Polishing composition and polishing method

Abstract

To provide a polishing composition and a polishing method, with which SiN can be selectively polished at a higher polishing rate than that of SiO2.SOLUTION: A polishing composition contains colloidal silica in which an organic acid is fixed on its surface and a pH adjusting agent, in which the average aspect ratio of the colloidal silica with the organic acid fixed on its surface is 1.38 or more.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] When manufacturing semiconductor devices, the so-called Chemical Mechanical Polishing (CMP) technique is used to polish and flatten the surface of a semiconductor substrate. CMP is a method for flattening the surface of an object to be polished, such as a semiconductor substrate, by using a polishing composition (slurry) containing abrasive grains such as silica, alumina, ceria, etc., an anticorrosive agent, a surfactant, etc. The semiconductor substrate to be polished is made up of various materials such as silicon, polysilicon (polycrystalline silicon), silicon oxide film (SiO2 film), silicon nitride film (SiN film), wiring and plugs made of metal, etc. For this reason, there is a demand to selectively polish only specific materials, and problems such as dishing, where a certain material is polished more than other materials, causing a dish-shaped depression in the center of the substrate, exist.

[0003] Since silicon nitride films have poor chemical reactivity and tend to have a lower polishing rate than other materials, there is a demand for polishing compositions that can polish SiN films at a higher polishing rate than SiO2 films, particularly when polishing semiconductor substrates by CMP. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-127442 Summary of the Invention [Problem to be solved by the invention]

[0005] Various compositions to which additives are added have been investigated in order to polish SiN films at a higher polishing rate than other materials, but no polishing compositions that focus on the shape of the abrasive grains themselves, regardless of the additives, have been investigated.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a polishing composition and a polishing method capable of polishing a SiN film at a high polishing rate. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above problems. As a result, they have found that the above problems can be solved by a polishing composition that contains colloidal silica having an organic acid fixed to its surface and a pH adjuster, and in which the average aspect ratio of the colloidal silica is 1.38 or more. Effect of the Invention

[0008] According to the present invention, there are provided a polishing composition and a polishing method capable of polishing a SiN film at a high polishing rate. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An embodiment of the present invention will be described in detail. Note that the following embodiment shows an example of the present invention, and the present invention is not limited to this embodiment. In addition, in this specification, "X to Y" indicating a range means "X or more and Y or less", and unless otherwise specified, the operation and measurement of physical properties are performed under the conditions of room temperature (20 to 25°C) and relative humidity of 40 to 50% RH.

[0010] One embodiment of the present invention is a polishing composition comprising colloidal silica having an organic acid fixed to the surface and a pH adjuster, wherein the colloidal silica has an average aspect ratio of 1.38 or more.

[0011] A polishing composition generally polishes an object to be polished by a physical action caused by rubbing the surface of a substrate, a chemical action caused by components other than the abrasive grains on the surface of the substrate, or a combination of these. Therefore, the shape and type of the abrasive grains have a large effect on the polishing rate.

[0012] The polishing composition according to this embodiment contains colloidal silica having an organic acid fixed to its surface, with an average aspect ratio of 1.38 or more. The average aspect ratio of 1.38 or more means that the colloidal silica is made of irregularly shaped particles. Since the colloidal silica is made of irregularly shaped particles, it is possible to suppress the rolling on the polishing surface, and the colloidal silica remains on the polishing surface, and mechanical force can be sufficiently applied, so that the polishing can be performed favorably.

[0013] The polishing method according to this embodiment is a method of polishing the object to be polished that contains SiO2 and SiN by using the polishing composition according to this embodiment.When the object to be polished that contains SiO2 and SiN is polished by using the polishing composition according to this embodiment, the polishing rate of SiN relative to SiO2 can be selectively increased.

[0014] <Polishing composition> (Colloidal silica with organic acids fixed on the surface) The polishing composition of the present invention contains, as an abrasive, colloidal silica having an organic acid fixed to its surface. "Colloidal silica having an organic acid fixed to its surface" refers to silica used as an abrasive having an organic acid chemically bonded to its surface.

[0015] In the colloidal silica having an organic acid fixed on the surface, the manufacturing method of the colloidal silica before fixing the organic acid includes the sodium silicate method and the sol-gel method. Although the colloidal silica manufactured by any manufacturing method may be used, from the viewpoint of reducing metal impurities, the colloidal silica manufactured by the sol-gel method is preferable. The colloidal silica manufactured by the sol-gel method is preferable because it has a low content of metal impurities and corrosive ions such as chloride ions that have the property of diffusing in semiconductors. The manufacturing of colloidal silica by the sol-gel method can be carried out using a conventionally known method, and specifically, the colloidal silica can be obtained by carrying out a hydrolysis-condensation reaction using a hydrolyzable silicon compound (e.g., alkoxysilane or its derivative) as a raw material.

[0016] In the colloidal silica having an organic acid fixed on the surface, the organic acid used for fixing on the surface can be, for example, sulfonic acid, carboxylic acid, phosphoric acid, etc. Among these, sulfonic acid or carboxylic acid is preferred, and sulfonic acid is more preferred because it is easily charged with negative charge. Note that, on the surface of the colloidal silica, acidic groups derived from the organic acid (for example, sulfo group, carboxyl group, phosphoric acid group, etc.) are fixed by covalent bond (sometimes via a linker structure).

[0017] The colloidal silica having an organic acid fixed on the surface may be a synthetic product or a commercially available product. The colloidal silica having an organic acid fixed on the surface may be used alone or in combination of two or more kinds.

[0018] The method of introducing organic acid to the surface of colloidal silica is not particularly limited, and examples thereof include a method of introducing organic acid to the surface of colloidal silica in the form of a mercapto group or an alkyl group, and then oxidizing it to a sulfonic acid or a carboxylic acid. Also, examples thereof include a method of introducing organic acid to the surface of colloidal silica in the form of an acidic group derived from an organic acid and then removing the protective group. Also, it is preferable that the compound used when introducing organic acid to the surface of colloidal silica has at least one functional group that can become an organic acid group, and further includes a functional group used for bonding with the hydroxyl group on the surface of colloidal silica, a functional group introduced to control hydrophobicity / hydrophilicity, a functional group introduced to control three-dimensional bulkiness, etc.

[0019] As a specific synthesis method, if sulfonic acid, which is a type of organic acid, is to be fixed on the surface of colloidal silica, it can be carried out by, for example, the method described in "Sulfonic acid-functionalized silica through quantitative oxidation of thiol groups", Chem. Commun. 246-247 (2003). Specifically, a silane coupling agent having a thiol group, such as 3-mercaptopropyltrimethoxysilane, is coupled to colloidal silica, and then the thiol group is oxidized with hydrogen peroxide to obtain colloidal silica having sulfonic acid fixed on the surface.

[0020] Alternatively, when a carboxylic acid is to be fixed on the surface of colloidal silica, this can be done by, for example, the method described in "Novel Silane Coupling Agents Containing a Photolabile 2-Nitrobenzyl Ester for Introduction of a Carboxy Group on the Surface of Silica Gel", Chemistry Letters, 3, 228-229 (2000). Specifically, a silane coupling agent containing a photoreactive 2-nitrobenzyl ester is coupled to colloidal silica, followed by light irradiation, to obtain colloidal silica having a carboxylic acid fixed on the surface.

[0021] The average aspect ratio of the colloidal silica having the organic acid in the polishing composition fixed on the surface is 1.38 or more, and more preferably 1.40 or more. In this range, rolling on the polishing surface is suppressed, and the object to be polished can be selectively polished at high speed. If the average aspect ratio is smaller than 1.38, the shape of the colloidal silica approaches a sphere, and the ability to polish the object to be polished tends to decrease. In addition, the upper limit of the average aspect ratio is not particularly limited, but is preferably 3.0 or less, more preferably 2.5 or less, and even more preferably 2.0 or less. In this range, the polishing speed can be further improved. The average aspect ratio is the average of the values ​​obtained by taking the smallest rectangle that circumscribes the image of the colloidal silica particle by a scanning electron microscope, and dividing the length of the long side of the rectangle by the length of the short side of the same rectangle, and can be obtained using general image analysis software.

[0022] Specifically, 150 or more silica particles are selected from an image measured with a scanning electron microscope (SEM) (Hitachi High-Tech Corporation, product name: SU8000), and the major and minor diameters of these particles are measured and calculated, and then the aspect ratio can be calculated using the formula "major diameter / minor diameter". Details of the method for measuring and calculating the aspect ratio of the abrasive grains are described in the Examples.

[0023] The aspect ratio of the colloidal silica particles having an organic acid fixed on the surface can be appropriately controlled by controlling the reaction conditions during the synthesis of colloidal silica, particularly the amount of alkali catalyst used during synthesis. For example, the average aspect ratio can be increased by reducing the content of the alkali catalyst. Also, the average aspect ratio can be decreased by increasing the content of the alkali catalyst.

[0024] In the present invention, the shape of the colloidal silica with an organic acid fixed on the surface is preferably non-spherical.Specific examples of the non-spherical shape include polygonal prisms such as triangular prisms and square prisms, cylinders, bales in which the center of the cylinder is bulging more than the ends, donuts in which the center of the disk is penetrated, plates, so-called cocoon shapes with a constriction in the center, so-called association-type spheres in which a plurality of particles are integrated, so-called confetti shapes with a plurality of protrusions on the surface, and rugby ball shapes, and various other shapes are not particularly limited.

[0025] In the particle size distribution of colloidal silica particles having organic acid fixed on the surface, which is determined by SEM, the number distribution ratio (D90-D10) / D50, which is the ratio of the particle diameter (D90) when the cumulative particle number reaches 90% of the total particle number from the fine particle side minus the particle diameter (D10) when the cumulative particle number reaches 10% of the total particle number of all particles, to the particle diameter (D50) when the cumulative particle number reaches 50% of the total particle number of all particles, is preferably 70% or more, more preferably 85% or more, even more preferably 90% or more, and particularly preferably 100% or more. In addition, in the particle size distribution of colloidal silica particles having organic acid fixed on the surface, which is determined by SEM, the number distribution ratio (D90-D10) / D50 is preferably 105% or less. In such a range, the polishing object can be selectively polished at a high polishing rate while suppressing surface defects. If the particle distribution rate is low, the particles will adhere too densely to the SiN surface, inhibiting the particles from rolling over and thus inhibiting the polishing rate of the SiN. Conversely, if the particle distribution rate is too high, the polishing rate of the SiO2 will increase, and in either case it will become impossible to selectively polish the SiN.

[0026] The average primary particle diameter of the colloidal silica having an organic acid fixed on the surface in the polishing composition is not particularly limited, and can be appropriately selected from the range of about 5 nm to 100 nm, for example. From the viewpoint of improving the ability to eliminate protuberances, the average primary particle diameter is preferably 5 nm or more, more preferably 7 nm or more, and even more preferably 10 nm or more. From the viewpoint of preventing the occurrence of scratches, the average primary particle diameter is usually advantageously 100 nm or less, preferably 80 nm or less, more preferably 50 nm or less, and even more preferably 30 nm. The value of the average primary particle diameter of the colloidal silica having an organic acid fixed on the surface can be calculated, for example, based on the specific surface area of ​​the colloidal silica having an organic acid fixed on the surface measured by the BET method. The average primary particle diameter of the silica particles can be controlled by the reaction conditions during the synthesis of colloidal silica, particularly the reaction temperature (i.e., the liquid temperature during the reaction). By increasing the reaction temperature, the average primary particle diameter can be made smaller. By decreasing the reaction temperature, the average primary particle diameter can be made larger.

[0027] In addition, the average secondary particle diameter of the colloidal silica having an organic acid fixed on the surface in the polishing composition is not particularly limited, and can be appropriately selected, for example, from the range of about 10 nm to 200 nm. The average secondary particle diameter of the colloidal silica having an organic acid fixed on the surface is preferably 10 nm or more, more preferably 15 nm or more, even more preferably 20 nm or more, even more preferably 25 nm or more, and particularly preferably 30 nm or more. In addition, the average secondary particle diameter of the colloidal silica having an organic acid fixed on the surface is preferably 200 nm or less, more preferably 180 nm or less, even more preferably 150 nm or less, and particularly preferably 100 nm or less. The value of the average secondary particle diameter of the colloidal silica having an organic acid fixed on the surface can be calculated, for example, based on a light scattering method measurement using laser light.

[0028] The number distribution rate ((D90-D10) / D50) of the colloidal silica particles having an organic acid fixed on the surface can be appropriately controlled by selecting the above aspect ratio, primary particle size, and the production method.

[0029] The concentration (content) of the abrasive grains is not particularly limited, but is preferably 0.1% by weight or more, more preferably 0.3% by weight or more, even more preferably 0.5% by weight or more, and particularly preferably 0.8% by weight or more, based on the total weight of the polishing composition. The upper limit of the concentration (content) of the abrasive grains is preferably 20% by weight or less, more preferably 15% by weight or less, even more preferably 10% by weight or less, and particularly preferably 5% by weight or less, based on the total weight of the polishing composition. That is, the concentration (content) of the abrasive grains is preferably 0.1% by weight or more and 20% by weight or less, more preferably 0.3% by weight or more and 15% by weight or less, even more preferably 0.5% by weight or more and 10% by weight or less, and particularly preferably 0.8% by weight or more and 5% by weight or less, based on the total weight of the polishing composition. Within such a range, the polishing rate can be improved while suppressing costs. In addition, when the polishing composition contains two or more kinds of abrasive grains, the concentration (content) of the abrasive grains means the total amount of these.

[0030] (pH adjuster) From the viewpoint of maintaining a high removal rate of SiN, the polishing composition according to this embodiment has a pH value of less than 7, preferably 6 or less, more preferably 4 or less, even more preferably 3 or less, and most preferably 2.5 or less. From the viewpoint of safety, the pH value of the polishing composition is preferably 1 or more, and more preferably 2 or more.

[0031] The pH value of the polishing composition can be adjusted by adding a pH adjuster. The pH adjuster used may be either an acid or a base, but is preferably an acid or a salt thereof.

[0032] The acid is not particularly limited, and may be an inorganic acid or an organic acid. Specific examples of inorganic acids include phosphoric acid (orthophosphoric acid), nitric acid, sulfuric acid, hydrochloric acid, boric acid, sulfamic acid, phosphinic acid, phosphonic acid, pyrophosphoric acid, tripolyphosphoric acid, tetrapolyphosphoric acid, hexametaphosphoric acid, carbonic acid, hydrofluoric acid, sulfurous acid, thiosulfuric acid, chloric acid, perchloric acid, chlorous acid, hydroiodic acid, periodic acid, iodic acid, hydrobromic acid, perbromic acid, bromic acid, chromic acid, and nitrous acid.

[0033] Specific examples of organic acids include citric acid, maleic acid, malic acid, glycolic acid, succinic acid, itaconic acid, malonic acid, iminodiacetic acid, gluconic acid, lactic acid, mandelic acid, tartaric acid, formic acid, acetic acid, propionic acid, butyric acid, adipic acid, oxalic acid, valeric acid, enanthic acid, caproic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, cyclohexanecarboxylic acid, phenylacetic acid, benzoic acid, crotonic acid, oleic acid, linoleic acid, linolenic acid, ricinoleic acid, and methacrylic acid. , glutaric acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, tartronic acid, glyceric acid, hydroxybutyric acid, hydroxyacetic acid, hydroxybenzoic acid, salicylic acid, isocitric acid, methylenesuccinic acid, gallic acid, ascorbic acid, nitroacetic acid, oxaloacetic acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid, and other organic carboxylic acids; glycine, alanine, glutamic acid, aspartic acid, valine, leucine, isoleucine, serine, threonine, cysteine, methionine, phenylalanine, tryptophan, tyrosine, proline, Amino acids such as lysine, cystine, glutamine, asparagine, lysine, and arginine; nicotinic acid; picric acid; picolinic acid; phytic acid; 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri(methylenephosphonic acid), ethylenediaminetetra(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, ethanehydroxy-1,1,2-triphosphonic acid, ethane-1 , organic phosphonic acids such as 2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, α-methylphosphonosuccinic acid, and aminopoly(methylenephosphonic acid); and organic sulfonic acids such as methanesulfonic acid, ethanesulfonic acid, aminoethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, 2-naphthalenesulfonic acid, sulfosuccinic acid, 10-camphorsulfonic acid, isethionic acid, and taurine.

[0034] Moreover, in place of or in combination with the above acids, salts such as ammonium salts or alkali metal salts of the above acids may be used.

[0035] The polishing composition according to the present embodiment may or may not contain a base as a pH adjuster. Specific examples of the base include alkali metal hydroxides such as potassium hydroxide, ammonia, quaternary ammonium salts such as tetramethylammonium and tetraethylammonium, and amines such as ethylenediamine and piperazine.

[0036] These pH adjusters may be used alone or in combination of two or more.

[0037] The pH of the polishing composition can be measured, for example, by a pH meter.

[0038] (dispersion medium) The polishing composition according to the 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 colloidal silica with an organic acid fixed on the surface, pH adjuster, etc.). Examples of the liquid medium include water and organic solvents, and one type can be used alone or two or more types can be mixed and used, but it is preferable to contain water. However, from the viewpoint of preventing the inhibition of the action of each component, it is preferable to use water that contains as few impurities as possible. Specifically, pure water or ultrapure water that has been filtered to remove foreign matter after removing impurity ions with an ion exchange resin, or distilled water is preferable.

[0039] (Water-soluble polymer) The polishing composition according to the embodiment of the present invention may or may not contain a water-soluble polymer.Specific examples of water-soluble polymers include celluloses such as methyl cellulose, methyl hydroxyethyl cellulose, methyl hydroxypropyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, and carboxymethyl hydroxyethyl cellulose, polysaccharides such as chitosan, and polymers such as polyalkylene glycols such as polyethylene glycol, polyethyleneimine, poly-N-vinylpyrrolidone, polyvinyl alcohol, polyacrylic acid (or its salt), polyacrylamide, and polyethylene oxide.Among these, polyethylene glycol is preferred, and can improve the selectivity of the polishing rate of SiN film to the polishing rate of SiO2 film.

[0040] (Corrosion inhibitor) The polishing composition according to the present embodiment may or may not contain an anticorrosive agent. The anticorrosive agent has the effect of suppressing the corrosion of the surface of the object to be polished. Specific examples of the anticorrosive agent include amines, pyridines, tetraphenylphosphonium salts, benzotriazoles, triazoles, tetrazoles, benzoic acid, etc.

[0041] (Preservatives, anti-mold agents) The polishing composition according to the present embodiment may or may not contain a preservative or a fungicide. Specific examples of the preservative and the fungicide include isothiazolin-based preservatives such as 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one, paraoxybenzoic acid esters, and phenoxyethanol.

[0042] (Oxidizing agent) The polishing composition according to the present embodiment may or may not contain an oxidizing agent. The oxidizing agent has a function of oxidizing the surface of the object to be polished, and when an oxidizing agent is added to the polishing composition, the polishing rate of the polishing composition is improved. Specific examples of peroxides include hydrogen peroxide, peracetic acid, percarbonates, urea peroxide, perchloric acid, and persulfates (for example, sodium persulfate, potassium persulfate, and ammonium persulfate).

[0043] (Other Ingredients) The polishing composition according to the embodiment of the present invention may or may not further contain other known components used in the field of polishing compositions. The other components are not particularly limited, but may include, for example, a polishing accelerator, a surfactant, an electrical conductivity adjuster, etc.

[0044] (Object to be polished) The polishing composition according to this embodiment can selectively increase the polishing rate of a silicon nitride film (SiN film) compared to a silicon oxide film (SiO2 film). For this reason, the object to be polished preferably includes a SiO2 film and a SiN film. However, the type of the object to be polished is not limited to a SiO2 film and a SiN film, and may be elemental silicon, silicon compounds other than a SiO2 film and a SiN film, metals, etc. Examples of elemental silicon include single crystal silicon, polysilicon, and amorphous silicon. Examples of silicon compounds include silicon dioxide and silicon carbide. Silicon dioxide may be a film formed using tetraethoxysilane ((Si(OC2H5)4)) (hereinafter, TEOS film).

[0045] (polishing speed) As described above, the polishing composition of the present invention can selectively polish SiN at a high polishing rate relative to SiO2. In the present invention, the polishing rate of SiN is preferably 180 Å / min or more, more preferably 200 Å / min or more, and even more preferably 250 Å / min or more. In addition, the polishing rate of SiO2 is preferably 40 Å / min or less, more preferably 45 Å / min or less, and even more preferably 30 Å / min or less.

[0046] (Selectivity) In the present invention, the selectivity ratio of the polishing rate of SiN to the polishing rate of SiO2 is preferably 7 or more, more preferably 8 or more, and even more preferably 10 or more. Moreover, the selectivity ratio of the polishing rate of SiN to the polishing rate of SiO2 is preferably 30 or less, more preferably 25 or less, and even more preferably 20 or less. If the selectivity ratio is out of the above range, the surface condition of the object to be polished after the final polishing may be poor.

[0047] <Polishing method> The present invention provides a polishing method for polishing an object to be polished with the polishing composition according to an embodiment of the present invention.

[0048] (Polishing Equipment Configuration) 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.

[0049] (polishing conditions) 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. In general, the higher the load, the higher the frictional force caused by the abrasive grains, and the mechanical processing force is improved, so that the polishing rate increases. Within this range, a higher polishing rate is achieved, and damage to the substrate caused by the load and defects such as scratches on the surface can be more suppressed. There is no particular restriction on the method of supplying the polishing composition to the polishing pad, and a method of continuously supplying the composition using a pump or the like is adopted. There is no restriction on the amount of supply, but it is preferable that the surface of the polishing pad is always covered with the polishing composition of one embodiment of the present invention.

[0050] The polishing composition according to the embodiment of the present invention 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 diluent such as water.

[0051] 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.

[0052] <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 section <Polishing method>. EXAMPLES

[0053] An embodiment of the present invention will be described in more detail using the following examples and comparative examples, but the following examples are merely examples of the present invention, and the present invention is not limited to the following examples. Unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass", respectively. In the following examples, unless otherwise specified, the operations were carried out under the conditions of room temperature (20 to 25°C) / relative humidity 40 to 50% RH.

[0054] The physical properties of each polishing composition were measured according to the following methods.

[0055] (Aspect Ratio) The particle shape of the colloidal silica with the organic acid fixed on the surface in each polishing composition was observed using a scanning electron microscope SU8000 (Hitachi High-Tech Corporation). The aspect ratio (average aspect ratio) was calculated from the captured SEM image using image analysis type particle size distribution measurement software Mac-View Ver.4 (Mountec Corporation).

[0056] The aspect ratio was determined by taking SEM images of 150 or more colloidal silica particles using an SEM and analyzing the images. The average aspect ratio was determined by determining the minor axis and major axis of the circumscribing rectangle with the smallest area for each particle, calculating the aspect ratio of each particle using the following formula, and averaging the calculated aspect ratios. The colloidal silica with organic acid fixed to the surface used to calculate the average aspect ratio covers all particles in the SEM image taken. In other words, the aspect ratio is determined according to the following formula. Aspect ratio = (longer diameter of the circumscribing rectangle with the smallest area) / (minor diameter of the circumscribing rectangle with the smallest area)

[0057] <Preparation of Polishing Composition> Example 1 A colloidal silica having sulfonic acid groups fixed on the surface (average aspect ratio 1.39, number distribution rate ((D90-D10) / D50)) 70.6) and nitric acid as a pH adjuster were added to water as a solvent, and the mixture was stirred to prepare a polishing composition (mixing temperature about 25°C, mixing time: about 10 minutes). The pH of the polishing composition measured with a pH meter was 2.3.

[0058] (Examples 2 to 5, Comparative Examples 1 to 7) Polishing compositions of Examples 2 to 5 and Comparative Examples 1 to 7 were prepared in the same manner as in Example 1, except that the average aspect ratio and number distribution rate of the colloidal silica having sulfonic acid groups fixed to the surface, and the pH of the polishing composition, etc. were changed as shown in Table 1.

[0059] Comparative Example 8 The polishing composition of Comparative Example 8 was prepared in the same manner as in Example 5, except that unmodified colloidal silica (average aspect ratio 1.42, number distribution rate 103.3) was used instead of the colloidal silica having sulfonic acid groups fixed to the surface.

[0060] <Polishing test> (Polishing equipment and polishing conditions) In Examples 1 to 5 and Comparative Examples 1 to 8, the surface of an object to be polished was polished under the following conditions using each prepared polishing composition. The object to be polished was a silicon wafer (300 mm, blanket wafer) having a 10,000 Å thick SiO2 film (TEOS film) or a 5,000 Å thick SiN film formed on the surface. Polishing equipment: Ebara Corporation 300mm CMP single-sided polishing equipment FREX300E Pad: Nitta Haas Co., Ltd. Hard polyurethane pad IC1000 Grinding pressure: 2.0psi Polishing platen rotation speed: 93 rpm Carrier rotation speed: 87 rpm Supply of polishing composition: free-flowing Polishing composition supply amount: 300ml / min Polishing time: 60 seconds

[0061] (Evaluation of polishing speed) The polishing rate was determined by measuring the thickness using an optical film thickness measuring device (ASET-f5x: manufactured by KLA-Tencor Corporation) and dividing the thickness before polishing by the polishing time (thickness before polishing) minus the thickness after polishing).

[0062] The evaluation results of the polishing rate are shown in Table 1.

[0063] [Table 1]

[0064] As shown in Table 1, when the polishing compositions of Examples 1 to 5 were used, the polishing rate of SiO2 was lower than 30 Å / min, the polishing rate of SiN was higher than the polishing rate of SiO2 film, and the polishing rate of SiO2 was lower than that when the polishing compositions of Comparative Examples 1 to 8 were used, and it was found that the SiN film, which is the object to be polished, could be selectively polished. In Comparative Example 8, in which unmodified colloidal silica was used as the abrasive, the polishing rate of SiN was lower than the polishing rate of SiO2, and it was found that the SiN film could not be selectively polished.

Claims

1. The colloidal silica has an organic acid fixed to its surface, and a pH adjuster is included. A polishing composition, wherein the colloidal silica has an average aspect ratio of 1.38 or more.

2. 2. The polishing composition according to claim 1, wherein in a particle size distribution of the colloidal silica calculated by SEM image analysis, a ratio (D90-D10) / D50 of a difference between a particle diameter D90 when the cumulative particle number from the fine particle side reaches 90% of the total particle number and a particle diameter D10 when the cumulative particle number from the fine particle side reaches 10% of the total particle number, and a particle diameter D50 when the cumulative particle number from the fine particle side reaches 50% of the total particle number, is 70% or more and 105% or less.

3. 3. The polishing composition according to claim 2, wherein the ratio (D90-D10) / D50 is 90% or more and 105% or less.

4. The polishing composition according to claim 1 or 2, having a pH of less than 7.

5. The polishing composition according to claim 4, having a pH of less than 4.

6. The polishing composition according to claim 1 or 2, wherein the pH adjuster is an acid.

7. The polishing composition according to claim 1 or 2, wherein the organic acid is a sulfonic acid.

8. SiO ２ When polishing an object containing SiO and SiN, ２ 3. The polishing composition according to claim 1, wherein the SiN has a selectively high polishing rate relative to silicon.

9. The polishing composition of claim 1 or 2 is used to polish SiO ２ A method for polishing an object containing SiO and SiN, ２ The polishing method according to claim 1, wherein the polishing rate of said SiN is selectively higher than the polishing rate of said SiO.

10. The SiO ２ 10. The polishing method according to claim 9, wherein a selectivity of a polishing rate of said SiN to a polishing rate of said SiO.sub.2 is 6.5 or more and 20 or less.

11. The polishing method according to claim 10 , wherein the selectivity is 10 or more and 20 or less.

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