U.S. patent application number 11/288294 was filed with the patent office on 2006-06-01 for polishing composition.
This patent application is currently assigned to Kao Corporation. Invention is credited to Shigeo Fujii, Kenichi Suenaga.
Application Number | 20060112647 11/288294 |
Document ID | / |
Family ID | 35580228 |
Filed Date | 2006-06-01 |
United States Patent
Application |
20060112647 |
Kind Code |
A1 |
Fujii; Shigeo ; et
al. |
June 1, 2006 |
Polishing composition
Abstract
The present invention provides a polishing composition
containing an organic nitrogen-containing compound, an organic
polybasic acid, an abrasive, and water, wherein the organic
nitrogen-containing compound has in the molecule two or more amino
groups, two or more imino groups, or one or more amino groups and
one or more imino groups; a method for manufacturing a substrate
with the polishing composition; and a method for reducing surface
stains of a substrate with the polishing composition. The polishing
composition can be suitably used, for example, in the manufacturing
step for a substrate for a hard disk such as a memory hard
disk.
Inventors: |
Fujii; Shigeo;
(Wakayama-shi, JP) ; Suenaga; Kenichi;
(Wakayama-shi, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Assignee: |
Kao Corporation
|
Family ID: |
35580228 |
Appl. No.: |
11/288294 |
Filed: |
November 29, 2005 |
Current U.S.
Class: |
51/295 ;
257/E21.237 |
Current CPC
Class: |
B24B 37/042
20130101 |
Class at
Publication: |
051/295 |
International
Class: |
B24D 11/00 20060101
B24D011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 30, 2004 |
JP |
2004-347212 |
Claims
1. A polishing composition comprising an organic
nitrogen-containing compound, an organic polybasic acid, an
abrasive, and water, wherein the organic nitrogen-containing
compound has in the molecule two or more amino groups, two or more
imino groups, or one or more amino groups and one or more imino
groups.
2. The polishing composition according to claim 1, wherein the
abrasive is an alumina.
3. The polishing composition according to claim 1, wherein the
organic nitrogen-containing compound has a molecular weight of from
150 to 100000.
4. The polishing composition according to claim 1, wherein the
organic nitrogen-containing compound is contained in an amount of
from 0.001 to 0.5% by weight of the polishing composition.
5. The polishing composition according to claim 1, wherein the
organic nitrogen-containing compound and the organic polybasic acid
are contained in a weight ratio of the organic nitrogen-containing
compound/the organic polybasic acid of from 1/10000 to 1/1.
6. The polishing composition according to claim 1, further
comprising an oxidizing agent.
7. The polishing composition according to claim 1, wherein the
polishing composition has a pH of from 1 to 7.
8. A method for manufacturing a substrate, comprising the steps of
feeding the polishing composition as defined in claim 1 to a
substrate to be polished at a flow rate of from 0.01 to 0.5
mL/minute per 1 cm.sup.2 of the substrate, and polishing the
substrate with a polishing pad.
9. The method according to claim 8, wherein a polishing pressure is
from 2 to 30 kPa.
10. A method for reducing surface stains on a substrate, comprising
the step of feeding the polishing composition as defined in claim 1
to a substrate to be polished at a flow rate of from 0.01 to 0.5
mL/minute per 1 cm.sup.2 of the substrate, and polishing the
substrate with a polishing pad.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a polishing composition, a
method for manufacturing a substrate with the polishing
composition, and a method for reducing surface stains on a
substrate with the polishing composition.
BACKGROUND OF THE INVENTION
[0002] In recent years, in order to progress in minimizing a unit
recording area and increasing storage capacity, hard disks are
demanded to have a smaller flying height of a magnetic head or be
prevented from surface defects such as surface stains.
[0003] Therefore, conventionally, as disclosed in JP2002-164307 A,
studies have been made on a polishing composition that enables
smoother polishing of the surface of a substrate for a hard disk
and that less likely causes surface defects. In addition, recently,
in order to obtain a substrate having a desired surface quality in
a given time period, studies have been made on the use of two or
more stages of polishing steps.
[0004] When abrasive grains used in a first-stage polishing step
and polishing debris remain on a substrate for a hard disk obtained
in the first-stage polishing step, the majority of these abrasive
grains and polishing debris are removed in the second-stage
polishing step. However, those that undesirably remain unremoved
lead to cause defects. Also, although the residual abrasive grains
and polishing debris in the first stage are indeed removed in the
second-stage polishing step, they have undesirably disadvantageous
influences on the second-stage polishing step, leading to generate
scratches or pits on the substrate. In addition, those residual
abrasive grains and polishing debris are even more undesirable in a
case where the polishing is carried out only in a single stage, or
a case where the polishing is carried out in a finishing step.
[0005] In order to solve these disadvantages, it is important that
the abrasive grains and the polishing debris are removed from the
substrate at the termination of each stage of the polishing step.
However, the studies on a polishing composition that gives a
substrate having reduced surface stains have been hardly conducted,
so that a technique of satisfactorily solving the disadvantage has
not so far been known.
SUMMARY OF THE INVENTION
[0006] The present invention relates to:
[0007] [1] a polishing composition containing an organic
nitrogen-containing compound, an organic polybasic acid, an
abrasive, and water, wherein the organic nitrogen-containing
compound has in the molecule two or more amino groups, two or more
imino groups, or one or more amino groups and one or more imino
groups;
[0008] [2] a method for manufacturing a substrate, including the
step of feeding the polishing composition as defined in the above
[1] to a substrate to be polished at a flow rate of from 0.01 to
0.5 mL/minute per 1 cm.sup.2 of the substrate, and polishing the
substrate with a polishing pad; and
[0009] [3] a method for reducing surface stains on a substrate,
including the step of feeding the polishing composition as defined
in the above [1] to a substrate to be polished at a flow rate of
from 0.01 to 0.5 mL/minute per 1 cm.sup.2 of the substrate, and
polishing the substrate with a polishing pad.
DETAILED DESCRIPTION OF THE INVENTION
[0010] The present invention relates to a polishing composition
giving fewer residual abrasive grains and polishing debris
generated by polishing on a polished substrate after polishing,
higher polishing rates, and being capable of maintaining smoothness
of the substrate; a method for manufacturing a substrate with the
polishing composition; and a method for reducing surface stains on
a substrate with the polishing composition.
[0011] Since the polishing composition of the present invention is
used, the effects that a substrate having excellent surface
smoothness, including fewer surface defects such as surface stains,
smaller waviness, or the like, can be efficiently manufactured are
exhibited.
[0012] These and other advantages of the present invention will be
apparent from the following description.
[0013] The feature of the polishing composition of the present
invention, as mentioned above, resides in that the polishing
composition contains an organic nitrogen-containing compound, an
organic polybasic acid, an abrasive, and water, wherein the organic
nitrogen-containing compound has in the molecule two or more amino
groups, two or more imino groups, or one or more amino groups and
one or more imino groups. Since the polishing composition has the
above feature, the effects that a substrate having excellent
surface smoothness, including fewer surface defects such as surface
stains, smaller waviness, or the like, can be efficiently
manufactured are exhibited.
[0014] Here, the function mechanism in which the abrasive grains
and polishing debris are prevented from remaining by the polishing
composition of the present invention is yet unknown. Although not
wanting to be limited by theory, the function is considered to be
exhibited due to a synergistic effect of a combined use of a
specified organic nitrogen-containing compound and an organic
polybasic acid as explained below.
[0015] Also, while the function mechanism is yet unknown, it is
deduced that an organic polybasic acid is adsorbed to the abrasive
grains and the polishing debris, so that their surfaces are charged
negatively and likely to deposit on the substrate, and an organic
nitrogen-containing compound is adsorbed to the surfaces of
abrasive grains and polishing debris adsorbed by the organic
polybasic acid to electrically neutralize, thereby suppressing them
to deposit or remain on the substrate.
[0016] The organic nitrogen-containing compound used in the present
invention refers to a compound having a total of two or more groups
selected from an amino group and an imino group in the molecule.
Specifically, the organic nitrogen-containing compound used in the
present invention has in the molecule two or more amino groups, two
or more imino groups, or one or more amino groups and one or more
imino groups. The total number of the amino groups and the imino
groups in the molecule is not particularly limited. The total
number of the amino groups and the imino groups in the molecule is
preferably from 2 to 2000, more preferably from 2 to 1000, even
more preferably from 2 to 200, and even more preferably from 2 to
50, from the viewpoint of increasing polishing rate and preventing
surface stains on a substrate. Specific examples thereof include
polyalkyleneimines, diethylenetriamine, triethylenetetramine,
tetraethylenepentamine, bis(3-aminopropyl)amine, 1,3-propanediamine
and the like.
[0017] Representative examples of the polyalkyleneimine include
polyethyleneimine, polypropyleneimine, polybutadieneimine and the
like, including those having a linear or branched structure, or
those having a cyclic structure. Among them, the polyethyleneimine
is preferable, from the viewpoint of increasing polishing rate and
preventing surface stains on a substrate. The polyalkyleneimine has
a molecular weight of preferably from 150 to 100000, more
preferably from 200 to 30000, even more preferably from 200 to
10000, and even more preferably from 300 to 2000, from the
viewpoint of increasing polishing rate and reducing surface stains
on a substrate. The above-mentioned molecular weight can be
determined as a number-average molecular weight according to
ebulioscopy or viscosity method.
[0018] In addition, the organic nitrogen-containing compound is
contained in an amount of preferably from 0.001 to 0.5% by weight,
more preferably from 0.001 to 0.3% by weight, and even more
preferably from 0.001 to 0.1% by weight, of the polishing
composition, from the viewpoint of increasing polishing rate and
preventing surface stains on a substrate.
[0019] The organic polybasic acid used in the present invention is
preferably a sulfur-containing organic acid, a carboxylic acid, and
a phosphorus-containing organic acid. Specific examples of the
organic polybasic acid include organic sulfonic acids such as
methanedisulfonic acid, ethanedisulfonic acid, phenoldisulfonic
acid, and naphthalenedisulfonic acid; polycarboxylic acids such as
oxalic acid, succinic acid, glutaric acid, adipic acid, maleic
acid, fumaric acid, itaconic acid, malic acid, tartaric acid,
citric acid, isocitric acid, phthalic acid, nitrilotriacetic acid,
and ethylenediaminetetraacetic acid; phosphorus-containing organic
acids such as hydroxyethylidene-1,1-diphosphonic acid,
phosphonobutanetricarboxylic acid, and
ethylenediaminetetramethylenephosphonic acid; and the like. Among
them, succinic acid, citric acid, malic acid, tartaric acid,
hydroxyethylidene-1,1-diphosphonic acid, and
ethylenediaminetetramethylenephosphonic acid are preferable, citric
acid, malic acid, and tartaric acid are more preferable, and citric
acid is even more preferable, from the viewpoint of increasing
polishing rate, reducing waviness and reducing roll-off. These
compounds may be used alone or in admixture of two or more
kinds.
[0020] The organic polybasic acid is contained in an amount of
preferably 0.002% by weight or more, more preferably 0.005% by
weight or more, even more preferably 0.007% by weight or more, and
even more preferably 0.01% by weight or more, of the polishing
composition, from the viewpoint of increasing polishing rate and
reducing waviness. In addition, the organic polybasic acid is
contained in an amount of preferably 20% by weight or less, more
preferably 15% by weight or less, even more preferably 10% by
weight or less, and even more preferably 5% by weight or less, of
the polishing composition, from the viewpoint of surface quality
and economic advantage. In other words, the organic polybasic acid
is contained in an amount of preferably from 0.002 to 20% by
weight, more preferably from 0.005 to 15% by weight, even more
preferably from 0.007 to 10% by weight, and even more preferably
from 0.01 to 5% by weight, of the polishing composition.
[0021] In addition, in the polishing composition of the present
invention, the organic nitrogen-containing compound and the organic
polybasic acid mentioned above are contained in a weight ratio,
i.e. organic nitrogen-containing compound/organic polybasic acid,
of preferably 1/1 or less, more preferably 1/2 or less, and even
more preferably 1/5 or less, from the viewpoint of increasing the
polishing rate. In addition, the weight ratio is preferably 1/10000
or more, more preferably 1/1000 or more, even more preferably 1/200
or more, and even more preferably 1/50 or more, from the viewpoint
of preventing surface stains on a substrate. In other words, the
weight ratio is preferably from 1/10000 to 1/1, more preferably
from 1/1000 to 1/2, even more preferably from 1/500 to 1/5, even
more preferably from 1/200 to 1/5, and even more preferably from
1/50 to 1/5, from the viewpoint of increasing polishing rate and
preventing surface stains on a substrate.
[0022] As the abrasive to be used in the present invention, any
abrasives generally employed for polishing can be used. Examples of
the abrasive include, for instance, metals; carbides of metals or
metalloids, nitrides of metals or metalloids, oxides of metals or
metalloids, borides of metals or metalloids; diamond, and the like.
The metals or metalloids include those elements belonging to the
Groups 2A, 2B, 3A, 3B, 4A, 4B, 5A, 6A, 7A or 8 of the Periodic
Table (long period form). Specific examples of the abrasive include
aluminum oxide (hereinafter referred to as "alumina" in some cases)
particles such as .alpha.-alumina particles and intermediate
alumina particles, silicon carbide particles, diamond particles,
magnesium oxide particles, zinc oxide particles, cerium oxide
particles, titanium oxide particles, zirconium oxide particles,
colloidal silica particles, fumed silica particles, and the like.
Among them, .alpha.-alumina particles, intermediate alumina
particles, cerium oxide particles, zirconium oxide particles,
colloidal silica particles, fumed silica particles, and the like
are preferable, and .alpha.-alumina particles, intermediate alumina
particles, colloidal silica particles and fumed silica particles
are more preferable, and .alpha.-alumina particles and intermediate
alumina particles are even more preferable. In addition, aluminum
oxide particles are preferable from the viewpoint of reducing
abrasive grains and polishing debris. Further, effects of an even
more increased polishing rate and reduction in waviness are
obtained by a combined use of .alpha.-alumina and an intermediate
alumina, or a combined use of .alpha.-alumina and colloidal silica
or fumed silica.
[0023] Among the .alpha.-alumina and the intermediate alumina
mentioned above, it is preferable that the alumina has a purity of
95% or more, more preferably 97% or more, and even more preferably
99% or more, from the viewpoint of reducing waviness, reducing
surface roughness, increasing polishing rate, and preventing
surface defects. In addition, .alpha.-alumina is preferable from
the viewpoint of increasing polishing rate, and intermediate
aluminas such as .gamma.-alumina, .delta.-alumina, .theta.-alumina,
.eta.-alumina, and .kappa.-alumina are preferable, from the
viewpoint of surface properties and reduction in waviness. Here,
the intermediate alumina used in the present invention is a generic
term referring to alumina particles other than .alpha.-alumina
particles. Specific examples thereof include .gamma.-alumina,
.delta.-alumina, .theta.-alumina, .eta.-alumina, .kappa.-alumina,
and mixtures thereof. Among the intermediate aluminas,
.gamma.-alumina, .delta.-alumina, .theta.-alumina, and mixtures
thereof are preferable, and .gamma.-alumina and .theta.-alumina are
even more preferable, from the viewpoint of increasing polishing
rate and reducing waviness.
[0024] Even more, in the case of the intermediate alumina, the
intermediate alumina has a specific surface area as determined by
BET method of preferably from 30 to 300 m 2/g, and more preferably
from 50 to 200 m.sup.2/g.
[0025] The primary particles of the above-mentioned abrasive have
an average particle size of preferably from 0.001 to 2 .mu.m, more
preferably from 0.005 to 0.8 .mu.m, and even more preferably from
0.01 to 0.5 .mu.m, from the viewpoint of increasing polishing rate
and reducing waviness. Further, when the primary particles are
aggregated to form secondary particles, the secondary particles
have an average particle size of preferably from 0.02 to 3 .mu.m,
more preferably from 0.05 to 1 .mu.m, even more preferably from 0.1
to 0.8 .mu.m, and even more preferably from 0.1 to 0.5 .mu.m, from
the viewpoint of increasing polishing rate, reducing waviness, and
inhibiting surface defects. The average particle size of the
primary particles of the abrasive is obtained by subjecting the
abrasive to an image analysis by observing with a scanning electron
microscope in a magnification of favorably from 3000 to 30000
times, or with a transmission electron microscope in a
magnification of favorably from 10000 to 500000 times, and
determining the particle size. In addition, the average particle
size of the secondary particles can be determined as a
volume-average particle size by using a laser diffraction
method.
[0026] The specific gravity of the abrasive is preferably from 1.5
to 8, and more preferably from 1.5 to 5, from the viewpoints of
dispersibility, feed ability to the polishing device and efficiency
of recovery and reuse.
[0027] The abrasive is contained in an amount of preferably from
0.05 to 40% by weight, more preferably from 0.1 to 30% by weight,
even more preferably from 0.5 to 25% by weight, even more
preferably from 1 to 20% by weight, and even more preferably from 1
to 10% by weight, of the polishing composition, from the viewpoint
of economic advantage and increase in polishing rate.
[0028] Water in the polishing composition of the present invention
is used as a medium, and the water is contained in an amount of
preferably from 55 to 99% by weight, more preferably from 60 to 97%
by weight, and even more preferably from 70 to 95% by weight, of
the polishing composition, from the viewpoint of efficiently
polishing the object to be polished.
[0029] In addition, the polishing composition of the present
invention can contain other components as occasion demands.
[0030] It is preferable that an inorganic acid is used together in
the polishing composition of the present invention, from the
viewpoint of further increasing the polishing rate and reducing the
waviness. The inorganic acid is preferably nitric acid, nitrous
acid, sulfuric acid, sulfurous acid and amide sulfuric acid, and
sulfuric acid, sulfurous acid and amide sulfuric acid are more
preferable, and sulfuric acid is even more preferable, from the
viewpoint of increasing the polishing rate. The inorganic acid is
contained in an amount of preferably from 0.002 to 20% by weight,
more preferably from 0.005 to 15% by weight, even more preferably
from 0.007 to 10% by weight, and even more preferably from 0.01 to
5% by weight, of the polishing composition, from the viewpoint of
polishing rate, surface quality and economic advantage.
[0031] In addition, it is preferable that the polishing composition
of the present invention contains an oxidizing agent, from the
viewpoint of increasing the polishing rate. The oxidizing agent is
roughly classified into inorganic oxidizing agents and organic
oxidizing agents. As the inorganic oxidizing agent, there can be
used hydrogen peroxide, a peroxide of an alkali metal or an
alkaline earth metal, a peroxosulfuric acid or a salt thereof,
peroxonitric acid or a salt thereof, a peroxophosphoric acid or a
salt thereof, a peroxoborate, a peroxochromate, a permanganate, a
halogeno-acid or a derivative thereof, a metal salt of an inorganic
acid or the like. As the organic oxidizing agent, there can be used
a percarboxylic acid, a peroxide, iron (III) citrate or the like.
Among them, the inorganic oxidizing agent is preferable, when an
increase of the polishing rate, availability, and easy handling,
such as water-solubility are compared. Especially, in consideration
of the environmental problems, an inorganic peroxide which does not
contain a heavy metal is preferable. In addition, hydrogen
peroxide, a peroxosulfate, a halogeno-acid or a derivative thereof
are more preferable, and hydrogen peroxide is even more preferable,
from the viewpoint of preventing the stains on the surface of the
substrate to be polished. In addition, these oxidizing agents can
be used alone or in admixture of two or more kinds.
[0032] The oxidizing agent is contained in an amount of preferably
from 0.002 to 20% by weight, more preferably from 0.005 to 15% by
weight, even more preferably from 0.007 to 10% by weight, and even
more preferably from 0.01 to 5% by weight, of the polishing
composition, from the viewpoint of increase in polishing rate,
reduction in waviness, surface quality, and economic advantage.
[0033] In addition, other components for the polishing composition
include celluloses such as cellulose, carboxymethyl cellulose, and
hydroxyethyl cellulose; water-soluble alcohols such as ethanol,
propanol, and ethylene glycol; and the like, and also include
surfactants such as alkylbenzenesulfonates, formalin condensates of
naphthalenesulfonic acid, polyacrylates, and ligninsulfonates;
water-soluble polymers such as polyvinyl alcohol; and the like.
These components can be used alone or in admixture of two or more
kinds. The other components can be each contained in an amount of
preferably from 0.001 to 20% by weight, more preferably from 0.01
to 5% by weight, and even more preferably from 0.01 to 2% by
weight, of the polishing composition, from the viewpoint of
exhibiting each of the functions and from the viewpoint of economic
advantages.
[0034] The concentration of each component mentioned above in the
polishing composition is a preferred concentration upon use. The
concentration upon the preparation of the polishing composition may
be in a concentration higher than those defined above. In many
cases, the polishing composition is usually prepared as a
concentrate, which is diluted upon use.
[0035] The polishing composition of the present invention can be
preferably used in polishing a substrate for a hard disk as a
substrate to be polished. The substrate for a hard disk is not
particularly limited as long as usually known ones are used, and
includes, for example, a substrate having a metal layer formed on a
surface layer such as a Ni--P plated aluminum alloy substrate, a
Ni--P plated glass substrate, and an aluminum disk, a substrate
made of a glassy substance or a ceramic material, such as a carbon
disk and a glass substrate, a substrate composed of composites of
the above substances and materials, and the like. Among them, when
the polishing composition of the present invention is used for a
substrate having a metal layer formed on a surface layer such as a
Ni--P plated aluminum alloy substrate, a Ni--P plated glass
substrate, and an aluminum disk, it is preferable because the
abrasive grains and the polishing debris can be remarkably
reduced.
[0036] It is preferable that the pH of the polishing composition is
properly determined depending upon the kinds of the substrate to be
polished. For example, it is preferable that the pH of the
polishing composition is preferably from 1 to 12, from the
viewpoint of rinsability of the substrate, corrosion inhibition of
the processing machine, and safety of an operator. When the main
subject for a substrate to be rinsed is a substrate having a metal
layer formed on a surface layer such as a Ni--P plated aluminum
alloy substrate, a Ni--P plated glass substrate, and an aluminum
disk, the pH is preferably from 1 to 7, more preferably from 1 to
5, even more preferably from 1 to 4, even more preferably from 2 to
4, and even more preferably 2 or more and less than 3, from the
viewpoint of increasing the polishing rate. The pH can be adjusted
by properly formulating an inorganic acid, an organic acid, or a
salt thereof, or a basic substance such as ammonia, sodium
hydroxide, potassium hydroxide, or amine as occasion demands.
[0037] In the present invention, the effects of preventing residual
abrasive grains and polishing debris by the polishing composition
can be evaluated by, for example, an observation with a microscope,
an observation with a scanning electron microscope, or the like of
the surface of the substrate after polishing. Among them, in the
substrate for a hard disk, the effect can be evaluated by observing
an edge portion of its inner diameter which is less likely to be
cleaned off with these equipments. In addition, the surface of the
substrate after polishing can be further evaluated by glow
discharge optical emission spectrometry (GDOES) or the like.
[0038] By using the polishing composition of the present invention
having the constitution mentioned above, in the step of polishing
in the method for manufacturing a substrate, such as a substrate
for a hard disk, the residual abrasive grains and polishing debris
generated by polishing on the substrate, in other words, surface
stains are prevented, so that the substrate has less surface
defects such as scratches and pits on its surface, whereby a
substrate having less abrasive grains and polishing debris can be
manufactured. Therefore, the present invention relates to a method
for manufacturing a substrate, and a method for reducing surface
stains of a substrate.
[0039] Each of the method for manufacturing a substrate and the
method for reducing surface stains of the present invention
includes the step of polishing a substrate to be polished with the
above-mentioned polishing composition. In this step, the substrate
to be polished can be polished by feeding the polishing composition
to the polishing side of the substrate pressed against platens to
which a porous organic polymer-based polishing pad is attached, and
moving the platens and/or the substrate, while applying a pressure.
Therefore, the present invention also relates to a method for
polishing a substrate using the above-mentioned polishing
composition.
[0040] In the method for manufacturing a substrate and the method
for reducing surface stains of a substrate of the present
invention, it is preferable that each method includes the step of
feeding the polishing composition to a substrate at a flow rate of
preferably from 0.01 to 0.5 mL/min, more preferably from 0.02 to
0.3 mL/min, even more preferably from 0.03 to 0.2 mL/min, per 1
cm.sup.2 of the substrate to be polished, and polishing the
substrate with a polishing pad, from the viewpoint of increase in
polishing rate and economic advantage. Therefore, an example of the
method for manufacturing a substrate or the method for reducing
surface stains of a substrate of the present invention includes a
method including the step of feeding the polishing composition of
the present invention to a substrate to be polished at a flow rate
of from 0.01 to 0.5 mL/minute per 1 cm.sup.2 of the substrate, and
polishing the substrate with a polishing pad
[0041] In addition, in the method for manufacturing a substrate of
the present invention, it is desired that the polishing pressure
upon polishing the substrate is adjusted to a range of from 2 to 30
kPa, preferably from 2 to 20 kPa, and more preferably from 4 to 15
kPa, from the viewpoint of increasing polishing rate and reducing
waviness.
[0042] In addition, other conditions when the polishing is carried
out, such as kinds of polishing machine, kinds of polishing pads,
polishing temperature, and polishing rate, are not particularly
limited. When a Ni--P plated aluminum alloy substrate is polished
with an abrasive containing aluminum oxide particles, the polishing
rate is preferably from 0.05 to 8 .mu.m/min, more preferably from
0.1 to 6 .mu.m/min, even more preferably from 0.2 to 5 .mu.m/min,
and even more preferably from 0.4 to 4 .mu.m/min, from the
viewpoint of productivity and operability.
[0043] 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.
EXAMPLES
[0044] 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.
Examples 1 to 13, Comparative Examples 1 to 5
[0045] There were mixed together given amounts of .alpha.-alumina
(average particle size of primary particles: 0.07 .mu.m, average
particle size of secondary particles: 0.3 .mu.m, specific surface
area: 15 m.sup.2/g, purity: 99.9%), .theta.-alumina (average
particle size of secondary particles: 0.2 .mu.m, specific surface
area: 120 m.sup.2/g, purity: 99.9%), an organic polybasic acid, an
organic nitrogen-containing compound, and other additives as listed
in Table 1, and balance ion-exchanged water, while stirring, to
give a polishing composition.
1. Polishing Process
[0046] Surfaces of a Ni--P plated aluminum alloy substrate having a
thickness of 1.27 mm, and a diameter of 3.5 inch (95 mm)
(short-wavelength waviness: 3.8 nm and long-wavelength waviness:
1.6 nm, as determined by "Zygo New View 5032") were polished, using
a double-sided processing machine under the following setting
conditions with each of the polishing compositions obtained in the
Examples and Comparative Examples, to give a polished object, a
Ni--P plated aluminum alloy substrate usable as a substrate for a
magnetic recording medium.
[0047] The setting conditions for the double-sided processing
machine are as follows.
<Setting Conditions for Double-Sided Processing Machine]
[0048] Double-sided processing machine: Model 9B, commercially
available from SPEEDFAM CO., LTD. [0049] Processing pressure: 9.8
kPa [0050] Polishing pad: a polishing pad for a substrate for hard
disk, commercially available from FUJIBO [0051] Rotational speed of
a platen: 50 r/min. [0052] Flow rate for a polishing composition:
100 mL/min (0.076 mL/min per 1 cm.sup.2 of a substrate to be
polished) [0053] Polishing time period: 4 min. [0054] Number of
substrates introduced: 10 3. Evaluation Methods (1) Polishing
Rate
[0055] Weights of each substrate before and after polishing were
measured using a device commercially available from Sartorius under
the trade name of BP-210S. Change in weight of each substrate was
obtained, and an average of the change of 10 substrates was
referred to as an amount reduced, and a value obtained by dividing
the amount reduced by the polishing time is referred to as a rate
of weight reduced. The rate of weight reduced is introduced into
the following equation and converted to a polishing rate
(.mu.m/min). Rate of Weight Reduced (g/min)=[Weight Before
Polishing (g)-Weight After Polishing (g)]/Polishing Time (min)
Polishing Rate (.mu.m/min)=Rate of Weight Reduced (g/min)/Area of
One Side of Substrate (mm.sup.2)/Ni--P Plating Density
(g/cm.sup.3).times.1000000
[0056] Here, a relative value of a polishing rate (relative rate)
for each of the Examples and Comparative Examples is shown in Table
1, assuming that the polishing rate of Comparative Example 1 (1.2
.mu.m/min) takes a standard value of 1.
(2) Surface Stains
[0057] The surface of each of the substrates after polishing was
observed with a scanning electron microscope S-4000 commercially
available from Hitachi, Ltd. in a magnification of 10,000, and the
following 5-rank evaluations were made. Here, those ranked in 1 and
2 are failures from the viewpoint of practical purposes. [0058] 5:
no alumina residue, polishing debris or the like is observed on the
surface at all on the surface; [0059] 4: alumina residue, polishing
debris or the like is observed but in less amounts on the surface;
[0060] 3: alumina residue, polishing debris or the like is observed
but in slight amounts on the surface; [0061] 2: alumina residue,
polishing debris or the like is observed but in large amounts on
the surface; and [0062] 1: alumina residue, polishing debris or the
like is observed but in much amounts on the surface. (3)
Waviness
[0063] The waviness of each substrate after the polishing was
determined for two kinds, short-wavelength waviness and
long-wavelength waviness in accordance with the following
conditions. A relative value of waviness for each of the Examples
and Comparative Examples is shown in Table 1, assuming that each
waviness of Comparative Example 1 (short-wavelength waviness: 0.40
nm, long-wavelength waviness: 0.42 nm) takes a standard value of 1.
The lower the numerical value, the more the waviness being reduced.
TABLE-US-00001 Device: Zygo New View 5032 Object Lens:
Magnification, 2.5 times, Michelson Zooming Ratio: 0.5 Remove:
Cylinder Filter type: FFT Fixed Band Pass Short-Wavelength
Waviness: 50 to 500 .mu.m Long-Wavelength Waviness: 0.5 to 5 mm
Area: 4.33 mm .times. 5.77 mm
[0064] TABLE-US-00002 TABLE 1 .alpha.- .theta.- Organic Organic
Nitrogen- Alumina Alumina Polybasic Acid Containing Compound Other
Component(s) (% by (% by Name of (% by (% by Name of (% by wt.)
wt.) Compound wt.) Name of Compound wt.) Compound wt.) Ex. No. 1 3
2 Citric Acid 1 Polyethyleneimine 0.05 Hydrogen 0.6/0.6 Molecular
Weight 300 Peroxide/ Sulfuric Acid 2 3 2 Citric Acid 1
Polyethyleneimine 0.003 Hydrogen 0.6/0.6 Molecular Weight 600
Peroxide/ Sulfuric Acid 3 3 2 Citric Acid 1 Polyethyleneimine 0.01
Hydrogen 0.6/0.6 Molecular Weight 600 Peroxide/ Sulfuric Acid 4 3 2
Citric Acid 1 Polyethyleneimine 0.05 Hydrogen 0.6/0.6 Molecular
Weight 600 Peroxide/ Sulfuric Acid 5 3 2 Citric Acid 1
Polyethyleneimine 0.05 Hydrogen 0.6/0.6 Molecular Weight 2000
Peroxide/ Sulfuric Acid 6 3 2 Citric Acid 1 Triethylenetetramine
0.05 Hydrogen 0.6/0.6 Peroxide/ Sulfuric Acid 7 3 2 Citric Acid 1
Bis(3- 0.05 Hydrogen 0.6/0.6 aminopropyl)amine Peroxide/ Sulfuric
Acid 8 3 2 Citric Acid 1 1,3-Propanediamine 0.05 Hydrogen 0.6/0.6
Peroxide/ Sulfuric Acid 9 3 2 Citric Acid 1 Polyethyleneimine 0.05
Polyphosphoric 0.04 Molecular Weight 600 Acid 10 3 2 Citric Acid 1
Polyethyleneimine 0.05 Ammonium 0.1 Molecular Weight 600 Sulfate 11
3 2 Citrc Acid/ 0.5/0.5 Polyethyleneimine 0.05 -- -- Succinic Acid
Molecular Weight 600 12 3 2 Succinic 1 Polyethyleneimine 0.05 -- --
Acid Molecular Weight 600 13 3 2 Malic Acid 1 Polyethyleneimine
0.05 -- -- Molecular Weight 600 Comp. Ex. No. 1 3 2 Citric Acid 1
-- -- -- -- 2 3 2 Citric Acid 1 -- -- Hydrogen 0.6/0.6 Peroxide/
Sulfuric Acid 3 3 2 Citric Acid 1 Laurylamine Acetate 0.05 -- -- 4
3 2 Citric Acid 1 N-(2-Hydroxypropyl)- 0.05 -- -- N,N,N-trimethyl-
ammonium formate 5 3 2 -- -- Polyethyleneimine 0.05 Glycolic Acid/
.sup. 1/0.04 Molecular Weight 600 Polyphosphoric Acid Evaluation
Results pH Polishing Rate Surface Stains Short-Wavelength Waviness
Long-Wavelength Waviness Ex. No. 1 2 2.5 5 0.98 0.70 2 2 2.3 4 0.94
0.73 3 2 2.2 4 0.94 0.75 4 2 2.1 5 0.93 0.77 5 2 1.8 4 0.93 0.80 6
2 2.2 4 0.95 0.88 7 2 2.2 4 0.96 0.82 8 2 2.2 4 0.97 0.83 9 2.5 1.0
5 0.96 1.0 10 2.5 1.0 4 0.97 1.0 11 2.5 1.1 5 0.95 0.98 12 2.5 1.1
5 1.0 0.98 13 2.5 1.0 5 1.0 1.0 Comp. Ex. No. 1 2.5 1 1 1 1 2 2 2.4
1 0.97 0.75 3 2.5 0.7 2 0.95 1.2 4 2.5 0.9 1 0.98 1.1 5 3 0.6 4 1.1
1.1
[0065] It can be seen from the above results shown in Table 1 that
the polishing compositions obtained in Examples 1 to 13 give
significantly reduced surface stains of the substrate after
polishing, and are less likely to generate waviness on the
substrate.
[0066] The polishing composition of the present invention can be
suitably used, for example, in the manufacturing step for a
substrate for a hard disk such as a memory hard disk.
[0067] 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.
* * * * *