JP6352060B2 - Polishing liquid composition for polishing silicon oxide film - Google Patents

Description

  The present invention relates to a polishing liquid composition for polishing a silicon oxide film and a method for producing a semiconductor substrate using the same.

  As semiconductor elements are highly integrated, miniaturized, and the number of wiring layers is increasing, steps are increasing in conductive layers or insulating layers formed in multiple layers on a wafer. In order to remove such steps on the substrate to be polished, a new process technology such as CMP (Chemical Mechanical Polishing) technology was developed in the late 1980s by IBM in the United States, combining chemical and mechanical removal processes. It was done. This CMP technique is to move the substrate to be polished and the polishing pad relative to each other while supplying the polishing liquid to these contact portions in a state where the surface of the substrate to be polished and the polishing pad are in contact with each other. In this technique, the surface uneven portion of the substrate to be polished is chemically reacted and mechanically removed to flatten the surface.

The performance of the CMP technique is determined by CMP process conditions, the type of polishing liquid, the type of polishing pad, and the like. Among these, the polishing liquid is a factor that has the greatest influence on the performance of the CMP process. As the abrasive particles contained in the polishing liquid, silica (SiO ₂ ) and ceria (CeO ₂ ) are widely used.

  At present, this CMP technique is an indispensable technique when performing planarization of an interlayer insulating film, formation of a shallow trench element isolation structure, formation of a plug and a buried metal wiring, etc. in a semiconductor element manufacturing process. . In recent years, the multi-layered and high-definition of semiconductor elements have progressed dramatically, and further improvements in the yield and throughput of semiconductor elements have been demanded. Along with this, with respect to the CMP process, there is a demand for polishing without scratches and at a higher speed. For example, in the formation process of the shallow trench isolation structure, the polishing selectivity of the polishing stopper film (for example, silicon nitride film) with respect to the film to be polished (for example, silicon oxide film) (in other words, the polishing stopper film is more polished. It is desired to improve the polishing rate of the film to be polished while improving the selectivity of polishing that is harder to polish than the like and preventing the occurrence of polishing scratches.

  In particular, in the memory field that is used for general purposes, increasing throughput is an important issue, and improvement of abrasives is also progressing to improve throughput. For example, when ceria is used as the abrasive particles, it is generally known to increase the particle size of the abrasive particles in order to improve the polishing rate of the film to be polished (silicon oxide film). If it is increased, the quality becomes inferior due to an increase in polishing scratches, resulting in a decrease in yield.

Therefore, as means for reducing polishing scratches while polishing a film to be polished at high speed, Non-Patent Document 1 uses an abrasive containing a large particle diameter ceria imparted with disintegration property to ceria, and a large particle ceria during polishing. Describes a technique for reducing polishing scratches while developing a high polishing rate by disintegrating. On the other hand, in the formation process of the shallow trench isolation structure, the polishing selectivity of the polishing stopper film (for example, silicon nitride film) with respect to the film to be polished (for example, silicon oxide film) is required. As an abrasive used for forming a shallow trench isolation structure, Patent Document 1 discloses cerium oxide particles, a dispersant, a free —COOM group, a phenolic OH group, a —SO ₃ M group, —O · SO. Addition selected from water-soluble organic small molecules having an anionic group such as ₃ H group, —PO ₄ M ₂ group or —PO ₃ M ₂ group (M is a metal atom such as H, NH ₄ , or Na, K) A CMP abrasive containing an agent and water is disclosed. A problem to be solved by the CMP abrasive disclosed in Patent Document 1 is high planarization of the silicon oxide insulating film. Patent Documents 2 and 3 disclose an aqueous composition for CMP containing modified cellulose such as carboxymethyl cellulose. A problem to be solved by these aqueous compositions is to perform CMP on the surface of a semiconductor wafer containing metal without excessive dishing of the metal wiring.

Hitachi review February 2008 pages 62-67

Japanese Patent Laid-Open No. 2001-7060 JP 2006-019747 A JP 2006-019746 A

  In recent years, high integration has been advanced in the semiconductor field, and the complexity and miniaturization of wiring have been demanded. Therefore, in the formation process of the shallow trench isolation structure, it is necessary to reduce the thickness of the silicon nitride film formed on one main surface side of the silicon wafer as much as possible. Therefore, in the polishing step of the silicon oxide film formed on the silicon nitride film, “high polishing selectivity” that the polishing of the silicon nitride film can be suppressed as much as possible and the polishing of the silicon oxide film can proceed at a high speed. Is increasingly demanding. In response to the above requirements, attempts have been made to improve polishing selectivity with a polishing aid such as polyacrylic acid. However, in order to solve excessive polishing of silicon nitride films and poor planarization, a high concentration of polishing aid is used. As a result, problems such as a reduction in the polishing rate of the silicon oxide film occur. Therefore, in this attempt, the effect of improving the polishing selectivity was insufficient. Further, agglomeration of abrasive particles proceeds with the addition of a high concentration of polishing aid, and as a result, the addition of the polishing aid is a factor that increases polishing scratches.

  INDUSTRIAL APPLICABILITY The present invention is used when a silicon oxide film is polished in a process of forming a shallow trench element isolation structure in the process of manufacturing a semiconductor substrate, while ensuring a polishing rate of the silicon oxide film necessary for ensuring high productivity. A polishing liquid composition for polishing a silicon oxide film that exhibits high polishing selectivity such that polishing of the silicon nitride film can be suppressed as much as possible and polishing of the silicon oxide film can proceed at a high speed, and can reduce polishing flaws, And the manufacturing method of a semiconductor substrate using the same is provided.

The polishing composition for polishing a silicon oxide film of the present invention contains the following components A to C.
Component A: Copolymer of (meth) acrylic acid monomer and sulfonic acid monomer having vinyl group Component B: Ceria-coated silica particles containing silica particles and granular ceria covering at least a part of the surface of the silica particles Component C: Aqueous media

  In a method for manufacturing a semiconductor substrate using the present invention, a trench is formed in a substrate including a silicon substrate and a silicon nitride film disposed on one main surface side of the silicon substrate, and then a silicon oxide film for filling the trench is formed. After forming the silicon oxide film on the substrate and polishing the silicon oxide film using a polishing composition until at least the silicon oxide film on the silicon nitride film is removed, the silicon nitride film is removed from the silicon substrate. Thus, in the method for producing a substrate including forming a shallow trench isolation structure, the polishing liquid composition for polishing a silicon oxide film of the present invention is used as the polishing liquid composition.

  According to the present invention, a polishing rate of a silicon oxide film necessary for high productivity is ensured, which is used in polishing a silicon oxide film performed in a process of forming a shallow trench isolation structure in the process of manufacturing a semiconductor substrate. However, a polishing composition for polishing a silicon oxide film that exhibits high polishing selectivity such that polishing of the silicon nitride film can be suppressed as much as possible and polishing of the silicon oxide film can proceed, and polishing flaws can be reduced. And a method for producing a semiconductor substrate using the polishing composition for polishing a silicon oxide film.

  The present invention relates to a polishing composition for polishing a silicon oxide film containing ceria-coated silica particles in which at least a part of the surface of silica particles is coated with ceria and an aqueous medium (hereinafter sometimes abbreviated as “polishing liquid composition”). In addition, a shallow trench isolation structure (hereinafter also referred to as “element isolation structure”) is obtained by adding a copolymer of a (meth) acrylic acid monomer and a sulfonic acid monomer having a vinyl group as a polishing aid. In the process of forming the silicon oxide film, it is possible to suppress the polishing of the silicon nitride film as much as possible and advance the polishing of the silicon oxide film at a high speed while securing the polishing speed of the silicon oxide film necessary for ensuring high productivity. Based on the knowledge that high polishing selectivity is exhibited and polishing scratches can be reduced. The (meth) acrylic acid monomer refers to at least one monomer selected from acrylic acid and methacrylic acid.

  Although the details of the mechanism of the effect of the present invention are not clear, it is estimated as follows. Nearly neutral, the surface of the silicon oxide film is negatively charged and hydrophilic, while the surface of the silicon nitride film is neutral or slightly positively charged and slightly hydrophobic. The copolymer contained in the polishing liquid composition of the present invention has little dissociation of carboxylic acid in the structural unit derived from the (meth) acrylic acid monomer, exhibits moderate hydrophobicity, and is anionic. Since it has a negatively charged carboxylic acid group and sulfonic acid group, it is easy to approach and adsorb to the silicon nitride film. Therefore, when the polishing of the silicon oxide film proceeds and the silicon nitride film is exposed, the polishing aid is selectively adsorbed on the silicon nitride film by both hydrophobic interaction and charge interaction. In the polishing composition of the present invention, the polishing of the silicon nitride film is suppressed by the presence of the coating film of the polishing aid adsorbed on the silicon nitride film, so that the polishing of the silicon nitride film is suppressed and the polishing of the silicon oxide film is performed. Can be advanced. In addition, the ceria particles produced by the pulverization method, which are currently widely used as abrasive particles, have many edges, whereas the ceria-coated silica particles contained in the polishing liquid composition of the present invention are silica. It is a structure in which at least a part of the particle surface is coated with granular ceria. For this reason, the polishing liquid composition of the present invention is less susceptible to polishing scratches than conventional polishing liquid compositions containing ceria particles produced by grinding as abrasive particles. Further, normally, when the particle shape of the abrasive particles is spherical, a high polishing rate cannot be expressed due to a decrease in frictional resistance with the surface to be polished, but the ceria-coated silica particles contained in the polishing liquid composition of the present invention Then, by coating fine granular ceria on the silica particles, it has a structure with fine irregularities on the particle surface. For example, even if the silica particle shape is substantially spherical, this special particle structure Therefore, it is estimated that the frictional resistance with the surface to be polished is improved and a high polishing rate is exhibited. Therefore, the combined use of the copolymer and the ceria-coated silica particles contained in the polishing composition of the present invention allows the polishing of the silicon oxide film to proceed at a high speed while suppressing the polishing of the silicon nitride film as much as possible. High polishing selectivity is exhibited, so that the level difference can be eliminated at a high level, and the generation of polishing flaws on the exposed silicon nitride film can also be suppressed. Due to this high polishing selectivity and the effect of suppressing generation of polishing flaws, in the present invention, a highly smooth surface including a silicon oxide film and a silicon nitride film can be obtained. However, these are estimations, and the present invention is not limited to these mechanisms.

  In one embodiment, the present invention relates to a polishing liquid composition for polishing a silicon oxide film containing the copolymer, ceria-coated silica particles, and an aqueous medium. By using the polishing composition for polishing a silicon oxide film of the present invention, the polishing rate of the silicon oxide film necessary for high productivity can be secured in the polishing of the silicon oxide film performed in the step of forming the element isolation structure. In addition, excessive polishing of the silicon nitride film can be suppressed, and excellent polishing selectivity can be achieved. Also, polishing scratches can be reduced.

  In this specification, when “polishing selectivity” is high, the ratio of the polishing rate of the silicon oxide film to the polishing rate of the silicon nitride film (the polishing rate of the silicon oxide film / the polishing rate of the silicon nitride film) increases.

[Copolymer: Component A]
The polishing liquid composition of the present invention is a (meth) acrylic acid monomer and a sulfonic acid monomer having a vinyl group from the viewpoint of ensuring the polishing selectivity improvement and the polishing rate of the silicon oxide film required for high productivity. Contains a copolymer (component A). The copolymer may be in an unneutralized state or a neutralized state with an alkali.

With respect to the state neutralized by the alkali, the alkali used for neutralization is K, Na or NH ₄ from the viewpoint of ensuring the polishing selectivity and the polishing rate of the silicon oxide film necessary for ensuring high productivity. preferable. In addition, the molar ratio of (meth) acrylic acid monomer and sulfonic acid monomer with vinyl group used for the synthesis of copolymer (number of moles of (meth) acrylic acid monomer / number of moles of sulfonic acid monomer with vinyl group) is From the viewpoint of securing the polishing rate of the silicon oxide film necessary for ensuring polishing selectivity and high productivity, it is preferably (60/40) or more, more preferably (70/30) or more, and even more preferably (80 / 20) or more, still more preferably (85/15) or more, preferably (98/2) or less, more preferably (95/5) or less, even more preferably (92.5 / 7.5). Hereinafter, it is still more preferably (91/9) or less. When the ratio of the (meth) acrylic acid monomer is large, the effect of suppressing the polishing of the silicon nitride film is excellent, and when the amount of sulfonic acid having a vinyl group is large, the polishing rate of the silicon oxide film can be improved. The molar ratio is also the molar ratio of the structural unit derived from the (meth) acrylic acid monomer contained in one molecule of the copolymer and the structural unit derived from the sulfonic acid monomer having a vinyl group.

  The weight average molecular weight (Mw) of the copolymer is preferably 1000 or more, more preferably 2000 or more, from the viewpoint of ensuring polishing selectivity and a polishing rate of the silicon oxide film necessary for ensuring high productivity. More preferably, it is 5000 or more, Preferably it is 50000 or less, More preferably, it is 30000 or less, More preferably, it is 25000 or less. When the weight average molecular weight is large, the effect of suppressing the polishing of the silicon nitride film is excellent, and when the weight average molecular weight is small, the polishing rate of the silicon oxide film is improved. In addition, the weight average molecular weight (Mw) of the said copolymer is the value measured using the liquid chromatography as described in the below-mentioned Example.

  As the copolymer contained in the polishing liquid composition of the present invention, acrylic acid and 2-acrylamide- are used from the viewpoint of improving the polishing selectivity and securing the polishing rate of the silicon oxide film necessary for ensuring high productivity. 2-methylpropanesulfonic acid copolymer, acrylic acid and vinylsulfonic acid copolymer, acrylic acid and methacrylsulfonic acid copolymer, methacrylic acid and 2-acrylamido-2-methylpropanesulfonic acid copolymer , A copolymer of methacrylic acid and vinyl sulfonic acid, a copolymer of methacrylic acid and methacryl sulfonic acid, and ammonium salts or alkali metal salts thereof. These can be used alone or in combination of two or more. Among these, from the viewpoint of ensuring polishing selectivity and ensuring the polishing rate of the silicon oxide film necessary for ensuring high productivity, a copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid And vinyl sulfonic acid copolymers, methacrylic acid and 2-acrylamido-2-methylpropane sulfonic acid copolymers, and methacrylic acid and vinyl sulfonic acid copolymers, their alkali metal salts, and their ammonium salts Preferably, at least one selected from the group consisting of: a copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid, or a copolymer of acrylic acid and vinylsulfonic acid, their alkali metal salts, and these More preferred is at least one selected from the group consisting of ammonium salts of acrylic acid and 2-a More preferred is at least one selected from the group consisting of a copolymer of rilamido-2-methylpropanesulfonic acid, an alkali metal salt thereof, and an ammonium salt thereof, and a copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid. Even more preferred is at least one selected from the group consisting of alkali metal salts of polymers and ammonium salts of copolymers of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid.

  Content of the said copolymer (component A) in the polishing liquid composition of this invention is the mass of the said copolymer (component A), a ceria coat silica particle (component B), and the said aqueous medium (component C). When the total is 100% by mass, it is preferably 0.05% by mass or more, more preferably 0.1% by mass, from the viewpoint of improving the polishing selectivity and securing the polishing rate of the silicon oxide film necessary for ensuring high productivity. % Or more, more preferably 0.2% by mass or more, still more preferably 0.25% by mass or more, preferably 5% by mass or less, more preferably 2.5% by mass or less, and further preferably 1.0% by mass. % Or less, still more preferably 0.75 mass% or less.

[Abrasive particles: Component B]
The polishing particles contained in the polishing liquid composition of the present invention have at least a part of the surface of the silica particles from the viewpoint of ensuring the polishing rate of the silicon oxide film necessary for high productivity and reducing polishing scratches. Ceria-coated silica particles coated with granular ceria are included.

  The average primary particle diameter of the ceria-coated silica particles measured by a dynamic light scattering method is preferably 30 nm or more, more preferably 45 nm or more, preferably 300 nm or less, more preferably 200 nm or less. When the average primary particle diameter of the ceria-coated silica particles is large, the polishing rate of the silicon oxide film is increased. Conversely, when the ceria-coated silica particles are small, the polishing scratches are reduced. The average primary particle diameter of the ceria-coated silica particles can be measured by the method described in Examples described later.

  From the viewpoint of improving the polishing rate of the silicon oxide film and reducing polishing scratches, the ceria that covers the silica particles has crystallinity, and the shape of the abrasive particles contained in the polishing liquid composition of the present invention is: It is granular and is preferably approximately spherical. Further, the average primary particle diameter measured by transmission electron microscopic observation of granular ceria is preferably 5 nm or more, more preferably 7.5 nm or more, further preferably 10 nm or more, preferably 40 nm or less from the viewpoint of polishing rate. More preferably, it is 30 nm or less, More preferably, it is 25 nm or less. When the average primary particle diameter of the granular ceria that coats the silica particles is 5 nm or more, the synthesis of the granular ceria becomes easy, and when it is 40 nm or less, the granular ceria is uniformly coated on the silica particles to effectively suppress the generation of polishing flaws. be able to. In addition, the average primary particle diameter of granular ceria can be measured by the method as described in the Example mentioned later.

  The silica particles coated with the granular ceria are preferably colloidal silica from the viewpoint of improving the polishing rate of the silicon oxide film and reducing polishing scratches, and the shape thereof is preferably substantially spherical. Further, the average primary particle diameter measured by transmission electron microscopic observation of the colloidal silica particles to be used is preferably 15 nm or more, more preferably 20 nm or more, still more preferably 40 nm or more, preferably 300 nm from the viewpoint of polishing rate. Hereinafter, it is more preferably 200 nm or less, and further preferably 150 nm or less. When the average primary particle diameter of the silica particles is 15 nm or more, the polishing rate of the silicon oxide film can be effectively improved, and when it is 300 nm or less, generation of polishing flaws can be effectively suppressed. In addition, the average primary particle diameter of a silica particle can be measured by the method as described in the Example mentioned later.

  In the process of producing ceria-coated silica particles, the amount of ceria used for coating the silica particles is expressed as a mass ratio with silica (ceria / silica), preferably 0.25 or more, more preferably 0.33 or more, More preferably, it is 0.4 or more, preferably 2 or less, more preferably 1.5 or less, and still more preferably 1.2 or less. Increasing the coating amount of ceria can increase the polishing rate of the silicon oxide film, and decreasing the coating amount of ceria suppresses the formation of ceria aggregates that cannot be coated on silica particles and become free. Thus, the generation of polishing scratches can be suppressed. Although the coating amount varies depending on the particle diameter of the granular ceria to be coated, good polishing characteristics can be obtained by covering with the generally described mass ratio. Further, “the amount of ceria used for coating silica particles” means the mass of ceria converted from the amount of ceria source used.

  A method for producing ceria-coated silica particles can be performed by depositing ceria on Syria particles. For example, a method in which an aqueous solution in which cerium nitrate is dissolved is dropped into a dispersion of silica particles to deposit ceria on the silica particles, a method by thermal hydrolysis of ammonium cerium nitrate, a method using alkoxide, etc. Any conventionally known method may be used as long as it can produce cerium hydroxide or cerium oxide. When producing cerium hydroxide on the silica particles, the cerium hydroxide may be converted to cerium oxide by firing. The ceria-coated silica particles produced by these methods may be used after being loosened so that the particles adhered to each other are separated by firing.

  The content of the ceria-coated silica particles (component B) in the polishing composition of the present invention is the mass of the copolymer (component A), ceria-coated silica particles (component B), and the aqueous medium (component C). Is 100% by mass, preferably 0.1% by mass or more, more preferably 0.2% from the viewpoint of ensuring polishing selectivity and ensuring a polishing rate of the silicon oxide film necessary for ensuring high productivity. % By mass or more, more preferably 0.25% by mass or more, still more preferably 0.5% by mass or more, preferably 5.0% by mass or less, more preferably 2.5% by mass or less, still more preferably 2%. It is 0.0 mass% or less, More preferably, it is 1.5 mass% or less.

  The mass ratio of the copolymer (component A) and the ceria-coated silica particles (component B) in the polishing liquid composition of the present invention (the mass of the copolymer / the mass of the ceria-coated silica particles) is improved in polishing selectivity. From the viewpoint of reducing polishing scratches, it is preferably 0.02 or more, more preferably 0.1 or more, and still more preferably 0.2 or more, to ensure the polishing rate of the silicon oxide film necessary for ensuring high productivity. In view of the above, it is preferably 25 or less, more preferably 10 or less, and still more preferably 1 or less.

[Aqueous medium: Component C]
The polishing liquid composition of the present invention contains an aqueous medium. Examples of the aqueous medium include water and a mixture of water and a water-soluble solvent. Examples of the water-soluble solvent include lower alcohols such as methanol, ethanol, and isopropanol, and ethanol is preferable from the viewpoint of safety in the polishing process. The aqueous medium is more preferably water such as ion-exchanged water, distilled water or ultrapure water from the viewpoint of improving the quality of the semiconductor substrate.

  The content of the aqueous medium (component C) in the polishing composition of the present invention is 100 mass of the total mass of the copolymer (component A), ceria-coated silica particles (component B), and aqueous medium (component C). %, It is sufficient if it is the remainder excluding the copolymer (component A) and ceria-coated silica particles (component B).

[Other ingredients]
The polishing composition of the present invention may contain a pH adjuster, a polishing aid other than the component (B), and the like as long as the effects of the present invention are not impaired. The content of these optional components is preferably 0.001% by mass or more, more preferably 0.0025% by mass or more, still more preferably 0.01% by mass or more, from the viewpoint of ensuring the polishing rate of the silicon oxide film. From the viewpoint of improving selectivity, it is preferably 1% by mass or less, more preferably 0.5% by mass or less, and further preferably 0.1% by mass or less.

[Polishing liquid composition]
The polishing composition of the present invention contains a copolymer of (meth) acrylic acid monomer and a sulfonic acid monomer having a vinyl group (component A), ceria-coated silica particles (component B), and an aqueous medium (component C). . The polishing composition of the present invention includes, for example, a step of mixing the copolymer of (meth) acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid, the aqueous medium, and an aqueous dispersion of the ceria-coated silica particles. It can manufacture by the manufacturing method containing. Preferably, an aqueous polishing aid solution obtained by dissolving an aqueous slurry of a copolymer of (meth) acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid as a polishing aid in an aqueous medium, and ceria-coated silica particles And a ceria-coated silica particle dispersion obtained by dispersing in a water-based medium, while stirring the polishing aid aqueous solution, the ceria-coated silica particle dispersion and, if necessary, other pH adjusting agents and the like. A component can be added (dropped) to the aqueous polishing aid solution to obtain a polishing composition.

  The pH of the polishing composition of the present invention at 25 ° C. is preferably 3 or more from the viewpoint of protecting the polishing apparatus, improving the polishing rate of the silicon oxide film, improving the polishing selectivity, and improving the dispersibility of the ceria-coated silica particles. More preferably 4 or more, still more preferably 5 or more, and even more preferably 5.5 or more. Improvement of controllability of polishing conditions, improvement of polishing selectivity, suppression of polishing of silicon nitride film and ceria-coated silica particles From the viewpoint of improving dispersibility, it is preferably 9 or less, more preferably 8.5 or less, still more preferably 7.5 or less, and even more preferably 6.5 or less. The details of the pH measurement conditions are as shown in the examples.

  The polishing composition of the present invention can be used by adjusting its pH within a range where the effects of the present invention are not impaired. The pH adjuster used for the adjustment is not particularly limited as long as it is an acidic compound. For example, inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid, and organic acids such as acetic acid, oxalic acid, citric acid, and malic acid are used. Is mentioned. Among these, hydrochloric acid, nitric acid and acetic acid are preferable from the viewpoint of versatility, and hydrochloric acid and acetic acid are more preferable.

  The pH adjuster used for adjusting the pH of the polishing composition to be high is not particularly limited as long as it is an alkaline compound. For example, ammonia and inorganic alkali compounds such as potassium hydroxide, alkylamine, and alkanolamine And organic alkali compounds such as Among these, from the viewpoint of improving the quality of the semiconductor substrate, ammonia and alkylamine are preferable, and ammonia is more preferable.

  As the polishing aid other than the component (B), an anionic compound and a nonionic compound are preferable from the viewpoint of improving dispersibility of the ceria-coated silica particles, and an anionic surfactant and a nonionic surfactant are more preferable. Examples of the anionic surfactant include anionic polymers such as polyacrylic acid, alkyl ether acetates, alkyl ether phosphates, and alkyl ether sulfates. Examples of nonionic surfactants include nonionic polymers such as polyacrylamide, and polyoxyalkylene alkyl ethers.

  The embodiment of the polishing composition of the present application is not limited to a so-called one-component type that is supplied to the market in a state where all components are pre-mixed, and may be a so-called two-component type that is mixed at the time of use. . In the two-pack type polishing liquid composition, the aqueous medium is divided into a first aqueous medium and a second aqueous medium. The polishing liquid composition includes, for example, ceria-coated silica particles, (meth) acrylic acid, 2 -A ceria-coated silica particle dispersion obtained by dispersing a part of a copolymer of acrylamide-2-methylpropanesulfonic acid in a first aqueous medium, and the remaining (meth) acrylic acid and 2-acrylamido-2-methyl You may comprise from the aqueous solution of a grinding aid obtained by melt | dissolving the copolymer of a propanesulfonic acid in a 2nd aqueous medium.

  The ceria-coated silica particle dispersion and the polishing aid aqueous solution 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. .

  In addition, although content of each component demonstrated above is content at the time of use at a grinding | polishing process, the polishing liquid composition of this embodiment is in the state concentrated in the range which does not impair the stability. It may be stored and supplied. In this case, it is preferable in that the production / transport cost can be reduced. This concentrated liquid can be appropriately diluted with the above-mentioned aqueous medium as necessary and used in the polishing step. The dilution ratio is preferably 5 to 100 times.

[Method for Manufacturing Semiconductor Substrate]
The polishing composition of the present invention can be suitably used for polishing performed in the step of forming an element isolation structure of a semiconductor substrate. As a specific example of the method for producing a semiconductor substrate of the present invention, first, a silicon substrate is exposed to oxygen in an oxidation furnace to grow a silicon dioxide layer on the surface, and then silicon nitride (Si3N) is formed on the silicon dioxide layer. ₄ ) A film is formed by, for example, CVD (chemical vapor deposition). Next, a photolithography technique is applied to a substrate including a silicon substrate and a silicon nitride film disposed on one main surface side of the silicon substrate, for example, a substrate in which a silicon nitride film is formed on a silicon dioxide layer of a silicon substrate. Is used to form a trench. Next, a silicon oxide (SiO ₂ ) film for filling a trench is formed by, for example, a CVD method using silane gas and oxygen gas to obtain a substrate to be polished in which the silicon nitride film is covered with the silicon oxide film. By forming the silicon oxide film, the trench is filled with silicon oxide of the silicon oxide film, and the surface of the silicon nitride film opposite to the silicon substrate side is covered with the silicon oxide film.

  The surface opposite to the surface on the silicon substrate side of the silicon oxide film thus formed has a step formed corresponding to the unevenness of the lower layer. Next, the silicon oxide film is polished by CMP until at least the opposite surface of the silicon nitride film to the silicon substrate side is exposed. More preferably, the surface of the silicon oxide film and the surface of the silicon nitride film are flush with each other. The silicon oxide film is polished until The polishing composition of the present invention is used in the step of polishing by this CMP method. In polishing by the CMP method, in a state where the surface of the substrate to be polished and the polishing pad are in contact with each other, by moving the substrate to be polished and the polishing pad relatively while supplying the polishing liquid composition to these contact portions, The uneven portion on the surface of the substrate to be polished is flattened. In the method of manufacturing a semiconductor substrate according to the present invention, another insulating film may be formed between the silicon dioxide layer and the silicon nitride film of the silicon substrate, or other insulating film may be formed between the silicon oxide film and the silicon nitride film. An insulating film may be formed.

  The rotational speed of the polishing pad is preferably 30 to 200 r / min, more preferably 45 to 150 r / min, even more preferably 60 to 100 r / min, regardless of whether the polishing composition is a one-component type or a two-component type. preferable. The rotational speed of the substrate to be polished is preferably 130 to 200 r / min, more preferably 45 to 150 r / min, and still more preferably 60 to 100 r / min.

The polishing load set in the polishing apparatus provided with the polishing pad is not affected by the adverse effect on the flattening caused by the load being too large, regardless of whether the polishing liquid composition is one-pack type or two-pack type. From the viewpoint of suppressing the generation of scratches, 500 gf / cm ² or less is preferable, 400 gf / cm ² or less is more preferable, and 350 gf / cm ² or less is more preferable. On the other hand, from the viewpoint of shortening the polishing time, 20 gf / cm ² or more is preferable, 50 gf / cm ² or more is more preferable, and 100 gf / cm ² or more is more preferable.

  From the viewpoint of polishing efficiency, the supply rate of the polishing composition is preferably 500 mL / min or less, more preferably 400 mL / min or less, and even more preferably 300 mL / min or less. On the other hand, the supply rate of the polishing composition is preferably 10 mL / min or more, and more preferably 30 mL / min or more from the viewpoint of improving the polishing rate of the silicon oxide film.

  The present disclosure further relates to one or more of the following embodiments.

<1> A polishing liquid composition for polishing a silicon oxide film for polishing a silicon oxide film on a silicon nitride film, the polishing liquid composition for polishing a silicon oxide film comprising the following components A to C:
Component A: Copolymer of acrylic acid monomer and sulfonic acid monomer having vinyl group Component B: Ceria-coated silica particles containing silica particles and granular ceria covering at least part of the surface of the silica particles Component C: aqueous medium <2> The molar ratio (number of moles of (meth) acrylic acid monomer / number of moles of sulfonic acid monomer having a vinyl group) in component A is preferably (60/40) or more, more preferably (70/30) or more. Even more preferably (80/20) or more, still more preferably (85/15) or more, preferably (98/2) or less, more preferably (95/5) or less, still more preferably (92 5 / 7.5) or less, and even more preferably (91/9) or less, the polishing composition for polishing a silicon oxide film according to <1>.
<3> The copolymer has a weight average molecular weight of preferably 1000 or more, more preferably 2000 or more, still more preferably 5000 or more, preferably 50000 or less, more preferably 30000 or less, and further preferably 25000 or less. The polishing composition for polishing a silicon oxide film according to <1> or <2>.
<4> The component A is preferably at least one selected from the group consisting of a copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid, an alkali metal thereof, and an ammonium salt thereof. The polishing composition for polishing a silicon oxide film according to any one of <1> to <3>.
<5> The component B is coated with silica particles having an average primary particle diameter of preferably 15 nm to 300 nm with granular ceria having an average primary particle diameter of preferably 5 nm to 40 nm, and the mass ratio of ceria to silica ( The polishing composition for polishing a silicon oxide film according to any one of <1> to <4>, wherein (ceria / silica) is preferably ceria-coated silica particles of 0.25 to 2.
<6> The average primary particle diameter of the granular ceria is more preferably 7.5 nm or more, further preferably 10 nm or more, more preferably 30 nm or less, and further preferably 25 nm or less, according to the above <5>. Polishing liquid composition for polishing silicon oxide film.
<7> The average primary particle size of the silica particles is more preferably 20 nm or more, further preferably 40 nm or more, more preferably 200 nm or less, and further preferably 150 nm or less, in the above <5> or <6> A polishing liquid composition for polishing a silicon oxide film according to the description.
<8> The mass ratio (ceria / silica) in the ceria-coated silica particles is preferably 0.33 or more, more preferably 0.4 or more, preferably 1.5 or less, more preferably 1.2 or less. The polishing composition for polishing a silicon oxide film according to any one of <5> to <7>, wherein
<9> The average primary particle diameter of the ceria-coated silica particles is preferably 30 nm or more, more preferably 45 nm or more, preferably 300 nm or less, more preferably 200 nm or less, from the above <1> to <8> The polishing composition for polishing a silicon oxide film according to any one of the above.
<10> The content of the component A in the polishing composition for polishing a silicon oxide film is the mass of the copolymer (component A), ceria-coated silica particles (component B), and the aqueous medium (component C). Is 100% by mass, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.2% by mass or more, and even more preferably 0.25% by mass or more. <1> to <9>, preferably 5% by mass or less, more preferably 2.5% by mass or less, further preferably 1.0% by mass or less, and still more preferably 0.75% by mass or less. The polishing composition for polishing a silicon oxide film according to any one of the above.
<11> The content of the (component B) in the polishing composition for polishing a silicon oxide film is such that the copolymer (component A), the ceria-coated silica particles (component B), and the aqueous medium (component C). )) Is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, still more preferably 0.25% by mass or more, and even more preferably 0.5% by mass. <1>, preferably 5.0% by mass or less, more preferably 2.5% by mass or less, still more preferably 2.0% by mass or less, and still more preferably 1.5% by mass or less. To <10>. A polishing liquid composition for polishing a silicon oxide film.
<12> Mass ratio of the copolymer (component A) and the ceria-coated silica particles (component B) in the polishing composition for polishing a silicon oxide film (mass of copolymer / mass of ceria-coated silica particles) However, it is preferably 0.02 or more, more preferably 0.1 or more, still more preferably 0.2 or more, preferably 25 or less, more preferably 10 or less, still more preferably 1 or less, <1> To <11>. A polishing liquid composition for polishing a silicon oxide film.
<13> The pH at 25 ° C. of the polishing composition for polishing a silicon oxide film is preferably 3 or more, more preferably 4 or more, still more preferably 5 or more, still more preferably 5.5 or more, preferably Polishing for polishing a silicon oxide film according to any one of <1> to <12>, which is 9 or less, more preferably 8.5 or less, still more preferably 7.5 or less, and even more preferably 6.5 or less. Liquid composition.
<14> The aqueous medium is divided into a first aqueous medium and a second aqueous medium,
The polishing composition for polishing a silicon oxide film comprises a ceria-coated silica particle dispersion obtained by dispersing ceria-coated silica particles (component B) and a part of the component A in the first aqueous medium, and the remaining The polishing composition for polishing a silicon oxide film according to any one of <1> to <13>, wherein the polishing composition is a two-component type comprising a polishing aid aqueous solution obtained by dissolving Component A in a second aqueous medium. object.
<15> Ceria-coated silica particles (component B) comprising a copolymer of acrylic acid monomer and a sulfonic acid monomer having a vinyl group (component A), silica particles and granular ceria covering at least a part of the surface of the silica particles. And a method for producing a polishing composition for polishing a silicon oxide film, comprising a step of mixing an aqueous medium (component C).
<16> In the above step, an aqueous polishing aid solution obtained by dissolving an aqueous slurry of a copolymer of (meth) acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid in an aqueous medium, and ceria-coated silica particles The method for producing a polishing composition for polishing a silicon oxide film according to <15>, wherein a ceria-coated silica particle dispersion obtained by dispersing in an aqueous medium is mixed.
<17> After forming a trench in a substrate including a silicon substrate and a silicon nitride film disposed on one main surface side of the silicon substrate, a silicon oxide film for filling the trench is formed on the substrate, and the oxidation After polishing the silicon film using a polishing composition until at least the silicon oxide film on the silicon nitride film is removed, the silicon nitride film is removed from the silicon substrate, thereby forming a shallow trench element isolation structure. In a method of manufacturing a semiconductor substrate including forming,
A method for producing a semiconductor substrate, wherein the polishing composition is the polishing composition for polishing a silicon oxide film according to any one of <1> to <14>.

1. Preparation of polishing liquid composition [Preparation Example 1 of polishing liquid composition]
As a component (B), a copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid and ion-exchanged water were uniformly mixed to obtain an aqueous polishing aid solution. While stirring the aqueous polishing aid solution, a ceria-coated silica particle dispersion (dispersion medium: ion-exchanged water) and a 1N hydrochloric acid aqueous solution as a pH adjuster are added to the aqueous solution, and ion-exchanged water is further added to the concentration. Adjustment was performed and the polishing liquid composition of Example 1 was obtained. The mass ratio of each component was adjusted to be the composition and pH of the polishing composition described in Table 1.

[Preparation Example 2 of Polishing Liquid Composition]
Except that the amount of each component was adjusted so as to be the composition and pH of the polishing composition described in Table 1, Examples 2 to 16, Reference Example 2 were prepared in the same manner as in Preparation Example 1 of the polishing composition. Polishing liquid compositions of Examples 1 to 3 and Comparative Examples 1 to 5 were obtained. As a pH adjuster, 1 mol / L hydrochloric acid was used when adjusting the pH low, and 1 mass% aqueous ammonia was used when adjusting the pH high.

[Method for producing ceria-coated silica particles]
(1) <Method 1 for producing ceria-coated silica particles>
The manufacturing method of the ceria coat silica particle used for preparation of the polishing liquid composition of Examples 1-9 , Reference Examples 1-3, and Comparative Examples 4-5 is as follows.
First, a 20% by mass aqueous dispersion of spherical silica particles (manufactured by JGC Catalysts & Chemicals, Cataloid SI-80PW) having an average primary particle size of 80 nm is prepared, and cerium nitrate is added as a CeO ₂ raw material to the spherical silica aqueous dispersion. A dissolved aqueous solution was dropped, and simultaneously, a 3 mass% ammonia aqueous solution was dropped separately, and cerium was deposited on silica while maintaining the pH at about 8. During this addition, the spherical silica aqueous dispersion was heated to maintain at 50 ° C. After completion of the dropwise addition, the reaction solution was aged by heating at 100 ° C. for 4 hours to crystallize the deposited ceria. Thereafter, the obtained particles were separated by filtration and sufficiently washed with water, and then dried at 100 ° C. with a dryer. The dried powder obtained in this state may be used for the preparation of the polishing composition, but here the dried powder is further baked at 1000 ° C. for 2 hours, and then the particles adhered to each other are separated by baking. The fired powder thus obtained was loosened to obtain ceria-coated silica particles having an average primary particle size of 110 nm. When the ceria-coated silica particles were observed with a TEM (transmission electron microscope), the surface of the silica particles was coated with granular ceria.

(2) <Method 2 for producing ceria-coated silica particles>
The manufacturing method of the ceria coat silica particle used for preparation of the polishing liquid composition of Examples 10-12 is as follows.
The average amount of cerium nitrate used as the CeO ₂ raw material was the same as in the <Method 1 for producing ceria-coated silica particles> except that the amount was 1/3 of that in the case of <Method 1 for producing ceria-coated silica particles> Ceria-coated silica particles having a primary particle size of 110 nm were obtained. When the ceria-coated silica particles were observed with a TEM (transmission electron microscope), the surface of the silica particles was coated with granular ceria.

(3) <Method 3 for producing ceria-coated silica particles>
The manufacturing method of the ceria coat silica particle used for preparation of the polishing liquid composition of Examples 13-14 is as follows.
Instead of a 20% by mass aqueous dispersion of spherical silica particles having an average primary particle size of 80 nm (manufactured by JGC Catalysts & Chemicals, Cataloid SI-80PW), spherical silica particles having an average primary particle size of 45 nm (manufactured by JGC Catalysts & Chemicals, Ceria-coated silica particles having an average primary particle diameter of 65 nm were obtained in the same manner as in <Method 1 for producing ceria-coated silica particles> except that a 20% by mass aqueous dispersion of cataloid SI-45P) was used. When the ceria-coated silica particles were observed with a TEM (transmission electron microscope), the surface of the silica particles was coated with granular ceria.

(4) <Method 4 for producing ceria-coated silica particles>
The manufacturing method of the ceria coat silica particle used for preparation of the polishing liquid composition of Examples 15-16 is as follows.
Instead of a 20% by mass aqueous dispersion of spherical silica particles having an average primary particle size of 80 nm (manufactured by JGC Catalysts & Chemicals, Cataloid SI-80PW), spherical silica particles having an average primary particle size of 120 nm (manufactured by JGC Catalysts & Chemicals, Ceria-coated silica particles having an average primary particle size of 160 nm were obtained in the same manner as in <Method 1 for producing ceria-coated silica particles> except that a 20% by mass aqueous dispersion of cataloid SI-120P) was used.

[Method for producing a copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid]
The manufacturing method of the copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid used for the preparation of the polishing liquid compositions of Examples 1 to 16 and Reference Examples 1 to 3 is as follows. These were polymerized so that the molar ratio of acrylic acid to 2-acrylamido-2-methylpropanesulfonic acid was 90:10 or 80:20 to obtain a copolymer. First, 125 g of ion-exchanged water was heated to 98 ° C., and a predetermined amount of each monomer was added dropwise thereto at the same time, and ammonium persulfate as an initiator diluted with ion-exchanged water was added dropwise to initiate polymerization. Polymerization was continued while maintaining the temperature of the reaction solution at about 98 ° C., and after a predetermined time, 35% by mass of hydrogen peroxide was added to the reaction solution to terminate the polymerization. Thereafter, the temperature of the reaction solution was lowered to 40 ° C., and then the reaction solution was neutralized with aqueous ammonia to obtain a copolymer. The weight average molecular weight of the copolymer was controlled by adjusting the initiator concentration.

  In preparing the polishing composition of the comparative example, in Comparative Examples 1 to 5, polyacrylic acid was used as a polymer, and in Comparative Examples 1 to 3, ceria particles (average primary particles) produced by the following pulverization method were used as abrasive particles. An aqueous dispersion having a particle diameter of 135 nm and an average crystallite diameter of 20 nm (manufactured by Baikowski, solid content of 40% by mass, dispersion medium: ion-exchanged water) was used.

  The pH of the polishing composition, the average primary particle diameter of the ceria-coated silica particles, the average primary particle diameter of the silica particles used in the production of the ceria-coated silica particles, and the average primary particle diameter of the granular ceria in the ceria-coated silica particles are as follows: Measured by the method.

(A) Measurement of pH of polishing liquid composition The pH value at 25 ° C of the polishing liquid composition is a value measured using a pH meter (Toa Denki Kogyo Co., Ltd., HM-30G). It is a numerical value 1 minute after immersion in the water.

(B) Average primary particle diameter of ceria-coated silica particles The average primary particle diameter of ceria-coated silica particles was prepared as a ceria-coated silica particle slurry having a solid content concentration of 0.1% by mass. Measurement was performed by nano ZS (dynamic light scattering method), and the obtained volume average particle size was defined as the average primary particle size.

(C) Average primary particle diameter of silica particles A silica particle slurry having a solid content concentration of 0.1% by mass is prepared as a volume average particle diameter (nm) of silica particles as a raw material of ceria-coated silica particles. Manufactured by Zeta Sizer Nano ZS (dynamic light scattering method), and the volume average particle size obtained was defined as the average primary particle size. The average primary particle diameter of the silica particles after ceria coating was obtained by measuring the size of 50 silica particles using an image obtained from a TEM (transmission electron microscope) and averaging these.

(D) Average primary particle diameter of granular ceria The average primary particle diameter of granular ceria on silica particles is measured by measuring the particle diameter of 100 granular ceria on silica particles using an image obtained from a TEM (transmission electron microscope). These were obtained on average. Alternatively, ceria-coated silica particles are subjected to powder X-ray diffraction measurement, using the half-width and diffraction angle of the ceria (1,1,1) plane that appears around 29-30 °, and the Scherrer equation It is good also considering the crystallite diameter obtained more as an average primary particle diameter.
Scherrer formula: crystallite diameter (Å) = K × λ / (β × cos θ)
K: Scherrer constant, λ: X-ray wavelength = 1.54056 mm, β: half-width, θ: diffraction angle 2θ / θ

(E) Measuring method of weight average molecular weight of polymer The measuring method of the weight average molecular weight of the polymer used for preparation of polishing liquid composition of Examples 1-16 , Reference Examples 1-3, and Comparative Examples 1-5 is the following. Street.
The weight average molecular weight of the polymer was measured under the following conditions by gel permeation chromatography (GPC) using liquid chromatography (manufactured by Hitachi, Ltd., L-6000 type high performance liquid chromatography).
Detector: Shodex RI SE-61 differential refractive index detector Column: G4000PWXL and G2500PWXL manufactured by Tosoh Corporation were connected in series.
Eluent: 0.2 M phosphate buffer / acetonitrile = 90/10 (volume ratio) was adjusted to a concentration of 0.5 g / 100 mL, and 20 μL was used.
Column temperature: 40 ° C
Flow rate: 1.0 mL / min
Standard polymer: monodispersed polyethylene glycol with known weight average molecular weight

2. Evaluation of polishing composition (Examples 1 to 16, Reference Examples 1 to 3, and Comparative Examples 1 to 5) [Creation of test pieces]
From a silicon oxide film (oxide film) having a thickness of 2000 nm formed on one side of a silicon wafer by TEOS-plasma CVD method, a 40 mm × 40 mm square piece was cut out to obtain an oxide film test piece. Similarly, from a silicon nitride film (nitride film) having a thickness of 300 nm formed on one side of a silicon wafer, a 40 mm × 40 mm square piece was cut out to obtain a nitride film test piece.

[Measurement of polishing rate of oxide film]
As a polishing apparatus, “MA-300” manufactured by Musashino Electronics Co., Ltd. having a surface plate diameter of 300 mm was used. As the polishing pad, a hard urethane pad “IC-1000 / Sub400” manufactured by Nitta Haas was used. The polishing pad was attached to the surface plate of the polishing apparatus. The test piece was set in a holder, and the holder was placed on the polishing pad so that the surface of the test piece on which the silicon oxide film was formed faced down (so that the oxide film faces the polishing pad). Further, a weight was placed on the holder so that the load applied to the test piece was 300 g weight / cm ² . While dropping the polishing composition at a speed of 50 mL / min on the center of the surface plate to which the polishing pad is attached, each of the surface plate and the holder is rotated in the same direction of rotation at 90 r / min for 2 minutes to obtain an oxide film. The specimen was polished. After polishing, the substrate was washed with ultrapure water and dried, and the oxide film test piece was used as a measurement object by an optical interference type film thickness measuring device described later.

Before and after polishing, the thickness of the oxide film was measured using an optical interference type film thickness measuring device (“Lambda Ace VM-1000” manufactured by Dainippon Screen). The polishing rate of the oxide film was calculated by the following formula. The polishing rate of the oxide film is shown in Table 1 below.
Polishing rate of oxide film (nm / min)
= [Oxide film thickness before polishing (nm)-Oxide film thickness after polishing (nm)] / Polishing time (min)

[Measurement of polishing rate of nitride film]
The nitride film was polished, the film thickness was measured, and the polishing rate was calculated in the same manner as in [Measurement of oxide film polishing rate], except that a nitride film test piece was used instead of the oxide film test piece. It was. The polishing rate of the nitride film is shown in Table 1 below.

[Polishing speed ratio]
The ratio of the polishing rate of the oxide film to the polishing rate of the nitride film was defined as the polishing rate ratio and was calculated by the following formula. The larger the value of the polishing rate ratio, the better the polishing selectivity and the higher the ability to eliminate the step. The results are shown in Table 1 below.
Polishing rate ratio = polishing rate of oxide film (nm / min) / polishing rate of nitride film (nm / min)

[Measurement method of polishing scratches (number of scratches)]
Measuring instrument: Optical microscope (Vision Tech, VMX-3100)
Evaluation: After polishing, cleaned and dried oxide film test pieces and nitride film test pieces were attached to a flat substrate, irradiated with a light source, then observed under dark field conditions, and polishing scratches were measured. In the present disclosure, the “polishing scratch” is a scratch having a length of 1 μm or more detected by an optical microscope.

As shown in Table 1, the polishing liquid compositions of Examples 1 to 16 using ceria-coated silica particles as abrasive particles and a copolymer of acrylic acid monomer and sulfonic acid monomer having a vinyl group as a polymer were used. In this case, the polishing selectivity was excellent and the polishing scratches were reduced while ensuring the polishing rate of the oxide film required for high productivity, compared with the case of using the polishing composition of the comparative example .

  The polishing liquid composition of the present invention can improve polishing selectivity and reduce polishing scratches while ensuring a polishing rate of an oxide film necessary for high productivity. This is useful in a method for manufacturing a semiconductor substrate for integration.

Claims (7)

A polishing liquid composition for polishing a silicon oxide film for polishing a silicon oxide film on a silicon nitride film, the polishing liquid composition for polishing a silicon oxide film comprising the following components A to C:
Component A: a copolymer of a (meth) acrylic acid monomer and a sulfonic acid monomer having a vinyl group, the molar ratio of monomers used for the synthesis of the copolymer (having a (meth) acrylic acid monomer / vinyl group) Copolymer component B having a sulfonic acid monomer) of (85/15) or more and (98/2) or less : Ceria-coated silica particles containing silica particles and granular ceria covering at least a part of the surface of the silica particles Component C: Aqueous media   The polishing composition for polishing a silicon oxide film according to claim 1, wherein a mass ratio (ceria / silica) in the ceria-coated silica particles is 0.4 or more and 2 or less. Wherein component B has an average primary particle diameter of 15nm or more 300nm or less of the silica particles, average primary particle diameter of ceria-coated silica particles coated with 40nm or less granular ceria than 5 nm, according to claim 1 or 2 Polishing liquid composition for polishing silicon oxide film. The component A is at least one selected from the group consisting of a copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid, an alkali metal thereof, and an ammonium salt thereof . The polishing composition for polishing a silicon oxide film according to any one of the items.   The polishing composition for polishing a silicon oxide film according to any one of claims 1 to 4, wherein the copolymer has a weight average molecular weight of 1,000 to 50,000. The content of the component A in the polishing composition for polishing a silicon oxide film is 0.5 % by mass or more and 5% by mass when the total mass of the component A, the component B, and the component C is 100% by mass. The polishing composition for polishing a silicon oxide film according to any one of claims 1 to 5, wherein the polishing composition is at most%.   The polishing liquid for polishing a silicon oxide film according to any one of claims 1 to 6, wherein a mass ratio of the component A and the component B (copolymer / ceria-coated silica particles) is 0.5 or more and 25 or less. Composition.