JP2024094876A - Polishing composition, polishing method and method for producing semiconductor substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide means for polishing a specific object using a polishing composition to enhance a polishing rate of the specific object.

SOLUTION: A polishing composition contains cationically modified silica particles, tetravalent cerium salts, and a dispersion medium.

SELECTED DRAWING: None

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a polishing composition, a polishing method, and a method for manufacturing a semiconductor substrate.

In recent years, with the trend toward multi-layer wiring on semiconductor substrate surfaces, the so-called chemical mechanical polishing (CMP) technique is used to polish and flatten semiconductor substrates when manufacturing devices. CMP is a method of flattening the surface of an object to be polished (workpiece to be polished), such as a semiconductor substrate, using a polishing composition.

In the field of CMP technology, research continues to be conducted to achieve the desired effects through polishing.

Patent Document 1 discloses that a chemical mechanical polishing composition containing a dicarboxylic acid having 7 to 13 carbon atoms, an oxidizing agent, abrasive grains, and water can suppress dishing and erosion, and simultaneously polish a barrier film and an insulating film at high speed while maintaining flatness. Patent Document 1 also discloses that colloidal silica is particularly desirable as the abrasive grains, and that the chemical mechanical polishing composition can be used in a wide pH range, particularly a pH range of 2 to 4 or 8 to 12. Patent Document 1 also discloses that a substrate having an insulating film with a recess, a barrier layer formed on the insulating film, and a wiring material film embedded in the recess so as to cover the barrier layer is polished with the chemical mechanical polishing composition. Patent Document 1 also discloses that the insulating film is a film of at least one inorganic silicon compound selected from the group consisting of SiO ₂ , SiN, SiNO, SiOC, SiCN, and mixtures thereof.

Patent Document 2 discloses that a relatively high silicon carbide removal rate can be achieved while selectively removing silicon carbide in preference to other materials present on the surface of a semiconductor wafer by chemically mechanically polishing a substrate having a silicon carbide layer on its surface using a polishing pad and a polishing composition containing silica particles, a polymer containing sulfonic acid monomer units, and water, and having a pH of about 2 to about 5. Patent Document 2 also discloses that the polishing composition preferably further contains an oxidizing agent. Patent Document 2 also discloses that the substrate further contains a silicon nitride layer or a silicon oxide layer on its surface.

JP 2006-229215 A JP 2020-505756 A

However, the inventors' investigations revealed that there are cases where the techniques of Patent Document 1 and Patent Document 2 do not provide sufficient polishing speed.

The present invention aims to provide a means for improving the polishing rate of a specific object to be polished when the specific object to be polished is polished using a polishing composition.

In order to solve the above-mentioned new problem, the inventors have conducted extensive research. As a result, they have discovered that the above-mentioned problem can be solved by a polishing composition containing specific silica particles and a specific cerium salt, and have completed the present invention.

One aspect of the present invention relates to a polishing composition that contains cation-modified silica particles, a tetravalent cerium salt, and a dispersion medium.

The present invention provides a means for improving the polishing rate of a specific object to be polished when polishing the specific object to be polished using a polishing composition.

The following describes an embodiment of the present invention. Note that the present invention is not limited to the following embodiment.

Unless otherwise specified in this specification, operations and measurements of physical properties are performed at room temperature (20°C or higher and 25°C or lower) and at a relative humidity of 40% RH or higher and 50% RH or lower.

<Polishing Composition>
One aspect of the present invention relates to a polishing composition comprising cation-modified silica particles (silica particles having a cationic group), a tetravalent cerium salt, and a dispersion medium.

The inventors speculate that the mechanism by which the above problem is solved is as follows.

The tetravalent cerium salt generates tetravalent cerium ions, and therefore functions as an oxidizing agent, embrittling the surface of the specific object to be polished. In addition, the cation-modified silica particles contained in the polishing composition according to this embodiment function as abrasive grains, and electrostatic attraction occurs between the cation-modified silica particles and the specific object to be polished, promoting contact between the cation-modified silica particles and the specific object to be polished. As a result, the polishing speed of the specific object to be polished is improved.

Note that the above mechanism is based on speculation, and its accuracy does not affect the technical scope of the present invention.

[Cation-modified silica particles]
In one embodiment, the cation-modified silica particles can function as abrasive grains. The polishing composition according to this embodiment includes abrasive grains, and the abrasive grains can be said to include cation-modified silica particles. The abrasive grains may be used alone or in combination of two or more kinds.

The zeta potential of the cation-modified silica particles (the zeta potential of the cation-modified silica particles in the polishing composition) is not particularly limited, but it is preferable that the cation-modified silica particles exhibit a positive zeta potential. The zeta potential of the cation-modified silica particles (the zeta potential of the cation-modified silica particles in the polishing composition) is not particularly limited, but is preferably greater than 0 mV, more preferably 5 mV or more, even more preferably 10 mV or more, even more preferably 20 mV or more, and particularly preferably 30 mV or more. When it is in the above range, the polishing speed when polishing a specific object to be polished is further improved. In addition, the ratio of the polishing speed of the specific object to the polishing speed of another specific object to be polished (polishing speed of the other specific object to be polished/polishing speed of the specific object to be polished. Here, the polishing speed of the other specific object to be polished>polishing speed of the specific object to be polished) (hereinafter, the ratio of the polishing speed of the specific object to the polishing speed of the other specific object to be polished" is also referred to as the "selectivity between specific objects to be polished") may be further improved. The zeta potential of the cation-modified silica particles (the zeta potential of the cation-modified silica particles in the polishing composition) is not particularly limited, but may be, for example, 100 mV or less. The zeta potential of the cation-modified silica particles in the polishing composition can be determined by the method described in the Examples.

The zeta potential of the cation-modified silica particles can be adjusted, for example, by the type and amount of the compound used to modify the silica particles, the amount of cationic groups, and the pH of the polishing composition. However, the method for adjusting the zeta potential of the cation-modified silica particles is not limited to these.

The cation-modified silica particles may be used alone or in combination of two or more types.

The cation-modified silica particles are not particularly limited, but cation-modified colloidal silica (colloidal silica having a cationic group) is preferred. The cation-modified silica particles may be used alone or in combination of two or more types. The cation-modified silica particles may be a commercially available product or a synthetic product.

Examples of methods for producing colloidal silica include the sodium silicate method and the sol-gel method, and colloidal silica produced by any of these methods can be used suitably. However, from the viewpoint of reducing metal impurities, colloidal silica produced by the sol-gel method is preferred. Colloidal silica produced by the sol-gel method is preferred because it contains less metal impurities and/or corrosive ions such as chloride ions that are diffusible in semiconductors. Colloidal silica can be produced by the sol-gel method using a conventionally known method. Specifically, colloidal silica can be obtained by hydrolysis and condensation reaction using a hydrolyzable silicon compound (e.g., alkoxysilane or its derivative) as a raw material.

The cation-modified silica particles preferably contain cation-modified colloidal silica. The content ratio of the cation-modified colloidal silica relative to the total mass of the cation-modified silica particles is not particularly limited, but is preferably 50% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 99% by mass or more and 100% by mass or less, relative to the total mass of the cation-modified silica particles. It is particularly preferable that the cation-modified silica particles consist only of cation-modified colloidal silica.

Cation-modified means that cationic groups (e.g., amino groups or quaternary ammonium groups) are bonded to the surface of silica particles. In a preferred embodiment, the cation-modified silica particles are amino-modified silica particles, and in a more preferred embodiment, they are amino-modified colloidal silica. These embodiments further improve the polishing rate when polishing a specific object to be polished. In addition, the selectivity between specific objects to be polished may be further improved.

To cationically modify silica particles, a silane coupling agent having a cationic group (e.g., an amino group or a quaternary ammonium group) is added to the silica particles and reacted at a predetermined temperature for a predetermined time. In a preferred embodiment, the cationically modified silica particles are formed by immobilizing a silane coupling agent having an amino group or a silane coupling agent having a quaternary ammonium group on the surface of the silica particles.

Examples of silane coupling agents include those described in JP 2005-162533 A. Specific examples of silane coupling agents include N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, γ-aminopropyltriethoxysilane ((3-aminopropyl)triethoxysilane), γ-aminopropyltrimethoxysilane, γ-triethoxysilyl-N-(α,γ-dimethyl-butylidene)propylamine, N-phenyl-γ-aminopropyltrimethoxysilane, N-(vinylbenzyl)-β-aminoethyl-γ-aminopropyltriethoxysilane hydrochloride, octadecyldimethyl-(γ-trimethoxysilylpropyl)-ammonium chloride, and N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride. Among these, from the viewpoint of good reactivity with silica particles, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, γ-aminopropyltriethoxysilane, and γ-aminopropyltrimethoxysilane are preferably used. The silane coupling agents may be used alone or in combination of two or more.

The silane coupling agent can be added to the silica particles as is or after diluting with a hydrophilic organic solvent, pure water or a mixed solvent thereof. The formation of aggregates can be suppressed by diluting with a hydrophilic organic solvent and/or pure water. When the silane coupling agent is diluted with a hydrophilic organic solvent and/or pure water, the concentration of the silane coupling agent is not particularly limited, but it is sufficient to dilute the silane coupling agent with a hydrophilic organic solvent and/or pure water so that the concentration of the silane coupling agent is preferably 0.01 g to 1 g, more preferably 0.1 g to 0.7 g, in 1 L of the hydrophilic organic solvent, pure water or a mixed solvent thereof. The hydrophilic organic solvent is not particularly limited, but examples thereof include lower alcohols such as methanol, ethanol, isopropanol, and butanol.

The amount of cationic groups introduced onto the surface of the silica particles can be adjusted by adjusting the amount of silane coupling agent added. The amount of silane coupling agent used is not particularly limited, but is preferably 0.1 mmol/L or more and 5 mmol/L or less, more preferably 0.2 mmol/L or more and 3 mmol/L or less, relative to the reaction solution.

The treatment temperature when cationic modifying silica particles with a silane coupling agent is not particularly limited, and may be from room temperature (e.g., 25°C) to a temperature about the boiling point of the dispersion medium in which the silica particles are dispersed, preferably from 0°C to 100°C, and more preferably from room temperature (e.g., 25°C) to 90°C.

The shape of the cation-modified silica particles (preferably cation-modified colloidal silica) is not particularly limited, and may be spherical (hereinafter also referred to as spherical) or non-spherical. Specific examples of non-spherical shapes include polygonal prisms such as triangular prisms and square prisms, cylinders, bale shapes in which the center of a cylinder is more bulging than the ends, donut shapes in which the center of a disk is penetrated, plate shapes, so-called cocoon shapes (cocoon-shaped shapes) with a constriction in the center, so-called association-type spheres in which multiple particles are integrated, so-called confetti shapes with multiple protrusions on the surface, and rugby ball shapes, and various other shapes are not particularly limited.

The average primary particle diameter of the cation-modified silica particles is not particularly limited, but is preferably 1 nm or more, more preferably 3 nm or more, and even more preferably 5 nm or more. The average primary particle diameter of the cation-modified silica particles is not particularly limited, but is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 30 nm or less. Preferred average primary particle diameters of the cation-modified silica particles include, for example, 1 nm or more and 100 nm or less, 3 nm or more and 50 nm or less, and 5 nm or more and 30 nm or less. However, the average primary particle diameter of the cation-modified silica particles is not limited to these ranges. When the cation-modified silica particles contain cation-modified colloidal silica, the preferred average primary particle diameter range of the cation-modified colloidal silica is also the same as the preferred range of the average primary particle diameter of the cation-modified silica particles listed above. The average primary particle diameter of the cation-modified silica particles can be calculated based on the specific surface area (SA) of the cation-modified silica particles calculated by the BET method and the density of the cation-modified silica particles. More specifically, the average primary particle size of the cation-modified silica particles can be measured and calculated by the method described in the Examples.

The average secondary particle diameter of the cation-modified silica particles is not particularly limited, but is preferably 15 nm or more, more preferably 20 nm or more, and even more preferably 25 nm or more. In the above range, the resistance during polishing is small, and stable polishing is possible. The average secondary particle diameter of the cation-modified silica particles is not particularly limited, but is preferably 500 nm or less, more preferably 400 nm or less, and even more preferably 300 nm or less. In the above range, the amount of the polished object scraped off is improved, and the polishing speed is further improved. Examples of preferred average secondary particle diameters of the cation-modified silica particles include 15 nm or more and 500 nm or less, 20 nm or more and 400 nm or less, and 25 nm or more and 300 nm or less. However, the average secondary particle diameter of the cation-modified silica particles is not limited to these ranges. When the cation-modified silica particles contain cation-modified colloidal silica, the preferred range of the average secondary particle diameter of the cation-modified colloidal silica is also the same as the preferred range of the average secondary particle diameter of the cation-modified silica particles listed above. The average secondary particle diameter of the cation-modified silica particles can be measured as the volume average particle diameter (volume-based arithmetic mean diameter; Mv) by dynamic light scattering. More specifically, the average secondary particle diameter of the cation-modified silica particles can be measured by the method described in the Examples.

The ratio of the average secondary particle diameter to the average primary particle diameter of the cation-modified silica particles (average secondary particle diameter/average primary particle diameter) (hereinafter, the ratio of the average secondary particle diameter to the average primary particle diameter is also referred to as the "average degree of association") is not particularly limited, but is preferably greater than 1.0, more preferably greater than 1.1, and even more preferably greater than 1.2. The average degree of association of the cation-modified silica particles is not particularly limited, but is preferably less than 4.0, more preferably less than 3.5, and even more preferably less than 3.0. Preferred average degrees of association of the cation-modified silica particles include, for example, greater than 1.0 and less than 4.0, 1.1 or more and 3.5 or less, and 1.2 or more and 3.0 or less. However, the average degree of association of the cation-modified silica particles is not limited to these ranges. When the cation-modified silica particles contain cation-modified colloidal silica, the preferred range of the average degree of association of the cation-modified colloidal silica is also the same as the preferred range of the average degree of association of the cation-modified silica particles listed above. The average degree of association of the cation-modified silica particles can be calculated by dividing the average secondary particle size of the cation-modified silica particles by the average primary particle size of the cation-modified silica particles (average secondary particle size of the cation-modified silica particles/average primary particle size of the cation-modified silica particles).

The shape and size (average primary particle size, average secondary particle size, average degree of association, etc.) of the cation-modified silica particles can be appropriately controlled, for example, by selecting a method for producing the cation-modified silica particles. However, the methods for controlling the shape and size of the cation-modified silica particles are not limited to these.

The content (concentration) of the cation-modified silica particles in the polishing composition is not particularly limited, but is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.5% by mass or more, and particularly preferably more than 0.5% by mass, relative to the total mass of the polishing composition. The content of the cation-modified silica particles in the polishing composition is not particularly limited, but is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 4% by mass or less, and particularly preferably less than 4% by mass, relative to the total mass of the polishing composition. When it is in the above range, the polishing speed when polishing a specific polishing object is further improved. In addition, when it is in the above range, the selectivity between specific polishing objects may be further improved. The preferred content of the cation-modified silica particles in the polishing composition is not particularly limited, but may be 0.1% by mass or more and 10% by mass or less, 0.2% by mass or more and 5% by mass or less, 0.5% by mass or more and 4% by mass or less, more than 0.5% by mass and less than 4% by mass, etc., relative to the total mass of the polishing composition. However, the content of cation-modified silica particles in the polishing composition is not limited to these ranges.

When the polishing composition according to one embodiment contains cation-modified silica particles as abrasive grains, the content of the cation-modified silica particles in the abrasive grains is not particularly limited, but is preferably 50% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 99% by mass or more and 100% by mass or less, relative to the total mass of the abrasive grains. It is particularly preferable that the abrasive grains consist only of cation-modified silica particles.

[Tetravalent cerium salt]
In one embodiment, the tetravalent cerium salt can function as an oxidizing agent. In this embodiment, it can be said that the polishing composition contains an oxidizing agent, and the oxidizing agent contains a tetravalent cerium salt. The oxidizing agent may be used alone or in combination of two or more.

Examples of tetravalent cerium salts include, but are not limited to, diammonium cerium (IV) nitrate, cerium (IV) sulfate, hydrate of cerium (IV) sulfate, hydrate of tetraammonium cerium (IV) sulfate, etc. Examples of hydrates of cerium (IV) sulfate include, but are not limited to, cerium (IV) sulfate tetrahydrate. Examples of hydrates of tetraammonium cerium (IV) sulfate include, but are not limited to, tetraammonium cerium (IV) sulfate dihydrate. Among these, diammonium cerium (IV) nitrate is particularly preferred. The tetravalent cerium salts may be used alone or in combination of two or more.

The tetravalent cerium salt preferably contains at least one compound selected from the group consisting of diammonium cerium (IV) nitrate, cerium (IV) sulfate, hydrate of cerium (IV) sulfate, and hydrate of tetraammonium cerium (IV) sulfate (hereinafter, this group is also referred to as "Group A"). The content ratio of the at least one compound selected from the above Group A in the tetravalent cerium salt is not particularly limited, but is preferably 50 mol% to 100 mol%, more preferably 90 mol% to 100 mol%, and even more preferably 99 mol% to 100 mol%. It is particularly preferable that the tetravalent cerium salt is only at least one compound selected from the above Group A.

It is more preferable that the tetravalent cerium salt contains at least one compound selected from the group consisting of diammonium cerium (IV) nitrate, cerium (IV) sulfate, cerium (IV) sulfate tetrahydrate, and tetraammonium cerium (IV) sulfate dihydrate (hereinafter, this group is also referred to as "Group B"). The content ratio of at least one compound selected from the above Group B in the tetravalent cerium salt is not particularly limited, but is preferably 50 mol% to 100 mol%, more preferably 90 mol% to 100 mol%, and even more preferably 99 mol% to 100 mol%, assuming that the total amount of the tetravalent cerium salt is 100 mol%. It is particularly preferable that the tetravalent cerium salt is only at least one compound selected from the above Group B.

It is more preferable that the tetravalent cerium salt contains diammonium cerium (IV) nitrate. The content of diammonium cerium (IV) nitrate in the tetravalent cerium salt is not particularly limited, but is preferably 50 mol% to 100 mol%, more preferably 90 mol% to 100 mol%, and even more preferably 99 mol% to 100 mol%, assuming that the total amount of the tetravalent cerium salt is 100 mol%. It is particularly preferable that the tetravalent cerium salt is only diammonium cerium (IV) nitrate.

The content (concentration) of the tetravalent cerium salt in the polishing composition is not particularly limited, but is preferably 0.01 mmol/L or more, more preferably 1 mmol/L or more, even more preferably 10 mmol/L or more, even more preferably 20 mmol/L or more, particularly preferably 40 mmol/L or more, and even more particularly preferably 80 mmol/L or more. When it is in the above range, the polishing rate when polishing a specific polishing object is further improved. The content (concentration) of the tetravalent cerium salt in the polishing composition is not particularly limited, but is preferably 10,000 mmol/L (10 mol/L) or less, more preferably 1,000 mmol/L (1 mol/L) or less, even more preferably 500 mmol/L or less, even more preferably 200 mmol/L or less, particularly preferably 120 mmol/L or less, and even more particularly preferably 100 mmol/L or less. When it is in the above range, the selectivity between specific polishing objects may be further improved. Preferred contents of the tetravalent cerium salt in the polishing composition include, for example, 0.01 mmol/L to 10,000 mmol/L, 1 mmol/L to 1,000 mmol/L, 10 mmol/L to 500 mmol/L, 20 mmol/L to 200 mmol/L, 40 mmol/L to 120 mmol/L, and 80 mmol/L to 100 mmol/L. However, the content of the tetravalent cerium salt in the polishing composition is not limited to these ranges.

When the polishing composition according to one embodiment contains a tetravalent cerium salt as an oxidizing agent, the content of the tetravalent cerium salt in the oxidizing agent is not particularly limited, but is preferably 50 mol% or more and 100 mol% or less, more preferably 90 mol% or more and 100 mol% or less, and even more preferably 99 mol% or more and 100 mol% or less, assuming that the total amount of the oxidizing agent is 100 mol%. It is particularly preferable that the oxidizing agent is only a tetravalent cerium salt.

[acid]
The polishing composition according to one embodiment preferably further contains an acid.

In one embodiment, the acid is preferably used as a pH adjuster. In this embodiment, the polishing composition contains a pH adjuster, and the pH adjuster can also be said to contain an acid. When an acid is used as a pH adjuster, the acid may have other functions in addition to its function as a pH adjuster. The pH adjuster may be used alone or in combination of two or more types.

Specific examples of acids include, but are not limited to, formic acid, acetic acid, propionic acid, butyric acid, 2-hydroxyisobutyric acid (HBA), valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, oleic acid, linoleic acid, linolenic acid, arachidonic acid, docosahexaenoic acid, eicosapentaenoic acid, lactic acid, malic acid, citric acid, benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, gallic acid, mellitic acid, cinnamic acid, oxalic acid, Examples of suitable organic acids include malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, maleic acid, aconitic acid, amino acids, anthranilic acid, nitrocarboxylic acid, methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, isethionic acid, taurine, and non-aromatic cross-linked cyclic compounds having an organic acid group; inorganic acids such as carbonic acid, hydrochloric acid, nitric acid, phosphoric acid, hypophosphorous acid, phosphorous acid, phosphonic acid, sulfuric acid, boric acid, hydrofluoric acid, orthophosphoric acid, pyrophosphoric acid, polyphosphoric acid, metaphosphoric acid, and hexametaphosphoric acid; and the like. Among these, organic acids are preferred from the viewpoint that the selectivity of the other specific object to be polished relative to the Si ₃ N ₄ film (polishing rate of the other specific object to be polished/polishing rate of the Si ₃ N ₄ film) may be improved.

A non-aromatic bridged cyclic compound having an organic acid group has a bulky structure, and when polishing a specific object to be polished and another specific object to be polished, the polishing rate of the other specific object to be polished is suppressed, which may further improve the selectivity between the polishing rates of the specific object to be polished.

In this specification, a non-aromatic bridged cyclic compound refers to a bridged compound that does not have an aromatic ring in the molecule and has a structure in which both ends of a linear structural portion of two or more substituents in one single ring structure are bonded, excluding structures that share one side (i.e., condensed ring compounds). Non-aromatic bridged cyclic compounds are not particularly limited, but examples thereof include camphor, adamantane, and derivatives in which the hydrocarbon groups forming the rings in these molecular structures are replaced with other atoms or functional groups.

The non-aromatic cross-linked cyclic compound having an organic acid group is not particularly limited, but is preferably a compound represented by the following general formula 1.

In the above general formula 1,
Z ₁ is CR ₁ R ₁ ′, C═O or O;
_Z2 is _{CR2R2 '} , C=O or O;
_Z3 is _{CR3R3 '} , C=O or O;
_Z4 is _{CR4R4 '} , C=O or O;
R ₁ , R ₁ ', R ₂ , R ₂ ', R ₃ , R ₃ ', R ₄ , R ₄ ', R ₅ , R ₆ , R ₇ and R ₈ are each independently a hydrogen atom, a deuterium atom, a halogen atom, a substituted or unsubstituted hydrocarbon group (e.g., a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, or a substituted or unsubstituted alkynyl group), a substituted or unsubstituted alkoxy group, a substituted or unsubstituted polyoxyalkylene group, or an organic acid group;
when at least one selected from the group consisting of R ₁ , R ₁ ', R ₂ , R ₂ ', R ₃ , R ₃ ', R ₄ , R ₄ ', R ₅ , R ₆ , R ₇ and R ₈ is a substituted group, the substituents are each independently a deuterium atom, a halogen atom, an unsubstituted hydrocarbon group (e.g., an unsubstituted alkyl group, an unsubstituted alkenyl group or an unsubstituted alkynyl group), an unsubstituted alkoxy group, an unsubstituted polyoxyalkylene group, or an organic acid group;
At least one selected from the group consisting of R ₁ , R ₁ ', R ₂ , R ₂ ', R ₃ , R ₃ ', R ₄ , R ₄ ', R ₅ , R ₆ , R ₇ and R ₈ contains an organic acid group.

In the above general formula 1, it is preferable that at least one selected from the group consisting of Z ₁ , Z ₂ , Z ₃ and Z ₄ is C═O, it is more preferable that at least one selected from the group consisting of Z ₁ and Z ₃ is C═O, it is further preferable that Z ₁ is C═O or Z ₃ is C═O, and it is particularly preferable that Z ₃ is C═O. In this case, the group other than C═O of Z ₁ , Z ₂ , Z ₃ and Z ₄ is preferably CRR′ (hereinafter, R represents R ₁ to R ₄ corresponding to Z ₁ to Z ₄ , respectively, and R′ represents R ₁ ′ to R ₄ ′ corresponding to Z ₁ to Z ₄ , respectively) or O, and it is more preferable that it is CRR′.

In R ₁ , R ₁ ', R ₂ , R ₂ ', R ₃ , R ₃ ', R ₄ , R ₄ ', R ₅ , R ₆ , R ₇ and R ₈ in the above general formula 1, the halogen atom is not particularly limited, but examples thereof include F, Cl, Br and I.

In _R1 , _R1 ', _R2 , _R2 ', _R3 , _R3 ', _R4 , _R4 ', _R5 , _R6 , _R7 and _R8 in the above general formula 1, examples of the hydrocarbon group include an alkyl group, an alkenyl group and an alkynyl group. Among these, an alkyl group is preferred.

The alkyl group may be linear, branched, or cyclic. The alkyl group is not particularly limited, but examples thereof include alkyl groups having 1 to 12 carbon atoms. Among these, non-cyclic alkyl groups having 1 to 5 carbon atoms are preferred, and specific examples thereof include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, and 2-methylbutyl groups. Among these, alkyl groups having 1 to 5 carbon atoms are preferred, with methyl, ethyl, n-propyl, n-butyl, and n-pentyl being more preferred, methyl, ethyl, and n-propyl being even more preferred, with methyl or ethyl being even more preferred, and methyl being particularly preferred.

The alkenyl group may be linear, branched, or cyclic. Examples of the alkenyl group include, but are not limited to, vinyl, 2-propenyl, 2-butenyl, 3-butenyl, 1-methyl-2-propenyl, 2-methyl-2-propenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl, 1-methyl-2-butenyl, 2-methyl-2-butenyl, 3-methyl-2-butenyl, 1-methyl-3-butenyl, 2-methyl-3-butenyl, 3-methyl-3-butenyl, 1,1-dimethyl-2-propenyl, 1,2-dimethyl-2-propenyl, and 1-ethyl-2-propenyl.

The alkynyl group may be linear, branched, or cyclic. Examples of the alkynyl group include, but are not limited to, 2-butynyl, 3-pentynyl, hexynyl, heptynyl, octynyl, and decynyl.

In R ₁ , R ₁ ', R ₂ , R ₂ ', R ₃ , R ₃ ', R ₄ , R 4 ', R ₅ , R ₆ , R ₇ and R ₈ in the above general formula 1, the alkoxy group is not particularly limited, but examples thereof include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, a sec _- butoxy group, a tert-butoxy group, an n-pentoxy group, an isopentoxy group, a neopentoxy group, a t-pentoxy group, a 2-methylbutoxy group and the like.

In R ₁ , R ₁ ', R ₂ , R ₂ ', R ₃ , R ₃ ', R ₄ , R ₄ ', R ₅ , R ₆ , R ₇ and R ₈ in the above general formula 1, the polyoxyalkylene group is not particularly limited, and examples thereof include a polyoxyethylene group, a polyoxypropylene group, a polyoxybutylene group, a block polyoxyalkylene group of a polyoxyethylene group and a polyoxypropylene group, a random polyoxyalkylene group of a polyoxyethylene group and a polyoxypropylene group, a block polyoxyalkylene group of a polyoxyethylene group and a polyoxybutylene group, a random polyoxyalkylene group of a polyoxyethylene group and a polyoxybutylene group, and the like.

In R ₁ , R ₁ ', R ₂ , R ₂ ', R ₃ , R ₃ ', R ₄ , R ₄ ', R ₅ , R ₆ , R ₇ and R ₈ in the above general formula 1, the organic acid group is not particularly limited, but as described above, is preferably at least one selected from the group consisting of a carboxy group, a sulfo group, a phosphonic acid group (-P(=O)(OH) ₂ ) and a phosphate group (-OP(=O)(OH) ₂ ). Of these, a carboxy group or a sulfo group is more preferable, and a sulfo group is even more preferable.

In the above general formula 1, when at least one selected from the group consisting of R ₁ , R ₁ ', R ₂ , R ₂ ', R ₃ , R ₃ ', R ₄ , R ₄ ', R ₅ , R ₆ , R ₇ and R ₈ is a substituted group, the halogen atoms, hydrocarbon groups (e.g., alkyl groups, alkenyl groups, alkynyl groups), alkoxy groups, polyoxyalkylene groups and organic acid groups as the substituents are the same as those explained for these groups in R ₁ , R ₁ ', R ₂ , R ₂ ', R ₃ , R ₃ ', R ₄ , R ₄ ', R ₅ , R ₆ , R ₇ and R ₈ in the above general formula 1, respectively.

In the above general formula 1, when at least one selected from the group consisting of R ₁ , R ₁ ', R ₂ , R ₂ ', R ₃ , R ₃ ', R ₄ , R ₄ ', R ₅ , R ₆ , R ₇ and R ₈ is a substituted hydrocarbon group (e.g., a substituted alkyl group, a substituted alkenyl group, a substituted alkynyl group), it is preferable that the substituents are each independently a deuterium atom, a halogen atom, an unsubstituted alkoxy group, an unsubstituted polyoxyalkylene group, or an organic acid group. In the above general formula 1, when at least one selected from the group consisting of R ₁ , R ₁ ', R ₂ , R ₂ ', R ₃ , R ₃ ', R ₄ , R ₄ ', R ₅ , R ₆ , R ₇ and R ₈ is a substituted alkoxy group, it is preferable that the substituents are each independently a deuterium atom, a halogen atom, an unsubstituted alkenyl group, an unsubstituted alkynyl group, an unsubstituted polyoxyalkylene group, or an organic acid group. In the above general formula 1, when at least one selected from the group consisting of R ₁ , R ₁ ', R ₂ , R ₂ ', R ₃ , R ₃ ', R ₄ , R ₄ ', R ₅ , R ₆ , R ₇ and R ₈ is a substituted polyoxyalkylene group, it is preferable that the substituents are each independently a deuterium atom, a halogen atom, an unsubstituted alkenyl group, an unsubstituted alkynyl group, an unsubstituted alkoxy group, or an organic acid group.

In the above general formula 1, it is preferable that at least one selected from the group consisting of R ₁ , R ₁ ', R ₂ , R ₂ ', R ₃ , R ₃ ', R ₄ , R ₄ ', R ₅ , R ₆ , R ₇ and R ₈ is an organic acid group or an alkyl group substituted with an organic acid group. Among these, it is more preferable that only one selected from the group consisting of R ₁ , R ₁ ', R ₂ , R ₂ ', R ₃ , R ₃ ', R ₄ , R ₄ ', R ₅ , R ₆ , R ₇ and R ₈ is an organic acid group or an alkyl group substituted with an organic acid group. In this case, the organic acid group or the alkyl group substituted with an organic acid group is more preferably a carboxy group, a sulfo group, a methyl group substituted with a carboxy group, or a methyl group substituted with a sulfo group, even more preferably a carboxy group or a methyl group substituted with a sulfo group, and particularly preferably a methyl group substituted with a sulfo group.

In the above general formula 1, it is particularly preferable that R ₁ , R ₁ ', R ₂ , R ₂ ', R ₃ , R ₃ ', R ₄ and R ₄ ' are each independently a hydrogen atom.

In the above general formula 1, it is _preferable that _Z1 is _CR1R1 ', _Z2 is _{CR2R2 ' , Z3} is C=O, _Z4 is _CR4R4 ', and _R1 , _R1'R2 , _R2 ', _R4 and _{R4 '} are each independently a hydrogen atom.

In the above formula 1, _R5 is preferably a hydrogen atom, an organic acid group, or a substituted or unsubstituted alkyl group, more preferably a substituted or unsubstituted alkyl group, even more preferably a substituted alkyl group, and particularly preferably an alkyl group substituted with an organic acid group. In this case, the alkyl group substituted with an organic acid group is preferably a methyl group substituted with a sulfo group.

In the above general formula 1, R ₆ is preferably a hydrogen atom or an organic acid group, more preferably a hydrogen atom or a carboxy group, and even more preferably a hydrogen atom.

In the above general formula 1, _R7 and _R8 are each preferably independently a substituted or unsubstituted alkyl group, more preferably an unsubstituted alkyl group, and particularly preferably a methyl group.

The non-aromatic cross-linked cyclic compounds having an organic acid group may be used alone or in combination of two or more.

Preferable specific examples of the non-aromatic bridged cyclic compound having an organic acid group include 10-camphorsulfonic acid, camphanic acid, and ketopinic acid. Among these, 10-camphorsulfonic acid is particularly preferable from the viewpoint that the selectivity of the other specific object to be polished relative to the Si ₃ N ₄ film (polishing rate of the other specific object to be polished/polishing rate of the Si ₃ N ₄ film) may be improved. Note that 10-camphorsulfonic acid may be any one stereoisomer, any mixture of stereoisomers, or a racemate.

The non-aromatic cross-linked cyclic compounds having an organic acid group may be used alone or in combination of two or more.

The acids may be used alone or in combination of two or more.

The acid preferably contains an organic acid. The content of the organic acid in the acid is not particularly limited, but is preferably 50% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 99% by mass or more and 100% by mass or less, relative to the total mass of the acid. It is particularly preferable that the acid is only an organic acid.

The acid preferably contains a non-aromatic cross-linked cyclic compound having an organic acid group. The content of the non-aromatic cross-linked cyclic compound having an organic acid group in the acid is not particularly limited, but is preferably 50% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 99% by mass or more and 100% by mass or less, relative to the total mass of the acid. It is particularly preferable that the acid is only a non-aromatic cross-linked cyclic compound having an organic acid group.

It is more preferable that the acid contains a compound represented by the above general formula 1. The content ratio of the compound represented by the above general formula 1 in the acid is not particularly limited, but is preferably 50% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 99% by mass or more and 100% by mass or less, relative to the total mass of the acid. It is particularly preferable that the acid is only the compound represented by the above general formula 1.

It is further preferred that the acid contains at least one compound selected from the group consisting of 10-camphorsulfonic acid, camphanic acid, and ketopinic acid (hereinafter, this group is also referred to as "Group C"). The content ratio of the at least one compound selected from Group C in the acid is not particularly limited, but is preferably 50% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 99% by mass or more and 100% by mass or less, relative to the total mass of the acid. It is particularly preferred that the acid is only at least one compound selected from Group C.

It is more preferable that the acid contains 10-camphorsulfonic acid. The content of 10-camphorsulfonic acid in the acid is not particularly limited, but is preferably 50% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 99% by mass or more and 100% by mass or less, relative to the total mass of the acid. It is particularly preferable that the acid is only 10-camphorsulfonic acid.

In one embodiment, the acid may include an inorganic acid. In one embodiment, the acid may include at least one acid selected from the group consisting of carbonic acid, hydrochloric acid, nitric acid, phosphoric acid, hypophosphorous acid, phosphorous acid, phosphonic acid, sulfuric acid, boric acid, hydrofluoric acid, orthophosphoric acid, pyrophosphoric acid, polyphosphoric acid, metaphosphoric acid, and hexametaphosphoric acid. In one embodiment, the acid may include nitric acid.

The content (concentration) of acid in the polishing composition is not particularly limited, but an appropriate amount may be selected so that the resulting polishing composition has the desired pH value, and it is preferable to select an amount so that the resulting polishing composition has a pH value within the range of the preferred polishing compositions described below.

When the polishing composition according to one embodiment contains an acid as a pH adjuster, the content of the acid in the pH adjuster is not particularly limited, but is preferably 50% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 99% by mass or more and 100% by mass or less, relative to the total mass of the pH adjuster. It is particularly preferable that the pH adjuster is only an acid.

[Anti-mold agent (preservative)]
The polishing composition according to one embodiment preferably further contains a fungicide (antiseptic).

The antifungal agent is not particularly limited, but specific examples include isothiazoline preservatives such as 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one; phenoxyethanol; and the like. Among these, isothiazoline preservatives are preferred, and 2-methyl-4-isothiazolin-3-one is more preferred.

Antifungal agents may be used alone or in combination of two or more.

The antifungal agent preferably contains an isothiazolinone preservative. The content of the isothiazolinone preservative in the antifungal agent is not particularly limited, but is preferably 50 mol% to 100 mol%, more preferably 90 mol% to 100 mol%, and even more preferably 99 mol% to 100 mol%, assuming that the total amount of the antifungal agent is 100 mol%. It is particularly preferable that the antifungal agent is only an isothiazolinone preservative.

It is more preferable that the antifungal agent contains 2-methyl-4-isothiazolin-3-one. The content of 2-methyl-4-isothiazolin-3-one in the antifungal agent is not particularly limited, but is preferably 50 mol% to 100 mol%, more preferably 90 mol% to 100 mol%, and even more preferably 90 mol% to 100 mol%, assuming the total amount of the antifungal agent to be 100 mol%. It is particularly preferable that the antifungal agent is only 2-methyl-4-isothiazolin-3-one.

The content (concentration) of the antifungal agent in the polishing composition is not particularly limited, but is preferably 0.0001 mmol/L or more, more preferably 0.001 mmol/L or more, and even more preferably 0.01 mmol/L or more. When it is in the above range, the deterioration of the performance of the polishing composition due to the generation of microorganisms such as mold is further suppressed. The content (concentration) of the antifungal agent in the polishing composition is not particularly limited, but is preferably 10 mmol/L or less, more preferably 1 mmol/L or less, and even more preferably 0.1 mmol/L or less. When it is in the above range, the effect on the performance of the polishing composition is smaller. Examples of the preferred content of the antifungal agent in the polishing composition include 0.0001 mmol/L or more and 10 mmol/L or less, 0.001 mmol/L or more and 1 mmol/L or less, and 0.01 mmol/L or more and 0.1 mmol/L or less. However, the content of the antifungal agent in the polishing composition is not limited to these ranges.

[Dispersion medium]
A dispersion medium is preferably used to dissolve and/or disperse each component.

The dispersion medium is not particularly limited, but examples thereof include water; alcohols such as methanol, ethanol, and ethylene glycol; ketones such as acetone; and mixtures thereof. Among these, water is particularly preferred. The dispersion medium preferably contains water, and more preferably consists essentially of water. Note that the above phrase "the dispersion medium consists essentially of water" means that a dispersion medium other than water may be included as long as the effects of the present invention can be achieved. More specifically, the dispersion medium preferably consists of 90% by mass to 100% by mass of water and 0% by mass to 10% by mass of a dispersion medium other than water, and more preferably consists of 99% by mass to 100% by mass of water and 0% by mass to 1% by mass of a dispersion medium other than water. Most preferably, the dispersion medium is water.

From the viewpoint of not inhibiting the action of the components contained in the polishing composition, it is preferable that the dispersion medium contains as few impurities as possible. Specifically, it is more preferable to use pure water or ultrapure water that has been filtered to remove foreign matter after removing impurity ions with an ion exchange resin, or distilled water.

[Other ingredients]
The polishing composition according to one embodiment may further contain other known components that can be used in polishing compositions, such as abrasives other than cation-modified silica particles, oxidizing agents other than tetravalent cerium salts, pH adjusters other than acids, complexing agents, etc., within a range that does not impair the effects of the present invention. The abrasives other than cation-modified silica particles may be any of inorganic particles, organic particles, or organic-inorganic composite particles. Specific examples of inorganic particles include, but are not limited to, unmodified silica particles, metal oxide particles such as alumina particles, ceria particles, and titania particles; silicon nitride particles; silicon carbide particles; boron nitride particles; and the like. Specific examples of organic particles include, but are not limited to, polymethylmethacrylate (PMMA) particles, etc. The oxidizing agent other than the tetravalent cerium salt is not particularly limited, but examples thereof include hydrogen peroxide, sodium peroxide, barium peroxide, ozone water, silver (II) salt, iron (III) salt, permanganic acid, chromic acid, dichromate, peroxodisulfuric acid, peroxolinic acid, peroxosulfuric acid, peroxoboric acid, performic acid, peracetic acid, perbenzoic acid, perphthalic acid, hypochlorous acid, hypobromous acid, hypoiodous acid, chloric acid, chlorous acid, perchloric acid, bromic acid, iodic acid, periodic acid, persulfuric acid, etc. The pH adjusting agent other than the acid is not particularly limited, but examples thereof include bases, amines, etc.

A preferred embodiment of the polishing composition may also include a polishing composition that does not contain other components. In this embodiment, the polishing composition may be substantially composed of cation-modified silica particles, a tetravalent cerium salt, an acid, an antifungal agent, and a dispersion medium. In this embodiment, "the polishing composition is substantially composed of X" means that the total content (total concentration) of X exceeds 99% by mass (upper limit: 100% by mass) with respect to the total mass of the polishing composition. Preferably, the polishing composition is composed of X (the total content = 100% by mass). For example, "the polishing composition is substantially composed of cation-modified silica particles, a tetravalent cerium salt, an acid, an antifungal agent, and a dispersion medium" means that the total content (total concentration) of the cation-modified silica particles, the tetravalent cerium salt, the acid, the antifungal agent, and the dispersion medium exceeds 99% by mass (upper limit: 100% by mass) with respect to the total mass of the polishing composition. In this case, it is more preferable that the polishing composition is composed of cation-modified silica particles, a tetravalent cerium salt, an acid, an antifungal agent, and a dispersion medium (the total content above = 100% by mass).

[pH]
The pH of the polishing composition according to an embodiment is not particularly limited, but is preferably more than 0, more preferably 0.1 or more, more preferably 0.2 or more, even more preferably 0.3 or more, particularly preferably 0.4 or more, and even more particularly preferably 0.5 or more. The pH of the polishing composition according to an embodiment is not particularly limited, but is preferably less than 7.0, more preferably 4.0 or less, even more preferably 2.0 or less, even more preferably 1.5 or less, particularly preferably 1.2 or less, and even more particularly preferably less than 1.0. Examples of preferred pH of the polishing composition include more than 0 and less than 7.0, 0.1 or more and 4.0 or less, 0.2 or more and 2.0 or less, 0.3 or more and 1.5 or less, 0.4 or more and 1.2 or less, and 0.5 or more and less than 1.0. However, the pH of the polishing composition is not limited to these ranges. The pH of the polishing composition can be measured by the method described in the examples.

In one embodiment, the polishing composition may be a one-component type or a multi-component type, including a two-component type.

[Method of manufacturing the polishing composition]
The method for producing the polishing composition is not particularly limited, but the polishing composition according to one embodiment can be obtained, for example, by stirring and mixing the cation-modified silica particles, the tetravalent cerium salt, and other components as necessary in a dispersion medium (for example, water). The details of each component are as described above.

The temperature at which the components are mixed is not particularly limited, but is preferably 10°C or higher and 40°C or lower, and may be heated to increase the dissolution rate. In addition, there is no particular limit to the mixing time as long as the components can be mixed uniformly.

The polishing composition of one embodiment may be prepared by diluting the stock solution of the polishing composition, for example, 10 times or more, with a diluent such as water.

[Object to be polished]
The polishing object to which the polishing composition according to one embodiment is applied is not particularly limited, but preferably contains a typical element. The typical element is not particularly limited, but preferred examples include carbon, nitrogen, oxygen, silicon, boron, germanium, phosphorus, etc. Among the typical elements, a typical element capable of taking a high oxidation state is preferred. In this specification, the term "high oxidation state" refers to a state in which the oxidation number of an element has a larger value compared to the oxidation number of the element constituting the polishing object before the polishing composition is applied. The typical element capable of taking a high oxidation state is not particularly limited, but examples thereof include carbon, silicon, boron, germanium, phosphorus, etc. The typical element may be contained alone or in combination of two or more types. The typical element capable of taking a high oxidation state may be contained alone or in combination of two or more types. The typical element capable of taking a high oxidation state may be contained in combination with another typical element. For this reason, the polishing composition of one embodiment is preferably used for polishing an object to be polished that contains a typical element, more preferably used for polishing an object to be polished that contains a typical element that can be in a higher oxidation state, and even more preferably used for polishing an object to be polished that contains at least one element selected from the group consisting of carbon, silicon, boron, germanium, and phosphorus.

The polishing composition according to one embodiment may be used to polish an object that further contains a transition element in addition to a typical element. The transition element may be contained alone or in combination of two or more elements.

In a preferred embodiment, the polishing object includes, for example, an object to be polished that contains at least one element selected from the group consisting of carbon, nitrogen, oxygen, silicon, boron, germanium, and phosphorus. In a more preferred embodiment, the polishing object includes, for example, an object to be polished that contains at least one element selected from the group consisting of carbon, nitrogen, oxygen, silicon, and boron.

Specific examples of preferred polishing objects include polishing objects containing at least one material selected from the group consisting of carbon, silicon nitride, and silicon oxide with added carbon. From the viewpoint of achieving a higher polishing rate improvement effect, the polishing object is preferably a polishing object containing at least one material selected from the group consisting of carbon and silicon oxide with added carbon. From the viewpoint of achieving a higher selectivity, the polishing object is preferably a polishing object containing at least one material selected from the group consisting of carbon, silicon nitride, and silicon oxide with added carbon, and more preferably a polishing object containing carbon and silicon nitride, or a polishing object containing silicon nitride and silicon oxide with added carbon.

Here, the carbon is not particularly limited, but examples thereof include amorphous carbon (non-crystalline carbon, amorphous carbon), spin-on carbon (SOC), diamond-like carbon (DLC), nanocrystalline diamond, graphene, etc.

The object to be polished may be an object to be polished that contains a material (other material) other than carbon, silicon nitride, and carbon-added silicon oxide. The object to be polished may be an object to be polished that further contains other materials in addition to at least one material selected from the group consisting of carbon, silicon nitride, and carbon-added silicon oxide. Specific examples of other materials include, but are not limited to, silicon oxide, single crystal silicon, polycrystalline silicon (polysilicon), amorphous silicon (amorphous silicon), polycrystalline silicon doped with n-type or p-type impurities, amorphous silicon doped with n-type or p-type impurities, SiGe, metal elements (e.g., tungsten, copper, cobalt, hafnium, nickel, gold, silver, platinum, palladium, rhodium, ruthenium, iridium, osmium, etc.), metal nitrides (e.g., tantalum nitride (TaN), titanium nitride (TiN), etc.), etc.

Films containing these materials can be formed by chemical vapor deposition (CVD), physical vapor deposition (PVD), spin coating, etc.

<Polishing method and semiconductor substrate manufacturing method>
Another aspect of the present invention relates to a polishing method, comprising polishing an object to be polished using the polishing composition according to the above aspect. The object to be polished in this aspect is also the same as the object to be polished to which the polishing composition according to the above aspect is applied. In a preferred embodiment, the object to be polished includes a main group element.

Yet another aspect of the present invention relates to a method for producing a semiconductor substrate, the method including polishing the semiconductor substrate by the polishing method according to the above aspect, the semiconductor substrate including an object to be polished. The object to be polished in this aspect is similar to the description of the object to be polished to which the polishing composition according to the above aspect is applied. In a preferred embodiment, the semiconductor substrate includes an object to be polished that includes a typical element. Thus, a preferred embodiment includes a method for producing a semiconductor substrate, the method including polishing the object to be polished by the polishing method according to the above aspect, the semiconductor substrate including an object to be polished that includes a typical element.

The polishing device is not particularly limited, but as a polishing device, for example, a general polishing device having a holder for holding a substrate including an object to be polished, a motor capable of changing the rotation speed, and a polishing platen to which a polishing pad (polishing cloth) can be attached can be used.

There are no particular limitations on the polishing pad, but examples of the polishing pad that can be used include general nonwoven fabric, polyurethane, and porous fluororesin. It is preferable that the polishing pad has grooves that allow the polishing liquid to accumulate.

The polishing conditions are not particularly limited. For example, the rotation speed of the polishing platen is preferably 10 rpm (0.17 s ⁻¹ ) or more and 500 rpm (8.33 s ⁻¹ ) or less. For example, the pressure applied to the substrate having the object to be polished (polishing pressure) is preferably 0.5 psi (3.4 kPa) or more and 10 psi (68.9 kPa) or less.

There are no particular limitations on the method of supplying the polishing composition to the polishing pad, and for example, a method of continuously supplying the composition using a pump or the like is used. There are no limitations on the amount of the composition supplied, but it is preferable that the surface of the polishing pad is always covered with the polishing composition. There are no particular limitations on the polishing time, and for example, a time that can achieve the desired polishing may be appropriately selected.

After polishing is completed, the substrate containing the object to be polished may be washed with running water, and the substrate may be dried by removing water droplets adhering to the substrate using a spin dryer or the like.

<Selectivity according to a preferred embodiment>
The selectivity ratio that can be realized by the polishing of the object to be polished using the polishing composition according to the above-mentioned aspect, the selectivity ratio that can be realized by the polishing method according to the above-mentioned aspect, and the selectivity ratio that can be realized by the manufacturing method of semiconductor substrate according to the above-mentioned aspect are not particularly limited.However, in one embodiment, the selectivity ratio between specific objects to be polished (for example, the ratio of the polishing speed of the object to be polished that is desired to be removed to the polishing speed of the object to be polished that is not desired to be removed (polishing speed of the object to be polished that is desired to be removed/polishing speed of the object to be polished that is not desired to be removed) etc.) is preferably higher.

Although the embodiments of the present invention have been described in detail, it is clear that the same are illustrative and exemplary and are not limiting, and the scope of the present invention should be interpreted by the appended claims.

The present invention encompasses the following aspects and configurations.
[1] A polishing composition comprising cation-modified silica particles, a tetravalent cerium salt, and a dispersion medium.
[2] The polishing composition according to [1], wherein the cation-modified silica particles exhibit a positive zeta potential.
[3] The polishing composition according to [1] or [2], wherein the tetravalent cerium salt contains diammonium cerium nitrate (IV).
[4] The polishing composition according to any one of [1] to [3], further comprising an acid.
[5] The polishing composition according to any one of [1] to [4], further comprising an antifungal agent.
[6] The polishing composition according to any one of [1] to [5], which has a pH of less than 7.0.
[7] A polishing method comprising polishing an object to be polished with the polishing composition according to any one of [1] to [6].
[8] The polishing method according to [7], wherein the object to be polished contains a main group element.
[9] A method for producing a semiconductor substrate, comprising: polishing an object to be polished, the object being a semiconductor substrate, by the polishing method according to [7].
[10] A method for producing a semiconductor substrate, comprising polishing an object to be polished, the object including a semiconductor substrate containing a main group element, by the polishing method according to [8].

The present invention will be described in more detail using the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples. Unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass", respectively.

<Measurement method>
(Average primary particle size of cation-modified silica particles)
The average primary particle size of the cation-modified silica particles was calculated from the specific surface area of the cation-modified silica particles measured by the BET method using "Flow Sorb II 2300" manufactured by Micromeritics, and the density of the cation-modified silica particles.

(Average secondary particle size of cation-modified silica particles)
The average secondary particle diameter of the cation-modified silica particles was measured as the volume average particle diameter (arithmetic mean diameter based on volume; Mv) using a dynamic light scattering particle diameter/particle size distribution device UPA-UTI151 (manufactured by Nikkiso Co., Ltd.).

(Average degree of association of cation-modified silica particles)
The average degree of association of the cation-modified silica particles was calculated by dividing the average secondary particle size of the cation-modified silica particles by the average primary particle size of the cation-modified silica particles.

(Zeta potential of cation modified silica particles)
The zeta potential of the cation-modified silica particles in the liquid to be measured was calculated by subjecting the liquid to a Zetasizer Nano manufactured by Malvern Panalytical, measuring the liquid at a measurement temperature of 25°C using a laser Doppler method (electrophoretic light scattering measurement method), and analyzing the obtained data using the Smoluchowski formula.

In Examples 1 to 8 and Comparative Examples 1 and 2 described below, the cation-modified silica particles used in the above measurement methods were cation-modified colloidal silica described below.

[pH of polishing composition]
The pH of the polishing composition was measured using a glass electrode type hydrogen ion concentration indicator (Model No. F-23, manufactured by Horiba, Ltd.) and three-point calibration was performed using standard buffer solutions (phthalate pH buffer solution pH: 4.01 (25°C), neutral phosphate pH buffer solution pH: 6.86 (25°C), carbonate pH buffer solution pH: 10.01 (25°C)). The glass electrode was then placed in the polishing composition and the value after stabilization for at least 2 minutes was recorded as the pH value.

The pH of liquids other than the polishing composition was evaluated in the same manner as in the above-mentioned method for measuring the pH of the polishing composition, except that the liquid to be measured was used instead of the polishing composition.

<Preparation of Polishing Composition>
(cation modified colloidal silica)
To 1 L of an aqueous dispersion of silica sol (silica concentration = 20 mass%), γ-aminopropyltriethoxysilane (APTES) was added dropwise as a silane coupling agent at a concentration of 0.225 mmol/L (0.225 mM) while stirring with a magnetic stirrer, and then the mixture was allowed to stand for 1 hour. In this way, a cocoon-shaped cation-modified colloidal silica with an average primary particle size of 25.0 nm, an average secondary particle size of 50.0 nm, and an average degree of association of 2.0 was produced.

(Polishing Composition of Example 1)
The cation-modified colloidal silica obtained above as an abrasive grain was added to pure water as a dispersion medium at room temperature (25° C.) so as to have a final concentration (concentration in the resulting polishing composition) of 1.8% by mass, and 2-methyl-4-isothiazolin-3-one (manufactured by THE DOW CHEMICAL COMPANY) was added as an antifungal agent to have a final concentration (concentration in the resulting polishing composition) of 0.027 mmol/L (0.027 mM) to obtain a mixed solution. Thereafter, 10-camphorsulfonic acid was added to the mixed solution so as to have a pH of 3.0, and diammonium cerium (IV) nitrate (manufactured by Tokyo Chemical Industry Co., Ltd.) was further added as an oxidizing agent to have a final concentration (concentration in the resulting polishing composition) of 5 mmol/L (5 mM), and the mixture was stirred and mixed at room temperature (25° C.) for 10 minutes to prepare a polishing composition. The pH of the resulting polishing composition was measured to be 1.6.

The zeta potential of the cation-modified colloidal silica was measured using a mixture obtained in the manufacturing process of the above polishing composition, the pH of which was adjusted to 3.0 by adding 10-camphorsulfonic acid, before the addition of diammonium cerium (IV) nitrate (manufactured by Tokyo Chemical Industry Co., Ltd.) as an oxidizing agent. As a result, the zeta potential of the cation-modified colloidal silica in the mixture to be measured was +31 mV.

The cation-modified colloidal silica shows a tendency for the zeta potential to increase as the pH decreases in the range of pH 3.0 or less, and the obtained polishing composition has a pH value lower than pH 3.0, which is the pH value of the mixture to be measured. From these facts, it was determined that the cation-modified colloidal silica in the obtained polishing composition exhibits a positive zeta potential.

The particle size (average primary particle size and average secondary particle size) of the cation-modified colloidal silica in the polishing composition was similar to the particle size (average primary particle size and average secondary particle size) of the cation-modified colloidal silica used.

(Polishing Compositions of Examples 2 to 8 and Comparative Example 3)
Each polishing composition was prepared in the same manner as in Example 1, except that the type and concentration of each component, and the pH were changed as shown in the following Table 1. In Comparative Example 3, sulfonic acid-modified colloidal silica (average primary particle size: 30 nm, average secondary particle size: 70 nm, average degree of association: 2.2, cocoon shape) was used as the abrasive grains.

More specifically, in the manufacturing method of the polishing composition of Examples 2 to 8 and Comparative Example 3, the above-obtained cation-modified colloidal silica or the above-mentioned sulfonic acid-modified colloidal silica was added as the abrasive grains to pure water as the dispersion medium at room temperature (25°C) so as to have a final concentration (concentration in the resulting polishing composition) of 1.8 mass%, and 2-methyl-4-isothiazolin-3-one (manufactured by THE DOW CHEMICAL COMPANY) was added as the fungicide to have a final concentration (concentration in the resulting polishing composition) of 0.027 mmol/L (0.027 mM) to obtain a mixed solution. Then, 10-camphorsulfonic acid, acetic acid or nitric acid was added to the mixed solution so as to have a pH of 3.0, and further diammonium cerium (IV) nitrate (manufactured by Tokyo Chemical Industry Co., Ltd.) was added as the oxidizing agent to have a final concentration (concentration in the resulting polishing composition), and the mixture was stirred and mixed at room temperature (25°C) for 10 minutes to prepare a polishing composition. Then, the pH of the resulting polishing composition was measured.

The zeta potential of the cation-modified colloidal silica was measured using the mixture obtained in the manufacturing process of the polishing compositions of Examples 2 to 8, which had a pH of 3.0 adjusted with 10-camphorsulfonic acid, acetic acid, or nitric acid before the addition of diammonium cerium (IV) nitrate (manufactured by Tokyo Chemical Industry Co., Ltd.) as an oxidizing agent. As a result, the zeta potential of the cation-modified colloidal silica in the mixture to be measured was +31 mV.

The cation-modified colloidal silica shows a tendency for the zeta potential to increase as the pH decreases in the pH range of 3.0 or less, and the obtained polishing composition has a pH value lower than pH 3.0, which is the pH value of the mixture liquid to be measured. From these facts, it was determined that the cation-modified colloidal silica in the obtained polishing compositions of Examples 2 to 8 each exhibits a positive zeta potential.

In Examples 2 to 8, the particle sizes (average primary particle size and average secondary particle size) of the cation-modified colloidal silica in the resulting polishing composition were similar to the particle sizes (average primary particle size and average secondary particle size) of the cation-modified colloidal silica used.

The zeta potential of the sulfonic acid-modified colloidal silica was measured using the mixture obtained in the manufacturing process of the polishing composition of Comparative Example 3, which had a pH of 3.0 adjusted by adding 10-camphorsulfonic acid before adding diammonium cerium (IV) nitrate (manufactured by Tokyo Chemical Industry Co., Ltd.) as an oxidizing agent. As a result, the zeta potential of the sulfonic acid-modified colloidal silica in the mixture to be measured was -40 mV.

Because sulfonic acid-modified colloidal silica shows a tendency for its zeta potential not to change significantly even when the pH changes in the pH range of 3.0 or less, it was determined that the sulfonic acid-modified colloidal silica in the polishing composition of Comparative Example 3 exhibits a negative zeta potential.

In Comparative Example 3, the particle size (average primary particle size and average secondary particle size) of the sulfonic acid-modified colloidal silica in the polishing composition was similar to the particle size (average primary particle size and average secondary particle size) of the sulfonic acid-modified colloidal silica used.

The average primary particle size, average secondary particle size, and average degree of association of the sulfonic acid-modified colloidal silica, as well as the zeta potential of the sulfonic acid-modified colloidal silica in the liquid to be measured, were evaluated in the same manner as the above-mentioned methods for measuring the average primary particle size, average secondary particle size, and average degree of association of the cation-modified silica particles, as well as the zeta potential of the cation-modified silica particles in the liquid to be measured, except that the objects to be measured were different.

(Polishing Compositions of Comparative Examples 1 and 2)
In the manufacturing method of the polishing composition of Comparative Examples 1 and 2, the cation-modified colloidal silica obtained above was added as an abrasive grain to pure water as a dispersion medium at room temperature (25° C.) so as to have a final concentration (concentration in the resulting polishing composition) of 1.8 mass %, and 2-methyl-4-isothiazolin-3-one (manufactured by THE DOW CHEMICAL COMPANY) was added as a fungicide to have a final concentration (concentration in the resulting polishing composition) of 0.027 mmol/L (0.027 mM) to obtain a mixed solution. Thereafter, 10-camphorsulfonic acid was added as a mixture so that the resulting polishing composition had a pH of 1.6, and in Comparative Example 2, hydrogen peroxide was added as an oxidizing agent to have a final concentration (concentration in the resulting polishing composition) of 10 mmol/L, and the mixture was stirred and mixed at room temperature (25° C.) for 10 minutes to prepare a polishing composition.

In Comparative Examples 1 and 2, the particle sizes (average primary particle size and average secondary particle size) of the cation-modified colloidal silica in the polishing composition were similar to the particle sizes (average primary particle size and average secondary particle size) of the cation-modified colloidal silica used.

The composition of each polishing composition is shown in Table 1 below. Note that "-" in Table 1 below indicates that the agent was not used.

<Evaluation>
Using each of the polishing compositions prepared above, the surface of an object to be polished was polished under the following conditions. The objects to be polished were a silicon wafer (300 mm, blanket wafer) having a 5,000 Å thick amorphous carbon (C) film formed on its surface, a silicon wafer (300 mm, blanket wafer) having a 5,000 Å thick carbon-added silicon oxide (SiOC) film (low-k insulating film) formed on its surface, and a silicon wafer (300 mm, blanket wafer) having a 2,500 Å thick silicon nitride (Si ₃ N ₄ ) film formed on its surface.

(Polishing Equipment and Polishing Conditions)
Polishing device: Polishing machine manufactured by Ebara Corporation (model FREX 300E)
Polishing pad: Nitta DuPont Polyurethane pad IC1000
Polishing pressure: 3.0 psi (1 psi = 6894.76 Pa)
Polishing platen rotation speed: 90 rpm
Supply of polishing composition: flow-through Supply amount of polishing composition: 200 mL/min Polishing time: 1 min.

(Evaluation of Polishing Rate)
The thicknesses of the C film, SiOC film, and Si ₃ N ₄ film before and after polishing were measured using an optical film thickness measuring device (ASET-f5x: manufactured by KLA Tencor Corporation). The polishing rate for each object to be polished was calculated from the measured thickness by dividing [(thickness before polishing [unit: Å]) - (thickness after polishing [unit: Å])] by the polishing time [unit: min].

In this evaluation, the polishing speed of the C film was evaluated as being preferable if it exceeded 200 Å/min, since a high polishing speed could be obtained. In this evaluation, the polishing speed of the SiOC film was evaluated as being preferable if it exceeded 300 Å/min, since a high polishing speed could be obtained.

Regarding the polishing speed of _{the Si3N4} film, from the viewpoint of being able to obtain a high selectivity between _{the Si3N4} film and the C film, and between _{the Si3N4} film and the SiOC film, in this evaluation, it was evaluated that a polishing speed of 80 Å/min or less is preferable, and a polishing speed of 50 Å/min or less is more preferable.

_{The higher the selectivity ratio of the C film to the Si3N4 film} (polishing rate of the C film/polishing rate of the _Si3N4 film) (shown as "C _{/ Si3N4} " in Table 2), the more preferable it was. The higher the selectivity ratio of the _{SiOC film to the Si3N4 film (} polishing rate of the SiOC film/polishing rate of the _Si3N4 film) (shown as " _{SiOC / Si3N4} " in Table 2), the more preferable it was.

The above evaluation results are shown in Table 2 below.

As is clear from Tables 1 and 2, it was confirmed that the polishing composition according to the embodiment can polish the specific object containing a typical element, such as C film and SiOC film, at a significantly higher polishing rate than the polishing composition according to the comparative example. On the other hand, it was found that the polishing composition according to the embodiment does not have a significant effect on the polishing rate of Si ₃ N ₄ film.

In addition, when the polishing compositions of Examples 1 to 6 were used, it was found that the selectivity ratio of the C film to the Si ₃ N ₄ film (polishing rate of the C film/polishing rate of the Si ₃ N ₄ film) and the selectivity ratio of the SiOC film to the Si ₃ N ₄ film (polishing rate of the SiOC film/polishing rate of the Si ₃ N ₄ film) were significantly higher than those of the polishing compositions of the comparative examples.

Claims (10)

A polishing composition comprising cation-modified silica particles, a tetravalent cerium salt, and a dispersion medium. The polishing composition according to claim 1, wherein the cation-modified silica particles exhibit a positive zeta potential. The polishing composition according to claim 1, wherein the tetravalent cerium salt comprises diammonium cerium (IV) nitrate. The polishing composition according to claim 1, further comprising an acid. The polishing composition according to claim 1, further comprising a fungicide. The polishing composition according to claim 1, wherein the pH is less than 7.0. A polishing method comprising polishing an object to be polished using the polishing composition according to any one of claims 1 to 6. The polishing method according to claim 7, wherein the object to be polished contains a typical element. The semiconductor substrate comprises an object to be polished,
A method for manufacturing a semiconductor substrate, comprising polishing the object by the polishing method according to claim 7. The semiconductor substrate includes an object to be polished that includes a main group element,
A method for manufacturing a semiconductor substrate, comprising polishing the object by the polishing method according to claim 8.