JP7718893B2 - polishing liquid composition - Google Patents

Description

This disclosure relates to a polishing composition for use in polishing silicon substrates, as well as a polishing method and a method for manufacturing semiconductor substrates using the same.

Polishing compositions containing silica particles are known as polishing compositions used to polish silicon substrates used in the manufacture of semiconductor substrates. In recent years, with the increasing demand for semiconductors, there has been a demand for polishing compositions that can be diluted at a high ratio to achieve high productivity (high surface quality, high polishing rate) while reducing the costs of using and disposing of the polishing liquid. In response to this demand, polishing compositions that achieve good surface quality (low haze surface) in the process of diluting the polishing composition stock solution by 50 times or more by volume, and polishing compositions containing cationic water-soluble polymers for the purpose of improving the polishing rate have been proposed (e.g., Patent Documents 1 and 2).

Patent Document 1 proposes a manufacturing method including a step of diluting a stock solution of a polishing composition containing abrasive grains, a basic compound, a water-soluble polymer, and water so that the pH change is 0.15 or more. The example of this document describes a polishing composition containing 0.06% colloidal silica, ammonia, and hydroxyethyl cellulose (HEC) with a weight-average molecular weight of 250,000.
Patent Document 2 proposes a semiconductor polishing composition containing abrasive grains, a basic compound, and two or more water-soluble polymers, the water-soluble polymers including a cationic water-soluble polymer containing a nitrogen-containing group. The examples of this document describe a semiconductor polishing composition containing 0.45% colloidal silica, ammonia, tetramethylammonium hydroxide, HEC having a weight-average molecular weight of 800,000, and polyethyleneimine (PEI).

JP 2016-53114 A Japanese Patent Application Laid-Open No. 2006-352042

The polishing solution described in Patent Document 1, in which the stock polishing composition is highly diluted and used with a silica concentration of 0.1% by mass or less, is insufficient because it significantly reduces the polishing rate. The polishing solution described in Patent Document 2, which contains a cationic water-soluble polymer with a nitrogen-containing group such as PEI, improves the polishing rate, but the polishing rate tends to decrease with continued use of the polishing pad, resulting in unstable polishing quality, increased polishing pad dressing requirements, a shorter period until the polishing pad needs to be replaced, and reduced productivity.

The present disclosure provides a polishing composition that can improve the polishing rate while suppressing a decrease in the polishing rate with continued use of a polishing pad, even with a low silica particle content, as well as a method for polishing silicon substrates and a method for manufacturing semiconductor substrates using the same.

In one aspect, the present disclosure relates to a polishing liquid composition containing the following component A and component B, wherein the content of component A is 0.1 mass % or less, the mass ratio B/A of the content of component B to the content of component A is 0.07 or more, and the pH is more than 8.5 and 14 or less.
Component A: Silica particles; Component B: A water-soluble polymer containing basic nitrogen atoms, at least some of which contain heteroatoms (excluding basic nitrogen atoms) at positions selected from the β-, γ-, and δ-positions.

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

In one aspect, the present disclosure relates to a method for manufacturing a semiconductor substrate, comprising the steps of polishing a silicon substrate to be polished using the polishing liquid composition of the present disclosure and cleaning the polished silicon substrate.

The present disclosure provides a polishing liquid composition that can improve the polishing rate while suppressing a decrease in the polishing rate with continued use of the polishing pad, even with a low silica particle content, as well as a method for polishing silicon substrates using the polishing liquid composition and a method for manufacturing semiconductor substrates.

This disclosure is based on the finding that by using a polishing liquid composition for silicon substrates that contains silica particles and a specific water-soluble polymer having a basic nitrogen atom and has a pH greater than 8.5 and not greater than 14, it is possible to improve the polishing rate while suppressing a decrease in the polishing rate during continued use of the polishing pad, even with a low silica particle content.

That is, in one aspect, the present disclosure relates to a polishing liquid composition (hereinafter also referred to as the "polishing liquid composition of the present disclosure") containing the following component A and component B, wherein the content of component A is 0.1 mass % or less, the mass ratio B/A of the content of component B to the content of component A is 0.07 or more, and the pH is more than 8.5 and 14 or less.
Component A: Silica particles; Component B: A water-soluble polymer containing basic nitrogen atoms, at least some of which contain heteroatoms (excluding basic nitrogen atoms) at positions selected from the β-, γ-, and δ-positions.

According to one or more embodiments of the present disclosure, even with a low silica particle content, it is possible to achieve both an improvement in the polishing rate and prevention of a decrease in the polishing rate during continued use of the polishing pad.

Although the details of the mechanism by which the effects of the present disclosure are exerted are not clear, it is presumed as follows.
Generally, even if a polishing solution containing a cationic water-soluble polymer with a nitrogen-containing group, such as polyethyleneimine, maintains a certain removal rate, the removal rate tends to decrease with continued use of the polishing pad. One of the reasons for this is thought to be clogging of the polishing pad. Typical cationic water-soluble polymers adhere not only to silicon substrates and silica particles, but also to the surface of the polishing pad. To prevent clogging, a sufficient amount of cationic water-soluble polymer must be added to the polishing pad, adsorbing it to form a protective film, suppressing excessive adhesion of silica particles to the polishing pad through steric and charge repulsion. However, typical cationic water-soluble polymers have a strong adsorption force to silica particles, which tends to cause aggregation and reduce product stability. Therefore, it is difficult to add a sufficient amount of cationic water-soluble polymer to adhere to the polishing pad.
In the present disclosure, a specific water-soluble polymer (component B) containing a basic nitrogen atom is adsorbed to silica particles (component A) without causing aggregation of the silica particles, allowing the content of component B to be increased relative to the content of component A. This is thought to be because component B has a heteroatom near the basic nitrogen atom, which alleviates the strong interaction between the nitrogen atom and the silica particles. As a result, some of the component B that is not adsorbed to the silica particles is adsorbed to the polishing pad to form a protective film, which can suppress the adhesion of the silica particles to the polishing pad, and the silica particles are appropriately discharged from the polishing pad, which is thought to suppress a decrease in the removal rate during continued use of the polishing pad.
Furthermore, under alkaline polishing conditions where the pH is greater than 8.5 and equal to or less than 14, both the silica abrasive grains and the silicon substrate to be polished have negative charges, and electrostatic repulsion is constantly generated. It is believed that alleviating this electrostatic repulsion is effective in improving the polishing rate.
In the present disclosure, a specific water-soluble polymer (component B) is adsorbed to silica particles (component A) and the silicon substrate to be polished by the van der Waals forces of the entire molecule, significantly reducing the electrostatic repulsion between the silica particles (component A) and the silicon substrate to be polished, thereby efficiently attracting a small amount of silica particles to the silicon substrate to be polished. Therefore, it is believed that the polishing rate can be improved even when the content of component A is 0.1 mass % or less.
However, the present disclosure need not be construed as being limited to these mechanisms.

[Silicon substrate to be polished]
In one or more embodiments, the polishing liquid composition of the present disclosure is a polishing composition for silicon substrates, and can be used, for example, in a polishing step of polishing a silicon substrate to be polished in a method for manufacturing a semiconductor substrate, or in a polishing step of polishing a silicon substrate to be polished in a method for polishing a silicon substrate. In one or more embodiments, examples of the silicon substrate to be polished using the polishing liquid composition of the present disclosure include silicon wafers and silicon substrates, and in one or more embodiments, examples of the silicon substrate to be polished include single-crystal silicon substrates, polysilicon substrates, substrates having a polysilicon film, SiN substrates, etc. From the viewpoint of exerting the effects of the polishing liquid composition of the present disclosure, the silicon substrate to be polished is preferably a single-crystal silicon substrate or a polysilicon substrate, and more preferably a single-crystal silicon substrate.

[Silica particles (component A)]
The polishing composition of the present disclosure contains silica particles (hereinafter also referred to as "Component A") as an abrasive. Examples of Component A include colloidal silica, fumed silica, pulverized silica, and surface-modified silica thereof. From the viewpoint of achieving both improved polishing rate and storage stability, and from the viewpoint of improving surface quality such as reducing surface roughness (haze), surface defects, and scratches, colloidal silica is preferred. Component A may be one type or a combination of two or more types.

From the viewpoint of ease of use, Component A is preferably used in the form of a slurry. When Component A contained in the polishing liquid composition of the present disclosure is colloidal silica, the colloidal silica is preferably obtained from an alkoxysilane hydrolysate, from the viewpoint of preventing contamination of silicon substrates by alkali metals, alkaline earth metals, and the like. Silica particles obtained from an alkoxysilane hydrolysate can be produced by conventionally known methods.

From the viewpoint of maintaining the polishing rate, the average primary particle diameter of Component A is preferably 10 nm or more, more preferably 15 nm or more, and even more preferably 20 nm or more, and from the viewpoint of improving storage stability and improving surface quality such as reducing surface roughness (haze), surface defects, and scratches, the average primary particle diameter of Component A is preferably 50 nm or less, more preferably 45 nm or less, even more preferably 40 nm or less, and even more preferably 30 nm or less. From the same viewpoint, the average primary particle diameter of Component A is preferably 10 nm or more and 50 nm or less, more preferably 15 nm or more and 45 nm or less, even more preferably 20 nm or more and 40 nm or less, and preferably 20 nm or more and 30 nm or less.
In the present disclosure, the average primary particle size of Component A is calculated using the specific surface area S ( ^m2 /g) calculated by the nitrogen adsorption method (BET method). The average primary particle size value is a value measured by the method described in the Examples.

From the viewpoint of maintaining the polishing rate, the average secondary particle diameter of component A is preferably 20 nm or more, more preferably 30 nm or more, and even more preferably 40 nm or more, and from the viewpoint of improving storage stability and improving surface quality such as reducing surface roughness (haze), surface defects, and scratches, it is preferably 100 nm or less, more preferably 90 nm or less, even more preferably 80 nm or less, even more preferably 70 nm or less, and even more preferably 60 nm or less. From the same viewpoint, the average secondary particle diameter of component A is preferably 20 nm or more and 100 nm or less, more preferably 30 nm or more and 90 nm or less, even more preferably 30 nm or more and 80 nm or less, even more preferably 30 nm or more and 70 nm or less, and even more preferably 40 nm or more and 60 nm or less.
In the present disclosure, the average secondary particle diameter is a value measured by dynamic light scattering (DLS) method, and is a value measured by the method described in the Examples.

The degree of association of component A is preferably 3 or less, more preferably 2.5 or less, and even more preferably 2.3 or less, from the viewpoint of improving storage stability and surface quality; and is preferably 1.1 or more, more preferably 1.5 or more, and even more preferably 1.8 or more, from the viewpoint of achieving both an improvement in the removal rate and storage stability and improving surface quality.
In the present disclosure, the degree of association of component A is a coefficient representing the shape of silica particles and is calculated by the following formula.
Degree of association = average secondary particle size / average primary particle size

Methods for adjusting the degree of association of component A include those described in, for example, JP-A Nos. 6-254383, 11-214338, 11-60232, 2005-060217, and 2005-060219.

The shape of component A is preferably spherical and/or cocoon-shaped, from the viewpoints of achieving both improved polishing speed and storage stability, as well as improving surface quality.

The content of component A in the polishing composition of the present disclosure is preferably 0.01 mass% or more, more preferably 0.02 mass% or more, and even more preferably 0.03 mass% or more, calculated as _SiO2 , from the viewpoint of improving the removal rate. From the viewpoints of reducing the environmental load, reducing wastewater treatment costs, improving storage stability, and improving surface quality, the content is 0.1 mass% or less, preferably less than 0.1 mass%, more preferably 0.09 mass% or less, even more preferably 0.08 mass% or less, and even more preferably 0.07 mass% or less. From the same viewpoint, the content of component A in the polishing composition of the present disclosure is preferably 0.01 mass% or more and 0.1 mass% or less, more preferably 0.02 mass% or more and 0.09 mass% or less, more preferably 0.02 mass% or more and 0.08 mass% or less, and even more preferably 0.03 mass% or more and 0.07 mass% or less. When component A is a combination of two or more types, the content of component A refers to the total content thereof.

[Water-soluble polymer containing a basic nitrogen atom (component B)]
The polishing liquid composition of the present disclosure contains a water-soluble polymer (hereinafter also referred to as "Component B") containing basic nitrogen atoms, at least some of which contain heteroatoms (excluding basic nitrogen atoms) at positions selected from the β, γ, and δ positions. Component B is believed to adjust the zeta potential of silica particles (Component A) and the silicon substrate to be polished, thereby reducing the electrostatic repulsion between the silica particles (Component A) and the silicon substrate to be polished and suppressing aggregation of the silica particles. In the present disclosure, "water-soluble" refers to a solubility of 0.5 g/100 mL or more, preferably 2 g/100 mL or more, in water (20°C). Examples of heteroatoms include oxygen atoms, sulfur atoms, nitrogen atoms (excluding basic nitrogen atoms), and halogens (e.g., fluorine, chlorine, etc.). In one or more embodiments, the heteroatom is an oxygen atom derived from glycidol modification.
In the present disclosure, the term "basic nitrogen atom" refers to a nitrogen atom contained in a basic nitrogen-containing functional group. Examples of the basic nitrogen-containing functional group include a primary amino group, a secondary amino group, a tertiary amino group, a quaternary ammonium group, and a nitrogen-containing aromatic ring group (e.g., a pyridyl group, an imidazolyl group).

From the viewpoint of achieving both an improvement in the removal rate and storage stability, Component B preferably contains a structural unit derived from one or more monomers selected from allylamine and diallylamine, and more preferably contains a structural unit derived from allylamine.
In one or more embodiments, from the viewpoint of availability, Component B is preferably an amino group-containing water-soluble polymer containing a constituent unit derived from allylamine (hereinafter also referred to as "Component B1"), and in one or more embodiments, it is preferably an amino group-containing water-soluble polymer containing a constituent unit derived from diallylamine (hereinafter also referred to as "Component B2").

(Component B1: Amino group-containing water-soluble polymer containing allylamine-derived structural units)
In one or more embodiments, at least a portion of the amino groups in the allylamine-derived structural unit preferably have a sterically shielding group from the viewpoint of achieving both improved removal rate and storage stability, as well as from the viewpoint of availability. In the present disclosure, the sterically shielding group refers to a sterically (bulky) substituent that can shield the nitrogen atom of the amino group of Component B1 to suppress cationization. From the same viewpoint, the amino group having the sterically shielding group is preferably a secondary amino group or a tertiary amino group containing a hydrocarbon group having 2 to 11 carbon atoms and a heteroatom. Examples of the heteroatom include an oxygen atom, a sulfur atom, a nitrogen atom (excluding basic nitrogen atoms), and a halogen atom (e.g., fluorine, chlorine, etc.), and among these, an oxygen atom is preferred. In one or more embodiments, the heteroatom is preferably an oxygen atom derived from glycidol modification. The number of carbon atoms in the hydrocarbon group is preferably 2 or more, more preferably 3 or more, from the viewpoint of improving the shielding property of the amino group (suppressing cationization of the nitrogen atom of the amino group) and from the viewpoint of achieving both an improvement in the polishing rate and storage stability. From the viewpoint of improving water solubility and availability, the number of carbon atoms in the hydrocarbon group is preferably 11 or less, more preferably 7 or less, even more preferably 5 or less, and even more preferably 4 or less.

In one or more embodiments, the amino group having a sterically shielding group is a modified amino group with a glycidol derivative. In one or more embodiments, the amino group is a group formed by reaction of an amino group in an allylamine-derived structural unit with a glycidol derivative. At least a portion of the amino groups in component B1 are modified with the glycidol derivative to form amino groups having a sterically shielding group. From the viewpoints of improving storage stability and surface quality, the equivalent of the glycidol derivative relative to the number of amino groups (1 equivalent) in the allylamine-derived structural unit (hereinafter also referred to as the "glycidol modification ratio") is preferably 0.3 or more, more preferably 0.5 or more, even more preferably 0.8 or more, even more preferably 1 or more, preferably greater than 1.1, more preferably 1.2 or more, even more preferably 1.3 or more, even more preferably 1.4 or more. From the viewpoint of improving the polishing rate, it is preferably 4 or less, more preferably 3 or less, even more preferably 2.5 or less, even more preferably 2 or less, even more preferably 1.9 or less, even more preferably 1.8 or less.

In the present disclosure, the glycidol modification rate is a value measured by the method described in the Examples using ¹³ C-NMR, although the glycidol modification rate can also be measured by the following method (1) or (2).
(1) It can be determined from the amino group equivalent of the allylamine polymer used as the reaction raw material and the number of moles of the glycidol derivative.
(2) The nitrogen content N (mass %) of the reaction product of a glycidol derivative and an allylamine polymer is measured, and the nitrogen content N can be calculated from the following formula:
Glycidol modification rate = A/B
Here, A=(100−N×molecular weight of allylamine monomer/14)/molecular weight of glycidol derivative, and B=N/14.

Examples of the glycidol derivative include glycidol and alkyl glycidyl ether. Glycidol is preferred from the standpoint of availability and from the standpoint of achieving both improved polishing rate and storage stability. From the standpoint of availability, the alkyl group of the alkyl glycidyl ether is preferably an alkyl group having 1 to 8 carbon atoms, such as methyl, ethyl, propyl, butyl, and 2-ethylhexyl. Examples of the alkyl glycidyl ether include methyl glycidyl ether and 2-ethylhexyl glycidyl ether.

In one or more embodiments, component B1 may be a polyallylamine in which at least some of the amino groups have sterically shielding groups, and in one or more embodiments, may be a reaction product of a polyallylamine with a glycidol derivative.

In one or more embodiments, Component B1 includes a compound (glycidol-modified polyallylamine) containing a structural unit represented by the following formula (I):

In formula (I), ^R1 and ^R2 each represent a hydrogen atom or a sterically shielding group. Examples of the sterically shielding group include modifying groups derived from glycidol derivatives, and in one or more embodiments, examples include one-molar and two-molar adducts of glycidol, such as _—CH2CH (OH) _CH2 (OH), _—CH2CH (OH) _CH2O — _CH2CH (OH) _CH2 (OH), and the like.

(Component B2: Amino group-containing water-soluble polymer containing a constitutional unit derived from diallylamine)
In one or more embodiments, from the viewpoint of achieving both an improvement in the removal rate and storage stability, at least a portion of the amino groups in the diallylamine-derived structural unit preferably have an electron-withdrawing group at the β- or γ-position of the amino group. Examples of the electron-withdrawing group include a group represented by the following formula (II):

In one or more embodiments, Component B2 includes a compound containing a constitutional unit derived from diallylamine and a constitutional unit derived from sulfur dioxide, and examples thereof include a compound containing a constitutional unit represented by the following formula (III):

In formula (III), ^R3 is an alkyl group having 1 to 3 carbon atoms which may have a hydroxyl group. From the viewpoints of availability and economy, ^R3 is preferably a methyl group. Furthermore, n+m=1, and n and m are 0 or 1. From the same viewpoint, a compound in which m=1 and n=0 is preferred. A mixture of a compound in which m=1 and n=0 and a compound in which m=0 and n=1 may also be used.

In one or more embodiments, Component B2 includes a compound containing a structural unit represented by the following formula (IV), and examples thereof include a methyldiallylamine/sulfur dioxide copolymer.

From the viewpoint of improving the polishing rate, the pKa of component B is preferably 5 or more, more preferably 5.5 or more, even more preferably 5.9 or more, and even more preferably 6.3 or more. From the viewpoint of improving surface quality, the pKa is preferably 8.5 or less, more preferably 8.3 or less, even more preferably 8.1 or less, and even more preferably 8 or less.

From the viewpoint of improving the polishing rate, the weight-average molecular weight of Component B is preferably 800 or more, more preferably 1,000 or more, even more preferably 2,000 or more, even more preferably 3,000 or more, even more preferably 4,000 or more, even more preferably 5,000 or more, even more preferably 6,000 or more, even more preferably 7,000 or more, even more preferably 8,000 or more, even more preferably 9,000 or more, and even more preferably 10,000 or more. From the viewpoint of achieving both improved polishing rate and storage stability, and reducing surface roughness and surface defects, the weight-average molecular weight is preferably 100,000 or less, more preferably 90,000 or less, even more preferably 80,000 or less, even more preferably 70,000 or less, even more preferably 60,000 or less, even more preferably 50,000 or less, and even more preferably 40,000 or less. The weight-average molecular weight of Component B in this disclosure can be measured, for example, by the method described in the Examples.

From the viewpoint of achieving both improved removal rate and storage stability, the content of component B in the polishing composition of the present disclosure is preferably 10 ppm or more, more preferably 30 ppm or more, and even more preferably 50 ppm or more. From the same viewpoint, the content is preferably 200 ppm or less, more preferably 150 ppm or less, and even more preferably 100 ppm or less. In this disclosure, 1% by mass is 10,000 ppm (the same applies hereinafter).

The ratio of the content of component B to the content of component A in the polishing liquid composition of the present disclosure (mass ratio B/A) is 0.07 or more, preferably 0.09 or more, and more preferably 0.11 or more, from the viewpoints of suppressing a decrease in the polishing rate during continued use of the polishing pad and improving the polishing rate, and from the same viewpoints, is preferably 0.4 or less, more preferably 0.3 or less, and even more preferably 0.25 or less.

[water]
In one or more embodiments, the polishing composition of the present disclosure may contain water. Examples of water include ion-exchanged water and ultrapure water. The content of water in the polishing composition of the present disclosure may be, for example, the remainder of Component A, Component B, and the optional components described below.

[Nonionic water-soluble polymer (component C)]
In one or more embodiments, the polishing liquid composition of the present disclosure may contain a nonionic water-soluble polymer (hereinafter also referred to as "component C") from the viewpoint of reducing surface roughness (haze). From the same viewpoint, component C is preferably a nonionic water-soluble polymer having an alkylene oxide group, a hydroxyl group, or an amide group in the molecule. Examples of the alkylene oxide group include an ethylene oxide group and a propylene oxide group. Component C may be one type or a combination of two or more types.

From the viewpoint of reducing surface roughness (haze), component C can be at least one selected from polyglycerin, polyglycerin alkyl ether, polyglycerin alkyl ester, hydroxyalkyl cellulose, polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyhydroxyethylacrylamide, and polyethylene glycol (PEG) or polypropylene glycol having a weight-average molecular weight of 1,000 or more and 20,000 or less.
From the viewpoint of achieving both an improvement in the polishing rate and a reduction in surface roughness (haze), and from the viewpoint of suppressing foaming of the polishing liquid, the alkyl group of the polyglycerol alkyl ether is preferably an alkyl group having 3 to 22 carbon atoms, more preferably an alkyl group having 5 to 16 carbon atoms, and even more preferably an alkyl group having 7 to 12 carbon atoms. The alkyl group may be a linear alkyl group or a branched alkyl group. From the viewpoint of improving wettability, the average degree of polymerization of the glycerol units of the polyglycerol alkyl ether is 5 or more, preferably 10 or more, more preferably 15 or more, and even more preferably 18 or more. From the viewpoint of achieving both an improvement in the polishing rate and a reduction in surface roughness (haze), the average degree of polymerization is 100 or less, preferably 60 or less, more preferably 45 or less, and even more preferably 25 or less. Examples of the polyglycerol alkyl ether include polyglycerol lauryl ether, polyglycerol decyl ether, and polyglycerol myristyl ether.
From the viewpoint of achieving both an improvement in the polishing rate and a reduction in surface roughness (haze), and from the viewpoint of suppressing foaming of the polishing liquid, the alkyl group of the polyglycerol alkyl ester is preferably an alkyl group having 3 to 22 carbon atoms, more preferably an alkyl group having 5 to 16 carbon atoms, and even more preferably an alkyl group having 7 to 12 carbon atoms. The alkyl group may be a linear alkyl group or a branched alkyl group. From the viewpoint of improving wettability, the average degree of polymerization of the glycerol units of the polyglycerol alkyl ester is 5 or more, preferably 10 or more, more preferably 15 or more, and even more preferably 18 or more. From the viewpoint of achieving both an improvement in the polishing rate and a reduction in surface roughness (haze), the average degree of polymerization is 100 or less, preferably 60 or less, more preferably 45 or less, and even more preferably 25 or less. Examples of the polyglycerol alkyl ester include polyglycerol lauryl ester, polyglycerol decyl ester, and polyglycerol myristyl ester.
From the viewpoint of achieving both an improvement in the polishing rate and a reduction in surface roughness (haze), the hydroxyalkyl cellulose is preferably at least one selected from hydroxyethyl cellulose (HEC), hydroxypropyl cellulose, and hydroxybutyl cellulose, and more preferably HEC.
Among these, from the viewpoint of reducing surface roughness (haze), component C is preferably at least one selected from polyethylene glycol (PEG) or polypropylene glycol having a weight-average molecular weight of 1,000 or more and 20,000 or less, and hydroxyethyl cellulose (HEC).

The weight average molecular weight of component C is preferably 1,000 or more, more preferably 1,500 or more, and even more preferably 2,000 or more, from the viewpoint of preventing a decrease in the polishing rate during continued use of the polishing/polishing pad and from the viewpoint of achieving both an improvement in the polishing rate and a reduction in surface roughness (haze). From the same viewpoint and from the viewpoint of the filterability of the polishing liquid, it is preferably 500,000 or less, more preferably 400,000 or less, and even more preferably 300,000 or less.
When component C is PEG or polypropylene glycol having a weight-average molecular weight of 1,000 or more and 20,000 or less, the weight-average molecular weight of component C is preferably 1,000 or more, more preferably 2,000 or more, even more preferably 3,000 or more, and even more preferably 4,000 or more, from the viewpoint of suppressing a decrease in the removal rate during continued use of the polishing pad and from the viewpoint of achieving both an improvement in the removal rate and a reduction in surface roughness (haze); and from the same viewpoint and from the viewpoint of the filterability of the polishing liquid, it is preferably 20,000 or less, more preferably 10,000 or less, even more preferably 8,000 or less, and even more preferably 6,000 or less.
When component C is HEC, from the same viewpoint, the weight average molecular weight of component C is preferably 50,000 or more, more preferably 100,000 or more, and even more preferably 150,000 or more, and is preferably 500,000 or less, more preferably 400,000 or less, and even more preferably 300,000 or less.
The weight average molecular weight of Component C can be measured by the method described in the Examples below.

When the polishing liquid composition of the present disclosure contains component C, the content of component C in the polishing liquid composition of the present disclosure is preferably 1 ppm or more, more preferably 3 ppm or more, and even more preferably 5 ppm or more from the viewpoint of reducing surface roughness (haze), and is preferably 200 ppm or less, more preferably 150 ppm or less, and even more preferably 100 ppm or less from the viewpoint of improving the removal rate. From the same viewpoint, the content of component C in the polishing liquid composition of the present disclosure is preferably 1 ppm or more and 200 ppm or less, more preferably 3 ppm or more and 150 ppm or less, and even more preferably 5 ppm or more and 100 ppm or less. When component C is a combination of two or more types, the content of component C refers to the total content of these components.

When the polishing liquid composition of the present disclosure contains component C, the ratio C/A of the content of component C to the content of component A (mass ratio C/A) in the polishing liquid composition of the present disclosure is, from the viewpoint of suppressing a decrease in the removal rate during continued use of the polishing pad and from the viewpoint of achieving both an improved removal rate and a reduced surface roughness (haze), preferably 0.001 or more, more preferably 0.005 or more, even more preferably 0.01 or more, even more preferably 0.015 or more, even more preferably 0.02 or more, even more preferably 0.025 or more, and preferably 1 or less, more preferably 0.7 or less, even more preferably 0.4 or less, more preferably 0.2 or less, and even more preferably 0.1 or less. From the same viewpoint, the mass ratio C/A in the polishing liquid composition of the present disclosure is preferably 0.005 or more and 0.2 or less, more preferably 0.01 or more and 0.1 or less, even more preferably 0.015 or more and 0.1 or less.

[Nitrogen-containing basic compound (component D)]
In one or more embodiments, the polishing liquid composition of the present disclosure preferably further contains a nitrogen-containing basic compound (hereinafter also referred to as "component D") from the viewpoint of adjusting the pH. Component D is preferably a water-soluble nitrogen-containing basic compound from the viewpoint of achieving both improved removal rate and storage stability, and from the viewpoint of improving surface quality. In the present disclosure, "water-soluble" refers to having a solubility in water (20°C) of 0.5 g/100 mL or more, preferably 2 g/100 mL or more. In the present disclosure, "water-soluble nitrogen-containing basic" refers to a nitrogen-containing compound that exhibits basicity when dissolved in water. In one or more embodiments, component D does not include component B. Component D may be one type or a combination of two or more types.

In one or more embodiments, component D includes at least one compound selected from an amine compound and an ammonium compound. Examples of component D include one or a combination of two or more compounds selected from ammonia, ammonium hydroxide, ammonium carbonate, ammonium hydrogencarbonate, dimethylamine, trimethylamine, diethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, N-methylethanolamine, N-methyl-N,N-diethanolamine, N,N-dimethylethanolamine, N,N-diethylethanolamine, N,N-dibutylethanolamine, N-(β-aminoethyl)ethanolamine, monoisopropanolamine, diisopropanolamine, triisopropanolamine, ethylenediamine, hexamethylenediamine, piperazine hexahydrate, anhydrous piperazine, 1-(2-aminoethyl)piperazine, N-methylpiperazine, diethylenetriamine, tetramethylammonium hydroxide, and hydroxyamine. Among these, from the viewpoint of achieving both improved removal rate and storage stability, ammonia or a mixture of ammonia and hydroxyamine is preferred as component D, with ammonia being more preferred.

When the polishing liquid composition of the present disclosure contains component D, the content of component D in the polishing liquid composition of the present disclosure is preferably 5 ppm or more, more preferably 10 ppm or more, and even more preferably 20 ppm or more, from the viewpoints of improving storage stability and polishing rate. From the viewpoints of improving storage stability, improving surface quality, and suppressing corrosion of the silicon substrate, the content is preferably 500 ppm or less, more preferably 300 ppm or less, even more preferably 150 ppm or less, and even more preferably 100 ppm or less. From the same viewpoint, the content of component D in the polishing liquid composition of the present disclosure is preferably 5 ppm to 500 ppm, more preferably 10 ppm to 300 ppm by mass, more preferably 20 ppm to 150 ppm, and even more preferably 20 ppm to 100 ppm. When component D is a combination of two or more types, the content of component D refers to the total content of these components.

When the polishing liquid composition of the present disclosure contains component D, the ratio D/A (mass ratio D/A) of the content of component D to the content of component A in the polishing liquid composition of the present disclosure is preferably 0.002 or more, more preferably 0.01 or more, even more preferably 0.02 or more, and even more preferably 0.05 or more, from the viewpoint of improving the polishing rate. From the viewpoints of improving storage stability, improving surface quality, and suppressing corrosion of the silicon substrate, it is preferably 1 or less, more preferably 0.5 or less, even more preferably 0.3 or less, and even more preferably 0.2 or less. From the same viewpoint, the mass ratio D/A in the polishing liquid composition of the present disclosure is preferably 0.002 or more and 1 or less, more preferably 0.01 or more and 0.5 or less, more preferably 0.02 or more and 0.3 or less, and even more preferably 0.05 or more and 0.2 or less.

[Other ingredients]
The polishing liquid composition of the present disclosure may further contain other components to the extent that the effects of the present disclosure are not impaired. In one or more embodiments, the other components include a water-soluble polymer other than Component B and Component C, a pH adjuster other than Component D, a preservative, an alcohol, a chelating agent, an oxidizing agent, and the like.

[pH]
From the viewpoint of achieving both improved removal rate and storage stability, the pH of the polishing liquid composition of the present disclosure is greater than 8.5, preferably greater than 9, more preferably greater than 9.5, and even more preferably greater than 10. From the viewpoint of improving surface quality, the pH is 14 or less, preferably 13 or less, more preferably 12.5 or less, even more preferably 12 or less, even more preferably 11.5 or less, and even more preferably 11 or less. From the same viewpoint, the pH of the polishing liquid composition of the present disclosure is greater than 8.5 and 14 or less, preferably 9 or more and 13 or less, more preferably 9 or more and 12.5 or less, even more preferably 9 or more and 12 or less, even more preferably 9.5 or more and 11.5 or less, even more preferably 10 or more and 11 or less. The pH of the polishing liquid composition of the present disclosure can be adjusted using component C or a known pH adjuster. In the present disclosure, the above pH is a value measured by the method described in the Examples.

The polishing composition of the present disclosure can be produced, for example, by blending components A and B, and, optionally, water, components C, D, and other components, using a known method. That is, the polishing composition of the present disclosure can be produced, for example, by blending at least components A and B. Therefore, in another aspect, the present disclosure relates to a method for producing a polishing composition, which includes blending at least components A and B. In this disclosure, "blending" includes mixing components A and B, and, if necessary, water, components C, D, and other components simultaneously or in any order. The blending can be performed using, for example, a stirrer such as a homomixer, homogenizer, ultrasonic disperser, wet ball mill, or bead mill. The preferred amounts of each component in the method for producing a polishing composition of the present disclosure can be the same as the preferred contents of each component in the polishing composition of the present disclosure.

In this disclosure, the "content of each component in the polishing composition" refers to the content of each component at the time of use, i.e., at the time when the polishing composition begins to be used for polishing.

The polishing liquid composition of the present disclosure may be produced as a concentrate from the standpoint of storage and transportation, and diluted at the time of use. The dilution ratio is preferably 2x or more, more preferably 10x or more, even more preferably 30x or more, and even more preferably 50x or more from the standpoint of production and transportation costs, and is preferably 300x or less, more preferably 250x or less, even more preferably 200x or less, and even more preferably 150x or less from the standpoint of storage stability. The polishing liquid composition concentrate of the present disclosure can be diluted with water at the time of use so that the content of each component is the content described above (i.e., the content at the time of use). In this disclosure, "at the time of use" of the polishing liquid composition concentrate refers to the diluted state of the polishing liquid composition concentrate.

[Polishing liquid kit]
In one aspect, the present disclosure relates to a polishing liquid kit for producing the polishing liquid composition of the present disclosure (hereinafter also referred to as the "kit of the present disclosure"). The kit of the present disclosure can provide a polishing liquid composition that can improve the removal rate while suppressing a decrease in the removal rate during continued use of a polishing pad, even with a small content of silica particles.
In one or more embodiments, the kit of the present disclosure includes a polishing liquid kit containing a solution containing component A and component B. The solution may contain the above-mentioned components C, D, and other components as needed. The solution may be diluted with water as needed before use.

[Method for polishing silicon substrate]
In one aspect, the present disclosure relates to a method for polishing a silicon substrate (hereinafter also referred to as the "polishing method of the present disclosure"), which includes a step of polishing a silicon substrate to be polished using the polishing liquid composition of the present disclosure (hereinafter also referred to as the "polishing step"). According to the polishing method of the present disclosure, since the polishing liquid composition of the present disclosure is used, even if the content of silica particles is small, it is possible to achieve both an improvement in the polishing rate and suppression of a decrease in the polishing rate during continued use of a polishing pad.

In one or more embodiments, the polishing step in the polishing method of the present disclosure is a step of supplying the polishing liquid composition of the present disclosure to the surface of a silicon substrate to be polished, bringing a polishing pad into contact with the surface to be polished, and moving at least one of the polishing pad and the silicon substrate to be polished to perform polishing.

When a polishing process is performed in multiple stages, the polishing process using the polishing liquid composition of the present disclosure is preferably performed in the second stage or later, and more preferably in the final polishing process or finish polishing process. In this case, separate polishing machines may be used for each process to avoid contamination with abrasives or polishing liquid compositions from the previous process. If separate polishing machines are used, it is preferable to clean the silicon substrate to be polished after each polishing process. Furthermore, the polishing liquid composition of the present disclosure can also be used in cyclic polishing, in which the used polishing liquid is reused. There are no particular limitations on the polishing machine, and any known polishing machine for substrate polishing can be used.

The polishing pad used in the polishing step is not particularly limited as long as it can be used continuously, but from the viewpoint of suppressing the decrease in the polishing rate during continuous use of the polishing pad, a polishing pad having a surface member containing a urethane resin can be preferably used. As the polishing pad, a suede type, a nonwoven fabric type, a polyurethane closed cell type, or a two-layer type in which these are laminated can be used, and a suede type polishing pad can be preferably used.
In one or more embodiments, a suede-type polishing pad may include a polishing pad having a foam layer (surface member) and a base layer, the foam layer (surface member) containing a urethane resin such as a polyurethane elastomer. In one or more embodiments, the foam layer has spindle-shaped pores relative to the base layer. The compressibility of the foam layer may be, for example, 2.5% to 20%. The compressibility can be measured using a compression tester based on the compressibility measurement method described in Japanese Industrial Standards (JIS) L1096. Examples of the base layer include polyethylene terephthalate (PET) film and polyester film. The Asker hardness of the polishing pad may be, for example, 50 degrees to 100 degrees.

From the viewpoint of achieving both improved polishing rate and extended pad life, the average pore size of the surface member of the polishing pad is preferably 5 μm or more and 100 μm or less, more preferably 10 μm or more and 90 μm or less, even more preferably 15 μm or more and 80 μm or less, and even more preferably 20 μm or more and 70 μm or less.

The polishing load in the polishing step is preferably 3 kPa or more, more preferably 4 kPa or more, and even more preferably 5 Pa or more, from the viewpoint of preventing a decrease in the polishing rate during continued use of the polishing pad and ensuring a high polishing rate. From the viewpoint of improving surface quality, it is preferably 20 kPa or less, more preferably 18 kPa or less, and even more preferably 16 kPa or less. In this disclosure, the polishing load refers to the pressure of the platen applied to the polishing surface of the substrate being polished during polishing. Furthermore, the polishing load can be adjusted by applying air pressure or a weight to at least one of the platen and the substrate being polished.

In the polishing step, the supply rate of the polishing composition of the present disclosure is preferably 0.05 to 15 mL/min, more preferably 0.06 to 10 mL/min, even more preferably 0.07 to 1 mL/min, and even more preferably 0.07 to 0.5 mL/min per 1 ^cm2 of the substrate to be polished, from the viewpoints of ensuring the polishing rate and improving the surface quality.

In the polishing step, the temperature of the polishing composition and the surface temperature of the polishing pad are preferably 15°C or higher and 40°C or lower, from the viewpoint of achieving both improved polishing rate and surface quality.

The polishing composition of the present disclosure can be supplied to a polishing machine, for example, by continuous supply using a pump or the like. When supplying the polishing composition to a polishing machine, it can be supplied as a single liquid containing all components. Alternatively, taking into consideration the stability of the polishing composition, the polishing composition can be divided into multiple blending component liquids and supplied as two or more liquids. In the latter case, the multiple blending component liquids are mixed, for example, in the supply pipe or on the substrate to be polished, to produce the polishing composition of the present disclosure.

[Method of manufacturing semiconductor substrate]
In another aspect, the present disclosure relates to a method for producing a semiconductor substrate (hereinafter also referred to as the "semiconductor substrate production method of the present disclosure"), which includes a step of polishing a silicon substrate to be polished using the polishing liquid composition of the present disclosure (hereinafter also referred to as the "polishing step") and a step of cleaning the polished silicon substrate (hereinafter also referred to as the "cleaning step"). According to the semiconductor substrate production method of the present disclosure, by using the polishing liquid composition of the present disclosure, even with a small content of silica particles, it is possible to achieve both an improvement in the removal rate and suppression of a decrease in the removal rate with continued use of the polishing pad, thereby enabling high-quality semiconductor substrates to be produced at high yield, high productivity, and low cost.

When the silicon substrate to be polished is a single crystal silicon substrate, the polishing step in the semiconductor substrate manufacturing method of the present disclosure can include, for example, a lapping (rough polishing) step in which the single crystal silicon substrate obtained by slicing a single crystal silicon ingot into a thin disk is planarized, and a finish polishing step in which the lapped single crystal silicon substrate is etched and then the surface of the single crystal silicon substrate is mirror-finished. The polishing composition of the present disclosure is more preferably used in the finish polishing step, from the viewpoint of achieving both improved polishing rate and improved surface quality.

When the silicon substrate to be polished is a polysilicon substrate, the polishing step in the semiconductor substrate manufacturing method of the present disclosure can include, for example, a step of removing irregularities in the polysilicon film and planarizing the substrate, which has a silicon substrate having a silicon dioxide film and a silicon nitride film and on which a polysilicon film has been formed by chemical vapor deposition (CVD), and a step of simultaneously polishing and planarizing the silicon dioxide film, silicon nitride film, and polysilicon film directly below. From the perspective of achieving both improved polishing rate and improved surface quality, the polishing liquid composition of the present disclosure is more preferably used in the step of removing irregularities in the polysilicon film and planarizing the substrate.

The polishing step in the semiconductor substrate manufacturing method of the present disclosure can be performed under the same conditions as the polishing step in the polishing method of the present disclosure described above.

In one or more embodiments, the semiconductor substrate manufacturing method of the present disclosure may include a dilution step of diluting a concentrate of the polishing liquid composition of the present disclosure prior to the polishing step. The diluent may be, for example, water.

In the cleaning step of the semiconductor substrate manufacturing method disclosed herein, inorganic cleaning is preferably performed from the perspective of reducing residues on the silicon substrate surface. Examples of cleaning agents used in inorganic cleaning include inorganic cleaning agents containing at least one selected from hydrogen peroxide, ammonia, hydrochloric acid, sulfuric acid, hydrofluoric acid, and ozone water.

In one or more embodiments, the semiconductor substrate manufacturing method of the present disclosure may further include, after the cleaning step, a step of rinsing the cleaned silicon substrate with water and drying it.

The present disclosure will be explained in more detail below using examples, but these are illustrative and the present disclosure is not limited to these examples.

1. Preparation of Polishing Composition Silica particles (component A) shown in Table 1, a basic nitrogen-containing water-soluble polymer (component B) shown in Table 1, a nonionic water-soluble polymer (component C) shown in Table 1, ammonia (component D), and ultrapure water were mixed and stirred to obtain polishing compositions of Examples 1 to 3, Comparative Examples 1 and 2, and Reference Example 1. The content of each component in Table 1 is the content (mass % or ppm, active ingredient) of each component at the time of use of the polishing composition. The content of ultrapure water is the remainder excluding components A, B, C, and D.

The following components A, B, C, and D were used to prepare each polishing composition.
(Component A)
Colloidal silica [average primary particle size 25 nm, average secondary particle size 49 nm, degree of association 2.0] Colloidal silica [average primary particle size 35 nm, average secondary particle size 70 nm, degree of association 2.0]
(Component B)
Glycidol-modified polyallylamine (modification ratio 1.5) [manufactured by Nittobo Medical Co., Ltd., weight-average molecular weight 30,000]
(Non-ingredient B)
PEI (polyethyleneimine) [Nippon Shokubai Co., Ltd., SP-200, weight-average molecular weight 10,000]
(Component C)
PEG (polyethylene glycol) [NOF Corporation, PEG #6000, weight-average molecular weight 6000]
HEC (hydroxyethyl cellulose) [Sumitomo Seika Chemicals, SE400, weight-average molecular weight 250,000]
HEC (hydroxyethyl cellulose) [Sumitomo Seika Chemicals, CF-V, weight-average molecular weight 800,000]
(Component D)
Ammonia [28% by mass ammonia water, manufactured by Kishida Chemical Co., Ltd., special grade reagent]

2. Measurement Methods of Various Parameters (1) Measurement of Average Primary Particle Diameter of Silica Particles (Component A) The average primary particle diameter (nm) of component A was calculated by the following formula using the specific surface area S (m ² /g) calculated by the BET (nitrogen adsorption) method.
Average primary particle diameter (nm) = 2727/S

The specific surface area S of component A was measured by the 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) after carrying out the following [pretreatment]. After that, about 0.1 g of the measurement sample was accurately weighed out to four decimal places into a measurement cell, and dried for 30 minutes in an atmosphere at 110°C immediately before measuring the specific surface area.
[Preprocessing]
(a) The pH of the slurry of component A is adjusted to 2.5±0.1 with an aqueous nitric acid solution.
(b) The slurry of component A adjusted to pH 2.5±0.1 is placed in a petri dish and dried in a hot air dryer at 150° C. for 1 hour.
(c) After drying, the obtained sample is finely crushed in an agate mortar.
(d) The pulverized sample is suspended in ion-exchanged water at 40°C and filtered through a membrane filter with a pore size of 1 µm.
(e) The residue on the filter is washed five times with 20 g of ion-exchanged water (40°C).
(f) The filter with the filtrate attached thereto is placed in a petri dish and dried in an atmosphere at 110°C for 4 hours.
(g) The dried filtered product (component A) was taken out, taking care not to mix in any filter debris, and finely pulverized in a mortar to obtain a measurement sample.

(2) Average Secondary Particle Diameter of Silica Particles (Component A) The average secondary particle diameter (nm) of component A was measured by adding an abrasive to ion-exchanged water so that the concentration of component A was 0.25% by mass, and then pouring the resulting aqueous dispersion into a Disposable Sizing Cuvette (a 10 mm polystyrene cell) to a height of 10 mm from the bottom, using a dynamic light scattering method (apparatus name: "Zetasizer Nano ZS", manufactured by Sysmex Corporation).

(3) Measurement of Weight-Average Molecular Weight of Water-Soluble Polymer The weight-average molecular weight of the water-soluble polymer (component B, component C) was calculated based on peaks in a chromatogram obtained by applying gel permeation chromatography (GPC) under the following conditions.
<Basic nitrogen atom-containing water-soluble polymer (component B)>
Apparatus: HLC-8320 GPC (Tosoh Corporation, detector integrated)
Column: α-M+α-M
Eluent: 0.15 mol/L Na ₂ SO ₄ , 1% CH ₃ COOH/water flow rate: 1.0 mL/min
Column temperature: 40°C
Detector: Shodex RI SE-61 differential refractive index detector Standard substance: monodisperse pullulan with known molecular weight (nonionic water-soluble polymer (component C))
Apparatus: HLC-8320 GPC (Tosoh Corporation, detector integrated)
Column: GMPWXL + GMPWXL (anion)
Eluent: 0.2 M phosphate buffer/CH ₃ CN=9/1
Flow rate: 0.5mL/min
Column temperature: 40°C
Detector: Shodex RI SE-61 differential refractive index detector Standard material: monodisperse polyethylene glycol with known molecular weight

(4) Glycidol Modification Ratio The glycidol modification ratio was determined using ¹³ C-NMR.
<Measurement conditions>
Sample: 200 mg of glycidol-modified polyallylamine dissolved in 0.6 mL of heavy water. Apparatus used: 400 MHz ¹³ C-NMR (Agilent 400-MR DD2, manufactured by Agilent Technologies, Inc.).
Measurement conditions: ¹³ C-NMR measurement, pulse interval time 5 seconds, tetramethylsilane as standard peak (σ: 0.0 ppm), number of measurement integrations: 5000, range of each peak used for integration:
A: 71.0 to 72.3 ppm (integrated value of the peak of C bonded to the secondary hydroxyl group of glycidol reacted with an amino group)
B: 32.0 to 41.0 ppm (integrated value of the peak of the main chain C of allylamine)
<Glycidol modification rate>
The glycidol modification rate (ratio of glycidol equivalents to amino group equivalents) is calculated using the following formula.
Glycidol modification rate (equivalent ratio) = 2A/B

(5) Measurement of pKa Using an HM-41K pH meter (Toa DKK Corporation), an aqueous solution of component B adjusted to 1 M was subjected to potentiometric titration with 0.1 M hydrochloric acid at room temperature. The pKa was calculated from the obtained titration curve.

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

3. Evaluation of the Polishing Liquid Compositions of Examples 1 to 3, Comparative Examples 1 and 2, and Reference Example 1 (1) Polishing Method, etc. Each polishing liquid composition was filtered with a filter (compact cartridge filter "MCP-LX-C10S", manufactured by Advantec Co., Ltd.) immediately before polishing, and finish polishing and cleaning were performed on the following silicon substrates to be polished under the following polishing conditions.
<Silicon substrate to be polished>
Single crystal silicon substrate [single-sided mirror-finished silicon substrate with a diameter of 200 mm, conductivity type: P, crystal orientation: 100, resistivity: 0.1 Ω cm or more but less than 100 Ω cm]
The single crystal silicon substrate was previously subjected to rough polishing using a commercially available polishing composition (GLANZOX 1302, manufactured by Fujimi Inc.). After rough polishing, the single crystal silicon substrate was subjected to finish polishing and had a haze of 2 to 3 ppm.

<Finishing polishing conditions>
Polishing machine: Single-sided 8-inch polishing machine "GRIND-X SPP600s" (manufactured by Okamoto Kogyo)
Polishing pad: Suede pad (manufactured by FILWEL, Asker hardness: 66, thickness: 1.45 mm, nap length: 500 μm, average pore size: 60 μm)
Polishing load: 9.8 kPa
Platen rotation speed: 60 rpm
Polishing time: 5 minutes Supply rate of polishing composition: 100 g/min (0.32 mL/min per 1 cm ² of substrate to be polished)
Temperature of polishing composition: 23°C
Carrier rotation speed: 62 rpm

<Measurement of surface roughness (haze) of silicon substrate>
The value (DWO haze) measured using a surface roughness measuring device "Surfscan SP1-DLS" (manufactured by KLA Tencor Corporation) in a dark field wide grazing incidence channel (DWO) was used.

<Cleaning method>
After the finish polishing, the silicon substrate was subjected to ozone cleaning and dilute hydrofluoric acid cleaning as follows. For the ozone cleaning, an aqueous solution containing 20 ppm ozone was sprayed from a nozzle toward the center of the silicon substrate rotating at 600 rpm at a flow rate of 1 L/min for 3 minutes. The ozone water was kept at room temperature. Next, dilute hydrofluoric acid cleaning was performed. For the dilute hydrofluoric acid cleaning, an aqueous solution containing 0.5% by mass of ammonium hydrogen fluoride (special grade, Nacalai Tesque, Inc.) was sprayed from a nozzle toward the center of the silicon substrate rotating at 600 rpm at a flow rate of 1 L/min for 6 seconds. Two sets of the ozone cleaning and dilute hydrofluoric acid cleaning were performed, and finally, spin drying was performed. For the spin drying, the silicon substrate was rotated at 1,500 rpm.

(2) Evaluation of Polishing Rate The weight of each silicon substrate before and after polishing was measured using a precision balance ("BP-210S" manufactured by Sartorius). The resulting weight difference was divided by the density, area, and polishing time of the silicon substrate to determine the single-side polishing rate per unit time, and the polishing rates for the second, fifth, and eighth substrates were calculated. The weight of the silicon substrate after polishing refers to the weight of the silicon substrate after the above-mentioned finish polishing and cleaning.

As shown in Table 1, the polishing liquid compositions of Examples 1 to 3 contained 0.1 mass % or less of component A, had a mass ratio B/A of 0.07 or more, and had a sufficient amount of water-soluble polymer containing basic nitrogen atoms (component B) relative to the silica particles (component A). Therefore, even with a low silica particle content, the polishing rate was higher than in Comparative Example 1, and the decrease in polishing rate with continued use of the polishing pad was suppressed more than in Comparative Example 2 and Reference Example 1. This is thought to enable increased productivity, such as higher polishing rate, fewer dressing cycles, and a longer polishing pad life, while reducing the costs of using and disposing of the polishing liquid.

By using the polishing liquid composition of the present disclosure, even with a low silica particle content, it is possible to achieve both an improved polishing rate and suppress a decrease in the polishing rate with continued use of the polishing pad. Therefore, the polishing liquid composition of the present disclosure is particularly useful as a polishing liquid composition used in the manufacturing process of silicon substrates.

Claims (5)

Contains the following component A and the following component B,
The content of component A is 0.1% by mass or less,
the mass ratio B/A of the content of component B to the content of component A is 0.07 or more;
A polishing composition having a pH of more than 8.5 and not more than 14.
Component A: Silica particles; Component B: A water-soluble polymer containing basic nitrogen atoms, at least some of which contain heteroatoms (excluding basic nitrogen atoms) at positions selected from the β-, γ-, and δ-positions of the basic nitrogen atoms , the water-soluble polymer containing allylamine-derived structural units, at least some of which have sterically shielding groups as amino groups. 2. The polishing composition according to claim 1 , wherein at least a portion of the amino groups in the structural units derived from allylamine are secondary amino groups or tertiary amino groups containing a hydrocarbon group having 2 to 11 carbon atoms and a heteroatom. 3. The polishing composition according to claim 1 , wherein Component B is a reaction product of polyallylamine and a glycidol derivative. A method for polishing a silicon substrate, comprising the step of polishing a silicon substrate to be polished with the polishing composition according to claim 1 . A step of polishing a silicon substrate to be polished using the polishing composition according to any one of claims 1 to 3 ;
and cleaning the polished silicon substrate.