Polishing composition

Abstract

To provide: a polishing composition capable of reducing a polishing removal rate of polysilicon; and means capable of reducing a polishing removal rate of polysilicon and further reducing defects on a surface of polysilicon after polishing.SOLUTION: A polishing composition contains abrasive grains and a polishing removal rate inhibitor that reduces a polishing removal rate of polysilicon, and the polishing removal rate inhibitor is a water-soluble polymer meeting all requirements below: 1) a number average molecular weight is 200 or more and 600 or less; 2) a compound is contained having a repeating unit formed of AO, where A is an alkylene group and O is an oxygen atom; and 3) a compound having a special repeating unit in which two oxygen atoms are further added to the repeating unit is contained in an amount of more than 0 mass% and less than 0.1 mass% with respect to the entire water-soluble polymer.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In today's semiconductor industry, technological development in semiconductor manufacturing processes is constantly progressing. In recent years, as the requirements for wafer surface quality have become increasingly strict, higher levels of smoothness and flatness are also required in wafer polishing.

[0003] It is already known that chemical mechanical polishing (CMP) can improve the surface quality of wafers. CMP utilizes the interaction of chemical and mechanical action to achieve flatness of the polished surface. The chemical action is provided by a composition also known as a CMP slurry. The mechanical action is usually achieved by a polishing pad mounted on a platen and pressed against the polished surface.

[0004] CMP is applied to, for example, the gate formation process in transistor fabrication. During transistor fabrication, Si-containing materials such as silicon, polycrystalline silicon (polysilicon), silicon oxide (silicon oxide), and silicon nitride (silicon nitride) are often polished, and depending on the transistor structure, it is necessary to control the polishing rate of each Si-containing material.

[0005] For example, Patent Document 1 provides a polishing composition that can be suitably used for polishing silicon materials such as elemental silicon and silicon compounds, and a polishing method using the same. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-251561 Summary of the Invention [Problem to be solved by the invention]

[0007] While there is a need to control the polishing rate of each Si-containing material as described above, the present inventors have found that there is a need to suppress the polishing rate of polysilicon in some cases.

[0008] However, polysilicon and silicon oxide (silicon dioxide) are soft and generally known to react easily with abrasives, making it difficult to suppress the removal rate of polysilicon.

[0009] Therefore, an object of the present invention is to provide a polishing composition that can suppress the removal rate of polysilicon.

[0010] Furthermore, in the course of investigating ways to solve the above problems, the present inventors discovered that defects and the like exist on the surface of the polished polysilicon.

[0011] Therefore, another object of the present invention is to provide a means for further reducing defects on the surface of polished polysilicon. [Means for solving the problem]

[0012] The present inventors have conducted extensive research to solve at least one of the above problems, and as a result, have found that this can be achieved by a polishing composition containing abrasive grains and a polishing rate suppressor that suppresses the polishing rate of polysilicon, wherein the polishing rate suppressor is a water-soluble polymer that meets all of the following requirements: 1) a number-average molecular weight of 200 to 600, 2) a compound having a repeating unit composed of A-O, where A is an alkylene group and O is an oxygen atom, and 3) a compound having a special repeating unit in which two additional oxygen atoms are added to the repeating unit, in an amount of more than 0% by mass and less than 0.1% by mass of the entire water-soluble polymer, thereby completing the present invention. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a polishing composition that can suppress the removal rate of polysilicon, and also to provide a means for further reducing defects on the surface of polished polysilicon. DETAILED DESCRIPTION OF THE INVENTION

[0014] In this specification, "X to Y" refers to the range of values ​​between X and Y, including the upper and lower limits of the preceding and following values. When multiple "X to Y" are used, such as "X1 to Y1" or "X2 to Y2," the disclosure of each value as an upper limit, the disclosure of each value as a lower limit, and combinations of these upper and lower limits are all disclosed (i.e., they constitute legitimate grounds for amendment). Specifically, amendments to X1 or greater, amendments to Y2 or less, amendments to X1 or less, amendments to Y2 or greater, amendments between X1 and X2, and amendments between X1 and Y2 must all be deemed legitimate. Unless otherwise specified, all operations and measurements of physical properties are performed at room temperature (20-25°C) and a relative humidity of 40-50% RH. The concentrations described herein may be concentrations at the point of use (POU) or concentrations before dilution to the POU concentration.

[0015] According to one aspect of the present invention, a polishing composition contains abrasive grains and a polishing rate suppressor that suppresses the polishing rate of polysilicon, wherein the polishing rate suppressor is a water-soluble polymer that meets all of the following requirements: 1) a number-average molecular weight of 200 to 600; 2) a compound having a repeating unit composed of AO, where A is an alkylene group and O is an oxygen atom; and 3) a compound having a special repeating unit in which two additional oxygen atoms are added to the repeating unit, in an amount greater than 0% by mass and less than 0.1% by mass of the water-soluble polymer. This configuration provides a polishing composition that can suppress the polishing rate of polysilicon. It also provides a means for further reducing defects on the surface of polished polysilicon.

[0016] In this specification, the term "residue" refers to foreign matter adhering to the surface of the polished object. Examples of the residue include organic residue, particle residue derived from abrasive grains contained in the polishing composition, and other residues other than particle residue and organic residue.

[0017] As used herein, organic residue refers to foreign matter adhering to the surface of a polished object, including components composed of organic substances such as organic low-molecular-weight compounds and polymeric compounds, and organic salts. Examples of organic residue adhering to a polished object include pad debris generated from the pad used in the polishing process described below, and components derived from additives contained in the polishing composition used in the polishing process. Because organic residue differs significantly in color and shape from other residues, determining whether a residue is organic can be done visually, for example, by observation with a scanning electron microscope (SEM). Furthermore, determining whether a residue is organic can also be done, if necessary, by elemental analysis using an energy dispersive X-ray analyzer (EDX) attached to the SEM.

[0018] As used herein, "water-soluble" means that the solubility in water (25°C) is 1 g / 100 mL or more, and "polymer" means a (co)polymer having at least one of a weight-average molecular weight (Mw) and a number-average molecular weight (Mn) of 200 or more.

[0019] [Abrasive grain] The polishing composition of the present invention contains abrasive grains, which have the function of mechanically polishing an object to be polished, thereby increasing the polishing rate of the object to be polished by the polishing composition.

[0020] The types of abrasive grains used in the polishing composition of the present invention include, for example, metal oxides such as silica, alumina, zirconia, and titania. The abrasive grains may be used alone or in combination of two or more. The abrasive grains may be commercially available products or synthetic products.

[0021] The abrasive grains are preferably silica, more preferably colloidal silica. Methods for producing colloidal silica include the sodium silicate method and the sol-gel method. Colloidal silica produced by either method is suitable for use as the colloidal silica of the present invention. However, from the viewpoint of reducing metal impurities, colloidal silica produced by the sol-gel method is preferred. Colloidal silica produced by the sol-gel method is preferred because it contains less metal impurities and corrosive ions such as chloride ions, which tend to diffuse in semiconductors. Colloidal silica can be produced by the sol-gel method using a conventionally known method. Specifically, colloidal silica can be obtained by hydrolysis and condensation reaction using a hydrolyzable silicon compound (e.g., alkoxysilane or its derivative) as a raw material. Commercially available colloidal silica may also be used. According to one embodiment of the present invention, 85% by mass or more, 90% by mass or more, 95% by mass or more, 98% by mass or more, or 99% by mass or more of the particles constituting the abrasive grains is silica (particularly colloidal silica) (up to 100% by mass).

[0022] The shape of the colloidal silica is not particularly limited and may be spherical or non-spherical. Specific examples of non-spherical shapes include polygonal prisms such as triangular prisms and quadrangular prisms, cylinders, bale-shaped cylinders in which the center is bulged more than the ends, doughnut-shaped discs with a hole in the center, plates, cocoons with a central constriction, associative spheres in which multiple particles are integrated, confetti-shaped colloids with multiple protrusions on the surface, and rugby ball-shaped colloids, and are not particularly limited.

[0023] In the polishing composition of the present invention, the colloidal silica may have cationic groups on its surface. That is, the colloidal silica may be cation-modified colloidal silica (cation-modified colloidal silica). Preferred examples of cation-modified colloidal silica include colloidal silica having amino groups fixed to its surface. Examples of methods for producing colloidal silica having such cationic groups include a method described in JP 2005-162533 A in which a silane coupling agent having an amino group, such as aminoethyltrimethoxysilane, aminopropyltrimethoxysilane, aminoethyltriethoxysilane, aminopropyltriethoxysilane, aminopropyldimethylethoxysilane, aminopropylmethyldiethoxysilane, or aminobutyltriethoxysilane, is fixed to the surface of silica particles. This method allows for the production of colloidal silica having amino groups fixed to its surface (amino-modified colloidal silica).

[0024] In the polishing composition of the present invention, the colloidal silica may have an anionic group on its surface. That is, the colloidal silica may be anion-modified colloidal silica (anion-modified colloidal silica). Preferred examples of anion-modified colloidal silica include colloidal silica having anionic groups, such as carboxylic acid groups, sulfonic acid groups, phosphonic acid groups, and aluminic acid groups, fixed to its surface. The method for producing colloidal silica having such an anionic group is not particularly limited, and examples thereof include a method of reacting colloidal silica with a silane coupling agent having an anionic group at its terminal.

[0025] As a specific example, sulfonic acid groups can be immobilized on colloidal silica by the method described in, for example, "Sulfonic acid-functionalized silica through quantitative oxidation of thiol groups," Chem. Commun. 246-247 (2003). Specifically, colloidal silica with sulfonic acid groups immobilized on its surface (sulfonic acid-immobilized colloidal silica, sulfonic acid-modified colloidal silica) can be obtained by reacting colloidal silica with a silane coupling agent having a thiol group, such as 3-mercaptopropyltrimethoxysilane, and then oxidizing the thiol group with hydrogen peroxide.

[0026] Carboxylic acid groups can be immobilized on colloidal silica 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, colloidal silica with carboxylic acid groups immobilized on the surface (carboxylic acid-immobilized colloidal silica, carboxylic acid-modified colloidal silica) can be obtained by coupling a silane coupling agent containing a photolabile 2-nitrobenzyl ester to colloidal silica and then irradiating the silica with light.

[0027] Among these, from the viewpoint of further suppressing the removal rate of polysilicon and further reducing defects on the surface of the polished polysilicon, the abrasive grains are preferably anion-modified colloidal silica, and more preferably colloidal silica having sulfonic acid groups fixed to the surface (sulfonic acid-fixed colloidal silica, sulfonic acid-modified colloidal silica).

[0028] The size of the abrasive grains according to the present invention is not particularly limited. For example, the average primary particle diameter of the abrasive grains is preferably 5 nm or more, more preferably 10 nm or more, even more preferably 15 nm or more, and particularly preferably 20 nm or more. As the average primary particle diameter of colloidal silica increases, the polishing rate of the object to be polished using the polishing composition increases. Furthermore, the average primary particle diameter of the abrasive grains is preferably 200 nm or less, more preferably 150 nm or less, even more preferably 100 nm or less, and particularly preferably 50 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 5 nm or more and 200 nm or less, more preferably 10 nm or more and 150 nm or less, even more preferably 15 nm or more and 100 nm or less, and particularly preferably 20 nm or more and 50 nm or less. 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, assuming that the abrasive grains are spherical. For example, the average primary particle size of the abrasive grains can be calculated from the specific surface area of ​​the abrasive grains measured by the BET method using a Micromeritics "Flow Sorb II 2300" and the true density of the abrasive grains.

[0029] The average secondary particle diameter of the abrasive grains is not particularly limited, but is preferably 10 nm or more, more preferably 15 nm or more, even more preferably 20 nm or more, and particularly preferably 25 nm or more. As the average secondary particle diameter of the abrasive grains increases, the resistance during polishing decreases, enabling stable polishing. Furthermore, the average secondary particle diameter of the abrasive grains is preferably 400 nm or less, more preferably 300 nm or less, even more preferably 200 nm or less, and particularly preferably 100 nm or less. As the average secondary particle diameter of the abrasive grains decreases, the surface area per unit mass of the abrasive grains increases, increasing the frequency of contact with the workpiece to be polished and further improving the polishing rate. That is, the average secondary particle diameter of the abrasive grains is preferably 10 nm or more and 400 nm or less, more preferably 15 nm or more and 300 nm or less, even more preferably 20 nm or more and 200 nm or less, and particularly preferably 25 nm or more and 100 nm or less. The average secondary particle diameter of the abrasive grains can be measured, for example, by dynamic light scattering, such as laser diffraction scattering.

[0030] The average degree of association of the abrasive grains is preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.0 or less. As the average degree of association of the abrasive grains decreases, defects can be further reduced. The average degree of association of the abrasive grains is also preferably 1.0 or more, more preferably 1.5 or more, and even more preferably 2.0 or more. As the average degree of association of the abrasive grains increases, there is an advantageous effect of improving the polishing rate of the object to be polished with the polishing composition. That is, the average degree of association of the abrasive grains is preferably 1.0 or more and 5.0 or less, more preferably 1.5 or more and 4.0 or less, and even more preferably 2.0 or more and 3.0 or less. This average degree of association is obtained by dividing the average secondary particle size of the abrasive grains by the average primary particle size.

[0031] The upper limit of the aspect ratio of the abrasive grains in the polishing composition is not particularly limited, but is preferably less than 2.0, more preferably 1.8 or less, and even more preferably 1.5 or less.Within this range, defects on the surface of the object to be polished can be further reduced.The aspect ratio is the average value obtained by taking the smallest rectangle that circumscribes the image of the abrasive grains using 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 calculated 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.

[0032] The size of the abrasive grains (average primary particle size, average secondary particle size, average degree of association, etc.) can be appropriately controlled by selecting the method for producing the abrasive grains, etc.

[0033] The concentration (content) of abrasive grains in the polishing composition is not particularly limited.In the case of the polishing composition (typically a slurry-like polishing liquid, sometimes referred to as working slurry or polishing slurry) that is used as a polishing liquid for polishing an object to be polished as it is, the lower limit of the concentration (content) of abrasive grains in the polishing composition is preferably 0.1 mass% or more, more preferably 0.5 mass% or more, more preferably 0.6 mass% or more, even more preferably 0.8 mass% or more, and particularly preferably 1 mass% or more, based on the total mass of the polishing composition.In addition, the upper limit of the concentration (content) of abrasive grains in the polishing composition is preferably 15 mass% or less, more preferably 10 mass% or less, more preferably 8 mass% or less, even more preferably 6 mass% or less, and particularly preferably 5 mass% or less, based on the total mass of the polishing composition.

[0034] That is, in the case of a polishing composition that is used as a polishing liquid directly for polishing an object to be polished, the concentration (content) of the abrasive grains is preferably 0.1 mass% or more and 15 mass% or less, more preferably 0.5 mass% or more and 10 mass% or less, even more preferably 0.6 mass% or more and 8 mass% or less, even more preferably 0.8 mass% or more and 6 mass% or less, and particularly preferably 1 mass% or more and 5 mass% or less, relative to the total mass of the polishing composition.

[0035] Furthermore, in the case of a polishing composition that is diluted and used for polishing (i.e., a concentrate, a raw solution for a working slurry), the concentration (content) of the abrasive grains is usually appropriate to be 30% by mass or less, and more preferably 25% by mass or less, from the viewpoints of storage stability, filterability, etc. Furthermore, from the viewpoint of utilizing the advantages of forming a concentrate, the concentration (content) of the abrasive grains is preferably more than 1% by mass, and more preferably 2% by mass or more.

[0036] When the polishing composition contains two or more types of abrasive grains, the concentration (content) of the abrasive grains means the total amount thereof.

[0037] [Polishing speed suppressor] The polishing rate suppressor contained in the polishing composition of the present invention is a water-soluble polymer that meets all of the following requirements: 1) the number average molecular weight is 200 or more and 600 or less, 2) it contains a compound having a repeating unit composed of AO, where A is an alkylene group and O is an oxygen atom, and 3) it contains more than 0% by mass and less than 0.1% by mass of a compound having a special repeating unit in which two more oxygen atoms are added to the repeating unit, based on the total mass of the water-soluble polymer.

[0038] 1) The water-soluble polymer used as a polishing rate suppressor in the polishing composition of the present invention has a number-average molecular weight of 200 to 600. If the number-average molecular weight is less than 200, the ability to suppress the polishing rate of polysilicon is weak, making it impossible to adjust the polishing rate to a desired level. If the number-average molecular weight exceeds 600, the water-soluble polymer is more likely to be adsorbed onto polysilicon, attracting organic residues through hydrophobic interactions and increasing the number of defects. The number-average molecular weight is preferably 250 or more, more preferably 300 or more, and even more preferably 350 or more. The number-average molecular weight of the water-soluble polymer is preferably 580 or less, more preferably 560 or less, and even more preferably 540 or less. That is, the number-average molecular weight of the water-soluble polymer used as a polishing rate suppressor is preferably 250 to 580, more preferably 300 to 560, and even more preferably 350 to 540. The number-average molecular weight of the water-soluble polymer used as a polishing rate suppressor can be measured by gel permeation chromatography (GPC), and details of the measurement method are described in the Examples.

[0039] 2) The water-soluble polymer as a polishing rate suppressor contained in the polishing composition of the present invention has a repeating unit composed of A-O, where A is an alkylene group and O is an oxygen atom. From another perspective, the water-soluble polymer as a polishing rate suppressor contained in the polishing composition of the present invention has a polyoxyalkylene chain. According to one embodiment of the present invention, the alkylene group represented by A preferably has 1 to 10 carbon atoms, more preferably 2 to 5 carbon atoms, even more preferably 2 to 4 carbon atoms, and particularly preferably 3 carbon atoms. Within such a range, the intended effect of the present invention can be achieved while maintaining the storage stability of the polishing composition.

[0040] Examples of water-soluble polymers having a polyoxyalkylene chain (having a repeating unit composed of AO, where A is an alkylene group and O is an oxygen atom) include polyethylene glycol (PEG), polypropylene glycol (PPG), polytetramethylene glycol, polytetramethylene ether glycol, polypentylene glycol, polyhexylene glycol, polyheptylene glycol, polyoctylene glycol, polynonylene glycol, polydecylene glycol; block or random copolymers of at least two selected from polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; random or block copolymers of ethylene oxide and propylene oxide, or ethylene oxide and butylene oxide; polyglycerin, polyethylene oxide-polyvinyl alcohol graft copolymer; and the like. Among these, the polishing rate suppressor is preferably at least one selected from the group consisting of polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and polyglycerin, more preferably at least one selected from the group consisting of polyethylene glycol, polypropylene glycol, and polytetramethylene glycol, with polypropylene glycol being particularly preferred. According to one embodiment of the present invention, the polishing rate suppressor contains polypropylene glycol, and the water-soluble polymer having a repeating unit composed of AO is composed of 80% by mass or more, 85% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or more (upper limit: 100% by mass).

[0041] 3) The water-soluble polymer used as a polishing rate suppressor in the polishing composition of the present invention contains a compound (also referred to herein as a structural defect compound) having a special repeating unit in which two additional oxygen atoms are added to a repeating unit composed of AO (not composed of AO), and the content of the structural defect compound is greater than 0% by mass and less than 0.1% by mass of the entire water-soluble polymer. Details of 3) will be explained using polypropylene glycol as an example. Polypropylene glycol can be easily prepared because its synthesis method has been established and it is commercially available. However, the present inventors have discovered through analysis using a liquid chromatography mass spectrometry (LC / MS) that such common polypropylene glycols contain trace amounts of compounds (also referred to as structural defect compounds (PPG+O)) that have a repeating unit in which two oxygen atoms are bonded to a polypropylene glycol repeating unit, which differs from the original polypropylene glycol structure. They found that polishing a polysilicon substrate with a polishing composition containing a polypropylene glycol containing such a structural defect compound (i.e., a mixture containing polypropylene glycol and a structural defect compound) results in defects (an increase in organic residues) in the polished polysilicon (Comparative Example 6). Therefore, in order to suppress defects (increase in organic residues), the present inventors attempted to polish a polishing object containing polysilicon with a polishing composition containing polypropylene glycol from which structurally defective compounds had been completely removed (i.e., polypropylene glycol itself). However, they found that other defects (mainly an increase in particle residues (abrasive residues)) occurred in the polished polysilicon (Comparative Example 1). The present inventors then prepared polypropylene glycol containing an extremely small amount of structurally defective compounds, and polished a polishing object containing polysilicon with a polishing composition containing the same. Surprisingly, they found that the amount of defects in the polysilicon could be suppressed, leading to the completion of the present invention (Example). Thus, the polishing rate suppressor of the present invention is a mixture consisting of a water-soluble polymer having a polyoxyalkylene chain (particularly polypropylene glycol) and a specific concentration of structurally defective compounds (compounds having a repeating unit in which two oxygen atoms are bonded to the repeating unit of polypropylene glycol).

[0042] The amount of structurally defective compounds contained in the polishing rate suppressor of the present invention (e.g., a mixture consisting of polypropylene glycol and a specific concentration of structurally defective compounds) can be controlled, for example, by adsorption treatment using a synthetic adsorbent. The adsorption treatment using a synthetic adsorbent can be performed, for example, by preparing an aqueous solution of a mixture containing a water-soluble polymer having a polyoxyalkylene chain (particularly a mixture consisting of polypropylene glycol and a structurally defective compound) at a desired concentration (e.g., 5-19% by mass, 6-18% by mass, 7-17% by mass, 8-16% by mass, 9-15% by mass, 10-14% by mass, or 11-13% by mass), and then mixing and stirring the aqueous solution with a synthetic adsorbent to adsorb impurities onto the synthetic adsorbent. The amount of synthetic adsorbent added can be adjusted appropriately so that the content of structurally defective compounds reaches a predetermined concentration. After the synthetic adsorbent treatment, the used synthetic adsorbent can be removed from the aqueous solution of the water-soluble polymer using a filter.

[0043] According to one embodiment of the present invention, the polishing rate suppressor of the present invention can be prepared by carrying out a treatment on a mixture of a water-soluble polymer having a polyoxyalkylene chain (particularly polypropylene glycol) and a structurally defective compound so that the concentration of the structurally defective compound is greater than 0% by mass and less than 0.1% by mass.

[0044] According to one embodiment of the present invention, a mixture of two or more water-soluble polymers having polyoxyalkylene chains, each having a different content of structural defect compounds, is mixed at an appropriately selected mass ratio to prepare a polishing rate suppressor of the present invention having a concentration of structural defect compounds greater than 0 mass% and less than 0.1 mass%. For example, a water-soluble polymer having polyoxyalkylene chains that does not contain structural defect compounds and a mixture of water-soluble polymers having polyoxyalkylene chains that contain structural defect compounds are mixed at an appropriately selected mass ratio to prepare a polishing rate suppressor of the present invention.

[0045] The polishing rate suppressor of the present invention may be used alone or in combination of two or more.

[0046] According to one embodiment of the present invention, the content (concentration) of the structural defect compound in the mixture of the water-soluble polymer having a polyoxyalkylene chain is 0.0001% by mass or more, 0.0003% by mass or more, 0.0005% by mass or more, 0.0007% by mass or more, 0.0009% by mass or more, 0.001% by mass or more, 0.0011% by mass or more, 0.0013% by mass or more, 0.0015% by mass or more, 0.0017% by mass or more, 0.0019% by mass or more, 0.0021 ... Mass% or more, 0.0023 mass% or more, 0.0025 mass% or more, 0.0027 mass% or more, 0.0029 mass% or more, 0.0031 mass% or more, 0.0033 mass% or more, 0.0035 mass% or more, 0.0037 mass% 0.0039 mass% or more, 0.0041 mass% or more, 0.005 mass% or more, 0.007 mass% or more, 0.01 mass% or more, 0.02 mass% or more, 0.03 mass% or more, or 0.035 mass% or more.

[0047] According to one embodiment of the present invention, the content (concentration) of the structural defect compound in the mixture of the water-soluble polymer having the polyoxyalkylene chain is 0.09% by mass or less, 0.08% by mass or less, 0.07% by mass or less, 0.06% by mass or less, 0.05% by mass or less, 0.04% by mass or less, 0.03% by mass or less, 0.035% by mass or less, 0.02% by mass or less, 0.01% by mass or less, 0.009% by mass or less, 0.007% by mass or less, 0.005% by mass or less, or 0.003% by mass or less.

[0048] The lower limit of the concentration (content) of the polishing rate suppressor in the polishing composition is not particularly limited, but is 0.05% by mass or more, 0.1% by mass or more, 0.15% by mass or more, 0.2% by mass or more, 0.25% by mass or more, 0.3% by mass or more, 0.35% by mass or more, 0.4% by mass or more, 0.45% by mass or more, 0.5% by mass or more, or 0.55% by mass or more. The upper limit of the concentration (content) of the polishing rate suppressor in the polishing composition is 10% by mass or less, 5% by mass or less, 4% by mass or less, 3% by mass or less, 2% by mass or less, 1% by mass or less, 0.9% by mass or less, 0.8% by mass or less, or 0.7% by mass or less. When two or more types are combined, it is recommended that the total concentration be set to the above-mentioned range.

[0049] [Defect reduction agent] The polishing composition of the present invention preferably contains a defect-reducing agent that reduces defects on the surface of polysilicon. The defect-reducing agent adsorbs to the surface of polysilicon and changes the wettability of the polysilicon surface from hydrophobic to hydrophilic. The action of the defect-reducing agent can prevent redeposition of residues and the like on the surface of the polished object.

[0050] The defect-reducing agent used in the present invention is not particularly limited as long as it has the above-mentioned effect, but examples thereof include those containing an alcoholic hydroxyl group, a carboxyl group, an acyloxy group, a sulfo group, a quaternary ammonium structure, a heterocyclic structure, or a vinyl structure in the molecule. From the viewpoint of more easily achieving the effects of the present invention, the defect-reducing agent is preferably a water-soluble polymer having an alcoholic hydroxyl group in the side chain.

[0051] The water-soluble polymer having an alcoholic hydroxyl group in the side chain is not particularly limited, but is preferably a compound containing a vinyl alcohol unit (a structural portion represented by -CH2-CH(OH)-; hereinafter also referred to as "VA unit") in its structure.

[0052] In a compound containing VA units in its structure, all repeating units may be substantially composed of VA units. Alternatively, a compound containing VA units in its structure may further contain non-vinyl alcohol units (structural units derived from monomers other than vinyl alcohol, hereinafter also referred to as "non-VA units") in addition to VA units. Non-VA units are not particularly limited, and examples thereof include structural units derived from ethylene, vinyl acetate, vinyl propionate, vinyl hexanoate, 2-butenediol, etc. When a polymer containing structural units derived from vinyl alcohol contains non-VA units, it may contain only one type of non-VA unit, or may contain two or more types of non-VA units. In a compound containing VA units in its structure, the proportion of the number of moles of VA units to the number of moles of all repeating units is not particularly limited, but is preferably 50% or more, more preferably 65% ​​or more, even more preferably 70% or more, and particularly preferably 75% or more (upper limit: 100%).

[0053] The water-soluble polymer having an alcoholic hydroxyl group in the side chain is preferably at least one selected from the group consisting of polyvinyl alcohol, polyvinyl alcohol derivatives (polyvinyl alcohol derivatives having an alcoholic hydroxyl group in the side chain), copolymers of vinyl alcohol and other monomers (copolymers of vinyl alcohol and other monomers having an alcoholic hydroxyl group in the side chain), and derivatives of such copolymers (derivatives of copolymers of vinyl alcohol having an alcoholic hydroxyl group in the side chain and other monomers).

[0054] The degree of saponification of polyvinyl alcohol is not particularly limited, but is preferably 50 mol% or more, more preferably 65 mol% or more, even more preferably 70 mol% or more, and particularly preferably 75 mol% or more (upper limit 100 mol%).

[0055] An example of a polyvinyl alcohol derivative is modified polyvinyl alcohol, etc. Modified polyvinyl alcohol contains, as non-VA units, a structure in which some of the alcoholic hydroxyl groups of the vinyl alcohol units are substituted with other functional groups (hereinafter also referred to as "modified VA units").

[0056] The modified polyvinyl alcohol is not particularly limited, but examples thereof include carboxy-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, phosphoric acid-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, epoxy-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, nitrile-modified polyvinyl alcohol, pyrrolidone-modified polyvinyl alcohol, silicone-modified polyvinyl alcohol, amino-modified polyvinyl alcohol, quaternary amino-modified polyvinyl alcohol, etc. Furthermore, the modified polyvinyl alcohol is not particularly limited, but examples thereof include compounds obtained by cyclic acetalization of polyvinyl alcohol (e.g., polyvinyl butyral, polyvinyl propylal, polyvinyl ethylal, polyvinyl methylal, etc.).

[0057] The derivatives of copolymers of vinyl alcohol and other monomers are not particularly limited, but examples thereof include compounds that further contain, in addition to VA units and modified VA units, structural units such as structural units derived from ethylene, structural units derived from vinyl ethers having a long-chain alkyl group, and structural units derived from compounds having at least one of an acryloyl group and a methacryloyl group.

[0058] Polysaccharides are also preferably used as the water-soluble polymer having an alcoholic hydroxyl group in the side chain. Examples of polysaccharides include dextrin, maltodextrin, isomaltodextrin (branched maltodextrin), cyclodextrin, branched cyclodextrin, roasted dextrin, polymeric dextrin, indigestible dextrin, inulin, inulin hydrolyzate, agave inulin, LM pectin, HM pectin, pullulan, guar gum, guar gum hydrolyzate, xanthan gum, gum arabic, gum ghatti, native gellan gum, deacylated gellan gum, locust bean gum, tara gum, galactomannan, glucomannan, konjac mannan, curdlan, and karage. Examples of suitable sugars include nan, karaya gum, cassia gum, tamarind seed gum, tragacanth gum, fenugreek gum, psyllium seed gum, succinoglycan, rhamsan gum, alginic acid, sodium alginate, PGA (propylene glycol alginate), soybean polysaccharides, methylcellulose, carboxymethylcellulose, hydroxypropyl cellulose, hydroxypropyl methylcellulose, agar, fucoidan, porphyran, laminaran, starch, resistant starch, isomaltulose, polydextrose, indigestible glucan, and arabinogalactan.

[0059] Among these, the defect reducing agent is more preferably at least one selected from the group consisting of polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, and vinyl alcohol-butenediol copolymer, and even more preferably vinyl alcohol-butenediol copolymer.

[0060] The weight-average molecular weight of the defect-reducing agent is not particularly limited, but is preferably 1,000 or more, preferably 3,000 or more, and more preferably 5,000 or more. The weight-average molecular weight of the defect-reducing agent is not particularly limited, but is preferably 1,000,000 or less, more preferably 100,000 or less, and even more preferably 50,000 or less. That is, the weight-average molecular weight of the defect-reducing agent is preferably 1,000 or more and 1,000,000 or less, preferably 3,000 or more and 100,000 or less, and even more preferably 5,000 or more and 50,000 or less.

[0061] The defect-reducing agent may be used alone or in combination of two or more. In addition, the defect-reducing agent may be a commercially available product or a synthetic product.

[0062] From the viewpoint of further enhancing the hydrophilicity of the polishing object, the lower limit of the concentration (content) of the defect-reducing agent in the polishing composition is preferably 0.005 mass% (50 mass ppm) or more, more preferably 0.01 mass% (100 mass ppm) or more, even more preferably 0.015 mass% (150 mass ppm) or more, and particularly preferably 0.02 mass% (200 mass ppm) or more. In addition, the upper limit of the concentration (content) of the defect-reducing agent in the polishing composition is preferably 1 mass% (10000 mass ppm) or less, more preferably 0.8 mass% (8000 mass ppm) or less, even more preferably 0.5 mass% (5000 mass ppm) or less, even more preferably 0.3 mass% (3000 mass ppm) or less, and particularly preferably 0.1 mass% (1000 mass ppm) or less. That is, the concentration (content) of the defect-reducing agent in the polishing composition is preferably 0.005 mass% (50 mass ppm) or more and 1 mass% (10000 mass ppm) or less, more preferably 0.01 mass% (100 mass ppm) or more and 0.8 mass% (8000 mass ppm) or less, even more preferably 0.015 mass% (150 mass ppm) or more and 0.5 mass% (5000 mass ppm) or less, even more preferably 0.02 mass% (200 mass ppm) or more and 0.3 mass% (3000 mass ppm) or less, particularly preferably 0.02 mass% (200 mass ppm) or more and 0.1 mass% (1000 mass ppm) or less. Note that when the polishing composition contains two or more kinds of defect-reducing agents, the concentration (content) of the defect-reducing agent means the total amount thereof.

[0063] [Inorganic salts] The polishing composition of the present invention preferably contains an inorganic salt. The inorganic salt increases the electrical conductivity of the polishing composition and compresses the electric double layer on the surface of the object to be polished, including materials other than polysilicon (e.g., silicon oxide). This improves the abrasive grain action and can increase the polishing rate of materials other than polysilicon. The inorganic salt can act as an agent for increasing the polishing rate of materials other than polysilicon.

[0064] Examples of inorganic salts include sodium nitrate, potassium nitrate, ammonium nitrate, magnesium nitrate, calcium nitrate, sodium nitrite, potassium nitrite, lithium carbonate, sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, lithium hydrogen carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, ammonium carbonate, sodium bicarbonate, sodium sulfate, potassium sulfate, ammonium sulfate, calcium sulfate, magnesium sulfate, sodium sulfite, potassium sulfite, calcium sulfite, magnesium sulfite, potassium thiosulfate, lithium sulfate, magnesium sulfate, sodium thiosulfate, sodium hydrogen sulfite, sodium hydrogen sulfate, potassium hydrogen sulfate, lithium fluoride, sodium fluoride, potassium fluoride, calcium fluoride, ammonium fluoride, potassium chloride, sodium chloride, ammonium chloride, calcium chloride, potassium bromide, sodium bromide, ammonium bromide, calcium bromide, sodium iodide, potassium iodide, potassium triiodide, calcium iodide, trilithium phosphate, tripotassium phosphate, trisodium phosphate, triammonium phosphate, sodium monohydrogen phosphate, potassium monohydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, and ammonium dihydrogen phosphate. These inorganic salts can be used singly or in combination of two or more. In addition, the inorganic salts to be used may be commercially available products or synthetic products.

[0065] Among these inorganic salts, ammonium sulfate, ammonium nitrate, ammonium carbonate, triammonium phosphate, and diammonium phosphate are preferred because they are free of metals and halogens. The use of inorganic salts free of metals and halogens leads to advantages such as suppression of metal residues, improved handling safety, and prevention of corrosion of the object to be polished.

[0066] The concentration (content) of the inorganic salt in the polishing composition is not particularly limited. In the case of a polishing composition that is used as a polishing liquid for polishing an object to be polished as is, the lower limit of the concentration (content) of the inorganic salt in the polishing composition is preferably 0.2 mass% or more, more preferably 0.3 mass% or more, even more preferably 0.4 mass% or more, and particularly preferably 0.5 mass% or more, relative to the total mass of the polishing composition. In addition, the upper limit of the concentration (content) of the inorganic salt in the polishing composition is preferably 3.0 mass% or less, more preferably 2.5 mass% or less, even more preferably 2.0 mass% or less, and particularly preferably 1.5 mass% or less, relative to the total mass of the polishing composition.

[0067] That is, the concentration (content) of the inorganic salt is preferably 0.2% by mass or more and 3.0% by mass or less, more preferably 0.3% by mass or more and 2.5% by mass or less, even more preferably 0.4% by mass or more and 2.0% by mass or less, and particularly preferably 0.5% by mass or more and 1.5% by mass or less, relative to the total mass of the polishing composition. When the polishing composition contains two or more inorganic salts, the concentration (content) of the inorganic salts means the total amount thereof.

[0068] [Dispersion medium] The polishing composition of the present invention preferably further contains a dispersion medium. Examples of dispersion mediums include water; alcohols such as methanol, ethanol, and ethylene glycol; ketones such as acetone; and mixtures thereof. Of these, water is preferred as the dispersion medium. That is, according to a more preferred embodiment of the present invention, the dispersion medium contains water. According to an even more preferred embodiment of the present invention, the dispersion medium consists essentially of water. Note that the above term "substantially" means that a dispersion medium other than water may be included as long as the intended effect of the present invention can be achieved. More specifically, the dispersion medium preferably consists of 90% by mass to 100% by mass of water and 0% by mass to 10% by mass of a dispersion medium other than water, and more preferably 99% by mass to 100% by mass of water and 0% by mass to 1% by mass of a dispersion medium other than water. Most preferably, the dispersion medium is water.

[0069] From the viewpoint of not inhibiting the action of the components contained in the polishing composition, it is preferable that the dispersion medium be water that contains as few impurities as possible. Specifically, pure water or ultrapure water that has had impurity ions removed using an ion exchange resin and then passed through a filter to remove foreign matter, or distilled water, is more preferable.

[0070] [pH and pH adjusters] From the viewpoint of safety, the pH of the polishing composition of the present invention is preferably 1.0 or higher, more preferably 1.5 or higher, and even more preferably 2.0 or higher. Furthermore, from the viewpoint of improving the removal rate of the surface of the object to be polished containing a material other than polysilicon (e.g., silicon oxide), the pH is preferably 7.0 or lower, more preferably less than 5.0, even more preferably 4.5 or lower, and particularly preferably 4.0 or lower. That is, the pH of the polishing composition of the present invention is preferably 1.0 or higher and 7.0 or lower, more preferably 1.0 or higher and lower than 5.0, and even more preferably 1.5 or higher and 4.5 or lower.

[0071] The polishing composition of the present invention may contain a pH adjuster for adjusting the pH. The pH adjuster may be either an acid or a base, and may be either an inorganic compound or an organic compound. The pH adjuster may be used alone or in combination of two or more kinds.

[0072] Specific examples of acids that can be used as pH adjusters include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid; and organic acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, lactic acid, diglycolic acid, 2-furancarboxylic acid, 2,5-furandicarboxylic acid, 3-furancarboxylic acid, 2-tetrahydrofurancarboxylic acid, methoxyacetic acid, methoxyphenylacetic acid, and phenoxyacetic acid.

[0073] Examples of bases that can be used as pH adjusters include amines such as aliphatic amines and aromatic amines, organic bases such as quaternary ammonium hydroxide, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, hydroxides of Group 2 elements, and ammonia.

[0074] The amount of pH adjuster added is not particularly limited, and may be appropriately adjusted so that the polishing composition has a desired pH. The pH of the polishing composition can be measured, for example, with a pH meter, specifically by the method described in the Examples.

[0075] [Electrical Conductivity of Polishing Composition] The electrical conductivity (EC) of the polishing composition of the present invention is not particularly limited, but is preferably 1 mS / cm or more, more preferably 3 mS / cm or more. The electrical conductivity (EC) of the polishing composition of the present invention is preferably 20 mS / cm or less, more preferably 15 mS / cm or less. That is, the electrical conductivity (EC) of the polishing composition of the present invention is preferably 1 mS / cm or more and 20 mS / cm or less, more preferably 3 mS / cm or more and 15 mS / cm or less. When the electrical conductivity (EC) of the polishing composition is within this range, the polishing rate of materials other than polysilicon (e.g., silicon oxide) can be improved. Furthermore, the repulsion between abrasive grains can be appropriately adjusted, ensuring stability. The electrical conductivity of the polishing composition can be adjusted by the type and amount of inorganic salts, pH adjusters, etc. The electrical conductivity (EC) of the polishing composition can be measured by the method described in the Examples.

[0076] [Other ingredients] The polishing composition of the present invention may further contain other components, if necessary, such as a complexing agent, a metal corrosion inhibitor, a preservative, an antifungal agent, an oxidizing agent, a reducing agent, a surfactant, etc. Preferable components, such as the preservative and the antifungal agent, will be described below.

[0077] (preservatives and fungicides) Examples of preservatives and antifungal agents that can be added to the polishing composition of the present invention include isothiazolin-based preservatives such as 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one, parahydroxybenzoic acid esters, and phenoxyethanol. These preservatives and antifungal agents may be used alone or in combination of two or more.

[0078] [Form of polishing composition] The polishing composition of the present invention is typically supplied to a polishing object in the form of a polishing liquid containing the polishing composition and used to polish the object. The polishing composition of the present invention may be used as a polishing liquid after dilution (typically with water), or may be used as a polishing liquid as is. That is, the concept of the polishing composition of the present invention encompasses both a polishing composition (working slurry) that is supplied to a polishing object and used to polish the object, and a concentrated liquid (raw solution of working slurry) that is diluted and used for polishing. The concentration ratio of the concentrated liquid can be, for example, about 2 to 100 times on a volume basis, and is usually about 3 to 50 times.

[0079] [Polished object] The object to be polished according to the present invention is not particularly limited, and examples thereof include single crystal silicon, polycrystalline silicon (polysilicon), polycrystalline silicon doped with n-type or p-type impurities, amorphous silicon, amorphous silicon doped with n-type or p-type impurities, silicon oxide, silicon nitride, silicon carbonitride (SiCN), metal, SiGe, carbon-containing materials, etc. According to one embodiment of the present invention, the object to be polished includes silicon oxide in addition to polysilicon.

[0080] Examples of polishing objects containing silicon oxide include TEOS-type silicon oxide films (hereinafter simply referred to as "TEOS" or "TEOS films") produced using tetraethyl orthosilicate as a precursor, HDP (High Density Plasma) films, USG (Undoped Silicate Glass) films, PSG (Phosphorus Silicate Glass) films, BPSG (Boron-Phospho Silicate Glass) films, and RTO (Rapid Thermal Oxidation) films.

[0081] Examples of metals include tungsten, copper, aluminum, cobalt, hafnium, nickel, gold, silver, platinum, palladium, rhodium, ruthenium, iridium, and osmium.

[0082] Examples of carbon-containing materials include amorphous carbon, spin Examples include silicon-on-carbon (SOC), diamond-like carbon (DLC), nanocrystalline diamond, graphene, and low-k materials such as SiOC (carbon-containing silicon oxide, i.e., SiO2 doped with C) and silicon carbide. Films containing carbon-containing materials can be formed by CVD, PVD, spin coating, etc.

[0083] The object to be polished may be a commercially available product or may be produced by a known method.

[0084] Among these, an object to be polished containing polysilicon is preferred. Therefore, according to a preferred embodiment of the present invention, the polishing composition is used for polishing an object to be polished containing polysilicon.

[0085] [Method for producing polishing composition] The method for producing the polishing composition according to this embodiment is not particularly limited, and the polishing composition can be obtained, for example, by stirring and mixing abrasive grains, a polishing rate suppressor, a dispersion medium, a defect-reducing agent, and other additives added as needed. The details of each component are as described above.

[0086] The temperature at which the components are mixed is not particularly limited, but is preferably 10° C. to 40° C. Heating may be used to increase the dissolution rate. The mixing time is also not particularly limited as long as uniform mixing is achieved.

[0087] [Polishing method and semiconductor substrate manufacturing method] As described above, the polishing composition of the present invention is particularly suitable for use in polishing an object containing polysilicon. Therefore, the present invention provides a polishing method for polishing an object containing polysilicon with the polishing composition of the present embodiment. The present invention also provides a method for producing a semiconductor substrate, comprising the step of polishing a semiconductor substrate containing polysilicon by the polishing method.

[0088] As the polishing device, a general polishing device can be used, which is equipped with a holder for holding a substrate or the like having an object to be polished, a motor whose rotation speed can be changed, and a polishing platen onto which a polishing pad (polishing cloth) can be attached.

[0089] The polishing pad may be made of any material, including ordinary nonwoven fabric, polyurethane, porous fluororesin, etc. The polishing pad is preferably provided with grooves to allow the polishing liquid to accumulate.

[0090] Regarding the polishing conditions, for example, the rotation speed of the polishing table (platen) and the carrier (head) was set independently at 10 rpm (0.17 s -1 ) or more 500rpm (8.33s -1 The pressure (polishing pressure) applied to the substrate having the object to be polished is preferably 0.5 psi (3.45 kPa) or more and 10 psi (68.9 kPa) or less.

[0091] The method for supplying the polishing composition to the polishing pad is not particularly limited, and for example, a method of continuously supplying the polishing composition using a pump, etc. There is no limit to the amount of the polishing composition supplied, but it is preferable that the surface of the polishing pad is always covered with the polishing composition of the present invention.

[0092] The polishing composition according to the present embodiment may be a one-component type or a multi-component type such as a two-component type. The polishing composition according to the present invention may also be prepared by diluting the stock solution of the polishing composition with a diluent such as water, for example, three times or more.

[0093] [Polishing speed] As described above, the polishing composition of the present invention can suppress the removal rate of polysilicon. Specifically, the removal rate of polysilicon is preferably 45 Å / min or less, more preferably 35 Å / min or less, even more preferably 32 Å / min or less, and even more preferably 30 Å / min or less.

[0094] [Selection ratio] According to one embodiment of the present invention, the polishing composition has a characteristic that the ratio of the polishing rate of silicon oxide (Å / min) to the polishing rate of polysilicon (Å / min) is 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, or 7 or more. According to one embodiment of the present invention, the polishing composition has a characteristic that the ratio of the polishing rate of silicon oxide (Å / min) to the polishing rate of polysilicon (Å / min) is 20 or less, 15 or less, 10 or less, or 9 or less.

[0095] [Number of defects (total)] As described above, the polishing composition of the present invention can reduce the number of defects on the surface of polysilicon after polishing. Specifically, the number of defects of 0.08 μm or more (total) is preferably 5,000 or less, and even more preferably 3,000 or less (lower limit: 0). The number of defects is a value measured by the method described in the Examples.

[0096] Although the embodiments of the present invention have been described in detail, it is clear that this is by way of illustration and example only and not of limitation, and that the scope of the present invention should be interpreted by the appended claims.

[0097] The present invention encompasses the following aspects and configurations.

[0098] 1. A polishing composition comprising abrasive grains and a polishing rate suppressor that suppresses the polishing rate of polysilicon, wherein the polishing rate suppressor is a water-soluble polymer that meets all of the following requirements: 1) the number average molecular weight is 200 or more and 600 or less; 2) the water-soluble polymer has a compound having a repeating unit composed of AO, where A is an alkylene group and O is an oxygen atom; and 3) the water-soluble polymer has a compound having a special repeating unit in which two more oxygen atoms are added to the repeating unit, in an amount of more than 0 mass% and less than 0.1 mass%.

[0099] 2. The polishing composition according to 1., wherein the alkylene group has 3 carbon atoms.

[0100] 3. The polishing composition according to 1. or 2., wherein the polishing rate suppressor contains polypropylene glycol.

[0101] 4. The polishing composition according to any one of 1. to 3., further comprising a water-soluble polymer having an alcoholic hydroxyl group in the side chain.

[0102] 5. The polishing composition according to any one of 1. to 4., wherein the abrasive grains contain anion-modified colloidal silica.

[0103] 6. The polishing composition according to any one of 1. to 5., which has a pH of 1.0 or more and less than 5.0.

[0104] 7. The polishing composition according to any one of 1. to 6., which contains a polishing rate enhancer made of a material other than polysilicon.

[0105] 8. The polishing composition according to 7., wherein the polishing rate enhancer is an inorganic salt.

[0106] 9. The polishing composition according to any one of 1. to 8., wherein the material other than polysilicon is silicon oxide.

[0107] 10. The polishing composition according to any one of 1. to 9., wherein the polishing rate for silicon oxide (Å / min) relative to the polishing rate for polysilicon (Å / min) is 5 or more. [Example]

[0108] The present invention will be described in more detail using the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples. Unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass", respectively. In the following examples, unless otherwise specified, operations were carried out under the conditions of room temperature (20°C to 25°C) and relative humidity of 40% RH to 50% RH. Each physical property was measured as follows.

[0109] <Average primary particle size of abrasive grains> The average primary particle size of the abrasive grains was calculated from the specific surface area of ​​the abrasive grains measured by the BET method using a Micromeritics "Flow Sorb II 2300" and the true density of the abrasive grains.

[0110] <Average secondary particle diameter of abrasive grains> The average secondary particle diameter of the abrasive grains was measured as the volume-average particle diameter (arithmetic mean diameter based on volume; Mv) using a dynamic light scattering particle diameter / particle size distribution analyzer UPA-UT151 (manufactured by Nikkiso Co., Ltd.).

[0111] <Zeta potential of abrasive grains> The zeta potential of the abrasive grains was measured using a zeta potential measuring device manufactured by Otsuka Electronics Co., Ltd. (product name "ELS-Z").

[0112] <pH of polishing composition> The pH of the polishing composition was measured using a glass electrode hydrogen ion concentration indicator (Model No. F-23, manufactured by Horiba, Ltd.) by performing three-point calibration using standard buffer solutions (phthalate pH buffer solution pH: 4.01 (25°C), neutral phosphate pH buffer solution pH: 6.86 (25°C), carbonate pH buffer solution pH: 10.01 (25°C)). The glass electrode was then placed in the polishing composition and the value measured after stabilization for at least two minutes.

[0113] <Number average molecular weight, weight average molecular weight> The number average molecular weight and weight average molecular weight were measured by gel permeation chromatography (GPC) using the following apparatus and conditions: GPC equipment: Shimadzu Corporation Model: Prominence + ELSD detector (ELSD-LTII) Column: VP-ODS (Shimadzu Corporation) Mobile phase A:MeOH B: 1% aqueous solution of acetic acid Flow rate: 1mL / min Detector: ELSD temp. 40℃, Gain 8, N2GAS 350kPa Oven temperature: 40°C Injection volume: 40μL.

[0114] <Electrical Conductivity of Polishing Composition> The electrical conductivity (EC) of the polishing composition was measured using a desktop electrical conductivity meter (manufactured by Horiba, Ltd., model number: DS-71 LAQUA (registered trademark)).

[0115] <Sulfonic acid immobilized colloidal silica> The sulfonic acid-functionalized colloidal silica contained in the polishing composition was prepared using colloidal silica with an average secondary particle diameter of 68.9 nm, according to the method described in “Sulfonic acid-functionalized silica through quantitative oxidation of thiol groups”, Chem. Commun. 246-247 (2003).

[0116] <Polypropylene glycol> (PPG-C6 preparation) A commercially available polypropylene glycol (Sanyo Chemical Industries, Newpol PP-400: PPG + O2 content 0.210 mass%) was prepared (PPG-C6). The PPG + O2 content was analyzed using a liquid chromatography mass spectrometer (LC / MS). The number average molecular weight of PPG-C6 is listed in Table 1.

[0117] LC / MS device (LC): Shimadzu Corporation Model: ProminenceUFLC Column: Cadenza CD-C18 (Intact Co., Ltd.) Mobile phase A: 0.1% formic acid in water B: Acetonitrile A:B=100:0(0min)→A:B=0:100(5min) →A:B=80:20(5.01min)→A:B=80:20(10min) →A:B=70:30(10.01min)→A:B=70:30(30min) →A:B=55:45(30.01min)→A:B=55:45(40min) →A:B=45:55(40.01min)→A:B=45:55(50min) Flow rate: 0.4mL / min Column temperature: 40℃ Injection volume: 5 μL.

[0118] LC / MS device (MS): Manufactured by AB SCIEX Model: Triple TOF 5600+ Ionization method: ESI IonSpray Voltage Floating: 5.5 kV (Positive mode) Chamber volume range: m / z 50-1500.

[0119] (PPG-C1 preparation) Urbanlite (registered trademark) FPX66, a synthetic adsorbent manufactured by Organo Corporation, was washed with alcohol and then further washed with pure water. After that, it was mixed with a 12% by mass aqueous solution of the above-mentioned PPG-C1 and stirred for 2 hours. The synthetic adsorbent was then filtered through a nylon mesh with 100 μm openings to prepare PPG-C1 (PPG + O2 content: 0%).

[0120] (Preparation of PPG-1 to PPG-5, PPG-C2 to PPG-C5) PPG-1 to PPG-5 and PPG-C2 to PPG-C5 were prepared by appropriately mixing PPG-C6 and PPG-C1 so that the content of PPG+O2 was as shown in Table 1. The number average molecular weights of PPG-1 to PPG-5 and PPG-C2 to PPG-C5 are also shown in Table 1.

[0121] Example 1 <Preparation of Polishing Composition> The sulfonic acid-immobilized colloidal silica (average primary particle size: 34.9 nm, average secondary particle size: 68.9 nm) prepared above was added to water as a dispersion medium to a final concentration of 2.3% by mass. Furthermore, PPG-1 was added to a final concentration of 0.6% by mass, butenediol-vinyl alcohol copolymer (degree of polymerization: 300, manufactured by Mitsubishi Chemical Corporation, product name: Nichigo G Polymer AZF8035W) to a final concentration of 750 ppm by mass, and ammonium sulfate (manufactured by Toyama Pharmaceutical Co., Ltd.) to a final concentration of 0.5% by mass, and the mixture was stirred and mixed (stirring temperature: 25°C, stirring time: 20 minutes). The pH of the polishing composition was adjusted to 2.1 with nitric acid to complete Polishing Composition 1. The zeta potential of the sulfonic acid-immobilized colloidal silica in the polishing composition was -55 mV, and the electrical conductivity (EC) of the polishing composition was 12.0 mS / cm.

[0122] (Examples 2 to 5, Comparative Examples 1 to 6) Polishing compositions were prepared in the same manner as in Example 1, except that PPG-1 was changed to PPG-2 to PPG-5 and PPG-C1 to PPG-C6, respectively.

[0123] (Comparative Example 7) A polishing composition was prepared in the same manner as in Example 1, except that PPG-1 was not added.

[0124] Example 6 A polishing composition was prepared in the same manner as in Example 5, except that the pH of the polishing composition was changed to pH 5.5 by changing the amount of nitric acid.

[0125] Example 7 A polishing composition was prepared in the same manner as in Example 5, except that the butenediol-vinyl alcohol copolymer (degree of polymerization: 300, manufactured by Mitsubishi Chemical Corporation, product name: Nichigo G Polymer AZF8035W) was replaced with polyvinyl alcohol (manufactured by Nippon Vaccination & Poval Corporation, product name: JMR-10HH, average molecular weight 9000, degree of polymerization 300).

[0126] [evaluation] As an object to be polished, a silicon wafer (300 mm, blanket wafer) having a polysilicon film with a thickness of 5000 Å formed on its surface was prepared.

[0127] As an object to be polished, a silicon wafer (300 mm, blanket wafer) having a silicon oxide film (derived from TEOS) with a thickness of 10,000 Å formed on its surface was prepared.

[0128] Using the polishing compositions obtained in the above Examples and Comparative Examples, objects were polished under the following conditions: <Polishing conditions> Polishing machine: 300mm polishing machine (manufactured by Ebara Corporation, model number: F-REX300E) Polishing pad: Polyurethane pad (Nitta DuPont, IC1000) Pressure: 2.0 psi (13.79 kPa) Polishing platen rotation speed: 31 rpm Carrier (head) rotation speed: 30 rpm Supply of polishing composition: free-flowing Polishing composition flow rate: 200 ml / min Polishing time: 60 seconds.

[0129] <Polishing speed> The polishing speed (polishing rate) of the object to be polished was calculated by the following formula.

[0130]

number

[0131] The film thickness of the object to be polished before and after polishing was measured using an optical interference film thickness measuring device (KLA Tencor Corporation, model number: ASET-F5X), and the polishing rate was calculated by dividing the difference by the polishing time.

[0132] (Cleaning equipment and cleaning conditions) After polishing the object under the above polishing conditions, the polished object was removed from the polishing table (platen). Then, in the same polishing apparatus, the polished object was cleaned by a cleaning method in which the polished object was rubbed with a cleaning brush made of polyvinyl alcohol (PVA) sponge under pressure using the following cleaning solution under the following conditions: Equipment: 300mm polishing machine (manufactured by Ebara Corporation, model number: F-REX300E) Cleaning solution: 0.3% ammonia water Cleaning brush rotation speed: 100 rpm Rotation speed of object to be cleaned (polished object): 100 rpm Cleaning solution flow rate: 1000 mL / min Cleaning time: 20 seconds.

[0133] The number of defects (organic residue count) ≥ 0.08 μm on the surface of the polished polysilicon substrate obtained by the above cleaning process was evaluated according to the following method. Specifically, defects ≥ 0.08 μm on the entire surface of the polished substrate (excluding a 5 mm periphery) were detected using a KLA-Tencor Corporation defect detection system (wafer inspection system) called the "Surfscan SP5." The detected defects were measured using a review SEM (RS-6000, Hitachi High-Technologies Corporation). Specifically, 100 foreign particles were sampled from the remaining area of ​​each substrate, excluding a 5 mm wide area from the outer periphery, using SEM observation. Next, the 100 foreign particles were visually identified as organic residue and abrasive residue using SEM observation, and the percentages of organic residue and abrasive residue were calculated by counting the number of particles. The number of organic residues was calculated as the product of the number of foreign matter particles (pieces) of 0.08 μm or larger detected by the above-mentioned defect detection device and the proportion (%) of organic residues in the foreign matter calculated from the SEM observation results, and the number of abrasive residues was calculated as the product of the number of foreign matter particles (pieces) of 0.08 μm or larger detected by the above-mentioned defect detection device and the proportion (%) of abrasive residues.

[0134] Furthermore, the number of organic residues and abrasive grain residues was subtracted from the number of foreign matters of 0.08 μm or larger to obtain the number of other defects.

[0135] The compositions and evaluation results of the polishing compositions of Examples and Comparative Examples are shown in Table 1 below.

[0136] [Table 1]

Claims

1. Abrasive grains and a polishing rate suppressor that suppresses the polishing rate of polysilicon; Contains A polishing composition, wherein the polishing rate suppressor is a water-soluble polymer that satisfies all of the following requirements: 1) The number average molecular weight is 200 or more and 600 or less. 2) A compound having a repeating unit consisting of AO, where A is an alkylene group and O is an oxygen atom; 3) The water-soluble polymer contains more than 0% by mass and less than 0.1% by mass of a compound having a special repeating unit in which two additional oxygen atoms are added to the repeating unit.

2. 2. The polishing composition according to claim 1, wherein the alkylene group has 3 carbon atoms.

3. The polishing composition according to claim 1 , wherein the polishing rate suppressor comprises polypropylene glycol.

4. The polishing composition according to claim 1 , further comprising a water-soluble polymer having an alcoholic hydroxyl group in a side chain.

5. The polishing composition according to claim 1 , wherein the abrasive grains comprise anion-modified colloidal silica.

6. 2. The polishing composition according to claim 1, having a pH of 1.0 or more and less than 5.

0.

7. The polishing composition according to claim 1 , further comprising a polishing rate enhancer other than polysilicon.

8. The polishing composition according to claim 7, wherein the polishing rate enhancer is an inorganic salt.

9. The polishing composition according to claim 7 , wherein the material other than polysilicon is silicon oxide.

10. 2. The polishing composition according to claim 1, wherein the ratio of the polishing rate (Å / min) of silicon oxide to the polishing rate (Å / min) of polysilicon is 5 or more.

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