Grinding composition

Abstract

The present invention provides a polishing composition that can polish carbon films at a high polishing rate, and that can polish carbon films at a higher polishing rate than silicon nitride films. [Solution] An abrasive composition comprising anionic modified silica particles, a nonionic surfactant, and an anionic polymer, with a pH of 1.0 or higher and 5.0 or lower.

Description

Technical Field

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

Background Art

[0002] In recent years, with the multi-layer wiring of the semiconductor substrate surface, when manufacturing a device, a so-called Chemical Mechanical Polishing (CMP) technique for polishing and planarizing the semiconductor substrate has been used. CMP is a method of planarizing the surface of an object to be polished (workpiece), such as a semiconductor substrate, using a polishing composition.

[0003] In the field of CMP technology, studies have been continuously conducted to achieve a desired effect by polishing.

[0004] Patent Document 1 discloses that a polishing composition containing inorganic particles having a specific particle size distribution and an organic acid immobilized on the surface, and an acidic compound can polish both silicon oxide and silicon nitride at a high polishing rate on a substrate containing silicon oxide and silicon nitride. Patent Document 1 also discloses that the object to be polished contains a carbon film.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] <着 Recently, in an object to be polished containing a carbon film and a silicon nitride film, there is a demand to control the so-called polishing rate selection ratio, which maintains or improves the polishing rate of the carbon film and suppresses the polishing rate of the silicon nitride film.

[0007] Therefore, the present invention aims to provide a polishing composition that can polish a carbon film at a high polishing rate, and that can polish the carbon film at a higher polishing rate than the silicon nitride film (i.e., a high selectivity ratio expressed as the polishing rate of the carbon film / the polishing rate of the silicon nitride film). [Means for solving the problem]

[0008] To solve the above problems, the inventors conducted extensive research. As a result, they discovered that the above problems could be solved by an abrasive composition containing anionic modified silica particles, a nonionic surfactant, and an anionic polymer, with a pH of 1.0 to 5.0, thus completing the present invention. [Effects of the Invention]

[0009] The present invention provides a polishing composition that can polish a carbon film at a high polishing rate, and can polish the carbon film at a higher polishing rate than the silicon nitride film (i.e., it can increase the selectivity ratio expressed as the polishing rate of the carbon film / the polishing rate of the silicon nitride film). [Modes for carrying out the invention]

[0010] The embodiments of the present invention will be described below, but the present invention is not limited to the embodiments described below and can be modified in various ways within the scope of the claims. The embodiments described herein can be combined in any way to form other embodiments. Unless otherwise specified herein, operations and measurements of physical properties, etc., are performed under conditions of room temperature (20°C to 25°C) and relative humidity of 40% RH to 50% RH.

[0011] <Polishing composition> One aspect of the present invention relates to an abrasive composition comprising anionic modified silica particles, a nonionic surfactant, and an anionic polymer, having a pH of 1.0 to 5.0. The abrasive composition according to the present invention can polish carbon films at a high polishing rate, and can polish carbon films at a higher polishing rate than silicon nitride films (i.e., it can increase the selectivity ratio expressed as carbon film polishing rate / silicon nitride film polishing rate). In this specification, the "selectivity ratio expressed as carbon film polishing rate / silicon nitride film polishing rate" is also simply referred to as the "carbon film / silicon nitride film selectivity ratio".

[0012] [Anion-modified silica particles] The polishing composition according to the present invention contains anionic modified silica particles. Anionic modified silica particles are silica particles having anionic groups. Anionic modified silica particles may be used alone or in combination of two or more types. Anionic modified silica particles may be commercially available or synthesized.

[0013] Anion-modified silica particles have a negative zeta potential in acidic environments, resulting in excellent dispersion stability.

[0014] The anion-modified silica particles are not particularly limited, but anion-modified colloidal silica (colloidal silica having anionic groups) is preferred. Examples of anion-modified colloidal silica include colloidal silica in which anionic groups such as carboxylic acid groups, sulfonic acid groups, phosphonic acid groups, and aluminic acid groups are immobilized on the surface.

[0015] The method for producing anionically modified colloidal silica is not particularly limited, and one example is a method of reacting colloidal silica with a silane coupling agent having anionic groups at its terminals.

[0016] Examples of methods for producing colloidal silica include the sodium silicate method and the sol-gel method, and colloidal silica produced by any of these methods is suitable for use. 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 has a low content of diffusible metal impurities and / or corrosive ions such as chloride ions in the semiconductor. Colloidal silica can be produced by the sol-gel method using conventionally known methods. Specifically, colloidal silica can be obtained by using a hydrolyzable silicon compound (e.g., alkoxysilane or its derivatives) as a raw material and carrying out a hydrolysis-condensation reaction.

[0017] As a specific example, if sulfonic acid groups are to be immobilized on colloidal silica, this can be done, for example, by the method described in “Sulfonic acid-functionalized silica through quantitative oxidation of thiol groups”, Chem.Commun. 246-247 (2003). Specifically, colloidal silica with sulfonic acid groups 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. In a preferred embodiment, the anion-modified silica particles include sulfonic acid-modified colloidal silica.

[0018] If the goal is to immobilize a carboxyl group on colloidal silica, this can be done, for example, by 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, by coupling a silane coupling agent containing a photoreactive 2-nitrobenzyl ester to colloidal silica and then irradiating it with light, colloidal silica with immobilized carboxyl groups on its surface (carboxylic acid-modified colloidal silica) can be obtained.

[0019] The average primary particle diameter of anion-modified silica particles is not particularly limited, but is preferably 1 nm or more, more preferably 3 nm or more, and even more preferably 5 nm or more. The average primary particle diameter of anion-modified silica particles is not particularly limited, but is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 30 nm or less. Preferred average primary particle diameters for anion-modified silica particles include, for example, 1 nm to 100 nm, 3 nm to 50 nm, and 5 nm to 30 nm. However, the average primary particle diameter of anion-modified silica particles is not limited to these ranges. When the anion-modified silica particles are anion-modified colloidal silica, the preferred range for the average primary particle diameter of anion-modified colloidal silica is the same as the preferred range for the average primary particle diameter of anion-modified silica particles listed above. The average primary particle diameter of anion-modified silica particles can be calculated based on the specific surface area (SA) of the anion-modified silica particles calculated by the BET method and the density of the anion-modified silica particles. More specifically, the average primary particle size of anion-modified silica particles can be measured and calculated by the method described in the examples.

[0020] The average secondary particle diameter of anion-modified silica particles is not particularly limited, but is preferably 15 nm or more, more preferably 20 nm or more, and even more preferably 25 nm or more. Within this range, the resistance during polishing is reduced, enabling stable polishing. The average secondary particle diameter of anion-modified silica particles is not particularly limited, but is preferably 500 nm or less, more preferably 400 nm or less, and even more preferably 300 nm or less. Within this range, the amount of material scraped off the polished object is improved, and the polishing speed is further improved. Preferred average secondary particle diameters for anion-modified silica particles include, for example, 15 nm to 500 nm, 20 nm to 400 nm, and 25 nm to 300 nm. However, the average secondary particle diameter of anion-modified silica particles is not limited to these ranges. When the anion-modified silica particles are anion-modified colloidal silica, the preferred range for the average secondary particle diameter of anion-modified colloidal silica is the same as the preferred range for the average secondary particle diameter of anion-modified silica particles listed above. The average secondary particle diameter of anion-modified silica particles can be measured as the volume-averaged particle diameter (volume-based arithmetic mean diameter; Mv) by dynamic light scattering. More specifically, the average secondary particle diameter of anion-modified silica particles can be measured by the method described in the examples.

[0021] The ratio of the average secondary particle diameter to the average primary particle diameter of the anionic modified silica particles (average secondary particle diameter / average primary particle diameter) (hereinafter, the "ratio of the average secondary particle diameter to the average primary particle diameter" is also referred to as the "average aggregation degree") is not particularly limited, but is preferably greater than 1.0, more preferably 1.1 or more, and even more preferably 1.2 or more. The average aggregation degree of the anionic modified silica particles is not particularly limited, but is preferably 4.0 or less, more preferably 3.5 or less, and even more preferably 3.0 or less. Preferred average aggregation degrees of the anionic modified silica particles include, for example, greater than 1.0 and 4.0 or less, 1.1 or more and 3.5 or less, 1.2 or more and 3.0 or less, etc. However, the average aggregation degree of the anionic modified silica particles is not limited to these ranges. When the anionic modified silica particles contain anionic modified colloidal silica, the preferred range of the average aggregation degree of the anionic modified colloidal silica is also the same as the preferred range of the average aggregation degree of the anionic modified silica particles described above. The average aggregation degree of the anionic modified silica particles can be calculated by dividing the value of the average secondary particle diameter of the anionic modified silica particles by the value of the average primary particle diameter of the anionic modified silica particles (value of the average secondary particle diameter of the anionic modified silica particles / value of the average primary particle diameter of the anionic modified silica particles).

[0022] The shape of the anionic modified silica particles (preferably anionic modified colloidal silica) is not particularly limited and may be spherical (hereinafter also referred to as spherical) or non-spherical. Specific examples of non-spherical shapes include polygonal columnar shapes such as triangular columns and square columns, cylindrical shapes, barrel-shaped with the central part of the cylinder bulging more than the ends, donut-shaped with the central part of the disk penetrated, plate-shaped, so-called cocoon-shaped (cocoon-shaped) with a constriction in the central part, so-called aggregated spherical shape where a plurality of particles are integrated, so-called sugar ball shape with a plurality of protrusions on the surface, rugby ball shape, etc., and there are various shapes and are not particularly limited.

[0023] The shape and size of the anionic modified silica particles (average primary particle diameter, average secondary particle diameter, average degree of aggregation, etc.) can be appropriately controlled, respectively, for example, by selecting the method for producing the anionic modified silica particles, etc. However, the methods for controlling the shape and size of the anionic modified silica particles are not limited to these, respectively.

[0024] The content (concentration) of the anionic modified silica particles in the polishing composition is not particularly limited, but it is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, still more preferably 0.1% by mass or more, and particularly preferably 0.3% by mass or more, based on the total mass of the polishing composition. The content of the anionic modified silica particles in the polishing composition is not particularly limited, but it is preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 2% by mass or less, and particularly preferably 1% by mass or less, based on the total mass of the polishing composition. When within the above ranges, the polishing rate when polishing a specific polishing object is further improved. Also, when within the above ranges, the selectivity between specific polishing objects may be further improved. The preferred content of the anionic modified silica particles in the polishing composition is not particularly limited, but examples include 0.01% by mass or more and 10% by mass or less, 0.05% by mass or more and 5% by mass or less, 0.1% by mass or more and 2% by mass or less, 0.3% by mass or more and 1% by mass or less, etc., based on the total mass of the polishing composition. However, the content of the anionic modified silica particles in the polishing composition is not limited to these ranges.

[0025] [Nonionic surfactant] The polishing composition according to the present invention contains a nonionic surfactant. The nonionic surfactant may be used alone or in combination of two or more. The nonionic surfactant may be a commercially available product or a synthetic product. [[ID=​​Nonionic surfactants can adsorb onto the hydrophobic surface of a carbon film, making the carbon film surface hydrophilic. The hydrophilic carbon film surface can then interact with hydrophilic anionic modified silica particles, increasing the frequency of contact and thus improving the polishing speed of the carbon film.

[0027] Examples of nonionic surfactants include alkyl betaines, alkylamine oxides, polyoxyalkylene glycols, polyoxyalkylene alkyl ethers, sorbitan fatty acid esters, glycerin fatty acid esters, polyoxyalkylene fatty acid esters, polyoxyalkylene alkylamines, and alkyl alkanolamides. From the viewpoint of being able to better exhibit the effects of the present invention, the nonionic surfactant is preferably a compound having a polyoxyalkylene glycol structure, such as polyoxyalkylene glycol or polyoxyalkylene alkyl ether (hereinafter also referred to as "polyoxyalkylene glycol-based compound").

[0028] In preferred embodiments, the nonionic surfactant includes a compound having a polyoxyalkylene glycol structure. Examples of compounds having a polyoxyalkylene glycol structure include oxyalkylene homopolymers, oxyalkylene copolymers, and polyoxyalkylene alkyl ethers.

[0029] The oxyalkylene homopolymers and oxyalkylene copolymers are not particularly limited, but examples include polyethylene glycol, polypropylene glycol, polyethylene glycol-polypropylene glycol random copolymer, polyethylene glycol-polytetramethylene glycol random copolymer, polypropylene glycol-polytetramethylene glycol random copolymer, polyethylene glycol-polypropylene glycol-polytetramethylene glycol random copolymer, polyethylene glycol-polypropylene glycol block copolymer, polypropylene glycol-polypropylene glycol-polypropylene glycol triblock copolymer, polyethylene glycol-polypropylene glycol-polypropylene glycol triblock copolymer, and the like.

[0030] In a more preferred embodiment, the nonionic surfactant includes a compound represented by the following formula 1 as a polyoxyalkylene alkyl ether.

[0031] [ka]

[0032] In formula 1, X is an alkylene group having 2 or 3 carbon atoms, m is an integer between 4 and 14, and n is an integer between 3 and 25.

[0033] In formula 1, X is preferably an alkylene group having 2 carbon atoms (i.e., an ethylene group).

[0034] In Equation 1, m is preferably an integer between 5 and 12, and more preferably an integer between 7 and 9.

[0035] In Equation 1, n is preferably an integer between 5 and 15, and more preferably an integer between 5 and 10.

[0036] The compound represented by Formula 1 is preferably at least one selected from the group consisting of polyoxyethylene(5) monooctyl ether, polyoxyethylene(6) monooctyl ether, polyoxyethylene(7) monooctyl ether, polyoxyethylene(8) monooctyl ether, polyoxyethylene(9) monooctyl ether, polyoxyethylene(10) monooctyl ether, polyoxyethylene(5) monononyl ether, polyoxyethylene(6) monononyl ether, polyoxyethylene(7) monononyl ether, polyoxyethylene(8) monononyl ether, polyoxyethylene(9) monononyl ether, polyoxyethylene(10) monononyl ether, polyoxyethylene(5) monodecyl ether, polyoxyethylene(6) monodecyl ether, polyoxyethylene(7) monodecyl ether, polyoxyethylene(8) monodecyl ether, polyoxyethylene(9) monodecyl ether, and polyoxyethylene(10) monodecyl ether.

[0037] The content (concentration) of the nonionic surfactant in the abrasive composition is not particularly limited, but is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, even more preferably 0.01% by mass or more, and particularly preferably 0.05% by mass or more, based on the total mass of the abrasive composition. The content (concentration) of the nonionic surfactant in the abrasive composition is preferably 3% by mass or less, more preferably 1% by mass or less, even more preferably 0.5% by mass or less, and particularly preferably 0.1% by mass or less, based on the total mass of the abrasive composition. The preferred content (concentration) of the nonionic surfactant in the abrasive composition is not particularly limited, but examples include 0.001% by mass or more and 3% by mass or less, 0.005% by mass or more and 1% by mass or less, 0.01% by mass or more and 0.5% by mass or less, and 0.05% by mass or more and 0.1% by mass or less, based on the total mass of the abrasive composition. However, the content (concentration) of the nonionic surfactant in the abrasive composition is not limited to these ranges. The effects of the present invention can be more fully realized if the content (concentration) of the nonionic surfactant is within the above range.

[0038] [Anionic polymers] The polishing composition according to the present invention contains an anionic polymer. In this specification, "anionic polymer" refers to a polymer having anionic groups such as carboxylic acid groups, sulfonic acid groups, and phosphate groups in its molecule. The anionic polymer may be used alone or in combination of two or more types. The anionic polymer may be a commercially available product or a synthetic product.

[0039] The anionic groups of anionic polymers are electrically attracted to the silicon nitride film, causing the anionic polymers to adsorb onto the surface of the silicon nitride film, thus suppressing the polishing rate of the silicon nitride film. Because anionic polymers have both hydrophobic parts (e.g., the main chain) and hydrophilic parts (anionic groups), they are thought to contribute to improving the polishing rate of the carbon film through surfactant-like action.

[0040] Anionic polymers only need to have anionic groups. Specific examples of anionic polymers include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polymethallyl sulfonic acid, poly(2-acrylamide-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, polyacrylic acid, polymethacrylic acid, (meth)acrylic acid-isoprene sulfonic acid copolymer, (meth)acrylic acid-[2-(meth)acrylamide-2-methylpropanesulfonic acid] copolymer, (meth)acrylic acid-isoprene sulfonic acid-[2-(meth)acrylamide-2-methylpropanesulfonic acid] copolymer, and the like. Anionic polymers may also exist in the form of neutralized salts.

[0041] As anionic polymers, not only those having the main chain structure described above, but also graft copolymers having anionic polymer structures in their side chains can be suitably used. The anionic polymer may be a polymer having identical (homopolymer) or different (copolymer) repeating structural units, and when the anionic polymer is a copolymer, the form of the copolymer may be a block copolymer, a random copolymer, a graft copolymer, or an alternating copolymer.

[0042] In preferred embodiments, the anionic polymer includes an anionic polymer containing a sulfonic acid group. The anionic polymer containing a sulfonic acid group is not particularly limited as long as it has a sulfonic acid group.

[0043] Examples of anionic polymers containing sulfonic acid groups include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polymethallyl sulfonic acid, poly(2-acrylamide-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, (meth)acrylic acid-isoprene sulfonic acid copolymer, (meth)acrylic acid-[2-(meth)acrylamide-2-methylpropanesulfonic acid] copolymer, and (meth)acrylic acid-isoprene sulfonic acid-[2-(meth)acrylamide-2-methylpropanesulfonic acid] copolymer. The anionic polymer containing sulfonic acid groups may also exist in the form of a neutralized salt.

[0044] In a more preferred embodiment, the anionic polymer containing a sulfonic acid group includes poly(2-acrylamido-2-methylpropanesulfonic acid).

[0045] The anionic group in an anionic polymer containing a sulfonic acid group may consist solely of a sulfonic acid group, or it may contain one or more anionic groups other than a sulfonic acid group.

[0046] The weight-average molecular weight of the anionic polymer is preferably 1,500 or more, more preferably 3,000 or more, even more preferably 4,000 or more, even more preferably 5,000 or more, particularly preferably 6,000 or more, particularly more preferably 7,000 or more, and most preferably 8,000 or more. The weight-average molecular weight of the anionic polymer is preferably 1,000,000 or less, more preferably 500,000 or less, even more preferably 100,000 or less, even more preferably 50,000 or less, particularly preferably 25,000 or less, particularly more preferably 20,000 or less, and most preferably 15,000 or less. In other words, the weight-average molecular weight of the anionic polymer is preferably 1,500 to 1,000,000, more preferably 3,000 to 500,000, even more preferably 4,000 to 100,000, even more preferably 5,000 to 50,000, particularly preferably 6,000 to 25,000, particularly more preferably 7,000 to 20,000, and most preferably 8,000 to 15,000. In this specification, the weight-average molecular weight of the anionic polymer can be measured by gel permeation chromatography (GPC) using polyethylene glycol as the standard substance. Detailed measurement methods are described in the examples.

[0047] The content (concentration) of anionic polymer in the polishing composition is not particularly limited, but is preferably 0.0001% by mass or more, more preferably 0.0005% by mass or more, even more preferably 0.001% by mass or more, and particularly preferably 0.01% by mass or more, based on the total mass of the polishing composition. The content (concentration) of anionic polymer in the polishing composition is preferably 3% by mass or less, more preferably 1% by mass or less, even more preferably 0.5% by mass or less, and particularly preferably 0.1% by mass or less, based on the total mass of the polishing composition. The preferred content (concentration) of anionic polymer in the polishing composition is not particularly limited, but examples include 0.0001% by mass or more and 3% by mass or less, 0.0005% by mass or more and 1% by mass or less, 0.001% by mass or more and 0.5% by mass or less, and 0.01% by mass or more and 0.1% by mass or less, based on the total mass of the polishing composition. However, the content (concentration) of anionic polymer in the polishing composition is not limited to these ranges. The effects of the present invention can be more fully realized if the content (concentration) of the anionic polymer is within the above range. In a preferred embodiment, the content of the anionic polymer in the polishing composition is less than the content of the nonionic surfactant.

[0048] [pH] The pH of the polishing composition according to the present invention is 1.0 or more and 5.0 or less. If the pH of the polishing composition according to the present invention is less than 1.0, it is undesirable because the components contained in the polishing composition may decompose. If the pH of the polishing composition according to the present invention is greater than 5.0, it is undesirable because the negative charge of the carbon film becomes stronger and the polishing speed decreases due to electrostatic repulsion with the anion-modified silica particles. The pH of the polishing composition according to the present invention is preferably 2.0 or more and 4.0 or less, more preferably 2.5 or more and 3.0 or less, and even more preferably 2.7 or more and 3.2 or less.

[0049] The abrasive composition according to the present invention may have its pH adjusted by an anionic polymer or by a pH adjusting agent. In one embodiment, the abrasive composition according to the present invention may contain a pH adjusting agent. The pH adjusting agent may be used alone or in combination of two or more. The pH adjusting agent may be a commercially available product or a synthetic product.

[0050] The pH adjusting agent is not particularly limited, and known pH adjusting agents used in the field of polishing compositions can be used. Known acids, bases, or salts thereof can be used as pH adjusting agents. Examples of pH adjusting agents include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, oleic acid, linoleic acid, linolenic acid, arachidonic acid, docosahexaenoic acid, eicosapentaenoic acid, lactic acid, malic acid, citric acid, benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, gallic acid, melitic acid, cinnamic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, and adipine. Examples include acids, carboxylic acids such as fumaric acid, maleic acid, aconitic acid, amino acids, and anthranilic acid, as well as organic acids such as sulfonic acid and organic phosphonic acid; inorganic acids such as nitric acid, carbonic acid, hydrochloric acid, hypophosphorous acid, phosphorous acid, phosphonic acid, boric acid, and hydrofluoric acid; alkali metal hydroxides such as potassium hydroxide (KOH); alkali metal carbonates such as potassium carbonate (K2CO3) and sodium carbonate (Na2CO3); hydroxides of group 2 elements; ammonia (ammonium hydroxide); and organic bases such as quaternary ammonium hydroxide compounds.

[0051] The amount of pH adjuster in the polishing composition should be appropriately selected to achieve the desired pH value of the polishing composition.

[0052] The pH of the polishing composition shall be the value measured by the method described in the examples.

[0053] [Dispersion medium] The polishing composition according to the present invention may contain a dispersion medium to dissolve and / or disperse each component. The dispersion medium may be used alone or in combination of two or more types.

[0054] The dispersion medium is not particularly limited and includes, for example, water; alcohols such as methanol, ethanol, and ethylene glycol; ketones such as acetone; and mixtures thereof. The dispersion medium is preferably water.

[0055] From the viewpoint of not inhibiting the action of the components contained in the polishing composition, water that contains as few impurities as possible is preferable. Preferably, the water has a total transition metal ion content of 100 ppb or less. The purity of the water can be increased, for example, by removing impurity ions using ion exchange resin, removing foreign matter by filtration, or distillation. More preferably, the water is selected from deionized water (ion-exchanged water), pure water, ultrapure water, and distilled water.

[0056] [Other ingredients] The polishing composition according to the present invention may further contain other known components that can be used in polishing compositions, as long as they do not impair the effects of the present invention. Examples of other components include abrasive particles other than anionic modified silica particles, oxidizing agents, antifungal agents (preservatives), complexing agents, and metal corrosion inhibitors. The abrasive particles other than anionic modified silica particles, oxidizing agents, and antifungal agents (preservatives) will be described below.

[0057] Abrasive particles other than anion-modified silica particles may be inorganic particles, organic particles, or organic-inorganic composite particles. Specific examples of inorganic particles are not particularly limited, but include unmodified silica particles, alumina particles, ceria particles, titania particles and other metal oxide particles; silicon nitride particles; silicon carbide particles; boron nitride particles; etc. Specific examples of organic particles are not particularly limited, but include polymethyl methacrylate (PMMA) particles, etc. Abrasive particles other than anion-modified silica particles may be used individually or in combination of two or more types.

[0058] Examples of oxidizing agents include hydrogen peroxide, sodium peroxide, barium peroxide, ozonated water, silver(II) salts, iron(III) salts, permanganate, chromic acid, dichromate, peroxodisulfate, peroxolinic acid, peroxosulfate, peroxoboric acid, performic acid, peracetic acid, perbenzoic acid, perphthalic acid, hypochlorous acid, hypobromous acid, hypoiodic acid, chloric acid, chlorous acid, perchloric acid, bromic acid, iodic acid, periodic acid, persulfate, dichloroisocyanuric acid and their salts (e.g., potassium salts, sodium salts, ammonium salts, etc.). Oxidizing agents may be used individually or in combination of two or more.

[0059] Examples of antifungal agents (preservatives) include isothiazoline preservatives such as 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one; phenoxyethanol; and others. Antifungal agents (preservatives) may be used individually or in combination of two or more.

[0060] [Method for producing abrasive compositions] The method for producing the polishing composition according to the present invention is not particularly limited, and can be obtained, for example, by stirring and mixing anionic modified silica particles, a nonionic surfactant and an anionic polymer, and optionally a pH adjuster, a dispersion medium and other components. Details of each component are as described above.

[0061] The temperature at which each component is mixed is not particularly limited, but it is preferably between 10°C and 40°C, and heating may be used to increase the dissolution rate. The mixing time is also not particularly limited as long as uniform mixing is achieved.

[0062] [Object to be polished] The abrasive composition according to the present invention preferably contains a carbon film and a silicon nitride film. The abrasive composition according to the present invention is preferably used for polishing objects containing a carbon film and a silicon nitride film.

[0063] In this specification, the term "carbon film" is not limited to films composed solely of carbon atoms, but also includes carbon films containing atoms other than carbon atoms (such as hydrogen atoms and oxygen atoms).

[0064] Examples of carbon films include spin-on carbon films, amorphous carbon films, diamond-like carbon films, nanocrystalline diamond films, graphene films, SiC films, and SiOC films. The carbon film may be used alone or in combination of two or more types. The carbon film is preferably selected from the group consisting of spin-on carbon films, amorphous carbon films, diamond-like carbon films, nanocrystalline diamond films, and graphene films, and is more preferably a spin-on carbon film.

[0065] The carbon content in the carbon film is defined as 10% or more by mass, 30% or more by mass, 50% or more by mass, 60% or more by mass, 70% or more by mass, 80% or more by mass, 90% or more by mass, 92% or more by mass, 95% or more by mass, 97% or more by mass, 98% or more by mass, and 99% or more by mass, based on the total mass of the carbon film. The amount is preferred in the order of mass% or more. The carbon film may be in a form that is substantially composed of carbon (substantially containing 100% by mass of carbon atoms).

[0066] Carbon films and silicon nitride films can be formed by methods such as CVD, PVD, and spin coating.

[0067] The polishing material to be polished by the polishing composition according to the present invention may further contain other materials in addition to the carbon film and silicon nitride film. Examples of other materials include 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, titanium nitride, elemental metals, SiGe, and the like.

[0068] Examples of polishing materials containing silicon dioxide include, for example, TEOS (Tetraethyl Orthosilicate) type silicon dioxide films (hereinafter also referred to as "TEOS" or "TEOS film") produced using tetraethyl orthosilicate as a precursor, HDP (High Density Plasma) films, USG (Undoped Silicate Glass) films, PSG (Phosphorus Silicate Glass) films, BPSG (Boron-Phospho Silicate Glass) films, and RTO (Rapid Thermal Oxidation) films.

[0069] Examples of elemental metals include tungsten, copper, cobalt, hafnium, nickel, gold, silver, platinum, palladium, rhodium, ruthenium, iridium, and osmium.

[0070] <Polishing method and method for manufacturing semiconductor substrates> One aspect of the present invention relates to a polishing method that includes the step of polishing an object to be polished, which contains a carbon film and a silicon nitride film, using the above-described polishing composition.

[0071] One aspect of the present invention relates to a method for manufacturing a semiconductor substrate, comprising the step of polishing a semiconductor substrate containing a carbon film and a silicon nitride film by the polishing method described above.

[0072] The polishing apparatus is not particularly limited, but a general polishing apparatus can be used, for example, one that has a holder for holding a substrate or the like containing the object to be polished, a motor with a changeable rotation speed, and a polishing platen to which a polishing pad (abrasive cloth) can be attached.

[0073] The polishing pad is not particularly limited, but for example, general nonwoven fabrics, polyurethanes, and porous fluororesins can be used without any particular restrictions. Preferably, the polishing pad has grooves that allow the polishing liquid to accumulate.

[0074] There are no particular restrictions on the polishing conditions. For example, the rotational speed of the polishing platen and head can be 10 rpm (0.17 s). -1 ) or more 500rpm (8.33s -1 Preferably, the pressure applied to the substrate having the object to be polished (polishing pressure) is between 0.5 psi (3.4 kPa) and 10 psi (68.9 kPa).

[0075] The method of supplying the polishing composition to the polishing pad is not particularly limited; for example, a method of continuous supply using a pump or the like can be employed. There is no limit to the amount supplied, but it is preferable that the surface of the polishing pad is always covered with the polishing composition. The polishing time is also not particularly limited; for example, a time that achieves the desired polishing can be appropriately selected.

[0076] After polishing is complete, the substrate containing the polished object may be washed with running water, and any water droplets adhering to the substrate may be removed and dried using a spin dryer or similar device.

[0077] The polishing composition according to the present invention may be a one-component type or a multi-component type, including a two-component type. Furthermore, the polishing composition according to the present invention may be prepared by diluting the stock solution of the polishing composition with a diluent such as water to, for example, three times or more (or, for example, five times or more).

[0078] [Polishing rate of carbon film and silicon nitride film, and selectivity ratio of carbon film / silicon nitride film] The polishing method according to the present invention can polish an object containing a carbon film and a silicon nitride film at a specific polishing rate ratio. The polishing method according to the present invention can be preferably applied to polishing an object containing a carbon film and a silicon nitride film (e.g., finish polishing).

[0079] The lower limit of the carbon film polishing rate is preferably 200 Å / min or higher, more preferably 215 Å / min or higher, and even more preferably 240 Å / min or higher. The upper limit of the carbon film polishing rate is not particularly limited, but is practically 6000 Å / min or lower. Note that 1 Å = 0.1 nm.

[0080] The upper limit of the polishing speed of the silicon nitride film is preferably 30 Å / min or less, more preferably 20 Å / min or less, and even more preferably 10 Å / min or less. The lower limit of the polishing speed of the silicon nitride film is not particularly limited, but for example, 0.5 Å / min or more.

[0081] The selectivity ratio of the carbon film / silicon nitride film is preferably 10 or more, and more preferably 30 or more. The selectivity ratio of the carbon film / silicon nitride film may be 100 or more, 150 or more, or 200 or more.

[0082] While embodiments of the present invention have been described in detail, these are descriptive and illustrative, and not limiting, and it is clear that the scope of the present invention should be interpreted by the appended claims.

[0083] The present invention encompasses the following embodiments and forms. [1] An abrasive composition comprising anionic modified silica particles, a nonionic surfactant, and an anionic polymer, with a pH of 1.0 or higher and 5.0 or lower. [2] The polishing composition according to [1], wherein the anionic modified silica particles are anionic modified colloidal silica. [3] The abrasive composition according to [1] or [2], wherein the nonionic surfactant comprises a compound having a polyoxyalkylene glycol structure. [4] The nonionic surfactant comprises a compound represented by the following formula 1, as described in [3]:

[0084] [ka]

[0085] In formula 1, X is an alkylene group having 2 or 3 carbon atoms, m is an integer between 4 and 14, and n is an integer between 3 and 25. [5] The polishing composition according to any one of [1] to [4], wherein the anionic polymer comprises an anionic polymer containing a sulfonic acid group. [6] A polishing composition according to any one of [1] to [5], used for polishing objects containing a carbon film and a silicon nitride film. A polishing method comprising the step of polishing an object to be polished, which includes a carbon film and a silicon nitride film, using a polishing composition described in any of [7][1] to [6]. [8] A method for manufacturing a semiconductor substrate, comprising the step of polishing a semiconductor substrate containing a carbon film and a silicon nitride film by the polishing method described in [7]. [Examples]

[0086] 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 "mass%" and "parts by mass," respectively. Unless otherwise specified, the operations were carried out under room temperature (20°C to 25°C) / relative humidity of 40% RH to 50% RH.

[0087] <Measurement method> (Average primary particle diameter of anion-modified silica particles) The average primary particle size of anion-modified silica particles was calculated from the specific surface area of ​​the anion-modified silica particles and the density of the anion-modified silica particles, both measured using the BET method with a "Flow Sorb II 2300" instrument from Micromerities.

[0088] (Average secondary particle diameter of anion-modified silica particles) The average secondary particle diameter of anion-modified silica particles was measured as the volume-average particle diameter (volume-based arithmetic mean diameter; Mv) using a dynamic light scattering particle size and particle size distribution analyzer UPA-UT151 (manufactured by Nikkiso Co., Ltd.).

[0089] (pH of the abrasive composition) The pH of the polishing composition was determined using a glass electrode type hydrogen ion concentration indicator (Horiba, Ltd., Model: F-23). ​​After three-point calibration using standard buffers (phthalate pH buffer pH: 4.01 (25°C), neutral phosphate pH buffer pH: 6.86 (25°C), carbonate pH buffer pH: 10.01 (25°C)), the glass electrode was placed in the polishing composition, and the pH value after stabilization for at least two minutes was taken as the pH value.

[0090] (Weight average molecular weight) The weight-average molecular weight (Mw) of the anionic polymer was determined using the weight-average molecular weight (converted to polyethylene glycol) measured by gel permeation chromatography (GPC). The weight-average molecular weight was measured using the following apparatus and conditions: GPC equipment: Manufactured by Shimadzu Corporation Model: Prominence + ELSD detector (ELSD-LTII) Column: VP-ODS (manufactured by Shimadzu Corporation) Mobile phase A:MeOH B: 1% aqueous solution of acetic acid Flow rate: 1mL / min Detector: ELSD, temp. 40℃, Gain 8, N2GAS 350kPa Oven temperature: 40℃ Injection volume: 40μL.

[0091] <Comparative Example 1> Sulfonic acid-modified colloidal silica (average primary particle size: 15 nm, average secondary particle size: 34 nm) was added to pure water as a dispersion medium to a final concentration of 0.4% by mass. Furthermore, polyoxyethylene (10) decyl ether was added as a nonionic surfactant to a final concentration of 0.08% by mass, and the mixture was stirred at room temperature (25°C) for 30 minutes. After that, nitric acid was added to adjust the pH to 2.9 to prepare the polishing composition.

[0092] <Example 1> To pure water used as a dispersion medium, sulfonic acid-modified colloidal silica (average primary particle diameter: 15 nm, average secondary particle diameter: 34 nm) was added to a final concentration of 0.4% by mass. Furthermore, polyoxyethylene (10) decyl ether was added as a nonionic surfactant to a final concentration of 0.08% by mass, and the sodium salt of a copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid (hereinafter referred to as "(acrylic acid / sulfonic acid) copolymer") (weight-average molecular weight 12,000) was added as an anionic polymer to a final concentration of 0.002% by mass. The mixture was then stirred at room temperature (25°C) for 30 minutes. Subsequently, nitric acid was added to adjust the pH to 2.9 to prepare the polishing composition.

[0093] <Example 2> To pure water used as a dispersion medium, sulfonic acid-modified colloidal silica (average primary particle diameter: 15 nm, average secondary particle diameter: 34 nm) was added to a final concentration of 0.4% by mass. Furthermore, polyoxyethylene (10) decyl ether was added as a nonionic surfactant to a final concentration of 0.08% by mass, and sodium salt of an acrylic acid / sulfonic acid copolymer (weight-average molecular weight 12,000) was added as an anionic polymer to a final concentration of 0.05% by mass. The mixture was stirred and mixed at room temperature (25°C) for 30 minutes to prepare an abrasive composition (pH 2.9).

[0094] Table 1 shows the composition of each polishing composition. A "-" in Table 1 indicates that the component was not used.

[0095] [Table 1]

[0096] <Rating> The surfaces of the objects to be polished were polished using each of the polishing compositions prepared above under the following conditions. The objects to be polished were a silicon wafer (300 mm, blanket wafer, manufactured by Advance Materials Technology Co., Ltd.) with a 2,000 Å thick spin-on carbon (SoC) film formed on its surface, and a silicon wafer (300 mm, blanket wafer, manufactured by Advance Materials Technology Co., Ltd.) with a 2,500 Å thick silicon nitride (Si3N4) film formed on its surface.

[0097] (Polishing equipment and polishing conditions) Polishing equipment: Polishing machine manufactured by Ebara Corporation (model FREX 300E) Polishing pad: Nitta DuPont Supreme RN-H suede pad. Polishing pressure: 1.5 psi (1 psi = 6894.76 Pa) Conditioner (dresser): 3M nylon brush Polishing plate rotation speed: 40 rpm Head rotation speed: 40 rpm Supply of polishing composition: flow-through Polishing composition supply amount: 200mL / min Polishing time: 30 seconds (SoC film), 1 minute (silicon nitride film).

[0098] (Evaluation of polishing speed) The thickness of the SoC film and Si3N4 film before and after polishing was determined using an optical film thickness measuring instrument (ASET-f5x: manufactured by KLA-Tencor Co., Ltd.). From the determined thickness, the polishing rate [unit: Å / min] for each object was calculated by dividing [(thickness before polishing [unit: Å]) - (thickness after polishing [unit: Å])] by the polishing time [unit: min]. In this invention, for SoC films, a polishing rate of 200 Å / min or higher is practical. In this invention, for Si3N4 films, a polishing rate of 10 Å / min or lower is practical. The selectivity ratio of the SoC film to the Si3N4 film (polishing rate of the SoC film / polishing rate of the Si3N4 film) (indicated as "SoC / Si3N4" in Table 2 below) was evaluated as preferable when it was high.

[0099] (Evaluation of defects) Using the Surfscan® SP-5 manufactured by KLA-Tencor Co., Ltd., the total number of defects (residues) with a size of 85 nm or larger (SoC film) or 50 nm or larger (Si3N4 film) remaining on the surface of polished damaged objects was measured.

[0100] Table 2 shows the evaluation results for polishing speed and defects. In Table 2, "overload" indicates that measurement was impossible due to an excessive number of defects (more than 300,000).

[0101] [Table 2]

[0102] As is clear from Table 2, when using the polishing composition according to the example, the SoC film can be polished at a higher polishing speed compared to the polishing composition according to the comparative example. Furthermore, when using the polishing composition according to the example, the polishing speed of the Si3N4 film can be significantly suppressed compared to the polishing composition according to the comparative example, and thus the selectivity ratio of the SoC film to the Si3N4 film can be significantly increased.

[0103] Comparing Example 1 and Example 2, it can be seen that increasing the content of anionic polymers leads to a higher selectivity ratio of the SoC film to the Si3N4 film, and a decrease in the number of defects.

Claims

1. It contains anionic modified silica particles, a nonionic surfactant, and anionic polymers. An abrasive composition having a pH of 1.0 or higher and 5.0 or lower.

2. The polishing composition according to claim 1, wherein the anion-modified silica particles are anion-modified colloidal silica.

3. The polishing composition according to claim 1, wherein the nonionic surfactant comprises a compound having a polyoxyalkylene glycol structure.

4. The nonionic surfactant comprises a compound represented by the following formula 1, wherein the polishing composition is as described in claim 3: 【Chemistry 1】 In formula 1, X is an alkylene group having 2 or 3 carbon atoms, m is an integer between 4 and 14, and n is an integer between 3 and 25.

5. The polishing composition according to claim 1, wherein the anionic polymer comprises an anionic polymer containing a sulfonic acid group.

6. The polishing composition according to claim 1, used for polishing objects containing a carbon film and a silicon nitride film.

7. A polishing method comprising the step of polishing an object to be polished, which includes a carbon film and a silicon nitride film, using the polishing composition described in any one of claims 1 to 6.

8. A method for manufacturing a semiconductor substrate, comprising the step of polishing a semiconductor substrate containing a carbon film and a silicon nitride film using the polishing method described in claim 7.

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