Polishing composition, polishing method, and method for manufacturing semiconductor substrate

Abstract

To provide means for improving a ratio of an SiOC polishing rate to an SiN polishing rate.SOLUTION: A polishing composition contains: abrasive grains including at least one kind of zirconia particles; a selectivity improver which contains at least one kind of salt comprising a monovalent anion and a monovalent or higher cation and improves a ratio of an SiOC polishing rate to an SiN polishing rate; and a pH adjuster containing at least one kind of acid. The polishing composition has a pH higher than 3.0 and lower than 7.0. The zeta potential of the abrasive grains is a positive value.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polishing composition, a polishing method, and a method for producing a semiconductor substrate. [Background technology]

[0002] In recent years, new microfabrication technologies have been developed in response to the increasing integration and performance of LSI (Large Scale Integration). Chemical mechanical polishing (CMP) is one such technology, and it is frequently used in the LSI manufacturing process, particularly in the multi-layer wiring formation process, for planarizing interlayer insulating films, forming metal plugs, and forming buried wiring (damascene wiring).

[0003] Low-k materials are increasingly being used as interlayer insulating films in the multilayer wiring formation process to reduce inter-wiring capacitance. SiOC (carbon-containing silicon oxide, formed by doping SiO2 with C) formed using plasma CVD is widely used as a low-k material.

[0004] As a technique for polishing SiOC, Patent Document 1 discloses a polishing composition containing cerium-containing abrasive grains and hydroxyalkyl cellulose, and having a pH of 6.0 or higher. According to Patent Document 1, this composition can improve the polishing rate of SiOC. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-139349 Summary of the Invention [Problem to be solved by the invention]

[0006] Recently, substrates containing both SiOC and SiN (silicon nitride) have been used, and there is an increasing demand for selective polishing of SiOC on such substrates. However, the polishing composition described in Patent Document 1 has a problem in that the ratio (selectivity) of the polishing rate of SiOC to the polishing rate of SiN is sometimes low.

[0007] Therefore, an object of the present invention is to provide a means for improving the ratio of the polishing rate for SiOC to the polishing rate for SiN. [Means for solving the problem]

[0008] The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result, have found that the above-mentioned problems can be solved by controlling the pH and the zeta potential of a polishing composition containing zirconia particles (abrasive grains), a salt (selectivity improver) consisting of a monovalent anion and a monovalent or polyvalent cation, and an acid (pH adjuster), within specific ranges, thereby completing the present invention.

[0009] That is, one aspect of the present invention is a polishing composition comprising abrasive grains containing at least one type of zirconia grains, a selectivity enhancer containing at least one salt composed of a monovalent anion and a monovalent or higher cation and which improves the ratio of the polishing rate for SiOC to the polishing rate for SiN, and a pH adjuster containing at least one acid, wherein the pH is greater than 3.0 and less than 7.0, and the zeta potential of the abrasive grains is a positive value. [Effects of the Invention]

[0010] According to the present invention, the ratio of the polishing rate for SiOC to the polishing rate for SiN can be improved. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described, but the technical scope of the present invention should be determined based on the claims and is not limited to the following embodiments.

[0012] Unless otherwise specified, in this specification, operations and measurements of physical properties are performed at room temperature (20°C to 25°C) and a relative humidity of 40% RH to 50% RH. In this specification, the ratio of the polishing rate of SiOC to the polishing rate of SiN is also simply referred to as the "selectivity ratio," and a selectivity enhancer that improves the ratio of the polishing rate of SiOC to the polishing rate of SiN is also simply referred to as the "selectivity enhancer." The embodiments described in this specification can be combined in any manner to form other embodiments.

[0013] One aspect of the present invention is a polishing composition comprising abrasive grains containing at least one type of zirconia grains, a selectivity enhancer containing at least one salt of a monovalent anion and a monovalent or higher cation, which enhances the ratio of the polishing rate for SiOC to the polishing rate for SiN, and a pH adjuster containing at least one acid, wherein the pH is greater than 3.0 and less than 7.0, and the zeta potential of the abrasive grains is positive. This configuration allows the ratio (selectivity) of the polishing rate for SiOC to the polishing rate for SiN to be improved.

[0014] The mechanism by which the above-described effects are obtained is believed to be as follows: However, the following mechanism is merely speculation, and the scope of the present invention is not limited thereby.

[0015] Zirconia particles as abrasive grains can polish SiOC at a higher rate than silica particles, ceria particles, and alumina particles.

[0016] In the case of salts consisting of monovalent anions and monovalent or higher cations used as selectivity enhancers, the monovalent anions adhere to the surface of abrasive grains, including zirconia particles, reducing the hydrophilicity of the surface. This allows the abrasive grains to more easily approach the highly hydrophobic SiOC surface, improving the SiOC removal rate. On the other hand, when salts consisting of divalent or higher anions and monovalent or higher cations are used, the anions adhere to the abrasive grains, causing the abrasive grains to have a negative zeta potential, which can repel the negatively charged SiOC surface from the abrasive grains. As a result, the SiOC removal rate decreases, and sufficient selectivity may not be achieved.

[0017] As mentioned above, the anions of the acid used as a pH adjuster adhere to the surface of the abrasive grains, including zirconia particles, reducing the hydrophilicity of the surface. This allows the abrasive grains to approach the highly hydrophobic surface of SiOC, thereby increasing the polishing rate of SiOC. The pH adjuster also controls the pH of the polishing composition to greater than 3.0 and less than 7.0. A pH within the above range provides a sufficient improvement in selectivity. On the other hand, if the pH is 3.0 or less, the surface of the SiOC becomes positively charged, repelling the abrasive grains, which have a positive zeta potential, potentially reducing the polishing rate of SiOC. If the pH is 7.0 or more, the zeta potential of the abrasive grains, including zirconia particles, approaches zero, reducing the repulsion between the abrasive grains and potentially causing aggregation. (Note that the isoelectric point of zirconia particles is typically pH 7.0 to 9.0 (near 8.0).)

[0018] Furthermore, when the pH is in the range of more than 3.0 and less than 7.0, the abrasive grains containing zirconia particles have a positive (+) zeta potential in the polishing composition, and the abrasive grains having a positive (+) zeta potential are attracted to the negatively (-) charged surface of the SiOC, thereby improving the polishing rate of the SiOC.

[0019] Therefore, by applying the polishing composition of this embodiment to an object to be polished that contains SiOC and SiN, it is possible to polish the SiOC at a high rate, and as a result, it is possible to significantly improve the ratio of the polishing rate of SiOC to the polishing rate of SiN.

[0020] The polishing composition according to this embodiment will be described in detail below.

[0021] [Polished object] The object to be polished with the polishing composition of this embodiment preferably contains SiOC (carbon-added silicon oxide) and SiN (silicon nitride).

[0022] The object to be polished may further include materials other than SiOC and SiN. Examples of other materials include silicon oxide, single crystal silicon, polycrystalline silicon (polysilicon), amorphous silicon (amorphous silicon), polycrystalline silicon doped with n-type or p-type impurities, amorphous silicon doped with n-type or p-type impurities, SiGe, metals (e.g., tungsten, copper, cobalt, hafnium, nickel, gold, silver, platinum, palladium, rhodium, ruthenium, iridium, osmium, etc.), metal nitrides (e.g., tantalum nitride (TaN), titanium nitride (TiN), etc.), and organic materials (e.g., amorphous carbon, spin-on carbon (SOC), diamond-like carbon (DLC), nanocrystalline diamond, graphene, etc.).

[0023] Films containing these materials can be formed by chemical vapor deposition (CVD), physical vapor deposition (PVD), spin coating, or the like.

[0024] [Abrasive grain] The polishing composition according to this embodiment contains zirconia particles as abrasive grains. The zirconia particles have the function of mechanically polishing an object to be polished. The zirconia particles may be used singly or in combination of two or more types. The zirconia particles may be commercially available or synthetic. Note that zirconia usually contains hafnia (HfO2), which is an unavoidable impurity. In this specification, values ​​related to the composition, such as the content, are values ​​calculated by regarding the unavoidable impurity hafnia (HfO2) as zirconia (ZrO2).

[0025] The zirconia particles are preferably colloidal zirconia particles or crushed / calcined zirconia particles, and more preferably colloidal zirconia particles. The zirconia particles may be undoped or may be doped with, for example, yttrium (Y) or its oxide, calcium oxide, or magnesium oxide. The crystal structure of the zirconia particles is not particularly limited and may be monoclinic, tetragonal, or cubic.

[0026] The shape of the zirconia particles is not particularly limited and may be spherical or non-spherical. Specific examples of non-spherical shapes include polygonal prisms such as triangular prisms and quadrangular prisms, cylinders, bale-shaped cylinders in which the center is bulged more than the ends, doughnut-shaped discs with a central hole, plate-shaped zirconia particles, cocoon-shaped zirconia particles with a central constriction, associative spheres in which multiple particles are integrated, confetti-shaped zirconia particles with multiple protrusions on the surface, rod-shaped zirconia particles, diamond-shaped zirconia particles, square zirconia particles, and rugby ball-shaped zirconia particles, and are not particularly limited thereto.

[0027] The zirconia particles are aggregates containing primary particles and / or secondary particles. The aggregates may be formed from a combination of individual particles, which are known in the art as primary particles, while the aggregated combination of particles is known in the art as secondary particles. The zirconia particles in the polishing composition may be in the form of primary particles or in the form of secondary particles, which are aggregates of primary particles. Alternatively, the zirconia particles may exist in both the form of primary particles and the form of secondary particles. In a preferred embodiment, the zirconia particles in the polishing composition are at least partially in the form of secondary particles.

[0028] The particle diameter of the zirconia particles according to this embodiment is preferably 5 nm to 200 nm, more preferably 10 nm to 150 nm, even more preferably 30 nm to 100 nm, and particularly preferably 50 nm to 90 nm. When the particle diameter of the zirconia particles is 5 nm or more, polishing becomes efficient and a sufficient polishing rate can be obtained. When the particle diameter of the zirconia particles is 200 nm or less, the dispersion stability of the polishing composition is excellent. In this specification, the particle diameter of the zirconia particles refers to the diameter of the particles when the cumulative particle volume from the fine particle side reaches 50% of the total particle volume in the particle size distribution determined by a laser diffraction scattering method (D50, hereinafter also simply referred to as "D50"). The D50 of the zirconia particles in this specification is a value measured by the method described in the Examples.

[0029] In this embodiment, one of the features of the polishing composition is that the abrasive grains (preferably zirconia particles) have a positive zeta potential. This allows the abrasive grains, which have a positive zeta potential, to be attracted to the negatively (-) charged surface of the SiOC, thereby improving the polishing rate of the SiOC. The zeta potential of the abrasive grains (preferably zirconia particles) in the polishing composition is preferably greater than 0 mV and not more than +70 mV, more preferably greater than +10 mV and not more than +60 mV, even more preferably greater than +20 mV and not more than +50 mV, and particularly preferably greater than +30 mV and not more than +45 mV. When the zeta potential of the abrasive grains (preferably zirconia particles) in the polishing composition is +10 mV or greater, the force with which the abrasive grains (preferably zirconia particles) are attracted to the negatively (-) charged surface of the SiOC increases, resulting in more efficient polishing. When the zeta potential of the abrasive grains (preferably zirconia particles) in the polishing composition is +70 mV or less, the abrasive grains can be easily removed by washing after polishing. The zeta potential of the abrasive grains in the polishing composition can be controlled by the type or amount of a pH adjuster or selectivity improver in the polishing composition. In this specification, the zeta potential of the abrasive grains is a value measured by the method described in the Examples.

[0030] The content (concentration) of abrasive grains (preferably zirconia grains) in the polishing composition is not particularly limited.In the case of the polishing composition (typically a slurry-like polishing liquid, sometimes referred to as working slurry or polishing slurry) that is used as a polishing liquid for polishing the object to be polished as it is, the content of abrasive grains is preferably 0.01 mass% or more and 10.0 mass% or less, more preferably 0.01 mass% or more and 5.0 mass% or less, even more preferably 0.01 mass% or more and 1.0 mass% or less, even more preferably 0.05 mass% or more and 1.0 mass% or less, particularly preferably 0.06 mass% or more and 0.50 mass% or less, and most preferably 0.07 mass% or more and 0.30 mass% or less.When the content of abrasive grains is within the above range, sufficient polishing speed can be obtained for SiOC, and a polishing composition with excellent cost performance can be obtained.

[0031] Furthermore, in the case of a polishing composition that is diluted and used for polishing (i.e., a concentrate or a working slurry stock solution), the content of abrasive grains is usually 30% by mass or less, preferably 25% by mass or less, from the viewpoints of storage stability, filterability, etc. Furthermore, from the viewpoint of utilizing the advantages of forming a concentrate, the content of abrasive grains is preferably 0.3% by mass or more, more preferably 0.5% by mass or more.

[0032] When the polishing composition contains two or more types of abrasive grains, the content of the abrasive grains refers to the total amount of these.

[0033] The polishing composition according to this embodiment may further contain abrasive particles other than zirconia particles, provided that the effects of the present invention are not impaired. Such other abrasive particles may be inorganic particles, organic particles, or organic-inorganic composite particles. Specific examples of inorganic particles include unmodified silica, cation-modified silica, particles made of metal oxides such as alumina, ceria, and titania, silicon nitride particles, silicon carbide particles, and boron nitride particles. Specific examples of organic particles include polymethyl methacrylate (PMMA) particles. The other abrasive particles may be used alone or in combination of two or more types. Furthermore, the other abrasive particles may be commercially available products or synthetic products.

[0034] However, the content of the other abrasive grains is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and particularly preferably 1% by mass or less, based on the total mass of the abrasive grains. Most preferably, the content of the other abrasive grains is 0% by mass, i.e., the abrasive grains are composed only of zirconia particles.

[0035] [Selectivity enhancer] The polishing composition of this embodiment contains a selectivity improver that improves the ratio of the polishing rate for SiOC to the polishing rate for SiN. The selectivity improver contains at least one salt composed of a monovalent anion and a monovalent or higher valent cation. The salts may be used alone or in combination.

[0036] The anions that make up the salt must be monovalent. If divalent or higher anions are used, the anions may adhere to the abrasive grains, causing the abrasive grains to have a negative zeta potential. As a result, the polishing rate for SiOC may decrease, and sufficient selectivity may not be achieved. Examples of monovalent anions include halide ions such as fluoride ion, chloride ion, bromide ion, and iodide ion, nitrate ion, acetate ion, formate ion, propionate ion, butyrate ion, valerate ion, 2-methylbutyrate ion, n-hexanoate ion, 3,3-dimethylbutyrate ion, 2-ethylbutyrate ion, 4-methylpentanoate ion, n-heptanoate ion, 2-methylhexanoate ion, n-octanoate ion, 2-ethylhexanoate ion, benzoate ion, glycolate ion, salicylate ion, glycerate ion, lactate ion, 2-furancarboxylate ion, 3-furancarboxylate ion, 2-tetrahydrofurancarboxylate ion, methoxyacetate ion, methoxyphenylacetate ion, phenoxyacetate ion, methanesulfonate ion, ethanesulfonate ion, and isethionate ion. Among these, from the viewpoint of further improving the selectivity, nitrate ion and acetate ion are preferred, and acetate ion is more preferred.

[0037] The valence of the cation constituting the salt is not particularly limited, and may be monovalent, divalent, trivalent, etc. Examples of cations with a valence of mono or higher include sodium ions, potassium ions, lithium ions, calcium ions, magnesium ions, and ammonium ions. Among these, from the viewpoint of further improving the selectivity, sodium ions, potassium ions, and ammonium ions are preferred, and ammonium ions are more preferred.

[0038] Specific examples of salts include ammonium acetate, sodium acetate, potassium acetate, lithium acetate, magnesium acetate, calcium acetate, ammonium nitrate, sodium nitrate, potassium nitrate, lithium nitrate, magnesium nitrate, calcium nitrate, ammonium fluoride, sodium fluoride, potassium fluoride, lithium fluoride, magnesium fluoride, calcium fluoride, ammonium chloride, sodium chloride, potassium chloride, lithium chloride, magnesium chloride, calcium chloride, ammonium bromide, sodium bromide, potassium bromide, lithium bromide, magnesium bromide, calcium bromide, ammonium iodide, sodium iodide, potassium iodide, lithium iodide, magnesium iodide, calcium iodide, and the like. However, from the viewpoint of further improving the selectivity, ammonium acetate, sodium acetate, potassium acetate, and ammonium nitrate are preferred, ammonium acetate, sodium acetate, and potassium acetate are more preferred, and ammonium acetate is even more preferred. That is, according to a preferred embodiment of the present invention, the selectivity enhancer contains ammonium acetate. According to a preferred embodiment of the present invention, the selectivity enhancer consists solely of ammonium acetate.

[0039] The content (concentration) of the selectivity improver (preferably ammonium acetate) in the polishing composition is not particularly limited. In the case of a polishing composition (typically a slurry-like polishing liquid, sometimes referred to as a working slurry or polishing slurry) that is used as a polishing liquid for polishing an object to be polished as is, the content (concentration) of the selectivity improver is preferably 30 ppm or more and 2000 ppm or less, more preferably 50 ppm or more and 1000 ppm or less, even more preferably 75 ppm or more and 750 ppm or less, particularly preferably 100 ppm or more and 700 ppm or less, and most preferably 300 ppm or more and 600 ppm or less, based on the total mass of the polishing composition, from the viewpoint of improving the selectivity. When the content of the selectivity improver is within the above range, the selectivity can be further improved. In this specification, "ppm" means "mass ppm".

[0040] Furthermore, from the viewpoint of further improving the stability of the polishing composition, the content (concentration) of the selectivity improver (preferably ammonium acetate) is preferably 50 ppm or more and 500 ppm or less, more preferably 50 ppm or more and 200 ppm or less, relative to the total mass of the polishing composition.

[0041] In addition, in the case of a polishing composition to be diluted and used for polishing (i.e., a concentrate, a raw solution of a working slurry), the content (concentration) of the selectivity improver (preferably ammonium acetate) is usually 3% by mass (30,000 ppm) or less, preferably 2% by mass (20,000 ppm) or less, from the viewpoints of storage stability, filterability, etc. In addition, from the viewpoint of utilizing the advantages of forming a concentrate, the content of the selectivity improver is preferably 100 ppm or more, more preferably 500 ppm or more.

[0042] When the polishing composition contains two or more selectivity improving agents, the content of the selectivity improving agents refers to the total amount thereof.

[0043] Furthermore, the ratio of the amount of selectivity improving agent to the amount of abrasive grains (amount of selectivity improving agent / amount of abrasive grains) (mass ratio) is preferably 0.01 or more and 5 or less, more preferably 0.05 or more and 1 or less, even more preferably 0.1 or more and 0.8 or less, and even more preferably 0.3 or more and 0.7 or less. When the ratio of the amount of selectivity improving agent to the amount of abrasive grains is within the above range, the selectivity can be further improved.

[0044] The polishing composition of this embodiment may further contain, as a selectivity enhancer, a substance other than the salt composed of the monovalent anion and the monovalent or polyvalent cation, which has the function of improving the selectivity, within a range that does not impair the effects of the present invention. However, the content of the other substance is preferably 20 mass% or less, more preferably 10 mass% or less, even more preferably 5 mass% or less, and particularly preferably 1 mass% or less, based on the total mass of the selectivity enhancer. Most preferably, the content of the other substance is 0 mass%, i.e., the selectivity enhancer is composed only of a salt composed of a monovalent anion and a monovalent or polyvalent cation.

[0045] [Dispersion medium] The polishing composition of this embodiment preferably contains a dispersion medium for dispersing each component. Examples of dispersion mediums include water; alcohols such as methanol, ethanol, and ethylene glycol; ketones such as acetone; and mixtures thereof. Of these, water is preferred as the dispersion medium. That is, according to a preferred embodiment of the present invention, the dispersion medium contains water. According to a more preferred embodiment of the present invention, the dispersion medium consists essentially of water. Note that the above term "substantially" means that a dispersion medium other than water may be included as long as the intended effect of the present invention can be achieved. More specifically, the dispersion medium preferably consists of 90% by mass to 100% by mass of water and 0% by mass to 10% by mass of a dispersion medium other than water, and more preferably 99% by mass to 100% by mass of water and 0% by mass to 1% by mass of a dispersion medium other than water. Most preferably, the dispersion medium is water.

[0046] From the viewpoint of not inhibiting the action of the components contained in the polishing composition, it is preferable that the dispersion medium be water that contains as few impurities as possible. Specifically, pure water or ultrapure water that has had impurity ions removed using an ion exchange resin and then passed through a filter to remove foreign matter, or distilled water, is more preferable.

[0047] [pH and pH adjusters] The polishing composition according to the present invention has a pH of more than 3.0 and less than 7.0. If the pH is 3.0 or less, the polishing rate of SiOC decreases as described above, and the desired selectivity may not be obtained. If the pH is 7.0 or more, abrasive grains may aggregate as described above.

[0048] From the viewpoint of improving the selectivity, the pH of the polishing composition is preferably 3.5 or more and 6.5 or less, more preferably 4.0 or more and 6.0 or less, and even more preferably 4.5 or more and 5.5 or less. The pH of the polishing composition can be measured with a pH meter. The pH in this specification is the value measured by the method described in the Examples.

[0049] The polishing composition according to this embodiment contains a pH adjuster. The pH adjuster contains at least one acid. The acid may be either an inorganic acid or an organic acid. The acids may be used alone or in combination of two or more.

[0050] Specific examples of inorganic acids include hydrochloric acid, hydrofluoric acid, and nitric acid. Specific 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, lactic acid, 2-furancarboxylic acid, 3-furancarboxylic acid, 2-tetrahydrofurancarboxylic acid, methoxyacetic acid, methoxyphenylacetic acid, phenoxyacetic acid, methanesulfonic acid, ethanesulfonic acid, and isethionic acid. Among these, nitric acid and acetic acid are preferred, and acetic acid is more preferred, from the viewpoint of further improving the selectivity. That is, according to a preferred embodiment of the present invention, the pH adjuster contains acetic acid. According to a preferred embodiment of the present invention, the pH adjuster consists solely of acetic acid.

[0051] The amount of pH adjuster added is not particularly limited, and may be adjusted appropriately so that the polishing composition has a desired pH.

[0052] Although a base may be used as a pH adjuster if necessary, according to a preferred embodiment of the present invention, the pH adjuster consists of at least one acid.

[0053] [Additives] The polishing composition of this embodiment may further contain known additives that can be used in polishing compositions, such as dispersants, oxidizing agents, complexing agents, preservatives, and antifungal agents, within the range that does not impair the effects of the present invention. Since the polishing composition of this embodiment is acidic, it is preferable to contain an antifungal agent. Furthermore, it is also a preferred embodiment to contain a dispersant, as this improves the dispersion stability of abrasive grains (particularly zirconia particles). That is, in a preferred embodiment of the present invention, the polishing composition contains abrasive grains containing at least one type of zirconia particle, a selectivity enhancer containing at least one salt composed of a monovalent anion and a monovalent or higher cation and improving the ratio of the polishing rate of SiOC to the polishing rate of SiN, a pH adjuster containing at least one acid, a dispersion medium, and at least one selected from the group consisting of antifungal agents and dispersants. In a more preferred embodiment of the present invention, the polishing composition is substantially composed of an abrasive containing at least one type of zirconia particles, a selectivity enhancer containing at least one salt of a monovalent anion and a monovalent or higher cation, which improves the ratio of the polishing rate of SiOC to the polishing rate of SiN, a pH adjuster containing at least one acid, a dispersing medium, and at least one selected from the group consisting of an anti-fungal agent and a dispersing agent. Here, the phrase "the polishing composition is substantially composed of an abrasive containing at least one type of zirconia particles, a selectivity enhancer containing at least one salt of a monovalent anion and a monovalent or higher cation, which improves the ratio of the polishing rate of SiOC to the polishing rate of SiN, a pH adjuster containing at least one acid, a dispersing medium, and at least one selected from the group consisting of an anti-fungal agent and a dispersing agent" means that the total content of the abrasive, selectivity enhancer, pH adjuster, dispersing medium, and anti-fungal agent and / or dispersing agent exceeds 99% by mass (upper limit: 100% by mass) of the polishing composition. Preferably, the polishing composition comprises abrasive grains, a selectivity improving agent, a pH adjuster, a dispersion medium, and an antifungal agent and / or a dispersant (the total content above=100% by mass).

[0054] The antifungal agent (preservative) is not particularly limited and can be appropriately selected depending on the desired use and purpose. Specific examples include isothiazolin-based preservatives such as 1,2-benzisothiazol-3(2H)-one (BIT), 2-methyl-4-isothiazolin-3-one, and 5-chloro-2-methyl-4-isothiazolin-3-one, and phenoxyethanol.

[0055] Alternatively, the antifungal agent (antiseptic) may be a compound represented by the following Chemical Formula 1:

[0056] [ka]

[0057] In the above chemical formula 1, R 1 ~R 5 are each independently a hydrogen atom or a substituent composed of at least two atoms selected from the group consisting of carbon atoms, hydrogen atoms, and oxygen atoms.

[0058] Examples of the substituent composed of at least two types of atoms selected from the group consisting of carbon atoms, hydrogen atoms, and oxygen atoms include, for example, a hydroxy group, a carboxy group, an alkyl group having from 1 to 20 carbon atoms, a hydroxyalkyl group having from 1 to 20 carbon atoms, an alkoxy group having from 1 to 20 carbon atoms, a hydroxyalkoxy group having from 1 to 20 carbon atoms, an alkoxycarbonyl group having from 2 to 21 carbon atoms, an aryl group having from 6 to 30 carbon atoms, an aralkyl group (arylalkyl group) having from 7 to 31 carbon atoms, an aryloxy group having from 6 to 30 carbon atoms, an aryloxycarbonyl group having from 7 to 31 carbon atoms, an aralkyloxycarbonyl group having from 8 to 32 carbon atoms, an acyl group having from 1 to 20 carbon atoms, and an acyloxy group having from 1 to 20 carbon atoms.

[0059] More specifically, examples of alkyl groups having 1 to 20 carbon atoms include linear alkyl groups such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl groups; isopropyl, isobutyl, s-butyl, t-butyl, t-amyl, neopentyl, 3-methylpentyl, 1,1-diethylpropyl, 1,1-dimethylbutyl, 1-methyl-1-propylbutyl, 1,1-dipropylbutyl, and 1,1-dimethyl-2-methylpentyl groups. branched alkyl groups such as 1-methyl-1-isopropyl-2-methylpropyl group; and cyclic alkyl groups such as cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, and norbornenyl group.

[0060] Examples of hydroxyalkyl groups having 1 to 20 carbon atoms include a hydroxymethyl group, a 2-hydroxyethyl group, a 2-hydroxy-n-propyl group, a 3-hydroxy-n-propyl group, a 2-hydroxy-n-butyl group, a 3-hydroxy-n-butyl group, a 4-hydroxy-n-butyl group, a 2-hydroxy-n-pentyl group, a 3-hydroxy-n-pentyl group, a 4-hydroxy-n-pentyl group, a 5-hydroxy-n-pentyl group, a 2-hydroxy-n-hexyl group, a 3-hydroxy-n-hexyl group, a 4-hydroxy-n-hexyl group, a 5-hydroxy-n-hexyl group, and a 6-hydroxy-n-hexyl group.

[0061] Examples of the alkoxy group having from 1 to 20 carbon atoms include linear alkoxy groups such as a methoxy group, an ethoxy group, an n-propyloxy group, an n-butyloxy group, an n-pentyloxy group, an n-hexyloxy group, an n-heptyloxy group, an n-octyloxy group, an n-nonyloxy group, and an n-decyloxy group; an isopropyloxy group, an isobutyloxy group, an s-butyloxy group, a t-butyloxy group, a t-amyloxy group, a neopentyloxy group, a 3-methylpentyloxy group, and a 1,1-diethyloxy group. branched alkoxy groups such as a 1,1-dimethylbutyloxy group, a 1-methyl-1-propylbutyloxy group, a 1,1-dipropylbutyloxy group, a 1,1-dimethyl-2-methylpropyloxy group, and a 1-methyl-1-isopropyl-2-methylpropyloxy group; and cyclic alkoxy groups such as a cyclobutyloxy group, a cyclopentyloxy group, a cyclohexyloxy group, a cycloheptyloxy group, a cyclooctyloxy group, and a norbornenyloxy group.

[0062] Examples of hydroxyalkoxy groups having from 1 to 20 carbon atoms include a hydroxymethoxy group, a 2-hydroxyethoxy group, a 2-hydroxy-n-propyloxy group, a 3-hydroxy-n-propyloxy group, a 2-hydroxy-n-butyloxy group, a 3-hydroxy-n-butyloxy group, a 4-hydroxy-n-butyloxy group, a 2-hydroxy-n-pentyloxy group, a 3-hydroxy-n-pentyloxy group, a 4-hydroxy-n-pentyloxy group, a 5-hydroxy-n-pentyloxy group, a 2-hydroxy-n-hexyloxy group, a 3-hydroxy-n-hexyloxy group, a 4-hydroxy-n-hexyloxy group, a 5-hydroxy-n-hexyloxy group, and a 6-hydroxy-n-hexyloxy group.

[0063] Examples of alkoxycarbonyl groups having 2 to 21 carbon atoms include a methoxycarbonyl group, an ethoxycarbonyl group, a propoxycarbonyl group, a butoxycarbonyl group, a pentyloxycarbonyl group, a hexyloxycarbonyl group, an octyloxycarbonyl group, and a decyloxycarbonyl group.

[0064] Examples of the aryl group having 6 to 30 carbon atoms include a phenyl group, a naphthyl group, an anthranyl group, and a pyrenyl group.

[0065] Examples of aralkyl groups (arylalkyl groups) having from 7 to 31 carbon atoms include benzyl groups and phenethyl groups (phenylethyl groups), and examples of aryloxy groups having from 6 to 30 carbon atoms include phenyloxy groups (phenoxy groups), naphthyloxy groups, anthranyloxy groups, and pyrenyloxy groups.

[0066] Examples of the aryloxycarbonyl group having from 7 to 31 carbon atoms include a phenyloxycarbonyl group, a naphthyloxycarbonyl group, an anthranyloxycarbonyl group, and a pyrenyloxycarbonyl group.

[0067] Examples of the aralkyloxycarbonyl group having from 8 to 32 carbon atoms include a benzyloxycarbonyl group and a phenethyloxycarbonyl group.

[0068] Examples of the acyl group having 1 to 20 carbon atoms include a methanoyl group (formyl group), an ethanoyl group (acetyl group), a propanoyl group, a butanoyl group, a pentanoyl group, a hexanoyl group, an octanoyl group, a decanoyl group, and a benzoyl group.

[0069] Examples of the acyloxy group having from 1 to 20 carbon atoms include a formyloxy group, an acetyloxy group, a propanoyloxy group, a butanoyloxy group, a pentanoyloxy group, a hexanoyloxy group, an octanoyloxy group, a decanoyloxy group, and a benzoyloxy group.

[0070] Furthermore, the antifungal agent represented by the above chemical formula 1 is preferably at least one selected from the group consisting of compounds represented by the following chemical formulas 1-a to 1-c.

[0071] [ka]

[0072] In the above chemical formula 1, R 1 ~R 3 are each independently a substituent composed of at least two atoms selected from the group consisting of carbon atoms, hydrogen atoms, and oxygen atoms.

[0073] Examples of the substituent composed of at least two types of atoms selected from the group consisting of carbon atoms, hydrogen atoms, and oxygen atoms are the same as those described above, and therefore, description thereof will be omitted here.

[0074] More specific examples of the compound represented by the above chemical formula 1 include parahydroxybenzoic acid esters such as methyl parahydroxybenzoate, ethyl parahydroxybenzoate, butyl parahydroxybenzoate, and benzyl parahydroxybenzoate; salicylic acid, methyl salicylate, phenol, catechol, resorcinol, hydroquinone, isopropylphenol, cresol, thymol, phenoxyethanol, phenylphenols (2-phenylphenol, 3-phenylphenol, 4-phenylphenol), and 2-phenylethyl alcohol. Among these, from the viewpoint of more effectively achieving the desired effects of the present invention, the compound represented by the above chemical formula 1 is preferably at least one selected from the group consisting of ethyl parahydroxybenzoate, butyl parahydroxybenzoate, and phenylphenol, and more preferably butyl parahydroxybenzoate.

[0075] Alternatively, the antifungal agent (preservative) may be an unsaturated fatty acid. Examples of unsaturated fatty acids include monounsaturated fatty acids such as crotonic acid, myristoleic acid, palmitoleic acid, oleic acid, and ricinoleic acid; diunsaturated fatty acids such as sorbic acid, linoleic acid, and eicosadienoic acid; triunsaturated fatty acids such as linolenic acid, pinolenic acid, and eleostearic acid; and stearidonic acid and arabinose. Examples of the unsaturated fatty acid include tetraunsaturated fatty acids such as chidonic acid, pentaunsaturated fatty acids such as bosopentaenoic acid and eicosapentaenoic acid, and hexaunsaturated fatty acids such as docosahexaenoic acid and nisinic acid. Among these, sorbic acid is preferred as the unsaturated fatty acid, from the viewpoint of more effectively achieving the desired effects of the present invention.

[0076] In addition to the above, 1,2-alkanediols such as 1,2-pentanediol, 1,2-hexanediol, and 1,2-octanediol; alkyl glyceryl ethers such as 2-ethylhexylglyceryl ether (ethylhexylglycerin); capric acid, dehydroacetic acid, and other compounds may also be used as antifungal agents (preservatives).

[0077] The above antifungal agents (antiseptics) may be used alone or in combination of two or more kinds.

[0078] When the polishing composition contains an antifungal agent (antiseptic), the content (concentration) of the antifungal agent (antiseptic) in the polishing composition is not particularly limited. For example, in the case of a polishing composition (typically a slurry-like polishing liquid, sometimes referred to as a working slurry or polishing slurry) that is used as a polishing liquid for polishing an object to be polished as is, the lower limit of the content (concentration) of the antifungal agent (antiseptic) in the polishing composition is preferably 0.0001% by mass or more, more preferably 0.001% by mass or more, and even more preferably 0.01% by mass or more. In addition, the upper limit of the content (concentration) of the antifungal agent (antiseptic) is preferably 3% by mass or less, more preferably less than 1% by mass. That is, the content (concentration) of the antifungal agent (antiseptic) in the polishing composition is preferably 0.0001% by mass or more and 3% by mass or less, more preferably 0.001% by mass or more and 3% by mass or less, and even more preferably 0.01% by mass or more and less than 1% by mass. Within this range, a sufficient effect of inactivating or destroying microorganisms can be obtained.

[0079] In addition, in the case of a polishing composition (i.e., a concentrate or a working slurry stock solution) that is diluted and used for polishing, the content of the antifungal agent (antiseptic) is usually 10% by mass or less, and more preferably 5% by mass or less, from the viewpoint of improving the polishing rate, etc. Furthermore, from the viewpoint of reducing the burden of treating the polishing composition after use for polishing, i.e., waste liquid treatment, the content of the antifungal agent (antiseptic) is preferably 0.03% by mass or more, more preferably 0.3% by mass or more.

[0080] When the polishing composition contains two or more types of antifungal agents (preservatives), the above content refers to the total amount of these.

[0081] The dispersant is not particularly limited and can be appropriately selected depending on the desired application and purpose. From the viewpoint of dispersibility after storage (especially of zirconia particles), it is preferable to use a sugar alcohol. The surface of zirconia particles (abrasive grains) is usually hydrophobic, and the abrasive grains tend to aggregate together. Furthermore, the polishing composition of the present invention contains at least one salt consisting of a monovalent anion and a monovalent or polyvalent cation as a selectivity enhancer, thereby improving the electrical conductivity (EC) and reducing the electrostatic repulsion between zirconia particles (abrasive grains), thereby making the abrasive grains more likely to aggregate together. When a sugar alcohol is mixed with zirconia particles (abrasive grains), the hydrophobic groups (hydrocarbon groups) of the sugar alcohol adhere to the hydrophobic surface of the zirconia particles, orienting the hydroxyl groups of the sugar alcohol toward the outside of the zirconia particles, thereby hydrophilizing the zirconia particle surface. This hydrophilization makes the zirconia particles more easily mixed with the dispersion medium (especially water) and allows them to exist as separate particles. Furthermore, the sugar alcohol adheres to the surface of the abrasive grains, causing steric hindrance and suppressing aggregation between the abrasive grains. The mechanism for improving the dispersibility of zirconia particles is speculative, and the present invention is not limited to this speculation.

[0082] That is, in one embodiment of the present invention, the polishing composition further contains at least one dispersant selected from the group consisting of sugar alcohols.

[0083] The sugar alcohol is not particularly limited, but preferably has three or more hydroxy groups in the molecule. Specific examples include pentaerythritol, dipentaerythritol, sorbitan, adonitol, maltitol, threitol, erythritol, arabinitol, ribitol, xylitol, iditol, sorbitol, mannitol, lactitol, galactitol, dulcitol, talitol, allitol, perseitol, volemitol, D-erythro-L-galaoctitol, D-erythro-L-talooctitol, erythromannooctitol, D-threo-L-galaoctitol, D-arabo-D-mannononitol, D-gluco-D-galadesitol, bornesitol, conduritol, inositol, ononitol, pinitol, pinpollitol, quebrachitol, valienol, and biscumitol. Among these, straight-chain sugar alcohols are more preferred, specifically xylitol, sorbitol, adonitol, threitol, erythritol, arabinitol, ribitol, iditol, mannitol, galactitol, talitol, allitol, and perseitol are preferred, with xylitol and sorbitol being more preferred, and sorbitol being even more preferred. These sugar alcohols can be used alone or in combination of two or more.

[0084] The molecular weight of the sugar alcohol is not particularly limited, but is preferably 80 or more, more preferably 100 or more, and even more preferably 120 or more. The molecular weight of the sugar alcohol is also not particularly limited, but is preferably less than 1000, more preferably 600 or less, even more preferably 400 or less, and particularly preferably 200 or less. That is, the molecular weight of the sugar alcohol is preferably 80 or more and less than 1000, more preferably 100 or more and 600 or less, even more preferably 120 or more and 400 or less, and particularly preferably 120 or more and 200 or less.

[0085] When the polishing composition of the present invention further comprises a dispersant (particularly sugar alcohol), the content (concentration) of the dispersant (particularly sugar alcohol) is not particularly limited, and can be appropriately selected according to desired use and purpose.For example, in working slurry (polishing slurry), the content (concentration) of the dispersant (particularly sugar alcohol) in the polishing composition is, for example, 10 ppm or more, preferably 50 ppm or more, more preferably 80 ppm or more, and even more preferably 90 ppm or more, based on the total mass of the polishing composition.In addition, the upper limit of the content (concentration) of the dispersant (particularly sugar alcohol) in the polishing composition is, for example, 500 ppm or less, preferably 300 ppm or less, more preferably 200 ppm or less, and even more preferably less than 200 ppm, based on the total mass of the polishing composition. That is, the content (concentration) of dispersant (particularly sugar alcohol) in the polishing composition is, for example, 10 ppm or more and 500 ppm or less, preferably 50 ppm or more and 500 ppm or less, more preferably 80 ppm or more and 500 ppm or less, even more preferably 90 ppm or more and 300 ppm or less, particularly preferably 90 ppm or more and 200 ppm or less, and most preferably 90 ppm or more and less than 200 ppm, based on the total mass of the polishing composition.If the content of dispersant is within this range, the abrasive grains (particularly zirconia grains) can maintain good dispersibility even after long-term storage.

[0086] The polishing composition according to this embodiment may be a one-component type or a multi-component type such as a two-component type. The polishing composition according to this embodiment may be prepared by diluting the stock solution of the polishing composition with a diluent such as water, for example, 2 to 100 times, preferably 2 to 50 times, more preferably 3 to 10 times, by volume.

[0087] [Method for producing polishing composition] The method for producing the polishing composition according to this embodiment is not particularly limited, and can be obtained, for example, by stirring and mixing abrasive grains, a selectivity improver, a pH adjuster, and, if necessary, additives in a dispersion medium (preferably water). The details of each component are as described above.

[0088] The temperature at which the components are mixed is not particularly limited, but is preferably 10° C. to 40° C. Heating may be used to increase the dissolution rate. The mixing time is also not particularly limited as long as uniform mixing is achieved.

[0089] [Polishing method and semiconductor substrate manufacturing method] The polishing composition described above is suitable for polishing an object to be polished, including SiOC and SiN. Therefore, according to another aspect of the present invention, there is provided a polishing method comprising the step of polishing an SiOC and SiN object to be polished using the polishing composition described above. In addition, according to another aspect of the present invention, there is provided a method for producing a semiconductor substrate, comprising the step of polishing a semiconductor substrate containing SiOC and SiN using the polishing method described above.

[0090] As the polishing device, a general polishing device can be used, which is equipped with a holder for holding a substrate or the like having an object to be polished, a motor whose rotation speed can be changed, and a polishing platen onto which a polishing pad (polishing cloth) can be attached.

[0091] The polishing pad may be made of any material, including ordinary nonwoven fabric, polyurethane, porous fluororesin, etc. The polishing pad is preferably provided with grooves to allow the polishing liquid to accumulate.

[0092] Regarding the polishing conditions, for example, the rotation speed of the polishing platen and carrier was 10 rpm (0.17 s -1 ) or more 500rpm (8.33s -1 The pressure (polishing pressure) applied to the substrate having the object to be polished is preferably 0.5 psi (3.4 kPa) or more and 10 psi (68.9 kPa).

[0093] The method for supplying the polishing composition to the polishing pad is not particularly limited, and for example, a method of continuously supplying the polishing composition using a pump, etc. There is no limit to the amount of the polishing composition supplied, but it is preferable that the surface of the polishing pad is always covered with the polishing composition of the present invention.

[0094] After polishing, the substrate is washed with running water, and water droplets adhering to the substrate are removed by a spin dryer or the like, followed by drying, to obtain a substrate having a metal-containing layer.

[0095] Although the embodiments of the present invention have been described in detail, it is clear that this is by way of illustration and example only and not of limitation, and that the scope of the present invention should be interpreted by the appended claims.

[0096] The present invention encompasses the following aspects and configurations. 1. An abrasive grain comprising at least one type of zirconia grain; a selectivity enhancer containing at least one salt composed of a monovalent anion and a monovalent or higher valent cation, which enhances the ratio of the polishing rate for SiOC to the polishing rate for SiN; a pH adjuster comprising at least one acid; Including, pH is greater than 3.0 and less than 7.0, A polishing composition, wherein the abrasive grains have a positive zeta potential. 2. The polishing composition according to 1 above, wherein the concentration of the selectivity improver is 50 ppm or more and 1000 ppm or less. 3. The polishing composition according to 1. or 2. above, which has a pH of 4.0 or more and 6.0 or less. 4. The polishing composition according to any one of 1. to 3., wherein the pH adjuster contains acetic acid. 5. The polishing composition according to any one of 1. to 4., wherein the selectivity improver contains ammonium acetate. 6. The polishing composition according to any one of 1. to 5., wherein the content of the abrasive grains is 0.01% by mass or more and 1.0% by mass or less. 7. The polishing composition according to any one of 1. to 6. above, further comprising at least one dispersant selected from the group consisting of sugar alcohols. 8. A polishing method comprising the step of polishing an object containing SiOC and SiN with the polishing composition according to any one of 1. to 7. above. 9. A method for manufacturing a semiconductor substrate, comprising a step of polishing a semiconductor substrate containing SiOC and SiN by the polishing method described in 8. above.

Example

[0097] The present invention will be described 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. Unless otherwise specified, “%” and “parts” mean “mass %” and “parts by mass”, respectively.

[0098] [Measurement methods for various physical properties] In this example, various physical properties were measured by the following methods.

[0099] [Measurement of particle size (D50)] The D50 value of the zirconia particles was adopted as the volume average particle size measured by the dynamic light scattering method using a particle size distribution measuring device (NanoTrack UPA-UT151, manufactured by Microtrac·BEL Corporation). More specifically, a dispersion liquid in which zirconia particles were dispersed in water was used to measure the particle size of the zirconia particles. By analyzing with the measuring instrument, in the particle size distribution of the zirconia particles, the diameter (D50) of the particles when the integrated particle volume reached 50% of the total particle volume from the fine particle side was calculated.

[0100] [Measurement of zeta potential] The zeta potential of the zirconia particles was measured using a zeta potential measuring device (trade name “Zetasizer Nano ZSP”) manufactured by Malvern Panalytical.

[0101] [Measurement of pH] The pH of the polishing composition was measured using a pH meter (manufactured by Horiba, Ltd., model number: F-71).

[0102] [Preparation of polishing composition] (Example 1) Colloidal zirconia (ZSL-20N (ZrO2 sol) manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.) as abrasive grains was added to a final concentration of 0.10 mass% and ammonium acetate as a selectivity enhancer was added to a final concentration of 50 ppm to pure water as a dispersion medium at room temperature (25°C). Furthermore, BIT (1,2-benzisothiazol-3(2H)-one manufactured by San-ai Oil Co., Ltd.) as a fungicide was added to a final concentration of 0.3 g / kg (0.03 mass%) to obtain a mixed solution. Acetic acid was added as a pH adjuster to adjust the pH to 5.0, and the mixture was stirred and mixed at room temperature (25°C) for 30 minutes to prepare a polishing composition. The zeta potential of the colloidal zirconia in the obtained polishing composition was +35 mV. The particle size of the colloidal zirconia in the polishing composition was the same as that of the colloidal zirconia described above.

[0103] Example 2 A polishing composition was prepared in the same manner as in Example 1, except that ammonium acetate was added to pure water to a final concentration of 100 ppm. The zeta potential of the colloidal zirconia in the obtained polishing composition was +35 mV.

[0104] Example 3 A polishing composition was prepared in the same manner as in Example 1, except that ammonium acetate was added to pure water to a final concentration of 200 ppm. The zeta potential of the colloidal zirconia in the obtained polishing composition was +35 mV.

[0105] Example 4 A polishing composition was prepared in the same manner as in Example 1, except that ammonium acetate was added to pure water to a final concentration of 500 ppm. The zeta potential of the colloidal zirconia in the obtained polishing composition was +35 mV.

[0106] Example 5 A polishing composition was prepared in the same manner as in Example 1, except that ammonium acetate was added to pure water to a final concentration of 1000 ppm. The zeta potential of the colloidal zirconia in the obtained polishing composition was +35 mV.

[0107] Example 6 A polishing composition was prepared in the same manner as in Example 4, except that acetic acid was added to the mixed solution so that the pH was 4.0. The zeta potential of the colloidal zirconia in the resulting polishing composition was +37 mV.

[0108] Example 7 A polishing composition was prepared in the same manner as in Example 4, except that acetic acid was added to the mixed solution so that the pH was 4.5. The zeta potential of the colloidal zirconia in the resulting polishing composition was +35 mV.

[0109] Example 8 A polishing composition was prepared in the same manner as in Example 4, except that acetic acid was added to the mixed solution so that the pH was 6.0. The zeta potential of the colloidal zirconia in the resulting polishing composition was +30 mV.

[0110] Example 9 Ammonium nitrate was used as a selectivity enhancer instead of ammonium acetate, and A polishing composition was prepared in the same manner as in Example 4, except that nitric acid was used as a pH adjuster instead of acetic acid and acetic acid. The zeta potential of the colloidal zirconia in the obtained polishing composition was +36 mV.

[0111] Example 10 A polishing composition was prepared in the same manner as in Example 4, except that nitric acid was used as a pH adjuster instead of acetic acid. The zeta potential of the colloidal zirconia in the obtained polishing composition was +35 mV.

[0112] Example 11 A polishing composition was prepared in the same manner as in Example 4, except that potassium acetate was used as a selectivity improver instead of ammonium acetate. The zeta potential of the colloidal zirconia in the resulting polishing composition was +36 mV.

[0113] Example 12 Colloidal zirconia (ZSL-20N (ZrO2 sol) manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.) as abrasive grains was added to a final concentration of 0.10 mass %, ammonium acetate as a selectivity enhancer was added to a final concentration of 500 ppm, and sorbitol as a dispersant was added to a final concentration of 10 ppm to pure water as a dispersion medium at room temperature (25°C). Furthermore, BIT (1,2-benzisothiazol-3(2H)-one manufactured by San-ai Oil Co., Ltd.) as a fungicide was added to a final concentration of 0.3 g / kg (0.03 mass%) to obtain a mixed solution. Acetic acid was added to the obtained mixed solution as a pH adjuster to adjust the pH to 5.0, and the mixture was stirred and mixed at room temperature (25°C) for 30 minutes to prepare a polishing composition. The zeta potential of the colloidal zirconia in the obtained polishing composition was +35 mV. The particle size of the colloidal zirconia in the polishing composition was the same as that of the above-mentioned colloidal zirconia.

[0114] Example 13 A polishing composition was prepared in the same manner as in Example 12, except that sorbitol was added to pure water to a final concentration of 50 ppm. The zeta potential of the colloidal zirconia in the obtained polishing composition was +35 mV.

[0115] Example 14 A polishing composition was prepared in the same manner as in Example 12, except that sorbitol was added to pure water to a final concentration of 80 ppm. The zeta potential of the colloidal zirconia in the obtained polishing composition was +35 mV.

[0116] Example 15 A polishing composition was prepared in the same manner as in Example 12, except that sorbitol was added to pure water to a final concentration of 100 ppm. The zeta potential of the colloidal zirconia in the obtained polishing composition was +35 mV.

[0117] Example 16 A polishing composition was prepared in the same manner as in Example 12, except that sorbitol was added to pure water to a final concentration of 200 ppm. The zeta potential of the colloidal zirconia in the obtained polishing composition was +35 mV.

[0118] Example 17 A polishing composition was prepared in the same manner as in Example 12, except that sorbitol was added to pure water to a final concentration of 500 ppm. The zeta potential of the colloidal zirconia in the obtained polishing composition was +35 mV.

[0119] Example 18 A polishing composition was prepared in the same manner as in Example 15, except that xylitol was used as a dispersant instead of sorbitol. The zeta potential of the colloidal zirconia in the obtained polishing composition was +35 mV.

[0120] (Comparative Example 1) A polishing composition was prepared in the same manner as in Example 1, except that no selectivity improving agent was added and that nitric acid was used as a pH adjuster instead of acetic acid. The zeta potential of the colloidal zirconia in the obtained polishing composition was +34 mV.

[0121] (Comparative Example 2) Except for not adding a selectivity improving agent, a polishing composition was prepared in the same manner as in Example 1. The zeta potential of colloidal zirconia in the resulting polishing composition was +36 mV.

[0122] (Comparative Example 3) A polishing composition was prepared in the same manner as in Example 4, except that ammonium oxalate monohydrate was used instead of ammonium acetate. The zeta potential of the colloidal zirconia in the obtained polishing composition was −32 mV.

[0123] Comparative Example 4 Except for using triammonium citrate instead of ammonium acetate, a polishing composition was prepared in the same manner as in Example 4. The zeta potential of the colloidal zirconia in the obtained polishing composition was −39 mV.

[0124] (Comparative Example 5) A polishing composition was prepared in the same manner as in Example 4, except that acetic acid was added to the mixed solution so that the pH was 3.0. The zeta potential of the colloidal zirconia in the resulting polishing composition was +39 mV.

[0125] (Comparative Example 6) A polishing composition was prepared in the same manner as in Example 4, except that acetic acid was added to the mixed solution so that the pH was 7.0. The zeta potential of the colloidal zirconia in the obtained polishing composition could not be measured because the colloidal zirconia was aggregated.

[0126] (Comparative Example 7) A polishing composition was prepared in the same manner as in Example 4, except that acetic acid was added to the mixture so that the pH was 8.0. The zeta potential of the colloidal zirconia in the resulting polishing composition could not be measured because the colloidal zirconia aggregated.

[0127] (Comparative Example 8) A polishing composition was prepared in the same manner as in Example 4, except that colloidal zirconia (ZSL00014 (ZrO sol), zirconia particle D50: 15 nm, manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.) was added as abrasive grains instead of colloidal zirconia (ZSL-20N) to pure water to a final concentration of 1.0 mass %. The zeta potential of the colloidal zirconia in the resulting polishing composition was -23 mV.

[0128] (Comparative Example 9) A polishing composition was prepared in the same manner as in Comparative Example 1, except that colloidal silica (D50: 70 nm) having amino groups fixed to the surface was used as the abrasive grains instead of colloidal zirconia (ZSL-20N). The zeta potential of the colloidal zirconia in the obtained polishing composition was +24 mV.

[0129] (Comparative Example 10) A polishing composition was prepared in the same manner as in Comparative Example 1, except that colloidal ceria (D50: 70 nm) was used as the abrasive grains instead of colloidal zirconia (ZSL-20N). The zeta potential of the colloidal zirconia in the obtained polishing composition was +33 mV.

[0130] (Comparative Example 11) A polishing composition was prepared in the same manner as in Comparative Example 1, except that colloidal alumina (D50: 300 nm) was used as abrasive grains instead of colloidal zirconia (ZSL-20N). The zeta potential of the colloidal zirconia in the obtained polishing composition was +29 mV.

[0131] [Polishing speed] As the objects to be polished (substrates), a 300 mm wafer ((SiOC film), manufactured by Advanced Materials Technology Co., Ltd., product name: BD2x 5kA Blanket) and a 300 mm wafer (SiN (silicon nitride film), manufactured by Advanced Materials Technology Co., Ltd., product name: LP-SiN 3.5KA Blanket) were prepared.

[0132] Using the polishing composition obtained above, the prepared substrate was polished under the following polishing conditions, and the removal rate was measured: (polishing conditions) Polishing machine: EJ-380IN-CH (Engis Japan Co., Ltd.) Polishing pad: Hard polyurethane pad (Nitta DuPont, IC1010) Polishing pressure: 3.0 psi (1 psi = 6894.76 Pa) Platen rotation speed: 60 rpm Head (carrier) rotation speed: 60 rpm Flow rate of polishing composition: 100 ml / min Polishing time: 30 seconds.

[0133] (polishing speed) The film thickness was measured using an optical interference film thickness measuring device (manufactured by SCREEN Holdings Co., Ltd., model number: Lambda Ace VM-2030), and the polishing rate was evaluated by dividing the difference in film thickness before and after polishing by the polishing time (see the formula below). The polishing rate for SiOC is preferably 1700 Å / min or more, and the polishing rate for SiN is preferably less than 30 Å / min.

[0134]

number

[0135] (selectivity) The selectivity was determined by dividing the polishing rate for the SiOC substrate obtained above by the polishing rate for the SiN substrate. The selectivity is preferably 100 or more.

[0136] [Storage stability] The average secondary particle size (D50) of the zirconia particles in each polishing composition was measured at room temperature (25°C) by dynamic light scattering using a particle size distribution analyzer (Nanotrac UPA-UT151, manufactured by Microtrac Bell). Specifically, the particle diameter D50 (nm) when the cumulative particle volume from the fine particle side reaches 50% of the total particle volume in the particle size distribution of the zirconia particles was calculated by analysis using the measuring instrument, and this was defined as the average secondary particle size (D50 A )(nm).

[0137] Separately, 100 g of each polishing composition was weighed into a plastic bottle. Then, each plastic bottle was placed in a thermostatic chamber set at 80° C. and left for 2 weeks. After being left for a predetermined period, the average secondary particle size (D50) of the zirconia particles in each polishing composition was measured. B ) (nm) is measured in the same manner as above.

[0138] The average secondary particle size (D50 A (nm) and D50 B Based on the calculated average secondary particle size (nm), the increase rate (%) of the average secondary particle size was calculated according to the following formula, and this was used as an index of storage stability. The smaller the absolute value of storage stability (increase rate of average secondary particle size) (%), the better the storage stability. An absolute value of storage stability (increase rate of average secondary particle size) (%) of 40% or less is acceptable, preferably 35% or less, more preferably 25% or less, even more preferably less than 10%, and particularly preferably less than 5%.

[0139]

number

[0140] The evaluation results of the polishing compositions of the Examples and Comparative Examples are shown in the following Table 1. In Table 1, "-" indicates that the agent was not used.

[0141] [Table 1]

[0142] As shown in Table 1, the polishing compositions of the examples can polish SiOC at a high polishing rate while keeping the polishing rate of SiN low, and therefore it is clear that the ratio (selectivity) of the polishing rate of SiOC to the polishing rate of SiN can be improved.

Claims

1. abrasive grains comprising at least one type of zirconia grain; a selectivity enhancer containing at least one salt composed of a monovalent anion and a monovalent or higher valent cation, which enhances the ratio of the polishing rate for SiOC to the polishing rate for SiN; a pH adjuster comprising at least one acid; Including, The pH is greater than 3.0 and less than 7.0, A polishing composition, wherein the abrasive grains have a positive zeta potential.

2. 2. The polishing composition according to claim 1, wherein the concentration of the selectivity improver is 50 ppm or more and 1000 ppm or less.

3. 2. The polishing composition according to claim 1, having a pH of 4.0 or more and 6.0 or less.

4. The polishing composition according to claim 1 , wherein the pH adjuster comprises acetic acid.

5. The polishing composition according to claim 1 , wherein the selectivity enhancer comprises ammonium acetate.

6. 2. The polishing composition according to claim 1, wherein the content of the abrasive grains is 0.01% by mass or more and 1.0% by mass or less.

7. The polishing composition according to claim 1 , further comprising at least one dispersant selected from the group consisting of sugar alcohols.

8. A polishing method comprising the step of polishing an object containing SiOC and SiN with the polishing composition according to any one of claims 1 to 7.

9. A method for manufacturing a semiconductor substrate, comprising the step of polishing a semiconductor substrate containing SiOC and SiN by the polishing method according to claim 8.

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