U.S. patent application number 17/096358 was filed with the patent office on 2021-05-20 for polishing composition, polishing method, and method for manufacturing substrate.
The applicant listed for this patent is FUJIMI INCORPORATED. Invention is credited to Jingzhi CHEN.
Application Number | 20210147714 17/096358 |
Document ID | / |
Family ID | 1000005385641 |
Filed Date | 2021-05-20 |
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United States Patent
Application |
20210147714 |
Kind Code |
A1 |
CHEN; Jingzhi |
May 20, 2021 |
POLISHING COMPOSITION, POLISHING METHOD, AND METHOD FOR
MANUFACTURING SUBSTRATE
Abstract
Provided are a polishing composition, a polishing method, and a
method for manufacturing a substrate. The polishing composition
contains polishing abrasive grains, an additive molecule, a pH
adjusting agent, and a dispersing medium. The polishing abrasive
grains contain silica particles, and the silanol group density on
the surface of the silica particles is 0 to 3.0 groups/nm.sup.2.
The silanol group density is calculated and determined based on the
specific surface area measured by the BET method and the amount of
silanol groups measured by titration. The pH adjusting agent is
used to adjust the pH of the polishing composition to a range of
1.5 or more and 4.5 or less. The additive molecule has a structure
represented by Formula (I). ##STR00001## (In Formula (I), R.sup.1,
R.sup.2, n, m, p, q, and r are as defined in the
specification.)
Inventors: |
CHEN; Jingzhi; (Taiwan,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FUJIMI INCORPORATED |
Aichi |
|
JP |
|
|
Family ID: |
1000005385641 |
Appl. No.: |
17/096358 |
Filed: |
November 12, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 21/3212 20130101;
C09G 1/02 20130101 |
International
Class: |
C09G 1/02 20060101
C09G001/02; H01L 21/321 20060101 H01L021/321 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 20, 2019 |
JP |
2019-209538 |
Claims
1. A polishing composition comprising: polishing abrasive grains
containing silica particles, a silanol group density on a surface
of the silica particles being 0 to 3.0 groups/nm.sup.2, the silanol
group density being calculated and determined based on a specific
surface area measured by a BET method and an amount of silanol
groups measured by titration; an additive molecule having a
structure represented by Formula (I): ##STR00005## wherein in
Formula (I), R.sup.1 and R.sup.2 are each independently H, a
C.sub.1 to C.sub.18 linear alkyl group, a C.sub.3 to C.sub.18
branched alkyl group, or a C.sub.2 to C.sub.18 linear alkenyl
group; n is an integer 2 to 40; and m, p, and q are each
independently 0 or 1, r is an integer 0 to 2, R.sup.1 is a C.sub.1
to C.sub.18 linear alkyl group, a C.sub.3 to C.sub.18 branched
alkyl group, or a C.sub.2 to C.sub.18 linear alkenyl group when m
is 1, and R.sup.2 is a C.sub.1 to C.sub.18 linear alkyl group, a
C.sub.3 to C.sub.18 branched alkyl group, or a C.sub.2 to C.sub.18
linear alkenyl group when p is 1; a pH adjusting agent used to
adjust a pH of the polishing composition to a range of 1.5 or more
and 4.5 or less; and a dispersing medium.
2. The polishing composition according to claim 1, wherein a
content of the additive molecule is 50 to 10,000 ppm by weight with
respect to a total weight of the polishing composition.
3. The polishing composition according to claim 1, wherein a weight
average molecular weight of the additive molecule is 100 to
10000.
4. The polishing composition according to claim 1, wherein in
Formula (I), R.sup.1 is H and R.sup.2 is a C.sub.1 to C.sub.18
linear alkyl group, a C.sub.3 to C.sub.18 branched alkyl group, or
a C.sub.2 to C.sub.18 linear alkenyl group; n is an integer 2 to
20; and m, p, q, and r are all 0.
5. The polishing composition according to claim 1, wherein in
Formula (I), R.sup.1 and R.sup.2 are both H; n is an integer 2 to
40; and m and p are both 0 and q and r are both 1.
6. The polishing composition according to claim 1, wherein in
Formula (I), R.sup.1 is a C.sub.1 to C.sub.18 linear alkyl group, a
C.sub.3 to C.sub.18 branched alkyl group, or a C.sub.2 to C.sub.28
linear alkenyl group and R.sup.2 is H; n is an integer 2 to 20; and
m and p are both 0 and q and r are both 1.
7. The polishing composition according to claim 1, wherein in
Formula (I), R.sup.1 is a C.sub.2 to C.sub.18 linear alkyl group, a
C.sub.3 to C.sub.18 branched alkyl group, or a C.sub.2 to C.sub.28
linear alkenyl group and R.sup.2 is H; n is an integer 2 to 20; and
m, q, and r are all 1 and p is 0.
8. The polishing composition according to claim 1, wherein in
Formula (I), R.sup.1 and R.sup.2 are both H; n is an integer 2 to
20; and m, p, and q are all 0 and r is 2.
9. The polishing composition according to claim 1, wherein a
content of the polishing abrasive grains is 0.1% to 10% by weight
with respect to a total weight of the polishing composition.
10. A polishing method comprising: polishing an object to be
polished using the polishing composition according to any one of
claims 1 to 9, wherein a material for the object to be polished
includes an oxide and a silicon-containing material, and the
silicon-containing material is represented by Si.sub.xGe.sub.1-x
where x=0.1 to 1.
11. The polishing method according to claim 10, wherein a removal
rate of the polishing composition with respect to the oxide is a
first removal rate R1 and a removal rate of the polishing
composition with respect to the silicon-containing material is a
second removal rate R2 when a polishing pressure is 1.0 psi, and a
ratio value R1/R2 of the first removal rate to the second removal
rate is 10 or more.
12. A method for manufacturing a substrate, the method comprising:
preparing a substrate, a surface of the substrate containing an
oxide and a silicon-containing material, the silicon-containing
material being represented by Si.sub.xGe.sub.1-x where x=0.1 to 1;
and polishing the substrate using the polishing composition
according to any one of claims 1 to 9.
Description
CROSS-REFERENCE TO RELATED APPLICATION
BACKGROUND
1. Technical Field
[0001] The present invention relates to a polishing composition, a
polishing method using this polishing composition, and a method for
manufacturing a substrate.
2. Description of Related Arts
[0002] In the semiconductor industry, planarization technologies to
improve the flatness of the surface of semiconductor substrates
(for example, wafers) are typically used. Chemical mechanical
polishing (CMP) is one of the planarization technologies commonly
used. The chemical mechanical polishing technique includes a method
in which the surface of an object to be polished (workpiece) such
as a semiconductor substrate is flattened using a polishing
composition containing abrasive grains such as silica, alumina, or
ceria, an anticorrosive, a surfactant and the like.
[0003] Furthermore, substrates formed of semiconductor materials
such as silicon or silicon-germanium (sometimes abbreviated as
"silicon-containing materials" in the present specification) have
already been widespread. Accordingly, the need for a polishing
composition applied to polish a substrate containing a
silicon-containing material has also gradually increased.
[0004] Taiwan Patent Application Publication No. 201311842 A1No.
201311842 discloses a chemical mechanical polishing composition
containing (A) inorganic particles, organic particles, or a mixture
or composite thereof, (B) at least one kind of oxidizing agent, and
(C) an aqueous medium. The chemical mechanical polishing
composition of Taiwan Patent Application No. 201311842 A1 can be
applied to perform chemical mechanical polishing on elemental
germanium or silicon-germanium.
SUMMARY
[0005] The demand for chemical mechanical polishing process has
been more and more severe in association with the miniaturization
of semiconductor devices. For example, in semiconductor devices,
semiconductor elements are usually separated from each other using
a shallow trench isolation (STI) structure formed of an oxide (for
example, silicon oxide). In the shallow trench isolation step,
excess oxide materials formed on the substrate can be removed by
performing chemical mechanical polishing. In order to stop chemical
mechanical polishing, it is common to form a polishing stop layer
having a relatively low polishing speed between the oxide layer and
the substrate. In addition, in order to accurately stop chemical
mechanical polishing at a desired position, it is necessary to
increase the polishing selectivity of the oxide layer to the
polishing stop layer. Materials often used in the polishing stop
layer may include nitrides, carbides, carbonitrides and the like,
for example, silicon nitride.
[0006] When forming an oxide layer on a substrate formed of a
silicon-containing material (for example, a silicon-germanium
substrate or a silicon substrate), a further polishing stop layer
(for example, a silicon nitride layer) may not be formed if the
polishing selectivity of the oxide to the substrate material can be
increased. In this case, the complexity of process can be
simplified and the time and cost required for production can be
decreased. In addition, if the polishing speed (in the present
specification, "polishing speed" may be referred to as "removal
rate") of the oxide can be increased, the time required for the
polishing step can be significantly shortened and eventually the
production efficiency of product increases.
[0007] However, in the existing polishing compositions, it is still
difficult to increase the polishing selectivity (in the present
specification, "polishing selectivity" may be referred to as
"polishing speed ratio" or a "removal rate ratio") of oxides to
silicon-containing materials (for example, silicon-germanium or
silicon) to a sufficient degree. In other words, it is still
difficult to use silicon-germanium or silicon as a polishing stop
layer when performing chemical mechanical polishing on oxides.
[0008] The present invention has been completed in view of the
actual circumstances described above, and an object thereof is to
provide a polishing composition capable of increasing the polishing
speed ratio of an oxide to silicon-germanium or silicon.
Furthermore, the polishing composition provided by the present
invention can also increase the polishing speed of an oxide. In
addition, the present invention provides a polishing method using
this polishing composition and a method for manufacturing a
substrate.
[0009] In order to achieve the above object, several embodiments of
the present invention provide a polishing composition as described
below, a polishing method using this polishing composition, and a
method for manufacturing a substrate.
[0010] [1] A polishing composition contains polishing abrasive
grains which contain silica particles and in which a silanol group
density on a surface of the silica particles is 0 to 3.0
groups/nm.sup.2 and the silanol group density is calculated and
determined based on a specific surface area measured by a BET
method and an amount of silanol groups measured by titration; an
additive molecule; a pH adjusting agent used to adjust a pH of the
polishing composition to a range of 1.5 or more and 4.5 or less;
and a dispersing medium. The additive molecule has a structure
represented by Formula (I).
##STR00002##
[0011] In Formula (I), R.sup.1 and R.sup.2 are each independently
H, a C.sub.1 to C.sub.18 linear alkyl group, a C.sub.3 to C.sub.18
branched alkyl group, or a C.sub.2 to C.sub.18 linear alkenyl
group; n is an integer 2 to 40; and m, p, and q are each
independently 0 or 1 and r is an integer 0 to 2, R.sup.1 is a
C.sub.1 to C.sub.18 linear alkyl group, a C.sub.3 to C.sub.18
branched alkyl group, or a C.sub.2 to C.sub.18 linear alkenyl group
when m is 1, and R.sup.2 is a C.sub.1 to C.sub.18 linear alkyl
group, a C.sub.3 to C.sub.18 branched alkyl group, or a C.sub.2 to
C.sub.18 linear alkenyl group when p is 1.
[0012] [2] In the polishing composition according to [1], a content
of the additive molecule is 50 to 10,000 ppm by weight with respect
to a total weight of the polishing composition.
[0013] [3] In the polishing composition according to [1] or [2], a
weight average molecular weight of the additive molecule is 100 to
10000.
[0014] [4] In the polishing composition according to any one of [1]
to [3], in Formula (I), R.sup.1 is H and R.sup.2 is a C.sub.1 to
C.sub.18 linear alkyl group, a C.sub.3 to C.sub.18 branched alkyl
group, or a C.sub.2 to C.sub.18 linear alkenyl group; n is an
integer 2 to 20; and m, p, q, and r are all 0.
[0015] [5] In the polishing composition according to any one of [1]
to [3], in Formula (I), R.sup.1 and R.sup.2 are both H; n is an
integer 2 to 40; and m and p are both 0 and q and r are both 1.
[0016] [6] In the polishing composition according to any one of [1]
to [3], in Formula (I), R.sup.1 is a C.sub.1 to C.sub.18 linear
alkyl group, a C.sub.3 to C.sub.18 branched alkyl group, or a
C.sub.2 to C.sub.18 linear alkenyl group and R.sup.2 is H; n is an
integer 2 to 20; and m and p are both 0 and q and r are both 1.
[0017] [7] In the polishing composition according to any one of [1]
to [3], in Formula (I), R.sup.1 is a C.sub.1 to C.sub.18 linear
alkyl group, a C.sub.3 to C.sub.18 branched alkyl group, or a
C.sub.2 to C.sub.18 linear alkenyl group and R.sup.2 is H; n is an
integer 2 to 20; and m, q, and r are all 1 and p is 0.
[0018] [8] In the polishing composition according to any one of [1]
to [3], in Formula (I), R.sup.1 and R.sup.2 are both H; n is an
integer 2 to 20; and m, p, and q are all 0 and r is 2.
[0019] [9] In the polishing composition according to any one of [1]
to [8], a content of the polishing abrasive grains is 0.1% to 10%
by weight with respect to a total weight of the polishing
composition.
[0020] [10] A polishing method includes polishing an object to be
polished using the polishing composition according to any one of
[1] to [9], in which a material for the object to be polished
includes an oxide and a silicon-containing material and the
silicon-containing material is represented by Si.sub.xGe.sub.1-x
where x=0.1 to 1.
[0021] [11] In the polishing method according to [10], a removal
rate of the polishing composition with respect to the oxide is a
first removal rate R1 and a removal rate of the polishing
composition with respect to the silicon-containing material is a
second removal rate R2 when a polishing pressure is 1.0 psi, and a
ratio value R1/R2 of the first removal rate to the second removal
rate is 10 or more.
[0022] [12] A method for manufacturing a substrate includes
preparing a substrate, in which a surface of the substrate contains
an oxide and a silicon-containing material and the
silicon-containing material is represented by Si.sub.xGe.sub.1-x
where x=0.1 to 1; and polishing the substrate using the polishing
composition according to any one of [1] to [9].
[0023] The polishing composition according to the present invention
contains polishing abrasive grains satisfying specific conditions
and an additive having a specific structure and can realize a high
polishing selectivity of an oxide to a silicon-containing material
in a specific pH environment. More specifically, in the polishing
composition according to the present invention, polishing abrasive
grains having a relatively low silanol group density are used, and
it is thus possible to increase the polishing speed of an oxide. In
addition, in the polishing composition according to the present
invention, an additive molecule having a specific structure (that
is, having a structure represented by Formula (I) to be described
later) is used, and it is thus possible to decrease the polishing
speed of a silicon-containing material (for example,
silicon-germanium or silicon). Furthermore, the polishing
composition according to the present invention is used in a
specific acidic pH (namely, a pH of 1.5 or more and 4.5 or less)
environment, and it is thus possible to avoid a decrease in the
removal rate of an oxide and the polishing selectivity of an oxide
to a silicon-containing material. When chemical mechanical
polishing is performed on an oxide layer formed on a
silicon-containing material layer using the polishing composition
according to the present invention, the silicon-containing material
layer can be used as a polishing stop layer as it is, and thus it
is not necessary to form a further polishing stop layer (for
example, a silicon nitride layer). It is thus possible to simplify
the complexity of process and to decrease the time and cost
required for production. In addition, in the polishing composition
according to the present invention, the removal rate of an oxide
can be adjusted by adjusting the kind and content of additive. For
example, the removal rate of an oxide can be further increased, and
the time required for the polishing step is shortened.
DETAILED DESCRIPTION
[0024] In order to make the above-mentioned and other purposes,
features, and advantages of the present invention clearer and
easier to understand, preferred embodiments will be given below and
described in detail.
[0025] Hereinafter, embodiments of the present invention will be
described. The present invention is not limited to these
embodiments.
[0026] One embodiment of the present invention provides a polishing
composition containing: polishing abrasive grains which contains
silica particles and in which a silanol group density on a surface
of the silica particles is 0 to 3.0 groups/nm.sup.2 and the silanol
group density is calculated and determined based on a specific
surface area measured by a BET method and an amount of silanol
groups measured by titration; an additive molecule; a pH adjusting
agent used to adjust a pH of the polishing composition to a range
of 1.5 or more and 4.5 or less; and a dispersing medium. The
additive molecule has a structure represented by Formula (I).
##STR00003##
[0027] In Formula (I), R.sup.1 and R.sup.2 are each independently
H, a C.sub.1 to C.sub.18 linear alkyl group, a C.sub.3 to C.sub.18
branched alkyl group, or a C.sub.2 to C.sub.18 linear alkenyl
group; n is an integer 2 to 40; and m, p, and q are each
independently 0 or 1 and r is an integer 0 to 2, R.sup.1 is a
C.sub.1 to C.sub.18 linear alkyl group, a C.sub.3 to C.sub.18
branched alkyl group, or a C.sub.2 to C.sub.18 linear alkenyl group
when m is 1, and R.sup.2 is a C.sub.1 to C.sub.18 linear alkyl
group, a C.sub.3 to C.sub.18 branched alkyl group, or a C.sub.2 to
C.sub.18 linear alkenyl group when p is 1.
[0028] In the present embodiment, in the polishing composition,
silica particles having a relatively low silanol group density are
used as polishing abrasive grains, an additive having a specific
structure is combined, and a high polishing selectivity of an oxide
to silicon-germanium or silicon (that is, the polishing selectivity
of oxide/silicon-containing material is high) can be realized in a
particular pH environment. When chemical mechanical polishing is
performed on an object to be polished containing a
silicon-containing material and an oxide using the polishing
composition of the present embodiment, it is possible to increase
the removal rate of the oxide as well as to increase the polishing
selectivity of the oxide to silicon-germanium or silicon. Hence,
the silicon-containing material can be used as a polishing stop
layer, and it is not necessary to form a further polishing stop
layer. As a result, the surface flatness of the object to be
polished is improved, and it is possible to simplify the complexity
of process and to decrease the time and cost required for
production.
[0029] The object to be polished applied to the polishing
composition according to the present invention is not particularly
limited, and any general semiconductor substrate can be applied.
The polishing composition according to the present invention is
particularly suitable to polish a substrate containing a
silicon-containing material and an oxide on the surface, and the
technical effect of the present invention is fully exhibited.
Specific examples of the oxide include silicon oxide. Examples of
the silicon-containing material include amorphous silicon,
monocrystalline silicon, polycrystalline silicon,
silicon-germanium, or any combination thereof. Specific examples of
the silicon-containing material include a silicon-containing
material represented by a molecular formula Si.sub.xGe.sub.1-x. The
value of x in the molecular formula is preferably 0.1 or more, more
preferably 0.2 or more, still more preferably 0.3 or more. The
value of x in the molecular formula is preferably 1 or less, more
preferably 0.9 or less, still more preferably 0.8 or less.
[0030] Furthermore, in the present specification, the "substrate
containing a silicon-containing material and an oxide" may be any
substrate containing a silicon-containing material and an oxide on
the surface, and the aspect thereof is not particularly limited.
For example, a patterned structure formed of an oxide and a
silicon-containing material may be present on the surface of an
arbitrary substrate, or an oxide layer may be present on a
substrate formed of a silicon-containing material, or a patterned
structure formed of an oxide layer and other materials may be
present on a substrate (or a silicon-containing material layer)
formed of a silicon-containing material. Several different aspects
of the "substrate containing a silicon-containing material and an
oxide" have been mentioned here, but these are not intended to
limit the present invention. The present invention may include
other possible aspects of an arbitrary "substrate containing a
silicon-containing material and an oxide".
[0031] Hereinafter, various kinds of components contained in the
polishing composition according to the present embodiment will be
described.
[Polishing Abrasive Grain]
[0032] The polishing composition of the present embodiment contains
silica as polishing abrasive grains. In several embodiments of the
present invention, the polishing abrasive grains are colloidal
silica. In several embodiments of the present invention, silica
particles having a relatively low silanol group density are used as
polishing abrasive grains. In the present specification, the term
"silanol group density" means the number of silanol groups per unit
area of the silica particle surface. The silanol group density is
an index for expressing the electrical or chemical properties of
the silica particle surface.
[0033] In the present specification, the silanol group density is
calculated and determined based on the specific surface area
measured by the BET method and the amount of silanol groups
measured by titration. The average silanol group density (unit:
groups/nm.sup.2) on the silica (polishing abrasive grain) surface
can be calculated, for example, by the Sears titration method using
neutralization titration described in "Analytical Chemistry, vol.
28, No. 12, 1956, 1982-1983" by G. W. Sears. The "Sears titration
method" is an analytical method commonly used by colloidal silica
manufacturers to evaluate silanol group densities and is a method
in which calculation is performed based on the amount of aqueous
sodium hydroxide solution required to change the pH from 4 to 9.
The details of silanol group density measurement will be described
in detail in the following Examples.
[0034] The silanol group density of the polishing abrasive grains
is 0 to 3.0 groups/nm.sup.2. When the silanol group density is
within the above range, the silica particles can favorably adsorb
the additive molecules in the present embodiment. As a result, the
additive molecules can be adsorbed and concentrated on the surface
of the polishing abrasive grains, and the aggregation of the
polishing abrasive grains can be avoided by the steric hindrance of
the additive molecules. Hence, the dispersion stability of the
polishing abrasive grains in the polishing composition is improved,
the polishing abrasive grains are less likely to aggregate, and the
storage stability is also improved. On the other hand, by adsorbing
and concentrating the additive molecules on the surface of the
polishing abrasive grains, the polishing selectivity of the oxide
to silicon-germanium or silicon can be improved. The silanol group
density of the polishing abrasive grains is preferably more than 0
group/nm.sup.2, more preferably 0.5 group/nm.sup.2 or more, still
more preferably 1.0 group/nm.sup.2 or more, yet still more
preferably 1.2 groups/nm.sup.2 or more. In addition, the silanol
group density of the polishing abrasive grains is preferably 2.5
groups/nm.sup.2 or less, more preferably 2.0 groups/nm.sup.2 or
less, still more preferably 1.8 groups/nm.sup.2 or less.
[0035] In an embodiment of the present invention, in order to set
the number of silanol groups per unit surface area of abrasive
grains to 0 to 3.0 groups/nm.sup.2, the number of silanol groups
can be controlled by selecting the method for manufacturing the
abrasive grains, and the like, for example, it is suitable to
perform a heat treatment such as firing. In an embodiment of the
present invention, firing is performed, for example, by holding
abrasive grains (for example, silica) in an environment of
120.degree. C. to 200.degree. C. for 30 minutes or longer. By
performing such a heat treatment, the number of silanol groups on
the abrasive grain surface can be set to a desired numerical value
such as 0 to 3.0 groups/nm.sup.2. Unless such a special treatment
is performed, the number of silanol groups on the abrasive grain
surface does not reach more than 0 group/nm.sup.2 and 3.0
groups/nm.sup.2 or less.
[0036] The average primary particle size of the polishing abrasive
grains is preferably 5 nm or more, more preferably 7 nm or more,
still more preferably 10 nm or more, particularly preferably 25 nm
or more. As the average primary particle size of the polishing
abrasive grains increases, the polishing speeds with respect to the
silicon-containing material and the oxide may further increase. The
average primary particle size of the polishing abrasive grains is
preferably 120 nm or less, more preferably 80 nm or less, still
more preferably 50 nm or less. As the average primary particle size
of the polishing abrasive grains decreases, a polished surface with
less scratches can be easily obtained when an object to be polished
is polished using the polishing composition. In addition, the value
of the average primary particle size of the polishing abrasive
grains can be calculated based on the specific surface area
measured by the BET method.
[0037] The average secondary particle size of the polishing
abrasive grains is preferably 10 nm or more, more preferably 20 nm
or more, still more preferably 30 nm or more, particularly
preferably 50 nm or more. As the average secondary particle size of
the polishing abrasive grains increases, the polishing speeds with
respect to the silicon-containing material and the oxide may
further increase. The average secondary particle size of the
polishing abrasive grains is preferably 250 nm or less, more
preferably 200 nm or less, still more preferably 150 nm or less,
particularly preferably 100 nm or less. As the average secondary
particle size of the polishing abrasive grains decreases, a
polished surface with less scratches can be easily obtained when an
object to be polished is polished using the polishing composition.
In addition, the value of the average secondary particle size of
the polishing abrasive grains can be measured by, for example, a
laser light scattering method.
[0038] In several embodiments of the present invention, the zeta
potential of the polishing abrasive grains under acidic conditions
is a positive value and thus the polishing abrasive grains can be
strongly repelled from each other and favorably dispersed. Hence,
the storage stability of the polishing composition increases.
Furthermore, in several embodiments of the present invention, the
surface zeta potential of the polishing abrasive grains is a
positive value, there is electrostatic force of attraction between
the polishing abrasive grains and a negatively charged object to be
polished (for example, an oxide), and thus the polishing speed of
the oxide can increase. In several embodiments of the present
invention, the zeta potential of the polishing abrasive grains
under specific acidic conditions (for example, the pH is 1.5 or
more and 4.5 or less) is preferably +10 mV or more, more preferably
+20 mV or more, still more preferably +30 mV or more. In addition,
the zeta potential of the polishing abrasive grains under specific
acidic conditions (for example, the pH is 1.5 or more and 4.5 or
less) is preferably +100 mV or less, more preferably +80 mV or
less, still more preferably +60 mV or less, particularly preferably
+40 mV or less.
[0039] In several embodiments of the present invention, the content
of the polishing abrasive grains is preferably 0.01% by weight or
more, more preferably 0.05% by weight or more, still more
preferably 0.1% by weight or more, particularly preferably 0.3% by
weight or more with respect to the total weight of the polishing
composition. In addition, the content of the polishing abrasive
grains is preferably 10.0% by weight or less, more preferably 5.0%
by weight or less, still more preferably 2.0% by weight or less,
particularly preferably 1.0% by weight or less. As the content of
polishing abrasive grains increases, the polishing speed with
respect to the object to be polished increases. On the other hand,
as the content of the polishing abrasive grains decreases, the
material cost of the polishing composition can decrease and the
aggregation of the polishing abrasive grains may be less likely to
occur. Furthermore, by decreasing the content of the polishing
abrasive grains, it is possible to prevent the surface of the
object to be polished after polishing from being uneven by
excessive polishing.
[Additive Molecule]
[0040] The polishing composition of the present embodiment contains
at least one additive molecule, and the additive molecule has a
structure represented by Formula (I):
##STR00004##
[0041] In Formula (I), R.sup.1 and R.sup.2 are each independently
H, a C.sub.1 to C.sub.18 linear alkyl group, a C.sub.3 to C.sub.18
branched alkyl group, or a C.sub.2 to C.sub.18 linear alkenyl
group; n is an integer 2 to 40; and m, p, and q are each
independently 0 or 1 and r is an integer 0 to 2, R.sup.2 is a Ci to
C.sub.18 linear alkyl group, a C.sub.3 to C.sub.18 branched alkyl
group, or a C.sub.2 to C.sub.18 linear alkenyl group when m is 1,
and R.sup.2 is a C.sub.1 to C.sub.18 linear alkyl group, a C.sub.3
to C.sub.18 branched alkyl group, or a C.sub.2 to C.sub.18 linear
alkenyl group when p is 1. In addition, in an embodiment, R.sup.2
is a C.sub.1 to C.sub.18 linear alkyl group, a C.sub.3 to C.sub.18
branched alkyl group, or a C.sub.2 to C.sub.18 linear alkenyl group
when m is 1, and R.sup.2 is a C.sub.1 to C.sub.18 linear alkyl
group, a C.sub.3 to C.sub.18 branched alkyl group, or a C.sub.2 to
C.sub.18 linear alkenyl group when p is 1.
[0042] Here, in the present specification, the C.sub.1 to C.sub.18
linear alkyl group (namely, a linear alkyl group having 1 to 18
carbon atoms) or the C.sub.3 to C.sub.18 branched alkyl group
(namely, a branched alkyl group having 3 to 18 carbon atoms) is not
particularly limited, and examples thereof include a n-propyl
group, an isopropyl group, a n-butyl group, an isobutyl group, a
sec-butyl group, a tert-butyl group, a n-pentyl group, an isopentyl
group, a 2-methylbutyl group, a sec-pentyl group, a neopentyl
group, a 1,2-dimethylpropyl group, a tert-pentyl group, a hexyl
group, an isohexyl group, a heptyl group, an octyl group, a nonyl
group, a decyl group, an undecyl group, a dodecyl group (lauryl
group), a 2-ethylhexyl group, a tridecyl group, a tetradecyl group,
a pentadecyl group, a hexadecyl group, a heptadecyl group, an
octadecyl group, and the like.
[0043] In the present specification, the C.sub.2 to C.sub.18 linear
alkenyl group (a linear alkenyl group having 2 to 20 carbon atoms)
is not particularly limited, and examples thereof include an
ethenyl group, a propenyl group, an allyl group, an isopropenyl
group, a 1-hexenyl group, a 2-hexenyl group, a 3-hexenyl group, a
1-heptenyl group, a 2-heptenyl group, a 3-heptenyl group, a
9-decenyl group, a 11-dodecenyl group, a (Z)-9-pentadecenyl group,
an oleyl group (Z-9-octadecenyl group), and the like.
[0044] As described above, the silanol group density on the surface
of the silica polishing abrasive grains is relatively low, and thus
the hydrophobicity of the polishing abrasive grains increases. In
addition, the surface of the silicon-containing material (for
example, silicon-germanium or silicon) that is the object to be
polished is also a surface having relatively high hydrophobicity.
In a case in which the above-described additive is not used, the
affinity between the hydrophobic polishing abrasive grains and the
hydrophobic silicon-containing material is relatively great, and
thus the polishing speed of the polishing abrasive grains with
respect to the silicon-containing material is high. In such a case,
the polishing speed ratio of the oxide to the silicon-containing
material is excessively low, and thus the silicon-containing
material cannot be used as a polishing stop layer when the oxide is
polished.
[0045] Please refer to the structure represented by Formula (I).
The additive molecule has a hydrophobic molecular chain segment,
for example, R.sup.1, R.sup.2, or an alkyl chain segment on the
main chain. The additive molecule is adsorbed and concentrated on
the hydrophobic surfaces of the polishing abrasive grains and the
silicon-containing material through the hydrophobic molecular chain
segment. Hence, one thin layer formed of the additive molecules is
adsorbed on the surfaces of the polishing abrasive grains and the
silicon-containing material. Direct contact between the polishing
abrasive grains and the silicon-containing material may be
decreased or avoided by causing hindrance due to the steric
structure of the additive molecules. In other words, the additive
molecule can form a protective layer-like structure on the surface
of the silicon-containing material and can significantly decrease
the polishing speed of the silicon-containing material. As a
result, the polishing speed ratio of the oxide to the
silicon-containing material increases, and thus the
silicon-containing material can be used as a polishing stop layer
at the time of oxide polishing.
[0046] In addition, please refer to the structure represented by
Formula (I). The additive molecule has a hydrophilic group at the
end position, for example, a hydroxyl (--OH) group. Accordingly,
after the additive molecules are adsorbed on the surface of the
polishing abrasive grains, the hydrophilic groups on the surface of
the polishing abrasive grains increase, and the hydrophilicity of
the polishing abrasive grains also increases in association with
this. Furthermore, the surface of the oxide of the object to be
polished is also a surface having relatively high hydrophilicity.
One thin layer formed of the additive molecules is adsorbed on the
surface of the polishing abrasive grains, but there is
electrostatic force of attraction between the polishing abrasive
grains and the oxide as well as the affinity between the
hydrophilic polishing abrasive grains and the hydrophilic oxide is
sufficiently high, and it is thus still possible to moderately
increase the polishing speed of the oxide. As a result, the
polishing speed ratio of the oxide to the silicon-containing
material further increases, and this is thus more advantageous in
order to use the silicon-containing material as a polishing stop
layer when the oxide is polished. In addition, an increase in
polishing speed of the oxide also leads to shortening of the time
required for the polishing step, and this contributes to the
improvement in production efficiency.
[0047] In several embodiments of the present invention, in the
structure represented by Formula (I), R.sup.1 is H and R.sup.2 is a
C.sub.1 to C.sub.18 linear alkyl group, a C.sub.3 to C.sub.18
branched alkyl groups, or a C.sub.2 to C.sub.18 linear alkenyl
group; n is an integer 2 to 20; and m, p, q, and r are all 0. In
such an embodiment, the molecular structure of the additive
molecule is relatively simple and is likely to be closely arranged.
For this reason, the additive molecules are likely to form a thin
layer having a relatively dense structure on the surfaces of the
polishing abrasive grains and the silicon-containing material, and
as a result, it is possible to properly protect the
silicon-containing material. Hence, the polishing speed of the
silicon-containing material can be significantly decreased.
Furthermore, in such an embodiment, the additive molecule has a
large number of hydrophilic groups, and thus the hydrophilicity of
the surface of the polishing abrasive grains may increase.
Accordingly, the affinity between the polishing abrasive grains and
the hydrophilic oxide increases, and eventually the polishing speed
of the oxide further increases. As a result, the polishing speed
ratio of the oxide to the silicon-containing material further
increases, and this is thus more advantageous in order to use the
silicon-containing material as a polishing stop layer when the
oxide is polished, and this also leads to shortening of the time
required for the polishing step.
[0048] In the present embodiment, R.sup.2 is preferably a C.sub.1
to C.sub.18 linear alkyl group, more preferably a C.sub.1 to
C.sub.10 linear alkyl group, still more preferably a C.sub.1 to
C.sub.5 linear alkyl group, yet still more preferably a C.sub.1 to
C.sub.3 linear alkyl group.
[0049] In several embodiments of the present invention, in the
structure represented by Formula (I), R.sup.1 and R.sup.2 are both
H; n is an integer 2 to 40; and m and p are both 0 and q and r are
both 1. In such an embodiment, the molecular structure of the
additive molecule is relatively simple and is likely to be closely
arranged. For this reason, the additive molecules are likely to
form a thin layer having a relatively dense structure on the
surfaces of the polishing abrasive grains and the
silicon-containing material, and as a result, it is possible to
properly protect the silicon-containing material. Hence, the
polishing speed of the silicon-containing material can be
significantly decreased. Furthermore, in such an embodiment, the
additive molecule has a large number of hydrophilic groups, and
thus the hydrophilicity of the surface of the polishing abrasive
grains may increase. Accordingly, the affinity between the
polishing abrasive grains and the hydrophilic oxide increases, and
eventually the polishing speed of the oxide further increases. As a
result, the polishing speed ratio of the oxide to the
silicon-containing material further increases, and this is thus
more advantageous in order to use the silicon-containing material
as a polishing stop layer when the oxide is polished, and this also
leads to shortening of the time required for the polishing
step.
[0050] In several embodiments of the present invention, in the
structure represented by Formula (I), R.sup.1 and R.sup.2 are both
H; and m, p, and q are all 0 and r is 2. In such an embodiment, the
molecular structure of the additive molecule is relatively simple
and is likely to be closely arranged. For this reason, the additive
molecules are likely to form a thin layer having a relatively dense
structure on the surfaces of the polishing abrasive grains and the
silicon-containing material, and as a result, it is possible to
properly protect the silicon-containing material. Hence, the
polishing speed of the silicon-containing material can be
significantly decreased. Furthermore, in such an embodiment, the
additive molecule has a large number of hydrophilic groups, and
thus the hydrophilicity of the surface of the polishing abrasive
grains may increase. Accordingly, the affinity between the
polishing abrasive grains and the hydrophilic oxide increases, and
eventually the polishing speed of the oxide further increases. As a
result, the polishing speed ratio of the oxide to the
silicon-containing material further increases, and this is thus
more advantageous in order to use the silicon-containing material
as a polishing stop layer when the oxide is polished, and this also
leads to shortening of the time required for the polishing
step.
[0051] In several embodiments of the present invention, in the
structure represented by Formula (I), R.sup.1 is a C.sub.1 to
C.sub.18 linear alkyl group, a C.sub.3 to C.sub.18 branched alkyl
groups, or a C.sub.2 to C.sub.18 linear alkenyl group and R.sup.2
is H; n is an integer 2 to 20; and m and p are both 0 and q and r
are both 1. In such an embodiment, the additive molecule has a
hydrophobic molecular chain segment (namely, an alkyl chain segment
positioned at the end). Accordingly, the additive molecules may be
more easily adsorbed on the hydrophobic surfaces of the polishing
abrasive grains and the silicon-containing material. Furthermore,
the hydrophobic molecular chain segment can change the steric
structure of the additive molecule to a larger one, and this is
thus advantageous in order to further decrease or avoid direct
contact between the polishing abrasive grains and the
silicon-containing material. As a result, the polishing speed of
the silicon-containing material further decreases, the polishing
speed ratio of the oxide to the silicon-containing material further
increases, and this is thus more advantageous in order to use the
silicon-containing material as a polishing stop layer when the
oxide is polished.
[0052] In the present embodiment, R.sup.1 is preferably a C.sub.3
to C.sub.18 linear alkyl group or a C.sub.2 to C.sub.18 linear
alkenyl group, more preferably a C.sub.5 to C.sub.18 linear alkyl
group or a C.sub.5 to C.sub.18 linear alkenyl group, still more
preferably a C.sub.10 to C.sub.18 linear alkyl group or a C.sub.10
to C.sub.18 linear alkenyl group, yet still more preferably a
C.sub.10 to C.sub.16 linear alkyl group or a C.sub.12 to C.sub.18
linear alkenyl group, particularly preferably a C.sub.10 to
C.sub.14 linear alkyl group.
[0053] In several embodiments of the present invention, in the
structure represented by Formula (I), R.sup.1 is H and R.sup.2 is a
C.sub.1 to C.sub.18 linear alkyl group, a C.sub.3 to C.sub.18
branched alkyl groups, or a C.sub.2 to C.sub.18 linear alkenyl
group; n is an integer 2 to 20; and m and p are both 0 and q and r
are both 1. In such an embodiment, the additive molecule has a
large number of hydrophobic molecular chain segments (namely, alkyl
chain segments positioned in the side chains). Accordingly, the
additive molecules may be more easily adsorbed on the hydrophobic
surfaces of the polishing abrasive grains and the
silicon-containing material. Furthermore, the large number of
hydrophobic molecular chain segments can change the steric
structure of the additive molecule to a larger one, and this is
thus advantageous in order to further decrease or avoid direct
contact between the polishing abrasive grains and the
silicon-containing material. As a result, the polishing speed of
the silicon-containing material further decreases, the polishing
speed ratio of the oxide to the silicon-containing material further
increases, and this is thus more advantageous in order to use the
silicon-containing material as a polishing stop layer when the
oxide is polished.
[0054] In the present embodiment, R.sup.2 is preferably a C.sub.3
to C.sub.18 linear alkyl group or a C.sub.2 to C.sub.18 linear
alkenyl group, more preferably a C.sub.5 to C.sub.18 linear alkyl
group or a C.sub.5 to C.sub.18 linear alkenyl group, still more
preferably a C.sub.10 to C.sub.18 linear alkyl group or a C.sub.10
to C.sub.18 linear alkenyl group, yet still more preferably a
C.sub.10 to C.sub.16 linear alkyl group or a C.sub.12 to C.sub.18
linear alkenyl group, particularly preferably a C.sub.10 to
C.sub.14 linear alkyl group.
[0055] In several embodiments of the present invention, in the
structure represented by Formula (I), R.sup.1 is a C.sub.1 to
C.sub.18 linear alkyl group, a C.sub.3 to C.sub.18 branched alkyl
groups, or a C.sub.2 to C.sub.18 linear alkenyl group and R.sup.2
is H; n is an integer 2 to 20; and m, q, and r are all 1 and p is
0. In such an embodiment, the additive molecule has a hydrophobic
molecular chain segment (namely, an alkyl chain segment positioned
at the end). Accordingly, the additive molecules may be more easily
adsorbed on the hydrophobic surfaces of the polishing abrasive
grains and the silicon-containing material. Furthermore, the
hydrophobic molecular chain segment can change the steric structure
of the additive molecule to a larger one, and this is thus
advantageous in order to further decrease or avoid direct contact
between the polishing abrasive grains and the silicon-containing
material. As a result, the polishing speed of the
silicon-containing material further decreases, the polishing speed
ratio of the oxide to the silicon-containing material further
increases, and this is thus more advantageous in order to use the
silicon-containing material as a polishing stop layer when the
oxide is polished.
[0056] In the present embodiment, R.sub.1 is preferably a C.sub.3
to C.sub.18 linear alkyl group or a C.sub.2 to C.sub.18 linear
alkenyl group, more preferably a C.sub.5 to C.sub.18 linear alkyl
group or a C.sub.5 to C.sub.18 linear alkenyl group, still more
preferably a C.sub.10 to C.sub.18 linear alkyl group or a C.sub.10
to C.sub.18 linear alkenyl group, yet still more preferably a
C.sub.10 to C.sub.16 linear alkyl group or a C.sub.12 to C.sub.18
linear alkenyl group, particularly preferably a C.sub.10 to
C.sub.14 linear alkyl group.
[0057] In several embodiments of the present invention, in the
structure represented by Formula (I), R.sup.1 is H and R.sup.2 is a
C.sub.1 to C.sub.18 linear alkyl group, a C.sub.3 to C.sub.18
branched alkyl groups, or a C.sub.2 to C.sub.18 linear alkenyl
group; n is an integer 2 to 20; and m is 0 and p, q, and r are all
1. In such an embodiment, the additive molecule has a large number
of hydrophobic molecular chain segments (namely, alkyl chain
segments positioned in the side chains). Accordingly, the additive
molecules may be more easily adsorbed on the hydrophobic surfaces
of the polishing abrasive grains and the silicon-containing
material. Furthermore, the large number of hydrophobic molecular
chain segments can change the steric structure of the additive
molecule to a larger one, and this is thus advantageous in order to
further decrease or avoid direct contact between the polishing
abrasive grains and the silicon-containing material. As a result,
the polishing speed of the silicon-containing material further
decreases, the polishing speed ratio of the oxide to the
silicon-containing material further increases, and this is thus
more advantageous in order to use the silicon-containing material
as a polishing stop layer when the oxide is polished.
[0058] In the present embodiment, R.sup.2 is preferably a C.sub.3
to C.sub.18 linear alkyl group or a C.sub.2 to C.sub.18 linear
alkenyl group, more preferably a C.sub.5 to C.sub.18 linear alkyl
group or a C.sub.5 to C.sub.18 linear alkenyl group, still more
preferably a C.sub.10 to C.sub.18 linear alkyl group or a C.sub.10
to C.sub.18 linear alkenyl group, yet still more preferably a
C.sub.10 to C.sub.16 linear alkyl group or a C.sub.12 to C.sub.18
linear alkenyl group, particularly preferably a C.sub.10 to
C.sub.14 linear alkyl group.
[0059] In several embodiments of the present invention, the weight
average molecular weight (MW) of the additive molecule is
preferably 100 or more, more preferably 200 or more, still more
preferably 300 or more. The weight average molecular weight (MW) of
the additive molecule is preferably 10000 or less, more preferably
6000 or less, still more preferably 4000 or less. The weight
average molecular weight in the present specification is measured
by gel permeation chromatography (GPC) using polystyrene as a
standard substance.
[0060] In several embodiments of the present invention, the weight
average molecular weight (MW) of the additive molecule is 100 or
more, 200 or more, 250 or more, 300 or more, 450 or more, 400 or
more, 500 or more, or 600 or more. In addition, in several
embodiments of the present invention, the weight average molecular
weight (MW) of the additive molecule is 1500 or less, 1000 or less,
950 or less, 900 or less, 800 or less, 700 or less, 650 or less, or
600 or less.
[0061] In several embodiments of the present invention, in a case
in which R.sup.1 is H and R.sup.2 is a C.sub.1 to C.sub.18 linear
alkyl group, a C.sub.3 to C.sub.18 branched alkyl groups, or a
C.sub.2 to C.sub.18 linear alkenyl group; n is an integer 2 to 20;
and m, p, q, and r are all 0 in Formula (I), the weight average
molecular weight (MW) of the additive molecule is 100 or more, 200
or more, 250 or more, 300 or more, or 400 or more. In addition, in
several embodiments of the present invention, in a case in which
R.sup.1 is H and R.sup.2 is a C.sub.1 to C.sub.18 linear alkyl
group, a C.sub.3 to C.sub.18 branched alkyl groups, or a C.sub.2 to
C.sub.18 linear alkenyl group; n is an integer 2 to 20; and m, p,
q, and r are all 0 in Formula (I), the weight average molecular
weight (MW) of the additive molecule is 1000 or less, 950 or less,
900 or less, 800 or less, 700 or less, 600 or less, or 500 or
less.
[0062] In several embodiments of the present invention, in a case
in which R.sup.1 and R.sup.2 are both H; n is an integer 2 to 40;
and m and p are both 0 and q and r are both 1 in Formula (I), the
weight average molecular weight (MW) of the additive molecule is
100 or more, 150 or more, 200 or more, 250 or more, 280 or more,
300 or more, 400 or more, 500 or more, 600 or more, or 700 or more.
In addition, in several embodiments of the present invention, in a
case in which R.sup.1 and R.sup.2 are both H; n is an integer 2 to
40; and m and p are both 0 and q and r are both 1 in Formula (I),
the weight average molecular weight (MW) of the additive molecule
is 3000 or less, 1500 or less, 1000 or less, 900 or less, or 800 or
less.
[0063] In several embodiments of the present invention, in a case
in which an alkyl ether is used as the hydrophobic molecular chain
segment, that is, in (i) a case in which R.sup.1 is H and R.sup.2
is a C.sub.1 to C.sub.18 linear alkyl group, a C.sub.3 to C.sub.18
branched alkyl groups, or a C.sub.2 to C.sub.18 linear alkenyl
group; n is an integer 2 to 20; and m and p are both 0 and q and r
are both 1 in Formula (I) and (ii) a case in which R.sup.1 is a
C.sub.1 to C.sub.18 linear alkyl group, a C.sub.3 to C.sub.28
branched alkyl groups, or a C.sub.2 to C.sub.18 linear alkenyl
group and R.sup.2 is H; n is an integer 2 to 20; and m and p are
both 0, and q and r are both 1 in Formula (I), the weight average
molecular weight (MW) of the additive molecule is 100 or more, 200
or more, 250 or more, 300 or more, 350 or more, or 400 or more. In
addition, in several embodiments of the present invention, in a
case in which an alkyl ether is used as the hydrophobic molecular
chain segment, the weight average molecular weight (MW) of the
additive molecule is 1500 or less, 1000 or less, 900 or less, 800
or less, 600 or less, or 500 or less.
[0064] In several embodiments of the present invention, in a case
in which a fatty acid ester is used as the hydrophobic molecular
chain segment, that is, in (i) a case in which R.sup.1 is H and
R.sup.2 is a C.sub.1 to C.sub.18 linear alkyl group, a C.sub.3 to
C.sub.18 branched alkyl groups, or a C.sub.2 to C.sub.18 linear
alkenyl group; n is an integer 2 to 20; and m is 0 and p, q, and r
are all 1 in Formula (I) and (ii) a case in which R.sup.1 is a
C.sub.1 to C.sub.18 linear alkyl group, a C.sub.3 to C.sub.28
branched alkyl groups, or a C.sub.2 to C.sub.28 linear alkenyl
group and R.sup.2 is H; n is an integer 2 to 20; and m, q, and r
are all 1 and p is 0 in Formula (I), the weight average molecular
weight (MW) of the additive molecule is 100 or more, 200 or more,
250 or more, 300 or more, 350 or more, or 400 or more. In addition,
in several embodiments of the present invention, in a case in which
a fatty acid ester is used as the hydrophobic molecular chain
segment, the weight average molecular weight (MW) of the additive
molecule is 1500 or less, 1000 or less, 900 or less, 800 or less,
700 or less, or 600 or less.
[0065] In several embodiments of the present invention, in a case
in which R.sup.1 and R.sup.2 are both H; n is an integer 2 to 20;
and m, p, and q are all 0 and r is 2 in Formula (I), the weight
average molecular weight (MW) of the additive molecule is 100 or
more, 150 or more, 200 or more, 220 or more, or 230 or more. In
addition, in several embodiments of the present invention, in a
case in which R.sup.1 and R.sup.2 are both H; n is an integer 2 to
20; and m, p, and q are all 0 and r is 2 in Formula (I), the weight
average molecular weight (MW) of the additive molecule is 1000 or
less, 800 or less, 600 or less, 500 or less, or 400 or less.
[0066] When the weight average molecular weight of the additive
molecule is excessively large, there is a possibility that the
steric structure of the additive molecule is too large. In such a
case, gaps are likely to be formed between the additive molecules
adsorbed on the polishing abrasive grains and silicon-containing
material, and as a result, it is difficult to form a thin layer
having a dense structure on the surfaces of the polishing abrasive
grains and the silicon-containing material. As a result, the
additive molecule cannot properly protect the silicon-containing
material, and the polishing speed of the silicon-containing
material cannot be sufficiently decreased. Hence, the polishing
speed ratio of the oxide to the silicon-containing material cannot
be increased, and this is disadvantageous in order to use the
silicon-containing material as a polishing stop layer when the
oxide is polished.
[0067] On the other hand, when the weight average molecular weight
of the additive molecule is excessively small, there is a
possibility that the number of hydrophobic chain segments of the
additive molecule is too small and the hydrophilicity of the
additive molecule is too high. In such a case, the additive
molecules may be less likely to be adsorbed on the surfaces of the
polishing abrasive grains and the silicon-containing material.
Accordingly, the additive molecule cannot properly protect the
silicon-containing material, and the polishing speed of the
silicon-containing material cannot be sufficiently decreased.
Furthermore, when the hydrophilicity of the additive molecule is
too high, there is a possibility that one thin layer formed of
additive molecules is adsorbed on the hydrophilic oxide surface,
and thus the polishing speed of the oxide may decrease. Hence, the
polishing speed ratio of the oxide to the silicon-containing
material decreases, and this is disadvantageous in order to use the
silicon-containing material as a polishing stop layer when the
oxide is polished.
[0068] Incidentally, as the weight average molecular weight of the
additive molecules, a value measured by the GPC method
(water-based, in terms of polyethylene oxide) can be adopted. The
weight average molecular weight can be determined in terms of
polyethylene glycol by gel permeation chromatography (GPC) using a
GPC instrument (model: Prominence+ELSD detector (ELSD-LTII)
manufactured by Shimadzu Corporation) and the like.
[0069] As the additive molecule, a commercially available product
may be used or a synthetic product may be used. The manufacturing
method in the case of synthesizing the additive molecule is not
particularly limited, and a known manufacturing method can be
used.
[0070] In several embodiments of the present invention, the content
of the additive molecule is preferably 10 ppm by weight or more,
more preferably 30 ppm by weight or more, still more preferably 50
ppm by weight or more, particularly preferably 70 ppm by weight or
more with respect to the total weight of the polishing composition.
In addition, the content of the additive molecule is preferably
10,000 ppm by weight or less, more preferably 5000 ppm by weight or
less, preferably 2000 ppm by weight or less, particularly
preferably 1000 ppm by weight or less.
[0071] In several embodiments of the present invention, the content
of the additive molecule is 60 ppm by weight or more, 80 ppm by
weight or more, 90 ppm by weight or more, 95 ppm by weight or more,
120 ppm by weight or more, 150 ppm by weight or more, or 200 ppm by
weight or more with respect to the total weight of the polishing
composition. In addition, in several embodiments of the present
invention, the content of the additive molecule is 900 ppm by
weight or less, 700 ppm by weight or less, 500 ppm by weight or
less, 400 ppm by weight or less, 350 ppm by weight or less, or 300
ppm by weight or less with respect to the total weight of the
polishing composition.
[0072] When the content of the additive molecule in the polishing
composition is excessively high, there is a possibility that an
excessively large number of additive molecules is adsorbed on the
surfaces of the polishing abrasive grains and the
silicon-containing material. In addition, when the content of the
additive molecule is excessively high, there is a possibility that
the additive molecules form one thin layer on the surface of the
oxide as well. As a result, both the polishing speed of the
silicon-containing material and the polishing speed of the oxide
decrease, and the polishing speed ratio of the oxide to the
silicon-containing material cannot be sufficiently increased, thus
this is disadvantageous in order to use the silicon-containing
material as a polishing stop layer when the oxide is polished, and
this is also disadvantageous in order to shorten the time required
for the polishing step.
[0073] On the other hand, when the content of the additive molecule
in the polishing composition is excessively small, it is difficult
for the additive molecules to form one thin layer on the surfaces
of the polishing abrasive grains and the silicon-containing
material, particularly it is difficult for the additive molecules
to cover the entire surfaces of the polishing abrasive grains and
the silicon-containing material. Accordingly, the additive molecule
cannot properly protect the silicon-containing material, and the
polishing speed of the silicon-containing material cannot be
sufficiently decreased. In addition, when the content of the
additive molecule is too small, the hydrophilicity of the polishing
abrasive grains is insufficient, it is difficult to effectively
increase the affinity between the polishing abrasive grains and the
hydrophilic oxide, and thus the polishing speed of the oxide cannot
be increased. As described above, when the content of the additive
molecule is too small, it is difficult to increase the polishing
speed ratio of the oxide to the silicon-containing material. Hence,
this is disadvantageous in order to use the silicon-containing
material as a polishing stop layer when the oxide is polished.
[pH Adjusting Agent]
[0074] The polishing composition of the present embodiment contains
a pH adjusting agent. The pH value of the polishing composition can
be adjusted to a range of 1.5 or more and 4.5 or less with a pH
adjusting agent. As the pH adjusting agent, a known acid or base
can be used.
[0075] The acid of a pH adjusting agent used in the polishing
composition of the present embodiment may be an inorganic acid or
an organic acid or may be a chelating agent. Specific examples of
the inorganic acid that can be used as a pH adjusting agent
include, for example, hydrochloric acid (HCl), sulfuric acid
(H.sub.2So.sub.4), nitric acid (HNO.sub.3), hydrofluoric acid (HF),
boric acid carbonic acid (H.sub.3BO.sub.3), (H.sub.2CO.sub.3),
hypophosphorous acid (H.sub.3PO.sub.2), phosphorous acid
(H.sub.3PO.sub.3), and phosphoric acid (H.sub.3PO.sub.4). Among
these inorganic acids, preferred ones are hydrochloric acid,
sulfuric acid, nitric acid, and phosphoric acid.
[0076] Specific examples of the organic acid that can be used as a
pH adjusting agent include, for example, formic acid, acetic acid,
propionic acid, butyric acid, valeric acid, 2-methylbutyric acid,
n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid,
4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid,
n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, hydroxyacetic
acid, salicylic acid, glyceric acid, oxalic acid, malonic acid,
succinic acid, glutaric acid, adipic acid, pimelic acid, maleic
acid, phthalic acid, malic acid, tartaric acid, citric acid, lactic
acid, glyoxylic acid, 2-furancarboxylic acid, 2,5-furandicarboxylic
acid, 3-furancarboxylic acid, 2-tetrahydrofuran carboxylic acid,
methoxyacetic acid, methoxyphenylacetic acid, and phenoxyacetic
acid. Organic sulfuric acids such as methanesulfonic acid,
ethanesulfonic acid, and 2-hydroxyethanesulfonic acid (isethionic
acid) may be used. Among these organic acids, preferred ones are
oxalic acid, malonic acid, succinic acid, glutaric acid, adipic
acid, pimelic acid, maleic acid, phthalic acid, malic acid,
tartaric acid, 2,5-furandicarboxylic acid, and citric acid.
[0077] Examples of the base of a pH adjusting agent used in the
polishing composition of the present embodiment include hydroxides
of alkali metals or salts thereof, hydroxides of group 2 elements
or salts thereof, and quaternary ammonium hydroxides or salts
thereof, ammonia, and amines. Specific examples of the alkali
metals include potassium, sodium, and the like.
[0078] As the pH of the polishing composition increases, the zeta
potential on the surface of the polishing abrasive grains shifts to
a negative value and the zeta potentials on the surfaces of the
oxide and the silicon-containing material also shift to a negative
value. Accordingly, when the pH of the polishing composition is
excessively high (for example, the pH is 5 or more), there is a
possibility that the zeta potential on the surface of the polishing
abrasive grains is a negative value and there is a possibility that
the zeta potential on the surface of the object to be polished is
also a negative value. Accordingly, as the electrostatic force of
repulsion between the polishing abrasive grains and the object to
be polished (including the oxide and the silicon-containing
material) increases, both the polishing speeds of the
silicon-containing material and the oxide significantly decrease
and it is difficult to increase the polishing speed ratio of the
oxide to the silicon-containing material. Hence, this is
disadvantageous in order to use the silicon-containing material as
a polishing stop layer when the oxide is polished, and this is also
disadvantageous in order to shorten the time required for the
polishing step.
[0079] The pH of the polishing composition of the present
embodiment is in a range of 1.5 or more and 4.5 or less. In such an
environment, the surface zeta potential of the polishing abrasive
grains is a positive value, and there is electrostatic force of
attraction between the polishing abrasive grains and a negatively
charged object to be polished (for example, an oxide). Accordingly,
the polishing speed of the oxide may increase. Furthermore, under
acidic conditions, silica particles as polishing abrasive grains
are less likely to cause aggregation by electrostatic repulsion,
and the storage stability of the polishing composition may
significantly increase. More specifically, the pH of the polishing
composition of the present embodiment is preferably 1.8 or more,
more preferably 2 or more, still more preferably 2.5 or more. In
addition, the pH of the polishing composition of the present
embodiment is preferably 4.2 or less, more preferably 4 or less,
still more preferably 3.5 or less.
[0080] In several embodiments, the polishing composition may have a
pH of 1.5 or more, 1.6 or more, 1.7 or more, 1.8 or more, 1.9 or
more, 2.0 or more, 2.1 or more, 2.2 or more, 2.3 or more, 2.4 or
more, 2.5 or more, 2.6 or more, or 2.7 or more. In addition, in
several embodiments, the polishing composition may have a pH of 4.5
or less, 4.4 or less, 4.3 or less, 4.2 or less, 4.1 or less, 4.0 or
less, 3.9 or less, 3.8 or less, 3.7 or less, 3.6 or less, or 3.5 or
less.
[0081] When the pH of the polishing composition is excessively
high, the polishing speed of the oxide significantly decreases and
the polishing speed ratio of the oxide to the silicon-containing
material also significantly decreases. Hence, this is
disadvantageous in order to use the silicon-containing material as
a polishing stop layer when the oxide is polished, and this is also
disadvantageous in order to shorten the time required for the
polishing step. Furthermore, when the pH value of the polishing
composition is excessively high, the storage stability of the
polishing composition may also decrease. On the other hand, when
the pH value of the polishing composition is excessively low, the
safety of process decreases and the burden of waste water treatment
increases.
[Dispersing Medium]
[0082] The polishing composition of the present embodiment contains
a dispersing medium (may be referred to as "solvent"). The
dispersing medium can be used to disperse or dissolve the
respective components in the polishing composition. In the present
embodiment, the polishing composition may contain water as a
dispersing medium. Water containing as little impurities as
possible is preferable from the viewpoint of preventing the action
of other components from being inhibited. More specifically, pure
water or ultrapure water from which impurity ions have been removed
using an ion exchange resin and then foreign matters have been
removed by allowing the water to pass through a filter, or
distilled water is preferable.
[Other Components]
[0083] The polishing composition used in the polishing method of
the present invention may further contain other components such as
a chelating agent, an oxidizing agent, a metal anticorrosive, an
antiseptic agent, and an antifungal agent, if necessary.
<Polishing Method and Method for Manufacturing Substrate>
[0084] As described above, the polishing composition according to
the present invention is particularly suitable to polish a
substrate containing a silicon-containing material and an oxide.
Accordingly, the present invention provides a polishing method in
which an object to be polished containing a silicon-containing
material and an oxide is polished using the polishing composition
according to the present invention. For example, such an object to
be polished may include a substrate formed of a silicon-containing
material and an oxide layer formed on this substrate. Specific
examples of the oxide include silicon oxide. Specific examples of
the silicon-containing material include a silicon-containing
material represented by a molecular formula Si.sub.xGe.sub.1-x
where x=0.1 to 1. In addition, the present invention also provides
a method for manufacturing a substrate, which includes a step of
performing polishing on a substrate containing a silicon-containing
material and an oxide-germanium material using the polishing
composition according to the present invention.
[0085] When an object to be polished containing a
silicon-containing material and an oxide is polished, it is more
preferable as the difference between the removal rate of the oxide
and the removal rate of the silicon-containing material is greater
in order to use the silicon-containing material as a polishing stop
layer at the time of oxide polishing. In other words, it is more
preferable as the polishing selectivity (polishing speed ratio or
removal rate ratio) of the oxide to the silicon-containing material
is higher. More specifically, when an object to be polished
containing a silicon-containing material and an oxide is polished
at a specific polishing pressure (for example, 1.0 psi), the ratio
value (R1/R2) of the removal rate R1 of the oxide to the removal
rate R2 of the silicon-containing material is 10 or more, and it is
more preferable as the ratio value R1/R2 is higher. In several
embodiments of the present invention, the removal rate of the
polishing composition with respect to the oxide is the first
removal rate R1 and the removal rate of the polishing composition
with respect to the silicon-containing material is the second
removal rate R2 when the polishing pressure is 1.0 psi, and the
ratio value R1/R2 of the first removal rate to the second removal
rate is preferably 10 or more, more preferably 15 or more, still
more preferably 20 or more, particularly preferably 30 or more. The
upper limit value of the ratio value (R1/R2) of the first removal
rate to the second removal rate is not particularly limited, and it
is more preferable as the ratio value is higher, but the ratio
value (R1/R2) can be set to 200 or less as an example.
[0086] As the polishing apparatus used in the polishing step, a
polishing apparatus used in a general chemical mechanical polishing
process can be used. Such a polishing apparatus is equipped with a
polishing table to which a polishing pad (or polishing cloth) can
be attached as well as is equipped with a carrier that holds the
object to be polished, a motor that can change the number of
rotations, and the like.
[0087] The polishing pad is not particularly limited, and general
non-woven fabrics, polyurethane resin pads, porous fluororesin
pads, and the like can be used. Furthermore, the polishing pad can
also be grooved so that the polishing composition accumulates in
the groove of the polishing pad if necessary.
[0088] The parameter conditions of the polishing step are also not
particularly limited and can be adjusted as actually required. For
example, the rotational speed of the polishing table can be set to
10 to 500 rpm, and the rotational speed of the carrier can be set
to 10 to 500 rpm, the flow rate of the polishing composition can be
set to 10 to 500 mL/min, the polishing pressure can be set to 0.1
to 10 psi, and the polishing time can be set to 10 seconds to 30
minutes. The method for supplying the polishing composition to the
polishing pad is also not particularly limited, and, for example, a
method by continuous supply using a pump and the like can be
adopted.
[0089] After the polishing step is finished, the object to be
polished is washed in a stream of water and dried by blowing off
the water droplets attached to the object to be polished using a
rotary dryer or the like to obtain a substrate having a flat
surface and no level difference.
Examples
[0090] The present invention will be described in more detail with
reference to the following Examples and Comparative Examples, but
the technical scope of the present invention is not limited only to
the following Examples. In addition, in the present specification,
operations and measurements of physical properties and the like are
performed under the conditions of room temperature (20.degree. C.
to 25.degree. C.)/relative humidity of 40% to 50% RH unless
otherwise stated.
[Preparation of Polishing Composition]
[0091] A polishing composition was prepared by mixing (mixing
temperature: about 25.degree. C., mixing time: about 10 minutes)
polishing abrasive grains, an additive, and a pH adjusting agent in
a dispersing medium (ultrapure water) according to the composition
presented in the following Table 1. The pH of the polishing
composition was confirmed using a pH meter (LAQUA manufactured by
HORIBA, Ltd.) (the temperature of the polishing composition at the
time of pH measurement: 25.degree. C.). In addition, "-" in Table 1
indicates that the component is not added. Details of the
respective components in Table 1 and Table 2 are as follows.
[Polishing Abrasive Grains and Additive Molecules]
[0092] Polishing abrasive grains a: Colloidal silica (primary
particle size: 30 nm, secondary particle size:
[0093] nm, silanol group density on surface of polishing abrasive
grains: 1.5 groups/nm.sup.2)
[0094] Polishing abrasive grain b: Colloidal silica (primary
particle size: 35 nm, secondary particle size: 70 nm, silanol group
density on surface of polishing abrasive grains: 4.4
groups/nm.sup.2)
[0095] Polishing abrasive grain c: Colloidal silica (primary
particle size: 35 nm, secondary particle size: nm, silanol group
density on surface of polishing abrasive grains: 4.5
groups/nm.sup.2)
[0096] Additive A: Glycerol (MW: 92 g/mol)
[0097] Additive B: Polypropylene glycol 400 (MW: 446 g/mol)
[0098] Additive C: Polyglycerin #310 (MW: 314 g/mol)
[0099] Additive D: Polyglycerin #500 (MW: 462 g/mol)
[0100] Additive E: Polyglycerin #750 (MW: 759 g/mol)
[0101] Additive F: Polyglycerin 40 (MW: 2978 g/mol)
[0102] Additive G: Polyglyceryl-4 lauryl ether (MW: 482 g/mol)
[0103] Additive H: Polyglyceryl-10 lauric acid ester (MW: 940
g/mol)
[0104] Additive I: Polyglyceryl-10 oleic acid ester (MW: 1022
g/mol)
[0105] HNO.sub.3: Nitric acid (concentration: 70%)
[0106] Additive J: Polyglyceryl-4 lauric acid ester (MW: 432
g/mol)
[0107] Additive K: Polyglyceryl-6 lauric acid ester (MW:
[0108] 548 g/mol)
[0109] Additive L: Polytetrahydrofuran (=polytetramethylene ether
glycol; MW: 250 g/mol).
[0110] Incidentally, the additive B corresponds to a compound
represented by Formula (I) in which R.sup.1 is H and R.sup.2 is a
C.sub.1 to C.sub.18 linear alkyl group, a C.sub.3 to C.sub.18
branched alkyl group, or a C.sub.2 to C.sub.18 linear alkenyl
group; n is an integer 2 to 20; and m, p, q, and r are all 0. In
addition, the additives C to F correspond to compounds represented
by Formula (I) in which R.sub.1 and R.sup.2 are both H; n is an
integer 2 to 40; and m and p are both 0 and q and r are both 1. The
additive G corresponds to a compound represented by Formula (I) in
which R.sub.1 is a C.sub.2 to C.sub.18 linear alkyl group, a
C.sub.3 to C.sub.18 branched alkyl group, or a C.sub.2 to C.sub.18
linear alkenyl group and R.sup.2 is H; n is an integer 2 to 20; and
m and p are both 0 and q and r are both 1. The additives H to K
correspond to compounds represented by Formula (I) in which R.sup.1
is a C.sub.2 to C.sub.18 linear alkyl group, a C.sub.3 to C.sub.18
branched alkyl group, or a C.sub.2 to C.sub.18 linear alkenyl group
and R.sup.2 is H; n is an integer 2 to 20; and m, q, and r are all
1 and p is 0. The additive L corresponds to a compound represented
by Formula (I) in which R.sup.1 and R.sup.2 are both H; n is an
integer 2 to 20; and m, p, and q are all 0 and r is 2.
[Measurement of Secondary Particle Size of Polishing Abrasive
Grain]
[0111] The average secondary particle size (unit: nm) of the
polishing abrasive grains (colloidal silica) was measured as the
volume average particle size (volume-based arithmetic average
diameter; Mv) for the polishing abrasive grain sample using a
dynamic light scattering type particle size distribution measuring
apparatus (manufactured by Nikkiso Co., Ltd.: UPA-UT151). The
measurement results on the secondary particle size of the polishing
abrasive grains are recorded in Table 1 and Table 2.
[Measurement of Surface Zeta Potential]
[0112] The surface zeta potential of the polishing abrasive grains
contained in the polishing composition was measured by the multiple
frequency electro-acoustic method using an interfacial potential
analyzer (manufactured by Colloidal Dynamics LLC: Zeta Probe
Analyzer). The measurement results on the surface zeta potential
are recorded in Table 1 and Table 2.
[Measurement of Silanol Group Density on Surface of Polishing
Abrasive Grain]
[0113] First, colloidal silica as a solid component was weighed by
1.50 g and placed in a 200 mL beaker, about 100 mL of pure water
was added to the colloidal silica to form a slurry, and then 30 g
of sodium chloride was added to and dissolved in the slurry.
Subsequently, 1 N hydrochloric acid was added to the slurry to
adjust the pH of the slurry to about 3.0 to 3.5, and then pure
water was added to the slurry to set the volume of the slurry to
150 mL. The pH of this slurry was adjusted to 4.0 with a 0.1 N
sodium hydroxide solution at 25.degree. C. and the volume V (unit:
L) of the 0.1 N sodium hydroxide solution required to raise the pH
of the slurry from 4.0 to 9.0 was measured by pH titration using an
automatic titrator (manufactured by Hiranuma Inc.: COM-1700). The
silanol group density on the surface of the polishing abrasive
grains can be calculated by the following equation. The measurement
results on the silanol group density on the surface of the
polishing abrasive grains are respectively recorded in the columns
of polishing abrasive grains a to polishing abrasive grains c in
the details of the respective components ([polishing abrasive
grains and additive molecules]) described above.
.rho.=(e.times.V.times.nA.times.10.sup.<)/(C.times.S) [Equation.
1]
[0114] In the equation,
[0115] .rho. denotes the silanol group density on the surface of
the polishing abrasive grains (unit: groups/nm.sup.2);
[0116] c denotes the concentration of sodium hydroxide solution
used for titration (unit: mol/L);
[0117] V denotes the volume of sodium hydroxide solution required
to raise the pH from 4.0 to 9.0 (unit: L);
[0118] N.sub.A denotes Avogadro's constant (unit: mol);
[0119] C denotes the total mass of silica (solid component) (unit:
g); and
[0120] S denotes the BET specific surface area of silica (unit:
nm.sup.2/g).
[Measurement of Removal Rate]
[0121] The removal rate was measured when polishing was performed
on a silicon-germanium (Si.sub.xGe.sub.1-x) (specifically x=0.75)
substrate having a diameter of 300 mm (manufacturer: Silicon Valley
Microelectronic, Inc.; film thickness: 1500 .ANG.), a Poly-Si
substrate having a diameter of 300 mm (manufacturer: Silicon Valley
Microelectronic, Inc.; film thickness: 5000 .ANG.), and a silicon
oxide (specifically, silicon oxide derived from tetraethyl
orthosilicate (TEOS)) substrate having a diameter of 300 mm
(hereinafter abbreviated as "TEOS substrate"; manufacturer: Silicon
Valley Microelectronic, Inc.; film thickness: 10000 .ANG.),
respectively using the polishing compositions obtained above under
the following polishing conditions. The measurement results on the
removal rate are recorded in Table 1 and Table 2.
[0122] Polishing apparatus: Single-sided CMP polishing apparatus
(FREX 300E; manufactured by EBARA CORPORATION)
[0123] Polishing pad: polyurethane pad
[0124] Rotational speed of polishing table: 90 rpm
[0125] Rotational speed of carrier: 90 rpm
[0126] Flow rate of polishing composition: 300 mL/min
[0127] Polishing time: 60 sec
[0128] Polishing pressure: 1.0 psi (about 6.9 kPa)
[0129] The thickness of the object to be polished before and after
polishing was measured using a film thickness measurement system
(manufactured by KLA-Tencor Corporation; ASET F5x). The removal
rate was calculated by the following equation.
[0130] Removal rate={[thickness before polishing]-[thickness after
polishing]}/[treatment time]
[0131] In the equation, the unit of thickness is .ANG., the unit of
treatment time is minutes, and the unit of removal rate is
(.ANG./min). Incidentally, 1 .ANG.=0.1 nm.
[Calculation of Ratio Value of Removal Rate]
[0132] The polishing step was performed at the above polishing
pressure (namely, 1.0 psi), and the removal rate R.sub.SiGe of the
silicon-germanium substrate, the removal rate R.sub.Si of the
Poly-Si substrate, and the removal rate R.sub.TEOS of the silicon
oxide substrate at this polishing pressure were determined by the
above equation, respectively. The ratio value
(R.sub.TEOS/R.sub.SiGe) of the removal rate R.sub.TEOS of the
silicon oxide substrate to the removal rate R.sub.SiGe of the
silicon-germanium substrate and the ratio value
(R.sub.TEOSR.sub.Si) of the removal rate R.sub.TEOS of the silicon
oxide substrate to the removal rate R.sub.Si of the Poly-Si
substrate when the polishing pressure was 1.0 psi were calculated.
These ratio values (R.sub.TEOS/R.sub.SiGe) and
(R.sub.TEOS/R.sub.Si) can be used in order to indicate the
polishing selectivity of the oxide to the silicon-containing
material at this specific polishing pressure (namely, 1.0 psi). The
polishing selectivity of the oxide to the silicon-containing
material is higher as the ratio value of removal rate is higher.
The removal rate ratio values (R.sub.TEOS/R.sub.SiGe) and
(R.sub.TEOS/R.sub.Si) in the respective Examples and Comparative
Examples are also presented in Table 1 and Table 2.
[0133] In the present specification, it should be noted that the
removal rate of the polishing composition with respect to the oxide
is the first removal rate R1 and the first removal rate R1 may
correspond to the removal rate R.sub.TEOS of the silicon oxide
substrate in Examples, and the removal rate of the polishing
composition with respect to the silicon-containing material is the
second removal rate R2 and the second removal rate R2 may
correspond to the removal rate R.sub.SiGe of the silicon-germanium
substrate or the removal rate R.sub.Si of the Poly-Si substrate.
The ratio value (R1/R2) of the first removal rate to the second
removal rate may correspond the ratio value (R.sub.TEOS/R.sub.SiGe)
of the removal rate of the silicon oxide substrate to the removal
rate of the silicon-germanium substrate or the ratio value
(R.sub.TEOS/R.sub.Si) of the removal rate of the silicon oxide
substrate to the removal rate of the Poly-Si substrate.
TABLE-US-00001 TABLE 1 Polishing abrasive grain Additive Removal
Content Secondary pH Content Zeta Removal rate rate ratio (% by
particle Compo- MW (ppm by potential (.ANG./min) R.sub.TEOS/
R.sub.TEOS/ Kind weight) size (nm) nent pH Kind (g/mol) weight)
(mV) R.sub.SiGe R.sub.Si R.sub.TEOS R.sub.SiGe R.sub.Si Exam-
Polishing 0.5 60 HNO.sub.3 3.0 Additive B 446 100 33.9 11 10 626
56.9 62.6 ple 1 abrasive grain a Exam- Polishing 0.5 60 HNO.sub.3
3.0 Additive C 314 250 33.9 16 12 637 39.8 53.1 ple 2 abrasive
grain a Exam- Polishing 0.5 60 HNO.sub.3 3.0 Additive D 462 250
34.1 18 12 595 33.1 49.6 ple 3 abrasive grain a Exam- Polishing 0.5
60 HNO.sub.3 3.0 Additive E 759 250 36.7 28 17 608 21.7 35.8 ple 4
abrasive grain a Exam- Polishing 0.5 60 HNO.sub.3 3.0 Additive F
2978 250 35.7 19 15 574 30.2 38.3 ple 5 abrasive grain a Exam-
Polishing 0.5 60 HNO.sub.3 3.0 Additive G 482 100 32.9 26 17 598
23.0 35.2 ple 6 abrasive grain a Exam- Polishing 0.5 60 HNO.sub.3
3.0 Additive H 940 100 34.5 28 45 556 19.9 12.4 ple 7 abrasive
grain a Exam- Polishing 0.5 60 HNO.sub.3 3.0 Additive I 1022 100
35.2 21 14 366 17.4 26.1 ple 8 abrasive grain a Exam- Polishing 0.5
60 HNO.sub.3 2.0 Additive E 759 250 33.9 20 16 222 11.1 13.9 ple 9
abrasive grain a Exam- Polishing 0.5 60 HNO.sub.3 4.0 Additive E
759 250 11.8 30 22 357 11.9 16.2 ple 10 abrasive grain a Compar-
Polishing 0.5 60 HNO.sub.3 3.0 -- -- -- 34.0 234 154 547 2.3 3.6
ative abrasive Exam- grain a ple 1 Compar- Polishing 0.5 60
HNO.sub.3 3.0 Additive A 92 2000 33.8 90 86 533 5.9 6.2 ative
abrasive Exam- grain a ple 2 Compar- Polishing 0.5 70 HNO.sub.3 3.0
Additive E 759 250 -132.0 13 14 9 0.7 0.6 ative abrasive Exam-
grain b ple 3 Compar- Polishing 0.5 70 HNO.sub.3 3.0 Additive E 759
250 7.0 45 22 205 4.6 9.3 ative abrasive Exam- grain c ple 4
Compar- Polishing 0.5 60 HNO.sub.3 5.0 Additive E 759 250 -87.8 26
32 12 0.5 0.4 ative abrasive Exam- grain a ple 5 Compar- Polishing
0.5 60 HNO.sub.3 7.0 Additive E 759 250 -240.7 14 16 14 1.0 0.9
ative abrasive Exam- grain a ple 6
TABLE-US-00002 TABLE 2 Polishing abrasive grain Additive Removal
Content Secondary pH Content Zeta Removal rate rate ratio (% by
particle Compo- MW (ppm by potential (.ANG./min) R.sub.TEOS/ Rteos/
Kind weight) size (nm) nent pH Kind (g/mol) weight) (mV) R.sub.SiGe
R.sub.Si R.sub.TEOS R.sub.SiGe R.sub.Si Exam- Polishing 0.5 60
HNO.sub.3 3.0 Additive J 432 100 26.9 10 11 518 51.8 47.1 ple 11
abrasive grain a Exam- Polishing 0.5 60 HNO.sub.3 3.0 Additive K
548 100 28.7 11 12 493 44.8 41.1 ple 12 abrasive grain a Exam-
Polishing 0.5 60 HNO.sub.3 3.0 Additive L 250 100 28.0 11 11 466
42.4 42.4 ple 13 abrasive grain a
[0134] Please refer to Examples 1 to 8 in Table 1, Examples 11 to
13 in Table 2, and Comparative Example 1 in Table 1. The other
experimental conditions in Examples 1 to 8 and 11 to 13 and
Comparative Example 1 are all the same or similar except that an
additive having the structure represented by Formula (I) is not
used in Comparative Example 1. From the experimental results, it is
indicated that the removal rate ratio values
(R.sub.TEOS/R.sub.SiGe) and (R.sub.TEOS/R.sub.Si) in Comparative
Example 1 are 2.3 and 3.6, respectively, that is, are both less
than 10. As compared to this, an additive having the structure
represented by Formula (I) (namely, additive B, C, D, E, F, G, H,
or I) is used in all of Examples 1 to 8, and the removal rate ratio
values (R.sub.TEOS/R.sub.SiGe) and (R.sub.TEOS/R.sub.Si) in
Examples 1 to 8 and 11 to 13 are all greater than 10. As can be
seen from this, the polishing composition containing an additive
having the structure represented by Formula (I) can significantly
increase the polishing selectivity of TEOS to silicon-germanium or
silicon.
[0135] Please refer to Examples 1 to 8 in Table 1, Examples 11 to
13 in Table 2, and Comparative Example 2 in Table 1. The other
experimental conditions in Examples 1 to 8 and 11 to 13 and
Comparative Example 2 are all the same or similar except that the
additive used in Comparative Example 2 is not an additive that
satisfies all the conditions of the structure represented by
Formula (I). From the experimental results, it is indicated that
the removal rate ratio values (R.sub.TEOS/R.sub.SiGe) and
(R.sub.TEOS/R.sub.Si) in Comparative Example 2 are 5.9 and 6.2,
respectively, that is, are both less than 10. Incidentally, it
should be noted that the additive used in Comparative Example 2 is
glycerol (weight average molecular weight: 92), the structure of
glycerol is similar to the structure represented by Formula (I),
the difference is that the chain segment of the main chain is
relatively short, the hydrophilicity of the additive molecule is
relatively strong, and the weight average molecular weight is also
relatively small. As can be seen from this, the number of
hydrophobic chain segments of the additive molecule excessively
decreases when the weight average molecular weight of the additive
molecule is excessively small or the hydrophilicity is excessively
strong even if the structure of the additive used is similar, and
this is insufficient to effectively increase the polishing
selectivity of TEOS to silicon-germanium or silicon. In addition,
the removal rate R.sub.TEOS (533 .ANG./min) of the TEOS substrate
in Comparative Example 2 is slightly lower than the removal rate
R.sub.TEOS (547 .ANG./min) of the TEOS substrate in Comparative
Example 1 in which an additive is not used. From this, it can be
seen that there is a possibility that the use of additives also
leads to a decrease in the removal rate of oxides.
[0136] Please refer to Example 4 and Comparative Example 3 in Table
1. The other experimental conditions in Example 4 and Comparative
Example 3 are all the same or similar except that the surface zeta
potential of the polishing abrasive grains b used in Comparative
Example 3 is a negative value (namely, -132.0 mV). From the
experimental results, it is indicated that the removal rate ratio
values (R.sub.TEOS/R.sub.SiGe) and (R.sub.TEOS/R.sub.Si) in
Comparative Example 3 are 0.7 and 0.6, respectively, that is, are
both far less than 10. Incidentally, it should be noted that the
removal rate of the TEOS substrate has significantly decreased and
thus the removal rate R.sub.TEOS (9 .ANG./min) of the TEOS
substrate is lower than the removal rate R.sub.SiGe (13 .ANG./min)
of the silicon-germanium substrate and the removal rate R.sub.Si
(14 .ANG./min) of the Poly-Si substrate in Comparative Example
3.
[0137] Please refer to Example 4 and Comparative Example 4 in Table
1. The other experimental conditions in Example 4 and Comparative
Example 4 are all the same or similar except that the silanol group
density on the surface of the polishing abrasive grains c used
in
[0138] Comparative Example 4 is 4.5 groups/nm.sup.2. From the
experimental results, it is indicated that the removal rate ratio
values (R.sub.TEOS/R.sub.SiGe) and (R.sub.TEOS/R.sub.Si) in
Comparative Example 4 are 4.6 and 9.3, respectively, that is, are
both less than 10. As can be seen from this, it is difficult to
effectively increase the polishing selectivity of TEOS to
silicon-germanium or silicon when polishing abrasive grains having
an excessively high silanol group density is used. Furthermore, in
Example 4 and Comparative Example 4, the removal rates R.sub.TEOS
of the TEOS substrate are 608 .ANG./min and 205 .ANG./min,
respectively. In other words, the removal rate R.sub.TEOS of the
TEOS substrate in Comparative Example 4 is only about 1/3 of that
in Example 4. As can be seen from this, the removal rate of the
TEOS substrate significantly decreases when polishing abrasive
grains having an excessively high silanol group density is used,
and this increases the time required for the polishing step.
[0139] Please refer to Examples 4, 9, and 10 and Comparative
Examples 5 and 6 in Table 1. The other experimental conditions in
Examples 4, 9, and 10 and Comparative Examples 5 and 6 are all the
same or similar except that the pH in Examples 4, 9 and 10 and
Comparative Examples 5 and 6 are 2.0, 3.0, 4.0, 5.0, and 7.0,
respectively. Incidentally, it should be noted that polishing
abrasive grains a are used in all of these, but the surface zeta
potentials of the polishing abrasive grains in Comparative Examples
5 and 6 are both negative values (-87.8 mV and -240.7 mV in
Comparative Examples 5 and 6, respectively) and the surface zeta
potentials of the polishing abrasive grains in Examples 4, 9, and
10 are all positive values (36.7 mV, 33.9 mV, and 11.8 mV in
Examples 4, 9, and 10, respectively). As can be seen from this, the
surface zeta potentials of the polishing abrasive grains also
differ under different pH conditions even when the same polishing
abrasive grains are used. From the experimental results, it is
indicated that the removal rate ratio values
(R.sub.TEOS/R.sub.SiGe) and (R.sub.TEOS/R.sub.Si) in Comparative
Example 5 are 0.5 and 0.4, respectively and the removal rate ratio
values (R.sub.TEOS/R.sub.SiGe) and (R.sub.TEOS/R.sub.Si) in
Comparative Example 6 are 1.0 and 0.9, respectively. In other
words, in Comparative Examples 5 and 6, the removal rate ratio
values (R.sub.TEOS/R.sub.SiGe) and (R.sub.TEOS/R.sub.Si) are both
much smaller than 10. Furthermore, in Comparative Examples 5 and 6,
the removal rate of the TEOS substrate has significantly decreased
and thus the removal rates R.sub.TEOS (12 .ANG./min and 14
.ANG./min, respectively) of the TEOS substrate are both equal to or
less than the removal rates R.sub.SiGe (26 .ANG./min and 14
.ANG./min, respectively) of the silicon-germanium substrate and the
removal rates R.sub.Si (32 .ANG./min and 16 .ANG./min,
respectively) of the Poly-Si substrate.
[0140] Please refer to Examples 1 to 10 in Table 1 and Examples 11
to 13 in Table 2. The polishing compositions respectively used in
Examples 1 to 10 all contain polishing abrasive grains (namely,
polishing abrasive grains a) that satisfy the specific silanol
group density range and an additive that satisfies all the
conditions of the structure represented by Formula (I) (namely,
additive B, C, D, E, F, G, H, I, J, K, or L), and the pH of the
polishing compositions satisfies the acidic range specified above
(namely, 2.0, 3.0, or 4.0). From the experimental results, it is
indicated that the removal rate ratio values
(R.sub.TEOS/R.sub.SiGe) and (R.sub.TEOS/R.sub.Si) in Examples 1 to
13 are all greater than 10. As can be seen from this, the polishing
selectivity of TEOS to silicon-germanium or silicon significantly
increases when a polishing composition in which an additive having
the structure represented by Formula (I) is combined with specific
polishing abrasive grains is used under a specific pH condition. In
addition, as compared to the removal rate R.sub.TEOS (533
.ANG./min) of the TEOS substrate in Comparative Example 2, the
removal rates R.sub.TEOS (626 .ANG./min, 637 .ANG./min, 595
.ANG./min, 608 .ANG./min, 574 .ANG./min, and 598 .ANG./min,
respectively) of the TEOS substrate in Examples 1 to 6 have all
increased by 8% or more. As can be seen from this, the removal rate
of oxides can be further increased and the time required for the
polishing step is shortened by adjusting the kind and content of
additive.
[0141] In summary, the polishing composition according to the
present invention contains polishing abrasive grains satisfying
specific conditions and an additive having a specific structure and
can significantly increase the polishing selectivity of an oxide to
a silicon-containing material in a specific pH environment. When an
object to be polished containing a silicon-containing material and
an oxide is polished using the polishing composition according to
the present invention, the silicon-containing material can be used
as a polishing stop layer at the time of oxide polishing. Hence,
the surface flatness of the object to be polished can be improved,
the complexity of process can be simplified, and the time and cost
required for production can be decreased. Furthermore, in the
polishing composition according to the present invention, the
removal rate of an oxide can be adjusted by adjusting the kind and
content of additive. For example, the removal rate of an oxide can
be further increased, and the time required for the polishing step
can be shortened.
[0142] In addition, the polishing composition according to the
present invention can be used in a chemical mechanical polishing
process and is useful to obtain a substrate having a flat surface.
Accordingly, the polishing composition has industrial
applicability.
[0143] The present invention has been disclosed above in some
preferred embodiments, but these do not limit the present
invention, and those skilled in the art can, of course, make any
changes and modifications without departing from the spirit and
scope of the present invention. Accordingly, the scope of
protection of the present invention is based on what is defined in
the claims to be described later.
[0144] This application is based on the foreign language
specification submitted as attachment to the application of
Japanese Patent Application No. 2019-209538 filed on Nov. 20, 2019,
the entire contents of which are incorporated herein by
reference.
REFERENCE SIGNS LIST
[0145] Nil
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