JP7519862B2 - Polishing liquid composition for silicon oxide film - Google Patents

Description

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

In recent years, semiconductor elements have become increasingly multi-layered and highly precise, and more fine patterning techniques are being used. As a result, the surface structure of semiconductor elements has become more complex, and the surface steps have become larger. When manufacturing semiconductor elements, chemical mechanical polishing (CMP) technology is used to flatten the steps (surface irregularities) formed on the substrate.

For example, Patent Document 1 proposes a chemical mechanical treatment composition that includes a liquid carrier, abrasive particles, metal cations, and a zwitterionic compound.
Patent Document 2 proposes a polishing method for polishing an object to be polished that contains two or more materials using a polishing composition, the polishing method including equalizing the surface zeta potential of the object to be polished. Furthermore, the document describes that the equalization is performed by immersing the object to be polished in a potential equalizing agent having an adsorption group that adsorbs two or more materials and a functional group that imparts a zeta potential.
Patent Document 3 proposes a polishing composition for silicon oxide films that contains water, cerium oxide particles, and a compound having an amino group and a sulfonic acid group and/or a phosphonic acid group in the molecule, in which the ratio of [the number of moles of acid groups contained in the compound]/[the total surface area of the cerium oxide particles] is 1.6 x ^10-5 mol/ ^m2 or more and 5 x ^10-2 mol/ ^m2 or less.

JP 2018-534836 A International Publication No. 2017/057156 International Publication No. 2016/047725

In recent years, the semiconductor industry has become highly integrated, and there is a demand for more complex and finer wiring. For this reason, in CMP polishing, there is a demand for further improvements in the polishing speed of silicon oxide films (films to be polished) to eliminate steps caused by high stacking. In addition, it is essential for the quality of the polishing composition, which is the slurry, to be stable in a state where abrasive grains and chemicals coexist, and there is a demand for improving the storage stability of the polishing composition.

In Patent Document 1, the effect of improving the removal rate is excellent by using a zwitterionic compound having a negatively charged phosphorus-containing group and a positively charged cationic group, but the storage stability is still not fully satisfactory.
In Patent Document 2, an amino group is cited as a functional group that imparts an electric charge, and the effect of imparting a zeta potential (the effect of flattening the polished surface and improving the polishing rate) is clearly stated, but the effect is not fully satisfactory. Furthermore, there is room for improvement in storage stability.
In Patent Document 3, the use of a compound having an amino group and a sulfonic acid group and/or a phosphonic acid group provides an excellent effect of improving the polishing rate, but the storage stability is still not fully satisfactory.

The present disclosure provides a polishing composition for silicon oxide films that can achieve both improved polishing speed for silicon oxide films and improved storage stability, as well as a manufacturing method and polishing method for semiconductor substrates that use the same.

前記式（Ｉ）中、Ｒ¹及びＲ²は同一又は異なって、水素原子又はヒドロキシル基を示し、Ｒ³はグアニジノ又はアルキルグアニジノ基を示し、Ｘは炭素数１以上１２以下のアルキレン基を示し、ｎは０又は１を示す。 In one aspect, the present disclosure relates to a polishing composition for silicon oxide films, which contains cerium oxide particles (component A), a compound represented by the following formula (I) (component B), and an aqueous medium.

In the formula (I), R ¹ and R ² are the same or different and each represents a hydrogen atom or a hydroxyl group; R ³ represents a guanidino or alkylguanidino group; X represents an alkylene group having 1 to 12 carbon atoms; and n represents 0 or 1.

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

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

According to one aspect of the present disclosure, it is possible to provide a polishing composition for silicon oxide films that can simultaneously improve the polishing speed of silicon oxide films and improve storage stability.

The inventors have conducted extensive research and have discovered that the use of a specific compound can improve the polishing speed and storage stability of silicon oxide films.

That is, in one aspect, the present disclosure relates to a polishing liquid composition for silicon oxide films (hereinafter also referred to as the "polishing liquid composition of the present disclosure") that contains cerium oxide particles (component A), a compound represented by the above formula (I) (component B), and an aqueous medium.

In one or more embodiments, the polishing composition disclosed herein can achieve both an improvement in the polishing rate of a silicon oxide film and an improvement in storage stability.

Although the details of the mechanism by which the effects of the present disclosure are manifested are not clear, it is presumed as follows.
It is known that the (100) plane of cerium oxide particles used as polishing abrasive grains is involved in polishing, while the (111) plane is not involved in polishing. In order to increase the polishing rate, it is necessary to increase the frequency with which the (100) plane of the cerium oxide particles comes into contact with the object to be polished (silicon oxide film).
In the present disclosure, it is believed that the phosphate group or phosphonate group of component B is adsorbed to the (111) face of the cerium oxide particle (component A), thereby reducing the adsorptivity of the (111) face to the object to be polished, increasing the frequency of contact of the (100) face with the object to be polished, and improving the polishing rate for the silicon oxide film.
In addition, it is generally known that a guanidino group or an alkylguanidino group is more basic than an amino group, and it is considered that the guanidino group or alkylguanidino group of component B in the present disclosure is highly effective in imparting a positive charge to component A in the polishing liquid composition. Therefore, the charge of component A, which decreases when the phosphoric acid group or phosphonic acid group of component B is adsorbed to component A, can be compensated for by the guanidino group or alkylguanidino group of component B, so that it is possible to suppress aggregation of component A in the polishing liquid composition before use in polishing, and it is considered that the storage stability of the polishing liquid composition is improved.
However, the present disclosure need not be construed as being limited to these mechanisms.

[Cerium oxide particles (component A)]
The polishing composition of the present disclosure contains cerium oxide (hereinafter also referred to as "ceria") particles (hereinafter also simply referred to as "component A") as abrasive grains. As component A, positively charged ceria or negatively charged ceria can be used. The chargeability of component A is not particularly limited, but positively charged ceria is preferred from the viewpoint of improving the polishing rate. The chargeability of component A can be confirmed, for example, by measuring the electric potential (surface potential) on the surface of the abrasive grains obtained by an electroacoustic method (ESA method: Electrokinetic Sonic Amplitude). The surface potential can be measured, for example, using a "Zeta Probe" (manufactured by Kyowa Interface Science Co., Ltd.), specifically, by the method described in the Examples. Component A may be one type or a combination of two or more types.

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

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

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

The content of component A in the polishing composition of the present disclosure is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, even more preferably 0.125% by mass or more, and even more preferably 0.15% by mass or more, and from the viewpoint of suppressing the occurrence of polishing scratches, it is preferably 6% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, even more preferably 0.5% by mass or less, and even more preferably 0.3% by mass or less. More specifically, the content of component A in the polishing composition of the present disclosure is preferably 0.01% by mass or more and 6% by mass or less, more preferably 0.05% by mass or more and 3% by mass or less, even more preferably 0.1% by mass or more and 1% by mass or less, even more preferably 0.125% by mass or more and 0.5% by mass or less, and even more preferably 0.15% by mass or more and 0.3% by mass or less. When component A is a combination of two or more types, the content of component A refers to the total content thereof.

[Compound represented by formula (I) (Component B)]
The polishing composition of the present disclosure contains a compound represented by the following formula (I) (hereinafter, also simply referred to as “Component B”). Component B may be one type or a combination of two or more types.

In formula (I), R ¹ and R ² are the same or different and each represents a hydrogen atom or a hydroxyl group; R ³ represents a guanidino or alkylguanidino group; X represents an alkylene group having 1 to 12 carbon atoms; and n represents 0 or 1.

In formula (I), R ¹ and R ² are preferably each a hydroxyl group from the viewpoint of improving the polishing rate.
From the viewpoint of improving the polishing rate, ^R3 is preferably an alkylguanidino group, more preferably an alkylguanidino group having an alkyl group having from 2 to 12 carbon atoms, even more preferably an alkylguanidino group having an alkyl group having from 2 to 4 carbon atoms, still more preferably a methylguanidino group, and even more preferably a 1-methylguanidino group.
From the viewpoint of improving the polishing rate, X is preferably an alkylene group having 1 to 10 carbon atoms, more preferably an alkylene group having 1 to 8 carbon atoms, even more preferably an alkylene group having 1 to 6 carbon atoms, preferably an alkylene group having 1 to 4 carbon atoms, more preferably an alkylene group having 2 or 3 carbon atoms, and preferably an alkylene group having 2 carbon atoms (ethylene group).
From the viewpoint of improving the polishing rate, n is preferably 1.

Examples of component B include creatinol phosphate.

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, even more preferably 0.0075% by mass or more, and even more preferably 0.01% by mass or more, from the viewpoint of improving the polishing rate, and is preferably 0.1% by mass or less, more preferably 0.075% by mass or less, even more preferably 0.05% by mass or less, and even more preferably 0.03% by mass or less, from the viewpoint of storage stability. More specifically, the content of component B in the polishing liquid composition of the present disclosure is preferably 0.001% by mass or more and 0.1% by mass or less, more preferably 0.005% by mass or more and 0.075% by mass or less, even more preferably 0.0075% by mass or more and 0.05% by mass or less, and even more preferably 0.01% by mass or more and 0.03% by mass or less. From the viewpoints of improving the polishing rate and storage stability, the content of component B in the polishing composition of the present disclosure is preferably 0.01 mM, more preferably 0.05 mM or more, even more preferably 0.1 mM or more, and preferably 5 mM or less, more preferably 1 mM or less, even more preferably 0.5 mM or less. When component B is a combination of two or more types, the content of component B refers to the total content thereof.

In the polishing composition of the present disclosure, the ratio of the content of component A to the content of component B (mass ratio A/B) is preferably 2 or more, more preferably 3 or more, even more preferably 6 or more, and even more preferably 10 or more from the viewpoint of storage stability, and is preferably 60 or less, more preferably 30 or less, even more preferably 20 or less, and even more preferably 15 or less from the viewpoint of improving the polishing rate. More specifically, the mass ratio A/B in the polishing composition of the present disclosure is preferably 2 or more and 60 or less, more preferably 3 or more and 30 or less, even more preferably 6 or more and 30 or less, even more preferably 6 or more and 20 or less, and even more preferably 10 or more and 15 or less.

[Aqueous medium]
The aqueous medium contained in the polishing liquid composition of the present disclosure includes water such as distilled water, ion-exchanged water, pure water, and ultrapure water, or a mixed solvent of water and a solvent. The above-mentioned solvent includes a solvent that can be mixed with water (e.g., alcohol such as ethanol). When the aqueous medium is a mixed solvent of water and a solvent, the ratio of water to the entire mixed medium is not particularly limited as long as the effect of the present disclosure is not hindered. From the viewpoint of economic efficiency, for example, 95 mass% or more is preferable, 98 mass% or more is more preferable, and less than 100 mass% is preferable. From the viewpoint of surface cleanliness of the polished substrate, the aqueous medium is preferably water, more preferably ion-exchanged water and ultrapure water, and even more preferably ultrapure water.
The content of the aqueous medium in the polishing composition of the present disclosure can be the remainder excluding Component A, Component B, and any optional components described below that are blended as necessary.

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

In one or more embodiments, the polishing composition of the present disclosure may not contain metal cations.

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

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

The pH of the polishing liquid composition of the present disclosure is preferably 3 or more, more preferably 4 or more, and even more preferably 4.5 or more, from the viewpoint of improving the polishing rate, and is preferably 8 or less, more preferably 7.5 or less, and even more preferably 7 or less, from the viewpoint of improving storage stability. In the present disclosure, the pH of the polishing liquid composition is a value at 25°C, and is a value measured using a pH meter. Specifically, the pH of the polishing liquid composition of the present disclosure can be measured by the method described in the Examples.

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

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

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

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

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

In a specific example of the method for manufacturing a semiconductor substrate according to the present disclosure, a silicon dioxide layer is grown on a surface of a silicon substrate by exposing the silicon substrate to oxygen in an oxidation furnace, and then a polishing stopper film such as a silicon nitride (Si ₃ N ₄ ) film or a polysilicon film is formed on the silicon dioxide layer by, for example, a CVD method (chemical vapor deposition method). Next, a trench is formed by photolithography in a substrate including a silicon substrate and a polishing stopper film disposed on one main surface side of the silicon substrate, for example, a substrate in which a polishing stopper film is formed on a silicon dioxide layer of the silicon substrate. Next, a silicon oxide (SiO 2 ) film, which is a polishing film to be filled in the trench, is formed by, for example, _a CVD method using silane gas and oxygen gas, to obtain a polishing substrate in which the polishing stopper film is covered with the polishing film (silicon oxide film). By forming the silicon oxide film, the trench is filled with silicon oxide of the silicon oxide film, and the surface of the polishing stopper film opposite to the surface on the silicon substrate side is covered with the silicon oxide film. The surface of the silicon oxide film formed in this manner opposite to the surface on the silicon substrate side has a step formed corresponding to the unevenness of the underlying layer. Next, the silicon oxide film is polished by a CMP method until at least the surface opposite to the surface on the silicon substrate side of the polishing stopper film is exposed, and more preferably, the silicon oxide film is polished until the surface of the silicon oxide film and the surface of the polishing stopper film are flush with each other. The polishing composition of the present disclosure can be used in the step of performing polishing by this CMP method. The width of the convex portion formed corresponding to the unevenness of the underlying layer of the silicon oxide film is, for example, 0.5 μm or more and 5000 μm or less, and the width of the concave portion is, for example, 0.5 μm or more and 5000 μm or less.

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

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

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

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

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

1. Preparation of polishing compositions [Preparation of polishing compositions of Examples 1 to 5 and Comparative Examples 1 to 4]
Cerium oxide particles (component A) shown in Table 2, compounds B1 to B4 (component B or non-component B) shown in Tables 1 and 2, and water were mixed to obtain polishing compositions of Examples 1 to 5 and Comparative Examples 1 to 4. The content (mass %, active content) of each component in the polishing composition is as shown in Table 2, and the content of water is the remainder excluding component A and component B or non-component B. The pH was adjusted using ammonia or nitric acid.

The cerium oxide particles (component A) shown in Table 2 were as follows.
Positively charged ceria (calcined ground ceria, average primary particle size: 28.6 nm, BET specific surface area: 29.1 m ² /g, surface potential = 102 mV)

The following compounds B1 to B4 shown in Tables 1 and 2 were used.
B1: Creatinol Phosphate [Tokyo Chemical Industry Co., Ltd.] (ingredient B)
B2: O-Phosphorylethanolamine [Tokyo Chemical Industry Co., Ltd.] (non-component B)
B3: Agmatine sulfate [Tokyo Chemical Industry Co., Ltd.] (non-ingredient B)
B4: Creatine Hydrate [Tokyo Chemical Industry Co., Ltd.] (non-ingredient B)

2. Method for measuring various parameters [pH of polishing composition]
The pH value of the polishing composition at 25° C. was measured using a pH meter (HM-30G, manufactured by Toa Denpa Kogyo Co., Ltd.) one minute after the electrode was immersed in the polishing composition. The results are shown in Table 2.

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

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

3. Evaluation of Polishing Compositions (Examples 1 to 5 and Comparative Examples 1 to 4) [Evaluation Samples]
As an evaluation sample, a commercially available CMP characteristic evaluation wafer (Advantec's "P-TEOS CMP464 PT wafer", diameter 200 mm) was prepared and cut into 40 mm x 40 mm. This evaluation sample had a silicon substrate with a silicon oxide film of 2000 nm thick arranged as convex portions, and a silicon oxide film of 2000 nm thick arranged as concave portions as well, with a linear concave-convex pattern formed by etching so that the step between the convex portions and the concave portions was 800 nm. The silicon oxide film was formed from P-TEOS, and the measurement object had a line width of 100 μm for the convex portions and the concave portions.

[Polishing conditions]
Polishing device: TriboLab CMP (manufactured by Bruker)
Plate rotation speed: 100 rpm
Head rotation speed: 107 rpm
Polishing load: 99.3N
Polishing solution supply amount: 50 mL/min Polishing time: 1/3 min

[Polishing speed]
The evaluation samples were polished under the above-mentioned polishing conditions using each of the polishing compositions of Examples 1 to 5 and Comparative Examples 1 to 4. After polishing, the evaluation samples were washed with ultrapure water and dried, and were used as measurement targets using an optical interference film thickness measuring device described below.
Before and after polishing, the thickness of the silicon oxide film on the convex parts was measured using an optical interference film thickness measurement device ("VM-1230" manufactured by SCREEN Semiconductor Solutions). The polishing rate of the silicon oxide film on the convex parts was calculated by the following formula. The results are shown in Table 2.
Polishing speed of convex part (nm/min)
= [thickness of silicon oxide film on the convex parts before polishing (nm) - thickness of silicon oxide film on the convex parts after polishing (nm)] / polishing time (min)

[Storage stability]
The zeta potential of the cerium oxide particles (component A) in each prepared polishing composition was measured using an electroacoustic high-concentration zeta potential meter (manufactured by Agilent Technologies), and the composition was placed in a 100 mL container and allowed to stand at room temperature. After one week had passed, the zeta potential was measured again, and the rate of change in zeta potential before and after storage was calculated using the following formula. The storage stability was then evaluated according to the following evaluation criteria. The results are shown in Table 2. The smaller the rate of change in zeta potential of the cerium oxide particles (component A) in the polishing composition, the more the inhibition of aggregation of component A is maintained, and the more excellent the storage stability is.
Rate of change in zeta potential before and after storage=(zeta potential before storage−zeta potential after storage)/(zeta potential before storage)×100
<Evaluation criteria>
A: The rate of change in zeta potential before and after storage is less than 30%. B: The rate of change in zeta potential before and after storage is 30% or more but less than 40%. C: The rate of change in zeta potential before and after storage is 40% or more.

As shown in Table 2, it was found that the polishing compositions of Examples 1 to 5 were able to achieve both improved polishing rate and improved storage stability compared to the polishing compositions of Comparative Examples 1 to 4.

The polishing composition disclosed herein is useful in a method for manufacturing semiconductor devices for high density or high integration.

Claims (7)

A polishing composition for silicon oxide films, comprising cerium oxide particles (component A), a compound represented by the following formula (I) (component B), and an aqueous medium:

In the formula (I), R ¹ and R ² are the same or different and each represents a hydrogen atom or a hydroxyl group; R ³ represents a guanidino or alkylguanidino group; X represents an alkylene group having 1 to 12 carbon atoms; and n represents 0 or 1. The polishing composition according to claim 1, wherein the ratio of the content of component A to the content of component B (mass ratio A/B) is 2 or more and 60 or less. The polishing composition according to claim 1 or 2, wherein the content of component B is 0.001% by mass or more and 0.1% by mass or less. The polishing composition according to any one of claims 1 to 3, wherein the content of component A is 0.01% by mass or more and 6% by mass or less. The polishing composition according to any one of claims 1 to 4, wherein the pH of the polishing composition at 25°C is 3 or more and 8 or less. A method for manufacturing a semiconductor substrate, comprising a step of polishing a film to be polished using the polishing composition according to any one of claims 1 to 5. A polishing method comprising a step of polishing a film to be polished using the polishing composition according to any one of claims 1 to 5, the film to be polished being a silicon oxide film formed during the manufacturing process of a semiconductor substrate.