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

Abstract

To provide a polishing composition capable of increasing the polishing selectivity ratio of SiOC to silicon nitride, a production method for the polishing composition, a polishing method, and a manufacturing method for a semiconductor substrate.SOLUTION: A polishing composition contains abrasives having a zeta potential of -5 mV or less, a cationic surfactant, a phosphonic acid-based chelating agent, and a cationic compound having a molecular weight of 300 or less.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] In recent years, with the multi-layer wiring of the semiconductor substrate surface, when manufacturing a semiconductor device (device), a so-called Chemical Mechanical Polishing (CMP) technique for polishing and planarizing the semiconductor substrate is utilized. CMP is a method of planarizing the surface of an object to be polished (workpiece), such as a semiconductor substrate, using a polishing composition (slurry) containing abrasive grains such as silica, alumina, ceria, a corrosion inhibitor, a surfactant, and the like. The object to be polished (workpiece) is made of silicon, polysilicon, silicon oxide, silicon nitride, wiring made of metal, plugs, and the like.

[0003] Regarding the polishing composition used when polishing a semiconductor substrate by CMP, various proposals have been made so far. For example, Patent Document 1 describes "a polishing composition used for polishing an object to be polished including a silicon oxide film, which contains abrasive grains, a compound having a logarithm value (LogP) of the partition coefficient 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

Summary of the Invention

Problems to be Solved by the Invention

[0005] In some cases, a SiOC film deposited on a silicon nitride film is polished. Conventional polishing compositions have not always satisfied user requirements regarding the polishing rate of the SiOC film relative to the polishing rate of the silicon nitride film (i.e., the polishing selectivity ratio of SiOC to silicon nitride). An improvement in the polishing selectivity ratio of SiOC to silicon nitride is desired.

[0006] The present invention has been made in view of these circumstances, and aims to provide a polishing composition capable of increasing the polishing selectivity ratio of SiOC to silicon nitride, a method for manufacturing the polishing composition, a polishing method, and a method for manufacturing a semiconductor substrate. [Means for solving the problem]

[0007] In view of the above problems, the inventors diligently conducted research. As a result, they discovered that by using an abrasive composition containing abrasive grains with a zeta potential of -5mV or less, a cationic surfactant, a phosphonic acid-based chelating agent, and a cationic compound with a molecular weight of 300 or less, the abrasive selectivity ratio of SiOC to silicon nitride is increased, and thus the invention was completed. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a polishing composition that can increase (improve) the polishing selectivity ratio of SiOC to silicon nitride, a method for manufacturing the polishing composition, a polishing method, and a method for manufacturing a semiconductor substrate. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will now be described in detail. The polishing composition according to an embodiment of the present invention (hereinafter, this embodiment) is a polishing composition comprising abrasive grains having a zeta potential of -5mV or less, a cationic surfactant, a phosphonic acid-based chelating agent, and a cationic compound having a molecular weight of 300 or less.

[0010] This polishing composition can be used to polish objects such as elemental silicon, silicon compounds, and metals. For example, it can be used to polish surfaces containing elemental silicon, polysilicon, silicon compounds, and metals in the semiconductor device manufacturing process, and is particularly suitable for polishing surfaces containing SiOC. For example, it is suitable for polishing SiOC films deposited on silicon nitride films. When polishing is performed using this polishing composition, it may be possible to polish surfaces containing SiOC or SiOC films deposited on silicon nitride films with a high selectivity ratio. The polishing composition according to this embodiment will be described in detail below.

[0011] <Abrasive grains> The polishing composition according to this embodiment contains abrasive grains having a zeta potential of -5mV or less. The abrasive grains having a zeta potential of -5mV or less may be anion-modified silica (for example, silica with an organic acid fixed to its surface). The silica may also 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 according to this embodiment preferably have a pH of 6 or less and a zeta potential of -5 mV or less, more preferably -8 mV or less, and particularly preferably -11 mV or less. Furthermore, the abrasive grains used in the polishing composition according to this embodiment preferably have a pH of 6 or less and a zeta potential of -20 mV or more, more preferably -18 mV or more, and particularly preferably -15 mV or more. Having a zeta potential within such a range of abrasive grains (e.g., colloidal silica) makes it possible to further increase (improve) the polishing selectivity ratio of SiOC to silicon nitride.

[0013] For example, in the polishing composition according to this embodiment, the zeta potential of the abrasive grains is -5mV or less and -20mV or more.

[0014] 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 the laser Doppler method (electrophoretic light scattering measurement method) with a flow cell at a measurement temperature of 25°C, and analyzing the obtained data using the Smoluchowski equation.

[0015] (Manufacturing method) Colloidal silica can be produced using either the sodium silicate method or the sol-gel method, and any 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 diffusible metal impurities and 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 (for example, alkoxysilane or its derivative) as a raw material and carrying out a hydrolysis-condensation reaction.

[0016] (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 performed, for example, by chemically bonding the functional groups of organic acids to the surface of colloidal silica, i.e., by immobilizing the organic acids. Alternatively, surface modification of colloidal silica can be performed by doping the surface of the silica particles with metals such as aluminum, titanium, or zirconium, or their oxides, by mixing them with colloidal silica.

[0017] In this embodiment, the colloidal silica contained in the polishing composition is, for example, colloidal silica with an organic acid immobilized on its surface. Colloidal silica with an organic acid immobilized on its surface tends to have a larger absolute value of zeta potential in the polishing composition compared to ordinary colloidal silica without an immobilized organic acid. Therefore, it is easy to adjust the zeta potential of the colloidal silica in the polishing composition to a range of -5mV or less.

[0018] Furthermore, the zeta potential of colloidal silica can be controlled to a desired range, for example, by using an acid described later as a pH adjuster.

[0019] Colloidal silica with organic acids immobilized on its surface includes colloidal silica with organic acids such as carboxylic acid groups, sulfonic acid groups, phosphonic acid groups, and aluminic acid groups immobilized on its surface. Of these, colloidal silica with sulfonic acid or carboxylic acid immobilized on its surface is preferred from the viewpoint of ease of production, and colloidal silica with sulfonic acid immobilized on its surface is more preferred.

[0020] Immobilizing organic acids onto the surface of colloidal silica cannot be achieved simply by having colloidal silica and organic acids coexist. For example, if one wants to immobilize sulfonic acid, a type of organic acid, onto colloidal silica, this can be done by the method described in, for example, “Sulfonic acid-functionalized silica through of 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.

[0021] Alternatively, if a carboxylic acid, which is one type of organic acid, is to be immobilized on colloidal silica, for example, it can be carried out 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, after coupling a silane coupling agent containing a photoreactive 2-nitrobenzyl ester to colloidal silica and then irradiating with light, colloidal silica having a carboxylic acid immobilized on the surface (carboxylic acid-modified colloidal silica) can be obtained.

[0022] (Average primary particle diameter) In the polishing composition of the present invention, the lower limit of the average primary particle diameter of abrasive grains (for example, colloidal silica) is preferably 1 nm or more, more preferably 5 nm or more, and even more preferably 10 nm or more. Further, in the polishing composition of the present invention, the upper limit of the average primary particle diameter of the abrasive grains is preferably 100 nm or less, more preferably 70 nm or less, even more preferably 50 nm or less, and particularly preferably 40 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 using the polishing composition can be suppressed. The average primary particle diameter of colloidal silica is calculated, for example, based on the specific surface area of colloidal silica measured by the BET method.

[0023] (Average secondary particle diameter) In the polishing composition of the present invention, the lower limit of the average secondary particle diameter of the abrasive grains (e.g., colloidal silica) 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 abrasive grains is preferably 250 nm or less, more preferably 150 nm or less, even more preferably 70 nm or less, and particularly preferably 40 nm or less. Within this 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.

[0024] Secondary particles refer to particles formed when abrasive grains (primary particles) aggregate in the polishing composition. The average secondary particle diameter of abrasive grains can be measured, for example, by dynamic light scattering methods such as laser diffraction scattering.

[0025] (Average degree of association) The average degree of aggregation of abrasive grains (e.g., colloidal silica) 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 aggregation of abrasive grains decreases, it becomes easier to obtain a polished surface with fewer surface defects by polishing the object to be polished using the polishing composition. Furthermore, the average degree of aggregation of abrasive grains is preferably 1.0 or more, and more preferably 1.2 or more. As the average degree of aggregation of abrasive grains increases, there is the advantage that the removal speed of the object to be polished by the polishing composition improves. The average degree of aggregation of abrasive grains is obtained by dividing the average secondary particle diameter of the abrasive grains by the average primary particle diameter.

[0026] (shape) In the present invention, the shape of the abrasive grains is not particularly limited and may be either spherical or non-spherical, but non-spherical is preferred. Specific examples of non-spherical shapes include polygonal prisms such as triangular prisms and square prisms, cylindrical shapes, barrel shapes where the center of the cylinder is wider than the ends, donut shapes where the center of the disc is penetrated, plate shapes, cocoon shapes with a constriction in the center (for example, two spheres joined together, with the joint narrowing like a constriction), aggregate spherical shapes where multiple particles are integrated, konpeito shapes with multiple protrusions on the surface, rugby ball shapes, and beaded shapes, and are not particularly limited.

[0027] (Content) The lower limit of the abrasive content is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more, relative to the polishing composition. The upper limit of the abrasive content is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, relative to the polishing composition. Within these ranges, the polishing speed can be further improved. Note that if the polishing composition contains two or more types of abrasives, the abrasive content refers to the total amount of these abrasives.

[0028] (Other particles besides silica) The polishing composition according to this embodiment may contain silica (e.g., anionically modified colloidal silica) with a zeta potential of -5mV or less, and other abrasive particles other than silica as abrasive particles. Alternatively, the polishing composition may contain other abrasive particles other than silica with a zeta potential of -5mV or less. Examples of other abrasive particles include metal oxide particles such as alumina particles, zirconia particles, and titania particles.

[0029] <Liquid media> The polishing composition according to this 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, pH adjuster, etc.). Examples of the liquid medium include water and organic solvents. One kind can be used alone, or two or more kinds can be mixed and used, but it is preferable to contain water. However, from the viewpoint of preventing the inhibition of the action of each component, it is preferable to use water that contains as few impurities as possible. Specifically, pure water, ultrapure water, or distilled water obtained by removing foreign substances through a filter after removing impurity ions with an ion exchange resin is preferable.

[0030] <pH adjuster> The pH value of the polishing composition according to this embodiment is preferably 6 or less, more preferably 5 or less, still more preferably 4 or less, and particularly preferably 3 or less. Also, the pH value is preferably 1 or more, more preferably 1.5 or more, and still more preferably 1.7 or more. If the polishing composition is acidic, the polishing selectivity of SiOC with respect to silicon nitride can be increased (improved). In order to achieve the above-mentioned pH value, the polishing composition may contain a pH adjuster.

[0031] 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.

[0032] Specific examples of acids 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 among these, sulfuric acid-based, nitric acid-based, and phosphoric acid-based inorganic acids are preferred, with nitric acid-based inorganic acids being even 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. Furthermore, specific examples of organic sulfuric acids include methanesulfonic acid, ethanesulfonic acid, and isethionic acid. These acids may be used individually or in combination of two or more. It is preferable to use carboxylic acid-based or phosphonic acid-based organic acids. Furthermore, these acids may be included in the polishing composition as pH adjusters, as additives to improve polishing speed, or in combination thereof.

[0033] Specific examples of alkalis used as pH adjusters include alkali metal hydroxides or their salts, alkaline earth metal hydroxides or their salts, ammonia, amines, etc. Specific examples of alkali metals include potassium and sodium. Specific examples of alkaline earth metals include calcium and strontium. Furthermore, specific examples of salts include carbonates, bicarbonates, sulfates, acetates, etc.

[0034] Specific examples of amines 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, and guanidine.

[0035] These alkalis may be used individually or in combination of two or more. Among these alkalis, ammonia, ammonium salts, alkali metal hydroxides, alkali metal salts, and amines are preferred, and ammonia, potassium compounds, sodium hydroxide, ammonium bicarbonate, ammonium carbonate, sodium bicarbonate, and sodium carbonate are more preferred. Furthermore, the polishing composition is even more preferably to contain potassium compounds as alkalis from the viewpoint of preventing metal contamination. Examples of potassium compounds include potassium hydroxides or potassium salts, specifically potassium hydroxide, potassium carbonate, potassium bicarbonate, potassium sulfate, potassium acetate, potassium chloride, and the like.

[0036] <Surfactants> The polishing composition according to this embodiment contains a cationic surfactant. The cationic 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 and other contaminants.

[0037] Specific examples of cationic surfactants include amine oxides, alkyltrimethylammonium salts, alkyldimethylammonium salts, alkylbenzyldimethylammonium salts, and alkylamine salts, with amine oxides and dimethylamine oxides being preferred among them.

[0038] 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 alkyldimethylamine oxide, trimethylamine-N-oxide, dodecyldimethylamine oxide, decyldimethylamine oxide, and tetradecyldimethylamine oxide, among which decyldimethylamine oxide is preferred.

[0039] These surfactants may be used individually or in combination of two or more types.

[0040] The higher the surfactant content in the overall polishing composition, the better the cleaning efficiency of the object to be polished after polishing. For this reason, the surfactant content (concentration) in the overall polishing composition is preferably 0.001 g / L or more, more preferably 0.01 g / L or more, and even more preferably 0.05 g / L or more.

[0041] Furthermore, the lower the surfactant content in the overall polishing composition, the less surfactant remains on the polished surface of the object after polishing, thereby improving cleaning efficiency. For this reason, the surfactant content in the overall polishing composition is preferably 10 g / L or less, more preferably 5.0 g / L or less, and even more preferably 1.0 g / L or less.

[0042] <Phosphonic acid chelating agents> The polishing composition according to this embodiment contains a phosphonic acid-based chelating agent. The phosphonic acid-based chelating agent functions as an inhibitor of silicon nitride polishing. By adding the phosphonic acid-based chelating agent to the polishing composition, the polishing of silicon nitride can be suppressed, and the polishing selectivity ratio of SiOC to silicon nitride can be increased (improved).

[0043] Examples of phosphonic acid-based chelating agents include ethylenediaminetetramethylenephosphonic acid (EDTMP), phytic acid, etidronic acid (HEDP), nitrilotrismethylenephosphonic acid (NTMP), and 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC).

[0044] The lower limit of the amount of phosphonic acid-based chelating agent in the entire polishing composition is not particularly limited, as even a small amount is effective; however, the higher the amount of phosphonic acid-based chelating agent, the faster the polishing speed of carbon by the polishing composition. For example, The content (concentration) of the phosphonic acid-based chelating agent 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.

[0045] Furthermore, the lower the content of the phosphonic acid-based chelating agent in the overall polishing composition, the less likely the carbon-containing material to dissolve, and the better the ability to eliminate unevenness. Therefore, the content of the phosphonic acid-based chelating agent in the overall 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.

[0046] <Cationic compounds with a molecular weight of 300 or less> The polishing composition according to this embodiment contains a cationic compound with a molecular weight of 300 or less as a selectivity enhancer to improve the polishing selectivity ratio of SiOC to silicon nitride. By adding a cationic compound with a molecular weight of 300 or less to the polishing composition, the polishing selectivity ratio of SiOC to silicon nitride can be increased (improved).

[0047] Cationic compounds with a molecular weight of 300 or less include amines and quaternary ammonium cations. Amines are a general term for primary amines, secondary amines, and tertiary amines. Cationic compounds with a molecular weight of 300 or less may contain amines, may contain quaternary ammonium cations, or may contain both amines and quaternary ammonium cations.

[0048] Specific examples of amines 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, and guanidine.

[0049] Specific examples of quaternary ammonium cations include tetrabutylammonium hydroxide (TBAH), tetraethylammonium hydroxide (TEAH), tetramethylammonium hydroxide (TMAH), and tetrapropylammonium hydroxide (TPAH). Among the quaternary ammonium cations, tetrabutylammonium hydroxide (TBAH) and tetraethylammonium hydroxide (TEAH) are preferred, with tetrabutylammonium hydroxide (TBAH) being more preferred.

[0050] These cationic compounds with a molecular weight of 300 or less may be used individually or in combination of two or more.

[0051] In the polishing composition as a whole, the selectivity ratio can be improved by increasing the content of cationic compounds with a molecular weight of 300 or less. For this reason, the content (concentration) of cationic compounds with a molecular weight of 300 or less in the polishing composition as a whole 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.

[0052] Furthermore, the lower the content of cationic compounds with a molecular weight of 300 or less in the overall polishing composition, the more coarse particles can be reduced. For this reason, the content (concentration) of cationic compounds with a molecular weight of 300 or less in the overall polishing composition is preferably 5 g / L or less, more preferably 3 g / L or less, and even more preferably 1 g / L or less.

[0053] For example, in the polishing composition according to this embodiment, the content of the cationic compound is 0.15 g / L or more and 0.25 g / L or less.

[0054] <Water-soluble polymer> The polishing composition according to this embodiment may contain a water-soluble polymer. If the object to be polished contains polysilicon, the polishing speed can be adjusted by adding a water-soluble polymer to the polishing composition, such as increasing or decreasing the polishing speed.

[0055] 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, hydroxyethylcellulose, dextrin, and pullulan. These water-soluble polymers may be used individually or in combination of two or more. Nonionic polymers are preferred among water-soluble polymers from the viewpoint of not interfering with the effect of surfactants on abrasive grains and the TEOS surface (not altering the zeta potential).

[0056] Furthermore, water-soluble polymers are not limited to nonionic polymers. Water-soluble polymers may be cationic or anionic. Examples of cationic polymers include polyethyleneimine, polyvinylimidazole, and polyallylamine. Examples of anionic polymers include polyacrylic acid, carboxymethylcellulose, polyvinyl sulfonic acid, polyanethol sulfonic acid, and polystyrene sulfonic acid.

[0057] <Oxidizing agent> The polishing composition according to this embodiment may contain an oxidizing agent. When the object to be polished contains silicon, for example, Poly-Si (polycrystalline silicon), the polishing speed can be adjusted by adding an oxidizing agent to the polishing composition. That is, by selecting the type of oxidizing agent to add to the polishing composition, the polishing speed of Poly-Si can be increased or decreased. Specific examples of oxidizing agents include hydrogen peroxide, peracetic acid, percarbonates, urea peroxide, perchloric acid, and persulfates. Specific examples of persulfates include sodium persulfate, potassium persulfate, and ammonium persulfate. These oxidizing agents may be used individually or in combination of two or more. Among these oxidizing agents, persulfates and hydrogen peroxide are preferred, and hydrogen peroxide is particularly preferred.

[0058] The higher the oxidizing agent content in the polishing composition as a whole, the easier it is to change the polishing speed of the object being polished by the polishing composition. Therefore, the oxidizing agent content (concentration) in the polishing composition as a whole 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 oxidizing agent content in the polishing composition as a whole, the lower the material cost of the polishing composition can be. In addition, the burden of processing the polishing composition after polishing, i.e., waste liquid treatment, can be reduced. Moreover, excessive oxidation of the surface of the object being polished by the oxidizing agent becomes less likely. Therefore, the oxidizing agent content in the polishing composition as a whole is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less.

[0059] <Antifungal agents, preservatives> The polishing composition may contain antifungal agents and preservatives. Specific examples of antifungal and preservative agents include isothiazolinoline preservatives (e.g., 2-methyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one), parahydroxybenzoic acid esters, and phenoxyethanol. These antifungal and preservative agents 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 this embodiment includes a step of mixing abrasive grains having a zeta potential of -5mV or less, a cationic surfactant, a phosphonic acid-based chelating agent, a cationic compound having a molecular weight of 300 or less, and a liquid medium. For example, the polishing composition according to this embodiment can be produced by stirring and mixing anionically modified colloidal silica as abrasive grains, amine oxide as a cationic surfactant, ethylenediaminetetramethylenephosphonic acid (EDTMP) or phytic acid as a phosphonic acid-based chelating agent, tetrabutylammonium hydroxide (TBAH) as a cationic compound having a molecular weight of 300 or less, and various additives as needed (e.g., pH adjusters, water-soluble polymers, oxidizing agents, antifungal agents, preservatives, etc.) in a liquid medium such as water. The mixing temperature is not particularly limited, but is preferably between 10°C and 40°C, and may be heated to improve the dissolution rate. The mixing time is also not particularly limited.

[0061] <Object to be polished> The polishing composition according to this embodiment can increase the polishing selectivity ratio of SiOC to silicon nitride. For this reason, the object to be polished is preferably a SiOC film deposited on a silicon nitride film, or a SiOC film deposited on a semiconductor substrate or the like via a silicon nitride film. However, in this embodiment, the type of object to be polished is not limited to SiOC with silicon nitride as the substrate. The type of object to be polished may be SiOC with a substrate other than silicon nitride. Furthermore, the type of object to be polished may be elemental SiOC without a substrate, elemental compounds containing SiOC, elemental mixtures containing SiOC, etc.

[0062] Furthermore, the type of material to be polished is not limited to materials containing SiOC, but may also include elemental silicon, silicon compounds other than silicon nitride films, metals, etc. Examples of elemental silicon include single-crystal silicon, polysilicon, amorphous silicon, etc. Examples of silicon compounds include silicon dioxide, silicon carbide, etc. The silicon dioxide may be a film formed using tetraethoxysilane ((Si(OC2H5)4)) (hereinafter referred to as TEOS film). The silicon compound film includes low dielectric constant films with a relative permittivity of 3 or less. Furthermore, examples of metals include tungsten, copper, aluminum, hafnium, cobalt, nickel, titanium, tantalum, gold, silver, platinum, palladium, rhodium, ruthenium, iridium, osmium, etc. These metals may be included in the form of alloys or metallic compounds.

[0063] <Polishing method> In the embodiments of this disclosure, an object to be polished containing SiOC is polished using the above-described polishing composition. The configuration of the polishing apparatus is not particularly limited, but for example, a general polishing apparatus can be used that includes a holder for holding a substrate or the like having the object to be polished, a drive unit such as a motor that can change the rotation speed, and a polishing platen to which a polishing pad (polishing cloth) can be attached. As the polishing pad, a general nonwoven fabric, polyurethane, porous fluororesin, etc. can be used without particular limitation. The polishing pad can be one which has grooves that allow the liquid polishing composition to accumulate.

[0064] There are no particular restrictions on the polishing conditions, but for example, the rotation speed of the polishing platen should be 10 rpm (0.17 s). -1 ) or more 500rpm (8.3s -1 ) is preferred. The pressure applied to the substrate having the object to be polished (polishing pressure) is preferably 0.5 psi (3.4 kPa) or more and 10 psi (68.9 kPa) or less. The method of supplying the polishing composition to the polishing pad is not particularly limited, and a method of continuously supplying it by a pump or the like is 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 according to one aspect of the present invention.

[0065] The polishing composition according to this embodiment may be a one-component type or a multi-component type, including a two-component type. Furthermore, the polishing composition may be prepared by diluting the stock solution of the polishing composition with a diluent such as water, for example, 10 times or more.

[0066] After polishing is complete, the substrate is washed with running water, for example, and dried by removing any water droplets adhering to the substrate using a spin dryer or the like, thereby obtaining a substrate having a layer containing, for example, SiOC. Thus, the polishing composition according to this embodiment can be used for the purpose of polishing substrates. By using the polishing composition according to this embodiment to polish the surface of a material to be polished, such as SiOC, which has been deposited on a semiconductor substrate (an example of a substrate), a polished semiconductor substrate can be manufactured. Examples of semiconductor substrates include silicon wafers having layers containing elemental silicon, silicon compounds such as silicon nitride films, metals, etc.

[0067] <Manufacturing method for semiconductor substrates> The method for manufacturing a semiconductor substrate according to this embodiment includes a step of polishing the surface of the semiconductor substrate (for example, an OCI film deposited on the semiconductor substrate) using the above-mentioned polishing composition. The polishing method in this step is as described in the section <Polishing Method>, for example. [Examples]

[0068] 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 modified or improved forms may also be included in the present invention.

[0069] <Method for preparing abrasive compositions> (Examples 1-3) As shown in Table 1 below, a mixture was prepared by stirring and mixing abrasive grains with a zeta potential of -5mV or less, a cationic surfactant, a phosphonic acid-based chelating agent, a cationic compound with a molecular weight of 300 or less, and water as a liquid medium. A pH adjuster was added to the prepared mixture as needed to produce the polishing compositions of Examples 1-3. In Table 1, "-" indicates that the component was not used or that there are no units.

[0070] In Examples 1 to 3, sulfonic acid-modified colloidal silica, a type of anionically modified colloidal silica, was used as the abrasive grain. In Examples 1 to 3, the concentration of sulfonic acid-modified colloidal silica in the polishing composition was 2% by mass. Hereafter, mass% will be denoted as wt%. In Examples 1 to 3, the primary particle size of the sulfonic acid-modified colloidal silica was 12 nm, the secondary particle size was 34 nm, and the zeta potential was -17 mV, -14 mV, or -20 mV.

[0071] In Examples 1-3, decyldimethylamine oxide was used as the cationic surfactant. In Examples 1-3, the concentration of decyldimethylamine oxide in the polishing composition was 0.1 g / L.

[0072] In Examples 1-3, ethylenediaminetetramethylenephosphonic acid (EDTMP) was used as the phosphonic acid-based chelating agent. In Examples 1-3, the concentration of EDTMP in the polishing composition was 5 g / L.

[0073] In Examples 1-3, no pH additive was added. However, EDTMP, added as a phosphonic acid chelating agent, functions as a pH adjuster for the polishing composition. In Examples 1-3, the pH of the polishing composition (liquid temperature: 25°C) was measured using a pH meter (manufactured by Horiba, Ltd., product name: LAQUA®), and was found to be 2.0 in each case.

[0074] In Examples 1 and 2, tetrabutylammonium hydroxide (TBAH) was used as the cationic compound with a molecular weight of 300 or less. In Examples 1 and 2, the concentration of TBAH in the polishing composition was 0.15 g / L and 0.25 g / L, respectively. In Example 3, tetraethylammonium hydroxide (TEAH) was used as the cationic compound with a molecular weight of 300 or less. In Example 3, the concentration of TEAH in the polishing composition was 0.25 g / L.

[0075] (Comparative Examples 1-5) Each polishing composition was prepared in the same manner as in Examples 1 to 3, except that the types, concentrations, and other components shown in Table 1 were used. [Table 1]

[0076] <Rating> A 300 mm diameter silicon wafer was polished using the polishing compositions of Examples 1-3 and Comparative Examples 1-5 under the following polishing conditions. • Polishing equipment: Ebara Corporation 300mm CMP single-sided polishing machine F-REX300E • Polishing pad: Nitta Haas Co., Ltd. hard polyurethane pad IC1010 • Polishing pressure: 2 psi (1 psi = 6894.76 Pa) • Grinding plate rotation speed: 107 rpm • Head rotation speed: 113 rpm • Supply of polishing composition: flow-through ·Polishing composition supply amount: 200mL / min • Polishing time: 60 seconds

[0077] The silicon wafers used for polishing were a 300mm silicon wafer with a SiOC film (thickness: 5000 Å) and a 300mm silicon wafer with a silicon nitride film (thickness: 3500 Å). Using an optical interferometry film thickness analyzer (ASET-f5x: KLA-Tencor), the film thickness of the SiOC film before polishing and after polishing were measured. Similarly, using the optical interferometry film thickness analyzer, the film thickness of the silicon nitride film before polishing and after polishing were measured. The polishing speed of the SiOC film and the silicon nitride film were then calculated from the film thickness difference and polishing time. The results for the polishing speed are shown in Table 1.

[0078] As shown in Table 1, it was confirmed that in all of Examples 1 to 3, the polishing rate of the SiOC film relative to the polishing rate of the silicon nitride film (i.e., the polishing selectivity ratio of SiOC to silicon nitride) was higher than that of Comparative Examples 1 to 5. A detailed comparison is provided below.

[0079] (Comparison of Examples 1-3 and Comparative Example 1) Examples 1-3 and Comparative Example 1 differ in whether or not the polishing composition contains a cationic compound with a molecular weight of 300 or less (for example, TBAH or TEAH). The polishing compositions of Examples 1-3 contain TBAH or TEAH, while the polishing composition of Comparative Example 1 does not contain TBAH or TEAH. In all other respects, Examples 1-3 and Comparative Example 1 are the same. From Examples 1-3 and Comparative Example 1, it was confirmed that adding a cationic compound with a molecular weight of 300 or less to the polishing composition increases (improves) the polishing selectivity ratio of SiOC to silicon nitride compared to when the compound is not added.

[0080] (Comparison of Examples 1-3 and Comparative Example 2) Examples 1-3 and Comparative Example 2 differ in whether or not the polishing compositions contain a cationic surfactant (for example, decyldimethylamine oxide). The polishing compositions of Examples 1-3 contain decyldimethylamine oxide, while the polishing composition of Comparative Example 2 does not. In all other respects, Examples 1-3 and Comparative Example 2 are the same. From Examples 1-3 and Comparative Example 2, it was confirmed that adding a cationic surfactant to the polishing composition increases (improves) the polishing selectivity ratio of silicon nitride (SiOC) to silicon nitride compared to when the surfactant is not added.

[0081] (Comparison of Comparative Examples 1 and 3) Comparative Examples 1 and 3 differ in whether or not the abrasive grains are anionically modified. In Comparative Example 1, the abrasive grains are anionically modified, while in Comparative Example 3, the abrasive grains are not anionically modified. The zeta (ζ) potential of the abrasive grains in Comparative Example 1 was -25mV, and the zeta (ζ) potential of the abrasive grains in Comparative Example 3 was 5mV. All other aspects were the same for Comparative Examples 1 and 3. From Comparative Examples 1 and 3, it was confirmed that a higher zeta potential of the abrasive grains resulted in a lower polishing rate of the SiOC.

[0082] (Comparison of Comparative Examples 1 and 4) Comparative Examples 1 and 4 differ in that their polishing compositions contain either a phosphonic acid chelating agent (e.g., EDTMP) or a carboxylic acid chelating agent (e.g., ethylenediaminetetraacetic acid (EDTA)). The polishing composition of Comparative Example 1 contains EDTMP, and the polishing composition of Comparative Example 4 contains EDTA. In all other respects, Comparative Examples 1 and 4 are the same. Comparative Examples 1 and 4 confirmed that the polishing rate of silicon nitride is reduced when a phosphonic acid chelating agent is used. It was confirmed that the phosphonic acid chelating agent functions as an anti-polishing agent for silicon nitride.

[0083] (Comparison of Examples 1-3 and Comparative Example 5) Examples 1-3 and Comparative Example 5 differ in that the molecular weight of the cationic compound contained in the polishing composition is 300 or less. The polishing compositions of Examples 1-3 contain TBAH or TEAH with a molecular weight of 300 or less, while the polishing composition of Comparative Example 5 contains hexadecyltrimethylammonium hydroxide with a molecular weight greater than 300. In all other respects, Examples 1-3 and Comparative Example 5 are the same. From Examples 1-3 and Comparative Example 5, it was confirmed that when the molecular weight of the cationic compound is greater than 300, the polishing rate of SiOC decreases.

Claims

1. Abrasive grains with a zeta potential of -5 mV or less, Cationic surfactants and Phosphonic acid chelating agents, A cationic compound with a molecular weight of 300 or less, The cationic surfactant is an amine oxide. The aforementioned cationic compound is a quaternary ammonium cation. Polishing composition.

2. The polishing composition according to claim 1, comprising the cationic compound as a selectivity enhancer to improve the polishing selectivity ratio of SiOC to silicon nitride.

3. The polishing composition according to claim 1 or 2, wherein the content of the cationic compound is 0.01 g / L or more and 5 g / L or less.

4. The polishing composition according to claim 1 or 2, wherein the cationic compound comprises tetrabutylammonium hydroxide (TBAH) or tetraethylammonium hydroxide (TEAH).

5. The zeta potential of the abrasive grains is -5 mV or less and -20 mV or more. The abrasive grains are anion-modified colloidal silica. The polishing composition according to claim 1 or 2.

6. The abrasive composition according to claim 1 or 2, wherein the cationic surfactant comprises dimethylamine oxide.

7. The abrasive composition according to claim 1 or 2, wherein the cationic surfactant comprises decyldimethylamine oxide.

8. The polishing composition according to claim 1 or 2, wherein the phosphonic acid-based chelating agent comprises ethylenediaminetetramethylenephosphonic acid (EDTMP).

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

10. The abrasive grain comprises anionically modified silica, The polishing composition according to claim 1 or 2, wherein the silica is silica on which an organic acid is fixed to its surface.

11. The polishing composition according to claim 1 or 2, used for polishing objects containing SiOC.

12. A method for producing the polishing composition according to claim 1 or 2, The process includes mixing abrasive particles having a zeta potential of -5 mV or less, a cationic surfactant, a phosphonic acid-based chelating agent, a cationic compound with a molecular weight of 300 or less, and a liquid medium. The cationic surfactant is an amine oxide. The aforementioned cationic compound is a quaternary ammonium cation. A method for producing an abrasive composition.

13. A polishing method comprising the step of polishing an object to be polished containing SiOC using the polishing composition described in claim 1 or 2.

14. A method for manufacturing a semiconductor substrate, comprising the step of polishing a film of SiOC deposited on a semiconductor substrate using the polishing composition described in claim 1 or 2.

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