Polishing composition for polishing silicon dioxide film and silicon nitride film, method for producing polishing composition for polishing silicon dioxide film and silicon nitride film, polishing method

Abstract

To provide a polishing composition capable of improving a polishing rate of a TEOS film, a method for manufacturing the polishing composition, and a polishing method.SOLUTION: A polishing composition contains cationized colloidal silica chemically surface-modified with an amino silane coupling agent and an anionic surfactant, in which a pH value is larger than 3 and smaller than 6.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] In recent years, with the multilayer wiring of the semiconductor substrate surface, when manufacturing a semiconductor device (device), a so-called Chemical Mechanical Polishing (CMP) technique for polishing and planarizing the semiconductor substrate 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, and the like. The object to be polished (workpiece) is silicon, polysilicon, a silicon oxide film (silicon oxide), a wiring made of silicon nitride, metal, or the like, and a plug.

[0003] Regarding the polishing composition used when polishing a semiconductor substrate by CMP, various proposals have been made so far. For example, Patent Document 1 describes "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, a first layer containing polysilicon or modified polysilicon, and at least one selected from the group consisting of silicon oxide, silicon nitride, silicon carbide, silicon carbonitride, silicon oxycarbide, and silicon oxynitride. Polishing a workpiece having at least a second layer containing". In Patent Document 1, it is disclosed that the colloidal silica particles exhibit a positive ζ potential by adsorbing a cationic compound on the surface of colloidal silica having a negative charge.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Among objects to be polished, especially with respect to the polishing rate of a silicon dioxide film (hereinafter referred to as a TEOS film) formed using tetraethoxysilane ((Si(OC2H5)4)), there has been room for improvement in conventional polishing compositions. 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 TEOS film, a method for producing the polishing composition, and a polishing method.

Means for Solving the Problems

[0006] In view of the above problems, the present inventors conducted intensive studies. As a result, by using a polishing composition containing cationized colloidal silica chemically surface-modified with an aminosilane coupling agent and an anionic surfactant, and having a pH value greater than 3 and less than 6, it was found that the polishing rate of the TEOS film can be increased (improved), and the invention was 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 TEOS film, a method for producing the polishing composition, and a polishing method.

Modes for Carrying Out the Invention

[0008] Embodiments of the present invention will be described in detail. The polishing composition of the present embodiment is a polishing composition containing cationized colloidal silica chemically surface-modified with an aminosilane coupling agent and an anionic surfactant, and having a pH value greater than 3 and less than 6. This polishing composition is suitable for use in polishing objects to be polished such as single crystal silicon, silicon compounds, and metals. For example, it is suitable for use in polishing the surface of single crystal silicon, polysilicon, silicon compounds, metals, etc. that are semiconductor substrates in the manufacturing process of semiconductor devices. And it is particularly suitable for use in polishing a silicon dioxide film formed using tetraethoxysilane (Si(OC2H5)4), that is, a TEOS film. By performing polishing using this polishing composition, particularly the TEOS film can be polished at a high polishing rate.

[0009] The polishing composition of the present embodiment will be described in detail below. <Abrasive grains> (Type of abrasive grains) The polishing composition according to an embodiment of the present invention contains colloidal silica as abrasive grains. Examples of the production method of colloidal silica include the sodium silicate method and the sol-gel method. Any colloidal silica produced by any production method may be used, but from the viewpoint of reducing metal impurities, colloidal silica produced by the sol-gel method is preferred. Colloidal silica produced by the sol-gel method is preferred because it has a low content of metal impurities having the property of diffusing in a semiconductor and corrosive ions such as chloride ions. 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 by performing a hydrolysis and condensation reaction, colloidal silica can be obtained.

[0010] (Surface modification) The colloidal silica is subjected to surface modification by chemical treatment with an aminosilane coupling agent. In this specification, surface modification by chemical treatment is also referred to as chemical surface modification. By chemical surface modification, amino groups are immobilized and cationized on the surface of the colloidal silica. This immobilization is a chemical bond, not physical adsorption. In this specification, the cationized colloidal silica is referred to as "cationized colloidal silica". As a method for producing colloidal silica having an amino group, there is a method of immobilizing a silane coupling agent having an amino group, such as aminoethyltrimethoxysilane, on the surface of silica particles, as described in JP-A-2005-162533. In this specification, a silane coupling agent having an amino group is referred to as an "aminosilane coupling agent".

[0011] Examples of the aminosilane coupling agent 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-trimethoxysilylpropyl diethyldiethylenetriamine, 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.

[0012] As the aminosilane coupling agent, for example, an aminotrialkoxysilane having a structure represented by the following formula (1) can be used. In formula (1), X is an alkyl group having 1 to 10 carbon atoms (denoted as C1 to C10; the same applies hereinafter), an aminoalkyl group (C1 to C10) containing 1 or more nitrogen atoms, or a single bond. R1, R2, and R3 are each independently an alkyl group (C1 to C3), hydrogen (H), or a salt thereof. The salt is, for example, a hydrochloride.

[0013] [Chemistry]

[0014] The above aminotrialkoxysilane includes 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-trimethoxysilylpropyldiethyldiethylenetriamine, etc. Among the above-mentioned aminosilane coupling agents, 3-aminopropyltriethoxysilane (APTES) has the structure shown in formula (2). When 3-aminopropyltriethoxysilane is used as the aminosilane coupling agent, an aminopropyl group is immobilized on the surface of colloidal silica and is cationized.

[0015] [Chemistry]

[0016] The zeta (ζ) potential of the cationized 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 stably obtaining a 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.

[0017] Aminosilane coupling agents undergo hydrolysis and dehydration condensation reactions in chemical treatment to form chemical bonds, such as Si-O-Si bonds, with colloidal silica. Thus, the zeta potential of cationized colloidal silica surface-modified by chemical treatment with a silane coupling agent has a large positive value under acidic conditions compared to unmodified colloidal silica. Thereby, the effects of the present invention are easily obtained. Ordinary colloidal silica has a zeta potential value close to zero under acidic conditions. Therefore, under acidic conditions, the colloidal silica particles do not electrically repel each other and tend to aggregate. In contrast, even under acidic conditions, the cationized colloidal silica particles strongly repel each other and are well dispersed, making aggregation difficult. As a result, the storage stability of the polishing composition is improved.

[0018] (Aspect ratio) The aspect ratio of the surface-modified cationized colloidal silica is preferably 1.0 or more, more preferably 1.02 or more, further preferably 1.05 or more, and even more preferably 1.10 or more from the viewpoint of the polishing rate. Also, the aspect ratio of the surface-modified cationized colloidal silica is preferably less than 1.4, more preferably 1.3 or less, and further preferably 1.25 or less. Thereby, the surface roughness of the object to be polished caused by the shape of the abrasive grains can be made good. Also, the occurrence of defects due to the shape of the abrasive grains can be suppressed. Note that this 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 particles by the length of the short side of the same rectangle, and can be obtained from the images of the colloidal silica particles obtained by a scanning electron microscope using general image analysis software.

[0019] (Average primary particle size) The average primary particle diameter of the surface-modified cationized colloidal silica is preferably 100 nm or less, more preferably 70 nm or less, still more preferably 50 nm or less, and in order, more preferably 40 nm or less and 35 nm or less. Also, the average primary particle diameter of the surface-modified cationized colloidal silica is preferably 5 nm or more, more preferably 10 nm or more, still more preferably 20 nm or more, and even more preferably 25 nm or more. Within such a range, the polishing rate of the object to be polished by the polishing composition is improved. Also, it is possible to further suppress the occurrence of dishing on the surface of the object to be polished after polishing using the polishing composition. The average primary particle diameter of the colloidal silica is calculated based on, for example, the specific surface area of the colloidal silica measured by the BET method.

[0020] (Average secondary particle diameter) The average secondary particle diameter of the surface-modified cationized colloidal silica is preferably 200 nm or less, more preferably 150 nm or less, still more preferably 100 nm or less, and in order, more preferably 80 nm or less and 75 nm or less. Also, the average secondary particle diameter of the surface-modified cationized colloidal silica is preferably 30 nm or more, more preferably 50 nm or more, still more preferably 60 nm or more, and even more preferably 65 nm or more. Within such a range, the polishing rate of the object to be polished by the polishing composition is improved. Also, it is possible to further suppress the occurrence of surface defects on the surface of the object to be polished after polishing using the polishing composition. The secondary particle refers to a particle formed by the aggregation of colloidal silica (primary particle) with an organic acid immobilized on its surface in the polishing composition. The average secondary particle diameter of the secondary particle can be measured, for example, by the dynamic light scattering method.

[0021] (Particle size distribution) In the particle size distribution of the surface-modified cationized colloidal silica, the ratio D90 / D10 of the particle diameter D90 when the cumulative particle mass from the fine particle side reaches 90% of the total particle mass to 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. Also, this ratio D90 / D10 is preferably 5.0 or less, more preferably 3.0 or less. Within such a range, the polishing rate 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 using the polishing composition can be further suppressed. The particle size distribution of the surface-modified cationized colloidal silica can be determined, for example, by the laser diffraction scattering method.

[0022] (Content) The content of the surface-modified cationized colloidal silica in the entire polishing composition is preferably 0.005% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.5% by mass or more, and still more preferably 0.75% by mass or more. Also, the content of the surface-modified cationized colloidal silica in the entire polishing composition is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and still more preferably 2% by mass or less, 1.5% by mass or less in this order. Within such a range, the polishing rate of the object to be polished is improved. Also, the content of the surface-modified cationized colloidal silica in the entire polishing composition is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less. Within such a range, the cost of the polishing composition can be suppressed. Also, the occurrence of surface defects on the surface of the object to be polished after polishing using the polishing composition can be further suppressed.

[0023] <Anionic surfactant> The polishing composition according to an embodiment of the present invention contains an anionic surfactant. As the anionic surfactant, an anionic surfactant having one or more functional groups selected from a sulfate group, a sulfonic acid group, and a phosphate group is preferable. The anionic surfactant includes an organic acid having these functional groups or a salt thereof. Examples of such anionic surfactants include sodium dodecyl sulfate, sodium linear alkylbenzene sulfonate, hexadecylmethyl(3-sulfopropyl)hydroxide inner salt, sodium 1-dodecanesulfonate, sodium bis-(2-ethylhexyl)sulfosuccinate, branched-chain alkylbenzene sulfonic acid, alkylnaphthalenesulfonic acid (butyl group), polyoxyethylene allyl phenyl ether phosphate amine salt, polyoxyethylene styrenated phenyl ether phosphate ester, ethyl acid phosphate, butyl acid phosphate, butoxyethyl acid phosphate, and the like. Note that, as long as the effects of the present invention are not impaired, the anionic surfactant can be used in combination with a nonionic surfactant. For example, among the above-described anionic surfactants, sodium linear alkylbenzene sulfonate has a structure represented by formula (3). In formula (3), R represents a linear alkyl group. The number of carbon (C) atoms in the linear alkyl group is, for example, 10 or more and 16 or less.

[0024] [Chemical formula]

[0025] When the anionic surfactant adsorbs on the surface of the TEOS film which is an object to be polished, the surface of the TEOS film is anionized by the functional group. Also, as described above, the zeta (ζ) potential of the cationized colloidal silica with surface modification is a positive value under acidic conditions. Therefore, the cationized colloidal silica which is an abrasive grain is attracted to the TEOS film which is an object to be polished by an electrostatic force under acidic conditions. Thereby, the polishing rate of the TEOS film is improved.

[0026] [Liquid medium] The polishing composition according to an embodiment of the present invention 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 surface-modified cationized 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 preferable to contain water. However, from the viewpoint of preventing 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 from which impurity ions have been removed with an ion exchange resin and foreign substances have been removed through a filter is preferable.

[0027] <pH adjuster> The pH value of the polishing composition according to an embodiment of the present invention is greater than 3 and less than 6. A more preferable range of the pH value is 3.5 or more and 5 or less. The pH value is more preferably 4 or less, and even more preferably less than 4. Also, the lower the pH of the polishing composition, the more likely the zeta (ζ) potential of the surface-modified cationized colloidal silica will be a positive value. This is advantageous for improving the polishing rate of the TEOS film. On the other hand, as the pH decreases below the above-mentioned lower limit value, the zeta potential of the TEOS film, which is the object to be polished, changes from a negative value to zero or a positive value. Therefore, when the pH is less than the lower limit value, the interaction between the cationized colloidal silica and the TEOS film weakens, and as a result, the polishing rate of the TEOS film decreases. Therefore, if the pH of the polishing composition is within the above-mentioned range, it is easier to improve the polishing rate of the TEOS film. To achieve the above-mentioned pH value, the polishing composition may contain a pH adjuster.

[0028] The pH value of the polishing composition can be adjusted by adding a pH regulator. As the pH regulator, an acid, a base, or both can be used, and an inorganic compound, an organic compound, or both can also be used. Specific examples of acids as pH adjusters include inorganic acids and organic acids. Specific examples of 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, among which sulfuric acid and nitric acid are more preferable, and nitric acid is particularly preferable. Organic acids include carboxylic acids and organic sulfuric acids. Specific examples of carboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, lactic acid, etc. Further, specific examples of organic sulfuric acids include methanesulfonic acid, ethanesulfonic acid, isethionic acid, etc. These acids may be used alone or in combination of two or more. Also, when the object to be polished contains SiN, by using a phosphoric acid-based inorganic acid or a carboxylic acid-based or phosphonic acid-based organic acid, the polishing rate of SiN can be improved. These acids may be contained as a pH adjuster in the polishing composition, may be contained as an additive for improving the polishing rate, or may be a combination of these.

[0029] Specific examples of bases as pH adjusters include hydroxides of alkali metals or their salts, hydroxides of alkaline earth metals or their salts, quaternary ammonium hydroxides or their salts, ammonia, amines, etc. Specific examples of alkali metals include potassium, sodium, etc. Also, specific examples of alkaline earth metals include calcium, strontium, etc. Further, specific examples of salts include carbonates, bicarbonates, sulfates, acetates, etc. Further, specific examples of quaternary ammonium include tetramethylammonium, tetraethylammonium, tetrabutylammonium, etc.

[0030] The quaternary ammonium hydroxide compound includes quaternary ammonium hydroxide or its salt. Specific examples include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, etc. Further, specific examples of the amine include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N-(β-aminoethyl)ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, piperazine anhydride, piperazine hexahydrate, 1-(2-aminoethyl)piperazine, N-methylpiperazine, guanidine, etc.

[0031] 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. Further, ammonia, potassium compounds, sodium hydroxide, quaternary ammonium hydroxide compounds, ammonium bicarbonate, ammonium carbonate, sodium bicarbonate, and sodium carbonate are more preferred. Also, from the viewpoint of preventing metal contamination, it is more preferable for the polishing composition to contain a potassium compound as the base. Examples of the potassium compound include potassium hydroxide or potassium salts, specifically potassium hydroxide, potassium carbonate, potassium bicarbonate, potassium sulfate, potassium acetate, potassium chloride, etc.

[0032] Furthermore, when using a buffer pH adjuster which is a mixture of an acid and a salt of the acid as the pH adjuster, it is preferable because there is no pH fluctuation during TEOS polishing. Combinations of the acid and the salt of the acid include, for example, combinations of acids such as acetic acid and lactic acid with salts such as ammonium salts, sodium salts, and potassium salts of the acid. From the viewpoint of impurities, it is particularly preferable to use an ammonium salt.

[0033] <Water-soluble polymer> The polishing composition according to an embodiment of the present invention may contain a water-soluble polymer. When polysilicon is contained in the object to be polished, the polishing rate can be adjusted by adding a water-soluble polymer to the polishing composition, such as increasing or decreasing the polishing rate. Examples of the water-soluble polymer include polyvinyl alcohol (PVA), polyvinyl pyrrolidone, polyethylene glycol (PEG), polypropylene glycol, polybutylene glycol, a copolymer of oxyethylene (EO) and oxypropylene (PO), methyl cellulose, hydroxyethyl cellulose, dextrin, pullulan, and the like. These water-soluble polymers may be used alone or in combination of two or more. From the viewpoint of not disturbing the influence of the surfactant on the abrasive grains and the TEOS surface (not fluctuating the zeta potential), nonionic polymers are preferred among the water-soluble polymers.

[0034] Note that 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, polyallylamine, and the like. Examples of the anionic polymer include polyacrylic acid, carboxymethyl cellulose, polyvinyl sulfonic acid, polyanethole sulfonic acid, polystyrene sulfonic acid, and the like.

[0035] When using PVA as the water-soluble polymer, it is preferable because the polishing rate of polysilicon can be increased. The average molecular weight of PVA is, for example, 100 or more and 150,000 or less. From the viewpoint of the ease of action on the hydrophobic film, a larger average molecular weight is preferable, and from the viewpoint of slurry dispersibility, a smaller average molecular weight is preferable. For example, from the viewpoint of the ease of action on the hydrophobic film, the average molecular weight of PVA is preferably 1,000 or more, more preferably 3,000 or more, and becomes more preferable as it becomes 6,000 or more and 8,000 or more. Also, from the viewpoint of slurry dispersibility, the average molecular weight of PVA is preferably 150,000 or less, more preferably 100,000 or less, and becomes more preferable as it becomes 80,000 or less, 40,000 or less, 20,000 or less, and 15,000 or less.

[0036] Also, when using PEG as the water-soluble polymer, it is preferable because the polishing rate of polysilicon can be decreased. The average molecular weight of PEG is, for example, 200 or more and 150,000 or less. From the viewpoint of the ease of action on the hydrophobic film, a larger average molecular weight is preferable, and from the viewpoint of slurry dispersibility, a smaller average molecular weight is preferable. For example, from the viewpoint of the ease of action on the hydrophobic film, the average molecular weight of PEG is preferably 1,000 or more, more preferably 3,000 or more, and becomes more preferable as it becomes 6,000 or more and 8,000 or more. Also, from the viewpoint of slurry dispersibility, the average molecular weight of PEG is preferably 150,000 or less, more preferably 100,000 or less, and becomes more preferable as it becomes 80,000 or less, 40,000 or less, 20,000 or less, and 15,000 or less.

[0037] <Oxidizing agent> The polishing composition according to an embodiment of the present invention 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, by selecting the type of oxidizing agent added to the polishing composition, the polishing rate of Poly-Si can be increased or decreased. Specific examples of the oxidizing agent include hydrogen peroxide, peracetic acid, percarbonate, urea peroxide, perchloric acid, persulfate, etc. Specific examples of the persulfate include sodium persulfate, potassium persulfate, ammonium persulfate, etc. 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.

[0038] 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% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more. Also, the lower the content of the oxidizing agent in the entire polishing composition, the more the material cost of the polishing composition can be suppressed. In addition, the load of treating the polishing composition after polishing, that is, 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% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less.

[0039] <Mildew-proofing agent, preservative> The polishing composition may contain a mildew-proofing agent and a preservative. Specific examples of the mildew-proofing agent and the preservative include isothiazoline-based preservatives (for example, 2-methyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one), paraoxybenzoic acid esters, and phenoxyethanol. These mildew-proofing agents and preservatives may be used alone or in combination of two or more.

[0040] <Method for manufacturing polishing composition> The method for manufacturing the polishing composition of the present embodiment is not particularly limited. Cationized colloidal silica subjected to surface modification by chemical treatment with an aminosilane coupling agent (that is, an amino group is immobilized on the surface), an anionic surfactant, a pH adjuster, and various additives (for example, water-soluble polymers, oxidizing agents, complexing agents, antifungal agents, preservatives, etc.) as necessary can be manufactured by stirring and mixing in a liquid medium such as water. The temperature during mixing is not particularly limited, but for example, 10°C or higher and 40°C or lower is preferable, and heating may be performed to improve the dissolution rate. Also, the mixing time is not particularly limited.

[0041] <Object to be polished> The polishing composition according to the embodiment of the present invention can improve the polishing rate of the TEOS film. Therefore, the object to be polished is preferably a TEOS film. However, the type of the object to be polished is not limited to TEOS, and it may be single crystal silicon, polysilicon, amorphous silicon, etc. as single silicon. Examples of silicon compounds include silicon nitride, silicon dioxide, silicon carbide, etc. The silicon compound film includes a low dielectric constant film having a relative dielectric constant of 3 or less. Further, examples of the metal include tungsten, copper, aluminum, hafnium, cobalt, nickel, titanium, tantalum, gold, silver, platinum, palladium, rhodium, ruthenium, iridium, osmium, etc. These metals may be contained in the form of an alloy or a metal compound.

[0042] <Polishing method> The configuration of the polishing apparatus is not particularly limited. For example, a general polishing apparatus including a holder for holding a substrate or the like having an object to be polished, a driving unit such as a motor whose rotation speed can be changed, and a polishing platen to which a polishing pad (polishing cloth) can be attached can be used. As the polishing pad, general non-woven fabrics, polyurethanes, porous fluororesins, etc. can be used without particular limitation. A polishing pad having grooves formed therein for accumulating a liquid polishing composition can be used.

[0043] The polishing conditions are not particularly limited. For example, the rotation speed of the polishing platen is preferably 10 rpm (0.17 s -1 ) or more and 500 rpm (8.3 s -1 ) or less. The pressure applied to the substrate having the object to be polished (polishing pressure) is preferably 0.5 psi (3.4 kPa) or more and 10 psi (68.9 kPa) or less. The method of supplying the polishing composition to the polishing pad is also not particularly limited, and a method of continuously supplying with a pump or the like is adopted. Although there is no limitation on this supply amount, it is preferable that the surface of the polishing pad is always covered with the polishing composition of one aspect of the present invention. The polishing composition according to the embodiment of the present invention may be a one-component type or a multi-component type including a two-component type. Further, the polishing composition may be prepared by diluting the stock solution of the polishing composition, for example, 10 times or more using a diluent such as water.

[0044] After polishing, 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 and dried, whereby a substrate having a layer containing, for example, a silicon-containing material can be obtained. Thus, the polishing composition according to the embodiment of the present invention can be used for the purpose of polishing a substrate. By polishing the surface of an object to be polished such as TEOS provided on a semiconductor substrate using the polishing composition according to the embodiment of the present invention, the surface of the semiconductor substrate can be polished at a high polishing rate to produce a polished semiconductor substrate. Examples of the semiconductor substrate include a silicon wafer having a layer containing single crystal silicon, a silicon compound, a metal, etc.

Examples

[0045] The present invention will be described in more detail with reference to the following Examples and Comparative Examples. However, the technical scope of the present invention is not limited only to the following Examples. Also, various changes or improvements can be made to the following Examples, and forms with such changes or improvements can also be included in the present invention.

[0046] <Method for Adjusting Polishing Composition> (Examples 1 to 17) As shown in Table 1 below, abrasive grains, an anionic surfactant, and water as a liquid medium were stirred and mixed to prepare a mixed solution. A pH adjuster was added to the prepared mixed solution so that the pH became the value in Table 1, and the polishing compositions of Examples 1 to 17 were produced. In Table 1, "-" indicates that the component was not used. In Examples 1 to 17, cationized colloidal silica whose surface was modified by chemical treatment with aminopropyltriethoxysilane (APTES), which is a coupling agent, was used as the abrasive grains. The concentration of the coupling agent in the polishing composition was 0.1 mmol / L. Hereinafter, mol / L is denoted as M. Also, the concentration of the abrasive grains in the polishing composition was 1% by mass as silica.

[0047] Specifically, APTES was added to a stock solution of colloidal silica (20% by mass) so as to have a concentration of 2 mM to prepare surface-modified cationized colloidal silica. The APTES added to the above stock solution was diluted with the abrasive grains so that the concentration became further 1 / 20 when preparing the polishing composition. Thereby, the concentration of APTES in the polishing composition was 0.1 mM during polishing. In the polishing composition, APTES can be contained in a state bound to the surface of colloidal silica and in a state of APTES itself. The particle diameter (average secondary particle diameter) of the abrasive grains in the polishing composition is 70 nm. The zeta (ζ) potential of the abrasive grains in the polishing composition is as shown in Table 1.

[0048] In Examples 1 to 17, the anionic surfactants used were those listed in Table 1. The functional group of the anionic surfactant was a sulfate group in Example 1, a sulfonic acid group in Examples 2 to 12, and a phosphate group in Examples 13 to 17. The concentration of the surfactant in the polishing composition was 50 ppm in Examples 1 to 6 and 8 to 19, and 100 ppm in Example 7. In Example 5, PVA with an average molecular weight of 100 or more and 150,000 or less was added as the water-soluble polymer. The addition amount of PVA in the polishing composition was 50 ppm. In Example 6, PEG with an average molecular weight of 200 or more and 150,000 or less was added as the water-soluble polymer. The addition amount of PEG in the polishing composition was 50 ppm.

[0049] In Examples 1 to 17, nitric acid (HNO3) or potassium hydroxide (KOH) was used as the pH adjuster. In Examples 1, 2, 5 to 17, the pH value of the polishing composition was adjusted to 3.5, in Example 3, the pH value of the polishing composition was adjusted to 4.0, and in Example 4, the pH value of the polishing composition was adjusted to 5.0. The pH of the polishing composition (liquid temperature: 25 °C) was measured using a pH meter (product name: LAQUA (registered trademark), manufactured by Horiba, Ltd.). Also, the electrical conductivity (EC) values of the pH-adjusted polishing compositions were as shown in Table 1.

[0050] (Comparative Examples 1 to 18) Using the components of the types, concentrations, etc. shown in Table 1, and adjusting the pH of each polishing composition to the value shown in Table 1, each polishing composition was prepared in the same manner as in Examples 1 to 17, except for the above operations. As differences from Examples 1 to 17, in Comparative Examples 1 and 2, the pH values of the polishing composition were adjusted to 3.0 and 6.0, respectively. Also, in Comparative Examples 3 to 11, 13, 15, 17, and 18, an anionic surfactant was not added. Note that in Comparative Examples 3 to 5, sodium p-toluenesulfonate, sodium p-styrenesulfonate, and o-cresolsulfonic acid all have short carbon chains in the hydrophobic group and do not function as surfactants. Further, in Comparative Examples 11 to 18, surface modification of colloidal silica by chemical treatment with an aminosilane coupling agent was not performed. Tetraethylammonium (TEAH) used in Comparative Examples 13 to 16 and tetrabutylammonium hydroxide (TBAH) used in Comparative Examples 17 and 18 both physically adsorb on the surface of colloidal silica but do not form chemical bonds.

[0051] [Table 1]

[0052] [Evaluation] Using the polishing compositions of Examples 1 to 17 and Comparative Examples 1 to 18, a 200-mm diameter silicon wafer was polished under the following polishing conditions. · Polishing apparatus: CMP single-sided polishing apparatus Mirra for 200 mm made by Applied Materials · Polishing pad: Hard polyurethane pad IC1010 made by Nitta Haas Co., Ltd. · Polishing pressure: 2 psi (1 psi = 6894.76 Pa) · Rotation speed of polishing platen: 43 rpm · Rotation speed of head: 47 rpm · Supply of polishing composition: Pouring · Supply rate of polishing composition: 200 mL / min · Polishing time: 60 seconds

[0053] The silicon wafers subjected to polishing were silicon wafers with a silicon dioxide film (TEOS film), silicon wafers with a silicon nitride film (SiN film), and silicon wafers with a polysilicon film (Poly-Si film). For each silicon wafer, the film thickness before and after polishing was measured using an optical interference film thickness measuring device. Then, the polishing rate of each film was calculated from the film thickness difference and the polishing time. The results are shown in Table 2.

[0054]

Table 2

[0055] As shown in Table 2, for the polishing rate of the TEOS film, all of Examples 1 to 16 were 260 Å / min or more, and all of Comparative Examples 1 to 18 were less than 260 Å / min. It was found that Examples 1 to 16 had a higher polishing rate of the TEOS film than Comparative Examples 1 to 18. As described above, in terms of the polishing rate of the TEOS film, the examples are superior to the comparative examples. Also, regarding the improvement rate of the polishing rate of the TEOS film (hereinafter referred to as the TEOS improvement rate), all of Examples 1 to 16 were 1.05 or more. The TEOS improvement rate is the ratio of the polishing rate when a surfactant is added to the polishing composition at the same pH to the polishing rate when no surfactant is added in each example and each comparative example. That is, when the pH is 3.0, 3.5, 4.0, 5.0, and 6.0, the ratio of the polishing rate to Comparative Examples 6, 7, 8, 9, and 10 was taken as the TEOS improvement rate, respectively. When the TEOS improvement rate exceeds 1, it means that the polishing rate is improved by adding a surfactant to the polishing composition. In Examples 1 to 16, the TEOS improvement rate was 1.05 or more in all cases, and it was found that the polishing rate of the TEOS film was increased by using a combination of an anionic surfactant and cationized colloidal silica chemically surface-modified with an aminosilane coupling agent.

[0056] The reason why the polishing rate of the TEOS film increases is as follows. That is, when an anionic surfactant adsorbs on the surface of the TEOS film, the surface of the TEOS film is anionized by functional groups. Also, the zeta (ζ) potential of cationized colloidal silica is a positive value under acidic conditions. Therefore, the cationized colloidal silica, which is an abrasive grain, is attracted to the TEOS film by electrostatic force under acidic conditions. As a result, the polishing rate of the TEOS film is improved.

[0057] As can be seen by comparing Examples 1 to 17, which are chemical surface modifications (chemical bonds), with Comparative Examples 13 to 18, which are physical adsorptions, at the same pH value, the zeta potential of the abrasive grains tends to be higher for the chemical surface modification (chemical bond) of the present invention than for the physical adsorption of the comparative examples. Also, in the case of physical adsorption, even when an anionic surfactant is added, no improvement effect on the polishing rate of the TEOS film can be obtained. Therefore, it can be seen that the chemical surface modification of the present invention is more likely to improve the polishing rate of the TEOS film. Furthermore, in the case of physical adsorption, if diluted, the zeta potential of the abrasive grains decreases due to a decrease in the concentration of the adsorbent. In contrast, for the chemical surface modification of the present invention, since amino groups are immobilized on the surface of the abrasive grains, fluctuations in the zeta potential due to dilution are less likely to occur. That is, the polishing composition of the present invention is less likely to have a decrease in the polishing rate even when used after dilution.

[0058] Also, from the comparison between Examples 1 to 17 (especially Examples 2 to 4) and Comparative Examples 1 and 2, it was found that when the pH value of the polishing composition is greater than 3 and less than 6, the polishing rate of the TEOS film increases. Also, when the pH value is 3.5, it was found that Examples 1, 2, 6 to 12 using a sulfonic acid-based surfactant had a higher polishing rate of the TEOS film than Examples 13 to 17 using a phosphoric acid-based surfactant. It was found that the polishing rate of the TEOS film further increases by using a sulfonic acid-based surfactant as the anionic surfactant.

[0059] In addition, in Examples 2 to 7 where linear alkylbenzene sulfonic acid was used as the anionic surfactant, it was found that the polishing rate of the SiN film was higher compared to other Examples 1, 8 to 17 using anionic surfactants other than linear alkylbenzene sulfonic acid. By using linear alkylbenzene sulfonic acid as the anionic surfactant, it was found that not only the polishing rate of the TEOS film but also that of the SiN film increased.

[0060] Also, when comparing Examples 2 and 5, the polishing rate of the Poly-Si film is higher in Example 5 than in Example 2. The difference between Examples 2 and 5 is that the polishing composition contains PVA. From this result, it was found that by adding PVA to the polishing composition according to the embodiment of the present invention, the polishing rate of the Poly-Si film increases. Also, when comparing Examples 2 and 6, the polishing rate of the Poly-Si film is lower in Example 6 than in Example 2. The difference between Examples 2 and 6 is that the polishing composition contains PEG. From this result, it was found that by adding PEG to the polishing composition according to the embodiment of the present invention, the polishing rate of the Poly-Si film decreases. From Examples 2, 5, and 6, it was found that by selectively adding PVA and PEG to the polishing composition according to the embodiment of the present invention, while improving the polishing rate of the TEOS film, the controllability of the polishing rate for the Poly-Si film can also be improved.

Claims

1. A polishing composition used for the purpose of polishing both a silicon dioxide film and a silicon nitride film, cationized colloidal silica chemically surface-modified with an aminosilane coupling agent, and an anionic surfactant, and contains, the pH value is greater than 3 and less than 6, the selection ratio of the polishing rate of the silicon dioxide film to the silicon nitride film is 51.47 or more and 87.61 or less, A polishing composition for polishing a silicon dioxide film and a silicon nitride film.

2. The anionic surfactant contains one or more selected from Na dodecyl sulfate, hexadecylmethyl(3-sulfopropyl)hydroxide inner salt, Na 1-dodecanesulfonate, Na bis-(2-ethylhexyl)sulfosuccinate, and polyoxyethylene allylphenyl ether phosphate amine salt. The polishing composition for polishing a silicon dioxide film and a silicon nitride film according to Claim 1.

3. The aminosilane coupling agent contains aminotrialkoxysilane. The polishing composition for polishing a silicon dioxide film and a silicon nitride film according to Claim 1 or 2.

4. The aminosilane coupling agent contains aminopropyltriethoxysilane. The polishing composition for polishing a silicon dioxide film and a silicon nitride film according to any one of Claims 1 to 3.

5. The zeta potential of the cationized colloidal silica is 30 mV or more. The polishing composition for polishing a silicon dioxide film and a silicon nitride film according to any one of Claims 1 to 4.

6. The anionic surfactant contains an organic acid salt having one or more functional groups selected from a sulfate group, a sulfonic acid group, and a phosphate group. The polishing composition for polishing a silicon dioxide film and a silicon nitride film according to any one of Claims 1, 3 to 5.

7. The anionic surfactant contains linear alkylbenzene sulfonic acid. The polishing composition for polishing a silicon dioxide film and a silicon nitride film according to any one of Claims 1, 3 to 6.

8. Further contains a water-soluble polymer. The polishing composition for polishing a silicon dioxide film and a silicon nitride film according to any one of Claims 1 to 7.

9. The water-soluble polymer contains polyvinyl alcohol having an average molecular weight of 100 or more and 150,000 or less. The polishing composition for polishing a silicon dioxide film and a silicon nitride film according to Claim 8.

10. The polishing composition for polishing a silicon dioxide film and a silicon nitride film according to claim 8 or 9, wherein the water-soluble polymer contains polyethylene glycol having an average molecular weight of 200 or more and 150,000 or less.

11. A method for producing a polishing composition for polishing a silicon dioxide film and a silicon nitride film according to any one of claims 1 to 10, The method for producing a polishing composition for polishing a silicon dioxide film and a silicon nitride film, comprising a step of mixing cationized colloidal silica chemically surface-modified with an aminosilane coupling agent, an anionic surfactant, and a pH adjuster in a liquid medium.

12. A polishing method comprising a step of polishing an object to be polished provided on a substrate using the polishing composition for polishing a silicon dioxide film and a silicon nitride film according to any one of claims 1 to 10, wherein the object to be polished includes both a silicon dioxide film and a silicon nitride film.

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