U.S. patent application number 10/175884 was filed with the patent office on 2003-03-06 for polishing composition.
Invention is credited to Fujii, Shigeo, Hagihara, Toshiya, Kitayama, Hiroaki, Yoshida, Hiroyuki.
Application Number | 20030041526 10/175884 |
Document ID | / |
Family ID | 27346995 |
Filed Date | 2003-03-06 |
United States Patent
Application |
20030041526 |
Kind Code |
A1 |
Fujii, Shigeo ; et
al. |
March 6, 2003 |
Polishing composition
Abstract
A polishing composition comprising an abrasive and water,
wherein the polishing composition has an index of degree of
sedimentation of 80 or more and 100 or less; a process for
producing a substrate comprising polishing a substrate to be
polished using the above-mentioned composition; a process for
preventing clogging of a polishing pad comprising applying the
above-mentioned composition; a process for preventing clogging of a
polishing pad comprising applying the above-mentioned composition
to polishing with a polishing pad for a nickel-containing object to
be polished; and a process for preventing clogging of a polishing
pad comprising applying a composition comprising a hydrophilic
polymer having two or more hydrophilic groups in its molecule and a
molecular weight of 300 or more, or a compound capable of
dissolving nickel hydroxide at a pH of 8.0, and water to polishing
with a polishing pad for a nickel-containing object to be
polished.
Inventors: |
Fujii, Shigeo;
(Wakayama-shi, JP) ; Yoshida, Hiroyuki;
(Wakayama-shi, JP) ; Hagihara, Toshiya;
(Wakayama-shi, JP) ; Kitayama, Hiroaki;
(Wakayama-shi, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
27346995 |
Appl. No.: |
10/175884 |
Filed: |
June 21, 2002 |
Current U.S.
Class: |
51/307 ; 106/3;
252/79.1 |
Current CPC
Class: |
C09K 3/1463 20130101;
C09K 3/1409 20130101; C09G 1/02 20130101 |
Class at
Publication: |
51/307 ; 106/3;
252/79.1 |
International
Class: |
C09K 003/14 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 21, 2001 |
JP |
2001-188722 |
Jul 26, 2001 |
JP |
2001-226322 |
Nov 12, 2001 |
JP |
2001-346468 |
Claims
What is claimed is:
1. A polishing composition comprising an abrasive and water,
wherein the polishing composition has an index of degree of
sedimentation of 80 or more and 100 or less.
2. The polishing composition according to claim 1, further
comprising a hydrophilic polymer compound or a compound capable of
dissolving nickel hydroxide at a pH of 8.0.
3. The polishing composition according to claim 2, wherein the
hydrophilic polymer compound is a hydrophilic polymer having two or
more hydrophilic groups in its molecule and a molecular weight of
300 or more.
4. The polishing composition according to claim 3, wherein the
hydrophilic group is an anionic group.
5. The polishing composition according to any one of claims 2 to 4,
wherein the compound capable of dissolving nickel hydroxide at a pH
of 8.0 is glycine, ascorbic acid or citric acid.
6. The polishing composition according to any one of claims 1 to 5,
further comprising: compound group (A): one or more compounds
selected from the group consisting of carboxylic acids having 2 to
20 carbon atoms and having either OH group or groups or SH group or
groups, monocarboxylic acids having 1 to 20 carbon atoms,
dicarboxylic acids having 2 to 3 carbon atoms, and salts thereof;
and/or compound group (B): one or more compounds selected from the
group consisting of polycarboxylic acids having 4 or more carbon
atoms and having neither OH group or groups nor SH group or groups,
aminocarboxylic acids, amino acids, and salts thereof.
7. The polishing composition according to any one of claims 1 to 6,
wherein the abrasive has a primary average particle size of 1 .mu.m
or less.
8. The polishing composition according to any one of claims 1 to 7,
which is used for polishing a magnetic disk substrate.
9. A process for producing a substrate comprising polishing a
substrate to be polished using the composition of any one of claims
1 to 8.
10. A process for preventing clogging of a polishing pad comprising
applying the composition of any one of claims 1 to 8.
11. A process for preventing clogging of a polishing pad comprising
applying the composition of any one of claims 1 to 8, to polishing
with a polishing pad for a nickel-containing object to be
polished.
12. A process for preventing clogging of a polishing pad comprising
applying a composition comprising: a hydrophilic polymer having two
or more hydrophilic groups in its molecule and a molecular weight
of 300 or more, or a compound capable of dissolving nickel
hydroxide at a pH of 8.0, and water, to polishing with a polishing
pad for a nickel-containing object to be polished.
13. The process according to claim 12, wherein the compound capable
of dissolving nickel hydroxide at a pH of 8.0 is one or more
compounds selected from the group consisting of carboxylic acids
having 2 to 20 carbon atoms and having either OH group or groups or
SH group or groups, monocarboxylic acids having 1 to 20 carbon
atoms, dicarboxylic acids having 2 to 3 carbon atoms, .alpha.-amino
acids having 2 to 3 carbon atoms, enolic organic acids having 3 to
10 carbon atoms, and salts thereof, wherein the content of the
compound is 0.01% by weight or more and less than 2% by weight.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a polishing composition, a
process for producing a substrate comprising applying the polishing
composition and a process for preventing clogging of a polishing
pad.
[0003] 2. Discussion of the Related Art
[0004] Hard disks have been greatly developed over the years in the
trends of miniaturization and high capacity, so that the trend of
high density has been progressed. Consequently, the minimum
recording area has become smaller, and the floating amount of a
magnetic head has been made increasingly smaller. Therefore, there
have been desired to reduce the surface roughness and the fine
waviness, and to reduce surface defects such as scratches and pits
in a hard disk substrate. With this trend of development, a harder
polishing pad having a smaller pore size has been used in a step of
polishing the substrate. Also, for the same reasons, the average
particle size of the abrasive has become smaller. However, in these
polishing pads, abrasive grain debris and polishing debris are
retained and likely to be adhered to the pad pores, so that
clogging is likely to take place during continuous polishing.
Consequently, the polishing rate is lowered and surface defects
such as pits are generated in the polished substrate, so that
frequent dressing of the polishing pad is necessitated, thereby
lowering the workability of polishing and lowering productivity of
the polished substrate. Therefore, there has been desired a
polishing composition which reduces clogging to the pad pores. As
polishing compositions in which the polishing pad is less likely to
be clogged, a composition comprising a molybdate and a specified
organic acid is disclosed in Japanese Patent Laid-Open No. Hei
7-216345; and a polishing composition comprising water, an alumina
abrasive and a molybdate is disclosed in Japanese Patent Laid-Open
No. Hei 5-311153. However, any of these composition do not
satisfactorily meet the requirements of the reduction in surface
defects and the reduction in clogging.
[0005] An object of the present invention is to provide a polishing
composition in which clogging of a polishing pad is reduced, a
process for producing a substrate comprising polishing a substrate
to be polished using the polishing composition, and a process for
preventing clogging of a polishing pad.
[0006] Another object of the present invention is to provide a
polishing composition by which there are eliminated the problems in
the lowering of the polishing rate when subjected to continuous
polishing due to generation of clogging, and in the prevention of
the generation of surface defects such as pits, whereby lowering
the frequency of the dressing, and thereby improving the
workability and the productivity; a process for producing a
substrate comprising polishing a substrate to be polished with the
polishing composition; and a process for preventing clogging of a
polishing pad comprising applying the above-mentioned polishing
composition.
[0007] These and other objects of the present invention will be
apparent from the following description.
SUMMARY OF THE INVENTION
[0008] According to the present invention, there are provided:
[0009] (1) a polishing composition comprising an abrasive and
water, wherein the polishing composition has an index of degree of
sedimentation of 80 or more and 100 or less;
[0010] (2) a process for producing a substrate comprising polishing
a substrate to be polished using the composition of item (1);
[0011] (3) a process for preventing clogging of a polishing pad
comprising applying the composition of item (1);
[0012] (4) a process for preventing clogging of a polishing pad
comprising applying the composition of item (1), to polishing with
a polishing pad for a nickel-containing object to be polished;
and
[0013] (5) a process for preventing clogging of a polishing pad
comprising applying a composition comprising:
[0014] a hydrophilic polymer having two or more hydrophilic groups
in its molecule and a molecular weight of 300 or more, or a
compound capable of dissolving nickel hydroxide at a pH of 8.0,
and
[0015] water,
[0016] to polishing with a polishing pad for a nickel-containing
object to be polished.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a view showing surface of a polishing pad before
polishing;
[0018] FIG. 2 is a view showing surface of a polishing pad after
20th polishing obtained in Example 1;
[0019] FIG. 3 is a view showing surface of a polishing pad after
20th polishing obtained in Comparative Example 3; and
[0020] FIG. 4 is a graph showing a roll-off in connection with the
detection curve.
DETAILED DESCRIPTION OF THE INVENTION
[0021] The polishing composition of the present invention comprises
an abrasive and water. The polishing composition has an index of
degree of sedimentation of 80 or more and 100 or less, preferably
85 or more and 100 or less, more preferably 90 or more and 100 or
less, from the viewpoint of reducing the clogging of the polishing
pad. One of the great features of the present invention resides in
that the polishing composition has an index of degree of
sedimentation of 80 or more and 100 or less. Since the polishing
composition has such a high index of degree of sedimentation, there
can be exhibited remarkable effects such that the clogging of the
polishing pad can be significantly reduced, so that the stable
production of polished object can be maintained.
[0022] In the present invention, the term "index of degree of
sedimentation" refers to a ratio of a sedimentation volume of a
suspension to an entire volume of a test liquid suspension, wherein
the test liquid suspension is prepared by adding nickel nitrate to
a polishing composition in a given amount, and the index of degree
of sedimentation can be obtained by the method described below. The
index of degree of sedimentation is an index showing the extent of
unlikelihood for the polishing composition of causing clogging in
the polishing pad.
[0023] The index of degree of sedimentation used in the present
invention is an index which is found by noting on the fact that the
suspension in which a given amount of nickel nitrate is added shows
the same level of dispersibility of the suspension as the polishing
liquid during polishing. By using the index, there is an advantage
that the unlikelihood for the polishing composition of causing
clogging can be readily evaluated.
[0024] Incidentally, the index of degree of sedimentation is
studied for conventional polishing compositions. As a result, those
substantially having high indices of degree of sedimentation as in
the present invention have not been found.
[0025] In the present invention, the index of degree of
sedimentation is obtained by the following method.
[0026] A test solution to be used for the determination of the
index of degree of sedimentation can be prepared in accordance with
two cases described below. In a case where a polishing composition
has an abrasive concentration exceeding 4.65% by weight, a
composition having an abrasive concentration of 4.65% by weight is
prepared by adding ion-exchanged water to the polishing
composition, and to the resulting composition is added 0.62 parts
by weight of nickel(II) nitrate hexahydrate (reagent special grade,
purity: 98% or more as determined by quantitative analysis), based
on 100 parts by weight of the composition having an abrasive
concentration of 4.65% by weight. Next, a pH of the mixture is
adjusted to 7.0 with a 25% by weight aqueous ammonia or a 20% by
weight aqueous nitric acid, and ion-exchanged water is added
thereto to give a test solution, so that the test solution has an
abrasive concentration of 4.5% by weight. On the other hand, in the
case where a polishing composition has an abrasive concentration of
less than 4.65% by weight, 0.62 parts by weight of nickel (II)
nitrate hexahydrate, based on 100 parts by weight of the polishing
composition, is added to the polishing composition, and thereafter
a pH of the mixture is adjusted to 7.0 with a 25% by weight aqueous
ammonia and a 20% by weight aqueous nitric acid, to give a test
solution.
[0027] Next, the above-mentioned test solution is thoroughly shaken
until the test solution is suspended. One-hundred milliliters of
the resulting test solution is placed in a glass calorimetric tube
with volume scales (Japanese Industrial Standards, JIS K 0071), and
thoroughly shaken until the test solution is re-suspended (shaking
conditions: inverting the calorimetric tube, and thoroughly shaking
the calorimetric tube in up-and-down movement until no sediments
are recognized at its bottom). Thereafter, the above-mentioned
glass calorimetric tube is allowed to stand at 20.degree. C. for 30
minutes to separate the test solution into two layers, in which an
upper supernatant layer is separated from a lower layer in which
aggregates mainly composed of abrasive grains are suspended or
dispersed. Thereafter, a sedimentation volume (unit: mL) is
obtained from scale reading at an interface of the upper and lower
layers of the test solution. A ratio of the sedimentation volume to
an entire volume of the test solution is calculated therefrom, and
the ratio is defined as the index of degree of sedimentation. When
100 mL of the test solution is used, the volume scale reading per
se, in terms of mL units, of the above-mentioned sedimentation
volume becomes the index of degree of sedimentation.
[0028] The process for elevating the above-mentioned index of
degree of sedimentation cannot be generally limited, because the
process differs depending upon the components of the polishing
composition. The process includes, for instance, 1) a process
comprising lowering a pH of the polishing composition (a process
comprising lowering a pH of the polishing composition to 6 or less,
preferably 3 or so, so that a pH of the mixture after polishing
becomes less than 7.7); 2) a process comprising adding a clogging
preventive described below to the polishing composition; and the
like.
[0029] As the abrasive used in the present invention, any abrasives
generally employed for polishing can be used. Examples of the
abrasive include 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). Concrete examples of the abrasive include .alpha.-alumina
particles, intermediate alumina particles such as .gamma.-alumina
particles, .delta.-alumina particles, .theta.-alumina particles,
.eta.-alumina particles and .kappa.-alumina particles, alumina sol,
silicon carbide particles, diamond particles, magnesium oxide
particles, zinc oxide particles, cerium oxide particles, zirconium
oxide particles, colloidal silica particles, fumed silica
particles, and the like. It is preferable to use these abrasives in
admixture of one or more kinds, from the viewpoint of increasing
the polishing rate. Among them, .alpha.-alumina particles,
intermediate alumina particles, cerium oxide particles, zirconium
oxide particles, colloidal silica particles, fumed silica
particles, and the like are more preferable, and .alpha.-alumina
particles and intermediate alumina particles are especially
preferable. Further, the combination of the .alpha.-alumina
particles and the intermediate alumina particles (especially
.theta.-alumina particles) described below is most preferable, from
the viewpoints of the increase in the polishing speed, prevention
in the surface defects and reduction in the surface roughness. In
accordance with its use, the rough polishing of the Ni--P plated
aluminum alloy substrate is preferably carried out with alumina
particles such as .alpha.-alumina particles and the intermediate
alumina particles, and the finish polishing of the Ni--P plated
aluminum alloy substrate is preferably carried out with silica
particles such as colloidal silica particles and fumed silica
particles. In the polishing of the glassy materials, cerium oxide
particles and alumina particles are preferable. In the polishing of
semiconductor wafers and semiconductor elements, cerium oxide
particles, alumina particles and silica particles are
preferable.
[0030] The average primary particle size of the abrasive is
preferably from 0.01 to 3 .mu.m, more preferably from 0.01 to 1
.mu.m, still more preferably from 0.01 to 0.8 .mu.m, still more
preferably from 0.02 to 0.8 .mu.m, especially preferably from 0.02
to 0.5 .mu.m, most preferably from 0.05 to 0.5 .mu.m, from the
viewpoint of increasing the polishing rate. Further, when the
primary particles are aggregated to form a secondary particle, the
average secondary particle size is preferably from 0.02 to 3 .mu.m,
more preferably from 0.05 to 3 .mu.m, still more preferably from
0.05 to 1.5 .mu.m, still more preferably from 0.1 to 1.5 .mu.m,
especially preferably from 0.1 to 1.2 .mu.m, most preferably from
0.2 to 1.2 .mu.m, from the viewpoint of increasing the polishing
rate in the same manner as above, and from the viewpoint of
reducing the surface roughness of a polished object. Especially
when compared to those having a large particle size, the effect of
the present invention is remarkable when using an abrasive having
an average primary particle size of 1 .mu.m or less, which is
likely to have unstable dispersion.
[0031] The average primary particle size of the abrasive is
obtained by subjecting the abrasive to an image analysis by
observing with a scanning electron microscope (favorably from 3000
to 30000 times) or a transmission electron microscope (favorably
from 10000 to 300000 times), and determining the particle size as a
number-average particle size. In addition, the average secondary
particle size can be determined as volume-average particle size by
using a laser diffraction method.
[0032] The specific gravity of the abrasive is preferably from 2 to
6, more preferably from 2 to 5, from the viewpoints of the
dispersibility, the feed ability to the polishing device and
recovery and reuse.
[0033] The content of the abrasive is preferably from 1 to 40% by
weight, more preferably from 2 to 30% by weight, still more
preferably from 3 to 15% by weight, of the polishing composition,
from the viewpoints of having economic advantages and making the
surface roughness of a polished object small, thereby efficiently
polishing the substrate.
[0034] In addition, it is preferable to add a clogging preventive
for the polishing pad (hereinafter also simply referred to as
"clogging preventive") to the polishing composition of the present
invention, from the viewpoint of facilitating the elevation of the
index of the degree of sedimentation. The clogging preventive
includes a hydrophilic polymer compound, and a compound capable of
dissolving nickel hydroxide at a pH of 8.0 (25.degree. C.).
[0035] The hydrophilic polymer compound used in the present
invention is a hydrophilic polymer having two or more hydrophilic
groups in its molecule, and the hydrophilic groups can be of the
same kind or different kinds. The hydrophilic polymer is a compound
which acts at an interface of a dispersoid (solid substance such as
an abrasive or polishing debris), thereby improving the
dispersibility of the dispersoid in the dispersion medium.
[0036] Among the above-mentioned hydrophilic polymer compounds, a
hydrophilic polymer having two or more hydrophilic groups and
having a molecular weight of 300 or more is preferable, from the
viewpoint of the clogging prevention described below.
[0037] The hydrophilic polymer compound has the number of
hydrophilic groups of preferably two or more, more preferably five
or more, from the viewpoint of the clogging prevention of the
polishing pad. However, the hydrophilic polymer compound has the
number of hydrophilic groups of preferably 10 or more, from the
viewpoint of not causing the polishing pad from being clogged by
the polishing debris (abrasive, debris such as small flakes of the
polished object), namely maintaining the dispersion stability of
the polishing debris by the electrostatic repulsion and steric
repulsion between the surfaces of the polished debris, and the
hydrophilic polymer compound has the number of hydrophilic groups
of preferably 3000 or less, from the viewpoint of preventing
instability due to interactions of the particles (e.g. due to
cross-linking or the like) caused by the hydrophilic polymer and
industrial availability. The hydrophilic polymer compound has the
number of hydrophilic groups of more preferably from 10 to 2000,
still more preferably from 20 to 1500, especially preferably from
20 to 1000.
[0038] In addition, the kinds of the hydrophilic groups are not
particularly limited, and the hydrophilic groups may be of the same
kinds or different kinds. The hydrophilic group includes, for
instance, nonionic groups representatively exemplified by ether
group (oxyethylene group and the like) and hydroxyl group; anionic
groups representatively exemplified by carboxylate groups,
sulfonate groups, sulfuric ester groups, and phosphate groups;
cationic groups representatively exemplified by quaternary ammonium
salts. Among them, ionic hydrophilic groups such as anionic groups
and cationic groups are preferable, from the viewpoint of the
clogging prevention of the polishing pad, and the anionic groups
are more preferable. In addition, it is desired that the
hydrophilic polymer has a weight-average molecular weight of from
300 to 1000000, preferably from 500 to 500000, more preferably from
1000 to 100000, especially preferably from 1000 to 50000, from the
viewpoint of the clogging prevention of the polishing pad, in which
the weight-average molecular weight is calculated as sodium
polystyrenesulfonate as determined by gel permeation
chromatography.
[0039] Concrete examples of the hydrophilic polymer compound used
in the present invention are as follows. Here, those within
quotation marks each indicate trade names.
[0040] Examples of the hydrophilic polymer compound having a
nonionic hydrophilic group include polyethylene oxide adducts added
to both terminals of polypropylene glycol, representatively
exemplified by "Pluronic L44" (commercially available from ASAHI
DENKA KOGYO K. K.), polyvinyl alcohols and derivatives thereof,
polyethylene glycol (meth)acrylate polymers and copolymers thereof,
and the like.
[0041] Examples of the hydrophilic polymer compound having an
anionic hydrophilic group include (meth)acrylic acid (or salt
thereof) polymers and copolymers thereof, representatively
exemplified by polyacrylic acid; maleic acid (or salt thereof)
polymers and copolymers thereof, representatively exemplified by
sodium salts of copolymers of styrene and maleic acid and sodium
salts of copolymers of diisobutylene and maleic acid;
polynaphthalenesulfonic acid (or salt thereof), representatively
exemplified by sodium salt of formalin condensate of
.beta.-naphthalenesulfonic acid; polymelaminesulfonic acids (or
salts thereof); sulfonated styrene (salt thereof) polymers and
copolymers thereof; (meth)acryloyloxyethyl phosphate polymer,
representatively exemplified by copolymers of (meth)acrylic acid
and (meth)acryloyloxyethyl phosphate; sodium alginate;
polysaccharides having an anionic group and derivative thereof,
representatively exemplified by carboxymethyl cellulose.
[0042] The (meth)acrylic acid (salt thereof) polymers and
copolymers thereof include "UC3120" (commercially available from
TOAGOSEI CO., LTD.), "Poise 530" (commercially available from Kao
Corporation), and the like. The polynaphthalenesulfonic acid (or
salt thereof) includes "DEMOL N" (commercially available from Kao
Corporation), "DEMOL AS" (commercially available from Kao
Corporation), and the like. The polymelaminesulfonic acids (or
salts thereof) include "Melflow" (commercially available from
MITSUI CHEMICALS, INC.), and the like.
[0043] Next, examples of the hydrophilic polymer compound having a
cationic hydrophilic group include polymers of quaternary ammonium
monomers, and copolymers thereof, polymers of
(meth)acryloyloxyethyl trimethylammonium chloride and copolymers
thereof, polymers of (trimethylammonium chloride) ethyl
(meth)acrylate and copolymers thereof, and the like.
[0044] The polymers of quaternary ammonium monomers and copolymers
thereof include "Merquat-100" (commercially available from
MATSUMOTO TRADING CO., LTD.), "Merquat-550" (commercially available
from MATSUMOTO TRADING CO., LTD.), and the like.
[0045] Furthermore, examples of the hydrophilic polymer compound in
which two or more hydrophilic polymers are admixed include
hydrophilic monomer-modified polyvinyl alcohols, representatively
exemplified by cationically modified- or carboxylated polyvinyl
alcohols; copolymers of a hydrophilic monomer and (meth)acrylic
acid (or (meth)acrylate), representatively exemplified by
acrylamide/acrylic acid copolymer; copolymers of a hydrophilic
monomer and a quaternary ammonium monomer, representatively
exemplified by acrylic acid/dimethyldiallylammonium chloride
copolymer; and the like. Among them, those having an ionic
hydrophilic group as the hydrophilic group are preferable, and
those having an anionic hydrophilic group are more preferable, from
the viewpoint of the clogging prevention.
[0046] The hydrophilic monomer-modified polyvinyl alcohol includes
"C-506" (commercially available from KURARAY CO., LTD.), "CM-308"
(commercially available from KURARAY CO., LTD.), "KL318"
(commercially available from KURARAY CO., LTD.), "SS2217"
(commercially available from KURARAY CO., LTD.), and the like. The
copolymers of the hydrophilic monomer and (meth)acrylic acid (or
(meth)acrylate) include "Aron A6016" (commercially available from
TOAGOSEI CO., LTD.), "FC-900" (commercially available from NIPPON
SHOKUBAI CO., LTD.), and the like. The copolymer of a hydrophilic
monomer and a quaternary ammonium monomer include "Merquat-280"
(commercially available from MATSUMOTO TRADING CO., LTD.), and the
like.
[0047] Among those having an anionic hydrophilic group, maleic acid
(or maleate) copolymers, representatively exemplified by sodium
salts of copolymers of styrene and maleic acid and sodium salts of
copolymers of diisobutylene and maleic acid;
polynaphthalenesulfonic acid (or polynaphthalenesulfonate),
representatively exemplified by sodium salts of formalin condensate
of .beta.-naphthalenesulfonic acid; sodium alginate;
polysaccharides having an anionic group and derivative thereof,
representatively exemplified by carboxymethyl cellulose are
especially preferable.
[0048] Another preferable clogging preventive is a compound capable
of dissolving nickel hydroxide at a pH of 8.0 (25.degree. C.). This
compound has a property such that its aqueous solution prepared
below clearly has no precipitates of nickel hydroxide or is in a
transparent aqueous solution state without any suspensions as
evaluated by naked eyes at 25.degree. C. immediately after the pH
adjustment to 8.0 described below. The aqueous solution to be
evaluated is prepared by adding 2% by weight of nickel(II) nitrate
hexahydrate (reagent special grade, purity: 98% or more as
determined by quantitative analysis) and 0.4% by weight of the
compound to water, and adjusting its pH with a 25% by weight
aqueous ammonia or a 20% by weight aqueous nitric acid. The
compound mentioned above includes a compound containing carboxyl
group, phosphate group, or the like, preferably a compound
containing carboxyl group. Examples of the compound include citric
acid, .alpha.-amino acids having 2 to 3 carbon atoms, and enolic
organic acids having 3 to 10 carbon atoms. Among them, from the
viewpoint of increase in the dissolution of nickel hydroxide and
from the viewpoint of the clogging prevention, glycine, ascorbic
acid and citric acid are preferable, glycine and citric acid are
more preferable, and citric acid is most preferable.
[0049] In addition, of the above-mentioned clogging preventives,
the acid compounds can be used in the form of salts. The salts of
these acids are not particularly limited. Concretely, there are
included salts with a metal, ammonium, an alkylammonium, an organic
amine, and the like. Concrete examples of the metal include metals
belonging to Group 1A, 1B, 2A, 2B, 3A, 3B, 4A, 6A, 7A or 8 of the
Periodic Table (long period form). Among these metals, from the
viewpoint of reducing the clogging, the metals belonging to Group
1A, 3A, 3B, 7A or 8 of the Periodic Table are preferable, and the
metals belonging to Group 1A, 3A or 3B of the Periodic Table are
more preferable. Sodium and potassium belonging to Group 1A are
most preferable. Concrete examples of the alkylammonium include
tetramethylammonium, tetraethylammonium, tetrapropylammonium,
tetrabutylammonium, and the like. Concrete examples of the organic
amine include dimethylamine, trimethylamine, alkanolamines, and the
like. Among these salts, ammonium salts, sodium salts and potassium
salts are especially preferable.
[0050] The content of the above-mentioned clogging preventive is
preferably 0.0001% by weight or more of the entire amount of the
polishing composition, from the viewpoint of the clogging
prevention and from the viewpoint of polishing performance, and the
content of the clogging preventive is preferably 5% by weight or
less of the entire amount of the polishing composition, from the
viewpoint of economic advantages and from the viewpoint of
improvement in the surface quality of the polished substrate. In
the case where the clogging preventive is a compound capable of
dissolving nickel hydroxide at a pH of 8.0 (25.degree. C.), the
content of the compound is preferably from 0.01 to 5% by weight,
more preferably from 0.01 to 3% by weight, still more preferably
from 0.01 to 1.5% by weight, especially preferably from 0.02 to 1%
by weight, of the entire polishing composition. Alternatively, in
the case where the clogging preventive is a hydrophilic polymer
having two or more hydrophilic groups in its molecule and having a
molecular weight of 300 or more, the content of the hydrophilic
polymer is preferably from 0.0001 to 5% by weight, more preferably
from 0.0005 to 3% by weight, still more preferably from 0.001 to
1.5% by weight, especially preferably from 0.005 to 0.5% by weight,
of the entire polishing composition, from the viewpoint of
increasing the polishing rate. The above-mentioned clogging
preventive can be used alone or in admixture of two or more
kinds.
[0051] In addition, in the polishing composition of the present
invention, other components can be formulated as desired. Other
components include, for instance:
[0052] compound group (A): carboxylic acids having 2 to 20 carbon
atoms and having either OH group or groups or SH group or groups,
monocarboxylic acids having 1 to 20 carbon atoms, dicarboxylic
acids having 2 to 3 carbon atoms, and salts thereof; and
[0053] compound group (B): polycarboxylic acids having 4 or more
carbon atoms and having neither OH group or groups nor SH group or
groups, aminocarboxylic acids, amino acids, and salts thereof.
[0054] Among these compound groups, it is desired that the
polishing composition preferably comprises one or more of the
compounds in the above compound groups, more preferably compounds
from both of the two compound groups. Also, one or more compounds
can be respectively selected from each compound group and added to
the polishing composition.
[0055] The compound group (A) used in the present invention has an
action of reducing edge rounding of end side of a substrate
(roll-off). The compound of the compound group (A) includes one or
more compounds selected from the group consisting of carboxylic
acids having 2 to 20 carbon atoms and having either OH group or
groups or SH group or groups, monocarboxylic acids having 1 to 20
carbon atoms, dicarboxylic acids having 2 to 3 carbon atoms, and
salts thereof.
[0056] The carboxylic acid having 2 to 20 carbon atoms and having
either OH group or groups or SH group or groups includes
oxycarboxylic acids, and compounds in which an oxygen atom of the
OH group of the oxycarboxylic acid is substituted by a sulfur atom.
It is desired that the number of carbon atoms of these carboxylic
acids is from 2 to 20, preferably from 2 to 12, more preferably
from 2 to 8, still more preferably from 2 to 6, from the viewpoint
of the solubility to water. In addition, as oxycarboxylic acids,
those having a hydroxyl group at .alpha.-position of a carboxyl
group are preferable, from the viewpoint of the roll-off reduction.
Also, oxypolycarboxylic acids having two or more carboxyl groups
are preferable.
[0057] It is desired that the number of carbon atoms of the
monocarboxylic acid is from 1 to 20, preferably from 1 to 12, more
preferably from 1 to 8, still more preferably from 1 to 6, from the
viewpoint of the solubility to water.
[0058] The dicarboxylic acid is those having 2 to 3 carbon atoms,
namely oxalic acid and malonic acid, from the viewpoint of the
roll-off reduction. Among these compounds in the compound group
(A), the oxycarboxylic acids are preferable, from the viewpoint of
increasing the polishing rate. In addition, the dicarboxylic acids
are preferable, from the viewpoint of the roll-off reduction.
[0059] Concrete examples of the carboxylic acid having 2 to 20
carbon atoms having either OH group or groups or SH group or groups
include glycolic acid, mercaptosuccinic acid, thioglycolic acid,
lactic acid, .beta.-hydroxypropionic acid, malic acid, tartaric
acid, citric acid, isocitric acid, allocitric acid, gluconic acid,
glyoxylic acid, glyceric acid, ascorbic acid, mandelic acid, tropic
acid, benzilic acid, salicylic acid, and the like. Concrete
examples of the monocarboxylic acid include formic acid, acetic
acid, propionic acid, butyric acid, isobutyric acid, valeric acid,
isovaleric acid, hexanoic acid, heptanoic acid, 2-methylhexanoic
acid, octanoic acid, 2-ethylhexanoic acid, nonanoic acid, decanoic
acid, lauric acid, and the like. Among them, acetic acid, oxalic
acid, malonic acid, glycolic acid, lactic acid, malic acid,
tartaric acid, glyoxylic acid, citric acid and gluconic acid are
preferable; oxalic acid, malonic acid, glycolic acid, lactic acid,
malic acid, tartaric acid, glyoxylic acid, citric acid and gluconic
acid are more preferable. Each of the monocarboxylic acid and the
dicarboxylic acid used in the present invention is selected from
carboxylic acids having neither OH group or groups nor SH group or
groups.
[0060] The salts of these acids are not particularly limited.
Concretely, there are included salts with a metal, ammonium, an
alkylammonium, an organic amine, and the like. Concrete examples of
the metal include metals belonging to Group 1A, 1B, 2A, 2B, 3A, 3B,
4A, 6A, 7A or 8 of the Periodic Table (long period form). Among
these metals, from the viewpoint of the roll-off reduction, those
metals belonging to Group 1A, 3A, 3B, 7A or 8 of the Periodic Table
are preferable, and those metals belonging to Group 1A, 3A or 3B of
the Periodic Table are more preferable. Sodium and potassium
belonging to Group 1A are most preferable.
[0061] Concrete examples of the alkylammonium include
tetramethylammonium, tetraethylammonium, tetrabutylammonium, and
the like.
[0062] Concrete examples of the organic amine include
dimethylamine, trimethylamine, alkanolamines, and the like.
[0063] Among these salts, ammonium salts, sodium salts and
potassium salts are especially preferable.
[0064] These compounds of the compound group (A) can be used alone
or in admixture of two or more kinds.
[0065] The total amount of the compound group (A) is preferably
from 0.01 to 5% by weight, more preferably from 0.015 to 3% by
weight, still more preferably from 0.03 to 2% by weight, of the
polishing composition, from the viewpoint of improvement in
roll-off, and from the viewpoint of economic advantages.
[0066] The compound group (A) also has an action of preventing
clogging of the polishing pad.
[0067] The compound group (B) usable in the present invention has
an action of increasing the polishing rate. The compound group (B)
includes polycarboxylic acids having 4 or more carbon atoms and
having neither OH group or groups nor SH group or groups,
aminocarboxylic acids, amino acids, and salts thereof.
[0068] Among the polycarboxylic acids having 4 or more carbon atoms
and having neither OH group or groups nor SH group or groups, those
having 4 to 20 carbon atoms are preferable, more preferably 4 to 10
carbon atoms, from the viewpoint of increasing the polishing rate.
The polycarboxylic acid has the number of carboxyl groups in one
molecule of from 2 to 10, preferably from 2 to 6, more preferably
from 2 to 4. Also, from the same viewpoint as above, the
aminocarboxylic acids preferably have the number of amino groups in
one molecule of from 1 to 6, more preferably from 1 to 4, and the
number of carboxyl groups in one molecule of preferably from 1 to
12, more preferably 2 to 8, and a number of carbon atoms of
preferably from 1 to 30, more preferably from 1 to 20. From the
same viewpoint as above, the amino acids preferably have a number
of carbon atoms of preferably from 2 to 20, preferably from 2 to
10.
[0069] Concrete examples thereof include succinic acid, maleic
acid, fumaric acid, glutaric acid, citraconic acid, itaconic acid,
tricarballylic acid, adipic acid, propane-1,1,2,3-tetracarboxylic
acid, butane-1,2,3,4-tetracarboxylic acid, diglycolic acid,
nitrilotriacetic acid, ethylenediaminetetraacetic acid (EDTA),
diethylenetriaminepentaacet- ic acid (DTPA),
hydroxyethylethylenediaminetetraacetic acid (HEDTA),
triethylenetetraminehexaacetic acid (TTHA), dicarboxymethylglutamic
acid (GLDA), glycine, alanine, and the like.
[0070] Among them, succinic acid, maleic acid, fumaric acid,
glutaric acid, citraconic acid, itaconic acid, tricarballylic acid,
adipic acid, diglycolic acid, nitrilotriacetic acid,
ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic
acid are preferable, and succinic acid, maleic acid, fumaric acid,
citraconic acid, itaconic acid, tricarballylic acid, diglycolic
acid, ethylenediaminetetraacetic acid and
diethylenetriaminepentaacetic acid are more preferable.
[0071] In addition, the salts of these acids are not particularly
limited. Concretely, there are included salts with a metal,
ammonium, an alkylammonium, an organic amine, and the like.
Concrete examples of the metal include metals belonging to Group
1A, 1B, 2A, 2B, 3A, 3B, 4A, 6A, 7A or 8 of the Periodic Table (long
period form). Among these metals, from the viewpoint of increasing
the polishing rate, the metals belonging to Group 1A, 3A, 3B, 7A or
8 of the Periodic Table are preferable, and the metals belonging to
Group 1A, 3A, 3B or 8 of the Periodic Table are more preferable.
Sodium and potassium belonging to Group 1A, cerium belonging to
Group 3A, aluminum belonging to Group 3B and iron belonging to
Group 8 are most preferable.
[0072] Concrete examples of the alkylammonium include
tetramethylammonium, tetraethylammonium, tetrabutylammonium, and
the like.
[0073] Concrete examples of the organic amine include
dimethylamine, trimethylamine, alkanolamines, and the like.
[0074] Among these salts, ammonium salts, sodium salts, potassium
salts and aluminum salts are especially preferable.
[0075] These compounds of the compound group (B) can be used alone
or in admixture of two or more kinds.
[0076] A total content of the compound group (B) is preferably from
0.01 to 10% by weight, more preferably from 0.02 to 7% by weight,
still more preferably from 0.03 to 5% by weight, of the polishing
composition, from the viewpoint of the effect of accelerating
polishing, the viewpoint of economic advantages, and the viewpoint
of improvement in the surface qualities.
[0077] In addition, the polishing composition of the present
invention may further comprise an intermediate alumina or alumina
sol as a surface roughness-reducing agent. In the present
invention, intermediate alumina is a generic term referring to
alumina particles other than .alpha.-alumina particles, which is
considered as an abrasive component in the present invention.
Concrete examples thereof include .gamma.-alumina particles,
.delta.-alumina particles, .theta.-alumina particles, .eta.-alumina
particles, .kappa.-alumina particles and mixtures thereof. Among
them, the following intermediate aluminas are preferable from the
viewpoints of increasing the polishing rate and reducing surface
roughness. The crystal forms of the intermediate alumina preferably
include .gamma.-alumina, .delta.-alumina, .theta.-alumina,
.eta.-alumina, and mixtures thereof, more preferably
.gamma.-alumina, .delta.-alumina, .theta.-alumina, and mixtures
thereof, especially preferably .gamma.-alumina and .theta.-alumina.
In addition, the intermediate alumina has a specific surface area
(BET method) of preferably from 30 to 300 m.sup.2/g, more
preferably from 50 to 200 m.sup.2/g, and an average particle size
of preferably from 0.01 to 5 .mu.m, more preferably from 0.05 to 5
.mu.m, still more preferably from 0.1 to 3 .mu.m, especially
preferably from 0.1 to 1.5 .mu.m. The average particle size can be
determined as a volume-average particle size by using a laser
diffraction method (for instance, one commercially available form
Horiba, LTD. under the trade name of LA-920). In addition, the
content of each of the alkali metal and the alkaline earth metal in
the intermediate alumina particles is preferably 0.1% by weight or
less, more preferably 0.05% by weight or less, especially
preferably 0.01% by weight or less.
[0078] For instance, in a case where aluminum hydroxide, an alumina
sol or the like which has a relatively large specific surface area
and a low content of the alkali metal and the alkaline earth metal
is used as a raw material, since there is little fusion of the
intermediate alumina produced and the particle strength is small,
no surface defects are caused on a polished substrate, thereby
making it especially effective in reducing the surface roughness of
a polished substrate.
[0079] As the raw material which can be used in the preparation of
the intermediate alumina, there can be used, for instance, aluminum
hydroxide, alumina sols, and the like, which can be represented by
the formulas Al(OH).sub.3, Al.sub.2O.sub.3.3H.sub.2O, AlOOH,
Al.sub.2O.sub.3.H.sub.2O, and Al.sub.2O.sub.3.nH.sub.2O, wherein n
is a number of 1 to 3. The specific surface area of the raw
material is preferably 10 m.sup.2/g or more, more preferably 30
m.sup.2/g or more, especially preferably 50 m.sup.2/g or more. In
addition, the total content of the alkali metal and the alkaline
earth metal in the raw material is preferably 0.1% by weight or
less, more preferably 0.05% by weight or less, especially
preferably 0.03% by weight or less. Further, in a case where an
intermediate alumina is prepared by thermally dehydrating aluminum
hydroxide, a forcible introduction of a dry air or nitrogen gas
during baking is further effective in the reduction of surface
defects and surface roughness of the polished substrate. Here, the
above-mentioned thermal dehydration treatment can be carried out by
a conventional method.
[0080] These intermediate aluminas are adjusted to a given particle
size by wet pulverization or dry pulverization by using a
pulverizer such as a ball-mill, a beads-mill, a high-pressure
homogenizer or a jet mill as occasion demands.
[0081] In addition, the alumina sol refers to those which can be
represented by the formulas AlOOH, AlOOH.nH.sub.2O, wherein n is a
number of 1 to 3, for instance, Al.sub.2O.sub.3.H.sub.2O and the
like. The crystal forms of the alumina sol include boehmite,
pseudo-boehmite and amorphous. The alumina sol can be prepared by
subjecting aluminum hydroxide, for instance, gibbsite, to a
hydrothermal treatment at 250.degree. C. or so, or hydrolyzing an
aluminum alcoholate. The alumina sol has an average particle size
of preferably from 0.01 to 5 .mu.m, more preferably from 0.05 to 5
.mu.m, still more preferably from 0.1 to 3 .mu.m, especially
preferably from 0.1 to 1.5 .mu.m. The average particle size can be
determined as a volume-average particle size by using a laser
diffraction method. The alumina sol has a specific surface area
(BET method) of preferably from 30 to 300 m.sup.2/g, more
preferably from 50 to 200 m.sup.2/g.
[0082] Since the intermediate alumina and the alumina sol are used
together with the compound group (A) and the compound group (B),
the increase in the polishing rate and prevention in surface
defects such as pits can be further accelerated. In this case, the
intermediate alumina and the alumina sol can be used alone or in
admixture. Especially, the intermediate alumina is more preferable,
from the viewpoints of the increase in the polishing rate, the
reduction in the clogging of the polishing pad, the extent of the
effect of preventing surface defects and the like, and the effect
of reducing the surface roughness.
[0083] A total content of the intermediate alumina and the alumina
sol in the polishing composition is preferably from 1 to 100 parts
by weight, more preferably from 2 to 70 parts by weight, still more
preferably from 4 to 40 parts by weight, based on 100 parts by
weight of the abrasive excluding the intermediate alumina and the
alumina sol, from the viewpoints of economic advantages, the effect
of accelerating polishing, the effect of reducing the clogging of
the polishing pad, the effect of reducing the surface roughness of
a polished object, and from the viewpoint of obtaining the
capability of preventing surface defects such as pits.
[0084] Other components include, for instance, inorganic acids and
salts thereof, oxidizing agents, thickeners, anticorrosive agents,
surfactants, and the like. Concrete examples of the inorganic acids
and salts thereof include nitric acid, oxoacid, salts of oxoacid,
sulfuric acid, lithium nitrate, lithium sulfate, sodium nitrate,
sodium sulfate, sodium thiosulfate, sodium chloride, sodium
acetate, potassium nitrate, potassium sulfate, potassium chloride,
magnesium nitrate, magnesium sulfate, magnesium chloride, magnesium
acetate, calcium nitrate, calcium chloride, zinc sulfate, zinc
chloride, zinc acetate, aluminum nitrate, aluminum sulfate,
aluminum phosphate, aluminum chloride, potassium alum, nickel
nitrate, nickel sulfate, nickel formate, nickel acetate, iron
nitrate, sodium nitrite, potassium nitrite, calcium nitrite,
magnesium nitrite, hydrogen peroxide, sodium peroxide, potassium
peroxide, calcium peroxide, barium peroxide, magnesium peroxide,
sodium peroxocarbonate, potassium peroxocarbonate, ammonium
peroxocarbonate, sodium peroxosulfate, potassium peroxosulfate,
ammonum peroxosulfate, sodium peroxophosphate, potassium
peroxophosphate, ammonium peroxophosphate, sodium peroxoborate,
potassium peroxoborate, ammonium peroxoborate, perpropionic acid,
tert-butyl hydroperoxide, performic acid, peracetic acid,
2,4-dinitrophenol, and the like.
[0085] These other components may be used alone or in admixture of
two or more kinds. In addition, the content of the other components
is preferably from 0.05 to 20% by weight, more preferably from 0.05
to 10% by weight, still more preferably from 0.05 to 5% by weight,
of the polishing composition, from the viewpoint of increasing the
polishing rate, from the viewpoint of exhibiting the respective
functions and from the viewpoint of economic advantages.
[0086] In addition, the polishing composition of the present
invention can optionally comprise other component including a
disinfectant and an antibacterial agent, such as
tetramethylammonium chloride, tetraethylammonium chloride,
tetramethylammonium hydroxide, tetraethylammonium hydroxide,
benzalkonium chloride, and benzethonium chloride. The content of
these disinfectants and antibacterial agents is preferably from
0.001 to 0.1% by weight, more preferably from 0.01 to 0.05% by
weight, still more preferably from 0.01 to 0.02% by weight, of the
polishing composition, from the viewpoint of exhibiting the
respective functions and from the viewpoint of not affecting the
polishing performance and substrate properties.
[0087] Water in the polishing composition of the present invention
is used as a medium, and the content of water is preferably from
19.9 to 97.9% by weight, more preferably 40 to 97% by weight, still
more preferably from 60 to 97% by weight, from the viewpoint of
efficiently polishing the object to be polished.
[0088] The concentration of each component of the above-mentioned
polishing composition is a preferable concentration during
polishing, and it may be a concentration during the preparation of
the composition. The composition is usually prepared as a
concentrate, and the concentrate is diluted upon use in many
cases.
[0089] The polishing composition of the present invention can be
prepared by adding an optional component such as a clogging
preventive, the compound group (A) and the compound group (B) as
occasion demands in proper amounts to water and an abrasive
mentioned above, and mixing the components by a known process.
[0090] It is preferable that the pH of the polishing composition is
appropriately adjusted depending upon the kinds and the required
qualities and the like of the substrate to be polished. For
instance, the pH of the polishing composition is preferably from 2
to 12, from the viewpoints of the cleanability of the substrate,
the anti-corrosiveness of the working machine, and the safety of
the operator. In addition, in a case where a substrate to be
polished is a substrate for precision parts which is mainly made of
a metal such as an Ni--P plated aluminum alloy substrate, the pH is
more preferably from 2 to 9, especially preferably from 3 to 8,
from the viewpoints of increasing the polishing rate and improving
the surface qualities. When the polishing composition is used for
polishing a semiconductor wafer, a semiconductor element, or the
like, especially for polishing a silicon substrate, a poly-silicon
film, an SiO.sub.2 film, or the like, the pH is preferably from 7
to 12, more preferably from 8 to 12, especially preferably from 9
to 11, from the viewpoints of increasing the polishing rate and
improving the surface qualities. Also, in a case where a substrate
to be polished is an Ni--P plated aluminum alloy substrate, the pH
is preferably from 2 to 10, more preferably from 2 to 9, still more
preferably from 2 to 8, still more preferably from 2 to 7,
especially preferably from 2 to 5, most preferably from 2 to 4,
from the viewpoint of reducing the clogging of the polishing pad.
The pH can be adjusted by adding properly an inorganic acid such as
nitric acid or sulfuric acid, an organic acid, a metal salt
thereof, or an ammonium salt thereof, or a basic substance such as
aqueous ammonia, sodium hydroxide, potassium hydroxide or amine in
a desired amount as occasion demands. Here, pH is determined at
20.degree. C. with a known pH meter.
[0091] The polishing composition of the present invention having
the above constituents has an effect of reducing clogging of the
polishing pad. Therefore, the clogging of the polishing pad can be
prevented by the use of the polishing composition. Embodiments of
the use of the polishing composition are not particularly limited,
as long as embodiments are based on a known polishing process using
a polishing pad. An example of such embodiments includes a
polishing process of a substrate to be polished described below and
the like.
[0092] The polishing pad used in the present invention may be a
polishing pad used during the polishing of an object to be
polished. The polishing pad includes a polishing pad made of
nonwoven fabric or a porous organic polymer, and a fixed grinding
wheel or a polishing pad in which the grinding wheel is fixed in
the polishing pad, and the like. Especially, the polishing pad made
of nonwoven fabric or a porous organic polymer is preferable.
[0093] The polishing pad is not particularly limited as to its
shape, size and the like. In addition, the materials for the
polishing pad is not particularly limited. The materials for the
polishing pad include organic polymers such as urethane, composites
in which various additives such as carbon or ceria are incorporated
into the organic polymer; and the like.
[0094] In the present invention, the clogging preventing effect of
the polishing pad can be estimated by, for instance, a microscopic
observation of the polishing pad surface after polishing or an
observation with a scanning electron microscope, or by a ratio of
decreasing the polishing rate when an object to be polished is
subjected to continuous polishing.
[0095] In addition, in the polishing process for a substrate for
precision parts, by using the clogging preventive in the present
invention, there are some advantages that the clogging of the
polishing pad can be remarkably lowered, and that the polishing
rate is increased and the roll-off is reduced. The term "roll-off"
as referred to herein means an edge rounding of end side of a
substrate to be polished.
[0096] The process for producing a substrate of the present
invention comprises polishing a substrate to be polished by using
the polishing composition of the present invention, or preparing a
polishing liquid by mixing each component so as to give the
composition of the polishing composition of the present invention.
Especially, the substrate for precision parts can be suitably
produced.
[0097] The material for an object to be polished as
representatively exemplified by the substrate to be polished used
in the present invention includes, for instance, metals or
metalloids such as silicon, aluminum, nickel, tungsten, copper,
tantalum and titanium; alloys made of these metals as main
components; glassy substances such as glass, glassy carbon and
amorphous carbons; ceramic materials such as alumina, silicon
dioxide, silicon nitride, tantalum nitride and titanium nitride;
resins such as polyimide resins; and the like. Among them, it is
preferable that an object to be polished is made of a metal such as
aluminum, nickel, tungsten or copper, or made of an alloy
containing these metals as the main components; or an object to be
polished is a semiconductor substrate made of semiconductor
elements containing these metals. Especially, in a case where the
polishing composition of the present invention is used when
polishing a nickel-containing substrate to be polished such as an
aluminum alloy substrate plated with Ni--P, it is preferable
because the clogging of the polishing pad can be efficiently
reduced. In this case, by properly adding the above-mentioned
clogging preventive, the compound group (A), the compound group
(B), the intermediate alumina or alumina sol to the polishing
composition of the present invention, it is preferable because the
extent of roll-off can be made small, the polishing rate is
increased, and the surface roughness can be reduced without further
causing surface defects.
[0098] Representative nickel-containing substrates to be polished
which are subjects for polishing in the present invention include,
for instance, semiconductor substrates made of a metal nickel, an
alloy containing nickel, a metalloid or an oxide, and semiconductor
elements containing these. Especially, Ni--P plated or Ni--Fe
plated disk substrates are preferable, and the substrate to be
plated includes a metal substrate made of an aluminum alloy or the
like, a ceramic substrate made of glass, carbon or the like, or a
substrate made of a resin, and the like.
[0099] The shape for the substrate to be polished is not
particularly limited. For instance, those having shapes containing
planar portions such as disks, 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 the disk-shaped substrates are especially
preferable in polishing.
[0100] The polishing composition of the present invention can be
favorably used in polishing the substrate for precision parts. For
instance, the polishing composition is suitable for polishing
substrates for precision parts such as substrates for magnetic
recording media such as magnetic disks, optical disks,
opto-magnetic disks, and the like; photomask substrates, optical
lenses, optical mirrors, optical prisms and semiconductive
substrates. The polishing of the semiconductive substrates
comprises the steps of polishing a silicon wafer (bare wafer),
forming separation layer for an embedding element, flattening an
interlayer insulation film, forming an embedded metal line, and
forming embedded capacitor, and the like. The polishing composition
of the present invention is especially suitable for polishing a
magnetic disk substrate.
[0101] The process for producing a substrate of the present
invention includes, for instance, a process for producing a
substrate comprising clamping a substrate with polishing disks to
which a polishing cloth made of nonwoven organic polymer fabric or
the like, is pasted; feeding a polishing composition of the present
invention to a polishing surface; and moving the polishing disks or
the substrate, with applying a given pressure.
[0102] As described above, when the polishing composition of the
present invention is used for polishing a substrate for precision
parts, especially a substrate to be polished made of Ni--P plated
aluminum alloy, clogging of the polishing pad can be remarkably
prevented, and consequently, there can be eliminated the problems
in the lowering of the polishing rate when subjected to continuous
polishing due to generation of clogging, and in the prevention of
the generation of surface defects such as pits, whereby the
frequency of the dressing can be lowered, and the workability and
the productivity can be improved.
[0103] Especially, by properly adding the clogging preventive, the
compounds of the compound group (A) and the compound group (B), the
intermediate alumina or alumina sol mentioned above, and the like
to the polishing composition of the present invention, in addition
to the reduction in the clogging of the polishing pad, the
polishing rate can be increased without causing surface defects on
the surface, so that a high-quality substrate having reduced
surface roughness and further reduced roll-off can be efficiently
produced.
[0104] The polishing composition of the present invention is
especially effective in the polishing method, and the polishing
composition can be similarly applied to polishing steps other than
the polishing method, for instance, lapping method, and the
like.
[0105] The present invention also relates to a process for
preventing clogging of a polishing pad. The process for preventing
clogging of a polishing pad of the present invention includes a
process for preventing clogging of a polishing pad with the
above-mentioned polishing composition of the present invention,
concretely a process comprising applying the polishing composition
of the present invention, to polishing with a polishing pad for a
nickel-containing object to be polished when the nickel-containing
object to be polished.
[0106] Also, the present invention relates to a process for
preventing clogging of a polishing pad comprising applying a
composition not containing an abrasive, to polishing with a
polishing pad for a nickel-containing object to be polished.
Specifically, a process for preventing clogging of a polishing pad
comprises applying a composition comprising:
[0107] a hydrophilic polymer having two or more hydrophilic groups
in its molecule and a molecular weight of 300 or more, or a
compound capable of dissolving nickel hydroxide at a pH of 8.0,
and
[0108] water, to polishing with a polishing pad for a
nickel-containing object to be polished is polished with a
polishing pad.
[0109] By using the process for preventing clogging of a polishing
pad as mentioned above, there can be eliminated the problems in the
lowering of the polishing rate when subjected to continuous
polishing due to generation of clogging, and in the prevention of
the generation of surface defects such as pits, whereby the
dressing frequency of the polishing pad can be lowered, and the
workability and the productivity in polishing can be improved.
[0110] As described above, each requirements for the
nickel-containing object to be polished, the polishing pad, the
polishing process, the hydrophilic polymer or the compound capable
of dissolving nickel hydroxide at a pH of 8.0, the carboxylic
acids, .alpha.-amino acid, and the enolic organic acids may be the
same as those described above.
EXAMPLES
Examples I-1 to I-12 and Comparative Examples I-1 to I-10
[0111] There were mixed together the components shown in Table 1
including, as abrasives, .alpha.-alumina particles having a primary
average particle size of 0.23 .mu.m and a secondary average
particle size of 0.65 .mu.m and .theta.-alumina particles having an
average particle size of 0.20 .mu.m was prepared, and balance
ion-exchanged water (pH being adjusted with aqueous ammonia), to
give 100% by weight of a polishing composition. A mixture prepared
by adding 5-folds amount of ion-exchanged water to this polishing
composition was used for the polishing test.
[0112] Next, the above-mentioned polishing composition was diluted
with ion-exchanged water so that the abrasive concentration was
4.65% by weight, and thereafter 1.0% by weight of nickel(II)
nitrate hexahydrate was added with stirring. Further, pH was
adjusted to 7.0 with a 25% by weight aqueous ammonia, to prepare a
test solution for sedimentation volume. The index of degree of
sedimentation was determined as mentioned above.
[0113] Table 1 and 2 show the index of degree of sedimentation
using the test solution for sedimentation volume and an ability of
preventing clogging of the polishing composition (ratio of the
polishing rate of 20th polishing to the ratio of the first
polishing rate).
[0114] In Examples I-1 to I-12 and Comparative Examples I-1 to
I-10, the polishing rate for the aluminum alloy substrate of the
polishing composition was determined with a double-sided processing
machine under Set Conditions I for Double-Sided Processing Machine
given below.
Set Conditions I for Double-Sided Processing Machine are as
Follows
[0115] Set Conditions I for Double-Sided Processing Machine
[0116] Double-sided processing machine: double-sided processing
machine, Model 9B, manufactured by SPEEDFAM CO., LTD.
[0117] Processing pressure: 9.8 kPa
[0118] Polishing Pad: "DPM2000" (commercially available from Rodel
Nitta K. K.).
[0119] Disc rotational speed: 50 r/min
[0120] Feeding flow rate for a polishing composition: 100
mL/min
[0121] Polishing time period: 5 minutes
[0122] Number of substrate introduced: 10
[0123] The polishing rate is defined as follows. The thickness of
the above-mentioned aluminum alloy substrate is determined by using
a thickness tester (a laser thickness tester, commercially
available from Mitsutoyo Corporation, Model LGH-110/LHC-11N). A
rate of decrease in the thickness was obtained from the changes in
the thicknesses of the aluminum alloy substrate before and after
polishing. This rate of decrease in the thickness is defined as the
polishing rate.
[0124] In addition, a clogging preventing ability is evaluated by
polishing the aluminum alloy substrate continuously for twenty
times without carrying out dressing under the above-mentioned
polishing conditions and estimating the clogging preventing effect
by using the ratio of the polishing rate of 20th polishing to the
ratio of the first polishing rate as a measure for the clogging
preventing ability. Here, the larger the ratio of the polishing
rate of 20th polishing to the ratio of the first polishing rate,
the higher the clogging preventing effect.
1 TABLE 1 Properties Index of Composition of Polishing Composition
(% by weight)* Degree of Clogging Ex. Clogging Compound Compound
Intermediate Sedimen- Preventing No. Abrasive Preventive Group (A)
Group (B) Alumina pH tation Ability I-1 .alpha.-Alumina (16) Citric
acid (0.50) Glycolic acid (0.50) Itaconic acid (0.50)
.theta.-Alumina (4) 3.0 97 0.99 I-2 .alpha.-Alumina (16) Citric
acid (0.50) Glycolic acid (0.50) Maleic acid (1.89) .theta.-Alumina
(4) 3.0 96 0.99 I-3 -- .alpha.-Alumina (16) Glycolic acid (0.50)
Itaconic acid (0.50) .theta.-Alumina (4) 3.0 93 0.98 I-4 --
.alpha.-Alumina (16) Glycolic acid (0.50) Maleic acid (1.89)
.theta.-Alumina (4) 3.0 93 0.97 I-5 .alpha.-Alumina (16) Citric
acid (0.10) Glycolic acid (0.50) Maleic acid (1.89) .theta.-Alumina
(4) 7.0 90 0.97 I-6 .alpha.-Alumina (16) Glycine (0.10) Glycolic
acid (0.50) Maleic acid (1.89) .theta.-Alumina (4) 7.0 87 0.84 I-7
.alpha.-Alumina (16) Sodium salt of a Glycolic acid (0.50) Maleic
acid (1.89) .theta.-Alumina (4) 7.0 83 0.88 copolymer of
diisobutylene and maleic acid.sup.1) (0.10) I-8 .alpha.-Alumina
(16) Sodium salt of formalin Glycolic acid (0.50) Maleic acid
(1.89) .theta.-Alumina (4) 7.0 84 0.85 condensate of
.beta.-naphthalenesulfonic acid.sup.2) (0.10) I-9 .alpha.-Alumina
(16) Alginic acid (0.10) Glycolic acid (0.50) Maleic acid (1.89)
.theta.-Alumina (4) 7.0 82 0.82 I-10 .alpha.-Alumina (20) Citric
acid (0.10) Glycolic acid (0.50) Maleic acid (1.89) -- 7.0 84 0.85
I-11 .alpha.-Alumina (20) Citric acid (0.10) Glycolic acid (0.50)
-- -- 7.0 83 0.84 I-12 .alpha.-Alumina (16) Citric acid (0.10)
Glycolic acid (0.50) Maleic acid (1.89) .theta.-Alumina (4) 5.0 93
0.98 *Balance being ion-exchanged water. .sup.1)Molar ratio of
diisobutylene/maleic acid: 1/1 (weight-average molecular weight:
4000) .sup.2)Weight-average molecular weight: 4000
[0125]
2 TABLE 2 Properties Index of Comp Composition of Polishing
Composition (% by weight)* Degree of Clogging Ex. Clogging Compound
Compound Intermediate Sedimen- Preventing No. Abrasive Preventive
Group (A) Group (B) Alumina pH tation Ability I-1 .alpha.-Alumina
(16) -- Glycolic acid (0.50) Maleic acid (1.89) .theta.-Alumina (4)
7.0 72 0.60 I-2 .alpha.-Alumina (16) -- Malic acid (0.10) Maleic
acid (1.89) .theta.-Alumina (4) 7.0 75 0.65 Glycolic acid (0.50)
I-3 .alpha.-Alumina (16) Ammonium Glycolic acid (0.50) Maleic acid
(1.89) .theta.-Alumina (4) 3.0 60 0.58 molybdate (0.10) I-4
.alpha.-Alumina (20) -- Glycolic acid (0.50) Maleic acid (1.89) --
7.0 68 0.60 I-5 .alpha.-Alumina (20) -- Glycolic acid (0.50) -- --
7.0 70 0.60 I-6 .alpha.-Alumina (20) -- -- Maleic acid (1.89) --
7.0 59 0.56 I-7 .alpha.-Alumina (20) -- Malic acid (1.89) -- -- 7.0
79 0.77 I-8 .alpha.-Alumina (40) Ammonium Malic acid (10.0) -- --
3.0 60 0.50 molybdate (10.0) I-9 .alpha.-Alumina (20) -- -- -- --
7.0 39 0.30 I-10 .alpha.-Alumina (40) Ammonium Citric acid (10.0)
-- -- 2.0 72 0.68 molybdate (10.0) *Balance being ion-exchanged
water.
[0126] It can be seen from the results of Tables 1 and 2 that the
polishing compositions of Examples I-1 to I-12 having an index of
degree of sedimentation of 80 or more and 100 or less all show
improvements in the clogging preventing ability, as compared to the
polishing compositions obtained in Comparative Examples I-1 to
I-10.
Examples II-1 to II-9 and Comparative Examples II-1 to II-6
[0127] There were mixed together 7 parts by weight of an abrasive
[.alpha.-alumina (purity: about 99.9%) having primary average
particle size: 0.23 .mu.m, and secondary average particle size:
0.53 .mu.m], a given amount of a clogging preventive used in
Examples or a compound used in Comparative Examples as listed in
Table 3, and balance ion-exchanged water, with stirring. Here, the
pH of each composition was adjusted to that shown in Table 3 with
an aqueous ammonia or with nitric acid, and water was added thereto
to give 100 parts by weight of each polishing composition.
[0128] Using each of the resulting polishing compositions, a
substrate surface made of an Ni--P plated aluminum alloy, the
substrate surface having Ra (an average deviation, of all points
from plane fit to test part surface) of 0.2 .mu.m, as determined by
Talystep commercially available from Rank Taylor-Hobson Limited
(size of tip end of profilometer: 25 .mu.m.times.25 .mu.m, by-pass
filter: 80 .mu.m, measurement length: 0.64 mm), a thickness of 0.8
mm and a diameter of 3.5 in was polished with a double-sided
processing machine under Set Conditions II for Double-Sided
Processing Machine given below, to give a polished Ni--P plated,
aluminum alloy substrate usable for magnetic recording media.
Set Conditions II for Double-Sided Processing Machine are as
Follows
[0129] Set Conditions II for Double-Sided Processing Machine
[0130] Double-sided processing machine: double-sided processing
machine, Model 9B, manufactured by SPEEDFAM CO., LTD.
[0131] Processing pressure: 9.8 kPa
[0132] Polishing Pad: "Bellatrix N0058" (manufactured by Kanebo,
LTD.).
[0133] Disc rotational speed: 50 r/min
[0134] Feeding flow rate for a polishing composition: 100
ml/min
[0135] Polishing time period: 5 minutes
[0136] Number of substrate introduced: 10
[0137] After polishing, the thickness of the aluminum alloy
substrate of Examples was determined by using a thickness tester (a
laser thickness tester, commercially available from Mitsutoyo
Corporation, Model LGH-110/LHC-11N). A rate of decrease in the
thickness was obtained from the changes in the thickness of the
aluminum alloy substrate before and after polishing, and expressed
as a relative value (relative polishing rate) on the basis of the
polishing rate of Comparative Example II-1.
[0138] In addition, a clogging preventing ability is evaluated by
polishing the aluminum alloy substrate continuously for twenty
times without carrying out dressing under the above-mentioned
polishing conditions and estimating the clogging preventing effect
by using the ratio of the polishing rate of 20th polishing to the
ratio of the first polishing rate as a measure for the clogging
preventing ability. Here, the larger the ratio of the polishing
rate of 20th polishing to the ratio of the first polishing rate,
the higher the clogging preventing effect.
[0139] In addition, the surface defects (pits) on each polished
substrate after 20th polishing under the above polishing conditions
were evaluated in accordance with the following methods.
[0140] [Determinations of Pits]
[0141] The surface of each substrate was observed with an optical
microscope (differential interference microscope) at a
magnification of 200 times at an interval of 30.degree. for 12
locations, and the number of pits in the 12 locations was counted
and evaluated as follows:
[0142] [Evaluation of Pits]
[0143] .circleincircle.: the number of pits being less than 2;
[0144] .largecircle.: the number of pits being 2 or 3;
[0145] .DELTA.: the number of pits being 4 to 9; and
[0146] x: the number of pits being 10 or more
[0147] The results for the polishing rate, the clogging preventing
ability and the surface defects mentioned above are shown in Table
4.
3 TABLE 3 Clogging Preventive Other Components Amount Amount (% by
(% by Compound weight) Compound weight) pH Ex. No. II-1 Citric acid
0.1 Itaconic acid 0.5 2.5 .theta.-Alumina.sup.1) 1.0 II-2 Citric
acid 1.5 Itaconic acid 0.5 2.5 .theta.-Alumina.sup.1) 1.0 II-3
Citric acid 0.1 -- -- 3 II-4 Citric acid 0.1 -- -- 4 II-5 Citric
acid 0.1 -- -- 7 II-6 Citric acid 0.3 -- -- 2.5 II-7 Citric acid
0.05 -- -- 3 II-8 Glycine 0.1 Itaconic acid 0.5 2.5
.theta.-Alumina.sup.1) 1.0 II-9 Ascorbic acid 0.1 Itaconic acid 0.5
2.5 .theta.-Alumina.sup.1) 1.0 Comp. Ex. No. II-1 Not added -- Not
added -- 7 II-2 Not added -- Succinic acid 0.5 2.5 II-3 Not added
-- Itaconic acid 0.5 2.5 .theta.-Alumina.sup.1) 1.0 II-4 Citric
acid 2.5 Itaconic acid 0.5 2.5 .theta.-Alumina.sup.1) 1.0 II-5
Ammonium molybdate 2.0 -- -- 2.5 Citric acid 2.0 Alumina sol.sup.2)
1.0 II-6 Ammonium molybdate 2.0 -- -- 2.5 Glycolic acid 2.0 Alumina
sol.sup.2) 1.0 .sup.1).theta.-Alumina: average particle size: 0.23
.mu.m, specific surface area: 80 m.sup.2/g .sup.2)Alumina sol:
commercially available from Nissan Chemical Industries, Ltd. under
the trade name of Alumina Sol-200
[0148]
4 TABLE 4 Polishing Clogging Rate Surface Preventing (Relative
Defects Ability Value) (Pits) Ex. No. II-1 0.95 2.4
.circleincircle. II-2 0.96 2.3 .largecircle. II-3 0.94 1.5
.circleincircle. II-4 0.93 1.3 .circleincircle. II-5 0.92 1.3
.circleincircle. II-6 0.96 1.8 .circleincircle. II-7 0.89 1.2
.circleincircle. II-8 0.88 2.1 .circleincircle. II-9 0.89 2.0
.circleincircle. Comp. Ex. No. II-1 0.53 1.0 X II-2 0.62 2.4
.DELTA. II-3 0.60 2.1 .DELTA. II-4 0.93 2.1 X II-5 0.92 1.8 X II-6
0.75 1.8 X
[0149] It can be seen from the results of Table 4 that the
polishing compositions obtained in each of Examples II-1 to II-9
all show remarkable improvements in the clogging preventing
ability, higher polishing rates, and less generation of surface
defects such as pits, as compared to those compositions obtained in
Comparative Examples II-1 to II-6.
[0150] In addition, as compared to the surface of the polishing pad
before polishing (shown in FIG. 1), only little polishing debris
were adhered to the pores of the polishing pad on the surface of
the polishing pad after 20th polishing obtained in Example II-1
(shown in FIG. 2). On the other hand, polishing debris were adhered
to a majority of the pores of the polishing pad on the surface of
the polishing pad after 20th polishing obtained in Comparative
Example II-3 (shown in FIG. 3). Therefore, when the polishing
composition obtained in Example II-1 was used, the frequency of
dressing of the polishing pad could be remarkably reduced as
compared to that of Comparative Example II-3. The surfaces of the
polishing pads shown in each of FIGS. 1 to 3 were observed using an
electron microscope commercially available from Hitachi, Ltd. under
the trade name of Field-Effect Scanning Electron Microscope
(FE-SEM), Model S-4000 with a magnification of 60 times.
Examples III-1 to III-16 and Comparative Examples III-1 to
III-7
[0151] Formulation Method 1
[0152] There were mixed together 7 parts by weight of an abrasive
[.alpha.-alumina (purity: about 99.9%) having primary average
particle size: 0.23 .mu.m, and secondary average particle size:
0.53 .mu.m], a given amount of a compound formulated for preventing
clogging as listed in Table 5, and balance ion-exchanged water,
with stirring. Here, the pH of each composition was adjusted to
that shown in Table 5 with an aqueous ammonia or with nitric acid,
and ion-exchanged water was added thereto to give 100 parts by
weight of each composition.
[0153] Formulation Method 2
[0154] There were mixed together 7 parts by weight of an abrasive
[.alpha.-alumina (purity: about 99.9%) having primary average
particle size: 0.23 .mu.m, and secondary average particle size:
0.53 .mu.m], 1 part by weight of an intermediate alumina
(.theta.-alumina, average particle size: 0.2 .mu.m, specific
surface area; 150 m.sup.2/g, purity: about 99.9%) serving both as a
surface roughness-reducing agent and a polishing rate-increasing
agent, 0.7 parts by weight of fumaric acid as a polishing
rate-increasing agent, 0.3 parts by weight of glycolic acid as a
roll-off reducing agent, a given amount of a compound formulated
for preventing clogging as listed in Table 6, and balance
ion-exchanged water, with stirring. Here, the pH of each
composition was adjusted to that shown in Table 6 with an aqueous
ammonia or with nitric acid, and ion-exchanged water was added
thereto to give 100 parts by weight of each composition.
[0155] Formulation Method 3
[0156] There were mixed together 7 parts by weight of an abrasive
[.alpha.-alumina (purity: about 99.9%) having primary average
particle size: 0.23 .mu.m, and secondary average particle size:
0.53 .mu.m], 1 part by weight of an intermediate alumina
(.theta.-alumina, average particle size: 0.2 .mu.m, specific
surface area; 150 m.sup.2/g, purity: about 99.9%) serving both as a
surface roughness-reducing agent and a polishing rate-increasing
agent, 1 part by weight of itaconic acid as a polishing
rate-increasing agent, 0.2 parts by weight of citric acid as a
roll-off reducing agent, a given amount of a compound formulated
for preventing clogging of the polishing pad as listed in Table 6,
and balance ion-exchanged water, with stirring. Here, the pH of
each composition was adjusted to that shown in Table 6 with an
aqueous ammonia or with nitric acid, and ion-exchanged water was
added thereto to give 100 parts by weight of each composition.
[0157] Using each of the compositions obtained by Formulation
Methods 1 to 3, a substrate surface made of an Ni--P plated
aluminum alloy, the substrate surface having an average deviation,
of all points from plane fit to test part surface Ra of 0.2 .mu.m,
as determined with Talystep commercially available from Rank
Taylor-Hobson Limited (size of tip end of profilometer: 25
.mu.m.times.25 .mu.m; by-pass filter: 80 .mu.m; measurement length:
0.64 mm), a thickness of 0.8 mm and a diameter of 3.5 in (8.89 cm)
was polished with a double-sided processing machine under the
following Set Conditions III for Double-Sided Processing Machine,
to give a polished Ni--P plated, aluminum alloy substrate usable
for magnetic recording media.
Set Conditions III for Double-Sided Processing Machine are as
Follows
[0158] Set Conditions III for Double-Sided Processing Machine
[0159] Double-sided processing machine: double-sided processing
machine, Model 9B, manufactured by SPEEDFAM CO., LTD.
[0160] Processing pressure: 9.8 kPa
[0161] Polishing Pad: "DPM2000" (manufactured by Rodel Nitta K.
K.).
[0162] Disc rotational speed: 50 r/min
[0163] Feeding flow rate for a polishing composition: 100
ml/min
[0164] Polishing time period: 5 minutes
[0165] Number of substrate introduced: 10
[0166] [Polishing Rate]
[0167] The thickness of the aluminum alloy substrate used above was
determined by using a thickness tester (a laser thickness tester,
commercially available from Mitsutoyo Corporation, Model
LGH-110/LHC-11N). A rate of decrease in the thickness was obtained
from the changes in the thickness of the aluminum alloy substrate
before and after polishing, and expressed as a relative value
(relative polishing rate) of the 1st polishing rate of each
Examples III-1 to III-16 and Comparative Examples III-2 to III-7 on
the basis of the 1st polishing rate of Comparative Example
III-1.
[0168] [Clogging Preventing Ability]
[0169] The aluminum alloy substrate was polished continuously for
twenty times without carrying out dressing under the
above-mentioned polishing conditions, and the clogging preventing
effect is estimated by using the ratio of the polishing rate of
20th polishing to the first polishing rate as a measure for the
clogging preventing ability. Here, the larger the ratio of the
polishing rate of 20th polishing to the first polishing rate, the
higher the clogging preventing effect.
[0170] [Surface Roughness]
[0171] The average deviation, of all points from plane fit to test
part surface Ra as determined using Talystep commercially available
from Rank Taylor-Hobson Limited having the following features:
[0172] Size of tip end of profilometer: 25 .mu.m.times.25 .mu.m
[0173] By-pass filter: 80 .mu.m
[0174] Measurement length: 0.64 mm
[0175] was defined as surface roughness.
[0176] The relative value of the first surface roughness of each of
Examples III-1 to III-16 and Comparative Examples III-1 to III-5
and III-7 on the basis of the first surface roughness of
Comparative Example III-6 was obtained.
[0177] [Roll Off]
[0178] The roll off was determined using a device commercially
available from Mitsutoyo Corporation under the trade name of "Form
Tracer SV-C624" under the following conditions:
[0179] Tip end radius of profilometer: 2 .mu.m (Code No.
178-381)
[0180] Pressure at profilometer: 0.7 mN or less
[0181] Speed: 0.2 mm/s
[0182] Analyzing software: SV-600 Fine Profile Analysis System,
Version 1.01
[0183] Filter: LPF (Gaussian) 0.800 mm
[0184] Using the device as specified above, the shape of the end
part of the disc at 42.5 mm to 47.5 mm away from the center of the
disc was determined, and D was obtained by taking points A, B and C
at 43 mm away from the center of the disc, at 47 mm away from the
center, and at 45 mm away from the center, respectively, as shown
in FIG. 4, by using an analyzing software in accordance with the
above determination method. The value obtained by dividing D by 1/2
the amount of change of thickness of the disc before and after
polishing is defined as the roll-off value.
[0185] The relative value for first roll off (relative roll off)
for each of Examples and Comparative Examples was determined on the
basis of the first roll off of Comparative Example III-6.
[0186] The polishing results when using the polishing compositions
obtained by the above-mentioned formulation method 1 (Examples
III-1 to III-10 and Comparative Examples III-1 to III-3) are shown
in Table 5. Also, the compositions and the polishing results when
using the polishing compositions obtained by the above-mentioned
formulation methods 2 and 3 (Examples III-11to III-16 and
Comparative Examples III-4 to III-7) are shown in Table 6.
5 TABLE 5 Polishing Compound Amount Clogging Rate Formulated for
(parts by Preventing (Relative Preventing Clogging weight) pH
Ability Value) Ex. No. III-1 Sodium salt of 0.005 7 0.90 1.1
copolymer of diisobutylene and maleic acid.sup.1) III-2 Sodium salt
of 0.2 9 0.92 1.2 copolymer of diisobutylene and maleic acid.sup.1)
III-3 Sodium salt of 0.01 5 0.88 1.1 copolymer of diisobutylene and
maleic acid.sup.1) III-4 Formalin condensate 0.2 3 0.75 1.0 of
sodium naphthalenesulfonate.sup.2) III-6 Sodium salt of 0.01 6 0.80
1.1 copolymer of vinyl acetate and maleic acid.sup.3) III-7 Aron
UC-3120 0.1 7 0.85 1.0 III-8 Aron A-6016 0.05 7 0.89 1.1 III-9
Sodium alginate 0.05 7 0.85 1.2 III-10 Catinal LC-200 0.01 7 0.77
1.0 Comp. Ex. No. III-1 Not Added -- 7 0.53 1.0 III-2 Sodium
alkylbenzene- 0.1 6 0.58 0.9 sulfonate III-3 Sodium laurate 0.05 9
0.58 0.8 Notes) Aron UC-3120: commercially available from TOAGOSEI
CO., LTD., polyacrylic acid-type polymer surfactant Aron A6016:
commercially available from TOAGOSEI CO., LTD., sulfonic
acid-modified polyacrylic acid-type polymer surfactant Catinal
LC-200: commercially available from Toho Kagaku K.K., cationized
cellulose-type polymer surfactant .sup.1)Diisobutylene/maleic acid
= 1/1 molar ratio (weight average molecular weight: 10000)
.sup.2)Weight-average molecular weight: 5000 .sup.3)Vinyl
acetate/maleic acid = 1/1 molar ratio (weight-average molecular
weight: 8000
[0187] It can be seen from the results of Table 5 that the
polishing compositions obtained in Examples III-1 to III-10 all
show remarkable improvements in the clogging preventing ability, as
compared to those compositions obtained in Comparative Examples
III-1 to III-3.
6 TABLE 6 Polishing Surface Amount Clogging Rate Roughness Roll Off
Formulation Compound to be formulated for (parts by Preventing
(Relative (Relative (Relative Method preventing clogging weight) pH
Ability Value) Value) Value) Ex. No. III-11 2 Sodium salt of
copolymer of 0.005 7 0.91 1.5 0.68 1.0 diisobutylene and maleic
acid.sup.1) III-12 2 Formalin condensate of 0.1 7 0.85 1.5 0.75 1.1
sodium naphthalenesulfonate.sup.2) III-13 2 Sodium salt of
copolymer of 0.05 7 0.88 1.4 0.71 1.1 vinyl acetate and maleic
acid.sup.3) III-14 3 Sodium salt of copolymer of 0.01 6 0.93 1.5
0.71 1.1 diisobutylene and maleic acid.sup.1) III-15 3 Aron UC-3120
0.05 6 0.78 1.4 0.69 1.2 III-16 3 Sodium alginate 0.01 6 0.82 1.4
0.67 1.1 Comp. Ex. No. III-1 1 Not added -- 7 0.53 1.0 1 Undeter-
minable III-4 2 Not added -- 7 0.48 1.5 0.70 1 III-5 2 Sodium
alkylbenzenesulfonate 0.01 7 0.52 1.3 -- -- III-6 3 Not added -- 6
0.50 1.4 0.67 1.1 III-7 3 Sodium laurate 0.05 6 0.55 1.3 -- --
[0188] It can be seen from the results of Table 6 that the
polishing compositions obtained in Examples III-11 to III-16 all
show remarkable improvements in the clogging preventing ability, as
compared to those compositions obtained in Comparative Examples
III-1, III-4 to III-7. Also, the polishing compositions of Examples
III-11 to III-16 containing a clogging preventive maintain the same
level of the surface roughness and the roll off as those of
Comparative Examples III-4 and III-6 in which the clogging
preventive was not added.
[0189] The polishing composition of the present invention has an
excellent clogging preventing effect. Therefore, when the polishing
composition is used for polishing a substrate for precision parts,
particularly a substrate made of an Ni--P plated aluminum alloy,
there can be exhibited such effects that the problems in lowered
polishing rate during continuous polishing generated by clogging of
the polishing pad, and in prevention of generation of surface
defects such as pits are eliminated, that the frequency of dressing
of the polishing pad is reduced, and that the workability of the
polishing and the productivity of the substrate can be
improved.
EQUIVALENTS
[0190] 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.
* * * * *