TWI829666B - Polishing composition, polishing composition manufacturing method, polishing method and semiconductor substrate manufacturing method - Google Patents

Abstract

An object of the present invention is to provide a means for polishing a polishing object containing at least one of impurity-doped polycrystalline silicon and impurity-doped amorphous silicon at a high polishing speed. The solution of the present invention is a polishing composition used for polishing a polishing object containing at least one of impurity-doped polycrystalline silicon and impurity-doped amorphous silicon, and is characterized by: Comprising abrasive particles, a dispersing medium, and a group selected from the group consisting of hydroxides of alkali metals, alkali metal salts of inorganic acids, ammonium salts of inorganic acids, alkali metal salts of organic acids, ammonium salts of organic acids, and ammonia At least one of the alkali compounds.

Description

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

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

In recent years, with the multi-layer wiring on the surface of a semiconductor substrate, when manufacturing a device, the semiconductor substrate is polished for planarization, that is, chemical mechanical polishing (CMP) technology is used. CMP uses a polishing composition (slurry) containing abrasive grains such as silica, aluminum oxide, cerium oxide, etc., a protective film forming agent, a surfactant, etc., to planarize a polishing object such as a semiconductor substrate (object to be polished) ) surface method, the object to be polished (object to be polished) is wiring, plugs, etc. made of silicon, polysilicon (polysilicon), silicon oxide film (silicon oxide), silicon nitride or metal. For example, as a technique for polishing a polysilicon film provided on a silicon substrate having a separation region, Patent Document 1 discloses a polishing method that uses a preparation method containing abrasive grains, an alkali, a water-soluble polymer, and water. The polishing composition is used to carry out the step of preliminary polishing, and the final polishing composition containing abrasive grains, alkali, water-soluble polymer and water is used to carry out the final polishing step. [Prior technical literature] [Patent Document] [Patent Document 1] Japanese Patent Application Publication No. 2007-103515

[Problem to be solved by the invention] Recently, as semiconductor substrates, substrates containing impurity-doped polycrystalline silicon or impurity-doped amorphous silicon have been used, and so-called new requirements for polishing the substrates are emerging. There has not been any research on such a requirement in the past. Therefore, the present invention aims to provide a means for polishing a polishing object containing at least one of impurity-doped polycrystalline silicon and impurity-doped amorphous silicon at a high polishing speed. [Means used to solve problems] In order to solve the above-mentioned novel problems, the present inventors have made repeated efforts in research. As a result, it was found that the above problems can be solved by a polishing composition containing abrasive grains, a dispersion medium, and an alkali metal salt selected from an alkali metal hydroxide, an inorganic acid, and an inorganic acid. At least one alkali compound selected from the group consisting of ammonium salts, alkali metal salts of organic acids, ammonium salts of organic acids, and ammonia is used to complete the present invention. [Effects of the invention] According to the present invention, there is provided a means for polishing a polishing object containing at least one of impurity-doped polycrystalline silicon and impurity-doped amorphous silicon at a high polishing speed.

The present invention is a polishing composition used for polishing a polishing object containing at least one of polycrystalline silicon doped with impurities and amorphous silicon doped with impurities, and is characterized by containing abrasive grains , and a dispersion medium, and at least one selected from the group consisting of hydroxides of alkali metals, alkali metal salts of inorganic acids, ammonium salts of inorganic acids, alkali metal salts of organic acids, ammonium salts of organic acids, and ammonia 1 kind of alkali compound. The polishing composition of the present invention having such a structure can polish a polishing object containing at least one of impurity-doped polycrystalline silicon and impurity-doped amorphous silicon at a high polishing speed. The mechanism for obtaining such an effect is considered to be as follows. However, the following mechanisms are only speculations and are not intended to limit the scope of the present invention. That is, by using an alkali compound as a component of the polishing composition, the pH can be adjusted in an alkaline region where silicon contained in the polishing object is easily dissolved. In addition, the alkali compound does not adsorb to the surface of the abrasive grains or the surface of the object to be polished during polishing, but is mostly dissolved in the dispersion medium. Therefore, it does not hinder the removal of silicon and enables efficient polishing. Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited only to the following embodiments. In this specification, unless otherwise stated, the operation and physical properties are measured under the conditions of room temperature (above 20°C and below 25°C)/relative humidity of 40% RH or more and 50% RH or less. [Polysilicon] The polishing object of the present invention contains at least one of impurity-doped polycrystalline silicon (polysilicon) and impurity-doped amorphous silicon. The impurities can be either n-type or p-type. Examples of p-type impurities include Group 13 elements such as boron (B), aluminum (Al), gallium (Ga), and indium (In). Examples of n-type impurities include Group 15 elements such as phosphorus (P), arsenic (As), bismuth (Bi), and antimony (Sb). Among these impurities, n-type impurities are preferred, and phosphorus is more preferred. Although the lower limit of the impurity content (doping amount) is not particularly limited, it is preferably 0.001 mass% or more, more preferably 0.005 mass% or more, and still more preferably 0.01 mass% based on 100 mass% of polycrystalline silicon or amorphous silicon. % or more, particularly preferably 0.05 mass % or more. In addition, although the upper limit of the impurity content (doping amount) is not particularly limited, in the case of polycrystalline silicon, it is preferably 0.5 mass% or less, more preferably 0.3 mass% or less, based on 100 mass% of polycrystalline silicon. 0.2% by mass or less, preferably 0.1% by mass or less. The object to be polished in the present invention may include other materials in addition to impurity-doped polycrystalline silicon (polysilicon) and impurity-doped amorphous silicon (amorphous silicon). Examples of other materials include silicon nitride, silicon carbonitride (SiCN), silicon oxide, undoped polycrystalline silicon (undoped polysilicon), undoped amorphous silicon (undoped amorphous silicon), Metal, SiGe, etc. As an example of the polishing object containing silicon oxide, for example, TEOS (Tetraethyl Orthosilicate) type silicon oxide surface (hereinafter, also referred to simply as "TEOS") produced by using tetraethyl orthosilicate (Tetraethyl orthosilicate) as a precursor ”), HDP (High Density Plasma) film, USG (Undoped Silicate Glass) film, PSG (Phosphorus Silicate Glass) film, BPSG (Boron-Phospho Silicate Glass) film, RTO (Rapid Thermal Oxidation) film, etc. Examples of the metal include tungsten, copper, aluminum, cobalt, hafnium, nickel, gold, silver, platinum, palladium, rhodium, ruthenium, iridium, osmium, and the like. [Abrasive grains] The polishing composition of the present invention contains abrasive grains. Examples of types of abrasive grains include metal oxides such as silica, alumina, zirconium oxide, and titanium dioxide. This abrasive grain can be used individually or in combination of 2 or more types. As the abrasive grains, commercially available products or synthetic products may be used. As the type of abrasive grains, silica is preferred, and colloidal silica is more preferred. Examples of methods for producing colloidal silica include the sodium silicate method and the sol-gel method. Colloidal silica produced by any production method can be suitably used as the abrasive grains of the present invention. However, from the viewpoint of reducing metal impurities, colloidal silica produced by a sol-gel method that can be produced with high purity is preferred. Here, the shape of the abrasive grains is not particularly limited and may be spherical or non-spherical. Specific examples of aspherical shapes include polygonal prisms such as triangular prisms and square prisms, cylindrical shapes, turtle shapes in which the central part of the cylinder is more expanded than the end parts, donut shapes penetrating the central part of the disk, and plate shapes. Various shapes such as a so-called cocoon shape with a shrinkage in the center, a so-called converging spherical shape with a plurality of particles integrated, a so-called golden candy shape with a plurality of protrusions on the surface, and a rugby ball shape are not particularly limited. Furthermore, the surface of the colloidal silica can be surface-modified with a silane coupling agent or the like. As a method of surface modification of the surface of the abrasive grain with a silane coupling agent, the following immobilization method can be cited. For example, the method described in "Sulfonic acid-functionalized silica through of thiol groups", Chem. Commun. 246-247 (2003) can be used. Specifically, sulfonic acid fixation can be obtained by coupling a silane coupling agent with a thiol group such as 3-mercaptopropyltrimethoxysilane to colloidal silica, and then oxidizing the thiol group with hydrogen peroxide. Colloidal silica on the surface. Or, 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) can be used. Specifically, colloidal silica with carboxylic acid immobilized on the surface can be obtained by coupling a silane coupling agent containing photoreactive 2-nitrobenzyl ester to colloidal silica and then irradiating it with light. Although the above is colloidal silica having an anionic group (anionic denatured colloidal silica), colloidal silica having a cationic group (cationic denatured colloidal silica) can be used. Examples of the colloidal silica having a cationic group include colloidal silica in which an amine group is immobilized on the surface. Examples of methods for producing colloidal silica having such a cationic group include aminoethyltrimethoxysilane and aminopropyltrimethoxysilane as described in Japanese Patent Application Laid-Open No. 2005-162533. , aminoethyltriethoxysilane, aminopropyltriethoxysilane, aminopropyldimethylethoxysilane, aminopropylmethyldiethoxysilane, aminobutyltriethoxysilane A method of fixing silane coupling agents with amine groups such as ethoxysilane on the surface of abrasive particles. In this way, colloidal silica with amine groups immobilized on the surface can be obtained. The size of the abrasive grains is not particularly limited. For example, when the abrasive grains are spherical, the average primary particle diameter of the abrasive grains is preferably 20 nm or more, more preferably 30 nm or more, still more preferably 50 nm or more, and particularly preferably 70 nm or more. As the average primary particle size of the abrasive grains increases, the polishing speed of the object to be polished by the polishing composition increases. Moreover, the average primary particle size of the abrasive grains is preferably 300 nm or less, more preferably 250 nm or less, still more preferably 200 nm or less, and particularly preferably 150 nm or less. As the average primary particle diameter of the abrasive grains decreases, it becomes easier to obtain a surface with fewer defects by polishing using the polishing composition. That is, the average primary particle diameter of the abrasive grains is preferably from 20 nm to 300 nm, more preferably from 30 nm to 250 nm, still more preferably from 50 nm to 200 nm, particularly preferably from 70 nm to 150 nm. Furthermore, the average primary particle diameter of the abrasive grains can be calculated, for example, based on the specific surface area (SA) of the abrasive grains calculated by the BET method and assuming that the shape of the abrasive grains is a true sphere. In this specification, the average primary particle size of abrasive grains is a value measured by the method described in the Examples. Furthermore, the average secondary particle size of the abrasive grains is preferably 50 nm or more, more preferably 80 nm or more, still more preferably 120 nm or more, and particularly preferably 200 nm or more. As the average secondary particle size of the abrasive grains increases, the resistance during grinding becomes smaller, allowing for stable grinding. Furthermore, the average secondary particle size of the abrasive grains is preferably 500 nm or less, more preferably 400 nm or less, still more preferably 350 nm or less, particularly preferably 300 nm or less. As the average secondary particle size of the abrasive particles decreases, the surface area per unit mass of the abrasive particles increases, increasing the frequency of contact with the grinding object and further increasing the grinding speed. That is, the average secondary particle diameter of the abrasive grains is preferably from 50 nm to 500 nm, more preferably from 80 nm to 400 nm, still more preferably from 120 nm to 350 nm, particularly preferably from 200 nm to 300 nm. Furthermore, the average secondary particle size of the abrasive grains can be measured, for example, by the dynamic light scattering method represented by the laser diffraction scattering method. The average degree of association of the abrasive grains is preferably 5.0 or less, more preferably 4.0 or less, still more preferably 3.0 or less. As the average association degree of abrasive particles decreases, defects can be further reduced. The average degree of association of the abrasive grains is preferably 1.0 or more, more preferably 1.5 or more, and still more preferably 2.0 or more. The average degree of association is obtained by dividing the average secondary particle diameter of the abrasive grains by the average primary particle diameter. As the average association degree of the abrasive grains increases, there is an advantageous effect of increasing the polishing speed of the object to be polished by the polishing composition. Although the upper limit of the aspect ratio of the abrasive grains in the polishing composition is not particularly limited, it is preferably less than 2.0, more preferably 1.8 or less, and still more preferably 1.5 or less. If it is within this range, defects on the surface of the object to be polished can be further reduced. However, the aspect ratio is the average of the values obtained by dividing the length of the long side of the rectangle by the length of the short side of the same rectangle in the smallest rectangle circumscribed with the image of the abrasive particle obtained by a scanning electron microscope. , can be obtained using general image analysis software. The lower limit of the aspect ratio of the abrasive grains in the polishing composition is not particularly limited, but is preferably 1.0 or more. In the particle size distribution determined by the laser diffraction and scattering method of abrasive grains, from the fine particle side, the diameter of the particle when the cumulative particle weight reaches 90% of the total particle weight (D90) and the total particle weight of the total particle. The ratio of particle diameters (D10) at 10%, that is, the lower limit of D90/D10, is not particularly limited, but is preferably 1.1 or more, more preferably 1.2 or more, and still more preferably 1.3 or more. In addition, the particle size distribution of the abrasive grains in the polishing composition was determined by the laser diffraction scattering method. From the fine particle side, the particle diameter (D90) when the cumulative particle weight reaches 90% of the total particle weight and the The upper limit of D90/D10, which is the ratio of particle diameters (D10) when the total particle weight is 10%, is not particularly limited, but is preferably 2.04 or less. If it is within this range, defects on the surface of the object to be polished can be further reduced. The size of the abrasive grains (average primary particle size, average secondary particle size, aspect ratio, D90/D10, etc.) can be appropriately controlled by selecting the manufacturing method of the abrasive grains. Although the content (concentration) of the abrasive grains is not particularly limited, it is preferably 0.1 mass% or more, more preferably 0.2 mass% or more, and still more preferably 1 mass% or more relative to the total mass of the polishing composition. Moreover, the upper limit of the abrasive grain content is preferably 20 mass% or less, more preferably 10 mass% or less, and still more preferably 5 mass% or less based on the total mass of the polishing composition. That is, the content of the abrasive grains relative to the total mass of the polishing composition is preferably 0.1 mass % or more and 20 mass % or less, more preferably 0.2 mass % or more and 10 mass % or less, and still more preferably 1 mass % or more 5 mass% or less. If it is within this range, the grinding speed can be increased while reducing costs. However, when the polishing composition contains two or more types of abrasive grains, the content of the abrasive grains should be the total amount. [Alkali compound] The polishing composition of the present invention contains alkali metal hydroxides, alkali metal salts of inorganic acids, ammonium salts of inorganic acids, alkali metal salts of organic acids, ammonium salts of organic acids, and ammonia salts. At least one alkali compound from the group consisting of. By using such alkali compounds, not only can the pH be adjusted in an alkaline region where silicon contained in the object to be polished is easily dissolved, but also the alkali compound will not be adsorbed to the surface of the abrasive grains or the surface of the object to be polished during grinding. Most of it is dissolved in the dispersion medium, so it does not hinder the removal of silicon and enables efficient grinding. Incidentally, in this specification, the term "alkaline compound" means a compound in which the pH of the aqueous solution is alkaline exceeding 7. The base compound of the present invention will be described in further detail. Examples of alkali metal hydroxides include lithium hydroxide, sodium hydroxide, potassium hydroxide, and the like. Examples of alkali metal salts of inorganic acids include alkali metal salts of nitrite such as sodium nitrite and potassium nitrite; alkali metal salts of nitric acid such as sodium nitrate and potassium nitrate; sodium molybdate and potassium molybdate. Alkali metal salts of molybdic acid; alkali metal salts of hypochlorous acid such as sodium hypochlorite and potassium hypochlorite; alkali metal salts of sulfuric acid such as sodium sulfate and potassium sulfate; alkali metal salts of carbonic acids such as sodium carbonate and potassium carbonate; sodium chloride , alkali metal salts of hydrochloric acid such as potassium chloride; alkali metal salts of phosphoric acid such as sodium phosphate, potassium phosphate, etc.; alkali metal salts of silicic acid such as sodium silicate, potassium silicate, etc.; alkali metal salts of boric acid such as sodium borate, potassium borate, etc. Alkali metal salts, etc. Examples of ammonium salts of inorganic acids include ammonium chloride, ammonium sulfate, ammonium amide sulfate, ammonium nitrate, monoammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium hypophosphite, ammonium carbonate, and hydrogen carbonate. Ammonium, ammonium sulfide, ammonium borate, ammonium borofluoride, etc. Examples of alkali metal salts of organic acids include sodium acetate, potassium acetate, sodium propionate, potassium propionate, sodium glycerate, potassium glycerate, sodium malate, potassium malate, sodium citrate, and potassium citrate. Sodium lactate, potassium lactate, sodium tartrate, potassium tartrate, sodium salicylate, potassium salicylate, sodium malonate, potassium malonate, sodium succinate, potassium succinate, sodium maleate, potassium maleate, benzene Sodium diformate, potassium phthalate, sodium oxalate, potassium oxalate, sodium glutarate, potassium glutarate, sodium abietate, potassium abietate, sodium sorbate, potassium sorbate, 2,4,6-octatriene- Sodium 1-carboxylate, potassium 2,4,6-octatriene-1-carboxylate, sodium oleostearic acid, potassium oleostearate, 2,4,6,8-dedecatetraene- Sodium 1-carboxylate, potassium 2,4,6,8-dedecatetraene-1-carboxylate, sodium retinoate, potassium retinoic acid, potassium iminodiacetate, etc. Examples of ammonium salts of organic acids include ammonium formate, ammonium acetate, diammonium oxalate, ammonium hydrogen oxalate, ammonium benzoate, monoammonium citrate, diammonium citrate, triammonium citrate, ammonium lactate, and phthalic acid. Ammonium, ammonium succinate, monoammonium tartrate, diammonium tartrate, ammonium aspartate, etc. Among these alkaline compounds, for the purpose of preventing malfunction of semiconductors, those selected from the group consisting of potassium hydroxide, potassium salts of inorganic acids, ammonium salts of inorganic acids, potassium salts of organic acids, ammonium salts of organic acids, and At least one of ammonia. More specifically, inorganic compounds selected from the group consisting of potassium hydroxide, potassium nitrite, potassium nitrate, potassium molybdate, potassium hypochlorite, potassium sulfate, potassium carbonate, potassium chloride, potassium phosphate, potassium silicate, potassium borate, etc. are preferred. Potassium salts of acids; ammonium chloride, ammonium sulfate, ammonium amide sulfate, ammonium nitrate, monoammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium hypophosphite, ammonium carbonate, ammonium bicarbonate, ammonium sulfide, boric acid Ammonium salts of inorganic acids such as ammonium and ammonium borofluoride; potassium acetate, potassium propionate, potassium glycerate, potassium malate, potassium citrate, potassium lactate, potassium tartrate, potassium salicylate, potassium malonate, amber Potassium acid, potassium maleate, potassium phthalate, potassium oxalate, potassium glutarate, potassium abietate, potassium sorbate, potassium 2,4,6-octatriene-1-carboxylate, potassium oil stearate , potassium salts of organic acids such as potassium 2,4,6,8-decatetraene-1-carboxylate, potassium retinoic acid, potassium iminodiacetate; ammonium formate, ammonium acetate, diammonium oxalate, ammonium hydrogen oxalate , ammonium benzoate, monoammonium citrate, diammonium citrate, triammonium citrate, ammonium lactate, ammonium phthalate, ammonium succinate, monoammonium tartrate, diammonium tartrate, ammonium aspartate and other organic acids At least one of the group consisting of ammonium salt; and ammonia. Furthermore, among these, at least one selected from the group consisting of potassium hydroxide, potassium carbonate, triammonium citrate, triammonium phosphate, potassium iminodiacetate, and ammonia is more preferred. Although the content (concentration) of the alkali compound is not particularly limited, it is preferably 0.01 mass % or more, more preferably 0.05 mass % or more, still more preferably 0.15 mass % or more, based on the total mass of the polishing composition. Moreover, the upper limit of the content of the alkali compound is preferably 10 mass% or less, more preferably 5 mass% or less, and still more preferably 2 mass% or less based on the total mass of the polishing composition. That is, the content of the alkali compound is preferably 0.01 mass% or more and 10 mass% or less, more preferably 0.05 mass% or more and 5 mass% or less, based on the polishing composition, more preferably 0.15 mass% or more and 2 mass% or less. . If it is within this range, the grinding speed can be increased while reducing costs. Furthermore, when the polishing composition contains two or more alkali compounds, the content of the alkali compounds should be the total amount of these compounds. [Dispersion Medium] The polishing composition of the present invention contains a dispersion medium for dispersing each component. Examples of the dispersion medium include water; alcohols such as methanol, ethanol, and ethylene glycol; ketones such as acetone; and mixtures thereof. Among these, water is preferred as the dispersion medium. That is, according to a preferred aspect of the present invention, the dispersion medium contains water. According to a more preferred aspect of the present invention, the dispersion medium consists essentially of water. Moreover, the above-mentioned "substantially" means that as long as the purpose and effect of the present invention can be achieved, dispersing media other than water may be included. More specifically, it is preferably composed of 90 mass % or more and 100 mass % or less water and It consists of 0 mass % or more and 10 mass % or less of a dispersion medium other than water, more preferably, it consists of 99 mass % or more and 100 mass % or less of water, and 0 mass % or more and 1 mass % or less of a dispersion medium other than water. The best system dispersing medium is water. From the viewpoint of not hindering the action of the components contained in the polishing composition, the dispersion medium is preferably water containing as little impurities as possible, and specifically, it is more preferred to use an ion exchange resin to remove impurities. After ionization, pure water, ultrapure water or distilled water is passed through a filter to remove foreign matter. [pH] The pH of the polishing composition of the present invention is preferably 8 or more. If the pH is 8 or above, the effect of further increasing the grinding speed is obtained. The pH is more preferably 8.5 or more, still more preferably 9 or more, and particularly preferably 9.5 or more. On the other hand, from the viewpoint of safety, the pH of the polishing composition is preferably 13 or less, more preferably 12 or less, and still more preferably 11.5 or less. Also, the pH of the polishing composition can be determined by using a pH meter (such as a glass electrode type hydrogen ion concentration indicator (model: F-23) manufactured by Horiba Manufacturing Co., Ltd.) and using a standard buffer solution (phthalate pH buffer pH: 4.01 (25°C), neutral phosphate pH buffer pH: 6.86 (25°C), carbonate pH buffer pH: 10.01 (25°C)), after performing 3-point calibration, place the glass electrode Add the grinding composition and measure the value after stabilization for more than 2 minutes to determine the value. Although the polishing composition of the present invention contains abrasive grains, a dispersion medium and an alkali compound as essential components, if it is difficult to obtain the desired pH by these alone, pH may be added within the range that does not hinder the effect of the present invention. Adjusters adjust pH. The pH adjuster may be any base other than an acid or the above-mentioned alkali compound, or may be any inorganic compound or organic compound. The pH adjuster can be used alone or in mixture of two or more types. Specific examples of the acid used as a pH adjuster include inorganic acids such as sulfuric acid, nitric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid; formic acid, acetic acid, propionic acid, butyric acid, gyrosic acid, 2 -Methylbutanoic acid, n-hexanoic acid, 3,3-dimethylbutanoic acid, 2-ethylbutanoic 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 Carboxylic acids such as acid, phthalic acid, malic acid, tartaric acid, citric acid and lactic acid, and organic acids such as organic sulfuric acid such as methanesulfonic acid, ethanesulfonic acid and 2-isethionic acid. Specific examples of the base that can be used as a pH adjuster include compounds other than the above-mentioned alkali compounds. Examples include hydroxides or salts of Group 2 elements, quaternary ammonium hydroxide or salts thereof, amines, and the like. Specific examples of salts include carbonates, bicarbonates, sulfates, acetates, and the like. The amount of the pH adjuster added is not particularly limited, and may be appropriately adjusted so that the polishing composition reaches a desired pH. [Other ingredients] The polishing composition of the present invention may further contain, if necessary, a dispersing agent, a preservative, an antifungal agent, a polishing accelerator, a protective film forming agent, etc. within the scope that does not significantly hinder the effect of the present invention. Known additives used in the composition are used. Hereinafter, the polishing accelerator and protective film forming agent preferably used in the present invention will be described. [Grinding accelerator] By adding a polishing accelerator to the polishing composition of the present invention, the polishing speed of the object to be polished can be further increased. The polishing accelerator is not particularly limited, but a compound having an amine group is preferred. Compounds having an amine group are considered to have electron donating properties, thereby relaxing the covalent bonds of the object to be polished, thereby accelerating the polishing speed. Specific examples of the polishing accelerator include N,N-bis(2-hydroxyethyl)glycine, N-(2-hydroxyethyl)iminodiacetic acid, iminodiacetic acid, aspartame Amino acid, aspartic acid, arginine, nitrogen-based ginseng (methylenephosphonic acid), 1-hydroxyethane-1,1-diphosphonic acid, 2-phosphonobutane-1,2, 4-tricarboxylic acid, N,N,N',N'-ethylenediamine quaternary (methylenephosphonic acid) hydrate, triethylenetetraminehexaacetic acid, glutamic acid, anhydrous piperazine, piperazine hexahydrate , 1-(2-aminoethyl)piperazine, N-methylpiperazine, N-(2-aminoethyl)piperazine, guanidine, triethanolamine, hydroxymethylaminomethane, N-methyl Base-D-reduced glucosamine, acetylglucosamine, ethanolamine, 2-amino-2-ethyl-1,3-propanediol, isopropanolamine, diisopropanolamine, triisopropanol Amine, diglycolamine, 2-amino-2-methyl-1-propanol, etc. A polishing accelerator may be used individually by 1 type or in combination of 2 or more types. In addition, a synthetic product or a commercial product may be used as a polishing accelerator. Among these polishing accelerators, N-(2-aminoethyl)piperazine, arginine, and glutamic acid are preferred. The content (concentration) of the polishing accelerator in the polishing composition (the total amount when there are two or more types) is not particularly limited, but it is preferably 0.1 g/kg or more based on the total amount of the polishing composition. , more preferably 0.5 g/kg or more, still more preferably 1.0 g/kg or more. Moreover, the content (concentration) of the polishing accelerator in the polishing composition is preferably 10.0 g/kg or less, more preferably 7.0 g/kg or less, and still more preferably 5.0 g/kg relative to the total amount of the polishing composition. /kg or less. [Protective Film Forming Agent] By adding a protective film forming agent to the polishing composition of the present invention, it is possible to further suppress the occurrence of depressions or steps on the surface of the polished object after polishing. Examples of protective film forming agents include water-soluble polymers. Examples of water-soluble polymers include guar gum, locust bean gum, quince seeds, carrageenan, galactan, acacia gum, tragacanth gum, pectin, mannose, xanthan gum, and dextran. , natural polymers such as succinate, codlan, hyaluronic acid, gelatin, casein, albumin, collagen, dextrin, pullulan, etc.; poly(meth)acrylic acid, polyvinyl methyl Ether, polyacrylamide, acrylic acid/acrylate copolymer, polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, ethyl cellulose , ethylhydroxyethylcellulose, carboxymethylcellulose, polyvinylimidazole, polyvinylcarbazole, polyvinylpyrrolidone, polyN-vinylformamide, polyvinylcaprolactam, polyethylene Synthetic polymers such as piperidine-based, vinyl alcohol·vinyl pyrrolidone copolymer, vinyl alcohol·ethylene copolymer, polyethylene oxide (PEO), ethylene oxide·propylene oxide copolymer, etc. In this specification, the term "copolymer" includes various copolymers such as random copolymers, alternating copolymers, block copolymers, and graft copolymers, unless otherwise specified. The above-mentioned water-soluble polymer may be used alone or in combination of two or more types. In addition, synthetic products or commercial products may be used as the above-mentioned water-soluble polymer. Among these water-soluble polymers, hydroxyethyl cellulose, polyvinylpyrrolidone, and vinyl alcohol vinylpyrrolidone copolymer are preferred, and polyvinylpyrrolidone and vinyl alcohol vinylpyrrolidone copolymer are more preferred. Although the weight average molecular weight of the water-soluble polymer is not particularly limited, in the case of a natural polymer, it is preferably from 100,000 to 2,000,000, more preferably from 800,000 to 1,500,000. Moreover, when it is a synthetic polymer, it is preferably 5,000 or more and 500,000 or less, more preferably 15,000 or more and 100,000 or less, still more preferably 20,000 or more and 60,000 or less. This weight average molecular weight is a value measured using gel permeation chromatography (GPC) using polyethylene oxide as a standard substance. If the protective film-forming agent contains the above-mentioned water-soluble polymer, it may contain a protective film-forming agent other than the above-mentioned water-soluble polymer. Examples of protective film-forming agents other than the above-mentioned water-soluble polymers include acid phosphates having an oxyalkyl group (C12, C14, C16, C18), isotridecanoic acid phosphate, oleic acid phosphate, and tetradecanoic acid. Phosphate, glycolic acid phosphate, 2-hydroxymethyl methacrylate acid phosphate, dibutyl phosphate, bis(2-ethylhexyl)phosphate, diethylbenzyl phosphate, triphenyl Phosphoric acid such as phosphine, monoethyl phosphate, mono-n-butyl phosphate, mono-n-octyl phosphate, mono-n-lauryl phosphate, mono(2-hydroxyethyl methacrylate) phosphate, etc. Esters; surfactants such as ammonium lauryl sulfate, triethanolamine lauryl sulfate, polyoxyethylene alkyl ether sulfate triethanolamine, etc.; hydrogen peroxide, sodium peroxide, barium peroxide, ozone water, silver (II) salt, iron (III) Salt, permanganic acid, chromic acid, dichromic acid, peroxydisulfuric acid, peroxyphosphoric acid, peroxysulfuric acid, peroxyboric acid, performic acid, peracetic acid, perbenzoic acid, perphthalic acid, hypochlorite Grinding objects such as acids, hypobromic acid, hypoiodic acid, chloric acid, chlorous acid, perchloric acid, bromic acid, iodic acid, periodic acid, persulfuric acid, dichloroisocyanuric acid and their salts Compounds (oxidants) that act on the surface; etc. In addition, polyethylene oxide (polyethylene glycol), ethylene oxide/propylene oxide copolymer, etc. having a weight average molecular weight of 2,000 or less can also be used as a protective film-forming agent in addition to the above-mentioned water-soluble polymers. Polyoxyethylene (polyethylene glycol) and ethylene oxide·propylene oxide copolymer with a weight average molecular weight of less than 2000 can replace the above-mentioned water-soluble polymer, or can be used together with the above-mentioned water-soluble polymer as a protective film forming agent. The role of the protective film-forming agent, when the protective film-forming agent is a polymer or a surfactant, is considered to be mainly through specific functional groups, through the polycrystalline silicon (polysilicon) doped with impurities and the non-toxicity of the doped impurities. The adsorption protective film of crystalline silicon (amorphous silicon) is formed. In addition, when the protective film forming agent is an oxidizing agent, it is considered that it mainly forms an oxide film on the surface of impurity-doped polycrystalline silicon (polysilicon) and impurity-doped amorphous silicon (amorphous silicon), and the resultant protective film is form. These protective film-forming agents other than water-soluble polymers may be used alone or in combination of two or more types. In addition, as the protective film-forming agent other than the water-soluble polymer, synthetic products or commercial products may be used. The content (concentration) of the protective film forming agent in the polishing composition (when there are two or more types, the total amount) is not particularly limited, but when it is a water-soluble polymer, the content (concentration) relative to the total amount of the polishing composition , preferably 0.01 g/kg or more, more preferably 0.1 g/kg or more, still more preferably 0.5 g/kg or more, particularly preferably 1.0 g/kg or more. Furthermore, when the content (concentration) of the protective film-forming agent in the polishing composition is a water-soluble polymer, it is preferably 10.0 g/kg or less, more preferably 5.0 g/kg relative to the total amount of the polishing composition. below, and more preferably below 3.0 g/kg. In addition, the content (concentration) of protective film-forming agents other than the water-soluble polymer used together with the water-soluble polymer (when there are two or more types, the total amount) is not particularly limited, but relative to the composition for polishing The total amount of substances is preferably 0.01 g/kg or more, more preferably 0.05 g/kg or more, and still more preferably 0.1 g/kg or more. Furthermore, the content (concentration) of the protective film-forming agent other than the water-soluble polymer used together with the water-soluble polymer in the polishing composition is preferably 1.0 g/kg or less relative to the total amount of the polishing composition. , more preferably 0.5 g/kg or less, still more preferably 0.4 g/kg or less. [Method for manufacturing the polishing composition] The method for manufacturing the polishing composition of the present invention is not particularly limited. For example, it can be by adding abrasive grains, alkali compounds, and other additives if necessary to a dispersion medium (such as water). Stir and mix. Details of each ingredient are as above. Accordingly, the present invention provides a method for producing the polishing composition of the present invention including the step of mixing the abrasive grains, the dispersion medium and the alkali compound. Although the temperature when mixing each component is not particularly limited, it is preferably not less than 10°C and not more than 40°C, and heating may be performed in order to increase the dissolution rate. In addition, the mixing time is not particularly limited as long as uniform mixing is possible. [Polishing Method and Manufacturing Method of Semiconductor Substrate] As described above, the polishing composition of the present invention is suitably used for polishing a polishing object containing at least one of impurity-doped polycrystalline silicon and impurity-doped amorphous silicon. Therefore, the present invention provides a polishing method in which a polishing object containing at least one of impurity-doped polycrystalline silicon and impurity-doped amorphous silicon is polished using the polishing composition of the present invention. Furthermore, the present invention provides a method for manufacturing a semiconductor substrate, which includes the step of polishing a semiconductor substrate containing at least one of impurity-doped polycrystalline silicon and impurity-doped amorphous silicon using the aforementioned polishing method. As a polishing device, a general polishing device including a holder that holds a substrate having a polishing object, a motor that can change the number of revolutions, etc., and a polishing platen to which a polishing pad (polishing cloth) can be attached can be used. As the polishing pad, general nonwoven fabrics, polyurethane, porous fluororesin, etc. can be used without particular limitation. In the polishing pad, it is preferable to carry out groove processing such that the polishing liquid is retained. Regarding grinding conditions, for example, the rotation speed of the grinding plate is preferably 10 rpm (0.17s ^-1 ) or more and 500rpm (8.3s ^-1 ) or less. The pressure (polishing pressure) applied to the substrate having the object to be polished is preferably 0.5 psi (3.4 kPa) or more and 10 psi (68.9 kPa) or less. The method of supplying the polishing composition to the polishing pad is not particularly limited. For example, a continuous supply method using a pump or the like may be used. Although this supply amount is not limited, it is generally preferable that the surface of the polishing pad is coated with the polishing composition of the present invention. After the polishing is completed, the substrate is washed in running water, and the water droplets attached to the substrate are dropped and dried using a spin dryer or the like to obtain a substrate having a layer containing metal. The polishing composition of the present invention may be a one-liquid type or a multi-liquid type that is initially a two-liquid type. Furthermore, the polishing composition of the present invention can be prepared by diluting the original solution of the polishing composition to a diluent such as water, for example, 10 times or more. [Examples] The present invention will be described in further detail using the following Examples and Comparative Examples. However, the technical scope of the present invention is not limited only to the following examples. However, unless otherwise stated, "%" and "parts" mean "mass %" and "mass parts" respectively. Prepare the following 300mm blank wafer for the grinding object. Individual wafers were cut into coupons of 60 mm × 60 mm wafers as test pieces, and a polishing test was performed. However, the content (doping amount) of impurities is relative to 100 mass% of polysilicon: •Polysilicon doped with n-type impurities (1) Polysilicon doped with phosphorus (phosphorus content: 0.05 mass%) (2) Phosphorus-doped polysilicon (phosphorus content: 0.1 mass%) (3) Arsenic-doped polysilicon (arsenic content: 0.01 mass%) (4) Arsenic-doped polysilicon (arsenic content: 0.05 mass%) •Doped Polysilicon doped with p-type impurities (1) Polysilicon doped with boron (boron content: 0.05 mass%) (2) Polysilicon doped with boron (boron content: 0.1 mass%) (3) Polysilicon doped with gallium (Gallium content: 0.05 mass%) (4) Gallium-doped polysilicon (Gallium content: 0.1 mass%). <Preparation of polishing composition> (Example 1) By combining abrasive grains (colloidal silica; average primary particle diameter: 90 nm, average secondary particle diameter: 220 nm) and potassium hydroxide as an alkali compound, Stir and mix the abrasive grain concentration in the dispersion medium (pure water) so that the concentration of the alkali compound becomes 0.19 mass%, and the pH becomes 10.0 to prepare a polishing composition (mixed Temperature: about 25°C, mixing time: about 10 minutes). Here, the average primary particle size of the abrasive grains is calculated from the specific surface area of the abrasive grains measured by the BET method using "Flow SorbII 2300" manufactured by Micromeritex Corporation, and the density of the abrasive grains. In addition, the average secondary particle size of the abrasive grains was measured using a dynamic light scattering particle size and particle size distribution apparatus UPA-UTI151 manufactured by Nikkiso Co., Ltd. The average degree of association of abrasive grains in Table 1 and Table 2 is a value obtained by dividing the value of the average secondary particle diameter of the abrasive grains by the value of the average primary particle diameter. Furthermore, the pH of the polishing composition (liquid temperature: 25°C) was confirmed with a pH meter (manufactured by Horiba Manufacturing Co., Ltd., model: LAQUA). (Examples 2 to 16, Comparative Examples 1 to 4) A polishing composition was prepared in the same manner as in Example 1, except that the type and content of the alkali compound and the content of the abrasive grains were changed as shown in Table 1 below. Incidentally, Comparative Example 3 is an example in which an alkali compound is not added, and Comparative Example 4 is an example in which abrasive grains are not added. <Evaluation 1: Evaluation of polishing speed> Using each of the polishing compositions obtained in Examples 1 to 16 and Comparative Examples 1 to 4, the polishing speed of each of the above-mentioned polishing objects was measured under the following polishing conditions. (Grinding device and grinding conditions) Grinding device: Wrapping machine EJ-380IN-CH manufactured by Nitta Haas Co., Ltd. Polishing pad: Hard polyurethane pad IC1010 manufactured by Nitta Haas Co., Ltd. Grinding pressure: 3.0 psi (20.7kPa) (still, 1psi=6894.76Pa) Number of rotations of the grinding plate: 60rpm Number of rotations of the head (carrier): 100rpm Supply of grinding composition: Pouring and grinding composition Supply volume: 100mL/min Grinding time: 60 Second. (Polishing rate) The polishing rate is calculated by the following formula. Still, 10Å =1nm. [Number 1] The film thickness was determined using Lambda AceVM-2030, an optical interference type film thickness measuring device manufactured by SCREEN Semiconductor Solutions Co., Ltd., and the polishing speed was evaluated by dividing the difference in film thickness before and after polishing by the polishing time. The results are shown in Table 1 below. It can be clearly seen from the above Table 1 that the polishing composition of the embodiment can increase the polishing speed of impurity-doped polycrystalline silicon (polysilicon) compared with the polishing composition of the comparative example. (Examples 17 to 19) A polishing composition was prepared in the same manner as in Example 1, except that abrasive grains having different particle sizes were used as shown in Table 2 below. Furthermore, potassium hydroxide was used as the alkali compound in any of Examples 17 to 19, and its concentration was set to 0.19 mass%. It was carried out similarly to the above-mentioned Evaluation 1, and measured the polishing speed when each of the above-mentioned polishing objects was polished under polishing conditions using each of the polishing compositions obtained in Examples 17 to 19. In addition, the polishing speed when polishing the TEOS substrate and the silicon nitride (SiN) substrate was measured under the same polishing conditions. The smaller the ratio of the polishing speed of polycrystalline silicon (polysilicon) doped with impurities and TEOS substrates or SiN substrates made of other materials means that the grinding speed of polishing objects containing polycrystalline silicon (polysilicon) doped with impurities and other materials is reduced even more. Surface differences. These evaluation results are shown in Table 2 below together with the evaluation results using the polishing composition of Example 1. As is clear from Table 2 above, the polishing compositions of Examples 17 to 19 are polycrystalline silicon (polysilicon) doped with impurities and have excellent polishing speeds. (Examples 20 to 27) Each polishing composition was prepared in the same manner as in Example 1, except that the polishing accelerator shown in Table 3 below was added. Each of the obtained polishing compositions was used in the same manner as the above-mentioned evaluation 1, and the polishing speed when each of the above-mentioned polishing objects was polished under polishing conditions was measured. These evaluation results are shown in Table 4 below. Table 4 below also shows the results of Example 1 in which no polishing accelerator was added. From the above Table 4, it is clear that the polishing compositions of Examples 20 to 27 can further increase the polishing speed of impurity-doped polycrystalline silicon (polysilicon) compared to Example 1 without adding a polishing accelerator. (Examples 28 to 49) As shown in Table 5 below, the same procedure as in Example 1 was performed except that the type and amount of the alkali compound, the type and amount of the polishing accelerator, and the type and amount of the protective film forming agent were changed. , to prepare each polishing composition. In addition, the types of protective film forming agents shown in Table 5 below are as follows: •PVP2: polyvinylpyrrolidone, weight average molecular weight 40,000 •PEG: polyethylene glycol, weight average molecular weight 200. Each of the obtained polishing compositions was used in the same manner as the above-mentioned evaluation 1, and the polishing speed when each of the above-mentioned polishing objects was polished under polishing conditions was measured. The evaluation results are shown in Table 6 below. Table 6 below also shows the results of Example 1 in which the polishing accelerator and the protective film forming agent were not added. From the above Table 6, it is clear that the polishing compositions of Examples 28 to 49 that add protective film forming agents can reduce the ratio of the polishing speed of impurity-doped polycrystalline silicon (polysilicon) to the polishing speed of other materials. It is thus revealed that the polishing compositions of Examples 28 to 49 can reduce the level of the surface of the object to be polished. (Examples 50 to 63) Preparation was carried out in the same manner as in Example 1, except that the type and content of the alkali compound, the type and content of the abrasive grains, and the type and content of the protective film forming agent were changed as shown in Table 7 below. Grinding compositions. However, the types of protective film forming agents shown in Table 2 are as follows: •PVP1: polyvinylpyrrolidone, weight average molecular weight 10,000 •PVP2: polyvinylpyrrolidone, weight average molecular weight 40,000 •PVP3: polyvinylpyrrolidone, Weight average molecular weight 360000 •HEC: hydroxyethyl cellulose, weight average molecular weight 1200000 •PVA-PVP: vinyl alcohol vinylpyrrolidone graft copolymer; the main chain is vinyl alcohol polymer (weight average molecular weight 80000) as a side chain , bonded vinylpyrrolidone polymer (weight average molecular weight of all side chain parts: 80,000) •SURF1: Mono-n-octylphosphate •SURF2: Ammonium lauryl sulfate •EO-PO-EO: Ethylene oxide-propylene oxide- In the ethylene oxide block copolymer, the EO portions at both ends have almost the same weight and are included in a proportion of about 10% by weight based on the entire copolymer. Moreover, the total weight average molecular weight is 1250. •H ₂ O ₂ : Hydrogen peroxide. <Evaluation 2: Evaluation of dents> To measure the amount of dents, first prepare polycrystalline silicon (polysilicon) doped with individual impurities and polish it until the insulating film is exposed, with alternately arranged 100-μm-wide wiring and 100-μm-wide insulating films. Area wafer. Then, polishing was performed using each of the polishing compositions described in Examples 50 to 63 under the same polishing conditions as the polishing speed evaluation in Examples 1 to 16. Then, using Wide areaAFM WA-1300 (manufactured by Hitachi Construction Machinery Co., Ltd.), the amount of dents (the depth of dents in polycrystalline silicon doped with individual impurities using the insulating film as a reference) was measured (unit: Å). The evaluation results of dents are shown in Table 8 below. Table 8 below also shows the evaluation results of dents when using the polishing composition of Example 1 that does not contain a protective film-forming agent. As is clear from Table 8 above, when the polishing compositions of Examples 50 to 63 containing a protective film-forming agent are used, sinking is further suppressed compared to the polishing composition of Example 1 which does not contain a protective film-forming agent. .

Claims (11)

A polishing composition used for polishing a polishing object containing at least one of impurity-doped polycrystalline silicon and impurity-doped amorphous silicon, characterized by containing abrasive grains, and dispersed Media, and at least one selected from the group consisting of hydroxides of alkali metals, alkali metal salts of inorganic acids, ammonium salts of inorganic acids, alkali metal salts of organic acids, ammonium salts of organic acids, and ammonia Alkaline compound; the average secondary particle diameter of the abrasive grains is 100 nm or more and 500 nm or less. The polishing composition of claim 1, wherein the abrasive particles are colloidal silica. The polishing composition of claim 1 or 2, wherein the average primary particle diameter of the abrasive grains is 20 nm or more and 300 nm or less. The polishing composition of claim 1 or 2, wherein the content of the abrasive grains is 0.1 mass % or more and 20 mass % or less based on the total mass of the polishing composition. The polishing composition of claim 1 or 2, wherein the pH is 8 or more. The polishing composition of claim 1 or 2, wherein the aforesaid alkali compound It is at least one selected from potassium hydroxide, potassium salt of inorganic acid, ammonium salt of inorganic acid, potassium salt of organic acid, ammonium salt of organic acid and ammonia. The polishing composition of claim 1 or 2 further contains a polishing accelerator. The polishing composition according to claim 7, wherein the polishing accelerator is a compound having an amine group. A method for producing a polishing composition according to any one of claims 1 to 8, which includes the step of mixing the abrasive grains, the dispersion medium and the alkali compound. A polishing method, which includes the step of polishing a polishing object containing at least one of impurity-doped polycrystalline silicon and impurity-doped amorphous silicon using the polishing composition according to any one of claims 1 to 8. A method for manufacturing a semiconductor substrate, which has the step of grinding a semiconductor substrate containing at least one of impurity-doped polycrystalline silicon and impurity-doped amorphous silicon by the grinding method of claim 10.