Polishing composition, concentrated liquid of polishing composition, and polishing method

Abstract

Provided is a polishing composition capable of improving the polishing speed in the preliminary polishing of a silicon wafer. The present disclosure relates to a polishing composition used in the preliminary polishing of a silicon wafer, the polishing composition containing abrasive grains and at least one imidazole compound selected from the group consisting of imidazole and derivatives thereof (excluding 1-(3-aminopropyl)imidazole), the content of the imidazole compound being 0.005 mass% or more and less than 0.08 mass% in relation to the total mass of the polishing composition.

Description

Polishing composition, concentrated polishing composition, and polishing method

[0001] The present invention relates to a polishing composition, a concentrated polishing composition, and a polishing method.

[0002] Conventionally, precision polishing using a polishing composition has been performed on the surfaces of materials such as metals, semi-metals, non-metals, and their oxides. For example, the surface of a silicon wafer, which is used as a component of a semiconductor product, is generally finished to a high-quality mirror surface through a lapping step and a polishing step (polishing step). The polishing step typically includes a preliminary polishing step (preliminary polishing step) and a final polishing step (final polishing step).

[0003] For example, Japanese Patent Application Laid-Open No. 2011-258825 discloses a polishing composition for use in a preliminary polishing step, which contains silica particles and NH ２ (CH ２ CH ２ NH) ｎ It is disclosed that a polishing composition containing a polyethyleneamine consisting of H (n is an integer of 2 or more) has a high removal rate in polishing silicon wafers.

[0004] However, in the polishing of silicon wafers, there is a demand for higher removal rates, and in particular, a polishing composition for use in the pre-polishing step of silicon wafers is required to have a high removal rate.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a means for improving the polishing rate.

[0006] In order to solve the above problems, the present inventors have conducted extensive research and have found that the above problems can be solved by a polishing composition containing an imidazole compound under specific conditions, thereby completing the present invention.

[0007] That is, the above-mentioned problems of the present invention can be solved by the following means.

[0008] One embodiment of the present invention that can solve the above-described problems is a polishing composition used for preliminary polishing of silicon wafers, comprising abrasive grains and at least one imidazole compound selected from the group consisting of imidazole and its derivatives (excluding 1-(3-aminopropyl)imidazole), wherein the content of the imidazole compound is 0.005 mass % or more and less than 0.08 mass % based on the total mass of the polishing composition.

[0009] Another embodiment of the present invention that can solve the above-described problems is a polishing composition used for preliminary polishing of silicon wafers, the polishing composition comprising abrasive grains and at least one imidazole compound selected from the group consisting of imidazole and its derivatives (excluding 1-(3-aminopropyl)imidazole), wherein the mass ratio of the content of the imidazole compound to the content of the abrasive grains is less than 0.1.

[0010] The following describes in detail the embodiments of the present invention. The embodiments described herein are merely illustrative examples for embodying the technical concept of the present invention and are not intended to limit the present invention. Therefore, all other embodiments, methods of use, and operational techniques conceivable by those skilled in the art without departing from the spirit of the present invention are included within the scope and spirit of the present invention, as well as within the scope of the claims and their equivalents. The embodiments described herein can be arbitrarily combined to form other embodiments. Furthermore, unless otherwise specified herein, operation and measurement of physical properties are performed at room temperature (20°C to 25°C) and a relative humidity of 40% RH to 60% RH.

[0011] One aspect of the present invention is a polishing composition used for preliminary polishing of silicon wafers, comprising abrasive grains and at least one imidazole compound selected from the group consisting of imidazole and its derivatives (excluding 1-(3-aminopropyl)imidazole), wherein the content of the imidazole compound is 0.005 mass % or more and less than 0.08 mass % based on the total mass of the polishing composition. In the polishing composition of this aspect, the imidazole compound is contained in a specific amount. The polishing composition of this aspect is also referred to as the "polishing composition of the first aspect."

[0012] Another aspect of the present invention is a polishing composition used in the preliminary polishing of silicon wafers, the polishing composition comprising abrasive grains and at least one imidazole compound selected from the group consisting of imidazole and its derivatives (excluding 1-(3-aminopropyl)imidazole), wherein the mass ratio of the content of the imidazole compound to the content of the abrasive grains is less than 0.1. In the polishing composition according to this aspect, the imidazole compound is contained in a specific amount relative to the abrasive grains. The polishing composition according to this aspect is also referred to as the "polishing composition according to a second aspect."

[0013] A polishing composition containing the above-mentioned imidazole compound under specific conditions can improve the removal rate. The inventors have speculated that the mechanism by which the polishing composition according to the above embodiment achieves such an effect is as follows. However, the following mechanism is merely speculation, and the scope of the present invention is not limited thereby.

[0014] The imidazole compound has a nitrogen atom with an unshared electron pair in a five-membered heterocyclic ring. The unshared electron pair of the nitrogen atom is highly nucleophilic, and nucleophilic attack on the silicon wafer surface weakens the silicon-silicon bond of the silicon wafer. This is thought to embrittle the silicon wafer film surface (i.e., the polishing surface), thereby improving the polishing rate of the silicon wafer. In this regard, the present inventors have found that polishing proceeds favorably when the imidazole compound is contained under specific conditions (i.e., the content of the imidazole compound is 0.005 mass% or more but less than 0.08 mass% relative to the total mass of the polishing composition, or the content of the imidazole compound is less than 0.1 mass% relative to the content of abrasive grains). The polishing composition of this embodiment contains the imidazole compound under specific conditions, allowing the imidazole compound to act on the polishing surface to an appropriate extent, thereby achieving the above-mentioned effects.

[0015] As described above, the present invention achieves the effects of the present invention by either the first embodiment, in which the content of the imidazole compound is 0.005 mass% or more and less than 0.08 mass% relative to the total mass of the polishing composition, or the second embodiment, in which the content of the imidazole compound is less than 0.1 mass% relative to the content of abrasive grains. The following features are common to the first embodiment and the second embodiment unless otherwise specified. That is, unless otherwise specified, "the polishing composition of this embodiment" or "the polishing composition according to this embodiment" includes both the polishing composition of the first embodiment and the polishing composition of the second embodiment.

[0016] [(A) Abrasive Grains] The polishing composition according to this embodiment contains abrasive grains. The abrasive grains have the effect of mechanically polishing the object to be polished and improve the polishing rate of the object to be polished by the polishing composition. The abrasive grains contained in the polishing composition according to this embodiment are not particularly limited, and examples thereof include inorganic particles, organic particles, and organic-inorganic composite particles. Among these, inorganic particles are preferred. In a preferred embodiment of the polishing composition according to this embodiment, the abrasive grains contain inorganic particles. The inorganic particles are not particularly limited, and examples thereof include oxide particles such as silica particles, alumina particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconium oxide particles, magnesium oxide particles, manganese dioxide particles, zinc oxide particles, and red iron oxide particles; nitride particles such as silicon nitride particles and boron nitride particles; carbide particles such as silicon carbide particles and boron carbide particles; diamond particles; and carbonates such as calcium carbonate and barium carbonate. Among these, silica particles are more preferred, colloidal silica and fumed silica are even more preferred, and colloidal silica is particularly preferred.

[0017] 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 that tend to diffuse in semiconductors and less corrosive ions such as chloride ions. 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.

[0018] The shape of the abrasive grains 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 out more than the ends, doughnut-shaped discs with a central hole, plate-shaped discs, cocoon-shaped discs with a central constriction, associative spheres in which multiple particles are integrated, confetti-shaped discs with multiple protrusions on the surface, and rugby ball-shaped discs, and are not particularly limited.

[0019] Although not particularly limited, the average value of the long axis / short axis ratio (average aspect ratio) of the abrasive grains is, in principle, 1.0 or more, preferably 1.05 or more, and more preferably 1.1 or more. By increasing the average aspect ratio, a higher polishing rate can be achieved. Furthermore, from the viewpoint of reducing scratches, etc., the average aspect ratio of the abrasive grains is preferably 3.0 or less, more preferably 2.0 or less, and even more preferably 1.5 or less.

[0020] The shape (outer shape) and average aspect ratio of abrasive grains can be determined, for example, by observation with an electron microscope. A specific procedure for determining the average aspect ratio involves, for example, using a scanning electron microscope (SEM), drawing the smallest rectangle circumscribing each particle image for a predetermined number (e.g., 200) of silica particles whose individual particle shapes can be recognized. Then, for each rectangle drawn for each particle image, the long side length (long diameter value) is divided by the short side length (short diameter value) to calculate the long diameter / short diameter ratio (aspect ratio). The average aspect ratio can be determined by arithmetically averaging the aspect ratios of the predetermined number of particles.

[0021] The abrasive grains contained in the polishing composition may be in the form of primary particles, or may be in the form of secondary particles in which a plurality of primary particles are aggregated. Furthermore, abrasive grains in the form of primary particles and abrasive grains in the form of secondary particles may be mixed. In a preferred embodiment, at least a portion of the abrasive grains are contained in the polishing composition in the form of secondary particles.

[0022] The average primary particle diameter of the abrasive grains contained in the polishing composition of this embodiment is not particularly limited, but is preferably 5 nm or more, more preferably 10 nm or more, even more preferably 15 nm or more, particularly preferably 20 nm or more, and most preferably 30 nm or more.In addition, the average primary particle diameter of the abrasive grains contained in the polishing composition of this embodiment is, for example, 120 nm or less, may be 100 nm or less, preferably 90 nm or less, more preferably 80 nm or less, even more preferably 75 nm or less, particularly preferably 70 nm or less, and most preferably 60 nm or less.By the average primary particle diameter of the abrasive grains being within the above range, the polishing speed can be further improved.

[0023] The average secondary particle diameter of the abrasive grains contained in the polishing composition of this embodiment is preferably 20 nm or more, more preferably 30 nm or more, even more preferably 50 nm or more, and particularly preferably 80 nm or more.In addition, the average secondary particle diameter of the abrasive grains contained in the polishing composition of this embodiment is, for example, preferably 250 nm or less, more preferably 230 nm or less, even more preferably 200 nm or less, particularly preferably 180 nm or less, and most preferably 150 nm or less.By the average secondary particle diameter of the abrasive grains being within the above range, the polishing speed can be further improved.

[0024] The preferred ranges of the average primary particle size and average secondary particle size of the abrasive grains described above are also the preferred ranges of the average primary particle size and average secondary particle size of the abrasive grains contained in the raw material dispersion liquid used for the preparation thereof.

[0025] In this specification, the average primary particle diameter is calculated from the specific surface area (BET value) measured by the BET method by the following formula: average primary particle diameter (nm) = 6000 / (true density (g / cm ３ ) × BET value (m ２The specific surface area refers to the particle size (BET particle size) calculated by the formula: (1 / g) / (2 / g). The specific surface area can be measured, for example, using a "Flow Sorb II 2300" manufactured by Micromeritics. The average secondary particle size of the abrasive grains is measured, for example, by dynamic light scattering, for example, using a "Nanotrac (registered trademark) UPA-UT151" manufactured by Nikkiso Co., Ltd.

[0026] When the polishing composition is in the form of a concentrated liquid that is used for polishing after diluting with a dispersion medium or the like, the content of abrasive grains in the concentrated liquid is not particularly limited, but is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, even more preferably 0.5% by mass or more, particularly preferably 1% by mass or more, even more particularly preferably 2% by mass or more, and most preferably 3% by mass or more. In this case, the content of abrasive grains in the concentrated liquid of the polishing composition is not particularly limited, but is preferably 50% by mass or less from the viewpoints of storage stability, filterability, etc.

[0027] When polishing composition is in the state of diluted solution (when it is the polishing composition used during polishing), from the viewpoint of further improving polishing speed, the content of abrasive grains in polishing composition is preferably 0.001 mass% or more, more preferably 0.01 mass% or more, even more preferably 0.025 mass% or more, particularly preferably 0.1 mass% or more, and most preferably 0.5 mass% or more relative to the total mass of polishing composition.In addition, in this case, the content of abrasive grains in polishing composition is not particularly limited, but is preferably 10 mass% or less, more preferably 8 mass% or less, even more preferably 6 mass% or less, particularly preferably 5 mass% or less, and most preferably 3 mass% or less.

[0028] When the content of the abrasive grains is within the above range, the imidazole compound acts more effectively on the silicon wafer surface, and the removal rate can be further improved. When the polishing composition contains two or more types of abrasive grains, the content of the abrasive grains means the total amount of these.

[0029] When the second form of polishing composition is made into a diluted liquid (i.e., when the polishing composition is in a concentrated liquid state and the concentrated liquid is diluted), the preferred abrasive grain content is preferably adjusted by diluting the concentrated polishing composition with a dispersant such as water, or a solution or dispersion containing an optional polishing aid therein.

[0030] According to one embodiment, the polishing composition of this embodiment may contain silica particles and other abrasive particles other than silica particles as abrasive particles.However, when the polishing composition of this embodiment is in a diluted state (when it is a polishing composition used during polishing), the content of the other abrasive particles is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 2% by mass or less, and particularly preferably 1% by mass or less, based on the total mass of the silica particles and the other abrasive particles.The most preferred embodiment is one in which the content of the other abrasive particles is 0% by mass, that is, one in which no abrasive particles other than silica particles are contained.

[0031] [Imidazole Compound] The polishing composition according to this embodiment contains at least one imidazole compound selected from the group consisting of imidazole and its derivatives (excluding 1-(3-aminopropyl)imidazole). The imidazole compound may be a commercially available product or a synthetic product. The imidazole compound preferably has a molecular weight of 400 or less, more preferably 350 or less, even more preferably 300 or less, particularly preferably 250 or less, and most preferably 200 or less. The lower limit of the molecular weight of the imidazole compound may be 68 or more. The molecular weight can be calculated from the composition formula of the imidazole compound.

[0032] Examples of imidazole derivatives include those in which at least one of the hydrogen atoms bonded to the nitrogen atom at position 1, the carbon atom at position 2, the carbon atom at position 4, and the carbon atom at position 5 of the imidazole ring is an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an aryl group having 6 to 24 carbon atoms, a hydroxy group (—OH), a carboxy group (—COOH), an amino group (—NR ａ２ ;R ａ each independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms), a halogeno group (-F, -Cl, -Br, or -I), a hydroxyalkyl group (-R ｂ -OH; R ｂ is an alkylene group having 1 to 20 carbon atoms), an alkylaminoalkylene group (-R ｂ -NR ａ ２ ;R ａ are each independently a hydrogen atom or an alkyl group having 1 to 20 carbon atoms; R ｂ is an alkylene group having 1 to 20 carbon atoms), an alkyloxyalkylene group (-R ｂ -OR ａ ;R ａ represents 1 to 20 alkyl groups, R ｂ is an alkylene group having 1 to 20 carbon atoms), and a haloalkyl group (-R ｂ -X; X is a halogeno group, R ｂ and (C1-C2 alkylene groups) are substituted with a substituent X selected from the group consisting of: (C1-C2 alkylene groups) In this case, two adjacent substituents X may be bonded to each other to form a ring (i.e., form a condensed ring with an imidazole ring).

[0033] The substituent X may be any of a group in which a hydrogen atom of the substituent X is substituted with an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an aryl group having 6 to 24 carbon atoms, a hydroxy group (—OH), a carboxy group (—COOH), an amino group (—NR ａ ２ ;R ａ each independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms), a halogeno group (-F, -Cl, -Br, or -I), a nitro group (-NO ２ ), hydroxyalkyl group (-R ｂ -OH; R ｂ is an alkylene group having 1 to 10 carbon atoms), and an aminoalkyl group (-R ｂ -NR ａ ２ ;R ａ are each independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms; Rｂ and an alkylene group having 1 to 10 carbon atoms).

[0034] The imidazole derivative may be any one of the hydrogen atoms bonded to the nitrogen atom at position 1, the carbon atom at position 2, the carbon atom at position 4, and the carbon atom at position 5 of the imidazole ring substituted with the substituent X. Two or more of the hydrogen atoms bonded to the nitrogen atom at position 1, the carbon atom at position 2, the carbon atom at position 4, and the carbon atom at position 5 of the imidazole ring may be substituted with the substituent X. In this case, the substituents X may each be independently selected from the substituents X, and the hydrogen atoms bonded to the nitrogen atom at position 1, the carbon atom at position 2, the carbon atom at position 4, and the carbon atom at position 5 of the imidazole ring may each be substituted with a different substituent X, or two adjacent substituents X may be bonded to each other to form a ring.

[0035] Examples of the alkyl group having from 1 to 20 carbon atoms include a linear, branched, or cyclic alkyl group having from 1 to 20 carbon atoms, such as a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, isobutyl group, tert-butyl group, n-pentyl group, isopentyl group, neopentyl group, n-hexyl group, 3-methylhexyl group, 2,2-dimethylpentyl group, 2,3-dimethylpentyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-tetradecyl group, n-octadecyl group, and cyclohexyl group.

[0036] Examples of the alkenyl group having from 2 to 20 carbon atoms include linear, branched, or cyclic alkenyl groups having from 2 to 20 carbon atoms, such as a vinyl group, an allyl group (2-propenyl group), a propenyl group (1-propenyl group), a 1-butenyl group, a 2-butenyl group, a 3-butenyl group, a 1-hexenyl group, a 2-hexenyl group, a 3-hexenyl group, a 4-hexenyl group, a 5-hexenyl group, a cyclopentenyl group, a cyclohexenyl group, and a cyclooctenyl group.

[0037] Examples of the aryl group having 6 to 24 carbon atoms include non-condensed hydrocarbon groups such as a phenyl group, a biphenyl group, and a terphenyl group; and condensed polycyclic hydrocarbon groups such as a pentalenyl group, an indenyl group, a naphthyl group, an azulenyl group, a heptalenyl group, a biphenylenyl group, a fluorenyl group, an acenaphthylenyl group, a pleiadenyl group, an acenaphthenyl group, a phenalenyl group, a phenanthryl group, an anthryl group, a fluoranthenyl group, an acephenanthrilenyl group, an aceanthrylenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, and a naphthacenyl group.

[0038] The imidazole derivative is preferably one in which at least one of the hydrogen atoms bonded to the nitrogen atom at position 1, the carbon atom at position 2, the carbon atom at position 4, and the carbon atom at position 5 of the imidazole ring is substituted with a substituent X selected from the group consisting of an alkyl group having from 1 to 20 carbon atoms, a hydroxy group, and a carboxy group.

[0039] Examples of the imidazole compound include imidazole, 1,2-dimethylimidazole, 1-methylimidazole, 2-methylimidazole, 4-methylimidazole, 2-ethyl-4-methylimidazole, 2-isopropylimidazole, benzimidazole, 5,6-dimethylbenzimidazole, 2-aminobenzimidazole, 2-chlorobenzimidazole, 2-methylbenzimidazole, 2-(1-hydroxyethyl)benzimidazole, 2-hydroxybenzimidazole, 2-phenylbenzimidazole, 2,5-dimethylbenzimidazole, 5-methylbenzimidazole, 2-ethylimidazole, and 5-nitrobenzimidazole. In the polishing composition of this embodiment, the imidazole compound is preferably imidazole, benzimidazole, 5,6-dimethylbenzimidazole, 2-aminobenzimidazole, 2-methylbenzimidazole, 2-(1-hydroxyethyl)benzimidazole, 2-hydroxybenzimidazole, 2,5-dimethylbenzimidazole, or 5-methylbenzimidazole; more preferably imidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-isopropylimidazole, or 2-ethylimidazole; even more preferably imidazole, 1-methylimidazole, 2-methylimidazole, or 4-methylimidazole; and from the viewpoint of improving the removal rate, imidazole is particularly preferred.

[0040] In the polishing composition according to the first embodiment, the content (concentration) of the imidazole compound is 0.005 mass% or more and less than 0.08 mass% relative to the total mass of the polishing composition. When the content (concentration) of the imidazole compound is 0.005 mass% or more and less than 0.08 mass%, the removal rate is improved.

[0041] The content (concentration) of imidazole compound in the polishing composition according to the first embodiment is preferably 0.006 mass% or more, more preferably 0.007 mass% or more, more preferably 0.008 mass% or more, and particularly preferably 0.009 mass% or more, based on the total mass of the polishing composition.In addition, the content (concentration) of imidazole compound in the polishing composition is preferably 0.079 mass% or less, more preferably 0.078 mass% or less, more preferably 0.076 mass% or less, and particularly preferably 0.075 mass% or less, based on the total mass of the polishing composition.That is, the content (concentration) of imidazole compound is preferably 0.006 mass% or more and 0.079 mass% or less, more preferably 0.007 mass% or more and 0.078 mass% or less, more preferably 0.008 mass% or more and 0.076 mass% or less, and particularly preferably 0.009 mass% or more and 0.075 mass% or less, based on the total mass of the polishing composition. The content (concentration) of the imidazole compound in the polishing composition may be 0.005 mass % or more and 0.078 mass % or less, or 0.006 mass % or more and 0.076 mass % or less.

[0042] When the content (concentration) of the imidazole compound is within this range, the imidazole compound acts more effectively on the polishing surface, and the polishing rate can be further improved. Note that, in the polishing composition according to the first embodiment, the content (concentration) of the imidazole compound when the polishing composition is in a diluted state (when the polishing composition is used during polishing) corresponds to the above.

[0043] When the polishing composition according to the first embodiment is in the form of a concentrated solution that is diluted with a dispersion medium or the like and used for polishing, the content (concentration) of imidazole in the concentrated solution is not particularly limited, but is preferably 0.01% by mass or more, more preferably 0.03% by mass or more, even more preferably 0.04% by mass or more, particularly preferably 0.05% by mass or more, and most preferably 0.06% by mass or more.In addition, in this case, the content (concentration) of imidazole compound in the concentrated solution of the polishing composition is not particularly limited, but from the viewpoint of storage stability, filterability, etc., is preferably 5% by mass or less, more preferably 2% by mass or less, even more preferably 1% by mass or less, particularly preferably 0.9% by mass or less, and most preferably 0.8% by mass or less.

[0044] In the polishing composition according to the first embodiment, the imidazole compound may be used alone or in combination of two or more. When two or more imidazole compounds are contained, the content of the imidazole compounds means the total amount thereof.

[0045] <Second embodiment> In the polishing composition according to the second embodiment, the mass ratio of the content of the imidazole compound to the content of the abrasive grains is less than 0.1. When the mass ratio of the content of the imidazole compound to the content of the abrasive grains is less than 0.1, the polishing rate is improved.

[0046] In the polishing composition according to the second embodiment, the content of the imidazole compound relative to the content of abrasive grains is less than 0.1. The content of the imidazole compound relative to the content of abrasive grains is preferably 0.095 or less, more preferably 0.090 or less, even more preferably 0.085 or less, and particularly preferably 0.084 or less. In addition, in the polishing composition according to the first embodiment, the content of the imidazole compound relative to the content of abrasive grains is preferably 0.0001 or more, more preferably 0.0005 or more, even more preferably 0.001 or more, and particularly preferably 0.005 or more. That is, in the polishing composition according to the second embodiment, the content of the imidazole compound relative to the content of abrasive grains is preferably 0.0001 or more and 0.095 or less, more preferably 0.0005 or more and 0.090 or less, even more preferably 0.001 or more and 0.085 or less, and particularly preferably 0.005 or more and 0.084 or less. In the polishing composition according to the first embodiment, the content of the imidazole compound relative to the content of abrasive grains in the polishing composition may be 0.01 or more and less than 0.10, or may be 0.03 or more and 0.09 or less.

[0047] When the content of the imidazole compound relative to the content of the abrasive grains falls within this range, the imidazole compound acts more effectively on the polishing surface, and the polishing rate can be further improved.

[0048] When the polishing composition according to the second embodiment is in the form of a concentrated solution that is diluted with a dispersion medium or the like and used for polishing, the content (concentration) of imidazole in the concentrated solution is not particularly limited, but is preferably 0.01% by mass or more, more preferably 0.03% by mass or more, even more preferably 0.04% by mass or more, particularly preferably 0.05% by mass or more, and most preferably 0.06% by mass or more.In addition, in this case, the content (concentration) of the imidazole compound in the concentrated solution of the polishing composition is not particularly limited, but from the viewpoint of storage stability, filterability, etc., is preferably 5% by mass or less, more preferably 2% by mass or less, even more preferably 1% by mass or less, particularly preferably 0.9% by mass or less, and most preferably 0.8% by mass or less.

[0049] When the polishing composition according to the second embodiment is in the form of a diluted solution (when it is a polishing composition used during polishing), the content (concentration) of the imidazole compound in the polishing composition may be 0.0001% by mass or more and 2% by mass or less, 0.0005% by mass or more and 1% by mass or less, 0.001% by mass or more and 0.5% by mass or less, or 0.005% by mass or more and 0.1% by mass or less. According to one embodiment, the content (concentration) of the imidazole compound in the polishing composition is preferably 0.0001% by mass or more and less than 0.08% by mass. The content (concentration) of the imidazole compound in the polishing composition is preferably 0.006% by mass or more, more preferably 0.007% by mass or more, even more preferably 0.008% by mass or more, and particularly preferably 0.009% by mass or more, based on the total mass of the polishing composition. In addition, the content (concentration) of imidazole compound in the polishing composition is preferably 0.079 mass% or less, more preferably 0.078 mass% or less, even more preferably 0.076 mass% or less, and particularly preferably 0.075 mass% or less, based on the total mass of the polishing composition.That is, the content (concentration) of imidazole compound is preferably 0.006 mass% or more and 0.079 mass% or less, more preferably 0.007 mass% or more and 0.078 mass% or less, even more preferably 0.008 mass% or more and 0.076 mass% or less, and particularly preferably 0.009 mass% or more and 0.075 mass% or less, based on the total mass of the polishing composition.The content (concentration) of imidazole compound in the polishing composition may be 0.005 mass% or more and 0.078 mass% or less, or may be 0.006 mass% or more and 0.076 mass% or less.

[0050] In the polishing composition according to the second embodiment, the imidazole compound may be used alone or in combination of two or more. When two or more imidazole compounds are contained, the content of the imidazole compounds means the total amount thereof.

[0051] [Alkali] The polishing composition according to this embodiment may contain an alkali (excluding imidazole compounds). The alkali plays a role in chemically polishing the silicon wafer, which is the object to be polished, and contributes to improving the polishing ability of the polishing composition. Examples of alkali include organic alkalis and / or inorganic alkalis. Preferably, the polishing composition according to this embodiment contains one or more alkalis selected from the group consisting of organic alkalis and inorganic alkalis.

[0052] Examples of organic alkalis include ammonia, amines (excluding imidazole compounds), and quaternary ammonium salts. Specific examples of amines include amines other than imidazole compounds, such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N-(β-aminoethyl)ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, anhydrous piperazine, piperazine hexahydrate, 1-(2-aminoethyl)piperazine, N-methylpiperazine, and guanidine. Examples of quaternary ammonium salts include quaternary ammonium halides (F salts, Cl salts, Br salts, or I salts) such as tetramethylammonium fluoride, tetramethylammonium chloride, tetraethylammonium chloride, tetrabutylammonium chloride, tetramethylammonium bromide, tetraethylammonium bromide, and tetrabutylammonium bromide; and quaternary ammonium hydroxides such as tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide, and tetrabutylammonium hydroxide. As the organic alkali, from the viewpoint of improving the polishing rate, quaternary ammonium hydroxides are preferred, and tetramethylammonium hydroxide (TMAH) is more preferred.

[0053] Examples of inorganic alkalis include hydroxides, carbonates, and bicarbonates of alkali metals such as lithium, sodium, and potassium, and alkaline earth metals (Group 2 metals) such as beryllium, magnesium, calcium, strontium, and barium. Specific examples of hydroxides, carbonates, and bicarbonates of alkali metals or alkaline earth metals (Group 2 metals) include lithium hydroxide, sodium hydroxide, potassium hydroxide, potassium carbonate, potassium bicarbonate, sodium carbonate, and sodium bicarbonate. From the viewpoint of improving the polishing rate, the inorganic alkali is preferably a carbonate or bicarbonate of an alkali metal or alkaline earth metal (Group 2 metal), more preferably a carbonate or bicarbonate of an alkali metal, even more preferably a carbonate of an alkali metal, and particularly preferably potassium carbonate.

[0054] In the polishing composition according to this embodiment, the alkali may be used alone or in combination of two or more. When two or more alkalis are contained, the content of the alkalis means the total amount thereof.

[0055] In the polishing composition of this embodiment, the alkali is preferably a combination of an organic alkali and an inorganic alkali.For example, as the alkali, it is preferable to use a quaternary ammonium hydroxide (e.g., one or more selected from the group consisting of tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide, and tetrabutylammonium hydroxide) in combination with an alkali metal carbonate (e.g., one or more selected from the group consisting of sodium carbonate and potassium carbonate), and it is more preferable to use a combination of tetramethylammonium hydroxide (TMAH) and potassium carbonate.By using an organic alkali and an inorganic alkali in combination as the alkali, the polishing rate can be further improved.

[0056] In the polishing composition of this embodiment, when an organic alkali and an inorganic alkali are used in combination as the alkali, the content ratio of the organic alkali to the inorganic alkali (organic alkali:inorganic alkali (mass ratio)) is preferably 10:90 or more and 95:5 or less, more preferably 20:80 or more and 90:10 or less, and even more preferably 30:70 or more and 80:20 or less.

[0057] In the polishing composition of this embodiment, the mass ratio of the imidazole compound content to the inorganic alkali content is preferably less than 0.5. When the mass ratio of the imidazole compound content to the inorganic alkali content is less than 0.5, polishing proceeds smoothly and the removal rate is further improved.

[0058] The mass ratio of the imidazole compound content to the inorganic alkali content in the polishing composition is preferably 0.49 or less, more preferably 0.48 or less, even more preferably 0.47 or less, and particularly preferably 0.45 or less.Furthermore, the mass ratio of the imidazole compound content to the inorganic alkali content in the polishing composition is preferably 0.01 or more, more preferably 0.05 or more, even more preferably 0.1 or more, and particularly preferably 0.2 or more.That is, the mass ratio of the imidazole compound content to the inorganic alkali content is preferably 0.01 or more and 0.49 or less, more preferably 0.05 or more and 0.48 or less, even more preferably 0.1 or more and 0.47 or less, and particularly preferably 0.2 or more and 0.46 or less.The mass ratio of the imidazole compound content to the inorganic alkali content in the polishing composition may be 0.01 or more and less than 0.50, or may be 0.03 or more and 0.48 or less.

[0059] When the polishing composition is in the form of a concentrated solution that is used for polishing after diluting with a dispersion medium or the like, the alkali content in the concentrated solution is not particularly limited, but is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.5% by mass or more, particularly preferably 1% by mass or more, and most preferably 2% by mass or more. In this case, from the viewpoints of storage stability, filterability, etc., the alkali content in the concentrated solution of the polishing composition is preferably 50% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, and particularly preferably 9% by mass or less.

[0060] When the polishing composition is in the state of a diluted solution (when it is a polishing composition used during polishing), the content of alkali in the polishing composition is preferably 0.01 mass% or more, more preferably 0.02 mass% or more, even more preferably 0.03 mass% or more, and particularly preferably 0.05 mass% or more, based on the total mass of the polishing composition, from the viewpoint of further improving the polishing rate.In addition, in this case, the content of alkali in the polishing composition is preferably 5 mass% or less, more preferably 3 mass% or less, even more preferably 2 mass% or less, particularly preferably 1 mass% or less, and most preferably 0.5 mass% or less.

[0061] If the alkali content is within the above range, the polishing rate can be further improved.

[0062] [Chelating Agent] The polishing composition according to this embodiment may contain a chelating agent. The chelating agent can perform multidentate coordination with metal ions and increase the solubility of the metal ions in the polishing composition, thereby contributing to the removal of particle residues such as abrasive grains from the polished surface after polishing. Examples of the chelating agent include aminocarboxylic acid chelating agents and organic phosphonic acid chelating agents.

[0063] Examples of aminocarboxylic acid chelating agents include ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetate, nitrilotriacetic acid, sodium nitrilotriacetate, ammonium nitrilotriacetate, hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetate, diethylenetriaminepentaacetic acid, sodium diethylenetriaminepentaacetate, triethylenetetraminehexaacetic acid, and sodium triethylenetetraminehexaacetate.

[0064] Organic phosphonic acid chelating agents include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri(methylenephosphonic acid), ethylenediaminetetrakis(methylenephosphonic acid) (EDTPO), diethylenetriaminepenta(methylenephosphonic acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, ethane-1-hydroxy-1,1,2-triphosphonic acid, ethane-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, and α-methylphosphonosuccinic acid.

[0065] Of these, organic phosphonic acid chelating agents are more preferred. Among these, preferred chelating agents include ethylenediaminetetrakis(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), and diethylenetriaminepentaacetic acid. Particularly preferred chelating agents include ethylenediaminetetrakis(methylenephosphonic acid) and diethylenetriaminepenta(methylenephosphonic acid).

[0066] The chelating agent may be used alone or in combination of two or more. When two or more chelating agents are used, the content of the chelating agents means the total amount thereof.

[0067] In the polishing composition of this embodiment, the mass ratio of the content of the imidazole compound to the content of the chelating agent is preferably less than 10. When the mass ratio of the content of the imidazole compound to the content of the chelating agent is less than 10, polishing proceeds smoothly, and the polishing rate is further improved.

[0068] The content of the imidazole compound relative to the content of the chelating agent in the polishing composition is preferably 9.5 or less, more preferably 9.0 or less, even more preferably 8.5 or less, and particularly preferably 8.4 or less. The content of the imidazole compound relative to the content of the chelating agent in the polishing composition is preferably 0.01 or more, more preferably 0.05 or more, even more preferably 0.1 or more, and particularly preferably 0.5 or more. That is, the content of the imidazole compound relative to the content of the chelating agent is preferably 0.01 or more and 9.5 or less, more preferably 0.05 or more and 9.0 or less, even more preferably 0.1 or more and 8.5 or less, and particularly preferably 0.5 or more and 8.4 or less. The content of the imidazole compound relative to the content of the chelating agent in the polishing composition may be 0.01 or more and less than 10, may be 0.5 or more and less than 10, or may be 0.5 or more and 9 or less.

[0069] When the polishing composition is in the form of a concentrated solution that is used for polishing after diluting with a dispersion medium or the like, the content of the chelating agent in the concentrated solution is not particularly limited, but is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, even more preferably 0.05% by mass or more, particularly preferably 0.06% by mass or more, and most preferably 0.08% by mass or more. In this case, from the viewpoint of storage stability, filterability, etc., the content of the chelating agent in the concentrated solution of the polishing composition is preferably 10% by mass or less, more preferably 8% by mass or less, even more preferably 5% by mass or less, particularly preferably 1% by mass or less, and most preferably 0.5% by mass or less.

[0070] When the polishing composition is in the form of a diluted solution (when it is a polishing composition used during polishing), the content of the chelating agent in the polishing composition is preferably 0.001% by mass or more, more preferably 0.002% by mass or more, even more preferably 0.003% by mass or more, and particularly preferably 0.004% by mass or more, based on the total mass of the polishing composition, from the viewpoint of further improving the polishing rate. Most preferably 0.005% by mass or more. In this case, the content of the chelating agent in the polishing composition is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 2% by mass or less, particularly preferably 1% by mass or less, and most preferably 0.5% by mass or less.

[0071] If the content of the chelating agent is within the above range, the removal rate can be further improved.

[0072] [pH] The pH of the polishing composition according to this embodiment is preferably 7.0 or more, more preferably 7.5 or more, even more preferably 8.0 or more, particularly preferably 8.5 or more, and most preferably 9.0 or more. The pH of the polishing composition is preferably 12.5 or less, more preferably 12.0 or less, even more preferably 11.8 or less, particularly preferably 11.6 or less, and most preferably 11.5 or less. That is, the pH of the polishing composition is preferably 7.0 or more and 12.5 or less, more preferably 7.5 or more and 12.0 or less, even more preferably 8.0 or more and 11.8 or less, particularly preferably 8.5 or more and 11.6 or less, and most preferably 9.0 or more and 11.5 or less. In one embodiment, the pH of the polishing composition is 9.5 or more and 11.0 or less. When the pH of the polishing composition is in this range, the imidazole compound acts more effectively on the silicon wafer surface, and the removal rate can be further improved. The pH of the polishing composition can be measured, for example, with a pH meter (for example, a pH meter (model number: LAQUA) manufactured by Horiba, Ltd.). Specific types of pH adjusters will be described in detail below.

[0073] [Dispersion medium] The polishing composition according to this embodiment preferably contains a dispersion medium for dispersing each component. The dispersion medium (particularly water) has the function of dissolving or dispersing the components contained in the polishing composition.

[0074] The dispersion medium may be a mixed solvent of water and an organic solvent for dispersing or dissolving each component. In this case, examples of the organic solvent used include water-miscible organic solvents such as acetone, acetonitrile, ethanol, methanol, isopropanol, glycerin, ethylene glycol, and propylene glycol. Alternatively, these organic solvents may be used without mixing with water, and then the components may be dispersed or dissolved in the organic solvent, followed by mixing with water. These organic solvents may be used alone or in combination. According to a preferred embodiment of this embodiment, the dispersion medium contains water. According to a more preferred embodiment of this embodiment, the dispersion medium consists essentially of water. Note that the term "substantially" as used above means that a dispersion medium other than water may be included, as long as the effects of the present invention can be achieved. More specifically, the dispersion medium preferably consists of 90% to 100% by mass of water and 0% to 10% by mass of a dispersion medium other than water, and more preferably 99% to 100% by mass of water and 0% to 1% by mass of a dispersion medium other than water. According to the most preferred embodiment of this embodiment, the dispersion medium consists solely of water.

[0075] It is preferable that the water contains as few impurities as possible to prevent contamination of the polishing object or inhibition of the action of other components. For example, a water having a total transition metal ion content of 100 ppb or less is preferable. The purity of the water can be increased by, for example, removing impurity ions using an ion exchange resin, removing foreign matter using a filter, or by distillation. Specifically, it is preferable to use, for example, deionized water (ion-exchanged water), pure water, ultrapure water, distilled water, etc.

[0076] [Other Components] The polishing composition of this embodiment may further contain known additives that can be used in polishing compositions, such as pH adjusters, antifungal agents (preservatives), water-soluble polymers, surfactants, etc., within the range that does not impair the effects of the present invention. Below, pH adjusters, antifungal agents (preservatives), and surfactants will be explained. Also, oxidizing agents will be explained.

[0077] [pH Adjuster] In the polishing composition of this embodiment, the pH can be adjusted by each component described above, but a pH adjuster may also be used to adjust to a desired pH. Therefore, the polishing composition of this embodiment may further contain a pH adjuster. Examples of pH adjusters include compounds other than the imidazole compounds, alkalis (organic alkalis and / or inorganic alkalis; excluding imidazole compounds), and chelating agents described above, such as inorganic acids and organic acids. These pH adjusters may be used alone or in combination of two or more. The content of the pH adjuster can be selected by appropriately adjusting it within the range that achieves the effects of the present invention.

[0078] Specific examples of inorganic acids that can be used as pH adjusters include hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid. Among these, hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid are preferred, and nitric acid is more preferred.

[0079] Specific examples of inorganic acids that can be used as pH adjusters include hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid. Among these, hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid are preferred, and nitric acid is more preferred.

[0080] Specific examples of organic acids that can be used as pH adjusters include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, lactic acid, diglycolic acid, 2-furancarboxylic acid, 2,5-furandicarboxylic acid, 3-furancarboxylic acid, 2-tetrahydrofurancarboxylic acid, methoxyacetic acid, methoxyphenylacetic acid, phenoxyacetic acid, methanesulfonic acid, ethanesulfonic acid, 10-camphorsulfonic acid, and isethionic acid.

[0081] As the pH adjuster, salts such as alkali metal salts of inorganic or organic acids may be used instead of or in combination with inorganic or organic acids. In the case of combinations of a weak acid and a strong base, a strong acid and a weak base, or a weak acid and a weak base, a pH buffering effect can be expected.

[0082] The antifungal agent (preservative) is not particularly limited and can be appropriately selected depending on the desired use and purpose. Specific examples include isothiazoline preservatives such as 1,2-benzisothiazol-3(2H)-one (BIT), 2-methyl-4-isothiazolin-3-one, and 5-chloro-2-methyl-4-isothiazolin-3-one, and phenoxyethanol.

[0083] [Water-soluble polymer] Examples of water-soluble polymers include cellulose derivatives, starch derivatives, polymers containing oxyalkylene units, polymers containing nitrogen atoms (excluding imidazole compounds), vinyl alcohol-based polymers, and polymers containing carboxylic acids (including anhydrides). Specific examples include hydroxyethyl cellulose, pullulan, random copolymers and block copolymers of ethylene oxide and propylene oxide, polyglycerin, polyvinyl alcohol, acetalized polyvinyl alcohol, butenediol polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, sulfonic acid group-modified polyvinyl alcohol, polyvinyl alcohol-polyvinylpyrrolidone graft copolymers, polyvinyl alcohol-polyvinylpyrrolidone random copolymers, polyvinyl alcohol-polyethylene oxide graft copolymers, polyvinyl alcohol-polyethylene oxide random copolymers, polyisoprene sulfonic acid, polyvinyl sulfonic acid, polyallylsulfonic acid, polyisoamylene sulfonic acid, polystyrene sulfonate, polyacrylate, polyvinyl acetate, polyethylene glycol, polyvinylcarbazole, polyvinylpyrrolidone, polyvinyl acetamide, polyacryloylmorpholine, polyhydroxyethylacrylamide, polyvinyl caprolactam, polyvinylpiperidine, olefin-maleic acid (anhydride) copolymers, styrene-maleic acid (anhydride) copolymers, etc. The water-soluble polymers can be used alone or in combination of two or more.

[0084] In some embodiments, the polishing composition disclosed herein can be implemented in an embodiment that is substantially free of a water-soluble polymer, i.e., an embodiment that does not contain a water-soluble polymer at least intentionally. Here, "the polishing composition is substantially free of a water-soluble polymer" means that a water-soluble polymer is not blended at least intentionally, and for example, the content of the water-soluble polymer in the polishing composition is 1×10 －６ Mass% or less (5×10 －７ It may be 1×10 mass% or less. －７ It may be 5×10 mass% or less. －８The content of the water-soluble polymer in the polishing composition may be 0% by mass. These contents can be applied to, for example, the content in a dilution solution (the content in the polishing composition used during polishing). The water-soluble polymer typically refers to a water-soluble compound having a weight-average molecular weight (Mw) of 5,000 or more.

[0085] The Mw of the water-soluble polymer can be calculated from a value (water-based, polyethylene oxide equivalent) based on aqueous gel permeation chromatography (GPC). A GPC measuring device such as "HLC-8320GPC" manufactured by Tosoh Corporation can be used. Measurements can be performed, for example, under the following conditions:

[0086] [GPC measurement conditions] Sample concentration: 0.1 wt% Column: TSKgel GMPW ＸＬ Detector: differential refractometer Eluent: 100 mM aqueous sodium nitrate solution Flow rate: 1 mL / min Measurement temperature: 40°C Sample injection volume: 200 µL

[0087] [Surfactant] The surfactant may be used alone or in combination of two or more. Examples of the surfactant are not particularly limited, and include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants.

[0088] Examples of anionic surfactants include polyoxyethylene alkyl ether acetates, polyoxyethylene alkyl sulfates, alkyl sulfates, polyoxyethylene alkyl sulfates, alkyl sulfates, alkyl benzene sulfonates, alkyl phosphates, polyoxyethylene alkyl phosphates, polyoxyethylene sulfosuccinates, alkyl sulfosuccinates, alkyl naphthalene sulfonates, alkyl diphenyl ether disulfonates, and salts thereof.

[0089] Examples of nonionic surfactants include oxyalkylene polymers such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; polyoxyalkylene derivatives (e.g., polyoxyalkylene adducts) such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkylamines, polyoxyethylene fatty acid esters, polyoxyethylene glyceryl ether fatty acid esters, and polyoxyethylene sorbitan fatty acid esters; copolymers of multiple types of oxyalkylenes (e.g., diblock copolymers, triblock copolymers, random copolymers, and alternating copolymers); etc. The nonionic surfactants can be used alone or in combination of two or more.

[0090] Examples of cationic surfactants include quaternary ammonium salts such as alkyltrimethylammonium salts, alkyldimethylammonium salts, and alkylbenzyldimethylammonium salts; alkylamine salts such as laurylamine hydrochloride; and pyridinium salts such as laurylpyridinium chloride.

[0091] Examples of amphoteric surfactants include alkyl betaines and alkyl amine oxides.

[0092] The molecular weight of the surfactant is, for example, less than 5000, and may be equal to or less than 3000. As the molecular weight of the surfactant, the value of the weight average molecular weight determined by GPC may be used, or the molecular weight calculated from the chemical formula may be used.

[0093] [Oxidizing Agent] The polishing composition according to some embodiments of this aspect preferably does not substantially contain an oxidizing agent. If an oxidizing agent is contained in the polishing composition, the surface of the object to be polished (particularly a silicon wafer) is oxidized to form an oxide film, which increases the required polishing time. Specific examples of the oxidizing agent include hydrogen peroxide (H ２ O ２), sodium persulfate, ammonium persulfate, sodium dichloroisocyanurate, etc. The phrase "the polishing composition is substantially free of oxidizing agents" means that the polishing composition does not contain an oxidizing agent, at least intentionally. Therefore, a polishing composition that inevitably contains a trace amount of oxidizing agent due to raw materials, manufacturing method, etc. (for example, a polishing composition in which the molar concentration of the oxidizing agent in the polishing composition is 0.001 mol / L or less, preferably 0.0005 mol / L or less, more preferably 0.0001 mol / L or less, even more preferably 0.00005 mol / L or less, and particularly preferably 0.00001 mol / L or less) can be included in the concept of a polishing composition that is substantially free of oxidizing agents.

[0094] [Method for producing polishing composition] The method for producing the polishing composition according to some embodiments of the present invention is not particularly limited. For example, the polishing composition can be produced by adding abrasive grains, an imidazole compound, and other components, such as an alkali and a chelating agent, to a dispersion medium all at once or sequentially, and stirring the mixture in the dispersion medium.

[0095] [Form of Polishing Composition, etc.] The polishing composition according to some embodiments of this aspect may be a one-component type or a multi-component type consisting of two or more components. The polishing composition described above may be used for polishing as is, or may be prepared by adding water to dilute the polishing composition concentrate, or in the case of a multi-component polishing composition, by diluting it with an aqueous solution containing water and some of the constituent components, and then used for polishing. For example, the polishing composition concentrate can be stored or transported, and then diluted at the time of use to prepare the polishing composition. Therefore, according to the present invention, a polishing composition concentrate according to this aspect is also provided (the polishing composition according to this aspect may be in the form of a concentrate).

[0096] A polishing composition in a concentrated form is advantageous from the viewpoints of convenience and cost reduction during production, distribution, storage, etc. The concentration ratio can be, for example, about 2 to 100 times in volume terms, and is usually about 5 to 50 times. The concentration ratio of the polishing composition (concentrate) according to a preferred embodiment (the concentration ratio when the polishing composition is in the form of a concentrate) is 8 to 40 times, for example, 10 to 30 times.

[0097] [Object to be polished] The polishing composition according to the present embodiment is applied to polishing of a silicon wafer (a substrate having a surface made of a silicon single crystal). That is, the object to be polished with the polishing composition according to the present embodiment is a silicon wafer. The polishing composition according to the present embodiment is applied to pre-polishing of a silicon wafer.

[0098] The silicon wafer to be polished with the polishing composition according to the present embodiment may be either p-type or n-type. The crystal orientation of the silicon wafer is not particularly limited and may be any of <100>, <110>, or <111>.

[0099] The shape of the object to be polished is not particularly limited. The polishing composition according to some embodiments of the present invention can be preferably used for polishing an object to be polished having a flat surface, such as a plate-like or polyhedral shape.

[0100] [Polishing Method] In another aspect of the present invention, there is provided a polishing method comprising polishing a silicon wafer with the polishing composition. For example, according to one embodiment, there is provided a polishing method comprising a step of polishing a silicon wafer with the polishing composition.

[0101] The surface of a silicon wafer is generally finished to a high-quality mirror finish through a lapping process and a polishing process. The polishing process is usually composed of multiple polishing steps, including a preliminary polishing process (a preliminary polishing process, a polishing process prior to the finish polishing process) and a finish polishing process (a final polishing process). For example, a polishing composition with high processing power (abrasive power) tends to be used in the stage of roughly polishing a silicon wafer (e.g., the preliminary polishing process), while a polishing composition with low abrasive power tends to be used in the stage of more delicate polishing (e.g., the finish polishing process). The polishing composition of this embodiment is used in the preliminary polishing process. Therefore, the present invention also provides a method for producing a silicon wafer, which includes a preliminary polishing process using the polishing composition.

[0102] The polishing composition according to the present invention is used for preliminary polishing of silicon wafers. The polishing composition according to the present invention can suitably polish silicon wafers having a surface condition with a surface roughness of 0.01 nm or more and 300 nm or less.

[0103] As the polishing apparatus, a general polishing apparatus 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 to which a polishing pad (polishing cloth) can be attached.

[0104] The polishing pad can be made of any material, including general nonwoven fabric, polyurethane, suede, etc. The polishing pad is preferably provided with grooves for collecting the polishing composition.

[0105] The polishing conditions are appropriately set depending on the stage of the polishing process in which the polishing composition is used.

[0106] In the preliminary polishing step, either a double-sided polishing machine or a single-sided polishing machine may be used. The rotation speed of the platen is usually about 5 rpm or more and 100 rpm or less, and preferably about 10 rpm or more and 50 rpm or less. When a double-sided polishing machine is used, the rotation speeds of the upper and lower rotating platens may be the same or different.

[0107] The object to be polished is usually pressed by a platen. The pressure at this time can be selected appropriately, but in the preliminary polishing step, it is usually preferably about 3 kPa or more and 60 kPa or less, and more preferably about 7 kPa or more and 50 kPa or less.

[0108] The supply rate of the polishing composition can also be selected appropriately depending on the size of the platen, but from an economical standpoint, in the case of the preliminary polishing step, it is usually preferably about 0.03 L / min or more and 10 L / min or less, and more preferably about 0.05 L / min or more and 5 L / min or less.

[0109] There are no particular restrictions on the temperature at which the polishing composition is maintained in the polishing apparatus, but from the standpoint of stabilizing the polishing rate and reducing defects, it is generally preferred that the temperature be approximately 15°C or higher and 40°C or lower, and more preferably approximately 18°C ​​or higher and 25°C or lower.

[0110] The above polishing conditions (polishing apparatus settings) are merely examples, and may be outside the above ranges or may be changed as appropriate. Such conditions can be appropriately set by a person skilled in the art.

[0111] Although the embodiments of the present invention have been described in detail, it is clear that this is for illustrative and exemplary purposes only and not for limitation, and that the scope of the present invention should be interpreted by the appended claims.

[0112] The present invention encompasses the following aspects and configurations.

[0113] [1] A polishing composition used for preliminary polishing of silicon wafers, comprising abrasive grains and at least one imidazole compound selected from the group consisting of imidazole and its derivatives (excluding 1-(3-aminopropyl)imidazole), wherein the content of the imidazole compound is 0.005 mass % or more and less than 0.08 mass % based on the total mass of the polishing composition.

[0114] [2] A polishing composition used for preliminary polishing of silicon wafers, comprising abrasive grains and at least one imidazole compound selected from the group consisting of imidazole and its derivatives (excluding 1-(3-aminopropyl)imidazole), wherein the mass ratio of the content of the imidazole compound to the content of the abrasive grains is less than 0.1.

[0115] [3] The polishing composition according to [1] or [2] above, further containing an alkali.

[0116] [4] The polishing composition according to any one of [1] to [3] above, further comprising a chelating agent.

[0117] [5] A concentrated polishing composition according to any one of [1] to [4] above.

[0118] [6] A polishing method comprising a step of polishing a silicon wafer with the polishing composition according to any one of [1] to [4] above.

[0119] 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.

[0120] <Average primary particle size of abrasive grains> The average primary particle size of abrasive grains was calculated from the specific surface area of ​​the abrasive grains measured by the BET method and the density of the abrasive grains. The specific surface area of ​​the abrasive grains measured by the BET method was measured using a "Flow Sorb II 2300" manufactured by Micromeritics.

[0121] <pH of Polishing Composition> The pH of the polishing composition was measured using a glass electrode hydrogen ion concentration indicator (Model: F-23, manufactured by Horiba, Ltd.). Three-point calibration was performed using standard buffer solutions: a phthalate pH buffer solution, pH: 4.01 (25°C), a neutral phosphate pH buffer solution, pH: 6.86 (25°C), and a carbonate pH buffer solution, pH: 10.01 (25°C). Thereafter, the glass electrode was immersed in the polishing composition for 2 minutes or more. After the pH of the polishing composition stabilized, the pH of the polishing composition was measured.

[0122] [Raw Materials for Polishing Composition] The polishing compositions shown in Table 1 below were prepared using the raw materials listed below.

[0123] Abrasive grains: colloidal silica Average primary particle size: 55 nm Imidazole compound: imidazole Alkali Inorganic alkali: potassium carbonate (K ２ CO ３ Organic alkali: tetramethylammonium hydroxide (TMAH) Chelating agent: ethylenediaminetetrakis(methylenephosphonic acid) (EDTPO) Dispersion medium: pure water.

[0124] [Preparation of Polishing Composition] (Example 1) The above-mentioned silica in the amount of the concentrate shown in Table 1 was used as abrasive grains, an imidazole compound in the amount of the concentrate shown in Table 1, and an inorganic alkali, potassium carbonate (K ２ CO ３ 1.66 mass% of tetramethylammonium hydroxide (TMAH) as an organic alkali, and 0.09 mass% of ethylenediaminetetrakis(methylenephosphonic acid) (EDTPO) as a chelating agent were added to pure water as a dispersion medium at room temperature (25°C) to obtain a concentrate. The amount of pure water added was such that the total amount of the concentrate was 100 mass%. The concentrate was stirred and mixed at room temperature (25°C) for 30 minutes, and then pure water as a dispersion medium was added to the mixture at the dilution ratio shown in Table 1 to prepare the polishing composition of Example 1. The pH of the obtained polishing composition of Example 1 was 10.7. In Table 1 below, "Imidazole compound / silica" represents the mass ratio of the imidazole compound content to the silica (abrasive grain) content.

[0125] (Examples 2 to 4, Comparative Examples 1 and 2) Polishing compositions of Examples 2 to 5 and Comparative Examples 1 and 2 were prepared in the same manner as in Example 1, except that the contents of abrasive grains and imidazole compound in the concentrated solution were changed as shown in Table 1 below. The pH of each polishing composition was 10.5 to 10.8. The particle size of the abrasive grains in each polishing composition was the same as the particle size of the abrasive grains used.

[0126] (Example 5) The content of the imidazole compound in the concentrated solution was changed as shown in Table 1 below, and the inorganic alkali potassium carbonate (K ２ CO３ A polishing composition of Example 5 was prepared in the same manner as in Example 1, except that the amount of ) was changed to 1.30 mass%. The pH of each polishing composition was 10.6. The particle size of the abrasive grains in each polishing composition was the same as the particle size of the abrasive grains used.

[0127] <Evaluation of Polishing Rate> The surface of a silicon wafer was pre-polished using the polishing compositions of Examples and Comparative Examples under the following polishing condition 1.

[0128] The polishing rate was calculated by dividing the difference in weight of the silicon wafer before and after pre-polishing [(weight before polishing) - (weight after polishing)] by the polishing time. In Table 1, the polishing rate is expressed as the relative ratio of the polishing rate of each polishing composition to the polishing rate of the polishing composition of Comparative Example 2.

[0129] [Polished object] Silicon wafer: bare-Si p-type crystal orientation <100> size 60 mm x 60 mm.

[0130] [Preliminary polishing: Polishing condition 1] Polishing machine: Single-sided polishing machine EJ-380IN (manufactured by Engis Japan Co., Ltd.) Polishing pad: Polyurethane foam pad MH-S15 (manufactured by Nitta DuPont Co., Ltd.) Polishing load: 16 kPa Platen rotation speed: 50 rpm (*Counterclockwise rotation is positive) Head rotation speed: 50 rpm (*Counterclockwise rotation is positive) Polishing time: 10 min Maintenance of polishing environment: 25°C Supply rate of polishing composition: 50 mL / min (*Flowing) Polishing composition for preliminary polishing: Polishing compositions of the Examples and Comparative Examples.

[0131] <Evaluation of Surface Quality> The surface of a silicon wafer was pre-polished using the polishing composition of Example 3 under the following polishing condition 2.

[0132] [Polished object] Silicon wafer: bare-Si p-type crystal orientation <100> size 4 inch etched surface (surface roughness Ra approximately 300 nm).

[0133] [Preliminary polishing: Polishing conditions 2] Polishing machine: Single-sided polishing machine EJ-380IN (manufactured by Engis Japan Co., Ltd.) Polishing pad: Polyurethane foam pad MH-S15 (manufactured by Nitta DuPont Co., Ltd.) Polishing load: 22 kPa Platen rotation speed: 50 rpm (*Counterclockwise rotation is positive) Head rotation speed: 50 rpm (*Counterclockwise rotation is positive) Polishing time: 20 min Polishing environment maintained: 25°C Supply rate of polishing composition: 50 mL / min (*Flowing) Polishing composition for preliminary polishing: Polishing composition of Example 3.

[0134] The surface roughness Ra of the silicon wafer after polishing was measured using a white light interferometer NewView 9000 manufactured by Zygo Corp. with an objective lens of 2.75x and a zoom lens of 0.5x. The surface roughness Ra of the silicon wafer after polishing with the polishing composition of Example 3 was 0.99 nm.

[0135]

[0136] As is clear from Table 1 above, the polishing compositions of Examples can improve the polishing rate. On the other hand, the polishing compositions of Comparative Examples have inferior polishing rates. Furthermore, the polishing composition of Example 3 not only improves the polishing rate but also enables the production of silicon wafers with good surface quality.

[0137] Therefore, it is clear that the polishing composition according to the present embodiment can improve the removal rate.

[0138] This application is based on Japanese Patent Application No. 2024-053664, filed on March 28, 2024, the disclosure of which is incorporated by reference in its entirety.

Claims

1. A polishing composition used for preliminary polishing of silicon wafers, comprising abrasive grains and at least one imidazole compound selected from the group consisting of imidazole and its derivatives (excluding 1-(3-aminopropyl)imidazole), wherein the content of the imidazole compound is 0.005 mass % or more and less than 0.08 mass % based on the total mass of the polishing composition.

2. A polishing composition used for preliminary polishing of silicon wafers, comprising abrasive grains and at least one imidazole compound selected from the group consisting of imidazole and its derivatives (excluding 1-(3-aminopropyl)imidazole), wherein the mass ratio of the content of the imidazole compound to the content of the abrasive grains is less than 0.

1.

3. The polishing composition according to claim 1 or 2, further comprising an alkali.

4. The polishing composition according to claim 1 or 2, further comprising a chelating agent.

5. A concentrated solution of the polishing composition according to claim 1 or 2.

6. A polishing method comprising the step of polishing a silicon wafer with the polishing composition according to claim 1 or 2.

Images