WO2024024413A1

WO2024024413A1 - Polishing composition

Info

Publication number: WO2024024413A1
Application number: PCT/JP2023/024731
Authority: WO
Inventors: 雄一郎中貝
Original assignee: 株式会社フジミインコーポレーテッド
Priority date: 2022-07-26
Filing date: 2023-07-04
Publication date: 2024-02-01
Also published as: TW202405129A; JP2024016448A

Abstract

The present invention provides means for preventing sedimentation of abrasive grains and improving redispersibility of abrasive grains, while improving polishing performance.　The present invention relates to a polishing composition comprising abrasive grains, an oxidant, a metal cation exhibiting a hydrated metal ion pKa of less than 7.0, a metal salt A which is a salt with an anion, a layered compound, and a dispersant, the polishing composition including the metal salt A at a concentration of 8 mM or more.

Description

polishing composition

The present invention relates to a polishing composition.

In general, when polishing semiconductor substrates such as silicon wafers and silicon carbide, it is important to not only improve surface quality due to the higher performance and higher integration density of semiconductor devices, but also to improve manufacturing efficiency in response to increased demand in recent years. is considered an important issue. As a technique for solving this problem, for example, Japanese Patent Laid-Open No. 2012-248569 discloses an oxidizing agent containing a transition metal with a redox potential of 0.5 V or more, and an oxidizing agent with an average secondary particle size of 0.5 μm or less. A polishing agent characterized by containing cerium particles and a dispersion medium is disclosed.

However, the polishing composition described in JP-A No. 2012-248569 has poor dispersibility of abrasive grains, so polishing performance (for example, polishing removal rate and surface roughness of the object to be polished) is not stable. Furthermore, there is a problem in that abrasive grains settle in piping or slurry supply tubes during manufacture or use of the polishing composition, thereby clogging the piping and the like. Furthermore, there was a problem in that the redispersibility of the abrasive grains after long-term storage was also poor. There is a strong demand for improving the polishing removal rate for materials with high hardness such as silicon carbide.

The present invention has been made in view of the above problems, and its purpose is to provide a means for improving polishing performance, preventing sedimentation of abrasive grains, and improving redispersibility of abrasive grains. .

In order to solve the above problems, the present inventor has conducted extensive research. As a result, it contains abrasive grains, an oxidizing agent, a metal salt A which is a salt of a metal cation with a pKa of hydrated metal ions smaller than 7.0, and an anion, a layered compound, and a dispersion medium, and contains metal salt A at a concentration of 8mM or more. It has been found that the above problems can be solved by a polishing composition containing the following. Based on the above findings, the present invention has been completed.

Hereinafter, the composition of the polishing composition of the present invention will be explained in detail. Note that the present invention is not limited only to the following embodiments. In addition, in this specification, unless otherwise specified, operations and measurements of physical properties, etc. are performed under conditions of room temperature (20° C. or higher and 25° C. or lower)/relative humidity of 40% RH or higher and 50% RH or lower.

[Abrasive]
The polishing composition of the present invention contains abrasive grains. The abrasive grains have the function of mechanically polishing the object to be polished.

Specific examples of abrasive grains used in the present invention include metal oxides such as aluminum oxide (alumina), silicon oxide (silica), cerium oxide (ceria), zirconium oxide, titanium oxide (titania), and manganese oxide. Metal carbides such as silicon carbide and titanium carbide; Metal nitrides such as silicon nitride and titanium nitride; Metal borides such as titanium boride and tungsten boride; and the like. The abrasive grains may be used alone or in combination of two or more kinds. Further, the abrasive grains may be commercially available products or synthetic products.

Among these abrasive grains, at least one kind selected from the group consisting of metal oxides and metal carbides is preferable, from the viewpoint that abrasive grains having various particle sizes are easily available and excellent polishing removal rates can be obtained. Aluminum oxide is more preferred.

The average secondary particle diameter of the abrasive grains is preferably 0.01 μm or more, more preferably 0.05 μm or more, even more preferably 0.1 μm or more, and particularly preferably 0.2 μm or more. As the average secondary particle diameter of the abrasive grains increases, the polishing removal rate of the object to be polished increases. Further, the average secondary particle diameter of the abrasive grains is preferably 10.0 μm or less, more preferably 5.0 μm or less, even more preferably 3.0 μm or less, and even more preferably 1.8 μm or less. It is even more preferable that it is 1.5 μm or less, even more preferably 1.0 μm or less, and most preferably 0.5 μm or less. As the volume average particle diameter of the abrasive grains becomes smaller, it becomes easier to obtain a surface with fewer defects and less roughness. From the above, the average secondary particle diameter of the abrasive grains is preferably 0.01 μm or more and 10.0 μm or less, more preferably 0.05 μm or more and 5.0 μm or less, and 0.1 μm or more and 3.0 μm or less. It is more preferable that it is, and it is particularly preferable that it is 0.2 μm or more and 1.0 μm or less.

Note that the average secondary particle diameter of abrasive grains in this specification is measured based on a laser diffraction scattering method unless otherwise specified. Specifically, the measurement can be performed using a laser diffraction/scattering particle size distribution analyzer (trade name "LA-950") manufactured by Horiba, Ltd.

The concentration (content) of abrasive grains in the polishing composition is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, and 0.01% by mass or more. is even more preferable. As the concentration (content) of abrasive grains increases, the polishing removal rate increases. The concentration (content) of abrasive grains in the polishing composition may be 0.05% by mass or more, or 0.1% by mass or more.

Furthermore, the concentration (content) of abrasive grains in the polishing composition is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 10% by mass or less. As the concentration (content) of abrasive grains decreases, the manufacturing cost of the polishing composition decreases, and it becomes easier to obtain a surface with fewer defects such as scratches by polishing with the polishing composition. Become. The concentration (content) of abrasive grains in the polishing composition may be 8% by mass or less, or 7% by mass or less.

From the above, the concentration (content) of abrasive grains in the polishing composition is preferably 0.001% by mass or more and 30% by mass or less, more preferably 0.005% by mass or more and 25% by mass or less. The content is preferably 0.01% by mass or more and 10% by mass or less. Moreover, the concentration (content) of abrasive grains in the polishing composition may be 0.05% by mass or more and 8% by mass or less, or 0.1% by mass or more and 7% by mass or less.

[Oxidant]
The polishing composition of the present invention contains an oxidizing agent. The oxidizing agent can cause an oxidation reaction with the substrate surface during the polishing process, lowering the hardness of the surface and making the surface brittle. By using an oxidizing agent, the polishing removal rate can be effectively improved.

The oxidizing agent is not particularly limited as long as it has a sufficient redox potential to oxidize the substrate surface. For example, the oxidizing agent can be a substance that has a redox potential that is higher than the redox potential of the substrate material at the pH at which polishing is performed. Here, the pH at which the polishing is performed is usually the same as the pH of the polishing composition. The redox potential of the substrate material can be determined by dispersing the powder of the material in water to make a slurry, adjusting the slurry to the same pH as the polishing composition, and then measuring the slurry using a commercially available redox potentiometer. The value obtained by measuring the oxidation-reduction potential (the oxidation-reduction potential with respect to a standard hydrogen electrode at a liquid temperature of 25° C.) is adopted. Note that the oxidizing agent in this specification does not include metal salt A, which will be described later.

Specific examples of oxidizing agents include peroxides such as hydrogen peroxide; nitric acids such as iron nitrate, silver nitrate, and aluminum nitrate; persulfuric acids such as persulfuric acid such as peroxomonosulfuric acid and peroxodisulfuric acid; Chloric acids; perchloric acids such as perchloric acid; bromic acids such as bromate; iodic acids such as iodic acid; periodic acids; ferrous acids such as potassium ferrate; Manganese acids; chromic acids such as potassium chromate and potassium dichromate; vanadic acids such as ammonium vanadate, sodium vanadate, and potassium vanadate; ruthenic acids such as perruthenic acid or its salts; molybdic acid and its salts. Examples thereof include molybdic acids such as ammonium molybdate and disodium molybdate; rhenium acids such as perrhenic acid or its salt; tungstic acids such as tungstic acid and its salt disodium tungstate; These may be used alone or in an appropriate combination of two or more.

In some preferred embodiments, the polishing composition contains a composite metal oxide as an oxidizing agent. Examples of the composite metal oxides include nitric acids, ferric acids, permanganic acids, chromic acids, vanadic acids, ruthenic acids, molybdic acids, rhenic acids, and tungstic acids. Among these, iron acids, permanganic acids, and chromic acids are more preferred, and permanganic acids are even more preferred. One type of composite metal oxide may be used alone, or two or more types may be used in an appropriate combination.

The polishing composition disclosed herein may or may not further contain an oxidizing agent other than the composite metal oxide. The technology disclosed herein can be preferably carried out in an embodiment in which substantially no oxidizing agent (for example, hydrogen peroxide) other than the above composite metal oxide is included as an oxidizing agent.

It is appropriate that the concentration (content) of the oxidizing agent in the polishing composition is 0.001 mol/L or more. From the viewpoint of improving the polishing removal rate, in some embodiments, the concentration (content) of the oxidizing agent is preferably 0.005 mol/L or more, more preferably 0.01 mol/L or more, and 0.05 mol/L or more. More preferred. In some preferred embodiments, the concentration (content) of the oxidizing agent is 0.10 mol/L or more, may be 0.15 mol/L or more, or may be 0.20 mol/L or more, For example, it is 0.25 mol/L or more. In addition, from the viewpoint of surface quality after polishing, it is appropriate that the concentration (content) of the oxidizing agent is 10 mol/L or less, preferably 5 mol/L or less, and 3 mol/L or less (e.g. 2.5 mol/L or less, or 2 mol/L or less) is more preferable. In some embodiments, the concentration (content) of the oxidizing agent may be less than 2 mol/L, may be 1.5 mol/L or less, or may be less than 1.5 mol/L.

From the above, the concentration (content) of the oxidizing agent in the polishing composition is suitably 0.001 mol/L or more and 10 mol/L or less, preferably 0.005 mol/L or more and 5 mol/L or less, and 0.01 mol/L or more. It is more preferable that it is 3 mol/L or more and 3 mol/L or less. In some embodiments, the concentration (content) of the oxidizing agent in the polishing composition may be 0.05 mol/L or more and 2.5 mol/L or less, and 0.10 mol/L or more and 2 mol/L or less. It may be. Further, in some preferred embodiments, the concentration (content) of the oxidizing agent in the polishing composition may be 0.15 mol/L or more and less than 2 mol/L, and 0.20 mol/L or more and less than 1.5 mol/L. /L or less, or 0.20 mol/L or more and less than 1.5 mol/L.

[Metal salt A]
The polishing composition of the present invention contains metal salt A. Metal salt A is a salt of a metal cation whose hydrated metal ion has a pKa of less than 7.0 and an anion. In addition, in this specification, a metal cation means a cation containing a metal. That is, the above-mentioned metal cation may be a cation composed only of a metal, or may be a cation composed of a metal and a nonmetal. The metal salts A can be used alone or in combination of two or more. By including metal salt A in addition to the oxidizing agent in the polishing composition used for polishing silicon carbide, the polishing removal rate and storage stability are improved.

Although not wishing to be bound by theory, the reason why such an effect is obtained is thought to be, for example, as follows. That is, in polishing performed by supplying a polishing composition containing an oxidizing agent to a polishing target having a surface made of silicon carbide, the oxidizing agent contained in the polishing composition is Oxidizing the surface and making it brittle can contribute to improving the polishing removal rate. However, the above oxidation can be a factor that increases the pH of the polishing composition supplied to the object to be polished. As a result, the pH of the polishing composition supplied to the polishing target increases from the initial pH (i.e., the pH of the polishing composition supplied to the polishing target) during polishing of the polishing target. If the pH is outside the appropriate pH range, the chemical polishing performance of the polishing composition on the object to be polished will be degraded. When a polishing composition containing an oxidizing agent contains a metal salt A containing a metal cation whose pKa of hydrated metal ions is smaller than 7.0, the metal salt A exhibits a buffering effect, thereby improving the polishing composition. It is thought that the pH increase is suppressed and maintained within an appropriate pH range, thereby maintaining the chemical polishing performance of the polishing composition, thereby improving the polishing removal rate. It is also believed that the buffering effect of the metal salt A contributes to the improvement in storage stability. However, the above considerations do not limit the scope of the present invention.

In some embodiments, as the metal salt A, a salt of a metal cation with a hydrated metal ion having a pKa of 6.5 or less and an anion can be preferably employed. Examples of metal cations whose hydrated metal ion pKa is 6.5 or less include Al ³⁺ (hydrated metal ion pKa is 5.0), Cr ³⁺ (hydrated metal ion pKa is 4.2), In ³⁺ (pKa of hydrated metal ion is 4.0), Ga ³⁺ (pKa of hydrated metal ion is 2.6), Fe ³⁺ (pKa of hydrated metal ion is 2.2), Hf ⁴⁺ (pKa of hydrated metal ion is 2.2), ion pKa is 0.2), Zr ⁴⁺ (hydrated metal ion pKa is -0.3), Ce ⁴⁺ (hydrated metal ion pKa is -1.1), Ti ⁴⁺ (hydrated metal ion pKa is -1.1), -4.0), but are not limited to these. In some embodiments, the pKa of the hydrated metal ion may be less than 6.5, may be less than or equal to 6.0, may be less than 6.0, and may be less than or equal to 6.5. 5.0 or less, 4.5 or less, 4.0 or less, 3.5 or less, 3.0 or less. Furthermore, the pKa of the hydrated metal ion is suitably approximately -5.0 or more, may be -1.5 or more, may be -0.5 or more, and may be 0.0 It is preferably at least 0.5, more preferably at least 0.5, it may be at least 1.0, it may be at least 1.5, it may be at least 2.0, it may be at least 2.5. The valence of the metal cation in metal salt A may be, for example, divalent, trivalent, or tetravalent. In some embodiments, metal salt A, which is a salt of a cation containing a trivalent metal and an anion, can be preferably employed.

From the above, the pKa of the hydrated metal ion may be -5.0 or more and 6.5 or less, -1.5 or more and less than 6.5, and -1.5 or more and 6.0 It may be -0.5 or more and less than 6.0, or -0.5 or more and 5.5 or less.

The metal cation in metal salt A may be, for example, a cation containing a metal belonging to Group 3 to Group 16 of the periodic table, or a cation containing a metal belonging to Group 4 to Group 14 of the periodic table. A cation containing a metal belonging to Group 6 to Group 14 of the periodic table is more preferable. The technology disclosed herein can be preferably carried out using a metal salt A, which is a salt of a cation and an anion containing, for example, a metal belonging to Group 13 of the periodic table.

In some embodiments, as the metal salt A, one that buffers the pH to 2.5 or more and 5.5 or less (for example, 3.0 or more and 4.5 or less) can be preferably employed. The pH at which metal salt A buffers can be determined by titrating an aqueous solution of metal salt A with sodium hydroxide.

The metal salt A may be an inorganic acid salt or an organic acid salt. Examples of inorganic acid salts include hydrohalic acids such as hydrochloric acid, hydrobromic acid, and hydrofluoric acid, and salts of nitric acid, sulfuric acid, carbonic acid, silicic acid, boric acid, and phosphoric acid. Examples of organic acid salts include carboxylic acids such as formic acid, acetic acid, propionic acid, benzoic acid, glycinic acid, butyric acid, citric acid, tartaric acid, and trifluoroacetic acid; methanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, and toluene. Examples include salts of organic sulfonic acids such as sulfonic acid; organic phosphonic acids such as methylphosphonic acid, benzenephosphonic acid, and toluenephosphonic acid; organic phosphoric acids such as ethylphosphonic acid; Among these, salts of hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid are preferred, and salts of hydrochloric acid, nitric acid, and sulfuric acid are more preferred. The technology disclosed herein includes, for example, a cation selected from the group consisting of Al ³⁺ , Cr ³⁺ , Fe ³⁺ , In ³⁺ , Ga ³⁺ and Zr ⁴⁺ as the metal salt A, and a nitrate ion (NO ₃ ⁻ ), It can be preferably carried out in an embodiment using a salt with an anion selected from the group consisting of chloride ion (Cl ⁻ ), sulfate ion (SO ₄ ²⁻ ), and acetate ion (CH ₃ COO ⁻ ).

The metal salt A is preferably a water-soluble salt. By using water-soluble metal salt A, a good surface with few defects such as scratches can be efficiently formed.

The concentration (content) of the metal salt A in the polishing composition is not particularly limited, and can be appropriately set depending on the purpose and manner of use of the polishing composition so as to achieve the desired effect. . The concentration (content) of the metal salt A in the polishing composition may be, for example, approximately 1000 mM or less, 500 mM or less, or 300 mM or less. From the viewpoint of effectively achieving both polishing removal rate and storage stability, in some embodiments, it is appropriate that the concentration (content) of metal salt A in the polishing composition is 200 mM or less, It is preferably 100mM or less, more preferably 50mM or less, 40mM or less, 30mM or less, 20mM or less, or 10mM or less. The concentration (content) of the metal salt A in the polishing composition may be, for example, 0.1 mM or more, and from the viewpoint of appropriately exerting the effect of using the metal salt A, it is necessary to be 8 mM or more, and 10 mM or more. It is preferable to set it as above, and it is more preferable to set it as 15mM or more (for example, 20mM or more). The technology disclosed herein can also be preferably implemented, for example, in an embodiment in which the concentration (content) of metal salt A in the polishing composition is 25 mM or more or 30 mM or more. In addition, 1mM=1mmol/L.

From the above, the concentration (content) of metal salt A in the polishing composition may be 0.1 mM or more and 1000 mM or less, 8 mM or more and 500 mM or less, or 10 mM or more and 300 mM or less. . In some embodiments, the concentration (content) of metal salt A in the polishing composition is suitably 15 mM or more and 200 mM or less, preferably 20 mM or more and 100 mM or less, and 15 mM or more and 50 mM or less. More preferably, the amount may be 20 mM or more and 40 mM or less, or 20 mM or more and 30 mM or less. Furthermore, in some embodiments, the concentration (content) of the metal salt A in the polishing composition may be 0.1 mM or more and 20 mM or less, or 0.1 mM or more and 10 mM or less.

Although not particularly limited, the concentration of metal salt A in the polishing composition (multiple metal salts Ratio (C2/C1) of the oxidizing agent concentration (if multiple oxidizing agents are included, their total concentration) C1 [mM] is suitably approximately 0.0002 or more, preferably 0.0005 or more, more preferably 0.0007 or more, may be 0.001 or more, may be 0.003 or more, and may be 0.005 or more. But that's fine. From the viewpoint of further improving the polishing removal rate, in some embodiments, C2/C1 may be, for example, 0.073 or more, preferably 0.01 or more, 0.015 or more, and 0.073 or more, preferably 0.01 or more, and 0.015 or more. It may be 02 or more. C2/C1 is not particularly limited, but is suitably approximately 200 or less, may be 100 or less, may be 75 or less, or may be 50 or less. In some preferred embodiments, C2/C1 may be 20 or less, 10 or less, 5 or less, 1 or less, 0.6 or less, 0.5 or less, 0.3 or less. It may be 0.2 or less. At such a concentration ratio of metal salt A and oxidizing agent (C2/C1), the polishing removal rate can be preferably improved by metal salt A.

From the above, C2/C1 is preferably 0.0002 or more and 200 or less, more preferably 0.0005 or more and 100 or less, may be 0.007 or more and 75 or less, and 0.001 or more and 50 or less. Good too. In some embodiments, C2/C1 may be, for example, 0.003 or more and 20 or less, 0.005 or more and 10 or less, 0.007 or more and 5 or less, and 0.007 or more and 5 or less, for example. It may be 01 or more and 1 or less, 0.015 or more and 0.6 or less, 0.02 or more and 0.5 or less, or 0.02 or more and 0.3 or less. It may be 0.02 or more and 0.2 or less.

[Layered compound]
In the polishing composition of the present invention, the layered compound does not form any chemical bonds (e.g., covalent bonds, ionic bonds, coordinate bonds, hydrogen bonds, etc.) with the abrasive grains, and It is neither physically attached nor supported on abrasive grains. In other words, the layered compound forms a weak attracting interaction with the abrasive grains due to the action of intermolecular force or electrostatic action with the abrasive grains, resulting in steric hindrance between the abrasive grains. It can exist. This suppresses agglomeration of abrasive grains, so it is thought that the effects of the present invention, such as preventing sedimentation and improving redispersibility while maintaining polishing performance, can be achieved.

In addition, by storing the polishing composition at a predetermined temperature for a predetermined period of time after preparing the polishing composition, the weak interaction between the above-mentioned layered compound and abrasive grain particles is promoted, and the effect of preventing sedimentation of the abrasive grains and improving the redispersibility is enhanced. It is thought that the effect will be further improved.

Note that the above mechanism is based on speculation, and whether it is correct or incorrect does not affect the technical scope of the present invention.

The layered compound used in the present invention is not particularly limited as long as it exhibits the above effects, but examples include clay minerals represented by layered silicate compounds, two-dimensional sheet-like compounds made of NbO ₆ octahedral units, etc. Layered niobate compounds with a structure, layered titanate compounds with a layered structure in which triangular bipyramids of TiO ₅ are connected in a plane, or a two-dimensional sheet-like structure consisting of TiO ₆ octahedral units, and phosphoric acid between the layers. Metal phosphates in which OH groups exist, layered double hydroxides in which hydroxide layers contain divalent and trivalent metal ions and anions exist between the layers, and metal atoms in octahedral or triangular shapes. Examples include metal chalcogen compounds having a prism-shaped structure surrounded by chalcogen atoms, boron nitride having a laminated structure of strongly bonded atomic layers, and graphite such as natural graphite and artificial graphite.

More specifically, for example, layered niobate compounds include layered titanates such as K ₄ Nb ₆ O ₁₇ , KNb ₃ O ₈ , HNb ₃ O ₈ , NaNbO ₃ , LiNbO ₃ , Cs ₄ Nb ₆ O ₁₇ , etc. Compounds include Na ₂ Ti ₃ O ₇ , K ₂ Ti ₄ O ₉ , K ₂ Ti ₂ O ₅ , Cs ₂ Ti ₅ O ₁₁ , Cs ₂ Ti ₆ O ₁₃ , etc. Metal phosphates include α-Zr (HPO ₄ ) ₂ , layered zirconium phosphates such as γ-ZrPO ₄ .H ₂ PO ₄ , layered double hydroxides such as hydrotalcite, and metal chalcogen compounds such as MoS ₂ , WS ₂ , TaS ₂ , NbS _{2 ,} etc. Can be mentioned. These layered compounds can be used alone or in combination of two or more. Among the above-mentioned layered compounds, layered silicate compounds are preferred from the viewpoint that the effects of the present invention can be stably and efficiently obtained. The layered silicate compound will be explained below.

(Layered silicate compound)
The basic structure of layered silicate compounds is that silicate tetrahedrons are connected in a planar manner, and the unit structure includes one or two silicate tetrahedral sheets and one alumina or magnesia octahedral sheet. It is a structure characterized by containing. Cations such as sodium, potassium, and calcium exist between the layers (between unit structures). Further, the layered silicate compound is a substance that has a property that crystals are peeled off thinly.

The layered silicate compound used in the present invention may be a natural product, a synthetic product, a commercially available product, or a mixture thereof. Examples of the method for synthesizing the layered silicate compound include a hydrothermal synthesis reaction method, a solid phase reaction method, and a melt synthesis method.

Specific examples of the layered silicate compounds include talc, pyrophyllite, smectite (saponite, hectorite, sauconite, stevensite, bentonite, montmorillonite, beidellite, nontronite, etc.), vermiculite, mica (gold), Mica, biotite, Chinwald mica, muscovite, paragonite, celadonite, glauconite, etc.), chlorite (clinochlore, chamosite, nimite, pennantite, sudoite, donbasite, etc.), brittle mica (clintonite, margarite, etc.) , soulite, serpentine (antigorite, lizardite, chrysotile, amethyte, cronstedite, verchelin, greenalite, garnierite, etc.), kaolin (kaolinite, dickite, nacrite, halloysite, etc.), and the like.

These layered silicate compounds can be used alone or in combination of two or more. Among them, smectite (saponite, hectorite, sauconite, stevensite, bentonite, montmorillonite, beidellite, Nontronite, etc.) are preferred, and hectorite (sodium hectorite) and bentonite (sodium bentonite) are more preferred.

The lower limit of the particle size of the layered silicate compound is preferably 0.01 μm or more, more preferably 0.02 μm or more, and even more preferably 0.05 μm or more. As the particle size of the layered silicate compound increases, the anti-sedimentation properties and redispersibility of the abrasive grains improve. Further, the upper limit of the particle size of the layered silicate compound is preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 5 μm or less. As the particle size of the layered silicate compound becomes smaller, the surface precision improves. From the above, the particle size of the layered silicate compound is preferably 0.01 μm or more and 10 μm or less, more preferably 0.02 μm or more and 8 μm or less, and even more preferably 0.05 μm or more and 5 μm or less. .

Note that in this specification, the particle size of the layered silicate compound is defined as a value determined using an electron microscope. More specifically, the particle size of the layered silicate compound can be measured by the method described in Examples.

The concentration (content) of the layered compound in the polishing composition is preferably 0.01% by mass or more, more preferably 0.02% by mass or more. From the viewpoint of preventing sedimentation of abrasive grains and improving dispersibility, in some embodiments, the concentration (content) of the layered compound in the polishing composition may be 0.05% by mass or more, and may be 0.08% by mass or more. It may be at least 0.1% by mass, or at least 0.1% by mass. Further, the concentration (content) of the layered compound in the polishing composition is preferably 5% by mass or less, more preferably 2% by mass or less. Within this range, the effects of the present invention described above can be efficiently obtained. The concentration (content) of the layered compound in the polishing composition may be 1% by mass or less, or 0.5% by mass or less.

From the above, the concentration (content) of the layered compound in the polishing composition is preferably 0.01% by mass or more and 5% by mass or less, more preferably 0.02% by mass or more and 2% by mass or less. preferable. In some embodiments, the concentration (content) of the layered compound in the polishing composition may be 0.05% by mass or more and 1% by mass or less, and 0.08% by mass or more and 0.5% by mass or less. It may be 0.1% by mass or more and 0.5% by mass or less.

Although not particularly limited, from the viewpoint of better exhibiting the effect of containing a layered compound in the polishing composition, the concentration of the layered compound in the polishing composition (if it contains multiple layered compounds, The ratio (D/A) of the abrasive grain concentration (total concentration thereof) D [mass %] and abrasive grain concentration (if a plurality of abrasive grains are included, their total concentration) A [mass %] is 0.008 It is appropriate to set it above, and it is preferable to set it as 0.01 or more, for example, it can be set as 0.03 or more, 0.04 or more, 0.05 or more. D/A is not particularly limited, but it is appropriate to set it to 5.0 or less, preferably 2.0 or less, for example, 1.0 or less, 0.5 or less, 0.2 or less. can. From the above, it is appropriate that D/A is 0.008 or more and 5.0 or less, preferably 0.01 or more and 2.0 or less, for example, 0.03 or more and 1.0 or less, 0.01 or more and 2.0 or less. 04 or more and 0.5 or less, or 0.05 or more and 0.2 or less.

[Dispersion medium]
The polishing composition according to the present invention includes a dispersion medium for dispersing each component. Water is preferred as the dispersion medium. From the viewpoint of preventing the effects of other ingredients from being inhibited, it is preferable to use water that contains as few impurities as possible. Specifically, after removing impurity ions with an ion exchange resin, pure water is obtained by removing impurity ions through a filter. Water, ultrapure water, or distilled water is preferred.

[pH of polishing composition]
The lower limit of the pH of the polishing composition of the present invention is not particularly limited, but is preferably 1.0 or more. The pH of the polishing composition may be, for example, more than 1.0, more than 1.5, more than 1.5, or more than 2.0. Further, the upper limit of pH is not particularly limited, but is preferably 8.0 or less, more preferably less than 8.0, even more preferably 7.0 or less, and less than 7.0. It is particularly preferable. From the viewpoint of improving the buffering effect of the metal salt A, the upper limit of the pH may be 6.5 or less, or may be 6.0 or less. From the above, the pH of the polishing composition of the present invention may be 1.0 or more and 8.0 or less, more than 1.0 and less than 8.0, and 1.5 or more and 7.0 or less. may be greater than 1.5 and less than 7.0, and may be greater than or equal to 2.0 and less than or equal to 6.5.

The pH of the polishing composition can be adjusted by adding an acid or a salt thereof, a base or a salt thereof, which will be explained below.

[Other ingredients]
The polishing composition of the present invention may optionally include an acid or a salt thereof or a base or a salt thereof for adjusting the pH, a metal salt B other than the metal salt A, and an aqueous solution that acts on the surface of the object to be polished or the surface of the abrasive grain. The polishing material may further contain other components such as a synthetic polymer, an anticorrosive or chelating agent that suppresses corrosion of the object to be polished, a preservative having other functions, and a fungicide.

As the acid, both inorganic acids and organic acids can be used. Examples of inorganic acids include hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid. Examples of organic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n- -Heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, Maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, lactic acid, diglycolic acid, 2-furancarboxylic acid, 2,5-furandicarboxylic acid, 3-furancarboxylic acid, 2-tetrahydrofurancarboxylic acid, methoxyacetic acid, methoxy Examples include phenylacetic acid, phenoxyacetic acid, methanesulfonic acid, ethanesulfonic acid, sulfosuccinic acid, benzenesulfonic acid, toluenesulfonic acid, phenylphosphonic acid, hydroxyethane-1,1-diphosphonic acid, and the like. Further, examples of the salts include Group 1 element salts, Group 2 element salts, aluminum salts, ammonium salts, amine salts, and quaternary ammonium salts. These acids or salts thereof can be used alone or in combination of two or more. Among these, nitric acid and sulfuric acid are preferred.

The concentration (content) of the acid or its salt in the polishing composition may be adjusted as appropriate so that it falls within the above pH range.

Examples of bases or their salts include amines such as aliphatic amines and aromatic amines, organic bases such as quaternary ammonium hydroxide, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, magnesium hydroxide, Examples include hydroxides of Group 2 elements such as calcium hydroxide, and ammonia.

The concentration (content) of the base or its salt in the polishing composition may be adjusted as appropriate so as to fall within the above pH range.

Examples of the metal salt B include alkaline earth metal salts (Group 2 element salts). As the metal salt B, one type of alkaline earth metal salt may be used alone, or two or more types of alkaline earth metal salts may be used in combination. It is preferable that the metal salt B contains one or more of Mg, Ca, Sr, and Ba as elements belonging to alkaline earth metals. Among them, either Ca or Sr is preferred, and Ca is more preferred.

The type of salt in metal salt B is not particularly limited, and may be an inorganic acid salt or an organic acid salt. Examples of inorganic acid salts include hydrohalic acids such as hydrochloric acid, hydrobromic acid, and hydrofluoric acid, and salts of nitric acid, sulfuric acid, carbonic acid, silicic acid, boric acid, and phosphoric acid. Examples of organic acid salts include carboxylic acids such as formic acid, acetic acid, propionic acid, benzoic acid, glycinic acid, butyric acid, citric acid, tartaric acid, and trifluoroacetic acid; methanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, and toluene. Examples include salts of organic sulfonic acids such as sulfonic acid; organic phosphonic acids such as methylphosphonic acid, benzenephosphonic acid, and toluenephosphonic acid; organic phosphoric acids such as ethylphosphonic acid;

Specific examples of alkaline earth metal salts that can be selected as metal salt B include chlorides such as magnesium chloride, calcium chloride, strontium chloride, and barium chloride; bromides such as magnesium bromide; magnesium fluoride, calcium fluoride, and fluoride. Fluorides such as strontium chloride and barium fluoride; Nitrates such as magnesium nitrate, calcium nitrate, strontium nitrate, and barium nitrate; Sulfates such as magnesium sulfate, calcium sulfate, strontium sulfate, and barium sulfate; Magnesium carbonate, calcium carbonate, and strontium carbonate , carbonates such as barium carbonate; carboxylates such as calcium acetate, strontium acetate, calcium benzoate, calcium citrate; and the like.

Examples of water-soluble polymers include polycarboxylic acids such as polyacrylic acid, polysulfonic acids such as polyphosphonic acid and polystyrene sulfonic acid, polysaccharides such as chitansan gum and sodium alginate, cellulose derivatives such as hydroxyethyl cellulose and carboxymethyl cellulose, and polyethylene glycol. , polyvinyl alcohol, polyvinylpyrrolidone, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, sorbitan monooleate, and oxyalkylene polymers having one or more types of oxyalkylene units. Moreover, salts of the above compounds can also be suitably used as water-soluble polymers.

Examples of anticorrosive agents include amines, pyridines, tetraphenylphosphonium salts, benzotriazoles, triazoles, tetrazoles, benzoic acid, and the like. Examples of chelating agents include carboxylic acid chelating agents such as gluconic acid, amine chelating agents such as ethylenediamine, diethylenetriamine, and trimethyltetraamine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, hydroxyethylethylenediaminetriacetic acid, and triethylenetetraminehexaacetic acid. , polyaminopolycarboxylic chelating agents such as diethylenetriaminepentaacetic acid, 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri(methylenephosphonic acid), ethylenediaminetetrakis (methylenephosphonic acid), diethylenetriaminepenta( Organic phosphonic acid chelating agents such as methylenephosphonic acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, methanehydroxyphosphonic acid, and 1-phosphonobutane-2,3,4-tricarboxylic acid. , phenol derivatives, 1,3-diketones, and the like.

Examples of preservatives include sodium hypochlorite. Examples of antifungal agents include oxazolines such as oxazolidine-2,5-dione.

[Object to be polished]
The object to be polished according to the present invention is not particularly limited. For example, the object to be polished according to the present invention is a substrate having a surface made of a semiconductor material, that is, a semiconductor substrate. Examples of constituent materials of the semiconductor substrate include semiconductors made of Group 14 elements such as silicon and germanium; SiC, SiGe, ZnS, ZnSe, InP, AlN, GaAs, GaN, AlGaAs, InGaAs, GaP, ZnTe, and CdTd. Compound semiconductors such as; and the like can be mentioned. Among these, compound semiconductor substrates are preferred, and SiC (silicon carbide) substrates are more preferred.

Further, the material included in the object to be polished according to the present invention has a Vickers hardness of 500 Hv or more, for example. The Vickers hardness is preferably 700 Hv or more, for example 1000 Hv or more, or 1500 Hv or more. The Vickers hardness of the material included in the object to be polished may be 1800 Hv or more, 2000 Hv or more, or 2200 Hv or more. The upper limit of the Vickers hardness of the material included in the object to be polished is not particularly limited, and may be, for example, approximately 7000 Hv or less, 5000 Hv or less, or 3000 Hv or less. In addition, in this specification, Vickers hardness can be measured based on JIS R 1610:2003. The international standard corresponding to the above JIS standard is ISO 14705:2000.

From the above, the Vickers hardness of the material included in the polishing object according to the present invention may be 700 Hv or more and 7000 Hv or less, 1000 Hv or more and 5000 Hv or less, or 1500 Hv or more and 3000 Hv or less. In some embodiments, the Vickers hardness of the material included in the object to be polished may be 1800 Hv or more and 3000 Hv or less, or 2000 Hv or more and 3000 Hv or less.

Materials having a Vickers hardness of 1500 Hv or more include silicon carbide, silicon nitride, titanium nitride, gallium nitride, and the like. The object to be polished in the technique disclosed herein may have a single crystal surface of the above-mentioned material which is mechanically and chemically stable. Among these, the surface of the object to be polished is preferably made of either silicon carbide or gallium nitride, and more preferably made of silicon carbide. Silicon carbide is expected to be a compound semiconductor substrate material with low power loss and excellent heat resistance, and the practical advantage of improving productivity by increasing polishing removal rate is particularly large. The technique disclosed herein can be particularly preferably applied to polishing the surface of a silicon carbide single crystal.

[Method for producing polishing composition]
The method for producing the polishing composition of the present invention is not particularly limited, and includes, for example, stirring and mixing the abrasive grains, oxidizing agent, metal salt A, layered compound, and other components as necessary in a dispersion medium. It can be obtained by

The temperature at which each component is mixed is not particularly limited, but is preferably 10°C or higher and 40°C or lower, and may be heated to increase the dissolution rate. Further, the mixing time is not particularly limited either.

The polishing composition of the present invention was produced from the viewpoint of promoting the formation of a weak interaction between the layered compound and the abrasive grains, further suppressing the sedimentation of the abrasive grains, and further improving the redispersibility of the abrasive grains. After that, it is preferable to store the polishing composition at a predetermined temperature for a predetermined period of time, and to polish a semiconductor substrate, which is an object to be polished, using the polishing composition after this storage.

Specifically, the lower limit of the storage temperature is preferably 10°C or higher, more preferably 40°C or higher. Further, the upper limit of the storage temperature is not particularly limited, but is preferably 80°C or lower, and more preferably 60°C or lower.

Furthermore, the lower limit of the storage period is preferably 20 days or more, more preferably 60 days or more. Further, there is no particular upper limit on the storage period.

[Polishing method]
As described above, the polishing composition of the present invention is suitably used for polishing semiconductor substrates.

When polishing an object to be polished using the polishing composition of the present invention, it can be carried out using equipment and conditions used for ordinary polishing. General polishing devices include single-sided polishing devices and double-sided polishing devices.In single-sided polishing devices, a holder called a template is used to hold the object to be polished (preferably a substrate-like object to be polished), and the polishing device is polished. One side of the object to be polished is polished by pressing a surface plate with an abrasive cloth attached to one side of the object to be polished and rotating the surface plate while supplying the polishing composition. In double-sided polishing equipment, the object to be polished is held using a holder called a carrier, and a polishing composition is supplied from above while a surface plate with a polishing cloth affixed to the opposite surface of the object is pressed against the surface of the object. Both sides of the object to be polished are polished by rotating them in relative directions. At this time, the object is polished by a physical action caused by friction between the polishing pad and the polishing composition and the object to be polished, and a chemical action brought about by the polishing composition on the object.

The polishing pad used in the polishing method using the polishing composition of the present invention has different materials, such as polyurethane type, foamed polyurethane type, nonwoven fabric type, and suede type, as well as physical properties such as hardness and thickness. There are many different types, including those that contain abrasive grains and those that do not contain abrasive grains, but these can be used without restriction.

When polishing an object to be polished using the polishing composition of the present invention, the polishing composition once used for polishing can be recovered and used again for polishing. An example of a method for reusing the polishing composition is a method in which the polishing composition discharged from the polishing device is collected into a tank, and the polishing composition is circulated into the polishing device again for use. Circulating the polishing composition reduces the environmental impact by reducing the amount of polishing composition discharged as waste liquid, and reduces the amount of polishing composition used to reduce the impact on the object to be polished. This is useful in that it can reduce manufacturing costs associated with polishing.

When using the polishing composition of the present invention in circulation, some or all of the abrasive grains, oxidizing agent, metal salt A, layered compound, and other additives consumed or lost during polishing can be replaced with a composition conditioner. It can be added during cyclic use. In this case, the composition adjusting agent may be a mixture of abrasive grains, an oxidizing agent, metal salt A, a layered compound, and some or all of other additives at an arbitrary mixing ratio. By additionally adding a composition adjusting agent, the polishing composition is adjusted to a composition suitable for reuse, and polishing is suitably maintained. The concentrations of the abrasive grains, oxidizing agent, metal salt A, layered compound, and other additives contained in the composition adjusting agent are arbitrary and not particularly limited, but can be adjusted as appropriate depending on the size of the circulation tank and polishing conditions. Preferably.

The polishing composition of the present invention may be a one-component type or a multi-component type such as a two-component type. Further, the polishing composition of the present invention may be prepared by diluting the stock solution of the polishing composition, for example, 10 times or more using a diluent such as water.

Although embodiments of the invention have been described in detail, it is to be understood that this is intended to be illustrative and exemplary, and not restrictive, and that the scope of the invention is to be construed in accordance with the appended claims. It is.

The present invention includes the following aspects and forms.

1. The metal salt A includes abrasive grains, an oxidizing agent, a metal cation whose hydrated metal ion has a pKa of less than 7.0, a metal salt A which is a salt of an anion, a layered compound, and a dispersion medium. A polishing composition containing 8mM or more of:
2. 1. above, wherein the layered compound is a layered silicate compound. Polishing composition described in:
3. 1. above, wherein the average secondary particle diameter of the abrasive grains is 1.8 μm or less; or 2. Polishing composition described in:
4. 1. The oxidizing agent is permanganic acids. ~3. The polishing composition according to any one of:
5. 1. The polishing composition is a polishing composition used for polishing a semiconductor substrate, and the semiconductor substrate is a compound semiconductor substrate. ~4. The polishing composition according to any one of:
6. Above 1. ~5. A polishing method comprising polishing a semiconductor substrate using the polishing composition according to any one of the above.

The present invention will be explained in more detail using the following examples and comparative examples. However, the technical scope of the present invention is not limited only to the following examples.

[Examples 1 to 10, Comparative Examples 1 to 3]
(Preparation of polishing composition)
The abrasive grains (average secondary particle diameter 0.4 μm) were diluted with water to a concentration (content) of 1.0% by mass, and the layered compound was diluted to a concentration (content) shown in Table 1 below. In addition, an oxidizing agent and metal salt A were added to the concentrations (contents) shown in Table 1 below, and the mixture was stirred at room temperature (25°C) to prepare the polishing agents of Examples 1 to 10 and Comparative Examples 1 to 3. A composition was obtained. The pH of the polishing compositions of Examples 1 to 10 and Comparative Examples 2 to 3 was 3.7, and the pH of the polishing composition of Comparative Example 1 was adjusted to 3.0 using nitric acid.

<Abrasive>
Aluminum oxide (alumina): The average secondary particle diameter was measured using a laser diffraction/scattering particle size distribution analyzer LA-950 manufactured by Horiba, Ltd.

<Layered compound>
Bentonite: particle size 0.15μm
Hectorite: particle size 4.0μm or 1.3μm
Note that the particle diameter of the layered compound was determined by the following measurement. That is, 100 layered silicate compound particles are observed using a scanning electron microscope "SU8000" manufactured by Hitachi High-Technologies Corporation, and the smallest rectangle circumscribing each particle image is drawn. Then, the length of the long side of each rectangle drawn on the particle image was measured, and the average value thereof was defined as the particle diameter of the layered compound.

(Evaluation of anti-settling properties of abrasive grains)
Using the polishing composition that had been prepared and stored at 25°C for 1 to 2 days, the polishing composition was poured into a 100ml capacity colorimetric tube (manufactured by As One Corporation) up to the 100ml mark for 2 hours. I left it still. After standing still, the scale of the volume of the interface between the abrasive grain layer and the supernatant liquid was read and judged according to the following criteria. Ratings A, B, and C are passing:
A: More than 40 ml B: More than 30 ml but not more than 40 ml C: More than 20 ml and not more than 30 ml D: Not more than 20 ml.

(Evaluation of redispersibility of abrasive grains)
After preparing and storing the polishing composition for 1 to 2 days at 25°C, put the polishing composition into a 1000ml capacity PP container (manufactured by As One Co., Ltd.) up to the 800ml mark, and let it stand still for 72 hours. I placed it. After standing still, the PP container was shaken up and down, and the number of times until the abrasive grain precipitate was redispersed and disappeared was measured, and judged according to the following criteria. Ratings A, B, and C are passing:
A: 1 to 3 times B: 4 to 6 times C: 7 to 9 times D: 10 times or more.

(Evaluation of polishing)
After preparing and storing the polishing composition at 25° C. for 1 to 2 days, polishing was performed under the following polishing conditions to determine the polishing removal rate. In addition, the surface roughness of each polished object after polishing was measured using the following method:
<Polishing conditions>
Polishing device: EJ-380IN (manufactured by Nippon Engis Co., Ltd.)
Polishing pad: SUBA800 (manufactured by Nitta DuPont Co., Ltd.)
Polishing load: 300g/ ^cm2
Surface plate rotation speed: 80 rpm (80 min ^-1 )
Polishing time: 30min
<Object to be polished>
SiC substrate: 2 inch N type 4H-SiC 4°off Vickers hardness 2000Hv or more and 2400Hv or less.

<Polishing removal rate>
The polishing removal rate was calculated from the difference in mass of the polished object before and after polishing. The polishing removal rate of each example obtained is shown as a relative value with the result of Comparative Example 1 set as 100.

<Surface roughness Ra>
The surface roughness Ra of the polished object after polishing was measured using an atomic force microscope (manufactured by Park Systems, NX-HDM). Note that the surface roughness Ra is a parameter indicating the average amplitude of the roughness curve in the height direction, and indicates the arithmetic mean of the height of the surface of the polishing object within a certain field of view.

<Storage stability>
The storage stability of the polishing composition prepared above was evaluated by conducting an accelerated test in which it was stored in a 60°C environment. Specifically, a transparent polyethylene resin container is filled with the polishing composition according to each example and sealed, and the container is left standing in an environment of 60° C. until the pH of the polishing composition in the container is adjusted. The number of days until the temperature increased by 2 or more was recorded as storage stability. Note that the storage stability of 19 days in the accelerated test of storage at 60°C corresponds to approximately 12 months of storage stability when stored at 25°C based on Arrhenius law. The values shown in Table 1 below are the number of days in an accelerated test of storage at 60°C.

The compositions and evaluation results of the polishing compositions of Examples 1 to 10 and Comparative Examples 1 to 3 are shown in Table 1 below. Note that "-" in Table 1 below indicates that the component was not added.

As is clear from Table 1 above, when the polishing composition of the example containing the layered compound was used, good results were obtained in terms of anti-sedimentation properties and redispersibility of abrasive grains, and polishing performance. In particular, compared to Comparative Example 1 in which no layered compound was added, it was found that the anti-sedimentation properties and redispersibility of abrasive grains were improved while maintaining polishing performance such as polishing removal rate and Ra. Furthermore, compared to Comparative Examples 2 and 3 in which other dispersants were used, it was found that the redispersibility of abrasive grains was improved while maintaining polishing performance such as polishing removal rate and Ra.

This application is based on Japanese Patent Application No. 2022-118579 filed on July 26, 2022, the entire disclosure of which is incorporated herein by reference.

Claims

abrasive grains, an oxidizing agent, a metal cation with a hydrated metal ion having a pKa of less than 7.0, a metal salt A which is a salt of an anion, a layered compound, and a dispersion medium,
A polishing composition containing 8mM or more of the metal salt A.
The polishing composition according to claim 1, wherein the layered compound is a layered silicate compound.
The polishing composition according to claim 1 or 2, wherein the abrasive grains have an average secondary particle diameter of 1.8 μm or less.
The polishing composition according to claim 1 or 2, wherein the oxidizing agent is a permanganate.
The polishing composition according to claim 1 or 2, wherein the polishing composition is a polishing composition used for polishing a semiconductor substrate, and the semiconductor substrate is a compound semiconductor substrate.
A polishing method comprising the step of polishing a semiconductor substrate using the polishing composition according to claim 1 or 2.