JP7475184B2 - Polishing composition for silicon oxide film - Google Patents

Description

The present invention relates to a polishing composition for silicon oxide films, and a manufacturing method and polishing method for semiconductor devices using the same.

Chemical mechanical polishing (CMP) is a technique in which the surface of the substrate to be polished is brought into contact with a polishing pad, and a polishing liquid composition is supplied to the contact area while the substrate and polishing pad are moved relative to each other, chemically reacting with the uneven surface of the substrate to be polished and mechanically removing and planarizing it.

Currently, CMP technology is essential in the manufacturing process of semiconductor devices when flattening interlayer insulating films, forming shallow trench isolation structures (hereinafter also referred to as "isolation structures"), forming plugs and buried metal wiring, etc. In recent years, semiconductor devices have become increasingly multi-layered and highly precise, and there is a demand for high-speed polishing while maintaining good flatness.

Patent Document 1 discloses a chemical mechanical polishing composition that contains a specific functionalized heterocycle and a cationic polymer (quaternary amine) for the purpose of improving the polishing rate of a silicon oxide film layer. Patent Document 2 discloses a CMP composition suitable for polishing a substrate containing a metal component such as tungsten, which contains silica, an amino compound, a radical-generating oxidizing agent, and a radical scavenger such as a hydroxyl-substituted polyunsaturated cyclic compound.

JP 2018-513229 A JP 2015-195391 A

In recent years, semiconductor elements have become finer, and the line width of the pattern (unevenness) of the object to be polished ranges from several hundred μm to a few μm. For surfaces with unevenness, the convex parts are preferentially polished, but conventional polishing compositions have a problem of high line width dependency, in that the polishing speed of convex parts with different line widths varies greatly depending on the difference in line width or pattern density. For example, as shown in Figure 1, when polishing both a region with a small line width (S1) and a region with a large line width (S2), the convex parts of region S1 are preferentially polished over region S2, resulting in poor flatness of the finished product.

The present invention provides a polishing composition for silicon oxide films that can reduce the line width dependency of the polishing speed in a concave-convex pattern while simultaneously achieving high-speed polishing, as well as a manufacturing method and polishing method for a semiconductor device that use the same.

In one aspect, the present invention relates to a polishing liquid composition for silicon oxide films, which contains cerium oxide particles, preferably negatively charged cerium oxide particles, a water-soluble polymeric compound, a nitrogen-containing heteroaromatic compound, and an aqueous medium, and the water-soluble polymeric compound is a water-soluble polymeric compound that contains a structural unit a that contains a betaine structure and a structural unit b that is a structural unit other than the structural unit a and contains at least one group selected from a primary amino group, a secondary amino group, a tertiary amino group, a quaternary ammonium group, and salts thereof.

In another aspect, the present invention relates to a method for manufacturing a semiconductor substrate, which includes a step of polishing a film to be polished using the polishing composition for silicon oxide films of the present invention.

In yet another aspect, the present invention relates to a polishing method including a step of polishing a film to be polished using the polishing composition for silicon oxide films of the present invention.

In yet another aspect, the present invention provides a polishing liquid kit for preparing a polishing composition for a silicon oxide film, comprising:
a first liquid in which cerium oxide particles are dispersed in an aqueous medium;
a second liquid that is contained in a container separate from the container in which the first liquid is contained and that contains an aqueous medium;
One or both of the first liquid and the second liquid further contains a water-soluble polymer compound;
One or both of the first liquid and the second liquid further contains a nitrogen-containing heteroaromatic compound;
the water-soluble polymer compound includes a structural unit a having a betaine structure and a structural unit b which is a structural unit other than the structural unit a and includes at least one group selected from a primary amino group, a secondary amino group, a tertiary amino group, a quaternary ammonium group, and salts thereof.

In yet another aspect, the present invention provides an additive composition for polishing a silicon oxide film, which is used together with a dispersion in which cerium oxide particles are dispersed in an aqueous medium, comprising:
The present invention comprises an aqueous medium, and a water-soluble polymer compound and a nitrogen-containing heteroaromatic compound dissolved in the aqueous medium,
The water-soluble polymer compound relates to an additive composition for polishing silicon oxide films, which is a water-soluble polymer compound containing a structural unit a containing a betaine structure and a structural unit b which is a structural unit other than the structural unit a and contains at least one group selected from a primary amino group, a secondary amino group, a tertiary amino group, a quaternary ammonium group, and salts thereof.

When the silicon oxide film polishing composition of the present invention, the polishing liquid kit for preparing the silicon oxide film polishing liquid composition of the present invention, and the additive composition for silicon oxide film polishing used in preparing the silicon oxide film polishing liquid composition of the present invention are used to polish a silicon oxide film that includes uneven patterns of mutually different widths, it is possible to reduce the line width dependency of the polishing speed in the uneven pattern and achieve high-speed polishing. A method for manufacturing a semiconductor device and a method for polishing a silicon oxide film using the silicon oxide film polishing liquid composition of the present invention can contribute to improving the productivity of semiconductor devices.

FIG. 1 is a schematic diagram showing one manufacturing process of a semiconductor device.

In one or more embodiments, the present invention provides a polishing composition for silicon oxide films, comprising cerium oxide particles (component A), a water-soluble polymeric compound (component B), a nitrogen-containing heteroaromatic compound (component C), and an aqueous medium, wherein the component B is a water-soluble polymeric compound comprising a structural unit a containing a betaine structure and a structural unit b other than the structural unit a, the structural unit b containing at least one group selected from a primary amino group, a secondary amino group, a tertiary amino group, a quaternary ammonium group, and salts thereof. By using the polishing composition for silicon oxide films of the present invention (hereinafter sometimes abbreviated as "polishing composition of the present invention") for polishing silicon oxide films, it is possible to achieve both a reduction in the line width dependency of the polishing rate in a concave-convex pattern and high-speed polishing.

In the present disclosure, a betaine structure refers to a structure having a positive charge and a negative charge in the same molecule, and the charges are neutralized. The betaine structure has the positive charge and the negative charge preferably in positions that are not adjacent to each other, and preferably in positions separated by one or more atoms.

Although the details of the mechanism by which the effects of the present disclosure are manifested are not clear, it is presumed as follows.
As shown in FIG. 1, the polishing rate of a concave-convex pattern having a relatively small line width may be faster than that of a concave-convex pattern having a large line width. The reason for this is considered to be due to the fact that the convex portion having a relatively small line width is pushed (deformed) by the polishing pressure to a greater extent, resulting in a greater frictional force. Although the water-soluble polymer compound (component B) is adsorbed to the silicon oxide film and the cerium oxide particles with a moderate strength and functions as a binder between the silicon oxide film and the cerium oxide particles to improve the polishing rate, it has been discovered that when the polishing liquid composition contains the component B, the polishing rate of a concave-convex pattern having a relatively large line width is faster than that of a concave-convex pattern having a small line width, and the inventors have found that the polishing liquid composition contains both the component B and the nitrogen-containing heteroaromatic compound (component C), and the component C complements the binder function of the concave-convex pattern having a relatively small line width of the component B, thereby improving the uniformity of the polishing rate for patterns having different line widths and reducing the line width dependency of the polishing rate.

[Cerium oxide particles (component A)]
The polishing composition of the present invention contains cerium oxide (hereinafter also referred to as "ceria") particles (hereinafter also simply referred to as "Component A") as abrasive grains. Component A may be one type or a combination of two or more types.
Component A may be positively or negatively charged. From the viewpoint of suppressing ceria residue, component A is preferably negatively charged cerium oxide particles (hereinafter also referred to as "negatively charged ceria"). When component A is negatively charged ceria, it is considered that the electrostatic interaction with the silicon oxide film exhibiting negative charging is weakened, and the residue of ceria on the silicon oxide film can be reduced. The chargeability of component A can be confirmed, for example, by measuring the electric potential (surface potential) on the surface of the abrasive grain obtained by an electroacoustic method (ESA method: Electrokinetic Sonic Amplitude). The surface potential can be measured, for example, using a "Zeta Probe" (manufactured by Kyowa Interface Science Co., Ltd.), and specifically, it can be measured by the method described in the Examples. From the viewpoint of suppressing ceria residue, the surface potential of component A is preferably -10 mV or less, more preferably -25 mV or less, and even more preferably -50 mV or less. And, from the viewpoint of suppressing a decrease in the polishing rate, the surface potential of component A is preferably -150 mV or more, more preferably -100 mV or more.

The manufacturing method, shape, and surface state of component A may not be particularly limited. Examples of component A include colloidal ceria, amorphous ceria, and ceria-coated silica. Colloidal ceria can be obtained by a build-up process, for example, by the method described in Examples 1 to 4 of JP-A 2010-505735. Examples of amorphous ceria include pulverized ceria. One embodiment of pulverized ceria includes sintered pulverized ceria obtained by sintering and pulverizing a cerium compound such as cerium carbonate or cerium nitrate. Other embodiments of pulverized ceria include single crystal pulverized ceria obtained by wet-pulverizing ceria particles in the presence of an inorganic acid or an organic acid. Examples of inorganic acids used during wet-pulverization include nitric acid, and examples of organic acids include organic acids having a carboxyl group, specifically at least one selected from polycarboxylates such as ammonium polyacrylate, picolinic acid, glutamic acid, aspartic acid, aminobenzoic acid, and p-hydroxybenzoic acid. For example, when at least one selected from picolinic acid, glutamic acid, aspartic acid, aminobenzoic acid, and p-hydroxybenzoic acid is used during wet grinding, positively charged ceria can be obtained, and when a polycarboxylate such as ammonium polyacrylate is used during wet grinding, negatively charged ceria can be obtained. Examples of wet grinding methods include wet grinding using a planetary bead mill or the like. Examples of ceria-coated silica include composite particles having a structure in which at least a part of the surface of silica particles is coated with granular ceria, as described in Examples 1 to 14 of JP 2015-63451 A or Examples 1 to 4 of JP 2013-119131 A, and the composite particles can be obtained, for example, by depositing ceria on silica particles.

Examples of the shape of component A include roughly spherical, polyhedral, and raspberry shapes.

From the viewpoint of improving the polishing rate, the average primary particle size of component A is preferably 5 nm or more, more preferably 10 nm or more, and even more preferably 20 nm or more, and from the viewpoint of suppressing the occurrence of polishing scratches, it is preferably 300 nm or less, more preferably 200 nm or less, even more preferably 150 nm or less, even more preferably 100 nm or less, and even more preferably 50 nm or less. In the present disclosure, the average primary particle size of component A is calculated using the BET specific surface area S ( ^m2 /g) calculated by the BET (nitrogen adsorption) method. The BET specific surface area can be measured by the method described in the Examples.

The content of component A in the polishing composition of the present invention is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, and even more preferably 0.15% by mass or more, from the viewpoint of improving the polishing rate of the silicon oxide film, and is preferably 6% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, and even more preferably 0.5% by mass or less, from the viewpoint of suppressing the occurrence of polishing scratches. More specifically, the content of component A is preferably 0.01% by mass or more and 6% by mass or less, more preferably 0.05% by mass or more and 3% by mass or less, even more preferably 0.1% by mass or more and 1% by mass or less, and even more preferably 0.15% by mass or more and 0.5% by mass or less. When component A is a combination of two or more types, the content of component A refers to the total content thereof.

[Water-soluble polymer compound (component B)]
The polishing composition of the present invention contains a water-soluble polymeric compound (hereinafter, also simply referred to as "component B") containing a betaine structure-containing structural unit a and a structural unit b, from the viewpoint of improving the polishing rate. The structural unit b is a structural unit other than the structural unit a, and contains at least one group selected from a primary amino group, a secondary amino group, a tertiary amino group, a quaternary ammonium group, and salts thereof. Here, "water-soluble" means that the compound has a solubility of 0.5 g/100 mL or more in water (20° C.), preferably a solubility of 2 g/100 mL or more. Component B may be one type or a combination of two or more types.

From the viewpoint of improving the polishing rate, the betaine structure of the structural unit a is preferably a sulfobetaine structure, a carbobetaine structure, or a phosphobetaine structure, more preferably a carbobetaine structure or a phosphobetaine structure, and even more preferably a phosphobetaine structure. The phosphobetaine structure is a betaine structure with a phosphate group from which the negative charge has been dissociated, the sulfobetaine structure is a betaine structure with a sulfonic acid group from which the negative charge has been dissociated, and the carbobetaine structure is a betaine structure with a carboxy group from which the negative charge has been dissociated.

(Structural unit a)
From the viewpoint of improving the polishing rate, component B preferably contains a structural unit a1 represented by the following formula (1) as the structural unit a. The structural unit a is, for example, a structural unit derived from an unsaturated monomer containing a betaine structure. The structural unit a may be one type or a combination of two or more types.

In the formula (1),
R ¹ to R ³ are the same or different and each is a hydrogen atom, a methyl group, or an ethyl group;
R ⁴ represents an alkylene group having 1 to 4 carbon atoms, or -Y ¹ -OPO ₃ ^- -Y ² -;
Y ¹ and Y ² are the same or different and each represents an alkylene group having 1 to 4 carbon atoms;
R ⁵ and R ⁶ are the same or different and each is a hydrocarbon group having 1 to 4 carbon atoms;
^X1 is O or ^NR7 ;
^R7 is a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms;
^X2 is ^a _hydrocarbon group having 1 to 4 carbon atoms, ^-R17SO3- or ^{-R18COO- ;}
R ¹⁷ and R ¹⁸ are the same or different and each represents an alkylene group having 1 to 4 carbon atoms.
However, X ² is --R ¹⁷ SO ₃ ^-- or --R ¹⁸ COO ^-- when R ⁴ is an alkylene group having 1 to 4 carbon atoms, and is a hydrocarbon group having 1 to 4 carbon atoms when R ⁴ is --Y ¹ --OPO ₃ ^{--Y 2} --.

From the viewpoints of availability of the unsaturated monomer, polymerizability of the monomer, and improvement of the polishing rate, R ¹ and R ² are each preferably a hydrogen atom.

From the viewpoints of availability of the unsaturated monomer, polymerizability of the monomer, and improvement of the polishing rate, R ³ is preferably a hydrogen atom or a methyl group, and more preferably a methyl group.

X ¹ is preferably O (oxygen atom) from the viewpoints of availability of the unsaturated monomer, polymerizability of the monomer, and improvement of the polishing rate.

From the viewpoint of improving the polishing rate, R ⁴ is preferably an alkylene group having 2 or 3 carbon atoms, or -Y ¹ -OPO ₃ ^- -Y ² -, more preferably an alkylene group having 2 carbon atoms or -Y ¹ -OPO ₃ ^- -Y ² -, and even more preferably -Y ¹ -OPO ₃ ^- -Y ² -. From the viewpoint of easy availability of the unsaturated monomer and polymerizability of the monomer, R 4 is preferably an alkylene group having 2 carbon atoms.

From the viewpoints of availability of the unsaturated monomer, polymerizability of the monomer, and improvement of the polishing rate, Y ¹ and Y ² are each preferably an alkylene group having 2 or 3 carbon atoms, and more preferably an alkylene group having 2 carbon atoms.

From the viewpoints of availability of the unsaturated monomer, polymerizability of the monomer, and improvement of the polishing rate, R ⁵ and R ⁶ are each preferably a methyl group or an ethyl group, and more preferably a methyl group.

When R ⁴ is an alkylene group having 1 to 4 carbon atoms, X ² is -R ¹⁷ SO ₃ ^- or -R ¹⁸ COO ^- , and from the viewpoint of improving the polishing rate, -R ¹⁸ COO ^- is preferable. When R ⁴ is -Y ¹ -OPO ₃ ^- -Y ² -, X ² is a hydrocarbon group having 1 to 4 carbon atoms, and from the viewpoint of improving the polishing rate, a methyl group is more preferable.

From the viewpoints of availability of the unsaturated monomer, polymerizability of the monomer, and improving the polishing rate, the number of carbon atoms in R ¹⁷ is preferably 1 or more and 3 or less, and more preferably 2 or more and 3 or less. From the viewpoints of availability of the unsaturated monomer, polymerizability of the monomer, and improving the polishing rate, the number of carbon atoms in ^{R 18} is preferably 1 or more and 3 or less, and more preferably 1 or more and 2 or less.

When synthesizing component B, specific examples of monomers that provide structural unit a (hereinafter also referred to as monomer a) are, from the viewpoint of improving the polishing rate, preferably at least one monomer selected from sulfobetaine methacrylate, methacryloyloxyethyl phosphorylcholine (MPC), and carboxybetaine methacrylate, more preferably at least one monomer selected from methacryloyloxyethyl phosphorylcholine (MPC) and carboxybetaine methacrylate, and even more preferably methacryloyloxyethyl phosphorylcholine (MPC).

(Structural unit b)
From the viewpoint of improving the polishing rate, component B includes a structural unit b containing at least one group selected from a primary amino group, a secondary amino group, a tertiary amino group, a quaternary ammonium group, and a salt thereof. The nitrogen atoms constituting these groups are preferably adjacent to a carbon atom of an alkylene group (however, the hydrogen atom of the alkylene group may be substituted with a hydroxyl group), and more preferably adjacent to a carbon atom of an alkylene group having two or more carbons (however, the hydrogen atom of the alkylene group may be substituted with a hydroxyl group). From the viewpoint of improving the polishing rate, structural unit b preferably contains at least one group selected from a secondary amino group, a tertiary amino group, a quaternary ammonium group, and a salt thereof, and more preferably contains at least one group selected from a quaternary ammonium group and a salt thereof. The structural unit b may be one type or a combination of two or more types.

Since component B is a copolymer containing a structural unit a containing a betaine structure and a structural unit b containing at least one group selected from a primary amino group, a secondary amino group, a tertiary amino group, a quaternary ammonium group, and salts thereof, it is presumed that the structural unit a contributes to the hydrophilization of the silicon oxide film, and the cerium oxide particles are efficiently supplied to the surface of the silicon oxide film, while the structural unit b exhibits an interaction with the silicon oxide film, promoting the adsorption of component B to the silicon oxide film and the hydrophilization of the silicon oxide film, thereby improving the polishing speed of the silicon oxide film.

From the viewpoint of improving the polishing rate, the structural unit b is preferably, for example, the structural unit b1 represented by the following formula (2).

However, in formula (2),
R ⁸ to R ¹⁰ are the same or different and each represents a hydrogen atom, a methyl group, or an ethyl group;
^X3 is O or ^NR19 ;
R ¹⁹ is a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms;
R ¹¹ is an alkylene group having 1 to 22 carbon atoms (however, a hydrogen atom of the alkylene group may be substituted with a hydroxyl group);
^X4 is N ⁺ R ¹² R ¹³ R ¹⁴ or NR ¹⁵ R ¹⁶ ;
R ¹² to R ¹⁴ are the same or different and each represents a hydrocarbon group having 1 to 4 carbon atoms;
R ¹⁵ and R ¹⁶ are the same or different and each represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms.

From the viewpoints of availability of the unsaturated monomer, polymerizability of the monomer, and improvement of the polishing rate, R ⁸ and R ⁹ are each preferably a hydrogen atom.

From the viewpoints of availability of the unsaturated monomer, polymerizability of the monomer, and improvement of the polishing rate, R ¹⁰ is preferably a hydrogen atom or a methyl group, and more preferably a methyl group.

^X3 is preferably O from the viewpoints of availability of the unsaturated monomer, polymerizability of the monomer, and improvement of the polishing rate.

From the viewpoints of availability of the unsaturated monomer, polymerizability of the monomer, and improvement of the polishing rate, ^X4 is preferably N ⁺ R ¹² R ¹³ R ¹⁴ , and from the same viewpoint, R ¹² to R ¹⁴ are each the same or different and are preferably a methyl group or an ethyl group, more preferably a methyl group. From the same viewpoint, R ¹⁵ to R ¹⁶ are preferably a hydrogen atom. The structural unit b may take the form of a neutralized salt. Examples of the counter ion include halogen ions such as chloride ions, methyl sulfate ions, ethyl sulfate ions, etc., and from the viewpoint of availability, chloride ions are preferred.

From the viewpoints of availability of the unsaturated monomer, polymerizability of the monomer, and improvement of the polishing rate, R ¹¹ is preferably an alkylene group having 1 to 22 carbon atoms (however, a hydrogen atom of the hydrocarbon group may be substituted with a hydroxyl group), and from the similar viewpoints, the number of carbon atoms of the alkylene group is preferably 2 or more, preferably 3 or less, and more preferably 3.

In synthesizing component B, specific examples of monomers that provide structural unit b (hereinafter also referred to as monomer b) are, from the viewpoints of availability of the unsaturated monomer, polymerizability of the monomer, and improvement of the polishing speed, preferably at least one monomer selected from unsaturated monomers having an amino group such as methacrylate having a primary amine, secondary amine, or tertiary amine in the structure, unsaturated monomers having a cationic group such as methacrylate having a quaternary ammonium cation in the structure, methacryloyloxyethyldimethylethylaminium (MOEDES), 2-hydroxy-3-(trimethylaminio)propyl methacrylate (THMPA), methacryloylethyltrimethylaminium (MOETMA), 2-aminoethyl methacrylate (MOEA), and 2-(diethylamino)ethyl methacrylate (MOEDEA), more preferably at least one monomer selected from THMPA, MOEA, and MOEDEA, and even more preferably THMPA.

(Molar ratio of structural unit b to structural unit a)
The molar ratio of the structural unit b to the structural unit a in component B (structural unit b/structural unit a) is preferably 90/10 or less, more preferably 70/30 or less, and even more preferably 40/60 or less from the viewpoint of improving the polishing rate, and from the same viewpoint, it is preferably 5/95 or more, more preferably 15/85 or more. More specifically, the molar ratio (structural unit b/structural unit a) is preferably 5/95 or more and 90/10 or less, more preferably 15/85 or more and 70/30 or less, and even more preferably 15/85 or more and 40/60 or less. In the present disclosure, the molar ratio (structural unit b/structural unit a) can be regarded as the molar ratio of monomer b and monomer a used in the polymerization of component B.

(Structural units other than structural unit a and structural unit b)
Component B may contain a structural unit other than the structural unit a and the structural unit b, as long as the effects of the present invention are not impaired. As the structural unit other than the structural unit a and the structural unit b, a structural unit derived from a hydrophobic unsaturated monomer such as styrene is preferable.

The sum of the content of structural unit a and the content of structural unit b in component B is preferably 99% by mass or more, more preferably 99.5% by mass or more, even more preferably 99.9% by mass or more, and even more preferably 99.95% by mass or more, and may be 100% by mass. In this disclosure, the sum of the content of structural unit a and the content of structural unit b in component B can be regarded as the sum of the mass of monomer b and the mass of monomer a relative to the mass of all monomers used in the polymerization of component B.

(Weight average molecular weight of component B)
From the viewpoint of improving the polishing rate, the weight average molecular weight of component B is preferably 1,000 or more, more preferably 5,000 or more, more preferably 10,000 or more, more preferably 50,000 or more, more preferably 100,000 or more, and more preferably 300,000 or more, and from the same viewpoint, it is preferably 3,000,000 or less, more preferably 2,000,000 or less, more preferably 1,000,000 or less, and more preferably 700,000 or less. More specifically, the weight average molecular weight of component B is preferably 1,000 or more and 3,000,000 or less, more preferably 5,000 or more and 2,000,000 or less, and more preferably 10,000 or more and 1,000,000 or less. The weight average molecular weight of component B can be measured by the method described in the examples.

The content of component B in the polishing composition of the present invention is preferably 0.0005% by mass or more, more preferably 0.001% by mass or more, even more preferably 0.002% by mass or more, even more preferably 0.003% by mass or more, and even more preferably 0.005% by mass or more, from the viewpoint of improving the polishing rate, and from the same viewpoint, it is preferably 1% by mass or less, more preferably 0.7% by mass or less, even more preferably 0.4% by mass or less, even more preferably 0.2% by mass or less, and even more preferably 0.08% by mass or less. More specifically, the content of component B is preferably 0.0005% by mass or more and 1% by mass or less, more preferably 0.001% by mass or more and 0.7% by mass or less, even more preferably 0.002% by mass or more and 0.4% by mass or less, even more preferably 0.003% by mass or more and 0.2% by mass or less, and even more preferably 0.005% by mass or more and 0.08% by mass or less. When component B is a combination of two or more kinds, the content of component B refers to the total content thereof.

The mass ratio A/B of components A and B (content of component A/content of component B) in the polishing composition of the present invention is preferably 0.1 or more, more preferably 1 or more, and even more preferably 5 or more from the viewpoint of improving the polishing rate, and from the same viewpoint, is preferably 500 or less, more preferably 200 or less, even more preferably 120 or less, even more preferably 80 or less, and even more preferably 40 or less. More specifically, the mass ratio A/B is preferably 0.1 or more and 500 or less, more preferably 1 or more and 200 or less, and even more preferably 5 or more and 80 or less.

[Nitrogen-containing heteroaromatic compound (component C)]
From the viewpoint of reducing the line width dependency of the polishing rate, Component C contained in the polishing composition of the present invention is preferably an N-oxide compound containing a nitrogen-containing heteroaromatic ring skeleton in which at least one hydrogen atom is substituted with a hydroxyl group, or a salt thereof. Examples of the salt include alkali metal salts, alkaline earth metal salts, organic amine salts, and ammonium salts. Component C may be used alone or in combination of two or more types.

In this disclosure, in one or more embodiments, an N-oxide compound refers to a compound having an N-oxide group (N→O group). An N-oxide compound can have one or more N→O groups, and from the standpoint of availability, the number of N→O groups is preferably one.

In the present disclosure, at least one nitrogen atom contained in the nitrogen-containing heteroaromatic ring skeleton forms an N-oxide. In one or more embodiments, the nitrogen-containing heteroaromatic ring contained in component C may be a monocyclic or bicyclic condensed ring. In one or more embodiments, the number of nitrogen atoms in the nitrogen-containing heteroaromatic ring contained in component C may be 1 to 3, and from the viewpoints of improving the polishing rate and reducing the line width dependency of the polishing rate, 1 or 2 is preferable, and 1 is more preferable. In one or more embodiments, the nitrogen-containing heteroaromatic ring skeleton contained in component C may be at least one selected from a pyridine N-oxide skeleton, a quinoline N-oxide skeleton, and the like. In the present disclosure, the pyridine N-oxide skeleton refers to a structure in which a nitrogen atom contained in a pyridine ring forms an N-oxide. The quinoline N-oxide skeleton refers to a structure in which a nitrogen atom contained in a quinoline ring forms an N-oxide.

In one or more embodiments, component C may be at least one selected from an N-oxide compound having a pyridine ring in which at least one hydrogen atom is substituted with a hydroxy group, an N-oxide compound having a quinoline ring in which at least one hydrogen atom is substituted with a hydroxy group, and salts thereof. Among these, from the viewpoint of improving the polishing rate, component B is preferably an N-oxide compound having a pyridine ring in which at least one hydrogen atom is substituted with a hydroxy group, or a salt thereof.

Specific examples of component C include 2-hydroxypyridine N-oxide, 3-hydroxypyridine N-oxide, and 8-hydroxyquinoline N-oxide.

The content of component C in the polishing composition of the present invention is preferably 0.001% by mass or more, more preferably 0.002% by mass or more, even more preferably 0.005% by mass or more, and even more preferably 0.01% by mass or more, from the viewpoint of improving the polishing rate and reducing the line width dependency of the polishing rate, and from the same viewpoint, it is preferably 1% by mass or less, more preferably 0.5% by mass or less, even more preferably 0.1% by mass or less, and even more preferably 0.05% by mass or less. More specifically, the content of component C is preferably 0.001% by mass or more and 1% by mass or less, more preferably 0.002% by mass or more and 0.5% by mass or less, even more preferably 0.005% by mass or more and 0.1% by mass or less, and even more preferably 0.01% by mass or more and 0.05% by mass or less. When component C is a combination of two or more types, the content of component C refers to the total content thereof.

The mass ratio A/C (content of component A/content of component C) of components A and C in the polishing composition of the present invention is preferably 0.001 or more, more preferably 0.1 or more, even more preferably 0.7 or more, even more preferably 1.6 or more, even more preferably 3 or more, even more preferably 10 or more, and preferably 6000 or less, more preferably 200 or less, even more preferably 70 or less, and even more preferably 25 or less, from the viewpoint of improving the polishing rate. More specifically, the mass ratio A/C is preferably 0.001 or more and 6000 or less, more preferably 0.1 or more and 200 or less, even more preferably 0.7 or more and 70 or less, and even more preferably 1.6 or more and 25 or less.

The mass ratio B/C (content of component B/content of component C) of components B to C in the polishing composition of the present invention is preferably 0.01 or more, more preferably 0.05 or more, even more preferably 0.1 or more, even more preferably 0.5 or more, and preferably 100 or less, more preferably 20 or less, even more preferably 10 or less, and even more preferably 5 or less, from the viewpoint of improving the polishing rate and reducing the line width dependency of the polishing rate. More specifically, the mass ratio B/C is preferably 0.01 or more and 100 or less, more preferably 0.05 or more and 20 or less, even more preferably 0.1 or more and 10 or less, and even more preferably 0.5 or more and 5 or less.

[Aqueous medium]
The polishing composition of the present invention contains an aqueous medium as a medium. Examples of the aqueous medium include water and a mixture of water and a water-soluble solvent. Examples of the water-soluble solvent include alcohols such as methanol, ethanol, and isopropanol, and ethanol is preferred from the viewpoint of improving safety when polishing a silicon oxide film. In addition, the aqueous medium is more preferably water such as ion-exchanged water, distilled water, and ultrapure water from the viewpoints of improving the quality of semiconductor devices, improving the handling of the polishing composition due to its low volatility, and improving safety when polishing a silicon oxide film.

The content of the aqueous medium in the polishing composition of the present invention can be the remainder excluding components A, B, C, and the optional components described below.

[Optional ingredients]
The polishing composition of the present invention may further contain optional components such as pH adjusters, surfactants, thickeners, dispersants, rust inhibitors, preservatives, basic substances, polishing rate enhancers, silicon nitride film polishing inhibitors, and polysilicon film polishing inhibitors. When the polishing composition of the present invention further contains optional components, the content of the optional components in the polishing composition of the present invention is preferably 0.001 mass% or more, more preferably 0.0025 mass% or more, even more preferably 0.01 mass% or more, and preferably 1 mass% or less, more preferably 0.5 mass% or less, and even more preferably 0.1 mass% or less, from the viewpoint of improving the polishing rate. More specifically, the content of the optional components is preferably 0.001 mass% or more and 1 mass% or less, more preferably 0.0025 mass% or more and 0.5 mass% or less, and even more preferably 0.01 mass% or more and 0.1 mass% or less.

[Polishing composition]
The polishing composition of the present invention can be produced by a production method including a step of blending a dispersion (slurry) containing cerium oxide particles (component A) and an aqueous medium, component B, component C, and other optional components as necessary, by a known method. For example, the polishing composition of the present invention is obtained by blending a slurry containing component A and an aqueous medium, a solution containing component B, component C, and an aqueous medium, and other optional components as necessary. In the present invention, "blending" includes mixing component A, component B, component C, and an aqueous medium, and other optional components as necessary, simultaneously or in sequence. The order of mixing is not particularly limited. The blending can be performed using a mixer such as a homomixer, a homogenizer, an ultrasonic disperser, and a wet ball mill. The blending amount of each component in the production method of the polishing composition of the present invention can be the same as the content of each component in the polishing composition of the present invention described above.

The polishing composition of the present invention may be of the so-called one-component type, in which all components are premixed and supplied to the market, or of the so-called two-component type, in which components are mixed at the time of use.

The pH of the polishing composition of the present invention is preferably 2.5 or more, more preferably 3 or more, even more preferably 3.5 or more, even more preferably 4 or more, and even more preferably 5.5 or more from the viewpoint of improving the polishing rate, and is preferably 12 or less, more preferably 11.5 or less, and even more preferably 11 or less from the viewpoint of storage stability. When the polishing composition of the present invention is used for polishing a silicon oxide film on a silicon nitride film, the pH of the polishing composition of the present invention is preferably 2.5 or more, more preferably 3 or more, even more preferably 3.5 or more, even more preferably 4 or more, and is preferably 9.5 or less, more preferably 8 or less, even more preferably 8.5 or less, and even more preferably 7.5 or less, from the viewpoint of ensuring the polishing rate of the silicon oxide film and improving the polishing selectivity. In the present invention, the pH of the polishing composition is a value at 25°C, and is a value measured using a pH meter. The pH of the polishing composition of the present invention can be specifically measured by the method described in the Examples.

In the present invention, the "content of each component in the polishing composition" refers to the content of each component at the time when the polishing composition is used for polishing. The polishing composition of the present invention may be stored and supplied in a concentrated state to the extent that its stability is not impaired. In this case, it is preferable in that the manufacturing and transportation costs can be reduced. If necessary, this concentrated liquid can be appropriately diluted with the above-mentioned aqueous medium and used in the polishing process. The dilution ratio is preferably 5 to 100 times.

[Film to be polished]
The polishing composition of the present invention enables high-speed polishing of silicon oxide films, and can therefore be suitably used for polishing silicon oxide films constituting a three-dimensional NAND-type flash memory in which recording elements are arranged three-dimensionally, or for polishing silicon oxide films used in the process of forming an element isolation structure of a semiconductor device or the like.

[Polishing liquid kit]
In another aspect, the present invention is a polishing liquid kit for preparing a polishing liquid composition for silicon oxide film, comprising a first liquid in which cerium oxide particles (component A) are dispersed in an aqueous medium, and a second liquid which is contained in a container separate from the container in which the first liquid is contained and contains an aqueous medium, wherein either or both of the first liquid and the second liquid further contain a water-soluble polymer compound (component B), either or both of the first liquid and the second liquid further contain a nitrogen-containing heteroaromatic compound (component C), and the water-soluble polymer compound (component B) is a water-soluble polymer compound which contains a structural unit a containing a betaine structure and a structural unit b which is a structural unit other than the structural unit a and contains at least one group selected from a primary amino group, a secondary amino group, a tertiary amino group, a quaternary ammonium group, and salts thereof. The polishing liquid kit of the present invention is composed of, for example, a cerium oxide particle dispersion liquid (first liquid) in which cerium oxide particles (component A) are dispersed in an aqueous medium, and the remainder (second liquid), each of which is contained in a separate container and stored in an unmixed state, and is mixed when used.

It is composed of a cerium oxide particle dispersion liquid (first liquid) and the remainder (second liquid), each of which is contained in a separate container and stored in an unmixed state, and is mixed when used. Component B may be contained in either or both of the first and second liquids. Component C may be contained in either or both of the first and second liquids. The first and second liquids may each contain the above-mentioned [optional components] as optional components as necessary. The first and second liquids may be mixed before being supplied to the surface of the object to be polished, or they may be supplied separately and mixed on the surface of the substrate to be polished.

The content of each component in the first liquid and the second liquid may be set so that when the first liquid and the second liquid are mixed, the content will be the preferred content in the polishing liquid composition at the time when the polishing liquid composition is used for polishing, or when the first liquid, the second liquid, and water are mixed, the content will be the preferred content in the polishing liquid composition at the time when the polishing liquid composition is used for polishing.

[Additive composition for polishing silicon oxide film]
In another aspect, the present invention relates to an additive composition for polishing silicon oxide films (hereinafter, abbreviated as "additive composition"), which is used together with a dispersion liquid (first liquid) in which cerium oxide particles are dispersed in an aqueous medium, and which contains an aqueous medium, a water-soluble polymer compound (component B) and a nitrogen-containing heteroaromatic compound (component C) dissolved in the aqueous medium. The water-soluble polymer compound (component B) is a water-soluble polymer compound containing a structural unit a containing a betaine structure and a structural unit b other than the structural unit a, which contains at least one group selected from a primary amino group, a secondary amino group, a tertiary amino group, a quaternary ammonium group, and salts thereof. The additive composition may contain the above-mentioned [optional component] as an optional component as required. The additive composition is mixed with an aqueous dispersion liquid of cerium oxide particles supplied separately from the additive composition at the time of use, and an aqueous medium and optional components are mixed as required, thereby obtaining a polishing liquid composition that can reduce the line width dependency of the polishing speed in a concave-convex pattern and achieve high-speed polishing at the same time.

The content of component B in the additive composition is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, and even more preferably 0.03% by mass or more, from the viewpoint of concentrating the additive composition, and is preferably 30% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, from the viewpoint of ease of handling when mixed with the aqueous dispersion of cerium oxide particles. More specifically, the content of component B in the additive composition is preferably 0.005% by mass or more and 30% by mass or less, more preferably 0.01% by mass or more and 10% by mass or less, and even more preferably 0.03% by mass or more and 5% by mass or less.

The content of component C in the additive composition is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, and even more preferably 0.03% by mass or more, from the viewpoint of concentrating the additive composition, and is preferably 30% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, from the viewpoint of ease of handling when mixed with the aqueous dispersion of cerium oxide particles. More specifically, the content of component C in the additive composition is preferably 0.005% by mass or more and 30% by mass or less, more preferably 0.01% by mass or more and 10% by mass or less, and even more preferably 0.03% by mass or more and 5% by mass or less.

[Method of Manufacturing Semiconductor Device]
In another aspect, the present invention relates to a method for manufacturing a semiconductor substrate (hereinafter also referred to as "the method for manufacturing a semiconductor substrate of the present invention"), which includes a step of polishing a film to be polished with the polishing composition of the present invention (hereinafter also referred to as "the polishing step using the polishing composition of the present invention"). The method for manufacturing a semiconductor substrate of the present invention relates to a method for manufacturing a semiconductor device, which includes, for example, a step of polishing a surface of a silicon oxide film opposite to a surface in contact with a silicon nitride film, for example, an uneven step surface of a silicon oxide film, with the polishing composition of the present invention. According to the method for manufacturing a semiconductor device of the present invention, a silicon oxide film can be polished at high speed, and therefore an effect of efficiently manufacturing a semiconductor device can be achieved.

The uneven step surface of the silicon oxide film may be formed naturally in correspondence with the uneven steps of the lower layer of the silicon oxide film when the silicon oxide film is formed by a method such as chemical vapor deposition, or may be obtained by forming an uneven pattern using a method such as lithography.

In a specific example of the method for manufacturing a semiconductor substrate of the present invention, a silicon dioxide layer is grown on the surface of a silicon substrate by exposing the silicon substrate to oxygen in an oxidation furnace, and then a polishing stopper film such as a silicon nitride (Si ₃ N ₄ ) film or a polysilicon film is formed on the silicon dioxide layer by, for example, a CVD method (chemical vapor deposition method). Next, a trench is formed by photolithography in a substrate including a silicon substrate and a polishing stopper film disposed on one main surface side of the silicon substrate, for example, a substrate in which a polishing stopper film is formed on a silicon dioxide layer of a silicon substrate. Next, a silicon oxide (SiO 2 ) film, which is a polishing film to be filled in the trench, is formed by, for example, _a CVD method using silane gas and oxygen gas, to obtain a polishing substrate in which the polishing stopper film is covered with the polishing film (silicon oxide film). By forming the silicon oxide film, the trench is filled with silicon oxide of the silicon oxide film, and the surface of the polishing stopper film opposite to the surface on the silicon substrate side is covered with the silicon oxide film. The surface of the silicon oxide film formed in this manner opposite to the surface on the silicon substrate side has a step formed in accordance with the unevenness of the underlying layer. Next, the silicon oxide film is polished by CMP until at least the surface of the polishing stopper film opposite to the surface on the silicon substrate side is exposed, and more preferably, the silicon oxide film is polished until the surface of the silicon oxide film and the surface of the polishing stopper film become flush with each other. The polishing composition of the present invention can be used in the step of performing polishing by CMP.

In a polishing process using the polishing composition of the present invention, the rotation speed of the polishing pad can be, for example, 30 to 200 r/min, the rotation speed of the substrate to be polished can be, for example, 30 to 200 r/min, the polishing load set in the polishing apparatus equipped with the polishing pad can be, for example, 20 to 500 gf/ ^cm2 , and the supply rate of the polishing composition can be, for example, 10 to 500 mL/min or less.

In the polishing process using the polishing composition of the present invention, the polishing pad may be made of any conventional material. Examples of the polishing pad material include organic polymer foams such as rigid polyurethane foam and non-foamed materials, with rigid polyurethane foam being preferred.

[Method of polishing silicon oxide film]
In another aspect, the present invention relates to a polishing method (hereinafter also referred to as "polishing method of the present invention") comprising a step of polishing a film to be polished with the polishing composition of the present invention. The polishing method of the present invention relates to a method for polishing a silicon oxide film, which comprises, for example, a step of polishing a silicon oxide film with the polishing composition for silicon oxide film of the present invention, and the silicon oxide film is an insulating film formed in the manufacturing process of a semiconductor device. The step includes, for example, a step of polishing a silicon oxide film on a silicon nitride film.

By using the polishing method of the present invention, the polishing speed can be improved, which can have the effect of improving the productivity of semiconductor devices. The specific polishing method and conditions can be the same as those of the manufacturing method of the semiconductor device of the present invention described above.

The present disclosure will be explained in detail below with reference to examples, but the present disclosure is not limited to these examples.

1. Preparation of polishing compositions [Preparation of polishing compositions of Examples 1 to 11 and Comparative Examples 1 to 4]
Polishing liquid compositions of Examples 1 to 11 and Comparative Examples 1 to 4 were prepared by mixing a cerium oxide particle slurry in which cerium oxide particles were dispersed in an aqueous medium with an additive composition obtained by dissolving a water-soluble polymeric compound and a nitrogen-containing heteroaromatic compound in an aqueous medium and adding a pH adjuster as necessary. However, the water-soluble polymeric compound and the nitrogen-containing heteroaromatic compound were not added to the polishing liquid composition of Comparative Example 1, and the nitrogen-containing heteroaromatic compound was not added to the polishing liquid composition of Comparative Example 2. A 1N nitric acid aqueous solution or a 1N ammonium aqueous solution was used as the pH adjuster. The pH at 25°C of the polishing liquid compositions of Examples 1 to 11 and Comparative Examples 1 to 4 is as shown in Table 2. The contents of the cerium oxide particles, the water-soluble polymeric compound, and the nitrogen-containing heteroaromatic compound in each polishing liquid composition were as shown in Table 2. The content of the aqueous medium is the remainder excluding the cerium oxide particles, the water-soluble polymeric compound, and the nitrogen-containing heteroaromatic compound. Water was used as the aqueous medium.

Details of the cerium oxide particles used in preparing the polishing compositions of Examples 1 to 11 and Comparative Examples 1 to 4 are as follows.
Negatively charged ceria (ground ceria, average primary particle size = 37.9 nm, surface potential = -57.2 mV)

Details of the nitrogen-containing heteroaromatic compounds used in the preparation of the polishing compositions of Examples 1 to 11 and Comparative Examples 3 and 4 are shown below and in Table 2.
C1: 2-hydroxypyridine N-oxide (Tokyo Chemical Industry Co., Ltd.)
C2: 3-hydroxypyridine N-oxide (Tokyo Chemical Industry Co., Ltd.)

Details of the constituent monomers of the water-soluble polymer compounds used in the preparation of the polishing compositions of Examples 1 to 11 and Comparative Examples 2 to 4 are shown below and in Table 1.
MPC: 2-methacryloyloxyethyl phosphorylcholine THMPA: 2-hydroxy-3-(trimethylaminio)propyl methacrylate MOEA: 2-aminoethyl methacrylate

[Water-soluble polymer compound B1]
Copolymer of THMAP (2-hydroxy-3-(trimethylaminio)propyl methacrylate) and MPC (2-methacryloyloxyethyl phosphorylcholine) (Lipidure-C, NOF Corporation, weight average molecular weight 500,000)

[Production of Water-soluble Polymer Compound B2]
52 g of ultrapure water was placed in a 500 mL four-neck flask and heated to 65°C. A solution of 5.0 g of 2-methacryloyloxyethyl phosphorylcholine (Tokyo Chemical Industry Co., Ltd.), 0.42 g of Blenmar QA (NOF Corp.), and 35 g of ultrapure water, and a solution of 0.048 g of V-50 (Wako Pure Chemical Industries, Ltd.), and 17 g of ultrapure water were separately added dropwise over 2 hours to polymerize. After aging for 6 hours, the mixture was returned to room temperature to obtain an aqueous polymer solution containing water-soluble polymer compound B2. The molar ratio (THMPA/MPC) of the structural units in water-soluble polymer compound B2 was 5/95, and the weight average molecular weight of water-soluble polymer compound B2 was 300,000.

[Production of Water-soluble Polymer Compound B3]
57 g of ultrapure water was placed in a 500 mL four-neck flask and heated to 65°C. A solution of 5.0 g of 2-methacryloyloxyethyl phosphorylcholine (Tokyo Chemical Industry Co., Ltd.), 0.70 g of 2-aminoethyl methacrylate hydrochloride (SIGMA-ALDRICH), and 38 g of ultrapure water, and a solution of 0.057 g of V-50 (Wako Pure Chemical Industries, Ltd.) and 19 g of ultrapure water were separately added dropwise over 2 hours to polymerize. After aging for 6 hours, the mixture was returned to room temperature to obtain an aqueous polymer solution containing water-soluble polymer compound B3. The molar ratio (MOEA/MPC) of the structural units in water-soluble polymer compound B3 was 20/80, and the weight average molecular weight of water-soluble polymer compound B3 was 330,000.

[Water-soluble polymer compound B4]
Copolymer of MPC (2-methacryloyloxyethyl phosphorylcholine), BMA (butyl methacrylate) and MAA (sodium methacrylate) (Lipidure-A, NOF Corporation, weight average molecular weight 500,000)

[Water-soluble polymer compound B5]
Homopolymer of DADMAC (diallyldimethylammonium chloride) (Unisense FPA100L, manufactured by Senka Co., Ltd., weight average molecular weight 350,000)

2. Measurement methods for various parameters [Weight average molecular weight of water-soluble polymer compound]
The weight average molecular weight of the water-soluble polymer compound used in preparing the polishing composition was calculated based on a peak in a chromatogram obtained by applying gel permeation chromatography (GPC) under the following conditions.
Apparatus: HLC-8320 GPC (Tosoh Corporation, detector integrated type)
Column: Two TSKgel α-M columns (manufactured by Tosoh Corporation) connected in series Eluent: 0.15 mol _{Na 2} SO ₄ /1% CH ₃ COOH/water Flow rate: 1.0 mL/min
Column temperature: 40°C
Detector: RI Detector standard material: Pullulan

[pH of polishing composition]
The pH value of the polishing composition at 25° C. was measured using a pH meter (Toa Denpa Kogyo Co., Ltd., HM-30G) and was the value one minute after the electrode was immersed in the polishing composition.

[Average primary particle size of cerium oxide particles]
The average primary particle diameter (nm) of cerium oxide particles means the particle diameter (converted into a spherical particle) calculated by the following formula using the specific surface area S ( ^m2 /g) calculated by the BET (nitrogen adsorption) method, and is calculated by the following formula.
In the following formula, the specific surface area S was determined by drying 10 g of a slurry of cerium oxide particles under reduced pressure at 110° C. to remove moisture, crushing the resultant powder in an agate mortar, and measuring the powder using a flow type automatic specific surface area measuring device Flowsorb 2300 (manufactured by Shimadzu Corporation).
Average primary particle size (nm) = 820/S

[Surface potential of cerium oxide]
The surface potential (mV) of the cerium oxide particles was measured using a surface potential measuring device (Zeta Probe manufactured by Kyowa Interface Science Co., Ltd.). Ultrapure water was used to adjust the cerium oxide concentration to 0.15%, which was then introduced into the surface potential measuring device, and the surface potential was measured under conditions of a particle density of 7.13 g/ml and a particle dielectric constant of 7. The measurement was performed three times, and the average value was used as the measurement result.

3. Evaluation of Polishing Compositions (Examples 1 to 11, Comparative Examples 1 to 4) [Evaluation Samples]
As an evaluation sample, a commercially available CMP characteristic evaluation wafer (Advantec's "T-TEOS MIT864 PT wafer", diameter 200 mm) was prepared and cut into 40 mm x 40 mm. This evaluation sample has a silicon substrate on which a silicon nitride film with a thickness of 150 nm as a first layer and a silicon oxide film with a thickness of 450 nm as a second layer are arranged as convex portions, and a silicon oxide film with a thickness of 450 nm is also arranged in the concave portions, and a linear concave-convex pattern is formed by etching so that the step between the convex portions and the concave portions is 350 nm. The silicon oxide film is formed of P-TEOS, and the measurement targets used were those with line widths of 25 μm and 500 μm for the convex portions and the concave portions, respectively.

[Polishing conditions]
Polishing device: Single-sided polishing machine [Technorise "TR15M-TRK1", platen diameter 380 mm] Polishing pad: Hard urethane pad [Nitta Haas "IC-1000/Suba400"]
Plate rotation speed: 90 rpm
Head rotation speed: 90 rpm
Polishing load: 300 g/ ^cm2
Polishing solution supply amount: 50 mL/min Polishing time: 1 minute

[Measurement of polishing rate]
The evaluation samples were polished under the above-mentioned polishing conditions using each of the polishing compositions of Examples 1 to 11 and Comparative Examples 1 to 4. After polishing, the evaluation samples were washed with ultrapure water and dried, and were used as measurement targets using an optical interference film thickness measuring device described below.
The thickness of the silicon oxide film was measured before and after polishing using an optical interference film thickness measuring device ("VM-1230" manufactured by SCREEN Semiconductor Solutions). The polishing rate of the silicon oxide film was calculated by the following formula. The calculation results are shown in Table 2.
Polishing speed of silicon oxide film (nm/min)
= [thickness of silicon oxide film before polishing (nm) - thickness of silicon oxide film after polishing (nm)] / polishing time (min)

[Line width dependency]
The polishing speed ratio of a silicon oxide film having a line width of 500 μm to the polishing speed of a silicon oxide film having a line width of 25 μm was calculated by the following formula and shown in the following Table 2. The polishing speed ratio closer to 1 indicates that the polishing speed is less dependent on the line width.
Polishing rate ratio=polishing rate (nm/min) of silicon oxide film having a line width of 500 μm/polishing rate (nm/min) of silicon oxide film having a line width of 25 μm

As shown in Table 2, the polishing compositions of Examples 1 to 11 are capable of achieving both reduced line width dependency and high polishing speed compared to the polishing compositions of Comparative Examples 1 to 4.

As described above, the polishing composition of the present invention is useful in the manufacturing method of semiconductor devices for high density or high integration.

Claims (7)

The composition contains cerium oxide particles, a water-soluble polymer compound, a nitrogen-containing heteroaromatic compound, and an aqueous medium,
The water-soluble polymer compound is a water-soluble polymer compound including a structural unit a containing a betaine structure and a structural unit b which is a structural unit other than the structural unit a and contains at least one group selected from a primary amino group, a secondary amino group, a tertiary amino group, a quaternary ammonium group, and salts thereof ;
The nitrogen-containing heteroaromatic compound is at least one compound selected from the group consisting of N-oxide compounds and salts thereof, which contain a nitrogen-containing heteroaromatic ring skeleton in which at least one hydrogen atom is substituted with a hydroxyl group . The polishing composition according to claim 1 , wherein the structural unit a comprises a structural unit a1 represented by the following formula (1):

In the formula (1),
R ¹ to R ³ are the same or different and each is a hydrogen atom, a methyl group, or an ethyl group;
R ⁴ represents an alkylene group having 1 to 4 carbon atoms, or -Y ¹ -OPO ₃ ^- -Y ² -;
Y ¹ and Y ² are the same or different and each represents an alkylene group having 1 to 4 carbon atoms;
R ⁵ and R ⁶ are the same or different and each is a hydrocarbon group having 1 to 4 carbon atoms;
^X1 is O or ^NR7 ;
^R7 is a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms;
^X2 is ^a _hydrocarbon group having 1 to 4 carbon atoms, ^-R17SO3- or ^{-R18COO- ;}
R ¹⁷ and R ¹⁸ are the same or different and each represents an alkylene group having 1 to 4 carbon atoms.
However, X ² is --R ¹⁷ SO ₃ ^-- or --R ¹⁸ COO ^-- when R ⁴ is an alkylene group having 1 to 4 carbon atoms, and is a hydrocarbon group having 1 to 4 carbon atoms when R ⁴ is --Y ¹ --OPO ₃ ^{--Y 2} --. The polishing composition according to claim 2 , wherein the structural unit b includes a structural unit b1 represented by the following formula (2):

However, in formula (2),
R ⁸ to R ¹⁰ are the same or different and each represents a hydrogen atom, a methyl group, or an ethyl group;
^X3 is O or ^NR19 ;
R ¹⁹ is a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms;
R ¹¹ is an alkylene group having 1 to 22 carbon atoms (however, a hydrogen atom of the alkylene group may be substituted with a hydroxyl group);
^X4 is N ⁺ R ¹² R ¹³ R ¹⁴ or NR ¹⁵ R ¹⁶ ;
R ¹² to R ¹⁴ are the same or different and each represents a hydrocarbon group having 1 to 4 carbon atoms;
R ¹⁵ and R ¹⁶ are the same or different and each represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms. 4. The polishing composition according to claim 1, wherein the nitrogen-containing heteroaromatic compound is at least one compound selected from the group consisting of an N-oxide compound having a pyridine ring in which at least one hydrogen atom is substituted with a hydroxyl group, an N-oxide compound having a quinoline ring in which at least one hydrogen atom is substituted with a hydroxyl group, and salts thereof. The polishing composition according to claim 1 , wherein the cerium oxide particles are negatively charged cerium oxide particles. 6. The polishing composition according to claim 1, wherein a mass ratio of the water-soluble polymer compound to the nitrogen-containing heteroaromatic compound in the polishing composition (water-soluble polymer compound/nitrogen-containing heteroaromatic compound) is 0.01 or more and 100 or less. The polishing composition according to claim 1 , wherein the pH of the polishing composition at 25° C. is 3.5 or more and 8.5 or less.