JP7685983B2 - Polishing liquid composition for silicon oxide film - Google Patents

Description

This disclosure relates to a polishing composition for silicon oxide films that contains cerium oxide particles, a method for manufacturing semiconductor substrates using the same, and a method for polishing substrates.

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 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 flattening it.

Currently, CMP technology is essential in the manufacturing process of semiconductor devices when planarizing 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 it is desirable to be able to polish at high speed while maintaining good flatness. For example, in the process of forming shallow trench isolation structures, in addition to high polishing speed, it is desirable to improve the polishing selectivity of the polishing stopper film (e.g., silicon nitride film) relative to the film to be polished (e.g., silicon oxide film) (in other words, the polishing selectivity such that the polishing stopper film is less easily polished than the film to be polished) and improve flatness.

For example, Patent Document 1 discloses a polishing liquid for chemical mechanical polishing that contains ceria particles having an average aspect ratio of 1.5 or more and an anionic polymer such as polyacrylic acid, and also discloses nitrogen-containing heteroaromatic ring compounds, 4-pyrone, and the like as optional components.
Patent Document 2 discloses a polishing liquid containing abrasive grains such as ceria and a copolymer having a structural unit derived from a styrene compound and a structural unit derived from at least one acid selected from acrylic acid and maleic acid.

WO2019/187977 WO2019/064524

In recent years, the semiconductor industry has been moving toward higher integration, which has led to demands for more complex and finer wiring. For this reason, in CMP polishing, there is a demand for further improvement in flatness while maintaining a sufficient polishing rate.
One of the reasons for the deterioration of the flatness of the substrate surface after polishing is believed to be that polishing of recesses is not sufficiently suppressed, resulting in the occurrence of dishing.

Therefore, the present disclosure provides a polishing composition for silicon oxide films that can improve the flatness of the substrate surface after polishing while maintaining the polishing rate, and a manufacturing method and polishing method for semiconductor substrates using the same.

In one embodiment, the present disclosure provides a composition comprising cerium oxide particles (component A), a water-soluble anionic polymer (component B), an unsaturated cyclic compound (component C), and an aqueous medium,
Component B has an aromatic group in the molecule,
Component C relates to a polishing composition for silicon oxide films, which has a functional group represented by the following formula (I) or formula (II) in a cyclic skeleton.
In formula (I), Y represents OM ¹ or SM ² , and M ¹ and M ² may be the same or different and represent an alkali metal ion, an alkaline earth metal ion, an organic cation, ammonium (NH ₄ ⁺ ) or a hydrogen atom.
In formula (II), M ³ represents an alkali metal ion, an alkaline earth metal ion, an organic cation, ammonium (NH ₄ ⁺ ) or a hydrogen atom.

In one aspect, the present disclosure relates to a method for manufacturing a semiconductor substrate, comprising a step of polishing a film to be polished using the polishing composition of the present disclosure.

In one aspect, the present disclosure relates to a polishing method that includes a step of polishing a film to be polished using the polishing composition of the present disclosure, the film to be polished being a silicon oxide film formed during the manufacturing process of a semiconductor substrate.

According to one aspect of the present disclosure, a polishing composition for silicon oxide films can be provided that can improve the flatness of the substrate surface after polishing while maintaining the polishing rate.

As a result of extensive research, the inventors discovered that by adding a specific anionic polymer and a specific unsaturated cyclic compound to a polishing composition that uses cerium oxide particles as an abrasive, it is possible to improve the flatness of the substrate surface after polishing while maintaining the polishing rate.

In one embodiment, the present disclosure provides a composition comprising cerium oxide particles (component A), a water-soluble anionic polymer (component B), an unsaturated cyclic compound (component C), and an aqueous medium,
The present invention relates to a polishing liquid composition for silicon oxide films (hereinafter also referred to as the "polishing liquid composition of the present disclosure"), in which component B has an aromatic group in the molecule, and component C has a functional group represented by the above formula (I) or formula (II) in the cyclic skeleton.
According to one aspect of the present disclosure, it is possible to provide a polishing composition for silicon oxide films that can improve the flatness of a substrate surface after polishing while ensuring a polishing rate.

Although the details of the mechanism by which the effects of the present disclosure are manifested are not clear, it is presumed as follows.
In order to suppress dishing while ensuring the polishing rate of the convex parts, it is necessary to suppress the polishing rate of the concave parts without significantly impairing the polishing rate of the convex parts. Component C can be adsorbed to a silicon oxide film or cerium oxide particles by the functional group represented by the above formula (I) or formula (II) in the cyclic skeleton, and can be detached when a high stress is applied. In other words, component C can be adsorbed to a silicon oxide film or cerium oxide particles in the concave parts where a load is not easily applied to form a protective film, and detached in the convex parts where a high load is applied, which is considered to be able to suppress dishing while ensuring the polishing rate of the convex parts. Component B is considered to be able to improve the strength of the protective film formed by component C by interacting with component C through the aromatic ring, and to suppress the polishing rate of the concave parts, thereby improving the flatness of the surface of the substrate after polishing.
However, the present disclosure need not be construed as being limited to these mechanisms.

[Cerium oxide particles (component A)]
The polishing liquid composition of the present disclosure contains cerium oxide (hereinafter also referred to as "ceria") particles (hereinafter also simply referred to as "component A") as abrasive grains. As component A, positively charged ceria or negatively charged ceria can be used. The chargeability of component A can be confirmed, for example, by measuring the electric potential (surface potential) on the surface of the abrasive grains 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.), specifically, by the method described in the Examples. Component A may be one type or a combination of two or more types.

There are no particular limitations on the manufacturing method, shape, and surface state of Component A. 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 the amorphous ceria include pulverized ceria. One embodiment of the pulverized ceria includes sintered pulverized ceria obtained by sintering and pulverizing a cerium compound such as cerium carbonate or cerium nitrate. Another embodiment of the pulverized ceria includes single crystal pulverized ceria obtained by wet pulverizing ceria particles in the presence of an inorganic acid or an organic acid. An example of the inorganic acid used in the wet pulverization is nitric acid, and an example of the organic acid is an organic acid 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 in the wet pulverization, positively charged ceria can be obtained, and when a polycarboxylate such as ammonium polyacrylate is used in the wet pulverization, negatively charged ceria can be obtained. An example of the wet grinding method is 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 portion of the surface of silica particles is coated with granular ceria, as described in Examples 1 to 14 of JP2015-63451A or Examples 1 to 4 of JP2013-119131A. The composite particles can be obtained, for example, by depositing ceria on silica particles.

The shape of component A can be, for example, roughly spherical, polyhedral, or raspberry-shaped.

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, even more preferably 20 nm or more, and even more preferably 30 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, even more preferably 80 nm or less, and even more preferably 60 nm or less. In the present disclosure, the average primary particle size of component A is calculated using the BET specific surface area S (m ² /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 disclosure is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, even 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, and from the viewpoint of suppressing the occurrence of polishing scratches, it 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 0.7% by mass or less. More specifically, the content of component A is preferably 0.001% by mass or more and 6% by mass or less, more preferably 0.01% by mass or more and 6% by mass or less, even 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 0.7% 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 anionic polymer (component B)]
The polishing composition of the present disclosure contains a water-soluble anionic polymer (hereinafter, also simply referred to as "component B"). Component B is a water-soluble anionic polymer having an aromatic group in the molecule. In one or more embodiments, the aromatic group is preferably a group containing an aromatic ring from the viewpoint of improving the polishing rate and improving the flatness. Examples of the aromatic ring include a benzene ring and a naphthalene ring. In one or more embodiments, component B can suppress the dishing rate during overpolishing while ensuring the polishing rate of the silicon oxide film, and is considered to be able to improve the flatness of the substrate surface after polishing. Note that dishing refers to a dish-shaped depression caused by excessive polishing of a recess. In the present disclosure, "water-soluble" refers to dissolving in the polishing composition of the present disclosure, and means having a solubility of preferably 0.5 g/100 mL or more in water (20° C.), more preferably 2 g/100 mL or more. Component B may be one type or a combination of two or more types.

In one or more embodiments, from the viewpoint of improving the polishing rate and flatness, component B may be a water-soluble anionic condensate having a benzene ring or a naphthalene ring in the main chain ("component B1" and "component B2" below), or a copolymer containing a structural unit derived from styrene and a structural unit derived from a monomer having an anionic group ("component B3" below).

<Component B1: Water-soluble anionic condensate>
In one or more embodiments, component B1 is a water-soluble anionic condensate having a benzene ring in the main chain. In one or more embodiments, component B1 is a co-condensate of monomers including a monomer represented by the following formula (III) (hereinafter also referred to as "constituent monomer b11") and a monomer represented by the following formula (IV) (hereinafter also referred to as "constituent monomer b12"). Component B1 may be one type or a combination of two or more types.

(Constituent Monomer b11)
The constituent monomer b11 is a monomer represented by the following formula (III).

In formula (III), R ¹ and R ² are the same or different and represent a hydrogen atom, a hydrocarbon group having 1 to 4 carbon atoms, or -OM ^5. In one or more embodiments, from the viewpoint of polymerization reactivity, at least one of ^{R 1} and R ² is preferably -OM ⁵ , and more preferably -OH. In one or more embodiments, from the viewpoint of improving the polishing rate and improving flatness, at least one of ^{R 1} and R ² is preferably a hydrogen atom.
^M4 and ^M5 are the same or different and each represents an alkali metal ion, an alkaline earth metal ion, an organic cation, ammonium ( _NH4 ⁺ ), or a hydrogen atom. In one or more embodiments, the organic cation may be an organic ammonium, such as an alkyl ammonium such as tetramethylammonium, tetraethylammonium, or tetrabutylammonium.
In one or a plurality of embodiments, from the viewpoint of improving the polishing rate and improving the flatness, ^M4 is preferably at least one selected from an alkali metal ion, ammonium ( _NH4 ⁺ ), and a hydrogen atom, and more preferably at least one selected from a sodium ion, a potassium ion, ammonium ( _NH4 ⁺ ), and a hydrogen atom.
In one or more embodiments, from the viewpoint of improving the polishing rate and improving the flatness, ^M5 is preferably at least one selected from an alkali metal ion, ammonium ( _NH4 ⁺ ), and a hydrogen atom, more preferably at least one selected from a sodium ion, a potassium ion, ammonium ( _NH4 ⁺ ), and a hydrogen atom, and even more preferably a hydrogen atom.

In one or more embodiments, from the viewpoint of improving the polishing rate and improving the flatness, the constituent monomer b11 is preferably hydroxybenzoic acid (HBA) or dihydroxybenzoic acid (DHBA), more preferably 4-hydroxybenzoic acid (4-HBA), 2-hydroxybenzoic acid (2-HBA), 2,4-dihydroxybenzoic acid (2,4-HBA), or 2,6-dihydroxybenzoic acid (2,6-HBA), and even more preferably 4-hydroxybenzoic acid (4-HBA).

(Constituent Monomer b12)
The constituent monomer b12 is a monomer represented by the following formula (IV).

In formula (IV), R ³ and R ⁴ are the same or different and represent a hydrogen atom, a hydrocarbon group having 1 to 4 carbon atoms, or -OM ^6. In one or more embodiments, from the viewpoints of improving the polishing rate and improving the flatness, at least one of R ³ and R ⁴ is preferably -OM ⁶ , and more preferably -OH. In one or more embodiments, from the viewpoints of improving the polishing rate and improving the flatness, at least one of R ³ and R ⁴ is preferably a hydrogen atom.
X ¹ represents --SO ₃ M ⁷ or --PO ₃ M ⁸ M ^9. In one or more embodiments, X ¹ is preferably --SO ₃ M ⁷ from the viewpoint of dissolution stability.
^M6 , ^M7 , ^M8 , and ^M9 are the same or different and each represents an alkali metal ion, an alkaline earth metal ion, an organic cation, ammonium ( _NH4 ⁺ ), or a hydrogen atom. In one or more embodiments, the organic cation may be an organic ammonium, such as an alkyl ammonium such as tetramethylammonium, tetraethylammonium, or tetrabutylammonium.
In one or more embodiments, from the viewpoint of improving the polishing rate and improving the flatness, ^M6 is preferably at least one selected from an alkali metal ion, ammonium ( _NH4 ⁺ ), and a hydrogen atom, and more preferably at least one selected from a sodium ion, a potassium ion, ammonium ( _NH4 ⁺ ), and a hydrogen atom.
^M7 , ^M8 and ^M9 are the same or different, and in one or more embodiments, from the viewpoint of improving the polishing rate and improving the flatness, are preferably at least one selected from an alkali metal ion, ammonium ( _NH4 ⁺ ) and a hydrogen atom, and more preferably at least one selected from a sodium ion, a potassium ion, ammonium ( _NH4 ⁺ ) and a hydrogen atom.

In one or more embodiments, constituent monomer b12 may be phenolsulfonic acid (PhS).

From the viewpoint of improving the polishing rate and improving the flatness, the molar ratio (%) of constituent monomer b11 to the sum of constituent monomer b11 and constituent monomer b12 in component B1 is preferably more than 30%, more preferably 35% or more, even more preferably 40% or more, even more preferably more than 40%, even more preferably 42% or more, even more preferably 43% or more, even more preferably 44% or more, even more preferably 45% or more, even more preferably 46% or more, and even more preferably 48% or more.

In one or a plurality of embodiments, from the viewpoint of improving the polishing rate and improving flatness, Component B1 is preferably an anionic condensate containing a structure represented by the following formula (V).

In formula (V), R ⁵ and R ⁶ are the same or different and each represents a hydrogen atom, a hydrocarbon group having 1 to 4 carbon atoms, or -OM ¹¹ .
In one or a plurality of embodiments, from the viewpoint of improving the polishing rate and improving the flatness, ^R5 and ^R6 are preferably a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms, and more preferably a hydrogen atom.
^M10 and ^M11 are the same or different and each represents an alkali metal ion, an alkaline earth metal ion, an organic cation, ammonium ( _NH4 ⁺ ), or a hydrogen atom. In one or more embodiments, the organic cation may be an organic ammonium, such as an alkyl ammonium such as tetramethylammonium, tetraethylammonium, or tetrabutylammonium.
In one or a plurality of embodiments, from the viewpoint of improving the polishing rate and improving the flatness, ^M10 is preferably at least one selected from an alkali metal ion, ammonium ( _NH4 ⁺ ), and a hydrogen atom, and more preferably at least one selected from a sodium ion, a potassium ion, ammonium ( _NH4 ⁺ ), and a hydrogen atom.
In one or more embodiments, from the viewpoint of improving the polishing rate and improving the flatness, ^M11 is preferably at least one selected from an alkali metal ion, ammonium ( _NH4 ⁺ ), and a hydrogen atom, more preferably at least one selected from a sodium ion, a potassium ion, ammonium ( _NH4 ⁺ ), and a hydrogen atom, and even more preferably a hydrogen atom.
In formula (V), X ² represents —SO ₃ M ¹² or —PO ₃ M ¹³ M ^14. In one or more embodiments, X ² is preferably —SO ₃ M ¹² from the viewpoint of dissolution stability.
M ¹² , M ¹³ and M ¹⁴ are the same or different and each represents an alkali metal ion, an alkaline earth metal ion, an organic cation, ammonium (NH ₄ ⁺ ) or a hydrogen atom. In one or more embodiments, the organic cation may be an organic ammonium, such as an alkyl ammonium such as tetramethylammonium, tetraethylammonium or tetrabutylammonium.
In formula (V), m and n are molar fractions when m+n=1, and in one or more embodiments, from the viewpoint of improving the polishing rate and improving the flatness, m is preferably more than 0.3, more preferably 0.35 or more, even more preferably 0.4 or more, even more preferably more than 0.4, even more preferably 0.42 or more, even more preferably 0.43 or more, even more preferably 0.44 or more, even more preferably 0.45 or more, even more preferably 0.46 or more, and even more preferably 0.48 or more. In one or more embodiments, m is 0.8 or less, 0.75 or less, 0.7 or less, or 0.65 or less.

Component B1 can be, for example, a co-condensate of 4-hydroxybenzoic acid (4-HBA) and phenolsulfonic acid (PhS).

Component B1 can be produced, for example, by polymerizing a monomer having constituent monomers b11 and b12 in the presence of formaldehyde by a known means such as an addition condensation method. From the viewpoint of improving hydrolysis resistance and improving storage stability in an acidic polishing solution, it is preferable to produce it by an addition condensation method.

In the present disclosure, as the content (mol %) of a certain constituent unit among all constituent units constituting component B1, depending on the synthesis conditions, the amount (mol %) of the compound for introducing the constituent unit charged in the reaction tank among the compounds for introducing all constituent units charged in the reaction tank in all steps of the synthesis of component B1 may be used. Also, in the present disclosure, when component B1 contains two or more kinds of constituent units, as the constituent ratio (molar ratio) of the two constituent units, depending on the synthesis conditions, the amount ratio (molar ratio) of the compounds for introducing the two constituent units charged in the reaction tank in all steps of the synthesis of component B1 may be used.

Component B1 may have a constituent unit derived from constituent monomer b11 and a constituent unit derived from constituent monomer b12, or other constituent units not included in the structure represented by formula (III).

The arrangement of each of the constituent units constituting component B1 may be random, block, or graft.

<Component B2: Water-soluble anionic condensate>
In one or more embodiments, component B2 is a water-soluble anionic condensate having a benzene ring or a naphthalene ring in the main chain. In one or more embodiments, component B2 is an anionic condensate containing a structural unit having an anionic group in the benzene ring or naphthalene ring in the main chain (hereinafter, also simply referred to as an "anionic structural unit").
In one or more embodiments, the anionic group in the anionic constitutional unit is -SO ₃ M ¹² or -PO ₃ M ¹³ M ¹⁴ , where M ¹² , M ¹³ and M ¹⁴ may be the same or different and are an alkali metal ion, an alkaline earth metal ion, an organic cation, ammonium (NH ₄ ⁺ ) or a hydrogen atom.
From the viewpoint of ensuring water solubility and suppressing the polishing rate and dishing rate of the silicon nitride film during overpolishing, the anionic structural unit preferably has a structure in which at least one hydrogen atom of the benzene ring or naphthalene ring constituting the main chain is replaced with a sulfonic acid group. The aromatic monomer from which the anionic structural unit is derived may be, for example, at least one selected from phenolsulfonic acid, naphthalenesulfonic acid, and salts thereof. Component B2 may be one type or a combination of two or more types. In one or more embodiments, component B2 does not include component B1. Component B1 and component B2 may be used in combination.

Component B2 may further contain a structural unit other than the anionic structural unit. In one or more embodiments, the structural unit other than the anionic structural unit may be at least one structural unit selected from structural unit b21 (hereinafter also simply referred to as "structural unit b21") represented by the following formula (VI) and structural unit b22 (hereinafter also simply referred to as "structural unit b22") represented by the following formula (VII), from the viewpoint of ensuring the polishing rate of the silicon oxide film and suppressing the polishing rate and dishing rate of the silicon nitride film during overpolishing.

(Structural unit b21)
The structural unit b21 is a structural unit represented by the following formula (VI).

In formula (VI), R ⁷ and R ⁸ are the same or different and represent a hydrogen atom or -OM ¹⁵ , M ¹⁵ represents at least one selected from an alkali metal, an alkaline earth metal, an organic cation, ammonium, and a hydrogen atom, R ⁹ and R ¹⁰ are the same or different and represent a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, or -OM ¹⁶ , M ¹⁶ represents at least one selected from an alkali metal, an alkaline earth metal, an organic cation, ammonium, and a hydrogen atom, X ³ represents a bond, -CH ₂ -, -S-, -SO ₂ -, -C(CH ₃ ) ₂ -, or
It is.
In formula (VI), ^R7 and ^R8 are preferably --OH from the viewpoints of ensuring the polishing rate and suppressing the polishing rate and dishing rate of the silicon nitride film during overpolishing. ^R9 and ^R10 are preferably a hydrogen atom or an alkyl group, more preferably a hydrogen atom, from the viewpoints of ensuring the polishing rate, and suppressing the polishing rate and dishing rate of the silicon nitride film during overpolishing. ^X3 is preferably _--SO2-- from the viewpoints of ensuring the polishing rate and suppressing the polishing rate and dishing rate of the silicon nitride film during overpolishing.

Examples of monomers that form the structural unit b21 include bis(4-hydroxyphenyl)sulfone (BisS) and bis(4-hydroxy-3-methylphenyl)sulfone (BSDM).

(Structural unit b22)
The structural unit b22 is a structural unit represented by the following formula (VII).

In formula (VII), R ¹¹ represents a hydrogen atom or -OM ¹⁷ , where M ¹⁷ is at least one selected from an alkali metal, an alkaline earth metal, an organic cation, ammonium, and a hydrogen atom; R ¹² represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, or -OM ¹⁸ , where M ¹⁸ is at least one selected from an alkali metal, an alkaline earth metal, an organic cation, ammonium, and a hydrogen atom.
In formula (VII), R ¹¹ is preferably —OH from the viewpoints of ensuring the polishing rate and suppressing the polishing rate and dishing rate of the silicon nitride film during overpolishing, and R ¹² is preferably a hydrogen atom or an alkyl group from the viewpoints of ensuring the polishing rate and suppressing the polishing rate and dishing rate of the silicon nitride film during overpolishing.

Examples of monomers that form the structural unit b22 include p-cresol and phenol.

From the viewpoint of ensuring the polishing rate and suppressing the polishing rate and dishing rate of the silicon nitride film during overpolishing, examples of component B2 include condensates of aromatic monomers having an aromatic ring and an anionic group, condensates containing an anionic constituent unit and a constituent unit other than the anionic constituent unit, and salts thereof. Examples of the salts include alkali metal ions such as sodium salts, ammonium salts, and organic amine salts.
As the condensate of an aromatic monomer having an aromatic ring and an anionic group, or a salt thereof, from the viewpoint of ensuring the polishing rate and suppressing the polishing rate and dishing rate of the silicon nitride film during overpolishing, a condensate having a structure in which at least one hydrogen atom of the aromatic ring constituting the main chain is substituted with a sulfonic acid group or a salt thereof is preferred, and at least one selected from phenolsulfonic acid, naphthalenesulfonic acid, and salts thereof is more preferred.
As the condensate or salt thereof containing an anionic structural unit and a structural unit other than the anionic structural unit, from the viewpoints of ensuring the polishing rate and suppressing the polishing rate and dishing rate of the silicon nitride film during overpolishing, at least one selected from a condensate containing an anionic structural unit and at least one structural unit selected from structural unit b21 and structural unit b22, and a salt thereof, is preferred.
Examples of component B2 include at least one selected from the group consisting of a condensate of phenolsulfonic acid, a condensate of naphthalenesulfonic acid, a condensate of bis(4-hydroxyphenyl)sulfone (BisS) and phenolsulfonic acid, a condensate of p-cresol and phenolsulfonic acid, a condensate of bis(4-hydroxy-3-methylphenyl)sulfone (BSDM) and phenolsulfonic acid, and a condensate of phenol and phenolsulfonic acid.

When component B2 is a condensate containing an anionic structural unit and at least one structural unit selected from structural unit b21 and structural unit b22, the molar ratio of the anionic structural unit to structural unit b21 or structural unit b22 (anionic structural unit/structural unit b21, or anionic structural unit/structural unit b22) among all structural units of component B2 is preferably 100/0 to 50/50, more preferably 99/1 to 60/40, and even more preferably 98/2 to 70/30, from the viewpoints of suppressing the polishing rate and dishing rate of the silicon nitride film during overpolishing and water solubility.

Component B2 may further have other structural units in addition to the anionic structural unit and the structural units b21 and b22. Examples of the other structural units include benzenesulfonic acid, halogenated derivatives of benzenesulfonic acid, alkylbenzenesulfonic acid, halogenated derivatives of naphthalenesulfonic acid, alkylnaphthalenesulfonic acid, toluenesulfonic acid, and benzoic acid.

<Component B3: Copolymer>
In one or more embodiments, component B3 is a copolymer containing a structural unit derived from styrene and a structural unit derived from a monomer having an anionic group. From the viewpoint of improving the polishing rate and improving the flatness, component B3 is preferably a copolymer containing a structural unit derived from styrene (St) (hereinafter also referred to as "structural unit b31") and a structural unit derived from at least one monomer selected from acrylic acid (AAc), methacrylic acid, maleic acid (MA) and salts thereof (hereinafter also referred to as "structural unit b32"). Examples of the salt include alkali metal salts, alkaline earth metal salts, ammonium salts, and organic ammonium salts. Component B3 may be one type or a combination of two or more types.

Component B3 may be, for example, at least one selected from styrene/acrylic acid copolymer (St/AAc) and styrene/maleic acid copolymer (St/MA).

The content (mol %) of structural unit b31 in all structural units of component B3 is preferably 3 or more, more preferably 5 or more, and even more preferably 8 or more, from the viewpoint of suppressing dishing, and is preferably 80 or less, more preferably 70 or less, and even more preferably 50 or less, from the viewpoint of water solubility.

Component B3 may further contain other structural units in addition to structural units b31 and b32. Examples of other structural units include vinyl phosphoric acid, styrene sulfonic acid, and 2-acrylamido-2-methylpropanesulfonic acid.

Component B3 can be obtained by a known method, such as polymerizing a monomer mixture containing styrene and at least one monomer selected from acrylic acid, methacrylic acid, maleic acid, and salts thereof, by a solution polymerization method. Examples of solvents used in solution polymerization include water; aromatic hydrocarbons such as toluene and xylene; alcohols such as ethanol and 2-propanol; ketones such as acetone and methyl ethyl ketone; and ethers such as tetrahydrofuran and diethylene glycol dimethyl ether. Examples of polymerization initiators used in polymerization include known radical initiators, such as ammonium persulfate salts. During polymerization, a chain transfer agent can be further used, such as thiol chain transfer agents such as 2-mercaptoethanol and β-mercaptopropionic acid. In this disclosure, the content of each structural unit in all structural units of component B3 can be regarded as the ratio of the amount of each monomer used to the total amount of monomers used in polymerization.

The arrangement of each of the constituent units constituting component B3 may be random, block, or graft.

The weight average molecular weight of component B is preferably 1,500 or more, more preferably 4,000 or more, and even more preferably 9,000 or more from the viewpoint of dishing suppression, and is preferably 100,000 or less, more preferably 80,000 or less, and even more preferably 50,000 or less from the viewpoint of polishing rate. More specifically, the weight average molecular weight of component B is preferably 1,500 or more and 100,000 or less, more preferably 4,000 or more and 80,000 or less, and even more preferably 9,000 or more and 50,000 or less. In the present disclosure, the weight average molecular weight is a value measured using gel permeation chromatography (GPC) under the conditions described in the examples.
When component B is component B1, the weight average molecular weight of component B1 is preferably 1,500 or more, more preferably 5,000 or more, and even more preferably 9,000 or more from the viewpoint of suppressing dishing, and is preferably 100,000 or less, more preferably 80,000 or less, and even more preferably 50,000 or less from the viewpoint of polishing rate. More specifically, the weight average molecular weight of component B1 is preferably 1,500 or more and 100,000 or less, more preferably 4,000 or more and 80,000 or less, and even more preferably 9,000 or more and 50,000 or less.
When component B is component B2, the weight average molecular weight of component B2 is preferably 1,500 or more, more preferably 2,000 or more, and even more preferably 4,000 or more from the viewpoint of suppressing dishing, and is preferably 50,000 or less, more preferably 40,000 or less, and even more preferably 20,000 or less from the viewpoint of polishing rate. More specifically, the weight average molecular weight of component B2 is preferably 1,500 or more and 50,000 or less, more preferably 2,000 or more and 40,000 or less, and even more preferably 4,000 or more and 20,000 or less.
When component B is component B3, the weight average molecular weight of component B3 is preferably 1,500 or more, more preferably 2,000 or more, and even more preferably 3,000 or more from the viewpoint of dishing suppression, and is preferably 100,000 or less, more preferably 50,000 or less, and even more preferably 30,000 or less from the viewpoint of polishing rate. More specifically, the weight average molecular weight of component B3 is preferably 1,500 or more and 100,000 or less, more preferably 2,000 or more and 50,000 or less, and even more preferably 3,000 or more and 30,000 or less.

The content of component B in the polishing composition of the present disclosure is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, and even more preferably 0.02% by mass or more, from the viewpoint of suppressing dishing, and is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, and even more preferably 0.1% by mass or less, from the viewpoint of polishing rate. More specifically, the content of component B is preferably 0.005% by mass or more and 0.5% by mass or less, more preferably 0.01% by mass or more and 0.3% by mass or less, and even more preferably 0.02% by mass or more and 0.1% by mass or less. When component B is a combination of two or more types, the content of component B refers to the total content thereof.

The mass ratio B/A of the content of component B to the content of component A in the polishing liquid composition of the present disclosure is preferably 0.01 or more, more preferably 0.03 or more, and even more preferably 0.05 or more, from the viewpoint of improving the polishing rate and improving flatness, and from the same viewpoint, is preferably 0.5 or less, more preferably 0.3 or less, and even more preferably 0.2. More specifically, the mass ratio B/A is preferably 0.01 or more and 0.5 or less, more preferably 0.03 or more and 0.3 or less, and preferably 0.05 or more and 0.2 or less.

[Unsaturated cyclic compound (component C)]
The polishing composition of the present disclosure contains an unsaturated cyclic compound (hereinafter, also simply referred to as "component C"). Component C is an unsaturated cyclic compound having a functional group represented by the following formula (I) or formula (II) in a cyclic skeleton. Component C may be one type or a combination of two or more types.

The unsaturated ring contained in the unsaturated cyclic compound may be, for example, an unsaturated heterocycle. From the viewpoint of improving the polishing rate and flatness, it is preferable that the unsaturated heterocycle has at least one nitrogen atom or oxygen atom in the heterocycle.

(Unsaturated cyclic compound having a functional group represented by formula (I) in the cyclic skeleton)
In one or more embodiments, component C is an unsaturated cyclic compound having a functional group represented by the following formula (I) in a cyclic skeleton.
In formula (I), Y represents OM ¹ or SM ² , and M ¹ and M ² may be the same or different and represent an alkali metal ion, an alkaline earth metal ion, an organic cation, ammonium (NH ₄ ⁺ ) or a hydrogen atom.
From the viewpoint of tautomerism, component C can also be considered as an unsaturated cyclic compound having a functional group represented by the following formula (I') in the cyclic skeleton.

In one or more embodiments, from the viewpoint of improving the polishing rate and improving the flatness, examples of the unsaturated cyclic compound having a functional group represented by formula (I) in the cyclic skeleton include an N-oxide compound containing a nitrogen-containing heteroaromatic ring skeleton having a hydroxyl group at the ortho position of the N-oxide group and a salt thereof (hereinafter also referred to as "component C1"), an N-oxide compound containing a nitrogen-containing heteroaromatic ring skeleton having a thiol group at the ortho position of the N-oxide group and a salt thereof (hereinafter "component C2"), etc.

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

<N-oxide compound (component C1)>
In one or more embodiments, component C1 is an N-oxide compound containing a nitrogen-containing heteroaromatic ring skeleton having a hydroxyl group at the ortho position of the N-oxide group, or a salt thereof. Examples of the salt include alkali metal salts, alkaline earth metal salts, organic amine salts, and ammonium salts. Component C1 may be used alone or in combination of two or more types.

In the present disclosure, at least one nitrogen atom contained in the nitrogen-containing heteroaromatic ring skeleton of component C1 forms an N-oxide. In one or more embodiments, the nitrogen-containing heteroaromatic ring contained in component C1 may be a monocyclic or bicyclic fused ring. In one or more embodiments, the number of nitrogen atoms in the nitrogen-containing heteroaromatic ring contained in component C1 is, for example, 1 to 3, and from the viewpoint of improving 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 C1 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 C1 may be at least one selected from an N-oxide compound containing a pyridine ring having a hydroxy group at the ortho position of the N-oxide group of the pyridine ring, an N-oxide compound containing a quinoline ring having a hydroxy group at the ortho position of the N-oxide group of the quinoline ring, and salts thereof. Among these, from the viewpoints of improving the polishing rate and water solubility, an N-oxide compound containing a pyridine ring having a hydroxy group at the ortho position of the N-oxide group of the pyridine ring or a salt thereof is preferred as component C1.

Component C1 can be, for example, at least one selected from 2-hydroxypyridine N-oxide and salts thereof.

<N-oxide compound (component C2)>
In one or more embodiments, component C2 is an N-oxide compound or a salt thereof that contains a nitrogen-containing heteroaromatic ring skeleton having a thiol group at the ortho position of the N-oxide group of the nitrogen-containing heteroaromatic ring skeleton. Examples of the salt include alkali metal salts, alkaline earth metal salts, organic amine salts, and ammonium salts. Component C2 may be used alone or in combination of two or more types.

In the present disclosure, at least one nitrogen atom contained in the nitrogen-containing heteroaromatic ring skeleton of component C2 forms an N-oxide. In one or more embodiments, the nitrogen-containing heteroaromatic ring contained in component C2 may be a monocyclic or bicyclic fused ring. In one or more embodiments, the number of nitrogen atoms in the nitrogen-containing heteroaromatic ring contained in component C2 is, for example, 1 to 3, and from the viewpoint of improving 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 C2 may be at least one selected from a pyridine N-oxide skeleton, a quinoline N-oxide skeleton, etc. 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 C2 may be at least one selected from an N-oxide compound containing a pyridine ring having a thiol group (-SH) at the ortho position of the N-oxide group of the pyridine ring, an N-oxide compound containing a quinoline ring having a thiol group (-SH) at the ortho position of the N-oxide group of the quinoline ring, and salts thereof. Among these, from the viewpoint of improving the polishing rate, component B2 is preferably an N-oxide compound containing a pyridine ring having a thiol group (-SH) at the ortho position of the N-oxide group of the pyridine ring, or a salt thereof.

Component C2 can be, for example, 2-mercaptopyridine N-oxide or a salt thereof.

(Unsaturated cyclic compound having a functional group represented by formula (II) in the cyclic skeleton)
In one or more embodiments, component C is an unsaturated cyclic compound having a functional group represented by the following formula (II) in a cyclic skeleton.
In formula (II), M ³ represents an alkali metal ion, an alkaline earth metal ion, an organic cation, ammonium (NH ₄ ⁺ ) or a hydrogen atom.

In one or more embodiments, the unsaturated cyclic compound having a functional group represented by formula (II) in the cyclic skeleton may be a compound containing an oxygen-containing heterocyclic skeleton having a keto group and a hydroxyl group at the ortho position of the keto group, or a salt thereof (hereinafter also referred to as "component C3"), from the viewpoint of improving the polishing rate and improving the flatness. Examples of the salt include alkali metal salts, alkaline earth metal salts, organic amine salts such as ethanolamine salts, and ammonium salts. Component C3 may be used alone or in combination of two or more types.

In one or more embodiments, the oxygen-containing heterocycle contained in Component C3 may be a monocyclic or bicyclic condensed ring. In one or more embodiments, the number of oxygen atoms in the oxygen-containing heterocycle contained in Component C3 is preferably 1 from the viewpoint of improving the polishing rate.
In one or a plurality of embodiments, the oxygen-containing heterocyclic skeleton contained in component C3 may be a pyran skeleton.

Examples of component C3 include maltol, ethyl maltol, etc.

In one or more embodiments, the content of component C in the polishing composition of the present disclosure is preferably 0.0001 mass% or more, more preferably 0.001 mass% or more, and even more preferably 0.0015 mass% or more, from the viewpoint of suppressing dishing, and is preferably 0.1 mass% or less, more preferably 0.04 mass% or less, and even more preferably 0.015 mass% or less, from the viewpoint of polishing rate. More specifically, the content of component C is preferably 0.0001 mass% or more and 0.1 mass% or less, more preferably 0.001 mass% or more and 0.04 mass% or less, and even more preferably 0.0015 mass% or more and 0.015 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.

In one or more embodiments, the mass ratio B/C of the content of component B to the content of component C in the polishing liquid composition of the present disclosure is preferably 1 or more, more preferably 2 or more, even more preferably 3 or more, even more preferably 5 or more, and even more preferably 8 or more, from the viewpoint of polishing rate, and is preferably 100 or less, more preferably 50 or less, even more preferably 30 or less, and even more preferably 25 or less, from the viewpoint of suppressing dishing. More specifically, the mass ratio B/C is preferably 1 or more and 100 or less, more preferably 2 or more and 100 or less, more preferably 3 or more and 50 or less, even more preferably 5 or more and 30 or less, and even more preferably 8 or more and 25 or less.

[Aqueous medium]
The aqueous medium contained in the polishing liquid composition of the present disclosure includes water such as distilled water, ion-exchanged water, pure water, and ultrapure water, or a mixed solvent of water and a solvent. The above-mentioned solvent includes a solvent miscible with water (e.g., alcohol such as ethanol). When the aqueous medium is a mixed solvent of water and a solvent, the ratio of water to the entire mixed medium is not particularly limited as long as the effect of the present disclosure is not hindered, and from the viewpoint of economy, for example, 95% by mass or more is preferable, and 98% by mass or more is more preferable. From the viewpoint of surface cleanliness of the polished substrate, the aqueous medium is preferably water, more preferably ion-exchanged water and ultrapure water, and even more preferably ultrapure water. The content of the aqueous medium in the polishing liquid composition of the present disclosure can be the remainder excluding component A, component B, component C, and optional components described below that are blended as necessary.

[Other ingredients]
The polishing liquid composition of the present disclosure may further contain other components such as a pH adjuster, a polymer other than component B, a surfactant, a thickener, a dispersant, a rust inhibitor, a preservative, and a basic substance.

[Polishing liquid composition]
The polishing liquid composition of the present disclosure can be produced by a production method including a step of blending, for example, component A, component B, component C, and an aqueous medium, and, if desired, the above-mentioned optional components (other components) by a known method. For example, the polishing liquid composition of the present disclosure can be produced by blending at least component A, component B, component C, and an aqueous medium. In the present disclosure, "blending" includes mixing component A, component B, component C, and an aqueous medium, and, if necessary, the above-mentioned optional components (other components) simultaneously or in order. The order of mixing is not particularly limited. The blending can be carried out 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 method for producing the polishing liquid composition of the present disclosure can be the same as the content of each component in the above-mentioned polishing liquid composition of the present disclosure.

The embodiment of the polishing liquid composition of the present disclosure may be a so-called one-liquid type in which all components are supplied to the market in a pre-mixed state, or a so-called two-liquid type in which the components are mixed at the time of use. For example, in one or more embodiments, a two-liquid type polishing liquid composition may be composed of a first liquid containing component A and a second liquid containing components B and C, and the first liquid and the second liquid are mixed at the time of use. The first liquid and the second liquid may be mixed before being supplied to the surface to be polished, or they may be supplied separately and mixed on the surface of the substrate to be polished. The first liquid and the second liquid may each contain the optional components described above as necessary.

The pH of the polishing composition of the present disclosure is preferably 3.5 or more, more preferably 4 or more, and even more preferably 5 or more, from the viewpoint of improving the polishing rate, and is preferably 9 or less, more preferably 8.5 or less, and even more preferably 8 or less, from the viewpoint of suppressing dishing. More specifically, the pH is preferably 3.5 or more and 9 or less, more preferably 4 or more and 8.5 or less, and even more preferably 5 or more and 8 or less. In the present disclosure, the pH of the polishing composition is a value at 25°C, and can be measured using a pH meter, specifically, it can be measured by the method described in the examples.

In the present disclosure, "the content of each component in the polishing liquid composition" refers to the content of each component at the time when the polishing liquid composition is first used for polishing. The polishing liquid composition of the present disclosure 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. This concentrated liquid can then be appropriately diluted with the aforementioned aqueous medium as necessary and used in the polishing process. The dilution ratio is preferably 5 to 100 times.

[Polished film]
The film to be polished using the polishing composition of the present disclosure may be, for example, a silicon oxide film formed during the manufacturing process of a semiconductor substrate. Therefore, the polishing composition of the present disclosure may be used in a process that requires the polishing of a silicon oxide film. In one or more embodiments, the polishing composition of the present disclosure may be suitably used for polishing a silicon oxide film performed in a process for forming an element isolation structure of a semiconductor substrate, polishing a silicon oxide film performed in a process for forming an interlayer insulating film, polishing a silicon oxide film performed in a process for forming embedded metal wiring, or polishing a silicon oxide film performed in a process for forming an embedded capacitor. In one or more other embodiments, the polishing composition of the present disclosure may be suitably used for manufacturing a three-dimensional semiconductor device such as a three-dimensional NAND flash memory.

[Polishing liquid kit]
In one aspect, the present disclosure relates to a kit for preparing the polishing liquid composition of the present disclosure (hereinafter also referred to as the "polishing liquid kit of the present disclosure").
The polishing liquid kit of the present disclosure may be, for example, a polishing liquid kit (two-liquid type polishing liquid composition) that contains an abrasive dispersion (first liquid) containing component A and an aqueous medium and an additive aqueous solution (second liquid) containing component B and component C in a mutually unmixed state, which are mixed when used and diluted with an aqueous medium as necessary. The aqueous medium contained in the abrasive dispersion (first liquid) may be the entire amount of the aqueous medium used in the preparation of the polishing liquid composition, or may be a part of the aqueous medium. The additive aqueous solution (second liquid) may contain a part of the aqueous medium used in the preparation of the polishing liquid composition. The abrasive dispersion (first liquid) and the additive aqueous solution (second liquid) may each contain the above-mentioned optional components (other components) as necessary. The abrasive dispersion (first liquid) and the additive aqueous solution (second liquid) may be mixed before being supplied to the surface of the polishing target, or they may be supplied separately and mixed on the surface of the substrate to be polished. According to the polishing liquid kit of the present disclosure, it is possible to obtain a polishing liquid composition that can improve the flatness of the substrate surface after polishing while ensuring the removal rate of the silicon oxide film.

[Polishing method]
In one aspect, the present disclosure relates to a polishing method (hereinafter also referred to as the polishing method of the present disclosure), which includes a step of polishing a film to be polished using the polishing liquid composition of the present disclosure, and the film to be polished is a silicon oxide film formed in the manufacturing process of a semiconductor substrate. By using the polishing method of the present disclosure, it is possible to improve the flatness of the substrate surface after polishing while ensuring the polishing rate of the silicon oxide film, and therefore it is possible to achieve an effect of improving the productivity of semiconductor substrates with improved quality. The specific polishing method and conditions can be the same as those of the manufacturing method of semiconductor substrates of the present disclosure described below.

[Method of manufacturing semiconductor substrate]
In one aspect, the present disclosure relates to a method for producing a semiconductor substrate (hereinafter also referred to as "the method for producing a semiconductor substrate of the present disclosure"), which includes a step of polishing a film to be polished using the polishing liquid composition of the present disclosure (hereinafter also referred to as "the polishing step using the polishing liquid composition of the present disclosure"). The method for producing a semiconductor substrate of the present disclosure relates to a method for producing 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, using the polishing liquid composition of the present disclosure. According to the method for producing a semiconductor device of the present disclosure, it is possible to improve the flatness of the substrate surface after polishing while ensuring the polishing rate of the silicon oxide film, and therefore it is possible to achieve an effect of efficiently producing a semiconductor device.

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 according to the present disclosure, a silicon dioxide layer is grown on a 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 the 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 corresponding to the unevenness of the underlying layer. Next, the silicon oxide film is polished by a CMP method until at least the surface opposite to the surface on the silicon substrate side of the polishing stopper film 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 are flush with each other. The polishing liquid composition of the present disclosure can be used in the step of performing polishing by this CMP method. The width of the convex portion formed corresponding to the unevenness of the underlying layer of the silicon oxide film is, for example, 0.5 μm or more and 5000 μm or less, and the width of the concave portion is, for example, 0.5 μm or more and 5000 μm or less.

In polishing by the CMP method, the surface of the substrate to be polished is brought into contact with a polishing pad, and the substrate to be polished and the polishing pad are moved relative to each other while the polishing liquid composition of the present disclosure is supplied to the contact site, thereby making it possible to flatten the uneven portions of the surface of the substrate to be polished.
In the method for manufacturing a semiconductor substrate according to the present disclosure, another insulating film may be formed between the silicon dioxide layer of the silicon substrate and the polishing stopper film, or another insulating film may be formed between the film to be polished (e.g., a silicon oxide film) and the polishing stopper film (e.g., a silicon nitride film, a polysilicon film).

In a polishing process using the polishing liquid composition of the present disclosure, the rotation speed of the polishing pad can be, for example, 30 to 200 rpm/min, the rotation speed of the substrate to be polished can be, for example, 30 to 200 rpm/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 liquid composition can be, for example, 10 to 500 mL/min or less.

In the polishing process using the polishing liquid composition of the present disclosure, 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.

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 (Examples 1 to 8, Comparative Examples 1 to 7)
Cerium oxide particles (component A), an anionic polymer (component B or non-component B) shown in Table 1, an unsaturated cyclic compound (component C) shown in Table 2, and water were mixed to obtain polishing liquid compositions of Examples 1 to 8 and Comparative Examples 1 to 7. The content (mass %) of each component in the polishing liquid composition is as shown in Table 3, and the content of water is the remainder excluding component A and component B, or non-component B and component C. The pH was adjusted using ammonia or nitric acid.

Cerium oxide particles (component A)
Ground ceria [average primary particle size: 49.5 nm, BET specific surface area: 16.8 ^{m 2} /g, surface potential: −50 mV]

Water-soluble anionic polymer (component B or non-component B)
Details of the water-soluble anionic polymers shown in Table 1 are shown below. Among the water-soluble anionic polymers shown in Table 1, the formaldehyde (co)condensates were synthesized by dropping formalin at 85-105° C. over 3-6 hours so that the amount of formaldehyde was 0.93-0.99 moles per mole of the total amount of monomers, and then carrying out a condensation reaction at 95-105° C. over 4-9 hours. The ratio of the constituent monomers in the copolymer was adjusted by the blending amounts (molar ratio) of the monomers.
It was confirmed by visual observation that each of the water-soluble anionic polymers listed below was completely dissolved in the polishing composition.
(Component B1)
HBA/PhS [formaldehyde condensate of 4-hydroxybenzoic acid (4-HBA) and p-phenolsulfonic acid (pPhS), molar ratio of constituent monomers HBA/PhS=50/50), weight average molecular weight 21,000]
(Component B2)
BisS/PhS [formaldehyde condensate of bis(4-hydroxyphenyl)sulfone and phenolsulfonic acid, constituent monomer molar ratio BisS/PhS=2.5/97.5), weight average molecular weight 5,000]
Naphthalenesulfone condensate [formaldehyde condensate of naphthalenesulfonic acid, weight average molecular weight 8,000]
(Component B3)
St/MA [styrene/maleic acid copolymer, constituent monomer molar ratio St/MA=50/50, weight average molecular weight 5,000]
St/AAc [styrene/acrylic acid copolymer, constituent monomer molar ratio St/AAc=10/90, weight average molecular weight 15,000]
(Non-ingredient B)
Polyacrylic acid [weight average molecular weight 24,000, manufactured by Kao Corporation]

Unsaturated cyclic compound (component C)
(Component C1)
HOPO [2-hydroxypyridine N-oxide, manufactured by Tokyo Chemical Industry Co., Ltd.]
(Component C3)
Ethyl maltol [Tokyo Chemical Industry Co., Ltd.]

2. Method for measuring each parameter (1) pH of polishing composition
The pH value of the polishing composition at 25° C. was measured using a pH meter (HW-41K, manufactured by DKK-TOA Corporation) and was the value measured one minute after the pH meter electrode was immersed in the polishing composition.

(2) Average Primary Particle Size of Cerium Oxide Particles (Ceria, Component A) The average primary particle size (nm) of the cerium oxide particles (Component A) was calculated using the specific surface area S ( ^m2 /g) obtained by the BET (nitrogen adsorption) method described below, and assuming the true density of the cerium oxide particles to be 7.2 g/ ^cm3 .

(3) BET specific surface area of cerium oxide particles (component A) The specific surface area was measured by drying the cerium oxide particle dispersion at 120° C. for 3 hours with hot air, and then pulverizing the dispersion in an agate mortar to obtain a sample. The sample was dried in an atmosphere at 120° C. for 15 minutes immediately before measurement, and then measured by a nitrogen adsorption method (BET method) using a specific surface area measuring device (Micromeritic automatic specific surface area measuring device "Flowsorb III2305", manufactured by Shimadzu Corporation).

(4) Surface potential of cerium oxide particles (component A) 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.). Using ultrapure water, the cerium oxide concentration was adjusted to 0.15%, and the particles were charged into the surface potential measuring device, and the surface potential was measured under the 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 taken as the measurement result.

(5) Weight Average Molecular Weight of Water-Soluble Anionic Polymers (Component B and Non-Component B) The weight average molecular weights of Component B and Non-Component B were measured by gel permeation chromatography (GPC) under the following conditions.
<Measurement conditions>
Column: G4000SWXL + G2000SWXL (Tosoh)
Eluent: 30mM _CH3COONa / _CH3CN =6/4
Flow rate: 0.7ml/min
Detection: UV 280 nm
Sample size: 0.2 mg/ml
Standard substance: Polystyrenesulfonate sodium salt (monodisperse polystyrenesulfonate: molecular weight: 206, 1,800, 4,000, 8,000, 18,000, 35,000, 88,000, 780,000) manufactured by Nishio Kogyo Co., Ltd.
Detector: Tosoh Corporation UV-8020

3. Evaluation of dishing of polishing compositions (Examples 1 to 8, Comparative Examples 1 to 7)
(1) Test piece (blanket substrate)
A silicon oxide film (blanket film) having a thickness of 2000 nm was formed on one side of a silicon wafer by TEOS-plasma CVD to obtain a silicon oxide film test piece (blanket substrate).
(Pattern board)
A commercially available CMP characteristic evaluation wafer (Advantec's "P-TEOS MIT864 PT wafer", diameter 300 mm) was used as the pattern substrate for evaluation. This pattern substrate for evaluation has a silicon nitride film with a thickness of 150 nm as the first layer and a silicon oxide film with a thickness of 450 nm as the second layer 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 silicon oxide film used as the measurement object has a line width of 100 μm for the convex portions and the concave portions.

(2) Polishing rate of silicon oxide film on convex portions The above test pieces were polished using each polishing composition under the following polishing conditions. After polishing, the test pieces were washed with ultrapure water and dried, and were used for measurement using an optical interference film thickness measuring device described below.
<Polishing conditions>
Polishing device: Single-sided polishing machine [Ebara Corporation, FREX-200]
Polishing pad: Hard urethane pad "IC-1000/Suba400" [manufactured by Nitta Haas]
Plate rotation speed: 100 rpm
Head rotation speed: 107 rpm
Polishing load: 300g/cm ²
Amount of polishing solution supplied: 200 mL/min Polishing time: 1 min Before and after polishing, the thickness of the silicon oxide film on the convex parts was measured using ASET F5x (KLA Tencor Corporation). The polishing rate of the silicon oxide film on the convex parts was calculated by the following formula. The calculation results are shown in Table 3.
Polishing speed of convex part (nm/min)
= [thickness of silicon oxide film on the convex parts before polishing (nm) - thickness of silicon oxide film on the convex parts after polishing (nm)] / polishing time (min)

(3) Amount of dishing during overpolishing After the silicon oxide film on the convex parts was planarized and the silicon nitride film was exposed, the silicon oxide film on the convex parts was overpolished for 20% of the time required for the silicon oxide film on the convex parts to be planarized (planarization time), and the thickness of the silicon oxide film on the concave parts before and after the overpolishing was measured using ASET F5x (manufactured by KLA Tencor Corporation). The amount of dishing during overpolishing was calculated by the following formula.
Amount of recess polished after nitride film is exposed (nm)
= Height of the convex portion when the nitride film is exposed (nm) - Height of the concave portion at the end of polishing (nm)
The results are shown in Table 3.

As shown in Table 3, in Examples 1 to 8, the amount of dishing of the silicon nitride film during overpolishing was reduced and flatness was improved while maintaining the polishing speed of the silicon oxide film on the convex parts, compared to Comparative Examples 1, 2, and 5 to 7 that did not contain component C, Comparative Example 3 that did not contain components B and C, and Comparative Example 4 that did not contain component B.

In one or more embodiments, the polishing composition of the present disclosure is useful in a method for manufacturing semiconductor substrates for high density or high integration.

Claims (5)

The composition contains cerium oxide particles (component A), a water-soluble anionic polymer (component B), an unsaturated cyclic compound (component C), and an aqueous medium;
Component B is an anionic condensate having an aromatic group in the molecule and including a structure represented by the following formula (V):
Component C is a polishing composition for silicon oxide films, which has a functional group represented by the following formula (I) or formula (II) in a cyclic skeleton:

In formula (I), Y represents OM ¹ or SM ² , and M ¹ and M ² may be the same or different and represent an alkali metal ion, an alkaline earth metal ion, an organic cation, ammonium (NH ₄ ⁺ ) or a hydrogen atom.
In formula (II), M ³ represents an alkali metal ion, an alkaline earth metal ion, an organic cation, ammonium (NH ₄ ⁺ ) or a hydrogen atom.

In formula (V), R5 ^and R6 ^are the same or different and represent a hydrogen atom, a hydrocarbon group having 1 to 4 carbon atoms, or -OM11; ^X2 is -SO3M12 or -PO3M13M14; M10, M11, M12, M13 ^and M14 are _the ^same or different _and represent an ^{alkali metal ion} , an alkaline earth metal ion, an organic cation, ammonium (NH4 + ⁾ _or ^a hydrogen ^{atom ; m} and n are mole fractions when m+n=1, and m is greater than 0.3. The polishing composition according to claim 1, wherein component C is an N-oxide compound or a salt thereof that contains a nitrogen-containing heteroaromatic ring skeleton having a hydroxyl group at the ortho position of the N-oxide group. The polishing composition according to claim 1, wherein the mass ratio B/C of the content of component B to the content of component C is 3 or more. A method for producing a semiconductor substrate, comprising a step of polishing a film to be polished with the polishing composition according to claim 1 . 4. A polishing method comprising the step of polishing a film to be polished with the polishing composition according to claim 1 , wherein the film to be polished is a silicon oxide film formed in the course of manufacturing a semiconductor substrate.