U.S. patent application number 11/692619 was filed with the patent office on 2007-07-19 for polishing composition.
Invention is credited to Toshiya Hagihara, Yuichi Homma, Shigeaki Takashima, Hiroyuki YOSHIDA.
Application Number | 20070167116 11/692619 |
Document ID | / |
Family ID | 34525537 |
Filed Date | 2007-07-19 |
United States Patent
Application |
20070167116 |
Kind Code |
A1 |
YOSHIDA; Hiroyuki ; et
al. |
July 19, 2007 |
POLISHING COMPOSITION
Abstract
The present invention relates to a polishing composition
containing an aqueous medium and silica particles, wherein the
silica particles in the polishing composition has a zeta potential
of from -15 to 40 mV; a method for manufacturing a substrate
including the step of polishing a substrate to be polished with a
polishing composition containing an aqueous medium and silica
particles, wherein the silica particles in the polishing
composition has a zeta potential of from -15 to 40 mV; and a method
for reducing scratches on a substrate to be polished with a
polishing composition containing an aqueous medium and silica
particles, including the step of adjusting a zeta potential of
silica particles in the polishing composition to -15 to 40 mV. The
polishing composition can be favorably used in polishing the
substrate for precision parts, including substrates for magnetic
recording media such as magnetic discs, optical discs and
opto-magnetic discs; photomask substrates; optical lenses; optical
mirrors; optical prisms; semiconductor substrates; and the
like.
Inventors: |
YOSHIDA; Hiroyuki;
(Wakayama-shi, JP) ; Homma; Yuichi; (Wakayami-shi,
JP) ; Takashima; Shigeaki; (Wakayama-shi, JP)
; Hagihara; Toshiya; (Wakayama-shi, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
34525537 |
Appl. No.: |
11/692619 |
Filed: |
March 28, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11081560 |
Mar 17, 2005 |
|
|
|
11692619 |
Mar 28, 2007 |
|
|
|
Current U.S.
Class: |
451/41 ;
51/308 |
Current CPC
Class: |
C09G 1/02 20130101; B24B
37/044 20130101; C09K 3/1463 20130101; C09K 3/1436 20130101 |
Class at
Publication: |
451/041 ;
051/308 |
International
Class: |
B24D 3/02 20060101
B24D003/02; B24B 7/30 20060101 B24B007/30 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 22, 2004 |
JP |
2004-081768 |
Jun 29, 2004 |
JP |
2004-191782 |
Claims
1. A method for reducing scratches on a substrate to be polished
with a polishing composition comprising an aqueous medium and
silica particles, comprising the step of adjusting a zeta potential
of silica particles in the polishing composition to -15 to 40
mV.
2. The method according to claim 1, wherein the silica particles
have an average primary particle size of 1 nm or more and less than
40 nm.
3. The method according to claim 1, wherein the substrate to be
polished is a memory hard disk substrate.
4. The method according to claim 1, further comprising the step of
pressing a polishing pad against the substrate to be polished while
feeding the polishing composition at a rate of from 0.01 to 3
mL/minute per 1 cm.sup.2 of the substrate to be polished.
Description
[0001] This application is a Divisional of co-pending application
Ser. No. 11/081,560, filed on Mar. 17, 2005, the entire contents of
which are hereby incorporated by reference and for which priority
is claimed under 35 U.S.C. .sctn. 120.
FIELD OF THE INVENTION
[0002] The present invention relates to a polishing composition and
a method for manufacturing a substrate.
[0003] In addition, the present invention relates to a method for
increasing a polishing rate of a substrate (hereinafter referred to
as a "polishing rate-increasing method"), a method for
manufacturing a substrate using the method, a polishing
composition, and a method for reducing scratches.
BACKGROUND OF THE INVENTION
[0004] Currently, steps for polishing various substrates have been
employed in the manufacture of various kinds of substrates. For
example, in the field of semiconductors, there has been employed a
step of polishing a silicon wafer substrate; a compound
semiconductor wafer substrate made of a compound such as gallium
arsenide, indium phosphide, or gallium nitride; or a silicon oxide
film, a metal film made of aluminum, copper, tungsten or the like,
or a nitride film made of silicon nitride, silicon oxynitride,
tantalum nitride, titanium nitride or the like, the film being
further formed on the water. In the field of memory hard disks,
there has been employed a step of polishing an aluminum substrate
or glass substrate. In the field of display devices such as lenses
and liquid crystals, there has been employed polishing of glass. In
the polishing step for these substrates to be polished, the
polishing rate is important in order to increase the productivity,
and various techniques for increasing the polishing rates have been
proposed.
[0005] In recent memory hard disk drives, high storage capacity and
miniaturization have been demanded. In order to increase the
recording density, it has been strongly urged to lower the flying
height of a magnetic head and to reduce the unit recording area.
Along with this trend, the surface qualities required after
polishing have become severely assessed every year even in a method
for manufacturing a substrate for a magnetic disk. 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 have been reduced, and the sizes and depths
of the scratches have become increasingly smaller.
[0006] 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
focal depth becomes more shallow with the increase in resolution
required for an exposure device during the exposure of a
photoresist, even more improvement in surface smoothness and
planarization is desired.
[0007] Conventionally, for these polishing applications, a slurry
polishing liquid mainly containing silica particles or cerium oxide
particles has been used. The slurry polishing liquid containing the
silica particles has been highly useful and is widely used, but has
a disadvantage that the polishing rate is low. On the other hand,
the slurry polishing liquid containing cerium oxide particles has
been used for polishing optical glass, a memory hard disk made of
glass, a semiconductor insulation film, or the like, and has a
feature of a high polishing rate, but has a disadvantage that
scratches tend to be easily formed.
[0008] In view of these disadvantages, JP2002-97459 A discloses a
polishing agent for simultaneously reducing scratches and dust,
while increasing the polishing rate by providing a silicon oxide
film to be polished, with an aqueous dispersion slurry liquid
containing oxide particles of which constituting atom is cerium,
wherein the zeta potential of the surface of the particles is
controlled to -10 mV or less. However, although scratches and dust
are reduced as compared to the case where the zeta potential of the
surface of the particles exceeds -10 mV, the polishing rate is also
lowered, so that both the reduction of scratches and dust and the
increase in polishing rate cannot be satisfied.
[0009] Further, JP2001-329250 A discloses a cerium oxide polishing
agent for polishing a surface to be polished, such as a SiO.sub.2
insulation film, at a high speed without damage, from a slurry
prepared by dispersing cerium oxide particles in a medium, wherein
the zeta potential of the surface of the particles is controlled to
-100 mV to -10 mV. However, the description of the polishing at a
high speed is made on the basis of comparison with a polishing
agent containing silica particles, which are heterogeneous
particles, so that the relationship between the polishing rate and
the zeta potential has not yet been elucidated.
[0010] Moreover, JP2003-193037 A discloses a polishing composition
for improving surface smoothness of a memory hard disk substrate.
However, the surface smoothness is still insufficient for obtaining
surface smoothness required for high density of the memory hard
disk substrate.
SUMMARY OF THE INVENTION
[0011] The present invention relates to the following: [0012] [1] a
polishing composition containing an aqueous medium and silica
particles, wherein the silica particles in the polishing
composition have a zeta potential of from -15 to 40 mV; [0013] [2]
a method of polishing a glass substrate with the polishing
composition as defined in the above [1]; [0014] [3] a method of
polishing a memory hard disk substrate with the polishing
composition as defined in the above [1]; [0015] [4] a method for
manufacturing a substrate including the step of polishing a
substrate to be polished with a polishing composition containing an
aqueous medium and silica particles, wherein the silica particles
in the polishing composition has a zeta potential of from -15 to 40
mV; [0016] [5] a method for increasing a polishing rate of a
substrate to be polished with a polishing composition containing an
aqueous medium and silica particles, including the step of
adjusting a zeta potential of silica particles in the polishing
composition to -15 to 40 mV; [0017] [6] a method for manufacturing
a substrate including the step of applying the method as defined in
the above [5] to a substrate to be polished; and [0018] [7] a
method for reducing scratches on a substrate to be polished with a
polishing composition containing an aqueous medium and silica
particles, including the step of adjusting a zeta potential of
silica particles in the polishing composition to -15 to 40 mV.
DETAILED DESCRIPTION OF THE INVENTION
[0019] As a result of intensive studies on the requirements for
achieving surface smoothness required for high density and high
integration of a substrate for a precision part such as a memory
hard disk substrate or a semiconductor substrate, the present
inventors have found for the first time that the generation of
"nano scratches" (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) which
could not be so far detected inhibit the high density in a memory
hard disk substrate, and high integration in a semiconductor
substrate. The present invention has been accomplished thereby.
[0020] Specifically, the present invention relates to a polishing
composition being capable of giving a polished object small surface
roughness and remarkably reduced nano scratches, and having a high
polishing rate, and a method for manufacturing a substrate having
small surface roughness and remarkably reduced nano scratches.
[0021] Also, the present invention relates to a method for
increasing the polishing rate of a substrate to be polished, while
satisfying together the improvement in the surface smoothness of a
surface to be polished, and a method for manufacturing a substrate
having excellent smoothness and high productivity using the above
method.
[0022] By using the polishing composition of the present invention
in, for example, a polishing step for a substrate for a precision
part for high density and high integration, the polished substrate
has excellent surface smoothness and is capable of remarkably
reducing conventionally undetected fine nano scratches at a high
polishing rate. Therefore, there is exhibited an effect that a
high-quality memory hard disk substrate and a substrate for a
precision part such as a semiconductor substrate, each having
excellent surface properties, can be efficiently manufactured.
[0023] These and other advantages of the present invention will be
apparent from the following description.
1. Polishing Composition
[0024] One of the features of the polishing composition of the
present invention resides in that the polishing composition is a
polishing composition containing an aqueous medium and silica
particles, wherein the silica particles in the polishing
composition have a zeta potential of from -15 to 40 mV. By
polishing a substrate to be polished with the polishing
composition, the polishing rate can be increased while also
satisfying surface smoothness.
[0025] The present invention makes it possible to provide excellent
surface properties and to remarkably reduce nano scratches
causative of the surface defects by adjusting the zeta potential of
the silica particles within a range of from -15 to 40 mV,
preferably from -15 to 30 mV. The nano scratches are important
properties in obtaining high density and high integration
especially in the memory hard disk substrate or semiconductor
substrate. Therefore, by using the polishing composition of the
present invention, a high-quality memory hard disk substrate having
excellent surface properties or a semiconductor substrate can be
manufactured at a high polishing rate.
[0026] Although not wanting to be limited by theory, the mechanism
for reducing the nano scratches has not been elucidated, and it is
presumably as follows. The closer the zeta potential of the silica
particles approximates an isoelectric point, the larger the
intergranular attraction between the silica particles, so that the
detachment of coarse grains or aggregates of fine particles which
are considered to cause scratches in the polishing to a surface of
a substrate to be polished is suppressed.
[0027] In the present invention, the zeta potential refers to a
potential obtained from an electrophoresing rate of an abrasive
when an electric field is applied to the silica particles in the
polishing composition from external. The determination device for
the zeta potential is preferably, for example, those devices using
the principle of electrophoresis, such as "ELS-8000" (commercially
available from Otsuka Electronics Co., Ltd.), "DELSA440SX"
(commercially available from Beckmann Coulter, Inc.) and "NICOMP
Model 380" (commercially available from Particle Sizing Systems).
Also, the determination can be substituted by applying the
principle of ultrasonic wave method such as "DT1200" (commercially
available from NIHON RUFUTO Co., Ltd.). In the determination
according to the principle of electrophoresis, it is necessary to
dilute the concentration of the silica particles in principle of
the device. The zeta potential of the silica particles in the
polishing composition in the present specification refers to a zeta
potential of a polishing composition of which silica particle
concentration is adjusted to a given concentration by an aqueous
solution for adjusting zeta potential, the aqueous solution of
which pH is previously adjusted to be the same as that of the
polishing composition (an aqueous solution composed of a zeta
potential-adjusting agent of the polishing composition and water,
provided that in a case where two or more kinds of zeta
potential-adjusting agents are contained in the polishing
composition, an aqueous solution is prepared by keeping the content
ratio thereof). In addition, the supernatant by centrifugation of
the polishing composition can be used in place of the
above-mentioned aqueous solution for adjusting zeta potential.
Also, when the zeta potential is determined with the
above-mentioned zeta potential-determination device, the
determinations are repeated at least three times with the same
sample under the same determination conditions in order to increase
the reliability of the found value, and an average of these values
is defined as a zeta potential.
[0028] The polishing rate can be increased by adjusting the zeta
potential of the silica particles of the polishing composition of
the present invention within a range from -15 to 40 mV. It is
desired that the zeta potential is adjusted within a range from -15
to 30 mV, preferably from -15 to 20 mV, more preferably from -15 to
10 mV, even more preferably from -10 to 10 mV, even more preferably
from -5 to 5 mV, from the viewpoint of reducing nano scratches.
[0029] In addition, it is desired that the above-mentioned zeta
potential is adjusted within a range from -15 to 30 mV, preferably
from -10 to 30 mV, more preferably from -5 to 30 mV, from the
viewpoint of reducing nano scratches.
[0030] Incidentally, in the present invention, the adjustment of
the zeta potential of the polishing composition is not particularly
limited, and it is preferable that the adjustment is carried out
before polishing. In addition, it is preferable that the zeta
potential is kept within the above-mentioned specified range until
the polishing is terminated. A specific method for adjusting the
zeta potential will be described later.
[0031] The silica particles in the present invention include
colloidal silica particles, fumed silica particles, and the like.
The colloidal silica can be obtained according to a water glass
method using an alkali metal silicate such as sodium silicate as a
raw material, subjecting the raw materials to a condensation
reaction in an aqueous solution, and allowing the silica particles
to grow, or according to an alkoxysilane method using
tetraethoxysilane or the like as a raw material, subjecting the raw
material to a condensation reaction in a water-soluble organic
solvent-containing water, such as an alcohol, and allowing the
silica particles to grow. The fumed silica can be obtained by a
method using a volatile silicon-containing compound such as silicon
tetrachloride as a raw material, and subjecting the raw material to
a vapor phase hydrolysis under a high temperature of 1000.degree.
C. or more with an oxyhydrogen burner.
[0032] Further, as the silica particles in the present invention,
surface-modified silica particles, composite silica particles and
the like can be used. The surface-modified silica particles refer
to those in which a metal such as aluminum, titanium or zirconium,
or an oxide thereof is adsorbed and/or bound to the surface of the
silica particles, directly or via a coupling agent, or those in
which a silane coupling agent, a titanium coupling agent or the
like is bound. The composite silica particles refer to those in
which nonmetal particles, such as polymer particles, and silica
particles are adsorbed and/or bound. These silica particles can be
used alone or in admixture of two or more kinds. Among these silica
particles, the colloidal silica is preferable from the viewpoint of
reducing scratches.
[0033] The silica particles have an average primary particle size,
regardless of whether or not one or more kinds of silica particles
are used in admixture, of preferably 1 nm or more and less than 40
nm, more preferably from 1 to 35 nm, even more preferably from 3 to
30 nm, even more preferably from 5 to 25 nm, even more preferably
from 5 to 20 nm, from the viewpoint of increasing the polishing
rate as to the lower limit, and from the viewpoint of reducing
surface roughness (an average surface roughness: Ra, a
peak-to-valley value: Rmax) as to the upper limit. Further, when
the primary particles are aggregated to form secondary particles,
the secondary average particle size is preferably from 5 to 150 nm,
more preferably from 5 to 100 nm, even more preferably from 5 to 80
nm, even more preferably from 5 to 50 nm, even more preferably from
5 to 30 nm, from the viewpoint of increasing the polishing rate as
to the lower limit, and from the viewpoint of reducing surface
roughness as to the upper limit in the same manner as above.
[0034] In addition, the silica particles have a particle size
distribution, regardless of whether or not one or more kinds of
silica particles are used in admixture, such that D90/D50 is
preferably from 1 to 5, more preferably from 1 to 4, even more
preferably from 1 to 3, from the viewpoint of achieving reduction
of scratches, reduction of surface roughness and a high polishing
rate.
[0035] Incidentally, the average primary particle size of the
silica particles, the particle size at 50% counted from a smaller
particle size side of the primary particles in a cumulative
particle size distribution on the number basis (D50), and the
particle size at 90% counted from a smaller particle size side of
the primary particles in a cumulative particle size distribution on
the number basis (D90) can be each determined, regardless of
whether or not one or more kinds of silica particles are used in
admixture, by the method described below. Specifically, the
photographs of the silica particles observed by a transmission
electron microscope "JEM-2000 FX" commercially available from JEOL
LTD. (80 kV, magnification: 10000 to 50000) are incorporated into a
personal computer as image data with a scanner connected thereto.
The projected area diameter of each silica particle is determined
using an analysis software "WinROOF" (commercially available from
MITANI CORPORATION), and considered as the diameter of the silica
particles. After analyzing data for 1000 or more silica particles,
the volume of the silica particles are calculated from the
diameters of the silica particles based on the analyzed data using
a spreadsheet software "EXCEL" (commercially available from
Microsoft Corporation). The average primary particle size and D50
as referred to herein mean the same thing.
[0036] The average secondary particle size of the silica particles
refers to a particle size at 50% counted from a smaller particle
size side of the particles in a cumulative particle size
distribution on a volume basis, as determined by electrophoretic
light scattering method, regardless of whether or not one or more
kinds of silica particles are used in admixture. As the
determination device for electrophoretic light scattering method,
there can be preferably used, for example, "ELS-8000" (commercially
available from Otsuka Electronics Co., Ltd.), "DELSA 440SX"
(commercially available from Coulter Beckman, Inc.) and "NICOMP
Model 380" (commercially available from Particle Sizing
Systems).
[0037] The content of the silica particles is preferably from 1 to
50% by weight, more preferably from 2 to 40% by weight, even more
preferably from 3 to 30% by weight, even more preferably from 5 to
25% by weight, of the above-mentioned polishing composition, from
the viewpoint of increase in the polishing rate and improvement in
surface qualities.
[0038] The aqueous medium in the present invention refers to water
and/or a water-soluble organic solvent. Water includes ion exchange
water, distilled water, ultrapure water and the like. The
water-soluble organic solvent includes primary to tertiary
alcohols, glycols and the like. The content of the aqueous medium
corresponds to the balance after subtracting the contents of the
silica particles, the zeta potential-adjusting agent, and other
components added as occasion demands from the entire weight (100%
by weight) of the polishing composition. The content of this medium
is preferably from 60 to 99% by weight, more preferably from 70 to
98% by weight, even more preferably from 75 to 98% by weight, of
the polishing composition.
[0039] The adjustment of the zeta potential of silica particles in
the polishing composition can be effectively carried out by adding
a zeta potential-adjusting agent to a polishing composition. The
zeta potential-adjusting agent refers to an agent for controlling
the surface potential of the silica particles by directly or
indirectly adsorbing the agent to the surface of the silica
particles or changing the property such as the degree of acidity or
basicity of the medium of the polishing composition. The zeta
potential-adjusting agent includes, for example, an acid, a base, a
salt and a surfactant.
[0040] The zeta potential-adjusting agent is used, for example, as
follows. When the zeta potential of the silica particle surface
contained in the polishing composition exceeds 40 mV, as the zeta
potential-adjusting agent, it is preferable to shift the zeta
potential to a negative side with an acid, an acidic salt, or an
anionic surfactant. On the other hand, when the zeta potential of
the silica particle surface contained in the polishing composition
is lower than -15 mV, as the zeta potential-adjusting agent, it is
preferable to shift the zeta potential to a positive side with a
base, a basic salt or a cationic surfactant. In addition, a neutral
salt, a nonionic surfactant or an amphoteric surfactant may be used
in the case where the zeta potential is adjusted without changing
the pH of the polishing composition.
[0041] As the acid, an inorganic acid or organic acid may be used.
The inorganic acid includes hydrochloric acid, nitric acid,
sulfuric acid, phosphoric acid, a polyphosphoric acid, amide
sulfuric acid, and the like. Also, the organic acid includes a
carboxylic acid, an organic phosphonic acid, an amino acid and the
like. The carboxylic acid includes, for example, a monocarboxylic
acid such as acetic acid, glycolic acid, and ascorbic acid; a
dicarboxylic acid such as oxalic acid and tartaric acid; a
tricarboxylic acid such as citric acid. The organic phosphonic acid
includes, for example, 2-aminoethylphosphonic acid,
1-hydroxyethylidene-1,1-diphosphonic acid (HEDP),
aminotri(methylenephosphonic acid),
ethylenediaminetetra(methylenephosphonic acid),
diethylenetriaminepenta(methylenephosphonic acid), and the like. In
addition, the amino acid includes, for example, glycine, alanine
and the like. Among them, the carboxylic acid and the organic
phosphonic acid are preferable, from the viewpoint of reducing
scratches and reducing nano scratches. For example, hydrochloric
acid, nitric acid, sulfuric acid, phosphoric acid, a polyphosphoric
acid, glycolic acid, oxalic acid, citric acid,
1-hydroxyethylidene-,1-diphosphonic acid,
aminotri(methylenephosphonic acid),
ethylenediaminetetra(methylenephosphonic acid), or
diethylenetriaminepenta(methylenephosphonic acid) is suitably
used.
[0042] The base includes an aqueous ammonia, hydroxylamine, an
alkylhydroxylamine, a primary to tertiary alkylamine, an
alkylenediamine, and alkylammonium hydroxide, and the like. The
preferred base is an aqueous ammonia or an alkanolamine, from the
viewpoint of reducing scratches and reducing nano scratches.
[0043] In addition, the salt includes salts of the above-mentioned
acid. The cation for forming the salt is preferably those metals
belonging to the Group 1A, 2A, 3B or 8 of the Periodic Table (long
period form), ammonium, hydroxyammonium, an alkanolammonium or the
like. Among them, the basic salt includes ammonium chloride,
ammonium nitrate, ammonium sulfate, aluminum nitrate, aluminum
sulfate, aluminum chloride, and the like. The basic salt includes
sodium citrate, sodium oxalate, sodium tartrate and the like. The
neutral salt includes sodium chloride, sodium sulfate, sodium
nitrate, and the like.
[0044] The surfactant includes a low-molecular weight surfactant
and a high-molecular weight surfactant, which is an agent that is
adsorbed or chemically bound to the surface of the silica
particles, and has one or more hydrophilic groups which may be
identical or different in the molecule. Especially, the surfactant
includes a nonionic surfactant having a nonionic group as
represented by an ether group (an oxyethylene group or the like),
or a hydroxyl group; an anionic surfactant having an anionic group,
as represented by a carboxylate group, a sulfonate group, a
sulfuric ester group or a phosphoric ester group; a cationic
surfactant having a cationic group represented by a quaternary
ammonium; and an amphoteric surfactant having an anionic group and
a cationic group.
[0045] In addition, as the preferred combination of the
above-mentioned silica particles and the zeta potential-adjusting
agent, the zeta potential-adjusting agent is preferably
hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, a
polyphosphoric acid, glycolic acid, oxalic acid, citric acid,
1-hydroxyethylidene-1,1-diphosphonic acid,
aminotri(methylenesulfonic acid),
ethylenediaminetetra(methylenephosphonic acid), or
diethylenetriaminepenta(methylenephosphonic acid), more preferably
hydrochloric acid, nitric acid, sulfuric aid, phosphoric acid,
citric acid, or 1-hydroxyethylidene-1,1-diphosphonic acid.
[0046] In addition, in the polishing composition used in the
present invention, alumina particles can be used together, from the
viewpoint of increasing the polishing rate. When the silica
particles and the alumina particles are used together, the zeta
potential-adjusting agent is preferably sulfuric acid, ammonium
sulfate, phosphoric acid, a polyphosphoric acid, oxalic acid,
citric acid, or 1-hydroxyethylidene-1,1-diphosphonic acid, more
preferably sulfuric acid, ammonium sulfate, phosphoric acid, a
polyphosphoric aid, citric acid, or
1-hydroxyethylidene-1,1-diphosphonic acid. Incidentally, it is
preferable that the average primary or secondary particle size of
the alumina particles is within the same range as those for the
above-mentioned silica particles.
[0047] Here, the content of the zeta potential-adjusting agent in
the polishing composition cannot absolutely be limited because the
content is determined depending upon the property of the liquid of
the polishing composition, the property of the silica particles,
and the obtained zeta potential. For example, the content of the
zeta potential-adjusting agent is preferably from 0.01 to 20% by
weight, more preferably from 0.05 to 15% by weight, of the
polishing composition, from the viewpoint of reducing scratches and
reducing nano scratches. In addition, the zeta potential-adjusting
agent may be previously contained in the polishing composition, or
the zeta potential-adjusting agent may be contained in the
polishing composition immediately before polishing.
[0048] Additionally, in the present invention, other abrasives can
be used together with the silica particles. As the other abrasive,
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 periodic form). Specific examples of the
abrasives include aluminum oxide (hereinafter referred to as
alumina), silicon carbide, diamond, magnesium oxide, zinc oxide,
titanium oxide, cerium oxide, zirconium oxide, and the like; those
in which the surface of these abrasives is subjected to
modification or surface improvement with a function group; those
formed into composite particles with the surfactant or the
abrasive; and the like. It is preferable to use one or more kinds
of these abrasives from the viewpoint of reducing surface
roughness.
[0049] The abrasive has an average primary particle size,
regardless of whether or not one or more kinds of the abrasives are
used in admixture, of 1 nm or more and less than 40 nm. The
abrasive has an average primary particle size of preferably 3 nm or
more, more preferably 5 nm or more, from the viewpoint of
increasing the polishing rate, and the abrasive has an average
primary particle size of preferably 35 nm or less, more preferably
30 nm or less, even more preferably 25 nm or less, even more
preferably 20 nm or less, from the viewpoint of reducing surface
roughness (an average surface roughness: Ra, a peak-to-valley
value: Rmax). Therefore, the average primary particle size is
preferably from 1 to 35 nm, more preferably from 3 to 30 nm, even
more preferably from 5 to 25 nm, even more preferably from 5 to 20
nm, from the viewpoint of economically reducing surface roughness.
Further, when the primary particles are aggregated to form
secondary particles, the secondary average particle size is
preferably from 5 to 150 nm, more preferably from 5 to 100 nm, even
more preferably from 5 to 80 nm, even more preferably from 5 to 50
nm, even more preferably from 5 to 30 nm, from the viewpoint of
increasing the polishing rate, and from the viewpoint of reducing
surface roughness of the substrate in the same manner as above.
[0050] Incidentally, the average primary particle size of the
abrasive (except for the silica particles), regardless of whether
or not one or more kinds of the abrasives are used in admixture, is
determined by obtaining a particle size at 50% counted from a
smaller particle size side of the primary particles in a cumulative
particle size distribution on the number basis (D50) by using an
image observed with a scanning electron microscope (magnification
preferably from 3000 to 100000), and this D50 is defined as an
average primary particle size. Here, one of the average primary
particle size employs an arithmetic mean of breadth and length (an
average of length and breadth). In addition, the secondary average
particle size can be determined as a volume-average particle size
using a laser diffraction method.
[0051] In addition, the abrasive (except for the silica particles)
has a particle size distribution, regardless of whether or not one
or more kinds of the abrasives are used in admixture, such that
D90/D50 is preferably from 1 to 5, more preferably from 2 to 5,
even more preferably from 3 to 5, from the viewpoint of achieving
reduction of nano scratches, reduction of surface roughness and a
high polishing rate. Here, D90 refers to a particle size at 90%
counted from a smaller particle size side of the primary particles
in a cumulative particle size distribution on the number basis
(D90) by using an image observed with a scanning electron
microscope (magnification preferably from 3000 to 100000).
[0052] The content of the abrasive (except for the silica
particles) is preferably 0.5% by weight or more, more preferably 1%
by weight or more, even more preferably 3% by weight or more, even
more preferably 5% by weight or more, of the polishing composition,
from the viewpoint of increasing the polishing rate. In addition,
the content of the abrasive (except for the silica particles) is
preferably 20% by weight or less, more preferably 15% by weight or
less, even more preferably 13% by weight or less, even more
preferably 10% by weight or less, of the polishing composition,
from the viewpoint of improving surface qualities. Specifically,
the content of the abrasive (except for the silica particles) 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, even more
preferably from 5 to 10% by weight, of the polishing composition,
from the viewpoint of economically improving surface qualities.
[0053] In addition, in the polishing composition usable in the
present invention, other components can be formulated as occasion
demands. The other components include an oxidizing agent such as
hydrogen peroxide, a radical scavenger, a clathrate compound, an
anticorrosive agent, a defoaming agent, an anti-bacterial agent and
the like. The content of these other components is preferably from
0 to 10% by weight, more preferably from 0 to 5% by weight, of the
polishing composition, from the viewpoint of polishing rate. The
above-mentioned polishing composition can be prepared by properly
mixing the above-mentioned components.
[0054] The concentration of each component in the above-mentioned
polishing composition may be any concentration during the
preparation of the composition and the concentration upon use. In
many cases, the polishing composition is usually prepared as a
concentrate, which is diluted upon use.
[0055] The pH of the above-mentioned polishing composition may be
determined depending upon the silica particles used and the degree
of surface modification such as surface treatment, from the
viewpoint of polishing rate, reduction in scratches, and reduction
in nano scratches. In the case where the silica particles are
composed of colloidal silica, the pH is preferably 9 or less, more
preferably 7 or less, even more preferably 6 or less, even more
preferably 5 or less, even more preferably 4 or less, even more
preferably 3 or less, even more preferably 2.5 or less, even more
preferably 2 or less.
[0056] Since the polishing composition having the above
constitution is used, there can be efficiently manufactured a
polished substrate such as a substrate for precision parts having
excellent surface properties such that there are very little
scratches, especially nano scratches.
[0057] The nano scratches in the present invention refer 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 by an atomic force microscope (AFM), and can be
quantitatively evaluated as the number of nano scratches as
determined by "Micromax" a visual testing device as described in
Examples set forth below.
[0058] In addition, the scratches refer to scratches on a substrate
surface having a depth of 100 nm or more.
[0059] 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 detected as a short wavelength of 10 .mu.m or less in
the AFM (atomic force microscope), and expressed as an average
surface roughness Ra. Specifically, the surface roughness is
obtained according to the method described in Examples set forth
below.
[0060] The polishing composition of the present invention can be
used for polishing an object to be polished by, for example,
feeding to a polishing device equipped with a jig having a
substrate to be polished and a polishing cloth. By this process,
the polishing rate of a substrate to be polished can be increased
while at the same time satisfying surface smoothness of the
substrate (reduction of scratches and nano scratches). The surface
of a substrate to be polished is polished by pressing to a
polishing device equipped with a jig having a substrate to be
polished, or setting a substrate to be polished with polishing
platens to which a polishing cloth made of a foamed article or
non-foamed article made of an organic polymer or the like or a
nonwoven fabric is attached; feeding the polishing composition to a
surface to be polished; and moving the polishing platens or the
substrate to be polished, while applying pressure.
[0061] The polishing load during polishing is preferably from 0.5
to 20 kPa, more preferably from 1 to 20 kPa, even more preferably
from 3 to 20 kPa, from the viewpoint of an increase in the
polishing rate and easy control of polishing.
[0062] The flow rate of the polishing composition to a substrate to
be polished is preferably from 0.01 to 3 mL/minute, more preferably
from 0.05 to 2.5 mL/minute, even more preferably from 0.1 to 2
mL/minute, per 1 cm.sup.2 of the substrate, from the viewpoint of
an increase in the polishing rate and easy control of nano
scratches.
[0063] The material of a substrate to be polished, which is an
object to be polished, with 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.
[0064] 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,
an Ni--P plated aluminum alloy substrate and a glass substrate made
of crystallized glass or reinforced glass are more preferable, and
an Ni--P plated aluminum alloy substrate is even more
preferable.
[0065] In addition, the polishing composition of the present
invention is suitably used for those made of at least silicon on
the side of the substrate to be polished. For example, a glass
substrate made of crystallized glass or reinforced glass or a
semiconductor substrate in which a thin film made of silicon is
formed on the surface of the substrate, even more preferably a
glass substrate made of crystallized glass or reinforced glass.
Therefore, the present invention relates to a method of polishing a
glass substrate with the polishing composition of the present
invention.
[0066] 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, those having disc-shaped substrates are even more
preferable in polishing.
[0067] The polishing composition of the present invention can be
preferably used in polishing a substrate for precision parts. For
example, the polishing composition is suitable for polishing
substrates for magnetic recording media such as magnetic disks
including memory hard disks, optical disks, and opto-magnetic
disks; and precision parts such as photomask substrates, optical
lenses, optical mirrors, optical prisms and semiconductor
substrates, and the like. Among them, since the polishing
composition of the present invention can remarkably reduce nano
scratches important in high density or high integration, the
polishing composition is more preferable for polishing a magnetic
disk substrate such as a memory hard disk substrate, or a
semiconductor substrate, even more preferable for polishing a
memory hard disk substrate. As the memory hard disk substrate, a
glass memory hard disk substrate or Ni--P plated substrate is more
preferable. Therefore, the present invention relates to a method of
polishing a memory hard disk substrate with the polishing
composition of the present invention.
[0068] The polishing of a memory hard disk substrate or a
semiconductor substrate includes, for example, the steps of
polishing a silicon wafer (bare wafer), forming a film for shallow
trench isolation, subjecting an interlayer dielectric to
planarization, forming an embedded metal line, and forming an
embedded capacitor, and the like.
[0069] The surface properties of the substrate before subjecting to
the polishing process with the polishing composition of the present
invention are not particularly limited. For example, those
substrates having surface properties that Ra is 1 nm are
preferable.
[0070] The polishing composition of the present invention is
especially effective in the polishing step, and the polishing
composition can be similarly applied to polishing steps other than
these, for example, lapping step, and the like.
2. Method for Manufacturing Substrate
[0071] The present invention relates to a method for manufacturing
a substrate.
[0072] One of the features 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 with a
polishing composition containing an aqueous medium and silica
particles, wherein the silica particles in the polishing
composition has a zeta potential of from -15 to 40 mV. By having
the feature, there are exhibited some effects that the polished
object has a small surface roughness with a high polishing rate,
and that nano scratches can be remarkably reduced.
[0073] In the method for manufacturing a substrate of the present
invention, the above-mentioned polishing composition of the present
invention is suitably used.
[0074] The silica particles used in the method for manufacturing a
substrate of the present invention may be the same ones as those
used in the above-mentioned polishing composition of the present
invention.
[0075] Among them, the silica particles having an average primary
particle size of 1 nm or more are preferable, more preferably 3 nm
or more, even more preferably 5 nm or more, from the viewpoint of
an increase in the polishing rate. Also, the silica particles
having an average primary particle size of less than 40 nm are
preferable, more preferably 35 nm or less, even more preferably 30
nm or less, even more preferably 25 nm or less, even more
preferably 20 nm or less, from the viewpoint of reducing surface
roughness. Therefore, the silica particles have an average primary
particle size of preferably 1 nm or more and less than 40 nm, more
preferably from 1 to 35 nm, even more preferably from 3 to 30 nm,
even more preferably from 5 to 25 nm, even more preferably from 5
to 20 nm, from the viewpoint of economically reducing surface
roughness. Further, when the primary particles are aggregated to
form secondary particles, the silica particles have a secondary
average particle size of preferably from 5 to 150 nm, more
preferably from 5 to 100 nm, even more preferably from 5 to 80 nm,
even more preferably from 5 to 50 nm, even more preferably from 5
to 30 nm, from the viewpoint of an increase in the polishing rate
and from the viewpoint of reduction of surface roughness of a
substrate in the same manner as above.
[0076] The polishing step used in the method for manufacturing a
substrate of the present invention may be the same ones as the
polishing step used in the above-mentioned polishing composition of
the present invention. The polishing step may be preferably carried
out in a second or subsequent step among the plural polishing
steps, and it is even more preferable to carry out the polishing
step as a final polishing step. In this polishing step, in order to
avoid admixing of the abrasive of the previous step or the
polishing composition, separate polishing machines may be used. 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.
b 3. Method for Increasing Polishing Rate of Substrate to be
Polished
[0077] In addition, the present invention relates to a method for
increasing a polishing rate of a substrate to be polished
(hereinafter referred to as "polishing rate-increasing
method").
[0078] One of the features of the polishing rate-increasing method
of the present invention resides in that the method includes the
step of adjusting a zeta potential of silica particles in a
polishing composition containing an aqueous medium and silica
particles to -15 to 40 mV. By having the above feature, the
polishing rate can be increased while also satisfying surface
smoothness.
[0079] The aqueous medium and the silica particles used in the
polishing rate-increasing method of the present invention may be
the same ones as those used in the above-mentioned polishing
composition of the present invention.
[0080] Therefore, the polishing composition of the present
invention can be suitably used for the polishing rate-increasing
method of the present invention.
[0081] Also, the polishing steps may be the same as those polishing
steps used in the polishing composition of the present invention as
mentioned above.
[0082] The polishing rate-increasing method of the present
invention can be preferably used in polishing a substrate for
precision parts. For example, the polishing composition is suitable
for polishing substrates for magnetic recording media, such as
magnetic disks, optical disks, opto-magnetic disks such as memory
hard disk substrates, and substrates for precision parts such as
photomask substrates, optical lenses, optical mirrors, optical
prisms and semiconductor substrates, and the like. The polishing of
a semiconductor substrate includes, for example, the steps of
polishing a silicon wafer (bare wafer), forming a film for shallow
trench isolation, subjecting an interlayer dielectric to
planarization, forming an embedded metal line, and forming an
embedded capacitor, and the like.
[0083] Also, another embodiment of the method for manufacturing a
substrate of the present invention includes a method for
manufacturing a substrate including the step of applying the
above-mentioned polishing rate-increasing method of the present
invention to a substrate to be polished. Specifically, one of the
features of this embodiment of the method for manufacturing a
substrate resides in that the method includes the step of applying
a method for increasing a polishing rate of a substrate to be
polished with a polishing composition containing an aqueous medium
and silica particles, including the step of adjusting a zeta
potential of silica particles in the polishing composition to -15
to 40 mV, to a substrate to be polished. By having the feature,
there are exhibited some effects that the polishing rate can be
increased while keeping a low scratching property owned by the
silica particles, and that the production efficiency can be
enhanced.
[0084] Since the method has the above feature, the method can be
applied to the manufacture of substrates for magnetic disks such as
glass memory hard disks, recording media such as optical disks and
opto-magnetic disks; manufacture of semiconductor substrates such
as memory ICs, logic ICs or system LSIs; and photomask substrates,
optical lenses, optical mirrors, optical prisms, and the like. The
method is preferably suitable for the manufacture of magnetic disks
such as glass memory hard disks, or the manufacture of
semiconductor substrates, more preferably for the manufacture of
magnetic disks such as glass memory hard disks.
4. Method for Reducing Scratches on Substrate to be Polished
[0085] In addition, the present invention relates to a method for
reducing scratches on a substrate to be polished with the polishing
composition (hereinafter simply referred to as "scratch-reducing
method").
[0086] One of the features of the scratch-reducing method of the
present invention resides in that the method for reducing scratches
on a substrate to be polished with a polishing composition
containing an aqueous medium and silica particles, including the
step of adjusting a zeta potential of silica particles in the
polishing composition to -15 to 40 mV. By having the feature, the
scratches on the substrate to be polished can be reduced.
[0087] The aqueous medium and the silica particles used in the
scratch-reducing method of the present invention may be the same
ones as those used in the above-mentioned polishing composition of
the present invention.
[0088] Therefore, the polishing composition of the present
invention can be suitably used for the scratch-reducing method of
the present invention.
[0089] Also, the polishing steps may be the same as those polishing
steps used in the polishing composition of the present invention as
mentioned above.
5. Manufactured Substrate
[0090] The substrate manufactured by using the polishing
composition of the present invention or using the method for
manufacturing a substrate of the present invention as described
above has excellent surface smoothness. For example, those
substrates having surface roughness (Ra) of 0.3 nm or less,
preferably 0.2 nm or less, more preferably 0.15 nm or less, even
more preferably 0.13 nm or less are obtained.
[0091] Also, the manufactured substrate has very little 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 preferably 120 G/inch.sup.2, and more
preferably 160 G/inch.sup.2, and when the substrate is a
semiconductor substrate, the substrate can meet the requirement of
a wire width of preferably 65 nm, and more preferably 45 nm.
EXAMPLES
[0092] 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.
[0093] Each of the polishing compositions in the following Examples
and Comparative Examples was evaluated for its polishing properties
by using an Ni--P plated, aluminum alloy substrate having a
thickness of 1.27 mm, an outer circumferential diameter of 95 mm
and an inner circumferential diameter of 25 mm, which was
previously roughly polished with a polishing liquid containing
alumina abrasives so that the substrate had a surface roughness
(Ra) of 1 nm as an object to be polished.
Examples I-1 to I-9 and Comparative Examples I-1 to I-5
[0094] There were added together Colloidal Silica I-A (commercially
available from Du Pont, average primary particle size: 27 nm,
D90/D50=3.1), Colloidal Silica I-B (commercially available from Du
Pont, average primary particle size: 15 nm, D90/D50=2.2), Colloidal
Silica I-C (commercially available from Du Pont, average primary
particle size: 19 nm, D90/D50=1.6), or a mixture of Colloidal
Silicas I-A and I-B corresponding to Example I-4 (commercially
available from Du Pont, average primary particle size: 18 nm,
D90/D50=3.0) as an abrasive; a 60% by weight aqueous HEDP solution,
a 98% by weight sulfuric acid, and/or citric acid as a zeta
potential controlling agent; and a 35% by weight aqueous hydrogen
peroxide as the other component, to give each of the polishing
compositions having a composition, pH, and a zeta potential of the
abrasive as shown in Table 1. Here, the balance was ion-exchanged
water.
[0095] The order of mixing each component was as follows: The
aqueous hydrogen peroxide was added to an aqueous solution prepared
by diluting a zeta potential controlling agent HEDP, sulfuric acid
or citric acid in water, thereafter the remaining components were
added, mixed and adjusted. The resulting mixture was added little
by little to the colloidal silica slurry while stirring, to give a
polishing composition.
[0096] Zeta potential, nano scratches, and surface roughness (Ra)
of each of the polishing compositions obtained in Examples I-1 to
I-9 and Comparative Examples I-1 to I-5 were determined and
evaluated in accordance with the following methods. The results are
shown in Table 1.
I-1. Polishing Conditions
[0097] Polishing testing machine: double-sided processing machine,
Model 9B, commercially available from SPEEDFAM CO., LTD. [0098]
Polishing cloth (pad): a cloth for finish-polishing commercially
available from FUJIBO (thickness: 0.9 mm, an open pore diameter: 30
.mu.m, Shore A hardness: 60.degree.) [0099] Rotational speed of the
platen: 32.5 r/min [0100] Flow rate for the polishing composition:
100 mL/min [0101] Polishing time: 4 minutes [0102] Polishing load:
7.8 kPa [0103] Number of substrates introduced: 10 I-2.
Determination Conditions for Zeta Potential [0104] Determination
device: "ELS-8000" commercially available from Otsuka Electronics
Co., Ltd. (flat plate cell type) [0105] Applied voltage: 80V [0106]
Determination temperature: 25.degree. C. [0107] Determination
sample: A polishing composition prepared by diluting an abrasive
with an aqueous solution of a zeta potential controlling agent
(corresponding to an aqueous solution containing a zeta potential
adjusting agent and water) of which the pH was adjusted to be the
same one as that of the polishing composition, so as to have an
abrasive concentration of 0.05% by weight as a determination
sample. [0108] Number of determinations: Determinations were made
three times using the same sample under the same determination
conditions, and an average of the three determinations was defined
as the zeta potential. I-3. Determination Conditions for Nano
Scratches [0109] Determination device: "Micromax VMX-2100CSP"
(commercially available from VISION PSYTEC CO., LTD.) [0110] Light
source: 2S.lamda. (250 W) and 3P.lamda. (250 W), both being 100%
[0111] Tilted angle: -6.degree. [0112] Magnification: Maximum
(vision scope: 1/120 of the entire area [0113] Observation scope:
Entire area (substrate having an outer circumferential diameter of
95 mm and an inner circumferential diameter of 25 mm) [0114] Iris:
notch [0115] Evaluation: Four substrates are selected at random
from the substrates introduced into a polishing test machine. The
number of nano scratches (without unit, -) per one side of the
substrate was calculated by dividing the total of the number of
nano scratches on each of both sides of the four substrates by a
factor of 8. Also, the nano scratches shown in the table were
evaluated relative to the number of nano scratches (/side) of
Comparative Example 1. I-4. Determination Conditions for Surface
Roughness (Ra) [0116] Determination device: "Nano Scope III,
Dimension 3000" commercially available from Digital Instrument
[0117] Scan rate: 1.0 Hz [0118] Scan area: 2.times.2 .mu.m
[0119] Evaluation: Determinations were made at three points at an
equidistance from the inner circumference and the outer
circumference in an interval of 120.degree., and the determinations
were made on both sides of the substrate. An average of a total of
6 points was obtained. TABLE-US-00001 TABLE I Composition of
Polishing Composition (% by weight).sup.1) Zeta Potential Other
Abrasive Controlling Agent Components Zeta Polishing Colloidal
Colloidal Colloidal Sulfuric Citric Hydrogen Potential Nano Ra Rate
Silica I-A Silica I-B Silica I-C HEDP Acid Acid Peroxide (mV) pH
Scratches (nm) (.mu.m/min) Ex. I-1 7 -- -- 5.6 -- -- -- 5 1 0.18
0.16 0.09 Ex. I-2 7 -- -- 0.13 0.55 -- -- 1 1.2 0.13 0.16 0.10 Ex.
I-3 -- 7 -- 0.28 -- -- -- -0.1 3 0.16 0.13 0.05 Ex. I-4 3.5 3.5 --
2 -- -- 0.6 -0.1 1.8 0.04 0.12 0.16 Ex. I-5 7 -- -- 2 -- -- -- -0.2
1.8 0.13 0.18 0.08 Ex. I-6 7 -- -- 0.24 -- -- -- -8 3 0.22 0.19
0.06 Ex. I-7 7 -- -- -- -- 0.67 -- -10 3 0.33 0.19 0.06 Ex. I-8 --
-- 7 0.3 -- -- -- -15 3 0.56 0.21 0.05 Ex. I-9 -- 7 -- 5.5 -- -- --
25 1.5 0.40 0.16 0.06 Comp. 7 -- -- 0.12 -- -- -- -73 7 1.00 0.38
0.01 Ex. I-1 Comp. 7 -- -- 0.16 -- -- -- -40 5 0.82 0.34 0.02 Ex.
I-2 Comp. -- 7 -- 0.15 -- -- -- -63 7 0.85 0.31 0.01 Ex. I-3 Comp.
-- -- 7 0.16 -- -- -- -72 7 1.31 0.29 0.01 Ex. I-4 Comp. -- 7 --
6.5 -- -- -- 35 1.0 0.70 0.19 0.07 Ex. I-5 Note .sup.1): The
balance of the polishing composition is ion-exchanged water.
[0120] It can be seen from the results shown in Table 1 that the
substrate obtained by using the polishing compositions of Examples
I-1 to I-9 suppressed the generation of nano scratches and reduced
surface roughness, as compared to those of Comparative Example I-1
to I-5.
(Determination Conditions for Zeta Potential)
[0121] The determination conditions for the zeta potential given
hereinbelow are as follows. [0122] Determination device: "NICOMP
Model-380 ZLS" (commercially available from Particle Sizing
Systems) [0123] Applied voltage: 1.0 to 5.0 V/cm [0124]
Determination sample: Each of the polishing compositions obtained
in Examples and Comparative Examples was separated by a centrifuge
(centrifugal force: 35000 g, 30 minutes), and the supernatant was
collected. The polishing composition was added in an amount of 0.2%
by weight to the supernatant while mixing, to be used as the
determination sample. [0125] Number of determinations:
Determinations were made three times using the same sample under
the same determination conditions, and an average of the three
determinations was defined as the zeta potential.
Example II-1
[0126] There were added together 20% by weight of Colloidal Silica
Slurry II-A (commercially available from Du Pont, average primary
particle size: 37 nm, D90/D50=2.2) as silica particles; 0.25% by
weight of a 36% by weight aqueous hydrochloric acid solution as a
zeta potential controlling agent, and the balance being
ion-exchanged water to give a polishing composition (zeta
potential: 26.5 mV, pH: 1.5).
[0127] The order of mixing each component was as follows: The zeta
potential controlling agent 36% by weight aqueous hydrochloric acid
solution prepared by diluting hydrochloric acid with water was
added to Colloidal Silica Slurry II-A little by little while
stirring, to give a polishing composition. The polishing properties
were evaluated on the basis of the following conditions by using
the polishing composition. As a result, the polishing rate was
0.197 .mu.m/minute, and a surface smoothness (Ra) of 0.23 nm.
II-1. Substrate to be Polished
[0128] A memory hard disk substrate made of crystallized glass, an
outer circumference of 65 mm, an inner circumference of 20 mm, a
thickness of 0.65 mm and surface roughness (Ra) of 0.2 to 0.3
nm
II-2. Polishing Conditions
[0129] Polishing device: "Musasino Denshi MA-300," (a single-sided
polishing machine, platen diameter: 300 mm, carrier forced driving
type) [0130] Rotational speed of platen: 90 r/min [0131] Rotational
speed of carrier: 90 r/min [0132] Flow rate for the polishing
composition: 50 mL/min (1.7 mL/min per 1 cm.sup.2 of the substrate
to be polished) [0133] Polishing time: 10 minutes [0134] Polishing
load: 14.7 kPa [0135] Polishing pad: "suede type, Bellatrix N0012"
(commercially available from Kanebo, LTD.) [0136] Dressing method:
Brush-dressing was carried out for 30 seconds for every polishing.
II-3. Calculation Method for Polishing Rate
[0137] Supposing that the specific gravity of the substrate to be
polished was 2.41, the polishing rate (.mu.m/minute) was calculated
from the amount of weight loss before and after the polishing.
[Method for Evaluating Surface Smoothness of Substrate]
[0138] The surface smoothness of the substrate was evaluated by
determining an average surface roughness (Ra) of the substrate. The
conditions were as follows. [0139] Device: Zygo New View 5032
[0140] Lens: Magnification, 10 times [0141] Zooming Ratio: 1 [0142]
Camera: 320.times.240 Normal [0143] Remove: Cylinder [0144] Filter:
FFT Fixed Band Pass [0145] 0.005 to 0.1 mm [0146] Area: 0.85
mm.times.0.64 mm
Examples II-2 to II-4, Comparative Example II-1
[0147] Each of the polishing compositions having a composition, a
pH and a zeta potential of the silica particles as shown in Table 2
was prepared in the same manner as in Example II-1, and the
polishing properties were evaluated. The results for the polishing
rate and the zeta potential are shown in Table 2. TABLE-US-00002
TABLE 2 Composition of Polishing Composition (% be weight) Silica
Particles Zeta Potential Zeta Polishing Colloidal Silica
Controlling Agent Potential Rate Slurry II-A Hydrochloric Acid (mV)
pH (.mu.m/min.) Ex. II-2 20 0.11 -0.7 4.0 0.154 Ex. II-3 20 0.09
-5.7 6.4 0.119 Ex. II-4 20 0.07 -9.0 8.0 0.100 Comp 20 0 -17.9 10.5
0.059 Ex. II-1
[0148] It can be seen from the results of Table 2 that the
polishing compositions obtained in Examples II-2 to II-4 in which
the zeta potential of the silica particles in the polishing
composition was adjusted within the range from -15 to 40 mV showed
remarkable increase in the polishing rates, as compared to that of
Comparative Example II-1.
Examples II-5 to II-6, Comparative Examples II-2
[0149] There were added together Colloidal Silica Slurry II-B
(commercially available from Du Pont, average primary particle
size: 17 nm, D90/D50=1.6) as silica particles, and a 36% by weight
aqueous hydrochloric acid solution as a zeta potential controlling
agent in amounts shown in Table 3, to give a polishing composition
having a composition, a pH and a zeta potential of the silica
particles as shown in Table 3. Here, the balance was ion-exchanged
water.
[0150] The order of mixing each component was as follows: The zeta
potential controlling agent aqueous hydrochloric acid solution
prepared by diluting hydrochloric acid with water was added to
Colloidal Silica Slurry II-B little by little while stirring, to
give a polishing composition. The polishing properties were
evaluated on the basis of the following conditions by using the
polishing composition. The results for the polishing rate and the
zeta potential are shown in Table 3. The substrate to be polished,
the polishing conditions and the calculation method for the
polishing rate are the same as those of Examples II-1 to II-4.
TABLE-US-00003 TABLE 3 Composition of Polishing Composition (% be
weight) Silica Particles Zeta Potential Zeta Polishing Colloidal
Controlling Agent Potential Rate Slurry II-B Hydrochloric Acid (mV)
pH (.mu.m/min) Ex. II-5 20 0.27 24.1 1.5 0.193 Ex. II-6 20 0.13 0.1
4.0 0.145 Comp. 20 0 -17.2 10.5 0.058 Ex. II-2
[0151] It can be seen from the results of Table 3 that the
polishing compositions obtained in Examples II-5 and II-6 in which
the zeta potential of the silica particles in the polishing
composition was adjusted within the range from -15 to 40 mV showed
remarkable increase in the polishing rates, as compared to that of
Comparative Example II-2.
Examples II-7 to II-8, Comparative Examples II-3
[0152] There were added together Colloidal Silica Slurry II-A as
silica particles, and a 36% by weight aqueous hydrochloric acid
solution as a zeta potential controlling agent in amounts shown in
Table 4, to give a polishing composition having a composition, a pH
and a zeta potential of the silica particles as shown in Table 4.
Here, the balance was ion-exchanged water. The order of mixing each
component was as follows: The zeta potential controlling agent
aqueous hydrochloric acid solution prepared by diluting
hydrochloric acid with water was added to Colloidal Silica Slurry
II-A little by little while stirring, to give a polishing
composition. The polishing properties were evaluated on the basis
of the following conditions by using the polishing composition. The
results for the polishing rate and the zeta potential are shown in
Table 4. The substrate to be polished, the polishing conditions and
the calculation method for polishing rate are the same as those of
Examples II-1 to II-4 except that a substrate made of reinforced
glass was used for the substrate to be polished. TABLE-US-00004
TABLE 4 Composition of Polishing Composition (% by weight) Silica
Particles Zeta Potential Zeta Polishing Colloidal Silica
Controlling Agent Potential Rate Slurry II-A Hydrochloric Acid (mV)
pH (.mu.m/min) Ex. II-7 20 0.25 26.5 1.5 0.538 Ex. II-8 20 0.09
-5.7 6.4 0.305 Comp 20 0 -17.9 10.5 0.177 Ex. II-3
[0153] It can be seen from the results of Table 4 that the
polishing compositions obtained in Examples II-7 and II-8 in which
the zeta potential of the silica particles in the polishing
composition was adjusted within the range from -15 to 40 mV showed
remarkable increase in the polishing rates, as compared to that of
Comparative Example II-3.
Example II-9 to II-10, Comparative Examples II-4
[0154] There were added together Colloidal Silica Slurry II-A as
silica particles, and a 36% by weight aqueous hydrochloric acid
solution as a zeta potential controlling agent in amounts shown in
Table 5, to give a polishing composition having a composition, a pH
and a zeta potential of the silica particles as shown in Table 5.
Here, the balance was ion-exchanged water. The order of mixing each
component was as follows: The zeta potential controlling agent
aqueous hydrochloric acid solution prepared by diluting
hydrochloric acid with eater was added to Colloidal Silica Slurry
II-A little by little while stirring, to give a polishing
composition. The polishing properties were evaluated on the basis
of the following conditions by using the polishing composition. The
results for the polishing rate and the zeta potential are shown in
Table 5.
II-4. Substrate to be Polished
[0155] PE-TEOS film having a thickness of 2000 nm was formed on an
8-inch (200 mm) silicon substrate, and the film-forming substrate
was cut into squares of 40 mm.times.40 mm.
II-5. Polishing Conditions
[0156] The polishing conditions were the same as those of Examples
II-1 to II-4 except that the flow rate for the polishing
composition, the polishing time, the polishing pad and the dressing
method were as follows. [0157] Flow rate for the polishing
composition: 200 mL/min (0.6 mL/min per 1 cm.sup.2 of the substrate
to be polished) [0158] Polishing time: 5 minutes [0159] Polishing
pad: "IC1000 050(P)/Suba400" (commercially available from RODEL
NITTA) [0160] Dressing method: Dressing was carried out with
"Diamond Dresser #100" for 30 seconds for every polishing. II-6.
Calculation Method for Polishing Rage
[0161] The polishing rate (nm/min) was determined from the
difference between the thickness of the remaining PE-TEOS film
before polishing and that of the remaining film after polishing.
The thickness of the remaining film was determined using a light
interference-type film thickness gauge (LAMBDA ACE VM-1000,
commercially available from DAINIPPON SCREEN MFG. CO., LTD.).
TABLE-US-00005 TABLE 5 Composition of Polishing Composition (% by
weight) Silica Particles Zeta Potential Zeta Polishing Colloidal
Silica Controlling Agent Potential Rate Slurry II-A Hydrochloric
Acid (mV) pH (.mu.m/min) Ex. II-9 20 0.25 26.5 1.5 0.184 Ex. II-10
20 0.09 -5.7 6.4 0.143 Comp 20 0 -17.9 10.5 0.139 Ex. II-4
[0162] It can be seen from the results of Table 5 that the
polishing compositions obtained in Examples II-9 and II-10 in which
the zeta potential of the silica particles in the polishing
composition was adjusted within the range from -15 to 40 mV showed
remarkable increase in the polishing rates, as compared to that of
Comparative Example II-4.
[0163] The polishing composition of the present invention can be
favorably used in polishing the substrate for precision parts,
including substrates for magnetic recording media such as magnetic
disks, optical disks and opto-magnetic disks; photomask substrates;
optical lenses; optical mirrors; optical prisms; semiconductor
substrates; and the like.
[0164] 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.
* * * * *