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

Abstract

To provide a polishing composition capable of polishing a layer containing an element from Group 13 of the periodic table with a content of 40 mass% or more, at a high polishing speed, while reducing surface defects resulting from polishing.SOLUTION: Provided is a polishing composition for use in polishing an object having a layer containing an element from group 13 of the periodic table with a content of 40 mass% or more. The polishing composition contains cationically modified silica, trialkylamine oxide, and an oxidizing agent, wherein the content of the trialkylamine oxide is 3 mass ppm or more and 40 mass ppm or less with respect to the total mass of the polishing composition, and the pH is less than 5.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

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

[0003] For example, as a technique for polishing a polysilicon film provided on a silicon substrate having a separation region, Patent Document 1 discloses a pre-polishing step using a pre-polishing composition containing abrasive grains, an alkali, a water-soluble polymer, and water, and a finishing step using a finishing polishing composition containing abrasive grains, an alkali, a water-soluble polymer, and water.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Recently, as a semiconductor substrate, a substrate having a layer with a content of Group 13 elements of 40% by mass or more has come to be used, and there has been a new demand for polishing such a substrate. Little consideration has been given to such demands in the past.

[0006] Therefore, the object of the present invention is to provide a polishing composition that can reduce surface defects in a layer having a Group 13 element content of 40% by mass or more, while enabling polishing at a high polishing speed. [Means for solving the problem]

[0007] In order to solve the above-mentioned new problems, the inventors diligently conducted research. As a result, they found that the above problems could be solved by an abrasive composition containing cation-modified silica, trialkylamine oxide, and an oxidizing agent, wherein the trialkylamine oxide content is 3 ppm by mass or more and 40 ppm by mass or less relative to the total mass of the abrasive composition, and the pH is less than 5, thus completing the present invention.

[0008] In other words, the present invention relates to a polishing composition used for polishing an object to be polished having a layer containing 40% by mass or more of Group 13 elements, comprising cation-modified silica, trialkylamine oxide, and an oxidizing agent, wherein the content of trialkylamine oxide is 3 ppm by mass or more and 40 ppm by mass or less based on the total mass of the polishing composition, and the pH is less than 5. [Effects of the Invention]

[0009] The present invention provides a polishing composition that enables polishing a layer having a Group 13 element content of 40% by mass or more at a high polishing speed while reducing surface defects in the layer caused by polishing. [Modes for carrying out the invention]

[0010] The present invention relates to a polishing composition used for polishing an object having a layer containing 40% by mass or more of Group 13 elements, comprising cationic modified silica, trialkylamine oxide, and an oxidizing agent, wherein the content of trialkylamine oxide is 3 ppm by mass or more and 40 ppm by mass or less of the total mass of the polishing composition, and the pH is less than 5. The polishing composition according to one embodiment of the present invention having such a configuration enables polishing of the layer containing 40% by mass or more of Group 13 elements at a high polishing speed while reducing surface defects caused by the polishing.

[0011] The embodiments of the present invention will be described below. However, the present invention is not limited to the embodiments described below.

[0012] In this specification, unless otherwise specified, operations and measurements of physical properties shall be performed under conditions of room temperature (20°C to 25°C) and relative humidity of 40% RH to 50% RH.

[0013] [Object to be polished] The object to be polished according to the present invention has a layer containing 40% by mass or more of a Group 13 element (hereinafter also simply referred to as the 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 present individually or in combination of two or more.

[0014] The Group 13 element layer may also contain elements other than the Group 13 elements. Examples of other elements include silicon (Si), hydrogen (H), nitrogen (N), oxygen (O), carbon (C), phosphorus (P), germanium (Ge), etc. These other elements may be included individually or in combination of two or more.

[0015] The lower limit of the amount of Group 13 elements contained in the Group 13 element layer is 40% by mass or more, preferably 45% by mass or more, and more preferably 50% by mass or more, relative to the total mass of the layer. Furthermore, the upper limit of the amount of Group 13 elements contained in the Group 13 element layer is preferably 100% by mass or less, relative to the total mass of the layer. In other words, the amount of Group 13 elements contained in the Group 13 element layer is preferably 40% by mass to 100% by mass, more preferably 45% by mass to 100% by mass, and even more preferably 50% by mass to 100% by mass, relative to the total mass of the layer.

[0016] The object to be polished according to this embodiment may further contain other materials in addition to the Group 13 element layer. Examples of other materials include silicon nitride, silicon carbonitride (SiCN), silicon oxide, polycrystalline silicon, amorphous silicon, polycrystalline silicon doped with n-type impurities, amorphous silicon doped with n-type impurities, titanium nitride, elemental metals, SiGe, and the like.

[0017] Examples of polishing targets containing silicon dioxide include TEOS (Tetraethyl Orthosilicate) type silicon dioxide 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.

[0018] Examples of elemental metals include tungsten, copper, cobalt, hafnium, nickel, gold, silver, platinum, palladium, rhodium, ruthenium, iridium, and osmium.

[0019] In addition, the object to be polished according to this embodiment may further contain a material having a content of group 13 elements of more than 0% by mass and less than 40% by mass. Examples of such materials include polycrystalline silicon doped with p-type impurities, amorphous silicon doped with p-type impurities, and the like.

[0020] [Cation-modified silica] The polishing composition according to 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. Also, commercially available products or synthetic products may be used as the cation-modified silica.

[0021] As the cation-modified silica, cation-modified colloidal silica (colloidal silica having a cationic group) is preferable.

[0022] Examples of the method for producing colloidal silica include the sodium silicate method and the sol-gel method. Colloidal silica produced by any production method can be suitably used as the abrasive grains according to the present invention. However, from the viewpoint of reducing metal impurities, colloidal silica produced by the sol-gel method is preferable. Colloidal silica produced by the sol-gel method is preferable because it contains less diffusible metal impurities and corrosive ions such as chloride ions in the semiconductor. The production of colloidal silica by the sol-gel method can be carried out using a conventionally known technique. Specifically, a hydrolyzable silicon compound (for example, alkoxysilane or its derivative) is used as a raw material, and a hydrolysis-condensation reaction is carried out to obtain colloidal silica.

[0023] Here, cation modification means a state in which a cationic group (for example, an amino group or a quaternary ammonium group) is bonded to the surface of silica (preferably colloidal silica). According to a preferred embodiment, the cation-modified silica particles are amino-group-modified silica particles, and more preferably amino-group-modified colloidal silica particles. According to such an embodiment, the above effects can be further improved.

[0024] To cation-modify silica (colloidal silica), a silane coupling agent having a cationic group (for example, an amino group or a quaternary ammonium group) may be added to the silica (colloidal silica) and reacted at a predetermined temperature for a predetermined time. In a preferred embodiment, the cation-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).

[0025] At this time, examples of the silane coupling agent used include those described in JP-A-2005-162533. Specifically, for example, 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, hydrochloride of N-(vinylbenzyl)-β-aminoethyl-γ-aminopropyltriethoxysilane, octadecyldimethyl-(γ-trimethoxysilylpropyl)-ammonium chloride, N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride and other silane coupling agents. Among them, 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 this embodiment, only one kind of silane coupling agent may be used alone, or two or more kinds may be used in combination.

[0026] The silane coupling agent can be added to silica (colloidal silica) either as is or diluted 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, it should be diluted so that the concentration of the silane coupling agent is preferably 0.01 g to 1 g, more preferably 0.1 g to 0.7 g, per liter of the 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.

[0027] Furthermore, the amount of cationic groups introduced to the surface of silica (colloidal silica) can be adjusted by controlling 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, and more preferably 0.5 mM or more and 3 mM or less, relative to the reaction solution.

[0028] The processing temperature when cationically modifying silica (colloidal silica) with a silane coupling agent is not particularly limited and can be any temperature from room temperature (e.g., 25°C) to around the boiling point of the dispersion medium in which the silica (colloidal silica) is dispersed. Specifically, it is 0°C to 100°C, preferably room temperature (e.g., 25°C) to around 90°C.

[0029] The shape of cation-modified silica is not particularly limited and may be spherical or non-spherical. Specific examples of non-spherical shapes include polygonal prisms such as triangular or square prisms, cylindrical shapes, cylindrical shapes with a bulge in the center, donut shapes with a hole in the center, plate shapes, so-called cocoon shapes with a constriction in the center, so-called aggregate spherical shapes where multiple particles are integrated, so-called konpeito shapes with multiple protrusions on the surface, rugby ball shapes, and many other shapes, and are not particularly limited.

[0030] 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. 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. If the average primary particle diameter of the cation-modified silica is within the above range, the polishing speed of the Group 13 element layer will be further improved.

[0031] In other words, the average primary particle diameter of cation-modified silica is preferably 1 nm to 100 nm, more preferably 3 nm to 50 nm, and even more preferably 5 nm to 30 nm. The average primary particle diameter of 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.

[0032] Furthermore, 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. Furthermore, 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, the frequency of contact with the object to be polished improves, and the polishing speed improves further. 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, even more preferably 25 nm or more and 100 nm or less, and particularly preferably 30 nm or more and 70 nm or less. Note that the average secondary particle diameter of the cation-modified silica is the value measured by the method described in the examples.

[0033] The ratio of the average secondary particle diameter to the average primary particle diameter of cation-modified silica (average secondary particle diameter / average primary particle diameter, hereinafter also referred to as "average degree of association") is preferably greater than 1.0, more preferably 1.1 or greater, and even more preferably 1.2 or greater. Furthermore, the average degree of association of cation-modified silica is preferably 4 or less, more preferably 3.5 or less, and even more preferably 3 or less. If the average degree of association of cation-modified silica is within the above range, the polishing speed of the group 13 element layer will be further improved. That is, the average degree of association of cation-modified silica is preferably greater than 1.0 and 4 or less, more preferably 1.1 or more and 3.5 or less, even more preferably 1.2 or more and 3 or less, and particularly preferably 1.5 or more and 2.5 or less.

[0034] The average degree of association of cation-modified silica can be obtained by dividing the average secondary particle diameter of the cation-modified silica by the average primary particle diameter.

[0035] The upper limit of the aspect ratio of cation-modified silica in the polishing composition is not particularly limited, but it 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 that circumscribes the image of cation-modified silica particles using a scanning electron microscope and dividing the length of the longer side of that rectangle by the length of the shorter side of the same rectangle, and can be determined using general image analysis software. The lower limit of the aspect ratio of cation-modified silica in the polishing composition is not particularly limited, but it is preferably 1.0 or more.

[0036] In the particle size distribution of cation-modified silica determined by laser diffraction scattering, the lower limit of D90 / D50, which is the ratio of the particle diameter (D90) when the cumulative particle weight from the fine particles reaches 90% of the total particle weight to the particle diameter (D50) when the cumulative particle weight from the fine particles reaches 50% of the total particle weight, is not particularly limited, but is preferably 1.1 or higher, more preferably 1.2 or higher, and even more preferably 1.3 or higher. Furthermore, in the particle size distribution of cation-modified silica in the polishing composition determined by laser diffraction scattering, the upper limit of the ratio D90 / D50, which is the ratio of the particle diameter (D90) when the cumulative particle weight from the fine particles reaches 90% of the total particle weight to the particle diameter (D50) when the cumulative particle weight from the fine particles reaches 50% of the total particle weight, is not particularly limited, but is preferably 2.0 or lower, more preferably 1.7 or lower, and even more preferably 1.5 or lower. Within this range, defects on the surface of the object to be polished can be further reduced.

[0037] The size of cation-modified silica (average primary particle diameter, average secondary particle diameter, aspect ratio, D90 / D50, etc.) can be appropriately controlled by selecting the appropriate manufacturing method for cation-modified silica.

[0038] The lower limit of the zeta potential of the cation-modified silica in the polishing composition is preferably 4 mV or higher, more preferably 4.5 mV, and even more preferably 5 mV or higher. The upper limit of the zeta potential of the cation-modified silica in the polishing composition is preferably 70 mV or lower, more preferably 65 mV or lower, and even more preferably 60 mV or lower. In other words, the zeta potential of the cation-modified silica in the polishing composition is preferably 4 mV to 70 mV, more preferably 4.5 mV to 65 mV, and even more preferably 5 mV to 60 mV.

[0039] If cation-modified silica with the zeta potential described above is used, the group 13 element layer can be polished at a higher polishing rate.

[0040] In this specification, the zeta potential of cation-modified silica is the value measured by the method described in the examples. The zeta potential of cation-modified silica can be adjusted by the amount of cationic groups present in the cation-modified silica, the pH of the polishing composition, etc.

[0041] 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. Furthermore, the upper limit of the content of cation-modified silica in the polishing composition is preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 6% by mass or less, relative to the total mass of the polishing composition. In other words, 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 8% by mass or less, and even more preferably 0.5% by mass or more and 6% by mass or less, relative to the total mass of the polishing composition. If the content of cation-modified silica is within this range, the Group 13 element layer can be polished at a higher polishing speed. In this specification, when a description of the content of a certain substance is made and two or more types of that substance are included, it means the total amount. For example, if an abrasive composition contains two or more types of cation-modified silica, the content of cation-modified silica refers to the total amount of these types.

[0042] The polishing composition according to this embodiment may further contain other abrasive particles other than cation-modified silica, as long as they do not impede the effects of the present invention. Such other abrasive particles may be inorganic particles, organic particles, or organic-inorganic composite particles. Specific examples of inorganic particles include, for example, 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, for example, polymethyl methacrylate (PMMA) particles. These other abrasive particles may be used alone or in mixtures of two or more types. Furthermore, these other abrasive particles may be commercially available or synthetically produced.

[0043] [Trialkylamine oxide] The polishing composition according to the present invention contains trialkylamine oxide. In the polishing composition according to the present invention, trialkylamine oxide has the function of promoting the polishing of the Group 13 element layer and further reducing defects on the surface of the object to be polished. The details of why trialkylamine oxide can promote the polishing of the object to be polished and further reduce defects on the surface of the object to be polished are unknown, but it is thought to be as follows. Trialkylamine oxide has a positive charge in the acidic region, and when the trialkylamine oxide adheres to the surface of an object to be polished that has a Group 13 element layer, an electrostatic attraction acts between it and the Group 13 elements. As a result, the bond distance of the Group 13 elements is extended, so the surface of the object to be polished becomes brittle, and it is thought that the polishing of the object to be polished can be promoted. In addition, when such positively charged trialkylamine oxide adheres to the surface of an object to be polished, the charge on the surface of the object to be polished is partially converted to positive. As a result, it is thought that abrasive grains are less likely to adhere to the surface of the object to be polished, and thus defects on the surface of the object to be polished can be reduced.

[0044] It should be noted that the above mechanism is speculative, and the present invention is not limited in any way to the above mechanism.

[0045] Trialkylamine oxides may be used individually or in combination of two or more types. Furthermore, commercially available or synthetic trialkylamine oxides may be used.

[0046] The number of carbon atoms in the alkyl group of the trialkylamine oxide according to this embodiment is not particularly limited, but is preferably 1 to 20. Furthermore, the alkyl group may be linear, branched, or cyclic.

[0047] Specific examples of alkyl groups include, for example, linear alkyl groups such as methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, lauryl group (n-dodecyl group), n-tridecyl group, myristyl group (n-tetradecyl group), n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, n-nonadecyl group, and n-icosyl group; Isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, 2-ethylbutyl group, 3,3-dimethylbutyl group, 1,1,3,3-tetramethylbutyl group, 1-methylbutyl group, 1-ethylpropyl group, 3-methylbutyl group, neopentyl group, 1,1-dimethylpropyl group, 2-methylpentyl group, 3-ethylpentyl group, 1,3-dimethylbutyl group, 2-propylpentyl group, 1-ethyl-1,2-dimethylpropyl group, 1-methylpentyl group, 4-methylpentyl group, 4-methylpentyl group Branched alkyl groups such as ethylhexyl group, 5-methylhexyl group, 2-ethylhexyl group, 1-methylhexyl group, 1-ethylpentyl group, 1-propylbutyl group, 3-ethylheptyl group, 2,2-dimethylheptyl group, 1-methylheptyl group, 1-ethylhexyl group, 1-propylpentyl group, 1-methyloctyl group, 1-ethylheptyl group, 1-propylhexyl group, 1-butylpentyl group, 1-methylnonyl group, 1-ethyloctyl group, 1-propylheptyl group, and 1-butylhexyl group; Cyclopropyl group, 1-methylcyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, 1-methylcyclohexyl group, 2-methylcyclohexyl group, 3-methylcyclohexyl group, 4-methylcyclohexyl group, 1,2-dimethylcyclohexyl group, 1,3-dimethylcyclohexyl group, 1,4-dimethylcyclohexyl group, 2,3-dimethylcyclohexyl group, 2,4-dimethylcyclohexyl group, 2,5-dimethylcyclohexyl group, 2,6-dimethylcyclohexyl group Cyclic cycloalkyl groups such as chlorohexyl group, 3,4-dimethylcyclohexyl group, 3,5-dimethylcyclohexyl group, 2,2-dimethylcyclohexyl group, 3,3-dimethylcyclohexyl group, 4,4-dimethylcyclohexyl group, cyclooctyl group, 2,4,6-trimethylcyclohexyl group, 2,2,6,6-tetramethylcyclohexyl group, 3,3,5,5-tetramethylcyclohexyl group, 4-pentylcyclohexyl group, 4-octylcyclohexyl group, and 4-decylcyclohexyl group; Examples include the three alkyl groups of the trialkylamine oxide. The three alkyl groups may be the same, different, or two may be the same alkyl group and one different alkyl group.

[0048] More specific examples of trialkylamine oxides include, for example, triethylamine oxide, tri(n-propyl)amine oxide, triisopropylamine oxide, tricyclopropylamine oxide, tri(n-butyl)amine oxide, tri(sec-butyl)amine oxide, triisobutylamine oxide, tri(tert-butyl)amine oxide, tricyclobutylamine oxide, tri(n-pentyl)amine oxide, tri(1-methylbutyl)amine oxide, tri(2-methylbutyl)amine oxide, triisopentylamine oxide, tri(tert- Pentyl)amine oxide, tri(1,2-dimethylpropyl)amine oxide, trineopentylamine oxide, tricyclopentylamine oxide, tri(n-hexyl)amine oxide, tri(1-methylpentyl)amine oxide, tri(2-methylpentyl)amine oxide, tri(3-methylpentyl)amine oxide, triisohexylamine oxide, tri(1,1-dimethylbutyl)amine oxide, tri(1,2-dimethylbutyl)amine oxide, tri(1,3-dimethylbutyl)amine oxide, tri(2,2-dimethylbutyl)amine oxide, tri(3,3-Dimethylbutylamine oxide, tricyclohexylamine oxide, tri(n-heptyl)amine oxide, tri(1-methylhexyl)amine oxide, tricycloheptylamine oxide, tri(n-octyl)amine oxide, tri(1-methylheptyl)amine oxide, triisooctylamine oxide, tricyclooctylamine oxide, tri(n-nonyl)amine oxide, tri(1-methyloctyl)amine oxide, tricyclononylamine oxide, tri (n-decyl)amine oxide, tri(1-methylnonyl)amine oxide, tricyclodecylamine oxide, tri(n-undecyl)amine oxide, tri(1-methyldecyl)amine oxide, tricycloundecylamine oxide, tri(n-dodecyl)amine oxide, tricyclododecylamine oxide, tri(n-tridecyl)amine oxide, tricyclotridecylamine oxide, tri(n-tetradecyl)amine oxide, tricyclotetradecylamine oxide, Tri(n-pentadecyl)amine oxide, tri(n-hexadecyl)amine oxide, tri(n-heptadecyl)amine oxide, tri(n-octadecyl)amine oxide, tri(n-nonadecyl)amine oxide, tri(n-icosyl)amine oxide; n-hexyldimethylamine oxide, n-heptyldimethylamine oxide, n-octyldimethylamine oxide, n-nonyldimethylamine oxide, n-decyldimethylamine oxide, n-undecyldimethylamine Examples include oxides, isododecyldimethylamine oxide, lauryldimethylamine oxide (n-dodecyldimethylamine oxide), myristyldimethylamine oxide (n-tetradecyldimethylamine oxide), isotridecyldimethylamine oxide, n-pentadecyldimethylamine oxide, n-hexadecyldimethylamine oxide, n-heptadecyldimethylamine oxide, n-octadecyldimethylamine oxide (stearyldimethylamine oxide), etc.

[0049] In particular, the number of carbon atoms in at least one alkyl group of the trialkylamine oxide is preferably 8 to 20, more preferably 10 to 18, and even more preferably 11 to 13. By having a long-chain alkyl group with a carbon number within the above range, the effects of the present invention can be obtained more efficiently.

[0050] The type of long-chain alkyl group is not particularly limited, but it is preferable to have at least one selected from the group consisting of n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, lauryl group (n-dodecyl group), n-tridecyl group, myristyl group (n-tetradecyl group), n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, n-nonadecyl group, and n-icosyl group, and more preferably at least one selected from the group consisting of n-decyl group, lauryl group, myristyl group, and n-octadecyl group. Having the above alkyl group allows the effects of the present invention to be obtained more efficiently.

[0051] The trialkylamine oxide according to this embodiment is preferably at least one selected from the group consisting of n-decyldimethylamine oxide, lauryldimethylamine oxide, myristyldimethylamine oxide, and n-octadecyldimethylamine oxide. Furthermore, lauryldimethylamine oxide is more preferable. By having the trialkylamine oxide be one of the above compounds, polishing can be more sufficiently promoted and surface defects caused by polishing can be more sufficiently reduced.

[0052] The trialkylamine oxide content in the polishing composition according to the present invention is 3 ppm by mass or more and 40 ppm by mass or less based on the total mass of the polishing composition. If the trialkylamine oxide content is less than 3 ppm by mass, the adsorption rate of the trialkylamine oxide to the surface of the object to be polished is low, so the cation-modified silica comes into excessive contact with the object to be polished during polishing, and surface defects caused by polishing cannot be sufficiently reduced. On the other hand, if the trialkylamine content exceeds 40 ppm by mass, the adsorption rate of the trialkylamine oxide to the surface of the object to be polished is high, so the approach of the cation-modified silica to the object to be polished is excessively suppressed during polishing, and the polishing speed decreases.

[0053] In this embodiment, the content of trialkylamine oxide is preferably 4 ppm by mass or more and 35 ppm by mass or less, and more preferably 5 ppm by mass or more and 30 ppm by mass or less, relative to the total mass of the polishing composition. By including trialkylamine oxide in the polishing composition within the above range, the effects of the present invention can be obtained more efficiently. If the polishing composition contains two or more types of trialkylamine oxide, the content of trialkylamine oxide refers to the total amount of these.

[0054] [Oxidizing agent] The polishing composition according to the present invention contains an oxidizing agent. The oxidizing agent promotes the polishing of an object to be polished that contains a group 13 element layer.

[0055] Examples of oxidizing agents include hydrogen peroxide, sodium peroxide, barium peroxide, ozonated water, silver(II) salt, iron(III) salt, 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, dichloroisocyanurate, and the like. These oxidizing agents may be used alone or in combination of two or more. Furthermore, commercially available or synthetic oxidizing agents may be used. Among these, hydrogen peroxide is preferred as the oxidizing agent from the viewpoint of further improving the effects of the present invention.

[0056] The content (concentration) of the oxidizing agent in the polishing composition is not particularly limited, but it is preferably 1% to 5% by mass, more preferably 2% to 4% by mass, and even more preferably 2.5% to 3.5% by mass, relative to the total mass of the polishing composition. When the oxidizing agent content is within this range, the Group 13 element layer can be polished at a sufficiently high polishing rate, and surface defects caused by polishing can be reduced more sufficiently. If the polishing composition contains two or more oxidizing agents, the content of the oxidizing agents refers to their total amount.

[0057] [pH] The pH of the polishing composition according to the present invention is less than 5. If the pH is 5 or higher, the zeta potential of the cation-modified silica decreases, making it difficult for electrostatic attraction to act with the object to be polished, which reduces the polishing speed and also increases the number of defects.

[0058] The pH of the polishing composition according to this embodiment is preferably 1 or more and less than 5, more preferably 2 or more and less than 4, and even more preferably 2 or more and 3 or less. Having the pH of the polishing composition within this range makes it possible to polish the Group 13 element layer at a higher polishing speed.

[0059] 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.), performing a 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)), then placing the glass electrode in the polishing composition and measuring the value after it has stabilized for at least two minutes.

[0060] The polishing composition according to the present invention comprises cation-modified silica, trialkylamine oxide, and an oxidizing agent as essential components. However, if it is difficult to obtain the desired pH using only these components, a pH adjusting agent may be added to adjust the pH, provided that it does not hinder the effects of the present invention.

[0061] The pH adjusting agent is not particularly limited as long as it is a compound that has a pH adjusting function, and known compounds can be used. The pH adjusting agent is not particularly limited as long as it has a pH adjusting function, but examples include acids, alkalis, etc.

[0062] Either an inorganic or organic acid may be used as the acid. Inorganic acids are not particularly limited, but examples include sulfuric acid, nitric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid. Organic acids are not particularly limited, but examples include 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), 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, as well as carboxylic acids, methanesulfonic acid, ethanesulfonic acid, and isethionic acid. Among these, organic acids are preferred, with 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), malic acid, citric acid, and maleic acid being more preferred. When inorganic acids are used, nitric acid, sulfuric acid, and phosphoric acid are preferred.

[0063] The alkali is not particularly limited, but examples include alkali metal hydroxides such as potassium hydroxide, ammonia, quaternary ammonium salts such as tetramethylammonium and tetraethylammonium, and amines such as ethylenediamine and piperazine. Among these, potassium hydroxide and ammonia are preferred.

[0064] pH adjusters can be used alone or in combination of two or more types.

[0065] The amount of pH adjuster added is not particularly limited and should be adjusted as appropriate so that the polishing composition reaches the desired pH.

[0066] [Anti-mold agent] The polishing composition according to this embodiment may contain an antifungal agent to the extent that it does not impair the effects of the present invention. As the antifungal agent, known agents that can be used in polishing compositions can be used, but examples include isothiazolinoline-based preservatives such as 1,2-benzoisothiazole-3(2H)-one, 2-methyl-4-isothiazolin-3-one, and 5-chloro-2-methyl-4-isothiazolin-3-one, parahydroxybenzoic acid esters, and phenoxyethanol. These preservatives and antifungal agents may be used individually or in combination of two or more.

[0067] [Dispersion medium] The polishing composition according to this embodiment may contain a dispersion medium for dispersing each component. Examples of dispersion media include water; alcohols such as methanol, ethanol, and ethylene glycol; ketones such as acetone; and mixtures thereof. Of these, water is preferred as the dispersion medium. That is, the dispersion medium of the polishing composition according to this embodiment preferably contains water, and it is even more preferable that the dispersion medium consists substantially of water. The term "substantially" above means that a dispersion medium other than water may be included insofar as the effects of the present invention can be achieved. More specifically, the dispersion medium preferably consists of 90% to 100% by mass of water and 0% to 10% by mass of a dispersion medium other than water, and more preferably consists of 99% to 100% by mass of water and 0% to 1% by mass of a dispersion medium other than water. Most preferably, the dispersion medium is water.

[0068] From the viewpoint of not inhibiting the action of the components contained in the polishing composition, the dispersion medium should preferably be water that contains as few impurities as possible. Specifically, pure water, ultrapure water, or distilled water obtained by removing impurity ions with an ion exchange resin and then removing foreign matter by passing it through a filter is more preferable.

[0069] [Other ingredients] The polishing composition according to this embodiment may further contain known additives that can be used in polishing compositions, such as complexing agents and preservatives, to the extent that they do not impair the effects of the present invention.

[0070] [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 cation-modified silica, trialkylamine oxide, an oxidizing agent, and other additives as needed in a dispersion medium (e.g., water). Details of each component are as described above.

[0071] 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.

[0072] [Polishing method and semiconductor substrate manufacturing method] As described above, the polishing composition according to this embodiment is suitably used for polishing objects having a Group 13 element layer. Therefore, the present invention provides a polishing method comprising the step of polishing an object having a layer containing 40% by mass or more of Group 13 elements with the polishing composition according to this embodiment. The present invention also provides a method for manufacturing a semiconductor substrate, comprising polishing a semiconductor substrate having a layer containing 40% by mass or more of Group 13 elements by the above polishing method.

[0073] As a polishing apparatus, a general polishing apparatus can be used that has a holder for holding a substrate or the like with the object to be polished, a motor with adjustable rotation speed, and a polishing platen to which a polishing pad (abrasive cloth) can be attached.

[0074] As the polishing pad, 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.

[0075] Regarding polishing conditions, for example, the rotation speed of the polishing platen is 10 rpm (0.17 s). -1 ) or more 500rpm (8.33s -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) to 10 psi (68.9 kPa). The method of supplying the polishing composition to the polishing pad is not particularly limited, and for example, a method of supplying it continuously by 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 according to the present invention.

[0076] After polishing is complete, the substrate is washed with running water, and any water droplets adhering to the substrate are removed using a spin dryer or the like to dry it, thereby obtaining a substrate having a group 13 element layer.

[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, for example, 10 times or more.

[0078] Although embodiments of the present invention have been described in detail above, this is descriptive and illustrative, and not limiting, and it is clear that the scope of the present invention should be interpreted by the appended claims.

[0079] The present invention encompasses the following aspects and embodiments: [1] A polishing composition used for polishing an object to be polished, having a layer containing 40% by mass or more of Group 13 elements, It contains cation-modified silica, trialkylamine oxide, and an oxidizing agent. The content of the trialkylamine oxide is 3 ppm by mass or more and 40 ppm by mass or less relative to the total mass of the polishing composition. A polishing composition having a pH of less than 5.

[0080] [2] The polishing composition according to [1] above, wherein the pH is 2 or more and less than 4.

[0081] [3] The polishing composition according to [1] or [2] above, wherein the trialkylamine oxide has at least one alkyl group having 8 or more carbon atoms and 20 or fewer carbon atoms.

[0082] [4] The polishing composition according to any one of [1] to [3] above, wherein the trialkylamine oxide has at least one selected from the group consisting of an n-decyl group, a lauryl group, a myristyl group, and an n-octadecyl group.

[0083] [5] The polishing composition according to any one of [1] to [4] above, wherein the trialkylamine oxide is at least one selected from the group consisting of n-decyldimethylamine oxide, lauryldimethylamine oxide, myristyldimethylamine oxide, and n-octadecyldimethylamine oxide.

[0084] [6] The polishing composition according to any one of [1] to [5] above, wherein the content of the oxidizing agent is 1% by mass or more and 5% by mass or less based on the total mass of the polishing composition.

[0085] [7] The polishing composition according to any one of [1] to [6] above, wherein the oxidizing agent is hydrogen peroxide.

[0086] [8] The polishing composition according to any one of [1] to [7] above, further comprising an antifungal agent.

[0087] [9] A polishing method comprising the step of polishing an object to be polished having a layer containing 40% by mass or more of a group 13 element using the polishing composition described in any of [1] to [8] above.

[0088]

[10] A method for manufacturing a semiconductor substrate, comprising polishing a semiconductor substrate having a layer containing 40% by mass or more of group 13 elements by the polishing method described in [9] above. [Examples]

[0089] 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.

[0090] <Average primary particle size of abrasive grains> The average primary particle size of the abrasive grains was calculated from the specific surface area of ​​silica particles measured by the BET method using a "Flow Sorb II 2300" manufactured by Micromerities, and the density of the abrasive grains.

[0091] <Average secondary particle size of abrasive grains> The average secondary particle diameter of the abrasive grains 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-UTI151 (manufactured by Nikkiso Co., Ltd.).

[0092] <Average degree of aggregation of abrasive grains> The average degree of abrasive particle aggregation was calculated by dividing the average secondary particle diameter of the abrasive particles by the average primary particle diameter of the abrasive particles.

[0093] <Zeta potential of abrasive grains> The zeta potential of abrasive grains in the polishing composition was calculated by subjecting the polishing composition to a Malvern Panalytical Zetasizer Nano and measuring it using laser Doppler (electrophoretic light scattering measurement) at a measurement temperature of 25°C. The obtained data was then analyzed using the Smoluchowski equation.

[0094] <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.

[0095] [Preparation of abrasive compositions] (Example 1) In the same manner as described in Example 1 of Japanese Patent Publication No. 2005-162533, 2 mmol (2 mM) of γ-aminopropyltriethoxysilane (APTES) was used as a silane coupling agent in 1 L of a methanol solution of silica sol (silica concentration = 20% by mass) to prepare cocoon-shaped cation-modified colloidal silica with an average primary particle diameter of 25.0 nm, an average secondary particle diameter of 50.0 nm, and an average degree of association of 2.0.

[0096] The cation-modified colloidal silica obtained above was added to pure water, which was used as a dispersion medium, at room temperature (25°C) to a final concentration of 4% by mass. BIT (1,2-benzoisothiazole-3(2H)-one, manufactured by San-ai Oil Co., Ltd.) was added as an antifungal agent to a final concentration of 0.3 g / kg to obtain a mixed solution.

[0097] Subsequently, lauryldimethylamine oxide (manufactured by NOF Corporation), a type of trialkylamine oxide, was added to the mixture as a water-soluble additive to a final concentration of 5 ppm by mass. Furthermore, a 31% by mass aqueous solution of hydrogen peroxide (manufactured by Santoku Chemical Industry Co., Ltd.) was added as an oxidizing agent to a final hydrogen peroxide concentration of 3.1% by mass. Next, nitric acid was used as a pH adjuster to adjust the pH of the mixture to 2.5, and the mixture was stirred and mixed at room temperature (25°C) for 30 minutes to prepare the polishing composition.

[0098] The zeta potential of the cation-modified colloidal silica in the obtained polishing composition was measured according to the method described above and was found to be +25 mV. Furthermore, the particle size of the cation-modified colloidal silica in the polishing composition was similar to that of the cation-modified colloidal silica used.

[0099] (Examples 2-12, Comparative Examples 1-13) Polishing compositions were prepared in the same manner as in Example 1, except that the type and concentration (mass ppm) of the water-soluble additive, the content (mass %) of the oxidizing agent, and the pH were changed as shown in Table 1 below. The composition of each polishing composition is shown in Table 1 below.

[0100] The water-soluble additives are specifically as follows: Lauryldimethylamine oxide: Manufactured by NOF Corporation n-decyldimethylamine oxide: Manufactured by Lion Corporation Myristyldimethylamine oxide: Manufactured by Fujifilm Wako Pure Chemical Corporation n-Octadecyldimethylamine oxide: Manufactured by ZHI SHANG CHEMICAL. Poly-N-vinylacetamide (PNVA): Weight-average molecular weight 31,000, manufactured by Showa Denko Corporation. Polyvinyl alcohol (PVA): Weight-average molecular weight 10,000, manufactured by Nippon Vinegar Vi-Bopal Co., Ltd. Polyethylene glycol (PEG): Weight-average molecular weight 200, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. Sorbitol: Manufactured by Fujifilm Wako Pure Chemical Corporation Vinylpyrrolidone-N,N-dimethylaminoethyl methacrylate copolymer diethyl sulfate: weight-average molecular weight 150,000, manufactured by Osaka Organic Chemical Industry Co., Ltd.

[0101] In Table 1 below, a "-" indicates that the agent was not used. For example, Comparative Examples 1, 9-11 are examples where water-soluble additives were not used.

[0102] [evaluation] The surface of the object to be polished was polished under the following conditions using each of the polishing compositions prepared above. As the object to be polished, a silicon wafer (300 mm, blanket wafer; manufactured by Advance Materials Technology Co., Ltd.) was prepared, on which a 3000 Å thick boron(B) film (100% by mass boron(B) content) (hereinafter also simply referred to as "B film") was formed on the surface. The pH of each polishing composition was measured before polishing, and the values ​​shown in Table 1 were obtained.

[0103] (Polishing equipment and polishing conditions) Polishing equipment: Ebara Corporation FREX300E 300mm CMP single-sided polishing machine Polishing pad: Polyurethane pad IC1010, manufactured by Nitta DuPont Corporation. Polishing pressure: 2.0 psi (1 psi = 6894.76 Pa) Polishing plate rotation speed: 90 rpm Carrier rotation speed: 91 rpm Supply of polishing composition: flow-through Polishing composition supply amount: 250ml / min Polishing time: 30 seconds.

[0104] (Evaluation of polishing speed) For film B, the thickness 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 speed for each object was calculated by dividing [(thickness before polishing) - (thickness after polishing)] by the polishing time. A polishing speed exceeding 300 Å / min is considered practical.

[0105] (Evaluation of the number of defects) The number of defects (individuals) larger than 60 nm present on the surface of the polished B film was measured using a KLA-TENCOR SURFSCAN SP5 optical inspection machine (wafer inspection system) in DC mode. A defect count of less than 700 is considered practical.

[0106] The evaluation results are shown in Table 1 below.

[0107] [Table 1-1]

[0108] [Table 1-2] As is clear from Table 1 above, when using the polishing composition of the example, it was found that, compared to the polishing composition of the comparative example, it was possible to polish film B at a higher polishing speed while reducing defects on the surface of film B caused by polishing. In contrast, with the polishing composition of Comparative Example 8, polishing could not be performed because the abrasive grains aggregated.

Claims

1. A polishing composition used for polishing an object to be polished, having a layer containing 40% by mass or more of Group 13 elements, It contains cation-modified silica, trialkylamine oxide, and an oxidizing agent. The content of the trialkylamine oxide is 3 ppm by mass or more and 40 ppm by mass or less relative to the total mass of the polishing composition. The pH is less than 5. The aforementioned Group 13 element is boron, The aforementioned trialkylamine oxide is an abrasive composition having at least one alkyl group having 8 to 20 carbon atoms.

2. The polishing composition according to claim 1, wherein the pH is 2 or more and less than 4.

3. The trialkylamine oxide has two identical alkyl groups and one different alkyl group, The number of carbon atoms in the aforementioned one different alkyl group is 8 or more and 20 or less. The polishing composition according to claim 1, wherein the two identical alkyl groups are selected from the group consisting of a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an isopropyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group.

4. The polishing composition according to claim 1, wherein the trialkylamine oxide has at least one selected from the group consisting of an n-decyl group, a lauryl group, a myristyl group, and an n-octadecyl group.

5. The polishing composition according to claim 1, wherein the trialkylamine oxide is at least one selected from the group consisting of n-decyldimethylamine oxide, lauryldimethylamine oxide, myristyldimethylamine oxide, and n-octadecyldimethylamine oxide.

6. The polishing composition according to claim 1, wherein the content of the oxidizing agent is 1% by mass or more and 5% by mass or less based on the total mass of the polishing composition.

7. The polishing composition according to claim 1, wherein the oxidizing agent is hydrogen peroxide.

8. The polishing composition according to claim 1, further comprising an antifungal agent.

9. The process includes polishing an object to be polished having a layer containing 40% by mass or more of a group 13 element using the polishing composition described in any one of claims 1 to 8, A polishing method wherein the aforementioned Group 13 element is boron.

10. The semiconductor substrate having a layer containing 40% by mass or more of Group 13 elements is polished by the polishing method described in claim 9. A method for manufacturing a semiconductor substrate, wherein the aforementioned Group 13 element is boron.

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