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

Abstract

To provide a polishing composition capable of improving the polishing speed with a silicon nitride film, a production method of a polishing composition, a polishing method and a substrate production method.SOLUTION: There is provided a polishing composition comprising: abrasive grains; and a nitrogen-containing compound having an adamantane skeleton, where the value of pH is smaller than 7.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] In recent years, with the trend toward multi-layer wiring on the surface of semiconductor substrates, a so-called chemical mechanical polishing (CMP) technique is used to polish and flatten semiconductor substrates when manufacturing semiconductor devices. CMP is a method for flattening the surface of an object to be polished (object to be polished) such as a semiconductor substrate using a polishing composition (slurry) containing abrasive grains such as silica, alumina, ceria, etc., an anticorrosive agent, a surfactant, etc. The object to be polished (object to be polished) is silicon, polysilicon, silicon oxide film (silicon oxide), silicon nitride, wiring, plugs, etc. made of metal, etc.

[0003] Various proposals have been made so far regarding polishing compositions used when polishing semiconductor substrates by CMP. For example, Patent Document 1 describes that "an object to be polished having at least a first layer containing polysilicon or modified polysilicon and a second layer containing at least one selected from the group consisting of silicon oxide, silicon nitride, silicon carbide, silicon carbonitride, silicon carbide oxide, and silicon oxynitride is polished using a polishing liquid containing colloidal silica particles having a positive ζ potential and an anionic surfactant and having a pH value in the range of 1.5 to 7.0." [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-216582 A Summary of the Invention [Problem to be solved by the invention]

[0005] Regarding the polishing rate of the silicon nitride film, the conventional polishing composition did not always satisfy the user's requirements. An improvement in the polishing rate of the silicon nitride film is desired. The present invention has been made in view of such circumstances, and an object thereof is to provide a polishing composition capable of improving the polishing rate of a silicon nitride film, a method for producing the polishing composition, a polishing method, and a method for producing a substrate.

Means for Solving the Problems

[0006] In view of the above problems, the present inventors have conducted intensive studies. As a result, by using a polishing composition containing abrasive grains and a nitrogen-containing compound having an adamantane skeleton and having a pH value smaller than 7, it has been found that the polishing rate of the silicon nitride film can be increased (improved), and the invention has been completed.

Effects of the Invention

[0007] According to the present invention, there are provided a polishing composition capable of improving the polishing rate of a silicon nitride film, a method for producing the polishing composition, a polishing method, and a method for producing a substrate.

Modes for Carrying Out the Invention

[0008] Embodiments of the present invention will be described in detail. The polishing composition according to this embodiment is a polishing composition containing abrasive grains and a nitrogen-containing compound having an adamantane skeleton and having a pH value smaller than 7. This polishing composition is suitable for uses such as polishing an object to be polished such as single crystal silicon, a silicon compound, or a metal, for example, for polishing a surface containing single crystal silicon, polysilicon, a silicon compound, a metal, etc. as a semiconductor substrate in a semiconductor device manufacturing process, and is particularly suitable for uses such as polishing a silicon nitride film (SiN film). If polishing is performed using this polishing composition, in particular, the SiN film can be polished at a high polishing rate. Hereinafter, the polishing composition of this embodiment will be described in detail.

[0009] <Abrasive Grains> (Type of Abrasive Grains) The polishing composition according to the present embodiment contains, as abrasive grains, cation-modified silica, anion-modified silica, or unmodified silica. The cation-modified silica may be rephrased as cation-modified silica, cation-modified silica, or silica having a cationic group. The anion-modified silica may be rephrased as anion-modified silica, anion-modified silica, or silica having an anionic group. The unmodified silica may be rephrased as silica that is not surface-modified, or unmodified silica.

[0010] In this embodiment, the abrasive grains may be cation-modified silica, anion-modified silica, or unmodified silica. The silica may be colloidal silica. That is, the abrasive grains may be cation-modified colloidal silica, anion-modified colloidal silica, or unmodified colloidal silica. The cation-modified colloidal silica can further improve the polishing speed of the polishing object containing a silicon oxide film. Furthermore, the polishing pad scraps generally have a positive zeta potential under acidic conditions. Therefore, under acidic conditions, the aggregation of the cation-modified colloidal silica with a positive zeta potential and the polishing pad scraps is further suppressed, coarse particles are less likely to be formed, and scratches on the surface of the polishing object can be further reduced.

[0011] Examples of methods for producing colloidal silica include the sodium silicate method and the sol-gel method. Colloidal silica produced by either method may be used, but colloidal silica produced by the sol-gel method is preferred from the viewpoint of reducing metal impurities. Colloidal silica produced by the sol-gel method is preferred because it contains less metal impurities and corrosive ions such as chloride ions that have the property of diffusing in semiconductors. Colloidal silica can be produced by the sol-gel method using a conventionally known method, and 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.

[0012] As the cation-modified colloidal silica, colloidal silica with amino group fixed on the surface can be preferably mentioned.As the method for producing such cation-modified colloidal silica, as described in JP-A-2005-162533, a method of fixing a silane coupling agent (hereinafter, aminosilane coupling agent) having amino group such as aminoethyltrimethoxysilane, aminopropyltrimethoxysilane, aminoethyltriethoxysilane, aminopropyltriethoxysilane, aminopropyldimethylethoxysilane, aminopropylmethyldiethoxysilane, aminobutyltriethoxysilane, etc. on the surface of abrasive grain can be mentioned.By this, colloidal silica with amino group fixed on the surface can be obtained.

[0013] Examples of aminosilane coupling agents include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane (APTES), 4-amino 3,3-dimethylbutyltriethoxysilane, N-methylaminopropyltrimethoxysilane, (N,N-dimethyl-3-aminopropyl)trimethoxysilane, 2-(4-pyridylethyl)triethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylsilanetriol, 3-trimethoxypropyldiethyldiethylenetriamine, N,N′-BIS[(3 -trimethoxysilyl)propyl]ethylenediamine, [3-(1-piperazinyl)propyl]methyldimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine, bis[3-(trimethoxysilyl)propyl]amine, and the like.

[0014] As the aminosilane coupling agent, for example, an aminotrialkoxysilane having a structure shown in the following formula (1) can be used. In formula (1), X is an alkyl group having 1 to 10 carbon atoms (C) (referred to as C1-C10, hereinafter the same), an aminoalkyl group (C1-C10) containing one or more nitrogen atoms, or a single bond. R1, R2, and R3 are each independently an alkyl group (C1-C3), hydrogen (H), or a salt thereof. The salt is, for example, hydrochloride.

[0015] [ka]

[0016] Examples of the amino trialkoxylane include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane (APTES), 4-amino 3,3-dimethylbutyltriethoxysilane, N-methylaminopropyltrimethoxysilane, (N,N-dimethyl-3-aminopropyl)trimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylsilanetriol, 3-trimethoxypropyldiethyldiethylenetriamine, and the like.

[0017] Among the above aminosilane coupling agents, 3-aminopropyltriethoxysilane (APTES) has a structure shown in formula (2). When 3-aminopropyltriethoxysilane is used as the aminosilane coupling agent, aminopropyl groups are fixed to the surface of the colloidal silica, which is cationized.

[0018] [ka]

[0019] The zeta (ζ) potential of the cation-modified colloidal silica surface-modified by chemical treatment with an aminosilane coupling agent is preferably 10 mV or more, more preferably 20 mV or more, and even more preferably 30 mV or more under acidic conditions. From the viewpoint of obtaining a stable positive zeta potential, it is preferable to use the above aminotrialkoxysilane as the aminosilane coupling agent, and among them, it is preferable to use APTES.

[0020] Since the zeta potential value of ordinary colloidal silica is close to zero under acidic conditions, the colloidal silica particles do not electrically repel each other under acidic conditions and tend to aggregate. In contrast, the zeta potential of cation-modified colloidal silica surface-modified by chemical treatment with an aminosilane coupling agent has a relatively large positive value under acidic conditions. Therefore, even under acidic conditions, the cation-modified colloidal silica particles strongly repel each other, disperse well, and are less likely to aggregate. As a result, the storage stability of the polishing composition is improved.

[0021] (shape) The shape of the cationically modified or unmodified colloidal silica is not particularly limited, but an example is a perfect sphere or a cocoon shape. The cocoon shape is a shape in which two spheres are joined together, and the joint is narrowed like a constriction. In this specification, the cocoon shape may be rephrased as a peanut shape.

[0022] (Aspect Ratio) The aspect ratio of the cation-modified or unmodified colloidal silica is preferably less than 1.4, more preferably 1.3 or less, and even more preferably 1.25 or less. This can improve the surface roughness of the object to be polished caused by the shape of the abrasive grains. The aspect ratio is the average value of the values ​​obtained by dividing the length of the long side of the smallest rectangle circumscribing the colloidal silica particle by the length of the short side of the same rectangle, and can be obtained from the image of the colloidal silica particle obtained by a scanning electron microscope using general image analysis software.

[0023] (Average primary particle size) The average primary particle size of the cation-modified or unmodified colloidal silica is preferably 5 nm or more, more preferably 7 nm or more, even more preferably 10 nm or more, even more preferably 20 nm or more, and most preferably 25 nm or more. The average primary particle size of the colloidal silica is preferably 100 nm or less, more preferably 70 nm or less, even more preferably 50 nm or less, even more preferably 40 nm or less, and most preferably 35 nm or less. Within such a range, the polishing rate of the polishing composition for the object to be polished is improved. In addition, the occurrence of dishing on the surface of the object to be polished after polishing with the polishing composition can be further suppressed. The average primary particle size of the colloidal silica is calculated based on the specific surface area of ​​the colloidal silica measured by the BET method, for example.

[0024] (Average secondary particle size) The average secondary particle diameter of the cationically modified or unmodified colloidal silica is preferably 30 nm or more, more preferably 50 nm or more, even more preferably 60 nm or more, and even more preferably 65 nm or more. The average secondary particle diameter of the cationically modified or unmodified colloidal silica is preferably 200 nm or less, more preferably 150 nm or less, even more preferably 100 nm or less, even more preferably 80 nm or less, and most preferably 75 nm. Within such a range, the polishing rate of the object to be polished by the polishing composition is improved. In addition, the occurrence of surface defects on the surface of the object to be polished after polishing with the polishing composition can be further suppressed. The secondary particles refer to particles formed by association in the polishing composition of colloidal silica (primary particles) having an organic acid fixed on the surface. The average secondary particle diameter of the secondary particles can be measured, for example, by dynamic light scattering.

[0025] (particle size distribution) In the particle size distribution of cation-modified or unmodified colloidal silica, the ratio D90 / D10 between the particle diameter D90 when the cumulative particle mass from the fine particle side reaches 90% of the total particle mass and the particle diameter D10 when the cumulative particle mass from the fine particle side reaches 10% of the total particle mass is preferably 1.5 or more, more preferably 1.8 or more, and even more preferably 2.0 or more. In addition, this ratio D90 / D10 is preferably 5.0 or less, and more preferably 3.0 or less. In such a range, the polishing speed of the object to be polished is improved, and the occurrence of surface defects on the surface of the object to be polished after polishing with the polishing composition can be further suppressed. The particle size distribution of cation-modified or unmodified colloidal silica can be determined, for example, by laser diffraction scattering method.

[0026] (Content) The content of the cationically modified or unmodified colloidal silica in the entire polishing composition is preferably 0.005 mass% or more, more preferably 0.05 mass% or more, even more preferably 0.5 mass% or more, and particularly preferably 0.75 mass% or more. Within such a range, the polishing speed of the object to be polished is improved.

[0027] In addition, the content of cation-modified or unmodified colloidal silica in the entire polishing composition is preferably 10 mass% or less, more preferably 5 mass% or less, even more preferably 3 mass% or less, even more preferably 2 mass% or less, and most preferably 1.5 mass% or less.Within such a range, the cost of the polishing composition can be reduced.In addition, the occurrence of surface defects on the surface of the object to be polished after polishing with the polishing composition can be further suppressed.

[0028] <Nitrogen-containing compounds having an adamantane skeleton> The polishing composition according to this embodiment includes a nitrogen-containing compound having an adamantane skeleton (hereinafter, nitrogen-containing adamantane compound). The nitrogen-containing adamantane compound may be, for example, an amine having an adamantane skeleton (hereinafter, adamantane amine). The adamantane skeleton may be referred to as an adamantane structure.

[0029] Examples of adamantane amines include hexamine (hexamethylenetetramine), 1-adamantamine, adamantane-1,3-diamine, 2-hydroxy-2-azaadamantane, 1,3,5-triaza-7-phosphaadamantane, mematine, rimantadine, tromantadine, vildagliptin, tetramethylenedisulfotetramine, (1r,3r,5r,7r)-6-tosyl-2-oxa-6-azaadamantane, 1-methyl-2-azaadamantane-N-oxyl, 2-azaadamantane, 1-azatricyclo[3.3.1.1(3,7)]decan-4-one, 3-amino-1-hydroxy-adamantane, and 1-acetylamidoadamantane.

[0030] For example, the adamantane skeleton has the structure shown in formula (3). Hexamine (hexamethylenetetramine) has the structure shown in formula (4). 1-adamantamine has the structure shown in formula (5). Adamantane-1,3-diamine has the structure shown in formula (6). 2-hydroxy-2-azaadamantane has the structure shown in formula (7). 1,3,5-triaza-7-phosphaadamantane has the structure shown in formula (8). Tetramethylenedisulfotetramine has the structure shown in formula (9). 2-azaadamantane has the structure shown in formula (10). 1-azatricyclo[3.3.1.1(3,7)]decan-4-one has the structure shown in formula (11).

[0031] [ka]

[0032] [ka]

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[0034] [ka]

[0035] [ka]

[0036] [ka]

[0037] [ka]

[0038] [ka]

[0039] [ka]

[0040] In this embodiment, the nitrogen-containing adamantane compound may contain a nitrogen (N) atom in the adamantane skeleton. The inclusion of an N atom in the adamantane skeleton means that at least one or more carbon (C) atoms in the adamantane skeleton shown in formula (2) are replaced with an N atom. Examples of compounds containing an N atom in the adamantane skeleton include hexamine (hexamethylenetetramine) shown in formula (2), tetramethylenedisulfotetramine shown in formula (8), 2-azaadamantane shown in formula (9), and 1-azatricyclo[3.3.1.1(3,7)]decan-4-one shown in formula (10).

[0041] The number of N atoms in the nitrogen-containing adamantane compound is preferably more than one. When an N atom is contained in the adamantane skeleton, the number of N atoms contained in the adamantane skeleton is also preferably more than one. Examples of compounds containing multiple N atoms in the adamantane skeleton include hexamine (hexamethylenetetramine) shown in formula (2) and tetramethylenedisulfotetramine shown in formula (8). The number of N atoms contained in the nitrogen-containing adamantane compound is preferably greater, for example, three is more preferable than two, and four is even more preferable than three. The reason for this is that, as described later in <Mechanism of improving polishing rate>, the lone electron pair of the N atom in the nitrogen-containing adamantane compound behaves as a nucleophile with respect to Si of the SiN film, which is the object to be polished. The more N atoms there are, the more easily they react with Si of the SiN film, which is the object to be polished, and the polishing rate of the SiN film tends to increase. Note that this mechanism is speculation, and the present invention is not limited to this mechanism.

[0042] The nitrogen-containing compound preferably contains a carbon (C) atom or a hydrogen (H) atom bonded to an N atom. Examples of nitrogen-containing compounds having a C atom or an H atom bonded to an N atom include hexamine (hexamethylenetetramine) shown in formula (2) and 2-azaadamantane shown in formula (9). When a sulfur (S) atom or an oxygen (O) atom is bonded to the N atom of a nitrogen-containing compound, the electron on the N atom is attracted to the S atom or the O atom, and the nucleophilicity of the N atom may decrease. However, when a C atom or an H atom is bonded to the N atom of a nitrogen-containing compound, the N atom of the nitrogen-containing compound can be prevented from bonding to an S atom or an O atom, and the nucleophilicity of the N atom is less likely to decrease.

[0043] <Liquid medium> The polishing composition according to this embodiment contains a liquid medium. It functions as a dispersion medium or a solvent for dispersing or dissolving each component of the polishing composition (additives such as cation-modified colloidal silica, anionic surfactant, pH adjuster, etc.). Examples of the liquid medium include water and organic solvents. One kind can be used alone, or two or more kinds can be mixed and used, but it is preferably water-containing. However, from the viewpoint of preventing the inhibition of the action of each component, it is preferable to use water that contains as few impurities as possible. Specifically, pure water, ultrapure water, or distilled water obtained by removing foreign substances through a filter after removing impurity ions with an ion exchange resin is preferable.

[0044] <pH adjuster> The pH value of the polishing composition according to this embodiment is less than 7, preferably 2 or more and 6 or less, more preferably 3 or more and 5 or less, and particularly preferably 3.5 or more and 5 or less. Also, a more preferable range of the pH value is 3.5 or more and 5 or less. If the polishing composition is acidic, the zeta (ζ) potential of the cation-modified colloidal silica with surface modification can be made a positive value. In order to achieve the above-mentioned pH value, the polishing composition may contain a pH adjuster. The pH value of the polishing composition can be adjusted by adding a pH regulator. The pH regulator used may be either an acid or an alkali, and may be either an inorganic compound or an organic compound.

[0045] Specific examples of the acid as the pH adjuster include inorganic acids and organic acids such as carboxylic acids and organic sulfuric acids. Specific examples of the inorganic acids include sulfuric acid, nitric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, phosphoric acid, etc. As the pH adjuster, it is preferable to use an inorganic acid, and among them, a phosphoric acid-based inorganic acid is more preferable. The organic acids include carboxylic acids, and organic sulfuric acids and organic phosphonic acids. Specific examples of the carboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, lactic acid, etc. Further, specific examples of the organic sulfuric acids include methanesulfonic acid, ethanesulfonic acid, isethionic acid, etc. Specific examples of the organic phosphonic acids include methanephosphonic acid, etidronic acid, phenylphosphonic acid, etc. These acids may be used alone or in combination of two or more. As the organic acid, it is preferable to use a carboxylic acid-based or phosphonic acid-based organic acid. Also, these acids may be included as a pH adjuster in the polishing composition, or may be included as an additive for improving the polishing rate, or may be a combination of these.

[0046] Specific examples of the base as the pH adjuster include hydroxides or salts of alkali metals, hydroxides or salts of alkaline earth metals, quaternary ammonium hydroxides or salts thereof, ammonia, amines, etc. Specific examples of the alkali metals include potassium, sodium, etc. Also, specific examples of the alkaline earth metals include calcium, strontium, etc. Further, specific examples of the salts include carbonates, bicarbonates, sulfates, acetates, etc. Further, specific examples of the quaternary ammonium include tetramethylammonium, tetraethylammonium, tetrabutylammonium, etc.

[0047] The quaternary ammonium hydroxide compound includes quaternary ammonium hydroxide or a salt thereof, and specific examples thereof include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, etc. Furthermore, specific examples of the amine include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N-(β-aminoethyl)ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, anhydrous piperazine, piperazine hexahydrate, 1-(2-aminoethyl)piperazine, N-methylpiperazine, guanidine, etc.

[0048] These bases may be used alone or in combination of two or more. Among these bases, ammonia, ammonium salts, alkali metal hydroxides, alkali metal salts, quaternary ammonium hydroxide compounds, and amines are preferred, and ammonia, potassium compounds, sodium hydroxide, quaternary ammonium hydroxide compounds, ammonium hydrogen carbonate, ammonium carbonate, sodium hydrogen carbonate, and sodium carbonate are more preferred. In addition, the polishing composition further preferably contains a potassium compound as a base from the viewpoint of preventing metal contamination. Examples of potassium compounds include potassium hydroxides or potassium salts, and specifically include potassium hydroxide, potassium carbonate, potassium hydrogen carbonate, potassium sulfate, potassium acetate, potassium chloride, and the like.

[0049] <Surfactant> A surfactant may be added to the polishing composition. The surfactant has the effect of imparting hydrophilicity to the polished surface of the polished object after polishing, so that the cleaning efficiency of the polished object after polishing can be improved and the adhesion of dirt can be suppressed. As the surfactant, any of anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants can be used.

[0050] Specific examples of anionic surfactants include fatty acids, polyoxyethylene alkyl ether acetates, polyoxyethylene alkyl sulfates, alkyl sulfates, polyoxyethylene alkyl sulfates, alkyl sulfates, alkyl benzene sulfonic acids, alkyl phosphates, polyoxyethylene alkyl phosphates, polyoxyethylene sulfosuccinic acids, alkyl sulfosuccinic acids, alkyl naphthalene sulfonic acids, alkyl diphenyl ether disulfonic acids, or salts thereof. From the viewpoint of storage stability of the polishing composition and prevention of metal contamination, fatty acids, polyoxyethylene alkyl ether acetates, alkyl sulfates, alkyl benzene sulfonic acids, polyoxyethylene alkyl phosphates, or ammonium salts and potassium salts thereof are preferred. Specific examples of preferred fatty acids and their salts include caprylic acid, pelargonic acid capric acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, or ammonium salts and potassium salts thereof. Specific examples of polyoxyethylene alkyl ether acetic acid and its salts include polyoxyethylene lauryl ether carboxylic acid, polyoxyethylene tridecyl ether carboxylic acid, and their ammonium salts and potassium salts. Specific examples of alkyl sulfate esters include octyl sulfate, nonacyl sulfate, decyl sulfate, undecyl sulfate, dodecyl sulfate, and their ammonium salts and potassium salts. Specific examples of alkyl benzene sulfonic acid and its salts include decyl benzene sulfonic acid, undecyl benzene sulfonic acid, dodecyl benzene sulfonic acid, tridecyl benzene sulfonic acid, tetradecyl benzene sulfonic acid, pentadecyl benzene sulfonic acid, hexadecyl benzene sulfonic acid, and their ammonium salts and potassium salts. Specific examples of polyoxyethylene alkyl phosphate esters include polyoxyethylene lauryl ether phosphate, dipolyoxyethylene lauryl ether phosphate, di(C12-15) pareth-2 phosphate, and their ammonium salts and potassium salts.

[0051] Specific examples of the cationic surfactant include alkyltrimethylammonium salts, alkyldimethylammonium salts, alkylbenzyldimethylammonium salts, and alkylamine salts.

[0052] Further, specific examples of amphoteric surfactants include alkyl betaines, alkyl amine oxides, and sulfobetaines.Specific examples of alkyl betaines include lauryl dimethyl aminoacetate betaine, myristyl betaine, and stearyl betaine.Specific examples of alkyl amine oxides include dimethyl lauryl amine oxide and (Z)-N,N-dimethyl octadec-9-en-12-1-amine oxide.Specific examples of sulfobetaines include sulfobetaines having carbon numbers of C7 to C15.

[0053] Further, specific examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyalkylene alkyl ethers, sorbitan fatty acid esters, glycerin fatty acid esters, polyoxyethylene fatty acid esters, polyoxyethylene alkylamines, and alkyl alkanolamides. From the viewpoint of storage stability of the polishing composition, polyoxyethylene alkyl ethers and polyoxyalkylene ethers are preferred. Specific examples of polyoxyethylene alkyl ethers include polyoxyethylene alkyl ethers having a carbon chain of C10-C16, etc. Specific examples of polyoxyalkyl ethers include polyoxypropylene alkyl ethers having a carbon chain of C12-C16, etc. These surfactants may be used alone or in combination of two or more.

[0054] The higher the surfactant content in the entire polishing composition, the better the cleaning efficiency of the polished object after polishing, so it is preferable that the surfactant content in the entire polishing composition be 0.0001 g / L or more, and more preferably 0.001 g / L or more. Furthermore, the lower the surfactant content in the entire polishing composition, the less surfactant remains on the polished surface of the object to be polished after polishing, and the more efficient the cleaning is. Therefore, it is preferable that the surfactant content in the entire polishing composition be 10 g / L or less, and more preferably 1 g / L or less.

[0055] <Water-soluble polymer> The polishing composition according to the present embodiment may contain a water-soluble polymer. When the object to be polished contains polysilicon, the polishing rate can be adjusted, for example, by increasing or decreasing the polishing rate, by adding a water-soluble polymer to the polishing composition. Examples of water-soluble polymers include polyvinyl alcohol (PVA), polyvinylpyrrolidone, polyethylene glycol (PEG), polypropylene glycol, polybutylene glycol, copolymers of oxyethylene (EO) and oxypropylene (PO), methylcellulose, hydroxyethylcellulose, dextrin, pullulan, etc. These water-soluble polymers may be used alone or in combination of two or more. Among water-soluble polymers, nonionic polymers are preferred from the viewpoint of not interfering with the effect of the surfactant on the abrasive grains and the TEOS surface (not changing the zeta potential).

[0056] The water-soluble polymer is not limited to a nonionic polymer. The water-soluble polymer may be cationic or anionic. Examples of the cationic polymer include polyethyleneimine, polyvinyl imidazole, and polyallylamine. Examples of the anionic polymer include polyacrylic acid, carboxymethyl cellulose, polyvinyl sulfonic acid, polyanethole sulfonic acid, and polystyrene sulfonic acid.

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

[0058] The higher the content of the oxidizing agent in the entire polishing composition, the easier it is to change the polishing rate of the object to be polished by the polishing composition. Therefore, the content of the oxidizing agent in the entire polishing composition is preferably 0.01 mass% or more, more preferably 0.05 mass% or more, and even more preferably 0.1 mass% or more. In addition, the lower the content of the oxidizing agent in the entire polishing composition, the more the material cost of the polishing composition can be reduced. In addition, the load of the treatment of the polishing composition after use for polishing, that is, the waste liquid treatment, can be reduced. Furthermore, excessive oxidation of the surface of the object to be polished by the oxidizing agent is less likely to occur. Therefore, the content of the oxidizing agent in the entire polishing composition is preferably 10 mass% or less, more preferably 5 mass% or less, and even more preferably 3 mass% or less.

[0059] <Complexing agent> The polishing composition according to the present embodiment may contain a complexing agent. By adding a complexing agent to the polishing composition, the polishing rate of the polishing object by the polishing composition can be improved. The complexing agent has the effect of chemically etching the surface of the polishing object. The lower limit of the content of the complexing agent in the entire polishing composition is not particularly limited because it is effective even in a small amount, but the more the content of the complexing agent, the more the polishing speed of the polishing composition improves, so the content of the complexing agent in the entire polishing composition is preferably 0.001g / L or more, more preferably 0.01g / L or more, and even more preferably 1g / L or more.In addition, the less the content of the complexing agent in the entire polishing composition, the less the dissolution of the polishing object occurs, and the more the step elimination property improves.Therefore, the content of the complexing agent in the entire polishing composition is preferably 20g / L or less, more preferably 15g / L or less, and even more preferably 10g / L or less.

[0060] <Anti-mold agents, preservatives> The polishing composition may contain a mildewproofing agent and a preservative. Specific examples of mildewproofing agents and preservatives include isothiazolin-based preservatives (e.g., 2-methyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one), paraoxybenzoic acid esters, and phenoxyethanol. These mildewproofing agents and preservatives may be used alone or in combination of two or more.

[0061] <Method of manufacturing the polishing composition> The method for producing the polishing composition of the present embodiment is not particularly limited, and can be produced by stirring and mixing cation-modified colloidal silica (or unmodified colloidal silica), a nitrogen-containing compound having an adamantane skeleton, a pH adjuster, and various additives (e.g., surfactant, water-soluble polymer, oxidizing agent, complexing agent, antifungal agent, preservative, etc.) in a liquid medium such as water. The temperature during mixing is not particularly limited, but is preferably, for example, 10°C or higher and 40°C or lower, and may be heated to improve the dissolution rate. The mixing time is also not particularly limited.

[0062] <Object to be polished> The polishing composition according to this embodiment can improve the polishing rate of a silicon nitride film (SiN film). For this reason, the object to be polished is preferably a SiN film. However, the type of the object to be polished is not limited to a SiN film, and may be elemental silicon, a silicon compound other than a SiN film, a metal, or the like. Examples of elemental silicon include single crystal silicon, polysilicon, and amorphous silicon. Examples of silicon compounds include silicon dioxide and silicon carbide. Silicon dioxide can be prepared by polishing tetraethoxysilane ((Si(OC 2 H 5 ) 4 )) (hereinafter, referred to as TEOS film). Silicon compound films include low dielectric constant films having a relative dielectric constant of 3 or less. Furthermore, examples of metals include tungsten, copper, aluminum, hafnium, cobalt, nickel, titanium, tantalum, gold, silver, platinum, palladium, rhodium, ruthenium, iridium, and osmium. These metals may be contained in the form of an alloy or a metal compound.

[0063] <Polishing method> The configuration of the polishing device is not particularly limited, but for example, a general polishing device can be used that includes a holder for holding a substrate having an object to be polished, a driving unit such as a motor that can change the rotation speed, and a polishing table to which a polishing pad (polishing cloth) can be attached. As the polishing pad, general nonwoven fabric, polyurethane, porous fluororesin, etc. can be used without any particular restrictions. As the polishing pad, a pad with grooves that can hold a liquid polishing composition can be used.

[0064] The polishing conditions are not particularly limited. For example, the rotation speed of the polishing plate is 10 rpm (0.17 s -1 ) or more 500rpm (8.3s -1) is preferred. The pressure (polishing pressure) applied to the substrate having the object to be polished is preferably 0.5 psi (3.4 kPa) or more and 10 psi (68.9 kPa) or less. There are no particular limitations on the method of supplying the polishing composition to the polishing pad, and a method of continuously supplying the composition with a pump or the like is used. There is no limitation on the amount of the polishing composition supplied, but it is preferred that the surface of the polishing pad is always covered with the polishing composition of one embodiment of the present invention.

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

[0066] After the polishing is completed, the substrate is washed with, for example, running water, and the water droplets adhering to the substrate are removed by a spin dryer or the like, followed by drying, to obtain a substrate having, for example, a layer containing a silicon-containing material. In this manner, the polishing composition according to this embodiment can be used for substrate polishing. By using the polishing composition according to this embodiment to polish the surface of an object to be polished, such as a SiN film provided on a semiconductor substrate (an example of a substrate), a polished semiconductor substrate can be produced. Examples of semiconductor substrates include silicon wafers having layers containing elemental silicon, silicon compounds, metals, and the like.

[0067] <Substrate manufacturing method> The method for manufacturing a substrate according to this embodiment includes a step of polishing the surface of a substrate with the above-mentioned polishing composition. The polishing method in this step is, for example, as described in the <Polishing method> section.

[0068] <Mechanism for improving polishing speed> The mechanism of the improvement in the polishing rate will be explained below. Note that the mechanism explained in this section is merely speculation, and the present invention is not limited to this mechanism. Equation (12) shows a schematic diagram of charge bias in silicon nitride (SiN).

[0069] [Chemical formula]

[0070] As shown in formula (12), SiN, which is the object to be polished, is an ionic compound and has an uneven distribution of electrons. Since electrons are easily attracted to the N atoms of SiN and the electron density on the Si atoms tends to be low, the Si atoms are in a state where they are easily subjected to nucleophilic attack. Formula (13) schematically shows the bond between SiN, which is the object to be polished, and adamantanamine.

[0071] [Chemical formula]

[0072] The lone pair of electrons on the N atom of adamantanamine makes a nucleophilic attack (acts as a nucleophile). As a result, as shown in formula (13), a bond is formed between the Si atom of SiN and the N atom of adamantanamine. Due to this bond, the bond distance between Si and N in SiN changes, and the structure of SiN is distorted. When the structure of SiN is distorted, it becomes more easily physically broken by abrasive grains. The above is the mechanism for improving the polishing rate of the SiN film when a nitrogen-containing adamantane compound is added to the polishing composition.

[0073] Note that adamantanamine in which an amine is arranged in the adamantane skeleton (for example, hexamine, etc.) has a structure in which the carbon bonded to the N atom of the amine is pulled backward compared to other amines. Therefore, adamantanamine in which an amine is arranged in the adamantane skeleton has less steric hindrance by a carbon chain or a carbon atom and easily reacts with Si of SiN, which is the object to be polished. Among such adamantanamines having such a structure, adamantanamines having a plurality of N atoms in the adamantane skeleton (for example, 1,3,5-triaza-7-phosphaadamantane, hexamine) have many N atoms per molecule of adamantanamine and many sites where they can react with Si of SiN. Therefore, they more easily react with Si of SiN.

[0074] In addition, as shown in the following formula (14), adamantaneamines (e.g., 1-adamantamine, adamantane-1,3-diamine) having a structure in which an amino group is bonded to an adamantane skeleton have a larger number of carbon atoms that can donate electrons to the N atom of the amine than other amines, resulting in a higher electron density on the N atom of the amine. For this reason, adamantaneamines having a structure in which an amino group is bonded to an adamantane skeleton are more likely to react with Si in SiN.

[0075] [ka] EXAMPLES

[0076] 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. In addition, various modifications or improvements can be made to the following examples, and such modifications or improvements can also be included in the present invention.

[0077] <Method of preparing polishing composition> (Examples 1 to 6) As shown in Table 1 below, a mixture was prepared by stirring and mixing the abrasive grains, a nitrogen-containing adamantane compound as an additive, and water as a liquid medium. A pH adjuster was added to the prepared mixture to prepare the polishing compositions of Examples 1 to 6. In Table 1, "-" indicates that the component was not used or that no measured value was available. In Examples 1 to 5, the abrasive grains used were colloidal silica cationically modified by chemical treatment with aminopropyltriethoxysilane (APTES), a coupling agent. In Example 6, the abrasive grains used were unmodified colloidal silica. The concentration of the abrasive grains in the polishing composition was 1 mass %. Hereinafter, mass % is expressed as wt %. The particle diameter (average secondary particle diameter) of the abrasive grains was 70 nm, and the shape of the abrasive grains was cocoon-shaped.

[0078] In Examples 1 and 6, hexamine was used as the nitrogen-containing adamantane compound. The number of nitrogen (N) atoms in hexamine was four. In Example 2, 1-adamantamine was used as the nitrogen-containing adamantane compound. The number of N atoms in 1-adamantamine was one. In Example 3, adamantane-1,3-diamine was used as the nitrogen-containing adamantane compound. The number of N atoms in adamantane-1,3-diamine was two. In Example 4, 2-hydroxy-2-adamantane was used as the nitrogen-containing adamantane compound. The number of N atoms in 2-hydroxy-2-adamantane was one. In Example 5, 1,3,5-triaza-7-phosphaadamantane was used as the nitrogen-containing adamantane compound. The number of N atoms in 1,3,5-triaza-7-phosphaadamantane was three. In Examples 1 to 6, the concentration of the nitrogen-containing adamantane compound in the polishing composition was 5 mmol / L. Hereinafter, mol / L will be abbreviated as M.

[0079] In Examples 1 to 6, nitric acid (HNO 3 ) or potassium hydroxide (KOH) was used. In Examples 1 to 6, the pH value of the polishing composition was adjusted to 3.5. The pH of the polishing composition (liquid temperature: 25°C) was measured with a pH meter (manufactured by Horiba, Ltd., product name: LAQUA (registered trademark)). The electrical conductivity (EC) value of each polishing composition with adjusted pH was as shown in Table 1.

[0080] (Comparative Examples 1 to 9) Each polishing composition was prepared in the same manner as in Examples 1 to 6, except that the components shown in Table 1 were used and the pH of each polishing composition was adjusted to the value shown in Table 1. The difference from Examples 1 to 6 is that no nitrogen-containing adamantane compound was added to the polishing composition in Comparative Examples 1 to 6 and 8. In Comparative Examples 5 to 9, unmodified colloidal silica was used as the abrasive grains.

[0081] [Table 1]

[0082] <Evaluation> Using the polishing compositions of Examples 1 to 6 and Comparative Examples 1 to 9, silicon wafers having a diameter of 200 mm were polished under the following polishing conditions. Polishing equipment: Applied Materials' 200mm CMP single-sided polishing equipment Mirra Polishing pad: Nitta Haas IC1010 hard polyurethane pad Grinding pressure: 2psi (1psi=6894.76Pa) Polishing platen rotation speed: 43 rpm Head rotation speed: 47 rpm Supply of polishing compound: free-flowing ·Polishing composition supply amount: 200mL / min Polishing time: 60 seconds

[0083] The silicon wafers used for polishing were silicon wafers with a silicon dioxide film (TEOS film) and silicon wafers with a silicon nitride film (SiN film). For each silicon wafer, the film thickness was measured before and after polishing using an optical interference film thickness measuring device. The polishing rate for each film was calculated from the film thickness difference and polishing time. The results are shown in Table 2.

[0084] [Table 2]

[0085] (When using cation-modified colloidal silica) As shown in Table 2, in all of Examples 1 to 5, in which cation-modified colloidal silica was used as the abrasive, the polishing speed for the SiN film was 30 Å / min or more. In contrast, in all of Comparative Examples 1 to 4, in which cation-modified colloidal silica was used as the abrasive, the polishing speed for the SiN film was less than 30 Å / min. From this result, it was found that when cation-modified colloidal silica is used, the polishing speed for SiN becomes higher (improved) by adding a nitrogen-containing adamantane compound.

[0086] From Examples 1 to 5, it was found that, among the nitrogen-containing adamantane compounds, the addition of hexamine, in particular, increases (improves) the polishing rate for both the SiN film and the polishing rate for the TEOS film. The improvement rate of the polishing rate of the SiN film (hereinafter, SiN improvement rate) was 4 or more in all of Examples 1 to 5. The SiN improvement rate is the ratio of the polishing rate of the SiN film when an additive is added to the polishing composition to the polishing rate when no additive is added in each Example and Comparative Example. In all of Examples 1 to 5, the SiN improvement rate was 4 or more, and it was found that the addition of a nitrogen-containing adamantane compound significantly improved the polishing rate of the SiN film.

[0087] From Examples 1 to 5, it was found that the more the number of N atoms (number of N) contained in the nitrogen-containing compound, the higher the polishing rate of SiN tends to be. Specifically, as shown in Tables 1 and 2, the polishing rate of SiN was higher in Example 3, in which the number of N atoms was 2, than in Examples 2 and 4, in which the number of N atoms was 1. Also, the polishing rate of SiN was higher in Example 5, in which the number of N atoms was 3, than in Example 3, in which the number of N atoms was 2. Also, the polishing rate of SiN was higher in Example 1, in which the number of N atoms was 4, than in Example 5, in which the number of N atoms was 3.

[0088] (When using unmodified colloidal silica) From Example 6 and Comparative Example 5, it was found that even when unmodified colloidal silica was used as the abrasive grains, the removal rate of the SiN film increased when a nitrogen-containing adamantane compound (for example, hexamine) was added. From Examples 1 to 6, it was found that when unmodified colloidal silica was used as the abrasive, the polishing rate of the TEOS film was lower (i.e., the etching selectivity of the SiN film relative to the TEOS film was higher) than when cation-modified colloidal silica was used. From Example 6 and Comparative Examples 7 and 9, it was found that when the pH value of the polishing composition was 7 or higher, the removal rate of the SiN film decreased.

Claims

1. A cationically modified colloidal silica, a nitrogen-containing compound having an adamantane skeleton, A polishing composition having a pH value of less than 7.

2. The polishing composition according to claim 1, wherein the cationically modified colloidal silica is cationically modified with 3-aminopropyltriethoxysilane (APTES).

3. The polishing composition described in claim 1 or 2, wherein the object to be polished is a film containing silicon nitride on the polishing surface.

4. The polishing composition according to claim 1 , wherein the nitrogen-containing compound contains a plurality of nitrogen atoms.

5. The polishing composition according to claim 1 , wherein the nitrogen-containing compound contains a nitrogen atom in the adamantane skeleton.

6. The polishing composition according to claim 1 , wherein the nitrogen-containing compound contains a plurality of nitrogen atoms in the adamantane skeleton.

7. The polishing composition according to claim 1 , wherein the nitrogen-containing compound contains a carbon atom or a hydrogen atom bonded to a nitrogen atom.

8. The polishing composition according to claim 1 , wherein the nitrogen-containing compound is an amine.

9. A method for producing the polishing composition according to any one of claims 1 to 8, comprising the steps of: A method for producing a polishing composition, comprising the step of mixing, in a liquid medium, cationically modified colloidal silica, a nitrogen-containing compound having an adamantane skeleton, and a pH adjuster.

10. The method includes a step of polishing an object to be polished provided on a substrate using the polishing composition according to any one of claims 1 to 8, The polishing method, wherein the object to be polished comprises silicon nitride on a polishing surface.

11. A method for producing a substrate, comprising a step of polishing a surface of a substrate with the polishing composition according to claim 1 .

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