Grinding composition

Abstract

A polishing composition is provided with which it is possible to obtain polished substrates having improved surface quality. The polishing composition comprises abrasive grains, a water-soluble polymer, a basic compound, and water. The polishing composition further contains a polyoxyalkylene alkyl ether in which a secondary carbon atom of the alkyl group has been bonded to the polyoxyalkylene by an ether linkage.

Description

[Technical Field]

[0001] The present invention relates to a polishing composition. This application claims priority to Japanese Patent Application No. 2020-63674, filed on March 31, 2020, the entire contents of which are incorporated herein by reference. [Background technology]

[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 (rough polishing step) and a polishing step (precise polishing step). The polishing step typically includes a pre-polishing step (preliminary polishing step) and a finish polishing step (final polishing step). Technical documents related to polishing compositions for silicon wafers include, for example, Patent Documents 1 and 2. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-22241 [Patent Document 2] Japanese Patent Application Publication No. 11-140431 Summary of the Invention [Problem to be solved by the invention]

[0004] Polishing compositions used for polishing semiconductor substrates such as silicon wafers and other substrates are required to achieve high-quality surfaces after polishing. Many polishing compositions for such applications contain, in addition to abrasive grains and water, a water-soluble polymer for purposes such as protecting the substrate surface and improving wettability. The water-soluble polymer contributes to reducing defects and haze on the polished surface by adsorbing to and desorbing from the abrasive grains and silicon wafers.

[0005] Furthermore, in the above-mentioned substrate polishing, for example, in the finish polishing step (particularly in the finish polishing step of semiconductor substrates such as silicon wafers and other substrates), a polished surface of higher quality is required, and it would be practically useful to provide a polishing composition that can efficiently realize a substrate surface with lower haze. Therefore, an object of the present invention is to provide a polishing composition that can improve the surface quality of a substrate after polishing. [Means for solving the problem]

[0006] According to the present specification, a polishing composition is provided. This polishing composition contains abrasive grains, a water-soluble polymer, a basic compound, and water, and further contains a polyoxyalkylene alkyl ether (hereinafter also referred to as "polyoxyalkylene secondary alkyl ether") in which the secondary carbon of the alkyl group is bonded to a polyoxyalkylene via an ether bond. Such a polishing composition can improve the surface quality of a substrate after polishing. For example, haze can be reduced.

[0007] In some embodiments, the molecular weight of the polyoxyalkylene secondary alkyl ether is preferably less than 4000. In a composition containing an abrasive grain and a basic compound, the use of a polyoxyalkylene secondary alkyl ether having the above molecular weight in addition to the inclusion of a water-soluble polymer can favorably exhibit a haze-improving effect.

[0008] In some preferred embodiments, the content of the polyoxyalkylene secondary alkyl ether is less than 0.01% by weight. In such embodiments where the content of the polyoxyalkylene secondary alkyl ether is small, the haze-improving effect can be suitably exhibited.

[0009] Silica particles are preferably used as the abrasive grains. The haze-improving effect of using polyoxyalkylene secondary alkyl ether is particularly effective in polishing using silica particles as the abrasive grains.

[0010] The polishing composition disclosed herein is suitable for polishing silicon wafers. By polishing a silicon wafer using the polishing composition, haze can be improved and a high-quality silicon wafer surface can be suitably achieved. In particular, the polishing composition disclosed herein can be suitably used in the finish polishing process of silicon wafers.

[0011] The present specification also provides a method for polishing a substrate using any of the polishing compositions disclosed herein. The polishing method includes a polishing step in which a substrate is polished using a polishing composition containing abrasive grains, a water-soluble polymer, a basic compound, and water, and further containing a polyoxyalkylene secondary alkyl ether. In some embodiments, the polishing method provided by the present specification is a method for polishing a silicon wafer. That is, the substrate to be polished is a silicon wafer. The haze improvement effect of the technology disclosed herein is suitably realized in polishing a silicon wafer. In some preferred embodiments, the polishing method includes a pre-polishing step and a finish polishing step. Then, in the finish polishing step, polishing is performed using the polishing composition disclosed herein. According to this polishing method, the wettability of the wafer surface after polishing is improved in the finish polishing step, and a higher-quality silicon wafer surface can be obtained. DETAILED DESCRIPTION OF THE INVENTION

[0012] Preferred embodiments of the present invention will be described below. It should be noted that matters necessary for carrying out the present invention other than those specifically mentioned in this specification can be understood as design matters for a person skilled in the art based on the prior art in the relevant field. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the relevant field.

[0013] <Abrasive grain> The polishing composition disclosed herein contains abrasive grains. The abrasive grains function to mechanically polish the surface of a substrate. The material and properties of the abrasive grains are not particularly limited and can be appropriately selected depending on the intended use and manner of use 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; carbonates such as calcium carbonate and barium carbonate; and the like. Specific examples of organic particles include polymethyl methacrylate (PMMA) particles, poly(meth)acrylic acid particles (here, (meth)acrylic acid refers collectively to acrylic acid and methacrylic acid), and polyacrylonitrile particles. Such abrasive grains may be used alone or in combination of two or more kinds.

[0014] The abrasive grains are preferably inorganic particles, and among these, particles made of metal or semi-metal oxides are preferred, with silica particles being particularly preferred. In polishing compositions that can be used for polishing (e.g., finish polishing) substrates having a silicon surface, such as silicon wafers, described below, it is particularly meaningful to employ silica particles as the abrasive grains. The technology disclosed herein can be preferably implemented, for example, in an embodiment in which the abrasive grains are essentially made of silica particles. Here, "substantially" means that 95% by weight or more (preferably 98% by weight or more, more preferably 99% by weight or more, and even 100% by weight) of the particles constituting the abrasive grains are silica particles.

[0015] Specific examples of silica particles include colloidal silica, fumed silica, precipitated silica, etc. Silica particles can be used alone or in combination of two or more types. Colloidal silica is particularly preferred because it is easy to obtain a polished surface with excellent surface quality after polishing. As colloidal silica, for example, colloidal silica produced by an ion exchange method using water glass (sodium silicate) as a raw material, or alkoxide method colloidal silica (colloidal silica produced by the hydrolysis and condensation reaction of alkoxysilane) can be preferably used. Colloidal silica can be used alone or in combination of two or more types.

[0016] The true specific gravity of the abrasive grain constituent material (e.g., silica constituting silica particles) is preferably 1.5 or more, more preferably 1.6 or more, and even more preferably 1.7 or more. There is no particular upper limit to the true specific gravity of silica, but it is typically 2.3 or less, preferably 2.2 or less, more preferably 2.0 or less, for example, 1.9 or less. The true specific gravity of the abrasive grain (e.g., silica particles) can be measured by a liquid displacement method using ethanol as the displacement liquid.

[0017] The average primary particle size of the abrasive grains (typically silica particles) is not particularly limited, but from the viewpoint of polishing efficiency, etc., it is preferably 5 nm or more, more preferably 10 nm or more. From the viewpoint of obtaining a higher polishing effect (e.g., effects such as haze reduction and defect removal), the average primary particle size is preferably 15 nm or more, more preferably 20 nm or more (e.g., more than 20 nm). Furthermore, from the viewpoint of scratch prevention, etc., the average primary particle size of the abrasive grains is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 45 nm or less. From the viewpoint of easily obtaining a surface with lower haze, in some embodiments, the average primary particle size of the abrasive grains may be 43 nm or less, or may be less than 40 nm, less than 38 nm, less than 35 nm, less than 32 nm, or less than 30 nm.

[0018] 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."

[0019] The average secondary particle diameter of the abrasive grains (e.g., silica particles) is not particularly limited and can be appropriately selected, for example, from a range of about 15 nm to 300 nm. From the viewpoint of improving polishing efficiency, the average secondary particle diameter is preferably 30 nm or more, more preferably 35 nm or more. In some embodiments, the average secondary particle diameter may be, for example, 40 nm or more, 42 nm or more, or preferably 44 nm or more. Furthermore, the average secondary particle diameter is usually advantageously 250 nm or less, preferably 200 nm or less, and more preferably 150 nm or less. In some preferred embodiments, the average secondary particle diameter is 120 nm or less, more preferably 100 nm or less, even more preferably 70 nm or less, for example, 60 nm or less, or even 50 nm or less.

[0020] 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 by dynamic light scattering using, for example, "Nanotrac (registered trademark) UPA-UT151" manufactured by Nikkiso Co., Ltd.

[0021] The shape (external shape) of the abrasive grains may be spherical or non-spherical. Specific examples of non-spherical particles include peanut-shaped (i.e., peanut shell-shaped), cocoon-shaped, confetti-shaped, and rugby ball-shaped. For example, abrasive grains in which most of the particles are peanut-shaped or cocoon-shaped can be preferably used.

[0022] Although not particularly limited, the average value of the ratio of the major axis to the minor axis of the abrasive grains (average aspect ratio) 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, higher polishing efficiency 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.

[0023] The shape (outline) and average aspect ratio of 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.

[0024] The content of abrasive grains in the polishing composition is not particularly limited, and is, for example, 0.01% by weight or more, preferably 0.05% by weight or more, more preferably 0.10% by weight or more, and even more preferably 0.15% by weight or more. By increasing the content of abrasive grains, higher polishing efficiency can be achieved. The content is suitably 10% by weight or less, preferably 7% by weight or less, more preferably 5% by weight or less, and even more preferably 2% by weight or less, and may be, for example, 1% by weight or less, or 0.5% by weight or less. This allows for a surface with lower haze. The above abrasive grain content can be preferably adopted in an embodiment in which the polishing composition is used in the form of a polishing liquid (working slurry).

[0025] <Water-soluble polymer> The polishing composition disclosed herein contains a water-soluble polymer. The water-soluble polymer can be useful for protecting the substrate surface and improving the wettability of the substrate surface after polishing. The effects of the technology disclosed herein can be achieved by coexisting the water-soluble polymer with a polyoxyalkylene secondary alkyl ether, as described below. In one embodiment of the present invention, the water-soluble polymer can be a compound containing a hydroxyl group, a carboxyl group, an acyloxy group, a sulfo group, an amide structure, an imide structure, a quaternary ammonium structure, a heterocyclic structure, a vinyl structure, or the like in its molecule. Examples of water-soluble polymers that can be used include cellulose derivatives, starch derivatives, polymers containing oxyalkylene units, polyvinyl alcohol polymers, and polymers containing nitrogen atoms. Examples of nitrogen-containing polymers that can be used include N-vinyl polymers and N-(meth)acryloyl polymers. The water-soluble polymer may be a polymer derived from a natural product or a synthetic polymer. One type of water-soluble polymer may be used alone, or two or more types may be used in combination.

[0026] In some embodiments, a polymer derived from a natural product is used as the water-soluble polymer. Examples of the natural polymer include cellulose derivatives and starch derivatives. The natural polymer may be used alone or in combination of two or more.

[0027] In some preferred embodiments, a cellulose derivative is used as the water-soluble polymer. Here, the cellulose derivative is a polymer containing β-glucose units as the main repeating unit. Specific examples of the cellulose derivative include hydroxyethyl cellulose (HEC), hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, and carboxymethyl cellulose. Among these, HEC is preferred. The cellulose derivative may be used alone or in combination of two or more.

[0028] In some other embodiments, a starch derivative is used as the water-soluble polymer. Starch derivatives are polymers containing α-glucose units as the main repeating unit, and examples thereof include pregelatinized starch, pullulan, carboxymethyl starch, and cyclodextrin. The starch derivatives may be used alone or in combination of two or more.

[0029] In some other embodiments, a synthetic polymer is used as the water-soluble polymer. The haze-improving effect disclosed herein is preferably exhibited in embodiments in which a synthetic polymer is used as the water-soluble polymer. The synthetic polymer may be used alone or in combination of two or more.

[0030] In some preferred embodiments, a polymer containing an oxyalkylene unit is used as the water-soluble polymer. Examples of polymers containing an oxyalkylene unit include polyethylene oxide (PEO), block copolymers of ethylene oxide (EO) and propylene oxide (PO) or butylene oxide (BO), and random copolymers of EO and PO or BO. Among these, block copolymers of EO and PO or random copolymers of EO and PO are preferred. The block copolymer of EO and PO may be a diblock copolymer containing a PEO block and a polypropylene oxide (PPO) block, or a triblock copolymer. Examples of the triblock copolymer include PEO-PPO-PEO triblock copolymers and PPO-PEO-PPO triblock copolymers. PEO-PPO-PEO triblock copolymers are usually more preferred.

[0031] In this specification, unless otherwise specified, the term "copolymer" refers collectively to various copolymers such as random copolymers, alternating copolymers, block copolymers, and graft copolymers.

[0032] In a block copolymer or random copolymer of EO and PO, the molar ratio of EO to PO (EO / PO) constituting the copolymer is preferably greater than 1, more preferably 2 or more, and even more preferably 3 or more (e.g., 5 or more), from the viewpoints of solubility in water, washability, etc.

[0033] In some preferred embodiments, a polyvinyl alcohol-based polymer is used as the water-soluble polymer. A polyvinyl alcohol-based polymer refers to a polymer containing vinyl alcohol units (hereinafter also referred to as "VA units") as its repeating units. A polyvinyl alcohol-based polymer may contain only VA units as repeating units, or may contain VA units and repeating units other than VA units (hereinafter also referred to as "non-VA units"). A polyvinyl alcohol-based polymer may be a random copolymer containing VA units and non-VA units, a block copolymer, an alternating copolymer, or a graft copolymer. A polyvinyl alcohol-based polymer may contain only one type of non-VA unit, or may contain two or more types of non-VA units.

[0034] The polyvinyl alcohol-based polymer may be unmodified polyvinyl alcohol (unmodified PVA) or modified polyvinyl alcohol (modified PVA). Unmodified PVA is a polyvinyl alcohol-based polymer produced by hydrolysis (saponification) of polyvinyl acetate, and substantially does not contain any repeating units other than repeating units (—CH—CH(OCOCH)—) formed by vinyl polymerization of vinyl acetate and VA units. The degree of saponification of the unmodified PVA may be, for example, 60% or more, and from the viewpoint of water solubility, may be 70% or more, 80% or more, or 90% or more.

[0035] The polyvinyl alcohol polymer may be a modified PVA containing VA units and non-VA units having at least one structure selected from oxyalkylene groups, carboxy groups, sulfo groups, amino groups, hydroxyl groups, amide groups, imide groups, nitrile groups, ether groups, ester groups, and salts thereof. Non-VA units that may be contained in the modified PVA include, but are not limited to, repeating units derived from N-vinyl monomers or N-(meth)acryloyl monomers, as described below, repeating units derived from ethylene, repeating units derived from alkyl vinyl ethers, and repeating units derived from vinyl esters of monocarboxylic acids having 3 or more carbon atoms. A preferred example of the N-vinyl monomer is N-vinylpyrrolidone. A preferred example of the N-(meth)acryloyl monomer is N-(meth)acryloylmorpholine. The alkyl vinyl ether may be a vinyl ether having an alkyl group having 1 to 10 carbon atoms, such as propyl vinyl ether, butyl vinyl ether, or 2-ethylhexyl vinyl ether. The vinyl ester of a monocarboxylic acid having 3 or more carbon atoms may be, for example, a vinyl ester of a monocarboxylic acid having 3 to 7 carbon atoms, such as vinyl propanoate, vinyl butanoate, vinyl pentanoate, or vinyl hexanoate. The polyvinyl alcohol polymer may also be a modified PVA in which some of the VA units contained in the polyvinyl alcohol polymer are acetalized with an aldehyde. As the aldehyde, for example, an alkyl aldehyde can be preferably used, and an alkyl aldehyde having an alkyl group having 1 to 7 carbon atoms is preferred, with acetaldehyde, n-propyl aldehyde, n-butyl aldehyde, and n-pentyl aldehyde being particularly preferred. The polyvinyl alcohol polymer may also be a cationically modified polyvinyl alcohol having a cationic group such as a quaternary ammonium structure introduced therein. Examples of the cationically modified polyvinyl alcohol include those having a cationic group derived from a monomer having a cationic group, such as a diallyldialkylammonium salt or an N-(meth)acryloylaminoalkyl-N,N,N-trialkylammonium salt.

[0036] The proportion of moles of VA units to the total number of moles of repeating units constituting the polyvinyl alcohol-based polymer may be, for example, 5% or more, 10% or more, 20% or more, or 30% or more. While not particularly limited, in some embodiments, the proportion of moles of VA units may be 50% or more, 65% or more, 75% or more, 80% or more, or 90% or more (e.g., 95% or more, or 98% or more). Substantially 100% of the repeating units constituting the polyvinyl alcohol-based polymer may be VA units. Here, "substantially 100%" means that the polyvinyl alcohol-based polymer does not, at least intentionally, contain non-VA units. Typically, the proportion of moles of non-VA units to the total number of moles of repeating units is less than 2% (e.g., less than 1%), including 0%. In some other embodiments, the ratio of the number of moles of VA units to the number of moles of all repeating units constituting the polyvinyl alcohol-based polymer may be, for example, 95% or less, 90% or less, 80% or less, or 70% or less.

[0037] The content of VA units in the polyvinyl alcohol-based polymer (content by weight) may be, for example, 5% by weight or more, 10% by weight or more, 20% by weight or more, or 30% by weight or more. While not particularly limited, in some embodiments, the content of VA units may be 50% by weight or more (e.g., more than 50% by weight), 70% by weight or more, or 80% by weight or more (e.g., 90% by weight or more, 95% by weight or more, or 98% by weight or more). Substantially 100% by weight of the repeating units constituting the polyvinyl alcohol-based polymer may be VA units. Here, "substantially 100% by weight" means that non-VA units are not, at least intentionally, included as repeating units constituting the polyvinyl alcohol-based polymer, and typically means that the content of non-VA units in the polyvinyl alcohol-based polymer is less than 2% by weight (e.g., less than 1% by weight). In some other embodiments, the content of VA units in the polyvinyl alcohol-based polymer may be, for example, 95% by weight or less, 90% by weight or less, 80% by weight or less, or 70% by weight or less.

[0038] A polyvinyl alcohol-based polymer may contain multiple polymer chains with different VA unit contents within the same molecule. Here, a polymer chain refers to a segment that constitutes part of a single polymer molecule. For example, a polyvinyl alcohol-based polymer may contain, within the same molecule, polymer chain A with a VA unit content of more than 50% by weight and polymer chain B with a VA unit content of less than 50% by weight (i.e., a non-VA unit content of more than 50% by weight).

[0039] The polymer chain A may contain only VA units as repeating units, or may contain non-VA units in addition to VA units. The content of VA units in the polymer chain A may be 60% by weight or more, 70% by weight or more, 80% by weight or more, or 90% by weight or more. In some embodiments, the content of VA units in the polymer chain A may be 95% by weight or more, or 98% by weight or more. Substantially 100% by weight of the repeating units constituting the polymer chain A may be VA units.

[0040] Polymer chain B may contain only non-VA units as repeating units, or may contain VA units in addition to non-VA units. The content of non-VA units in polymer chain B may be 60% by weight or more, 70% by weight or more, 80% by weight or more, or 90% by weight or more. In some embodiments, the content of non-VA units in polymer chain B may be 95% by weight or more, or 98% by weight or more. Substantially 100% by weight of the repeating units constituting polymer chain B may be non-VA units.

[0041] Examples of polyvinyl alcohol-based polymers containing polymer chain A and polymer chain B in the same molecule include block copolymers and graft copolymers containing these polymer chains. The graft copolymer may be a graft copolymer having a structure in which polymer chain B (side chain) is grafted to polymer chain A (main chain), or a graft copolymer having a structure in which polymer chain A (side chain) is grafted to polymer chain B (main chain). In one embodiment, a polyvinyl alcohol-based polymer having a structure in which polymer chain B is grafted to polymer chain A can be used.

[0042] Examples of polymer chain B include polymer chains having a repeating unit derived from an N-vinyl type monomer as the main repeating unit, polymer chains having a repeating unit derived from an N-(meth)acryloyl type monomer as the main repeating unit, and polymer chains having an oxyalkylene unit as the main repeating unit. In this specification, the term "main repeating unit" refers to a repeating unit contained in an amount of more than 50% by weight, unless otherwise specified.

[0043] A suitable example of the polymer chain B is a polymer chain having an N-vinyl monomer as the main repeating unit, i.e., an N-vinyl polymer chain. The content of repeating units derived from N-vinyl monomers in the N-vinyl polymer chain is typically more than 50% by weight, and may be 70% by weight or more, 85% by weight or more, or even 95% by weight or more. Substantially all of the polymer chain B may be repeating units derived from N-vinyl monomers.

[0044] In this specification, examples of N-vinyl monomers include monomers having a nitrogen-containing heterocycle (e.g., a lactam ring) and N-vinyl linear amides. Specific examples of N-vinyl lactam monomers include N-vinylpyrrolidone, N-vinylpiperidone, N-vinylmorpholinone, N-vinylcaprolactam, N-vinyl-1,3-oxazin-2-one, and N-vinyl-3,5-morpholinedione. Specific examples of N-vinyl linear amides include N-vinylacetamide, N-vinylpropionic acid amide, and N-vinylbutyric acid amide. Polymer chain B may be, for example, an N-vinyl polymer chain in which more than 50% by weight (e.g., 70% by weight or more, 85% by weight or more, or 95% by weight or more) of its repeating units are N-vinylpyrrolidone units. Substantially all of the repeating units constituting polymer chain B may be N-vinylpyrrolidone units.

[0045] Another example of polymer chain B is a polymer chain whose main repeating unit is a repeating unit derived from an N-(meth)acryloyl-type monomer, i.e., an N-(meth)acryloyl-based polymer chain. The content of repeating units derived from N-(meth)acryloyl-type monomers in the N-(meth)acryloyl-based polymer chain is typically more than 50% by weight, and may be 70% by weight or more, 85% by weight or more, or even 95% by weight or more. Substantially all of polymer chain B may be repeating units derived from N-(meth)acryloyl-type monomers.

[0046] In this specification, examples of N-(meth)acryloyl type monomers include linear amides having an N-(meth)acryloyl group and cyclic amides having an N-(meth)acryloyl group. Examples of linear 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 cyclic amides having an N-(meth)acryloyl group include N-(meth)acryloylmorpholine and N-(meth)acryloylpyrrolidine.

[0047] Another example of the polymer chain B is a polymer chain containing an oxyalkylene unit as a main repeating unit, i.e., an oxyalkylene-based polymer chain. The content of the oxyalkylene unit in the oxyalkylene-based polymer chain is typically more than 50% by weight, and may be 70% by weight or more, 85% by weight or more, or even 95% by weight or more. Substantially all of the repeating units contained in the polymer chain B may be oxyalkylene units.

[0048] Examples of oxyalkylene units include oxyethylene units, oxypropylene units, oxybutylene units, etc. Such oxyalkylene units may be repeating units derived from the corresponding alkylene oxides. The oxyalkylene units contained in the oxyalkylene polymer chain may be one type or two or more types. For example, the oxyalkylene polymer chain may contain a combination of oxyethylene units and oxypropylene units. In an oxyalkylene polymer chain containing two or more types of oxyalkylene units, the oxyalkylene units may be a random copolymer, a block copolymer, an alternating copolymer, or a graft copolymer of the corresponding alkylene oxides.

[0049] Further examples of polymer chain B include a polymer chain containing a repeating unit derived from an alkyl vinyl ether (e.g., a vinyl ether having an alkyl group having 1 to 10 carbon atoms), a polymer chain containing a repeating unit derived from a monocarboxylic acid vinyl ester (e.g., a vinyl ester of a monocarboxylic acid having 3 or more carbon atoms), and a polymer chain into which a cationic group (e.g., a cationic group having a quaternary ammonium structure) has been introduced.

[0050] From the viewpoint of improving haze reduction performance, the polyvinyl alcohol-based polymer as the water-soluble polymer in the technology disclosed herein is preferably a modified polyvinyl alcohol, which is a copolymer containing VA units and non-VA units. Furthermore, the degree of saponification of the polyvinyl alcohol-based polymer as the water-soluble polymer is usually 50 mol% or more, preferably 65 mol% or more, more preferably 70 mol% or more, for example, 75 mol% or more. In principle, the degree of saponification of the polyvinyl alcohol-based polymer is 100 mol% or less.

[0051] In some other embodiments, an N-vinyl polymer can be used as the water-soluble polymer. Examples of N-vinyl polymers include polymers containing repeating units derived from a monomer having a nitrogen-containing heterocycle (e.g., a lactam ring). Examples of such polymers include homopolymers and copolymers of N-vinyl lactam monomers (e.g., copolymers containing more than 50% by weight of N-vinyl lactam monomers), homopolymers and copolymers of N-vinyl linear amides (e.g., copolymers containing more than 50% by weight of N-vinyl linear amides), and the like.

[0052] 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, N-vinyl-3,5-morpholinedione, etc. 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 chain amides include N-vinylacetamide, N-vinylpropionic acid amide, and N-vinylbutyric acid amide.

[0053] In some other embodiments, an N-(meth)acryloyl polymer can be used as the water-soluble polymer. 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.

[0054] 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).

[0055] 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.

[0056] In the technology disclosed herein, the weight average molecular weight (Mw) of the water-soluble polymer is not particularly limited. The Mw of the water-soluble polymer is, for example, about 200×10 4 It may be less than or equal to approximately 150 x 10 4 From the viewpoint of cleaning properties, it is preferable to use a value of approximately 100×10 4 is less than 50×10 4 From the viewpoint of protecting the polishing surface, the Mw of the water-soluble polymer may be, for example, 0.2 × 10 4 It may be 0.5 x 10 or more. 4 In some embodiments, the Mw is 1.0×10 or more. 4 The above is appropriate, and 2 x 10 4 or more, for example, 5×10 4 More than that is fine.

[0057] In the technology disclosed herein, the preferred molecular weight range of the water-soluble polymer compound may vary depending on the type of polymer used. For example, the Mw of cellulose derivatives and starch derivatives is approximately 200×10 4 It can be 150 x 10 4 The following is appropriate. The above Mw is approximately 100 x 10 4 It may be less than 50 × 10 4 Less than (for example, approximately 30 × 10 4 From the viewpoint of protecting the polishing surface, the Mw may be, for example, about 0.2 × 10 4 That's about 0.5 x 10 4 It is appropriate that the density is equal to or greater than 1.0×10 4 or more, more preferably about 3.0×10 4 More preferably, approximately 10×10 4 That's about 20 x 10 4 It may be more than that.

[0058] For example, the Mw of a polyvinyl alcohol polymer and a polymer containing a nitrogen atom is 100×10 4 It can be 60 x 104 From the viewpoint of concentration efficiency, the above Mw is 30 × 10 4 or less, preferably 20×10 4 For example, 10 x 10 4 Below, typically 8 x 10 4 From the viewpoint of suitably protecting the polished surface and reducing haze, Mw may be, for example, 0.2 × 10 4 It can be more than 0.5 × 10 4 In some embodiments, Mw is 1.0×10 or greater. 4 The above is appropriate, and preferably 1.5 × 10 4 More preferably, 2×10 4 More preferably, 3 × 10 4 For example, 4 × 10 4 May be more than 5 x 10 4 More than that is fine.

[0059] The Mw of the water-soluble polymer can be calculated from a value based on aqueous gel permeation chromatography (GPC) (aqueous, polyethylene oxide equivalent). A GPC measuring device such as the "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: 100mM sodium nitrate aqueous solution / acetonitrile = 108 / 02 Flow rate: 1mL / min Measurement temperature: 40℃ Sample injection volume: 200 μL

[0060] From the viewpoint of reducing agglomerates and improving cleaning properties, a nonionic polymer can be preferably used as the water-soluble polymer. Also, from the viewpoint of easy control of chemical structure and purity, a synthetic polymer can be preferably used as the water-soluble polymer. For example, when the technology disclosed herein is implemented in an embodiment including a synthetic polymer as the water-soluble polymer, the polishing composition may be one that does not substantially use a polymer derived from a natural product as the water-soluble polymer. Here, "substantially not using" means that the amount of the polymer derived from a natural product used per 100 parts by weight of the total content of the water-soluble polymer is typically 3 parts by weight or less, preferably 1 part by weight or less, and includes 0 parts by weight or below the detection limit.

[0061] The content (weight-based content) of the water-soluble polymer in the polishing composition is not particularly limited. -4 From the viewpoint of reducing haze, the preferred content is 5.0 × 10 -4 % by weight or more, more preferably 1.0 × 10 -3 % by weight or more, more preferably 2.0 × 10 -3 % by weight or more, e.g., 5.0 x 10 -3 % by weight or more. Also, from the viewpoint of polishing removal rate, etc., the content is preferably 0.2% by weight or less, more preferably 0.1% by weight or less, and even more preferably 0.05% by weight or less (for example, 0.02% by weight or less). When the polishing composition contains two or more water-soluble polymers, the content refers to the total content (weight-based content) of all water-soluble polymers contained in the polishing composition. These contents can be preferably applied to the content in the polishing liquid (working slurry) supplied to the substrate, for example.

[0062] The content of the water-soluble polymer (when two or more water-soluble polymers are contained, the total amount thereof) can also be determined by its relative relationship with the abrasive grains. Although not particularly limited, in some embodiments, the content of the water-soluble polymer per 100 parts by weight of the abrasive grains can be, for example, 0.01 parts by weight or more. From the viewpoint of haze reduction, etc., it is appropriate to set it to 0.1 parts by weight or more, preferably 0.5 parts by weight or more, more preferably 1 part by weight or more, even more preferably 3 parts by weight or more, for example, 4 parts by weight or more. Furthermore, the content of the water-soluble polymer per 100 parts by weight of the abrasive grains may be, for example, 50 parts by weight or less, or may be 30 parts by weight or less. From the viewpoint of dispersion stability of the polishing composition, etc., in some embodiments, the content of the water-soluble polymer per 100 parts by weight of the abrasive grains is appropriate to set it to 15 parts by weight or less, preferably 10 parts by weight or less, or may be 8 parts by weight or less, or may be 7 parts by weight or less.

[0063] <Basic compounds> The polishing composition disclosed herein contains a basic compound. In this specification, the term "basic compound" refers to a compound that dissolves in water and increases the pH of the aqueous solution. Examples of basic compounds that can be used include nitrogen-containing organic or inorganic basic compounds, phosphorus-containing basic compounds, alkali metal hydroxides, alkaline earth metal hydroxides, various carbonates and hydrogen carbonates, etc. Examples of nitrogen-containing basic compounds include quaternary ammonium compounds, ammonia, amines (preferably water-soluble amines), etc. Examples of phosphorus-containing basic compounds include quaternary phosphonium compounds. These basic compounds can be used alone or in combination.

[0064] Specific examples of alkali metal hydroxides include potassium hydroxide and sodium hydroxide. Specific examples of carbonates or bicarbonates include ammonium bicarbonate, ammonium carbonate, potassium bicarbonate, potassium carbonate, sodium bicarbonate, and sodium carbonate. Specific examples of amines include 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, guanidine, and azoles such as imidazole and triazole. Specific examples of quaternary phosphonium compounds include quaternary phosphonium hydroxides such as tetramethylphosphonium hydroxide and tetraethylphosphonium hydroxide.

[0065] As the quaternary ammonium compound, a quaternary ammonium salt (typically a strong base) such as a tetraalkylammonium salt or a hydroxyalkyltrialkylammonium salt can be used. The anion component in such a quaternary ammonium salt is, for example, OH - , F - , Cl - , Br - , I - , ClO4 - , BH4 - Examples of the quaternary ammonium compounds include those in which the anion is OH. - Specific examples of quaternary ammonium hydroxides include tetraalkylammonium hydroxides such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrapentylammonium hydroxide, and tetrahexylammonium hydroxide; hydroxyalkyltrialkylammonium hydroxides such as 2-hydroxyethyltrimethylammonium hydroxide (also known as choline); and the like.

[0066] Among these basic compounds, at least one basic compound selected from, for example, alkali metal hydroxides, quaternary ammonium hydroxides, and ammonia can be preferably used. Among these, tetraalkylammonium hydroxides (e.g., tetramethylammonium hydroxide) and ammonia are more preferred, and ammonia is particularly preferred.

[0067] The content of the basic compound relative to the total amount of the polishing composition is not particularly limited. From the viewpoint of improving the polishing rate, the content is usually suitably 0.0005% by weight or more, preferably 0.001% by weight or more, and more preferably 0.003% by weight or more. From the viewpoint of reducing haze, the content is suitably less than 0.1% by weight, preferably less than 0.05% by weight, and more preferably less than 0.03% by weight (for example, less than 0.025% by weight). When two or more basic compounds are used in combination, the content refers to the total content of the two or more basic compounds. These contents can be preferably applied to the content in the polishing liquid (working slurry) supplied to the substrate, for example.

[0068] <Polyoxyalkylene secondary alkyl ether> The polishing composition disclosed herein contains a polyoxyalkylene alkyl ether (i.e., a polyoxyalkylene secondary alkyl ether) in which the secondary carbon of the alkyl group is bonded to a polyoxyalkylene via an ether bond. In this specification, polyoxyalkylene secondary alkyl ether refers to a secondary alcohol alkoxylate in which a secondary alcohol is ether-bonded to the end of a polyoxyalkylene (POA) chain via the oxygen atom of its hydroxyl group. By incorporating a polyoxyalkylene secondary alkyl ether in combination with a water-soluble polymer into the polishing composition, haze on the substrate surface after polishing can be effectively reduced. The reason for this is not particularly limited, but it is believed that the ether bond between the hydrophilic POA chain and the hydrophobic secondary alkyl group allows the polyoxyalkylene secondary alkyl ether to have a balanced hydrophilic / hydrophobic balance, thereby contributing to the protection of the substrate surface and reducing haze on the polished substrate surface.

[0069] The molecular weight of the polyoxyalkylene secondary alkyl ether is not limited to a specific range, as it may vary depending on the substrate to be polished and the composition of the polishing composition. In some embodiments, the molecular weight of the polyoxyalkylene secondary alkyl ether is less than 4000, preferably 3000 or less, more preferably 2500 or less, and even more preferably 2000 or less, and may be 1500 or less, or 900 or less (e.g., 700 or less). Polyoxyalkylene secondary alkyl ethers with relatively small molecular weights are advantageous in terms of filterability, washability, etc. Furthermore, the molecular weight of the polyoxyalkylene secondary alkyl ether is suitably 200 or more from the viewpoint of surface activity, etc., and is preferably 250 or more (e.g., 300 or more) from the viewpoint of haze reduction effect, etc., and may be 400 or more, 500 or more, 600 or more, or 800 or more (e.g., 1000 or more). As the molecular weight of the polyoxyalkylene secondary alkyl ether, the weight average molecular weight (Mw) determined by the above-mentioned GPC or the molecular weight calculated from the chemical formula can be used.

[0070] The number of carbon atoms in the secondary alkyl group contained in the polyoxyalkylene secondary alkyl ether molecule is not particularly limited. The number of carbon atoms in the secondary alkyl group may be 3 or more, 5 or more, or 7 or more. From the viewpoint of surface protection, etc., the number of carbon atoms in the secondary alkyl group is preferably 8 or more, more preferably 10 or more, and even more preferably 12 or more. The number of carbon atoms in the secondary alkyl group may be 27 or less, 25 or less, or 20 or more. From the viewpoint of solubility, etc., the number of carbon atoms in the secondary alkyl group is preferably 18 or less, more preferably 16 or less, and even more preferably 14 or less. The two alkyl groups bonded to the secondary carbon of the secondary alkyl group may be the same or different. The two alkyl groups bonded to the secondary carbon may each be linear or branched.

[0071] The polyoxyalkylene (POA) chain contained in the polyoxyalkylene secondary alkyl ether is a polymer chain containing oxyalkylene units as the main repeating units. The content of oxyalkylene units in the POA chain is, for example, more than 50% by weight, and may be 70% by weight or more, 85% by weight or more, or 95% by weight or more. Substantially all of the repeating units contained in the POA chain may be oxyalkylene units.

[0072] The number of moles of alkylene oxide added can be adjusted to obtain a polyoxyalkylene secondary alkyl ether of an appropriate molecular weight. 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, preferably 60 or less, more preferably 40 or less, and 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).

[0073] 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. The oxyalkylene units contained in the POA chain may be of one type or two or more types. For example, the POA chain may contain a combination of an oxyethylene unit and an oxypropylene unit. In a POA chain containing two or more types of oxyalkylene units, the oxyalkylene units may be random copolymers, block copolymers, alternating copolymers, or graft copolymers of the corresponding alkylene oxides.

[0074] In a POA chain containing two or more types of oxyalkylene units, the content ratio of these oxyalkylene units is not particularly limited. For example, of the number of moles of added alkylene oxide, 0 to 100% may be ethylene oxide (EO), 0 to 100% may be propylene oxide (PO), or 0 to 100% may be butylene oxide (BO). For example, in the case of a POA chain containing oxyethylene units and oxypropylene units as examples of oxyalkylene units, the ratio of the number of moles of added EO to the number of moles of added PO among the number of moles of added alkylene oxide may be in the range of 90:10 to 10:90, 80:20 to 20:80, or 75:35 to 35:75.

[0075] The polyoxyalkylene secondary alkyl ether may be used alone or in combination of two or more. The content of the polyoxyalkylene secondary alkyl ether in the polishing composition is not particularly limited. For example, 1.0 × 10 -6 From the viewpoint of reducing haze, the preferred content is 5.0 × 10 -6 % by weight or more, more preferably 1.0 × 10 -5 % by weight or more, more preferably 5.0 × 10 -5 % by weight or more, e.g., 1.0 x 10 -4% by weight or more. Also, from the viewpoint of cleaning property, the content is preferably less than 0.2% by weight, preferably less than 0.05% by weight, more preferably less than 0.01% by weight, and may be, for example, less than 0.005% by weight, or may be less than 0.001% by weight. When the polishing composition contains two or more kinds of polyoxyalkylene secondary alkyl ethers, the content refers to the total content of all polyoxyalkylene secondary alkyl ethers contained in the polishing composition. These contents can be preferably applied to the content in the polishing liquid (working slurry) supplied to the substrate, for example.

[0076] The content of polyoxyalkylene secondary alkyl ether (when two or more kinds of polyoxyalkylene secondary alkyl ethers are contained, their total amount) can also be determined by the relative relationship with the abrasive grain. Although not particularly limited, in some embodiments, the content of polyoxyalkylene secondary alkyl ether per 100 parts by weight of abrasive grain can be, for example, 0.0001 parts by weight or more, and from the viewpoint of haze reduction, it is appropriate to set it to 0.001 parts by weight or more, preferably 0.005 parts by weight or more, more preferably 0.01 parts by weight or more, and even more preferably 0.05 parts by weight or more. In addition, the content of polyoxyalkylene secondary alkyl ether per 100 parts by weight of abrasive grain can be, for example, 0.5 parts by weight or less, or even 0.3 parts by weight or less. From the viewpoint of the dispersion stability of the polishing composition, in some embodiments, the content of polyoxyalkylene secondary alkyl ether per 100 parts by weight of abrasive grains is suitably less than 0.30 parts by weight, preferably 0.20 parts by weight or less, and may be 0.10 parts by weight or less.

[0077] Water-soluble polymer content W A and the content of polyoxyalkylene secondary alkyl ether W S Weight ratio (W A / W S ) is not particularly limited. A / W SThe lower limit of the weight ratio (W) can be, for example, 0.01 or more, and usually 0.05 or more is preferable, and 0.1 or more is more preferable. A / W S The lower limit of the weight ratio (W A / W S The upper limit of ) can be, for example, 200 or less, and usually 100 or less is preferable, and 80 or less is more preferable.

[0078] <Water> The water contained in the polishing composition disclosed herein can preferably be ion-exchanged water (deionized water), pure water, ultrapure water, distilled water, or the like. To minimize the inhibition of the functions of other components contained in the polishing composition, the water used preferably contains, for example, 100 ppb or less of transition metal ions in total. 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, or by distillation. The polishing composition disclosed herein may further contain, as needed, an organic solvent (e.g., a lower alcohol or a lower ketone) that is uniformly miscible with water. Preferably, 90% by volume or more of the solvent contained in the polishing composition is water, and more preferably 95% by volume or more (e.g., 99 to 100% by volume) is water.

[0079] <Other ingredients> The polishing composition disclosed herein may further contain, as needed, known additives that can be used in polishing compositions (e.g., polishing compositions used in the finish polishing step of silicon wafers), such as surfactants, organic acids, organic acid salts, inorganic acids, inorganic acid salts, chelating agents, preservatives, and antifungal agents, within the range that does not significantly impair the effects of the present invention.

[0080] The polishing composition disclosed herein can contain a surfactant as an optional component within a range that does not impair the effects of the present invention. Note that the surfactant in this specification can include polyoxyalkylene alkyl ethers other than the above-mentioned polyoxyalkylene secondary alkyl ethers, such as polyoxyalkylene primary alkyl ethers, but does not include the above-mentioned polyoxyalkylene secondary alkyl ethers.

[0081] As the surfactant, any of anionic, cationic, nonionic, and amphoteric surfactants can be used. Anionic or nonionic surfactants can be employed. From the viewpoint of low foaming and ease of pH adjustment, nonionic surfactants can be used. In addition, as the surfactant, for example, a surfactant having a Mw of 0.2 × 10 4 From the viewpoint of the filterability of the polishing liquid and the cleanability of the polishing object, the Mw of the surfactant is 0.2 × 10 4 In a preferred embodiment of the technology disclosed herein, the Mw of the surfactant is 100 or more, more preferably 200 or more, even more preferably 250 or more, and particularly preferably 300 or more. Increasing the Mw of the surfactant tends to improve the polishing rate.

[0082] Examples of 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 types of oxyalkylenes (e.g., diblock copolymers, triblock copolymers, random copolymers, and alternating copolymers). The surfactants may include surfactants containing a polyoxyalkylene structure. The surfactants may be used alone or in combination of two or more.

[0083] When the polishing composition disclosed herein contains a surfactant, its content is not particularly limited as long as it does not significantly impair the effects of the present invention. The content of the surfactant per 100 parts by weight of abrasive grains is, for example, 20 parts by weight or less, and may be less than 10 parts by weight, less than 3 parts by weight, less than 1 part by weight, or less than 0.3 parts by weight (e.g., less than 0.1 parts by weight). The polishing composition disclosed herein can be preferably implemented in an embodiment that is substantially free of the surfactant.

[0084] Organic acids and their salts, and inorganic acids and their salts can be used alone or in combination. Examples of organic acids include fatty acids such as formic acid, acetic acid, and propionic acid; aromatic carboxylic acids such as benzoic acid and phthalic acid; itaconic acid, citric acid, oxalic acid, tartaric acid, malic acid, maleic acid, fumaric acid, succinic acid, glycolic acid, malonic acid, gluconic acid, alanine, glycine, lactic acid, organic sulfonic acids such as hydroxyethylidene diphosphate (HEDP) and methanesulfonic acid; and organic phosphonic acids such as nitrilotris(methylene phosphoric acid) (NTMP) and phosphonobutanetricarboxylic acid (PBTC). Examples of organic acid salts include alkali metal salts (sodium salts, potassium salts, etc.) and ammonium salts of organic acids. Examples of inorganic acids include hydrochloric acid, phosphoric acid, sulfuric acid, phosphonic acid, nitric acid, phosphinic acid, boric acid, and carbonic acid. Examples of inorganic acid salts include alkali metal salts (sodium salts, potassium salts, etc.) and ammonium salts of inorganic acids.

[0085] The chelating agent may be used alone or in combination of two or more. Examples of the chelating agent include aminocarboxylic acid chelating agents and organic phosphonic acid chelating agents. Suitable examples of the chelating agent include ethylenediaminetetrakis(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), and diethylenetriaminepentaacetic acid. Examples of the preservatives and antifungal agents include isothiazolinone compounds, parahydroxybenzoic acid esters, phenoxyethanol, etc.

[0086] The polishing composition disclosed herein preferably contains substantially no oxidizing agent. If the polishing composition contains an oxidizing agent, supplying the polishing composition to a substrate (e.g., a silicon wafer) can oxidize the surface of the substrate, forming an oxide film, which can reduce the removal rate. Specific examples of oxidizing agents include hydrogen peroxide (HO), sodium persulfate, ammonium persulfate, and sodium dichloroisocyanurate. The term "substantially free of oxidizing agent" 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. (e.g., a molar concentration of the oxidizing agent in the polishing composition of 0.0005 mol / L or less, preferably 0.0001 mol / L or less, more preferably 0.00001 mol / L or less, and particularly preferably 0.000001 mol / L or less) can be included in the concept of a polishing composition that does not contain an oxidizing agent.

[0087] <ph> The pH of the polishing composition disclosed herein is not particularly limited, and an appropriate pH can be adopted depending on the substrate, abrasive type, etc. In some embodiments, the pH of the polishing composition is suitably 8.0 or higher, preferably 8.5 or higher, and more preferably 9.0 or higher. As the pH of the polishing composition increases, the polishing efficiency tends to improve. On the other hand, from the viewpoint of preventing dissolution of abrasive grains (e.g., silica particles) and suppressing a decrease in mechanical polishing action, the pH of the polishing composition is usually suitably 12.0 or lower, preferably 11.0 or lower, more preferably 10.8 or lower, and even more preferably 10.5 or lower.

[0088] In the technology disclosed herein, the pH of the polishing composition can be determined by using a pH meter (for example, a glass electrode type hydrogen ion concentration indicator (model number F-72) manufactured by Horiba, Ltd.) and performing three-point calibration using standard buffer solutions (phthalate pH buffer solution pH: 4.01 (25°C), neutral phosphate pH buffer solution pH: 6.86 (25°C), carbonate pH buffer solution pH: 10.01 (25°C)), then placing the glass electrode in the composition to be measured and measuring the value after stabilization for at least two minutes.

[0089] <Polishing liquid> The polishing composition disclosed herein is typically supplied to the surface of a substrate in the form of a polishing liquid containing the polishing composition and used to polish the substrate. The polishing liquid can be prepared, for example, by diluting any of the polishing compositions disclosed herein (typically with water). Alternatively, the polishing composition can be used as a polishing liquid as is. That is, the concept of the polishing composition in the technology disclosed herein encompasses both a polishing liquid (working slurry) that is supplied to a substrate and used to polish the substrate, and a concentrated liquid (stock polishing liquid) that is diluted and used as a polishing liquid. Another example of a polishing liquid containing the polishing composition disclosed herein is a polishing liquid obtained by adjusting the pH of the composition.

[0090] <Concentrate> The polishing composition disclosed herein may be in a concentrated form (i.e., in the form of a concentrated polishing liquid) before being supplied to a substrate. 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 can be, for example, about 2 to 100 times in volume terms, and is usually about 5 to 50 times (e.g., about 10 to 40 times). Such a concentrate can be diluted at a desired time to prepare a polishing liquid (working slurry), which can then be supplied to a substrate. The dilution can be performed, for example, by adding water to the concentrate and mixing the mixture.

[0091] Furthermore, in the case of a polishing composition (i.e., a concentrate) that is diluted before use in polishing, the content of abrasive grains in the concentrate can be, for example, 25% by weight or less. From the viewpoints of dispersion stability and filterability of the polishing composition, the content is usually preferably 20% by weight or less, more preferably 15% by weight or less. In a preferred embodiment, the content of abrasive grains may be 10% by weight or less, or may be 5% by weight or less. From the viewpoints of convenience and cost reduction during production, distribution, storage, etc., the content of abrasive grains in the concentrate can be, for example, 0.1% by weight or more, preferably 0.5% by weight or more, more preferably 0.7% by weight or more, and even more preferably 1% by weight or more.

[0092] <Preparation of Polishing Composition> The polishing composition used in the technology 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 polishing liquid is prepared by mixing a part A containing at least abrasive grains among the components of the polishing composition with a part B containing at least a portion of the remaining components, and then mixing and diluting these at an appropriate timing as needed.

[0093] The method for preparing the polishing composition is not particularly limited. For example, the components constituting 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.

[0094] <Application> The polishing composition disclosed herein can be used to polish substrates of various materials and shapes. The substrate material can be, for example, a metal or semimetal, such as silicon, aluminum, nickel, tungsten, copper, tantalum, titanium, or stainless steel, or an alloy thereof; a glassy material, such as quartz glass, aluminosilicate glass, or glassy carbon; a ceramic material, such as alumina, silica, sapphire, silicon nitride, tantalum nitride, or titanium carbide; a compound semiconductor substrate material, such as silicon carbide, gallium nitride, or gallium arsenide; or a resin material, such as polyimide resin. The substrate may be made of a combination of these materials. The shape of the substrate is not particularly limited. The polishing composition disclosed herein can be used to polish, for example, a flat substrate, such as a plate or polyhedron, or the edge of a substrate (e.g., wafer edge polishing).

[0095] The polishing composition disclosed herein can be particularly preferably used for polishing a surface made of silicon (typically, polishing a silicon wafer). A typical example of the silicon wafer referred to here is a silicon single crystal wafer, for example, a silicon single crystal wafer obtained by slicing a silicon single crystal ingot.

[0096] The polishing composition disclosed herein can be preferably applied to a polishing process of a substrate (e.g., a silicon wafer). Before the polishing process with the polishing composition disclosed herein, the substrate may be subjected to a general treatment that can be applied to a substrate in a process upstream of the polishing process, such as lapping or etching.

[0097] The polishing composition disclosed herein is effective when used in the finishing step of a substrate (e.g., a silicon wafer) or in the polishing step immediately preceding it, and its use in the finishing polishing step is particularly preferred. Here, the finishing polishing step refers to the final polishing step in the manufacturing process of the target object (i.e., a step in which no further polishing is performed after that step). The polishing composition disclosed herein may also be used in a polishing step upstream of the finishing polishing (referring to a preliminary polishing step between the rough polishing step and the final polishing step, which typically includes at least a primary polishing step and may further include secondary, tertiary, etc. polishing steps), for example, a polishing step performed immediately preceding the finishing polishing.

[0098] The polishing composition disclosed herein is effective, for example, for polishing (typically finish polishing or polishing immediately before) silicon wafers that have been prepared to a surface roughness of 0.01 nm to 100 nm in an upstream process. Its application to finish polishing is particularly preferred. The surface roughness Ra of the substrate can be measured, for example, using a laser scanning surface roughness meter "TMS-3000WRC" manufactured by Schmitt Measurement Systems Inc.

[0099] <Polishing> The polishing composition disclosed herein can be used for polishing a substrate, for example, in an embodiment including the following steps: Hereinafter, a preferred embodiment of a method for polishing a silicon wafer as a substrate using the polishing composition disclosed herein will be described. That is, a polishing liquid containing any of the polishing compositions disclosed herein is prepared. The preparation of the polishing liquid may include adjusting the concentration (e.g., diluting) of the polishing composition, adjusting the pH, or the like to prepare the polishing liquid. Alternatively, the polishing composition may be used as is as the polishing liquid.

[0100] Next, the polishing liquid is supplied to the substrate, and polishing is performed by a conventional method. For example, when performing finish polishing of a silicon wafer, typically, a silicon wafer that has undergone a lapping process is set in a general polishing device, and a polishing liquid is supplied to the surface to be polished of the silicon wafer through the polishing pad of the polishing device. Typically, while continuously supplying the polishing liquid, the polishing pad is pressed against the surface to be polished of the silicon wafer, and the two are moved relative to each other (for example, rotated). Polishing of the substrate is completed through this polishing process.

[0101] The polishing pad used in the polishing step is not particularly limited. For example, a polishing pad of a foamed polyurethane type, a nonwoven fabric type, a suede type, or the like can be used. Each polishing pad may contain abrasive grains or may not contain abrasive grains. Usually, a polishing pad that does not contain abrasive grains is preferably used.

[0102] Substrates polished with the polishing composition disclosed herein are typically cleaned. Cleaning can be performed using an appropriate cleaning solution. The cleaning solution used is not particularly limited, and examples include SC-1 cleaning solution (a mixture of ammonium hydroxide (NH4OH), hydrogen peroxide (HO2), and water (HO)) and SC-2 cleaning solution (a mixture of HCl, HO2, and HO), which are commonly used in the semiconductor field. The temperature of the cleaning solution can be, for example, in the range from room temperature (typically about 15°C to 25°C) to about 90°C. From the viewpoint of improving the cleaning effect, a cleaning solution of about 50°C to 85°C can be preferably used.

[0103] As described above, the technology disclosed herein can include a method for manufacturing a polished product (e.g., a method for manufacturing a silicon wafer) that includes a polishing step (preferably finish polishing) by any of the polishing methods described above, and the provision of a polished product (e.g., a silicon wafer) manufactured by the method. [Example]

[0104] 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, "parts" and "%" are by weight unless otherwise specified.

[0105] <Preparation of Polishing Composition> Example 1 A concentrated solution of the polishing composition according to this example was prepared by mixing abrasive grains, a water-soluble polymer, a basic compound, a polyoxyalkylene alkyl ether, and deionized water. Colloidal silica (average primary particle diameter: 27 nm) was used as the abrasive grains, and a water-soluble polymer having a weight-average molecular weight of about 2.8 × 10 5 Hydroxyethyl cellulose (HEC) of the formula (I) was used, and ammonia was used as the basic compound. The polyoxyalkylene alkyl ether used had a secondary alkyl group with approximately 13 carbon atoms, a molecular weight shown in Table 1, and the number of moles of alkylene oxide added shown in Table 1. The oxyalkylene unit of the polyoxyalkylene alkyl ether in this example was an oxyethylene unit. The resulting concentrated polishing composition was diluted 20 times by volume with deionized water (DIW) to obtain a polishing composition according to this example with an abrasive concentration of 0.175%, a water-soluble polymer concentration of 0.0088%, a basic compound concentration of 0.005%, and a polyoxyalkylene alkyl ether concentration of 0.00015%.

[0106] Examples 2 to 4 Polishing compositions according to each example were prepared in the same manner as in Example 1, except that the polyoxyalkylene alkyl ether used was a polyoxyalkylene secondary alkyl ether having the molecular weight shown in Table 1 and the number of moles of alkylene oxide added shown in Table 1. In each example, the number of carbon atoms in the secondary alkyl group of the polyoxyalkylene alkyl ether was about 13, and the oxyalkylene units were oxyethylene units and oxypropylene units.

[0107] (Comparative Example 1) The polishing composition of this example was prepared in the same manner as in Example 1, except that a polyoxyalkylene alkyl ether having a primary alkyl group with approximately 10 carbon atoms, a molecular weight of 378, and 5 moles of ethylene oxide added was used as the polyoxyalkylene alkyl ether.

[0108] Examples 5 to 7 As a water-soluble polymer, the weight-average molecular weight is approximately 7.0 × 10 4 Polishing compositions according to each example were prepared in the same manner as in Example 1, except that polyvinyl alcohol (hereinafter referred to as "PVA") of the above formula was used, and that polyoxyalkylene alkyl ethers were polyoxyalkylene secondary alkyl ethers having the molecular weights shown in Table 2 and the number of moles of alkylene oxide added shown in Table 2. In each example, the number of carbon atoms in the secondary alkyl group of the polyoxyalkylene alkyl ether was about 13, and the oxyalkylene unit was an oxyethylene unit.

[0109] (Examples 8 and 9) As a water-soluble polymer, the weight-average molecular weight is approximately 7.0 × 10 4 Polishing compositions according to each example were prepared in the same manner as in Example 1, except that a PVA of the formula (I) was used, and that a polyoxyalkylene alkyl ether was used having a molecular weight shown in Table 2 and a molar number of alkylene oxide added shown in Table 2. In each example, the number of carbon atoms in the secondary alkyl group of the polyoxyalkylene alkyl ether was about 13, and the oxyalkylene units were oxyethylene units and oxypropylene units.

[0110] (Comparative Example 2) A polishing composition according to this example was prepared in the same manner as in Example 5, except that the polyoxyalkylene alkyl ether was replaced with a polyalkylene oxide having an alkylene oxide addition molar number of 190 and a molecular weight of approximately 3000, and the content was set to 0.00125%. In this example, the oxyalkylene units of the polyalkylene oxide were oxyethylene units and oxypropylene units.

[0111] (Comparative Example 3) The polishing composition of this example was prepared in the same manner as in Example 5, except that a polyoxyalkylene alkyl ether having a primary alkyl group with approximately 10 carbon atoms, a molecular weight of 378, and an ethylene oxide addition mole count of 5 was used.

[0112] <Silicon wafer polishing> The substrate was a commercially available silicon single crystal wafer with a diameter of 200 mm (conductivity type: P type, crystal orientation: <100> Silicon wafers (COP (Crystal Originated Particle)-free) were prepared by pre-polishing under the following polishing condition 1. Pre-polishing was performed using a polishing solution containing 1.0% abrasive grains (colloidal silica with an average primary particle diameter of 42 nm) and 0.068% potassium hydroxide in deionized water.

[0113] [Polishing conditions 1] Polishing equipment: Single-wafer polishing equipment model "PNX-322" manufactured by Okamoto Machine Tools Manufacturing Co., Ltd. Polishing load: 15kPa Rotation speed of the surface plate: 30 rpm Head (carrier) rotation speed: 30 rpm Polishing pad: Fujibo Ehime Co., Ltd. Product name "FP55" Pre-polishing liquid supply rate: 550 mL / min Pre-polishing liquid temperature: 20℃ Plate cooling water temperature: 20℃ Polishing time: 3min

[0114] The polishing compositions according to the examples prepared above were used as polishing liquids to polish the silicon wafers that had been pre-polished as described above under the following polishing conditions 2.

[0115] [Polishing conditions 2] Polishing equipment: Single-wafer polishing equipment model "PNX-322" manufactured by Okamoto Machine Tools Manufacturing Co., Ltd. Polishing load: 15kPa Rotation speed of the surface plate: 30 rpm Head (carrier) rotation speed: 30 rpm Polishing pad: Fujibo Ehime Co., Ltd. Product name "POLYPAS27NX" Polishing liquid supply rate: 400 mL / min Polishing solution temperature: 20℃ Plate cooling water temperature: 20℃ Polishing time: 4 min

[0116] The polished silicon wafer was removed from the polishing machine and cleaned using a cleaning solution of NH4OH (29%): HO2 (31%): deionized water (DIW) = 1:1:12 (volume ratio) (SC-1 cleaning). Specifically, two cleaning tanks, the first and second, were prepared, and each was filled with the above cleaning solution and maintained at 60°C. The polished silicon wafer was immersed in the first cleaning tank for 5 minutes, then passed through a rinse tank in which it was immersed in ultrapure water and subjected to ultrasonic waves, and then immersed in the second cleaning tank for 5 minutes, passed through a rinse tank in which it was immersed in ultrapure water and subjected to ultrasonic waves, and then dried using a spin dryer.

[0117] <Haze measurement> After cleaning, the surface of the silicon wafer was inspected using a wafer inspection device manufactured by KLA Tencor, product name "Surfscan SP2 XP The haze (ppm) was measured in DWO mode using a meter. The results obtained were converted into relative values ​​(haze ratios) with the haze value for Comparative Example 1 set to 100% and are shown in Table 1, and the results were converted into relative values ​​(haze ratios) with the haze value for Comparative Example 3 set to 100% and are shown in Table 2. If the haze ratio is less than 100%, it can be said that a significant haze improvement effect can be confirmed, and a smaller haze ratio value indicates a greater haze improvement effect.

[0118] [Table 1]

[0119] [Table 2]

[0120] As shown in Tables 1 and 2, the polishing compositions of Examples 1 to 9, which used a polyoxyalkylene secondary alkyl ether, showed a superior haze improvement effect compared to the polishing compositions of Comparative Examples 1 and 3, which used a polyoxyalkylene primary alkyl ether. Furthermore, the polishing compositions of Examples 5 to 9 showed a superior haze improvement effect compared to the polishing composition of Comparative Example 2, which used a polyalkylene oxide instead of a polyoxyalkylene secondary alkyl ether. The above results show that a polishing composition containing abrasive grains, a water-soluble polymer, a basic compound, and water, and further containing a polyoxyalkylene alkyl ether in which the secondary carbon of the alkyl group is bonded to a polyoxyalkylene by an ether bond, can improve the surface quality of a substrate after polishing.

[0121] 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.< / ph>

Claims

1. A polishing composition used for polishing silicon wafers, comprising: The abrasive includes an abrasive grain, a water-soluble polymer, a basic compound, and water. Further included are polyoxyalkylene alkyl ethers in which the secondary carbon of the alkyl group is bonded to a polyoxyalkylene via an ether bond; the alkyl group having a secondary carbon in the polyoxyalkylene alkyl ether has 5 or more carbon atoms, The polishing composition has a polyoxyalkylene alkyl ether content of 1.0×10 −5 wt % or more and less than 0.005 wt %.

2. 2. The polishing composition according to claim 1, wherein the polyoxyalkylene alkyl ether has a molecular weight of less than 4,000.

3. The polishing composition according to claim 1 or 2, comprising silica particles as the abrasive grains.

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