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

Abstract

To provide a polishing composition, a manufacturing method for the same, a polishing method, and a manufacturing method for a semiconductor substrate, capable of increasing the polishing speed of carbon.SOLUTION: The polishing composition includes abrasive grains whose zeta potential is -5 mV or less, a surfactant, and a phosphonic acid chelating agent.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In recent years, with the increasing number of multilayer wiring layers on semiconductor substrate surfaces, a technique known as chemical mechanical polishing (CMP) has been used to polish and planarize semiconductor substrates when manufacturing semiconductor devices. CMP is a method for planarizing the surface of an object to be polished, such as a semiconductor substrate, using a polishing composition (slurry) containing abrasive grains such as silica, alumina, or ceria, an anticorrosive agent, a surfactant, etc. The object to be polished (the object to be polished) can be a wiring or plug made of silicon, polysilicon, silicon oxide (SiO), silicon nitride (SiN), or a metal.

[0003] Various proposals have been made so far regarding polishing compositions used when polishing semiconductor substrates by CMP. For example, Patent Document 1 describes "a polishing composition used to polish an object to be polished, including a silicon oxide film, which contains abrasive grains, a compound having a logarithm of the partition coefficient (LogP) of 1.0 or more, and a dispersion medium, and has a pH of less than 7." [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-37669 Summary of the Invention [Problem to be solved by the invention]

[0005] In some cases, a carbon film formed on a semiconductor substrate is polished. Conventional polishing compositions do not necessarily satisfy user requirements regarding the polishing rate of the carbon film. There is a demand for an improvement in the polishing rate of the carbon film.

[0006] The present invention has been made in consideration of the above circumstances, and aims to provide a polishing composition that can increase the carbon removal rate, a method for producing a polishing composition, a polishing method, and a method for producing a semiconductor substrate. [Means for solving the problem]

[0007] In view of the above problems, the present inventors have conducted extensive research and have found that the polishing rate of carbon can be increased by using a polishing composition containing abrasive grains having a zeta potential of -5 mV or less, a surfactant, and a phosphonic acid chelating agent, thereby completing the present invention. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a polishing composition that can increase (improve) the removal rate of carbon, a method for producing a polishing composition, a polishing method, and a method for producing a semiconductor substrate. DETAILED DESCRIPTION OF THE INVENTION

[0009] The polishing composition according to an embodiment of the present invention (hereinafter referred to as the present embodiment) is a polishing composition containing abrasive grains having a zeta potential of −5 mV or less, a surfactant, and a phosphonic acid chelating agent.

[0010] This polishing composition may be used for polishing objects such as elemental silicon, silicon compounds, metals, etc., for example, for polishing surfaces containing elemental silicon, polysilicon, silicon compounds, metals, etc., such as semiconductor substrates in the manufacturing process of semiconductor devices, and is suitable for polishing surfaces containing carbon. For example, it is suitable for polishing carbon films formed on semiconductor substrates. When polishing is performed using this polishing composition, it may be possible to polish carbon-containing surfaces or carbon films formed on semiconductor substrates at a high polishing rate. The polishing composition according to this embodiment will be described in detail below.

[0011] <Abrasive grain> The polishing composition according to this embodiment contains abrasive grains having a zeta potential of -5 mV or less. The abrasive grains having a zeta potential of -5 mV or less may be anion-modified silica. The silica may be colloidal silica. That is, the abrasive grains may be anion-modified colloidal silica.

[0012] (zeta potential) The abrasive grains used in the polishing composition of this embodiment preferably exhibit a zeta potential of -5 mV or less at a pH of 7 or less. The zeta potential of the abrasive grains is preferably -10 mV or less, more preferably -20 mV or less, even more preferably -30 mV or less, and particularly preferably -35 mV or less. When the colloidal silica has a zeta potential in this range, the removal rate for carbon can be further improved.

[0013] Here, the zeta potential of the abrasive grains in the polishing composition is calculated by subjecting the polishing composition to an ELS-Z2 manufactured by Otsuka Electronics Co., Ltd., measuring it using a flow cell at a measurement temperature of 25°C by the laser Doppler method (electrophoretic light scattering measurement method), and analyzing the obtained data using the Smoluchowski formula.

[0014] (Manufacturing method) Methods for producing colloidal silica include the sodium silicate method and the sol-gel method, and colloidal silica produced by either method is suitable for use as the colloidal silica of the present invention. However, from the viewpoint of reducing metal impurities, colloidal silica produced by the sol-gel method is preferred. Colloidal silica produced by the sol-gel method is preferred because it contains less metal impurities that are diffusible in semiconductors and less corrosive ions such as chloride ions. Colloidal silica can be produced by the sol-gel method using a conventionally known method. Specifically, colloidal silica can be obtained by hydrolysis and condensation reaction using a hydrolyzable silicon compound (e.g., alkoxysilane or its derivative) as a raw material.

[0015] (Surface modification) The type of colloidal silica used is not particularly limited, but for example, surface-modified colloidal silica can be used. Surface modification of colloidal silica can be achieved, for example, by chemically bonding a functional group of an organic acid to the surface of the colloidal silica, i.e., by immobilizing the organic acid. Alternatively, surface modification of colloidal silica can be achieved by mixing colloidal silica with a metal such as aluminum, titanium, or zirconium, or an oxide thereof, and doping the surface of the silica particles.

[0016] In this embodiment, the colloidal silica contained in the polishing composition is, for example, colloidal silica having an organic acid fixed on its surface. Colloidal silica having an organic acid fixed on its surface tends to have a higher absolute value of zeta potential in the polishing composition than ordinary colloidal silica having no organic acid fixed on its surface. Therefore, the zeta potential of the colloidal silica in the polishing composition can be easily adjusted to a range of -5 mV or less.

[0017] The zeta potential of colloidal silica can be controlled within a desired range, for example, by using an acid described below as a pH adjuster.

[0018] Examples of colloidal silica having an organic acid fixed to its surface include colloidal silica having an organic acid such as a carboxylic acid group, a sulfonic acid group, a phosphonic acid group, or an aluminic acid group fixed to its surface. Of these, from the viewpoint of ease of production, colloidal silica having a sulfonic acid or a carboxylic acid fixed to its surface is preferred, and colloidal silica having a sulfonic acid fixed to its surface is more preferred.

[0019] Immobilization of an organic acid on the surface of colloidal silica cannot be achieved by simply coexisting colloidal silica with an organic acid. For example, immobilization of sulfonic acid, a type of organic acid, on colloidal silica can be achieved by the method described in "Sulfonic acid-functionalized silica through thiol groups," Chem. Commun. 246-247 (2003). Specifically, colloidal silica with sulfonic acid immobilized on its surface (sulfonic acid-modified colloidal silica) can be obtained by coupling a silane coupling agent having a thiol group, such as 3-mercaptopropyltrimethoxysilane, to colloidal silica and then oxidizing the thiol group with hydrogen peroxide.

[0020] Alternatively, immobilizing a carboxylic acid, which is a type of organic acid, on colloidal silica can be achieved by, for example, the method described in "Novel Silane Coupling Agents Containing a Photolabile 2-Nitrobenzyl Ester for Introduction of a Carboxy Group on the Surface of Silica Gel," Chemistry Letters, 3, 228-229 (2000). Specifically, colloidal silica with a carboxylic acid immobilized on its surface (carboxylic acid-modified colloidal silica) can be obtained by coupling a silane coupling agent containing a photolabile 2-nitrobenzyl ester to colloidal silica and then irradiating the resulting mixture with light.

[0021] (Average primary particle size) In the polishing composition of the present invention, the lower limit of the average primary particle size of the abrasive grains is preferably 1 nm or more, more preferably 10 nm or more, and even more preferably 20 nm or more.In addition, in the polishing composition of the present invention, the upper limit of the average primary particle size of the colloidal silica is preferably 100 nm or less, more preferably 80 nm or less, even more preferably 65 nm or less, and particularly preferably 50 nm or less.Within such a range, defects such as scratches that may occur on the surface of the object to be polished after polishing with the polishing composition can be suppressed.The average primary particle size of the colloidal silica is calculated, for example, based on the specific surface area of ​​the colloidal silica measured by the BET method.

[0022] (Average secondary particle size) In the polishing composition of the present invention, the lower limit of the average secondary particle diameter of the abrasive grains is preferably 10 nm or more, more preferably 20 nm or more, even more preferably 40 nm or more, and particularly preferably 50 nm or more.Furthermore, in the polishing composition of the present invention, the upper limit of the average secondary particle diameter of the colloidal silica is preferably 250 nm or less, more preferably 150 nm or less, even more preferably 120 nm or less, and particularly preferably 90 nm or less.Within such a range, defects such as scratches that may occur on the surface of the object to be polished after polishing with the polishing composition can be suppressed.

[0023] The secondary particles are particles formed by the aggregation of abrasive grains (primary particles) in the polishing composition. The average secondary particle size of the abrasive grains can be measured, for example, by a dynamic light scattering method, such as a laser diffraction scattering method.

[0024] (Average degree of association) The average degree of association of the abrasive grains is preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.0 or less. As the average degree of association of colloidal silica decreases, a polished surface with fewer surface defects is more likely to be obtained by polishing an object to be polished using the polishing composition. Furthermore, the average degree of association of the abrasive grains is preferably 1.0 or more, more preferably 1.2 or more. As the average degree of association of the abrasive grains increases, there is an advantage in that the removal rate of the object to be polished by the polishing composition improves. The average degree of association of the abrasive grains is obtained by dividing the average secondary particle size of the abrasive grains by the average primary particle size.

[0025] (shape) In the present invention, the shape of the abrasive grains is not particularly limited and may be either spherical or non-spherical, but is preferably non-spherical. Specific examples of non-spherical shapes include polygonal prisms such as triangular prisms and square prisms, cylinders, bale-shaped cylinders in which the center is more bulging than the ends, doughnut-shaped discs with a central hole, plate-shaped discs, cocoon-shaped discs with a central constriction (e.g., two spheres joined together, with the joint narrowing like a constriction), associative spheres in which multiple particles are integrated, confetti-shaped discs with multiple protrusions on the surface, rugby ball-shaped discs, and string-of-beads shapes, and are not particularly limited.

[0026] (Content) The lower limit of the content of abrasive grains is preferably 0.1 mass% or more, more preferably 0.3 mass% or more, and even more preferably 0.5 mass% or more, based on the polishing composition.The upper limit of the content of abrasive grains is preferably 20 mass% or less, more preferably 10 mass% or less, and even more preferably 5 mass% or less, based on the polishing composition.Within this range, the polishing rate can be further improved.In addition, when the polishing composition contains two or more types of abrasive grains, the content of abrasive grains means the total amount of these.

[0027] (Particles other than silica) In addition, the polishing composition according to the present embodiment may contain, as abrasive grains, silica having a zeta potential of -5 mV or less (for example, anion-modified colloidal silica) and other abrasive grains other than silica. Alternatively, the polishing composition may contain other abrasive grains other than silica having a zeta potential of -5 mV or less. Examples of other abrasive grains include metal oxide grains such as alumina grains, zirconia grains, and titania grains.

[0028] <Liquid medium> The polishing composition according to the present embodiment can contain a liquid medium. It functions as a dispersion medium or a solvent for dispersing or dissolving each component of the polishing composition (for example, additives such as anion-modified colloidal silica, cationic surfactant, and pH adjuster). Examples of the liquid medium include water and organic solvents. One type can be used alone, or two or more types can be mixed and used, but it is preferable to contain water. However, from the viewpoint of preventing inhibition of the action of each component, it is preferable to use water that contains as few impurities as possible. Specifically, pure water or ultrapure water obtained by removing impurity ions with an ion exchange resin and then removing foreign substances through a filter, or distilled water is preferable.

[0029] <pH adjuster> The pH value of the polishing composition according to the present embodiment is preferably 7 or less, more preferably 5 or less, even more preferably 4 or less, and particularly preferably 3 or less. Also, the pH value is preferably 0.5 or more, more preferably 1 or more, and even more preferably 1.5 or more. If the polishing composition is acidic, the polishing rate of the carbon film can be improved. To achieve the above-mentioned pH value, the polishing composition may contain a pH adjuster.

[0030] The pH value of the polishing composition can be adjusted by adding a pH regulator. The pH regulator used may be either an acid or an alkali, and may be either an inorganic compound or an organic compound.

[0031] Specific examples of acids that can be used as pH adjusters include inorganic acids and organic acids such as carboxylic acids and organic sulfuric acids. Specific examples of inorganic acids include sulfuric acid, nitric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid. It is preferable to use inorganic acids as pH adjusters, and phosphoric acid-based inorganic acids are more preferred. Organic acids include carboxylic acids and organic sulfuric acids. Specific examples of carboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, and lactic acid. Specific examples of organic sulfuric acids include methanesulfonic acid, ethanesulfonic acid, and isethionic acid. These acids may be used alone or in combination of two or more. As the organic acid, it is preferable to use a carboxylic acid or a phosphonic acid. These acids may be contained in the polishing composition as a pH adjuster, or as an additive for improving the polishing rate, or a combination thereof.

[0032] Specific examples of alkalis used as pH adjusters include alkali metal hydroxides or salts thereof, alkaline earth metal hydroxides or salts thereof, quaternary ammonium hydroxides or salts thereof, ammonia, amines, etc. Specific examples of alkali metals include potassium and sodium. Specific examples of alkaline earth metals include calcium and strontium. Specific examples of salts include carbonates, bicarbonates, sulfates, acetates, etc. Specific examples of quaternary ammonium include tetramethylammonium, tetraethylammonium, tetrabutylammonium, etc.

[0033] The quaternary ammonium hydroxide compound includes quaternary ammonium hydroxide or a salt thereof, and specific examples thereof include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, etc. Furthermore, specific examples of the amine include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N-(β-aminoethyl)ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, anhydrous piperazine, piperazine hexahydrate, 1-(2-aminoethyl)piperazine, N-methylpiperazine, guanidine, etc.

[0034] These alkalis may be used alone or in combination of two or more. Among these alkalis, ammonia, ammonium salts, alkali metal hydroxides, alkali metal salts, quaternary ammonium hydroxide compounds, and amines are preferred, and ammonia, potassium compounds, sodium hydroxide, quaternary ammonium hydroxide compounds, ammonium bicarbonate, ammonium carbonate, sodium bicarbonate, and sodium carbonate are more preferred. Furthermore, from the viewpoint of preventing metal contamination, it is more preferred that the polishing composition contains a potassium compound as the alkali. Examples of potassium compounds include potassium hydroxides or potassium salts, and specific examples include potassium hydroxide, potassium carbonate, potassium bicarbonate, potassium sulfate, potassium acetate, and potassium chloride.

[0035] <Surfactant> The polishing composition according to this embodiment contains a surfactant. The surfactant has the effect of imparting hydrophilicity to the polished surface of the object to be polished after polishing, thereby improving the cleaning efficiency of the object to be polished after polishing and suppressing the adhesion of dirt, etc. The surfactant may be a cationic surfactant.

[0036] Specific examples of cationic surfactants include amine oxides, alkyltrimethylammonium salts, alkyldimethylammonium salts, alkylbenzyldimethylammonium salts, and alkylamine salts, with amine oxides being preferred among them.

[0037] Specific examples of amine oxides include N,N-dimethyldecylamine-N-oxide, N,N-dimethyldodecylamine-N-oxide, pyridine-N-oxide, N-methylmorpholine-N-oxide, coconut oil alkyl dimethylamine oxide, trimethylamine-N-oxide, dodecyldimethylamine oxide, decyldimethylamine oxide, and tetradecyldimethylamine oxide, and among these, decyldimethylamine oxide is preferred.

[0038] These surfactants may be used alone or in combination of two or more.

[0039] The higher the content of the surfactant in the entire polishing composition, the more efficient the cleaning of the polished object after polishing. Therefore, the content (concentration) of the surfactant in the entire polishing composition is preferably 0.01 g / L or more, more preferably 0.05 g / L or more, and even more preferably 0.1 g / L or more.

[0040] In addition, the smaller the content of surfactant in the entire polishing composition, the less the amount of surfactant remaining on the polished surface of the object to be polished after polishing, and the more improved the cleaning efficiency. Therefore, the content of surfactant in the entire polishing composition is preferably 10 g / L or less, more preferably 5.0 g / L or less, and even more preferably 2.0 g / L or less.

[0041] <Phosphonic acid chelating agent> The polishing composition according to this embodiment contains a phosphonic acid chelating agent. By adding a phosphonic acid chelating agent to the polishing composition, the polishing rate of carbon can be improved.

[0042] Examples of phosphonic acid chelating agents include ethylenediaminetetramethylenephosphonic acid (EDTMP), phytic acid, etidronic acid (HEDP), nitrilotrismethylenephosphonic acid (NTMP), and 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC).

[0043] The lower limit of the content of the phosphonic acid chelating agent in the entire polishing composition is not particularly limited because even a small amount is effective, but the higher the content of the phosphonic acid chelating agent, the higher the carbon removal rate with the polishing composition. For example, the content (concentration) of the phosphonic acid chelating agent in the entire polishing composition is preferably 0.01 g / L or more, more preferably 0.1 g / L or more, and even more preferably 1 g / L or more.

[0044] Furthermore, the lower the content of the phosphonic acid chelating agent in the entire polishing composition, the less likely the carbon-containing object to be dissolve, and the better the ability to eliminate unevenness. Therefore, the content of the phosphonic acid chelating agent in the entire polishing composition is preferably 20 g / L or less, more preferably 10 g / L or less, and even more preferably 5 g / L or less.

[0045] <Water-soluble polymer> The polishing composition according to this embodiment may contain a water-soluble polymer. When the object to be polished contains polysilicon, the polishing rate can be adjusted, for example, by increasing or decreasing the polishing rate, by adding a water-soluble polymer to the polishing composition.

[0046] Examples of water-soluble polymers include polyvinyl alcohol (PVA), polyvinylpyrrolidone, polyethylene glycol (PEG), polypropylene glycol, polybutylene glycol, copolymers of oxyethylene (EO) and oxypropylene (PO), methylcellulose, hydroxyethyl cellulose, dextrin, and pullulan. These water-soluble polymers may be used alone or in combination of two or more. Among water-soluble polymers, nonionic polymers are preferred from the viewpoint of not interfering with the effect of surfactants on the abrasive grains and the TEOS surface (not changing the zeta potential).

[0047] The water-soluble polymer is not limited to a nonionic polymer. The water-soluble polymer may be cationic or anionic. Examples of cationic polymers include polyethyleneimine, polyvinylimidazole, and polyallylamine. Examples of anionic polymers include polyacrylic acid, carboxymethyl cellulose, polyvinyl sulfonic acid, polyanethole sulfonic acid, and polystyrene sulfonic acid.

[0048] <Oxidizing agent> The polishing composition according to this embodiment may contain an oxidizing agent. When the object to be polished contains silicon, for example, polycrystalline silicon (Poly-Si), the polishing rate can be adjusted by adding an oxidizing agent to the polishing composition. That is, the polishing rate of Poly-Si can be increased or decreased by selecting the type of oxidizing agent to be added to the polishing composition. Specific examples of oxidizing agents include hydrogen peroxide, peracetic acid, percarbonate, urea peroxide, perchloric acid, and persulfates. Specific examples of persulfates include sodium persulfate, potassium persulfate, and ammonium persulfate. These oxidizing agents may be used alone or in combination of two or more. Among these oxidizing agents, persulfates and hydrogen peroxide are preferred, with hydrogen peroxide being particularly preferred.

[0049] The higher the content of the oxidizing agent in the entire polishing composition, the easier it is to change the polishing rate of the object to be polished by the polishing composition. Therefore, the content (concentration) of the oxidizing agent in the entire polishing composition is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more. Furthermore, the lower the content of the oxidizing agent in the entire polishing composition, the more the material cost of the polishing composition can be reduced. Furthermore, the burden of treating the polishing composition after use for polishing, i.e., waste liquid treatment, can be reduced. Furthermore, excessive oxidation of the surface of the object to be polished by the oxidizing agent is less likely to occur. Therefore, the content of the oxidizing agent in the entire polishing composition is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less.

[0050] <Mold inhibitors, preservatives> The polishing composition may contain an antifungal agent and a preservative. Specific examples of the antifungal agent and the preservative include isothiazolinone preservatives (e.g., 2-methyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one), paraoxybenzoic acid esters, and phenoxyethanol. These antifungal agents and preservatives may be used alone or in combination of two or more.

[0051] <Method for producing polishing composition> The method for producing a polishing composition according to this embodiment includes mixing abrasive grains having a zeta potential of −5 mV or less, a surfactant, a phosphonic acid chelating agent, and a liquid medium. For example, the polishing composition according to this embodiment can be produced by stirring and mixing anion-modified colloidal silica as abrasive grains, a cationic surfactant (e.g., amine oxide) as a surfactant, ethylenediaminetetramethylenephosphonic acid (EDTMP) or phytic acid as a phosphonic acid chelating agent, and various additives (e.g., pH adjusters, water-soluble polymers, oxidizing agents, fungicides, preservatives, etc.) in a liquid medium such as water. The temperature during mixing is not particularly limited, but is preferably 10°C to 40°C, and may be heated to improve the dissolution rate. The mixing time is also not particularly limited.

[0052] <Object to be polished> The polishing composition according to this embodiment can improve the removal rate of carbon. Therefore, the object to be polished is preferably carbon, a carbon-containing object, or a carbon film formed on a semiconductor substrate or the like. However, in this embodiment, the type of object to be polished is not limited to carbon, and may be elemental silicon, silicon compounds other than SiN film, metals, etc. Examples of elemental silicon include single crystal silicon, polysilicon, and amorphous silicon. Examples of silicon compounds include silicon dioxide and silicon carbide. Silicon dioxide may be a film formed using tetraethoxysilane ((Si(OC2H5)4)) (hereinafter referred to as a TEOS film). Silicon compound films include low-dielectric-constant films with a relative dielectric constant of 3 or less. Examples of metals include tungsten, copper, aluminum, hafnium, cobalt, nickel, titanium, tantalum, gold, silver, platinum, palladium, rhodium, ruthenium, iridium, and osmium. These metals may be present in the form of an alloy or a metal compound.

[0053] <Polishing method> The configuration of the polishing apparatus is not particularly limited, but for example, a general polishing apparatus including a holder for holding a substrate or the like having an object to be polished, a drive unit such as a motor capable of changing the rotation speed, and a polishing table to which a polishing pad (polishing cloth) can be attached can be used. As the polishing pad, general nonwoven fabric, polyurethane, porous fluororesin, etc. can be used without any particular limitation. The polishing pad can be one with grooves formed to allow the liquid polishing composition to accumulate.

[0054] There are no particular restrictions on the polishing conditions. For example, the rotation speed of the polishing platen is 10 rpm (0.17 s -1 ) or more 500rpm (8.3s -1 ) is preferred. 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) or less. The method for supplying the polishing composition to the polishing pad is not particularly limited, and a method of continuously supplying the polishing composition using a pump or the like is used. There is no limit to the amount of supply, but it is preferred that the surface of the polishing pad is always covered with the polishing composition of one embodiment of the present invention.

[0055] 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 may also be prepared by diluting the stock solution of the polishing composition, for example, 10 times or more, with a diluent such as water.

[0056] After polishing is complete, the substrate is washed with, for example, running water, and water droplets adhering to the substrate are removed using a spin dryer or the like, followed by drying, thereby obtaining a substrate having, for example, a layer containing a silicon-containing material. In this way, the polishing composition of this embodiment can be used for substrate polishing. By using the polishing composition of this embodiment to polish the surface of an object to be polished, such as a carbon film provided on a semiconductor substrate (an example of a substrate), a polished semiconductor substrate can be produced. Examples of semiconductor substrates include silicon wafers having layers containing elemental silicon, silicon compounds such as SiN films, metals, etc.

[0057] <Method of manufacturing semiconductor substrate> The method for manufacturing a semiconductor substrate according to this embodiment includes a step of polishing the surface of a semiconductor substrate using the polishing composition. The polishing method in this step is, for example, as described in the section entitled "Polishing Method." [Example]

[0058] 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. Furthermore, various modifications or improvements can be made to the following examples, and such modifications or improvements can also be included in the present invention.

[0059] <Method for preparing polishing composition> Examples 1 to 5 As shown in Table 1 below, a mixture was prepared by stirring and mixing abrasive grains having a zeta potential of -5 mV or less, a phosphonic acid chelating agent, a cationic surfactant, and water as a liquid medium. A pH adjuster was added to the prepared mixture as needed to produce the polishing compositions of Examples 1 to 5. In Table 1, "-" indicates that the component was not used or that there is no unit.

[0060] In Examples 1 to 5, anion-modified colloidal silica was used as the abrasive grains. In Examples 1, 2, 4, and 5, the concentration of anion-modified colloidal silica in the polishing composition was 2.0 mass%. Hereinafter, mass% is abbreviated as wt%. In Example 3, the concentration of anion-modified colloidal silica in the polishing composition was 0.5 wt%. In Examples 1 to 5, the primary particle diameter of the anion-modified colloidal silica was 35 nm, the secondary particle diameter was 70 nm, and the zeta potential was -40 mV.

[0061] In Examples 1 to 4, decyldimethylamine oxide was used as the cationic surfactant. In Examples 1 to 4, the concentration of decyldimethylamine oxide in the polishing composition was 0.4 g / L. In Example 5, octyldimethylethylammonium ethyl sulfate was used as the cationic surfactant. In Example 5, the concentration of octyldimethylethylammonium ethyl sulfate in the polishing composition was 0.4 g / L.

[0062] In Examples 1 and 3 to 5, ethylenediaminetetramethylenephosphonic acid (EDTMP) was used as the phosphonic acid chelating agent. In Examples 1 and 3 to 5, the concentration of EDTMP in the polishing composition was 2.0 g / L. In Example 2, phytic acid was used as the phosphonic acid chelating agent. In Example 2, the concentration of phytic acid in the polishing composition was 1.0 g / L.

[0063] In Example 2, nitric acid (HNO3) was used as the pH additive. In Examples 1 to 3 and 5, the pH value of the polishing composition was adjusted to 2. In Example 4, the pH value of the polishing composition was adjusted to 5. The pH of the polishing composition (liquid temperature: 25°C) was measured with a pH meter (manufactured by Horiba, Ltd., product name: LAQUA (registered trademark)).

[0064] (Comparative Examples 1 to 5) Each polishing composition was prepared in the same manner as in Examples 1 to 5, except that the components shown in Table 1 were used and the pH of each polishing composition was adjusted to the value shown in Table 1.

[0065] The differences from Examples 1 to 5 were that no surfactant was added to the polishing composition in Comparative Examples 1 and 2. The zeta potential of the abrasive grains was set to 0 mV and 35 mV in Comparative Examples 3 and 4. In Comparative Examples 2 and 5, no phosphonic acid chelating agent was added to the polishing composition. [Table 1]

[0066] <Evaluation> Using the polishing compositions of Examples 1 to 5 and Comparative Examples 1 to 5, silicon wafers having a diameter of 200 mm were polished under the following polishing conditions. Polishing equipment: Applied Materials 200mm CMP single-sided polishing equipment Mirra Polishing pad: Nitta Haas IC1010 hard polyurethane pad Polishing pressure: 5 psi (1 psi = 6894.76 Pa) Polishing platen rotation speed: 107 rpm Head rotation speed: 113 rpm Polishing compound supply: free-flowing ·Polishing composition supply amount: 200mL / min Polishing time: 60 seconds

[0067] The silicon wafers used for polishing were silicon wafers with a carbon film. Using an optical interference film thickness measurement device, the thickness of the carbon film before and after polishing was measured. The carbon film polishing rate was calculated from the difference in film thickness and the polishing time. The inspection rate results are shown in Table 1.

[0068] As shown in Table 1, it was confirmed that Examples 1 to 5 all had higher carbon polishing rates than Comparative Examples 1 to 5. A detailed comparison will be made below.

[0069] (Comparison between Example 1 and Comparative Example 1) Example 1 and Comparative Example 1 differ from each other in that the polishing composition contains a surfactant or not. The polishing composition of Example 1 contains a cationic surfactant, while the polishing composition of Comparative Example 1 does not contain a surfactant. Other points are the same between Example 1 and Comparative Example 1. From Example 1 and Comparative Example 1, it was confirmed that when a cationic surfactant is added to a polishing composition, the carbon removal rate is increased (improved) compared to when a cationic surfactant is not added.

[0070] (Comparison between Example 1 and Comparative Example 2) Example 1 and Comparative Example 2 differ from each other in whether the polishing composition contains a surfactant and a phosphonic acid chelating agent. The polishing composition of Example 1 contains a cationic surfactant and a phosphonic acid chelating agent, while the polishing composition of Comparative Example 2 does not contain a surfactant or a phosphonic acid chelating agent. In Comparative Example 2, nitric acid is added as a pH adjuster to adjust the pH to 2. Other points are the same between Example 1 and Comparative Example 2. From Example 1 and Comparative Example 2, it was confirmed that when a cationic surfactant and a phosphonic acid chelating agent are added to a polishing composition, the carbon removal rate is increased (improved) compared to when these are not added.

[0071] (Comparison of Example 1 and Comparative Examples 3 and 4) The zeta potentials of the abrasive grains contained in the polishing compositions of Example 1 and Comparative Examples 3 and 4 are different from each other. The zeta potential of the abrasive grains contained in the polishing composition of Example 1 is -40 mV, and the zeta potentials of the abrasive grains contained in the polishing compositions of Comparative Examples 3 and 4 are 0 mV and 35 mV, respectively. Other points are the same between Example 1 and Comparative Examples 3 and 4. From Example 1 and Comparative Examples 3 and 4, it was confirmed that the carbon removal rate was higher when the zeta potential of the abrasive grains contained in the polishing composition was -40 mV than when it was 0 mV or 35 mV.

[0072] (Comparison between Example 4 and Comparative Example 5) Example 4 and Comparative Example 5 differ from each other in whether the polishing composition contains a phosphonic acid chelating agent or not. The polishing composition of Example 4 contains a phosphonic acid chelating agent, while the polishing composition of Comparative Example 5 does not contain a phosphonic acid chelating agent. In Comparative Example 5, nitric acid is added as a pH adjuster to adjust the pH to 5. Other points are the same between Example 4 and Comparative Example 4. From Example 4 and Comparative Example 5, it was confirmed that when a phosphonic acid chelating agent is added to a polishing composition, the carbon removal rate is increased (improved) compared to when a phosphonic acid chelating agent is not added.

[0073] (Comparison of Examples 1 and 3) Examples 1 and 3 differ in the concentration of abrasive grains contained in the polishing composition. The concentration of abrasive grains in Example 1 is 2.0 wt%, and the concentration of abrasive grains in Example 3 is 0.5 wt%. Other points are the same between Examples 1 and 3. From Examples 1 and 3, it was confirmed that the carbon removal rate was higher when the abrasive grain concentration was 2.0 wt% than when it was 0.5 wt%.

[0074] (Comparison of Examples 1 and 4) The pH of the polishing composition differs between Examples 1 and 4. The pH of the polishing composition of Example 1 is 2, and the pH of the polishing composition of Example 4 is 5. Other points are the same between Examples 1 and 4. From Examples 1 and 4, it was confirmed that the carbon removal rate is higher when the polishing composition has a pH of 2 than when it has a pH of 5.

Claims

1. A polishing composition used for polishing a carbon-containing object, comprising: abrasive grains having a zeta potential of −5 mV or less; A surfactant, a phosphonic acid chelating agent, the surfactant is a cationic surfactant, The concentration of the cationic surfactant is 0.1 g / L or more and 2.0 g / L or less. Polishing composition.

2. The polishing composition of claim 1 , wherein the cationic surfactant comprises an amine oxide.

3. The polishing composition of claim 1 , wherein the cationic surfactant comprises dimethylamine oxide.

4. The polishing composition according to claim 1 , wherein the phosphonic acid chelating agent contains ethylenediaminetetramethylenephosphonic acid (EDTMP).

5. The polishing composition according to claim 1 , wherein the phosphonic acid chelating agent comprises phytic acid.

6. The polishing composition according to claim 1 , which has a pH of 3 or less.

7. The polishing composition according to claim 1 , wherein the abrasive grains comprise anionically modified silica.

8. 8. The polishing composition according to claim 7, wherein the silica has an organic acid fixed to the surface thereof.

9. 9. The polishing composition according to claim 7, wherein the silica is colloidal silica.

10. A method for producing the polishing composition according to any one of claims 1 to 9, comprising: A method for producing a polishing composition, comprising the step of mixing the abrasive grains having a zeta potential of −5 mV or less, the surfactant, the phosphonic acid chelating agent, and a liquid medium.

11. A polishing method comprising the step of polishing an object containing carbon with the polishing composition according to claim 1 .

12. A method for producing a semiconductor substrate, comprising a step of polishing a carbon film formed on a semiconductor substrate with the polishing composition according to claim 1 .

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