Polishing composition

Abstract

To provide a polishing composition that allows high-speed polishing of an object to be polished including an organic film, and can suppress the residue of abrasive grains after polishing.SOLUTION: The polishing composition for polishing an object to be polished comprises abrasive grains and a liquid medium. The abrasive grains include zirconia particles. The composite elastic modulus of the zirconia particles is 50 to 220 GPa.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polishing composition. [Background technology]

[0002] In recent years, new microfabrication technologies have been developed in response to the increasing integration and performance of semiconductor integrated circuits (hereinafter referred to as "LSIs"). CMP is one such technology, and is frequently used in LSI manufacturing processes (especially for planarizing interlayer insulating materials in the multilayer wiring formation process, forming metal plugs, forming buried wiring, etc.).

[0003] Films primarily composed of organic compounds are often used in LSI manufacturing processes, and several publications have attempted to provide polishing solutions capable of polishing such organic film-based films using the CMP process. For example, Patent Document 1 provides a polishing solution for polishing organic films, which has a pH of 5.0 or less and contains 2.0 to 15.0 mass% of an organic solvent, abrasive grains, and water, with the abrasive grains having a degree of association (measured by the ratio of secondary particle size to primary particle size) of 2.7 or less. This publication discloses that adding an organic solvent to the polishing solution makes the organic film-based film more easily polishable (i.e., a state of enhanced reactivity), thereby enabling the film-based film to be polished at a good polishing rate. This publication also discloses that, while examples of abrasive grains include silica, alumina, ceria, titania, zirconia, and germania, silica is preferred for achieving a desired polishing rate for organic films and for ease of selecting the abrasive grain size. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-60888 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a polishing composition capable of polishing an object containing an organic film at high speed.

[0006] In the course of intensive research to solve this problem, the present inventors have also discovered a new problem that abrasive grains may remain on the polished object after polishing. Therefore, a further object of the present invention is to provide a polishing composition that can suppress the remaining abrasive grains after polishing. [Means for solving the problem]

[0007] One aspect of the present invention is a polishing composition for polishing an object to be polished, comprising abrasive grains and a liquid medium, wherein the abrasive grains include zirconia grains, and the zirconia grains have a composite elastic modulus of 50 to 220 GPa. [Effects of the Invention]

[0008] According to the present invention, there is provided a polishing composition capable of polishing an object containing an organic film at high speed, and a polishing composition capable of suppressing the residual abrasive grains on the surface of the polished object after polishing. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing a layer-by-layered structure of zirconia and polystyrene sulfonic acid (PS). [Figure 2] 1 shows cross-sectional SEM images of the ZrO 2 layer of zirconia particles of Example 1, zirconia particles of Example 5, and zirconia particles of Comparative Example 2. [Figure 3] FIG. 1 is a diagram showing a load-displacement curve of zirconia particles. [Figure 4] This is a schematic diagram of a mechanochemical reaction using a shaker. [Figure 5] FIG. 1 shows curve fitting of an XPS C1s spectrum. DETAILED DESCRIPTION OF THE INVENTION

[0010] In this specification, "X to Y" means "X or more and Y or less," with the preceding and following numerical values ​​(X and Y) being included as upper and lower limits. When multiple "X to Y" are used, for example, "X1 to Y1" or "X2 to Y2," the disclosure of each numerical value as an upper limit, the disclosure of each numerical value as a lower limit, and combinations of these upper and lower limits are all disclosed (i.e., they serve as legitimate grounds for correction). Specifically, corrections of X1 or more, corrections of Y2 or less, corrections of X1 or less, corrections of Y2 or more, corrections of X1 to X2, and corrections of X1 to Y2, etc., must all be deemed legitimate. Unless otherwise specified, operations and measurements of physical properties are performed at room temperature (20 to 25°C) and a relative humidity of 40 to 50% RH. The concentrations described herein may be concentrations at the point of use (POU) or concentrations before dilution to the POU concentration. The dilution ratio may be 2 to 10 times. Furthermore, it should be understood that all combinations of embodiments and explanations disclosed in this specification are disclosed in the present application. In other words, it should be understood that they can be used as a basis for amendment. Furthermore, when the content or concentration of each component is described, if two or more components are included, it may be the total amount.

[0011] <Polishing composition> The present invention provides a polishing composition for polishing an object to be polished, comprising abrasive grains and a liquid medium, the abrasive grains comprising zirconia particles, the zirconia particles having a composite elastic modulus of 50 to 220 GPa. This configuration provides a polishing composition capable of polishing an object to be polished, including an organic film, at high speed. Furthermore, the present invention provides a polishing composition capable of suppressing the residual abrasive grains on the surface of the object to be polished after polishing.

[0012] [Polished object] The object to be polished preferably includes an organic film, more preferably a material containing a graphite component. Examples of the object to be polished include graphene, graphite, amorphous carbon, spin-on carbon (SOC), and diamond-like carbon (DLC). Among them, sp such as graphene or graphite is preferred. 2 It is preferable that the film has a sheet-like substance of carbon atoms having hybrid orbitals.The film having the object to be polished can be formed by, for example, CVD, PVD, or spin coating.

[0013] The object to be polished may be silicon oxide, single crystal silicon, polycrystalline silicon (polysilicon), amorphous silicon, polycrystalline silicon doped with n-type or p-type impurities, amorphous silicon doped with n-type or p-type impurities, a metal element, or SiGe. Examples of objects to be polished that contain silicon oxide include TEOS (Tetraethyl Orthosilicate)-type silicon oxide surfaces produced using tetraethyl orthosilicate as a precursor. Examples of metal elements include tungsten, copper, cobalt, hafnium, nickel, gold, silver, platinum, palladium, rhodium, ruthenium, iridium, and osmium.

[0014] According to one embodiment of the present invention, the object to be polished is substantially free of materials having metal-nitrogen bonds. Examples of materials having metal-nitrogen bonds include silicon nitride (SiN), tantalum nitride (TaN), and titanium nitride (TiN). The phrase "the object to be polished is substantially free of materials having metal-nitrogen bonds" means that the object to be polished does not contain materials having metal-nitrogen bonds, or if it does contain materials, the amount is below the detection limit.

[0015] [Abrasive grain] In the present invention, the abrasive grains contain zirconia grains having a composite elastic modulus of 50 to 220 GPa. The zirconia grains of the present invention have an appropriate hardness, with a composite elastic modulus of 50 to 220 GPa. By using such abrasive grains, it is possible to polish the object to be polished (organic film, particularly sp such as graphite). 2 The present invention can polish a sheet-like material of carbon atoms having hybrid orbitals at high speed, and can suppress the residue of abrasive grains (zirconia particles) after polishing. The mechanism, which does not limit the present invention, will be explained below. The zirconia particles of the present invention have a composite elastic modulus of 50 GPa or more, i.e., a sufficiently high hardness, and can apply a high mechanical stress to the object to be polished when they come into contact with the object to be polished. When the object to be polished is particularly made of sp such as graphite, 2 Zirconia is a sheet-like material of carbon atoms with hybrid orbitals, and its high mechanical stress causes the zirconium atoms that make up zirconia to separate into sp atoms such as those in graphite. 2 A covalent bond (Zr-C) is formed between the zirconia particles and the carbon atoms with hybrid orbitals. The energy of the covalent bond (Zr-C) formed is stronger than the interlayer bond energy in the graphite structure, so when the zirconia particles are pressed against the object to be polished by the polishing pad and slide over the object, delamination of the graphite structure is easily caused.

[0016] On the other hand, if the composite modulus of zirconia particles is too high, the formation of covalent bonds (Zr-C) between carbon atoms is excessively promoted, resulting in the formation of sp bonds such as those in graphite. 2 The bonding strength of the carbon atoms with hybrid orbitals with the sheet material becomes too strong, resulting in an increase in the number of zirconia particles remaining after polishing. In the present invention, the composite elastic modulus of the zirconia particles contained in the abrasive grains is 220 GPa or less, so excessive covalent bonds (Zr-C) are not formed, thereby suppressing the remaining abrasive grains.

[0017] According to an embodiment of the present invention, the composite elastic modulus of the zirconia particles is 55 to 200 GPa, 60 to 190 GPa, 70 to 180 GPa, 80 to 170 GPa, 90 to 160 GPa, or 100 to 155 GPa. By being in such a range, the polishing rate of the object to be polished can be significantly improved, and the remaining of abrasive grains after polishing can be suppressed.

[0018] In addition, the formation of a covalent bond (Zr-C) between zirconia and graphite by polishing graphite with zirconia particles having a composite elastic modulus of 50 to 220 GPa can be confirmed by simulating / simulating the environment when polishing graphite with zirconia particles, that is, the environment in which mechanical stress is generated by pressing the zirconia particles against the polishing surface by a polishing pad or the like and sliding on the graphite, by forcibly inducing the mechanochemical reaction between zirconia and graphite using a shaker (see <Measurement of Zr-C ratio> in the Examples section). Thus, it is preferable that the abrasive grains of the present invention include those that form a covalent bond with the object to be polished.

[0019] Incidentally, the degree of the above-mentioned covalent bond (Zr-C) can also be confirmed in the <Measurement of Zr-C ratio> section of the Examples. The Zr-C ratio is an index indicating the degree of covalent bond between zirconium atoms constituting zirconia and carbon atoms that may be contained in the object to be polished. When the Zr-C ratio is high, a covalent bond is likely to be formed, and when it is low, the opposite is true. Speaking plainly, the Zr-C ratio of zirconia particles is an index of the ease of covalent bond formation between zirconium atoms contained in the zirconia particles and carbon atoms that may be contained in the object to be polished. Carbon atoms are not contained in the zirconia particles. According to one embodiment of the present invention, the Zr-C ratio calculated in the <Measurement of Zr-C ratio> section of the Examples is 5.5 to 21%. By setting the Zr-C ratio to 5.5% or more, the covalent bond (Zr-C) with the object to be polished can be made sufficient, and the polishing rate can be improved. Also, by setting the Zr-C ratio to 21% or less, the formation of the covalent bond (Zr-C) with the object to be polished can be made appropriate, and the remaining abrasive grains after polishing can be suppressed. According to one embodiment of the present invention, the Zr-C ratio of the zirconia particles is 5.8% or more, 6.0% or more, 8.0% or more, 10.0% or more, 12.0% or more, 14.0% or more, or 16.0% or more. According to one embodiment of the present invention, the Zr-C ratio of the zirconia particles is 20% or less, 18% or less, 16% or less, 14% or less, 13% or less, or 11% or less.

[0020] According to one embodiment of the present invention, the polishing composition is substantially free of components that inhibit the covalent bond (Zr-C). The substantial absence of components that inhibit the covalent bond can improve the polishing rate of the object to be polished. Here, "substantially free of components that inhibit the covalent bond (Zr-C)" means that the polishing composition does not contain any components that inhibit the covalent bond (Zr-C) at all (below the detection limit), or that even if it does contain such components, the amount in the polishing composition is less than 0.00001 mass%. Typical examples of components that inhibit the covalent bond include water-soluble polymers (particularly water-soluble polymers having polar groups), surfactants (particularly anionic surfactants having anionic groups), and non-aromatic crosslinked cyclic compounds. Therefore, according to one embodiment of the present invention, the component that inhibits the covalent bond is a water-soluble polymer. Here, "surfactant" refers to a compound having at least one hydrophilic moiety (typically a hydrophilic group) and one or more hydrophobic moieties (typically a hydrophobic group) in one molecule. Furthermore, "water-soluble" means that the solubility in water (25°C) is 1 g / 100 mL or more, and "polymer" refers to a (co)polymer having a repeating unit in its molecular structure and a weight-average molecular weight (Mw) of 1,000 or more. In this specification, the "weight-average molecular weight" can be the weight-average molecular weight (polyethylene glycol equivalent) measured by gel permeation chromatography (GPC).

[0021] According to one embodiment of the present invention, 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 calcium (Ca) or an oxide thereof. Colloidal zirconia particles doped with yttrium (Y) or an oxide thereof are preferred. The following describes Y-stabilized zirconia particles doped with yttrium (Y) or an oxide thereof.

[0022] The concentration (mol %) of yttrium (yttria equivalent) in the Y-stabilized zirconia particles is defined as follows: The concentration of yttrium may be adjusted by adding, for example, yttrium carboxylate.

[0023]

number

[0024] The molar percentage of yttrium can be determined by X-ray fluorescence (XRF) or any other method known in the art. The concentration of yttrium in the Y-stabilized zirconia particles is at least 3 mol%, 4 mol%, 5 mol%, 6 mol%, 7 mol%, 8 mol%, 9 mol%, 10 mol%, 11 mol%, 12 mol%, 13 mol%, 14 mol%, or 15 mol%. The concentration of yttrium in the Y-stabilized zirconia particles is less than 45 mol%, 40 mol%, 35 mol%, 30 mol%, 25 mol%, or 20 mol%. The concentration of yttrium in the Y-stabilized zirconia particles is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 mol%, or any range therebetween.

[0025] The concentration of yttrium in the Y-stabilized zirconia particles is 0.2 mol% or more, 1 mol% or more, 2 mol% or more, 3 mol% or more, 4 mol% or more, 5 mol% or more, 6 mol% or more, 7 mol% or more, 8 mol% or more, 9 mol% or more, 10 mol% or more, 11 mol% or more, 12 mol% or more, 13 mol% or more, 14 mol% or more, 15 mol% or more, 16 mol% or more, 17 mol% or more, 18 mol% or more, 19 mol% or more, 20 mol% or more, 21 mol% or more, 22 mol% or more, 23 mol% or more, 24 mol% or more, or 25 mol% or more. The yttrium concentration of the colloidal zirconia particles in the examples of the present invention can be 0.3 to 17 mol %.

[0026] In some embodiments, the Y-stabilized zirconia particles comprise a monoclinic phase (e.g., the yttrium in the Y-stabilized zirconia particles is at a concentration sufficient to provide a monoclinic phase). In some embodiments, the Y-stabilized zirconia particles comprise a tetragonal phase (e.g., the yttrium in the Y-stabilized zirconia particles is at a concentration sufficient to provide a tetragonal phase). In some embodiments, the Y-stabilized zirconia particles comprise a cubic phase (e.g., the yttrium in the Y-stabilized zirconia particles is at a concentration sufficient to provide a cubic phase). Note that the expression "greater than or equal to X (X is a numerical value)" used herein means that the value may be greater than or equal to X or may be less than or equal to X. In other words, when making a correction, the numerical value X can be the basis for both a lower limit and an upper limit.

[0027] The abrasive grains (particularly zirconia particles) according to the present invention preferably have a particle diameter (D50, hereinafter simply referred to as "D50") of 5 nm or more and 150 nm or less when the cumulative particle volume from the fine particle side reaches 50% of the total particle volume in the particle size distribution determined by laser diffraction scattering. If the D50 of the abrasive grains (particularly zirconia particles) is less than 5 nm, the polishing rate will be significantly reduced. On the other hand, if the D50 of the abrasive grains (particularly zirconia particles) exceeds 150 nm, scratches may occur on the polished surface. The D50 of the abrasive grains (particularly zirconia particles) may be 10 nm or more, 25 nm or more, 30 nm or more, 40 nm or more, 50 nm or more, 60 nm or more, 70 nm or more, 80 nm or more, or 90 nm or more. The D50 of the abrasive grains (particularly zirconia particles) may be 110 nm or less, 90 nm or less, 80 nm or less, 70 nm or less, 60 nm or less, 50 nm or less, 40 nm or less, or 30 nm or less. More specifically, the D50 of the abrasive grains (particularly zirconia particles) can be measured by the method described in the Examples.

[0028] The shape of the abrasive grains (particularly 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 out more than the ends, donut-shaped disks with a central hole, plate-shaped, cocoon-shaped shapes with a central constriction, associative spheres in which multiple particles are integrated, confetti-shaped shapes with multiple protrusions on the surface, rod-shaped, diamond-shaped, horn-shaped, and rugby-ball-shaped shapes, and are not particularly limited.

[0029] The lower limit of the zeta potential of the abrasive grains (particularly zirconia particles) in the polishing composition is not particularly limited, but may be 5 mV or more, 10 mV or more, 20 mV or more, 25 mV or more, 30 mV or more, 32 mV or more, or 35 mV or more. The upper limit of the zeta potential of the abrasive grains (particularly zirconia particles) in the polishing composition is not particularly limited, but may be 70 mV or less, 65 mV or less, 55 mV or less, 50 mV or less, 45 mV or less, 40 mV or less, 35 mV or less, 33 mV or less. V or less, 31 mV or less, 29 mV or less, or 28 mV or less.

[0030] In this specification, the zeta potential of the abrasive grains (particularly zirconia particles) is a value measured by the method described in the Examples. The zeta potential of the abrasive grains (particularly zirconia particles) can be adjusted by the pH of the polishing composition, etc.

[0031] The content (concentration) of abrasive grains (particularly zirconia particles) in the polishing composition is not particularly limited, but may be 0.01 mass% or more, 0.05 mass% or more, 0.08 mass% or more, 0.1 mass% or more, 0.2 mass% or more, 0.3 mass% or more, or 0.4 mass% or more, based on the total mass of the polishing composition. The upper limit of the content of abrasive grains (particularly zirconia particles) in the polishing composition may be 10 mass% or less, 5 mass% or less, 4 mass% or less, 3 mass% or less, 2 mass% or less, 1 mass% or less, or 0.8 mass% or less, based on the total mass of the polishing composition.

[0032] The polishing composition of the present invention may further contain abrasive particles other than zirconia particles, as long as 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. Furthermore, the other abrasive particles may be commercially available or synthetic. If particles other than zirconia particles are used in combination, silica or ceria is preferred. Ceria is preferably used together with zirconia particles because it can form covalent bonds with the object to be polished.

[0033] 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.

[0034] [Liquid medium] The polishing composition of the present invention contains a liquid medium. Examples of liquid media include water; alcohols such as methanol, ethanol, and ethylene glycol; ketones such as acetone; and mixtures thereof. Of these, water is preferred as the liquid medium. That is, according to a preferred embodiment of the present invention, the liquid medium contains water. According to a more preferred embodiment of the present invention, the liquid medium consists essentially of water. Note that the above term "substantially" means that a liquid medium other than water may be included as long as the intended effect of the present invention can be achieved. More specifically, the liquid medium preferably consists of 90% by mass to 100% by mass of water and 0% by mass to 10% by mass of a liquid 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 liquid medium other than water. Most preferably, the liquid medium is water.

[0035] From the viewpoint of not inhibiting the action of the components contained in the polishing composition, it is preferable that the liquid 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.

[0036] [pH and pH adjusters] The pH of the polishing composition according to the present invention is, for example, less than 6, 5.9 or less, 5.7 or less, 5.5 or less, or less than 5.5. When the pH of the polishing composition is less than 6, the stability of the polishing composition is further improved. The pH of the polishing composition according to the present invention is preferably more than 2, 2.4 or more, 2.8 or more, 3.2 or more, 3.6 or more, 3.7 or more, or more than 3.7. When the pH of the polishing composition is 2 or less, the polishing composition is preferably polished to a graphite component-containing material (particularly sp such as graphite) as the object to be polished. 2 Therefore, according to one embodiment of the present invention, the pH of the polishing composition is greater than 3.7 and less than 5.5.

[0037] The polishing composition of the present invention may contain a pH adjuster for adjusting the pH. The pH adjuster may be any of an inorganic acid, an organic acid, and a base. The pH adjuster may be used alone or in combination of two or more.

[0038] Specific examples of inorganic acids that can be used as pH adjusters include hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid. Among these, hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid are preferred.

[0039] Specific examples of organic acids that can be used as pH adjusters include formic acid, acetic acid, camphorsulfonic 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, methoxyphenylacetic acid, phenoxyacetic acid, methanesulfonic acid, ethanesulfonic acid, and isethionic acid.

[0040] Specific examples of bases that can be used as pH adjusters include ammonia, sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide, etc. The amount of pH adjuster added is not particularly limited, and may be appropriately adjusted so that the polishing composition has a desired pH.

[0041] The pH adjuster contained in the polishing composition of the present invention is preferably an inorganic acid such as nitric acid, as compared with an organic acid such as acetic acid or camphorsulfonic acid.

[0042] According to one embodiment of the present invention, the polishing composition does not contain an alkali compound. If the polishing composition contains an alkali compound, aggregation of abrasive grains will progress, increasing the contact area between the abrasive grains and the workpiece to be polished, which may lead to an increase in particle residue.

[0043] The alkaline compound may be a substance that dissolves in water (25°C), exhibits basicity, and neutralizes with acid. Examples of the alkaline compound include ammonia, potassium hydroxide, amine compounds such as AEPD (2-amino-2-ethyl-1,3-propanediol), DGA (diglycolamine), and tetramethylammonium hydroxide, basic amino acids, and nitrogen-containing heterocyclic compounds having an isothiazolinone skeleton.

[0044] The pH of the polishing composition can be measured, for example, with a pH meter, specifically by the method described in the Examples.

[0045] [Other ingredients] The polishing composition of the present invention may or may not contain further known additives that can be used in polishing compositions, such as oxidizing agents, complexing agents, preservatives, and antifungal agents, within the range that does not inhibit the effects of the present invention.

[0046] Examples of oxidizing agents include hydrogen peroxide, sodium peroxide, barium peroxide, ozone water, silver (II) salts, iron (III) salts, permanganic acid, chromic acid, dichromate, peroxodisulfuric acid, peroxolinic acid, peroxosulfuric acid, peroxoboric acid, performic acid, peracetic acid, perbenzoic acid, perphthalic acid, hypochlorous acid, hypobromous acid, hypoiodous acid, chloric acid, chlorous acid, perchloric acid, bromic acid, iodic acid, periodic acid, persulfuric acid, dichloroisocyanuric acid, and salts thereof. These oxidizing agents can be used alone or in combination. Among these, hydrogen peroxide, potassium permanganate, sodium permanganate, ammonium persulfate, periodic acid, hypochlorous acid, and sodium dichloroisocyanurate are preferred, with hydrogen peroxide, potassium permanganate, and sodium permanganate being more preferred, and potassium permanganate being even more preferred.

[0047] According to one embodiment of the present invention, the lower limit of the oxidizing agent content in the polishing composition is 0.001 mass% or more, or 0.01 mass% or more. According to one embodiment of the present invention, the upper limit of the oxidizing agent content in the polishing composition is 30 mass% or less, 10 mass% or less, or 1 mass% or less, 0.01 mass% or less, or less than 0.001 mass%.

[0048] According to one embodiment of the present invention, the polishing composition is substantially free of a metal-containing oxidizing agent. Metals in metal-containing oxidizing agents include, for example, manganese, cerium, vanadium, and iron. For example, examples of metal-containing oxidizing agents include KMnO4, (NH4)2Ce(NO3)6, NaVO3, NH4VO3, and Fe(NO3)3. The phrase "the polishing composition is substantially free of a metal-containing oxidizing agent" includes cases where the polishing composition contains no metal-containing oxidizing agent at all (below the detection limit), as well as cases where the polishing composition contains less than 0.05 mM of a metal-containing oxidizing agent. In the present invention, abrasive grains containing zirconia particles with a composite elastic modulus of 50 to 220 GPa are used, so that the polishing composition can be polished without any sputtering, such as on an organic film, particularly on graphite. 2It is possible to polish a sheet-like material of carbon atoms having hybrid orbitals at high speed without containing a metal-containing oxidizing agent. Furthermore, since the polishing composition is substantially free of a metal-containing oxidizing agent, it is possible to prevent metal components from remaining on the polished surface, and it is also possible to significantly suppress the occurrence of current leakage. Furthermore, since the polishing composition is substantially free of a metal-containing oxidizing agent, wastewater treatment is easy, making it environmentally friendly.

[0049] According to one embodiment of the present invention, the polishing composition is substantially free of oxidizing agents (except nitric acid). The phrase "the polishing composition is substantially free of oxidizing agents (except nitric acid)" refers to cases where the polishing composition contains no oxidizing agents other than nitric acid (below the detection limit) and also includes cases where the polishing composition contains less than 0.001 mass% of oxidizing agents other than nitric acid. In the present invention, abrasive grains containing zirconia particles having a composite elastic modulus of 50 to 220 GPa are used, so that the polishing composition can be polished without polishing the object to be polished (organic film, particularly sp such as graphite). 2 The polishing composition can polish a sheet-like material of carbon atoms having hybrid orbitals at high speed without containing an oxidizing agent (except nitric acid). The polishing composition has improved storage stability because it is substantially free of an oxidizing agent (except nitric acid).

[0050] [Method for producing polishing composition] Next, the method for producing the polishing composition of the present invention will be described. The method for producing the polishing composition of the present invention is not particularly limited, and can be obtained, for example, by stirring and mixing abrasive grains containing specific zirconia particles and other additives as necessary in a liquid medium (preferably water). The details of each component are as described above.

[0051] The method for producing zirconia particles having a composite elastic modulus of 50 to 220 GPa (appropriate hardness) is not particularly limited, and they can be prepared by appropriately referring to conventionally known methods. For example, there is a method for obtaining an yttrium oxide-stabilized zirconium oxide aqueous sol having very good transparency and almost no secondary aggregation of colloidal particles by hydrothermally treating a mixed aqueous solution in which a carboxylate of yttrium and zirconium oxyacetate are dissolved in water in a specific ratio range (see International Publication No. 2010 / 071135), or a method for obtaining a yttrium oxide-stabilized zirconium oxide aqueous sol having very good transparency and almost no secondary aggregation of colloidal particles by neutralizing an aqueous solution of zirconium salt and removing the resulting salt to prepare a slurry, and adding a predetermined amount of a predetermined calcium compound to the slurry and heating it to 80 to 100°C, thereby obtaining a powder X-ray diffraction spectrum of a half-peak of a main peak. In a method for producing calcia-stabilized zirconia powder with a modulus of elasticity within a certain angle (see JP 2020-75859 A), or in a method for producing zirconia powder by preparing a raw material blend by neutralization coprecipitation or the like to achieve a predetermined raw material composition, calcining the blend at a predetermined temperature (500-1200°C), and then crushing the resulting raw material powder, which is then molded and sintered at a predetermined temperature (1300-1650°C) (see JP 09-188562 A), the composite modulus of elasticity of zirconia particles can be controlled within a predetermined range by appropriately selecting these production methods and production conditions according to the desired purpose. For example, in the case of WO 2010 / 071135 A, increasing the temperature of the hydrothermal treatment disclosed therein (e.g., particularly 290°C or higher, 400°C or higher, with an upper limit of 600°C or lower) can easily control the hardness of zirconia particles. In addition, in the case of JP 2020-75859 A, increasing the solution concentration (concentration of zirconium salt) (for example, more than 1.0 mol / kg or 1.5 mol / kg or more, with an upper limit of 3.0 mol / kg or less) makes it easier to obtain zirconia particles with an appropriate hardness. In addition, in the case of JP 09-188562 A, increasing the firing temperature for sintering (for example, 1700°C or more, 1900°C or more, with an upper limit of 2200°C or less) makes it easier to obtain zirconia particles with an appropriate hardness. Furthermore, in the method for producing a polishing composition of the present invention, a confirmation step of confirming the composite elastic modulus of the zirconia particles may be included to produce abrasive grains containing zirconia particles with a modulus of 50 to 220 GPa.If commercially available, zirconia particles having a composite elastic modulus of 50 to 220 GPa may be used. Zirconia particles having a Zr-C ratio of 5.5 to 21% can also be prepared in a similar manner to the above. The disclosures of these publications are incorporated herein by reference in their entirety.

[0052] 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.

[0053] [Polishing method and semiconductor substrate manufacturing method] As described above, the polishing composition of the present invention is effective for polishing an object to be polished (organic film, particularly sp such as graphite). 2 Therefore, the present invention is suitable for polishing the object to be polished (organic film, especially sp such as graphite). 2 The present invention also provides a polishing method for polishing a substrate (a sheet-like material of carbon atoms having hybrid orbitals) with the polishing composition of the present invention. 2 and polishing a substrate (including a sheet-like material of carbon atoms having hybrid orbitals) by the polishing method.

[0054] 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.

[0055] 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.

[0056] 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 -1The 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) or less.

[0057] 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.

[0058] 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.

[0059] The polishing composition of the present invention may be a one-component type or a multi-component type such as a two-component type. The polishing composition of the present invention may also be prepared by diluting the stock solution of the polishing composition, for example, 2 to 10 times, with a diluent such as water.

[0060] The present invention encompasses the following aspects and configurations.

[0061] 1. A polishing composition for polishing an object to be polished, comprising abrasive grains and a liquid medium, wherein the abrasive grains contain zirconia grains, and the zirconia grains have a composite elastic modulus of 50 to 220 GPa.

[0062] 2. The polishing composition according to 1., wherein the object to be polished comprises a material containing a graphite component.

[0063] 3. The object to be polished is sp 2 2. The polishing composition according to 2, which contains a sheet-like material of carbon atoms having hybrid orbitals.

[0064] 4. The polishing composition according to any one of 1. to 3., wherein the abrasive grains include those that form a covalent bond with the object to be polished.

[0065] 5. The polishing composition according to 4, which does not contain any component that inhibits the covalent bond.

[0066] 6. The polishing composition according to 5, wherein the component that inhibits covalent bonding is a water-soluble polymer.

[0067] 7. The polishing composition according to any one of 1. to 6., wherein the object to be polished is substantially free of a material having a metal-nitrogen bond.

[0068] 8. The polishing composition according to any one of 1. to 7., which does not contain an alkaline compound.

[0069] 9. The polishing composition according to any one of 1. to 8., which is substantially free of a metal-containing oxidizing agent.

[0070] 10. The polishing composition according to any one of 1. to 9., which is substantially free of an oxidizing agent (except nitric acid).

[0071] 11. The polishing composition according to any one of 1. to 10., which has a pH of less than 6.

[0072] 12. The polishing composition according to 11, having a pH greater than 3.7 and less than 5.5. [Example]

[0073] 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 to the following examples. Unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass", respectively.

[0074] [Evaluation of physical properties, etc.] <Measurement of composite elastic modulus> The measurement of the composite elastic modulus will be described below.

[0075] (nanoindentation) The lower limit of particle size that can be evaluated using a nanoindenter is roughly submicron. 1)Optical microscopes are used to identify particle locations, making it difficult to pinpoint the indenter directly onto particles smaller than this size. To solve this problem, the inventors invented a method in which nanoparticles are layered on a substrate and multiple particles are indented simultaneously. The mechanical properties obtained in this way can be treated as average information, enabling relative comparisons between particles. A spherical indenter with a diameter of 1 μm was selected for the indentation test. This is because when a sharp indenter, such as a Berkovich-type indenter, is indented, elastic and plastic deformation of the sample occur simultaneously from the initial stage of indentation, which is expected to cause the layered structure to collapse. On the other hand, when a spherical indenter is indented, only elastic deformation occurs initially, and plastic deformation occurs once the yield contact pressure is exceeded. Therefore, using a spherical indenter allows for measurement of mechanical properties while suppressing sample collapse.

[0076] Thus, one aspect of the present invention provides a method for measuring the composite elastic modulus of ZrO2 particles, which includes pressing a spherical indenter into a ZrO2 particle layer formed by spreading a plurality of ZrO2 particles on a substrate. In one embodiment, the ZrO2 particle layer is formed by laminating a plurality of ZrO2 particle layers (e.g., 1 to 15 layers). In one embodiment, an adsorption layer that electrostatically adsorbs to the ZrO2 particle layer is interposed between one ZrO2 particle layer and an adjacent ZrO2 particle layer to adhere them. In one embodiment, the adsorption layer is made of polystyrene sulfonic acid. In one embodiment, the thickness of the ZrO2 particle layer (including the thickness of the plurality of layers when a plurality of ZrO2 particle layers are laminated; including the thickness of one or more adsorption layers when such layers are present) is 30 to 250 nm.

[0077] (Sample preparation) The laminated substrate shown in Figure 1 was fabricated using the Layer-by-Layer (LbL) method. 2)These were used as nanoindentation measurement samples. First, the zirconia particles of Example 1, Example 5, and Comparative Example 2 were prepared as ZrO2 nanoparticles (NPs). A silicon wafer was used as the substrate to which each zirconia particle was fixed. This was subjected to ultrasonic cleaning in acetone, ethanol, and ultrapure water, successively, for 1 minute each, and then treated in a UV / O3 cleaning device for 20 minutes to obtain a clean oxide film. The LbL structure was fabricated using the following procedure.

[0078] i) Immerse a silicon wafer in 1 w / w% ZrO2 slurry (pH: approximately 3.5) for 10 minutes to electrostatically adsorb ZrO2 nanoparticles onto the wafer surface; ii) The product obtained in i) is exposed to pure water for 10 seconds to remove unadsorbed components, and then dried by spraying clean, dry air. iii) The product obtained in ii) was immersed in a 1 w / w% polystyrene sulfonic acid (PS, pH: about 1.7) aqueous solution for 10 minutes, and PS was electrostatically adsorbed onto the ZrO2 nanoparticles. iv) The product obtained in iii) was exposed to pure water for 10 seconds to remove unadsorbed components, and then dried by spraying clean, dry air. v) Repeat iii) and iv) 12 times. vi) The moisture was removed by heating on a hot plate set at 50°C for 30 minutes.

[0079] According to cross-sectional SEM images of the produced substrates, the thickness of each layered particle was approximately 60 to 200 nm for the zirconia particles of Example 1, 70 to 140 nm for the zirconia particles of Example 5, and 200 to 300 nm for the zirconia particles of Comparative Example 2 (see Figure 2).

[0080] (measurement) Using a TriboIndenter manufactured by Hysitron, whitish areas (areas where particles were thickly deposited) were randomly selected on the substrate through microscope observation, and the following measurements were carried out.

[0081] A spherical indenter (made of diamond) was pressed onto each layered particle to a depth of approximately 8 to 10 nm. The maximum load applied to the indenter was 150 μN for the zirconia particles of Example 1, and 30 μN for the zirconia particles of Example 5 and Comparative Example 2, with the measurement time being 5 seconds in each case. The maximum load differs depending on the particle because the composite elastic modulus of the zirconia particles of Example 5 and Comparative Example 2 is significantly lower than that of the zirconia particles of Example 1, and therefore there is a risk that they will be strongly affected by the substrate. The load-displacement curve of each particle was calculated using Hertz's contact solution expressed by equation (1): 3) The composite elastic modulus was calculated by fitting based on the above (the load-displacement curve of Example 1 is shown in FIG. 3). Here, P is the indentation load, R is the radius of the spherical indenter, h is the indentation depth, and Er is the composite elastic modulus. The range of the load-displacement curve was set to an indentation depth of 0 to 6 nm. This setting makes it clear which range of the load-displacement curve should be used for fitting.

[0082]

number

[0083] In this way, the composite elastic modulus of each particle was obtained, and the results are shown in Table 2.

[0084] The composite elastic modulus was also measured using the same method for the zirconia particles of the other examples and comparative examples. The maximum loads applied to the indenter in Examples 2 to 4 and Comparative Examples 1 and 3 were 100 μN, 150 μN, 100 μN, 30 μN, and 200 μN, respectively, and the measurement time was 5 seconds in each case. The results are shown in Table 2. The composite elastic modulus for each example and comparative example was measured three times using the same method as above, and the arithmetic mean value was used.

[0085] (References) 1) Takahito Omura, Journal of the Japan Society for Precision Engineering, Vol. 79, No. 12, pp. 1181-1184, (2013) 2) Katsuhiko Araga, Surface Technology, Vol. 70, No. 7, pp.336-342, (2019) 3) Junji Miyoshi et al., Transactions of the Japan Society of Mechanical Engineers, Part C, Vol. 71, No. 701, pp. 280-285, (2005).

[0086] <Measurement of Zr-C ratio> Subsequently, an explanation regarding the measurement of the Zr-C ratio will be provided below.

[0087] (Preparation of zirconia / graphite mixture) An aqueous dispersion of zirconia particles of Example 1 was prepared as follows. This was placed in a glass beaker and heated in a water bath set at 100 °C to remove the moisture. The obtained dried product was crushed in a mortar for a predetermined time to obtain powdery particles.

[0088] Also, graphite powder manufactured by Fujifilm Wako Pure Chemical Corporation was prepared.

[0089] 4 mL each of zirconia particles and graphite powder were weighed using a graduated cylinder and gently mixed in a 50 mL resin container using a spatula to prepare a zirconia / graphite mixture (ZrO2 / graphite).

[0090] (Mechanochemical reaction of the mixture) The resin container (sample tube) containing the above mixture was stirred at room temperature and normal pressure using a reciprocating shaker. A schematic diagram thereof is shown in Fig. 4. By forcibly colliding the particles with each other in this way, a mechanochemical reaction was forcibly induced to obtain the reaction product. The rotation speed during shaking was 200 rpm and the treatment time was 60 minutes. Also, as a comparative sample, the same shaking test was carried out with graphite powder alone. <00003​​​The various reaction products obtained by shaking were sprinkled onto a sample stage with carbon tape attached, pressed through a packing paper, and then the excess was removed by air blowing. For XPS measurements, a PHI5000 VersaProbe II (manufactured by ULVAC-PHI, Inc.) was used. The chamber vacuum level was 5.0 x 10 -8 The excitation X-ray conditions were Al-Kα radiation, 25 W output, and 100 μm diameter. The detection conditions were pass energy 46.95 eV, eV step 0.1 eV, detection angle 45 degrees, detection time 20 ms / step, and accumulation count 20. C1s (277-297 eV) spectra were collected with n = 8.

[0092] (Zr-C ratio calculation) To calculate the Zr-C ratio, waveform separation of the C1s spectrum was performed using the analysis software MultiPak ver. 9.9.3 (ULVAC-PHI). 2 Hybrid orbital-derived C=C bond peak is 284.2 eV 1) After shift correction to 2 ), CC(sp 3 ), CO, OC=O, π-π * The six peaks were separated into those due to the bond (Figure 5), of which π-π * The ratio of Zr-C was calculated when the sum of the peak areas excluding bonds was taken as 100%. The results are shown in Table 2. The position and full width at half maximum (FWHM) of each peak were fixed under the conditions shown in Table 1.

[0093] The Zr—C ratios of the zirconia particles of the other examples and comparative examples were determined in the same manner as above. The results are shown in Table 2.

[0094] [Table 1]

[0095] <References> 1) Takayuki Ota et al., Surface Technology, Vol. 73, No. 1, pp. 47-52, (2022).

[0096] Therefore, one aspect of the present invention has a Zr-C ratio measurement method including calculating the peak area value of Zr-C when the sum of the peak area values of Zr-C, C=C(sp 2 ), C-C(sp 3 ), C-O and O-C=O is set to 100% by performing waveform separation of the C1s spectrum. In one embodiment of the present invention, a reaction mixture obtained through a mechanochemical reaction caused by forcibly colliding zirconia particles and graphite particles can be obtained, and a C1s spectrum can be obtained from the reaction mixture.

[0097] <Measurement of particle size> For the value of D50 of zirconia particles, the value measured as the volume average particle size by the dynamic light scattering method using a particle size distribution measuring device (UPA-UT151, manufactured by Nikkiso Co., Ltd.) was adopted. Specifically, a dispersion liquid in which zirconia particles were dispersed in water was used to measure the particle size of the zirconia particles. By analysis using the measuring instrument, the diameter D50 of the particles when the integrated particle volume reached 50% of the total particle volume from the fine particle side in the particle size distribution of the zirconia particles was calculated.

[0098] <Measurement of zeta potential> The zeta potential of the zirconia particles was measured using a zeta potential measuring device (trade name "ELS-Z") manufactured by Otsuka Electronics Co., Ltd.

[0099] <Measurement of pH> The pH of the polishing composition was measured using a pH meter (manufactured by Horiba, Ltd., model number: F-71).

[0100] [Preparation of polishing composition] (Example 1) An aqueous dispersion of colloidal zirconia with a composite modulus (152 GPa) and a particle size (D50) of 43 nm was prepared as the abrasive grains. This was used to prepare a polishing composition by adding the colloidal zirconia to pure water (liquid medium) at room temperature (25°C) so that the final concentration of colloidal zirconia was 0.5% by mass, and by adding nitric acid as a pH adjuster to adjust the pH to 4.5, followed by uniform mixing. The zeta potential of the colloidal zirconia in the resulting polishing composition was 27.9 mV. The crystallinity of the zirconia particles was confirmed by measuring the peak positions of the diffraction pattern obtained by X-ray diffraction.

[0101] (Examples 2 to 9, Comparative Examples 1 to 3) A polishing composition was prepared in the same manner as in Example 1, except that the colloidal zirconia was changed to a colloidal zirconia shown in Table 2 and the pH adjuster was changed to a pH adjuster shown in Table 2.

[0102] [Polishing speed] As an object to be polished (substrate), a single crystal silicon wafer on which a spin-on carbon film having a graphite structure was formed to a thickness of 5000 Å was prepared.

[0103] 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 equipment: Ebara Corporation FREX300E Polishing pressure: 2.0 psi (1 psi = 6894.76 Pa) Platen rotation speed: 60 rpm Polishing composition supply amount: 300mL / min.

[0104] (polishing speed) The film thickness was determined using an X-ray fluorescence analyzer (Rigaku Corporation, model number: ZSX400), 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).

[0105]

number

[0106] <Particle residue> The particle residue was measured using the KLA Tencor wafer defect inspection system SP-5. did.

[0107] First, the polished surface was washed with a polyvinyl alcohol brush and pure water at a brush pressure of 1 mm and a rotation speed of 100 rpm for 60 seconds, after which the single crystal silicon substrate was dried by rotating at a rotation speed of 1500 rpm for 60 seconds to prepare a washed substrate.

[0108] The target of detection was foreign matter present in the remaining area, excluding a 5 mm wide area from the outer edge of one side of the cleaned substrate (the area from 0 mm wide to 5 mm wide, assuming the outer edge is 0 mm). Foreign matter in 100 field samples randomly sampled from this area was observed using a Review SEM RS6000 manufactured by Hitachi, Ltd., and the number of particles visually identified was confirmed.

[0109] The evaluation results of the polishing compositions of the Examples and Comparative Examples are shown in Table 2 below.

[0110] [Table 2]

[0111] This application is based on Japanese Patent Application No. 2024-056618, filed on March 29, 2024, the disclosure of which is incorporated herein by reference in its entirety.

Claims

1. abrasive grains and a liquid medium; the abrasive grains include zirconia particles; A polishing composition for polishing an object to be polished, wherein the zirconia particles have a composite elastic modulus of 50 to 220 GPa.

2. The polishing composition according to claim 1 , wherein the object to be polished comprises a material containing a graphite component.

3. The object to be polished is sp ２ 3. The polishing composition according to claim 2, comprising a sheet material of carbon atoms having hybrid orbitals.

4. The polishing composition according to claim 1 , wherein the abrasive grains include those that form a covalent bond with the object to be polished.

5. The polishing composition according to claim 4 , which does not contain any component that inhibits the covalent bond.

6. The polishing composition according to claim 5 , wherein the component that inhibits covalent bonding is a water-soluble polymer.

7. 2. The polishing composition according to claim 1, wherein the object to be polished is substantially free of a material having a metal-nitrogen bond.

8. The polishing composition according to claim 1 , which does not contain an alkali compound.

9. The polishing composition of claim 1 , which is substantially free of a metal-containing oxidizing agent.

10. 10. The polishing composition of claim 9, which is substantially free of oxidizing agents (except nitric acid).

11. 2. The polishing composition according to claim 1, wherein the pH is less than 6.

12. The polishing composition according to claim 11, having a pH greater than 3.7 and less than 5.5.

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