JP2023154963A - Polishing liquid composition for silicon substrate - Google Patents

Abstract

To provide a polishing liquid composition for silicon substrates that can both improve polishing speed and storage stability of the concentrate, a method for polishing silicon substrates using the composition, and a method for manufacturing semiconductor substrates.SOLUTION: A polishing liquid composition for silicon substrates includes silica particles, a water-soluble polymer having an amino group to which a hydroxyalkyl group is attached, and water. In a silicon substrate polishing method in which the silicon substrate finishing and polishing steps 1 and 2 are performed in this order, the silicon substrate is polished in the finishing and polishing step 1 using this polishing liquid composition for silicon substrates. In the finishing and polishing step 2, the silicon substrate is polished using a polishing liquid composition containing silica particles and water-soluble polymers.SELECTED DRAWING: None

Description

The present disclosure relates to a polishing liquid composition for silicon substrates, a polishing method using the same, and a method for manufacturing a semiconductor substrate.

2. Description of the Related Art Polishing liquid compositions containing silica particles are known as polishing liquid compositions used for polishing silicon substrates used in the manufacture of semiconductor substrates. In this type of polishing liquid composition, the occurrence of surface defects (LPD: Light point defects) on the silicon substrate due to agglomeration of silica particles, and the need for a filter when filtering the polishing liquid composition to remove aggregates. Clogging has become a problem (see, for example, Patent Document 1). Further, polishing liquid compositions containing water-soluble polymers are known for the purpose of improving the surface quality of a substrate after polishing (see Patent Documents 2 and 3).

Patent Document 1 proposes a polishing liquid composition containing an abrasive such as silica particles and a polymer having a structural unit derived from a 2-oxazoline compound or a 2-oxazine compound.
Patent Document 2 proposes a polishing liquid composition containing abrasive grains, a basic compound, and a cationic water-soluble polymer containing a nitrogen-containing group (for example, polyethyleneimine).
Patent Document 3 discloses a polishing composition used for polishing (intermediate polishing) before final polishing, which comprises abrasive grains such as silica particles, a basic compound, and a weight average molecular weight higher than 30 x ¹⁰⁴ . Polishing compositions containing a water-soluble polymer (eg, hydroxyethyl cellulose) and a dispersant have been proposed.

Japanese Patent Application Publication No. 2010-99757 Japanese Patent Application Publication No. 2007-19093 International Publication No. 2018/150945

However, polishing using the polishing liquid compositions of Patent Documents 1 and 3 cannot be said to have a sufficient polishing rate.
When the polishing liquid composition of Patent Document 2 is used, there is a problem in that the silica particles aggregate due to the cationic water-soluble polymer containing a nitrogen-containing group, resulting in deterioration of the surface condition of the silicon substrate such as generation of scratches.
Furthermore, the polishing liquid composition is usually stored and transported in the form of a concentrate, and storage stability in the form of a concentrate is also required.

The present disclosure provides a polishing liquid composition for a silicon substrate that can achieve both an improvement in polishing rate and storage stability of a concentrate, a method for polishing a silicon substrate using the same, and a method for manufacturing a semiconductor substrate.

In one aspect, the present disclosure relates to a polishing liquid composition for silicon substrates, which includes silica particles (component A), a water-soluble polymer having an amino group to which a hydroxyalkyl group is bonded (component B), and water. .

In one aspect, the present disclosure relates to a method for polishing a silicon substrate, including 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 includes a final polishing process 2 for final polishing a silicon substrate, and a final polishing process 1 that is a polishing process before the final polishing process 2, and the final polishing process 1 and the final polishing process 2 A method of polishing a silicon substrate in which the following steps are performed in this order, wherein in the final polishing step 1, polishing is performed using a polishing liquid composition of the present disclosure, and in the final polishing step 2, a polishing composition containing silica particles and a water-soluble polymer is used. The present invention relates to a method of polishing a silicon substrate using a polishing liquid composition.

In one aspect, the present disclosure relates to a method for manufacturing a semiconductor substrate, which includes performing the polishing method of the present disclosure.

According to the present disclosure, a polishing liquid composition for a silicon substrate that can achieve both an improvement in polishing rate and storage stability of a concentrate, a method for polishing a silicon substrate using the polishing liquid composition, and a method for manufacturing a semiconductor substrate. can be provided.

The present disclosure is based on the knowledge that by using a polishing liquid composition for silicon substrates containing silica particles and a specific amino group-containing water-soluble polymer, silicon substrates can be polished at high speed and the concentrate has excellent storage stability. .

That is, in one aspect, the present disclosure provides a silicon substrate polishing liquid containing silica particles (component A), a water-soluble polymer having an amino group to which a hydroxyalkyl group is bonded (component B), and water. The present invention relates to a composition (hereinafter also referred to as "polishing liquid composition of the present disclosure").

According to the present disclosure, in one or more embodiments, it is possible to provide a polishing liquid composition for silicon substrates that can achieve both improvement in polishing rate and storage stability of a concentrate.

Although the details of the effect expression mechanism of the present disclosure are not clear, it is presumed as follows.
Under alkaline polishing conditions, both the silica particles and the silicon substrate to be polished have negative charges, and electrostatic repulsion is generated. Therefore, it is difficult for silica particles to approach the silicon substrate, and it is thought that a sufficient polishing rate is not achieved. On the other hand, the cationic polymer (for example, polyethyleneimine) blended into the polishing liquid reduces the negative charge on the silica particles and the silicon substrate, and the cationic polymer itself acts as a binder, so the silica particles on the silicon substrate The polishing rate can be improved by promoting the approach of the two. However, since a cationic polymer such as polyethyleneimine also acts as a binder between silica particles, the silica particles tend to aggregate, and furthermore, in a concentrated solution with a high silica concentration, silica precipitates.
In the present disclosure, a water-soluble polymer having an amino group to which a hydroxyalkyl group is bonded, that is, a cationic polymer having a steric repulsion group in the amino group, is blended into a polishing liquid. As a result, the effect of reducing the negative charges of the silica abrasive grains and the silicon substrate remains, and the effect of promoting the approach of the silica particles (ie, the effect of improving the polishing rate) is exhibited. Furthermore, the cationic polymer covering the surface of the silica particles has a steric repulsion group, which also has the effect of mitigating aggregation between silica particles. Therefore, it is considered that agglomeration of silica particles can be suppressed, and both improvement in polishing rate and storage stability of the concentrate can be achieved.
However, the present disclosure does not need to be interpreted as being limited to these mechanisms.

[Silicon substrate to be polished]
The polishing liquid composition of the present disclosure is a polishing composition for a silicon substrate, and is used, for example, in a polishing step of polishing a silicon substrate to be polished in a method of manufacturing a semiconductor substrate, or in a polishing process of polishing a silicon substrate to be polished in a method of polishing a silicon substrate. It can be used in polishing processes. In one or more embodiments, the silicon substrate to be polished polished using the polishing liquid composition of the present disclosure includes a silicon substrate, etc. In one or more embodiments, a single crystal silicon substrate, a polysilicon substrate, etc. A substrate, a substrate having a polysilicon film, a SiN substrate, etc. may be mentioned, and from the viewpoint of exhibiting the effects of the polishing liquid composition of the present disclosure, a single crystal silicon substrate or a polysilicon substrate is preferable, and a single crystal silicon substrate is more preferable. .

[Silica particles (component A)]
The polishing liquid composition of the present disclosure contains silica particles (hereinafter also referred to as "component A") as an abrasive. Component A includes colloidal silica, fumed silica, pulverized silica, or silica surface-modified with these, and is useful for achieving both improvement in polishing speed and storage stability of concentrates, and for suppressing agglomeration of silica particles. Colloidal silica is preferred from the viewpoint of improving surface quality such as reduction of surface roughness (haze), surface defects (LPD), and scratches. Component A may be used alone or in combination of two or more.

From the viewpoint of operability, component A is preferably used in a slurry form. When component A contained in the polishing liquid composition of the present disclosure is colloidal silica, the colloidal silica is obtained from a hydrolyzate of alkoxysilane from the viewpoint of preventing contamination of the silicon substrate with alkali metals, alkaline earth metals, etc. It is preferable that the Silica particles obtained from a hydrolyzate of alkoxysilane 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 20 nm or more, and even more preferably 30 nm or more, and the average primary particle size of component A is from the viewpoint of maintaining the polishing rate. From the viewpoint of improving surface quality such as reduction in , the thickness is preferably 50 nm or less, more preferably 45 nm or less, and even more preferably 40 nm or less. More specifically, the average primary particle diameter of component A is preferably 10 nm or more and 50 nm or less, more preferably 20 nm or more and 45 nm or less, and even more preferably 30 nm or more and 40 nm or less.
In the present disclosure, the average primary particle diameter of component A is calculated using the specific surface area S (m ² /g) calculated by the nitrogen adsorption method (BET method). The value of the average primary particle diameter 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, even more preferably 40 nm or more, and even more preferably 60 nm or more, and it is suitable for surface roughness (haze) and surface defects. (LPD) and from the viewpoint of improving surface quality such as reducing scratches, the thickness is preferably 100 nm or less, more preferably 90 nm or less, and even more preferably 80 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 40 nm or more and 90 nm or less, and even more preferably 60 nm or more and 80 nm or less.
In the present disclosure, the average secondary particle diameter is a value measured by a dynamic light scattering (DLS) method, and is a value measured by the method described in Examples.

The degree of association of component A is preferably 3 or less, more preferably 2.5 or less, and 2.3 or less, from the viewpoint of improving surface quality such as reducing surface roughness (haze), surface defects (LPD), and scratches. is more preferable, and from the viewpoint of improving the polishing rate and surface quality, it is preferably 1.1 or more, more preferably 1.5 or more, and even more preferably 1.8 or more.

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

Examples of methods for adjusting the degree of association of component A include JP-A-6-254383, JP-A-11-214338, JP-A-11-60232, JP-A-2005-060217, and JP-A-2005-060219. The method described in the above publication can be adopted.

The shape of component A is preferably a so-called spherical shape and/or a so-called cocoon shape from the viewpoint of improving the polishing rate and surface quality.

From the viewpoint of improving the polishing rate, the content of component A in the polishing liquid composition of the present disclosure is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and more preferably 0.2% by mass or more in terms of SiO ₂ . It is more preferably 3% by mass or more, and from the viewpoint of suppressing agglomeration of silica particles, the storage stability of concentrates, and improving the surface quality, it is preferably 5% by mass or less, and 2.5% by mass or less. It is more preferably 1% by mass or less, and even more preferably 1% by mass or less. Therefore, the content of component A in the polishing liquid composition of the present disclosure is preferably 0.1% by mass or more and 5% by mass or less, more preferably 0.2% by mass or more and 2.5% by mass or less, and 0.3% by mass or more. It is more preferably 1% by mass or more and 1% by mass or less. When Component A is a combination of two or more types, the content of Component A refers to their total content.

[Water-soluble polymer having an amino group bound to a hydroxyalkyl group (component B)]
The polishing liquid composition of the present disclosure contains a water-soluble polymer having an amino group to which a hydroxyalkyl group is bonded (hereinafter also referred to as "component B"). In one or more embodiments, component B is an amino group-containing water-soluble polymer that includes a nitrogen atom in its main chain and has an amino group to which a hydroxyalkyl group is bonded to the nitrogen atom in the main chain. In one or more embodiments, component B is an amino group-containing aqueous solution having at least one amino group and having a hydroxyalkyl group bonded to the nitrogen atom of at least some of the amino groups among all the amino groups. Polymer. 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 one or more embodiments, the hydroxyalkyl group is preferably a hydroxyalkyl group having 1 or more and 5 or less carbon atoms, more preferably a carbon number from the viewpoint of achieving both improvement in polishing rate and storage stability of the concentrate. Examples include 1 to 3 hydroxyalkyl groups, such as hydroxymethyl group, hydroxyethyl group, hydroxypropyl group, hydroxybutyl group, propanediol group, and the like.
In one or more embodiments, the amino group to which the hydroxyalkyl group is bonded is an amino group having a steric repulsion group, and from the viewpoint of achieving both improvement in polishing rate and storage stability of the concentrate, Preferably, it is a modified group using epoxides. In one or more embodiments, the modification group is a group formed by reacting an amino group with an epoxide. In one or more embodiments, at least some of the amino groups of component B are modified with epoxides to become amino groups with steric repulsion. As the epoxides, ethylene oxide (EO), propylene oxide (PO), and glycidol derivatives are preferable, and propylene oxide (PO) or glycidol derivatives are more preferable from the viewpoint of achieving both improvement in polishing rate and storage stability of the concentrate. Preferably, propylene oxide (PO) is more preferable. Examples of glycidol derivatives include glycidol, alkyl glycidyl ethers, etc. From the viewpoint of availability, improving the polishing rate and maintaining the storage stability of concentrates, and suppressing aggregation of silica particles, glycidol is preferred. preferable. From the viewpoint of availability, the alkyl group of the alkyl glycidyl ether is preferably an alkyl group having 1 to 8 carbon atoms, such as a methyl group, an ethyl group, a propyl group, a butyl group, a 2-ethylhexyl group, and the like. Specific examples of alkyl glycidyl ether include methyl glycidyl ether, 2-ethylhexyl glycidyl ether, and the like.

In one or more embodiments, component B can be obtained by reacting a water-soluble polymer having a primary amino group or a secondary amino group with an epoxy. Examples of the water-soluble polymer having a primary amino group or a secondary amino group include polyethyleneimine, polyallylamine, polydiallylamine, and the like.

In one or more embodiments, component B is an amino group-containing water-soluble polymer having a structure represented by the following formula (1) from the viewpoint of achieving both improvement in polishing rate and storage stability of the concentrate. It is preferable that there be.
In the above formula (1), R represents a hydrogen atom, a methyl group or a hydroxymethyl group. From the viewpoint of achieving both improvement in polishing rate and storage stability of the concentrate, and from the viewpoint of suppressing aggregation of silica particles, R is preferably a methyl group or a hydroxymethyl group, and more preferably a methyl group.

In one or more embodiments, component B is a total amino acid of a water-soluble polymer having a primary amino group or a secondary amino group, from the viewpoint of improving the polishing rate and improving the storage stability of the concentrate. It is preferable to use an amino group-containing water-soluble polymer in which at least some of the amino groups among the groups are modified with epoxies.

The ratio of primary amino groups and secondary amino groups in the total amino groups of component B is determined from the viewpoint of achieving both improvement in polishing rate and storage stability of the concentrate, and from the viewpoint of suppressing aggregation of silica particles. , preferably 50% or less, more preferably 40% or less, even more preferably 30% or less, even more preferably 20% or less, even more preferably 10% or less, even more preferably 5% or less, even more preferably 1% or less, 0 % is more preferable. The ratio of primary amino groups to secondary amino groups in all amino groups of component B can be measured, for example, by the method described in Examples.

Examples of component B include polyethyleneimine having the structure of formula (1) above, a reaction product of propylene oxide (PO) and polyethyleneimine, a reaction product of glycidol and polyethyleneimine, and the like.

From the viewpoint of improving the polishing rate, the weight average molecular weight of component B is preferably 200 or more, more preferably 800 or more, even more preferably 1,000 or more, even more preferably 1,500 or more, and even more preferably 2,000 or more. , from the viewpoint of achieving both an improvement in polishing rate and storage stability of the concentrate, from the viewpoint of suppressing aggregation of silica particles, and from the viewpoint of improving surface quality, it is preferably 200,000 or less, and 100,000 or less. It is more preferably 50,000 or less, even more preferably 30,000 or less, even more preferably 20,000 or less, even more preferably 15,000 or less, and even more preferably 12,000 or less. More specifically, the weight average molecular weight of component B is preferably 200 or more and 200,000 or less, more preferably 800 or more and 100,000 or less, even more preferably 1,000 or more and 50,000 or less, and 1,500 or more and 30 ,000 or less, more preferably 2,000 or more and 20,000 or less, even more preferably 2,000 or more and 15,000 or less, even more preferably 2,000 or more and 12,000 or less. The weight average molecular weight of component B in the present disclosure can be measured, for example, by the method described in the Examples.

From the viewpoint of improving the polishing rate, the content of component B in the polishing liquid composition of the present disclosure is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, and 0.008% by mass or more. More preferably, from the viewpoint of suppressing aggregation of silica particles and storage stability of the concentrate, it is preferably 0.1% by mass or less, more preferably 0.05% by mass or less, even more preferably 0.03% by mass or less, More preferably, it is 0.02% by mass or less. More specifically, the content of component B is preferably 0.001% by mass or more and 0.1% by mass or less, more preferably 0.005% by mass or more and 0.05% by mass or less, and 0.008% by mass or more. It is more preferably 0.03% by mass or less, and even more preferably 0.008% by mass or more and 0.02% by mass or less.

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 preferably 0.002 or more, and 0.01 or more from the viewpoint of improving the polishing rate. is more preferable, 0.014 or more is still more preferable, and from the viewpoint of suppressing aggregation of silica particles and storage stability of the concentrate, it is preferably 0.1 or less, more preferably 0.06 or less, and 0.04 or less. More preferred. More specifically, the mass ratio B/A is preferably 0.002 or more and 0.1 or less, more preferably 0.01 or more and 0.06 or less, and even more preferably 0.014 or more and 0.04 or less.

[water]
The polishing liquid composition of the present disclosure may contain water in one or more embodiments. Examples of water include water such as ion exchange water and ultrapure water. The content of water in the polishing liquid composition of the present disclosure can be, for example, component A, component B, and the remainder of optional components described below.

[Nitrogen-containing basic compound (component C)]
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 C") from the viewpoint of adjusting pH. Component C is preferably a water-soluble nitrogen-containing basic compound from the viewpoint of achieving both improvement in polishing rate and storage stability of the concentrate, and from the viewpoint of suppressing aggregation of silica particles. 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 C does not include an amino group-containing water-soluble polymer (component B). Component C may be used alone or in combination of two or more.

In one or more embodiments, component C includes at least one selected from amine compounds and ammonium compounds. Component C includes, for example, ammonia, ammonium hydroxide, ammonium carbonate, ammonium hydrogen carbonate, 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. One type or a combination of two or more types can be mentioned. Among these, from the viewpoint of achieving both an improvement in polishing rate and storage stability of the concentrate, and from the viewpoint of suppressing agglomeration of Syrian particles, component C is preferably ammonia or a mixture of ammonia and hydroxyamine. is more preferable.

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 determined from the viewpoint of achieving both improvement in polishing rate and storage stability of the concentrate, and silica. From the viewpoint of suppressing particle aggregation, it is preferably 0.0005% by mass or more, more preferably 0.001% by mass or more, even more preferably 0.002% by mass or more, and from the same viewpoint, preferably 0.05% by mass or less. , more preferably 0.03% by mass or less, even more preferably 0.015% by mass or less, even more preferably 0.01% by mass or less. From the same viewpoint, the content of component C in the polishing liquid composition of the present disclosure is preferably 0.0005% by mass or more and 0.05% by mass or less, and more preferably 0.001% by mass or more and 0.03% by mass or less. , more preferably 0.002% by mass or more and 0.015% by mass or less, and still more preferably 0.002% by mass or more and 0.01% by mass or less. When component C is a combination of two or more types, the content of component C refers to their total content.

When the polishing liquid composition of the present disclosure contains component C, the ratio C/A (mass ratio C/A) of the content of component C to the content of component A in the polishing liquid composition of the present disclosure is the polishing rate. From the viewpoint of achieving both improvement in the storage stability of the concentrate and prevention of agglomeration of silica particles, it is preferably 0.001 or more, more preferably 0.002 or more, and even more preferably 0.004 or more. From the same viewpoint, it is preferably 0.1 or less, more preferably 0.06 or less, and even more preferably 0.02 or less. More specifically, the mass ratio C/A in the polishing liquid composition of the present disclosure is preferably from 0.001 to 0.1, more preferably from 0.002 to 0.06, and from 0.004 to 0. More preferably, it is .02 or less.

[Other ingredients]
The polishing liquid composition of the present disclosure may further contain other components as long as the effects of the present disclosure are not impaired. In one or more embodiments, other components include water-soluble polymers other than component B, pH adjusters other than component C, preservatives, alcohols, chelating agents, oxidizing agents, and the like.

[pH]
The pH of the polishing liquid composition of the present disclosure is preferably higher than 8.5, more preferably 9 or higher, from the viewpoint of improving the polishing rate and the storage stability of the concentrate, and from the viewpoint of suppressing aggregation of silica particles. Preferably, 9.3 or more is more preferable, and from the same viewpoint, 14 or less is preferable, 13 or less is more preferable, 12.5 or less is still more preferable, 12 or less is still more preferable, and 11.5 or less is still more preferable. It is more preferably 11 or less. More specifically, the pH of the polishing liquid composition of the present disclosure is preferably greater than or equal to 8.5 and less than or equal to 14, more preferably greater than or equal to 9 and less than or equal to 13, still more preferably greater than or equal to 9 and less than or equal to 12.5, and still more preferably greater than or equal to 9 and less than or equal to 12. It is more preferably 9.3 or more and 11.5 or less, even more preferably 9.3 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 the pH of the polishing liquid composition at 25° C., and can be measured using a pH meter. The above pH can be, for example, a value measured by the method described in the Examples.

The polishing liquid composition of the present disclosure can be produced, for example, by blending component A and component B, water, and optionally the above-mentioned optional components (component C and other components) by a known method. That is, the polishing liquid composition of the present disclosure can be produced, for example, by blending at least component A, component B, and water. Therefore, in another aspect, the present disclosure relates to a method for producing a polishing liquid composition, which includes a step of blending at least component A, component B, and water. In the present disclosure, "blending" includes mixing component A, component B, water, and, if necessary, optional components (component C and other components) simultaneously or in any order. The blending can be carried out using, for example, a stirrer such as a homomixer, a homogenizer, an ultrasonic disperser, a wet ball mill, or a bead mill. The preferable blending amount of each component in the method for manufacturing the polishing liquid composition of the present disclosure can be the same as the preferable content of each component in the polishing liquid composition of the present disclosure described above.

In the present disclosure, "the content of each component in the polishing liquid composition" refers to the content of each component at the time of use, that is, at the time when the polishing liquid composition starts to be used for polishing.

The polishing liquid composition of the present disclosure may be manufactured as a concentrate and diluted at the time of use for storage and transportation purposes. The dilution ratio is preferably 2 times or more, more preferably 5 times or more, still more preferably 10 times or more, and even more preferably 15 times or more, from the viewpoint of manufacturing and transportation costs and the storage stability of the concentrate. From the viewpoint of storage stability of the concentrate, it is preferably 40 times or less, more preferably 30 times or less, still more preferably 20 times or less. The concentrate of the polishing liquid composition of the present disclosure can be used by diluting it with water so that the content of each component becomes the above-mentioned content (that is, the content at the time of use). In the present disclosure, "at the time of use" of the concentrate of the polishing liquid composition refers to a state in which the concentrate of the polishing liquid composition is diluted.

In one or more embodiments, the polishing liquid composition of the present disclosure is preferably used for final polishing in multiple stages of polishing a silicon substrate from the viewpoint of improving both polishing speed and surface quality.
In one or more embodiments, the polishing liquid composition of the present disclosure is used for polishing that is a step before final polishing in multiple stages of polishing a silicon substrate, from the viewpoint of improving both polishing speed and surface quality. It is preferable. In one or more embodiments, the polishing that is a step before the final polishing includes a final polishing step 2 that performs final polishing of the silicon substrate, and a final polishing step 1 that is a polishing step before the final polishing step 2. An example is the final polishing step 1 in a silicon substrate polishing method in which the polishing step 1 and the final polishing step 2 are performed in this order.

[Polishing liquid kit]
In one aspect, the present disclosure relates to a polishing liquid kit (hereinafter also referred to as "kit of the present disclosure") for manufacturing the polishing liquid composition of the present disclosure. According to the kit of the present disclosure, a polishing liquid composition that can achieve both an improvement in polishing speed and storage stability of a concentrate can be obtained.
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 optional components (component C and other components) as necessary. The solution may be diluted with water if necessary at the time of use.

[Silicon substrate polishing method]
In one aspect, the present disclosure provides a method for polishing a silicon substrate (hereinafter referred to as "the present disclosure") including a step of polishing a silicon substrate to be polished using the polishing liquid composition of the present disclosure (hereinafter also referred to as "polishing step"). (also referred to as "polishing method").
According to the polishing method of the present disclosure, since the polishing liquid composition of the present disclosure is used, it is possible to achieve both improvement in polishing rate and storage stability of the concentrate. Furthermore, according to the polishing method of the present disclosure, surface quality such as reduction of surface roughness (haze), surface defects (LPD), and scratches can be improved.

In the polishing step in the polishing method of the present disclosure, for example, the silicon substrate to be polished can be pressed against a surface plate to which a polishing pad is attached, and the silicon substrate to be polished can be polished with a polishing pressure of 3 to 20 kPa. In the present disclosure, polishing pressure refers to the pressure of a surface plate applied to the polished surface of the silicon substrate to be polished during polishing.

In the polishing step in the polishing method of the present disclosure, for example, a silicon substrate to be polished is pressed against a surface plate to which a polishing pad is attached, and a polishing liquid composition of 15° C. or more and 40° C. or less and a polishing pad surface temperature are applied to the silicon substrate to be polished. can be polished. The temperature of the polishing liquid composition and the surface temperature of the polishing pad are preferably 15°C or higher or 20°C or higher, and 40°C or lower or The temperature is preferably 30°C or lower.

In one or more embodiments, the polishing step in the polishing method of the present disclosure is preferably a final polishing step from the viewpoint of achieving both improvement in polishing rate and storage stability of the concentrate.

In one or more embodiments, the polishing step in the polishing method of the present disclosure is performed before the final polishing step from the viewpoint of achieving both improvement in polishing speed and storage stability of the concentrate, and from the viewpoint of improving surface quality. Preferably, the polishing process is a stepwise polishing process.
In one or more embodiments, the polishing process that is a pre-stage of the final polishing process includes a final polishing process 2 that performs final polishing of the silicon substrate, and a final polishing process 1 that is a polishing process that precedes the final polishing process 2. , final polishing step 1 in a silicon substrate polishing method in which final polishing step 1 and final polishing step 2 are performed in this order. In one or more embodiments, the final polishing step 1 and the final polishing step 2 are continuous polishing steps from the viewpoint of achieving both an improvement in the polishing rate and the storage stability of the concentrate, and from the viewpoint of improving the surface quality. Preferably, it is a process.
From the viewpoint of achieving both an improvement in the polishing rate and the storage stability of the concentrate, and from the viewpoint of improving the surface quality, the polishing liquid composition of the present disclosure is used in the final polishing step 1, and the polishing liquid composition of the present disclosure is used in the final polishing step 2. It is preferable to use a polishing liquid composition containing particles and a water-soluble polymer such as HEC. Examples of water-soluble polymers contained in the polishing liquid composition used in the final polishing step 2 include hydroxyethyl cellulose (HEC), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), (polyethylene glycol (PEG)), etc. As the polishing liquid composition used in the final polishing step 2, a conventionally used polishing liquid composition for final polishing can be used.
That is, in one embodiment, the present disclosure includes a final polishing step 2 for final polishing a silicon substrate, and a final polishing step 1 which is a polishing step before the final polishing step 2, and the final polishing step 1 and the final polishing A method of polishing a silicon substrate in which step 2 is performed in this order,
In the final polishing step 1, polishing is performed using the polishing liquid composition of the present disclosure,
The final polishing step 2 relates to a method of polishing a silicon substrate, in which polishing is performed using a polishing liquid composition containing silica particles and a water-soluble polymer.
The polishing conditions for the final polishing steps 1 and 2 include the same polishing conditions as in the polishing step in the polishing method of the present disclosure described above.
The final polishing step 1 and the final polishing step 2 can be performed using one polishing surface plate (the same polishing surface plate). Alternatively, the final polishing process 1 and the final polishing process 2 may be performed using different polishing plates, that is, the final polishing process 2 may be performed on a polishing plate that is different from the polishing plate used in the final polishing process 1. can.

[Method for manufacturing semiconductor substrate]
In one aspect, the present disclosure relates to a method for manufacturing a semiconductor substrate (hereinafter also referred to as "the semiconductor substrate manufacturing method of the present disclosure"), which includes performing the polishing method of the present disclosure. In one or more embodiments, the semiconductor substrate manufacturing method of the present disclosure 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 a "polishing step"), The method may include a step of cleaning the silicon substrate (hereinafter also referred to as a "cleaning step").
According to the semiconductor substrate manufacturing method of the present disclosure, by using the polishing liquid composition of the present disclosure, it is possible to achieve both an improvement in polishing rate and storage stability of the concentrate, so that high quality semiconductor substrates can be produced at a high yield. It can be manufactured with good productivity and at low cost.

The polishing step in the semiconductor substrate manufacturing method of the present disclosure includes, for example, a lapping (rough polishing) step of planarizing a single crystal silicon substrate obtained by slicing a single crystal silicon ingot into thin disk shapes, and After etching the silicon substrate, the method may include a final polishing step of mirror-finishing the surface of the single-crystal silicon substrate. The polishing liquid composition of the present disclosure is preferably used in the final polishing step in one or more embodiments from the viewpoint of both improving the polishing rate and improving the surface quality.

In the polishing step in the semiconductor substrate manufacturing method of the present disclosure, for example, a substrate in which a polysilicon film is formed by a chemical vapor deposition (CVD) method on a silicon substrate having a silicon dioxide film and a silicon nitride film is polished. It can include a step of removing and planarizing, and a step of simultaneously polishing and planarizing the silicon dioxide film, silicon nitride film, and polysilicon film immediately below. The polishing liquid composition of the present disclosure is more preferably used in the process of removing the unevenness of the polysilicon film and flattening it, from the viewpoint of both improving the polishing rate and improving the surface quality.

The polishing step in the semiconductor substrate manufacturing method of the present disclosure can be performed under the same conditions (polishing pressure, polishing liquid composition, surface temperature of the polishing pad, etc.) 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 the concentrate of the polishing liquid composition of the present disclosure before the polishing step. For example, water can be used as the diluent.

In the cleaning step in the semiconductor substrate manufacturing method of the present disclosure, inorganic cleaning is preferably performed from the viewpoint of reducing residue on the silicon substrate surface. Examples of the cleaning agent 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 can further include, after the cleaning step, a step of rinsing the cleaned silicon substrate with water and drying it.

In one or more embodiments, the polishing step in the semiconductor substrate manufacturing method of the present disclosure is preferably a final polishing step from the viewpoint of achieving both improvement in polishing rate and storage stability of the concentrate.
In one or more embodiments, the polishing step in the semiconductor substrate manufacturing method of the present disclosure is a final polishing step from the viewpoint of achieving both improvement in polishing rate and storage stability of the concentrate, and from the viewpoint of improving surface quality. It is preferable that the polishing step is a preceding step. In one or more embodiments, the polishing step that is a pre-stage of the final polishing step includes the final polishing step 1 in the polishing method of the present disclosure described above.

When the polishing step in the semiconductor substrate manufacturing method of the present disclosure is a polishing step in which the above-described final polishing step 1 and final polishing step 2 are performed in this order, the final polishing steps 1 and 2 are the polishing steps of the present disclosure. Polishing can be performed under the same conditions (polishing pressure, polishing liquid composition, surface temperature of the polishing pad, etc.) as in the final polishing steps 1 and 2 in the method.

When the polishing step in the semiconductor substrate manufacturing method of the present disclosure is a polishing step in which the above-mentioned final polishing step 1 and final polishing step 2 are performed in this order, cleaning and drying are performed after performing the final polishing step 1. , a final polishing step 2 may be performed. Further, after performing the final polishing step 1, the final polishing step 2 may be performed without cleaning and drying. From the viewpoint of improving productivity, after performing the final polishing step 1, it is preferable to perform the final polishing step 2 without washing or drying.

Hereinafter, the present disclosure will be explained in more detail with reference to Examples, but these are merely illustrative and the present disclosure is not limited to these Examples.

1. Preparation of polishing liquid composition (Examples 1 to 3, Comparative Examples 1 to 2)
(Concentrate of polishing liquid composition)
The silica particles (component A) shown in Table 1, the water-soluble polymer (component B or non-component B) shown in Table 1, and ultrapure water are stirred and mixed to form a concentrate (20 times) of the polishing liquid composition. Obtained. An appropriate amount of ammonia (component C) was used for pH adjustment. The pH of the concentrate at 25°C was 9.6-10.5.
(Polishing liquid composition)
The above concentrate was diluted 20 times with ion-exchanged water to obtain polishing liquid compositions of Examples 1 to 3 and Comparative Examples 1 and 2.
The content of each component in Table 1 is the content (% by mass, effective content) of each component when the diluted polishing liquid composition is used. The content of ultrapure water is the remainder after removing component A and component B or non-component B and component C. The pH of each polishing liquid composition (when used) at 25° C. was the value shown in Table 1.

The following components were used as component A, component B, non-component B, and component C used to prepare each polishing liquid composition.
(Component A)
Colloidal silica [average primary particle diameter 35 nm, average secondary particle diameter 70 nm, degree of association 2.0]
(Component B)
PO-modified PEI: PO (propylene oxide)-modified polyethyleneimine [manufactured by Nippon Shokubai Co., Ltd., PP-061, weight average molecular weight 5,000, ratio of primary amino groups and secondary amino groups in the total amino groups of PEI: 0%]
(Non-ingredient B)
PEI: Polyethyleneimine [manufactured by Nippon Shokubai Co., Ltd., SP-006, weight average molecular weight 2,000]
HEC: Hydroxyethylcellulose [manufactured by Daicel, SE-400, weight average molecular weight 250,000]
(Component C)
Ammonia [28% by mass ammonia water, manufactured by Kishida Chemical Co., Ltd., special reagent grade]

2. Methods for measuring various parameters (1) Measurement of average primary particle diameter of silica particles (component A) The average primary particle diameter (nm) of component A is the specific surface area S (m ² / g) using the following formula.
Average primary particle diameter (nm) = 2727/S

The specific surface area S of component A is calculated by weighing approximately 0.1 g of a measurement sample into a measurement cell to four decimal places after the following [pretreatment], and heating it at 30°C in an atmosphere of 110°C immediately before measuring the specific surface area. After drying for a minute, measurement was performed by a nitrogen adsorption method (BET method) using a specific surface area measuring device (Micromeritic automatic specific surface area measuring device "Flowsorb III 2305", manufactured by Shimadzu Corporation).
[Preprocessing]
(a) Component A in slurry form is adjusted to pH 2.5±0.1 with an aqueous nitric acid solution.
(b) Component A in the form of slurry 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 ground 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) Wash the filtrate on the filter 5 times with 20 g of ion-exchanged water (40°C).
(f) Take the filter with the filtrate attached to it in a petri dish and dry it in an atmosphere of 110° C. for 4 hours.
(g) The dried filtrate (component A) was taken to avoid contamination with filter debris, and finely ground 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 is determined by adding silica particles to ion-exchanged water so that the concentration of component A is 0.5% by mass. After that, the obtained aqueous dispersion was placed in a Disposable Sizing Cuvette (polystyrene 10 mm cell) to a height of 10 mm from the bottom, and subjected to dynamic light scattering method (device name: "Zetasizer Nano ZS", manufactured by Sysmex Corporation). Measured using

(3) Measurement of weight average molecular weight of water-soluble polymer The weight average molecular weight of water-soluble polymer is calculated based on the peak in the chromatogram obtained by applying gel permeation chromatography (GPC) method under the following conditions. did.
<Measurement conditions for water-soluble polymers>
Equipment: HLC-8320 GPC (manufactured by Tosoh Corporation, integrated detector)
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℃
Detector: Shodex RI SE-61 differential refractive index detector Standard material: Monodisperse polyethylene glycol with known molecular weight

(4) Ratio of primary amino groups and secondary amino groups in all amino groups of component B The ratio of primary amino groups and secondary amino groups in all amino groups of component B is determined by 13C-NMR. It was calculated using
<Measurement conditions>
Sample: 200 mg of PO modified PEI dissolved in 0.6 mL of heavy water Equipment used: 400 MHz 13C-NMR (“Agilent 400-MR DD2” manufactured by Agilent Technologies, Inc.)
Measurement conditions: 13C-NMR measurement, pulse interval time 5 seconds, tetramethylsilane as standard peak (σ: 0.0 ppm) Number of measurement integrations: 5000 Each peak range used for integration:
A: 39.0 to 42.0 ppm (integral value of primary amine peak)
B: 47.0 to 52.0 ppm (integral value of secondary amine peak)
C: 53.0 to 58.0 ppm (integral value of tertiary amine peak)
<Ratio of primary amino groups and secondary amino groups in all amino groups>
The ratio of primary amino groups and secondary amino groups in all amino groups is determined by the following formula.
Ratio (equivalence ratio) of primary amino groups and secondary amino groups in all amino groups = (A+B)/(A+B+C)

(5) pH of polishing liquid composition
The pH at 25°C is the value measured using a pH meter (Toa Denpa Kogyo Co., Ltd., HM-30G), and the value is the value 1 minute after immersing the electrode of the pH meter in the polishing liquid composition or its concentrate. It is.

3. Evaluation of polishing liquid compositions of Examples 1 to 3 and Comparative Examples 1 to 2 (1) Polishing method, etc. For each polishing liquid composition, final polishing and cleaning were performed on the following silicon substrates under the following polishing conditions. .
<Silicon substrate to be polished>
Single-crystal silicon substrate [silicon single-sided mirror substrate with a diameter of 200 mm, conductivity type: P, crystal orientation: 100, resistivity: 0.1 Ω·cm or more and less than 100 Ω·cm]
The single-crystal silicon substrate was roughly polished in advance using a commercially available polishing composition (GLANZOX 1302, manufactured by Fujimi Incorporated). The haze of the single crystal silicon substrate subjected to final polishing after rough polishing was 2 to 3 ppm.

<Final polishing conditions>
Grinding machine: Single-sided 8-inch grinding machine "GRIND-X SPP600s" (manufactured by Okamoto Kosaku)
Polishing pad: Suede pad (manufactured by Toray Cortex, Asker hardness: 64, thickness: 1.37mm, nap length: 450um, opening diameter: 60um)
Silicon substrate polishing pressure: 100g/cm ²
Surface plate rotation speed: 60 rpm
Polishing time: 5 minutes Supply rate of polishing liquid composition: 150g/min
Temperature of polishing liquid composition: 23°C
Carrier rotation speed: 62rpm

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

<Washing method>
After final polishing, the silicon substrate was subjected to ozone cleaning and dilute hydrofluoric acid cleaning as described below. In ozone cleaning, an aqueous solution containing 20 ppm of ozone was sprayed from a nozzle at a flow rate of 1 L/min toward the center of the silicon substrate rotating at 600 rpm for 3 minutes. At this time, the temperature of the ozonated water was set to room temperature. Next, dilute hydrofluoric acid cleaning was performed. In dilute hydrofluoric acid cleaning, an aqueous solution containing 0.5% by mass of ammonium hydrogen fluoride (special grade, Nacalai Techs Co., Ltd.) is sprayed from a nozzle at a flow rate of 1 L/min toward the center of the silicon substrate rotating at 600 rpm for 6 seconds. did. A total of two sets of the above ozone cleaning and dilute hydrofluoric acid cleaning were performed as one set, and finally spin drying was performed. In spin drying, the silicon substrate was rotated at 1,500 rpm.

(2) Evaluation of polishing speed The weight of each silicon substrate before and after polishing was measured using a precision balance (BP-210S manufactured by Sartorius), and the resulting weight difference was calculated based on the density, area, and polishing time of the silicon substrate. The single-sided polishing rate per unit time was determined. The results are shown in Table 1 as relative values with Comparative Example 2 set as 100. Note that the weight of the silicon substrate after polishing is the weight of the silicon substrate after the above-mentioned final polishing and cleaning.

(3) Evaluation of storage stability of concentrate 100g of the concentrate of each polishing liquid composition was placed in a 100ml screw tube and sealed, and the storage stability after one day was evaluated according to the following evaluation criteria. The polishing liquid composition concentrate was stored in a room at 23°C. The results are shown in Table 1.
<Evaluation criteria>
A: One day after preparing the concentrate of the polishing liquid composition, no aggregates or separation occur and the dispersion stability is maintained.
B: One day after preparing the concentrate of the polishing composition, slight aggregates and separation were observed.
C: Agglomerates and separation have occurred one day after preparing the concentrate of the polishing liquid composition.

(4) Average particle diameter Da of silica particles (component A)
The average particle diameter Da of component A was determined by applying a dynamic light scattering method (apparatus name: " The measurement was performed using a Zetasizer Nano ZS (manufactured by Sysmex Corporation).

As shown in Table 1, the polishing liquid compositions of Examples 1 to 3 were able to achieve both improved polishing speed and storage stability of the concentrate compared to the polishing liquid compositions of Comparative Examples 1 and 2. I found out that there is.

4. Evaluation of two-stage finishing (multi-stage) polishing (Example 4, Comparative Example 3)
(1) (Multi-stage) Continuous Polishing After performing the final polishing step 1, multi-stage polishing was performed in which the polishing machine (polishing surface plate) was changed and the final polishing step 2 was performed continuously without washing or drying. In the final polishing step 1, the polishing liquid composition shown in Table 2 (Example 1, Comparative Example 1) was used, and in the final polishing step 2, the following polishing liquid composition was used. Final polishing step 2 was performed under the same polishing conditions as the final polishing in 3. above.
<Polishing liquid composition for final polishing step 2>
Finish polishing liquid compositions of Example 4 and Comparative Example 3 were prepared by stirring and mixing the silica particles shown in Table 2, the water-soluble polymers (HEC, PEG) shown in Table 2, and ultrapure water. An appropriate amount of ammonia was used for pH adjustment. The pH of the prepared polishing liquid composition at 25°C was 10.3. This final polishing composition was used as it was as a polishing liquid in the final polishing step 2.
The content (mass%, effective content) of each component is as shown in Table 2. The content of ultrapure water is the remainder after removing silica particles, water-soluble polymers (HEC, PEG), and ammonia.
The following components were used to prepare the polishing liquid composition in the final polishing step 2.
(Silica particles)
Colloidal silica [average primary particle diameter 35 nm, average secondary particle diameter 70 nm, degree of association 2.0]
(Water-soluble polymer)
HEC: Hydroxyethylcellulose [manufactured by Daicel, SE-400, weight average molecular weight 250,000]
PEG: Polyethylene glycol [manufactured by Wako Pure Chemical Industries, Ltd., grade 1, weight average molecular weight 6,000]
(ammonia)
Ammonia [28% by mass ammonia water, manufactured by Kishida Chemical Co., Ltd., special reagent grade]

(2) Measurement of surface defects (LPD) of silicon substrate Surface defects (LPD) of the silicon substrate after the multi-stage polishing and cleaning were measured in the same manner as described above. The results are shown in Table 2 as relative values with Comparative Example 3 set as 100.

As shown in Table 2, in Example 4, the number of surface defects after final polishing step 2 ( LPD) was reduced.

By using the polishing liquid composition of the present disclosure, it is possible to achieve both improvement in polishing rate and storage stability of the concentrate. Therefore, the polishing liquid composition of the present disclosure is useful as a polishing liquid composition used in the manufacturing process of various semiconductor substrates, and is particularly useful as a polishing liquid composition for final polishing of silicon substrates.

Claims (9)

A polishing liquid composition for silicon substrates, comprising silica particles (component A), a water-soluble polymer having an amino group to which a hydroxyalkyl group is bonded (component B), and water. The polishing liquid composition according to claim 1, wherein component B is an amino group-containing water-soluble polymer having a structure represented by the following formula (1).
In formula (1), R represents a hydrogen atom, a methyl group or a hydroxymethyl group. The polishing liquid composition according to claim 1 or 2, wherein component B has a weight average molecular weight of 200 or more and 200,000 or less. The polishing liquid composition according to any one of claims 1 to 3, wherein the content of component B is 0.001% by mass or more and 0.1% by mass or less. The polishing liquid composition according to any one of claims 1 to 4, wherein the content of component A is 0.3% by mass or more. The polishing liquid composition according to any one of claims 1 to 5, for use in a pre-stage polishing of final polishing in multiple stages of polishing of a silicon substrate. A method for polishing a silicon substrate, comprising the step of polishing a silicon substrate to be polished using the polishing liquid composition according to any one of claims 1 to 6. The silicon substrate includes a final polishing step 2 for final polishing the silicon substrate, and a final polishing step 1 which is a polishing step before the final polishing step 2, and the final polishing step 1 and the final polishing step 2 are performed in this order. A method for polishing a substrate, the method comprising:
In the final polishing step 1, polishing is performed using the polishing liquid composition according to any one of claims 1 to 6,
In the final polishing step 2, polishing is performed using a polishing liquid composition containing silica particles and a water-soluble polymer.
A method for polishing silicon substrates. A method for manufacturing a semiconductor substrate, comprising performing the polishing method according to claim 7 or 8.