle preparation after the
step (II'), and the ratio is preferably 0.0008% by weight or less,
more preferably 0.0007% by weight or less, even more preferably
0.0006% by weight or less, and even more preferably 0.0005% by
weight or less, from the viewpoint of reducing the nano
scratches.
[0169] In addition, the ratio of polishing particles having sizes
of 3 .mu.m or more is, for example, 0.0008% by weight or less to
the entire polishing particles in the polishing particle
preparation after the step (II'), and the ratio is preferably
0.0007% by weight or less, more preferably 0.0006% by weight or
less, even more preferably 0.0005% by weight or less, and even more
preferably 0.0004% by weight or less, from the viewpoint of
reducing the nano scratches.
[0170] The number of polishing particles having sizes of 0.56 .mu.m
or more and less than 1 .mu.m is preferably 1,000,000 or less per 1
cm.sup.3 of the intermediate filtrate supplied to the step (II'),
and in order to realize this, besides subjecting to the step (I'),
a general dispersion or particle removal step may be provided
before and/or after the step (I') in the same manner as in the
above-mentioned process for producing the polishing
composition.
[0171] Here, the filtration methods and the filtration conditions
in the steps (I') and (II') may be the same as those in the
above-mentioned process for producing the polishing composition
[0172] The pre-purification polishing particle preparation usable
in the present invention refers to an aqueous dispersion of an
abrasive before being supplied to the above-mentioned step (I').
The abrasive and water may be the same ones as those usable in the
above-mentioned polishing composition. In addition, the
pre-purification polishing particle preparation is preferably in
the state in which the polishing particles are dispersed.
[0173] In the present invention, the above-mentioned polishing
particle preparations (Embodiments A-1 to A-7) can be produced
economically advantageously by subjecting the pre-purification
polishing particle preparation to the steps (I') and (II'). The
polishing particle preparation can be used in the preparation of
the above-mentioned polishing composition.
[0174] The present invention further relates to a method for
manufacturing a substrate including the step of polishing a
substrate for precision parts such as memory hard disks and
semiconductor elements, wherein the above-mentioned nano scratches
which are an important factor in high densification are remarkably
reduced, and the substrate can be polished economically.
Embodiment 3 of the Present Invention
[0175] The feature of the method for manufacturing a substrate of
the present invention resides in that the method includes the step
of polishing a substrate to be polished while feeding the polishing
composition mentioned above to the polishing machine containing a
platen at a flow rate of 0.06 cm.sup.3/minute or more per 1
cm.sup.2 of an area to be polished of the substrate. Therefore, the
nano scratches which cause defects can be remarkably reduced, so
that a substrate having excellent surface smoothness can be
provided. As mentioned above, the nano scratches are a property
that is an important factor in high densification and high
integration in the substrate for a memory hard disk or a
semiconductor element. Therefore, by using the method for
manufacturing a substrate of the present invention, a high-quality
substrate for a memory hard disk or a semiconductor element having
excellent surface properties can be manufactured.
[0176] It is elucidated in the present invention that the nano
scratches can be reduced by controlling the polishing pressure
during polishing with the above-mentioned polishing
composition.
[0177] The polishing composition usable in the present invention
may be the above-mentioned polishing composition. Among them, the
polishing composition as described below is preferable.
[0178] Specifically, the number of polishing particles having sizes
of 0.56 .mu.m or more and less than 1 .mu.m in the polishing
composition is preferably 300,000 or less, more preferably 200,000
or less, even more preferably 100,000 or less, and even more
preferably 10,000 or less, from the viewpoint of reducing nano
scratches.
[0179] Also, the ratio of the polishing particles having sizes of 1
.mu.m or more to the entire polishing particles in the polishing
composition is preferably 0.0008% by weight or less, more
preferably 0.0007% by weight or less, even more preferably 0.0006%
by weight or less, and even more preferably 0.0005% by weight or
less, from the viewpoint of reducing nano scratches.
[0180] In addition, the ratio of the polishing particles having
sizes of 3 .mu.m or more to the entire polishing particles in the
polishing composition is preferably 0.0008% by weight or less, more
preferably 0.0007% by weight or less, even more preferably 0.0006%
by weight or less, even more preferably 0.0005% by weight or less,
and even more preferably 0.0004% by weight or less, from the
viewpoint of reducing nano scratches.
[0181] In order to reduce the number of polishing particles having
sizes of 0.5 .mu.m or more and less than 1 .mu.m, the filtration or
the like with a filter is effective. For example, when a pleated
type filter having high filtration precision of a pore size of 0.45
.mu.m is used, the nano scratches can be reduced. Further, the
platen pressure during the polishing is adjusted to 3 to 50 kPa in
order to avoid the penetration of the aggregates of polishing
particles or coarse polishing particles that may cause the nano
scratches into a space between the substrate and polishing pad,
whereby there is an advantage that the nano scratches can be
remarkably reduced.
[0182] As the filter material for the precision filtration, a
depth-type filter or a pleated type filter can be used. The
depth-type filter includes, for example, ones usable in the control
of the content of the coarse particles in the above-mentioned
polishing composition.
[0183] The filtration method may be same as the filtration method
in the above-mentioned polishing composition. Further, in
consideration of economic advantages, a depth-type filter having a
pore size larger than that of a pleated type filter can be used
prior to the pleated type filter. The depth-type filter has a pore
size of preferably 10 .mu.m or less, more preferably 5 .mu.m or
less, and even more preferably 3 .mu.m or less. The pleated type
filter has a pore size of preferably 1 .mu.m or less, more
preferably 0.8 .mu.m or less, even more preferably 0.6 .mu.m or
less, and even more preferably 0.5 .mu.m or less.
[0184] The content of the abrasive in the polishing composition is,
for example, 1% by weight or more, preferably 3% by weight or more,
more preferably 5% by weight or more, and even more preferably 7%
by weight or more, from the viewpoint of occurrences of the nano
scratches due to polishing vibration. Also, the content is for
example, 20% by weight or less, preferably 15% by weight or less,
more preferably 13% by weight or less, and even more preferably 10%
by weight or less, from the viewpoint of economic advantages. In
other words, the content is, for example, from 1 to 20% by weight,
preferably from 3 to 15% by weight, more preferably from 5 to 13%
by weight, and even more preferably from 7 to 10% by weight. These
content may be any content during the production of the polishing
composition and the content upon use. In many cases, the polishing
composition is usually prepared as a concentrate, which is diluted
upon use.
[0185] The abrasive may be the abrasive usable in the
above-mentioned polishing composition. Among them, aluminum oxide,
fumed silica, colloidal silica, cerium oxide, zirconium oxide,
titanium oxide and the like are suitable for polishing a substrate
for precision parts such as a semiconductor wafer or semiconductor
element, or a substrate for magnetic recording medium.
[0186] The shape of the abrasive is preferably spherical colloidal
particles, in order to increase the packing density of the
abrasive, thereby obtaining a smooth surface. Further, colloidal
cerium oxide particles, colloidal silica particles,
surface-modified colloidal silica particles, and the like are
preferable, and the colloidal silica particles are even more
preferable, from the viewpoint of reducing nano scratches which
cause surface defects. Here, the colloidal silica particles can be
obtained by a process of generating silica particles from, for
example, an aqueous silicic acid solution. The colloidal silica is
suitable for finish polishing a substrate for a high-recording
density memory magnetic disk, preferably a substrate for a memory
hard disk, requiring an even higher degree of smoothness, and also
suitable for preferably final polishing use, or polishing use for a
semiconductor device substrate.
[0187] The balance of the polishing composition is water. The
content thereof is not particularly limited.
[0188] In addition, the polishing composition may at least contain
an abrasive and water. Components such as an acid, a salt, and an
oxidizing agent may be contained from the viewpoint of giving the
desired action.
[0189] The pH of the polishing composition usable in the present
invention is from 0.1 to 7. When the pH exceeds 7, in the case
where the colloidal silica is used as an abrasive, the nano
scratches increase. In general, the polishing of the substrate is
established by a balance between physical polishing power and
chemical polishing power. Specifically, the substrate surface is
corroded by the chemical polishing power, thereby making it easier
to grind the substrate, and the corroded portion is scraped off by
physical polishing power, whereby the polishing progresses. For
example, in the case of a Ni--P plated substrate, when the pH
exceeds 7, the chemical polishing power becomes very weak, so that
the physical polishing power becomes dominant, whereby not only the
number of nano scratches become larger, but also the polishing rate
is dramatically lowered.
[0190] The pH of the polishing composition is preferably 5 or less,
and more preferably 4 or less, from the viewpoint of increasing the
polishing rate, and the pH is 0.1 or more, preferably 0.5 or more,
more preferably 1 or more, and even more preferably 1.4 or more,
from the viewpoint of influence to human bodies and corrosion of
machines. Even more preferably, in the substrate for working
precision parts which are a metal of a nickel-phosphorus
(Ni--P)-plated aluminum alloy substrate, the pH is preferably 4.5
or less, and more preferably 3.5 or less. Therefore, the pH may be
adjusted in accordance with the purposes that are respected. Even
more preferably, in the substrate for working precision parts which
are a metal of a nickel-phosphorus (Ni--P)-plated aluminum alloy
substrate, the pH is preferably from 0.1 to 6, more preferably 1 to
4.5, and even more preferably from 1.4 to 3.5, from the
above-mentioned viewpoints.
[0191] Further, the difference between the pH of the polishing
composition before polishing and the pH of the polishing waste
liquid after polishing is preferably 2 or less, more preferably 1
or less, and even more preferably 0.5 or less. Here, the polishing
composition before polishing refers to a polishing composition
before supplying to a polishing surface, and the polishing waste
liquid after polishing refers to a waste liquid of the polishing
liquid after supplying the polishing composition to the substrate
and polishing. When the fluctuation of the above-mentioned pH is
large, the abrasive particles contained in the polishing
composition are likely to be aggregated during polishing, and the
aggregates can be the causing substances of the nano scratches. On
the other hand, when the pH difference is adjusted to 2 or less,
the aggregation of the abrasive grains is more likely to be
suppressed, so that a substrate having reduced nano scratches can
be more suitably manufactured.
[0192] In order to adjust the above-mentioned pH difference to 2 or
less, the flow rate of the polishing composition, for example, can
be adjusted. When a polishing composition giving a large pH
difference is used, the pH difference can be controlled by making
the flow rate large.
[0193] The flow rate of the polishing composition supplied to the
polishing machine is 0.06 cm.sup.3/minute or more, per 1 cm.sup.2
of an area to be polished of the substrate. When the flow rate is
less than 0.06 cm.sup.3/minute, vibration of the polishing machine
is generated due to a large frictional resistance, thereby
undesirably increasing the gap between the polishing side of the
substrate and the polishing pad, whereby the aggregates of the
polishing particles are penetrated between the gap to cause
increase in the number of nano scratches. The flow rate is
preferably 0.09 cm.sup.3/minute or more, more preferably 0.12
cm.sup.3/minute or more, and even more preferably 0.15
cm.sup.3/minutes or more, from the viewpoint of occurrences of nano
scratches due to polishing vibration, and the flow rate is
preferably 0.46 cm.sup.3/minute or less, more preferably 0.30
cm.sup.3/minute or less, and even more preferably 0.23
cm.sup.3/minute or less, from the viewpoint of economic advantages.
In addition, the flow rate is preferably from 0.09 to 0.46
cm.sup.3/minute, more preferably from 0.12 to 0.30 cm.sup.3/minute,
and even more preferably from 0.15 to 0.23 cm.sup.3/minute.
[0194] During polishing, the polishing step is carried out by
feeding the polishing composition between a polishing pad, such as
a nonwoven organic polymer-based polishing pad, and a substrate to
be polished, i.e. feeding the polishing composition to the
polishing side of the substrate pressed against platens to which
the polishing pad is attached, wherein the polishing composition is
in contact with the substrate, and moving the platens and/or the
substrate, while applying a given pressure.
[0195] The platen pressure in the present invention refers to a
pressure of the platen applied to the polishing surface of the
substrate to be polished during polishing. Although not wanting to
be limited by theory, when this platen pressure is adjusted to a
range of preferably from 3 to 50 kPa, the gap between the polishing
surface of the substrate and the polishing pad is appropriately
narrowed, so that it is deduced that aggregates of polishing
particles causing the nano scratches are less likely to flow out
onto the substrate, thereby reducing the nano scratches. For
example, when the platen pressure is adjusted to 3 kPa or more, the
aggregates of polishing particles and the like are less likely to
be penetrated into the gap between the polishing surface of the
substrate and the polishing pad, so that the nano scratches are
reduced. In addition, when the platen pressure is adjusted to 50
kPa or less, the vibration of the polishing machine is
appropriately maintained due to low frictional resistance, so that
the gap between the polishing surface of the substrate and the
polishing pad caused by vibration is narrowed, whereby the
aggregates of the polishing particles are less likely to be placed
between the platens, so that nano scratches are reduced. The platen
pressure is preferably 3 kPa or more, more preferably 5 kPa or
more, and even more preferably 8 kPa or more, from the viewpoint of
productivity. Therefore, the platen pressure is preferably from 5
to 40 kPa, and more preferably from 10 to 30 kPa, from the
viewpoint of economically advantageously reducing the nano
scratches.
[0196] Here, the above-mentioned platen pressure can be adjusted by
applying air pressure or a weight to the platen and/or the
substrate.
[0197] In the above-mentioned polishing step, the substrate to be
polished can be polished by feeding the polishing composition to
the polishing side of the substrate placed between platens to which
a porous organic polymer-based polishing pad is attached, and
moving the platens or the substrate, while applying a given load.
Other conditions during polishing (kinds of polishing machine,
kinds of polishing pad and the like) are not particularly limited.
In addition, the method of feeding a polishing composition to a
polishing side, the method of moving platens or a substrate and the
like may be carried out by known methods.
[0198] The materials of the substrate which is an object to be
polished suitably used in the present invention may be the same as
the material of the object to be polished suitable for the
above-mentioned polishing composition.
[0199] Effectively, in the method for manufacturing a substrate,
the present invention is preferably used in a second or subsequent
step in the case where the method includes plural polishing steps
including rough polishing step, the present invention is, for
example, preferably used in a final polishing step. The substrate
manufactured as described above has remarkably reduced nano
scratches and excellent surface smoothness.
[0200] As described above, by using the method for manufacturing a
substrate of the present invention, the occurrences of nano
scratches are remarkably reduced, so that a high-quality substrate
having excellent surface properties, for example, a substrate for
precision parts such as a memory hard disk or a semiconductor
element can be suitably manufactured.
EXAMPLES
[0201] The following examples further describe and demonstrate
embodiments of the present invention. The examples are given solely
for the purposes of illustration and are not to be construed as
limitations of the present invention.
Example I
[0202] Polishing was evaluated with a Ni--P-plated aluminum alloy
substrate having a thickness of 1.27 mm, an outer diameter of 95 mm
and an inner diameter of 25 mm as a substrate to be polished,
wherein the substrate was previously roughly polished with a
polishing composition containing an alumina abrasive to adjust its
AFM-Ra to 10 .ANG. (1 nm).
Example I-1
[0203] As an abrasive, 25 L of colloidal silica slurry
(commercially available from DuPont, average particle size of
primary particles: 22 nm, a product having a concentration of
silica particles: 40% by weight) was filtered with a bag style
depth-type filter (commercially available from Sumitomo 3M Limited,
Liquid Filter 522), thereafter filtered with a pleated type filter
(commercially available from Advantec Toyo Kaisha, Ltd.,
TCS-E045-S1FE), to give a polishing particle preparation a of Table
1 (Preparation Example 1). The polishing particle preparation a was
added while stirring to an aqueous solution prepared by adding
given amounts of an aqueous 35% by weight-hydrogen peroxide
solution (commercially available from Asahi Denka Co., Ltd.), an
aqueous 60% by weight-HEDP (1-hydroxyethylidene-1,1-diphosphonic
acid) solution (commercially available from Solutia Japan Limited),
and 95% by weight-sulfuric acid (commercially available from Wako
Pure Chemical Industries, Ltd.) to ion-exchanged water while
mixing, so as to have the concentrations shown in Table 2, to give
a polishing composition A.
Example I-2
[0204] The same procedures as in Example I-1 were carried out
except that an HDCII (MCY1001J012H13) commercially available from
Nihon Pall Ltd. was used as a pleated type filter, to give a
polishing particle preparation b of Table 1 (Preparation Example 2)
and a polishing composition B.
Example I-3
[0205] The same procedures as in Example I-1 were carried out
except that Zetapor (70006-01N-120PG) commercially available from
CUNO Incorporated was used as a pleated type filter, to give a
polishing particle preparation c of Table 1 (Preparation Example 3)
and a polishing composition C.
Example I-4
[0206] The same procedures as in Example I-1 were carried out
except that a pleated type filter was changed to a filter
commercially available from Advantec Toyo Kaisha, Ltd.
(TCPD-05A-S1FE), to give a polishing particle preparation d of
Table 1 (Preparation Example 4) and a polishing composition D.
Example I-5
[0207] The polishing particle preparation a of Preparation Example
1 was added while stirring to an aqueous solution prepared by
adding given amounts of a 60% by weight-aqueous HEDP solution and a
95% by weight-sulfuric acid to ion-exchanged water while mixing, to
give a polishing composition E.
Example I-6
[0208] The same procedures as in Example I-1 were carried out
except that the pleated type filter was changed to Ultipleat
Profile (PUY1UY020H13) commercially available from Nihon Pall Ltd.
having an intermediate structure, to give a polishing particle
preparation g of Table 1 (Preparation Example 5) and a polishing
composition G.
Example I-7
[0209] The polishing particle preparation a of Preparation Example
1 was added while stirring to an aqueous solution prepared by
adding given amounts of a 35% by weight-hydrogen peroxide solution,
a 60% by weight-aqueous HEDP solution and a 95% by weight-sulfuric
acid to ion-exchanged water while mixing, to give a polishing
composition I.
Example I-8
[0210] Eighty-six percent of the amount of the ion-exchanged water
necessary for the concentration shown in Table 2 was added to the
polishing particle preparation a of Preparation Example 1, to
prepare a diluted slurry. Separately, an acidic aqueous solution
prepared by mixing given amounts of a 35% by weight-hydrogen
peroxide solution (commercially available from Asahi Denka Co.,
Ltd.), a 60% by weight-aqueous HEDP solution (commercially
available from Solutia Japan Limited) and a 95% by weight-aqueous
sulfuric acid (commercially available from Wako Pure Chemical
Industries, Ltd.) with the remaining 14% of the above-mentioned
amount of ion-exchanged water was prepared. This acidic aqueous
solution was added to the above-mentioned diluted slurry while
stirring, to give a polishing composition K.
Comparative Example I-1
[0211] The same procedures as in Example I-1 were carried out
except that WAVE STAR (W-004-S-DO-E) commercially available from
Daiwabo Co., Ltd. was used as a pleated type filter, to give a
polishing particle preparation f of Table 1 (Preparation Example 6)
and a polishing composition F.
Comparative Example I-2
[0212] The polishing particle preparation a of Preparation Example
1 was added to ion-exchanged water while stirring so as to have the
concentration shown in Table 2, to give a polishing composition
H.
Comparative Example I-3
[0213] Colloidal silica slurry (commercially available from Nissan
Chemical Industries, Ltd., Snowtex ST-50, average particle size: 30
nm, a product having a concentration of silica particles: 48% by
weight) was added to ion-exchanged water while stirring.
Furthermore, the mixture was subjected to suction-filtration with a
membrane filter made of cellulose acetate (0.45 .mu.m, diameter: 90
mm), to give a polishing composition J.
Comparative Example I-4
[0214] One-hundred and five liters of a colloidal silica slurry
(commercially available from DuPont, average particle size of
primary particles: 22 nm, a product having a concentration of
silica particles: 40% by weight) was prepared, and 100 L of the
slurry was filtered with a bag style depth-type filter
(commercially available from Sumitomo 3M Limited, "Liquid Filter
522"), and then two-step depth-type cartridge filters (commercially
available from Nihon Pall Ltd., RM1F010H21 and RM1F005H21 connected
in series). After the colloidal silica slurry was allowed to stand
in the filter in a state where the filter was fully packed with the
colloidal silica slurry for 3 days, the remaining 5 L of the
above-mentioned colloidal silica slurry was filtered in the same
manner as above, to give about 5 L of a polishing particle
preparation m (Preparation Example 7).
[0215] The same procedures as in Example I-1 were carried out
except that the polishing particle preparation m was used in place
of the polishing particle preparation a, to give a polishing
composition M from the polishing particle preparation m.
[0216] Using the polishing particle preparations and the polishing
compositions obtained in Examples I-1 to I-8 and Comparative
Examples I-1 to I-4, the coarse particles, polishing rate and
surface roughness were determined or evaluated according to the
following conditions and methods, and the nano scratch was also
determined or evaluated according to "Nano Scratch Standard Test"
described herein. Furthermore, the relative evaluation to the
number of the nano scratches of Comparative Example I-1
(number/side) was carried out as the evaluation of the nano
scratches. Here, the polishing rate and the surface roughness are
values under the polishing conditions for Nano Scratch Standard
Test. The results obtained are shown in Table 2.
[Measurement Conditions for Polishing Particles]
[0217] Measuring Instrument: "Accusizer 780APS," commercially
available from Particle Sizing Systems (PSS) [0218] Injection Loop
Volume: 1 ml [0219] Flow Rate: 60 mL/min. [0220] Data Collection
Time: 60 sec. [0221] Number Channels: 128 [Determination Conditions
for Polishing Rate]
[0222] The polishing rate per unit time (.mu.m/min) was calculated
by dividing a weight difference (g) between an object to be
polished and the object after polishing by the density (8.4
g/cm.sup.3) of the object, and further dividing the resultant
quotient by the surface area (65.97 cm.sup.2) of the disk and the
polishing time period (min.).
[Method for Evaluating Surface Roughness (AFM-Ra)]
[0223] Measuring Instrument: "TM-M5E," commercially available from
Veeco [0224] Mode: non-contact [0225] Scan rate: 1.0 Hz [0226] Scan
area: 10.times.10 .mu.m
[0227] Evaluation: Determinations for the average surface roughness
(AFM-Ra) were taken on three points equidistant from both the inner
circumference and the outer circumference of the disk on both the
sides per one disk in a circumferential direction every
120.degree., and an average of the total of 6 points was obtained.
TABLE-US-00001 TABLE 1 Polishing Particles in Polishing Particle
Preparation Average Number of Polishing Particles Concentration of
Particles Concentration of Particles Polishing Particle Having
Sizes of 0.56 .mu.m or Having Sizes of 1 .mu.m or More Having Sizes
of 3 .mu.m or More Prep. Particle Size More and Less Than 1 .mu.m
to Entire Polishing Particles to Entire Polishing Particles Ex. No.
Preparation (nm) (number/cm.sup.3) (% by weight) (% by weight) 1 a
22 23,500 0.000037 0.000035 2 b 22 154,000 0.000104 0.000098 3 c 22
281,000 0.000032 0.000029 4 d 22 403,000 0.000116 0.000108 5 g 22
341,000 0.000146 0.000145 6 f 22 934,000 0.000024 0.000010 7 m 22
340,000 0.001180 0.001160
[0228] TABLE-US-00002 TABLE 2 Polishing Composition Abrasive Number
of Polishing Concentration.sup.1) of Concentration.sup.1) Particles
Having Sizes Particles Having Sizes of Particles Content.sup.1) of
0.56 .mu.m or More of 1 .mu.m or More to Having Sizes of 3 .mu.m or
of Entire and Less Than 1 .mu.m Entire Polishing More to Entire
Polishing Polishing Hydrogen Sulfuric Kind (number/cm.sup.3)
Particles Particles Particles Peroxide.sup.1) HEDP.sup.1)
Acid.sup.1) pH Ex. No. I-1 A 29,600 0.000248 0.000223 7.0 0.6 0.13
0.4 1.4 I-2 B 194,000 0.000525 0.000450 7.0 0.6 0.13 0.4 1.4 I-3 C
354,000 0.000162 0.000135 7.0 0.6 0.13 0.4 1.4 I-4 D 487,000
0.000585 0.000495 7.0 0.6 0.13 0.4 1.4 I-5 E 32,500 0.000124
0.000098 7.0 -- 0.13 0.4 1.4 I-6 G 430,000 0.000981 0.000924 7.0
0.6 0.13 0.4 1.4 I-7 I 36,400 0.000166 0.000148 7.0 0.6 0.03 0.1
5.0 I-8 K 38,500 0.000322 0.000290 7.0 0.6 0.13 0.4 1.4 Comp. Ex.
No. I-1 F 1,176,000 0.000161 0.000064 7.0 0.6 0.13 0.4 1.4 I-2 H
90,000 0.000086 0.000069 7.0 -- -- -- 9.6 I-3 J 47,600 0.000651
0.000626 24.0 -- -- -- 9.4 I-4 M 418,000 0.002370 0.002200 7.0 0.6
0.13 0.4 1.4 Number of Nano Scratches According to Standard Test
Polishing Relative Surface Rate.sup.2) Value (number/side)
(number/cm.sup.2) Roughness.sup.3) Ex. No. I-1 0.14 0.26 29 0.44
1.4 I-2 0.13 0.46 51 0.77 1.4 I-3 0.15 0.57 63 0.95 1.4 I-4 0.14
0.70 77 1.2 1.4 I-5 0.06 0.40 44 0.67 1.4 I-6 0.12 0.82 91 1.4 1.5
I-7 0.04 0.81 89 1.3 1.5 I-8 0.14 0.52 57 0.86 1.4 Comp. Ex. No.
I-1 0.14 1.00 110 1.7 1.5 I-2 0.02 22.2 2440 37 1.6 I-3 0.02 23.5
2590 39 1.4 I-4 0.14 1.05 116 1.8 1.5 .sup.1)% by weight
.sup.2).mu.m/min .sup.3)AFM-Ra (.ANG., 0.1 nm)
[0229] It can be seen from the results shown in Table 2 that the
occurrences of nano scratches in the substrates obtained using the
polishing compositions of Examples I-1 to I-8 are suppressed as
compared to that of Comparative Example I-1 or I-4, and that the
polishing rates are excellent and the occurrences of nano scratches
are suppressed in the substrates obtained using the polishing
compositions of Examples I-1 to I-8 as compared to those of
Comparative Example I-2 or I-3.
[0230] Furthermore, each of the substrates obtained in Examples I-1
to I-8 has very low surface roughness.
Example II
[0231] Coarse particles and nano scratches were evaluated in the
same manner as in Example I using the polishing compositions a' to
i' obtained in the following Examples II-1 to II-5 and Comparative
Examples II-1 to II-4. The results are shown in Table 3.
[0232] Furthermore, as an evaluation index for productivity in
filtration, in the case where at least 200 kg of a polishing
composition could be filtered without clogging, the productivity
evaluation is acceptable, and in the case where clogging was formed
so that filtration became difficult with 200 kg or less of a
polishing composition, the amount of the filtrate up to that point
was listed in Table 3.
[0233] Here, the differential pressure of the filters in Examples
and Comparative Examples was controlled by the flow rate so as to
have a pressure of 150 kPa or less in a depth-type filter, or 160
kPa or less in a pleated type filter.
Example II-1
[0234] As a pre-purification polishing composition, a colloidal
silica slurry (commercially available from DuPont, average particle
size of primary particles: 20 nm, a product having a concentration
of silica particles: 40% by weight, the number of polishing
particles having sizes of 0.56 .mu.m or more and less than 1 .mu.m:
6,875,000/cm.sup.3) was used. Using a diaphragm pump commercially
available from Yamada Corporation (model No. DP-10BT) as a pump and
a pulsation dumper commercially available from Yamada Corporation
(Model No. AD-10ST) at an outlet of the pump, the slurry was
conveyed with a 10 m tetoron braided hose (outer diameter: 18 mm,
inner diameter: 12 mm) as a pipe. Thereafter, the slurry was
filtered with a bag style depth-type filter (commercially available
from Sumitomo 3M Limited, "Liquid Filter 522") directly connected
to a pressure gauge in a housing as a filter in the first step and
serially placing two "TCP-JX"s commercially available from Advantec
Toyo Kaisha, Ltd. (pore size: 1.0 .mu.m) 250 mm in length as
pleated type filters in the subsequent step under the conditions
that the average flow rate was 10.3 kg/min, to give a polishing
composition a. The fluctuation range of the inlet pressure of the
depth-type filter was 30 kPa, and clogging was not formed at a
point where the amount of the filtrate was 200 kg. The polishing
composition a was added to an aqueous solution prepared by adding
given amounts of an aqueous 35% by weight-hydrogen peroxide
solution (commercially available from Asahi Denka Co., Ltd.), an
aqueous 60% by weight-HEDP solution (commercially available from
Solutia Japan Limited), and 95% by weight-sulfuric acid
(commercially available from Wako Pure Chemical Industries, Ltd.)
to ion-exchanged water while stirring, so as to have the
concentration shown in Table 3, to give a polishing composition
a'.
Example II-2
[0235] The same ones as those used in Example II-1 were used in the
same manner for the pre-purification polishing composition, and the
diaphragm pump, the dumper, the tetoron braided hose and the bag
style depth-type filter. Next to the bag style depth-type filter,
using "TCPD-03A" commercially available from Advantec Toyo Kaisha,
Ltd. (pore size: 3.0 .mu.m) 250 mm in length as a cartridge style
depth-type filter, and two serially placed "TCP-JX"s commercially
available from Advantec Toyo Kaisha Ltd. (pore size: 1.0 .mu.m) 250
mm in length as pleated type filters, the pre-purification
polishing composition was filtered under the conditions of an
average flow rate of 8.1 kg/min, to give a polishing composition b.
The fluctuation range of the inlet pressure of the depth-type
filter was 35 kPa, and clogging was not formed at a point where the
amount of the filtrate was 200 kg. A polishing composition b' was
obtained in the same manner as in Example II-1 using the resulting
polishing composition b.
Example II-3
[0236] The same ones as those used in Example II-1 were used in the
same manner for the pre-purification polishing composition and the
diaphragm pump, the damper, the tetoron braided hose and a bag
style depth-type filter. Next to the bag style depth-type filter,
using "TCPD-03A" commercially available from Advantec Toyo Kaisha,
Ltd. (pore size: 3.0 .mu.m), and "Profile II-010" commercially
available from Nihon Pall Ltd. (pore size: 1.0 .mu.m) each being
250 mm in length as cartridge style depth-type filters in this
order, and two serially placed "TCYE-HS" s commercially available
from Advantec Toyo Kaisha, Ltd. (pore size: 0.65 .mu.m) 250 mm in
length as pleated type filters, the pre-purification polishing
composition was filtered under the conditions that the average flow
rate was 5.2 kg/min, to give a polishing composition c. The
fluctuation range of the inlet pressure of the depth-type filter
was 32 kPa, and clogging was not formed at a point where the amount
of the filtrate was 200 kg. A polishing composition c' was obtained
in the same manner as in Example II-1 using the resulting polishing
composition c.
Example II-4
[0237] The same ones as those used in Example II-1 were used in the
same manner for the pre-purification polishing composition and the
diaphragm pump, the damper, the tetoron braided hose and the bag
style depth-type filter. Next to the bag style depth-type filter,
using "Profile II-020" commercially available from Nihon Pall Ltd.
(pore size: 2.0 .mu.m) and "Profile II-005" commercially available
from Nihon Pall Ltd. (pore size: 0.5 .mu.m) each being 250 mm in
length in this order as cartridge style filters, and two serially
placed "TCYE-HS"s commercially available from Advantec Toyo Kaisha,
Ltd. (pore size: 0.65 .mu.m) 250 mm in length as pleated type
filters, the pre-purification polishing composition was filtered
under the conditions of an average flow rate of 6.4 kg/min, to give
a polishing composition d. The fluctuation range of the inlet
pressure of the depth-type filter was 21 kPa, and clogging was not
formed when the amount of the filtrate was 200 kg. A polishing
composition d' was obtained in the same manner as in Example II-1
using the resulting polishing composition d.
Example II-5
[0238] The same ones as those used in Example II-1 were used in the
same manner for the pre-purification polishing composition and the
diaphragm pump, the damper, the tetoron braided hose and the bag
style depth-type filter. As a step of obtaining an intermediate
filtrate, the pre-purification polishing composition was first
filtered with a bag style depth-type filter under the conditions
that the average flow rate was 15.3 kg/min. The fluctuation range
of the inlet pressure of the depth-type filter was 39 kPa, and the
amount of the filtrate was 250 kg. The resulting primary filtrate
was treated using a KS TYPE SUPER HIGH SPEED CENTRIFUGE
(commercially available from KANSAI CENTRIFUGAL SEPARATOR MFG. CO.,
LTD., model No. U1-160, rotational cylinder size: 105 mm diameter,
730 mm height, maximum holding solid content: about 6 L), under the
conditions of a rotational speed of 18500 r/min, centrifugal
acceleration: 20000 G, average flow rate: 12.5 kg/min. This
intermediate filtrate was placed in a pressurizable 1
M.sup.3-stainless tank, and two "TCP-JX"s commercially available
from Advantec Toyo Kaisha, Ltd. (pore size: 1.0 .mu.m) 250 mm in
length were serially set as pleated type filters in the outlet-line
of the tank. The intermediate filtrate was filtered under the
pressurization conditions of 1.7 kg/cm.sup.2, to give a polishing
composition e. Clogging was not formed when the amount of the
filtrate was 200 kg. A polishing composition e' was obtained in the
same manner as in Example II-1 using the resulting polishing
composition e.
Comparative Example II-1
[0239] The same ones as those used in Example II-1 were used for
the pre-purification polishing composition and the bag style
depth-type filter. Using a 2-m tetoron braided hose (outer
diameter: 18 mm, inner diameter: 12 mm) as a pipe, the
pre-purification polishing composition was conveyed to a diaphragm
pump commercially available from Yamada Corporation (model No.
DP-10BT) and a depth-type filter. Next to the bag style depth-type
filter, using two serially placed "TCP-JX"s commercially available
from Advantec Toyo Kaisha, Ltd. (pore size: 1.0 .mu.m) 250 mm in
length as pleated type filters, the pre-purification polishing
composition was filtered under the conditions that the average flow
rate was 12.6 kg/min, to give a polishing composition f. The
fluctuation range of the inlet pressure of the depth-type filter
was 75 kPa, and clogging was not formed when the amount of the
filtrate was 200 kg. A polishing composition f' was obtained in the
same manner as in Example II-1 using the resulting polishing
composition f.
Comparative Example II-2
[0240] The same ones as those used in Example II-1 were used in the
same manner for the pre-purification polishing composition and the
diaphragm pump, the damper, the tetoron braided hose and the bag
style depth-type filter. The pre-purification polishing composition
was filtered with a bag style depth-type filter alone under the
conditions that the average flow rate was 13.5 kg/min, to give a
polishing composition g. The fluctuation range of the inlet
pressure of the depth-type filter was 50 kPa, and clogging was not
formed when the amount of the filtrate was 200 kg. A polishing
composition g' was obtained in the same manner as in Example II-1
using the resulting polishing composition g.
Comparative Example II-3
[0241] The same ones as those used in Example II-1 were used in the
same manner for the pre-purification polishing composition and the
diaphragm pump, the damper, and the tetoron braided hose. Using two
serially set "TCP-JX"s commercially available from Advantec Toyo
Kaisha, Ltd. (pore size: 1.0 .mu.m) 250 mm in length as pleated
type filters, the pre-purification polishing composition was
filtered under the conditions that the average flow rate was 8.9
kg/min, to give a polishing composition h. The fluctuation range of
the inlet pressure of the pleated type filter was 45 kPa, and
clogging was formed when the amount of the filtrate was 43 kg. A
polishing composition h' was obtained in the same manner as in
Example II-1 using the resulting polishing composition h.
Comparative Example II-4
[0242] The same ones as those used in Example II-1 were used in the
same manner for the pre-purification polishing composition and the
diaphragm pump, the damper, and the tetoron braided hose. Using two
serially set "TCYE-HS"s commercially available from Advantec Toyo
Kaisha, Ltd. (pore size: 0.65 .mu.m) 250 mm in length as pleated
type filters, the pre-purification polishing composition was
filtered under the conditions that the average flow rate was 7.5
kg/min, to give a polishing composition i. The fluctuation range of
the inlet pressure of the pleated type filter was 61 kPa, and
clogging was formed when the amount of the filtrate was 20 kg. A
polishing composition i' was obtained in the same manner as in
Example II-1 using the resulting polishing composition i.
TABLE-US-00003 TABLE 3 Conc. of Conc. of polishing polishing No. of
No. of particles particles Polishing polishing Having Having
Particles particles Sizes of Sizes of Having Having 1 .mu.m or 3
.mu.m or Sizes of Sizes of more to more to 0.56 .mu.m 0.56 .mu.m
Entire Entire or more or more Polishing Polishing Number and less
and less Particles Particles of Pleated Fluctuation Average than 1
.mu.m than 1 .mu.m After After Number of Type Range of Flow Before
After Step II Step II Productivity Depth Filter Filter Pressure
Rate Step II Step II (% by (% by (amount of A B C E F
Centrifugation G H (kPa) (kg/min) (#/cm.sup.3) (#/cm.sup.3) weight)
weight) filtration/kg) Ex. No. II-1 1 2 30 10.3 985,000 436,000
0.000598 0.000412 >200 II-2 1 1 2 35 8.1 685,000 241,000
0.000284 0.000108 >200 II-3 1 1 1 2 32 5.2 498,000 95,600
0.000301 0.000214 >200 II-4 1 1 1 2 21 6.4 395,000 67,300
0.000364 0.000154 >200 II-5 1 1 2 39 15.3 754,000 386,000
0.000352 0.000239 >200 Comp. Ex. No. II-1 1 2 75 12.6 1,426,000
724,000 0.000642 0.000326 >200 II-2 1 50 13.5 1,196,000 --
0.008515 0.000925 >200 II-3 2 45 8.9 6,875,000 1,325,000
0.002016 0.000951 43 II-4 2 61 7.5 6,875,000 127,000 0.000351
0.000218 20 The Number of Nano Hydrogen Sulfuric Scratches
According to Abrasive Peroxide HEDP Acid the Standard Test
Polishing (% by (% by (% by (% by Relative Composition weight)
weight) weight) weight) pH Value (#/side) (#/cm.sup.2) Ex. No. II-1
a' 7.0 0.6 0.13 0.4 1.4 0.68 82 1.2 II-2 b' 7.0 0.6 0.13 0.4 1.4
0.52 62 0.94 II-3 c' 7.0 0.6 0.13 0.4 1.4 0.37 44 0.67 II-4 d' 7.0
0.6 0.13 0.4 1.4 0.36 43 0.65 II-5 e' 7.0 0.6 0.13 0.4 1.4 0.64 77
1.2 Comp. Ex. No. II-1 f' 7.0 0.6 0.13 0.4 1.4 1.00 120 1.8 II-2 g'
7.0 0.6 0.13 0.4 1.4 1.20 144 2.2 II-3 h' 7.0 0.6 0.13 0.4 1.4 1.23
148 2.2 II-4 i' 7.0 0.6 0.13 0.4 1.4 0.47 56 0.85
[0243] It can be seen from the results in Table 3 that the
polishing compositions a' to e' obtained in Examples II-1 to II-5
can remarkably reduce nano scratches productively as compared to
the polishing compositions f' to i' obtained in Comparative
Examples II-1 to II-4.
Example III
[0244] Polishing was evaluated with a Ni--P plated aluminum alloy
substrate having a thickness of 1.27 mm and a diameter of 95 mm as
a substrate to be polished, wherein the substrate was previously
roughly polished with a polishing liquid containing an alumina
abrasive to adjust its surface roughness (Ra) to 1 nm and waviness
(Wa) to 4.8 nm.
Preparation of Polishing Composition 1
[0245] Seven percent by weight colloidal silica particles
(commercially available from DuPont, average particle size of
primary particles: 22 nm, a product having a concentration of
silica particles: 40% by weight) as an abrasive, 0.6% by weight of
a 35% by weight hydrogen peroxide (commercially available from
Asahi Denka Co., Ltd.) were added to ion-exchanged water, and an
aqueous HEDP solution (60% by weight-product, commercially
available from Solutia Japan Limited) was added thereto so as to
adjust the pH to 1.5, to give a polishing composition. The
polishing composition was filtered with a pleated type filter
(commercially available from Advantec Toyo Kaisha, Ltd.,
"MCS-045-C10S"), to give a polishing composition 1. The polishing
particles in the polishing composition 1 were determined. As a
result, the number of silica particles having sizes of 0.56 .mu.m
or more and less than 1 .mu.m (the number of coarse polishing
particles in the table) was 53,000 per 1 cm.sup.3, and the
polishing particles having sizes of 1 .mu.m or more was 0.000042%
by weight to the entire polishing particles.
[0246] Also, the polishing composition 1 was subjected to Nano
Scratch Standard Test. As a result, the number of nano scratches
was 0.08/cm.sup.2.
Preparation of Polishing Composition 2
[0247] Seven percent by weight colloidal silica particles
(commercially available from DuPont, average particle size of
primary particles: 10 nm, a product having a concentration of
silica particles: 40% by weight) as an abrasive, and 0.6% by weight
of a 35% by weight hydrogen peroxide (commercially available from
Asahi Denka Co., Ltd.) were added to ion-exchanged water, and an
aqueous HEDP solution (60% by weight-product, commercially
available from Solutia Japan Limited) was added thereto so as to
adjust the pH to 1.5, to give a polishing composition. The
polishing composition was filtered with a pleated type filter
(commercially available from Advantec Toyo Kaisha, Ltd.,
"MCP-JX-C10S"), to give a polishing composition 2. The polishing
particles in the polishing composition 2 were determined. As a
result, the number of silica particles having sizes of 0.56 .mu.m
or more and less than 1 .mu.m was 137,400 per 1 cm.sup.3, and the
polishing particles having sizes of 1 .mu.m or more was 0.000086%
by weight to the entire polishing particles.
[0248] Also, the polishing composition 2 was subjected to Nano
Scratch Standard Test. As a result, the number of nano scratches
was 0.35/cm.sup.2.
Preparation of Polishing Composition 3
[0249] The same procedures as those in the preparation of the
polishing composition 1 were carried out except that a pleated type
filter was not used to give a polishing composition 3. The
polishing particles in the polishing composition 3 were determined.
As a result, the number of silica particles having sizes of 0.56
.mu.m or more and less than 1 .mu.m was 520,500 per 1 cm.sup.3, and
the polishing particles having sizes of 1 .mu.m or more was
0.000242% by weight to the entire polishing particles.
[0250] Also, the polishing composition 3 was subjected to Nano
Scratch Standard Test. As a result, the number of nano scratches
was 5.5/cm.sup.2.
Preparation of Polishing Composition 4
[0251] The same procedures as those in the preparation of the
polishing composition 1 were carried out except that the polishing
composition was filtered with a pleated type filter (commercially
available from Advantec Toyo Kaisha, Ltd., "MCP-FX-C10S") to give a
polishing composition 4. The polishing particles in the polishing
composition 4 were determined. As a result, the number of silica
particles having sizes of 0.56 .mu.m or more and less than 1 .mu.m
was 181,200 per 1 cm.sup.3, and the polishing particles having
sizes of 1 .mu.m or more was 0.000166% by weight to the entire
polishing particles.
[0252] Also, the polishing composition 4 was subjected to Nano
Scratch Standard Test. As a result, the number of nano scratches
was 1.3/cm.sup.2.
Preparation of Polishing Composition 5
[0253] The same procedures as those in the preparation of the
polishing composition 1 were carried out except that the pH was
adjusted to 9.5, and that the abrasive concentration in the
polishing composition was 2% by weight to give a polishing
composition. The resulting polishing composition was further
filtered with a pleated type filter (commercially available from
Advantec Toyo Kaisha, Ltd., "MCP-JX-C10S"), to give a polishing
composition 5. The polishing particles in the polishing composition
5 were determined. As a result, the number of silica particles
having sizes of 0.56 .mu.m or more and less than 1 .mu.m was
101,000 per 1 cm.sup.3, and the polishing particles having sizes of
1 .mu.m or more was 0.000042% by weight to the entire polishing
particles.
Preparation of Polishing Composition 6
[0254] The same procedures as those in the preparation of the
polishing composition 1 were carried out except that the abrasive
concentration in the polishing composition was 3.5% by weight to
give a polishing composition. This polishing composition was
further filtered with a pleated type filter (commercially available
from Advantec Toyo Kaisha, Ltd., "MCS-045-C10S"), to give a
polishing composition 6. The polishing particles in the polishing
composition 6 were determined. As a result, the number of silica
particles having sizes of 0.56 .mu.m or more and less than 1 .mu.m
was 26,000 per 1 cm.sup.3, and the polishing particles having sizes
of 1 .mu.m or more was 0.000062% by weight to the entire polishing
particles.
Preparation of Polishing Composition 7
[0255] The same procedures as those in the preparation of the
polishing composition 2 were carried out except that the abrasive
concentration in the polishing composition was 2% by weight to give
a polishing composition. This polishing composition was further
filtered with a pleated type filter (commercially available from
Advantec Toyo Kaisha, Ltd., "MCS-045-C10S"), to give a polishing
composition 7. The polishing particles in the polishing composition
7 were determined. As a result, the number of silica particles
having sizes of 0.56 .mu.m or more and less than 1 .mu.m was 85,000
per 1 cm.sup.3, and the polishing particles having sizes of 1 .mu.m
or more was 0.000065% by weight to the entire polishing
particles.
Examples III-1 to III-11 and Comparative Examples III-1 to
III-4
[0256] A substrate was polished with each of the polishing
compositions 1 to 7 under the polishing conditions as shown below
and in Table 4.
III-1. Polishing Conditions
[0257] Polishing testing machine: commercially available from
SpeedFam Co., Ltd., Double-sided 9B Polishing Machine [0258]
Polishing pad: commercially available from FUJI SPINNING Co., Ltd.,
polishing pad made of urethane (thickness: 0.9 mm, average pore
size: 30 .mu.m) [0259] Rotational speed of platen: 32.5 r/min
[0260] Feeding rate of polishing composition per 1 cm.sup.2 of area
to be polished of a substrate: 0.03 to 0.15 cm.sup.3/min [0261]
Polishing time period: 4 minutes [0262] Platen pressure (polishing
pressure): 2 to 20 kPa [0263] Number of substrates introduced:
10
[0264] The nano scratches of each of the substrates obtained in
Examples III-1 to III-11 and Comparative Examples III-1 to III-4
were determined in the same manner as in Example I except that the
conditions of the feeding rate (flow rate) of the polishing
composition and platen pressure were changed. The results obtained
are shown in Table 4. TABLE-US-00004 TABLE 4 Number of Polishing
Coarse Polishing Platen Concentration pH of Nano Composition
Particles Flow Rate Pressure of Abrasive Polishing Scratches No.
(#/cm.sup.3)*) (cm.sup.3/min.) (kPa) (% by weight) Waste Liquid
(#/side) Ex. No. III-1 1 53,000 0.15 3 7 1.6 26 III-2 1 53,000 0.15
8 7 1.7 5 III-3 1 53,000 0.15 15 7 1.8 18 III-4 1 53,000 0.06 8 7
1.9 25 III-5 6 26,000 0.15 8 3.5 1.6 25 III-6 2 137,400 0.15 8 7
1.7 23 III-7 2 137,400 0.09 8 7 1.7 25 III-8 4 181,200 0.15 8 7 1.6
89 III-9 7 85,000 0.15 8 2 1.6 65 III-10 1 53,000 0.15 2 7 1.6 78
III-11 1 53,000 0.15 20 7 1.9 65 Comp. Ex. No. III-1 3 520,500 0.15
8 7 1.7 361 III-2 3 520,500 0.15 2 7 1.6 226 III-3 4 181,200 0.03 8
7 1.7 266 III-4 5 101,000 0.15 8 2 10.2 3655 *)The number of
polishing particles having sizes of 0.56 .mu.m or more and less
than 1 .mu.m per 1 cm.sup.3 of polishing composition.
[0265] It can be seen from the results in Table 4 that nano
scratches are significantly reduced in the substrates obtained in
Examples III-1 to III-11 as compared to those of Comparative
Examples III-1 to III-4.
[0266] The polishing composition of the present invention is
suitable for polishing substrates for precision parts including,
for example, recording disk substrates, such as magnetic disks,
optical disks, and opto-magnetic disks, photomask substrates,
optical lenses, optical mirrors, optical prisms and semiconductor
substrates, and the like.
[0267] The present invention being thus described, it will be
obvious that the same may be varied in many ways. Such variations
are not to be regarded as a departure from the spirit and scope of
the invention, and all such modifications as would be obvious to
one skilled in the art are intended to be included within the scope
of the following claims.
* * * * *