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

Abstract

To provide a polishing composition by which such a layer that the content of Group 13 elements is 40 mass% or more can be polished at a high polishing speed.SOLUTION: A polishing composition is to be used to polish a polished target having a layer of which the content of Group 13 elements is over 40 mass%. The polishing composition comprises cation-modified silica, polyalkylene glycol, and acid.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In recent years, with the increasing number of multilayer wirings on semiconductor substrate surfaces, so-called chemical mechanical polishing (CMP) technology has been used to polish and planarize semiconductor substrates when manufacturing devices. 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, or ceria, an anticorrosive agent, a surfactant, etc. The object to be polished (workpiece) can be silicon, polysilicon, silicon oxide film (silicon oxide), silicon nitride, or wiring or plug made of metal, etc.

[0003] For example, Patent Document 1 discloses a polishing method for polishing a polysilicon film provided on a silicon substrate having an isolation region, which includes a preliminary polishing step using a preliminary polishing composition containing abrasive grains, an alkali, a water-soluble polymer, and water, and a final polishing step using a final polishing composition containing abrasive grains, an alkali, a water-soluble polymer, and water. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-103515 Summary of the Invention [Problem to be solved by the invention]

[0005] Recently, semiconductor substrates have come into use that have a layer containing 40% by mass or more of a Group 13 element, and this has created a new demand for polishing such substrates, a demand that has not been addressed to date.

[0006] Therefore, an object of the present invention is to provide a polishing composition capable of polishing a layer having a Group 13 element content of 40 mass % or more at a high removal rate.

[0007] Another object of the present invention is to provide a polishing composition having a higher polishing rate for a layer having a Group 13 element content of 40 mass % or more than that for other materials (i.e., a high selectivity). [Means for solving the problem]

[0008] In order to solve the above-mentioned new problems, the present inventors have conducted extensive research and have found that the above-mentioned problems can be solved by a polishing composition containing cation-modified silica, polyalkylene glycol, and an acid, thereby completing the present invention.

[0009] That is, in the present invention, the content of the Group 13 element is 40 mass% That's all The polishing composition is used for polishing an object having a layer, and contains cation-modified silica, polyalkylene glycol, and an acid. [Effects of the Invention]

[0010] The present invention provides a polishing composition capable of polishing a layer having a Group 13 element content of 40% by mass or more at a high polishing rate. The present invention also provides a polishing composition having a higher polishing rate for a layer having a Group 13 element content of 40% by mass or more than the polishing rate for other materials (i.e., a high selectivity). DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention relates to a glass fiber having a Group 13 element content of 40% by mass. That's allThe polishing composition is used for polishing a layer-containing object, and comprises cation-modified silica, polyalkylene glycol, and an acid. The polishing composition according to one embodiment of the present invention, having such a configuration, is capable of polishing a layer containing 40% or more by mass of a Group 13 element at a high polishing rate. Furthermore, the polishing composition according to another embodiment of the present invention has a higher polishing rate for a layer containing 40% or more by mass of a Group 13 element than for other materials (i.e., a high selectivity).

[0012] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

[0013] In this specification, unless otherwise specified, operations and measurements of physical properties are carried out at room temperature (20° C. or higher and 25° C. or lower) and at a relative humidity of 40% RH or higher and 50% RH or lower.

[0014] [Polished object] The object to be polished according to the present invention has a layer containing 40 mass % or more of a Group 13 element (hereinafter simply referred to as a Group 13 element layer). Examples of Group 13 elements include boron (B), aluminum (Al), gallium (Ga), and indium (In). The Group 13 elements may be used alone or in combination of two or more.

[0015] The Group 13 element layer may contain elements other than Group 13 elements. Examples of the other elements include silicon (Si), hydrogen (H), nitrogen (N), oxygen (O), carbon (C), phosphorus (P), and germanium (Ge). These other elements may be contained alone or in combination of two or more.

[0016] The lower limit of the amount of the Group 13 element contained in the Group 13 element layer is 40 mass% or more, preferably 45 mass% or more, more preferably 47 mass% or more, and even more preferably 50 mass% or more, based on the mass of the entire layer. The upper limit of the amount of the Group 13 element contained in the Group 13 element layer is preferably 100 mass% or less, more preferably 95 mass% or less, and even more preferably 90 mass% or less, based on the mass of the entire layer.

[0017] The object to be polished according to the present invention may further contain other materials in addition to the Group 13 element layer, such as silicon nitride, silicon carbonitride (SiCN), silicon oxide, polycrystalline silicon (polysilicon), amorphous silicon, polycrystalline silicon doped with n-type impurities, amorphous silicon doped with n-type impurities, titanium nitride, elemental metals, and SiGe.

[0018] Examples of polishing objects containing silicon oxide include TEOS (Tetraethyl Orthosilicate) type silicon oxide surfaces (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.

[0019] Examples of elemental metals include tungsten, copper, cobalt, hafnium, nickel, gold, silver, platinum, palladium, rhodium, ruthenium, iridium, and osmium.

[0020] The object to be polished according to the present invention may further include a material having a Group 13 element content of more than 0 mass % and less than 40 mass %. Examples of such a material include polycrystalline silicon doped with p-type impurities and amorphous silicon doped with p-type impurities.

[0021] [Cation-modified silica] The polishing composition of the present invention contains cation-modified silica (silica having a cationic group) as abrasive grains. The cation-modified silica may be used alone or in combination of two or more. In addition, the cation-modified silica may be a commercially available product or a synthetic product.

[0022] The cation-modified silica is preferably cation-modified colloidal silica (colloidal silica having a cationic group).

[0023] Methods for producing colloidal silica include the sodium silicate method and the sol-gel method, and colloidal silica produced by either method is suitable for use as the abrasive grains of the present invention. However, from the viewpoint of reducing metal impurities, colloidal silica produced by the sol-gel method is preferred. Colloidal silica produced by the sol-gel method is preferred because it contains less metal impurities that are diffusible in semiconductors and less corrosive ions such as chloride ions. Colloidal silica can be produced by the sol-gel method using a conventionally known method. Specifically, colloidal silica can be obtained by hydrolysis and condensation reaction using a hydrolyzable silicon compound (e.g., alkoxysilane or its derivative) as a raw material.

[0024] Here, cation-modified refers to a state in which cationic groups (e.g., amino groups or quaternary ammonium groups) are bonded to the surface of silica (preferably colloidal silica). According to a preferred embodiment of the present invention, the cation-modified silica particles are amino-modified silica particles, more preferably amino-modified colloidal silica particles. According to such an embodiment, the above-mentioned effects can be further improved.

[0025] To cationically modify silica (colloidal silica), a silane coupling agent having a cationic group (e.g., an amino group or a quaternary ammonium group) is added to the silica (colloidal silica) and reacted at a predetermined temperature for a predetermined time. In a preferred embodiment of the present invention, the cationically modified silica is obtained by immobilizing a silane coupling agent having an amino group or a silane coupling agent having a quaternary ammonium group on the surface of silica (more preferably colloidal silica).

[0026] In this case, examples of the silane coupling agent used include those described in JP-A-2005-162533.Specific examples include silane coupling agents such as N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, γ-aminopropyltriethoxysilane ((3-aminopropyl)triethoxysilane), γ-aminopropyltrimethoxysilane, γ-triethoxysilyl-N-(α,γ-dimethyl-butylidene)propylamine, N-phenyl-γ-aminopropyltrimethoxysilane, N-(vinylbenzyl)-β-aminoethyl-γ-aminopropyltriethoxysilane hydrochloride, octadecyldimethyl-(γ-trimethoxysilylpropyl)-ammonium chloride, and N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride. Among these, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, γ-aminopropyltriethoxysilane, and γ-aminopropyltrimethoxysilane are preferably used because of their good reactivity with colloidal silica. In the present invention, the silane coupling agent may be used alone or in combination of two or more.

[0027] The silane coupling agent can be added to silica (colloidal silica) either directly or after dilution with a hydrophilic organic solvent or pure water. Dilution with a hydrophilic organic solvent or pure water can suppress the formation of aggregates. When diluting the silane coupling agent with a hydrophilic organic solvent or pure water, the silane coupling agent should be diluted to a concentration of preferably 0.01 g to 1 g, more preferably 0.1 g to 0.7 g, per 1 L of hydrophilic organic solvent or pure water. The hydrophilic organic solvent is not particularly limited, but examples include lower alcohols such as methanol, ethanol, isopropanol, and butanol.

[0028] In addition, the amount of cationic groups introduced onto the surface of silica (colloidal silica) can be adjusted by adjusting the amount of silane coupling agent added. The amount of silane coupling agent used is not particularly limited, but is preferably 0.1 mM (mmol / L) or more and 5 mM or less, more preferably 0.5 mM or more and 3 mM or less, relative to the reaction solution.

[0029] The treatment temperature when silica (colloidal silica) is cationically modified with a silane coupling agent is not particularly limited, and may be from room temperature (e.g., 25°C) to a temperature approximately equal to the boiling point of the dispersion medium in which the silica (colloidal silica) is dispersed; specifically, the temperature is from 0°C to 100°C, and preferably from room temperature (e.g., 25°C) to 90°C.

[0030] The shape of the cation-modified 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 prisms such as triangular prisms and quadrangular prisms, cylinders, bale-shaped cylinders in which the center is bulging more than the ends, doughnut-shaped discs with a hole in the center, plate-shaped, cocoon-shaped discs with a constriction in the center, associative spheres in which multiple particles are integrated, confetti-shaped discs with multiple protrusions on the surface, and rugby ball-shaped discs, and are not particularly limited.

[0031] The average primary particle diameter of the cation-modified silica is preferably 1 nm or more, more preferably 3 nm or more, and even more preferably 5 nm or more. As the average primary particle diameter of the cation-modified silica increases, the polishing rate of the Group 13 element layer increases. Furthermore, the average primary particle diameter of the cation-modified silica is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 30 nm or less. As the average primary particle diameter of the cation-modified silica decreases, the polishing rate of the Group 13 element layer increases compared to the polishing rate of other materials (the selectivity increases).

[0032] That is, the average primary particle diameter of the cation-modified silica is preferably 1 nm or more and 100 nm or less, more preferably 3 nm or more and 50 nm or less, and even more preferably 5 nm or more and 30 nm or less. The average primary particle diameter of the cation-modified silica can be calculated, for example, based on the specific surface area (SA) of the cation-modified silica calculated by the BET method and the density of the cation-modified silica. More specifically, the average primary particle diameter of the cation-modified silica is a value measured by the method described in the Examples.

[0033] The average secondary particle diameter of the cation-modified silica is preferably 15 nm or more, more preferably 20 nm or more, and even more preferably 25 nm or more. As the average secondary particle diameter of the cation-modified silica increases, the resistance during polishing decreases, enabling stable polishing. The average secondary particle diameter of the cation-modified silica is preferably 200 nm or less, more preferably 150 nm or less, and even more preferably 100 nm or less. As the average secondary particle diameter of the cation-modified silica decreases, the surface area per unit mass of the cation-modified silica increases, increasing the frequency of contact with the workpiece to be polished and further improving the polishing rate. That is, the average secondary particle diameter of the cation-modified silica is preferably 15 nm or more and 200 nm or less, more preferably 20 nm or more and 150 nm or less, and even more preferably 25 nm or more and 100 nm or less. The average secondary particle diameter of the cation-modified silica is measured by the method described in the Examples.

[0034] The ratio of the average secondary particle size to the average primary particle size of the cation-modified silica (average secondary particle size / average primary particle size, hereinafter also referred to as "average degree of association") is preferably greater than 1.0, more preferably greater than 1.1, and even more preferably greater than 1.2. As the average degree of association of the cation-modified silica increases, the polishing rate for the Group 13 element layer increases. Furthermore, the average degree of association of the cation-modified silica is preferably 4 or less, more preferably 3.5 or less, and even more preferably 3 or less. As the average degree of association of the cation-modified silica decreases, the polishing rate for the Group 13 element layer becomes higher compared to the polishing rate for other materials (the selectivity becomes higher). That is, the average degree of association of the cation-modified silica is preferably greater than 1.0 and 4 or less, more preferably 1.1 to 3.5, and even more preferably 1.2 to 3.

[0035] The average degree of association of the cation-modified silica can be obtained by dividing the average secondary particle size of the cation-modified silica by the average primary particle size.

[0036] The upper limit of the aspect ratio of the cation-modified silica in the polishing composition is not particularly limited, but is preferably less than 2.0, more preferably 1.8 or less, and even more preferably 1.5 or less.Within this range, defects on the surface of the object to be polished can be further reduced.The aspect ratio is the average of the values ​​obtained by taking the smallest rectangle circumscribing the image of the cation-modified silica particles using a scanning electron microscope and dividing the length of the long side of the rectangle by the length of the short side of the same rectangle, and can be determined using general image analysis software.The lower limit of the aspect ratio of the cation-modified silica in the polishing composition is not particularly limited, but is preferably 1.0 or more.

[0037] In the particle size distribution of cation-modified silica measured by laser diffraction scattering, the ratio of particle diameter (D90) when the cumulative particle weight from the fine particle side reaches 90% of the total particle weight to particle diameter (D50) when the cumulative particle weight of all particles reaches 50% of the total particle weight of all particles is not particularly limited, but the lower limit of D90 / D50 is preferably 1.1 or more, more preferably 1.2 or more, and even more preferably 1.3 or more. In addition, in the particle size distribution of cation-modified silica in a polishing composition measured by laser diffraction scattering, the ratio of particle diameter (D90) when the cumulative particle weight from the fine particle side reaches 90% of the total particle weight to particle diameter (D50) when the cumulative particle weight of all particles reaches 50% of the total particle weight of all particles is not particularly limited, but the upper limit of D90 / D50 is preferably 2.0 or less, more preferably 1.7 or less, and even more preferably 1.5 or less. Within this range, defects on the surface of the object to be polished can be further reduced.

[0038] The size of the cation-modified silica (average primary particle size, average secondary particle size, aspect ratio, D90 / D50, etc.) can be appropriately controlled by selecting a method for producing the cation-modified silica, for example.

[0039] The lower limit of the zeta potential of the cation-modified silica in the polishing composition is preferably 4 mV or more, more preferably 4.5 mV or more, and even more preferably 5 mV or more. The upper limit of the zeta potential of the cation-modified silica in the polishing composition is preferably 70 mV or less, more preferably 65 mV or less, and even more preferably 60 mV or less. That is, the zeta potential of the abrasive grains in the polishing composition is preferably 4 mV or more and 70 mV or less, more preferably 4.5 mV or more and 65 mV or less, and even more preferably 5 mV or more and 60 mV or less.

[0040] Cation-modified silica having the above-mentioned zeta potential can polish a Group 13 element layer at a higher polishing rate, and the polishing rate for the Group 13 element layer is higher than that for other materials (higher selectivity).

[0041] In this specification, the zeta potential of the cation-modified silica is a value measured by the method described in the Examples. The zeta potential of the cation-modified silica can be adjusted by the amount of cationic groups in the cation-modified silica, the pH of the polishing composition, etc.

[0042] The content (concentration) of cation-modified silica in the polishing composition is not particularly limited, but is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.5% by mass or more, and particularly preferably more than 0.5% by mass, relative to the total mass of the polishing composition. The upper limit of the content of cation-modified silica in the polishing composition is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 4% by mass or less, and particularly preferably less than 4% by mass, relative to the total mass of the polishing composition. That is, the content of cation-modified silica is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.2% by mass or more and 5% by mass or less, even more preferably 0.5% by mass or more and 4% by mass or less, and particularly preferably more than 0.5% by mass but less than 4% by mass, relative to the total mass of the polishing composition.

[0043] When the content of cation-modified silica is within this range, the Group 13 element layer can be polished at a higher polishing rate. Furthermore, the polishing rate for the Group 13 element layer becomes higher than the polishing rate for other materials (the selectivity becomes higher). When the polishing composition contains two or more types of cation-modified silica, the content of the cation-modified silica refers to the total amount of these.

[0044] The polishing composition of the present invention may further contain abrasive particles other than cation-modified silica, provided that the effects of the present invention are not impaired. Such other abrasive particles may be inorganic particles, organic particles, or organic-inorganic composite particles. Specific examples of inorganic particles include unmodified silica, particles made of metal oxides such as alumina, ceria, and titania, silicon nitride particles, silicon carbide particles, and boron nitride particles. Specific examples of organic particles include polymethyl methacrylate (PMMA) particles. The other abrasive particles may be used alone or in combination of two or more types. Furthermore, the other abrasive particles may be commercially available or synthetic products.

[0045] [Polyalkylene glycol] The polishing composition of the present invention contains polyalkylene glycol. The polyalkylene glycol has the function of accelerating the polishing of the Group 13 element layer (improving the polishing rate). The polyalkylene glycol may be used alone or in combination of two or more. Furthermore, the polyalkylene glycol may be a commercially available product or a synthetic product.

[0046] The type of polyalkylene glycol is not particularly limited, and examples thereof include polyethylene glycol, polypropylene glycol, polytetramethylene 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-polyethylene glycol-polypropylene glycol triblock copolymer, polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer, etc. Among these, polyethylene glycol and polypropylene glycol are preferred, and polyethylene glycol is more preferred.

[0047] The weight-average molecular weight (Mw) of the polyalkylene glycol is preferably 100 or more, more preferably 150 or more, and even more preferably 200 or more. The weight-average molecular weight (Mw) of the polyalkylene glycol is preferably 30,000 or less, more preferably 10,000 or less, and even more preferably 1,000 or less. That is, the weight-average molecular weight (Mw) of the polyalkylene glycol is preferably 100 or more and 30,000 or less, more preferably 150 or more and 10,000 or less, even more preferably 150 or more and 1,000 or less, particularly preferably 200 or more and 1,000 or less, and most preferably 200 or more and 350 or less.

[0048] In this specification, the weight-average molecular weight of the polyalkylene glycol can be measured by gel permeation chromatography (GPC) using polyethylene glycol as a standard substance. The detailed measurement method is as described in the Examples.

[0049] The content (concentration) of polyalkylene glycol in the polishing composition is not particularly limited, but is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and even more preferably 0.03% by mass or more, based on the total mass of the polishing composition. Furthermore, the content of polyalkylene glycol in the polishing composition is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, particularly preferably 0.2% by mass or less, and most preferably 0.15% by mass or less, based on the total mass of the polishing composition. That is, the content of polyalkylene glycol is preferably 0.001% by mass or more and 10% by mass or less, more preferably 0.01% by mass or more and 5% by mass or less, more preferably 0.03% by mass or more and 1% by mass or less, particularly preferably 0.03% by mass or more and 0.2% by mass or less, and most preferably 0.03% by mass or more and 0.15% by mass or less. When the content of polyalkylene glycol is within this range, the Group 13 element layer can be polished at a higher polishing rate. Furthermore, the polishing rate for the Group 13 element layer is higher than the polishing rate for other materials (higher selectivity).

[0050] [acid] The polishing composition according to the present invention contains an acid. Examples of the acid include formic acid, acetic acid, propionic acid, butyric acid, 2-hydroxyisobutyric acid (HBA), 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, mellitic acid, cinnamic acid, oxalic acid, malonic acid, Examples of suitable acids include succinic acid, glutaric acid, adipic acid, fumaric acid, maleic acid, aconitic acid, amino acids, anthranilic acid, and nitrocarboxylic acids; sulfonic acids such as methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, 10-camphorsulfonic acid, isethionic acid, and taurine; and inorganic acids such as carbonic acid, hydrochloric acid, nitric acid, phosphoric acid, hypophosphorous acid, phosphorous acid, phosphonic acid, sulfuric acid, boric acid, hydrofluoric acid, orthophosphoric acid, pyrophosphoric acid, polyphosphoric acid, metaphosphoric acid, and hexametaphosphoric acid. These acids may be used alone or in combination of two or more.

[0051] Among these, from the viewpoint of further improving the effects of the present invention, the acid is preferably at least one selected from the group consisting of an acid having a nitric acid group and an acid having a sulfonic acid group. The acid having a nitric acid group is more preferably nitric acid. The acid having a sulfonic acid group is more preferably 10-camphorsulfonic acid or isethionic acid.

[0052] The content (concentration) of the acid in the polishing composition is not particularly limited, but is preferably 0.001 mass% or more, more preferably 0.005 mass% or more, based on the total mass of the polishing composition. Furthermore, the content of the acid in the polishing composition is preferably 10 mass% or less, more preferably 5 mass% or less, based on the total mass of the polishing composition. When the acid content is within this range, the Group 13 element layer can be polished at a higher polishing rate. Furthermore, the polishing rate for the Group 13 element layer becomes higher than the polishing rate for other materials (the selectivity becomes higher).

[0053] [Dispersion medium] The polishing composition of the present invention preferably contains a dispersion medium for dispersing each component. Examples of dispersion mediums include water; alcohols such as methanol, ethanol, and ethylene glycol; ketones such as acetone; and mixtures thereof. Of these, water is preferred as the dispersion medium. That is, according to a preferred embodiment of the present invention, the dispersion medium contains water. According to a more preferred embodiment of the present invention, the dispersion medium consists essentially of water. Note that the above term "substantially" means that a dispersion medium other than water may be included as long as the effects of the present invention can be achieved. More specifically, the dispersion medium preferably consists of 90% by mass to 100% by mass of water and 0% by mass to 10% by mass of a dispersion medium other than water, more preferably 99% by mass to 100% by mass of water and 0% by mass to 1% by mass of a dispersion medium other than water. Most preferably, the dispersion medium is water.

[0054] From the viewpoint of not inhibiting the action of the components contained in the polishing composition, the dispersion medium is preferably water containing as few impurities as possible. Specifically, pure water or ultrapure water, which has been subjected to removal of impurity ions with an ion exchange resin and then passed through a filter to remove foreign matter, or distilled water is more preferred.

[0055] [pH] The pH of the polishing composition of the present invention is preferably 1 or higher, more preferably 2 or higher. The pH is preferably less than 6, more preferably 5 or lower. That is, the pH of the polishing composition of the present invention is preferably 1 or higher and lower than 6, more preferably 2 or higher and lower than 5, even more preferably 2 or higher and lower than 4, and particularly preferably 2 or higher and lower than 4.

[0056] The pH of the polishing composition can be obtained by using a pH meter (for example, a glass electrode type hydrogen ion concentration indicator (model number: F-23) manufactured by Horiba, Ltd.) and performing three-point calibration using standard buffer solutions (phthalate pH buffer solution pH: 4.01 (25°C), neutral phosphate pH buffer solution pH: 6.86 (25°C), carbonate pH buffer solution pH: 10.01 (25°C)), then placing the glass electrode in the polishing composition and measuring the value after stabilizing for at least two minutes.

[0057] The polishing composition of the present invention has abrasive grains, polyalkylene glycol, and acid as essential components, but if it is difficult to obtain the desired pH using these alone, the pH may be adjusted by adding a pH adjuster within a range that does not inhibit the effects of the present invention.

[0058] The pH adjuster is preferably a base, and may be either an inorganic compound or an organic compound. The pH adjuster may be used alone or in combination of two or more kinds.

[0059] Specific examples of bases that can be used as pH adjusters include hydroxides or salts of Group 1 elements, hydroxides or salts of Group 2 elements, quaternary ammonium hydroxides or salts thereof, amines, etc. Specific examples of salts include carbonates, hydrogen carbonates, sulfates, acetates, etc.

[0060] The amount of pH adjuster added is not particularly limited, and may be adjusted appropriately so that the polishing composition has a desired pH.

[0061] [Other ingredients] The polishing composition of the present invention may further contain known additives that can be used in polishing compositions, such as oxidizing agents, complexing agents, preservatives, and antifungal agents, within the range that does not inhibit the effects of the present invention.

[0062] [Method for producing polishing composition] The method for producing the polishing composition of the present invention is not particularly limited, and can be obtained, for example, by stirring and mixing cation-modified silica, polyalkylene glycol, acid, and, if necessary, other additives in a dispersion medium (e.g., water). The details of each component are as described above.

[0063] The temperature at which the components are mixed is not particularly limited, but is preferably 10° C. to 40° C. Heating may be used to increase the dissolution rate. The mixing time is also not particularly limited as long as uniform mixing is achieved.

[0064] [Polishing method and semiconductor substrate manufacturing method] As described above, the polishing composition of the present invention is suitably used for polishing an object having a layer of a Group 13 element. That's all The present invention also provides a polishing method for polishing an object to be polished having a layer with the polishing composition of the present invention. That's all The present invention also provides a method for manufacturing a semiconductor substrate, which comprises polishing a semiconductor substrate having a layer thereon by the polishing method described above.

[0065] As the polishing device, a general polishing device can be used, which is equipped with a holder for holding a substrate or the like having an object to be polished, a motor whose rotation speed can be changed, and a polishing platen onto which a polishing pad (polishing cloth) can be attached.

[0066] The polishing pad may be made of any material, including ordinary nonwoven fabric, polyurethane, porous fluororesin, etc. The polishing pad is preferably provided with grooves to allow the polishing liquid to accumulate.

[0067] Regarding the polishing conditions, for example, the rotation speed of the polishing platen is 10 rpm (0.17 s -1 ) or more 500rpm (8.33s -1) or less is preferable. The pressure (polishing pressure) applied to the substrate having the object to be polished is preferably 0.5 psi (3.4 kPa) or more and 10 psi (68.9 kPa) or less. The method of supplying the polishing composition to the polishing pad is not particularly limited, and for example, a method of continuously supplying it using a pump or the like is used. There is no limit to the amount of supply, but it is preferable that the surface of the polishing pad is always covered with the polishing composition of the present invention.

[0068] After polishing, the substrate is washed with running water, and water droplets adhering to the substrate are removed by a spin dryer or the like, followed by drying, to obtain a substrate having a metal-containing layer.

[0069] The polishing composition of the present invention may be a one-component type or a multi-component type such as a two-component type. The polishing composition of the present invention may also be prepared by diluting the stock solution of the polishing composition, for example, 10 times or more, with a diluent such as water. [Example]

[0070] The present invention will be described in more detail using the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples. Unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass", respectively.

[0071] <Average primary particle size of abrasive grains> The average primary particle size of the abrasive grains was calculated from the specific surface area of ​​the silica particles measured by the BET method using a Micromeritics "Flow Sorb II 2300" and the density of the abrasive grains.

[0072] <Average secondary particle size of abrasive grains> The average secondary particle diameter of the abrasive grains was measured as the volume-average particle diameter (arithmetic mean diameter on a volume basis; Mv) using a dynamic light scattering particle diameter / particle size distribution analyzer UPA-UTI151 (manufactured by Nikkiso Co., Ltd.).

[0073] <Average degree of association of abrasive grains> The average degree of association of the abrasive grains was calculated by dividing the value of the average secondary particle size of the abrasive grains by the value of the average primary particle size of the abrasive grains.

[0074] <Zeta potential of abrasive grains> The zeta potential of the abrasive grains in the polishing composition was calculated by subjecting the polishing composition to a Zetasizer Nano manufactured by Malvern Panalytical, measuring it using the laser Doppler method (electrophoretic light scattering measurement method) at a measurement temperature of 25°C, and analyzing the obtained data using the Smoluchowski equation.

[0075] <Weight-average molecular weight of polyalkylene glycol> The weight-average molecular weight of the polyalkylene glycol was measured by gel permeation chromatography (GPC) using polyethylene glycol as a standard substance. The detailed conditions are as follows: GPC equipment: Shimadzu Corporation Model: Prominence + ELSD detector (ELSD-LTII) Column: VP-ODS (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°C Injection volume: 40μl.

[0076] <pH of polishing composition> The pH of the polishing composition was measured using a glass electrode hydrogen ion concentration indicator (Model F-23, manufactured by Horiba, Ltd.) and three-point calibration was performed using standard buffer solutions (phthalate pH buffer solution pH: 4.01 (25°C), neutral phosphate pH buffer solution pH: 6.86 (25°C), carbonate pH buffer solution pH: 10.01 (25°C)).The glass electrode was then placed in the polishing composition and the value measured after stabilizing for at least two minutes was taken as the pH value.

[0077] [Preparation of Polishing Composition] Example 1 In the same manner as described in Example 1 of JP 2005-162533 A, γ-aminopropyltriethoxysilane (APTES) was used as a silane coupling agent at a concentration of 2 mmol (2 mM) per 1 L of a methanol solution of silica sol (silica concentration = 20 mass %) to prepare cocoon-shaped cation-modified colloidal silica having an average primary particle size of 24.6 nm, an average secondary particle size of 47.2 nm, and an average degree of association of 1.92.

[0078] The cation-modified colloidal silica obtained above was added as abrasive grains to pure water as a dispersion medium at room temperature (25°C) to a final concentration of 4 mass % and polyethylene glycol (PEG, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., weight-average molecular weight: 200) as a polyalkylene glycol to a final concentration of 0.05 mass %, to obtain a mixed solution.

[0079] Thereafter, nitric acid was added to the mixed solution as an acid to a final concentration of 0.0252 mass %, and the mixture was stirred and mixed at room temperature (25° C.) for 30 minutes to prepare a polishing composition.

[0080] The pH of the obtained polishing composition was 2.5. The zeta potential of the cation-modified colloidal silica in the obtained polishing composition was measured according to the above-mentioned method, and was found to be +27 mV. The particle size of the cation-modified colloidal silica in the polishing composition was the same as that of the cation-modified colloidal silica used.

[0081] (Examples 2 to 21, Comparative Examples 1 to 4) A polishing composition was prepared in the same manner as in Example 1, except that the particle size and shape of the abrasive grains, the amount of APTES used, the content of the abrasive grains, the type and content of the polyalkylene glycol, and the type and content of the acid were changed as shown in Table 1 below.

[0082] In Table 1 below, "-" indicates that the agent was not used. Comparative Examples 1 and 2 are examples in which unmodified colloidal silica was used, but polyalkylene glycol was not used. Comparative Example 4 is an example in which polyalkylene glycol was not used.

[0083] The composition of each polishing composition is shown in Table 1 below.

[0084] [Table 1]

[0085] [evaluation] Using each of the polishing compositions prepared above, the surface of a workpiece was polished under the following conditions. The workpieces were prepared as follows: a silicon wafer (300 mm, blanket wafer; manufactured by Advantec Co., Ltd.) with a 5000 Å-thick boron (B)-silicon (Si) film (boron (B) content 50 mass %: silicon (Si) content 50 mass %) formed on its surface; a silicon wafer (300 mm, blanket wafer; manufactured by Advantec Co., Ltd.) with a 2500 Å-thick SiN (silicon nitride) film formed on its surface; and a silicon wafer (300 mm, blanket wafer; manufactured by Advanced Materials Technology Co., Ltd.) with a 3600 Å-thick TiN (titanium nitride) film formed on its surface. (Polishing equipment and polishing conditions) Polishing equipment: Ebara Corporation 300mm CMP single-sided polishing equipment FREX300E Polishing pad: Fujibo Holdings Co., Ltd. Nonwoven fabric pad H800 Polishing pressure: 3.0 psi (1 psi = 6894.76 Pa) Polishing platen rotation speed: 90 rpm Carrier rotation speed: 91 rpm Supply of polishing composition: free-flowing Polishing composition supply amount: 250ml / min Polishing time: 60 seconds.

[0086] (polishing speed) The thickness of the B-Si and SiN films before and after polishing was measured using an optical film thickness measuring instrument (ASET-f5x, manufactured by KLA-Tencor Corporation), and the thickness of the TiN film before and after polishing was measured using a sheet resistance measuring instrument (VR-120, manufactured by Kokusai Electric Semiconductor Services Co., Ltd.). The polishing rate for each polishing target was calculated from the measured thickness by dividing [(thickness before polishing) - (thickness after polishing)] by the polishing time.

[0087] (Polishing rate selectivity) The selectivity of the polishing rate was calculated using the following formula: B-Si / SiN = B-Si polishing rate (Å / min) / SiN polishing rate (Å / min) B-Si / TiN = B-Si polishing rate (Å / min) / TiN polishing rate (Å / min).

[0088] The evaluation results are shown in Table 2 below.

[0089] [Table 2]

[0090] As is clear from Table 2 above, it was found that the polishing compositions of Examples improved the polishing rate of B-Si film compared to the polishing compositions of Comparative Examples. It was also found that the polishing compositions of Examples had a higher ratio (selectivity) of the polishing rate of B-Si film to the polishing rate of other materials compared to the polishing compositions of Comparative Examples.

[0091] This application is based on Japanese Patent Application No. 2021-45750, filed on March 19, 2021, the disclosure of which is incorporated by reference in its entirety.

Claims

1. A polishing composition used for polishing an object to be polished having a layer with a Group 13 element content of more than 40 mass%, comprising: Cation-modified silica, polyalkylene glycol, and acid, Including, The zeta potential of the cation-modified silica in the polishing composition is 5 mV or more and 60 mV or less; The polyalkylene glycol has a weight average molecular weight of 100 or more and 30,000 or less.

2. 2. The polishing composition according to claim 1, wherein the average primary particle size of the cation-modified silica is 5 nm or more and 30 nm or less.

3. 3. The polishing composition according to claim 2, wherein the ratio of the average secondary particle size of the cation-modified silica to the average primary particle size of the cation-modified silica (average secondary particle size / average primary particle size) is 1.2 or more and 3 or less.

4. 4. The polishing composition according to claim 1, wherein the polyalkylene glycol is polyethylene glycol.

5. 5. The polishing composition according to claim 1, wherein the acid is at least one selected from the group consisting of an acid having a nitrate group and an acid having a sulfonic acid group.

6. 6. The polishing composition according to claim 1, wherein the pH is 1 or more and less than 6.

7. A polishing method comprising the step of polishing an object to be polished having a layer with a Group 13 element content of more than 40 mass %, using the polishing composition according to any one of claims 1 to 6.

8. A method for producing a semiconductor substrate, comprising polishing a semiconductor substrate having a layer with a Group 13 element content of more than 40 mass % by the polishing method according to claim 7.

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