JP2023038579A - Chemical mechanical polishing particles - Google Patents

Abstract

To provide chemical mechanical polishing particles capable of improving the polishing rate of a silicon oxide film and reducing scratches, and a polishing liquid composition using the same, a polishing method, and a method for manufacturing a semiconductor substrate.SOLUTION: Chemical mechanical polishing particles according to an embodiment are cluster-type cerium oxide particles in which cerium oxide particles are associated, and satisfy the following conditions 1 to 4. The condition 1: Average primary particle size by BET method is 10 nm or more and 50 nm or less. The condition 2: Average particle size measured by image analysis method is 100 nm or more and 300 nm or less. The condition 3: Average sphericity measured by image analysis method is 0.76 or more. The condition 4: Average density is 6.5 g/cm3 or more.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present disclosure relates to chemical mechanical polishing particles, a polishing composition containing the chemical mechanical polishing particles, a semiconductor substrate manufacturing method using the same, and a substrate polishing method.

A chemical mechanical polishing (CMP) technique is a technique in which the surface of a substrate to be polished and a polishing pad are brought into contact with each other, and a polishing liquid is supplied to the contact area between the substrate and the polishing pad. This is a technique for chemically reacting uneven portions on the surface of the substrate to be polished and mechanically removing and flattening the substrate by moving the substrate.

At present, this CMP technology is essential for the planarization of interlayer insulating films, the formation of shallow trench isolation structures, the formation of plugs and embedded metal wiring, etc. in the manufacturing process of semiconductor devices. . 2. Description of the Related Art In recent years, the number of layers of semiconductor elements and the increase in definition thereof have progressed dramatically, and there has been a demand for further improvement in the yield and throughput of semiconductor elements. Accordingly, in the CMP process as well, there is a growing demand for scratch-free polishing at a higher speed.

Especially in the field of advanced logic, the reduction of scratches is an important issue, and the improvement of abrasives is also progressing. For example, when cerium oxide (ceria) is used as the abrasive particles, it is generally known to reduce the particle diameter of the abrasive particles in order to reduce scratches. There is a problem that the productivity drops significantly and the productivity deteriorates significantly.

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

Special table 2011-511751 publication Japanese Patent Application Laid-Open No. 2016-127139

2. Description of the Related Art In recent years, the field of semiconductors has progressed toward higher integration, and wiring has been required to become more complicated and finer. Cerium oxide particles used as polishing particles include, for example, cerium oxide particles of various shapes and sizes obtained by firing and pulverizing cerium compounds such as cerium carbonate and cerium nitrate (hereinafter referred to as "amorphous cerium oxide ”) are widely used. However, in polishing using abrasive grains such as amorphous cerium oxide, since the structure has many edges, it has been a problem to reduce scratches. For this reason, attempts have been made to reduce the number of scratches by reducing the particle size of the cerium oxide particles.
In addition, since particles such as those disclosed in Patent Document 2 contain silica, they tend to stick to the periphery of a polishing apparatus after drying, which can be a problem.

The present disclosure provides chemical mechanical polishing particles capable of simultaneously improving the polishing rate of a silicon oxide film and reducing scratches, a polishing liquid composition containing the chemical mechanical polishing particles, a polishing method using the same, and a semiconductor substrate. A manufacturing method is provided.

In one aspect, the present disclosure relates to chemical mechanical polishing particles, wherein the chemical mechanical polishing particles are cluster-type cerium oxide particles in which cerium oxide particles are associated, and satisfy conditions 1 to 4 below. for particles.
Condition 1: Average primary particle diameter measured by BET method is 10 nm to 50 nm Condition 2: Average particle diameter measured by image analysis is 100 nm to 300 nm Condition 3: Average sphericity measured by image analysis is 0. 76 or more Condition 4: Average density of 6.5 g/cm ³ or more

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

In one aspect, the present disclosure 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 in the process of manufacturing a semiconductor substrate. Regarding the method.

The present disclosure, in one aspect, relates to a method for manufacturing a semiconductor substrate, comprising polishing a film-to-be-polished using the polishing composition described in the present disclosure.

INDUSTRIAL APPLICABILITY According to the present disclosure, chemical mechanical polishing particles capable of simultaneously improving the polishing rate of a silicon oxide film and reducing scratches, a polishing liquid composition containing the chemical mechanical polishing particles, a polishing method using the same, and a semiconductor A method for manufacturing a substrate can be provided.

FIG. 1 is a schematic diagram for explaining a method of measuring sphericity. FIG. 2 is an example of a scanning electron microscope (hereinafter also referred to as “SEM”) observation 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 predetermined conditions as particles for chemical mechanical polishing, it is possible to both improve the polishing rate of a silicon oxide film and reduce scratches.

That is, in one aspect, the present disclosure relates to chemical mechanical polishing particles, wherein the chemical mechanical polishing particles are cluster-type cerium oxide particles in which cerium oxide particles are associated, and satisfy conditions 1 to 4 below. The present invention relates to mechanical polishing particles (hereinafter also referred to as “chemical mechanical polishing particles of the present disclosure”).
Condition 1: Average primary particle diameter measured by BET method is 10 nm to 50 nm Condition 2: Average particle diameter measured by image analysis is 100 nm to 300 nm Condition 3: Average sphericity measured by image analysis is 0. 76 or more Condition 4: Average density of 6.5 g/cm ³ or more According to the chemical mechanical polishing particles of the present disclosure, it is possible to improve both the polishing rate of a silicon oxide film and reduce scratches.

Although the details of the mechanism by which the effects of the present disclosure are manifested are not clear, it is speculated as follows.
Cerium oxide particles are generally used as the abrasive particles for the silicon oxide film. Normally, cerium in cerium oxide particles is tetravalent, and in rare cases oxygen (O) is dropped to become trivalent. It is believed that trivalent cerium in the cerium oxide particles weakens the Si—O bond of the silicon oxide film, weakens the silicon oxide film, and promotes polishing. At present, amorphous cerium oxide particles (unshaped ceria) are widely used as particles for polishing silicon oxide films. Amorphous cerium oxide particles have a structure with many edges, whereas the chemical mechanical polishing particles of the present disclosure are cluster-type particles in which cerium oxide particles having an average primary particle diameter of 10 to 50 nm according to the BET method are associated. It is a cerium oxide particle and has a structure close to a spherical shape. Therefore, the use of a polishing composition containing the chemical mechanical polishing particles of the present disclosure suppresses the occurrence of scratches compared to the use of a conventional polishing composition containing amorphous cerium oxide particles.
Moreover, when the particle shape of the polishing particles is spherical, it tends to be difficult to develop a high polishing rate due to the phenomenon of frictional resistance with the surface to be polished. However, in the chemical mechanical polishing particles of the present disclosure, cerium oxide particles having an average primary particle diameter of 10 to 50 nm are associated, and the average particle diameter measured by image analysis is 100 to 300 nm, as shown in FIG. It is a cluster-type cerium oxide particle having fine unevenness on its surface. Since the average particle size is 100 to 300 nm, the number of contact points of the fine irregularities on the surface with the surface to be polished increases, and the frictional resistance with the surface to be polished is improved, and the silicon oxide film becomes fragile. It is considered that the polishing rate is developed. Furthermore, since the density is 6.5 g/cm ³ or more, stress is likely to occur when contacting the substrate to be polished, and it is presumed that high polishing efficiency can be imparted even if the contact point is small.
Therefore, it is believed that the use of the chemical mechanical polishing particles of the present disclosure enables the surface to be polished to be polished at high speed and suppresses the occurrence of scratches on the surface to be polished.
In the particles containing silica, the interaction between the silica and the dispersant is small, the dispersant is detached during drying, and the silica particles are strongly bonded to each other through the surface hydroxyl groups (silanol groups), resulting in the formation of a hard aggregated dried product. As a result, it is considered that the redispersibility deteriorates. On the other hand, cerium oxide, which constitutes the chemical mechanical polishing particles of the present disclosure, has a stronger interaction with the dispersing agent than silica, suppressing bonding between particles, and 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, and satisfy Conditions 1 to 4 above.
In the present disclosure, cluster-type cerium oxide particles refer to secondary aggregates (associated cerium oxide particles) in which at least two or more cerium oxide particles (primary particles) are aggregated (see FIG. 2).

<Average primary particle size (condition 1)>
In the present disclosure, the average primary particle size of the chemical mechanical polishing particles indicates the average primary particle size of the cerium oxide particles (primary particles) that constitute the cluster-type cerium oxide particles.
The average primary particle size 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 still more preferably 30 nm or more, from the viewpoint of achieving both an improvement in polishing rate and a reduction in scratches. and, from the same point of view, it 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 size 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 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, still more preferably 28 m ^{2 /} g, from the viewpoint of achieving both an improvement in polishing rate and a reduction in scratches. g or less, and from the same viewpoint, it is preferably 18 m ² /g or more, more preferably 20 m ² /g or more, and still more preferably 22 m ² /g or more.

<Average particle size (condition 2)>
The average particle diameter of the chemical mechanical polishing particles of the present disclosure is 100 nm or more, preferably 110 nm or more, more preferably 120 nm or more, and even more preferably 125 nm or more, from the viewpoint of achieving both an improvement in polishing rate and a reduction in scratches. From the same point of view, it 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, which is a value measured by the method described in Examples.

<Association degree>
The association degree of the chemical mechanical polishing particles of the present disclosure is preferably 3 or more, more preferably 3.2 or more, still more preferably 3.5 or more, from the viewpoint of achieving both improvement in polishing speed and reduction in scratches, and , from the same point of view, it is preferably 10 or less, more preferably 8.5 or less, and still more preferably 6 or less.
In the present disclosure, the association degree of the chemical mechanical polishing particles is a coefficient representing the shape of the chemical mechanical polishing particles 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 chemical mechanical polishing particles of the present disclosure include controlling the reaction temperature, changing the concentration of the cerium oxide particles during synthesis, and controlling the concentration of the primary particles during aggregation. Examples include changing the concentration of the flocculant.

<Average sphericity (Condition 3)>
The average sphericity of the chemical mechanical polishing particles of the present disclosure is 0.76 or more, preferably 0.8 or more, more preferably 0.815 or more, from the viewpoint of achieving both improvement in polishing speed and reduction in scratches. , more preferably 0.83 or more, and from the viewpoint of suppressing a decrease in polishing rate, it is preferably 0.95 or less, more preferably 0.925 or less, and still more preferably 0.9 or less.
In the present disclosure, the average sphericity of the chemical mechanical polishing particles is the average value of the sphericity of at least 100 chemical mechanical polishing particles. The sphericity of the chemical mechanical polishing particles is a value measured by an image analysis method. For example, as shown in FIG. The projected area S and the projected peripheral length L can be obtained and calculated from the following equations.
Sphericality = 4π x S/(L) ²
The sphericity of individual chemical mechanical polishing particles 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 6.5 g/cm 3 or more, preferably 6.8 g/cm ³ or more, more preferably 6.8 g/cm ³ or more, from the viewpoint of achieving both improvement in polishing rate and reduction in scratches. 6.9 g/cm ³ or more, more preferably 7 g/cm ³ or more, and from the same viewpoint, preferably 7.15 g/cm ³ or less, more preferably 7.1 g/cm ³ or less, still more preferably 7.05 g/cm ³ or less.
In the present disclosure, "density" refers to a value measured by a gas replacement method. The average density can be measured by the method described in Examples.

<Oxygen storage capacity>
The oxygen storage amount 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 still more preferably 100 μmol/g or more, from the viewpoint of achieving both improvement in polishing speed and reduction in scratches. Yes, and from the viewpoint of long-term stability of the cerium oxide particles, it is preferably 500 μmol/g or less, more preferably 250 μmol/g or less, and even more preferably 200 μmol/g or less.
In the present disclosure, the oxygen storage capacity refers to the function of absorbing and releasing oxygen along with the oxidation-reduction of cerium ions, and it can be determined that the larger the value of the oxygen storage capacity, the better the oxygen storage capacity and the higher the oxidation-reduction characteristics. .
In the present disclosure, the oxygen storage amount 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 of the present disclosure is preferably negative from the viewpoint of achieving both dispersion stability of the particles and improvement of the polishing rate.

From the viewpoint of reducing scratches, the shape of the chemical mechanical polishing particles of the present disclosure is preferably substantially spherical.
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 unevenness on the surface as shown in FIG.

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

[Polishing liquid composition]
In one aspect, the present disclosure relates to a polishing composition (hereinafter also referred to as "polishing composition of the present disclosure") comprising 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 of 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 still more preferably 0.2% by mass, from the viewpoint of improving the polishing rate. From the viewpoints of scratch reduction and cost reduction, the content is preferably 5% by mass or less, more preferably 2.5% by mass or less, and even more preferably 1% by mass or less. When component A is a combination of two or more, the content of component A refers to their total content.

<Aqueous medium>
The aqueous medium contained in the polishing 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 water-miscible solvents (for example, 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 may not be particularly limited as long as the effects of the present disclosure are not hindered. , is preferably 95% by mass or more, more preferably 98% by mass or more, and even more preferably substantially 100% by mass. From the viewpoint of surface cleanliness of the substrate to be polished, the aqueous medium is preferably water, more preferably ion-exchanged water or ultrapure water, and still more preferably ultrapure water.
The content of the aqueous medium in the polishing composition of the present disclosure can be the remainder after removing the component A and optional components described later that are blended as necessary.

<Anionic Dispersant (Component B)>
The polishing composition of the present disclosure can further contain an anionic dispersant (hereinafter also referred to as "component B"). Component B, in one or more embodiments, is a compound with anionic groups. Examples of anionic groups include carboxylic acid groups and sulfonic acid groups. These anionic groups may take the form of neutralized salts. When the anionic group takes the form of a salt, counter ions include metal ions, ammonium ions, alkylammonium ions and the like, and ammonium ions are preferred from the viewpoint of improving the quality of the semiconductor substrate.

Component B includes, for example, at least one selected from anionic polymers having carboxylic acid groups or salts thereof (component B1) and anionic condensates having sulfonic acid groups or salts thereof (component B2). .

An anionic polymer having a carboxylic acid group or a salt thereof (component B1) is, in one or more embodiments, a polymer containing a carboxylic acid group or a salt thereof, and a carboxylic acid group or a salt thereof and a sulfonic acid group or a salt thereof. and at least one selected from polymers containing, for example, polyacrylic acid, polymethacrylic acid, a copolymer of (meth)acrylic acid and styrenesulfonic acid, (meth)acrylic acid and 2-acrylamidopropanesulfone Copolymer with acid (AMPS), copolymer of (meth)acrylic acid and styrene, copolymer of (meth)acrylic acid and alkyl (meth)acrylate, (meth)acrylic acid and polyalkylene glycol ( At least one selected from a copolymer with meth)acrylate, an alkali metal salt thereof, and an ammonium salt thereof, from the viewpoint of improving both the polishing rate of a silicon oxide film and reducing scratches, and a semiconductor substrate. At least one selected from polyacrylic acid and its ammonium salt is preferable from the viewpoint of improving the quality of.
In one or more embodiments, the anionic condensate (component B2) having a sulfonic acid group or a salt thereof includes a formalin condensate having a sulfonic acid group or a salt thereof, such as phenolsulfonic acid (PhS). formalin condensate, formalin condensate of naphthalenesulfonic acid, formalin condensate of bis(4-hydroxyphenyl)sulfone (BisS) and phenolsulfonic acid (PhS) (BisS/PhS), p-cresol and phenolsulfonic acid (PhS) selected from formalin condensates, formalin condensates of bis(4-hydroxy-3-methylphenyl)sulfone (BSDM) and phenolsulfonic acid (PhS), and formalin condensates of phenol (Ph) and phenolsulfonic acid (PhS) At least 1 type is mentioned. Among these, the formalin condensate (BisS/PhS) of bis(4-hydroxyphenyl)sulfone (BisS) and phenolsulfonic acid (PhS) is preferable from the viewpoint of simultaneously improving the polishing rate of the silicon oxide film and reducing scratches. .

The weight-average molecular weight of component B is preferably 300 or more, more preferably 500 or more, and still more preferably 700 or more from the viewpoint of dispersion stability of particles, and preferably 1,000 or more from the viewpoint of suppressing a decrease in polishing rate. 000,000 or less, more preferably 500,000 or less, and still more preferably 100,000 or less.
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 10,000 or more, from the viewpoint of particle dispersion stability. From the viewpoint of suppressing a decrease in polishing rate, it is preferably 1,000,000 or less, more preferably 500,000 or less, and even more preferably 100,000,000 or less.
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, still more preferably 700 or more, from the viewpoint of dispersion stability of particles, and 20,000 or less is preferable, 10,000 or less is more preferable, and 5,000 or less is still more preferable from the viewpoint of suppressing a decrease in polishing rate.

In the present disclosure, the weight average molecular weight of component B can be measured under the following conditions by gel permeation chromatography (GPC) using liquid chromatography (L-6000 high performance liquid chromatography manufactured by Hitachi, Ltd.). .
<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: 1.0 mL/min
Standard polymer: monodisperse polyethylene glycol with known molecular weight <measurement conditions: component B2>
Detector: RI
Column: TSKgelGMPWXL + TSKgelGMPWXL (manufactured by Tosoh Corporation)
Eluent: 0.2 M phosphate buffer/acetonitrile = 7/3 (volume ratio)
Column temperature: 40°C
Flow rate: 1.0 mL/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, from the viewpoint of dispersion stability of particles. It is preferably 0.0025% by mass or more, still more preferably 0.005% by mass or more, and from the viewpoint of suppressing a decrease in polishing rate, preferably 0.1% by mass or less, more preferably 0.05% by mass or less. , and more preferably 0.02% by mass or less. When component B is a combination of two or more, the content of component B is their total content.

When the polishing composition of the present disclosure contains component B, the mass ratio A/B between the content of component A and the content of component B in the polishing composition of the present disclosure is , preferably 5 or more, more preferably 10 or more, still more preferably 25 or more, and from the viewpoint of the dispersion stability of the particles, preferably 500 or less, more preferably 250 or less, still more preferably 100 or less .

[Other ingredients]
The polishing composition of the present disclosure may further contain other components as long as the effects of the present disclosure are not impaired. Other components include, for example, pH adjusters, pH buffers, surfactants other than component B, polymers other than component B, thickeners, dispersants, rust inhibitors, antiseptics, basic substances, and polishing speed. Enhancers, counter ions and the like are included.
When the polishing composition of the present disclosure further contains other components, the content of the other components in the polishing composition of the present disclosure is preferably 0.001% by mass or more from the viewpoint of improving the polishing rate. 0.0025% by mass or more is more preferable, 0.01% by mass or more is still more preferable, and 1% by mass or less is preferable, 0.5% by mass or less is more preferable, and 0.1% by mass or less is even more preferable.

[Method for producing polishing composition]
The polishing composition of the present disclosure can be produced, for example, by a production method that includes a step of blending component A and an aqueous medium, and optionally the above optional components (component B and other components) by a known method. For example, the polishing composition of the present disclosure can be made 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. In the present disclosure, "blending" includes mixing component A and an aqueous medium, and optionally the above optional components (component B and other components) simultaneously or in order. 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 method for producing the polishing composition of the present disclosure can be the same as the content of each component in the polishing composition of the present disclosure described above.

Embodiments of the polishing composition of the present disclosure may be a so-called one-component type in which all components are premixed and supplied to the market, or a so-called two-component type in which they are mixed at the time of use. There may be. The two-part polishing composition is composed of, for example, a first liquid containing a component A and a second liquid containing a component B, and the first liquid and the second liquid are mixed at the time of use. mentioned. The first liquid and the second liquid may be mixed before being supplied to the surface to be polished, or they may be separately supplied and mixed on the surface of the substrate to be polished. The first liquid and the second liquid can each contain the optional components described above as necessary.

The pH of the polishing 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 dispersion stability of particles. 9 or less is preferable, 8.5 or less is more preferable, 8 or less is still more preferable, less than 8 is still more preferable, 7 or less is still more preferable, and 6 or less is even more preferable. From the same viewpoint, the pH of the polishing composition of the present disclosure is preferably 3.5 to 9, more preferably 4 to 8.5, even more preferably 4.5 to 8, and 4.5 to 8. Less than is more preferable, 4.5 or more and 7 or less is still more preferable, and 4.5 or more and 6 or less is still more preferable. In the present disclosure, the pH of the polishing composition is a value at 25° C. and can be measured using a pH meter, specifically by the method described in Examples.

In the present disclosure, "the content of each component in the polishing composition" refers to the content of each component at the time of polishing, that is, when the polishing composition is started to be used for polishing. The polishing 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 manufacturing and transportation costs can be reduced. This concentrated solution can be diluted with water as necessary and used in the polishing process. The dilution ratio is preferably 5 to 100 times.

[Film to be Polished]
Examples of films to be polished that are 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 a process that requires polishing of a silicon oxide film. Polishing of a silicon oxide film in a forming process, polishing of a silicon oxide film in a process of forming an embedded metal wiring, or polishing of a silicon oxide film in a process of forming an embedded capacitor, three-dimensional NAND flash It can be suitably used for polishing a silicon oxide film performed in the manufacturing process of three-dimensional semiconductor devices such as memories.

[Polishing liquid kit]
In another aspect, the present disclosure relates to a kit for producing the polishing composition of the present disclosure (hereinafter also referred to as "polishing liquid kit of the present disclosure").
As the polishing liquid kit of the present disclosure, for example, a polishing liquid kit (two-liquid type polishing liquid composition). The abrasive grain dispersion and the additive aqueous solution are mixed at the time of use and diluted with an aqueous medium as necessary. The aqueous medium contained in the abrasive grain dispersion may be the total amount or a part of the aqueous medium used for preparing the polishing composition. The aqueous additive solution may contain a part of the aqueous medium used for preparing the polishing composition. The abrasive grain dispersion and the additive aqueous solution may each contain the optional components (other components) described above, if necessary.
According to the polishing liquid kit of the present disclosure, it is possible to obtain a polishing liquid composition capable of improving the polishing rate of a silicon oxide film while reducing scratches.

[Polishing method]
In one aspect, the present disclosure 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 in the process of manufacturing a semiconductor substrate. The present invention relates to a method (hereinafter also referred to as “polishing method of the present disclosure”). By using the polishing method of the present disclosure, it is possible to improve the polishing speed of a silicon oxide film and reduce 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 of the semiconductor substrate manufacturing method of the present disclosure, which will be described later.

[Method for manufacturing semiconductor substrate]
In one aspect of the present disclosure, a method for manufacturing a semiconductor substrate (hereinafter referred to as "method for manufacturing a semiconductor substrate of the present disclosure") includes a step of polishing a silicon oxide film using a polishing composition of the present disclosure (polishing step). Also called).
According to the method for manufacturing a semiconductor substrate of the present disclosure, it is possible to improve the polishing speed of a silicon oxide film and reduce scratches, so that a semiconductor substrate with improved quality can be efficiently manufactured.

As one or more embodiments of the method for manufacturing a semiconductor substrate of the present disclosure, first, a silicon substrate is exposed to oxygen in an oxidation furnace to grow a silicon dioxide layer on the surface thereof, and then a silicon dioxide layer is grown on the silicon dioxide layer. A polishing stopper film such as a silicon nitride (Si ₃ N ₄ ) film or a polysilicon film is formed by, eg, CVD (chemical vapor deposition). Next, 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 having a polishing stopper film formed on a silicon dioxide layer of a silicon substrate is subjected to a photolithographic technique. is used to form trenches. Next, a silicon oxide (SiO ₂ ) film, which is a film to be polished for embedding trenches, is formed by, for example, a CVD method using silane gas and oxygen gas, and the polishing stopper film is covered with the film to be polished (silicon oxide film). A substrate to be polished is obtained. By forming the silicon oxide film, the trench is filled with the silicon oxide of the silicon oxide film, and the surface of the polishing stopper film opposite to the silicon substrate side is covered with the silicon oxide film. The surface of the silicon oxide film thus formed opposite to the surface facing the silicon substrate has steps formed corresponding to the unevenness of the lower layer. Next, the silicon oxide film is polished by a CMP method until at least the surface of the polishing stopper film opposite to the silicon substrate side is exposed, and more preferably, the surface of the silicon oxide film and the surface of the polishing stopper film are flush with each other. Polish the silicon oxide film until it becomes The polishing liquid composition of the present disclosure can be used in this step of polishing by the CMP method. The width of the protrusion formed corresponding to the unevenness of the lower layer of the silicon oxide film is, for example, 0.1 μm or more and 5000 μm or less, and the width of the recess is, for example, 0.1 μm or more and 5000 μm or less.

In the CMP method, while the surface of the substrate to be polished and the polishing pad are in contact with each other, the substrate to be polished and the polishing pad are relatively moved while supplying the polishing liquid composition of the present disclosure to the contact area. As a result, uneven portions on the surface of the substrate to be polished are flattened.
In the method of 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. Another insulating film may be formed between the polishing stopper film (for example, silicon nitride film).

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

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 viewpoint of improving productivity.

EXAMPLES The present disclosure will be described below with reference to Examples, but the present disclosure is not limited thereto.

1. Measurement method of each parameter (1) pH of polishing composition
The pH value of the polishing composition at 25° C. is a value measured using a pH meter (“HM-30G” manufactured by Toa Denpa Kogyo Co., Ltd.). It is the number after minutes.

(2) Average Primary Particle Size of Chemical Mechanical Polishing Particles The average primary particle size (nm) of the chemical mechanical polishing particles is determined using the specific surface area S (m ² /g) obtained by the BET (nitrogen adsorption) method described below. The true density of the cerium oxide particles was calculated as 7.2 g/cm ³ .
The theoretical density of the cerium oxide particles was used for the calculation in the process that cerium oxide was uniformly present on the silicon oxide particles on the surface of the 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 is determined by the nitrogen adsorption method (BET method) using a fully automatic specific surface area measuring device (Macsorb HM model-1201, manufactured by Mountec). It was measured. 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. After that, the sample was placed in a glass cell, set in an apparatus, dried in a nitrogen atmosphere at 300° C. for 45 minutes immediately before measurement, and then measured for BET specific surface area.

(4) Average particle size of chemical mechanical polishing particles 10,000 times, manufactured by Hitachi High-Tech), the material is observed according to the instructions attached by the manufacturer, and the SEM image is taken. Using this data analysis software "WinROOF 2015" (sold by Mitani Shoji Co., Ltd.), the equivalent circle diameter of each chemical mechanical polishing particle that can be identified was determined, and the equivalent circle diameter of 100 or more particles was determined. Calculated as diameter.

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

(6) Average sphericity of chemical mechanical polishing particles 150,000 times (manufactured by Hitachi High-Tech Co., Ltd.), the material is observed according to the instructions attached by the manufacturer, and an SEM image is taken. Using the analysis software "WinROOF 2015" (sold by Mitani Shoji Co., Ltd.), the projected area (S) of each particle that can be identified and the circumference (L) of the particle can be calculated using the following formula. was calculated. The numerical values in Table 1 below are obtained by calculating the average value of the sphericity of 100 chemical mechanical polishing particles.
・Sphericality = 4π x S/(L) ²

(7) Oxygen Storage Amount of Chemical Mechanical Polishing Particles The oxygen storage amount of the chemical mechanical polishing particles was measured by the following method using a thermogravimetric differential thermal analyzer (Thermo plus TG8110, manufactured by Rigaku).
After the chemical mechanical polishing particle dispersion was dried with hot air at 600° C. for 3 hours, it was finely pulverized in an agate mortar. After that, the chemical mechanical polishing particles were placed in a Pt pan and set in the apparatus. A gas of nitrogen:hydrogen=1:1 was filled in the apparatus, 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 inside of the system was replaced with nitrogen and maintained for 30 minutes. Then, the chemical mechanical polishing particles were oxidized with a gas of oxygen:nitrogen=1:9. At this time, the amount of oxygen absorbed by the chemical mechanical polishing particles was used to calculate the oxygen storage amount (μmol/g).

(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 Mountec). 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. After that, the sample was put into a sample pod, and the average density was measured using He gas.

2. Preparation of polishing composition (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 Examples 1 to 10 and Comparative Examples 1 to 1. No. 3 polishing composition was obtained. The content of each component in each polishing composition is as shown in Table 3. The water content is the remainder after component A or non-component A and component B are removed. pH adjustments were performed using ammonia or nitric acid.

The details of Component A, Non-Component A and Component B used in the preparation of 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 produce core ceria, and hydrolyzing a separately prepared cerium salt in the presence of the core ceria to grow the core ceria. In addition, FIG. 2 shows an SEM observation photograph of component A2.
(Non-component 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 composition (Examples 1 to 10 and Comparative Examples 1 to 3) (1) Preparation of test piece (blanket substrate) On one side of a silicon wafer, a 2000 nm thick silicon oxide film ( A 40 mm×40 mm square piece was cut from the substrate on which the blanket film) was formed to obtain a silicon oxide film test piece (blanket substrate).

(2) Polishing Rate of Silicon Oxide Film Using the polishing liquid compositions of Examples 1 to 10 and Comparative Examples 1 to 3, the 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"
Surface plate rotation speed: 100 rpm
Head rotation speed: 107 rpm
Polishing load: 300g weight/cm ²
Polishing liquid supply rate: 50 mL/min Polishing time: 1 minute Before and after polishing, the film thickness of the silicon oxide film was measured using an optical interference film thickness measuring device (VM-1230, manufactured by SCREEN Semiconductor Solutions Co., Ltd.). bottom.
The polishing rate of the silicon oxide film (film to be polished) was calculated by the following formula. Table 3 shows the results.
Polishing rate of silicon oxide film (Å/min)
= [silicon oxide film thickness before polishing (Å) - silicon oxide film thickness after polishing (Å)]/polishing time (minutes)

(3) Scratch Measurement Method After polishing, a cleaned and dried silicon oxide film blanket substrate was attached to a flat substrate, and the scratches were measured using a macro defect apparatus (Micro-MAX VMX-3100, manufactured by Mipox). After setting the substrate in the macro defect apparatus, it was irradiated with a light source and measured at a magnification of 20 and a tilt angle of -5°. Table 3 shows the results. In the present disclosure, "scratches" refer to flaws with a length of 1 μm or more that are detected by a macrodefect device.

(4) Method for evaluating redispersibility The redispersibility of the polishing composition was evaluated by measuring the particle diameter of the chemical mechanical polishing particles before and after drying with a disc centrifugal particle size distribution analyzer (CPS DC24000UHR, manufactured by CPS Instrument). It was measured under the following measurement conditions. Specifically, the particle size (hereinafter referred to as D99) was measured, and the rate of increase in D99 was obtained from the following formula and used as an index of redispersibility. It can be evaluated that the lower the D99 increase rate, the higher the redispersibility. Evaluation of redispersibility was performed 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 polishing composition of Examples 1 to 10 and Comparative Examples 1 to 3 ・After drying: 10 g of each polishing composition of Examples 1 to 10 and Comparative Examples 1 to 3 was put into a sample bottle. , and dried at room temperature. After that, the amount of evaporated water was determined, the same amount of ultrapure water was added, ultrasonic waves were applied, and the mixture was dispersed again.
<Measurement conditions>
Measurement range: 0.02-3 μm
Extinction coefficient of particles: 0.1
Particle shape factor: 1.2 or 1.0
Rotation speed: 17,000 rpm
Measurement temperature: 25°C
<Evaluation Criteria>
A: D99 increase rate is 10% or less B: D99 increase rate is more than 10% and 100% or less C: D99 increase rate is more than 100%

As shown in Table 3, Examples 1 to 10 using cluster-type cerium oxide particles (Component A) satisfying Conditions 1 to 4 as chemical mechanical polishing particles are comparable to Comparative Examples 1 to 3 for chemical mechanical polishing. Compared to using particles (non-component A), the silicon oxide film could be polished at a higher polishing rate, and the number of scratches on the polished silicon oxide film was reduced. Furthermore, the redispersibility of the polishing compositions of Examples 1 to 10 was good.

The polishing composition of the present disclosure is useful in methods of manufacturing semiconductor substrates for high density or high integration.

Claims (11)

chemical mechanical polishing particles,
The chemical mechanical polishing particles are cluster-type cerium oxide particles in which cerium oxide particles are associated, and satisfy the following conditions 1 to 4.
Condition 1: Average primary particle diameter measured by BET method is 10 nm to 50 nm Condition 2: Average particle diameter measured by image analysis is 100 nm to 300 nm Condition 3: Average sphericity measured by image analysis is 0. 76 or more Condition 4: Average density of 6.5 g/cm ³ or more 2. The chemical mechanical polishing particles according to claim 1, wherein the chemical mechanical polishing particles have an average sphericity of 0.8 or more. 3. The chemical mechanical polishing particles according to claim 1, wherein the chemical mechanical polishing particles have an average density of 6.8 g/cm ³ or more. 4. The chemical mechanical polishing particles according to claim 1, wherein the chemical mechanical polishing particles have an oxygen storage amount of 50 μmol/g or more. 5. The chemical mechanical polishing particles according to claim 1, wherein the chemical mechanical polishing particles have an oxygen storage amount of 75 μmol/g or more. 6. The chemical mechanical polishing particles according to claim 1, wherein the chemical mechanical polishing particles have an association degree of 3 or more and 10 or less. A polishing composition comprising the chemical mechanical polishing particles according to any one of claims 1 to 6 and an aqueous medium. 8. The polishing composition according to claim 7, further comprising an anionic dispersant. The polishing liquid according to claim 8, wherein the anionic dispersant is at least one selected from 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. Composition. 10. Polishing comprising polishing a film-to-be-polished using the polishing composition according to any one of claims 7 to 9, wherein the film-to-be-polished is a silicon oxide film formed in the process of manufacturing a semiconductor substrate. Method. A method for manufacturing a semiconductor substrate, comprising the step of polishing a film-to-be-polished using the polishing composition according to any one of claims 7 to 9.

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