JP7760294B2 - Chemical mechanical polishing particles - Google Patents

Description

This disclosure relates to chemical mechanical polishing particles, a polishing composition containing the chemical mechanical polishing particles, a method for manufacturing a semiconductor substrate using the same, and a method for polishing a substrate.

Chemical mechanical polishing (CMP) is a technique in which the surface of the substrate to be polished is brought into contact with a polishing pad, and a polishing liquid is supplied to the contact point while the substrate and polishing pad are moved relative to each other, chemically reacting with and mechanically removing the uneven surface of the substrate to achieve planarization.

Currently, CMP technology has become essential in the semiconductor device manufacturing process for processes such as planarizing interlayer insulating films, forming shallow trench isolation structures, and forming plugs and buried metal wiring. In recent years, semiconductor devices have become increasingly multi-layered and highly precise, creating demands for further improvements in semiconductor device yield and throughput. Accordingly, there is a growing demand for scratch-free and faster polishing in the CMP process.

Reducing scratches is a particularly important issue in the field of advanced logic, and improvements in abrasives are being made. For example, when cerium oxide (ceria) is used as the abrasive particle, it is generally known that reducing the particle size of the abrasive particle reduces scratches, but reducing the particle size significantly reduces the polishing speed, resulting in a significant decline in productivity.

Therefore, for example, Patent Document 1 proposes a particulate material containing cerium oxide having a secondary particle size distribution in the range of 80 to 199 nm and a density of at least 6.6 g/cm ³ as a means for achieving both a high polishing rate and a good surface finish. Claim 11 of the same document states that the particulate material has a circularity of 1.28 or less.
Patent Document 2 proposes polishing particles for silicon oxide films, in which crystalline ceria particles having an average primary diameter of 5 nm or more and 40 nm or less are arranged on amorphous silica particles, as a means for achieving both a high polishing rate and reduced scratches.

Special table 2011-511751 publication JP 2016-127139 A

In recent years, the semiconductor industry has witnessed increasing integration density, resulting in a demand for more complex and finer wiring. Widely used cerium oxide particles for polishing purposes are various shapes and sizes of cerium oxide particles (hereinafter also referred to as "irregular cerium oxide"), which are obtained by calcining and pulverizing cerium compounds such as cerium carbonate and cerium nitrate. However, in polishing using abrasive grains such as amorphous cerium oxide, the structure of the surface has many edges, making it difficult to reduce scratches. Therefore, attempts to reduce scratches have been made by reducing the particle size of cerium oxide particles, but this approach results in a problem of a decrease in the polishing rate, and there is a demand for an improvement in the polishing rate of silicon oxide films.
Furthermore, since the particles described in Patent Document 2 contain silica, there is a problem that they tend to adhere to the surroundings of the polishing device after drying, and therefore improvement in redispersibility is desired.

This disclosure provides chemical mechanical polishing particles that can improve the polishing rate of silicon oxide films while reducing scratches, as well as a polishing composition containing the chemical mechanical polishing particles, a polishing method using the same, and a method for manufacturing semiconductor substrates.

In one aspect, the present disclosure relates to particles for chemical mechanical polishing, the particles for chemical mechanical polishing being cluster-type cerium oxide particles in which cerium oxide particles are associated, and satisfying the following conditions 1 to 4:
Condition 1: An average primary particle diameter measured by the BET method is 10 nm or more and 50 nm or less. Condition 2: An average particle diameter measured by image analysis is 100 nm or more and 300 nm or less. Condition 3: An average sphericity measured by image analysis is 0.76 or more. Condition 4: An average density is 6.5 g/cm ³ or more.

In one aspect, the present disclosure relates to a polishing liquid composition comprising the chemical mechanical polishing particles of the present disclosure and an aqueous medium.

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

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 composition described herein.

This disclosure provides chemical mechanical polishing particles that can improve the polishing rate of silicon oxide films while reducing scratches, as well as a polishing composition containing the chemical mechanical polishing particles, a polishing method using the same, and a method for manufacturing semiconductor substrates.

FIG. 1 is a schematic diagram for explaining a method for measuring sphericity. FIG. 2 is an example of a scanning electron microscope (hereinafter also referred to as "SEM") photograph of the chemical mechanical polishing particles (A2).

In one aspect, the present disclosure is based on the finding that by using cluster-type cerium oxide particles that satisfy certain conditions as chemical mechanical polishing particles, it is possible to improve the polishing rate of silicon oxide films while reducing scratches.

That is, in one aspect, the present disclosure relates to particles for chemical mechanical polishing, which are cluster-type cerium oxide particles in which cerium oxide particles are associated, and which satisfy the following conditions 1 to 4 (hereinafter also referred to as "particles for chemical mechanical polishing of the present disclosure").
Condition 1: An average primary particle diameter measured by the BET method is 10 nm or more and 50 nm or less. Condition 2: An average particle diameter measured by image analysis is 100 nm or more and 300 nm or less. Condition 3: An average sphericity measured by image analysis is 0.76 or more. Condition 4: An average density is 6.5 g/cm3 or ^more. The chemical mechanical polishing particles disclosed herein can improve the removal rate of a silicon oxide film while reducing scratches.

Although the details of the mechanism by which the effects of the present disclosure are manifested are not clear, it is presumed as follows.
Cerium oxide particles are generally used as abrasive particles for silicon oxide films. Typically, cerium in cerium oxide particles is tetravalent, but in rare cases, oxygen (O) is lost to make it trivalent. It is believed that the trivalent cerium in cerium oxide particles weakens the Si—O bonds in the silicon oxide film, weakening the silicon oxide film and facilitating polishing. Currently, amorphous cerium oxide particles (amorphous ceria) are widely used as abrasive particles for silicon oxide films. While amorphous cerium oxide particles have a structure with many edges, the chemical mechanical polishing particles of the present disclosure are cluster-type cerium oxide particles formed by the aggregation of cerium oxide particles having an average primary particle diameter of 10 to 50 nm as measured by the BET method, and have a structure close to a spherical shape. Therefore, when a polishing composition containing the chemical mechanical polishing particles of the present disclosure is used, the occurrence of scratches is suppressed compared to when conventional polishing compositions containing amorphous cerium oxide particles are used.
Furthermore, when abrasive particles have a spherical particle shape, they tend to be less likely to achieve a high polishing rate due to reduced frictional resistance with the polished surface. However, the chemical mechanical polishing particles of the present disclosure are cluster-type cerium oxide particles formed by aggregation of cerium oxide particles having an average primary particle diameter of 10 to 50 nm, an average particle diameter of 100 to 300 nm measured by image analysis, and having fine irregularities on the surface as shown in FIG. 2. The average particle diameter of 100 to 300 nm increases the number of contact points of the fine irregularities on the surface to be polished, improving frictional resistance with the polished surface and promoting weakening of the silicon oxide film, which is thought to result in a high polishing rate. Furthermore, since the density is 6.5 g/cm ³ or higher, stress is more likely to be generated during contact with the polished substrate, and it is presumed that high polishing efficiency can be achieved even with small contact points.
Therefore, it is believed that by using the chemical mechanical polishing particles of the present disclosure, the surface to be polished can be polished at high speed and the occurrence of scratches on the surface to be polished can be suppressed.
In particles containing silica, the interaction between the silica and the dispersant is small, and the dispersant is released during drying, and the silica particles are strongly bonded to each other via surface hydroxyl groups (silanol groups), resulting in the formation of hard agglomerated dried products, which is thought to result in poor redispersibility.On the other hand, the cerium oxide constituting the chemical mechanical polishing particles of the present disclosure has a stronger interaction with the dispersant than silica, which suppresses interparticle bonding, which is thought to improve redispersibility.
However, the present disclosure need not be construed as being limited to these mechanisms.

[Chemical mechanical polishing particles (component A)]
The chemical mechanical polishing particles of the present disclosure are cluster-type cerium oxide particles in which cerium oxide particles are associated with each other, and satisfy the above conditions 1 to 4.
In the present disclosure, cluster-type cerium oxide particles refer to secondary aggregates (associated cerium oxide particles) formed by gathering at least two or more cerium oxide particles (primary particles) (see FIG. 2).

<Average primary particle diameter (condition 1)>
In this disclosure, the average primary particle size of the chemical mechanical polishing particles refers to the average primary particle size of the cerium oxide particles (primary particles) that make up the cluster-type cerium oxide particles.
The average primary particle diameter of the chemical mechanical polishing particles of the present disclosure is 10 nm or more, preferably 20 nm or more, more preferably 25 nm or more, and even more preferably 30 nm or more, from the viewpoint of achieving both an improvement in the polishing rate and a reduction in scratches, and from the same viewpoint, is 50 nm or less, preferably 45 nm or less, more preferably 40 nm or less, and even more preferably 38 nm or less. In the present disclosure, the average primary particle diameter of the chemical mechanical polishing particles is calculated using the BET specific surface area S (m ² /g) calculated by the BET (nitrogen adsorption) method. The BET specific surface area can be measured by the method described in the Examples.

<BET specific surface area>
The BET specific surface area of the chemical mechanical polishing particles of the present disclosure is preferably 42 m ² /g or less, more preferably 33 m ² /g or less, and even more preferably 28 m ² /g or less, from the viewpoint of achieving both improved polishing rate and reduced scratches, and from the same viewpoint is preferably 18 m ² /g or more, more preferably 20 m ² /g or more, and even more preferably 22 m ² /g or more.

<Average particle diameter (condition 2)>
The average particle size of the chemical mechanical polishing particles of the present disclosure is, from the viewpoint of achieving both an improved polishing rate and a reduced scratch, 100 nm or more, preferably 110 nm or more, more preferably 120 nm or more, and even more preferably 125 nm or more, and from the same viewpoint, is 300 nm or less, preferably 250 nm or less, more preferably 200 nm or less, and even more preferably 150 nm or less.
In the present disclosure, the average particle size of the chemical mechanical polishing particles is a value measured by an image analysis method, and is a value measured by the method described in the Examples.

<Meeting rate>
From the viewpoint of achieving both an improved polishing rate and a reduced scratch, the degree of association of the particles for chemical mechanical polishing of the present disclosure is preferably 3 or more, more preferably 3.2 or more, and even more preferably 3.5 or more, and from the same viewpoint, is preferably 10 or less, more preferably 8.5 or less, and even more preferably 6 or less.
In the present disclosure, the degree of association of the chemical mechanical polishing particle is a coefficient representing the shape of the chemical mechanical polishing particle, and is calculated by the following formula.
Degree of association = average particle size / average primary particle size Methods for adjusting the degree of association of the particles for chemical mechanical polishing of the present disclosure include controlling the reaction temperature, changing the concentration of cerium oxide particles during synthesis, and changing the concentration of the aggregating agent used to aggregate the primary particles.

<Average sphericity (condition 3)>
The average sphericity of the particles for chemical mechanical polishing according to the present disclosure is, from the viewpoint of achieving both an improvement in the polishing rate and a reduction in scratches, 0.76 or more, preferably 0.8 or more, more preferably 0.815 or more, and even more preferably 0.83 or more, and from the viewpoint of suppressing a decrease in the polishing rate, is preferably 0.95 or less, more preferably 0.925 or less, and even more preferably 0.9 or less.
In the present disclosure, the average sphericity of the chemical mechanical polishing particle is the average value of the sphericities of at least 100 particles for chemical mechanical polishing. The sphericity of the chemical mechanical polishing particle is a value measured by image analysis. For example, as shown in FIG. 1 , the projected area S and projected perimeter L of the chemical mechanical polishing particle are determined using SEM observation and image analysis software, and the sphericity can be calculated from the following formula:
Sphericity = 4π×S/(L) ²
The sphericity of each individual chemical mechanical polishing particle is preferably in the same range as the average sphericity.

<Average density (condition 4)>
The average density of the chemical mechanical polishing particles of the present disclosure is, from the viewpoint of achieving both an improved polishing rate and reduced scratches, 6.5 g/cm ^or more, preferably 6.8 g/cm ^or more, more preferably 6.9 g/cm ^or more, and even more preferably 7 g/cm ^or more, and from the same viewpoint, is preferably 7.15 g/cm ^or less, more preferably 7.1 g/cm ^or less, and even more preferably 7.05 g/cm ^or less.
In the present disclosure, "density" refers to a value measured by a gas displacement method. The average density can be measured by the method described in the examples.

<Oxygen storage capacity>
The oxygen storage capacity of the chemical mechanical polishing particles of the present disclosure is preferably 50 μmol/g or more, more preferably 75 μmol/g or more, and even more preferably 100 μmol/g or more, from the viewpoint of achieving both an improved polishing rate and a reduced scratch, and is preferably 500 μmol/g or less, more preferably 250 μmol/g or less, and even more preferably 200 μmol/g or less, from the viewpoint of long-term stability of the cerium oxide particles.
In the present disclosure, oxygen storage capacity refers to the function of absorbing and releasing oxygen in association with the oxidation and reduction of cerium ions, and it can be determined that the larger the oxygen storage amount, the better the oxygen storage capacity and the higher the oxidation and reduction characteristics.
In the present disclosure, the oxygen storage capacity can be measured using a thermogravimetric differential thermal analyzer, specifically, by the method described in the Examples. The oxygen storage capacity of the chemical mechanical polishing particles can be adjusted by controlling the crystallinity of the cerium oxide particles.

The surface potential of the chemical mechanical polishing particles disclosed herein is preferably negative from the viewpoint of achieving both particle dispersion stability and improved polishing rate.

The shape of the chemical mechanical polishing particles of the present disclosure is preferably approximately spherical from the viewpoint of reducing scratches.
From the viewpoint of improving the polishing rate of a silicon oxide film, the chemical mechanical polishing particles of the present disclosure preferably have fine irregularities on the surface as shown in FIG.

<Method of manufacturing chemical mechanical polishing particles>
The chemical mechanical polishing particles of the present disclosure can be produced by referring to the method described in, for example, JP-A-2006-82994.

[Polishing liquid composition]
In one aspect, the present disclosure relates to a polishing liquid composition (hereinafter also referred to as the "polishing liquid composition of the present disclosure") containing the chemical mechanical polishing particles of the present disclosure and an aqueous medium.

<Chemical mechanical polishing particles (component A)>
The polishing composition of the present disclosure contains the above-described chemical mechanical polishing particles of the present disclosure (hereinafter also referred to as "Component A"). Component A may be one type or a combination of two or more types.
The content of Component A in the polishing composition of the present disclosure is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.2% by mass or more from the viewpoint of improving the polishing rate, and is preferably 5% by mass or less, more preferably 2.5% by mass or less, and even more preferably 1% by mass or less from the viewpoint of reducing scratches and reducing costs. When Component A is a combination of two or more types, the content of Component A refers to the total content thereof.

<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. Examples of the solvent include a solvent miscible with water (e.g., alcohol such as ethanol). When the aqueous medium is a mixed solvent of water and a solvent, the proportion of water relative to the total mixed medium is not particularly limited as long as the effects of the present disclosure are not hindered. From the viewpoint of economic efficiency, for example, 95% by mass or more is preferred, 98% by mass or more is more preferred, and substantially 100% by mass is even more preferred. From the viewpoint of surface cleanliness of the substrate to be polished, 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 and the optional components described below that are blended as needed.

<Anionic Dispersant (Component B)>
The polishing liquid composition of the present disclosure may further include an anionic dispersant (hereinafter also referred to as "component B"). In one or more embodiments, component B is a compound having an anionic group. Examples of the anionic group include a carboxylic acid group and a sulfonic acid group. These anionic groups may be in the form of a neutralized salt. When the anionic group is in the form of a salt, examples of the counter ion include a metal ion, an ammonium ion, and an alkylammonium ion. From the viewpoint of improving the quality of the semiconductor substrate, an ammonium ion is preferred.

Component B can be, for example, at least one selected from an anionic polymer having a carboxylic acid group or a salt thereof (component B1) and an anionic condensate having a sulfonic acid group or a salt thereof (component B2).

In one or more embodiments, the anionic polymer having a carboxylic acid group or a salt thereof (component B1) is at least one selected from a polymer containing a carboxylic acid group or a salt thereof, and a polymer containing a carboxylic acid group or a salt thereof and a sulfonic acid group or a salt thereof. Examples include at least one selected from polyacrylic acid, polymethacrylic acid, a copolymer of (meth)acrylic acid and styrenesulfonic acid, a copolymer of (meth)acrylic acid and 2-acrylamidopropanesulfonic acid (AMPS), a copolymer of (meth)acrylic acid and styrene, a copolymer of (meth)acrylic acid and an alkyl (meth)acrylate, a copolymer of (meth)acrylic acid and a polyalkylene glycol (meth)acrylate, alkali metal salts thereof, and ammonium salts thereof. From the viewpoint of simultaneously improving the polishing rate for the silicon oxide film and reducing scratches, and from the viewpoint of improving the quality of the semiconductor substrate, at least one selected from polyacrylic acid and an ammonium salt thereof is preferred.
In one or more embodiments, the anionic condensate having a sulfonic acid group or a salt thereof (component B2) may be a formalin condensate having a sulfonic acid group or a salt thereof, and examples thereof include at least one selected from formalin condensates of phenolsulfonic acid (PhS), formalin condensates of naphthalenesulfonic acid, formalin condensates of bis(4-hydroxyphenyl)sulfone (BisS) and phenolsulfonic acid (PhS) (BisS/PhS), formalin condensates of p-cresol and phenolsulfonic acid (PhS), formalin condensates of bis(4-hydroxy-3-methylphenyl)sulfone (BSDM) and phenolsulfonic acid (PhS), and formalin condensates of phenol (Ph) and phenolsulfonic acid (PhS). Among these, from the viewpoint of achieving both an improvement in the polishing rate of the silicon oxide film and a reduction in scratches, a formalin condensate of bis(4-hydroxyphenyl)sulfone (BisS) and phenolsulfonic acid (PhS) (BisS/PhS) is preferred.

The weight average molecular weight of Component B is preferably 300 or more, more preferably 500 or more, and even more preferably 700 or more, from the viewpoint of particle dispersion stability, and is preferably 1,000,000 or less, more preferably 500,000 or less, and even more preferably 100,000 or less, from the viewpoint of suppressing a decrease in the polishing rate.
When Component B is an anionic polymer (Component B1), the weight-average molecular weight of Component B1 is preferably 1,000 or more, more preferably 5,000 or more, and even more preferably 10,000 or more, from the viewpoint of particle dispersion stability, and is preferably 1,000,000 or less, more preferably 500,000 or less, and even more preferably 1,000,000 or less, from the viewpoint of suppressing a decrease in the polishing rate.
When component B is an anionic condensate (component B2), the weight-average molecular weight of component B2 is preferably 300 or more, more preferably 500 or more, and even more preferably 700 or more, from the viewpoint of particle dispersion stability, and is preferably 20,000 or less, more preferably 10,000 or less, and even more preferably 5,000 or less, from the viewpoint of suppressing a decrease in the polishing rate.

In the present disclosure, the weight average molecular weight of Component B can be measured by gel permeation chromatography (GPC) using liquid chromatography (Hitachi, Ltd., L-6000 high performance liquid chromatography) under the following conditions.
<Measurement conditions: Component B1>
Detector: RI
Column: G4000PWXL + G2500PWXL (manufactured by Tosoh Corporation)
Eluent: 0.2 M phosphate buffer/acetonitrile = 9/1 (volume ratio)
Column temperature: 40°C
Flow rate: 1.0mL/min
Standard polymer: monodisperse polyethylene glycol with known molecular weight <Measurement conditions: component B2>
Detector: RI
Column: TSKgel GMPWXL + TSKgel GMPWXL (manufactured by Tosoh Corporation)
Eluent: 0.2 M phosphate buffer/acetonitrile = 7/3 (volume ratio)
Column temperature: 40°C
Flow rate: 1.0mL/min
Standard polymer: Monodisperse sodium polystyrene sulfonate with known molecular weight

When the polishing composition of the present disclosure contains component B, the content of component B in the polishing composition of the present disclosure is preferably 0.0001% by mass or more, more preferably 0.0025% by mass or more, and even more preferably 0.005% by mass or more, from the viewpoint of particle dispersion stability, and is preferably 0.1% by mass or less, more preferably 0.05% by mass or less, and even more preferably 0.02% by mass or less, from the viewpoint of suppressing a decrease in the polishing rate. When component B is a combination of two or more types, the content of component B is the total content thereof.

When the polishing composition of the present disclosure contains component B, the mass ratio A/B of the content of component A to the content of component B in the polishing composition of the present disclosure is preferably 5 or more, more preferably 10 or more, and even more preferably 25 or more, from the viewpoint of suppressing a decrease in the polishing rate, and is preferably 500 or less, more preferably 250 or less, and even more preferably 100 or less, from the viewpoint of particle dispersion stability.

[Other ingredients]
The polishing composition of the present disclosure may further contain other components within the scope of not impairing the effects of the present disclosure. Examples of other components include a pH adjuster, a pH buffer, a surfactant other than Component B, a polymer other than Component B, a thickener, a dispersant, a rust inhibitor, a preservative, a basic substance, a polishing rate enhancer, and a counter ion.
When the polishing liquid composition of the present disclosure further contains other components, the content of the other components in the polishing liquid composition of the present disclosure is, from the viewpoint of improving the polishing rate, 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.

[Method of manufacturing the polishing composition]
The polishing composition of the present disclosure can be produced, for example, by a production method including a step of blending component A, an aqueous medium, and, if desired, the above-mentioned optional components (component B, other components) using a known method. For example, the polishing composition of the present disclosure can be produced by blending at least component A and an aqueous medium. When component A is a combination of multiple types of chemical mechanical polishing particles, component A can be obtained by blending multiple types of chemical mechanical polishing particles separately. In the present disclosure, "blending" includes simultaneously or sequentially mixing component A, an aqueous medium, and, if necessary, the above-mentioned optional components (component B, other components). The order of mixing is not particularly limited. The blending can be carried out using a mixer such as a homomixer, a homogenizer, an ultrasonic disperser, or a wet ball mill. The blending amount of each component in the production method of the polishing composition of the present disclosure can be the same as the content of each component in the above-mentioned polishing composition of the present disclosure.

Embodiments of the polishing liquid composition disclosed herein may be so-called one-component types, in which all components are supplied to the market in a pre-mixed state, or so-called two-component types, in which the components are mixed at the time of use. Examples of two-component polishing liquid compositions include those composed of a first liquid containing component A and a second liquid containing component B, with the first liquid and the second liquid being mixed at the time of use. The first liquid and the second liquid may be mixed before being supplied to the surface to be polished, or they may be supplied separately and mixed on the surface of the substrate to be polished. The first liquid and the second liquid may each contain the optional components described above, as necessary.

From the viewpoint of particle dispersion stability, the pH of the polishing liquid composition of the present disclosure is preferably 3.5 or higher, more preferably 4 or higher, and even more preferably 4.5 or higher. From the viewpoint of improving the polishing rate, it is preferably 9 or lower, more preferably 8.5 or lower, even more preferably 8 or lower, even more preferably less than 8, even more preferably 7 or lower, and even more preferably 6 or lower. From the same viewpoint, the pH of the polishing liquid composition of the present disclosure is preferably 3.5 or higher and 9 or lower, more preferably 4 or higher and 8.5 or lower, even more preferably 4.5 or higher and 8 or lower, even more preferably 4.5 or higher and less than 8, even more preferably 4.5 or higher and 7 or lower, and even more preferably 4.5 or higher and 6 or lower. In the present disclosure, the pH of the polishing liquid composition is a value at 25°C and can be measured using a pH meter, specifically, by the method described in the examples.

In this disclosure, the "content of each component in the polishing composition" refers to the content of each component at the time of polishing, i.e., at the time when the polishing composition begins to be used for polishing. The polishing composition of this disclosure may be stored and supplied in a concentrated state to the extent that its stability is not impaired. This is preferable in that it reduces production and transportation costs. This concentrated liquid can then be diluted appropriately with water as needed and used in the polishing process. A dilution ratio of 5 to 100 times is preferred.

[Polished film]
Examples of films to be polished using the polishing composition of the present disclosure include silicon oxide films. Therefore, the polishing composition of the present disclosure can be used in processes requiring polishing of silicon oxide films, and can be suitably used for, for example, polishing of silicon oxide films carried out in a process for forming an element isolation structure of a semiconductor substrate, polishing of silicon oxide films carried out in a process for forming an interlayer insulating film, polishing of silicon oxide films carried out in a process for forming buried metal wiring, polishing of silicon oxide films carried out in a process for forming buried capacitors, and polishing of silicon oxide films carried out in a process for manufacturing three-dimensional semiconductor devices such as three-dimensional NAND flash memories.

[Polishing liquid kit]
In another aspect, the present disclosure relates to a kit for producing 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-component polishing liquid composition) containing a polishing abrasive dispersion containing component A and an aqueous medium, and an additive aqueous solution containing component B, in a mutually unmixed state. The polishing abrasive dispersion and the additive aqueous solution are mixed at the time of use and diluted with an aqueous medium as needed. The aqueous medium contained in the polishing abrasive dispersion may be the entire amount of the aqueous medium used in preparing the polishing liquid composition, or may be a portion thereof. The additive aqueous solution may contain a portion of the aqueous medium used in preparing the polishing liquid composition. The polishing abrasive dispersion and the additive aqueous solution may each contain the optional components (other components) described above as needed.
According to the polishing liquid kit of the present disclosure, it is possible to obtain a polishing liquid composition that can improve the removal rate of a silicon oxide film and reduce scratches at the same time.

[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, wherein the film to be polished is a silicon oxide film formed during the manufacturing process of a semiconductor substrate. Use of the polishing method of the present disclosure can improve the polishing rate of the silicon oxide film while reducing scratches, thereby improving the productivity of semiconductor substrates with improved quality. The polishing method and conditions in the polishing method of the present disclosure can be the same as those in the manufacturing method of a semiconductor substrate of the present disclosure, which will be described later.

[Method of 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 a step (polishing step) of polishing a silicon oxide film using the polishing composition of the present disclosure.
According to the method for manufacturing a semiconductor substrate of the present disclosure, it is possible to improve the polishing rate of a silicon oxide film and reduce scratches at the same time, so that semiconductor substrates with improved quality can be manufactured efficiently.

In one or more embodiments of the method for manufacturing a semiconductor substrate according to the present disclosure, a silicon substrate is first exposed to oxygen in an oxidation furnace to grow a silicon dioxide layer on the surface thereof. A polishing stopper film, such as a silicon _nitride ( _Si3N4 ) film or a polysilicon film, is then formed on the silicon dioxide layer by, for example, a CVD (chemical vapor deposition) method. Next, a trench is formed using photolithography in a substrate including a silicon substrate and a polishing stopper film disposed on one main surface of the silicon substrate, e.g., a silicon dioxide ( _SiO2 ) film, which serves as a polishing film to fill the trench, is then formed by, for example, a CVD method using silane gas and oxygen gas, to obtain a polished 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 from the silicon oxide film, and the surface of the polishing stopper film opposite the surface facing the silicon substrate is covered with the silicon oxide film. The surface of the silicon oxide film formed in this manner opposite to the surface facing the silicon substrate has steps formed corresponding to the unevenness of the underlying layer. The silicon oxide film is then polished by CMP until at least the surface opposite to the surface facing the silicon substrate of the polishing stopper film is exposed, more preferably 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 this CMP polishing process. The width of the convex portions formed corresponding to the unevenness of the underlying layer of the silicon oxide film is, for example, 0.1 μm or more and 5000 μm or less, and the width of the concave portions is, for example, 0.1 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 according to the present disclosure, another insulating film may be formed between the silicon dioxide layer of the silicon substrate and the polishing stopper film, or another insulating film may be formed between the film to be polished (e.g., a silicon oxide film) and the polishing stopper film (e.g., a silicon nitride film).

In the polishing step, the rotation speed of the polishing pad can be set to, for example, 30 to 200 rpm, the rotation speed of the substrate to be polished can be set to, for example, 30 to 200 rpm, the polishing load set in the polishing apparatus equipped with the polishing pad can be set to, for example, 20 to 500 gf/cm ² , and the supply rate of the polishing composition can be set to, for example, 10 to 500 mL/min or less. When the polishing composition is a two-component polishing composition, the respective polishing rates of the polishing film and the polishing stopper film, and the polishing rate ratio between the polishing film and the polishing stopper film (polishing selectivity), can be adjusted by adjusting the respective supply rates (or supply amounts) of the first and second liquids.

In the polishing step, the polishing rate of the film to be polished (silicon oxide film) is preferably 50 nm/min or more, more preferably 80 nm/min or more, and even more preferably 90 nm/min or more, from the perspective of improving productivity.

The following examples illustrate the present disclosure, but are not intended to limit the scope of the present disclosure.

1. Measurement Method of Each Parameter (1) 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.), and was the value measured one minute after the electrode of the pH meter was immersed in the polishing composition.

(2) Average primary particle size of chemical mechanical polishing particles The average primary particle size (nm) of the chemical mechanical polishing particles was calculated using the specific surface area S ( ^m2 /g) obtained by the BET (nitrogen adsorption) method described below, assuming the true density of the cerium oxide particles to be 7.2 g/ ^cm3 .
The calculation was carried out using the theoretical density of cerium oxide particles, assuming that cerium oxide was uniformly distributed on silicon oxide particles on the surfaces of chemical mechanical polishing particles A-5.

(3) BET Specific Surface Area of Chemical Mechanical Polishing Particles The specific surface area of the chemical mechanical polishing particles was measured by the nitrogen adsorption method (BET method) using a fully automatic specific surface area measurement device (Macsorb HM model-1201, manufactured by Mountec Co., Ltd.). As a pretreatment, the chemical mechanical polishing particles were dried with hot air at 650°C for 1 hour and then finely pulverized in an agate mortar to prepare a sample. The sample was then placed in a glass cell and set in the device. Immediately before measurement, the sample was dried under a nitrogen atmosphere at 300°C for 45 minutes, and then the BET specific surface area was measured.

(4) Average Particle Diameter of Chemical Mechanical Polishing Particles The average particle diameter of the chemical mechanical polishing particles was determined by observing the chemical mechanical polishing particles using a scanning electron microscope (SEM) with a product name of "S-4800" (10 kV, 100,000 to 150,000 magnification, manufactured by Hitachi High-Tech Corporation) according to the manufacturer's instructions, and taking an SEM image. This data was then analyzed using analysis software "WinROOF 2015" (sold by Mitani Corporation) to determine the circle-equivalent diameter of each identifiable chemical mechanical polishing particle, and the circle-equivalent diameters of 100 or more particles were calculated as the average particle size.

(5) Degree of Association of Chemical Mechanical Polishing Particles The degree of association of the chemical mechanical polishing particles was calculated using the following formula.
Degree of association = average particle size/average primary particle size

(6) Average Sphericity of Chemical Mechanical Polishing Particles The average sphericity of the chemical mechanical polishing particles was measured by observing the chemical mechanical polishing particles using a scanning electron microscope (SEM) with a trade name "S-4800" (10 kV, 100,000 to 150,000 magnification, manufactured by Hitachi High-Tech Corporation) according to the manufacturer's instructions, and taking an SEM image. This data was analyzed using the analysis software "WinROOF 2015" (sold by Mitani Shoji) to calculate the sphericity by using the projected area (S) of a single identifiable particle and the perimeter (L) of the particle using the following formula. The values in Table 1 below were calculated by determining the sphericity of 100 chemical mechanical polishing particles and then averaging these values.
・Sphericity = 4π×S/(L) ²

(7) Oxygen Storage Capacity of Chemical Mechanical Polishing Particles The oxygen storage capacity of the chemical mechanical polishing particles was measured using a thermogravimetric differential thermal analyzer (Thermo plus TG8110, manufactured by Rigaku) by the method described below.
The chemical mechanical polishing particle dispersion was dried with hot air at 600°C for 3 hours and then finely pulverized in an agate mortar. The chemical mechanical polishing particles were then placed in a Pt pan and set in the device. A nitrogen:hydrogen gas (1:1) was filled into the device, and the temperature was raised from room temperature to 800°C to reduce the chemical mechanical polishing particles. While maintaining the temperature at 800°C, the system was substituted with nitrogen and maintained for 30 minutes. The chemical mechanical polishing particles were then oxidized with an oxygen:nitrogen gas (1:9). The oxygen storage capacity (μmol/g) was calculated using the amount of oxygen absorbed by the chemical mechanical polishing particles.

(8) Average Density of Chemical Mechanical Polishing Particles The average density of the chemical mechanical polishing particles was measured using a fully automatic true density measuring device (Macpycno MP-310, manufactured by Mountech Co., Ltd.). As a pretreatment, the chemical mechanical polishing particles were dried with hot air at 650°C for 1 hour and then finely pulverized in an agate mortar to prepare a sample. The sample was then placed in a sample pod, and the average density was measured using He gas.

2. Preparation of Polishing Compositions (Examples 1 to 10 and Comparative Examples 1 to 3)
Chemical mechanical polishing particles (component A and non-component A shown in Tables 1 and 3), dispersant (component B shown in Tables 2 and 3), and water were mixed to obtain polishing compositions of Examples 1 to 10 and Comparative Examples 1 to 3. The content of each component in each polishing composition is as shown in Table 3. The content of water is the remainder excluding component A or non-component A and component B. pH adjustment was performed using ammonia or nitric acid.

Details of the component A, non-component A, and component B used in preparing the polishing compositions of Examples 1 to 10 and Comparative Examples 1 to 3 are shown in Tables 1 and 2 and below.
(Component A)
A1: Cluster-type cerium oxide particles [BET specific surface area: 32.0 m ² /g]
A2: Cluster-type cerium oxide particles [BET specific surface area: 23.9 m ² /g]
Components A1 and A2 were obtained by hydrolyzing a cerium salt to form ceria nuclei, and then hydrolyzing a separately prepared cerium salt in the presence of the ceria nuclei to grow the ceria nuclei. An SEM photograph of component A2 is shown in Figure 2.
(Non-ingredient A)
A3: amorphous ceria [BET specific surface area: 21.5 m ² /g]
A4: Colloidal ceria [BET specific surface area: 10.0 m ² /g]
A5: Composite particles in which cerium oxide particles are coated on silica particles [BET specific surface area: 23.8 m ² /g]
(Component B)
B1: Ammonium polyacrylate B2: BisS/PhS formalin condensate [formalin condensate of bis(4-hydroxyphenyl)sulfone and phenolsulfonic acid, molar ratio (BisS/PhS): 80/20]

3. Evaluation of Polishing Compositions (Examples 1 to 10 and Comparative Examples 1 to 3) (1) Preparation of Test Pieces (Blanket Substrates) A silicon oxide film (blanket film) having a thickness of 2000 nm was formed on one side of a silicon wafer by a TEOS-plasma CVD method, and a 40 mm x 40 mm square piece was cut out from the formed film to obtain a silicon oxide film test piece (blanket substrate).

(2) Polishing Rate of Silicon Oxide Film Using each of the polishing compositions of Examples 1 to 10 and Comparative Examples 1 to 3, the above test pieces (blanket substrates of silicon oxide films) were polished under the following polishing conditions.
<Polishing conditions>
Polishing device: Single-sided polishing machine [TribolaB CMP, manufactured by Bruker]
Polishing pad: hard urethane pad "IC-1000/Suba400, manufactured by Nitta DuPont"
Plate rotation speed: 100 rpm
Head rotation speed: 107 rpm
Polishing load: 300g/ ^cm2
Polishing solution supply rate: 50 mL/min Polishing time: 1 min The thickness of the silicon oxide film was measured before and after polishing using an optical interference film thickness measuring device (VM-1230, manufactured by SCREEN Semiconductor Solutions).
The removal rate of the silicon oxide film (film to be polished) was calculated using the following formula: The results are shown in Table 3.
Polishing rate of silicon oxide film (Å/min)
= [thickness of silicon oxide film before polishing (Å) - thickness of silicon oxide film after polishing (Å)] / polishing time (minutes)

(3) Scratch Measurement Method After polishing, cleaning, and drying, a silicon oxide film blanket substrate was attached to a flat substrate and measured using a macro-defect detection device (Micro-MAX VMX-3100, manufactured by Mipox Corporation). After setting the substrate in the macro-defect detection device, a light source was irradiated and measurements were taken at a magnification of 20x and a tilt angle of -5°. The results are shown in Table 3. In this disclosure, "scratch" refers to a flaw with a length of 1 μm or more that can be detected by the macro-defect detection device.

(4) Method for Evaluating Redispersibility The redispersibility of the polishing composition was measured by measuring the particle diameter of the chemical mechanical polishing particles before and after drying using a disk centrifugal particle size distribution analyzer (CPS DC24000UHR, manufactured by CPS Instrument) under the following measurement conditions. Specifically, the particle diameter (hereinafter referred to as D99) at which the cumulative frequency from the small diameter side is 99% in the particle size distribution calculated by weight using the disk centrifugal particle size distribution analyzer for the polishing composition prepared under the following conditions was measured, and the increase rate of D99 was calculated using the following formula, which was used as an index of redispersibility. The lower the increase rate of D99, the higher the redispersibility can be evaluated. The redispersibility was evaluated based on the following evaluation criteria, and the results are shown in Table 3.
D99 increase rate = [D99 (after drying) - D99 (before drying)] / D99 before drying x 100
<Preparation of sample for D99 measurement>
Before drying: Each of the polishing compositions of Examples 1 to 10 and Comparative Examples 1 to 3. After drying: 10 g of each of the polishing compositions of Examples 1 to 10 and Comparative Examples 1 to 3 was placed in a sample bottle and dried at room temperature. Thereafter, the amount of evaporated water was determined, and the same amount of ultrapure water was added, followed by ultrasonic irradiation and re-dispersion.
<Measurement conditions>
Measurement range: 0.02 to 3 μm
Particle extinction coefficient: 0.1
Particle shape factor: 1.2 or 1.0
Rotation speed: 17,000 rpm
Measurement temperature: 25℃
<Evaluation criteria>
A: D99 increase rate is 10% or less B: D99 increase rate is more than 10% but less than 100% C: D99 increase rate is more than 100%

As shown in Table 3, Examples 1 to 10, which used cluster-type cerium oxide particles (Component A) satisfying conditions 1 to 4 as chemical mechanical polishing particles, were able to polish silicon oxide films at a higher polishing rate and produced fewer scratches on the polished silicon oxide film than Comparative Examples 1 to 3, which used chemical mechanical polishing particles (non-Component A). Furthermore, the redispersibility of the polishing compositions of Examples 1 to 10 was good.

The polishing composition disclosed herein is useful in methods for manufacturing semiconductor substrates for high density or high integration.

Claims (10)

1. A chemical mechanical polishing particle comprising:
The chemical mechanical polishing particles are cluster-type cerium oxide particles in which cerium oxide particles are associated with each other, and satisfy the following conditions 1 to 4:
The chemical mechanical polishing particles have an oxygen storage capacity of 50 μmol/g or more .
Condition 1: An average primary particle diameter measured by the BET method is 10 nm or more and 50 nm or less. Condition 2: An average particle diameter measured by image analysis is 100 nm or more and 300 nm or less. Condition 3: An average sphericity measured by image analysis is 0.76 or more. Condition 4: An average density is 6.5 g/cm ³ or more. The chemical mechanical polishing particles according to claim 1, wherein the average sphericity of the chemical mechanical polishing particles is 0.8 or more. 3. The chemical mechanical polishing particle according to claim 1, wherein the average density of the chemical mechanical polishing particle is 6.8 g/cm ^<3> or more. 4. The chemical mechanical polishing particle according to claim 1, wherein the chemical mechanical polishing particle has an oxygen storage capacity of 75 μmol/g or more. 5. The chemical mechanical polishing particles according to claim 1 , wherein the degree of association of the chemical mechanical polishing particles is 3 or more and 10 or less. A polishing composition comprising the chemical mechanical polishing particles according to claim 1 and an aqueous medium. The polishing composition according to claim 6 , further comprising an anionic dispersant. 8. The polishing composition according to claim 7 , wherein the anionic dispersant is at least one selected from the group consisting of an anionic polymer having a carboxylic acid group or a salt thereof and an anionic condensate having a sulfonic acid group or a salt thereof. 9. A polishing method comprising the step of polishing a film to be polished with the polishing composition according to claim 6 , wherein the film to be polished is a silicon oxide film formed in the process of manufacturing a semiconductor substrate. A method for producing a semiconductor substrate, comprising a step of polishing a film to be polished with the polishing composition according to claim 6 .