Grinding composition

Abstract

Provided is a polishing composition capable of achieving at a high level both suppression of a reduction in polishing rate and elimination of bulging in HLM periphery. Provided is a polishing composition that is for use in a step for preliminary polishing of a silicon wafer. The polishing composition comprises abrasive grains, a basic compound, a chelating agent, a surfactant, a nitrogen-containing water-soluble polymer, and water. The ratio (B / S) of the weight concentration (B) of the basic compound to the weight concentration (S) of the surfactant is 50 or more.

Description

[Technical Field]

[0001] The present invention relates to a polishing composition. More specifically, it relates to a polishing composition for pre-polishing silicon wafers. This application claims priority to Japanese Patent Application No. 2021-5836, filed on January 18, 2021, the entire contents of which are incorporated herein by reference. [Background technology]

[0002] The surface of silicon wafers used in the manufacture of semiconductor products, etc., is generally finished to a high-quality mirror surface through a lapping process (rough polishing process) and a polishing process (precision polishing process). The polishing process typically includes a preliminary polishing process and a finish polishing process. The preliminary polishing process typically includes a rough polishing process (primary polishing process) and an intermediate polishing process (secondary polishing process).

[0003] For purposes such as identification, silicon wafers may be marked with a barcode, number, symbol, or other mark (hard laser mark; hereinafter, sometimes referred to as "HLM") by irradiating the front or back surface of the silicon wafer with laser light. The application of HLM is generally performed after the silicon wafer lapping process is completed and before the polishing process begins. Typically, the irradiation of laser light for applying HLM creates an altered layer on the silicon wafer surface around the HLM. Although the HLM portion of the silicon wafer itself is not used in the final product, if the altered layer is not properly polished in the polishing process (particularly the pre-polishing process) after HLM application, it may cause a protrusion, resulting in an unnecessarily low yield. However, because the altered layer is transformed into polysilicon or the like by the energy of the laser light and is difficult to polish, it has been difficult to effectively suppress the occurrence of such protrusions using conventional polishing compositions for silicon wafers. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 189124 [Patent Document 2] Japanese Patent Application Publication No. 2020-021810 Summary of the Invention [Problem to be solved by the invention]

[0005] Technical documents related to eliminating the protrusions around the HLM (hereinafter simply referred to as "protrusions") include Patent Documents 1 and 2. The above patent documents propose eliminating the protrusions by using a specific type of surfactant, but they still do not sufficiently achieve both a high polishing rate suitable for the pre-polishing step and the elimination of the protrusions.

[0006] Therefore, an object of the present invention is to provide a polishing composition for use in the preliminary polishing step of silicon wafers, which can simultaneously suppress a decrease in the polishing rate and eliminate the protrusion around the HLM at a high level. [Means for solving the problem]

[0007] According to the present invention, there is provided a polishing composition for use in a pre-polishing step of silicon wafers. The polishing composition comprises abrasive grains, a basic compound, a chelating agent, a surfactant, a nitrogen-containing water-soluble polymer, and water. The ratio (B / S) of the weight concentration (B) of the basic compound to the weight concentration (S) of the surfactant is 50 or more. A polishing composition having such a configuration can effectively eliminate the protrusion around the HLM while suppressing a decrease in the polishing rate.

[0008] In this specification, "eliminating the protrusion around the HLM" means reducing the height from the reference plane around the HLM of the silicon wafer to the highest point of the protrusion. The height from the reference plane around the HLM of the silicon wafer to the highest point of the protrusion can be measured, for example, by the method described in the examples below.

[0009] In a preferred embodiment of the polishing composition disclosed herein, the ratio (P / S) of the weight concentration (P) of the nitrogen-containing water-soluble polymer to the weight concentration (S) of the surfactant is greater than 0.5. In this configuration, the protrusion around the HLM can be more effectively eliminated while suppressing a decrease in the polishing rate.

[0010] In a preferred embodiment of the polishing composition disclosed herein, the surfactant comprises a nonionic surfactant, which can more effectively eliminate the protrusion around the HLM while suppressing a decrease in the polishing rate.

[0011] In a preferred embodiment, the nonionic surfactant is a polyoxyalkylene alkyl ether, which can more effectively eliminate the protrusion around the HLM while suppressing a decrease in the polishing rate.

[0012] In another preferred embodiment of the polishing composition disclosed herein, the abrasive grains include silica grains. In polishing using silica grains as abrasive grains, the surfactant can more effectively eliminate the protrusion around the HLM while suppressing a decrease in the polishing rate. DETAILED DESCRIPTION OF THE INVENTION

[0013] <Abrasive grain> The polishing composition disclosed herein contains abrasive grains. The material and properties of the abrasive grains are not particularly limited and can be appropriately selected depending on the use mode of the polishing composition. Examples of abrasive grains include inorganic particles, organic particles, and organic-inorganic composite particles. Specific examples of inorganic particles 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. Specific examples of organic particles include polymethyl methacrylate (PMMA) particles, poly(meth)acrylic acid particles, and polyacrylonitrile particles. Here, (meth)acrylic acid refers collectively to acrylic acid and methacrylic acid. Abrasive grains can be used singly or in combination of two or more types.

[0014] The abrasive grains are preferably inorganic particles, and particularly preferably particles made of metal or semi-metal oxides. Silica grains are a suitable example of abrasive grains that can be used in the technology disclosed herein. The reason for this is as follows: When polishing a silicon wafer, if silica grains made of the same element as the object to be polished and oxygen atoms are used as abrasive grains, no residue of metals or semi-metals other than silicon is generated after polishing. This eliminates the risk of contamination of the silicon wafer surface or deterioration of the electrical properties of the silicon wafer due to the diffusion of metals or semi-metals other than silicon into the object to be polished. Furthermore, since the hardness of silicon and silica is similar, polishing can be performed without causing excessive damage to the silicon wafer surface. Specific examples of silica particles include colloidal silica, fumed silica, precipitated silica, etc. From the viewpoint of preventing scratches from occurring on the surface of the object to be polished and realizing a surface with lower haze, preferred silica particles include colloidal silica and fumed silica. Of these, colloidal silica is preferred.

[0015] In the technology disclosed herein, 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. Also, 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.

[0016] The average primary particle diameter of the abrasive grains (typically silica particles) is not particularly limited, but from the viewpoint of simultaneously suppressing a decrease in the polishing rate and improving the ability to eliminate bumps, it is preferably 5 nm or more, more preferably 10 nm or more, and particularly preferably 20 nm or more. From the viewpoint of obtaining a higher polishing effect, the average primary particle diameter is preferably 25 nm or more, and even more preferably 30 nm or more. Abrasive grains having an average primary particle diameter of 40 nm or more may be used. Furthermore, from the viewpoint of preventing scratches, the average primary particle diameter of the abrasive grains is preferably 200 nm or less, more preferably 150 nm or less, for example 100 nm or less.

[0017] In this specification, the average primary particle size is calculated from the specific surface area (BET value) measured by the BET method as follows: average primary particle size (nm) = 6000 / (true density (g / cm 3 )×BET value(m 2 / g) The specific surface area can be measured using, for example, a surface area measuring device manufactured by Micromeritics, under the trade name "Flow Sorb II 2300."

[0018] The average secondary particle diameter of the abrasive grains (e.g., silica particles) is not particularly limited, but is preferably 15 nm or more, more preferably 30 nm or more, from the viewpoint of simultaneously suppressing a decrease in the polishing rate and improving the ability to eliminate bumps. From the viewpoint of obtaining a higher polishing effect, the average secondary particle diameter is preferably 50 nm or more. Furthermore, from the viewpoint of preventing scratches, the average secondary particle diameter of the abrasive grains is suitably 300 nm or less, preferably 260 nm or less, more preferably 220 nm or less.

[0019] In this specification, the average secondary particle size refers to the particle size (volume average particle size) measured by dynamic light scattering. The average secondary particle size of the abrasive grains can be measured, for example, using an Otsuka Electronics FPAR-1000 or an equivalent.

[0020] The shape (external shape) of the abrasive grains may be spherical or non-spherical. Specific examples of non-spherical abrasive grains include peanut-shaped (i.e., the shape of a peanut shell), cocoon-shaped, confetti-shaped, and rugby ball-shaped.

[0021] Although not particularly limited, the average value of the long axis / short axis ratio (average aspect ratio) of the primary particles of the abrasive grains is preferably 1.05 or more, more preferably 1.1 or more. By increasing the average aspect ratio of the abrasive grains, a higher polishing rate can be achieved. Furthermore, from the viewpoint of reducing scratches, the average aspect ratio of the abrasive grains is preferably 3.0 or less, more preferably 2.0 or less. In some embodiments, the average aspect ratio of the abrasive grains may be, for example, 1.5 or less, 1.4 or less, or 1.3 or less.

[0022] The shape (outline) and average aspect ratio of the abrasive grains can be determined, for example, by observation using 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 abrasive grains 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.

[0023] The content of abrasive grains in the polishing composition is not particularly limited, but is typically 0.1% by weight or more. From the viewpoint of simultaneously suppressing a decrease in the polishing rate and improving the ability to eliminate bumps, it is preferably 0.2% by weight or more, more preferably 0.5% by weight or more, and even more preferably 1.0% by weight or more. By increasing the content of abrasive grains, a higher polishing rate can be achieved. In addition, the content is usually 10% by weight or less, preferably 5% by weight or less, more preferably 3% by weight or less or 2% by weight or less (for example, 1.3% by weight or less).

[0024] <Basic compounds> The polishing composition disclosed herein contains a basic compound. Here, the basic compound refers to a compound that has the function of increasing the pH of the polishing composition when added to the composition. The basic compound may be an organic basic compound or an inorganic basic compound. The basic compound may be used alone or in combination of two or more.

[0025] Examples of the organic basic compound include quaternary ammonium salts such as tetraalkylammonium salts. The anion in the ammonium salts is, for example, OH. - , F - , Cl - , Br - , I - , ClO4 - , BH4 - , HCO3 - For example, quaternary ammonium salts such as choline, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and tetramethylammonium hydrogen carbonate can be preferably used. Among these, tetramethylammonium hydroxide is preferred. Other examples of organic basic compounds include quaternary phosphonium salts such as tetraalkylphosphonium salts. The anion in the phosphonium salts is, for example, OH - , F - , Cl- , Br - , I - , ClO4 - , BH4 - , HCO3 - For example, halides or hydroxides of tetramethylphosphonium, tetraethylphosphonium, tetrapropylphosphonium, tetrabutylphosphonium, etc. can be preferably used. Other examples of organic basic compounds include amines such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N-(β-aminoethyl)ethanolamine, hexamethylenediamine, diethylenetriamine, and triethylenetetramine; piperazines such as 1-(2-aminoethyl)piperazine and N-methylpiperazine; azoles such as imidazole and triazole; guanidine; and the like.

[0026] Examples of inorganic basic compounds include ammonia; hydroxides of ammonia, alkali metals, or alkaline earth metals; carbonates of ammonia, alkali metals, or alkaline earth metals; hydrogen carbonates of ammonia, alkali metals, or alkaline earth metals; etc. Specific examples of the hydroxides include potassium hydroxide and sodium hydroxide. Specific examples of the carbonates or hydrogen carbonates include ammonium hydrogen carbonate, ammonium carbonate, potassium hydrogen carbonate, potassium carbonate, sodium hydrogen carbonate, sodium carbonate, etc.

[0027] Preferred basic compounds include ammonia, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, ammonium hydrogen carbonate, ammonium carbonate, potassium hydrogen carbonate, potassium carbonate, sodium hydrogen carbonate, and sodium carbonate. Among these, preferred compounds include ammonia, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide, and potassium carbonate. More preferred compounds include tetramethylammonium hydroxide and potassium carbonate.

[0028] The content of the basic compound in the polishing composition is usually 0.005% by weight or more. From the viewpoint of polishing rate, etc., the content is preferably 0.01% by weight or more, more preferably 0.05% by weight or more, and even more preferably 0.1% by weight or more. The content of the basic compound is usually 1% by weight or less, preferably 0.5% by weight or less, and more preferably 0.3% by weight or less. In a polishing composition that is used as a polishing liquid as it is, the content may be, for example, 0.5% by weight or less, or 0.2% by weight or less.

[0029] <Surfactant> The polishing composition disclosed herein further contains a surfactant. The ratio (B / S) of the weight concentration (B) of the basic compound to the weight concentration (S) of the surfactant is preferably 50 or more. A B / S ratio of 50 or more achieves a favorable balance between the promotion of polishing by the basic compound and the protection of the polished surface by the surfactant. Furthermore, by using a nitrogen-containing water-soluble polymer in combination, the nitrogen-containing water-soluble polymer acts on the protrusions around the HLM, and the surfactant can efficiently act on the protrusions via the nitrogen-containing water-soluble polymer. This effectively improves the ability to eliminate protrusions while suppressing a decrease in the polishing rate. Note that the above mechanism is the inventor's speculation based on experimental results, and the technology disclosed herein should not be interpreted as being limited to the above mechanism.

[0030] In some embodiments, the B / S ratio is preferably 70 or more, more preferably 120 or more, and may be 150 or more, 200 or more, 300 or more, or 400 or more. By increasing the B / S ratio, the effect of improving the ability to eliminate protuberances while suppressing a decrease in the polishing rate can be more preferably achieved. Furthermore, from the viewpoint of the surface quality after polishing, in some embodiments, the B / S ratio can be, for example, 5000 or less, preferably 2000 or less, more preferably 1200 or less, and may be 800 or less, or 600 or less.

[0031] Surfactants can be any of anionic, cationic, nonionic, and amphoteric surfactants. Typically, anionic or nonionic surfactants are preferred. Nonionic surfactants are more preferred from the standpoints of low foaming and ease of pH adjustment. 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; and copolymers of multiple oxyalkylenes (e.g., diblock copolymers, triblock copolymers, random copolymers, and alternating copolymers). The surfactant preferably includes a surfactant containing a polyoxyalkylene structure (a repeating structure of oxyalkylene units, i.e., a polyoxyalkylene chain; hereinafter, sometimes referred to as a "POA chain"). The surfactants can be used alone or in combination.

[0032] Examples of the oxyalkylene unit include an oxyethylene unit, an oxypropylene unit, and an oxybutylene unit. Each of these oxyalkylene units may be a repeating unit derived from the corresponding alkylene oxide, but is not limited thereto. The oxyalkylene unit contained in the POA chain of the surfactant may be one type or two or more types. In a POA chain containing two or more types of oxyalkylene units, the content ratio of these oxyalkylene units is not particularly limited. Furthermore, in a POA chain containing two or more types of oxyalkylene units, these oxyalkylene units may be random copolymers, block copolymers, alternating copolymers, or graft copolymers of the corresponding alkylene oxides. One surfactant may be used alone, or two or more surfactants may be used in combination.

[0033] Specific examples of surfactants include polyoxyalkylene alkyl ethers (e.g., polyoxyethylene alkyl ether, polyoxypropylene alkyl ether, polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene polyoxybutylene alkyl ether); polyoxyalkylene alkenyl ethers (e.g., polyoxyethylene oleyl ether); polyoxyalkylene phenyl ethers (e.g., polyoxyethylene phenyl ether; polyoxyethylene styrenated phenyl ether; polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene dodecyl phenyl ether, and other polyoxyalkylene alkyl phenyl ethers); polyoxyalkylene alkylamines (e.g., polyoxyethylene laurylamine, polyoxyethylene stearylamine, polyoxyethylene oleylamine); polyoxyalkylene fatty acid esters (e.g., polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene monoesters and diesters of saturated or unsaturated fatty acids, such as polyoxyethylene monooleate, polyoxyethylene distearate, and polyoxyethylene dioleate; polyoxyalkylene sorbitan fatty acid esters (e.g., polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopaltimate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, and polyoxyethylene sorbitan trioleate); fatty acid polyoxyalkylene sorbits (e.g., polyoxyethylene sorbitan tetraoleate); block copolymers of ethylene oxide (EO) and propylene oxide (PO) (e.g., diblock copolymers, PEO (polyethylene oxide)-PPO (polypropylene oxide)-PEO triblock copolymers, and PPO-PEO-PPO triblock copolymers); random copolymers of EO and PO; and other surfactants, such as polyoxyethylene glycol, polyoxyethylene castor oil, and polyoxyethylene hydrogenated castor oil. In some embodiments, polyoxyalkylene alkyl ethers may be preferably used as surfactants.

[0034] The number of oxyalkylene units contained in the surfactant, i.e., the number of moles of alkylene oxide added, can be selected so that the effects of using the surfactant are appropriately exhibited. The upper limit of the number of moles of alkylene oxide added is not particularly limited, and is, for example, 100 or less, suitably 80 or less. From the viewpoint of suppressing a decrease in the polishing rate, it is preferably 60 or less, more preferably 40 or less, even more preferably 30 or less, and may be 25 or less, or may be 18 or less (e.g., 14 or less). The lower limit of the number of moles of alkylene oxide added is not particularly limited, and is, for example, 3 or more, suitably 5 or more, preferably 7 or more (e.g., 9 or more), may be 10 or more, may be 12 or more, or may be 15 or more (e.g., 20 or more).

[0035] In order to effectively suppress a decrease in the polishing rate while improving the ability to eliminate protuberances, surfactants having a POA chain containing at least oxyethylene units can be preferably used in some embodiments. The proportion of the number of oxyethylene units (EO number) to the total number of oxyalkylene units contained in the surfactant may be, for example, 1% or more, preferably 5% or more, more preferably 10% or more, 20% or more, 30% or more, 45% or more, or 55% or more. 100% of the oxyalkylene units may be oxyethylene units. When the surfactant contains a combination of oxyethylene units and oxypropylene units, the ratio of the number of oxypropylene units (PO number) to the number of oxyethylene units (PO / EO) may be, for example, 5.0 or less, preferably 3.0 or less, and more preferably 2.0 or less. In some embodiments, the ratio (PO / EO) may be, for example, 1.5 or less, 1.0 or less, or 0.8 or less. Furthermore, the ratio (PO / EO) may be, for example, 0.1 or more, 0.2 or more, 0.4 or more, 0.6 or more, 0.9 or more, or 1.3 or more.

[0036] When a polyoxyalkylene alkyl ether is used as a surfactant, the number of carbon atoms in the alkyl group in the alkyl ether is not particularly limited and can be selected so that the effects of using the surfactant are appropriately exhibited. From the viewpoint of easily exhibiting surfactant activity, the number of carbon atoms in the alkyl group is suitably 3 or more, preferably 5 or more. Furthermore, from the viewpoint of surface protection of the object to be polished, the number of carbon atoms in the alkyl group is preferably 7 or more, more preferably 8 or more. In some embodiments, the number of carbon atoms in the alkyl group may be 10 or more or may be 12 or more. The number of carbon atoms in the alkyl group may be, for example, 27 or less, 25 or less, or 20 or less. From the viewpoint of the solubility of the surfactant, in some embodiments, the number of carbon atoms in the alkyl group is preferably 18 or less, more preferably 16 or less, and even more preferably 14 or less. The alkyl group may be linear or branched. Specific examples of the alkyl group in the alkyl ether include, but are not limited to, a propyl group, a butyl group, a pentyl group, a hexyl group, an octyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, an isodecyl group, a lauryl group, a tridecyl group, a cetyl group, a stearyl group, and an isostearyl group.

[0037] The polyoxyalkylene alkyl ether preferably includes those in which the primary carbon of an alkyl group is bonded to a polyoxyalkylene via an ether bond (hereinafter also referred to as "polyoxyalkylene primary alkyl ether") and those in which the secondary carbon of an alkyl group is bonded to a polyoxyalkylene via an ether bond (hereinafter also referred to as "polyoxyalkylene secondary alkyl ether"). In the polyoxyalkylene primary alkyl ether, the alkyl group may be linear or branched. In the polyoxyalkylene secondary alkyl ether, the two alkyl groups bonded to the secondary carbon may be the same or different. The two alkyl groups bonded to the secondary carbon may each independently be linear or branched.

[0038] In some embodiments, polyoxyalkylene primary alkyl ethers can be preferably used as surfactants from the viewpoint of improving the ability to eliminate bumps. The weight ratio of polyoxyalkylene primary alkyl ethers in the surfactants may be, for example, 50% by weight or more, 70% by weight or more, 90% by weight or more, or even 100% by weight. The polyoxyalkylene primary alkyl ethers may be used alone or in combination of two or more.

[0039] In the polishing composition disclosed herein, the weight-average molecular weight (Mw) of the surfactant is not particularly limited and can be appropriately selected within a range in which the effects of the present invention are adequately exhibited. From the viewpoint of suppressing a decrease in the polishing rate, etc., in some embodiments, the Mw of the surfactant is suitably less than 4000, preferably 3000 or less, more preferably 2500 or less, even more preferably 2000 or less, and may be 1500 or less. Furthermore, from the viewpoint of surface activity, etc., the Mw of the surfactant is suitably 200 or more, and from the viewpoint of improving the ability to eliminate protuberances, etc., it is preferably 300 or more (e.g., 350 or more). In some embodiments, the Mw of the surfactant may be 400 or more, 500 or more, 600 or more, or 700 or more.

[0040] In this specification, the Mw of a surfactant is the molecular weight calculated from the chemical formula. Alternatively, similar to the nitrogen-containing water-soluble polymer described below, the molecular weight can be calculated from a value based on aqueous gel permeation chromatography (GPC) (aqueous, polyethylene oxide equivalent).

[0041] The content of the surfactant in the polishing composition is not particularly limited as long as it is within a range that does not significantly impair the effects of the present invention. -6 % by weight or more, and from the viewpoint of improving the swelling elimination property, -6 It is appropriate to set the content to 1.0×10 wt% or more. -5 Weight% or more, 5.0×10 -5% by weight or more, or even 1.0 × 10 -4 It is preferable that the content of the surfactant is 0.5% by weight or more. In addition, the content of the surfactant can be, for example, 0.5% by weight or less, and from the viewpoint of suppressing a decrease in the polishing rate, it is appropriate to set it to 0.25% by weight or less, preferably 0.1% by weight or less, more preferably 0.05% by weight or less, and may be 0.01% by weight or less. In addition, when the polishing composition disclosed herein contains two or more surfactants, the content refers to the total content of these surfactants. The content of the surfactant can be preferably adopted in an embodiment in which the polishing composition is used in the form of a polishing liquid.

[0042] <Nitrogen-containing water-soluble polymer> The polishing composition disclosed herein further contains a nitrogen-containing water-soluble polymer. The nitrogen-containing water-soluble polymer is not particularly limited as long as it is a water-soluble polymer having one or more nitrogen atoms (N) in the molecule, and may be a homopolymer or a copolymer. The copolymer may be, for example, a diblock copolymer, a triblock copolymer, a random copolymer, an alternating copolymer, or the like. The nitrogen-containing water-soluble polymer may be used alone or in combination of two or more.

[0043] The nitrogen-containing water-soluble polymer may be, for example, a water-soluble polymer containing a nitrogen atom in the main chain, a water-soluble polymer containing a nitrogen atom in the side chain, etc. Specific examples of water-soluble polymers containing a nitrogen atom in the main chain include homopolymers and copolymers (for example, copolymers in which the copolymerization ratio of alkyleneimine monomers exceeds 50% by weight) of alkyleneimine monomers (for example, ethyleneimine, propyleneimine, N-acetylethyleneimine, N-propanoylethyleneimine, N-acetylpropyleneimine, N-formylethyleneimine).

[0044] Specific examples of water-soluble polymers containing nitrogen atoms in their side chains include N-vinyl polymers and N-(meth)acryloyl polymers. Specific examples of N-vinyl polymers include polymers containing repeating units derived from monomers having nitrogen-containing heterocycles (e.g., lactam rings). Examples of such polymers include homopolymers and copolymers of N-vinyl lactam monomers (e.g., copolymers in which the copolymerization ratio of N-vinyl lactam monomers exceeds 50% by weight), homopolymers and copolymers of N-vinyl linear amides (e.g., copolymers in which the copolymerization ratio of N-vinyl linear amides exceeds 50% by weight), and the like.

[0045] Specific examples of N-vinyl lactam monomers (i.e., compounds having a lactam structure and an N-vinyl group in one molecule) include N-vinylpyrrolidone (VP), N-vinylpiperidone, N-vinylmorpholinone, N-vinylcaprolactam (VC), N-vinyl-1,3-oxazin-2-one, and N-vinyl-3,5-morpholinedione. Specific examples of polymers containing N-vinyl lactam monomer units include polyvinylpyrrolidone, polyvinylcaprolactam, random copolymers of VP and VC, random copolymers of one or both of VP and VC with other vinyl monomers (e.g., acrylic monomers, vinyl ester monomers, etc.), block copolymers, alternating copolymers, and graft copolymers containing polymer chains containing one or both of VP and VC. Specific examples of N-vinyl linear amides include N-vinylacetamide, N-vinylpropionic acid amide, and N-vinylbutyric acid amide.

[0046] Specific examples of N-(meth)acryloyl polymers include homopolymers and copolymers of N-(meth)acryloyl monomers (typically copolymers in which the copolymerization ratio of N-(meth)acryloyl monomers exceeds 50% by weight). Examples of N-(meth)acryloyl monomers include linear amides having an N-(meth)acryloyl group and cyclic amides having an N-(meth)acryloyl group.

[0047] Examples of chain amides having an N-(meth)acryloyl group include (meth)acrylamide; N-alkyl(meth)acrylamides such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, N-isopropyl(meth)acrylamide, and Nn-butyl(meth)acrylamide; and N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, and N,N-di(n-butyl)(meth)acrylamide. Examples of polymers containing chain amides having an N-(meth)acryloyl group as a monomer unit include homopolymers of N-isopropylacrylamide and copolymers of N-isopropylacrylamide (for example, copolymers in which the copolymerization ratio of N-isopropylacrylamide exceeds 50% by weight).

[0048] Examples of cyclic amides having an N-(meth)acryloyl group include N-acryloylmorpholine, N-acryloylthiomorpholine, N-acryloylpiperidine, N-acryloylpyrrolidine, N-methacryloylmorpholine, N-methacryloylpiperidine, and N-methacryloylpyrrolidine. Examples of polymers containing cyclic amides having an N-(meth)acryloyl group as monomer units include acryloylmorpholine-based polymers (PACMO). Typical examples of acryloylmorpholine-based polymers include homopolymers of N-acryloylmorpholine (ACMO) and copolymers of ACMO (e.g., copolymers with a copolymerization ratio of ACMO exceeding 50% by weight). In acryloylmorpholine-based polymers, the proportion of moles of ACMO units in the total moles of repeating units is typically 50% or more, and suitably 80% or more (e.g., 90% or more, typically 95% or more). All repeating units of the water-soluble polymer may be substantially composed of ACMO units.

[0049] The weight average molecular weight (Mw) of the nitrogen-containing water-soluble polymer is not particularly limited. The Mw of the nitrogen-containing water-soluble polymer is, for example, 5×10 3 From the viewpoint of improving the ability to eliminate bumps, 4 It is preferable that the ratio is 1.2×10 or more, and more preferably 1.2×10 4 More preferably, 1.5 × 10 4 The Mw of the nitrogen-containing water-soluble polymer is, for example, 80×10 4 From the viewpoint of the filterability of the polishing composition and the cleanability of the object to be polished, it is preferable that the polishing composition has a particle size of 60×10 or less. 4 It is appropriate that the value is less than 40 x 10 4 From the viewpoint of suppressing a decrease in the polishing rate, in some embodiments, the Mw of the nitrogen-containing water-soluble polymer is preferably 25×10 or less. 4 Preferably, it is 15 x 10 or less. 4 It is more preferable that it is 9×10 or less. 4 Less than 6×10 is also acceptable. 4 Less than 3×10 is also acceptable. 4 The following is also acceptable.

[0050] In this specification, the Mw of the nitrogen-containing 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. Similar methods are also used in the examples described below. [GPC measurement conditions] Sample concentration: 0.1% by weight Column: TSKgel GMPWXL Detector: differential refractometer Eluent: 100 mM sodium nitrate aqueous solution / acetonitrile = 108 / 02 Flow rate: 1mL / min Measurement temperature: 40℃ Sample injection volume: 200 μL

[0051] The content of the nitrogen-containing water-soluble polymer in the polishing composition is not particularly limited as long as it is within a range that does not significantly impair the effects of the present invention. -6 % by weight or more, and from the viewpoint of improving the swelling elimination property, -6 It is appropriate to set the content to 1.0×10 wt % or more, preferably 1.0×10 -5 % by weight or more, more preferably 5.0 × 10 -5 % by weight or more, more preferably 1.0 × 10 -4 % by weight or more. The content of the nitrogen-containing water-soluble polymer can be, for example, 0.5% by weight or less, and from the viewpoint of suppressing a decrease in the polishing rate, it is appropriate to set it to 0.25% by weight or less, preferably 0.1% by weight or less, more preferably 0.05% by weight or less, and may be 0.01% by weight or less, or may be 0.001% by weight or less. When the polishing composition disclosed herein contains two or more nitrogen-containing water-soluble polymers, the above content refers to the total content of these nitrogen-containing water-soluble polymers. The above content of the nitrogen-containing water-soluble polymer can be preferably adopted, for example, in an embodiment in which the polishing composition is used in the form of a polishing liquid.

[0052] The ratio (P / S) of the weight concentration (P) of the nitrogen-containing water-soluble polymer to the weight concentration (S) of the surfactant in the polishing composition is not particularly limited as long as it is within a range that does not significantly impair the effects of the technology disclosed herein. The P / S ratio is typically 0.1 or more, preferably 0.2 or more, more preferably 0.5 or more (greater than 0.5), and may be 1.0 or more (greater than 1.0), or even 2.0 or more. By increasing the P / S ratio, the effects of suppressing a decrease in the polishing rate and improving the ability to eliminate protuberances can be preferably achieved at the same time. Furthermore, the P / S ratio can be, for example, 10 or less, preferably 8.0 or less, more preferably 6.0 or less, and may be 5.0 or less, or 4.0 or less.

[0053] <Chelating agent> The polishing composition disclosed herein contains a chelating agent. The chelating agent forms complex ions with metal impurities that may be contained in the polishing composition and captures them. This serves to suppress contamination of the object to be polished by metal impurities. The chelating agents can be used alone or in combination of two or more. Examples of the chelating agent include aminocarboxylic acid chelating agents, organic phosphonic acid chelating agents, and organic sulfonic acid chelating agents. Examples of the aminocarboxylic acid chelating agent include ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetate, nitrilotriacetic acid, sodium nitrilotriacetate, ammonium nitrilotriacetate, hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetate, diethylenetriaminepentaacetic acid, sodium diethylenetriaminepentaacetate, triethylenetetraminehexaacetic acid, and sodium triethylenetetraminehexaacetate. Examples of organic phosphonic acid chelating agents include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri(methylenephosphonic acid), ethylenediaminetetrakis(methylenephosphonic acid), 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. Examples of organic sulfonic acid chelating agents include ethylenediaminetetrakismethylenesulfonic acid. Of these, organic phosphonic acid chelating agents or organic sulfonic acid chelating agents are more preferred, and ethylenediaminetetrakis(methylenephosphonic acid) is particularly preferred.

[0054] The content of the chelating agent in the polishing composition is usually 0.0001 wt% or more. The content is preferably 0.0005 wt% or more, and more preferably 0.001 wt% or more. The content of the chelating agent is usually 0.05 wt% or less, preferably 0.01 wt% or less, more preferably 0.008 wt% or less, and even more preferably 0.005 wt% or less.

[0055] <Water> The polishing composition disclosed herein contains water. Ion-exchanged water (deionized water), pure water, ultrapure water, distilled water, etc. can be preferably used as the water. To minimize the inhibition of the functions of other components contained in the polishing composition, the water used preferably has a total transition metal ion content of, for example, 100 ppb or less. For example, the purity of the water can be increased by removing impurity ions using an ion exchange resin, removing foreign matter using a filter, distillation, or other procedures.

[0056] <Preparation of Polishing Composition> The method for producing the polishing composition disclosed herein is not particularly limited. For example, the components contained in the polishing composition may be mixed using a well-known mixing device such as a blade mixer, an ultrasonic disperser, or a homomixer. The manner in which these components are mixed is not particularly limited. For example, all the components may be mixed at once, or may be mixed in an appropriately set order.

[0057] The polishing composition disclosed herein may be a single-component type or a multi-component type such as a two-component type. For example, the polishing composition may be configured so that a liquid A containing some of the components of the polishing composition and a liquid B containing the remaining components are mixed together and used to polish an object to be polished.

[0058] <Polishing liquid> The polishing composition disclosed herein is typically supplied to an object to be polished in the form of a polishing liquid containing the polishing composition. The polishing liquid is then used to polish the object to be polished. The polishing liquid may be prepared, for example, by diluting any of the polishing compositions disclosed herein. Here, dilution typically refers to dilution with water. Alternatively, the polishing composition may be used as a polishing liquid as is. Another example of a polishing liquid containing the polishing composition disclosed herein is a polishing liquid obtained by adjusting the pH of the composition.

[0059] The pH of the polishing liquid is preferably 8.0 or higher, for example, 8.5 or higher, more preferably 9.0 or higher, even more preferably 9.5 or higher, and particularly preferably 10.0 or higher, for example, 10.5 or higher. As the pH of the polishing liquid increases, the polishing rate tends to improve. The upper limit of the pH of the polishing liquid is not particularly limited, but is preferably 12.0 or lower, for example, 11.8 or lower, and more preferably 11.5 or lower.

[0060] <Concentrate> The polishing composition disclosed herein may be in a concentrated form before being supplied to an object to be polished. Such a concentrated polishing composition is advantageous from the viewpoints of convenience and cost reduction during production, distribution, storage, etc. The concentration ratio is not particularly limited, and is, for example, about 2 to 80 times, preferably about 5 to 60 times, or may be about 15 to 40 times, or may be about 25 to 40 times, in terms of volume.

[0061] The polishing composition in the form of such a concentrated liquid can be diluted at a desired time to prepare a polishing liquid, and the polishing liquid can be supplied to the object to be polished. The dilution can typically be performed by adding water to the concentrated liquid and mixing. In addition, as will be described later, in the case of a multi-agent polishing composition, some of the agents may be diluted and then mixed with other agents to prepare a polishing liquid, or multiple agents may be mixed and then the mixture may be diluted to prepare a polishing liquid.

[0062] The content of abrasive grains in the concentrate can be, for example, 50% by weight or less. From the viewpoint of the stability and filterability of the polishing composition, the content is usually preferably 45% by weight or less, more preferably 40% by weight or less. Here, the stability of the polishing composition refers to, for example, the dispersion stability of the abrasive grains. Furthermore, from the viewpoint of convenience and cost reduction during production, distribution, storage, etc., the content of abrasive grains can be, for example, 1.0% by weight or more, preferably 3.0% by weight or more, more preferably 5.0% by weight or more, and even more preferably 7.0% by weight or more.

[0063] The content of the basic compound in the concentrate is usually 0.03% by weight or more. The content is preferably 0.15% by weight or more, more preferably 0.3% by weight or more, and even more preferably 1% by weight or more. The content of the basic compound is usually 15% by weight or less, preferably 10% by weight or less, more preferably 6% by weight or less, and may be 4% by weight or less, or may be 3% by weight or less.

[0064] The surfactant content in the concentrate may be, for example, 0.0001% by weight or more, preferably 0.001% by weight or more, more preferably 0.005% by weight or more, and even more preferably 0.01% by weight or more. The surfactant content is usually suitably 1% by weight or less, preferably 0.5% by weight or less, and may be 0.1% by weight or less, 0.05% by weight or less, or 0.03% by weight or less.

[0065] The content of the nitrogen-containing water-soluble polymer in the concentrate may be, for example, 0.0001% by weight or more, preferably 0.001% by weight or more, more preferably 0.005% by weight or more, and even more preferably 0.01% by weight or more. The content of the nitrogen-containing water-soluble polymer is usually suitably 1% by weight or less, preferably 0.5% by weight or less, or may be 0.1% by weight or less, 0.05% by weight or less, or 0.03% by weight or less.

[0066] The content of the chelating agent in the concentrate is usually 0.003% by weight or more. The content is preferably 0.005% by weight or more, more preferably 0.01% by weight or more, even more preferably 0.03% by weight or more, and particularly preferably 0.05% by weight or more. The content of the chelating agent is usually 1.5% by weight or less, preferably 1% by weight or less, more preferably 0.5% by weight or less, even more preferably 0.3% by weight or less, and particularly preferably 0.1% by weight or less.

[0067] <Application> The polishing composition disclosed herein is used for polishing an object having a surface made of silicon. The technology disclosed herein is particularly preferably applicable to a polishing composition containing silica particles as abrasive grains, for example, when the object to be polished is silicon. Typically, the polishing composition contains only silica particles as abrasive grains. The shape of the object to be polished is not particularly limited. The polishing composition disclosed herein can be preferably applied to polishing an object to be polished having a flat surface, such as a plate or polyhedron, or the edge of the object to be polished. For example, it can be preferably applied to polishing a wafer edge.

[0068] <Polishing method> The polishing composition disclosed herein is used as a polishing composition for pre-polishing a single crystal or polycrystalline silicon wafer when the silicon wafer is to be polished. The silicon wafer typically has a surface made of silicon. A typical example of the silicon wafer is a silicon single crystal wafer, such as a silicon single crystal wafer obtained by slicing a silicon single crystal ingot. A preferred embodiment of a method for polishing an object to be polished using the polishing composition disclosed herein is described below. That is, a polishing liquid (slurry) containing any of the polishing compositions disclosed herein is prepared. Preparing the polishing liquid may include adjusting the concentration of the polishing composition to prepare the polishing liquid. Here, concentration adjustment may be, for example, dilution. Alternatively, the polishing composition may be used as the polishing liquid as it is. In addition, in the case of a multi-agent polishing composition, preparing the polishing liquid may include mixing the agents, diluting one or more agents before the mixing, or diluting the mixture after the mixing.

[0069] Next, the polishing liquid is supplied to the object to be polished, and polished by a conventional method. For example, when performing a primary polishing process (first preliminary polishing process) of the object to be polished, the object to be polished that has undergone a lapping process is set in a general polishing device. In the primary polishing process, double-sided polishing is typically performed. The polishing liquid is supplied to the surface of the object to be polished through the polishing pad of the polishing device. Typically, while continuously supplying the polishing liquid, the polishing pad is pressed against the surface of the object to be polished, and the two are moved relative to each other (for example, rotated). Thereafter, if necessary, a secondary polishing process (second preliminary polishing process) is performed, and finally, a finish polishing process is performed to complete the polishing of the object to be polished. In the secondary polishing process, single-sided polishing is typically performed. The polishing pad used in the polishing process using the polishing composition disclosed herein is not particularly limited. For example, any of nonwoven fabric type, suede type, polyurethane type, abrasive type, and abrasive type may be used.

[0070] According to this specification, a method for manufacturing an abrasive article is provided, which includes a step of polishing an object to be polished using the polishing composition disclosed herein. The method for manufacturing an abrasive article disclosed herein may further include a step of performing final polishing on the object to be polished after the polishing step using the polishing composition. Here, final polishing refers to the last polishing step in the manufacturing process of the object, i.e., a step in which no further polishing is performed after that step. The final polishing step may be performed using the polishing composition disclosed herein, or may be performed using another polishing composition. In a preferred embodiment, the polishing process using the polishing composition is a polishing process upstream of the final polishing. In particular, it can be preferably applied to a preliminary polishing process after the lapping process. For example, it can be preferably used in a double-side polishing process (typically a first polishing process) after the lapping process, or in the first single-side polishing process (typically a first second polishing process) performed on a substrate that has undergone the double-side polishing process. The double-side polishing process and the first single-side polishing process require a higher polishing rate than the final polishing. Therefore, the polishing composition disclosed herein is suitable as a polishing composition used to polish an object to be polished in at least one (preferably both) of the double-side polishing process and the first single-side polishing process.

[0071] The polishing composition may be used in a manner in which it is used once for polishing and then disposed of (so-called "flow-through"), or may be recycled and reused. An example of a method for recycling a polishing composition is a method in which the used polishing composition discharged from a polishing apparatus is collected in a tank and the collected polishing composition is then supplied to the polishing apparatus again. When recycling a polishing composition, the amount of used polishing composition that is treated as waste liquid is reduced compared to when the polishing composition is used in a flow-through manner, thereby reducing the environmental impact. Furthermore, the reduced amount of polishing composition used can reduce costs. When recycling the polishing composition disclosed herein, new components, components that have decreased with use, or components that are desired to be increased may be added to the polishing composition during use at any time. [Example]

[0072] Several examples of the present invention will be described below, but it is not intended that the present invention be limited to those shown in these examples. In the following description, "%" is by weight unless otherwise specified.

[0073] <Preparation of Polishing Composition> Examples 1 to 6 A concentrated polishing composition was prepared by mixing abrasive grains, a surfactant, a basic compound, a chelating agent, a nitrogen-containing water-soluble polymer, and deionized water. Silica particles (average primary particle size: 55 nm) were used as the abrasive grains. Surfactants A to F, which are polyoxyalkylene alkyl ethers with the structures shown in Table 1, were used. In Table 1, "EO number" indicates the number of moles of ethylene oxide added, "PO number" indicates the number of moles of propylene oxide added, and "carbon number" indicates the number of carbon atoms in the alkyl group. In the "Carbon chain" column, a "linear" chain is defined as a chain in which the primary carbon of the alkyl group is bonded to the polyoxyalkylene via an ether bond, and a "branched" chain is defined as a chain in which the secondary carbon of the alkyl group is bonded to the polyoxyalkylene via an ether bond. The molecular weights of surfactants A to F were as shown in the "Molecular Weight" column in Table 1. Tetramethylammonium hydroxide (TMAH) and potassium carbonate (KCO) were used as basic compounds. Ethylenediaminetetrakis(methylenephosphonic acid) (hereinafter referred to as "EDTPO") was used as the chelating agent. 4 Polyvinylpyrrolidone (hereinafter referred to as "PVP") of 100% was used. The abrasive grain content in the concentrated polishing composition was 33%, the surfactant content was 0.007%, the TMAH content was 2.3%, the K2CO3 content was 1.1%, the EDTPO content was 0.08%, and the PVP content was 0.014%. The ratio B / S of the weight concentration of the basic compound (B) to the weight concentration of the surfactant (S) was 486.

[0074] (Comparative Example 1) A concentrated polishing composition according to this example was prepared in the same manner as in Example 1, except that no surfactant was added.

[0075] (Comparative Example 2) A concentrated polishing composition of this example was prepared in the same manner as in Example 1, except that PVP was not added.

[0076] (Comparative Example 3) A concentrated polishing composition according to this example was prepared in the same manner as in Example 1, except that neither the surfactant nor PVP was added.

[0077] <Evaluation of silicon polishing rate> The polishing test was carried out on silicon wafers using a polishing solution prepared by diluting the concentrated solution of the polishing composition according to each example with water 30 times, and the silicon removal rate and the ability to eliminate bumps were evaluated. The object to be polished was a 100 mm diameter silicon single crystal wafer (conductivity type: P type, crystal orientation: <100> , resistivity: 1 Ω·cm or more and less than 100 Ω·cm) was used. (a) Change in wafer thickness before and after polishing [cm] = Difference in weight of silicon wafer before and after polishing [g] / Density of silicon [g / cm 3 ](=2.33g / cm 3 ) / polished area [cm 2 ] (b) Polishing rate [μm / min] = Change in wafer thickness before and after polishing [cm] × 10 4 / Polishing time [min]

[0078] (polishing conditions) Polishing device: Single-sided polishing device manufactured by Engis Japan Co., Ltd., model "EJ-380IN" Polishing pressure: 12kPa Platen rotation speed: +50 rpm (counterclockwise is positive rotation. The same applies below.) Head rotation speed: +45 rpm Polishing pad: Nitta DuPont, product name "SUBA800" Polishing liquid supply rate: 100 mL / min (flowing) Polishing environment temperature: 25℃ Polishing allowance: 4 μm

[0079] <Evaluation of bump removal> For the polished silicon wafers, the surface shape of the site including the HLM was measured using a stylus-type surface roughness and shape measuring instrument (SURFCOM 1500DX, manufactured by Tokyo Seimitsu Co., Ltd.), and the height from the reference plane around the HLM to the highest point of the protrusion was measured. The greater the protrusion height, the poorer the evaluation result indicated the protrusion resolution. The results obtained are shown in the "Protrusion Height" column in Table 1.

[0080] [Table 1]

[0081] As shown in Table 1, it was confirmed that the polishing compositions of Examples 1 to 6, which contained a combination of a nitrogen-containing water-soluble polymer and a surfactant, exhibited a clearly improved ability to eliminate bumps while maintaining a polishing rate equivalent to that of the polishing compositions of Comparative Examples 1 and 2, which did not contain either the nitrogen-containing water-soluble polymer or the surfactant. Examples 1 to 3 tended to exhibit a higher ability to eliminate bumps than Examples 4 to 6. Furthermore, as can be seen from a comparison between Comparative Example 3 and Comparative Example 2, in the polishing composition not containing the nitrogen-containing water-soluble polymer, the addition of a surfactant slightly decreased the removal rate, but did not improve the ability to eliminate bumps. In contrast, as can be seen from a comparison between Comparative Example 1 and Example 1, in the polishing composition containing the nitrogen-containing water-soluble polymer, the addition of a surfactant in combination significantly improved the ability to eliminate bumps while maintaining the removal rate.

[0082] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

Claims

1. A polishing composition for use in a pre-polishing step of a silicon wafer, comprising: The composition comprises abrasive grains, a basic compound, a chelating agent, a surfactant, a nitrogen-containing water-soluble polymer, and water; The polishing composition has a ratio (B / S) of the weight concentration (B) of the basic compound to the weight concentration (S) of the surfactant of 50 or more.

2. 2. The polishing composition according to claim 1, wherein the ratio (P / S) of the weight concentration (P) of the nitrogen-containing water-soluble polymer to the weight concentration (S) of the surfactant is greater than 0.

5.

3. The polishing composition according to claim 1 or 2, wherein the surfactant comprises a nonionic surfactant.

4. 4. The polishing composition according to claim 3, wherein the nonionic surfactant is a polyoxyalkylene alkyl ether.

5. 5. The polishing composition according to claim 1, wherein the abrasive grains comprise silica particles.

6. A concentrated polishing composition according to any one of claims 1 to 5.

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