JP2018101693A - Polishing liquid composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing liquid composition which can suppress the agglomeration of ceria particles used to increase the polishing selectivity of a stopper film (silicon nitride) for a polished film (silicon oxide) in formation of a shallow-trench element isolation structure and therefore enables the increase in polishing speed.SOLUTION: A polishing liquid composition comprises: complex particles including silica particles and ceria particles disposed on surfaces of the silica particles; an inorganic salt; and an aqueous medium. The polishing liquid composition can suppress the particle agglomeration without reducing an inter-particle repulsive force. The use of a polishing liquid composition containing ceria-coated silica particles and an inorganic salt for polishing can suppress the occurrence of a polishing flaw and increase the polishing speed.SELECTED DRAWING: None

Description

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

  Chemical mechanical polishing (CMP) technology is a method in which a polishing substrate and a polishing pad are relatively moved while supplying a 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. This is a technique in which the surface unevenness portion of the substrate to be polished is chemically reacted and mechanically removed and flattened by being moved.

  At present, when performing planarization of an interlayer insulating film, formation of a shallow trench isolation structure (hereinafter also referred to as “element isolation structure”), formation of a plug and a buried metal wiring, etc. in a semiconductor element manufacturing process, CMP technology is an essential technology. 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, a silicon nitride film) with respect to the film to be polished (for example, the silicon oxide film) (in other words, the polishing stopper film of the polishing stopper film as well as the high polishing rate). It is desired to improve the selectivity of polishing (which is harder to polish than the film to be polished).

  For example, Patent Document 1 contains an inorganic abrasive such as cerium oxide (ceria), a conductivity adjusting agent, and a dispersant, and has a conductivity of 8 to 1000 mS / m and a pH of 3.0 to 7. 0.0 polishing liquid for CMP is disclosed.

  Patent Document 2 discloses a polishing liquid suitable for polishing a semiconductor substrate, containing 0.1 to 40% by weight of silica particles, 0.001 to 2% by weight of a thermoplastic polymer, and 0.001 to 1% by weight of polyvinylpyrrolidone. A composition is disclosed.

  In Patent Document 3, as a polishing composition used for polishing a silicon oxide film, at least one selected from (A) abrasive particles containing ceria, (B) linear and branched alkylene oxide homopolymers and copolymers. Disclosed is an aqueous polishing composition comprising a seed water-soluble or water-dispersible polymer and (C) an anionic phosphate dispersant.

  Patent Document 4 discloses a polishing liquid for silicon oxide film containing crystalline ceria particles arranged on the surface of amorphous silica particles, and containing abrasive particles having an average primary particle diameter of 5 to 40 nm. A composition is disclosed.

JP 2009-218558 A JP 2005-244229 A Special table 2013-540849 gazette JP 2006-127139 A

  In recent years, silica particles have been commonly used as abrasive particles used in CMP, but ceria particles having excellent polishing selectivity have been used. However, since ceria particles are likely to aggregate, when polished with a polishing composition containing ceria particles, many polishing flaws tend to occur on the substrate to be polished. Furthermore, there was room for improvement in the polishing rate.

  The present disclosure provides a polishing liquid composition that can suppress particle aggregation and improve a polishing rate, and a semiconductor substrate manufacturing method and polishing method using the same.

  In one aspect, the present disclosure relates to a polishing liquid composition containing composite particles A composed of silica particles having ceria particles arranged on the surface, an inorganic salt B, and an aqueous medium.

  In one aspect, the present disclosure relates to a method for manufacturing a semiconductor substrate, including a step of polishing a substrate to be polished using the polishing composition according to the present disclosure.

  In one aspect, the present disclosure relates to a method for polishing a substrate, including a step of polishing a substrate to be polished using the polishing composition according to the present disclosure.

  According to the present disclosure, it is possible to provide an effect that it is possible to provide a polishing liquid composition that can suppress aggregation of particles and improve a polishing rate.

FIG. 1 is an example of a transmission electron microscope (hereinafter also referred to as “TEM”) observation photograph of ceria-coated silica particles.

  As a result of intensive studies by the present inventors, it has been found that when an inorganic salt is contained in a polishing composition containing ceria-coated silica particles as polishing particles, aggregation of particles can be suppressed and polishing rate can be improved. The invention has been completed.

  That is, in one aspect, the present disclosure provides a polishing liquid composition (hereinafter referred to as “polishing according to the present disclosure”) containing composite particles A composed of silica particles having ceria particles arranged on the surface, an inorganic salt B, and an aqueous medium. Also referred to as “liquid composition”. According to the polishing liquid composition according to the present disclosure, particle aggregation can be suppressed and the polishing rate can be improved. Moreover, since the aggregation of particles can be suppressed, polishing scratches can be reduced.

The details of the mechanism of the effect of the present disclosure are not clear, but are estimated as follows.
Normally, ceria particles are likely to aggregate, and when polished with a polishing composition containing ceria particles, many polishing scratches are generated. On the other hand, in the present disclosure, it is considered that the combined use of the composite particles A and the inorganic salt B does not reduce the repulsive force between the particles in the polishing composition and suppresses the aggregation of the particles. And it is thought by grinding | polishing using the polishing liquid composition containing the composite particle A and the inorganic salt B that generation | occurrence | production of a polishing flaw can be suppressed and a grinding | polishing rate can be improved further.

[Composite particle A]
The polishing liquid composition according to the present disclosure contains composite particles A (hereinafter also simply referred to as “particles A”) made of silica particles having ceria particles arranged on the surface as abrasive particles. The surface potential of the composite particle A is preferably negative from the viewpoints of improving the polishing rate, suppressing particle aggregation, and reducing polishing scratches. The surface potential can be measured using, for example, “Zetasizer Nano ZS” (manufactured by Sysmex Corporation). Usually, the surface potential of the ceria particles is positive. The particles A can be used singly or in combination of two or more.

  The average particle diameter (hereinafter also referred to as “DLS particle diameter”) of the particle A measured by the dynamic light scattering method (DLS) is 30 nm or more from the viewpoint of improving the polishing rate, suppressing particle aggregation, and reducing polishing scratches. Is preferably 45 nm or more, more preferably 50 nm or more, and from the same viewpoint, 500 nm or less is preferable, 400 nm or less is more preferable, and 300 nm or less is still more preferable. The DLS particle diameter of the particle A can be measured by the method described in Examples described later.

  The ceria contained in the particles A preferably has crystallinity from the viewpoint of improving the polishing rate and reducing polishing scratches. The shape of the ceria is granular from the viewpoint of improving the polishing rate and reducing polishing scratches, and is preferably approximately spherical. Accordingly, examples of the particles A include ceria-coated silica particles in which at least a part of the surface of the silica particles is coated with granular ceria.

  The average primary particle size measured by transmission electron microscopic observation of ceria contained in the particles A is preferably 5 nm or more, more preferably 7.5 nm or more, more preferably 10 nm from the viewpoint of improving the polishing rate and ease of ceria synthesis. The above is more preferable, and from the viewpoint of reducing polishing scratches, 40 nm or less is preferable, 30 nm or less is more preferable, and 25 nm or less is more preferable. The average primary particle diameter of ceria can be measured by the method described in Examples described later.

  The silica particles contained in the particles A are preferably colloidal silica from the viewpoint of improving the polishing rate and reducing polishing scratches. From the same viewpoint, the shape of the silica particles is preferably approximately spherical.

  From the viewpoint of improving the polishing rate, the average primary particle diameter measured by transmission electron microscopic observation of the silica particles used for the preparation of the particles A is preferably 15 nm or more, more preferably 20 nm or more, further preferably 40 nm or more, and From the viewpoint of reducing polishing scratches, it is preferably 300 nm or less, more preferably 200 nm or less, and even more preferably 150 nm or less. The average primary particle diameter of the silica particles can be measured by the method described in Examples described later. The average primary particle diameter measured by transmission electron microscope observation of the silica particles contained in the particles A can be the same as the silica particles used for the preparation of the particles A.

The degree of association of the silica particles used for the preparation of the particles A is preferably 3.0 or less, more preferably 2.5 or less, and even more preferably 2.3 or less, from the viewpoints of ensuring the polishing rate and reducing polishing scratches. And from the same viewpoint, 1.0 or more is preferable, 1.2 or more is more preferable, and 1.3 or more is still more preferable. The degree of association is a coefficient representing the shape of the particle and is calculated by the following formula. The degree of association of the silica particles contained in the particles A can be the same as that of the silica particles used for the preparation of the particles A.
Degree of association = DLS particle size / average primary particle size

  The method for adjusting the degree of association is not particularly limited. For example, JP-A-6-254383, JP-A-11-214338, JP-A-11-60232, JP-A-2005-060217, JP-A-2005. The method described in JP-A-060219 can be employed.

  The mass ratio (silica / ceria) of silica and ceria contained in the particle A is preferably 0.25 or more, more preferably 0.5 or more, still more preferably 0.8 or more, from the viewpoint of improving the polishing rate. From the viewpoint of suppressing particle aggregation and reducing polishing scratches, 3.0 or less is preferable, 2.5 or less is more preferable, and 2.0 or less is even more preferable.

  The particles A can be obtained, for example, by depositing ceria on Syria particles. Therefore, as a manufacturing method of the particle A, a conventionally known method can be used as long as it can generate cerium hydroxide or cerium oxide on the silica particle. Specific methods for producing the particles A include a method in which an aqueous solution in which cerium nitrate is dissolved is dropped onto a dispersion of silica particles to deposit ceria on the silica particles, a method by thermal hydrolysis of ammonium cerium nitrate, and an alkoxide. The method used etc. are mentioned. When producing cerium hydroxide on silica particles, for example, cerium hydroxide can be converted to cerium oxide by hydrothermal treatment or firing. The particles A produced by these methods may be used after being loosened so that the particles adhered to each other are separated by firing. As a method for producing the particles A, for example, methods described in JP-A No. 2015-063451, JP-A No. 2013-119131 and the like can be employed.

  The content of the particles A in the polishing liquid composition according to the present disclosure is set from the viewpoint of securing the polishing rate and improving the polishing selectivity when the total mass of the particles A, the inorganic salt B, and the aqueous medium is 100% by mass. 0.1% by mass or more, preferably 0.2% by mass or more, more preferably 0.25% by mass or more, still more preferably 0.5% by mass or more, and 5.0% by mass or less. Preferably, 2.5 mass% or less is more preferable, 2.0 mass% or less is further more preferable, and 1.5 mass% or less is still more preferable.

[Inorganic salt B]
The polishing liquid composition according to the present disclosure contains the inorganic salt B. Examples of the inorganic salt B include one or more selected from an inorganic metal salt and an inorganic ammonium salt from the viewpoint of ensuring a polishing rate and suppressing particle aggregation. Examples of the inorganic metal salt include one or more selected from potassium chloride and sodium chloride. Examples of the inorganic ammonium salt include one or more selected from ammonium chloride, ammonium bromide, and ammonium iodide. From the viewpoint of not containing a metal element, the inorganic salt B is preferably an inorganic ammonium salt, and more preferably ammonium chloride.

  The content of the inorganic salt B in the polishing composition according to the present disclosure is 0.2 parts by mass or more with respect to 100 parts by mass of the particles A from the viewpoint of improving the polishing rate, suppressing aggregation of the particles, and reducing polishing scratches. Preferably, 1 part by mass or more is more preferable, 2 parts by mass or more is more preferable, 5 parts by mass or more is further preferable, and from the same viewpoint, 80 parts by mass or less is preferable, 60 parts by mass or less is more preferable, 20 parts by mass Part or less is more preferable.

The content of the inorganic salt B in the polishing liquid composition according to the present disclosure is preferably 1 μmol / m ² or more with respect to the surface area of the particles A from the viewpoints of improving the polishing rate, suppressing particle aggregation, and reducing polishing scratches. , more preferably from 5 [mu] mol / m ² or more, more preferably 10 .mu.mol / m ² or more, more preferably 25 [mu] mol / m ² or more, and, from the same viewpoint, preferably 400μmol / m ² or less, and more is 300 [mu] mol / m ² or less 100 μmol / m ² or less is more preferable.

  The content of the inorganic salt B in the polishing liquid composition according to the present disclosure is that the polishing mass is secured and the polishing selectivity is improved when the total mass of the particles A, the inorganic salt B, and the aqueous medium is 100% by mass. Therefore, 0.001% by mass or more is preferable, 0.005% by mass or more is more preferable, 0.01% by mass or more is further preferable, 0.025% by mass or more is further preferable, and 0.4% by mass or less is preferable. Preferably, 0.3 mass% or less is more preferable, and 0.1 mass% or less is still more preferable.

[Aqueous medium]
The polishing liquid composition according to the present disclosure 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 in the polishing liquid composition according to the present disclosure is that the particle A, the inorganic salt B, and an inorganic salt B, and an optional component described later and an aqueous medium are 100% by mass. It can be set as the remainder except arbitrary components.

[Optional ingredients]
The polishing composition according to the present disclosure contains a compound C having an anionic group (hereinafter, also simply referred to as “compound C”) as a polishing aid from the viewpoint of ensuring a polishing rate and improving polishing selectivity. It is preferable. Compound C does not include inorganic salt B.

  Examples of the anionic group of Compound C include a carboxylic acid group, a sulfonic acid group, a sulfate ester group, a phosphate ester group, and a phosphonic acid group. These anionic groups may take the form of neutralized salts. Examples of the counter ion when the anionic group is in the form of a salt include metal ions, ammonium ions, alkylammonium ions, and the like. From the viewpoint of improving the quality of the semiconductor substrate, ammonium ions are preferable.

  Examples of compound C include at least one selected from citric acid and anionic polymers. Specific examples when Compound C is an anionic polymer include polyacrylic acid, polymethacrylic acid, polystyrene sulfonic acid, a copolymer of (meth) acrylic acid and monomethoxypolyethylene glycol mono (meth) acrylate, an anionic group Copolymers of (meth) acrylate and monomethoxypolyethylene glycol mono (meth) acrylate having a copolymer, copolymers of alkyl (meth) acrylate, (meth) acrylic acid and monomethoxypolyethylene glycol mono (meth) acrylate, and the like And at least one selected from these ammonium salts, and from the viewpoint of improving the quality of the semiconductor substrate, at least one selected from polyacrylic acid and its ammonium salt is preferred.

  The weight average molecular weight of Compound C is preferably 1,000 or more, more preferably 10,000 or more, still more preferably 20,000 or more, and 5.5 million or less, from the viewpoint of ensuring a polishing rate and improving polishing selectivity. Is preferable, 1 million or less is more preferable, and 100,000 or less is still more preferable.

In the present disclosure, the weight average molecular weight of Compound C can be measured under the following conditions by gel permeation chromatography (GPC) using liquid chromatography (manufactured by Hitachi, Ltd., L-6000 type high performance liquid chromatography). .
<Measurement conditions>
Detector: Shodex RI SE-61 Differential refractive index detector Column: G4000PWXL and G2500PWXL manufactured by Tosoh Corporation were used 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 molecular weight

  The content of the compound C in the polishing composition according to the present disclosure is preferably 0.01 parts by mass or more with respect to 100 parts by mass of the particles A from the viewpoint of ensuring the polishing rate and improving the polishing selectivity. 05 parts by mass or more is more preferable, 0.1 parts by mass or more is more preferable, and from the same viewpoint, 100 parts by mass or less is preferable, 10 parts by mass or less is more preferable, and 1 part by mass or less is more preferable.

  The content of the compound C in the polishing composition according to the present disclosure is 100 masses of the total mass of the particles A, the inorganic salt B, the compound C, and the aqueous medium from the viewpoint of ensuring the polishing rate and improving the polishing selectivity. % Is preferably 0.001% by mass or more, more preferably 0.0015% by mass or more, still more preferably 0.0025% by mass or more, and preferably 1.0% by mass or less, and 0.8% by mass or less. Is more preferable, and 0.6 mass% or less is still more preferable.

  The polishing liquid composition according to the present disclosure can contain optional components such as a pH adjuster and a polishing aid other than Compound C as long as the effects of the present disclosure 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, and improves polishing selectivity. From a viewpoint, 1 mass% or less is preferable, 0.5 mass% or less is more preferable, and 0.1 mass% or less is still more preferable.

  Examples of the pH adjuster include acidic compounds and alkali compounds. Examples of the acidic compound include inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid; organic acids such as acetic acid, oxalic acid, citric acid, and malic acid; Among these, from the viewpoint of versatility, at least one selected from hydrochloric acid, nitric acid and acetic acid is preferable, and at least one selected from hydrochloric acid and acetic acid is more preferable. Examples of the alkali compound include inorganic alkali compounds such as ammonia and potassium hydroxide; organic alkali compounds such as alkylamine and alkanolamine; and the like. Among these, from the viewpoint of improving the quality of the semiconductor substrate, at least one selected from ammonia and alkylamine is preferable, and ammonia is more preferable.

  Examples of polishing aids other than Compound C include anionic surfactants other than Compound C and nonionic surfactants. Examples of anionic surfactants other than Compound C include alkyl ether acetates, alkyl ether phosphates, and alkyl ether sulfates. Examples of nonionic surfactants include nonionic polymers such as polyacrylamide, polyoxyalkylene alkyl ethers, polyoxyethylene distyrenated phenyl ethers, and the like.

[Polishing liquid composition]
The polishing liquid composition according to the present disclosure can be produced by, for example, a production method including a step of blending the particles A, the inorganic salt B, the aqueous medium, and, if desired, the optional components described above by a known method. For example, the polishing liquid composition according to the present disclosure may be formed by blending at least the particles A, the inorganic salt B, and an aqueous medium. In the present disclosure, “mixing” includes mixing the particles A, the inorganic salt B, the aqueous medium, and optionally the above-described optional components simultaneously or sequentially. The order of mixing is not particularly limited. The said mixing | blending can be performed using mixers, such as a homomixer, a homogenizer, an ultrasonic disperser, and a wet ball mill, for example. The compounding quantity of each component in the manufacturing method of the polishing liquid composition which concerns on this indication can be made the same as content of each component in the polishing liquid composition which concerns on this indication mentioned above.

  The embodiment of the polishing liquid composition according to the present disclosure may be a so-called one-component type that is supplied to the market in a state where all components are mixed in advance, or may be a so-called two-component type that is mixed at the time of use. It may be.

  The pH of the polishing composition according to the present disclosure is preferably 4.0 or more, more preferably 5.0 or more, still more preferably 6.0 or more, from the viewpoint of ensuring a polishing rate and improving polishing selectivity. 10.0 or less is preferable, 9.0 or less is more preferable, and 8.0 or less is still more preferable. In the present disclosure, the pH of the polishing composition is a value at 25 ° C. and is a value measured using a pH meter. Specifically, the pH of the polishing composition in the present disclosure can be measured by the method described in Examples.

  In the present disclosure, the “content of each component in the polishing liquid composition” refers to the content of each component at the time when the polishing liquid composition is used for polishing. The polishing composition according to the present disclosure may be stored and supplied in a concentrated state as long as its stability is not impaired. 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.

  Examples of the polishing target of the polishing liquid composition according to the present disclosure include a silicon oxide film. Therefore, the polishing composition according to the present disclosure can be suitably used for polishing a silicon oxide film performed in the step of forming an element isolation structure of a semiconductor substrate.

[Polishing liquid kit]
In one aspect, the present disclosure is a kit for producing a polishing liquid composition, which includes a particle A, an inorganic salt B, an aqueous medium, and, if necessary, the above-described optional components, and includes a particle A, an inorganic salt B, and an aqueous system. The medium and at least one of the above optional components are contained in a state where they are not mixed with other components, and relate to a polishing liquid kit that is mixed with other components at the time of use. According to the polishing liquid kit according to the present disclosure, it is possible to provide a polishing liquid kit capable of improving the polishing rate and obtaining a polishing liquid composition capable of suppressing particle aggregation.

  As one embodiment of the polishing liquid kit according to the present disclosure, for example, a dispersion liquid (first liquid) containing particles A and an aqueous medium, and a solution (second liquid) containing an inorganic salt B and an aqueous medium are used. A polishing liquid kit (a two-component polishing liquid composition) is included that is included in a state where they are not mixed with each other and that is mixed when used. As other embodiments of the polishing liquid kit according to the present disclosure, for example, a dispersion liquid (first liquid) containing particles A, an inorganic salt B and an aqueous medium, and a solution (second liquid) containing component C and an aqueous medium. Liquid) in a state where they are not mixed with each other, and a polishing liquid kit (two-component polishing liquid composition) in which these are mixed at the time of use. The first liquid and the second liquid may be mixed before being supplied to the surface to be polished, or may be separately supplied and mixed on the surface of the substrate to be polished. After the first liquid and the second liquid are mixed, the liquid may be diluted with an aqueous medium as necessary. Each of the first liquid and the second liquid may contain the above-described optional components as necessary.

[Method for Manufacturing Semiconductor Substrate]
In one aspect, the present disclosure includes a step of polishing a substrate to be polished using the polishing liquid composition according to the present disclosure (hereinafter, also referred to as “polishing step using the polishing liquid composition according to the present disclosure”). The present invention relates to a method for manufacturing a semiconductor substrate (hereinafter also referred to as “method for manufacturing a semiconductor substrate according to the present disclosure”). According to the method for producing a semiconductor substrate according to the present disclosure, by using the polishing liquid composition of the present disclosure, it is possible to improve the polishing rate in the polishing step, and further, it is possible to reduce the polishing scratches by suppressing the aggregation of particles, The effect that a semiconductor substrate with improved substrate quality can be produced efficiently can be achieved.

As a specific example of the method of manufacturing a semiconductor substrate according to the present disclosure, first, a silicon dioxide layer is grown on the surface of the silicon substrate by exposing the silicon substrate to oxygen in an oxidation furnace, and then silicon nitride ( A polishing stopper film such as a Si ₃ N ₄ ) film or a polysilicon film is formed by, for example, a chemical vapor deposition method (CVD method). Next, a photolithography technique is applied to a substrate including a silicon substrate and a polishing stopper film disposed on one main surface side of the silicon substrate, for example, a substrate in which a polishing stopper film is formed on a silicon dioxide layer of a silicon substrate. Is used to form a trench. Next, a silicon oxide (SiO ₂ ) film, which is a film to be polished for trench filling, 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 polished substrate is obtained. By forming the silicon oxide film, the trench is filled with silicon oxide of the silicon oxide film, and the surface opposite to the surface of the polishing stopper film on 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 surface of the polishing stopper film on the silicon substrate side is exposed. More preferably, the surface of the silicon oxide film and the surface of the polishing stopper film are flush with each other. The silicon oxide film is polished until The polishing composition according to the present disclosure can be used in the step of polishing by the CMP method.

  In polishing by the CMP method, the surface of the substrate to be polished and the polishing pad are in contact with each other, and the polishing substrate composition and the polishing pad are relatively moved while supplying the polishing composition according to the present disclosure to these contact portions. By doing so, the uneven portions on the surface of the substrate to be polished are flattened. In the method for manufacturing a semiconductor substrate according to the present disclosure, another insulating film may be formed between the silicon dioxide layer of the silicon substrate and the polishing stopper film, or the polishing target film (for example, a silicon oxide film) and the polishing may be performed. Another insulating film may be formed between the stopper film (for example, silicon nitride film).

In the polishing process using the polishing composition according to the present disclosure, the polishing pad has a rotation speed of, for example, 30 to 200 r / min, and the rotation speed of the substrate to be polished is, for example, 30 to 200 r / min. The polishing load set in the polishing apparatus can be set to, for example, 20 to 500 g weight / cm ² , and the supply rate of the polishing composition can be set to, for example, 10 to 500 mL / min or less. When the polishing liquid composition is a two-part polishing liquid composition, the respective polishing speeds of the film to be polished and the polishing stopper film are adjusted by adjusting the respective supply speeds (or supply amounts) of the first liquid and the second liquid. In addition, the polishing rate ratio (polishing selectivity) between the film to be polished and the polishing stopper film can be adjusted.

  In the polishing step using the polishing composition according to the present disclosure, the polishing rate of the film to be polished (for example, silicon oxide film) is preferably 2000 kg / min or more, more preferably 3000 kg / min, from the viewpoint of improving productivity. More preferably, it is 4000 kg / min or more.

  In the polishing process using the polishing liquid composition according to the present disclosure, the polishing rate of the polishing stopper film (for example, silicon nitride film) is preferably 500 mm / min or less from the viewpoint of improving the polishing selectivity and shortening the polishing time. More preferably, it is 300 kg / min or less, and still more preferably 150 kg / min or less.

  In the polishing step using the polishing composition according to the present disclosure, the polishing rate ratio (polishing rate of the film to be polished / polishing rate of the polishing stopper film) is preferably 5.0 or more from the viewpoint of shortening the polishing time. 10.0 or more are more preferable, 20.0 or more are still more preferable, and 40.0 or more are still more preferable. In the present disclosure, the polishing selectivity is synonymous with the ratio of the polishing rate of the film to be polished to the polishing rate of the polishing stopper (polishing rate of the film to be polished / polishing rate of the polishing stopper film), and high polishing selectivity means This means that the polishing rate ratio is large.

[Polishing method]
In one aspect, the present disclosure relates to a substrate polishing method (hereinafter, also referred to as a polishing method according to the present disclosure) including a polishing step using the polishing composition according to the present disclosure. By using the polishing method according to the present disclosure, it is possible to improve the polishing rate in the polishing process, and further to suppress the aggregation of particles and reduce polishing scratches, so that it is possible to efficiently manufacture a semiconductor substrate with improved substrate quality. An effect can be produced. Specific polishing methods and conditions can be the same as those of the semiconductor substrate manufacturing method according to the present disclosure described above.

  Hereinafter, the present disclosure will be described in more detail by way of examples. However, these examples are illustrative, and the present disclosure is not limited to these examples.

1. Manufacturing method or details of abrasive particles The manufacturing method or details of the abrasive particles used in the preparation of the polishing liquid compositions of Examples 1 to 11 and Comparative Examples 1 to 7 are as follows.
<Method for producing ceria-coated silica particles A>
First, a 20% by mass aqueous dispersion of spherical silica particles (average primary particle size: 80 nm, association degree: 1.4) is prepared, and cerium nitrate as a CeO ₂ raw material is dissolved in the spherical silica particle aqueous dispersion. Aqueous solution (concentration: 6% by mass) was added dropwise (feed rate: 2 g / min), and at the same time, a 3% by mass aqueous ammonia solution was added dropwise separately to maintain the pH at about 8 (average primary particle size: 15 nm) Was deposited on spherical silica particles. During this dropping, the spherical silica aqueous dispersion was maintained at 50 ° C. by heating. 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 sufficiently filtered and washed with water, and then dried at 100 ° C. with a dryer. The obtained dry powder may be used for the preparation of the polishing composition, but here, after further drying the dried powder at 1000 ° C. for 2 hours, the particles adhered to each other by baking are separated. By loosening, ceria-coated silica particles A (DLS particle diameter: 140 nm) were obtained. When the particle A was observed with a transmission electron microscope (TEM), the silica particle surface was covered with granular ceria as shown in FIG. The mass ratio of silica to ceria in Particle A was 0.87.
<Crushing ceria>
Ground ceria (DLS particle size: 130nm)

2. Preparation of polishing liquid compositions (Examples 1 to 11 and Comparative Examples 1 to 7) Abrasive particles (ceria-coated silica particles A or pulverized ceria), inorganic salt B, and ion-exchanged water are uniformly mixed, and if necessary. The pH adjuster was added and the polishing liquid composition (Examples 1-11 and Comparative Examples 1-7) of pH 6.0 in 25 degreeC was 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. The contents and types of the abrasive particles and inorganic salt B in each of the polishing liquid compositions of Examples 1 to 11 and Comparative Examples 1 to 7 were as shown in Table 1.

3. Measuring method of various parameters The pH of the polishing composition, the DLS particle diameter of the abrasive particles, the BET specific surface area of the abrasive particles, the average primary particle diameter of the silica particles, and the average primary particle diameter of the ceria particles are measured by the following methods. did.

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

(B) DLS particle size of abrasive particles The DLS particle size of the abrasive particles is Malvern obtained by stirring and mixing abrasive particles and ultrapure water so that the concentration of abrasive particles is 0.1% by mass. Measurement was performed with “Zeta Sizer Nano ZS” (dynamic light scattering method) manufactured by the company, and the obtained volume average particle size was defined as the DLS particle size of the abrasive particles.

(C) BET specific surface area of abrasive particles The specific surface area of the abrasive particle dispersion was dried with hot air at 120 ° C for 3 hours, and then finely pulverized in an agate mortar to obtain a sample. The sample was dried for 15 minutes in an atmosphere of 120 ° C. immediately before the measurement, and then measured by a nitrogen adsorption method (BET method) using a micromeritic automatic specific surface area measuring device “Flowsorb III2305” (manufactured by Shimadzu Corporation).

(D) Average primary particle diameter of silica particles The average primary particle diameter of the silica particles used as the raw material of the composite particles and the average primary particle diameter of the silica particles in the composite particles are obtained by using an image obtained from TEM. 50 sizes were measured and averaged. The average primary particle diameter of the silica particles did not change before and after coating with ceria.

(E) Average primary particle diameter of the ceria particles The average primary particle diameter of the ceria particles on the silica particles is obtained by measuring the particle diameters of 100 ceria particles on the silica particles using an image obtained from TEM, and averaging these. I got it. As another method, powder of ceria-coated silica particles is subjected to powder X-ray diffraction measurement, and the half width of the peak of ceria (1,1,1) plane appearing in the vicinity of 29-30 ° and the diffraction angle are used. 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: wavelength of X-ray = 1.54056Å, β: half width, θ: diffraction angle 2θ / θ

4). Evaluation of polishing composition (Examples 1 to 11 and Comparative Examples 1 to 7) [Creation of test pieces]
A 40 mm × 40 mm square piece was cut out from a silicon oxide film having a thickness of 2000 nm formed on one side of a silicon wafer by TEOS-plasma CVD method to obtain a silicon oxide film test piece.

[Measurement of polishing rate of silicon oxide]
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 of an apparatus having a diameter of 120 mm, 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 silicon 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 was attached, each of the surface plate and the holder was rotated in the same rotational direction at 90 r / min for 2 minutes to obtain a test piece. Was polished. After polishing, the sample was washed with ultrapure water and dried, and the test piece was used as a measurement object by an optical interference film thickness measuring device described later.

Before and after polishing, the film thickness of silicon oxide was measured using an optical interference type film thickness measuring device (“Lambda Ace VM-1000” manufactured by Dainippon Screen). The polishing rate of the silicon oxide film was calculated by the following formula. As for the polishing rate of the silicon oxide film using each polishing composition, Table 1 shows relative values with the polishing rate being 100 when the polishing particles of Comparative Example 1 are used. In Table 1, the relative value is shown in 5 units.
Polishing rate of silicon oxide film (nm / min)
= [Silicon oxide film thickness before polishing (nm) -silicon oxide film thickness after polishing (nm)] / polishing time (min)

[Measurement of sedimentation height]
First, 100 mL of the polishing liquid composition shown in Table 1 was prepared, poured into a glass sample bottle (“Screw tube No. 8” manufactured by Maruem Co., Ltd.), shaken to be uniform, and allowed to stand for 1 hour. And the sedimentation height (mm) which is the height of the sedimentation layer produced by sedimentation of the component contained in polishing liquid composition was measured with calipers. The results are shown in Table 1.

  As shown in Table 1, in the polishing composition of Examples 1 to 11 containing ceria-coated silica particles A and inorganic salt B, aggregation of abrasive particles was suppressed. And when it grind | polished using the polishing liquid composition of Examples 1-11, the polishing rate was able to be improved compared with Comparative Examples 1-7.

  The polishing composition according to the present disclosure is useful in a method for manufacturing a semiconductor substrate for high density or high integration.

Claims (12)

  Polishing liquid composition containing the composite particle A which consists of the silica particle which arrange | positioned the ceria particle on the surface, inorganic salt B, and an aqueous medium.   The polishing composition according to claim 1, which is used for polishing a silicon oxide film.   The polishing composition according to claim 1 or 2, wherein the content of the inorganic salt B is 0.2 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the composite particles A. The content of the inorganic salt B is, with respect to the surface area of the composite particles A, is 1 [mu] mol / m ² or more 400μmol / m ² or less, the polishing liquid composition according to any one of claims 1 to 3.   The polishing composition according to any one of claims 1 to 4, wherein the content of the inorganic salt B in the polishing composition is 0.001 mass% or more and 0.4 mass% or less.   The polishing composition according to any one of claims 1 to 5, wherein the inorganic salt B is ammonium chloride.   The polishing composition according to any one of claims 1 to 6, wherein a mass ratio (silica / ceria) of silica and ceria contained in the composite particle A is 0.25 or more and 3.0 or less.   The polishing composition according to any one of claims 1 to 7, wherein the average particle diameter of the composite particles A measured by a dynamic light scattering method is 30 nm or more and 500 nm or less.   The polishing liquid composition according to any one of claims 1 to 8, wherein the degree of association of silica particles contained in the composite particles A is 1.0 or more and 3.0 or less.   The polishing composition according to any one of claims 1 to 9, wherein the pH is 4.0 or more and 10.0 or less.   The manufacturing method of a semiconductor substrate including the process of grind | polishing a to-be-polished board | substrate using the polishing liquid composition in any one of Claim 1 to 10.   A method for polishing a substrate, comprising a step of polishing a substrate to be polished using the polishing composition according to claim 1.